838
FXUS62 KCAE 200654
AFDCAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
254 AM EDT SAT OCT 20 2018
SYNOPSIS
A COLD FRONT WILL CROSS THE AREA THIS AFTERNOON. COOL AND
DRY HIGH PRESSURE WILL BUILD ACROSS THE AREA SUNDAY AND MONDAY.
NEAR TERM /THROUGH TODAY/
AN UPPER LEVEL TROUGH DIGGING ACROSS THE EASTERN STATES WILL
DRIVE A COLD FRONT THROUGH THE AREA THIS AFTERNOON. MODELS
CONTINUE TO INDICATE SCATTERED TO NUMEROUS SHOWERS CROSSING THE
THE FORECAST AREA AHEAD OF THE FRONT IN SPITE OF DOWNSLOPE
850MB FLOW. PWAT IS FORECAST TO BE IN THE 1.5 TO 1.9 INCH RANGE.
GUIDANCE POPS RANGED FROM 30 TO 70 PERCENT. HAVE INDICATED LOW
CHANCE FOR MEASURABLE RAINFALL DUE TO DOWNSLOPE FLOW AND LITTLE
UPPER LEVEL SUPPORT. WEAK INSTABILITY COULD PROVIDE AN ISOLATED
THUNDER THREAT IN THE AFTERNOON ACROSS THE CSRA AND SOUTHERN
MIDLANDS, BUT CONFIDENCE LIMITED. GUIDANCE TEMPERATURES WERE FAIRLY
CONSISTENT...IN THE MID 70S WEST TO LOWER 80S EAST.
SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/
THE COLD FRONT WILL QUICKLY MOVE OFFSHORE TONIGHT, USHERING IN A
COOLER AND DRIER AIRMASS. WINDS WILL INCREASE WITH THIS FRONTAL
PASSAGE, SHIFTING TO THE NORTHWEST TONIGHT, AND THEN TO THE NORTH TO
NORTHEAST ON SUNDAY. DUE TO WARM LAKE WATER TEMPS, WITH LATEST LAKE
MURRAY TOP WATER TEMP 76-77F, WINDS ARE EXPECTED TO STAY UP ON
AREA LAKES, WITH FREQUENT GUSTS UP TO 25 KTS THROUGH EARLY SUNDAY
AFTERNOON. A LAKE WIND ADVISORY IS THEREFORE BEING ISSUED FOR
SATURDAY NIGHT THROUGH 2 PM SUNDAY.
THE COOLEST AIR MASS SO FAR THIS FALL ALSO PUSHES INTO THE
REGION DURING THIS PERIOD. LOW TEMPERATURES SUNDAY NIGHT INTO
MONDAY MORNING WILL BE IN THE MID 30S TO LOW 40S. SOME WIND MAY BE A
LIMITING FACTOR FOR FROST, HOWEVER LIGHT WINDS OVER NORTHERN AREAS
CLOSER TO THE SURFACE HIGH CENTER, AND IN OTHER WIND PROTECTED
LOCATIONS, MAY BE AT RISK.
HIGH PRESSURE WILL KEEP THE AREA DRY THROUGH MONDAY NIGHT, AND
TEMPERATURES WILL BEGIN TO SLOWLY REBOUND. HIGHS WILL BE IN THE MID
60S TO LOW 70S, WITH OVERNIGHT LOWS IN THE 40S.
LONG TERM /TUESDAY THROUGH FRIDAY/
AS SURFACE HIGH PRESSURE MOVES OFFSHORE, THE BRIEF WARMING TREND
WILL CONTINUE INTO WEDNESDAY WITH NEAR NORMAL TEMPERATURES. WEDGE
CONDITIONS THEN DEVELOP ON THURSDAY AND FRIDAY AS SURFACE HIGH
PRESSURE REMAINS IN PLACE WHILE WARMER AIR ALOFT MOVES IN FROM THE
SOUTHWEST. THERE ARE STILL SIGNIFICANT MODEL DIFFERENCES HOWEVER,
AND A LOT OF UNCERTAINTY AS TO HOW MUCH MOISTURE WILL MAKE ITS WAY
NORTH. HAVE THEREFORE MAINTAINED A CONSENSUS FORECAST WITH A LOW
CHANCE OF RAIN.
AVIATION /06Z SATURDAY THROUGH WEDNESDAY/
SHALLOW LOW-LEVEL MOISTURE WILL ADVECT INTO THE REGION THIS
MORNING AHEAD OF A COLD FRONT. OBSERVATIONS INDICATED PATCHES OF
MVFR CEILINGS, SO HAVE INCLUDED CIGS 2500-3000 FEET THROUGH
EARLY AFTERNOON. THERE APPEARS TO BE A RELATIVELY STRONG LOW-
LEVEL JET OVERNIGHT 30-35KTS AT 2000 FT SUGGESTING POSSIBLE
LLWS THROUGH 14Z AS SURFACE WINDS EXPECTED TO BE LIGHT.
THE COLD FRONT WILL CROSS THE AREA THIS AFTERNOON...MOVING EAST
OF THE TAF SITES BY 22Z. LOW LEVEL MOISTURE CONVERGENCE APPEARS
WEAK WITH MAINLY WEST FLOW AHEAD OF THE FRONT. SHOWERS ARE
EXPECTED TO BE WIDELY SCATTERED AS FRONT WILL HAVE LIMITED
MOISTURE. WEST WINDS 10 TO 20 KNOTS WITH SOME HIGHER GUSTS
POSSIBLE LATE IN THE AFTERNOON DUE TO MIXING AND COLD ADVECTION
DEVELOPING BEHIND THE FRONT. AFTER 23Z EXPECT CLEARING SKIES
WITH WEST TO NORTHWEST WINDS 10 TO 15 KNOTS.
EXTENDED AVIATION OUTLOOK...NO RESTRICTIONS TO AVIATION EXPECTED
THROUGH WEDNESDAY.
CAE WATCHES/WARNINGS/ADVISORIES
GA...LAKE WIND ADVISORY FROM 10 PM THIS EVENING TO 2 PM EDT SUNDAY
FOR GAZ040-063>065-077.
SC...LAKE WIND ADVISORY FROM 10 PM THIS EVENING TO 2 PM EDT SUNDAY
FOR SCZ015-016-018-020>022-025>031-035>038-041.
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