Severe Thunderstorm Warning 99, NWS Baltimore/Washington

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
256 PM EDT THU JUN 18 2015

.SYNOPSIS...

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY AND FRIDAY
AS A WARM FRONT SLOWLY MOVES NORTH TODAY AND THEN RETURNS SOUTH AS
A COLD FRONT FRIDAY. THE REMNANTS OF TROPICAL STORM BILL WILL
BRING AN INCREASING CHANCE OF SHOWERS AND THUNDERSTORMS TO THE MID
ATLANTIC SATURDAY NIGHT INTO SUNDAY. ANOTHER FRONTAL BOUNDARY
WILL STALL IN THE AREA NEXT WEEK ALLOWING THE CHANCE OF SHOWERS
AND THUNDERSTORMS TO CONTINUE.

&&

.NEAR TERM /TONIGHT/...

A WARM FRONT IS LOCATED ACROSS PA/NJ TO THE DELMAVA PENNISULA
WHILE A COLD FRONT MOVES SOUTH THROUGH THE OHIO VALLEY THIS
AFTERNOON. THIS PUTS THE MID-ATLANTIC IN THE WARM SECTOR IN A VERY
MOIST ENVIONMENT.

THE REGION IS UNSTABLE AT THIS TIME WITH 1-2K J/KG OF SBCAPE WITH
UPWARDS OF 3.5K J/KG IN CENTRAL VA NEAR THE PIEDMONT AND TIDEWATER.
EFFECTIVE SHEAR OF 35-45 KTS IS ALSO ACROSS THE REGION WITH PWATS
NEAR 1.7 INCHES. THIS LEADS TO A SET-UP FOR STRONG TO SEVERE STORMS
ACROSS THE REGION. HOWEVER...SYNOPTIC FORCING IS LIMITED WITH A SFC
TROUGH EAST OF THE BAY AT THIS TIME. STORMS HAVE FORMED ON THE
HIGHER TERRAIN ACROSS THE APPALACHAINS WITH ISO-SCT STORMS ACROSS
THE HIGHER TERRAIN INCLUDING THE BLUE RIDGE. THIS AREA IS PRIME FOR
UPDRAFTS TO MAINTAIN THEMSELVES AND MOVE EASTWARD INTO THE UNSTABLE
ENVIRONMENT. AT THIS TIME...THE REGION IS IN A SLGT RISK OF SEVERE
WEATHER WITH DMG WINDS AND LARGE HAIL BEING THE MAIN THREATS AT THIS
TIME. ANY STORMS THAT NEAR THE SFC TROUGH MAY INGEST LOW LEVEL
VORTICITY AND FOR THAT ISOLATED TORS AND WATERSPOUTS ARE
POSSIBLE...MAINLY NEAR S MD/PIEDMONT AND SURRONDING WATERS.

THE COLD FRONT WILL MOVE INTO THE APPALACHIAN REGION TONIGHT. A
MOIST ATMOSPHERE WILL CONTINUE ACROSS THE REGION AND SHOWERS AND
THUNDERSTORMS FROM THE NORTH AND WEST MAY ENTER THE REGION INTO THE
EVENING HOURS AFTER THE LOSS OF DAYTIME HEATING. AN APPROACHING
DISTURBANCE MAY ALSO INTIATE SOME STORMS MAINLY ACROSS WV. MODELS
ARE KEEPING QPF WEST OF APPALACHIANS BUT WITH WESTERLY FLOW ALOFT
AND DEWPTS STILL HIGH KEPT CHANCE OF SHOWERS THIS EVENING.

&&

.SHORT TERM /FRIDAY/...

THE COLD FRONT WILL MOVE INTO THE REGION FRIDAY MORNING. CLOUDS AND
SHOWERS ARE POSSIBLE FRIDAY. CLOUDS SHOULD LIMIT DESTABILIZATION
FRIDAY AFTERNOON BUT THE FORCING OF THE FRONT MAY ALLOW FOR A
ISOLATED THUNDERSTORM. TEMPS WILL RISE INTO THE UPPER 80S TO LOW
90S.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...

THE PRIMARY CONCERN IN THE 1ST PART OF THE XNTD WL BE THE ARRIVAL
OF THE MOISTURE IN ASSO W/ THE DECAYING T.S. WHICH IS CURRENTLY
OVR THE OK/AR BORDER. THIS IS FCST TO GET PICKED UP IN THE UPR LVL
FLOW AND TRACK E AS A SHORT WV...REACHING KY SAT...THEN THE MID
ATLC SAT NGT THRU SUN MRNG. TROPICAL STORMS ARE OFTEN DIFFERENT FM
NRML LOW PRES SYSTEM REGARDING MOISTURE CONTENT...BUT BY THE TIME
IT REACHES THE MID ATLC IT WL HV BEEN OVR LAND FOR SVRL DAYS AND MOVG
STEADILY E. THERE IS PSBL FLSH FLDG WRDG IN THE HWO - THIS WL NEED
TO BE WATCHED IN THE COMING DAYS.

SUNDAY LOOKS TO BE ANOTHER HOT DAY W/ HIGHS OVR 90 FM I-81 AND E.

SUNDAY NIGHT THROUGH WEDNESDAY/...500MB SHORTWAVE WILL
CROSS THE MID ATLANTIC REGION SUNDAY NIGHT. ZONAL FLOW OVER THE
REGION WILL SHIFT TO NORTHWEST AS A SHORTWAVE ON NORTHERN TRACK
CROSSES NEW YORK/PENNSYLVANIA MONDAY NIGHT THROUGH TUESDAY MORNING.
WEAK TO MODERATE WILL AFFECT THE AREA THROUGH THE PERIOD. THERE IS A
SLIGHT CHANCE FOR DEVELOPMENT OF AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS EACH DAY.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...

SHRA/TSRA FORMING ACROSS THE MTNS THIS AFTERNOON. VCTS EXPECTED
AT THE TERMINALS THIS AFTERNOON AND EARLY EVENING. SUB-VFR
CONDITIONS POSSIBLE IN TSRA WITH GUSTY WINDS AND HAIL. ANOTHER
ROUND OF SHRA/TSRA POSSIBLE LATE TONIGHT AS A DISTURBANCE NEARS.
AT THIS TIME...ACTIVITY MAY STRUGGLE MOVING OVER THE MTNS SO KEPT
IT OUT OF THE TAFS.

VFR CONDITIONS EXPECTED FRIDAY AS A COLD FRONT MOVES THROUGH THE
TERMINALS. N/NW WINDS EXPECTED BEHIND THE FRONT MOVING IN DRIER AIR.

DIMINISHED SKY CONDS PSBL SAT NGT/1ST PART OF SUN AS THE REMAINS
OF TS BILL MOVE INTO THE MID ATLC. THERE WL BE THE PTNL FOR A PD
OF HVY RAIN.

&&

.MARINE...

SRLY WINDS 5-10 KTS EXPECTED ON THE WATERS TODAY. SHOWERS AND
THUNDERSTORMS MAY PROMPT MWS/SMW ISSUANCE THIS AFTERNOON AND
EVENING WITH GUSTY WINDS...LIGHTNING AND WATERSPOUTS. SHOWERS ARE
POSSIBLE TONIGHT. A COLD FRONT WILL CROSS THE WATERS FRIDAY AND
WINDS SHOULD BECOME NRLY. SCA IS IN EFFECT FOR THE UPPER/MIDDLE
POTOMAC AND THE BAY NORTH OF DRUM PT AS THE GRADIENT IS STRONGER
IN THIS REGION.

BIGGEST CONCERN IN XTND IS PTNL FOR A PERIOD OF GUSTY S-SW WINDS
AND RAIN/THUNDERSTORMS SAT NGT-SUN AS THE REMNANTS OF TROPICAL
STORM BILL MOVE THRU THE MID ATLC. SCA CONDITIONS ARE PSBL DURING
THIS TIME.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EDT FRIDAY FOR
     ANZ530>533-535-536-538>541.

&&

PRODUCTS...HAS/WOODY!/CEM

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