Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
340 PM EDT Thu Oct 27 2016
high pressure will prevail through the weekend. A backdoor cold
front will move through the Carolinas on Monday, followed by high
pressure into the middle of the upcoming week.
Near term /until 6 am Friday morning/...
this evening and tonight: high pressure will gradually weaken aloft
in advance of a h5 shortwave approaching the southeast late this
evening and tonight. At the sfc, low pressure will track over the
northeast with a cold front that trails to the south/southwest,
eventually approaching northern areas late tonight. The setup will
favor dry conditions and mild temps well ahead of the approaching
front/trough tonight, with possibly a light wind shift in northern
areas just before daybreak. Few to scattered clouds should help
maintain somewhat mild low temps overnight, ranging in the mid 50s
inland to lower 60s near the coast.
The main concern for the overnight period will be the possibility of
fog late tonight into daybreak. Calm winds, favorable crossover
temps and fog fsi values between 10-20 support patchy/areas of fog
away from the coast, especially in southeast Georgia. Greatest
chances for fog should remain west of I-95 where temps dip into
the mid 50s. Patchy fog may need to be introduced for the rest of
southeast South Carolina should cloud cover be less than anticipated
Short term /6 am Friday morning through Sunday/...
Friday through sunday: a very quiet weekend is on tap. The pattern
aloft will feature a ridge expanding across the region Friday and
Saturday before flattening out a bit on Sunday ahead of a low
amplitude trough. At the surface, a weak and diffuse front may brush
the northern zones early Friday with high pressure prevailing
through the remainder of the period. Deep dry air will encompass the
region through the period and the forecast is rain free. We will
likely still see decent coverage of high clouds early Friday, but
this will thin with time through the day and the remainder of the
period is expected to be mostly clear. The main story will be well
above normal temperatures, with highs in the low 80s each day, and
lows in the mid 50s inland ranging to around 60 at the coast. Such
values would be on the order of 6-8 degrees above normal on
Long term /Sunday night through Thursday/...
expansive deep layered ridging looks to persist through the
period across the southeast states. During Monday or early
Tuesday, a dry backdoor cold front will pass south through the
forecast area while surface high pressure builds south from the
mid-Atlantic region. The European model (ecmwf) suggests a few coastal showers are
possible with shallow moist onshore flow, but we maintained a dry
forecast as upper ridging only strengthens with time while
moisture looks too shallow to expect any precipitation. Deep
layered ridging will persist past mid week with any rain chances
beyond the forecast period. Very warm temps will prevail, most
days in the lower 80s with mild lows in the upper 50s on average.
Aviation /20z Thursday through Tuesday/...
VFR conditions will prevail at both chs and sav terminals through
18z Friday. However, there is a low chance of MVFR vsbys Friday
morning due to fog, mainly between 08z-14z.
Extended aviation outlook: VFR conditions expected to prevail
through this weekend with low probabilities for late night or
early morning restrictions in patchy fog prior to the weekend.
this evening and tonight: high pressure will dominate the coastal
waters through the overnight period. Expect winds/seas to remain
well below Small Craft Advisory levels while a weak pressure
gradient persists over all waters. In general, east/southeast winds
will remain at or below 10 kt while seas will peak between 3-5 ft,
highest in offshore Georgia waters.
Friday through tuesday: high pressure will prevail across the local
waters through the weekend. Then late Monday into early Tuesday, a
backdoor cold front could push in from the north. Through the
weekend, winds will generally be no more than 10-15 knots, with much
of the time being 10 knots or less. A more notable surge could occur
Tuesday behind the backdoor cold front. Seas will be in the 2-3 foot
range out to 20 nm through the weekend, and 3-4 feet beyond 20 nm.
Seas could then increase a bit early next week depending on how much
winds increase with the possible backdoor cold front.