Scientific Forecaster Discussion

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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
733 AM EDT THU APR 17 2014

.SYNOPSIS...
A LARGE AREA OF HIGH PRESSURE WILL REMAIN OVER THE NORTHEASTERN
U.S. THROUGH FRIDAY KEEPING A RELATIVELY COOL AIR MASS ACROSS THE
REGION. AN AREA OF LOW PRESSURE WILL MOVE VERY SLOWLY THROUGH THE
SOUTHEASTERN STATES INTO SATURDAY...WHICH WILL BRING CLOUDS TO THE
ENTIRE AREA AND A CHANCE OF RAIN TO NORTH CAROLINA AND FAR
SOUTHERN VIRGINIA. A STRONGER COLD FRONT WILL APPROACH THE REGION
FROM THE WEST EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 415 AM EDT THURSDAY...

BENIGN FORECAST THROUGH THE NEAR TERM AS LARGE AREA OF COLD...DRY
HIGH PRESSURE ANCHORED OVER NEW ENGLAND DOMINATES THE REGION. LOW
PRESSURE DEVELOPING ACROSS THE SOUTHEAST STATES/EASTERN GULF LATE
IN THE PERIOD WILL REMAIN SUFFICIENTLY FAR SOUTH THROUGH THIS TIME
FRAME TO HAVE NO IMPACT ON THE REGION THROUGH THIS TIME FRAME. A
NORTHERN STREAM UPPER SHORT WAVE APPROACHING FROM THE NORTHWEST
WILL ALSO HAVE LITTLE IMPACT OTHER THAN ALSO SOME HIGH CLOUDS
LATE IN THE PERIOD. MAIN CONCERN THROUGH THIS TIME FRAME WILL ONCE
AGAIN BE FREEZING TEMPERATURES AND FROST POTENTIAL. WILL LET
CURRENT FREEZE WARNING FOR THE PIEDMONT RUNS ITS COURSE THROUGH 9
AM. FOR FRIDAY MORNING...ANY FREEZING TEMPERATURES LOOK VERY
SPOTTY AS AIR MASS CONTINUES TO SLOWLY MODIFY. MORE
IMPORTANTLY...HOWEVER...WILL BE STRENGTHENING EASTERLY FLOW IN
RESPONSE TO DEVELOPING LOW PRESSURE IN THE SOUTHEAST. THE EXTENT
OF THIS WIND FLOW IS NOT TOTALLY CLEAR AT THIS POINT...BUT ENOUGH
CONFIDENCE THAT WEST OF THE BLUE RIDGE IN THE SOUTHERN SHENANDOAH
VALLEY THAT ENOUGH DECOUPLING WILL EXIST FOR DEVELOPMENT OF
WIDESPREAD FROST AS TEMPERATURES DROP INTO THE LOWER AND MID 30S
AFTER LATE TONIGHT/EARLY FRIDAY. THUS...HAVE GONE AHEAD AND ISSUED
A FROST ADVISORY FOR BOTETOURT...AMHERST...AND ROCKBRIDGE...THE
MAIN AREA OF CONCERN AT THIS POINT. DAY SHIFT MAY NEED TO CONSIDER
EXPANDING THIS FURTHER EAST AND SOUTH DEPENDING ON DEGREE OF
CONFIDENCE IN DECOUPLING ALLOWING FOR FROST FORMATION. GROUND IS
QUITE MOIST...SO IF WINDS REMAIN LIGHT...TEMPERATURES SHOULD BE
COLD ENOUGH FOR FROST TO DEVELOP.

FOR TEMPERATURES...HAVE ONCE AGAIN FAVORED THE COLDER ECMWF MOS
GUIDANCE...WHICH HAS BEEN HANDLING THE LAST FEW DAYS QUITE WELL.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
AS OF 300 AM EDT THURSDAY...

FRIDAY INTO FRIDAY NIGHT...A COLD AIR DAMMING RIDGE WILL BE IN PLACE 
ACROSS THE LEE OF THE APPALACHIANS. PROGRESSIVELY INCREASING 
MOISTURE OFF THE ATLANTIC WILL PROGRESS INTO THE AREA ON SOUTHEAST 
WINDS...ROUNDING THE BASE OF THE RIDGE. ANTICIPATE AT LEAST A MOSTLY 
CLOUDY SKY ON FRIDAY WITH INCREASING CLOUD COVER FRIDAY NIGHT. 
ANOTHER FEATURE ALSO WILL BE CONTRIBUTING TO INCREASED CLOUD 
COVER TO AREA IN GENERAL...AND POTENTIALLY SOME PRECIPITATION TO THE 
SOUTHERN AND SOUTHEASTERN PORTION OF THE REGION. 00Z/8PM GUIDANCE 
AMONG THE GFS...ECMWF...AND CANADIAN SOLUTIONS BRING A CLOSED LOW 
SLOWLY NORTHEAST THROUGH THE GULF COAST STATES WITH THE NORTHERN 
EXTENT OF ITS PRECIPITATION SHIELD BRUSHING OUR SOUTHERN TIER 
COUNTIES BY FRIDAY EVENING...CONTINUING THROUGH THE NIGHT...AND 
CONCLUDING INTO SATURDAY MORNING. THE LOW ITSELF IS PROGGED TO 
CONTINUE A SLOW NORTHEAST TRACK AND EXIT THE U.S. OFF THE GA/SC 
COAST AROUND SATURDAY EVENING.

WHILE THESE THREE SOLUTIONS ARE SIMILAR...THEY ARE A SHIFT NORTH 
AS COMPARED TO THEIR EARLIER COUNTERPARTS THAT HAD DRY 
SOLUTIONS...AND THE 00Z/8PM NAM SOLUTION HAS MAINTAINED A MORE 
SOUTHERLY...AND THUS DRIER AND WARMER SOLUTION FOR OUR REGION. GIVEN 
THIS...WILL OFFER NO MORE THAN A SLIGHT CHANCE OF LIGHT RAIN FROM 
THE NORTHERN MOUNTAINS OF NC EASTWARD ALONG THE NC/VA BORDER DURING 
THE FRIDAY EVENING/NIGHT TIME FRAME...AND GREATER CLOUD COVER...AND 
COOLER TEMPERATURES ACROSS THE FORECAST AREA AS A WHOLE.

WILL REFRAIN FROM CONTINUING THE SLIGHT CHANCE INTO SATURDAY AT THIS 
POINT...AND ALLOW OUR FORECAST TO CONTINUE FORWARD NEARLY UNCHANGED 
THROUGH THE REMAINDER OF THE WEEKEND. THIS SOLUTION IS ONE THAT 
KEEPS THE REGION WITHIN A ZONE OF DRY...HIGH PRESSURE...WITH EVER 
SLOWLY RISING HEIGHTS THROUGH THE PERIOD...WHILE THE CLOSED LOW 
SPINS OFF THE COAST OF THE SOUTHEAST U.S.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 330 PM EDT WEDNESDAY...

UPPER RIDGING BUILDING BEHIND A CLOSE UPPER LOW OFF THE SOUTHEAST
COAST WILL PROVIDE A NICE BOOST IN TEMPS FOR MUCH OF THE LONG
TERM. DESPITE CLOUDS AHEAD OF ANOTHER WEAK SYSTEM APPROACHING FROM
THE GREAT LAKES...WARM SW FLOW SHOULD SHOVE +10C H85 AIR OUR WAY
INTO TUESDAY. H8H TEMPS ARE ONLY SLIGHTLY COOLED BY THIS BOUNDARY
WITH SHOWERS PROBABLY CONFINED TO TUESDAY NIGHT OR WEDNESDAY
MORNING. HEIGHTS BUILD QUICKLY BEHIND THIS DISTURBANCE IN RESPONSE
TO A CLOSED LOW AND DIGGING NEGATIVELY TILTED TROUGH THROUGH THE
ROCKIES...WITH THE WARM PATTERN CONTINUING THROUGH THE END OF THE
FORECAST.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
AS OF 730 AM EDT THURSDAY...

VFR CIGS/VSBYS EXPECTED TO CONTINUE THROUGH THE PERIOD AS A LARGE
COLD...DRY HIGH PRESSURE AREA ANCHORS ACROSS THE NORTHEASTERN U.S.
THROUGH THE PERIOD. LOW PRESSURE ALOFT WILL BE DEEPENING ACROSS
THE EASTERN GULF SE GA/SC/NORTHERN FL THROUGH THE PERIOD...WHICH
WILL PROLONG THE E-NE SFC FLOW INTO THE REGION FOR SEVERAL DAYS.
AS THE FLOW BECOMES MORE ESE-SE THU NIGHT INTO FRI AND INCREASED
MARITIME FLOW...SOME LOW CLOUDS MAY BEGIN TO DEVELOP ACROSS THE
PIEDMONT...ESPECIALLY IN UPSLOPE AREAS ALONG THE BLUE RIDGE...BUT
THIS SHOULD REMAIN BEYOND THIS VALID TAF PERIOD. A FEW HIGH CLOUDS
WILL SKIRT THE AREA FROM THE WEST TODAY...BUT HIGH CLOUDS WILL
INCREASE CONSIDERABLY OVERNIGHT AND AFT 06Z COULD BECOME BKN-OVC
IN MOST AREAS AT 250. WINDS ENE- ESE THROUGH THE PERIOD AT
6-9KTS...WITH LOW END GUSTS POSSIBLE LYH/ROA DURING THE DAYTIME.
BLF CONTINUES TO EXHIBIT TYPICALLY GUSTY SE WINDS FOR SYNOPTIC
PATTERN...AND THIS SHOULD CONTINUE THROUGH MUCH OF THE TAF VALID
PERIOD WITH PERIODIC GUSTS TO 20KTS POSSIBLE.

HIGH CONFIDENCE IN VFR CIGS/VSBYS THROUGH THE TAF VALID PERIOD.
MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID
PERIOD.

EXTENDED AVIATION DISCUSSION...
THE NEXT COLD FRONT APPROACHES FROM THE WEST FRIDAY WHILE ANOTHER
SYSTEM STAYS OFF THE SOUTHEAST COAST. THERE IS POTENTIAL FOR
INCREASE CLOUDS FRIDAY-SATURDAY OVER THE SOUTHEAST BUT MOST PLACES
SHOULD STAY VFR...POTENTIALLY MVFR EARLY FRI ACROSS THE PIEDMONT.
VFR FOR SUNDAY WITH HIGH PRESSURE REMAINING ACROSS THE NORTHEAST
AND MID ATLANTIC. THE NEXT SYSTEM TO BRING MVFR TO POTENTIALLY IFR
CIGS AND -SHRA TO THE AREA DOES NOT ARRIVE UNTIL EARLY TO MID PART
OF NEXT WEEK.

&&

.CLIMATE...
AS OF 1000 AM EDT WEDNESDAY...

RECORD LOWS AT BLACKSBURG...BLUEFIELD AND LEWISBURG THIS MORNING

BLACKSBURG TIED THEIRS AT 24...BLUEFIELD TIED THEIRS AT 23 AND
LEWISBURG BROKE THEIRS AT 23.


APRIL 17TH RECORD LOWS

ROANOKE 27F 1980......FORECASTED LOW 31F. 
LYNCHBURG 27F 1904....FORECASTED LOW 30F. 
DANVILLE 28F 1962.....FORECASTED LOW 30F. 
BLUEFIELD 25F 2001....FORECASTED LOW 32F. 
BLACKSBURG 20F 1974...FORECASTED LOW 26F. 
LEWISBURG 25F 2001....FORECASTED LOW 20F.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR VAZ022>024-
     032>035-043>047-058-059.
     FROST ADVISORY FROM 4 AM TO 9 AM EDT FRIDAY FOR VAZ023-024-035.
NC...FREEZE WARNING UNTIL 9 AM EDT THIS MORNING FOR NCZ003>006-019-
     020.
WV...NONE.

&&

$$
SYNOPSIS...RAB
NEAR TERM...RAB
SHORT TERM...DS
LONG TERM...KM
AVIATION...KK/RAB
CLIMATE...JC/KM