Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 201413
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
1013 AM EDT Thu Jul 20 2017

.SYNOPSIS...
A weak upper-level low just off the South Carolina and Georgia
coasts today will drift southwestward and be along the northern
Gulf Coast Friday and Saturday. North of the low ridging will
become more dominate over the forecast area over the weekend.
This pattern will restrict the thunderstorm chance and bring
some of the hottest weather so far this season. Heat index
values will peak around 105.

&&

.NEAR TERM /THROUGH TONIGHT/...
Upper high to our NW with closed low spinning just offshore the
lower SC coast. Weak surface trough appears to be stretched across
the northern forecast area (FA). Slightly lower precipitable water
(PW) values across much of the FA today compared to yesterday. PW
values from latest SPC mesoanalysis and other satellite-derived
sources indicate PW values 1.6-1.8 inches from the CSRA and southern
Midlands down towards the coast, with lower PW values of 1.4-1.5
inches across the northern FA. Forecast soundings indicate slightly
higher LFC heights, with slightly lower overall moisture. This may
reduce overall areal coverage of convection. Latest high resolution
models indicate widely scattered shower and thunderstorm activity
may develop along the surface trough across portions of the northern
and possibly central FA, with additional activity across the CSRA
and southern Midlands and points southward where a little better
moisture exists and ahead of an upper vort moving counterclockwise
around the northern periphery of the upper low, possibly enhanced by
a sea breeze boundary. All in all, slight chance POPs continue
to look ok for most of the FA. Anything that does develop could
produce a wind threat given considerable DCAPE values. Will
expect any convection to dissipate this evening. Max temps in
the mid to upper 90s look in order for this afternoon. Guidance
indicating dewpoints mixing down in the upper 60s to near 70,
yielding max heat index values 100-104.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY/...
Bermuda surface ridging will continue to extend westward along
the Gulf Coast. North of the ridge lee-side troughing will be
in the forecast area. The models show the upper ridge axis
extending eastward trough North Carolina and be more dominate
in the forecast area with the weak upper over the northern Gulf
Coast. Deeper moisture is depicted suppressed south of the
forecast area closer to the upper feature. The pattern supports
a diminished thunderstorm chance. All the GFS and NAM MOS have
pops 20 percent or less. The MOS supports high temperatures near
100 with heat index values peaking around 105...a little below
the heat advisory criteria of 110.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The GFS and ECMWF display surface ridging extending from the
Atlantic westward into the Gulf Coast during the medium-range
period. North of the ridge lee-side troughing is shown in the
forecast area. A slow moving cold front may be in the region
Tuesday and Wednesday. The models display upper troughing
developing early next week with increased moisture. The pattern
supports an increasing thunderstorm chance during the period.
The GFS and ECMWF MOS have pops 20 to 30 percent Sunday,
and 30 to 40 percent during the rest of the period. The MOS
continues to show hot conditions Sunday and Monday. Expect
highs mainly 95 to 100 with heat index values near 105. Somewhat
lower temperatures should occur during the rest of the medium-
range period associated with upper troughing and more cloudiness.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
VFR expected outside of any widely scattered showers or
thunderstorms this afternoon. At this time, convective chance
appears too low to include mention in the TAFs at this time. Limited
precip coverage/cooling combined with warm overnight temps expected
to preclude significant fog/stratus threat.

EXTENDED AVIATION OUTLOOK...No significant aviation related
issues expected at this time.

&&

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

&&

$$



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