Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 181450 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1050 AM EDT SAT APR 18 2015 .SYNOPSIS...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. && .NEAR TERM /TODAY AND TONIGHT/...
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AS OF 1050 AM SATURDAY... BULK OF LIGHT RAIN ASSOCIATED WITH A MINOR S/W CROSSING SC EARLIER THIS MORNING HAS PRETTY MUCH DEPARTED OUR FAR SE COUNTIES AS THE S/W HAS REACHED THE COAST. 12Z UPPER AIR ANALYSIS DEPICT A WEAK TROUGH AXIS LINGERING ACROSS CENTRAL NC. THIS FEATURE WILL LIKELY PERSIST INTO THE AFTERNOON-EARLY EVENING HOURS AS WINDS ARE FAIRLY LIGHT. LOW LEVEL FLOW WILL BECOME ELY THIS AFTERNOON AND INCREASE WITH TIME. THIS WILL RESULT IN WEAK CONVERGENCE ALONG LOW LEVEL TROUGH. WITH AFTERNOON HEATING OF THE RELATIVELY MOIST AIR MASS IN PLACE...WILL LIKELY SEE THE DEVELOPMENT OF ISOLATED SHOWERS (T- STORM?) ALONG THIS BOUNDARY ACROSS CENTRAL NC AFTER 3 PM. EXPECT A MIXTURE OF SUN AND CLOUDS THIS AFTERNOON WITH CLOUDY SPELLS MORE PREVALENT THAN MOSTLY SUNNY CONDITIONS. MOST LOCATIONS SHOULD BE WITHIN A DEGREE OR TWO OF 80 DEGREES FOR AFTERNOON HIGH TEMPS. IF CLOUD COVER REMAINS MOSTLY CLOUDY THROUGH MID AFTERNOON...HIGH TEMPS IN THE MID-UPPER 70S WILL BE MORE COMMON. TONIGHT...ANY SHOWERS OCCURRING AT SUNSET WILL DIMINISH WITH LOSS OF HEATING. SHOULD SEE INCREASING/THICKENING CLOUD COVER SPREADING OVER HEAD FROM THE SW AS A POTENT LOW PRESSURE SYSTEM MOVES TOWARD OUR REGION. WILL PROBABLY SEE A FEW SHOWERS SKIRT ACROSS THE SOUTHERN- WESTERN PIEDMONT COUNTIES PRIOR TO DAYBREAK WITH BEST CHANCE OF MEASURABLE RAIN OCCURRING SOUTH OF A LEXINGTON-LAURINBURG LINE. MIN TEMPS 60-64 WITH A FEW UPPER 50S PROBABLE ACROSS THE FAR NORTHEAST WHERE CLOUD COVER WILL BE INITIALLY THINNER.
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&& .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 400 AM SATURDAY... OVERVIEW: THE SHORTWAVE RIDGE IN PLACE TONIGHT WILL SHIFT OFFSHORE THE CAROLINA/MID-ATLANTIC COAST ON SUNDAY AS A SOMEWHAT DEAMPLIFIED UPPER LEVEL LOW TRACKS EASTWARD FROM THE CENTRAL PLAINS INTO THE CENTRAL MS RIVER VALLEY...PROPELLING A WEAK WARM FRONT /LOW-LEVEL TROUGH/ NORTHEASTWARD FROM THE DEEP SOUTH INTO THE CAROLINAS. PRECIPITATION: EXPECT AN EXCELLENT CHANCE FOR PRECIP ACROSS ALL OF CENTRAL NC SUN/SUN NIGHT IN ASSOC/W DPVA ATTENDANT INCREASINGLY NUMEROUS SMALL AMPLITUDE WAVES EMBEDDED WITHIN STRENGTHENING SW FLOW ALOFT AND LOW-LEVEL CONVERGENCE ATTENDANT THE WEAK WARM FRONT /LOW- LEVEL TROUGH/ PROGRESSING ACROSS CENTRAL NC IN THE PRESENCE OF A VERY MOIST (PWAT ~1.75") ALBEIT MARGINALLY UNSTABLE AIRMASS. FORCING MAY BE FURTHER AUGMENTED BY THE PRESENCE OF AN MCV AND/OR OUTFLOW ATTENDANT ONGOING CONVECTION PROGRESSING INTO THE REGION FROM THE SW...DEPENDING ON THE EVOLUTION OF UPSTREAM CONVECTION LATE TONIGHT AND EARLY SUN. REGARDLESS...EXPECT PRECIP CHANCES INCREASING FROM SW- NE SUN MORNING...WITH WIDESPREAD PRECIPITATION BY SUN AFTERNOON. EXPECT THE HEAVIEST PRECIPITATION TO FALL ACROSS THE WESTERN PIEDMONT...IN CLOSER VICINITY TO STRONGER DPVA AND ATTENDANT SFC CYCLONE TRACKING NE THROUGH THE TN VALLEY AND IN CLOSER VICINITY TO THE MOUNTAINS WHERE FORCING WILL BE LOCALLY AUGMENTED BY CONVERGENCE /OROGRAPHIC ASCENT/ ATTENDANT A STRENGTHENING SOUTHEASTERLY LLJ BETWEEN 15-21Z. PRECIP CHANCES SHOULD RAPIDLY DECREASE FROM SW-NE ACROSS CENTRAL NC SUN EVE AS THE LOW-LEVEL TROUGH PROGRESSES NORTHWARD ALONG THE MID-ATLANTIC COAST. RE-DEVELOPMENT OF ISOLD SHOWER ACTIVITY CANNOT BE RULED OUT LATE SUN NIGHT GIVEN A CONTINUED POTENTIAL FOR DPVA IN SW FLOW ALOFT...THOUGH POOR DIURNAL TIMING...MID-LEVEL DRYING...AND THE LACK OF A LOW-LEVEL FOCUS WILL ACT TO LIMIT AND/OR HINDER FURTHER DEVELOPMENT. TEMPS: HIGHS SUN WILL BE LIMITED BY PRECIPITATION (WEST) AND PERVASIVE CLOUD COVER FOLLOWED BY PRECIP (EAST)...IN THE 70S. LOWS SUN NIGHT IN THE LOW/MID 60S GIVEN A SOUTHERLY BREEZE AND LITTLE IN THE WAY OF AIRMASS CHANGE. HAZARDS: CONVECTIVE DETAILS FOR CENTRAL NC REMAIN DIFFICULT TO ASCERTAIN DUE TO BELOW NORMAL CONFIDENCE IN THE EVOLUTION OF UPSTREAM CONVECTION IN THE DEEP SOUTH (AND ULTIMATE IMPACT ON DOWNSTREAM ENV) TONIGHT /EARLY SUN/. FROM A PATTERN RECOGNITION STANDPOINT...SEVERE WEATHER APPEARS UNLIKELY GIVEN THAT THE BEST DPVA WILL REMAIN UPSTREAM ACROSS THE TN/OH VALLEY...DIURNAL TIMING WILL BE POOR IN THE WESTERN PIEDMONT...AND DIURNAL DESTABILIZATION WILL BE SIGNIFICANTLY HAMPERED ELSEWHERE/OTHERWISE BY MOIST- ADIABATIC MID-LEVEL LAPSE RATES AND PERVASIVE CLOUD COVER. GIVEN DEEP MOISTURE (PWAT ~1.75")...ISOLD FLASH FLOODING WILL BE POSSIBLE...PARTICULARLY IN URBAN AND FLOOD PRONE AREAS ACROSS THE TRIAD/WESTERN PIEDMONT. -VINCENT && .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...WSS SHORT TERM...VINCENT LONG TERM...BADGETT AVIATION...BADGETT

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