Area Forecast Discussion
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000 FXUS61 KPBZ 061827 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 127 PM EST FRI MAR 6 2015 .SYNOPSIS... CLEAR SKIES WILL GRADUALLY BE REPLACED BY CLOUDS THROUGH SATURDAY AS COLD AIR SLOWLY ERODES THIS WEEKEND. MORE SEASONABLE TEMPERATURES LOOK TO FINALLY RETURN BY MIDWEEK. && .NEAR TERM /THROUGH SATURDAY/... MID AND HIGH CLOUDS HAVE BEGUN TO INCREASE ACROSS THE AREA AS AN EXCEEDINGLY WEAK...MOISTURE STARVED...AND ESSENTIALLY SURFACE DISCONNECTED SYSTEM IS TRACKING THROUGH THE REGION. WITH LITTLE INCREASE IN LOW LEVEL MOISTURE...NO PRECIPITATION IS EXPECTED FROM THIS SYSTEM. THE MAIN IMPACTS WILL BE A SLOW INCREASE IN SOUTHWESTERLY FLOW AS SURFACE HIGH PRESSURE MOVES OFF TO THE EAST...AS WELL AS THE AFOREMENTIONED MID AND HIGH CLOUD INCREASE. THE EFFECTS OF THIS WILL BASICALLY BE TO HOLD BACK TEMPERATURES THROUGH SUNSET...WITH LITTLE MORE FANFARE THAN THAT. GOING INTO TONIGHT...THE GRADIENT FLOW FROM THE SOUTHWEST SHOULD INCREASE JUST A BIT...ALTHOUGH THE PREPONDERANCE OF GUIDANCE SUGGESTS OUR BOUNDARY LAYER MAY DECOUPLE FROM THE WEST VIRGINIA PANHANDLE EASTWARD BEFORE THIS OCCURS. ADDITIONALLY...SOME CLEARING MAY BE POSSIBLE FOR AN INTERLUDE BETWEEN THE WEAK SYSTEM THIS EVENING AND ANOTHER NORTHERN STREAM WAVE THAT APPROACHES FOR SATURDAY AFTERNOON. DECOUPLING COMBINED WITH COME CLEARING SHOULD ALLOW FOR MANY AREAS TO DROP A FAIR BIT TONIGHT...EVEN AS MOS GUIDANCE FAILS TO SHOW MUCH DIURNAL FALL AT ALL. THAT SAID...LOWS WERE FORECAST COMBINING THE COLDER END OF GUIDANCE...AND SHOULD CLEARING MATERIALIZE IN A MORE WIDESPREAD FASHION...SINGLE DIGITS MAY AGAIN BE POSSIBLE. BY SATURDAY...CLOUDS WILL AGAIN BE ON THE INCREASE. WHILE MODEL SOLUTIONS REALLY HAVE FAILED TO TREND MUCH STRONGER WITH THE NORTHERN STREAM WAVE...THEY ARE MANAGING TO KICK UP LAYER MOISTURE A BIT. ADDITIONALLY...FAIRLY UNSTABLE LOW LEVEL LAPSE RATES SEEM TO BE GENERATED...AND THE MAJORITY OF THE LIFT IN TIME HEIGHT SECTIONS SEEMS TO BE WORKING ON THE UNSTABLE PORTION OF THE PROFILE AS THE SYSTEM PASSES. BECAUSE THE MAJORITY OF THE LIFT TRAVERSES TO OUR NORTH...POPS WERE GENERALLY BUILT TO FAVOR THE I-80 CORRIDOR AND TAPER SOUTHWARD...WITH MOISTURE LIKELY BEING TOO LEAN TO SQUEEZE OUT ANYTHING SOUTH OF PITTSBURGH. SOUNDINGS FROM BOTH THE NAM AND GFS SUGGEST THAT WET BULBING SHOULD KEEP ANY PRECIPITATION THAT FALLS ON SATURDAY AFTERNOON AS SNOW. THIS SEEMS LIKELY EVEN AS WARM ADVECTION AND EFFICIENT MIXING AHEAD OF THE SYSTEM MAY WELL WARM VIRTUALLY THE ENTIRE CWA ABOVE FREEZING BY AFTERNOON. IN FACT...ACROSS THE FAR SOUTHERN CWA...EVEN A 40 DEGREE READING WOULD NOT BE TOO SHOCKING. THIS IS A FAR CRY FROM THE BELOW ZERO READINGS WE HAD THIS MORNING...AND DOWNRIGHT TROPICAL COMPARED TO WHAT FEBRUARY WAS LIKE. IT CERTAINLY SEEMS LIKE OLD MAN WINTER MAY BE HAVING HIS BACK BROKEN IN OUR AREA VERY SHORTLY. FRIES && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... SYNOPTIC PATTERN IN THE SHORT TERM BEGINS WITH NORTHWEST FLOW ALOFT...AND MULTIPLE WEAK SHORTWAVE TROFS PASSING THROUGH THE GREAT LAKES. THIS WILL KEEP TEMPERATURES RELEGATED TO JUST BELOW AVERAGE THROUGH THE WEEKEND AND AT LEAST SLIGHT CHANCE POPS IN ALONG THE NORTH. DEEPER MID-LEVEL WAVE PASSING LATE SATURDAY NIGHT INTO SUNDAY MORNING WILL REINFORCE LOW-LEVEL MOISTURE POOLING SOUTH OF LAKE ERIE AND DAMMED UP AGAINST THE HIGHER TERRAIN TO OUR EAST. MEANWHILE...MOISTURE ABOVE 700MB IS TRANSIENT AND MOVES QUICKLY EAST OF THE AREA. THINKING THAT REALLY LIGHT SNOW WILL BE THE MAIN PRECIPITATION TYPE. BUT...WITH THE BULK OF THE MOISTURE CONFINED TO THE LOW-LEVELS AND THE TOP OF THAT MOISTURE AROUND -8C...THE POTENTIAL FOR FREEZING DRIZZLE EXISTS. STILL SOME UNCERTAINTY SURROUNDING EXTENT OF MOISTURE AND TIMING...SO CONFIDENCE NOT HIGH ENOUGH TO INCLUDE FREEZING DRIZZLE IN THE GRIDS. WILL NEED TO CONTINUE TO MONITOR THIS WITH FUTURE RUNS OF HIGHER-RES MODELS. FLOW BEGINS TO GO MORE ZONAL TOWARDS THE BEGINNING OF NEXT WEEK...ALLOWING TEMPERATURES TO MODERATE UNDER MOSTLY DRY CONDITIONS. TAX && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... THE EXTENDED PERIOD LOOKS TO BE RELATIVELY QUIET AS ZONAL FLOW SETS UP ACROSS THE FORECAST AREA AND WE SEE A GRADUAL WARMING TREND IN TEMPERATURES...EXTENDING SLIGHTLY ABOVE NORMAL BY LATE WEEK. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... MID AND HIGH CLOUDS IN ASSOCIATION WITH A WEAK SYSTEM WILL MOVE THROUGH THE AREA THIS AFTERNOON. A BRIEF BREAK BEFORE MVFR CIGS WITH SOME LIGHT SNOW SHOWERS ACROSS THE NORTHERN SITES WILL BE POSSIBLE BY AFTERNOON. WINDS WILL INCREASE SLOWLY FROM THE SOUTHWEST AND BECOME GUSTY BY SATURDAY AFTERNOON. .OUTLOOK.../FRIDAY NIGHT THROUGH TUESDAY/... RESTRICTIONS ARE POSSIBLE THROUGH THE WEEKEND. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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