Area Forecast Discussion
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000 FXUS61 KPBZ 241016 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 516 AM EST TUE FEB 24 2015 .SYNOPSIS... A REINFORCING COLD FRONT WILL MOVE THROUGH TUESDAY NIGHT WITH LIGHT SNOW MAINLY NORTH OF PITTSBURGH. BELOW AVERAGE TEMPERATURES WILL REMAIN THROUGH THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... ...BITTERLY COLD TEMPERATURES THROUGH MID-MORNING... CURRENT IR SATELLITE IMAGERY SHOWING CLEAR SKIES ACROSS THE CWA. THE CLEAR SKIES...CALM WINDS...AND SIGNIFICANT DRY AIR HAVE COMBINED FOR YET ANOTHER ROUND OF TEMPERATURES AT OR BELOW ZERO FOR MOST LOCATIONS. SEVERAL LOCATIONS...MAINLY NORTH OF PITTSBURGH ARE ALREADY AROUND -20F. SOME OF THE WARMER LOCATIONS AT THIS HOUR ARE THE URBAN HEAT ISLAND OF DOWNTOWN PITTSBURGH...MORGANTOWN...AND SELECT LOCATIONS IN THE HIGHER ELEVATIONS THAT ARE ABOVE THE INVERSION. ALTHOUGH THESE AREAS ARE WARMER...THEY STILL REMAIN NEAR 0F. WITH A FEW MORE HOURS OF COOLING TO GO...EXPECT TEMPERATURES TO CONTINUE CREEPING DOWNWARDS. THE ONLY RELIEF IN SIGHT IS A THIN VEIL OF HIGH CIRRUS THAT MAY SKIRT OUR NORTHWEST ZONES BY 12Z...WHICH COULD HELP CURTAIL SOME OF THE RADIATIONAL COOLING. OTHERWISE...TEMPERATURES WILL STAY BITTERLY COLD UNTIL MIXING BEGINS TO KICK IN NEAR SUNRISE. WINDS HAVE BEEN CALM THROUGH THE NIGHT...BUT AS WE BEGIN TO MIX AND RE-COUPLE THE ATMOSPHERE...THERE WILL BE A SEVERAL HOUR WINDOW WHERE THE COLD TEMPERATURES WILL COMBINE WITH THE RELATIVELY LIGHT 5-10KT WINDS TO KEEP WIND CHILLS BELOW NEGATIVE 10F. THINKING IT WILL TAKE A FEW MORE HOURS FOR THIS TO OCCUR THAN PREVIOUSLY FORECAST...SO THE WIND CHILL ADVISORY HAS BEEN EXTENDED UNTIL 11AM. UNLIKE THE REMARKABLE COLD OF LAST WEEK...WHERE NEAR RECORD 850MB TEMPERATURES WERE SAMPLED...THE LOW-LEVEL TEMPERATURES ABOVE THE CURRENT INVERSION ARE ACTUALLY MUCH WARMER. IN FACT...SINCE 00Z THE 850MB TEMPERATURES HAVE RISEN NEARLY 7C AS WARM AIR ADVECTION TAKES PLACE ABOVE THE INVERSION. THIS SHOULD PROVIDE A GLIMMER OF HOPE ACROSS OUR FROSTY LANDSCAPE AS A RELATIVELY QUICK WARM-UP IS POISED TO OCCUR. INCREASINGLY STRONG LATE FEBRUARY SUNSHINE AND ENHANCED SOUTHERLY FLOW SHOULD EFFECTIVELY ERADICATE THE COLD AIR AND REBOUND DAYTIME HIGHS NICELY. DIURNAL RANGES COULD BE 30 TO 40 DEGREES TODAY. TONIGHT...YET ANOTHER COLD FRONT WILL ARRIVE TO REINFORCE THE BELOW AVERAGE TEMPERATURES. MID- AND UPPER-LEVEL MOISTURE COMPLETELY OVERRUNS THE LOW-LEVEL FRONT AND ASSOCIATED MOISTURE. THIS WILL HELP TAKE THE PUNCH OUT OF AN ALREADY RELATIVELY DRY FRONT. CLOUDS WILL OVERSPREAD THE FORECAST AREA THIS AFTERNOON/EVENING...FOLLOWED BY LIGHT SNOW SHOWERS. THE BEST FORCING AND DEEPEST MOISTURE STAYS WELL TO OUR NORTH...BUT OUR NORTHERN ZONES SHOULD SEE A AT LEAST A FEW HOURS OF LIGHT SNOW. SNOW GENERATION SHOULD BE FAIRLY EFFICIENT WITH SNOW RATIOS PROGGED AT 15 OR 20 TO 1. ALL TOLD 0.5 TO 1" IS POSSIBLE ALONG AND NORTH OF I-80. MOISTURE DEPTH REALLY DROPS OFF NEAR PITTSBURGH AND SOUTH...SO CONFIDENCE IN MEASURABLE SNOWFALL IS NOT HIGH. LOWS TONIGHT WILL BE CONSIDERABLY WARMER THAN CURRENT TEMPERATURES...BUT THATS NOT SAYING MUCH. TAX && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... EXPECT THE SURFACE FRONT TO BE ACROSS THE RIDGES BY 12Z WEDNESDAY...BUT COLDER AIR WILL LAG THE BOUNDARY A BIT AND NOT ARRIVE IN EARNEST UNTIL LATER IN THE DAY. LOW LEVEL NW FLOW AND MOISTURE IN THE DENDRITIC GROWTH LAYER WILL ALLOW SOME ISOLATED SHSN TO CONTINUE THROUGH MIDDAY...WITH ONLY AN ADDITIONAL LIGHT COATING OF SNOW AT MOST. AFTERNOON CLEARING WILL BE SHORT-LIVED...AS MIDLEVEL FLOW SETTLES TOWARDS THE WEST AND THEN SOUTHWEST WEDNESDAY NIGHT...PULLING MID AND HIGH CLOUDS BACK INTO THE REGION. UPPER LOW EJECTS OUT OF THE SOUTHWEST U.S. TONIGHT AND TRACKS ACROSS THE SOUTHERN STATES...BEFORE SWINGING ACROSS THE CAROLINAS AS A SHEARING WAVE INTO THURSDAY MORNING. NAM KEEPS A SHARPER WAVE AND MORE NORTHERLY LOW THAN OTHER MODELS...WHICH ARE A LITTLE MORE SUPPRESSED. WHILE THIS IS HAPPENING...ENERGY DROPS FROM THE NORTHERN PLAINS INTO THE SOUTHERN GREAT LAKES INTO FRIDAY...WHICH DRAGS ANOTHER ARCTIC FRONT TOWARDS US. AHEAD OF THE FRONT...MOISTURE GETS INTO THE REGION IN DEEP SW FLOW. MODELS SEEM TO BE STRUGGLING WITH DETAILS...BUT SLIGHTLY INCREASED CONFIDENCE IN PRECIP LED TO CHANCE POPS AREAWIDE FOR THURSDAY AND THURSDAY NIGHT. STILL APPEARS TO BE A LOW QPF EVENT...WITH PERHAPS AN INCH OF SNOW IN SOME LOCATIONS. HIGH PRESSURE BRIDGES IN FROM THE MISSISSIPPI VALLEY ON FRIDAY...WITH DRY WEATHER. BELOW ZERO READINGS EXPECTED AGAIN THURSDAY NIGHT...WITH HIGHS STILL IN THE TEENS ON FRIDAY. CL && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... DRY WEATHER CONTINUES THROUGH FRIDAY NIGHT AND SATURDAY. AFTER ANOTHER FRIGID NIGHT...SW RETURN FLOW BEHIND HIGH ON SATURDAY SHOULD ALLOW FOR SOME TEMPERATURE MODERATION. PATTERN MUDDIES THEREAFTER AS MAIN BAROCLINIC ZONE SETS UP SHOP IN OR JUST SOUTH OF OUR REGION FROM SUNDAY INTO EARLY NEXT WEEK. MOIST SW FLOW AND A FEW SHORTWAVES WILL PROVIDE OPPORTUNITIES FOR PRECIPITATION...THE BEST OF WHICH APPEARS TO BE SUNDAY NIGHT INTO MONDAY AT PRESENT TIME. PRECIPITATION TYPE REMAINS UNCERTAIN THROUGH THIS PERIOD. ENSEMBLES LIKELY WOULD PROVIDE THE PATH OF LEAST REGRET AT THIS POINT. NEVERTHELESS...THE RISING H500 HEIGHTS POINT TO TEMPERATURES AT LEAST GETTING WITHIN THE REALM OF SEASONABLE VALUES BY THE END OF THE EXTENDED PERIOD. CL && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... MAINLY CLEAR SKIES WILL CONTINUE AS DRY AIR ADVECTS IN WITH NORTHWEST FLOW. VFR IS EXPECTED TO CONTINUE THROUGH TUESDAY WITH HIGH PRESSURE OVER THE GREAT LAKES. TONIGHT ANOTHER RELATIVELY DRY COLD FRONT WILL APPROACH FROM THE NORTHWEST. EXPECTING LOW MVFR CIGS WITH THE FRONT. SNOW SHOULD REMAIN MOSTLY LIGHT...BUT ANY INDIVIDUAL MODERATE SNOW BANDS MAY REDUCE VISIBILITIES AT TIMES TO BELOW MVFR. CONFIDENCE IN TIMING AND LOCATION NOT HIGH ENOUGH FOR INCLUSION OF SUB-MVFR RESTRICTIONS AT THIS TIME. TAX OUTLOOK.../TUESDAY NIGHT THROUGH SATURDAY/... RESTRICTIONS ARE POSSIBLE AREA WIDE WITH A LATE THURSDAY DISTURBANCE SOUTH OF PIT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR MDZ001. OH...WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR OHZ039>041-048>050-057>059. PA...WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR PAZ007>009-013>016-020>023-029-031-073>076. WV...WIND CHILL ADVISORY UNTIL 11 AM EST THIS MORNING FOR WVZ001>004-022-023-041. && $$

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