Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 190914

Area Forecast Discussion
National Weather Service Des Moines IA
314 AM CST Sun Nov 19 2017

.SHORT TERM.../Today through Tonight/
Issued at 300 AM CST Sun Nov 19 2017

Thermal trof currently across the state on the backside of departing
system.  Winds have continued quite brisk overnight and this has
helped support temperatures that otherwise would have fallen even
more given the clear skies.  Warm advection will get underway
shortly as flow aloft becomes more westerly and surface ridge axis
passes through the state.  Soundings indicate the atmosphere will be
dry through tonight with little in the way of cloudiness during this
period.  Despite a relatively cold start this morning, readings
should warm nicely with plenty of sunshine and increasing warm
advection.  Temperatures near normal are expected by mid afternoon
with increasing southwest winds.  With little change in sky cover or
winds tonight and thermal ridge building toward the state, lows
overnight should be a good 5 to 10 degrees warmer than the current

.LONG TERM.../Monday through Saturday/
Issued at 300 AM CST Sun Nov 19 2017

Bottom Line Up Front...
Forecast remains locked in for a sunny week, with no significant
precipitation chances until possibly next weekend. Temperatures
will be warm Monday, cooler through the mid-week, and then well
above- normal Friday into Saturday.

09z GOES-16 water vapor imagery picking up on an upper low
continuing to remain nearly stationary over northern Manitoba.
Models continue to show this low being nudged eastward as a
ridge/thermal ridge reaching well into Alberta shifts eastward.
Feel confident with temperatures into the low to mid 50s across
the DMX CWA as 850mb temps will rise from -4C to -6C on 12z Sun,
up to +6C to +9C by 12z Mon. Channel 8 GOES-16 imagery picking up
on a widespread swath of upper-level moisture centered over the
Pacific NW which will accompany the WAA into Iowa, leading to a
day of filtered sunshine/widespread cirrostratus.

Tuesday through Thursday...
Pivoting around the southern lobe of the aforementioned upper low
over Manitoba will be a very fast-moving shortwave slated to
traverse across Canada and phase with this upper low by Tuesday
morning. Though the sfc reflection will remain in Canada, strong
CAA will blast into the Midwest, punching towards the Ozarks. This
cold slug is progged to lower 850mb temps to the -6C to -9C range
by late Tuesday into Wednesday... around -1 to -2 std dev per
NAEFS ensembles. Normal high temperatures for this time of year
are in the mid 40s, ultimately supporting max temps in the 30s to
low 40s.

Friday and Beyond...
Long-range models and ensemble members continue to suggest a
major warm-up for Friday as another thermal ridge, following on
the heels of the Tue-Thu slug of cold air, looks to crash over
Iowa. Compared to the ridge from Monday, the Friday setup looks to
be warmer, with 850mb temps at 12z Fri suggested to be in the
+10C to +15C range across Iowa. With the exception of perhaps a
singular hiccup in the 12z Sat ECMWF run, the ECMWF has had a lock
on this warmup since the 240 hour output at 12z Wed. So will
continue to lean towards this solution, though the GFS has finally
caught up it seems.

Picking up from yesterday... going forecast temps could very well be
5 to 10 degrees too cool... perhaps closer to 10 degrees too cool.
If run-to-run consistency is maintained today`s runs, will be
bumping these forecast temperatures up several degrees in tomorrow
morning`s update. Depending on the timing of the WAA passage,
Saturday morning temperatures could be a solid 10 to 15 degrees too
cool. CAA throughout Saturday may mitigate a record high min 45
(2011) from occurring on Saturday as the 11:59 PM temp would likely
fall under 45. Record max temp for Friday is 67 (2011)... still
cannot rule out this record being broken on Friday at this time.


.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1128 PM CST Sat Nov 18 2017

Little has changed since 00z. There is high confidence in VFR
conditions with nothing beyond patchy high cloudiness later Sun.
NW winds will continue to slowly diminish overnight before becoming
W then S by early Sun evening.




LONG TERM...Kotenberg
AVIATION...Small is the U.S. government's official web portal to all federal, state and local government web resources and services.