Area Forecast Discussion
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000 FXUS61 KPBZ 080047 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 747 PM EST SUN FEB 7 2016 .SYNOPSIS... LOW PRESSURE IS POISED TO SPREAD RAIN AND SNOW OVER THE REGION ON MONDAY...AND SNOW ON TUESDAY AND WEDNESDAY. && .NEAR TERM /THROUGH MONDAY/... THE UPR OH REGION IS EXPECTED TO REMAIN DRY THROUGH MIDNGT WITH RIDGING BETWEEN WRN GREAT LAKES AND SERN COASTAL LOW PRESSURE SYSTEMS. TEMPERATURES WILL ONCE AGAIN BE ABOVE SEASONAL AVERAGES. THE WRN LOW WL BE THE PROBLEM FOR THE NXT FEW DAYS AS IT IS FORECAST TO DEEPEN OVR THE MIDWEST AND PLAGUE THE ARE WITH BROAD ASCENT...DEEP MOISTURE...WITH SHORTWAVE SUPPORT ROTATING ARND THE CUTOFF LOW. FOR TONIGHT...MOISTURE AND ASCENT VIA WARM ADVCTN AND WEAKLY DIVERGENT FLOW ALOFT ARE LIKELY TO SUPPORT PRECIPITATION DEVELOPMENT OVER WESTERN ZONES TOWARD MORNING...WITH EASTWARD PROGRESSION AFTER DAYBREAK MONDAY AS PER SLOWER MDL CONSENSUS. AS THAT SOLN SEEMS REASONABLE GIVEN SBSDNC ON THE WRN FLANK OF THE EXPLODING SE COAST/WRN ATLANTIC LOW...HAVE ADJUSTED GRIDS FOR THAT SCENARIO AND RETREATED FROM OVRNGT POPS. PRECIP TYPE REMAINS AN ISSUE GIVEN THE AFOREMENTIONED WARM ADVECTION AND LINGERING BOUNDARY LAYER WARMTH. EXPECT A RAIN/SNOW OR A PRIMARY SNOW SITUATION WITH MELTING AT THE SFC AS THE SYSTEMS COLD FRONT PLOUGHS TOWARD THE I 77 CORRIDOR DURING THE PREDAWN HOURS. GIVEN THE TEMP LIMITATIONS AND SLOWER PROGRESSION...ANY LIGHT ACCUMULATION IS NOT EXPECTED TO BE PROBLEMATIC FOR THE RUSH HOUR. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... SOME PROBLEMATIC TRENDS SEEM TO BE DEVELOPING IN THE MORE RECENT MODEL RUNS VIS-A-VIS THE NORTHWARD PROGRESSION OF A SECONDARY LOW LEVEL FRONTOGENETICAL REGION ON THE FRONT SIDE OF THE PUSH OF GENUINE ARCTIC AIR. THE SIGNAL IS QUITE PRESENT ON THE GFS...NAM...AND CANADIAN GLOBAL...HOWEVER THE LOCATION OF THE BEST FORCING FOR ASCENT DOES VARY FROM MODEL-TO-MODEL. THE INCOMING 18Z GFS DOES LINE UP FAIRLY WELL WITH THE CANADIAN GLOBAL...HOWEVER THE NAM PLACEMENT IS QUITE A BIT FARTHER SOUTH WITH THE FRONTOGENETICAL ZONE. THIS YIELDS A LOW CONFIDENCE FORECAST IN TERMS OF NORTHWARD SPREAD OF MORE SUBSTANTIAL SNOW ON MONDAY NIGHT INTO TUESDAY. THE COMMON THEMES AMONGST THE GUIDANCE FROM MONDAY NIGHT INTO TUESDAY GENERALLY REVOLVE AROUND GOOD DEFORMATION FROM THE SURFACE TO 700 MB ALIGNING WITH FRONTOGENETICAL FORCING AND SOME ATLANTIC MOISTURE FEED BACK INTO A TROWAL AIR STREAM THAT FEEDS TOWARD THE OHIO VALLEY. HOWEVER...LOW LEVEL SPECIFICS WILL BE IMPORTANT. THUS...THE FORECAST WAS FOCUSED ON INCREASING SNOW CHANCES AND INTENSITY GENERALLY FROM PITTSBURGH SOUTHWARD THROUGH THE PERIOD WITH BROAD ADVISORY TYPE ACCUMULATIONS DURING THE DURATION. HOWEVER...IT IS QUITE POSSIBLE THAT THIS FGEN ZONE WILL LINGER IN SOME PARTICULAR AREA DURING THAT INTERVAL. IF THAT SHOULD OCCUR...GOOD MICROPHYSICAL SUPPORT FOR MODERATE TO HIGH RATIO SNOWS COULD WELL RESULT IN WARNING TYPE ACCUMULATIONS IN THE CORRIDOR IT LINGERS. FRIES BY WEDNESDAY...THE CUTOFF LOW IS FORECAST TO BE FILLED/PHASED WITH THE UPR OH UNDER THE AXIS OF A HIGH-AMPLITUDE ERN CONUS TROUGH. SNOW SHOWER POTENTIAL WILL THUS CONTINUE AS INCREASINGLY COLDER AIR IS POISED TO FLOW OVR THE REGION AS THAT AXIS SHIFTS EWD. IN ADDITION...THE LATEST DETERMINISTIC TREND IS TO ROTATE A VORT CENTER/SHORTWAVE INTO THE BASE OF THAT LOW. PRECIP PROBS WERE THUS INCRSD FOR WEDNESDAY...CUMULATING IN CATEGORICAL NUMBERS FOR THE HIGHER ELEVATIONS...BUT DRY ADVCTN AND INCREASING COLD IN THE SNOW-SOURCE REGION SHOULD DEGRADE EFFICIENCY SO TOTALS WERE NOT AMPED MUCH AT THIS STAGE OF THE FORECAST PROCESS. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... THE AFOREMENTIONED UPPER TROUGHING PTN IS PROGGED TO CONTINUE FUNNELING COLD AIR OVR THE AREA THROUGH THE WEEKEND. SUB AVG TEMPS CAN BE EXPECTED WITH READINGS ABOUT 20 DEGREES UNDER THE NORMALS ANTICIPATED BY THE WEEKEND. THE I 80 CORRIDOR AND RIDGE ZONES WL HAVE THE BETTER SNOW SHOWER POTENTIAL DURING THIS PERIOD GIVEN THE COLD ...OFF-THE-LAKES UPSLOPING FLOW. THE LONG TERM WAS CONSTRUCTED USING THE SUPERBLEND GUIDANCE. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... LITTLE TO CHANGE AS VFR IS EXPECTED TO CONTINUE TONIGHT UNTIL MOISTURE INCREASES IN ADVANCE OF THE COLD FRONT. TIMING OF PRECIPITATION ONSET HAS CHANGED LITTLE BASED ON THE LATEST MODEL RUNS...WITH SNOW OR RAIN/SNOW EXPECTED FROM WEST TO EAST ACROSS THE TERMINALS. A DETERIORATION TO MVFR...WITH PATCHY IFR IS ANTICIPATED AS THE BOUNDARY CROSSES STARTING 12Z AT ZZV...AND PROGRESSING EASTWARD INTO WESTERN PA BY 18Z. FURTHER DETERIORATION IS EXPECTED AS THE TERMINALS THAT EXPERIENCE RAIN TRANSITION BACK TO SNOW. .OUTLOOK.../TUESDAY THROUGH FRIDAY/... RESTRICTIONS CAN BE EXPECTED THROUGH THU WITH THE AREA UNDR UPR TROFG. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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