Area Forecast Discussion
Issued by NWS Columbia, SC

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000
FXUS62 KCAE 300325
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
1125 PM EDT FRI APR 29 2016

.SYNOPSIS...
A WEAK SURFACE TROUGH WILL BE IN THE FORECAST AREA THROUGH THE
WEEKEND. DRY UPPER RIDGING OVER THE AREA TONIGHT WILL BEGIN TO
SHIFT EAST OF THE REGION SATURDAY ALLOWING A MOISTURE INCREASE.

&&

.NEAR TERM /THROUGH SATURDAY/...
AN UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION PREVENTING
PRECIPITATION OVERNIGHT. A LARGE CONVECTIVE COMPLEX TO THE WEST
WILL WEAKEN AS IT MOVES UNDER THE UPPER RIDGE AND INTO SYNOPTIC
SCALE SUBSIDENCE. HIGH CLOUDS FROM THE UPSTREAM CONVECTION WILL
STREAM INTO THE FORECAST AREA OVERNIGHT. THE HRRR INDICATES THE
POTENTIAL FOR FOG IN THE EASTERN MIDLANDS WHERE THERE MAY BE LESS
CLOUD COVERAGE AND INCREASING MOISTURE IN LIGHT SOUTHERLY FLOW.
HOWEVER CLOUD COVERAGE IN THE HRRR MAY BE UNDERDONE WHICH WOULD
LIMIT FOG POTENTIAL. IN ADDITION A 20 KT LLJ WILL PROMOTE SOME
LOWER LEVEL MIXING. LOW TEMPERATURES ARE FORECAST TO BE IN THE
LOWER TO MID 60S ACROSS THE AREA.

SATURDAY...HIGH PRESSURE WILL RIDGE INTO THE MID-ATLANTIC STATES
REINFORCING A BOUNDARY JUST NORTH OF THE FORECAST AREA. WARM
ADVECTION AND SOUTHERLY FLOW WILL LEAD TO INCREASED MOISTURE
ACROSS THE REGION AND OROGRAPHIC LIFT IN THE UPSTATE. A NUMBER OF
HI RESOLUTION MODELS INDICATE CONVECTION DEVELOPING ALONG THE
HIGHER TERRAIN IN THE UPSTATE AS WELL AS ALONG THE BOUNDARY IN
NC. THIS SUGGESTS A CHANCE OF SHOWERS AND THUNDERSTORMS DEVELOPING
IN THE NORTHERN AND EXTREME WESTERN PORTIONS OF THE FORECAST AREA
SATURDAY AFTERNOON. THE CONVECTION WOULD TEND TO MOVE E/NE IN THE
STEERING FLOW BRINGING THE CHANCE FOR PRECIPITATION FURTHER INTO
THE CENTRAL AND NORTHERN MIDLANDS DURING THE LATE AFTERNOON. THE
REMNANTS OF THE CONVECTIVE COMPLEX MAY ALSO PLAY A ROLE IN THE
LOCATION OF CONVECTIVE INITIATION WHICH INCREASES UNCERTAINTY.

TEMPERATURES...TEMPERATURES WILL BE IN THE UPPER 80S MOST
EVERYWHERE...POSSIBLY A LITTLE COOLER FAR NORTH AS THE MORNING
HEATING WILL BE A LITTLE SLOWER DUE TO CLOUD COVER.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
SATURDAY NIGHT...WITH THE MEAN FLOW AT MID LEVELS BEING WEST
SOUTHWESTERLY...THE CONVECTION THAT DEVELOPS NORTH AND WEST OF THE
AREA SATURDAY AFTERNOON AND EVENING SHOULD DRIFT OVER THE CWA
OVERNIGHT...KEEPING CLOUDS AND SPOTTY SHOWERS/TSTORMS A THREAT ALL
NIGHT. PWS WILL BE INCREASING TO >1.5 INCHES...BUT THE MAIN JET AT
UPPER LEVELS REMAINS WELL TO THE NORTH OF THE CWA AND SURFACE
CONVERGENCE WILL BE MAINLY INDUCED BE EARLIER CONVECTION...SO I
HAVE NOT GONE AS HIGH AS THE GFS WOULD SUGGEST FOR POPS SATURDAY
NIGHT. MIN TEMPS WILL REMAIN ABOVE NORMAL IN THE MID 60S WITH
CLOUDS SUPPRESSING THE DIURNAL TEMP DROP.

SUNDAY...SIMILAR TO SATURDAY NIGHT...PLENTIFUL MOISTURE WILL BE
IN PLACE TO ALLOW FOR SIGNIFICANT CLOUDINESS. HOWEVER...A CLEAR
FOCUSING MECHANISM FOR CONVECTION WILL BE LACKING OVER THE
CWA...AND THE CLOUDS WILL KEEP MAX TEMPS SEVERAL DEGREES LOWER
THAN SATURDAY...LIMITING THE INSTABILITY. I HAVE KEPT A CHANCE OF
SHOWERS AND THUNDERSTORMS...BUT AGAIN AM LEANING TOWARD LOWER
GUIDANCE VALUES.

SUNDAY NIGHT AND MONDAY...NOT MUCH CHANGE TO THE PATTERN. THERE
MAY BE A SLIGHT INCREASE IN SOUTHWESTERLY WINDS AS ANOTHER FRONT
TRIES TO APPROACH FROM THE NORTHWEST...BUT IT SHOULD REMAIN NORTH
OF THE CWA THROUGH MONDAY. PWS MAY ALSO DROP A BIT...BUT THAT
MEANS A LITTLE BIT WARMER TEMPERATURES AGAIN...PRODUCING SOME
MODEST LOW LEVEL INSTABILITY BY AFTERNOON. CHANCE OF THUNDERSTORMS
LOOKS APPROPRIATE.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
THE BEST CHANCE OF WIDESPREAD RAIN LOOKS TO BE TUESDAY AS THE
UPPER JET WHICH WILL BE HELD OFF TO THE NORTH OVER THE WEEKEND
INTO MONDAY FINALLY STARTS TO DIVE SOUTHEASTWARD AS A MORE
SIGNIFICANT TROUGH DEVELOPS IN EASTERN NORTH AMERICA. THERE IS
SOME GLOBAL MODEL TIMING DIFFERENCES WITH HOW FAST THE UPPER
DISTURBANCE DEVELOPS A SURFACE LOW WHICH DRAGS A COLD FRONT
THROUGH THE CWA. THE 12Z GFS QUICKLY RACES THE SYSTEM THROUGH AND
BRINGS COOLER AND DRIER WEATHER IN FOR WEDNESDAY...WHILE THE
SLOWER 00Z ECMWF DOES NOT BRING THE POLAR AIR MASS IN UNTIL
THURSDAY. THEREFORE...I HAVE KEPT SCATTERED CONVECTION IN THE
FORECAST THROUGH WEDNESDAY IN DEFERENCE TO THE ECMWF. IN EITHER
CASE...A MODIFIED POLAR AIR MASS SHOULD MOVE IN FOR THE END OF THE
WEEK.

&&

.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
HIGH CONFIDENCE FOR VFR CONDITIONS THROUGH 06Z.

HIGH LEVEL CLOUDS OVER THE REGION. GUIDANCE IS INDICATING THE
POTENTIAL FOR IFR VSBYS/CIGS IN FOG ACROSS THE MIDLANDS TAF SITES
EARLY SATURDAY MORNING...BUT THERE IS SOME UNCERTAINTY IN WHAT
IMPACT THE HIGH CLOUDS WILL HAVE ON FOG FORMATION. HAVE INDICATED
MVFR CONDITIONS IN PATCHY FOG AT KAGS/KOGB FROM 09-14Z. OTHERWISE...
VFR CONDITIONS FORECAST. ISOLATED TO SCATTERED CONVECTION TO
DEVELOP SATURDAY AFTERNOON...BUT CONFIDENCE IS TOO LOW TO INCLUDE
IN TAFS AT THIS TIME.

EXTENDED AVIATION OUTLOOK...SCATTERED AFTERNOON/EVENING CONVECTION
COULD CAUSE SOME TEMPORARY RESTRICTIONS THROUGH MONDAY. EARLY
MORNING LOW CIGS LOOK POSSIBLE AT ALL THE TERMINALS SUNDAY/MONDAY
MORNING WITH MOISTURE INCREASING AND LOW LEVEL WINDS REMAINING
LIGHT. BETTER CHANCES FOR CONVECTIVELY INDUCED MVFR/IFR CONDITIONS
SEEM TO BE IN LINE FOR TUESDAY. WEDNESDAY IT BECOMES MORE UNCERTAIN
DUE TO DIFFERENCES BETWEEN THE MODELS.

&&

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

&&

$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99



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