Tuesday, October 29, 2013

Storms Possible for Halloween

By Jay Grymes & Steve Caparotta

We had some pockets of rather heavy fog develop earlier this morning as the winds were a bit lighter than expected, allowing for better radiational cooling (heat loss from the ground) even with the morning cloud deck above. Lows were about 1° to 3° cooler this morning than anticipated.

Today’s skies became partly cloudy a little sooner than expected as fair-weather cumulus clouds (‘cotton ball’ clouds) combined with a thin veil of high cirrus clouds (wispy ‘ice’ clouds) by the lunch hour. The clouds didn’t generate so much as a sprinkle over the region, but they were just sufficient enough to filter the mid-day sunshine and slow the early afternoon warm-up. Still just about all WAFB neighborhoods managed to reach the low 80°s -- all in all, not a bad afternoon.

As for the forecast for the coming days, our thinking hasn’t changed much from yesterday.
Wednesday will start off on the mild side with sunrise temps in the low to mid 60°s for metro Baton Rouge. Be ready again for areas of fog during Wednesday’s early-morning commute, with some pockets of locally-dense fog especially in the usual-suspect spots. The fog will lift by mid to late morning, with upper-level ridging adding to the daytime warm-up even while under mostly cloudy skies -- we’re expecting highs in the mid 80°s for the ‘Red Stick.’ We can’t rule out a spotty shower or two between Wednesday afternoon and early evening, but the vast majority will stay dry through the day.

Our next Pacific cool front will be getting its act together over the Southern Plains on Wednesday and will be tracking towards us throughout the day and into and through Thursday. With persistent southeast winds ahead of the front, inflow of warm-and-moist Gulf air will keep Thursday morning minimums in the mid to upper 60°s for most of us. By Thursday’s sunrise, we could even see some spotty showers developing on Titan9 Doppler that continue into the mid-day.

But the big Thursday weather question is: will Mother Nature will be in the mood for an outdoor “Treat” or a “Trick” for the youngsters?

It’s going to be close. While we are fairly confident that the cool front will not arrive until early Friday, showers and t-storms ahead of the advancing front will make the Thursday evening window from roughly 5-9pm rather dicey in terms of rain chances. Based on an early-afternoon review of three of our reliable models -- the GFS (American), the ECMWF (European) and our in-house RPM -- the outlook is not promising. However, it is not a total slam-dunk for a Thursday evening rainout just yet either.

The GFS has the rain right over us during the neighborhood “door-knocking” hours. The ECMWF is maybe a tad slower, but still suggests that the rains would be arriving at a critical time and make a mess of things. Only our RPM appears to want to delay the rains until later that night. So for now, we’ll say “rain likely” during the key hours for the candy grab, with isolated t-storms possible as well.

For the sake of percentages, we’ll say 60% to 70% chance during the “street haunting” hours. As we said yesterday, be thinking about a “Plan B” for the young ghosts and goblins.

It looks like just about everyone gets the rain between late Thursday and Friday morning, with early NWS Hydrometeorological Prediction Center estimates running on the order of 1” to 2” for most of the viewing area before the front slowly clears the region on Friday. While we do not expect a severe-weather outbreak during the overnight hours, northern portions of the WAFB viewing area are included under a “Slight Risk” for severe storms by the NWS Storm Prediction Center from late Thursday into early Friday.

The rains likely linger into early Friday morning, very possibly into the morning commute, especially for WAFB’s southern communities. With the front still draped over southeast Louisiana on Friday morning, we won’t start to feel the effects of the cooler-and-less-humid air behind the front until later in the day. By Friday afternoon and evening, however, clearing should be well underway from west-to-east -- and you’ll certainly feel the difference.

This all sets us up for a wonderful weekend weatherwise. We’re going with 50°s for the Capital City on Saturday morning and 40°s for Sunday morning with highs both days in the 70°s. Expect sunny skies for Saturday and mainly sunny skies for Sunday -- just about perfect!

Our next best chance of rain after Friday morning looks to be next Tuesday.

Elsewhere ... nothing to speak of in the tropics as we close out the month of October -- and no complaints about that either.

And as an early reminder, remember that we “fall back” with the clocks this weekend -- we get back the hour of sleep we lost last spring. The official ‘reset’ time is Sunday morning at 2:00am.

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