Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210642 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 240 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 235 AM MONDAY... TODAY THROUGH TONIGHT: A DAMP AND VOLATILE ATMOSPHERE WILL HOLD OVER CENTRAL NC AT LEAST THROUGH TONIGHT. THE LATEST SURFACE ANALYSIS SHOWS A FRONTAL ZONE STRETCHING ACROSS THE GULF COAST THROUGH CENTRAL GA/SC AND ACROSS SE NC... ASSOCIATED WITH A MID LEVEL TROUGH OVER THE INTERIOR SOUTHEAST STATES AND MIDSOUTH. THIS TROUGH ALOFT DEEPENS TO A BAGGY CLOSED LOW OVER SRN AL/GA BY TONIGHT... WITH A WEAK BUT DISTINCT SHEAR AXIS STRETCHING NE ACROSS NC. PW VALUES ARE ALREADY ON THE HIGH SIDE (120-140% OF NORMAL) AND ARE PROJECTED TO RISE FURTHER... SURPASSING 2 INCHES OVER NEARLY THE ENTIRE CWA AND PERHAPS 2.25 INCHES IN THE SE CWA... AS LOW LEVEL FLOW REMAINS FROM THE SSE AND DRAWS IN ATLANTIC MOISTURE WHILE PRONOUNCED MID LEVEL MOISTURE AND CONVECTIVE DEBRIS CLOUDS PERSIST WITHIN A WEAK STEERING REGIME. THE LATEST HIGH-RES AND CONVECTION-ALLOWING MODELS SUGGEST THAT THE PIEDMONT/WRN SANDHILLS WILL SEE THE GREATEST COVERAGE OF SHOWERS AND ISOLATED STORMS THROUGH EARLY AFTERNOON... WHICH WOULD THEN DRIFT EASTWARD INTO THE ERN SANDHILLS/COASTAL PLAIN DURING THE AFTERNOON AND EARLY EVENING... BEFORE DECREASING IN COVERAGE BY MIDNIGHT. THE GENERAL AGREEMENT ON THIS EVOLUTION BOOSTS FORECAST CONFIDENCE... AND WILL FOLLOW THIS TREND IN THE FORECAST WITH GOOD CHANCE POPS EAST AND LIKELY WEST EARLY... TRENDING DOWN IN THE WEST AND UP IN THE EAST THIS AFTERNOON. BUT GIVEN THAT THE FLOW IS SO WEAK WITH AN INCREASINGLY MOIST COLUMN AND SUBTLE MESOSCALE BOUNDARIES GENERATED BY OUTFLOWS AND DIFFERENTIAL HEATING... SHOWERS AND STORMS COULD POP UP ANYWHERE TODAY AND SIMPLY MEANDER. SLOW STORM MOTION AND A FAIRLY DEEP WARM LAYER (AROUND 3.5 KM) TO FOSTER WARM RAIN PROCESSES WILL BRING A RISK OF LOCALLY HEAVY RAINFALL TODAY... ALTHOUGH NOT OVER A LARGE ENOUGH AREA TO NECESSITATE A FLASH FLOOD WATCH AT THIS TIME. RAINFALL COULD BE EXACERBATED OVER THE FAR WRN PIEDMONT WHERE LOW LEVEL MOIST UPGLIDE ATOP THE RETREATING SHALLOW SURFACE RIDGE MAY ENHANCE LIFT. WILL TREND POPS DOWN TO LOWER CHANCE TONIGHT... LOWER IN THE NE AND BETTER IN THE SW WHERE MODELS SHOW SLIGHTLY BETTER MOISTURE TRANSPORT. CONSIDERABLE CLOUDINESS WILL CUT DOWN ON HEATING TODAY ESPECIALLY EAST AND SE... AND EXPECT HIGHS FROM THE LOW 80S NW TO MID 80S IN THE COASTAL PLAIN. LOWS 68-72... LARGELY FOLLOWING PERSISTENCE. -GIH && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/... AS OF 250 PM SUNDAY... 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. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 230 AM MONDAY... WEDNESDAY THROUGH FRIDAY: AN UPPER LEVEL TROUGH WILL APPROACH AND MOVE INTO CENTRAL NC DURING THIS PERIOD. EXPECT THE USUAL SUMMERTIME DIURNAL SHOWERS AND STORMS FOR WEDNESDAY AS A THE PIEDMONT TROUGH SETS UP OVER THE AREA AND SURFACE WINDS SHIFT TO SOUTHWESTERLY. THE INCREASING WARM MOIST SOUTHWEST FLOW WILL YIELD HIGHS AROUND 90 DEGREES AND LOWS IN THE LOW TO MID 70S. PWAT VALUES WILL BE BETWEEN 1.50 AND 2.00 INCHES...AND WITH CAPE AROUND 1500 J/KG AND RELATIVELY WEAK SHEAR...EXPECT THE MAIN STORM THREATS TO BE HEAVY RAIN AND STRONG GUSTY WINDS. THE UPPER LEVEL TROUGH WILL BE SLOW TO TRAVERSE THE CAROLINAS AT THE END OF THE WORK WEEK. THE 00Z GFS INDICATES AN INITIAL FRONT MOVING INTO CENTRAL NC THURSDAY NIGHT INTO FRIDAY MORNING...WITH WINDS VEERING TO NORTHWESTERLY...AND STALLING OVER THE AREA ON FRIDAY. A SECONDARY FRONT ASSOCIATED WITH THE MAIN PUSH OF COOLER AIR IS EXPECTED TO MOVE INTO THE REGION LATE FRIDAY/FRIDAY NIGHT...WITH HIGH PRESSURE OVER THE OH VALLEY. THE HIGHEST CHANCES FOR SHOWERS AND STORMS IN THE NORTHWEST AND LOWEST CHANCES IN THE SOUTHEAST ON THURSDAY...WITH THE REVERSE BEING THE CASE FOR FRIDAY. HIGHS THURSDAY WILL BE MAINLY IN THE LOW TO MID 90S...AND OVERNIGHT LOWS IN THE UPPER 60S TO LOW 70S. WITH THE NW WINDS ON FRIDAY... EXPECT HIGHS 3-5 DEGREES COOLER THAN THURSDAY...MID TO UPPER 80S... AND LOWS IN THE MID 60S TO AROUND 70 DEGREES. SATURDAY AND SUNDAY: THE AFOREMENTIONED HIGH OVER THE OH VALLEY WEAKENS AND THE BOUNDARY THAT LINGERED ACROSS THE AREA BECOMES WASHED OUT OVER THE WEEKEND. GIVEN THE LACK OF A DOMINATING SURFACE FEATURE AND THE GENERAL TROUGHINESS ALOFT...EXPECT A RETURN TO MORE SEASONAL CONDITIONS FOR THE WEEKEND...WITH CHANCES FOR AFT/EVE SHOWERS AND STORMS AND NEAR NORMAL TEMPERATURES...HIGHS IN THE UPPER 80S TO AROUND 90 DEGREES AND LOWS IN THE UPPER 60S TO LOW 70S. && .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...HARTFIELD SHORT TERM...WSS LONG TERM...KCP AVIATION...HARTFIELD

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