Severe Thunderstorm Warning 49, NWS Pittsburgh, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1036 AM EDT MON MAY 31 2010

.SYNOPSIS...
SHOWERS AND STORMS WILL RETURN TO THE AREA TODAY AND CONTINUE
THROUGH TUESDAY. CONDITIONS SHOULD BRIEFLY DRY OUT ON WEDNESDAY
BEFORE ANOTHER CHANCE OF THUNDERSTORMS ARRIVES LATE WEDNESDAY.

&&

.NEAR TERM /UNTIL 10 PM THIS EVENING/...
RUC 500MB ANALYSIS INDICATES A WEAK RIDGE EXTENDING FROM THE
DELMARVA PENINSULA NORTHWESTWARD ACROSS THE UPPER OHIO VALLEY. A
WEAK MID-LEVEL LOW IS LOCATED ACROSS THE TENNESSEE VALLEY ALONG
WITH A SHORT WAVE ADVECTING NORTHWARD ACROSS CENTRAL OHIO. WITH
THE LOW ADVECTING INTO THE AREA...THE MID-LEVEL FLOW HAS BECOME
MORE SOUTHERLY WITH ABUNDANT MOISTURE ADVECTING INTO THE AREA. AT
THE SURFACE...A 1006 MB LOW IS ACROSS THE NORTHERN GREAT LAKES
WITH A COLD FRONT EXTENDING SOUTHWEST FROM THE FEATURE ACROSS THE
MISSOURI VALLEY AND INTO THE SOUTHERN PLAINS. A WARM FRONT EXTENDS
SOUTHEAST FROM THE LOW...WITH A FRONTAL BOUNDARY EXTENDING ACROSS
NEW ENGLAND. LOCALLY...SOUTH OF THE BOUNDARY...A WARM AND MOIST
SOUTHERLY FLOW ACROSS THE AREA HAS ALLOWED FOR TDS IN THE MID 60S
TO ADVECT NORTHWARD INTO THE UPPER OHIO VALLEY. SCATTERED
CONVECTION IS MOVING NORTHWARD ACROSS CENTRAL OHIO AHEAD OF THE
SHORT WAVE WITH MORE ISOLATED DEVELOPMENT IN EASTERN OHIO THUS
FAR.

THROUGH THIS EVENING...THE MID-LEVEL LOW WILL ADVECT EASTWARD ACROSS
TENNESSEE AND CONTINUE TO AID IN THE ADVECTION OF WARM AND MOIST AIR
IN THE 1000-500MB LAYER INTO THE UPPER OHIO VALLEY. WITH MODERATE
ELEVATED INSTABILITY BY THE LATE AFTERNOON THIS WILL ALLOW FOR
ISOLATED CONVECTION TO INCREASE IN COVERAGE...BECOMING MORE
SCATTERED BY THIS AFTERNOON. ALTHOUGH A FEW OF THE STORMS MAY BECOME
STRONG WITH SMALL HAIL AND GUSTY WINDS NOT OF THE QUESTION...WEAK WIND
SHEAR AND THE LACK OF A STRONG FORCING MECHANISM SHOULD MOSTLY
LIMIT THE SEVERE THREAT. WITH FCST PWAT VALUES NEAR 1.50 INCHES
AND SLIGHTLY HIGHER ACROSS EASTERN OHIO...LOCALIZED HEAVY RAINFALL
IS POSSIBLE. HAVE GONE WITH LIKELY POPS THIS AFTERNOON WITH MOST
LOCATIONS SEEING SHOWERS AND THUNDERSTORMS. LITTLE CHANGE IN TEMP
FORECAST TODAY...AS BREAKS IN CLOUD COVERAGE SHOULD ALLOW HIGHS IN
THE LOWER TO MID 80S ACROSS THE AREA.

&&

.SHORT TERM /10 PM THIS EVENING THROUGH WEDNESDAY/...
COLD FRONT WILL TRACK ACROSS OHIO INTO PENNSYLVANIA LATE TONIGHT.
INSTABILITY VALUES WILL REMAIN HIGH ENOUGH OVERNIGHT TO KEEP A
CHANCE FOR THUNDERSTORMS. HOWEVER MODELS ARE IN GOOD AGREEMENT
THAT ATMOSPHERE WILL STABILIZE DURING THE NIGHT. IN ADDITION, MAIN
UL WAVE IN THE TROUGH AXIS WILL ROTATE NORTHWARD OVER THE GREAT
LAKES. IN THE FORECAST DURING THAT TIME PERIOD. PRECIPITABLE
WATER VALUES REMAIN HIGH, BUT NOT SURE HOW MUCH CONVECTION WILL BE
SUSTAINABLE OVERNIGHT.

BY MID-MORNING ON TUESDAY...THE 1000-500MB LAYER WILL BECOME NEARLY
SATURATED AHEAD OF THE FRONTAL PASSAGE...MAKING WARM-RAIN PROCESSES
MORE LIKELY AND INCREASING THE RISK FOR HEAVY RAINFALL ACROSS THE
AREA. THE COLD FRONT WILL CROSS THE AREA TUESDAY...WITH SHOWERS
AND THUNDERSTORMS DIMINISHING IN ITS WAKE. DRIER AIR WILL THEN
MOVE IN FOR TUESDAY NIGHT...ALTHOUGH CLOUDS WILL BE ON THE
INCREASE WEDNESDAY IN ADVANCE OF ANOTHER COLD FRONT TRACKING
ACROSS THE WESTERN GREAT LAKES. HIGHS WILL DECREASE A FEW DEGREES
WITH TUESDAYS COLD FRONT...BUT REBOUND BACK INTO THE 80S ON
WEDNESDAY WITH PARTLY SUNNY SKIES.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
MOST ENSEMBLE MODEL OUTPUT SHOWS DEVELOPMENT OF EASTERN CONUS TROUGH
BY NEXT WEEKEND.  HENCE FORECAST WILL PERSIST WITH PRECIP CHANCES
DEPENDENT ON LOW-CONFIDENCE TIMING OF TROUGH/FRONT PASSAGE AND
EMBEDDED SHORTWAVES CROSSING THE UPPER OHIO VALLEY.  INITIALLY WARM
TEMPERATURES WILL MODERATE TO NEAR, OR JUST UNDER SEASONAL AVERAGES
AS THE TROUGH DEVELOPS.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
MID AND UPR LEVEL CLOUDS WILL INCREASE TODAY AS MOISTURE SURGES
NORTHEAST WITH A WARM FRONTAL PUSH OVER THE UPPER OHIO VALLEY.

RESTRICTIONS MAY BE EXPECTED THIS AFTERNOON AND EVENING AS SHOWER AND
THUNDERSTORM COVERAGE INCREASES. RESTRICTIONS WILL CONTINUE INTO
TUESDAY AS A COLD FRONT CROSSES THE REGION.

HIGH PRESSURE SHOULD RETURN VFR TO AREA AIRPORTS BY WEDNESDAY, BUT
ANOTHER LOW IS FORECAST TO INITIATE RESTRICTIONS IN SHOWERS
POSSIBLE THUNDERSTORMS FOR THURSDAY INTO THURSDAY NIGHT. HIGH
PRESSURE FRIDAY WILL PROVIDE VFR CONDITIONS.

&&

.EQUIPMENT...
THE WSR 88D AT PITTSBURGH...KPBZ...IS OPERATIONAL BUT IN DEGRADED
MODE DUE TO LOW POWER OUTPUT. ADDITIONAL PARTS ARE ON ORDER AND
MORE MAINTENANCE WILL BE COMPLETED DURING THE NEXT COUPLE OF DAYS.

ALTERNATE RADARS INCLUDE KRLX...KILN...KC LE...AND KCCX.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
719 AM EDT MON MAY 31 2010

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029>032-WVZ001>004-012-021>023-041-011130-
GARRETT-TUSCARAWAS-CARROLL-COLUMBIANA-COSHOCTON-HARRISON-
JEFFERSON OH-MUSKINGUM-GUERNSEY-BELMONT-NOBLE-MONROE-MERCER-VENANGO-
FOREST-LAWRENCE-BUTLER-CLARION-JEFFERSON PA-BEAVER-ALLEGHENY-
ARMSTRONG-INDIANA-WASHINGTON-WESTMORELAND-GREENE-FAYETTE-HANCOCK-
BROOKE-OHIO-MARSHALL-WETZEL-MARION-MONONGALIA-PRESTON-TUCKER-
719 AM EDT MON MAY 31 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN MARYLAND...EAST
CENTRAL OHIO...NORTHWEST PENNSYLVANIA...SOUTHWEST
PENNSYLVANIA...WEST CENTRAL PENNSYLVANIA...NORTHERN WEST VIRGINIA
AND NORTHERN PANHANDLE OF WEST VIRGINIA.

.DAY ONE...TODAY AND TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PITTSBURGH PA
129 PM EDT MON MAY 31 2010

PAZ007>009-015-311815-
CLARION PA-FOREST PA-MERCER PA-VENANGO PA-
129 PM EDT MON MAY 31 2010

...THUNDERSTORMS...

THUNDERSTORMS TO MOVE THROUGH THE FOLLOWING COUNTIES...
VENANGO...FOREST...CLARION AND MERCER...

AT 124 PM EDT NATIONAL WEATHER SERVICE DOPPLER RADAR IN PITTSBURGH
INDICATED SCATTERED STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM
10 MILES WEST OF FREDONIA TO 4 MILES SOUTHEAST OF FRYBURG...OR ALONG
A LINE EXTENDING FROM 5 MILES NORTH OF HERMITAGE TO 4 MILES
SOUTHEAST OF FRYBURG...MOVING NORTHEAST AT 20 MPH.

STORMS ALONG THIS LINE WILL PRODUCE HEAVY RAINFALL AT THE RATE OF
ONE TO TWO INCHES PER HOUR...SMALL HAIL UP TO THE SIZE OF
DIMES...AND POSSIBLY SOME WIND GUSTS OF 40 TO 50 MPH.

SOME LOCATIONS THAT WILL BE IMPACTED BY THESE STORMS INCLUDE...
  VAN...                KENNERDELL...         FREDONIA...
  STONEBORO...          FRYBURG...            POLK...
  SENECA...             SUGARCREEK...
  MAURICE K GODDARD STATE PARK...             OIL CITY...
  TIONESTA...           OIL CREEK STATE PARK...

MOVE TO A SAFE PLACE IF THUNDERSTORMS APPROACH AND BE ALERT FOR
PONDING OF WATER ON ROADS.

PLEASE REPORT HAIL...STRONG WINDS OR WIND DAMAGE TO THE NATIONAL
WEATHER SERVICE BY CALLING TOLL FREE...1-877-633-6772.

LAT...LON 4163 7906 4126 7929 4123 8053 4149 8052
      4148 8014 4149 8013 4149 8001 4159 7990
      4161 7984

15

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PITTSBURGH PA
133 PM EDT MON MAY 31 2010

MDZ001-311830-
GARRETT MD-
133 PM EDT MON MAY 31 2010

...THUNDERSTORMS WITH LOCALLY HEAVY RAINFALL...

THUNDERSTORMS TO MOVE THROUGH THE FOLLOWING COUNTY...
GARRETT...

AT 124 PM EDT NATIONAL WEATHER SERVICE DOPPLER RADAR IN PITTSBURGH
INDICATED STRONG THUNDERSTORMS 5 MILES SOUTH OF BIG RUN STATE PARK...
MOVING NORTH AT 15 MPH.

SOME LOCATIONS THAT WILL BE IMPACTED BY THESE STORMS INCLUDE...
  MOUNTAIN LAKE PARK... KITZMILLER...         GORMAN...
  DEEP CREEK LAKE STATE PARK...               MCHENRY...
  BIG RUN STATE PARK... BITTINGER...          ACCIDENT...
  MERRILL...            NEW GERMANY...        GRANTSVILLE...
  PINEY GROVE...

KEEP AN EYE TO THE SKY AND MOVE TO A SAFE PLACE IF THUNDERSTORMS
APPROACH. STORMS MAY REDEVELOP IN THE SAME LOCATIONS AND LEAD TO
MINOR FLOODING OF LOW LYING AREAS.

PLEASE REPORT HAIL...STRONG WINDS OR WIND DAMAGE TO THE NATIONAL
WEATHER SERVICE BY CALLING TOLL FREE...1-877-633-6772.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HEAVY RAINS MAY FLOOD LOW LYING AREAS SUCH AS DITCHES AND
UNDERPASSES. AVOID THESE AREAS AND DO NOT CROSS FLOODED ROADS AS THEY
MAY BE WASHED OUT. WATER LEVELS OF SMALL STREAMS AND CREEKS MAY ALSO
RISE...THEREFORE SEEK HIGHER GROUND IF THREATENED BY FLOOD WATERS.

&&

LAT...LON 3972 7895 3942 7912 3941 7914 3941 7916
      3939 7917 3934 7926 3930 7929 3929 7935
      3925 7939 3923 7944 3971 7932

WOODRUM

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