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Early Jan cold and/or snow threat


Cheeznado

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'packbacker'

Seems like a pretty good wintery run of the GFS in the long range...hopefully it's not drunk!

Almost appears to setup some blocking in the long run.

Best I've seen by far. Gets the ball really rolling with a Miller Bish/apps runnerday 9-10 then drives the cold down the rest of the run.

00zGFS11-15day850mbTempAnomalyNA.gif

HAPPY NEW YEAR EVERYONE:

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Thanks, your probably in the know more than me. I did a double take trying to discern the if the -18 was the shade beside it as well as retrace the shades starting with the first blue color 0 850's and working my way backwards toward the color in NW NC. Unfortunately they are packed so tight that method doesn't work to well with this spell/outbreak.

Yeah, wasn't trying to nitpick, I was just keying on some of the comparison 850 numbers that Foothills threw out from last year's cold outbreaks.

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This may bring a few flurries to ne Ga , northern SC and part of the western piedmont and foothills of NC, not to mention the excellent upslope snow event this is going to be in all the mountain Chain.

the NAM is added a little more moisture for late monday night early tuesday morn...may have to be on flurry watch for sure! Dead on to what Robert has been saying for 2 days now...dang genius!!

Yep, Foothills was the first to mention the flurry possibility east of the mtns.

We have a fairly strong 500mb vort max that is gaining strength as it dives into the base of the longwave trough, with a good 500mb wind field accompanying the vort max. The amount of moisture is going to be very limited, but the incoming air mass will be quite cold and may be able to squeeze out a few flurries anywhere northeast of a line from Chattanooga to Columbia to Myrtle Beach (north of the track of the 500mb vort max).

I'm on board with the HI-RES NMM's radar simulation of the flurries/stray snow showers in the eastern 1/2 of TN, the mtn upslope snow, and the stray flurries east of the mtns, Mon aftn / evening.

usaabsv500mb051j.gif

usagrd500mb048.gif

hrwnmmeus045simradar.gif

hrwnmmeus048simradar.gif

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A good indicator of a bona fide cold air mass here is single digit dewpoints. GFS output is showing dewpoints around 0 degrees Tuesday afternoon into Wed morning.

A little test here to see which one of these is most accurate with the 72 hour forecast...

Forecasted High Temp on Tues for Charlotte:

NAM Model Output: 33

NAM MOS (MET): 40

GFS Model Output: 32

GFS MOS (MAV): 36

GFS MOS (MEX): 36

NWS: mid-30s

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Morning folks, Hope everyone was safe last night! Here is the short term from GSP:

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...

AT 2 AM EST SUNDAY...AN UPPER LOW WILL BE LOCATED NORTHEAST OF THE

GREAT LAKES MONDAY MORNING...WITH AN ASSOCIATED TROUGH EXTENDING

SOUTH INTO THE APPALACHIANS. A STRONG SHORTWAVE WILL ROUND THE BASE

OF THIS TROUGH MONDAY...ACCOMPANIED BY AN SURGE IN LOW LEVEL

MOISTURE IN ROBUST NW FLOW. THIS WILL RESULT IN AN INCREASE IN NW

FLOW SHOWERS IN THE NC MOUNTAINS BORDERING TN...WITH SNOW AT ALL BUT

THE LOWEST VALLEY FLOORS. WINDS WILL INCREASE TO NEAR WIND ADVISORY

CRITERIA IN THE MOUNTAINS.

EVEN COLDER AIR AND MORE MOISTURE WILL MOVE INTO THE NC MOUNTAINS

FROM THE NW ON MONDAY NIGHT...WHEN SNOW LEVELS FALL TO THE VALLEY

FLOORS...AND THE HEAVIEST PRECIPITATION RATES ARE EXPECTED. AT THIS

POINT IT APPEARS THAT ADVISORY CRITERIA SNOWFALL IS POSSIBLE NEAR

THE TN BORDER...ESPECIALLY NORTH OF INTERSTATE 40. WINDS WILL

CONTINUE AT NEAR ADVISORY CRITERIA... PRODUCING WIND CHILL VALUES

NEARING ADVISORY CRITERIA. MOISTURE AND WINDS RAPIDLY DECREASE

TUESDAY MORNING IN THE WAKE OF THE DEPARTING SHORTWAVE...ENDING THE

SNOW EVENT.

MAXIMUM TEMPERATURES WILL FALL FROM AROUND FIVE DEGREES BELOW NORMAL

ON MONDAY...TO 15 DEGREES BELOW NORMAL ON TUESDAY AS A RESULT OF

COLD ADVECTION. MINIMUM TEMPERATURES WIL RUN 7 TO 10 DEGREES BELOW

NORMAL...WITH TUESDAY NIGHT BEING THE COLDER NIGHT AS WINDS DECREASE.

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Yep, some guidance drops dew points for clt below 0 at times with this outbreak. Pure arctic air.

A good indicator of a bona fide cold air mass here is single digit dewpoints. GFS output is showing dewpoints around 0 degrees Tuesday afternoon into Wed morning.

A little test here to see which one of these is most accurate with the 72 hour forecast...

Forecasted High Temp on Tues for Charlotte:

NAM Model Output: 33

NAM MOS (MET): 40

GFS Model Output: 32

GFS MOS (MAV): 36

GFS MOS (MEX): 36

NWS: mid-30s

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CAE... :weight_lift:

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...

BELOW NORMAL TEMPS WILL CONTINUE THROUGH THE MIDDLE OF THE WEEK.

MODELS CONTINUE TO INDICATE STRONG UPPER RIDGE OVER THE WESTERN

CONUS WITH DEEP UPPER TROUGH OVER THE EAST. THIS PROVIDES A NW

FLOW ALOFT INTO OUR REGION FROM NORTHERN CANADA...WHICH IS A COLD

DRY FLOW. STRONG HIGH PRESSURE CENTER/COLD AIR MASS TO PUSH INTO

THE LOWER MISS VALLEY/DEEP SOUTH BY TUESDAY NIGHT...WHILE STRONG LOW

PRESSURE MOVES EAST ACROSS EASTERN CANADA...AND ANOTHER OFFSHORE

THE NE US COAST. GFS/ECMWF BUILD THE HIGH CENTER INTO OUR REGION

BY TUE NT/WED...PROVIDING APPEARANCES OF GOOD RADIATIONAL COOLING

AND POTENTIAL FOR THE COLDEST TEMPS EARLY WED MORNING. GFS

ENSEMBLE AVERAGE MIN TEMPS TRENDING DOWN WITH LATEST RUN. TEMPS

EARLY WED MORNING COULD DIP INTO THE TEENS. ANOTHER LOW/TROUGH MAY

SWING BY TO OUR NE THU...INCREASING THE WIND AND POSSIBLY ADDING

SOME CLOUDS...SO MIN TEMPS NOT AS COOL. MODELS INDICATE INCREASING

UPPER HEIGHTS OVER OUR REGION LATE WEEK INTO SATURDAY AS

TROUGHINESS DEVELOPS OVER THE WESTERN CONUS...WHILE SURFACE HIGH

PRESSURE GRADUALLY WEAKENS IN THE VICINITY OF THE SE CONUS AND

SHIFTS SLOWLY SE. THIS WILL RESULT IN MODERATING TEMPS FRI/SAT.

GFS/ECMWF INDICATE AN APPROACHING FRONT WITH INCREASING

ATMOSPHERIC MOISTURE AFFECTING OUR REGION BY SATURDAY.

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Ok some tell me if I am correct here. Looking at 48 hr accum. Precip. On the 12z Nam. It looks like the Mnts. could get .15 to .30 of moisture. I know the ratio is going to go way up but, if you were to use 15-1. as an average. Would we be looking at 2-5" depending on elevation? Thanks in advance.

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The 06z GFS, and 12z NAM, valid at 12z Tue:

post-38-0-29677800-1325430980.gif

post-38-0-53210800-1325430996.gif

the 12z NAM has the surface freezing line from central NC down to Athens and back toward Huntsville, and upper 20's in the western piedmont/foothills and northern GA and northern Upstate.

post-38-0-97324700-1325431389.gif

Yeah I wouldn't be surprised if we only top out at 28 in Knoxville.

Ok some tell me if I am correct here. Looking at 48 hr accum. Precip. On the 12z Nam. It looks like the Mnts. could get .15 to .30 of moisture. I know the ratio is going to go way up but, if you were to use 15-1. as an average. Would we be looking at 2-5" depending on elevation? Thanks in advance.

It'll probably be around 10-15 degrees above 6000', so I'd say 2-5" isn't out of the question and is probably likely. Leconte at 6500' got 4.5" from the last system. With the strong winds and orographic precip, I wouldn't be surprised if totals around 6" happened at the highest elevations.

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Canadian RGEM is farther south with the vort max and cold compared to the GFS and NAM. It has 850 -16C just south of Atlanta. HIRES-NMM is also farther south with the vort max like the RGEM, but not quite as cold...it has -15C just north of ATL.

You can see the scattered snow shower look east of the mtns on the HIRES NMM 700mb RH.

hrwnmmeus039700rhht.gif

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GSP afternoon AFD:

MONDAY WILL BE UNSEASONABLY COLD AND BLUSTERY. TEMPERATURES WILL

STRUGGLE TO MAKE IT ABOVE FREEZING ACROSS THE MTNS...EVEN IN THE

LOWER VALLEYS...WHILE THE HIGH ELEVATIONS ARE EXPECTED TO REMAIN IN

THE TEENS. DOWNSLOPE WARMING SHOULD SOMEWHAT OFFSET THE COLD AIR

MASS FOR AREAS EAST OF THE MTNS...BUT MOST PIEDMONT/FOOTHILLS

LOCATIONS WILL ONLY TOP OUT IN THE 40-45 RANGE. BY THE END OF THE

DAY...MOISTURE BEGINS TO DEEPEN IN ADVANCE OF A NW FLOW SHORT WAVE

TROUGH. THIS SHOULD ENHANCE THE PROBABILITY OF NW FLOW SNOW

SHOWERS...AND POPS WILL INCREASE TO CHANCE BY 00Z TUESDAY.

-- End Changed Discussion --

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...

-- Changed Discussion --

AS OF 2 PM SUNDAY...WITHIN THE DEEP CYCLONIC FLOW...A BLUSTERY AND

COLD NIGHT IS ON TAP INTO EARLY TUESDAY MORNING. THE PATTERN IS VERY

FAVORABLE TO SUPPORT THE DEVELOPMENT OF NUMEROUS NC MTN SNOW

SHOWERS. MODEL CROSSSECTIONS DEPICT A MODERATELY STRONG NW

FLOW...AND MOISTURE EXTENDING UP TO A VERY COLD -20 DEG C. BASED ON

THIS...ADVISORY LEVEL SNOW ACCUMULATIONS ARE LIKELY...ESPECIALLY

ACRS THE HIGHER ELEVATIONS AND WEST FACING SLOPES. GUSTY NW WINDS

SHOULD ALSO PROMOTE AREAS OF BLOWING SNOW. MIN TEMPS TUESDAY MORNING

ARE SLATED TO BE ABT 10 DEG F BELOW NORMAL AND THIS SHOULD RESULT IN

HIGHER ELEVATION NC MTN WIND CHILL INDEX VALUES NEARING TEN BELOW

ZERO.

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This simulated radar loop is a good look for how the snow should break out in E KY, SW VA, E TN, W NC with the vort max diving in from the NW (last 4 frames of the loop - goes through 7PM Mon)

http://www.meteo.psu..._12z/jloop.html

Looks like the higher elevations (above 2000') in East TN are favored for snow there. I'm not sure much will make it to the valley but the cumberland plateau might get an inch, and so will the ridge on I75 near LaFollette.

I'd go with 4-6" above 6000' definitely.

Pity I have plans on Monday or I'd hike up to Leconte again for this.

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Canadian RGEM is farther south with the vort max and cold compared to the GFS and NAM. It has 850 -16C just south of Atlanta. HIRES-NMM is also farther south with the vort max like the RGEM, but not quite as cold...it has -15C just north of ATL.

You can see the scattered snow shower look east of the mtns on the HIRES NMM 700mb RH.

hrwnmmeus039700rhht.gif

I like the looks of that blob of moisture in the golden corner of SC!!

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man I wish that low would pop 100 miles further west.... the 18z GFS is pretty close to snowfall for the beaches of NC

yeah thats a very sharp trough. It almost was a cutoff like the ecmwf had a while back, but its a little too progressive. But there still could be a very close call to the outer banks esp.

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I'm under a WWA for 1-2 inches and 2-4 inches for areas above 2500. Not too shabby.

I know how this works but it is a bit discouraging when you see yourself surrounded by purple. I'm in Kingsport BTW. For those of you who don't know the area geography, I'm just west of the interstate that is west of Bristol, TN on the VA/TN line.

post-769-0-87258400-1325458164.jpg

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