Area Forecast Discussion
Issued by NWS Sterling, VA

Home | 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 060104
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
904 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/...
AN UPPER LEVEL LOW IS LOCATED OVER KY WITH AN EMBEDDED SHORTWAVE
TROUGH ENTERING WV. A STATIONARY FRONT IS DRAPED ACROSS THE NC/VA
BORDER THIS EVENING. SHOWERS AND THUNDERSTORMS HAVE BEEN ONGOING
ACROSS SOUTHERN VA THIS AFTERNOON AND EARLY EVENING IN VICINITY OF
THE FRONT AND UPPER LOW. THE STEERING FLOW IS WEAK AND ORIENTED
S-SWTO N-NE AND ACTIVITY IS SLOW MOVING. THE MID- ATLANTIC IS
STARTING TO SEE ACTIVITY MOVE INTO THE CENTRAL FOOTHILLS AND
PIEDMONT THIS EVENING. VERY HEAVY RAIN IS EXPECTED OVERNIGHT AS
PWATS RANGE FROM 1.5-2.0 ACROSS VA. EXPECT THIS TREND TO CONTINUE
AS THE SHORTWAVE TROUGH APPORACHES TONIGHT. HEAVY SHOWERS WITH
ISOLATED THUNDERSTORMS WILL SPREAD THE REGION BY MONDAY MORNING.
AT THIS TIME...FLASH FLOOD WATCH CONTINUES ACROSS HIGHLAND AND
PENDLETON COUNTIES WHERE FFG IS LOW. FURTHER EAST AND NEAR THE
CENTRAL FOOTHILLS...LOCALIZED FLOODING IS POSSIBLE AS MULTIPLE
ROUNDS OF SHOWERS BEGIN TO MOVE INTO THE AREA. COVERAGE WILL BE
WEAK AND THEREFORE NO FF WATCH EXTENSION WAS DONE. AROUND 1 INCH
IS EXPECTED IN HEAVY SHOWERS WITH THE POTENTIAL OF 2 INCHES IN
AREAS THAT SEE TRAINING THIS EVENING.

PREVIOUS DISCUSSION...
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 /01Z MONDAY THROUGH FRIDAY/...
VFR/MVFR CONDITIONS EXPECTED THIS EVENING BEFORE BECOMING MVFR/IFR
BY MONDAY MORNING. SHRA WILL MOVE INTO THE TERMINALS FROM S TO N
IMPACTING CHO ALREADY. VSBYS MAY DROP TO IFR/SUB-IFR IN SHRA/TSRA BUT
MAIN IMPACT WILL BE LOW CIGS INTO MONDAY MORNING. ISOLATED TS
EXPECTED TONIGHT AND CONFIDENCE IS LOW TO PUT IN TAFS.

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 UNTIL 6 AM EDT MONDAY FOR VAZ503-504.
WV...FLASH FLOOD WATCH UNTIL 6 AM EDT MONDAY 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/HAS
SHORT TERM...MSE
LONG TERM...IMR
AVIATION...SEARS/HAS/IMR/MSE
MARINE...SEARS/HAS/IMR/MSE


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