Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 260752 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 252 AM EST MON JAN 26 2015 .SYNOPSIS... A STRONG UPPER LEVEL DISTURBANCE WILL CROSS THE REGION TODAY INTO EARLY TONIGHT. CHILLY HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST TUESDAY THROUGH WEDNESDAY NIGHT. A CLIPPER LOW PRESSURE SYSTEM WILL MOVE THROUGH THE AREA THURSDAY INTO EARLY FRIDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 250 AM MONDAY... INFRARED SATELLITE SHOWS LOW PRESSURE ASSOCIATED WITH THE CLIPPER SYSTEM MOVING IN FROM THE NORTHWEST OVER EASTERN KY AT THIS TIME. THIS SYSTEM WILL COMBINE WITH SOUTHERN STREAM MOISTURE OFF OF THE SOUTHWEST ATLANTIC TO AND RESULT IN A DEEPENING LOW PRESSURE SYSTEM THAT IS EXPECTED TO STRENGTHEN CONSIDERABLY AS IT MOVES UP THE EASTERN SEABOARD MONDAY INTO TUESDAY. CENTRAL NC WILL NOT HAVE TO DEAL WITH THE EXTENSIVE PLUME OF MOISTURE OVER THE OCEAN SO THE WAVE...WHICH IS PROGGED TO MOVE ACROSS NORTHERN SECTIONS OF THE THE CWA LATER TODAY WILL NOT BRING MUCH PRECIPITATION WITH IT. WHAT IT DOES BRING WILL BE IN THE FORM OF RAIN AS AND MAINLY ACROSS THE NORTHERN HALF OF THE CWA AS TEMPERATURES RISE INTO THE UPPER 40S TO LOWER 50S ACROSS TEH SOUTH. TIMING IS TRICKY AS IT LOOKS LIKE THERE COULD BE DIFFERENT PERIODS OF RAIN AS SMALLER WAVE IMPULSES MOVE THROUGH THE AREA BRINING POCKETS OF FAVORABLE DYNAMICS. THERMODYNAMICS WILL ALSO GET BETTER AFTER 18Z AND MODELS HINT AT SOME INSTABILITY THROUGH 00Z WITH VERY SKINNY...MOSTLY ELEVATED CAPE AND GOOD LAPSE RATES. THEREFORE CANNOT RULE OUT AN ISOLATED THUNDERSTORM LATE THIS AFTERNOON. AFTER 00Z THE LOW REALLY BEGINS TO DEEPEN OFF OF THE COAST AND THE PRESSURE GRADIENT OVER CENTRAL NC WILL TIGHTEN UP CAUSING BREEZY NORTHERLY WINDS WITH GUSTS OF 20-25 KTS POSSIBLE INTO THE OVERNIGHT HOURS MONDAY NIGHT INTO TUESDAY MORNING. WITH BREEZY WINDS AND SOME CLOUDS LINGERING IN THE EAST...RADIATIONAL COOLING PROSPECTS WILL NOT BE AS GOOD AS BACK TO THE WEST WHERE BOTH WIND AND CLOUD COVER SHOULD BE LESS. LOW TEMPERATURES WILL BOTTOM OUT IN THE UPPER 20S WEST TO LOWER 30S IN THE EAST.
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&& .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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AS OF 250 AM MONDAY... BY TUESDAY MORNING...LOW PRESSURE OFF OF THE NEW ENGLAND COAST WILL HAVE EVOLVED INTO A MATURE NOR`EASTER AND HAVE GROWN CONSIDERABLY IN SIZE. CENTRAL NC WILL SET UP JUST ON THE WESTERN SIDE OF THE UPPER LEVEL TROUGH AXIS WITH NORTHERLY WINDS AT THE SURFACE AND NORTHWESTERLIES ALOFT. MODELS CURRENTLY SHOW VARYING DEGREES OF WRAP AROUND MOISTURE STILL AFFECTING EASTERN PORTIONS OF THE CWA INTO TUESDAY MORNING. WHILE IMPACTS OF THIS WILL BE MINUTE...IF SATURATION UP THROUGH THE SNOW GROWTH ZONE HOLDS ON LONG ENOUGH...THERE IS A CHANCE OF SEEING SOME SNOW FLURRIES OR A BRIEF SNOW OR RAIN SHOWER ON TUESDAY MORNING. BEST CHANCES FOR THIS WILL BE ACROSS THE NORTHEASTERN COUNTIES OF THE CWA. THIS VERY BRIEF ACTIVITY COULD CONTINUE ON AND OFF THROUGH TUESDAY MORNING BEFORE THE STORM EVENTUALLY MOVES FAR ENOUGH TO THE NORTHEAST TO PUT CENTRAL NC IN THE COLD AND DRY SECTOR. THE EFFECT OF ALL THAT COLD AIR ADVECTION WILL BE A MUCH COOLER DAY ON TUESDAY WITH HIGHS IN THE LOW TO MID 40S NORTHEAST TO SOUTHWEST. COUPLE THAT WITH A BREEZY NORTHERLY WIND IT WILL FEEL MORE LIKE THE UPPER 20S TO LOWER 30S THAN IT WILL THE 40S. DRYING WILL CONTINUE INTO TUESDAY NIGHT WITH DEWPOINTS FALLING INTO THE TEENS AND LOW TEMPERATURES IN THE MIDDLE 20S.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... AS OF 210 AM MONDAY... WED/WED NIGHT: QUIET WEATHER WITH MID LEVEL SHORTWAVE RIDGING SHIFTING OVERHEAD AS HIGH PRESSURE RIDGING MOVES OVERHEAD. COLUMN IS STABLE AND FAIRLY DRY WED... SO EXPECT PLENTY OF SUNSHINE. BELOW- NORMAL THICKNESSES (BY 25-30 M) AND STATISTICAL GUIDANCE SUPPORT COOL HIGHS OF 42-47. HIGH CLOUDS WILL INCREASE AND THICKEN WED NIGHT... WITH A FLATTENING AND ACCELERATING WRLY FLOW ALOFT AND INITIALLY WEAK MID LEVEL DPVA AHEAD OF A CLIPPER SHORTWAVE TROUGH DIVING THROUGH THE UPPER MIDWEST. THESE HIGH CLOUDS MAY TAKE THE EDGE OFF AN OTHERWISE GOOD NIGHT FOR RADIATIONAL COOLING... WITH GENERALLY LIGHT WINDS AND LOW DEWPOINTS... BUT STILL EXPECT CHILLY LOWS MOSTLY IN THE MID 20S. THU/THU NIGHT: THIS WILL BE OUR NEXT CHANCE AT PRECIP... ALTHOUGH SPECIFIC TIMING AND AMOUNTS ARE IN QUESTION AS GFS/ECMWF SOLUTIONS DIVERGE. THE GREAT LAKES SHORTWAVE TROUGH WILL TRACK ESE THEN EASTWARD ACROSS THE NORTHEAST/MIDATLANTIC STATES -- TRACKING THROUGH THE BASE OF THE POLAR LOW OVER HUDSON BAY -- WHILE ITS CORRESPONDING SURFACE LOW CROSSES THE OH VALLEY AND MIDATLANTIC COAST. GFS BUFR SOUNDINGS SHOW CLOUD BASES STEADILY LOWERING THU MORNING AS LOW LEVEL FLOW STRENGTHENS FROM THE WSW... PUSHING PW VALUES UP... ALTHOUGH THEY PEAK AT JUST SLIGHTLY ABOVE-NORMAL VALUES... WITH A LINGERING DRY SUBCLOUD LAYER OVER MUCH OF THE CWA. MOISTURE IS DEEPEST AND MOST PRONOUNCED IN THE EASTERN PART OF THE FORECAST AREA IN BOTH THE GFS AND ECMWF... HOWEVER THE ECMWF AND ITS DEEPER WAVE GENERATES MORE QPF MUCH LATER (THU EVENING/NIGHT) COMPARED TO THE LIGHTER/EARLIER GFS (BEST PRECIP CHANCES THU MORNING). WILL LEAN TOWARD THE ECMWF... WHICH HAS DONE BETTER SHOWING DEEPER WAVES IN RECENT WEEKS... BUT WILL KEEP POPS NO GREATER THAN 20-30% LATE THU THROUGH THU NIGHT... FOCUSED ON THE EASTERN CWA. OVERALL MOISTURE INFLUX DOES NOT APPEAR SUFFICIENT ENOUGH TO WARRANT ANYTHING MORE THAN LIGHT QPF. SURFACE WET BULBS SHOULD BE INCHING ABOVE THE FREEZING MARK BY THE TIME PRECIP BEGINS... AND THE LATER ARRIVAL TIME SHOULD ENSURE THAT TEMPS THU NIGHT STAY MOSTLY ABOVE FREEZING. EVEN SO... WE`RE LIKELY TO SEE DRYING ALOFT THU NIGHT AFTER THE MID LEVEL TROUGH AXIS SWINGS THROUGH... WHICH WOULD LIMIT THE NON-LIQUID PRECIP THREAT ANYWAY. TOTAL QPF SHOULD BE LIGHT... UNDER A QUARTER INCH. HIGHS THU 47-52. LOWS THU NIGHT IN THE MID-UPPER 30S. FRI-SUN: THE POLAR FRONT DROPS TO OUR SOUTH FRI... AND LOW LEVEL THICKNESSES SLIP BACK TO AROUND 20 M BELOW NORMAL... YIELDING BELOW- NORMAL HIGHS IN THE MID 40S TO LOWER 50S DESPITE FAIR SKIES AS COOL HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. LOWS FRI NIGHT IN THE MID-UPPER 20S. UNCERTAINTY INCREASES FOR SAT/SUN AS THE GFS/ECMWF SOLUTIONS CONTINUE TO DIVERGE IN IMPORTANT WAYS. BOTH HAVE A POLAR LOW OVER HUDSON BAY/JAMES BAY AND ANOTHER LOW OVER NRN BAJA EARLY SAT. THE GFS REMAINS FOCUSED ON THE POLAR STREAM... TAKING YET ANOTHER CLIPPER WAVE THROUGH THE DAKOTAS AND MIDWEST THROUGH THE NORTHEAST AND MIDATLANTIC THROUGH SUN... BRINGING ENHANCED CLOUDINESS AND PERHAPS LIGHT PRECIP TO CENTRAL NC SAT (LIMITED BY THE WEAK MOISTURE RETURN). THE ECMWF ON THE OTHER HAND IS MORE FOCUSED ON THE SOUTHERN STREAM... EASING THE BAJA LOW SLIGHTLY EASTWARD INTO NW MEXICO WITH SURFACE LOW PRESSURE FORMING IN THE NW GULF... WHILE SRN STREAM ENERGY BEGINS TO SHEARS ENE TOWARD NC. THE LATTER SOLUTION IS WARMER AND DRIER BUT STARTS TO BRING IN MOIST OVERRUNNING FLOW BY LATE SUN. GIVEN THIS DISPARITY... PREFER JUST A SMALL CHANCE POP ON SUN FOR NOW... WITH TEMPS REMAINING BELOW NORMAL. -GIH && .AVIATION /06Z MONDAY THROUGH FRIDAY/... AS OF 105 AM MONDAY... 24 HOUR TAF PERIOD: VFR CONDITIONS CONTINUING TO PREVAIL THIS MORNING AS HIGH CLOUDS ARE NOW OVERSPREADING THE AREA FROM THE WEST IN ASSOCIATION WITH THE APPROACHING CLIPPER SYSTEM. BETWEEN NOW AND 12Z MODELS AGREE ON SOME LOWERING OF CEILINGS BUT UPSTREAM OBSERVATIONS HAVE YET TO SHOW MUCH OF A HINT OF THIS. THIS IS A LOW CONFIDENCE FORECAST AT THIS TIME AND WILL COVER IN THE TAFS WITH SOME MVFR VISIBILITIES AND CEILINGS IN THE NORTHWEST LATER THIS MORNING BUT WILL HOLD OFF IN THE EAST ON ANY DETERIORATION IN CONDITIONS AT KRDU AND KRWI UNTIL LATER IN THE AFTERNOON. KFAY MAY REMAIN VFR THROUGH THE TAF PERIOD AS MOST OF THE LIGHT RAIN ASSOCIATED WITH THIS SYSTEM IS EXPECTED TO REMAIN ACROSS THE NORTH. FORECAST SOUNDINGS SHOW SOME ELEVATED INSTABILITY LATER IN THE AFTERNOON AND AN ISOLATED THUNDERSTORM CANNOT BE RULED OUT BUT THIS WILL BE THE EXCEPTION TO THE RULE. AS THE WAVE PASSES THROUGH WINDS WILL SHIFT TO NORTHWESTERLY AND BEGIN GUSTING UP TO 20-25 KTS...PRIMARILY AFTER 00Z TUESDAY. GUSTS WILL CONTINUE THROUGH THE END OF THE TAF PERIOD. LONG TERM: ONCE VFR CONDITIONS RETURN ON THE HEELS OF THIS SYSTEM...THEY SHOULD REMAIN VFR UNTIL THE NEXT SYSTEM APPROACHES FORM THE NORTHWEST ON THURSDAY NIGHT INTO FRIDAY. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...ELLIS SHORT TERM...ELLIS LONG TERM...HARTFIELD AVIATION...ELLIS

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