Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 190900 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 459 AM EDT SUN APR 19 2015 .SYNOPSIS...A STALLED FRONTAL ZONE OVER CENTRAL NORTH CAROLINA WILL LIFT NORTHWARD INTO VIRGINIA AS A WARM FRONT LATE THIS AFTERNOON AND EVENING...AS A DEVELOPING LOW PRESSURE SYSTEM TRACKS NORTHEAST INTO THE OHIO VALLEY. AN ASSOCIATED COLD FRONT WILL APPROACH THE MOUNTAINS FROM THE WEST ON MONDAY...THEN TRACK EAST TO THE CAROLINA COAST MONDAY NIGHT. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 340 AM SUNDAY... OVERVIEW: A SHORTWAVE RIDGE IN PLACE EARLY THIS MORNING WILL SHIFT OFFSHORE THE CAROLINA/MID-ATLANTIC COAST TODAY AS AN UPPER LEVEL LOW TRACKS EASTWARD FROM THE CENTRAL PLAINS INTO THE CENTRAL MS RIVER VALLEY...PROPELLING A WEAK WARM FRONT /LOW-LEVEL TROUGH/ NORTHEASTWARD THROUGH THE CAROLINAS. PRECIPITATION: EXPECT NEAR 100% CHANCES FOR PRECIPITATION TODAY... IN ASSOC/W DPVA ATTENDANT INCREASINGLY NUMEROUS SMALL AMPLITUDE WAVES EMBEDDED WITHIN STRENGTHENING SW FLOW ALOFT AND LOW-LEVEL CONVERGENCE ATTENDANT A WEAK WARM FRONT /LOW-LEVEL TROUGH/ PROGRESSING SW-NE OR SSW-NNE ACROSS CENTRAL NC IN THE PRESENCE OF A VERY MOIST (PWAT ~1.75") ALBEIT MARGINALLY UNSTABLE AIRMASS. EXPECT PRECIP INCREASING IN COVERAGE/INTENSITY FROM SW-NE AFTER ~12Z THIS MORNING...REACHING THE TRIANGLE BY LATE MORNING (~15Z) AND FAR NE COASTAL PLAIN (I.E. HALIFAX COUNTY) BY EARLY AFTERNOON (16-18Z). EXPECT THE HEAVIEST PRECIPITATION TO FALL ALONG/WEST OF THE YADKIN RIVER...IN CLOSER VICINITY TO STRONGER DPVA /ATTENDANT SFC CYCLONE/ TRACKING NE THROUGH THE TN VALLEY AND WHERE FORCING WILL BE LOCALLY AUGMENTED BY CONVERGENCE /OROGRAPHIC ASCENT/ ASSOCIATED WITH A STRENGTHENING SOUTHEASTERLY LLJ BETWEEN 15-21Z. PRECIP CHANCES WILL DECREASE FROM SW-NE OR SSW-NNE ACROSS CENTRAL NC LATE THIS EVENING (00-04) AS THE LOW-LEVEL TROUGH /WARM FRONT/ LIFTS NORTHWARD INTO THE DELMARVA AND A DRIER MID-LEVEL AIRMASS ADVECTS INTO THE REGION FROM THE SW/WSW. AS COVERAGE BEGINS TO DECREASE...INTENSIFICATION OF LINGERING CONVECTION WILL BE POSSIBLE...PRIMARILY IN THE 00-06Z TIME FRAME AS MID-LEVEL LAPSE RATES STEEPEN IN ADVANCE OF MORE POTENT SHORTWAVE ENERGY TRACKING INTO THE REGION FROM THE SOUTHWEST. PRECIP CHANCES WILL RAPIDLY DIMINISH IN THE 06-12Z TIME FRAME AS SUBSIDENCE COMMENCES IN THE WAKE OF THE SHORTWAVE. TEMPS: HIGHS WILL BE LIMITED BY PRECIPITATION (WEST) AND PERVASIVE CLOUD COVER FOLLOWED BY PRECIP (EAST)...RANGING FROM THE MID/UPPER 60S FAR NW PIEDMONT TO LOWER 70S ELSEWHERE. GIVEN A SOUTHERLY BREEZE AND LITTLE CHANGE IN AIRMASS...EXPECT LOWS TONIGHT IN THE LOW TO MID 60S. SEVERE: SEVERE WEATHER IS NOT ANTICIPATED TODAY (12-00Z) WITH UPPER LEVEL FORCING ON THE MARGINAL END OF THE SPECTRUM AND DIURNAL DESTABILIZATION SIGNIFICANTLY HAMPERED BY WEAK/MOIST-ADIABATIC MID- LEVEL LAPSE RATES AND PERVASIVE CLOUD COVER. A PERIOD OF CONVECTIVE INTENSIFICATION WILL BE POSSIBLE BETWEEN 00-06Z WHEN STRONGER DPVA ARRIVES IN THE PRESENCE OF STEEPENING MID-LEVEL LAPSE RATES. SHOULD DISCRETE INTENSIFICATION OCCUR...A BRIEF/LOW-END TORNADO OR WIND THREAT COULD NOT BE RULED OUT THIS EVENING...LOW AS THE PROBABILITY MAY BE. FLOODING: GIVEN DEEP MOISTURE (PWAT ~1.75") AND A GOOD ~6-9 HR PERIOD OF MODERATE TO HEAVY PRECIPITATION EXPECTED IN WESTERN PORTIONS OF THE STATE...ISOLD FLASH FLOODING WILL BE POSSIBLE... PARTICULARLY IN URBAN AND FLOOD PRONE AREAS ACROSS THE TRIAD. GIVEN THAT THE HEAVIEST PRECIPITATION 9AND GREATEST COVERAGE THEREOF) IS EXPECTED TO FALL WEST OF THE YADKIN RIVER (WEST OF NWS RALEIGH CWA) AND THAT THE WESTERN PIEDMONT HAS EXPERIENCED BELOW NORMAL PRECIPITATION DURING THE PAST 6 MONTHS...A FLASH FLOOD WATCH WILL NOT BE NECESSARY EAST OF THE YADKIN. -VINCENT && .SHORT TERM /MONDAY AND MONDAY NIGHT/... AS OF 400 AM SUNDAY... EXPECT A CLEARING TREND MONDAY MORNING THROUGH EARLY AFTERNOON AS LINGERING LOW STRATUS LIFTS AND BECOMES CU/TCU WITH BASES OF 3-4 KFT BY EARLY AFTERNOON. A MODIFIED ELEVATED MIXED LAYER CHARACTERIZED BY H7-H5 LAPSE RATES ON THE ORDER OF 7 C/KM IS PROGGED TO ADVECT INTO THE REGION LATE TONIGHT...MAINTAINED BY WSW/SW FLOW ALOFT DURING THE DAY MONDAY. LOW-LEVEL MOISTURE (SFC DWPT UPPER 50S TO LOWER 60S) WILL PERSIST THROUGHOUT THE DAY...WITHIN AN INCREASINGLY WELL-MIXED WARM SECTOR DOWNSTREAM OF A COLD FRONT APPROACHING THE MOUNTAINS FROM THE WEST DURING THE LATE AFT/EVE. GIVEN STRONG DIURNAL HEATING AND STEEP MID-LEVEL LAPSE RATES ATOP SEASONABLY IMPRESSIVE LOW-LEVEL MOISTURE...MODERATE DESTABILIZATION IS EXPECTED WITH MLCAPE VALUES SOLIDLY IN THE 1500-2500 J/KG RANGE. THOUGH LITTLE IN THE WAY OF A CAP IS PRESENT MON AFTERNOON PER THE LATEST GUIDANCE/FORECAST SOUNDINGS...CONVECTION IS UNLIKELY TO DEVELOP BEYOND THE `TURKEY TOWER` STAGE THROUGH MID AFTERNOON (~21Z) GIVEN SUCH A DRY AIRMASS ALOFT...AN INSUFFICIENT FOCUS...AND AN OVERAL LACK OF DEEPER ASCENT. BY LATE AFTERNOON (~21Z)...MODERATE/UNTAPPED INSTABILITY AND AN ABSENCE OF CONVECTIVE INHIBITION ARE EXPECTED TO ALLOW RAPID CONVECTIVE DEVELOPMENT ALONG THE COLD FRONT /PRE-FRONTAL TROUGH/ PROGRESSING INTO THE FOOTHILLS...GROWING UPSCALE INTO A SQUALL LINE BETWEEN 21-00Z AS ADDITIONAL CONVECTION DEVELOPS ALONG OUTFLOW IN AN ENVIRONMENT CHARACTERIZED BY WESTERLY LOW-LEVEL SHEAR AND MODERATE/ HIGH DCAPE. WILL INDICATE A 50% CHANCE OF SHOWERS/STORMS MOVING WEST- EAST ACROSS CENTRAL NC BETWEEN 21-03Z. SEVERE THREAT: WITH THE ABOVE ENVINRONMENT IN MIND...ANY STORMS THAT DEVELOP COULD BECOME SEVERE...WITH A PRIMARY THREAT OF DAMAGING WINDS. QUARTER TO GOLFBALL SIZE HAIL WOULD BE POSSIBLE IN ASSOC/W ROTATING UPDRAFTS...PARTICULARLY DISCRETE UPDRAFTS (I.E. INITIALLY IN WESTERN PIEDMONT). AN ENHANCED THREAT OF DAMAGING WINDS WILL BE PRESENT ALONG/EAST OF HWY 1 IF UPSCALE GROWTH INTO A MATURE MCS OCCURS WITHIN THE ENVIRONMENT PROGGED BY GUIDANCE. -VINCENT && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 100 AM SUNDAY... ...DRIER CONDITIONS FOR MUCH OF THE UPCOMING WEEK... THE MAIN COLD FRONT WILL BE OFFSHORE BY 12Z/TUE. COOL AND DRY ADVECTION WILL OVERSPREAD CENTRAL AND EASTERN NORTH CAROLINA TUESDAY AS THE SURFACE HIGH SHIFTS EAST ALONG THE GULF COAST STATES. HIGHS SHOULD STILL REACH 70-75 IN MOST AREAS EXCEPT UPPER 60S IN THE NORTHWEST PIEDMONT INCLUDING WINSTON-SALEM AND GREENSBORO. BREEZY W-NW WINDS AT 10-20 MPH ARE EXPECTED FROM MID MORNING THROUGH THE AFTERNOON... DIMINISHING LATE AFTERNOON. THE SURFACE HIGH PRESSURE WILL PUSH EAST ALONG THE SE STATES THEN OFFSHORE TUESDAY NIGHT AND WEDNESDAY. THIS OCCURS AS A DRY COLD FRONT IS FORECAST TO APPROACH THE REGION WEDNESDAY AFTERNOON DRIVEN BY THE NW FLOW ALOFT. A RETURN SW SURFACE FLOW SHOULD COMMENCE FROM THE TENNESSEE VALLEY NORTHEAST ACROSS THE CENTRAL APPALACHIANS AND NW NC TUESDAY NIGHT. THE SW RETURN FLOW WILL ARRIVE OVER THE REST OF NORTH CAROLINA WEDNESDAY. THERE WILL BE LITTLE TO NO GULF MOISTURE RETURN OUT AHEAD OF THIS FRONT WITH ONLY SOME MID AND HIGH CLOUDINESS EXPECTED. THEREFORE... EXPECT PARTLY CLOUDY SKIES TUESDAY NIGHT AND PARTLY SUNNY WEDNESDAY. LOWS IN THE MID 40S. HIGHS IN THE LOWER TO MID 70S WEDNESDAY. THE COLD FRONT IS EXPECTED TO STALL JUST TO OUR SOUTH ON WEDNESDAY NIGHT AND THURSDAY BEFORE THE NEXT SURGE OF ENERGY IN THE WNW FLOW ALOFT EVENTUALLY DRIVES ANOTHER COLD FRONT TOWARD THE AREA LATE THURSDAY. THE GULF AND ATLANTIC APPEAR TO BE CUT OFF DURING THIS TIME IN THE PREDOMINATELY WESTERLY FLOW - HOWEVER HARD TO TIME ENERGY ALOFT MAY BRING A SMALL CHANCE OF LIGHT SHOWERS LATE WED NIGHT AND THURSDAY. WE WILL ONLY CARRY A SLIGHT CHANCE AT THE CURRENT TIME DUE TO THE LACK OF AVAILABLE MOISTURE EXPECTED. LOWS AND HIGHS SHOULD RETURN TO NORMAL (LOWER TO MID 50S/LOWER TO MID 70S) INTO THURSDAY. FRIDAY AND SATURDAY... DRY CONDITIONS SHOULD CONTINUE THROUGH LATE WEEK BEHIND THE COLD FRONT THURSDAY. HOWEVER... LOW CONFIDENCE OF TIMING AND STRENGTH OF A POTENTIAL SOUTHERN BRANCH SYSTEM TOWARD THE WEEKEND INCREASING THE CHANCE OF SHOWERS BY SATURDAY. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 150 AM SUNDAY... 24 HOUR PERIOD: CIGS WILL DROP TO MVFR... THEN IFR... AT KINT AND KGSO BETWEEN 09Z AND 12Z... AND PROGRESS NORTHEAST THROUGH THE MORNING AS RAIN AND EMBEDDED HEAVY RAIN SHOWERS OVERSPREAD THE AREA AHEAD OF A WARM FRONT. THE HEAVIEST RAIN WITH ISOLATED THUNDERSTORMS WILL LIKELY OCCUR BETWEEN 21Z/SUN AND 03Z/MON WHEN LIFR CIGS/VSBYS CAN BE EXPECTED. THE HEAVY RAIN WILL PUSH NORTH OF THE REGION BETWEEN 03Z-07Z/MON... LEAVING WIDESPREAD IFR/MVFR CEILINGS THROUGH 12Z/MON. VFR CONDITIONS ARE EXPECTED MONDAY. HOWEVER... A COLD FRONT WILL BRING MVFR CIGS DURING THE MID TO LATE AFTERNOON. SW WINDS 15-25KT WILL PRECEDE THE FRONT... SHIFTING TO THE WEST DURING THE EVENING AT 10KT. SCATTERED CIGS/VSBYS OF IFR TO MVFR WILL OCCUR IN SHOWERS AND THUNDERSTORMS MONDAY AFTERNOON AND EVENING UNTIL THE FRONT PASSES. A RETURN TO VFR CONDITIONS ARE FORECAST FOR LATE MONDAY NIGHT THROUGH THURSDAY AS HIGH PRESSURE BUILDS IN. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...BADGETT AVIATION..BADGETT

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