Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261040
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
540 AM CDT FRI AUG 26 2016

.SHORT TERM...(Today through Saturday)
Issued at 245 AM CDT Fri Aug 26 2016

A ripple in the upper level flow slated to spin out of the southern
plains today, moving across the local area overnight/Sat morning.
West-east running frontogenetic boundary slated to set up around the
IA/MN border between 06-12z, lifting northeast by 18z Sat. 25kt low
level jet/850 mb moisture transport nose into northeast IA
overnight, working into and across the boundary. Add in some help
from the 300 mb jet`s right entrance region and there should be
ample, although not overly impressive, lifting mechanisms for
showers/storms. Little if any instability indicated...mostly
shunted south...so any storm threat may be more isolated to
scattered in nature.

Looking at heavy rain parameters...warm cloud depths via the GFS/NAM
roughly 3500-3800m south of I-90, while pws range from 1 1/2 to 1
3/4. Variables not as high as they were for other heavy rain events
of this summer, but still high enough where heavy rain could/will be
a concern...again. QPF relatively low in the models...generally
suggesting 1/2 to locally 1 inch as the rain bands move northeast
across the area between 06-18z Sat. That said...northeast IA and
southwest WI look the most likely to be under the gun for the
rainfall. While not a lot by most standards, with significant
flooding ongoing for parts of these areas, any additional rainfall
is the last thing they need. Coverage/amounts may not warrant a
widespread flash flood watch, but if signals continue to point to
the hard hit areas, and the heavy rain threat would increase, a
watch could/would be needed.

.LONG TERM...(Sunday through Thursday)
Issued at 245 AM CDT Fri Aug 26 2016

Fairly messy weather pattern for next week as the upper level flow
transitions from zonal to ridge building over the plains/upper
mississippi river valley thu/fri. The models produce a smattering of
rain chances early in the week as bits of upper level energy transit
through the flow. The ridge building would then favor northern
MN/northern WI for the storm track for the later half of the week.
EC leans toward a drier solution for the local area compared to the
GFS, although still paints periodic QPF through the upcoming week.
That said, certainly some hope for more dry rather than wet
conditions - desperately needed for many across the region. For now,
will stick with consensus solution for rain chances.

Rising heights and warming low level temps will return a taste of
summer for the end of August. 850 mb temps warm from around 12 c to
18 c for much of next week. Not a huge jump, but should result in
low to mid 80s for highs - a few degrees above normal.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 540 AM CDT Fri Aug 26 2016

High pressure continues to build over the area this morning.
KLSE decoupled early this morning with calm winds and
temperature/dew point at 58 degrees as of 10z. Would normally be
thinking fog/stratus in the Mississippi Valley as a result, but
cirrus cloud seems to be preventing it. However, will maintain a
close watch over the next hour. Pretty confident though that
cirrus cloud cover will mitigate widespread fog/stratus formation
this morning. For now, have included a 6SM BR through 14z. KRST
seems to maintaining some light west wind which is also keeping
fog from forming. Beyond this, VFR expected through majority of
the period, then mvfr cloud/shra sneaking in after 08-11z as a
trough of low pressure lift out of the Plains into the Upper
Mississippi River Valley.

&&

.HYDROLOGY...thru Saturday.
Issued at 245 AM CDT Fri Aug 26 2016

Flooding continues on portions of the Turkey and Upper Iowa rivers
and their tributaries in northeast Iowa. Warnings continue for much
of this area. Some high water also in Kickapoo River basin in
southwest Wisconsin but that is improving.

Per the "short term" portion of the discussion, heavy rain
parameters not as high as some previous heavy rain events this
summer, but still high enough that heavy rain will be a threat with
any storms late tonight/Saturday. Modeled QPF relatively low
though...generally 1/2 inch with locally 1 inch. In addition...the
forcing mechanisms look to be transitory, moving northeast across
the area. Still, the places hard hit from a few days ago look to get
more rain tonight/Sat. Any additional rainfall could impact clean up
work and slow falls on some river systems. If heavier and/or more
qpf then currently forecast, the threat for flash flooding returns.
Stay up to date on latest forecast and statements.

&&

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

$$

SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...DAS
HYDROLOGY....Rieck



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