Jan 6-8 SE Clipper/Upslope Obs, Last Minute Forecasts and Obs Options

[1234snow]

I'm starting a new obs thread for this clipper threat that has already started here in Northeast TN/Southwest VA and in the NC/TN border counties. This is only just the start and I think areas in the higher elevations (hillbilly weather) could see up to 6-10 inches by Saturday. This is been progged to occur for several days now but no thread has really been made as the bigger interest is for early next week.

Both the NAM and the GFS show a band of enhanced precip forming tomorrow morning-afternoon over the Cumberland Plateau and Northeast TN (Knoxville to the Tri Cities) and into the mountains.

0z NAM QPF:



0z GFS QPF:



For you folks in North Carolina if enough moisture makes it across the mountains you could see a couple of inches. It would be a nice surprise as I'm sure many are not expecting it. Both models show some nice enhancement of precip associated with the low pressure system as it crosses NC and off the coast.

Then upslope should continue Friday Night/Saturday for the higher elevations.

This post has been edited by 1234snow: Jan 6 2011, 11:33 PM

[connercconner]

How much do you think Knoxville will get?

[1234snow]

How much do you think Knoxville will get?

I'm thinking around 2-3 inches maybe if that band of enhanced precip moves over the area.

[Justin-Atlanta]

THIS JUST IN THIS JUST IN......
PLEASE NOTE THAT NO ADVISORIES ARE SHOWING UP ON THE NOAA HOME PAGE....

FXUS62 KRAH 070727
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
225 AM EST FRI JAN 7 2011

.SYNOPSIS...
-- Changed Discussion --A POWERFUL UPPER LEVEL DISTURBANCE IN NORTHWEST FLOW ALOFT WILL
CROSS THE REGION THIS EVENING. COLD HIGH PRESSURE WILL BUILD INTO
THE REGION FROM THE NW SATURDAY AND LINGER OVER THE REGION THROUGH
MONDAY.-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --AS OF 225 AM FRIDAY...

A WINTER WEATHER ADVISORY HAS BEEN ISSUED FOR PORTIONS OF CENTRAL NC
FROM 4 PM TODAY THROUGH TONIGHT...
A STRONG MID/UPPER WAVE OVER THE GREAT LAKES WILL GET ABSORBED
BY THE DIGGING POLAR VORTEX OVER SOUTH CENTRAL CANADA...WITH
THE DEEP CLOSED CYCLONE SHIFTING SOUTH INTO THE MID-ATLANTIC BY
SATURDAY MORNING. SEVERAL NOTABLE SHORTWAVE DISTURBANCES WILL
REVOLVE AROUND THE DIGGING POLAR VORTEX...PRODUCING SNOW FROM THE
GREAT LAKES WAY SOUTH INTO THE CAROLINAS.

FOR CENTRAL NC...THE UPPER WAVE OF CONCERN IS THE INITIALLY-SHEARED
TROPOPAUSE DISTURBANCE -- AND ACCOMPANYING 100+KT MID LEVEL JET --
IN NW FLOW ALOFT OVER THE DAKOTAS. THE DISTURBANCE WILL AMPLIFY AS
IT RACES SOUTHEASTWARD INTO THE BASE OF THE DEEPENING L/W TROUGH AND
PLACE CENTRAL NC IN A STRONGLY AGEOSTROPHIC MID-UPPER JET EXIT
REGION. AT THE SURFACE...A MIGRATORY AND DEEPENING SURFACE WAVE WILL
QUICKLY RACE THROUGH THE MIDDLE MS AND TN VALLEY THIS MORNING AND
TRAVERSE THE SOUTHERN APPALACHIANS THIS AFTERNOON BEFORE TRACKING
ACROSS SOUTH CENTRAL NC THIS EVENING AS A 994/995MB SURFACE LOW.

THIS FAVORABLE TRACK AND THE STRONG MESOSCALE FORCING ACCOMPANYING
THE MID/UPPER WAVE/JETSTREAK WILL PRODUCE A SWATH OF HEAVIER
BANDING PRECIPITATION ACROSS CENTRAL NC...WITH A QUICK BURST OF
ADVISORY CRITERIA SNOW OF ONE TO THREE INCHES IN THE VICINITY OF
US HIGHWAY 64. ADDITIONALLY...WHILE IT IS RARE FOR NW FLOW
EVENTS/DISTURBANCE TO BRING WARNING CRITERIA SNOW (3 TO 5 INCHES) TO
CENTRAL NC...MODELS ARE SHOWING SOME NOT SO SUBTLE SIGNALS(TOTAL
TOTALS>55...STRONG FGEN EXTENDING FROM THE SFC TO H5...MID-LEVEL
LAPSE RATES 7.5 TO 8.5)THAT A NARROW CONVECTIVE BAND OF
WARNING/HIGHER AMOUNTS IS POSSIBLE IN THE ADVISORY AREA. THIS WOULD
BE QUITE RARE IN DEED...AS REVIEWING SNOW/ICE EVENTS OVER THE LAST
40 TO 50 YEARS ACROSS CENTRAL NC SHOW THAT THERE HAS NEVER BEEN A
MEASURABLE WINTRY PRECIPITATION EVENT AT GSO WITH PARTIAL
THICKNESSES OF 1300/AND SUB-1500 METERS (ACCORDING TO THE EXTENSIVE
KEETER WINTER WEATHER DATABASE)...AS FORECAST AT GSO FOR 00Z/8TH.
WHILE THIS WOULD ARGUE AGAINST ANY SNOW...MUCH LESS AN ADVISORY...WE
MUST KEEP IN MIND THAT THE CURRENT ATMOSPHERIC PATTERN ACROSS
NORTHERN HEMISPHERIC PATTERN
IS IN A HIGHLY ANOMALOUS STATE.

TIMING...AFTER 12 AND 18Z FROM YESTERDAY SPED UP THE ONSET OF
PRECIP...THE NEW 00Z GUIDANCE HAS SLOWED THE TIMING BACK DOWN TO
BETWEEN 21 TO 00Z IN THE WEST...AND 00 TO 06Z IN THE EAST. WITH
DAYTIME TEMPERATURES IN THE LOWER TO MID 40S...EXPECT PRECIPITATION
IN THE WESTERN PIEDMONT TO START AS A SNOW/RAIN MIXTURE BEFORE
CHANGING OVER TO ALL SNOW WITH THE HEAVIER RATES. THE ABOVE FREEZING
LAYER NEAR IN THE LOWEST 1 TO 2 KFT WILL INITIALLY OFFSET SNOW
RATIOS...AND LIMIT ACCUMULATION AT THE ONSET...SO IF THE PRECIP
COMES IN EARLIER THAN MODELS SUGGEST...IMPACTS SHOULD BE NEGLIGIBLE.
BUT ONCE THE HEAVIER PRECIP RATES START...THE MELTING/EVAPORATION
WILL COOL COLUMN AND SUPPORT ALL SNOW ALONG AND NORTH OF US HWY
64...WITH NOCTURNAL TIMING AIDING IN THE PROCESS AS WE HEAD INTO THE
EVENING. COULD SEE A BRIEF CHANGEOVER FROM RAIN TO SNOW ACROSS THE
SOUTHERN TIER BEFORE THE PRECIP QUICKLY PULLS OUT...WITH ONLY TRACE
AMOUNTS EXPECTED.

QPF...MODEL AVERAGE SUGGESTS 0.20-0.30 OF LIQUID EQUIVALENT ALONG
THE HIGHWAY 64 SWEET SPOT...WITH A SHARP DROP OFF SOUTH AND NORTH OF
THE PRECIP AXIS. SO ALTHOUGH AREAS THE NC/VA BORDER WILL HAVE MORE
COLD AIR TO WORK WITH...QPF WILL BE LIMITED. ANY CHANGE IN THE TRACK
OF THE SURFACE LOW WILL ALTER THESE AMOUNTS AND RESULTANT IMPACTS
WITH
A SHIFT OF THE HEAVIER QPF AXIS TO THE SOUTH RESULTING IN LESS
QPF AND SNOW IN THE ADVISORY AREA.


STRONG CAA THROUGH THE COLUMN IN THE WAKE OF THE EXITING SURFACE LOW
AND UPPER DISTURBANCE WILL SUPPORT EARLY MORNING TEMPERATURES IN THE
25 TO 30 DEGREE RANGE SATURDAY MORNING. THIS COULD MAKE FOR SOME
TREACHEROUS ROAD CONDITIONS ACROSS ALL OF CENTRAL NC...INCLUDING
SOUTH OF THE ADVISORY AREA WITH THE WATER FREEZING ON ROADS AND
OVERPASSES RESULTING IN BLACK ICE. WILL HIGHLIGHT THE THREAT IN THE
HWO.-- End Changed Discussion --

[calculus1]

WWA for western piedmont and foothill locations of NC too!!

[calculus1]

From GSP:

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
MAJOR CHANGES WILL BE REQUIRED TO THE FORECAST THIS MORNING...AS
MODEL GUIDANCE IS TRENDING TOWARD A STRONGER/WETTER SOLUTION WITH
THE CLIPPER SYSTEM CURRENTLY SEEN IN WV IMAGERY MOVING RAPIDLY OUT
OF THE NORTHERN PLAINS. IN FACT...THE MODELS ARE TRENDING TOWARD
RESPECTABLE CYCLOGENESIS OCCURRING ACROSS THE SOUTHERN APPALACHIANS
THIS AFTERNOON...WHICH MOVES RAPIDLY ACROSS NORTHERN SC THROUGH THE
EVENING. THE RESULTANT INCREASE IN LOW-TO-MID LEVEL FRONTOGENESIS IS
QUITE IMPRESSIVE...ESP OVER THE PIEDMONT.

AS THE CLIPPER APPROACHES THE MTNS LATER THIS MORNING...UPSLOPE
SNOWFALL SHOULD BECOME ENHANCED OVER THE WESTERN MTNS...AIDED BY THE
DEVELOPING FRONTOGENESIS/INCR ISENTROPIC LIFT AND UPPER DIVERGENCE
AT THE NOSE OF AN IMPRESSIVE 150+ KT H3 JET STREAK. FORCING WILL
CONTINUE TO INCREASE AS THE SURFACE LOW MOVES ACROSS THE PIEDMONT
LATE THIS AFTERNOON/EVENING...WHEN WE SHOULD SEE A NICE BAND OF E-W
ORIENTED PRECIP MOVE OVER THAT REGION.

WHILE MOSTLY SNOW IS ANTICIPATED OVER THE MOUNTAINS...THE SITUATION
OVER THE PIEDMONT/FOOTHILLS IS COMPLICATED BY THE FACT THAT TEMPS
WILL LIKELY WARM TO THE 40S...THANKS TO THE LATE PRECIP ONSET. THIS
WILL RESULT IN PRECIP OUTSIDE THE MTNS STARTING MAINLY AS RAIN.
HOWEVER...STRONG DIABATIC COOLING WILL TAKE PLACE WITHIN THE REGION
OF STRONG FRONTOGENETICAL FORCING...AND TEMPS WILL LIKELY DROP
QUICKLY AS PRECIP BEGINS...ALLOWING FOR A TRANSITION TO ALL
SNOW...ESP NORTH OF I-85. A WINTER WEATHER ADVISORY WILL BE ISSUED
FOR MUCH OF OUR NC PIEDMONT/FHILL ZONES FROM LATE AFTERNOON THROUGH
THIS EVENING. UP TO 2 INCHES OF SNOW IS EXPECTED IN THESE AREAS. THE
DISCONCERTING ASPECT OF THIS EVENT IS THAT THERE ARE RATHER STRONG
SIGNALS THAT MESOSCALE BANDS OF HEAVIER SNOW WILL BECOME ESTABLISHED
WITHIN THE LARGER AREA OF PRECIP (OWING TO MODEL DEPICTION OF AREAS
OF INSTABILITY WITHIN THE REGION OF STRONGEST FORCING). THEREFORE...
LOCALLY HIGHER AMOUNTS OF MUCH GREATER THAN 2 INCHES WILL BE
POSSIBLE...ALTHOUGH WHERE THIS MIGHT OCCUR (OR EVEN IF IT OCCURS
WITHIN THE GSP CWA OR SOMEWHERE TO OUR EAST) IS HIGHLY UNCERTAIN.

ONCE THE SYNOPTIC FORCING MOVES QUICKLY TO THE EAST THIS EVENING...
THE CONCERN SHIFTS TO THE WESTERN MTNS AND A CONTINUING NORTHWEST
FLOW SNOW EVENT. THERE WILL BE SOME IMPRESSIVE INGREDIENTS IN PLACE.
H8 TEMPS BY 12Z SAT WILL BE AROUND -11...THE FLOW IS STRONG (AROUND
40 KT)...MOISTURE IS RELATIVELY DEEP...AND THERE ARE STEEP LOW LEVEL
LAPSE RATES. HOWEVER...THE FLOW IS QUITE BACKED...MORE WNW THAN TRUE
NW. THEREFORE...THIS MAY NOT BE A TRUE HEAVY SNOW NW FLOW EVENT.
HOWEVER...WITH THE PRECURSOR SNOWFALL LATER TODAY...THE ADDITIONAL
NORTHWEST FLOW SHOULD RESULT IN 24 HOUR ACCUMS MEETING OR EXCEEDING
THE WARNING THRESHOLD OF 5 INCHES IN AREAS FROM MADISON COUNTY SOUTH
TO GRAHAM COUNTY. THEREFORE...THE ADVISORY WILL BE UPGRADED TO A
WARNING IN THESE AREAS.
-- End Changed Discussion --

[1234snow]

Right now the temp is 33 with light snow fallling, flakes are fine.

Picked up an inch up to this point.

[1234snow]

Some heavier snow in KY is moving southeast:

http://www.accuweather.com/us/radar/sir/tn...r.asp?play=true

[mclean02]

looks like its making it over in to nc http://radar.weather.gov/Conus/southeast_loop.php

[davenc]

Thought I would bump this up a bit. Precip developing in the foothills and into the northern and central piedmont of NC. Most of Central NC including Charlotte metro under winter weather advisory. Its 50 at my house but supposedly once the precip starts temps are supposed to fall.

Please post obs for those affected by this clipper. I will be at work til probably 11 so won't be able to post and obs until later.

This post has been edited by davenc: Jan 7 2011, 03:21 PM

[1234snow]

Snow here has picked up some and is trying to stick again as the sun angle goes down. Knoxville and areas down that way here stayed warmer than I thought they would yesterday so accumulations will be cut down alot there.

Temp has fallen to 32.

[calculus1]

42.3 at my house. Very cloudy. Maybe a few sprinkles. Lots of virga!! Now, if it would just change to snow...

This post has been edited by calculus1: Jan 7 2011, 04:39 PM

[calculus1]

Here's a view from Boone, NC, at the moment:

[1234snow]

Have some pretty good sized flakes right now.

[newcster315]

I got to laugh soooooo hard on this.. I know it sounds like I am being negative on this forum all the time but you just got to wonder how sooooo many mets can just screw a forecast up or over hype a system.
Earlier this morning they issued a winter weather advisory and I posted it waaay early this morning. They said the rain/snow would begin between 2-5pm..NADDDDAAAA... I also posted at the same time how this system was too week to make it across the mountain..and IM RIGHT.. like usual... nothing is happening in my area oF Greensboro, NC and NOTHING will happen. METS STOP hyping all the time and get ppl so worked up about nothing. Maybe I should start taking classes to become a MET so I can make about $40,000 a year just to screw the weather up all the time.

[newcster315]

42.3 at my house. Very cloudy. Maybe a few sprinkles. Lots of virga!! Now, if it would just change to snow...

If it didnt start to fall earlier this afternoon... and your west of me... forget it.. u wont see nothing nor will any part of central nc

[WinterWishes]

42F light rain~

[calculus1]

36.6 and very light flurries.

WWA has just been canceled for foothills and piedmont of NC

This post has been edited by calculus1: Jan 7 2011, 07:38 PM

[WinterWishes]

39.1 light rain
although we did just have a sudden burst of heavier rain with a light mix in it....lasted all of about 25 seconds