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000
FXUS62 KCHS 190601
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
101 AM EST Sun Jan 19 2020

.SYNOPSIS...
A cold front is expected to move through late tonight into
Sunday morning. In the wake of the front, a cold and dry air
mass will build over the region early next week and will remain
until Thursday. A low pressure system will bring warmer
temperatures and showers beginning Friday.

&&

.NEAR TERM /THROUGH TODAY/...
Midnight update: Forecast on track, only minor tweaks to sky
cover and POPs.

Extensive mid and high level cloud cover has overspread the
forecast area in advance of a cold front that will move into
local counties prior by daybreak. Warm advection in advance of
the front and the blanketing affects of the clouds will hold
temps fairly steady or even allow them to climb a couple of
degrees overnight. Through 6 am the bulk of the region will
experience temps in the lower or middle 60s, far above normal,
as a 35-45 kt low level jet spreads overhead between 06Z and
12Z. This will yield increasing southwesterly winds that reach
as high as 20-30 mph at times overnight.

Forcing aloft with strung out vorticity and the right entrance
region of the upper jet, plus modest isentropic ascent will
allow for scattered to numerous showers to spread in ahead of
the cold front. The highest PoP of 50-60% will cover the west-
northwest tier prior to 4 am, with the higher PoP spreading
closer to the coast closer to daybreak.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
Sunday: As the cold front progresses through the area during the
morning hours, showers are expected to continually decrease until
the afternoon, when cool and dry high pressure moves into the
area. This will help decrease POPs quickly, with a mostly dry
afternoon/evening. Temperatures are expected to be in the low to mid
60s. Throughout the night, temps will trend much cooler with lows in
the high 30s, low 40s.

Monday and Tuesday: As high pressure continues to prevail,
temperatures will be much lower than we have seen in recent days.
While mid 40s to low 50s are expected, temps could actually stay
lower. Into the night, temps will drop into the low 30s along the
coast while inland will see upper 20s. Tuesday will start off quite
cold and warm up to similar temps as Monday, just a little chiller.

It is interesting that a clipper-like system is expected to quickly
ripple over the region on Tuesday, slowly closing off at H5. As the
system passes over the CWA, H85 temperatures cool to -6 to -9C.
Using a blend of MOS, highs on Tuesday are expected to remain 10-13
degrees below normal. The core of the mid and high level moisture is
expected to pass to the south, however, cloud cover is expected to
increase through the daylight hours on Tuesday. By late Tuesday, the
mid-level disturbance will pass over the cold front over the western
Atlantic, resulting in cyclogenesis east of the Gulf Stream. As a
result, a few showers are forecast to develop across the outer GA
waters, temperatures in the upper 40s to low 50s should support all
liquid.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
A large area of sfc high pressure will dominate much of the East
Conus with its center shifting across the Midwest midweek, then into
the Northeast by Friday. Aloft, a large trough of low pressure will
begin to shift offshore midweek, setting up a period of mid-lvl
ridging through late week. The pattern will favor cold temps Tuesday
night with lows in the mid/upper 20s away from the coast, before
conditions gradually warm as winds become more directly onshore
through late week. Temps will likely warm into the low/mid 50s
Wednesday, then mid 50s well inland to upper 50s/lower 60s on
Thursday. On Friday, onshore winds should prevail as high pressure
shifts off the East Coast. A developing coastal trough could also
bring some showers onshore. In general, temps should approach the
mid/upper 60s. Chances of precip should increase during the weekend
as low pressure over the Gulf of Mexico merges with a cold front
approaching from the west on Saturday. Scattered to potentially
numerous showers are possible during peak forcing/moisture across
the area Saturday afternoon.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
VFR conditions at both terminals much of tonight and Sunday.
However, scattered SHRA will move through the area with a cold
front late tonight and Sunday morning, and this could result in
several hours of MVFR conditions.

We`ll be close to LLWS mid morning, but surface winds currently
look to be too strong to prevent us from adding to the latest
TAF set. Gusty surface winds will then persist behind the cold
front through about sunset.

Extended Aviation Outlook: VFR conditions are expected at both
terminals Monday through the middle of next week.

&&

.MARINE...
Overnight: Increasing low level winds that reach as high as
35-40 kt in advance of the next cold front will be tempered
somewhat by warm advection. However, given geostrophic wind
fields that are as great as 30 or 35 kt, we have Small Craft
Advisories in effect for the South Carolina Atlantic waters and
the outermost Georgia waters. SW winds will reach as high as
20-25 kt and gusty across these marine zones, with seas as large
as 5 or 6 ft within 20 nm and up to 7 ft further out. Conditions
will be close to advisory thresholds in Charleston Harbor for
several hours late tonight and Sunday morning.

Sunday: A cold front will sweep across the waters on Sunday. Winds
are forecast to veer from SW during the morning from the WNW by the
afternoon. Conditions are expected to become gusty, with frequent
gusts to around 25 kts across AMZ350 and 374. Seas across these
zones are forecast to range between 4 to 7 ft. Small Craft
Advisories will remain until 6 PM Sunday.

On Monday, large high pressure centered over the Mid West will build
SE across region. The pressure gradient across the marine zones
should support gusts in the low 20s early Monday morning, decreasing
to 20kts or less during the daylight hours.

Tuesday through Wednesday night: Low pressure will organize and
deepen offshore as a mid-level disturbance arrives from the NW. The
marine zones will remain between the developing low to the east and
high pressure centered to the NW. This pattern will likely yield
Small Craft Advisory conditions outside the CHS Harbor Tuesday
through Wednesday night with gusty NE winds and building seas. On
Thursday, seas above 6 ft may linger across AMZ374 through much of
the day. High pressure will build over the area on Thursday, with
gradually lowering wind gusts and seas.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory from 4 AM to 10 AM EST this morning for
     AMZ352.
     Small Craft Advisory until 6 PM EST this evening for AMZ350-
     374.

&&

$$
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...