Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 180833 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 433 AM EDT SAT APR 18 2015 .SYNOPSIS...
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HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTH TONIGHT...THEN SHIFT OFFSHORE ON SUNDAY AS A WARM FRONT PROGRESSES INTO THE REGION FROM THE SOUTHWEST. A COLD FRONT WILL APPROACH THE MOUNTAINS FROM THE WEST ON MONDAY...THEN TRACK EASTWARD THROUGH THE CAROLINAS MONDAY NIGHT.
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&& .NEAR TERM /TODAY AND TONIGHT/...
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AS OF 400 AM SATURDAY... CONFIDENCE: BELOW AVERAGE CONFIDENCE IN FORECAST DETAILS DUE TO A SPLIT FLOW SYNOPTIC REGIME AND ENHANCED UNCERTAINTY WITH REGARD TO THE EVOLUTION OF UPSTREAM CONVECTION OVER THE NEXT 24 HRS. OVERVIEW: A DEEP UPPER LEVEL LOW CENTERED OVER COLORADO AT 06Z WILL TRACK SLOWLY EAST INTO THE CENTRAL/SOUTHERN PLAINS BY 12Z SUN... SLIGHTLY IN ADVANCE OF NORTHERN STREAM SHORTWAVE ENERGY DIGGING SOUTHEAST ACROSS WESTERN CANADA INTO THE UPPER MIDWEST. IN THE LOWER LEVELS...THE ILL-DEFINED MSLP/HEIGHT PATTERN IN PLACE TODAY WILL GIVE WAY TO A STRONGER GRADIENT /BETTER DEFINED PATTERN/ LATER TONIGHT AS A WEAK SFC LOW DEVELOPS UPSTREAM ACROSS THE LOWER/CENTRAL MS RIVER VALLEY AND HIGH PRESSURE EXTENDS SOUTHWARD THROUGH EASTERN CANADA INTO THE MID-ATLANTIC IN ASSOC/W SUBSIDENCE IN THE WAKE OF SHORTWAVE ENERGY MOVING OFFSHORE THE NEW ENGLAND COAST IN SPEEDY NW FLOW ALOFT. PRECIPITATION: DPVA ATTENDANT A DEAMPLIFYING SHORTWAVE PROGRESSING EAST INTO A MOIST AND MARGINALLY UNSTABLE (MLCAPE ~100 J/KG) AIRMASS IN PLACE ACROSS THE CAROLINAS HAS ALLOWED LIGHT SHOWER ACTIVITY TO PERSIST OVER THE SW PIEDMONT AND SANDHILLS EARLY THIS MORNING. EXPECT SHOWER ACTIVITY TO SHIFT EAST INTO THE SANDHILLS/SE COASTAL PLAIN BY ~12Z IN CONCERT WITH THE AFOREMENTIONED WAVE. SUBSIDENCE (ALBEIT WEAK) IN THE WAKE OF THE DEAMPLIFYING SHORTWAVE SHOULD ACT TO SUPPRESS ACTIVITY THE REMAINDER OF THE MORNING. A SHORTWAVE RIDGE WILL DEVELOP OVER THE REGION THIS AFTERNOON INTO TONIGHT... DOWNSTREAM OF THE UPPER LOW PROGRESSING INTO THE CENTRAL PLAINS. SHOWER ACTIVITY SHOULD RE-DEVELOP OVER SC AND EASTERN NC THIS AFTERNOON IN THE PRESENCE OF ABUNDANT MOISTURE/MARGINAL DIURNAL DESTABILIZATION AND WEAK DPVA ATTENDANT TRANSIENT SMALL AMPLITUDE WAVES ALOFT...TRACKING WESTWARD INTO CENTRAL NC LATER THIS AFTERNOON THROUGH THIS EVENING IN ASSOC/W THE DEVELOPMENT OF AN EASTERLY /ONSHORE/ LOW-LEVEL FLOW. GIVEN WEAK FORCING...WEAK MID-LEVEL LAPSE RATES AND ABUNDANT CLOUD COVER...EXPECT SCATTERED LOW-TOPPED SHOWERS AT BEST...WITH ACTIVITY SHIFTING WESTWARD AND DECREASING IN COVERAGE WITH NOCTURNAL STABILIZATION OVERNIGHT. TEMPS: HIGHS TODAY WILL BE TEMPERED BY CLOUD COVER AND AN INCREASINGLY ONSHORE /EASTERLY/ LOW-LEVEL FLOW...IN THE MID/UPPER 70S. LOWS TONIGHT IN THE 60S...PERHAPS UPPER 50S IN THE FAR NE COASTAL PLAIN IN CLOSER VICINITY TO THE SFC RIDGE AXIS EXTENDING INTO THE REGION FROM THE NORTH. -VINCENT
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&& .SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
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AS OF 400 AM SATURDAY... EXPECT AN EXCELLENT CHANCE FOR PRECIPITATION DURING THE DAY SUNDAY...ESP FROM THE TRIANGLE WEST AND SOUTH...AS THE SOMEWHAT DEAMPLIFIED UPPER LEVEL LOW TRACKS FROM THE CENTRAL PLAINS INTO THE CENTRAL MS RIVER VALLEY...THE SHORTWAVE RIDGE OVER THE REGION SHIFTS OFFSHORE THE CAROLINA/MID-ATLANTIC COAST...AND A WEAK WARM FRONT /LOW-LEVEL TROUGH/ TRACKS INTO THE REGION FROM THE SOUTHWEST. CONVECTIVE DETAILS FOR CENTRAL NC REMAIN DIFFICULT TO ASCERTAIN DUE TO BELOW NORMAL CONFIDENCE IN THE EVOLUTION OF UPSTREAM CONVECTION (AND ULTIMATE IMPACT ON DOWNSTREAM ENV) ACROSS THE DEEP SOUTH TONIGHT. FROM A PATTERN RECOGNITION STANDPOINT...DEEP CONVECTION AND SEVERE WEATHER APPEAR UNLIKELY GIVEN THAT THE BEST DPVA WILL REMAIN WELL UPSTREAM ACROSS THE OH VALLEY AND WESTERN TN VALLEY AND THAT DIURNAL DESTABILIZATION WILL BE SIGNIFICANTLY HAMPERED BY WEAK MID-LEVEL LAPSE RATES AND PERVASIVE CLOUD COVER. -VINCENT
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&& .LONG TERM /MONDAY THROUGH FRIDAY/... AS OF 245 AM SATURDAY... THE DEEP MOISTURE FLUX IS EXPECTED TO BE PUSHING EAST OF OUR REGION BY 12Z/MONDAY. THE TIMING OF THE BACK EDGE OF THE MAIN SHIELD OF WIDESPREAD RAIN IS STILL DIFFICULT TO PIN DOWN. USING THE ENSEMBLE APPROACH... IT APPEARS THAT THE SIGNIFICANT WEATHER SHOULD BEGIN TO CLEAR OUT BETWEEN 09Z-15Z OR SO FROM WEST TO EAST MONDAY MORNING. ONCE THE MID LEVELS DRY OUT MONDAY... THE SW FLOW IN THE WARM SECTOR SHOULD ALLOW FOR AT LEAST PARTIAL CLEARING DURING MONDAY AFTERNOON. THIS WOULD SET US UP FOR SCATTERED CONVECTIVE DEVELOPMENT PARTICULARLY ALONG THE PRE-FRONTAL TROUGH AND/OR COLD FRONT EXPECTED TO ARRIVE LATE IN THE DAY AND DURING THE EVENING. THE LATEST STATICAL MOS SUGGESTS HIGHS OF 75-80 IN THE NW RANGING TO POSSIBLY 85 IN THE SANDHILLS. THIS COMBINED WITH FORECAST DEW POINTS IN THE MID 50S NW TO LOWER 60S COASTAL PLAIN WOULD YIELD MUCAPE VALUES OF 1500+ J/KG WITH 2000 J/KG POSSIBLE IN THE COASTAL PLAIN AND EASTERN PIEDMONT. THE WINDS FROM THE SURFACE TO ALOFT WILL BECOME UNIDIRECTIONAL FROM THE SW SUGGESTING THAT THE MAIN SEVERE WEATHER MODE WOULD MOST LIKELY BE THE THREAT OF STRAIGHT LINE WIND GUSTS. AFTER THE LULL IN THE POP MONDAY MORNING... WE WILL RAISE POP MONDAY AFTERNOON AND EVENING INTO THE 40-50 PERCENT RANGE AND CONTINUE TO HIGHLIGHT THE POTENTIAL FOR A COUPLE OF STRONG TO SEVERE THUNDERSTORMS MONDAY AFTERNOON INTO THE EVENING. FOR MONDAY NIGHT THROUGH FRIDAY... THE PATTERN WILL CHANGE BACK TO ONE THAT IS MUCH DRIER AND COOLER WITH A PREDOMINATE NW FLOW ALOFT OVER NC. A DRY COLD FRONT IS FAVORED TO PUSH SOUTH THROUGH NC ON THURSDAY AFTERNOON OR NIGHT. THE TEMPERATURES SHOULD BE WARMEST WEDNESDAY AND THURSDAY OUT AHEAD OF THE FRONT (70S)... AND COOL BACK INTO THE 65-70 RANGE BY FRIDAY. LOWS SHOULD BE IN THE MID 40S TO MID 50S MUCH OF THE WEEK. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... AS OF 123 AM SATURDAY... VFR CONDITIONS ARE EXPECTED TODAY AND TONIGHT. HOWEVER... VFR TO MVFR CIGS CAN BE EXPECTED TODAY. THERE IS A CHANCE OF MVFR VSBYS THIS MORNING WITH A CHANCE OF SHOWERS MAINLY AT KFAY. A WARM FRONT WILL MOVE NORTH OVER NC SUNDAY. THIS WILL LOWER CIGS AND VSBYS SUNDAY AS RAIN ARRIVES FROM THE SOUTH DURING THE DAY. IFR TO LIFR CIGS AND VSBYS WITH RAIN AND FOG ARE EXPECTED LATE SUNDAY INTO SUNDAY NIGHT. MONDAY... CIGS WILL BREAK OUT INTO VFR DURING THE MORNING. THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS WITH THE COLD FRONT MONDAY AFTERNOON AND EVENING. THE OUTLOOK BEYOND MONDAY... A RETURN TO VFR CONDITIONS IS EXPECTED MONDAY NIGHT THROUGH FRIDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...BADGETT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...BADGETT AVIATION...BADGETT

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