Area Forecast Discussion
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FXUS61 KPBZ 010139
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
939 PM EDT SAT APR 30 2016

.SYNOPSIS...
A COUPLE OF LOW PRESSURE SYSTEMS WILL PROVIDE RAIN OVER THE REGION
THROUGH SUNDAY NIGHT. TEMPERATURES ARE EXPECTED TO RISE ABOVE
AVERAGE SUNDAY AFTERNOON.

&&

.NEAR TERM /THROUGH SUNDAY/...
MADE SLIGHT ADJUSTMENTS TO POPS BASED ON LATEST RADAR TRENDS TO
THE LATE EVENING UPDATE. PREVIOUS DISCUSSION FOLLOWS.

A SPLIT FLOW PATTERN WITH AN UPPER LEVEL LOW CENTERED OVER THE
CENTRAL PLAINS HAS ALLOWED DEEP MOISTURE TO ADVECT OVER THE REGION
WITH EMBEDDED UPPER LEVEL SHORTWAVES PROGGED TO CROSS THE FORECAST
AREA THROUGH TONIGHT. AT THE SURFACE...A BROAD AREA OF LOW
PRESSURE OVER THE MIDWEST IS EXPECTED TO SHIFT OVER THE UPPER OHIO
VALLEY BY SUNDAY MORNING. AS A RESULT...A WARM FRONT HAS HELPED
FORM STRATIFORM RAIN THIS AFTERNOON AND THUS CATEGORICAL POPS
REMAIN IN THE FORECAST UNTIL SUNDAY MORNING WHEN THE CENTER OF LOW
PRESSURE EXITS EAST.

STRONG UPPER LEVEL FORCING SEEMS LESS FAVORABLE FOR SUNDAY
AFTERNOON AS THE UPPER LOW IS PROGGED TO PHASE WITH THE TROUGH
ACROSS THE WESTERN GREAT LAKES. HOWEVER...ANOTHER DEVELOPING
SURFACE LOW OVER THE OHIO VALLEY IS EXPECTED TO HELP CREATE AREAS
OF CONVECTION AS IT CROSSES THE REGION LATE SUNDAY. THE BREAK
BETWEEN THE TWO SYSTEMS MAY INCLUDE SOME CLEARING AS INDICATED BY
MODELS AND IN TURN INCREASE INSTABILITY. UNCERTAINTY REMAINS IN
THE APPROACH OF THE SECONDARY LOW PRESSURE AND BREAKS IN CLOUDS...AND
WHILE THE AFOREMENTIONED UPPER LEVEL FORCING REMAINS WEAK...A
MARGINAL RISK FOR SEVERE WEATHER IS FORECAST BY SPC. A BLEND OF
MODEL DATA WAS USED DUE TO THE UNCERTAINTY WITH THE EVOLUTION OF
THE LATE SUNDAY LOW PRESSURE.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
LOW PRESSURE WILL TRACK FROM EASTERN OHIO TO WESTERN NEW YORK SUNDAY
NIGHT. HAVE CONTINUED WITH LIKELY POPS DURING THIS TIME PERIOD. WILL
NEED TO MONITOR POTENTIAL FOR STRONGER THUNDERSTORMS DURING THIS
TIME PERIOD BASED ON POTENTIAL INCREASING INSTABILITY AS
TEMPERATURES COOL ALOFT. RAIN WILL RAPIDLY SHIFT EAST MONDAY AS
THE LOW CONTINUES ON TO NEW ENGLAND.

A DIGGING UPPER LEVEL TROUGH OVER THE NORTHEAST WILL HELP SUPPORT
A LOW PRESSURE SYSTEM TO SHIFT OVER THE EAST COAST. POPS
ASSOCIATED WITH THIS PASSING SYSTEM ARE CONFINED TO THE ZONES
SOUTH AND EAST OF PITTSBURGH WHERE GREATER FORCING IS PROGGED.
TEMPERATURES WILL BE AT OR SLIGHTLY BELOW NORMAL.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
LOW PRESSURE WILL TRACK ACROSS CANADA TUESDAY NIGHT AND
WEDNESDAY...DRAGGING A COLD FRONT ACROSS THE REGION. ALTHOUGH MODELS
ARE IN GOOD AGREEMENT WITH THE LOW TRACK AND TRAILING COLD
FRONT...MODEL TIMING OF THE FRONT IS ALL OVER THE PLACE. TUESDAY
NIGHT APPEARS TO REMAIN DRY...AND HAVE GONE WITH CHANCE POPS
WEDNESDAY INTO WEDNESDAY NIGHT. AN UPPER LEVEL LOW WILL THEN DROP
ACROSS THE GREAT LAKES AND REMAIN ACROSS THE EASTERN UNITED STATES
THROUGH THE REST OF THE 7 DAY FORECAST. THIS WILL KEEP THE FORECAST
COOL WITH SCATTERED SHOWERS AS IMPULSES ROTATE ACROSS THE AREA.

&&

.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
RAIN WILL CONTINUE TO SPREAD EAST AND REMAIN THROUGH THE
OVERNIGHT AS LOW PRESSURE OVER THE CENTRAL PLAINS SLOWLY SHIFTS
EAST. LOW LEVELS WILL SATURATE WITH WEAK MIXING AS THE NIGHT
PROGRESSES WITH A PERIOD OF IFR BEFORE AND TOWARD MIDNIGHT AND
EXTENDING TO MID MORNING SUNDAY. SURFACE LOW WILL TRY PUSH REGION
INTO THE WARM SECTOR SUNDAY AFTERNOON WHICH MAY ALLOW FOR MVFR
CIGS AS RAIN DIMINISHES FOR A TIME. IF CLOUDS BREAK SUNDAY
AFTERNOON INSOLATION MAY ALLOW ENOUGH LOW LEVEL INSTABILITY FOR
THUNDERSTORMS...BUT VERY LOW CONFIDENCE IN THAT OCCURRING. SOUTH
WINDS OVERNIGHT WILL SHIFT TO SOUTHWEST UNDER 10 KTS SUNDAY.

.OUTLOOK /SUNDAY NIGHT THROUGH THURSDAY/...
RESTRICTIONS ARE EXPECTED THRU MON AS LOW PRESSURE COMPLETES
PASSAGE OVER THE REGION. ANOTHER ROUND OF RESTRICTIONS WILL BE
POSSIBLE WEDNESDAY AND WEDNESDAY NIGHT WITH A COLD FRONT.

&&

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

&&

$$



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