255
FXUS63 KDMX 091727
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1227 PM CDT Thu May 9 2024

 ...Updated for the 18z Aviation Discussion...

.KEY MESSAGES...

- Lingering showers and thunderstorms today. Severe weather is
  unlikely.

- A few quick moving showers and thunderstorms Friday afternoon
  and evening. Severe weather chances are low.

- Cool and cloudy today with highs only in the lower 60s, but
  then somewhat milder for the remainder of the forecast with
  highs in the 70s each day.

&&

.DISCUSSION...
Issued at 225 AM CDT Thu May 9 2024

The thunderstorms that affected much of the northern half of
Iowa late Wednesday have gradually diminished, but are still
affecting parts of east central Iowa, with areas of showers
falling in the north. The mid-level trough providing the impetus
for this convection has largely stalled over northern Iowa, and
will gradually sink southward during the day and into this
evening. This will result in scattered to numerous showers and
occasional thunderstorms during the day, and have increased to
60-70 POPs across the area accordingly. The good news is
instability and shear are markedly diminished from Wednesday and
severe weather is not anticipated today. The bad news is that
the slow-moving nature of the showers and storms will maintain a
threat for locally heavy rainfall, especially early this morning
over northern Iowa where multiple rivers and streams are already
experiencing minor flooding that could be exacerbated or
prolonged by the additional rainfall. However, rain intensity
should gradually diminish today as the system weakens and then
moves out to the southeast around this evening.

A weak but deep-layer ridge will slide across Iowa late tonight
and Friday morning, providing a brief respite from
precipitation. However, a pronounced 500 mb trough will then
dive from southern Canada down over Minnesota and Wisconsin on
Friday, with the associated surface trough providing a focus for
renewed shower and thunderstorm development. Have increased POPs
somewhat on Friday afternoon and evening to account for this,
but they are still limited by the widely scattered nature
expected for the showers/storms. In terms of magnitude,
instability and moisture will be limited but there may be an
opportunity for localized gusty winds around a few of the
storms. Fortunately, any showers/storms will be small enough and
moving quickly enough to preclude any additional heavy rain
threat or flooding impacts.

Once the trough clears quickly to the east on Friday night we
will have another break from active weather as ridging dominates
the region Saturday and Saturday night. From Sunday into early
next week the pattern gets much messier, as very broad troughing
slowly meanders into and through the region over the course of
several days. This results in persistent chance POPs in the
extended forecast, but with little to no confidence in the
timing or placement of precipitation within the broad trough.
This portion of the forecast will need to be sussed out in the
coming days.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1226 PM CDT Thu May 9 2024

Bkn to ovc stratus remains draped over much of the area as we head
into the afternoon hours. The stratus varies between MVFR and VFR
cig heights with some isolated pockets of IFR. Shower activity has
been less expansive than previously forecast and confidence has
diminished that we will see -shra activity at most terminals, and
thus have limited or completely removed precip mention from the
forecasts. Cigs gradually improve this evening and into tonight, and
eventually give way to VFR prevailing across the forecast area into
Friday.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Lee
AVIATION...Martin