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Pay attention to the clipper tonight in NC


HKY_WX

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An excellent blurb from RAH tonight on this system.

ATTENTION THEN TURNS TO THE INITIALLY-SHEARED TROPOPAUSE DISTURBANCE

-- AND ACCOMPANYING 100+KT MID LEVEL JET -- IN NW FLOW ALOFT OVER

SASKATCHEWAN THIS EVENING. SNOW OVER THE NORTHERN PLAINS AND UPPER

MIDWEST WILL STREAK RAPIDLY SOUTHEASTWARD TO THE WESTERN SLOPES OF

THE NC BLUE RIDGE BY FRIDAY MORNING. THE DISTURBANCE WILL AMPLIFY AS

IT RACES SOUTHEASTWARD INTO THE BASE OF THE L/W TROUGH OVER THE

EASTERN US...AND PLACE CENTRAL NC IN A STRONGLY AGEOSTROPHIC

MID-UPPER JET EXIT REGION...ON THE NW SIDE OF A DEEPENING MIGRATORY

SURFACE WAVE FROM THE NORTHERN PLAINS TONIGHT TO SOUTHERN NC FRIDAY

AFTERNOON AND EVENING - A VERY FAVORABLE TRACK OF THESE FEATURES

ALOFT AND AT THE SURFACE FOR PRECIPITATION IN CENTRAL NC. THE DEGREE

OF FORCING AND STEEPENING OF LAPSE RATES ALOFT (IN EXCESS OF 6.5

C/KM) SUGGESTS THE POTENTIAL FOR A BAND OF HIGHER INTENSITY

PRECIPITATION...POSSIBLY A QUICK BURST OF ADVISORY CRITERIA SNOW IN

THE VICINITY OF US HIGHWAY 64...AS THE DAY SHIFT HAS ALREADY NOTED

(BELOW). IT IS INTERESTING TO NOTE...HOWEVER...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.

THIS WOULD ARGUE AGAINST ANY SNOW...OR THAT THIS WOULD BE A VERY

RARE...HIGHLY ANOMALOUS EVENT. THE NORTHERN HEMISPHERIC PATTERN IS

HIGHLY ANOMALOUS AT PRESENT...AFTER ALL... -MWS

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Don't know what is causing the problem with the NAM's qpf output for the area along the KY/VA border. This area generally gets some of the highest totals from NW flow events. Just look at the radar during these, let alone obs. The above depiction clearly shows the upslope enhancement along the Tn/Nc border and in West Va but clearly ignores the favored SE,KY/SWVA area.???

Both the NAM and GFS have under forecasted qpf during every snow event this season thus far. Just yesterday for example, both had just a few hundredths total qpf for much of East Tn . Many area received a quarter inch or better with upwards of 3 inches of snow.

I know the models probably get less data ingested in them from this area and also the terrain has it's effects but, it seems this problem has been more prevalent of late. I'm curious if anyone knows if any "upgrades" that affects qpf output has been done recently.? I know the Nam has been known to have a wet bias so, that's why with the recent happenings I'm curious.

A little late to the conversation, but I thought I'd toss in an agreement.

Models certainly butchered last night's storm, which caught many off-guard. Erwin easily would have had three to five inches but unfortunately is just far enough south that temperatures remained at or just above freezing the entire event. We wound up with an inch and a half, with some areas reaching two inches. You're certainly correct in saying that was not the first time this year that models haven't handled QPF very well in this area.

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FWIW, the NMM gives a very narrow but intense band of heavy qpf for the system tomorrow. It makes since given the dynamics are very strong with it, VV's of -40 on the NAM which is the end of the scale. Also, a 994mb low is very strong for a clipper, more like a mauler :thumbsup: Anyways, could be a narrow band of 4-5" tomorrow, wouldn't surprise me at all. Surface temps east of Raleigh shouldn't be a problem either as the models wetbulb us to around 32 when the event starts.

hiresw_p24_033l.gif

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Should be very interesting to see how things play out tomorrow with this clipper. Already some excellent posts already by Brandon and Allan. I'm pretty much in agreement with their thoughts... showing a setup that is similar to the January 23rd, snowstorm. Its not an identical setup, as there was a bit stronger jet with the 2003 event. However, heights are actually lower with the current setup, although the 500mb low is a bit more broad. I'll try to give a more detailed assessment tomorrow in my blog.

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Winter Weather Advisory

URGENT - WINTER WEATHER MESSAGE

NATIONAL WEATHER SERVICE NEWPORT/MOREHEAD CITY NC

315 AM EST FRI JAN 7 2011

...ACCUMULATING SNOW EXPECTED FOR EASTERN NORTH CAROLINA TONIGHT...

.LOW PRESSURE WILL MOVE QUICKLY ACROSS EASTERN NORTH CAROLINA

TONIGHT. AS A RESULT...SNOW OR A RAIN AND SNOW MIX WILL BEGIN THIS

EVENING CHANGING TO ALL SNOW BY AROUND MIDNIGHT.

NCZ029-044>047-079>081-091-072100-

/O.NEW.KMHX.WW.Y.0001.110107T2300Z-110108T1200Z/

MARTIN-PITT-WASHINGTON-TYRRELL-MAINLAND DARE-GREENE-BEAUFORT-

MAINLAND HYDE-LENOIR-

INCLUDING THE CITIES OF...WILLIAMSTON...ROBERSONVILLE...

GREENVILLE...PLYMOUTH...COLUMBIA...SNOW HILL...HOOKERTON...

WASHINGTON...RIVER ROAD...KINSTON

315 AM EST FRI JAN 7 2011

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Major props to HKY_WX! Here is the Near term AFD from GSP this AM.

.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

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Raleigh NWS on Board. WWA up for most of FA calling for 1-2 inches. Gonna have to cool from the top-down with this one coming in late afternoon, so need some heavy precip rates.Be awesome to lay a few inches down and hold onto it until Sun/Mon, then get the Nam and GFS to verify. I'm still gung ho about a nice snow event here Sun/Mon. The pattern dictates it! :snowman:

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I am not a fan of this one being I will probably be just south of any real accumulation potential but it will be interesting to see how the surface layer is overcome.

Whoops I forgot to change maps... in my blog I went over how its going to be very difficult to judge just where the bands set up, so anywhere within that yellow circle can get under that 1-2" band.

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Right now RAH thinks the inhanced band will set up along US 64. But as you stated we'll have to wait and see.

Yeah...I'm not too far north of 64 so maybe I can get under that band. It looks like the 6Z GFS was a little further north...with higher qpf totals all the way to the VA border...so maybe you and me both will get under that band.

This is going to be fun to watch unfold, regardless if it materializes for me or not.

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Yeah...I'm not too far north of 64 so maybe I can get under that band. It looks like the 6Z GFS was a little further north...with higher qpf totals all the way to the VA border...so maybe you and me both will get under that band.

This is going to be fun to watch unfold, regardless if it materializes for me or not.

Yes, it always seem we're always in that US1/64 sweet spot. Must be something about this area.

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