FXUS63 KDMX 011135

Area Forecast Discussion
National Weather Service Des Moines IA
635 AM CDT Mon Jun 1 2020

...Updated Aviation Discussion...

.DISCUSSION.../Today through Sunday/
Issued at 354 AM CDT Mon Jun 1 2020

Today...Scattered showers and a few isolated storms have
developed on the nose of the LLJ and WAA regime early this
morning. Increased the coverage to much of the CWA through 12z
this morning and have the highest pops going across the northeast
per hires models suggesting a bit more widespread rain in this
location. Expecting this shower activity to exit the forecast area
by 15z at the latest with the shortwave riding the upper level
ridge pushing into the Great Lakes region. The strong WAA
continues throughout the day and winds atop the mixed layer reach
near 35-40 knots. However, the mid-level cloud deck looks to stick
around for much of the day, so not entirely confident the very
deep mixing will develop until late this afternoon when clouds
thin out. Certainly the sharp pressure gradient and strong winds
just off the deck should lead to gusts over 30 knots at times
today. For maximum temperatures, went slightly above the majority
of guidance today even with the cloud cover and rain chances this
morning. But with the very warm start this morning as temperatures
range in the middle 60s, the temperatures won`t have far to go to
reach the middle-upper 80s by this afternoon.

Tuesday...sultry conditions across much of the state with maximum
temperatures rising into the lower 90s and dew points in the
upper 60s to lower 70s. Heat index values are likely to rise well
into the 90s to near 100 degrees by Tuesday afternoon. Still below
advisory level but likely hot enough to possibly cause some heat
related issues for outdoor activities.

Late Tuesday afternoon into Wednesday...boundary over southern
Minnesota will be the focus for convection to develop past 00z
Wednesday.  The latest ECMWF is a bit more in line with the further
north GFS solution in the convective initiation being along the
I-90 corridor in southern Minnesota. Thus, pulled back pops for
much of the forecast area until after 00z and mainly kept them
to north of Hwy 30. Even the HOPWRF, HREF, GEFS, and latest
NAMNest suggest a further north initialization. With
aforementioned heat and humidity present, tremendous MUCAPE
values across central to northern Iowa into Minnesota. However,
the shear remains weak and mainly unidirectional until 03-06z as
the front begins to sag into northern Iowa. The primary concern
for northern Iowa appears to be the damaging wind threat with
decent DCAPE values 500-1000 J/kg Tuesday evening. Not overly
concerned with the tornado threat with the very weak low-level
shear and helicity values. In fact, not entirely confident with
the overall severe convection in central Iowa. Storms move out of
the forecast area by 12z Wednesday with maybe some lingering
storms in the east after that time period.

Thursday through Saturday...unsettled weather pattern continues
through the weekend with Iowa generally remaining in northwest
flow aloft as a strong upper ridge holds in place over the
Southern Plains and Texas. Thus, timing of weak shortwaves riding
this upper level ridge remains challenging and low confidence
forecast wrt to pops past Thursday.


.AVIATION.../For the 12Z TAFS through 12Z Tuesday morning/
Issued at 630 AM CDT Mon Jun 1 2020

VFR conditions are likely through the TAF period. There might be
some brief visibility restrictions at MCW and ALO from the rain
across northern Iowa this morning, but left out mention as the
duration should be limited. Otherwise, south winds will increase
late this morning through the afternoon. Some gusts to 30 knots
are possible. Winds persist tonight into Tuesday morning but not
as gusty.






NWS DMX Office Area Forecast Discussion