-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KRAH 281930
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
330 PM EDT SUN JUL 28 2014

.SYNOPSIS...A STRONG COLD FRONT WILL MOVE OFF THE NC COAST THIS
EVENING...THEN STALL OFFSHORE TUESDAY. CANADIAN HIGH PRESSURE WILL
OTHERWISE EXPAND ACROSS THE CAROLINAS AND MIDDLE ATLANTIC THROUGH
MID-WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 325 PM MONDAY...

AT 19Z THE SFC FRONT/CONFLUENCE AXIS/NORTHERN BOUND OF SFC DEWPOINTS
AOA 70 DEGREES EXTENDED FROM THE SOUTHERN NC OUTER BANS WSW TO NEAR
KCTZ TO NEAR KCAE. SHOWERS/STORMS HAVE RECENTLY INITIATED INVOF THE
ASSOCIATED CONVERGENCE AXIS BETWEEN KLBT AND KFLO; AND THESE WILL
SPREAD QUICKLY EASTWARD ACROSS SOUTHEASTERN NC...INCLUDING SAMPSON
COUNTY IN THE RAH CWFA...DURING THE NEXT 2-3 HOURS. THE AIR MASS
SOUTH OF THE FRONT...BENEATH A RESIDUAL PLUME OF STEEP MID LEVEL
LAPSE RATES IN EXCESS OF 7 C/KM PER THE 12Z KMHX RAOB AND MORE
RECENT SPC MESOANALYSIS DATA...HAS BECOME MODERATELY TO STRONGLY
UNSTABLE THIS AFTERNOON. IN ADDITION...A BELT OF STRONG (40-50 KT)
MID LEVEL FLOW OBSERVED FROM THE NORTHERN PLAINS-TN VALLEY-NC COAST
WILL PROVIDE AMPLE DEEP LAYER SHEAR...CHARACTERIZED BY LONG AND
STRAIGHT FORECAST HODOGRAPHS AT KFAY AND KILM THROUGH 00Z -
SUPPORTIVE OF A CONDITIONAL SVR RISK OF DAMAGING WIND GUSTS AND
LARGE HAIL (LIKELY FROM SPLITTING SUPERCELLS PROVIDED STORMS DO NOT
SUCCUMB TO ENTRAINMENT OF DRY AIR ALOFT NOTED ON MOISTURE CHANNEL
AND BLENDED TPW IMAGERY).

THE PASSAGE OF A TRAILING MID LEVEL TROUGH OVERNIGHT COULD PRODUCE A
FEW PATCHES OF HIGH STRATOCUMULUS OR LOW ALTOCUMULUS PER UPSTREAM/OH
VALLEY OBSERVATIONS...AND NWP GUIDANCE...BUT SKY CONDITIONS SHOULD
BE NO WORSE THAN PARTLY CLOUDY. COOLER AS THE CANADIAN HIGH
CONTINUES TO NOSE EAST OF THE APPALACHIANS - LOWS WITHIN A FEW
DEGREES EITHER SIDE OF 65.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
AS OF 255 PM MONDAY...

BENEATH AND WEST OF CYCLONIC FLOW ALOFT WITHIN A MID-UPPER TROUGH
AXIS NEAR 85W...CANADIAN HIGH PRESSURE WILL EXTEND SOUTHEASTWARD
INTO THE MIDDLE ATLANTIC AND CAROLINAS TUE AND TUE NIGHT. COOLER AIR
CHARACTERIZED BY H85 TEMPERATURES AROUND 13C...WHICH WAS ALREADY ON
THE DOORSTEP OF THE RAH CWFA/AT KRNK AND KBNA AT 12Z MON...WILL HAVE
FULLY OVERSPREAD CENTRAL NC THIS PERIOD - SUPPORTIVE OF HIGH
TEMPERATURES IN THE LOWER TO MIDDLE 80S. WITH DEWPOINTS EXPECTED IN
THE 50S BASED ON UPSTREAM OBSERVATIONS OVER THE OH VALLEY...THE
COMBINATION OF LOW RH AND MILD TEMPERATURES WILL FEEL FAR FROM LATE
JULY. LOW LEVEL THICKNESS VALUES OF AROUND 1380 METERS OR SO AT 12Z
WED FAVORS LOWS IN THE UPPER 50S TO AROUND 60 DEGREES ON AVG.

&&

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

WEDNESDAY AND WEDNESDAY NIGHT... A STABLE LONGWAVE PATTERN WILL KEEP
THE EAST/WEST COAST UPEPR TROUGH/RIDGE SETUP IN PLACE FOR THE
REMAINDER OF THIS WEEK AND POTENTIALLY INTO NEXT WEEK.  THE
UNSEASONABLY DEEP TROUGH OVER THE EASTERN CONUS WILL LEAD TO
THICKNESSES AS MUCH AS 20-25 DEGREES BELOW NORMAL WEDNESDAY...WITH
ONLY A SLOW MODERATION THROUGH THE END OF THE WEEK.

PW FALLS WELL BELOW ONE INCH WEDNESDAY...ABOUT 50
PERCENT OF NORMAL...WITH DEWPOINTS WILL INTO THE 50S ACROSS THE
PIEDMONT.  THE ECMWF PRODUCES A LITTLE QPF OVER THE SOUTHERN COASTAL
PLAIN AS A SPEED MAX ON THE BACK SIDE OF THE UPEPR TROUGH NOSES
ACROSS THE SOUTHERN APPALACHIANS.  HOWEVER... PW FALLS WELL BELOW
ONE INCH WEDNESDAY...ABOUT 50 PERCENT OF NORMAL...WITH DEWPOINTS
WELL INTO THE 50S. THIS RESULTS IN ONLY A SHALLOW LAYER OF
INSTABILITY AND LIKELY JUST A DECENT CU FIELD OVER THE COASTAL
PLAIN.  HIGHS 82-86.  LOWS WEDNESDAY NIGHT IN THE LOW TO MID 60S.

THURSDAY THROUGH MONDAY... MODELS SHOW SOME ADDITIONAL ENERGY DIVING
INTO THE BACKSIDE OF THE TROUGH ON THURSDAY...WHILE THE TROUGH AXIS
SHIFTS SLIGHTLY WESTWARD AND HEIGHTS BUILD OVER THE WESTERN
ATLANTIC. THIS SHOULD LEAD INCREASING PRECIP CHANCES...MAINLY
DIURNAL...AS 1) PW BEGINS TO INCREASE BACK TOWARD NORMAL...2)AN
INVERTED COASTAL TROUGH POTENTIALLY SHIFTS WESTWARD AND INLAND...AND
3) AN UPPER JET BECOMES POSITIONED ALONG THE SPINE OF THE
APPALACHIANS.   GIVEN THAT FORCING SHOULD MAINLY COME FROM AFTERNOON
DIFFERENTIAL HEATING AND/OR THE SEABREEZE...CHANCE POPS AROUND
CLIMATOLOGY SEEM MOST REASONABLE THROUGH THE WEEKEND.

THERE IS ALSO THE POTENTIAL FOR WEAK COLD AIR DAMMING AS THE UPPER
LEVEL FLOW BECOMES MORE CONFLUENT OVER NEW ENGLAND AND A WEAK RIDGE
OF HIGH PRESSURE EXTENDS THROUGH THE MID-ATLANTIC STATES.  NOT
SURPRISINGLY...FORECAST SOUNDINGS SHOW NOW SIGN OF LOW CLOUDS AT
THIS POINT...AND ITS HARD TO TELL HOW MUCH IMPACT THERE WOULD BE.
GIVEN THIS AND A GENERAL INCREASE IN CLOUD COVER...HIGHS WILL REMAIN
ONE OR TWO CATEGORIES BELOW NORMAL.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AS OF 150 PM MONDAY...

A COLD FRONT NEAR KFAY WILL SETTLE SOUTHEASTWARD AND OUT OF THE RAH
FORECAST AREA THROUGH SUNSET. WHILE THERE REMAINS A VERY SLIGHT
CHANCE OF A SHOWER OR STORM AT KFAY WITH THE PASSAGE OF THE FRONT
DURING THE NEXT FEW HOURS...IT IS MORE LIKELY THAT ANY SUCH STORM
DEVELOPMENT WILL OCCUR ALONG COASTAL/SE NC WHERE LOW AND DEEP LAYER
MOISTURE IS (MARGINALLY) MORE SUPPORTIVE. OTHERWISE...A BREEZY
WESTERLY WIND WILL GRADUALLY VEER TO NW...AND SUBSIDE AROUND
SUNSET...WITH LIGHT NW WINDS EXPECTED OVERNIGHT. DIURNAL CUMULUS
SHOULD LIKEWISE DIMINISH AROUND SUNSET...THOUGH THE PASSAGE OF A
TRAILING MID LEVEL TROUGH OVERNIGHT COULD PRODUCE A FEW PATCHES OF
HIGH STRATOCUMULUS OR LOW ALTOCUMULUS PER UPSTREAM/OH VALLEY
OBSERVATIONS...AND NWP GUIDANCE.

PREDOMINATELY VFR CONDITIONS SHOULD OTHERWISE PREVAIL THROUGH MOST
OF THE FORECAST PERIOD...AS CANADIAN HIGH PRESSURE BECOMES CENTERED
OVER THE TN VALLEY AND CENTRAL APPALACHIANS THROUGH MID-WEEK...THEN
YIELDS TO AN INVERTED SURFACE TROUGH AND SMALL CHANCE OF A SHOWER OR
STORM BY FRI-SAT.

&&

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

&&

$$

SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...BLS
AVIATION...MWS