Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 221652
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1152 AM CDT WED JUN 22 2016

.SHORT TERM...(Today and tonight)
Issued at 300 AM CDT Wed Jun 22 2016

Main focus is on the convective potential today, including heavy
rainfall this morning, and severe possibilities this afternoon.

Surface low center is over south-central SD at 07z with the warm
front reaching east across IA to central IL. Lots of elevated
convection north of the front from eastern SD all the way to IL.
The line is quasi-stationary, with individual cells moving east-
southeast across the same general area. So the position of the
Flash Flood Watch, and a few Warnings appear to be well placed for
the time being. Radar loops do show the back edge of the heaviest
activity will be passing through between 4 and 7 am. For now, will
leave the Flash Flood Watch in place through 10 am, but will
likely be able to be cancelled early if this present speed and
trajectory continue. There are additional showers and storms
further to the west...remnants of strong convection over the
Dakotas last evening. This is on a weakening trend and will
actually be key to how the afternoon convection may redevelop.

The main short wave trough was centered over far southern
Saskatchewan at 07z, and it is forecast to move to near Grand Forks
by 21z this afternoon. There is a pretty strong jet associated with
this wave, and it is resulting in rather strong bulk shear of
70-80 kts by afternoon. Moderate moisture transport into the the
warm front which will be located from eastern IA into northern IL by
afternoon. So the dynamic forcing is definitely there for a
significant event this afternoon/evening. But there are some caveats
as well. Current activity will leave behind a sizable cold pool that
will have to be overcome. Plus, if the trailing activity lingers, or
leaves behind enough remnant cloud cover, we may not be able to
realize as much instability. This will be especially true if the low
and warm front track further to the south. The cap will come into
play as well, with 700 mb temperatures expected to climb to +12
across northeast IA by afternoon. Model soundings do show incredible
shear and helicity, so strong to severe storms including supercells
with tornadic potential are indeed possible. But current thinking is
that the atmosphere will not be able to recover until after 21-22z,
or even later. By that time, the best focal area looks to be just
south and east of Dubuque...just south of the forecast area. SPC
initial Day 1 outlook paints the Dubuque area in a Moderate Risk for
much of the same reasoning as above. But we coordinated directly
with them, and there may be some south and eastward shift with the
13z update, depending on how things play out in the next few hours.

Outside of the severe potential, there may also be some convection
associated with the wave as it translates across MN into northern WI
tonight. Maintaining higher POPS over the northern portion of the
forecast area to account.

.LONG TERM...(Thursday through Tuesday)
Issued at 300 AM CDT Wed Jun 22 2016

A few showers could linter into early Thursday as the wave pulls
away. Beyond that, ridging builds in to provide a pleasant end to
the work week. But for the weekend, a strong closed circulation and
upper trough moves eastward along the international border toward
the dakotas. This will induce a strong return flow of moisture and
instability, and a resulting chance for showers and thunderstorms.
The highest likelihood will be Saturday night as a cold front
sweeps through. Given the timing, instability, and available shear,
there is a risk for severe weather with this. More on this
later...once we get through today`s event.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1152 AM CDT Wed Jun 22 2016

Currently watching a warm front just to our south across northeast
IA into northern IL. Expecting storms to develop along this warm
front but remaining well south of KRST/KLSE. Main concern then
going through the afternoon will be vfr/mvfr stratus cloud cover
which looks to be persistent going into the evening. In fact,
thinking cigs may deteriorate into some ifr going into the
overnight hours along with reduced visibility in fog. Also,
will be watching an upper level wave of low pressure coming
through later this evening which looks to produce a few more
shra/ts. For now, will carry vcsh at KRST in the 01 to 04z time
frame and 01-07z time frame at KLSE.Look for conditions to
gradually improve Thursday morning as high pressure builds in.

&&

.HYDROLOGY...
Issued at 1152 AM CDT Wed Jun 22 2016

There is some potential for heavy rainfall again this afternoon
as new storms develop. However, these storms are expected to be
more progressive, so do not anticipate them lingering in any one
place too long. Some responses may be seen on some of the rivers
but flooding is not anticipated.

&&

.ARX Watches/Warnings/Advisories...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...MW
LONG TERM...MW
AVIATION...DAS
HYDROLOGY...DAS



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