Area Forecast Discussion
Issued by NWS Huntsville, AL

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735
FXUS64 KHUN 240510
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1210 AM CDT Thu May 24 2018

.UPDATE...
For 06Z TAFS.

&&

.NEAR TERM...(Tonight)
Issued at 836 PM CDT Wed May 23 2018

Much of the shower/storms this afternoon and evening have remained
W/S of the area. This is a result of high pressure building across
the OH Valley. 00z soundings from OHX/BMX show vastly different
environments and were likely closer to what the OHX sounding looked
like today. A few light showers continue along remnant outflow
boundaries and along the higher terrain in eastern TN. For the moment
have held onto low end PoPs but have removed all mention of thunder
from the grids for tonight as we lack any real forcing and the drier
profiles evident to our north should prevent any storms from
developing.

Temps overnight should end up pretty close to values last night in
the mid to upper 60s. There is still some debris cirrus from storms
to our south moving over the area but think by midnight skies should
start to clear. If this is the case, we could end up with a bit more
fog than last night with the best chances in river/valley locations.
We`ll keep an eye on trends tonight and see if any patchy dense fog
might be possible. The rest of the forecast is in good shape.

.SHORT TERM...(Thursday through Friday night)
Issued at 238 PM CDT Wed May 23 2018

On Thursday, the mid to upper level ridge should suppress convection
overall as the convergence zone today will likely shift even further
south. However, a weak upper level MCV is noted in the NAM drifting
northeast into north AL/south TN, so have held onto a 15-20 PoP
Thursday afternoon. Highs should warm into the u80s-a90 Thursday
afternoon with a bit more mixing up to 825-850mb. CAPEs also look
quite skinny as compared to today.

Low level flow will become more southerly on Friday into Friday night
as mid-upper flow also becomes southwesterly in response to the
trough advancing into the lower MO and mid MS valley. The shifting to
more southerly flow alone will advect deeper moisture and PW`s above
1.5 inches and dew points to around 70 or into the lower 70s.
Resulting CAPE values may exceed 2000 j/kg once again. Thus,
thunderstorm chances return Friday afternoon, with at least scattered
coverage expected. Generally weak southwesterly oriented mid-high
layer shear will continue to steer thunderstorms northeastward into
the nighttime hours. There will be a diurnal component with these,
but will maintain a chance PoP through at least 06Z/26.

.LONG TERM...(Saturday through Tuesday)
Issued at 238 PM CDT Wed May 23 2018

The extended portion of the forecast can be summed up in one word:
soggy. There will be daily chances for showers and storms, between
40-60% each day, and overnight chances for showers and storms as well
(30-50%). This is all in response to an upper/sfc low that will form
and move inland somewhere in the northern GOMEX. Depending on your
model of choice, that `landfall` will be between the E Coast of FL
and the SErn portion of LA. The GFS is currently the outlier with the
farthest E `track` over FL, but most model consensus is with the
Wrn-most tracks, coming ashore over SErn LA and the meandering N/E
from there later next week. That said, exactly where this feature
ends up going, this will heavily weight the PoPs/Wx for late this
upcoming holiday weekend throughout much of next week. While there`s
no preferred day for torrential rainfall, and gusty winds up to
40mph, these threats will be especially important to note for anyone
celebrating Memorial Day outdoors (with the threat for lightning as
well). PWats increase over the weekend from 1.7" to upwards of 2" by
Sunday/Monday, lingering between 1.8-2" for the entire week ahead.
This may lead to some hydrologic concerns by next weekend, depending
on the amount of rainfall received each day and which basin that
runoff filters into. For now, storm total for the weekend/Memorial
Day is upwards of 2-3", but again, that is heavily dependent on
individual thunderstorms and where they form/train. As such, these
threats have been highlighted in the HWO, especially for the upcoming
holiday weekend.

Daily temps this weekend and much of next week will be in the
lower/middle 80s for aftn highs, and upper 60s to around 70 degrees
for overnight lows.

Late in the extended, the upper pattern shifts a bit such that the
CWFA will be sandwiched in-between the Bermuda High to the E/SE and a
building ridge to our W over TX/LA. This will help squeeze out any
remaining moisture lingering from the sub/tropical system that
arrived and meandered around the region, with hopefully a pattern
change (or at least a break) by next weekend from the soggy/humid
conditions recently. The upper ridge to the W moving E should help
dry things out and end the daily chances for rain.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1210 AM CDT Wed May 23 2018

VFR conditions are expected to continue across north AL/southern
middle TN for the next 24 hours. Fog formation may occur between
10Z-13Z but not enough confidence to include in the TAFs at this
time given high cloud cover across the area and likely patchy nature
to the fog. May amend if any patchy fog begins to reduce the VIS.
Isolated storms may also develop late in the period between 18-00Z.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

NEAR TERM...Stumpf
SHORT TERM...17
LONG TERM...BCC
AVIATION...SL.77


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