Saturday evening

The wet part of the holiday weekend has started with a late afternoon thunderstorm.  Now it looks like hours and hours of light to moderate rainfall tonight and tomorrow.  Rain this evening will concentrate from along the Ohio River and northward into southern Indiana.  As the night goes on, however, the heaviest rain will shift  southward into Kentucky.  Overall, by early afternoon tomorrow, rainfall could easily reach one inch or higher along the Ohio and the northern third of Kentucky.  Rain should move away by mid-afternoon tomorrow.  The clouds and rain will make tomorrow one the the “coolest” days we’ve seen in about two weeks (lower 80’s).

Weather news looks better for Labor Day…partly cloudy, but still very warm and humid…high near 90 again.

Friday midday

One small difference to the models compared to yesterday.  The upper level ridge building that has been going on should end tonight.  The eastern side of the ridge should slowly collapse tomorrow into Sunday.  As this transition progresses, it provides the opportunity for a return of a period of thunderstorms tomorrow night.  Whether or not it rains tomorrow night, Sunday’s weather should remain hot, but with lower humidity.  Sunday should be the hottest day with the highest temperatures (mid 90’s) but the heat index should peak today at slightly over 100 degrees.  As for rain chances…10% this afternoon…20% tonight and tomorrow…30% late afternoon tomorrow and tomorrow night…10% Sunday.

Thursday afternoon

Well, yesterday’s update didn’t fare well for the afternoon, but it was better for last night.  Left unanswered were the “whys” for my thinking.  They are equally important for the next few days, and today they’ve been working much better.  Yesterday, the models were showing significant warming in the upper atmosphere – something we refer to as “building heights”.  That process makes the atmosphere more stable and reduces the chances for thunderstorms to form.  Secondly, when the upper air “builds” it forces the weak impulses farther north and east – essentially forcing them to go around the Ohio Valley rather than over it.  So, instead of the almost daily upper impulses coming along a line from Iowa to Indiana to Kentucky (we’ve seen our share of these over the past two weeks), the building heights will push the primary path to NE Indiana to Ohio to West Virginia/east KY.

Obviously, it took longer than yesterday for this process to evolve, but it is firmly in place today and should build a little more for next few days.  So, the result is more heat and less chance of rain, probably through the weekend and beyond.  Current thinking from the GFS is for this to end by next Thursday.

So, for tomorrow and the weekend…

Friday:  Partly cloudy, hot and humid…high…93.  Rain chance: 10%                                     Saturday:  Partly cloudy, hot and humid…high…94.  Rain chance: 10%                                 Sunday: Partly cloudy, hot and humid…high…95.     Rain chance:  10%                                Daily heat index near 100 each day.  Nighttime lows in the mid 70’s.

Beautiful Aurora

Solar activity has been weak lately, but still strong enough for some displays of the Aurora Borealis.       This example is from Lithuania, where auroras are pretty rare.  It’s from www.spaceweather.com .

Wednesday Noon

Quick update.  Seems to me the official forecasts for the area are off base today.  The 50% chance for t-storms this afternoon and 50% again tonight, I feel, are way too high.  There are several reasons for this, which I’ll explain later.  For now:

Afternoon:  Partly cloudy, hot and humid…high near 90 (heat index- mid 90’s.  Chance for a thunderstorm: 20%

Tonight: Partly cloudy, warm and humid…20% chance for showers/t-storm…low…mid 70’s.

More later.

Tuesday Afternoon

Another weak upper air disturbance will pass through the lower Ohio Valley tonight.  Most of the dynamic energy is moving across the southern Great Lakes, but the heat and humidity over us has grown into a large concern for its thermodynamic  energy contributions.  As a result, an outbreak of  thunderstorms looks likely for this evening and tonight.  The Storm Prediction Center has us in a “slight risk” area for tonight; I’d prefer to use their soon-to-come Marginal Risk category.  Gusty winds and some brief heavy downpours should move across the area roughly between 8 P.M. and 1 A.M.  Chance for an isolated severe storm will be diminishing as the evening wears on.

Looks like the same story again tomorrow.

Live by the models; die by the models.

In today’s case it’s death by the models.  For the past couple of days I’ve mentioned a little upper air system that was supposed to stall over Missouri for about 12 hours, then drift ESE toward Kentucky.  But, nature doesn’t really care what the models predict.  Nature has a mind of its own.

Everything was moving along as expected – lots of rain/storms over eastern MO last night as the upper system was expected to pause south of St. Louis for about 12 hours then start moving toward us by late morning with our round of showers/storms to arrive by tonight and continue into Monday.  Sounded pretty reasonable EXCEPT the upper disturbance never stopped!  So push everything up 12 hours and we have a rainy Sunday with the showers/storms moving away tonight.  That leaves much better weather prospects for Monday, but , of course, poorer prospects today.

We’ll see a break from the rain for a few hours this afternoon, but then a renewal (probably between 5-9 P.M. ) of heavier rain, then decreasing lighter showers ending after midnight.

The week ahead looks like we’ll be slowly evolving into a heat wave (highs of 90+) by mid to late week.  Unlike past  heat waves this summer that have built for a few days then quickly ended, this one should last longer – at least into next week.

Now it’s back to the drawing board for this embarrassed forecaster.