THE BIG DIPPER...
Spring fronts come and go on a regular basis. Some of them can still carry a little clout as the remnants of winters chill lingers in Canada, I call them big dippers. The one good thing about this time of year is that when you do get one of these bursts of cool air ( a dipper), they usually don't stick around and their impacts are modified by the Sun. After all, big Sol's rays have been growing stronger since the winter solstice five months ago. As a result, cold fronts just don't have the same clout as they did in previous months.
I bring this up because a cold front of this nature is swinging through the Midwest early Thursday. It's impact on temperatures Friday will be noticeable with readings running 10-18 degrees cooler than just 24 hours earlier. A fresh breeze will also have a cooling effect.
You can see where the cold front is projected to be by looking at the simulated radar for 6:00am Friday. A broken line of showers and a few thunderstorms is attending the front as it charges southeast. These won't put out much in the way of rain early Friday but they mark the wind shift that opens the door for the cooler conditions.
Any remaining rain should be out of my far southern counties early Friday. Skies will break allowing a mixture of sun, clouds, breezy, and cooler weather to move in. Temperatures won't go up much and may even fall a few degrees in the south. Temperatures at 4:00pm are projected to look like this on the 3k NAM. That's a little fresh by mid-May standards.
Friday night as winds decrease the dry air under fair skies will quickly cool. The GFS and 3k NAM indicate the potential for lows around 39 to 40 in some of the cold air drainage locations of the north. In general, lows of 40-45 look widespread. Here's what the 3k NAM shows.
The GFS paints a 39 degree low on Dubuque.
As I mentioned these types of cold air masses usually modify quickly and that will be the case with this one. Under high pressure Saturday, winds should be gentle and after the cold start temperatures will warm as much as 30 degrees from lows. That sets highs in the upper 60s NE to the low 70s SW. Sunday see's more improvement with even warmer temperatures. Highs in the low to mid 70s will be widespread with full sunshine. It looks to be a spectacular day!
SWING INTO SUMMER AT ONE OF THE MOST UNIQUE ACCOMMODATIONS IN THE MIDWEST...
HOW HIGH DO WE GO?
Following the weekend temperatures continue to increase and the question becomes, just how high do we climb? The EURO ensemble is very bullish with a 9-10 day stretch of 80 degree highs.
The GFS ensemble is not as aggressive with the 80 degree warmth lasting only 2 days without producing a single high greater than 80.
I think the EURO has the right idea with its burst of heat but I am a bit concerned about a sympathetic trough (a weakness) in the 500mb flow over the east around day 10. It would not take much for energy to amplify and dig into that weakness sometime in the 8-10 day period. That would allow one of those back door cold fronts (dippers) to sneak into the region. Northeasterly winds would return with a big high in Canada forcing the warmth back to the southwest for a time around the beginning of June.
That is something to watch with the EURO indicating a tropical cyclone developing in the western Pacific that recurves east of Japan. The rule of thumb is thumb is if the cyclone recurves into the N. Pacific, it will buckle the jet over into NW flow over U.S. in 6-10 days. That would open the door for a cooler pattern than what the EURO is advertising on its meteogram around May 29th. Just one of those little items I'm prone to seeking out in my fascination of the weather world. Time will tell if this is realized but until then we turn up the heat next week.
The other thing about the coming pattern is the potential for below normal precipitation. The EURO shows these rainfall deficits over the next 15 days.
The GFS is in good agreement.
The primary reason for the dry look is the lack of moisture. Available water vapor June 1st is shown at 30% of normal. That's an air mass that's not going to get it done if you're looking for rain.
With abnormally dry conditions already in place over SE Iowa and other parts of the central Midwest that is not a trend we like to see, especially at a time of year when spring rains tend to be generous.
Just one more thing to keep an eye on going forward. Meantime, it's Friday and the weekend is upon us. Make it a good one and rest assured Saturday and Sunday look to be outstanding days. Roll weather...TS
