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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCAE 101807
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
207 PM EDT Sat Jun 10 2023

.SYNOPSIS...
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High pressure along with dry air will remain in control of the
region through early tonight. Moisture will quickly return to
the area tonight along with chances of showers and thunderstorms
for Sunday through Monday, with a front passing on Monday night.
A return to a more summertime pattern will begin early this
week along with chances of mainly diurnal showers and storms
Tuesday onward. There is the potential for a couple rounds of
strong storms later this week, but there are details to iron
out.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Seasonable temperatures this afternoon as dry air mass remains
in place. A few cumulus clouds and high clouds advecting east.

Deep upper low over the Canadian Maritimes with near zonal or
west- northwest flow aloft across the Carolinas and Georgia. A
relatively dry air mass remains in place at the moment with
precipitable water around 0.7 inches. The ridge will be off
shore this evening and overnight. This will result in an
increasing south flow and resulting moisture advection into the
area late tonight. Models suggest a warm front will move from
southern Georgia this evening to near the Savannah River by
daybreak. With some increasing clouds late tonight and warm air
advection developing, temperatures tonight are expected to be
about 10 degrees warmer than last night, lows in the mid 60s.
Any showers should remain across central Ga through daybreak as
moisture will be shallow.
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&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Deep trough that will be the key to our weather in the long term is
progged to begin digging into the Great Lakes on Sunday. This is the
head of an unusually meridional & complex mid/upper level pattern
across North America for this time of year, and the weather will
behave as such. The trough will begin closing off in between the
northern and southern streams of the jet stream on Sunday/Monday,
deepening and meandering over the Great Lakes through 12z Tuesday.
Southwest of this, a southern stream long wave trough will begin
interacting with this closed low by Monday, with multiple shortwaves
passing through the flow amidst increasingly strong westerlies. The
first shortwave trough is progged to move through on Sunday, with a
surface warm front preceding it across the southeastern US. This is
forecast to replace a very dry airmass with a moisture rich one by
midday Sunday, with showers and thunderstorms developing as a
response to the approaching shortwave. There is some uncertainty
regarding details, however. CAMs are all over the place regarding
destabilization by early tomorrow afternoon, ranging from nothing
across the area to ~1500 j/kg of MLCAPE depicted by the HRRR/RAP
across the CSRA. The truth is likely somewhere in the middle, but it
does look like there will be quite a gradient of CAPE across the
region due to the presence of low dewpoints at 850 hPa. My
expectation is that showers and storms develop across central GA and
the CSRA by 16z-18z tomorrow and progress eastward throughout the
day as the shortwave approaches. Strong, gusty winds are the primary
threat from any stronger storm, but even DCAPE in forecast soundings
looks <1000 j/kg. The soundings do look very moisture rich as the
trough approaches, with skinny CAPE being the characterization of
the profile across the CSRA. As such, heavy rain is almost a
certainty with the storms, and any training could cause some
localized flooding issues. Expecting a gradient in high temps from
west to east given the earlier timing of showers and storms. Highs
should range from the mid 80s west to near 90 in the east.

Some showers/storms may redevelop overnight as showers and storms
upstream push eastward. These are likely to weaken however, and I
think we`ll have some subsidence behind the parent shortwave. Will
still hold some PoPs overnight with this, and expecting lows to be
in the mid and upper 60s. The parent shortwave will be pushing
eastward by Monday morning, as timing on this has sped up quite a
bit in recent runs. The GFS and Canadian have our forecast area well
south of the best forcing by Monday afternoon, even as the surface
front remains to our west. I`m growing increasingly skeptical of
actually seeing much precip Monday afternoon, as CAMs are also
painting a big ole MCS that dives towards the FL Panhandle and would
rob us of big time moisture recovery. Will be bumping PoPs down on
Monday afternoon as a result of all of this. Highs still should be
in the mid and upper 80s, with lows in the mid 60s.
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&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
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An active long term period could be on tap, with at least multiple
days of storms possible. Additionally, a round or two of severe
weather is not out of the question, either. Aforementioned closed
low is shown by ensemble guidance to be slowly moving eastward
across the Great Lakes by Tuesday morning. Much drier air is progged
to be across the FA on Tuesday, with PWs below 1" across much of the
area behind Monday`s frontal passage. Highs will be seasonal in the
mid and upper 80s, with lows in the 60s. Front will begin to lift
northward again as a pseudo warm/stationary front, and is progged to
sit to our north again by Wednesday, with most guidance suggesting
it will stay this way for several days to end the week. The
placement of this boundary is key to our overall thunderstorm threat
later this week. This will be critical, as there will be plenty of
forcing through the end of the week. The closed low will slowly push
into the northeast, while also not dragging a strong front through
the area. So several shortwaves passing within anomalously strong
westerly flow (U Wind at 500 hPa 90th+ Percentile from Wed-Fri) will
certainly set us up from a shear perspective from strong storms,
with forcing in place as well. The real question is where the front
will set up during this period. South of the front, GEFS & CMC Ens
are painting high probabilities (>60%) of >1000 j/kg of CAPE
developing on these days. So the general ingredients are in
place to favor multiple rounds of at least strong storms later
this week, but the devil is in the details as always. I will
note that the shear/CAPE combo is impressive for this time of
year, so it bears close watching in the coming days. The CSU
Machine Learning probabilities certainly paint the picture of a
potential severe threat, honing in on Wednesday & Thursday
specifically. Seasonal, summertime weather is likely to return
next weekend with warm temps and more pulse convection as mid-
level flow looks to weaken a good bit. In summary, the long term
period looks potentially active, but there are definitely some
details to iron out over the coming days.
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&&

.AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
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VFR conditions expected through at least 06z. Low clouds may
develop near the AGS/DNL toward 12z but confidence low.

Pressure ridge and relatively dry air mass over the region
through this evening. The ridge will be moving off the coast and
south-southeast low level flow will develop. This will result
in an increase in low level moisture late tonight into Sunday
morning. Some guidance suggests stratus may develop near the
Savannah River toward morning but confidence is low on any
restrictions. Included MVFR fog at AGS toward daybreak due to
persistence and the increase in low-level moisture. High
resolution models suggest some convection will develop over
central GA late tonight and expected to move into the AGS/DNL
terminal area during the morning. Winds will be variable/ or
favor south this afternoon less than 10 knots. Light and
variable winds overnight and south-southwest 5 to 10 knots
Sunday.

EXTENDED AVIATION OUTLOOK...Periodic restrictions are possible
in afternoon convection Sunday associated with a warm front. A
cold front will approach from the west late Monday and scattered
thunderstorms expected ahead of the front. Diurnal showers and
thunderstorms midweek may lead to brief restrictions.
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&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.

&&

$$