000
FXUS63 KDMX 090846
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
346 AM CDT Thu Apr 9 2020

.SHORT TERM.../Today through Friday/
Issued at 346 AM CDT Thu Apr 9 2020

Confidence: High

Plenty to discuss for the next 7 days...beginning today with a
potent upper level wave and accompanying front dropping south this
afternoon. Today will be windy with sustained winds around 30 mph at
times along with cumulus quickly developing later this morning and
afternoon. Steep lapse rates and strong winds through the column
support fairly vigorous rain and snow showers as we move into the
daytime heating hours of 18-22z this afternoon. Though accumulations
will be light, expecting that a few of the snow showers may drive
visibility down to under a mile at times today over the north and
northeast. Wind gusts, with the very top of the mixed layer
approaching 40 to 45kts, may reach about 45 to 50 mph in some of the
more vigorous showers today. Afternoon high temperatures will
struggle to top off in the lower 40s over the north to about 50 in
the south this afternoon. The diurnally forced cloud deck will
gradually thin out by 23-00z and finally this evening skies should
become clear and winds decouple a bit as high pressure settles into
the region overnight tonight.  Tonight will be rather cold compared
to recent overnights as lows drop to the mid 20s from northwest
areas through the Nisnabotna River Valley into Friday morning.
Elsewhere lows will drop to the upper 20s across the region.  As the
high swings southwest of the region by 12z Friday, a broad area of
weak warm air advection will overspread Iowa with warming H850
temperatures and some mid level clouds overspread the region during
the day. Despite the increasing cloud cover, highs will recover
nicely to the lower to 50 northeast in around 55 in the southwest.

.LONG TERM.../Friday Night through Wednesday/
Issued at 346 AM CDT Thu Apr 9 2020

Confidence: Medium

No shortage of weather in the extended...The upcoming weekend will
quickly turn active as the current cutoff southwest US upper level
low begins to open up and track east northeast while a potent northern
stream system drops into the northern CONUS and eventually phases
from the Southern Plains into the mid Mississippi River Valley by
Sunday. Already early today, water vapor imagery shows a long fetch
of subtropical moisture streaming across Mexico into the southwest
and Gulf Coast states. A pool of high moisture is already forming
over eastern Mexico, southern Texas and the Gulf Coast states
ahead of the closed southwest system. For us, an initial push of
moisture will arrive late Friday night into Saturday morning in
the form of showers. The lead wave will track across Iowa Saturday
and bring rain showers through the day. Increasing instability
south of Iowa will reach the southwest and south late day and
evening with chances for iso/sct thunder there Saturday evening
and night. By Saturday night the H850 moisture channel slides just
east of our area with a period of less widespread showers expected
overnight, then increasing again Sunday as the main system
arrives. Saturday will be the warmer of the two days this weekend.
After lows in the upper 30s to lower 40s Friday night, Saturday
highs will reach the lower to mid 50s northeast to 60 in the
southwest. Sunday will see a rapid amplification of the H500
pattern over the CONUS with the southwest system and associated
strong sub-tropical jet moving east northeast while the northern
stream begins to amplify/phase with the sub-tropical/wave. Euro
wind patterns suggest the potential for a potent severe event
from eastern Texas northeast through the Gulf Coast northeast
through the Mid Atlantic area from Sunday morning through 12z
Monday. North across our region, a quick deepening of the upper
level system with colder air arriving on the back side should
promote a rather wet/windy Easter Sunday with rain/possible
thunder south Sunday morning giving way to rain/snow then snow
across the west and north during the late afternoon/evening.
Though there are still some differences between the GFS/Euro
through the weekend, both are much more similar today than
previous model packages. The GFS is a bit colder with
thickness/H850 that would support heavier snowfall from southwest
Iowa to northeast sections, while the Euro would indicated a bit
slower cooling and lesser snow amounts. That being said, in either
case H850 flow currently forecast at 45 to 50kts supports very
windy conditions as the low tracks just to the east of Iowa Sunday
night. Early indications are the possibility of several inches of
snow during the passage of the storm though initially rain or a
mixture is most likely. Lows Sunday night will fall to the lower
30s northwest and in the upper 40s southeast with Sunday highs in
the upper 30s northwest/mid 50s southeast early then falling in
the afternoon. The system will pull northeast quickly Sunday night
with another shot of cold air. Mid 20s northwest to the lower 30s
southeast with Monday highs only in the upper 30s northwest to
the mid 40s south; about 15 to 20 degrees below normal. Though the
storm will have moved into eastern Quebec by 12z Tuesday, we will
still see its effects with another surge of Arctic air arriving
Monday night into Tuesday as the H500 gyre expands over the
eastern half of Canada. This will push H850 temps down to minus 10C
to minus 12C over the area and currently there is good agreement
between the GFS/Euro. The bulk of the area should remain cloudy
with highs in the 30s to around 40 Tuesday. Wednesday will be
slightly warmer with a few passing showers and highs in the 40s.
Thankfully some moderation is expected as we move into late next
week.

&&

.AVIATION.../For the 06Z TAFS through 06Z Thursday night/
Issued at 1157 PM CDT Wed Apr 8 2020

Little has changed in expectations since 00z. Confidence is high
in VFR conditions through at least Saturday morning, and also with
strong NW winds from midday Thursday into the afternoon. Wind
gusts of 35+kts may occur during peak mixing of the day, which
will be quite deep. Otherwise expect increasing mid clouds over
the northeast half of Iowa into Thursday with scattered showers
developing as well. There could be brief MVFR conditions during
showers, but the duration and predictability is too low for
inclusion at this time. Expect decreasing clouds and winds into
Saturday evening.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 9 AM this morning to 7 PM CDT this evening
for IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097.

&&

$$

SHORT TERM...REV
LONG TERM...REV
AVIATION...Small

NWS DMX Office Area Forecast Discussion