Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291317 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 920 AM EDT WED OCT 29 2014 .SYNOPSIS... A COLD FRONT WILL CROSS OUR REGION THIS AFTERNOON AND EVENING. HIGH PRESSURE WILL FOLLOW FOR THU THROUGH FRI. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 920 AM WEDNESDAY... AS OF 13Z SURFACE COLD FRONT HAS JUST CROSSED THE MOUNTAINS AND INTO WESTERN NC...WITH ANA-FRONTAL PRECIP LAGGING EVER SO SLIGHTLY. WITH THE SWLY FLOW ALOFT ORIENTED PARALLEL TO THE FRONT...FRONT WILL BE SLOW TO ADVANCE EASTWARD THROUGHOUT THE DAY...WITH EXPECTED FROPA TIMING IN THE NW PIEDMONT BETWEEN 20-22Z...THE TRIANGLE BETWEEN 22- 00Z...AND THE COASTAL PLAIN AND EASTERN SANDHILLS BETWEEN 00-03Z(~3 HOURS SLOWER THAN WHAT MODELS WERE SHOWING THIS TIME YESTERDAY). THE SLOWER TIMING WILL ALLOW FOR MODEST INSOLATION THROUGH AN OPAQUE CIRRUS SHIELD THROUGH THE AFTERNOON...ALLOWING TEMPERATURES TO WARM INTO THE LOWER 70S WEST TO LOWER 80S EAST. WHILE THE ONGOING SHOWERS MAY CONTINUE TO DIMINISH AS THEY APPROACH AND MOVE EAST OF THE APPALACHIANS...REDEVELOPMENT IS LIKELY AS THE DIVERGENT RIGHT ENTRANCE OF A JET STREAK IN THE NORTHERN STREAM SPREADS EAST ACROSS CENTRAL NC AND PROVIDES DEEPER/COUPLED ASCENT ATOP THE FRONTAL CIRCULATION THIS AFTERNOON. DESPITE THE COUPLED FORCING...WEAK LAPSE RATES AND ASSOCIATED INSTABILITY WILL OTHERWISE HINDER PRECIPITATION INTENSITY...AND ONLY AN ISOLATED STORM OR TWO IS EXPECTED AMIDST AN OTHERWISE BAND OF SHOWERS. THOUGH SOME 4-8 THOUSAND FT CLOUDINESS WILL LINGER BEHIND THE FRONT THROUGH THIS EVENING...CLEARING WILL EVENTUALLY SPREAD EAST OVERNIGHT. CAA-DRIVEN LOWS MOSTLY BETWEEN 45 TO 55 DEGREES.
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&& .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... AS OF 310 AM WEDNESDAY... SHORTWAVE RIDGING AND UNDERLYING 1020 MB SURFACE HIGH PRESSURE... BEHIND THE TROUGH ALOFT FORECAST TO MOVE INTO AND AFFECT THE EASTERN US DURING THE NEAR TERM...WILL BUILD EAST ACROSS THE TN/OH VALLEYS AND MIDDLE ATLANTIC STATES ON THU. THE RESULT WILL BE SUNNY AND COOLER CONDITIONS...WITH HIGH TEMPERATURES GENERALLY IN THE MIDDLE 60S TO NEAR 70 DEGREES. FORECAST GUIDANCE INDICATES ANOTHER SHORTWAVE TROUGH OVER THE PAC NW THIS MORNING WILL AMPLIFY SOUTHEASTWARD AND INTO THE SOUTHERN APPALACHIANS BY FRI MORNING...WHILE A MUCH STRONGER ONE IN A PRONOUNCED EARLY SEASON ARCTIC STREAM AMPLIFIES SOUTH SOUTHEASTWARD FROM CENTRAL CANADA TO THE WESTERN GREAT LAKES DURING THE SAME TIME. DESPITE THE ASSOCIATED STEADILY FALLING HEIGHTS ALOFT IN ASSOCIATION WITH THE PAIR OF AMPLIFYING SHORTWAVE TROUGHS...PRECEDING DRYNESS/LIMITED DEEP MOISTURE SUGGESTS THE MAIN IMPACT THROUGH FRI MORNING SHOULD BE MERELY AN UPTICK IN MID LEVEL CLOUDINESS AS THE FLOW ALOFT BACKS TO SOUTHWESTERLY THU NIGHT...WITH LOW TEMPERATURES WITHIN A FEW DEGREES EITHER SIDE OF 40. && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 310 AM WEDNESDAY... WEAK HIGH PRESSURE WILL BE OVER THE AREA EARLY ON FRIDAY... AHEAD OF STRONG SHORTWAVE DIVING IN TO THE BASE OF A TROUGH OVER THE EASTERN US. RECENT MODEL TRENDS HAVE SHOWN THIS SHORTWAVE MOVING MUCH FURTHER SOUTHWARD THAN PREVIOUS RUNS... AND INCREASINGLY AMPLIFIED MIDLEVEL FLOW... WITH A CLOSED UPPER LOW CROSSING THE AREA AND INDUCING COASTAL SURFACE LOW DEVELOPMENT. THE RESULTING STRONG PRESSURE GRADIENT WILL BRING BLUSTERY WINDS SATURDAY. IF THIS SCENARIO PLAYS OUT... WE WILL SEE A COLD AND WET DAY... WITH HIGHS IN THE 40S. HAVE BEGUN TO TREND HIGHS LOWER... AND INCREASED TO CHANCE POPS SATURDAY. AS NOTED BY WPC... THE FORECASTED PATTERN IS QUITE ANOMALOUS... AND THEREFORE CONFIDENCE REMAINS BELOW NORMAL AT THIS TIME. SUBSIDENCE IN THE WAKE OF THE DEPARTING LOW WILL BRING CLEARING CONDITIONS ON SUNDAY... WHICH WILL WORK TO PARTIALLY OFFSET COLD ADVECTION... WITH HIGHS REACHING THE 50S. STRONG AND COLD HIGH PRESSURE BUILDING IN TO THE OHIO VALLEY ON SUNDAY WILL MOVE DIRECTLY OVER THE AREA ON MONDAY... WITH FROST AND POSSIBLY FREEZE POTENTIAL SUNDAY AND MONDAY MORNINGS. THE HIGH MOVES OFF THE EAST COAST ON TUESDAY... BEGINNING A MODERATING TREND IN TEMPERATURES... WITH HIGHS BACK IN THE 60S MONDAY AND TUESDAY. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... AS OF 645 AM WEDNESDAY... LATEST INDICATIONS ARE THAT THE STRATUS OVER EASTERN SC WILL MAKE LITTLE ADDITIONAL NORTHWESTWARD PROGRESS OWING TO A VEERING OF THE SURFACE WIND TO SOUTHWESTERLY DURING THE PAST FEW HOURS...SUCH THAT THE WESTERN EDGE OF THE LOW CLOUDS SHOULD REMAIN TO THE EAST AND SOUTHEAST OF FAY THIS MORNING. AS SUCH...VFR CONDITIONS ARE EXPECTED UNTIL A COLD FRONT AND ASSOCIATED BAND OF ALONG AND POST-FRONTAL SHOWERS - AND ASSOCIATED IFR-MVFR CEILINGS AND MVFR VISIBILITY RESTRICTIONS - MOVES EAST ACROSS CENTRAL NC THIS AFTERNOON AND EVENING. THE SHOWERS AND SUB-VFR CONDITIONS ARE EXPECTED TO LAST ONLY AROUND 2-5 HOURS AT ANY ONE LOCATION...LONGEST AT EASTERN SITES. A PERIOD OF VFR CEILINGS BETWEEN 4-8 THOUSAND FT WILL LINGER FOR A FEW HOURS EVEN AFTER THE SHOWERS AND SUB-VFR CONDITIONS MOVE EAST...AS THE SLOW APPROACH OF A TROUGH ALOFT DRAWS MOISTURE BACK UP AND OVER THE SURFACE FRONT. OTHERWISE...SW SURFACE WINDS BETWEEN 7-13 KTS...STRONGEST AND OCCASIONALLY GUSTY INTO THE UPPER TEENS KTS AT FAY AND RWI...WILL VEER TO WNW OR NW BEHIND THE FRONT BY THIS EVENING. OUTLOOK: THE PASSAGE OF A STRONG POLAR FRONT AND SUBSEQUENT DEVELOPMENT OF A STRONG COASTAL LOW WILL RESULT IN A CHANCE OF RAIN...AND BLUSTERY NW WINDS...FRI NIGHT THROUGH SAT. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...CBL/MWS SHORT TERM...MWS LONG TERM...SEC AVIATION...MWS

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