Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 060310

Area Forecast Discussion
National Weather Service Columbia SC
1110 PM EDT Mon Jun 5 2023

Warm weather continues to build for Tuesday and Wednesday with
some chances for showers and storms each day. Rain chances
should be highest on Thursday as a front slowly crosses the area
before more typical summer weather returns for late week and
the weekend.


Convection continues to struggle over the mountains with only a
few cells on regional WSR-88D returns. Although instability
remains weak to moderate across the central and western
portions of the forecast area with sunset and temperatures
falling into the low to mid 70s expect instability to diminish
quickly over the next couple hours. By 06z low and mid level
lapse rates will be less then 6.0 C/Km and with minimal forcing
expect only a few showers moving through the central portions of
the forecast area overnight. As such have lowered pops through
the overnight with mainly low chance pops in the western
Midlands and slight chance elsewhere. Overnight lows will be in
the low to mid 60s.


Large scale synoptic pattern will be fairly similar to the past
few days to start the period, but models indicate that it will
begin breaking down by Wednesday night. A strong, 99th
percentile 500 hPa ridge will still be centered over the
southern Canada prairies, with a deepening closed low over
southeastern Canada. We`ll continue to experience weak troughing
across the region early Tuesday. Shortwave in the flow will
have pushed to our southeast by Tuesday morning, with
northwesterly flow persisting. Expectation is that by Wednesday
night, the ridge will have weakened significantly and shifted
its primary axis in two directions - across western Canada and
then another axis through the Hudson bay. This progression will
force the closed low to intensify and retrograde back over
Maine. As this happens, shortwaves will continue to push through
the flow before a primary, strong shortwave pushes towards the
region on Wednesday night. At the surface, a weak boundary will
be persistently set up to our north on both days. With dewpoints
in the mid 60s and high temperatures in the upper 80s and low
90s both days, instability is forecast to develop south of the
boundary. The SPC has part or all of the area in a Marginal Risk
for severe storms on both Tuesday and Wednesday, mainly for
isolated damaging winds/large hail.

The issue is that on Tuesday, I don`t expect coverage to be all
that impressive. The shortwave from today will be well to our
east, and there won`t be another one to replace it during peak
heating. Additionally, the convergence along the front will be
marginal at best, leading to scattered coverage as the best case
scenario. This trend is shown well in the 12z HREF suite, as
none of the models warrant PoPs higher than 30% across the FA.
Still, we will have >1000 j/kg of CAPE and a weak boundary, so
isolated to scattered storms are still expected. With deep
mixing tomorrow, expect damaging winds to be the primary threat
with the strongest storms. Wednesday looks fairly similar,
though the timing of everything is a bit worse. The front will
be coming through at night, with little forcing for anything
during the day. So I don`t think there is a significant severe
threat with the activity Wednesday, either. I do think there
will be storms within the rain overnight, though, as guidance
suggest we will hang onto modest instability. Highs both days
will be around 90, with lows in the low/mid 60s.


Pattern change will continue on Thursday, as a deep and closed
mid/upper level low stalls and spins around across the
northeastern US. This closed low will have multiple spokes
rotating through it, with the central trough axis pushing over
and through the region on Thursday. The cold front from
Wednesday will be pushing through by 8a Thursday, with the
southern half of the FA still in the warm sector of it. Guidance
is fairly split on rain chances for Thursday, but I think the
trend is generally lower when compared to Wednesday and
Wednesday night. Some showers are possible across the southern
half of the area by the afternoon hours, but I am not confident
that there will be significant coverage. The severe threat looks
minimal. Look for highs in the upper 70s and low 80s across the
FA, with clouds remaining widespread even despite the frontal
passage. Lows overnight will be seasonally cool as a very dry
airmass pushes in from the north - lows should be in the mid to
upper 50s.

From there, the pattern will continue to evolve across the
eastern  US in the weekend. Ensembles and operational models
are in decent agreement on the Friday through Monday period,
with increasingly warm temperatures each day and dry weather
persisting through Saturday. Winds will shift out of the south
and southwest by Saturday, increasing moisture across the region
and helping bump temperatures up as well. Expect seasonal highs
in the mid-upper 80s Friday and highs near 90 on Saturday. The
weather begins getting interesting on Sunday and Monday. Models
are in good agreement for this time range, especially with
respect to how they have been performing recently, so take that
for what it is worth. Nevertheless, they are showing the front
from late this week, which will be stalled to our south and
southwest, lifting northward towards us on Sunday. This occurs
as a large area of low pressure begins to develop across the
central and eastern US in response to a sharp and strong
shortwave digging out of Canada. Widespread moisture is expected
to return to the forecast area, and ensembles are actually
showing good (40-60%) probabilities of >500 j/kg of CAPE on both
Sunday and Monday. As a result, I`m expecting at least
scattered storms on Sunday with the lifting front, and then more
widespread convection with the primary system on Monday. We are
several days out from this being an issue, but the ensemble
means agreeing with one another and their operation counterparts
gives confidence that the pattern is likely to push in this
direction late in the period. There could be a severe threat
with this, but it is too early to get into the weeds with that
just yet. Look for highs to be seasonal and in the mid 80s to
lower 90s, with overnight lows quite warm (mid-upper 60s) due to
the increase in moisture.


VFR conditions expected through the period with brief
restrictions possible during the late night/early morning hours

Satellite imagery show some scattered low clouds across the area
with mainly cirrus from upstream convection drifting over the
terminals. Overnight there is potential for scattered convection
mainly at CAE/CUB as an upstream disturbance moves toward the
area. Convection has been slow to develop with this disturbance
so confidence in showers and associated restrictions continues
to diminish and have kept mention out of TAFs. With sunrise and
heating diurnal cumulus will again develop and winds will become
SW around 8 knots.

EXTENDED AVIATION OUTLOOK...Scattered mainly afternoon showers
and thunderstorms and associated restrictions possible through
Thursday however confidence in coverage remains low at this




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