Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 232331 AAA
AFDHUN

Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
631 PM CDT Fri Jun 23 2017

.UPDATE...
For 00Z TAFS.

&&

.NEAR TERM...(This afternoon and Tonight)
Issued at 247 PM CDT Fri Jun 23 2017

A Tornado Watch remains in effect for portions of the TN Valley
through 8 PM CDT this evening. The remnants of TD Cindy continue to
push across the area this afternoon and as of 230pm are over the
central portions of our area. The wind field associated with the
remnants of Cindy has resulted in 30-40kts of shear and anywhere
from 300-500 m2/s2 of helicity. These values have allowed any of the
more vigorous updrafts to spawn brief rotational couplets on radar
and potentially a few tornadoes. In addition to that the stronger
gradient winds 25-35 mph out ahead of the line has resulted in a few
downed trees primarily due to the very saturated soils.

The atmosphere is also extremely saturated with PWATs upwards of 2.5
inches, which is at or above the climo max for this time of year. So,
any of the storms that continue to move over the area will be very
efficient rainfall producers. So, flash flooding is certainly
possible with any of these storms and especially in areas that
received heavy rainfall yesterday.

For tonight, there is some uncertainty, as the line moves off to the
east a cold front dropping through the central Plains/Midwest could
push additional showers and storms into the area. A complex of storms
has developed over southern MO/NW AR and is quickly advancing S/SE.
Right now the track of the storms and mean wind flow would suggest
that these storms should remain to our west. However, there has been
adequate heating ahead of these storms and the forcing with the
outflow and cold front could generate storms a bit more to the east
of this complex. If that does happen we could see some additional
storms dropping into the area late tonight. Believe that with the
atmosphere getting worked over this afternoon that storms will remain
below severe limits. Hires guidance is fairly consistent in showing
that the complex will stay to our west. But we will need to watch
this closely over the next few hours.

.SHORT TERM...(Saturday through Saturday night)
Issued at 247 PM CDT Fri Jun 23 2017

The cold front is expected to be over the area Saturday morning and
a weak disturbance moving along the front out of the OK/TX area could
generate some showers and storms during the day Saturday. So, have
slowed down the removal of PoPs from the forecast at this time. But
could easily see a situation where the front pushes through and ends
up just south of the area that we remain dry tomorrow. The good news
with the front is that much drier air will be arriving Saturday and
Sunday. Dewpoints will drop into the mid 60s Saturday and then into
the upper 50s by Sunday. This will be a welcome change from the high
humidity values we have had over the past few days.

Temps remain in the low to mid 80s for highs on Saturday but
overnight lows Saturday into Sunday drop down to around 60 degrees.

.LONG TERM...(Sunday through Thursday)
Issued at 247 PM CDT Fri Jun 23 2017

A broad trough is forecast to encompass much of the Great Lakes and
Midwest on Sunday with a surface high building into the area. This
will keep temps on the cooler side for this time of year with values
only in the upper 70s and lower 80s. While the airmass over the area
is drier and a bit on the stable side, a vort max dropping out of
the northern US could spawn thunderstorms over the central US. Latest
model guidance is showing a bit more activity with this shortwave and
storms could approach the area late Monday into Tuesday. Nudged PoPs
up for the northern half of the area but due to the expected
dry/stable environment have kept PoPs below 15 percent at this time.
Will wait another run before adding PoPs back into the forecast for
Monday night into Tuesday.

The high pressure shifts off to the east of the area on Wednesday and
winds begin to switch back to the south. Gulf moisture will begin to
stream back into the area towards the latter half of the week. Temps
will be back in the mid to upper 80s by Thursday and with the
increased moisture we could see afternoon and evening thunderstorms.

Temps from Sunday through Tuesday remain below normal and with the
drier air (dewpoints <60 degrees) we could have a few cooler mornings
with lows for some portions of the area in the upper 50s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 630 PM CDT Fri Jun 23 2017

OVC/BKN decks of low MVFR stratus will continue at both terminals
early this evening. Some breaks in the cloud cover look as if they
will occur at KMSL thanks to a pocket of drier air moving in.
However, this will be short-lived as a line of TSRA will track into
NW Alabama along a cold front between 03-05z, producing localized
gusty winds and IFR/MVFR conditions. This activity should weaken
significantly as it approaches KHSV, so have gone with a TEMPO -SHRA
there. Winds will gradually shift to the NW behind front, bringing
in some drier air and some clearing late in the period. However, low
clouds/light fog will produce prevailing MVFR to IFR ceilings and
visibilities late tonight into early Saturday morning.

&&

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

$$

NEAR TERM...Stumpf
SHORT TERM...Stumpf
LONG TERM...Stumpf
AVIATION...AMP.24


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at weather.gov/huntsville.



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