000
FXUS63 KDMX 011733
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1233 PM CDT Wed Apr 1 2020

.DISCUSSION.../Today through Tuesday/
Issued at 411 AM CDT Wed Apr 1 2020

Key Points:

 1.) Today: Above-normal temperatures statewide, showers northeast.
 2.) Thursday: Widespread precipitation likely
 3.) Friday: Freezing rain possible northwest, with rain and
cooling temps elsewhere.

----------------------------------------------------

1.) Today: Above-normal temperatures statewide, showers
northeast...

 Scattered, light showers are ongoing across the central to
northern Iowa. 08z GOES-R water vapor imagery clearly picking up
on an upper low spinning over Alberta. With the associated
longwave trough dropping down over the intermountain west, a
shortwave has ejected off the Rockies near South Dakota and is
propagating northeastward. Attendant to the shortwave has been a
boundary that extends southeastward through Iowa. Strong
frontogenetical forcing, well- phased with a band of 850mb
moisture-flux convergence, has been present from 750mb to 650mb. A
vertical cross-section shows dry air around 900mb. This dry air
has been severely hampering precip efficiency and should serve to
confine amounts to around the 0.1" range.

This setup will continue to slowly propagate northeastward, with
scattered showers likely continuing across our northeastern CWA
through much of this afternoon. Strong WAA builds into western/SW
Iowa throughout today... warming temperatures relative to the past
few days. Though there will be more cloud cover, 850mb temps warming
to the +6C to +8C range will support an advection-driven warmup near
70 degrees in central to SW Iowa.

2.) Thursday: Widespread precipitation likely...

 A presently disorganized shortwave located over eastern Arizona
looks to become more organized throughout today and propagate
northeastward towards the Midwest. Concurrently, the longwave trough
associated with the upper low in Canada will help usher this
shortwave quickly through Iowa on Thursday. Easily depicted on the
1.5 PVU sfc, this shortwave starts at 00z Thu in SW Kansas, and ends
the day at 00z in the northwoods region of Wisconsin. Given the
speed of this system`s progression across the middle of the country,
it does not have much time to well-organize itself. Overall low-
level forcing/phasing is very weak and light, scattered showers is
likely the only impacts of this system. At this time, rainfall
amounts should be less than 0.1 inches.

3.) Friday: Freezing rain possible northwest, with rain and
cooling temps elsewhere.

 Will start by saying that this time of year, freezing
rain/freezing drizzle is very difficult to come by. Shortwave
radiative properties, even through stratus, are becoming strong
enough to where it is hard to not warm temperatures during the
day. For the past few days, models have suggested a potent cold
front setting up from Canada through the Midwest associated with
an area of low pressure that is slated to push across Canada.
Compared to yesterday`s model runs, the timing of this boundary
has accelerated ever so slightly... At 03z Fri, it should be near
the western edge of the DMX CWA, and by 15z to 18z Fri, it should
be near I-35. Thermodynamical forcing, especially at 950mb,
continues to be very high.

 Temperatures will be the big key with this fropa. Looking at
KEST soundings, a well-pronounced freezing rain sounding has
established itself. In trying to narrow down where any freezing
rain would potentially be, the position of the boundary overnight
will be key... ahead of the boundary, sfc temperatures will likely
be in the 40s... which will help keep pavement temperatures above
freezing. Once daytime heating kicks in, the pavement
temperatures at these locations will likely prevent much freezing
of precip. As of now, Emmet county to Crawford county and to the
west are areas behind the boundary that may keep temperatures cool
enough for freezing precip to be realized. Strong CAA and NW sfc
winds of 15 to 25 kts also expected. Will be watching this area
very closely over the next 24 hours for possible need for a
headline.

 High pressure should dry us out for Saturday through Sunday
morning, with highs on Saturday in the 40s to low 50s. With
another reinforcing upper low that sets up near the Pacific Coast
region of the CONUS, Iowa will likely remain in SW to westerly
flow to start off next week. Subsequently, the shortwave parade
may continue to march across the upper Midwest, next week active
through Tuesday. With the Gulf potentially open Monday and
Tuesday, have kept thunder in the forecast.

&&

.AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/
Issued at 1232 PM CDT Wed Apr 1 2020

Isolated IFR ceilings appear to have exited northeast sections
with high confidence in VFR conditions into at least the evening.
Clouds will lower and thicken into early Thursday however with
scattered showers developing west to east and the potential for
MVFR ceilings.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

DISCUSSION...Kotenberg
AVIATION...Small

NWS DMX Office Area Forecast Discussion