Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210534 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 130 AM EDT MON JUL 21 2014 .SYNOPSIS...A LOW PRESSURE AREA WILL HOLD OVER THE DEEP SOUTH THROUGH TUESDAY... RESULTING IN A MOIST ATLANTIC FLOW FROM THE SOUTHEAST INTO NORTH CAROLINA... AND UNSETTLED WEATHER TO START THE WORK WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1040 PM SUNDAY... THE LATEST DATA ANALYSIS AND MODEL ASSESSMENT INDICATE SMALL CLUSTERS OF SHOWERS AND THUNDERSTORMS MOVING NORTHWARD ACROSS CENTRAL NC. THESE SHOWERS AND STORMS CONTINUE FORMING ALONG A NEARLY STATIONARY FRONT OVER CENTRAL NC... THEN LIFTING NORTHWARD AND SLOWLY DISSIPATE WITH TIME NORTH OF THE BOUNDARY. THE LATEST HI-RES MODELS DID NOT FAVOR ONE PARTICULAR AREA OVERNIGHT SUPPORTING THE EARLIER FORECAST OF MAINLY DIURNAL ACTIVITY... WEAKENING AFTER MIDNIGHT. WHILE THIS MAY STILL OCCUR... THE CONVECTION OVER NORTHERN SOUTH CAROLINA HAS PROMPTED SOME ISOLATED FLASH FLOOD CONCERNS IN THE CAE AREA RECENTLY. A FEW OF THE MODELS SUGGEST THAT THE REMNANTS OF THIS CLUSTER MAY AFFECT OUR PIEDMONT AND WESTERN SANDHILLS OVERNIGHT. THE FLASH FLOOD GUIDANCE IS CURRENTLY RUNNING HIGH... GENERALLY IN THE 2.5 TO 3.5 INCH RANGE IN 3 HOURS... LOWER IN URBAN AREAS OF COURSE. THE WEAK STEERING FLOW AND RELATIVELY SLOW PROPAGATION AND TRAINING OF CELLS MAY STILL DROP LOCAL 2 INCH TOTALS IN A FEW AREAS. THEREFORE... THERE MAY BE SOME MINOR WATER ISSUES ON A LOCALIZED BASIS... WIDESPREAD CONCERNS OF FLASH FLOODING APPEAR TO BE MINIMAL AT THE CURRENT TIME. PREVIOUS UPDATE AT 800 PM... A WARM FRONT CONTINUED TO BACK INLAND THROUGH THE SANDHILLS AND COASTAL PLAIN INTO THE SOUTHEASTERN PIEDMONT OF NC THIS EVENING. THIS IS THE CURRENT FOCI FOR SHOWERS AND SCATTERED THUNDERSTORMS. THERE CONTINUED TO BE INCREASING LOW LEVEL MOISTURE INTO AND UP AND OVER THE BOUNDARY WITH DEW POINTS HAVING INCREASED INTO THE LOWER TO MID 70S WELL INTO THE SE PIEDMONT AND SANDHILLS. THE MID/UPPER SUPPORT IS FAIRLY WEAK BUT STILL PRESENT WITH THE STILL SIGNIFICANT MID/UPPER TROUGH OVER THE TENNESSEE VALLEY TO THE GULF COAST. WE WILL RAISE POP TO LIKELY NEAR THE BOUNDARY THROUGH THE LATE EVENING WITH THE POP LARGELY DIURNAL. THERE WILL STILL BE A CHANCE OF SHOWERS AND THUNDERSTORMS OVERNIGHT IN THE MOIST AIR MASS NEAR THE BOUNDARY. QPF RAISED INTO THE 0.25 TO 0.50 INCH RANGE NEAR THE BOUNDARY FROM NEAR SOP TO RDU AS WELL. LOWS WILL BE MUCH HIGHER TONIGHT THAN IN PREVIOUS NIGHTS... REMAINING 70+ ALONG AND NEAR THE BOUNDARY... WITH MID 60S N-NW. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 330 PM SUNDAY... MONDAY...SOUTH CAROLINA S/W PROJECTED TO LIFT E-NE INTO SE NC BY EARLY AFTERNOON THEN OFFSHORE BY EARLY EVENING. THIS FEATURE INTERACTING WITH THE AVAILABLE MOISTURE AND SLIGHTLY FAVORABLE DIVERGENCE ALOFT SHOULD TRIGGER/SUSTAIN SCATTERED-NUMEROUS SHOWERS AND A FEW THUNDERSTORMS...ESPECIALLY DURING THE AFTERNOON HOURS. EXPECT BULK OF PRECIP TO OCCUR OVER THE SOUTHERN AND EASTERN SECTIONS OF THE FORECAST AREA. A LINGERING SFC RIDGE OVER THE NORTHERN-NORTHWEST PIEDMONT MAY SUPPRESS CONVECTIVE DEVELOPMENT. PLAN TO VARY POPS FROM CHANCE ACROSS THE FAR NORTH-NW TO LIKELY ACROSS THE SE THIRD. SIMILAR TO TODAY...CLOUDS AND SCATTERED SHOWERS WILL RESULT IN TEMPS SEVERAL DEGREES BELOW NORMAL. WITH CONVECTION EXPECTED TO FIRE BY LATE MORNING/EARLY AFTERNOON DUE TO CLOSE PROXIMITY OF THE S/W...FAVOR MAX TEMPS ON THE COOLER SIDE OF MOS GUIDANCE (LOWER 80S). IF CONVECTION ABSENT AT EARLY AFTERNOON...TEMPS MAY END UP REACHING THE MID 80S. MONDAY NIGHT... SCATTERED-NUMEROUS SHOWERS WILL GRADUALLY DIMINISH AS THE S/W LIFTS OFFSHORE AND ATMOSPHERE BEGINS TO STABILIZE WITH LOSS OF HEATING. STILL COULD SEE A FEW SHOWERS PERSIST OR RE- GENERATE AS ADDITIONAL MINOR LIFT NEWD. POPS CAPPED AT 30-40 PERCENT FOR NOW. MIN TEMPS UPPER 60S-LOWER 70S. && .LONG TERM /TUESDAY THROUGH SUNDAY/... AS OF 250 PM SUNDAY... TUESDAY: CENTRAL NC WILL BE POSITIONED BETWEEN A CLOSED UPR LOW OVER THE DEEP SOUTH AND THE RIDGE OFF THE SE COAST...WITH A WEAK SHEAR AXIS ELONGATED ACROSS OUR SOUTHERN ZONES. MEANWHILE...INVERTED TROUGH IS PROGGED TO REMAIN NEAR THE COAST. FORECAST SOUNDINGS CONTINUE TO SHOW PLENTY OF PWAT (AOA 2 INCHES) ACROSS OUR CWA...BUT FORECAST CAPE STILL AOB 1000 J/KG AND VERY WEAK DEEP LAYER FLOW. AS SUCH...LOOK FOR SCATTERED MAINLY AFTERNOON/EVENING SHOWERS AND TSTMS...WITH THE MAIN CONCERN BEING LOCALIZED SLOW-MOVING HEAVY DOWNPOURS WHICH MAY RESULT IN SOME POOR DRAINAGE FLOODING. OTHERWISE...NOT MUCH OF A CONCERN FOR DAMAGING WIND OR HAIL GIVEN MODEST INSTABILITY AND SHEAR. AIRMASS SHOULD SUPPORT NEAR-NORMAL HIGHS AROUND 90 IF SOME SUNSHINE CAN BREAK THROUGH THE CLOUDS. LOWS TUESDAY NIGHT AROUND 70. WEDNESDAY: WE`LL SEE A CHANGE TO A MORE TYPICAL WEATHER PATTERN WITH THE PIEDMONT SFC TROUGH SETTING UP AS MID LEVEL WESTERLY FLOW INCREASES AHEAD OF AN APPROACHING SHORT WAVE TROUGH THAT WILL BE MOVING ACROS THE GREAT LAKES REGION. LOOK FOR BETTER COVERAGE OF SCATTERED AFTERNOON AND EVENING SHOWERS/TSTMS. FORECAST SOUNDINGS INDICATE CAPE INCREASING TO 1500 J/KG NEAR AND EAST OF THE TRIANGLE...BUT 0-6KM BULK SHEAR EXPECTED TO REMAIN AOB 20KT. THUS...THE STRONGER STORMS MAY BE CAPABLE OF PRODUCING SOME STRONG WIND GUSTS AND/OR SOME HAIL...BUT THE MAIN CONCERN WILL ONCE AGAIN BE HEAVY DOWNPOURS AND POOR DRAINAGE FLOODING WITH PWAT STILL AROUND 2 INCHES. HIGHS IN THE LOWER 90S AND LOWS IN THE LOWER 70S. THURSDAY AND FRIDAY: DECENT MODEL AGREEMENT THAT THE COLD FRONT WILL MOVE INTO OUR CWA LATER IN THE DAY THURSDAY AND STALL ACROSS OUR EASTERN/SOUTHERN ZONES ON FRIDAY. AS SUCH...POPS WILL TREND FROM HIGHEST NORTHWEST TO LOWEST SOUTHEAST ON THURSDAY...THEN FLIPPING TO HIGHEST SOUTH/EAST TO LOWEST NORTHWEST ON FRIDAY. TEMPS ON THURSDAY STILL ABOVE NORMAL (HIGHS IN THE MID 90S AND LOWS IN THE LOWER 70S) GIVEN THE LATE ARRIVAL OF THE FRONT...THEN COOLING BACK TO NEAR NORMAL FOR FRIDAY WITH THE FRONT ACROSS OR JUST EAST OF OUR AREA. NEXT WEEKEND: AT THIS POINT IT LOOKS LIKE THE AFOREMENTIONED BOUNDARY WILL BE WEAKENED OR DISSIPATED TO OUR SOUTH AND EAST. EXPECT A MORE TYPICAL SUMMER PATTERN DURING THIS TIME WITH SCATTERED AFTERNOON/EVENING SHOWERS AND TSTMS AND TEMPS NEAR 90 FOR HIGHS AND NEAR 70 FOR LOWS. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... AS OF 130 AM MONDAY... SMALL CLUSTERS OF SHOWERS AND A FEW STORMS WILL PERSIST OVER CENTRAL NC FOR MUCH OF THE TAF VALID PERIOD... BUT CONFIDENCE IS LOW AS TO WHICH AIRFIELDS WILL BE MOST AFFECTED... AS SHOWERS/STORMS COULD FORM ANYWHERE AND MEANDER/MOVE SLOWLY AROUND THE AREA. BUT IT APPEARS THAT INT/GSO WILL SEE THE BEST COVERAGE THROUGH TODAY. A WEAK TROUGH ALOFT OVER THE DEEP SOUTH IS EXPECTED TO CLOSE OFF INTO A LOW OVER AL/GA TODAY AND TONIGHT... WHICH WILL KEEP A VERY MOIST AND UNSETTLED ATMOSPHERE OVER NC... WITH A LIGHT FLOW FROM THE SE AND S DRAWING IN ATLANTIC MOISTURE. GSO/INT AND TO A LESSER EXTENT RDU HAVE THE BEST CHANCE OF SEEING MVFR CONDITIONS WITHIN SHOWERS/STORMS THROUGH DAYBREAK. OTHERWISE... EVEN AWAY FROM SHOWERS/STORMS... INT/GSO/RDU HAS A GOOD CHANCE OF SEEING IFR-LIFR CIGS/VSBYS 08Z-13Z... AS THEY`VE SEEN THE MOST PRECIP IN THE LAST 24 HRS RESULTING IN A WET GROUND... SUSCEPTIBLE TO FOG/STRATUS GIVEN THE LIGHT SURFACE WINDS. RWI/FAY ARE EXPECTED TO SEE A SHORTER PERIOD OF MVFR-IFR CONDITIONS IN THE 08Z-13Z TIME FRAME. THESE CIGS ARE EXPECTED TO LIFT SLOWLY AFTER DAYBREAK BUT STAY MVFR UNTIL AROUND NOON... WHEN VFR CONDITIONS SHOULD RETURN WITH CIGS BASED AT 10 000 TO 15 000 FT AGL... ALTHOUGH LINGERING MVFR CIGS REMAIN POSSIBLE THROUGH THE AFTERNOON. MORE SUB-VFR SHOWERS AND STORMS ARE LIKELY TO DEVELOP AND DRIFT TO THE N OR NW TODAY THROUGH TONIGHT... AND IT APPEARS ALL CENTRAL NC AIRFIELDS HAVE AN EQUAL CHANCE OF SEEING SUCH STORMS LATER TODAY INTO TONIGHT. LOOKING BEYOND 06Z TONIGHT... GOOD CHANCE OF IFR CIGS REDEVELOPING BY LATE EVENING OR SOON AFTER MIDNIGHT TONIGHT... LASTING THROUGH THE NIGHT... AT ALL TAF SITES... ACCOMPANIED BY MVFR FOG. THESE SHOULD LIFT TO VFR BY LATE TUE MORNING. PATCHY SHOWERS AND ISOLATED STORMS WILL REMAIN A GOOD BET THROUGH TONIGHT... WITH A LOW LEVEL FLOW FROM THE EAST OR SE. SUB-VFR CONDITIONS SHOULD RETURN ONCE AGAIN TUE NIGHT-WED MORNING AS THE MOIST UNSETTLED PATTERN HOLDS. SCATTERED TO NUMEROUS SHOWERS AND STORMS ARE EXPECTED EACH DAY... MAINLY AFTERNOON THROUGH EVENING... WITH CHANCES IMPROVING EACH DAY THROUGH FRI. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...32 SHORT TERM...WSS LONG TERM...NP AVIATION...HARTFIELD

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