Friday, April 26, 2013

Good Rain Chances by Sunday

By Jay Grymes & Steve Caparotta


Friday afternoon turned out to be an active mix of sunshine and clouds: nearly-clear skies over many WAFB communities around the lunch hour but skies becoming mostly cloudy for most WAFB neighborhoods by the mid-afternoon.  You also may have noticed the air becoming more humid as the day progressed thanks to persistent low-level southerly flow.  Dewpoint readings rose from the upper 40°s near sunrise into the 60°s by the afternoon thanks to the inflow of Gulf moisture -- not oppressive by any stretch, but enough to ‘feel’ the difference.
The moist air mass stays with us through the weekend, keeping morning lows in the 60°s for both days and helping fuel wet weather for Sunday.  Fortunately, Saturday is looking “mostly dry” -- were going with rain chances at less than 20% (“isolated”) for Saturday afternoon with highs in the low 80°s under partly-sunny/mostly-cloudy skies. So, while Live After Five, LSU baseball, Jazz Fest and many other outdoor events will be fine tonight, the news isn't so good for the latter half of the weekend.

A mid/upper-level disturbance currently to our north will slowly move eastward while a cold front associated with this system becomes better-defined, extending from Arkansas into Texas on Saturday.  By Sunday, that front will begin a steady march to the south and southeast through Louisiana, delivering showers and t-storms along the way.  At this point we are not too terribly concerned about a widespread severe weather outbreak on Sunday (like we suffered Wednesday morning!), but be prepared for a few t-storms to become strong to severe.  IN addition, the NWS has noted a concern for locally-heavy rains on Sunday afternoon and evening, in part due to the expected slow movement of the boundary.

In addition, the guidance has the front slowing and possibly stalling near the coastal zone -- that helps keep decent rain chances in the forecast for both Monday and Tuesday.
In the extended outlook, we’re anticipating south Louisiana’s next frontal system moving from the U.S. Northwest into the U.S. Plains between Tuesday into early Wednesday.  That mid-week front will continue towards the central Gulf Coast region late Wednesday into early Thursday.  That should mean another round of rains and t-storms, but the guidance is also suggesting that system moves through fairly quickly, with a dose of cooler and much drier continental air settling into the viewing area on Friday.

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