Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 252126
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
526 PM EDT THU JUN 25 2015

.SYNOPSIS...
A WARM FRONT WILL STALL OUT NEAR NORTHERN MARYLAND THIS EVENING.
LOW PRESSURE WILL MOVE ACROSS THE AREA TONIGHT AND A COLD FRONT
WILL STALL ACROSS THE AREA FRIDAY. THE BOUNDARY WILL BUILD NORTH
AS A WARM FRONT FRIDAY NIGHT INTO SATURDAY BEFORE LOW PRESSURE
PASSES BY TO THE NORTH SATURDAY EVENING. THE COLD FRONT WITH THE
LOW WILL MOVE THROUGH THE AREA SATURDAY NIGHT AND HIGH PRESSURE
WILL BUILD TOWARD THE AREA EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
A POTENT UPPER-LEVEL DISTURBANCE IS TRACKING THROUGH THE OHIO
VALLEY THIS AFTERNOON. A WARM FRONT IS MOVING NORTH TOWARD
NORTHERN VIRGINIA.

THE WARM FRONT WILL STALL OUT NEAR NORTHERN MARYLAND AREA LATE
THIS AFTERNOON AND EVENING. A SOUTHERLY FLOW BEHIND THE BOUNDARY
WILL USHER IN MUCH MORE MOISTURE...WITH DEWPOINTS RETURNING TO THE
UPPER 60S AND LOWER 70S. THE INCREASED MOISTURE WILL ALLOW FOR
INSTABILITY TO DEVELOP. THE UPPER-LEVEL DISTURBANCE...WHICH IS THE
REMNANTS FROM AN MCS EARLIER TODAY...WILL ALSO BE MOVING THROUGH
OUR AREA LATE THIS AFTERNOON AND EVENING. THIS WILL CAUSE SHOWERS
AND THUNDERSTORMS TO INCREASE IN COVERAGE FROM WEST TO EAST DURING
THIS TIME. THERE IS A THREAT FOR SEVERE THUNDERSTORMS...WITH
DAMAGING WIND GUSTS AND LARGE HAIL BEING THE PRIMARY THREATS.
CERTAINTY IS STILL A BIT LOW DUE TO QUESTIONS ABOUT EXACTLY HOW
UNSTABLE THE ATMOSPHERE WILL BE. ALTHOUGH SEVERE WEATHER CANNOT BE
RULED OUT ACROSS THE ENTIRE CWA...THE BEST CHANCE FOR SEVERE
THUNDERSTORMS AT THIS TIME APPEARS THAT IT WILL BE ACROSS CENTRAL
VIRGINIA INTO SOUTHERN MARYLAND...AND A SEVERE THUNDERSTORM WATCH
IS NOW IN EFFECT FOR THIS AREA UNTIL MIDNIGHT. THIS IS WHERE
CONFIDENCE IS HIGHEST FOR MORE INSTABILITY DUE TO SOUTHERLY WINDS
AND GREATER SUNSHINE TODAY. ALSO...WITH THE BOUNDARY OVERHEAD
THERE IS A THREAT FOR AN ISOLATED TORNADO AS WELL.

THE DEEP MOISTURE WILL ALSO CAUSE PWATS TO SURGE LATE THIS
AFTERNOON AND EVENING. THUNDERSTORMS WILL CONTAIN VERY HEAVY
RAINFALL. LOCALIZED FLASH FLOODING IS POSSIBLE DURING THIS TIME.
DID NOT ISSUE A FLASH FLOOD WATCH AT THIS TIME DUE TO THE FAST
MOVEMENT OF THUNDERSTORMS DUE TO STRONGER WINDS ALOFT. COVERAGE OF
CONVECTION SHOULD DISSIPATE OVERNIGHT...BUT LEFT CHANCE POPS IN
SINCE THE STALLED BOUNDARY WILL REMAIN NEARBY.

THE BOUNDARY WILL DROP SLOWLY SOUTH AS A COLD FRONT FRIDAY...BUT
THERE WILL BE LITTLE DEWPOINT OR TEMPERATURE GRADIENT ASSOCIATED
WITH IT. LOW PRESSURE WILL STRENGTHEN AS IT MOVES THROUGH THE
MIDWEST...BUT IT SHOULD REMAIN FAR ENOUGH AWAY NOT TO HAVE
SIGNIFICANT IMPACT ON OUR WEATHER YET. A FEW SHOWERS AND
THUNDERSTORMS ARE EXPECTED DUE TO THE HEATING OF THE DAY. THE BEST
CHANCE FOR THUNDERSTORMS WILL BE FROM THE POTOMAC HIGHLANDS INTO
CENTRAL VIRGINIA WHERE INSTABILITY WILL BE A BIT HIGHER SOUTH AND
WEST OF THE BOUNDARY. MAX TEMPS WILL RANGE FROM THE UPPER 70S IN
NORTHERN MARYLAND TO THE MID AND UPPER 80S ACROSS CENTRAL
VIRGINIA.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
LOW PRESSURE WILL TRACK INTO THE OHIO VALLEY FRIDAY NIGHT AND IT
WILL STRENGTHEN AS IT DOES SO...THANKS TO A POTENT UPPER-LEVEL
TROUGH THAT WILL BE DEVELOPING OVERHEAD. THE STALLED BOUNDARY WILL
REMAIN OVER OUR REGION DURING THIS TIME...AND WITH THE INCREASED
WIND FIELD THIS WILL ALLOW FOR SOUTHERLY WINDS ALOFT TO OVERRUN
RELATIVELY COOLER AIR NEAR THE SURFACE. ISENTROPIC LIFT AND A
STRENGTHENING LOW-LEVEL JET WITH SUBTROPICAL MOISTURE WILL LEAD TO
MORE SHOWERS AND THUNDERSTORMS. LOCALLY HEAVY RAIN IS
POSSIBLE...ESPECIALLY ACROSS THE POTOMAC HIGHLANDS AND SHENANDOAH
VALLEY WHERE FORCING WILL BE STRONGER CLOSER TO THE APPROACHING
LOW.

LOW PRESSURE WILL INTENSIFY AS IS DRIFTS NORTHEAST FROM OHIO
SATURDAY MORNING...REACHING LAKE ONTARIO SATURDAY NIGHT. HEAVY RAIN
IS EXPECTED TO BREAK OUT LATE SATURDAY NIGHT AS A WARM FRONT LIFTS
NORTH ACROSS THE AREA. THE CWA WILL BE IN THE WARM SECTOR OF THE LOW
SATURDAY WITH LIFTED INDEX OF MINUS 5-10 AND PWATS WILL BE AROUND
TWO INCHES. PLENTY OF DYNAMICS FROM THE LOW TO THE NW. THEREFORE A
SEVERE...TORNADO...AND FLASH FLOOD THREAT EXISTS FOR THE DAY INTO
THE EVENING. MAX TEMPS DEPEND ON TEMPERATURE ADVECTION VS CLOUDS AND
RAIN. CURRENTLY THINKING LOW TO MID 70S NWRN HALF OF THE CWA AND UPR
70S LOW 80S SERN HALF.

COLD FRONT CROSSES THE AREA LATE SATURDAY NIGHT WITH NWLY FLOW
CUTTING OFF PRECIP. MIN TEMPS LOW TO MID 60S INLAND...AROUND 70
URBAN/NEAR SHORE.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AFTER A WET SAT...RAIN BEGINS TO CLEAR THE AREA BY SUN MORNING...AS
THE COLD FRONT PUSHES THROUGH THE AREA. COULD BE A FEW SHOWERS LEFT
ON THE BACK SIDE IN THE HIGHER TERRAIN OF OUR FAR WEST...THOUGH
EXPECT THOSE TO BE RATHER LIGHT. OTHER THAN THAT...IF WE ARE ABLE TO
CLEAR SOON ENOUGH...SUN COULD BE A VERY NICE DAY WITH TEMPS IN U60S
WEST AND M/U 70S ALONG 95 CORRIDOR...DEWPOINTS ALSO IN M/U 50S.

MON LOOKS QUIET...WITH TEMPS REMAINING AOB NORMAL AND NO CHANCE OF
PRECIP. NEXT CHANCE FOR UNSETTLED WEATHER TUE WITH WARM FRONT NEAR
AREA. WHILE MODELS BEGIN TO DIVERGE BEYOND TUE...REMAINDER OF PERIOD
APPEARS RELATIVELY QUITE...COMPARED TO RECENT DAYS...WITH TEMPS NEAR
NORMAL AND LITTLE CLEAR SIGNAL FOR PRECIP.

&&

.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
TERMINALS WILL BE IMPACTED THIS EVENING DUE TO SHOWERS AND
THUNDERSTORMS. A FEW STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE
MAINLY AROUND KCHO. COVERAGE OF CONVECTION SHOULD DIMINISH
OVERNIGHT...BUT A COUPLE SHOWERS CANNOT BE RULED OUT.

SHRA/TSRA EXPECTED TO MOVE IN FROM WEST TO EAST BETWEEN 21Z AND
3Z THIS AFTERNOON/EVENING. SOME THUNDERSTORMS MAY BECOME SEVERE
WITH LOCALLY DAMAGING WINDS AND LARGE HAIL BEING THE PRIMARY
THREATS. AN ISOLATED TORNADO CANNOT BE RULED OUT. THE BEST CHANCE
FOR SEVERE STORMS WILL BE ACROSS THE SOUTHERN
TERMINALS...KCHO...KIAD AND KDCA.

PATCHY FOG IS POSSIBLE LATE TONIGHT INTO EARLY FRIDAY MORNING. VFR
CONDITIONS ARE EXPECTED FOR MOST OF FRIDAY. A FEW SHOWERS AND
THUNDERSTORMS ARE POSSIBLE FRIDAY AFTERNOON...ESPECIALLY ACROSS
KCHO. SHOWERS AND THUNDERSTORMS WILL INCREASE IN COVERAGE FRIDAY
NIGHT AS LOW PRESSURE APPROACHES FROM THE WEST. AN EASTERLY FLOW
AHEAD OF THIS WILL ALSO CAUSE LOW CLOUDS. IFR CONDITIONS ARE
POSSIBLE.

REDUCED AVIATION CONDS ALL DAY SATURDAY THROUGH THE EVENING AS A
WARM FRONT LIFTS THROUGH THE AREA EARLY SATURDAY MORNING AND A HUMID
AND UNSTABLE AIRMASS IS IN PLACE UNTIL A COLD FRONT LATE SATURDAY
NIGHT. HEAVY THUNDERSTORMS WITH A SEVERE...TORNADO...AND FLOOD
THREAT. STORMS END SATURDAY NIGHT AS A COLD FRONT CROSSES THE AREA
FROM THE NW. NWLY FLOW COULD BE GUSTY (20 TO 25 KT) IN THE WAKE OF
THE LOW.

VFR CONDS EXPECTED SUN/MON. SUB-VFR POSSIBLE TUE IN ANY TSTM
ACTIVITY.

&&

.MARINE...
SOUTHERLY WINDS WILL INCREASE LATE THIS AFTERNOON AND EVENING
BEHIND A WARM FRONT. LOW PRESSURE WILL RIDE ALONG THE
BOUNDARY...PASSING OFF TO OUR EAST OVERNIGHT. A SMALL CRAFT
ADVISORY IS IN EFFECT FOR THE MIDDLE PORTION OF THE BAY AND LOWER
TIDAL POTOMAC RIVER. SHOWERS AND THUNDERSTORMS WILL BE CAPABLE OF
PRODUCING GUSTY WINDS...LARGE HAIL AND WATERSPOUTS THIS
EVENING...MAINLY IN CENTRAL AND SOUTHERN PORTIONS OF THE BAY.

CONVECTION WILL DISSIPATE IN COVERAGE OVERNIGHT. AN EASTERLY FLOW
WILL DEVELOP FRIDAY AND THE FLOW WILL STRENGTHEN FRIDAY NIGHT. A
SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY
AND LOWER TIDAL POTOMAC RIVER FRIDAY NIGHT. A FEW SHOWERS AND
THUNDERSTORMS ARE POSSIBLE...ESPECIALLY FRIDAY NIGHT.

SELY FLOW INCREASES SATURDAY NIGHT WARRANTING AN SCA FOR MOST
WATERS AFTER MIDNIGHT. SCA EXPECTED SATURDAY INTO SUNDAY NIGHT AS
LOW PRESSURE PERSISTS OVER THE ERN GREAT LAKES. HEAVY THUNDERSTORMS
EXPECTED SATURDAY WITH DAMAGING WINDS/WATER SPOUTS POSSIBLE THROUGH
THE EVENING HOURS. NORTHWEST FLOW OVERSPREADS THE WATERS LATE
SATURDAY NIGHT AS A COLD FRONT CROSSES.

SCA CONDS APPEAR LIKELY THROUGH SUN. ATM WINDS APPEAR NEAR SCA
CRITERIA TUE WITH ADDITIONAL MARINE CONCERNS IN ANY TSTM ACTIVITY.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES ARE AROUND ONE-HALF FOOT ABOVE NORMAL. THE
ANOMALIES MAY INCREASE A BIT THIS EVENING...BUT WATER LEVELS
SHOULD REMAIN BELOW MINOR FLOODING THRESHOLDS. ANOMALIES WILL
DECREASE LATE INTO FRIDAY AS THE FLOW TURNS OFFSHORE.

AS LOW PRESSURE APPROACHES SATURDAY...THE FLOW WILL PROMOTE A
STRONGER PUSH UP THE BAY AND THE POTENTIAL FOR MINOR FLOODING WILL
INCREASE.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT FRIDAY NIGHT TO 6 AM EDT
     SATURDAY FOR ANZ531>534-536>543.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT FRIDAY FOR ANZ532>534-537-
     540>543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL/RCM
SHORT TERM...BJL
LONG TERM...MSE
AVIATION...BAJ/BJL/MSE/RCM
MARINE...BAJ/BJL/MSE/RCM
TIDES/COASTAL FLOODING...RCM/HTS


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