November Weather Discussion. Rollercoaster Pattern.

[biggerbyte]

If we keep getting these readings come early next week...

Hello, Winter.

Monday will be telling. Excitement for the forum.

[srainhoutx]

I wanted to post a snip from the HPC regarding the models and their differences and the forecasting challenges ahead...I suspect the night crew will get active...

...AFTERNOON UPDATE...
LASTEST CMC REMAINS SIMILAR HOLDING THE MAIN FULL LATITUDE TROF
WELL WEST OF OTHER MODEL SOLUTIONS WHILE THE 12Z GFS IS MORE
PROGRESSIVE THAN ITS 06Z RUN. A MINOR COMPROMISE IN TIMING USED
FOR DAYS 6 AND 7 WED/THU WITH ERN CONUS FRONTAL TIMING BETWEEN
PRIOR HPC PRELIM PROGS AND LASTEST 12Z GFS AS 12Z GFS ENS MEANS
REMAIN CLOSER TO THE SLOWER FRONTAL TIMING AND MID LEVEL TROF
PROGRESSION OF THE 06Z GFS RUN. LATEST 12Z ECMWF MUCH SLOWER THAN
ITS PRIOR RUN AND HAS CONSIDERABLE MORE DIGGING OF THE TROF TO THE
LEE OF THE ROCKIES. THIS WAS ACCOUNTED FOR BY USING A LAGGED
AVERAGE FORECAST AND THE 06Z GFS FOR MORNING PRELIMS AND THIS
AFTERNOONS FINALS....HOWEVER WE COULD STILL BE FAST CONSIDERING
THE SLOWER CMC AND NOW MUCH SLOWER ECMWF. CERTAINLY DOES NOT
INCREASE CONFIDENCE. THE 06Z GFS USED EARLIER REMAINS A REASONABLE
COMPROMISE AT THIS TIME.

[srainhoutx]

Water Vapor Imagery is showing the progression of all the players tonight. The Arctic boundary is heading S from the NW Territories and our Upper Air storm is dropping S along the Pacific Coast...

[wxman57]

Current Houston NWS forecast for Thanksgiving is for "Sunny with a high in the mid 60s". That would be exactly like today. Somehow, I think it may be a tad colder than mid 60s. More likely upper 40s for the high. I think it may be cloudy as well. No winter precip, if any of you is thinking that. Just cold air.

[srainhoutx]

Current Houston NWS forecast for Thanksgiving is for "Sunny with a high in the mid 60s". That would be exactly like today. Somehow, I think it may be a tad colder than mid 60s. More likely upper 40s for the high. I think it may be cloudy as well. No winter precip, if any of you is thinking that. Just cold air.

Sounds like a sharp 'blue norther' to me...

[biggerbyte]

Poor Turkey is going to freeze.

[helloitsb]

Current Houston NWS forecast for Thanksgiving is for "Sunny with a high in the mid 60s". That would be exactly like today. Somehow, I think it may be a tad colder than mid 60s. More likely upper 40s for the high. I think it may be cloudy as well. No winter precip, if any of you is thinking that. Just cold air.

Anymore input on this? Most of the local stations are saying mid 60s also so just wanted your thoughts and/or any changes on the models.

[wxman57]

NWS changed their tune slightly overnight, now going for LOW 60s Thanksgiving Day with clouds and "sprinkles". No more "Sunny and mid 60s".

Models paint a quite different story. Canadian/Arctic air won't allow temps anywhere near the low 60s. More likely temps holding in the 40s all day with lots of clouds. No precip, though.

[C2G]

I miss summer already. Thanks for the info wxman.

[srainhoutx]

Good Morning. Another thing to keep in mind is the Euro and Canadian models are suggesting a strong Upper Air feature rotating along the base of the trough. The GFS is still somewhat progressive and doesn't show this feature at this time. As wxman57 stated, throw out those MOS temps that the NWS has at this time. It is likely that they are too warm. Perhaps as much as 10 degrees+ too warm. As we get closer to the event, we'll see those numbers change. Also of note the Arctic boundary is sinking S along the US/Canadian border this morning with some subzero degree readings. Dallas/Ft Worth has a great discussion regarding how they think this will play out...

SUB-ZERO ARCTIC AIR HAS ALREADY SLIPPED SOUTH OF THE CANADIAN
BORDER...BUT THE AIR MASS OF INTEREST REMAINS IN NORTHERN CANADA.
SITE ON ELLESMERE ISLAND IS CURRENTLY AT -35F. THIS BITTER COLD
WILL SPILL SOUTH INTO THE PRAIRIE PROVINCES EARLY NEXT WEEK.
LITTLE CHANGE TO FROPA TIMING IN NORTH TEXAS WEDNESDAY. RATHER
UNCHARACTERISTICALLY...GFS REMAINS AMONG THE FASTEST SOLUTIONS.
SHALLOW ARCTIC FRONTS TYPICALLY ARRIVE MORE QUICKLY THAN THE
VERTICAL RESOLUTION OF THE GFS CAN PREDICT...BUT LOOKING AT THE
LIKELY EVOLUTION OF THE SURFACE FRONT EARLY NEXT WEEK...ARCTIC
AIR WOULD BE HARD PRESSED TO ARRIVE MUCH SOONER THAN CURRENT
FORECAST. PATTERN SHOULD ASSURE THAT COLDEST AIR IMPACTS GREAT
LAKES AND NORTHEAST STATES...BUT THANKSGIVING WILL BE A CHILLY ONE
FOR NORTH TEXAS.

[wxman57]

How about a new meteogram? OK. Now keep in mind that this is just raw 2 meter GFS data that I'm posting.

First, the current NWS forecast for Thanksgiving at IAH:
WEDNESDAY NIGHT...CLOUDY. A 40 PERCENT CHANCE OF SHOWERS AND
THUNDERSTORMS IN THE EVENING...THEN A SLIGHT CHANCE OF SHOWERS
AND THUNDERSTORMS AFTER MIDNIGHT. MUCH COOLER. LOWS IN THE UPPER
40S.

THANKSGIVING DAY...MOSTLY CLOUDY WITH A SLIGHT CHANCE OF
SPRINKLES EARLY IN THE MORNING...THEN MOSTLY CLOUDY IN THE LATE
MORNING AND AFTERNOON. COOLER. HIGHS IN THE LOWER 60S.

Low 60s, huh? Let's see what every model is now forecasting for temps (some are colder). GFS forecasts temps holding in the mid 40s all day. The high COULD be near 60, but only if the cold front arrives late Wednesday night and it's 60 at midnight. But that's not what the NWS is forecasting. They just don't forecast extreme changes in the weather beyond the next day or two.

[srainhoutx]

IF the Euro is correct, temps may well be even a 'cooler' than what wxman57's meteogram depicts. We will see...

[snowman65]

That looks pretty cold for Central Tenn. Too bad that isn't for Wed.....We leave to come home Friday

[srainhoutx]

Some early differences showing up via the 12Z NAM and GFS regarding the Upper Air Features through hour 84...

[srainhoutx]

The 12Z GFS suggests a Wednesday evening frontal passage with some gusty winds and some moisture left behind as a shortwave (Upper Air Feature) rotates into NM and the TX Panhandle on Thanksgiving day. If the GFS is correct, Thanksgiving day looks rather raw. Black Friday looks down right cold in GFS world as well...

[wxman57]

Ed, you don't like dry cold? How about wet cold then? See the new GFS. Here's a meteogram. Temps falling into the 40s during the day Thanksgiving with a persistent light rain. Again, this is just the CURRENT GFS forecast, not necessarily my forecast. I'm not sure if the rain will materialize on Thursday or not, but I do think Thursday's high will occur at midnight Wednesday night, and temps during the day will fall into the 40s.

[srainhoutx]

Interesting to see the GGEM develop a Coastal Low along the Mid/Lower TX Coast at the 144 hour range. Hmmm...

[Mr. T]

Ed, you don't like dry cold? How about wet cold then? See the new GFS. Here's a meteogram. Temps falling into the 40s during the day Thanksgiving with a persistent light rain. Again, this is just the CURRENT GFS forecast, not necessarily my forecast. I'm not sure if the rain will materialize on Thursday or not, but I do think Thursday's high will occur at midnight Wednesday night, and temps during the day will fall into the 40s.

Looks like a classic blue norther wxman. Thanks for the graphics...

[srainhoutx]

HPC Final Discussion paints an interesting picture as well as the forecast challenges ahead regarding the Upper Air disturbances expected next week along the Western trough and Arctic Frontal Boundary. Also of note is the widespread nature of this Arctic Air and the effects it will have across the Country...

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
205 PM EST FRI NOV 19 2010

VALID 12Z MON NOV 22 2010 - 12Z FRI NOV 26 2010

A HIGHLY AMPLIFIED AND POSITIVELY TILTED UPPER TROUGH WILL START
OFF THE MEDIUM RANGE PERIOD NEXT WEEK ACROSS THE WEST INTO THE
UPPER MIDWEST. THIS COLD LARGE SCALE FEATURE WILL HELP STEER TWO
PAC/POLAR SHORT WAVE FEATURES OUT OF THE WEST INTO THE PLAINS.
THIS SHOULD INCLUDE A QUICK ARCTIC INTRUSION ACROSS THE
ROCKIES/PLAINS STATES...WITH A SUBSEQUENT AND POTENTIALLY QUITE
WAVY FRONTAL PUSH/REDEVELOPMENT OUT ACROSS THE EAST-CENTRAL US
ACTING TO FOCUS CONVERGENCE/OVERRUNNING WITH LEAD THETA-E
ADVECTION WORKING UNDER FAVORABLE DYNAMIC SUPPORT OVER THE
HOLIDAYS.

THE FIRST SHORT WAVE IMPULSE STARTING OFF MON IS EJECTING OUT INTO
THE NRN/CENTRAL PLAINS...BUT QUICKLY LIFTS UP INTO ONTARIO BY TUE.
THE NEXT UPSTREAM IMPULSE IS ARRIVING INTO CA BY MON...MOVING
THROUGH THE GREAT BASIN AND LIFTING THROUGH THE CENTRAL PLAINS
INTO THE GREAT LAKES INTO MIDWEEK. ALSO BY TUE...A SIGNIFICANT
SHOT OF ARCTIC AIR AND FAVORABLE POST-FRONTAL UPSLOPE SNOW
GRADIENTS WILL SURGE SOUTH FROM CANADA INTO THE NRN
ROCKIES/PLAINS...CONTINUING ON OVER THE WEEK. AS THIS OCCURS...THE
LONGWAVE UPPER TROUGH AND WIDESPREAD UNSETTLED WINTERY CONDITIONS
INCLUDING TERRAIN ENHANCED SNOWS OVER THE WRN US SHOULD BE ON THE
MOVE AND GRADUALLY SLIDE INTO THE PLAINS/MS VALLEY MIDWEEK AND
INTO THE ERN THIRD OF THE COUNTRY INTO THU/FRI. THIS ALSO MEANS
THEN THE IMPRESSIVE SERN/MID-ATL RIDGE SHOULD BEGIN TO GRADUALLY
WEAKEN. FOLLOWING THE AMPLIFIED UPPER TROUGH OUT WEST WILL BE A
SIGNIFICANT INCREASE IN UPPER HEIGHTS AND A SOLID RIDGE BUILDING
BY THU/FRI AS A NEW UPSTREAM MID-UPPER LEVEL TROUGH AMPLIFIES OVER
THE NERN PACIFIC...TRANSITIONING FROM MORE BLOCKY FLOW.

OVERALL...MODEL AND ENSEMBLE SPREAD IN THIS PATTERN ALOFT HAS
BECOME LOWER THAN NORMAL SO FORECAST CONFIDENCE IS ABOVE NORMAL
WITH THE EVOLUTION OF THE MID-LARGER SCALE PATTERN.
HOWEVER...LOW-LEVEL COLD AIR SPECIFICS AND ASSOCIATED FRONTAL WAVE
DEVELOPMENT ARE OFTEN NOT WELL DEPICTED BY THE MODELS AS PER THE
TIGHT BAROCLINIC ZONES SO FORECAST CONFIDENCE IS TEMPERED TO SOME
DEGREE WITH THESE SENSIBLE WEATHER FOCUSING FEATURES. THIS HAS
ONLY BEEN MORE THE CASE AFTER SEEING VARIED 12 UTC MODEL GUIDANCE
SURFACE DEPICTIONS NEXT WEEK. ACCORDINGLY...HPC MEDIUM RANGE
GUIDANCE REMAINS PRIMARILY DERIVED FROM A 3-WAY BLEND OF THE 00
UTC ECMWF/GFS/GEFS IN AN EFFORT TO MAINTAIN CONTINUITY AMID
LINGERING UNCERTAINTY. THIS SOLUTION OFFERS REASONABLY SIMILAR
LARGER SCALE FLOW EVOLUTIONS AND A BLEND OF THEIR SMALLER SCALE
AND LOWER LEVEL FEATURES SEEM TO BEST MITIGATE LESS PREDICTABLE
DIFFERENCES.

MUSHER/SCHICHTEL

[wxman57]

Ed, you don't like dry cold? How about wet cold then? See the new GFS. Here's a meteogram. Temps falling into the 40s during the day Thanksgiving with a persistent light rain. Again, this is just the CURRENT GFS forecast, not necessarily my forecast. I'm not sure if the rain will materialize on Thursday or not, but I do think Thursday's high will occur at midnight Wednesday night, and temps during the day will fall into the 40s.

http://myweb.cableone.net/nolasue/iahgfs12znov19.gif

Cold and wet with thunder-sleet, like Thanksgiving 1993 when I was visiting the parents in the DFW area rocks. Cold rain is just cold rain.


I drove into a convective snow squall back Winter 84-85 near Albany when I was in the Navy. Mostly clear skies, and one big humungous TCU, with near blinding snow inside.

That rocked.

Don't get your hopes up for a 1993-type event. I had actually saved all the prog charts and surface analyses that I had done from Monday, Nov 22, 1993-Friday the 26th. This air is not nearly as cold as the airmass that came down in 1993. 850mb temps behind the front are forecast to be about 10C-15C warmer than 1993. Just 40s and light rain for us. Might have a shot at some sleet as far south as north or northeast Texas. But there may not be much moisture there.