Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 302329
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
529 PM CST Mon Jan 30 2023

...Updated for the 00z Aviation Discussion...

.DISCUSSION.../Tonight through Monday/
Issued at 139 PM CST Mon Jan 30 2023

Key Messages:

- Very cold again tonight, with another Wind Chill Advisory in
  effect roughly north of Highway 30.
- Slow warming from Tuesday into Thursday, a brief shot of cold
  again Thursday night, then even warmer by Saturday.
- No precipitation chances in the forecast through at least
  Sunday.

A surface high pressure ridge will slide quickly across Iowa
tonight. As a result, winds will go lighter after sunset but then
swing around to southwesterly overnight into Tuesday morning. In
addition, a deck of mid-level clouds around 6-8 kft is covering
most of southern Nebraska, Missouri, and far southern Iowa and
short-range models indicate it will persist for much of the
evening before moving out. Finally, there are significant
differences in depth and character of snow pack across the area,
with deeper and fresher snow in the north as opposed to the south.
The combination of these factors should allow temperatures to fall
sharply after dark, especially across the north, but then steady
out and even rise a bit overnight, first in the south and
southwest and then eventually in the northeast. Have incorporated
these non-diurnal trends as much as possible into the official
forecast, and resulting wind chill values support another advisory
from the Highway 30 corridor northward, beginning at 8 pm and
continuing into Tuesday morning. Despite the relatively light
winds, air temperatures falling into the double digits below zero
in the north mean that even a 5 kt wind will get us to dangerous
WC levels.

With the onset of southwesterly low-level flow by Tuesday morning,
a slow warming trend should set in for a couple of days. The
surface flow and any associated warm air advection are weak enough
initially that it will not feel much warmer, but at least
Wednesday morning wind chills will only be in the single digits
below zero or so, as opposed to teens and 20s below zero. By
Wednesday afternoon air temperatures will even rise into the low
to mid 30s roughly south of I-80, readings that will feel
positively balmy after the preceding stretch of cold weather, and
likely into the upper teens or even lower 20s in northern Iowa.
Another surface trough will then swing through during the day on
Thursday, bringing gusty winds and a return of cooler weather,
albeit briefly, with temperatures falling to around 10 below zero
in the north on Friday morning and single digits above zero in the
south. Thereafter, however, a mid-level ridge will build across
the region and bring notably warmer weather for next weekend,
especially Saturday when afternoon highs should peak in the mid
30s north to 40s south. By the end of next weekend another large
500 mb trough will be digging into the western U.S. and should
bring a return of precipitation chances and changeable weather
conditions early the following week...but that is beyond the scope
of the current forecast and any degree of confidence with regard
to details.

&&

.AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/
Issued at 528 PM CST Mon Jan 30 2023

Confidence is high that VFR conditions will persist through the
period with nothing beyond mid or high level cloudiness, much of
which will be over southern IA this evening. Winds will remain
fairly light and back as high pressure drifts across the state.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory until 10 AM CST Tuesday for IAZ004>007-
015>017-023>028-033>039-044>050.

&&

$$

DISCUSSION...Lee
AVIATION...Small


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