Area Forecast Discussion
Issued by NWS Charleston, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KCHS 062132
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
432 PM EST SAT FEB 6 2016

.SYNOPSIS...
LOW PRESSURE WILL TRACK NORTH AND DEEPEN OFF THE SOUTHEAST COAST
TONIGHT THROUGH SUNDAY....THEN WILL MOVE AWAY TOWARD THE NORTHEAST
SUNDAY NIGHT. A COLD FRONT WILL CROSS THE AREA MONDAY. THEN...A
DEEP TROUGH WILL REMAIN IN PLACE THROUGH THE MIDDLE OF NEXT
WEEK...BRINGING UNSEASONABLY COOL CONDITIONS TO THE AREA. HIGH
PRESSURE WILL BUILD OVER THE REGION LATE WEEK INTO NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
TONIGHT WE FIND AN IMPRESSIVE LOW LATITUDE AND DEEPENING LOW AND
ASSOCIATED SHORT WAVE THAT DROPS 500 MB HEIGHTS DOWN TO SOME 2
STANDARD DEVIATIONS BELOW NORMAL BY 12Z SUNDAY. THIS FEATURE TAKES
ON NEUTRAL OR EVEN A SLIGHT NEGATIVE TILT BY DAYBREAK SUNDAY AS IT
SWEEPS IN FROM THE WEST. THIS INDUCES STRONG CYCLOGENESIS OVER THE
SW ATLANTIC...BUT THE EVOLUTION OF THIS SYSTEM HAS HUGE
IMPLICATIONS ON THE LOCAL FORECAST. WE CONTINUE TO IGNORE THE
WORST CASE SCENARIO FORECAST OF THE NAM WHICH HAS ACCUMULATING
SNOWS IN OUR CWFA. THUS OUR FORECAST IS GEARED HEAVILY TOWARD THE
HPC FORECAST AND A BLEND OF OF THE GLOBAL MODELS...WHICH PROVIDES
US WITH A MORE CONSERVATIVE FORECAST IN REGARDS TO WINTER WEATHER
FOR LATE TONIGHT INTO SUNDAY.

A COASTAL TROUGH OFF THE SE COAST WILL BECOME MORE ORGANIZED
TONIGHT. THE APPROACH OF THE MID/UPPER LOW TONIGHT AND IT/S TREND
TOWARD A NEGATIVE TILT WILL COMBINE WITH A STRONG 35-45 KT LOW
LEVEL JET TO PRODUCE POTENT FORCING FOR ASCENT. UPWARD VERTICAL
VELOCITY WILL STRENGTHEN AND DEEP LAYERED MOISTURE ARRIVES IN
CONCERT WITH DEEPENING LOW PRESSURE THAT FORMS OFF THE FLORIDA
COAST AND LIFTS NORTH/NE SEVERAL HUNDRED MILES OFF THE LOCAL
COAST. IN RESPONSE THERE IS A RAPID ONSET OF RAIN THAT OCCURS WITH
PLENTY OF LOW LEVEL FORCING IN TANDEM WITH UPPER DIFLUENCE. AN
ORGANIZED RAINFALL EVENT WILL TRANSPIRE WITH WIDESPREAD RAINS
EXPECTED NEAR AND EAST OF I-95...WITH GRADUATED COVERAGE FURTHER
WEST WHERE A SHARP GRADIENT WILL BE FOUND. QPF LOOKS TO RANGE FROM
ABOUT 1/10 INCH FAR INTERIOR SE GA TO MORE THAN 1 INCH AT THE
MOUTH OF THE SANTEE RIVER. THIS IS NOT ENOUGH FOR A FLASH FLOOD
WATCH...BUT ENOUGH TO CAUSE AT LEAST SOME NUISANCE FLOODING GIVEN
THE SATURATED GROUNDS FROM THE CONSIDERABLE RAINS EARLIER IN THE
WEEK. THERE COULD BE A CONCERN FOR FLOODING IN DOWNTOWN CHARLESTON
WITH RAINS ONGOING WITH THE HIGH TIDE EARLY SUNDAY MORNING.

WHILE NOT IN THE FORECAST THERE CERTAINLY COULD BE SOME ELEVATED
CONVECTION GIVEN THE POTENCY OF THIS SYSTEM.

BETWEEN 09Z-12Z...RAIN COULD MIX WITH WET SNOW MAINLY WEST OF
INTERSTATE 95. HOWEVER...BECAUSE TEMPERATURES WILL REMAIN ABOVE
FREEZING AND BECAUSE THE COMMA CLOUD/ASSOCIATED DEEP LAYERED
MOISTURE WILL BEGIN TO RETREAT TOWARD THE EAST...ANY SNOW THAT
FALLS IN THIS AREA SHOULD REMAIN OF LIGHT INTENSITY AND SHOULD NOT
BE ABLE TO ACCUMULATE.

LAKE WINDS...A LAKE WIND ADVISORY IS IN EFFECT LATE TONIGHT DUE
TO WINDS RESULTING FROM THE TIGHT PRESSURE GRADIENT AROUND THE
ATLANTIC CYCLONE AND COLD ADVECTION ATOP THE WARMER WATERS OF LAKE
MOULTRIE.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
SUNDAY BEGINS WITH MAINLY RAIN...AND MORNING POPS AREA GRADUATED
FROM CATEGORICAL ALONG/EAST OF INTERSTATE 95 TO SLIGHT CHANCE/CHANCE
INLAND. WHILE COLD ADVECTION/DYNAMIC COOLING COULD SUPPORT RAIN
MIXING WITH WET SNOWFLAKES JUST ABOUT ANYWHERE IN THE MORNING...THE
COMMA CLOUD/ASSOCIATED DEEP LAYERED MOISTURE WILL ADVANCE TOWARD THE
NORTHEAST AND WILL RESIDE LONGEST ACROSS SOUTH CAROLINA
COUNTIES...ESPECIALLY ALONG AND NORTH OF THE EDISTO RIVER.
HERE...FOCUSED FORCING FOR ASCENT COULD TRANSLATE TO RAIN MIXING
WITH WET SNOW...AND THERE IS A LOW PROBABILITY THAT RAIN COULD
CHANGE OVER TO WET SNOW IN SOME AREAS. IF PRECIPITATION BECOMES
SIGNIFICANTLY CONVECTIVE...LOCALIZED HEAVIER BURSTS OF WET SNOW
COULD DEPOSIT A QUICK COUPLE OF INCHES ACCUMULATION WHICH COULD
TEMPORARILY PRODUCE SLICK ROADS WITHIN THE CHARLESTON QUAD-COUNTY
REGION SUNDAY MORNING. HOWEVER...EVEN IF/WHERE SNOW TEMPORARILY
ACCUMULATES...SNOW WILL MELT QUICKLY WHEN SNOW ENDS AND/OR CHANGES
BACK TO RAIN. ALSO OF NOTE...12Z GUIDANCE HAS TRENDED SLIGHTLY
WARMER WITHIN THE 1000-850 MB LAYER...AND THERE IS A DECENT CHANCE
FOR MOST/ALL PRECIPITATION TO REMAIN LIQUID. GIVEN THE LOW
PROBABILITY FOR HIGHLY LOCALIZED ACCUMULATING SNOW AND ONGOING
UNCERTAINTY REGARDING PRECIPITATION TYPE...WINTER WEATHER HEADLINES
ARE NOT WARRANTED.

OTHERWISE...POPS WILL STEADILY DIMINISH AS DEEP LAYERED MOISTURE
RETREATS TOWARD THE NORTHEAST SUNDAY AFTERNOON...AND POPS FALL TO
LESS THAN 15 PERCENT SUNDAY NIGHT. ALSO OF NOTE...WINDS PRODUCED BY
THE DEEPENING ATLANTIC LOW COULD PRODUCE WIND GUSTS AS HIGH AS 40
MPH ESPECIALLY NEAR THE CHARLESTON COUNTY COAST. AFTER COLLABORATION
WITH WFO ILM...ISSUED A WIND ADVISORY FOR CHARLESTON COUNTY SUNDAY.

MONDAY...TEMPERATURES COULD BRIEFLY PUSH INTO THE 55-60F RANGE
BEFORE A STRONG COLD FRONT CROSSES THE REGION DURING THE
AFTERNOON/EVENING. PER AREA CONSENSUS...MONDAY AFTERNOON FEATURES
SLIGHT CHANCE POPS...ALTHOUGH DRY MODEL SOUNDINGS SUGGEST MOST
LOCATIONS WILL REMAIN RAIN-FREE.

AS COLD ADVECTION SURGES INTO THE REGION BENEATH AN UPPER TROUGH
MONDAY NIGHT...CANNOT RULE OUT AN ISOLATED SNOW FLURRY OR TWO.
OTHERWISE...EXPECT CHILLY LOWS IN THE 30S/WIND CHILLS IN THE 20S
MONDAY NIGHT...FOLLOWED BY DRY...BRISK AND COLD CONDITIONS WITH
HIGHS ONLY IN THE 40S TUESDAY.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE FORECAST AREA WILL REMAIN SOLIDLY UNDER THE INFLUENCE OF THE
COLD TROUGH ALOFT THROUGH MID TO LATE WEEK. HIGH PRESSURE WILL
GRADUALLY BUILD IN FROM THE WEST AND THE OVERALL FORECAST CONTINUES
TO LOOK COOL AND DRY. IN FACT...TEMPERATURES WILL BE WELL BELOW
NORMAL WEDNESDAY AND THURSDAY BEFORE MODIFYING TO NEAR NORMAL BY THE
END OF THE WEEK AND THE START OF THE WEEKEND.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
THROUGH 18Z SUNDAY...VFR WILL PREVAIL INTO EARLY THIS EVENING.
LIGHT RAIN WILL CONTINUE INTO THIS EVENING IN RESPONSE TO THE
COMBINATION OF A COASTAL TROUGH OFFSHORE AND AN UPPER LEVEL TROUGH
APPROACHING THE REGION. CEILINGS WILL LOWER TO MVFR THIS EVENING.
AS LOW PRESSURE FORMS OFFSHORE LATE THIS EVENING AND TONIGHT
MODERATE OR MAYBE A PERIOD OF LOCALLY HEAVY RAINS ARE POSSIBLE.
LOW END MVFR IS EXPECTED AT THIS TIME...THOUGH IFR IS
POSSIBLE...ESPECIALLY IN SOME OF THE HEAVIER RAIN BANDS. COLD AIR
MOVING INTO THE AREA AROUND DAYBREAK SUNDAY MAY LEAD TO SOME SNOW
MIXING IN WITH THE RAIN...ESPECIALLY AT KCHS. PRECIPITATION WILL
GRADUALLY DIMINISH SUNDAY MORNING...LEADING TO IMPROVING CEILINGS.
GUSTY NORTHERLY WINDS WILL ALSO DEVELOP.

EXTENDED AVIATION OUTLOOK...VFR.

&&

.MARINE...
TONIGHT...STRENGTHENING LOW PRESSURE OFFSHORE WILL LEAD TO
DETERIORATING MARINE CONDITIONS. NORTHERLY WINDS WILL RISE THIS
EVENING...CONTINUING UPWARD OVERNIGHT. THE WORST CONDITIONS ARE
EXPECTED ACROSS MARINE ZONES 350 AND 374...WHERE GALE WARNINGS ARE
IN EFFECT. FOR ZONE 350...GUSTS MAY APPROACH 40 KT BEFORE
DAYBREAK WITH HAZARDOUS SEAS BUILDING TO THE 8-10 FT
RANGE...MAINLY BEYOND 10 NM. FOR ZONE 374...GUSTS MAY APPROACH 40
KT BEFORE DAYBREAK WITH HAZARDOUS SEAS BUILDING TO THE 10-12 FT
RANGE. FOR MARINE ZONE 352...A SMALL CRAFT ADVISORY IN EFFECT
FOLLOWED BY A GALE WATCH OVERNIGHT. THERE IS A GOOD CHANCE THIS
WILL BE UPGRADED TO A GALE WARNING FOR WIND GUSTS UP TO 35 KT
BEFORE DAYBREAK...MAINLY BEYOND 10 NM. SEAS WILL BUILD TO 6-8
FT...MAINLY BEYOND 10 NM. FOR MARINE ZONE 354...A SMALL CRAFT
ADVISORY IS IN EFFECT. WINDS WILL GUST TO AROUND 30 KT WITH SEAS
BUILDING TO 5-7 FT...MAINLY BEYOND 10 NM. FINALLY CHARLESTON
HARBOR HAS A SMALL CRAFT ADVISORY FOR GUSTS APPROACHING 30 KT.

SUNDAY THROUGH THURSDAY...HAZARDOUS MARINE CONDITIONS WILL
PREVAIL THROUGH SUNDAY AS OFFSHORE/PASSING LOW PRESSURE DEEPENS
RAPIDLY AND GALES BECOME COMMON. EVEN AS LOW PRESSURE PULLS AWAY
SUNDAY NIGHT INTO MONDAY...ELEVATED WINDS AND SEAS WILL MAINTAIN
SCA CONDITIONS MOST AREAS. THEN...IN THE WAKE OF A STRONG COLD
FRONT...ANOTHER PERIOD OF GALES IS LIKELY MONDAY NIGHT INTO
TUESDAY...ESPECIALLY NEAR 20 NM AND BEYOND. ELEVATED WINDS/SEAS
SHOULD PERSIST INTO WEDNESDAY...THEN CONDITIONS SHOULD BEGIN TO
IMPROVE AS HIGH PRESSURE EXPANDS INTO THE REGION BEGINNING
THURSDAY.

&&

.TIDES/COASTAL FLOODING...
ASTRONOMICAL HIGH TIDES WILL SOON BE UPON US AND DEPARTURES ARE
ALREADY RUNNING AS MUCH AS 1 FOOT ABOVE PREDICTED ALONG THE ENTIRE
STRETCH OF THE COAST. THIS SUGGESTS AT LEAST A LOW END CHANCE OF
SHALLOW COASTAL FLOODING WITH THE MORNING HIGH TIDES ALONG PARTS
OF THE SC COAST FOR THE BEGINNING OF NEXT WEEK.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM 4 AM TO 6 PM EST SUNDAY FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST MONDAY FOR AMZ352.
     GALE WATCH FROM 1 AM EST SUNDAY THROUGH SUNDAY AFTERNOON FOR
     AMZ350.
     SMALL CRAFT ADVISORY UNTIL 1 AM EST SUNDAY FOR AMZ350.
     SMALL CRAFT ADVISORY UNTIL 1 AM EST MONDAY FOR AMZ354.
     GALE WATCH FROM 10 PM EST THIS EVENING THROUGH SUNDAY
     AFTERNOON FOR AMZ374.
     SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR AMZ374.
     SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 6 PM EST SUNDAY
     FOR AMZ330.

&&

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.