Area Forecast Discussion
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000
FXUS61 KPBZ 070721
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
321 AM EDT THU MAY 7 2015

.SYNOPSIS...
ABOVE NORMAL TEMPERATURES THROUGH THE THE START OF THE WEEKEND
WITH SCATTERED SHOWERS AND STORMS POSSIBLE EACH AFTERNOON...MAINLY
OVER THE HIGHER TERRAIN.

&&

.NEAR TERM /THROUGH TONIGHT/...
CURRENT IR SATELLITE IMAGERY SHOWING OVERALL LACK OF CLOUDS AS
RIDGING ALOFT IS MAXIMIZING EARLY THIS MORNING. THE ONLY AREA OF
CLOUDS...EVIDENT ON THE IR FOG CHANNEL...IS A BANK OF LOW STRATUS ALONG
AND EAST OF OUR EXTREME NORTHEASTERN ZONES. THIS REMNANT LOW-LEVEL
MOISTURE...FROM THE WASHED OUT BROAD FRONTAL ZONE THAT WAS IN THE
AREA OVER THE LAST SEVERAL DAYS...IS GETTING DAMMED UP AGAINST THE
HIGHER TERRAIN BY LIGHT SOUTH-SOUTHEASTERLY FLOW. THIS STRATUS MAY
SLOWLY OOZE WESTWARD ACROSS AND NORTH OF I-80...THROUGH THE PRE-
DAWN HOURS...BUT IS NOT EXPECTED TO BE WIDESPREAD.

ELSEWHERE...CLEAR SKIES AND CALM SURFACE FLOW IS DECOUPLING THE
BOUNDARY LAYER. EXPECTING DEWPOINT SPREADS TO DECREASE AND AREAS
OF FOG TO DEVELOP BEFORE SUNRISE. POCKETS OF DRIER AIR MAY HOLD
OFF THE FOG...PARTICULARLY NEAR MORGANTOWN OR ZANESVILLE...BUT
THE FORECAST REFLECTS FAIRLY GENEROUS FOG DEVELOPMENT.

ANOTHER MOSTLY DRY AND SUNNY DAY IS ON TAP AS THE UPPER-LEVEL
RIDGE STICKS AROUND. THE AFOREMENTIONED BANK OF LOW-LEVEL
MOISTURE ALONG OUR EASTERN EDGE WILL SLOWLY PULL SOUTHWARD TODAY.
THIS WILL GIVE BIRTH TO DIURNALLY DRIVEN CONVECTIVE
SHOWERS/THUNDERSTORMS OVER THE ELEVATED HEATING SURFACES OF THE
RIDGES...IN A PATTERN MORE REMINISCENT OF LATE SUMMER. MODEL
SOUNDINGS SHOW ESSENTIALLY NO FLOW FROM THE SURFACE THROUGH THE
UPPER-LEVELS...INDICATING THAT ANY THUNDERSTORMS THAT DEVELOP
COULD BE QUASI-STATIONARY.

ANY SHOWERS OR THUNDERSTORMS WILL DISSIPATE AGAIN TONIGHT AT OR
NEAR SUNSET. ANOTHER DRY AND MILD NIGHT IS EXPECTED WITH
TEMPERATURES A FEW DEGREES WARMER THAN CURRENT LOW TEMPERATURES.
TAX

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
VERY MINIMAL CHANGE TO THE LARGE SCALE PATTERN LOOKS TO BE IN
STORE DURING THE SHORT TERM PERIOD OF THE FORECAST AS A SPRAWLING
UPPER RIDGE REMAINS IN CONTROL OF THE AREA THROUGH THE PERIOD.
WITH THE RIDGE AXIS SLIGHTLY TO THE EAST OF THE AREA...LARGE SCALE
SOUTHWESTERLY FLOW WILL CONTINUALLY PUMP WARM AND MOIST AIR TOWARD
THE CWA THROUGH THE PERIOD AS WELL. THIS WILL KEEP HUMIDITIES
UP...AND LIKEWISE ALLOW FOR DECENT MIXING IN THE BOUNDARY LAYER.
THE NET RESULT WILL BE MUCH ABOVE NORMAL TEMPERATURES THROUGH THE
PERIOD...WITH AT LEAST MID 80S QUITE LIKELY FOR MOST AREAS.

WITH LITTLE IMPETUS FOR LARGE SCALE LIFT...THE CHANCES FOR SHOWERS
WILL BE FAIRLY MINIMAL AND ISOLATED...EVEN WITH THE MOIST/WARM AIR
MASS IN PLACE. CAPE VALUES WILL BE SUFFICIENT TO ALLOW FOR
CONVECTION...HOWEVER WEAK SHEAR AND A LACK OF A LIFTING MECHANISM
WILL PRECLUDE ORGANIZED CONVECTION. IT IS REALLY ONLY ON SUNDAY
AFTERNOON THAT A FEW OF THE ENSEMBLE SOLUTIONS SUGGEST A WEAK
SHORT WAVE WILL EJECT IN THE SOUTHWESTERLY FLOW ALOFT...WHICH
WOULD INCREASE THE CHANCES FOR SHOWERS/STORMS BY THAT TIME.
OTHERWISE...THE MAJORITY OF THE PERIOD LOOKS FAIRLY DRY.  FRIES

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
THE UPPER LEVEL RIDGE CONTINUES TO HOLD SWAY OVER THE CWA INTO
EARLY NEXT WEEK AS OVERNIGHT MODEL AND ENSEMBLE SOLUTIONS ARE
FAVORING A LESS PROGRESSIVE BREAKDOWN OF THE PATTERN OVER EASTERN
NORTH AMERICA EARLY NEXT WEEK. AS A RESULT...A CONTINUATION OF
VERY WARM CONDITIONS IS QUITE LIKELY THROUGH AT THE VERY LEAST
MONDAY. IN FACT...SOLUTIONS HAVE NOW REALLY SPLIT AS TO WHETHER
THE WARM AIR MAY EVEN HOLD OUT TO LINGER INTO TUESDAY.
REGARDLESS...THE PATTERN STILL DOES LOOK TO BREAK DOWN MONDAY
NIGHT OR TUESDAY...WITH MUCH COLDER AIR POISED TO BLAST INTO THE
REGION THEREAFTER.

AS HAS BEEN THE CASE IN MANY RECENT MONTHS...GFS/ECMWF LOW LEVEL
TEMPERATURE EXPECTATIONS SEEM RIDICULOUSLY COLD GOING INTO THE
MIDDLE OF NEXT WEEK AS 850 MB TEMPERATURES OFF OF THE GFS DROP
TOWARD -5C AND ECMWF APPROACHES 0C. WHILE THESE VALUES ARE
THEORETICALLY POSSIBLE...THE LIKELIHOOD OF THEM LINGERING OVER THE
AREA IN SUCH A MANNER AS RECENT GFS SOLUTIONS IS VERY UNLIKELY. AS
A RESULT...THE FORECAST WAS BUILT USING A COMBINATION OF ENSEMBLE
TEMPERATURES AND GRIDDED MOS...WHICH RESULTS IN TEMPERATURES
TRENDING ROUGHLY 10 DEGREES BELOW NORMAL BY MID-WEEK. FRIES

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
LIFR CIGS SHOULD BE RELEGATED TO DUJ THIS MORNING AS LOW STRATUS
LINGERING IN NORTH-CENTRAL PA HAS SLOWLY OOZED WESTWARD. AT THE
MOMENT EXPECTING FKL TO STAY JUST WEST OF THE STRATUS...BUT THIS
WILL NEED TO BE WATCHED CLOSELY IN THE COMING HOURS.

ELSEWHERE...THERE IS POTENTIAL FOR IFR FOG TO DEVELOP AROUND
DAWN AS CLEAR AND CALM CONDITIONS LOWER DEWPOINT SPREADS THROUGH
THE AREA. ANY RESTRICTIONS THAT DO OCCUR WILL GRADUALLY IMPROVE
TO VFR AS DAYTIME HEATING INITIATES.
TAX

.OUTLOOK.../FRIDAY THROUGH MONDAY/...
NEXT CHANCE FOR WIDESPREAD RESTRICTIONS WILL BE MONDAY WITH AN
APPROACHING COLD FRONT.

&&

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

&&

$$



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