Scientific Forecaster Discussion
fxus62 kchs 171146
Area forecast discussion
National Weather Service Charleston SC
646 am EST Fri Nov 17 2017
high pressure will prevail through Saturday. A cold front will
pass through the region Saturday night into Sunday morning,
followed by a return of high pressure for next week.
Near term /through tonight/...
today: the pattern aloft will continue to feature west-
northwest flow across the southeast. At the surface, high
pressure will begin the day centered over the central
Appalachians, before gradually shifting into the Lee and
settling across eastern North Carolina. This setup will result
in cool northeast flow across the forecast area within a very
dry airmass with precipitable water values less than half of an
inch. Clear skies and plentiful sunshine are expected to prevail
through the day, though temperatures will run below normal.
Forecast highs range from the low to mid 60s across southeast
South Carolina to near 70 in parts of southeast Georgia. Such
values would be about 3-6 degrees below normal for mid November.
Tonight: no significant change to the overall pattern, though
the surface high will begin to shift offshore allowing low level
flow to become more southeasterly or southerly. The forecast
remains dry and lows will range from the low 40s in inland
locations to around 50 at the coast. Given the change in the low
level flow pattern we should see a modest increase in cloud
cover as marine stratocumulus attempt to push onshore.
Short term /Saturday through Monday/...
deep layered ridging will persist into Saturday, maintaining
dry conditions and yielding above normal temps in the low/mid
70s. A potent shortwave will push into the area Saturday night,
forcing a cold front through by Sunday morning. Only a thin band
of moisture will accompany the front and forcing for ascent
will be weak and short-lived. We therefore continue to only show
scattered showers late Saturday night, tapering off Sunday
Cold high pressure will expand across the southeast Sunday into
Monday, with highs in the low to mid 60s and morning lows in
the mid/upper 30s. Cannot rule out some patchy frost in
sheltered areas Sunday night but winds are forecast to be 3-5 kt
overnight which would preclude more extensive frost formation.
Long term /Monday night through Thursday/...
dry high pressure is expected to prevail much of next week but
a Gulf surface low could lift northeast late in the week and
potentially bring some precipitation.
Aviation /12z Friday through Tuesday/...
VFR conditions are expected to prevail through 12z Saturday.
Extended aviation outlook: brief flight restrictions possible
due to scattered showers along a cold front late Saturday night
into early Sunday.
today and tonight: a subtle front will push southward across
the local waters this morning as high pressure builds in from
the north. This will tighten the northeast oriented pressure
gradient for much of the morning and result in strengthening
northeast flow for at least much of the morning. Winds are
expected to top out in the 15- 20 knot range across the South
Carolina waters, with a solid 15 knots expected elsewhere. By
the late afternoon hours, the gradient will begin to relax and
speeds will drop off to the 10-15 knot range. Winds overnight
will weaken further as the surface high moves offshore. The flow
will become more southeasterly with time and drop off to the
5-10 knot range. The increase in northeast flow will help seas
tick upward for a time this morning, but overall seas will be in
the 2-4 foot range through the period.
High pressure will persist on Saturday, maintaining relatively
weak winds over the waters. However, a potent shortwave moving
through Saturday night, with 850 mb winds 40-50 kt, will yield
increasing southwest winds. A period of Small Craft Advisory
conditions is expected overnight Saturday night into Sunday
morning. Winds/seas will diminish fairly quickly on Sunday as
high pressure builds in and low-level winds drop quickly.
northeast winds within a prolonged high pressure pattern along
with astronomical influences associated with the upcoming new
moon this weekend could produce tide levels that approach
coastal flood advisory status through Saturday, mainly during
high tides each morning along the southeast South Carolina