Scientific Forecaster Discussion
fxus62 kchs 261144
Area forecast discussion
National Weather Service Charleston SC
644 am EST sun Feb 26 2017
cool high pressure with critical relative humidity will build into the region today,
then shift offshore tonight and early this week, as a warm and moist
air mass gradually builds from the Atlantic and Gulf of Mexico. A
cold front will move through Wednesday night into Thursday, followed
by high pressure for the end of the week.
Near term /through tonight/...
today: a fast moving zonal flow within a de-amplified pattern aloft
will prevail, as cool and dry Canadian high pressure in the Tennessee
Valley at the start of the day progresses to the coast of NC/SC
by evening. This scenario will provide US with abundant bright
sunshine and offshore winds this morning shifting onshore over
the coastal corridor during this afternoon. We stayed relatively
close to the low level thickness forecast scheme, which will
support a brief change from the abnormally warm springlike
weather of late. Today will actually only be the 8th day this
month at kchs and just the 7th time at ksav, where we fail to
Tonight: high pressure will cover much of the east and southeast parts of the
nation, with a modifying clockwise return flow from off the Atlantic
across the local district. Winds will quickly decouple away from the
coast this evening, allowing for a rapid fall of temps the first
half of the night. However, low level warm advection will slow the
overnight fall of temps, as minimums on average will make it down to
the upper 30s or lower 40s inland from US-17, closer to 50f on the
barrier islands. Skies will begin the night clear, but some jet
stream cirrus will arrive overnight, having little to no effect on
Short term /Monday through Wednesday/...
surface high pressure will slide into the Atlantic Monday and
persist through Wednesday. Southerly flow on the back side of the
high will bring warm and moist air into the area. Aloft, a series of
shortwaves will eject out of the southwest flow and pass over the
forecast area late Monday into early Tuesday. This could spur some
showers, however coverage does not look to be that impressive.
Models actually seem to have trended drier, so have decreased
precipitation chances. Slight chance/chance pops seem reasonable.
Otherwise, a few diurnal showers/thunderstorms possible Tuesday and
Another warming trend will get underway with temperatures expected
to be well above late February/early March normals. Highs in the mid
70s Monday will warm to the low/mid 80s by Wednesday. Lows in the
upper 50s/low 60s.
Long term /Wednesday night through Saturday/...
models are in decent agreement that a cold front will approach and
cross the forecast area late Wednesday night into early Thursday.
Showers and maybe a few rumbles of thunder possible with the front.
High pressure will return in its wake and remain the dominant
feature through Saturday. Temperatures will be on a slight cooling
trend through the period.
Aviation /12z Sunday through Thursday/...
Extended aviation outlook: flight restrictions possible in early
morning fog/stratus Tuesday and Wednesday. A cold front will move
through early Thursday with brief restrictions possible in
today: cool advection and continued isallobaric pressure rises this
morning will allow for Small Craft Advisory conditions to persist
across the Atlantic waters. However, there is quick improvement by
mid to late morning (if not sooner) once cool advection slackens and
the gradient around Continental high pressure relaxes. Offshore
winds as high as 15 or 20 kt and gusty this morning, will shift to
onshore at considerably less speeds (no more than 10 or 12 kt) this
afternoon, as Continental high pressure slides to the southeast coast and a
"pure" but light sea breeze occurs. Seas will be highest this
morning, up to 3-5 ft, before they subside to no greater than 2-3 ft
by late day.
Tonight: high pressure will expand over the western Atlantic, with
it's associated ridge axis to align itself to the north of the
maritime area. E'erly winds will dominate, generally at or below 15
kt and seas will climb about a foot or so within the onshore
Monday through friday: east/southeast flow Monday will veer to the
south by Tuesday as high pressure shifts into the Atlantic. Wind
speeds will then increase Wednesday as the pressure gradient
tightens ahead of an approaching cold front. Conditions look to
remain below Small Craft Advisory criteria at this time. The front
will cross the waters early Thursday with high pressure to return in
Sea fog: warm southerly flow moving over the cooler shelf waters may
result in patchy sea fog developing late Tuesday into Wednesday.
Marine...Small Craft Advisory until 10 am EST this morning for amz374.