General Weather Discussion - March 2015

[venture]

Day 1 convective outlook
nws storm prediction center norman ok
1156 pm cdt wed mar 18 2015

valid 191200z - 201200z

...there is a mrgl risk of svr tstms across portions of southern
oklahoma and northern texas...

...summary...
A few storms with a threat for marginally severe hail and gusty
winds may occur across parts of the southern plains this afternoon
and evening.

...synopsis...

A weak upper low in southern stream flow over baja/northern mexico
will shift slowly eastward today. This will result in a band of
enhanced southwesterly mid to upper level flow across the southern
plains. At the surface...a relatively moist and warm airmass will
exist as far north as the red river in north tx/southern ok. A weak
surface trough will extend south/southwest from a low over western
north tx into southwest tx. At the same time...a cold front will
track southeastward across the southern plains and a few strong to
perhaps severe thunderstorms will be possible during the afternoon
and evening near the intersection of the sfc low and cold front.

...portions of southern ok and northern tx...

Surface dewpoints in the low 60s should extend as far north as
southwest and south-central ok this afternoon...while temperatures
warm into the upper 60s to mid 70s. While cloud cover may inhibit
greater heating...this should be sufficient to achieve mlcape values
approaching 750 j/kg. Isolated convection is expected to develop
near the triple point in the vicinity of cds to sps by 21-00z. While
instability will be marginal...effective shear near 35-45 kt and
modest lapse rates could be enough for some short-lived supercell
structures...capable mainly of marginally severe hail. These storms
should quickly become undercut by the southeastward advancing cold
front with only a brief window for surface based convection...but a
few stronger wind gusts may be possible as well.

...southwest tx...

A storm or two may also develop in the vicinity of the surface
trough...where stronger insolation is expected. If storms
develop...they will be diurnal in nature as convergence along the
trough will be much weaker than that near the cold front further to
the north. Still...should a storm develop...marginally severe hail
may be possible. Low confidence in coverage and conditional nature
of the threat will preclude severe probabilities at this time.

..leitman/dean.. 03/19/2015

[venture]

Wednesday looks like the day to watch for severe weather chances across Oklahoma. Still really early and not not a long of run-to-run consistency yet on the magnitude of things for the 25th but so far this is appearing the best setup we've had yet this year. Moderate to high instability, good moisture, and a boundary to focus convection. Won't get much more specific for now as the numbers will continue to change as we approach the day.

[venture]

SPC has a 15% area, equivalent to a Slight risk in Day 1 to 3 outlooks, for Tuesday so far.


06Z GFS would also pull more of Central and Southern OK into the risk area, but we'll see what the 12Z models put out later this morning and early this afternoon.

[Bobby821]

That looks to be primarily NE Oklahoma probably wont affect us here in central and points west and SW if this hold true come next week.

[venture]

That looks to be primarily NE Oklahoma probably wont affect us here in central and points west and SW if this hold true come next week.

That's not really how the map should be viewed. Day 4-8 maps are always going to show the area of greatest risk for those days...as best as they can forecast that far out. I'll post a discussion once the 12Z models are all in.

[Bobby821]

This was posted on News OK, I don't subscribe so I can not read the full article but this is a blurb at the top. So are we looking at a calm March and April with hardly any tornadoes or high end severe weather? Curious because that would give us just a month and a half of high end severe weather events in May and first part of June before active weather subsides.

As spring begins, forecasters say a relatively calm beginning of the tornado season could be in store. They expect to see little severe weather through the rest of March and April.

[venture]

This was posted on News OK, I don't subscribe so I can not read the full article but this is a blurb at the top. So are we looking at a calm March and April with hardly any tornadoes or high end severe weather? Curious because that would give us just a month and a half of high end severe weather events in May and first part of June before active weather subsides.

As spring begins, forecasters say a relatively calm beginning of the tornado season could be in store. They expect to see little severe weather through the rest of March and April.

Full article was readable to those without a subscription, so not sure why it isn't working for you. However, to take away a lot of assumptions just from the title isn't the best thing. What the NOAA reps are saying in the article is that with typical Weak El Nino patterns like we are in now, it generally translates to a quieter/wetter spring. We had similar El Ninos during 2012-2013, 2003-2005, and 1992-1994. How did it translate into tornadoes for those years?

1992: March - 2, April - 9, May - 25, Jun - 9, July - 2, Sept - 16 (monthly record), October - 1
1993: March - 6, April - 17, May - 20, Jun - 13, Sept - 5, Oct - 2, Nov - 1
1994: March - 1, April - 15, May - 11, Jun - 2, July - 6, Aug - 2, Oct - 3
2003: March - 4, April - 15, May - 59
2004: March - 12, April 13, May - 26, Jun - 4, Oct - 1, Nov - 6
2005: March - 8, April - 7, Jun - 10, Sept - 1, Oct - 1
2012: March - 5, April - 54 (Monthly record), May - 3, Oct - 1
2014: Jan - 2, March - 2, April - 12, May - 63, Jul - 2, Aug - 1

NWS Norman put out a good post about this on FB a week or so ago, that was previously discussed. Slow starts to the season mean absolutely nothing and people that focus on it are putting themselves into a false sense of what the season will actually do. It is hard to say how the season will turn out, but it takes just one tornado day to make the year memorable.

We already have 2 severe weather days on tap for this coming week, so chances are we'll start to working on our annual tally for severe reports.

[venture]

Storm Outlook

Tuesday

Two main days of potential severe weather coming up for Oklahoma. First is going to be Tuesday March 24th. This is going to be based off of the 12Z GFS since the Euro isn't fully available just yet. Tuesday will have a system drop through Oklahoma by Mid-Late afternoon. Temps ahead of the boundary will be in the 70s and 80s. Moisture seems to be pretty sufficient, especially for March systems, over much of the state with dews in the mid to upper 50s by early afternoon. This could increase into the low 60s, especially SE of I-44 and south of I-40. This will help cause a moderately unstable atmosphere over much of Central, Southwest, and Eastern OK. By late afternoon we could be looking at surface-based CAPE figures at or above 1500 j/kg stretch from the Tulsa area, through the Southeast Metro, and back over Southern OK between I-44 and I-35. Convective Inhibition may be an issue for many areas, especially south of the OKC Metro area. This would limit any storm development or eventual coverage of storms. CIN is also forecast to be decent over NE OK as well, but greater forcing should help break that up. Outside of early morning precip chances, storms should initiate from Northeast to Southwest along the boundary starting around the Tulsa/Bartlesville areas and build back towards Norman/Chickasha by early Evening. Conditions during this time should be favorable for a few severe storms with large hail and damaging winds. Tornado threat appears low, not zero, at this time. Being on the tail end of the line of storms always means we need to watch for the tail end charlie scenario of a more intense storm. Storm movements should be ESE at about 20 mph.

Wednesday

Overnight into Wednesday the entire setup backs up and reloads. The dryline heads back to the TX/Ok border and the surface boundary pushes back north of the KS line. Should this happen, a deep moisture return will happen sending dewpoints well into the low 60s by afternoon. If this plays out it will be one of those mornings where the moisture is thick, it'll smell like Spring, and you'll see the low broken cloud deck in the morning with the relatively fast moving clouds. Instability by afternoon is expected to be high to very high with lifted indexes at or below -8 along I-44 from Tulsa through the Metro to the south and southwest. CAPE values could very well exceed 2500 j/kg especially over the OKC metro area.

The dryline will rush east but then park it around US 81 out west of the Metro - at this time it will not pass the Metro. The cold front/surface boundary will plow down from the north very late into the overnight hours. This could very well set us up for two rounds of storms - one from the dryline and another more squall line setup along the front. Initiation should start somewhere near Central OK - it will all depend on boundary placement. Best time for storm chances will be from 5PM through 10PM for the first batch, then through 4AM for the second wave (should be less intense).

Forecast sounding from Norman by mid-afternoon is pretty stout. No cap in place (which could be a good thing), very high instability, and numbers are are pretty favorable for all modes of severe weather. As far as the tornado threat (which it is very early to really get into this since things will continue to evolve) the chance will be there, but there are a few things going against it. Wind field isn't cookie cutter ideal with surface winds out of the SSW and only getting barely WSW with height in the lower parts of the potential storms. This tends to favor more large hail and damaging winds. However, localized environments can modify this and as we get closer we will have to watch for any backing to the winds (more of a southeasterly direction at the surface) to see if that improves overall shear. Regardless, seeing EHI values over 2, helicity over 153...we still need to watch it.

As usual...all this can change from run to run, so this is just based off the one model and the fact where it has been mostly consistent in highlighting these two days. At this point I like Wednesday more for the severe weather chances for Oklahoma, but that could change on the next run.

[venture]

Discussion Update

This is going to be fairly short and will focus on differences from the GFS to the 12Z Euro. Tuesday is pretty similar in nature, but it is a bit further south with initiation and closer to Central OK. Instability is pretty similar in the moderate to high category with the highest further SW.

Wednesday is where the differences lie. Euro is significantly faster with the cold front and brings in through during the morning. Good chance for showers and storms along it, especially across Northern OK. Severe weather chances obviously much lower with it, but could see some higher winds with those storms.

So right now Tuesday seems pretty well in place for severe weather with just some of the smaller details needed to put in place. Wednesday has significant differences in system placements and speeds that we need to see with solution the models focus on. We will start entering the NAM's forecast window soon, so that will help give us more data to look at.

[venture]

Quick update. GFS seems to be getting more in line with the others now. This is a pretty typical move and something I normally expect for March storms. Both Tuesday and Wednesday will still have chances for severe storms, but it'll mostly be confined to SE of I-44 and east of I-35. NAM is even more bearish on any precip at all south of I-70 in MO. The main push of energy with this next storm though won't be on shore until late Sunday/Monday - so expect things to still move around and change.

[silvergrove]

Did we match or break the record yet for the slowest start to the storm season?

[venture]

We tied the record for latest SVR warning today.

[venture]

Marginal Risk for severe weather for Tuesday over NW OK.

SPC discussion... ...CENTRAL PLAINS...
WEAK SHORT-WAVE TROUGH IS EXPECTED TO EJECT ACROSS THE CNTRL/SRN
ROCKIES INTO THE CNTRL PLAINS BY 24/00Z. IN RESPONSE...LEE
TROUGH/DRY LINE SHOULD BECOME BETTER DEFINED ACROSS THE ERN TX
PANHANDLE WITH A PRONOUNCED WARM FRONT EXPECTED TO SHARPEN OVER SRN
KS/MO. MODELS ARE FAIRLY CONSISTENT ALLOWING A NARROW CORRIDOR OF
50S SFC DEW POINTS TO ADVANCE NWD ACROSS THE EDWARDS PLATEAU ACROSS
WRN OK INTO EXTREME SRN KS. FORECAST SOUNDINGS SUGGEST INHIBITION
WILL WEAKEN CONSIDERABLY ALONG THE DRY LINE OVER THE ERN TX
PANHANDLE BUT IT/S NOT CLEAR IF ANY STORMS WILL ACTUALLY ROOT INTO
THIS MODIFIED AIR MASS. WHILE AN ISOLATED HIGH-BASED SUPERCELL
CANNOT BE RULED OUT ALONG THE DRY LINE...A STRONGER SIGNAL FOR
CONVECTION DEVELOPS AFTER DARK AS 50KT+ LLJ IMPINGES ON WARM FRONT
ACROSS KS. PARCELS LIFTED NEAR 850MB COULD YIELD MUCAPE IN EXCESS
OF 1000 J/KG WITHIN A SHEARED ENVIRONMENT FAVORABLE FOR ROTATING
STORMS. FOR THIS REASON HAVE INTRODUCED 5 PERCENT SEVERE PROBS TO
ACCOUNT FOR HAIL WITHIN STRONGEST ELEVATED CONVECTION AFTER DARK.

[venture]

3 days of severe weather possible across portions of the state...

Monday - Marginal Risk over NW OK. Moderately unstable atmosphere over all of W OK tomorrow, but also plenty of convective inhibition as well. Weakest area of CIN is going to be in the NW sections where 1 or 2 storms may get going. Hail and wind main threat.

Tuesday - Slight Risk over far NE and East Central OK, surrounded by a Marginal risk into SE OK. 12Z NAM suggests this area could be moved further west closer to the eastern edges of the Metro area. High to Very High Instability ahead of the boundary with CAPE values possible approaching 3000 j/kg. Main risks Hail and Wind, tornado threat appears more probably closer to NE OK. Initiation is expected to be mostly in NE OK, so areas closer to central OK will be much more isolated if at all.

Wednesday - Severe risk, likely a Slight Risk, most areas SE of I-44. Right now SPC has this area SE of the Metro area, but 12 NAM does suggest the Metro will be in play. Very High instability around 3000 j/kg (CAPE) over the area, especially Central OK. All modes of severe weather possible, but more favored towards damaging winds. Initiation expect over Central OK by late afternoon.

More details with the runs tonight.

[okatty]

Well it's a chamber of commerce day today!! Gorgeous!!

[John1744]

3 days of severe weather possible across portions of the state...

Monday - Marginal Risk over NW OK. Moderately unstable atmosphere over all of W OK tomorrow, but also plenty of convective inhibition as well. Weakest area of CIN is going to be in the NW sections where 1 or 2 storms may get going. Hail and wind main threat.

Tuesday - Slight Risk over far NE and East Central OK, surrounded by a Marginal risk into SE OK. 12Z NAM suggests this area could be moved further west closer to the eastern edges of the Metro area. High to Very High Instability ahead of the boundary with CAPE values possible approaching 3000 j/kg. Main risks Hail and Wind, tornado threat appears more probably closer to NE OK. Initiation is expected to be mostly in NE OK, so areas closer to central OK will be much more isolated if at all.

Wednesday - Severe risk, likely a Slight Risk, most areas SE of I-44. Right now SPC has this area SE of the Metro area, but 12 NAM does suggest the Metro will be in play. Very High instability around 3000 j/kg (CAPE) over the area, especially Central OK. All modes of severe weather possible, but more favored towards damaging winds. Initiation expect over Central OK by late afternoon.

More details with the runs tonight.

[venture]

The TLDR Overview...
Monday - One...maybe two storms far NW with hail/wind. Tuesday - Line of storms southeast of a line from Bentonville-Eufaula-Ardmore with hail and wind primary, maybe a tornado (best chance up in MO). Wednesday - As it appears right now, could be a good sized severe event - all modes possible. Our Severe weather drought will end, and I also expect the nation's tornado drought to end this week as well.

Forecast Discussion

Forecast is a bit of a blend between NAM and GFS, leaning a bit more on NAM just with a bit tamer numbers (some of them are pretty wild for March). GFS is lagging a bit behind the adjustments the other models but setting everything too far east. We'll have to see how things continue to trend. NAM continues to intensify and setup things further west.

Monday
Risk Area in Blue


Monday appears to a modest day severe weather wise due to limited coverage. Conditions do appears favorable for a severe storm or two should anything be able to form. Forecast sounding from NW OK shows a moderately unstable atmosphere with a marginal cap. Shear looks favorable for rotating storms, but LCLs will be too high for any tornado potential - not saying it can't happen - just extremely unlikely at this point.

Tuesday
CAPE (first map), My Storm Outlook (second map)


Tuesday is likely the day Oklahoma's severe weather drought ends. I have an area outlined in blue and gold on the map. East of the Blue area are those with the chance to see storms form. The area in the gold outline is the severe risk area. I think this is a pretty solid slight risk day with no need to go higher. Current storm mode appears to be more linear with some broken areas with embedded supercells. Some things to watch for. One is moisture return. NAM wants to bump a ton of 60+ dewpoints into Central and Eastern OK by early Afternoon. The highest the moisture content the more you will see instability soar.
Impacts to Central OK will be limited by the advancing boundary that will clear the Metro by mid Afternoon and allow for storms to initiate further east. Main threats will be hail and wind. Tornado threat will be there, best chance for Oklahoma appears to be over far NEl OK with the initial storms before things line out. I think SPC will go Slight and stay there...unless we see moisture return go crazy and warrant an enhanced risk.

Wednesday

This is going to be the big day this week. Do not be shocked to see SPC go with an Enhanced Risk this day, and if NAM verifies this could be the first Moderate risk of the year. I'm not sold on moisture return, so no need to go crazy yet. I did outline an area of enhanced risk on the map in dark blue over Central into NE OK. This is the most likely area to see all modes of severe weather. We are going to have two waves. 1) Over Western OK just west of the Metro area that will be supercells firing during the mid to late afternoon. 2) Along the cold front as it blasts down during the late evening from Kansas. Initial storms will be supercells and have the risk for very large hail, damaging winds, and probably a few tornadoes as it appears now. The setup for these storms will be pretty classic for the Spring, just not really for March.

Good moisture return/recovery expected with dews in the 60s over much of Oklahoma. Temps into the mid to upper 70s, even low 80s west of I-35 possible. Winds appears to be favorable and backing from the south-southeast across Central and Eastern OK. Now GFS, even though it is further east, does have similar moisture return. It is much tamer instability wise, but we are talking CAPE 1500-2000 j/kg versus NAM which has CAPE over 3000 j/kg. So we have to see which one is going to play out. I am a little concern on recovery of the atmosphere and position of boundaries from Tuesday's activity. If NAM plays out as the scenario we have, this will be a pretty big day severe weather wise that we've had in a while.

Below is the forecast sounding for near Norman for Wednesday afternoon/evening. You'll note backing of the winds to the SSE at the surface. Helicity and EHI values are quite high as well. Instability (CAPE) is very high. Other parameters such as LI, SWEAT, and TT are pretty high to extreme. Now take all this with the understanding a lot of this depends on moisture return and daytime heating - as well as boundary positioning. Severe threats are obviously going to include all modes with large hail and tornadoes possible with the initial storms and the more of a damaging wind threat with the cold front storms.

[venture]

SPC Outlooks are coming out...

Monday - Marginal Risk over NW and West Central OK.

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1238 AM CDT MON MAR 23 2015

VALID 231200Z - 241200Z

...THERE IS A MRGL RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING
ACROSS PARTS OF THE CENTRAL PLAINS...

...SUMMARY...
A FEW THUNDERSTORMS MAY BE ACCOMPANIED BY THE RISK FOR MARGINALLY
SEVERE HAIL ACROSS PARTS OF THE CENTRAL PLAINS LATE TODAY INTO
TONIGHT.

...SYNOPSIS...
AS A STRONG MID-LATITUDE PACIFIC JET NOSES EAST OF THE INTERNATIONAL
DATE LINE LATER TODAY AND TONIGHT...A GRADUAL AMPLIFICATION MAY
COMMENCE WITHIN BRANCHING DOWNSTREAM FLOW ACROSS THE EASTERN
PACIFIC...WITH MID/UPPER RIDGING BEGINNING TO BUILD WEST OF THE U.S.
PACIFIC COAST. OTHERWISE...FLOW ACROSS MUCH OF THE U.S. WILL REMAIN
MORE OR LESS ZONAL...IN THE WAKE OF A PROMINENT CLOSED LOW AND
TRAILING UPPER TROUGHING FORECAST TO PROGRESS EAST OF THE CANADIAN
MARITIMES AND NORTH ATLANTIC COAST.

WITHIN A LINGERING STREAM ACROSS THE SOUTHERN TIER STATES...MODELS
INDICATE THAT REMNANT UPPER TROUGHING WILL ACCELERATE THROUGH A
CONFLUENT REGIME ACROSS THE EASTERN GULF INTO SOUTH ATLANTIC COAST
STATES DURING THE DAY TODAY. IN ITS WAKE...SUBSTANTIVE LOW-LEVEL
COOLING AND/OR DRYING IS FORECAST ACROSS MUCH OF THE NORTHERN AND
WESTERN GULF OF MEXICO. THIS PROBABLY WILL TEND TO INHIBIT...OR AT
LEAST DELAY...INCREASING CONVECTIVE POTENTIAL WHICH COULD OCCUR WITH
UPPER TROUGHING NOW PROGRESSING INLAND ACROSS THE PACIFIC COAST.
THIS LATTER FEATURE MAY DECOMPOSE INTO A NUMBER OF SMALLER SCALE
PERTURBATIONS AS IT CONTINUES INLAND ACROSS THE INTERMOUNTAIN WEST
AND ROCKIES...BUT GUIDANCE REMAINS SUGGESTIVE THAT ONE IMPULSE MAY
SUPPORT AT LEAST MODEST SURFACE CYCLOGENESIS ACROSS THE SOUTH
CENTRAL HIGH PLAINS LATE THIS AFTERNOON THROUGH TONIGHT.

...CENTRAL PLAINS...
NORTHWARD MOISTURE RETURN TO THE EAST OF DEVELOPING SOUTHERN INTO
CENTRAL HIGH PLAINS SURFACE TROUGHING IS LIKELY TO BE LIMITED TO
THAT NOW PRESENT ACROSS THE SOUTHERN PLAINS...WHICH MAY ONLY SUPPORT
A CORRIDOR OF LOWER/MID 50S SURFACE DEW POINTS DURING PEAK AFTERNOON
HEATING/MIXING. MID-LEVEL LAPSE RATES WILL REMAIN
STEEP...ASSOCIATED WITH WARM MIXED LAYER AIR ADVECTING OFF THE
HIGHER TERRAIN TO THE WEST...BUT INHIBITION MAY SUPPRESS ANYTHING
MUCH BEYOND...PERHAPS...ONE OR TWO STORMS IN THE WARM SECTOR OF THE
DEVELOPING LOW. IF THIS OCCURS...IT CURRENTLY SEEMS MOST PROBABLE
ROUGHLY BETWEEN GAGE AND DODGE CITY...WHERE VERTICAL SHEAR SHOULD BE
FAVORABLE FOR SUPERCELLS GIVEN SUSTAINED CONVECTIVE DEVELOPMENT.

THUNDERSTORM ACTIVITY BASED WITHIN A STRENGTHENING LOWER/MID
TROPOSPHERIC WARM ADVECTION REGIME SEEMS MORE PROBABLE AFTER
DARK...INTO THE OVERNIGHT HOURS...ACROSS PARTS OF NORTHERN KANSAS.
IT IS POSSIBLE THAT CLOUD BEARING LAYER SHEAR MAY BE SUFFICIENT TO
ENHANCE THE HAIL POTENTIAL...DESPITE THE SOMEWHAT MARGINAL CAPE FOR
VIGOROUS UPDRAFTS.

Tuesday - SPC has done what I had posted in my last discussion. Slight Risk area expanded over much of Eastern Oklahoma.


DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1220 AM CDT MON MAR 23 2015

VALID 241200Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN OK INTO SWRN MO...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK FROM
NERN TX INTO NRN MO...

...SUMMARY...
SCATTERED SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP FROM PORTIONS
OF SOUTHERN MISSOURI...EASTERN OKLAHOMA...WESTERN ARKANSAS...AND
EXTREME NORTHEAST TEXAS TUESDAY AFTERNOON AND EVENING. LARGE HAIL
AND DAMAGING WINDS ARE THE PRIMARY THREATS.

...MO TO NORTHEAST TX...

STRONG SHORT-WAVE TROUGH WILL EJECT ACROSS THE CNTRL ROCKIES INTO
THE CNTRL PLAINS BY 24/18Z. THIS FEATURE SHOULD PROGRESS INTO THE
MID MS VALLEY BY EARLY EVENING WITH MARKED DIFLUENT HIGH LEVEL FLOW
AND FOCUSED ASCENT EXPECTED NORTH OF WARM FRONT. SUBSTANTIAL
CLOUDS/PRECIPITATION WILL BE NOTED WITHIN THE STRONGLY FORCED AIR
MASS FROM NEB INTO IA/NRN IL. HOWEVER...INSTABILITY SHOULD PROVE
INSUFFICIENT FOR ORGANIZED SEVERE THUNDERSTORMS ACROSS THE COOL
SECTOR. OF MORE CONCERN IS THE GRADUALLY MOISTENING WARM SECTOR
AHEAD OF COLD FRONT/DRY LINE. LATEST GUIDANCE SUPPORTS EARLIER
MODELS WITH 50S SFC DEW POINTS ADVANCING NEWD INTO MO...SOUTH OF THE
WARM FRONT WITH PERHAPS A NARROW CORRIDOR OF 60F DEW POINTS EXPECTED
OVER ERN OK BY 25/00Z. STRONG CAPPING AND VEERED LOW LEVEL FLOW
SHOULD DELAY CONVECTIVE INITIATION OVER THE PLAINS...BUT TSTMS ARE
EXPECTED TO DEVELOP ALONG THE BOUNDARY FROM WRN MO...SWWD ACROSS ERN
OK BETWEEN 22-23Z. ENVIRONMENTAL SHEAR FAVORS DISCRETE SUPERCELL
STRUCTURES WITH SFC-6KM BULK SHEAR ON THE ORDER OF 40-50KT. IT/S
NOT CLEAR HOW FAR SW CONVECTION WILL DEVELOP BUT THERE IS SOME
CHANCE TSTMS EVOLVE OVER EXTREME NE TX DURING THE EVENING HOURS
BEFORE DRY LINE STALLS ACROSS THIS REGION. LARGE HAIL AND DAMAGING
WINDS SHOULD BE THE PRIMARY THREATS...ALTHOUGH AN ISOLATED TORNADO
CANNOT BE RULED OUT. THUNDERSTORMS SHOULD WEAKEN BY LATE EVENING AS
THEY ENCOUNTER LESS FAVORABLE ENVIRONMENT OVER SERN MO/ERN AR AND
DUE TO THE LLJ/FORCING SHIFTING WELL NORTH OF THIS REGION ACROSS NRN
IL.

[venture]

SPC Outlook Updates...

Day 1 (Today) Marginal risk area expanded to include parts of NE OK now. Just looking for mainly a couple hailers today.

Day 3 - Slight Risk for pretty much every but far NW and W OK, and far SE.

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0217 AM CDT MON MAR 23 2015

VALID 251200Z - 261200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS TO THE
LOWER OH VALLEY...

...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK FROM
NW TX TO SWRN IND...

...SUMMARY...
SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP ALONG A COLD FRONT
STRETCHING FROM PORTIONS OF THE MID MISSISSIPPI VALLEY...SOUTHWEST
INTO THE SOUTHERN PLAINS OF OKLAHOMA AND TEXAS WEDNESDAY
AFTERNOON/EVENING. LARGE HAIL AND DAMAGING WINDS ARE THE PRIMARY
THREATS CONTINUING INTO THE OVERNIGHT HOURS.

...SRN PLAINS TO LOWER OH VALLEY...

SECONDARY SHORT-WAVE TROUGH...WITHIN NWLY FLOW...WILL DIG ACROSS THE
CNTRL ROCKIES INTO THE HIGH PLAINS FROM WRN KS INTO THE TX PANHANDLE
BY 26/00Z. WITH TIME...FLOW WILL STRENGTHEN ON DOWNSTREAM SIDE OF
THIS FEATURE AND UPPER TROUGH SHOULD MIGRATE EAST TOWARD THE MS
VALLEY. IN THE WAKE OF THIS DIGGING SHORT WAVE...SFC HIGH WILL
BUILD SWD ACROSS THE HIGH PLAINS FORCING A COLD FRONT THROUGH MUCH
OF KS INTO THE NRN TX PANHANDLE BY PEAK HEATING.

AT THE SFC...IT APPEARS A WEAK LEE CYCLONE WILL EVOLVE AHEAD OF THE
SURGING COLD FRONT OVER THE TX PANHANDLE...THEN SHIFT INTO EXTREME
SWRN OK JUST PRIOR TO CONVECTIVE DEVELOPMENT. LATEST MODEL GUIDANCE
SUGGESTS STRONG HEATING WILL DEVELOP ACROSS THE SRN HIGH
PLAINS...EXTENDING NEWD AHEAD OF THE COLD FRONT INTO CNTRL OK. SFC
TEMPERATURES WILL LIKELY SOAR WELL INTO THE 80S ACROSS PARTS OF NWRN
TX WITH SLIGHTLY COOLER READINGS EXPECTED AHEAD OF WIND SHIFT ACROSS
OK INTO SWRN MO. MODELS ARE IN GENERAL AGREEMENT THAT CONVECTION
WILL EVOLVE ALONG THE COLD FRONT BETWEEN 21-00Z WITHIN A STRONGLY
SHEARED ENVIRONMENT SUPPORTIVE OF ROTATING UPDRAFTS. WHILE DISCRETE
SUPERCELLS ARE POSSIBLE...ESPECIALLY EARLY IN THE CONVECTIVE
CYCLE...IT APPEARS FRONTAL FORCING COULD LEAD TO AN ELONGATED BAND
OF ORGANIZED SEVERE STORMS ALONG THE ADVANCING COLD FRONT. LESS
CERTAINTY EXISTS ALONG THE DRY LINE ACROSS NWRN TX. IN ALL
LIKELIHOOD CONVECTION WILL REMAIN SOMEWHAT ISOLATED SOUTH OF THE RED
RIVER...THOUGH STRONGLY SHEARED STORMS SHOULD EXHIBIT SUPERCELL
CHARACTERISTICS. LARGE HAIL IS EXPECTED WITH CONVECTION ALONG WITH
DAMAGING WINDS. ACTIVITY SHOULD SPREAD INTO SRN IL/IND DURING THE
LATE EVENING HOURS...AND SOUTH OF THE RED RIVER AS THE COLD FRONT
DRIVES DEEP INTO TX.

[venture]

12Z NAM 4KM Outputs for simulated reflectivity (radar) has the following solutions...

Tonight (around 3AM)...


Tuesday at 7PM


Wednesday at 7PM

[Soonerman12]

Wednesday evening looks like we could get some pretty decent supercells. Only thing about it though is the time of evening these would be happening. These will likely be the type that blow up and COULD produce brief tornadoes but quickly die off after sunset. If the graphic is correct, we could be in for a busy night Wednesday. As all of you know it is now spring time in Oklahoma. As much as people hate it and despise storm chasers, this stuff will happen in OK no matter what. Please everyone just pay attention to the forecast and be aware. It is very important to keep an eye on this situation especially due to the time this could happen. These will most likely be night time storms which can be even more dangerous. Remember, even if this doesn't pan out it is important to have a plan of action and a weather radio ready.... Spring is here Oklahoma, be prepared not scared! -Taylor

[LocoAko]

The TLDR Overview...
Wednesday

I'm not sold on moisture return, so no need to go crazy yet. ... Good moisture return/recovery expected with dews in the 60s over much of Oklahoma.... Now GFS, even though it is further east, does have similar moisture return. It is much tamer instability wise, but we are talking CAPE 1500-2000 j/kg versus NAM which has CAPE over 3000 j/kg. So we have to see which one is going to play out.... I am a little concern on recovery of the atmosphere and position of boundaries from Tuesday's activity. If NAM plays out as the scenario we have, this will be a pretty big day severe weather wise that we've had in a while....Now take all this with the understanding a lot of this depends on moisture return and daytime heating - as well as boundary positioning.

Looks like there are still big-time differences with moisture return on this morning's NAM and GFS runs, with the NAM having mid-upper 60s dewpoints in central OK by 00Z and the GFS only having mid-upper 40s at best -- making huge differences here in the metro. Don't like seeing such a huge discrepancy. Front is further NW slicing through the metro on the NAM and southeast of it on the GFS (at 00Z), obviously playing a big role in this. Like you said, the good moisture return is just further east on the GFS, so it does exist... but based on little more than the current drought situation I'm wary of accepting the NAM's mega dewpoints and subsequent instability. If I had to focus on one thing, I think moisture return is the thing to watch.

[AFCM]

Wednesday evening looks like we could get some pretty decent supercells. Only thing about it though is the time of evening these would be happening. These will likely be the type that blow up and COULD produce brief tornadoes but quickly die off after sunset. If the graphic is correct, we could be in for a busy night Wednesday. As all of you know it is now spring time in Oklahoma. As much as people hate it and despise storm chasers, this stuff will happen in OK no matter what. Please everyone just pay attention to the forecast and be aware. It is very important to keep an eye on this situation especially due to the time this could happen. These will most likely be night time storms which can be even more dangerous. Remember, even if this doesn't pan out it is important to have a plan of action and a weather radio ready.... Spring is here Oklahoma, be prepared not scared! -Taylor

Coincidentally, this Wednesday (March 25th) is the anniversary of the first-ever forecasted tornado, and it was an evening one (around 6 pm). Just a little Tinker AFB history for you all. There's a nice little monument in the park just outside the Air Depot gate.

[John1744]

Hmm out here in Harrah they just did a test of the tornado sirens. At 1:15 on a Monday.

Glad to see they're getting prepared.

[venture]

18Z GFS is a bit slower with the dryline/front on Wednesday now, not exactly with the NAM...but possibly a trend.