Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 240456
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1056 PM CST Thu Nov 23 2017

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

.SHORT TERM.../Tonight through Friday/
Issued at 311 PM CST Thu Nov 23 2017

The primary weather story into tomorrow will be temperature
trends. Initially pressure falls and warm advection will push
across the northern Plains into the Great Lakes into tonight
setting the stage for further warming across Iowa Friday. SSW
surface flow will develop and remain steady into tomorrow until a
weak frontal passage by afternoon. There will be a good deal of
thermodynamic and kinematic forcing associated with its parent PV
anomaly/short wave as it moves from off the Pacific NW coast today
to the northern Plains by 18z, but it should come through dry
with limited moisture.

There will be some mid/high cloudiness with the system tomorrow,
but judging from upstream temps and advection with wind/mixing
driving cool season temps more than insolation highs shouldn`t
have a problem reaching the upper 50s and 60s. Readings in the 60s
would approach or exceed records in spots. Good mixing either
side of the trough/front passage will also be conducive for a
brief window of 35+mph gusts, especially west.

.LONG TERM.../Friday night through Thursday/
Issued at 311 PM CST Thu Nov 23 2017

Our recent dry and mild sensible weather trend will continue to
hold steady into early next week. The flow will amplify behind
the passage of Friday`s wave leading to Rockies upper level
ridging advancing into the Midwest by early next week. This will
lead to another system very similar to what is expected Friday
with persistent return flow boosting temps into Monday and a weak,
dry frontal passage due to limited moisture more than a lack of
forcing. Highs should again be in the upper 50s/low 60s central
and south, but these would be off records which are higher Monday
vs Friday.

The trend behind this system will generally stay dry, but with
temperatures closer to normal as cooler high pressure settles into
Iowa late Tuesday. There is one potential window for precipitation
where confidence decreases into midweek however. Although track
and timing vary, the 12z GFS and ECMWF both suggest some sort of
closed low to our south and the ECMWF does suggest a farther north
track with light precip possible late Wed. Both the ECMWF and GFS
have shown very poor run to run consistency over the past few
days however, and there really isn`t any ensemble support yet, so
will stick with a time-lagged blend which still suggests dry for
now. The models are in better agreement with a Great Lakes trough
passage and lowering heights to end the work week which would
keep temps cooler and closer to normal.

&&

.AVIATION.../For the 06Z TAFS through 06Z Friday night/
Issued at 1056 PM CST Thu Nov 23 2017

A high confidence forecast of VFR conditions continues at
terminals across central Iowa. Winds from the southwest or south-
southwest will persist overnight before becoming breezy tomorrow
morning. Winds will shift and become from the northwest later in
the morning into the afternoon with gust over 25 knots as a weak
cold front moves through the state. Mid and high level clouds will
surround the front, but ceilings will remain in VFR well above
any restrictions.

&&

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

$$

SHORT TERM...Small
LONG TERM...Small
AVIATION...Ansorge


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