Here are are into August already – the transition period into fall. Below are the GFS outlooks for the next several days (through next Tuesday). We should see a period of cooler and wetter than normal weather. Hopefully we should see a much needed soaking rain over the period beginning later Wednesday.
A weak area of high pressure over the Central Appalachians will draw up increasing amounts of moisture into the region today through Wednesday The atmosphere will become warm and unstable. This could lead to a few showers or thunderstorms. A stronger wave of low pressure tracks eastward through the region Thursday into Friday. As a result more numerous showers and thunderstorms will be possible. A cooler airmass moves in behind this system to start the weekend.
A few thunderstorms will be possible this afternoon into tonight. Severe weather is not forecasted. Scattered thunderstorms are possible on Wednesday and they could become numerous Thursday into Thursday night. A marginal risk for severe thunderstorms exists Thursday afternoon into Thursday night.
Here are the updated forecast guesses from the CPC for August.
HRRR and Futurecast models runs are for 12 hours beginning at 7am – a second model run begins at 3pm
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The main challenges in the short term deals with the timing and strength of any convection…along with the temperatures. To start the moisture will increase somewhat today especially for the I-94 corridor. Thus as we warm up this afternoon the atmosphere will end up more unstable than Monday for Kalamazoo to Jackson. This may support an isolated storm or two. Some high res models do show this potential. Will maintain this in the forecast.
I did bump up temperatures once again…especially along the lakeshore for today and Wednesday. A weak boundary drops down from the northwest later tonight into Wednesday and then dissipates over the region. This may support a storm or two as well. Overall this risk looks lower than it did 24 hrs ago. Will keep mainly chance POPs going.
Plenty of dynamics arrive on Thursday as a mid to upper level wave digs down from the Canadian Prairies to support increasing amounts of convection. The atmosphere will be moist and unstable as the PWAT values top 1.5 inches and lifted index values lower to at least – 4 deg C. Will keep the POPs high for the day. .
Sure looks like we`re going to see some rain Thursday-Friday. Both the ecmwf and gfs continue to advertise low pressure moving across Wisconsin into the Straits Thursday night and an occluded front pushing across the cwa. Aloft, a strong short wave will drive this system east and make it more dynamic.
Given that we`ll remain on the warm side of the system, we should see scattered to numerous thunderstorms Thursday night. Both models show a tight pressure gradient behind the low so we may see some wind with this system too. Shear values are only around 30kts.
This suggests to me that a few strong storms may be possible, but I have my doubts regarding svr storms. The late night timing of the front doesn`t help either. There will be a cool push of air behind the front though and highs Friday will only be in the lower 70s…pretty refreshing for early August standards. Highs Saturday through Monday are also expected to remain in the 70s too and overnight lows in the 55 to 60 range. An upper trough will remain over the Great Lakes through Monday and it`s possible a transient short wave could touch off a isolated shower.