Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 251118

Area Forecast Discussion
National Weather Service La Crosse WI
618 AM CDT WED MAY 25 2016

.SHORT TERM...(Today and Tonight)
Issued at 302 AM CDT Wed May 25 2016

Streak of minimal convective activity in the area may change later
today. Main focus will be trying to time convection into the area
and any associated severe weather threats from that.

Tracking short wave trough early this morning as it ejects across
the Central Plains in broad southwest flow. Several convective
systems upstream and as wave approaches this morning. Expect much of
this activity to advect into the area, sweeping northeast through
the day. Uncertainties exist exactly how this will happen though.

Some meso-scale guidance suggest convection could split our area,
with one area lifting northeast associated with the wave proper, and
a 2nd complex staying across Iowa, riding northern edge of deeper
moisture gradient and low level moisture transport. Most unstable
CAPE is still fairly limited across the area, and deeper shear is
marginal at best so how organized this activity might be with
regards to severe weather is still in question.

Trends to slow approach of convection has been accounted for in
forecast, but did raise rain chances as main line moves through the
area. Thinking Slight Risk in Day 1 may be a bit overdone given
uncertainties and marginal set up, but could not completely rule
out a few stronger storms or spotty severe weather.

More wholesale changes made for tonight as wave passes and storm
threat drops off pretty quick. Short term model guidance all over
the place with convective development but feel we could see more
subsidence and break in activity once wave passes. Lowered rain
threat towards a dry trend by Thursday morning. Will have to watch
for fog development as well.

.LONG TERM...(Thursday thru Tuesday)
Issued at 302 AM CDT Wed May 25 2016

Noisy pattern to end the week as more short wave energy moves into
the Midwest in southwest flow aloft. First potential wave could
develop another convective complex to the southwest on Thursday but
we will likely be between waves here and could see a relatively
quiet day with warm temperatures. As wave approaches Thursday night,
could see a few storms move in overnight, but timing and overall
marginal set up will likely limit severe weather potential.

Late in the week and into the holiday weekend, medium range guidance
suggesting upper low could eject out of southwest as large scale
upper pattern begins gradual change. This low will likely lead to
more widespread convection with better dynamics and shear, but some
questions about how much instability will be in place this far
north. While rain chances will be on the higher side Friday into
Saturday, unsure how extensive any severe weather risk could be.
These details will have to be worked out later, but proximity of
passing low and associated shear will bear watching.

Upper low passes by Sunday so could see breaks in rain threats for
latter half of holiday weekend, but unsettled zonal flow looks
likely into next week with waves transversing northern states. Off
and on rain threats sort of blanket the later forecast periods but
there could be dry periods in there most certainly. Temperatures
remain seasonal.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 618 AM CDT Wed May 25 2016

Complex of showers and storms continues to lift northeast across
central Iowa this morning. The 25.09Z run of the HRRR continues to
show this activity holding together as it lifts northeast and
moves across both airports late this morning into the early
afternoon. Based on these trends, changed the VCTS over to a tempo
group with the possibility of MVFR conditions as the rain moves
through. Once this activity moves past, there could still be some
pop up showers for the remainder of the afternoon so will maintain
the VCSH with VFR conditions. Subsidence in the wake of the short
wave trough that comes through with the rain should allow the
clouds to scatter out this evening setting up the possibility of
some fog for the overnight hours. The 25.06Z NAM forecast
soundings indicate saturation will occur at both airports for fog
overnight and have gone to prevailing MVFR late tonight with the
possibility of IFR at KRST.


.ARX Watches/Warnings/Advisories...


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