Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 230510

Area Forecast Discussion
National Weather Service Huntsville AL
1210 AM CDT Fri Mar 23 2018

For 06Z TAFS.


.NEAR TERM...(Tonight)
Issued at 850 PM CDT Thu Mar 22 2018

High pressure that is currently to our north will be shifting east
through the night. Expecting winds to be light and variable overnight
and should allow temps to fall quickly this evening. However, off to
the west a low pressure system was forming in the Lee of the Rockies
with a warm front extending E/SE towards W TN. The system is forecast
to lift due north but a few shortwaves will move across the southern
Plains and TN Valley tonight. The lift associated with these weak
waves will be enough to generate some mid-level cloud cover. Some of
these clouds can already be seen taking shape on the SW flank of the
warm front near the KS/OK/MO border. With clouds increasing believe
that temps should stay above the freezing mark. The only exceptions
might be in the favored cool spots in NE AL and S Mid TN. Based on
that idea did nudge lows down a degree or so for much of the area.

Latest hires guidance suggest some very light rain showers may
develop along the boundary mentioned above. However, with much of
this forming between 8-10kft and decent amount of dry air near the
surface, think anything that does form will end up as virga. So, have
kept PoPs dry tonight for those reasons.

.SHORT TERM...(Friday through Saturday Night)
Issued at 218 PM CDT Thu Mar 22 2018

The warm advection regime will expand precipitation across the upper
Midwest into the lower TN valley on Saturday. The southern extent of
the best lift and moisture will remain in this zone to our north-
northwest through Friday, so have kept our forecast dry at this time.
As the 8h-7h flow becomes more west-southwest Friday night into
Saturday, a capping inversion will likely suppress any chance of deep
convection in the warm sector, including our forecast area. However,
model soundings indicate low level moistening will be sufficient for
a few light rain showers or sprinkles later Friday night into
Saturday. As the surface low tracks into southern KY and middle TN
Saturday night, SB-CAPE may increase a bit along and just in advance
of the trailing cold front through southeast MO and AR. However,
this becomes very diffuse to non-existent as the front tracks
southeast as the 8h flow veers to the west/west-northwest. This is a
likely sign that the warm sector may become even more effectively
capped off. However, will keep a low to moderate chance of light
showers going through Saturday night as a weak cold front drops
southeast given modest convergence and moisture beneath the capping

.LONG TERM...(Sunday through Wednesday)
Issued at 218 PM CDT Thu Mar 22 2018

Weak upper ridging will try to build eastward on Sunday, while a
weak frontal boundary remains draped in the vicinity of the TN
Valley. Given the weak nature of this boundary, models differ
somewhat on the placement, however its proximity will bring scattered
light showers across the area during the day Sunday. Despite cloud
cover and precip, temperatures will still be able to warm into the
mid to upper 60s given the weak low and mid level height rises. Rain
chances will increase overnight Sunday, into Monday, as a shortwave
rounds the northern periphery of the ridge and southerly flow returns
at the surface as the boundary lifts further north. A fairly strong
cap should keep the area stable for the most part, so not
anticipating any thunder with this wave.

As the upper ridge continues to shift east on Monday, additional
waves are expected to move across the area. Meanwhile, at the
surface, high pressure will try to build along the east coast and
then funnel into the TN Valley. This CAD set-up will bring an
easterly flow at the surface and keep temperatures rather cool on
Monday, compared to those on Sunday, with highs only warming into
lower 50s across the east to lower 60s across the west. Although this
may also limit the coverage of precip during the day Monday, have
kept high chance pops in for the area. A low level inversion will
persist through the day thanks to the cooler surface temperatures and
building low level ridge, so only looking at light showers with no
thunder anticipated.

The axis of the upper ridge will shift east of the area on Monday
night as a trough digs southward out of Canada, with southerly flow
returning at the surface. Although lingering light rain is possible
late Monday evening, the coverage of precip will diminish through the
overnight hours. With cloud cover and southerly flow, temperatures
will only fall into the mid 40s to lower 50s Monday night. A dry day
is in store on Tuesday as the TN Valley remains on the western
periphery of the upper ridge. Despite lingering cloud cover,
temperatures will warm into the mid to upper 60s by Tuesday
afternoon. A cold front associated with the aforementioned trough
will push eastward and into Ohio and Lower Mississippi Valley Tuesday
night. This front will bring our next shot of widespread showers,
potentially heavy at times, beginning as early as Wednesday. Models
differ on the overall solution of this front, but the best chances of
rain look to come just beyond the forecast period.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1210 AM CDT Fri Mar 23 2018

Light and variable winds will continue through the early morning
hours with winds less than 10kts for the rest of today. Bkn to ovc
cigs around 8kft will move in late this morning and remain through
the TAF period. VFR conditions are expected.




NEAR TERM...Stumpf

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