Area Forecast Discussion
Issued by NWS Columbia, SC
FXUS62 KCAE 010148
Area Forecast Discussion
National Weather Service Columbia SC
948 PM EDT WED AUG 31 2016
Tropical Storm Hermine is forecast to move out of the eastern
Gulf of Mexico and move NE across North Florida and over portions
of the Southeast later this week. Behind the cyclone, drier and
cooler high pressure will build into the region for the weekend.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Weakening upper low will be tracking off to the northeast of the
area, ahead of a digging trough moving into the Ohio Valley. At
this time not expecting much in the way of precipitation tonight
but some clouds will remain. Nocturnal cooling and high low-level
moisture should result in areas of fog late. The NAM and GFS MOS
indicated fog. Expect overnight lows mostly in the lower 70s.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
The threat from Tropical Storm Hermine, now developing in the
Gulf of Mexico...is increasing for central SC and East Central
Georgia/CSRA. The main threat appears to be heavy rain...resulting
in possible flash flooding...along with an elevated tornado
threat and potential gusts to tropical storm strength.
Tropical Storm Hermine developing in the Gulf of Mexico is
expected to track northeast toward the big bend Florida
coast...then northeast toward eastern South Carolina Friday.
Upper-level trough over the Great Lakes region and Northeastern
States will amplify Thursday and drive a cold front into northern
SC late Thursday. The front appears to become stationary across
the Midlands through Friday providing a focus for enhanced low-
level convergence. The model ensembles...global and statistical
guidance continues to slow the northward movement of the tropical
storm and thus the storm track is now farther west than previous
forecast. The operational GFS/Nam and ECMWF have the storm moving
across eastern SC resulting in a significant threat for the
region. The upper-level trough to the north is influencing
northward movement of cyclone and ridge offshore appears
stronger...so westward track adjustment appears appropriate.
Moisture will increase during the afternoon Thursday with
precipitable water near 2 inches. Instability weak to
moderate...expect scattered showers and a few thunderstorms...but
convection should remain unorganized and focus mainly in the
southeast Midlands or coastal plain. Warm day expected with
temperatures in the low 90s.
As front moves into the area from the north Thursday night and
moisture advection continues to increase...expect scattered to
numerous showers to develop toward daybreak possibly near frontal
boundary but confidence low on location...although models hit CSRA
early Friday morning. Guidance temperatures appear ok...although
favor warmer guidance with warm advection.
Frontogenetic forcing may enhance rainfall amounts across the
area as tropical moisture spreads north ahead of the cyclone.
Widespread heavy rain possible Friday as the tropical storm moves
across the region. The GFS ensemble mean QPF for CAE is 4 to 5
inches. Increased QPF across the area but stayed close to WPC
guidance. Generally 3 to 5 inches. The situation is being
monitored closely for potential flash flood watch. Tropical storm
wind gusts are possible especially from the east Midlands and Pee
Dee. The models indicate very strong low-level shear 0-1 km...and
enhanced SR helicity near front. Weak instability. Threat for
isolated Tornadoes elevated along storm path and to the east.
Storm movement a little slower so threat continues Friday night
but diminishing from southwest to northeast.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Tropical Storm Hermine will move northeast of the area
Saturday. Northwest/west flow in the wake of the system will work to
dry out the air mass. Skies will be clearing throughout the day
Saturday. Downslope flow through the weekend should promote diabatic
heating which suggests higher daytime temperatures than model
guidance. Lows will be in the mid 60s.
Early next week through midweek, an upper-level ridge will build
into the region. This supports a warming trend to above normal
temperatures with generally dry weather. Lee-side troughing may
bring a slight chance for showers and thunderstorms into the
forecast near the end of the period but certainty is low at this
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
There will be a trough near the coast with a cold front
approaching from the northwest during the TAF period. Deepest
moisture will be northwest and east of the terminals. The pattern
supports scattered showers and thunderstorms mainly near the time
of maximum heating. Thunderstorms were not included at issuance
because of timing uncertainty. Low-level moisture will remain
high. This moisture combined with nocturnal cooling may result in
stratus and fog during the early morning hours. The NAM and GFS
MOS were in good agreement indicating MVFR or IFR fog. We followed
the GFS LAMP for the timing of fog in the forecasts. Heating and
mixing should help dissipate fog beginning 13z to 14z.
EXTENDED AVIATION OUTLOOK...Widespread IFR or MVFR conditions may
occur Thursday night through Friday night associated with a cold
front moving into the area from the northwest. There will also be
added moisture associated with Tropical Storm Hermine forecast to
move northeastward and interacting with the front during this