Texas Winter 2013-2014

[dhweather]

000
FXUS64 KFWD 020303 AAB
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
903 PM CST SAT MAR 1 2014

.AVIATION...
THE COLD FRONT IS MOVING A LITTLE FASTER TO THE SOUTH THAN WE HAD
ORIGINALLY PLANNED. THE 03Z TAF UPDATES WILL SHOW THE WIND SHIFT AT
THE METROPLEX TAF SITES FOR 06Z AND WACO FOR 12Z. THIS WILL RESULT
IN US NEEDING TO INCLUDE FREEZING RAIN AN HOUR OR TWO EARLIER.

.../PREVIOUS AVIATION DISCUSSION/...
CONCERNS...TIMING OF AN ARCTIC COLD FRONT EARLY SUNDAY. SHOWERS
AND ISOLATED THUNDERSTORMS AROUND AND SEVERAL HOURS AFTER THE
FRONT. FREEZING RAIN AND SLEET POSSIBLE LATE MORNING INTO THE
EARLY EVENING IN THE METROPLEX.

AN ARCTIC COLD FRONT IS TREKKING SOUTH ACROSS OKLAHOMA LATE THIS
AFTERNOON. THE FRONT WILL MOVE THROUGH THE METROPLEX TAF SITES
AROUND 09Z. SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED ALONG
AND FOR SEVERAL HOURS BEHIND THE FRONT. TEMPERATURES ARE EXPECTED
TO FALL TO FREEZING 16-17Z SUNDAY /10-11 AM CST/ IN THE
METROPLEX. AT THAT TIME...THE RAIN WILL CHANGE TO FREEZING
RAIN...AND THE FREEZING RAIN MAY MIX WITH SLEET DURING THE
AFTERNOON. THERE WILL CONTINUE TO BE THE POSSIBILITY OF ISOLATED
THUNDERSTORMS INTO THE AFTERNOON AND IF THIS
HAPPENS...PRECIPITATION AMOUNTS WILL END UP BEING HEAVIER THAN
THE CURRENT FORECAST. ALSO NOTE THAT THE FORECAST ACCUMULATIONS
ARE FOR THE GROUND...AND ICING ON ELEVATED SURFACES WILL START AS
TEMPERATURES DROP BELOW FREEZING. THE PRECIPITATION WILL DIMINISH
DURING THE EARLY EVENING...SHUTTING OFF AROUND 02Z. WINDS WILL
SHIFT TO THE NORTH AT 15-20 KNOTS WITH THE FRONTAL PASSAGE AND
WITH GUSTS TO 30 KNOTS LIKELY. MVFR CEILINGS WILL MOVE INTO THE
AREA THIS EVENING AND CEILINGS WILL DECREASE TO IFR OVERNIGHT
/AROUND 08Z/. CEILINGS MAY IMPROVE TO LOWER END MVFR AROUND
MIDDAY AND THESE CEILINGS WILL HOLD IN THROUGH SUNDAY EVENING.

AT WACO...A SIMILAR SCENARIO IS EXPECTED. MVFR CEILINGS WILL MOVE
BACK IN THIS EVENING. CEILINGS WILL FALL TO IFR BY 06Z. THE
ARCTIC FRONT IS EXPECTED TO MOVE THROUGH 13-15Z...WITH NORTHERLY
WINDS 15-20 KNOTS WITH GUSTS TO AROUND 30 KNOTS. IFR CONDITIONS
ARE EXPECTED FOR MOST OF THE DAY IN WACO. SHOWERS AND ISOLATED
THUNDERSTORMS ARE POSSIBLE ALONG AND BEHIND THE FRONT. AS
TEMPERATURES FALL TO FREEZING MID TO LATE AFTERNOON
/21-22Z/...THE RAIN WILL BECOME LIGHT FREEZING RAIN.

[TheProfessor]

They would likely include Denton too if they think it us along and east of I-35.

[Ntxw]

Here's the latest snippet out of FW

****

THE NAM...TX TECH WRF...RAP...AND OUR LOCAL WRF ALL HAVE
REASONABLE PRECIPITATION TRENDS TOMORROW AND AM LEANING TOWARDS
THEIR SOLUTIONS. THEY HAVE PRECIP OCCURRING ALONG AND BEHIND THE
FRONT IN THE EARLY MORNING HOURS WITH A LITTLE LULL IN THE
ACTIVITY DURING THE LATE MORNING HOURS AND AROUND MIDDAY. THEN THE
PRECIPITATION REDEVELOPS BEHIND THE FRONT AS THE UPPER LEVEL TROUGH
MOVES JUST NORTH OF THE REGION. MOST OF THE PRECIPITATION...OCCURS
OVER ROUGHLY THE NORTHERN HALF OF THE REGION. THIS IS WHEN WE
EXPECT THE HEAVIER QPF AMOUNTS. ISOLATED THUNDERSTORMS COULD ALSO
OCCUR AND SOUNDINGS INDICATE THUNDERSLEET MAY OCCUR IN THE
AFTERNOON HOURS.

THE WINTER WEATHER ADVISORY WILL REMAIN AS IS BUT HAVE UPGRADED
OUR NORTHEASTERN COUNTIES TO A WINTER STORM WARNING...ALONG AND
EAST OF A BONHAM TO GREENVILLE LINE. ICE ACCUMULATIONS IN THESE
COUNTIES COULD REACH A QUARTER OF AN INCH WITH THE HEAVIER
PRECIPITATION THAT IS EXPECTED IN THE AFTERNOON HOURS. THE WARNING
WILL BE FROM NOON UNTIL 9 PM. IT IS POSSIBLE THAT THE WARNING MAY
NEED TO BE EXPANDED WEST...POSSIBLY INTO THE DFW METROPLEX
AREA...AND IT IS POSSIBLE THAT THE ADVISORY MAY HAVE TO EXPANDED
SOUTH ALONG AND EAST OF I-35. HOWEVER...WILL CONTINUE TO ANALYZE
NEW MODEL DATA TONIGHT BEFORE MAKING ANY MORE CHANGES TO THE
ADVISORY AND WARNING LOCATIONS/PRODUCTS.



How dare they use the word thundersleet!

[TheProfessor]

It looks like the local mets are being more conservative with this event, their temperatures are closer to the GFS.

[ronyan]

0z GFS comes in a few degrees colder for Houston, now showing 34 tomorrow night.

[SouthernMet]

wow cold front is moving FAST thru oklahoma it's already 19 el reno, 21 in okc..

[TrekkerCC]

While everyone is watching the cold front speed up and make it across the DFW metroplex, I do want to remind people of the College of DuPage website at http://weather.cod.edu

They have an incredible array of model, surface analysis, and other products that you might need. The webmasters over there recently added limited HRRR and NAM-4KM products, including simulated radar reflectivity.

And I may bust on my prediction of a non-event here, I knew it was going to be very cold but I wasn't convinced about the necessary precipitation to fall into the cold air, but it seems like all the models are trending towards a copious amount of precipitation post-frontal today, especially the NAM. Especially, when I see moisture ahead of and with the upper level disturbance on the nationwide water vapor, I can believe the precipitation projections of the NAM, etc. Last night, I looked at the 700-850mb temperatures of the sites upstream (ND, International Falls, and Candad) last night as suggested in a update (relevant portion pasted below and quoted for historical interest) issued by FWD before the December 2013 event and the temperatures were even colder than in December, so I have no trouble believing the cold coming down here and remaining around here for the next few days. I feel if we do get a lot of precipitation tomorrow, we are going to be in a huge lot of trouble, especially with thundersleet which can sheet up a street or parking lot very quickly.

--------

WHILE SURFACE TEMPS ARE THE GO-TO FOR SEEING HOW COLD AN AIR MASS
IS...IT IS ACTUALLY BETTER TO ANALYZE THE LOW-MID LEVEL TEMPS
UPSTREAM TO SEE HOW COLD THE AIR IS THERE. THIS IS BECAUSE AIR
BEHIND A COLD FRONT UNDERGOES SLOW SUBSIDENCE AS IT MAKES ITS WAY
SOUTH FROM THE ARCTIC. BACKWARD TRAJECTORIES OF PAST COLD FRONTS
SHOW US TO CHECK 500-700MB TEMPS IN THE ARCTIC REGION SEVERAL DAYS
OUT...AND 700-850MB TEMPS ACROSS SOUTHERN CANADA 2 TO 3 DAYS OUT
TO GET A ROUGH IDEA ON HOW COLD IT IS GOING TO GET. THUS IT IS
CONCERNING THAT THE UPPER AIR ANALYSIS FROM 00Z REVEALS
EXCEPTIONALLY COLD AIR AT 700MB-850MB ACROSS MONTANA AND INTO
ALBERTA. GREAT FALLS MONTANA HAD A 700MB TEMP OF -24C AND -20C AT
850MB. THESE TEMPS ARE RUNNING 2 TO 3 STANDARD DEVIATIONS BELOW
NORMAL...WHICH IS AKIN TO SAYING THIS WOULD BE NEAR RECORD COLD
IF WE KEPT RECORDS AT THIS POINT IN SPACE. MODEL GUIDANCE HAS BEEN
2-4 DEG C TOO WARM WITH 6-12 HOUR FORECAST TEMPS AT THIS LEVEL AS
WELL...BUT IS BEGINNING TO CATCH ON.

[ronyan]

Taken from HGX, they mention the possibility of freezing rain for North zones.

#################
IT`S ALL IN THE TIMING AND...CONSIDERING THE ANTICIPATED SHARP DECLINE
OF LATE DAY INTO EVENING NORTHERN COUNTY LOWER LEVEL TEMPERATURES...THERE
EXISTS A MENTIONABLE CHANCE FOR LIGHT FREEZING RAIN AND/OR DRIZZLE.
IF THIS FRONT IS AS AGGRESSIVE AS FORECAST...THEN MOST OF THE PRECIPITATION
WILL BE EAST OF THOSE COUNTIES WHERE THE MERCURY DIPS BELOW FREEZING.
WITH THAT BEING SAID...ANY LINGERING LIGHT PRECIPITATION WILL BE FALLING
THOUGH A SHALLOW NEAR SURFACE SUB-FREEZING LAYER. WET ELEVATED ROADWAYS/BRIDGES
MAY BECOME SLICK AS A THIN LAYER OF BLACK ICE FORMS UPON THOSE SURFACES.
THE WINDOW FOR THE BEST CHANCE OF FREEZING RAIN/DRIZZLE WILL BE FROM
9 PM THROUGH AROUND MIDNIGHT MONDAY. THE HWOHGX PRODUCT HAS BEEN UPDATED
TO INCLUDE THIS LATE SUNDAY NIGHT (TRAVELING) HAZARD. 31

[Texas Snowman]

Wind has shifted to the north in Denison, down to 51 degrees.

[ravyrn]

Not often you see this kind of cold air pouring down the plains on March 1st.

Sorry HeatMiser

[ravyrn]

Three things I've learned this winter.

1. Pay attention to the EPO. That warm pool of water in the GOA is a doozy. (Thx Ntxw!)

2. A significant warm nose can cause moderate to heavy precipitation to draw that warmer air to the surface. That may play a role in the upcoming event tomorrow.

3. The Ouachita mountains can create a dam hindering the progress of cold air towards the ArkLaTex. That may play a role in the upcoming event tomorrow as well.

I'm very interested to see how the next 36 hours play out.

[SouthernMet]

cold front is here, screaming in & knocking on dfw atm..

Mineral Wells dropped 24 degrees in 2 hours and has 25mph winds..

Graham is at 33 with fog
w falls down to 25

[Ralph's Weather]

Three things I've learned this winter.

1. Pay attention to the EPO. That warm pool of water in the GOA is a doozy. (Thx Ntxw!)

2. A significant warm nose can cause moderate to heavy precipitation to draw that warmer air to the surface. That may play a role in the upcoming event tomorrow.

3. The Ouachita mountains can create a dam hindering the progress of cold air towards the ArkLaTex. That may play a role in the upcoming event tomorrow as well.

I'm very interested to see how the next 36 hours play out.

If I understand the mountain's role correctly, their effect is felt when the cold is filtering in from the NE. This year many of our cold spells have come from the "Polar Vortex" over the Great Lakes so the cold has had to traverse the mountains. This front is pulling air from the Plains so the mountains should not have an effect on our weather this time.
Your note on the very warm air aloft is valid though and will likely have an effect on the heavier stuff until the deeper cold filters in.

[orangeblood]

cold front is here, screaming in & knocking on dfw atm..

Mineral Wells dropped 24 degrees in 2 hours and has 25mph winds..

Graham is at 34 with fog
w falls down to 25

Have you Noticed the RAP model has almost no post frontal precip in DFW ? Strange

[ravyrn]

If I understand the mountain's role correctly, their effect is felt when the cold is filtering in from the NE. This year many of our cold spells have come from the "Polar Vortex" over the Great Lakes so the cold has had to traverse the mountains. This front is pulling air from the Plains so the mountains should not have an effect on our weather this time.
Your note on the very warm air aloft is valid though and will likely have an effect on the heavier stuff until the deeper cold filters in.

No, their E-W alignment is most noticed when the cold comes from the NW or NNW. If the cold comes from the NE, the damming affect isn't as deep or noticed. The ArkLaTex is SE of the Ouachita mountains.

[TheProfessor]

Down to about 55 here already.

[TheProfessor]

Wow it has already drop another 8+ degrees FWD has 47, but that was 20 minutes ago. Weather bug has me down to 42.

[SouthernMet]

Bridgeport, Bowie, & Gainesville all below freezing reporting frozen precip at 3am.

Graham at 26 already with freezing fog.

[TheProfessor]

33 here according to accuweather. 35 according to weather bug

[Ntxw]

cold front is here, screaming in & knocking on dfw atm..

Mineral Wells dropped 24 degrees in 2 hours and has 25mph winds..

Graham is at 34 with fog
w falls down to 25

Have you Noticed the RAP model has almost no post frontal precip in DFW ? Strange

Proverbial dry slot ! Westplexers run this risk most, eastplexers has some wiggle room.

GFS has quietly been lowering its lows to mid teens (it was 22-25 not long ago and wxman57 refused to take the split!). Nam is back to 10-16with single digis along the Red River