Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Columbia SC
738 am EDT Sat Jul 22 2017
upper ridging will remain over the forecast area today then
weaken Sunday into early next week. Along with the troughing
moisture will increase across the area with slowly increasing
chances of thunderstorms through Wednesday. It will remain hot
this weekend with heat index values peaking between 105 and 115
Near term /until 6 PM this evening/...
the upper level trough over the northeast US will try to bring
a weak shortwave through the region today. This will create a
weakness between the Bermuda high and high pressure over the
central part of the country. Therefore, scattered afternoon
thunderstorms will again be possible across the midlands, with a
better chance across the upstate due to the Lee trough. Storm
motion will be slow, and moisture will increase slightly
compared to yesterday, so in addition to isolated strong outflow
winds, localized flooding could also be possible. Another
concern for Saturday will be the heat index as temperatures will
rise to the upper 90s to around 100 and push heat index values
to 105 to 113. Several counties will meet the criteria for a
heat advisory of 110 to 115 degrees, and have issued for the
Short term /6 PM this evening through Sunday night/...
upper level trough over the eastern conus through Sunday night
with most of the short wave energy passing north of the
midlands. Lee side surface trough will reside across the
Piedmont. Models indicate a lack of a strong trigger and
moderate instability during peak heating...so will continue low
chance pops with a diurnal trend. Locally heavy rainfall
possible given precipitable water near 2.00 inches. Followed guidance
consensus for lows in the middle 70s and highs in the mid to
upper 90s on Sunday.
Long term /Monday through Friday/...
upper level weather pattern for the long term features a trough
across the eastern states and a ridge in the west. At the
surface...a Lee side trough will linger over the western
Carolinas on Monday. Models indicate potential for a weak
surface boundary to move into the area Tuesday and linger
through Thursday. This would result in increased pops...but with
confidence low in this scenario have remained with chance pops.
Near normal temperatures are expected with highs in the low to
mid 90s and lows in the low to mid 70s.
Aviation /12z Saturday through Wednesday/...
VFR conditions and mostly clear skies with only a few mid-
level clouds through the morning. Do not expect early morning
fog development for most of the area due to a 15 knot low level
jet which has promoted mixing in the boundary layer, but there
have been brief MVFR restrictions at fog prone ags and ogb. Ogb
has improved, but ags continues to fluctuate so added a tempo
group through 13z. Expect scattered showers and thunderstorms
to develop again this afternoon and evening, but coverage is too
uncertain at this time to include in tafs.
Extended aviation outlook...increasing chances of afternoon/evening
thunderstorms, and late night/early morning fog/stratus, Monday
Georgia...heat advisory from noon today to 6 PM EDT this evening for
SC...heat advisory from noon today to 6 PM EDT this evening for