Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 240923

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

High pressure will gradually move 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.


Today: The pattern aloft will begin with the upper low just off the
New England coast on a persistent northeastward track. In its wake,
500 mb heights will quickly build across the forecast area as broad
riding builds east of the Mississippi valley. At the surface, high
pressure will shift across the forecast area in the afternoon and
will set up off the southeast coast. Plentiful dry air will reside
in the mid and upper levels, with just enough moisture noted between
5-8 kft to result in a nice diurnal cumulus field. The forecast is
dry thanks to very warm mid level temperatures. The main forecast
issue for the day will be how much warmer surface temperatures will
get thanks to the increasing heights aloft and a shift to a
prevailing low level southerly flow. The forecast calls for a solid
coverage of mid 80s, with some potential for upper 80s closer to the

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 06Z Wed.

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


Today and tonight: Another quite period is on tap for the local
waters. High pressure will shift off the southeast coast today and
will remain situated just to the east through the overnight. Winds
this morning will be rather light and variable as the high shifts
through, becoming south to southeast this afternoon. The strongest
winds will occur along the land/sea interface with the seabreeze 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 will be
1-2 feet out to 20 nm, and 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 late this week into
the Memorial Day weekend should there be some sort of low pressure
wave in the Atlantic.




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