Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 160600 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 100 AM EST TUE DEC 16 2014 .SYNOPSIS...
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A COLD FRONT WILL PUSH EAST THROUGH THE REGION TODAY. HIGH PRESSURE WILL BUILD SLOWLY INTO THE AREA THROUGH FRIDAY.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 1015 PM MONDAY... A BAND OF THIN CIRRUS HAD PUSHED EAST OF THE REGION... WHILE A BAND OF MUCH THICKER CLOUDINESS WAS APPROACHING THE YADKIN RIVER AT LATE EVENING. THE TEMPERATURES HAVE LIKELY BOTTOMED OUT IN THE WEST... BUT STILL HAVE A FEW HOURS TO FALL BEFORE THE THICKER CLOUDS ARRIVE AFTER MIDNIGHT. LOWS (MOST LIKELY BEFORE MIDNIGHT) WILL BE IN THE MID 30S TO NEAR 40. TEMPERATURES WILL COME UP A FEW DEGREES LATER TONIGHT WITH THE THICK CLOUDINESS ARRIVING. SOME SPOTTY LIGHT RAIN IS POSSIBLE IN THE WEST AND NORTHWEST PIEDMONT LATE TONIGHT. HOWEVER... TEMPERATURES WILL BE WELL ABOVE THE CRITICAL THRESHOLDS FOR ANYTHING OTHER THAN ALL RAIN. && .SHORT TERM /TUESDAY AND THURSDAY NIGHT/... AS OF 305 PM MONDAY... THE CLOSED LOW AND OCCLUDING LOW PRESSURE SYSTEM CURRENTLY OVER THE MID-MISSISSIPPI VALLEY REGION WILL CONTINUE TO LIFT NORTHEAST TOWARD THE GREAT LAKES TONIGHT. MEANWHILE...EXPECT TO SEE THE CURRENT BAND OF SHOWERS STRETCHING FROM NASHVILLE TO BIRMINGHAM WEAKEN THIS EVENING AS IT MOVES AWAY FROM THE BETTER FORCING...THEN RE-INTENSIFY LATER TONIGHT AND INTO TUESDAY AS A TRAILING SPEED MAX/SHEAR VORTICITY ROUND THE BASE OF THE TROUGH AND LIFT ACROSS THE SOUTHERN CENTRAL APPALACHIANS. THE WARM CONVEYOR BELT ASSOCIATED WITH THIS SYSTEM IS QUITE NARROW AND MOISTURE TRANSPORT FROM THE GULF IS LIMITED. RELYING ON MAINLY UPPER FORCING FROM DCVA AND 60-100M HEIGHT FALLS...THERE MAY BE JUST ENOUGH LOW-LEVEL WARM/MOIST ADVECTION TO COINCIDE WITH 6-6.5 C/KM MID-LEVEL LAPSE RATES AND YIELD A FEW HUNDRED J/KG OF ELEVATED CAPE. NOT VERY CONFIDENT IN HOW MUCH THUNDER THERE WOULD BE GIVEN SOME OVERALL DOWNWARD TREND ON COVERAGE NOTED IN RECENT CAM FORECASTS. NO SEVERE WEATHER IS EXPECTED...SO PREFER TO LEAVE THUNDER OUT OF THE CURRENT FORECAST AND RE-EVALUATE THE MESOSCALE LATER. FORCING SHOULD BE STRONGER TO THE NORTH...SO WE WILL HAVE THE GREATEST POPS (50-60%) FROM THE TRIANGLE TO THE NORTHEAST WHERE FORCING...MOISTURE AND DIURNAL TIME SHOULD BE MAXIMIZED. QPF WILL BE LIGHT...MOSTLY BELOW A TENTH OF AN INCH FOR MOST LOCATIONS. HIGHS IN THE MID 50S NORTH TOP AROUND 60 IN THE SOUTH. THE ACTUAL COLD FRONT WILL TRAIL THE PRE-FRONTAL SHOWERS BY A FEW HOURS...CROSSING THE AREA DURING THE LATER AFTERNOON AND EVENING HOURS. DRIER AIR ALOFT AND WEAKER FORCING SHOULD KEEP THE FROPA DRY. LITTLE AIRMASS CHANGE IS EXPECTED IMMEDIATELY BEHIND THE WEAK FRONT...AND LOWS WILL ONLY FALL INTO THE MID/UPPER 30S. -BLS WEDNESDAY THROUGH THURSDAY NIGHT SHOULD FEATURE FAIR WEATHER AS THE UPPER FLOW BECOMES ZONAL BEHIND THE UPPER TROUGH THAT MOVES OFF THE COAST TUESDAY NIGHT. HIGH PRESSURE INITIALLY CENTERED OVER SOUTHERN MANITOBA WEDNESDAY MORNING SLIPS INTO THE EASTERN GREAT LAKES AND OHIO VALLEY THURSDAY NIGHT. THE LOW LEVEL FLOW IS GENERALLY LIGHT NORTHWESTERLY THROUGH THE PERIOD WITH MODEST COLD ADVECTION ON WEDNESDAY FOLLOWED BY A SECONDARY SURGE OF COOLER AIR THAT MOVES INTO THE REGION ON THURSDAY. A VERY DRY AIR MASS PERSISTS IN PLACE THROUGH THE PERIOD WITH PW VALUES RANGING AROUND A THIRD OF AN INCH. THE RESULT SHOULD BE A GOOD DEAL OF SUNSHINE BOTH DAYS WITH SOME INCREASING CIRRUS CLOUDS ON THURSDAY. HIGHS ON WEDNESDAY WIL RANGE IN THE MID 50S TO NEAR 60 WITH COOLER MAXES ON THURSDAY WITH HIGHS IN THE LOWER TO MID 50S. LOWS WILL RANGE IN THE LOWER 30S BOTH NIGHTS. -BLAES && .LONG TERM /FRIDAY THROUGH MONDAY/... AS OF 315 PM MONDAY... ...ACTIVE WEATHER SETTING UP FOR THE WEEKEND... A SHORT WAVE TROUGH MOVING ON THE CA COAST LATE TUESDAY MAKES IT TO SOUTHEASTERN TX BY FRIDAY MORNING AND INTO MS/AL BY FRIDAY NIGHT. A MODEST 1025 MB SURFACE HIGH PRESSURE SYSTEM CENTERED ACROSS THE NORTHERN GREAT LAKES DURING THIS PERIOD ONLY WEAKLY EXTENDS INTO THE MID ATLANTIC. AS THE RIDGE AXIS ALOFT MOVES EAST...EXPECT HIGH AND MID LEVEL CLOUDINESS TO INCREASE ON FRIDAY AS LIGHT PRECIPITATION BREAKS OUT OVER THE DEEP SOUTH. HIGHS ON FRIDAY WILL RANGE FROM AROUND 50 NEAR THE VA BORDER TO AROUND 55 NEAR THE SC BORDER. THE SOUTHERN STREAM SHORT WAVE AMPLIFIES ON FRIDAY NIGHT INTO SATURDAY AS A STRAIGHT SUBTROPICAL JET STRENGTHENS WITH WINDS GREATER THAN 130KTS. CYCLOGENESIS SHOULD COMMENCE ACROSS THE NORTHERN GULF OF MEXICO FRIDAY NIGHT WITH THE SURFACE LOW LIKELY MAKING SOME TURN UP THE SOUTHEAST COAST SATURDAY. THERE IS STILL A LARGE SPREAD IN SOLUTIONS FOR THIS SCENARIO WITH A KEY INGREDIENT BEING THE AMOUNT OF PHASING BETWEEN THE SOUTHERN STREAM ENERGY AND THE POLAR JET. THE OPERATIONAL EC DEVELOPS A STRONG SURFACE LOW THAT MOVES UP A GOOD PORTION OF THE EAST COAST. THE OPERATIONAL GFS HAS A MUCH FLATTER SOLUTION WITH A SET OF MUCH WEAKER SURFACE LOWS AND LIGHT PRECIPITATION. THE PARALLEL VERSION OF THE GFS TENDS TO LOOK MORE LIKE THE EC THAN THE CURRENT GFS. STILL SOME OF THE VARIOUS ENSEMBLE MEMBERS SHOW A MORE SUPPRESSED SYSTEM WITH THE LOW MOVING MORE EASTWARD OFF THE COAST. ONE DETAIL THAT IS CONSISTENT WITH ALL OF THE VARIOUS SCENARIOS IS A LACK OF A SOURCE OF COLD DRY AIR TO EASILY SUPPORT WINTRY PRECIPITATION. AT THIS POINT WITH THE SOUTHERN STREAM SYSTEM YET TO REACH THE PACIFIC COAST AND WITH LIMITED CONFIDENCE WE ARE HESITANT TO BUY INTO ANY GIVEN SOLUTION. IT IS WORTH NOTING THAT THE EC COULD SUPPORT SOME WET SNOW ACROSS THE INTERIOR PIEDMONT BUT THIS SCENARIO IS AN OUTLIER AT THIS POINT. WITH BOUNDARY LAYER TEMPERATURES JUST ABOVE FREEZING AND THE NEED FOR DYNAMICAL COOLING TO SUFFICIENTLY COOL THE PROFILE...THIS APPEARS UNLIKELY AT THIS TIME. IT IS MUCH MORE LIKELY THAT A CHILLY RAIN WITH TEMPS IN THE 30S. IT ALSO APPEARS THAT ANY THUNDERSTORM THREAT WOULD BE SUPPRESSED TO THE IMMEDIATE COASTAL AREAS. HIGHS ON SATURDAY WILL BE CHILLY AND WILL RANGE IN THE LOWER 40S ACROSS THE TRIAD TO THE LOWER 50S ACROSS THE SOUTHERN COASTAL PLAIN. LOWS SATURDAY NIGHT SHOULD RANGE JUST ABOVE FREEZING IN THE MID 30S. PRECIPITATION SHOULD MOST LIKELY END FROM SOUTHWEST TO NORTHEAST ON SUNDAY WITH HIGHS ONLY IN THE MID TO UPPER 40S. DRIER WEATHER RETURNS FOR MONDAY WITH SOME SHORT WAVE RIDGING ALOFT AND WEAK HIGH PRESSURE OVERHEAD. HIGHS WILL RANGE IN THE MID 40S TO NEAR 50. -BLAES && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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AS OF 100 AM TUESDAY... 24 HOUR TAF PERIOD: HIGH-LEVEL CLOUDS WILL SPREAD INTO THE AREA OVERNIGHT IN ADVANCE OF AN APPROACHING COLD FRONT. EASTERN TERMINALS (KFAY AND KRWI)MAY SEE A BRIEF PERIOD OF MVFR VISIBILITY RESTRICTIONS BEFORE THE ARRIVAL OF THE THICKER CLOUD COVER. OTHERWISE...PREDOMINATELY VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH 12Z. A PRE-FRONTAL BAND OF SHOWERS WILL CROSS THE AREA BETWEEN 12 TO 16Z IN THE WEST...EXITING EASTERN TERMINALS AOA 21Z. FCST SOUNDINGS AND UPSTREAM TRENDS SUGGEST CIGS WILL LOWER TO MVFR WITHIN THE BAND OF SHOWERS AND WILL REMAIN SUB-VFR UNTIL THE TRAILING SFC COLD FRONT CROSSES THE AREA DURING THE EARLY EVENING(AOA 21Z IN THE WEST TO 03Z IN THE EAST). OUTLOOK...DRIER AIR FILTERING INTO THE AREA BEHIND THE FRONTAL PASSAGE THIS EVENING SHOULD RESULT IN WEST-EAST CLEARING WITH EASTERN TERMINALS RETURNING TO VFR CONDITIONS BY 06Z. VFR CONDITIONS SHOULD DOMINATE WEDNESDAY THROUGH EARLY FRIDAY. A LOW PRESSURE SYSTEM TRACKING FROM THE GULF OF MEXICO NORTHEASTWARD AND ALONG THE SOUTHEAST COAST WILL RESULT IN ADVERSE AVIATION CONDITIONS LATE FRIDAY AND INTO THE WEEKEND.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BADGETT NEAR TERM...BADGETT SHORT TERM...BLS/BLAES LONG TERM...BLAES AVIATION...BSD/BLS

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