Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 030121
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
921 PM EDT TUE SEP 2 2014

.SYNOPSIS...
A WEAK COLD FRONT TRACKS SOUTHEAST INTO OUR AREA OVERNIGHT...BEFORE
STALLING ACROSS THE CAROLINAS AND WASHING OUT ON WEDNESDAY. HIGH
PRESSURE SETS BACK UP OVER THE EAST BY FRIDAY WITH YET ANOTHER
COLD FRONT MOVING TOWARD US THIS WEEKEND.
&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 910 PM EDT TUESDAY...

BAND OF DEEP CONVECTION CONTINUES TO PUSH EAST TOWARD THE BLUE
RIDGE THIS EVENING AND DESPITE DECREASING INSTABILITY APPEARS
PROGRESSION AIDED VIA OUTFLOW AND UPPER DYNAMICS. THIS MORE IN
LINE WITH THE EARLIER NAM OUTPUT AND LATEST LOCAL WRF WHICH TEND
TO PUSH MUCH OF THIS COVERAGE ACROSS MUCH OF THE CWA PAST
MIDNIGHT. THIS SEEMS SUPPORTED BY LINGERING HIGHER CAPES JUST EAST
OF THE BLUE RIDGE SO HAVE UPPED POPS FURTHER TO
CATEGORICAL/LIKELYS OUT TO THE FOOTHILLS AND PUSHED CHANCES EAST
ACROSS THE REMAINDER OF THE REGION. EVENING SOUNDINGS WERE ALSO
QUITE UNSTABLE WITH HIGH DCAPES SO STILL AN ISOLATED SEVERE THREAT
BETWEEN NOW AND MIDNIGHT WITH QUICK BURSTS OF RAINFALL RESULTING
IN OVER AN INCH IN 30 MINUTES OR SO. SOME DOWNWARD ADJUSTS TO LOW
TEMPS BUT OVERALL 60S TO LOW 70S GIVEN THE MUGGY AIR AROUND.

UPDATED DISCUSSION AS OF 735 PM EDT TUESDAY...

WITH THE NEXT ROUND OF CONVECTION RIDING UP THE DEVELOPING LINE
JUST WEST OF THE CWA...WENT AHEAD AND RAISED POPS TO
CATEGORICAL/HIGH LIKELYS FAR WEST FOR A FEW HOURS AND EXTENDED
HIGHER CHANCES EAST ACROSS THE BLUE RIDGE. LINGERING INSTABILITY
AND HIGH DCAPES STILL SUPPORT LOCALIZED MICROBURSTS WITH SLOW
MOVING STORMS ABLE TO PRODUCE HEAVY RAIN IN A SHORT PERIOD. FEW
OTHER CHANGES FOR NOW.

PREVIOUS DISCUSSION AS OF 245 PM EDT TUESDAY...

GOING TO SEE TWO AREAS OF CONVECTION THIS AFTERNOON INTO EARLY
EVENING. ONE FIRING ACROSS THE BLUE RIDGE/FOOTHILLS FROM FLOYD SOUTH
TO WILKES...AND OTHER MOVING INTO SE WV...ALLEGHANY HIGHLANDS. THE
12Z NAM IS DOING EXCELLENT ATTM WITH HAVING THIS...BUT AT 00Z THIS
EVENING FIRES UP A LINE FROM THE SHENANDOAH VALLEY TO THE SOUTHWEST
ACROSS THE MOUNTAINS OF FAR SW VA/SE KY. BY THIS TIME...LEANED
TOWARD A SOLUTION CLOSER TO THE 12Z ECMWF/GFS...AND AT THE SAME TIME
KEEP CONVECTION MOVING EAST INTO THE VA/NC PIEDMONT ALONG LEE
TROUGH.  UPSTREAM THE SHORTWAVE THAT IS OVER SRN OHIO AND ANOTHER
OVER INDIANA WILL STAY MAINLY NORTH OF US BUT FRONTAL BOUNDARY WILL
WORK SE THROUGH THE NIGHT. EXPECT TO SEE BEST THREAT OF SHOWERS AND
STORMS ACROSS SE WV EARLY THIS EVENING...THEN TAPER POPS OVERNIGHT
TO SLIGHT CHANCE...WITH LACK OF FORCING.

LOWS TONIGHT KEEP THE PERSISTENT MUGGY TEMPS WE HAVE HAD...WITH
MID 60S WEST TO LOWER 70S SOUTHEAST.

WEDNESDAY...FRONT SHIFTS INTO NC AND WILL SEE MAIN FOCUS OF SHOWERS
AND STORMS DO LIKEWISE...WHILE NORTH WINDS TRY TO DRY THINGS OUT
OVER THE NRN CWA. HOWEVER 8H FRONT EDGES INTO THE NRN CWA ONLY...SO
KEEPING MOST OF OUR REGION IN THE SOMEWHAT HUMID AIRMASS. FOR POPS
WILL HAVE SLIGHT CHANCE SOUTH OF BLF-ROA-LYH LINE...MAINLY DRY
NORTH...WITH THE SRN TIER OF THE CWA ACROSS THE NC/VA BORDER AND
SOUTH IN THE LOW CHANCE. TEMPS WILL DROP A FEW DEGREES UP NORTH BUT
STILL WARM ACROSS THE CWA...WITH LOWER 80S WEST...TO MID TO UPPER
80S EAST.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 330 PM EDT TUESDAY...

STRONG LATE SEASON UPPER RIDGE OVER THE SOUTHERN CONUS REMAINS IN
CONTROL THROUGH THE SHORT-TERM WHICH WILL MAINTAIN THE VERY WARM AND
HUMID CONDITIONS ACROSS OUR AREA. A WEAK SURFACE RIDGE OVER PA WILL
BE DRIFTING OFF THE COAST BY EARLY THURSDAY WITH THE WEAK FRONTAL
BOUNDARY LOCATED ACROSS NC. THIS BOUNDARY MAY ACT AS THE FOCUS
FOR SHOWER AND THUNDERSTORM ACTIVITY WHICH WILL REMAIN MAINLY
SOUTH OF THE CWA ON THURSDAY WHERE BETTER CONVERGENCE AND DEEPER
MOISTURE EXISTS. THE ACTIVE NORTHERN STREAM WILL REMAIN WELL
POLEWARD OF OUR REGION IN THE SHORT TERM WITH SEVERAL STRONG
IMPULSES TRACKING ACROSS SOUTHERN CANADA. THE FIRST OF THESE WILL
DRAG A COLD FRONT DOWN FROM THE UPPER MIDWEST REACHING THE OHIO
VALLEY BY LATE FRIDAY. SOME PRE-FRONTAL CONVECTION IS POSSIBLE
FRIDAY AFTERNOON ACROSS OUR CWA BUT BETTER COVERAGE MORE LIKELY ON
SATURDAY. TEMPS WILL CONTINUE TO BE REMAIN WELL ABOVE NORMAL BOTH
THU AND FRI WITH HIGHS 5 TO 8F ABOVE EARLY SEPTEMBER
CLIMATOLOGY...RUNNING MID 80S TO LOW 90S FOR HIGHS AND LOWS FROM
NEAR 60 NW TO NEAR 70 SE.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 330 PM TUESDAY...

SLOW-MOVING COLD FRONT APPROACHES DURING THE DAY SATURDAY WITH
DECENT CHANCES FOR SHOWERS AND POSSIBLE THUNDERSTORMS BY AFTERNOON
WITH THE HIGHEST POPS ACROSS THE MOUNTAINS. FRONT WILL CONTINUE TO
DRIFT SLOWLY SOUTH THROUGH THE CAROLINAS ON SUNDAY AND LIKELY ACT AS
FOCUS FOR RENEWED CONVECTION SUNDAY AFTERNOON...BUT WITH THE BEST
COVERAGE SOUTH OF VA-NC BORDER. DRIER AND SOMEWHAT COOLER CONDITIONS
LIKELY MON-TUE UNDER HIGH PRESSURE AS 850 MB TEMPS ARE KNOCKED BACK
TO 12-14C RANGE..YIELDING AT LEAST NEAR NORMAL HIGHS/LOWS BEFORE
RIDGE TRIES TO AMPLIFY AGAIN.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
AS OF 705 PM EDT TUESDAY...

CLUSTERS/BANDS OF SHRA/TSRA CONTINUE TO AFFECT THE SOUTHEAST WEST
VA SITES WITH SOME OF THIS COVERAGE NOW SPREADING EAST OUT TO
AROUND KROA/KLYH ATTM. THINK LOSS OF HEATING SHOULD START TO
DECREASE WESTERN COVERAGE IN THE NEXT COUPLE OF HOURS BUT GIVEN
UPSTREAM SHRA/TSRA WILL NEED TO KEEP PREVAILING LOW END VFR/HIGH
END MVFR IN AT KBLF/KLWB THROUGH MUCH OF THE EVENING. COULD EVEN
SEE A PERIOD OF IFR IN STRONGER STORMS EARLY ON. ELSW INCLUDING
MORE VCSH/VCTS OUTSIDE OF KDAN WITH TEMPO GROUPS FOR STRONGER
WINDS AND ISOLATED TSRA THROUGH MIDNIGHT.

HOWEVER SHOWERS AND STORMS MAY LINGER EVEN PAST MIDNIGHT TO SOME
DEGREE PER LATEST GUIDANCE BUT EXPECTING COVERAGE TO WANE IN
INTENSITY. THUS LEAVING IN VCSH ACROSS THE MOUNTAINS AS CIGS/VSBYS
START TO LOWER IN FOG DEVELOPMENT DURING THE EARLY MORNING HOURS.

OVERNIGHT THE ISSUE TURNS TOWARD FOG...AS LOW LVL MOISTURE WILL
BE HIGH. QUESTION IS HOW MUCH CLEARING OCCURS AND IF IT RAINS NEAR
A TERMINAL. THINK CONFIDENCE IN FOG OCCURRING IS HIGHER AT
KLWB...KBCB AND KBLF...MAINLY MVFR TEMPO IFR.

FOG GOES AWAY AFTER 14Z/10AM...WITH VFR EXPECTED INTO THE
AFTERNOON BEFORE ADDED SHRA/TSRA START TO POP UP MAINLY ALONG THE
KBLF-KDAN CORRIDOR AND POINTS SOUTH IN THE AFTERNOON. THINKING
COVERAGE QUITE LESS THAN TODAY BUT ENOUGH TO INCLUDE A VCTS
MENTION AT KDAN WHILE LEAVING OUT ELSW FOR NOW.

EXTENDED AVIATION DISCUSSION...

FRONT STALLS SOUTH OF US WEDNESDAY AND MODELS FAVOR CONVECTION
SOUTH OF A DAN-TNB LINE. IN THE AFTERNOON. MAINLY VFR EXCEPT ANY
LATE NIGHT FOG IN THE BCB/LWB AREA THU. FRONT WASHES OUT TO THE
SOUTH OF THE AREA FRIDAY WITH MORE WIDELY SCATTERED DIURNAL NATURE
SHOWERS AND STORMS...THEN PERHAPS BECOMING MORE WIDESPREAD
SATURDAY INTO SUNDAY WITH PERIODIC MVFR IN MORE ORGANIZED
COVERAGE AHEAD OF ANOTHER COLD FRONT ARRIVING FROM THE NORTHWEST
LATE. OTRW WILL SEE A DAILY TREND OF EARLY MVFR/IFR IN
FOG...FOLLOWED BY BRIEF VFR...THEN INCREASING AFTERNOON/EVENING
CONVECTION WHEN MVFR TO LOCAL IFR WILL BE POSSIBLE.

&&

.EQUIPMENT...
AS OF 730 AM EDT FRIDAY ...

THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL
BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED.

&&

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

&&

$$
SYNOPSIS...JH/WP
NEAR TERM...JH/WP
SHORT TERM...PC
LONG TERM...PC
AVIATION...JH/KK/RAB/WP
EQUIPMENT...RAB



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