Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 010845 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 345 AM EST SUN MAR 1 2015 .SYNOPSIS... WHILE COLD HIGH PRESSURE WILL EXTEND ACROSS THE AREA TODAY...INCREASING MOISTURE WILL HELP PROVIDE FOR UNSETTLED WEATHER. A COLD FRONT WILL MOVE THROUGH THE AREA MONDAY...FOLLOWED BY HIGH PRESSURE FOR TUESDAY...BEFORE ANOTHER COLD FRONT MOVES INTO THE REGION LATE WEDNESDAY. && .NEAR TERM /THROUGH TODAY/...
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AS OF 345 AM SUNDAY... TODAY...RIDGE EXTENDING FROM PARENT ARCTIC HIGH OVER THE NORTHERN MID ATLANTIC MAINTAIN A SUPPLY OF COLD DRY AIR INTO CENTRAL NC THIS MORNING. RETURN SLY FLOW ON THE BACKSIDE OF THE RETREATING 925-850MB HIGH OFF THE SE U.S. COAST ADVECTING OVER THE COLD STABLE AIR MASS AT THE SURFACE. THIS HAS RESULTED IN PATCHES OF LIGHT PRECIP TO BEAK OUT OVER OUR FAR SOUTHERN COUNTIES SHORTLY AFTER MIDNIGHT ...AND BEGINNING TO SPREAD ACROSS THE WESTERN PIEDMONT AT 08Z. WITH SFC DEWPOINTS SPREAD OF 12-16 DEGREES ACROSS THE PIEDMONT AND NORTHERN COASTAL PLAIN...EVAPORATIVE COOLING SHOULD DROP SFC TEMPS TO BELOW FREEZING FOR SEVERAL HOURS ONCE THE PRECIPITATION SETS IN. OVER THE FAR SOUTH-SE...THIS TIME BELOW FREEZING SHOULD BE NO MORE THAN A COUPLE OF HOURS (IF THAT). APPEARS BEST THREAT FOR ICE ACCRUAL OF A TENTH OF AN INCH OR A LITTLE MORE WILL BE ACROSS THE FAR NORTHERN PIEDMONT/VA BORDER COUNTIES...AND INTO THE NORTHERN SECTIONS OF FORSYTH...GUILFORD AND ALAMANCE COUNTIES. ELSEWHERE...EXPECT ENOUGH ICE ACCRUAL ON EXPOSED SURFACE OBJECTS AS WELL AS BRIDGES AND OVERPASSES TO FORM A THIN GLAZE...ENOUGH TO MAKE TRAVEL HAZARDOUS IN SPOTS ACROSS THE PIEDMONT THIS MORNING. FAIRLY SUBSTANTIAL WARM NOSE ALOFT (APPROACHING 8 DEGREES C IN THE NW PIEDMONT BY LATE MORNING) MAY BE ENOUGH TO OVERCOME THE SUB FREEZING CONDITIONS AT THE SURFACE. THUS WHILE SFC TEMPS IN THE NORTHERN PIEDMONT MAY BE 31-32 DEGREES BY MID DAY...ADDITIONAL ICE ACCRUAL WILL BE SEVERELY LIMITED. PLAN TO MAINTAIN ADVISORY ACROSS THE FAR NORTH-NW UNTIL 4 PM BUT WILL ASSESS TEMP RESPONSE LATER THIS MORNING WITH A POSSIBILITY OF ENDING THE ADVISORY A FEW HOURS EARLIER. ELSEWHERE CURRENT ADVISORY END TIMES APPEAR ON TARGET. MAX TEMPS THIS AFTERNOON DEPENDENT UPON ON HOW EXTENSIVE THE PRECIP BECOMES AND WHEN IT TAPERS OFF. COUNTING ON PRECIP LINGERING THROUGH A GOOD PART OF THE AFTERNOON ACROSS THE EAST SO HAVE LOWERED TEMPS THERE A FEW DEGREES FROM PREVIOUS FORECAST. CONVERSELY...HAVE ADJUSTED MAX TEMPS UP A DEGREE OR TWO ACROSS THE WEST-SW WHERE PRECIP MAY TAPER OFF BY EARLY-MID AFTERNOON.
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&& .SHORT TERM /TONIGHT AND MONDAY/...
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AS OF 345 AM SUNDAY... TONIGHT...EXTENSIVE LOW CLOUDS AND AREAS OF FOG EXPECTED WHILE A SLY SFC WIND WILL BEGIN TO STIR AS A COLD FRONT APPROACHES FROM THE WEST- NW. THESE CONDITIONS SHOULD CAUSE TEMPS TO HOLD STEADY OVERNIGHT. MIN TEMPS IN THE MID-UPPER 30S. MONDAY...SFC COLD FRONT SHOULD CROSS THE AREA IN THE MORNING. APPEARS MOISTURE DEPTH FAIRLY LIMITED TO GENERATE ANY PRECIP ACROSS THE NW BUT MAY BE ENOUGH ACROSS THE FAR SOUTH-SE TO DEVELOP A FEW PATCHES OF LIGHT RAIN. NWLY FLOW BEHIND THE FRONT WILL AID TO ADVECT A DRIER AIR MASS IN THE REGION. THIS WILL SLOWLY ERODE CLOUD COVERAGE FROM THE NW DURING THE AFTERNOON. SHOULD SEE TEMPS REBOUND INTO THE LOW AND MID 50S WITH PARTIAL SUNSHINE OVER MOST OF THE PIEDMONT BY AFTERNOON (LESS SO ACROSS THE FAR SOUTH-SE). FAVORED COOLER NAM MOS GUIDANCE VERSUS THE WARMER MOS GUIDANCE.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... AS OF 320 PM SUNDAY... MONDAY NIGHT AND TUESDAY: SURFACE HIGH PRESSURE LOCATED JUST TO THE NORTH OF CENTRAL NC AND AND MID LEVEL RIDGING EXTENDING INTO THE AREA FROM THE SOUTH WILL BOTH QUICKLY SHIFT EASTWARD ON MONDAY NIGHT INTO TUESDAY. HOWEVER... THE LINGERING COLD DRY SURFACE AIR DEPOSITED BY THE SURFACE HIGH WILL AGAIN SET THE STAGE FOR AN INSITU CAD EVENT ON TUESDAY INTO TUESDAY NIGHT... POSSIBLY LINGERING INTO WEDNESDAY MORNING ACROSS THE FAR NORTHWEST PIEDMONT. WARM MOIST AIR WILL INCREASING IN SOUTHERLY TO SOUTHWESTERLY FLOW ALOFT. GIVEN THIS AND THE LINGERING COLD SURFACE AIRMASS... WE SHOULD SEE SOME ISENTROPICALLY DRIVEN PRECIP DEVELOP TUESDAY MORNING INTO THE AFTERNOON. TUESDAY MORNING LOW TEMPS ARE EXPECTED TO BE AROUND 30 NORTH TO NEAR 40 SOUTH. MODELS CONTINUE TO BRING THE LIGHT PRECIP IN AFTER SURFACE TEMPS AND DEWPOINTS INCREASE ENOUGH TO AVOID AND NUISANCE FREEZING RAIN. HOWEVER... HIGH TEMPS WILL BE WELL BELOW NORMAL AND GREATLY AFFECTED BY THE CAD AIRMASS. MAV STATISTICAL GUIDANCE APPEARS TO BE WAY TOO WARM FOR TUESDAY... WITH THE RAW GFS TEMPS CLOSER TO MET GUIDANCE VALUES. FOR NOW WILL LOWER TEMPS FURTHER... AND THIS MAY NOT EVEN BE FAR ENOUGH. WILL WO WITH HIGH TEMPS RANGING FROM THE UPPER 30S NORTH TO NEAR 50 IN THE FAR SOUTHEAST. TUESDAY NIGHT THROUGH THURSDAY NIGHT: ANOTHER STRONG ARCTIC COLD FRONT WILL APPROACH THE REGION ON TUESDAY NIGHT... BEFORE SLOWLY MOVING ACROSS THE AREA WEDNESDAY INTO THURSDAY MORNING. THE FRONT IS EXPECTED TO BECOME PARALLE WITH THE MID LEVEL FLOW AS THE MID/UPPER LEVEL TROUGH BECOMES MORE OF A FULL LATITUDE TROUGH... WHICH APPEARS TO PHASE SOME THE THE SOUTHERN STREAM ENERGY WITH THE NORTHERN STREAM... RESULTING IN A DEEP FETCH OF SOUTHWESTERLY MID LEVEL FLOW... ALONG WITH SEVERAL SURFACE LOWS TRACKING ALONG THE FRONT FROM TIME TO TIME. MOST OF THE SHOWERS WILL BE ALONG AND BEHIND THE FRONT... MAINLY FROM WEDNESDAY MID-MORNING INTO THE AFTERNOON UNTIL LATE THURSDAY (WITH A GOOD CHANCE OF PRECIP... POSSIBLY SOME HEAVY AMOUNTS OF RAIN). IN ADDITION... MODELS HAVE TRENDED FASTER WITH SURGING THE STRONG/DEEP COLD LOW LEVEL AIRMASS INTO THE REGION. IF THIS WERE TO OCCUR... WE COULD POSSIBLE SEE SOME WINTRY P-TYPES ON THURSDAY. HOWEVER... GIVEN WE ARE STILL TALKING ABOUT DAY 5 IN THE FORECAST AND WE ARE NOW IN THE MONTH OF MARCH... WILL WAIT TO ADD ANY NON-LIQUID P-TYPE TO THE FORECAST. DRY WEATHER IS EXPECTED TO RETURN FOR AT LEAST FRIDAY. HOWEVER... THE SYNOPTIC PATTERN MAY REMAIN CONDUCIVE FOR WAVES OF LOW PRESSURE TO DEVELOP AND TRACK ALONG THE FRONT... WHICH IS EXPECTED TO BE LOCATED OFF THE CAROLINA COAST LATE WEEK INTO THE WEEKEND. THUS... WE COULD CONCEIVABLY SEE SOME PRECIP IF ONE SUCH SYSTEM DEVELOPS NEXT WEEKEND. TEMPS DURING THE MEDIUM RANGE WILL INCLUDE SOME DECENT SWINGS... WITH HIGHS TEMPS WEDNESDAY IN THE 60S AND 70S... THURSDAY 40S AND 50S (MAYBE COLDER)... WITH FRIDAY BACK IN THE 40S (WITH MAYBE SOME 30S EVEN). WE WILL SEE SOME MODERATING BY SATURDAY... GENERALLY BACK INTO THE 50S... GIVEN WE REAMIN DRY. LOWS WILL FOLLOW A SIMILAR PATTERN. AS MENTIONED ABOVE... ALL PRECIP AS OF NOW APPEARS TO BE IN THE FORM OF LIQUID FOR THE MEDIUM RANGE... OUTSIDE OF *MAYBE* A BRIEF PERIOD AS THE PRECIP ENDS ON THURSDAY. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 100 AM SUNDAY... ADVERSE AVIATION CONDITIONS WILL OVERSPREAD CENTRAL NC FROM THE SOUTH THROUGH 12Z WITH MVFR/IFR CEILINGS AND PATCHES OF LIGHT RAIN OR LIGHT FREEZING RAIN. BY 12Z...EXPECT WIDESPREAD LOW END MVFR/IFR CEILINGS ALONG WITH AREAS OF LIGHT FREEZING RAIN OVER THE PIEDMONT AND SANDHILLS...AND EITHER LIGHT RAIN OR FREEZING RAIN IN THE COASTAL PLAIN. BETWEEN 12Z- 15Z...THE LIGHT FREEZING RAIN IN THE SANDHILLS AND EASTERN PIEDMONT SHOULD TRANSITION TO A COLD RAIN. IN ADDITION...A STRENGTHENING LOW LEVEL JET JUST ABOVE THE SURFACE WILL RESULT IN LOW LEVEL WIND SHEAR CONDITIONS...ESPECIALLY IN VICINITY OF KRDU...KFAY AND KRWI. THE FREEZING RAIN IN THE NW PIEDMONT WILL GRADUALLY CHANGE TO A COLD RAIN BY MID AFTERNOON. ELSEWHERE EXPECT AREAS OF LIGHT RAIN OR DRIZZLE WITH IFR/LIFR CEILINGS. WHILE THE BULK OF THE RAIN WILL TAPER OFF BY SUNSET...WIDESPREAD FOG AND DRIZZLE ALONG WITH IFR/LIFR CEILINGS WILL PERSIST INTO TONIGHT. MONDAY...A COLD FRONT WILL CROSS THE REGION. WEST-NW FLOW BEHIND THE BOUNDARY WILL ADVECT A DRIER AIR MASS...LEADING TO A SCOURING OF THE MURKY NEAR SURFACE AIR MASS. EXPECT IMPROVING AVIATION CONDITIONS LATE MONDAY THROUGH MONDAY NIGHT. HIGH PRESSURE OVER THE AREA TUESDAY WILL PROVIDE VFR CONDITIONS. ANOTHER COLD FRONT WILL APPROACH WEDNESDAY AND CROSS THE REGION WEDNESDAY NIGHT AND THURSDAY. THIS WEATHER SYSTEM WILL LIKELY CAUSE ANOTHER PERIOD OF SUB VFR CONDITIONS ACROSS CENTRAL NC. && .RAH WATCHES/WARNINGS/ADVISORIES...
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WINTER WEATHER ADVISORY UNTIL 10 AM EST THIS MORNING FOR NCZ042-077- 078-083>086-088-089. WINTER WEATHER ADVISORY UNTIL NOON EST TODAY FOR NCZ008>011-024>028-040-041-043-073>076. WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR NCZ007-021>023-038-039.
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&& $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...BSD AVIATION...WSS

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