Rain, Snow, and Everything in Between

In Winter Weatherby Henry LukerLeave a Comment

Good morning. Winter still exists.

1. Looking at the Radar

Satellite/Radar/MSLP as of 4:45 am

Our weather situation early this morning is defined by a strengthening broad area of surface low pressure near northeast Kansas. Regional radar shows frontogenetic precipitation extending from Montana to Illinois courtesy of a cold front pushing south through the area. The majority of this precipitation is rain in Iowa with plenty of thunder and lightning being noted on the GOES-16 lightning mapper from Huron to Grinnell.

The rain/snow line appears to be between Interstate 90 and Minnesota Highway 30/South Dakota Highway 34, with Huron and Pipestone reporting thundersnow, while Madison, Sioux Falls, and Lu Verne report thunderstorms. If snow is indeed falling between Huron and Brookings, it’s likely quite heavy per radar imagery. Otherwise, our band of rain continues to push east-to-northeast with up to a half inch of rain possible.

2. What to Expect Today: Rain/Snow Far North, Rain/Wind Elsewhere

Today’s Forecast (4/10/2019)
HRRR Model Output for Most of Today (4/10/2019, 07z)

The aforementioned rain-snow line continues to try to creep southward. We will likely see a band of snow (or at least a rain-snow mix) over our far northern counties early this morning with cooling aloft. This should changeover back to rain this afternoon but ultimately creates the biggest problems for those nearest to the Iowa-Minnesota border. Not expecting any huge accumulations with this band, but a couple inches would be a reasonable expectation. Huge contrast in temperatures today – mid-30s north to almost 70 south.

Stronger storms are expected to develop in the Central Plains by the mid-afternoon. A few of these storms may be capable of producing large hail, gusty winds, and perhaps an isolated tornado. The better part of this threat will be west of our area, but wouldn’t be particularly surprised to see a few severe cells nudge the far southwestern counties. The WPC also has a marginal risk of excessive rainfall; grounds are already pretty saturated, so low-lying areas and rising rivers are likely to be exasperated today.

Wind advisories generally go into effect this morning (west) to later this afternoon (east). Winds will be very strong around the low, sustained at 25-35 MPH with gusts to 45. These will be easterly winds, so north-south roads (i.e. Interstate 35) will be heavily impacted.

3. Snow Possible Far North Tonight, Otherwise Rainy and Windy

Showers and thunderstorms will continue to be the story tonight with some mixing possible over the northern counties. Lows will bottom out in the low 30s north to the low 50s south. The best chance for any snowfall accumulation will be in Lyon, Osceola, and Dickinson counties, where a Winter Storm Watch goes into effect at 7:00 p.m. This will probably be upgraded to an advisory or blizzard warning this afternoon.

4. LONG-TERM: Thursday through Friday

Thursday will see another day of widespread showers and thunderstorms across the state. Highs will range from the low 40s north to almost 70 southeast. Another day of windy conditions with a rain/snow mix possible north. Snow moves out of the state late Friday morning.

5. The Big Picture

Ultimately, the biggest threat more than anything we’re going to be taking away from this storm is the hydrologic issues. The Weather Prediction Center is plotting almost three inches of pure liquid over the next five years for some parts of northwest and northeast Iowa, but generally at least an inch-and-a-half north of Highway 20. This is going to exasperate already-existing flooding issues, especially along the Mississippi.

Otherwise, the highest snowfall accumulations will be over far northwest Iowa, where six-to-eight inches is possible. One-to-three inches will be possible northwest of a line from Onawa to Elkader.

6. EXTENDED: Looking Ahead

Another round of rainfall, perhaps mixed with some light snow, seems probable for Sunday night over southeastern Iowa. Chances exist for Wednesday night as well, but confidence is low this far out. Overall, temperatures seem to moderate back into the 60s by the middle portion of next week with dryer conditions.

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