November Weather Discussion. Rollercoaster Pattern.

[srainhoutx]

Midland/Odessa chimes in...

WEDNESDAY WE WILL SEE A COLD FRONT DURING THE MORNING HOURS. COOLER
HIGHS ARE EXPECTED THAT AFTERNOON...AND COOLER LOW TEMPERATURES WILL
FOLLOW THURSDAY MORNING. THERE ARE INDICATIONS THAT AND ARCTIC AIR
MASS WILL BEGIN TO MAKE ITS WAY INTO THE CENTRAL UNITED STATES NEXT
WEEKEND.



As well as Dallas/Ft Worth...

LOOKING AHEAD BEYOND THE FORECAST PERIOD...MODELS CONTINUE TO SHOW
A CHANGE IN THE UPPER PATTERN THAT WOULD BE FAVORABLE FOR OUR
FIRST MAJOR COLD OUTBREAK OF THE SEASON THE WEEK OF THANKSGIVING.
PLENTY OF TIME FOR THIS TO CHANGE...BUT SOMETHING TO WATCH OVER
THE NEXT WEEK.

[Mr. T]

Looks like a possible icy scenario setting up for some across the Midwest.

It'll be interesting to see how much of that cold air can bleed down this way. It'll be a shallow front, so models will probably handle this poorly, per the usual

We'll probably see a huge warmup ahead of the front judging by how much heights really build and turn parallel to the front before any potential arctic airmasses begin to bleed this way.

La Nina ahoy

[Andrew]

GFS still continues to show a cold one for Thanksgiving:



GFS still seems to be having trouble with the setup though. It seems like the ridge breaks down way to fast and doesn't make its way south but being 250+ hours away this is to be expected. Looks like it will actually feel like the holidays.

[snowman65]

GFS still continues to show a cold one for Thanksgiving:

Andrew, what is that depicting for Central/Eastern Tennessee? That's where I will be for the entire week of Thanksgiving...

[srainhoutx]

00Z NAM suggests some light showers across the Houston area with heavier rains to our E and offshore, for what it's worth...

[Andrew]

GFS still continues to show a cold one for Thanksgiving:

Andrew, what is that depicting for Central/Eastern Tennessee? That's where I will be for the entire week of Thanksgiving...

Well that picture above showed the possibility of some freezing precip in Tennessee, but this far out it is all just speculation. What I do know is that it will be real cold there.

[srainhoutx]

Looks like a wet afternoon around the area. Regarding the Arctic Front. The models have flip flopped again and now suggest the coldest air will stay to our N and W arriving after Thanksgiving Day. With that said, past experience tells us that models do not handle shallow cold airmasses well at this range and there may well be a switch back in a day or so. We will see...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
359 AM CST SUN NOV 14 2010

.DISCUSSION...
FRONT NOW SITUATED FROM ROUGHLY NEW ORLEANS TO JUST OFF THE LOWER
TX COAST. EXPECT A SFC WAVE TO DEVELOP ALONG THE BOUNDARY TODAY AND
MOVE NEWD UP THE COAST TONIGHT. AS THIS OCCURS ISENTROPIC LIFT
WILL ALLOW CLOUDS TO THICKEN THRU THE DAY (BUT STILL ANTICIPATE
SOME BREAKS ACROSS N/NE AREAS) AND RAIN CHANCES TO INCREASE.
GENERALLY KEPT THE ONGOING FCST THINKING BUT DID SHIFT POPS BACK
IN TIME...MORE IN LINE WITH WHAT NAM12 HAS BEEN ADVERTISING FOR
THE PAST 24 HOURS. LOCATIONS OUT TOWARD MATAGORDA BAY MAY SEE SOME
POCKETS OF -RA DEVELOP LATER THIS AFTN...THEN INCREASE IN AREAL
COVERAGE ACROSS THE SERN 2/3 OF THE CWA OVERNIGHT. IN THE UPPER
LEVELS...FAVORABLE JET POSITION AND WEAK S/W ACTIVITY MOVING WWD
ACROSS THE AREA SHOULD AID IN OVERALL LIFT. BULK OF INLAND
RAINFALL SHOULD PUSH EAST MON MORNING WITH THE SFC LOW/WAVE...BUT
STILL EXPECT SOME ISO/SCT ACTIVITY THRU THE DAY WITH OVERRUNNING
MOISTURE CONTINUING. BROAD LOW OVER THE CNTRL US SHOULD DIG SWD
INTO CNTL TX MON & MON NIGHT AS STRONG JET & S/W ENERGY DIVES SWD
THRU THE ROCKIES. MODELS ARE STILL SHOWING AN IMPRESSIVE VORT
ROUNDING THE BASE OF THE TROF AND PUSHING OVERHEAD MON NIGHT.
NUDGED POPS UPWARDS INTO THE CHC CATEGORY ACROSS NRN PARTS OF THE
REGION DURING THIS TIME PERIOD. DRIER WX IS THEN EXPECTED TUES AS
THE TROF AXIS PUSHES OFF TO THE EAST. THE NEXT COLD FRONT SHOULD
ARRIVE WED EVNG BUT SHOULD BE MOISTURE STARVED. EXTENDED FCST
SHOULD REMAIN MOSTLY DRY. SHOULD SEE A NEARLY ZONAL PATTERN ALOFT.
OFFSHORE FLOW IN THE WAKE OF THE FRONT SHOULD TRANSITION TO
ONSHORE ON FRI AS SFC HIGH MOVES EAST. WARMING TEMPS GOING INTO
NEXT WEEKEND. AT THIS POINT IT APPEARS CHCS OF RAIN WILL HOLD OFF
UNTIL THE FOLLOWING WORK WEEK AS MOISTURE GRADUALLY INCREASES. 47

[wxman57]

Well, this is really great weather - NOT! Give me a sunny drought any day. Went riding yesterday afternoon at 4pm and got back at 6:30pm. Felt like my face had frostbite. Next time I wear my neoprene ski mask when I ride with temps in the 50s. I long for July warmth (or at least the mid 80s of a few weeks ago).

Could see a few 80 deg days early next week ahead of the front. Front appears to arrive late Wed or early Thu (Thanksgiving). Looks like a strong one. Line of storms ahead of the front and sharply colder behind it. No risk of anything frozen. Rain ends as cold air arrives. Could knock our Thanksgiving highs down to around 50 with lows following of mid 30s.

[srainhoutx]

Well, this is really great weather - NOT! Give me a sunny drought any day. Went riding yesterday afternoon at 4pm and got back at 6:30pm. Felt like my face had frostbite. Next time I wear my neoprene ski mask when I ride with temps in the 50s. I long for July warmth (or at least the mid 80s of a few weeks ago).

Could see a few 80 deg days early next week ahead of the front. Front appears to arrive late Wed or early Thu (Thanksgiving). Looks like a strong one. Line of storms ahead of the front and sharply colder behind it. No risk of anything frozen. Rain ends as cold air arrives. Could knock our Thanksgiving highs down to around 50 with lows following of mid 30s.

Yep. The 12Z GFS suggests late Wednesday for FROPA...

[wxman57]

Couldn't get to the forum for a few hours, but it's back now. Here's a meteogram I made from the 12Z GFS extended run. It's for IAH. Note that the only temps plotted are 12Z and 00Z (6am and 6pm), so the lower temps on the trace are fairly close to the morning lows, but the 6pm temps are about 4 hours past the afternoon high. May have to add 5-7 degrees to the 00Z temps for the afternoon high. Shows near freezing conditions right after Thanksgiving with highs in the 50 deg range:

[srainhoutx]

Interesting pattern on the 500mb 12Z Euro. A mighty deep trough portrayed by that model at hour 240. What is different though, where there was a big N Pacific ridge (omega block) is no longer showing up via this model. Interesting...Edit to add the HPC Final Update...

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
226 PM EST SUN NOV 14 2010

VALID 12Z WED NOV 17 2010 - 12Z SUN NOV 21 2010


FINAL PROGS CONTINUED THIS MORNINGS UPDATED BLEND OF 40% ECMWF
MEAN AND 30% EACH OF THE DETERMINISTIC 00Z GFS/ECMWF. THE 00Z/14
ECENS MEAN HAD BEEN SUBSTITUTED FOR THE OLDER 12Z/13 MEAN IN THE
EARLY PRELIM BLEND THU-SAT DAYS 5-7. THE NEW 00Z/14 ECENS MEAN WAS
IN LINE WITH MOST OTHER 00Z/14 MODEL AND ENSEMBLE GUIDANCE IN
KEEPING A SHARP TROF DESCENDING SSE FROM 50N/140W WED DAY 3 TO OFF
THE PACIFIC NW COAST FRI DAY 5. THE 12Z ECMWF MEAN LOOKED TOO
ROUNDED OFF WITH THE TROF OFF THE W COAST OF CANADA.

ANOMALOUSLY STRONG 500MB RIDGING OVER SOUTHWESTERN/SOUTH-CENTRAL
ALASKA LATER IN THE WEEK TELECONNECTS TO A DEEPENING TROF OVER THE
WESTERN COAST OF THE US. AFTER AN INITIAL SYSTEM CLEARS THE EAST
COAST WED/DAY 3...WEAK LONGWAVE RIDGING WILL ENSUE THERE BY NEXT
WEEKEND DOWNSTREAM OF THE WESTERN TROUGH. MODERATE SPREAD EXISTS
IN THE ENSEMBLES OVER THE WEST...BUT GOOD AGREEMENT BETWEEN THE
OPERATIONAL 00Z/14 ECMWF/GFS SUGGESTS A BIT HIGHER CONFIDENCE
THAN OTHERWISE MIGHT BE WARRANTED.

12Z MODELS: THE MODELS OVERALL HAVE TRENDED W WITH THE TRACK OF
FIRST SIGNIFICANT SYS AFFECTING THE E COAST AND APPALACHIANS DAY
3. THE NEW UKMET IS A REASONABLE COMPROMISE IN THIS AREA BETWEEN
THE FAR WRN SOLUTION OF THE CANADIAN AND THE FLAT SOLUTION OF THE
NAM....AND FINAL MANUAL PROGS WERE ADJUSTED ACCORDINGLY. SOME
MODERATE TO HEAVY QPF WILL ACCOMPANY THE SYS. THE FOLLOWING
SHORTWAVE TROF MOVES ACROSS THE SERN QUARTER OF THE NATION A DAY
LATER WITH WITH LITTLE FANFARE.

THE NEXT POINT OF INTEREST CONCERNS THE DEEP TROF OR CLOSED LOW
THAT WILL BE DEVELOPING DAYS 3-4 NEAR THE COAST OF BRITISH
COLUMBIA IN RESPONSE TO THE VERY STRONG BLOCKING HIGH FORMING OVER
THE ALEUTIANS. THRU DAY 4...MODEL CONSENSUS IS QUITE GOOD
CONCERNING THE EVOLUTION OF THE FIRST SYS DEVELOPING DOWNSTREAM OF
THE ALEUTIAN BLOCK. SOME SHEARING OF THE LOW OCCURS ACROSS SWRN
CANADA A DAY LATER...WITH THE BULK OF ENERGY REMAINING OFFSHORE.
THEN THE TROF RE-LOADS SAT DAY 6 FROM BRITISH COLUMBIA TO
OFFSHORE NRN CA.

BY DAY 7...A FAIR AMOUNT OF SPREAD EXISTS IN THE LATITUDE OF THE
MOST INTENSE PORTION OF THIS UPPER TROF...RANGING FROM OREGON IN
THE UKMET TO OFF THE CA COAST IN THE CANADIAN. THE DAY 7 UKMET
VORT MAX OVER WRN OREGON WAS ESTIMATED GIVEN ITS DAY 6 DIGGING
BEHINDS ITS BRITISH COLUMBIA CENTER. THE 00Z/14 ECENS MEAN WAS
STILL A COMFORTABLE FIT HERE BETWEEN THE NEW 12Z CANADIAN...A SWRN
OUTLIER...AND THE NEW UKMET. AS THE MAIN WRN TROF SUNKS SLOWLY SSE
ALONG THE W COAST...FREQUENT OROGRAPHIC PCPN WILL TEND TO WORK
FARTHER S IN CA...FALLING AS SN AT HIGHER ELEVATIONS. THE NEW
12Z/14 ECMWF IS FAIRLY WELL BEHAVED COMPARED TO CONSENSUS OVER THE
CONUS THRU THE MEDIUM RANGE....BUT IS A BIT N OF CONSENSUS WITH
THE STRONGEST VORT NEAR THE NRN CA COAST ON DAY 7.

FLOOD

[srainhoutx]

Afternoon AFD's are being issued...

Midland/Odessa...

THERE ARE INDICATIONS
THAT AND ARCTIC AIR MASS WILL BEGIN TO MAKE ITS WAY INTO THE CENTRAL
UNITED STATES NEXT WEEKEND...AND PERHAPS REACH THE AREA BY MID NEXT
WEEK.



Dallas Ft/Worth...after cancelling the pattern change this morning, the forecaster is somewhat interested...

STILL APPEARS THAT THE A PATTERN SHIFT MAY ALLOW FOR SOME OF THE
COLDER AIR TO ARRIVE JUST IN TIME FOR THE THANKSGIVING HOLIDAY.

[srainhoutx]

This is one of the best discussions from a local WFO I have seen in a long time regarding all the players and the effects felt downstream...

Dodge City, KS...

DAYS 3-7...

TROPICAL THUNDERSTORMS REMAIN ACTIVE IN THE INDIAN OCEAN, BUT
ACTIVITY HAS DECREASED IN THE MARITIME CONTINENT IN RECENT DAYS.
ATMOSPHERIC RELATIVE ANGULAR MOMENTUM HAS DECREASED TO NEARLY TWO
STANDARD DEVIATIONS BELOW CLIMATOLOGY, AND TENDENCIES STILL ARE
NEGATIVE. HOWEVER, MOUNTAIN TORQUE HAS BEGUN TO INCREASE LARGELY DUE
TO A POSITIVE CONTRIBUTION FROM THE ANDES IN SOUTH AMERICA. THE
WHEELER-HENDON MJO PHASE SPACE DIAGRAM SUGGESTS THAT THE REMNANTS OF
A MJO OSCILLATION MAY BE PROGRESSING RAPIDLY EASTWARD ACROSS THE
WESTERN HEMISPHERE. THIS FEATURE LIKELY WILL ENHANCE CONVECTION IN
THE INDIAN OCEAN LATE THIS WEEK INTO NEXT WEEK. THE ATMOSPHERE
APPEARS TO BE OSCILLATING THROUGH PHASE 1-2 TOWARD PHASE 3-4 OF THE
BERRY/WEICKMANN GLOBAL WIND OSCILLATION. PHASES 3 AND 4 FAVOR
RIDGING IN THE WESTERN UNITED STATES AND UPPER LEVEL HIGH PRESSURE
AROUND 160W WITH A MEAN TROUGH IN THE EASTERN PACIFIC.

THE NUMERICAL MODELS TODAY ARE IN GOOD AGREEMENT ON THE EVOLUTION OF
THE LARGE SCALE FLOW THROUGH LATE NOVEMBER. THE UPPER LEVEL RIDGE
NEAR 135-140W WILL BUILD INTO THE WESTERN UNITED STATES WHILE A
SHARP UPPER LEVEL RIDGE BUILDS AROUND 160W BY 18 NOVEMBER. A SLOWLY
PROGRESSIVE LONG WAVE PATTERN SUPPORTS PROGRESSION OF A LONG WAVE
TROUGH TO THE CENTRAL PLAINS BY 22-23 NOVEMBER. A LOBE OF THE POLAR
VORTEX WILL DEEPEN IN CENTRAL CANADA BY THE WEEKEND, AND A STRONG
TROUGH ROTATING AROUND THE VORTEX WILL MOVE ACROSS SOUTHERN CANADA
22-23 NOVEMBER. THIS WILL OPEN THE DOOR FOR AN INVASION OF
SHALLOW ARCTIC AIR IN THE CENTRAL UNITED STATES AROUND 22
NOVEMBER, ALTHOUGH CONFIDENCE IN SYNOPTIC SCALE DETAILS THAT FAR OUT
IS LOW. THE ECMWF IS MORE PROGRESSIVE WITH THE CENTRAL UNITED STATES
TROUGH THAN THE GFS AND PROBABLY IS MORE REASONABLE.

IN THE DAY 4-7 PERIOD, THE NUMERICAL MODELS AGREE REMARKABLY WELL.
THE STRONG UPPER LEVEL TROUGH NEAR 165W WILL PROPAGATE OVER THE
WEAKENING EASTERN PACIFIC RIDGE AND MOVE ACROSS THE CENTRAL PLAINS
TUESDAY NIGHT AND WEDNESDAY MORNING. LOW LEVEL OFFSHORE FLOW WILL
CONTINUE ALONG THE GULF COAST THROUGH WEDNESDAY, AND LOW LEVEL
MOISTURE WILL BE EXTREMELY LIMITED IN THE CENTRAL PLAINS AS THE
UPPER LEVEL TROUGH RIPPLES THROUGH THE FLOW. INSTABILITY WITH THE
UPPER LEVEL COLD POOL AND UPPER LEVEL DIVERGENCE IN THE EXIT REGION
OF THE JET STREAK MAY BE SUFFICIENT TO SUPPORT LIGHT PRECIPITATION
IN NORTHERN KANSAS AND SOUTHERN NEBRASKA LATE TUESDAY NIGHT AND
EARLY WEDNESDAY, BUT THE POTENTIAL FOR MEASURABLE PRECIPITATION IS
VERY LOW SOUTH OF INTERSTATE 70. TEMPERATURES IN THE LOWER LEVELS OF
THE ATMOSPHERE WILL BE WARM ENOUGH THAT PRECIPITATION SHOULD FALL IN
LIQUID FORM.

AS THE LONG WAVE TROUGH DEEPENS IN THE EASTERN PACIFIC LATE THIS
WEEK, INCREASING FLOW PERPENDICULAR TO THE ROCKIES WILL SUPPORT
STRONG TROUGHING IN THE LEE OF THE MOUNTAINS THURSDAY AND FRIDAY.
TEMPERATURES SHOULD WARM BACK INTO THE 60S NEAR THE COLORADO BORDER
THURSDAY, AND HIGHS NEAR 70 CAN BE EXPECTED IN FAR WESTERN KANSAS
FRIDAY. DEWPOINTS WILL BE IN THE 20S IN MOST AREAS, AND RELATIVE
HUMIDITIES WILL APPROACH RED FLAG CRITERIA BOTH THURSDAY AND FRIDAY.
AN UPPER LEVEL TROUGH WILL MOVE THROUGH SOUTHERN CANADA TO THE GREAT
LAKES BY SATURDAY MORNING, AND A SHALLOW SURGE OF COOL AIR WILL WORK
ACROSS KANSAS FRIDAY NIGHT. THERE WILL BE A SUBSTANTIAL TEMPERATURE
GRADIENT IN WESTERN KANSAS SATURDAY WITH TEMPERATURES IN THE UPPER
60S AND LOWER 70S WHERE THE SHALLOW COLD AIR MIXES OUT AND NEARLY 20
DEGREES COOLER NORTH OF THE BOUNDARY. ANOTHER UPPER LEVEL TROUGH
WILL MOVE FROM THE SOUTHWESTERN UNITED STATES TO THE NORTHERN PLAINS
SUNDAY. THE SHALLOW COLD AIR WILL RETREAT NORTHWARD SATURDAY NIGHT
AND MAKE ANOTHER SURGE SOUTHWARD ON SUNDAY. CONFIDENCE IN THE
STRENGTH AND TIMING OF THE TROUGHS RIPPLING THROUGH THE STRONG
SOUTHWEST UPPER LEVEL FLOW IS NOT HIGH, AND THE PRESENCE OF A SHARP
LOW LEVEL BAROCLINIC ZONE WALLOWING BACK AND FORTH IN KANSAS MAKES
TEMPERATURE FORECASTS HIGHLY SUSCEPTIBLE TO SIGNIFICANT ERRORS
DURING THE WEEKEND. THE ECMWF SEEMS TO HAVE A TENDENCY TO SCOUR OUT
SHALLOW COOL AIR TOO QUICKLY, AND THE GFS LARGELY WAS USED AS A
FIRST GUESS ON FRONTAL POSITIONS SATURDAY AND SUNDAY.

[Ptarmigan]

Whatever happens on the other side of the world can impact us.

[weatherguy425]

Interesting fin regarding potential colder air...

http://stormtopia.com/US-outlooks.php

[Mr. T]

18z GFS has a fairly strong cold front through here just in time for the Turkey Day

[srainhoutx]

Finally some rain on my yard!

[Mr. T]

I wonder if that NWS met in Kansas is "HM", the pro-met at the former Eastern Wx site. He talks mountain torques and GLAAM.

HM works for a private company, not the NWS

[srainhoutx]

Interesting disco from HGX this evening. I wondered if we were seeing some elevated storm in Western Harris County earlier...

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
808 PM CST SUN NOV 14 2010

.DISCUSSION...
EARLY THIS EVENING...LOW PRESSURE LOCATED ALONG A SURFACE FRONT
LOCATED JUST OFF THE COAST AND ISENTROPIC LIFT WAS COMBINING WITH
A STRONG JET ALOFT TO PRODUCE AREAS OF LIGHT RAIN. THE SURFACE
TEMPERATURE/DEW POINT SPREAD WAS AROUND 10 DEGREES EARLIER THIS
EVENING. WHEN THE RAIN AREAS FIRST DEVELOPED DURING THE LATE
AFTERNOON...THERE WAS A REPORT OF PEA SIZE HAIL IN WESTERN HARRIS
COUNTY. THIS LOOKED TO BE CAUSED BY ELEVATED SHALLOW CONVECTION
OCCURRING ABOVE THE DRY LAYER AND A "WET BULBING" PROCESS BETWEEN
900 AND 950 MB. DEW POINTS IN THIS LAYER WERE WELL BELOW -10
DEGREES CELSIUS DURING THE LATE AFTERNOON. THE MODEL FORECAST
SOUNDINGS INDICATE THAT THIS SHALLOW DRY LAYER WILL MOISTEN
QUICKLY THIS EVENING AND DO NOT EXPECT ANY OTHER REPORTS OF SMALL
ICE PELLETS.

DO EXPECT THE SURFACE LOW PRESSURE LOCATED ALONG THE FRONT JUST
OFF THE MID TEXAS COAST TO STRENGTHEN TONIGHT. AS THE LOW PRESSURE
MOVES UP THE COAST...THE RAIN AREA WILL BECOME MORE WIDESPREAD
ACROSS SE TX. ALSO EXPECT ISOLATED ELEVATED THUNDERSTORMS.

UPDATED THE FORECAST TO INCLUDE ISOLATED THUNDER FOR TONIGHT.

[srainhoutx]

Good morning. Looks like another batch of rain is heading in with a shortwave currently near Lubbock heading ESE. The Arctic Front is still on the table as well. The overnight guidance has come into better agreement bringing the front into our area late Tuesday/early Wednesday of next week. One fly in the ointment is a coastal low in Deep S TX now showing up that could bring a chilly over running rain event during the day on Wednesday (24th). Stay tuned. The change to a colder pattern looks to continue beyond that in an active flow pattern.