Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 271158
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
730 AM EDT SUN JUL 27 2014

.SYNOPSIS...A SURFACE TROUGH WILL PERSIST OVER THE CAROLINAS TODAY.
A STRONG COLD FRONT WILL CROSS THE AREA ON MONDAY...BRINGING
NOTICEABLY COOLER AND LESS HUMID AIR INTO THE AREA.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 700 AM SUNDAY...

AN UNSEASONABLY STRONG POSITIVELY TILTED SHORTWAVE TROUGH WILL TAKE
ON AN INCREASINGLY NEUTRAL TILT AS IT DIGS SEWD FROM THE UPPER MS
VALLEY THROUGH THE OHIO VALLEY AND GREAT LAKES REGION TODAY AND
TONIGHT.  AT THE SURFACE...A PRE-FRONTAL SURFACE TROUGH WILL REMAIN
CENTERED OVER THE FORECAST AREA TODAY AS A STRONG SURFACE COLD FRONT
APPROACHES FROM THE NORTHWEST OVERNIGHT.

NEAR TERM FORECAST WILL BE INFLUENCED BY POTENTIALLY MULTIPLE
ROUNDS/WAVES OF UPSTREAM CONVECTION--INITIALLY BY THE MCV ENTERING
THE CENTRAL/SOUTHERN APPALACHIANS AND THEN PERHAPS LATE THIS
AFTERNOON AND EVENING BY CONVECTIVE CLUSTERS THAT MAY OR MAY NOT
FORM UPSTREAM IN ADVANCE OF THE UPPER-LEVEL TROUGH AND ASSOCIATED 60-
70KT MID-LEVEL JET SPREADING SOUTHEASTWARD TOWARDS THE REGION.

MCV AND ASSOCIATED CONVECTION IS EXPECTED TO MOVE EASTWARD INTO THE
MID-ATLANTIC STATES...INCLUDING CENTRAL/SOUTHERN VIRGINIA THROUGH
MIDDAY. A BAND OF SHOWERS AND PERHAPS A THUNDERSTORM OR TWO SHOULD
PROGRESS EASTWARD IN WEAKENING FASHION AS IT ENCOUNTERS A LESS
FAVORABLE ENVIRONMENT. SUBSIDENCE IN THE WAKE OF THE MORNING MCV
COULD RESULT IN A LULL IN CONVECTION THIS AFTERNOON...WITH POPS
PERHAPS INCREASING THIS EVENING AS UPSTREAM CONVECTION CURRENTLY
OVER THE SOUTHERN OHIO VALLEY COULD MAKE A RUN FOR THE AREA. GIVEN
UNCERTAINTY IN THE EVOLUTION OF UPSTREAM CONVECTION AND SUFFICIENT
INSTABILITY OF 500-1000J/KG OF MLCAPE WILL WARRANT AT LEAST SLIGHT
CHANCE POPS OVERNIGHT.

IF CONVECTION DOES DEVELOP ACROSS THE AREA...STRENGTHENING SHEAR OF
35 TO 40 KNOTS COUPLED WITH THE EASTWARD ADVECTION OF A MODIFIED
ELEVATED MIXED LAYER CHARACTERIZED BY MID-LEVEL LAPSE RATES OF 7.0-
7.25 WILL SUPPORT A FEW STORMS CAPABLE OF PRODUCING LARGE HAIL AND
DAMAGING WIND GUSTS.

TEMPERATURES: CONSIDERABLE CLOUDINESS AND THE THREAT OF CONVECTION
WILL LIMIT INSOLATION THROUGH AT LEAST LUNCH TIME...AND POSSIBLY ON
INTO THE AFTERNOON. THIS WILL TEMPER AFTERNOON TEMPERATURES AND HAVE
LOWERED MAX TEMPERATURES. HIGHS 90 TO 95....WHICH WILL ALSO KEEP
HEAT INDICES 100 F OR LESS.  MILD OVERNIGHT LOWS IN THE LOWER TO MID
70S.

&&

.SHORT TERM /MONDAY AND MONDAY NIGHT/...
AS OF 315 AM SUNDAY...

FOR THE LAST COUPLE OF RUNS MODELS HAVE PERSISTENT IN SHIFTING THE
MOIST UNSTABLE AIRMASS SOUTHEASTWARD OVER THE NC COASTAL PLAIN
MONDAY AFTERNOON WITH THE SURFACE COLD FRONT JUMPING
EASTWARD...MERGING WITH THE PRE-FRONTAL SFC TROUGH AS MID-LEVEL DRY
AIR SPREADS IN RAPIDLY FROM THE WEST. IN FACT IF THESE RECENT TRENDS
CONTINUE OF SHIFTING THE CONVECTION EAST AND SOUTH OF THE
AREA...MUCH OF THE FORECAST AREA COULD END UP BEING DRY ON MONDAY.
WILL CONTINUE TO MONITOR THIS TREND ANOTHER MODEL ITERATION OR TWO
BEFORE DECREASING POPS.

SEVERE THREAT: STRONG 40-50KT MID-LEVEL FLOW COUPLED WITH STRONG
DESTABILIZATION WITH ML CAPE VALUES OF 2000-3000 J/KG WILL RESULT IN
A THREAT OF SUPERCELLS ACROSS EASTERN NC...ALONG AND EAST OF
INTERSTATE 95. VERY LARGE HAIL ON THE ORDER OF 1.50 - 2.00 INCH
DIAMETER AND DAMAGING WINDS IS POSSIBLE.

HIGH TEMPERATURES MONDAY IN THE MID/UPPER 80S NW TO LOWER/MID 90S
SE. THE COOL AIR BEGINS TO FILTER INTO THE AREA MONDAY NIGHT WITH
LOWS RANGING FROM LOWER 60W NW TO MID/UPPER 60 SE.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 300 AM SUNDAY...

UPPER LEVEL TROUGHING WILL STAY IN PLACE OVER THE EAST COAST
THROUGHOUT THE ENTIRE LONG TERM PERIOD...WHILE AT THE SURFACE
COOL...CANADIAN HIGH PRESSURE WILL GRADUALLY SETTLE EAST OVER THE
EAST COAST...KEEPING THE FRONT OFFSHORE. ALL OF THIS WILL LEAD TO
BELOW NORMAL TEMPS...WITH HIGHS GENERALLY IN THE LOW/MID 80S AND
OVERNIGHT LOWS IN THE LOW/MID 60S...POSSIBLY EVEN SOME UPPER 50S IN
THE NORMAL COOLER SPOTS. IN ADDITION...MOSTLY DRY CONDITIONS ARE
EXPECTED THROUGH AT LEAST THURSDAY AS NORTHWESTERLY FLOW ALOFT
MAINTAINS A DRY COLUMN...WITH PWAT VALUES PROGGED TO HOVER JUST
ABOVE 1 INCH.

BY LATE IN THE WEEK AND ESPECIALLY INTO THE WEEKEND...THE HIGHLY
AMPLIFIED RIDGE OVER THE ATLANTIC WILL SHIFT WESTWARD...NUDGING THE
UPPER LEVEL TROUGH BACK TOWARDS THE OHIO/MS RIVER VALLEYS. AS A
RESULT...THE FRONT WILL WILL ALSO MOVE CLOSER TO THE COAST AND
MODELS INDICATE A WAVE(S) A LOW PRESSURE TRACKING ALONG IT BY THE
WEEKEND. ALSO...MOISTURE WILL GRADUALLY INCREASE (PWATS RISING BACK
OVER 1.5 INCHES) AS FLOW ALOFT BECOMES MORE SOUTHWESTERLY. AS A
RESULT OF ALL OF THIS...WILL SHOW PRECIP CHANCES INCREASING INTO THE
LOW END CHANCE RANGE BY SATURDAY. HIGH TEMPS WILL STILL BE IN THE
LOW/MID 80S...WITH OVERNIGHT LOWS IN THE LOW/MID 60S.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
AS OF 730 AM SUNDAY...

AN MCV WILL MOVE THROUGH THE AREA THIS MORNING. BAND OF CONVECTION
ASSOCIATED WITH THIS UPPER DISTURBANCE WILL PROGRESS EASTWARD INTO
THE WESTERN AND CENTRAL PIEDMONT OVER THE NEXT COUPLE OF
HOURS...POSSIBLY RESULTING IN A BRIEF PERIOD MVFR CONDITIONS AT KINT
AND KGSO. STORMS ARE EXPECTED TO WEAKEN AS THEY MOVE EAST INTO A
LESS FAVORABLE ENVIRONMENT. WILL MONITOR RADAR TRENDS OVER THE NEXT
COUPLE OF HOURS AND AMEND KRDU...KRWI AND KFAY IF STORMS POSE A
THREAT.

A SECOND ROUND OF CONVECTION IS POSSIBLE LATE THIS AFTERNOON AND
EVENING AS UPSTREAM CONVECTION CURRENTLY OVER THE SOUTHERN OHIO
VALLEY/KENTUCKY COULD POTENTIALLY TRACK SOUTHEAST INTO THE AREA.
HOWEVER...WILL NOT INCLUDE ANY SIGNIFICANT WEATHER AT THIS TIME AS
EVOLUTION OF THIS CONVECTION IS STILL HIGHLY UNCERTAIN.

BEYOND THE 24 HOUR TAF PERIOD...A COLD FRONT WILL MOVE ACROSS
CENTRAL NC ON MONDAY...BRINGING A THREAT OF SHOWERS AND TSTMS AND
ASSOC REDUCED FLIGHT CONDITIONS MONDAY AFTERNOON MAINLY ALONG
EASTERN NC IN PROXIMITY TO KRWI AMD KFAY. VFR CONDITIONS ARE
EXPECTED TO RETURN BEHIND THE FRONT FOR THE MIDWEEK
PERIOD.

&&

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

&&

$$

SYNOPSIS...WSS
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...KRD
AVIATION...CBL


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