← Previous May 30, 2023 6:28 AM

FXUS63 KDMX 301128

Area Forecast Discussion
National Weather Service Des Moines IA
628 AM CDT Tue May 30 2023

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

.DISCUSSION.../Today through Monday/
Issued at 312 AM CDT Tue May 30 2023

Key messaging highlights:

* Prolonged warm spell with seasonal humidities
* Also prolonged, generally low chances for mainly afternoon and evening
  showers and storms
* Widespread precipitation unlikely with minimal appreciable drought impacts

A very summer-like weather pattern will be locked in place into 
early next week with warm temperatures, weak flow through the 
column of the atmosphere, and generated nondescript forcing 
mechanisms. One current exception is early this morning however, 
with several MCS clusters over KS/NE, and from northwest IA into 
MN, driven with some kinematic support on the trailing lobe of 
forcing from the current ND short wave and further supported by 
relatively weak moisture transport in the SSW low level jet 
traversing the MO Valley. The storms have generally be unorganized
with weak effective shear and instability continuing to diminish 
into the night with the loss of MLCAPEs. Some spotty weak 
convection may advect or re-develop into western sections early 
this morning until the low level jet support weakens, and our 
attention turns to the potential for re-development later today.

The models suggest the aforementioned ND short wave should only 
be entering MN by this afternoon with its trailing lobe of support
now into central IA. The better low level theta-e axis and 
instability should ooze a bit farther east into IA by this 
afternoon with uncapped 1500-2500 J/kg MLCAPEs. Although there is 
little low level focus with fairly uniform light southerly surface
flow, the large scale support and uncapped airmass suggests 
additional development into peak heating of the afternoon. Overall
the strong to severe threat is low, although steep low level 
lapse rates and weak effective shear would support a few strong 
storms with wind and microburst potential, and mainly west. 
Similar to what is presently occurring, a weak low level jet may 
support what storms do form into the evening, but any convection 
should again diminish into the night as low levels stabilize.

The airmass will be relatively unchanged into tomorrow, with 
another similar convective cycle possibly later Wednesday into 
Wednesday evening, possibly driven by a weak short wave now moving
out of the Four Corners region reaching the MO Valley by peak 
heating tomorrow. The severe weather potential would again be low,
with isolated strong storms with gusty winds possible due to weak
deep shear and steeper low lapse rates.

Looking further ahead, this diurnally focused afternoon/early 
evening weak convection cycle will likely persist through the 
week. With little airmass change, temps will remain warm and above
normal. Although confidence in details is low with nebulous and 
ill- defined focusing mechanisms, the generally uncapped 
weak/moderate instability airmass will remain in place. The mean 
wind and effective shear will rarely exceed 20kts for at least 
several days, so the severe weather potential will remain low with
isolated very heavy rains some concern. Although the moisture 
parameter space is seasonal and not extreme, any healthy 
convection will be slow moving and could lead to isolated heavy 
rains. The coverage will likely be quite limited however with 
appreciable drought recovery not anticipated.

Looking very late in the period (late Monday) or just beyond, 
these precip chances may be aided by another back door cool front 
passage. The models are not in great agreement with the strength 
of the eastern upper low, but do suggest a stronger western Great 
Lakes/Ontario surface high with northeasterly low level flow and 
reduced low level moisture through the Upper MS Valley into IA by
next week.


.AVIATION.../For the 12Z TAFS through 12Z Wednesday morning/
Issued at 628 AM CDT Tue May 30 2023

VFR conditions are in place across central IA at 12z with isolated
storms north central. These are expected to dissipate later this
morning, but addition chances for showers and storms return later
this afternoon and this evening. The coverage will be limited
however, with low confidence, so any mention will be omitted 
until trends become more clear. Conditions should remain VFR 
outside of the stronger storms, which again should be isolated 
with limited predictability for any particular location.