Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KLWX 051926
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
326 PM EDT SUN JUL 5 2015

.SYNOPSIS...
A STATIONARY FRONT WILL REMAIN TO THE SOUTH THROUGH
TONIGHT...BEFORE LIFTING NORTH AS A WARM FRONT MONDAY. A WEAK
COLD FRONT WILL APPROACH THE REGION WEDNESDAY...THEN LINGER OVER
OUR AREA THROUGH THE EXTENDED.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
CONVECTION BEGINNING TO DEVELOP LATE THIS AFTN...MAINLY WEST OF
THE BLUE RIDGE. OVERALL PICTURE...STATIONARY FRONT HOVERING ALONG
THE VA/NC BORDER WITH UPPER LVL TROUGH WITH ASSOCIATED SHORTWAVE
NOTED OVER THE OH RIVER VALLEY...PER LATEST WATER VAPOR IMAGERY.
EXPECTING THE CONVECTION TO INCREASE IN COVERAGE THRU THE
REMAINDER OF THE AFTN INTO TONIGHT AS THESE FACTORS COME INTO
PLAY.

FOR THIS EVENING AND OVERNIGHT...FLASH FLOOD WATCH HAS BEEN ISSUED
FOR HIGHLAND AND PENDLETON COUNTIES. SHORTWAVE PIVOTING MAINLY WEST
OF THE BLUE RIDGE WILL TRIGGER NUM SHOWERS AND EMBEDDED TSTMS
LASTING THRU NEAR DAYBREAK MON MORNING. WATER VAPOR IMAGERY SHOWS
STRONG SURGE OF MOISTURE FROM THE GOM REACHING THE WESTERN
AREAS...INCRSG PWATS TO AROUND 1.75 INCHES TONIGHT. THIS COMBINED
WITH A GENERALLY SLOW FLOW WILL RESULT IN HEAVY RAINFALL...WHICH
COULD LEAD TO FLASH FLOODING. HAVE ISSUED THE WATCH FOR THE AREAS
THAT ARE SHOWING THE BEST CHC FOR CONVECTION AND THE LOWEST FFG
GUIDANCE...WITH 1 HR SHOWING AROUND 1 INCH. OTHER AREAS WEST OF THE
BLUE RIDGE COULD SEE HEAVY DOWNPOURS TONIGHT...BUT WITH THE HIGHER
FFG FELT THE THREAT WAS MORE MINIMAL.

THE STATIONARY FRONT WILL EVENTUALLY BEGIN TO LIFT NORTH AS A WARM
FRONT TONIGHT...EVENTUALLY PUSHING NORTH OF THE AREA BY MONDAY
NIGHT. THINKING THE FRONT WILL PROVIDE THE NEEDED FORCING TO TRIGGER
SHOWERS EAST OF THE BLUE RIDGE AS THE SHORTWAVE ENERGY LOOKS TO STAY
MORE TO THE WEST. AS SUCH...HAVE HIGHER POPS WEST FIRST HALF OF THE
NIGHT...THEN PUSHING EAST SECOND HALF OF THE NIGHT. SOME QUESTION AS
TO HOW LONG THE PCPN LINGERS IN THE MORNING...THOUGH GENERAL IDEA
WOULD BE SOME CLEARING MON MORNING BEFORE THE NEXT ROUND OF
CONVECTION THEN MON AFTN AS THE WARM FRONT LIFTS THROUGH AND THE
NEXT SHORTWAVE MOVES THROUGH. THIS SHORTWAVE LOOKS TO BE FURTHER
EAST...SO THE THREAT OF OF TSTMS ENCOMPASSES THE ENTIRE AREA MON
AFTN/EVENING. SVR THREAT LOOKS TO BE MORE MARGINAL AS INSTABILITY IS
CURRENTLY LIMITED. HOWEVER...IF WE CAN SCATTER OUT MORE IN THE
MORNING...COULD SEE BETTER INSTABILITY. SHEAR IS STRONGER ON
MONDAY...THOUGH STILL NOT COMPLETELY SELLING ON SVR. BACKING WINDS
WITH THE WARM FRONT COULD HINT AT PSBL TOR THREAT...BUT STILL ON THE
LOW END. WILL HIGHLIGHT THAT HEAVY RAIN WILL BE A THREAT AGAIN MON
AFTN AS PWATS STAY WELL ABV NORMAL...ESP OVER EASTERN AREAS. PCPN
WILL SLOWLY TAPER OFF MON NIGHT AS THE FRONT CLEARS TO THE NORTH.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
MID/UPPER LEVEL LOW STARTS PULLING AWAY FROM OUR AREA TUESDAY
MORNING...AS IT IS SHEARED APART...AND IS INGESTED INTO MAIN BELT OF
WESTERLIES ASSOCIATED WITH THE NORTHERN STREAM. MOST OF TUE APPEARS
TO BE RELATIVELY DRY UNDER SUBSIDENCE FROM DEPARTING LOW AND LITTLE
IN THE WAY OF LIFTING MECHANISMS IN THE AREA. ALTHOUGH...CANNOT
ENTIRELY RULE OUT AN ISOLATED AFTN TSTM WITH SFC HEATING COMBINED
WITH MESOSCALE FEATURES (SUBTLE BOUNDARIES...TERRAIN)...THOUGH ATTM
CHCS APPEAR VERY LOW. GUIDANCE HAS BEEN TRENDING HIGHER WITH
TEMPS...LIKELY DUE TO MORE INSOLATION...SO NUDGED THEM UP A BIT WITH
TEMPS IN THE U80S ACROSS THE REGION. LIGHT SWLY WINDS USHER IN SOME
DRIER AIR...WHICH KEEP HEAT INDICES IN L90S.

WEAK COLD FRONT APPROACHES THE REGION WED. INCREASED POPS SOMEWHAT
IN THE AFTN...AS QPF SIGNAL IS BECOMING MORE CONSISTENT. DEEP LAYER
FLOW REMAINS RATHER WEAK THROUGH THE PERIOD AND INSTABILITY IS ALSO
RATHER LIMITED...SO EXPECTING MOST ACTIVITY TO BE UNORGANIZED. TEMPS
INCREASE SLIGHTLY UNDER CONTINUED AIRMASS MODIFICATION...BUT SHOULD
ONLY BE A FEW DEGREES ABOVE CLIMO NORMS.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
COLD FRONT MOVES OVER THE CWA
WED NIGHT AND LINGERS THROUGH THE WEEKEND. INSTABILITY FROM THIS
SYSTEM WILL ALLOW FOR THE RISK OF ISOLATED/SCATTERED SHOWERS AND/OR
TSTMS EACH DAY. TEMPS WILL BE NEAR NORMAL FOR THIS TIME OF THE YEAR.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
GENERALLY VFR CONDITIONS THRU THIS EVENING. LOW CONFIDENCE OF PCPN
IMPACTING TERMINALS OTHER THAN KCHO THRU THE EVENING. INCRSG
CONFIDENCE FOR THE SECOND HALF OF THE NIGHT FOR ALL SITES WITH
SHOWERS...PSBL THUNDER...AND SUB-VFR CONDITIONS. HEAVY DOWNPOURS
WILL PRODUCE IFR CIGS AND VIS.

VFR CONDITIONS RETURN MON MORNING AS THE PCPN TAPERS OFF. ANOTHER
ROUND OF SHOWERS AND TSTMS LIKELY MON AFTN WHICH ONCE AGAIN WILL
RESULT IN SUB-VFR CONDITIONS.

WINDS GENERALLY 10 KTS OR LESS FROM THE SE THRU MON. ANY TSTM
COULD PRODUCE SPORADIC GUSTS UP TO 40 KTS.

EXPECT VFR CONDS TUE...AS MID/UPPER LOW DEPARTS OUR AREA AND WE ARE
IN REGION OF SUBSIDENCE. ATTM VERY LOW CHC FOR AFTN TSTM TUE WITH
LOCALIZED SUB-VFR CONDS IF THEY OCCUR. BETTER CHCS FOR
SHWRS/TSTMS...AND LOCALIZED SUB-VFR CONDS ON WED AS COLD FRONT
APPROACHES THE REGION.

VFR CONDITIONS EXPECTED FOR
WED NIGHT AND THURS. SUB-VFR CONDITIONS PSBL DUE TO SHOWERS AND/OR
TSTMS.

&&

.MARINE...
SUB-SCA CONDITIONS ON ALL WATERS THRU MON MORNING. HAVE ISSUED A
SCA FOR THE LOWER TIDAL POTOMAC AND CHESAPEAKE BAY MON AFTN AND
EVENING FOR INCRG SLY FLOW RESULTING IN GUSTS UP TO 20 KTS. SUB-
SCA CONDITIONS RETURN FOR ALL WATERS MON NIGHT.

WINDS EXPECTED TO SUBSIDE TUE MORNING AS PRESSURE GRADIENT RELAXES
AND REGION IS UNDER SUBSIDENCE FROM DEPARTING LOW. WINDS EXPECTED TO
REMAIN BELOW SCA CRITERIA THROUGH WED...THOUGH MARINERS SHOULD WATCH
OUT FOR TSTM CHCS WED AFTN.

SUB-SCA CONDITIONS EXPECTED FOR WED NIGHT AND THURS. PSBL SHOWERS
AND TSTMS ACROSS THE WATERS DURING THIS PERIOD.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR VAZ503-504.
WV...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR WVZ505-506.
MARINE...SMALL CRAFT ADVISORY FROM 2 PM MONDAY TO 2 AM EDT TUESDAY FOR
     ANZ534-537-543.

&&

$$
SYNOPSIS...SEARS/MSE
NEAR TERM...SEARS
SHORT TERM...MSE
LONG TERM...IMR
AVIATION...SEARS/IMR/MSE
MARINE...SEARS/IMR/MSE


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.