Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 041944
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
344 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 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 /20Z WEDNESDAY THROUGH MONDAY/...
AS OF 130 PM EDT WEDNESDAY...

CONDITIONS WILL BEGIN THE PERIOD VFR BUT WILL BECOME MVFR IN THE
OVER NIGHT HOURS AHEAD OF AN APPROACHING FRONTAL SYSTEM IN THE OHIO
VALLEY. CONFIDENCE IN RAIN AND LOW CIGS IS HIGH...SOME LOCATIONS
PARTICULARLY AT ELEVATION MAY GO IFR IN PRECIP. FOR LOCATIONS WHERE
PRECIP IS FORECAST TO END...AN MVFR DECK IS EXPECTED TO BE LEFT
BEHIND. WINDS SHOULD PICK UP A BIT FOR THE DAYTIME HOURS TOMORROW
HOWEVER NO SIGNIFICANT HAZARDS ARE EXPECTED.

EXTENDED DISCUSSION...

A CLOSED UPPER LOW WILL REMAIN OVER THE MID ATLANTIC STATES TO
CLOSE OUT THE WEEK. CONDITIONS EXPECTED TO BE MVFR OR WORSE FOR
MUCH OF THE REMAINDER OF THE WEEK DUE TO PERIODIC SHOWERS AND
ISOLATED THUNDERSTORMS...BUT SOME VFR IS POSSIBLE OUTSIDE SHOWERS
AND ESPECIALLY EAST OF THE BLUE RIDGE. THE AVIATION CONDITION
SHOULD START IMPROVING BY THIS WEEKEND AS THE UPPER LOW MOVES EAST
OF THE APPALACHIANS OFF THE MID ATLANTIC COAST.

&&

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

&&

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


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