Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 190735 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 334 AM EDT SUN OCT 19 2014 .SYNOPSIS....HIGH PRESSURE WILL BUILD ACROSS THE TN VALLEY TODAY AND SETTLE DIRECTLY OVER NC AND VA TONIGHT. THE HIGH WILL DRIFT OFFSHORE MON...AHEAD OF AN UPPER LEVEL TROUGH THAT WILL MOVE INTO OUR REGION MON NIGHT. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 330 AM SUNDAY... A COMPACT AND VIGOROUS SHORTWAVE TROUGH CENTERED DIRECTLY OVER CENTRAL NC AT 07Z WILL MOVE QUICKLY EAST AND OFFSHORE THE VA/NC COAST BY 12Z. DESPITE LIMITED MOISTURE...THE VIGOROUS AND CONCENTRATED LIFT AND PRESENCE OF THE COLD POOL ALOFT HAS ALSO SUPPORTED THE RECENT DEVELOPMENT OF SCATTERED...FAST-MOVING (45-50 MPH) SHOWERS FROM THE EASTERN SANDHILLS TO THE COASTAL PLAIN. ANY SUCH SHOWER ACTIVITY WILL COME TO AN ABRUPT END/MOVE EAST BEFORE DAYBREAK...SO SUBSIDENCE AND CLEARING IN STRONG HEIGHT RISES ALOFT... AND 1025 MB SURFACE HIGH PRESSURE BUILDING SOUTHEAST FROM THE UPPER MIDWEST...WILL OTHERWISE OVERSPREAD OUR REGION TODAY. A PERIOD OF BREEZY NORTHWEST WINDS CAN BE EXPECTED AS THE MIXED LAYER DEEPENS THIS MORNING AND TAPS INTO 20 KT WINDS JUST ABOVE THE SURFACE...MAINLY OVER THE COASTAL PLAIN...BEFORE LESSENING AS THE PRESSURE GRADIENT AND CAA RELAXES THIS AFTERNOON. PROJECTED 00Z LOW LEVEL THICKNESSES AROUND 1350 METERS WILL SUPPORT NOTICEABLY COOLER CONDITIONS DESPITE THE ABUNDANT SUNSHINE...GENERALLY IN THE MIDDLE 60S. TONIGHT: THE APPROACH OF A DEAMPLIFYING UPPER WAVE THAT WAS LOCATED OVER WESTERN OK THIS MORNING...AND A COMPLEX UPPER TROUGH AMPLIFYING SOUTHEASTWARD FROM CENTRAL CANADA...WILL RESULT IN INCREASING HIGH CLOUDS FROM THE WEST...PARTICULARLY AFTER MIDNIGHT. WITH THE CENTER OF THE SURFACE HIGH EXPECTED TO BE DIRECTLY OVERHEAD...CALM AND INITIALLY IDEAL RADIATIONAL COOLING CONDITIONS WILL SUPPORT QUICKLY FALLING TEMPERATURES AFTER SUNSET...WITH A SLOWER FALL OR NEUTRAL TENDENCY AS THE CIRRUS SPREAD EAST LATE. PROJECTED 12Z MON LOW LEVEL THICKNESSES BETWEEN 1345-1350 METERS SHOULD SUPPORT LOWS MOSTLY IN THE MIDDLE AND UPPER 30S...TO AROUND 40 DEGREES IN URBAN AREAS...SUPPORTIVE OF PATCHY FROST IN THE TYPICALLY COOLER AREAS.
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&& .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... AS OF 305 PM SATURDAY... SUNDAY...SFC HIGH PRESSURE WILL BUILD INTO THE REGION WHILE SUBSIDENCE IN THE WAKE OF THE EXITING S/W WILL RESULT IN SUNNY SKIES. 850MB TROUGH PROJECTED TO LIE ACROSS THE REGION. LOW LEVEL THICKNESSES WILL AVERAGE 20M BELOW NORMAL...YIELDING HIGH TEMPS ABOUT 5-7 DEGREES BELOW NORMAL. MAX TEMPS EXPECTED TO RANGE FROM THE MID-UPPER 60S NORTH TO NEAR 70 SOUTH. SUNDAY NIGHT...HIGH PRESSURE WILL RESIDE OVERHEAD INITIALLY THEN DRIFT EAST TOWARD DAYBREAK. UNDER THE CLEAR SKIES AND LIGHT/CALM WIND REGIME...TEMPS SHOULD PLUMMET AFTER SUNSET INTO THE 40S. A S/W APPROACHING CENTRAL NC IN THE WLY FLOW ALOFT MAY SPREAD HIGH LEVEL CLOUDS ACROSS CENTRAL NC PRIOR TO DAYBREAK. STILL SOME UNCERTAINTY AS TO THE COVERAGE/THICKNESS OF THIS CLOUD SHIELD. A THICKER CLOUD COVER WILL AID TO KEEP TEMPS UP WHILE A THINNER LAYER WILL NOT HAVE AN EFFECT ON RADIATIONAL COOLING AT THE SURFACE. SINCE GFS HAS A TENDENCY TO BE TOO WET ALOFT (IT`S CURRENTLY VERY BULLISH ON THE VEIL OF HIGH CLOUDS LATE SUNDAY NIGHT)...CURRENT THINKING ID THAT WHAT HIGH CLOUDS ARE THERE WILL BE THIN. THUS...EXPECT MIN TEMPS TO RANGE FROM THE UPPER 30S-LOWER 40S WITH MID 30S IN THE NORMALLY COLDER LOCATIONS. WHERE TEMPS REACH COLDER THAN 37 DEGREES...COULD SEE SPOTTY LIGHT FROST. && .LONG TERM /TUESDAY THROUGH SATURDAY/... AS OF 315 AM SUNDAY... SHORTWAVE ENERGY CURRENTLY OVER THE CANADIAN ROCKIES WILL DIVE THROUGH THE MIDWEST AND CROSS THE AREA EARLY TUESDAY...IMMEDIATELY FOLLOWED BY ANOTHER WAVE...AND ITS ASSOCIATED COLD FRONT...DIGGING THROUGH THE DEEPENING LONGWAVE TROUGH TUESDAY EVENING. DURING THE DAY...A WEST-SOUTHWESTERLY WIND AND LIMITED CLOUD COVER AHEAD OF THE COLD FRONT WILL ALLOW TEMPS TO WARM BACK INTO THE UPPER 60S AND LOWER 70S. AS THE COLD FRONT MOVES THROUGH TUESDAY EVENING...A SHOT OF STRONG DCVA WILL HAVE TO OVERCOME LIMITED MOISTURE...PW BELOW 0.75"...IN ORDER TO TO SQUEAK OUT A FEW ISOLATED...LIGHT SHOWERS...MAINLY ACROSS THE FAR NORTHERN COASTAL PLAIN WHERE MOISTURE PROFILES ARE SLIGHTLY MORE CONDUCIVE FOR PRECIP. HOWEVER...MODELS ARE ONLY GENERATING A HUNDREDTH OR TWO OF QPF IN SPOTS...SO SLIGHT CHANCE POPS CONTINUE TO BE THE BEST BET. BEHIND THE FRONT...A NORTHWESTERLY WIND WILL PERSIST THROUGH MOST OF THE WEEK AS THE UPPER TROUGH CLOSES OFF INTO AN UPPER LOW OVER THE MID-ATLANTIC COAST. MODELS HAVE HINTED AT A FEW SHOWERS ON WEDNESDAY AFTERNOON AS THE CORE OF THE COLD AIR ALOFT AND SOME VERY WEAK INSTABILITY DEVELOPS. HOWEVER...MOISTURE WILL STILL EB SEVERELY LACKING AND JUST ENHANCE CLOUD COVER SEEMS MORE LIKELY. THICKNESSES ARE FORECAST TO BRIEFLY TOUCH 1340M ON WEDNESDAY MORNING...THEN CLIMB BACK TOWARD NORMAL VALUES AROUND 1360M BY THE END OF THE WEEK AS THE UPPER BEGINS TO DRIFT NORTHEAST AWAY FROM THE REGION. THUS...HIGHS WILL BE COOLEST WEDNESDAY IN THE LOW TO MID 60S AND TREND BACK INTO THE UPPER 60S TO LOWER 70S. THERE ARE SIGNIFICANT MODEL DIFFERENCES BY NEXT WEEKEND AS ENERGY CROSSING THE CENTRAL US IS FORCED INTO THE DEEP SOUTH AND THEN EITHER MOVES EAST ACROSS THE SOUTHEAST US (GFS SOLUTION) OR CUTS OFF OVER THE GULF COAST (ECMWF SOLUTION). WPC HAS A STRONG PREFERENCE FOR THE ECMWF AND ITS ENSEMBLE MEAN. EITHER WAY THE FORECAST WILL REMAIN DRY AND NEAR NORMAL THROUGH THE END OF THE EXTENDED PERIOD. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/... AS OF 205 AM SUNDAY... A POTENT SHORTWAVE TROUGH (DISTURBANCE) ALOFT AND ASSOCIATED MID LEVEL CEILINGS WILL EXIT EAST-CENTRAL NC THROUGH AROUND 09Z. CLEAR SKIES IN STRONG SUBSIDENCE BEHIND THE DEPARTING TROUGH WILL FOLLOW FOR TODAY. NORTHWESTERLY SURFACE WINDS WILL BECOME BRIEFLY GUSTY INTO 15-20 KT RANGE BETWEEN 13-17Z...STRONGEST AND MOST FREQUENT AT EASTERN TERMINALS...BEFORE LESSENING THIS AFTERNOON AND BECOMING CALM AT SUNSET...AS HIGH PRESSURE BUILDS INTO...AND SETTLES OVER... NC. OUTLOOK: MOISTURE IN SSE RETURN FLOW WILL RESULT IN A GOOD CHANCE OF SCATTERED TO BROKEN STRATOCUMULUS BASED AROUND 3000 FT - MAINLY ALONG COASTAL AREAS - THOUGH THE WESTERN EDGE OF THIS CLOUDINESS COULD BRUSH KFAY AND KRWI MON AFTERNOON. THE DEVELOPMENT OF AN UPPER LOW OVER THE MIDDLE ATLANTIC STATES...AND ASSOCIATED PASSAGE OF A SURFACE COLD FRONT...WILL RESULT IN A CHANCE OF SHOWERS TUE AFTERNOON. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MWS NEAR TERM...MWS SHORT TERM...WSS LONG TERM...BLS AVIATION...MWS

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