Oklahoma Weather Discussion - February/March 2013

[Anonymous.]

Winter event is looking better and better. Looks like some decent snowfall over the bottom half of state. [right now]

[s00nr1]

[venture]

12Z pulled snow way back again. Almost nothing east of I-35 and capping out at 3-5" in SW OK. At this point I'm more interested in the track consistency than anything. We can worry about snow totals in a few days when we get closer.

[s00nr1]

12Z pulled snow way back again. Almost nothing east of I-35 and capping out at 3-5" in SW OK. At this point I'm more interested in the track consistency than anything. We can worry about snow totals in a few days when we get closer.

QPF amounts actually increased from 06z to 12z on the GFS (and pretty much along the same track). However, temperature profiles along and east of I-35 warmed about 3-5 degrees between the two runs.

[venture]

QPF amounts actually increased from 06z to 12z on the GFS (and pretty much along the same track). However, temperature profiles along and east of I-35 warmed about 3-5 degrees between the two runs.

Right. My comments were purely on the snow fall amounts. If we look at Norman proper this is what GFS is spitting out.

Prior to 12Z Tue dry.
12Z to 18Z Tue - 0.3" of QPF. Appears to be mix of rain, graupel, and sleet based on upper air sounding.
18Z Tue to 00Z Wed - 0.4" of QPF. Wet snow, graupel, and rain.
00Z and beyond dry.

Surface temps appear to be 2-3 degrees above freezing, but below freezing just above the surface. During that morning period there will still be some warm air in a very thin layer around 1000' and then back below freezing until going above at the surface. If that can cool some and get rid of that warm pocket upstairs, the sleet risk goes away.

So yeah, it's pretty border line right now from getting 3-5" of heavy wet snow to a very sold rain/sleet/snow mix.

[venture]

00Z GFS continues to dry out even more for next week's potential winter weather. It's also pretty low in QPF for the weekend as well. So who knows. It might just be low balling things right now.

[venture]

Slight Risk today for Western and Southern Oklahoma.

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1148 PM CST FRI FEB 08 2013

VALID 091200Z - 101200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN AND TONIGHT
ACROSS PARTS OF THE SOUTHERN PLAINS...

...SYNOPSIS...
AS AMPLIFIED UPPER RIDGING WEST OF THE PACIFIC COAST BUILDS
NORTHEASTWARD INTO WESTERN CANADA...A SIGNIFICANT SHORT WAVE
TROUGH...NOW DIGGING INTO NORTHERN BRITISH COLUMBIA/ALBERTA...
APPEARS LIKELY TO TURN MORE SHARPLY SOUTHWARD TOWARD THE NORTHERN
ROCKIES TODAY. AS THIS OCCURS...ANOTHER VIGOROUS SHORT WAVE IMPULSE
IS FORECAST TO LIFT OUT OF BROADER SCALE SOUTHWESTERN U.S. UPPER
TROUGHING. PHASING OF THIS LATTER FEATURE WITH A BELT OF WESTERLIES
EMERGING FROM THE SUBTROPICAL EASTERN PACIFIC IS ALREADY
UNDERWAY...AND VERY STRONG WEST SOUTHWESTERLY MID/HIGH LEVEL FLOW IS
EXPECTED TO GRADUALLY OVERSPREAD MUCH OF THE CENTRAL AND SOUTHERN
PLAINS.

LATE THIS AFTERNOON INTO TONIGHT...MODELS SUGGEST THAT A CYCLONIC
500 MB JET STREAK ON THE ORDER OF 100 KT WILL NOSE ACROSS THE
TEXAS/OKLAHOMA PANHANDLE REGION INTO THE CENTRAL PLAINS. THIS
APPEARS LIKELY TO BE ACCOMPANIED BY SIGNIFICANT SURFACE CYCLOGENESIS
ACROSS EASTERN COLORADO INTO SOUTH CENTRAL NEBRASKA...WITH A
TRAILING COLD FRONT ADVANCING EAST OF THE CENTRAL/SOUTHERN ROCKIES
INTO THE CENTRAL/SOUTHERN PLAINS.

AT THE SAME TIME...GUIDANCE IS SUGGESTIVE THAT A SERIES OF LESS
PROMINENT SPEED MAXIMA ASSOCIATED WITH THE SUBTROPICAL JET WILL
PROPAGATE EAST NORTHEASTWARD ALONG AN AXIS NEAR/SOUTH OF THE TEXAS
BIG BEND...TOWARD THE LOWER MISSISSIPPI VALLEY.

...CENTRAL/SOUTHERN PLAINS...
THE EVOLVING LARGE-SCALE PATTERN...IN MANY RESPECTS...IS TYPICAL OF
ONE THAT MIGHT BE ACCOMPANIED BY A SIGNIFICANT INCREASE IN SEVERE
WEATHER POTENTIAL TO THE LEE OF THE ROCKIES. HOWEVER...THE BOUNDARY
LAYER OVER THE NORTHWESTERN GULF OF MEXICO IS NOT PARTICULARLY MOIST
OR DEEP...AND A SUBSTANTIVE INLAND MOISTURE RETURN IS EXPECTED TO BE
SLOW TO DEVELOP...PARTICULARLY NEAR THE SURFACE...IN THE WAKE RECENT
LOW-LEVEL COOLING. THE NAM/SREF SUGGEST THAT EVEN RATHER MODEST
MID/UPPER 50S SURFACE DEW POINTS MAY NOT REACH PORTIONS OF THE TEXAS
SOUTH PLAINS UNTIL AT LEAST LATE AFTERNOON/EARLY EVENING. AND
BETTER BOUNDARY LAYER MOISTENING/DESTABILIZATION PROBABLY WILL
REMAIN WELL SOUTH OF THE STRONGER MID-LEVEL HEIGHT FALLS
OVERSPREADING THE CENTRAL PLAINS.

EVEN WITH LIMITED MOISTURE...STEEPENING LAPSE RATES/STRONG FORCING
FOR UPWARD VERTICAL MOTION MAY BE SUFFICIENT TO SUPPORT VIGOROUS
LOW-TOPPED CONVECTIVE DEVELOPMENT...PROBABLY IN A BROKEN
LINE...ROUGHLY NEAR/EAST OF THE COLORADO/KANSAS BORDER...SOUTHWARD
INTO THE TEXAS PANHANDLE...DURING THE 21-00Z TIME FRAME. IT DOES
APPEAR THAT THERE MAY BE A WINDOW OF OPPORTUNITY FOR BETTER COUPLING
OF LOW-LEVEL MOISTENING/DESTABILIZATION AND STRONGER LIFT...ON THE
DEVELOPING DRY LINE ACROSS PARTS OF THE EASTERN TEXAS
PANHANDLE/NORTHWEST TEXAS...FOR SOMEWHAT MORE VIGOROUS STORM
DEVELOPMENT. THIS MAY INCLUDE POTENTIAL FOR SUPERCELLS WITH A RISK
FOR TORNADOES...IN THE PRESENCE OF SIZABLE CLOCKWISE CURVED
LOW-LEVEL HODOGRAPHS.

THEREAFTER...EVOLUTION OF CONVECTIVE DEVELOPMENT AND CONVECTIVE
POTENTIAL REMAIN A BIT UNCLEAR. IT IS POSSIBLE THAT THE SOUTHERN
FLANK OF THE INITIAL CONVECTIVE ACTIVITY MAY PERSIST AND GROW
UPSCALE...OR NEW DEVELOPMENT MAY OCCUR OFF TO THE EAST
SOUTHEAST...WITHIN STRENGTHENING LOW-LEVEL WARM ADVECTION ACROSS
NORTHWEST INTO NORTH CENTRAL TEXAS LATER DURING THE
EVENING/OVERNIGHT HOURS. THIS ACTIVITY COULD BE ENHANCED BY FURTHER
DESTABILIZATION ASSOCIATED WITH CONTINUING SLOW MOISTURE
RETURN...AND DIVERGENT UPPER FLOW BETWEEN THE POLAR AND SUBTROPICAL
JET AXES. GIVEN THE STRENGTH OF THE DEEP LAYER MEAN FLOW...DAMAGING
WIND GUSTS MAY BE THE PRIMARY SEVERE THREAT...THOUGH THERMODYNAMIC
PROFILES MAY BE SUPPORTIVE OF LARGE HAIL.

[Anonymous.]

NAM finally latching onto winter event. GFS coming back with heavier amounts today in terms of snow. However, it is pushing the decent banding into NW OK.

[venture]

Severe weather risk today looks marginal as usual. This early widespread rain, expect over most of the Metro area (LOL), will push off to the east through the afternoon. Then we are looking at some storms popping up along the dryline/cold front later in SW OK (8-9PM) and move NE. The line should fill back out as it moves through Central OK overnight. Could see a few strong/severe storms mixed in with it all, so just stay aware.

Snow chances...

12Z NAM has total QPF over the OKC area of 0.1" to the north side and 0.4" on the south.
12Z GFS has total QPF ranging from 0.75 to 1.0" over much of Central OK. A higher band of 1 to 1.25" from Tulsa to Enid to Elk City.

Everything comes down to how the air temps are going to be playing upstairs. The upper air forecasts/precip type is all based on forecast soundings from Norman, so it could fluctuate depending on where you are.

NAM (Precip Starts ~ 6AM Tuesday)
Tues 6AM - Rain/Snow mix. Freezing through 700 feet and then up into the mid/upper 30s at the surface.
9AM - Mostly snow, maybe some rain/graupel mixed in. Freezing almost all the way except warmer at the surface.
12PM - Rain/Snow mix, probably a very wet snow. Surface temps remain well above freezing.
3PM - Rain/Snow mix, more of the same.
6PM - Rain mostly, maybe with some snow mixed in. Freezing level raising up a bit here, but precip should be very light by this time if not over.

NAM is mostly light in precip and holds of any snow accumulation. Main driver for that is the ground/surface temps being pretty warm. So its solution would be a fairly wet/slushy snowfall.

GFS (Precip starts before 6AM Tuesday)
Tues 6AM - Light rain over much of Oklahoma south of I-40. About 0.1 - 0.2".
12PM - Moderate precip kicks in from Elk City to Perry (0.5 - 0.75"), around 0.4 to 0.5" elsewhere. Norman looks like mostly rain still, maybe some snow mixing in.
6PM - Heavy precip mostly over North central and NE OK now (0.5 to 0.75") with some 0.3 to 0.5" areas in SW OK and through Central OK mainly along and east of I-35. This looks like mainly snow with some graupel or rain still mixing.
12AM Weds - Precip pushing off very quickly east, maybe some lingering drizzle or flurries.

NAM is just now getting this data to play with. GFS has been fairly consistent with something happening for several runs (and a few days) now. Except for a dip in last nights 00Z run, amounts have been pretty steady. So my thoughts?

Some place in OK has the potential to see a good dumping of snow. This is a highly complicated setup since temperatures are going to be right on the edge. It very well could go from a good rainfall event to a heavy snowfall event. I would not be shocked that a winter storm watch gets put up tomorrow to cover Tuesday at the potential. It very well could go completely rain or be too warm at the surface for any significant accumulation. The other part here is the NAM keeps precip amounts, if it were all snow, easily in Winter Wx Advisory (not Travelers Advisory you stupid local media...grrr) criteria and nothing near Winter Storm criteria.

[venture]

A line of severe storms is approaching SW OK right now. Max hail report appears to be 1.75". The official slight risk for overnight is for South Central and Southeast Oklahoma, but obviously it won't be limited to this area.

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0653 PM CST SAT FEB 09 2013

VALID 100100Z - 101200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SERN OK AND
INTO NRN/CENTRAL TX...

...SERN OK/TX...
THUNDERSTORMS ARE EXPECTED TO DEVELOP ACROSS PARTS OF OK AND TX
OVERNIGHT AS A COLD FRONT ADVANCES EWD ACROSS THE SRN PLAINS. WHILE
THE PRE-FRONTAL AIRMASS REMAINS CAPPED AND STABLE...MODELS SUGGEST
THAT ASCENT INVOF FRONT WILL ERODE THE CAP...ALLOWING A LINE OF
SHOWERS AND STORMS TO DEVELOP BY LATE EVENING.

WITH A VERY FAVORABLE FLOW FIELD IN PLACE...POTENTIAL FOR UPDRAFT
ROTATION WITH A STRONGER UPDRAFT OR TWO EXISTS...THUS WILL MAINTAIN
2% TORNADO PROBABILITY ACROSS CENTRAL AND INTO N CENTRAL/NERN TX.
OTHERWISE...MARGINAL HAIL AND PERHAPS A LOCALLY DAMAGING GUST WILL
PERSIST AS STORMS SHIFT EWD TOWARD WRN AR AND ACROSS NERN TX THROUGH
THE END OF THE PERIOD.

..GOSS.. 02/10/2013

[venture]

Tuesday Update - 00Z NAM

This is just for the new NAM run coming in now, GFS will be in later tonight. So here is the timeline...

Midnight - 3AM: Light precip starts over Western OK. Up to 0.1" far SW and much less further north you go. Should be all rain, maybe some light snow mixing in far NW.

3AM - 6AM: Precip increases significantly. Precip chances most areas except North Central, NE, and SE OK. NW OK around 0.1", SW OK around 0.1-0.2", and South Central OK from 0.1-0.2" just north of OKC to 0.3 to 0.5" from Norman south. Rain snow line will like run from near Ponca south to Guthrie and then south and west to Anadarko to Altus. East of that line mostly rain, but might see some snow/graupel mix in the closer to the line you get. Areas that are all snow could see 1-2".

6AM - 9AM: Light amounts far SW and far NE. Then going from NW to SE, looking at 0.2 to 0.3" in NW OK to 0.3 to 0.4" in Central to 0.4 to 0.7" in SE OK. Rain/snow line looks to be pretty much I-44 from border to border. OKC metro will be right on the line still so Northern areas could be all snow and Norman/Purcell could be all rain or at least a rain/graupel mix.

9AM - 12PM: Rain/snow line pushed further south and east. All but far SE and SC OK should be below freezing above the surface to allow for all snow. Surface temps will likely still be above freezing though, which will impact accumulations. Precip continues for most of the state, dry slot working in from the SW from Altus to Lawton to Pauls Valley to Durant. North of that line precip amounts 0.1" to 0.2" West of I-35, and 0.2 to 0.4" east of I-35.

12PM - 3PM: Precip continues in most areas except far Western OK and most areas south of SR 29 (those areas could still see drizzle/light snow). Otherwise light to moderate snow will continue with an additional 0.1" to 0.3" of precip.

3PM - 6PM: Almost all the state should be snow by this time. Precip continues to slowly move east. Ended west of US 281 and mostly drizzle/flurries south of SR 29. Still maybe 0.1" of precip from the OKC area to the east.

6PM - 9PM: Precip is mostly out of the state now except for eastern OK with some lingering light precip.

That's the NAM outlook. Surface temps will still play a factor here on what actually sticks though. Once GFS is out I'll post thoughts on that so we can compare.

[Anonymous.]

Winter event:

Looking at the new runs out, NAM and GFS both pretty much agree someone in OK is going to get dumped on. [at this time]



Right now it looks like Central OK is the bullseye.

[venture]

Time for the GooFuS model. For the most part i'm ignoring the snowfall forecasts since ground melting I think is going to be a concern. So I'm going to give the worst case scenario guess when it comes to them.

Tuesday
12AM - 6AM: Light rain moving up into South central OK, mainly around 0.1" or less.

6AM - 12PM: Precip picks up a good deal over much of OK. Light far west and North. Heaving precip over Central OK back into the Lawton/Duncan area. Good swatch of 0.4" precip. Forecast sounding for Norman is right on the borderline of all snow or a snow/graupel/sleet/rain mix.

12PM - 6PM: Mainly light precip over much of the state. Less than a 0.10" NW, 0.1-0.2" SW and then about the same for central into NE. Less elsewhere. Norman sounding shows all snow at this point.

6PM - 12AM Weds: Light precip left, mainly flurries and drizzle from I-44 and east.

[venture]

Winter event:

Looking at the new runs out, NAM and GFS both pretty much agree someone in OK is going to get dumped on. [at this time]

Right now it looks like Central OK is the bullseye.

Disagree that we can say for certain this is a 100% winter event. NAM is warmer than GFS still. This is going to be one of those where it'll come down to the last minute to see how the upper air temps setup. Someone could see an inch of rain or a 6 inches of heavy wet snow. While i'm a die hard winter guy (being a yankee), I'm not sold on this yet.

[Anonymous.]

Hey I am not forecasting, I am simply commenting on the models and what they say @ each run.

Definitely not sold on it either (as we all learned on Christmas).

[Bunty]

MESSAGE SUMMARY:
Snow possible tuesday across much of oklahoma and western north texas...
A storm system taking shape across the western part of the country will approach the southern plains of oklahoma and western north texas early this week. It will bring the potential for accumulating snow to much of the area. A cold front will move south across oklahoma and north texas late today and tonight bringing cooler air to the area. Meanwhile... An upper level storm system dropping south across the western part of the country will begin to move east monday and move across the southern plains on tuesday. Rain is expected to develop in advance of this storm system monday night across much of oklahoma possible mixing with or changing to light snow across portions of western oklahoma. This change to snow is then expected to occur from west to east across oklahoma and western north texas during the day on tuesday. Indications are that some accumulation of snow will likely occur...

However uncertainties still remain as to how much snow will fall and exactly where the heaviest accumulations may occur. Continue to monitor the latest forecast from the national weather service as this potential winter storm takes shape... As changes to the forecast are likely to occur.

FROM: Stillwater Weather Advisories, Watches, Warnings, Etc.

[venture]

The back and forth continues with the models. They continue to show accumulating snow, but they aren't set on where.

12Z GFS is now mainly along and north of I-40. With 3-5" from I-35 and to the west.
12Z NAM is north of I-40 and west of I-35, with 6-8" over NW OK.

Not really anything has changed from my thoughts as of last night though. It is going to be very close on what happens over much of the area.

[Anonymous.]

Crazy how much the NAM has come around for this storm.

Whatever falls from the sky, it will definitely help start a dent in the on going drought.


Hopefully tonight's runs will further pinpoint where the snow/rain line is. This event is only 36-48 hours away and no watches are up yet.

[LocoAko]

Day 2 outlook from the Hydrometeorological Prediction Center - exciting! :P

[venture]

Last 2 runs, NAM has come in decided warmer pushing for all rain in Central OK. Though I don't like midday model runs, so will wait until later tonight to see what those show.

[Easy180]

Bring it on I guess since regardless of how it plays out its looking like it will only be a one day impact judging from the rest of the 7 day

[SomeGuy]

Time to get a snow shovel?

[venture]

Norman is going with NAM it seems...

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE NORMAN OK
257 PM CST SUN FEB 10 2013


OKZ004>006-009>011-014>017-021-110500-
/O.NEW.KOUN.WS.A.0001.130212T0900Z-130213T0000Z/
HARPER-WOODS-ALFALFA-ELLIS-WOODWARD-MAJOR-ROGER MILLS-DEWEY-
CUSTER-BLAINE-BECKHAM-
INCLUDING THE CITIES OF...BUFFALO...ALVA...CHEROKEE...ARNETT...
WOODWARD...FAIRVIEW...CHEYENNE...TALOGA...WEATHERF ORD...CLINTON...
WATONGA...ELK CITY...SAYRE
257 PM CST SUN FEB 10 2013


...WINTER STORM WATCH IN EFFECT FROM LATE MONDAY NIGHT THROUGH
TUESDAY AFTERNOON...


THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A WINTER STORM
WATCH...WHICH IS IN EFFECT FROM LATE MONDAY NIGHT THROUGH TUESDAY
AFTERNOON.


* TIMING:LATE MONDAY NIGHT THROUGH TUESDAY.


* MAIN IMPACT:SNOW IS EXPECTED TO DEVELOP IN WESTERN OKLAHOMA LATE
MONDAY NIGHT AND SPREAD NORTHEASTWARD TUESDAY. SNOW
ACCUMULATIONS OF 3 TO 6 INCHES WILL BE POSSIBLE ACROSS PARTS OF
WESTERN AND NORTHERN OKLAHOMA.


* OTHER IMPACTS:SNOW ACCUMULATIONS MAY RESULT IN SLICK AND
HAZARDOUS ROADWAYS FROM LATE MONDAY NIGHT THROUGH TUESDAY.


PRECAUTIONARY/PREPAREDNESS ACTIONS...


KEEP UP WITH THE LATEST WEATHER INFORMATION...ESPECIALLY IF YOU
PLAN TO TRAVEL.

[Anonymous.]

As it looks right now, NW OK is in for the fun stuff.

[venture]

GFS this afternoon lined up well with NAM, but again...I hate the mid day cycles and this snow track continues to bounce around from run to run. So we'll see what the next couple show.