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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

                            
000
FXUS62 KCHS 231955
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
355 PM EDT Thu May 23 2019

.SYNOPSIS...
Unseasonably hot high pressure will dominate into late next
week. 

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 350 PM: The latest Cirrus Band from GOES-East indicated a
thin veil of cirrus drifting SE across the Carolinas. Fair 
weather Cu across the inland counties have decreased with the 
arrival of the thin high clouds. As a result, the isolated 
showers over northern Charleston County have dissipated. Radar 
returns over the outer SC waters is associated with chaff. Given
the deep ridging across the forecast area, I will keep the 
forecast through tonight dry. Using a blend of MOS, I will 
forecast low temperatures in the upper 60s inland to the low to 
mid 70s along the coast.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
High confidence this period that temperatures will remain much above 
normal with rain chances much below normal as deep-layer high 
pressure dominate the weather pattern. A backdoor cold front looks 
to approach from the north Friday night, possibly making it to 
around the Savannah River before dissipating and getting absorbed by 
an inland trough. This pattern will then persist through the rest of 
the weekend. 

The best chance for any rain should be across SC on Saturday with 
the front in the area and increased low-level moisture. Isolated 
thunderstorms will be possible, mainly in the afternoon, possibly 
becoming marginally severe with damaging winds due to the high 
amount (1000+ J/kg) of downdraft CAPE according to model soundings. 

Temperatures will definitely be the big story however with highs 
peaking well above normal near record levels (see Climate section 
below), especially by Sunday when lower 100s will be possible 
inland. Heat indices are forecast to peak around 100 degrees inland 
Friday and then closer to 105 degrees by Sunday when our first Heat 
Advisories of the season may be needed. Interestingly, Saturday 
could end up being a bit warmer than forecast depending on the 
potential for some frontal compression. Unfortunately overnight lows 
will also be well above normal which means not much relief is 
expected. 

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
There does not appear to be any relief in the dangerous and 
prolonged heat wave through at least Thursday. Continued sinking 
motion, a dry atmosphere above the boundary layer which will result 
in nearly full sun, a dry ground, and 850 mb temperatures generally 
within a degree or two of 20 Celsius all point to high temperatures 
from 97 to 103 degrees away from the coast. Heat indices at or above 
105 which would prompt a heat advisory may occur on any of the days. 
The need for a heat advisory seems mostly likely to be needed on 
Monday and/or Tuesday. Air quality issues may develop at any point 
during this period due to the excessive heat and generally stagnant 
air pattern. Even though winds will be on the lighter side, hot 
conditions and dry fuels could aid in the development of wild fires.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
VFR.

Extended Aviation Outlook: VFR.

&&

.MARINE...
The center of sfc high pressure will slide south across the marine 
zones tonight. Winds are forecast to shift from the southeast to 
south during the overnight hours, speeds remaining around 10 kts. 
Wave heights between 2-3 ft should remain common across the
waters.

Friday through Tuesday: Summer-like pattern will prevail with 
Atlantic high pressure to the east. This will lead to increasing 
winds during the afternoon as the sea breeze develops near the coast 
which will then subside a bit overnight but not much. Overall wind 
gust should stay 20 knots or less and with seas about 3-4 ft or less 
we don't anticipate any Small Craft Advisories will be required. 

&&

.CLIMATE...
A very significant, hazardous and prolonged heat wave will challenge 
or break many of these records.

RECORD FOR THU 05/23...

Station     Record High Min   Year
-------     ---------------   ---- 
KCXM            77            1998 

RECORDS FOR FRI 05/24...

Station     Record High       Year(s)
-------     -----------       -------
KCHS            97            1953
KSAV            98            2011, 1953

RECORDS FOR SAT 05/25...

Station     Record High       Year(s)
-------     -----------       -------
KCHS            97            2000, 1953
KSAV           100            1953

Station     Record High Min   Year(s)
-------     ---------------   -------
KCHS            75            1953
KSAV            76            1878
KCXM            79            1998

RECORDS FOR SUN 05/26...

Station     Record High       Year(s)
-------     -----------       -------
KCHS            98            1953
KSAV           100            1953

Station     Record High Min   Year(s)
-------     ---------------   -------
KCHS            75            1998
KCXM            79            1998

RECORDS FOR MON 05/27...

Station     Record High       Year(s)
-------     -----------       -------
KCHS            98            1989
KSAV            98            1989, 1962
KCXM            95            1962, 1926

Station     Record High Min   Year(s)
-------     ---------------   -------
KCHS            76            1991
KSAV            77            1878
KCXM            78            1991

RECORDS FOR TUE 05/28...

Station     Record High       Year(s)
-------     -----------       -------
KCHS            97            1967, 1964
KSAV            96            1964, 1898
KCXM            93            2000

Station     Record High Min   Year(s)
-------     ---------------   -------
KCHS            76            2000
KSAV            76            1885
KCXM            80            2000

RECORDS FOR WED 05/29...

Station     Record High       Year(s)
-------     -----------       -------
KCHS            95            1945
KSAV            98            1945, 1898

Station     Record High Min   Year(s)
-------     ---------------   -------
KCHS            76            2018
KSAV            75            1885
KCXM            77            1998

RECORDS FOR THU 05/30...

Station     Record High       Year(s)
-------     -----------       -------
KCHS            95            2004
KSAV           101            1898

Station     Record High Min   Year(s)
-------     ---------------   -------
KCHS            75            1982
KSAV            75            1924
KCXM            78            1998

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$
NEAR TERM...NED
SHORT TERM...RJB
LONG TERM...
AVIATION...NED
MARINE...NED/RJB
CLIMATE...