Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 120755
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
355 AM EDT SAT APR 12 2014

.SYNOPSIS...
HIGH PRESSURE WILL MOVE ACROSS THE REGION TODAY AND PUSH OFFSHORE
THIS EVENING. A WARM FRONT WILL LIFT NORTH ACROSS THE REGION
TONIGHT AND SUNDAY. A COLD FRONT WILL SLOWLY MOVE THROUGH THE
REGION MONDAY NIGHT THROUGH TUESDAY NIGHT. CANADIAN HIGH PRESSURE
BUILDS INTO THE AREA WEDNESDAY AND THURSDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
PATCHY DENSE FOG DUE TO RADIATIONAL COOLING AND RESIDUAL MOISTURE
FROM EARLIER RAINS HAS DEVELOPED IN VALLEY AREAS OF EAST OF THE BLUE
RIDGE AND INTO THE WESTERN DC METRO. THIS FOG SHOULD LIFT SHORTLY
AFTER SUNRISE WHEN DAYTIME HEATING AND MIXING ENSUE. WILL MONITOR
FOR POSSIBLE DENSE FOG ADVISORY IF COVERAGE OF <1/4SM INCREASES
EARLY THIS MORNING. RIDGE OF SURFACE HIGH PRESSURE WILL SLOWLY PUSH
ACROSS THE CWA AND OFFSHORE TODAY AS SURFACE WINDS VEER AND THERMAL
RIDGE BEGINS ITS RETURN NORTH. TEMPERATURES WILL BE A BIT COOLER
THAN YESTERDAY YET STILL WELL ABOVE NORMAL TODAY. WEAK ISENTROPIC
LIFT ALONG WITH DAYTIME HEATING CONVERGENCE AND A FEW HUNDRED JOULES
OF MLCAPE MAY RESULT IN SOME AFTERNOON POP-UP SHOWERS OVER THE
SOUTHERN POTOMAC HIGHLAND. HAVE GONE WITH LOW CHANCE POPS AS OVERALL
MOISTURE AND LIFT REMAIN LOW.

AS LEADING EDGE OF SOUTHWEST 30KT LOW LEVEL JET NUDGES EAST OVER
THE REGION TONIGHT AFTER 03Z...FORECAST SOUNDINGS ARE SHOWING
INCREASING LOW LEVEL MOISTURE WITH STRONG WAA PUSH. COULD SEE SOME
STRATUS...ESPECIALLY CLOSER TO ONSHORE WINDS NEAR NORTHERN SIDE OF
THE BAY. HAVE ALSO INCREASED LOW TEMPS FOR TONIGHT WITH FULL
DECOUPLING NOT EXPECTED.

MID-ATLANTIC IS WELL INTO THE WARM SECTOR FOR SUNDAY WITH AND
INCREASING SOUTHWEST FLOW/WIND FAVORING GOOD MIXING. DEWPOINTS
WILL BE A BIT HIGHER...BUT SHOULD STILL SEE TEMPERATURES AROUND OR
INTO THE 80S.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
FLOW THRUOUT THE TROPOSPHERE BECOMES INCREASINGLY MERIDIONAL/SLY
OVER THE ERN SEABOARD SUN NGT AND MON AS AN AMPLIFYING UPPER TROUGH
AND SFC COLD FRONT APPROACH FROM THE CENTRAL CONUS AND DOWNSTREAM
RIDGE BUILDS OVER THE WRN ATLANTIC. WARM CONDITIONS WILL CONTINUE AS
A RESULT. FCST LOWS IN THE 50S SUN NGT AND HIGHS IN THE 70S MON ARE
MORE REPRESENTATIVE OF CLIMO FOR LATE MAY THAN FOR MID APRIL.

THE COLD FRONT WILL PROGRESS EWD TOWARD THE WRN SIDE OF THE
APPALACHIANS ON MON. CLOUDS WILL INCREASE THRUOUT THE DAY AS A
40-50KT SLY LLVL JET AHEAD OF THE FRONT TRANSPORTS DEEPER MOISTURE
UP THE ERN SEABOARD. THE GREATEST LIFT WILL STILL REMAIN UPSTREAM OF
THE AREA ON MON SO COVERAGE OF SHOWERS WILL BE LOW DURING THE AFTN.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
MODELS INDICATE A WEAK REX BLOCK FORMING OVER THE ATLANTIC NEAR 60W
NEXT WEEK...WHICH WOULD WILL CAUSE THE COLD FRONT TO SLOW DOWN AS IT
MOVES EWD TOWARD THE ERN SEABOARD. AN EXTENDED PERIOD OF CLOUDY AND
WET CONDITIONS ARE IN THE FCST MON NGT THRU TUE NGT WITH THE FRONT
LOCATED OVER THE AREA. COVERAGE OF PRECIP SHOULD BE WIDESPREAD WITH
FAVORABLE JET DYNAMICS IN RIGHT ENTRANCE REGION OF ULVL JET STREAK
AND A PERSISTENT FEED OF MOISTURE FROM THE GULF OF MEXICO AND
ATLANTIC ALONG THE FRONTAL BOUNDARY. 00Z GUIDANCE HAS GENERALLY
BACKED OFF ON HIGHER QPF AMOUNTS A BIT COMPARED TO YDA/S RUNS BUT
THE POSSIBILITY FOR A HEAVY RAINFALL EVENT STILL CANNOT BE DISMISSED
GIVEN THE AFOREMENTIONED SYNOPTIC SETUP.

THE COLD FRONT MOVES OFF THE EAST COAST WED. CANADIAN HIPRES
EVENTUALLY BUILDS INTO THE AREA DURING THE SECOND HALF OF THE WEEK.
WELL-BELOW NORMAL TEMPS ARE FCST FOR WED WITH HIGHS ONLY IN THE 40S
AND LOW WED NGT NEAR FREEZING. FROST/FREEZE HEADLINES MAY BE NEEDED
EAST OF THE BLUE RIDGE WHERE THE GROWING SEASON HAS STARTED.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
IFR/LIFR VSBYS IN AREAS OF FOG ACROSS VALLEY AREA
AFFECTING MRB/IAD WILL LIFT AFTER SUNRISE. VFR CONDITIONS ARE
EXPECTED TO PREVAIL THROUGH THE DAY. HIGH PRESSURE WILL MOVE
OFFSHORE LATER TODAY AS WINDS VEER TO THE SOUTHEAST. WINDS WILL
INCREASE TONIGHT INTO SUNDAY AS A WARM FRONT PUSHES NORTH. AREAS OF
MVFR STRATUS MAY DEVELOP LATE TONIGHT...MAINLY EXPECTED TO AFFECT
BWI/MTN. CONFIDENCE ON DEVELOPMENT AND COVERAGE OF STRATUS IS LOW.

PATCHY FOG OR LOW STRATUS MAY DEVELOP SUN NGT UNDER MOIST SLY
FLOW. SLY WINDS WILL BE BREEZY ON MON WITH GUSTS 25-30 KT
POSSIBLE DURING THE AFTN BUT VFR CONDITIONS. COLD FRONT SLOWS
DOWN AS IT MOVE THRU THE TERMINALS MIDWEEK...RESULTING IN A
PROLONGED RISK OF FLGT RESTRICTIONS AND SHOWERS LATE MON THRU ERY
WED.

&&

.MARINE...
HIGH PRESSURE WILL MOVE ACROSS THE WATERS TODAY AS LIGHT WINDS
VEER FROM NORTH TO SOUTHEAST. WINDS WIND WILL INCREASE OVERNIGHT
AND SCA CONDITIONS ARE EXPECTED SUNDAY BEHIND A WARM FRONT.

SCA MAY NEED TO BE EXTENDED INTO SUN NGT FOR THE MAIN STEM OF THE
CHSPK BAY WHERE SLY WINDS WILL CHANNEL. SCA CONDITIONS LIKELY ACROSS
ALL MARINE ZONES ON MON INTO TUE AS SLY WINDS INCREASE AHEAD OF A
COLD FRONT. A STRONG PRESSURE GRADIENT LOOKS TO DEVELOP BEHIND THE
FRONT DURING MIDWEEK AS THE FRONT MOVES OFFSHORE AND HIPRES BUILDS
IN FROM THE GREAT LAKES. NW WINDS DURING THIS TIME SHOULD CONTINUE
TO PRODUCE SCA CONDITIONS WITH GALES POSSIBLE BRIEFLY BEHIND THE
FRONT SOMETIME EITHER LATE TUE OR ERY WED.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TO 6 PM EDT SUNDAY FOR
     ANZ530>543.

&&

$$
SYNOPSIS...AEB
NEAR TERM...AEB
SHORT TERM...JRK
LONG TERM...JRK
AVIATION...JRK/AEB
MARINE...JRK/AEB









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