Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 311132 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 631 AM EST SAT JAN 31 2015 .SYNOPSIS...HIGH PRESSURE CONTINUES TO BUILD OVER THE REGION TODAY. THE CENTER OF THE HIGH MOVES OFFSHORE TONIGHT AHEAD OF A LOW PRESSURE SYSTEM THAT MOVES INTO THE MID-ATLANTIC MONDAY MORNING. THE TRAILING COLD FRONT PUSHES EAST OF THE CAROLINAS MONDAY...FOLLOWED BY HIGH PRESSURE AGAIN FOR THE MIDDLE OF NEXT WEEK. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 115 AM SATURDAY... ASIDE FROM SOME JET-STREAK CIRRUS OVER PART OF CENTRAL NORTH CAROLINA ON THE LATEST IR SATELLITE IMAGES...CLEAR CONDITIONS WERE IN PLACE OVER CENTRAL NORTH CAROLINA. THE JET ALOFT IS FORECAST BY THE GFS AND NAM TO MOVE NORTHEAST AND OUT OF CENTRAL NORTH CAROLINA DURING THE DAY...ALTHOUGH A FLAT RIDGE AXIS ALOFT WILL APPROACH THE STATE TONIGHT WITH A GRADUAL INCREASE IN HIGH CLOUDS AND MAYBE EVEN MORE MID-LEVEL CLOUDS IN THE 12000FT TO 15000FT RANGE OVERNIGHT BASED ON THE MOISTURE PROFILES FROM BOTH THE NAM AND GFS BUFR SOUNDINGS. K INDICES ARE NEGATIVE UNTIL LATE TONIGHT IN THE INTERSTATE 85 CORRIDOR WHERE THE CLOUD BASES MAY BE A LITTLE LOWER RELATIVE TO THE REST OF CENTRAL NORTH CAROLINA...BUT THE AIR MASS BELOW 700MB REMAINS DRY AT LEAST THROUGH TONIGHT. THE CANADIAN CLOUD COVER MODEL WHICH TENDS TO DO PRETTY WELL WITH THE ONSET AND COVERAGE OF HIGHER CLOUDS INCREASES THE COVERAGE OF THOSE CLOUDS GRADUALLY THIS AFTERNOON THROUGH TONIGHT WITH AREAS FROM KFAY TO KRWI AND EAST TAKING LONGER TO GET AT LEAST BROKEN COVERAGE. GFS BUFR SOUNDINGS ARE SLIGHTLY HIGHER THAN NAM BUFR SOUNDINGS WITH REGARD TO THE POTENTIAL FOR A FEW WIND GUSTS IN THE TEENS KNOTS THIS MORNING. BASED ON SOME STIRRING OF THE WINDS CONTINUING EARLY THIS MORNING WILL LEAN TOWARD THE GFS AND ANTICIPATE A FEW WIND GUSTS IN THE TEENS KNOTS THIS MORNING BEFORE ANY GUSTINESS SHOULD DIMINISH INTO THE AFTERNOON AS THE SURFACE HIGH CONTINUES TO BUILD IN. WINDS WILL BECOME LIGHT SOUTH TO SOUTHWEST BY THIS EVENING. UNDER GOOD SUNSHINE...1000-850MB THICKNESSES AND A BLEND OF THE MAV AND MET MOS GUIDANCE SUGGEST HIGHS FROM THE MID 40S TO LOWER 50S...HIGHEST SOUTHWEST WHERE THE THICKNESSES WILL BE GREATER AND WINDS BECOME WEST TO SOUTHWEST SOONER. TEMPERATURES SHOULD FALL SOMEWHAT QUICKLY THIS EVENING THEN TEND TO STABILIZE AS CLOUDS MOVE IN. LOWS TONIGHT 25 TO 30 NEAR AND EAST OF INTERSTATE 95 AND AROUND 30 ELSEWHERE. MINIMUM RELATIVE HUMIDITIES TODAY COULD FALL TO NEAR 15 PERCENT BASED ON THE EXPECTED SURFACE DEW POINTS...BUT WINDS WILL BE MUCH LIGHTER COMPARED TO FRIDAY AND BY THE TIME DEW POINTS WOULD FALL TO THOSE LEVELS THE FREQUENCY OF ANY MODEST GUSTS SHOULD BE MUCH LOWER. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... AS OF 300 AM SATURDAY... SUNDAY: MINOR MID-LEVEL IMPULSES EMANATING FROM THE UPPER TROUGH/CLOSED LOW OVER THE SOUTHWEST US WILL EJECT EASTWARD AND MOVE THROUGH THE AREA IN ADVANCE OF THE NORTHERN STREAM TROUGH AMPLIFYING OVER THE CENTRAL PLAINS. ASSOCIATED WEAK DPVA WILL RESULT IN EXTENSIVE MID/HIGH LEVEL CLOUDINESS OVER THE AREA ON SUNDAY...HOWEVER GRADUAL MOISTENING OF AN INITIALLY DRY ~10KFT SUB- CLOUD LAYER LEFT(REMAINS OF THE MODERATING CP AIRMASS)WILL KEEP IT DRY ACROSS MUCH OF CENTRAL NC DURING THE DAYLIGHT HOURS. THE EXCEPTION WILL BE ACROSS THE FAR WESTERN ZONES WHERE A FEW SHOWERS COULD DEVELOP LATE IN THE AFTERNOON AS THE WARM MOIST CONVEYOR FEED BEGINS TO PUSH EAST OF THE MOUNTAINS. HIGHS SUNDAY IN THE LOWER 50S NORTH TO MID 50S SOUTH. SUNDAY NIGHT: AFOREMENTIONED NORTHERN STREAM TROUGH WILL CONTINUE TO PROGRESS EASTWARD...REACHING THE SOUTHERN/CENTRAL APPALACHIANS BY DAYBREAK MONDAY. DEEPENING SURFACE LOW....MOVING EASTWARD ALONG THE LEADING EDGE OF THE ASSOCIATED 180-200 METER 500MB HEIGHT FALLS... WILL TRACK ACROSS THE SOUTHERN OHIO VALLEY AND THROUGH THE VIRGINIAS DURING THE PREDAWN HOURS...DRAGGING A SFC COLD FRONT INTO THE NC FOOTHILLS. STRONG DEEP MOISTURE TRANSPORT IN ADVANCE OF THE FRONT...WITHIN THE STRENGTHENING 60-65KT SOUTHERLY LLJ WILL SUPPORT A 4-6 HOUR WINDOW OF CATEGORICAL POPS ACROSS THE AREA SUNDAY NIGHT. QPF AMOUNTS LOOK TO BE IN THE 0.25-0.50" RANGE...LIMITED BY THE INTRUSION OF A MID-LEVEL SLOT RACING IN FROM THE WEST. HAVE NO PLANS TO INCLUDE ANY THUNDER AT THIS TIME AS MODELS CONTINUE TO SHOW MODEST MID-LEVEL LAPSE RATES (6.5-6.8 C/KM)WITH LESS THAN <200 J/KG OF MUCAPE ACROSS THE AREA. EXPECT A NON-DIURNAL TEMP TREND SUNDAY NIGHT...WITH LOWS OCCURRING BEFORE MIDNIGHT...WITH TEMPERATURES THEN WARMING OVERNIGHT OWING TO STRONG WAA. LOWS SUNDAY NIGHT IN THE MID 40S NORTHWEST TO LOWER 50S SOUTH. MONDAY AND MONDAY NIGHT: 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 DURING THE MID TO LATE MORNING. EQUALLY IMPRESSIVE WILL BE STRONG POST- FRONTAL DRY COLD AIR ADVECTION REGIME...WITH BREEZY/BLUSTERY CONDITIONS AS BUFR SOUNDINGS INDICATING 38-40KTS AT THE TOP OF THE MIXED LAYER(SIMILAR TO IF NOT STRONGER THAN THE GUSTS WE HAD YESTERDAY). LOOK FOR TEMPERATURES FALLING THROUGH THE AFTERNOON AS YET ANOTHER CP AIRMASS BUILDS INTO THE AREA MONDAY NIGHT AND INTO THE DAY ON TUESDAY. MORNING HIGHS RANGING FROM MID UPPER 40S NORTHWEST TO MID 50S SOUTHEAST. IF PROJECTED LOW-LEVEL THICKNESSES AOA 1270M VERIFY AND WE DECOUPLE AS MODELS SUGGEST...EXPECT LOWS TUESDAY MORNING IN THE LOWER 20S...WITH UPPER TEENS POSSIBLE IN THE TYPICALLY COLDER LOCATIONS. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 300 AM SATURDAY... BOTH THE ECMWF AND THE GFS PASS A MID-LEVEL SHORTWAVE THROUGH CENTRAL NORTH CAROLINA TUESDAY AS A BROAD...PROGRESSIVE TROUGH ALOFT MOVES THROUGH. HOWEVER...WITH SURFACE HIGH PRESSURE IN PLACE AND EXTENDING ACROSS THE GULF A PERIOD OF PARTLY TO POSSIBLY MOSTLY CLOUDY SKIES SHOULD ONLY ACCOMPANY THE SHORTWAVE. AFTER EXPECTED BRIEF CLEARING BEHIND THE MID-LEVEL WAVE...IN THE FAST AND SLOWLY BACKING FLOW ALOFT BOTH THE ECMWF AND THE GFS FORECAST INCREASING UPPER-LEVEL MOISTURE WEDNESDAY INTO WEDNESDAY NIGHT WITH A COLD FRONT MOVING THROUGH WEDNESDAY NIGHT. BOTH THE GFS AND ECMWF ARE DRY INTO THE OVERNIGHT HOURS OF WEDNESDAY WITH SURFACE HIGH PRESSURE AHEAD OF THE COLD FRONT EXTENDING OVER THE GULF COAST AND LIMITING LOW-LEVEL MOISTURE RETURN. FOR THIS FORECAST...WILL HAVE DRY CONDITIONS TUESDAY INTO THE OVERNIGHT HOURS OF WEDNESDAY. MEX MOS AND ECMWF MOS GUIDANCE POPS ARE BELOW CLIMATOLOGY DURING THIS PERIOD. GUIDANCE DIFFERENCES ARE FAIRLY OBVIOUS BY LATE WEDNESDAY NIGHT. MUCH WILL DEPEND ON HOW DEEP THE UPPER TROUGH MOVING THROUGH SOUTHERN CANADA ENDS UP BEING DURING THE MIDDLE OF THE WEEK. THE ECMWF HAS BEEN CONSISTENT OVER THE LAST COUPLE OF RUNS OR SO WITH A DEEPER UPPER TROUGH EXTENDING THROUGH THE GREAT LAKES INTO THE OHIO VALLEY. THIS SUPPRESSES THE TRACK OF AN UPPER LOW FORECAST BY BOTH THE GFS AND THE ECMWF TO DEVELOP OVER OLD MEXICO...KEEPING DEEPER MOISTURE TO OUR SOUTH AND RESULTING IN DRY CONDITIONS FOR CENTRAL NORTH CAROLINA THROUGH THE END OF THE WEEK. THE GFS...ALSO CONSISTENT WITH ITSELF...IS NOTICEABLY LESS AMPLIFIED WITH THE CANADIAN UPPER TROUGH SUCH THAT THE WEAKENING UPPER LOW IS ABLE TO MOVE TOWARD THE CAROLINAS BY THURSDAY ALONG WITH MORE MOISTURE. THE GFS FORECASTS PRECIPITATION OVER CENTRAL NORTH CAROLINA BY 12Z THURSDAY WHICH...IF IT OCCURS...WOULD BE LIQUID AS GFS PARTIAL THICKNESSES ARE WELL INTO THE RAIN REGIME AT THAT TIME. DUE TO THE GUIDANCE UNCERTAINTY...THE PRUDENT COURSE APPEARS TO BE MAINTAINING CONSISTENCY WITH THE ONGOING FORECAST...A CHANCE OF RAIN IN CENTRAL NORTH CAROLINA OVERNIGHT WEDNESDAY INTO THURSDAY WITH CHANCES LOWEST AND BASICALLY NEAR SLIGHT IN THE TRIAD TO HIGHER CHANCES ALONG AND EAST OF A LINE FROM ABOUT KMEB TO KRWI. IF THE GFS VERIFIES EXACTLY THERE WOULD BE CONCERN ABOUT PRECIPITATION TYPE IN THE LINGERING MOISTURE BY THURSDAY NIGHT...BUT A DRY ECMWF WITH NEAR SOUTHEAST CONUS LOW PRESSURE MOVING OFFSHORE AND A DRY PREVIOUS FORECAST WILL RESULT IN A DRY CURRENT FORECAST THURSDAY NIGHT THROUGH FRIDAY NIGHT...THOUGH TURNING CHILLY AT THE END OF THE WEEK. THE WARMEST DAY OF THE PERIOD SHOULD BE WEDNESDAY. 1000-850MB THICKNESSES WOULD SUGGEST HIGHS AT LEAST IN THE MID TO UPPER 50S... FAIRLY COINCIDENT WITH THE MEX AND MEE MOS GUIDANCE...BUT WILL LEAN ABOUT A CATEGORY COOLER TOWARD THE HPC GUIDANCE FOR HIGHS IN THE LOWER TO MID 50S DUE TO THE ANTICIPATED PRESENCE OF AT LEAST SOME UPPER-LEVEL CLOUD COVER. THICKNESSES COOL AT THE END OF THE WEEK AND...DESPITE DIFFERENCES IN OTHER DETAILS...1000-850MB THICKNESSES...AND HPC AND MUCH OF THE MOS GUIDANCE...KEEP HIGHS ONLY IN THE MID 30S TO LOWER 40S FRIDAY. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... AS OF 630 AM SATURDAY... VFR CONDITIONS CONTINUE FOR THE 12Z VALID TAF PERIOD. SATELLITE IMAGES STILL SHOWED A FEW JET-STREAK CIRRUS IN CENTRAL NORTH CAROLINA AROUND DAYBREAK...AND DURING THE DAY TODAY AND THROUGH THE OVERNIGHT HOURS HIGH- AND MID-LEVEL CLOUDS WILL GRADUALLY MOVE IN FROM THE WEST. EXPECT MORE OF THE MID-LEVEL CLOUDS TO APPEAR IN CENTRAL NORTH CAROLINA TONIGHT...FROM AROUND 03Z AND LATER. FORECAST SOUNDINGS ESPECIALLY FROM THE GFS SUGGEST A FEW WIND GUSTS INTO THE TEENS KNOTS WITH INITIAL MIXING THIS MORNING...BUT THE TREND OF ANY GUSTINESS SHOULD DIMINISH BY EARLY AFTERNOON AS THE SURFACE HIGH CONTINUES TO BUILD IN. RAP SOUNDINGS ARE A COUPLE OF KNOTS LIGHTER...SO IT IS POSSIBLE THAT THE TAFS REFLECT GUSTS IN THE TEENS KNOTS THAT ARE ON THE HIGHER END OF WHAT MAY OCCUR WITH MIXING THIS MORNING INTO EARLY AFTERNOON...ESPECIALLY TOWARD THE TRIAD. LIGHT SOUTH TO SOUTHWEST WIND BY THIS EVENING. BEYOND THE 12Z VALID TAF PERIOD...VFR SUNDAY...WITH AN INCREASING POSSIBILITY OF MVFR CLOUDS DURING THE AFTERNOON...THEN SUB-VFR CONDITIONS AND AREAS OF RAIN LIKELY OVERNIGHT SUNDAY AHEAD OF A COLD FRONT THAT WILL MOVE THROUGH CENTRAL NORTH CAROLINA EARLY MONDAY. AHEAD OF THE COLD FRONT SUNDAY NIGHT...WINDS ALOFT WILL INCREASE TO SOUTHWEST AOA 50KT BY 2500FT. VFR CONDITIONS RETURN BY MONDAY AFTERNOON WITH GUSTY WEST-NORTHWEST AND NORTHWEST SURFACE WINDS. VFR CONDITIONS SHOULD THEN CONTINUE THROUGH WEDNESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DJF NEAR TERM...DJF SHORT TERM...CBL LONG TERM...DJF AVIATION...DJF

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