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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 150524
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
125 AM EDT SAT JUN 15 2013

.SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE CONTINUES TO BUILD OVER THE REGION TODAY. THE HIGH
MOVES OFF OF THE SOUTHEAST COAST SUNDAY. THE AIR BECOMES
INCREASINGLY MOIST SUNDAY INTO MONDAY...AHEAD OF A COLD FRONT THAT
MOVES INTO THE REGION TUESDAY.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 955 PM FRIDAY...

QUIET NIGHT EXPECTED. A MID LEVEL VORTICITY MAXIMA WHICH DROPPED
SOUTHEASTWARD OVER THE FORECAST AREA THIS AFTERNOON HAS MOVED TO OUR
SOUTHEAST... AND THE RESULTING COMBINATION OF NVA... QUICKLY DRYING
AND STABILIZING MID LEVEL AIR... INCOMING CONFLUENT UPPER LEVEL FLOW
(AS THE 100 KT NORTHWESTERLY UPPER JET OVER THE SRN APPALACHIANS
WEAKENS AND SHIFTS EAST)... AND LOSS OF DAYTIME HEATING HAS RAPIDLY
CLEARED OUT SKIES THIS EVENING. FORECAST SOUNDINGS SHOW FEW TO NO
CLOUDS OVERNIGHT... AND LOOKING TO OUR NORTHWEST... THE ONLY CLOUDS
OF NOTE ARE HIGH CLOUDS BLOWN OFF OF MIDWEST MCS ACTIVITY... AND
THESE ARE DISSIPATING AND SHOULD HOLD TO OUR WEST OVERNIGHT BASED ON
OBSERVED STEERING WINDS ALOFT. TEMPS ARE RUNNING A BIT BELOW
FORECAST PACE... AND BY SEVERAL DEGREES IN THE NORMALLY COOLER
OUTLYING AREAS... SO WILL NUDGE OVERNIGHT LOWS DOWNWARD BY 1-4
DEGREES... TO 55-62. OBSERVED TRENDS AND LATEST MODEL OUTPUT SHOW NO
CHANGES ARE NEEDED AT THIS TIME TO THE SATURDAY FORECAST. -GIH

&&

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

THE UPPER LEVEL TROUGH WILL CONTINUE TO PUSH FURTHER OFFSHORE ON
SATURDAY WITH THE NORTHWEST FLOW ALOFT BECOMING MORE ZONAL ON
SATURDAY NIGHT. THE SURFACE HIGH WILL SHIFT SOUTHEAST ACROSS THE
REGION EARLY SATURDAY AND WILL BE LOCATED OFFSHORE BY SATURDAY
AFTERNOON. FAIR WEATHER IS EXPECTED DURING THE PERIOD BUT A SHALLOW
LAYER OF MOISTURE IS PROGGED TO BE TRAPPED BELOW A STRENGTHENING
SUBSIDENCE INVERSION AND RESULT IN THE DEVELOPMENT OF FLAT CUMULUS
CLOUDS DURING THE LATE MORNING AND AFTERNOON WITH MOSTLY TO PARTLY
SUNNY SKIES. THE DIURNALLY DRIVEN CLOUDS WILL ABATE DURING THE
EVENING ON SATURDAY BUT SOME MID LEVEL CLOUDINESS WILL MOVE INTO THE
AREA FROM THE WEST LATE SATURDAY NIGHT IN A WARM ADVECTION PATTERN.
HIGHS ON SATURDAY WILL RANGE IN THE 83 TO 88 RANGE WITH OVERNIGHT
LOWS IN THE MID 60S. -BLAES

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 250 PM FRIDAY...

A BROAD UPPER TROUGH OVER THE EASTERN TWO-THIRDS OF THE NATION WILL
GRADUALLY AMPLIFY THIS PERIOD AS AN UPPER RIDGE BUILDS OVER THE
SOUTHERN PLAINS INTO THE ROCKIES. A SERIES OF S/WS IN THE DEVELOPING
W-NW FLOW ALOFT WILL BRING A THREAT FOR SHOWERS AND T-STORMS TO THE
REGION EARLY NEXT AND AGAIN LATE IN THE WEEK. THE MAIN WEATHER
HEADLINE FOR NEXT WEEK WILL BE THE GOOD PROBABILITY OF MAX TEMPS 4-7
DEGREES BELOW NORMAL FOR THE THIRD WEEK IN JUNE. THE UPPER LEVEL JET
FORECAST TO BE FARTHER SOUTH THAN NORMAL FOR THIS TIME OF YEAR. THIS
SWD POSITION WILL ALLOW COOLER CANADIAN AIR TO SPILL INTO THE
NORTHERN THIRD OF THE U.S. WITH SOME RESIDUAL AFFECTS BEING FELT IN
THE CAROLINAS.

SUNDAY...SURFACE HIGH OVER THE REGION EARLY IN THE DAY WILL MOVE
OFFSHORE. THE RESULTANT SLY FLOW ON THE BACK SIDE OF THE HIGH WILL
ADVECT WARM MOIST AIR INTO THE PIEDMONT BY AFTERNOON-EARLY EVENING.
IT APPEARS THAT ANY CONVECTION THAT DEVELOPS IN THE HIGHER TERRAIN
OF WESTERN NC WILL STAY JUST EAST OF THE PIEDMONT AS STEERING FLOW
SHOULD KEEP THE CONVECTION PARALLEL TO THE RIDGES. LOW LEVEL
THICKNESSES FAIRLY CLOSE TO NORMAL WHICH SUGGEST AFTERNOON TEMPS
SOLIDLY IN THE MID 80S.

MONDAY THROUGH TUESDAY...THE FIRST S/W IN THE W-NW FLOW ADVANCES
TOWARD OUR REGION MONDAY...AND EXITS THE REGION TUESDAY. THE
ASSOCIATED COLD FRONT WILL ENHANCE LOW LEVEL CONVERGENCE WHILE THE
SYSTEM ALOFT SUPPLIES ADDED LIFT. WITH PRECIP WATER VALUES PROJECTED
TO BE 1.75-1.9 INCHES...EXPECT SCATTERED TO NUMEROUS SHOWERS AND A
FEW THUNDERSTORMS WITH THIS SYSTEM...MAINLY IN THE WEST LATE MONDAY
AND AREAWIDE MONDAY NIGHT INTO TUESDAY. IF LATER MODEL GUIDANCE
REMAINS CONSISTENT...WILL NEED TO INCREASE POPS TO LIKELY OR LOW END
CATEGORICAL MONDAY NIGHT INTO TUESDAY.

WEDNESDAY THROUGH THURSDAY SHOULD SEE A RELATIVELY TRANQUIL WEATHER
PATTERN AS HIGH PRESSURE OVER THE LOWER GREAT LAKES NOSES SEWD INTO
OUR REGION. DEVELOPING ELY FLOW BY THURSDAY MAY ADVECT ATLANTIC
MOISTURE INTO CENTRAL NC RESULTING IN CONSIDERABLE CLOUDINESS.

MODEL GUIDANCE DIFFERS LATE IN THE WEEK AS THE GFS IS MUCH MORE
PROGRESSIVE WITH AN UPPER LEVEL CROSSING THE PACIFIC NW INTO THE
NORTHERN ROCKIES WHILE THE ECMWF IS SLOWER WITH THIS EWD
TRANSLATION DUE TO PRESENCE OF UPPER RIDGE OVER THE ROCKIES/HIGH
PLAIN. SINCE GFS HAS A HISTORY OF BEING TOO FAST IN THIS TYPE OF
PATTERN...PREFER THE ECMWF SOLUTION. THIS MODEL CHOICE SUGGEST
ANOTHER S/W APPROACHING CENTRAL NC BY FRIDAY. MOISTURE ADVECTION
AHEAD OF THIS SYSTEM MAY CAUSE A THREAT FOR LIGHT RAIN SHOWERS BY
THE END OF THE WEEK. DUE TO LIKELY MODEL ADJUSTMENTS IN TIMING OR
STRENGTH OF THE SYSTEM...PREFER TO KEEP POPS AT OR BELOW 20 PERCENT
FOR FRIDAY.
&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
AS OF 125 AM SATURDAY...

VFR CONDITIONS OCCUR DURING THE 06Z VALID TAF PERIOD...OUTSIDE OF
SOME AREAS OF MAINLY MVFR FOG ESPECIALLY TOWARD KRWI AND POSSIBLY
KFAY. EXPECT DIURNAL CU TO DEVELOP ONCE AGAIN THIS AFTERNOON ACROSS
CENTRAL NORTH CAROLINA...POSSIBLY NOT AS MUCH AS OCCURRED FRIDAY
AFTERNOON IN MOST PLACES BUT STILL FEW-TO-SCATTERED DURING THE
AFTERNOON. VARIABLE SURFACE WINDS BECOME WEST-SOUTHWEST DURING THE
MORNING...BUT WITH HIGH PRESSURE OVERHEAD 10KT OR LESS...AND A FEW
TYPICAL MIXING GUSTS IN THE LOWER TEENS KNOTS DURING DAYLIGHT HOURS.

BEYOND THE 06Z VALID TAF PERIOD...THE AIR BECOMES INCREASINGLY MOIST
IN CENTRAL NORTH CAROLINA SUNDAY INTO MONDAY. AN ISOLATED SHOWER OR
THUNDERSTORM IS POSSIBLE SUNDAY NIGHT...WITH CHANCES FOR SHOWERS AND
THUNDERSTORMS...AND ASSOCIATED LOCAL SUB-VFR CONDITIONS...INCREASING
ALONG WITH THE MOISTURE MONDAY INTO TUESDAY. THERE IS SOME
PROBABILITY OF LOW CLOUDS LATE MONDAY NIGHT INTO TUESDAY MORNING
BASED ON THE MODEL SOUNDINGS OF THE GFS. CHANCES FOR SHOWERS AND
THUNDERSTORMS CURRENTLY SEEM TO DIMINISH WEDNESDAY RELATIVE TO
MONDAY AND TUESDAY...WITH THE BETTER POTENTIAL FOR ISOLATED SHOWERS
AND STORMS TOWARD KFAY COMPARED TO OTHER CENTRAL NORTH CAROLINA TAF
SITES.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...DJF
NEAR TERM...HARTFIELD
SHORT TERM...BLAES
LONG TERM...WSS
AVIATION...DJF