Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 261954
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
254 PM CDT Tue Mar 26 2024

.KEY MESSAGES...

- Large system responsible for the widespread /and beneficial/
 rainfall the past few days continues to move away from the area
 tonight.

- Drying out and cold Wednesday, with a warming trend late-week

- Next chance of precipitation /20-40%/ returns on
 Friday/Friday night

&&

.DISCUSSION...
Issued at 252 PM CDT Tue Mar 26 2024

Tonight...

The potent low pressure system responsible for the significant
rainfall /and some snow/ over the past few days continues to eject
to the north and east over the Great Lakes. 3-day rainfall amounts
of 0.5" to 2.5" were common across the state of Iowa, with heaviest
axis from about Creston, to Fort Dodge, to Estherville. Radar mosaic
and METARs continue to depict scattered flurries across the far
north, but at this point any impacts should be minimal. Otherwise,
broad sfc high pressure will begin to build into the region
overnight resulting in drier and cold conditions - at least for late
March standards.  Lows tonight will fall into the mid 20s southeast
and into the lower teens far northwest where snow cover exists. Low
stratus in the cold cyclonic flow will persist overnight, as is
typical in these situations.

Wednesday and Thursday...

The upper level pattern on Wednesday will remain northwesterly as
the large upper low slowly tracks near Hudson Bay. 850mb temps will
remain below climo, ranging from -5C south to -10C north. While the
profile will continue to dry out, model soundings and time sections
do indicate periods of mid level clouds passing through.  In
addition, the cold low level profile may support stratocumulus
development during peak heating, so generally partly cloudy skies
expected. A residual breezy northwest sfc wind of 10 to 20 mph will
persist, and even with some sun, temperatures will struggle to rise.
Highs on Wednesday are forecast to range from the mid 40s south, to
the mid 30s north.

On Thursday, the upper pattern will begin to undergo change, with
upper riding building from west to east across the central CONUS as
low pressure develops along the Pacific Coast. In concert, a low
level WAA pattern will develop over IA with 850mb temps rising into
the single digits above zero Celsius. As expected, this should
result in a warming trend, with highs responding nicely into the
lower 60s south, to the upper 40s north. A few models continue
to generate periods of thicker mid-level clouds on Thursday
afternoon. Not expecting any pcpn with these clouds as the PBL
remains very dry, but thickness/opaqueness of clouds could
hinder high temps a bit.

Extended Forecast - Friday into early Next Week...

The upper level ridging across the Midwest will be short lived, as
the next upper trough moving through the western US collapses upper
heights pretty quickly. A lead shortwave will eject out of the mean
trough on Friday, spurring the development of a lee sfc low over the
central Plains. As this low scoots across the region on Friday,
modest isentropic ascent is depicted on the 290K-300K sfcs. This
combined with upper level PVA /Q-convergence/ and resulting lift
will likely lead to a period of deeper saturation and possible QPF.
At this point, no sense in getting too cute with details, but GEFS
and ECMWF ensemble consensus does indicate at least chance PoPs
/20-40%/from Friday into Friday night. At this point, the amount of
moisture return from the Gulf of Mexico is uncertain, with some
ensemble members showing robust moisture advection/return, while
other show the Gulf mostly closed for business. Additional periods
of precipitation /30-50%/ will continue into the upcoming
weekend, as the large low pressure system slowly progresses
eastward out of the west. While there is some ensemble spread,
temperatures in the extended period should not depart too far
from late March climatological values, with highs in the 50s and
low 60s and lows in the 30s and 40s.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1230 PM CDT Tue Mar 26 2024

Widespread MVFR CIGs are expected the remainder of today, and
into tonight at all terminals. In addition, radar and short term
guidance continues to suggest a continuation of MVFR VSBYs due
to light snow at at KMCW/KALO, gradually diminishing after 21z.
Other terminals may see occasional flurries, but impacts will be
inconsequential. Timing the dissipation of the MVFR stratus
overnight will be challenging. At this point, generally went
with the more pessimistic guidance, and kept the lower CIGS
thru 08z to 12z on Wednesday. Winds will continue to range from
15 to 30kts out of the northwest through this evening, before
gradually weakening after 06Z.

&&

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

&&

$$

DISCUSSION...Fowle
AVIATION...Fowle


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