Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 190707 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 305 AM EDT SAT APR 19 2014 .SYNOPSIS...LOW PRESSURE OVER THE NORTHEASTERN GULF OF MEXICO THIS MORNING WILL DRIFT VERY SLOWLY ALONG THE SOUTHEAST US COAST THROUGH THE WEEKEND. && .NEAR TERM /THROUGH SUNDAY NIGHT/...
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AS OF 305 AM SATURDAY... FOR TODAY/TONIGHT: THE MOST DREARY WEATHER OF THE WEEKEND WILL OCCUR IN THE NEXT 12-18 HOURS... WITH CERTAIN RAIN FOR ALL. THE LATEST SURFACE AND UPPER AIR ANALYSES SHOW THE RESPECTIVE LOW CENTERS OVER NE FL AND SRN AL... SHIFTING VERY SLOWLY EASTWARD. THE SURFACE HIGH TO OUR NNE OVER DELMARVA-NJ THAT IS SUPPLYING THE CHILLY NE FLOW IS POISED TO BE SUPPLANTED BY A LARGER AND COLDER HIGH NOW CENTERED OVER ONTARIO... WHICH WILL BE USHERED INTO OUR REGION THANKS TO A WEAK NRN STREAM FRONT EXTENDING FROM UPSTATE NY THROUGH THE OH VALLEY AND PUSHING TO THE ESE... ATTENDING A SWIFT-MOVING MID LEVEL TROUGH. IDEALLY JUXTAPOSED UPPER JET CORES ON THE EAST SIDE OF THIS TROUGH (RIGHT REAR QUAD OVER NC) AND ON THE EAST SIDE OF THE VORTEX OVER AL (LEFT FRONT QUAD OVER NC) HAVE STRENGTHENED THE UPPER DIVERGENCE OVER NC... SUPPORTING A BROAD SWATH OF MOSTLY LIGHT-MDT RAIN OVER NC. WITH ABUNDANT MID LEVEL MOISTURE IN PLACE AND THIS UPPER LEVEL FORCING FOR ASCENT COMBINED WITH MID LEVEL DEFORMATION AND MASS CONVERGENCE AROUND 850 MB SHOULD CONTINUE TO GENERATE WIDESPREAD RAIN THROUGH THIS MORNING. LARGE SCALE MODELS DEPICT THE BEST LIFT IN A BAND ACROSS THE SW PORTION OF CENTRAL NC... WHERE THE UPPER DIVERGENCE AND LOW LEVEL CONVERGENCE WILL BE WELL CORRELATED IN THE VERTICAL... AND THIS IS INDICATED AS WELL BY SREF PROBABILITIES AND THE LATEST HRRR RUNS. THIS AREA COULD SEE UP TO AN ADDITIONAL 1.0-1.5 INCHES OF RAIN... MOST FALLING THIS MORNING. LATEST OBSERVED RAINFALL SO FAR RANGES FROM JUST A FEW HUNDREDTHS NEAR THE VA BORDER TO JUST UNDER AN INCH IN THE FAR SOUTH (SCOTLAND TO SAMPSON CO)... WITH AREAS FROM THE TRIANGLE ACROSS THE SOUTHWEST CWA SEEING AROUND 0.30-0.40 INCH SO FAR. WHILE THE FLASH FLOOD GUIDANCE IS LOWEST IN THIS SW QUADRANT OF THE FORECAST AREA (AROUND 1.75" IN 1 HR)... THE ADDITIONAL RAINFALL IS EXPECTED TO BE LIGHT ENOUGH SUCH THAT THIS RATE WON`T BE ACHIEVED. BUT A GRAND TOTAL OF 2 INCHES OR MORE OF RAIN IN THIS AREA COULD LEAD TO SOME STREET FLOODING ESPECIALLY IN THOSE VULNERABLE AREAS NEAR CREEKS AND IN TOWNS. THEN BY THIS AFTERNOON... THE AFOREMENTIONED WEAK NRN STREAM FRONT WILL HAVE ALLOWED THE CHILLIER HIGH TO BUILD SOUTHWARD INTO NC AS IT CROSSES SRN QUEBEC AND THE ST LAWRENCE VALLEY THROUGH TONIGHT... HELPING TO DRY OUT THE LOW LEVELS OVER NC FROM THE NORTH. ALSO LATER TODAY THE UPPER LEVELS WILL GRADUALLY DRY OUT AS THE DRY SLOT ALOFT PUNCHES IN FROM THE SOUTH... AND THIS DRYING ABOVE 0C SHOULD LEAD TO A SLOW TREND TO MOSTLY LIGHT PATCHY DRIZZLE... WITH THE TRANSITION LAST TO OCCUR OVER THE NW PIEDMONT WHERE THE DEFORMATION BAND WILL MOST LONG-LIVED. SO... IN TERMS OF SENSIBLE WEATHER... WILL START THE DAY WITH 100% POPS... GRADUALLY TRENDING DOWN TO GOOD CHANCES OF RAIN OR DRIZZLE DURING THE LATE AFTERNOON AS THE CHANCES FOR MEASURABLE PRECIP DROP. MODELS DISAGREE ON EXACTLY WHERE AND HOW MUCH PRECIP THERE MIGHT BE TONIGHT... BUT BASED ON THE LARGE SCALE PATTERN... WILL KEEP A LOW CHANCE OF LIGHT RAIN LATE TONIGHT OVER THE SOUTHEAST... WHERE ONSHORE-DIRECTED FLOW WILL LAST THE LONGEST. TEMPS ARE CHALLENGING TO SAY THE LEAST... WITH SOME STATISTICAL GUIDANCE APPEARING OVERLY OPTIMISTIC GIVEN THE WIDESPREAD CLOUDS AND RAIN FOR MUCH OF THE DAY. HAVE FOLLOWED HIGH- RES AND RAPID-UPDATE GUIDANCE INCLUDING THE LOCAL WRF / HRRR / RAP / GRIDDED LAMP FOR TEMPS TODAY... GIVING HIGHS FROM THE MID 50S IN THE SOUTH TO UPPER 50S IN THE FAR NORTHWEST. EXPECT CLOUDS TO LINGER THROUGH TONIGHT... BUT WITH RAIN/DRIZZLE DWINDLING ESPECIALLY FROM NW TO SE. LOWS 45-50. FOR SUN/SUN NIGHT: THE MID LEVEL LOW IS EXPECTED TO SHIFT SLOWLY OFF SAVANNAH EARLY SUN THEN SLOWLY FILL AS IT HEADS ESE THROUGH SUN NIGHT. MODELS INDICATE ABUNDANT MOISTURE HANGING ON IN THE 850-700 MB LAYER OVER NC SUNDAY... WITH A PERSISTENT COOL AND BRISK NORTHEAST LOW LEVEL FLOW FEEDING IN FROM THE CHILLY BUT PROGRESSIVE AND MODIFYING SURFACE HIGH TO OUR NE. LOW LEVEL THICKNESSES ARE EXPECTED TO BE AROUND 15-20 M BELOW NORMAL... INDICATING HIGHS NEARLY 2 CATEGORIES BELOW NORMAL. EXPECT HIGHS OF 64-68... WITH PARTIAL SUNSHINE LATE IN THE DAY AS MID LEVEL RIDGING STARTS TO BUILD IN FROM THE WEST. CLEARING SKIES SUN NIGHT... ALTHOUGH THERE MAY BE ENOUGH RESIDUAL MOISTURE IN THE NORTHEAST CWA WITH A CONTINUED ATLANTIC FETCH TO BRING ABOUT PATCHY LOW STRATUS DEVELOPMENT OVERNIGHT. LOWS 40-47. -GIH
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 255 AM SATURDAY... THE SLOW MOVING CUT OFF LOW IMPACTING THE REGION THIS WEEKEND IS FORECAST TO BE EAST OF THE CAROLINAS SUNDAY NIGHT...WITH AN ELONGATED SURFACE RIDGE EXTENDING FROM THE MID-ATLANTIC STATES INTO THE NC. AS THE LOW MOVES OFF TO THE NORTHEAST...WINDS SHOULD BACK AROUND TO MORE NORTHERLY THAN NORTHEASTERLY AND ALLOW SOME DRIER AIR TO WORK INTO CENTRAL NC FROM THE NORTH. THE NAM ISNT QUITE AS DRY AS THE GFS AND ECMWF...SHOWING SOME MOISTURE LINGERING AROUND 850MB EAST OF I-95. WHILE THE AIRMASS WONT BEGIN TO MODERATE SIGNIFICANTLY UNTIL TUESDAY...STRONGER HEATING SHOULD SUPPORT HIGHS REACHING THEIR POTENTIAL OF UPPER 60S AND LOWER 70S. A PROGRESSIVE TROUGH MOVING THROUGH THE CENTRAL US WILL APPROACH THE REGION MONDAY NIGHT AND EARLY TUESDAY...WITH THE ASSOCIATED FRONTAL ZONE PROJECTED TO CROSS CENTRAL NC TUESDAY AFTERNOON AND EVENING. AHEAD OF THE SYSTEM...LOWS WILL BE MUCH MORE MILD MONDAY NIGHT WITH INCREASING MID/HIGH CLOUDS AND A WEAK RETURN FLOW ACROSS THE WESTERN PIEDMONT. LOWS IN THE LOWER 50S WEST AND UPPER 40S EAST. SOUTH TO SOUTHWESTERLY FLOW WILL INCREASE ON TUESDAY AHEAD OF THE APPROACHING FRONT. MODELS CURRENTLY FORECAST A DEWPOINT RECOVERY INTO THE MID AND UPPER 50S...WHICH COMBINED WITH HIGHS IN THE UPPER 70S TO AROUND 80 AND WEAK MID-LEVEL LAPSE RATES WOULD SUGGEST WEAK INSTABILITY...MAINLY ACROSS THE WEST. MODEST SHEAR MAY SUPPORT A FEW STRONG STORMS...BUT WITHOUT BETTER UPPER SUPPORT THE THREAT OF SEVERE WEATHER LOOKS ISOLATED AT THIS POINT. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 255 AM SATURDAY... BEHIND TUESDAYS SYSTEM...CANADIAN HIGH PRESSURE WILL BUILD ACROSS MUCH OF THE EASTERN US ON WEDNESDAY AND THURSDAY. THURSDAY LOOKS TO BE THE COOLEST DAY AS THICKNESSES FALL BACK BELOW NORMAL...WITH HIGHS MAYBE 5-10 DEGREES BELOW NORMAL...BUT THEN QUICKLY REBOUND ON FRIDAY AS ANOTHER PROGRESSIVE UPPER TROUGH APPROACHES FROM THE WEST. THIS NEXT SYSTEM RESEMBLES THE EARLY WEAK SYSTEM...THOUGH POTENTIALLY WITH A LITTLE MORE MOISTURE AVAILABLE FROM THE GULF. THE CURRENT FORECAST WILL REMAIN DRY...WITH THE BETTER CHANCE OF PRECIP JUST BEYOND THE END OF THE FORECAST ON FRIDAY NIGHT AND SATURDAY. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 145 AM SATURDAY... AN EXPANSIVE STORM SYSTEM CENTERED ON THE FL GULF COAST WILL AFFECT THE SOUTHEAST STATES AND CAROLINAS THROUGHOUT TODAY AND TONIGHT. CURRENTLY... DESPITE FAIRLY WIDESPREAD LIGHT RAIN... WITH THE EXCEPTION OF FAY... VFR CONDITIONS DOMINATE WITH MOST VSBYS AOA 6SM AND CIGS AOA 4 000 FT... WHILE FAY HAS SEEN A BAND OF HEAVIER RAIN BRINGING IN IFR CIGS AND MVFR VSBYS. THESE IFR CIGS ARE LIKELY TO CONTINUE TO ADVECT INTO FAY THROUGH 12Z... AND MAY CREEP INTO THE VICINITY OF RWI. AT INT/GSO/RDU... VFR CIGS AND VSBYS ARE EXPECTED TO PREVAIL THROUGH 12Z... ALTHOUGH VSBYS MAY BRIEFLY DROP TO MVFR IN ANY HEAVIER RAIN BANDS. AFTER 12Z... RDU/RWI SHOULD FALL TO MAINLY MVFR... LASTING UNTIL AROUND 19-21Z... WITH BRIEF IFR CIGS POSSIBLE BETWEEN 12Z AND 16Z. INT/GSO SHOULD REMAIN VFR... ALTHOUGH A BRIEF DROP TO MVFR 12Z-16Z THIS MORNING IS POSSIBLE. FAY IS LIKELY TO EXPERIENCE THE WORST AVIATION CONDITIONS WITH IFR CONDITIONS HOLDING THROUGH 06Z TONIGHT. AT INT/GSO/RWI/RDU... CIGS ARE EXPECTED TO IMPROVE TO VFR AFTER 21Z AS DRIER LOW LEVEL AIR NOSES IN FROM HIGH PRESSURE TO THE NORTH... WITH JUST PATCHY DRIZZLE AT MOST FROM 21Z THROUGH THE END OF THE TAF VALID PERIOD (06Z SUN). LOOKING BEYOND 06Z SUN... EXPECT IMPROVEMENT TO MVFR AT FAY 06Z-09Z THEN TO VFR BY 12Z... AND MAINLY VFR CIGS AT ALL OTHER SITES THROUGH SUNDAY. EXPECT VFR CONDITIONS TO DOMINATE THROUGH MON NIGHT. PASSAGE OF A MID LEVEL TROUGH AND SURFACE COLD FRONT FROM THE NW WILL BRING A RISK OF SUB-VFR CONDITIONS TUE/TUE NIGHT. VFR CONDITIONS RETURN FOR WED. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...SMITH NEAR TERM...HARTFIELD SHORT TERM...SMITH LONG TERM...SMITH AVIATION...HARTFIELD

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