Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 130955
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
555 AM EDT SAT SEP 13 2014

.SYNOPSIS...
A SURFACE TROUGH WILL MOVE ACROSS THE REGION TODAY...WHILE LOW
PRESSURE PASSES TO THE SOUTH AND EAST. HIGH PRESSURE BUILDS ACROSS
THE MID-ATLANTIC SATURDAY EVENING THROUGH MONDAY. A WEAK
DISTURBANCE PASSES THROUGH THE AREA MONDAY NIGHT. HIGH PRESSURE
BUILDS IN THROUGH MIDWEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
EARLY MORNING SURFACE TROUGH EXTENDS FROM EASTERN OHIO THROUGH
WV...SWRN VA AND INTO NC. SOME LIGHT RAIN HAS DEVELOPED ACROSS
PORTIONS OF EASTERN WV AND WESTERN VA. MODELS CONTINUE TO INDICATE
SHOWER ACTIVITY SHOULD SPREAD WEST TO EAST ACROSS THE FORECAST AREA
TODAY. PLENTY OF MOISTURE EXPECTED IN THE ATMOSPHERE TODAY...WITH
PWATS NEAR 2.0 INCHES...BUT INSTABILITY WILL BE LIMITED WITH A NOSE
OF WARM AIR BETWEEN 700 AND 800MB AND LIMITED LAPSE RATES ABOVE IT
OF AROUND 5 OR 6 DEGREES C/KM. END RESULT IS THAT MOST AREAS SHOULD
SEE LESS THAN A QUARTER INCH OF RAIN TODAY...ALTHOUGH SOME AREAS MAY
GET BRIEF MODERATE/HEAVY RAIN AND THEREFORE HIGHER AMOUNTS.

HIGH TEMPERATURES GENERALLY IN THE LOW TO MID 70S EAST OF THE BLUE
RIDGE...WITH UPPER 60S TO AROUND 70 WEST OF THE BLUE RIDGE.

TROUGH IS EXPECTED TO BE OFFSHORE BY THIS EVENING. HIGH PRESSURE
BUILDS IN TO THE NORTH...WITH SKIES BECOMING CLEAR TO PARTLY CLOUDY
OVERNIGHT. COOLER AIR MOVES INTO THE REGION UNDER LIGHT NORTHERLY
WINDS. THE LACK OF CLOUD COVER WILL SUPPORT GOOD RADIATIONAL
COOLING. TEMPS WILL BECOME QUITE CHILLY OVERNIGHT. LOWS DROP INTO
THE 40S ALONG AND WEST OF THE BLUE RIDGE...AND EVEN INTO THE UPPER
30S ALONG PORTIONS OF THE POTOMAC HIGHLANDS. AREAS ALONG AND EAST OF
THE I-95 CORRIDOR SHOULD STAY IN THE 50S.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
THE HIGH BUILDS OVERHEAD SUNDAY...WITH MOSTLY SUNNY SKIES AND LIGHT
NORTH WINDS. MILD TEMPS EXPECTED...WITH HIGHS IN THE LOW 70S
ACROSS MOST OF THE REGION. BLUE RIDGE MOUNTAINS AND POTOMAC
HIGHLANDS WILL BE SLIGHTLY COOLER WITH HIGHS IN THE MID TO UPPER
60S.

HIGH PRESSURE REMAINS SPRAWLED ACROSS THE AREA SUNDAY NIGHT.
SUBSIDENCE AND DRY AIR ALOFT WILL SUPPORT CLEAR TO PARTLY CLOUDY
SKIES. TEMPERATURES SUNDAY NIGHT SHOULD BE SIMILAR TO SATURDAY
NIGHT...WITH LOWS AGAIN IN THE 40S AND 50S.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
SFC HIPRES WL BE MVG OFFSHORE MON. WL HV FAIRLY FAST FLOW ALOFT...SO
THE TRANSITION SHUD BE RATHER SUDDEN...AS ISENT LIFT WL SPRED CLDS
ACRS THE AREA DURING THE AFTN. DONT QUITE THINK WE/LL HV ENUF TIME
FOR COMPLETE MSTR RECOVERY...SO HV KEPT POPS OUT OF THE FCST...XCPT
FOR A SCHC LT DAY HIGHLAND/PENDLTN EWD TO S OF CHO. INSTEAD...THE
PCPN PROGGED TO HOLD OFF TIL MON NGT. THERE ARE TWO PSBL SOURCES--
THE PACKET OF THTE GLIDING ACRS VA AND A WK CDFNT/TROF AXIS APPRCHG
FM THE NW. AM NOT SURE HOW WELL THESE TWO FEATURES WL PLAY WITH EACH
OTHER. IN SITUATIONS W/ CONFLICTING PRIORITIES...THE TYPICAL OUTCOME
IS FOR LOTSA CLDS BUT LTL PCPN. THATS THE ROUTE TAKEN HERE. THE RRQ
OF UPR JET DOES RESIDE IN THE NRN MID ATLC...SO HV LKLY POPS ALONG
I-95. QPF LGT THO. WL GIVE CREDENCE TO WAA...AND BUMP MAXT UP TO
MID /PERHAPS UPR/ 70S. THINK THERE WL BE JUST TOO MUCH CLDCVR FOR
THE LWR 80S SUGGESTED BY MAV. MIN-T NOT FAR OFF FM DEWPTS...LWR 60S
SE OF CHO-DCA-DMH...BUT IN THE 50S POINTS NW. HV STRONG CAA IN THE
MTNS AFTR MIDNGT...AND THAT SHUD RESULT IN A FAIRLY WIDESPREAD RGN
OF MIN-T LWR-MID 50S.

THE REST OF THE XTNDD FCST WL BE DOMINATED BY SPRAWLING HIPRES. MAY
HV A LINGERING SHRA NEAR THE BAY TUE MRNG. OTRW DRY WX. SKIES SHUD
BE MOSUN/SUNNY BY DAY /CLR BY NGT/ TIL THU...WHEN A S/WV PASSAGE
INTHE NERN CONUS MAY CONTRIBUTE A FEW CLDS. OTR CHALLENGE WL BE TEMP
FCSTG. WL BE IN NW FLOW...WHICH SUGGESTS COOLER THAN CLIMO. GRIDS HV
PLENTY OF UPR 60S-LWR 70S FOR MAXT. MIN-T MID 40S-MID 50S.

&&

.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
SHOWER ACTIVITY IS EXPECTED DEVELOP SATURDAY AS A TROUGH MOVES
ACROSS THE REGION. RAIN SHOULD BE LIGHT FOR MOST PART...WITH MVFR
VSBYS. CIGS AROUND 2-3KFT EXPECTED TO DEVELOP DURING MID-LATE
MORNING AND PERSIST THROUGH MOST OF THE AFTERNOON. GENERALLY LIGHT
NORTHERLY WINDS...ALTHOUGH WIND DIRECTION MAY SHIFT TO THE SE BY THE
END OF THE AFTERNOON OVER DC METRO TERMINALS.

VFR EXPECTED SATURDAY NIGHT THROUGH SUNDAY NIGHT WITH LIGHT WINDS.

CLDS WL BE INCRSG MON...BUT FLGT RESTRICTIONS SHUD HOLD OFF TIL MON
NGT. MVFR TO PERHAPS IFR DUE TO CIGS/VSBYS IN SHRA MAY LINGER INTO
THE ELY PORTION OF THE TUE MRNG PUSH. VFR THEREAFTER.

&&

.MARINE...
WINDS XPCTD TO REMAIN BELOW SCA VALUES THROUGH THE DAY SAT.
RAIN EXPECTED AT TIMES LATE SATURDAY MORNING THROUGH MID-LATE
AFTERNOON.

GRADIENT INCREASES SATURDAY EVENING WITH LOW PRESSURE OFFSHORE AND
HIGH PRESSURE BUILDING TO THE NORTH AND WEST. SMALL CRAFT ADVISORY
IS IN EFFECT. THE ADVISORY HAS BEEN EXTENDED INTO MID MORNING FOR
THE SOUTHERNMOST MARINE ZONES. WINDS DIMINISH QUICKLY SUNDAY
AFTERNOON AND CONTINUE TO BE LIGHT SUNDAY NIGHT WITH HIGH PRESSURE
BUILDING OVER THE WATERS.

A WK DISTURBANCE WL CROSS THE WATERS MON NGT. CAA BHD THIS FEATURE
TUE WL KICK NW WNDS UP...W/ SUFFICIENT MIXING FOR SCA POTL AT THAT
TIME. WNDS WL GRDLY DIMINISH AFTR THAT AS HIPRES BLDS.

&&

.TIDES/COASTAL FLOODING...
WATER LEVELS HAVE SHOT UP ON THE BAY SINCE MIDNIGHT...WITH
DEPARTURES RUNNING AROUND 3/4 OF A FOOT. THE TIDE IS NEAR SOLOMONS
AND LEWISETTA AS OF 6AM. FORTUNATELY...THE INCREASE HAS NOT CAUSED
ANY PROBLEMS YET. WILL NEED TO WATCH ANNAPOLIS CLOSELY. CURRENT
THINKING IS THAT THEY WILL EXCEED THEIR CAUTION STAGE...BUT NOT
QUITE REACH MINOR FLOOD. SAME THINKING FOR BALTIMORE.

THE TIDE HAS NOT AFFECTED THE UPPER POTOMAC YET...BUT EXPECT SHARP
INCREASES AS IT WORKS UPRIVER. THE HEC-RAS MODEL SUGGESTS SW DC
MAY COME CLOSE TO MINOR...BUT THINK ITS RUNNING TOO HIGH. CAUTION
STAGE IS A MORE LIKELY SCENARIO.

SOUTHERN AND NORTHERN STREAM DISTURBANCES WILL AFFECT THE REGION
TODAY. WINDS WILL TURN NW IN ITS WAKE TONIGHT...RESULTING IN A
BLOWOUT TIDE. LOCATIONS THAT WILL RECEIVE THE PM TIDE PRIOR TO
WIND SHIFT MAY BE SUSCEPTIBLE TO MINOR FLOODING. ANNAPOLIS IS THE
BIGGEST CONCERN. THINK THE WIND SHIFT WILL REACH BALTIMORE AND DC
FIRST. WILL BE ADDING WORDING TO THE HWO.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EDT
     SUNDAY FOR ANZ531-532-538>540-542.
     SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 10 AM EDT
     SUNDAY FOR ANZ533-534-537-541-543.

&&

$$
SYNOPSIS...KS
NEAR TERM...KS
SHORT TERM...KS
LONG TERM...HTS
AVIATION...KS/HTS
MARINE...KS/HTS
TIDES/COASTAL FLOODING...HTS






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