Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 300736
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
230 AM CDT Sun Apr 30 2017

.SHORT TERM...(Today through Tuesday)
Issued at 230 AM CDT Sun Apr 30 2017

Models remain in good agreement with bringing a deepening,
strengthening low pressure system across the Plains today, driving
the stacked, negatively tilted low over WI by 18z Mon. There are 3
distinct areas of pcpn with this storm system.

1) Strong west-east orientated 925-700 mb warm air advection and
sloping frontogenetic region (running out ahead of the approaching
low) slides northward across the Upper Mississippi River Valley
today/tonight. Rain will fall across the local area, with moderate
to potentially heavy rain favored in the late afternoon-evening time
frame. From 1/2 to 1 inch looks reasonable with this band.

THe low level jet/moisture transport feeds the eastern portion of
this band, eventually wrapping north and west of the low. The nose
of the 850 mb jet could spark a few thunderstorms late this
afternoon/tonight - mostly for western WI.

2) Line of convection expected to develop on the eastern edge of the
upper level trough/main push of shortwave energy, in the axis of
instability, today/tonight - out ahead of the storm`s cold front.
Models have been consistent over the past few days with keeping this
activity to the east of the local area.

3) Deformation region of the low will have low level moisture
transport to fuel it, along with bits of upper level energy rotating
around the parent low to periodically enhance the available lift.
The track of the low will keep the bulk of what falls with this
across MN - with accumulating snows likely for western/northern
parts of the gopher state.

Nutshell: its going to be wet today-tonight, although looks fairly
light and scattered through the better part of today, with the band
of moderate (heavy?) rain moving in tonight. Showers should
persist through Monday and Monday night.

.LONG TERM...(Wednesday through Saturday)
Issued at 230 AM CDT Sun Apr 30 2017

Both the GFS and EC favor the upper level northwest flow to hang
around for a few days post the exiting storm system Wed-Thu. Ripples
on the flow could bring more shower chances, with Thu currently the
most likely period. Amounts would be relatively light compared to
what is expected today-Monday.

500 mb ridge builds eastward into the Plains this weekend, bringing
warmer (seasonable to above) temperatures along with the promise of
a few days of drier conditions.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1126 PM CDT Sat Apr 29 2017

VFR conditions remain in place late this evening but a quick look to
our south reveals lower MVFR conditions creeping northward as deeper
moisture increases. Will need to watch a developing batch of showers
first thing early this morning that could potentially clip RST with
some very light rain, but confidence remains low.
Higher confidence that we will see MVFR conditions overspread the
area during the morning hours, with increasing coverage of showers
into the afternoon and especially evening hours as low pressure
approaches. It is that late evening period when IFR ceilings will
also likely start to make an appearance, with winds the next 24
hours steady-state from the northeast and becoming gusty to around
25 knots through much of Sunday.

&&

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

$$

SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...Lawrence


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