Area Forecast Discussion
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025 FXUS61 KPBZ 101729 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1229 PM EST WED FEB 10 2016 .SYNOPSIS...
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SNOW SHOWERS THIS AFTERNOON AND TONIGHT WILL GRADUALLY DIMINISHING THURSDAY. TEMPERATURES WILL CONTINUE TO FALL THROUGH THE WEEK WITH BITTER COLD TO START THE WEEKEND.
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&& .NEAR TERM /THROUGH THURSDAY/...
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FOR THE AFTERNOON UPDATE CHANGES TO HOURLY TEMPERATURES AND WINDS WERE MINOR. HI-RES MODELS CONTINUE TO SHOW BAND OF SNOW ALONG LAKE ERIE TRANSITIONING SOUTH LATE AFTERNOON AND EVENING AS TROUGH AND WIND SHIFT PASSES. PREVIOUS DISCUSSION BELOW. SNOW SHOWERS SHOULD CONTINUE THIS AFTERNOON AHEAD OF AN ADVANCING SHORTWAVE TROUGH. THE TROUGH WILL SWING THROUGH THIS AFTERNOON/EVENING...FURTHER DEEPENING THE BOUNDARY LAYER AND GIVING RISE TO SNOW SQUALLS. NEAR TERM MODELS ALL SHOW FAVORABILITY FOR SNOW SQUALLS FROM 18-00Z IN THE BTV SNOW SQUALL PARAMETER. THIS WILL HAVE THE POTENTIAL TO IMPACT THE EVENING COMMUTE...ESPECIALLY FOR AREAS FROM PITTSBURGH NORTH WHERE DEEPER LAKE-ENHANCED MOISTURE RESIDES. LAKE-ENHANCEMENT WILL CONTINUE IN THE WAKE OF THE DEPARTING UPPER TROUGH TONIGHT. CURRENT GUIDANCE CONTINUING THE TREND OF SHOWING MULTIPLE LAKE-TO-LAKE SNOW BANDS SETTING UP. UPSLOPE SNOW WILL CONTINUE AND EVEN STRENGTHEN TONIGHT AS THE COLDER AIR POURS IN AND THE DENDRITIC SNOW GROWTH ZONE DESCENDS THROUGH THE COLUMN. EXPECTING SNOW RATIOS TO MAXIMIZE THIS EVENING THROUGH TONIGHT...WHICH WILL ALLOW FOR EFFICIENT ACCUMULATION. TEMPERATURES WILL CONTINUE THEIR DESCENT INTO THE WELL-BELOW NORMAL RANGE. MANY LOCATIONS WILL BE REACHING INTO THE SINGLE DIGITS BEFORE SUNRISE THURSDAY. A COMPLICATED HEADLINE CONFIGURATION PLAYED OUT THIS MORNING...INCLUDING AN EXTENSION OF THE CURRENT LONG-DURATION WINTER WEATHER ADVISORY IN THE RIDGE COMMUNITIES. IN ADDITION...HAVE OPTED TO ISSUE A NEW ADVISORY FOR TODAY THROUGH EARLY THURSDAY FOR PITTSBURGH METRO NORTH FOR THE POTENTIAL IMPACT TO THE EVENING COMMUTE AND THE PROLONGED EFFICIENT LAKE-EFFECT SNOWS. DECIDED TO KEEP AREAS SOUTH OF ALLEGHENY COUNTY OUT OF THE ADVISORY AS SNOW SHOWERS SHOULD BE MORE SCATTERED IN NATURE. TAX
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... A BIT OF A BREAK IN THE ACTION LOOKS TO BE IN STORE FOR THURSDAY NIGHT INTO EARLY FRIDAY AS LOW LEVEL FLOW BACKS TO BE A BIT MORE SOUTHWESTERLY. THIS WILL CUT OFF THE OVER-LAKE FLOW COMPONENT...ALLOWING FOR THE BOUNDARY LAYER TO DRY OUT AND SKIES TO TEMPORARILY SCATTER OUT. INVERSION HEIGHTS ALSO FALLING WILL YIELD A CLEARING AND COLD NIGHT ON THURSDAY NIGHT...HOWEVER WITH FLOW TURNING SOUTHWEST...THINGS HIGH SINGLE DIGITS SEEM A GOOD BET WITH NEW SNOW COVER. THE NEXT SYSTEM IN THE NORTHWESTERLY FLOW ALOFT LOOKS TO DIVE SOUTHEASTWARD TOWARD OUR AREA FOR FRIDAY EVENING OR SO. MODEL TIMING WITH THIS SYSTEM HAS BEEN SUSPECT OVER THE PAST FEW RUNS...AND THE TREND ON THE 00Z CYCLE WAS TO BRING IT IN A BIT LATER FRIDAY THAN IN PREVIOUS CYCLES. THAT SAID...LAPSE RATES LOOK TO RAPIDLY INCREASE THROUGH THE DENDRITIC LAYER CONCURRENT WITH STRONG DIFFERENTIAL PVA MOVING THROUGH THE AREA IN THE LEFT EXIT OF THE UPPER JET STREAK. LOW LEVEL FRONTOGENESIS MAXIMIZES AHEAD OF THE VORT MAXIMA AND A BOUT OF SNOW SQUALLS SEEMS LIKELY TO MOVE SOUTHEASTWARD THROUGH THE AREA. BEHIND THE ROUND OF SQUALLS...DEEP LAYER NORTHWESTERLY FLOW SHOULD ALLOW FOR LAKE EFFECT SNOW SHOWERS TO RESUME WITH A STRONG UPSLOPE COMPONENT INTO THE RIDGES. ACCUMULATIONS WILL BE LIKELY MOST EVERYWHERE AS THIS SITUATION UNFOLDS. FRIES && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... AS LAKE EFFECT WINDS DOWN AND DRIER AIR MOVES OVER THE AREA BY SATURDAY NIGHT...SKIES SHOULD START TO BREAK UP. TEMPERATURES AT 850 MB ON ALL MODELS DROP INTO THE MID -20S CELSIUS BY SATURDAY NIGHT...MAKING THIS LIKELY THE COLDEST AIR FOR THIS WINTER TO WANDER ACROSS OUR AREA. A MULTI-MODEL CONSENSUS FAVORS SATURDAY NIGHT AS THE COLDEST NIGHT OF THE PATTERN...WITH WIDESPREAD NUMBERS BELOW 0F AT THE SURFACE LIKELY OVERNIGHT. SHORTWAVE RIDGING AND WARM ADVECTION FOLLOWS THE BRUNT OF THE COLD AIR GOING INTO EARLY NEXT WEEK...HOWEVER LARGE SCALE CYCLONIC FLOW WILL RE-ESTABLISH ITSELF THEREAFTER. THIS MEANS PERIODIC SYSTEMS MOVING THROUGH THE AREA WITH GENERALLY NORMAL OR BELOW NORMAL TEMPERATURES AND CHANCES OF SNOW SHOWERS THROUGH THE PERIOD. FRIES && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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WHILE MOST TERMINALS ARE BOUNCING BACK AND FORTH BETWEEN MVFR AND IFR IN OCCASIONAL SNOW SHOWERS...PRIMARY FOCUS IN THE FIRST SIX HOURS IS ON A HEAVIER SNOW BAND CURRENTLY ACROSS THE LAKE ERIE SHORELINE THAT IS SUPPOSED TO MOVE ACROSS THE REGION LATER THIS AFTERNOON AND EVENING. THE NORTHEAST TO SOUTHWEST ORIENTED BAND HAS BEEN MOVING SLOWER THAN ANTICIPATED BY MODEL FORECASTS...AND THE TIMING IN THE TAFS STILL COULD BE AN HOUR OR TWO EARLIER CONSIDERING RECENT TRENDS. HAVE GENERALLY GONE WITH 1 MILE VISIBILITY FOR A FEW HOUR WINDOW...BUT POTENTIAL IS DEFINITELY THERE FOR VISIBILITIES TO DROP TO 1/2 MILE OR LESS. CONFIDENCE WAS NOT HIGH ENOUGH TO INCLUDE THAT SPECIFIC MENTION IN 18Z TAFS. THE BAND MAY STAY FAR ENOUGH NORTH AS TO NOT IMPACT THE ZZV/MGW TERMINALS. AFTER THE BAND MOVES THROUGH...WINDS SHOULD SHIFT A LITTLE MORE WEST-NORTHWEST...ALLOWING LAKE EFFECT SNOW SHOWERS TO DEVELOP. STRONGEST SNOW SHOWERS WILL BE AT FKL/DUJ...WITH IFR/LIFR CONDITIONS EXPECTED. ELSEWHERE...THINK THAT INTENSITY OF SNOW SHOWERS WILL BE LIGHT ENOUGH AND CEILINGS HIGH ENOUGH TO KEEP MVFR FLIGHT CATEGORIES INSTEAD OF IFR FLIGHT CATEGORIES. COVERAGE OF SHOWERS SHOULD DECREASE BY THURSDAY MORNING...ALTHOUGH SNOW WILL CONTINUE AT FKL/DUJ. .OUTLOOK.../THURSDAY THROUGH MONDAY/... OCCASIONAL RESTRICTIONS ARE EXPECTED THROUGH THE PERIOD UNDER COLD UPPER-LEVEL TROUGHING. WHILE THURSDAY AND SUNDAY SHOULD BE GENERALLY DRY...SCATTERED TO WIDESPREAD SNOW SHOWERS ARE EXPECTED FRIDAY...SATURDAY...AND MONDAY.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...WINTER WEATHER ADVISORY UNTIL 7 PM EST THURSDAY FOR MDZ001. OH...WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR OHZ041. PA...WINTER WEATHER ADVISORY UNTIL 7 PM EST THURSDAY FOR PAZ007>009- 015-074-076. WINTER WEATHER ADVISORY UNTIL 7 AM EST THURSDAY FOR PAZ013-014- 016-020>023-073-075. WV...WINTER WEATHER ADVISORY UNTIL 7 PM EST THURSDAY FOR WVZ510>514.
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