758
FXUS62 KCHS 192343
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
743 PM EDT WED SEP 19 2018
SYNOPSIS
HIGH PRESSURE WILL THEN PREVAIL INTO THE WEEKEND. A COASTAL
TROUGH OF LOW PRESSURE COULD IMPACT THE AREA EARLY NEXT WEEK,
WHILE HIGH PRESSURE REMAINS OVER THE ATLANTIC INTO THE MIDDLE
OF NEXT WEEK.
NEAR TERM /THROUGH THURSDAY/
TONIGHT: HIGH PRESSURE WILL CONTINUE TO BUILD IN FROM THE WEST-
NORTH. WITH HIGH PRESSURE, LIGHT/CALM WINDS, AND CLEAR SKIES,
WOULD NOT BE SURPRISED TO SEE SOME SHALLOW/PATCHY GROUND FOG,
ESPECIALLY ACROSS THE NORTHERN 1/3 OF THE FORECAST AREA WHERE
THE GROUND/SURFACE CONDITIONS ARE A LITTLE MORE MOIST FROM LAST
WEEKENDS RAIN. OTHERWISE, EXPECT TRANQUIL CONDITIONS WITH LOWS
FALLING INTO THE UPPER 60S WEST OF I-95, AND LOWER 70S CLOSER TO
THE COAST. DESPITE THESE TEMPERATURES BEING COOLER THAN THEY
HAVE BEEN FOR A LONG TIME, THEY WILL STILL BE ABOVE
CLIMATOLOGICAL NORMALS BY 4 TO 6 DEGREES.
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/
A DEEP LAYER RIDGE WILL BE CENTERED JUST NORTH OF THE REGION ON
THURSDAY, THEN SHIFT EASTWARD INTO THE ATLANTIC BY LATER FRIDAY AND
SATURDAY. OVERALL, PRECIP. CHANCES ARE EXPECTED TO BE LOW. THE ONLY
POPS MENTIONED DURING THE PERIOD ARE ON FRIDAY OVER THE SOUTHERN
GA REGION, WHERE A BAND OF RELATIVELY HIGHER MOISTURE FROM A WEAK
BACKDOOR FRONT MEETS SOME ATLANTIC MOISTURE FROM THE EAST. LOW LEVEL
WINDS WILL BE EASTERLY THROUGH THE PERIOD, GENERALLY 5-10 MPH OVER
THE LAND, AND 10-15 MPH AT THE COAST. THE EASTERLY FLOW
WILL ALSO KEEP TEMPERATURES COOLER AT THAT COAST, BUT STILL EXPECT
GENERALLY AFTERNOON HIGHS IN THE UPPER 80S TO AROUND 90, WHICH IS 4
TO 6 DEGREES ABOVE NORMAL. HOWEVER, HUMIDITY VALUES WILL BE LOWER
THAN THEY HAVE BEEN FOR THE PAST SEVERAL WEEKS, WITH INLAND DEWPOINT
TEMPERATURES MIXING DOWN INTO THE MID TO UPPER 60S EACH AFTERNOON.
LOWER DEWPOINTS WILL ALLOW NIGHTTIME LOWS TO REACH THE UPPER 60S
INLAND, BUT STILL LOWER 70S CLOSER TO THE COAST. ALTHOUGH THESE
LOW TEMPERATURES ARE EXPECTED TO BE COOLER THAN THEY HAVE BEEN FOR
WEEKS, THEY WILL STILL BE ABOVE SEASONAL NORMAL LEVELS.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
THE LARGE/EXPANSIVE RIDGE OF HIGH PRESSURE OVER THE SOUTHEAST UNITED
STATES WILL BECOME MORE CENTERED OVER THE WESTERN ATLANTIC BY EARLY
NEXT WEEK WHILE A FRONT APPROACHES FROM THE NORTH, BUT LIKELY STALLS
WELL NORTH/NORTHWEST OF THE REGION. MOST SHOWER/THUNDERSTORM
ACTIVITY SHOULD REMAIN OFFSHORE LATE WEEKEND INTO EARLY NEXT WEEK.
HOWEVER, SOME MODELS CONTINUE TO FAVOR SHOWERS AND/OR THUNDERSTORMS
OVER COASTAL GEORGIA WHERE MID-LVL ENERGY PROVIDES SUFFICIENT
FORCING AND AN ONSHORE WIND ADVECTS MOISTURE OVER LAND. THERE COULD
BE SOME ENHANCEMENT TO PRECIP COVERAGE EARLY IN THE WEEK AS A
COASTAL TROUGH SHIFTS ONSHORE AND PWATS APPROACH 2.0 INCHES OVER THE
AREA. THEREAFTER, A PERSISTENT ONSHORE FLOW ALONG THE SOUTHWEST EDGE
OF THE ATLANTIC HIGH COULD PRODUCE CHANCES OF SHOWERS/THUNDERSTORMS
INTO MID WEEK WITH PRECIP COVERAGE PEAKING DURING MAXIMUM SFC
HEATING EACH DAY. HIGH TEMPS WILL GENERALLY RANGE IN THE MID/UPPER
80S ACROSS SOUTHEAST SOUTH CAROLINA THIS WEEKEND AND EARLY NEXT
WEEK. SOME AREAS COULD TOUCH 90 DEGREES ACROSS SOUTHEAST GEORGIA.
OVERNIGHT LOWS SHOULD RANGE IN THE UPPER 60S TO AROUND 70 DEGREES
INLAND TO MID/UPPER 70S ALONG THE COAST.
AVIATION /00Z THURSDAY THROUGH MONDAY/
SOME MODEL GUIDANCE INDICATING THE POTENTIAL FOR PATCHY
SHALLOW/GROUND FOG. GIVEN THE RIDGE BUILDING IN, CLEAR SKIES AND
LIGHT WINDS, IT SEEMS REASONABLE. HAVE INTRODUCED BCFG FOR NOW,
WITH VSBYS STILL REMAINING VFR. FEEL CONDITIONS ARE SLIGHTLY
MORE FAVORABLE FOR CHS TO GET SHALLOW FOG VS SAV, BUT GIVEN
UNCERTAINTY, PUT IT IN SAV TAF TOO.
EXTENDED AVIATION OUTLOOK: VFR CONDITIONS ARE EXPECTED TO PREVAIL
AT BOTH KCHS AND KSAV TERMINALS THROUGH SUNDAY. DEEP LAYER
MOISTURE MAY BEGIN TO RETURN BY MONDAY, WHICH COULD INCREASE THE
CHANCES FOR SHOWERS/THUNDERSTORMS AND THE THREAT FOR BRIEF
FLIGHT RESTRICTIONS.
MARINE
TONIGHT: HIGH PRESSURE WILL CONTINUE TO BUILD SOUTH INTO THE COASTAL
WATERS. VARIABLE WINDS GENERALLY 5 KNOTS OR LESS WILL RESULT WITH
SEAS AVERAGING 1-2 FEET, 3 FEET BEYOND 30 NM.
THURSDAY THROUGH MONDAY: NO HIGHLIGHTS ARE EXPECTED AT THIS TIME
THROUGH THE PERIOD. DEEP HIGH PRESSURE WILL REMAIN CENTERED
GENERALLY NORTH OF THE WATERS THROUGH THE PERIOD, WITH EASTERLY
WINDS OF 15 KNOTS OR LESS AND SEAS OF 2 TO 4 FEET. A WEAK
BACKDOOR FRONT IS INDICATED BY THE MODELS TO MOVE IN FROM THE
NORTH THURSDAY NIGHT AND EARLY FRIDAY. THIS FEATURE MAY INCREASE
THE PRESSURE GRADIENT ENOUGH TO PUSH WINDS UP TO 15 TO 20 KNOTS
THROUGH FIRST PART OF FRIDAY, BEFORE COMING BACK DOWN AGAIN. NO
SIGNIFICANT CHANCES FOR SHOWERS/THUNDERSTORMS UNTIL VERY LATE
IN THE WEEKEND AND EARLY NEXT WEEK, WHEN BETTER DEEP LAYER
MOISTURE MOVES INTO THE AREA.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...JMC/RFM
SHORT TERM...RFM
LONG TERM...DPB
AVIATION...JMC/RFM
MARINE...JMC/RFM
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