Area Forecast Discussion
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000 FXUS61 KPBZ 262343 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 643 PM EST THU FEB 26 2015 .SYNOPSIS... A DISTURBANCE WILL BRING CHANCES FOR LIGHT SNOW THROUGH THIS EVENING. DRY AND FRIGID CONDITIONS WILL END THE WEEK. && .NEAR TERM /THROUGH FRIDAY/...
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WITH 630PM UPDATE...PRIMARY CHANGES TO FORECAST WERE TO SKY COVER AND TEMPERATURES. LOW LEVEL CLOUDS ARE BEGINNING TO SCATTER OUT IN NORTHEAST OHIO AND NORTHWEST PENNSYLVANIA AWAY FROM THE IMMEDIATE LAKE ERIE SHORELINE...AND WITH NORTHWESTERLY FLOW COMING OVER FROZEN LAKE ERIE...NOT SURE THERE WILL BE MUCH OF A MOISTURE SOURCE FOR CLOUDS TO REFORM. AS A RESULT...HAVE MADE SOME DECREASE TO CLOUDS IN THIS AREA OVERNIGHT...ALTHOUGH CLOUD COVER IS STILL EXPECTED TO BE EXTENSIVE ACROSS SOUTHEASTERN PORTIONS OF THE FORECAST AREA. FOLLOWING THE CLEARING TREND...HAVE BLENDED SOME RAP TEMPERATURES INTO THE FORECAST. THIS STARTS TO BRING OVERNIGHT LOWS DOWN A FEW DEGREES WHERE THE GREATEST CLEARING WILL OCCUR...WITH LITTLE TO NO CHANGE IN THE FORECAST WHERE CLOUDS WILL REMAIN THICKEST. AS PREVIOUSLY DISCUSSED...IF MORE SCATTERING OCCURS THAN CURRENTLY FORECAST...SOME LOCATIONS NORTH OF INTERSTATE 80 COULD EASILY HAVE TEMPERATURES CRATER TO MINUS 10 OR LOWER. AT THIS POINT...DO NOT THINK SUCH AN AGGRESSIVE CHANGE NEEDS TO BE MADE TO THE FORECAST. PREVIOUS DISCUSSION FOLLOWS. VERY LIGHT SNOW WILL CONTINUE THROUGH THE REST OF THE EVENING AS THE ARCTIC FRONT CROSSES THE AREA. THE MOST RECENT RUN OF THE HI RES MODELS HAVE A BRIEF BREAK IN THE SNOWFALL BEFORE RAMPING UP AGAIN AS THE ENTIRE COLUMN COOLS AND FALLS INTO THE -15 TO -20 RANGE. HOWEVER...THIS WINDOW IS RATHER SMALL FOR ALL BUT THE RIDGES BEFORE SUBSIDENCE TAKES PLACE. THUS...SNOWFALL FORECAST CHANGES WERE RATHER MINIMAL...ONLY ADDING ABOUT AN INCH TO THE HIGHEST ELEVATIONS OF PA/WV/MD...AND GENERALLY LESS THAN AN INCH ELSEWHERE THROUGH THE FIRST HALF OF THE NIGHT. COLD ADVECTION WILL ALLOW FOR TEMPERATURES TO ONCE AGAIN FALL INTO THE SINGLE DIGITS OR JUST BELOW ZERO OVERNIGHT. AT THIS POINT...STAYED ON THE WARMER SIDE OF GUIDANCE AS EXPECT CLOUD COVER TO KEEP TEMPERATURES FROM BOTTOMING OUT. HOWEVER...IF CLOUDS WERE TO SCATTER OUT EARLY...TEMPERATURES COULD FALL OFF MUCH MORE WITH THE SNOWPACK AND LIGHT WINDS EXPECTED. EVEN IF TEMPS WERE TO FALL OFF MORE THAN CURRENTLY FORECAST...THE LOW WINDS EXPECTED WITH BUILDING HIGH PRESSURE SHOULD LIMIT ANY CONCERNS FOR WIND CHILL ADVISORIES OVERNIGHT. THUS...NO HEADLINES WERE ISSUED ON THIS SHIFT. COLD ADVECTION AND SHOULD LIMIT HIGH TEMPERATURES TOMORROW.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/... WITH HIGH PRESSURE OVERHEAD FRI NIGHT/SAT MORNING TEMPERATURES SHOULD DROP SIGNIFICANTLY ONCE AGAIN...WITH THE HELP OF STRONG RADIATIONAL COOLING AND SNOWPACK. TEMPERATURES SHOULD MODERATE ON SATURDAY HOWEVER...AS WINDS SHIFT TO THE SOUTHWEST AND WARM ADVECTION ENSUES. NEXT SYSTEM WILL MAKE ITS APPROACH ON SUNDAY. AS OF NOW...THE SURFACE LOW LOOKS TO MOVE RIGHT ACROSS THE FORECAST AREA...WITH WARM ADVECTION AND 850 TEMPERATURES WARM ENOUGH TO BRING A MIX TO AREAS SOUTH OF I 80...WITH MAINLY SNOW TO THE NORTH. A BRIEF PERIOD OF FREEZING RAIN IS POSSIBLE BUT NOT ENOUGH CONFIDENCE IN THE DETAILS TO INCLUDE AT THIS TIME. HAVE HIGHLIGHTED THIS FEATURE IN THE HWO AS SOME ACCUMULATING SNOW MAY BE POSSIBLE...DEPENDING ON THE TRACK AND WARM AIR ALOFT. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... A PATTERN CHANGE AND RELATIVE WARM UP THEN SETS UP THROUGH MUCH OF NEXT WEEK AS WESTERN CONUS TROUGHING DEVELOPS. SHORTWAVES ARE PROGGED TO EJECT OUT OF THE TROUGH AND MOVE ACROSS THE OHIO VALLEY REGION IN SOUTHWEST FLOW...KEEPING PERIODIC RAIN AND SNOW CHANCES THROUGH LATE WEEK. THE BEST CHANCE APPEARS TO BE WITH A TUESDAY/TUESDAY NIGHT WAVE. MODEL QPF AMOUNTS APPEAR TO BE OVERDONE IN THE WARM ADVECTION REGIME...BUT WILL MONITOR AS A DECENT SNOWPACK REMAINS. ENSEMBLE BASED WPC GUIDANCE OFFERED A REASONABLE START TO THE FORECAST...THOUGH MADE ADJUSTMENTS TO THE LATEST GFS TO WARM SOME TEMPS...WITH ADJUSTMENTS FOR PRECIP TYPE BASED ON GFS CRITICAL THICKNESSES. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/...
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LOW LEVEL NORTHWESTERLY FLOW HAS ADVECTED PROGRESSIVELY DRIER AIR OVER THE AREA EARLY THIS EVENING. WHILE THE SUN WAS UP...EVEN WITH DRY ADVECTION...SOME STRATOCUMULUS DEVELOPED OFF THE GREAT LAKES EVEN WITH THE ICE COVER DUE TO DIURNAL HEATING WORKING WITH MODEST HEAT/MOSITURE FLUX OFF THE FEW CRACKS THAT DO EXIST IN THE ICE. AS THE EVENING ENSUES...EXPECT LOW LEVEL STABILITY TO MAKE LAKE INDUCED STRATUS MORE DIFFICULT TO MAINTAIN...WHICH SHOULD LEAD TO A SCATTERING OUT OF LOW CLOUDS. THAT SAID...MID CLOUDS ARE SET TO INCREASE THROUGH THE MAJORITY OF THE NIGHT AS AN AREA OF INCREASED MID-LEVEL MOISTURE MOVES FROM INDIANA THROUGH WESTERN PENNSYLVANIA. THIS SHOULD CLEAR THE AREA BY MORNING...RESULTING IN VFR CONDITIONS FOR FRIDAY WITH LIGHT WNW WINDS. FRIES OUTLOOK.../FRIDAY THROUGH MONDAY/... RESTRICTIONS ARE LIKELY WITH CROSSING LOW PRESSURE SUNDAY INTO MONDAY.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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