Friday afternoon

Weekend weather picture seems to be getting into better focus.  One thing is a sure bet- cooler temperatures.  Should be near 80 tomorrow and 78-80 on Sunday.  Much lower humidity slowly arrives tomorrow with its full effect felt by Sunday.  The question remains about rain.

I mentioned yesterday that any rain probably would not arrive until Saturday.  Now I’m starting to ask the question, “Will we get any rain at all?”  My answer is still “yes”, but it’s a pretty shaky yes.  Right now we’ve got a little of everything – warm, humid air mass, upper level energy approaching, and lower level convergence with a weak cool front.  Perfect set-up. But, the timing is all messed up!  First, the moisture is confined to the lower atmosphere – no help from the mid-levels (a negative).  Second, the strongest surge of upper air support should pass over the area around Midnight-3 A.M.  That’s several hours earlier than the cold front.  So, the energy arrives while the moisture is confined to low levels and the cold front is not around to support lifting air (another negative).  Third, when the cool front arrives (around 8 A.M.), the upper air support will be gone but the moisture will be higher in the mid-levels.  Without the upper support, the combination of a weak cool front and marginal moisture may squeeze out a few morning showers, but they will be light (probably .10″ or less).  Any appreciable rain should be gone by Noon or 1 P.M.

So, as you can see, there are a lot of things to consider for the next 24-hour forecast.  But, here’s what I’m thinking now…

Tonight:  partly cloudy and muggy…30% chance for a brief shower or thunderstorm after midnight.   Low… 74

Tomorrow:  Cloudy in the morning with a 30% chance for light showers, then mostly cloudy and cooler during the afternoon…high…80.  Clearing and cooler tomorrow night…low…60.

Sunday:  Mostly sunny and pleasant…high…78.

Forecasting note

Yesterday morning when I checked the forecast models, I was pretty convinced that today would be rain free around here, so I was pretty surprised the weather service went as high as 40% chance for this afternoon. During the afternoon, I did a quick check of some local media sites and they were generally leaning to the “low or no” rain chances scenario as well.  So, frankly, I was surprised when the weather service forecast continued with 40% storm chance for this afternoon.  This is one of the things I found really frustrating when I was working – when they latch onto a forecast, they seem to hold on far too long EVEN when everything they are looking at is telling a different story.    (Sorry about that, but I’m trying to work through years of frustration.)

Anyway. by their morning forecast today, they had dropped down to 20%.  Still too high as the rain train had left the station by that time,  but at least an acknowledgement they were catching on.

Another forecasting point about that forecast.  In general, since Tuesday, most forecasts had both yesterday and today with highs in the 90’s.  As it turns out, an accurate forecast.  But, yesterday with the weather service’s 40% chance for rain, the high predicted for today was dropped to the upper 80s.  That’s a good move – with a higher rain chance (which would cool the air) and most likely more clouds even if rain didn’t fall,  temperatures should be lower.  However, this morning when they pretty much dropped rain out of today’s forecast, they forecast a high in the upper 80’s.  Why?  (With rain and clouds gone, isn’t it reasonable that it should be a few degrees warmer?)