Area Forecast Discussion
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000 FXUS61 KPBZ 140521 AAC AFDPBZ AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PITTSBURGH PA 121 AM EDT MON APR 14 2014 .SYNOPSIS... A STRONG COLD FRONT WILL BRING SHOWERS AND STORMS TO THE AREA LATER TODAY AND OVERNIGHT. MUCH COLDER AIR TUESDAY WITH THE CHANCE FOR SNOW SHOWERS. && .NEAR TERM /THROUGH TODAY/... LITTLE CHANGE TO OVERNIGHT PERIOD. PREVIOUS FORECAST STILL ON TRACK. STRONG COLD FRONT WILL MOVE THROUGH THE MIDWEST THIS MORNING... SLOWING AS IT REACHES WESTERN OHIO THIS AFTERNOON. LATEST MODEL DATA IS SHOWING A DISCONNECTION BETWEEN THE UPPER LEVEL WAVES AND THE SURFACE BOUNDARY. WAVE NUMBER ONE WILL MOVE THROUGH THE REGION THIS AFTERNOON AHEAD OF THE COLD FRONT. LOOKING FURTHER WEST...THE UPPER LEVEL SUPPORT BECOMES NEGLIGIBLE AS THE NEXT MAIN SHORTWAVE...CLOSELY ASSOCIATED WITH THE TROUGH AND IN THE HEART OF THE VERY COLD AIR...IS WELL TO THE WEST OF THE SURFACE BOUNDARY. WITH THE LACK OF UPPER LEVEL SUPPORT...RAINFALL AMOUNTS WILL BE LIGHT. WITH THE ENTIRE SYSTEM SLOWING...IT WILL TAKE SOME TIME FOR THE DEEP MOISTURE TO REACH US. CONCERNING CONVECTION... ATMOSPHERE DOES DESTABILIZE LATER TODAY WITH LI`S OF -1 TO -2. CAPE VALUES ARE NOT IMPRESSIVE DUE TO THE LACK OF A LOW LEVEL SURGE OF MOISTURE. BIGGEST CONCERN AT THIS POINT WILL BE THE THREAT FOR STRONG WIND GUSTS...PARTICULARLY DURING THE AFTERNOON. WITH SURFACE TEMPS AGAIN WARMING INTO THE UPPER 60S AND 70S...MIXING HEIGHTS THIS AFTERNOON RISE TO THE 5000 TO 6000 FT RANGE. THIS ELEVATION WILL EASILY REACH INTO THE STRONGER WINDS ALOFT WHICH SHOULD HAVE NO PROBLEM MIXING DOWN. HAVE DECIDED TO INCREASE WIND GUSTS TO 35 TO 40 MPH. TEMPS WILL BE A LITTLE TRICKY AS THERE IS PLENTY OF PRE-FRONTAL CLOUD COVER MOVING IN. WILL DROP TODAY`S HIGHS JUST A BIT FROM PREVIOUS FORECAST. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... FRONT SLOWLY MOVES THROUGH THE AREA LATE TONIGHT/EARLY TUESDAY MORNING. THE CONVECTIVE THREAT WILL DECREASE TONIGHT AND WINDS WILL RELAX. MOST OF THE PRECIPITATION WILL MOVE THROUGH DURING FRONTAL PASSAGE. MUCH COLDER AIR WILL QUICKLY RUSH IN BEHIND THE FRONT...WHICH SHOULD BE COLD ENOUGH TO CHANGE POST FRONTAL RAIN SHOWERS TO SNOW SHOWERS. LOOKING WESTWARD...FRONT IS SEPARATING A WIDE RANGE OF TEMPS WITH READINGS EAST OF THE FRONT IN THE MID 60S TO TEMPERATURES BEHIND THE FRONT IN THE UPPER 30S TO MID 40S. LOW CONFIDENCE IN THE CURRENT AMOUNT OF QPF MODELS ARE CREATING BEHIND THE FRONT. AT THIS TIME...IT LOOKS AS IF THERE IS A PERIOD DIRECTLY BEHIND THE FRONT WHERE THE MODELS ARE OVER DOING THE AMOUNT OF LIFT. THIS SHORT PERIOD OF STRONG OMEGA IS LIKELY CAUSING AN OVER AMPLIFICATION OF QPF AMOUNTS TUESDAY MORNING. TEMPS WILL BE VERY TRICKY ON TUESDAY...LATEST MODEL SOUNDINGS ARE INITIALLY SHOWING A RAPID DROP OF SURFACE TEMPERATURES WITH FROPA...AS A SHALLOW LAYER OF LOW LEVEL COLD AIR SETTLES IN. THIS FEATURE SHOWS UP WELL WITH AN EXAMINATION OF LAYERED THICKNESSES. LOW LEVEL THICKNESS WILL BECOME COLD ENOUGH FIRST TO SUPPORT SNOW...HOWEVER THE COLD MID LEVEL THICKNESSES ARE LAGGING BEHIND BY ABOUT 3 HOURS. THIS SETUP WOULD LIKELY PRODUCE A MIX OF RAIN AND SNOW WHICH WOULD EVENTUALLY CHANGE TO ALL SNOW. THE OTHER QUESTION IS HOW FAR DO TEMPS DROP AND WILL THERE BE ANY RECOVERY DURING THE DAY WITH STRONG CAA ONGOING THROUGHOUT THE DAY. THE NEXT HEADACHE WILL ARRIVE LATE TUESDAY AFTERNOON THROUGH TUESDAY EVENING. VERY COLD AIR WILL CROSS THE GREAT LAKES AND STRONG WINDS ALOFT WILL BE OUT OF THE NORTHWEST. THE MAIN SHORTWAVE TROUGH SWINGS THROUGH DURING THIS TIME AND MODELS ARE HINTING AT A PERIOD OF LAKE EFFECT/ENHANCED SNOW SHOWERS. INVERSIONS TUESDAY EVENING ARE PLENTY DEEP ENOUGH TO SUPPORT LES. INVERSIONS QUICKLY DROP TUESDAY NIGHT AS WINDS ALOFT VEER TO THE NORTH AND A STRONG SURFACE HIGH WILL BUILD IN FROM THE WEST. THIS WILL BRING A QUICK END TO ANY SNOW SHOWERS THAT DEVELOP. COLD AIR WILL EVACUATE TOWARD THE NORTH WEDNESDAY...THIS WILL ALLOW FOR A QUICK DECREASE IN CLOUD COVER AND A MODERATION IN TEMPS. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... A RETURN TO SPRING FOR THE LONG TERM...WITH THE RISK FOR SHOWERS FRIDAY NIGHT/SAT. && .AVIATION /05Z MONDAY THROUGH FRIDAY/... PRIMARY AVIATION CONCERN OF THE MRNG WL BE LLVL WIND SHEAR AS LLVL JET STREAKS ACRS THE REGION. MIXING AFTER DAYBREAK WL THEN SPPRT SFC GUSTS OF 25 TO 35KT. OTHERWISE...VFR CAN BE EXPECTED INTO AFTN...BUT CONDITION DETERIORATION SHOULD BE ANTICIPATED THEREAFTER AS SHWRS DVLP WITH THE ADVN OF A CDFNT ACRS THE MIDWEST. WIDESPREAD RAIN AND RESTRICTIONS ARE FORECAST AS EVE FALLS. .OUTLOOK.../TUESDAY THROUGH FRIDAY/... RESTRICTIONS ARE EXPECTED UNTIL COLD HIGH PRES BLDS LTR ON TUESDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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