519
FXUS62 KCHS 160515
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1215 AM EST THU JAN 16 2025
SYNOPSIS
HIGH PRESSURE WILL PREVAIL THROUGH THE WEEK. A LOW PRESSURE
SYSTEM AND ASSOCIATED COLD FRONT WILL IMPACT THE REGION THIS
WEEKEND. ANOTHER LOW PRESSURE SYSTEM COULD IMPACT THE REGION
EARLY TO MID NEXT WEEK.
NEAR TERM /THROUGH TODAY/
AFTER MIDNIGHT, THE FORECAST APPEARED ON TRACK. THE UPDATE WILL
ALIGN HOURLY TEMPERATURES AND DEWPOINTS WITH RECENT
OBSERVATIONS.
A DAMPENING SHORT WAVE WILL PASS THROUGH THE APPALACHIANS AND
SOUTHERN MISSISSIPPI VALLEY OVERNIGHT, PRECEDED BY A 135-145 KT
UPPER JET ACROSS THE IMMEDIATE VICINITY. THIS FEATURE WILL
GENERATE VARYING AMOUNTS OF CIRRUS AND SOME ALTOCUMULUS CLOUDS
THROUGH THE NIGHT AS THEY ARRIVE FROM THE WEST AND SOUTHWEST. AT
THE SURFACE, CONTINENTAL HIGH PRESSURE WILL STAY IN CONTROL,
ALLOWING FOR WINDS TO BE LIGHT OR CALM FOR MUCH OF THE NIGHT,
BEFORE SOME SLIGHT RECOUPLING COULD OCCUR CLOSER TO DAYBREAK
WITH A 20-25 KT LOW LEVEL JET APPROACHING. THE EXPECTATION IS
FOR EXCELLENT RADIATIONAL COOLING THROUGH MUCH OF THE NIGHT
GIVEN SUCH A DRY AIR MASS. BUT IF ANY MIXING OCCURS LATE AND/OR
THERE IS ENOUGH MID AND HIGH LEVEL CLOUD COVER, THIS COULD
CHANGE OUR HOURLY AND MIN TEMPERATURES. AS BEFORE THOUGH, WE
ESSENTIALLY HAVE UPPER 20S AND LOWER 30S INLAND (EVEN SOME MID
20S IN BERKELEY COUNTY), WITH UPPER 30S TO NEAR 40F AT AND NEAR
THE COAST.
SHORT TERM /TONIGHT THROUGH SATURDAY/
THURSDAY THROUGH FRIDAY: THIS WILL BE THE QUIET PART OF THE
PERIOD AS A DRY COLD FRONT PASSES THROUGH THURSDAY AND THURSDAY
NIGHT AND HIGH PRESSURE SPREAD IN FOR FRIDAY. PLENTY OF DRY AIR
WILL KEEP THE FORECAST DRY, AND WITH CLEAR SKIES WE WILL SEE
PLENTY OF SUN. TEMPERATURES WILL WARM UP TO NEAR NORMAL EACH
DAY, WITH SEASONAL LOWS OVERNIGHT THURSDAY.
FRIDAY NIGHT AND SATURDAY: HIGH PRESSURE WILL PUSH OFF THE
COAST FRIDAY NIGHT AS A SURFACE LOW DEVELOPS AND ORGANIZES
ACROSS THE LOWER MISSISSIPPI VALLEY. THERE IS GOOD MODEL
AGREEMENT THAT A LARGE AREA OF SHOWERS WILL BEGIN PUSHING INTO
THE FORECAST AREA FROM THE WEST LATE FRIDAY NIGHT AND IMPACT THE
ENTIRE AREA THROUGH THE DAY ON SATURDAY. IN FACT, PRECIPITABLE
WATER VALUES SURGE INTO THE 1.25-1.50" RANGE WHICH WOULD BE
ABOVE THE 90TH PERCENTILE FOR THE DATE AND NEAR THE MAXIMUM
ACCORDING TO SPC'S SOUNDING CLIMATOLOGY. THIS WILL SET THE STAGE
FOR A WIDESPREAD SIGNIFICANT RAIN EVENT, WITH FORECAST RAINFALL
AMOUNTS IN THE 0.75-1.25" RANGE. RAIN CHANCES WILL TAPER OFF
FROM WEST TO EAST LATER IN THE DAY.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
WHILE THERE COULD BE A FEW LINGERING SHOWERS AROUND SUNDAY
MORNING, MODEL GUIDANCE SUGGESTS THAT SUNDAY WILL BE MOSTLY DRY
AND THE COLD FRONT WILL PUSH OFFSHORE THROUGH THE EVENING. FOR
MONDAY AND MONDAY NIGHT, COLD HIGH PRESSURE WILL BUILD INTO THE
REGION AND THE FORECAST IS DRY.
AS WE MOVE INTO TUESDAY AND BEYOND, THE FORECAST BECOMES
EXCEEDINGLY TRICKY AND ALSO POTENTIALLY VERY IMPACTFUL. MOST
MODEL SOLUTIONS BROADLY AGREE THAT WE WILL HAVE VERY COLD AIR
COINCIDENT WITH PRECIPITATION ASSOCIATED WITH AN AREA OF LOW
PRESSURE PASSING BY TO THE SOUTH OR OFF THE COAST. VARIOUS
DETERMINISTIC MODELS AND ENSEMBLE SOLUTIONS CONTINUE TO
HIGHLIGHT THE POTENTIAL FOR WINTER WEATHER ACROSS THE FORECAST
AREA AS A RESULT. HOWEVER, CONSIDERABLE UNCERTAINTY REMAINS
REGARDING THE TIMING OF PRECIPITATION, PRECIPITATION TYPES AND
AMOUNTS, AND SPECIFIC IMPACTED AREAS. ALL SCENARIOS ARE ON THE
TABLE, INCLUDING SEEING LITTLE TO NO PRECIPITATION AT ALL.
AVIATION /05Z THURSDAY THROUGH MONDAY/
6Z TAFS: VFR CONDITIONS EXPECTED ACROSS THE TERMINALS THROUGH
THE TAF PERIOD. FORECAST SOUNDINGS INDICATE THAT MIXING WILL
DEEPEN TO AROUND 5 KFT DURING THIS AFTERNOON. THE COMBINATION OF
2-3 MB PRESSURE GRADIENT AND DEEP MIXING SHOULD RESULT IN GUSTS
BETWEEN 20-25 KTS BETWEEN 16-23Z. THE REST OF THE EVENING SHOULD
FEATURE SOUTHWEST WINDS BETWEEN 5 TO 10 KTS WITH CLEAR SKY
CONDITIONS.
EXTENDED AVIATION OUTLOOK: VFR CONDITIONS ARE EXPECTED TO
PREVAIL THROUGH THE END OF THE WEEK. A FRONT IS EXPECTED TO
BEGIN IMPACTING THE AREA SATURDAY, BRINGING THE POTENTIAL FOR
SHOWERS AND BRIEF PERIODS OF FLIGHT RESTRICTIONS.
MARINE
OVERNIGHT: THERE ARE NO CONCERNS AS HIGH PRESSURE SETTLES INTO
THE REGION. VARIABLE WINDS 10 KT OR LESS WILL BECOME MORE W AND
NW AT 10 TO PERHAPS 15 KT OVERNIGHT AS LAND BREEZE INFLUENCES
DEVELOP. SEAS ARE LIMITED TO NO HIGHER THAN 1-3 FEET DUE TO
SMALL SWELLS AND THE OFFSHORE FETCH THAT DEVELOPS.
THURSDAY THROUGH MONDAY: THE PERIOD WILL BEGIN WITH A SURGE OF
WESTERLY AND/OR WEST-SOUTHWESTERLY FLOW THURSDAY THROUGH
THURSDAY NIGHT. THIS COULD BRING A PERIOD OF SMALL CRAFT
ADVISORY WINDS TO AT LEAST PORTIONS OF THE LOCAL WATERS, WITH
THE BEST CHANCES BEING THE CHARLESTON COUNTY WATERS AND THE
OUTER GA WATERS. CONDITIONS WILL TURN VERY QUIET FRIDAY
AFTERNOON INTO FRIDAY NIGHT AS HIGH PRESSURE SETTLES INTO THE
AREA. SOUTHERLY AND SOUTHWESTERLY FLOW WILL INCREASE SATURDAY
AHEAD OF AN APPROACHING FRONT, WITH A STRONGER SURGE OF
NORTHWESTERLY FLOW BEHIND THE DEPARTING SYSTEM SUNDAY NIGHT.
SMALL CRAFT ADVISORIES APPEAR MORE LIKELY DURING THIS TIME
PERIOD. SEAS WILL VARY QUITE A BIT ACROSS THE ENTIRE FORECAST
PERIOD, BEING ELEVATED THURSDAY NIGHT THEN DECREASING
SIGNIFICANTLY FRIDAY AND FRIDAY NIGHT AS HIGH PRESSURE PASSES
THROUGH. THE HIGHEST SEAS CAN BE EXPECTED WITH THE SYSTEM OVER
THE WEEKEND AND INTO EARLY NEXT WEEK.
CHS WATCHES/WARNINGS/ADVISORIES
GA...NONE.
SC...NONE.
MARINE...NONE.
NEAR TERM...NED
SHORT TERM...
LONG TERM...
AVIATION...NED
MARINE...
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