Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 251639 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1240 PM EDT SAT JUL 25 2015 .SYNOPSIS...A WEAK SURFACE RIDGE WILL SETTLE OVERHEAD THROUGH THE WEEKEND THEN DRIFT EAST MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1000 AM SATURDAY... LITTLE CHANGE REQUIRED TO NEAR TERM FORECAST. 12Z UPPER AIR ANALYSIS DEPICTS A WEAK SHEAR AXIS ALOFT DRIFTING SEWD ACROSS THE REGION THIS MORNING. DUE TO THE RELATIVELY DRY AIR MASS IN PLACE (PW AT GSO THIS MORNING WAS 1.0 INCH)...THIS FEATURE EXPECTED TO TRAVERSE THE AREA WITH LITTLE ADVERSE EFFECT SIDE FROM A FEW CLOUDS. DECENT DRY ADIABATIC MIXING WILL RESULT IN DEWPOINTS AS LOW AS THE UPPER-MID 50S THIS AFTERNOON...A NICE BREAK FROM THE RECENT SPELL OF HIGH HUMIDITY. THIS MIXING ALONG WITH LOW LEVEL THICKNESSES IN THE 1420S SUPPORT MAX TEMPS IN THE UPPER 80S-LOWER 90S. WEAK HIGH PRESSURE EXTENDING SW-NE ACROSS THE REGION WILL MAINTAIN THE RELATIVELY DRY AIR MASS OVER CENTRAL NC. UNDER MOSTLY CLEAR SKIES AND LIGHT/CALM WIND...OVERNIGHT TEMPS IN THE MID-UPPER 60S WILL BE COMMON. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... AS OF 340 AM SATURDAY... UPPER LEVEL RIDGING WILL CONTINUE ACROSS MOST OF THE SOUTHERN US ON SUNDAY...WITH HIGH PRESSURE SHIFTING OVER THE MID-ATLANTIC COAST AND MOISTURE BEGINNING A SLOW RECOVERY ACROSS CENTRAL NC. FORECAST SOUNDINGS AGAIN SHOW A WELL-CAPPED ENVIRONMENT AND LITTLE CHANCE OF AFTERNOON CONVECTION. ALL OF THE OPERATIONAL MODELS SHOW SHORTWAVE ENERGY TRACKING THROUGH THE ACROSS THE MIDWEST AND EVENTUALLY REACHING CENTRAL NC VIA NORTHWESTERLY FLOW ALOFT....WHICH COULD BRING A LOW END CHANCE OF PRECIP LATE SUNDAY NIGHT...BUT THE TIMING OF THIS FEATURE PRESENTS LOW CONFIDENCE... AND EVEN IF THE FASTER GFS/NAM SOLUTIONS ARE CORRECT...POOR DIURNAL TIMING AND LIMITED MOISTURE RECOVERY SUGGESTS MODEL QPF IS OVERDONE. WILL LEAVE THE MENTION OF PRECIP OUT UNTIL MONDAY AFTERNOON WHEN SCATTERED CONVECTION SEEMS MORE LIKELY. HIGHS SUNDAY WILL BE A COUPLE DEGREES WARMER AGAIN...90-93. LOWS SUNDAY NIGHT WILL BE MILDER AS WELL WITH A LITTLE MORE CLOUD COVER OWING TO CONVECTION UPSTREAM...68-72 && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 355 AM SATURDAY... AFTER THE PASSAGE OF A WEAK MID LEVEL TROUGH IN NW FLOW ALOFT ACROSS NC MON-MON NIGHT...A SUB-TROPICAL RIDGE CENTERED OVER THE SOUTHERN PLAINS AND MID-MS VALLEY WILL EXTEND EAST INTO THE SOUTHERN APPALACHIANS/CAROLINAS THROUGH MID-WEEK...BEFORE RETROGRESSING INTO THE SOUTHWESTERN US THROUGH THE END OF THE PERIOD. THE RETROGRESSION OF THE RIDGE WILL CAUSE HEIGHTS TO GRADUALLY LOWER WITH THE ESTABLISHMENT OF A MEAN TROUGH OVER THE EASTERN US FRI THROUGH AT LEAST NEXT WEEKEND. THE SURFACE PATTERN WILL BE DOMINATED BY AN APPALACHIAN LEE TROUGH UNTIL A COLD FRONT RELATED TO THE AFOREMENTIONED DEVELOPING EASTERN CONUS TROUGH SETTLES INTO THE MIDDLE ATLANTIC AND CAROLINAS FRI-SAT. THE RELATIVE HIGHEST PROBABILITY OF PRECIPITATION WILL BOOKEND THE PERIOD...ON MON AND FRI...WITH OTHERWISE WARM TEMPERATURES/WEAK LAPSE RATES ALOFT AND CONSEQUENT LIMITED CHANCES OF AFTERNOON-EARLY EVE CONVECTION. THE PATTERN WILL ALSO SUPPORT A RELATIVELY STAGNANT TEMPERATURE FORECAST OF HIGHS IN THE UPPER 80S TO LOWER 90S...AND LOWS AROUND 70 DEGREES OR SO. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... AS OF 1240 PM SATURDAY... AN AREA OF HIGH PRESSURE WILL EXTEND SOUTHWEST-NORTHEAST ACROSS CENTRAL NC THROUGH SUNDAY. THIS WEATHER SYSTEM WILL MAINTAIN VFR CONDITIONS AND LIGHT SURFACE WINDS THROUGH SUNDAY. THE EXCEPTION WILL BE A BRIEF PERIOD OF MVFR VISIBILITY DUE TO FOG IN THE VICINITY OF KRDU...KFAY...AND ESPECIALLY KRWI...BETWEEN 09Z-13Z SUNDAY. THE AREA OF HIGH PRESSURE WILL DRIFT EAST LATE SUNDAY AND SUNDAY NIGHT. THE RETURN FLOW ON THE BACKSIDE OF THE HIGH WILL USHER LOW LEVEL MOISTURE INTO CENTRAL NC...INCREASING THE PROBABILITY OF EARLY MORNING MVFR/IFR CONDITIONS DUE TO FOG AND/OR LOW CLOUDS. IN ADDITION...THE ATMOSPHERE ACROSS CENTRAL NC IS EXPECTED TO BECOME INCREASINGLY MOIST AND UNSTABLE THROUGH THE WORK WEEK. THIS WILL INCREASE THE CHANCE FOR ISOLATED-SCATTERED AFTERNOON-EVENING CONVECTION. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...22 LONG TERM...26 AVIATION...WSS

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