Oklahoma Weather Discussion - February/March 2013

[venture]

Local offices modify these a bit based on various conditions. For instance a Winter Weather Advisory issued by NWS North Webster, IN will cover 2-4" of snow, by NWS Cleveland they require 3-5" of snow.

College of DuPage/NEXLAB Watch, Warning and Advisory Criteria Page

SNOW ADVISORY -- A Snow Advisory will be issued when 3-5 inches is expected to fall.

*Check with your NWS office for local snowfall requirements.

BLOWING SNOW ADVISORY -- A Blowing Snow advisory will be posted for events in which visibility is intermittently 1/4 mile or less.

FREEZING RAIN / FREEZING DRIZZLE ADVISORY -- This requires that hazardous driving conditions be taking place and/or up to 1/4 inch of freezing rain on tree branches and/or if power lines break.

WINTER WEATHER ADVISORY -- A Winter Weather Advisory will be issued if conditions warranting two separate winter advisories are met.

WINTER STORM WATCH -- A Winter Storm Watch may be issued when conditions are forecast to meet the criteria for more than one warning with in the next 36 hours. A watch for a single winter weather event does not exist, for example a Wind Chill Watch or a Heavy Snow Watch. Just the same, if a forecaster thinks there will be significant snow and ice tomorrow, he/she will issue a Winter Storm Watch.

WINTER STORM WARNING -- A Winter Storm Warning will be issued if conditions are forecast to meet the criteria for two separate warnings in the next 12-24 hours. Example: If you have Heavy Snow Warning conditions along with Wind Chill Warning conditions, a Winter Storm Warning will be issued.

BLIZZARD WARNING -- A Blizzard Warning will be issued when the following conditions are forecast to last at least 3 hours. Falling and/or blowing snow frequently reducing visibility to < 1/4 mile AND sustained winds or frequent gusts > 35 mph.

ICE STORM WARNING -- An Ice Storm Warning will be issued if freezing rain/drizzle is occurring with a significant accumulation of ice (more than 1/4 inch) or accumlation of 1/2 inch of sleet.

HEAVY SNOW WARNING -- A Heavy Snow Warning will be issued if 6 or more inches of snow is expected in a 12 hour period.

[Anonymous.]

The thick clouds are holding steady in N TX, OKC has already dropped to 47 with the sun setting right now. [which btw, looks awesomely red, atm]

[Anonymous.]

My thermometer already says it is 42F.

Just looked outside, skies are basically clear, a few high clouds streaming in from southwest and that is it.


Wet bulb temp is 34 atm.

[LocoAko]

OUN has drastically changed their snowfall forecast map -- thinking nearly all precip in the metro will be rain:

FWIW, based on an exchange I saw on FB involving one of the NWS forecasters, that is specifically an accumulation map. I think they still expect snow in the metro but that little, if any, will actually stick.

[venture]

New NAM has cut off heavy snow in Western OK a ton. Heaviest area (around 3"+) From OKC area up to Ponca.

[LocoAko]

Soundings also show it much colder than before, and the NAM had previously been the warmest solution (that I'm aware of). It would be snow from mid-morning on in the metro... Yikes. I don't envy the workers at the Norman WFO this evening.

Noon in Norman:

[Anonymous.]

40 degrees now and still clear skies... So are we going to see a WSWatch for metro or are they going to let this be a disaster?





So the models think it is going to be warmer longer and thus bringing down all the snow totals, yet the temperatures are already approaching the zone?

[s00nr1]

Unfortunately we are still quite a ways from 32* and the main concern (for those wanting the temp to drop further) has to be the warmer air in S OK and the winds that are now shifting in that area advecting that warmer air into central OK. Here are the temp and wind maps:

[s00nr1]

I have to say it again....OUN is walking a fine line in my opinion with this storm considering the 00z NAM's output. I still have to say I'd issue a watch just to have my bases covered even on the 20% chance this were to verify:

[soonerguru]

Interesting discussion. Makes me want to geek out and read it all night.

[Dustin]

Western OK is finally getting some precip!

[Anonymous.]

venture, those wind speeds are basically stationary and more out of the northeast than any southern changes.

The dewpoint over C OK right now is in the low to mid twenties and wet-bulb is ranging around 34-36. Both of these combined = OKC will be cold enough for snow from the get go of precip, or very shortly thereafter. I keep checking outside to see cloud cover, and I see stars. I am worried that this could be a total bust in terms of forecast [in which tomorrow is all white].

[s00nr1]

Anonymous,
You have to remember that the orientation of this storm will lend itself to fairly substantial warm air advection especially considering the amount of moisture being pulled in. Clouds are already becoming the norm overhead here in Moore and cloudcover will only become more dense as the low pressure draws closer.

[venture]

venture, those wind speeds are basically stationary and more out of the northeast than any southern changes.

The dewpoint over C OK right now is in the low to mid twenties and wet-bulb is ranging around 34-36. Both of these combined = OKC will be cold enough for snow from the get go of precip, or very shortly thereafter. I keep checking outside to see cloud cover, and I see stars. I am worried that this could be a total bust in terms of forecast [in which tomorrow is all white].

I've seen snow down here with surface temps in the upper 30s before, so I'm not worried. All that is going to matter is the depth of cold air upstairs and how borderline it is. I really don't know what else to add outside of what we've been discussing for days now. We are all viewing the setup the same way and I'm just a little stumped Norman is not being a little more cautious. If this does go all snow, it'll be around an inch an hour. Any heavy snowfall at that rate is going to overcome ground melting fairly quickly. I just worry about people complaining about being caught off guard and unprepared if this does go all snow.

[LocoAko]

Winter Storm Watch just issued (for Cleveland County at least). Still waiting on the text.

[Anonymous.]

Yes, no doubt warm air will be a problem, this is the downfall of very wet systems that you want to produce snow.

The clouds you see out now are very spotty and pocketed low level clouds, these will not hold our temps up as the night progresses. In my opinion, this combination will allow for lower temps from the start, once precip begins and we have rapid evaporation cooling taking place - things will go downhill quick.



And now the back pedaling begins...




URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE NORMAN OK
942 PM CST MON FEB 11 2013

OKZ008-013-019-020-023>029-035-036-038-TXZ083-121145-
/O.EXB.KOUN.WS.A.0001.130212T1300Z-130213T0200Z/
KAY-NOBLE-LOGAN-PAYNE-CADDO-CANADIAN-OKLAHOMA-LINCOLN-GRADY-
MCCLAIN-CLEVELAND-KIOWA-JACKSON-COMANCHE-HARDEMAN-
INCLUDING THE CITIES OF...PONCA CITY...PERRY...GUTHRIE...
STILLWATER...ANADARKO...YUKON...EL RENO...MUSTANG...
OKLAHOMA CITY...CHANDLER...CHICKASHA...PURCELL...NORMAN...M OORE...
HOBART...ALTUS...LAWTON...QUANAH...CHILLICOTHE
942 PM CST MON FEB 11 2013

...WINTER STORM WATCH IN EFFECT FROM 7 AM CST TUESDAY THROUGH
TUESDAY EVENING...

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A WINTER STORM
WATCH...WHICH IS IN EFFECT FROM 7 AM CST TUESDAY THROUGH TUESDAY
EVENING.

* MAIN IMPACT: RAIN IS EXPECTED TO BEGIN IN CENTRAL OKLAHOMA
BEFORE SUNRISE TUESDAY MORNING. RAIN IS EXPECTED TO MIX WITH AND
CHANGE TO SNOW BEFORE NOON. SNOW ACCUMULATION OF 3 TO 6 INCHES
IS POSSIBLE ACROSS CENTRAL OKLAHOMA.

* OTHER IMPACTS:SNOW ACCUMULATIONS MAY RESULT IN SLICK AND
HAZARDOUS ROADWAYS TUESDAY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

[s00nr1]

Winter Storm Watch just issued (for Cleveland County at least). Still waiting on the text.

IMO this had to be done after looking at the 00z data....if at worst just as a CYA move.

[venture]

Anonymous,
You have to remember that the orientation of this storm will lend itself to fairly substantial warm air advection especially considering the amount of moisture being pulled in. Clouds are already becoming the norm overhead here in Moore and cloudcover will only become more dense as the low pressure draws closer.

Looking at the quality of the air south of us, there isn't really a lot of warm air to push in...except right at the surface.

[venture]

They listened!

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE NORMAN OK
942 PM CST MON FEB 11 2013


OKZ008-013-019-020-023>029-035-036-038-TXZ083-121145-
/O.EXB.KOUN.WS.A.0001.130212T1300Z-130213T0200Z/
KAY-NOBLE-LOGAN-PAYNE-CADDO-CANADIAN-OKLAHOMA-LINCOLN-GRADY-
MCCLAIN-CLEVELAND-KIOWA-JACKSON-COMANCHE-HARDEMAN-
INCLUDING THE CITIES OF...PONCA CITY...PERRY...GUTHRIE...
STILLWATER...ANADARKO...YUKON...EL RENO...MUSTANG...
OKLAHOMA CITY...CHANDLER...CHICKASHA...PURCELL...NORMAN...M OORE...
HOBART...ALTUS...LAWTON...QUANAH...CHILLICOTHE
942 PM CST MON FEB 11 2013


...WINTER STORM WATCH IN EFFECT FROM 7 AM CST TUESDAY THROUGH
TUESDAY EVENING...


THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A WINTER STORM
WATCH...WHICH IS IN EFFECT FROM 7 AM CST TUESDAY THROUGH TUESDAY
EVENING.


* MAIN IMPACT: RAIN IS EXPECTED TO BEGIN IN CENTRAL OKLAHOMA
BEFORE SUNRISE TUESDAY MORNING. RAIN IS EXPECTED TO MIX WITH AND
CHANGE TO SNOW BEFORE NOON. SNOW ACCUMULATION OF 3 TO 6 INCHES
IS POSSIBLE ACROSS CENTRAL OKLAHOMA.


* OTHER IMPACTS:SNOW ACCUMULATIONS MAY RESULT IN SLICK AND
HAZARDOUS ROADWAYS TUESDAY.


PRECAUTIONARY/PREPAREDNESS ACTIONS...


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

[venture]

Warning Details...

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE NORMAN OK
942 PM CST MON FEB 11 2013


OKZ009>011-014>017-021-022-121145-
/O.UPG.KOUN.WS.A.0001.130212T0900Z-130213T0000Z/
/O.NEW.KOUN.WS.W.0001.130212T1300Z-130213T0200Z/
ELLIS-WOODWARD-MAJOR-ROGER MILLS-DEWEY-CUSTER-BLAINE-BECKHAM-
WA****A-
INCLUDING THE CITIES OF...ARNETT...WOODWARD...FAIRVIEW...
CHEYENNE...TALOGA...WEATHERFORD...CLINTON...WATONG A...ELK CITY...
SAYRE...CORDELL
942 PM CST MON FEB 11 2013


...WINTER STORM WARNING IN EFFECT FROM 7 AM TO 8 PM CST TUESDAY...


THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A WINTER STORM
WARNING FOR SNOW...WHICH IS IN EFFECT FROM 7 AM TO 8 PM CST
TUESDAY. THE WINTER STORM WATCH IS NO LONGER IN EFFECT.


* MAIN IMPACT: SNOW IS EXPECTED TO DEVELOP IN WESTERN OKLAHOMA
BEFORE SUNRISE TUESDAY MORNING AND SPREAD EAST DURING THE DAY.
SNOW ACCUMULATION OF 5 TO 9 INCHES IS POSSIBLE ACROSS PARTS OF
WESTERN OKLAHOMA.


* OTHER IMPACTS: SNOW ACCUMULATIONS WILL RESULT IN SLICK AND
HAZARDOUS ROADWAYS TUESDAY.


PRECAUTIONARY/PREPAREDNESS ACTIONS...


AVOID TRAVEL. BE SURE YOU CAN TAKE CARE OF YOURSELF AND YOUR
FAMILY IF YOU LOSE ELECTRICAL POWER. MONITOR WEATHER FORECASTS
AND INFORMATION.

[ZYX2]

Now I hope the Tulsa office believes the same way...

[s00nr1]

Well that is certainly ramped up wording from the afternoon forecast crew and I still say they should have done this much earlier this afternoon. None of the model data throughout the day has completely ruled out heavy snowfall somewhere near central OK. However I still say there are many hurdles to overcome for a heavy snow event in the metro.

[Anonymous.]

No explanation from them? Weak...

"Uhhhh yea OKC, you shouldn't really see anything except for a dusting around 5pm."


"Oh hey, OKC, I know you're going to bed right now, but it will be snowing when you wake up, gnight!"

[LocoAko]

Cursory glance at the 00Z GFS keeps it warm and wouldn't change Norman over to a wet snow until after sunset. Meanwhile the NAM which had been the warm outlier is now the colder solution. Nasty forecast situation shaping up.

[s00nr1]

Uhhhh, so reading this their view of the models hasn't changed yet they've waited until now to issue the watch? Definitely SMH on this one:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
945 PM CST MON FEB 11 2013

.DISCUSSION...
EARLY EVENING MODEL RUNS ARE FAIRLY CONSISTENT WITH PREVIOUS RUNS IN
POSITION OF THE SNOW ACCUMULATION FOR TUESDAY. WITH PERSISTENT
AMOUNTS, INCREASED FORECAST AMOUNTS IN WHAT LOOKS LIKE THE BELT OF
GREATEST SNOWFALL POTENTIAL FROM WEST CENTRAL OKLAHOMA TO THE EAST
OR NORTHEAST. THE WATCH WAS EXPANDED EAST TO INCLUDE CENTRAL
OKLAHOMA AND WAS CONVERTED TO A WARNING BEGINNING AROUND SUNRISE
FOR WEST CENTRAL OKLAHOMA. IF RAIN CHANGES TO SNOW EARLY ENOUGH,
SNOFALL RATES MAY BE SUFFICIENT TO INSULATE THE RELATIVELY WARM
GROUND AND ALLOW FOR MORE ACCUMULATION. NEW WSW HAS BEEN ISSUED.