Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 241442
AFDRAH

AREA FORECAST DISCUSSION
1045 AM EDT FRI APR 24 2015

.SYNOPSIS...COOL HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE
NORTHWEST TODAY. A WARM FRONT WILL MOVE IN FROM THE SOUTHWEST LATE
TONIGHT...AND THEN STALL ACROSS THE REGION THROUGH THE WEEKEND...
BRINGING UNSETTLED WEATHER AS WAVES OF LOW PRESSURE TRACKING EAST
ALONG THE FRONT.

&&

.NEAR TERM /THROUGH THIS AFTERNOON/...
AS OF 1045 AM FRIDAY...

SFC HIGH WILL SETTLE OVERHEAD THIS AFTERNOON WHILE MID-UPPER LEVEL
HEIGHTS INCREASE AS S/W RIDGE EDGES EAST FROM THE MS RIVER VALLEY.
SUBSIDENCE ALOFT WILL MAINTAIN MOSTLY CLEAR SKIES OVER THE REGION.
850MB THERMAL TROUGH WILL LIFT NORTH-NE THIS AFTERNOON. THIS WILL
COMMENCE A LOW LEVEL WARM AIR ADVECTION REGIME.

AFTER THE CHILLY START TO THE DAY WITH MIN TEMPS IN THE 30S ACROSS A
LARGE PORTION OF CENTRAL NC...MOST PLACES WILL WARM TO AROUND 60-
LOWER 60S BY MID DAY...TOPPING OUT IN THE 65-70 DEGREE RANGE AT MID-
AFTERNOON. THESE AFTERNOON TEMPERATURES COMBINED WITH DEWPOINTS IN
THE UPPER TEENS AND 20S WILL YIELD MINIMUM RH VALUES IN THE 15-20
PERCENT RANGE THIS AFTERNOON...ABNORMALLY LOW FOR THIS TIME OF YEAR.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
AS OF 325 AM FRIDAY...

A PLUME OF PACIFIC MOISTURE CROSSING MEXICO WILL BE DRAWN EASTWARD
TODAY AS A WEAK UPPER LOW NEAR THE CA/AZ BORDER AREA OPENS UP AND
LIFTS ACROSS THE PLAINS STATES.  THE ASSOCIATED SURFACE WILL MOVE
INTO THE MID-MISSISSIPPI RIVER VALLEY WHILE THE ATTENDANT WARM FRONT
LIFTS THROUGH THE SOUTHEAST US.  MID-CLOUDS WILL THICKEN FROM WEST
TO EAST FRIDAY NIGHT AS WARM ADVECTION SPREADS ACROSS THE
REGION....RESULTING IN LOWS RANGING FROM THE LOW 40S IN THE CLEARER
EASTERN AREAS AND UPPER 40S TO AROUND 50 IN THE OVERCAST WESTERN
AREAS. SOME AREAS OF LIGHT RAIN MAY REACH THE WESTERN PIEDMONT PRIOR
TO 12Z SATURDAY...BUT THE MORE INTENSE 290-300K LAYER ISENTROPIC
ASCENT IS PROGGED TO COME DURING THE DAY ON SATURDAY...AND MORE SO
DURING THE AFTERNOON...AS THE SURFACE LOW MOVES TOWARD THE LOWER
OHIO VALLEY REGION.  A BAND OF RAIN DURING THE DAY SHOULD LOCK IN A
COLD POOL OVER CENTRAL NC AND KEEP THE WARM FRONT DRAPED ACROSS THE
SOUTHERN PORTIONS OF THE AREA...WHERE THE PROSPECTS OF SOME WEAK
DESTABILIZATION...MAINLY ELEVATED...WILL BE GREATEST DURING THE LATE
AFTERNOON AND EVENING HOURS BASED ON THE PREFERRED NAM AND ECMWF
SOLUTIONS. WILL TRANSITION THE CHARACTER OF PRECIP IN THE FORECAST
FROM RAIN TO SHOWERS DURING THE LATER AFTERNOON...WITH A SLIGHT
CHANCE OF THUNDER FROM THE SOUTHERN PIEDMONT TO THE SANDHILLS DURING
THE EVENING.  WHILE MODELS STILL SHOW SOME DIFFERENCES IN QPF
AMOUNTS...THE ECMWF AND SREF SHOW WHAT SEEMS TO BE THE MORE
REASONABLE DISTRIBUTIONS...WITH THE HIGHER AMOUNTS AROUND A THIRD OF
AN INCH ACROSS THE SOUTH AND LIGHTER AMOUNTS TO THE NORTH.

TEMPS ARE TRICKY FOR SATURDAY AND WILL DEPEND ON THE TIMING OF
PRECIP DURING THE FIRST HALF OF SATURDAY.  HAVE SLOWED THE ARRIVAL
OF PRECIP A LITTLE IN THE EAST...SO WILL NUDGE TEMPS UP OVER THE
COASTAL PLAIN...BUT STILL EXPECT A STRONG GRADIENT FROM LOWER 50S
NORTHWEST TO LOWER 60S SOUTHEAST.

THERE SHOULD THEN BE A DECREASE IN SHOWER ACTIVITY SATURDAY NIGHT AS
A DRY SLOT SURGES IN FROM THE WEST AND THE SURFACE LOW TRANSITIONS
OFFSHORE.  EXPECT SKIES TO REMAIN OVERCAST...HOWEVER...AND TEMPS
WILL ONLY FALL A FEW DEGREES INTO THE UPPER 40S TO MID 50S.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
AS OF 400 AM FRIDAY...

A WPC-FAVORED BLEND OF THE 00Z/24TH ECMWF AND NAM SUGGESTS A LEAD
SFC LOW WILL BE MOVING AWAY FROM THE NC COAST EARLY SUN...IN
ASSOCIATION WITH THE PASSAGE AND SHEARING/DEAMPLIFICATION OF THE
SOUTHERN STREAM UPPER LOW LOCATED OVER NW MEXICO THIS MORNING. A
COLD FRONT WILL EXTEND WNW INVOF THE NC/SC BORDER...TO A SECONDARY
SFC LOW FORECAST TO DEVELOP EAST ACROSS THE SOUTHERN-CENTRAL
APPALACHIANS AND OFF THE SC COAST BY SUN EVE. LOW LEVEL
FRONTOGENESIS AND ISENTROPIC UPGLIDE AHEAD OF THE SECONDARY LOW WILL
SUPPORT CONTINUED WIDESPREAD LOW CLOUDS...AND A GOOD TO LIKELY
PROBABILITY OF RAIN SUN...MORE SHOWERY IN NATURE INVOF THE SFC FRONT
NEAR THE SC BORDER. THE PROXIMITY OF THE SFC FRONT WILL ALSO SUPPORT
A LARGE RANGE IN TEMPERATURES FROM THE 50S OVER THE NORTHERN
PIEDMONT AND NORTHERN-CENTRAL COASTAL PLAIN WHERE OVERCAST WILL
LIKELY HOLD THROUGHOUT THE DAY...TO LOWER 70S NEAR THE SC
BORDER...WHERE BRIEF PARTIAL CLEARING WILL BE POSSIBLE DURING THE
MIDDAY TO EARLY AFTERNOON HOURS INVOF THE FRONT.

A PERIOD OF RELATIVELY TRANQUIL AND COOL CONDITIONS...WITH LOWS IN
THE 40S AND HIGHS IN THE MIDDLE 60S TO LOWER 70S (WARMEST TUE)...
CAN BE EXPECTED EARLY NEXT WEEK...AS A DEEP VORTEX MIGRATES SLOWLY
AWAY FROM THE NE US. THE PRESENCE OF THE VORTEX AND UNSEASONABLY
DEEP CYCLONIC FLOW CENTERED OFF THE NEW ENGLAND COAST...BENEATH
HIGHER LATITUDE BLOCKING FLOW...WILL MAINTAIN A SOUTHWARD-SUPPRESSED
STORM TRACK AND FOCUS FOR PRECIPITATION ACROSS THE SOUTHEAST STATES
BY THE MIDDLE OF NEXT WEEK.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AS OF 640 AM FRIDAY...

HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE NEXT 24 HOURS...WITH
SUB-VFR CONDITIONS TO FOLLOW.

RELATIVELY LIGHT NORTH-NORTHWESTERLY WINDS WILL CONTINUE FOR MOST
AREAS THIS MORNING...INCREASING TO AROUND 10KT TODAY AS HIGH
PRESSURE OVER THE OHIO VALLEY REGION BUILDS EAST.  MOSTLY CLEAR
SKIES WILL SLOWLY GIVE WAY TO HIGH CLOUDS FROM THE SOUTHWEST THIS
EVENING AND THEN MORE MID CLOUDS BETWEEN 7-10K FT OVERNIGHT.

OUTLOOK... THE APPROACH OF A WARM FRONT AND LOW PRESSURE SYSTEM WILL
BRING WIDESPREAD RAIN AND MVFR/IFR CEILINGS SATURDAY AND SATURDAY
NIGHT.  MODELS ARE A BIT SLOWER IN BRINGING IN SUB-VFR CEILINGS ON
SATURDAY...HOLDING OFF MVFR CONDITIONS UNTIL LATE MORNING OR EARLY
AFTERNOON. LOW CEILINGS ARE EXPECTED TO LINGER INTO SUNDAY... WITH A
GRADUAL IMPROVEMENT EXPECTED SUNDAY AFTERNOON. VFR CONDITIONS SHOULD
RETURN BY MONDAY AND PERSIST INTO TUESDAY AS WEAK HIGH PRESSURE
BUILDS INTO OUR REGION FROM THE NORTH-NW.

&&


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

&&

$$

SYNOPSIS...RAH
NEAR TERM...WSS
SHORT TERM...22
LONG TERM...RAH
AVIATION...22


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