Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 161557 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1050 AM EST TUE DEC 16 2014 .SYNOPSIS...A COLD FRONT WILL PUSH EAST THROUGH THE REGION TODAY. HIGH PRESSURE WILL BUILD SLOWLY INTO THE AREA THROUGH FRIDAY. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1045 AM TUESDAY... MORNING UPDATE WILL TWEAK POPS UPWARDS TO LIKELY IN THE CENTRAL AND EAST INTO THE MID AFTERNOON AND DOWNWARD IN THE WEST AS THE PREFRONTAL BAND RACES EAST. ALSO ADJUSTING TEMP TRENDS AS WARM AIR ADVECTION AHEAD OF SHOWERS HAS PRODUCED A WIDE RANGE OF TEMPS...FROM MID 40S TO UPPER 50S. TODAY: WEAKENING SOUTHERN STREAM TROUGH ENTERING THE OHIO VALLEY WILL WILL MOVE EAST-NORTHEASTWARD INTO THE GREAT LAKES AND MID- ATLANTIC REGION TODAY. PRE-FRONTAL BAND OF CONVECTION(CURRENTLY APPROACHING THE MOUNTAINS)EMBEDDED IN THE LLJ ASSOCIATED WITH THE WARM CONVEYOR BELT WILL TRANSLATE QUICKLY EASTWARD ACROSS THE AREA BETWEEN 12 TO 21Z...BRINGING A BRIEF 2 TO 3 HOUR WINDOW OF SCATTERED SHOWERS AS MOISTURE PROFILES CONTINUE TO LOOK MODEST...PRIMARILY CONFINED TO THE 850-700 MB LAYER. AS SUCH...HAVE CHOSEN TO KEEP POPS AT HIGH CHANCE WITH ONLY LIGHT PRECIP AMOUNTS EXPECTED OF A TENTH OF AN OR LESS. AS THE CONVEYOR BELT SHIFTS OFFSHORE...MID- LEVEL DRYING WILL RACE EASTWARD...AHEAD OF THE SFC COLD FRONTAL PASSAGE WHICH WILL RESULT ONLY ISOLATED SHOWERS ALONG THE IMMEDIATE FRONT. CANNOT RULE OUT A RUMBLE OF THUNDER AS SOUNDINGS SHOW VERY WEAK INSTABILITY ALOFT (200-350J/KG OF MUCAPE)...BUT WILL NOT INCLUDE ANY MENTION AT THIS TIME. BOTH THE GFS AND NAM BUFR SOUNDINGS SUGGEST THAT THE RAIN AND LINGERING LOW CLOUDS WILL SUPPRESS TEMPERATURES IN THE MID/UPPER 50S...COOLER THAN PREVIOUS FORECAST AND IN-LINE WITH COOLER MET STATISTICAL GUIDANCE. THE EXCEPTION MAY BE ACROSS THE FAR SE...WHERE LATER ARRIVAL OF PRECIP COULD ALLOW TEMPS TO WARM INTO THE LOWER 60S. TONIGHT: CLEARING WILL SPREAD EASTWARD LATE THIS EVENING IN THE WAKE OF THE COLD FRONT. A LIGHT NWLY BREEZE WILL KEEP THINGS STIRRED UP OVERNIGHT WITH RESULTANT WEAK CAA SUPPORTING OVERNIGHT LOWS IN THE MID/UPPER 30S NW TO LOWER 40S SE.
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&& .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... AS OF 240 AM TUESDAY... FAIR WEATHER IS EXPECTED ON WEDNESDAY AS THE UPPER FLOW BECOMES ZONAL BEHIND THE UPPER TROUGH THAT MOVES OFF THE COAST TUESDAY NIGHT. AT THE SURFACE...HIGH PRESSURE OVER THE CENTRAL US WILL BE VERY SLOW TO BUILD EASTWARD WITH NEUTRAL TEMPERATURE ADVECTION AT 850MB NOTED...WHICH SHOULD SUPPORT NEAR TO SLIGHTLY ABOVE NORMAL HIGHS IN THE MID TO UPPER 50S. AN ACTIVE PACIFIC WAVE TRAIN MOVING ONSHORE ACROSS CALIFORNIA AND THEN THROUGH THE SOUTHWEST WILL REINVIGORATE THE PACIFIC JET THAT EXTENDS ACROSS THE SOUTHERN CONUS. AN OPAQUE CIRRUS SHIELD COULD SPREAD EAST INTO THE AREA AS EARLY AS WEDNESDAY AFTERNOON BUT DEFINITELY BY WEDNESDAY NIGHT. THIS CLOUD COVER SHOULD TEMPER MIN TEMPS...AND COULD QUITE POSSIBLY RESULT IN A NON-DIURNAL TEMPERATURE TREND WITH TEMPERATURES HOLDING STEADY OR RISING AFTER MIDNIGHT. LOWS IN MIDS 30S TO UPPER 30S. && .LONG TERM /THURSDAY THROUGH MONDAY/... AS OF 245 AM TUESDAY... THROUGH FRIDAY: SURFACE HIGH PRESSURE WILL CONTINUE TO RIDGE INTO THE REGION THROUGH FRIDAY. THE ZONAL FLOW ALOFT WILL SLOWLY BECOME MORE AMPLIFIED THROUGH THIS PERIOD...WITH GENERALLY WEST-NORTHWEST FLOW OVER CENTRAL NC. EXPECT DRY WEATHER TO DOMINATE DURING THIS TIME...HOWEVER THE MODELS ARE TRYING TO GENERATE SOME LIGHT PRECIP FOR A BRIEF PERIOD ON THURSDAY...MAINLY IN THE FAR NW. FOR NOW WILL KEEP THIS PART OF THE FORECAST DRY UNTIL THE MODELS SHOW A BIT MORE RUN-TO-RUN CONSISTENCY WITH THE PRECIP. HIGHS IN THE UPPER 40S NORTH TO MAINLY MID 50S SOUTH THURSDAY AND FRIDAY. EXPECT THURSDAY NIGHT LOWS MAINLY IN THE LOW TO MID 30S. FRIDAY NIGHT SATURDAY NIGHT: EXPECT RAPIDLY INCREASING CLOUDINESS FRIDAY NIGHT AS A LOW PRESSURE SYSTEM APPROACHES FROM THE GULF. THE INCREASED CLOUD COVER MAY YIELD LOWS A FEW DEGREES HIGHER THAN PREVIOUS NIGHTS...GENERALLY IN THE MID 30S. IT APPEARS AS THOUGH THE MODELS HAVE TRENDED TOWARD ONE ANOTHER OVER THE PAST FEW RUNS WITH RESPECT TO THE APPROACHING UPPER LEVEL TROUGH/SHORTWAVE AND SURFACE LOW. THE ECMWF IS STILL A BIT MORE AMPLIFIED THAN THE GFS ALOFT... BUT THEY ARE MUCH CLOSER THAN PREVIOUS RUNS. THE GFS IS STILL JUST A BIT FASTER...LARGELY DUE TO THE TROUGH BEING LESS AMPLIFIED...BUT BOTH HAVE PRECIP MOVING INTO THE AREA FROM THE WEST-SOUTHWEST BY 12Z SATURDAY. FOR NOW EXPECT TEMPS ACROSS OUR AREA TO REMAIN ABOVE FREEZING FRIDAY NIGHT...THUS DO NOT EXPECT ANY WINTERY PRECIP AT THIS TIME. HOWEVER...IF THE HIGH RIDGING IN FROM THE NE FRIDAY NIGHT RESULTS IN TEMPS FALLING BELOW FREEZING THE CHANCE FOR PRECIP OF THE FROZEN VARIETY MAY BE IN THE REALM OF POSSIBILITY. THE SURFACE LOW IS EXPECTED TO MOVE ALONG THE GULF COAST AND UP ALONG THE CAROLINA COAST SATURDAY AND SATURDAY NIGHT AND PRECIP CHANCES AND AMOUNT WILL DEPEND ON THE EXACT TRACK THE LOW TAKES AS IT MOVES THROUGH THE REGION. GIVEN THE CURRENT LOW TRACK...ANY THUNDERSTORMS WILL BE LIMITED TO THE FAR SOUTHEAST AND COASTAL AREAS. TEMPS WILL ALSO DEPEND ON WHERE THE LOW TRACKS...BUT FOR NOW EXPECT HIGHS AROUND 40 DEGREES IN THE NW TO LOW 50S IN THE SE. OVERNIGHT LOWS VERY SIMILAR TO FRIDAY NIGHT...MAINLY IN THE MID 30S. SUNDAY AND MONDAY: THE MAIN UPPER LEVEL SHORTWAVE MOVES OUT OF THE REGION TO THE NORTHEAST SUNDAY MORNING...WHILE THE SURFACE LOW REMAINS OFF THE COAST OF THE CAROLINAS THROUGH THE DAY. THE MODELS INDICATE THE CHANCE FOR SOME LIGHT PRECIP TO LINGER ACROSS THE EAST THROUGH SUNDAY AS THE SURFACE LOW REMAINS IN CLOSE PROXIMITY... WITH CHANCES DECREASING LATE SUNDAY AND SUNDAY NIGHT AS THE LOW RAPIDLY MOVES OFF TO THE NE AND AWAY FROM NC. FOR NOW...EXPECT SUNDAY NIGHT AND MONDAY TO BE DRY. HIGHS SUNDAY AND MONDAY WILL GENERALLY BE IN THE MID 40S NORTH TO AROUND 50S DEGREES SOUTH...WITH OVERNIGHT LOWS IN THE UPPER 20S TO LOW 30S. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... AS OF 648 AM TUESDAY... 24 HOUR TAF PERIOD: LIFR TO IFR RESTRICTIONS IN FOG HAVE DEVELOPED ACROSS THE EAST. HRRR SUGGESTS THESE VISIBILITY RESTRICTIONS AND LOW CLOUDS COULD LINGER THROUGH THE LATE MORNING ~15 TO 16Z. A PRE- FRONTAL BAND OF SHOWERS WILL CROSS THE AREA BETWEEN 14 TO 17Z IN THE WEST...EXITING EASTERN TERMINALS AOA 21Z. FCST SOUNDINGS AND UPSTREAM TRENDS SUGGEST CIGS WILL LOWER TO MVFR WITHIN THE BAND OF SHOWERS AND WILL REMAIN SUB-VFR UNTIL THE TRAILING SFC COLD FRONT CROSSES THE AREA DURING THE EARLY EVENING...WITH CLEARING SPREADING WEST TO EAST BETWEEN 00 TO 06Z. OUTLOOK...VFR CONDITIONS SHOULD DOMINATE WEDNESDAY THROUGH EARLY FRIDAY. A LOW PRESSURE SYSTEM TRACKING FROM THE GULF OF MEXICO NORTHEASTWARD ALONG THE SOUTHEAST COAST WILL RESULT IN ADVERSE AVIATION CONDITIONS LATE FRIDAY AND INTO THE WEEKEND. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...MLM/CBL SHORT TERM...CBL LONG TERM...KC AVIATION...CBL

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