551
FXUS61 KAKQ 131418
AFDAKQ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WAKEFIELD VA
1018 AM EDT THU AUG 13 2020
SYNOPSIS
A TROUGH OF LOW PRESSURE ACROSS THE AREA, WILL RESULT IN NUMEROUS
SHOWERS AND AND THUNDERSTORMS THROUGH FRIDAY. A COLD FRONT PUSHES
SOUTH INTO VIRGINIA FRIDAY NIGHT, THEN STALLS NEAR THE VIRGINIA
NORTH CAROLINA BORDER OVER THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
AS OF 1015 AM EDT THURSDAY...
LATEST SURFACE OBSERVATIONS SUGGEST A TROUGH AXIS ALONG THE I-95
CORRIDOR EXTENDING SOUTHWARD TO WEAK LOW PRESSURE OVER THE
COASTAL CAROLINAS. ALREADY PLENTY OF RAINFALL NORTH AND WEST OF
RIC THIS MORNING BEING AIDED BY BEING IN THE RIGHT REAR QUAD OF
AN UPPER JETLET. EXPECT THE FOCUS FOR PRECIP TO SHIFT TO MORE
ALONG THE TROUGH AXIS THIS AFTERNOON EXTENDING FROM THE NORTHERN
NECK AND SOUTHWARD INTO SOUTHERN VA. THIS TROUGH AXIS COMBINED
WITH INCREASED LOW LEVEL MOISTURE TRANSPORT FROM THE INCREASING
EASTERLY FLOW FROM THE LOW PRESSURE OVER THE CAROLINAS SHOULD
ALLOW FOR ANOTHER ROUND OF LOCALLY HEAVY PRECIPITATION IN AREAS
THAT ALREADY SAW HEAVY RAINFALL YESTERDAY. IN FACT, IN THE AREA
FROM THE NORTHERN NECK THROUGH RIC INTO THE FARMVILLE AREA,
FLASH FLOOD GUIDANCE IS GENERALLY 1.25"/HR OR LESS. THESE TYPES
OF RATES COULD EASILY BE OBTAINED THIS AFTERNOON GIVEN THE
PRECIPITABLE WATER VALUES OF 2.2"-2.3" FORECAST LATER TODAY
(AND OBSERVED AT MHX AT 12Z). AS SUCH, WILL MAINTAIN THE FLASH
FLOOD WATCH FOR THE ALL OF OUR VA AND MD COUNTIES TODAY,
ALTHOUGH THE FOCUS AREA WILL CERTAINLY BE ACROSS CENTRAL VA
INTO THE NORTHERN NECK.
OVERALL THE CURRENT FORECAST IS IN GOOD SHAPE WITH ONLY MINOR
TWEAKS NEEDED AT THIS TIME. HIGHS TODAY GENERALLY IN THE LOWER
80S NORTH WITH MORE CLOUD COVER TO MID-UPPER 80S SOUTH AND EAST
WITH MORE SUNSHINE.
AS OF 640 AM EDT THURSDAY...
LATEST MSAS SHOWS THE SFC TROF ACROSS THE PIEDMONT, BASICALLY ALONG
THE I-95 / I-85 CORRIDORS SW TO A WEAK SFC LOW ACROSS UPSTATE SC.
ANOTHER LOW WAS FORMING OFF THE NC COAST. MEANWHILE, A QUASI-STNRY
FRONT REMAINS TO THE NW.
ANOTHER ACTIVE DAY AHEAD AS THE RADAR IS ALRDY SHOWING CONVECTION
POPPING UP ALONG THE SFC TROF NORTH OF RIC. MODELS AGREE IN MORE
WIDESPREAD COVERAGE OF THE CONVECTION TODAY ENHANCED BY LOW PRES
MOVING NORTH ALONG THE NC COAST. PARAMETERS ARE SIMILIAR TO
YESTERDAY (PW'S UPWARDS OF 2 IN, COPIOUS AMTS OF TRPLCL MOISTURE
ALONG WITH WEAK STEERING CURRENTS) ALL LEAD TO ANTHR ROUND OF
LCLLY HEAVY DOWNPOURS. WITH WPC KEEPING THE AREA NORTH OF THE
VA/NC BORDER IN A DAY1 ERO SLIGHT RISK, WENT AHEAD AND ISSUED
ANTHR FLASH FLOOD WATCH FOR ALL AKQ VA/MD ZONES THRU MIDNITE TONITE.
KEPT POPS CAPPED AT IN THE HIGH LIKELY RANGE TODAY, BUT MAY NEED TO
INCREASE TO CAT POPS IN SOME AREAS THIS AFTRN BASED ON RADAR COVERAGE
AS THE DAYS WEARS ON. COOLER TODAY (TEMP WISE BUT REMAINING RATHER
HUMID) GIVEN MORE CLOUD AND PCPN COVERAGE. HIGHS IN THE LOW-MID 80S.
LIKELY POPS THIS EVE, TAPER OFF TO CHC POPS AFTER MIDNITE. STILL
SOME LCLLY HVY DOWNPOURS INTO THE EARLY EVE, BUT LIKE YESTERDAY, THE
RAINFALL INTENSITY SHOULD DIMINISH AFTER SUNSET. OTW, MSTLY CLDY
WITH PTCHY FOG LATE. LOWS 70-75.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
AS OF 330 AM EDT THURSDAY...
MORE OF THE SAME PROGGED FRI EXCEPT THE MODELS SHOW THE FRONTAL
BNDRY TO THE NORTH PUSHING THE SFC TROF A BIT FARTHER SOUTH. THIS
SCENARIO KEEPS ABUNDANT MOISTURE OVER THE AREA RESULTING IN ANTHR
DAY OF WIDESPREAD SHWRS/TSTMS ACROSS THE AREA. WPC HAS THE LOCAL
AREA IN A DAY2 MARGINAL ERO. WILL CARRY HIGH CHC TO LIKELY POPS
IN THE GRIDS FOR NOW. LATER SHIFTS WILL NEED TO ACCESS THE NEED
FOR YET ANTHR FLASH FLOOD WATCH FRI. OTW, MSTLY CLDY WITH HIGHS
IN THE LOW- MID 80S. CONVECTION CONTS FRI EVE THEN TAPERS OFF AFTER
MIDNITE. KEPT CHC POPS GOING THROUGH THE NITE HIGHEST IN EVE. LOWS
70-75.
AS YESTERDAYS SHIFT NOTED THAT FRONTS GENERALLY STALL OUT ACROSS THE
LOCAL AREA THIS TIME OF YEAR. APPEARS THIS TO BE TRUE COME SAT AS
THE DATA NOW SUGGESTS THE FRNTL BNDRY STALLS IVOF THE NC/VA BORDER
AS LOW PRESSURE APPRCHS THE MTS FROM THE WEST. ONCE AGAIN, EXPECT
NMRS SHWRS/TSTMS TO DVLP ACROSS THE AREA SAT GIVEN THIS SCENARIO.
LOCAL HVY RAINFALL PSBL ACROSS THE PIEDMONT WHERE WPC NOW HAS A DAY3
ERO SLIGHT RISK TO THE AKQ WRN BORDER WITH MARGINAL RISK AS FAR EAST
AS THE CHES BAY. THUS, CHC TO LIKELY POPS WILL BE MAINTAINED, HIGHEST
WEST. HIGHS SAT 80-85. CHC TO LIKELY POPS SAT EVE (HIGHEST WEST)
THEN CHC POPS AFTER MIDNITE. LOWS SAT NITE 70-75.
TOTAL QPF THROUGH 72 HRS AVERAGES 1.5 TO 3 INCHES WITH LCLLY HIGHER
AMTS POSSIBLE.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
AS OF 400 PM EDT WEDNESDAY...
UNSETTLED WEATHER CONTINUES INTO SUNDAY AND EVEN INTO MONDAY WITH
THE SURFACE TROUGH REMAINING IN PLACE. A UPPER TROUGH FINALLY DIGS
INTO THE GREAT LAKES AND NORTHEAST EARLY NEXT WEEK.
UNFORTUNATELY, IT IS UNCLEAR IF THIS TROUGH WILL ALLOW THE
FRONT/TROUGH TO ACTUALLY CLEAR THE AREA. MODEL GUIDANCE SUGGESTS
THAT IT WILL CONTINUE TO HANG UP NEARBY THROUGH MIDWEEK. AS
SUCH, WILL NEED TO MAINTAIN CHANCE POPS EACH AFTERNOON/EVENING
THROUGH THE EXTENDED. AM NOT EXPECTING AS MUCH HEAVY RAINFALL AS
THE PRECIPITABLE WATER VALUES WILL NOT BE AS HIGH. OTHERWISE,
TEMPERATURES SHOULD BE SEASONABLE WITH HIGHS IN THE MID-UPPER
80S AND LOWS IN THE MID 60S/LOWER 70S.
AVIATION /14Z THURSDAY THROUGH MONDAY/
AS OF 640 AM EDT THURSDAY...
PTCHY FOG AND STRATUS WILL QUICKLY BURN OFF OVER THE ENXT 1-2 HRS.
MVFR TO VFR CIGS (BTWN 2-4K FT) EXPECTED TODAY. NMRS SHWRS AND TSTMS
WILL DVLP ALONG A LINGERING SFC TROF. ADDITION MOISTURE FROM BOTH
LOW PRESSURE ALONG THE NC COAST AND UPSTATE SC WILL ENHANCE THE PCPN
THREAT TODAY. POPS AND CONFIDENCE RATHER HIGH THAT MOST AREAS WILL
SEE AT LEAST VCTS IF NOT TSTMS THIS AFTRN. THUS, THUNDER WAS ADDED
TO THE FORECAST IN THE 6-12 HR FORECAST PERIOD. ESE WINDS BLO 10 KTS.
SCT CONVECTION CONTINUES INTO THE EVENING HRS BUT SLOWLY DISSIPATED
AFTER MIDNITE. PTCHY STRATUS / FOG WILL LIKELY DEVELOP ONCE AGAIN.
OUTLOOK:
NMRS SHWRS/TSTMS CONT FRI THRU SAT AS DEEP MOISTURE CONTINUES TO
ALONG THE THE SFC TROF/COLD FRONT.
MARINE
AS OF 330 AM EDT THURSDAY...
FAIRLY BENIGN MARINE CONDITIONS EXPECTED TO CONTINUE THROUGH FRIDAY.
THE MAIN CONCERN BOTH TODAY AND AGAIN FRIDAY WILL BE THE THREAT FOR
SHOWERS AND THUNDERSTORMS, POTENTIALLY BRINGING LOCALLY GUSTY WINDS
OVER THE WATERS. OUTSIDE OF ANY SHOWERS/STORMS, S TO SE WINDS WILL
RANGE FROM 5 TO 15 KNOTS. STILL EXPECTING AN AREA OF SURFACE LOW
PRESSURE TO TRACK OFF THE VA COAST LATER FRIDAY THROUGH SATURDAY.
WINDS BECOME NE THIS WEEKEND AND INCREASE TO AROUND 10 TO 20 KNOTS
(HIGHEST WINDS STILL EXPECTED FOR THE NORTHERN COASTAL WATERS).
THUNDERSTORM CHANCES DECREASE OVER THE WEEKEND.
WAVES IN THE CHESAPEAKE BAY GENERALLY RANGE FROM 1 TO 2 FEET THROUGH
THE FORECAST PERIOD. SEAS BUILD FROM 1 TO 2 FEET TODAY/FRIDAY TO 3
TO 6 FEET BY THIS WEEKEND DUE TO ONSHORE FLOW. SMALL CRAFT
ADVISORIES MAY BE NEEDED FOR AT LEAST THE NORTHERN COASTAL WATERS
THIS WEEKEND DUE TO BUILDING SEAS.
AKQ WATCHES/WARNINGS/ADVISORIES
MD...FLASH FLOOD WATCH THROUGH THIS EVENING FOR MDZ021>025.
NC...NONE.
VA...FLASH FLOOD WATCH THROUGH THIS EVENING FOR VAZ048-060>062-
064>069-075>090-092-093-095>100-509>525.
MARINE...NONE.
SYNOPSIS...MPR/MRD
NEAR TERM...MPR
SHORT TERM...MPR
LONG TERM...MRD
AVIATION...MPR
MARINE...AJB
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