Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 260128
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
928 PM EDT FRI JUL 25 2014

.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE TO PUSH OFFSHORE TONIGHT. A WEAK
TROUGH WILL SET UP OVER THE AREA SATURDAY. AN UNSEASONABLY STRONG
COLD FRONT WILL APPROACH THE AREA SUNDAY BEFORE MOVING THROUGH
MONDAY. CANADIAN HIGH PRESSURE WILL RETURN FOR TUESDAY AND
WEDNESDAY.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 01Z...1018 MB SFC HIGH CENTERED OVER SERN VA/NERN NC BORDER.
SELY FLOW FROM THIS IS ACROSS THE LWX CWA...ALLOWING DEWPOINTS TO
RETURN TO THE MID TO UPR 50S...LOW TO MID 60S FOR CNTRL VA. MIN
TEMPS GENERALLY LOW 60S NW...MID 60S SOUTH...AND UPR 60S TO 70F
FOR URBAN NEAR SHORE LOCALES.

HIGH PRESSURE WILL BE WELL OFF THE EAST COAST SATURDAY MORNING AND
SLY FLOW WILL CONTINUE TO DRAW IN HIGHER DEWPTS AS WELL AS WARMER
TEMPS. FCST MAX TEMPS WILL REACH THE MID TO UPPER 80S SATURDAY
AFTERNOON. WESTERLY FLOW ALOFT WILL LEAD TO UPSTREAM DISTURBANCES
REACHING THE MID-ATLANTIC AND A LEE TROUGH TO FORM. A SHORTWAVE
TROUGH CURRENTLY RESPONSIBLE FOR SHOWERS AND THUNDERSTORMS ACROSS
IA-IL WILL REACH THE AREA SATURDAY AFTERNOON. IT IS EXPECTED TO
WEAKEN BUT WITH THE SLY FLOW ADVECTING WARM AND MOIST CONDITIONS
INTO THE REGION A FEW SHOWERS WILL BE POSSIBLE IN THE HIGHLANDS
AND AHEAD OF THE LEE TROUGH. SCATTERED SHOWERS WITH ISOLATED
THUNDERSTORMS ARE POSSIBLE ACROSS THE I-95 CORRIDOR SAT LATE
MORNING THROUGH THE AFTERNOON. ACTIVITY WILL WANE TOWARDS SUNSET.

A STRONG SHORTWAVE TROUGH WILL DROP INTO THE NRN PLAINS SATURDAY
WHILE CONVECTION WILL BE ONGOING AHEAD OF A COLD FRONT ACROSS THE
MIDWEST SATURDAY AFTERNOON AND EVENING. SOME SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO BECOME SEVERE AND THIS ACTIVITY WILL PROPAGATE
EASTWARD AND POTENTIALLY IMPACT THE POTOMAC HIGHLANDS LATE
SATURDAY NIGHT/EARLY SUNDAY MORNING. THERE ARE UNCERTAINTIES
PERTAINING TO THE TRACK OF A POTENTIAL MCS SUNDAY MORNING WHICH
WILL THEN IMPACT THE AMT OF CLOUD COVER AND THEREFORE INSTABILITY
THE MID- ATLANTIC GAINS ON SUNDAY.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
A WARM FRONT WILL MOVE ACROSS THE REGION SATURDAY NIGHT/SUN
MORNING AND MOISTURE WILL CONTINUE TO ADVECT INTO THE MID-ATLANTIC
SUNDAY. LOW PRESSURE WILL BE ACROSS THE GREAT LAKES AND A COLD
FRONT WILL BE STRETCHED FROM PA TO OHIO TO MO. AS THE STRONG
SHORTWAVE TROUGH NEARS SHEAR WILL INCREASE AND SHOWERS AND
THUNDERSTORMS ARE LIKELY. DEPENDING ON THE AMT OF INSTABILITY THE
REGION GETS WITH THE DEPARTING MCS FROM THE OHIO VALLEY... SEVERE
STORMS MAY BE POSSIBLE WITH THE THREATS OF DMG WINDS LARGE HAIL
ISOLATED TORNADOES AND HEAVY RAIN. SREF ENSEMBLE MEMBERS SHOW A
RANGE OF CAPE SOLUTIONS FOR SUNDAY WITH 500 TO 3000 J/KG POSSIBLE.
ONE THING THAT IS CERTAIN IS THAT SHEAR PROFILES INCREASE SUNDAY
AND HODOGRAPHS BECOME LINEAR WITH 40-50 KTS AT 10-15K FEET. A
STRONG LINE OF THUNDERSTORMS WILL BE POSSIBLE SUN AFTERNOON AND
EVENING.

OUTFLOW BOUNDARIES AND THE CLOSE PROXIMITY TO THE SFC LOW ACROSS
OH/PA/NY WILL LEAD TO THE THREAT OF SVR THUNDERSTORMS CAPABLE OF
PRODUCING TORNADOES.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
SHEAR PROFILES INCREASE MARKEDLY SUNDAY EVENING...INCLUDING IN THE
LOWEST FEW KILOMETERS. THIS WILL ENHANCE/ORGANIZE CONVECTION ON THE
NOSE OF A 50+ KNOT 500 MB JET. HIGH PWATS AND MODERATE CAPE SUGGEST
A MYRIAD OF HAZARDS FROM SEVERE WEATHER TO HEAVY RAIN PERSISTING
WELL INTO SUNDAY EVENING AS A STRONG SHORTWAVE TROUGH DIVES TOWARDS
THE REGION FROM THE GREAT LAKES.

MODELS DIFFER IN HOW QUICKLY THE UPPER TROUGH AND SURFACE COLD FRONT
CROSS THE AREA...BUT IF THE FRONT DOES NOT CLEAR THE COAST BY MONDAY
AFTERNOON THEN A SEVERE WEATHER THREAT COULD ARISE AGAIN. BEST
CHANCE FOR THIS WOULD BE EAST OF THE BLUE RIDGE MOUNTAINS.

FOLLOWING AN ACTIVE START TO THE WEEK...A LARGE AREA OF HIGH
PRESSURE WILL BUILD TOWARD THE REGION FROM CANADA RESULTING IN DRY
WEATHER AND BELOW NORMAL TEMPERATURES AND HUMIDITY FOR MOST OF THE
WEEK.

&&

.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS PREVAIL OUTSIDE OF VALLEY FOG LOCATIONS TONIGHT AS
MOISTURE INCREASES WITH THE HIGH NOW OFF THE COAST. SLY WINDS
AROUND 10-15 KTS WILL OCCUR THROUGH THE AFTERNOON. A FEW ISO
SHOWERS WILL BE POSSIBLE NEAR DCA-BWI-MTN SATURDAY AFTERNOON.
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE SUNDAY AND MVFR/IFR
CONDITIONS WILL BE POSSIBLE. A FEW THUNDERSTORMS MAY PRODUCE GUSTY
WINDS...LARGE HAIL AND ISOLATED TORNADOES.

MVFR OR LWR CIGS/VSBYS IN SHWRS/TSTMS SUN NIGHT-MON...IMPROVING TO
VFR MON NIGHT. SW WIND AROUND 10 KTS BECOMING NW 15-20 KTS AND GUSTY
MON EVENING W/ COLD FROPA.

&&

.MARINE...
SLY FLOW 10 TO 15 KT...WITH SOME POSSIBLE SCA GUSTS LATE
TONIGHT...MIDNIGHT SHIFT WILL HAVE TO MONITOR THIS. SLY FLOW WILL
INCREASE SATURDAY AFTERNOON AS CHANNELING OCCURS. A SCA IS IN
EFFECT FROM THE MD CHESAPEAKE BAY SOUTH OF POOLES ISLAND AND LOWER
TIDAL POTOMAC RIVER SUN AFTERNOON THROUGH THE EVENING. ISOLATED
SHOWERS ARE POSSIBLE SAT AFTERNOON.

A COLD FRONT APPROACHES SUNDAY AND SHOWERS AND THUNDERSTORMS ARE
LIKELY. SOME STORMS MAY PRODUCE GUSTY WINDS LARGE HAIL AND
WATERSPOUTS CREATING LOW VSBYS.

SHOWERS/STRONG STORMS LIKELY SUN NIGHT-MON...SUBSIDING MON EVENING.
SCA WINDS/SEAS PROBABLE MON EVENING INTO TUES WITH GUSTY NW FLOW
BEHIND COLD FRONT.

&&

.CLIMATE...
A RECORD EVENT REPORT (RER) WAS SENT FOR THE 57F THAT BWI REACHED
THIS MORNING. THAT IS A NEW MIN TEMP RECORD FOR BALTIMORE. IT
BROKE THE OLD RECORD OF 59F.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 1 PM SATURDAY TO 2 AM EDT SUNDAY FOR
     ANZ531>534-537-539>543.

&&

$$
SYNOPSIS...BAJ/HAS
NEAR TERM...BAJ/HAS
SHORT TERM...HAS/DFH
LONG TERM...DFH
AVIATION...BAJ/HAS/DFH
MARINE...BAJ/HAS/DFH
CLIMATE...BAJ







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