Just a quick update on today’s weather.
It would appear from the latest hi-res models, like the RAP, the HRRR and ESRL HRRR that band of showers head of the weakening frontal system will in fact strengthen as they cross Lake Michigan this evening and this could bring up to a tenth of an inch of rain to parts of Southwest Lower Michigan, mostly west of US-131. This is due to the strength of the warm advection lift just ahead of the front. The RAP model is now showing CPD values near 1 mb in a narrow band between 8 pm and 11 pm moving northwest to southwest into our CWA. I update our forecast grids and zones to reflect the greater chance of showers and isolated thunderstorms.
HRRR and Futurecast models runs are for 12 hours beginning at 7am – a second model run begins at 3pm
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We find ourselves in a very dry weather pattern as the longwave pattern has us near the axis of the upper trough, which means most of the significant rainfall will be east of our area for well beyond two weeks (note the CPC 6 to 10 and 8 to 14 day show it dry through 14 days).
While there are two fronts that come through the area, the way they come through does little to bring significant rainfall to the area. The frontal system tonight dissipates as it comes through so that will be very unsupportive for rainfall. Even so the western sections of our CWA could see some sprinkles or light rain showers (remote chance of a thunderstorm near the lake shore).
We are between systems on Sunday so it will be dry with temperatures near normal. Then that deep trough I have been writing about for two weeks comes in. That will have two cold fronts with it. The first is the one that comes through Labor Day during the evening. The problem is the upper jet does not get close enough to get deep lift and moisture in this area until the front front is nearly through. This results in the convective line developing near I-94 late in the day and moving toward I-80.
I remain unimpressed with the chances for anything significant from this and the SPC SREF probability for thunderstorms and severe storms backs this idea strongly. .
Rain chances will begin to diminish Monday night as a cold front moves across the cwa and pushes the pcpn east. A deep upper trough will move over the Great Lakes Tuesday through Friday. Another surge of cooler weather will follow. Much of that time frame will be dry. However, minor waves rotating through the trough may produce a shower Wednesday afternoon. Temperatures through the period will remain below normal with highs mostly in the mid 60s and lows in the 40s.