Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 270014
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
814 PM EDT TUE APR 26 2016

.SYNOPSIS...
A FRONTAL BOUNDARY FROM CENTRAL ILLINOIS EXTENDING EASTWARD THROUGH
CENTRAL NEW JERSY THIS AFTERNOON WILL SLOWLY PUSH SOUTHWARD AND
INTO THE CENTRAL APPALACHIAN REGION TONIGHT AND INTO WEDNESDAY AS
WAVES OF LOW PRESSURE TRACK ALONG IT. ONE WAVE WILL MOVE ACROSS
WEDNESDAY MORNING FROM THE WEST...AND A MORE SIGNIFICANT WAVE WILL
TRACK JUST NORTHWEST OF OUR AREA ON THURSDAY...BRINGING ADDITIONAL
MOISTURE BACK ACROSS THE SURFACE BOUNDARY STILL DRAPED OVER THE
REGION.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 750 PM EDT TUESDAY...

CONVECTIVE WATCH NO. 111 ISSUED FOR THE FAR N-NW PART OF THE
CWA...INCLUDING ALL WV COUNTIES AND ALLEGHANY/BATH COUNTIES IN VA.
CONFIDENCE IN STRONG TO SEVERE CONVECTION REACHING THESE AREAS IS
LOW...BUT CONCERNS ABOUT UPSTREAM CONVECTION AND POSSIBLE DAMAGING
WINDS REACHING THESE AREAS LATER IN THE EVENING. WILL LIKELY NEED
TO MAKE SOME ADJUSTMENTS TO POP GRIDS AS THE EVENING PROGRESSES AS
MOST MODELS DO NOT SUGGEST MUCH CONVECTION REACHING THE MAJORITY
OF THE CWA EAST OF THE ALLEGHANY FRONT UNTIL AFTER SUNSET. THERE
IS THE POTENTIAL FOR AN UPSTREAM MCS TO REACH THE REGION LATE
TONIGHT/EARLY WED MORNING IN THE FORM OF DIMINISHING RAIN SHOWERS
AND A FEW RUMBLES OF THUNDER...BUT INSTABILITY DIMINISHES RAPIDLY
AFTER SUNSET.

AS OF 405 PM EDT TUESDAY...

SFC FRONTAL BOUNDARY REMAINS WELL TO THE NORTH OVER CENTRAL OHIO
AND PA...WITH SCATTERED CONVECTION DEVELOPING ALONG IT AND ALSO A
LITTLE SOUTH NEAR AN OUTFLOW BOUNDARY. INSTABILITY OVER THE
CENTRAL APPALACHIANS REMAINS RELATIVELY LOW THANKS TO QUICK
DEVELOPMENT OF BROKEN CUMULUS FIELD EARLIER TODAY. ALSO DRY AIR
ALOFT LIKELY SUPRESSING DEEPER CONVECTIVE DEVELOPMENT IN OUR
MTNS. SCATTERED CONVECTION MAY DRIFT IN TO PARTS OF SOUTHEAST WV
BETWEEN 5 AND 6PM...BUT NOT EXPECTING MOST OF THE ACTIVITY TO MOVE
IN GENERALLY NORTH OF U.S. 460 UNTIL AFTER 6PM...AND BY THAT TIME
INSTABILITY BEGINNING TO WEAKEN EVEN MORE. STILL...ISOLATED DEEPER
UPDRAFTS THAT MAY STILL DEVELOP OR MOVE IN CAN TAP SOME DRIER AIR
ALOFT AND RESULT IN VERY GUST DOWNDRAFT GIVEN DCAPE VALUES IN THE
700-900 J/KG RANGE. BELIEVE SEVERE THREAT THIS EVENING IS VERY
MINIMAL...IF ANY...BUT STILL WORTH KEEPING AN EYE ON THROUGH THE
LATE EVENING HOURS NORTH OF U.S. 460.

UNCERTAINTY REGARDING IMPACTS OF SIGNIFICANT WAVE APPROACHING FROM
THE WEST TOWARD MORNING...IN ASSOCIATE WITH MESOSCALE CONVECTIVE
SYSTEM CROSS MISSISSIPPI RIVER NEAR ST LOUIS THIS AFTERNOON.
MODELS EACH HANDLE THIS A BIT DIFFERENTLY...WITH MOST BRINGING IT
AT LEAST INTO ERN KY...BUT MANY BRINGING LINGERING SHOWERS AND
STORMS INTO MOUNTAINS DURING THE MORNING HOURS. AT THE SAME
TIME...THE SFC BOUNDARY TO THE NORTH BEGINS TO BACK DOOR FROM THE
NORTHEAST THROUGH THE LYNCHBURG AREA DURING THE DAY
WEDNESDAY...AND REMNANTS OF THIS WAVE FROM THE WEST COULD
INTERSECT THIS IN THE EAST EITHER ALLOWING CONVECTION TO
CONTINUE...OR REDEVELOPING IN THE PIEDMONT. DECIDED TO JUST
MAINTAIN LOW LIKELY TO HIGH CHANCE POPS MOST OF THE DAY
TOMORROW...WITH CHC THUNDER PRETTY MUCH ALL DAY. MIDNIGHT SHIFT
CAN REASSESS AS THIS WAVE FROM THE WEST APPROACHES AND WE MAY
NEED TO REMOVE THUNDER CHANCES DURING THE MORNING...AND RE-
INTRODUCE LATER IN AFTERNOON. BUT IN GENERAL MOST LOCATIONS STAND
A GOOD CHANCE OF SEE A PERIOD OF SHOWERS AND MAYBE A THUNDER STORM
AS WELL. SEVERE CHANCES APPEAR MINIMAL...AND WILL DEPEND ON
HEATING...BUT NOT A ZERO THREAT.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 230 PM EDT TUESDAY...

A FRONTAL BOUNDARY WILL REMAIN STALLED AROUND OR JUST SOUTH OF THE
VA/NC BORDER WEDNESDAY NIGHT INTO THURSDAY. DISTURBANCES FROM THE
MIDDLE MISSISSIPPI VALLEY WILL PINWHEEL EASTWARD FROM A PARENT UPPER
TROUGH LOCATED OVER THE UPPER MISSISSIPPI VALLEY. THESE FEATURES
WILL RIDE ALONG THE BOUNDARY BRINGING EXTRA ENERGY TO THE REGION TO
SUPPORT BETTER ORGANIZATION OF SHOWERS/STORMS. ONE SUCH FEATURE IS
PROGGED TO ARRIVE THURSDAY MORNING IN THE WEST AND TRANSLATE ACROSS
THE REGION DURING THE COURSE OF THE DAY. NOTABLE SURFACE BASED
INSTABILITY AND WEAK LOW LEVEL SHEAR WILL BE SUFFICIENT FOR SOME
STORMS TO BE ON THE STRONG SIDE. NORTHEAST PARTS OF THE AREA ARE
EXPECTED TO EXPERIENCE THE LEAST COVERAGE OF STORMS. HERE...A NOSING
RIDGE OF HIGH PRESSURE WILL HELP TO KEEP AT LEAST SURFACE BASED
CONVECTION AT BAY.

BY THURSDAY EVENING...A COLD FRONT ASSOCIATED WITH THE PARENT UPPER
LOW WILL BE REACHING THE WESTERN PART OF THE AREA...AND MOVE TROUGH
THE REGION THURSDAY NIGHT. LOOK FOR A CONTINUATION OF SHOWERS INTO
THE OVERNIGHT HOURS...WITH ISOLATED STORMS STILL POSSIBLE IN THE
EVENING.

BY FRIDAY...THE UPPER LEVEL TROUGH AXIS WILL CROSS THE REGION. THE
BEST DYNAMICS ARE PROGGED TO STAY NORTH OF THE AREA.
HOWEVER...ENOUGH INSTABILITY IS EXPECTED TO REACH A LEAST THE
NORTHERN HALF THE AREA FOR THE FOCUS FOR SHOWERS...AND A FEW
STORMS...TO BE THERE. ALSO...DAYTIME HEATING IN THE EAST WILL
COINCIDE WITH THE PASSAGE OF THE TROUGH...SO EXPECT ISOLATED TO
SCATTERED COVERAGE OF SHOWERS AND ISOLATED STORMS IN THE EAST AS
WELL.

TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL AVERAGE A FEW
DEGREES ABOVE NORMAL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 310 PM EDT TUESDAY...

FRIDAY NIGHT...ANTICIPATE SOME LINGERING ISOLATED SHOWERS AS THE
UPPER TROUGH AXIS DEPARTS THE REGION. THE FOCUS FOR ANY ACTIVITY
WILL BE IN THE NORTHEAST PART OF THE FORECAST AREA.

OVER THE WEEKEND...UPPER RIDGING WILL TAKE PLACE ACROSS THE REGION
AS ANOTHER LOW WITH ASSOCIATED FRONTAL FEATURES DEVELOPS IN THE
CENTRAL PORTION OF THE COUNTRY. THIS FEATURES WILL ADVECT MOISTURE
AND BITS OF SHORTWAVE ENERGY TOWARDS THE REGION. WHILE IT WILL
INITIALLY BE DAMPENED BY THE RIDGE...BY THE END OF THE WEEKEND...THE
RIDGE WILL HAVE BEEN DISPLACED BY ZONAL FLOW...AND BY
MONDAY...LOW/TROUGH SYSTEM PROGRESSING THROUGH THE REGION.

ANTICIPATE INCREASING CHANCES OF SHOWERS DURING THE WEEKEND...WITH
THE GREATEST COVERAGE IN THE WEST. ISOLATED THUNDERSTORMS ARE
POSSIBLE WITH THE BEST CHANCES OF THESE IN THE WEST AND SOUTH.

BY LATE SUNDAY NIGHT INTO MONDAY...MODERATE RAIN SHOWERS ARE
LIKELY WITH ISOLATED STORMS AS THE UPPER SYSTEM PASSES THE REGION.

ANOTHER SYSTEM ON THE HEELS OF THE MONDAY ACTIVITY IS PROGGED TO
SWING THROUGH THE AREA ON TUESDAY...HELPING TO MAINTAIN OUR CHANCES
OF SCATTERED SHOWERS.

TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL AVERAGE FIVE
DEGREES ABOVE NORMAL THROUGH MONDAY. ON TUESDAY...NEAR NORMAL
TEMPERATURES ARE FORECAST.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 800 PM EDT TUESDAY...

VERY LOW CONFIDENCE THROUGH THE TAF VALID PERIOD. NORTHWEST TO
SOUTHEAST ORIENTED FRONTAL BOUNDARY WILL DRIFT SLIGHTLY FURTHER
SOUTH OVERNIGHT AND THEN BECOME QUASI-STATIONARY ACROSS THE REGION
WED. IT WILL CERTAINLY SERVE AS THE FOCUSING MECHANISM FOR
CONVECTION WITH A MARGINALLY UNSTABLE ATMOSPHERE. MORE IMPORTANTLY
WILL NEED TO KEEP AN EYE ON UPSTREAM CONVECTION/MCSS RIDING ALONG
THE BOUNDARY/BAROCLINIC ZONE FROM THE OH VALLEY OVERNIGHT/EARLY
THURSDAY. TIMING...INTENSITY...AND WHETHER OR NOT THESE FEATURES
WILL EVEN HOLD TOGETHER TO REACH THE RNK CWA IS QUESTIONABLE.
HOWEVER...ENOUGH MODELS SUGGEST THAT PRECIPITATION WILL AT LEAST
REACH THE NW PART OF THE CWA LATE TONIGHT/EARLY WED THAT IT
WARRANTED INCLUDING IN THE TAFS. BETTER THREAT FOR REDEVELOPMENT
OF CONVECTION WED AFTERNOON AFT 16Z ACROSS MUCH OF THE CWA NEAR
THE FRONTAL BOUNDARY.

WITH RESPECT TO CIGS/VSBYS...POTENTIAL EXISTS FOR MVFR IN
-SHRA/-TSRA BR OVERNIGHT/EARLY WED...BUT OVERALL EXPECTING VFR
CIGS/VSBYS OUTSIDE CONVECTION. GREATER POTENTIAL FOR LOCAL MVFR-
IFR CIGS/VSBYS IN SHRA/TSRA WED AFTERNOON AFT 18Z...BUT AGAIN
CONFIDENCE IN TIMING/EXTENT/DURATION IS LOW.

WINDS MOSTLY SW-WSW 5-7KTS WITH SOME LOW END GUSTS THROUGH THE
PERIOD...BUT POTENTIALL BECOMING E-NE AT KLYH WED AFTERNOON BEHIND
THE FRONTAL BOUNDARY WITH SOME POTENTIAL FOR WEDGE DEVELOPMENT
LATE IN THE PERIOD.

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

EXTENDED AVIATION DISCUSSION...

BACK DOOR FRONT WILL SLOWLY PUSH THROUGH WEDNESDAY NIGHT AND THEN
REMAIN STALLED OR SLOWLY DRIFT BACK NORTH ON THURSDAY...BEFORE A
STRONGER COLD FRONT ENTERS FROM THE WEST TO PUSH THE WEAKER FRONT
OFFSHORE LATE THURSDAY. DURING THIS TIME...SCATTERED SHOWERS WITH
A FEW AFTERNOON THUNDERSTORMS APPEAR LIKELY. THE GREATEST CHANCE
OF RAIN AND MVFR/IFR CONDITIONS WILL ACCOMPANY THE STRONGER COLD
FRONT ON THURSDAY. SOME CLEARING SHOULD TAKE PLACE DURING
FRIDAY...ALTHOUGH A FEW MOUNTAIN SHOWERS AND MVFR CLOUDS ARE
POSSIBLE.

&&

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

&&

$$
SYNOPSIS...AMS/SK
NEAR TERM...RAB/SK
SHORT TERM...DS
LONG TERM...DS
AVIATION...AMS/DS/RAB/SK


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