Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 222024

Area Forecast Discussion
National Weather Service Des Moines IA
324 PM CDT Sun Apr 22 2018

.DISCUSSION.../Tonight through Monday/
Issued at 324 PM CDT Sun Apr 22 2018

Low pressure situated over the Ozarks is spinning high level
clouds northward over the state this afternoon as GOES-East Day
Cloud Phase Distinction RGB shows the snowpack over northern Iowa
eroding slowly on the southern fringe. Patchy clouds may linger
over southern Iowa through the night into Monday morning before
drier air from high pressure over the western Great Lakes works in
on the back side of the departing low pressure. Winds will also
become light this evening and over far northern Iowa where the
snowpack is melting, may see some patchy fog develop. SREF
probabilities as well as some of the high resolution guidance
suggest reduction in visibilities due to fog over these areas.
Best chance for this will be generally west of I-35 to Highway 71
and along/north of Highway 18.

Otherwise on Monday, high pressure prevails over the region and with
the continuation of dry air into the state should have ample
sunshine across central Iowa. This along with slightly higher 850mb
temperatures will boost temperatures into the 60s with a few places
eclipsing 70 degrees. There will still be some 50s over the snow
covered areas of north central Iowa.

Attention then turns to the shortwave trough that is moving toward
the northern Rockies early Sunday afternoon. This shortwave will
move our area late Tuesday into early Wednesday bringing a cold
front across the state. The GFS has continued its shift of
precipitation westward toward the drier CMC/EC/NAM. Therefore,
dropped PoPs and any QPF over eastern areas of our forecast area
Tuesday night. The air behind this front is not drastically colder,
but will bring temperatures slightly below climatology for Wednesday.

Another shortwave trough will be entering western Canada Wednesday
and moving across the state Thursday or Thursday night. The GFS and
CMC are faster by about 6 to 12 hours compared to the ECMWF with the
CMC cutting off the 500mb low with the GFS and ECMWF remaining an
open, progressive wave. While won`t be able to peg down the details,
expect another cold front accompanied by precipitation chances to
move through central Iowa on Thursday or Thursday night. Beyond
Thursday, most guidance shows higher temperatures near to above
normal for Saturday as 850mb temperatures increase from Friday into


.AVIATION.../For the 18Z TAFS through 18Z Monday afternoon/
Issued at 1205 PM CDT Sun Apr 22 2018

VFR conditions are expected as patchy high clouds mainly over
southern Iowa clear out this afternoon. Winds from the east will
become light from the northeast or variable overnight. While not
mentioned in the TAF, there is still a low chance of some patchy
fog toward sunrise Monday toward MCW with a better chance west at




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