792
FXUS61 KRNK 241332
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
932 AM EDT MON SEP 24 2018
SYNOPSIS
A WEDGE OF HIGH PRESSURE WILL KEEP OVERALL COOL AND DAMP
CONDITIONS TODAY INTO TUESDAY MORNING. TEMPERATURES WILL BEGIN
TO WARM TUESDAY AFTERNOON BEFORE THE NEXT FRONTAL PASSAGE
WEDNESDAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 915 AM EDT MONDAY...
MEASURABLE RAIN HAS BEEN LIMITED TO THE GREENBRIER VALLEY AND
ALLEGHANY HIGHLANDS SOUTH INTO THE ROANOKE VALLEY THIS MORNING.
AS A WARM FRONT ALOFT TRACKS NORTH, RAIN COVERAGE SHOULD
DIMINISH ACROSS THE AREA. HOWEVER, WEAK ISENTROPIC AND
OROGRAPHIC LIFT SHOULD KEEP EXTENSIVE CLOUD COVER, DRIZZLE AND
FOG ALONG THE BLUE RIDGE AND FOOTHILL COUNTIES INTO THE
AFTERNOON. WITH THIS IN MIND, LOWERED POPS FOR MEASURABLE
PRECIPITATION THROUGH THE AFTERNOON. NO OTHER CHANGES MADE TO
OTHER PARAMETERS.
AS OF 215 AM EDT MONDAY...
LOW LEVEL WEDGE REMAINS IN PLACE THIS MORNING WITH THE RESIDUAL
FRONT ACROSS THE CAROLINAS AND WEAK BUBBLE HIGH PRESSURE JUST EAST
OF THE BLUE RIDGE. THIS PERSISTENT SCENARIO LOOKS TO REMAIN LOCKED
IN PLACE TODAY INTO TONIGHT WITH THE PARENT SURFACE HIGH PASSING
WELL TO THE NORTHEAST BY THIS EVENING BENEATH SLOWLY BUILDING
HEIGHTS FROM THE SOUTHEAST. THIS WHILE UPPER LEVEL ENERGY RIDES TO
OUR NORTHWEST AROUND THE RIDGING ALOFT AND AIDS SOUTH TO SOUTHEAST
850 MB FLOW ABOVE THE COOL POOL. HOWEVER APPEARS MAIN FORCING ALOFT
TODAY TO STAY JUST TO THE NORTH AND WEST WITH PERHAPS THE FAR
NORTHWEST SECTIONS SEEING ENOUGH COVERAGE TO WARRANT SOME HIGHER
CHANCE POPS. ALSO BETTER UPSLOPE MAY LEAD TO MORE LIGHT RAIN/DRIZZLE
BLUE RIDGE UNTIL THE FLOW TURNS MORE SOUTHERLY ABOVE THE WEDGE LATER
TONIGHT BUT IFFY. OTHERWISE EXPECT MUCH OF THE REGION TO STAY IN A
LIGHTER RAINFALL REGIME TODAY WITH PATCHY LIGHT RAIN SOUTH/WEST
EARLY THIS MORNING, FOLLOWED BY MAINLY SPOTTY LIGHT
RAIN/DRIZZLE DURING THE DAY. HIGHS MOSTLY 60S TO PERHAPS A FEW
70S ALONG THE WESTERN AND SOUTHERN PERIMETER OF THE WEDGE WHERE
A FEW BREAKS OF SUNSHINE COULD OCCUR.
WEDGE WILL SHALLOW OUT SOME TONIGHT AS WARM ADVECTION ALOFT STARTS
TO WIN OUT IN RESPONSE TO A BIT STRONGER WAVE SHEARING BY TO THE
NORTH LATE. THIS MAY TEND TO BRING SOME INCREASE IN RAIN COVERAGE
NORTH AS LIFT DEVELOPS JUST SOUTH OF THIS FEATURE AND PERHAPS A FEW
MORE BANDS OF SHOWERS FAR WEST CLOSER TO THE TRAILING TROUGH AXIS.
THUS KEPT A SWATH OF LIKELY POPS NORTHWEST WITH CHANCE ELSEWHERE
INCLUDING PERHAPS MORE LIGHT RAIN/DRIZZLE CENTRAL SECTIONS WHERE THE
WEDGE WILL REMAIN STRONGEST. DIURNAL TEMP RANGE TO REMAIN SMALL WITH
LOWS MOSTLY IN THE 60S.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
AS OF 230 AM EDT MONDAY...
UPPER TROUGH DEEPENS OVER THE CENTRAL UNITED STATES AND SLIDES EAST
THROUGH WEDNESDAY NIGHT. COOL WEDGE BECOME SHALLOW AND ERODE ON
TUESDAY AS HIGH CENTER SLIDE EAST. HIGH TEMPERATURES TUESDAY WILL
RANGE FROM THE UPPER 60S IN THE MOUNTAINS TO AROUND 80 DEGREES IN
THE PIEDMONT.
SCATTERED SHOWERS WILL CONTINUE TUESDAY NIGHT IN THE WEST. LOW
TEMPERATURES WILL VARY FROM AROUND 60 DEGREES IN THE WEST TO THE
UPPER 60S IN THE EAST.
LEADING EDGE OF THE BEST LIFT AHEAD OF THE FRONT AND DIFFLUENCE WITH
THE UPPER JET NOW SLOWER ON THE GUIDANCE ARRIVE IN THE CENTRAL
APPALACHIANS WEDNESDAY MORNING. THE COLD FRONT WILL MOVE SOUTH
WEDNESDAY INTO WEDNESDAY NIGHT. HIGH TEMPERATURES ON WEDNESDAY WILL
FEATURE READINGS FROM THE UPPER 60S IN THE NORTHWEST MOUNTAINS TO
THE MID 80S IN THE PIEDMONT.
SHOWERS AND STORMS CONTINUE WEDNESDAY NIGHT AS FRONTAL BOUNDARY
SLOWS AND STALLS. THE RAIN MAY BE HEAVY WITH PWATS AROUND TWO INCHES
WITH GOOD LIFT. LOW TEMPERATURES WEDNESDAY NIGHT WILL GENERALLY BE
FROM THE MID 50S IN THE NORTHWEST MOUNTAINS TO THE UPPER 60S IN THE
PIEDMONT.
LONG TERM /THURSDAY THROUGH SUNDAY/
AS OF 1210 PM EDT SUNDAY...
UPPER PATTERN BECOMES ZONAL BY FRIDAY WITH MID ATLANTIC REGION
BETWEEN THE NORTHERN JET STREAM ACROSS THE GREAT LAKES AND
NORTHEAST UNITED STATES AND A RETROGRADING UPPER RIDGE OVER THE
GULF OF MEXICO AND SOUTHEAST UNITED STATES.
THE ECMWF WAS THE SLOWER THAN GFS AND CANADIAN WITH THE PASSAGE
OF THE SURFACE COLD FRONT ON THURSDAY. SHORT-LIVED PERIOD OF
WEAK COLD AIR ADVECTION AND NORTHWEST WINDS ON FRIDAY, THEN BACK
TO WEST TO SOUTHWEST 850 MB WINDS FOR SUNDAY. HIGH PRESSURE AND
DRIER AIR, WITH PRECIPITABLE WATER VALUES POTENTIALLY BELOW ONE
INCH, ALSO COME IN BEHIND THE FRONT FOR FRIDAY AND SATURDAY.
CONFIDENCE WAS AVERAGE FOR ALL ELEMENTS.
AVIATION /13Z MONDAY THROUGH FRIDAY/
AS OF 700 AM EDT MONDAY...
POOR FLYING CONDITIONS TO PERSIST TODAY INTO TONIGHT AS A WEDGE
OF COOL AIR KEEPS LOW CLOUDS AND FOG INCLUDING PERIODS OF LIGHT
RAIN OR DRIZZLE AROUND. ONLY EXCEPTION PERHAPS AROUND KBLF
WHERE CIGS MAY OSCILLATE UP TO HIGH END MVFR OR BETTER AT TIMES
BY THIS AFTERNOON OR EVENING. ALSO LEFT IN A MENTION OF LIGHT
RAIN AT TIMES AT KBLF/KLWB WHERE BEST CHANCE FOR STEADY RAIN
WILL PREVAIL MAINLY THIS MORNING. OTHERWISE LOOKING AT MOSTLY
IFR/MVFR WITH MOUNTAIN OBSCURATIONS IN THE LOW CIGS TODAY
WITH SOME GRADUAL IMPROVEMENT THIS AFTERNOON. WINDS EAST TO
NORTHEAST AROUND 4-10 KTS, BUT WILL BECOME MORE SOUTHEAST AT
KBLF LATER TODAY.
LOW CIGS AND VSBYS LOOK TO PERSIST INTO TONIGHT BUT MAY IMPROVE
BY EARLY TUESDAY AS THE WEDGE WEAKENS. HOWEVER STILL MOSTLY
SUB-VFR CEILINGS AT THIS POINT WITH MORE LIGHT RAIN/DRIZZLE
AND FOG RESULTING IN MVFR VSBYS OR WORSE AT TIMES LATER TONIGHT
ESPCLY ALONG/WEST OF THE BLUE RIDGE.
HIGH CONFIDENCE IN WINDS AND FLIGHT CATEGORIES, BUT LOW ON
TIMING CEILING/VSBY CATEGORY CHANGES.
EXTENDED DISCUSSION...
STATIONARY FRONT OVER THE SOUTHERN APPALACHIANS WILL BE THE
FOCUS FOR WIDESPREAD CLOUD COVER THROUGH MID WEEK WITH POTENTIAL
FOR RAIN, LOW CIGS/VSBYS. MAY SEE BRIEF IMPROVEMENT TO VFR/MVFR
LATER TUESDAY INTO WEDNESDAY BEFORE ANOTHER PERIOD OF SUB- VFR
LIKELY WITH COLD FRONT LATE WEDNESDAY INTO WEDNESDAY NIGHT.
UNLIKELY TO SEE IMPROVEMENT THURSDAY OR FRIDAY WITH CONTINUED
SUB-VFR AS THE FRONT MAY STALL NEAR OR JUST SOUTH OF THE AREA
WITH WEAK LOW PRESSURE KEEPING LOW CIGS/VSBYS WITHIN RAIN
AROUND.
RNK WATCHES/WARNINGS/ADVISORIES
VA...NONE.
NC...NONE.
WV...NONE.
SYNOPSIS...JH/RCS
NEAR TERM...JH/RCS
SHORT TERM...KK
LONG TERM...AMS
AVIATION...JH/RCS
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