Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 051140
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
740 AM EDT THU MAY 5 2016

.SYNOPSIS...
AN UPPER LEVEL LOW PRESSURE SYSTEM MOVES FROM KENTUCKY THIS
MORNING TO ALONG THE NC/VA COAST BY FRIDAY MORNING....THEN TO THE
MID ATLANTIC COAST OF PA/NY BY SATURDAY. THIS WILL KEEP UNSETTLED
CONDITIONS THROUGH FRIDAY NIGHT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 435 AM EDT THURSDAY...

GETTING SOME CLOUD TO GROUND LIGHTNING STRIKES IN THE
PIEDMONT...WITH SBCAPES OF 100-200 J/KG. PER HRRR ADDED ISOLATED
THUNDER CHANCES THROUGH THE MORNING OVER THE PIEDMONT AREAS OF
VA/NC.

PREVIOUS MORNING DISCUSSION...

VERY WET SCENARIO SHAPING UP TODAY INTO TONIGHT. ALREADY SEEING
RAIN EXPANDING ACROSS THE NW NC PIEDMONT INTO THE
FOOTHILLS/PIEDMONT OF VA AT 320 AM.

QUESTION TODAY IS NOT IF IT IS GOING TO RAIN...IT IS WHERE WILL AXIS
OF HEAVIER RAINS SET UP...AND HOW HEAVY WILL THE RAIN BE...IN TERMS
OF AMOUNTS AND MOVEMENT. MODELS SEEM TO BE DECENT AGREEMENT THAT A
CORRIDOR OF STRONG LOW LVL MOISTURE CONVERGENCE WITH PERIODS OF
UPPER DIFLUENCE FAVOR A SE WV TO SOUTHSIDE VA REGION FOR STEADIER
RAINS...HEAVY AT TIMES...ESPECIALLY NORTH OF A ROANOKE TO SOUTH
BOSTON LINE. STILL IFFY AS TO HOW MUCH FALLS AND SPEED OF MOVEMENT.
AT THE MOMENT WILL HOLD OFF ON ANY FLOOD WATCHES...THOUGH AM
CONCERNED SINCE SOME OF THE RIVERS IN THE PIEDMONT HAVE BEEN RUNNING
HIGH...WITH SOUTH BOSTON ALONG THE DAN RIVER STILL ABOVE FLOOD
STAGE...THAT SOME MINOR FLOODING MAY OCCUR AGAIN LATER TODAY INTO
FRIDAY. FOR NOW WILL HIT THIS IN THE HAZARDOUS WEATHER OUTLOOK FOR
POTENTIAL STREAM OR RIVER FLOODING. FORECAST RAINFALL TODAY WILL
RANGE FROM ONE HALF TO JUST OVER AN INCH FROM LEWISBURG WV SOUTHEAST
TO DANVILLE AND POINTS NORTHEAST TO LESS THAN A QUARTER INCH OVER
THE NC MTNS/FOOTHILLS.

AS FAR AS CONVECTION/THUNDER GOES...IT APPEARS CLOUD COVER AND
COOLER SFC TEMPS WILL LIMIT LOW LVL LAPSE RATES AND THERMODYNAMIC
INSTABILITY...THOUGH MID LEVEL LAPSE RATES ARE THERE ALONG WITH
COOLER AIR ALOFT THAT POTENTIAL FOR SMALL HAIL MAY EXIST WITH
ISOLATED LIGHTNING. THE CONFIDENCE IN HAVING THIS IN THE FORECAST IS
LOW...THINKING ANY THUNDER WILL BE ISOLATED AND ANY BREAKS IN THE
CLOUD COVER WILL BE SOUTH AND WELL EAST OF OUR CWA THIS AFTERNOON.

WE ARE GOING TO SEE SHOWERS/RAIN WORK IN A NW TO SE PATTERN THEN
PIVOT TO AN EAST-WEST AXIS LATER TODAY INTO TONIGHT. AS THE UPPER
LOW MOVES EAST OF US TONIGHT...THE SHOWERS SHOULD SPIN AROUND TO
MORE A N-S AXIS WITH BANDS SETTING UP ALONG AND WEST OF A BUCKINGHAM
TO BOONE LINE BY EVENING WHILE HEAVIER SHOWERS WORK EAST OF OUR
FORECAST AREA. OVERNIGHT WILL KEEP POPS HIGH THOUGH QPF WILL BE
LOW...GENERALLY UNDER ONE QUARTER INCH.

NEEDLESS TO SAY IT WILL BE COOL TODAY WITH POTENTIAL RECORD COOL
HIGH TEMPERATURES BEING BROKEN MAINLY AT BLUEFIELD...BLACKSBURG AND
ROANOKE. SEE CLIMATE SECTION BELOW FOR DETAILS. HIGHS WILL RANGE
FROM THE UPPER 40S TO LOWER 50S WEST...TO MID TO UPPER 50S EAST.

WITH CLOUDS AROUND TONIGHT...TEMPS SHOULD BE SLOW TO FALL..WITH
MIXING OCCURRING AS SFC LOW OFF THE COAST SHIFTS NORTH. LOWS WILL
RANGE FROM THE UPPER 30S TO LOWER 40S IN THE NC MTNS/FAR SW VA INTO
SE WV...TO MID TO UPPER 40S ELSEWHERE.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
AS OF 400 AM EDT THURSDAY...

THE OMEGA BLOCK PATTERN OVER THE UNITED STATES SHOULD SHIFT EASTWARD
AND WEAKEN DURING FRIDAY.  AS A RESULT, THE UPPER LEVEL LOW OVERHEAD
SHOULD DRIFT TOWARD THE EAST COAST. MOISTURE WRAPPING AROUND THE
SURFACE LOW THAT IS VERTICALLY STACKED WITH THE UPPER LEVEL LOW WILL
KEEP MAINLY OVERCAST SKIES AND SCATTERED SHOWERS FOR THE MID-
ATLANTIC.  BY FRIDAY NIGHT, 500 MB HEIGHTS BEGIN TO BUILD AS THE
AFOREMENTIONED LOW DEPARTS AND THE UPPER LEVEL RIDGE OVER THE PLAINS
HEADS EASTWARD.  LINGERING SHOWER ACTIVITY SHOULD DIMINISH
OVERNIGHT, BUT THE REPRIEVE WILL NOT LAST LONG IN THE MOUNTAINS.

A WEAK COLD FRONT WILL APPROACH FROM THE GREAT LAKES ON SATURDAY,
WHICH WILL INCREASE THE CHANCE OF SHOWERS.  HIGHER POPS WERE
INSERTED WEST OF THE BLUE RIDGE.  MODELS ARE IN GOOD AGREEMENT WITH
THE COLD FRONT STALLING OVERHEAD BY SUNDAY, BUT THE RAINFALL AMOUNTS
REMAIN UNCERTAIN AS THE GFS CARRIES LOWER QPF THAN THE ECMWF. WHILE
CLOUD COVER AND SCATTERED SHOWERS COULD LOWER THE HIGH TEMPERATURES,
THE UPPER LEVEL RIDGE SHOULD TRUMP THESE VARIABLES TO ALLOW A
WARMING TREND THROUGH THE WEEKEND. MODEL SOUNDINGS SHOW LITTLE CAPE,
SO THUNDER WAS REMOVED FROM THIS PORTION OF THE FORECAST DUE TO
CONSIDERABLE UNCERTAINTY. IF DIURNAL HEATING AND OROGRAPHICAL
EFFECTS CAN OVERCOME THIS LACK OF INSTABILITY, THE NORTH CAROLINA
MOUNTAINS MAY SEE A STRAY THUNDERSTORM DEVELOP ON SUNDAY AFTERNOON.

&&

.LONG TERM /SUNDAY NIGHT 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 /12Z THURSDAY THROUGH MONDAY/...
AS OF 735 AM EDT THURSDAY...

LOOKING AT POOR FLYING WEATHER TODAY INTO TONIGHT AS UPPER LOW
PIVOTS FROM ERN KY TO THE VA TIDEWATER THROUGH 12Z FRIDAY. EXPECT
MVFR TO IFR CIGS/VSBYS WITH PERIODS OF MODERATE TO HEAVY
RAINFALL...ESPECIALLY IN A CORRIDOR FROM LWB-DAN AND NORTHEAST TO
LYH. CANNOT RULE OUT SOME THUNDER BUT OVERALL THREAT WILL STAY
SOUTHEAST OF DANVILLE/LYH THROUGH THE AFTERNOON/EVENING.

WITH ANY DRYING...RAINFALL ENDING TRENDS...EXPECT CIGS/VSBYS TO
DROP BELOW 1KFT AND 3-4SM. THIS IS LIKELY AFTER MIDNIGHT AT
BLF/LWB/BCB.

CONFIDENCE IN SUB VFR CIGS/VSBYS THIS PERIOD IS HIGH.

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.

MONDAY WILL BE MAINLY VFR WITH SOUTHWEST FLOW IN PLACE THOUGH WARM
FRONT MAY BRING SOME MVFR CIGS AND POSSIBLE SHOWERS TO THE
MOUNTAINS.

&&

.CLIMATE...
A SEASONABLY COOL AIR MASS WILL IMPACT THE REGION THROUGH THE END
OF THE WORK WEEK. HIGH TEMPERATURES TODAY MAY APPROACH BREAK THE
RECORD FOR COOLEST HIGHS FOR MAY 5TH. BELOW ARE THE CURRENT
RECORD COOL HIGH 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...WP
SHORT TERM...PW
LONG TERM...KK
AVIATION...AMS/WP
CLIMATE...CF/WP



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