Area Forecast Discussion
Issued by NWS Charleston, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KCHS 231118
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
718 AM EDT WED JUL 23 2014

.SYNOPSIS...
HIGH PRESSURE WILL PREVAIL IN THE ATLANTIC THROUGH LATE WEEK...WHILE
AN INLAND TROUGH OF LOW PRESSURE THURSDAY DRAWS CLOSER TO THE COAST
FRIDAY...BEFORE DISSIPATING DURING THE WEEKEND. A COLD FRONT WILL
APPROACH FROM THE NW EARLY NEXT WEEK...AND WILL THEN STALL OUT OVER
OR NEAR THE REGION BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
THIS MORNING...THE WET GROUNDS FROM RECENT RAINS AND POOLING OF
LOW LEVEL MOISTURE WILL LEAD TO PATCHY FOG THROUGH MID MORNING.
THE LOWEST CONDENSATION PRESSURE DEFICITS ARE INLAND...AND IT/S
THERE WHERE THE FOG WILL OCCUR. WHILE WE CAN/T RULE OUT A FEW
SHOWERS/T-STORMS SKIRTING THE IMMEDIATE COASTAL SECTIONS...AS THE
SYNOPTIC FLOW VEERS TO WESTERLY THE BULK OF THE MARITIME
CONVECTION WILL STAY OFFSHORE.

TODAY...THE UPPER LOW OVER NEW ORLEANS WILL WEAKEN BUT THE SURFACE
TROUGH OF LOW PRESSURE WILL PERSIST ACROSS INLAND SC/GA. THE SEA
BREEZE WILL ALSO BE A FOCUS FOR SOME SHOWERS AND THUNDERSTORMS
ALTHOUGH SOME DRIER MID-LEVEL AIR IS FORECAST TO MOVE NORTHWARD
INTO SOUTH-CENTRAL GEORGIA DURING THE DAY WHICH COULD LIMIT
COVERAGE. THE BEST RAIN CHANCES /30 PERCENT/ SHOULD OCCUR NEAR THE
COAST THIS MORNING BEFORE TRANSITIONING INLAND AS THE SEA BREEZE
KICKS IN...ESPECIALLY ACROSS SOUTH CAROLINA GIVEN THE LOW-LEVEL SOUTHERLY
FLOW. WITH PWATS EXPECTED TO REMAIN NEAR 2 INCHES ACROSS SOUTHERN
SOUTH CAROLINA AND STORM MOTIONS WEAK THERE COULD BE SOME HEAVY
RAINFALL AND POSSIBLE FLOODING. HIGHS CLOSER TO NORMAL...IN THE
LOWER TO POSSIBLY MID 90S INLAND...WITH MID-UPPER 80S AT THE
COAST.

TONIGHT...UPPER TROUGHING WILL STRENGTHEN TO THE NORTHWEST. SOME
SHOWERS COULD SKIRT FAR INLAND AREAS NEAR THE SURFACE TROUGH BUT
BETTER CHANCES WILL COME OVER THE MORE UNSTABLE ATLANTIC...SOME OF
WHICH COULD SKIRT THE CENTRAL SC COAST. LOWS LIKELY A BIT ABOVE
NORMAL GIVEN THE SLIGHT SW BREEZE...GENERALLY IN THE MID 70S
INLAND AND CLOSER TO 80 AT THE COAST.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
THE LARGE SCALE PATTERN WILL FEATURE AN ELONGATED AND ROBUST 594-596
DAM RIDGE OVER THE PLAINS AND SW STATES...WITH ANOTHER BUT SLIGHTLY
WEAKER AND MORE COMPACT ANTICYCLONE OVER THE SW ATLANTIC...BAHAMAS
AND FLORIDA. IN BETWEEN WE/LL FIND A SOMEWHAT AMPLIFIED LONG WAVE
TROUGH ACROSS THE EASTERN AND SE PART OF THE COUNTRY THAT WILL
DAMPEN OUT BY LATE IN THE FORECAST PERIOD. AT THE SURFACE A WELL
PRONOUNCED NE-SW ALIGNED TROUGH WILL BE SITUATED INLAND FROM THE
LOCAL REGION THURSDAY...IT BECOMES NUDGED A LITTLE CLOSER TO US ON
FRIDAY...THEN IT LOOKS TO BECOME MORE ILL-DEFINED INLAND ON
SATURDAY. MEANTIME...THE BERMUDA RIDGE OF HIGH PRESSURE WILL REMAIN
ANCHORED IN PLACE AS IT STRETCHES WESTWARD FROM THE ATLANTIC ALONG
28-30N.

FOR THE DAY TO DAY DETAILS...
THURSDAY...A PIECE OF ENERGY FROM THE DEEP LAYERED LOW IN THE LOWER
MS VALLEY FROM TODAY WILL LIFT INTO THE FORECAST AREA LATE IN THE
DAY...IN SYNC WITH A SHORT WAVE DROPPING THROUGH THE EASTERN TROUGH.
THAT ALONG WITH 25-35 KT MID LEVEL WINDS WILL ALLOW FOR SOME
ORGANIZATION OF UPSTREAM CONVECTION TO DEVELOP IN ASSOCIATION WITH
THE SURFACE TROUGH...PERHAPS ENOUGH FOR ISOLATED SEVERE STORMS WHERE
UPDRAFT STRENGTH IS ENHANCED WHERE BOUNDARY INTERACTIONS OCCUR.
HOWEVER...WITH A WESTERLY FLOW THROUGHOUT THE TROPOSPHERE AND POOR
LAPSE RATES THIS IS A LOW END PROBABILITY. WE/LL HOLD OFF ON T-STORM
INITIATION UNTIL THE CAP BREAKS DURING THE MID AFTERNOON...SHOWING
POPS IN THE 20-40 PERCENT RANGE...HIGHEST NW TIER. THE DEEP
WESTERLIES WILL HOLD THE SEA BREEZE CLOSE TO THE SHORELINE AND WILL
EASILY BOOST TEMPS TO THEIR HIGHEST LEVELS IN OVER A WEEK...WITH
LOWER AND MIDDLE 90S AWAY FROM THE BEACHES.

FRIDAY...ANOTHER IMPULSE WILL ARRIVE WITHIN THE MID/UPPER TROUGH AND
WITH THE SURFACE TROUGH IN CLOSER PROXIMITY TO THE FORECAST AREA A
SOLID 30-50 POPS WILL BE FORECAST. THERE IS MORE INLAND PENETRATION
TO THE SEA BREEZE WITH A LITTLE LESS OFFSHORE FLOW THROUGH THE
VERTICAL...AND THAT ALONG WITH A GREATER DEGREE OF CLOUDINESS WILL
CAUSE TEMPS TO DROP A COUPLE OF DEGREES FROM THURSDAY. POOR LAPSE
RATES...LESS WIND FIELDS AND A LOWER AMOUNT OF INSOLATION POINTS
TOWARD VERY LOW...BUT NOT QUITE ZERO RISK...OF SEVERE WEATHER.

SATURDAY...WHAT/S LEFT OF THE SURFACE TROUGH WILL BE IN A WEAKENING
OR DIFFUSE STATE...BUT WE STILL MIGHT SEE ONE MORE WEAK PERTURBATION
ALOFT. THAT ALONG WITH THE SEA BREEZE BOUNDARY AND AMPLE
MOISTURE/INSTABILITY SHOULD SUPPORT SCATTERED POPS YET AGAIN. AN
EXPANSION OF THICKNESS...A SUBTLE RISE TO HEIGHTS AND LESS CLOUD
COVER WILL SUPPORT TEMPS AGAIN IN THE LOWER AND MIDDLE 90S AWAY FROM
THE BARRIER ISLANDS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
A FLAT LONG WAVE PATTERN OVER THE EASTERN STATES SUNDAY WILL BECOME
MORE AMPLIFIED EARLY NEXT WEEK AS THE WESTERN RIDGE POKES NORTHWARD
AND A DIGGING TROUGH DROPS THROUGH THE GREAT LAKES AND OHIO VALLEY.
THIS SENDS A FAIRLY STRONG COLD FRONT TOWARD SOUTHERN SC AND SE GA
LATE MONDAY INTO TUESDAY. NOT YET SURE HOW MUCH PUSH THERE IS BEHIND
THE FRONT...SO IT LOOKS TO HANG UP SOMEWHERE OVER OR NEARBY INTO THE
MIDDLE OF NEXT WEEK. OTHER THAN THE SEA BREEZE THERE IS NO TRIGGER
FOR CONVECTION...SO ONLY SLIGHT CHANCE POPS. BUT COVERAGE WILL BE ON
THE INCREASE LATER MONDAY INTO TUESDAY INTO THE CHANCE RANGE DUE TO
FORCING FROM THE COLD FRONT. WE/LL THEN SHOW SLIGHT CHANCE TO CHANCE
POPS WEDNESDAY SINCE THERE IS SOME SEMBLANCE OF THE FRONT STILL
NEARBY. TEMPS WILL BE ABOVE SEASONAL NORMS SUNDAY AND MONDAY...THEN
DOWN BELOW LATE JULY NORMS TUESDAY AND WEDNESDAY WITH INCREASED RAIN
CHANCES AND A GREATER COVERAGE OF CLOUDINESS.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
THE MAIN MECHANISM FOR ANY CONVECTION AT THE TERMINALS TODAY IS
THE SEA BREEZE...THUS COVERAGE SHOULD BE LIMITED AND MAINLY VFR
CONDITIONS WILL RULE. SHOULD ANY DIRECT IMPACTS OCCUR FROM SHRA OR
TSRA THEN BRIEF FLIGHT RESTRICTIONS CAN OCCUR...MAINLY FROM ABOUT
18-23Z.

EXTENDED AVIATION OUTLOOK...ALTHOUGH VFR CONDITIONS WILL PREVAIL
THROUGH THE EXTENDED RANGE...PERIODIC FLIGHT RESTRICTIONS ARE
POSSIBLE IN SCATTERED AND MAINLY DIURNALLY DRIVEN CONVECTION LATE
THURSDAY THROUGH SUNDAY.

&&

.MARINE...
TODAY AND TONIGHT...NO SIGNIFICANT CONCERNS WITH ATLANTIC HIGH
PRESSURE IN CONTROL. SOME WIND SURGING EXPECTED THIS AFTERNOON
NEAR THE COAST DUE TO THE SEA BREEZE AND THEN TONIGHT DUE TO
NOCTURNAL SURGING BUT WINDS SHOULD MOSTLY REMAIN 15 KT OR LESS.
SEAS MAINLY 3 FT OR LESS NEAR SHORE AND UP TO 4 FT OFFSHORE.
GIVEN LIGHT WIND FIELDS AND VARIOUS BOUNDARIES...CONDITIONS WILL
FAVOR SOME WATERSPOUTS THIS MORNING. THUS WE HAVE ISSUED A MARINE
WEATHER STATEMENT TO HIGHLIGHT. LET US KNOW IF ANY ARE SIGHTED
AS SPOUTS ARE DIFFICULT TO OBSERVE ON RADAR SINCE THEY ARE SHORT-
LIVED AND SMALL IN SCOPE.

THURSDAY THROUGH SATURDAY...THE LOCAL WATERS WILL LIE WITHIN A
WEST/SW FLOW BETWEEN THE SUB-TROPICAL ATLANTIC RIDGE TO THE SE AND
SOUTH...AND A TROUGH OF LOW PRESSURE INLAND OVER THE SE STATES.
THERE WILL BE SOME FLUCTUATIONS DUE TO THE SEA BREEZE CIRCULATIONS
AND MODEST PINCHING WITH THE NEARBY TROUGH...BUT OVERALL NOTHING
HIGHER THAN 10 OR 15 KT WITHIN 20 NM OF THE COAST AND IN CHARLESTON
HARBOR...AND MAYBE UP TO 15 OR PERHAPS BRIEFLY 20 KT ACROSS THE
OUTER GA WATERS. SEAS WILL BE HELD IN CHECK DUE TO THE LIMITED
OFFSHORE FETCH...PEAKING AT 2-4 FT.

SUNDAY THROUGH MONDAY...THE GRADIENT LOOKS TO TIGHTEN IN RESPONSE TO
LOW PRESSURE DEVELOPING IN THE GREAT LAKES AND TRACKING INTO THE
NE...WHILE THE BERMUDA-AZORES HIGH HOLDS IN PLACE. PRETTY TOUGH TO
GET SMALL CRAFT ADVISORY CONDITIONS THIS TIME OF YEAR...BUT
CERTAINLY COULD SEE WINDS UP NEAR 15 OR 20 KT AND SEAS UP TO 3 OR 4
FT.

&&

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

&&

$$

NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.