Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS62 KRAH 211910 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 305 PM 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 1100 AM MONDAY... UPDATE...UPPER LOW CUTTING OFF OVER ALABAMA WILL SEND PERTURBATIONS NORTHEAST ACROSS THE AREA...CONCURRENT WITH WESTWARD ADVECTION OF VERY MOIST AIR OFF THE ATLANTIC DUE TO LOW LEVEL SOUTHEAST FLOW. WE WILL SEE COVERAGE INCREASE...SLOW MOVING CONVECTION ALONG A FRONTAL BOUNDARY ACROSS THE SOUTHERN TIER OF THE AREA INTO EARLY AFTERNOON. VERY HEAVY RAINFALL RATES OF 1 TO 2 INCHES PER HOUR WILL BECOME PROBLEMATIC FOR FLOODING IN AREAS WHERE THE STORMS MERGE OR TRAIN. PREVIOUS DISCUSSION...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 /WEDNESDAY THROUGH FRIDAY NIGHT/... AS OF 305 PM MONDAY... AN UPPER LEVEL TROUGH WILL DIVE FROM THE WESTERN GREAT LAKES REGION WEDNESDAY INTO THE SOUTHERN APPALACHIANS BY THURSDAY MORNING. THE ASSOCIATED COLD FRONT WILL STAY WEST OF THE APPALACHIANS THROUGH WEDNESDAY EVENING. THE AIR MASS ACROSS CENTRAL NC ON WEDNESDAY AFTERNOON WILL BE WARM AND UNSTABLE WITH WEAK TO MODERATE INSTABILITY VALUES OF AROUND 1000-2000 J/KG. THE AIR MASS WILL BE MOIST WITH PRECIPITABLE WATER VALUES OF 1.75 TO 2.0 INCHES. CONVECTIVE COVERAGE IS NOT EXPECTED TO BE OVERWHELMING AND LIKELY MOST FOCUSED ACROSS THE COASTAL PLAIN...EAST OF THE PIEDMONT TROUGH AND TO THE WEST ACROSS THE HIGHER TERRAIN. HIGH TEMPERATURES IN THE 88 TO 92 RANGE ARE SUPPORTED BY CONSENSUS THICKNESS VALUES AND IN BETWEEN THE WARMER MAV AND COOLER MET GUIDANCE. SCATTERED CONVECTION IS APT TO CONTINUE IN THE EARLY EVENING HOURS AND THEN BECOME ISOLATED OVERNIGHT...AGAIN THE BEST COVERAGE IS EXPECTED ACROSS THE COASTAL PLAIN AND PERHAPS MORE SO IN THE WESTERN PIEDMONT CLOSER TO THE UPPER TROUGH AND AS CONVECTION INITIATED NEAR THE MOUNTAINS MOVES EAST. OVERNIGHT LOWS SHOULD BE MODERATED BY CLOUD COVER AND SOME MIXING AHEAD OF THE APPROACHING WITH LOWS IN THE LOWER 70S. THE UPPER TROUGH REACHES THE SOUTHERN APPALACHIANS ON THURSDAY MORNING AS THE COLD FRONT SLOWLY MOVES FROM THE FOOTHILLS INTO THE PIEDMONT DURING THE MORNING AND AFTERNOON. THE AIR MASS ACROSS CENTRAL NC IS POSSIBLY EVEN MORE MOIST THAN ON WEDNESDAY WITH PRECIPITABLE WATER VALUES AROUND OR IN EXCESS OF 2 INCHES. EXPECT A GOOD AMOUNT OF CLOUD COVER WHICH MAY LIMIT INSTABILITY A BIT. THE APPROACHING TROUGH WILL RESULT IN STRONGER FLOW ALOFT AND BULK SHEAR VALUES WILL INCREASE INTO THE 20-30 KTS RANGE AND SUPPORT MORE CONVECTIVE STORM ORGANIZATION AND A SLIGHTLY ELEVATED SEVERE THREAT. POPS HAVE BEEN INCREASED TO THE HIGH CHANCE CATEGORY. MAX TEMP GUIDANCE IS EVEN WARMER COMPARED TO WEDNESDAY WITH THE WARMER MAV GUIDANCE SUGGESTING S HIGHS IN THE 94-95 RANGE AT RDU AND FAY. NOT READY TO GO THAT HIGH BUT WE HAVE INCREASED MAX TEMPS A BIT AND IF CLOUDS COVER IS LESS THAN EXPECTED...WARMER TEMPERATURES AND INCREASED INSTABILITY CAN BE EXPECTED. THE THUNDERSTORM THREAT CONTINUES INTO THURSDAY EVENING WITH THE BEST COVERAGE IN THE EAST. HIGHS THURSDAY SHOULD RANGE IN THE 88 TO 93 RANGE WITH LOWS IN THE UPPER 60S TO LOWER 70S. THE FRONT SLOWLY CLEARS CENTRAL NC FRIDAY AFTERNOON AND THEN STALLS ALONG THE NC COAST AND EXTENDS BACK INTO CENTRAL SC BY LATE FRIDAY NIGHT. A CONTINUED THREAT OF SHOWERS AND THUNDERSTORMS PERSISTS ON FRIDAY WITH THE GREATEST CHANCES ACROSS THE COASTAL PLAIN. HIGHS WILL BE NOTICEABLY COOLER THAN ON THURSDAY WITH FRIDAY MAXES IN THE MID TO UPPER 80S. LOWS WILL RANGE IN THE MID 60S TO THE NORTHWEST AND UPPER 60S TO THE SOUTHEAST. -BLAES && .LONG TERM /SATURDAY THROUGH SUNDAY/... AS OF 230 AM MONDAY... 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 /18Z MONDAY THROUGH SATURDAY/... AS OF 143 PM MONDAY... LOTS OF UNCERTAINTY AS TO SHORT TERM DETAILS AS WIDESPREAD LIGHT RAIN... WITH SCATTERED HEAVIER SHOWERS AND THUNDERSTORMS...IS EXPECTED IN THE MOIST AND QUITE UNSTABLE ENVIRONMENT OVER CENTRAL NORTH CAROLINA. CEILINGS AND VISIBILITY WILL BE LARGELY VFR WITH MVFR TO IFR CONDITIONS IN RAIN AND SCATTERED CONVECTION. THE PRECIPITATION WILL DIMINISH IN THE EVENING...AFTER 02Z...BUT CONDITIONS WILL GRADUALLY DETERIORATE AS WE COOL OVERNIGHT. MVFR VISIBILITY AND IFR TO LIFR CEILINGS WILL BE WIDESPREAD IN THE USUAL 08-13Z TIME FRAME...POTENTIALLY LINGERING INTO THE MID MORNING BEFORE LIFTING TO VFR VISIBILITY AND MVFR-VFR CEILINGS BY THE END OF THE TAF PERIOD. IN THE LONGER RANGE...WE REMAIN IN THE UNSETTLED PATTERN THROUGH FRIDAY. SCATTERED MAINLY LATE DAY CONVECTION IS EXPECTED AGAIN TUESDAY AND WEDNESDAY...THEN A BETTER CHANCE OF WIDESPREAD CONVECTION IS EXPECTED THURSDAY AND THURSDAY NIGHT AS A COLD FRONT MOVES SOUTHEAST THROUGH THE AREA. VFR CONDITIONS ARE EXPECTED FRIDAY AND SATURDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...MLM/HARTFIELD SHORT TERM...BLAES LONG TERM...KCP AVIATION...MLM

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.