Southern Plains winter wx thread (2008-2009)

[iorange55]

The 00z NAM is showing the following liquid equivalents during this event (7am Mon - 7am Wed):

Oklahoma City, OK = 0.28" (all of which falls while temperatures are below 32F)
Norman, OK = 0.32" (all of which falls while temperatures are below 32F)
Tulsa, OK = 0.41" (all of which falls while temperatures are below 32F)
Wichita Falls, TX = 0.25" (all of which falls while temperatures are below 32F)
Dallas, TX = 0.59" (about 0.31 to 0.35" of which falls while temperatures are below 32F)

These numbers will be pretty nasty if the precipitation falls solely as freezing rain. Usually 0.25" is considered the cutoff for when you start to see power/tree problems, so all the cities mentioned above could potentially be at risk. One thing I am still watching closely though, especially in the northern cities, is the possibility of a precipitation-type changeover during the event. If the NAM is correct, then some of the areas may see a changeover to all sleet or perhaps even snow toward the end of the event. This changeover, IF it happens, may help to A) Reduce the icing threat and B) Provide higher ground accumulations (aka 0.10" of liquid = ~1.00" of snow). For the sake of our power supply and our trees, lets hope and pray that the changeover does indeed take place.

So right now do you trust the NAM model the most? If I remember correctly it has been the one that has been more accurate this winter, right?

[Extremeweatherguy]

The 00z NAM is showing the following liquid equivalents during this event (7am Mon - 7am Wed):

Oklahoma City, OK = 0.28" (all of which falls while temperatures are below 32F)
Norman, OK = 0.32" (all of which falls while temperatures are below 32F)
Tulsa, OK = 0.41" (all of which falls while temperatures are below 32F)
Wichita Falls, TX = 0.25" (all of which falls while temperatures are below 32F)
Dallas, TX = 0.59" (about 0.31 to 0.35" of which falls while temperatures are below 32F)

These numbers will be pretty nasty if the precipitation falls solely as freezing rain. Usually 0.25" is considered the cutoff for when you start to see power/tree problems, so all the cities mentioned above could potentially be at risk. One thing I am still watching closely though, especially in the northern cities, is the possibility of a precipitation-type changeover during the event. If the NAM is correct, then some of the areas may see a changeover to all sleet or perhaps even snow toward the end of the event. This changeover, IF it happens, may help to A) Reduce the icing threat and B) Provide higher ground accumulations (aka 0.10" of liquid = ~1.00" of snow). For the sake of our power supply and our trees, lets hope and pray that the changeover does indeed take place.

So right now do you trust the NAM model the most? If I remember correctly it has been the one that has been more accurate this winter, right?

The NAM is always a decent wintertime model to look at, but I don't know if I would say that I trust it "the most". At this point, I am giving equal weighting to all the models and will wait until I see how this storm starts playing out tomorrow before I begin to favor one model over another. One thing I will say though is that the NAM has been the model that has been underplaying precipitation totals the most (compared to the GFS and ECMWF) for next week, so the fact that it is now trending wetter tonight with 0.25"+ in all the cities I listed above is definitely a bit alarming.

[Extremeweatherguy]

00z GFS precipitation totals (7am Mon - 7am Wed):

Oklahoma City, OK = 0.30" (all of which falls while temperatures are below 32F)
Norman, OK = 0.35" (all of which falls while temperatures are below 32F)
Tulsa, OK = 0.39" (all of which falls while temperatures are below 32F)
Wichita Falls, TX = 0.36" (about 0.25" of which falls while temperatures are below 32F)
Dallas, TX = 0.63" (about 0.07 to 0.11" of which falls while temperatures are below 32F)

[iorange55]

So the gfs is warmer and wetter and the NAM is colder and a little less drier. I have the feeling that for at least in Dallas it'll be one of those you won't know what the temp will be till it happens. For once i would just like to know.

[Extremeweatherguy]

Latest from Norman...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
942 PM CST SUN JAN 25 2009

.DISCUSSION...
UPDATED THE FORECAST EARLIER TO LOWER EVENING AND MINIMUM
TEMPERATURES SLIGHTLY... BASED ON TRENDS AT THE TIME. TEMPERATURES
HAVE CONTINUED TO DROP EVEN BEYOND THOSE EXPECTATIONS... DUE TO
THE MAINLY CLEAR SKIES AND VERY LOW DEW POINTS... ALONG WITH
RELATIVELY LIGHT WINDS IN MOST LOCATIONS. SO... WE WILL LOWER
TEMPERATURES AGAIN. ISENTROPIC DATA AND SOUNDINGS SUGGEST THAT
CLOUDS WILL BE SLOW TO REFORM OVERNIGHT OVER MOST OF OUR FORECAST
AREA. CLOUDS SHOULD RETURN TO OUR SOUTHERN COUNTIES A FEW HOURS
BEFORE SUNRISE... THEN EXPAND QUICKLY NORTH IN THE MORNING. THIS
SCENARIO SHOULD ALLOW TEMPERATURES TO FALL WELL INTO THE TEENS
ACROSS OUR NORTHWEST HALF OR SO... AND 20S ELSEWHERE. THESE LOW
TEMPERATURES SHOULD OCCUR A FEW HOURS EARLIER THAN THE USUAL TIME
OF THE MINIMUM TEMPERATURE... AGAIN DUE TO THE TIMING OF THE CLOUD
FORMATION. IF THE CLOUDS DO FORM AS CURRENTLY EXPECTED... THIS
WILL RESULT IN A NEAR-MAXIMUM OF COOLING OF THE LOWER LEVELS OF THE
ATMOSPHERE... SETTING THE STAGE FOR FREEZING PRECIPITATION LATER
ON MONDAY AND INTO TUESDAY.

Latest from Tulsa...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OK
938 PM CST SUN JAN 25 2009

.DISCUSSION...
WILL LEAVE WATCH AND WARNING CONFIGURATION AS IS FOR THIS EVENING.

SO FAR MODEL DATA FROM THIS EVENING HAS ACTUALLY CONFUSED THE
ISSUE MORE THAN HELPED. NEARLY ALL OF THE WATCH AREA REMAINS WITH
THE POTENTIAL OF EXCEEDING ICE/WINTER STORM WARNING CRITERIA.

HAVE REMOVED THE MENTION OF THUNDER ALONG AND NORTH OF INTERSTATE
44 WHERE STABILITIES ARE LOWER. HAVE REWORKED AND ADJUSTED SOME
SLEET AND SNOW ACCUMULATIONS ACCORDING THE LATEST INFORMATION.

MODEL DATA DOES INDICATE AN INCREASE IN LIQUID EQUIVALENT AMOUNTS
A LITTLE HIGHER THAN WHAT WE CURRENTLY HAVE WHICH IF SUPPORTED
BY LATER DATA WOULD MEAN AN CONSIDERABLE EXPANSION WOULD BE NEEDED
TO THE WARNING AREA.

WILL HAVE PRODUCTS OUT SHORTLY.

Latest from Dallas...

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
941 PM CST SUN JAN 25 2009

.UPDATE...
NEXT COLD FRONT IS ALREADY SITUATED ACROSS SOUTHERN OKLAHOMA
THROUGH WICHITA FALLS. THIS COLD FRONT WILL REMAIN NEARLY
STATIONARY FOR MOST OF THE NIGHT BUT WILL SAG SOUTH TO THE RED
RIVER OVERNIGHT. WILL LIKELY SEE OVERNIGHT LOWS ALONG THE RED RIVER
NEAR FREEZING WHILE THE REST OF NORTH TEXAS SEES LOWS FROM THE MID
30S TO UPPER 40S. OVERNIGHT LOWS WILL AGAIN BE DEPENDENT ON LOW
CLOUD COVER WHICH IS ADVANCING NORTH FROM THE SOUTHERN EXTENT OF
THE CWA AT THIS TIME. HAVE ADJUSTED OVERNIGHT LOWS ACCORDING TO
CLOUD COVER AND LATEST TEMPERATURE TRENDS. THIS INCLUDED LOWERING
TEMPS A FEW DEGREES IN MOST LOCATIONS. BY DAYBREAK...OVERCAST
SKIES...FOG...AND PATCHY DRIZZLE WILL BE ONGOING ACROSS THE
REGION...EXCEPT LIGHT RAIN WILL BE POSSIBLE IN THE FAR SOUTHERN
COUNTIES. HAVE RAISED POPS TO 20 PERCENT ACROSS THE SOUTH AFTER
MIDNIGHT BUT BEST TIMING FOR PRECIPITATION TOMORROW STILL LOOKS
TO BE AFTER DAYBREAK.

00Z RUN OF THE NAM CONTINUES TO COME IN COLD FOR MONDAY THROUGH
WEDNESDAY. WENT AHEAD AND LOWERED DAYTIME HIGHS TOMORROW INTO THE
UPPER 30S TO LOWER 60S AS THE COLD FRONT SLOWLY MOVES SOUTH AND
OVERCAST SKIES AND RAIN WILL PREVENT MUCH HEATING. ACTUAL HIGH
TEMPERATURES MAY END UP REMAINING IN THE 30S AND 40S AREAWIDE BUT
WILL WAIT UNTIL FULL 00Z MODEL SUITE COMES IN TO ADJUST
TEMPERATURES COLDER. LATEST NAM IS ALSO INDICATING FREEZING RAIN
MAY OCCUR FARTHER SOUTH TUESDAY NIGHT AND WEDNESDAY.
ALSO...FREEZING RAIN MAY OCCUR DURING THE DAY ON TUESDAY...BUT
AGAIN WILL WAIT UNTIL THE FULL MODEL SUITE COMES IN BEFORE
DECIDING TO ISSUE A WINTER WEATHER ADVISORY OR WATCH.

[wx247]

We are now under an Ice Storm Warning. Oh boy!

[CrazyC83]

I am definitely going to be spending part of the day tomorrow getting prepared for loss of power. I won't be caught off guard like I was in January of 2007. I knew it was going to ice, but I wasnt prepared to be without power for 14 days!

Sounds like me in 1998!

[iorange55]

Winter storm watch now for Dallas

.WINTER STORM WATCH IN EFFECT FROM TUESDAY MORNING THROUGH LATE
TUESDAY NIGHT...

THE NATIONAL WEATHER SERVICE IN FORT WORTH HAS ISSUED A WINTER
STORM WATCH FOR LIGHT ICING...WHICH IS IN EFFECT FROM TUESDAY MORNING
THROUGH 6 AM WEDNESDAY.

LIGHT FREEZING RAIN WILL DEVELOP ACROSS THE AREA ON TUESDAY AND
CONTINUE DURING THE OVERNIGHT HOURS. ICE ACCUMULATIONS BETWEEN ONE
TENTH AND TWO TENTHS OF AN INCH ARE POSSIBLE. LIGHT FREEZING RAIN
MAY CONTINUE INTO WEDNESDAY MORNING.

ADDITIONAL WATCHES...ADVISORIES...OR WARNINGS MAY BE NEEDED. KEEP
UP TO DATE WITH THE LATEST FORECAST FROM YOUR NATIONAL WEATHER
SERVICE IN FORT WORTH.

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.

[Extremeweatherguy]

[Extremeweatherguy]

WINTER STORM WARNING up for my area. We are expecting the potential for up to 0.2-0.5" of ice. Some good news though is that there now appears to be a possibility that some of this liquid could fall as sleet. Let's hope that actually happens! The more sleet we can get, the better.

[Portastorm]

Yeah EWG, looks like you are going to get hammered by this one. Ice storms aren't much fun if the light switch doesn't work in your house when you're home from work or school. Stay safe up there!

[PTrackerLA]

Looks like there will be a widespread area of heavy icing. Could be looking at massive power outages, stay safe up there and get ready!

[ntxweatherwatcher]

What do you think we can expect here in DFW ice wise?

[Portastorm]

Well, your NWS forecast office says "light icing" between tomorrow morning and Wednesday morning. That suggests amounts less than 0.25 inches. I'd just pay close attention to your local forecasts as the event unfolds. As in most cases with Texas winter weather events, there always seems to be surprises ... either you get more than you were promised or you get less. But keep us posted on your weather up there!

[mysterymachinebl]

Well, your NWS forecast office says "light icing" between tomorrow morning and Wednesday morning. That suggests amounts less than 0.25 inches. I'd just pay close attention to your local forecasts as the event unfolds. As in most cases with Texas winter weather events, there always seems to be surprises ... either you get more than you were promised or you get less. But keep us posted on your weather up there!

True. It really is going to depend on the temps. The "light" icing a few weeks ago was bad enough on the trees and powerlines to knock the electricity out in my area for over 6 hours. I really wish we would get sleet this time instead of freezing rain!

[Extremeweatherguy]

Starting to get light ice accumulations here on the SE side of OKC. It is going to be a nasty afternoon...

[Ed Mahmoud]

Someone wiser than I can perhaps say how thick a sub-freezing layer is required to turn rain drops solid before they reach the ground.

[Dave]

Well we are now under a Winter Storm Watch for tonight through Wednesday morning. Statement issued from our local weather office at Wilmington OH....

"A winter storm will move across southeast Indiana, northern Kentucky, and much of central and southwestern Ohio tonight through early Wednesday. During this period, there is the potential for significant accumulations of snow and possibly ice for the Cincinnati, Dayton, and Columbus metro areas.

The storm initially will bring all snow to the area tonight into Tuesday. By Tuesday afternoon, sleet and freezing rain will begin to mix in with snow along and south of the Ohio River, and spread northward into portions of central Ohio by Tuesday night. These locations will see the potential for significant ice accumulation in addition to snowfall. At this time, the most likely area for significant snow accumulations of 4 inches or more will be along and south of the Interstate 70 corridor through Wednesday."
----------------

Winter storm warning is in effect out of the Louisville NWS at this time, 1 county to my south. May be an interesting week around here also.

[jasons2k]

Hi Ed,

Yes, a pro-met would have to chime-in with the actual calculations that will tell you.

I can tell you this much, it depends on a number of factors; not just the thickness. The temp-dewpoint spread and also how supercooled the droplets are enter into the equation as well -- but I'm sure you already knew that much

I can eyeball it and be right most of the time, but as far as doing the calculations, not so much...I go into model watching mode (& observations) at that point.

FWIW I think the accuracy rate of determining one over the other in borderline situations isn't the best.

This link may help: http://www4.ncsu.edu/~nwsfo/storage/cst ... terial.ppt

[ntxweatherwatcher]

Well, it looks pretty certain we will see ice as we are under an ice storm warning now!! It has been a long time since we have seen a warning for ice here!!