Area Forecast Discussion
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPBZ 011934 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 234 PM EST SUN MAR 1 2015 .SYNOPSIS...
-- Changed Discussion --
SIGNIFICANT SNOW ACCUMULATIONS ARE EXPECTED ACROSS THE REGION THIS AFTERNOON INTO THIS EVENING. SNOW WILL MIX WITH RAIN THIS AFTERNOON FROM PITTSBURGH TO INDIANA SOUTHWARD. A SECOND STORM...ACCOMPANIED BY MILDER TEMPERATURES...WILL BRING POTENTIALLY HEAVY RAINFALL TO THE REGION TUESDAY AND TUESDAY NIGHT...LIKELY BEGINNING AS A PERIOD OF SLEET AND FREEZING RAIN EARLIER IN THE DAY. ICE ACCUMULATIONS ARE POSSIBLE. TEMPERATURES WILL GRADUALLY TREND WARMER THROUGH WEDNESDAY...BEFORE COLDER AIR RETURNS LATER IN THE WEEK.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH THIS EVENING/...
-- Changed Discussion --
HIGHLIGHTS: WATER-LADEN SNOW (SNOW/RAIN MIX SOUTH) TO CONTINUE THROUGH THIS EVENING...AND OVERNIGHT OVER THE EASTERN RIDGES. IMPACTS: A VERY HEAVY (WEIGHT) WET SNOW WILL MAKE SNOW REMOVAL DIFFICULT. SLUSHY NATURE TO SNOW WILL MAKE UNTREATED ROADS VERY SLICK AND HAZARDOUS. AMALGAMATION OF SNOW REPORTS FROM VARIOUS SOURCES SHOWS THAT THE SNOW MEASURING IS AN ART FORM THAT IS NOT WELL UNDERSTOOD NOR UNIFORMLY MASTERED. FACTORING IN THE MICROPHYSICAL CHALLENGES OF SURFACE TEMPS ABOVE FREEZING AND SNOW-LIQUID RATIOS AS LOW AS 5:1...AND THE HUMAN ISSUES LIKE MEASUREMENT INTERVALS AND LOCATIONS...IT`S NO WONDER THAT HALF THE PEOPLE THINK THE FORECAST IS SPOT ON AND THE OTHER HALF THINKS IT`S WRONG. MELTING...COMPACTION... COMPRESSION...SETTLING...AND ALL THE OTHER ISSUES WE`VE NOT HAD TO DEAL WITH DURING THE MANY RECENT BOUTS OF ARCTIC POWDER SNOW MAKE THIS EVENT A GREAT CHALLENGE IN COMMUNICATION. THUS THE FOCUS SHOULD REMAIN ON IMPACTS. IN A NUTSHELL...NO CHANGES TO THE PREVIOUS MID MORNING UPDATE. AS EXPECTED...IT`S TAKEN EVERY BIT OF 35F 2-METER TEMPERATURES FOR RAIN TO MIX IN FROM PITTSBURGH SOUTHWARD WITH A DEEP ISOTHERMAL LAYER ALOFT JUST BELOW 0C. ELSEWHERE...SURFACE TEMPS ARE GENERALLY AT OR JUST ABOVE FREEZING ACROSS ALL BUT THE FAR NORTHERN TIER...AND EXPECT SNOW TO CONTINUE IN THESE AREAS FOR THE DURATION. PRIMARY FOCUS FOR THIS AFTERNOON WILL BE ALONG AND SOUTH OF ZZV-BVI-DUJ WHERE STRONGER LIFT REMAINS AND TERRAIN ACTS TO ENHANCE THE SOUTHWEST FLOW. SEVERAL ADDITIONAL INCHES OF "MELT AS IT FALLS" SNOW ARE LIKELY THROUGH EARLY EVENING BENEATH A RATHER PRONOUNCED DENDRITIC GROWTH ZONE. A WEST-TO-EAST TEMPORARY LULL IN THE PRECIP MAY ALSO OVERSPREAD THE AREA AFTER 20Z...WHERE A TEMPORARY SWITCH TO DRIZZLE MAY OCCUR...BUT THIS SHOULD BE BE SHORT-LIVED AS ADDITIONAL BANDING DEVELOPS FURTHER WEST. BOOKBINDER
-- End Changed Discussion --
&& .SHORT TERM /LATE TONIGHT THROUGH TUESDAY/...
-- Changed Discussion --
OVERNIGHT: ---------- HIGHLIGHTS: ANY RAIN/MIX CHANGES BACK TO SNOW WITH FRONTAL PASSAGE. SNOW ENDS EXCEPT LAUREL HIGHLANDS & MD/WV RIDGES WHERE IT COULD BECOME HEAVY AT TIMES THIS EVENING. GUSTY WINDS DEVELOPING ACROSS THE RIDGES AS WELL. FOR MOST OF THE CWA...SNOW SHOULD TAPER OFF WEST-EAST THIS EVENING WITH THE PASSAGE OF A WEAK COLD FRONT. THE PRIMARY IMPACT OVERNIGHT WILL BE A RE-FREEZE AS TEMPERATURES SETTLE BACK INTO THE LOW-MID 20S. COULD EVEN SEE SOME AREAS OF FREEZING FOG DEVELOP IF THE WINDS DECOUPLE SUFFICIENTLY. SOME CLEARING POSSIBLE LATE OVER OHIO AND POSSIBLY THE NRN WV PANHANDLE TOWARD DAYBREAK. FOR THE EASTERN RIDGES...SNOW MAY ACTUALLY INCREASE IN INTENSITY THIS EVENING AS THE COLD FRONT DOES NOT APPEAR TO BE DEEP ENOUGH TO CLEAR THE HIGH TERRAIN. STRONG WESTERLY MOMENTUM AND UPSLOPE FLOW WILL LIKELY RESULT...YIELDING A PERIOD OF POTENTIALLY HEAVY SNOW AND GUSTY WINDS FROM 03-09Z. THIS IS WHERE MOST OF THE 6-8" TOTAL SNOWFALL FORECAST ALONG THE RIDGES IS ACCOUNTED FOR IN THE PREVIOUS UPDATE. MONDAY AND MONDAY NIGHT: ------------------------ A BRIEF LULL IN THE ACTIVE PERIOD AS HIGH PRESSURE SLIDES ACROSS THE REGION. WITH A FRESH SNOW PACK...HIGHS WILL STRUGGLE TO REACH THE MELTING POINT TOMORROW EVEN WITH SOME SUNNY INTERVALS EXPECTED. AT FIRST GLANCE...WOULD EXPECT TEMPERATURES TO FREE FALL TOMORROW NIGHT UNDER THE INFLUENCE OF HIGH PRESSURE AND FRESH SNOW. HOWEVER... MODEL CROSS SECTIONS SHOW RAPID ADVANCEMENT OF MID-HIGH LEVEL OVERCAST DURING THE EVENING AHEAD OF THE NEXT SYSTEM. THUS THIS BECOMES A HUGE TIMING ISSUE OF HOW FAST READINGS PLUMMET DURING THE EVENING BEFORE THE LONGWAVE RADIATION OUTBURST CEASES. HAVE DROPPED LOW TEMPS CONSIDERABLY OVER THE NORTHEAST CWA WHERE CONDITIONS ARE OPTIMAL THE LONGEST. VERY LOW CONFIDENCE TEMPERATURE FORECAST...ESPECIALLY IN THE NORTHERN MOUNTAINS WHERE THERE IS AN EQUAL POTENTIAL OF SEEING LOWS -5 TO -10...OR +5 TO +10 DEPENDING ON THE TIMING OF CLOUD COVER. WILL GO LOW SINGLE DIGITS FOR NOW ON A HEDGE...AND TEENS TO LOWER 20S ELSEWHERE. TUESDAY AND TUESDAY NIGHT: -------------------------- HIGHLIGHTS: A MAJOR STORM SYSTEM AND WARMER AIR WILL BRING RAINFALL (POTENTIALLY HEAVY) TO THE REGION. IMPACTS: INCREASING CONCERNS FOR BOTH RUNOFF AND ICE JAM INDUCED FLOODING. ADDITIONAL CONCERNS ABOUT SIGNIFICANT FREEZING RAIN/SLEET POTENTIAL EARLY IN THE EVENT. NUMEROUS FORECAST CHALLENGES THIS PERIOD AS MODELS CONTINUE TO DEPICT A TWO PART STORM PHASING AND DEEPENING AS IT CROSSES THE GREAT LAKES BENCHMARK. THIS PUTS THE CWA WELL INTO THE WARM SECTOR ALOFT...WITH ANOMALOUSLY HIGH MOISTURE CONTENT ROOTED IN BOTH THE PACIFIC AND GULF. INFLUX OF DEEP MOISTURE...COUPLED WITH STRONG AND PROLONGED WARM ADVECTION...AND A FAVORABLE JET STRUCTURE WILL COLLECTIVELY BRING PERIODS OF MODERATE TO HEAVY RAIN TO THE REGION TUESDAY AND TUESDAY NIGHT. KEY ISSUE NUMBER 1 IS AT THE ONSET. HAVING STARTED THE DAY OVERCAST WITH TEMPERATURES IN THE TEENS (IF NOT SINGLE DIGITS)...IT SEEMS TO REASON THAT A SIGNIFICANT ICING EVENT IS LIKELY TO OCCUR BETWEEN MID MORNING AND THE EARLY AFTERNOON BEFORE PRECIPITATION DRAG/WARM ADVECTION WARM THE BOUNDARY LAYER ABOVE FREEZING...PARTICULARLY OF CONCERN WOULD BE THOSE SAME NORTHEAST COUNTIES. SLEET/FREEZING RAIN ARE ACCOUNTED FOR IN THIS FORECAST UPDATE. KEY ISSUE NUMBER 2 IS WITH THE QPF. SEVERAL ENSEMBLE MEMBERS CONTINUE TO SHOW WIDESPREAD LIQUID QPF AMOUNTS ON THE ORDER 1-1.50" THROUGH TUESDAY NIGHT. THESE AMOUNTS ARE CERTAINLY JUSTIFIED...ALBEIT HIGHLY UNUSUAL FOR EARLY MARCH. A RAIN EVENT OF THIS MAGNITUDE...COUPLED WITH AN EXISTING HIGH-WATER CONTENT SNOW PACK...FROZEN GROUND AND ICED-OVER RIVERS/CREEKS...CERTAINLY HAS ME CONCERNED ABOUT FLOOD POTENTIAL -- BOTH FROM RUNOFF AND POTENTIAL ICE JAMS AS TEMPERATURES WARM INTO THE 40S TO THE SOUTH. KEY ISSUE NUMBER 3 IS WITH SURFACE TEMPERATURES. AS EXPECTED...A HUGE MODEL SPREAD EXISTS WITH RESPECT TO HIGH TEMPERATURES ON TUESDAY...NEVER MIND THE HOURLY TRANSITION. EXISTING SNOW PACK...PREVIOUS MORNING LOWS...PRECIPITATION INTENSITY AND THERMAL ADVECTION WILL ALL COMPETE TO WHAT LEADS TO A HIGH BUST POTENTIAL FORECAST ON TEMPERATURES -- THEREBY PLAYING INTO BOTH PRECIPITATION TYPE AND FLOODING POTENTIAL. THIS IS A HIGH CONFIDENCE...POTENTIALLY HIGH IMPACT EVENT WITH LOW CONFIDENCE DETAILS. HEADLINES FOR FREEZING RAIN AND/OR FLOODING MAY BE NECESSARY OVER THE NEXT 24 HOURS. PERSONS ARE URGED TO CLOSELY MONITOR FORECASTS OVER THE 24-36 HOURS. BOOKBINDER
-- End Changed Discussion --
&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
COLD FRONT CROSSES THE REGION TUESDAY NIGHT...REACHING THE MID- ATLANTIC REGION AROUND DAWN WEDNESDAY. RAIN WILL CONTINUE TO FALL AS THE FRONT PASSES THROUGH. WILL DECREASE POPS FROM NORTHWEST TO SOUTHEAST WEDNESDAY WITH COLDER AND DRIER AIR ADVECTING IN. ANY LINGERING PRECIPITATION WEDNESDAY AFTERNOON...WILL CHANGE TO SNOW SHOWERS AS COLDER AIR RUSHES IN FROM THE NORTHWEST. SURFACE HIGH MOVES IN THURSDAY...KEEPING THE REMAINDER OF THE LONG TERM DRY AND COLD.
-- End Changed Discussion --
&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/... IFR/OCCASIONAL LIFR CONDITIONS WILL CONTINUE INTO THE EARLY EVENING IN LOW CIG/VIS FROM SN. RAIN WILL MIX IN AT SEVERAL TERMINALS...ESPECIALLY SOUTH OF I-70...WHICH COULD ALLOW FOR TEMPORARY IMPROVEMENT TO MVFR. NORTH OF PIT...PRECIP REMAINS ALL SNOW WHICH WILL LOCK IN IFR. CIGS AT IFR/MVFR WILL BE MAINTAINED THROUGH THE NIGHT AS ANY MIXED PRECIP CHANGES BACK OVER TO SNOW. SLOW IMPROVEMENT BEGINS AFTER MIDNIGHT AS SNOW TAPERS FROM WEST TO EAST...WITH MVFR CIGS MAINTAINING THROUGH THE REST OF THE TAF PERIOD. SW WINDS THIS AFTERNOON AROUND 10 KNOTS WILL SETTLE TOWARDS WEST WITH TIME. CL .OUTLOOK.../SUNDAY NIGHT THROUGH THURSDAY/... CEILING RESTRICTIONS LIKELY WILL PERSIST THROUGH MUCH OF MONDAY. LOW PRESSURE CROSSING THE GREAT LAKES IS LIKELY TO SPAWN WIDESPREAD RESTRICTIONS ONCE AGAIN BY LATE TUESDAY. && .HYDROLOGY... MANY OF THE AREA RIVERS AND STREAMS ARE ICE COVERED. AN INCREASE IN FLOW AND STAGE IS EXPECTED TO CAUSE ICE MOVEMENT STARTING TUESDAY...BEGINNING ON THE SOUTHERNMOST RIVER BASINS. THE CURRENT FORECAST CONTINUES TO HAVE A HIGH LEVEL OF UNCERTAINTY ABOUT PRECIPITATION PHASE AND AMOUNTS AS WELL AS THE DEGREE OF SNOW MELT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR MDZ001. OH...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR OHZ039>041- 048>050-057>059. PA...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR PAZ007>009- 013>016-020>023-029-073>076. WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST MONDAY FOR WVZ001>003- 023-041. && $$

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.