National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDMX Received: 2018-12-06 05:31 UTC


692 
FXUS63 KDMX 060531
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1131 PM CST Wed Dec 5 2018

...Updated for 06z Aviation Discussion...

.DISCUSSION.../Tonight through Wednesday/
Issued at 334 PM CST Wed Dec 5 2018

The forecast remains quiet overall, but with a cold snap over the
next few days. An approaching cold front is already evident in
surface observations and satellite imagery, currently stretching
from south central South Dakota up into central Minnesota. The
front will surge south/southeastward across Iowa overnight
tonight, accompanied by clouds and perhaps just a few light
flurries. Precipitation is low probability at any given point and
is not advertised in the outgoing forecast, as anything more
widespread or accumulating will fall southeast of our forecast 
area across Missouri and Illinois. Unfortunately the cold front
will also bring an abrupt halt to the mild weather experienced
today, as it will push temperatures down to the lowest levels seen
thus far in most areas. During the day on Thursday brisk north
northwest winds will make for a cold and blustery day, with
temperatures beginning to fall in the late afternoon. The area of
cold surface high pressure building in behind the front now
appears to be moving in a bit more quickly than it did yesterday,
meaning it will be centered right over Iowa late Thursday night
into Friday morning. While this will still lead to very cold
temperatures, it will also result in lighter winds and wind chills
more in the -10 to zero range than the previously feared -15
readings in the north. Still, anyone venturing outside Friday
morning will need to bundle up.

The aforementioned high pressure area will remain anchored nearby
or a little to our east through at least the first half of the
weekend, providing light winds and mostly clear skies but also a
continuation of cold temperatures. Toward the end of the weekend,
Sunday/Sunday night, a mid/upper level low pressure system
will sink southward across western Iowa or thereabouts, however,
this will be a weak system with dry/stable air below it and it
should only result in clouds and perhaps a few flurries. Otherwise
the forecast is dry through this period, and a brief ridging
episode on Tuesday may actually provide a little warming with 
temperatures rising into the upper 20s to upper 30s in the 
afternoon. Long-range models then move a mid/upper level trough
across the region in one or more phases between Tuesday night and
Thursday night, providing some opportunity for precipitation.
However, the details of this scenario have varied widely between
model runs over the last couple days and the details thus remain
unclear a week out.

&&

.AVIATION.../For the 06Z TAFS through 06Z Thursday night/
Issued at 1122 PM CST Wed Dec 5 2018

Made notable changes to CIGs in this update. Broken stratus with 
bases near 1500 ft to 2500 ft have made it into northern Iowa,
impacting KFOD, KALO, and KMCW. Satellite shows these clouds
extending back into North Dakota, so am thinking they will persist
in some form into Thursday afternoon.

Timing of departure will likely need to be adjusted in subsequent
updates.

&&

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

$$

DISCUSSION...Lee
AVIATION...Kotenberg