Sunrise 6:26 AM   Sunset 8:00 PM Moonrise 1:58 PM   Moonset 3:30 AM

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FXUS63 KDMX 180450 AFDDMX

Area Forecast Discussion National Weather Service Des Moines IA 1150 PM CDT Wed Apr 17 2024


Updated for the 06z Aviation Discussion

KEY MESSAGES

- Rain to move in tonight with thunderstorms southwest. Some could be strong to severe with gusty winds and hail.

- Rain exits Thursday afternoon with below average temperatures behind for the remainder of the week. Below freezing lows likely (>75%) this weekend.

- Next precipitation window early next week.

DISCUSSION
Issued at 251 PM CDT Wed Apr 17 2024

The low pressure that impacted the state continues to lift to the northeast this afternoon. Diurnal mixing has eliminated some of the stratus in the southwest half of the state, allowing temperatures there to rise into the 60s. The clear skies and fair weather will be short-lived.

Morning upper air analysis showed a wave in the High Plains as well as an area of low pressure over the Texas panhandle. This low will lift northeastward overnight and bring with it moisture from the Gulf. The wave from the west will be accompanied by Pacific moisture. The two areas of moisture will be out of phase with each other, but both will bring rain to the state starting tonight lasting into Thursday. The Pacific moisture will impact all but the bottom third of the state and will depart with the synoptic wave Thursday afternoon.

The southern stream of moisture will precipitate along an fgen band that spans into southwest Iowa this evening. The instability axis will span into this region as well, but with higher values remaining in MO. The base of the trough with an intensifying midlevel jet will center over the area tonight with some diffluence on the exiting half. Paired with the front mentioned earlier, this is a favorable setup to produce mesoscale gravity waves (MGW). CAMs are keying in on evening convection positioned just behind the front and are producing spots of 40kt+ wind gusts with the MCS as it interacts with the MGW and transfers winds aloft towards the surface. Soundings support this possibility with time series cross sections with pockets of large positive omega reaching the surface. While most of these storms storms will not organize until they sink into MO, cannot rule out gusty winds in Iowa along. Some hail will be possible given the available MUCAPE.

Beyond Thursday, broad troughing will deepen over the region and keep a colder airmass overhead, keeping temperatures in the 50s for the rest of the week. Lows will be in the low 30s and even 20s in spots in the weekend which will warrant frost/freeze headlines. High pressure will keep precipitation away until a shortwave arrives early next week.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
Issued at 1150 PM CDT Wed Apr 17 2024

Light showers are moving from Nebraska into Iowa and will affect the terminals overnight, with a few thunderstorms likely in southern Iowa including at OTM during the early morning hours Thursday. Have gone with prevailing SHRA for much of the night but visibility restrictions will be generally light/MVFR and intermittent. Meanwhile, a large area of low stratus clouds will move through with the rain and produce prevailing low ceilings below FL020 for much of the night/morning. There is potential for several hours of IFR within this time, however confidence is not high enough to include in the TAFs at this time. Amendments are likely overnight based on radar/observational trends.

DMX WATCHES/WARNINGS/ADVISORIES
None.

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Des Moines, IA,