Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 271759

Area Forecast Discussion
National Weather Service Charleston SC
159 PM EDT FRI MAY 27 2016

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.


Today: deep layered dry air and subsidence will maintain mostly
sunny skies with highs in the mid to upper 80s. Few to scattered
cumulus will likely develop along the sea breeze and quickly push
inland this afternoon given the prevailing onshore flow.

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.


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.


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.


VFR at KCHS/KSAV through 12Z Sat though there is a small chance
for MVFR ceilings at KCHS around daybreak Sat. Increasing chances
for showers moving into the KCHS terminal during the day Sat but
the best chances will be after 18Z when the Atlantic low moves
closer to the coast.

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


Low pressure northeast of the Bahamas and sprawling high pressure
from Bermuda to the mid-Atlantic states will maintain onshore flow
through tonight. Slowly backing wind directions will range ENE to
E 10 kt or less this morning, increasing to near 15 kt tonight.
Seas will be on a slow uptick with 2 ft 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.




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