Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 162254

Area Forecast Discussion
National Weather Service Huntsville AL
554 PM CDT Wed Oct 16 2019

For 00Z TAFS.


.NEAR TERM...(Tonight)
Issued at 345 PM CDT Wed Oct 16 2019

Moderately strong northwest flow aloft will persist across the
region overnight, as the longwave trough axis which crossed the
region earlier today continues to deepen and shift eastward through
New England. At the surface, a ridge of high pressure will build
slowly eastward from the central Plains and should become centered
across the Ozarks/mid-South regions by 17/12Z. Although conditions at
the surface appear quite favorable for a strong radiational cooling
event with diminishing northerly flow and dewpoints in the u30s-
l40s, at least scattered high cloud cover associated with the
subtropical jet may continue to impact the southern half of the
forecast area overnight. The cloud cover should be sufficiently
high/thin to allow lows to fall into the upper 30s for most outlying
areas and lower 40s in urban locations, with patchy frost possible in
our southern TN counties where lows may reach the mid 30s.

.SHORT TERM...(Thursday through Friday)
Issued at 345 PM CDT Wed Oct 16 2019

A dry/tranquil weather pattern will continue across the TN Valley on
Thursday-Friday, as northwest flow aloft will persist in the wake of
an amplifying longwave trough axis across the eastern Seaboard. At
the surface, a broad ridge will continue to shift slowly eastward
across the TN Valley, resulting in light/variable flow. In the
absence of low-level thermal advection, max temps on Thursday will be
in the mid 60s once again, but should rebound into the l-m 70s on
Friday as a shortwave ridge aloft translates across the CWFA. Lows on
Friday morning will be in the u30-l40s once again, with a few
patches of frost possible once again across southern middle TN.

.LONG TERM...(Friday night through Tuesday)
Issued at 345 PM CDT Wed Oct 16 2019

Deep-layer moisture is expected to return to the region rather
quickly on Friday night, as southwest flow aloft strengthens
downstream from a longwave trough oriented across the central Plains.
The strengthening flow aloft should allow tropical moisture
associated with the area of disturbed weather (currently in the Bay
of Campeche) to be advected northward into the region, with some
light showers possible south of the TN River prior to sunrise
Saturday morning. However, there is considerable uncertainty
regarding how far northward precipitation will advance during the day
on Saturday, with the sheared remnants of the tropical disturbance
expected to pass well to the south/east of the region and most
guidance maintaining a wedge of dry air in the boundary layer across
at least the northern portion of our forecast area. Due to the
uncertainties in the model guidance mentioned above, we have only
included chance POPs during the afternoon hours, with activity
expected to shift steadily eastward and out of the region Saturday
evening. Clouds and precipitation should result in slightly cooler
max temps on Saturday, with lingering cloud cover and drizzle/fog
resulting in warmer lows on Sunday morning as well. Although a few
showers will remain possible across the eastern portion of the region
on Sunday morning, skies should clear sufficiently during the
afternoon for temps to warm into the m-u 70s.

At the end of the extended period, we will be closely monitoring the
progress of another mid-level shortwave trough, which is predicted
to deepen as it tracks eastward across the northern Plains Sunday,
before eventually carving out another broad longwave trough on Sunday
night/Monday. Deep-layer southwesterly flow will strengthen rapidly
by late Sunday afternoon in response to this feature, with a
preceding disturbance lifting northeastward from the Gulf coast
perhaps bringing a few showers and thunderstorms to the region early
Monday morning. However, a more significant/widespread convective
event is expected to unfold from late Monday afternoon into Monday
evening, as the cold front attached to the system`s deepening surface
low sweeps east-southeastward through the TN Valley. Conditions do
appear favorable for a risk of organized/severe thunderstorms, likely
in the form of a QLCS, based on the orientation of deep-layer shear
vectors w.r.t. to axis of low-level convergence and strength of
forcing for ascent. Cooler/drier, and windy conditions are expected
in the wake of the cold front on Tuesday.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 554 PM CDT Wed Oct 16 2019

VFR conditions will persist throughout the TAF period. Northwesterly
winds will begin to die down after sunset and will remain below
10kts through the next 24 hours.





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