FXUS61 KRNK 082037
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
337 PM EST TUE DEC 8 2009
.SYNOPSIS...
HIGH PRESSURE WILL BE OVER THE MID ATLANTIC THIS AFTERNOON WHILE A
STRONG AREA OF LOW PRESSURE MOVES INTO THE GREAT LAKES REGION
TONIGHT INTO WEDNESDAY...BRINGING A COMPLEX SERIES OF FRONTS
THROUGH OUR REGION.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
SHORTWAVE STREAMING NEWD ACROSS THE TN VALLEY ATTM...IS SPREADING
MOISTURE/PRECIP INTO THE AREA. TEMPS WERE ABLE TO WARM UP A LITTLE
MORE THAN EARLIER ANTICIPATED...BUT WET BULBS AND DEWPOINTS ARE
AROUND FREEZING IN SOME OF THE MTN VALLEYS. AS THE PRECIP CONTINUES
TO OVERRUN THE HIGH PRESSURE WEDGE...AIRMASS SHOULD COOL TO THE WET
BULB AND THIS WILL CREATE SOME WINTRY PRECIP ISSUES THIS EVENING.
HOWEVER...THE CURRENT STATE OF THE GROUND TEMPS AND HIGHER AIR TEMPS
SUGGEST THAT SLEET AT THE ONSET WILL BE SHORT LIVED AND ACCUMULATE A
FEW TENTHS OVER THE HIGHLANDS OF VA AT BEST. AS THE STRONG WAA
CONTINUES THIS EVENING...PRECIP OVER THE COLDER VALLEYS OF SW VA/SE
WV AND EVEN NW NC WILL SWITCH TO FREEZING RAIN. ATTM ONLY EXPECTING
A LIGHT GLAZE IN THE VALLEYS OF FAR SW VA/NW NC BUT WILL KEEP
ADVISORIES IN PLACE AS IS...ALTHOUGH THIS SHOULD BE ABLE TO BE
CLEARED BY MIDNIGHT AS ALL RAIN EXPECTED BY THEN.
FURTHER NORTH...OVER THE GREENBRIER VALLEY EAST TO THE BLUE RIDGE
NORTH OF PEAKS OF OTTER...COLDER AIR WILL LINGER A LITTLE LONGER BUT
EVEN THIS WILL BE DISLODGED BY 09Z WED. NOT EXPECTING AS MUCH ICE AS
PREVIOUS FORECASTS THOUGH LESS THAN A QUARTER INCH WILL OCCUR IN
SPOTS...SPECIALLY ACROSS THE HIGHLANDS OF BATH COUNTY INTO ALLEGHANY
COUNTY VA...AND ALSO ALONG THE BLUE RIDGE PARKWAY NORTH OF THE JAMES
RIVER HEADING TOWARD MONTEBELLO. WILL CONTINUE TO KEEP ADVISORIES AS
IS...AS THE PRECIP IS NOW MOVING IN.
OTHER THAN THE WINTRY MIX...LOOKING AT A DECENT RAIN EVENT...WITH AN
INCH EXPECTED AT MOST LOCATIONS.
WENT CLOSER TO THE MET MOS TONIGHT...AS IT WAS HANDLING CURRENT
TEMPS AND TRENDS A LITTLE BETTER THAN MAV. LOOKING AT AIR TEMPS
SURGING ABOVE FREEZING AFTER MIDNIGHT...AND ESPECIALLY TOWARD 12Z.
LOW TEMPS WILL BE ESTABLISHED IN THE EVENING WITH RISING MOST PLACES
OVERNIGHT.
THE SURGE OF WARM AIR WILL DISLODGE THE HIGH PRESSURE WEDGE
WEDNESDAY WITH RAIN SHOWERS ENDING FROM SW TO NE. ATTM...LEFT
THUNDER OUT BUT THE STRONG DYNAMICS MAY LEAD TO A FEW CLOUD TO
GROUND STRIKES IN THE FAR SW AS THE WARMER AIR SURGES WHILE COLDER
AIR ALOFT INCREASES LAPSE RATES....BUT BY THEN MOISTURE WILL BE
GETTING SHALLOWER.
HAVE UPDATED THE HAZARD GRIDS TO REFLECT A PROLONGED PERIOD OF
STRONG WIND GUSTS THROUGH THE DAY WEDNESDAY. 850 MB WINDS ARE
PROGGED TO TURN SOUTHWEST TOMORROW AROUND 12Z AND INCREASE TO AROUND
50 TO 55 KTS OFF THE PREFERRED GFS SOLUTION. HAVE INCREASED IN TIME
THE WIND ADVISORY AND HIGH WIND WARNING THAT WAS IN EFFECT THROUGH
100 PM TO NOW 600 PM...AND EXPANDED BOTH TO INCLUDE MORE OF THE
REGION WEST OF THE BLUE RIDGE. MORE OF THE MOUNTAIN EMPIRE REGION OF
SOUTHWEST VIRGINIA IS INCLUDED IN THE WARNING...AND NOW THE NEW
RIVER VALLEY NORTH INTO THE UPPER JAMES RIVER BASIN IS INCLUDED.
EAST OF THE BLUE RIDGE...WILL BE EMPHASIZING THE POTENTIAL FOR
STRONG WIND GUSTS POTENTIALLY BEING ABLE TO DOWN SOME TREES GIVEN
WET SOIL CONDITIONS DESPITE NON-WARNING OR NON-ADVISORY WIND SPEEDS.
THE COLD/OCCLUDED FRONT SWINGS EAST ACROSS THE CWA DURING THE DAY
AND SHOULD BE EAST OF THE CWA IN THE AFTERNOON. WITH LAGGING COLDER
AIR...WILL WARM HIGHS UP A BIT IN THE EAST TO THE LOWER 60S.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS THE LOW EXITS THE REGION...AND THE CENTER OF HIGH PRESSURE DRAWS
CLOSER...WE WILL EXPERIENCE WIND SPEEDS TAPERING OFF THROUGH
WEDNESDAY NIGHT. CURRENT HIGH WIND WARNING AND ADVISORY ENDS IN THE
VERY EARLY EVENING WEDNESDAY. AS WE GET CLOSER TO THAT TIME...THERE
MAY BE A NEED TO CONTINUE A WIND ADVISORY IN THE LOCATION OF THE
CURRENT WARNING THROUGH ABOUT MIDNIGHT OR SO WEDNESDAY NIGHT. THE
DECISION TO DO OR NOT TO DO THAT WOULD HAVE TO COME TOWARDS THE END
OF THE CURRENT WARNING...BUT IT THERE IS THAT POTENTIAL.
AS NORTHWEST FLOW CONTINUES WITH RESIDUAL UPSLOPE MOISTURE...LOOK
FOR A CONTINUATION OF SCATTERED SNOW SHOWERS IN THE SE WV
MOUNTAINS...SOUTH INTO THE NORTHERN MOUNTAINS OF NORTH CAROLINA. A
REINFORCING TROUGH BEHIND THE INITIAL COLD FRONT WILL ALSO ADD SOME
INSTABILITY. BEST COVERAGE LOOKS TO BE LATE WEDNESDAY INTO EARLY
THURSDAY MORNING. HEADING INTO THURSDAY NIGHT...COVERAGE WILL BE ON
THE DECREASE AND THEN END.
HIGH PRESSURE SETTLES OVER THE AREA ON FRIDAY WITH NOTABLE COLDER
TEMPERATURES. HAVE UNDERCUT GUIDANCE TEMPERATURES GIVEN THE PROGGED
STRENGTH OF THE HIGH.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
THERE ARE TWO SYSTEMS THAT CAN POTENTIALLY IMPACT THE LONG TERM
FORECAST. AN AREA OF LOW PRESSURE WILL MOVE ACROSS THE SOUTHEAST AND
TO THE ATLANTIC COAST SATURDAY. IN COMPARISON TO YESTERDAYS LONG
RANGE SUITE...MODELS ARE FURTHER SOUTH WITH THE TRACK...ESPECIALLY
THE 12Z ECMWF. THIS TREND HOWEVER WAS HINTED AT IN THE 12Z GEFS
RUNS. WITH NOT MUCH AMPLITUDE IN THE UPPER FLOW...AND THE ABSENCE
OF ANY HIGH LATITUDE BLOCKING ACROSS THE NORTH ATLANTIC...DIFFICULT
TO SEE THIS SYSTEM TAKE THE MORE NORTHERLY TRACK ALONG THE COAST
THAT THE 12Z GFS SUGGESTS. HIGH PRESSURE WHICH ARRIVES BEFORE THE
STORM FRIDAY AND FRIDAY NIGHT MAY BE STRONG ENOUGH TO KEEP THE
SYSTEM SOUTH. WITH THIS IN MIND...LOWERED POPS SOMEWHAT NORTH OF THE
VA/NC BORDER AND LOWERED SOUTH OF THE NC/VA BORDER. WILL KEEP
PTYPE JUST RAIN/SNOW FOR NOW...BUT SLEET MAY ALSO MIX IN AT TIMES.
ALSO...THINK THAT THE MOST PRECIP WILL FALL LATE SATURDAY AND
SATURDAY NIGHT. BASICALLY TRIED TO FOLLOW THE 12Z ECMWF AND THE
12Z GEFS. FOR NOW...WILL LEAVE ANY MENTION OUT OF THE HWO
CONSIDERING THE SOUTHWARD TREND. AT THE END OF THE LONG
TERM...BOTH THE ECMWF AND GFS HAVE A SYSTEM AFFECTING THE CWA WITH
WINTRY PRECIPITATION POSSIBLE AGAIN. THE ECMWF MOVES THE POLAR
VORTEX TO JAMES BAY BY NEXT TUESDAY. THIS CAUSES ONE OF THE
DISTURBANCES MOVING OUT OF THE SOUTHERN STREAM TO PHASE. IT IS NOT
UNCOMMON FOR STRONG SYSTEMS TO FORM WITH SUCH A DRASTIC MOVEMENT
OF THE POLAR VORTEX INTO SE CANADA. ALSO...HIGH LATITUDE BLOCKING
MAY BE IN PLACE WITH THIS SYSTEM...WITH AN UPPER RIDGE CENTERED
JUST EAST OF GREENLAND. PLENTY OF TIME TO WATCH THIS SYSTEM WHICH
HAS PROMISE.
&&
.AVIATION /21Z TUESDAY THROUGH SUNDAY/...
HIGH IMPACT EVENT FOR THE AVIATION COMMUNITY THIS PERIOD. LOOKING
AT CIGS DROPPING TO MVFR THIS AFTERNOON AND EVENING. PRECIPITATION
WILL MOVE INTO BLF/LWB BY 22Z. THE THREAT FOR FREEZING
PRECIPITATION WILL BE CONFINED TO THE LWB AIRPORT EARLY THIS
EVENING AND POINTS NORTHEAST TOWARD HSP. ROANOKE WILL BE ON THE
EDGE THIS AFTERNOON BUT MAINLY EXPECTING A FEW ICE PELLETS MIXED
WITH RAIN. LYH WILL ALSO BE CLOSE TO THE FREEZING RAIN LINE EARLY
BUT WARM AIR ON STRONG SOUTHERLY WINDS WILL PREVENT ICING AT THE
LYH AIRPORT. STRONG LOW LVL JET ABOVE THE COOL WEDGE WILL CREATE
LOW LVL WIND SHEAR CONDITIONS THIS EVENING INTO EARLY WEDNESDAY
MORNING AT ALL TAF SITES. THE BLF AIRPORT WILL ALSO EXPERIENCE
STRONG WINDS AFTER MIDNIGHT TONIGHT INTO WED MORNING WHERE GUSTS
UP TO 50 MPH ARE POSSIBLE.
ANY FREEZING PRECIP WILL CHANGE TO RAIN OVERNIGHT BUT CIGS WILL
STAY IN THE IFR/MVFR RANGE AND AT TIMES LIFR. AS WINDS VEER TO THE
SOUTHWEST WEDNESDAY MORNING WILL EXPECT TO SEE SOME GUSTS AS THE
WEDGE ERODES...BUT STRONGER WINDS WILL BE AT OR AFTER THE END OF
THIS PERIOD FOR THE ROA/LYH/DAN SITES.
WINDS WILL STAY STRONG AND GUSTY THROUGH WEDNESDAY NIGHT...BUT
WILL BE OUT OF THE WEST TO NORTHWEST BEHIND THE COLD FRONT.
WINDY AND GUSTY CONDITIONS POSSIBLE INTO THURSDAY NIGHT. HIGH
PRESSURE BUILDS IN ON FRIDAY BRINGING A RETURN TO VFR ACROSS THE
REGION ALONG WITH LIGHTER WINDS. ANOTHER WEAK STORM SYSTEM LOOKS
TO BRING A POSSIBLE MIXED BAG OF PRECIP BACK TO THE AREA WITH
MVFR/IFR CONDITIONS ON SATURDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR
VAZ018>020-023-024-034-035.
WIND ADVISORY FROM 6 AM TO 7 PM EST WEDNESDAY FOR VAZ011-013-
014-016>019.
HIGH WIND WARNING FROM 6 AM TO 7 PM EST WEDNESDAY FOR VAZ010-
012.
WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR
VAZ010>016.
HIGH WIND WARNING UNTIL 7 PM EST WEDNESDAY FOR VAZ007-009-015.
WIND ADVISORY UNTIL 7 PM EST WEDNESDAY FOR VAZ020.
NC...WIND ADVISORY FROM 6 AM TO 7 PM EST WEDNESDAY FOR NCZ002.
HIGH WIND WARNING UNTIL 7 PM EST WEDNESDAY FOR NCZ001-018.
WV...WINTER WEATHER ADVISORY UNTIL 6 AM EST WEDNESDAY FOR
WVZ043>045.
WIND ADVISORY FROM 6 AM TO 7 PM EST WEDNESDAY FOR WVZ044.
HIGH WIND WARNING UNTIL 7 PM EST WEDNESDAY FOR WVZ042.
WIND ADVISORY UNTIL 7 PM EST WEDNESDAY FOR WVZ043-045.
&&
$$
SYNOPSIS...AMS/WP
NEAR TERM...DS/WP
SHORT TERM...DS
LONG TERM...KM
AVIATION...AMS/WP
