Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 041440 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1040 AM EDT SAT JUL 4 2015 .SYNOPSIS...
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A SERIES OF DISTURBANCES ALOFT WILL MOVE OVERHEAD AND INTERACT WITH A SURFACE FRONT THAT WILL WAVER ACROSS VA AND NC THROUGH MONDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1040 AM SATURDAY... LITTLE ADJUSTMENT REQUIRED TO THE NEAR TERM FORECAST. 12Z UPPER AIR ANALYSIS DEPICTS DECENT SPEED CONVERGENCE AT 850-700MB ACROSS GA-SC WITH WEAKER CONVERGENCE ACROSS CENTRAL NC. WEAK 850- 700MB TROUGH NOTED ACROSS THE NW PIEDMONT WITH A MORE PRONOUNCED TROUGH DRAPED ACROSS THE OH VALLEY INTO THE MID MS VALLEY. SURFACE BASED INSTABILITY NOMINAL AT 14Z BUT ADDITIONAL HEATING SHOULD CAUSE THE ATMOSPHERE TO BECOME SLIGHT-MODERATELY UNSTABLE BY EARLY AFTERNOON. A WEAK MID LEVEL VORTICITY NOTED BY THE NEAR TERM MODELS SOMEWHAT DISCERNIBLE ON WATER VAPOR IMAGERY AT 14Z ABOUT TO EXIT NE GA INTO UPSTATE SC. THIS FEATURE COUPLED WITH THE DESTABILIZING ATMOSPHERE AND THE CONFLUENCE ZONE OVER SC SHOULD INITIATE AND SUSTAIN SCATTERED CONVECTION OVER OUR SOUTHERN COUNTIES THIS AFTERNOON. DEEP W-SW FLOW THROUGH THE COLUMN WITH 850-700MB WINDS ON THE ORDER OF 30-40KTS. THIS SUGGEST THE POTENTIAL FOR ORGANIZED STORMS IN THE FORM OF BROKEN N-S ORIENTATED BANDS. IF ENOUGH HEATING OCCURS...REALIZING LOW LEVEL LAPSE RATES OF 8-9 DEG C/KM...COULD SEE THE STRONGER STORMS PRODUCE LOCALIZED WIND GUSTS 40- 50KTS. ACROSS THE NORTH...EXPECT SCATTERED CONVECTION TO DEVELOP IN VICINITY OF THE WEAK LOW LEVEL TROUGH BY MID AFTERNOON. WHILE LIKELY NOT AS ROBUST AS THE STORMS TO THE SOUTH...STILL COULD SEE STRING GUSTY WINDS (35-40KTS) WITH THESE STORMS. HAVE NUDGED MAX TEMPS UP A DEGREE OR TWO DUE TO MOSTLY-PARTLY SUNNY SKIES WHICH MAY PERSIST UNTIL EARLY AFTERNOON. AFTERWHICH...CLOUDS THICKEN IN RESPONSE TO HEATING/CONVECTIVE DEVELOPMENT. AREA SOUNDINGS DEPICT LOW LEVEL WINDS JUST ABOVE THE SURFACE CLOSE TO 25- 30KTS. ONCE LOW LEVEL INVERSION LIFTS (ONCE TEMPS EXCEED 80-LOWER 80S)...SHOULD SEE BREEZY W-SW WINDS WITH FREQUENT GUSTS AROUND 25 MPH...ESPECIALLY ACROSS THE SOUTHERN COUNTIES. EXPECT SCATTERED CONVECTION TO DIMINISH EARLY THIS EVENING AS UPPER LEVEL SUPPORT WANES AND LOW LEVEL CONVERGENCE WEAKENS. BULK OF SCATTERED CONVECTION SHOULD DIMINISH BY 9-10 PM.
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&& .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 430 AM SATURDAY... A SHORTWAVE TROUGH OVER THE CENTRAL PLAINS THIS MORNING WILL AMPLIFY INTO THE BASE OF THE L/W TROUGH AND CAUSE A MID LEVEL LOW TO BRIEFLY CLOSE OFF AND LIFT THROUGH THE SOUTHERN AND CENTRAL APPALACHIANS SUN- SUN NIGHT...WHILE A GENERALLY EAST-WEST ORIENTED LOW LEVEL FRONTAL ZONE WILL LINGER NEAR OR JUST SOUTH OF THE VA/NC BORDER. STORMS INITIALLY WILL LIKELY FIRE OVER OR JUST OUTSIDE OF THE RAH CWFA BORDERS...TO THE WEST IN ASSOCIATION WITH THE INFLUENCE OF THE CLOSED LOW; ALONG THE NORTHERN PIEDMONT INVOF THE SURFACE FRONT; AND TO THE EAST ALONG THE SEA BREEZE. EACH WILL SEND OUTFLOW AND ASSOCIATED MULTI-CELL STORM DEVELOPMENT DIRECTED THROUGHOUT THE REMAINDER OF CENTRAL NC. HIGH PWAT (>1.75") AND LIMITED CINH/LOW LFC HEIGHTS WILL FAVOR NUMEROUS COVERAGE...WITH A PRIMARY THREAT OF LOCALIZED FLOODING OWING TO BOTH SLOW MOVEMENT AND PROBABLE PERPETUAL REDEVELOPMENT ATOP THE CONVECTIVE OUTFLOW-MODULATED FRONTAL ZONE. HIGHS IN THE 80S...WARMEST NEAR 90 DEGREES OVER THE SANDHILLS...WITH LOWS MOSTLY IN THE LOWER 70S. && .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 410 AM SUNDAY... A SHORTWAVE TROUGH AXIS...ATTENDANT TO THE UPPER LOW OVER THE OHIO VALLEY REGION MONDAY MORNING...WILL LIFT ACROSS CENTRAL NC ON MONDAY...WHILE A WEAK FRONTAL ZONE AT THE SURFACE SHIFTS NORTH INTO VA. FORCING ASSOCIATED WITH THE TROUGH AXIS AND A CONTINUED MOIST AIRMASS AND PW AROUND 1.8" SHOULD RESULT IN SHOWERS AND AND ISOLATED STORMS ACROSS THE WEST EARLY MONDAY...POTENTIALLY EXPANDING WITH TIME TO THE NORTH AND EAST WHERE AFTERNOON DESTABILIZATION IS EXPECTED TO BE MAXIMIZED GIVEN THE TIMING OF THE FORCING AND A SLIGHTLY BACKED SOUTH-SOUTHEASTERLY WIND OVER THE COASTAL PLAIN. RELATIVELY WEAK MID TROPOSPHERIC FLOW SHOULD LIMIT THE OVERALL SEVERE THREAT...BUT A CONCERN OF SOME LOCALIZED FLOODING MAY STILL EXIST IN THE ACTIVE PATTERN. THE UPPER LOW IS THEN FORECAST TO OPEN UP AND SHEAR OUT ON TUESDAY AS THE SUBTROPICAL RIDGE TRIES TO BUILD BACK ACROSS THE SOUTHEAST US. HOWEVER...PROGRESSIVE FLOW AND A SERIES OF SHORTWAVES CROSSING THE NORTHERN US WILL KEEP HEIGHTS FROM RISING TO STRONGLY OVER OUR REGION...WITH A COLD FRONT MOVING INTO THE OH/TN VALLEY BY MIDWEEK. WHILE THE FRONT MAY NOT MAKE IT ALL THE WAY INTO THE NC...WE SHOULD SEE A SHARPENING LEE TROUGH AND FAIRLY TYPICAL SCATTERED AFTERNOON STORMS...WITH SOME INFLUENCE FROM WEST-EAST MOVING DISTURBANCES TO OUR NORTH BY LATE WEEK. HIGHS MONDAY WILL REMAIN BELOW NORMAL...WITH A WARMING TREND ENSUING TUESDAY ONWARD...THOUGH HIGHS WILL LIKELY REMAIN JUST A DEGREE OR TWO ON THE WARMER SIDE SIDE OF NORMAL. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 745 AM SATURDAY... THE THREAT OF IFR-MVFR CEILINGS WILL CONTINUE IN THE VICINITY AND ESPECIALLY NORTH OF A FRONTAL ZONE DRAPED NEAR THE VA/NC BORDER THIS MORNING...LIKELY JUST TO THE NORTH OF NORTHERN RAH TAF SITES WHERE VFR CONDITIONS ARE EXPECTED. MEANWHILE...A SERIES OF DISTURBANCES OVER THE NORTHERN GULF COAST STATES TODAY WILL TRACK ENE ACROSS THE CAROLINAS THROUGH THIS EVENING...WITH AN ASSOCIATED CONVECTIVE CLUSTER PROBABLY ACCOMPANYING EACH...THE FIRST OF WHICH MAY AFFECT FAY/RDU/RWI BETWEEN 15-20Z BASED ON EXTRAPOLATION OF PAST MOVEMENT. STABILIZING EFFECTS OF EACH PASSING CLUSTER OF STORM SUGGESTS MUCH LOWER PREDICTABILITY WITH ANY SUBSEQUENT DISTURBANCE AND STORM CLUSTER FROM MID AFTERNOON ONWARD...BUT IT SEEMS REASONABLE THAT ADDITIONAL STORMS THAT FIRE ALONG A COLD FRONT APPROACHING FROM WV WILL DRIFT INTO THE VICINITY OF NORTHERN RAH TAF SITES BETWEEN 22- 03Z. OTHERWISE...A RELATIVELY STRONG PRESSURE GRADIENT BETWEEN LOW PRESSURE MOVING ACROSS VA AND HIGH PRESSURE ALONG THE GULF COAST WILL RESULT IN THE DEVELOPMENT OF BREEZY CONDITIONS BY 14-15Z...AS SOUTHWEST WINDS STRENGTHEN INTO THE 10-20 KT RANGE WITH GUSTS IN THE 20S KTS - HIGHEST AT FAY AND RWI. OUTLOOK: THE FRONT WILL DRIFT SOUTH INTO NC LATE TONIGHT AND EARLY SUN. STRATUS WILL AGAIN BE POSSIBLE NEAR AND ESPECIALLY NORTH OF THE FRONT...NEAR AND MORE LIKELY JUST NORTH OF NORTHERN CENTRAL NC TAF SITES SUN MORNING. OTHERWISE...AN ABOVE AVERAGE PROBABILITY OF SHOWERS AND STORMS AND ASSOCIATED SUB-VFR CONDITIONS WILL ACCOMPANY THE APPROACH/PASSAGE OF AN UPPER LOW THROUGH THE SOUTHERN AND CENTRAL APPALACHIANS SUN-MON...BEFORE A RETURN TO MORE TYPICAL SUMMERTIME CONDITIONS FOR THE MIDDLE OF THE UPCOMING WEEK.
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&& ..RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...WSS SHORT TERM...26 LONG TERM...22 AVIATION...26

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