Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 211958

Area Forecast Discussion
National Weather Service Huntsville AL
258 PM CDT Wed Apr 21 2021

.NEAR TERM...(Tonight)
Issued at 258 PM CDT Wed Apr 21 2021

A generalized zonal flow continued over the greater CONUS. More
details were evident upon a closer look at the flow. An upper low
over SE Canada has resulted in a weak troughing feature, mainly over
the Great Lakes and New England. It`s influence extended southward
along the eastern quarter of the lower-48. A Rex-style block over
Alaska and the Aleutians has somewhat slowed a normally quicker
motion of this low to the east.

At the surface, quite a change in the sensible weather has obviously
occurred with a passage of a cold front last night. That frontal
boundary has rocketed well to the east-south, now extending from the
northern Chesapeake Bay, across the Carolinas and Georgia Piedmont,
to east of Apalachicola and Brownsville. Mid afternoon temperatures
have only risen into the low/mid 50s across the Tennessee Valley.
Brisk northerly winds of 5-15 mph, with some gusts over 25 mph have
made for a raw mid spring day. Adding to the chill earlier was an
area of stratus; which continued breaking into the cumulus and
stratocumulus. Normal high temperatures for today are around 75
degrees for reference. And standing record cold high temperatures for
today are 56/1947 and 52/1904 at Huntsville and Muscle Shoals
respectively. Muscle Shoals has already warmed to 54, saving that
record. It remains to see if Huntsville will do likewise over the
next several hours.

Clouds should further diminish tonight, as high pressure builds
across the region. With lighter winds, clear skies, and cold air
in place, night lows will tumble into the low/mid 30s most locations
by daybreak Thursday. Readings this cold will result in widespread
frost formation; thus a Frost Advisory will remain place from 1AM -
8AM Thu morning. Those with sensitive vegetation should take
appropriate measures to minimize damage that frost can produce.

.SHORT TERM...(Thursday through Friday)
Issued at 258 PM CDT Wed Apr 21 2021

Clear skies and chilly temperatures should greet the start of a new
day, in an unusual frosty start for the latter half of April.
Temperatures should rise more than today, into the low to maybe a few
mid 60s, a good 10 or more degrees below seasonable norms. As the
high slides to the east, not as cool for Thu night with lows from the
upper 30s to lower 40s. The lower end of this could again support
patchy frost development in those normally cooler areas. Otherwise
even as clouds increase from the west, high temperatures on Friday
should moderate more, into the mid/upper 60s.

.LONG TERM...(Friday night through Tuesday)
Issued at 258 PM CDT Wed Apr 21 2021

The above noted clouds are with another system approaching from the
west. The models in this time frame were in generally good agreement,
moving the system across Tennessee during Saturday. The nearing of
this system will bring a good chance of showers beginning Friday
evening over NW Alabama, overspreading the region from west to east
during the course of the evening and overnight. Have introduced
isolated to scattered thunderstorms in late Fri night into Sat. Some
of the showers Fri night and early Sat could become locally heavy.
Thinking that overall dry conditions for the last few days should
help alleviate flooding concerns. The low itself should move well
east of the region during late Sat, with dry weather returning Sat
night and on Sunday.

Temperatures should finally return into the lower 70s on Sat, slowly
rising into the upper 70s/near 80 by Monday (which will be close to
seasonable norms). Highs above normal into the lower 80s are expected
for Tue/Wed. Yet another frontal boundary should move across the
region sometime on Wed. This will bring more chance of showers and a
few thunderstorms for late Tue into Wed.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1214 PM CDT Wed Apr 21 2021

VFR conditions prevail through the remainder of the TAF period. Gusty
northwest winds continue with gusts up to 20 kts until the late
afternoon. Scattered to broken VFR cumulus decks will dissipate this
evening. Winds become light or calm overnight and then become
westerly tomorrow near 5-8 kts.


AL...Frost Advisory from 1 AM to 8 AM CDT Thursday for ALZ001>010-016.

TN...Frost Advisory from 1 AM to 8 AM CDT Thursday for TNZ076-096-097.




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