Severe Thunderstorm Warning 235, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
307 PM EDT FRI JUL 27 2012

.SYNOPSIS...
A COLD FRONT WILL APPROACH THIS EVENING AND SLOWLY MOVE THROUGH
THE REGION TONIGHT. THE FRONT WILL REMAIN JUST TO THE SOUTH
THROUGH THE WEEKEND. A TROUGH OF LOW PRESSURE WILL BRING UNSETTLED
CONDITIONS TO THE AREA DURING THE EARLY AND MIDDLE PORTION OF NEXT
WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT FOR PORTIONS OF
CENTRAL VIRGINIA UNTIL 10 PM.

COLD FRONT CURRENTLY DRAPED ACROSS NORTHERN OH/PA WILL SAG SOUTHEAST
TOWARD THE CENTRAL MID ATLANTIC THIS EVENING. A PRE-FRONTAL TROUGH
EXTENDS FROM THE NE CORNER OF MD SWWD INTO SRN WV. SHOWERS AND
TSTMS HAVE FIRED ALONG THIS FRONT. THE MOST SIGNIFICANT ACTIVITY
IS ACROSS SRN WV. OVER OUR CWA...ACTIVITY IS SO FAR LIMITED TO
ISOLATED HEAVY SHOWERS OVER NE MD AND A LINE OF HEAVY SHOWERS OVER
THE POTOMAC HIGHLANDS. THIS ACTIVITY WILL MOVE GENERALLY ESE THIS
AFTERNOON AND INTO THE EVENING. CLOUD COVER ACROSS NRN VA AND MD
HAS LIMITED INSTABILITY THIS AFTERNOON...WITH 1200 J/KG CAPE NOTED
ON 18Z KIAD RAOB. 750MB CAP IS ERODED THOUGH. WITHOUT THE CAP AND
FAVORABLE SHEAR...ENVIRONMENT REMAINS FAVORABLE FOR POTENTIAL
SEVERE WIND GUSTS/HAIL WITH ANY STORMS THAT DEVELOP. SEVERE TSTM
WATCH IS IN EFFECT FOR THE SOUTHERN TIER COUNTIES IN THE CWA.

REGARDING TEMPS...HAVE CONTINUED HEAT ADVISORY OVER THE
BALTIMORE/WASHINGTON METROS. HEATING HAS BEEN LIMITED BY CLOUD
COVER...WITH TEMPS IN THE LOW 90S OVER METRO DC AND BALTIMORE
EARLY AFTERNOON. THE CLOUD CANOPY IS THIN WITH SOME BREAKS AND DEW
POINTS ARE IN THE LOW 70S...SO NOT CONFIDENT ENOUGH THAT CRITERIA
WILL NOT BE REACHED TO CANCEL THE ADVISORY. THIS WILL BE
MONITORED...AND IT MAY BE CANCELED EARLY IF NECESSARY.

COLD FRONT MOVES THROUGH THE REGION TONIGHT. SHOWER/TSTM ACTIVITY
POSSIBLE OVER WESTERN PORTIONS OF THE FORECAST AREA ASSOCIATED
WITH THE FRONT...ALONG WITH CONTINUED TSTM THREAT LATE THIS
EVENING NEAR CHES BAY WITH THE PRE-FRONTAL TROUGH. DIURNAL
INSTABILITY WILL DECREASE OVERNIGHT...SO GENERAL THREAT OF
TSTMS WILL DIMINISH. OVERNIGHT LOWS RANGE FROM THE 60S OVER THE
POTOMAC HIGHLANDS TO THE UPPER 70S OVER METRO BALTIMORE/WASHINGTON.

&&

.SHORT TERM /SATURDAY/...
SURFACE COLD FRONT EXPECTED TO BE EAST OF THE AREA
SATURDAY...WHILE AN UPPER TROUGH APPROACHES FROM THE WEST. COULD
SEE SOME SHOWER/TSTM ACTIVITY TRIGGERED BY THE TROUGH AND DAYTIME
INSTABILITY. TEMPERATURES WILL BE HOT AGAIN...BUT WITH LOWER
DEWPOINTS IN THE 60S...HEAT INDICES SHOULD REMAIN BELOW 100.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
AN UPPER-LEVEL TROUGH OF WILL REMAIN OVER THE REGION DURING THE
WEEKEND WHILE A STATIONARY BOUNDARY WEAKENS TO OUR SOUTH.
DISTURBANCES ASSOCIATED WITH THE UPPER-LEVEL TROUGH WILL PASS
THROUGH THE REGION AS WELL. DESPITE BEING ON THE COOL SIDE OF THE
STATIONARY BOUNDARY...THERE WILL BE ENOUGH MOISTURE AND LIFT
ASSOCIATED WITH THE TROUGH FOR POSSIBLE SHOWERS AND
T-STORMS...ESPECIALLY SATURDAY EVENING AND AGAIN SUNDAY AFTERNOON
AND EVENING. HOWEVER...MUCH OF THE TIME WILL TURN OUT DRY WITH
SEASONABLE TEMPERATURES.

MIN TEMPS SATURDAY NIGHT WILL RANGE FROM THE LOWER 60S IN THE
POTOMAC HIGHLANDS TO THE LOWER AND MIDDLE 70S IN WASHINGTON. MAX
TEMPS SUNDAY WILL RANGE FROM THE 70S IN THE MOUNTAINS TO THE UPPER
80S/NEAR 90 ACROSS MOST OTHER LOCATIONS. MIN TEMPS SUNDAY NIGHT WILL
RANGE FROM THE 50S IN THE POTOMAC HIGHLANDS TO THE LOWER AND MIDDLE
70S IN WASHINGTON/BALTIMORE.

THE UPPER-LEVEL TROUGH WILL REMAIN OVERHEAD FOR MONDAY AND TUESDAY.
THE STATIONARY BOUNDARY TO OUR SOUTH WILL CONTINUE TO DISSIPATE AND
HIGH PRESSURE OVER THE ATLANTIC WILL CAUSE A SOUTHERLY RETURN FLOW
TO DEVELOP. INCREASED MOISTURE FROM THE SOUTHERLY FLOW WILL COMBINE
WITH COOLER AIR ALOFT FROM THE TROUGH TO CAUSE UNSETTLED CONDITIONS.
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED DURING THIS
TIME...ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS EACH DAY.

A WEAK COLD FRONT WILL PASS THROUGH THE AREA WEDNESDAY WHILE THE
TROUGH REMAINS OVERHEAD. MORE SHOWERS AND T-STORMS ARE POSSIBLE.
LITTLE CHANGE IN TEMPERATURE OR HUMIDITY IS EXPECTED BEHIND THE
BOUNDARY FOR LATE IN THE WEEK. MORE UNSETTLED CONDITIONS ARE
POSSIBLE WITH THE TROUGH REMAINING IN PLACE.

NEAR SEASONABLE TEMPERATURES ARE EXPECTED THROUGHOUT THE
PERIOD...BUT IT WILL FEEL HUMID.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
SHOWERS AND THUNDERSTORMS HAVE DEVELOPED NEAR THE VA/WV BORDER.
THIS ACTIVITY LIKELY TO IMPACT KCHO LATE THIS AFTERNOON.
ADDITIONAL SHOWERS/TSTMS MAY DEVELOP FURTHER NORTH AND IMPACT THE
OTHER TERMINALS WITH BRIEF IFR CONDITIONS AND GUSTY WINDS. OUTSIDE
OF THE STORMS...SOME GUSTY NW WINDS EXPECTED AT BALTIMORE/DC
TERMINALS THIS AFTERNOON.

COLD FRONT SLOWLY CROSSES TONIGHT. GENERALLY VFR CONDITIONS UNDER
MID-LEVEL CLOUDS...BUT MVFR FOG PSBL AT KCHO/KMRB.

VFR PREVAILING SATURDAY. A FEW SHOWERS/TSMS ARE POSSIBLE WITH
OCCASIONAL SUB-VFR.

A STATIONARY BOUNDARY WILL REMAIN SOUTH OF THE TERMINALS SATURDAY
NIGHT THROUGH SUNDAY...BUT AN UPPER-LEVEL TROUGH WILL TRIGGER
SCATTERED SHOWERS/T-STORMS...MAINLY SATURDAY EVENING AND AGAIN
SUNDAY AFTERNOON/EVENING. VFR CONDITIONS ARE EXPECTED MOST OF THE
TIME. HOWEVER...PATCHY BR MAY REDUCE VSBYS TO MVFR LEVELS EARLY
SUNDAY MORNING.

A SOUTHERLY FLOW WILL DEVELOP EARLY NEXT WEEK...AND MOISTURE WITH
THE SOUTHERLY FLOW WILL COMBINE WITH THE TROUGH OVERHEAD FOR MORE
SHOWERS AND T-STORMS. A COLD FRONT MAY PASS THROUGH THE TERMINALS
WEDNESDAY.

&&

.MARINE...
WLY/NWLY FLOW AROUND 10 KT CONTINUE THROUGH THIS AFTERNOON.
OCCASIONAL GUSTS TO NEAR 20 KT PSBL ON THE WATERS NEAR WASHINGTON
DC AND BALTIMORE INNER HARBOR...SO ISSUED MWS. SCATTERED
THUNDERSTORMS EXPECTED LATE THIS AFTERNOON AND INTO THE OVERNIGHT
WITH A DAMAGING WIND THREAT AHEAD/ALONG A SLOW MOVING COLD FRONT.

THE FRONT WILL BECOME STATIONARY AND WEAKEN JUST SOUTH OF THE
WATERS SATURDAY AND SUNDAY. A RETURN FLOW WILL DEVELOP EARLY NEXT
WEEK BEFORE A WEAK COLD FRONT APPROACHES WEDNESDAY. UNSETTLED
CONDITIONS ARE EXPECTED THROUGHOUT THIS TIME WITH SCATTERED
SHOWERS AND T-STORMS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...HEAT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR DCZ001.
MD...HEAT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR MDZ006-007-011-
     013-014-016>018.
VA...HEAT ADVISORY UNTIL 7 PM EDT THIS EVENING FOR VAZ052>057.
WV...NONE.
MARINE...NONE.

&&

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

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
403 PM EDT FRI JUL 27 2012

VAZ025-026-037>039-272045-
GREENE VA-MADISON VA-ROCKINGHAM VA-ALBEMARLE VA-AUGUSTA VA-
403 PM EDT FRI JUL 27 2012

...STRONG THUNDERSTORM TO AFFECT GREENE...MADISON...ROCKINGHAM...
ALBEMARLE AND AUGUSTA COUNTIES...

AT 403 PM EDT...A STRONG THUNDERSTORM WAS LOCATED OVER ROCKY BAR...
MOVING EAST AT 35 MPH.

LOCATIONS IMPACTED INCLUDE STANARDSVILLE.

WIND GUSTS OF 40 TO 50 MPH CAN BE EXPECTED WITH THIS STORM.

&&

LAT...LON 3842 7831 3813 7840 3822 7889 3841 7882
TIME...MOT...LOC 2003Z 272DEG 30KT 3832 7871

HTS