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JACK BE NIMBLE, JACK BE QUICK AND COLD


As I indicated a week ago all the ingredients for frost will be on the table Wednesday morning. That includes:

  1. A large 1036mb Canadian high

  2. Dry air

  3. Light winds

  4. Clear skies

  5. Maximum radiational cooling

With all those ingredients in play, it looks like old "Jack" will be nimble quick and cold Tuesday night. For now, the biggest question is how cold? Some of the high-res CAM models are indicating lows at or below freezing near and north of I-80. The coldest scenarios are highly dependent on winds decoupling early and the ridge being directly overhead. Assuming that happens, it would not be at all out of the question for some of the valley locations (where cold air drainage is a thing), to hit 30-32. In general the most common range should be 32-37 with the coldest readings just NW of the Quad Cities. I expect frost to be widespread but the freeze potential is far less certain. I do expect frost advisories will be issued by the NWS for at least the NW half of the region Tuesday.


The GFS shows a 70-80 percent chance of a temperature less than 32 in my northern counties up near HWY 20.

If by chance a 32 degree reading makes it to the Quad Cities (which is unlikely), it would be the 9th earliest on record. In other words, an an event that is in the top 6.8 percent of all fall freezes going back to 1874. The earliest was on September 20th, 1991. The latest November 12, 1946.

Here are the earliest fall freezes from around the area from the NWS in the Quad Cities.

Still 24 hours out, here are what various models are suggesting for lows Wednesday morning.


This is the official NWS forecast at this time.

Now the various models starting with the coldest solutions.


The 3K NAM

The 12K NAM

The GFS

The national model blend

The EURO, I think at this time its warmer solution is an outlier. We shall see.

Aside front the frost potential Wednesday, the rest of the week and coming weekend looks to be pleasant and uneventful. Readings will be cool through Thursday before a slow warming trend kicks in as the weekend arrives. Nights will be crisp but daytime highs will moderate from 55-60 Tuesday and Wednesday, to 60-65 Thursday and Friday, to near 70 Saturday and Sunday. Here's what the meteogram has for Quad Cities the next 7 days.

The last week has been dry over most of the region and this is a trend that currently shows no tendency to end. Here in Dubuque, only 5 of the days 26 days have seen measurable rain. The monthly total is at just .59 inches and the grass around here is toast. We really need a soaking rain and that's the case for surrounding counties in NE Iowa.

Both the EURO and GFS show little if any rain prospects the next two weeks. Here's the respective rainfall departures over that period. Widespread dryness is shown over much of Canada and the central U.S.


The EURO

The GFS

One area that will see rain is the southeast where the tropics are about to let loose. A significant hurricane named Ian is expected to rapidly intensify the next 24 hours and move north over western Cuba. From there the storm heads for the west coast of Florida where a landfall is possible in the vicinity of Tampa. Models are still getting a handle on the track and intensity but it is likely that Ian will be a major hurricane (at least a cat. 3). Wobbles and changes are common with the track right up to landfall. At least for now. the area near and south of Tampa is favored for a hit.

Below you can see the center of the hurricane Wednesday evening on the GFS just SW of Tampa.

If the storm tracks north of the city a dangerous storm surge of 5-10 feet is possible.

A surge of that magnitude would impact many parts of the city as depicted in this potential surge flooding inundation map.

If the storm turns sooner and passes south of the city, the surge is significantly less. However, the winds would be maximized over the city with some gusts on the EURO 120-130 mph at 10 meters.


Both scenarios would be highly impactful. The best case situation would be for the storm to weaken substantially before landfall or move far enough west to keep the surge and winds over the Gulf. Time will tell.


One of the few things we don't have to worry about in the Midwest in terms of natures extremes are raging winds and storm surge. That is fine by me! Have an outstanding day and roll weather...TS

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