Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 020557
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
157 AM EDT MON MAY 2 2016

.SYNOPSIS...
A WEAK AREA OF LOW PRESSURE ACROSS THE OHIO VALLEY WILL DRIFT EAST
OVERNIGHT WITH ITS ASSOCIATED SURFACE COLD FRONT APPROACHING THE
MOUNTAINS BY EARLY MONDAY. THIS SLOW MOVING FRONT WILL HEAD INTO
THE MOUNTAINS MONDAY...STALLING ACROSS THE BLUE RIDGE MONDAY
NIGHT...THEN FINALLY SLIDING SOUTHEAST BY MIDWEEK. FOR WEDNESDAY
THROUGH FRIDAY...AN UPPER LOW WILL DRIFT SOUTHWARD INTO THE REGION
FROM THE GREAT LAKES...KEEPING AN UNSETTLED AND UNSEASONABLY COOL
PATTERN THROUGHOUT THE REGION.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 1113 PM EDT SUNDAY...

UPDATED TO DROP SEVERE WATCH 135 AS DEEPER CONVECTION HAS EITHER
MOVED EAST OF THE WATCH BOX OR HAS WEAKENED ACROSS THE CENTRAL CWA
ALONG THE BOTTOM EDGE OF THE BOX. HOWEVER STILL EXPECTING SOME
CLUSTERS OF SHRA/TSRA DURING THE NEXT FEW HOURS ESPCLY EASTERN AND
SOUTHERN SECTIONS WHERE INSTABILITY REMAINS AROUND 1K J/KG. THUS
KEEPING HIGHER POPS GOING OVER THE NEXT FEW HOURS BEFORE CUTTING
POPS BACK TO ISOLATED PER LATEST HRRR. ALSO FOG LIKELY TO BECOME
AN ISSUE GIVEN THE WET GROUND AND IN THE WAKE OF THE HEAVIER
RAINFALL FROM THIS EVENING SO BEEFED UP COVERAGE. OTRW ONLY SOME
SLIGHT UPWARD ADJUSTS TO TEMPS OVERNIGHT PER SATURATION AND
LINGERING CLOUDS.


UPDATE AS OF 1000 PM EDT SUNDAY...

BROKEN LINE OF CONVECTION CONTINUES TO SPILL EAST/SE TOWARD AND
ACROSS THE BLUE RIDGE SO WILL HANG ON TO THE GOING WATCH A WHILE
LONGER AND PERHAPS DROP AROUND 11 PM PENDING TRENDS. HOWEVER
EARLIER HRRR WAS ON TRACK WITH CELLS EVOLVING INTO A LINE AND
DIPPING SOUTH SO WILL KEEP HIGHER POPS GOING FARTHER SOUTH GIVEN
LINGERING 1500 J/KG MLCAPE SEEN OFF THE SPC ANALYSIS. ALSO
CONVECTION DEVELOPING OVER NW NC TO THE SOUTH OF THE LINE MAY
IMPACT SOUTHERN SECTIONS LONGER OVERNIGHT SO SOMETHING TO WATCH.
OTRW FEW ADDED CHANGES UNTIL CONVECTION FADES SOME AS THE
REMAINDER LOOKS ON TRACK FOR NOW.

UPDATE AS OF 750 PM EDT SUNDAY...

UPDATE TO INCLUDE SEVERE THUNDERSTORM WATCH 135 FOR PARTS OF THE
NORTH AND WEST UNTIL MIDNIGHT. STORMS CONTINUE TO ROLL ACROSS THE
HIGHER TERRAIN INTO RESIDUAL INSTABILITY AHEAD OF WEAK LOW
PRESSURE IN THE OHIO VALLEY. ENOUGH RECOVERY HAS OCCURRED SINCE
EARLIER RAINFALL FOR SOME OF THESE STORMS TO MAINTAIN SEVERE
STRENGTH UNTIL WELL AFTER SUNSET. HOWEVER EASTWARD EXTENT OF THE
DEEPER CONVECTION REMAINS IFFY GIVEN LESS CAPE EAST OF THE
MOUNTAINS. FEW OTHER CHANGES FOR NOW.


PREVIOUS DISCUSSION AS OF 320 PM EDT SUNDAY...

FEW SHOWERS THIS AFTERNOON BETWEEN UPPER WAVES. LOOKING FURTHER
WEST...ENVIRONMENT INCREASINGLY UNSTABLE OVER KY IN ASSOCIATION WITH
UPPER SHORTWAVE AND STEEPER LAPSE RATES. AS WE HEAD TOWARD EVENING
THIS WAVE IS GOING TO NOSE EAST TOWARD THE CENTRAL APPALACHIANS BY
LATE AFTERNOON INTO THE EVENING. THINKING IS THE SAME AS
EARLIER...IN THAT SHOWERS AND STORMS WILL INCREASE AGAIN BY EARLY
EVENING OVER THE MOUNTAINS...WITH A SCT/BKN LINE OF CONVECTION
POSSIBLY SHIFTING EAST/SOUTHEAST FROM SE WV TO THE PIEDMONT THIS
EVENING. SVR PARAMETERS FAVOR STRONGER STORMS IN WV/KY/FAR SW
VA...BUT WEAKEN FURTHER EAST...BUT CANNOT RULE OUT STRONGER STORMS
TO THE BLUE RIDGE THIS EVENING. ORIENTATION OF THE CONVECTION AND
SPEED OF MOVEMENT SHOULD PREVENT A FLASH FLOOD THREAT...THOUGH
LOCALIZED FLOODING IS POSSIBLE...GIVEN THE 1 INCH+ WE HAD EARLIER
TODAY IN PORTIONS OF THE REGION. STILL NOT ENOUGH FOR A FLOOD
WATCH.

FOR LATE TONIGHT...SHOWERS WANE AND WILL SEE CONTINUED SW ALOFT.
CANNOT RULE OUT A FEW SHOWERS AT TIMES ESPECIALLY GIVEN HIGHER
MOISTURE IN THE LOW LVLS. FOG PARAMETERS ALSO FAVOR GOOD COVERAGE OF
FOG ACROSS THE RIVER VALLEYS AND WHERE IT RAINS THIS
EVENING...DEPENDENT ON HOW MUCH CLEARING TAKES PLACE BEHIND THE
CONVECTION.

MONDAY...WE WILL SEE THE COLD FRONT MOVE FROM THE EASTERN OHIO
VALLEY SOUTHWEST TO MIDDLE TN IN THE MORNING...SLOWLY EAST TO THE
CENTRAL APPALACHIANS TO CUMBERLAND PLATEAU BY AFTERNOON. EXPECTING
TO SEE A FEW SHOWERS OR STORMS ACROSS THE MOUNTAINS IN THE MORNING.
CLOUD COVER WILL BE INCREASING ALOFT BUT WILL STILL SEE SOME
SUNSHINE AT TIMES AND THIS SHOULD LEAD TO MUCAPES OF 1500-2500 J/KG
BY MID AFTERNOON. MODELS ARE IN SOMEWHAT AGREEMENT THAT THE 2ND OF
THE UPPER SHORTWAVES WILL PASS ACROSS THE CENTRAL AND SOUTHERN
APPALACHIANS DURING THE LATE AFTERNOON LEADING TO MORE ROBUST
CONVECTION. THE STORM PREDICTION CENTER HAS MARGINAL RISK FOR MOST
OF THE AREA. IF THE FRONT MOVES QUICKER THEN CLOUD COVER WILL HINDER
LOW LVL INSTABILITY. THE BEST SHEAR LOOKS TO SITUATE ITSELF FROM FAR
SW VA/SE KY NORTHWARD INTO THE MD/PA AREA...SO THIS COULD LEAD TO
MORE OF A WIND THREAT IN OUR FAR WRN CWA...WITH MARGINALLY STRONG TO
SEVERE STORMS EAST.

BETTER LOW LVL AND UPPER LEVEL SUPPORT DOES NOT REALLY GET GOING
UNTIL AFTER 21Z/5PM OVER THE MOUNTAINS SO COULD BE ANOTHER LATE
AFTERNOON INTO EVENING EVENT.

WITH NO WEDGE MONDAY AND DEPENDING ON SKY COVER...TEMPS SHOULD WARM
INTO THE 70S IN THE MOUNTAINS...TO LOWER 80S EAST.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 400 PM EDT SUNDAY...

SURFACE COLD FRONT WILL SLOWLY MOVE ACROSS THE FORECAST AREA MONDAY
NIGHT SUBJECTING AREA TO NEAR CATEGORICAL POPS. PENDING THUNDERSTORM
COVERAGE...QPF MAY EXCEED AN INCH WITH POTENTIAL FOR STRONGEST
STORMS TO PRODUCE LARGE HAIL AND DAMAGING WINDS BEFORE MIDNIGHT
MONDAY NIGHT. SHOWERS ARE EXPECTED TO TAPER OFF AFTER MIDNIGHT AS
FRONT MOVES EAST ACROSS THE PIEDMONT.

TUESDAY INTO WEDNESDAY...AN UPPER LEVEL TROUGH OVER EASTERN CANADA
WILL BEGIN TO DIG SOUTHWARD INTO THE EASTERN GREAT LAKES. THIS WILL
SEND ANOTHER SURFACE FRONT THROUGH THE FORECAST AREA LATE
WEDNESDAY...BEGINNING A TREND TOWARD COOLER TEMPERATURES FOR THE
LATER HALF OF THE WEEK.  OTHER THAN SOME AFTERNOON INSTABILITY...NOT
MUCH SUPPORT FOR SHOWERS TUESDAY.  FRONTAL LIFT WILL PROVIDE A
BETTER CHANCE WEDNESDAY EVENING.

TEMPERATURES TUESDAY AND WEDNESDAY FAVOR READINGS NEAR NORMAL.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 400 PM EDT SUNDAY...

TEMPERATURES ARE EXPECTED TO TAKE A TUMBLE FOR THE END OF THE WEEK
AS HIGH AMPLITUDE UPPER LEVEL TROUGH SINKS SOUTH FROM THE GREAT
LAKES AND A CUTOFF LOW DEVELOPS OVER THE MID ATLANTIC REGION.  85H
TEMPS OF 0 TO +5 DEG C ARE PROGGED TO BE OVER THE FORECAST AREA BY
THURSDAY NIGHT...AND IF THIS VERIFIES...IT WILL SUPPRESS
TEMPERATURES AT LEAST 10 TO 15 DEGREES BELOW NORMAL.  AS THE UPPER
LOW PASSES OVERHEAD...COLD POOL ALOFT WILL COMBINE WITH DAYTIME
HEATING FOR A DAILY THREAT OF INSTABILITY SHOWERS AND CONSIDERABLE
CLOUDINESS.

CUTOFF LOW WILL LIKELY BE SLOW TO MOVE OUT PER BLOCKY LOOK TO THE
UPPER AIR PATTERN...WITH CUTOFF LOWS ON THE WEST AND EAST COASTS AND
A RIDGE UP THROUGH THE CENTRAL CONUS. UNLIKE THE LAST OMEGA BLOCK
WHERE THE MID ATLANTIC ENJOYED UNSEASONABLY WARM AND DRY CONDITIONS
UNDER THE UPPER LEVEL RIDGE...JUST THE OPPOSITE IS OCCURRING THIS GO
ROUND.

OVER THE WEEKEND THE MODELS INDICATE THE CUTOFF LOW WILL GRADUALLY
DRIFT EAST TO JUST OFF THE MID ATLANTIC COAST...TEMPERATURES ALOFT
MODERATING.  THIS SHOULD ALLOW FOR A GRADUAL WARMING TREND WITH
TEMPERATURES RETURNING TO NORMAL BY THE START OF NEXT WEEK.
ATTM...WEEKEND AS A WHOLE LOOKS DRY.  WE HAVE A SLIGHT CHANCE OF
SHOWERS OVER THE MOUNTAINS TO ACCOUNT FOR THE INSTABILITY...BUT NOT
CONFIDENT THERE WILL BE MUCH COVERAGE.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
AS OF 155 AM EDT MONDAY...

EARLIER SHOWERS AND THUNDERSTORMS HAVE MOSTLY SUBSIDED...BUT
PLENTY OF CLOUD COVER LINGERS ACROSS THE MID ATLANTIC TONIGHT.
WHILE CONDITIONS REMAIN VFR FOR MOST TAF SITES...THE EXCEPTION IS
KBLF WHERE CEILINGS HAVE FALLEN TO LIFR ALONG WITH 1/2SM FOG. DUE
TO THE MOIST GROUND FROM RECENT RAINFALL...IT SEEMS MORE LIKELY
THAT MOST TAF SITES WILL DROP TO IFR DUE TO GROUND FOG. CONFIDENCE
IS LOWEST FOR IFR AT KROA WHERE CLOUDS AND VISIBILITIES MAY STAY
AT VFR...ALTHOUGH BRIEF MVFR CANNOT BE RULED OUT ENTIRELY.

WINDS SHOULD PICK UP FROM THE SOUTHWEST DURING MONDAY...AS A COLD
FRONT APPROACHES FROM THE WEST. ALL TAF SITES SHOULD IMPROVE TO
VFR BY LATE MORNING...BUT EXPECT SOME BROKEN CUMULUS TO DEVELOP AS
SOME SUNSHINE DESTABILIZES THE ATMOSPHERE. SHOWERS AND
THUNDERSTORMS SHOULD BE ON THE INCREASE BY MONDAY AFTERNOON. SOME
OF THE STRONGER STORMS MAY CONTAIN LARGE HAIL AND DAMAGING WINDS.
THE THREAT FOR CONVECTION SEEMS MORE WIDESPREAD...SO A MENTION OF
VCTS WAS INCLUDED AT ALL SITES.

EXTENDED AVIATION DISCUSSION...

THE COLD FRONT WILL STALL OVERHEAD ON MONDAY EVENING...AND WAVES
OF LOW PRESSURE SHOULD TRACK ALONG THE STALLED FRONTAL BOUNDARY
DURING TUESDAY. THIS PATTERN SHOULD KEEP THE MID ATLANTIC IN
MVFR/IFR CONDITIONS DURING TUESDAY...BEFORE THE FRONTAL BOUNDARY
IS PUSHED EASTWARD BY TUESDAY NIGHT. A DEEP UPPER LEVEL TROUGH
WILL ARRIVE OVER THE MID ATLANTIC ON WEDNESDAY...AND SETTLE
OVERHEAD THROUGH THE END OF THIS WORK WEEK. OVERALL...FLYING
CONDITIONS APPEAR RATHER POOR FOR LATE THIS WEEK DUE TO THE
LIKELIHOOD OF LOW CLOUDS...PERIODS OF SHOWERS...AND PATCHY FOG.

&&

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

&&

$$
SYNOPSIS...JH/RAB/WP
NEAR TERM...JH/WP
SHORT TERM...PM
LONG TERM...PM
AVIATION...PW



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