Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 232356
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
653 PM CDT Tue May 23 2017

.SHORT TERM.../Tonight through Wednesday/
Issued at 326 PM CDT Tue May 23 2017

Upper low will continue to dominate the weather in the short term.
With cool temperatures aloft associated with this low, numerous
showers have developed across central Iowa this afternoon.  Even a
few reports of funnel clouds have been received and this may
continue into the early evening.  However, much of this is diurnally
driven and would expect coverage and any funnel threat to diminish
rapidly this evening as sunset approaches.  Will continue to see
some threat of showers overnight in vicinity of the low as it slides
southward into Missouri and will continue with low pops overnight.

The upper low will continue to influence the weather into Wednesday
with plenty of cloudiness to start the day and thermal trof
lingering over the state.  A few showers may continue across the
area, however this threat will diminish as the cooler temperatures
aloft depart the area as the low pulls away.  Highs will continue to
remain well below seasonal normals with cool northerly winds through
the day.  Some drying in the low levels in the west will likely lead
to some partial clearing in the western half of the state later in
the day.

.LONG TERM.../Wednesday night through Tuesday/
Issued at 326 PM CDT Tue May 23 2017

Main forecast concern was focused on periodic rain/storm chances
through early next week. Models are is complete dismay beginning
Friday with the only main aspect they do agree upon is placing
Iowa within northwest flow aloft as a the ECMWF/GFS plant an upper
low over the Great Lakes/Ontario region through early next week.
Leaned closer to the GFS as the 23.12z ECMWF has trended more
towards the 23.12z GFS solution, at least for Friday into
Saturday.

Wednesday night through Saturday...Surface high pressure builds
into the region behind the slow moving upper level trough of low
pressure. Weak upper ridge moves across the region Thursday and a
very subtle shortwave rides the backside of the ridge Thursday
night, but with limited forcing and moisture present, low
confidence with any widespread rain. Kept only slight pops going
across the north Tuesday evening. With the GFS keeping the surface
high in place over the state Friday, leaned toward a
significantly drier forecast on Friday. The ECMWF has a weak
shortwave cutting across Missouri Friday afternoon/evening and
kept some higher pops going over southern Iowa during this time.
By Saturday, decent shortwave (per GFS) to provide showers and
thunderstorms chance over the central to southern portions of the
forecast area.

Sunday into Tuesday...both the GFS and ECMWF have a large upper
level low develop and stall across the Great Lakes region placing
Iowa within northwest flow.  Several shortwaves ridge the upper
level flow and impact the forecast area Sunday through early next
week and timing of these shortwaves remains problematic. Mainly
kept with afternoon pops during this time frame as low
confidence with timing and location of any significant
precipitation chances.

&&

.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 653 PM CDT Tue May 23 2017

Broad cyclonic circulation will continue across Iowa for much of the
forecast period.  Lower stratus is expected to develop over the TAF
locations after 05Z pivoting down from northern Iowa into southern
Iowa.  There may be a few lingering showers past sunset but the
majority of the precip should diminish after 02Z.  Surface wind will
be northerly at 10 to 15kts. MVFR stratus will likely lift or break
up late in the TAF period.

&&

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

&&

$$

SHORT TERM...Cogil
LONG TERM...Podrazik
AVIATION...FAB


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