Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 031243 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 743 AM EST TUE MAR 3 2015 .SYNOPSIS...HIGH PRESSURE OVER THE REGION WILL SHIFT OFFSHORE THIS AFTERNOON AS A LOW PRESSURE SYSTEM TRACKS NORTHEAST FROM THE CENTRAL PLAINS INTO THE GREAT LAKES. A WARM FRONT WILL LIFT NORTHWARD THROUGH THE REGION LATE TONIGHT AND EARLY WEDNESDAY. THE NEXT COLD FRONT WILL APPROACH FROM THE NORTHWEST WEDNESDAY NIGHT...TRACKING THROUGH THE CAROLINAS ON THURSDAY. && .NEAR TERM /TODAY AND TONIGHT/... AS OF 400 AM TUESDAY... TODAY: THE 12Z GSO RAOB WILL LOOK LESS LIKE THE 00Z TUE RAOB AND MORE LIKE THE 12Z MON RAOB. A COLD AIR DAMMING WEDGE IS RE- DEVELOPING ACROSS THE AREA THIS MORNING AS PROGRESSIVE HIGH PRESSURE SHIFTS OFFSHORE AND LOW-LEVEL WARM ADVECTION QUICKLY STRENGTHENS ATOP A RECENTLY REPLENISHED COOL/DRY SFC AIRMASS. THOUGH MODEST/ PERSISTENT WARM ADVECTION WILL BE PRESENT THROUGHOUT THE DAY... LITTLE IF ANY UPPER LEVEL FORCING WILL BE PRESENT WITH RIDGING ALOFT ALONG THE SOUTHEAST COAST. AS A RESULT...PRECIP CHANCES AND COVERAGE ARE VERY MUCH IN DOUBT...THOUGH AMOUNTS SHOULD BE LIGHT REGARDLESS. EXPECT PERIODS OF LIGHT RAIN/DRIZZLE TO DEVELOP OVER THE SW PIEDMONT AND SPREAD NORTHEASTWARD TO THE TRIANGLE BY THIS AFTERNOON...AND NE COASTAL PLAIN BY SUNSET. MARGINAL AMOUNTS OF ELEVATED INSTABILITY MAY ALLOW PRECIP TO BECOME MORE CONVECTIVE (ELEVATED) AND MODERATE/HEAVIER AT TIMES...AS EVIDENCED BY 08-09Z REGIONAL RADAR IMAGERY OVER THE SW PIEDMONT...THOUGH THE BREVITY AND ISOLATED NATURE OF SUCH ACTIVITY WOULD STILL SUGGEST LIGHT AMOUNTS. HIGH TEMPERATURES FOR THE CALENDAR DAY HAVE LIKELY ALREADY OCCURRED IN MOST LOCATIONS. EXPECT TEMPS TO FALL IN ASSOC/W EVAP COOLING THIS MORNING...WITH AFTERNOON TEMPS RANGING FROM THE LOWER/MID 30S (NORTH/NE) TO UPPER 30S/LOWER 40S (SOUTH/SW). TONIGHT: LOW CONFIDENCE WITH TEMPERATURES OVERNIGHT. LOW TEMPS FOR WED MORNING (CALENDAR DAY) WILL LIKELY OCCUR AT MIDNIGHT TONIGHT IN MOST AREAS. A WARM FRONT LIFTING NORTHWARD INTO CENTRAL NC WILL RESULT IN RISING TEMPS FROM SOUTH-NORTH AFTER MIDNIGHT...THOUGH THE PROGRESS OF THE FRONT AND EXTENT OF CAD EROSION IS DIFFICULT TO GAUGE...ESP WITH AN ATYPICAL REGIME CHARACTERIZED BY A LARGELY UNAMPLIFIED SYNOPTIC PATTERN AND LACK OF A WELL DEFINED UPSTREAM CYCLONE /WARM SECTOR/ AND MORE CHARACTERISTIC OF DEVELOPING RETURN FLOW IN THE WAKE OF A DEPARTING SFC HIGH...AND IN ADVANCE OF AN INCREASINGLY STALLED/WSW-ENE ORIENTED COLD FRONT (WELL SEPARATED FROM THE PARENT LOW) APPROACHING THE WESTERN SLOPES OF THE APPALACHIANS. ONE WOULD TYPICALLY BE SKEPTICAL OF SIGNIFICANT CAD EROSION DURING THE OVERNIGHT HOURS IN SUCH A SCENARIO...THOUGH WEDGE EROSION IS A FUNCTION OF MANY FACTORS...PARTICULARLY THE STRENGTH AND CHARACTERISTIC OF THE CAD WEDGE. IF THE CAD WEDGE IS SUFFICIENTLY SHALLOW...MODEL GUIDANCE MAY WELL BE REASONABLE IN SHOWING SIGNIFICANT WARMING OVERNIGHT ACROSS MOST OF THE AREA TONIGHT...THOUGH IF A STRONGER/DEEPER WEDGE IS PRESENT THEN SFC TEMPS MAY REMAIN STEADY AND GRADUALLY/MARGINALLY INCREASE BY SUNRISE...PARTICULARLY NORTH OF HWY 64. WITH LITTLE TO GO ON ONE WAY OR THE OTHER...PLAN ON SPLITTING THE DIFFERENCE. REGARDLESS...SUCH A REGIME CERTAINLY FAVORS AN ENHANCED POTENTIAL FOR THE DEVELOPMENT OF DENSE FOG OVERNIGHT. PTYPE: BASED ON THE LATEST OBSERVATIONAL DATA AND MOST RECENT MODEL GUIDANCE...WETBULB TEMPERATURES SHOULD NOT BE SUPPORTIVE OF FZRA THIS MORNING ACROSS VIRTUALLY THE ENTIRE AREA....EXPECT PERHAPS THE NE COASTAL PLAIN WHERE PRECIP WOULD ARRIVE TOO LATE AND AT A DIURNALLY UNFAVORABLE TIME...ESP FOR EARLY MARCH. -VINCENT && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 400 AM TUESDAY... IF THE WARM FRONT HAS NOT PROGRESSED THROUGH THE BULK OF CENTRAL NC BY SUNRISE WED...IT SHOULD DO SO SHORTLY THEREAFTER AS THE INCREASINGLY SHALLOW CAD WEDGE DISSIPATES VIA INCREASING INSOLATION/MIXING AND STRENGTHENING SOUTHWEST FLOW. INITIALLY OVERCAST SKIES WILL BECOME SCT/BKN BY AFTERNOON...WITH A BREEZY SOUTHWEST WIND. THE GFS SUGGESTS DEEP/MORE VIGOROUS MIXING AND A POTENTIAL FOR GUSTS AS HIGH AS 30-40 KT...THOUGH THE NAM INDICATES LESS MIXING AND GUSTS NO HIGHER THAN 20-25 KT. GIVEN LITTLE IN THE WAY OF DIURNAL DESTABILIZATION....UNIDIRECTIONAL SW FLOW ALOFT WITH FEW (IF ANY) SHORTWAVE DISTURBANCES...AND UNIDIRECTIONAL SW LOW- LEVEL FLOW...EXPECT LARGELY DRY CONDITIONS OVER CENTRAL NC DURING THE DAY. AN AMPLIFYING TROUGH DIGGING SE INTO THE CENTRAL MS RIVER VALLEY WED EVE/NIGHT WILL RESULT IN CYCLOGENESIS ALONG A SLOW MOVING FRONTAL ZONE PROGRESSING INTO THE AREA WED NIGHT...THOUGH THE BULK OF PRECIPITATION IS EXPECTED TO BE ANAFRONTAL...OCCURRING AFTER SUNRISE. RAIN CHANCES WILL BE RELATIVELY HIGHEST NEAR THE VA BORDER AND IN THE NW PIEDMONT /TRIAD/. -VINCENT && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 400 AM TUESDAY... THE LATEST MODELS ARE IN GOOD AGREEMENT IN BRING THE COLD FRONT SOUTH THROUGH CENTRAL NORTH CAROLINA THURSDAY MORNING. A WAVE IS EXPECTED TO FORM ALONG THE FRONT OVER UPSTATE SC... WHICH IN TURN HELPS TO HOLD UP THE COLD FRONT FOR SEVERAL HOURS FROM REACHING THE SOUTHERN ZONES. THE STRONGEST CAA SHOULD ALSO LAG THE FRONTAL PASSAGE BY SEVERAL HOURS IT APPEARS. THIS SUPPORTS THE CONTINUATION OF OUR CURRENT PREDOMINATELY RAIN FORECAST FOR THURSDAY WITH LIMITED POTENTIAL FOR WINTERY MIX NEAR THE END OF THE EVENT BETWEEN 18Z AND 23Z OR SO THURSDAY AFTERNOON FOR THE NORTHERN PIEDMONT AND NORTHERN COASTAL PLAIN. P-TYPE NOMOGRAMS SUPPORT SOME MIX WITH OR CHANGE TO FREEZING RAIN THEN EVEN A BRIEF PERIOD OF LIGHT SNOW/SLEET AT THE VERY VERY END OF THE EVENT...ACROSS THE FAR NORTHERN PIEDMONT DURING THE MID TO LATE AFTERNOON. FORECAST WET BULB TEMPERATURES DEPENDING ON THE MODEL OF CHOICE WITH SOME MODEL VARIABILITY ALSO TARGET THE NORTHERN ZONES FOR THIS POTENTIAL CHANGEOVER (ESPECIALLY NORTH OF A LINE EXTENDING FROM DAVIDSON TO RANDOLPH TO WAKE TO WARREN COUNTIES. PRECIPITATION SHOULD END QUICKLY BETWEEN 21Z-00Z...LIMITING THE WINDOW OF OPPORTUNITY FOR ICE TO BECOME A SIGNIFICANT WEATHER HAZARD. TO THE SOUTH...ALL RAIN IS EXPECTED WITH THE SLOWER TO COOL TEMPERATURES THERE. ALL IN ALL...A SIGNIFICANT WINTER WEATHER EVENT IS NOT EXPECTED AT THIS TIME WITH THE PREDOMINATE P-TYPE EXPECTED TO BE RAIN. THE CHANGEOVER WOULD OCCUR DURING THE AFTERNOON IN THE NORTH (IF AT ALL)... AND THE WARM GROUND TEMPERATURES AND TIME OF DAY WOULD LIMIT THE POTENTIAL TO MOSTLY ELEVATED SURFACES. THURSDAY NIGHT...BREEZY AND COLDER CONDITIONS COULD LEAD TO A QUICK FREEZE OF RESIDUAL WATER LEFT BEHIND WHICH MAY BECOME A WEATHER HAZARD. OTHERWISE...SIMPLY CLEARING AND COLD WITH LOWS IN THE 20-25 RANGE. FRIDAY IS EXPECTED TO BE MOSTLY SUNNY AND COLD WITH THE HEART OF THE ARCTIC COLD EXPECTED OVER THE OHIO VALLEY AND NORTHERN MID ATLANTIC STATES. WE WILL STILL BE A GOOD 20 DEGREES BELOW NORMAL WITH HIGHS EXPECTED IN THE UPPER 30S TO LOWER 40S. MODERATION WILL OCCUR IN THE TEMPERATURES OVER THE WEEKEND AS THE HIGH SLIPS SOUTH AND A WESTERLY FLOW DEVELOPS. HIGHS SHOULD RAPIDLY WARM INTO THE MID 40S TO LOWER 50S SATURDAY AND MID 50S TO LOWER 60S SUNDAY. A DRIER PATTERN IS ALSO ANTICIPATED THROUGH THE WEEKEND. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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AS OF 730 AM TUESDAY... 24-HR TAF PERIOD: DETERIORATING CONDITIONS EXPECTED THROUGH THE TAF PERIOD...ESPECIALLY THIS EVENING INTO TONIGHT WHEN 1/4SM +FG VV001 IS EXPECTED AT MOST OR ALL TERMINALS. CEILINGS WILL LOWER TO MVFR THIS MORNING AND LOW MVFR/IFR THIS AFTERNOON AS POCKETS OF LIGHT RAIN AND DRIZZLE DEVELOP SW-NE ACROSS THE REGION IN ASSOC/W PERSISTENT WARM ADVECTION. CEILINGS WILL LOWER TO IFR/LIFR AFTER SUNSET...QUICKLY FOLLOWED BY VISBYS FALLING TO LIFR/VLIFR WITH WIDESPREAD DENSE FOG AS A WARM FRONT PROGRESSES NORTHWARD INTO THE COLD AIR DAMMING WEDGE IN PLACE OVER CENTRAL NC AFTER ~03Z. AVIATION CONDITIONS WILL REMAIN POOR THROUGH THE REMAINDER OF THE TAF PERIOD (12Z WED). LOOKING AHEAD: CEILINGS WILL IMPROVE WED MORNING AS A WARM FRONT PROGRESSES THROUGH THE REGION AND A BREEZY SW FLOW DEVELOPS...THOUGH MVFR CEILINGS MAY PERSIST THROUGH THE DAY. SOUTHWEST WINDS MAY BECOME SUSTAINED AT 20-25 KT WITH GUSTS AS HIGH AS 30-35 KT WED AFTERNOON...DEPENDING ON CLOUD COVER/MIXING. ADVERSE AVIATION CONDITIONS ARE EXPECTED TO PREVAIL THU/THU NIGHT IN ASSOC/W A COLD FRONTAL PASSAGE EARLY THU AND SUBSEQUENT CAD WEDGE DEVELOPMENT THU AFTERNOON/EVENING. A PERIOD OF VFR CONDITIONS IS EXPECTED ON FRIDAY...THOUGH ADVERSE CONDITIONS APPEAR LIKELY ONCE AGAIN OVER THE WEEKEND. -VINCENT
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...VINCENT LONG TERM...BADGETT AVIATION...VINCENT

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