Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 302156
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
556 PM EDT THU OCT 30 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD OVER THE STATE THROUGH FRIDAY. ANOTHER
COLD FRONT WILL SWEEP THROUGH THE AREA FRIDAY NIGHT. MUCH COLDER
AIR WILL FOLLOW THIS FRONT. THE FIRST WIDESPREAD FROST ALONG WITH
THE FIRST FREEZE OF THE SEASON FOR SOME AREAS MAY OCCUR THIS
WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
MODELS IN AGREEMENT WITH HIGH PRESSURE BUILDING OVER THE AREA
THROUGH TONIGHT. SKIES WILL BE CLEAR AND THE WINDS WILL LIGHT TO
CALM. OVERNIGHT LOWS WILL GENERALLY RANGE FROM 40 TO 45 DEGREES.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
SIGNIFICANT CHANGE IN THE WEATHER PATTERN EXPECTED DURING THIS
PERIOD AS A DEEP 535 DECAMETER CLOSED UPPER LOW DIVES SOUTHWARD FROM
CENTRAL CANADA...ACROSS THE OHIO VALLEY ON FRIDAY AND OVER THE
CAROLINAS ON SATURDAY.

THE DRY AIRMASS IN PLACE WILL CONTINUE TO PERSIST OVER THE FORECAST
AREA ON FRIDAY WITH WEAK SURFACE HIGH PRESSURE IN PLACE BUT
INCREASING MOISTURE LATE IN THE AFTERNOON AS LOW LEVEL FLOW BACKS IN
RESPONSE TO THE APPROACHING UPPER LOW.  TEMPERATURES ON FRIDAY
SHOULD BE SIMILAR TO TODAY IN THE UPPER 60S NORTHERN MIDLANDS TO
AROUND 70 OR LOWER 70S IN THE CSRA.

THE APPROACHING CLOSED UPPER LOW WILL INDUCE CYCLOGENESIS OFF THE
CAROLINA COAST WHICH WILL DRIVE A STRONG COLD FRONT SOUTHEASTWARD
THROUGH THE FORECAST AREA FRIDAY NIGHT.  THERE SHOULD BE ENOUGH
MOISTURE AVAILABLE TO SUPPORT SCATTERED SHOWERS DEVELOPING ACROSS
THE NORTHERN PORTION OF THE FORECAST AREA FRIDAY NIGHT AS STRONG
UPPER FORCING ASSOCIATED WITH POSITIVE VORTICITY ADVECTION MOVES
OVER THE REGION.  POPS CONTINUE TO INCREASE EARLY SATURDAY TO
LIKELY/CATEGORICAL ACROSS THE NORTHERN MIDLANDS AND PEE DEE REGION
WITH A GRADIENT TO LOWER POPS TO THE SOUTH. THE SIGNIFICANT COLD
POOL ALOFT IS SUFFICIENT TO SUPPORT FROZEN PRECIPITATION LATE FRIDAY
NIGHT INTO EARLY SATURDAY BUT EXPECT THE BOUNDARY LAYER TO BE TOO
WARM TO SEE ANYTHING OTHER THAN RAIN AT THE SURFACE.

ON SATURDAY WITH THE UPPER LOW CROSSING THE FORECAST AREA WITH 500MB
TEMPERATURES AROUND -26C AND 850MB TEMPERATURES AROUND -3C TO -5C
THERE IS THE POSSIBILITY OF SOME GRAUPEL MIXING IN WITH ANY OF THE
STRONGER SHOWERS DUE TO STEEP LAPSE RATES WITH THE CONVECTIVE
PRECIPITATION. TEMPERATURES ON SATURDAY WILL BE SIGNIFICANTLY
COLDER...NEARLY 15-20 DEGREES COLDER THAN FRIDAY...WITH HIGHS
STRUGGLING TO REACH THE 50S IN THE MIDLANDS! MAX TEMPERATURES WILL
RANGE FROM THE MID TO UPPER 40S NORTHERN MIDLANDS TO MID 50S IN THE
CSRA. WINDS COULD ALSO BE SIGNIFICANT LATE FRIDAY NIGHT THROUGH
SATURDAY WITH VERY STRONG WINDS...CLOSE TO 50 KNOTS AT
850MB...ASSOCIATED WITH THE DEEP UPPER LOW CAPABLE OF MIXING DOWN TO
THE SURFACE.  A LAKE WIND ADVISORY CERTAINLY WILL BE NECESSARY
FRIDAY NIGHT THROUGH SATURDAY NIGHT GIVEN THE STRENGTH OF THE COLD
ADVECTION AND RELATIVE WARM WATER TEMPS OF AREA LAKES.  SUSTAINED
WINDS 15 TO 25 MPH WITH GUSTS AS HIGH AS 35 TO 40 MPH EXPECTED ON
SATURDAY.

THE UPPER LOW QUICKLY MOVES OFFSHORE LATE SATURDAY WITH COLD DRY
CANADIAN HIGH PRESSURE BUILDING OVER THE AREA FOR THE REMAINDER OF
THE WEEKEND.  A STRONG PRESSURE GRADIENT WILL PERSIST THROUGH THE
OVERNIGHT HOURS SATURDAY NIGHT WHICH WILL PREVENT STRONG RADIATIONAL
COOLING BY KEEPING BOUNDARY LAYER WELL MIXED AND LOW TEMPS WILL BE
DETERMINED BY THE COLD ADVECTION TAKING PLACE WITH LOWS GENERALLY IN
THE MID 30S.

SUNDAY WILL FEATURE MOSTLY SUNNY SKIES WITH SLIGHTLY WARMER BUT
STILL WELL BELOW NORMAL TEMPERATURES WITH HIGHS IN THE 50S. SUNDAY
NIGHT APPEARS TO BE THE BEST NIGHT FOR A POTENTIAL WIDESPREAD FROST
ACROSS THE FORECAST AREA WITH SOME LOCAL FREEZE CONDITIONS POSSIBLE
IN SHELTERED VALLEYS AND OUTLYING AREAS.  IDEAL RADIATIONAL COOLING
CONDITIONS ARE EXPECTED WITH A VERY DRY AIRMASS IN PLACE WITH PWAT
VALUES AROUND 0.20...CLEAR SKIES AND NEAR CALM WINDS...AS SURFACE
HIGH PRESSURE SETTLES OVERHEAD.  OVERNIGHT LOWS WILL FALL INTO THE
LOWER TO MID 30S...ALTHOUGH SOME OF THE TYPICAL COLD SPOTS LIKE
CEDAR CREEK...PELION AND CHERAW COULD SEE TEMPS FALL INTO THE UPPER
20S POSSIBLY.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
THE MEDIUM RANGE MODEL GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT
IN THE OVERALL UPPER PATTERN EARLY IN THE EXTENDED FORECAST
PERIOD...BUT DIFFERENCES INCREASE FOR THE WED/THU TIME FRAME.

A 1032MB SURFACE RIDGE WILL BE ANCHORED OVER THE CAROLINAS MONDAY
AND MONDAY NIGHT...WHILE AN UPPER RIDGE AXIS OVER THE
OHIO/MISSISSIPPI VALLEYS WILL SHIFT EASTWARD OVER THE FORECAST AREA.
MONDAY MORNING TEMPERATURES WILL START OFF WELL BELOW NORMAL IN THE
LOWER TO MID 30S...WITH WIDESPREAD FROST POSSIBLE...AND SOME
POSSIBLE FREEZING TEMPERATURES IN SHELTERED VALLEYS AND OUTLYING
AREAS.  FULL SUNSHINE EXPECTED WITH A DRY AIRMASS IN PLACE WILL
YIELD SLIGHTLY WARMER TEMPERATURES COMPARED TO SUNDAY BUT STILL
REMAINING WELL BELOW NORMAL.  THE SURFACE RIDGE WILL SHIFT OFFSHORE
ON TUESDAY WITH A RETURN SOUTHERLY FLOW EXPECTED AROUND THE SURFACE
HIGH...WHICH WILL PROVIDE WARMER TEMPERATURES AND INCREASED LOW
LEVEL MOISTURE.  NEAR NORMAL TEMPERATURES EXPECTED TUESDAY WITH
HIGHS IN THE UPPER 60S TO LOWER 70S AND MUCH WARMER MIN
TEMPERATURES TUESDAY NIGHT IN THE UPPER 40S.

THE FORECAST BECOMES A BIT MORE CHALLENGING AND LESS CONFIDENT BY
MID WEEK. THE GFS SHOWS A FRONTAL BOUNDARY APPROACHING THE
REGION...DRIVEN BY NORTHERN STREAM SHORTWAVE ENERGY MOVING ACROSS
THE NORTHERN TIER STATES AND CROSSING THE FORECAST AREA LATE
THURSDAY AND THURSDAY NIGHT.  THE ECMWF IS SIMILAR WITH THE FRONTAL
POSITION MID WEEK AND PUSH IT ACROSS THE AREA SOMETIME
THURSDAY...BUT HAS LESS MOISTURE ASSOCIATED WITH THE FRONT AND
DEPICTS A CUTOFF UPPER LOW OVER THE DESERT SOUTHWEST...INFUSED WITH
ENERGY AND MOISTURE ASSOCIATED WITH THE REMNANTS OF TD 21.  WILL
CONTINUE TO CARRY SLIGHT CHANCE POPS WED/THU WITH APPROACHING
FRONT.  TEMPERATURES WILL WARM BACK TO NEAR OR SLIGHTLY ABOVE NORMAL
VALUES.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...

FRONT OFFSHORE. CLEAR SKIES AND LIGHT NE WINDS OVER MOST OF OUR
FORECAST AREA (FA) CURRENTLY. DEWPOINT GRADIENT EXISTS OVER THE FA
WITH LATE AFTERNOON DEWPOINTS/CROSSOVER TEMPS NEAR 40 AT MOST
TERMINALS EXCEPT MID 40S OGB. IT APPEARS ANY SIGNIFICANT FOG
POTENTIAL WOULD BE RESTRICTED TO THE FOG PRONE SITES OGB AND AGS.
MOST MODEL OUTPUT NOT INDICATING MUCH IN THE WAY OF FOG...ALTHOUGH
LOCAL RADIATION FOG SCHEME INDICATES SOME FOG POTENTIAL ONLY AT OGB.
THOUGH RELATIVELY LIGHT SURFACE AND BOUNDARY LAYER WINDS EXPECTED
OVERNIGHT...SOME QUESTION ABOUT THAT EXISTS AS WAVE OF LOW PRESSURE
EXPECTED TO DEVELOP TONIGHT ALONG THE FRONT OFFSHORE...AND
THAT MAY KEEP THE PRESSURE GRADIENT JUST TIGHT ENOUGH TO KEEP UP
SOME WIND OVERNIGHT. ALSO...A PESKY BAND OF SCT TO BKN SCU WITH
BASES AROUND 050 MAY LINGER NEAR THE E/SE FA NEAR OGB. GIVEN
UNCERTAINTY AND LACK OF MOST MODEL SUPPORT...WILL FOREGO ANY FOG
MENTION AT THIS TIME. TRENDS AND LATEST GUIDANCE WILL BE MONITORED
THIS EVENING FOR POSSIBLE INCLUSION OF VSBY RESTRICTIONS AT THE FOG
PRONE SITES OGB AND AGS IN LATER TAF ISSUANCES IF/WHEN CONFIDENCE
WARRANTS.

VFR CONDITIONS EXPECTED FRIDAY.

.EXTENDED AVIATION OUTLOOK...
SOME SHOWER ACTIVITY AND MVFR CIGS POSSIBLE FRIDAY NIGHT AND
SATURDAY. BREEZY TO POSSIBLY WINDY CONDITIONS EXPECTED SATURDAY.
NO SIGNIFICANT IMPACTS TO AVIATION EXPECTED SUN THRU TUE.

&&

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

$$






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