FXUS61 KRNK 090744
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
244 AM EST WED DEC 9 2009
.SYNOPSIS...
INTENSE LOW PRESSURE WILL MOVE NORTHEAST ACROSS THE GREAT LAKES
OVERNIGHT. A COLD FRONT TRAILING FROM THIS SYSTEM WILL APPROACH FROM
THE WEST LATE TONIGHT AND PASS THROUGH THE AREA ON WEDNESDAY. COLD
HIGH PRESSURE FOLLOWS THE FRONT WITH DRIER BUT MUCH COLDER AIR ON
STRONG WESTERLY WINDS WEDNESDAY NIGHT INTO THURSDAY.
&&
.NEAR TERM /THROUGH TODAY/...
WILL ISSUE A QUICK UPDATE WITH SOME OF THE NEAR TERM CHANGES IN
THE FCST. MAIN CONCERN IS CONTINUED ICING IN THE HIGH ELEVATIONS
OF BATH COUNTY- WILL UPGRADE THEM TO AN ICE STORM WARNING. THE
OTHER NEAR TERM ISSUES ARE THE CONTINUED MODERATE TO HEAVY RAIN IN
THE MTNS. WITH FFG AS LOW AS 2 INCHES FOR 6 HOURS...AND RAINFALL
APPROACHING THOSE LEVELS...HAVE OPTED TO ISSUE A FLOOD WATCH THRU
15Z. HAVE ALSO OPTED TO RAISE THE WIND ADVISORIES IN THE MTNS TO A
HIGH WIND WARNING...SINCE MODELS CONTINUE TO SHOW A VERY STRONG
LLJ FROM THE SW WITH THE FROPA.
PREVIOUS DISCUSSION...
INITIAL BATCH OF DECENT RAINFALL ASSOCIATED WITH ISENTROPIC LIFT
THROUGH THE WEDGE HAS BASICALLY PUSHED NE WITH MORE PRE- FRONTAL
NATURE RAINFALL SET TO WORK INTO THE AREA FROM THE SW SHORTLY.
THIS SHOULD OVERSPREAD THE REGION THROUGH THE OVERNIGHT AS THE
FLOW ALOFT VEERS MORE SW AND THE AXIS OF BETTER LIFT ARRIVES.
TEMPS HAVE STABILIZED ACROSS THE REGION IN THE PAST COUPLE OF
HOURS AND EXPECT A SLOW RISE AFTER MIDNIGHT...AND PERHAPS MORE OF
A JUMP WHERE WARM ADVECTION WORKS TO THE SURFACE IN THE WEST.
SINCE THE 00Z RNK RAOB SHOWED A RATHER LARGE AREA OF BELOW
FREEZING BOUNDARY LAYER TEMPS UNDER EASTERLY FLOW EXPECT MANY OF
THE RIDGES HAVE SOME GLAZING WITH MORE SNOW/SLEET ACROSS THE NW
WHERE THE COLD AIR WAS A BIT DEEPER. FORECAST SOUNDINGS SHOW A
TREND TOWARD A BIT MORE FREEZING RAIN THRU ABOUT 06Z BEFORE ALL
EXCEPT THE VA HIGHLANDS EDGE ABOVE FREEZING. SINCE HAS BEEN SUCH A
MIXED BAG ACROSS BATH CTY WONT UPGRADE TO A WARNING THERE FOR NOW
AND BASICALLY HANG ONTO CURRENT UPDATED WINTER WX ADVISORYS FROM
EARLIER A WHILE LONGER. OTRW AFTER A BRIEF LULL ROLLING WITH HIGH
CAT POPS OVERNIGHT UNTIL LATE AND INCLUDING AN ISOLATED -TSRA
MENTION FAR WEST WHERE NAM INDICATES AT LEAST SOME ELEVATED
CONVECTIVE POTENTIAL BY MORNING. THINK ANOTHER ONE TO POSSIBLY TWO
INCHES OF QPF BY MORNING BUT AGAIN APPEARS RATES LOW ENOUGH TO
PRECLUDE A FLOOD WATCH AT THIS POINT.
SE WINDS CONTINUE TO GUST TO NEAR 50 MPH IN TAZEWELL/MERCER CTYS
AND EXPECT A FEW MORE HOURS OF STRONGER GUSTS UNTIL THE FLOW VEERS
MORE SW TOWARD MORNING. OTHER GOING WIND PRODUCTS LOOK IN GOOD
SHAPE. HOWEVER GIVEN PROGGED 60-70 KTS OFF THE 00Z NAM AT 85H
EAST OF THE BLUE RIDGE AND BUFKIT SHOWING 40-50 KTS NEAR THE
SURFACE WEDNESDAY...PLAN TO EXTEND THE WIND ADVISORY ACROSS THE
REST OF THE CWA FOR WED ESPCLY WITH THE GROUND SO WET. ALSO MADE
SOME SLIGHT ADJUSTS TO DELAY TEMP RISES PER CURRENT OBS AND TO
LOWER LOWS SOME BASED ON ONGOING OBS ATTM.
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 /TONIGHT 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 /08Z WEDNESDAY THROUGH SUNDAY/...
THE THREAT FOR FREEZING PRECIPITATION WILL BE CONFINED TO THE LWB AIRPORT
AND POINTS NORTHEAST TOWARD HSP THRU LATE TONIGHT. TEMPS AT LWB/BLF
REMAIN ABV FREEZING. ICE PELLETS WILL ALSO MIX IN WITH THE RAIN
BEFORE TEMPS PERHAPS WARM SLOWLY LATE TONIGHT. ELSW ONLY RAIN IS
EXPECTED WITH WIDESPREAD POOR FLYING CONTINUING OVERNIGHT BEFORE
WINDS BECOME MORE SW AND START TO MIX THINGS OUT EARLY WED
MORNING. A STRONG LOW LVL JET ABOVE THE COOL WEDGE WILL CREATE LOW
LVL WIND SHEAR CONDITIONS OVERNIGHT INTO EARLY WEDNESDAY MORNING
AT ALL TAF SITES. THE BLF AIRPORT WILL ALSO EXPERIENCE STRONG
WINDS AFTER MIDNIGHT TONIGHT INTO WED MORNING WITH GUSTS UP TO 50
MPH POSSIBLE.
ANY FREEZING PRECIP WILL CHANGE TO RAIN IN THE PREDAWN HOURS 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...WITH STRONG WINDS DURING THE AFTERNOON
ACROSS ALL SITES INCLUDING THE EAST WHERE WEST WINDS MAY GUST
ABOVE 30-35 KTS AT TIMES.
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 INTO SAT. ANOTHER WEAK STORM SYSTEM
LOOKS TO BRING A POSSIBLE MIXED BAG OF PRECIP BACK TO THE AREA
WITH MVFR/IFR CONDITIONS BY SUNDAY.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...HIGH WIND WARNING FROM 6 AM THIS MORNING TO 7 PM EST THIS
EVENING FOR VAZ010>014-016>020.
WINTER WEATHER ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR
VAZ016>019-023-024-034-035.
FLOOD WATCH UNTIL 10 AM EST THIS MORNING FOR VAZ007-009>015.
HIGH WIND WARNING UNTIL 7 PM EST THIS EVENING FOR VAZ007-009-
015.
WIND ADVISORY FROM 6 AM THIS MORNING TO 7 PM EST THIS EVENING
FOR VAZ022>024-032>035-043>047-058-059.
WIND ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR VAZ020.
ICE STORM WARNING UNTIL 7 AM EST THIS MORNING FOR VAZ020.
NC...HIGH WIND WARNING FROM 6 AM THIS MORNING TO 7 PM EST THIS
EVENING FOR NCZ002.
FLOOD WATCH UNTIL 10 AM EST THIS MORNING FOR NCZ001-002-018.
HIGH WIND WARNING UNTIL 7 PM EST THIS EVENING FOR NCZ001-018.
WIND ADVISORY FROM 6 AM THIS MORNING TO 7 PM EST THIS EVENING
FOR NCZ003>006-019-020.
WV...HIGH WIND WARNING FROM 6 AM THIS MORNING TO 7 PM EST THIS
EVENING FOR WVZ043>045.
FLOOD WATCH UNTIL 10 AM EST THIS MORNING FOR WVZ042>045.
HIGH WIND WARNING UNTIL 7 PM EST THIS EVENING FOR WVZ042.
WIND ADVISORY UNTIL 6 AM EST EARLY THIS MORNING FOR WVZ043-045.
&&
$$
SYNOPSIS...JH
NEAR TERM...JH/JJ/WP
SHORT TERM...DS
LONG TERM...KM
AVIATION...JH/KM/WP
