Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 300320 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1020 PM EST THU JAN 29 2015 .SYNOPSIS... A COLD FRONT WILL MOVE ACROSS THE REGION TONIGHT. HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST FRIDAY...WHICH WILL RESULT IN DRY CONDITIONS INTO THE WEEKEND. && .NEAR TERM /THROUGH FRIDAY/...
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AS OF 1020 PM EST THURSDAY... OVERNIGHT...MID LEVEL TROUGH AND ACCOMPANYING SFC COLD FRONT WILL CROSS CENTRAL NC OVERNIGHT. LEAD MID-UPPER LEVEL TROUGH RESPONSIBLE FOR THE BAND OF RAIN/SLEET THIS AFTERNOON HAS LONG EXITED THE REGION. FORCING WITH THE SFC FRONT MAY LEAD TO FEW LIGHT RAIN SHOWERS LATER TONIGHT...MAINLY EAST OF HIGHWAY 1. SFC FRONT SHOULD CROSS THE WESTERN PIEDMONT BETWEEN MIDNIGHT- 2AM...THE HIGHWAY 1 CORRIDOR 2-4 AM...AND EXIT OUR COASTAL PLAIN COUNTIES SHORTLY BEFORE DAYBREAK. DUE TO THE CLOUD COVER AND LIGHT MIXING...TEMPS WILL HOLD STEADY FOR A GOOD PART OF THE OVERNIGHT HOURS THAN FALL TOWARD DAYBREAK WITH THE PASSAGE OF THE 850MB TROUGH. MIN TEMPS NEAR 30 NW TO UPPER 30S SE. -WSS A BLUSTERY/WINDY DAY UNDER CHILLY TEMPS IN STORE ON FRIDAY AS STRONG HIGH PRESSURE SLIDES EAST WHILE THE PRESSURE GRADIENT REMAINS QUITE TIGHT BETWEEN THE RIDGE AND DEEPENING LOW PRESSURE OFF NEW ENGLAND. APPEARS GUSTS TOPPING 30-35 MPH AT TIMES MAY APPROACH ADVISORY LEVELS FOR A BRIEF PERIOD GIVEN DEEP MIXING AND AIDED VIA A FINAL PASSING MID LEVEL WAVE TO THE NORTH. OTHERWISE STRONG SUBSIDENCE SHOULD LEAD TO MAINLY SUNNY SKIES WITH HIGHS MOSTLY IN THE 40S GIVEN HEATING OF VERY DRY AIR.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... AS OF 235 PM EST THURSDAY... COLD ADVECTION CONTINUES AS SURFACE HIGH APPROACHES FROM WEST BUT WITH SURFACE HIGH STILL WEST OF APPALACHIANS BY 12Z SAT DO NOT THINK CENTRAL NORTH CAROLINA WILL COMPLETELY DECOUPLE...DESPITE MAINLY CLEAR SKIES. CHANCE OF SOME CIRRUS MOVING IN LATE FRIDAY NIGHT TOO THOUGH. SO WILL NOT GO ANY COLDER THAN GUIDANCE FOR LOWS...WHICH IS PRETTY CONSISTENT IN THE LOW 20S MOST OF THE AREA. DRY HIGH PRESSURE DOMINATES THEN THROUGH SATURDAY NIGHT...AND MAY CONTINUE ITS INFLUENCE INTO EARLY SUNDAY BEFORE MOISTURE INCREASES FROM THE WEST AHEAD OF NEXT CLIPPER TYPE SYSTEM. WITH DRY LOW LEVELS INITIALLY IT COULD TAKE PRECIP A WHILE TO MAKE IT TO THE GROUND ON SUNDAY...STARTING IN WEST BY MIDDAY AND SPREADING TO THE EAST BY LATE IN DAY OR EARLY EVENING. GIVEN DAYTIME START TO PRECIP AND WARM ADVECTION AHEAD OF DEVELOPING BUT RATHER WEAK SURFACE LOW OVER TENNESSEE VALLEY...NO CONCERNS ABOUT ANY LIGHT WINTRY PRECIP DESPITE EVAPORATIVE COOLING INTO DRY AIRMASS. MODEL CONSENSUS DOES AGREE THAT PRECIP CHANCES WILL BE HIGHEST SUNDAY NIGHT AND QPF VALUES OF A QUARTER INCH OR HIGHER ARE POSSIBLE...GFS WITH ALMOST A HALF AN INCH...BUT SEE NO CONCERNS AT ALL FOR BOUNDARY LAYER OF SURFACE TEMPS TO SUPPORT ANY WINTRY PRECIP EVEN OVERNIGHT AHEAD OF THE FRONT. IN FACT IT MAY BE WARMING OVERNIGHT SUNDAY NIGHT...BUT AS YET HAVE NOT REFLECTED THAT ON HOURLY TEMPS...BUT DO NOT HAVE IT DROPPING VERY MUCH EITHER SUNDAY NIGHT. LATEST MEX GUIDANCE FROM GFS MUCH MILDER AND TRENDED UP A BIT BUT NOT THAT HIGH AS OF YET. LOWS SUNDAY NIGHT IN UPPER 30S NORTHWEST TO MID 40S SOUTHEAST...BUT SEE POTENTIAL FOR IT TO BE EVEN MILDER. && .LONG TERM /MONDAY THROUGH WEDNESDAY/... AS OF 300 PM EST THURSDAY... MONDAY: MODEL TRENDS...AND NOW A LITTLE BETTER CONSENSUS...TO DEEPEN AND SLOW THE EXITING LOW PRESSURE SYSTEM AND FRONT AS IT MOVES OFF THE MID ATLANTIC COAST COULD NOW MEAN SOME LINGERING SHOWERS ACROSS CENTRAL NORTH CAROLINA FOR AT LEAST EARLY IN THE DAY MONDAY...BUT SHOULD PUSH EAST BY AFTERNOON. STILL GOING TO KEEP A SLIGHT CHANCE EAST OF RALEIGH FOR SECOND HALF OF DAY IN CASE ADDITIONAL SLOWING OCCURS. COLDER AIR THEN ALSO A LITTLE SLOWER TO FILTER IN BEHIND SYSTEM...SO BUMPED UP HIGHS JUST A COUPLE DEGREES. MAY END UP BEING NEARLY STEADY MUCH OF DAY AND DROPPING QUICKLY BY EARLY AFTERNOON BUT GIVEN THE UNCERTAINTY IN TIMING BEING FOUR DAYS OUT...DECIDED NOT TO SHOW THIS NON DIURNAL TREND JUST YET. MONDAY NIGHT THROUGH TUESDAY NIGHT: CHILLY HIGH PRESSURE TO BUILD IN BEHIND THE FRONT...1025 TO 1030 MB STRENGTH. HIGH CONFIDENCE THAT ANY PRECIP WILL BE WELL EAST OF THE AREA BY MONDAY NIGHT...WITH THE COLD AND DRY HIGH PRESSURE IN CONTROL THROUGH TUESDAY AND INTO TUESDAY NIGHT....BUT MILDER TUES NIGHT WITH WARM ADVECTION AND CLOUD COVER ALREADY INCREASING AHEAD OF NEXT SYSTEM IN THIS PROGRESSIVE PATTERN. MORE UNCERTAINTY COMES INTO PLAY BY MID WEEK AS NORTHER AND SOUTHERN BRANCHES OF THE JET STREAM TRY TO PHASE...AND A COLD FRONT APPROACHES FROM THE WEST BY LATE WED...WHILE SHORT WAVE ENERGY IN THE SOUTHERN STREAM TAPS SOME MOISTURE FROM THE GULF WHICH HEADS NORTHEAST TOWARD NORTH CAROLINA. CURRENTLY THERE ARE FAIRLY SIGNIFICANT DIFFERENCES IN THE TIMING AND AMOUNT OF MOISTURE WITH THIS SYSTEM...WITH 00Z ECMWF FASTER AND INCREASING THE CHANCES FOR PRECIP AS EARLY AS LATE TUESDAY NIGHT INTO WED MORNING...WITH THE 12Z GFS NOT UNTIL DURING THE DAY WED. MOST GFS ENSEMBLES SEEM TO BE IN THIS CAMP AS WELL. SO AM NOT INDICATING ANY CHANCE POPS UNTIL DURING THE DAY WED AT THIS POINT. GFS MODEL SOUNDINGS SUGGEST IF THIS COMES IN EARLY ENOUGH THERE COULD BE SOME LIGHT WINTRY MIX AT THE ONSET BUT THINK THIS WILL BE VERY LIGHT AND HAVE NO IMPACT. MOST LIKELY PRECIP WILL HOLD OFF UNTIL LATER WHEN BOUNDARY LAYER TEMPS ARE WARM ENOUGH TO SUPPORT RAIN ONLY. DO HAVE SOME CHANCE RAIN AND SNOW IN THE GRIDS FOR WHEN TEMPS ARE AT OR BELOW FREEZING EARLY WED...AND AGAIN LATE WED NIGHT BEHIND COLD FRONT...BUT THIS MAY AMOUNT TO NO MORE THAN FLURRIES. THEN BETTER CONFIDENCE IN BLUSTERY AND COLDER FOR THURSDAY BEHIND FRONT...AND MAY EVENTUALLY NEED TO GO COLDER THAN CURRENT FCST BUT HEDGING SOMEWHAT FOR NOW SINCE GFS IN PARTICULAR TENDS TO HAVE A COLD BIAS BEHIND FRONTS THAT FAR OUT. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... AS OF 740 PM THURSDAY... 24 HOUR TAF PERIOD: VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE 24 HOUR TAF PERIOD. HOWEVER... BREEZY NORTHWESTERLY WINDS ARE EXPECTED ON FRIDAY. A BAND OF PRE-FRONTAL SHOWERS AND SLEET HAS GENERALLY PUSHED TO THE EAST AND SOUTH OF THE AREA THIS EVENING... WITH BRIEF CLEARING FILTERING INTO THE AREA IN THE WAKE OF THE PRECIP. HOWEVER... VFR CLOUD COVER (GENERALLY THE LOWEST CLOUD BASES WILL BE IN THE 5 TO 7 KFT RANGE) WILL INCREASE LATE THIS EVENING INTO THE EARLY MORNING HOURS OF FRIDAY AS A COLD FRONT AND ASSOCIATED MID LEVEL TROUGH ALOFT APPROACHES AND MOVES ACROSS THE REGION. EXPECTED GENERALLY DRY CONDITIONS AS THE FRONT MOVES THROUGH THE AREA. HOWEVER... WE COULD SEE SOME SPOTTY SHOWERS ACROSS EASTERN AND SOUTHERN PORTIONS OF CENTRAL NC... WITH KFAY STANDING THE BEST CHANCE OF SEEING ANY OF THESE SHOWERS. GIVEN CONFIDENCE IS LOW FOR SHOWERS... WILL LEAVE OUT ANY MENTION OF PRECIP FROM THE TAFS. SKIES ARE EXPECTED TO CLEAR WITHIN A COUPLE OF HOURS AFTER SUNRISE AS THE MID LEVEL TROUGH AXIS SHIFTS TO THE EAST OF THE AREA. HOWEVER... BREEZY WNW TO NW WINDS WILL OCCUR FROM MID MORNING INTO THE AFTERNOON... WITH SUSTAINED WINDS IN THE 15 TO 20 MPH RANGE... WITH GUSTS OF UP TO 30 MPH POSSIBLE... MAYBE EVEN 35 MPH. LONG TERM: SUB-VFR CONDITIONS WILL BE POSSIBLE WITH A LOW PRESSURE SYSTEM THAT WILL CROSS THE AREA LATE SUNDAY INTO MONDAY. VFR CONDITIONS WILL PREVAIL ON TUESDAY AS HIGH PRESSURE BUILDS EAST BEHIND THIS SYSTEM. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...JK/BSD NEAR TERM...WSS/JH SHORT TERM...SK LONG TERM...SK AVIATION...BSD

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