Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 181906 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 305 PM EDT SAT OCT 18 2014 .SYNOPSIS...
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.ANOTHER DRY COLD FRONT WILL CROSS CENTRAL NC THIS EVENING. HIGH PRESSURE WILL BUILD INTO OUR AREA SUNDAY AND SETTLE OVERHEAD SUNDAY NIGHT THEN DRIFT EAST ON MONDAY.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 305 PM SATURDAY... A S/W DIGGING ON THE BACK SIDE OF A L/W OVER THE NORTHERN MID ATLANTIC-SOUTHERN NEW ENGLAND WILL CROSS CENTRAL NC THIS EVENING...EXITING OUR REGION PRIOR TO DAYBREAK. THIS FEATURE MAY ENHANCE MID LEVEL CLOUDINESS ACROSS THE REGION AS WELL AS MAINTAIN A LIGHT BUT STEADY N-NW WIND. MOISTURE CONFINED TO A RELATIVELY NARROW LAYER SO NOT EXPECTING MUCH IN THE MANNER OF PRECIP. PASSAGE OF THE MID LEVEL TROUGH WILL INCREASE LOW LEVEL COLD AIR ADVECTION LATER TONIGHT...SENDING OVERNIGHT TEMPS INTO THE 40S.
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&& .SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
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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.
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&& .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 /18Z SATURDAY THROUGH THURSDAY/... AS OF 140 PM SATURDAY... A DRY AND STABLE AIR MASS OVER CENTRAL NC WILL RESULT IN VFR CONDITIONS THROUGH EARLY NEXT WEEK. SURFACE HIGH PRESSURE WILL BUILD INTO OUR REGION TONIGHT AND SETTLE OVERHEAD SUNDAY AND SUNDAY NIGHT. BREEZY NW WINDS WILL OCCUR THROUGH THIS AFTERNOON WITH FREQUENT GUSTS 15-20KTS. THE WINDS WILL SUBSIDE TO 5-8KTS AROUND SUNSET. AN UPPER LEVEL DISTURBANCE CROSSING SOUTHERN NEW ENGLAND MAY SPREAD A FEW CLOUDS WITH BASES 5000-8000FT ACROSS OUR REGION THIS EVENING WITH CLEAR SKIES EXPECTED AREAWIDE BY DAYBREAK SUNDAY. A L/W TROUGH WILL SETTLE ALONG THE EASTERN SEABOARD TUESDAY AND WEDNESDAY THEN LIFT OFF TO THE NE THURSDAY. A SERIES OF DISTURBANCES ROUNDING THE BASE OF THIS TROUGH WILL CAUSE PERIODS OF CLOUDINESS AND POSSIBLY A FEW SHOWERS ACROSS CENTRAL NC THOUGH VFR CONDITIONS SHOULD PERSIST. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...WSS LONG TERM...HARTFIELD AVIATION...WSS

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