Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 272007
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
ISSUED BY NATIONAL WEATHER SERVICE WILMINGTON NC
307 PM EST TUE JAN 27 2015

.SYNOPSIS...
HIGH PRESSURE WILL RIDGE DOWN INTO THE AREA FROM THE NORTHWEST
TONIGHT BEHIND A COLD FRONT. THIS HIGH PRESSURE WILL MIGRATE ACROSS
THE CAROLINAS THROUGH THURSDAY. ANOTHER COLD FRONT WILL CROSS LATE
THURSDAY NIGHT WITH COOLER TEMPERATURES INTO THE WEEKEND. A
COASTAL TROUGH WILL DEVELOP BY LATE WEEKEND...THEN LIFT NORTH
AHEAD OF A STORM SYSTEM THAT PASSES OVER THE AREA LATE SUNDAY INTO
MONDAY. HIGH PRESSURE SHOULD THEN BUILD OVER THE REGION INTO NEXT
TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
AS OF 300 PM...MID-LEVEL CLOUDS CONTINUE TO STREAM OVERHEAD THIS
AFTERNOON AS THE FORECAST AREA REMAINS UNDER THE INFLUENCE OF A
BROAD AND DEEP UPPER TROUGH. WE STILL CAN EXPECT NORTHWEST WINDS
AROUND 10-15 MPH WITH GUSTS UP TO 20 MPH FOR THE REST OF TODAY...BUT
WINDS WILL QUICKLY SUBSIDE THIS EVENING AS THE GRADIENT OVER GA/SC
RELAXES. AS STRONG LOW PRESSURE OFF THE NEW ENGLAND COAST CONTINUES
TO LIFT NORTHWARD...CLOUD COVER WILL DIMINISH WITH CLEAR CONDITIONS
PREVAILING AFTER MIDNIGHT. CANADIAN HIGH PRESSURE RIDGING DOWN
THROUGH THE GREAT LAKES WILL HELP MAINTAIN N-NW FLOW ACROSS THE
REGION OVERNIGHT. THERE IS VERY GOOD AGREEMENT BETWEEN THE GFS/NAM
MOS NUMBERS AS LOWS ARE EXPECTED TO DROP BELOW FREEZING...UPPER 20S
TO LOWER 30S...AT MOST LOCATIONS AWAY FROM THE BEACHES. EVEN THE
COASTAL ZONES WILL FALL INTO THE MID 30S. PERSISTENT NORTH WINDS
THROUGH DAYBREAK WILL CREATE WIND CHILL VALUES IN THE LOW TO MID 20S
EARLY WEDNESDAY MORNING.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
AS OF 300 PM TUESDAY...LAST PIECE OF ENERGY EMBEDDED WITHIN A HIGHLY
AMPLIFIED UPPER TROUGH WILL BE MOVING OFFSHORE WEDNESDAY MORNING.
HIGH PRESSURE BUILDS DOWN FROM THE GREAT LAKES ON
WEDNESDAY...ACCOMPANIED BY COLD ADVECTION...AND WHILE WINDS WILL BE
DECREASING THROUGH THE DAY A CHILLY BUT SUNNY DAY IS IN STORE. 925MB
TEMPS FALL TO AROUND -2C THROUGH THE EVENING...WHICH IS EXPECTED TO
BE THE DEPTH OF THE SHALLOW MIXED LAYER...AND THIS SUPPORTS HIGHS
RANGING FROM JUST THE UPPER 40S ACROSS THE EXTREME NORTHERN
COUNTIES...TO THE LOWER 50S IN THE GEORGIA ZONES. THIS SURFACE HIGH
WILL MOVE DIRECTLY OVERHEAD WEDNESDAY NIGHT...IN CONJUNCTION WITH
THE SHUT OFF OF COLD ADVECTION AS SHORTWAVE RIDGING DEVELOPS
OVERHEAD...WILL LEAD TO A VERY GOOD RADIATIONAL COOLING NIGHT.
ALTHOUGH A BIT OF MOISTURE INCREASES ABOVE 700MB...DEWPOINT
DEPRESSIONS REMAIN GREATER THAN 10C AND THUS NO REDUCTION IN
LONGWAVE COOLING IS EXPECTED. THEREFORE...EXPECT MINS BY DAWN
THURSDAY TO BE A SOLID 10 DEGREES BELOW NORMAL...WITH UPPER 20S
INLAND AND LOW 30S NEAR THE BEACHES.

THE AFOREMENTIONED SHORTWAVE RIDGING WILL PERSIST THE FIRST HALF OF
THURSDAY...BUT THE MID LEVEL FLOW DEVELOPS A VERY SHORT WAVELENGTH
AS ANOTHER VORTICITY IMPULSE DROPS ACROSS THE EAST THURSDAY NIGHT.
THIS WILL QUICKLY DRIVE THE SURFACE HIGH PRESSURE OFFSHORE...AND A
BRIEF PERIOD OF RETURN FLOW WILL HELP DRIVE HIGHS THURSDAY TO MORE
SEASONABLE VALUES IN THE UPPER 50S...LOW 60S TOWARDS SAVANNAH. THIS
SHORTWAVE WILL DRIVE A COLD FRONT THROUGH THE REGION THURSDAY NIGHT
WITH A RETURN TO COOL ADVECTION AND NW FLOW. SOME GUIDANCE SUGGESTS
A LITTLE LIGHT PRECIP WILL ACCOMPANY THIS FRONT. HOWEVER...THE
STRONGEST THETA-E RIDGING REMAINS JUST SOUTH OF THE AREA...WHILE THE
BEST FORCING STAYS JUST TO THE NORTH. SREF PROBABILITIES PEAK AT
20-30 PERCENT THURSDAY NIGHT...NOT A SIGNAL TYPICALLY ASSOCIATED
WITH SHOWERS. HAVE INHERITED VERY LOW-SCHC POP AND WILL LEAVE THIS
UNCHANGED...BUT MOST OF THE AREA WILL BE DRY THURSDAY NIGHT. MINS
WILL BE ELEVATED THURSDAY NIGHT AS COLD ADVECTION ONLY BEGINS VERY
LATE...AND EXPECT LOWS TO RANGE FROM ABOUT 42 WELL NW...TO AROUND 50
AT THE COAST.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
FRIDAY...DRY HIGH PRESSURE WILL THEN MOVE INTO THE AREA BEHIND
THE FRONT WHILE WINDS QUICKLY BECOME NORTHWEST. TEMPS SHOULD BE A
FEW DEGREES COOLER POST FROPA...BUT A DOWNSLOPING WIND COMPONENT
ALONG WITH A FULL DAY OF INSOLATION SHOULD STILL RESULT IN MAX
TEMPS NEAR THE UPPER 50S OVER MOST LOCATIONS FRIDAY AFTERNOON.

FAIRLY DRY AND BELOW NORMAL TEMPS ARE ANTICIPATED ON SATURDAY AS SFC
HIGH PRESSURE BUILDS FROM THE NORTH. A COASTAL TROUGH IS THEN
EXPECTED TO DEVELOP OFF THE SOUTHEAST COAST BY SUNDAY...PRODUCING
CHANCES OF SHOWERS THAT SHIFT ONSHORE AS IT LIFTS NORTH/NORTHWEST
AHEAD OF A LOW PRESSURE SYSTEM TRACKING FROM THE SOUTH CENTRAL
UNITED STATES TO THE OHIO RIVER VALLEY. TEMPS WILL BE SLIGHTLY MORE
MILD AS THE COASTAL TROUGH MAKES A SHIFT ONSHORE...WITH OVERALL
TEMPS PEAKING IN THE MID 50S NORTH TO LOW 60S SOUTH. CHANCES OF
SHOWERS WILL REMAIN IN THE FORECAST THROUGH MONDAY ALONG WITH CLOUDY
CONDITIONS AS MOISTURE IS DRAWN FROM THE SOUTHEAST AND ISENTROPIC
LIFT OCCURS AHEAD OF AN APPROACHING COLD FRONT. CONDITIONS SHOULD
RESULT IN BELOW NORMAL TEMPS MONDAY AFTERNOON THROUGH TUESDAY AS
HIGH PRESSURE BUILDS INTO THE AREA POST FROPA. A DEVELOPING LOW PRESSURE
CENTER OVER THE GULF OF MEXICO COULD RESULT IN A FEW SHOWERS
DRIFTING BACK NORTH AND INTO EXTREME SOUTHEAST GEORGIA BY TUESDAY
AFTERNOON.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
STRONG LOW PRESSURE OF THE COAST OF NEW ENGLAND WILL SLOWLY PULL
AWAY TO THE NORTHEAST THIS AFTERNOON. NORTH NORTHWEST WINDS WILL BE
OBSERVED OVER THE REGION THIS AFTERNOON...ALONG WITH SCATTERED
MAINLY MID CLOUD. WINDS DIMINISH FOR DIURNAL REASONS THIS
EVENING...HOWEVER WITH FALLING DEWPOINTS AND WEAK COLD AIR
ADVECTION...DO NOT EXPECT ANY FOG FORMATION. WEDNESDAY...SUNNY SKIES
WITH WITH A MODERATE NORTHERLY WIND.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED AT BOTH CHS
AND SAV TERMINALS THROUGH THE WEEKEND...BUT A FEW SHOWERS ARE
POSSIBLE THURSDAY NIGHT WITH A PASSING COLD FRONT.

&&

.MARINE...
THROUGH TONIGHT...A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR
THE GA WATERS FROM 20-60 NM. EXPECT 4-6 FT SEAS IN THE ADVISORY
AREA WITH NORTHWEST WINDS 15-20 KT AND GUSTS UP TO 25 KT. IN THE
0-20 NM NEARSHORE ZONES...EXPECT NORTHWEST WINDS AROUND 15 KT WITH
GUSTS UP TO 20 KT. CONTINUED OFFSHORE FLOW WILL ALLOW SEAS TO
SUBSIDE IN THE NEARSHORE WATERS...GENERALLY 3-4 FT BECOMING 2-3 FT
TONIGHT. AS HIGH PRESSURE RIDGES DOWN FROM THE NORTHWEST
OVERNIGHT...THE GRADIENT WILL ONCE AGAIN TIGHTEN OVER THE
WATERS...MAINTAINING NORTHERLY FLOW 15-20 KT WITH HIGHER
GUSTS...ESPECIALLY OVER THE OUTER WATERS.

WEDNESDAY THROUGH MONDAY...GUSTY NORTH WINDS WILL START THE PERIOD
AS HIGH PRESSURE BUILDS DOWN FROM THE GREAT LAKES. WIND SPEEDS
WILL BE 15-20 KTS EARLY...BUT WILL EASE AND VEER TO THE NE
WEDNESDAY NIGHT WHEN HIGH PRESSURE MOVES OVERHEAD. THIS HIGH
PRESSURE WILL DRIFT OFFSHORE EARLY THURSDAY...CREATING A BRIEF
PERIOD OF RETURN FLOW AND SOUTHERLY WINDS OF 10 KTS OR LESS DURING
THE DAY. THURSDAY NIGHT...COLD FRONT WILL APPROACH FROM THE NW
CAUSING WINDS TO RISE TO 15-20 KTS FROM THE SW...BEFORE ABRUPTLY
TURNING TO THE NW LATE BEHIND THE COLD FRONT. SEAS INITIALLY WILL
BE 3-4 FT ON THE GUSTY NW WINDS...WITH A FEW 5 FT WAVES STILL
EXPECTED IN THE OUTER GEORGIA WATERS. THESE WILL FALL TO 1-3 FT
EVERYWHERE WEDNESDAY NIGHT AND DURING THURSDAY...BEFORE RISING
AGAIN LATE THURSDAY NIGHT.

A COASTAL TROUGH WILL DEVELOP JUST OFF THE SOUTHEAST COAST ON
SATURDAY...PRODUCING SHOWERS THAT EVENTUALLY SHIFT OVER NEARSHORE
WATERS. THE COASTAL TROUGH SHOULD THEN LIFT NORTH AND ONSHORE ON
SUNDAY AHEAD OF ANOTHER LOW PRESSURE SYSTEM THAT STRENGTHENS WHILE
TRACKING WELL NORTH OF THE AREA INTO MONDAY. A SOUTHWARD EXTENDING
COLD FRONT FROM THIS LOW PRESSURE SYSTEM IS EXPECTED TO SWEEP
THROUGH THE SOUTHEASTERN UNITED STATES...THEN OFFSHORE BY MONDAY
NIGHT...WITH WINDS/SEAS POSSIBLY REACHING SMALL CRAFT ADVISORY
LEVELS OVER ALL NEARSHORE WATERS EARLY NEXT WEEK.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EST WEDNESDAY FOR AMZ374.

&&

$$

NEAR TERM...BJR
SHORT TERM...JDW
LONG TERM...
AVIATION...
MARINE...









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