-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 240702
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
301 AM EDT THU APR 24 2014

.SYNOPSIS...HIGH PRESSURE WILL BUILD SOUTH ACROSS THE MIDDLE
ATLANTIC STATES TODAY...THEN OFFSHORE TONIGHT. A WARM FRONT WILL
LIFT NORTH THROUGH NC AND VA FRIDAY MORNING...FOLLOWED BY THE
PASSAGE OF A COLD FRONT FRIDAY EVENING.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 245 AM THURSDAY...

A REINFORCING BACKDOOR COLD FRONT...EVIDENT AS A RADAR FINE LINE ON
KAKQ/KRAX/KMHX BETWEEN 00-06Z...HAD SETTLED INTO THE SOUTHERN
COASTAL PLAIN/SANDHILLS/SOUTHERN PIEDMONT DURING THE PAST HOUR OR
TWO. THIS BOUNDARY MARKS THE LEADING EDGE OF A 1021 MB HIGH OVER
EASTERN MI...WHICH WILL BUILD SOUTH ACROSS THE MIDDLE ATLANTIC
STATES TODAY...AND RESULT IN TEMPERATURES 2-3 DEGREES COOLER THAN
THOSE OF WED. SKIES WILL BE SUNNY TO START...BECOMING MOSTLY TO
PARTLY SO FROM SOUTH TO NORTH...AS A RESULT OF A BAND OF 10-15
THOUSAND FT MOISTURE OVER THE UPPER MIDWEST AND OH VALLEY FORECAST TO
SKIRT IN NW MID LEVEL FLOW MAINLY THE NORTHERN HALF OF THE FORECAST
AREA THIS AFTERNOON. OTHERWISE SOME PASSING THIN CIRRUS OVER THE TN
VALLEY THIS MORNING WILL ARRIVE AREA-WIDE ABOUT THE SAME TIME.

THE SURFACE RIDGE AXIS WILL HAVE SHIFTED OFFSHORE BY THIS EVENING
AND PROMOTE A DEVELOPING RETURN/SOUTHERLY FLOW (PARTICULARLY JUST
ABOVE A STABLE/NOCTURNAL INVERSION)...AND CONSEQUENTLY ALLOW THE
SURFACE BOUNDARY TO RETREAT NORTH AS A WARM FRONT IN ADVANCE OF A
SHORTWAVE TROUGH ALOFT AND ATTENDANT SURFACE LOW LIFTING TOWARD THE
OH VALLEY/LOWER GREAT LAKES. THE APPROACH AND PASSAGE OF THE
BOUNDARY VERY LATE TONIGHT THROUGH EARLY FRI WILL RESULT IN THE
DEVELOPMENT OF STRATUS...LOWEST AND WITH GREATEST COVERAGE OVER
THE WESTERN/SOUTHERN PIEDMONT. SCATTERED ELEVATED SHOWERS ARE ALSO
APT TO DEVELOP NORTHWARD WITH THE PASSAGE OF THE FRONT...AS
MOISTENING AT THE NOSE OF THE LLJ AND INVOF THE BOUNDARY DRIVE
WEAK/SHALLOW ELEVATED INSTABILITY AMIDST A LIFT-INDUCING REGIME OF
LOW LEVEL WAA AND HEIGHT FALLS ALOFT (AHEAD OF THE AFOREMENTIONED
SHORTWAVE TROUGH). WIDE RANGING LOWS FROM THE MID 40S IN CLOSEST
PROXIMITY TO THE DEPARTING SFC RIDGE AXIS AND PERIODS OF CALM OVER
THE COASTAL PLAIN...TO LOWER 50S OVER THE SOUTHERN PIEDMONT.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
-- Changed Discussion --
AS OF 300 AM THURSDAY...

FRIDAY AND FRIDAY NIGHT:
A DEAMPLIFYING SHORTWAVE TROUGH WILL APPROACH AND CROSS THE REGION
DURING THE DAY ON FRIDAY...WITH THE ASSOCIATED TRAILING WEAK COLD
FRONT EXPECTED TO MOVE THROUGH THE REGION FRIDAY AFTERNOON/EVENING.
AS A RESULT...PRECIP CHANCES WILL INCREASE FROM WEST TO EAST FRIDAY
MORNING...BEFORE GRADUALLY DECREASING DURING THE EVENING HOURS.
THERE ARE STILL SEVERAL DIFFERENCES IN THE MODELS...MOST NOTABLY
BEING THE STRENGTH/TIMING OF THE SHORTWAVE ENERGY...WHICH WILL HAVE
IMPLICATIONS ON OUR PRECIP AND SUBSEQUENT SEVERE THREAT. THE GFS
MOVES THE WEAK ENERGY ACROSS THE AREA EARLY IN THE DAY...WHILE THE
ECMWF IS STRONGER/DEEPER WITH THIS FEATURE AND THEREFORE SOMEWHAT
SLOWER IN ITS PROGRESSION (WITH THE NAM BEING IN THE MIDDLE). WITH
THE EARLIER ARRIVAL OF THE SHORTWAVE (PER GFS)...SHOWERS SHOULD BE
ONGOING DURING THE MORNING AHEAD OF THE APPROACHING SURFACE FRONT...
THUS LIMITING THE AFTERNOON DESTABILIZATION. IN ADDITION...OUR AREA
WOULD BE ON THE SUBSIDENT SIDE OF THE SHORTWAVE BEFORE THE FRONT
MOVES THROUGH. ALL OF THIS WOULD LEAD TO A LIMITED SEVERE WEATHER
THREAT. HOWEVER...WITH THE SLOWER PROGRESSION...FEATURES COULD LINE
UP MORE FAVORABLY...ESPECIALLY ACROSS THE EASTERN HALF OF THE
FORECAST AREA. THIS WILL CONTINUED TO BE CLOSELY MONITORED OVER THE
NEXT COUPLE OF DAYS. NEVERTHELESS...EVEN THE GFS INDICATES SOME
MARGINAL INSTABILITY (MOSTLY ACROSS THE EAST) AS TEMPS RISE TO NEAR
80 DEGREES AND THEREFORE CANNOT RULE OUT AN ISOLATED STRONG TO
SEVERE STORM.

SATURDAY THROUGH SUNDAY NIGHT:
DRY WEATHER WITH SEASONABLE TEMPERATURES WILL ENSUE FOR THE WEEKEND
IN THE WAKE OF THE COLD FRONT FRIDAY NIGHT AS A MILD SURFACE HIGH
SURFACE BUILDS INTO THE AREA LOWER MS VALLEY/NORTHERN GULF COAST
STATES. A COMPACT UPPER LOW/TROUGH OVER THE UPPER GREAT LAKES WILL
MOVE EASTWARD-SOUTHEASTWARD THROUGH SOUTHERN NEW ENGLAND ON SUNDAY.
ATTENDANT HEIGHT FALLS ALOFT ACROSS THE NORTHERN MID-ATLANTIC STATES
WILL ATTEMPT TO DRIVE A BACK-DOOR COLD FRONT SOUTHWARD INTO THE AREA
ON SUNDAY...BUT GIVEN S/W RIDGE ALOFT BUILDING IN FROM THE
WEST...THINK THIS WIL CURTAIL SOUTHWARD PUSH OF THE FRONT...WITH
EXPECTATIONS OF THE FRONT STALLING NORTH OF THE AREA. HIGHS IN THE
70S. LOWS IN THE 50S.
-- End Changed Discussion --


&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
AS OF 300 AM THURSDAY...

AN ACTIVE AND UNSETTLED WEATHER PATTERN LOOKS TO BE SETTING UP
ANYWHERE FROM THE SOUTHERN PLAINS EASTWARD FOR AT LEAST THE FIRST
HALF OF NEXT WEEK..IF NOT LONGER OWING TO THE BLOCKING PATTERN OVER
THE SOUTHEAST CANADA TOWARDS GREENLAND THAT WILL HAMPER THE
EASTWARD PROGRESSION OF A STRONG CLOSED LOW FROM THE SOUTHWEST INTO
THE CENTRAL CONUS.

REGARDING SENSIBLE WEATHER IMPACTS...WHILE MODEL SPREAD IS CURRENTLY
TOO HIGH TO ELABORATE ON FORECAST SPECIFICS/DETAILS...GIVEN SUCH A
POTENT SYSTEM WITH A HIGH LIKELIHOOD OF DEEP GULF MOISTURE TRANSPORT
NORTHWARD INTO THE AREA DURING THE CLIMATOLOGICALLY FAVORED SPRING
CONVECTIVE SEASON OF LATE APRIL/EARLY MAY...CENTRAL NC WILL HAVE TO
BE ON THE LOOKOUT FOR THE POSSIBILITY OF EXCESSIVE RAINFALL AND
SEVERE STORMS MONDAY THROUGH WEDNESDAY. PROSPECTS OF WIDESPREAD
CLOUDS AND PRECIP WILL KEEP TEMPERATURES NEAR NORMAL.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 300 PM WEDNESDAY...

HIGH PRESSURE OVER THE AREA ON SUNDAY WILL RESULT IN QUIET WEATHER
FOR CENTRAL NC...WITH TEMPS NEAR TO SLIGHTLY ABOVE NORMAL. THE HIGH
WILL SHIFT OFFSHORE LATE SUNDAY INTO MONDAY AHEAD OF A STRONG SYSTEM
THAT WILL LIKELY BE A BIG SEVERE WEATHER MAKER FOR THE CENTRAL CONUS
OVER THE WEEKEND AND EARLY NEXT WEEK. THERE IS STILL A LOT TO BE
WORKED OUT WITH REGARD TO THE DETAILS OF THIS SYSTEM...THEREFORE
FORECAST UNCERTAINTY REMAINS HIGH. OVERALL THIS CUTOFF LOW WILL
SLOWLY MAKE ITS WAY EAST THROUGH THE MIDDLE OF NEXT WEEK...WITH OUR
BEST PRECIP CHANCES LOOKING TO BE ON TUESDAY...ALTHOUGH SOME
OVERRUNNING PRECIP WILL BEGIN EARLY MONDAY MORNING. TEMPS SHOULD BE
NEAR TO SLIGHTLY BELOW NORMAL...BUT WILL ULTIMATELY DEPEND ON THE
AMOUNT/TIMING OF CLOUDS/PRECIP.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 155 AM THURSDAY...

HIGH PRESSURE WILL BUILD SOUTH FROM THE GREAT LAKES AND RESULT IN A
HIGH CONFIDENCE OF VFR CONDITIONS THROUGH THE TAF PERIOD. IN
ANTICYCLONIC FLOW AROUND THE HIGH...NNE SURFACE WINDS THIS MORNING
WILL BECOME LIGHT AND VARIABLE BENEATH THE RIDGE AXIS BY MIDDAY...
THEN LIGHT SOUTHERLY...THIS AFTERNOON AT TRIAD TERMINALS...AND THIS
EVENING ELSEWHERE. PASSING MID CLOUDS (BETWEEN 10 AND 15 THOUSAND
FEET) IN WNW FLOW ALOFT WILL SKIRT THE NORTHERN PIEDMONT THIS
AFTERNOON.

OUTLOOK: THE DEVELOPING SOUTHERLY RETURN FLOW AND ASSOCIATED
APPROACH OF A SURFACE WARM FRONT FROM THE SOUTH WILL RESULT IN THE
DEVELOPMENT OF IFR-MVFR STRATUS LATE TONIGHT AND EARLY FRI...LOWEST
AND MOST LIKELY AT TRIAD TERMINALS. THE PASSAGE OF THE WARM FRONT
WILL ALSO SUPPORT SCATTERED SHOWERS FRI MORNING...FOLLOWED BY A
BREEZY SW SURFACE WIND AND ANOTHER ROUND OF SCATTERED SHOWERS - AND
THUNDERSTORMS - ALONG AND AHEAD OF A COLD FRONT FRI AFTERNOON AND
EVENING. UNSETTLED WEATHER WILL RETURN AGAIN EARLY NEXT WEEK..AND
WILL LIKELY LINGER THROUGH MID-WEEK.



&&

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

&&

$$

SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...KRD/CBL
LONG TERM... CBL
AVIATION...MWS