Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 301136 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 636 AM EST FRI JAN 30 2015 .SYNOPSIS...FOLLOWING A COLD FRONT MOVING THROUGH CENTRAL NORTH CAROLINA THIS MORNING AND OFFSHORE BY AFTERNOON...HIGH PRESSURE BUILDS OVER THE REGION FROM THE NORTHWEST. THE HIGH MOVES OFFSHORE SATURDAY NIGHT INTO SUNDAY. A LOW PRESSURE SYSTEM SHOULD MOVE INTO THE REGION BY SUNDAY NIGHT. && .NEAR TERM /THROUGH TODAY/... AS OF 300 AM FRIDAY... A COLD FRONT WAS SLOWLY MOVING ACROSS THE STATE EARLY THIS MORNING...AND ALL OF THE GUIDANCE SUGGESTS STEADY PROGRESS WITH THE FRONT AS IT MOVES THROUGH CENTRAL NORTH CAROLINA THIS MORNING AND OFFSHORE BY EARLY AFTERNOON. JUST BEHIND THE FRONT...WATER VAPOR IMAGERY SHOWS A GOOD DRY PUNCH MOVING ACROSS THE NORTH CAROLINA MOUNTAINS...AS AN UPPER TROUGH EXTENDING FROM HUDSON BAY THROUGH THE GREAT LAKES AND INTO THE OHIO VALLEY MOVES EAST. THIS MORNING...THE NEAR-TERM GUIDANCE VARIES ON THE POTENTIAL FOR RENEWED PRECIPITATION ACCOMPANYING THE FRONT AND THE LEFT-ENTRANCE REGION OF A 130KT 250MB JET THAT WILL BE OVER OR NEAR SOUTHERN PARTS OF CENTRAL NORTH CAROLINA THIS MORNING INTO THE AFTERNOON. BEHIND THE FRONT...850MB THETA-E VALUES FALL SHARPLY AND K INDICES GO NEGATIVE...BUT WITH THE FRONT THERE IS WEAK SPEED CONVERGENCE ON THE 295K SURFACE OF THE GFS ESPECIALLY TOWARD THE SANDHILLS AND SOUTHERN COASTAL PLAIN. AS OF THIS WRITING A FEW...FAINT ECHOES WERE NOTED ON THE KRAX WSR-88D JUST EAST OF KGSO TOWARD KBUY...BUT BETTER SURFACE DEW POINTS WERE OFF TO THE EAST AND SOUTHEAST TOWARD KETC...KFAY...AND KCTZ. PLAN TO AT LEAST HAVE A SLIGHT CHANCE OF EARLY MORNING SHOWERS MAINLY ALONG AND EAST OF ABOUT U.S. 1...WITH A CHANCE IN SOME LOCATIONS TOWARD INTERSTATE 95 WHERE THE LOW-LEVEL MOISTURE WILL BE GREATER AS THE FRONT MOVES THROUGH WITH THE UPPER SUPPORT. SKIES SHOULD START TO CLEAR IN GENERAL BEHIND THE FRONT...THOUGH THE NAM AND GFS BUFR SOUNDINGS ESPECIALLY FROM THE TRIANGLE NORTH AND EAST SUGGEST A PERIOD OF BROKEN STRATOCU OR SHALLOW CU DURING THE EARLY TO MID AFTERNOON AS THE TROUGH AXIS AND MODERATE VORTICITY MOVE THROUGH CENTRAL NORTH CAROLINA. IN FACT...THE GFS BUFR SOUNDINGS NEAR KRDU IN PARTICULAR WOULD SUGGEST ENOUGH LIFT...ALBEIT SHALLOW...TO GET A PARCEL A LITTLE COLDER THAN -10C AND POSSIBLY PROVIDE FOR VIRGA OR A SPRINKLE. WILL LEAVE THE AFTERNOON FORECAST DRY...THOUGH SHOW A PERIOD OF GREATER CLOUD COVER FROM THE TRIANGLE NORTH AND EAST DURING A PART OF THE AFTERNOON. IN ADDITION...THE SURFACE GRADIENT TIGHTENS BEHIND THE FRONT WITH 850MB WINDS OF 30 TO 35KT AND 925MB WINDS DIMINISHING FROM NEAR 40KT EARLY THIS MORNING TO AROUND 30KT BY 18Z. PURE LIFT FROM THE GFS BUFR SOUNDINGS UP THE DRY ADIABAT WOULD SUGGEST WIND GUSTS ABOVE 30KT POSSIBLE...BUT THE NAM AND RAP SOUNDINGS SUGGEST A LITTLE LOWER GUSTS AND MOMENTUM TRANSFER FIELDS FROM ALL THREE MODELS ON BUFKIT CAP GUSTS AT 30KT. WILL KEEP THE GUSTS TO 30KT OR 35MPH IN THE FORECAST WHILE ANTICIPATING A SPOT OR THREE TO BE BRIEFLY A LITTLE ABOVE THAT. THICKNESSES IN MANY PARTS OF CENTRAL NORTH CAROLINA FALL DURING THE DAY...AND 1000-850MB THICKNESSES WOULD SUGGEST A LEAN TOWARD THE SLIGHTLY COOLER MET MOS FOR HIGHS TODAY. BASED ON CURRENT READINGS AND EXPECTED SUN OFFSET BY COOL ADVECTION...WILL HAVE HIGHS FROM THE MID 40S TO AROUND 50 AND SHADING TOWARD THE MET MOS. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... AS OF 300 AM FRIDAY... WINDS WILL DIMINISH TONIGHT UNDER CLEAR SKIES. THERE SHOULD BE ENOUGH OF A GRADIENT FOR AT LEAST A SLIGHT STIR TO THE WIND THROUGH THE NIGHT...AS 925MB WINDS REMAIN TO 35KT. SURFACE DEW POINTS SHOULD CONTINUE TO DRY...AND 1000-850MB THICKNESSES WOULD SUGGEST LOWS FROM THE TEENS TO THE LOWER 20S. THIS WILL ESSENTIALLY BE THE FORECAST FOR LOWS OVERNIGHT...19 TO 20 IN THE NORTHWEST PIEDMONT TO NEAR 25 TOWARD KFAY...CLOSE TO THE AVERAGE OF THE MET AND MAV MOS. ON SATURDAY...925MB WINDS DIMINISH TO AROUND 15KT BY 18Z...AND BUFR SOUNDINGS FROM BOTH THE NAM AND GFS SUGGEST A FEW WIND GUSTS IN THE TEENS KNOTS WITH INITIAL MIXING BEFORE THE WINDS DIMINISH AS HIGH PRESSURE CONTINUES TO BUILD IN FROM THE NORTHWEST. SATURDAY AFTERNOON...A FLAT RIDGE AXIS ALOFT GETS CLOSE TO CENTRAL NORTH CAROLINA AS SOME MID-LEVEL VORTICITY ADVECTION MOVES INTO AND ACROSS CENTRAL NORTH CAROLINA DURING THE LATE AFTERNOON AND NIGHTTIME HOURS...FORECAST BY BOTH THE GFS AND NAM. GFS AND NAM BUFR SOUNDINGS SUGGEST INCREASING UPPER-LEVEL MOISTURE SUCH THAT INCREASING HIGH CLOUDS SHOULD GRADUALLY OCCUR FROM SATURDAY AFTERNOON INTO SATURDAY NIGHT. WITH MOST IF NOT ALL OF CENTRAL NORTH CAROLINA EXPECTED TO BE MOSTLY CLOUDY BY THE MIDDLE OF THE NIGHT SATURDAY...OVERNIGHT LOWS SHOULD BE WARMER...MID TO UPPER 20S IN THE NORTHERN COASTAL PLAIN TO AROUND 30 ELSEWHERE. -DJF MINOR MID-LEVEL IMPULSES EMANATING FROM THE UPPER TROUGH/CLOSED LOW OVER THE SOUTHWEST US WILL GET KICKED EASTWARD...IN ADVANCE OF AN AMPLIFYING NORTHERN STREAM OVER THE CENTRAL PLAINS...ON SUNDAY. ASSOCIATED CYCLOGENESIS WILL TRACK EASTWARD ACROSS THE LOWER MS VALLEY/TN VALLEY ON SUNDAY...THEN ACROSS THE CAROLINAS/VIRGINIA SUNDAY NIGHT BEFORE MOVING OFF THE MID-ATLANTIC COAST MONDAY MORNING. NWP MODEL GUIDANCE CONTINUES TO EXHIBIT CONSIDERABLE SPREAD WITH THE TRACK OF THE SURFACE LOW AS IT MOVES THROUGH THE REGION SUNDAY NIGHT...WITH A DEFINITE NORTHWARD SHIFT OBSERVED IN THE LATEST 00Z/30 MODEL ITERATION. THIS RESULTS IN A SLIGHTLY SLOWER/DELAYED ONSET OF PRECIP ACROSS THE AREA LATE SUNDAY AFTERNOON AND EVENING...BUT IMPORTANTLY DISPLACES THE HEAVIER QPF NORTH OF THE AREA. AS SUCH...SUNDAY WILL END UP MOSTLY DRY ACROSS CENTRAL NC WITH THICKENING CLOUD COVER THROUGH THE AFTERNOON WITH HIGHS RANGING FROM MID 40S NORTH TO LOWER 50S SOUTH. RAIN CHANCES WILL QUICKLY RAMP UP SUNDAY EVENING...WITH CATEGORICAL POPS SUNDAY NIGHT...CUTTING OFF FROM WEST TO EAST MORNING MONDAY AS THE MID-LEVEL DRY SLOT RACES EASTWARD. ESTIMATED QPF AMOUNTS NOW LOOK TO BE IN THE 0.25-0.50" RANGE. WITH ONLY WEAK ELEVATED INSTABILITY AT BEST EXPECTED ACROSS THE COASTAL PLAIN AND WITH THE SURFACE LOW NOW DISPLACED NORTH OF THE AREA...WILL KEEP OUT THE MENTION OF ANY THUNDER ACROSS THE EASTERN ZONES. EXPECT A NON-DIURNAL TEMP TREND SUNDAY NIGHT...WITH LOWS OCCURRING BEFORE MIDNIGHT...THEN TEMPERATURES WARMING OVERNIGHT OWING TO STRONG WAA. LOWS SUNDAY NIGHT IN THE LOWER 40S NORTHWEST TO UPPER 40S SOUTHEAST. -CBL && .LONG TERM /MONDAY THROUGH THURSDAY/... AS OF 300 AM FRIDAY... MONDAY THROUGH TUESDAY: AGGRESSIVE MID-LEVEL DRY AIR INTRUSION WILL OVERTAKE THE AREA FROM THE WEST BETWEEN 12 TO 18Z MONDAY IN ADVANCE OF THE PASSAGE OF THE NORTHERN STREAM TROUGH PASSAGE MONDAY AFTERNOON. THIS WILL BRING AN ABRUPT END TO PRECIP ACROSS THE AREA MONDAY MORNING...WITH RAIN/SHOWERS EXITING THE COASTAL PLAIN BY MID TO LATE MORNING. EQUALLY IMPRESSIVE WILL BE STRONG POST-FRONTAL DRY COLD AIR ADVECTION REGIME...WITH TEMPERATURES FALLING BY THE AFTERNOON AS CONTINENTAL POLAR HIGH PRESSURE BUILDS INTO THE AREA MONDAY NIGHT AND INTO THE DAY ON TUESDAY. IF PROJECTED LOW-LEVEL THICKNESSES VERIFY AND WE DECOUPLE AS THE SURFACE HIGH MOVES OVERHEAD... EXPECT LOWS TUESDAY MORNING IN THE UPPER TEENS TO LOWER 20S. UNDER FULL COMPLIMENTS OF SUN...TEMPS TUESDAY WILL STRUGGLE TO WARM THROUGH THE 30S. HIGHS RANGING FROM MID/UPPER 30S NORTH TO LOWER 40S SOUTH. WEDNESDAY THROUGH THURSDAY: MODEL SPREAD REMAINS HIGH WITH THE EVOLUTION OF THE SLOW MOVING UPPER LOW/TROUGH EJECTING EASTWARD FROM MEXICO AND SUBSEQUENT DEVELOPMENT OF A LOW PRESSURE AREA TRACKING ALONG THE SOUTHEAST COAST. IN A COMPLETE ROLE REVERSAL... THE GFS IS NOW MORE PROGRESSIVE THAN THE EC WITH BRINGING PRECIP BACK INTO THE AREA DURING THE DAY ON WEDNESDAY...WITH THE EC NEARLY 24 HOURS SLOWER...DELAYING UNTIL THURSDAY. GIVEN LATER TIMING OF ONSET OF PRECIP...LOW-LEVEL THICKNESSES CURRENTLY SUPPORT ALL RAIN. HOWEVER IF FUTURE MODEL RUNS SPEED UP THE TIMING OF THE SYSTEM...ANY PRECIP INTO THE AREA TUESDAY NIGHT/EARLY WEDNESDAY MORNING COULD BE OF THE FROZEN VARIETY. WILL CONTINUE TO MONITOR TRENDS...BUT FOR NOW GIVEN UNCERTAINTY WILL KEEP POPS AT SMALL CHANCE FOR WEDNESDAY AND THURSDAY WITH A CONTINUATION OF BELOW NORMAL TEMPERATURES. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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AS OF 635 AM FRIDAY... VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE 12Z VALID TAF PERIOD. A COLD FRONT MOVES THROUGH CENTRAL NORTH CAROLINA THIS MORNING WHICH WILL RESULT IN RAPIDLY VEERING WINDS TO THE NORTHWEST WITH SPEEDS INCREASING TO GUSTS AROUND 30KT BY LATE MORNING. ALREADY...THE WIND HAD GUSTED TO 26KT AT KINT. WHILE THE GFS MODEL SHOWS THE POTENTIAL FOR WIND GUSTS A LITTLE ABOVE THAT...THE NAM AND RAP MODELS ARE LESS...AND MOMENTUM TRANSFER SPEEDS TOP OUT AT MOST ABOUT 30KT ON ALL THREE WHICH WILL BE THE CAP FOR THE CENTRAL NORTH CAROLINA TAFS. SHOWERS WERE MOVING AWAY FROM THE COASTAL PLAIN AND... EXCEPT FOR KRWI INITIALLY...THE TAFS SHOW A DRY FORECAST. WITH A STRONG MID-LEVEL DISTURBANCE MOVING THROUGH TODAY...THERE IS THE POTENTIAL FOR SHALLOW CONVECTION...BROKEN VFR CLOUDS AND MAYBE A LITTLE VIRGA KRDU AND EAST EARLY THIS AFTERNOON. WINDS DIMINISH THIS EVENING DIURNALLY. HOWEVER...AVIATION INTERESTS SHOULD EXPECT NORTHWEST WINDS AOA 30KT AT AND ABOVE 2000FT. BEYOND THE 12Z VALID TAF PERIOD...VFR CONDITIONS CONTINUE INTO SUNDAY...WITH AREAS OF HIGH CLOUDS MOVING IN SATURDAY NIGHT GRADUALLY LOWERING SUNDAY. A CHANCE OF RAIN IN THE WESTERN PIEDMONT SUNDAY AFTERNOON FOLLOWED BY BETTER CHANCES BY SUNDAY NIGHT ALONG WITH THE POTENTIAL OF SUB-VFR CONDITIONS INTO MONDAY MORNING. VFR CONDITIONS ARE EXPECTED TO RETURN BY MONDAY AFTERNOON ACCOMPANIED BY BREEZY CONDITIONS ONCE AGAIN...WITH THE VFR CONDITIONS THEN CONTINUING THROUGH TUESDAY.
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&& .FIRE WEATHER... AS OF 300 AM FRIDAY... WIND GUSTS TO 30KT TODAY...OR TO AROUND 35 MPH...ARE CERTAINLY POSSIBLE AS THE SURFACE GRADIENT TIGHTENS BEHIND THE COLD FRONT. SURFACE DEW POINTS WILL FALL BEHIND THE FRONT AS WELL...WITH THE LOWEST GUIDANCE OF THE RAP SUGGESTING SOME DEW POINTS IN SINGLE FIGURES LATE IN THE DAY IN THE NORTHWEST PIEDMONT. THE GFS IS HIGHER...AND THE NAM IS MORE OF A COMPROMISE...WHICH IS CONSISTENT WITH THE MOS GUIDANCE. BY 00Z SATURDAY...THE GRIDDED FORECAST WILL SHOW A DEW POINT NEAR 10F IN THE TRIAD...BUT EVEN THERE THE MINIMUM RELATIVE HUMIDITY IS IN THE UPPER 20S PERCENT. BASED THOSE DEW POINTS...RECENT RAIN...AND EARLIER FORECAST SERVICE COORDINATION... WILL FOR NOW HIGHLIGHT THE ADVERSE CONDITIONS OF THE WIND GUSTS IN THE DISCUSSION OF THE FIRE WEATHER FORECAST. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...DJF SHORT TERM...DJF/CBL LONG TERM...CBL AVIATION...DJF FIRE WEATHER...DJF

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