Area Forecast Discussion
Issued by NWS

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 212034 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 334 PM EST SUN DEC 21 2014 .SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE DEPARTS ON MONDAY. EXPECT INCREASING PRECIPITATION CHANCES TUESDAY. STORM SYSTEM BRINGS RAIN AND WIND CHRISTMAS EVE...AND SNOW SHOWERS CHRISTMAS DAY.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH MONDAY/...
-- Changed Discussion --
CLOUDS CONTINUE TO SLOWLY ERODE FROM THE SOUTH EVEN WITH SUN ANGLE AT ITS MINIMUM...AS DRIER AIR WORKS INTO THE CLOUD BEARING LAYER. THIS WILL CONTINUE INTO THE EVENING...WITH THE FKL/DUJ AREAS BEING THE LAST TO SEE THE LOW CLOUDS BREAK. SURFACE HIGH AND H500 RIDGE AXIS PULL AWAY DURING THE EVENING HOURS. WARM ADVECTION BEGINS IN EARNEST AS WELL...BRINGING H850 TEMPS ABOVE ZERO FOR THE SOUTHERN CWA BY 12Z MONDAY. MID/UPPER CLOUDS WILL BE ON THE INCREASE IN THIS PATTERN. SOME LOWER CLOUDS COULD BE REALIZED PRIOR TO 12Z ALONG EAST-FACING SLOPES IN GARRETT/TUCKER COUNTIES...BUT EXPECT PRECIP TO HOLD OFF UNTIL AFTER 12Z. GENERALLY LEANED TOWARDS THE WARMER TEMPERATURE GUIDANCE FOR LOWS. ON MONDAY...INVERTED TROUGH SETS UP ALONG THE CAROLINA COAST. WITH DEPARTING HIGH ACROSS NEW ENGLAND...A COLD AIR DAMMING SCENARIO LOOKS TO BE SETTING UP FOR THE EAST-FACING RIDGES. FOR MOST AREAS...IT WILL SIMPLY BE A MOSTLY CLOUDY DAY. HOWEVER...BETTER MOISTURE SPINS AROUND THE INVERTED TROUGH TOWARDS THE SOUTHEAST CORNER OF THE CWA BEGINNING LATER MONDAY MORNING. WITH THE OVERNIGHT WARM ADVECTION ALOFT AND COLD AIR EXPECTED TO BE TRAPPED IN THE VALLEYS...A TEMPERATURE STRUCTURE IDEAL FOR FREEZING RAIN WILL BE PRESENT ACROSS GARRETT/PRESTON/TUCKER COUNTIES. HOWEVER...QPF WILL BE THE LIMITING FACTOR AS MOISTURE AND LIFT ARE TOO SHALLOW TO SUPPORT PRECIPITATION OF ANY SIGNIFICANCE. CANNOT JUSTIFY ANYTHING HIGHER THAN CHANCE POPS AT PRESENT. ONLY A COUPLE HUNDREDTHS OF AN INCH OF LIQUID ARE EXPECTED AT MOST. WILL NOT BE ISSUING ANY HEADLINES AT THE PRESENT TIME. SPS CAN BE USED IN THE MORNING IF THE THREAT INCREASES. CONTINUED WARM ADVECTION WEST OF THE RIDGES WILL PUSH MONDAY HIGH TEMPS AT LEAST SEVERAL DEGREES ABOVE NORMAL...WHILE TEMPS REMAIN IN THE 30S ALONG THE EASTERN CWA BORDER.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
-- Changed Discussion --
UPPER TROUGH WILL AMPLIFY AND SLOWLY PIVOT EASTWARD DURING THIS TIME FRAME...BECOMING MORE NEGATIVELY TILTED WITH THE HELP OF A STRENGTHENING UPPER LEVEL JET BY LATE WEDNESDAY. EARLY ON...THERE STILL REMAINS SOME UNCERTAINTY IN REGARD TO THE AMOUNT OF PRECIP THAT WE WILL SEE ON TUESDAY...AS WE WILL BE PARKED IN BETWEEN THE BETTER MOISTURE FROM THE WEAK COASTAL SYSTEM...AND THE DEEPENING MOISTURE ASSOCIATED WITH THE COLD FRONT TO OUR WEST. IN ADDITION...S-SE WIND SHOULD HELP PROVIDE SOME DOWNSLOPING AND DRYING JUST EAST OF THE RIDGES IN PA/WV. WITH THIS IN MIND...OPTED TO STAY WITH THE CHANCE POPS FOR THE DAY TUESDAY. WILL INCREASE POPS OVERNIGHT AS THE LOW LEVEL JET STRENGTHS AND HELPS TO PULL MOISTURE FROM THE GULF NORTHWARD. WITH THE NEARLY NORTHWARD PROGRESSION OF THE DEVELOPING SURFACE LOW...BOTH THE ECMWF AND GFS SUGGEST THE BULK OF THE HEAVIEST RAIN WILL STAY JUST WEST OF THE FORECAST AREA...WITH THE BEST CHANCE FOR MODERATE RAIN TO BE AS THE COLD FRONT CROSSES WEDNESDAY NIGHT. THIS SHOULD LIMIT ANY FLOOD THREAT FOR THE PERIOD. STRONG WARM ADVECTION WILL BE ONGOING THROUGH THE ENTIRE TIME PERIOD. EVEN WITH CLOUD COVER...HIGH TEMPERATURES ON BOTH TUESDAY AND WEDNESDAY SHOULD BE WELL ABOVE SEASONAL VALUES WITH HIGHS LIKELY TO REACH THE MID 50`S.
-- End Changed Discussion --
&& .LONG TERM /THURSDAY THROUGH SUNDAY/...
-- Changed Discussion --
WITH THE TRACK OF THE CYCLONE DUE N...COLD AIR INJECTED INTO THE AREA WILL BE OF MIDWEST ORIGIN...SO TEMPS WILL RETREAT BACK TO SEASONAL BENCHMARKS CHRISTMAS DAY. FOR THOSE WHO ARE LOOKING FOR SNOW ON CHRISTMAS...A CHANCE OF SNOW SHOWERS EXIST...BUT GIVEN TRAJECTORY FROM THE SOUTHWEST ANY ACCUMULATION ASSOCIATED WITH THE UPPER LEVEL SYSTEM WILL BE LIGHT AT BEST. HISTORICALLY...THERE IS ONLY A 17 PERCENT CHANCE OF AT LEAST ONE INCH OF SNOW ON THE GROUND AT PITTSBURGH CHRISTMAS MORNING. H8 WINDS PUSH 50KTS INTO THURSDAY AND HIGHEST ANOMALIES RESIDE ALONG THE LAKE SHORE...SO EXPECT HIGHEST GUSTS WOULD DO SO AS WELL. NONETHELESS...PERIOD FROM WEDNESDAY NIGHT INTO THURSDAY STRONG ISALLOBARIC FLOW COULD YIELD GUSTS IN EXCESS OF 40 MPH ESPECIALLY IN THE MOUNTAINS OF WRN MD AND NRN WV. BALANCE OF THE EXTENDED IS CHARACTERIZED BY UNCERTAINTY AS ONE WOULD EXPECT IN THE DAY 6 -7 TIME FRAME. ECMWF HAS A STRONGER SYSTEM CROSSING FRIDAY NIGHT VERSUS GFS WHICH IS MUCH WEAKER. EITHER CASE PTYPE SHOULD BE RAIN WITH SNOW SHOWERS ON THE BACKSIDE. NO PLUNGES OF ARCTIC AIR ARE FORECAST IN THE NEXT 10 DAYS. MAX/MIN TEMPERATURES WERE A BLEND OF THE FORECAST AND ECMWF BIAS CORRECTED DATA SET.
-- End Changed Discussion --
&& .AVIATION /21Z SUNDAY THROUGH FRIDAY/... MVFR CLOUD DECK IS SLOWLY ERODING FROM THE SOUTH. EXPECT ALL SITES TO ACHIEVE VFR BY 00Z...SAVE FOR POSSIBLY FKL/DUJ WHERE THE CLOUDS WILL HANG ESPECIALLY TOUGH. VFR THROUGH MOST OF THE NIGHT...ALTHOUGH SOME MVFR CIGS COULD REDEVELOP TOWARDS DAWN ALONG THE RIDGES IN SE FLOW. HIGH CLOUDS WILL INCREASE AFTER SUNRISE MONDAY...AND EXPECT A STRATOCU DECK TO FORM UP WITH TIME. ANY CIGS SHOULD REMAIN LOW VFR THROUGH 18Z. SPOTTY FREEZING RAIN MAY BE POSSIBLE IN A FEW VALLEYS IN NORTHEAST WV/WESTERN MD. OUTLOOK.../SUNDAY NIGHT THROUGH THURSDAY/... NEXT STORM SYSTEM WILL BEGIN TO IMPACT THE REGION ON TUESDAY AND RESULT IN WIDESPREAD RAIN...CIG/VIS RESTRICTIONS...AND PERIODS OF LLWS INTO THURSDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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