Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 210146
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
946 PM EDT MON APR 20 2015

.SYNOPSIS...
A COLD FRONT WILL CONTINUE TO MOVE EAST THROUGH THE REGION TONIGHT
BRINGING AN END TO MOST OF THE SHOWERS AND THUNDERSTORMS AFTER
MIDNIGHT. IN THE WAKE OF THE FRONT...A COOLER...BREEZY...AND
SOMEWHAT UNSETTLED PATTERN EXPECTED THROUGH THE MIDDLE OF THE WORK
WEEK...WITH THE BEST CHANCE OF MORE SHOWERS AND THUNDERSTORMS
ARRIVING WITH ANOTHER FRONT ON WEDNESDAY.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 935 PM EDT MONDAY...

WILL BE ALLOWING SEVERE WATCH 89 TO EXPIRE AT 10 PM. LATEST RADAR
TRENDS SHOW MUCH OF THE DEEPER CONVECTION IN A WEAKENED STATE WITH
LOSS OF HEATING. HOWEVER A FEW CLUSTERS RIGHT ALONG THE COLD
FRONT OVER THE WESTERN MOUNTAINS MAY CONTINUE TO PRODUCE BRIEF
STRONGER WIND GUSTS OVER THE NEXT HOUR OR SO. OTHERWISE WILL KEEP
THE GOING DRIER SCENARIO ESPCLY AFTER MIDNIGHT WITH MUCH DRIER AIR
SURGING IN BEHIND THE FRONT THAT SHOULD BE EAST OF THE REGION
DURING THE EARLY MORNING HOURS. MODELS STILL SHOW A BIT OF UPSLOPE
DRIVEN SHOWERS REDEVELOPING WEST LATE SO KEPT IN SOME LOW POPS FOR
SCATTERED COVERAGE WHILE DRYING OUT AREAS FROM THE BLUE RIDGE EAST
AFTER MIDNIGHT WITH SOME CLEARING AS WELL. QUICK INCREASE IN 85H
WINDS ALONG WITH A BRIEF SHOT OF COOL ADVECTION AND DECENT
PRESSURE RISES SUPPORT SOME STRONGER POST FRONTAL GUSTS TO 35-40
MPH ON THE RIDGES TOWARD DAYBREAK SO BUMPED UP GUSTS. NOT A LOT OF
CHANGE WITH LOWS GIVEN CLOUDS WEST AND MIXING MOST SPOTS THAT
COULD HOLD LOCATIONS FROM THE BLUE RIDGE EAST IN THE 50S OVERNIGHT
WITH MOSTLY 40S OUT WEST.


PREVIOUS DISCUSSION AS OF 310 PM EDT MONDAY...

SEVERE THUNDERSTORM WATCH 89 IS IN EFFECT UNTIL 10 PM THIS EVENING.

SHOWERS AND THUNDERSTORMS...SOME STRONG TO SEVERE WILL DEVELOP THIS
AFTERNOON INTO TONIGHT AHEAD AND ALONG A COLD FRONT.  THE MAIN
THREATS ARE FOR THUNDERSTORMS WITH DAMAGING WINDS AND LARGE
HAIL...ALONG WITH LOCALLY HEAVY RAIN. THE 18Z RNK SOUNDING SHOWED A
CAP AROUND 700 MB THAT WILL BREAK QUICKLY THIS AFTERNOON WITH
HEATING AND EXPECTED CAPE ABOVE 1000 J/KG. DEEP LAYER SHEAR OVER 40
KTS AND STRONG UPDRAFTS ARE POSSIBLE LATER THIS AFTERNOON INTO THIS
EVENING.

REGIONAL WSR88D IMAGE SHOWED STRONG TO SEVERE CONVECTION OVER
WESTERN NORTH CAROLINA EXPANDING NORTHEAST INTO OUR AREA.

THE COLD FRONT WILL PUSH EAST OF OUR AREA THIS EVENING INTO
TONIGHT. STRONG 6H PRESSURE RISES BEHIND THE FRONT WILL BRING
BREEZY AND GUSTY WESTERLY WINDS TO THE AREA THIS EVENING INTO
TONIGHT. LOW TEMPERATURES TONIGHT WILL DROP INTO THE UPPER 30S IN
THE MOUNTAINS TO THE LOWER 50S IN THE PIEDMONT. HIGH PRESSURE
WILL BUILD SOUTHEAST INTO OUR AREA TUESDAY. HIGHS TEMPERATURES ON
TUESDAY WILL WARM INTO THE LOWER 50S IN THE NORTHWEST MOUNTAINS
TO THE LOWER 70S.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 214 PM EDT MONDAY...

UPPER TROUGH WILL BE SITUATED RIGHT OVER THE AREA TUESDAY NIGHT WITH
NEXT SFC FRONT WORKING ACROSS BY WEDNESDAY...THOUGH WITH MORE WNW
FLOW ALOFT AND LACK OF SOUTHERLY INFLOW AHEAD OF THIS
SYSTEM...MOISTURE WILL BE LIMITED. AS SUCH HAVE LIMITED CHANCE POPS
OVER THE MOUNTAINS WITH SOME CHANCE INTO THE NE PIEDMONT OF
VA...WITH LESS COVERAGE INTO THE NC PIEDMONT...AS WE SHOULD SEE SOME
DOWNSLOPE DRYING AND SHEARING OF THE VERTICAL DEVELOPMENT. JUST
ENOUGH INSTABILITY WITH COLDER AIR ALOFT TO MENTION THUNDER IN THE
AFTERNOON WEDNESDAY. SHOULD BE A BREEZY DAY WITH HIGHS FROM THE
UPPER 50S OVER SE WV TO LOWER 70S SOUTHEAST.

WEDNESDAY NIGHT THROUGH THURSDAY WILL BE MAINLY DRY WITH CONTINUED
UPPER TROUGH SLIDING ACROSS THE AREA...BUT AXIS SHIFTING MORE OVER
THE COAST. NW FLOW MAY KEEP SHOWERS GOING INTO THE MOUNTAINS WED
EVENING.  UPPER RIDGING ARRIVES OVER THE LOWER MS VALLEY WITH SFC
HIGH IN THE TN VALLEY.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 130 PM EDT MONDAY...

NOT MUCH CHANGE TO THIS FORECAST. HIGH PRESSURE AT THE SFC BUILDS
SOUTHEAST FROM THE OHIO VALLEY INTO FRIDAY. A SOUTHERN STREAM LOW
ARRIVES OVER THE AR/OK BORDER BY SATURDAY MORNING WITH OVERRUNNING
CLOUDS WORKING INTO THE AREA FRIDAY AHEAD OF A WARM FRONT. BY
SATURDAY ENOUGH MOISTURE TO ALLOW FOR SHOWERS TO FORM BY SATURDAY
MORNING WITH BEST FORCING ACROSS THE CAROLINAS. THIS SYSTEM EXITS BY
SAT NIGHT WITH SUNDAY BEING A DRY AND COOL/MILD DAY WITH HIGHS IN
THE 50S MOUNTAINS TO 60S EAST. HIGH PRESSURE TO ASSUME POSITION OVER
THE OHIO VALLEY INTO THE SRN APPALACHIANS MONDAY TO KEEP THINGS DRY.
NEXT SOUTHERN STREAM SYSTEM MAY WORK SOME SHOWERS OUR WAY BY TUESDAY.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
AS OF 651 PM EDT MONDAY...

BROKEN BANDS OF CONVECTION ACROSS THE REGION WILL LIKELY LINGER
INTO EARLY THIS EVENING BEFORE FADING WITH LOSS OF HEATING AS A
COLD FRONT WORKS THROUGH THE REGION BY MIDNIGHT. THIS SHOULD
CONTINUE TO PRODUCE BRIEF PERIODS OF MVFR IN ISOLATED SHRA/TSRA
WITH LOCAL IFR POSSIBLE IF A HEAVIER CLUSTER MOVES RIGHT ACROSS A
TAF SITE. FOR NOW WILL KEEP THINGS MOSTLY VFR WITH INCLUSION OF A
TEMPO OR VICINITY MENTION TO COVER SHORT TERM COVERAGE OVER THE
NEXT FEW HOURS WITH MOST CELLS LIKELY BELOW SEVERE LIMITS FOR THE
MOST PART.

PRESSURE RISES BEHIND THE FRONT WILL BRING BREEZY AND GUSTY
WESTERLY WINDS TO THE AREA LATER THIS EVENING INTO THE OVERNIGHT.
ALSO THIS EVENING INTO TONIGHT BEHIND THE FRONT...SOME MVFR
CEILINGS ARE POSSIBLE IN THE MOUNTAINS. UNCERTAINTY ON HOW LOW
CLOUD BASES WILL GET ONCE THE SHOWERS CLEAR OUT TONIGHT. ANOTHER
ISSUE IS THAT ANY LOCATION THAT RECEIVED OVER AN INCH OF RAIN MAY
SEE FOG DEVELOPING OVERNIGHT INTO TUESDAY. VFR CONDITIONS SHOULD
RETURN LATER TONIGHT AND TUESDAY WITH HIGH PRESSURE BUILDING IN
BEHIND THE FRONT WITH A DRIER AIRMASS AND CONTINUED GUSTY NW
WINDS.

EXTENDED AVIATION...

THEN THE NEXT CHANCE OF MVFR CONDITIONS AND PRECIPITATION WILL BE
IN THE MOUNTAINS ON WEDNESDAY AND THURSDAY. HIGH PRESSURE
AT THE SURFACE BUILDS SOUTHEAST FROM THE OHIO VALLEY THURSDAY
NIGHT INTO FRIDAY. OVERRUNNING CLOUDS WORKING INTO THE AREA
FRIDAY AHEAD OF A WARM FRONT. BY SATURDAY...ENOUGH MOISTURE TO
ALLOW FOR SHOWERS TO FORM BY SATURDAY MORNING WITH BEST FORCING
ACROSS THE CAROLINAS.

&&

.HYDROLOGY...
AS OF 940 PM EDT MONDAY...

AFTER THE IMPRESSIVE RAINFALL SINCE YESTERDAY MORNING...WHICH SAW
OVER 6 INCHES AT A FEW GAGES IN ALLEGHANY COUNTY NC...RIVERS AND
LARGE CREEKS IN THE NEW RIVER AND UPPER ROANOKE VALLEYS HAVE
MOSTLY CRESTED AND ARE FALLING EARLY TONIGHT. STAGES ALONG THE
MAINSTEM NEW WILL CONTINUE TO RISE DOWNSTREAM FROM RADFORD
OVERNIGHT WITH GLEN LYN EXPECTED TO JUST TOP THE 15 FOOT FLOOD
STAGE JUST AFTER MIDNIGHT. RADFORD FLOODING WILL CONTINUE INTO
TONIGHT AS WATER FROM ABOVE CLAYTOR LAKE IS PASSED THROUGH.
ADDED RIVER FLOOD WARNINGS NOW ISSUED FOR THE LOWER ROANOKE RIVER
AT RANDOLPH AND AT SOUTH BOSTON ON THE DAN FOR MINOR FLOODING.
LOCATIONS AROUND DANVILLE WILL ALSO BE CLOSE TO FLOOD OVERNIGHT AS
WELL AS PACES LATE TUESDAY.

&&

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

&&

$$
SYNOPSIS...JH/KK
NEAR TERM...JH/KK
SHORT TERM...WP
LONG TERM...WP
AVIATION...AMS/JH/KK
HYDROLOGY...JH/PC


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