Southern Plains winter wx thread (2008-2009)

[srainhoutx]

Calgary's warm-up is due to the chinook winds....map below shows where chinook winds are most prevelent in canda (red being the most)...can't really say for sure that the Winnipeg and Yellowknife temps are coming from that, I didn't find any reference to chinook winds under the climate profiles. Their temps are probably more a result of a moderation of the airmass...possibly because the cold air is being displaced further east.

But I would hazard to say this....whereas the presence of arctic air in ak/canada/nw terr is not an absolute sign that an arctic blast is headed for the deep south.....i think it would be tough to get a severe arctic blast into the deep south without the presence of below normal arctic air in ak/canada/nw terr moving into the plains. Haven't heard of too many severe arctic airmasses in the deep south (talking temps near or below record lows) generating over long island or chicago. The significance of this...chinook effect in calgary aside...is more likely downstream...and may indicate a building ridge from west to east...with a resulting warm-up across the east later in the month.

Good old Chinook winds will do this every time.

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
843 AM EST MON JAN 12 2009

VALID 12Z FRI JAN 16 2009 - 12Z MON JAN 19 2009

PRELIMINARY UPDATE...

THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3-7 WERE UPDATED
USING A PROGRESSIVE BLEND FROM THE 00Z ECMWF TOWARD ITS ENSEMBLE
MEAN. THIS BLEND HAS SHOWN HIGHER SKILL OVER THE LAST THREE
MONTHS FOR SURFACE PRESSURE OVER THE CONTIGUOUS UNITED STATES
DURING THE MEDIUM RANGE THAN THE GFS...GEFS MEAN...OR ECMWF
ALONE...THOUGH THE GFS/GEFS MEAN ARE NOT FUNDAMENTALLY DIFFERENT
THAN THE EUROPEAN CENTRE PRODUCTS THIS PARTICULAR FORECAST. A
POSITIVE PNA PATTERN WILL HOLD THROUGH THE PERIOD...WITH THE
CURRENT COLD SNAP EAST OF THE ROCKIES PEAKING DAY 4.
THEREAFTER...THE CHINOOK WILL FRAY THE WESTERN EDGE OF THE
AIRMASS...WITH ONLY NEW ENGLAND STAYING IN THE DEEP FREEZE
INDEFINITELY. ENOUGH AMPLIFICATION OF A WAVE DROPPING THROUGH THE
GREAT LAKES MID PERIOD COULD SPELL A BOUT OF SNOW FOR THE
NORTHEAST ONCE THE SYSTEM DEVELOPS OVER THE ATLANTIC. THE
REMAINDER OF THE NATION LOOKS HIGH AND DRY...WITH THE SEASONAL
INVERSION IN PLACE OVER THE GREAT BASIN AND INTERMOUNTAIN WEST.

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
246 AM AKST MON JAN 12 2009
.DISCUSSION...
ECMWF/GFS SFC/500 MB PROGS ARE IN GENERALLY GOOD AGREEMENT
THROUGH 12Z FRI. A WEAKENING SHORT WAVE TROUGH MOVING
NORTHWARD ACROSS MAY PRODUCE SOME LIGHT SNOW TODAY OVER
THE SOUTHERN PARTS OF THE WEST COAST AND WESTERN INTERIOR.
THE SOUTHEASTERN INTERIOR AND ALASKA RANGE MAY SEE SOME
FRINGE SNOWFALL FROM THE SURFACE LOW MOVING NORTHEASTWARD
ACROSS THE GULF OF ALASKA. SNOW AMOUNTS WILL LIKELY BE
LESS THAN AN INCH IN MOST AREAS...EXCEPT THE EASTERN PARTS
OF THE ALASKA RANGE WHERE AN INCH OR TWO MAY BE POSSIBLE.
SOME LEFTOVER LIGHT SNOW OR FLURRIES MAY OCCUR OVER
THE WEST COAST AND SOUTHEAST INTERIOR TONIGHT.

THE MAJOR WARMUP WILL OCCUR TUE THROUGH WED AS THE STRONG
UPPER RIDGE BUILDS OFF THE WEST COAST OF NORTH AMERICA AND
NORTHWESTWARD INTO ALASKA. HIGH ENERGY SCENARIO TUE THROUGH
SAT WITH SEVERAL 100+ KT JET STREAKS MOVING NORTHWARD ACROSS
THE STATE. 700 MB WINDS ACROSS THE ALASKA RANGE WILL FREQUENTLY
EXCEED 50 KT AND MAY MAX OUT AT AS HIGH AS 90 KT LATER IN THE
WEEK. EXPECT STRONG SOUTHERLY CHINOOK WINDS ALONG THE ALASKA
RANGE...AVIATORS CAN EXPECT SIGNIFICANT TURBULENCE AND WIND
SHEAR. MAXIMUM SURFACE WIND GUSTS NEAR WINDY AND ISABEL PASSES
WILL ALMOST CERTAINLY REACH OR EXCEED 70 MPH...ISOLATED 80-90
MPH GUSTS ARE A POSSIBILITY.

TEMPERATURES OVER HIGHER TERRAIN OVER MUCH OF THE INTERIOR
WILL APPROACH OR EXCEED FREEZING WED THROUGH SAT...IN ALASKA
RANGE PASSES...40 DEGREE TEMPERATURES AND SLICK ROAD CONDITIONS
LIKELY. WIDESPREAD PRECIPITATION SPREADING TO THE WEST COAST AND
WESTERN INTERIOR WED THROUGH THUR...AND WITH TEMPERATURES
ALOFT RISING TO FREEZING OR ABOVE IN SOME AREAS...SEVERAL
PRECIPITATION TYPES ARE LIKELY. MIXED PRECIPITATION ALSO
LIKELY IN THE ALASKA RANGE.


Just sayin...

[jinftl]

Right, but i don't believe Yellowknife or Winnipeg are in chinook areas...the all-time high temp for Yellowknife (not part of Alaska Range..or Alaska...elevation 675 feet) in January is 38 deg....chinook winds can cause much warmer temps even in mid-winter in places like Calgary.

Winnipeg is not in the mountains either...very close to the Upper Midwest and Great Lakes (red dot on map)...warmer temps there wouldn't be caused by chinook conditions...they would come from the airmass warming (due to wind shift, etc). If it warms up in the winter say, in Duluth, it's not because of the chinook...i still will say then that the air in Winnipeg is very much an indicator of arctic airmasses that are moving into the eastern half of the u.s.....if they move into the u.s. further east, they will primarily impact the northeast.



From the excerpt posted below

WITH THE CURRENT COLD SNAP EAST OF THE ROCKIES PEAKING DAY 4.

Airmasses due modify..even before they move south. But this could still translate into temps 10 or so degrees below normal once it hits the Deep South of the U.S by late week before modifying....noteworthy enough.

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
843 AM EST MON JAN 12 2009

VALID 12Z FRI JAN 16 2009 - 12Z MON JAN 19 2009

PRELIMINARY UPDATE...

THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3-7 WERE UPDATED
USING A PROGRESSIVE BLEND FROM THE 00Z ECMWF TOWARD ITS ENSEMBLE
MEAN. THIS BLEND HAS SHOWN HIGHER SKILL OVER THE LAST THREE
MONTHS FOR SURFACE PRESSURE OVER THE CONTIGUOUS UNITED STATES
DURING THE MEDIUM RANGE THAN THE GFS...GEFS MEAN...OR ECMWF
ALONE...THOUGH THE GFS/GEFS MEAN ARE NOT FUNDAMENTALLY DIFFERENT
THAN THE EUROPEAN CENTRE PRODUCTS THIS PARTICULAR FORECAST. A
POSITIVE PNA PATTERN WILL HOLD THROUGH THE PERIOD...WITH THE
CURRENT COLD SNAP EAST OF THE ROCKIES PEAKING DAY 4.
THEREAFTER...THE CHINOOK WILL FRAY THE WESTERN EDGE OF THE
AIRMASS...WITH ONLY NEW ENGLAND STAYING IN THE DEEP FREEZE
INDEFINITELY.

THE MAJOR WARMUP WILL OCCUR TUE THROUGH WED AS THE STRONG
UPPER RIDGE BUILDS OFF THE WEST COAST OF NORTH AMERICA AND
NORTHWESTWARD INTO ALASKA. HIGH ENERGY SCENARIO TUE THROUGH
SAT WITH SEVERAL 100+ KT JET STREAKS MOVING NORTHWARD ACROSS
THE STATE. 700 MB WINDS ACROSS THE ALASKA RANGE WILL FREQUENTLY
EXCEED 50 KT AND MAY MAX OUT AT AS HIGH AS 90 KT LATER IN THE
WEEK. EXPECT STRONG SOUTHERLY CHINOOK WINDS ALONG THE ALASKA
RANGE...AVIATORS CAN EXPECT SIGNIFICANT TURBULENCE AND WIND
SHEAR. MAXIMUM SURFACE WIND GUSTS NEAR WINDY AND ISABEL PASSES
WILL ALMOST CERTAINLY REACH OR EXCEED 70 MPH...ISOLATED 80-90
MPH GUSTS ARE A POSSIBILITY.



Just sayin...

[srainhoutx]

Right, but i don't believe Yellowknife or Winnipeg are in chinook areas...the all-time high temp for Yellowknife (not part of Alaska Range..or Alaska...elevation 675 feet) in January is 38 deg....so the 40 deg chinook-induced weather is not in that area.

From the excerpt posted below

WITH THE CURRENT COLD SNAP EAST OF THE ROCKIES PEAKING DAY 4.

Airmasses due modify..even before they move south. But this could still translate into temps 10 or so degrees below normal once it hits the Deep South of the U.S by late week before modifying....noteworthy enough.

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
843 AM EST MON JAN 12 2009

VALID 12Z FRI JAN 16 2009 - 12Z MON JAN 19 2009

PRELIMINARY UPDATE...

THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3-7 WERE UPDATED
USING A PROGRESSIVE BLEND FROM THE 00Z ECMWF TOWARD ITS ENSEMBLE
MEAN. THIS BLEND HAS SHOWN HIGHER SKILL OVER THE LAST THREE
MONTHS FOR SURFACE PRESSURE OVER THE CONTIGUOUS UNITED STATES
DURING THE MEDIUM RANGE THAN THE GFS...GEFS MEAN...OR ECMWF
ALONE...THOUGH THE GFS/GEFS MEAN ARE NOT FUNDAMENTALLY DIFFERENT
THAN THE EUROPEAN CENTRE PRODUCTS THIS PARTICULAR FORECAST. A
POSITIVE PNA PATTERN WILL HOLD THROUGH THE PERIOD...WITH THE
CURRENT COLD SNAP EAST OF THE ROCKIES PEAKING DAY 4.
THEREAFTER...THE CHINOOK WILL FRAY THE WESTERN EDGE OF THE
AIRMASS...WITH ONLY NEW ENGLAND STAYING IN THE DEEP FREEZE
INDEFINITELY.

THE MAJOR WARMUP WILL OCCUR TUE THROUGH WED AS THE STRONG
UPPER RIDGE BUILDS OFF THE WEST COAST OF NORTH AMERICA AND
NORTHWESTWARD INTO ALASKA. HIGH ENERGY SCENARIO TUE THROUGH
SAT WITH SEVERAL 100+ KT JET STREAKS MOVING NORTHWARD ACROSS
THE STATE. 700 MB WINDS ACROSS THE ALASKA RANGE WILL FREQUENTLY
EXCEED 50 KT AND MAY MAX OUT AT AS HIGH AS 90 KT LATER IN THE
WEEK. EXPECT STRONG SOUTHERLY CHINOOK WINDS ALONG THE ALASKA
RANGE...AVIATORS CAN EXPECT SIGNIFICANT TURBULENCE AND WIND
SHEAR. MAXIMUM SURFACE WIND GUSTS NEAR WINDY AND ISABEL PASSES
WILL ALMOST CERTAINLY REACH OR EXCEED 70 MPH...ISOLATED 80-90
MPH GUSTS ARE A POSSIBILITY.



Just sayin...

I'll agree jinftl. One trait if the GFS is to show extreme colder 850mb temps in the 7-10 range and beyond, when in fact they usually end up 5-7 degrees higher in the 2-4 day range. One of reasons why I will not "predict" temps in advance of "seeing" 2mb or surface temps inadvance of a 24 hour period. It's like perdicting that a Cat 5 Hurricane will hit S FL at day 5. I will look for patterns in model guidance, but as stated in this Topic, there are many tools in the tool bag for our use.

[Ed Mahmoud]

I always thought the Chinook was the same thing as the Santa Ana, just in a different spot, compressional warming of a dry airmass as it moves from higher elevation to lower elevation.

[jinftl]

Gotta love the long-range GFS! But, it's the long range GFS that causes great dialogue on here..and drives folks crazy since of course the naturally tendency for some is to 'run with' the most extreme run...esp the one that shows 'once in a (choose a number of years) cold event.'

There is serious cold moving into the U.S. this week...the trajectory is such that really the worst of it will avoid the western u.s....and i hesitate to say it, Texas and even parts of Florida (which will turn much colder but not aware of widespread damaging freeze threat being considered imminent for orange groves....it can and does happen and that is 'serious' cold in florida) aren't going to see the very worst of it. Temps may be 10 deg below normal for a few days, maybe a bit more even in florida. Compare that to a forecast high of -19 deg in Duluth mid-week.....that's 36 deg below normal!

Things can change but this event is about to start happening...the models really need to come together....if they are still showing a wide range of solutions in places like Texas for mid to late week....how can we give them anything but a quick glance 1 to 2 weeks out?
It is still January so of course even a weak front can make it cold, but i am not finding support for an even 'colder' airmass to follow the one this week. Most areas will see big modifications...in some case that means close to normal...across the country. Even Duluth will warm to a balmy 17 deg on Sunday....just about normal.

I'll agree jinftl. One trait if the GFS is to show extreme colder 850mb temps in the 7-10 range and beyond, when in fact they usually end up 5-7 degrees higher in the 2-4 day range. One of reasons why I will not "predict" temps in advance of "seeing" 2mb or surface temps inadvance of a 24 hour period. It's like perdicting that a Cat 5 Hurricane will hit S FL at day 5. I will look for patterns in model guidance, but as stated in this Topic, there are many tools in the tool bag for our use.

[Ed Mahmoud]

Good news, and I learned this watching the JB Big Dog, and it is the difference between two rules of thumb, Binghampton and add 13ºF, and Albany and add 7ºF, for NYC temperature, when flow is coming from one of those cities.

Current 12Z GFS says only 2 or 3ºF Friday morning. OK, coldest in a decade, but it doesn't break the psycological barrier, the technical support level of 0º F.

JB showed UK Met and Euro from their 0Z runs, and GFS, and handling on the clipper low. GFS takes clipper far enough North, that winds come from Binghampton, UK Met and Euro are farther South, winds are coming from Albany.

OK, current GFS is about 3ºF in NYC.
Flow is from the NW


Don't have Euro yet, but lets look at Canadian, which looked like the Euro and UK Met at 0Z.

Flow into NYC from almost due North.


So a minus zero day, a technical support day, based on Fibonacci numbers (ok, just kidding on that part) is still breakable.


The GFS ALB 2 meter number is -26ºC. Adding 7ºF would put NYC between -6 and -7ºF early Friday morning, which would be the coldest since 1943, and I might have to go into work late to see Ann Curry and Willard Scott or Al Roker talking to tourists from Iowa in -6ºF weather.


Iowa tourists should have the clothes for that, it gets that cold there, but did they pack them with the new charges for extra baggage rule? Will Ann Curry wear a ski mask on the air?

[tropicana]

Right, but i don't believe Yellowknife or Winnipeg are in chinook areas...the all-time high temp for Yellowknife (not part of Alaska Range..or Alaska...elevation 675 feet) in January is 38 deg....chinook winds can cause much warmer temps even in mid-winter in places like Calgary.

[/quote]

yup... all time high for Yellowknife in January is 3.4C 38F set January 3 1985

-justin-

[Ed Mahmoud]

New Euro

based on track of low, and 850 and 700 mb RH over 90%, and good fluff factors, some snow first, who knows how many inches, followed the next morning by 498 DM 1000-500 mb thickness and -22ºC 850 mb temps at NYC.


I am not at all pessimistic on temps colder than -2ºF in NYC, and Al Roker wearing one of those Soviet era big fur lined hats as he talks to tourists from Kentucky.

Matt Lauer will stay indoors, of that I am certain.

[x-y-no]

Matt Lauer will stay indoors, of that I am certain.

If he's wearing that dress, I think he should.

[srainhoutx]

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1231 PM EST MON JAN 12 2009

VALID 12Z THU JAN 15 2009 - 12Z MON JAN 19 2009

PRELIMINARY UPDATE...

THE PRELIMINARY FRONTS AND PRESSURES FOR DAYS 3-7 WERE UPDATED
USING A PROGRESSIVE BLEND FROM THE 00Z ECMWF TOWARD ITS ENSEMBLE
MEAN. THIS BLEND HAS SHOWN HIGHER SKILL OVER THE LAST THREE
MONTHS FOR SURFACE PRESSURE OVER THE CONTIGUOUS UNITED STATES
DURING THE MEDIUM RANGE THAN THE GFS...GEFS MEAN...OR ECMWF
ALONE...THOUGH THE GFS/GEFS MEAN ARE NOT FUNDAMENTALLY DIFFERENT
THAN THE EUROPEAN CENTRE PRODUCTS THIS PARTICULAR FORECAST. A
POSITIVE PNA PATTERN WILL HOLD THROUGH THE PERIOD...WITH THE
CURRENT COLD SNAP EAST OF THE ROCKIES PEAKING DAY 4.
THEREAFTER...THE CHINOOK WILL FRAY THE WESTERN EDGE OF THE
AIRMASS...WITH ONLY NEW ENGLAND STAYING IN THE DEEP FREEZE
INDEFINITELY. ENOUGH AMPLIFICATION OF A WAVE DROPPING THROUGH THE
GREAT LAKES MID PERIOD COULD SPELL A BOUT OF SNOW FOR THE
NORTHEAST ONCE THE SYSTEM DEVELOPS OVER THE ATLANTIC. THE
REMAINDER OF THE NATION LOOKS HIGH AND DRY...WITH THE SEASONAL
INVERSION IN PLACE OVER THE GREAT BASIN AND INTERMOUNTAIN WEST.

FINAL...

THE 12Z GFS IS HARMONIOUS WITH THE BLEND CHOSEN FOR THE UPDATE
PACKAGE THROUGH ABOUT DAY 6...THEN DIVERGES SHARPLY OFF THE
NORTHEAST COAST DAY 7 WHERE IT BUILDS A SHORTWAVE RIDGE AHEAD OF
ANOTHER POLAR LOBE DROPPING THROUGH THE GREAT LAKES. THE 12Z GEFS
MEAN...HOWEVER...IS IN SYNC WITH THE EARLIER PROGS THROUGH THE
ENTIRE PERIOD...AND IS THE MAIN REASON ALMOST NO CHANGES WILL BE
MADE FOR THE FINAL ISSUANCE. DID PULL THE CLIPPER NORTHWARD TO
THE MASON DIXON LINE DAY 3 WITH RESPECT TO THE GFS/GEM/UKMET
CLUSTER WHICH IS EVEN FARTHER NORTH. THE GEFS MEAN IS WHERE THE
OLD ECMWF WAS...HOWEVER...OVER NORTHERN MARYLAND THURSDAY MORNING.

THE AIRMASS SPREADING ACROSS THE CENTRAL AND EASTERN STATES DAYS 4
AND 5 LOOKS TO BE THE COLDEST OF THE SEASON SO FAR...WITH A HARD
FREEZE INDICATED FOR PARTS OF THE FLORIDA PENINSULA SATURDAY
MORNING...DAY 5.


CISCO

[jinftl]

NWS Hazards Assessment issued today (blue markings included)...pretty much in line with what the consensus from the board is saying too....scary!

[srainhoutx]

NWS Hazards Assessment issued today (blue markings included)...pretty much in line with what the consensus from the board is saying too....scary!

Prognostic Discussion Issued today...

http://www.cpc.ncep.noaa.gov/products/p ... xus06.html

[Ed Mahmoud]

Good news, 18Z GFS is back to sub-zero Farenheit weather in NYC Friday morning, with about three tenths liquid equivalent falling the day before- normally, that is about 3 inches in NYC area, where snow falls with surface temps near freezing, but as my man JB likes to point out, 15:1, even 30:1 ratios are possible when 850 mb temps are below 20ºC, so six or more inches of sweepable fluff possible, added benefit for Friday morning- keeps the ground from warming the air near the surface, and, of course, albedo city during the day keeps daytime highs nice and cool, mid teens per GFS.

Look how tightly the isobars pack together (and light snow continues six more hours per GFS in NYC after this) as the snow falls in NYC. Wind whipped and cold, and fluffy snow...




Even better a few hours later (and yes, the snow continues beyond this point), snow and 25 to 35 knot sustained winds in SE Massachusetts



Checking my AccuWx PPV temps from the 18Z GFS- the heaviest snow is falling with those strong winds and upper teens on the coast, low teens just inland.


I'm a little excited.

[KatDaddy]

Now that is a classic photo!

[srainhoutx]

Now that is a classic photo!

I about fell out of my chair when I saw that, but I digress.. That's our Ed to find that one.

[MGC]

That picture is nearly "R" rated......So, who is the Queen-for-a-day?...MGC

[Ed Mahmoud]

That picture is nearly "R" rated......So, who is the Queen-for-a-day?...MGC

That is Matt Lauer.

[JBG]

Right, but i don't believe Yellowknife or Winnipeg are in chinook areas...the all-time high temp for Yellowknife (not part of Alaska Range..or Alaska...elevation 675 feet) in January is 38 deg....chinook winds can cause much warmer temps even in mid-winter in places like Calgary.

Winnipeg is not in the mountains either...very close to the Upper Midwest and Great Lakes (red dot on map)...warmer temps there wouldn't be caused by chinook conditions...they would come from the airmass warming (due to wind shift, etc). If it warms up in the winter say, in Duluth, it's not because of the chinook...i still will say then that the air in Winnipeg is very much an indicator of arctic airmasses that are moving into the eastern half of the u.s.....if they move into the u.s. further east, they will primarily impact the northeast.

While Yellowknife and Winnipeg are technically not in the Chinook belt, the same forces that allow chinooks to form, i.e. a return of zonal flow conditions, also alleviate the normal cold typical of Yellowknife and Winnipeg.

[Ed Mahmoud]

GFS-NYC about 492 thickness and -22ºC


Canadian
495 DM and -24ºC at 850 mb


GFS 2 meter temps about -2ºF for NYC, but that is the day after about a quarter inch, usually good for 2 or 3 inches, but this time good for probably double that, with both JB and local NWS offices mentioning 20:1 fluff factors. Wind, powdery snow, below zero temps.

I see a possible cold weather day, at least for the public school kids in Massapequa, who get the day off for almost any weather, and maybe even the Holy Grail of school closings, St. Martin of Tours Parochial School (Diocese of Rockville Center) in Amityville, NY

[CrazyC83]

The stronger chinooks can easily bring it into the 50s and 60s in southern Alberta in mid-winter (on rare occasions into the 70s).

On the most extreme days, it could be below zero when you go to work in the morning - and in the 50s when you go home.