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.

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.

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.

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.

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).

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. (http://stillwaterweather.com/advisories.php?zone=OKC119#WL1)

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.

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.

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

http://www.hpc.ncep.noaa.gov/noaa/noaad3.gif

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.

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

Time to get a snow shovel?

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.

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

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.

00Z NAM is in for the Winter Storm next week. It continues to maintain nearly all snow to the NW quarter of OK with a little spill over into far NC OK. Snow amounts generally 3-6" over most areas. So I wanted to show how this has evolved. The last 6 runs of the NAM have shown...

Date = Model initialization date, not forecast day
18Z Feb 09 - Winter Mix, < dusting of snow North Central and far NE.
00Z Feb 10 - Snow mainly along and north of Altus to Pauls Valley to Fort Smith line. Generally 1-3", 3-4" Central back to NW, and far NE OK.
06Z Feb 10 - Snow all but far southern and SE OK. 6-10" Western OK into Central OK. 3-6" around that area in most locations and 1-3" NE.
12Z Feb 10 - Snow only NW quarter of OK. 6-9" of snow from Enid to Clinton and back west.
18Z Feb 10 - Snow NW quarter into NC OK. 3-6" most areas.
00Z Feb 11 - Snow NW quarter into NC OK. 3-6" most areas.

So we always want to look at consistency. The last three runs have been pretty much on the nose when it comes to being consistent. So what about OKC area?

Start around 6-9AM Tue - Rain/Sleet mix
9AM through 12PM - Rain, maybe some sleet here and there.
12PM - 9PM - Rain with some snow mixing in
9PM - 12AM - Sleet/Snow
Weds 12AM - 3AM - Snow ending

Now one thing to point out is that precip may stick around 6-9 hours longer that previous forecast. Snowfall amounts will be mitigated by warm and wet ground. Though if there was any accumulation we are looking at 1-2" North of I-40, dusting south of I-40 for the OKC metro area. Total rain fall outside of the snowfall potential (for the periods before change over) looks like around a 0.4" to 0.75" inch of rain...more NW side, less SE side.

Upper air profiles with NAM continue to be borderline, in my opinion, that just a couple degrees cooler or an additional 500-800 feet of below freezing air above the surface can turn this from a 1-2" snowfall for some in Central OK, to a 6-10" snowfall...if we went on a straight 10 to 1 ratio. Though with the air temps as borderline as they are, snow will probably be fairly wet and there will be an influx of graupel and sleet which will hold totals down as well. Plus we also need to take into consideration as the precip falls it could, by itself, cool the air further to make a transition happen sooner - if at all.

Clear as mud? Good. :)

Venture, you nailed it on the head with that summary. Here is a graphic that illustrates that very detailed overview:

http://wxcaster4.com/nam/CONUS1_ETA212_SFC_ACCUM-SNOWFALL_60HR.gif

It should be noted that the NAM was the last model to latch onto this system and was also the furthest off 36 hours out in regards to the Christmas storm.

0z GFS coming in.....digs the storm much further south than the NAM bringing accumulating snows into W and C OK.

Mmhmm. It has a bullseye of the heaviest snow from like El Reno out to Weatherford of around 6" of snow. Just cementing my earlier points. We'll know what will happen probably Tuesday evening. ;)

Mmhmm. It has a bullseye of the heaviest snow from like El Reno out to Weatherford of around 6" of snow. Just cementing my earlier points. We'll know what will happen probably Tuesday evening. ;)A bit optimistic there venture ;P

A bit optimistic there venture ;P

Just reinforcing my point that I really think this is a setup to bust a lot of forecasts. If the temp swings 2 degrees cooler it is a completely different story for central OK.

Example...

http://www.twisterdata.com/data/tmp/scratch/models/processing/GFS_3_2013021100_F39_35.5000N_97.5000W.png

That is the Norman forecast sounding for 15Z / 9AM Tuesday. The red line is air temp. The zero at the bottom is in Celsius. So follow that line up diagonally to the right and you see that the air temp reaches freezing right around...1200-ish feet up. If the cold air is deeper (lower to the ground) than forecast or the a couple degrees cooler from that 1200 feet and down to the surface - it's all snow.

Yeah I know, I'm just joking haha... I was thinking we wait till' wednesday to see what really happened seeing as this is Oklahoma lol...

As my thoughts last night were alluding to.....the NAM is now pulling the storm a bit further south and east -- as it did at the last second for the Christmas Day storm -- bringing some decent snowfall amounts into the OKC metro:

http://wxcaster4.com/nam/CONUS1_ETA212_SFC_ACCUMSNOWFALL_48HR.gif

This is going to be close...

I think the models were (still are) underestimating the cool/cold air that will be filtering down into OK tonight. The Central and Northern plains just got a blizzard dumped on them and the air is extra refrigerated as it moves south.


I agree, that this looks just like the Christmas Day storm that busted for most of OK; last minute changes in track after days of consistency.

Like I said on page 2 of this thread, the storm looks like it is going to track very similarly to the 09 Christmas Eve storm that dumped 14 inches on OKC. This time the ground is not as cold and the overall temperatures wont be as cold, and this will be a very wet snow event.

Will have to monitor the wet-bulb temperatures tomorrow as the preceip moves in, this is a tough forecast.

While I agree to an extent, the one issue I see with that is the southerly to calm surface winds across much of Kansas tomorrow morning. One thing to keep an eye on tonight will be to see the strength and direction of the surface winds across southern Nebraska and northern Kansas to get an idea of whether that cold air might have a chance of filtering down into this system tomorrow.

I am definitely looking through my snow goggles at the moment, but if the skies can stay clear for a majority of the night tonight..... o boy! :D

Channel 4 is saying just a dusting here.

Channel 4 is saying just a dusting here.


Yea the locals will go with the NAM on this and keep OKC in rain. Will be interesting to see their same forecasts tonight...

Storms that come down to a handful of degrees will make you go insane trying to forecast.

12z GFS again inching things further south and east toward the OKC metro.....will load up snowfall maps here in a bit.

GFS continues with its trend of heavier snow from West Central to Central OK. Like I said a couple days ago, they just need to blanket a winter storm watch for much of the area and let it play out from there. Awareness will be there, but this is going to be a last minute call.

One thing is certain, precip will not be an issue (even with the faster-moving GFS solution):

http://www.twisterdata.com/data/models/gfs/3/maps/2013/02/11/12/GFS_3_2013021112_F36_PCPIN_24_HR.png

Yeah, Venture, I would be shocked if OUN hasn't expanded the WSW into central OK by early this afternoon.

Norman slightly adjusted the accumulating snowfall a bit further south.

http://www.srh.noaa.gov/images/fxc/oun/graphicast/image5.jpg

In my meteorology classes at OU, we used to call this a "snow hole":

http://climate.cod.edu/data/forecast/WRF/12/SP/wrfSP_2_temp_60.gif

I have an odd feeling that Oklahoma city is going to get snowed on. I remember when they said nothing would happen on december 28th of 2012 and turns out we got a few inches of snow

I have a jeep so I won't be snowed in

I have a jeep so I won't be snowed in

Having a Jeep and knowing how to drive it in snow are two different things. ;)

I have a jeep so I won't be snowed in
My dad had a jeep for several years and even it had a hard time in the snow due to lack of certain tires, I hope you have snow tires or whatever they are called.

Having a Jeep and knowing how to drive it in snow are two different things. ;)


Exactly… And I have seen snow way too deep for a Jeep.............................................. ....................... in Kansas.

Looking at the 12z GFS....another snowfall might be possible Friday afternoon/evening with a fast-moving NW flow system.

http://grib2.com/gfs/CONUS_GFS0P5_SFC_12HR-ACCUM-SNOW_114HR.gif

that would be great

Looking at the 12z GFS....another snowfall might be possible Friday afternoon/evening with a fast-moving NW flow system.



Shhh. We weren't suppose to talk about that yet...or next week's. :)

Having a Jeep and knowing how to drive it in snow are two different things. ;)

That is true but I grew up in Nebraska and know how to drive in the snow. :)

Now, don't be holding out on us with a snow forecast, Venture :) We snow-types have to grab at whatever crumbs we can get :) (mind you, not wanting any of the nasty ice business, just some of the pretty fluffy stuff)

From Aaron Tuttle

Snow Storm Update: Let me start off by saying this is the hardest forecast I've seen in a long time. This is where you can play 3 options, all listed below. Depending on which one pans out, you will either be happy or be mad.

Option 1: Wet bulbing of temperature and dewpoint drop to near freezing along the I-44 corridor with warm air advection stopping short of this boundary over SE OK. Meaning w...e start out your morning drive with snow and it snows all day across OKC metro, with rain across SE OK and of course all snow W/SW/NW OK. As a result, snow totals peak around 8-10" across OKC for the duration of the event which ends by late tomorrow evening.

Option 2: (safe option most forecasters will choose) Temps stay above freezing throughout the day but drop enough to transition from rain to snow around noon over the C OK region producing about half an inch of rain and around 4-5" of snow.

Option 3: Warm air advection stronger than anticipated and it rains all day east of an El Reno line, snow west, and doesn't change over to all snow in metro until 5pm leaving us with .75" of rain and about 2" of snow.

In all of these scenarios, W OK and the TX panhandle get dumped on. A foot of snow is very likely in several areas. The upper level system is actually weakening slowly as it moves across OK so less snow in the East Tuesday evening as a result. May only see a dusting to an inch or two as a result.

As you can see, timing is crucial to snow totals. Also to your attitude when you drive to work in the morning. If you head out and it's already snowing and the forecast wasn't for it to change over until after lunchtime, you'll be upset due to the delay/accidents. If the rain doesn't transition to snow until evening and all we get is a dusting or an inch or two, you'll be upset. So as you can see, there isn't a solution to please everyone.

So here's the take away. We have a winter storm coming. Temperatures will be close to freezing in C OK and west. We are going to get a lot of good precipitation. Amounts ranging anywhere from .50" to 1.25" of liquid equivalent. West it's all snow. East it's pretty much all rain. Central it's a mix. The later the temperatures in the column of the atmosphere cool the less snow. The earlier they cool the more snow. The snow that falls will be large wet flakes and will fall at 1-2"/hour rates accumulating quickly. Ground temps near mid 40s will cool quickly as well so only an inch of melting at most.

Truth is, we cannot give you the exact amount or timing with today's technology/knowledge. We have to guess. At this point, I"m guessing a foot of snow out west, 5-8" central, and 1-2" east with the timing of change over around drive time tomorrow morning in the metro. Snow will start around 2am across W OK/TX. Light rain/showers across S OK at this time moving north. The rain/snow line during the day will likely stall just east of the I-44 boundary say about 30 miles and hang there until late afternoon. That's how close of a call this whole system is for C OK.

Ugh. In the morning, I'm leaving out of SW OKC around 6:00 am for a class south of Lawton (starts at 9:00). Supposed to start back home at 3:30. Is this going to be a terrible, no good, horrible, bad idea drive?

Tomorrow's afternoon drive in the metro is either going to be very wet, or very slick. Definnitely not dry.


It is seriously going to come down to the temperature setup in C OK. West Central OK is going to get creamed regardless.

So channel 4 said this morning 1-3 inches , I will believe it when I see it. I have an odd feeling we will get 6-9 inches in OKC and west oklahoma will get rained upon

Ugh. In the morning, I'm leaving out of SW OKC around 6:00 am for a class south of Lawton (starts at 9:00). Supposed to start back home at 3:30. Is this going to be a terrible, no good, horrible, bad idea drive?

Sounds to me like you wanna play it safe. Just get a hotel room in Lawton and drive back Wednesday.


So channel 4 said this morning 1-3 inches , I will believe it when I see it. I have an odd feeling we will get 6-9 inches in OKC and west oklahoma will get rained upon

I think it was News9 I was watching at noon where the forecaster said it may be in the 40s & 50s in parts of Kansas tomorrow but it'll be dumping snow in W/NW Oklahoma. That's pretty crazy.

I keep hoping they will reschedule but they haven't yet. Watching it close. Of course, we need the rain so much that even if I miss this class that I've tried to go to for two years, water is water and that is more important.

18z NAM is in and it's pretty much more of the same except maybe just slightly further north and west with the rain/snow line. My gut tells me that there simply won't be deep enough cold air in the metro for more than maybe an inch late in the day. Very promising precip amounts regardless:

http://www.twisterdata.com/data/models/nam/221/maps/2013/02/11/18/NAM_221_2013021118_F33_PCPIN_24_HR.png

If this snow cancels my Taco Tuesday I am going to be sooooooo pissed!

Question to all the weathermen in this thread. Are the amounts predicted so far what is expected to fall or what is excepted to accumulate?

Forecasted snowfall totals are for total accumulation.

I want a foot of snow so I can go play.... haven't had much rain for mud the past couple years but snow will do :)

18z NAM snowfall estimate:

http://wxcaster4.com/nam/CONUS1_MESO-ETA212_SFC_ACCUMSNOWFALL-KUCHERA_48HR.gif

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

http://www.srh.noaa.gov/images/fxc/oun/graphicast/image5.jpg

Well, then, so much for that.

OUN must be pretty confident in their forecast.

Still no advisory other than the initial WSWatch.


I would not be so confident with wet bulb temps still below freezing and clear skies above heading into this evening.

Winter Storm Watch was expanded into North central OK some...

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


OKZ007-012-018-022-120545-
/O.EXA.KOUN.WS.A.0001.130212T0900Z-130213T0000Z/
GRANT-GARFIELD-KINGFISHER-WA****A-
INCLUDING THE CITIES OF...MEDFORD...ENID...KINGFISHER...CORDELL
335 PM CST MON FEB 11 2013


...WINTER STORM WATCH IN EFFECT FROM 3 AM CST TUESDAY THROUGH
TUESDAY AFTERNOON...


THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A WINTER STORM
WATCH...WHICH IS IN EFFECT FROM 3 AM CST TUESDAY THROUGH TUESDAY
AFTERNOON.


* MAIN IMPACT: SNOW IS EXPECTED TO DEVELOP IN WESTERN OKLAHOMA
EARLY TUESDAY MORNING AND SPREAD EAST THROUGH THE DAY ON
TUESDAY. SNOW ACCUMULATIONS OF 3 TO 5 INCHES WILL BE POSSIBLE
ACROSS PARTS OF WESTERN AND NORTHERN 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.

That's why I think all these forecast models are junk. I'm going to forecast in the "now" tomorrow.