Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 241909
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
309 PM EDT WED SEP 24 2014

.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL DEVELOP OFF THE DELMARVA PENINSULA
TONIGHT...AND MOVE ACROSS THE WATERS SOUTH OF NEW ENGLAND ON
THURSDAY. HIGH PRESSURE WILL FORM OVER THE GREAT LAKES REGION
THURSDAY NIGHT...AND REMAIN ACROSS THE NORTHEAST UNITED STATES
THROUGH THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
19Z KNHK AND KEZF OBS FINALLY SHOWING LIGHT RAIN IN THE CWA. THE
ANTICYCLONIC FLOW AROUND THE INVERTED RIDGE HAS HELD TOUGH OVER
THE AREA SO FAR TODAY. THE 12Z ECMWF CAME IN WITH MUCH LESS QPF
THAN 00Z RUN...MAKING THE 12Z GFS AND NAM THE WETTEST MODEL SOLNS.
STILL ANTICPATING ABOUT AN INCH TO 1.5 INCHES OF RAINFALL TONIGHT
ALONG AND EAST OF I-95 ONCE THE INVERTED RIDGE BREAKS DOWN EARLY
THIS EVENING. STILL TOO MUCH UNCERTAINTY WITH THE DIFFERING MODEL
SOLUTIONS TO CONSIDER TAKING DOWN FLOOD WATCH...BUT WILL PASS ON
TO THE EVENING SHIFT TO MAKE THAT FINAL DECISION. STILL A VERY
STRONG LLVL JET CENTERED AT 950 MB TO CONTEND WITH OFF THE GULF
STREAM CONVERGING INTO THE CWA.

MIN TEMPS TONIGHT WILL BE IN THE LOWER 60S IN URBAN AREAS AND IN
THE MID TO UPPER 50S ELSEWHERE IN A WELL MIXED ENVIROMENT AS A NE 35KT
LLVL JET PER THE 12Z GFS MAKES IT WAY THROUGH THE CHESAPEAKE BAY
REGION OVERNIGHT.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
RAIN WILL CONTINUE TO LINGER INTO THE MORNING HOURS ACROSS MUCH OF
THE AREA BEFORE PULLING OFF TO THE NORTHEAST IN THE EARLY
AFTERNOON. WINDS SHOULD CONTINUE TO BE GUSTY FROM THE NE AGAIN ON
THURSDAY AS THE LOW DEEPENS AS IT MOVES TOWARDS CAPE COD AND HIGH
PRESSURE STARTS TO BUILD OVER THE GREAT LAKES. HIGHS ON THURSDAY
WILL BE IN THE UPPER 60S BUT WITH A GUSTY NE WIND WILL MAKE IT
FEEL COOLER. THURSDAY NIGHT AND FRIDAY WILL BE FAIR WITH NEAR
NORMAL TO SLIGHTLY ABOVE NORMAL TEMPS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
HIGH PRESSURE WILL DOMINATE THE REGION FRIDAY NIGHT THROUGH SUNDAY
MORNING...PROVIDING PLENTY OF SUNSHINE THAT WILL LEAD TO WARM
AFTERNOONS AND COMFORTABLE NIGHTS. HIGHS SHOULD REACH 80 IF NOT A
FEW DEGREES ABOVE DURING EACH AFTERNOON.

A WEAK COLD FRONT COULD DROP IN ACROSS THE REGION LATE SUNDAY INTO
SUNDAY NIGHT. LITTLE OR INSUFFICIENT MOISTURE COULD LEAD TO NO
PRECIPITATION AHEAD OF AND ALONG THE FRONT.

A REINFORCING AREA OF HIGH PRESSURE WILL BUILD BEHIND THE FRONT
MONDAY THROUGH TUESDAY. THIS WILL LEAD TO HIGHS REACHING THE UPPER
70S TO NEAR 80. SOME UPPER LEVEL ENERGY MONDAY NIGHT INTO TUESDAY
COULD TRY TO WORK SOUTHEASTWARD ACROSS THE REGION. THERE MAY BE JUST
ENOUGH UPPER ENERGY TO SUPPORT A COUPLE OF RAIN SHOWERS IN A FEW
AREAS...MAINLY IN THE UPSLOPE PORTIONS OF OUR REGION. WE HAVE SLIGHT
CHANCE OR CHANCE POPS TO ACCOUNT FOR THIS. SURFACE WINDS COULD BE
EAST TO SOUTHEAST WITH HIGH PRESSURE OVER NEW ENGLAND.
&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
CLOUD COVER WILL CONTINUE TO SPREAD INTO THE AREA THIS AFTERNOON
AHEAD OF LOW PRESSURE ALONG THE COAST OF THE CAROLINAS. CIGS MAY
VARY BETWEEN HIGHER MVFR AND LOWER VFR AT KCHO AND
BALTIMORE/WASHINGTON METRO TERMINALS. LOW PRESSURE WILL MOVE NORTH INTO THE
MID-ATLANTIC TONIGHT. ASSOCIATED RAINFALL WITH MVFR/IFR CIGS AND
VSBYS WILL MOVE INTO THE AREA BY THIS EVENING AND CONTINUE
OVERNIGHT. CONDITIONS WILL BE SLOW TO IMPROVE THURSDAY...WITH
LINGERING MVFR CIGS EXPECTED MOST OF THE DAY. SHORT-TERM AMENDMENTS
LIKELY FOR PERIODS OF HEAVY RAIN AND REDUCED CIGS/VSBYS THIS EVENING
AND OVERNIGHT.  GENERALLY NE WINDS AROUND 10KT THROUGH THURSDAY
AFTERNOON. SOME GUSTS TO 20KT AT TIMES...MOSTLY AT KBWI/KDCA/KMTN.

VFR CONDITIONS AT ALL TERMINALS FRIDAY NIGHT THROUGH SATURDAY. WINDS
NORTH BECOMING VARIABLE 5 TO 10 KNOTS GUSTS 15 KNOTS FRIDAY NIGHT
THROUGH SATURDAY.

&&

.MARINE...
GUSTY NE WINDS ACROSS ALL THE WATERS THROUGH THE NEXT 36 HOURS
CAUSING SCA TO BE EXTENDED THROUGHOUT THE DAY ON THURSDAY. WINDS
AND SEAS SHOULD SUBSIDE THURSDAY NIGHT INTO FRIDAY.

NO MARINE HAZARDS EXPECTED FRIDAY NIGHT THROUGH SATURDAY.

&&

.HYDROLOGY...
THE THOUGHT ON QPF HAS SHIFTED A BIT THE PAST COUPLE OF HOURS AS
THE 12Z ECMWF CAME IN LESS WET THAN THE PREVIOUS RUN. THIS MAKES
THE GFS AND THE NAM THE WETTEST SOLNS AND SHOULD GIVE THE REGION
BETWEEN 1.0 AND 1.5 INCHES OF RAIN ALONG AND E OF I-95
OVERNIGHT...WITH 0.5 TO 1 INCH BETWEEN I-95 AND THE SHEN VALLEY.
THIS MAY NOT BE QUITE ENOUGH FOR FLOODING BUT STILL ENOUGH
UNCERTAINTY NOT TO TAKE DOWN THE FLOOD WATCH ATTM.

&&

.TIDES/COASTAL FLOODING...
ESTOFS GUIDANCE FROM 06Z SHOWS TIDAL ANOMALIES AOB 1.2 FT IN THE
TIDAL POTOMAC AND MD BAY. THUS NOT EXPECTING ANY TIDAL FLOODING ATTM.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT
     FOR DCZ001.
MD...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT
     FOR MDZ006-007-009>011-013-014.
VA...FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH LATE TONIGHT
     FOR VAZ053-054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THURSDAY FOR ANZ530>543.

&&

$$
SYNOPSIS...LEE
NEAR TERM...LEE
SHORT TERM...LEE
LONG TERM...KLW
AVIATION...KS/KLW
MARINE...LEE/KLW
HYDROLOGY...LEE
TIDES/COASTAL FLOODING...LEE







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