December-Wet/Stormy New Years Eve Ahead

[wxman57]

Model runs are coming into a LITTLE better agreement on a Southern Plains winter storm system developing during the day on Christmas. The GFS and Euro are still quite a bit apart as to the timing and location of the heaviest snow. Nothing indicated for our area, but there could be snow developing across north Texas on Christmas as the storm system moves across the state. Perhaps even down to Waco (just a touch of it).

18Z GFS has our highs in the mid 70s on Christmas just ahead of the front, but falling fast the afternoon of the 26th. Note that the times of the temperature readings on the second graph are at 12AM and 12PM, so they are not lows/highs. That's all we get until the event is within 8 days. It DOES indicate precip ends here before temps are anywhere near freezing at the surface and aloft. Most of the precip would be along and ahead of the front, not behind it (this far south).

Could get interesting up in Dallas through Oklahoma and Kansas by Christmas afternoon and the following day. In the wake of the storm, we could see lows in the mid 20s across Houston for lows Thu/Fri with highs only in the low-mid 40s. Note that today's 12Z Euro was not forecasting any freezing temps here on the 12Z run. However, if there is a snow pack across KS/OK and north TX, the Canadian air may not modify much as it moves southward.

[Portastorm]

The 0z GFS operational run is the most extreme solution (for the GFS) yet for the storm right after Christmas. It pretty much dumps anywhere from a trace up to nearly a foot across portions of west, north, and central Texas.

Here's a projected snowfall depth map through 228 hours from this run:

[Ptarmigan]

If the forecast of rain holds up, it would be the second time it rained on Christmas back to back.

[srainhoutx]

Well the overnight guidance and ensembles are certainly interesting with the Christmas Day storm and just beyond, but first things first. It does look like that a Canadian front will arrive Wednesday into Thursday with some rain chances to our N and E. A light freeze across areas N of I-10 look likely Friday Morning.

SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
358 AM EST TUE DEC 18 2012

VALID 12Z TUE DEC 18 2012 - 12Z THU DEC 20 2012

...ACCUMULATING SNOWS ARE EXPECTED ACROSS INTERIOR NEW ENGLAND ON
TUESDAY...

...ACTIVE WEATHER WILL CONTINUE FOR THE NORTHWESTERN CORNER OF THE
COUNTRY AS ANOTHER PACIFIC SYSTEM APPROACHES THE COAST...

...FIRST WINTER STORM OF THE SEASON IS IN THE FORECAST FOR THE
CENTRAL PLAINS...


CONDITIONS SHOULD QUICKLY DRY OUT ACROSS THE SOUTHEAST AND
MID-ATLANTIC STATES ON TUESDAY AS A COLD FRONT EXITS INTO THE
ATLANTIC. HOWEVER...THE ANCHORING SURFACE LOW IS EXPECTED TO
TRACK THROUGH PENNSYLVANIA AND DEEPEN OFF THE NORTHEAST COAST. AN
ABUNDANCE OF ATLANTIC MOISTURE STREAMING INLAND WILL HELP PRODUCE
AN ORGANIZED AREA OF MODERATE TO HEAVY PRECIPITATION ACROSS NEW
ENGLAND ON TUESDAY...AND ENOUGH COLD AIR NOSING DOWN FROM CANADA
SHOULD LEAD TO SIGNIFICANT SNOWFALL ACCUMULATIONS OVER INTERIOR
NEW ENGLAND. BY EARLY WEDNESDAY...THE LOW WILL BE WELL OFF THE
COAST AND ONLY A FEW LIGHT SHOWERS WILL LINGER OVER NEW ENGLAND
FOR THE REMAINDER OF THE FORECAST PERIOD.

THE NORTHWESTERN U.S. WILL NOT GET MUCH OF A BREAK FROM THE ACTIVE
WEATHER PATTERN OVER THE NEXT FEW DAYS. SHOWER ACTIVITY WILL
LIGHTEN UP A BIT ON TUESDAY...BUT THEN THE NEXT PACIFIC SYSTEM
APPROACHING THE COAST WILL BEGIN IMPACTING THE REGION BY EARLY
WEDNESDAY. STEADY RAINS ARE EXPECTED ALONG COASTAL AREAS...WHILE
MODERATE TO HEAVY SNOWS WILL BE IN THE FORECAST FARTHER INLAND
OVER THE WASHINGTON/OREGON CASCADES.

FINALLY...ENERGY AMPLIFYING OVER THE SOUTHWEST WILL BRING
WIDESPREAD SNOW SHOWERS ACROSS THE FOUR CORNER STATES ON TUESDAY.
BY WEDNESDAY AFTERNOON...THE ENERGY WILL SWING OUT INTO PLAINS AND
HELP DEVELOP A SURFACE LOW IN THE LEE OF THE COLORADO ROCKIES.
THE STRENGTHENING SURFACE CYCLONE SHOULD QUICKLY TRACK
NORTHEASTWARD TOWARDS THE MIDDLE MISSISSIPPI VALLEY...BRINGING
STRONG WINDS AND A SWATH OF MODERATE SNOWS ACROSS THE CENTRAL
PLAINS WEDNESDAY NIGHT INTO THURSDAY. IN ADDITION...INCREASING
AMOUNTS OF GULF MOISTURE FUNNELING NORTHWARD AHEAD OF THE TRAILING
COLD FRONT SHOULD HELP FIRE UP SHOWERS AND THUNDERSTORMS ACROSS
THE LOWER MISSISSIPPI VALLEY BY THE END OF THE FORECAST
PERIOD...SOME OF THESE DEVELOPING STORMS MAY BECOME STRONG OR EVEN
SEVERE.


GERHARDT


All eyes turn W as a potent trough and developing 5H and surface low exits the Great Basin and begins to trek slowly E. There are some subtle timing issues that one would expect at this range for Christmas Day and beyond. The Euro is a bit faster and brings showers/storms ahead of a deepening surface low crossing N Central Texas while the GFS is about 24 hours slower with the low and a bit further S and much slower to move the storm across the Lone Star State. With both models suggesting a hard freeze potential and with some folks away for the Holidays, plans should probably be made for some winterizing in the event that temps fall into the low to mid twenties. The HPC is aleady advertising this winter weather event in their medium range discussion, so we will continue to monitor over the next couple of days. Needless to say there is a great deal of uncertainty at the range, so expect changes. The one thing that does look likely is that we are headed toward a rather cold period and there is a potential for high impact wintry weather beginning near Boxing Day, or the day after Christmas, Stay Tuned!

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
159 AM EST TUE DEC 18 2012

VALID 12Z FRI DEC 21 2012 - 12Z TUE DEC 25 2012

...A HIGHLY ACTIVE WINTER PATTERN REMAINS ON TAP...

THE BULK OF GUIDANCE FROM MOST MODELS AND ENSEMBLES OFFER A
REASONABLY SIMILAR LARGER SCALE PATTERN EVOLUTION FOR THE NEXT
WEEK. THIS FLOW IS HIGHLIGHTED ALOFT THIS WEEKEND BY AN AMPLIFIED
TROUGH JUST OFF/ALONG THE WEST COAST...AN AMPLIFIED RIDGE OVER THE
W-CENTRAL US...AND ANOTHER AMPLIFIED TROUGH/CLOSED LOW CENTERED
OVER THE NORTHEAST. THE LEAD SYSTEM AND ASSOCIATED DEEP SURFACE
LOW/SYSTEM AND ASSOCIATED SENSIBLE WINTER WEATHER FOCUS SHOULD
PROVE SLOW TO EXIT INTO THE CANADIAN MARITIMES WORKING INTO
BLOCKED FLOW. THIS WILL LEAVE PLENTY OF ROOM FOR COOLING BACK
ACROSS THE ERN AND CENTRAL US DOWN THROUGH THE SRN TIER STATES
WELL IN ITS WAKE...INCLUDING PROTRACTED LAKE EFFECT SNOW
POTENTIAL. UPSTREAM...ERN PACIFIC TROUGH ENERGIES AND ASSOCIATED
UNSETTLED WEATHER/COOLING/PCPN ARE EXPECTED TO WORK INLAND ACROSS
THE WRN US BY SUN/MON BEFORE EMERGING INTO THE CENTRAL US NEXT TUE
WHERE SRN PLAINS CYCLOGENESIS/GULF INFLOW/DEVELOPING PCPN COULD
OCCUR TUCKED UNDERNEATH A MID-HIGHER LATITUDE DOME OF COLDER HIGH
PRESSURE.

HPC OVERNIGHT MEDIUM RANGE SURFACE FRONTS/PRESSURES AND 500 MB
PROGS ALONG WITH ASSOCIATED NEW HPCGUIDE OVERNIGHT SENSIBLE
WEATHER GRIDS WERE PRIMARILY DERIVED FROM A COMPOSITE BLEND OF
GENERALLY COMPATABLE GUIDANCE...AT LEAST AT MID-LARGER
SCALES...FROM THE GFS/ECMWF AND GEFS/ECMWF ENSEMBLE MEANS.

SCHICHTEL

[hlewis]

i'm dreaming of a white christmas (in Wharton County)

[wxman57]

Ed,

I don't see any indications of frozen precip in Houston on the 26th. I see rain ending with the cold front passage as temps drop into the 40s. 00Z Euro has an inch or less of snow into the Red River counties (nothing for Dallas) with the bullseye from NE Oklahoma through western Missouri and western Iowa. Euro doesn't have any freezing temps here next week, though I think it's mistaken in that respect. GFS drops temps to around 29 degrees by the 27th with highs in the low-mid 40s one day and near 50 the next.

Note that temps on the graphic below are NOT highs/lows, they're 6am and 6pm temps. Morning low may be a few degrees colder and the afternoon high perhaps 3-4 deg warmer than the 6pm temp. It'll be another 48 hours before the high-res GFS goes out to the 27th and we get 3-hourly temps.

[srainhoutx]

I wanted to make mention of the CFSv2 extended range forecast for January since David Paul mentioned last night on his evening weather segment about a potential big arctic air mass dropping S near the New Year time frame...Brrr...

[srainhoutx]

HPC Update:

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
936 AM EST TUE DEC 18 2012

VALID 12Z FRI DEC 21 2012 - 12Z TUE DEC 25 2012


...A HIGHLY ACTIVE WINTER PATTERN REMAINS ON TAP...

THE BULK OF GUIDANCE FROM MOST MODELS AND ENSEMBLES OFFER A
REASONABLY SIMILAR LARGER SCALE PATTERN EVOLUTION FOR THE NEXT
WEEK. THIS FLOW IS HIGHLIGHTED ALOFT THIS WEEKEND BY AN AMPLIFIED
TROUGH JUST OFF/ALONG THE WEST COAST...AN AMPLIFIED RIDGE OVER THE
W-CENTRAL US...AND ANOTHER AMPLIFIED TROUGH/CLOSED LOW CENTERED
OVER THE NORTHEAST. THE LEAD SYSTEM AND ASSOCIATED DEEP SURFACE
LOW/SYSTEM AND ASSOCIATED SENSIBLE WINTER WEATHER FOCUS SHOULD
PROVE SLOW TO EXIT INTO THE CANADIAN MARITIMES WORKING INTO
BLOCKED FLOW. THIS WILL LEAVE PLENTY OF ROOM FOR COOLING BACK
ACROSS THE ERN AND CENTRAL US DOWN THROUGH THE SRN TIER STATES
WELL IN ITS WAKE...INCLUDING PROTRACTED LAKE EFFECT SNOW
POTENTIAL. UPSTREAM...ERN PACIFIC TROUGH ENERGIES AND ASSOCIATED
UNSETTLED WEATHER/COOLING/PCPN ARE EXPECTED TO WORK INLAND ACROSS
THE WRN US BY SUN/MON BEFORE EMERGING INTO THE CENTRAL US NEXT TUE
WHERE SRN PLAINS CYCLOGENESIS/GULF INFLOW/DEVELOPING PCPN COULD
OCCUR TUCKED UNDERNEATH A MID-HIGHER LATITUDE DOME OF COLDER HIGH
PRESSURE.

THE DAYTIME PACKAGE IS BASED ON THE 00Z/18 ECENS MEAN, THE
ROBUSTNESS OF WHICH HAS STRENGTHENED CYCLE BY CYCLE OVER THE PAST
FEW DAYS. BOTH THE 00Z/18 GFS AND ECMWF ARE SOLIDLY CORRELATED
WITH THIS MEAN, AND SHOULD SERVE ADEQUATELY FOR LOCAL DETAILS
THROUGH AT LEAST DAY 6.

CISCO/SCHICHTEL

[wxman57]

00Z GFS had no precip on the 27th. Don't know where that meteogram saw any on the 27th.

[jasons2k]

The overnight disco from the NWS HGX was a good one and provides a nice overview of next week's possibilities (locally).

[wxman57]

MAJOR differences in 12Z GFS over last night's 00Z run. I wouldn't trust it as far as I could throw it. Showing all the signs of a classic MRF/GFS error in driving cold dense air back to the north into Oklahoma ahead of the advancing upper trof. Typically, the cold air continues moving south regardless of the upper flow.

[srainhoutx]

Rather impressive and potent storm system suggested by the 12Z GFS. If this upper low/trough does in fact close off and we see such an impressive deepening (neutral/negative tilted) as it exits New Mexico, things may get rather interesting. What concerns me is the severe weather potential ahead of that low. This storm appears to have multiple potential problems during the Christmas Holiday period where it be severe/wintry or what not for a large portion of our region.

The attachment 12182012 12Z GFS 12zgfs500mbHGHTNA192.gif is no longer available

[wxman57]

IF WE BAN WXMAN FROM POSTING HIS NEGATIVE COMMENTS ABOUT COLD AND SNOW,WE WILL HAVE A BETTER CHANCE OF COLD AND SNOW. WE CANT TOLERATE NEGATIVITY.
IN DEC 2008 I MEASURED 2.1 INCHES OF SNOW IN EASTERN HARRIS COUNTY AT MY LOCATION. I REMEMBER WXMAN SAYING THAT DAY" HOUSTON MIGHT SEE SOME FROZEN PRECIP,BUT NOTHING MORE THAN A FEW FLURRIES".
YEAH RIGHT,WXMAN.

Better check my post again. I said I don't believe the models are correct in driving the cold air back north. I think it'll be colder across Texas on the 26th. My current thinking is that none of the models is handling next week's weather correctly. There is the potential for a hard freeze here next Wed-Fri, even though neither the GFS nor the Euro forecasts such temps.

On the bright side, temps are already up into the lower 80s in south Texas. Nice warm-up here today. Don't know if we'll hit the 80 degrees I heard forecast on the radio this morning, but that sure would be nice for mid December.

[Katdaddy]

Model runs continue to advertise a very active weather week on the way. I too am concerned that severe weather be threat early next week. Thankfully we will have nice travel days Friday and Saturday across much of Texas. As far Winter precip possiblity for SE TX, remember how rare that is for us. I remember many times seeing models with snow for SE TX only to be dissappointed. Now days I wait for the cold air to be in place before I jump on the Winter precip bandwagon. Models continue to show colder air headed S next week so there is a little hope at this point.

[MontgomeryCoWx]

While I enjoy your enthusiasm for cold weather, your posts hurt my brain.

[srainhoutx]

500mb animation (30 Days) of the Northern Hemisphere does suggest that our pattern has indeed changed...

[MontgomeryCoWx]

1993 Thanksgiving game ... Cowgirls and Dolphins.

We tailgated for the A&M-Texas game in light sleet that day while listening to that game.

[MontgomeryCoWx]

I'm going to enjoy the end of December and January... looks like a prolonged period of cold cold weather!

Thank God!

[JackCruz]

80 degrees today and possibly tomorrow too! Summer's back, hopefully it stays.. what pattern change? Lol

[Andrew]

While the 12z GFS might send some of the colder air back north into the Oklahoma area the big picture looks very promising. To see the slowing down that is present in the current model runs leads me to believe that we will get a good dumping of colder air. Taking a look at the mid level voriticity and heights show the air contained in the NW before heights lower and it all comes shooting south thanks to nice ridging in the eastern and northern part of Canada. The 12z Euro further supports this with the 1-5 day 500mb height anomalies (below). We also see a pretty potent jet associated with this trough with winds in excess of 150kts. Looks encouraging all around but of course the smaller details make or break events down here. How deep will the cold air be, what will be the timing of the cold air with any precip, and will we see any reinforcing shots? All things to be seen as we get closer to the event and away from the lower resolution runs.