Back from Seattle!


Thanks to Pierce Larkin for filling in on a very active week across the country. Another very active week with frequent rounds of showers and storms again this week.

1. On Monday a warm frontal boundary will be north of the region separating the wintertime and summer seasons. To the north of this boundary isentropic lift will lead to overrunning precipitation south of the boundary the threat for complexes of showers and thunderstorms is present starting late monday night into early Tuesday for our region. Highs could have a wide range from the 60’s north to low 80’s south with increasing southerly winds. These storms may produce  damaging winds and isolated tornadoes in a few spots but with limited instability these storms will mainly form due to the low level jet interacting with the boundary and mainly produce a heavy rain and lighting show with local rainfall amounts of 1/2 to 1 inch.

2. With a similar temperature spread Tuesday Thunderstorms should end in the morning as the low level jet  weakens some and the front shifts slightly north. This will allow for clearing and the advection of unstable air into the region ahead of the front which will be turning back into a cold front as the low pressure moves northeast along it. Along the warm front a high shear ( changing of winds with direction and height)  will be present coupled with a high instability enviroment in an already warm and moist set-up with the clash of airmasses will lead to another severe outbreak Tuesday afternoon to our northwest. Numerous reports of large hail, tornadoes and damaging winds should occur. Storms should fire over southeast Missouri and southern Illinois by early evening once the CAP breaks some due to the approaching front. This zone at this time appears the intersection point of the high shear and instability regions. Storms will fire as supercells then organize into a squall line overnight Tuesday night. Overnight temperatures shouldn’t change much either Monday or Tuesday night due to the LLJ only falling into the 60’s. Another 1/2 inch or so of rain could fall.

 3. A squall line with widespread storms containing damaging winds, large hail and tornadoes will be moving west to east across the region. Right now cloud freezing levels appear favorable for a hail threat. the LLJ which will be even stronger Tuesday night than Monday night ia expected to maintain the line overnight Tuesday night. With our region being in the region of a higher shear a higher than usual tornado threat will be present also I expect numerous occurences of strong gusty winds along this line. During the day Wednesday clearing should occur late with somewhat cooler temps. This timing favors the GFS and is faster than the NAM and slower than the ECMWF. All models are similar in the overall atmospheric set-up. I see at least the target region west of us getting upgraded to a moderate day 2 risk.

4. Thursday the front will be south of the region but the next low pressure over the plains will form a warm front on the tail of this departing system which will result in more thunderstorm chances along the front for Thursday night through the weekend.  A significant hydrologic situation could develop in regions around the front due to heavy rain. In addition if we get into the warm sectors more severe events could occur. I’m going to leave details limited here due to differences in the ECMWF and GFS.

5. the AAG conference went very well in the Seattle this week as it was another chance to network and present my research. Thanks again for staying with the site with my absence for a few days and to Pierce for filling in.


2 Responses to “Back from Seattle!”

  1. mitchg Says:

    red flag warning in effect.

  2. mitch Says:

    hvy rain still present for this weekend, no changes to thoughts on severe threat tue night.

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