000
FXUS62 KCHS 072315
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
715 PM EDT SUN SEP 7 2008
.SYNOPSIS...
HIGH PRESSURE WILL CONTINUE BUILDING TO THE NORTHEAST AS TROPICAL
CYCLONE IKE REMAINS WELL SOUTH OF THE AREA THROUGH MONDAY. A
COASTAL TROUGH IS EXPECTED TO TIGHTEN LATER THIS WEEK AND FOCUS
MOISTURE CONVERGENCE ACROSS THE REGION. HIGH PRESSURE WILL RETURN
BY THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
SHOWER ACTIVITY WILL BE DIMINISHING AFTER SUNSET WITH THE LOSS OF
DAYTIME HEATING. SKIES ARE EXPECTED TO CLEAR AND WITH LIGHT SURFACE
WINDS AND PLENTY OF LOW LEVEL MOISTURE IN PLACE...EXPECT PATCHY FOG
AND POSSIBLY SOME LOW STRATUS TO DEVELOP AGAIN OVERNIGHT ACROSS THE
COUNTY WARNING AREA.
LOW TEMPERATURES WILL BE IN THE MID 70S NEAR THE COAST TO LOWER
70S INLAND.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
TROPICAL CYCLONE IKE WILL BE MAKING ITS PASS SOUTH OF FLORIDA MONDAY
AFTERNOON AS HIGH PRESSURE CONTINUES TO PUSH FURTHER NORTHEAST INTO
THE ATLANTIC. WITH ONSHORE WINDS PUMPING MOISTURE INTO THE AREA AND
LOW LEVEL CONVERGENCE ASSOCIATED WITH THE SEA BREEZE...HAVE
MAINTAINED SLIGHT CHANCE POPS MAINLY INLAND ACROSS THE FORECAST
AREA.
MAX TEMPERATURES WILL RANGE FROM THE UPPER 80S NEAR THE COAST TO
AROUND 90 INLAND.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
AS TROPICAL CYCLONE IKE PASSES SOUTH OF THE REGION...HIGH PRESSURE TO
THE NORTH WILL SHIFT OFF THE COAST MON NIGHT AND TUE...RESULTING
IN A PREVAILING ONSHORE FLOW. THIS REGIME MAY FAVOR COASTAL TROUGH
DEVELOPMENT BY WED-THU. MEANWHILE...ANOTHER HIGH WILL BUILD FROM
THE NW INTO THE MID-ATLANTIC REGION BY MIDWEEK...PUSHING A SURFACE
BOUNDARY TOWARD THE REGION. THIS BOUNDARY WILL THEN STALL OVER THE
REGION DURING THE WED-THU TIME FRAME...POOLING DEEP LAYER MOISTURE
OVER THE REGION AND SETTING THE STAGE FOR A PERIOD OF UNSETTLED
CONDITIONS FOR MID TO LATE WEEK...PERHAPS LINGERING INTO NEXT
WEEKEND.
THIS FORECAST DISCOUNTED SOME ASPECTS OF THE 12Z NAM...WHICH
AGGRESSIVELY PUSHES DEEP LAYER MOISTURE INTO THE REGION AS EARLY AS
MONDAY NIGHT...AND SOME ASPECTS OF THE 12Z GFS...WHICH DEVELOPS A
RATHER STRONG LOW PRESSURE ALONG THE COAST THU. HOWEVER...IN GENERAL
12Z GUIDANCE CONTINUES TO DEPICT DEEP LAYER FLOW BECOMING S-SE BELOW
500 MB BY LATE TUE NIGHT WITH PRECIPITABLE WATER INCREASING TO AT
LEAST 2.25 INCHES. WITH CONTINUED SE FLOW AROUND THE 300K THETA
SURFACE...AN INCREASE IN MOIST ISENTROPIC ASCENT IS EXPECTED TO
SUPPORT SCATTERED SHOWERS/THUNDERSTORMS TUE INTO TUE NIGHT.
WED THROUGH THU...DEEP LAYER MOISTURE AND ENHANCED LOW LEVEL
CONVERGENCE PROVIDED BY THE STATIONARY FRONT AND COASTAL TROUGH
AND UPPER DIVERGENCE SHOULD SUPPORT SHOWERS/THUNDERSTORMS. RAISED
POPS TO LIKELY WED AND THU. MAY NEED TO RAISE POPS FOR THIS ENTIRE
PERIOD WITHIN LATER FORECASTS.
THE COMBINATION OF PWATS OVER 2 INCHES...0-6 KM WIND VECTORS ONLY
5-10 KT AND THE ABUNDANCE OF BOUNDARIES MAY SUPPORT SLOW...
BACK-BUILDING CELL MOTIONS AND A HEAVY RAINFALL EVENT.
WITH THE SURFACE BOUNDARY/BAROCLINIC ZONE PERSISTING OVER THE
REGION...MAINTAINED CHANCE POPS FRIDAY AND SATURDAY. AS THE SURFACE
BOUNDARY WEAKENS NEXT WEEKEND...ATLANTIC HIGH PRESSURE AT THE
SURFACE AND ALOFT SHOULD BUILD OVER THE AREA...PROVIDING SUBSIDENCE
AND SLIGHTLY DRIER AIR.
TEMPERATURES MID TO LATE WEEK WILL GENERALLY BE BELOW NORMAL DUE TO
PREVAILING MOSTLY CLOUDY SKIES. THEN...EXPECT A GRADUAL RETURN OF
NEAR NORMAL TEMPERATURES NEXT WEEKEND.
&&
.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
OUTSIDE OF FOG EARLY MONDAY...EXPECT MAINLY VFR CONDITIONS TO PREVAIL
THROUGH THE PERIOD. INCREASING LOW-LEVEL MOISTURE...CLEARING SKIES AND
LIGHT WINDS SUGGEST SHALLOW GROUND FOG IS LIKELY AT BOTH TERMINALS
LATE TONIGHT. FORECAST SOUNDINGS SUGGEST LOW-LEVEL MOISTURE REMAINS
VERY SHALLOW...SO EXPECT ONLY MVFR VISIBILITIES IN THE 09-13Z TIME
FRAME.
EXTENDED AVIATION OUTLOOK...VFR CONDITIONS WILL PREVAIL TUESDAY.
SHOWERS WITH ACCOMPANYING LOWER CEILINGS AND VISIBILITIES MAY
ALSO COME INTO PLAY IN THE WEDNESDAY-THURSDAY TIME FRAME.
&&
.MARINE...
EASTERLY WINDS WILL BE LIGHT OVER THE COASTAL WATERS THE REST OF THE
EVENING AND TONIGHT BEFORE INCREASING TO 10 TO 15 KNOTS MONDAY
AFTERNOON. MAIN CONCERN THROUGH THE SHORT TERM WILL BE THE LONG
PERIOD SWELL FROM TROPICAL CYCLONE IKE BUILDING TO 5 TO 7 FEET
THROUGH MUCH OF THIS WEEK FOR THE OFFSHORE GEORGIA WATERS. WITH
WINDS REMAINING BELOW ADVISORY CRITERIA WILL ISSUE A SMALL CRAFT
ADVISORY FOR HAZARDOUS SEAS IN EFFECT TOMORROW AFTERNOON THROUGH
THURSDAY. ELSEWHERE...SEAS ARE EXPECTED TO REMAIN BELOW SMALL
CRAFT ADVISORY THRESHOLDS THROUGH THIS WEEK.
MEANWHILE...AS HIGH PRESSURE SHIFTS EAST...A SURFACE TROUGH MAY
DEVELOP OVER THE COASTAL WATERS BY MIDWEEK. ALSO...A COLD FRONT WILL
PUSH INTO THE REGION THEN WILL STALL AROUND MIDWEEK. THESE FEATURES
MAY SUPPORT A TIGHTENING SURFACE PRESSURE GRADIENT AND INCREASING
EASTERLY WINDS. HOWEVER...ODDS FAVOR WINDS REMAINING BELOW SMALL
CRAFT ADVISORY THRESHOLDS...NO HIGHER THAN 15-20 KNOTS...THROUGH
LATE WEEK.
RIP CURRENTS...A MODERATE RISK OF RIP CURRENTS WILL CONTINUE ON AREA
BEACHES THROUGH MONDAY. THE ELEVATED RISK OF RIP CURRENTS...PRODUCED
MAINLY BY THE LONG PERIOD SWELL...MAY PERSIST INTO MID WEEK.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 12 PM MONDAY TO 6
PM EDT THURSDAY FOR AMZ374.
&&
$$
