Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 011100 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 700 AM EDT WED OCT 01 2014 .SYNOPSIS...WEAK HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTH TODAY THROUGH THURSDAY. A COLD FRONT WILL APPROACH FROM THE WEST LATE FRIDAY... AND SWEEP EAST THROUGH THE AREA FRIDAY NIGHT INTO SATURDAY MORNING. COOL HIGH PRESSURE WILL PUSH IN FROM THE WEST SATURDAY AFTERNOON THROUGH SUNDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 235 AM WEDNESDAY... FOR TODAY: AS WAS THE CASE LAST NIGHT... THE MOST IMMEDIATE CONCERN IS THE DEVELOPMENT OF DENSE FOG EARLY THIS MORNING... FOSTERED BY CLEAR SKIES AND CALM WINDS. THUS FAR THE LOWEST VSBYS HAVE BEEN OVER NORTHERN SECTIONS OF THE FORECAST AREA. RECENT HRRR MODEL RUNS SHOW THIS FOG/STRATUS SPREADING OVER NEARLY THE ENTIRE FORECAST AREA OVER THE NEXT COUPLE OF HOURS... AND NOT IMPROVING UNTIL THE 14Z-16Z TIME FRAME... REASONABLE CONSIDERING THE SLOW DISPERSION SEEN YESTERDAY. A DENSE FOG ADVISORY WILL LIKELY BE NEEDED FOR A LARGE CHUNK OF CENTRAL NC THROUGH MID MORNING. WE SHOULD ALSO SEE POCKETS OF VERY LIGHT MIST WITHIN THE MORE DENSE FOG. THE DISSOLUTION OF THE FOG/STRATUS WILL POST THE NEXT CHALLENGE... GIVEN YESTERDAY`S SLOW IMPROVEMENT... AND WILL FOLLOW PERSISTENCE AS WELL AS THE HRRR TRENDS AND SHOW SLOWLY INCREASING SUNSHINE DURING THE LATE MORNING AND EARLY AFTERNOON... WITH THE SUN BREAKING THROUGH LAST OVER THE NORTHERN TIER. EXPECT A FEW HIGH THIN CLOUDS TO SPREAD OVER THE AREA LATE THIS AFTERNOON. THESE CLOUDS... NOTED ON IR AND WATER VAPOR IMAGERY... NOW EXTEND OVER TN INTO THE LOWER MISS VALLEY AND ARE ASSOCIATED WITH A WEAK WAVE UNDERCUTTING THE WEAK MID LEVEL RIDGE BUILDING IN FROM THE WEST. OVERALL... THIS EQUATES TO A TREND FROM DAYBREAK FOG/STRATUS TO PARTLY THEN MOSTLY SUNNY SKIES. THICKNESSES ARE 5-10 M HIGHER THAN NORMAL... SO EXPECT HIGHS FROM THE UPPER 70S TO NEAR 80 OVER PIEDMONT (WHERE CLOUDS SHOULD LINGER THE LONGEST) TO THE LOWER 80S ELSEWHERE. FOR TONIGHT: MOSTLY CLEAR SKIES IN THE EVENING SHOULD GIVE WAY TO ANOTHER ROUND OF PATCHY FOG/STRATUS... LIKELY LESS WIDESPREAD AND LESS DENSE THAN THIS MORNING OR YESTERDAY. IN ADDITION TO THE FEW HIGH CLOUDS PASSING OVERHEAD... NAM/GFS BUFR SOUNDINGS INDICATE A SHOT OF MOISTURE IN THE 925-700 MB LAYER ASSOCIATED WITH SUBTLE MASS CONVERGENCE ALONG A WEAK LOW-MID LEVEL RETREATING WARM FRONT. THE NAM IS MUCH MORE BULLISH WITH SUCH CLOUDS THAN THE GFS... SO SOME UNCERTAINTY REGARDING EXTENT AND COVERAGE REMAINS. BUT IF THESE CLOUDS COME TO PASS... THEY WOULD MITIGATE FOG DEVELOPMENT TONIGHT. WILL REFRAIN FROM INCLUDING FOG IN THE FORECAST FOR NOW... AS IT COULD SIMPLY BE LIGHT FOG. WILL SHOW A TREND TO PARTLY CLOUDY SKIES TONIGHT ESPECIALLY ACROSS THE NORTH AND NE. MILD LOWS OF 58-62. -GIH && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... AS OF 250 AM WEDNESDAY... FOR THU/THU NIGHT: THE MID LEVEL CLIPPER LOW CONTINUES MOVING OFF THE NORTHEAST COAST THU/THU NIGHT... WHILE DEEP AND AMPLIFYING MID LEVEL TROUGHING SHIFTS EAST OVER THE PLAINS.... AND THIS WILL BRING A MODEST MID LEVEL RIDGE OVER NC. THE SURFACE HIGH CENTERED OVER THE CANADIAN MARITIMES WILL CONTINUE TO EXTEND WEAKLY TO THE SW/SOUTH INTO NC... ALTHOUGH ITS SOUTHERN END WILL START TO WEAKEN AND SHIFT A BIT TO THE NE IN RESPONSE TO THE ENCROACHING WARM SECTOR AND SLOWLY INCREASING LOW LEVEL WINDS FROM THE SW. EXPECT FAIR TO PARTLY CLOUDY SKIES AS LOW LEVEL MOISTURE TRANSPORT STRENGTHENS (ESPECIALLY OVER THE WESTERN HALF OF NC). THE MODELS DEVELOP PATCHES OF VERY LIGHT PRECIP OVER CENTRAL/ERN NC EARLY THU THROUGH THU AFTERNOON... WITH ADDITIONAL LIGHT PRECIP MAINLY OVER THE VA PIEDMONT THU NIGHT. WITH THE MID LEVELS STILL DRY WITH SUBSIDENCE WITHIN THE RIDGE ALOFT... ANY MOISTURE AND FORCING FOR ASCENT WOULD BE ROOTED VERY LOW. AND AT THIS TIME... WE DON`T QUITE SEE THE LIFT AND MOISTURE NECESSARY FOR ANYTHING BETTER THAN SPRINKLES. THUS... WILL LEAVE POPS UNDER 15% AND MENTION NOTHING GREATER THAN SPRINKLES. THICKNESSES INCH UP FURTHER... SUGGESTING HIGHS NEAR 80 TO 84 (COOLER READINGS NORTHEAST). LOWS MAINLY IN THE LOW 60S... AND WE SHOULD SEE AREAS OF CLOUDS AND LIGHT FOG THU NIGHT AHEAD OF THE INCOMING STORM SYSTEM. -GIH && .LONG TERM /FRIDAY THROUGH TUESDAY/... AS OF 250 AM WEDNESDAY... FRIDAY AND FRIDAY NIGHT: A DEEPENING UPPER LEVEL LOW OVER THE UPPER MID-WEST WILL MOVE EASTWARD FRIDAY AND FRIDAY NIGHT...WHILE THE TROUGH DIGS SOUTH INTO THE OH/TN RIVER VALLEY. A POTENT COLD FRONT WILL ACCOMPANY THE SURFACE TROUGH APPROACHING THE REGION FRIDAY AND FRIDAY NIGHT AS THE LOW CONTINUES ITS NORTHWARD TREK INTO CANADA. THE MODELS ARE STILL IN GOOD AGREEMENT WITH BOTH THE TIMING OF THE FRONT AND THE PRECEDING CONVECTION. THERE HAS BEEN LITTLE CHANGE IN THE MODELS SINCE THE LAST FORECAST UPDATE...THUS HAVE KEPT RAINFALL CHANCES AND AMOUNTS NEARLY THE SAME. EXPECT CHANCES TO INCREASE FROM NW TO EAST LATE FRIDAY MORNING THROUGH FRIDAY EVENING...DECREASING AGAIN THROUGH EARLY SATURDAY MORNING AS THE COLD FRONT MOVES INTO THE AREA. ALTHOUGH THERE IS DESCENT SHEAR AND LOW LEVEL LAPSE RATES...THE WEAK INSTABILITY AND MID-LEVEL LAPSE RATES...COMBINED WITH THE LATE DIURNAL TIMING...SHOULD MINIMIZE THE SEVERE THREAT. EXPECT HIGHS GENERALLY IN THE MID 70S TO LOW 80S AND LOWS MAINLY IN THE MID 50S NW TO MID 60S SE...ALTHOUGH BOTH WILL BE DEPENDENT ON THE CONVECTION AND TIMING OF THE FRONT. SATURDAY THROUGH TUESDAY: THE COLD FRONT WILL MOVE THROUGH THE REGION BY SATURDAY EVENING...WITH COOLER AND DRIER AIR MOVING IN BEHIND IT AS HIGH PRESSURE BUILDS IN. ONCE THE PRE-FRONTAL CONVECTION MOVES OUT OF THE AREA...THE REST OF THE WEEKEND SHOULD REMAIN DRY. THE UPPER LEVEL TROUGH WILL LINGER OVER THE ATLANTIC COAST...WITH POSSIBLE DISTURBANCES YIELDING A SLIGHT CHANCE FOR SOME RAIN MONDAY AND TUESDAY. ASIDE FROM THAT...THE REMAINDER OF THE FORECAST SHOULD ALSO BE MOSTLY DRY. HOWEVER...THERE IS QUITE A BIT MORE UNCERTAINTY AND DISAGREEMENT BETWEEN THE MODELS IN THIS PART OF THE FORECAST...THUS CONFIDENCE IS LOW AT THIS TIME. HIGHS SATURDAY WILL AGAIN BE DEPENDENT ON THE FRONT...BUT FOR NOW EXPECT MID 60S NW TO MID 70S SE WHILE LOWS SATURDAY NIGHT WILL BE QUITE A BIT COOLER THAN PREVIOUS NIGHTS...MID 40S NW TO LOW 50S SE. HIGHS ON SUNDAY SHOULD BE THE LOWEST OF THE EXTENDED PERIOD...MID 60S TO LOW 70S. HIGHS MONDAY AND TUESDAY WILL BE GENERALLY IN THE LOW TO MID 70S. MEANWHILE...LOWS SHOULD INCREASE FROM THE UPPER 40S TO LOW 50S SUNDAY NIGHT INTO THE LOW TO MID 50S MONDAY AND TUESDAY NIGHTS. && .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... AS OF 700 AM WEDNESDAY... IFR/LIFR CONDITIONS ARE LIKELY TO HOLD AT ALL SITE UNTIL MID MORNING. THE COMBINATION OF MOSTLY CLEAR SKIES AND CALM WINDS HAS PROMPTED FORMATION OF WIDESPREAD FOG... DENSE IN SPOTS. THIS FOG IS EXPECTED TO HOLD THROUGH 14Z OR 15Z BEFORE SLOWLY DISPERSING. AFTER THIS TIME... EXPECT A TREND TO VFR CONDITIONS AT ALL CENTRAL NC TAF SITES THROUGH THE REST OF TODAY... AS WEAK HIGH PRESSURE EXTENDS OVER THE REGION. RENEWED MVFR OR IFR FOG DEVELOPMENT IS EXPECTED STARTING SOON AFTER 06Z EARLY THU MORNING... HOWEVER CONFIDENCE IS LOWER THAN TODAY... AS THE POTENTIAL FOR HIGHER CLOUDS COULD CURB FOG/STRATUS DEVELOPMENT LATE TONIGHT. SURFACE WINDS WILL STAY LIGHT/VARIABLE THROUGH THE TAF VALID PERIOD. LOOKING BEYOND 12Z THU MORNING... MVFR OR IFR VSBYS IN FOG MAY LAST UNTIL 13Z OR 14Z THU MORNING. OTHERWISE... EXPECT VFR CONDITIONS THU. A FEW SPRINKLES OR SHOWERS ARE POSSIBLE MAINLY AT RWI/FAY THU AFTERNOON/EVENING... BUT SUB-VFR CONDITIONS ARE NOT EXPECTED. PATCHY FOG MAY AGAIN DEVELOP EARLY FRI MORNING. A STRONG FRONTAL SYSTEM WILL BRING INCREASING SURFACE WINDS FROM THE SW AND A GOOD CHANCE OF SUB-VFR CONDITIONS IN SHOWERS AND STORMS LATE FRI AFTERNOON THROUGH FRI NIGHT/EARLY SAT MORNING. VFR CONDITIONS SHOULD THEN RESUME SAT AFTERNOON... LASTING THROUGH SUNDAY. -GIH && .RAH WATCHES/WARNINGS/ADVISORIES... DENSE FOG ADVISORY UNTIL 10 AM EDT THIS MORNING FOR NCZ007>011- 021>028-038>043-073>078-083>086-088-089. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...KC AVIATION...HARTFIELD

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