February: Tracking Rain/Wintry Mix & Arctic Front

[wxman57]

I Made some graphics off my workstation using the 12z EC. Note that this forum doesn't seem to have the capability to thumbnail the images. To see Houston on the large-ish images you need to view each individual image separately. They go all the way to Louisiana.

First, 6am CST temps next Wed:

and next Thursday morning:

Projected snowfall Tuesday. The map is contoured for every 0.25" using a 10:1 ratio. Blue dots are major cities.

[wxman57]

Steve, you'll have to remind me how to "thumbnailerize" my images.

[srainhoutx]

Steve, you'll have to remind me how to "thumbnailerize" my images.

Save your images to your computer, which you did and use the upload attachment feature at the bottom left. Select your image for upload through the browse feature and Add the file. That resizes the images to a format that the entire image can be viewed.

[srainhoutx]

The afternoon Update from the Climate Prediction Center has shifted the cold air further West and also has some interesting Analogs that many longtimers may remember for our Region. There is that 1976 showing up again wxman57...

[wxman57]

OK, let's try that out. I attached a more zoomed-in image of lowest temps the EC is forecasting between midnight and 6am next Thursday.

[ticka1]

What happened in 1976? Was that the year where it snowed three times here in SE Texas?

[stonewall]

What happened in 1976? Was that the year where it snowed three times here in SE Texas?

1973 was the year it snowed in Houston three times. It snowed on Jan. 11th, Feb. 9th and Feb. 17th.
It seemed like it snowed about 2 to 3 inches on each of those days.

[Ptarmigan]

The afternoon Update from the Climate Prediction Center has shifted the cold air further West and also has some interesting Analogs that many longtimers may remember for our Region. There is that 1976 showing up again wxman57...

02112015 CPC Day 8+ Analogs 610analog_off.gif

02112015 CPC Day 6 to 10 Temps 610temp_new.gif

02112015 CPC Day 6 to 10 Precip 610prcp_new.gif

What happened in 1976? Was that the year where it snowed three times here in SE Texas?

There was a light freeze on February 7-8, 1976. Another freeze happened on February 22-24, 1976.

KIAH Record
2/7/1976 51/32
2/8/1976 68/31

2/22/1976 57/31
2/23/1976 71/27
2/24/1976 73/31

Not often you see highs of 70s with a freeze at night in Houston. Winter of 1975-1976 was La Nina.

[srainhoutx]

Evening briefing from Jeff:

Another extended streak of very mild days in early February…but this will all be ending by this time next week as a 1048mb arctic high crashes down the plains.

Not much to speak about in the short range (through the weekend). A weak cold front will cross the area Wednesday and knock temperatures back down to near or slightly above normal for this time of year. Moisture is extremely limited and do not expect any rainfall with this front. Lows will fall into the 40’s Thursday and Friday with highs in the lower 60’s. Highs return to the 60’s and 70’s over the weekend, but clouds also begin to increase. Rain chances look to return by Monday of next week as warm air advection increases moisture off the Gulf of Mexico and mid/high level moisture streams into the region from the southwest.

Upper air pattern of late that has been locked in place with cold arctic air aimed at the NE US with frequent winter storms and ridging over the SW US into the southern plains resulting in the dry and warm weather locally. This streak of mild and dry weather will end by early to mid next week as the ridge over the SW US repositions off the US west coast and amplifies into Alaska. A very cold air mass currently resides over NW Canada with temperatures in the -25F to -35F range. The west coast ridge punching into the Alaska will force a large downstream central US trough which will unleash a strong arctic high pressure cell out of NW Canada into the central plains early next week. Medium range models are in decent agreement on the developing upper air pattern which adds confidence that some fairly cold air will be heading southward by the middle of next week. Since we are still about 7 days out will not attempt to resolve low temperatures and just how cold it might get. Current guidance suggests sub-freezing temperatures are certainly possible all the way to the coast.

Other item of interest is a short wave which drops through the longwave trough and across TX in the Tuesday/Wednesday time period. Suspect cold arctic air mass will either be moving into the region or already in place as this shortwave moves across. Not sure at this point if there will be enough moisture to squeeze out any precipitation, but thermal profiles suggest a wintry mix would be possible over portions of the area if moisture is available.

[Ptarmigan]

Evening briefing from Jeff:

Another extended streak of very mild days in early February…but this will all be ending by this time next week as a 1048mb arctic high crashes down the plains.

Not much to speak about in the short range (through the weekend). A weak cold front will cross the area Wednesday and knock temperatures back down to near or slightly above normal for this time of year. Moisture is extremely limited and do not expect any rainfall with this front. Lows will fall into the 40’s Thursday and Friday with highs in the lower 60’s. Highs return to the 60’s and 70’s over the weekend, but clouds also begin to increase. Rain chances look to return by Monday of next week as warm air advection increases moisture off the Gulf of Mexico and mid/high level moisture streams into the region from the southwest.

Upper air pattern of late that has been locked in place with cold arctic air aimed at the NE US with frequent winter storms and ridging over the SW US into the southern plains resulting in the dry and warm weather locally. This streak of mild and dry weather will end by early to mid next week as the ridge over the SW US repositions off the US west coast and amplifies into Alaska. A very cold air mass currently resides over NW Canada with temperatures in the -25F to -35F range. The west coast ridge punching into the Alaska will force a large downstream central US trough which will unleash a strong arctic high pressure cell out of NW Canada into the central plains early next week. Medium range models are in decent agreement on the developing upper air pattern which adds confidence that some fairly cold air will be heading southward by the middle of next week. Since we are still about 7 days out will not attempt to resolve low temperatures and just how cold it might get. Current guidance suggests sub-freezing temperatures are certainly possible all the way to the coast.

Other item of interest is a short wave which drops through the longwave trough and across TX in the Tuesday/Wednesday time period. Suspect cold arctic air mass will either be moving into the region or already in place as this shortwave moves across. Not sure at this point if there will be enough moisture to squeeze out any precipitation, but thermal profiles suggest a wintry mix would be possible over portions of the area if moisture is available.

This could get interesting.............

[Heat Miser]

1973 was the year it snowed in Houston three times. It snowed on Jan. 11th, Feb. 9th and Feb. 17th.
It seemed like it snowed about 2 to 3 inches on each of those days.

Was but a little chap then living in a neighborhood near the Astrodome, but I remember it well. I remember how cold you'd get playing in the snow for just a few minutes and how soaked your clothes got.

[Paul Robison]

Is there a difference between a "wintry mix" and a full-fledge ice storm? Curious

Message for moderator: UPDATE:

Have seen latest GFS precip type run. 12Z keeps rain liquid over Houston w/snow (in blue; just snow) north of area. long way out, I know, but if model trend continues, the area should be spared your wintry mix.

[srainhoutx]

A dry cold front has arrived and temperatures today will be cooler than yesterday. The temperatures will be near normal for this time of year and some moderating is likely into the weekend before a backdoor front arrives Sunday.

The Major weather headliner will be the strong Arctic front arriving early next week. The overnight guidance continues to be at odds with the GFS being about 18 to 24 progressive ejecting the Baja Storm across Texas with limited light precipitation ending before the coldest air arrives. The European model is slower suggesting light QPF continues after the cold air arrives suggesting p-type issues and much colder air work in tandem creating wintry mischief across a large portion of the Lone Star State into Louisiana. There is a slight hint of a Coastal trough/low attempting to develop on Monday along the Lower Texas Coast, but great uncertainty continues in what the sensible weather may hold moisture wise. It does appear that we will get a significant late Winter cold shot and areas North of the Coastal set of Counties could see freezing temperatures Tuesday night into early Wednesday. Highs may struggle to reach the mid to upper 30's for highs on Wednesday. This is a complex and complicated forecast, so expect day to day changes as we get additional information. Typically these Baja upper lows create tremendous forecasting challenges and with potential phasing of a strong shortwave dropping S across the Great Basin/Southern Rockies, the uncertainty should continue into the weekend as the computer models attempt to resolve all the moving parts and what our sensible weather will actually be. It is noteworthy that the ensembles are further West with the shortwave trough than the operational GFS which is more inline with the European solution. Regardless, the string of Spring like weather appears to be coming to an abrupt halt reminding us that it is still February and Winter. The ensembles are in rather good agreement that temperatures will be around 2 Standard Deviations below normal Tuesday into Thursday next week.

The attachment 02122015 00Z GEFS gfs-ens_z500a_namer_23.png is no longer available

[srainhoutx]

55 Years ago today a nice snowstorm impacted SE Texas and Houston. I recently received some old photos from my Mom of me playing in the snow during that event. I guess I need to scan them and share what a real snowstorm looked like in the Houston Area...

[wxman57]

For now, I'm not expecting any snow across SE TX. Moisture looks quite limited once the cold air is in place. I'd look for lows in the mid to upper 20s Wednesday with highs near 40 then upper 20s on Thursday. Climbing back up near 70 by the weekend.

By the way, a "wintry mix" could be a few sleet pellets mixed in with the rain as it ends.

[BlueJay]

Sounds like we will need to be prepared to check on people, pamper pets, cover plants and protect pipes for this winter event. Grrr!

[srainhoutx]

The WPC Morning Update suggests early next week into Wednesday/Thursday may be very cold and unsettled. As the overnight ensembles suggested, the Western Upper Ridge looks to shift offshore of the West Coast allowing some very cold air to settle South across areas that have been very warm with near or record breaking warmth the past week. This very cold air is being pulled South into the Lower 48 due to a very strong upper low (Polar Vortex) developing across the Great Lakes into New England. The fly in the ointment will be what happens as the Upper Ridge builds North into Alaska producing a cross polar flow that sets up into the Great Basin/Inter Mountain West and the Great Plains on East. The ejection of Eastern Pacific moisture being pulled NE as a Upper Low near the Baja Peninsula begins its move E. What we do know today is that it is going to get cold and perhaps bring the coldest air of the Winter Season into our Region. What is not known is how quickly that Eastern Pacific moisture will arrive or how far South that moisture may spread E. As of today interest is growing that somewhere across our Region may experience winter precipitation in some form or fashion. If the cold shallow dense air travels South quickly as we typically experience, then attention turns to the potential for a bit more widespread Winter event that has the potential to extend well beyond our Region into the Eastern United States including the Northern Gulf Coast and the SE United States on up the Eastern Seaboard. There is a lot of potential for a major societal impact event beyond Texas and Louisiana, so it warrants our attention as the weekend nears and particularly early next week when the 'finer details' become a bit more certain. The 12Z GFS has a 1055+mb Arctic High dropping South out of Canada which is impressive by February standards.

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1042 AM EST THU FEB 12 2015

VALID 12Z SUN FEB 15 2015 - 12Z THU FEB 19 2015

...FRIGID ARCTIC BLASTS WITH STORMY WINTER WEATHER...

...GUIDANCE/UNCERTAINTY ASSESSMENT...

LATEST GUIDANCE CONTINUE TO OFFER BELOW NORMAL FORECAST SPREAD
INTO TUE/DAY 5. THIS LENDS PREFERENCE FOR A COMPOSITE BLEND OF
COMPATABLE 06 UTC GFS AND 00 UTC ECMWF/CANADIAN MODELS AS A
BASEMAP FOR WPC SURFACE FRONTS/PRESSURES AND 500 MB PROGS. THIS
BLEND OF DETERMINISTIC MODEL INPUT INCORPORATES MORE SMALLER SCALE
DETAIL THAN NORMAL AS CONSISTENT WITH PREDICTABILITY.

FORECAST SPREAD INCREASES ENOUGH INTO DAYS 6/7 TO INCREASE
UNCERTAINTY TO AT LEAST AVERAGE LEVELS SO BY THEN USED A MUCH MORE
ENSEMBLE MEAN BASED FORECAST APPROACH WITH A 30/70 MIX OF THE 00
UTC ECMWF/ECMWF ENSEMBLE MEAN. THESE REPRESENT SOLUTIONS ON THE
AMPLIFIED SIDE OF THE FULL ENVELOPE OF GUIDANCE. WATER VAPOR LOOPS
SHOW QUITE AN AMPLIFYING UPSTREAM RIDGE PATTERN ALONG/OFF THE NOAM
WEST COAST ALONG WITH POTENT/WELL SPACED ERN PACIFIC AND DATELINE
LOWS FEEDING INTO THAT RIDGE. THE ECMWF IS A STARK OUTLIER
AMPLIFIED SOLUTION THOUGH SO PREFER TO LIMIT INCLUSION GIVEN
UNCERTAINTY AT LONGER TIME FRAMES.

...PATTERN OVERVIEW AND SENSIBLE WEATHER HIGHLIGHTS...

A DANGEROUS AND HIGHLY AMPLIFIED NERN US/CANADIAN MARITIMES POLAR
VORTEX SUN-MON WILL USHER IN DEEP COLD AIR ACROSS THE CENTRAL AND
ERN US IN THE WAKE OF A DEEP NERN US COASTAL LOW AND TRAILING
FRONT. THIS OFFERS AN AMPLE STORM THREAT FOR NEW ENGLAND IN
PARTICULAR ALONG WITH A HUGE WIND/WAVE EVENT SPREAD WELL INTO THE
WRN ATLANTIC. THIS COLD ONSET AIR ALSO SETS THE STAGE FOR A LARGE
SCALE WINTER WEATHER THREAT EARLY-MID NEXT WEEK.

MEANWHILE...MODELS AND ENSEMBLES HAVE TRENDED/COME INTO BETTER
AGREEMENT TODAY IN SHOWING THE UPSTREAM WRN US RIDGE RETROGRESSION
AND STRONG AMPLIFICATION OFFSHORE AND UP TOWARD ALASKA INTO EARLY
NEXT WEEK IN RESPONSE TO UPSTREAM DEEP PACIFIC LOW DEVELOPMENTS.
THIS SHOULD ALLOW UNSETTLING TROUGH DIGGING ALOFT WITH LOWERING
HEIGHTS AND COOLING THROUGH THE WRN AND CENTRAL US INTO EARLY-MID
NEXT WEEK ALONG WITH A POTENT COLD SURFACE HIGH INFUSIONS. THIS
SUPPORTS AN EMERGING SW US AND S-CENTRAL GREAT BASIN/ROCKIES SNOW
THREAT AIDED BY TERRAIN/UPSLOPE FETCH.

WRN NOAM FLOW AMPLIFICATION ALSO LEADS TO AN INCREASINGLY
FAVORABLE GULF OF MEXICO MOISTURE/WAA RETURN FLOW PATTERN MON-WED
INTO/OVER AMBIENT AND SLOWLY RECEEDING LOWER LEVEL COLD AIR ACROSS
THE EAST-CENTRAL US DOWNSTREAM ALONG/AHEAD OF A WAVY COLD FRONT.
PENDING STREAM INTERACTION EFFECTS AND SWEATING THE IMPORTANT
SMALLER SCALE DETAILS...THIS OFFERS SOME PROLONGED HEAVIER PERIODS
OF SNOW AND DANGEROUS/TRANSITIONAL HEAVY ICING ACROSS A
POTENTIALLY LARGE THREAT AREA IN VICINITY FROM THE S-CENTRAL
PLAINS/MS VALLEY MON NEWD ACROSS THE E-CENTRAL US AND ERN/NERN US
ON THE NRN PERIPHERY OF THE EXPANDING OVERALL PCPN SHIELD. WPC
WEATHER/PCPN TYPE GRIDS OFFER A GRAPHICAL DEPICTION AND A MORE
AMPLIFIED DAY 6/7 WPC SCENARIO LEAVES THE DOOR MORE OPEN FOR
POSSIBLE TRAILING SURFACE FRONTAL WAVE DEVELOPMENTS THAT COULD ADD
CONVERGENCE/PCPN THREAT.

SCHICHTEL

[wxman57]

I see that the latest run of the GFS has lost the cold air as far as Texas is concerned. It's forecasting only a light freeze in Houston next Wednesday and a low near 40 on Thursday morning. This run looks a bit odd, so we'll have to wait for future runs to nail down next week's temps.

[Heat Miser]

Sounds like we will need to be prepared to check on people, pamper pets, cover plants and protect pipes for this winter event. Grrr!

I wouldn't go as far as wrapping the pipes.

[wxman57]

I agree that pipes are likely going to be just fine. It would really take a temperature into the teens to 20 to cause pipe issues - or a very prolonged period of temps 25-28F.