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000
FXUS64 KHUN 060808
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
308 AM CDT Thu May 6 2021

.NEAR TERM...(Today)
Issued at 308 AM CDT Thu May 6 2021

Temperatures vary a good bit early this morning. The sheltered
valleys of northeast Alabama and southern Middle Tennessee have
dropped down into the mid 40s with low 50s in locations that are
reporting light winds. Temperatures should continue to fall a couple
of more degrees before sunrise with most locations starting the day
in the mid to upper 40s. There is some patchy fog in these sheltered
valleys this morning and expect conditions will improve quickly after
sunrise.

The upper level pattern is characterized by a broad longwave trough
across the Eastern 2/3rd`s of the CONUS with a ridge over the Western
CONUS. At the surface, high pressure is centered to the north of the
area across the Ohio River Valley. An area of low pressure is
centered across northwestern Illinois with a cold front stretching
to the southwest into the central Plains. This cold front will race
to the southeast today into the Mid-Mississippi River Valley and
eventually into the Tennessee River Valley later this evening. The
atmosphere across the Tennessee Valley is rather dry currently with
PW values around 0.4-0.5 inches. Westerly to northwesterly flow ahead
of the front will limit moisture ahead of this boundary with PW
values only climbing into the 0.7-0.8 inch range. These values are
still below the median value for early May. A shortwave trough will
swing through the region late this afternoon and into the evening
with rather impressive height falls. These height falls will lead to
steep mid-level lapse rates. The main limiting factor will be the dry
air. Model soundings are more reminiscent of inverted-V soundings
from out west. SBCAPE values are generally under 500 J/Kg. Deep layer
shear is supportive to maintain updraft intensity. However, with the
low SBCAPE and dry airmass, do not anticipate anything more than a
strong storm or two. The main threat with these storms would be gusty
winds and small hail. The window for this activity would also be
small from roughly 22z-03z.

Otherwise, expect skies will be mostly sunny today with the dry
airmass in place. Clouds will increase later this afternoon ahead of
the approaching front. Highs today will climb into the low 70s for
most locations.

.SHORT TERM...(Tonight through Saturday)
Issued at 308 AM CDT Thu May 6 2021

Drier and cooler air will advect into the Tennessee Valley tonight
behind the departing cold front. High pressure will be centered to
the west across Arkansas with northerly to northwesterly winds
forecast overnight. PW values will crash down into the 0.2-0.3 inch
range. All of these conditions will set the stage for another cold
night with lows down in the mid 40s Friday morning. The dry airmass
will continue during the day on Friday with sunny skies forecast.
Temperatures will warm into the upper 60s to low 70s. Surface high
pressure will continue to slowly drift to the southeast Friday night.
Dry conditions will continue with lows in the mid 40s to low 50s.

Seeing a good bit of model disagreement going into the day on
Saturday. There is a surface boundary that will set up over the area
or just to the north. A weak shortwave trough within the
northwesterly flow aloft will lead to light showers developing along
this boundary. The latest NAM and GFS indicate a round of light
showers across southern Middle Tennessee and northeast Alabama late
Saturday morning into the afternoon and due to these showers,
temperatures remain in the 50s all day in these locations. The ECMWF,
Canadian, and majority of the GFS Ensembles are much further north
with this boundary keeping the precipitation well to the north in
Tennessee and Kentucky. For the forecast, decided to carry a slight
chance PoP north of the Tennessee River on Saturday to account for
these further south solutions. Regardless, any precipitation that
does develop should be light and not amount to more than a few
hundreths of an inch.

.LONG TERM...(Saturday night through Wednesday)
Issued at 308 AM CDT Thu May 6 2021

Models indicate that this surface boundary eventually pushes to the
north Saturday night into Sunday as the 850 mb ridge axis shifts to
the east. Overnight lows Saturday night into Sunday should be a bit
warmer with the front to the north. Expect lows will be in the mid to
upper 50s for most locations.

The latest model guidance is a bit slower with the system on Sunday
and beginning to think that much of the day could be dry. There isn`t
much forcing in the warm sector on Sunday. However, skies will be
cloudy and southerly winds will be rather strong in the 10-15 mph
range with gusts up to 25 mph. Due to the latest guidance, decreased
PoPs on Sunday. Better chances of showers and storms will arrive late
in the day on Sunday into early Monday morning. Not thinking there
will be a risk for strong to severe storms due to the lack of
instability with the timing and the lack of any strong forcing.

Models differ on how far south the boundary will make it. Due to
this, showers/storms continue throughout much of the long-term
forecast period.

Temperatures will continue to be on the cooler side of climatology
into next week with highs generally in the upper 60s to low 70s and
lows in the upper 40s to low 50s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1053 PM CDT Wed May 5 2021

VFR flight conditions will persist through the TAF period at both
terminal locations. Some patchy fog development is possible during
the early morning hours, but confidence is not high enough to include
in TAFs at this time. Northwesterly flow will continue Thursday, with
afternoon wind gusts to 15kts possible.


&&

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

$$

NEAR TERM...MA
SHORT TERM...MA
LONG TERM...MA
AVIATION...25


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