Oh Snowy Night

In Evening Brief by Henry LukerLeave a Comment

Marvelous Monday to you. Okay, yes, we couldn’t do anything about the wind. We saw 15-25 MPH winds regularly with gusts to 40 (43 MPH in Dubuque). Highs were in the upper 30s in northwest Iowa (yes, I know) to the upper 50s in southwest Iowa (61 in Council Bluffs). Southeast Iowa actually on the cooler side of the totem pole for once.

1. Here Comes the Snow

HRRR Simulated Radar through Tonight
Snowfall Forecast through Tomorrow

A look at the radar on this Monday evening shows returns from Spirit Lake extending into northeastern Nebraska. Our system is showing this as snow and seems to be verifying — Jackson, MN, Sheldon, and Estherville are all reporting light snow. Spencer is reporting an unknown precipitation which typically equates to a rain/snow mix. The heaviest of this activity seems to center around Sioux county north of Orange City.

What’s happening: Initially, most of this activity should just melt on contact or seem like a very wet snow. Road temperatures in northwest Iowa are in the mid-30s. But as temperatures fall tonight, minor accumulations are possible, up to an inch or two locally. High-res models are wanting to paint this strip from Monona to Kossuth county but confidence in any specific totals are low. Ultimately, anywhere northwest of a line from Logan to Prairie Du Chien may wake up and find some minor snow accumulations.

Bottom line: This won’t make it into tomorrow with warm temperatures, but if you do have travel plans tonight, especially in northwest Iowa, make sure to take note of the weather.

2. Dry Tuesday

Lingering rain and snow showers will be possible along and east of the Interstate 380 corridor tomorrow morning. Slick/wet travel is expected for portions of the morning commute in Waterloo, Cedar Rapids, Iowa City, Dubuque, and Quad Cities; please make sure to note this possibility and give yourself a little extra time if needed. We should see a transition to all-rain by mid-morning with clouds and precipitation quickly leading off to the east.

The day will turn out nice and seasonal with high temperatures ranging in the low 50s north to the mid-50s south. Winds will westerly at 5-15 MPH, gusting to 20 MPH.

3. Another Round of Rain Wednesday through Thursday

WPC QPF Forecast through Saturday night
ECMWF Model Output from Wendesday Morning through Thursday Night

Another round of rain will affect the state beginning Wednesday afternoon over far southwestern Iowa, slowly propagating to the rest of the state by the overnight hours. Bit of an interesting synoptic setup with an open upper-level trough digging near the region; at the surface, two boundaries will collide near the area (cold vs warm air). Warmer air will overrun more moisture aloft and create a solid environment for precipitation chances.

The best chance for measurable precipitation will be along and south of US-20. A half inch to an inch of rainfall can be expected; those in low-lying areas and flood-prone areas should be aware. Those north of 20 (ala Spencer, Mason City, Decorah, et al) may see drizzle or rain showers Thursday, but accumulations won’t add to much. Rain should fizzle out or move to the east by overnight Friday.

4. …And Another Sunday

After a few quiet days, Sunday will come back storming (literally) with a boom as a surface low approaches the area. This still still near the end of the seven day so specific details will need to be ironed out, but we can say fairly confidently that rain can be expected.

What they’re saying: The 12z ECMWF and the 18z GFS both seem to bring a low up from the southern Plains towards the Ohio Valley with plenty of precipitation to go along with it. The GFS is much faster on the evolution than the Euro, parking precipitation closer to Saturday, while the ECMWF sits from late Sunday afternoon through Monday morning. The earlier run of the GFS at 12z was actually a lot closer in timing to the Euro than the likely-outlier at 18z, so unless this is a new trend, we’re sticking with the ECMWF — much more consistent.

Our thoughts: While the finer timing details will need to be worked out, it’s keeping the same relative story on track and the amount of moisture that will be involved. Both show dew points reaching the 60s (!) in some parts of the state, which we haven’t seen since last fall. PWATs sit above an inch for many areas. Essentially, these are two important markers showing for the potential of significant rainfall. And while severe weather isn’t expected, enough surface-based CAPE should exist for thunderstorms to be less of a stretch than what we’ve seen with recent storms.

Bottom line: Showers and thunderstorms will be likely beginning Sunday afternoon, sooner the farther west you go, and continuing into Monday morning. It’s much too early to accurately predict any accumulations, but significant rainfall is possible. This may cause issues once again on rivers, in a seemingly continual state of flooding more often than not.

5. Seven Day + Goonie Period

The seven day is marked by two rounds of precipitation — one on Wednesday and Thursday (see point three) and on Sunday and Monday (see point four). Otherwise, on our recovery days, partly cloudy skies can be expected. Temperatures will remain seasonal for most of the work week, hampered by rain unfortunately. Warming begins on Friday with 70s becoming more common towards this weekend and next weekend. If there’s any day for you to go absolutely wild, pick Saturday. Dry and warm.

Most of next week right now looks dry and warm in the 60s, dominated by high pressure. Towards the later part of the week and towards two weeks out, the GFS is extremely active with frequent lows and rain chances.

Be smart: This is the gooney-period of the run with EXTREMELY LOW PREDICTABILITY, so take it for what you will.

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