Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 181820
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
220 PM EDT MON AUG 18 2014

.SYNOPSIS...A SERIES OF UPPER LEVEL DISTURBANCES WILL CROSS THE
REGION THROUGH MID-WEEK IN ASSOCIATION WITH A NORTHWEST FLOW ALOFT.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1115 AM MONDAY...

OVERVIEW: A POTENT SHORTWAVE LOCATED OVER SOUTHERN WV AND
SOUTHWESTERN VA AT 15Z IS PROGGED TO FURTHER DEAMPLIFY AS IT TRACKS
ESE THROUGH SOUTHERN VA AND NORTHEAST NC THIS AFTERNOON. THE COMPACT
NATURE OF THIS FEATURE SUGGESTS DPVA WILL BE CONFINED IN CLOSE
PROXIMITY THEREOF...I.E. NORTH OF HWY 64 TO THE VA BORDER. THIS
FEATURE IS ALREADY AIDING CONVECTIVE DEVELOPMENT IN THE TRIAD...AND
SHOULD CONTINUE TO SUPPORT SCATTERED DEVELOPMENT INVOF BUY-IGX-TDF-
HNZ-LHZ-IXA THROUGH 18-21Z (W-E). ANOTHER DISTURBANCE LOCATED OVER
NORTHERN GA AND NORTHWEST SC AT 15Z IS PROGGED TO TRACK EAST/ESE
ACROSS UPSTATE SC AND SOUTHERN NC LATE THIS AFTERNOON THROUGH THIS
EVENING...FURTHER COMPLICATING THE CONVECTIVE FORECAST. PERVASIVE
CLOUD COVER AND INTERMITTENT PRECIP WILL SIGNIFICANTLY HAMPER
DIURNAL DESTABILIZATION. HOWEVER...MARGINAL INSTABILITY AND TROPICAL-
LIKE MOISTURE (PWAT 1.80-2.00") WILL BE MORE THAN SUFFICIENT TO
SUPPORT SCT/WIDESPREAD CONVECTION AS LONG AS THE APPROPRIATE FORCING
IS IN PLACE.

PRECIP/TEMPS: EXPECT THE BEST CHANCE OF CONVECTION THROUGH EARLY/MID
AFTERNOON TO BE ALONG AND NORTH OF HWY 64 ACROSS THE NORTHERN
PIEDMONT/NE COASTAL PLAIN...WITH A SUBSIDENT PERIOD FOR SEVERAL
HOURS THEREAFTER IN THAT REGION. BY MID/LATE AFTERNOON INTO THIS
EVENING...EXPECT THE BEST CHANCE FOR CONVECTION SOUTH OF HWY 64 NEAR
THE SC BORDER AS THE UPSTREAM WAVE IN GA/SC TRACKS NEAR OR JUST
SOUTH OF THE NC/SC BORDER. WILL CONTINUE TO MENTION A LOW CHANCE OF
CONVECTION OVERNIGHT GIVEN DEEP MOISTURE IN THE PRESENCE OF AN
ACTIVE UPPER LEVEL PATTERN. DUE TO PERVASIVE CLOUD COVER AND
INTERMITTENT CONVECTION...HIGHS TODAY WILL BE COOLER THAN EXPECTED
SEVERAL DAYS AGO...ESP ACROSS THE N/NW PIEDMONT. WILL INDICATE HIGHS
FROM THE LOWER/MID 80S TO UPPER 80S/NEAR 90F IN THE SANDHILLS AND SE
COASTAL PLAIN. LOWS TONIGHT IN THE LOWER 70S. -VINCENT

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
AS OF 300 AM MONDAY...

MID/UPPER LEVEL SHORTWAVE VORT DISTURBANCE INVOF OF ARKLATEX THIS
MORNING IS FORECAST TO PROGRESS EAST ACROSS THE LOWER MS VALLEY
TODAY AND ACROSS THE SOUTHEAST DURING PRIME HEATING TUESDAY
AFTERNOON. CONVECTIVE COVERAGE SHOULD BE MORE SCATTERED IN NATURE
WITH HIGHEST POPS IN THE EAST WITHIN THE CONTINUED HIGH +2.0 PWAT
AS DRIER AIR BEGINS TO SPREAD IN FROM THE WEST. 0-6KM SHEAR DROPS
OFF TO 10-15KTS BUT STRONGER HEATING AND RESULTANT MODERATE
DESTABILIZATION COULD SUPPORT AN ISOLATED STRONG TO SEVERE STORM
TUESDAY AFTERNOON. MUCH LIKE MONDAY NIGHT...PERIOD OF SYNOPTIC SCALE
SUBSIDENCE TUESDAY EVENING/NIGHT IN THE WAKE OF THE UPPER WAVE
MOVING OFF THE SE COAST SHOULD RESULT IN DRY CONDITIONS TUESDAY
NIGHT.

WARMER ON TUESDAY WITH HIGHS RANGING FROM UPPER 80S NW TO LOWER
90S SE. LOWS TUESDAY NIGHT IN THE UPPER 60S NW TO LOWER 70S SE.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
AS OF 220 PM MONDAY...

THE MAJOR PROBLEM THROUGH THE LONG TERM PERIOD WILL BE DISCERNING
WHEN AND WHERE A HIGHER PROBABILTY OF PRECIPITATION WILL OCCUR.
THERE IS GOOD MODEL CONSENSUS AS TO THE TRANSITION TO A LARGER SCALE
BLOCKING PATTERN OVER THE EASTERN CONUS THROUGH THE WEEKEND. THE
GRADUAL MIGRATION OF AN UPPER LOW ACROSS THE GREAT LAKES AND OFF THE
MID ATLANTIC COAST WEDNESDAY THROUGH FRIDAY WILL AMPLIFY INTO A
DEEPER UPPER TROF DOWN THE COAST INTO EARLY NEXT WEEK. CONCURRENT
AMPLIFICATION OF AN UPPER RIDGE WEST OF THE AREA WILL PRODUCE
PERSISTENT NORTHWEST FLOW WHICH WILL PRESENT THE USUAL PROBLEMS WITH
TIMING FEATURES THAT WILL BE STEERED INTO THE AREA. AIRMASS WILL BE
REASONABLY WARM (UPPER 80S TO LOW 90S) AND MOIST...PW ~1.5 INCHES...
BUT MOISTURE ADVECTION WILL BE HAMPERED BY WESTERLY FLOW ACROSS THE
DEEP SOUTH...SO CHANCES OF RAIN WILL BE IN THE CLIMATOLOGICAL
RANGE...30 PERCENT-ISH...WEDNESDAY THROUGH FRIDAY.

A COOL SURGE WILL PROGRESS SOUTH AND ACROSS THE AREA FRIDAY NIGHT AS
 HIGH PRESSURE OVER FAR EASTERN CANADA IS SHUNTED DOWN THE EASTERN
SLOPES OF APPALACHIANS. THIS WILL ENHANCE A COASTAL TROF IN PLACE
OFFSHORE AND RESULT IN DEEP NORTH TO NORTHEAST FLOW FLOW WITH
ACCOMPANYING MOIST AND COOLER MARINE-FLAVORED AIRMASS PERSISTING
THROUGH MONDAY. ISENTROPIC LIFT WILL BE MINIMAL...AND MID LEVEL
FEATURES IN THE NORTHWEST FLOW WILL BE NIL-CONFIDENCE THIS FAR IN
ADVANCE. WOULD EXPECT PATCHY LIGHT RAIN/SHOWERS TO BE THE
PREDOMINANT TYPE OF PRECIP...WITH POTENTIAL FOR CONVECTION HINGING
ON UPSTREAM FEATURES WE MIGHT SEE 24-48 HOURS IN ADVANCE.
THICKNESSES WOULD INDICATE A 3-5 DEGREE COOL DOWN FOR SATURDAY...AND
ANOTHER 1-2 DEGREES SUNDAY AND MONDAY. THIS WOULD KEEP US IN THE MID
TO UPPER 80S EACH DAY...WHICH IS MORE LIKELY TO ERR ON THE HIGH SIDE
GIVEN THE LOOK OF THE PATTERN AND POTENTIAL FOR SOCKING IN SOME
SATURATED MARINE LAYER AIR OVERNIGHT WITH ACCOMPANYING DENSE FOG/LOW
STRATUS TO START THE DAYS.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AS OF 1115 AM MONDAY...

24-HR TAF PERIOD: PERIODS OF MVFR CEILINGS AND VISBYS ASSOCIATED
WITH SHOWERS AND THUNDERSTORMS ARE EXPECTED AT MOST IF NOT ALL
TERMINALS THROUGH THIS EVENING. WINDS WILL BE LIGHT/VARIABLE AT
NORTHERN TERMINALS AND SOUTHWEST AT 5-10 KT AT SOUTHERN TERMINALS
(FAY). A PERIOD OF SUB-VFR CEILINGS AND/OR FOG WILL BE POSSIBLE AT
ALL TERMINALS EARLY TUE MORNING (08-13Z)...WITH THE BEST CHANCE IN
AREAS THAT RECEIVE RAINFALL THIS AFT/EVE...THOUGH CONFIDENCE REMAINS
TOO LOW TO INCLUDE MENTION THEREOF WITH THE 18Z TAF ISSUANCE.

LOOKING AHEAD: EXPECT A CLIMATOLOGICAL POTENTIAL FOR AFT/EVE SHOWERS
AND STORMS THROUGH MID TO LATE WEEK...ALONG WITH A POTENTIAL FOR FOG
AND/OR LOW CEILINGS DURING THE EARLY MORNING HOURS. -VINCENT

&&

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

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...VINCENT
SHORT TERM...VINCENT
LONG TERM...MLM
AVIATION...VINCENT


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