Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 211731

Area Forecast Discussion
National Weather Service Huntsville AL
1231 PM CDT Sat Apr 21 2018

For 18Z TAFS.


.NEAR TERM...(Rest of Today)
Issued at 1015 AM CDT Sat Apr 21 2018

Today will be the last nice day for awhile as high pressure over the
OH Valley remains in control of the weather. A system will be moving
into the Plains today and this will push the high east into the Mid-
Atlantic states. Expect winds to remain out of the E/SE with only a
slight breeze. Sunny skies are expected with just some passing high
level cirrus as the system to our west nears the area. Temps are
about on track to warm up into the low to mid 70s and only made minor
changes to the trends.

The latest 12z soundings showed a fairly dry environment remains in
place over the area. It won`t be until late tonight as mid/upper
level winds become more S/SW do we start to see an increase in
moisture/clouds. Any rain will hold off until closer to sunrise on
Sunday. We`ll be taking a closer look at what the latest guidance
gives us this morning and see if we need to make any changes to the
current forecast.

.SHORT TERM...(Tonight through Monday)
Issued at 420 AM CDT Sat Apr 21 2018

The above noted system will travel in an easterly direction tonight
and on Sunday. Clouds preceding it will overspread the Valley this
evening, with showers beginning after midnight (mainly across the
region west of I-65). Have rain chances increasing to near 100
percent on Sunday, as a comma head portion of the system affects
the region. Even though the main surface low should track and remain
south of this region, enough shear and minimal instability will keep
an isolated thunderstorm or two in the forecast. Storms that form
should remain "general" in intensity, and be mainly embedded within
more widespread showers.

Precipitable water amounts rising into the 1 to 1.5 inch range, and
decent upglide of deep moisture from the Gulf could result in locally
heavy rainfall. Rainfall amounts from the various models range in the
2-4" range into late Monday. This could result in excessive rainfall
overrunning and producing mainly hydrological issues, aka stream,
creek, river rises. Flash flooding could not be totally ruled out,
but given we`re on the northern side of this next system, short-term
intense rainfall is not as likely. After a warm day today, clouds and
showers will keep high temperatures on Sunday/Monday almost 10
degrees cooler, in the mid 60s. Very good rain chances will continue
on Monday, as the system slows its eastward progress, and remains
over the Tennessee Valley and Deep South.

.LONG TERM...(Monday night through Friday)
Issued at 420 AM CDT Sat Apr 21 2018

Fairly messy forecast will continue into the new week for the cntrl
TN Valley. Potent upper low/trough axis pretty much centered over the
mid TN Valley will continue to gradually translate ewd Mon night
into Tue, as the attendant sfc low S of the local area lifts into the
mid/srn Atlantic Basins. As the trough pattern begins to lift newd
away from the area, it is xpcted to weaken or open more into a broad
upper trough axis across the mid Atlantic states. Rainfall/showers
look to be ongoing over parts of the area thru Tue as these systems
exit the region. Rainfall may then taper off quickly from the W Tue
evening, as drier air above H85 briefly filters into the area.
Overall temps at least look to remain near seasonal for the first
half of next week, with highs on Tue mainly in the upper 60s/near 70F
while lows Mon/Tue nights trend predom in the lower/mid 50s.

Unfortunately, the dry spell looks to be short lived, as another
upper trough axis and attendant cold front out of the nrn/mid Plains
dives sewd into the Midwest/Lower MS Valley regions on Wed. Forecast
time heights indicate a rapid increase in moisture along/just ahead
of this next front, which should translate into more sct showers
spreading ewd into the TN Valley Wed/Wed night. Weak dynamic forcing
increasing along the approaching cold front should aid in the shower
development across the area. Even with more clouds/rain moving into
the region, little change in overall temps is xpcted, with highs on
Wed again mainly in the upper 60s/around 70F and lows early Thu
morning near 50F for most locations.

Another brief reprieve in the rainfall may then develop late Thu into
Thu evening, with the passage of this next front, as drier air above
H7 quickly mixes into the area. This will be followed though by
another rapid increase in moisture to close out the work week, as
yet another cold front out of the Plains states dives swd into the
region. This should at least result in more sct showers spreading
into parts of the area on Fri along/ahead of this next front. This
cold front however may have a bit more cold air advection with its
passage, as highs Fri struggle to climb higher than the upper 60s
while lows that night fall more into the lower/mid 40s.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1231 PM CDT Sat Apr 21 2018

VFR conditions are forecast through at least 06z tonight as high
pressure to our north keeps drier air in place over the area. A
system moving across the Plains will start to stream moisture north
into the area tonight and cigs begin drop through the night. By 12z
both HSV and MSL should see cigs between 2,000-4,000ft with a few
light showers. The heavier rain should hold off until just past the
end of the current forecast period. Between 18-00z cigs could fall to
below 1,000ft under the heaviest showers with vsbys as low as 2-3SM.
A few rumbles of thunder are possible but will be isolated in nature
and have kept out of the current TAF package.




NEAR TERM...Stumpf

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