Area Forecast Discussion
Issued by NWS Columbia, SC

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000
FXUS62 KCAE 250230
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
1030 PM EDT SUN MAY 24 2015

.SYNOPSIS...
AN ONSHORE FLOW ASSOCIATED WITH HIGH PRESSURE OFF THE MID ATLANTIC
COAST WILL RESULT IN A GRADUAL RISE IN MOISTURE THROUGH WEDNESDAY.
THIS WILL ALSO INCREASE THE CHANCE OF AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS ACROSS THE AREA THROUGH MID WEEK.

&&

.NEAR TERM /UNTIL 8 AM MONDAY MORNING/...
MID AND UPPER LEVEL RIDGE TO HOLD ACROSS THE EASTERN HALF OF THE
CONUS. SURFACE HIGH PRESSURE CENTERED OFF THE MID ATLANTIC COAST
WILL CONTINUE TO RIDGE INTO THE FORECAST AREA OVERNIGHT. SKIES
MAINLY CLEAR THIS EVENING WITH DEWPOINTS RANGING THROUGH THE 50S.

A SOUTHEAST ONSHORE FLOW WILL CONTINUE TO INCREASE LOW LEVEL
MOISTURE OVERNIGHT. BOTH NAM/GFS SHOW WEAK LOW LEVEL ISENTROPIC
LIFT ALONG/WEST OF THE SAVANNAH RIVER VALLEY AND INDICATE A 20-25
KT LOW LEVEL JET. SHOULD SEE LOW CLOUDS/STRATUS TO DEVELOP ACROSS
THE SOUTHERN AND WESTERN COUNTIES DURING THE PREDAWN HOURS.
OVERNIGHT LOWS IN THE LOW TO MID 60S STILL LOOK REASONABLE.

&&

.SHORT TERM /8 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
UPPER RIDGE AXIS SHIFTS TO THE EAST ON MONDAY AS A SERIES OF
SHORTWAVES LIFT NORTHEASTWARD THROUGH THE TN/OH VALLEYS THROUGH A
BROAD UPPER TROUGH ON MONDAY AND TUESDAY. SURFACE HIGH PRESSURE
CENTERED OVER THE WESTERN ATLANTIC WILL CONTINUE TO RIDGE INTO THE
SOUTHEAST AND MID ATLANTIC STATES THROUGH THIS PERIOD RESULTING IN
CONTINUED SOUTHEASTERLY FLOW AND INCREASING ATMOSPHERIC MOISTURE.
PRECIPITABLE WATER VALUES WILL RISE FROM AROUND AN INCH MONDAY
MORNING TO CLOSE TO 1.5-1.7 INCHES BY MONDAY EVENING WHILE THERE
WILL BE A GRADIENT IN MOISTURE...DRIER IN THE NORTHEASTERN MIDLANDS
AND PEE DEE REGION.  INSTABILITY WILL ALSO INCREASE ACROSS THE
FORECAST AREA WITH FORECAST LIFTED INDEX VALUES AROUND -3C TO -4C
ALONG AND WEST OF THE I-26 CORRIDOR WITH MORE STABLE AIR TO THE
NORTHEAST.  THE INFLUENCE OF THE UPPER RIDGE AND NO FORCING OR
TRIGGERS FOR CONVECTION ARE LIMITING FACTORS FOR CONVECTION SO WILL
CONFINE POPS TO THE CSRA AND WESTERN MIDLANDS WHERE BETTER MOISTURE
WILL EXIST.

THE MOISTURE CONTINUES TO INCREASE WITH DEWPOINTS ALSO ON THE RISE
ON TUESDAY WHICH WILL SUPPORT BETTER INSTABILITY ACROSS THE ENTIRE
FORECAST AREA AND WEAK SHORTWAVE ENERGY PUSHING INTO THE WESTERN
FRINGE OF THE UPPER RIDGE MAY PROVIDE A BETTER OPPORTUNITY FOR
AFTERNOON CONVECTION...MAINLY ACROSS THE UPPER CSRA AND WESTERN
MIDLANDS...SO WILL CARRY HIGHEST POPS THERE.  TEMPERATURES ON BOTH
MONDAY AND TUESDAY WILL REMAIN NEAR TO ABOVE NORMAL IN THE UPPER 80S
TO NEAR 90.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
THE EXTENDED FORECAST FEATURES A PATTERN MORE INDICATIVE OF THE
MIDDLE OF SUMMER WITH A BROAD UPPER RIDGE INFLUENCING THE
SOUTHEASTERN STATES WITH A SURFACE BERMUDA HIGH CENTERED OVER THE
WESTERN ATLANTIC RIDGING INTO THE SOUTHEAST WITH A MOIST SOUTH TO
SOUTHEASTERLY FLOW.  MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT
WITH THE OVERALL PATTERN ALTHOUGH THE OPERATIONAL GFS IS A BIT
STRONGER THAN THE ECWMF WITH SHORTWAVE ENERGY PUSHING ACROSS THE
OHIO VALLEY INTO THE MID ATLANTIC...SIGNIFICANTLY WEAKENING THE
UPPER RIDGE AXIS AND DISPLACING IT TO THE EAST OFF THE COAST.  THIS
SOLUTION WOULD LEAD TO MORE AVAILABLE MOISTURE AND SOME UPPER
FORCING TO ENHANCE THE THUNDERSTORM THREAT.

THE FORECAST WILL BE TAILORED TO SHOW SLIGHTLY HIGHER POPS ON
WED/THU WITH POSSIBLE SHORTWAVE ENERGY IMPACTING THE AREA WITH
BETTER MOISTURE BUT THEN TREND TOWARD SUMMER PATTERN WITH DAILY
DIURNAL CHANCES OF AFTERNOON/EVE THUNDERSTORMS.  TEMPERATURES DURING
THE PERIOD WILL GENERALLY BE NEAR TO ABOVE NORMAL FOR HIGHS AND
ABOVE NORMAL FOR LOWS WITH STRONG SUPPORT FROM ENSEMBLE GUIDANCE
SHOWING VERY LITTLE SPREAD.

&&

.AVIATION /03Z MONDAY THROUGH FRIDAY/...
CEILINGS ARE EXPECTED TO DEVELOP OVERNIGHT AS LOW LEVEL MOISTURE
FLOWS IN OFF THE COAST. MVFR CIGS AT AGS/DNL ARE PROBABLE AND ARE
POSSIBLE AT OGB/CAE/CUB.

LOW LEVEL MOISTURE INCREASING OVERNIGHT. THE BEST ISENTROPIC LIFT
WILL BE ALONG THE SAVANNAH RIVER BASIN AND IS MOST LIKELY TO
EFFECT AGS/DNL. WINDS MAY BECOME LIGHT AND VARIABLE AT AGS
POSSIBLY ALLOWING ALLOWING FOR PATCHY FOG...HOWEVER LOW LEVEL
STRATUS WILL BE THE MAIN AVIATION RESTRICTION. THERE IS A LARGE
SPREAD BETWEEN MODELS ON CIGS AT CAE/CUB/OGB. THE NAM KEEPS VFR
CEILINGS THROUGHOUT THE PERIOD WHILE THE GFS HAS MVFR OVERNIGHT
AND DROPS CIGS INTO IFR FOR A BRIEF PERIOD IN THE EARLY MORNING.
HAVE KEPT CIGS VFR AS OF NOW DUE TO UNCERTAINTY. THERE IS
POTENTIAL FOR LOW CIGS AT ALL TAF SITES MONDAY MORNING.

EXPECT THE LOW CLOUDS TO GRADUALLY LIFT THROUGH THE DAY ON MONDAY AS
DAYTIME HEATING BEGINS AND THE LOW LEVEL JET/LIFT WEAKENS. EXPECT
VFR CONDITIONS AT THE REMAINING TAF SITES THROUGH THE PERIOD.
SURFACE WINDS WILL BE NEAR 10 KTS OUT OF THE SE MONDAY AFTERNOON.

EXTENDED AVIATION OUTLOOK...AS HIGH PRESSURE DRIFTS EAST LOW LEVEL
MOISTURE WILL RETURN TO THE AREA. EARLY MORNING RESTRICTIONS ARE
POSSIBLE THROUGH MID WEEK.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.

&&

$$



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