Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 011540
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1140 AM EDT SUN MAY 1 2016

.SYNOPSIS...
A COOL AIR WEDGE ERODES THIS AFTERNOON...AS SOUTHWEST FLOW
INCREASES AHEAD OF A COLD FRONT. THIS FRONT WILL STALL TO OUR
SOUTH MONDAY AS A WAVE OF LOW PRESSURE RIDES ALONG THE FRONT
MONDAY INTO TUESDAY. 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 TONIGHT/...
AS OF 1130 AM EDT SUNDAY...

FORECAST UPDATED TO SHOW LESS COVERAGE OF SHOWERS AS WE ARE
BETWEEN UPPER WAVES...WITH SOME SUBSIDENCE COMBINED WITH THE
HEAVIER SHOWERS TO ERODE THE WEDGE A LITTLE FASTER OVER THE
SOUTHWEST CWA. GETTING MORE SUNSHINE BREAKING OUT...SO THIS WILL
ACT TO INCREASE INSTABILITY. HOWEVER...WILL HAVE TO AWAIT FOR THE
NEXT SHORTWAVE OVER WRN KY LATE THIS MORNING TO SHIFT TO THE AREA
BY THE END OF THE DAY. UNTIL THEN...COULD SEE SOME POP UP SHOWERS
OR ISOLATED STORMS WITH INCREASING POPS IN THE WEST AFTER 4 PM.

SVR THREAT STILL FAVORS KY/TN/OHIO INTO WV...AND MAY SEE SOME
STRONGER STORMS MAKE IT TO FAR SW VA INTO SE WV BY 8PM.

GIVEN MORE SUNSHINE...UPPED HIGHS A FEW DEGREES WITH MOST AREAS
SEEING 70S. WEDGE MAY STICK AROUND LONGER FROM AMHERST TO
KEYSVILLE VA...BUT EVEN THEN STRONG SUN ANGLE SHOULD ALLOW FOR
SOME SUNSHINE AT TIMES LATER THIS AFTERNOON.

PREVIOUS VALID DISCUSSION...

THE AREA IS LEFT WITH SOUTHWEST FLOW ALOFT THANKS TO A PERSISTENT
BROAD AREA OF LOW PRESSURE IN THE SOUTHWEST U.S. ADDITIONAL WEAK
DISTURBANCES ARE EMBEDDED WITHIN THE UPPER FLOW...ONE WHICH WILL
HELP PUSH A NEW COLD FRONT INTO THE REGION OVERNIGHT...WHICH WILL
THEN STALL JUST TO OUR SOUTH BY MON. FEEL THAT WHATEVER IS LEFT OF
THE WEDGE IN EASTERN SECTIONS WILL FINALLY ERODE OVERNIGHT INTO
MONDAY MORNING...ALLOWING TEMPERATURES TO CONTINUE TO MODERATE
WITH MINIMAL COOLING OVERNIGHT. AREAS EAST OF THE BLUE RIDGE MAY
SEE MIN TEMPS MONDAY MORNING CLOSE TO MAX TEMPS THIS AFTERNOON.

&&

.SHORT TERM /MONDAY 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 SATURDAY/...
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 /16Z SUNDAY THROUGH THURSDAY/...
AS OF 1138 AM EDT SUNDAY...

UPDATE TO CLEAR LOWER CLOUDS AND SHOWERS IN THE WEST WITH WEDGE
ERODING. THINK DAN/LYH/ROA WILL ALSO SCOUR OUT THIS AFTERNOON AT
LEAST TO MVFR/LOW END MVFR. CONVECTION MAY IMPACT LWB/BLF AND
POSSIBLY BCB BETWEEN 21-01Z.

PREVIOUS VALID AVIATION DISCUSSION...

ANY UPPER SUPPORT FOR THUNDERSTORMS WILL MOVE EAST OF THE REGION
AFTER MIDNIGHT AWAITING THE NEXT STRONGER UPPER IMPULSE APPROACHES
THE REGION LATER MONDAY AFTERNOON.

NOT CONFIDENT THAT WEDGE WILL COMPLETELY ERODE IN EASTERN AREAS.
VSBYS...WHICH COULD ALLOW LOCATIONS EAST OF THE BLUE RIDGE TO SEE
IFR-LIFR CIGS/VSBYS AFTER 06Z MON IN DENSE FOG.

WINDS MOSTLY E-SE 5-7KTS...BECOMING SW KBLF/KLWB THIS
MORNING...THEN SW ELSEWHERE AFT 18Z...WITH SPEEDS INCREASING
7-10KTS WITH LOW END GUSTS WEST OF THE BLUE RIDGE. IT MAY TAKE
UNTIL MID OR LATE AFTERNOON FOR ANY SOUTHWEST WINDS TO REACH
KLYH/KDAN. WINDS WILL DIMINISH AND BACK TOWARD THE SSW AFT
00Z...FURTHER AIDING THE DEVELOPMENT OF POTENTIAL LOW CLOUDS AND
FOG AFTER MIDNIGHT...ESPECIALLY WITH WET GROUND IN PLACE ALL
AREAS.

LOW TO MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH THE TAF VALID
PERIOD.
MEDIUM CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD.

EXTENDED AVIATION DISCUSSION...

THE AFOREMENTIONED LOW PRESSURE SYSTEM SHOULD CROSS OVER THE MID
ATLANTIC DURING SUNDAY NIGHT...BUT THE 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...RAB/WP
SHORT TERM...PW
LONG TERM...PW
AVIATION...PW/RAB/WP



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