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

Cut-Off Low instead of Big Trough

As we head into the work week another very strong upper level low will dig into the central and Northern Plains. So my forecast last week was not all together correct as I failed to see the stronger ridge in the east. So we're heading into another split flow where a piece of energy gets stuck underneath the main jet stream. Here is the latest forecasted 500mb level for the exact time I showed you in the last post.

You can notice the lack of support from the northern jet by the time we get into tomorrow evening. This will leave the upper level low to stall and spin across portions of the Central Plains. This will first cause a strong cold front to plow south into the warm and moist air over the Southern Plains. So severe weather is a possibility for portions of Texas, Oklahoma and western Arkansas today. Here is the latest outlook from the SPC.

Temperatures will plunge behind this front to below normal high for several days. I'll have another update on how cool temperatures will be this week here later this afternoon. Plus take a look as I might be just a week off from the Cold Canadian push of air down into the East.

Change in Wx pattern brings Chaos to the Wx Models

Oh GFS and your lovely pros and cons...Here is a quick run down of how I think things will play out early next week.

Typical GFS fashion with its horrible feedback issues at times. Let me show you here with two graphics which indicate the same time period. However the first one was created during the 0z run Tuesday evening and the second one is only 6 hours later from the 6z run. Notice any difference to the 500mb patter and heights? Ya you can say huge difference as the first run has low 60s and breezy in St. Louis. While 6 hours later its says its probably sunny and in the upper 70s.



Now when I say feedback issues this is what I mean. Models sometime have a hard time trying to determine the production and how to transfer latent heat in the atmosphere. Well on this example you can see in the 0z a very powerful trough digging south with a strong vorticity max in front of the trough. The 6z model still has the energy by splits it into two separate energy bundles. One across the four corners and another piece connected with the trough in Canada. You'll see a lot of this this winter as we'll likely have a stronger than average southern jet and the Polar jet diving southeast trying to merge. As there will likely be a split flow in the west with the two jet streams merging across the Central and East.

In this example and why I have hinted at the pretty strong outbreak of cooler than normal temperatures next week and into the following weekend. The models see it but it just doesn't know how to handle it. So instead of the energy being bundled ahead of the trough in the Ohio Valley. The energy will be back a little farther west and stretched a little more west to east. As the trough will want to dive south toward Oklahoma, Arkansas, Louisiana area. As compared to the 0z where the trough axis will head toward Georgia and the southeast states.

So expect places like Northern and Central Plains to see their pinpoint forecast that the NWS uses to vary a lot over the next couple of days. Typically the GFS figures these kinds of issues out about 2-4 days prior to the event. I believe the Northern Plains will see their end to the growing season by next week. This colder air will filter into the Great Lakes and into the Ohio Valley. Overnight lows will probably dip down to near or below freezing north of I-80 (Dakotas, Minnesota, Wisconsin). As temperatures in the 40s will be common elsewhere. Right now MOS numbers for Indianapolis for Wednesday morning is 61 Thursday morning 58. I will go with both mornings around the 44 to 47 degree range.

High temperatures down in my area by next Tuesday and Wednesday will be in the Lower to middle 70s. MOS temperature prediction has a high temperatures in Lawton on Tuesday and Wednesday of 87 degrees.

So we'll see if I'm correct or if the model is correct on our first big push of cold air from the northern reaches of Canada.

Alright time to get some sleep... Justin

Summer heat is coming to a end....

Heavy rains across Texas and the Southern Plains marks the end of the summer heat. As the weather pattern is changing and will completely change in the next 2-3 weeks. Until then we'll continue with the summer pattern but a tempered one.

Flooding rains are on going here in Texas and across the I-35 corridor in Texas. As some locations have received up to 11 inches of rain which has caused some flooding. The upper level low has pretty much stalled out and will slowly weaken over the next 3 days. So expect the rain to continue across the Southern Plains and Southeast.

This also has pretty big affects on the winter in these locations. Which also supports my winter prediction mentioned a couple months ago. That the south tier of the nation will be cooler and wetter then average this winter. As I'm continuing to study and fine tune my winter forecast.

Have a great weekend everyone!