Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 251103

Area Forecast Discussion
National Weather Service Huntsville AL
603 AM CDT Sun Jun 25 2017

For 12Z TAFS.


.NEAR TERM...(Today)
Issued at 334 AM CDT Sun Jun 25 2017

For the start of this new week, a cooler change is in the works, as
abnormally deep troughing for late June becomes established across
the eastern half of North America. Even though we are starting the
first full week of summer time, it will not feel like it, as there
apparently is plenty of cold air from up north headed southbound.
Another disturbance was forming on the western half of this trough
across northern Saskatchewan and Northwest Territories. This system
will bring more clouds and unsettled weather later tomorrow and on
Tuesday -- more details on that below.

Another area of concern, mainly for the rest of tonight and this
morning is a weak upper disturbance approaching from the southwest.
Satellite trends indicated colder cloud tops with this system. More
importantly, local and regional radar was picking up showers, with
reports of measurable rain in Memphis. Despite a dry forecast from
the mesoscale and shorter term models, have introduced light rain for
this morning. Thinking is that drier air filtering in from the north
should keep shower activity suppressed this afternoon and evening.

High pressure building southward from Canada will be the primary
controlling influence on the weather today. As noted above,
unseasonably cold air associated with this ridge will result in
cooler than normal conditions for the Tennessee Valley. With more
clouds than sun expected, highs today should only warm into the lower
80s, with "brisk" for this time of year northerly winds of 5-15 mph.
Normal high temperatures today are around 90.

.SHORT TERM...(Tonight through Tuesday)
Issued at 334 AM CDT Sun Jun 25 2017

The cooler trends will continue tonight as effects from the high
predominate. Lows will cool into the upper 50s, with light northerly
winds. Given that the region has received copious amounts of rainfall
over the past few days, residual moisture and temperature/dewpoint
convergence could lead to patchy fog in sheltered locations. The
winds should otherwise remain up enough to keep fog formation tamped
down elsewhere.

A reinforcing shot of cooler air from the north will keep the cool
trend going on Monday, with highs only in the lower 80s, despite
more sun than clouds. The above noted disturbance (clipper like)
heading southward from Canada, will bring more clouds and a slight
chance of showers Monday night and Tuesday morning. These showers are
expected only to affect far northern Alabama and our Tennessee
counties. Similar cool conditions Monday night with lows in the mid
and upper 50s. Highs on Tuesday in the lower 80s are expected.

.LONG TERM...(Tuesday night through Saturday)
Issued at 334 AM CDT Sun Jun 25 2017

Fairly large dome of high pressure should be in place across the OH
Valley region by the start of this forecast period, with relatively
quiet/mild conditions in place over the cntrl TN Valley. After one
more early morning with lows near 60F, afternoon highs should begin
to rebound back into the mid/upper 80s, as the sfc high to the n
shifts ewd into the mid Atlantic Basin. Weak upper ridging should
also be quickly making its way ewd across the cntrl/wrn Gulf states
into Wed night, thereby aiding with the gradual warming trend. With
cloud cover spreading back into the area from the wsw and return flow
developing across the region, overnight lows early Thu look to trend
more in the mid/upper 60s. With Gulf moisture also spreading back
into the area from the n coupled with some weak insentropic lift
forming, iso showers/tstms also look to return to the forecast
Thu/Thu night. This coverage of showers/tstms increases into the sct
cat Fri/Sat, as moisture continues to stream into the region and a
weak frontal boundary approaches from the nw. Overall temps near the
end of the work week look to trend right around seasonal averages,
with highs near 90F and lows in the upper 60s for many spots.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 603 AM CDT Sun Jun 25 2017

An upper level disturbance approaching from the southwest could bring
a light shower to the two terminals early in the TAF. VFR weather
otherwise should prevail across the region for the remainder of the
period, as high pressure builds southward across the region.
Northerly winds will increase into the 5-15 knot range later this
morning and afternoon, and then become light and variable after
sunset this evening.





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