Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 251722
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1222 PM CDT SAT JUN 25 2016

.SHORT TERM...(Today and tonight)
Issued at 355 AM CDT Sat Jun 25 2016

At 3 AM, a 1020 mb high was centered over southeast Lower
Michigan. Meanwhile a cold front was located over the central
Dakotas and the Nebraska panhandle. A warm front extended
southeast from the cold front across southeast South Dakota and
western Iowa. South and southeast winds ahead of this front have
kept the temperatures in the Upper Mississippi River valley in
the 65 to 70 degree range early this afternoon.

For this morning and early afternoon, the models show that the
warm front will move east across the forecast area. While the CR
NAM Nest, NAM12, and NSSL WRF have this front moving through the
area dry, the NMM, ARW, and NMM shows scattered showers and
storms moving east across northeast Iowa and southwest Wisconsin.

In the wake of this front, the 925 mb temperatures climb up to
26C. This is 5C warmer than Friday afternoon. Mixing these
temperatures to the surface results in the temperatures climbing
into the upper 80s north of Interstate 94 and into the lower 90s
across the remainder of the area. The combination of these
temperatures and dew points in the lower 70s will result in
afternoon heat indices approaching 100 degrees.

During the mid- to late evening, it still looks like scattered
supercells will develop across northeast, east-central, and
central Minnesota. These thunderstorms will be capable of
producing large hail, damaging winds, and a couple of tornadoes.
With the best shear being in the 0-3 km layer and the cold front,
expect that these will evolve into a line of strong to severe
storms. This line will likely move through southeast Minnesota and
northeast Iowa between 6 PM and 10 PM...and western Wisconsin
between 9 PM and 2 AM. As these storms move east, the instability
and shear will be decreasing. As a result, the threat for severe
weather will gradually decrease as they move east across the
forecast area. The main severe weather threat in our area will
likely be damaging winds, but there may still be an isolated
tornado threat in parts of southeast Minnesota and west-central
and north-central Wisconsin. As far as hail, soundings continue to
show a rather skinny CAPE profile; thus, only anticipating hail
maybe up to quarters.

.LONG TERM...(Sunday through Friday)
Issued at 355 AM CDT Sat Jun 25 2016

On Sunday, the 925 mb and 850 mb temperatures only cool about 2C.
In addition, we will mix up to 775 mb which is about 100 mb deeper
than this afternoon. This will allow high temperatures to top out
in the mid to upper 80s. With the soundings showing quite a bit of
dry air aloft, the mixed down tool suggests that the afternoon
dew points could potentially range from the mid-40s to lower 50s.
This would be in the same range as the dew points currently over
southern Alberta and Saskatchewan. Since this would be a large
change from the current forecast, opted to drop them from the
upper 50s to the lower 50s for now. This would lower the
afternoon relative humidities into the 25 to 30 percent range.

From Monday afternoon into Monday night, a much stronger Canadian
cold front will move south through the region. This would drop the
925 mb and 850 mb temperatures anywhere from 12 to 18C colder than
what they were on Sunday afternoon. With much of the forcing and
moisture transport being located across northern Minnesota and
northern Wisconsin, we are still expecting that this front will
move through much of the region dry. At this time, only north-
central Wisconsin has a slight chance of showers.

In the wake of this cold front, high temperatures will be below-
normal for both Tuesday and Wednesday. The high temperatures will
be in the lower and mid-70s on Tuesday and in the mid- to upper
70s on Wednesday.

Small chances of showers and thunderstorms will continue for the
latter part of the week as short wave troughs move through the
area from Wednesday night into Thursday and from Friday afternoon
into Friday night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1222 PM CDT Sat Jun 25 2016

Good VFR conditions expected this afternoon in a well mixed airmass
ahead of an approaching cold front. Tighter gradient ahead of the
front and the deeper mixing resulting in south winds 14-18kt g22-
26kt thru the afternoon hours. Cold front approaches, then passes
this evening, roughly around 03Z at KRSt and 06Z at KLSE. This is a
bit slower than earlier expected. A band of SHRA/TSRA are expected
to accompany the front across the area. cigs/ vsbys looking to be
MVFR, locally IFR, in TSRA and heavier SHRA with the frontal
passage. Continued the trend of a tempo MVFR period with passage of
the front/TSRA with it, but delayed it an hour or 2 from the
previous TAF set. Once the front goes by a drier airmass as
southwest to west winds to spread across the TAF sites. Good VFR
conditions then expected for the late night hours and on Sunday with
this drier airmass spreading in.

&&

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

$$

SHORT TERM...BOYNE
LONG TERM....BOYNE
AVIATION.....RRS



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