FXUS63 KARX 232323

Area Forecast Discussion
National Weather Service La Crosse WI
623 PM CDT Sat Jun 23 2018

.SHORT TERM...(Tonight through Sunday Night)
Issued at 205 PM CDT Sat Jun 23 2018

Partly sunny skies prevailed across the region this afternoon.
Temperatures were in the middle 70s to lower 80s.

For tonight and Sunday, there is still a lot of uncertainty in
timing and location of precipitation chances. Models do show a weak
disturbance moving across the area on Sunday which could trigger
shower activity along with a small chance of thunderstorms. Per
coordination with surrounding offices, slowed down the chances of
rain until very late tonight, and more likely Sunday morning. The
GFS/Canadian are more aggressive with rainfall totals while the
ECMWF indicated the lowest rainfall totals during the day Sunday
which gives uncertainty in rainfall amounts and actual coverage of
showers. Based on the latest model trends, highest chances of rain
will be across southeast Minnesota, northeast Iowa and southwest
Wisconsin north of Interstate 90.

Took a blend of model guidance for lows tonight similar to the
trends of last night although slightly warmer in spots. Did not
stray far from guidance for highs on Sunday.

Shower/slight thunderstorm chances shift westward Sunday night as
better moisture transport redirects across central IA into southwest

.LONG TERM...(Monday through Saturday)
Issued at 205 PM CDT Sat Jun 23 2018

Main concern through this period will be heavy rain/severe potential
mainly Monday night into Tuesday as a vigorous mid-level closed
low/surface low rotates northeast through the area. NAM/GFS models
in good agreement with increasing feed of moisture transport into
the area which is maximized Monday night into early Tuesday morning
with noctural 850mb jet. As a result, precipitable water values
increase into the 1.5-2 inch range Tuesday. CAPE and bulk shear will
depend on track of the mid-level low. NAM keeps higher CAPE pool
south of I-90 while the GFS brings in a respectable n/s corridor of
2-3KJ/Kg across the entire area along with bulk shear in the 20-40Kt
range (mainly south of I-90). So, will definitely have to keep an
eye on heavy rain and severe thunderstorm potential for this time

Wednesday is looking dry at this point as a ridge of high pressure
builds over the area.

Thursday through Saturday could be active as several convective
complexes make their way out of the Plains and over the ridge into
our area. Bulk of this activity looks like it would be along and
north of I-94. Otherwise, look for high through the period well into
the 80s.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 623 PM CDT Sat Jun 23 2018

A few showers have developed late this afternoon as a weak short
wave trough moves across Iowa. Very limited instability in place
with maybe 750 J/kg of MUCAPE, but enough that there could be a
rumble of thunder. The showers are drifting slowly to the
southeast and will include a VCSH at KRST for a couple of hours
until the instability dissipates with the loss of daytime heating.
After that, some concern again for fog in the river valleys. The
cloud cover should diminish overnight but expecting some clouds to
remain for much of the night. Light winds again through a deep
layer will be favorable for formation but the 23.18Z NAM and
23.21Z RAP do not show saturation occurring at the surface. For
now, will not include any mention of fog and will monitor trends
through the evening for possible inclusion with later forecasts.
Another small chance for some showers Sunday afternoon west of the
Mississippi River as a short wave drifts into central Minnesota
and will maintain the VCSH at KRST.


Issued at 205 PM CDT Sat Jun 23 2018

Area rivers continue to run higher than normal with some minor
flooding occurring or forecast to occur in places. Concern is there
for the possibility of more flooding heading into next week. A
vigorous storm system rotating through the region Monday night
through Tuesday night may have the biggest impact as precipitable
water values increase into the 1.5-2 inch range. This could
translate into pockets of very heavy rainfall which could lead to
some flooding. Will be keeping a close eye on the evolution of this
system. Wednesday looks dry but then there is the potential for
several convective complex to rumble through the area Thursday
through Saturday. This keeps the concern for flooding notched up a




Back to Main Forecast Discussion Page