Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 260759 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 359 AM EDT THU MAR 26 2015 .SYNOPSIS...A COLD FRONT WILL APPROACH THE MOUNTAINS FROM THE WEST THIS AFTERNOON AND EVENING...THEN TRACK SOUTHEAST THROUGH CENTRAL NORTH CAROLINA LATE TONIGHT. THE COLD FRONT WILL BRIEFLY STALL OFFSHORE THE CAROLINA COAST ON FRIDAY AS A POTENT UPPER LEVEL DISTURBANCE APPROACHES FROM THE WEST. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 325 AM THURSDAY... TODAY: LOW-LEVEL MOISTURE ADVECTION VIA A 30-KT SOUTHERLY LLJ BENEATH THE MODIFIED ELEVATED MIXED LAYER IN PLACE ACROSS THE REGION THIS MORNING IS RESULTING IN NOCTURNAL DESTABILIZATION...WITH MUCAPE ON THE ORDER OF 500-1000 J/KG (MUCAPE) OVER CENTRAL NC. GIVEN FAVORABLE THERMODYNAMICS...LOW-LEVEL WARM ADVECTION AND SFC CONVERGENCE IN VICINITY OF A QUASI-STATIONARY FRONT SEPARATING THE WARM SECTOR (EAST) FROM RESIDUAL CAD WEDGE (WEST) NEAR THE HWY 1 CORRIDOR WILL BE SUFFICIENT FOR SCATTERED TO NUMEROUS SHOWERS AND PERHAPS AN ISOLD THUNDERSTORM THROUGH SUNRISE...WITH ACTIVITY SHIFTING INTO EAST/NE PORTIONS OF THE STATE BY MID/LATE MORNING AS WARM ADVECTION SHIFTS DOWNSTREAM AND FLOW VEERS TO THE SOUTHWEST... ADVECTING A DRIER LOW-LEVEL AIRMASS INTO CENTRAL NC. THIS...IN ADDITION TO DEEPER VERTICAL MIXING (IN COMPARISON TO PRIOR DAYS) AND THE PRESENCE OF A MODIFIED ELEVATED MIXED LAYER (7.0-7.5 C/KM H7-H5 LR) WILL RESULT IN A CAPPED THERMODYNAMIC ENVIRONMENT CHARACTERIZED BY WEAK DIURNAL DESTABILIZATION AND ~50 J/KG OF CIN DURING PEAK HEATING. ASIDE FROM THE POTENTIAL FOR A ROGUE SMALL AMPLITUDE WAVE IN STRENGTHENING SW FLOW ALOFT...FORCING FOR ASCENT WILL OTHERWISE BE DIFFICULT TO COME BY. WITH THE ABOVE IN MIND...WILL INDICATE A DRY FORECAST THIS AFTERNOON...WITH THE EXCEPTION OF A SLIGHT CHANCE OF A LOW-TOPPED SHOWER IN THE SE COASTAL PLAIN DURING THE LATE AFTERNOON WHEN SFC WINDS BACK TO THE SOUTH IN ADVANCE OF AN APPROACHING COLD FRONT...RESULTING IN WEAK LOW-LEVEL CONVERGENCE AND RELATIVELY BETTER LOW-LEVEL MOISTURE ACROSS PORTIONS OF THE COASTAL PLAIN. EXPECT HIGHS IN THE 70S...LOWER/MID 70S NW PIEDMONT AND UPPER 70S ALONG/EAST OF HWY 1. SEVERE POTENTIAL THIS MORNING: A VERY LOW-END POTENTIAL FOR AN ISOLD SVR STORM WILL BE PRESENT THIS MORNING BETWEEN 09-15Z AS DEEP LAYER SHEAR INCREASES FROM THE WEST IN THE PRESENCE OF NOCTURNAL DESTABILIZATION DRIVEN BY LOW-LEVEL WARMING/MOISTENING BENEATH THE MODIFIED ELEVATED MIXED LAYER IN PLACE. THOUGH CONVECTION WOULD LARGELY BE ELEVATED WEST OF HWY 1...CONVECTIVE ACTIVITY WILL EVENTUALLY BECOME SFC-BASED AS IT PROPAGATES/RE-DEVELOPS EASTWARD INTO THE COASTAL PLAIN ALONG THE NOSE OF THE SOUTHERLY LLJ. HAZARDS WITH DEEP CONVECTION IN THIS ENVIRONMENT WOULD INCLUDE SEVERE WIND...HAIL...OR A BRIEF LOW-END TOR. GIVEN LITTLE IN THE WAY OF UPPER LEVEL FORCING...CONFIDENCE IS EXTREMELY LOW WITH REGARD TO WHETHER OR NOT SUCH A THREAT WILL EVEN MATERIALIZE. TONIGHT: THE AFOREMENTIONED COLD FRONT WILL PROGRESS INTO CENTRAL NC OVERNIGHT...THOUGH FORWARD PROGRESS WILL BEGIN TO SLOW AS STRONG DPVA /HEIGHT FALLS/ ATTENDANT AN AMPLIFYING UPPER LEVEL TROUGH APPROACHES FROM THE WEST. WITH SUFFICIENT MOISTURE AND STRONG DEEP- LAYER FORCING...EXPECT WIDESPREAD RAIN TO DEVELOP AFTER MIDNIGHT... PREDOMINATELY OF THE ANAFRONTAL /ELEVATED/ VARIETY...THOUGH A NARROW LINE OF LOW-TOPPED SFC-BASED SHOWERS CANNOT BE RULED OUT ALONG THE FRONT EAST OF HWY 1. LOW TEMPS WILL DEPEND ON A COMBINATION OF COLD ADVECTION AND PRECIP /EVAP COOLING/...FALLING FROM THE LOWER/MID 60S TO THE LOWER/MID 40S FROM WNW TO ESE AFTER MIDNIGHT...EXCEPT IN THE FAR SOUTHEAST (I.E. FAY/CTZ/GSB) WHERE THE WARM SECTOR COULD PERSIST INTACT THROUGH 12Z AND TEMPS WOULD HOVER AT OR NEAR 60F. -VINCENT && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 340 AM THURSDAY... FRIDAY: EXPECT LINGERING ANAFRONTAL PRECIPITATION AND CHILLY TEMPERATURES ON FRIDAY AS SOUTHWEST FLOW ALOFT /WARM ADVECTION/ PERSISTS ATOP A DEVELOPING POST-FRONTAL CAD WEDGE...IN ADVANCE OF AN AMPLIFYING UPPER LEVEL TROUGH APPROACHING FROM THE WEST. EXPECT CLOUDY CONDITIONS WITH RAIN PERSISTING THROUGH MUCH OF THE DAY...ESP EAST OF HWY 1. AFTERNOON HIGHS ARE UNLIKELY TO EXCEED THE LOW/MID 40S...EXCEPT IN THE WESTERN PIEDMONT WHERE CLOUD COVER MAY BREAK SEVERAL HRS PRIOR TO SUNSET AND A WARM-UP INTO THE UPPER 40S /NEAR 50F/ WOULD BE POSSIBLE. -VINCENT THE UPPER TROF AND AN ASSOCIATED VIGOROUS VORT MAX ROTATES EAST ACROSS THE AREA ON FRIDAY NIGHT. MOISTURE WILL BE ON THE WANE AFTER THE COLD FRONTAL PASSAGE...BUT STRONG OMEGA AND RESIDUAL LOW LEVEL MOISTURE ARE SUFFICIENT TO MAINTAIN POPS IN THE LOW CHANCE RANGE. AS AN ADDED BONUS...THE ICE NUCLEATION ZONE DOES BECOME SATURATED AFTER MIDNIGHT AS TEMPS ACROSS THE AREA FALL INTO THE MID TO PERHAPS SOME LOWER 30S. WILL OPTIMISTICALLY ADD A SLIGHT CHANCE OF MIXED RAIN/SNOW SHOWERS IN THE EASTERN CWFA AS POPS ARE TAILING OFF IN THE PREDAWN. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 350 AM THURSDAY... THE UPPER TROUGH WILL MOVE EAST OF THE AREA WITH COLD SURFACE HIGH PRESSURE BUILDING DOWN THE ATLANTIC COAST THROUGH THE WEEKEND. COLDEST TEMPS WILL BE SATURDAY AND SATURDAY NIGHT...WITH THICKNESSES SUPPORTING PERSISTENT MOS GUIDANCE OF UPPER 40S TO LOWER 50S ON SATURDAY. THE UNSEASONABLY COOL AIRMASS WILL RADIATE NICELY SATURDAY NIGHT...AND MINS SUNDAY MORNING WILL BE MOSTLY IN THE UPPER 20S...WITH SOME MID 20S IN OUTLYING AREAS. RISING HEIGHTS AND RETURN FLOW AS THE HIGH MOVES OFFSHORE WILL ALLOW RECOVERY TO COMMENCE ON SUNDAY...WITH HIGHS IN THE MID 50S. A FRONT WILL MOVE SOUTHEAST AND ACROSS THE AREA ON MONDAY. THIS FRONT WILL HAVE LITTLE MOISTURE TO WORK WITH AS FLOW REMAINS PREDOMINANTLY WESTERLY...WHICH WILL ALSO PREVENT THE FRONTS REINFORCING THE COLD AIRMASS SIGNIFICANTLY. WILL HAVE SLIGHT CHANCES FOR SHOWERS DURING THE DAY...WITH HIGHS REACHING THE LOW TO MID 60S AFTER MORNING LOWS IN THE UPPER 30S...WITH DRY WEATHER TUESDAY AND HIGHS A TOUCH WARMER WITH MORE SUN...MID TO UPPER 60S. FLATTER MID LEVEL FLOW ADDS UNCERTAINTY TO THE TIMING OF OUR NEXT WEATHER MAKER IN THE MID WEEK PERIOD. THE CHANCE OF RAIN WILL BE INCREASING INTO THURSDAY...HOWEVER...AND WILL INCREASE POPS INCREMENTALLY THROUGH THURSDAY WITH CONTINUED WARMING INTO THE LOW TO MID 70S FOR BOTH WEDNESDAY AND THURSDAY. && .AVIATION /06Z THURSDAY THROUGH SUNDAY/... AS OF 300 AM THURSDAY... 24-HR TAF PERIOD: IFR/LIFR CEILINGS AND SHOWERS WILL PREVAIL THIS MORNING...THOUGH CONDITIONS WILL IMPROVE TO MVFR AND PERHAPS VFR DURING THE AFTERNOON AS A SLIGHTLY DRIER LOW-LEVEL AIRMASS ADVECTS INTO THE REGION AND A BREEZY SOUTHWEST FLOW DEVELOPS...BECOMING SUSTAINED AT 10-15 KT WITH GUSTS TO 20-25 KT. IMPROVED CONDITIONS WILL BE SHORT-LIVED...HOWEVER...AS A COLD FRONT PROGRESSES INTO THE REGION TONIGHT. A WIND SHIFT TO THE NORTHWEST AT 10-15 KT (GUSTS TO 20 KT) ALONG WITH THE REDEVELOPMENT OF IFR/LIFR CEILINGS IS EXPECTED IN THE WAKE OF THE FRONT BETWEEN 06-12Z FRI...WITH ONLY MARGINAL IMPROVEMENT TO IFR BY THE END OF THE TAF PERIOD. LOOKING AHEAD: IFR CEILINGS AND PRECIPITATION WILL GRADUALLY END FROM WEST-EAST LATE FRI/FRI EVENING...AND VFR CONDITIONS MAY RETURN FOR A PERIOD. HOWEVER...A POTENT UPPER LEVEL TROUGH CROSSING THE REGION WILL LIKELY RESULT IN ANOTHER PERIOD OF MVFR/IFR CEILINGS AND A CHANCE OF SHOWERS AT EASTERN TERMINALS AFTER 06Z SAT. VFR CONDITIONS WILL PREVAIL THE REMAINDER OF THE WEEKEND AS HIGH PRESSURE BUILDS TOWARD THE AREA FROM THE WEST. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT/MLM LONG TERM...MLM AVIATION...VINCENT

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