December: Warm Days & Cool-Foggy Nights To End 2011

[wxman57]

12Z GFS indicates an extended period of very light rain - less than 1/2" total for the event. Quite cold and drizzly on Monday. Upper air forecast is for temps quite a bit too warm for anything but rain. Not even close.

Upper Air Plot:
http://www.twisterdata.com/data/tmp/scr ... .5000W.png

[srainhoutx]

The 12Z Euro continues to advertise a 1-2 punch of upper air disturbances ejecting out of Arizona. The overall trend has been a NAM GFS camp ~vs~ Euro/Canadian/UKMET solution regarding the timing and strength of these upper air features. The Euro scores better than the GFS, so credence is given to its solution by many when forecasting. It does appear some very chilly air will settle S behind the modified Arctic boundary with some over running light precip until the second disturbance ejects E across N MX into the S Plains. Of note is wintry weather is looking more likely for parts of W TX and the Panhandle with both disturbance. Freezing rain mixed with some snow with the first system and the stronger second disturbance could bring snow showers across those regions. Further S it appears that nothing but a chilly drizzle/light rain with the upper flow out of the SW until the second 500mb disturbance/trough sweeps E ending the precip and setting the stage for some rather cold nights early next week.

[wxman57]

Yep, Canadian has the front reaching/passing Houston by noon Sunday (see below). But it stays just offshore until Monday evening. Quite similar to the GFS. May not get any sun through Wednesday. Could see a high in the mid 40s on Monday with light rain. Maybe low to mid 40s for the high on Tuesday.

[srainhoutx]

Looking longer range at the 12Z Euro, some mighty cold air and yet another upper air disturbance has been suggested by guidance. This is la la land territory and should be taken with a grain of salt, but it does provide some hints as to what the pattern could offer later next week...

[wxman57]

12Z GFS is a bit colder early next week. Still way too "warm" for anything but rain Sunday/Monday. Could be a freeze on Wednesday. GFS and Canadian are in agreement. Monday just looks miserably cold with light rain and low-mid 40s.

[srainhoutx]

All sort of Winter Weather Advisories/Watch/Warnings are being hoisted from Las Vegas, NV to the TX Panhandle for the first in a series of storm systems expected the next several days. I see a Freezing Rain Advisory up for W TX and the Lubbock area. weatherguy 425 may be able to take some pictures for us. I wouldn't be surprised to see additional advisories of the wintry mischief variety to be issued as the afternoon and weekend unfolds...

[srainhoutx]

An interesting discussion from Corpus Christi this afternoon:

WHILE COLDER AIR ENTERS THE CWA/MSA SUNDAY
NIGHT/MONDAY...ISENTROPIC LIFT CONTINUES (THE UPPER LOW/TROUGH AXIS
STILL TO THE WEST) AND THUS WILL MAINTAIN LIGHT RAIN SHOWER ACTIVITY
THROUGH MONDAY. MONDAY NIGHT/EARLY TUESDAY...LIGHT RAIN/SHOWERS
LIKELY TO PERSIST BASED ON GFS ISENTROPIC LIFT/LOW CONDENSATION
PRESSURE DEFICITS AT 300K...YET GRADUALLY DECREASE FROM WEST TO
EAST. RECALL HWR THAT THE GFS IS FASTER. THE SLOWER ECMWF SUGGEST
PCPN THROUGH TUESDAY. HWR WILL FCST THE PCPN TO END OVER THE CWA BY
12Z TUESDAY. THE GFS PROGS 06-12Z TUESDAY 1000-850MB AND 850-700MB
THICKNESS VALUES CLOSE TO A FREEZING RAIN SCENARIO...ESPECIALLY OVER
THE CNTRL/WRN CWA. WL FCST MIN TEMPS TUESDAY IN THE MID/UPPER 30S
HWR WET BULB TEMPS MAY CONTRIBUTE TO A BRIEF PERIOD OF ICE PELLETS.
THE CONFIDENCE IN FREEZING/FROZEN PCPN IS VERY LOW AT THIS TIME AND
THUS WILL NOT FCST SUCH.

Edit to add a snip from Norman, OK for our neighbors to the N:

AS COLD AIRMASS SETTLES SOUTH OVER THE AREA SUNDAY NIGHT INTO MONDAY
MAIN UPPER TROUGH BEGINS TO SHEAR OUT AND MOVE EAST OVER THE
SOUTHERN PLAINS. THIS MIGHT PRODUCE SOME VERY LIGHT SNOW FLURRIES
ACROSS MAINLY SOUTHERN OKLAHOMA INTO NORTH TEXAS MONDAY/MONDAY
NIGHT... SO HAVE LEFT A MENTION OF THIS POSSIBILITY IN THE FORECAST.


Add San Angelo to the mix:

FROM SUNDAY INTO MONDAY NIGHT...THE UPPER LEVEL TROUGH HAS A HARD
TIME MAKING PROGRESS TO THE EAST...SO WE WILL HAVE LINGERING
SLIGHT CHANCE POPS...ESPECIALLY FOR SOUTHEASTERN AREAS WHERE MORE
MOISTURE IS AVAILABLE. HOWEVER...THE PROBLEM WITH THE
PRECIPITATION IS THAT TEMPERATURES WILL BE COLD ENOUGH BEHIND THIS
COLD FRONT BY SUNDAY NIGHT THAT A RAIN/SNOW MIX OR SNOW WILL BE
POSSIBLE ACROSS THE CWA. WILL KEEP A LINGERING CHANCE FOR FLURRIES
INTO MONDAY AS THE LOW FINALLY BEGINS TO MOVE AWAY FROM THE AREA.
THE COLDEST AIR OF THE SEASON IS EXPECTED FOR MONDAY AS COLD AIR
ADVECTION IS REINFORCED BEHIND THE TROUGH MONDAY...WITH
TEMPERATURES HAVING A HARD TIME MAKING IT OUT OF THE
30S...ESPECIALLY IF ANY PRECIPITATION OCCURS.



Also add Houston/Galveston in the interesting catagory:

THE STRONG UPPER LEVEL LOW PRESSURE SYSTEM RESPONSIBLE FOR THE
STRONG WINDS ACROSS SOUTHERN CALIFORNIA WILL BEGIN TO WEAKEN AND
MOVE EASTWARD BY SATURDAY. AS THE UPPER LOW APPROACHES THE REGION
IT WILL PUSH THE COLD FRONT SOUTHWARD THROUGH OUR REGION SUNDAY
MORNING. SHOWERS AND THUNDERSTORMS ARE EXPECTED ALONG AND AHEAD OF
THE FRONT AND STRONG ISENTROPIC LIFT IN THE WAKE OF THIS FRONT
WILL ALLOW FOR WIDESPREAD LIGHT RAIN THROUGH THE DAY SUNDAY AND
MONDAY WITH MUCH CHILLIER CONDITIONS EXPECTED. THE RAIN SHOULD
TAPER OFF MONDAY NIGHT INTO TUESDAY AS COOLER AIR MOVES INTO THE
REGION. AT THIS TIME IT APPEARS THAT THE RAIN WILL MOVE OUT OF THE
REGION BEFORE THE TEMPERATURE PROFILE WOULD BE SUPPORTIVE OF ANY
WINTRY PRECIPITATION...ALTHOUGH A FEW MODELS SUGGEST THAT THERE
COULD BE A BRIEF PERIOD OF MIXED PRECIPITATION ACROSS OUR FAR
NORTHERN COUNTIES. GIVEN THAT THIS IS A LOW PROBABILITY OUTCOME
AND FAIRLY FAR INTO THE FORECAST PERIOD IT WILL NOT BE REFLECTED
IN THE CURRENT FORECAST PACKAGE.

[JackCruz]

Just checked the GFS again...it changed....and now KHOU, ABC and FOX's forecast are pretty much the same....and so is accuweather....only extreme cold and precip shown is from the weather.com forecast that's the only one. Guess next time oops.


Hope we get some white stuff though. It'll be fun!

[skidog38]

the day snow is predicted no snow
no snow is predicted it snows


is it a close call srain

[JackCruz]

I suspect that, with the warm-up now in progress, many will be taken aback by just how cold it will get on Sunday afternoon. The surge of cold air across the Intermountain Region and Upper Midwest is on the move, however. And despite claims from some sources of the cold blast staying "out west", the this rude introduction to "real winter" will take a bit out of Texas by early next week. If the various schemes verify, sleet could make a brief appearance in the Houston northern suburbs on Monday. And cities such as Dallas and Abilene could have enough mixed precipitation to create driving and power line issues.

The first storm developing along the frontal structure, in the Texas Panhandle on Friday night, will move into the Great Lakes with little effect locally. We may see a few pockets of drizzle or rain showers on Saturday afternoon and night, but the frozen types and severe weather threats will be well to our north. The trailing cold front will run into additional energy and a parallel flow (southwesterly) aloft, stalling just below the western shoreline of the Gulf of Mexico. Wave cyclogenesis (Galveston Bay Spin-Up type) will increase rainfall rates and northerly winds through the eastern half of the Lone Star State before the surface center pulls out (later Monday). In the process the Bayou City and environs should see 1 - 3 inches of rain, Lingering moisture could create a window for wet snow and sleet along and north of a line from College Station to Nacogdoches, with that outside chance of a few ice pellets above the Sam Houston Tollway late Monday night into early Tuesday.


Continue reading on Examiner.com Weekend Weather Forecast For Houston And Vicinity, Friday, December 2, 2011 - Houston Weather | Examiner.com http://www.examiner.com/weather-in-hous ... z1fLAUhzWm

[skidog38]

sunday forecast:

fox low :60

abc low :49

nbc low :58
cbs low: 59
msn:low: 39

weather.com low 46
accuweather low 42
channel 39 low:50

[srainhoutx]

The change via overnight guidance is to slow the ending of precip on Tuesday. The HPC is suggesting a Euro/GFS ensemble blend with a slight slowing of the ejection of the upper air distubance in the SW on Sunday night into Monday. Cold temps and light over running precip still look likely before clearing out possibly as late as Tuesday afternoon. Nasty cold/raw weather ahead from Sunday night until everything shifts E. The early morning chatter with the NWS offices is to include possible wintry mischief, mainly to our N and W. There remains a lot of uncertainty, so further 'fine tuning' can be expected...

[Andrew]

Very interesting to note the GFS has freezing rain briefly in the forecast for College Station and snow up in Dallas:

KCLL:

Code: Select all

 KCLL   GFSX MOS GUIDANCE  12/02/2011  0000 UTC                       
 FHR  24| 36  48| 60  72| 84  96|108 120|132 144|156 168|180 192      
 FRI  02| SAT 03| SUN 04| MON 05| TUE 06| WED 07| THU 08| FRI 09 CLIMO
 X/N  69| 55  73| 52  52| 41  47| 32  50| 30  54| 33  59| 36  59 43 65
 TMP  62| 57  68| 60  44| 43  40| 34  44| 32  48| 35  53| 38  52      
 DPT  53| 54  63| 53  40| 37  35| 27  28| 24  25| 27  31| 31  33      
 CLD  OV| OV  OV| OV  OV| OV  OV| OV  OV| OV  CL| CL  CL| CL  CL      
 WND  11| 11  17| 10  14| 15  17| 17  16|  8   8|  4   9|  6   9      
 P12  45| 15  35| 56  75| 75  63| 45  36| 28  13| 11  13| 16  16999999
 P24    |     40|     89|     85|     56|     39|     22|     23   999
 Q12   1|  0   0|  2   4|  4   3|  2   1|  1   0|  0    |             
 Q24    |      1|      4|      5|      2|      1|       |             
 T12   1|  3   4| 42  24| 19   9|  7   4|  4   4|  1   5|  5   5      
 T24    |  4    | 42    | 34    | 14    |  7    |  7    |  7          
 PZP   0|  2   0|  2   0|  2   3| 18  22| 11   4|  4   0|  4   1      
 PSN   0|  0   0|  0   0|  0   0|  0   0|  0   7|  8   5|  0   0      
 PRS   1|  0   0|  0   0|  0   7|  9  10| 17   0|  5   0|  5   1      
 TYP   R|  R   R|  R   R|  R   R|  R   Z|  R   R|  R   R|  R   R      
 SNW    |      0|      0|      0|      0|      0|       |             
                                                                  

KDFW:

Code: Select all

 KDFW   GFSX MOS GUIDANCE  12/02/2011  0000 UTC                       
 FHR  24| 36  48| 60  72| 84  96|108 120|132 144|156 168|180 192      
 FRI  02| SAT 03| SUN 04| MON 05| TUE 06| WED 07| THU 08| FRI 09 CLIMO
 X/N  58| 47  67| 36  46| 37  42| 30  44| 28  55| 33  56| 36  57 38 59
 TMP  53| 49  60| 38  40| 39  37| 32  40| 30  48| 36  51| 38  50      
 DPT  47| 44  54| 29  31| 31  30| 23  16| 20  24| 27  27| 29  31      
 CLD  OV| OV  OV| OV  OV| OV  OV| OV  OV| CL  CL| CL  CL| CL  CL      
 WND   8| 12  20| 14  14| 16  20| 18  14|  8  10|  8  13|  9  12      
 P12  49| 39  57| 63  57| 61  53| 28  22| 15   4|  7  14| 11  12 12 11
 P24    |     72|     83|     76|     34|     23|     14|     21    17
 Q12   1|  1   2|  2   2|  3   2|  0   0|  0   0|  0    |             
 Q24    |      2|      4|      4|      0|      0|       |             
 T12   1|  3  31| 35   9|  6   6|  4   3|  2   3|  2   4|  4   4      
 T24    |  3    | 44    | 18    |  7    |  5    |  5    |  6          
 PZP   3|  5   4|  7  16| 17  23| 31  15| 13  12|  9   5| 10   9      
 PSN   0|  0   0|  0   0|  0   0| 22  55| 43  17|  6   8|  0   0      
 PRS   0|  0   0|  0   8|  8  21| 26  12| 15   7|  8   1| 11   6      
 TYP   R|  R   R|  R   R|  R   Z|  Z   S|  S   R|  R   R|  R   R      
 SNW    |      0|      0|      0|      0|      0|       |     

Also while looking at the gfs the 06z comes in colder with even more moisture overriding the cold air. unfortunately while looking at the predicted soundings for the area there is a distinct area of warm temperatures (40C) at 800-850mb. The only thing that could result from this would be freezing rain or sleet.

[redneckweather]

I sure wish this front would've rolled through this morning! Oh well, gotta go with what we got for the hunt I guess. I'm fixing to hit the road and hunt the weekend in cool/rainy weather which isn't all that bad for deer movement. I'll be checking in with the latest updates while I"m there so keep the updates coming!

[wxman57]

Looks like very cold rain for us Mon/Tue (100% chance). Highs in the 40s, maybe low 40s by Tuesday for the high. Slight chance of a stray sleet pellet, as there could be a shallow sub-freezing layer between 2000-3000 feet up, but close to zero chance of freezing rain as surface temps will be well above freezing during the event. Forget the snow with this system. Too warm aloft.

[srainhoutx]

The 06Z GFS has trended slightly slower with the Upper Air features in the SW as well as the northern stream. That model run has also come in a bit 'cooler' behind the front. This trend would tend to be more in line with what the Euro has shown. That said, this is still a very complicated and volatile forecasting challenge, so expect further adjusting as the weekend evolves. The concern in the near term is heavy rainfall chances. This will need to be monitored throughout the weekend as we see just how this all plays out. Some much for boring hot and dry weather...



PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
742 AM EST FRI DEC 02 2011

VALID 12Z TUE DEC 06 2011 - 12Z FRI DEC 09 2011

A DEEPENING/BROADENING MID-UPPER LEVEL TROF ACROSS CANADA INTO THE
CONUS IS FORECAST TO EJECT AN ELONGATED MEAN TROF INITIALLY
EXPECTED TO EXTEND FROM HUDSON BAY SWWD INTO THE SWRN CONUS. THE
EXACT DETAILS OF HOW ENERGY WITHIN THE LEADING TROF WILL EVOLVE AS
IT CROSSES THE LOWER 48 WILL LIKELY TAKE SOME TIME TO BE RESOLVED
GIVEN CURRENT GUIDANCE SPREAD AND RECENT CONTINUITY CHANGES. THE
BEST CLUSTERING OF SOLUTIONS LIES WITH THE 00Z
ECMWF/UKMET/CMC/ECMWF ENSEMBLE MEAN AND TO A LESSER EXTENT THE GFS
ENSEMBLE MEAN WHICH ARE ALL SLOWER THAN THE 00/06Z GFS RUNS.
THESE GFS RUNS HAVE NOT TRENDED MUCH SLOWER WITH THE NRN PART OF
THE TROF OVER THE PAST DAY...BUT HAVE TENDED TO HOLD BACK MORE
ENERGY IN THE SRN PART. VERIFICATION AND TRENDS WITH SHORT RANGE
FEATURES OVER THE WEST GENERALLY FAVOR THE SLOWER WRN HALF OF THE
OVERALL SOLUTION ENVELOPE. THUS A NON-GFS CONSENSUS IS THE MOST
LIKELY SCENARIO. THE SAME IS THE CASE FOR FLOW AMPLIFYING FROM
CANADA...WITH THE GFS ON THE FAST SIDE OF THE SPREAD FOR THE
LEADING COLD FRONT THAT SHOULD REACH THE US NRN TIER BY DAY 5 WED.

SPREAD IN NERN PACIFIC DETAILS BY DAYS 6-7 LOWERS CONFIDENCE IN
ANY ONE PARTICULAR SOLUTION...BUT THERE IS A GENERAL THEME TOWARD
BRINGING LESS ENERGY INTO THE ERN PAC MEAN RIDGE THAN FORECAST BY
THE 00/06Z GFS RUNS. THIS PREFERENCE LEADS TO LOWER HEIGHTS
DOWNSTREAM OVER THE WRN US. TELECONNECTIONS RELATIVE TO THE CORE
OF POSITIVE HEIGHT ANOMALIES OVER THE ERN PAC AS OF D+8...EVEN
WHERE FORECAST BY THE 00Z GFS...FAVOR LOWER WRN OR W-CENTRAL CONUS
HEIGHTS THAN FORECAST BY THE GFS AND TO A LESSER EXTENT THE GFS
ENSEMBLE MEAN. THE ECMWF HAS THOUGH MODERATED ITS WWD EXTENT OF
ITS LATE PERIOD WRN TROF COMPARED TO ITS PREVIOUS TWO RUNS WHILE
THE CMC IS A LITTLE FARTHER EWD AND THE ECMWF ENSEMBLE MEAN NOW
SOMEWHAT BROADER AND FLATTER WITH ITS TROF. AS SUCH UNCERTAINTY
IS NO BETTER THAN AVERAGE FOR THIS TIME RANGE GIVEN THE UNCLEAR
NATURE OF EMBEDDED UPSTREAM KICKER IMPULSE WAVELENGTH SPACING.

ACCORDINGLY TO REFLECT CONSENSUS PREFERENCES THAT LEAN AWAY FROM
THE 00Z GFS FOR SIGNIFICANT FEATURES DURING THE PERIOD...HPC DAYS
3-7 MON-FRI GUIDANCE WAS PRIMARILY DERIVED FROM A BLEND OF THE 00Z
ECMWF AND ECMWF ENSEMBLE MEAN BUT HEDGED IN 20% GFS ENSEMBLE MEAN
AMID LINGERING UNCERTAINTY.

[wxman57]

I'd lean toward the slower Canadian model for the passage of the upper trof and the development of the west Gulf low on Tuesday morning vs. Monday afternoon (GFS). Could even mean highs near 40 on Tuesday with a fair chance of some sleet pellets as the precip ends. No snow, though (chances near zero). Air aloft will just be way too warm above 4000ft.

[randybpt]

All this talk of wintry mischief is great but the big picture is rain. That we desperately need how
Much can we expect hopefully we can get 1-3 inches area wide hopefully more in line with 2-4 any input would be greatful

[Andrew]

I'd lean toward the slower Canadian model for the passage of the upper trof and the development of the west Gulf low on Tuesday morning vs. Monday afternoon (GFS). Could even mean highs near 40 on Tuesday with a fair chance of some sleet pellets as the precip ends. No snow, though (chances near zero). Air aloft will just be way too warm above 4000ft.

gfs sounding 2.gif

[srainhoutx]

All this talk of wintry mischief is great but the big picture is rain. That we desperately need how
Much can we expect hopefully we can get 1-3 inches area wide hopefully more in line with 2-4 any input would be greatful

I'll be focusing more on this aspect of the storm system later. HPC QPF guidance suggests around 1-3, but as wxman57 just mentioned, there is a possibility of a Coastal Low/Trough developing down near Corpus, so that may add another kink in the forecast.