Tuesday, May 14, 2013

Increasing Clouds, Humidity Next Couple of Days

By Jay Grymes & Steve Caparotta

Today was another beauty, although a tad warmer than Monday.  And as we mentioned yesterday, today’s humidity began a slow upward climb and will continue to do so into Wednesday as a southerly flow brings more low-level Gulf moisture into the viewing area.

The dome of surface high pressure that has given us these three great spring days will continue to slide eastward, helping to strengthen the inbound flow off the Gulf.  At the same time, a broad upper-level ridge extends over most of the western half of the U.S., bringing unusually warm conditions to the Central and Northern Plains for yet another day.

We expect the upper-level ridge to continue to ease its way to the east: it should be centered over the Mississippi Valley for Friday and Saturday.   As you recall, upper-level ridging typically brings warm and mainly-dry weather for those under it.

The only fly in the weather ointment for us is that same upper-level low that has been sitting over northern Mexico and the Gulf of California during the past several days.  That low is beginning to “open-up,” meaning that it is losing its “closed” low structure and will come under the influence of the larger-scale mid- and upper-level atmospheric steering.   In fact, we’re already seeing some slow movement to the east-northeast today.

We expect the upper low to move across the Southern Plains and stay to our north on Wednesday and Thursday.  That low is a contributing component to our Wednesday afternoon forecast, which calls for increasing clouds and a sun/cloud mix for most of the WAFB viewing area for Wednesday afternoon and evening.  In fact, the low will get just close enough to give us a slight chance of rain on Thursday.  At this point, we’re staying with rain chances at 20% or less: that most of us stay dry, but we could see a few blips on Doppler radar.

Once that upper “wave” moves to the east, the broader upper-level ridge will take charge of our local weather.  Combine that upper ridge with a steady south-to-southeast flow for Friday, Saturday and Sunday and you have the makings of some dry but very warm days.  Highs will climb into the upper 80°s for many WAFB neighborhoods by week’s end and through the weekend -- factor in some Gulf humidity (dew points in the mid to upper 60°s) and you’ve got afternoons that will feel almost summer-like.

But then it is mid-May, so the summer feel is just around the corner!

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