Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 270756
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
356 AM EDT WED APR 27 2016

.SYNOPSIS...
A COLD FRONT WILL STALL OUT NEAR THE POTOMAC HIGHLANDS INTO
NORTHEASTERN NORTH CAROLINA TODAY AND IT WILL REMAIN NEARLY
STATIONARY THROUGH FRIDAY. WAVES OF LOW PRESSURE WILL RIDE ALONG
THE BOUNDARY DURING THIS TIME. THE BOUNDARY MAY DROP A BIT FARTHER
SOUTH SATURDAY...BUT ANOTHER WAVE OF LOW PRESSURE WILL TRACK ALONG
THE FRONT FOR SUNDAY INTO MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AT 3 AM...SFC COLD FRONT WAS NEAR THE US-50 CORRIDOR.
SHOWERS...MAINLY REMNANTS OF PREVIOUS CONVECTION...CONTINUE TO PUSH
ACROSS SOUTHERN PARTS OF THE CWA. GUIDANCE IS INSISTENT ON ACTIVITY
TRENDING A LITTLE NORTHWARD THROUGH DAYBREAK AS DYING CONVECTION AND
ATTENDANT SHORTWAVE PUSH EAST FROM THE OHIO VALLEY.

AS FRONT PUSHES SOUTH TODAY...HIGH PRESSURE WILL WEDGE SOUTHWARD
EAST OF THE APPALACHIANS. WE SHOULD SEE DECREASING COVERAGE OF
SHOWERS THROUGH THE MORNING HOURS. HOWEVER CLOUDY SKIES WILL
PREVAIL. HIGHEST CHANCES OF SHOWERS THROUGH THE AFTERNOON WILL BE
OVER SOUTHERN PARTS OF THE AREA AS DEEP MOISTURE SHUNTS A LITTLE TO
THE SOUTH...WHILE OVERRUNNING CONTINUES. THUNDER CHANCES WILL BE
CONFINED TO FAR SOUTHERN PORTIONS OF THE CWA. SOME GUIDANCE ALLOWS
HIGH TO RISE TO THE MID 70S IN THIS AREA...BUT AM SKEPTICAL GIVEN
THE BUILDING HIGH. THE SOUTHERN ALLEGHENY HIGHLANDS MAY HAVE THE
BEST CHANCE OF SEEING SOME INSTBY BUILD. EXPECT HIGHS BELOW NORMAL
ACROSS THE REST OF THE AREA...AND VERY LITTLE MOVEMENT TO
TEMPERATURES ALL DAY ACROSS THE NORTH.

THERE MAY BE SOME BRIEF DRYING TONIGHT AS SHORTWAVE RIDGING MOVES
OVERHEAD...BUT WILL CONTINUE WITH CHANCE POPS GIVEN THE CONTINUED
OVERRUNNING ENVIRONMENT. WILL LIKELY SEE LOWERING CLOUDS AND PERHAPS
SOME LIGHT FOG. LOWS WILL RANGE FROM MID 40S NORTH TO MID 50S SOUTH.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AREA OF BROAD LOW PRESSURE WILL BE REACHING THE OHIO VALLEY THURSDAY
MORNING. THIS WILL INCREASE LIFT...WITH SHOWERS SPREADING FROM WEST
TO EAST ACROSS THE AREA DURING THE DAY. HAVE KEPT POPS IN LIKELY
CATEGORY...BUT THESE COULD INCREASE AS TIMING AND AREAL COVERAGE
COMES INTO MORE AGREEMENT. SPC PLACES MUCH OF THE SOUTHWESTERN CWA
IN A MARGINAL RISK FOR SEVERE STORMS...AND DEEP LAYER SHEAR WILL
INCREASE. HOWEVER...MAJORITY OF GUIDANCE SHOWS A STRONG CAD WEDGE IN
PLACE...SO HAVE LOW CONFIDENCE ON RISK IN OUR CWA. AGAIN...ALLEGHENY
HIGHLANDS (OUTSIDE OF WEDGE INFLUENCE) MAY HAVE THE BEST CHANCE AT
SEEING THUNDER. HIGHS WILL STRUGGLE TO REACH 60 IN THE NORTH BUT
PERHAPS REACH THE UPPER 60S IN THE FAR SW.

AS SHORTWAVE ENERGY PASSES THURSDAY EVENING...DRYING WILL TAKE PLACE
IN THE COLUMN AND SHOULD SEE A DOWNTURN IN SHOWER COVERAGE. HOWEVER
WITH THE FRONT AND WEAK SFC LOW REMAINING NEARBY...WILL MAINTAIN
CHANCE POPS...ALTHOUGH PRECIP MAY BECOME LIGHTER/DRIZZLY. A STRONGER
SHORTWAVE TROUGH WILL CROSS THE REGION ON FRIDAY. HOWEVER IN WITH
DECREASED PWATS...SHOWERS SHOULD BE LIGHT AND HAVE THUS HELD POPS IN
THE CHANCE CATEGORY. AFTER THIS SYSTEM PASSES...FRIDAY NIGHT WILL
HAVE DECREASING CHANCES OF MEASURABLE PRECIP...ALTHOUGH SOME DRIZZLE
WILL REMAIN POSSIBLE. DAYTIME TEMPERATURES WILL CONTINUE TO RUN
BELOW NORMAL WITH MUTED DIURNAL CURVES.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
SURFACE HIGH PRESSURE WILL STRENGTHEN OVER NEW ENGLAND BEHIND A
DEPARTING UPPER-LEVEL DISTURBANCE SATURDAY. THIS WILL CAUSE A
SURFACE RIDGE AXIS TO STRENGTHEN OVER THE MID-ATLANTIC...PUSHING A
COLD FRONT FARTHER OFF TO OUR SOUTH. WITH HIGH PRESSURE
STRENGTHENING...THIS WILL LIKELY ALLOW FOR DRY CONDITIONS
SATURDAY. LOW CLOUDS AND POSSIBLE DRIZZLE ARE LIKELY UNDERNEATH
THE SUBSIDENCE INVERSION SATURDAY MORNING...BUT ANY DRIZZLE WILL
DIMINISH SATURDAY AFTERNOON AND THERE SHOULD EVEN BE BREAKS OF
SUNSHINE.

LOW PRESSURE WILL DEVELOP OVER THE MIDWEST AND IT WILL BEGIN
TRACKING TO THE EAST SATURDAY NIGHT. THIS WILL ALLOW FOR WARM AND
MOIST AIR TO OVERRUN THE COOLER AIR IN PLACE...RESULTING IN MORE
CLOUDS AND INCREASING CHANCES FOR RAIN. THE LOW WILL TRACK THROUGH
THE OHIO VALLEY SUNDAY...AND THEN ALONG THE BOUNDARY JUST TO OUR
SOUTH FOR MONDAY. PLENTY OF CLOUDS ALONG WITH RAIN IS LIKELY
DURING THIS TIME. EXACT TIMING IS STILL A BIT UNCERTAIN THIS FAR
OUT.

THE LOW WILL MOVE OFF TO THE EAST DURING THE MIDDLE PORTION OF
NEXT WEEK AND HIGH PRESSURE WILL LIKELY BUILD OVERHEAD...BRINGING
A RETURN OF DRY AND SEASONABLE CONDITIONS.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
FRONT IS CURRENTLY SINKING SOUTH ACROSS THE AREA WITH WINDS TURNING
TO THE NE. ALSO AN AREA OF STRATUS MOVING FROM NE TO SW...ALREADY
MOVING PAST BWI AT 07Z. THIS HAS VERIFIED IN THE IFR CATEGORY SO
FAR...SO HAVE THESE CIGS SPREADING TO DCA/IAD. LESS CERTAIN WHETHER
IFR REACHES MRB/CHO. PERIODIC SHOWERS WILL CONTINUE THROUGH THE
MORNING BUT FOR THE MOST PART FAIL TO REDUCE VSBY. HAVE CIGS LIFTING
BY THIS AFTERNOON...BUT LOW CONFIDENCE ON WHETHER THEY REACH VFR.

CIGS WILL LOWER AGAIN TONIGHT. WILL LIKELY PLAY THIS CONSERVATIVELY
FOR NOW...BUT MORE IFR IS POSSIBLE. VSBYS MAY ALSO REDUCE IN LIGHT
FOG...DZ AND -SHRA. FAIRLY NUMEROUS SHOWERS CROSS THE AREA THURSDAY
WITH SUB-VFR CONDITIONS LIKELY TO CONTINUE. WITH CAD WEDGE REMAINING
IN PLACE...CAN/T REALLY GIVE AN OPTIMISTIC OUTLOOK AT ANY POINT
THROUGH FRIDAY NIGHT WITH LOW CLOUDS AND OCCASIONAL SHOWERS
CONTINUING THROUGH THE PERIOD.

HIGH PRESSURE WILL STRENGTHEN OVER THE AREA SATURDAY. THIS WILL
ALLOW FOR CIGS TO IMPROVE TO MVFR AND POSSIBLE VFR LEVELS.
HOWEVER...THE HIGH WILL WEAKEN SATURDAY NIGHT AND LOW PRESSURE
WILL TRACK THROUGH THE MIDWEST. OVERRUNNING WILL DEVELOP NORTH OF
AN APPROACHING WARM FRONT...RESULTING IN LOW CLOUDS ALONG WITH
INCREASING CHANCES FOR RAIN.

RAIN AND LOW CLOUDS ARE LIKELY EARLY NEXT WEEK AS THE LOW SLOWLY
PASSES BY TO THE SOUTH.

&&

.MARINE...
COLD FRONT MOVING SOUTH ACROSS THE AREA EARLY THIS MORNING. PRESSURE
SURGE CAUSING SOME GUSTS TO 20 KT...ALTHOUGH MAINLY OVER THE BAY.
THESE SHOULD SUBSIDE AS THE FRONT CONTINUES SOUTH...BUT EXTENDED THE
SCA FOR THE SOUTHERN MOST ZONES UNTIL 11 AM TO CAPTURE ANY LINGERING
GUSTS. THEN JUST LOOKING AT AN EXTENDED PERIOD OF MAINLY E OR NE
FLOW THROUGH THE END OF THE WEEK. THE MAJORITY OF THE TIME WILL BE
SUB-SCA...BUT AN AREA OF LOW PRESSURE MAY ENHANCE WINDS A BIT BY
LATE FRIDAY AND COULD LEAD TO SOME 20 KT GUSTS.

HIGH PRESSURE WILL BUILD TOWARD THE WATERS SATURDAY. NO MARINE
HEADLINES ARE EXPECTED. A WARM FRONT WILL APPROACH FROM THE SOUTH
SATURDAY NIGHT THROUGH SUNDAY. LOW PRESSURE WILL RIDE ALONG THE
BOUNDARY...PASSING BY JUST TO THE SOUTH SUNDAY NIGHT INTO
MONDAY. UNSETTLED CONDITIONS ARE EXPECTED DURING THIS TIME. A
SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS
LATER SUNDAY INTO MONDAY.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES HAVE DROPPED CLOSER TO NORMAL THIS MORNING DUE TO
A WESTERLY COMPONENT THE LOW-LEVEL FLOW OVERNIGHT. THE WINDS HAVE
TURNED TO THE NORTHEAST...AND NORTHEASTERLY WINDS WILL CONTINUE
THROUGH FRIDAY. WATER LEVELS WILL REMAIN BELOW MINOR FLOODING
THRESHOLDS TODAY...BUT GUIDANCE DIVERGES SIGNIFICANTLY FOR THE
TIDE CYCLE TONIGHT THROUGH THURSDAY. THE ETSS KEEPS WATER LEVELS
WELL BELOW FLOODING THRESHOLDS...WHILE THE CBOFS SHOWS SOLID MINOR
FLOODING FOR MOST AREAS. AS OF NOW...THE CURRENT FORECAST LEANS
TOWARD THE ETSS GIVEN THE FACT THAT THE FLOW WILL BE LIGHT AND
NORTH OF EAST. WILL CONTINUE TO MONITOR TIDAL ANOMALIES TODAY TO
SEE WHICH GUIDANCE IS PERFORMING BETTER.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT THIS MORNING FOR
     ANZ530>533-535-536-538>542.
     SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR ANZ534-
     537-543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...ADS
SHORT TERM...ADS
LONG TERM...BJL
AVIATION...BJL/ADS
MARINE...BJL/ADS
TIDES/COASTAL FLOODING...BJL



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