Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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543 FXUS62 KRAH 070831 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 329 AM EST SUN FEB 7 2016 .SYNOPSIS...A STRONG COASTAL LOW WILL DEVELOP OFF THE SOUTH CAROLINA COAST TODAY AND MOVE AWAY TONIGHT AND MONDAY. AN UPPER LEVEL DISTURBANCE AND COLD FRONT WILL APPROACH THE REGION LATE MONDAY. && .NEAR TERM /THROUGH TODAY/...
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AS OF 329 AM SUNDAY... THE MAIN PROBLEM OF THE DAY ARE HOW FAR NORTH AND WEST THE MAIN PRECIPITATION SHIELD WILL REACH INTO THE AIR THAT IS COLD ENOUGH FOR A WINTRY MIXTURE OF SNOW AND SLEET. THE LATEST SATELLITE AND RADAR DATA INDICATED AN EXPANDING SHIELD OF PRECIPITATION EXTENDING AS FAR NW AS ROCKINGHAM... RAEFORD... CLAYTON AND WILSON. THE PRECIPITATION BEGAN AS A MIXTURE OF SLEET AND RAIN IN MANY AREAS OF THE SANDHILLS BUT QUICKLY BECAME RAIN. AMOUNTS HAVE BEEN LESS THAN A TENTH OF AN INCH OF RAIN THUS FAR. SURFACE WET BULBS HAVE COME UP TO ABOVE 32 FOR ALL AREAS SOUTH AND EAST OF WADESBORO TO SOUTHERN PINES TO CLAYTON... AND THIS IS WHERE MOST OF THE PRECIPITATION IS EXPECTED TODAY. HOWEVER... THE OPERATIONAL EUROPEAN MODEL WHICH HAD BEEN DRY FOR AREAS AROUND SANFORD AND RALEIGH NOW HAS TURNED WETTER WITH A QPF AROUND 0.25 TO 0.3 OF AN INCH AT RALEIGH... WITH AMOUNTS OF BETTER THAN 0.50 IN THE SE ZONES. IF THE OPERATIONAL EC (WHICH IS CONSIDERED NOW TO THE THE NW OUTLIER FOR SIGNIFICANT QPF) WERE TO VERIFY... THE TRIANGLE AREA WOULD SEE MORE IN THE WAY OF LIGHT SNOW MIXED WITH SLEET WITH SOME ACCUMULATION. THE PARTIAL THICKNESS FORECASTS ARE SOLIDLY IN THE MEASURABLE SNOW WITH SLEET CATEGORY FOR RALEIGH BETWEEN 13Z-18Z (THE EXPECTED WINDOW OF OPPORTUNITY) FOR THE BEST CHANCE OF PRECIPITATION TO GET THIS FAR NW. THIS SCENARIO IS NOT FAVORED BY THE MAJORITY OF THE OPERATIONAL MODELS AND ENSEMBLES INCLUDING THE HI-RES MODELS (WHICH KEEPS THE PRECIPITATION JUST SE OF THE RALEIGH AREA). RADAR TRENDS ARE HARD TO IGNORE WHICH DEPICT THE EDGE OF THE MAIN SHIELD OF PRECIPITATION ALREADY TO NEAR SOUTHERN PINES AND CLINTON AND IT MAY BE ABLE TO EXTEND NW ANOTHER ROW OF COUNTIES PER THE LATEST EUROPEAN MODEL. THIS SUGGESTS THAT THIS WILL BE A CLOSE CALL FOR WAKE... LEE... CHATHAM... AND FRANKLIN COUNTIES FOR SOME LIGHT ACCUMULATING SNOW/SLEET LATER THIS MORNING. THE SITUATION IS SO CLOSE THAT IT WILL HAVE TO BE NOWCAST BY WATCHING HOURLY TRENDS ON RADAR AND SATELLITE. THE PRECIPITATION SHOULD BEGIN TO PULL EASTWARD BY AROUND EARLY AFTERNOON... CLOSING THE OPPORTUNITY FOR THIS REGION. IN GENERAL... LOW PRESSURE FORMING OFF THE SOUTHEAST COAST WILL INTENSIFY LATER TODAY AND TONIGHT REACHING NEAR 980 MB BY MONDAY MORNING. THE UPSTREAM MID/UPPER TROUGH WILL BE STRENGTHENING AS IT MOVES ACROSS THE REGION WITH STRONG HEIGHT FALLS TODAY. ONE GOOD BIT OF NEWS IS THAT THE BAROCLINIC ZONE HAD DEVELOPED JUST OFFSHORE WITH THE MAIN DEVELOPMENT OF HEAVY QPF EXPECTED IN THE GULF STREAM. EVEN SO... THE HEIGHT FALLS INLAND WILL LEAD TO AN EXPANSION OF PRECIPITATION OVER NORTHERN SC AND SOUTHERN AND EASTERN NORTH CAROLINA THIS MORNING. RAIN IS EXPECTED TO DOMINATE THE SE ZONES... WITH RAIN MIXED WITH A LITTLE SLEET/SNOW TO THE NW. PARTIAL THICKNESSES AND SURFACE WET BULB FORECASTS WERE USED EXTENSIVELY FOR P-TYPE. YET QPF IS AGAIN THE MAIN PROBLEM... THE MODEL SPREAD CONTINUED TO BE A BIT TOO LARGE FOR OUR LIKING ESPECIALLY THIS LATE IN THE GAME... AND WITH THE RALEIGH AREA IN THE ZONE OF MOST UNCERTAINTY FOR GETTING SIGNIFICANT PRECIPITATION. TO THE NORTH AND WEST OF RALEIGH... POP WILL ESSENTIALLY BE LESS THAN 20 PERCENT WITH ONLY A FLURRY OR SLEET PELLET EXPECTED. TO THE SOUTH AND EAST OF RALEIGH... A COLD RAIN IS EXPECTED. THIS RAIN SHOULD BE MIXED WITH A BIT OF SLEET AND SNOW ON THE NORTHWEST SIDE. THIS ZONE SHOULD BE CONFINED TO AREAS ALONG A LINE EXTENDING FROM ROCKINGHAM TO CLAYTON TO WILSON. THIS REGION SHOULD SEE ONLY A TRACE OF LIGHT SLEET/SNOW WITH THE RAIN. AREAS TO THE SOUTH AND EAST FROM LAURINBURG TO FAYETTEVILLE TO GOLDSBORO AND TARBORO SHOULD SEE RAIN WITH TEMPERATURES IN THE MID 30S TO NEAR 40. THE SANFORD... RALEIGH AND LOUISBURG AREAS REMAIN IN THE REGION OF MOST CONCERN. IF THE PRECIPITATION CAN REACH THIS FAR NW... IT WOULD MOST LIKELY BE IN THE FORM OF LIGHT SNOW/SLEET WITH THE POTENTIAL FOR LIGHT ACCUMULATIONS. HOWEVER... WET BULB TEMPERATURES SHOULD BE AROUND 32 THIS AFTERNOON... WHICH WOULD SUGGEST THAT ANY ACCUMULATION WOULD BE SLUSHY OR MELT ON AREA ROADS. FOR NOW... WE WILL CARRY A 40-50 PERCENT CHANCE AS FAR NW AS THE RALEIGH AND SANFORD AREAS... WITH HIGHS IN THE UPPER 30S. VERY LITTLE IF ANY IMPACTS ARE CURRENTLY EXPECTED.
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&& .SHORT TERM /TONIGHT AND MONDAY/... AS OF 321 AM SUNDAY... REGARDLESS OF HOW CLOSE TO THE COAST A COASTAL LOW WOBBLES AS IT BOMBS OFF THE SOUTHEAST US COAST DURING THE NEXT 24-36 HOURS...THE RESULTANT DEEP CYCLONE IS FORECAST TO ACCELERATE NORTHEASTWARD AND AWAY FROM THE NC COAST TONIGHT...IN RESPONSE TO A "KICKER" VORTEX AND ACCOMPANYING ELONGATED SHORTWAVE TROUGHS IN SHORT WAVELENGTH FLOW ALOFT...FORECAST TO PIVOT FROM THE UPPER MIDWEST TO THE TN AND LOWER MS VALLEYS THROUGH EARLY MON. CLEARING SKIES ARE EXPECTED TONIGHT WITH LOWS IN THE UPPER 20S TO LOWER 30S. AN AREA OF BROAD BUT STRONG 100-150 METER HEIGHT FALLS AND COOLING/FGEN ALOFT...AND ASSOCIATED FORCING FOR ASCENT AND POCKET OF STEEP (7.5 C/KM) 850-500 MB LAPSE RATES...WILL SUPPORT THE EASTWARD MAINTENANCE OF A BAND OF SHOWERS INTO CENTRAL NC DURING THE AFTERNOON AND EVENING. A "WARMING" DEEP LAYER SOUTHWEST FLOW...INCLUDING A SSW SURFACE BREEZE AND TEMPERATURES MONDAY AFTERNOON IN THE 40S TO MIDDLE 50S...WILL ENSURE THIS ACTIVITY WILL FALL AS RAIN. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 245 PM SATURDAY... NORTHWEST FLOW...IN A HIGHLY AMPLIFIED PATTERN CHARACTERIZED BY WESTERN NOAM RIDGING AND A MEAN TROUGH OVER EASTERN NOAM...WILL MAINTAIN A GENERALLY DRY PERIOD EAST OF THE NC BLUE RIDGE...BUT WITH A FEW OPPORTUNITIES FOR LIGHT...LEE-SIDE PRECIPITATION. WITHIN THE COLD...STEEP LAPSE RATE-BEARING...CYCLONIC FLOW ALOFT...PERIODS OF ENHANCED CLOUDINESS AND VIRGA WILL BE SUPPORTED BY A SERIES OF DISTURBANCES MIGRATING THROUGH THE BASE OF THE EAST COAST TROUGH. IF THOSE DISTURBANCES AND ENHANCED MOISTURE/LIFT ARE MAXIMIZED WITH (NEAR) PEAK DIURNAL HEATING...WITH THE RESULTANT DEVELOPMENT OF WEAK INSTABILITY (LESS THAN 100 J/KG)...THEN A FEW SNOW SHOWERS COULD RESULT...AMIDST AN AREA OF OTHERWISE SCATTERED FLURRIES/SPRINKLES; AND THIS SCENARIO APPEARS MOST LIKELY TUE AFTERNOON OVER THE NORTHERN PIEDMONT. THEN...AS A LEAD MID-UPPER VORTEX LIFTS AND FILLS...AND THE FLOW ALOFT BRIEFLY RELAXES/HEIGHTS RISE DOWNSTREAM OF A NEW VORTEX SETTLING OUT OF SOUTHERN CANADA...A BRIEF EPISODE OF LOW-MID LEVEL WAA AND ACCOMPANYING WEAK MSL PRESSURE FALLS/WAVE DEVELOPMENT ALONG THE FRONT MAY SUPPORT THE DEVELOPMENT OF AN AREA OF LIGHT PRECIPITATION OVER THE SOUTHEASTERN STATES/CAROLINAS FRI-SAT. HOWEVER...THERE IS CONSIDERABLE MODEL SPREAD DURING THIS TIME...AND TEMPERATURES WOULD BE ONLY MARGINALLY SUPPORTIVE FOR ANY WINTRY PRECIPITATION...IF IN THE LOW PROBABILITY EVENT THAT PRECIPITATION OCCURS AT ALL. IT WILL OTHERWISE BE A CHILLY WEEK...BUT NOT BRUTALLY SO...WITH TEMPERATURES AVERAGING ABOUT 5-10 DEGREES BELOW "NORMAL". PERHAPS THE MOST EXCITING WEATHER LURKS JUST BEYOND DAY 7...AS THE AFOREMENTIONED NEW VORTEX MIGRATES ACROSS THE GREAT LAKES AND CONSEQUENTLY SUPPRESSES THE NORTHERN STREAM/PROMOTES CONFLUENT FLOW ALOFT THAT WOULD SUPPORT THE SOUTHEASTWARD MAINTENANCE OF A 1040- 1045 MB HIGH FROM THE ARCTIC. WHILE THIS WOULD YIELD INITIALLY JUST COLD CONDITIONS FOR THE WEEKEND...AN INCREASINGLY ACTIVE SOUTHERN STREAM WOULD RAISE THE PROBABILITY OF STREAM INTERACTION...AND STORMINESS AND APPALACHIAN COLD AIR DAMMING...EARLY TO MID NEXT WEEK. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 323 AM SUNDAY... THROUGH THE 24 HOUR TAF PERIOD: CIGS WILL QUICKLY LOWER SOUTH OF A KAFP-KRDU-KHNZ LINE AS LOW PRESSURE TAKES SHAPE OFF THE SE COAST. WHILE CONFIDENCE HAS INCREASED IN IN TERMS OF PRECIP TYPE...WE STILL HAVE CHALLENGES OF HOW FAR NW THE PRECIPITATION WILL REACH. IF THE PRECIPITATION REACHES THE KRDU AREA... IT WOULD BE PREDOMINATELY LIGHT SNOW/SLEET BETWEEN 13Z-18Z OR SO... WITH A MIXTURE OF SLEET AND RAIN AT KRWI. KFAY SHOULD EXPERIENCE RAIN TODAY. THE PRECIP WILL STAY TO THE SE OF THE KGSO AREA. CIGS AND VSBYS TO FALL TO IFR TO MVFR AT KFAY WITH MAINLY MVFR CIGS AT KRDU AND KRWI. THE WINDS WILL ALSO INCREASE AS THE LOW DEVELOPS OFFSHORE TODAY... TO 10-20KT FROM THE NORTH. GUSTS TO 25KT IN THE KFAY AREA EXPECTED INTO TONIGHT. CLEARING TO VFR TONIGHT AT ALL TAF LOCATIONS AS THE LOW PULLS AWAY. OUTLOOK...A COUPLE OF UPPER LEVEL DISTURBANCES WILL BRING ADDITIONAL CHANCES OF LIGHT SHOWERS AND BRIEF SUB-VFR CONDITIONS....ALONG WITH GUSTY WINDS...LATE MONDAY... AND AGAIN MAINLY AT NORTHERN TAF SITES LATE TUESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BADGETT NEAR TERM...BADGETT SHORT TERM...BADGETT/SMITH LONG TERM...2 AVIATION...BADGETT/2

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