Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 271135
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
735 AM EDT SUN JUL 27 2014

.SYNOPSIS...
LOW PRESSURE OVER MINNESOTA IS EXPECTED TO TRACK ACROSS PENNSYLVANIA
TONIGHT. AN ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION MONDAY.
HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BRINGING COOLER AND
DRIER CONDITIONS DURING MIDWEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATE...COASTAL FLOOD ADVISORY FOR ANNE ARUNDEL COUNTY IS CANCELED.

A SERIES OF UPPER-LEVEL DISTURBANCES ARE LOCATED IN THE WESTERLY
FLOW ALOFT. ONE IS OVERHEAD EARLY THIS MORNING WHILE ANOTHER ONE IS
TRACKING THROUGH THE OHIO VALLEY. A SOUTHERLY FLOW AROUND HIGH
PRESSURE OVER THE ATLANTIC HAS USHERED IN MORE MOISTURE...CAUSING
INSTABILITY TO INCREASE. THE COMBINATION OF INCREASED INSTABILITY
AND FORCING FROM THE UPPER-LEVEL DISTURBANCES HAS TRIGGERED SOME
SHOWERS AND THUNDERSTORMS.

THE FIRST DISTURBANCE WILL MOVE OFF TO OUR EAST EARLY THIS
MORNING...BUT THE OTHER ONE IS EXPECTED TO PASS THROUGH OUR AREA
LATER THIS MORNING INTO EARLY THIS AFTERNOON...BRINGING MORE SHOWERS
AND THUNDERSTORMS. AS OF NOW...IT APPEARS THAT ANY THREAT FOR SEVERE
THUNDERSTORMS THIS MORNING INTO EARLY THIS AFTERNOON WILL BE LIMITED
DUE TO CLOUD COVER...MARGINAL PROFILES AND PRECIPITATION KEEPING
INSTABILITY SOMEWHAT LIMITED.

HOWEVER...THERE MAY BE A BREAK IN THE ACTION AS THE UPPER-LEVEL
DISTURBANCE MOVES OFF TO OUR EAST THIS AFTERNOON. THERE SHOULD AT
LEAST BE SOME BREAKS OF SUNSHINE...AND WITH DEWPOINTS IN THE UPPER
60S AND 70S...THIS SHOULD BE ENOUGH TO CAUSE MODERATE AMOUNTS OF
INSTABILITY TO DEVELOP. NAM/GFS BUFKIT ARE INDICATING BETWEEN 1000
AND 2000 J/KG OF MLCAPE LATER THIS AFTERNOON INTO THIS EVENING. A
POTENT SHORTWAVE AND COLD FRONT WILL TRACK INTO THE OHIO VALLEY THIS
EVENING. THIS WILL STRENGTHEN THE UPPER-LEVEL AND LOWER-LEVEL FLOW
OVER OUR AREA...CAUSING SHEAR PROFILES TO BE HIGHLY FAVORABLE FOR
SEVERE THUNDERSTORMS.

SHOWERS AND THUNDERSTORMS ARE EXPECTED TO BREAK OUT AHEAD OF THE
COLD FRONT OVER THE OHIO VALLEY INTO WEST VIRGINIA THIS
AFTERNOON...AND THIS ACTIVITY WILL LIKELY SPREAD THROUGH OUR AREA
LATER THIS AFTERNOON AND EVENING. THIS IS GOING TO BE THE TIME WHEN
SEVERE WEATHER IS MOST LIKELY...WHICH WOULD BE LATER THIS AFTERNOON
INTO EARLY THIS EVENING WEST OF THE BLUE RIDGE MOUNTAINS AND THIS
EVENING EAST OF THE BLUE RIDGE MOUNTAINS. HOWEVER...KEEP IN MIND
THAT SEVERE STORMS OUT AHEAD OF THIS LINE MAY DEVELOP ACROSS ALL
AREAS THIS AFTERNOON. THE COMBINATION OF THE INSTABILITY...SHEAR
PROFILES AND LIFTING MECHANISMS SUCH AS OUTFLOW BOUNDARIES...A
SURFACE TROUGH AND THE APPROACHING COLD FRONT WILL ENHANCE THE
THREAT FOR SEVERE THUNDERSTORMS. IN FACT SUPERCELLS WITH SIGNIFICANT
SEVERE WEATHER IS POSSIBLE THIS AFTERNOON AND EVENING IF THE
INGREDIENTS ALL COME TOGETHER. DAMAGING WINDS...LARGE HAIL AND
ISOLATED TORNADOES WILL BE THE PRIMARY THREATS ALONG WITH VERY HEAVY
RAINFALL.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
THE POTENT SHORTWAVE WILL MOVE INTO UPSTATE NEW YORK LATER TONIGHT
WHILE THE POTENT COLD FRONT LIKELY JUMPS TO THE PRESSURE TROUGH OFF
TO OUR EAST BY MONDAY MORNING. THE DRY SLOT ALONG WITH COLD
ADVECTION SHOULD SUPPRESS CONVECTION LATE TONIGHT. MIN TEMPS WILL
RANGE FROM THE 50S IN THE ALLEGHENY HIGHLANDS TO THE LOWER AND
MIDDLE 70S IN WASHINGTON AND BALTIMORE.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
THE NEXT 24 HRS LOOK TO BE VERY ACTIVE WX WISE...WITH A DOWNWARD
TREND IN ACTIVITY EXPECTED THEREAFTER. CD FNT LOOKS TO BE MOVING
OFFSHORE MIDDAY MON...BRINGING AN END TO THE CNVCTV CHCS AND
USHERING IN THE COOLER AIR THAT WL END WHAT IS TYPICALLY THE
HOTTEST TIME IN THE HOTTEST MONTH OF THE YR (CLIMATOLOGICALLY
TEMPS BEGIN TO DROP IN EARLY AUG). BRZY CONDS AREA XPCTD MON AFTN.

AFTR THAT SVRL DAYS OF M CLR SKIES W/ COMFORTABLE TEMPS ARE XPCTD.
DWPTS IN THE 50S...HARD NOT TO ENJOY THAT IN JUL. HIGH TEMPS TUE-THU
SHOULD BE IN THE LM80S (COOLER IN THE MTNS) W/ LOWS IN THE MU50S.
(WARMER IN THE CITIES). NO REALLY HOT WX ON TAP FOR THE MID ATLC RGN.

AS HAS BEEN DISCUSSED B4 THE PRIMARY REASON FOR THIS IS THE UPR
LVL WRN RDG/ERN TROF. DRY AND HOT IN THE W - NW ICC WEB SITE SHOWS
MULTIPLE WILDFIRES ONGOING IN OR/WA - W/ 2 IN WA BEING ESPECIALLY
LARGE. THIS PATTERN LOOKS TO RMN IN PLACE UNTIL AT LEAST NEXT
WKND.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED THROUGH THIS
EVENING. THUNDERSTORMS MAY BECOME SEVERE...ESPECIALLY LATER THIS
AFTERNOON AND EVENING. DAMAGING WINDS...LARGE HAIL AND ISOLATED
TORNADOES ARE POSSIBLE. CIGS/VSBYS WILL BE REDUCED TO MVFR/IFR
LEVELS BRIEFLY DURING TIMES OF CONVECTION.

CONVECTION SHOULD DISSIPATE OVERNIGHT AS A COLD FRONT MOVES OFF TO
OUR EAST.

CD FNT WL CROSS THE AREA MON MRNG. LINGERING SHOWERS/ANY LOWER CIGS
SHOULD IMPROVE BY AFTN THEN GUSTY NWRLY WINDS. THESE SHOULD
DIMINISH BY EVE. VFR CONDS MON NGT THRU THU.

&&

.MARINE...
A SOUTHERLY FLOW WILL CONTINUE THROUGH TONIGHT. A SMALL CRAFT
ADVISORY IS IN EFFECT FOR THE WATERS THIS AFTERNOON AND EVENING.
IT WILL BE MARGINAL DUE TO RELATIVELY COOLER WATERS...BUT A
STRENGHENING PRESSURE GRADIENT AND WIND FIELD SHOULD CAUSE GUSTS
AROUND 20 KNOTS. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR LATE
TONIGHT ALONG THE MARYLAND CHESAPEAKE BAY FROM SANDY POINT TO
SMITH POINT AND THE LOWER TIDAL POTOMAC RIVER FROM COBB ISLAND TO
SMITH POINT. ROUNDS OF SHOWERS AND THUNDERSTORMS ARE EXPECTED
THROUGH TONIGHT. SEVERE THUNDERSTORMS ARE A CONCERN...ESPECIALLY
LATER THIS AFTERNOON THROUGH THIS EVENING. DAMAGING WINDS...LARGE
HAIL AND ISOLATED WATERSPOUTS ARE POSSIBLE. PLEASE PAY ATTENTION
TO THE LATEST FORECASTS REGARDING WATCHES AND WARNINGS FOR SEVERE
WEATHER.

SCA IN EFFECT FOR ALL OF THE WATERS DURG THE DAY MON AS A CD FNT
MOVES OFFSHORE AND WNW WINDS STRENGTHEN. NO PROBS FORESEEN MON
NGT-MIDWK.

&&

.TIDES/COASTAL FLOODING...
A SOUTHERLY FLOW HAS CAUSED TIDAL ANOMALIES BETWEEN ONE HALF AND ONE
FOOT ABOVE NORMAL EARLY THIS MORNING. WILL HAVE TO KEEP AN EYE
ALONG THE UPPER TIDAL POTOMAC SHORE NEAR WASHINGTON DC. AT THIS
TIME...THE FLOW APPEARS THAT IT IS LIGHT ENOUGH FOR WATER LEVELS
TO REMAIN JUST BELOW MINOR FLOODING THRESHOLDS NEAR HIGH TIDE THIS
MORNING.

THE HIGH TIDE THIS AFTERNOON WILL BE THE LOWER OF THE TWO...SO NO
TIDAL FLOODING IS EXPECTED. THE FLOW WILL BEGIN TO TURN OFFSHORE
LATE TONIGHT SO ANOMALIES SHOULD COME DOWN A BIT. THEREFORE...TIDAL
FLOODING IS NOT EXPECTED.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO MIDNIGHT EDT
     TONIGHT FOR ANZ530-531-535-536-538-539-542.
     SMALL CRAFT ADVISORY FROM 10 AM TO 7 PM EDT MONDAY FOR ANZ530-
     531-535-536-538-539-542.
     SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 7 PM EDT
     MONDAY FOR ANZ532>534-537-540-541-543.

&&

$$
UPDATE...HAS
PREVIOUS DISCUSSION...BJL/WOODY!







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