HIT AND RUN...

Another stunning day of weather graced the Midwest Wednesday. Sunny skies, meager humidity, and highs in the 70s are the stuff of smiles, and I'm sure there were plenty of those to go around. This was the 4th consecutive day in Dubuque where highs have held in the range of 74-76, with nary a cloud to be found. Choice!

Looking back at this year's temperatures to date, it's plain to see that it's been a mild year across the state of Iowa with all but the far west averaging 2–5 degrees above average. Interestingly enough, the core of the warmth was centered in the NE quadrant.

When you look at the specific numbers, 125 of our 248 days in Dubuque have experienced highs in the range of 70-89 degrees (about 50%). The very good news is that extreme heat, days 90 or above have been at a minimum. So far the hottest of the 4 days was 94, which did tie a record.

One thing few places have seen in recent summers is a 100 degree high. Here in Dubuque, the last time we hit the century mark was July 26th of 2012 (a stretch of 4,423 days which continues to grow). To break the all-time record we have a long way to go though. Back on August 12th of 1941, after eclipsing 100, readings never got that hot again until June 19th of 1988, a period of 17,114 days (almost 5 decades).

A ONE-DAY BOUNCE

Thursday will be a day of what could be classified as summery conditions thanks to a pre-frontal draw of SW winds. Temperatures should punch into the low to mid 80s in most area. Clouds will increase in the afternoon, especially across the north with the approach of a cold front. The associated forcing should spark a few showers and perhaps some rumbles of thunder as the front advances southeast. Some skinny instability tries to get established but with CAPE less than 500 j/kg vigorous updrafts will be tough to support.

With meager moisture, instability, and the rapid movement of the front, rainfall is expected to be light. Some spots could scare up 1/4" but in most places amounts will be considerably less. Here's what guidance is suggesting for rain totals. The convective allowing models such as the HRRR and 3k NAM are the most aggressive on amounts, particularly in the south. That is questionable.

The EURO

The GFS

The HRRR

The 3k NAM

NOW THAT'S WHAT I CALL A DOWNER...

Behind the front a stout upper air low digs into the Great Lakes driving a quick but potent shot of cold air into region.

The cold core circulation rotates over the area Friday afternoon and night dropping 850 temperatures to 3 degrees C. That type of cold air aloft will no doubt generate strong lapse rates that creates afternoon cumulus or pockets of stratus Friday afternoon.

The extent of the clouds could impact Friday's temperatures, especially in the northeast where some low to mid 60s are possible. A few brief light showers are also possible. However, most areas should see enough sun to reach the upper 60s with some low 70s in the far south. North winds of 15-25 deliver the cool air. Check out the big 1030mb high building over Canada.

Cold air advection kicks in big time Friday night allowing skies to clear and winds to decrease in the late evening. Temperatures should tank and lows of 40-45 seem to be a good bet, especially if winds taper off quickly after sunset. The GFS has this for lows.

Around daybreak Saturday it has wind chills in the 30s for many. Ugh...

I suspect it's too cold and a worst case scenario, but the 3k NAM has lows Saturday morning in the 30s as far south as I-80. It shows Decorah Iowa down to 32. Some readings in WC Wisconsin are shown in the mid 20s! We would need perfect radiational cooling to see anything close to what the 3k is depicting.

Later Saturday the high shifts east allowing return flow by afternoon. With full sunshine highs remain cool with readings in the range of 65 north to 70 south. Sunday and Monday look exceptional with highs in the low 70s Sunday and mid to upper 70s Monday. Bottom line, this round of chilly air will be of the hit-and-run variety.

After that, upper level ridging builds into the Midwest ensuring a warming trend that carries us through next week. The EURO shows the warmth building with 80s back in the area Tuesday though Friday.

The NWS 8-14 day outlook shows a strong chance of above normal temperatures along with below normal rainfall September 12-18th.