Area Forecast Discussion
Issued by NWS

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FXUS61 KPBZ 020855
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
455 AM EDT SAT MAY 2 2015

.SYNOPSIS...
HIGH PRESSURE WILL BRING DRIER AND WARMER WEATHER FOR THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
NORTHERLY FLOW CONTINUES TO RULE THE ROOST IN THE UPPER OHIO
VALLEY...WITH MUCH MORE STABLE AIR ALREADY TAKING CONTROL OF THE
ENTIRE REGION. ON THE HEELS OF NORTHERLY FLOW...SLIGHTLY DRIER
DEWPOINTS ARE BEING FILTERED SOUTHWARD. ALONG WITH THE LOSS OF
DIURNALLY-DRIVEN INSTABILITY...SKIES ARE RAPIDLY CLEARING IN ALL
SECTORS OF THE CWA. THE RESULT LOOKS TO BE A DRY AND CLEAR
NIGHT...WITH TEMPERATURES LIKELY FALLING OFF FROM THE READINGS OF
LAST NIGHT. OVERNIGHT LOW TEMPERATURES WERE ADJUSTED DOWNWARD A
BIT...OWING TO DEWPOINTS ALREADY FALLING OFF INTO THE MID 30S IN
OHIO AND NORTHWEST PENNSYLVANIA.

A CONTINUATION OF THE WIDE DEWPOINT DEPRESSIONS IN THE BOUNDARY
LAYER LOOKS TO BE ON TAP FOR SATURDAY. OTHER THAN A FEW FLAT
CUMULUS...SUNNY SKIES AGAIN SEEM TO BE IN STORE. LIKEWISE...STRONG
LOW LEVEL LAPSE RATES WILL PROMOTE DECENT MIXING. EVEN THOUGH
THERE WILL LIKELY BE A LACK OF LOW LEVEL FLOW RELATIVE TO
TODAY...A MIX OUT TO 850 MB SEEMS LIKELY. AS A RESULT...MUCH OF
THE REGION WILL AGAIN JUMP INTO THE LOWER 70S AS 850 MB
TEMPERATURES JUMP PAST 8C. FRIES

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
THE WARMING TREND WILL CONTINUE SUNDAY AND MONDAY AS RIDGING
CONTINUES TO BUILD OVER THE REGION. FLOW WILL BECOME MORE
SOUTHWESTERLY LATE SUNDAY INTO MONDAY WHICH WILL ALLOW FOR
ADDITIONAL MOISTURE ADVECTION ACROSS THE REGION. MODELS HAVE
TRENDED SLOWER IN TRANSITIONING A BOUNDARY SOUTH AND OVER THE
FORECAST AREA WHICH NOW LOOKS MOST LIKELY TO OCCUR LATE MONDAY
INTO TUESDAY MORNING. WITH THAT AND CONTINUED WARMING
ALOFT...SURFACE BASED LIFT LOOKS LIKELY TO BE CAPPED OFF BETWEEN
6-8KFT AND EXPECT NOTHING MORE THAN AN INCREASE IN CLOUD COVERAGE
MONDAY AFTERNOON.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
THE AFOREMENTIONED BOUNDARY WILL SAG SOUTH ACROSS THE REGION LATE
MONDAY INTO TUESDAY WITH PRECIPITATION SPREADING FROM NORTH TO
SOUTH AS THIS OCCURS. BY TUESDAY PRECIPITABLE WATER VALUES ARE
PROGGED TO BE AROUND 1.25" ON AVERAGE WHICH IS IN THE 90TH-95TH
PERCENTILE FOR EARLY MAY. AT THE MOMENT TUESDAY DOES NOT LOOK TO
BE OVERLY UNSTABLE WITH CAPE VALUES AROUND 500 JOULES ON AVERAGE
...BUT DO EXPECT THUNDERSTORM DEVELOPMENT DURING THE AFTERNOON
WITH THE INCREASED LOW LEVEL INSTABILITY AND SLIGHT COOLING ALOFT
AS THE BOUNDARY SAGS SOUTH. ONE CONCERN FOR TUESDAY WILL BE THE POTENTIAL
FOR LOCALIZED AREAS OF HEAVY RAIN. WITH HIGH PRECIPITABLE WATER
VALUES AND FORECAST SOUNDINGS INDICATING A FAIRLY DEEP WARM CLOUD
LAYER...LOW LCLS...WEAK VERTICAL WIND SHEAR AND STEERING LAYER
FLOW...AND LOW MBE VELOCITIES...THE POTENTIAL FOR A BACK BUILDING
SCENARIO TO SET UP ALONG THE SLOW SOUTHWARD MOVING BOUNDARY IS
DEFINITELY THERE.  AT THIS POINT IT IS FAR FROM A CERTAINTY BUT
DEFINITELY BEARS WATCHING. ANOTHER POSSIBLE SCENARIO ON TUESDAY
FOR LOCALIZED HEAVY RAIN IN THE ABSENCE OF BACKBUILDING CONVECTION
WOULD BE WITH CONTINUED UPSTREAM CONVECTION RIDING OVER THE RIDGE
AND MOVING OVER THE SAME AREAS UNDER WESTERLY FLOW.

THE POTENTIAL FOR PRECIPITATION WILL DECREASE WEDNESDAY MORNING AS
THE BOUNDARY CONTINUES SOUTH OF THE FORECAST AREA...AND THE
INCREASING TREND IN TEMPERATURES WILL CONTINUE THROUGH THE
REMAINDER OF THE PERIOD AS AS RIDGING PUMPS UP OVER THE EASTERN
STATES AND A DEEP LOW CLOSES OFF OVER THE WEST. MAX TEMPERATURES
ARE FORECAST TO RANGE FROM THE LOW TO MID 80S ACROSS THE REGION.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS THROUGH THE PERIOD. PATCHY CIRRUS MAY BE SEEN
OVERNIGHT AND INTO SATURDAY...AND SOME SCATTERED FLAT CU ARE
POSSIBLE DURING SATURDAY AFTERNOON. WINDS WILL GENERALLY REMAIN
UNDER 10 KNOTS FROM THE NORTH AND NORTHWEST.

.OUTLOOK.../SATURDAY THROUGH WEDNESDAY/...
THE NEXT CHANCE FOR GENERAL RESTRICTIONS IS EXPECTED WITH TUESDAY
FRONTAL ENCROACHMENT.

&&

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

&&

$$



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