Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 222302
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
602 PM CDT Thu Jun 22 2017

.UPDATE...
For 00Z TAFS.

&&

.NEAR TERM...(Tonight)
Issued at 326 PM CDT Thu Jun 22 2017

A couple of concerns for this afternoon and into this evening. The
first is the threat for strong to severe storms, which could impact
the eastern half of the area. We`ve been watching the storms moving
north out of the Birmingham area and the rainfall from this morning
has kept temperatures on the cooler side, which has prevented any
deeper updrafts from developing. However, the clearer skies over
eastern AL/western GA allowed temps to warm up into the low to mid
80s and with the strong S/SE flow pointed directly at our NE AL
counties temps have gradually warmed in the past hour or two. The
storms are starting to maintain their strength as they move into
Blount county and approach Marshall/DeKalb counties. Both wind shear
and low level helicity values are extremely favorable for tornado
development and we will be watching the storms very closely this
afternoon. With that said, there is potential for a few stronger
storms to develop over central/northern MS as the clearer skies have
allowed temps to warm into the mid to upper 80s. These may clip far
NW AL but storms will be more isolated in nature based on latest
GOES-16 visible imagery showing limited CU development.

The second concern for this afternoon and tonight is the potential
for flash flooding. Areas along and east of I-65 have received
upwards of 2-2.5 inches of rain from storms this morning. The
showers/storms moving through central AL will be moving right over
where the heavier rain fell earlier today. PWATs via the 12/18z BMX
sounding are upwards of 2.5 inches and we could easily see those
type of amounts fall in an hour in the stronger storms. Thankfully,
we`ve had a break in the rainfall and that has allowed for some
stabilization in the runoff and reports from those counties suggest
only ponding of water in low lying areas at this time. But the influx
of these heavier storms and potential for an additional 1-2 inches
of rain this afternoon could result in localized flash flooding.

Have decided against issuing any type of Flash Flood Watch as we
would only be concerned with the next few hours for NE AL and at
this point it`s too late for one. Will mention flooding concerns in
HWO and other public products.

For the rest of the evening we can expect a gradual downward trend in
the coverage of rainfall as the drier air that is wrapping around the
eastern side of TD Cindy will keep precip limited. This additional
break in rainfall will help with any flooding that develops this
afternoon before additional rain arrives on Friday. As TD Cindy
begins to lift N/NE up through LA/AR this evening, expect winds to
increase with gusts of 20-25 mph possible tonight. The wind and
cloudy conditions will keep temps on the warmer side and values are
only forecast to drop into the low to mid 70s.

.SHORT TERM...(Friday through Saturday night)
Issued at 326 PM CDT Thu Jun 22 2017

For Friday, TD Cindy is expected to weaken to a post-tropical
cyclone as it moves further inland. The current forecast track will
take it through western TN Friday morning and then up across northern
TN/southern KY during the day. We can expect winds to be a bit higher
on Friday as we are closer to the center of the system and gusts up
to 30 mph are possible. Wouldn`t be surprised to see a few isolated
reports of 35-40 mph in a few locations tomorrow.

With the storm to our north during the day we can expect partly
cloudy skies, which should allow for temps to warm into the mid 80s.
Those values combined with dewpoints remaining the low to mid 70s
should be more than enough for the development of strong to severe
storms on Friday. While the shear vectors and overall low level
helicity values won`t be as strong as this afternoon, the potential
for more vigorous thunderstorm development should allow for an
increased threat for severe storms. Tornadoes, damaging wind gusts,
and flash flooding will be the hazards with storms tomorrow. We
remain in a Slight Risk via SPC and that is warranted based on the
parameters expected tomorrow.

The only good news in terms of flooding threat is that the areas that
received the heaviest rain today are expected to see lower values on
Friday and the areas that haven`t seen much will get the brunt of the
rainfall tomorrow. With QPF values forecast to remain below flash
flood guidance for much of the area have held off on issuing any type
of Flash Flood Watch for tomorrow as well. Will be mainly concerned
with any type of banding/training of storms tomorrow.

The remnants of Cindy will be pushed off to the east by a cold front
that is expected to drop into the area behind the departing system.
Models have delayed the arrival of the front a bit compared to
previous guidance and don`t move it completely through the area until
Saturday afternoon/evening. So, adjusted PoPs a bit to leave them in
a bit longer on Saturday. Drier air in the lower levels will be quick
to rush in during the day Saturday and likely keep any activity
limited to showers. By Saturday night all precip will be south of the
area and much cooler air spreads in with overnight lows Saturday into
Sunday will be in the low to mid 60s. This will be a welcome change
from the high humidity values we have had the past past few days.

.LONG TERM...(Sunday through Wednesday)
Issued at 326 PM CDT Thu Jun 22 2017

Dry conditions will persist through the long term period, as surface
high pressure slides southward into the region. Temperatures will be
on the "cool" side for late June, given a broad upper level trough
that will remain anchored over the eastern CONUS. High temperatures
will generally remain in the lower 80s on Sunday through Tuesday,
with a gradual warming trend beginning Wednesday. Under good
radiational cooling conditions, overnight lows will cool into the
upper 50s each night.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 600 PM CDT Thu Jun 22 2017

Large expanse of rain/embedded convection associated with remnants of
Cindy continue to move off to the northeast early this evening. Thus
expect a general lull in the precipitation for most areas across
north Alabama through the overnight hours, though will maintain
vicinity shower wording for occasional light/scattered development at
both TAF sites. Pressure gradient will remain rather tight due to
associated low pressure system and kept gusty winds in the forecast
through the period. Based on movement of the remnant low and a rather
unstable atmosphere expect an abundance of shower/thunderstorm
development during the midday/afternoon hours on Friday and trended
TAFs as such. Otherwise, the very moist/tropical environment will
maintain fairly low ceilings and kept predominant MVFR CIGS in
through the period.

&&

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

$$

NEAR TERM...Stumpf
SHORT TERM...Stumpf
LONG TERM...Barron
AVIATION...15


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at weather.gov/huntsville.



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