Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 031532 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1132 AM EDT FRI JUL 3 2015 .SYNOPSIS... SURFACE LOW PRESSURE WILL TRACK EAST ACROSS NC AND VA LATER TODAY AND TONIGHT...ALONG A FRONTAL ZONE THAT WILL LINGER OVER THE REGION THROUGH THE HOLIDAY WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1132 AM FRIDAY... CURRENT FORECAST PRETTY MUCH ON TRACK AS SHOWER/T-STORM COVERAGE WILL INCREASE THIS AFTERNOON AS MID LEVEL S/W APPROACHES THEN CROSSES THE REGION. 15Z MESO-ANALYSIS DEPICTS CONVECTIVE INHIBITION WANING...RESULTING IN A SLIGHT UPTICK IN CONVECTION OVER THE WESTERN-SOUTHERN PIEDMONT SINCE 14Z. THE MID LEVEL S/W CURRENTLY LIFTING E-NE OUT OF EASTERN TN AND SHOULD CROSS NEAR OR TO OUR NORTH THIS AFTERNOON. SINCE FEATURE CROSSING DURING PRIME HEATING AND AIR MASS QUITE MOIST (PRECIP WATER VALUES VARY BETWEEN 1.7-1.9 INCHES)...SHOULD SEE NUMEROUS SHOWERS AND STORMS DEVELOP BY MID AFTERNOON. 850-700MB WINDS ARE A BIT STRONGER THAN PROJECTED BY THE GFS...CLOSER TO THE NAM PROJECTIONS. LOW LEVEL JET ON THE ORDER OF 35KTS CROSSING AL-GA PER 12Z ANALYSIS WITH 50KT JET AT 700MB OVER CENTRAL AL. THIS FEATURE HAS INCREASED THE SHEAR OVER THIS PART OF THE COUNTRY RESULTING IN THE UPGRADE TO AN ENHANCED RISK THIS AFTERNOON. CLOSER TO HOME...THE ADDED SHEAR AND THE UNIDIRECTIONAL FLOW SHOULD CAUSE STORMS TO ORGANIZE INTO A BROKEN NORTH-SOUTH ORIENTATED BANDS. IN THIS TYPE OF ENVIRONMENT...THE SEVERE HAZARDS WILL EITHER BE FROM LOCALLY DAMAGING STRAIGHT LINE WINDS OR DAMAGING MICROBURSTS DUE TO PRECIP LOADING. AS MENTIONED IN EARLIER DISCUSSION...AN ISOLATED TORNADO RISK STILL EXISTS OVER MAINLY THE SOUTHERN CONTINUES AS THIS REGION IN CLOSER PROXIMITY TO THE LOW LEVEL JET AND BETTER NEAR SURFACE HELICITY. AFTERNOON TEMPS HIGHLY DEPENDENT ON CLOUD/CONVECTIVE COVERAGE THIS AFTERNOON. FEEL THAT CURRENT MAX TEMP FORECAST IS THE BEST CASE SCENARIO. IF CONVECTION CONTINUES TO BLOSSOM...MAY NEED TO ADJUST TEMPS DOWN A FEW DEGREES...ESPECIALLY ACROSS THE WEST AND SOUTH. TONIGHT...SCATTERED-NUMEROUS SHOWERS/STORMS SHOULD BEGIN TO DIMINISH FROM THE WEST-SW BY EARLY EVENING AS BEST UPPER LEVEL SUPPORT LIFTS FARTHER TO THE E-NE. EXPECT BULK OF ACTIVITY TO END PRIOR TO 03Z. STILL...A MOIST ATMOSPHERE COUPLED WITH MINOR PERTURBATIONS CROSSING OVERHEAD MAY TRIGGER/SUSTAIN ISOLATED SHOWERS ABOUT ANYWHERE THROUGH THE NIGHT. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 435 AM FRIDAY... THE MODELS CONTINUE TO INDICATE THE FRONTAL ZONE WILL REMAIN JUST TO THE NORTH OF CENTRAL NC ON SAT...WITH A SHARP LEE TROUGH AND A BREEZY SOUTHWEST FLOW AND MODEST MIXING OUT OF BOUNDARY LAYER MOISTURE OVER THE CAROLINAS. TEMPERATURES SHOULD CONSEQUENTLY WARM...INTO THE MID 80S TO LOW 90S...WITH THE FOCUS FOR AFTERNOON AND EVENING CONVECTION OVER THE NORTHERN AND NW NC PIEDMONT...IN CLOSEST PROXIMITY TO THE FRONTAL ZONE. CONTINUED SEASONABLY STRONG SW MID LEVEL FLOW IN THE 30-35 KT RANGE WILL FAVOR ORGANIZATION... AND DCAPE SHOULD BE HIGH WITH STEEP LOW LEVEL LAPSE RATES AND SURFACE DEWPOINT DEPRESSIONS AROUND 25 DEGREES...SO ANY STORMS THAT DO FORM WILL BE CAPABLE OF PRODUCING STRONG TO SEVERE WIND GUSTS...AND PERHAPS MARGINALLY SEVERE HAIL. ALTHOUGH THE MODELS INDICATE LIMITED QPF SAT NIGHT...THE FRONT IS FORECAST TO DRIFT SOUTH INTO CENTRAL NC LATE SAT NIGHT-EARLY SUN...SO A SLIGHT CHANCE OF A SHOWER OR STORM OVERNIGHT SEEMS JUSTIFIED. LOWS AGAIN AROUND 70. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 345 PM FRIDAY... A LOW AMPLITUDE SHORTWAVE CURRENTLY OVER THE US NORTHERN ROCKIES WILL DIVE INTO THE BASE OF THE BROAD EASTERN US TROUGH ON SATURDAY BEFORE ESSENTIALLY CUTTING OFF FROM THE FLOW AND DRIFTING UP THE APPALACHIANS ON SUNDAY AND MONDAY...WHILE THE PERSISTENT SURFACE FRONT/TROUGH FROM EARLIER IN THE WEEKEND REMAINS DRAPED ACROSS CENTRAL NC. THERE MAY BE SOME UNCERTAINTY IN INSTABILITY GIVEN CONSIDERABLE CLOUDINESS EXPECTED EARLY SUNDAY...BUT THE COMBINATION OF THE UPPER LOW...ALBEIT WEAK...AND SURFACE BOUNDARY AMIDST PW OVER 1.75" SHOULD LEAD TO NUMEROUS SHOWERS AND STORMS SUNDAY AND INTO SUNDAY NIGHT. BY THE MONDAY THE FRONT IS FORECAST SHIFT NORTH INTO VA AND THE FOCUS OF SHOWERS/STORMS MAY SHIFT MORE TOWARD THE COASTAL PLAIN. THE LOW/MID LEVEL FLOW IS MUCH WEAKER SUNDAY/MONDAY AND SEVERE STORMS MAY BE LESS OF A THREAT...BUT LOCALIZED FLOODING MAY REAR ITS HEAD...PARTICULARLY IN THE VICINITY OF THE BOUNDARY. CLOUDS AND PRECIP WILL LIKELY KEEP HIGHS LITTLE BELOW NORMAL IN THE MID TO UPPER 80S...SLIGHTLY WARMER ON MONDAY. BEYOND MONDAY... THERE ARE SOME SIGNS OF WARMING FOR THE MIDDLE OF NEXT WEEK AND A LITTLE LESS PRECIP COVERAGE AS THE PROGRESSIVE PATTERN EVENTUALLY YIELDS SOME REESTABLISHMENT OF THE SUB-TROPICAL RIDGE OVER THE SOUTHEAST US WITH A COLD FRONT DYING JUST TO OUR NORTH AROUND MIDWEEK. HOWEVER...THE OVERALL PATTERN IS NOT VERY AMPLIFIED AND TEMPS SHOULD REMAIN WITHIN A COUPLE DEGREES OF NORMAL. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... AS OF 755 AM FRIDAY... THE PRESENCE OF A SURFACE FRONT DRAPED ACROSS THE NORTHERN NC PIEDMONT --AND ASSOCIATED MOISTURE CONVERGENCE-- WILL MAINTAIN A BAND OF IFR-MVFR STRATUS THAT WILL GRADUALLY ERODE FROM THE EDGES (ESPECIALLY FROM THE NORTHEAST) AND LIFT/MORPH INTO A CUMULUS FIELD...WHOSE BASES ARE APT TO FLIRT WITH THE 3000 FT/MVFR THRESHOLD THROUGH MIDDAY-EARLY AFTERNOON. PRIOR CONVECTION AND ASSOCIATED AIR MASS STABILIZATION OVER CENTRAL NC WILL CAUSE UPSTREAM CONVECTION CROSSING THE SOUTHERN APPALACHIANS TO WEAKEN AS IT APPROACHES... THOUGH A FEW REMNANT SHOWERS CANNOT BE RULED OUT IN THE 12-18Z TIME FRAME. HOWEVER...A BETTER CHANCE OF SHOWERS AND STORMS WILL OCCUR WITH THE COMBINATION OF DIURNAL HEATING AND THE APPROACH OF A DISTURBANCE ALOFT INITIALLY OVER THE TN VALLEY...AND AND INTERACTION WITH THE AFOREMENTIONED FRONTAL ZONE...LATER THIS AFTERNOON THROUGH EARLY THIS EVENING. OUTLOOK: THE AFOREMENTIONED FRONT WILL STALL OVER VA/NC AND RESULT IN ABOVE AVERAGE PROBABILITIES OF SHOWERS AND STORMS AND ASSOCIATED SUB-VFR CONDITIONS THROUGH MON...WITH THE RELATIVE HIGHEST PROBABILITY SUN-MON. PERIODS OF MVFR CEILINGS WILL BE POSSIBLE EVEN OUTSIDE OF STORMS DURING THAT TIME...ESPECIALLY DURING THE MORNING TO EARLY AFTERNOON HOURS. && ..RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...WSS SHORT TERM...26 LONG TERM...22 AVIATION...26

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