Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 270759 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 300 AM EST FRI FEB 27 2015 .SYNOPSIS... COLD HIGH PRESSURE OVER THE CENTRAL PLAINS WILL BUILD INTO THE MID ATLANTIC TODAY THROUGH SATURDAY. && .NEAR TERM /THROUGH SATURDAY NIGHT/... AS OF 300 AM FRIDAY... ...WINTER WEATHER ADVISORY FOR BLACK ICE IN EFFECT THROUGH 10 AM THIS MORNING... PLAN TO MAINTAIN CURRENT WSW FOR BLACK ICE AS IS UNTIL 10 AM. WITH TEMPS ACROSS THE REGION CURRENTLY IN THE 25-30 DEGREE RANGE...REFREEZING OF MELTED ICE/SNOW LIKELY UNDERWAY. EVENING CREW ON THEIR WAY HOME EARLIER REPORTED SCATTERED SLICK SPOTS ON AREA ROADWAYS HAD DEVELOPED. TOYED WITH THE IDEA OF A NPW FOR FREEZING FOG ADVISORY AS VISIBILITIES HAVE LOWERED TO AT OR BELOW A QUARTER OF A MILE AT A FEW SITES ACROSS THE NORTH. HOWEVER...AFTER COORDINATING WITH SURROUNDING WFOS...WANT THE EMPHASIS TO BE MORE ON THE BLACK ICE VERSUS THE DENSE FOG SO WILL INCORPORATE THE MENTION OF DENSE/FREEZING FOG IN THE UPDATED WSW STATEMENT. OTHERWISE...FAST SW FLOW ALOFT WILL MAINTAIN A DECK OF HIGH LEVEL CLOUDS OVER THE REGION WHILE THE APPROACH OF A S/W CROSSING THE LOWER OH VALLEY WILL CAUSE PERIODS OF MID CLOUDS AS WELL. LIFT APPEARS TO BE ENOUGH TO GENERATE CLOUDS BUT NOT ENOUGH TO GENERATE PRECIPITATION THOUGH COULD SEE A POCKET OF DRIZZLE OR SNOW FLURRIES THIS AFTERNOON WHEN THE TAIL END OF THE S/W CROSSES OUR REGION. LOW LEVEL THICKNESSES THIS AFTERNOON AVERAGE 50-60M BELOW AVERAGE...SUPPORTIVE OF MAX TEMPS WELL BELOW NORMAL FOR LATE FEBRUARY. FAVOR MAX TEMPS ON THE COOL SIDE OF MOS GUIDANCE. EXPECT MAX TEMPS IN THE UPPER 30S TO AROUND 40 NORTH TO THE LOW-MID 40S SOUTH. THE FOREMENTIONED S/W WILL USHER A SFC COLD FRONT ACROSS CENTRAL NC LATE THIS AFTERNOON/EARLY THIS EVENING. THE AIR MASS BEHIND THIS SFC FEATURE WILL BE NOTICEABLY DRIER AND COOLER. EXPECT SOME MINOR DECREASE IN CLOUDINESS OVERNIGHT BUT NOT EXPECTING TOTALLY CLEAR SKIES. THICKNESSES IN THE 1260-1265M RANGE HISTORICALLY SUGGEST MIN TEMPS CLOSE TO 20 DEGREES. FAVOR THE COOLER MAV GUIDANCE VERSUS THE WARMER MET. SATURDAY...1040+MB HIGH CENTERED OVER SOUTHERN NEW ENGLAND WILL NOSE SOUTHWARD INTO THE CAROLINAS. THIS DRY AIR RIDGE AND ACCOMPANYING 850MB THERMAL TROUGH WILL RESULT IN ANOTHER DAY OF WELL BELOW NORMAL TEMPS. FAVOR THE COOLER MAV GUIDANCE THOUGH IF PEEKS OF SUN MORE PREVALENT THEN CURRENT THINKING...AFTERNOON TEMPS COULD END UP BEING 3-4 DEGREES WARMER THAN FORECAST. THE NEXT LOW PRESSURE SYSTEM WILL BE DEVELOPING/APPROACHING FROM THE WEST-SW SATURDAY NIGHT. MEANWHILE DRY AIR SFC RIDGE WILL BEGIN TO SHIFT OFFSHORE BUT STILL MAINTAIN A PRESENCE ACROSS OUR REGION. MOS GUIDANCE...MAINLY THE MAV...APPEARS TOO COLD CONSIDERING THE INCREASING/THICKENING CLOUD COVERAGE. WHILE ISENTROPIC UPGLIDE WILL BE ON THE INCREASE TOWARD DAYBREAK SUNDAY...LIFT APPEARS TOO WEAK TO GENERATE PRECIPITATION. THUS WILL MAINTAIN A DRY FORECAST. MIN TEMPS UPPER TEENS TO AROUND 20 NE TO THE MID 20S FAR SOUTH AND WEST. && .SHORT TERM /SUNDAY THROUGH MONDAY/... AS OF 300 AM FRIDAY... SURFACE HIGH PRESSURE OVER THE AREA SUNDAY MORNING WILL QUICKLY SHIFT OFFSHORE BY SUNDAY AFTERNOON AS A QUICK MOVING S/W DISTURBANCE MOVES EASTWARD FROM THE NORTHERN PLAINS INTO THE GREAT LAKES REGION... WITH AND ASSOCIATED COLD FRONT APPROACHING THE AREA FROM THE NORTHWEST. IN RESPONSE TO THE APPROACHING SYSTEM... A MOIST SOUTH/SOUTHWESTERLY LOW LEVEL FLOW ATOP A DEPOSITED COLD SURFACE AIRMASS WILL INCREASE THROUGHOUT THE DAY ON SUNDAY... WITH PRECIP POSSIBLY DEVELOPING ACROSS WESTERN PORTIONS OF THE CWA. THE LATEST NAM CONTINUES TO BE AN OUTLIER IN BRING PRECIP IN DURING THE EARLY MORNING HOURS ON SUNDAY. IF THIS INDEED OCCURRED THEN WE MAY HAVE SOME P-TYPE ISSUES (GENERALLY SLEET AND/OR FREEZING RAIN) ACROSS MAINLY WESTERN PORTIONS OF THE AREA. HOWEVER... WITH BOTH THE GFS AND ECMWF REMAINING DRY UNTIL THE AFTERNOON ACROSS THE WESTERN PORTION OF THE AREA... WILL ONLY SHOW A CHANCE OF RAIN ACROSS THE WESTERN PIEDMONT DURING THE AFTERNOON HOURS (CHILLY RAIN THOUGH). NONETHELESS... WITH THE SURFACE RIDGE AXIS EXTENDING BACK INTO THE AREA AFTER IT MOVES OFFSHORE ALONG WITH SOME PRECIP POSSIBLE ACROSS AT LEAST WESTERN PORTIONS OF THE AREA BY AFTERNOON EXPECT SKIES WILL BE CLOUDY WITH HIGHS EXPECTED TO BE WELL BELOW NORMAL AGAIN. FOR NOW WILL ONLY LOWER PREVIOUS HIGH TEMPS BY A COUPLE OF DEGREES. THIS YIELDS HIGHS RANGING FROM THE UPPER 30S NW TO THE MID TO UPPER 40S SE. THE SURFACE COLD FRONT WILL APPROACH AND MOVE THROUGH CENTRAL NC ON SUNDAY NIGHT INTO MONDAY... HELPING TO SOUR OUT ANY COLD AIR DAMMING AIRMASS THAT IS ABLE TO DEVELOP. HOWEVER... AHEAD OF THE FRONT EXPECT WE WILL SEE POCKETS OF LIGHT RAIN AND DRIZZLE TO DEVELOP ON SUNDAY NIGHT... WITH POSSIBLY A BAND OF LIGHT SHOWERS ON MONDAY ALONG AND AHEAD OF THE COLD FRONT. LOWS AND HIGHS WILL BE TRICKY AND DEPEND ON THE EXTENT OF THE CAD AND HOW QUICKLY THE FRONT MOVES THROUGH. FOR NOW WILL TREND TEMPS COOLER. LOW TEMPS MONDAY MORNING RANGING FROM THE MID 30S NORTH/NORTHWEST TO THE LOWER 40S SE. HIGHS MONDAY IN THE LOWER TO MID 50S (WITH A HIGH BUST POTENTIAL... ESPECIALLY IF THERE IS A LINGERING CAD BOUNDARY ACROSS THE AREA). && .LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 320 PM THURSDAY... THERE IS A LOT OF UNCERTAINTY AS TO PRECIPITATION TIMING AS SPLIT FLOW PATTERN CONTINUES INTO NEXT WEEK. INITIAL COLD AIR DAMMING SUNDAY WILL BE NUDGED OFFSHORE BY A NORTHERN STREAM SHORT WAVE AND ASSOCIATED COLD FRONT WHICH WILL BE MOVING ACROSS THE AREA SUNDAY NIGHT...WITH PRECIP AHEAD OF THE FRONT EARLY SUNDAY NIGHT SPREADING INTO THE EAST AFTER MIDNIGHT. HIGHS SUNDAY WILL BE MOSTLY IN THE LOW TO MID 40S. MINS WILL BE MODERATING A BIT SUNDAY NIGHT WITH HEAVIER CLOUDINESS AND SCOURING OF THE ARCTIC AIRMASS KEEPING MINS IN THE 30S. THE AIRMASS SETTLING IN BEHIND THE FRONT WILL BE CONSIDERABLY MILDER...BUT THE OVERALL PATTERN CONTINUES TO FAVOR YET ANOTHER TRANSITION TO A DAMMING SCENARIO BY TUESDAY. A BACKDOOR FRONT SAGS SOUTH ON MONDAY...WITH GOOD CHANCES OF RAIN WHICH WOULD DAMPEN/DELAY THE POTENTIAL WARMUP INTO MID WEEK. WILL MAINTAIN A WARMUP INTO THE 50S PRE-FROPA ON MONDAY...ALONG WITH RAIN WHICH WOULD PRODUCE AN IN- SITU COOLOFF ON TUESDAY...WITH HIGHS IN THE MID 40S WEST TO MID 50S EAST. PROBABILITY OF RAIN WILL REMAIN AT LEAST IN THE CHANCE CATEGORY ON WEDNESDAY INTO THURSDAY AHEAD OF A STRONG FRONTAL SYSTEM APPROACHING FROM THE WEST. THIS SLOW MOVING SYSTEMS TIMING IS NOT VERY CERTAIN AT THIS TIME...BUT IT LOOKS LIKE IT WOULD BE ON WEDNESDAY NIGHT...WITH WARM AIR ADVECTION AHEAD OF THE SYSTEM WARMING US INTO THE 60S ON WEDNESDAY AND EVEN THURSDAY AS COLD AIR ADVECTION IS DELAYED TIL LATE DAY. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 1245 AM FRIDAY... MAIN AVIATION HAZARD THROUGH MID MORNING WILL BE IFR/LIFR VISIBILITY DUE TO FREEZING FOG. THE PROBABILITY OF LIFR VISIBILITY IS HIGHEST IN THE COASTAL LAIN...SANDHILLS AND EASTERN PIEDMONT INCLUDING IN VICINITY OF KRWI...KFAY...AND KRDU. VISIBILITIES WILL IMPROVE BETWEEN 12Z-14Z. OTHERWISE...EXPECT A DECK OF HIGH END MVFR/LOW END VFR CEILINGS AROUND MID DAY THROUGH AFTERNOON AS AN UPPER LEVEL DISTURBANCE SKIRTS ACROSS THE REGION. SFC WINDS WILL GO FROM LIGHT AND VARIABLE EARLY TO NORTHERLY NEAR 10KTS BY LATE MORNING-EARLY AFTERNOON. EXPECT VFR CONDITIONS TONIGHT THROUGH SATURDAY NIGHT AS HIGH PRESSURE WILL BUILD INTO THEN SETTLE OVER THE AREA. AS THE HIGH SHIFTS EAST SUNDAY...SOUTHERLY RETURN FLOW WILL ADVECT A WARMER MOIST AIR MASS INTO OUR AREA...RESULTING IN AN INCREASED PROBABILITY OF MVFR CEILINGS ALONG WITH PATCHES OF RAIN. THE ADVERSE AVIATION WEATHER CONDITIONS ARE EXPECTED TO PERSIST INTO TUESDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER WEATHER ADVISORY IN EFFECT THROUGH 10 AM EST THIS MORNING FOR NCZ007>011-021>028-038>043- 073>078-083>086-088-089. && $$ SYNOPSIS...BADGETT NEAR TERM...WSS SHORT TERM...BSD LONG TERM...MLM AVIATION...WSS

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