Altoona, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

539
FXUS63 KDMX 041115
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
615 AM CDT Fri Apr 4 2025

 ...Updated for the 12z Aviation Discussion...

.KEY MESSAGES...

- Southern stream system brings more rain chances later
  today/into early Saturday
- Return of pleasant and drier weather Sun through Tuesday
  afternoon with rather cold morning temperatures and potential
  frost/freeze
- Milder by Wednesday/Thursday with chances for light rain
  amounts Tuesday night and Thursday
- Late period uncertainty of timing of precipitation

&&

.DISCUSSION...
Issued at 245 AM CDT Fri Apr 4 2025

.Short Term /Today through Saturday/...

Confidence: High

Overall quiet pattern for our area with higher end impactful weather
remaining south of Iowa and in areas that have already had a rough
week. Weak high pressure over northern Iowa and southern Minnesota
will drift east today while an inverted trough slowly edges east.
Subjective sfc map at 05z shows the high over Iowa now with clouds
slowly arriving from the west and south. Moisture has been creeping
northwest toward the inverted trough at H850 from the Gulf northwest
to eastern Colorado. The high at H850 is currently keeping the area
dry. Another area of low pressure over Texas is forcing a moisture
plume across the lower to mid Mississippi River Valley today through
tomorrow and will result in significant rainfall/flooding and severe
weather potential there. As that southern stream low pulls
northeast, a shield of light rain will build into southern Iowa by
late morning and continue over the area this afternoon/night into
just after the midnight hour. Most of the area has a decent chance
for precipitation with the exception of areas north of US20 nearer
Mason City and west toward Estherville which will not quite get into
the moisture plume for very long. As mentioned yesterday, rainfall
totals will be very light north to around US30 and south of there
only a tenth or two is anticipated the next 3 days. Both today and
tomorrow will be quite cool. In fact with normal highs ranging from
52 at MCW and 58 at DSM, our forecast highs in the south today will
be around 5 to 10 degrees cooler than average. Saturday will be even
chillier for early April with afternoon readings in the mid 40s
north to the upper 40s south; some 8 to 10 degrees cooler than
average. At least some sunshine will return to much of the northwest
on Saturday but it will also be breezy with northwest winds of 15 to
30 mph through morning and then slowly diminishing in the afternoon.
Lows tonight with clouds and some light rain will hold in the upper
20s north to the upper 30s in the southeast. Some light snow may mix
in with the rain northwest with no impacts expected.

.Long Term /Saturday Night through Thursday/...

Confidence: Medium

Though the extended period will remain benign and temperatures
forecasts continue with consistency, the timing of the late week
warming and precipitation diverges between the EC/GFS model suites.
Saturday night will see colder north flow with light winds by Sunday
morning. This will allow for temperatures to drop into the mid 20s
over the north two thirds while the south sees mid to upper 20s by
Sunday morning under clear skies. Another weak northern stream
system and cold front will slowly drop south across the Northern
Plains/Iowa by Sunday night into Monday. A pool of more winter like
air near Hudson Bay today will make its way back into the Great
Lakes with the EC pushing H850 temperatures to -8C to -12C by 18z
Monday. Though the GFS deterministic/GEFs suite support each other
with milder temperatures than the EC, the general bias of the GFS is
likely again playing out here. Our current Monday forecast is
leaning toward the EC, but it may still need to be tweaked down a
few degrees due to the cold air heading our way. The cold air is
likely to stick around a few days and gradually moderate for
Wednesday through Thursday. After highs in the lower 40s northeast
to the upper 40s south Monday, we will hit rock bottom Monday night
as lows track to the upper teens northwest to the mid to upper 20s
south. Both models show two weak systems approaching next week; one
Wednesday and the second Thursday. The EC has more temporal
separation between weak waves and is also tracking slightly farther
south compared the GFS. These are all known biases with the GFS.
Some modification on timing, location and coverage of light rain can
be expected for both periods the closer we get to those events. The
overall trends in the height fields across the CONUS look favorable
for a warming trend as we move into mid to late week next week. The
slower EC would suggest late Thursday into Saturday while the GFS is
faster. Our blended  approach appears generally on track with 50s
and 60s expected Wednesday with similar highs anticipated for
Thursday. Rain chances will run about 40 to 50% for each event, but
only light amounts are expected and not expected to help our
rainfall deficit all that much.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 615 AM CDT Fri Apr 4 2025

Main challenge will be period of lower cigs to MVFR/IFR aft 04
to 05z northern sites (FOD/MCW/ALO) and for southern sites
(DSM/OTM) aft 19z. Light rain and vsby 3-5sm expected in heavier
showers. Wind less impactful generally east becoming northwest
aft 00z. /rev



&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...REV
AVIATION...REV