Des Moines, Iowa

• Rain lifting by the end of the night with dry conditions remaining Sunday.
• Rain returns Sunday night. Marginal Risk for severe weather Monday afternoon.
• Rain remains likely through at least Wednesday.

A few lingering showers are traversing our northern and eastern areas at the current time, and once those clear out the forecast is dry through the day today. Weak mid-level ridging will move overhead during the day supporting some thinning of the clouds and there may even be a few breaks at times. This should also allow temperatures to rise a little above yesterday`s levels, though any warming will be mitigated by the remaining cloud cover and relatively light nature of southeasterly breezes. Even so, highs in the mid to upper 60s are forecast and it should be a pleasant day overall.

A deep 500 MB trough will mover across the western CONUS today and then over the Rockies tonight. The trough will be split into several pieces with a northern stream component moving across west central Canada, a southern component nearing the Four Corners region by late tonight, and two leading shortwave troughs moving northeastward over the High Plains tonight after dark. The broad forcing for ascent associated with these leading waves, overlying a swath of theta-e advection and in conjunction with deep atmospheric moisture content, will promote the development of a large area of showers that will move into mainly western and northern portions of our forecast area after midnight. However, even ahead of this slug of rain/showers, within a broad warm air advection regime aloft there may be some more isolated preceding shower development which is supported by some hi-res model solutions such as the 00Z HRRR and FV3 runs. In light of this potential, have added slight chance (20%) POPs over about the western half of our area between 9 PM and midnight tonight, leading into the more robust POPs later.

The trough has closed northern and southern stream components to it, which look to merge together over the region Monday night. Ahead of then, the southern feature will mature as it ejects into the Plains. The midlevel reflection of the jet will round the trough base and cover the warm sector Monday afternoon. 700mb temperatures have trended warmer in southern Iowa, so lapse rates are closer to 7 C/km. MUCAPE values could surpass 500 J/kg in far southern Iowa. A line of storms will form along the cold front, but its threats will depend on how much clearing can take place ahead of its arrival. REFS ensemble soundings and hodographs have favorable shear parameters for damaging winds and tornadoes, but are at the mercy of the lower thermal profile. There is not much spread in the PBL temperature values, which struggle to mix in most all ensemble members. Without near-surface instability, the threat will be mainly isolated damaging winds.

Another notable trend is the timing of the front arriving in Iowa. This is because the two aforementioned components of the trough will be merging together, causing the resultant closed low to stall. The delayed arrival means severe weather chances are lower, since storms would be arriving after dark. The slowed movement then increases the rainfall amounts, as the front will utilize the 1.5" PWATs and drop 1-2" in southern Iowa. Something else we`ll need to watch is storm potential in eastern Iowa on Tuesday afternoon due to the front`s late exit. That said, the thermal profile looks less impressive on Tuesday, by comparison. Cooler temperatures will advect in on the backside. Precipitation chances linger through much of the week due to the TROWAL of the system.

A combination of LIFR to VFR observations exist across central Iowa. KMCW is socked in with LIFR fog with the other sites seeing transient low CIGS, lowered VSBY and patchy drizzle. This is to be expected through the overnight before weak surface high pressure arrives tomorrow and CIGS improve to VFR mid-morning Sunday. VFR conditions will prevail through much of the day before lowering CIGS arrive Sunday evening with the approach of a surface wave from the west. Outside of fluctuating CIGS, winds will remain light but will begin to increase out of the southeast between 5 and 10 knots after 14Z.

None.