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A FALL PREVIEW AS SUMMER TAKES A BREAK...

The future of our weather this week is going to be determined in a positive way by tropical storm (or hurricane) Isaias as it makes a run up the east coast Monday and Tuesday. While wind and heavy rain batters that area, high pressure on the storms backside will keep things nice and comfortable here in the Midwest.

This is the storm Sunday night as it churns off the coast of Florida. Winds are pushing 70 mph as it maintains high end tropical storm credentials. It's possible that at some point between now and landfall the next 24 hours an upgrade to hurricane status will be needed.

These are the spaghetti tracks from various models of Isaias' eventual path up the eastern US. Good consistency with the system traveling just to my west here in Portland, Maine as a tropical storm Tuesday night.

In essence, the energy of Isaias is eventually absorbed in a trough that deepens and slowly digs its way out of the Midwest in the coming week.Below you can see Isaias separated from the trough east of Florida Sunday night.

By Monday night you can see Isaias getting drawn into the trough as the storm approaches the Carolina's.

Finally, Tuesday.evening Isaias is sling shot into the main trough as it heads for New Jersey and eventually weakens and becomes extra-tropical in nature over Canada

This is all relevant to the Midwest because it means the work week weather will be dominated by cool dry air. Here's the PWAT values which show available water vapor Tuesday night. On the backside of the trough with northerly flow in the Midwest, PWATs are around 1/2 an inch, very dry air for early August. On the leading edge of the trough and southerly winds over the east, values are greater than 3.25 inches in New Jersey.

By Wednesday water vapor is about 30-40 percent of what is normal from my area into the Ohio Valley.

That means little in the way of precipitation around the Midwest until Friday at the earliest when return flow and warm advection can be re-established. The EURO shows this for total precipitation through Wednesday. You can clearly see the path of the tropical storm over the east with heavy rains from Florida to Maine.

As for temperatures, readings are likely to stay in the 70s at least until Friday resulting in some very comfortable conditions. Here's the 5 day temperature departures for Monday-Friday on the GFS. Wow...

The big take away for us in the central US. is that we have a fall preview ahead of us this week. Cool nights and pleasant days will rule. A nice break from summer! Roll weather...TS

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