Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 071024
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
524 AM EST SUN FEB 7 2016

.SYNOPSIS...
STRONG LOW PRESSURE WILL TRACK NORTH AND NORTHEAST AND INTENSIFIES
OFF THE SOUTHEAST COAST TODAY...THEN MOVES AWAY FROM THE REGION
TONIGHT. A COLD FRONT WILL CROSS THE AREA MONDAY. A DEEP TROUGH
WILL REMAIN IN PLACE THROUGH THE MIDDLE OF THE WEEK...BRINGING
UNSEASONABLY COLD CONDITIONS TO THE AREA. HIGH PRESSURE WILL
BUILD OVER THE REGION LATE WEEK INTO NEXT WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
STRONG LOW PRESSURE AROUND 250 MILES EAST OF SAVANNAH THIS MORNING
WILL INTENSIFY FURTHER AS IT DROPS TO AROUND 985 MB AS IT HEADS
NORTH/NE THROUGH THE DAY. A POWERFUL AND SLIGHTLY NEGATIVELY
TILTED MID/UPPER TROUGH OF CLOSE TO 3 STANDARD DEVIATIONS BELOW
THE NORM WILL RACE THROUGH THE CWFA THIS MORNING AND INTO THE
ATLANTIC THIS AFTERNOON. ALTHOUGH THIS IS A PROGRESSIVE FEATURE IT
IS RESPONSIBLE FOR PREVENTING THE SURFACE CYCLONE FROM GETTING
KICKED OUT TOO FAST...AS IT ATTEMPTS TO TRAP THE ATLANTIC LOW
CLOSER UNDERNEATH. HOWEVER...GIVEN AN ALREADY VAST AND PRE-
EXISTING BAROCLINIC ZONE OVER THE ATLANTIC...THIS WILL PROVIDE THE
NECESSARY MOMENTUM TO LIFT THE ATLANTIC GYRE FURTHER AWAY FROM
THE SE LATER TODAY AND INTO TONIGHT.

RAINFALL LOW LEVEL WINDS ARE QUITE IMPRESSIVE WITH AS MUCH AS
50-60 KT EVIDENT DOWN TO JUST ABOUT 2-3K FT OFF THE SURFACE. THE
ASSOCIATED LARGE SCALE FORCING FROM THIS...THE IMPRESSIVE TROUGH
ALOFT AND IT/S ACCOMPANIED UPPER DIFLUENCE...PLUS CONSIDERABLE
HEIGHT FALLS WILL GENERATE WIDESPREAD RAINFALL THIS MORNING. SOME
OF THE RAIN WILL BE HEAVY...AND DUE TO THE SATURATED GROUNDS IT
WON/T TAKE MUCH TO PROMPT AT LEAST MINOR FLOODING CONCERNS. IN
FACT IT WILL ALSO CONTRIBUTE TO SHALLOW COASTAL FLOODING IN
DOWNTOWN CHARLESTON THROUGH MID-MORNING. /SEE TIDES AND COASTAL
FLOODING SECTION BELOW/. ADDITIONAL QPF WILL AVERAGE FROM AROUND
1/2 INCH IN THE CHARLESTON TRI-COUNTY...TO 1/4 INCH OF LESS FOR
BEAUFORT...SAVANNAH AND WALTERBORO...TO GENERALLY 1/10 INCH OR
LESS NEAR THE ALTAMAHA AND NEAR STATESBORO.

AS THE SURFACE LOW IS FINALLY LIFTED FURTHER OFFSHORE WITH THE
PASSAGE OF THE TROUGH UPSTAIRS...RAIN CHANCES WILL DIMINISH
CONSIDERABLY FROM WEST/SW TO EAST/NE LATE THIS MORNING AND THIS
AFTERNOON. THE BACK EDGE OF THE RAIN SHIELD WILL CLEAR THE
SAVANNAH RIVER BY 12-1 PM...THE CHARLESTON METRO AROUND 3 PM...AND
FINALLY THE SANTEE RIVER DELTA BY NIGHTFALL.

WINTER WEATHER...THE POTENTIAL FOR SNOW IS DIMINISHING WITH TIME.
BUT WITH COOLING OF THE VERTICAL COLUMN AND FREEZING LEVELS DOWN
NEAR 1500-2000 FT THERE STILL MIGHT BE A LITTLE ON THE BACK EDGE
OF THE WIDESPREAD RAINS BEFORE THEY COMPLETELY END. BUT GIVEN
THAT MOST TEMPS AND ASSOCIATED DEW POINTS WILL REMAIN IN THE MID
AND UPPER 30S WE DON/T ANTICIPATE ANYTHING MORE THAN A LITTLE WET
SNOW FROM ABOUT 8-10 AM...MAINLY ALONG THE NW TIER FROM BERKELEY
TO HAMPTON COUNTIES. THE RISK FOR ANY MEASURABLE SNOW IS PRETTY
MUCH ZERO GIVEN THE WARM AIR AND WET GROUNDS. ALTHOUGH IT IS WORTH
NOTING THAT WPC DOES STILL SHOW A 40-50 PROBABILITY OF 1 INCH OR
GREATER ACROSS MUCH OF THE CWFA NORTH OF I-16 IN GA. BUT NO WINTER
WEATHER HEADLINES ARE REQUIRED.

STRONG WINDS...THE TIGHT CYCLONIC GRADIENT ACROSS THE AREA WILL BE
MOST EXTREME ACROSS CHARLESTON COUNTY...AND THAT ALONG WITH STRONG
ISALLOBARIC PRESSURE FALLS AND THE PASSAGE OF A 50-60 KT LOW LEVEL
JET WILL CAUSE NORTHERLY WINDS TO REACH 25-30 MPH WITH GUSTS TO 40
MPH DURING THE LATE MORNING INTO THIS AFTERNOON. THIS IS
SUFFICIENT FOR A WIND ADVISORY IN CHARLESTON COUNTY...ESPECIALLY
CLOSER TO THE COAST. GIVEN THE WET GROUNDS FROM RECENT HEAVY RAINS
IT WON/T TAKE MUCH FOR WEAK TREES AND THOSE THAT ARE POORLY ROOTED
TO COME DOWN. THERE MIGHT EVEN BE A FEW POWER OUTAGES. OTHER AREAS
WILL EXPERIENCE BREEZY TO WINDY CONDITIONS...WITH NW AND NORTH
WINDS OF 20-25 MPH WITH GUSTS TO 30-35 MPH. EVEN THESE WINDS MIGHT
BE STRONG ENOUGH TO TOPPLE A COUPLE OF SMALL AND WEAK TREES.

LAKE WINDS...SUFFICIENT MIXING ACROSS THE WARMER LAKE WATERS WILL
ALLOW FOR A CONTINUATION OF THE LAKE WIND ADVISORY ON LAKE
MOULTRIE INTO THIS EVENING.

TEMPERATURES...THERE WILL BE A LARGE MAX TEMP GRADIENT FROM
NORTH/NE TO SOUTH/SW DUE TO SKIES CLEARING OUT QUICKER ACROSS GA
THAN IN SC. LOOKING FOR HIGHS IN THE MID 40S FAR NORTH TO MID 50S
FAR SOUTH...AS MUCH AS 10-15F BELOW NORMAL FOR MANY LOCATIONS.

TONIGHT...THE ENTIRE SITUATION QUIETS DOWN CONSIDERABLY EVEN
THOUGH THE ATLANTIC LOW CONTINUES TO BOMB OUT...AS IT/S FOUND NEAR
BERMUDA COME DAYBREAK MONDAY AND RIDING BOTH SURFACE AND ALOFT
MOVES IN TO TAKE IT/S PLACE. THERE ISN/T MUCH COLD ADVECTION...SO
WE CURRENTLY DON/T HAVE TEMPS GETTING ANY LOWER THAN THE MID OR
UPPER 30S. PROBABLY JUST WARM ENOUGH FOR NO CONCERNS IN REGARDS TO
BLACK ICE.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
MONDAY AND MONDAY NIGHT...THE PATTERN ALOFT WILL FEATURE A POTENT
SHORTWAVE DIVING SOUTHEASTWARD AND HELPING TO AMPLIFY THE DEEP
LONGWAVE ACROSS THE EASTERN HALF OF THE CONUS. AT THE SURFACE...A
CLIPPER TYPE LOW ORIGINATING FROM THE GREAT LAKES WILL PUSH ACROSS
THE APPALACHIANS AND EVENTUALLY OFF THE MID ATLANTIC COAST
OVERNIGHT. A COLD FRONT WILL CROSS THE FORECAST AREA IN THE
AFTERNOON AND WILL BRING WITH IT ENOUGH MOISTURE TO KICK OFF
ISOLATED TO SCATTERED SHOWERS IN THE AFTERNOON/EVENING HOURS.
TEMPERATURES WILL RISE INTO THE UPPER 50S AHEAD OF THE FRONT WITH
BREEZY WEST-SOUTHWEST WINDS THROUGH THE DAY. OVERNIGHT...CLOUDS WILL
CLEAR OUT FROM THE WEST WITH COOLER AIR FILTERING IN. AS THE
MOISTURE MOVES OUT AND TEMPERATURES DROP...CANNOT COMPLETELY RULE
OUT A FEW FLURRIES EARLY IN THE NIGHT. LOWS WILL RANGE FROM THE LOW
30S INLAND TO THE MID 30S CLOSER TO THE COAST.

TUESDAY THROUGH WEDNESDAY...THE DEEP AND COLD TROUGH ALOFT WILL
PERSIST ACROSS THE EASTERN CONUS. AT THE SURFACE...BREEZY AND COOL
WESTERLY FLOW WILL CONTINUE. HIGHS ARE ONLY EXPECTED TO REACH INTO
THE UPPER 40S EACH DAY WHICH WOULD BE ON THE ORDER OF 12-14 DEGREES
BELOW NORMAL.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
THE LONGWAVE TROUGH ALOFT WILL DEAMPLIFY THURSDAY AND
FRIDAY...THOUGH THE REGION WILL SOLIDLY REMAIN WITHIN THE CYCLONIC
FLOW AROUND THE DEEP UPPER LOW CENTERED OVER EASTERN CANADA. MOST
OF THE PERIOD LOOKS RATHER UNEVENTFUL AS HIGH PRESSURE BUILDS IN
FOR THE LATTER PART OF THE WEEK. THE NEXT CHANCE FOR RAIN COULD
COME TO START THE WEEKEND AS A COLD FRONT ASSOCIATED WITH A WEAK
LOW DRAGS ACROSS THE REGION. OTHERWISE THE PERIOD LOOKS DRY WITH
TEMPERATURES MODERATING INTO THE MID/UPPER 50S...WHICH IS STILL
SEVERAL DEGREES BELOW NORMAL FOR MID FEBRUARY.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
KCHS...MVFR CONDITIONS INITIALLY WILL GIVE WAY TO DETERIORATING
CONDITIONS AS RAIN PERSISTS AND CAUSES CLOUD DECKS TO LOWER INTO
THE IFR CATEGORY BY 13Z. LOW PRESSURE IN THE SW ATLANTIC WILL
PULL FAR ENOUGH AWAY THIS AFTERNOON TO ALLOW FOR IMPROVING
CONDITIONS BY MID OR LATE AFTERNOON...WITH SOLID VFR CONDITIONS TO
RETURN BY EVENING. NORTHERLY WINDS WILL CONTINUE TO INCREASE AS
THE GRADIENT AROUND THE ATLANTIC LOW TIGHTENS AND A VERY STRONG
LOW LEVEL JET OF 45-55 KT MOVES THROUGH THE AREA. WINDS WILL
AVERAGE CLOSE TO 20 KT SUSTAINED WITH GUSTS UP NEAR 30 KT AT
TIMES. WINDS WILL DIMINISH LATE SUNDAY AND SUNDAY NIGHT.

KSAV...MVFR/IFR CONDITIONS WILL THIS MORNING WITH A CONTINUATION
OF RAIN DUE TO STRONG CYCLOGENESIS OFF THE SE COAST. IT/LL TAKE
UNTIL THE AFTERNOON BEFORE VFR CONDITIONS FINALLY RETURN AND
PERSIST THEREAFTER. WINDS WON/T BE QUITE AS STRONG AS IN THE KCHS
AREA...BUT STILL QUITE GUSTY THROUGH LATE AFTERNOON.

EXTENDED AVIATION OUTLOOK...VFR.

&&

.MARINE...
TODAY...EXTREMELY DANGEROUS MARINE CONDITIONS ARE UNDERWAY ACROSS
THE ENTIRE COASTAL WATERS...AND THEY WILL ACTUALLY GET EVEN MORE
PERILOUS DUE TO A RAPIDLY INTENSIFYING SURFACE LOW NOT TOO FAR TO
THE EAST OF THE LOCAL WATERS THIS MORNING. THIS LOW LIFTS NORTH/NE
THIS AFTERNOON...AND FALLS SOME 10-15 MB DURING THIS 12 HOUR
PERIOD. THIS AND LARGE AND STEEP-FACED WAVE SETS SHOULD DISCOURAGE
ANY MARINERS FROM NAVIGATING ON THE LOCAL WATERS TODAY.

GALE FORCE WINDS OF 35 OR 40 KT WILL BE OBTAINED IN CHARLESTON
HARBOR AND THE 0-20 NM WATERS FROM EDISTO BEACH SOUTH TO THE
ALTAMAHA SOUND...WITH SOLID GALES ON THE OUTER GA WATERS WHERE
WINDS WILL PEAK AROUND 45 KT. WHILE A FEW GUSTS COULD APPROACH 50
KT NEAR 60 NM OFFSHORE...THIS IS NOT ENOUGH TO HOIST A STORM
WARNING. INSTEAD WE HAVE A STORM WARNING IN PLACE FOR THE AMZ350
WATERS. THESE CONDITIONS WON/T ENCOMPASS EVERYWHERE WITHIN THE
MARINE GROUPING...BUT MAINLY THE NE QUADRANT WHERE A FEW GUSTS
NEAR 50 KT ARE EXPECTED. THIS MATCHES UP WELL WITH THE GALE
WARNING TO THE NORTH AND THE HURRICANE FORCE WIND WARNING BEYOND
20 NM OFFSHORE. FOR THE MAJORITY OF THE AMZ350 WATERS MARINERS CAN
EXPECT HIGHEST WIND GUSTS OF 35-45 KT.

TONIGHT...WHILE IT WILL TAKE SOME TIME FOR CONDITIONS TO
IMPROVE...THEY EVENTUALLY DO AS THE CYCLONIC CIRCULATION AROUND
THE FURTHER DEEPENING ATLANTIC LOW GIVES WAY TO RIDGING FROM THE
WEST OVERNIGHT. GALE AND STORM WARNINGS WILL COME DOWN THIS
EVENING...REPLACED BY SMALL CRAFT ADVISORIES ON AMZ350-374 WATERS.

MONDAY THROUGH THURSDAY...A COLD FRONT WILL CROSS THE LOCAL WATERS
MONDAY EVENING AND THE TIGHT PRESSURE GRADIENT AND COLD ADVECTION
WILL WORK TO BRING YET ANOTHER ROUND OF STRONG WINDS AND ELEVATED
SEAS THAT WILL LAST THROUGH AT LEAST MID WEEK. THE BRIEF WEAKENING
OF FLOW ON MONDAY MORNING WILL QUICKLY RAMP UP IN THE AFTERNOON AND
CONTINUE THEREAFTER. SOLID SMALL CRAFT ADVISORY CONDITIONS ARE
EXPECTED WITH A CHANCE FOR GALES OVER THE OUTER GEORGIA WATERS
MONDAY NIGHT AND TUESDAY. ADVISORIES WILL THEN CONTINUE TO BE NEEDED
THROUGH WEDNESDAY BEFORE CONDITIONS START IMPROVING DURING THE
LATE WEEK.

&&

.TIDES/COASTAL FLOODING...
IT SEEMS A SAFE BET THAT WE/LL EXPERIENCE SHALLOW COASTAL FLOODING
ALONG MUCH THE SC COAST...THE COMBINATION OF THE ONGOING
RAINS...ELEVATED SURF AND DEPARTURES THAT ARE RUNNING AROUND 1.25
FT MLLW ABOVE PREDICTED LEVELS. AS SUCH WE HAVE A COASTAL FLOOD
ADVISORY THROUGH 9 AM FOR CHARLESTON...COASTAL COLLETON AND
BEAUFORT COUNTIES. IT/LL BE CLOSE TO COASTAL FLOODING LEVELS
FURTHER SOUTH AND WE STILL MIGHT NEED TO HOIST AN ADVISORY FOR THE
REST OF THE COASTAL ZONES WITH A PRE-DAWN UPDATE.

ASTRONOMICAL INFLUENCES MIGHT AGAIN LEAD TO SHALLOW COASTAL
FLOODING WITH THE EARLY MORNING HIGH TIDE MONDAY.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY UNTIL 7 PM EST THIS EVENING FOR SCZ045.
     WIND ADVISORY FROM 10 AM THIS MORNING TO 7 PM EST THIS EVENING
     FOR SCZ050.
     COASTAL FLOOD ADVISORY UNTIL 9 AM EST THIS MORNING FOR
     SCZ048>050.
MARINE...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR AMZ352-354.
     STORM WARNING FROM 10 AM THIS MORNING TO 7 PM EST THIS EVENING
     FOR AMZ350.
     GALE WARNING UNTIL 10 AM EST THIS MORNING FOR AMZ350.
     GALE WARNING UNTIL 10 PM EST THIS EVENING FOR AMZ374.
     SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FOR AMZ330.
     GALE WARNING FROM 10 AM THIS MORNING TO 5 PM EST THIS
     AFTERNOON FOR AMZ330.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...BSH
LONG TERM...BSH
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...


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