Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 011142 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 745 AM EDT FRI AUG 1 2014 .SYNOPSIS...A PROLONGED PERIOD OF UNSETTLED WEATHER CAN BE EXPECTED THROUGH EARLY NEXT WEEK AS AN UPPER LEVEL TROUGH SLOWLY APPROACHES FROM THE WEST. && .NEAR TERM /THROUGH TONIGHT/... AS OF 330 AM FRIDAY... ...LOCALLY EXCESSIVE RAINFALL PROBABLE TODAY THROUGH SATURDAY NIGHT MAINLY EAST OF HIGHWAY 1... MOISTURE RICH AIR MASS ADVECTING INTO CENTRAL NC THIS MORNING AS EVIDENT OF SATELLITE BLENDED TOTAL PRECIP WATER IMAGERY DEPICTING PW VALUES AROUND 2 INCHES IN VICINITY OF NC/SC BORDER LIFTING SLOWLY NWD. ALSO...WATER VAPOR IMAGERY DEPICTS A NICE PLUME OF TROPICAL MOISTURE ORIGINATING IN THE YUCATAN CHANNEL/SOUTHERN GULF EXTENDING NEWD TO THE SE U.S. COAST. L/W TROUGH OVER THE MS VALLEY DIGGIN SWD THANKS TO A SERIES OF S/WS DIVING SEWD OVER THE PLAINS STATES THIS MORNING. LEAD S/W THAT WAS OVER THE SOUTHERN PLAINS/RED RIVER VALLEY THIS TIME YESTERDAY LIFTING NEWD ACROSS THE SOUTHERN APPALACHIANS THIS MORNING. THIS FEATURE COUPLED WITH SFC-850MB FLOW OUT OF THE E- SE (UPSLOPE COMPONENT) WILL FOCUS AREAS OF RAIN (AT TIMES HEAVY) OVER WESTERN NC...EXTENDING AS FAR EAST AS OUR WESTERN PIEDMONT COUNTIES THIS MORNING. CLOSER TO THE COAST...AN INVERTED SURFACE TROUGH WILL SLOWLY RETROGRADE...EVENTUALLY TAKING UP A POSITION OVER THE INLAND COASTAL PLAIN (JUST EAST OF I-95) LATE THIS AFTERNOON. THIS FEATURE TOO WILL BE A FOCUS FOR CONVECTIVE DEVELOPMENT THIS MORNING DUE TO ENHANCE LOW LEVEL SPEED CONVERGENCE. THIS WILL LEAVE THE HIGHWAY 1 CORRIDOR BRACKETED BY TWO ENHANCED REGIONS OF PRECIP THIS MORNING WITH SHOWERS AND SCATTERED T-STORMS TO OUR IMMEDIATE EAST-SE...AND WIDESPREAD RAIN TO OUR WEST-SW. FOR THIS MORNING...PLAN TO HAVE LIKELY POPS OVER THE EASTERN SANDHILLS AND SOUTHERN COASTAL PLAIN...AND OVER THE WESTERN PIEDMONT...WITH HIGH CHANCE POPS ALONG THE HIGHWAY 1 CORRIDOR. LATER THIS AFTERNOON...S/W WILL EXIT THE SOUTHERN APPALACHIANS. THIS SHOULD LEAD TO DECREASE IN PRECIP COVERAGE AND INTENSITY OVER OUR WESTERN PIEDMONT. IN THE EAST...SLOWLY RETROGRADING SFC TROUGH COUPLED WITH HEATING AND ADDITIONAL LIFT IN THE RIGHT ENTRANCE REGION OF A 75-80KT 300MB JET SHOULD TRIGGER NUMEROUS SHOWERS WITH SCATTERED THUNDERSTORMS. POTENTIAL FOR SOME SHOWERS/STORMS TO TRAIN ACROSS THE SAME LOCATION WHICH WILL LEAD TO LOCALLY HEAVY/EXCESSIVE RAINFALL. ALSO...A STORM OR TWO WILL HAVE THE POTENTIAL TO BE STRONG/SEVERE AS BULK SHEAR WILL BE 35-45 KTS (SUPPORTIVE OF ORGANIZED CONVECTION). INSTABILITY RATHER MEAGER FOR EARLY AUGUST (MLCAPE 5000-1000 J/KG) BUT SHEAR MORE THAN SUFFICIENT TO OVERCOME THIS LIMITATION. MAIN WEATHER HAZARD (ASIDE FROM HEAVY RAIN) WILL BE DAMAGING WIND GUSTS. LOW LEVEL HELICITY WILL BE ENHANCE IN VICINITY OF THE COASTAL TROUGH SO SOME WEAK ROTATION WILL LIKELY BE OBSERVED. MAX TEMPS TODAY WILL BE SEVERAL DEGREES BELOW NORMAL DUE TO THE EXTENSIVE CLOUDINESS AND AREAS OF PRECIP. MAX TEMPS RANGING FROM THE 70S IN THE PIEDMONT OT THE LOWER 80S SANDHILLS/SOUTHERN COASTAL PLAIN. TONIGHT...SFC TROUGH WILL CONTINUE TO BE A FOCUS FOR CONTINUED SHOWER/ISOLATED THUNDERSTORM DEVELOPMENT. THUS POPS WILL BE HIGHER IN THE COASTAL PLAIN AND SANDHILLS VERSUS THE PIEDMONT. POPS WIL RANGE FROM LIKELY IN THE EAST-SE...TO CHANCE IN THE FAR WEST-NW. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... AS OF 330 AM FRIDAY... THE SLOW MOVING L/W TROUGH TO OUR WEST WILL MAINTAIN THE MOIST AIR MASS OVER OUR REGION WITH THE SFC TROUGH PROJECTED TO BE ALIGNED SSW- NNE OVER THE COASTAL PLAIN. MODEL GUIDANCE IN GENERAL AGREEMENT WITH THE TIMING OF THE NEXT POTENT VORT MAX 9SATURAY AFTERNOON-SATURDAY EVENING). THIS SUGGEST SHOWERS AND THUNDERSTORMS INCREASING IN COVERAGE DURING THE AFTERNOON...WANING SOMETIME CLOSE TO MIDNIGHT. SIMILAR TO FRIDAY...POTENTIAL FOR SHOWERS AND STORMS TO TRAIN OVER THE SAME LOCATION. IF THIS OCCURS IN THE AREAS THAT GET HIT TODAY...WILL SEE HIGH AMOUNT OF RUN-OFF LEADING TO FLOODING ISSUES...PARTICULARLY IN URBAN AREAS AS WELL AS CREEKS/STREAMS. CONFIDENCE NOT HIGH ENOUGH YET TO ISSUE A FLOOD WATCH BUT ONE MAY NEED TO BE CONSIDERED. STORM INTENSITY/SEVERITY NOT EXPECTED TO BE AS MUCH OF A THREAT SATURDAY AS SHEAR VALUES ARE A LITTLE WEAKER. POPS STILL LIKELY IN THE EAST TRENDING TO HIGH CHANCE IN THE WEST. ANOTHE DAY OF BELOW NORMAL TEMPS SATURDAY WITH AN UNIFORMED MAX TEMP FIELD EXPECTED DUE TO EXTENSIVE CLOUD COVERAGE AND MORE SHOWERS/STORMS EAST VERSUS WEST. MAX TEMPS UPPER 70S/LOWER 80S. SHOWERS AN STORMS SHOULD TAPER OFF LATE SATURDAY NIGHT WITH BETTER CHANCES STILL EXPECTED IN VICINITY OF THE STALLED SFC TROUGH IN THE COASTAL PLAIN. MIN TEMPS UPPER 60S-LOWER 70S. && .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 315 AM FRIDAY... THOUGH NWP GUIDANCE INDICATES THE PARENT VORTEX NEAR THE SOUTHERN TIP OF HUDSON BAY WILL GRADUALLY FILL AND LIFT OUT DURING THE NEXT COUPLE OF DAYS...A POSITIVELY-TILTED TROUGH ALOFT WILL LINGER FROM THE FROM THE NE US TO THE LOWER MS VALLEY THROUGH TUE. SOUTHWESTERLY AND PERTURBED MID LEVEL FLOW WILL CONSEQUENTLY MAINTAIN AN AXIS OF DEEP MOISTURE CHARACTERIZED PRECIPITABLE WATER VALUES AOA TWO INCHES OVER THE EASTERN THIRD OF NC (INCLUDING THE RAH COASTAL PLAIN) SUN- MON...WITH PROGRESSIVELY LOWER VALUES TO AROUND 1.5 INCHES OVER THE WESTERN PIEDMONT. THE DEEP MOIST AXIS WILL THEN BE SHUNTED OFFSHORE DURING THE MIDDLE OF THE WEEK...WHEN GUIDANCE SUGGESTS A SUCCESSION OF SHORTWAVE TROUGHS WILL FORCE THE NORTHERN STREAM PORTION OF THE TROUGH OFF THE NE AND MID ATLANTIC COAST. THE MOVEMENT OF THE NORTHERN PORTION OF THE TROUGH SHOULD THEN LEAVE BEHIND TROUGHINESS/ A WEAK UPPER LOW OVER THE GULF COAST STATES THROUGH THE END OF THE WEEK. MEANWHILE...IN THE LOW LEVELS AND AT THE SURFACE...THE FRONTAL ZONE/INVERTED TROUGH WILL LINGER OVER EAST-CENTRAL NC THROUGH MON...THEN DRIFT EAST AND OFFSHORE IN RESPONSE TO THE EASTWARD PROGRESSION OF THE NORTHERN PORTION OF THE TROUGH ALOFT. THE RESULT OF THE EVOLVING PATTERN DESCRIBED ABOVE WILL BE CONTINUED UNSETTLED CONDITIONS OVER ESPECIALLY THE EASTERN HALF OF THE RAH FORECAST AREA THROUGH EARLY WEEK. SPECIFICALLY...A CONTINUED LIKELY PROBABILITY OF SHOWERS AND STORMS ROUGHLY EAST OF US HWY 1 ARE WARRANTED ON SUN...TAPERING TO CHANCE OVER THE WESTERN PIEDMONT (AND PERHAPS NOT MUCH OF ANY COVERAGE INVOF AND WEST OF THE YADKIN RIVER). THAT POP DISTRIBUTION WILL THEN EDGE EASTWARD ON MON...WITH COVERAGE FOCUSED OVER THE RAH COASTAL PLAIN AND ESPECIALLY POINTS EASTWARD. MID LEVEL FLOW WILL BE MODEST...15-25 KTS AND RELATIVELY STRONGEST ON SUN...SUPPORTIVE OF MAINLY MULTI-CELL ORGANIZATION. IN THE ABSENCE OF STRONGER FLOW AND/OR STEEPER LAPSE RATES ALOFT... LOCALLY HEAVY RAIN...AMIDST THE CONTINUED HIGH MOISTURE CONTENT AIR...WILL POSE A PRIMARY HAZARD. THE DEVELOPMENT OF DRYING WESTERLY FLOW AS THE NORTHERN STREAM MOVES OFFSHORE BY THE MIDDLE OF THE WEEK WILL FAVOR A RETURN TO MORE TYPICAL SUMMERTIME CONDITIONS OVER THE CAROLINAS...CHARACTERIZED BY WARMING TEMPERATURES INTO THE 80S TO NEAR 90 DEGREES - AFTER SUN-MON TEMPERATURES TRANSITIONING THROUGH THE LOWER TO MIDDLE 80S - AND ISOLATED TO WIDELY SCATTERED DIURNAL CONVECTION. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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AS OF 745 AM FRIDAY... HIGH CONFIDENCE OF A PROLONGED PERIOD OF SUB VFR CONDITIONS ACROSS CENTRAL NC...STARTING TODAY AND PERSISTING THROUGH THE WEEKEND. A MOIST EAST-SOUTHEAST FLOW NEAR THE SURFACE COUPLED WITH A MOIST SW FLOW ALOFT WILL MAINTAIN A NEARLY SATURATED AIR MASS THROUGH SUNDAY. THIS WILL RESULT IN WIDESPREAD MVFR CEILINGS WITH PERIODS OF IFR/LIFR CEILINGS. THE IFR/LIFR SHOULD MAINLY OCCUR IN THE LATE NIGHT-EARLY MORNING HOURS. A SERIES OF UPPER LEVEL DISTURBANCES IN THE FLOW ALOFT WILL TRIGGER AREAS OF SHOWERS AND A FEW THUNDERSTORMS. THE MOST WIDESPREAD COVERAGE ANTICIPATED TODAY WITH THE PASSAGE OF A POTENT UPPER LEVEL SYSTEM...AND AGAIN SATURDAY AFTERNOON-SATURDAY NIGHT WITH THE APPROACH/PASSAGE OF ANOTHER DISTURBANCE. A FEW STRONG STORMS MAY OCCUR IN THE VICINITY OF KFAY AND KRWI THIS AFTERNOON AND AGAIN SATURDAY AFTERNOON AS LOW LEVEL INSTABILITY WILL BE BETTER IN THE SANDHILLS AND COASTAL PLAIN COMPARED TO THE PIEDMONT. AVIATION CONDITIONS ARE EXPECTED TO SLOWLY IMPROVE MONDAY INTO TUESDAY AS THE AIR MASS SLOWLY DRIES OUT AND THE BETTER LIFT FOR SHOWERS AND THUNDERSTORMS DRIFTS EAST TOWARD THE IMMEDIATE COASTLINE. STILL...THERE WILL BE PERIODS OF MVFR/IFR CEILINGS DUE TO RESIDUAL MOISTURE...MAINLY IN THE LATE NIGHT-EARLY MORNINGS HOURS.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...WSS SHORT TERM...WSS LONG TERM...MWS AVIATION...WSS

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