FXUS63 KDMX 210439

Area Forecast Discussion
National Weather Service Des Moines IA
1139 PM CDT Mon Mar 20 2023

...Updated for the 06z Aviation Discussion...

.DISCUSSION.../Tonight through Monday/
Issued at 221 PM CDT Mon Mar 20 2023

Key Messages:

- Chances for light rain Tuesday
- Additional precip chances Wednesday night into Thursday. Few
  storms south. Light wintry precip possible north

GOES water vapor imagery shows a progressive pseudo-zonal pattern
over the CONUS. Several embedded waves of varying amplitude were
embedded within the mean flow, and most notably a pair of waves
pushes through the Rockies. Precip chances increase Tuesday
morning and afternoon as the waves push east. Most appreciable
model QPF more or less splits the forecast area as the mechanical
lift with each respective wave passes just north and south. May
still see QPF near 0.10" or more close the state borders and only
a trace to few hundredths in between. WAA overnight into Tuesday
and the timing of precip onset should support all rain.

A deep trough carves out over the western conus Wednesday. A lead
shortwave ejects northeast and induces surface cyclogenesis over the
Plains. This sharpens a frontal boundary draped across KS into
northern MO. Showers and storms develop as a low level jet pushes
warmer/moist air northward Wed evening and night. Some of this
activity may bleed north of the frontal boundary into southern Iowa
where models develop varying degrees of elevated instability.
Stronger convection with a threat for hail will be possible Wed
night into early Thursday should a more unstable environment be
realized, although that remains quite uncertain at this time.

Further north another axis of precip skirts across NE/SD and into
northern Iowa along a corridor of enhanced mid-level fgen. A
cold/dry Canadian high impinging south will favor wintry precip
types, although dry air both near the surface and aloft will make
ptypes and amounts more tricky. While snow is initially favored, a
loss of DGZ ice introduction may switch ptypes over the fzra or ice
pellets Thursday morning. Amounts are expected to be on the lighter
side, but the combo of wintry precip types could still lead to slick
road conditions in the morning hours. Temps near freezing + higher
seasonal sun angle should limit any impacts by the afternoon.

Pattern remains active Friday and into the weekend with a plethora
of low-amplitude waves translating through the mean upper flow.
These will keep chances for additional precip around, however a
relatively dry airmass should limit potential precipitation
amounts. A fair share of ensemble members keep much of the area
dry late week.


.AVIATION.../For the 06Z TAFS through 06Z Tuesday night/
Issued at 1139 PM CDT Mon Mar 20 2023

VFR conditions will prevail through the night, but with LLWS
around 30-40 KT at some terminals. Low clouds and light rain will
spread in from the southwest during the day on Tuesday, with MVFR
ceilings reaching DSM/OTM by around midday and the other terminals
later in the afternoon. By Tuesday night IFR ceilings will become
increasingly likely, possibly with some visibility restriction in
BR/DZ, but the details of that deterioration will be refined in
later TAF issuances.






NWS DMX Office Area Forecast Discussion