Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 050139
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
939 PM EDT WED MAY 4 2016

.SYNOPSIS...
AN UPPER LEVEL LOW PRESSURE SYSTEM WILL MOVE OUT OF THE GREAT
LAKES AND LINGER OVER THE MID ATLANTIC REGION INTO THE WEEKEND.
THIS WILL BRING A GOOD CHANCE OF RAINFALL AND QUITE CHILLY
CONDITIONS TO THE REGION INTO THE WEEKEND. UNSETTLED CONDITIONS
WILL PERSIST AS WARMER TEMPERATURES WORK INTO THE AREA FOR THE
FIRST PART OF NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 930 PM EDT WEDNESDAY...

NO MAJOR CHANGES THIS EVENING. SCATTERED SHOWERS MAINLY WEST OF
THE BLUE RIDGE THIS EVENING. DID NOTICE THUNDER BEING REPORTED IN
THE CHARLOTTESVILLE AREA BUT HAVE NOT SEEN ANY REPORTS OF THUNDER
IN OUR FORECAST AREA. WILL CONTINUE TO LEAVE THE MENTION OF
THUNDER OUT OF THE GRIDS AT THIS POINT. BOTH THE NCEP WRF AND THE
HRRR SEEM TO HAVE A GOOD HANDLE ON THE PRECIP THIS EVENING AND
BOTH PIVOT A NARROW AREA OF WEAK PRECIP THROUGH OUR FORECAST AREA
BY THURSDAY MORNING. THE BULK OF THE HEAVIER PRECIP THURSDAY STILL
APPEARS TO BE ALONG AND NORTH OF I64...SO NO CHANGES WERE MADE
WITH QPF AMOUNTS.

AS OF 330 PM EDT WEDNESDAY...

DIURNAL INSTABILITY COMBINED WITH COOL AIR ALOFT HAVE KEPT WIDELY
SCATTERED SHOWERS ON THE RADAR THIS AFTERNOON MAINLY WEST OF THE
BLUE RIDGE AND NORTH OF ROUTE 460 IN VIRGINIA. THUNDER HAS BEEN
QUITE LIMITED WITH ONLY AN OCCASIONAL LIGHTNING FLASH NOTED ACROSS
BUCKINGHAM COUNTY VA. HOWEVER...AN APPROACHING COLD FRONT BEING
DRIVEN BY AN UPPER CLOSED LOW MOVING OUT OF THE GREAT LAKES WILL
BRING A COHESIVE BAND OF SHOWERS TO OUR WESTERN DOORSTEP BY EARLY
THIS EVENING.

AS THE SHOWERS PROGRESSIVELY SPREADS ACROSS THE REGION TONIGHT A
SURFACE LOW SILL DEVELOP ALONG THE MID ATLANTIC COAST WITH A
DEFORMATION ZONE EXTENDING BACK ACROSS THE NORTHEASTERN PORTION OF
THE REGION WITH MULTIPLE SHORT WAVE IMPULSES ROTATING AROUND THE
UPPER LOW. THIS IS SETTING THE STAGE FOR SOME HEAVY PRECIPITATION
TO FALL THROUGH THE END OF THE WEEK WITH CUMULATIVE RAINFALL
AMOUNTS OF 1.5 TO 2 IN A RELATIVELY NARROW CORRIDOR IN VIRGINIA
FROM NORTHERN CHARLOTTE COUNTY THROUGH APPOMATTOX AND BUCKINGHAM
TO AMHERST. THERE IS STILL UNCERTAINTY IN EXACTLY WHERE THE RAIN
WILL SET UP AND HOW HEAVY IT WILL BE SO WILL HOLD OFF ON ANY
WATCHES UNTIL THE SITUATION COMES INTO SHARPER FOCUS OVER THE NEXT
FEW MODEL RUNS. PRECIPITATION ELSEWHERE WILL BE LESS PRONOUNCED
WITH AMOUNTS TAILING OFF TOWARD THE FOOTHILLS OF NORTH CAROLINA.

WITH THE POOL OF COLD AIR ACCOMPANYING THE UPPER CLOSED LOW LAPSE
RATES WILL BE STEEP SO SOME EMBEDDED THUNDER MAY BE PRESENT BUT
WILL LEAVE IT OUT OF THE GIRDS FOR NOW SINCE EXPECT IT WILL BE
LOCALIZED AND EPHEMERAL. THERE WILL ALSO BE A LITTLE WET SNOW
POSSIBLE AT THE HIGHEST PEAKS OF THE GRAYSON HIGHLANDS INTO THE
MOUNTAINS OF NORTH CAROLINA BUT JUST SOME WET FLAKES WITH NO
ACCUMULATION EXPECTED. NEEDLESS TO SAY TEMPERATURES WILL BE WELL
BELOW NORMAL WITH HIGHS ON THURSDAY GENERALLY REMAINING IN THE
UPPER 40S/LOWER 50S WEST OF THE RIDGE AND ONLY REACHING THE
MID/UPPER 50S TO THE EAST.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
AS OF 330 PM EDT WEDNESDAY...

AN UPPER LOW WILL DROP SOUTH INTO OUR REGION AND SLOWLY MOVES EAST
ACROSS THE AREA INTO THE WEEKEND. AS A RESULT...COOL...CLOUDY...AND
DAMP CONDITIONS EXPECTED INTO THE WEEKEND. RAINFALL THURSDAY NIGHT
WILL RANGE FROM 0.15 TO AROUND AN HALF INCH. LOCALLY AMOUNTS AROUND
INCH MAY BE POSSIBLE WITH A THUNDERSTORM. HOWEVER...THE BEST
INSTABILITY WITH LIS AND CAPE IS TO OUR EAST. THE COLDEST NIGHT
DURING THE PERIOD WILL BE THURSDAY NIGHT. LOW TEMPERATURES THURSDAY
NIGHT WILL RANGE FROM THE UPPER 30S IN THE MOUNTAINS TO THE UPPER
40S IN THE PIEDMONT.

THE CLOSED LOW WILL SLOWLY MOVE EAST FRIDAY. BEHIND THIS LOW...COLD
AIR ADVECTION SHOULD ENSUE COURTESY OF A DECENT NORTHWEST WIND WHICH
MAY GUST UP TO 30 MPH ALONG THE HIGHEST RIDGETOPS FRIDAY AFTERNOON.
HIGH TEMPERATURES FRIDAY WILL VARY FROM AROUND 50 IN THE NORTHWEST
MOUNTAINS TO THE MID 60S IN THE PIEDMONT. FRIDAY AFTERNOON INTO
FRIDAY NIGHT...SCATTERED SHOWERS SHOULD GRADUALLY WANE. RAIN AMOUNTS
FRIDAY WILL VARY FROM THE AROUND A TENTH TO ABOUT 0.75 INCH. THE 3
HOUR FFG WAS AROUND 1.1 INCHES IN THE NORTHWEST TO NEAR 3 INCHES IN
THE PIEDMONT. ANY FLOODING POTENTIAL WILL DEPEND ON STORM
TRAINING...RAINFALL RATE AND LOCATIONS. LOW TEMPERATURES FRIDAY
NIGHT WILL GENERALLY BE FROM LOWER 40S IN THE WEST TO AROUND 50
DEGREES IN THE EAST.

THE LATEST ECMWF AND GFS ARE CONSISTENT WITH BREAKING DOWN THE OMEGA
BLOCK PATTERN ON SATURDAY. IT WILL BE A WARMER AFTERNOON SATURDAY
WITH HIGH TEMPERATURES FROM THE MID 60S IN THE MOUNTAINS TO THE MID
70S IN THE PIEDMONT. ISOLATED TO SCATTERED SHOWERS MAY BE POSSIBLE
IN THE WEST SATURDAY NIGHT. THE GFS AND ECMWF HAS COME IN WETTER
WITH AMOUNTS UP TO 0.5 INCH. LOW TEMPERATURES SATURDAY NIGHT INTO
SUNDAY MORNING WILL DROP INTO THE LOWER 50S IN IN THE WEST TO MID
50S IN THE EAST.

&&

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

CUTOFF LOW OFF THE MID ATLANTIC COAST DRIFTS EAST IN THE ATLANTIC
OCEAN AS FLOW ALOFT SLOWLY EVOLVES INTO A MORE PROGRESSIVE PATTERN
FOR THE SECOND WEEK OF MAY.

A COLD FRONT TO OUR NORTHWEST WILL DROP SOUTH SUNDAY INTO OUR AREA
AND STALL SOUTH OF THE REGION SUNDAY NIGHT BEFORE RETURNING AS A
WARM FRONT MONDAY INTO TUESDAY. MOISTURE CONVERGENCE ALONG THIS
FRONT WILL RESULT IN A RISK FOR SHOWERS AND PERHAPS A FEW
THUNDERSTORMS DURING THE PERIOD...BUT NOT CONFIDENT ON TIMING OR
AMOUNTS ATTM. IT DOES LOOK LIKE THE BEST CHANCES WILL BE WEST OF
INTERSTATE 77 EARLY NEXT WEEK. ON WEDNESDAY...OUR AREA IN THE WARM
SECTOR WITH WARM FRONT TO THE NORTH AND COLD FRONT TO OUR WEST IN
THE OHIO VALLEY. TEMPERATURES WILL BE NEAR NORMAL FOR SUNDAY...THEN
MODERATE INTO MIDWEEK. BEHIND THE COLD FRONT...A COOL DOWN IS
POSSIBLE FOR THE END OF THE WEEK.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
AS OF 750 PM EDT WEDNESDAY...

UPPER LOW WILL MOVE SOUTHEAST OUT OF WISCONSIN AND CLOSE OFF.
THIS LOW WILL TRACK INTO WESTERN NORTH CAROLINA THEN ROTATE
NORTHEAST INTO MARYLAND. SYNOPTIC MODELS WERE IN GOOD AGREEMENT WITH
THE TIMING AND TRACK OF THIS FEATURE. SHOWERS WILL COVER MUCH OF
THE REGION AFTER MIDNIGHT. SIMILAR ARRIVAL TIME OF THE SHOWERS IN
THE HI-RES MODELS AS WELL AS THE HRRR AND LOCAL WRF. LOWER
CONFIDENCE ON THE OCCURRENCE OF ANY THUNDER. HAVE LEFT OUT OF THE
TAFS AT THIS TIME. HIGH CONFIDENCE THAT CEILINGS WILL LOWER TO
MVFR STARTING IN THE MOUNTAINS OVERNIGHT AND SPREADING EAST
THURSDAY MORNING. AT THE SURFACE LOW PRESSURE OVER VIRGINIA ON
THURSDAY WILL RESULT IN UPSLOPE CONDITIONS AT KBLF...KLWB...AND
KLYH WILL WILL HELP SUPPORT LOWER CEILINGS.

EXTENDED DISCUSSION...

THE CLOSED UPPER LOW WILL REMAIN OVER THE MID ATLANTIC STATES
THROUGH FRIDAY. MVFR OR LOWER CEILINGS AND REDUCED VISIBILITY WITH
SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED INTO FRIDAY. SOME
VFR IS POSSIBLE EAST OF THE BLUE RIDGE SATURDAY. CONDITIONS WILL
BE BETTER ON SATURDAY AS THE UPPER LOW MOVES OFF THE COAST...BUT
AS ANOTHER SHORT WAVE REACHES THE AREA FROM THE NORTHWEST ON
SATURDAY NIGHT AND SUNDAY MORE SHOWERS AND SUB-VFR CONDITIONS ARE
LIKELY.

&&

.CLIMATE...
A SEASONABLY COOL AIR MASS WILL IMPACT THE REGION THROUGH THE END
OF THE WORK WEEK. HIGH TEMPERATURES ON THURSDAY MAY APPROACH
LOW MAXIMUM RECORDS. BELOW ARE THE CURRENT RECORD LOW MAXIMUM
TEMPERATURES FOR MAY 5TH.

THURSDAY 05/05/2016
SITE    LOMAX YEAR
KBLF      50  1988
KDAN      51  1994
KLYH      51  1908
KROA      52  1917
KRNK      48  1994

&&

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

&&

$$
SYNOPSIS...WP
NEAR TERM...CF/MBS
SHORT TERM...KK
LONG TERM...KK
AVIATION...AMS/JR
CLIMATE...CF


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