Severe Thunderstorm Warning 166, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
234 PM EDT WED JUL 9 2014

.SYNOPSIS...
A COLD FRONT WILL SLOWLY MOVE INTO THE AREA TONIGHT. THE BOUNDARY
WILL STALL OUT AND DISSIPATE OVER THE REGION FOR THURSDAY AND
FRIDAY. HIGH PRESSURE OVER THE ATLANTIC WILL BRING HOT AND HUMID
CONDITIONS FOR THE WEEKEND INTO EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
ANALYSIS THIS AFTERNOON SHOWS A COLD FRONT OVER PENNSYLVANIA AND
HIGH PRESSURE OVER THE ATLANTIC. A SURFACE TROUGH EXTENDS FROM
NORTH-CENTRAL MARYLAND INTO THE SHENANDOAH VALLEY.

MID-LEVEL CLOUDS HAVE GIVEN WAY TO SOME SUNSHINE...ALLOWING MORE
WARM AND HUMID CONDITIONS. MAX TEMPS WILL RANGE FROM THE 70S IN
THE MOUNTAINS TO THE UPPER 80S/NEAR 90 ACROSS MOST OTHER
LOCATIONS. THE WARM AND HUMID CONDITIONS HAVE LED AN UNSTABLE
ATMOSPHERE. THE LATEST MESOANALYSIS SHOWS 1000-1500 J/KG OF
MLCAPE...WITH THE HIGHEST TOTALS ALONG AND EAST OF THE SURFACE
TROUGH. THE TROUGH HAS ACTED AS THE MAIN LIFTING MECHANISM FOR
CONVECTION THAT HAS ALREADY DEVELOPED NEAR THE BLUE RIDGE
MOUNTAINS. SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS
AFTERNOON AND EVENING...AND WITH MODERATE CAPE AND MARGINAL SHEAR
PROFILES...THERE IS A THREAT FOR LOCALLY DAMAGING WIND GUSTS AND
LARGE HAIL. THE BEST CHANCE FOR SEVERE THUNDERSTORMS WILL BE
NEAR AND EAST OF THE BLUE RIDGE MOUNTAINS WHICH IS WHERE
INSTABILITY IS HIGHEST EAST OF THE SURFACE TROUGH. STILL DO NOT
EXPECT THE EVENT TO BE NEARLY AS WIDESPREAD AS TUESDAY SINCE SHEAR
AND INSTABILITY WILL NOT BE AS STRONG AND THE LIFTING MECHANISM
WILL NOT BE AS STRONG EITHER.

THE COLD FRONT WILL SLOWLY DROP INTO THE REGION TONIGHT.
CONVECTION SHOULD DISSIPATE ACROSS MOST AREAS DUE TO THE LOSS OF
DAYTIME HEATING...BUT AN ISOLATED SHOWER OR THUNDERSTORM CANNOT BE
RULED OUT MAINLY NEAR AND EAST OF INTERSTATE 95.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
AN UPPER-LEVEL TROUGH WILL BUILD OVERHEAD THURSDAY THROUGH
THURSDAY NIGHT. THE COLD FRONT OVER THE REGION WILL GRADUALLY
DISSIPATE...AND A LIGHT RETURN FLOW WILL DEVELOP DURING THIS TIME.
THIS MEANS THAT LITTLE DRY AIR WILL MAKE IT INTO THE AREA. WITH
HIGHER DEWPOINTS AND THE UPPER-LEVEL TROUGH BUILDING
OVERHEAD...MORE SHOWERS AND THUNDERSTORMS ARE POSSIBLE MAINLY IN
THE AFTERNOON AND EVENING. STILL FEEL CONVECTION COVERAGE WILL BE
SCATTERED SINCE THE SHEAR WILL BE WEAK AND ANY LIFTING MECHANISM
FROM THE BOUNDARY OR TERRAIN CIRCULATION WILL ALSO BE WEAK. HE
COLD FRONT WILL STALL OUT OVER THE REGION AND DISSIPATE. MAX TEMPS
WILL RANGE FROM THE 70S IN THE MOUNTAINS TO THE MIDDLE AND UPPER
80S ACROSS MOST OTHER LOCATIONS.

CONVECTION COVERAGE SHOULD DISSIPATE OVERNIGHT THURSDAY...BUT WITH
THE UPPER-LEVEL TROUGH OVERHEAD AN ISOLATED SHOWER OR THUNDERSTORM
CANNOT BE RULED OUT...ESPECIALLY ACROSS THE SOUTHEASTERN CWA WHERE
MOISTURE WILL BE DEEPEST.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
ILL-DEFINED SURFACE BOUNDARY WILL RETREAT NORTHWARD AS WARM FRONT
FOR FRIDAY. SUBSIDENCE ALOFT SHOULD HINDER CONVECTIVE DEVELOPMENT
FOR FRIDAY ALONG THIS FRONT ACROSS THE MAJORITY OF THE
AREA...ALTHOUGH STRONGER MOISTURE GRADIENT AND VORT MAX ALOFT MAY
TRIGGER DEVELOPMENT TOWARD SOUTHERN MARYLAND...ALONG WITH TERRAIN
CIRCULATION CONVECTIVE DEVELOPMENT ACROSS THE POTOMAC HIGHLANDS.
MOISTURE ADVECTS ACROSS THE REGION FOR SATURDAY AS HIGH PRESSURE
PUSHES OFF THE NORTHEAST COAST. WHILE INSTABILITY INCREASES WITH
THIS MOISTURE RETURN...SHORT WAVE RIDGING ALOFT SHOULD LIMIT
CONVECTIVE DEVELOPMENT. HOWEVER...CANNOT RULE OUT TERRAIN AND
SURFACE HEATING INDUCED AFTERNOON CONVECTION AT THIS TIME AND HAVE
LEFT POPS IN THE FORECAST. AS CLOSED CANADIAN LOW DIVES SOUTH OVER
THE GREAT LAKES...WESTERLY FLOW ALOFT INCREASES SUNDAY AND MONDAY.
SHORT WAVES IN THIS FLOW WILL BRING BETTER CHANCES FOR ORGANIZED
CONVECTION TO PUSH THROUGH SUNDAY AND MONDAY AHEAD OF SYNOPTIC COLD
FRONT. A MORE COMFORTABLE AIRMASS LOOKS TO ADVECT INTO THE REGION
FOR MID WEEK.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED THIS AFTERNOON
AND EVENING. LOCALLY GUSTY WINDS AND HAIL ARE POSSIBLE IN THE
STRONGER STORMS...BUT SEVERE STORMS WILL NOT BE AS WIDESPREAD AS
TUESDAY. A COLD FRONT WILL MOVE INTO THE AREA TONIGHT AND IT WILL
STALL OUT AND WEAKEN THURSDAY THROUGH THURSDAY NIGHT. A LIGHT
NORTHERLY FLOW IS EXPECTED BEHIND THE FRONT LATE TONIGHT INTO
THURSDAY MORNING...BUT WINDS WILL TURN TOWARD THE SOUTHEAST LATER
THURSDAY AND SPEEDS WILL REMAIN LIGHT. SCATTERED SHOWERS AND
THUNDERSTORMS ARE EXPECTED THURSDAY AFTERNOON AND EVENING.

PATCHY FOG IS POSSIBLE LATE TONIGHT INTO EARLY THURSDAY. MVFR
VSBYS ARE EXPECTED DURING THIS TIME...BUT IFR CONDITIONS CANNOT BE
RULED OUT ESPECIALLY ACROSS KMRB AND KCHO. MORE FOG IS POSSIBLE
THURSDAY NIGHT INTO FRIDAY MORNING.

A STALLED FRONT AND SURFACE TROUGH WILL BRING CHANCES OF
AFTERNOON STORMS TO THE REGION FRIDAY AND SATURDAY. AN APPROACHING
COLD FRONT WILL BRING A BETTER CHANCE OF MORE WIDESPREAD STORMS
SUNDAY AND MONDAY.

&&

.MARINE...
A SOUTHERLY FLOW WILL CONTINUE OVER THE WATERS THROUGH THIS
EVENING. WINDS WILL SHIFT TO THE NORTH LATE TONIGHT INTO THURSDAY
BEFORE GRADUALLY TURNING TOWARD THE SOUTHEAST THURSDAY AFTERNOON.
SPEEDS SHOULD REMAIN BELOW SCA CRITERIA. SHOWERS AND THUNDERSTORMS
ARE POSSIBLE...ESPECIALLY THIS AFTERNOON AND EVENING...AND AGAIN
THURSDAY AFTERNOON AND EVENING. THUNDERSTORMS MAY CONTAIN GUSTY
WINDS AND HAIL.

A STALLED FRONT AND SURFACE TROUGH WILL BRING CHANCES OF
AFTERNOON STORMS TO THE REGION FRIDAY AND SATURDAY. AN APPROACHING
COLD FRONT WILL BRING A BETTER CHANCE OF MORE WIDESPREAD STORMS
SUNDAY AND MONDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...AEB
AVIATION...BJL/AEB
MARINE...BJL/AEB

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