Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 301746
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
146 PM EDT THU JUL 30 2015

.SYNOPSIS...
A WEAK PRESSURE PATTERN WILL PERSIST TODAY. A WEAK COLD FRONT
WILL STALL OVER THE REGION FRIDAY INTO EARLY NEXT WEEK. ATLANTIC
HIGH PRESSURE WILL GRADUALLY BUILD INTO THE REGION BY THE MIDDLE
OF NEXT WEEK. AN INLAND TROUGH WILL THEN DEVELOP BY LATE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
EARLY THIS AFTERNOON...THE CUMULUS FIELD IS MORE DEVELOPED ACROSS
THE FORECAST AREA THAN IT WAS 24 HOURS AGO. SHOWERS AND
THUNDERSTORMS ARE DEVELOPING UPSTREAM ACROSS THE MIDLANDS...AND
THESE WILL MOVE SOUTHWARD WITHIN THE PREVAILING DEEP LAYER
NORTHERLY FLOW. INSTABILITY IS STILL NOT IMPRESSIVE WITH WEAK MID
LEVEL LAPSE RATES. THE SEVERE THREAT IS STILL QUITE LOW...THOUGH
WE WILL LIKELY SEE MORE COVERAGE THAN WE DID WEDNESDAY AFTERNOON.
NO CHANGES WERE MADE TO THE GOING FORECAST AS IT IS STILL ON
TRACK.

TONIGHT...A WEAK SW SYNOPTIC FLOW WILL ENSUE IN THE WAKE OF THE
GULF STREAM LOW AND THE APPROACH OF A WEAK COLD FRONT. MODELS
DEEPEN MOISTURE PROFILES OVERNIGHT AND SUGGEST A FEW SHOWERS AND
TSTMS COULD LINGER OVERNIGHT ACROSS THE AREA. WE HELD ONTO SLIGHT
CHANCE POPS ALL ZONES AFTER THE MID EVENING HOURS.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
FRIDAY...A WEAK COLD FRONT WILL PUSH INTO THE REGION FROM THE
NORTHWEST. THIS FEATURE WILL HELP FOCUS A BAND OF MOISTURE FEATURING
PWATS EXCEEDING 2 INCHES...1-3 STANDARD DEVIATIONS ABOVE NORMAL...
WITHIN THE WEAK UPPER TROUGH/WEAKNESS BETWEEN ATLANTIC AND INLAND
RIDGES. THIS SCENARIO IS STILL EXPECTED TO SUPPORT AN ACTIVE
CONVECTIVE REGIME ESPECIALLY FRIDAY AFTERNOON...WHEN THE LATEST
FORECAST INCLUDES LIKELY POPS AT MANY LOCATIONS...AND SCATTERED
SHOWERS/THUNDERSTORMS SHOULD LINGER THROUGH FRIDAY NIGHT. A COMPLEX
CONVECTIVE OUTFLOW ENVIRONMENT SHOULD DEVELOP...AND THIS WILL IN
TURN MODULATE PROPAGATION THROUGH THE PERIOD. THUS...THE LATEST
GENERALIZED PRECIPITATION FORECAST WILL REQUIRE SIGNIFICANT
SHORT/NEAR TERM ADJUSTMENTS TO ADDRESS AS YET UNKNOWN DETAILS.
OVERALL...A FEW PULSE SEVERE THUNDERSTORMS WITH DAMAGING WET
MICROBURSTS WILL BE POSSIBLE...AND WEAK STEERING WINDS/HIGH
PRECIPITATION EFFICIENCY COULD SUPPORT LOCALLY HEAVY RAINFALL.
TEMPERATURES COULD TOP OUT IN THE LOWER 90S AWAY FROM THE COAST
PRIOR TO THUNDERSTORM DEVELOPMENT...THEN HOURLY TEMPERATURES
COULD TURN OUT MUCH COOLER WHERE THUNDERSTORMS DEVELOP.

SATURDAY AND SUNDAY...MODEL DISAGREEMENT REGARDING THE PROGRESS OF
DRIER AIR FROM THE NORTH/NORTHWEST TRANSLATES TO FORECAST
UNCERTAINTY REGARDING POPS AND TEMPERATURES. THE 30/00Z NAM APPEARS
TOO DRY AND WAS NOT EXPLICITLY INCORPORATED INTO THE LATEST
FORECAST. THE 30/00 GFS DEPICTS A FAIR DEGREE OF DRYING ACROSS
NORTHERN/INLAND COUNTIES...RESULTING IN SOMEWHAT REDUCED COVERAGE OF
DIURNAL CONVECTION AND ALLOWING INLAND TEMPERATURES TO RECOVER INTO
THE LOWER/MID 90S. ON THE OTHER HAND...THE 30/00Z EUROPEAN SOLUTION
DEPICTS SUFFICIENT MOISTURE TO SUPPORT ABOVE NORMAL POPS ESPECIALLY
EACH AFTERNOON/EVENING...WITH THE RESULTING PRECIPITATION/CLOUD
COVER HOLDING DOWN TEMPERATURES. AS A COMPROMISE...GRADUATED
SATURDAY PM POPS FROM CHANCE NORTH/INLAND TO LIKELY SOUTH...AND
SUNDAY AFTERNOON POPS ARE TAPERED FROM 30-40 PERCENT NORTH/INLAND TO
AROUND 50 PERCENT SOUTH. DUE TO UNEVEN MODEL TRENDS/RUN TO RUN
CONSISTENCY...FORECAST CONFIDENCE REMAINS LESS THAN IDEAL THIS
WEEKEND...AND ADDITIONAL ADJUSTMENTS CAN BE EXPECTED WITHIN
SUBSEQUENT FORECASTS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
THE REMNANTS OF THE STATIONARY FRONT WILL GRADUALLY DISSIPATE EARLY
NEXT WEEK...AND THE BAND OF DEEPEST MOISTURE SHOULD PUSH JUST OFF
THE COAST. THEN...ATLANTIC HIGH PRESSURE IS EXPECTED TO EXPAND INTO
THE REGION THROUGH MIDWEEK. THUS...AFTERNOON/EVENING POPS REMAIN
SLIGHTLY ABOVE NORMAL MONDAY...THEN DIURNAL POPS DIMINISH TUESDAY
THROUGH THURSDAY. BY LATE WEEK...A TROUGH OF LOW PRESSURE COULD
DEVELOP INLAND...AND DEPENDING ON THE POSITION OF THE TROUGH A
SOMEWHAT MORE ACTIVE CONVECTIVE REGIME COULD DEVELOP. OTHERWISE...
THIS PATTERN SHOULD SUPPORT NORMAL TO ABOVE NORMAL TEMPERATURES.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH 18Z FRIDAY. THE
BEST COVERAGE OF SHOWERS AND STORMS THIS AFTERNOON WILL REMAIN
INLAND AND AWAY FROM THE TERMINALS. THEN OVERNIGHT...THE
POTENTIAL FOR FOG/STRATUS DEVELOPMENT IS QUITE LOW.

EXTENDED AVIATION OUTLOOK...THUNDERSTORMS COULD PRODUCE FLIGHT
RESTRICTIONS AT TERMINALS ANYTIME FRIDAY AFTERNOON THROUGH
MONDAY...ESPECIALLY DURING THE AFTERNOON/EVENING HOURS. OUTSIDE
THUNDERSTORMS...MAINLY VFR.

&&

.MARINE...
A WEAK PRES PATTERN REMAINS TODAY AS AN OFFSHORE LOW MOVES TO THE
NE OF THE WATERS BY THIS EVENING. LIGHT AND VARIABLE FLOW TODAY
WITH A BIT OF NW COMPONENT AREA AND ONSHORE COMPONENT LATE. FLOW
WILL BECOME SW TONIGHT WITH A SURGE TO AROUND 15 KT OFFSHORE AND
PERHAPS ALONG THE CHARLESTON COUNTY COAST. SEAS 1 TO 2 FT THIS
MORNING WILL BE MORE IN THE 2 TO 3 FT RANGE TONIGHT.

FRIDAY THROUGH TUESDAY...AS A COLD FRONT APPROACHES THEN STALLS
OVER THE REGION...S/SW WINDS WILL PREVAIL MUCH OF THE TIME. THE
SEA BREEZE CIRCULATION WILL CAUSE WINDS TO BACK TO THE S/SE AND
INCREASE IN SPEED EACH AFTERNOON...AND NOCTURNAL SURGES OF
SOUTH/SOUTHWEST WINDS COULD OCCUR EACH NIGHT. THIS REGIME WILL BE
DISRUPTED BY THE LATE NIGHT/EARLY MORNING LAND BREEZE...WHEN
LIGHTEST WINDS/ BOUNDARIES COULD SUPPORT WATERSPOUTS...AND BY
THUNDERSTORMS WHICH WILL PERIODICALLY CROSS THE WATERS. OUTSIDE
THESE EXCEPTIONS... HIGHEST WINDS SHOULD REMAIN CAPPED AT 15-20
KNOTS...ALTHOUGH THE PROBABILITY FOR SMALL CRAFT ADVISORY GUSTS TO
25 KT WILL INCREASE DURING THE NIGHTTIME EARLY NEXT WEEK. SEAS
WILL REMAIN 2-4 FT MUCH OF THE TIME...ALTHOUGH PERIODS OF 4-5 FT
SEAS ARE POSSIBLE AT NIGHT ESPECIALLY LATE WEEKEND INTO EARLY NEXT
WEEK.

&&

.TIDES/COASTAL FLOODING...
COASTAL FLOOD ADVISORIES ARE LIKELY ALONG THE SOUTH CAROLINA
COAST AROUND THE TIME OF HIGH TIDE THIS EVENING. AN ADVISORY
IS ALSO POSSIBLE AT FORT PULASKI AS HIGH TIDE EXCEEDS 9 FT MLLW.

ELEVATED HIGH TIDE LEVELS WILL CONTINUE FRIDAY THROUGH THE UPCOMING
WEEKEND THANKS TO THE UPCOMING PERIGEAN SPRING TIDE. SHALLOW COASTAL
FLOODING IS LIKELY INTO EARLY NEXT WEEK ESPECIALLY DURING EACH
EVENING HIGH TIDE. WILL CONTINUE TO HIGHLIGHT THE SHALLOW COASTAL
FLOOD THREAT WITHIN THE HAZARDOUS WEATHER OUTLOOK. ALSO OF
NOTE...THERE IS A CHANCE THAT HEAVY RAIN COULD COINCIDE WITH THE
ELEVATED HIGH TIDES. IF THIS OCCURS...MORE SERIOUS LOCALIZED
FLOODING COULD OCCUR...PARTICULARLY IN DOWNTOWN CHARLESTON.

&&

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

&&

$$

NEAR TERM...BSH
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...BSH
MARINE...SPR
TIDES/COASTAL FLOODING...



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