Area Forecast Discussion
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000 FXUS61 KPBZ 270535 AAC AFDPBZ AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PITTSBURGH PA 135 AM EDT THU AUG 27 2015 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD AND END THE SPARSE SHOWER CHANCES AND COOL WEATHER BY THE END OF THE WEEK.
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&& .NEAR TERM /THROUGH TODAY/...
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BROKEN RECORD FOR THE OVERNIGHT PERIOD...DEALING WITH STRATOCU CLOUD DECK DUE TO THE ANTICYCLONIC FLOW AND WEAK COLD AIR ADVECTION. WILL MAKE MINOR ADJUSTMENTS TO CLOUD COVER OVERNIGHT AND TWEAK TEMPERATURES TO LATEST GUIDANCE. THE CLOSED UPPER LOW...OVER THE QUEBEC PROVINCE...WILL DRIFT NORTHEASTWARD TOWARD THE NEWFOUNDLAND AND LABRADOR PROVINCES TODAY. A WEAK SHORTWAVE TROUGH WILL SWING THROUGH THE UPPER OHIO VALLEY LATER TODAY. THIS SHOULD KEEP A CU DECK IN PLACE ACROSS MUCH OF THE AREA. TEMPERATURES WILL REMAIN WELL BELOW NORMAL.
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&& .SHORT TERM /TONIGHT THROUGH SATURDAY/...
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UPPER LEVEL HEIGHTS FINALLY BEGIN TO RISE ON FRIDAY AND BROAD SURFACE HIGH PRESSURE WILL SETTLE IN OVER THE REGION. THIS WILL ALLOW FOR A RETURN OF SUNSHINE AND MODERATING TEMPERATURES. UPPER LEVEL RIDGE WILL REMAIN IN PLACE THROUGH THE FIRST HALF OF SATURDAY AND SURFACE HIGH WILL MOVE OFF THE EASTERN SEABOARD. FLOW ON BACK SIDE OF EXITING HIGH WILL PROMOTE AN INCREASE IN TEMPERATURES AND HUMIDITY LEVELS. A WEAK SHORTWAVE...THAT WILL SLOWLY FLATTEN THE UPPER LEVEL RIDGE...MAY PROVIDE ENOUGH LARGE SCALE ASCENSION TO SPARK SCATTERED CONVECTION OVER THE WEST LATE SATURDAY. TEMPERATURES RETURN TO MORE SEASONABLE LEVELS ON SATURDAY.
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&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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MODEL DIFFERENCES IN LOCATION AND SIZE OF EASTERN UPPER TROUGH MAKE FOR A LOW CONFIDENCE LONG TERM FORECAST. SHOWER/STORM CHANCE WILL INCREASE SUNDAY WITH PASSAGE OF UPPER WAVE...BUT DIFFERENCES IN OVERALL LARGE SCALE PATTERN BY EARLY NEXT WEEK LEAD TO A FORECAST BASED ON CONSISTENCY RATHER THEN JUMPING ON A CHANGE IN ONE MODEL RUN.
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&& .AVIATION /06Z THURSDAY THROUGH MONDAY/... COMPLEX AVIATION FORECAST TONIGHT AS THE UPPER LOW STILL MAINTAINS A GRIP ON THE REGION. RECENT VISIBLE SATELLITE TRENDS HAVE SHOWN EROSION OF THE STRATO CUMULUS DECK SOUTH TO NORTH AS DRIER AIR BEGINS TO FEED IN AND THE SUN SETS. STILL...THE UPPER-LEVEL TROF AXIS HAS YET TO TRAVERSE THE FORECAST AREA. THIS WILL ULTIMATELY REINFORCE COOL AIR ALOFT AND LOW-LEVEL MOISTURE MAINLY NORTH OF KPIT. THIS IS WHERE LOW STRATO CUMULUS CLOUDS SHOULD HOLD THROUGH THE NIGHT. ELSEWHERE...MODEL GUIDANCE IS DROPPING VISIBILITIES DOWN TO AT LEAST IFR WITH PRE-DAWN FOG DEVELOPMENT. WITH DEWPOINTS CURRENTLY AT OR JUST ABOVE FORECAST LOWS...THIS SEEMS PLAUSIBLE...BUT WOULD RELY HEAVILY ON FURTHER EROSION OF EXISTING CLOUD DECK. TAF ISSUANCE REFLECTS A SOUTH TO NORTH GRADIENT OF STRATO CUMULUS TONIGHT WITH SOUTHERN TERMINALS CONTAINING FOG/BR MENTION AND NORTHERN TERMINALS HOLDING THE LOW CIGS. WITH RAPIDLY CHANGING CLOUD DECK...HOWEVER...CONFIDENCE IN THIS EXACT SCENARIO HOLDING IS LOWER THAN AVERAGE. TAX OUTLOOK...THURSDAY THROUGH SUNDAY... NO EXTENSIVE IFR IS EXPECTED THROUGH THE WEEKEND. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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