Special Weather Statement, NWS La Crosse, WI

Area Forecast Discussion
National Weather Service La Crosse WI
606 AM CDT Wed Jun 14 2017

.SHORT TERM...(Today and tonight)
Issued at 349 AM CDT Wed Jun 14 2017

Main short-term fcst concerns are SHRA/TSRA chances thru the period
and severe TSRA risk mainly this afternoon/evening.

06z data analysis had a 999mb low over central ND with a mid level
low over the ND/MT border. Main cold front with the low extended
south thru eastern SD. Band of SHRA/TSRA extended from NE MN to NE
NEB, lifting steadily NE. Convection with the band across southern
MN to central IA weakening as it outruns the forcing/lift and
contends with weakening low level moisture transport, decreasing
CAPE, increasing CIN and warmer 700-500mb temps closer to the mid
level ridge axis. Convection in NE NEB/SW IA showing a bit more
life, aided by a shortwave lifting out of central KS.

Model runs of 14.00z initialized well, except for GFS once again as
much as 10-15F too high with sfc dew points across parts of southern
MN to northern MO. Solutions remain quite similar at the larger
scale as the eastern MT mid level low lifts to near Lk Winnipeg by
12z Thu. However, smaller/meso scale detail differences continue to
impact the sensible weather outcome across the area in the short
term. Short term confidence is average average this cycle.

For the short term, reasonable model consensus for convection to
continue to weaken as it moves into/across the fcst the area early
this morning, as it faces weakening moisture transport/CAPE and the
warmer mid level temps. A shortwave to be lifting from KS into
western IA by 12z. This look to provide some lift for persistence
of convection across the SW half of IA to continue spreading NE
into the fcst area thru before diminishing by mid morning. After
that, signal among many of the high-res/CAMs models that much of
the fcst area may well end up dry thru at least the 15-21z hours.
After a late morning/early afternoon lull, question then becomes
when/where will convection re- fire this afternoon. Model
consensus now wants to shift the CAPE axis east of the fcst area
this afternoon with the main lower level moisture transport
shifted east as well. Hgts do lower thru today as the mid level
low lifts to near Lk Winnipeg, with mid level cooling and diurnal
warming working to reduce the capping this afternoon. Convection
this afternoon may fire over the east end of the fcst area around
mid afternoon, ahead of a shortwave approaching/already east of
the MS river by 18z, may not fire at all, or near the MS river
around 00z. This is the variety of solutions presented. No matter
which may be more correct, appears upscaling to a more organized
convective complex may not occur until this evening and likely to
be SE of the fcst when it does. Still will be 1500-2500 j/kg
MUCAPE across the area this afternoon, along with an increase of
deep shear as the hgts fall ahead of the low/trough lifting NE
into Canada. Severe storms would be possible when TSRA refire,
with slight risk per swody1 reasonable at this time. However, risk
this afternoon into the evening may be somewhat conditional
depending on how much cloud cover may remain over the area today
impacting diurnal warming. For now will carry some higher SHRA/
TSRA chances early this morning, lower thru the mid-day hours then
more in the 30-50% range later this afternoon/into the evening,
highest over the east half of the fcst area.

Sfc cold front and sfc-850mb drying is pushed thru the area
tonight as the sfc-500mb flow becomes more westerly behind the low
lifting into south-central Man. Good model agreement for
convection in the area to come to an end/exit east around or
shortly after midnight. A more comfortable night later tonight
with the drying set to lower sfc dew points into the upper
50s/lower 60s by 12z Thu. Blend of the guidance highs/lows for
today/tonight looks good.

.LONG TERM...(Thursday through Tuesday)
Issued at 349 AM CDT Wed Jun 14 2017

For Thursday thru Friday night: main fcst concerns this period are
SHRA/TSRA chances Thu night thru Fri night.

Model runs of 14.00z in good agreement on the mid level low lifting
into northern Ont thru 12z Sat with a generally westerly flow aloft
over the region this period. Detail differences with shortwaves in
this flow. Good agreement for one stronger wave with the mid level
low to pass The morning, then lesser agreement on a wave to
approach/pass around 12z Fri and another Fri night. Fcst confidence
this period is average given the wave timing/strength differences
impacting SHRA/TSRA chances.

Thu should see a quiet, mostly sunny day on deep layered westerly
flow from the central/northern plains. However GFS and now NAM are
wanting to bring some increase of moisture and lower level forcing
NE into the area Thu afternoon, for a SHRA/TSRA chance across mainly
the SW half of the fcst area. Model soundings showing diurnal mixing
to as deep as 750mb Thu afternoon, with around 500 j/kg SBCAPE and
minimal CIN. Cannot rule out isolated-sct SHRA/TSRA Thu afternoon
but will leave fcst dry for now. With a better signal for a
shortwave trough axis to pass Thu night/Fri, and more time since
late Wed night for some moisture to return ahead of it, some small
SHRA/TSRA chances mainly across the south 1/2 of the fcst area these
periods look OK. Lesser agreement on details, but with another surge
of moisture increase ahead of yet another shortwave progged for Fri
night. Model soundings Fri night showing that if elevated layers in
the 850-700mb range can saturate and be lifted there is as much as
500-1500 j/kg CAPE and minimal CIN. The 30=40% consensus SHRA/TSRA
chances Fri night appear reasonable for now. With some stronger
deep=layered shear Fri/Fri night and as much as 1000 j/kg MUCAPE or
more, a few TSRA Fri afternoon could be strong. See swody3 for more
details. With the westerly flow and little cooling at 925-850mb,
consensus highs/lows this period remaining as much as 5 to 10F above
normal appear well trended.

For Saturday thru Tue (days 4-7): main fcst concerns this period are
SHRA/TSRA chances Sat and again Mon, cooler temperatures for Sun
into Tue.

14.00z medium range models in rather good agreement on a stronger
shortwave trough to come thru the flow and across the region later
Sat/Sat night, setting up longwave troughing over the great lakes
for Sun/Mon. Shortwave detail differences by Tue, impacting
progressiveness, or not, of the troughing over the region. Overall
day 4-7 fcst confidence is average.

Stronger shortwave trough to approach/pass Sat/Sat night bring a
stronger round of deep layered forcing/lift across the area. This
with PW values progged to be in the 1.5 inch range, as much as 1k-2k
j/kg MUCAPE and deep shear of around 40kts. Consensus SHRA/TSRA
chances in the 30-60% range Sat afternoon/evening reasonable. A few
of these storms may be severe as well. Plenty of time to detail
this. Behind this system, good agreement for some stronger cooling
to arrive as troughing sets up over the great lakes. Highs returning
to near or below normal for Sun-Tue continue to look well trended.
With the cold pool aloft spreading in Sun and deep cyclonic flow,
some small mainly diurnal SHRA/TSRA chances are reasonable. Lesser
confidence with any small consensus precip chances Mon/Tue, as
models at are at odds on strength/timing of shortwaves thru the flow
and if the longwave troughing is progressive or not.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 606 AM CDT Wed Jun 14 2017

An area of showers and storms advancing northeast out of Iowa has
been slowly diminishing. Still expecting this to impact KRST this
morning with some light rain that falls out of a VFR mid level
deck. Confidence that this will hold together and get to KLSE is
low so will only include a VCSH for the morning. After that,
pretty low confidence on how much additional convection will form.
A cold front across the Missouri River Valley will advance east
into the area this afternoon and then move out of the area this
evening. The 14.10Z RAP brings a decent short wave trough through
later this morning but after that, there is not much to help kick
off any convection. Some of the meso-scale models still try to
form some scattered activity late this afternoon along the front
and since a VCTS was already in the KLSE forecast, will keep this
for continuity. Skies should clear out fairly quickly this evening
behind the front for quiet VFR conditions overnight.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

SHORT TERM...RRS
LONG TERM....RRS
AVIATION...04

Hazardous Weather Outlook
National Weather Service La Crosse WI
526 AM CDT Wed Jun 14 2017

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-
032>034-041>044-053>055-061-151100-
Mitchell-Howard-Winneshiek-Allamakee-Floyd-Chickasaw-Fayette-
Clayton-Wabasha-Dodge-Olmsted-Winona-Mower-Fillmore-Houston-
Taylor-Clark-Buffalo-Trempealeau-Jackson-La Crosse-Monroe-Juneau-
Adams-Vernon-Crawford-Richland-Grant-
526 AM CDT Wed Jun 14 2017

This hazardous weather outlook is for parts of southeast
Minnesota...northeast Iowa and western Wisconsin.

.DAY ONE...Today and Tonight

Scattered thunderstorms will move across the area this morning.
The main threat from these storms will be lightning.

There is a chance for thunderstorms this afternoon and evening,
mainly along and east of the Mississippi River. A few of these
could be strong to severe, with the main threats being damaging
winds, large hail and locally heavy rain.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

More thunderstorms are possible Thursday night into Sunday. The
risk of severe weather is low with any of the storms from
Thursday night through Friday night as well as Sunday.

Though there is some uncertainty, Saturday afternoon and evening
will have to be watched for the potential of strong to severe
storms. At this time, the main threats would be damaging winds and
large hail.

.SPOTTER INFORMATION STATEMENT...

Spotter groups may be needed this afternoon and evening, mainly in
Wisconsin.

.EMERGENCY MANAGEMENT COORDINATION...

No webinar is scheduled.

RRS/04

Special Weather Statement
National Weather Service La Crosse WI
1128 AM CDT WED JUN 14 2017

IAZ011-030-WIZ053>055-061-141745-
Clayton-Allamakee-Richland-Vernon-Crawford-Grant-
1128 AM CDT WED JUN 14 2017

...Scattered thunderstorms will bring lightning and gusty
winds...

A cluster of thunderstorms was moving through northeast Iowa late
this morning with a history of gusty winds, brief heavy rain, and
lightning. There is also some small hail from time to time.

These storms will move into southwest Wisconsin for the first couple
hours this afternoon.

If you have outdoor plans in this region, take shelter as storms
move in. Be alert for gusty winds, up to 40 mph.

If you are on the Mississippi River, also be alert for these storms.
Move to shore until the storms pass and be especially cautious with
lightning risks.

LAT...LON 4264 9071 4268 9090 4265 9090 4265 9161
      4350 9161 4350 9122 4358 9123 4362 9127
      4373 9126 4373 9031 4356 9031 4355 9019
      4317 9019 4321 9029 4320 9043 4251 9043
      4251 9064
TIME...MOT...LOC 1624Z 204DEG 37KT 4334 9182 4272 9155

Shea

Special Weather Statement
National Weather Service La Crosse WI
1208 PM CDT WED JUN 14 2017

IAZ011-030-WIZ042>044-053>055-061-141800-
Clayton-Allamakee-Juneau-Richland-Vernon-Adams-Crawford-Monroe-Grant-
1208 PM CDT WED JUN 14 2017

...STRONG THUNDERSTORMS FORMING AND MOVING INTO SOUTHWEST WISCONSIN
EARLY THIS AFTERNOON...

Radar continues to show more and more thunderstorm development
across southwest Wisconsin early this afternoon. Meanwhile, other
storms are moving into the area from northeast Iowa.

These storms are producing occasional lightning and heavy rain, but
also produce hail and gusty winds at times. Wind gusts could reach
40 mph and nickel to penny size hail is possible.

If storms move into your area, take shelter. Be alert for gusty
winds and hail, in addition to the lightning risk. Boaters on the
Mississippi River should head to shore until storms pass.

LAT...LON 4264 9071 4268 9090 4264 9160 4265 9160
      4350 9161 4350 9122 4373 9126 4373 9091
      4415 9091 4425 8991 4407 9003 4365 8979
      4364 9031 4355 9031 4355 9019 4317 9019
      4321 9029 4320 9043 4251 9042 4251 9064
TIME...MOT...LOC 1705Z 207DEG 37KT 4343 9082

Shea