Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 291730
AFDDMX

AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
1130 AM CST Tue Nov 29 2016

.SHORT TERM.../Today through Tonight/
Issued at 344 AM CST Tue Nov 29 2016

The upper level low pressure is currently over the tri-state
region of the Dakotas and west central Minnesota this morning
with the sfc reflection beginning to slowly fill and shift
northeast. A few patches of light rain and light snow ongoing over
far northern Iowa in response to a short wave lifting northeast
around the upper low. Subsidence and drier air will move in the
next few hours and end the precipitation. Some sun and good mixing
is expected over central and southern Iowa today and will lead to
highs in the mid 40s to lower 50s. Clouds will likely linger over
the northwest and limit readings to the upper 30s. Another
shortwave will rotate around the upper low and drop south late
this afternoon and overnight. This will bring increasing chances
for precipitation over the northwest. With sub freezing
temperatures aloft, the precipitation type will be dependent on
near surface wet bulb temperatures. The surface wet bulb
temperatures will be near 34 into the evening and these readings
tend to be the transition area from rain to snow. Therefore have a
mix of rain and snow initially then gradually switching to all
snow as profiles cool later in the night. Minor snow accumulations
may occur over the northwest third of the forecast area.

.LONG TERM.../Wednesday through Monday/
Issued at 344 AM CST Tue Nov 29 2016

Fairly quiet weather pattern throughout the work week and into
the weekend. Leaned closer to the GFS through Friday and then a
blend of the ECMWF/GFS over the weekend as there remains some
significant discrepancies with each solution.

Wednesday into Wednesday night...Large upper low looks to continue
to churn over the Dakotas into the western Great Lakes Wednesday
into Wednesday evening placing the forecast area within the CAA
regime into Thursday. Light snow accumulations are possible along
and north of Highway 30 during the morning hours Wednesday and
then some lingering light snow across northern Iowa towards the
evening. Surface temperatures warm up enough to provide the chance
of rain by the late morning into the afternoon Wednesday. Nudged
up winds during this time frame with the surface pressure gradient
remaining strong across Iowa before relaxing by Thursday morning.

The aforementioned upper low finally gives way to zonal flow by
Thursday and the pattern remains zonal through the weekend. With
the stubborn upper low slow to move east, the low level moisture
remains across the region and thus the persistent stratus
throughout the week and likely into the early part of the weekend.
Thus, this will have a grave impact on daytime highs and overnight
low temperatures resulting in a small diurnal difference. In
summary, cold, cloudy, and breezy through Thursday evening and
then mainly cold and cloudy into the weekend.

&&

.AVIATION.../For the 18Z TAFS through 18Z Wednesday afternoon/
Issued at 1130 AM CST Tue Nov 29 2016

MVFR CIGS to continue to spread across northern IA today and into
central and southern IA this evening. Light snow chances will
increase tonight into KMCW and through the latter portion of the
period at KALO and KFOD. May have some close in on KDSM just
beyond the current forecast period. Gusty SW to westerly winds
expected this afternoon, with gusts diminishing this evening.

&&

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

&&

$$

SHORT TERM...Donavon
LONG TERM...Podrazik
AVIATION...Beerends


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