Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 280235 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1035 PM EDT FRI MAR 27 2015 .SYNOPSIS...A POTENT UPPER LEVEL TROUGH WILL MOVE THROUGH THE REGION OVERNIGHT. DRY HIGH PRESSURE WILL BUILD INTO THE REGION OVER THE WEEKEND. && .NEAR TERM /TONIGHT/... AS OF 1035 PM FRIDAY... SATELLITE IMAGERY AND 00Z RAOB DATA DEPICT A POTENT SHORTWAVE TROUGH OVER NORTHERN GA THIS EVENING...WITH ASSOCIATED 140 METER 500 MB HEIGHT FALLS (/12 HRS) FROM FFC TO GSO. THIS WILL BE A TEXTBOOK CASE FOR THE UTILITY OF Q-VECTORS...WHERE THE SIGN OF THE DIFFERENTIAL VORTICITY ADVECTION TERM IS FORECAST TO OVERWHELM THE FORCING FOR DESCENT ASSOCIATED WITH STRONG LOW-MID LEVEL CAA...AND RESULT IN STRONG AND FOCUSED Q-VECTOR CONVERGENCE SQUARELY OVERHEAD TONIGHT. IN FACT...NWP GUIDANCE...INCLUDING RECENT RUNS OF THE HRRR AND RAP...SUGGEST THE ASSOCIATED FORCING FOR ASCENT WILL PROVIDE FOR A RENEWED INCREASED IN (SHOWERY) PRECIPITATION COVERAGE OVER EAST- CENTRAL NC OVERNIGHT....WITH THE RELATIVE HIGHEST CHANCES IN TWO AREAS: 1) THE SOUTHERN RAH CWFA IN ASSOCIATION WITH THE AREA OF PRECIPITATION FORECAST TO TRACK ENE FROM OVER CENTRAL SC THIS EVENING...AND 2) A SEPARATE AREA OF SHOWERS FORECAST TO DEVELOP FROM CENTRAL VA TO THE NE NC PIEDMONT AND COASTAL PLAIN. OTHERWISE... SPRINKLES OR LIGHT RAIN IN ASSOCIATION WITH MID TO HIGH LEVEL- GENERATED PRECIPITATION WITHIN AN AXIS OF COUPLED SOUTHERN AND NORTHERN STREAM JET STREAKS OVERHEAD WILL STREAM NE ACROSS OUR REGION OVERNIGHT. AS AN ASIDE...THE PRESENCE AND RAPID STRENGTHENING OF THESE JETS DURING THE PAST 6-12 HOURS RESULTED IN SEVERAL REPORTS OF SEVERE FLIGHT LEVEL TURBULENCE OVER NC THIS PAST AFTERNOON AND EVENING. WHILE THE MAIN SFC FRONTAL ZONE HAD MOVED WELL OFFSHORE THE COAST OF THE CAROLINAS...A SECONDARY POLAR FRONT HAD JUST BEGUN TO SPILL EAST OF THE APPALACHIANS AT 02Z. THE ASSOCIATED COLDER AND DRIER AIR WILL SURGE SOUTHEASTWARD ACROSS CENTRAL NC WITH OCCASIONAL GUSTINESS UP TO 20 OR SO MPH OVERNIGHT; AND AS IT DOES SO...IT WILL CAUSE FREEZING LEVELS TO DROP AND BOUNDARY-LAYER-WET BULB THERMAL PROFILES TO COOL...SUCH THAT A FEW WET SNOW FLAKES COULD MIX WITH THE RAIN SHOWERS AFTER 4 AM MAINLY NE OF THE TRIANGLE...IN AREAS FROM HENDERSON TO WARRENTON TO NASHVILLE AND ROCKY MOUNT - A CLASSIC CASE ALSO OF COLD AIR CHASING THE MOISTURE. TEMPERATURES BY MORNING ARE FORECAST TO RANGE FROM AROUND 30 NW TO AROUND 40 SE. && .SHORT TERM /SATURDAY AND SATURDAY NIGHT/... AS OF 230 PM FRIDAY... ...FREEZE WATCH HAS BEEN ISSUED FOR SOUTHER PORTIONS OF THE FORECAST AREA SATURDAY NIGHT/SUNDAY MORNING... A DEEP UPPER TROUGH(H5 2 TO 3 STANDARD DEVIATIONS BELOW NORMAL)...WITH EQUALLY ANOMALOUS H8 TEMPERATURES OF -8 TO -10C WILL BE IN PLACE ACROSS THE EASTERN US SATURDAY-SATURDAY. DESPITE COMPLIMENTS OF FULL SUNSHINE...HIGHS SATURDAY WILL AVERAGE 15 TO 20 DEGREES BELOW NORMAL...WITH A STEADY 10 TO 15 MPH NWLY BREEZE MAKING IT FEEL EVEN COLDER. HIGHS RANGING FROM LOWER 40S NORTHWEST TO AROUND 50 SOUTHEAST. STRENGTHENING 1030MB SURFACE SLIDING EAST OVER THE CAROLINAS UNDERNEATH DRY DEEP NWLY FLOW ALOFT WILL PROVIDE OPTIMAL RADIATIONAL CONDITIONS. THUS...EXPECT LOWS SUNDAY MORNING TO LIE WITHIN THE COOLER 1275-1280M OBSERVED THICKNESS RANGE. LOWS IN THE LOWER TO MID 20S...WHICH WILL CHALLENGE RECORD MIN TEMPS AT AREA CLIMATE SITES. WILL ISSUE A FREEZE WATCH WITH THE AFTERNOON PACKAGE ACROSS THE SOUTHERN PORTIONS OF THE FORECAST AREA WHERE THE SPRING FROST/FREEZE PROGRAM IS ACTIVATED. && .LONG TERM /SUNDAY THROUGH FRIDAY/... AS OF 210 PM FRIDAY... TO BEGIN THE PERIOD...HIGH PRESSURE WILL QUICKLY MIGRATE OVER THE AREA...BECOMING SITUATED OFF THE SOUTHEAST COAST BY SUNDAY AFTERNOON/EVENING. AS A RESULT...TEMPS WILL BEGIN TO MODERATE SOME AS RETURN FLOW BEGINS TO SET UP OVER THE REGION...WITH GENERALLY MID 50S EXPECTED. OVERNIGHT...CLOUDS WILL INCREASE THROUGH THE OVERNIGHT HOURS AS ANOTHER SHORT WAVE/ASSOCIATED COLD FRONT APPROACHES THE AREA. THIS (ALONG WITH SOME WARM AIR ADVECTION) WILL KEEP TEMPS IN THE MID/UPPER 30S. AS THE AFOREMENTIONED FRONT CROSSES THE AREA ON MONDAY...PRECIP CHANCES WILL INCREASE. ALTHOUGH WITH VERY LIMITED MOISTURE RETURN EXPECTED...WILL NOT GO ANY HIGHER THEN LOW END CHANCE POP. DESPITE THE FRONTAL PASSAGE AND ITS ASSOCIATED CLOUDS AND LIGHT PRECIP... TEMPS WILL WARM EVEN MORE ON MONDAY (OVER SUNDAY) GIVEN THE WESTERLY DOWNSLOPE FLOW. HIGHS SHOULD RISE INTO THE 60S. EVEN MORE MODIFICATION WILL OCCUR INTO MID WEEK GIVEN MORE IN THE WAY OF SUNSHINE. HIGHS ON TUESDAY WILL BE MOSTLY IN THE UPPER 60S (MAYBE APPROACHING 70 DEGREES ACROSS THE SOUTH)...WITH MOSTLY LOWER 70S EXPECTED BY WEDNESDAY. OUR NEXT SOUTHERN STREAM SYSTEM IS PROGGED TO APPROACH THE AREA BY THE LATTER HALF OF THE WEEK. AS CAN BE EXPECTED THIS FAR OUT IN THE FORECAST PERIOD...CONFIDENCE IN THE EXACT DETAILS IS NOT HIGH. FOR NOW...WILL INTRODUCE POPS BACK INTO THE FORECAST BY THURSDAY...WITH PRECIP LINGERING INTO FRIDAY. TEMPS ARE EXPECTED TO REMAIN SLIGHTLY ABOVE NORMAL. && .AVIATION /00Z SATURDAY THROUGH TUESDAY/... AS OF 805 PM FRIDAY... 24-HR TAF PERIOD: MAINLY VFR CONDITIONS ACROSS THE AREA... WITH THE EXCEPTION OF SOME BRIEF MVFR CIGS/VISBYS WITH PATCHES OF LIGHT RAIN/DRIZZLE IN ASSOCIATION WITH AN UPPER LEVEL TROUGH CROSSING THE AREA. SKIES SHOULD BEGIN TO CLEAR BETWEEN 09-12Z... AND WINDS WILL BE FROM THE NW WITH GUSTS OF 15-20 KTS DURING THE AFTERNOON HOURS. LOOKING AHEAD: VFR CONDITIONS WILL RULE OVER THE WEEKEND AS HIGH PRESSURE BUILDS INTO THE REGION FROM THE WEST/NW. THE NEXT POTENTIAL FOR ADVERSE CONDITIONS WILL BE ASSOC/W AN UPPER LEVEL DISTURBANCE MONDAY AFTERNOON...WITH VFR CONDITIONS EXPECTED THEREAFTER. && .CLIMATE... WE COULD APPROACH RECORD LOW TERRITORY SUNDAY MORNING ON THE 29TH. BELOW ARE THE LIST OF THE RECORD MINIMUM TEMPERATURES FOR MARCH 29TH. RECORD MINIMUM TEMPERATURE GSO 20-1966 RDU 20-1966 FAY 24-1982 && .RAH WATCHES/WARNINGS/ADVISORIES... FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING FOR NCZ028-042-043-073>078-083>086-088-089. && $$ SYNOPSIS...CBL/VINCENT NEAR TERM...RAH SHORT TERM...CBL LONG TERM...KRD AVIATION...RAH/CBL CLIMATE...CBL

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