Monday, June 22, 2009

Heat Advisory, severe storms later

Weather Headlines

* Heat Advisory in effect for much of the Midwest, including the immediate Twin Cities region, through Tuesday night. Factoring temperature and relative humidity it may FEEL like 100-105 by mid afternoon.

* Slight severe risk later today: isolated large hail, damaging straight-line winds, even an isolated tornado or two possible - best chance around the dinner hour. Watches and warnings likely.

* Minnesota Lake (Faribault county) reports 4.67" of rain from Sunday night storms!

* Models print out .25 to .50" of rain tonight as cooler front arrives.

* Drying out Wednesday, only a minimal, isolated shower/thunder risk by late afternoon.

* Dry Thursday, warm sunshine - quiet.

* More showers/storms possible late Friday and Friday night.

* Potential for a fine, lake-worthy weekend, with ample sun and daytime highs well up into the 80s, even up north at the cabin.

Paul's Outlook

Today: Heat Advisory. Hot sun, steamy humidity levels. Strong/severe storms possible by late afternoon. Winds: SW 10-20. High: 95 (Heat Index: 100-105 by mid afternoon).

Tonight: Lingering showers and storms, possibly severe evening hours. Low: 66

Wednesday: Cooler, with more clouds than sun, an isolated thundershower can't be ruled out. High: 84

Thursday: Warm sun, quite pleasant. High: 87

Friday: Sun giving way to increasing clouds, T-storms possible PM hours. High: 89

Saturday: Sun on the increase, lower humidity, warm enough for the lake or pool. High: 86

Sunday: Warm sun, statistically significant risk of memorable sunburn. High: 88

Monday: Fading sun, passing PM shower or storm. High: 88

SPC Outlook for Tuesday, showing a slight risk of isolated T-storms over central and southern Minnesota. I do expect some watches and warnings to be issued after 2 pm or so, the best chance of severe weather coming right after the maximum heating of the day, after the daytime "high", which usually comes around 4 pm or so. Any reports of large hail, damaging winds or isolated tornadoes will be spotty and extremely rare - most of us will just see a generic (heavy) thunderstorm. There's no way to predict, even 12-24 hours in advance, exactly which part of a county will be impacted by violent weather. All we can do is say that conditions should be ripe overhead, conditions condusive for isolated severe weather, which should affect far less than 1/10th of 1% of the state.
WRF/NAM Forecast for 7 pm today showing heavy/severe storms marching east across Minnesota. Much of the day will be sunny, but clouds increase during the afternoon hours, the heaviest rains coming from late afternoon into the nighttime hours.
Observed rainfall over the last week, showing significant, 1.5-3" rains soaking much of west central and central Minnesota, along with south central counties around Albert Lea and Austin. But very little rain fell along the Minnesota River Valley and along the North Shore - the rain later today will be welcome indeed across much of the state.
I am cautiously optimistic for the upcoming weekend. This is the 132 GFS Outlook, valid 7 pm Saturday evening, showing rain/storms moving into Milwaukee and the Chicago area, and dry weather for much of Wisconsin, Minnesota and the Dakotas, with a west to northwest wind flow at the surface. Right now it appears dry, sunny, seasonably warm weather will linger most of the weekend. What can possibly go wrong?
The Heat Index (courtesy of the National Weather Service). Find the predicted temperature and relative humidity and you can calculate the Heat Index, which later today should be approaching 100 over central Minnesota, maybe 100-105 over southern Minnesota and the immediate Twin Cities metro area.

All those counties in pink (including Hennepin and Ramsey Counties) are under a Heat Advisory through Tuesday night, calling for an elevated risk of heat-related ailments. Map courtesy of Weather Underground.

(graphic courtesy of the National Weather Service office in Chanhassen, MN).

Tornado Reports From Sunday; Survey to be Conducted Tuesday

The National Weather Service in Chanhassen will conduct a storm survey on Tuesday of potential tornado touchdown areas in south central Minnesota from Sunday evening. These will mainly be in Faribault and Freeborn Counties. Information attained on this survey combined with pictures and videos from Skywarn storm spotters will be used to assess when and where tornadoes touched down on Sunday night, as well as rate their intensity.

No comments:

Post a Comment