Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 201449
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1049 AM EDT MON OCT 20 2014

.SYNOPSIS...
A DEEPENING TROUGH OF LOW PRESSURE WILL APPROACH THE AREA TODAY AND
CROSS THE REGION TONIGHT INTO TUESDAY...AND THEN STALL AND
TRANSITION INTO AN UPPER LOW PRESSURE SYSTEM ACROSS THE MID-ATLANTIC
REGION BY WEDNESDAY. FOR OUR REGION THIS SERIES OF EVENTS WILL
RESULT IN INCREASED CHANCES OF SHOWERS...ESPECIALLY ACROSS THE
MOUNTAINS AND GUSTY NORTHWEST WINDS.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1045 AM EDT MONDAY...

ALL FROST/FREEZE PRODUCTS HAVE EXPIRED AND VISIBLE SATELLITE
IMAGERY IS SHOWING A GOOD AMOUNT OF SUNSHINE ACROSS THE REGION
THIS MORNING. HOWEVER...UPSTREAM RADARS SHOW A BAND OF PCPN
APPROACHING FROM THE WEST ASSOCIATED WITH A SHORT WAVE ROTATING
AROUND THE UPPER TROF MOVING THROUGH THE EASTERN US. MESO MODELS
SEEM TO HAVE A GOOD GRASP OF THE SITUATION AND BASED ON
THIS...WILL BUMP TIMING OF POPS UP A COUPLE OF HOURS TO REFLECT
EXPECTED TRENDS. OTHER PARAMETERS ARE ON TRACK WITH CURRENT GRID
SET SO WILL FRESHEN WITH CURRENT DATA AND MAKE ONLY MINOR TREND
ADJUSTMENTS.

.PREVIOUS AFD...

TEMPERATURES WILL RISE QUICKLY MELTING AWAY ANY FROST AFTER
SUNRISE. SOUTHWEST WINDS WILL START TO INCREASE AROUND NOON...AND
BE NEAR 10 MPH AT MOST LOCATIONS BY THE AFTERNOON. HIGH LEVEL
CLOUD COVER WILL BE ON THE INCREASE INTO THIS AFTERNOON FROM WEST
TO EAST ACROSS THE REGION WITH THE APPROACH OF THE UPPER TROUGH.
LEANED HIGH TEMPERATURES THIS AFTERNOON CLOSE TO THE ADJMETBC
WITH READINGS FROM THE MID 50S IN THE NORTHWEST MOUNTAINS TO THE
UPPER 60S IN THE PIEDMONT.

SCATTERED SHOWERS TONIGHT ESPECIALLY ACROSS THE MOUNTAINS AS
ANOTHER WEAK UPPER LEVEL DISTURBANCE PASSES ALONG THE APPALACHIAN
CHAIN IN ADVANCE OF OUR NEXT COLD FRONT. THE SOUTHWESTERLY WIND
FLOW AND INCREASED CLOUD COVER WILL MAKE FOR WARMER OVERNIGHT
TEMPERATURES WITH LOWS GENERALLY IN THE 40S IN MOST
LOCATIONS...ALTHOUGH A FEW OF THE HIGHER RIDGES MAY REMAIN IN THE
LOWER 50S.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
AS OF 415 AM EDT MONDAY...

FOCUS THROUGH THE ENTIRE SHORT TERM WILL BE ON A SLOW MOVING
CLOSED UPPER LOW THAT AT THE BEGINNING OF THE PERIOD WILL BE
ACROSS THE WESTERN GREAT LAKES...MEANDERING TOWARD THE MID-
ATLANTIC REGION WED-THU. AFTER SEVERAL DAYS OF MODEL RUNS TAKING
THE CENTER OF THIS SYSTEM FURTHER NORTH...THE LATEST MODEL RUNS
HAVE TRENDED FURTHER SOUTH ONCE AGAIN...BUT REMAINING FAR ENOUGH
EAST THAT IT WILL STILL LEAVE THE CWA ON THE DRIER SOUTHWEST SIDE
OF THE SYSTEM. THE PRIMARY...LEADING WAVE AND ASSOCIATED LIGHT
PRECIPITATION WILL TRACK FROM NW TO SE ACROSS THE REGION
TONIGHT...THEN TUE INTO EARLY WED...THE UPPER LOW WILL DIVE TO ITS
SOUTHERN MOST POSITION...TOWARD EAST CENTRAL VA. IN SO DOING...THE
NEXT LOBE OF PVA WILL WILL TRACK FROM NORTH TO SOUTH ACROSS THE
REGION AND RESULT IN A SLIGHT UPTICK IN RAIN SHOWER COVERAGE.
OTHERWISE...MUCH OF THE PERIOD WILL BE CHARACTERIZED BY CYCLONIC
FLOW...ABUNDANT CLOUD COVER...SCT -SHRA...MAINLY MOUNTAINS AND
AREAS NORTH OF U.S. 460. THE BEST OVERALL COVERAGE OF
PRECIPITATION THROUGH THE PERIOD SHOULD COME WITH THIS
AFOREMENTIONED LOBE OF PVA AS THE UPPER LOW ROTATES TO A POSITION
JUST OFF THE DELMARVA BY WED EVENING. TOTAL QPF THROUGH THE PERIOD
WILL RANGE FROM ABOUT 1/3 INCH NORTHERN GREENBRIER COUNTY TO TRACE
AMOUNTS AT BEST ACROSS MOST OF THE NC AND VA PIEDMONT COUNTIES.
THE MAJORITY OF THE CWA WILL SEE LESS THAN 1/10 INCH OF
PRECIPITATION THROUGH THE ENTIRE EVENT. SLOW IMPROVEMENT CAN BE
EXPECTED THU AS THE UPPER LOW ROTATES BACK TOWARD NEW
ENGLAND...ALLOWING DRIER AIR FROM THE MIDWEST TO BEGIN TO SPREAD
INTO WESTERN AREAS.

TEMPERATURES WILL BE QUITE COOL THROUGH THE PERIOD WITH ABUNDANT
CLOUD COVER AND 850MB TEMPS HOVERING IN THE LOW SINGLE DIGIT
CENTIGRADE RANGE. THERE IS A POCKET OF NEAR 0C 850MB TEMPS ON THE
BACK SIDE OF THE UPPER LOW THAT SETTLES DOWN OVER THE WESTERN PART
OF THE CWA EARLY THU...BUT THE CHANCE OF PCPN AT THAT TIME IN
THAT REGION IS NEAR ZERO...SO NO CONCERNS WITH WINTER
PRECIPITATION THROUGHOUT THIS EVENT...EVEN AT HIGHER ELEVATIONS.
WE MAY NEED TO ENTERTAIN FROST/FREEZE ADVISORIES LATE IN THE WEEK
ONCE AGAIN...BUT AGAIN APPEARS TO BE A MARGINAL SITUATION.

USED A MODEL BLEND OF MAX/MIN TEMPS THROUGHOUT THE PERIOD. MAX
TEMPS WILL BE ABOUT 10 DEGREES BELOW NORMAL THROUGH MUCH OF THE
PERIOD...WITH MIN TEMPS NEAR NORMAL.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 445 AM EDT MONDAY...

THE CLOSED UPPER LOW WILL FINALLY LIFT AWAY FROM THE REGION FRI-
SAT AS A BROAD UPPER RIDGE BUILDS FROM THE CENTRAL U.S. INTO THE
EASTERN U.S. THIS UPPER RIDGE WILL EFFECTIVELY SHUT OFF ALL
GULF MOISTURE FROM THE REGION FOR SEVERAL DAYS AS WELL AS LOCKING
ANY REALLY COLD AIR WELL NORTH OF THE CANADIAN BORDER. A
WEAK...DRY UPPER DISTURBANCE WILL TRACK FROM NW TO SE ACROSS THE
REGION FRI-SAT...WHICH AT THIS POINT APPEARS TO DO LITTLE MORE
THAN BRING A FEW MID/HIGH CLOUDS. HIGH PRESSURE AT THE SURFACE AND
ALOFT WILL THEN DOMINATE FOR THE WEEKEND. THIS WILL PROVIDE MOSTLY
SUNNY CONDITIONS FOR A CHANGE ALONG WITH SEASONAL
TEMPERATURES...LOWS IN THE 40S AND HIGHS IN THE 60S WEST AND 70S
EAST. SHOULD BE A BEAUTIFUL WEEKEND FOR THE ENTIRE REGION.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
AS OF 730 AM EDT MONDAY...

SURFACE HIGH PRESSURE ALREADY EAST OF THE REGION. THIS ALLOWED
RETURN SW FLOW TO RETURN EARLY IN ADVANCE OF NEXT UPSTREAM UPPER
LOW POISED OVER THE GREAT LAKES TO MOVE SOUTHEAST TOWARD THE
REGION TODAY. CIRRUS CLOUDS ALREADY SPREADING OVER THE REGION FROM
THE NORTHWEST...AND CLOUD CIGS WILL LOWER TOWARD 100 BY
AFTERNOON...THEN TOWARD 050 IN WESTERN AREAS BY EVENING AS THE
COLD FRONT APPROACHES. CLOUD SITUATION OVERNIGHT SOMEWHAT
PROBLEMATIC...BUT WITH UPSLOPE FLOW DEVELOPING BEHIND THE FRONT
EASTERN WV...EXPECT CIGS TO LOWER TO MVFR AFT 04Z...INCLUDING
KLWB/KBLF/KBCB WITH TIME. EAST OF THE BLUE RIDGE...CIGS SHOULD
REMAIN VFR...BUT WILL LOWER TOWARD 050 EXCEPT KDAN. SCT -SHRA MAY
DEVELOP EASTERN WV WITH THE FRONT LATE AFTERNOON/EVENING AND WITH
UPSLOPE FLOW THEREAFTER. SFC MOISTURE IS INITIALLY LACKING...SO
HAVE NOT ADVERTISED ANY RESTRICTIONS TO VSBY AT THIS POINT. LIFR-
IFR VSBYS ADVERTISED FOR LWB IN THE MOS GENERATED TAFS APPEAR TO
BE CLIMO BASED AND DO NOT SUPPORT ONGOING SYNOPTIC SITUATION.
WINDS...SW 7-10KTS TODAY WITH LOW END GUSTS THROUGH
AFTERNOON...BECOMING WSW-W OVERNIGHT AT SPEEDS OF 6-8KTS BEHIND
THE FRONT. THE IMMEDIATE GRADIENT BEHIND THE FRONT IS NOT
IMPRESSIVE.

HIGH CONFIDENCE IN CIGS THROUGH 00Z...THEN MEDIUM CONFIDENCE.
HIGH CONFIDENCE IN VSBYS THROUGH 06Z...THEN MEDIUM CONFIDENCE WEST
OF THE BLUE RIDGE.
MEDIUM TO HIGH CONFIDENCE IN WIND DIR/SPD THROUGH THE TAF VALID
PERIOD.

EXTENDED AVIATION DISCUSSION...

AN UPPER LEVEL TROUGH WILL CROSS THE AREA TUESDAY MORNING AND
DEEPEN INTO A NEARLY STATIONARY CLOSED LOW OVER THE MID-ATLANTIC
REGION BY WEDNESDAY. THE SYSTEM WILL MAKE SLOW MOVEMENT NORTHEAST
THROUGH THURSDAY. FOR OUR REGION...THE MAIN IMPACT WITH BE A
PERSISTENT NORTHWEST GUSTY WIND AND SCATTERED RAIN SHOWERS THAT
WILL IMPACT PRIMARILY THE PREFERRED UPSLOPE REGION OF SOUTHEAST
WEST VIRGINIA. MVFR CLOUDS WILL ALSO BE COMMON ACROSS THE
MOUNTAINS DURING THIS TIME PERIOD...BUT FROM ROA TO LYH TO DAN
CONDITIONS ARE LIKELY TO REMAIN VFR THROUGH THIS PERIOD. THE
PERSISTENT TROUGH WITH NORTHWEST FLOW AND LOW-LEVEL UPSLOPE
CLOUDS IN WEST WILL LIKELY BE REPLACED BY AN UPPER LEVEL RIDGE BY
FRIDAY OR SATURDAY...FOR DRY AND WARM CONDITIONS.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...KK
NEAR TERM...MBS/KK
SHORT TERM...RAB
LONG TERM...NF/RAB
AVIATION...KK/RAB



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