November 2014: Nice Seanonal Thanksgiving Ahead

[srainhoutx]

Interesting discussion regarding the Extended Range for the Weather Prediction Center and just how dramatic that Pacific Typhoon that transitioned to a extratropical low shuffled the entire pattern to near record breaking territory...

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1100 AM EST WED NOV 12 2014

VALID 12Z SAT NOV 15 2014 - 12Z WED NOV 19 2014

...NORTH AMERICAN 'COLD SNAP' CONTINUES THROUGH EARLY NEXT WEEK...

...OVERVIEW...
DE-AMPLIFICATION OF THE FLOW OVER THE LOWER 48 TAKES SHAPE ALONG
THE WEST COAST AND INTERMOUNTAIN WEST---EARLY NEXT WEEK...WITH
UNSEASONABLY COLD AIR DRAPED ACROSS NEARLY ALL OF THE CONUS---EAST
OF THE CONTINENTAL DIVIDE.

...UNCERTAINTY ASSESSMENT...
FASCINATING 'SHAKE-UP' OR 'RE-SHUFFLE' IN THE WESTERN HEMISPHERIC
CIRCULATION HIGH-LATITUDE FLOW PATTERN TAKING PLACE---STARTED IN
MOTION BY ENERGY AND MOISTURE ORIGINATING IN THE SOUTHWEST PACIFIC
(TROPICAL SYSTEM 'NURI'). THE ENTIRE AIRMASS HAS PUSHED NORTH OF
THE ARCTIC CIRCLE. BARROW ALASKA WAS WARMER EARLIER THIS MORNING
(UTC TIME) THAN AMARILLO TEXAS.

USING THE WPC TELECONNECTION TOOLS IS INTERESTING---THE POSITIVE
ANOMALY (UPPER-LEVEL HIGH) CENTERED OVER NORTHEAST ALASKA SUGGESTS
MAINTAINING A STEADY DRAW OF CANADIAN ARCTIC AIR INTO
MONTANA...WYOMING AND THE DAKOTAS---SIMILAR TO THE CURRENT
CONDITIONS---THROUGH THE DAY +8/+11 TIME FRAME. CONTRAST THIS TO
THE NEGATIVE ANOMALY---TELECONNECTING THE FORECAST CALLING FOR AN
UPPER-LEVEL LOW OVER SOUTHEAST HUDSON BAY. THE TELECONNECTION
SHIFTS THE ENTIRE COLD 'FOCUS' AT DAY +8/+11 TO THE
MIDWEST...GREAT LAKES AND SOUTHERN PLAINS---ESSENTIALLY THE ENTIRE
LANDMASS AREA EAST OF THE CONTINENTAL DIVIDE. SO THE QUESTION
IS---WHICH ANOMALY TO BASE THE FORECAST ON? OR EVEN BETTER---WHICH
TELECONNECTION IS MORE SIGNIFICANT AND 'UNUSUAL'?
THE UPPER-LEVEL RIDGE IS THERE NOW...AND THE UPPER-LEVEL LOW?
ANOTHER 36 HOURS AWAY AND HARD TO TELL TODAY WITH THE AIR
TEMPERATURES AHEAD OF THE FRONT---ALONG THE EAST COAST
TODAY---UNSEASONABLY MILD.

THE TEMPERATURE ANOMALIES RANGE FROM 5F TO 8F BELOW NORMAL---AND
HAVE THE DAKOTAS 'TARGETED' IN EITHER SCENARIO...WITH 2F-5F BELOW
NORMAL ALONG THE OUTER FRINGES OF THE SHALLOW AIRMASS.

...MODEL PREFERENCES...
THE 12/00Z ECENS/GEFS MEANS SEEM TO BE REACHING A MIDDLE
GROUND---CENTERED ON DAY 5---WITH THE CYCLONIC LOW-LEVEL FLOW
EMERGING OVER QUEBEC AND THE WEAK WARM ADVECTION/SPREAD OF ARCTIC
AIR SEQUENCING ACROSS NEW ENGLAND AND THE NORTHEAST. IN THE
WEST...THE 12/00Z GEFS/ECENS MEANS WERE A GENERAL COMPROMISE WITH
THE MARITIME FLOW REVERSAL SEQUENCE/THEME EMERGING AND THE
'DE-AMPLIFYING' PROCESS. IN GENERAL TERMS...THE TRAJECTORIES OF
THE CANADIAN SURFACE HIGHS ACROSS THE INTERIOR PORTION OF THE
NATION SEEM REASONABLE FOR AN ENSEMBLE MEAN SOLUTION AND BOTH
DETERMINISTIC RUNS HAVE SUBTLE BUT NOT UNUSUAL VARIATIONS---EVEN
INTO DAY 7.

THE DETERMINISTIC 12/00Z GFS/ECMWF SEEM TO HANDLE BOTH
ANOMALIES...WITH LITTLE EFFORT AND WERE REASONABLE GUIDES TO THE
'PERSISTENCE' OF THE NORTH AMERICAN AND LOWER 48 WEATHER PATTERN.
BOTH SHOW LITTLE CHANGE IN THE TRAJECTORY OF THE LOW-LEVEL
FLOW---ALLOWING THE CONTINENTAL POLAR/ARCTIC AIRMASS TO FAN OUT
ACROSS BOTH SIDES OF THE CONTINENTAL DIVIDE. WHERE THEY
DIFFER...IS ALONG BOTH COASTAL FRINGES---WITH THE TIMING OF
ONSHORE FLOW ALONG THE WEST COAST AND THE DEPTH/TRAJECTORY OF A
SURFACE WAVE GLIDING ALONG THE WESTERN ATLANTIC GULF STREAM. WITH
SO MUCH COLD BUT SHALLOW AIR IN PLACE...THE PATTERN SUGGESTS A
RELATIVELY-DRY WEATHER PATTERN NATIONWIDE. THE NEXT PARAGRAPH
HEADER DESCRIBES THESE SUBTLE VARIATIONS.

...SENSIBLE WEATHER HIGHLIGHTS...
LAKE-EFFECT SNOWS SHOULD PREVAIL ACROSS ALL FIVE GREAT LAKES
DURING MUCH OF THE PERIOD---THANKS TO BROAD CYCLONIC AND VERY COLD
LOW-LEVEL FLOW IN SOUTHEAST CANADA. SYSTEMS MIGRATING
SOUTHEASTWARD AND EASTWARD FROM THE UPPER MIDWEST TO THE OHIO
VALLEY AND ACROSS THE NORTHEAST SHOULD PRODUCE WIDESPREAD
RAIN/SNOW INVOF THE MOISTURE SOURCE...THOUGH THE VERY DRY AIRMASS
WILL LIMIT THE PRECIPITATION EFFICIENCY AND INTENSITY DOWNSTREAM
TO WINDWARD SLOPES AND LOCAL OROGRAPHIC FEATURES PERPENDICULAR TO
THE FLOW.

SHEETS OF CANADIAN ARCTIC AIR SHOULD CONTINUE PROVIDING A
REPLENISHMENT OF WELL-BELOW TEMPERATURES TO THE EASTERN HALF OF
THE NATION...RANGING FROM 10-25F BELOW AVERAGE FOR THE MIDWEST AND
PLAINS. THE AIRMASS AND TEMPERATURE CHANGE WILL LIKELY REACH THE
GULF COAST AND FLORIDA PENINSULA.

SECONDARY SURGE OF CANADIAN AIR MIGRATES WEST OF THE DIVIDE AND
INTO THE PACIFIC NORTHWEST-GREAT BASIN THIS WEEKEND AND THROUGH
MONDAY. THEN A SERIES OF MID-LEVEL WAVES WILL GRADUALLY REVERSE
THE LOW-LEVEL FLOW ALONG MUCH OF THE WEST COAST AND POINTS INLAND
AFTER DAY 6. UNTIL THEN...THE THREAT OF FREEZING DRIZZLE AND RAIN
REMAINS A FORECAST CONCERN---EAST OF THE CASCADES AND WITHIN THE
COLUMBIA RIVER BASIN. THE GENERAL FLOW PATTERN TAKES ON THE
APPEARANCE---OF A NEGATIVE-TILT TROUGH--TOWARDS THE END OF THE
FORECAST PERIOD WITH AN AIRMASS CHANGE (TO ONSHORE FLOW) MIGRATING
SOUTHWARD INTO CALIFORNIA AND THE SIERRA-SISKIYOU MOUNTAIN COMPLEX.

VOJTESAK

[ticka1]

Being that Thanksgiving will be two weeks away from tomorrow - any early hints of what the weather will be like that week through the weekend (end of November)?

[wxman57]

Being that Thanksgiving will be two weeks away from tomorrow - any early hints of what the weather will be like that week through the weekend (end of November)?

Latest GFS run has another moderate cold front moving through Tuesday evening of Thanksgiving week. Sunny & cold for Thanksgiving. Maybe lows in the mid to lower 30s and highs in the 50s.

[snowman65]

Sounds like a perfect Thanksgiving forecast to me...

[srainhoutx]

Latest Euro run suggest we may see a bit colder temperatures early next week than we may see early Friday morning with this second surge of Arctic Air. I believe wxman57 has access to the higher resolution Euro. Perhaps he can give us a clue just how cold it may get.

[snowman65]

TWC is already showing that in the forecast for Golden Triangle area.

[Andrew]

Euro is showing temps down to mid to upper 20s across the northern counties with coldest temps over the northeastern counties as usual. The immediate Houston metro area gets down to the freezing mark with coastal counties a degree or two warmer.

Edit to add that this is for next Monday and Tuesday.

[jasons2k]

Well, a couple of days ago I checked the Euro for Friday AM and it had 39 at IAH. We all know now that's gonna be wrong so take it with a grain of salt.

[srainhoutx]

Some very impressive analog years showing up in the updated Climate Prediction Center Day 8+ Analogs.

[Texaspirate11]

Just putting my 2 cents in, I hate winter. Bah.

[Andrew]

Well, a couple of days ago I checked the Euro for Friday AM and it had 39 at IAH. We all know now that's gonna be wrong so take it with a grain of salt.

Yea a lot of the models (especially global) are having issues with the location and movement of the shortwave over the four corners region. As a result location of the high pressure and associated cold air has been off in many locations. I do suspect it will be hard to get a freeze across much of the area overnight tonight or tomorrow as cloud cover is becoming more apparent.

http://www.ssd.noaa.gov/goes/east/sc/mflash-vis.html

[BlueJay]

That is great news Andrew! I hope the cloud cover keeps those temperatures above freezing until at least February 2015.

[Andrew]

Keep an eye out, moisture is tracking further inland than previously predicted. Looks like those in Harris County and points South could see some light rain.

[srainhoutx]

37F and Very cold rain in NW Harris County at this time.

[unome]

yup, rain & wind chimes woke me up

http://www.wrh.noaa.gov/mesowest/gmap.p ... &density=2

[Katdaddy]

A weak shortwave provided a large area of light to moderate rains overnight which are now moving out of SE TX and into LA. Areas to the SW of Houston picked up .25-50". Temps are currently running in the mid to upper 30s across SE TX and low 40s along the immediate coast. Wind chills are very cold running in the mid to upper 20s. Temps will remain in the 40s today across SE TX with our first widespread freeze tonight. Freeze Warnings for a all but the coastal counties which are currently under a Freeze Watch. The coastal Freeze Watches will likely be upgraded to a Freeze Warnings later today. Do not forget the pipes, plants, or pets.

[ticka1]

35 degrees and light rain...winter has arrived

[srainhoutx]

The coldest morning of the Fall season is in progress across SE Texas. Temperatures have fallen rather dramatically with the over night rain and is currently in the mid to upper 30's except right along the Coast where it is hovering around 40. Isolated sleet has fallen overnight across portions of the Hill Country and N Texas while light snow is falling across the Panhandle into Kansas and Oklahoma. The upper air disturbance in association with an Eastern Pacific tropical disturbance that moved inland and crossed Mexico is responsible for the overnight moisture. Later today the Arctic High that ushered in all this cold weather will settle into Texas. Today will be a raw cold day across Texas. Skies may clear later today and winds relax allowing for ideal radiational cooling that will set the stage for freezing temperatures. Areas mainly along and N of I-10 may see freezing temperatures for about 10 hours. Closer to the Coast, freezing temps are possible for 3-5 hours.

Friday afternoon will begin a very short moderation period into Saturday as a Coastal Low develops near the Middle Texas Coast and the high pressure responsible for the cold air slides off to the E. The upper air pattern remain well in tack, so this very brief reprieve will not last. Saturday afternoon/night as the Coastal Low develops and yet another disturbance arrives from the Pacific NW elevated rain chances begin. There is a chance that a warm front may attempt to develop along the Coast and thunderstorms may be possible S of that boundary. Moisture will increase as uplift from the inbound upper air disturbance and the Coastal Low matures Saturday night, to very wet conditions are likely. To our N across Canada, a powerful upper low/trough is dropping S and will enter Montana Saturday night ushering in another Arctic Blast into the Plains. A strong cold front will follow the Coastal low and upper air feature as they move E of Sunday.

The next in a series of upper air disturbances will move inland across California and rapidly progress E along the base of the deep trough Sunday night. The cold Arctic air will have already arrived setting the stage for a Winter Weather potential across the Southern/Central Plains and at least the northern half of Texas. Precipitation amounts are expected to be light with this disturbance, but there is some disagreement with the guidance as to the strength of the disturbance. As we witnessed overnight, the computer models are having a very difficult time with this unusual pattern and the magnitude of the cold air. Monday night may bring even colder air than tonight with a more prolonged period of below freezing temperatures if the GFS solutions are correct with a slower moving disturbance Sunday night into Monday morning. Stay Warm. Things look to finally begin to moderate by mid to late next week.

[ticka1]

Email from Jeff Lindner Thursday Morning 11/13/2014:

***Freeze Warning in effect for tonight and Friday morning for all SE TX counties except along the immediate coast***

***Freeze Watch in effect for the coastal counties will likely be upgraded to a freeze warning this afternoon.***

A couple degrees away from a big mess this morning with the light to moderate rain falling into a very cold surface layer with temperature hovering in the 34 to 38 degree range. Short wave responsible for the large area of rain overnight is quickly moving eastward with back edge of the light rain along US 59 currently. Should see all precipitation end by 900am for most areas. Clouds will remain most of the day and with strong cold air advection continuing there will be very little temperature recovery today. Highs in the mid 40’s look reasonable for most areas.

Upstream air mass is bitter cold with Denver currently at -11 and Casper at -15 which is breaking 70 year old records this morning. Amarillo has fallen to 14 this morning after a high on Wednesday of only 21. To give an idea of just how impressive this arctic outbreak has been: Borger, TX had a record high of 85 on Monday ahead of the front and recorded a record low of 15 degrees yesterday morning which equates to a 70 degree temperature change in a little over 24 hours.

Tonight/Friday morning:
Very cold arctic air mass with large arctic high over the plains will continue to build into TX. Shortwave exiting to the east will allow skies to clear late this afternoon and with low dewpoints in place and winds decreasing a widespread killing freeze is likely over much of SE TX Friday morning. Expected morning lows for Friday morning:

N of HWY 105: 25-28
N of US 59: 29-32
Inside Beltway 8: 30-32
Interior coastal counties: 30-33
Immediate coast: 35-38

Duration of sub-freezing temperatures will be on average 8-12 hours north of I-10 and 4-8 hours elsewhere across the region where the temperatures fall to freezing.

Temperatures of this magnitude will effectively end the growing season and result in damage to sensitive vegetation and citrus that is not protected. Exposed outside pipes should be protected, but do not expect any big concerns with damage to pipes as we are currently not looking at a prolonged hard freeze.

Weekend:
Strong short wave moves across TX Saturday and Saturday night forcing a coastal trough over the lower TX coast that moves northward on Saturday. Moisture rapidly increases over the surface cold dome resulting in increasing rain chances. Clouds will begin to increase from SW to NE Saturday morning with showers developing by mid to late afternoon. Warm front will approach the coastal counties and may move inland Saturday evening and Saturday night with a heavy rainfall and strong thunderstorm threat along and south of US 59. Coastal low heads for SW LA early Sunday with another dump of very cold arctic air into the region and off the coast. Temperatures will be tricky on Saturday as strong warm air advection tries to erode the arctic dome in place. Models are usually too aggressive in eroding shallow cold arctic air and hence tend to be too warm in treating arctic air mass situations. Additionally the increasing clouds and rain will help to hold down the warning to advective processes only. The exception will be near the coast where the warm front may move inland allowing a warm humid air mass to push onshore. Could be a fairly significant temperature gradient across the area Saturday evening with near 70 at the coast to the 40’s inland. As the coastal low moves east on Sunday the next dump of arctic air will keep temperatures steady or falling into the 40’s during the day.


Models want to bring another disturbance across TX in the cold air Sunday night into Monday with winter precipitation across the northern portions of the state. Not sure how much moisture will be available by Sunday night into Monday as the upstream air mass is very dry, but this is something to keep an eye on over the next 48 hours.

Next cold air surge looks to be even colder than the current one with widespread freezing temperatures possible by next Tuesday morning. Guidance is already showing lows into the 20’s by the middle of next week and this far out is usually too warm.

[ticka1]

Being that Thanksgiving will be two weeks away from tomorrow - any early hints of what the weather will be like that week through the weekend (end of November)?

Latest GFS run has another moderate cold front moving through Tuesday evening of Thanksgiving week. Sunny & cold for Thanksgiving. Maybe lows in the mid to lower 30s and highs in the 50s.

Thanks wxman57 for the reply - love the cooler okay cold weather for Thanksgiving!