Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 180532
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
123 AM EDT SAT APR 18 2015

.SYNOPSIS...HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTH
TODAY... THEN SHIFT SLOWLY OFFSHORE SUNDAY AS A WARM FRONT
APPROACHES FROM THE SOUTH. THE WARM FRONT WILL MOVE NORTH ON SUNDAY
NIGHT. THIS WILL BE FOLLOWED BY A COLD FRONT THAT WILL PUSH WEST TO
EAST ACROSS CENTRAL NORTH CAROLINA LATE MONDAY INTO MONDAY EVENING.
&&

.NEAR TERM /TONIGHT/...
AS OF 950 PM FRIDAY...

A WELL-DEFINED SHORTWAVE TROUGH OVER NORTHERN AL/GA WILL MOVE
GENERALLY EAST ACROSS THE SOUTHERN APPALACHIANS...SC...AND FAR
SOUTHERN NC TONIGHT...TO A POSITION INVOF KILM BY 12Z SAT. AN
EXPANSIVE AREA OF SHOWERS WILL ACCOMPANY THIS FEATURE AS IT MOVES
EAST...WITH THE ASSOCIATED HIGHEST PROBABILITY OF RAIN OVER THE
SOUTHERN PIEDMONT/SANDHILLS/SOUTHERN COASTAL PLAIN AFTER
MIDNIGHT...WITH PROGRESSIVELY LOWER CHANCES TOWARD AND ESPECIALLY
NORTH OF HIGHWAY 64. IT APPEARED THAT A COUPLE UPSTREAM  CONVECTIVE
CLUSTERS OVER VA...WHICH INITIATED ALONG A LEE SURFACE TROUGH...MAY
MAINTAIN INTENSITY AS THEY PROPAGATED SOUTHEASTWARD ALONG THEIR
ASSOCIATED OUTFLOW INTO A WEAK INSTABILITY AXIS CENTERED OVER THE
NORTHERN NC PIEDMONT...BUT THAT ACTIVITY HAS MOSTLY DIMINISHED
DURING THE PAST FEW HOURS. SO WHILE A SHOWER OR TWO CANNOT BE
ENTIRELY RULED OUT OVER THE NORTHERN PIEDMONT AS BOTH PAIR OF
OUTFLOW DRIFT SOUTH...THE PROBABILITY OF OCCURRENCE IS QUITE LOW
RELATIVE TO THE INCOMING SHOWERS ASSOCIATED WITH THE AFOREMENTIONED
SHORTWAVE TROUGH. LOWS CLOSE TO CURRENT SURFACE DEWPOINT
TEMPERATURES...MOSTLY IN THE LOWER TO MIDDLE 60S. IF ANY APPRECIABLE
BREAKS IN THE CLOUDS OCCUR...MOST LIKELY OVER THE NORTHERN PIEDMONT
WHERE INFLUENCE FROM THE SHORTWAVE TROUGH AND ASSOCIATED
LIFT/MOISTURE WILL BE LESS PREVALENT...THEN PATCHY FOG WOULD BE
PROBABLE IN THOSE AREAS.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
AS OF 300 PM FRIDAY...

SHOWERS WILL LINGER IN THE MORNING...ESPECIALLY IN THE SOUTHEAST...
AS THE SHORT WAVE MOVES OFFSHORE. COOL AIR ADVECTION IN NORTHEAST
FLOW WILL PROVIDE AN ISENTROPIC SURFACE TO INDUCE WEAK LOW LEVEL
FORCING IN THE SOUTH. MEANWHILE...UPPER RIDGING TRANSITIONS ACROSS
THE AREA DURING THE AFTERNOON TO EARLY OVERNIGHT...WHICH SHOULD BE
ANOTHER AID TO LIMITING CONVECTION LARGELY TO THE SOUTHERN TIER IN
THE AFTERNOON. WILL HAVE CHANCE POPS ACROSS THE FAR SOUTH TO SLIGHT
CHANCE ELSEWHERE. HIGHS WILL HAVE TO BE TONED DOWN DUE TO INCREASING
CLOUD COVERAGE AND WEAK COOL AIR ADVECTION. THICKNESSES SUPPORT A
COUPLE OF DEGREES EITHER SIDE OF 80.

THE UPPER RIDGING SHOULD DAMPEN ACTIVITY OVERNIGHT...BUT A WARM
FRONT WILL BE LIFTING NORTH...WITH H85 FLOW VEERING TO
SOUTHEAST...UPSLOPE...AND INCREASING. EXPECT PARTLY CLOUDY ACROSS
THE NORTH...WITH MORE CLOUDINESS IN THE SOUTH OVERNIGHT...AND COULD
SEE SHOWERS MIGRATE INTO THE FAR SOUTHWEST PIEDMONT BY MORNING. MINS
WILL BE COOLER ACROSS THE NORTH...MID 50S...GRADUATED TO AROUND 60
ACROSS THE SOUTHERN TIER.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
AS OF 245 PM FRIDAY...

SUN-MON NIGHT: A VERY WET AND POTENTIALLY STORMY PERIOD. THE
NORTHERN STREAM SHORTWAVE TROUGH OVER SW CANADA WILL HAVE PICKED UP
THE OPENING LOW THAT IS NOW OVER THE FOUR CORNERS REGION... WITH THE
FORMER FEATURE AMPLIFYING OVER THE UPPER MIDWEST WHILE THE LATTER
FEATURE IS TOSSED NORTHEASTWARD TOWARD LOWER MI. A BATCH OF MID
LEVEL VORTICITY AND SUBTLE TROUGH NOW OFF THE COAST OF NW MEXICO
WILL TRACK QUICKLY EAST THEN NE WITHIN THE STRONG SUBTROPICAL
FLOW... AND IT IS THE MERGING OF THIS WAVE WITH THE OLD SOUTHWEST
LOW INTO A DISTINCT TROUGH AXIS THAT WILL HELP TRIGGER WIDESPREAD
RAIN OVER NC SUN INTO EARLY MON. THE MODELS HAVE TRENDED STRONGER
WITH THESE TWO MERGED FEATURES AND THEIR RESULTANT TROUGH... AND
THUS ARE STRONGER WITH AN ASSOCIATED SURFACE LOW NEAR THE MO
BOOTHEEL SUN MORNING... EXPECT TO MOVE QUICKLY NORTHWARD THROUGH WRN
MI THROUGH SUN NIGHT. MEANWHILE... THE BACKDOOR FRONT THAT DROPS
SOUTHWARD TOWARD THE NC/VA BORDER -- PROPELLED BY AN INTENSE MID
LEVEL SHORTWAVE TROUGH EXITING NEW ENGLAND AND COLD DENSE SURFACE
HIGH PRESSURE CENTERED OVER SRN QUEBEC PUSHING SOUTHWARD -- NOW
APPEARS LIKELY TO MAKE AT LEAST SOME PROGRESS DOWN THROUGH THE NC
PIEDMONT. AND IT LOOKS LIKE THIS FRONT WILL MERGE WITH THE WEAK
FRONTAL ZONE TO OUR SOUTH AS THE LATTER MOVES NORTHWARD... YIELDING
A STRONGER SURFACE FRONTAL ZONE THROUGH NC BY LATE SUN. CONFIDENCE
IS HIGH THAT WE`LL SEE A STRONG SURGE OF LOW LEVEL GULF- AND
ATLANTIC-SOURCE MOISTURE INTO NC... STARTING FIRST IN SW NC AND
SPREADING ENE SUN/SUN NIGHT IN CONJUNCTION WITH THE PRIMARY LIFT
MECHANISMS FORCING ASCENT... INCLUDING MID LEVEL DPVA... UPPER
DIVERGENCE... AND LOWER LEVEL (850-925 MB) MASS CONVERGENCE.
MOISTURE SHOULD BE DEEP AND PLENTIFUL WITH PW WELL OVER 200% OF
NORMAL AND A DEEP LCL-TO-0C LAYER NEAR 3.5 KM SUPPORTIVE OF WARM
RAIN PROCESSES... AND A PERIOD OF HEAVY RAIN APPEARS LIKELY. OVERALL
RAINFALL IS EXPECTED TO BE 1-2 INCHES... WITH THE LESSER VALUES EAST
AND HIGHER TOTALS WEST. GIVEN SUCH DEEP LIFT AND ANOMALOUSLY HIGH
MOISTURE CONTENT... AND IF MODELS TREND EVEN WETTER WITH HIGHER QPF
OVER A LARGE AREA... WE MAY NEED TO CONSIDER A FLASH FLOOD WATCH ON
TOMORROW`S SHIFTS. MODEL TIMING HAS BEEN TRENDING A BIT SLOWER WITH
PRECIP ONSET BUT NOW APPEARS TO BE ZEROING IN ON A COMMON
SOLUTION... AND WILL CONTINUE TO RAMP UP POPS TO LIKELY WEST/CHANCE
NE SUN MORNING... GOING TO CATEGORICAL WEST/LIKELY CENTRAL/GOOD
CHANCE EAST SUN AFTERNOON... AND CATEGORICAL EVERYWHERE LATE SUN
AFTERNOON THROUGH SUN NIGHT... BEFORE TRENDING POPS DOWN WSW TO ENE
MON MORNING. WHILE THE LARGE SCALE MODELS DON`T DEPICT MUCH
INSTABILITY AT ALL SUNDAY WITH PRIMARILY MOIST ADIABATIC FORECAST
PROFILES... WE DO HAVE SOME CONCERN ABOUT POCKETS OF CONVECTION AND
AN ISOLATED THREAT OF A QUICK WEAK SPIN-UP ALONG AND NEAR THE
AFOREMENTIONED BACKDOOR/WARM FRONT ACROSS NRN/WRN NC... ESPECIALLY
LATE SUN AFTERNOON THROUGH SUN EVENING AND INTO THE EARLY OVERNIGHT
HOURS... WHEN THE SURFACE FRONT SHOULD BE RETREATING BACK TO THE
NNE... PROVIDING A FOCUS FOR ENHANCED LOW LEVEL VORTICITY. THIS
CONCERN PEAKS SUN EVENING WITH THE COMBINATION OF 30-40 KTS OF DEEP
LAYER SHEAR... AN UPPER DIVERGENCE MAXIMUM OVER THE SRN
APPALACHIANS AND WRN/CENTRAL NC... INCOMING DRIER AIR IN THE MID
LEVELS... AND A 40-50 KT 850 MB JETLET FROM THE SSE... AND FORECAST
SOUNDINGS SHOW A STRONGLY CURVED HODOGRAPH. WILL CONTINUE TO
MONITOR. WILL TAPER POPS DOWN MON MORNING WSW TO ENE AS THE MID
LEVEL TROUGH AXIS AND CONVEYOR BELT OF PEAK MOISTURE PUSH TO OUR
NORTHEAST... PLACING US FULLY IN THE WARM SECTOR WITH A PUNCH OF MID
LEVEL DRY AIR ARRIVING FROM THE SW AND FLOW-MID LEVEL FLOW BECOMING
MORE UNIDIRECTIONAL. MUCAPE IS EXPECTED TO REACH 1500-2500 J/KG MON
AFTERNOON (AND COULD BE LOCALLY HIGHER IF WE GET MORE HEATING)...
WITH BULK SHEAR NEAR 30-35 KTS AND SW 850 MB WINDS AROUND 30 KTS.
DYNAMIC FORCING FOR ASCENT WILL HAVE DECREASED BY MON AFTERNOON...
BUT WE`LL STILL BE BENEATH CYCLONIC MID LEVEL FLOW WITH WEAK DPVA...
AND ANOTHER ROUND OF DECENT UPPER DIVERGENCE IN THE LEFT EXIT REGION
OF THE STRAIGHT 140 KT SUBTROPICAL JET ACROSS TX AND THE GULF
STATES. SO STILL EXPECT A FEW STRONG CELLS MON AFTERNOON INTO EARLY
EVENING WITH STRAIGHT LINE WINDS THE PRIMARY THREAT. HIGHS SUN FROM
THE MID 60S TO LOWER 70S WEST OF HIGHWAY 1... AND LOW-MID 70S FROM
HIGHWAY 1 EAST. LOWS UPPER 50S NW TO MID 60S SE. STILL EXPECT HIGHS
IN THE UPPER 70S TO LOWER 80S MON. LOWS MON NIGHT MID 50S NW TO
LOWER 60S SE WITH COLD FRONTAL PASSAGE EXPECTED AFTER MIDNIGHT WITH
DIMINISHING PRECIP CHANCES.

TUE THROUGH FRI: A MAINLY QUIET PERIOD. LARGE AND DEEP MID LEVEL LOW
PRESSURE CENTERED OVER AND NORTH OF THE NRN GREAT LAKES WILL COVER
MUCH OF CENTRAL AND EASTERN NOAM... BRINGING SEASONABLY COOL TEMPS
AS IT SITS AND SPINS THROUGH MID WEEK. HIGH PRESSURE WILL BUILD INTO
OUR AREA FROM THE WEST TUE... PASS OVERHEAD EARLY WED... THEN SHIFT
OFF THE COAST LATE WED INTO THU (GFS IS FASTER THAN THE ECMWF WITH
THIS) WHILE A WARM FRONT MOVES NORTHWARD THROUGH NC. ENERGY
EMANATING OUT OF THE BASE OF DEEP TROUGHING JUST OFF THE WEST COAST
WILL CROSS THE DESERT SOUTHWEST THEN MOVE INTO OUR AREA LATE THU
INTO FRI. WITH A SOUTHERLY LOW LEVEL FLOW ON THE BACK SIDE OF THE
EXITING HIGH... WE SHOULD SEE INCREASING PW AND RETURNING CHANCES
FOR SHOWERS LATE THU INTO FRI... HOWEVER THE MOISTURE INFLUX STILL
DOESN`T LOOK GREAT WITH LIGHT AND DIFFLUENT LOW LEVEL FLOW... SO
WILL KEEP POPS BELOW CLIMATOLOGY. TEMPS SHOULD HOLD NEAR OR JUST
BELOW NORMAL THROUGH THE PERIOD. -GIH

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
AS OF 123 AM SATURDAY...

VFR CONDITIONS ARE EXPECTED TODAY AND TONIGHT. HOWEVER... VFR TO
MVFR CIGS CAN BE EXPECTED TODAY. THERE IS A CHANCE OF MVFR VSBYS
THIS MORNING WITH A CHANCE OF SHOWERS MAINLY AT KFAY.

A WARM FRONT WILL MOVE NORTH OVER NC SUNDAY. THIS WILL LOWER CIGS
AND VSBYS SUNDAY AS RAIN ARRIVES FROM THE SOUTH DURING THE DAY. IFR
TO LIFR CIGS AND VSBYS WITH RAIN AND FOG ARE EXPECTED LATE SUNDAY
INTO SUNDAY NIGHT.

MONDAY... CIGS WILL BREAK OUT INTO VFR DURING THE MORNING. THERE IS
A CHANCE OF SHOWERS AND THUNDERSTORMS WITH THE COLD FRONT MONDAY
AFTERNOON AND EVENING.

THE OUTLOOK BEYOND MONDAY...
A RETURN TO VFR CONDITIONS IS EXPECTED MONDAY NIGHT THROUGH FRIDAY.



&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SYNOPSIS...BADGETT
NEAR TERM...RAH
SHORT TERM...MLM
LONG TERM...HARTFIELD
AVIATION...BADGETT



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