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Area Forecast Discussion
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000
FXUS61 KPBZ 211147
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
747 AM EDT THU AUG 21 2014

.SYNOPSIS...
UNSETTLED WEATHER WILL CONTINUE THROUGH THE WEEKEND WITH
OCCASIONAL SHOWERS AND THUNDERSTORMS.

&&

.NEAR TERM /THROUGH TONIGHT/...
800 AM UPDATE...MADE MINOR ADJUSTMENT TO POPS THIS MORNING BASED ON
SHOWERS ACROSS THE NORTH AND CONVECTION APPROACHING FROM THE WEST.

PREVIOUS DISCUSSION...

FRONTAL BOUNDARY WILL CONTINUE TO HANG AROUND THE CWA TODAY AND 
TONIGHT...ALTHOUGH IT WILL GET A SLIGHT NORTHWARD PUSH LATER IN THIS 
PERIOD.  DEEPER MOISTURE MAKES A RUN BACK TO THE EAST...WITH THE 1.5 
INCH PWAT LINE GETTING CLOSE TO PIT THIS AFTERNOON.  EXPECT SOME 
POCKETS OF UP TO 2500 J/KG OF CAPE TO DEVELOP...WHICH WILL ONCE 
AGAIN ALLOW FOR DIURNAL STORM DEVELOPMENT.  0-6KM BULK SHEAR OF 
30-40 KNOTS MAY BE JUST ENOUGH TO ALLOW FOR SOME STRONG TO 
MARGINALLY SEVERE STORMS...ALTHOUGH ORGANIZATION WILL REMAIN LOW.  
EXPECTING HIGHER COVERAGE ALONG/SOUTH OF BOUNDARY WITH THE JUICIER 
AIRMASS...AND HAVE THE LIKELY POPS TARGETED IN THIS AREA.  CHANCE 
POPS ARE FORECAST IN THE FKL/DUJ FAR NORTHERN REGION.

DESPITE ALL THIS...AM NOT SOLD ENOUGH ON THREAT OF HEAVY 
RAINFALL/FLOODING TO HOIST ANY FLOOD WATCHES.  BEST ORGANIZATION AND 
RAINFALL POTENTIAL WILL LIE OFF TO THE SOUTH AND WEST...WHERE 
ISENTROPIC UPGLIDE ALONG WITH H250 UPPER DIVERGENCE IN RRQ OF MODEST 
JET WILL ALLOW FOR ENHANCED LIFT...NOT TO MENTION THE 2 INCH PLUS 
PWAT VALUES.  THINK THE WET AREAS IN EASTERN OHIO WILL BE ABLE TO 
ESCAPE ANY FURTHER IMPACTS TODAY.

TONIGHT...ACTIVITY WILL DIURNALLY DECREASE AND CLOUDS WILL BREAK 
SOMEWHAT.  CANNOT RULE OUT A SHOWER ANYWHERE OVERNIGHT THOUGH GIVEN 
THE AIRMASS AND FRONT.  THERE ARE HINTS IN THE MODELS THAT SOME SORT 
OF CONVECTIVE CLUSTER/MCS MAY ATTEMPT TO FORM AND RIDE THROUGH THE 
OHIO VALLEY.  AGAIN...EXPECT THIS TO BE MAINLY OFF TO THE 
SOUTHWEST...BUT COULD SEE THE ZZV VICINITY GET CLIPPED AROUND 12Z.  
WILL NEED TO KEEP AN EYE ON THIS.

NEAR OR SLIGHTLY ABOVE NORMAL TEMPS CONTINUE TO BE FORECAST.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
WEAK WARM FRONT LIFTS NORTHEAST EARLY FRI...ALLOWING COPIOUS DEEP 
MOISTURE TO SHIFT FURTHER EAST REACHING THE WRN EDGE OF THE FORECAST 
AREA BY DAYBREAK. A SFC LOW PRESSURE SYSTEM WILL SLIDE ALONG THE 
BOUNDARY FRI...SUPPORTED ALOFT BY A RELATIVELY WEAK H7-H5 SW TROF. 
SHOWERS AND THUNDERSTORMS SHOULD OVERSPREAD A MAJORITY OF THE CWA BY 
AFTERNOON. WIND PROFILES ARE SUPPORTIVE OF A FEW STRONGER STORMS 
WITH ROUGHLY 30KTS OF 0-6KM BULK SHEAR...HOWEVER...RESIDUAL CLOUD 
COVER AHEAD OF THE SYSTEM SHOULD ACT TO KEEP SFC TEMPS AND 
ULTIMATELY INSTABILITY LIMITED. 

EVEN WITH SEVERE POTENTIAL LIMITED...SHOWERS AND THUNDERSTORMS WILL 
BE ABLE TO TAP INTO A WARM AND HUMID AIR MASS WITH PWAT VALUES AT OR 
JUST ABOVE 2"...VALUES APPROACHING 2SD ABOVE THE MEAN. 
ADDITIONALLY...FREEZING LEVELS SHOULD BE NEARING 13KFT ALLOWING FOR 
IMPRESSIVE WARM CLOUD LAYER DEPTHS. MODERATE TO HEAVY RAIN SHOWERS 
COULD PRODUCE LOCAL WATER PROBLEMS...ESPECIALLY IN THOSE AREAS 
ALREADY SATURATED FROM TUES/WEDS RAINS. WILL CONTINUE TO MENTION THE 
HEAVY RAIN THREAT IN THE HWO FRI. 

TEMPS FRI WILL BE HIGHLY DEPENDENT ON TIMING OF WAVE AND RESULTANT 
CLOUD COVER AS WELL AS HOW FAR NORTHEAST THE WARM FRONT ADVANCES. 
BECAUSE OF THESE FACTORS...LARGE SPREAD EXISTS ACROSS THE MOS 
GUIDANCE. KNOCKED DOWN HIGH TEMPS FRI A DEGREE OR TWO...BUT TRIED TO 
STAY CLOSER TO THE WARMER MAV VALUES AS ANY BREAKS IN THE CLOUDS 
COULD SHOOT TEMPERATURES QUICKLY UP UNDER THE STILL POTENT AUGUST 
SUN.
TAX

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
MORE CLARITY EXISTS IN THE EXTENDED FORECAST WITH THE LATEST ROUND 
OF MODEL GUIDANCE. BY SUN THE SFC LOW FROM THE EARLY WEEKEND DEEPENS 
OVER THE PIEDMONT OF VA/NC PULLING THE DEEPER MOISTURE SOUTH WITH 
IT. IN THE MEANTIME...THE UPPER RIDGE CURRENTLY SETTING UP OVER THE 
SRN MS VALLEY WILL BUILD NORTH FURTHER WITH ITS AXIS SHIFTING EAST 
THROUGH SUN. THIS WILL WORK TO DEFLECT AN ADVANCING LOW PRESSURE 
SYSTEM WELL NORTH OF THE GREAT LAKES EARLY NEXT WEEK...RESULTING IN 
A WARMING AND DRYING TREND. TEMPERATURES SHOULD REMAIN AT OR EVEN 
JUST ABOVE AVERAGE INTO THE MIDDLE OF NEXT WEEK. 
TAX

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
A FEW ISOLATED SHRA CONTINUED OVERNIGHT. MOST LOCATIONS ARE VFR
OUTSIDE OF FKL/DUJ. BOUNDARY LAYER REMAINED A LITTLE MORE MIXED
THAN EXPECTED OVERNIGHT...RESULTING IN LESS FOG.

VFR CONDITIONS ARE FORECAST FOR THE BALANCE OF THE MORNING ONCE
WHATEVER FOG THERE IS LIFTS. STILL LOOKING AT THE BEST PRECIP
CHANCES ACROSS NORTHERN WEST VIRGINIA AND SOUTHEAST OHIO THIS
AFTERNOON...LESS TO THE NORTH. KEPT PREVAILING SHRA AT ZZV/MGW AND
HAVE ONLY VCTS MENTIONED TO THE NORTH.  IFR POSSIBLE IN ANY THUNDERSTORM.
SHOULD SEE A DECREASE IN COVERAGE WITH LOSS OF HEATING DURING THE
EVENING. PUT IN MVFR FOG AT SOME LOCATIONS LATE.  WILL NEED TO
WATCH EASTERN OHIO LATE TONIGHT FOR POSSIBLE INTRUSION OF MCS. ZZV
WOULD HAVE THE BEST CHANCE OF BEING AFFECTED.


OUTLOOK.../FRIDAY THROUGH MONDAY/...
SEVERAL CROSSING DISTURBANCES WILL CAUSE PERIODIC RESTRICTIONS
INTO THE WEEKEND.

&&

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

&&

$$






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