General Weather Discussion - March 2015

[Bobby821]

Still chance for one or two days next week...nothing in stone. Stop worrying.

I am not worrying, just wanting to start getting things lined out for tracking them in and I have people I keep updated with regards to the weather. So it is not me worrying about the storms it is me doing my preperational studying of the upcoming setup etc. Thanks Guys!!

[venture]

Preliminary information is that there were multiple tornadoes through OKC and Moore, and we should have that number by early next week. Strongest damage area would rate as a high end EF1.

[LocoAko]

Yes, thanks, I too saw the Mesonet total, but I was hoping for someone's backyard rain gauge measurement. I should probably just get one then I wouldn't waste anyone's time here!

Oh, you know, I'm not sure why I didn't think of this earlier but we can check the CoCoRAHS reports. Here they are for Oklahoma County:

http://www.cocorahs.org/Maps/GetMap....3/26/2015&cp=0

[venture]

Sand Springs tornado, which killed one person, rated an EF-2.

March 25, 2015 Severe Weather

[venture]

Glimpse ahead with the 06Z GFS (12Z isn't out yet)...

Still looking like we will be in this cycle of storm chances going up early-mid week, then down at the end of the week and back up...for probably 2 more weeks at least. It is Spring after all, so this could set in for awhile.

So quiet from now until Sunday, then a chance of storms SE OK. Severe risk very low.
Monday - Maybe a storm or two south of I-40, severe risk very low.
Tuesday - More widespread showers or storms, marginal severe risk.
Wednesday - Strong cap, but much higher instability. If any storms form, severe weather possible, but not locked in at all.
Thursday - Maybe a storm or two far SE OK, severe risk low.

Next Friday & Saturday - calm.
Sunday the 4th - Maybe a couple storms West and Central, severe risk low, otherwise quiet.
Monday - Maybe a couple storms again along/southeast of I-44, severe risk low.
Tuesday - Rain possible, severe risk low.
Wednesday - Storms possible, eastern OK, possible severe.
Thursday - More storms possible East, low severe risk.
Quiet from that following Friday through Sunday.

Confidence of course drops significantly the farther out the forecast goes. Use this as a guide, but it will change significantly as we get with in 2-4 days of a specific day.

[LocoAko]

For those who are interested, I think this is a great and easy-to-understand writeup about the small scale conditions that contributed to the Moore tornado. Definitely a must read.

The science behind the Oklahoma and Arkansas tornadoes of March 25, 2015 | United States Tornadoes

[okatty]

For those who are interested, I think this is a great and easy-to-understand writeup about the small scale conditions that contributed to the Moore tornado. Definitely a must read.

The science behind the Oklahoma and Arkansas tornadoes of March 25, 2015 | United States Tornadoes

That is REALLY good! Thanks.

[Bunty]

Yes, thanks, I too saw the Mesonet total, but I was hoping for someone's backyard rain gauge measurement. I should probably just get one then I wouldn't waste anyone's time here!

Get a rain gauge, and it will always be interesting to see how much less or more your measurements are compared to everyone else's.

[Bunty]

I second this. After today I am pretty nervous about what is to come in April and May. I hate the seasonal anxiety yang comes with springtime in Oklahoma. One thing is certain is severe weather season cannot be predicted. Just last week NewsOK ran a story predicting a slow season this year.

I deal with storm anxiety by living in a house for the past 10 years where one of the closets is a safe room. Since then, I have thankfully not become frightened enough during storm conditions to actually use it for that purpose. But I'm sure as hell headed for it during a tornado warning should the electricity suddenly go off and/or hear a roar.

I also pray during tornado warnings. My friend does, too. It seems to work. One tornado headed straight for town had just lifted back into the clouds when it arrived. Another tornado chose to carve a path through a rural area from SW to NE while staying just a mile or two from city limits. It hit the large home of my dentist, though, and caused much roof damage.

[venture]

As advertised all last week, severe weather chances return. Officially we have a Marginal Risk for Central and Southern Oklahoma on Tuesday. Then there is a 15% Severe Risk (if it sticks, this translates to a Slight) for Thursday across the Eastern half of OK.

[venture]

Marginal Risk issued for this afternoon/evening for SE OK.

...SERN OK/NERN TX EWD TO THE MID-SOUTH...
THE RETURN OF PARTIALLY MODIFIED GULF MOISTURE AHEAD OF THE
AFOREMENTIONED FRONT IS UNDERWAY ACROSS THE SRN PLAINS...WITH
50S-LOWER-60S SFC DEWPOINTS ANALYZED ACROSS MUCH OF SRN/ERN TX.
PREFRONTAL SFC SLYS WILL CONTINUE TO MAINTAIN A STEADY INFLUX OF
SIMILAR MOISTURE TOWARD THE RED RIVER OF THE SOUTH TO THE LOWER MS
VALLEY THROUGH THE DAY. HOWEVER...SUBSTANTIAL CAPPING ALOFT AT THE
BASE OF AN EML SAMPLED BY THE 12Z OUN AND FWD RAOBS WILL LIKELY KEEP
DIURNAL THUNDERSTORM CHANCES MINIMAL DESPITE THE INCREASE IN
CONVECTIVE INSTABILITY.

BY THIS EVENING...THE FRONT WILL BE INTERCEPTING THE AFOREMENTIONED
MODEST RETURN MOISTURE ACROSS THE REGION...FAVORABLY COINCIDENT WITH
GLANCING DCVA/FORCING FOR ASCENT ATTENDANT TO THE SHORTWAVE
TROUGH...TO ENCOURAGE TSTM DEVELOPMENT. FURTHERMORE...WITH A
STRENGTHENING NOCTURNAL BOUNDARY-LAYER WIND MAXIMUM AUGMENTING
FRONT-PRECEDING WAA ALONG A LLJ /STRONGEST ACROSS THE LOWER MS
VALLEY/...ISOLATED TO SCATTERED THUNDERSTORMS WILL LIKELY DEVELOP
INVOF THE FRONTAL ZONE IN THE 00Z-04Z PERIOD. THIS ACTIVITY WILL
LIKELY BE ELEVATED ABOVE A NOCTURNALLY STABILIZING PBL LAYER AND
PERHAPS UNDERCUTTING BAROCLINIC ZONE.

THE LATEST FORECAST SOUNDINGS SUGGEST THAT 500-1000 J/KG OF MUCAPE
WILL BE COMMON ACROSS THE AREA...WHICH WILL SUPPORT SOME HAIL
POTENTIAL GIVEN 25-40 KT OF EFFECTIVE BULK SHEAR YIELDING ORGANIZED
CONVECTIVE STRUCTURES /POSSIBLE SUPERCELLS/. GIVEN H7-H5 LAPSE RATES
AROUND 7-8 C/KM SAMPLED BY 12Z FWD/OUN RAOBS...WITH SIMILAR VALUES
SPREADING EWD WITH TIME...NORMALIZED CAPE/UPDRAFT ACCELERATIONS WILL
BE SUFFICIENTLY ROBUST -- IN THE PRESENCE OF THE AFOREMENTIONED DEEP
SHEAR -- FOR ISOLATED SVR-HAIL POTENTIAL THIS EVENING INTO TONIGHT.
THIS SCENARIO IS AFFIRMED BY THE LATEST AVAILABLE
CONVECTION-PERMITTING MODEL GUIDANCE...AND WARRANTS THE UPGRADE TO
MARGINAL-RISK DELINEATION.

HOWEVER...GIVEN THE UNDERCUTTING NATURE OF THE SFC BOUNDARY...AND
THE PROPENSITY FOR INCREASING CELL INTERACTIONS TO EVENTUALLY IMPEDE
INDIVIDUAL-CELL INFLOW IN THIS REGIME OF BOUNDARY-PARALLEL DEEP
FLOW...A MORE SUBSTANTIAL SVR-TSTM RISK IS NOT EXPECTED TO EVOLVE.

[venture]

Here are the SPC risks for the week...

Today - General Storms, possibly marginal svr risk late tonight over Southeast OK.

Tuesday - Marginal Risk for nearly the entire state, except for Northern counties. Possible upgrade to Slight Risk if more forcing appears likely. Right now we'll be unstable but there just won't be any major lift contributor to focus storms in any particular area.

Wednesday - Marginal Risk west of line from Ponca City to El Reno to Frederick. Chance for a couple grumpy storms to get going along the dryline later in the day.

Thursday - 15% Risk (translates to Slight in Days 1-3) for all of Central and Eastern OK. Triple point setup, strong low level jet expected by evening, and high instability. This could very well be the main day this week for severe weather.

Rest of the week/weekend look mostly quiet.

[Roger S]

Thursday - 15% Risk (translates to Slight in Days 1-3) for all of Central and Eastern OK. Triple point setup, strong low level jet expected by evening, and high instability. This could very well be the main day this week for severe weather.

Ummmmm.... NO! ..... You have to change this one... This is supposed to be the first night of my offices weekly Thursday night golf group.... Severe weather is completely unnacceptable!

[venture]

Ummmmm.... NO! ..... You have to change this one... This is supposed to be the first night of my offices weekly Thursday night golf group.... Severe weather is completely unnacceptable!

I know there is a pun for golf ball sized hail somewhere here.

[Roger S]

I know there is a pun for golf ball sized hail somewhere here.

After hearing reports of golf ball size hail last week I had told the wife I was headed out to grab my pitching wedge to get some practice in.

Instead we ended up diving in the storm shelter we had installed on March 18th when David Payne started yelling about a tornado on the ground at 12th Street in Moore.

[venture]

Western Oklahoma upgrades to a Slight Risk for tomorrow.

...SOUTHERN PLAINS...

WV IMAGERY DEPICTS A WELL-DEFINED UPPER LOW OFF THE BAJA PENINSULA
NEAR 120W...DRIFTING SEWD IN LINE WITH LATEST MODEL GUIDANCE. THIS
FEATURE SHOULD BEGIN TO EJECT EWD TUESDAY WITH NRN PORTIONS OF
DEAMPLIFYING LOW EXPECTED NEAR THE BIG BEND OF WEST TX BY 01/00Z.
WHILE STRONGEST MID-LEVEL FLOW WILL TRANSLATE ACROSS DEEP SOUTH
TX...MODEST SFC-6KM SHEAR WILL EXIST ACROSS THE SRN
PLAINS...ESPECIALLY ALONG WARM FRONT THAT WILL BE DRAPED ACROSS SRN
OK. WHILE LARGE-SCALE FORCING IS NOT EXPECTED TO BE PARTICULARLY
FOCUSED/SIGNIFICANT...STRONG HEATING ALONG DRY LINE SHOULD EASILY
REMOVE INHIBITION SUCH THAT TSTMS WILL DEVELOP AFTER 22Z.

FORECAST SOUNDINGS ALONG DRY LINE ACROSS EXTREME SWRN OK INTO NWRN
TX SUGGEST SFC TEMPERATURES WILL SOAR INTO THE UPPER 80S...POSSIBLY
TO NEAR 90F IF HIGH-LEVEL CLOUDS REMAIN SUFFICIENTLY THIN. FOR THIS
REASON HAVE INCREASED SEVERE PROBS ACROSS SWRN OK INTO NWRN TX WHERE
CONVECTIVE TEMPERATURES SHOULD BE BREACHED AND SBCAPE SHOULD BE ON
THE ORDER OF 2500 J/KG. ANALOGS SUGGEST LARGE HAIL COULD BE NOTED
WITH THIS ACTIVITY AND THIS IS THE PRIMARY SEVERE THREAT.
CONVECTION THAT EVOLVES SHORTLY AFTER PEAK HEATING SHOULD PROPAGATE
SEWD ALONG/NEAR WARM FRONT INTO NONDESCRIPT LLJ ON THE ORDER OF
15KT.

[venture]

Welcome to Severe Weather Season Week 2...

We have three days of severe weather this week. We should see a smattering of everything week to add up to our storm report totals for the week in all three columns. Nothing very upper end this week, but Thursday is probably the most concerning of all three days. So here we go...

Tuesday
One of the warmest days of the season for many areas, with temps well into the 80s and near 90 in spots. Instability will be high to very high over much of the state, but that also comes with relatively little forcing over much of the state. So a lot of it will go to waste if you will. Map below is for 7PM Tuesday with the dryline drawn on and I highlighted an area that I would find to be most favorable tomorrow. Good convergence along the projected bulge area of the dryline should spark storms there. Elsewhere we are going to watch for locations getting above the convective temp to allow the high to rise enough to a few isolated storms to go away from the boundary. 00Z NAM has storms firing by late afternoon along the dryline and also a few isolated storms in South Central OK. It continues to bring storms east through the evening into Central OK after 9PM. Main threat tomorrow is going to be large hail.



Wednesday

Wednesday is going to be a pretty marginal day with some instability, decent moisture, but just not a lot to get things going it appears. This can all change especially if we get some good left over boundaries from Tuesday's storms. Right now it appears to be mostly isolated storms along the dryline and scattered about where enough lift manages to fire something off. Main threat hail.

Thursday

It all comes down to timing and how fast the front and dryline push through. 00Z pushes this into the Metro by early afternoon. GFS is a hair slower with the front, but blasts the dryline east of I-35 by mid afternoon. Out ahead of the boundaries the atmosphere will be highly unstable and plenty of lift to get storms fired off. We'll probably see a familiar setup of a squall line along the front, and sups around the dryline. Conditions seem pretty favorable for wind and hail along the front. Near the triple point that will be moving through Central OK will be the most likely area for rotating storms and the associated very large hail and tornado threat.

Looking ahead...break for Friday & Saturday - mostly - and then main chances for storms again on Sunday and Monday. Then another break until probably Thursday. Welcome to Spring.

[Anonymous.]

SPC slight risk for basically southern half of OK for this evening. Doesn't look terribly exciting, but could get some good hailers out of any discrete cells.

[venture]

HRRR really wants to get storms going in the next hour or two over South Central OK and then fire Western OK by mid afternoon.

12Z NAM coming in substantially slower with boundary movement on Thursday. It has front/dryline about 40 miles further west by mid afternoon instead of out past Shawnee.

[venture]

Area of CU where we could see a few storms go up early in Southern OK...



Narrow cloud deck overhead Central OK should burn off soon.

[Anonymous.]

New SPC Outlook moves SLIGHT risk zone further north, now encompasses about northern 3/4 of OK, and an added 2% tornado area in S OK. Highest hail risk is around I-40 and to the south.

[SoonerDave]

I would REALLY like a peaceful Thursday evening...family outing downtown. Really don't want to dodge hailstones in downtown OKC...

Man, seems the rumbly weather is catching up with a vengeance.....(grumble)

[venture]

Day 2 outlook expanded as well. Slight Risk now covers NW OK. Marginal risk covers the entire state except SE and the PH.

[venture]

Temps approaching the convective temperatures in the Southwest. Expect storms to fire in the next 2 hours and move east. Most likely area for the Metro is after 9PM, but we also have developing CU around here and could get an isolated storm to go.

[venture]

MESOSCALE DISCUSSION 0163
NWS STORM PREDICTION CENTER NORMAN OK
0327 PM CDT TUE MAR 31 2015

AREAS AFFECTED...MUCH OF WESTERN/SOUTHERN OK AND NORTH TX/FAR
EASTERN TX PANHANDLE

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 312027Z - 312230Z

PROBABILITY OF WATCH ISSUANCE...60 PERCENT

SUMMARY...MONITORING FOR INCREASING SIGNS OF DEEP CONVECTIVE
DEVELOPMENT ACROSS PORTIONS OF SOUTHERN/WESTERN OK AND ADJACENT
PARTS OF NORTH TX/EASTERN TX PANHANDLE. A WATCH IS POSSIBLE BY LATE
AFTERNOON/EARLY EVENING...AT LEAST ACROSS PARTS OF THIS REGION.
LARGE HAIL IS EXPECTED TO BE THE PRIMARY RISK.

DISCUSSION...VISIBLE SATELLITE IMAGERY AT MID-AFTERNOON SHOWS AN
INCREASINGLY DEEP CU FIELD PARTICULARLY ACROSS PARTS OF
SOUTH-CENTRAL/SOUTHEAST OK...WITH OTHER/NEWER CU NOTED AS FAR WEST
AS KIOWA COUNTY OK. THIS WEST-EAST CORRIDOR ROUGHLY COINCIDES WITH A
WIND SHIFT AND ZONE OF DIFFERENTIAL HEATING THROUGH THE FIRST PART
OF THE AFTERNOON. LARGE-SCALE INFLUENCES ARE RELATIVELY WEAK...BUT
CONTINUED HEATING/WEAK MASS CONVERGENCE WILL LIKELY RESULT IN AT
LEAST ISOLATED/WIDELY SCATTERED STRONGER THUNDERSTORM DEVELOPMENT BY
LATE AFTERNOON/EARLY EVENING.

ALTHOUGH CONFIDENCE IN THE DETAILS IS NOT PARTICULARLY HIGH GIVEN
WEAKER-CALIBER FORCING MECHANISMS...THE MOST PROBABLE SCENARIO IS
FOR DEEP CONVECTIVE DEVELOPMENT TO OCCUR ACROSS SOUTHWEST OK AND/OR
THE EAST/SOUTHEAST TX PANHANDLE AND ADJACENT NORTH TX. IN VICINITY
OF A WEAK SURFACE WAVE...THAT IS WHERE DEEPER MIXING /HIGH-BASED CU
NOTED ACROSS TX PANHANDLE/ WILL COINCIDE WITH WEAK LOW-LEVEL
EASTERLIES/SOMEWHAT RICHER BOUNDARY LAYER MOISTURE NEAR/NORTH OF THE
AFOREMENTIONED BOUNDARY. ELSEWHERE...DEVELOPMENT COULD OCCUR THROUGH
LATE AFTERNOON/EARLY EVENING ACROSS OTHER PARTS OF
SOUTH-CENTRAL/SOUTHEAST OK IN VICINITY OF THE SURFACE BOUNDARY WHERE
CONVECTIVE INHIBITION IS VIRTUALLY NIL AND THE BOUNDARY IS QUITE
UNSTABLE.

WITH MORNING SOUNDINGS SAMPLING VERY STEEP MID-LEVEL LAPSE RATES /IN
EXCESS OF 8C PER KM/...80S F SURFACE TEMPERATURES/LOWER 60S F
SURFACE DEWPOINTS ARE SUPPORTIVE OF 3000+ J/KG MLCAPE ACROSS THE
SOUTHERN HALF OF OK AND IMMEDIATELY ADJACENT NORTH-CENTRAL TX. WINDS
THROUGH THE LOWEST FEW KM AGL WILL REMAIN WEAK...BUT WHERE STORMS DO
FORM...ADEQUATE VEERING/STRONGER HIGH-LEVEL WINDS AROUND 35 KT OF
EFFECTIVE BULK SHEAR WILL SUPPORT SUPERCELLS CAPABLE OF VERY LARGE
HAIL.