Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 150227 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1027 PM EDT MON APR 14 2014 .SYNOPSIS...A WARM MOIST SOUTHERLY FLOW WILL INCREASE OVER THE AREA THROUGH TONIGHT. A COLD FRONT WILL APPROACH THE MOUNTAINS FROM THE WEST LATE TONIGHT... THEN PROGRESS EAST ACROSS THE CAROLINAS TUESDAY AFTERNOON AND EVENING. COOL HIGH PRESSURE WILL EXTEND INTO THE AREA FROM THE NORTH WEDNESDAY THROUGH THURSDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1015 PM MONDAY... WARM MOIST AIR CONTINUES TO FILTER INTO CENTRAL NC THIS EVENING WITH DEWPOINTS INCREASING INTO THE LOWER TO MID 60S AS SOUTH TO SOUTHEASTERLY FLOW IS INCREASING IN ADVANCE OF A STRONG COLD FRONT... CURRENTLY EXTENDING FROM THE EASTERN GREAT LAKES REGION SOUTH-SOUTHWESTWARD TO THE AROUND NEW ORLEANS. THIS FRONT WILL CONTINUE PUSHING EASTWARD OVERNIGHT... APPROACHING THE CENTRAL TO SOUTHERN APPALACHIANS BY 12Z TUESDAY. THE WEAK PRE-FRONTAL BAND OF CONVECTION THAT MOVED ACROSS TN/GA/SC AND WESTERN NC EARLIER TODAY WEAKENED FURTHER THIS EVENING AND HAS LEFT AN OUTFLOW BOUNDARY ACROSS PORTIONS OF THE WESTERN PIEDMONT. NEW SHOWERS AND STORMS ARE NOW FORMING ON THE BOUNDARY. INSTABILITY IS INCREASE ACROSS THE AREA IN GENERAL... WITH A NOSE OF MLCAPE (SMALL AMOUNT 100-250 J/KG) EXTENDING UP TOWARDS THE DAVIDSON/ROWAN COUNTY LINE. THIS COUPLE WITH STRONG DEEP LAYER SHEAR (0-6 KM SHEAR OF AROUND 40-50 KTS) AND A FAVORABLE LOW LEVEL WIND PROFILE (0-1KM SRH OF 150-200 M2/S2) HAS YIELDED SOME WEAK ROTATION WITH THESE VERY SHALLOW SHOWERS/STORMS FROM TIME TO TIME. AT THIS TIME DO NOT THINK ANY WEAK ROTATION WILL RESULT IN ANY ISOLATED BRIEF TORNADOES AS THE UPDRAFTS DO NO APPEAR STRONG ENOUGH. THAT SAID... WE WILL NEED TO KEEP AN EYE ON THE RADAR FOR ANY QUICK SPIKE IN INTENSITY WITH THESE SHOWERS/STORMS SINCE THEY ARE INVOF THE REMNANT OUTFLOW BOUNDARY FROM EARLIER. GIVEN THE ABOVE MENTIONED DEEP SHEAR AND FAVORABLE ATLANTIC LOW LEVEL SOUTHEASTERLY INFLOW WE WILL NEED TO WATCH ANY CONVECTION THAT FORMS OVER THE AREA OVERNIGHT... ESPECIALLY WITH THE LATEST RAP SHOWING AS MUCH AS 500 J/KG OF MLCAPE MOVING INTO OUR SOUTH/SOUTHEASTERN HALF OF CENTRAL NC OVERNIGHT. LATEST HRRR AND RAP SHOW AN INCREASE IN ACTIVITY AFTER 06Z TONIGHT. THUS... WILL MAINTAIN HIGH POPS AFTER 06Z TONIGHT AND MAINTAIN MENTION OF SOME STRONG WIND GUSTS. EXPECT OVERNIGHT LOWS WILL BE WARM GIVEN THE INCREASING MOISTURE/CLOUD COVER. THUS... EXPECT LOW TEMPS WILL BE IN THE LOWER TO MID 60S.
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 300 PM MONDAY... WEAKENING LIFT BUT WITH INCREASING 0-3KM SHEAR MOVES EAST ACROSS CENTRAL NORTH CAROLINA EARLY TUESDAY...THEN THERE IS FORECAST A BRIEF RESPITE IN THE CHANCES FOR SHOWERS AROUND MID-MORNING WITH A SLIGHT DECREASE IN 850MB THETA-E VALUES AND INSTABILITY. AS THE AFTERNOON APPROACHES...850MB WINDS SHOULD INCREASE TO 50 TO 55KT AS A 120KT 300MB JET MOVES THROUGH THE AREA...COINCIDENT WITH THE RIGHT ENTRANCE REGION OF A 90KT 500MB JET. WHILE 1000-500MB LAPSE RATES ARE ONLY FORECAST AROUND 6C/KM...AND THOSE MAINLY EAST OF U.S. 1... MUCAPE THAT INCREASES OVERNIGHT TO NEARLY 1000J/KG ON THE NAM OVER THE FAR SOUTHWEST PIEDMONT CONTINUES TO PUSH ACROSS CENTRAL NORTH CAROLINA WITH VALUES FROM 1000-1500J/KG DURING TUESDAY. 0-3KM SHEAR IS ON THE ORDER OF 40-50KT TUESDAY AFTERNOON...INCREASING FURTHER TOWARD THE INTERSTATE 95 CORRIDOR LATE. MODEST LAPSE RATES IN A BROADLY MOIST AIR MASS SHOULD HELP TO LIMIT AVAILABLE INSTABILITY... BUT SYSTEM DYNAMICS ALONG AND AHEAD OF THE FRONT COULD COMPENSATE FOR THIS AND MAKE FOR THE POTENTIAL FOR ISOLATED SEVERE STORMS TUESDAY. IF A LOCATION SEEMED TO HAVE A BETTER CHANCE OF ISOLATED SEVERE STORMS...IT WOULD SEEM TO BE ALONG AND EAST OF U.S. 1 WHERE THE OVERALL INSTABILITY AND SHEAR WILL BE BETTER TUESDAY AFTERNOON...AS LIFTED INDICES THERE SHOULD BE -2C TO -4C...WITH BETTER HEATING EXPECTED. THE PRIMARY SEVERE THREAT IS ANTICIPATED TO BE WIND...BUT WITH 0-3KM HELICITY VALUES FROM 100-300 M2/S2...AN ISOLATED TORNADO CANNOT BE RULED OUT. HIGHS WERE LEANED TOWARD THE WARMER MAV GUIDANCE ANTICIPATING A BREAK IN PRECIPITATION DURING THE MORNING...UPPER 60S NORTHWEST TO AROUND 80 SOUTHEAST. STRONG COLD AIR ADVECTION TAKES PLACE TUESDAY NIGHT AS HIGH PRESSURE MOVES IN. ONCE THE STRONG MID-LEVEL TROUGH MOVES THROUGH THE THREAT OF PRECIPITATION SHOULD END...THEN IMPACTS TURN TOWARD THE POTENTIAL FOR FREEZING CONDITIONS. THE GUIDANCE HAS BEEN CONSISTENT FORECASTING LOWS AT OR BELOW FREEZING FOR A COUPLE OF RUNS MAINLY ALONG AND WEST OF INTERSTATE 95...AND WHILE WINDS IN MANY LOCATIONS SHOULD STAY UP THROUGH A LARGE PART OF THE NIGHT IN A TIGHT GRADIENT BEHIND THE COLD FRONT AS THE HIGH BUILDS IN...LATE AT NIGHT THERE SHOULD BE JUST ENOUGH WIND REDUCTION IN COMBINATION WITH SIMPLE ADVECTION TO RESULT IN SEVERAL AREAS WITH TEMPERATURES BELOW FREEZING. WILL ISSUE A FREEZE WATCH FOR A LARGE PART OF CENTRAL NORTH CAROLINA FOR TUESDAY NIGHT INTO EARLY WEDNESDAY MORNING... KEEPING OUT THE IMMEDIATE INTERSTATE 95 CORRIDOR FOR NOW DUE TO GREATER WIND AND MIXING EXPECTED THERE. LOWS TUESDAY NIGHT 29 TO 32 MOSTLY FROM U.S. 1 WEST...33 TO 37 IN THE INTERSTATE 95 CORRIDOR. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... AS OF 300 PM MONDAY... FOR WED THROUGH THU NIGHT: THE INTENSE BUT DAMPENING TROUGH WILL TRACK QUICKLY TO OUR NORTHEAST IN THE PREDAWN HOURS WED...AND WILL BE FOLLOWED BY GENERALLY FLAT SW FLOW OVER THE SOUTHEAST/MIDSOUTH/ CAROLINAS THROUGH WED. FORECAST SOUNDINGS ARE VERY DRY AND STABLE AS THE CENTER OF THE COOL SURFACE HIGH PRESSURE MOVES FROM THE OHIO VALLEY NORTHEASTWARD OVER THE ST LAWRENCE VALLEY WHILE NOSING DOWN THROUGH NC. EXPECT BREEZY AND COOL WINDS FROM THE NE WED... DIMINISHING LATE WED INTO THU AS THE MSLP GRADIENT RELAXES. LOW LEVEL THICKNESSES ARE EXPECTED TO PLUNGE TUE NIGHT TO OVER 70 M BELOW NORMAL...WITH ONLY MODEST RECOVERY DURING THE DAY... TRANSLATING TO HIGHS IN THE LOW-MID 50S. (AND THIS MAY EVEN BE OPTIMISTIC CONSIDERING THE PROJECTED 925 MB TEMPS BROUGHT DOWN DRY ADIABATICALLY YIELD HIGHS ONLY AROUND 50 OVER MUCH OF CENTRAL NC.) EXPECT MOSTLY CLEAR SKIES TO CONTINUE THROUGH THU NIGHT WITH DEEP DRY/STABLE AIR AS THE SLOWLY RETREATING AND MODIFYING SURFACE RIDGE NOSES INTO NC FROM THE NORTH... ALTHOUGH WE COULD START TO SEE PATCHY STRATUS LATE THU NIGHT WITH INCREASING ONSHORE-DIRECTED FLOW. LIGHT WINDS AND A CONTINUED ANOMALOUSLY COOL AIR MASS WILL FOSTER GOOD RADIATIONAL COOLING CONDITIONS... AND ANOTHER LIGHT FREEZE IS POSSIBLE WED NIGHT... PARTICULARLY IN THE RURAL AREAS OF THE PIEDMONT. NOT QUITE AS COOL THU WITH HIGHS EXPECTED TO BE 59-64. LOWS THU NIGHT 37-42 WITH RISING DEW POINTS. FOR FRI THROUGH MON: LONGWAVE TROUGHING THAT DRIFTS EAST ACROSS CENTRAL NOAM THU IS EXPECTED TO AMPLIFY SLIGHTLY AS IT HEADS EASTWARD INTO ERN NOAM FRI/SAT. THE APPROACH OF THIS TROUGH IS EXPECTED TO DRAW ENERGY FROM THE NRN GULF TOWARD THE NE... INDUCING SURFACE CYCLOGENESIS OVER THE NE GULF OR FL... WHICH WOULD THEN TRACK NORTHEASTWARD OVER OR JUST OFF THE SOUTHEAST COAST FRI NIGHT/SAT. THE GFS IS FAIRLY DRY HERE... HOLDING ITS SRN STREAM PRECIP TO OUR SE AND ANY NRN STREAM PRECIP TO OUR NORTH. THE ECMWF IS STRONGER WITH THE SOUTHERN WAVE... DEEPENING IT OVER SRN GA AND FL... BUT IT TOO HOLDS MOST OF THE PRECIP WITH THIS WAVE TO OUR SE. WILL RETAIN THE BASIC STRUCTURE OF THE PRECIP CHANCES WE CURRENTLY HAVE IN THERE... BUT REDUCE THEM AND CONFINE THE BETTER POPS TO OUR SOUTHEAST SECTIONS. AFTER BOTH THE NORTHERN AND SOUTHERN TROUGHS SHIFT EAST OF OUR LONGITUDE LATE SAT INTO SAT NIGHT... MID LEVEL RIDGING OVERSPREADS THE GULF/MIDSOUTH INTO THE SOUTHEAST AS ANOTHER HIGH PRESSURE BRIEFLY BUILDS IN FROM THE NORTH ON SUNDAY. EXPECT DECREASING CLOUDS SAT NIGHT AND A GOOD BIT OF SUNSHINE EASTER SUNDAY WITH MODERATING TEMPS CLOSE TO SEASONAL NORMALS. LOW CONFIDENCE IN MONDAY`S FORECAST AS THE GFS DEEPENS A MID LEVEL LOW OVER THE LOWER GREAT LAKES... LEADING TO SURFACE LOW FORMATION ALONG A ROUGHLY E-W FRONT ACROSS THE REGION WITH WIDESPREAD RAIN MOVING IN... WHILE THE ECMWF IS MUCH WEAKER/SLOWER AND KEEPS NC DRY MON. WILL GO WITH THE WEAKER ECMWF SOLUTION AND KEEP MONDAY DRY FOR NOW... BUT STAY TUNED. EXPECT TEMPS CLOSE TO NORMAL MON. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... AS OF 800 PM MONDAY... MOSTLY VFR CONDITIONS REMAIN ACROSS THE REGION AT THIS HOUR...BUT THIS WILL CHANGE FAIRLY SOON AS AVIATION CONDITIONS DETERIORATE WITHIN A RAPIDLY MOISTENING AIR MASS AHEAD OF AN APPROACHING COLD FRONT. WIDELY SCATTERED SHOWERS WILL CONTINUE ACROSS THE REGION...WITH BRIEF SUB-VFR CONDITIONS OCCURRING WITHIN ANY SHOWER. IT STILL APPEARS THAT SHOWER COVERAGE WILL INCREASE AFTER MIDNIGHT AS THE LOW LEVEL FLOW STRENGTHENS EVEN MORE (GUSTS OF 20-25 KNOTS WILL BE POSSIBLE). REGARDLESS...CIGS SHOULD FALL INTO THE IFR TO LIFR RANGE OVER THE NEXT COUPLE OF HOURS AND THEN REMAIN THERE THROUGH THE MORNING HOURS. THERE COULD BE A BRIEF LULL IN THE PRECIP TUESDAY MORNING AND THIS IS WHEN CIGS MAY BRIEFLY RISE INTO THE MVFR RANGE. HOWEVER...THIS WILL BE SHORT-LIVED AS SHOWERS AND ISOLATED THUNDERSTORMS WILL MOVE ACROSS THE AREA FROM WEST TO EAST AHEAD AND ALONG THE COLD FRONT. FRONTAL PASSAGE IS EXPECTED TO OCCUR LATE TUESDAY AFTERNOON INTO EARLY TUESDAY EVENING (MAYBE JUST AFTER THE CURRENT TAF PERIOD IN THE EAST)...WITH CLOUDS GRADUALLY LIFTING AND CLEARING AS WINDS SHIFT TO THE NORTHWEST AND REMAIN GUSTY...LIKELY 25-30 KNOTS. OUTLOOK...CONDITIONS WILL IMPROVE TUESDAY NIGHT BEHIND THE DEPARTING FRONT AND THEN MOSTLY VFR CONDITIONS WILL PERSIST THROUGH THE END OF THE WORK WEEK. THERE COULD BE SOME MORNING STRATUS BOTH FRIDAY AND SATURDAY MORNING AS MOISTURE ONCE AGAIN INCREASES AHEAD OF OUR NEXT SYSTEM APPROACHING FROM THE SOUTH THIS WEEKEND. && .CLIMATE... THE FOLLOWING ARE THE RECORD LOW TEMPERATURES FOR WED AND THU MORNING... AND THE RECORD LOW MAXIMUM TEMPERATURES FOR WED: WED 04/16 THU 04/17 LOW/YEAR LOW MAX/YEAR LOW/YEAR FAY: 28/1943 56/1950 31/1953 GSO: 25/1943 48/1929 29/1953 RDU: 28/1950 46/1890 29/1962 && .RAH WATCHES/WARNINGS/ADVISORIES... FREEZE WATCH FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY MORNING FOR NCZ007>010-021>026-038>041-073>077-083-084. && $$ SYNOPSIS...HARTFIELD NEAR TERM...BSD SHORT TERM...DJF LONG TERM...HARTFIELD AVIATION...KRD CLIMATE...MWS

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