Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 190238 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1038 PM EDT SAT OCT 18 2014 .SYNOPSIS....HIGH PRESSURE WILL BUILD INTO OUR AREA SUNDAY AND SETTLE OVERHEAD SUNDAY NIGHT THEN DRIFT EAST ON MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1035 PM SATURDAY... THE 00Z UPPER AIR ANALYSES SHOW THE UPPER LEVEL JET OVER MUCH OF NC...WITH THE MAIN TROUGH AXIS EXTENDING SW INTO KY/TN. EXPECT A SHORTWAVE TO TRAVERSE THE AREA OVERNIGHT AS THE TROUGH PIVOTS EASTWARD AND LIFTS AWAY FROM THE CAROLINAS. THE DISTURBANCE MAY KEEP SOME SCATTERED MID CLOUDS AROUND INTO THE EARLY OVERNIGHT HOURS... HOWEVER SKIES ARE EXPECTED TO CLEAR OUT BY DAYBREAK SUNDAY. DO NOT EXPECT ANY PRECIP WITH THIS DISTURBANCE AS THERE IS STILL QUITE A BIT OF DRY AIR OVERHEAD. WITH THE PRESSURE GRADIENT REMAINING STRONG ACROSS THE STATE...WINDS OVERNIGHT SHOULD REMAIN AROUND 5-10 KTS OUT OF THE NW. THE WINDS MAY KEEP TEMPS FROM GETTING AS LOW AS THEY WOULD OTHERWISE BEHIND THE COLD FRONT...GENERALLY IN THE MID 40S ACROSS THE AREA. && .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 /MONDAY THROUGH SATURDAY/... AS OF 240 PM SATURDAY... FOR MON-TUE: AFTER A BIT OF A COOL START MON... TEMPS SHOULD REBOUND NICELY AS THICKNESSES START TO CLIMB BACK UP TOWARD NORMAL. THE SURFACE HIGH CENTERED OVER ERN NC/ERN VA WILL MOVE SWIFTLY EAST AND OFF THE COAST... FOLLOWED BY A CONFLUENT BUT LIGHT S/SW FLOW INTO NC. CIRCULATION AROUND A LARGE SURFACE LOW PRESSURE AREA COVERING MUCH OF THE GULF AND ADJACENT MEXICO WILL LIMIT MOISTURE RETURN INTO THE AREA... SO EXPECT DRY WEATHER MON... BUT WITH INCREASING CLOUDS. A POTENT CLIPPER WAVE OVER THE UPPER MIDWEST SUN NIGHT WILL DROP SOUTH AND SE... HELPING TO CARVE OUT ANOTHER ROUND OF DEEP TROUGHING OVER ERN NOAM... AS AN ASSOCIATED SURFACE FRONT APPROACHES FROM THE NW MON NIGHT. THE INCREASING DPVA AND MID LEVEL SPEED MAX OVER NC WILL BE ACCOMPANIED BY A MODEST UPPER DIVERGENCE MAX IN THE RRQ/LFQ OF 80+ KT JETS TO OUR NE/SW RESPECTIVELY. BUT THIS ASCENT MAY NOT BE ENOUGH TO OVERCOME THE LIMITED MOISTURE AS PW VALUES ARE PROJECTED TO BARELY REACH NEAR NORMAL AHEAD OF THE CLIPPER FRONT. A SERIES OF WEAK SURFACE TROUGHS ARE EXPECTED TO SWING THROUGH CENTRAL NC MON NIGHT THROUGH TUE WITH INCREASINGLY CYCLONIC FLOW ALOFT... WITH THE MAIN FRONT TIMED BY THE GFS/ECMWF TO DROP THROUGH THE AREA TUE NIGHT... AS THE DIGGING TROUGH CULMINATES IN A CLOSED LOW OVER THE MIDATLANTIC REGION (WITH THE ECMWF FARTHER SOUTH INTO NC THAN THE GFS). BALANCING THE STRENGTHENING DYNAMICS AND KINEMATICS WITH WHAT SHOULD AMOUNT TO JUST SHALLOW MOISTURE AND MUCAPE OF LESS THAN 200 J/KG... WILL KEEP POPS NO WORSE THAN SLIGHT CHANCE TUE AFTERNOON AND NIGHT MAINLY ACROSS THE FAR NORTH AND EAST. THE SW CWA HAS THE BEST CHANCE OF STAYING DRY DUE TO ITS MORE PROFOUND INFLUENCE OF DOWNSLOPE FLOW. EXPECT HIGHS JUST SLIGHTLY BELOW NORMAL MON... 67- 72... AND A TAD MILDER TUE (68-74) WITH MINOR WARMING AHEAD OF THE FRONT. SLIGHTLY ABOVE NORMAL LOWS BOTH NIGHTS 47-53 AS THE LOW LEVELS REMAIN A BIT STIRRED OVERNIGHT. FOR WED THROUGH SAT: DRY AND FAIRLY SEASONABLE WEATHER PERSISTS. THE CLOSED MID LEVEL LOW WILL POSSESS SOMEWHAT STEEP MID LEVEL LAPSE RATES... AND IF IT SETS UP FARTHER SOUTH (COVERING NE NC) AS THE ECMWF INDICATES... WE WOULD HAVE A BETTER CHANCE OF SEEING BETTER INSTABILITY AND A FEW SHOWERS OVER THE NE CWA WED. WILL RETAIN JUST A SLIGHT CHANCE OVER THE FAR NE CWA FOR THE TIME BEING. BY THU A WEAK BUT FAIRLY AMPLIFIED FULL-LATITUDE TROUGH PUSHING THROUGH THE FRONT RANGE INTO THE PLAINS TRIES TO NUDGE THE MIDATLANTIC LOW EASTWARD WITH LITTLE SUCCESS... KEEPING NC UNDER THE INFLUENCE OF NNW MID LEVEL FLOW... WITH POCKETS OF VORTICITY ROTATING AROUND THE LOW`S CENTER... AND A CYCLONIC NW/N SURFACE FLOW AS SURFACE HIGH PRESSURE STARTS TO BUILD IN FROM THE NW. EXPECT DRY WEATHER THU WITH A FEW CONVECTIVE CLOUDS IN THE AFTERNOON. MODEL SOLUTIONS START TO DIVERGE REGARDING HOW MUCH CANADIAN ENERGY DROPS INTO THE VORTEX JUST TO OUR NORTHEAST... BUT REGARDLESS IT LOOKS LIKE THIS LOW WILL DRIFT TO THE NNE AWAY FROM NC AS A PORTION OF THE WEAK PLAINS TROUGH DROPS SOUTHWARD TOWARD TX... YIELDING A BAGGING POSITIVELY TILTED TROUGH AXIS THROUGH NC AND A LIGHT NW FLOW OVER NC. WITH HIGH PRESSURE CENTERED TO OUR NW OR WEST EXTENDING OVER NC... EXPECT FAIR SKIES AND DRY WEATHER. SEE NO REASON FOR THICKNESSES TO DEVIATE MUCH FROM NORMAL VALUES... SO AFTER COOL CONDITIONS WED... WILL TREND TEMPS UP TO WITHIN A FEW DEGREES OF NORMAL... LOWS IN THE MID-UPPER 40S AND HIGHS MAINLY IN THE UPPER 60S TO LOWER 70S. -GIH && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... AS OF 745 PM SATURDAY... 24 HOUR TAF PERIOD: VERY HIGH CONFIDENCE OF VFR CONDITIONS THROUGH THE TAF PERIOD. BREEZY GUSTS UP TO 20 KTS WILL BE SUBSIDING OVER THE NEXT COUPLE OF HOURS AND WINDS WILL SETTLE INTO A SUSTAINED 5-10 KTS OVERNIGHT OUT OF THE NORTHWEST. LINGERING SCATTERED TO BROKEN CEILINGS AT 5-10 KFT SHOULD LIFT OUT AND EVENTUALLY CLEAR OUT OVERNIGHT. FOR SUNDAY...THERE WILL BE A FEW HOURS AFTER SUNRISE WHERE SOME GUSTS TO PLUS OR MINUS 15 KTS WILL BE POSSIBLE BEFORE SURFACE HIGH PRESSURE MOVES MORE DIRECTLY OVERHEAD...CALMING THE GUSTS AND WEAKENING THE SUSTAINED WINDS TO 5 KTS OR LESS ON SUNDAY AFTERNOON. SKIES SHOULD REMAIN MOSTLY CLEAR THROUGH THE TAF PERIOD. LONG TERM: THE NEXT CHANCE FOR ADVERSE AVIATION CONDITIONS COULD COME WITH A STRONG UPPER LEVEL LOW THAT WILL MOVE NORTH OF THE AREA TUESDAY NIGHT INTO WEDNESDAY. OTHERWISE...VFR CONDITIONS EXPECTED THROUGH THE LONG TERM. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...KC SHORT TERM...WSS LONG TERM...HARTFIELD AVIATION...ELLIS

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