Thursday, June 10, 2010

Extra-Soggy Friday (but a pretty decent weekend)

"Beam Me Up Scotty!"
No, it's not a UFO, although it does look (a little) like the Starship USS Enterprise (after a few cocktails, which I don't condone on a Friday, btw). This is one of the most spectacular examples of "lenticularis" clouds I've ever seen, wave clouds, caused by air rising up and over mountain formations, rising into a layer of stable air (temperatures rising with altitude), resulting in a smooth, laminar, "lens-like" shape to the cloud formation. Impressive.

Potential for Street Flooding. If we do pick up 2-3" rainfall amounts today expect standing water on area highways, even some overflowing streams and wet basements. This photo is from Marysville, Washington - the YouTube clip is here.

To quote Kurt Vonnegut, "and so it goes..."

Take the bad news with the good news: the upside? The weekend looks comfortably-cool and mostly-dry, temperatures a few degrees cooler than average, a bit cool for the lake (up north), but all things considered, not bad at all.

Now the good news for today: 1). free car wash. 2). free lawn/garden/field watering over the next 12-18 hours.

Friday Soaking, Part 1. Here is a NWS projection of how much rain will fall over the next 24 hours, amounts exceeding 2" across most of the area.

Friday Soaking, Part 2. But wait, there's more! Rainfall amounts (NAM) are predicted to exceed 4" from Litchfield into the northern suburbs of the Twin Cities and much of northwestern Wisconsin. This assumes an MCS system will sprout, thunderstorms potentially reforming much of the day today over a nearly stationary frontal boundary draped from east to west - located almost directly over the Twin Cities.

Computer models print out some 1-2" rainfall amounts by late tonight, with some isolated 2-4" rainfall amounts south of the Minnesota River. For the last 48 hours I've been babbling about the potential for an MCS system, a mesoscale convective system, a sprawling smear of heavy thunderstorms that form late at night, reach their peak early/mid morning, before petering out by afternoon. The can produce torrential/tropical rains and nearly-continuous lightning, winds can gust over 40-50 mph, but they rarely produce widespread damage. They are copious rain-producers, providing much of the summer rain that does fall across the Plains and Upper Midwest. And today we will be in the cross-hairs of one of these MCS systems, especially central and southern Minnesota, the heaviest rains coming during the morning/midday hours, but the models keep us mostly-soggy through the evening hours.

Drought Update. Here's why I can't get too upset about today's drenching rains - over 50% of the state is still too dry, 19% of Minnesota suffering through a moderate drought (which includes northern Washington and southern Chisago counties). Severe drought conditions are being reported over roughly 4% of Minnesota, the eastern tip of the MN Arrowhead. See for yourself by clicking on the NWS's Drought Monitor.

Yesterday I thought the MCS system would keep on pushing east into Wisconsin, resulting in a clearing trend by afternoon/evening. Now it appears the warm frontal boundary will stall directly overhead, surface winds blow from the east/northeast much of the day, meaning we'll probably be socked in with rain (and thunder) much of the day, a significantly lesser chance of PM clearing behind this expansive shield of rain and embedded thunderstorms. We'll see, but I'm pretty much writing off today, in terms of outdoor activities. With off 'n on rain much of the day and thick cloud cover I'll be surprised if temperatures get out of the 60s, maybe some low to mid 70s up north where there's a better chance of actually spying the sun.

Now, the really good news: we salvage a pretty decent weekend. Not perfect, but a far cry better than last Saturday, when it poured most of the day as a wave of low pressure rippled east along a stalled frontal boundary. Yes, that 8-12 hour soaking has been seared into my memory banks. When you "bust" on a (precious, perishable) summer weekend in Minnesota, you remember it for a long time.

The thundery, waterlogged frontal boundary responsible for some gulley-gushing rains today will get a southward nudge Saturday as surface winds pick up from the north, blowing at 10-20 mph. Dew points remain in the 60s, still rather humid, with a potential for an ISOLATED shower, even a thundershower (although instability will be marginal). Right now the NAM model doesn't print out any rain Saturday or Sunday, although I'm a little dubious, a stray shower or T-storm may mushroom near the cool front over far southern MN, a slight risk of a 20 minute instability shower up north by mid or late afternoon. But MOST of the state will be dry Saturday, again Sunday.

Windiest Day: Saturday, blowing from the north at 10-20 mph, choppy on area lakes.
Most Humid Day: Saturday, dew points in the 60s.
Warmest Day: Saturday, highs in the mid 70s (metro lakes) to upper 60s (northern lakes).

Nicer Day? Toss-up right now. Saturday will be milder, potentially better at the lake or pool (if you don't mind a gusty north breeze). Winds ease up a little Sunday under a partly sunny sky, but temperatures will be a few degrees cooler.

* What We Didn't Expect To Happen Up At The Lake. A great story from C.M. columnist Nick Steinmetz is here.

Skies should be partly sunny both days, the best chance of a few hours of uninterrupted sunshine coming in the morning, when the airmass overhead is still relatively stable. Keep in mind the sun is as powerful, as high in the sky, as it ever gets - strong heating of the ground and the air immediately above the ground will result in thermals of warm, rising air each afternoon, setting off some "popcorn" cumulus, even a few bloated cumulus congestus clouds, capable of leaking a few light showers, especially up north - best chance of a fleeting shower (or isolated T-shower) between 3 and 6 pm both days. But rain will be the exception, not the rule.

That stubborn frontal boundary lurking to our south surges north yet again Monday, triggering steadier, heavier rain, with puddles lingering into next Tuesday morning. We should gradually dry out next Tuesday PM, with sunshine next Wednesday, temperatures mellowing back up to "average" (highs near 80) by Thursday of next week. No sign of sizzling heat or controversial humidity levels - no dog day afternoons in sight for the next week or so. After that all bets are off.

One humble, well-intentioned word of advise if you're heading north (or any direction for that matter): take sunscreen (just because temperatures are in the 60s does NOT mean you are suddenly immune from a frying sun overhead - you watch, some of your friends and colleagues will come back to work next Monday beet-red). You will instantly know who did and did not apply sunscreen generously. Take a sweatshirt or jacket too, nights will be cool up north, readings dipping into the 50s, even some 40s possible north of the Whitefish Chain. Seems odd, coming a little more than a week before the Summer Solstice, when the sun is as high in the sky as it ever gets. Consider this payback for the second warmest spring on record, since 1874. Summer is arriving only tentatively this year.

Enlightening Facts For Your Pet. People aren't the only ones who can be traumatized by an electrical storm. At least you can try to explain the weather to your kids - your dog just knows that something evil is lurking outside, inexplicable flashes followed by terrifying rumbles of thunder. No explaining this rationally to Fifi or Fido. Click here for some sound advice on how to acclimate your dog (or other pet) to the vicissitudes of Mother Nature. Some good, sound, practical advice from an expert.

Speaking of lightning: (from Friday's print Star Tribune column).

Paul's SC Times Outlook for St. Cloud and all of central Minnesota:

Today: Showers and thunderstorms likely, locally heavy rain, minor flooding possible. A few severe storms can't be rule out, mainly over southwestern MN. Winds: E/NE 10-15. High: near 70

Friday night: Showers and storms linger. Low: 56

Saturday: Partly sunny, breezy - isolated shower or T-shower, but most of the day should be dry. High: 69. Winds: N 10-20

Saturday night: Partly cloudy, stray shower possible (mainly up north). Low: 59 (upper 40s and low 50s up north).

Sunday: A mix of clouds and sun, less humid. High: 71. Winds: N/NW 10-15

Monday: Cloudy with a period of steadier, heavier rain possible. High: 67

Tuesday: Wet start, then gradual PM clearing. High: 71

Wednesday: More sun, pleasant. High: 74

Thursday: Clouds increase with showers and T-storms likely. High: 78

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