007
FXUS63 KDMX 101923
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
223 PM CDT Wed Jul 10 2024

.KEY MESSAGES...

- Scattered storms today; with some strong to severer storms
  this afternoon and evening.
- Seasonal Temps Through Friday; approaching 90 Saturday
- Heating up into the 90s by Sunday and Monday with heat indices
  over 100F during the period. Late in the period, cooler back
  down.

&&

.DISCUSSION...
Issued at 222 PM CDT Wed Jul 10 2024

.Short Term /Tonight through Thursday Night/...

Confidence Short Term:  Medium to High

In between pattern changes with continued warm and humid conditions
and scattered showers/storms today into tonight with lesser chances
on Thursday/Friday but increasing again Friday night. Old Beryl, now
a plain ole synoptic low, is currently heading into southern lower
Michigan this morning at 12z. A weak trough stretches back to the
west from the system and is located along the Iowa Minnesota border.
As the remnants of Beryl moved northeast, it phased slightly with a
preexisting upper level system and brought lower heights into Iowa
overnight. This has helped to expand the area of showers/weak
thunderstorms across the region this morning. While widely scattered
storms continue in central Iowa at 1330z, a more widespread area is
located along the main/upper troughs in southern Minnesota. The
trough will likely set up shop over central to southern Iowa by late
afternoon/evening. With sufficient instability, and a small area of
shear in southwest Iowa, a few more organized storms may occur into
the evening with wind or hail, or a few funnels. We are now
outlooked for a slight risk in the far southwest for larger hail and
perhaps a bit of wind. Otherwise, the weak wind shift and
instability over areas along and south of I80 may lead to a few
funnel clouds this afternoon. The other area to watch will be over
northern to northeast Iowa where NST parameters ramp up this
afternoon into the early evening hours. Though soundings are not
particularly moist, we do have H850 dewpoints of 10 to 12C over the
region along the approaching trough.  PWATs are running 1 to 1.5
inches with warm cloud depths around 10kft. Upstream qpf amounts in
southern MN overnight and earlier today have been in the 1 to 2 inch
range, mainly due to the slow moving storms and the upper level PV
max. Though spotty, some random 1 to 1.5+ inch amounts may occur
this afternoon into the evening hours. Overnight tonight, the system
will pull into southern Iowa/northern Missouri with some lingering
showers early southeast. With nearly calm winds by morning, some
patchy fog is expected and especially in valley areas. Tomorrow we
remain with a similar airmass, but less forcing. A few afternoon
showers/iso storms may again occur mainly east of I35 during the
afternoon hours. By nightfall, light south southeast flow returns to
the region as lee side troughing commences into the region.
Temperatures and humidity levels will begin to increase as we move
into the weekend. Lows tonight will fall into the lower 60s over the
area with afternoon highs tomorrow in the lower to mid 80s. Tomorrow
night, with increasing warm air advection, lows will fall only to
the lower to mid 60s.

.Long Term /Friday through Wednesday/...

Confidence: Medium to High

Friday will see some clouds increase by late afternoon as a warm
front approaches late in the day. With afternoon H850 temperatures
warming up to 16C northeast to 21C southwest. Deterministic models
are forecasting a 25 to 35kt low level jet overnight Friday night
into early Saturday morning. Efficient rainfall parameters are again
ramping up overnight. Depending on how quickly storms can ramp up
overnight, brief heavy rainfall may occur with some of the scattered
thunderstorms. Current blended output puts rainfall chances at
around 20 to 30%, though we may need to raise those values. Friday
night will see warmer overnight mins with readings with upper 60s to
lower 70s. Over the weekend, we will again be saddled with a humid
airmass with either weak impulses or warm air advection processes
aiding in some lift. The current forecast calls for the H700 cap to
be building toward eastern Iowa by afternoon. This should keep rain
chances toward a minimum over our area. For the weekend, the hot
dome over the southwest will build east for Saturday and Sunday.
Highs Saturday will already reach the upper 80s to lower 90s. By
Sunday, our H850 temperatures warm to 20 to 25C with increased
mixing. Sunday appears to be the hotter of the two days with H850
temps peaking at 25 to 28C. This will lead to highs in the mid 90s
during the afternoon. By Monday, some cloud cover may hold temps
back a degree or so, but overall the medium range models suggest
that a boundary north of the forecast area will drop south
later Monday night into early Tuesday, when temperatures will
cool further. With increasing temps over the weekend and
dewpoints on the way up, heat indices will be up above 100 for
Sunday and possibly into Monday. There`s a fair amount of
uncertainty from Tuesday into Wednesday with regard to rain
chances, though as the front drops south, chances for a few
storms should go up as the H700 cap cools. We round off the
extended with highs falling back to the lower to mid 80s by
Wednesday central to south with upper 70s over the north.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1241 PM CDT Wed Jul 10 2024

Scattered showers/storms over the area through about 01z with
higher chances at ALO/FOD/DSM/OTM. Upper level wave tracking
south with sfc trough expected to move south of the region aft
06z. Main challenge timing/coverage but some storms will lower
cigs to MVFR with vsby 2-5sm possible with brief heavy
downpours. Patchy fog also expected 10-13z. Aft 13z, remainder
of period fairly benign. /rev

&&

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

&&

$$

DISCUSSION...REV
AVIATION...REV