Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 231902
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
302 PM EDT WED APR 23 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE AREA THROUGH THURSDAY. A COLD
FRONT WILL PASS THROUGH THE AREA FRIDAY AND ANOTHER COLD FRONT IS
EXPECTED TO MOVE THROUGH SATURDAY. HIGH PRESSURE WILL BUILD
OVERHEAD SUNDAY AS THE COLD FRONT STALLS TO OUR SOUTH. WAVES OF
LOW PRESSURE WILL DEVELOP ALONG THE STALLED BOUNDARY...BRINGING
UNSETTLED CONDITIONS TO THE AREA NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY NIGHT/...
AT 18Z...A 1025 MB SFC HIGH IS POSITIONED OVER THE UPPER MIDWEST/
GREAT LAKES WHILE A COLD FRONT ASSOCIATED WITH A 995 MB SFC LOW NEAR
THE GULF OF MAINE STRETCHES SOUTHWESTWARD TOWARD THE SERN ATLANTIC
COAST. GUSTY NW WINDS WILL CONTINUE THRU SUNSET AS A RESULT OF A
TIGHT PRESSURE GRADIENT BETWEEN THESE TWO SYSTEMS ACROSS THE
MID-ATLANTIC STATES. MAX TEMPS WILL LIKELY FALL SHORT OF 60F THIS
AFTN ACROSS NRN VA...ERN WV AND WRN/CENTRAL MD DUE TO CAA AND
STRATOCU THAT HAS BEEN STUBBORN TO ERODE. EXPECT CLOUDS TO DIMINISH
FROM S TO N THRU SUNSET AS SUBSIDENCE STRENGTHENS WHILE THE LOW
PULLS AWAY FROM THE EAST COAST.

HIPRES CONTINUES TO BUILD EWD TNGT WITH SFC RIDGE AXIS REACHING THE
CENTRAL APPALACHIANS LATE TNGT. WINDS WILL RELAX AFTER SUNSET AND
BECOME LGT ALONG AND WEST OF THE BLUE RIDGE. DESPITE FCST MIN TEMPS
IN THE MID 30S ACROSS THE WRN AND NRN SUBURBS OF DC/BALTIMORE...
WINDS AND DRY AIRMASS SHOULD INHIBIT FROST FORMATION. PATCHY FROST
POSSIBLE TOWARD THE CENTRAL FOOTHILLS...WHERE THE GROWING SEASON IS
ACTIVE.

HIPRES MOVES OVERHEAD ON THU. THERE IS STILL SOME TIMING DIFFERENCES
CONCERNING HOW QUICKLY THE HIGH MOVES IN WHICH WILL PLAY A FACTOR IN
HOW STRONG THE WINDS ARE IN NORTH-CENTRAL MD. THE 12Z GFS WAS
PROGRESSIVE ENOUGH WITH THIS SYSTEM THAT WINDS ARE LGT ACROSS THE
ENTIRE AREA ALL DAY WHILE THE SLOWER NAM KEEPS WINDS OF 15-25 MPH
TOWARD THE GREATER BALTIMORE METRO. UNDER FULL SUNSHINE...MAX TEMPS
SHOULD REACH THE MID TO UPPER 60S ACROSS THE MAJORITY OF THE CWA
EXCEPT FOR COOLER SPOTS NEAR THE MASON-DIXON LINE AND IN THE MTS.

HIPRES MOVES OFFSHORE THU NGT. SLY RETURN FLOW DEVELOPS AND CLOUDS
SPREAD IN FROM THE WEST AHEAD OF THE NEXT LOPRES SYSTEM THAT WILL BE
MOVING INTO THE UPPER MIDWEST. OVERRUNNING SHOWERS WILL BE ON THE
DOORSTEP OF THE ALLEGHENY FRONT TOWARD DAYBREAK FRI MRNG.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
A WEAK COLD FRONT SHOULD BE MOVING ACROSS THE APPALACHIANS MTNS
FRIDAY MORNING AS A SFC LOW MOVES ACROSS THE GREAT LAKES. RETURN
FLOW WILL BE USHERING IN WARM AND MOIST CONDITIONS AHEAD OF THE
FRONT AND PWAT VALUES ARE EXPECTED TO RISE AROUND 1.3 INCHES BY FRI
AFTERNOON. MID LEVEL FORCING ALONG THE SFC FROPA WILL BE MOVING
ACROSS THE MID ATLANTIC FRIDAY AFTERNOON. SHOWERS ARE EXPECTED TO
SPREAD ACROSS THE REGION AHEAD AND ALONG THE FROPA. SFC HEATING IN
CENTRAL VA WILL LIKELY LEAD TO HEAVIER SHOWERS AND EVEN A ISO
THUNDERSTORM.

A BRIEF PERIOD OF DRYING WILL MOVE INTO THE REGION BEHIND THE FROPA
SATURDAY NIGHT. A SECOND COLD FRONT WILL ROTATE AROUND THE GREAT
LAKES LOW AND MOVE ACROSS THE MID ATLANTIC SATURDAY. DEPENDING ON
THE SPEED OF THE FROPA TEMPS WILL RANGE FROM THE 50S TO THE MID 70S
ACROSS THE REGION. AT THIS TIME KEPT TEMPS EAST OF THE BLUE RIDGE
AND VALLEY LOCATIONS IN THE MID TO UPPER 70S. IF THE FROPA MOVES
FASTER TEMPS WILL BE LOWER. LITTLE QPF IF ANY IS EXPECTED WITH
THE FROPA. LEANED TOWARDS THE GFS AND PUT CHANCE OF SHOWERS FOR
THE POTOMAC HIGHLANDS AND NW SUBURBS OF DC AND BALTIMORE SATURDAY
DUE TO A SHORTWAVE TROUGH CROSSING THE REGION.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
THE PRESSURE GRADIENT OVER THE AREA WILL SLOWLY WEAKEN AND LEAD TO
GRADUALLY SUBSIDING NORTHWEST WINDS SATURDAY NIGHT INTO SUNDAY.
BREEZY AND DRY CONDITIONS ARE EXPECTED WITH TEMPERATURES NEAR
NORMAL. HIGH PRESSURE WILL ANCHOR ITSELF OVER NEW ENGLAND BY SUNDAY
NIGHT AS A LARGE AND SLOW-MOVING LOW PRESSURE SYSTEM TAKES SHAPE
OVER THE GREAT PLAINS.

CLOUDS WILL SPILL OVER THE RIDGE IN PLACE OVER THE AREA...STARTING
AS THIN HIGH CIRRUS DURING THE DAY SUNDAY BUT LOWERING AND
THICKENING SUNDAY NIGHT THROUGH MONDAY. CHANCES FOR RAIN GRADUALLY
INCREASE FROM SOUTHWEST TO NORTHEAST MONDAY INTO MONDAY NIGHT AS THE
ATMOSPHERE CONTINUES TO MOISTEN.

LOW PRESSURE SLOWLY MOVES NORTHEASTWARD INTO THE OHIO VALLEY TUESDAY
INTO WEDNESDAY. THERE IS A LARGE SPREAD IN THE GUIDANCE REGARDING
THE EXACT TIMING AND EXTENT OF RAINFALL...AS WELL AS THE TRACK OF
LOW PRESSURE AND THE NORTHWARD PROGRESSION OF A DEVELOPING WARM
FRONT OVER THE CAROLINAS. THIS IS DUE TO A VERY COMPLEX
PATTERN...WITH A STRONG CUTOFF LOW OVER THE CANADIAN MARITIMES
INTERACTING WITH THE LOW PRESSURE MOVING OUT OF THE CENTRAL UNITED
STATES...AND A RIDGE OF HIGH PRESSURE PINCHED IN BETWEEN OVER NEW
ENGLAND. THEREFORE...THERE IS A HIGH LEVEL OF UNCERTAINTY IN DETAILS
SUCH AS THE CHANCES FOR THUNDERSTORMS...WINDS AND RAINFALL AMOUNTS.

DEPENDING ON THE EVOLUTION OF LOW PRESSURE...UNSETTLED WEATHER COULD
LINGER INTO THE MIDDLE OF NEXT WEEK.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
BREEZY NW WINDS WINDS 15-20 KT WILL CONTINUE TO GUST TO AROUND 30 KT
THRU 22Z. WINDS GRADUALLY SUBSIDE THIS EVE PARTICULARLY AFTER
SUNSET. CU FIELD AROUND 5 KFT QUICKLY DISSIPATING THIS AFTN. NW
WINDS AROUND 10-15 KT TNGT...BECOMING LGT TOWARD DAYBREAK AT CHO/MRB
AS HIPRES SHIFTS OVERHEAD. THE PRESSURE GRADIENT AND WIND FIELD
CONTINUES TO WEAKEN FROM WEST TO EAST ON THU WITH THE HIGH MOVING
OVERHEAD. NW WINDS NEAR 15 KT STILL EXPECTED AT BWI/MTN. LGT SLY
WINDS DEVELOP THU NGT ONCE HIPRES PROGRESSES OFFSHORE.

SHOWERS ARE EXPECTED FRIDAY AS A WEAK COLD FRONT MOVES ACROSS THE
MID ATLANTIC. VCTS IS POSSIBLE FOR CENTRAL VA FRIDAY AFTERNOON AND
EARLY EVENING. SLY WINDS WILL BECOME W-NW BEHIND THE FROPA FRIDAY
NIGHT INTO SATURDAY. ANOTHER COLD FRONT WILL CROSS THE REGION
SATURDAY. GUSTS UP TO 30KTS ARE POSSIBLE SATURDAY AFTERNOON.

MODERATE CONFIDENCE IN VFR CONDITIONS WITH NORTHWEST WINDS 10 TO 15
KNOTS SUNDAY INTO SUNDAY NIGHT.

&&

.MARINE...
LATEST MARINE OBS INDICATE HIGH-END SCA OCCURRING AREA WIDE. OPTED
TO KEEP THE GALE WARNING GOING WITH OCCASIONAL GUSTS IN THE LOW TO
MID 30S STILL BEING OBSERVED. WINDS SUBSIDE A BIT AFTER SUNSET BUT
NW WINDS 15-25 KT SHOULD STILL CONTINUE TNGT. SCA REMAINS IN EFFECT
FOR THU BUT CONDITIONS MORE MARGINAL. SCA MAY BE ABLE TO BE
CANCELLED A FEW HRS EARLY ON THU DEPENDING ON HOW QUICKLY THE AXIS
OF THE HIGH BUILDS OVER THE WATERS.

SLY WINDS WILL INCREASE FRIDAY AHEAD OF A WEAK COLD FRONT. SCA
MAY BE NEEDED AS GUSTS INCREASE IN THE LOWER BAY AND LOWER TIDAL
POTOMAC. WINDS WILL BECOME WRLY BEFORE ANOTHER FROPA CROSS THE
WATERS SATURDAY AFTERNOON. GUSTY NW WINDS ARE LIKELY SATURDAY
AFTERNOON AND A GALE WARNING IS EVEN POSSIBLE.

SMALL CRAFT ADVISORY GUSTS MAY LINGER THROUGH SATURDAY NIGHT AND
INTO SUNDAY FOR PORTIONS OF THE WATERS. WINDS BECOME LIGHTER LATE
SUNDAY INTO SUNDAY NIGHT AS HIGH PRESSURE PASSES NEAR THE REGION.

&&

.FIRE WEATHER...
A RED FLAG WARNING REMAINS IN EFFECT FOR THE ENTIRE AREA THRU 8 PM.
CLOUD COVER HAS KEPT TEMPS DOWN AND RH UP SO FAR ACROSS THE NRN
VA...ERN WV AND NRN MD WHERE NW WINDS OF 20-25 MPH HAVE BEEN
GUSTING TO 35 MPH. CLOUDS CONTINUE TO ERODE THOUGH AND RH IS NOW
IN THE 30S SO WILL KEEP THE RED FLAG WARNING IN EFFECT. FARTHER
SOUTH IN CENTRAL VA...RH HAS DROPPED BELOW 30 PERCENT BUT WINDS
ARE GENERALLY AROUND 15 MPH. AFTER COORDINATING WITH VA STATE FIRE
OFFICIALS...WILL ALSO KEEP RED FLAG WARNING IN EFFECT. WINDS
SUBSIDE TOWARD SUNSET AND RH VALUES WILL INCREASE ABOVE CRITICAL
THRESHOLDS.

DRIER AIR WILL CAUSE EVEN LOWER RH VALUES THURSDAY...BUT WINDS
WILL NOT BE AS STRONG. A FIRE WEATHER WATCH IS IN EFFECT FOR
PORTIONS OF CENTRAL AND NORTHEASTERN MARYLAND WHERE THE WINDS WILL
BE STRONGEST.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR DCZ001.
     FIRE WEATHER WATCH FROM THURSDAY MORNING THROUGH THURSDAY
     AFTERNOON FOR DCZ001.
MD...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR MDZ003>007-
     009>011-013-014-016>018-502.
     FIRE WEATHER WATCH FROM THURSDAY MORNING THROUGH THURSDAY
     AFTERNOON FOR MDZ004>007-009>011-013-014-018.
VA...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR VAZ025>031-
     036>040-042-050>057-501-502-504.
     FIRE WEATHER WATCH FROM THURSDAY MORNING THROUGH THURSDAY
     AFTERNOON FOR VAZ054.
WV...RED FLAG WARNING UNTIL 8 PM EDT THIS EVENING FOR WVZ050>053-
     055-502-504-506.
MARINE...SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 6 PM EDT
     THURSDAY FOR ANZ530>543.
     GALE WARNING UNTIL 6 PM EDT THIS EVENING FOR ANZ530>543.

&&

$$
SYNOPSIS...JRK
NEAR TERM...JRK
SHORT TERM...HAS
LONG TERM...DFH
AVIATION...JRK/HAS/DFH
MARINE...JRK/HAS/DFH
FIRE WEATHER...JRK







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