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Area Forecast Discussion

278
FXUS62 KCHS 270822
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
422 AM EDT FRI MAY 27 2016

.SYNOPSIS...
Atlantic high pressure will prevail today. A wave of low pressure
will develop over the Southwest Atlantic and approach the Southeast
coast Saturday and Sunday. The low could affect the area into early
next week before eventually lifting northeast.

&&

.NEAR TERM /THROUGH TONIGHT/...
Pre-dawn: Clear skies and near calm winds across the region. Weak
but lingering mid-level vorticity over the CSRA and Midlands producing
areas of mid clouds. Similar to the past couple of mornings; there
may be a few patches of mid clouds across the forecast area around
daybreak. There could also be patchy shallow ground fog in a few
spots, but nothing significant.

Today: deep layered dry air and subsidence will prevail with plenty
of sunshine on tap. Few to scattered cumulus will likely develop
along the sea breeze and quickly push inland this afternoon as the
low level synoptic flow is now onshore; most pronounced across
Southeast Georgia. No Significant changes to our overall temp
scheme today; highs ranging from the upper 80s inland to the mid
80s to the east of U.S. 17.

Tonight...Mainly clear skies this evening will give way to an
increase in clouds along and east of I-95 later tonight. Deeper
moisture ahead of an advancing inverted trough and surface low
pres north of the Bahamas will be approaching the Carolina Coast.
Model timing and low level convergence patterns remain consistent
and we maintained a slight chance of showers late tonight with
chance pops along upper Charleston County nearing daybreak. Given
the advancing cloud shield late...some lows may be reached earlier
in the overnight with rising temps along coastal areas late.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
The forecast through the short term period remains quite complex and
uncertain as it is dependent on the evolution of developing low
pressure over the western Atlantic.

An area of low pressure will be located around 250-300 miles off
coastal SC/GA Saturday morning. The strength and classification of
the low is still uncertain, however the latest National Hurricane
Center outlook indicates that the low has a high likelihood of
becoming a tropical or sub-tropical system within 48 hours. A
reconnaissance aircraft is scheduled to investigate the system
Friday afternoon.

Models are in fairly good agreement that the low will track
northwest towards the SC coast Saturday into Saturday night.
Thereafter, model solutions diverge. Consensus takes the low into
Charleston county sometime Sunday afternoon. Regardless of whether
or not this system is classified as tropical, the primary hazard of
interest at this time is potential heavy rain. Should persistent
heavy rain affect coastal areas coincident with high tide, the
threat for localized flooding will be enhanced. Currently, the SC
coast looks to have the biggest threat for heavy rain/localized
flooding. Of course, a shift in forecast track could result in a
different scenario. Continued uncertainty into Monday as the low
could meander over the area or in the vicinity. GFS and NAM keep the
low spinning in the vicinity for a couple days, while the Euro is
more progressive and has it lifting northeast pretty quickly...
similar to it`s run 24 hours ago.

Overall, the weather will be fairly unsettled given the deep-layered
moisture in place and the low pressure system in the vicinity.
The forecast features at least chance POPs through the period,
highest on Sunday. Needless to say, significant adjustments will
likely be needed with future forecast packages when details are
better defined.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
Forecast for the work week continues to be quite uncertain as it
remains highly dependent on the evolution of a low pressure system
that will impact the Southeast. A couple models are more progressive
in lifting the low northeast away from the area quickly leaving a
rather benign weather pattern mid week, while others want to keep it
spinning in the vicinity before eventually dissipating. Have
maintained rain chances in the forecast through the period.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
VFR at KCHS/KSAV through 06Z. There could be some very shallow
ground fog around daybreak this morning, but no impacts are
expected.

EXTENDED AVIATION OUTLOOK...Chances for at least periodic flight
restrictions increase this weekend into early next week as a low
pressure system approaches from the southeast.

&&

.MARINE...
Low pres to the ne of the Bahamas and sprawling high pres from
Bermuda the Mid Atlc States will combine to deliver an onshore
flow over the coastal waters through tonight. Slowly backing wind
directions will range ene to e with speeds 10 kt or less this
morning, increasing to near 15 kt tonight. seas will be on a slow
uptick with 2 ft sea heights building to 3 to 4 ft tonight.

Saturday through Wednesday: The marine forecast remains low confidence
as it is highly dependent on evolution of a low pressure system over
the Western Atlantic. On Saturday, pressure gradient will tighten
as an area of low pressure lifts northeast towards the area and
potentially develops into a tropical or sub-tropical system. This
will result in northeast winds increasing to 15-20 knots.
Thereafter, models differ greatly on the strength and track of the
low, but general consensus takes the low into Charleston county
Sunday afternoon. Then, it could either lift northeast or remain
spinning in the vicinity through early next week. Given this
uncertainty, significant changes should be expected in future
forecast packages.

Rip Currents: An increased risk of rip currents for the upcoming
holiday weekend appears likely as onshore flow and swell energy
increases in advance of an approaching low pressure system.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...Dense Smoke Advisory until 9 AM EDT this morning for SCZ045-
     050-052.
MARINE...None.

&&

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



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