The heat is well and truly ON over the Midwest and has been since yesterday when Des Moines, IA not only experienced their latest 100 degree day on record but also tied their hottest ever September reading of 101. Today the heat has shifted slightly to the southeast as the jet nudges further south. This will keep Minneapolis and much of Iowa some 5-10 degrees cooler than yesterday.

As for Chicago, well their well on the way to hitting between 95-97 degrees this afternoon which would set a new daily record. Below are the projected highs today according to weather.com

After a hot, humid afternoon, there is little cooling overnight, helped not only by the heat of the day but the high, Gulf-level dew points. Take the Northeast for example. Temperatures though warming up from low 70s yesterday to mid 80s today, will stay in the mid 70s tonight and it will be largely down to the humid air in place thanks to strong low to upper level southwest winds.

By tomorrow, the jet nudges that bit further south but not far enough south to stop another hot day in Chicago where it may get close to 95. However that slightly further south dip will help force the Midwest heat core into the Northeast. By tomorrow, highs are expected to hit 95 in Washington, 93 in Philadelphia and New York and possibly 92 in Boston.

Here’s the ECMWF 500mb and 850 temps for tomorrow.

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Projected highs for tomorrow from weather.com

If you like it hot, make the most of it as a MAJOR temperature drop comes Thursday into Friday.

Here’s the ECMWF chart by Friday.

How much of a drop can we expect? Check out these temperatures for Friday afternoon. Note Chicago goes from the upper 90s today to potentially the low 60s Friday and it’s back to the 70s in the Northeast.

On Saturday the unusually deep trough with low heights centres itself over the Northeast with the Philadelphia to Boston section of the I-95 corridor struggling to get out of the low 60s.

Take a look at these morning lows Saturday. Wow! Yes, that’s not a mistake, 49 in Chicago! Could see 30s in west suburban areas.

Sat AM

Sat PM

Given the depth of trough and cold air in place and the likely clear skies and light winds, we could well see 40s to start Saturday in Philadelphia, New York and Boston with pockets of 20s showing up over northwest New Jersey, Pennsylvania into western Maryland and West Virginia.

Mexico/Texas Tropical Threat

As for the tropics, the focus by this weekend should turn to the southwest Gulf of Mexico where a system is seen to develop and possibly threaten Mexico or even far south Texas.

Interestingly the ECMWF doesn’t see this scenario too well but check out the GFS by Saturday.

The model shows a slow approach to the coast likely due to strong heights over Texas to the north and Mexico to the west. By 120 hrs, the GFS takes the some sort of slow circulation into the Rio Grande River Valley Monday.

This will be worth keeping a close eye on as heights lower widely over the western Caribbean and Gulf towards the weekend.

Western Pacific Typhoon’s May Drop Significant Troughs Into Eastern US Late In Sept

As for the longer term. We have not one but two potential typhoons in the western Pacific over the next 7-10 days. The reason I mention this in today’s US post is because typhoons which develop and RECURVE by clipping Japan and or the Koreas and then turn north northeast towards the North Pacific, often lead to buckling of the upper pattern both over the Pacific as well as over North America.

There is the potential, if the models are anything to go by, of a typhoon, possibly even super typhoon developing and setting it’s sights on Japan early next week. Modelling is back and forth but some runs suggest a recurve and so this may lead to a significant eastern North America trough late in the month. Usually you count 6-10 days after the recurve, for reaction over North America. The models also show another typhoon AFTER the first and if both were to recurve, then we could see a few shots of cold into eastern Canada and the US. Certainly the ECMWF keeps the troughs coming while the CFSv2 shows a lot of heat centred over the Plains and Prairies which pulses in and out over the next 4 weeks. The CFSv2 doesn’t support the frequent shots of cool int0 the east.

Here’s the ECMWF chart for the Pacific and you can see the recurving of the typhoon.

144 hr

168 hrs

Note TWO systems heading northeast from Japan towards Alaska.

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