First Fall Severe Weather Outbreak Wednesday and Thursday

Here are some maps to show you the threat for severe weather. Starting Wednesday afternoon and continuing into Friday morning. I'll have more details on the timing of event tomorrow afternoon.

Fall Severe Wx Season Starts Later this Week

Our active weather pattern that I have been alluding to kicks in later this week. As it still looks like the next 10-14 days will be very active. As several troughs with pressing cold air try to work itself south against the waning summer heat. This will provide places in the northern Rockies and Plains with their first snowfall. The greatest impact most likely will be a couple possible significant fall season severe weather outbreaks. The first one will likely take place on Thursday afternoon and evening. Here is a graphic that sums up the scenario for the central and southern Plains. Still over 4 days away so a lot of things can change but I'll have more detailed forecast in the next couple of days. Thursday could be a chase day for me as I have been dealing with serious withdrawal symptoms from a long summer.

Below Normal Summer Temperatures

Looking at the 90 day temperature means you can see during the Summer months June, July and August. A good portion of the nation had below normal temperatures. Much below normal temperatures in the North and Central Plains and including the upper Mississippi Valley. Above normal temperatures were in a couple locations such a California and parts of New Mexico and Texas. Then the graphic next to the temperatures shows the 3 month precipitation compared to normal. You can see the places that had below normal precipitation matched up with places with higher than normal temperatures. This is easily visible across the drought stricken areas of south Texas.

Stormy Start to October?

My ideas of a stormy start to October continue to be support by teleconnections, ensembles and now some of the medium range models. Here is a look at the latest 8-14 500mb analog composite. With this kind of pattern I can see some pretty nice size severe weather outbreaks for fall standards across the Plains and into the Ohio and Mississippi Valley.

Temperatures So Far This Month

This is what a split flow in the jet stream does at the end of Summer. Cool underneath and warm over top. As several upper level lows have been affecting the South where near record warmth has occurred in Big Sky Country. Here is a graphic that shows temperatures compared to normal for the first 21 days of the month.

Quick Post on Winter Forecast ideas

Quick post here showing that the atmosphere is starting to show signs and clues of its winter Pattern. Here is the latest 8-14 Analog composite of the 500mb flow center on October 3rd. Notice the reds in Canada representing ridging aloft or warmer than normal heights. As the height lines indicating the flow moving from a ridge off the West Coast. To a fast west to east flow across the lower 48 with lower than average heights. This indicates an active jet stream under an area with higher heights helping to develop high pressures across Canada. So Cold areas of high pressure in Canada with an active jet stream underneath. Hmm can you see what clues i'm pointing out and what kinda of winter we might being headed to?
Looking at the latest ensembles I believe October will come in like a lion. Stormy weather with possible severe weather and heavy rains will set up from the Southern Plains and into the Mississippi, Ohio Valley. As the Northern Rockies get their first cold shot of air with first significant snowfall. As you can see a nice jet indicated by the packed height lines in the above graphic. As NAO looks to be tanking in the negative side by around the 7th of October indicating a trough in the East. PNA looks to be near neutral for the time period so a firehouse jet might come into the West. This is really good as they need the cool down and rainfall to increase to damper the fire threat. AO index looks to go negative then strong positive then strongly negative. This would be an good indication that there will be a good source of some cross Polar air from Siberia. High temperatures currently are in the 20s and 30s with lows in the teens. However have been drastically decreasing over the couple of weeks. So all together winter is preparing itself but we still have a good month or so. The United States really don't start seeing snow storms outside the higher elevations till after Halloween.

Thanks for reading and please leave your comments on my guest book.
Justin