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Area Forecast Discussion

FXUS62 KCHS 241409

Area Forecast Discussion
National Weather Service Charleston SC
1009 AM EDT TUE MAY 24 2016

High pressure will gradually shift off the Southeast coast by
late today. The region will then remain under the western
periphery of Atlantic high pressure through Friday. A wave of low
pressure may develop offshore over the weekend, before dissipating
or moving away early next week.


Rest of today: Tuesday morning forecasts remained in great shape
and required no significant changes. The 12z KCHS sounding
revealed a shallow zone of enhanced moisture around 8 kft agl, so
the combination of patchy altocumulus and diurnal cumulus will
produce partly sunny skies at times. Even so, temperatures away
from the coast are still expected to recover into the mid/upper
80s at many locations. On the beaches, the early developing sea
breeze will hold temps in the 70s. Some high resolution guidance
depicts a few showers developing along the inland-progressing sea
breeze this afternoon/early evening, but a building ridge/warming
temps aloft and the dry environment samples by the 12z KCHS
sounding suggest that the chance for measurable precipitation
will remain very low today.

Tonight: Ridging will prevail aloft and high pressure will remain
centered to the east, promoting a mild south to southwest flow. The
forecast continues to be dry with milder temperatures. Lows are
expected to fall into the low to mid 60s in most areas.


Wednesday: Sub-tropical Atlantic high pressure will be established
across the area, while aloft ridging will also develop as an
anticyclone over Mexico builds over parts of the southeast. While
there is a subtle short wave that moves through Kentucky and
Tennessee from today that arrives in the afternoon, given the lack
of any appreciable moisture where PWAT is only near the 25th
percentile, we have maintained a rain free forecast. We stayed
close to the low level thickness forecast in regards to max temps,
showing highs mainly in the upper 80s, with a few places 90 over
interior Georgia.

Thursday: The Atlantic ridge is shunted a little to the north and
northeast as a wave of low pressure forms underneath a cut off low
near the Bahamas island chain. Locally this pattern produces a Col
region aloft, but with heights lower than 24 hours prior. Again
there is little significant moisture and other than the sea breeze
no forcing for convection. So another day with the lack of any
rainfall. 850 mb temps are expected to reach near the 75th
percentile for late May, and supports max temps similar to

Friday: The cut off low found about a few hundred miles off the east
coast of Florida will start to drift northward and pulls an
associated surface wave or very weak area of low pressure along with
it. This surface system, should it form, may start to have some
tropical or sub-tropical characteristics. But there remains enough
subsidence over South Carolina and Georgia to maintain another day
without any showers or t-storms. A deeper easterly flow will knock
down max temps a couple of degrees from the previous 2 days.


Considerable uncertainty this weekend and into early next week,
pending the formation of some sort of sub-tropical or hybrid system
that will lift into a position somewhere over or near the forecast
area. If model consensus is accurate and any system remains weak,
then climatologically speaking it would likely stay off our coast.
But whatever it does it will be a slow process as it remains trapped
beneath the upper low that is rather sluggish in moving northward
due to ridging to the north. Eventually the upper low could become
absorbed into a larger and stronger trough over the eastern states
late in the period. Our forecast for the long term is highly
conservative, with no more than chance Pops each day. Should the
system stay over the Atlantic we`d be on the drier side, whereas if
it moves into the area or to the south it could bring some decent
rains. It is worth noting that both the GFS and the CMC Phase
Diagram shows a Symmetric Warm Core system. So, expect many
adjustments to the forecast over the next several days. Temps will
be near or above normal into early next week.


VFR through 12Z Wed.

Extended Aviation Outlook: VFR through at least Friday, with low
end chances of flight restrictions Saturday.


Rest of today and tonight: High pressure will shift off the
southeast coast this afternoon and will remain situated just to
the east through the overnight. Light onshore winds to start will
become more uniformly south to southeast due to the combination of
the high pressure and the sea breeze circulation this afternoon.
The strongest winds will occur along the land/sea interface with
the sea breeze and will likely top out in the 10-15 knot range.
Overnight, winds will be south to southwest and no stronger than
10-15 knots. Seas through this period will remain 1-2 feet out to
20 nm and no higher than 2-3 feet beyond.

Wednesday through Thursday: Bermuda high pressure will be firmly in
control as it extends west across the marine area Wednesday,
before lifting a little northeast/east Thursday. The result will be a
somewhat summerlike pattern with south/southwest winds at or below
10-15 kt Wednesday, that back around to the east/southeast at
similar speeds Thursday. No convection will occur and seas will be
generally 3 ft or less.

Friday through Sunday:  A retreating Atlantic ridge and the approach
of a surface wave/weak hybrid low will produce more of an
east/northeast flow into the weekend. The gradient doesn`t appear to
be too strong at this time, with winds to remain below 15 kt or so.
However, seas will build some in response to the wave of low
pressure and some 6 footers might make it at least into the outer
Georgia waters at some point. Thus Small Craft Advisory conditions
may occur.

Rip Currents: Due to considerable uncertainty, it`s probably still
too early to include anything in the Hazardous Weather Outlook. But
there could be an enhanced risk of rip currents due to possible
swells late this week into the Memorial Day weekend should there
be some sort of low pressure wave in the Atlantic.


Grays Reef Buoy 41008 has been returned to service.





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