Gorgeous Weekend Ahead

In Evening Brief by Henry LukerLeave a Comment

Happy Friday. What a beautiful day; temperatures this afternoon are ranging from the upper 50s in northeast Iowa to almost 70 in Council Bluffs, under sunny skies. Haven’t said that condition for quite a while…

1. Rain Northwest Tonight

Forecast for Tonight 4/5-4/6
18z HRRR simulated radar from this evening through tomorrow afternoon

The overnight will be highlighted by a disturbance moving through the northern part of the state. The bulk of the rain should hold off until past midnight, but spotty showers are already being observed on the radar out of Sioux Falls.

SPC mesoanalysis this afternoon shows about 250 j/kg of MUCAPE, which is an indicator of some weak instability over the area, but just enough to cause thunderstorms. The heaviest rain will be in far northwest Iowa where up to an inch is expected.

Otherwise, cloudy skies will be possible elsewhere, with low temperatures not dropping a whole bunch — towards the 40s to potentially over 50 in areas with the thickest clouds.

2. 70s on Saturday

Forecast for Tomorrow 4/6/2019

Aside from general cloudiness throughout the day and some lingering showers early tomorrow morning north, Saturday should be a marvelous day with highs ranging from the upper 60s in the far north to the low 70s south. An isolated shower or two is possible during the day, but nothing widespread is expected.

The one downside is that, as per usual with nice weather at this time of year, southerly winds will pick up on the eastern flank of the surface low in the Plains — to the tune of 10-20 MPH with higher gusts.

3. Late Weekend Rain

Forecast for Tomorrow Night 4/6-4/7

Another system moves in tomorrow night from the southwest bringing more rain to the area. Models have been showing the bulk of this precipitation in two distinct bands on a northeast-to-southwest angle – the ECMWF has one affecting areas west of Interstate 35 and another towards southeast Iowa, while the GFS is much more southeast and primarily targets southwest to northeast Iowa.

Bottom line: In general, the majority of the state should at least expect SOME rain on Saturday night into Sunday. The heaviest activity will be Sunday afternoon, but where this exactly sets up will need to continue to be tweaked into tomorrow.

4. Terrific Start to the Work Week

Seven Day Forecast for Des Moines

Terrific start to the week ahead with Monday and Tuesday seeing relatively sunnier skies than recent days. Highs will range in the 60s and 70s, the warmest coming on Monday; lows will range in the 40s and 50s. A weather system looks to impact the area Tuesday night through Thursday morning, which is covered in the section below, but below normal temperatures seem to take hold for the latter part of the week into the weekend.

5. Still Monitoring Mid-Week System

A disturbance is expected to develop off the coast of the Aleutians of Alaska by Saturday evening and become a formal trough by Sunday night. This will strength off the Pacific coastline and eventually come inland over northern California by midnight Tuesday morning. By Wednesday morning, it will broaden over Colorado, followed by a rapid deepening over the Plains toward Wednesday evening. The GFS and ECMWF are surprisingly in broad consensus as of the 12z runs this morning. The other global model, the GEM, puts it much slower, closer to Thursday and Friday.

At the surface, a low pressure system will form over Nevada and move through Utah on Monday and Tuesday, deepening near the trough in Colorado on Wednesday, before settling on southeastern Kansas by Wednesday evening, according to the GFS. The Euro is much farther north toward the far northeast corner of Kansas. This is another seemingly minor detail that actually will play a huge role in the exact synoptic setup.

This is especially prevalent when looking at QPF numbers, with the Euro painting widespread amounts over an inch (of pure liquid precipitation) through the entire state, whereas the GFS pushes things much farther south. These are the details that are going to be have to be tweaked in the coming days, especially as the wave comes inland towards the CONUS upper-air network.

The one word we hate to mention yet is snow. We have high confidence that snow will fall on the north part of the system. However, where this “north part” ends up being is dependent on the location of the low. We could see it being anywhere from northern Iowa to southern Iowa, and it would be prudent to put a “best guess” out on that. There are going to be so many factors at play – the location of the low, first and foremost, but also the specific timing of the system, how quickly temperatures change, etc.

We’re fairly confident that precipitation will begin late Tuesday night with the bulk of it coming towards the afternoon and evening hours on Wednesday, lingering into Thursday morning. The one thing of concern, with any winter weather problems, is that we’re also confident that winds will be strong with this system – towards the range of 20-30 MPH sustained, with gusts to 45 MPH. For context, blizzard conditions is generally defined as frequent gusts of 35 MPH. If any snow does fall, near-blizzard conditions would be possible. It’s way too early to start throwing numbers and locations out, as we said, but it’s something to keep an eye on.

Stay aware: The entire state should be keeping a close eye on this as we go through the early part of next week.

6. The Goonie Period

The GFS is still showing an active long-term, with another storm (looks to be predominantly rain) on Sunday the 18th, though the ECMWF is saying “Storm? What storm?” So take it for what you will. GFS shows several other rain chances towards Wednesday/Thursday 17-18, and Sunday the 21st. Hopefully we’ll get luckier with dry conditions, especially as we head towards graduation season.

Temperatures look to moderate close to normal by mid-week with much warmer temperatures by next weekend.

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