National Weather Service Raw Text Product

656 
FXUS63 KDMX 252340
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
640 PM CDT Fri May 25 2018

...Updated for 00z Aviation Discussion...

.DISCUSSION.../Tonight through Friday/
Issued at 319 PM CDT Fri May 25 2018

Severe weather potential and unseasonable hot weather were the
main forecast concerns through the weekend. No major changes to 
the ongoing maximum temperature forecast for Saturday and Sunday 
as they remain on track for near or record highs for both days. 

Storms already developing over south-central Minnesota and slowly 
tracking east-southeast. Tremendous instability present across 
northern Iowa where SBCAPE and MUCAPE topping out around 4000 
J/kg. The effective shear has increased through the day to around 
20-25 knots, but with minimal 0-1km bulk shear and helicity (at 
any level), low tornado threat this afternoon and tonight. 
Elevated supercells as LCLs range from 1500-2000 feet but do look 
to persist until the sun sets. Storm motion projects the current 
storm in Freeborn County Minnesota may clip the far northeast 
portions of the CWA through around 5 PM or so. Further west, 
latest IR satellite trends suggest an updraft developing north of 
Estherville with the cloud tops cooling to near -30C as of 2022z. 

With the high instability and low shear present, expecting main 
threat of large hail. However, with the DCAPE around 1000 J/kg 
and the microburst composite parameter around 2-3 which suggest a 
slight chance of a microburst (per SPC Mesoanalysis) occurring 
over the northeast corner of the forecast area. The majority of 
the hires models are not handling the current convection too well.
A few members of the HREF, such as the NSSL and ARW WRF might be 
doing the best with the trends. Regardless, have pops ending 
fairly quickly this evening past 03z with a few lingering storms 
possible across the east prior to 06z. 

Saturday through Friday...heat looks to persist for several days 
with the large upper level ridge remaining in control of the 
weather pattern. Records look possible Saturday through Monday 
with most standing records in the lower to middle 90s for the 
26-28 of May. The GFS and ECMWF suggest a shortwave trough to push
into the region by Tuesday into Wednesday and are somewhat in 
good agreement with timing. GFS is slightly stronger, but still 
have low confidence with any severe weather potential as the 
timing looks to be an overnight event.

&&

.AVIATION.../For the 00Z TAFS through 00Z Saturday evening/
Issued at 638 PM CDT Fri May 25 2018

VFR conditions expected at all TAF sites. Thunder to impact KALO
and potentially KDSM within the next few hours. Will be watching
KDSM closely. Outflow boundary from storms in Story county would
shift winds to being from the North if the make it to the airport.
May need to amend within the next hour or two... at this point,
not confident enough to add new FM group. 

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...Podrazik
AVIATION...Kotenberg