Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS61 KLWX 271406
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1006 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/...

SEVERE WEATHER EXPECTED TODAY AND TONIGHT FOR THE MID-ATLANTIC REGION.

AS OF 14Z...AN UPPER LEVEL DISBURBANCE HAS REACHED THE
APPALIACIANS IN THE WESTERLY FLOW ALOFT. SHOWERS ARE EXITING THE
NRN PIEDMONT AND SRN MD THIS MORNING IN RESPONSE TO A DISTURBANCE
THAT CAME THROUGH THIS MORNING. SUBSIDENCE BEHIND THE FIRST
DISTURBANCE HAS LED TO CLEARING ACROSS NRN MD AND THE POTOMAC
HIGHLANDS. ALTHOUGH MID TO HIGH LEVEL CLOUDS ARE BEGINING TO
STREAM INTO FROM THE NEXT DISTURBANCE...PATCHES OF CLEARING WILL
CONTINUE FROM WEST TO EAST AHEAD OF THE NEXT DISTURBANCE LEADING
TO DESTABILIZATION ACROSS THE AREA. A LULL OF ACTIVITY IS EXPECTED
THIS MORNING AS THE ATM BECOMES MORE UNSTABLE. PER THE 12Z IAD
RAOB...CAPE VALUES ARE EXPECTED TO BE AROUND 2K-2.5K J/KG BY THIS
AFTERNOON AND EVENING. 0-6KM SHEAR OF 42KTS AND 0-1KM OF 17 KTS
ARE OBSERVED IN THE SOUNDING RAOB. THIS SHEAR PROFILE IS FAVORABLE
FOR ORGANIZED CONVECTION TODAY AND WILL LIKELY INCREASE THIS
AFTERNOON AND EVENING.

THUNDERSTORMS ACROSS IN/OH/KY WILL MOVE EASTWARD WITH TIME. THESE
SHOWERS WILL HAVE A OVERALL SE-E TRACK AND REACH THE CENTRAL
FOOTHILLS BY MIDDAY. MID TO HIGH LEVEL CLOUDS WILL LIMIT
INSTABILITY SOME AND THEREFORE CONVECTION SHOULD BE ISO-SCT AS IT
REACHES THE REGION. ELSEWHERE...THUNDERSTORMS ARE EXPECTED TO
INTIATE THIS AFTERNOON ACROSS THE OHIO VALLEY FROM LAKE ERIE
THROUGH THE OHIO VALLEY AHEAD OF THE MAIN SHORTWAVE TROUGH AND
COLD FRONT. THESE STORMS WILL TRACK EASTWARD AND BE STRONG. ANY
HEATING BOUNDARY OR OUTFLOW FROM DECAYING THUNDERSTORMS WILL ALSO
LIKELY CAUSE THUNDERSTORM INTIATION ACROSS THE REGION THIS
AFTERNOON. COVERAGE IS EXPECTED TO BE SCATTERED THIS AFTERNOON BUT
CONDITIONS ARE FAVORABLE FOR SEVERE THUNDERSTORMS.

PREVIOUS DISCUSSION...
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 /13Z 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 DISCUSSIONS...BJL/WOODY!







USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.