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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 201800
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
200 PM EDT MON MAY 20 2013

.SYNOPSIS...
AN UPPER LEVEL DISTURBANCE OVER THE AREA WILL DISSIPATE THROUGH
MID WEEK WHILE ATLANTIC HIGH PRESSURE PREVAILS UNTIL LATE WEEK. A
COLD FRONT WILL DROP THROUGH THE AREA LATE FRIDAY INTO SATURDAY...
FOLLOWED BY HIGH PRESSURE THROUGH NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
EARLY THIS AFTERNOON...CONVECTION HAS BEEN SLOWER TO DEVELOP TODAY
COMPARED TO THIS PAST WEEKEND...PRESUMABLY DUE TO THE MORE
EXPANSIVE CLOUD COVER IN PLACE THIS MORNING. ALSO...MUCH OF THE
SHOWER/THUNDERSTORM ACTIVITY HAS BEEN CONFINED TO THE TRI-COUNTY
WHICH IS LIKELY EXPERIENCING MORE OF THE INFLUENCE OF THE BAGGY
TROUGH ALOFT. FURTHER SOUTH...INITIATION APPEARS TO BE MORE
CLOSELY RELATED TO CONVERGENCE ALONG THE SEABREEZE. I HAVE MADE
SOME MODIFICATIONS TO POPS TO PLACE LIKELIES IN THE TRI-COUNTY AND
A STRIP DOWN ALONG THE COAST TO THE ALTAMAHA. NO CHANGE IN
THINKING FOR THE SEVERE THREAT...COULD SEE ONE OR TWO NECESSITATE
A WARNING WITH STRONG DAMAGING WIND GUSTS AND HAIL POSSIBLE.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
UPPER LEVEL TROUGHING OVER THE AREA IS NOT GOING ANYWHERE TONIGHT
BUT WE DO EXPECT CONVECTION TO DECREASE IN COVERAGE AND INTENSITY
DURING THE EVENING. LOW LEVEL COASTAL MOISTURE CONVERGENCE WILL
INCREASE TOWARD DAYBREAK ON TUE ALONG COASTAL SOUTH CAROLINA AND
CONVECTIVE RAINS MAY BREAK OUT ONCE AGAIN THERE. WILL ALSO NEED TO
WATCH TRENDS FOR FOG DEVELOPMENT TONIGHT IF CLOUDS BREAK. WITH
WIDESPREAD CONVECTIVE RAINS EXPECTED TODAY...THERE SEEMS TO BE
INCREASING CHANCES FOR FOG...ESPECIALLY INLAND.

A MOIST AIRMASS WILL PERSIST DURING THE PERIOD ALTHOUGH WE SHOULD
SEE A SLIGHT DECREASE IN PW VALUES BY THURSDAY. THE UPPER
SHORTWAVE WILL SLOWLY DISSOLVE OVERHEAD ON TUESDAY BUT ANOTHER
WAVE WILL APPROACH LATE WEDNESDAY THROUGH THURSDAY. AT THE SURFACE
ATLANTIC HIGH PRESSURE WILL MAINTAIN ITS CONTROL...KEEPING
SOUTHERLY FLOW IN LOW-LEVELS AND ALLOWING DAILY SEABREEZE
CIRCULATIONS TO DEVELOP. CONVECTIVE COVERAGE WILL VARY SOMEWHAT
BETWEEN THE THREE DAYS WITH WEDNESDAY CURRENTLY LOOKING LIKE THE
LEAST ACTIVE DAY DUE TO A LACK OF APPRECIABLE UPPER ENERGY TO WORK
WITH. HIGH TEMPS WILL CLIMB INTO THE MID TO UPPER 80S WITH LOWS IN
THE MIDDLE 60S.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
FAIRLY GOOD MODEL CONSISTENCY REGARDING AN UPPER TROUGH SHIFTING
SOUTHEAST AND A COLD FRONTAL PASSAGE FRIDAY OR FRIDAY NIGHT. DRY AND
SLIGHTLY COOLER CANADIAN HIGH PRESSURE LOOKS TO BUILD IN FOR THE
WEEKEND BEFORE SHIFTING OFFSHORE EARLY NEXT WEEK.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
-- Changed Discussion --
AT KCHS...SHOWERS AND A POSSIBLE THUNDERSTORM WILL CONTINUE IN THE
VICINITY FOR THE NEXT COUPLE OF HOURS AND THEN ACTIVITY SHOULD BE
FURTHER AWAY AFTER THE ATMOSPHERE HAS BEEN WORKED OVER. THE OTHER
ISSUE THIS FORECAST PERIOD IS THE POTENTIAL FOR SHOWERS AND MVFR
CEILINGS LATE TONIGHT. I HAVE ADDED A VCSH MENTION FOR NOW WITH
HAVE KEPT CONDITIONS VFR.

AT SAV...THE MOST IMMEDIATE CONCERN IS THE POTENTIAL FOR
THUNDERSTORMS DIRECTLY IMPACTING THE TERMINAL. THE FIRST
SHOWERS/THUNDERSTORMS OF THE AFTERNOON ARE STARTING TO DEVELOP AND
WILL BE IN THE VICINITY THROUGH 21Z. I HAVE KEPT IT AS JUST A VCTS
MENTION FOR NOW AND WILL AMEND BASED ON RADAR OBSERVATIONS. THEN
TONIGHT THE FOCUS SHIFTS TO THE POTENTIAL FOR FOG AND/OR STRATUS.
AFTER A COUPLE OF DAYS WORTH OF CONVECTIVE RAINS...THE SOIL SHOULD
BE SUFFICIENTLY MOIST FOR FOG TO BE A CONCERN. THERE ARE SOME
INDICATIONS OF THE MID/UPPER LEVEL DRYING A BIT AND WITH COOLER
TEMPS AND THE POTENTIAL FOR CLEARER SKIES...FOG/STRATUS POTENTIAL
IS INCREASED. SOME OF THE GUIDANCE INDICATES POTENTIAL FOR IFR
FOG/STRATUS. I HAVE INTRODUCED MVFR FOG STARTING AT 10Z AND JUST
HINTED AT MVFR CEILINGS.

EXTENDED AVIATION...THE MAIN CONCERN WILL BE SPORADIC REDUCTIONS
IN CEILINGS AND VISIBILITIES...MAINLY ASSOCIATED WITH SCATTERED
SHOWERS AND THUNDERSTORMS THROUGH THE PERIOD. THE GREATEST CHANCES
WILL BE IN THE AFTERNOON HOURS TUE THROUGH THU...ALTHOUGH EARLY
MORNING FLIGHT RESTRICTIONS CANNOT BE RULED OUT EACH DAY.
-- End Changed Discussion --

&&

.MARINE...
THROUGH TONIGHT...A STRONG RIDGE OF HIGH PRESSURE CENTERED OVER
THE ATLANTIC WILL EXTEND W ACROSS THE COASTAL WATERS...GENERATING
SE AND S WINDS OF 10-15 KT OR LESS AND SEAS IN THE 2-4 FOOT RANGE.

HIGH PRESSURE WILL REMAIN OVER THE WESTERN ATLANTIC THROUGH THURSDAY
NIGHT WITH SEABREEZE CIRCULATIONS DEVELOPING EACH AFTERNOON. A COLD
FRONT WILL DROP THROUGH FRIDAY EVENING OR SATURDAY MORNING WITH A
NORTHEAST FLOW DEVELOPING AS CANADIAN HIGH PRESSURE BUILDS IN. WINDS
AND SEAS WILL LIKELY INCREASE OVER THE WEEKEND IN RESPONSE.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

$$

SYNOPSIS...
NEAR TERM...BSH
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...BSH
MARINE...JRL