Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 012008
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
408 PM EDT SUN MAY 1 2016

.SYNOPSIS...
A 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 MONDAY/...
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 /MONDAY NIGHT THROUGH WEDNESDAY/...
AS OF 530 AM EDT SUNDAY...

THE COLD FRONT SHOULD PUSH EASTWARD OVER THE MID ATLANTIC ON
MONDAY...AND BRING ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS. SPC
HIGHLIGHTS THE CWA FOR A MARGINAL RISK OF SEVERE WEATHER...AND THE
MODEL SOUNDINGS APPEAR FAVORABLE FOR CONVECTIVE DEVELOPMENT. HIGHS
FOR MONDAY REACH THE LOWER 70S TO THE LOWER 80S...WHICH WILL ALLOW
CAPE VALUES TO EXCEED 1000 J/KG BY THE AFTERNOON IN THE PIEDMONT. IF
ANY STRONGER STORMS MATERIALIZE AHEAD OF THE COLD FRONT...LARGE HAIL
AND DAMAGING WINDS WOULD BE THE MAIN THREATS. THIS FRONT IS
PROJECTED TO WEAKEN AND STALL DURING MONDAY NIGHT INTO TUESDAY...BUT
HOW FAR SOUTH IT CAN REACH BEFORE IT BECOMES STATIONARY REMAINS A
LITTLE QUESTIONABLE. REGARDLESS...IT WILL KEEP SCATTERED SHOWERS IN
THE FORECAST THROUGHOUT THIS TIME.

SEVERAL MORE WAVES OF LOW PRESSURE RIDE NORTHWARD ALONG THE STALLED
FRONTAL BOUNDARY DURING TUESDAY AND WEDNESDAY. WHILE THE CHANCE OF
SHOWERS SHOULD LINGER THROUGH THESE TWO DAYS...THE THREAT OF
THUNDERSTORMS APPEARS LIMITED TO MAINLY NORTHWEST NORTH CAROLINA ON
TUESDAY AFTERNOON DUE TO LINGERING INSTABILITY AND THE PROXIMITY OF
THE STALLED FRONT. HIGH TEMPERATURES ON TUESDAY SHOULD DIP FIVE TO
TEN DEGREES LOWER THAN ON MONDAY. THE CHANCE OF THUNDERSTORMS
DIMINISHES ON TUESDAY NIGHT...AS THE WAVES OF LOW PRESSURE
SUCCESSFULLY PUSH THE FRONTAL BOUNDARY TOWARD THE COAST BY
WEDNESDAY. THAT SITUATION SHOULD KEEP JUST A CHANCE OF SHOWERS
THROUGH WEDNESDAY...WITH HIGHS NEARLY THE SAME COMPARED TO TUESDAY.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
AS OF 545 AM EDT SUNDAY...

AS THE COLD FRONT FINALLY GAINS ENOUGH ENERGY TO LIFT OFFSHORE ON
WEDNESDAY NIGHT...A DEEP UPPER LEVEL TROUGH WILL MIGRATE FROM THE
HUDSON BAY IN CANADA TOWARD THE GREAT LAKES. THE TROUGH SHOULD REACH
THE APPALACHIAN MOUNTAINS BY THURSDAY...AND EVENTUALLY CUT OFF
OVERHEAD. MEANWHILE...ANOTHER CLOSED UPPER LEVEL LOW WILL ALSO CUT
OFF OVER THE ROCKY MOUNTAINS. IN BETWEEN THESE TWO LOWS...A STRONG
UPPER LEVEL RIDGE WILL RESIDE OVER THE PLAINS. THIS ATMOSPHERIC
PATTERN CREATES ANOTHER OMEGA BLOCK OVER THE UNITED STATES SIMILAR
TO WHAT WAS WITNESSED BACK IN MID APRIL...WHICH BOTH THE LATEST
ECMWF AND GFS MODELS DEPICT IN REASONABLY GOOD AGREEMENT.

UNLIKE THE LAST OMEGA BLOCK WHERE THE MID ATLANTIC ENJOYED
UNSEASONABLY WARM AND DRY CONDITIONS UNDER THE UPPER LEVEL
RIDGE...JUST THE OPPOSITE WILL OCCUR DUE TO BEING UNDER THE UPPER
LEVEL LOW...WITH COOL AND WET CONDITIONS EXPECTED THROUGH THE END OF
THIS WORK WEEK. HIGHS WILL ONLY REACH THE 50S AND 60S BY THURSDAY
AND FRIDAY. ON SATURDAY...THE OMEGA BLOCK GRADUALLY WEAKENS...WHILE
UPPER LEVEL RIDGING SLOWLY BEGINS OVERHEAD. IT APPEARS THAT WARMER
AND DRIER CONDITIONS COULD ARRIVE TOWARD THE END OF THIS WEEKEND.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
AS OF 137 PM EDT SUNDAY...

FORECAST REFLECTS A BLEND OF THE LATEST RAP/NAM MODELS. SHOULD
SEE ALL SITES BECOME VFR THIS AFTERNOON AS CLOUDS ERODE AND SW
FLOW DIMINISHES THE WEDGE. AS WE HEAD TOWARD LATE AFTERNOON WILL
BE SEEING ANOTHER UPPER IMPULSE MOVING FROM KY INTO THE CENTRAL
APPALACHIANS AND SHENANDOAH VALLEY. UNTIL THEN...ISOLATED
SHOWERS/STORMS MAY POP...BUT LOOKS LIKE BEST THREAT WILL NOT BE
UNTIL AFTER 21Z ACROSS BLF/LWB THEN POSSIBLY ROA/BCB BY 00Z. STILL
MODELS ARE SHOWING SCT/BKN COVERAGE SO FOR POINTS LIKE LYH/ROA
WILL ONLY PUT IN VCSH FOR NOW...THOUGH THUNDERSTORMS CANNOT BE
RULED OUT.

ONCE THIS IMPULSE MOVES EAST BY MIDNIGHT...A BREAK IN THE SHOWERS
SHOULD OCCUR OVERNIGHT. QUESTION WILL BE LOW LVL MOISTURE LEADING
TO LOWER CIGS AND/OR VSBYS. NOT SEEING ANY RETURN TO WEDGE AS FLOW
STAYS SW AT THE SFC. KEPT CLOSE TO THE PREVIOUS FORECAST AND KEPT
TEMPO IN AT LWB/BCB...BUT ALL SITES COULD SINK TO IFR OR WORSE
DURING THE 06-13Z TIME FRAME.

AS SW FLOW KICKS IN MONDAY MORNING A TRANSITION TO SCT/BKN VFR
CIGS TO TAKE PLACE AT ALL SITES...WITH SHOWERS AND STORMS EXPECTED
IN THE AFTERNOON.



EXTENDED AVIATION DISCUSSION...

FRONTAL BOUNDARY WILL STALL OVERHEAD BY MONDAY. MORE WAVES OF LOW
PRESSURE WILL MOVE ALONG THE STALLED BOUNDARY FROM TUESDAY THROUGH
THURSDAY...WHICH SHOULD HELP PUSH THE BOUNDARY OFFSHORE. A DEEP
UPPER LEVEL TROUGH IS PROJECTED TO DIVE SOUTHWARD OVER THE
APPALACHIAN MOUNTAINS BY WEDNESDAY INTO THURSDAY. OVERALL...FLYING
CONDITIONS APPEAR RATHER POOR THROUGH MOST OF THIS WEEK DUE TO THE
LIKELIHOOD OF LOW CLOUDS...PERIODS OF RAIN...AND PATCHY FOG.

&&

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

&&

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



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