Altoona, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

352
FXUS63 KDMX 240959
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
359 AM CST Sun Nov 24 2024

.KEY MESSAGES...

- Final mild day of the forecast Sunday, drizzle and cloudiness
  to arrive after sunset.

- Monday now dry, but chilly with highs in the 30s. Highs to
  remain the same for much of the work week.

- Precipitation chances have broadened on Wednesday due to
  location uncertainty. Highest confidence remains in southern
  Iowa. Rain and snow both in play. Continue to monitor the
  forecast.

- Colder temperatures likely (80%+ confidence) Thanksgiving and
  beyond. Highs in the 20s and teens forecasted next weekend.
  Expect this pattern to stay into at least early next week.

&&

.DISCUSSION...
Issued at 355 AM CST Sun Nov 24 2024

WAA continued last night and paired with cloud cover, temperatures
will largely be spared from freezing this morning. Clouds will have
the opposite effect during the day, putting a damper on highs in
especially the north. Before stratus encapsulates the south in the
late afternoon, highs should reach the mid to upper 50s. The north
will be held in the 40s. Models have come into better phase
regarding precipitation chances tonight into tomorrow, with most of
the moisture staying southeast and northeast of the area. However,
some low level moisture will build beneath the midlevel drying in
the north. This will lead to drizzle across the north after sunset
this evening, with perhaps some fog. Drizzle will continue overnight
and begin to push east Monday morning. At this time, saturation
looks to be lost right a temperatures drop below freezing, sparing
the area from freezing drizzle. Nonetheless, ground temperatures
Monday morning would be too warm to allow for much in the way of
accumulation. Have introduced drizzle mentions, but have left out
fog mentions for now so that conditions can continue to be
evaluated. At this time, there wasn`t enough consensus in model
visibility fields to indicate fog would be widespread and impactful.

Precipitation chances exit the picture during the day Monday, but it
will feel chilly. Highs will be in the 30s for much of the area,
save for the far south, and conditions will remain this way for much
of the work week. Breezy conditions Monday will bring wind chills
down into the teens in the north in the afternoon.

In regards to the midweek system: arrival has sped up since last
night and is evidenced by the PoPs now mostly being on Wednesday and
Wendesday night. Precip chances are also now notably more
widespread, but low, with the highest chances in the south. This is
due to a divergence in the two main ensemble camps. The ECMWF
intensifies an upper-level jet in the Northern Plains faster than
the GEFS, which deepens the trough more, thus increasing southerly
flow, allowing for more moisture to follow the warm conveyor belt of
the cyclone into Iowa, increasing rain/snow amounts. While the dry
deterministic GFS is an outlier, GEFS members do have some hints of
snow in southern Iowa, but drop off significantly north of Highway
34. Amounts overall in that ensemble are much lower than the EC as
well. Expect the broad-brushed nature of precipitation chances for
the event to narrow with time as models consolidate on the behavior
of the upper air pattern. What can be said with certainty is the
warm sector will remain somewhere in the Mid South as this aligns
better with where the Pacific Moisture has been consistently
advected to.

Northwest flow settles in for Thanksgiving and beyond, opening the
region up to more chances for waves of energy to propagate
around the parent low center amd give way to more precipitation
chances, all of which remain low confidence at this time (~20%).
There is high confidence (80%+) in even colder air settling in
for the holiday weekend into early next week. Ensemble guidance
into early next week hangs onto the northwest flow which could
mean this upcoming wintry airmass will be here to stay for a
good portion of next week, too.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1149 PM CST Sat Nov 23 2024

VFR cloud cover will continue into Sunday with ceilings
decreasing to MVFR from north by midday to south by the
evening. Winds will remain light but shift from out of the
southeast to out of the northwest by Sunday evening. At the same
time, low level saturation in northern Iowa may allow for
drizzle or fog development late Sunday into Monday morning. At
this time confident is low so have kept any fog/drizzle mention
from the TAFs at this time.

&&

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

&&

$$

DISCUSSION...Jimenez
AVIATION...Hagenhoff