Southern Plains winter wx thread (2008-2009)

[Ed Mahmoud]

GFS suggests about .2 inches of freezing/frozen for OKC, just enough to cancel school without snapping trees and powerlines.

[wx247]

We got a few flurries and sleet pellets... atmosphere was too dry to support much. Am closely watching this next system though and will keep updated from my area here in SW MO... the weather magnet zone of America it always seems.

[Extremeweatherguy]

OKC uses some strong wording in their morning AFD...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
347 AM CST SAT JAN 24 2009

.DISCUSSION...
ONE OF THE MORE CHALLENGING FORECASTS IN A WHILE - ESPECIALLY
CONSIDERING THE PREVAILING DRY CONDITIONS LATELY. CONCERN IS
INCREASING FOR A POTENTIAL ICE STORM EARLY-MID PART OF NEXT
WEEK... BUT UNUSUALLY HIGH MODEL VARIANCE LEADS TO LOW CONFIDENCE
IN THE DETAILS.

CONCERN FOR A SIGNIFICANT WINTER WX EVENT REMAINS BOLSTERED BY THE
BIG ARCTIC RIDGE WHICH CONTINUES TO BUILD S/SE/E OVER MUCH OF THE
CONUS E OF THE ROCKIES. WITH THE ANCHORING SFC HIGH AT 1054 MB
OVER W CANADA AND TEMPS THERE IN THE -40 RANGE... THINKING IS
THAT THIS AIR WILL BE HIGHLY AVERSE TO BEING DISPLACED ANY TIME
SOON. THUS LOWER IS BETTER WHEN IT COMES TO TEMPS... ESPECIALLY
THE HIGHS... GOING INTO NEXT WEEK. HEIGHT FALLS OVER THE
INTERMOUNTAIN W WILL INITIATE RESPONSES DOWNSTREAM AT LOW
LEVELS... INCLUDING REINFORCEMENT OF THE ARCTIC AIR FROM THE N AND
A MODEST RETURN FLOW OF LOW-LEVEL MOISTURE FROM THE SE/S. THIS
ALL LEADS TO A STRENGTHENING FRONTAL ZONE IN OR NEAR N TX. WE
APPEAR DESTINED TO REMAIN ON THE COLD SIDE OF THIS FRONT GIVEN THE
TYPICAL STUBBORNNESS OF THE ARCTIC AIR. ISENTROPIC LIFT MAY BEGIN
TO FEED A SHALLOW LOW LAYER OF MOISTURE OVER THE FRONTAL SURFACE
TO INITIATE SOME -DZ/-FZDZ LATE SUNDAY NIGHT AND WE WILL KEEP
SLIGHT CHANCES THEREOF IN THE GRIDS.

GENERAL EVOLUTION OF THE FLOW ALOFT IS FOR TROFING BY MON NIGHT
FROM THE N PLAINS SW TOWARD THE FAR SW CONUS... AND A RELATIVELY
FLAT ZONAL FLOW DOWNSTREAM ACROSS THE CONUS. THERE MAY OR MAY NOT
BE SOME BROAD WEAK RIDGING OVER THE SCENTRAL CONUS - DEPENDS ON
WHICH MODEL AND WHICH RUN ONE IS LOOKING AT - BUT THIS LARGE-SCALE
PATTERN IS UNLIKELY TO STRONGLY ENHANCE OR SUPPRESS MID-LEVEL
FORCING. THUS IT GOES BACK TO ISENTROPIC LIFT AND FRONTOGENETIC
FORCING AT LOW LEVELS AS THE MAIN PLAYERS. THESE PROCESSES SHOULD
BECOME MORE EFFICIENT WITH TIME... LEADING TO BETTER CHANCES OF
MORE APPRECIABLE PRECIP IN THE MON-TUE TIME PERIOD. GFS IS DRIER
THAN ECMWF... PROBABLY DUE TO FLATTER FLOW ALOFT AND NOT AS MUCH
BROAD RIDGING IN THE LATTER. SFC TEMPS IN BOTH MODELS ARE FORECAST
TO HOLD BELOW FREEZING IN MOST AREAS N OF THE SFC FRONT WHILE LOW-
MID LEVEL THICKNESSES AND 850MB TEMPS ARE TOO HIGH TO SUPPORT
FROZEN PRECIP. THEREFORE... ZR APPEARS LIKELY TO PREVAIL MONDAY-
TUESDAY AND PERHAPS BEYOND. MODEL DIFFERENCES HAVE RANGED FROM
LARGE TO ENORMOUS AS FAR AS HANDLING THE EVOLUTION OF THE
NORTHERN-PLAINS-TO-SW TROUGH LATER IN THE WEEK. THERE IS SOME
GENERAL AGREEMENT THAT ANOTHER TROF WILL DROP FROM THE NE PACIFIC
INTO THE N/CENTRAL CONUS BY MIDWEEK AND THAT THE TROF AXIS WILL
STILL BE OVER OR W/NW OF THE AREA INTO THURSDAY. THERE COULD BE A
SECOND PERIOD OF ENHANCED PRECIP POTENTIAL... INCLUDING SNOW OR
MORE ICE... WHEN THIS TROF MOVES ACROSS. THUS POPS HAVE BEEN
STRETCHED INTO THURSDAY. THROUGHOUT THE MON-THU PERIOD... DIURNAL
TEMP RANGES LIKELY WILL BE MINIMIZED BY CLOUDS AND PERIODS OF
PRECIP.

EVEN THE LOWER QPF FROM THE GFS - RUN TOTALS 0.25-0.5
INCHES - WOULD BE ENOUGH TO CAUSE TROUBLE NEXT WEEK. IF THE ECMWF
RUN TOTALS OF 1-2.5" WERE TO VERIFY... WE COULD BE LOOKING AT
ANOTHER CRIPPLING ICE STORM SOMEWHERE IN THE CWA. GIVEN THE
CURRENT FORECAST TEMPERATURES... ONLY A FEW DEGREES COULD MEAN
THE DIFFERENCE BETWEEN A COLD RAIN AND A BIG ICE STORM FOR PARTS
OF THE AREA. THE QUESTIONS OF WHEN... WHERE... AND HOW MUCH ARE
VERY MUCH UP IN THE AIR... AND WILL LIKELY REMAIN SO AS LONG AS
THE MODELS CONTINUE TO FLIP FLOP. RIGHT NOW THE MOST LIKELY
SCENARIO IS ICE... WITH MAX AMOUNTS POTENTIALLY REACHING ICE STORM
CRITERIA... NEAR OR PARALLEL TO THE I-44 CORRIDOR E AND NE-WARD.
THESE DETAILS WILL CHANGE NO DOUBT IN THE COMING DAYS. WE WILL
ADDRESS THE HIGHER-THAN-USUAL UNCERTAINTY AS BEST WE CAN IN THE
HWO... BUT WILL NOTE THERE IS SOME POTENTIAL FOR A SIGNIFICANT ICE
EVENT WITH ATTENDANT POTENTIAL FOR DAMAGE TO TREES... POWER
LINES... AND OTHER STRUCTURES EARLY NEXT WEEK. THIS ONE IS APT TO
BE AT LEAST A REALLY CLOSE CALL FOR SOME AREAS.

&&

.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK 37 23 47 28 / 0 0 0 20
HOBART OK 37 24 49 27 / 0 0 0 10
WICHITA FALLS TX 40 27 54 33 / 0 0 10 20
GAGE OK 32 19 41 19 / 0 0 0 10
PONCA CITY OK 32 19 37 21 / 0 0 10 20
DURANT OK 43 28 46 33 / 0 0 10 20

[Extremeweatherguy]

The 12z GFS is coming in even wetter than the 0z, and is now showing ~0.95" of freezing rain falling in OKC next week. If these models are right, then we could be looking at a pretty nasty storm around these parts.

BTW - The 12z MOS is also looking pretty bad. It is showing a high of 31F on Monday with a 36% chance of precipitation, and then a high of only 26F on Tuesday with an 83% chance of precipitation. Low temperatures are also very chilly, with 29F on Monday, 23F on Tuesday and 23F on Wednesday.

[srainhoutx]

Looking more like a fairly widespread freezing rain, sleet, and snow event "may" be in the making for you Extremeweatherguy as well as points N and E. Hopefully nothing crippling, but please send some rain to your friends in TX. We need it badly.





Also will add another NOAA dropsonde mission is scheduled...

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1030 AM EST SAT 24 JAN 2009
SUBJECT: WINTER STORM PLAN OF THE DAY (WSPOD)
VALID 25/1100Z TO 26/1100Z JAN 2009
WSPOD NUMBER.....08-055

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK.....NEGATIVE.

II. PACIFIC REQUIREMENTS
1. FLIGHT ONE -- TEAL 75
A. P17/ 39.0N 158.0W/ 25/1200Z
B. AFXXX 04WSC TRACK17
C. 25/0500Z
D. 16 DROPS ON TRACK AS PUBLISHED
E. AS HIGH AS POSSIBLE/ 25/1800Z

2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
JWP

[Extremeweatherguy]

[srainhoutx]

HPC Snow/Ice Update today...

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
328 PM EST SAT JAN 24 2009

VALID 00Z SUN JAN 25 2009 - 00Z WED JAN 28 2009


DAYS 1 AND 2...

INTERMOUNTAIN WEST...
GOOD MODEL AGREEMENT REGARDING THE DEEPENING AND ELONGATING
WESTERN TROUGH WITH DEVELOPING SFC LOW OVER THE GREAT BASIN.
MOIST DIFFLUENT SW FLOW AHEAD OF THE TROUGH WILL ADVECT 2+ STD DEV
PW VALUES INTO THE HIGH TERRAIN FOR THE NEXT 24 HOURS CREATING A
PROLONGED PERIOD OF TERRAIN-ENHANCED SNOW FROM THE SIERRA NEVADA
ALL THE WAY TO WY/MT...INCLUDING VALLEY FLOORS. 12Z SUITES HAVE
TRENDED A TAD MORE PROGRESSIVE WHICH WILL END THE SNOW MACHINE
SLIGHTLY EARLIER...SO AMOUNTS WERE TEMPERED SLIGHTLY.
STILL...FOOT PLUS AMOUNTS ARE LIKELY IN THE SIERRA
NEVADA...WASATCH/UNITAS RANGES...TETONS...AND CO/WY ROCKIES.

SRN WYOMING/WESTERN NEBRASKA...
STRONG SURFACE HIGH PRESSURE OVER THE CENTRAL U.S. WILL DRIVE
UPSLOPE FLOW TO THE TERRAIN OF WY/NEB/MT SUNDAY AND MONDAY.
SHORTWAVE ENERGY AND A BROAD AXIS OF MID-LEVEL FRONTOGENESIS WILL
ENHANCE THIS PROCESS SATURDAY NIGHT THEN AGAIN LATE SUNDAY.
MODERATE TO HEAVY SNOWFALL WILL DEVELOP ACROSS SOUTHEASTERN
WYOMING AND THE NEBRASKA PANHANDLE...WITH 6-10 INCHES ALONG THE
WYOMING/NEBRASKA BORDER AND 4-8 INCHES EASTWARD ALONG THE PLATTE
VALLEY OF CENTRAL NEBRASKA. THE SNOWFALL FORECAST AND AXIS OF
HIGHEST SNOWFALL CLOSELY FOLLOWS THE ECMWF/GFS...WITH SNOW TO
LIQUID EQUIVALENT RATIOS IN THE 15-20:1 RANGE DURING THE EVENT.


THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

DAY 3...

SOUTH CENTRAL PLAINS THROUGH LOWER OH VALLEY...
POTENTIAL DANGEROUS WINTER WEATHER SCENARIO IS SHAPING UP ACROSS A
PORTION OF THE THE CENTRAL U.S. FROM OK TO WV ON MONDAY NIGHT AND
TUESDAY. THE ELONGATED TROUGH WILL STRETCH ACROSS VIRTUALLY THE
ENTIRE CONUS WITH A SIGNIFICANT PIECE OF VORT ENERGY EJECTING FROM
THE 4 CORNERS THAT WILL SLOWLY RIDE THE PATHLENGTH OF THE TROUGH.
VV FIELDS WILL BE STRONG ACROSS THE ENTIRE REGION AS A 185+KT JETS
DEVELOPS WITHIN THE TROUGH. AS THE FLOW BCMS MORE SW...GULF
MOISTURE WILL BECOME INVOLVED WITH THE SYSTEM...AND PERSISTENT
OVERRUNNING WILL OCCUR ALONG/NORTH OF THE BOUNDARY SEPARATING THE
ARCTIC AIR MASS. COMPLEX THERMAL PROFILE WILL ENSURE MIXED
P-TYPES...BUT MODELS ARE CONVERGING ON THE IDEA OF .50-.75 INCH
ICING FROM NORTHEAST OK TO CENTRAL TN...AND POSSIBLE A GREAT AREA
OF AROUND .25 INCH ICE. IMMEDIATELY NORTH OF THE BOUNDARY WILL BE
AN AXIS OF HEAVY SNOW.

SOWKO

[iorange55]

New models showing north texas could get on the snow/ice train this week.


Lets hope that trend continues this might be one of the last shots we get this winter.

[jinftl]

Shaping up to be a January to remember in Dallas....current avg temp month-to-date (1/1 - 1/23) is running well above normal:

From NWS DFW CF-6 Climate Page, January 2009 month to date (through 1/23):
AVERAGE MONTHLY: 50.8
DPTR FM NORMAL: 7.0

http://www.nws.noaa.gov/climate/index.php?wfo=fwd


NWS FW not biting yet on much in the way of wintry weather in the week ahead...but of course that can always change closer in....excerpt from Discussion this pm:

AFTER A COLD DAY TODAY DUE TO ABUNDANT CLOUD COVER AND STRONG COLD
AIR ADVECTION...CLOUDS WILL SLOWLY CLEAR TONIGHT AND ALLOW FOR
SOME RADIATIONAL COOLING BEFORE SUNRISE. TEMPERATURES WILL BE NEAR
OR ABOVE NORMAL SUNDAY WITH AMPLE SUNSHINE AND THE START OF WARM
AIR ADVECTION. WARM AIR ADVECTION WILL INCREASE SUNDAY NIGHT AS
THE TROUGH DEEPENS IN THE WEST. CLOUDS AND LIGHT DRIZZLE SHOULD
DEVELOP OVERNIGHT AND CONTINUE THROUGH MONDAY MORNING.

INCREASING LARGE SCALE LIFT AND LOW LEVEL MOISTURE WILL BRING A CHANCE OF
LIGHT RAIN MONDAY AFTERNOON WITH THE BEST CHANCES IN THE NORTHEAST
ZONES NEAR THE RED RIVER IN THE VICINITY OF A WEAK BACK DOOR COLD
FRONT. THIS FRONT IS PROGGED TO BUILD SOUTH/SOUTHWEST THROUGH
TUESDAY WHILE THE UPPER TROUGH SPINS IN THE WEST AND BRINGS
INCREASING MID LEVEL MOISTURE AND LIFT. WILL KEEP CHANCE POPS
GOING THROUGH WEDNESDAY MORNING. RAIN AMOUNTS FOR THE ENTIRE
EVENT SHOULD AVERAGE ONE QUARTER INCH OR LESS. HOWEVER A FEW SPOTS
NEAR THE RED RIVER MAY PICK UP AS MUCH AS ONE HALF INCH.

AT THIS TIME...IT APPEARS THAT ABUNDANT CLOUD COVER WILL KEEP TEMPERATURES
FROM FALLING BELOW FREEZING MONDAY NIGHT AND TUESDAY NIGHT SO
DO NOT EXPECT ANY FREEZING RAIN/FREEZING DRIZZLE. THE UPPER TROUGH
WILL TRANSLATES EAST ACROSS THE REGION WEDNESDAY AND ALLOW THE
COLD FRONT TO PUSH INTO SOUTH TEXAS WITH COOLER AND DRIER AIR
BEHIND IT.

WEST TO NORTHWEST FLOW WILL SET UP WEDNESDAY NIGHT THROUGH
SATURDAY WITH DRY AND SEASONALLY COOL AIR EXPECTED.

[iorange55]

Shaping up to be a January to remember in Dallas....current avg temp month-to-date (1/1 - 1/23) is running well above normal:

From NWS DFW CF-6 Climate Page, January 2009 month to date (through 1/23):
AVERAGE MONTHLY: 50.8
DPTR FM NORMAL: 7.0

http://www.nws.noaa.gov/climate/index.php?wfo=fwd


NWS FW not biting yet on much in the way of wintry weather in the week ahead...but of course that can always change closer in....excerpt from Discussion this pm:

AFTER A COLD DAY TODAY DUE TO ABUNDANT CLOUD COVER AND STRONG COLD
AIR ADVECTION...CLOUDS WILL SLOWLY CLEAR TONIGHT AND ALLOW FOR
SOME RADIATIONAL COOLING BEFORE SUNRISE. TEMPERATURES WILL BE NEAR
OR ABOVE NORMAL SUNDAY WITH AMPLE SUNSHINE AND THE START OF WARM
AIR ADVECTION. WARM AIR ADVECTION WILL INCREASE SUNDAY NIGHT AS
THE TROUGH DEEPENS IN THE WEST. CLOUDS AND LIGHT DRIZZLE SHOULD
DEVELOP OVERNIGHT AND CONTINUE THROUGH MONDAY MORNING.

INCREASING LARGE SCALE LIFT AND LOW LEVEL MOISTURE WILL BRING A CHANCE OF
LIGHT RAIN MONDAY AFTERNOON WITH THE BEST CHANCES IN THE NORTHEAST
ZONES NEAR THE RED RIVER IN THE VICINITY OF A WEAK BACK DOOR COLD
FRONT. THIS FRONT IS PROGGED TO BUILD SOUTH/SOUTHWEST THROUGH
TUESDAY WHILE THE UPPER TROUGH SPINS IN THE WEST AND BRINGS
INCREASING MID LEVEL MOISTURE AND LIFT. WILL KEEP CHANCE POPS
GOING THROUGH WEDNESDAY MORNING. RAIN AMOUNTS FOR THE ENTIRE
EVENT SHOULD AVERAGE ONE QUARTER INCH OR LESS. HOWEVER A FEW SPOTS
NEAR THE RED RIVER MAY PICK UP AS MUCH AS ONE HALF INCH.

AT THIS TIME...IT APPEARS THAT ABUNDANT CLOUD COVER WILL KEEP TEMPERATURES
FROM FALLING BELOW FREEZING MONDAY NIGHT AND TUESDAY NIGHT SO
DO NOT EXPECT ANY FREEZING RAIN/FREEZING DRIZZLE. THE UPPER TROUGH
WILL TRANSLATES EAST ACROSS THE REGION WEDNESDAY AND ALLOW THE
COLD FRONT TO PUSH INTO SOUTH TEXAS WITH COOLER AND DRIER AIR
BEHIND IT.

WEST TO NORTHWEST FLOW WILL SET UP WEDNESDAY NIGHT THROUGH
SATURDAY WITH DRY AND SEASONALLY COOL AIR EXPECTED.

I'm not sure why you showed that when they updated with this.

ONE SIGNIFICANT NOTE FOR THE COMING WEEK IS THE POTENTIAL FOR A
WINTER PRECIPITATION EVENT NEXT TUESDAY AND WEDNESDAY. LATEST
MODEL RUNS /INCLUDING THE LATEST 00Z RUNS/ ARE COMING IN WITH
COLDER SURFACE AND LOW LEVEL TEMPERATURES BEHIND THE FRONT ON
TUESDAY. WITH ON GOING PRECIPITATION...THIS SITUATION BEARS CLOSE
WATCHING OVER THE NEXT SEVERAL DAYS FOR A FREEZING RAIN AND
POSSIBLY SNOW EVENT. BASED ON THE LATEST INCOMING MODEL DATA...THE
MOST LIKELY LOCATION AT THIS TIME WOULD BE ACROSS THE NORTHERN
HALF OF THE CWA.

[Extremeweatherguy]

The latest model guidance continues to show the potential for a major winter storm across Oklahoma early next week. Both the GFS and NAM MOS drop Oklahoma City below freezing on Monday morning and keep the city below freezing through Tuesday and into Wednesday. At the same time, precipitation chances increase to 50-75% across the area, with freezing rain and sleet being the most likely precipitation types. There are some indications of a possible changeover to all sleet or perhaps even snow during the event (as seen on the 00z NAM), but confidence in that happening is currently quite low. The main thing we can get out of the models tonight is that the risk of a significant winter storm remains quite high. In what form the winter precipitation will fall, and where/when the greatest totals will occur is still undetermined though. Hopefully these answers will become more apparent during the day tomorrow.

Here is a look at the 00z model precipitation totals between 12z Monday and 12z Wednesday for OKC:

00z GFS = 0.35" << Mostly in the form of freezing rain
00z NAM = 0.30" <<Mostly in the form of sleet/snow (meaning actual ground accumulations could be much greater than the liquid equivalent. Perhaps as much as 1-3")

[somethingfunny]

I'm seriously thinking about making the drive up to OKC to witness snow this week. The tricky part is figuring out where to position myself so that I don't end up stuck on US 75 or I-35 in an icestorm.

Did NOAA ever fly that reconnaisance mission, resulting in the new runs showing more cold air reaching farther south? I'll trust the models a bit more if that's the case.

[srainhoutx]

Looks as if a couple of NOAA Missions have helped out with modeling issues. Latest HPC Snow/Ice Update is rather expansive...

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
437 AM EST SUN JAN 25 2009

VALID 12Z SUN JAN 25 2009 - 12Z WED JAN 28 2009

DAYS 1/2...
INTER-MOUNTAIN WEST...
GOOD MODEL AGREEMENT COMING FROM THE ECMWF AND GFS WITH RESPECT TO
THE POSITION OF THE DEEP/UNSTABLE WESTERN US TROUGH... EMBEDDED
SHORTWAVE ENERGY MOVING EASTWARD IN WEST TO SOUTHWEST FLOW ALOFT
ACROSS THE GREAT BASIN AND ROCKIES...AND UPSLOPE FLOW PENETRATING
ACROSS THE INTERIOR VALLEYS THROUGH MONDAY MORNING. BEST
OROGRAPHICS AND INSTABILITY FOCUS HEAVIEST SNOWFALLS...IN EXCESS
OF 12 INCHES ACROSS THE CENTRAL SIERRA...WASATCH/UINTA RANGES OF
NORTHEAST UTAH...SOUTHERN TETONS AND ALONG THE CONTINENTAL DIVIDE
OF NORTHERN COLORADO WITH ISOLATED 4-8 INCH SNOWS POSSIBLE ACROSS
PORTIONS OF EASTERN NEVADA...SOUTHERN IDAHO AND SOUTHERN WYOMING
WITH UPSLOPE FLOW AND MID-LEVEL FRONTOGENESIS GENERATING BANDS OF
MODERATE SNOW SHOWERS OVER THESE AREAS.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

DAYS 2/3...
SOUTHERN PLAINS/OZARKS/OHIO VALLEY/MID ATLANTIC...
COMPLEX AND SLOW-MOVING WINTER STORM DEVELOPS ACROSS THE SOUTHERN
PLAINS...OZARKS AND LOWER OHIO VALLEY ON DAY 2...WITH COLD HIGH
PRESSURE SETTLING IN ACROSS THE PLAINS STATES AND MIDWEST. A
STRONG SHORTWAVE AND ASSOCIATED PACIFIC JET STREAK EXITING THE
CENTRAL ROCKIES WILL GENERATE A BROAD AREA OF OVERRUNNING AND
FREEZING AND/OR FROZEN PRECIPITATION ON MONDAY NIGHT ALONG THE
I-40 AND I-44 CORRIDORS FROM THE TEXAS PANHANDLE EASTWARD INTO THE
OZARKS. BEST MOISTURE CONVERGENCE IS EXPECTED ACROSS EASTERN
OKLAHOMA...NORTHERN ARKANSAS AND SOUTHERN MISSOURI WITH
SIGNIFICANT ICE ACCUMULATIONS LIKELY BY TUESDAY MORNING FROM
OKLAHOMA CITY EASTWARD TO THE BOOT HEEL OF SOUTHEASTERN
MISSOURI...WITH A NARROW BAND OF 4+ INCH SNOWFALLS EXPECTED WITH
THE OVERRUNNING PRECIPITATION TURNING TO SNOW IN THE COLD/DEEP/DRY
AIRMASS ASSOCIATED WITH THE SURFACE HIGH. THE NARROW BAND OF 4+
INCH SNOWS ARE EXPECTED TO DEVELOP ALONG AND SOUTH OF THE I-70
CORRIDOR FROM CENTRAL MISSOURI EASTWARD INTO SOUTHWESTERN OHIO
BENEATH THE CORE OF THE UPPER-LEVEL JET.

A SURFACE WAVE DEVELOPING ALONG THE LEADING EDGE OF THE COLD
AIRMASS TUESDAY MORNING...WILL SURGE A WARM NOSE OF MOIST
SOUTHERLY FLOW ACROSS THE DRAPED FRONTAL BOUNDARY TUESDAY
AFTERNOON INTO THE OHIO VALLEY AND INTO THE MID ATLANTIC STATES
LATE TUESDAY NIGHT. SIGNIFICANT ACCUMULATIONS OF FROZEN AND
FREEZING PRECIPITATION WILL REMAIN AN ISSUE ACROSS THE SOUTHERN
PLAINS AND OZARKS ON DAY 3...BUT THE HIGHEST ACCUMULATIONS OF ICE
ARE ANTICIPATED ACROSS KENTUCKY...SOUTHERN OHIO...NORTHERN
TENNESSEE AND MUCH OF WEST VIRGINIA. ICE...SLEET AND SNOWFALL
ACCUMULATIONS ARE EXPECTED TUESDAY EVENING INTO WEDNESDAY MORNING
ACROSS PORTIONS OF PENNSYLVANIA...MARYLAND AND NORTHERN VIRGINIA
AS THE SURFACE WAVE AND JET STREAM DRIVE PRECIPITATION EASTWARD
THROUGH THE BLUE RIDGE AND ALLEGHENY MOUNTAINS...AND INTO THE MID
ATLANTIC COASTAL PLAINS.
VOJTESAK

[srainhoutx]

HPC Prelim Update seems to show that the NOAA Flights have been very helpful with model discrepancies of the past week...

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
306 AM EST SUN JAN 25 2009

VALID 12Z THU JAN 29 2009 - 12Z SUN FEB 01 2009

AS A PIECE OF THE POLAR VORTEX SLIPS DOWN FROM NUNAVUT TOWARDS
HUDSON BAY...A LONGWAVE TROUGH ATTEMPTS TO MAINTAIN ITSELF ACROSS
THE MIDWEST WHILE GENERAL RIDGING PREVAILS IN WESTERN NORTH
AMERICA. WHILE THE GUIDANCE GENERALLY SHARES THIS
VIEWPOINT...DETAIL DIFFERENCES ARE SEEN BETWEEN THE 00Z GFS/00Z
GEFS MEAN AND 00Z ECMWF/12Z ECMWF ENSEMBLE MEAN. AS USUAL...THE
CANADIAN IS THE SLOWEST TO PROGRESS THE LONGWAVE TROUGH. EARLY
ON...THE GFS IS TOO QUICK TO MOVE A SYSTEM OFF THE EAST COAST.
LATER ON...THE ECMWF/CANADIAN ARE THE QUICKEST TO SEND A CYCLONE
TOWARDS THE NORTHERN PLAINS/GREAT LAKES. PER COORDINATION WITH
OPC AND TO MAINTAIN REASONABLE CONTINUITY WITH OUR SHORT RANGE
PREFERENCE...USED A COMPROMISE BETWEEN THE 00Z ECMWF/00Z UKMET
SOLUTIONS INTO FRIDAY. THEREAFTER... USED A BLEND OF THE 00Z
GFS/00Z GEFS MEAN WHICH RESEMBLED THE 12Z ECMWF ENSEMBLE MEAN
SOLUTION. THIS CHANGED CONTINUITY BY SPEEDING UP FRONTAL
PROGRESSION ACROSS THE SOUTH LATE THIS WEEK...WHICH WAS
UNAVOIDABLE CONSIDERING THE CHANGES SEEN IN THE GUIDANCE SINCE
THIS TIME YESTERDAY.
ROTH

Nationwide Watches/Warnings this early morning...

http://www.srh.noaa.gov/nat_hazard.php

[Extremeweatherguy]

I'm seriously thinking about making the drive up to OKC to witness snow this week. The tricky part is figuring out where to position myself so that I don't end up stuck on US 75 or I-35 in an icestorm.

Did NOAA ever fly that reconnaisance mission, resulting in the new runs showing more cold air reaching farther south? I'll trust the models a bit more if that's the case.

While snow is certainly possible, I wouldn't count on it as being the main precipitation type just yet. The NWS office, in their morning discussion, noted that they still think Freezing rain and sleet will be the main issue in and around OKC during this event.

[Extremeweatherguy]

Here is the latest forecast for OKC...

Tonight: A slight chance of freezing drizzle after midnight. Mostly cloudy, with a low around 25. East wind between 9 and 13 mph.

Monday: Rain or freezing rain likely. Cloudy, with a high near 31. East northeast wind between 10 and 13 mph. Chance of precipitation is 60%. Little or no ice accumulation expected.

Monday Night: Occasional freezing rain. Low around 25. North northeast wind between 10 and 14 mph, with gusts as high as 18 mph. Chance of precipitation is 80%.

Tuesday: Freezing rain and sleet likely. Cloudy, with a high near 30. North wind between 11 and 15 mph, with gusts as high as 21 mph. Chance of precipitation is 60%.

Tuesday Night: A chance of freezing rain and sleet. Cloudy, with a low around 22. Chance of precipitation is 50%.

Wednesday: A chance of snow and sleet before noon. Mostly cloudy, with a high near 37. Chance of precipitation is 30%.

Wednesday Night: Partly cloudy, with a low around 21.

[CrazyC83]

Major ice storm it appears?

[Extremeweatherguy]

[Ed Mahmoud]

DFW AFD
(snip)

THE MODELS ARE FALLING MORE IN LINE WITH ONE ANOTHER REGARDING THE
MOVEMENT OF THE COLD FRONT TUESDAY THROUGH WEDNESDAY. THAT BEING
SAID...EXPECT TEMPERATURES TUESDAY TO RANGE FROM THE UPPER 30S IN
THE NORTHWEST TO THE LOWER 60S IN THE SOUTH. TEMPERATURES TUESDAY
NIGHT SHOULD FALL BELOW FREEZING ACROSS THE NORTHERN TWO THIRDS OF
THE REGION...GENERALLY NORTHWEST OF A LINE FROM LAMPASAS...WACO...
TO ATHENS. TO COMPLICATE MATTERS...THESE SUBFREEZING TEMPERATURES
WILL OCCUR ABOUT THE SAME TIME THE UPPER LOW IN THE WEST BEGINS TO
MOVE EAST/NORTHEAST. IT APPEARS THAT FREEZING RAIN WILL POSSIBLE
IN THE NORTHWEST TUESDAY EVENING AND FOR MUCH OF THE AREA...EXCEPT
THE SOUTHEAST ZONES...BEFORE SUNRISE WEDNESDAY. QPF FROM BOTH THE
NAM AND ECMFW ARE FAIRLY IMPRESSIVE WEDNESDAY MORNING BASED ON
THE FACT THAT SURFACE TEMPERATURES WILL BE BELOW FREEZING. AT THIS
TIME IT APPEARS THAT THE COLD AIR WILL BE VERY SHALLOW SO
FREEZING RAIN WILL BE THE MOST LIKELY PRECIP TYPE. OF COURSE THIS
EVENT IS STILL 3 DAYS OUT AND MANY THINGS COULD CHANGE WITH THE
PRECIP AND TEMPERATURE FORECAST. FOR NOW WE WILL NOT ISSUE ANY
TYPE OF WATCH...BUT WILL ISSUE A SPECIAL WEATHER STATEMENT TO
HIGHLIGHT THE POTENTIAL FOR A FREEZING RAIN EVENT.

[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.