438
FXUS63 KDMX 192006
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
306 PM CDT Sat Oct 19 2024

.KEY MESSAGES...

- Well above normal temperatures in the upper 70s to low 80s
  Sunday into Monday with continued elevated fire danger.

- System will bring welcome precipitation chances to the area
  later Monday into Tuesday, however amounts remain quite low
  (~20-30% chance for greater than 0.10" in southern Iowa).

- Cooling temperatures mid week but rebounding temperatures
  into next weekend.

&&

.DISCUSSION...
Issued at 240 PM CDT Sat Oct 19 2024

We continue to watch the closed low in the southwest U.S. near the
Four Corners region today as it eventually dislodges and treks
towards the area on Monday bringing some precipitation chances with
it. Before then, blocking high pressure remains dominant with
increasing temperatures as H850 temperatures rise from +12/13C today
to +15-18C on Sunday resulting in another several degrees of
temperature increase from our mid to upper 70s today with Sunday
highs topping out in the upper 70s to climbing back near to over 80!
Similar temperatures are expected to occur again Monday central to
east with a few degrees of cooling in the west as clouds ahead of
the approaching system increase over western Iowa in the afternoon.
These highs in the upper 70s/low 80s are well above normal for mid
October with normal high temperature values in the upper 50s to low
60s.

We likely sound like a broken record at this point but these warm
temperatures will be combined with lowering humidity values and
breezy winds on Sunday afternoon to result in elevated fire weather
conditions given our dry crops and continually drying grasses
in our expanding drought conditions. Although the wind gusts
won`t be as high as a few days ago, conditions have over
performed today with a few higher gusts and lower dew points
leading to following suit in the forecast for tomorrow when
winds were already expected to be a little higher, especially in
the north. The highest gusts of around 20-25 mph are expected
to be in northern Iowa which will be offset from the lowest
relative humidity values near to below 25-35% in central to
southern Iowa but with the number of fire starts in the last few
days and the ease of fire/start spread in the dry conditions,
precautions should continue to be taken to prevent fires Sunday
and again Monday, especially in crop fields.

As our aforementioned system arrives Monday night and moves out by
Tuesday morning/midday. The better forcing with this system remains
to the south of the state with deterministic and ensemble data
continuing to decrease the overall rain amounts in Iowa. This is
generally not surprising given the overall meager plume of moisture
and the amount of dry air that has to be overcome for any
precipitation to reach the ground. Still anything is better than
nothing with our void of precipitation in the last two months, as
noted in the previous discussion. Probabilities for QPF > 0.10
inches in southern Iowa have decreased to around 20-30%, though
probabilities for at least measurable rain (0.01 inches) remain
>60% roughly south of I-80 and west of I-35, but decrease east
of I-35 and north of I-80. All this to say, yes there is rain in
the forecast, but unfortunately amounts continue to remain on
the low side. A rumble of thunder can`t be completely ruled out
but instability values are small and diminish with time given
the timing of any shower/storm arrival so not expecting any
stronger storms at this time.

Behind the departing system, a strong cold front arrives later
Tuesday into Wednesday sending temperatures falling into the 60s
through midweek but this will be short lived as temperatures warm
again to the 70s by next weekend. The front is unfortunately also
moisture starved so although there are some low, <20% chances, for
showers in northern Iowa early Wednesday in the current forecast,
these may be fleeting and not much to speak of either.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1229 PM CDT Sat Oct 19 2024

VFR conditions ongoing and expected to continue through the TAF
period. Some scattered-broken higher level clouds remain
north/northwest but these are expected to continue to dissipate
through the afternoon. Winds out of the southwest generally are
near to below 10-15 knots, but a few higher gusts to around 20
knots are possible this afternoon. Lighter winds return overnight
before winds pick up again Sunday, especially in northern Iowa.

&&

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

&&

$$

DISCUSSION...KCM
AVIATION...KCM