300
FXUS61 KRNK 042256
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
656 PM EDT SAT JUL 4 2020
SYNOPSIS
A WEAK COLD FRONT WILL MOVE SOUTH THROUGH THE MID-ATLANTIC REGION
TONIGHT INTO SUNDAY AND STALL ACROSS THE VIRGINIA PIEDMONT. THIS
WILL BRING A CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS THROUGH
EARLY NEXT WEEK.
NEAR TERM /THROUGH SUNDAY/
AS OF 645 PM EDT SATURDAY...
CONVECTION IS ISOLATED ACROSS THE FORECAST AREA LATE THIS
AFTERNOON, MOST FIRING UP ALONG OUTFLOW BOUNDARIES AND POCKETS
OF MOISTURE CONVERGENCE AND HIGHER CAPES. SHOULD SEE A GRADUAL
WEAKENING TREND THIS EVENING, BUT CAP WEAKENS, SO NOT SEEING A
COMPLETELY RAINFREE RADAR INTO LATE TONIGHT, BUT MOST WILL BE
DRY/MUGGY.
PREVIOUS AFTERNOON DISCUSSION...
A COLD FRONT HAS STALLED JUST NORTH OF DC AND ALONG THE NE VA
COAST THIS AFTERNOON. SINCE THIS SYSTEM HAS NO JET SUPPORT AND
LACKING STRONG CONVECTION, IT WILL HAVE A TOUGH TIME MOVING
SOUTH ESPECIALLY INTO 90F TEMPERATURES TODAY. AS WE COOL
OVERNIGHT, THIS FRONT IS EXPECTED TO ADVANCE SOUTH AND WEST,
STALLING IN THE VICINITY OF A LINE FROM CHARLOTTESVILLE (KCHO)
TO DANVILLE (KDAN) BY SUNRISE.
MORNING SOUNDINGS SHOWING A FAIRLY STRONG CAP AROUND 9-11 KFT
ACROSS THE MOUNTAINS AND 11-13 KFT OVER THE PIEDMONT. JUST LIKE
YESTERDAY, DIURNAL HEATING AND AMPLE MOISTURE UNDER THIS HIGH
INVERSION WILL ALLOW FOR CUMULUS CLOUDS TO FORM THROUGH THE
AFTERNOON AND EARLY EVENING. INVERSION MAY BE LOW ENOUGH TO
DETER THUNDERSTORMS THIS AFTERNOON, BUT WITH A HIGHER INVERSION
THAN YESTERDAY, WE MAY SEE MORE AREAL COVERAGE OF SHOWERS. IF AN
AREA HAS A WEAKENING INVERSION, A STRONG TO SEVERE PULSE STORM
IS NOT OUT OF THE QUESTION. THE CENTRAL PIEDMONT OF VIRGINIA
(LYNCHBURG AREA) WOULD BE THE AREA WITH THE WEAKEST INVERSION AS
IT IS CLOSER TO THE FRONT. WITH DRY AIR ALOFT, DAMAGING WIND
GUSTS WILL BE A THREAT. HOWEVER, THE THREAT FOR STRONG TO SEVERE
STORMS IS VERY LOW. SHOWERS WILL WANE THIS EVENING, BUT COULD
LINGER LONGER INTO THE EVENING WITH A VERY WARM ENVIRONMENT AND
THE COLD FRONT EDGES CLOSER TO THE AREA.
SUNDAY COVERAGE OF STORMS WILL DEFINITELY BE GREATER WITH THE
COLD FRONT IN THE VICINITY. THE CHANCES FOR THUNDERSTORMS WILL
ALSO BE HIGHER WITH A WEAKER CAPPING INVERSION AND CONTINUED
WARM AND HUMID CONDITIONS. THE CHANCES FOR A STRONG TO SEVERE
PULSE STORMS WILL ALSO BE HIGHER WITH DAMAGING WIND GUSTS BEING
THE PRIMARY THREAT AND LARGE HAIL A SECONDARY THREAT. THE FRONT
IS EXPECTED TO STALL IN OR NEAR THE AREA, THEREFORE STORMS COULD
LINGER THROUGH THE NIGHT.
HIGHS TODAY WILL RANGE IN THE MID TO UPPER 80S ACROSS THE
MOUNTAINS TO MID 90S EAST OF THE BLUE RIDGE. SLIGHTLY LOWER
HEIGHTS TOMORROW WILL RESULT IN COOLER TEMPERATURES, BUT STILL
LOOKING AT A WARM AND HUMID DAY WITH HIGHS IN THE 80S WEST OF
THE BLUE RIDGE TO LOW 90S EAST. SUNDAY'S DEWPOINTS WILL RANGE
FROM THE MID 60S TO LOWER 70S.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/
AS OF 200 PM EDT SATURDAY...
SOUTHERLY WINDFLOW WILL BECOME BETTER ESTABLISHED ON MONDAY,
ALLOWING DEEPER MOISTURE TO FLOW INTO THE MID-ATLANTIC AND
CENTRAL APPALACHIANS REGION. THIS WILL SUPPORT GRADUALLY
INCREASING COVERAGE OF AFTERNOON SHOWERS AND THUNDERSTORMS EACH
DAY AS THE WORKWEEK PROGRESSES. COVERAGE IS EXPECTED TO REMAIN
WIDELY SCATTERED ON MONDAY AS THE MID-ATLANTIC REMAINS UNDER THE
INFLUENCE OF WEAK RIDGING EXTENDING FROM ACROSS THE SOUTHEAST
STATES. CONVECTION IS EXPECTED TO BE OF THE HIT-AND-MISS
VARIETY, STARTING OFF ALONG THE RIDGELINES DURING LATE MORNING,
BEFORE EXPANDING EAST ACROSS THE PIEDMONT BY MID AFTERNOON.
GIVEN THE INSTABILITY DERIVED FROM STRONG AFTERNOON HEATING,
THERE IS POTENTIAL FOR A FEW STORMS TO BECOME SEVERE, PACKING
LOCALLY DAMAGING WINDS, AS WELL AS HEAVY DOWNPOURS.
THIS PATTERN WILL REPEAT ON TUESDAY, THOUGH WITH GREATER
COVERAGE OF RAINFALL EXPECTED MORE SO SOUTH OF HIGHWAY 460 AS A
BROAD BUT WEAK UPPER LEVEL TROUGH DRIFTS EASTWARD ACROSS THE
LOWER MISSISSIPPI VALLEY.
WEATHER FORECAST MODELS ARE STILL TRYING TO RESOLVE HOW MUCH
IMPACT THE UPPER LEVEL TROUGH/DEVELOPING ASSOCIATED SURFACE LOW
PRESSURE WILL HAVE ON OUR WEATHER PATTERN FROM MID-WEEK ONWARD,
WHICH IS TYPICAL OF WEAK SYSTEMS THAT DRIFT SLOWLY. WHILE LARGE
AREAS OF HEAVY RAIN ARE NOT EXPECTED, CAN STILL SEE LOCALIZED
AREAS OF HEAVY RAIN DEVELOPING GIVEN PRECIPITABLE WATER VALUES
WILL BE AROUND 2 INCHES - AN INDICATOR OF A VERY MOIST
ATMOSPHERE - IN A PATTERN THAT CAN SUPPORT STORMS TRAINING OVER
THE SAME LOCATIONS. AS FOR TEMPERATURES WEDNESDAY, UNDERCUT
MODEL GUIDANCE FOR AFTERNOON HIGHS BY 2-3 DEGREES BASED ON
WIDESPREAD CLOUD COVER AND SOUTHEASTERLY WINDFLOW OFF THE
ATLANTIC.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
AS OF 200 PM EDT SATURDAY...
AN UPPER LEVEL TROUGH AND ASSOCIATED SURFACE LOW PRESSURE
DEVELOPING ALONG THE COASTAL CAROLINAS WILL MAINTAIN DEEP
MOISTURE ACROSS THE MID-ATLANTIC ON THURSDAY AND FRIDAY,
PROMOTING SCATTERED SHOWERS AND THUNDERSTORMS EACH DAY. SOME OF
THIS ACTIVITY MAY PRODUCE LOCALLY HEAVY RAIN. WITH THE SURFACE
LOW LIFTING GRADUALLY NORTHWARD, WINDS WILL SHIFT MORE EAST TO
NORTHEASTERLY, MAINTAINING A FLOW OF COOL ATLANTIC AIR THAT WILL
KEEP AFTERNOON TEMPERATURES BELOW NORMAL FOR EARLY JULY, THOUGH
AT THIS TIME IT'S STILL HARD TO PINPOINT BY HOW MUCH.
BY SATURDAY, WINDS ACROSS OUR AREA WILL SHIFT WEST-
NORTHWESTERLY AS THE LOW EXITS TOWARD NEW ENGLAND. THE RETURN OF
DOWNSLOPING WINDS WILL RESULT IN WARMER AFTERNOON TEMPERATURES
AND A DECREASE IN RAINFALL COVERAGE, THOUGH A FEW SHOWERS AND
THUNDERSTORMS ARE STILL POSSIBLE IN THE RESIDUAL MOISTURE.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
AS OF 650 PM EDT SATURDAY...
CONVECTION AT THE START OF THE TAF PERIOD WILL BE ISOLATED AND
MAY SEE SOME SHOWERS IN VICINITY OF LYH/PERHAPS LWB. OVERALL
WILL AMEND AS NECESSARY AS COVERAGE IS WIDELY SCATTERED.
OTHERWISE, VFR THROUGH THE PERIOD, THOUGH SOME FOG AT LWB
POSSIBLE LATE TONIGHT.
A COLD FRONT ENTERS THE PIEDMONT TONIGHT AND STALLS. THIS WILL
BE THE FOCUS FOR MORE SHOWERS AND THUNDERSTORMS ON SUNDAY
AFTERNOON, BUT AGAIN COVERAGE SEEMS WIDELY SCATTERED SO NO
PINPOINTING TIMING OF WHEN/IF AIRPORTS GET IMPACTED.
EXTENDED AVIATION DISCUSSION...
THE THREAT FOR SCATTERED AFTERNOON AND EVENING THUNDERSTORMS
CONTINUES INTO NEXT WEEK AS MOISTURE AND INSTABILITY BECOME
MORE WIDESPREAD.
RNK WATCHES/WARNINGS/ADVISORIES
VA...NONE.
NC...NONE.
WV...NONE.
SYNOPSIS...RCS
NEAR TERM...RCS/WP
SHORT TERM...NF
LONG TERM...NF/VFJ
AVIATION...RCS/WP
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