Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 260704
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
304 AM EDT TUE MAY 26 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OFFSHORE THIS WEEK. A SOUTHERLY FLOW
WILL BRING WARM HUMID CONDITIONS TO THE MID ATLANTIC THROUGH
SATURDAY. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE EACH
AFTERNOON AND EVENING. A COLD FRONT WILL APPROACH THE AREA EARLY
NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AN UPPER-LEVEL RIDGE WILL SLIDE OFF THE MID-ATLANTIC COAST TODAY
WHILE HIGH PRESSURE REMAINS OVER THE ATLANTIC OCEAN. THE SURFACE
HIGH AND UPPER-LEVEL RIDGE WILL REMAIN OVER THE ATLANTIC OCEAN
TONIGHT. A SOUTHWEST FLOW FROM THE SURFACE THROUGH THE UPPER-
LEVELS OF THE ATMOSPHERE WILL USHER IN MORE MOISTURE DURING THIS
TIME. MAX TEMPS TODAY ARE FORECAST TO RANGE FROM THE 70S IN THE
MOUNTAINS...TO THE LOWER AND MIDDLE 80S WEST OF THE BLUE RIDGE
MOUNTAINS...TO THE MID AND UPPER 80S EAST OF THE BLUE RIDGE
MOUNTAINS. TEMPS HAVE BEEN TWEAKED DOWN A COUPLE DEGREES DUE TO A
BKN/OVC DECK OF HIGH AND MID-LEVEL CLOUDS THAT WILL OVERSPREAD THE
AREA EARLY THIS MORNING AND REMAIN IN PLACE THROUGH THIS
AFTERNOON.

THE INCREASED MOISTURE WILL LEAD TO A FEW SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND EVENING. COVERAGE SHOULD REMAIN
ISOLATED TO SCATTERED FOR MOST AREAS SINCE THERE WILL NOT BE A
STRONG LIFTING MECHANISM. HOWEVER...THE HEAT AND HUMIDITY ALONG
WITH LOWER HEIGHTS BEHIND THE DEPARTING RIDGE SHOULD BE ENOUGH TO
COMBINE WITH WEAK SHORTWAVE ENERGY FOR CONVECTION TO DEVELOP. THE
BEST CHANCE FOR CONVECTION WILL BE NORTH AND WEST OF INTERSTATE 95
AND FOR LOCATIONS WEST OF THE BLUE RIDGE MOUNTAINS. LOWER HEIGHTS
AND MORE SHORTWAVE ENERGY WILL BE OVER THESE AREAS. LATEST
GUIDANCE ALSO SHOWS A THETA E RIDGE SETTING UP FOR LOCATIONS JUST
NORTH AND WEST OF INTERSTATE 95. SHEAR PROFILES WILL REMAIN
RELATIVELY WEAK AND INSTABILITY SHOULD BE MARGINAL DUE TO HIGH AND
MID-LEVEL CLOUDS. THEREFORE...THE THREAT FOR SEVERE WEATHER IS LOW
THIS AFTERNOON AND EVENING. HOWEVER...ANY THUNDERSTORMS THAT DO
DEVELOP MAY PRODUCE LOCALLY HEAVY RAIN AND GUSTY WINDS.

A SOUTHWEST FLOW WILL CONTINUE TONIGHT...CAUSING WARM AND HUMID
CONDITIONS. A FEW SHOWERS ARE POSSIBLE DUE TO THE COPIOUS AMOUNTS
OF MOISTURE...ESPECIALLY NEAR THE ALLEGHENY HIGHLANDS WHERE
MOISTURE WILL BE DEEPEST 500MB HEIGHTS WILL BE LOWEST FURTHER AWAY
FROM THE UPPER-LEVEL RIDGE.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
A SIMILAR SYNOPTIC SETUP IS EXPECTED WEDNESDAY THROUGH WEDNESDAY
NIGHT WITH AN UPPER-LEVEL RIDGE AND SURFACE HIGH OVER THE ATLANTIC
OCEAN. IN FACT...A COLD FRONT IS EXPECTED TO SLIDE THROUGH THE
GREAT LAKES DURING THIS TIME. THIS SHOULD WEAKEN THE RIDGE A BIT
MORE...ALLOWING FOR LOWER HEIGHTS OVER OUR AREA.

WARM AND HUMID CONDITIONS WILL CONTINUE THANKS TO A SOUTHWEST FLOW
AROUND THE SURFACE HIGH OVER THE ATLANTIC. A BKN/OVC DECK OF HIGH
AND MID-LEVEL CLOUDS WILL CONTINUE TO MOVE THROUGH THE AREA ALONG
WITH MORE SHORTWAVE ENERGY IN THE SOUTHWEST FLOW ALOFT. THE WARM
AND HUMID CONDITIONS ALONG WITH THE SHORTWAVE ENERGY WILL LEAD TO
MORE SHOWERS AND THUNDERSTORMS. COVERAGE MAY BE MORE WIDESPREAD
COMPARED TO TUESDAY DUE TO LOWER HEIGHTS. SHEAR PROFILES MAY BE A
BIT STRONGER...BUT STILL RELATIVELY WEAK. HOWEVER...LATEST
GUIDANCE CONTINUES TO SUGGEST THAT THERE WILL BE A MAX IN
INSTABILITY NEAR AND EAST OF THE BLUE RIDGE MOUNTAINS...ESPECIALLY
NEAR THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS INTO NORTH-
CENTRAL MARYLAND. THIS IS LIKELY DUE TO DIFFERENTIAL HEATING. MID
AND HIGH-LEVEL CLOUDS ARE FORECAST TO BE THICKER TO THE WEST WITH
MORE BREAKS OF SUNSHINE FURTHER EAST ACROSS THESE AREAS. SHOULD
THIS DEVELOP...THEN INSTABILITY HAS THE POTENTIAL TO BE HIGH WHICH
WOULD INCREASE THE CHANCE FOR SEVERE THUNDERSTORMS. AS OF
NOW...CERTAINTY IS TOO LOW TO MENTION IN THE FORECAST BUT THIS
WILL HAVE TO BE MONITORED.

MOST CONVECTION SHOULD DISSIPATE OVERNIGHT WEDNESDAY...BUT IT
WILL REMAIN WARM AND QUITE HUMID THANKS TO THE SOUTHWESTERLY FLOW.


&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
SFC LOW IN SE CANADA WILL DRAG AN ASSOCIATED COLD FRONT THROUGH
THE NORTHEAST ON THURSDAY. THE FRONT BECOMES NEARLY STATIONARY
LATE THURS INTO FRI MORNING...EVENTUALLY DISSIPATING BY SAT
MORNING AS EMBEDDED SHORTWAVE TROUGH RIDING THE FLOW ALOFT IS
PUSHED OFF TO THE NORTH AND EAST AS THE RIDGE TAKES CONTROL YET
AGAIN OF THE EASTERN US. MAINTAINING UPPER END CHC POPS THRU THESE
TWO DAYS TO ACCOUNT FOR TSTM POTENTIAL...SFC HIGH SITTING OFFSHORE
WILL KEEP WARM AIR AND MOISTURE ADVECTION OVER THE
REGION...RESULTING IN DECENT INSTABILITY VALUES. SHEAR ON THE
LIGHTER SIDE...AND AS SUCH THINK ANY SVR THREAT WILL BE MINIMAL.
WHILE CONFIDENCE EXISTS THAT TSTMS WILL DEVELOP...ESP DURING THE
AFTN/EVENING HOURS...TRYING TO PINPOINT LOCATION AND TIMING STILL
TOO EARLY SO WILL KEEP SCT WORDING FOR NOW. HAVE ONLY ISO SHOWERS
IN THURS/FRI NIGHT WITH THE LOSS OF DIURNAL HEATING.

THE NEXT COLD FRONT APPROACHES SAT...NEARING THE WESTERN AREAS BY
LATE SAT. COULD SEE SHOWERS/TSTMS POP UP AHEAD OF THE FRONT IN THE
WARM/MOIST ATMO...BUT NOT EXPECTING ANYTHING REALLY ORGANIZED AT
THIS TIME. THE FRONT BECOMES NEARLY STATIONARY AS WELL NEAR THE
MASON-DIXON WITH THE LOSS YET AGAIN OF ANY UPPER LVL FLOW. MODEL
DIVERGENCE IN THE 00Z SOLUTIONS WITH THE HANDLING OF THIS
FRONT...WITH THE GFS DEVELOPING A MORE DEFINED SFC LOW ALONG THE
FRONT AND TRACKING IT INTO THE OH RIVER VALLEY. AS SUCH WILL KEEP
CHC POPS IN...THOUGH WITH THE PAST COUPLE OF RUNS HINTING AT THE
FRONT STALLING IN THE VICINITY...IT IS LOOKING MORE LIKELY WE WILL
SEE PCPN OCCURRING SUN-MON WITH THIS BOUNDARY.

TEMPS ABV NORMAL THRU THE EXTENDED PERIOD...WITH 850MB TEMPS
HOVERING BETWEEN 10 AND 15 DEGREES CELSIUS. DESPITE THE WARMER
TEMPS..EXPECTING ONLY ISOLATED SPOTS TO REACH 90 DUE TO ON GOING
PCPN/CLOUD COVER. LOWS WILL REMAIN MILD IN THE 60S AND 70S.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
VFR CONDITIONS ARE EXPECTED MOST OF THE TIME THROUGH THIS EVENING.
A COUPLE THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND EVENING.
COVERAGE WILL REMAIN SCATTERED DUE TO A LACK OF A STRONG LIFTING
MECHANISM SO MUCH OF THE TIME WILL BE DRY. HOWEVER...BRIEF SUBVFR
CONDITIONS ARE POSSIBLE ALONG WITH LOCALLY GUSTY WINDS IN ANY
THUNDERSTORM THAT MOVES OVER A TERMINAL.

PATCHY FOG IS POSSIBLE LATE TONIGHT INTO WEDNESDAY MORNING. MORE
SHOWERS AND THUNDERSTORMS ARE POSSIBLE LATER WEDNESDAY INTO
WEDNESDAY EVENING. COVERAGE MAY BE MORE WIDESPREAD DUE TO LOWER
HEIGHTS BEHIND A DEPARTING RIDGE OVER THE ATLANTIC OCEAN. PATCHY
FOG IS POSSIBLE AGAIN LATE WEDNESDAY NIGHT.

VARYING CONDITIONS THROUGH THIS WEEKEND...WITH PERIODS
OF MVFR OR LOWER PSBL WITH ANY SHOWER/TSTM. ANY TSTM COULD PRODUCE
GUSTY WINDS...WITH WINDS GENERALLY 10 KTS OR LESS OUTSIDE OF PCPN
THE REMAINDER OF THE EXTENDED.

&&

.MARINE...
HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC OCEAN THROUGH
WEDNESDAY NIGHT. A SOUTH TO SOUTHWEST FLOW IS EXPECTED DURING THIS
TIME. A SMALL CRAFT ADVISORY REMAINS IN EFFECT THROUGH THIS
EVENING FOR THE MARYLAND CHESAPEAKE BAY SOUTH OF POOLES ISLAND AND
THE LOWER TIDAL POTOMAC RIVER. A SMALL CRAFT ADVISORY IS IN EFFECT
LATE TONIGHT THROUGH WEDNESDAY FOR THE MARYLAND CHESAPEAKE BAY
SOUTH OF SANDY POINT AND THE LOWER TIDAL POTOMAC RIVER...AND A
SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS
WEDNESDAY NIGHT. WILL HAVE TO WATCH THE GRADIENT WIND TODAY FOR
THE UPPER TIDAL POTOMAC AND NORTHERN CHESAPEAKE BAY. SOUTHWEST
WINDS WILL APPROACH SCA CRITERIA...BUT THE FORECAST HAS WINDS
CAPPED AT 15 KNOTS FOR NOW DUE TO A WEAKER PRESSURE GRADIENT
COMPARED TO MONDAY.

THUNDERSTORMS ARE POSSIBLE...ESPECIALLY THIS AFTERNOON AND
EVENING...AND AGAIN WEDNESDAY AFTERNOON AND EVENING. COVERAGE
TODAY SHOULD BE ISOLATED TO SCATTERED. THERE MAY BE A BETTER
CHANCE FOR THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING DUE TO
LOWER HEIGHTS BEHIND A DEPARTING UPPER-LEVEL RIDGE. ANY
THUNDERSTORMS THAT DO DEVELOP MAY PRODUCE GUSTY WINDS AND LOCALLY
HEAVY RAINFALL THAT CAN BRIEFLY REDUCE VSBYS BELOW ONE MILE AT
TIMES.

EXPECTING SUB-SCA CONDITIONS THURS AND FRI FOR MOST OF THE ZONES
WITH WEAKENING PRESSURE GRADIENT. MID CHESAPEAKE BAY COULD SEE
GUSTS TO 20 KTS EACH AFTN THRU FRI DUE TO SOUTHERN CHANNELING.

A TIGHTENING PRESSURE GRADIENT YET AGAIN WITH THE NEXT COLD FRONT ON
SAT WILL INCREASE WINDS...WITH PSBL SCA CONDITIONS ON ALL WATERS SAT-
SAT NIGHT.

OUTSIDE OF THE SYNOPTIC FLOW...EACH DAY WILL BRING A CHC FOR SHOWERS
AND TSTMS...WHICH COULD ALSO RESULT IN GUSTY WINDS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ531-538-
     539.
     SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR ANZ532>534-
     537-540>543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...SEARS
AVIATION...BJL/SEARS
MARINE...BJL/SEARS


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