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FXUS63 KDMX 052345

Area Forecast Discussion
National Weather Service Des Moines IA
545 PM CST Thu Dec 5 2019

.DISCUSSION.../Tonight through Thursday/
Issued at 318 PM CST Thu Dec 5 2019

An outstanding day across much of Iowa today with high temperatures
in the 50s though far northwest Iowa was still in the 30s. A cold
front was already stretched across northwest Iowa this afternoon 
and will sweep across Iowa through this evening. A patch work of 
thin stratus is trailing the boundary by nearly 150 miles and will
reach Iowa this evening. A period of gusty northwest winds will 
arrive overnight coincident of the stronger cold advection and 
close to the arrival of the clouds. High pressure will enter the 
state during the day Friday. The area of high pressure will bring 
diminishing winds and clearing skies, similar to what is occurring
under the system now over southeast Saskatchewan. Friday will be 
nearly 20 degrees cooler than today but it will be just a glancing
blow of colder air. Warm advection will commence already Friday 
night as the high passes to the east and will set up for a mild 
Saturday with highs in the upper 30s to upper 40s. 

A boundary will enter Iowa on Sunday. Stratus will increase along
on boundary, especially along the the warm side. Possible some 
drizzle develops as saturation depths increase on Sunday. This all
could lead to a situation where the high temperatures are being 
overforecast on the warm side of the boundary. Current forecast 
has high temperatures in the mid 30s north to near 50 far south. 
In the situation above, temperatures would be close to surface dew
points, which will be in the upper 30s to low 40s. If the signal 
persists, will need to drop the high temperature forecast around 5
degrees over the south. Readings cross the north look reasonable 
at this time.

The big weather story for early next week remains the cold air
intrusion. A Hudson Bay low will establish by Sunday then will
rotate a couple waves of cold air south. The first wave arrives on
Monday and will be accompanied with a chance of snow with the
greatest chance over northern Iowa with some accumulations
possible. Gusty northwest winds are also possible on Monday with
gusts in excess of 35 mph possible ushering in colder air and
falling temperatures. Wind chill values may already be below zero
over northwest Iowa Monday afternoon. Breezy winds will persist
Monday evening and will drop wind chill values into the 10 below
to 20 below over northern Iowa by early Tuesday morning. The next
wave of cold advection will arrive on Wednesday followed by cold
high pressure. High temperatures on Tuesday will be single digits
north to 20s south. Breezy winds may hold wind chill values over
the north below zero all day. The coldest night of the period
looks to be Tuesday night as cold high settles over the state.
Overnight lows below zero are likely north to single digits above
south. A few minor chances at light snow mid next week but at this
time nothing significant.


.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 545 PM CST Thu Dec 5 2019

A cold front will pass through the state this evening.  MVFR/IFR 
stratus will will move in this evening and overnigh. VFR conditions 
will resume over TAf locations after 12Z.  Northwest winds will 
become gusty overnight but are expected to diminish some during the 
day Friday.



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