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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
354 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 6 AM MONDAY MORNING/...
HIGH PRESSURE CENTERED FROM OFF THE MID ATLANTIC COAST WILL
CONTINUE TO RIDGE INTO THE FORECAST AREA OVERNIGHT. AN
ONSHORE...EAST/SOUTHEAST FLOW WILL INCREASE LOW LEVEL MOISTURE.

SATELLITE AND OBS SHOW SCATTERED STRATOCUMULUS ACROSS THE AREA
THIS AFTERNOON. EXPECT THESE CLOUDS TO DISSIPATE WITH LOSS OF
DAYTIME HEATING THIS EVENING.

BOTH NAM/GFS SHOW SOME WEAK LOW LEVEL ISENTROPIC LIFT ALONG/WEST
OF THE SAVANNAH RIVER VALLEY AND INDICATE A STRENGTHENING LOW
LEVEL 30 KT JET TONIGHT. EXPECT LOW CLOUDS/STRATUS TO DEVELOP
ACROSS THE SOUTHERN/SOUTHWEST...MAINLY CSRA...AFTER MIDNIGHT.
GUIDANCE AND LOCAL NUMBERS INDICATING A BIG SPREAD FOR OVERNIGHT
LOWS. HAVE STAYED CLOSE TO CURRENT FORECAST/NEAR MAV TEMPS WITH
WITH LOWS IN THE LOW/MIDDLE 60S.

&&

.SHORT TERM /6 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 /18Z SUNDAY THROUGH FRIDAY/... 
VFR CONDITIONS EXPECTED THROUGH MOST OF THE TAF PERIOD. MAIN
ISSUE WILL BE THE POTENTIAL DEVELOPMENT OF LOW CLOUDS ACROSS THE
CSRA OVERNIGHT.

SURFACE WINDS THIS AFTERNOON WILL CONTINUE TO BE OUT OF THE E/SE
AROUND 8 TO 10 KTS WITH GUSTS UP TO 15 KTS. LOW LEVEL MOISTURE
HAS CONTINUED TO INCREASE THROUGH THE AFTERNOON WITH SCATTERED
STRATOCU DEVELOPING THROUGH THE DAY. THIS EVENING AND 
OVERNIGHT...WINDS WILL BECOME LIGHT AND VARIABLE. AS
MENTIONED...DEVELOPMENT OF STRATUS ALONG THE SAVANNAH RIVER
VALLEY/CSRA OVERNIGHT IS INDICATED BY LAMP/HRRR GUIDANCE. THIS
LOOKS REASONABLE BASED ON LOW LEVEL JET...LIFT AND INCREASING LOW
LEVEL MOISTURE. WILL ADD A PERIOD OF MVFR CONDITIONS AT BOTH
AGS/DNL FROM 10Z THROUGH 16Z. DID NOT INCLUDE AT OGB AT THIS
TIME...GUIDANCE NOT INDICATING LOW CLOUDS AND NOT CONFIDENT ENOUGH
TO ADD BUT WILL NEED TO BE MONITORED THIS EVENING. ON
MONDAY...EXPECT THE LOW CLOUDS TO GRADUALLY LIFT THROUGH THE DAY
AS DAYTIME HEATING BEGINS AND LOW LEVEL JET/LIFT WEAKENS. EXPECT
VFR CONDITIONS AT THE REMAINING TAF SITES THROUGH THE PERIOD. 
 
EXTENDED AVIATION OUTLOOK...RETURN FLOW WILL ALLOW SOME LOW-LEVEL 
MOISTURE TO SPREAD OVER THE AREA MONDAY NIGHT INTO MIDWEEK WHICH
MAY LEAD TO SOME MVFR RESTRICTIONS ESPECIALLY DURING THE EARLY
MORNING HOURS.

&&

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

&&

$$

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