Area Forecast Discussion
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000 FXUS61 KPBZ 021037 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 637 AM EDT SAT MAY 2 2015 .SYNOPSIS... HIGH PRESSURE WILL BRING DRIER AND WARMER WEATHER FOR THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...
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635 AM...MADE SOME MINOR CHANGES TO SKY COVER AND HOURLY TEMP/DEWPOINT GRIDS. FORECAST ON TRACK OVERALL. PREVIOUS DISCUSSION... MIDLEVEL RIDGING WILL PERSIST THROUGH TONIGHT...WITH A CONTINUED RUN OF QUIET WEATHER. SOME ALTOCUMULUS CONTINUES TO LINGER ACROSS THE SOUTHEAST CWA...EXPECT THESE TO DISSIPATE OVER THE NEXT FEW HOURS. WEAK SHORTWAVE IS RUNNING INTO THE RIDGE DURING THE PREDAWN HOURS...REALIZED ONLY AS CIRRUS. SOME FLAT CU REMAIN POSSIBLE DURING THE AFTERNOON. DESPITE DEEP MIXING POTENTIALLY TO H750...THERE IS SIMPLY NOT ENOUGH LOW LEVEL MOISTURE TO SUPPORT VERTICAL DEVELOPMENT WITH THE CU. THUS A MOSTLY SUNNY FORECAST HAS BEEN MAINTAINED FOR TODAY. THERE ARE SOME HINTS ON BUFKIT SOUNDINGS OF SOME MODEST INSTABILITY LASTING INTO THE NIGHT...AS WELL AS THE CONTINUED PRESENCE OF CIRRUS SPILLING OVER THE H500 RIDGE AXIS...SO PARTLY CLOUDY CONDITIONS WILL PERSIST TONIGHT. THE DEEP MIXING MENTIONED ABOVE...PLUS THE DRY AIRMASS AND ABUNDANT SUNSHINE...LED TO A HIGH TEMPERATURE FORECAST ON THE WARM SIDE OF THE GUIDANCE ENVELOPE. THOSE SAME DRY CONDITIONS TONIGHT SUGGEST THAT THE COOOLER NUMBERS ARE BETTER TONIGHT...WITH A DECENT DIURNAL TEMPERATURE RANGE OF 25-30 DEGREES IN SOME LOCATIONS. CL
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&& .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 /12Z SATURDAY THROUGH WEDNESDAY/...
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VFR WILL BE MAINTAINED THROUGH THE PERIOD. SOME CIRRUS WILL MOVE ACROSS THIS MORNING WITH A WEAK UPPER DISTURBANCE. SCATTERED FLAT CU ARE EXPECTED BY AFTERNOON. THESE MAY PERSIST INTO THE EVENING WITH BUFKIT SOUNDINGS SHOWING SOME MINOR INSTABILITY LINGERING. WINDS WILL GENERALLY BE UNDER 10 KNOTS OUT OF THE NORTH AND NORTHWEST. .OUTLOOK.../SATURDAY THROUGH WEDNESDAY/... THE NEXT CHANCE FOR GENERAL RESTRICTIONS IS EXPECTED WITH TUESDAY FRONTAL ENCROACHMENT.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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