Area Forecast Discussion
Issued by NWS

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000 FXUS61 KPBZ 142111 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 411 PM EST SUN FEB 14 2016 .SYNOPSIS...
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TEMPERATURES WILL CONTINUE TO MODERATE. LIGHT SNOW IS EXPECTED OVERNIGHT...AND MIXED PRECIPITATION WILL BECOME A THREAT FOR MANY AREAS MONDAY AFTERNOON AND NIGHT.
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&& .NEAR TERM /THROUGH MONDAY/...
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SHORTWAVE SYSTEM CROSSING THE GREAT LAKES TONIGHT WILL HELP TO SPREAD LIGHT SNOW ACROSS THE REGION OVERNIGHT IN AN ISENTROPIC LIFT/OVERRUNNING PATTERN. LOW LEVEL DRY AIR FROM THE LINGERING ARCTIC AIR MASS WILL HELP TO KEEP QPF IN CHECK. SNOW ACCUMULATIONS SHOULD BE EITHER SIDE OF AN INCH BY 12Z...WITH THE HIGHEST ACCUMULATIONS ACROSS THE SOUTHERN COUNTIES. AFTER EVENING LOWS...TEMPERATURES WILL BEGIN TO RISE OVERNIGHT AS S/SW FLOW TAKES HOLD. EXPECT LIGHT SNOW TO CONTINUE INTO MONDAY MORNING...ALTHOUGH ISENTROPIC LIFT WILL BE WANING WITH THE DEPARTURE OF THE MIDLEVEL WAVE. PRECIP TYPE QUESTIONS THEN BECOME MORE INTERESTING AS WE HEAD INTO THE AFTERNOON. STRONG SOUTHERLY PUSH OF WARM AIR ALOFT PUNCHES INTO THE SOUTHERN CWA FROM MIDDAY ON. COLUMN BECOMES SUFFICIENTLY WARM TO TURN MUCH OF THE PRECIPITATION TO RAIN AT LEAST FROM PIT ON SOUTH. THE ISSUE LIES IN THE RECENT ARCTIC OUTBREAK. GIVEN THE RECENT BITTERLY COLD TEMPERATURES...THERE IS SOME CONCERN THAT SURFACES SUCH AS ROADS WILL REMAIN COLD ENOUGH TO PROMOTE FREEZING EVEN WHEN THE AIR TEMPERATURE RISES A FEW DEGREES ABOVE 32. TRIED TO KEEP MORE FREEZING RAIN MENTION IN THE GRIDS TO ACCOUNT FOR THIS POSSIBILITY. FOR NOW...GIVEN UNCERTAINTIES IN AREAL EXTENT AND TIMING OF THIS PHENOMENON...WE WILL BE HOLDING OFF ON ISSUING AN ADVISORY FOR TOMORROW AFTERNOON. THE HWO MENTION WILL BE MAINTAINED...AND WE PLAN ON MENTIONING THIS SPECIFIC THREAT IN OUR BRIEFING PACKAGES.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
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MODEL CONSENSUS CONTINUES TO EMPHASIZE A MORE WESTERLY TRACK FOR THE LOW PRESSURE SYSTEM...PROGGED NOW TO RIDE NORTHEASTWARD ACROSS THE OHIO VALLEY AND INTO NEW YORK/NEW ENGLAND BY TUESDAY NIGHT. THIS TRACK SUPPORTS MIXED PRECIPITATION EVENT FOR MUCH OF THE REGION...WITH A VERY STRONG LOW LEVEL JET BRINGING WARM AIR AHEAD OF THE LOW INTO THE FORECAST AREA. THIS STRONG WARM ADVECTION SHOULD EVENTUALLY MAKE THE PREDOMINANT PRECIPITATION TYPE RAIN HOWEVER...AT ONSET...A PERIOD OF FREEZING RAIN APPEARS LIKELY AS TEMPERATURES WILL BE SLOW TO WARM AHEAD OF THIS SYSTEM MONDAY. IN ADDITION...GROUND TEMPERATURES ARE VERY COLD DUE TO THE LAST SEVERAL DAYS OF TEMPERATURES IN THE SINGLE DIGITS AND TEENS. THE EASTERLY FLOW WOULD ALSO LEAD TO SHELTERED VALLEYS STAYING COLD LONGEST...WHICH SUPPORTS A PROLONGED PERIOD OF FREEZING RAIN OVER THE HIGHER TERRAIN...MAINLY GARRETT COUNTY. THE UNCERTAINTY STILL LIES IN OUR MOST NORTHWESTERN ZONES...WHERE SNOW MAY ACCUMULATE RAPIDLY IF THE LOW TRACK WOBBLES ANY FURTHER EAST. THERE WILL BE SUFFICIENT QPF THAT DESPITE VERY LOW SNOW RATIOS...ADVISORY LEVEL THRESHOLDS MAY BE EXCEEDED. WITH THE AFOREMENTIONED ICE AND SNOW CONCERNS...A WINTER WEATHER ADVISORY WAS CONSTRUCTED TO REFLECT THE NORTHERN ZONES AND EASTERN RIDGES. THE FREEZING RAIN IS ENOUGH OF A CONCERN THAT AN EXPANSION OF THE ADVISORY IS LIKELY...PENDING ADDITIONAL ANALYSIS AND MODEL RUNS THIS EVENING/OVERNIGHT. THE LOW WILL QUICKLY SHIFT EASTWARD...WITH ANOTHER FAST-MOVING SYSTEM QUICKLY ON ITS HEELS. THE MODEL PLACEMENT OF THIS WAVE CONTINUES TO DIFFER...SO POPS WERE GENERALLY KEPT LOW. TEMPERATURES WILL NOT BE COOLING OFF VERY QUICKLY...SO LOW SNOW RATIOS SHOULD LEAD TO LIGHT ACCUMULATIONS...AT LEAST FOR NOW.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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RIDGING AND A WARM UP LOOKS TO TAKE PLACE BY LATE IN THE PERIOD WITH A SYSTEM PROGGED TO CLIP THE REGION FOR THE START OF THE WEEKEND. HEAVY EMPHASIS WAS USED ON THE SUPERBLEND FOR THE LONG TERM.
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&& .AVIATION /21Z SUNDAY THROUGH FRIDAY/... SOME BKN MVFR CU HAVE FORMED UP IN A LINE FROM YNG THROUGH BTP TO NEAR LBE...LIKELY FROM LEFTOVER LAKE PLUME MOISTURE. THESE SHOULD BREAK UP OVER THE NEXT FEW HOURS. OTHERWISE...MID AND HI CLOUDS WILL BE INCREASING AHEAD OF THE NEXT STORM SYSTEM. A PERIOD OF LIGHT SNOW IS EXPECTED OVERNIGHT AND INTO MONDAY MORNING. MVFR CIGS ARE LIKELY WITH THE SNOW. VIS COULD DROP BRIEFLY INTO IFR TERRITORY BUT TIMING THAT REMAINS TRICKY. A GENERAL LULL IN PRECIPITATION WILL FOLLOW FOR MIDDAY AND EARLY AFTERNOON. PRECIPITATION THEN INCREASES AGAIN FROM THE SOUTH LATE IN THE DAY...ALONG WITH A WARMER PUSH OF AIR. ADDED A FZRA POSSIBILITY TO THE TAIL END OF THE 30 HOUR PIT TAF. .OUTLOOK.../MONDAY THROUGH FRIDAY/... LOW PRESSURE SYSTEMS WILL BRING WIDESPREAD RESTRICTIONS LATER MONDAY THROUGH WEDNESDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...WINTER WEATHER ADVISORY FROM 7 PM MONDAY TO 1 PM EST TUESDAY FOR MDZ001. OH...NONE. PA...WINTER WEATHER ADVISORY FROM 7 PM MONDAY TO 1 PM EST TUESDAY FOR PAZ007>009-013>016-022-023-074-076. WV...WINTER WEATHER ADVISORY FROM 7 PM MONDAY TO 1 PM EST TUESDAY FOR WVZ511>514.
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&& $$

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