Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 251438
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
938 AM EST SUN JAN 25 2015

.SYNOPSIS...
HIGH PRESSURE WILL SHIFT EAST OF THE AREA THIS AFTERNOON.
LOW PRESSURE WILL PASS NORTH OF THE REGION TONIGHT INTO MONDAY.
THIS WILL ALLOW A COLD FRONT TO SWING THROUGH THE AREA LATE TONIGHT
AND EARLY MONDAY...WITH ANOTHER REINFORCING COLD FRONT ON TUESDAY.
HIGH PRESSURE WILL THEN PREVAIL THROUGH THURSDAY...BEFORE ANOTHER
COLD FRONT PUSHES THROUGH THE AREA FRIDAY. HIGH PRESSURE WILL THEN
PREVAIL THROUGH NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A LEAD SHORTWAVE NOTED ON WATER VAPOR IMAGERY HAD PRODUCED A
RAPIDLY EXPANDING SHIELD OF CIRRUS WHICH WAS RACING ACROSS THE
REGION SUNDAY MORNING. ADJUSTED CLOUD COVER ACCORDINGLY TO ACCOUNT
FOR PARTLY/MOSTLY CLOUDY SKIES FOR A FEW HOURS. THIS
AFTERNOON...THE SHORTWAVE AND ASSOCIATED CIRRUS SHOULD ADVANCE
OFFSHORE...LEAVING MAINLY SUNNY SKIES. CLOUDS COULD SLOW HOURLY
TEMPERATURE TEMPERATURE RECOVERY FOR A COUPLE OF HOURS...BUT
TEMPERATURES THIS AFTERNOON WILL STILL TOP OUT IN THE UPPER
50S/LOWER 60S MOST AREAS. AS SYNOPTIC WINDS BACK TOWARD THE SOUTH
AHEAD OF AN APPROACHING LONGWAVE UPPER TROUGH AND ASSOCIATED COLD
FRONT...COOLER TEMPERATURES IN THE LOWER TO MID 50S WILL PREVAIL
ON THE BEACHES THIS AFTERNOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
TONIGHT...THE SHARP UPPER TROUGH AND ITS ATTENDANT CLIPPER SYSTEM
WILL APPROACH RAPIDLY FROM THE NORTHWEST TONIGHT. THE 25/00Z
NAM/GFS/ECMWF WITH SUPPORT FROM THE 25/03Z SREF ARE SIMILAR IN
SHOWING A BAND OF MAINLY LIGHT SHOWERS DEVELOPING OVER NORTHERN
FLORIDA INTO THE WESTERN WALL OF THE GULF STREAM OFF THE LOWER
SOUTH CAROLINA COAST LATE TONIGHT WHERE THE COMBINATION OF DEEPER
MOISTURE...DPVA INDUCED BY THE UPPER TROUGH AND 160 KT LEFT EXIT
REGION OF THE 250 HPA JET WILL ALIGN. A FEW SHOWERS COULD BRUSH
PORTIONS OF THE GEORGIA COAST LATE...BUT THE BULK OF THIS
ACTIVITY IS EXPECTED TO REMAIN JUST OFFSHORE AND TO THE SOUTH. DRY
CONDITIONS WILL PREVAIL OTHERWISE. LOWS WILL RANGE FROM AROUND 40
WELL INLAND TO THE MID-UPPER 40S AT THE COAST.

MONDAY...AN IMPRESSIVE SHORTWAVE WILL ROUND THE BASE OF LONGWAVE
TROUGH SHIFTING OVER THE EASTERN CONUS. THE SHORTWAVE WILL HELP PUSH
A SFC LOW THROUGH THE MID ATLANTIC STATES NEAR DAYBREAK...WITH A
TRAILING COLD FRONT THAT EXTENDS SOUTHWARD. DEEP MOISTURE WILL BE
LACKING OVER THE SOUTHEAST AS COLD FROPA OCCURS EARLY MONDAY...BUT A
STRONG COLD POOL ASSOCIATED WITH THE SHORTWAVE ALOFT WILL PRODUCE
STEEP LAPSE RATES AND THE POSSIBILITY OF A FEW SHOWERS...MAINLY OVER
NORTHERN AREAS. GIVEN THE STRENGTH OF THE COLD AIR OFF THE
SFC...THERE REMAINS A POSSIBILITY OF SOME GRAUPEL WITH ANY
SHOWERS...BUT GIVEN THE SMALL CHANCE PRECIP AND WESTERLY WINDS
QUICKLY DRYING OUT CONDITIONS MONDAY AFTERNOON/EVENING HAVE OPTED TO
MENTION JUST SHOWERS AT THIS POINT. A DOWNSLOPING WIND COMPONENT
WILL LIKELY OFFSET SOME COLD AIR ADVECTION...BUT TEMPS SHOULD ONLY
PEAK IN THE UPPER 50S OVER MOST LOCATIONS. DESPITE COOLER AFTERNOON
TEMPS...GUSTY WINDS BETWEEN 20-25 MPH ARE POSSIBLE THROUGHOUT THE
DAY. DRY CONDITIONS WILL PREVAIL MONDAY NIGHT WHILE TEMPS COOL INTO
THE MID TO UPPER 30S.

TUESDAY AND WEDNESDAY...LOW PRESSURE OFF THE MID ATLANTIC COAST WILL
DEEPEN SUBSTANTIALLY WHILE LIFTING NORTHEAST AND AWAY FROM THE
REGION...ALLOWING A REINFORCING COLD FRONT TO SHIFT OVER THE AREA.
MOISTURE WILL ONCE AGAIN BE LACKING OVER THE REGION...THUS DRY FROPA
IS ANTICIPATED. HIGH PRESSURE WILL THEN BUILD FROM THE NORTH AND
NORTHWEST THROUGH WEDNESDAY WITH COOLER AND EVEN DRYER CONDITIONS
INTO MIDWEEK. IN GENERAL...EXPECT OVERALL HIGH TEMPS IN THE LOW/MID
50S ON TUESDAY AHEAD OF THE FRONT....THEN LOW 50S ON WEDNESDAY.
OVERNIGHT LOWS WILL RANGE IN THE LOW/MID 30S AWAY FROM THE COAST
TUESDAY NIGHT.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
SFC HIGH PRESSURE WILL BUILD FROM THE NORTH/NORTHWEST WEDNESDAY
NIGHT...BECOME CENTERED OVER THE SOUTHEASTERN UNITED STATES EARLY ON
THURSDAY...THEN CONTINUE TO SHIFT OFFSHORE AHEAD OF ANOTHER LOW
PRESSURE SYSTEM PASSING OVER THE MIDWEST. THE PATTERN WILL FAVOR A
SLIGHT WARMING TREND THROUGH EARLY THURSDAY NIGHT AS WEAK MID LVL
RIDGING OCCURS AND A LIGHT SOUTHERLY FLOW DEVELOPS WELL AHEAD OF THE
LOW PRESSURE SYSTEM PASSING TO THE NORTH. IN GENERAL...AFTERNOON
HIGH TEMPS SHOULD PEAK IN THE UPPER 50S TO AROUND 60 ON THURSDAY. A
COLD FRONT EXTENDING SOUTHWARD FROM THE LOW PRESSURE SYSTEM PASSING
OVER THE NORTHEAST WILL THEN SHIFT OVER THE SOUTHEASTERN UNITED
STATES THURSDAY NIGHT INTO EARLY FRIDAY. MOISTURE IS RATHER LACKING
DURING THE TIME OF FROPA...SO HAVE MAINTAINED A DRY FORECAST AT THIS
POINT...BUT A FEW SHOWERS ARE NOT OUT OF THE QUESTION. DRY AND
SLIGHTLY BELOW NORMAL TEMPS ARE THEN ANTICIPATED AS HIGH PRESSURE
BUILDS FROM THE NORTH BEHIND THE DEPARTING COLD FRONT ON
FRIDAY...BUT A WEAK COASTAL TROUGH COULD DEVELOP OFF THE SOUTHEAST
COAST DURING THE WEEKEND...THUS INCREASING PRECIP CHANCES ALONG THE
COASTAL AREAS.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
VFR. LOW PROBABILITY FOR MVFR CEILINGS AHEAD OF A COLD FRONT LATER
TONIGHT. LOW-LEVEL WIND SHEAR COULD DEVELOP TONIGHT...BUT WILL
ASSESS 12Z GUIDANCE AND ADD TO 18Z TAFS IF NEEDED.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED AT BOTH CHS
AND SAV TERMINALS THROUGH THURSDAY. HOWEVER...WE COULD SEE GUSTY
WINDS AT BOTH TERMINALS ON MONDAY BEHIND A PASSING COLD FRONT.

&&

.MARINE...
TODAY...OFFSHORE WINDS 10-15 KT WILL TURN SOUTHERLY AROUND 10 KT
THIS AFTERNOON AS THE SURFACE RIDGE SHIFTS OFFSHORE AND A COLD
FRONT APPROACHES FROM THE WEST. SEAS 2-4 FT WILL REMAIN COMMON...
HIGHEST BEYOND 20 NM.

TONIGHT...SOUTHWEST WINDS WILL INCREASE AHEAD OF A CLIPPER SYSTEM
AND THE ASSOCIATED UPPER TROUGH. WINDS LOOK TO PEAK 15-20 KT...BUT
MAY BE CLOSER TO 20 KT OVER THE GEORGIA OFFSHORE LEG. SEAS WILL
BUILD TO 2-4 FT NEARSHORE AND 4-5 FT OFFSHORE. CONDITIONS WILL BE
CLOSE TO SMALL CRAFT ADVISORY CRITERIA FOR THE GEORGIA OFFSHORE
LEG...BUT CONDITIONS LOOK TO REMAIN JUST SHY OF CRITERIA AT THIS
TIME. FLAGS WILL NOT BE ISSUED WITH THIS FORECAST CYCLE...BUT MAY
EVENTUALLY BE NEEDED.

MONDAY AND TUESDAY...AN AREA OF LOW PRESSURE WILL TRACK OVER THE MID
ATLANTIC STATES THEN PUSH OFFSHORE WITH A COLD FRONT THAT EXTENDS
SOUTHWARD OVER THE REGION. A TIGHTENED PRESSURE GRADIENT ASSOCIATED
WITH THE PASSING LOW PRESSURE SYSTEM AND COLD FRONT WILL LIKELY
MAINTAIN ELEVATED WINDS AND ENHANCED SEAS THROUGH MUCH OF MONDAY AND
MONDAY NIGHT...POSSIBLY RESULTING IN SMALL CRAFT ADVISORY CONDITIONS
OVER COASTAL WATERS OUTSIDE CHS HARBOR...AND LIKELY CONTINUING
SMALL CRAFT ADVISORY CONDITIONS IN OFFSHORE GEORGIA WATERS. BY
TUESDAY...LOW PRESSURE WILL DEEPEN WHILE LIFTING NORTHEAST ALONG THE
NEW ENGLAND COAST...ALLOWING A REINFORCING COLD FRONT TO SHIFT OVER
COASTAL WATERS BY TUESDAY NIGHT. WINDS/SEAS SHOULD BE JUST BELOW
ADVISORY CRITERIA FOR MOST WATERS DURING FROPA...EXCEPT IN OUTER
GEORGIA WATERS WHERE MARGINAL SMALL CRAFT ADVISORY CONDITIONS SHOULD
BE ONGOING.

WEDNESDAY THROUGH SATURDAY...HIGH PRESSURE WILL BUILD OVER THE
WATERS BEHIND A DEPARTING COLD FRONT...WITH MUCH QUIETER CONDITIONS
OVER THE COASTAL WATERS THROUGH THURSDAY. A COLD FRONT WILL THEN
SHIFT OVER THE AREA THURSDAY NIGHT INTO EARLY FRIDAY...CHANGING A
SOUTHERLY WIND TO NORTH/NORTHWEST AS HIGH PRESSURE BUILDS IN BEHIND
IT. A WEAK COASTAL TROUGH COULD DEVELOP OFFSHORE NEXT WEEKEND...WITH
A FEW SHOWERS EVENTUALLY SHIFTING OVER NEARSHORE WATERS.
HOWEVER...WINDS/SEAS ARE EXPECTED TO REMAIN WELL BELOW SMALL CRAFT
ADVISORY LEVELS DURING THIS TIME FRAME.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 8 AM MONDAY TO 11 PM EST TUESDAY FOR
     AMZ374.

&&

$$

NEAR TERM...SPR
SHORT TERM...
LONG TERM...
AVIATION...SPR
MARINE...SPR






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