Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 121847 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 247 PM EDT SAT APR 12 2014 .SYNOPSIS...PERSISTENT HIGH PRESSURE IN THE WESTERN ATLANTIC WILL MAINTAIN A DRY SURFACE RIDGE ACROSS THE CAROLINAS THROUGH SUNDAY. A COLD FRONT ASSOCIATED WITH A DEVELOPING LOW PRESSURE SYSTEM WILL SLOWLY APPROACH THE REGION FROM THE WEST ON MONDAY...THEN MOVE EAST ACROSS NORTH CAROLINA AND VIRGINIA MONDAY NIGHT AND TUESDAY. && .NEAR TERM /THROUGH SUNDAY NIGHT/... AS OF 230 PM SATURDAY... WITH SHORTWAVE RIDGING OVERHEAD AND OFFSHORE SURFACE HIGH PRESSURE STILL EXTENDING INTO THE REGION...EXPECTING CONTINUED QUIET WEATHER FOR CENTRAL NC. SOUTHERLY FLOW WILL DEVELOP AREAWIDE AS A BOUNDARY THAT WAS DRAPED ACROSS THE AREA THIS MORNING WASHES OUT. THIS WILL CAUSE LOW LEVEL MOISTURE TO BEGIN TO SLOWLY INCREASE THROUGH THE OVERNIGHT HOURS. AS A RESULT...OVERNIGHT LOWS WILL LIKELY BE A COUPLE OF DEGREES WARMER...GENERALLY IN THE MID TO UPPER 50S. BOTH THE UPPER LEVEL AND SURFACE RIDGING WILL PUSH FURTHER OFFSHORE ON SUNDAY AHEAD OF AN APPROACHING DEEP TROUGH/STRONG COLD FRONT. STRENGTHENING SOUTHWESTERLY FLOW WILL BEGIN TO ADVECT MOISTURE EVEN MORE SO INTO CENTRAL NC. DESPITE THIS INCREASING MOISTURE...IN THE ABSENCE OF ANY SIGNIFICANT FORCING AND A FAIRLY CAPPED AIR MASS (PER FORECAST SOUNDINGS)...SUNDAY IS EXPECTED TO REMAIN DRY. MAX LOW LEVEL THICKNESS VALUES ARE PROGGED TO BE SIMILAR THOSE SEEN ON SATURDAY AND THEREFORE...HIGHS SHOULD ONCE AGAIN BE IN THE UPPER 70S TO LOWER 80S. CLOUDS WILL BE ON THE INCREASE... ESPECIALLY LATE SUNDAY INTO EARLY MONDAY. THEREFORE OVERNIGHT LOWS WILL BE EVEN WARMER...WITH TEMPS ONLY EXPECTED TO FALL INTO THE UPPER 50S TO AROUND 60 DEGREES. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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AS OF 244 PM SATURDAY... DEEP TROUGH OVER THE CENTRAL US WILL PUSH EASTWARD. AN INITIAL SHORTWAVE WILL EJECT NORTHEASTWARD... WITH SECOND TRAILING SHORTWAVE DIGGING INTO THE SOUTHERN PLAINS. MOISTURE WILL BEGIN TO INCREASE AHEAD OF THIS SYSTEM ACROSS THE AREA... AND MODEL TRAJECTORIES SHOW GULF MOISTURE BEGINNING TO STREAM IN TO THE AREA MONDAY AFTERNOON... AND SHALLOW ISENTROPIC LIFT MAY INDUCE SOME SHOWER ACTIVITY... WITH THE POSSIBILITY OF A THUNDERSTORM. CONTINUED MILD HIGHS IN THE MID TO UPPER 70S. TIMING OF THE FRONTAL PASSAGE LOOKS TO BE BETWEEN 18Z TUES AND 06Z WED... DIFFICULT TO PINPOIN BASED ON THE POTENTIAL WAVY NATURE OF THE FRONT. INSTABILITY LOOKS LIKELY TO REMAIN LIMITED... WITH CLOUD COVER ACROSS THE AREA... ALTHOUGH BASED ON THE LATER DAY TIMING SOME WEAKER INSTABILITY IS POSSIBLE... AND IN CONCERT WITH MARGINAL SHEAR... A 120 KT JET SITUATED ALONG THE APPALACHIANS... AND FRONTOGENETICAL FORCING... MAY SUPPORT A FEW STRONGER STORMS. HEAVY RAIN IS ALSO A THREAT... WITH PWS CLIMBING ABOVE 1.5 INCHES... 2 STD DEV ABOVE CLIMATOLOGY. COOLER HIGHS IN THE UPPER 60S TO LOW 70S.
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&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
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AS OF 245 PM SATURDAY... ECMWF REMAINS SLOWER AND SHARPER WITH THE PROGRESSION OF THE SHORTWAVE ACROSS THE AREA... AND THE POTENTIAL EXISTS FOR SECONDARY SURFACE WAVE DEVELOPMENT... WHICH COULD RESULT IN LINGERING PRECIPITATION CHANCES INTO WEDNESDAY. AS THE SYSTEM DEPARTS... A 1035 MB HIGH BUILDS IN TO THE NORTHEAST AND WEDGES DOWN THE EAST COAST... BRINGING NORTHEASTERLY FLOW TO THE AREA. COLDEST NIGHT LOOKS TO BE WEDNESDAY NIGHT ... WITH FROST/FREEZE CONCERNS LOOKING INCREASINGLY LIKELY ACROSS MUCH OF THE AREA. THE WEDGE MAY STAY IN PLACE THROUGH THE REMAINDER OF THE PERIOD... AS THE DETAILS OF THE EROSION MECHANISM IN THE FORM OF A NORTHERN STREAM ARE QUITE UNCERTAIN AT THIS TIME PERIOD. WEDGE REGIME WILL RESULT IN BELOW NORMAL TEMPERATURES... POTENTIALLY LASTING INTO SATURDAY.
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&& .AVIATION /18Z SATURDAY THROUGH FRIDAY/... AS OF 130 PM SATURDAY... VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE CURRENT TAF PERIOD. WINDS WILL BE GENERALLY LIGHT AND VARIABLE ACROSS THE NORTHERN HALF OF THE FORECAST AREA AS A WEAK BOUNDARY REMAINS DRAPED ACROSS THE CENTRAL NC...WITH LIGHT SOUTHWESTERLY WINDS ELSEWHERE. HOWEVER...AS THE BOUNDARY WASHES OUT...WINDS SHOULD BECOME MORE SOUTHERLY AT ALL TAF SITES THROUGH THE AFTERNOON/EVENING HOURS. THEN AFTER LIGHT AND VARIABLE WINDS OVERNIGHT...SOUTHERLY WINDS WITH GUSTS UP TO 15-20 MPH WILL DOMINATE ON SUNDAY. JUST SOME SCATTERED FLAT DIURNAL CU WITH BASES BETWEEN 4-6 KFT WILL BE POSSIBLE TODAY AND THEN EVEN MORE SO ON SUNDAY. OUTLOOK...VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE REMAINDER OF THE WEEKEND. LOW STRATUS/FOG MAY DEVELOP LATE SUNDAY NIGHT/EARLY MONDAY MORNING AS LOW LEVEL MOISTURE REALLY BEGINS TO INCREASE. THEN A PERIOD OF WIDESPREAD ADVERSE AVIATION CONDITIONS IS EXPECTED LATE MONDAY THROUGH TUESDAY AS A STRONG COLD FRONT APPROACHES FROM THE WEST. CONDITIONS WILL THEN IMPROVE AGAIN BY MIDWEEK. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...KRD SHORT TERM...SEC LONG TERM...SEC AVIATION...KRD

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