Daily Rain Chances, But Why? No One Tells Us

I watched several weathercasts today, and they all show the SE streamline wind flow from the Gulf increasing our low-level moisture at the surface.  But no one seems to connect what is happening at the various upper levels that might help explain why only a small band of rain has been drenching SE Louisiana the past two days.  Frankly, all I can see is a boundary that has formed right over us, as there are no distinct features on the Water Vapor imagery.  Let me begin at the surface, where the nose of the Atlantic Ridge/Bermuda High extends westward across the northern Gulf.

Low level Gulf moisture/humidity has increased, but why isn't it raining in Houston, Lafayette to our west, or Biloxi, Mobile & the beaches to our east?  I've drawn in this boundary (lime circle) that is the focus for numerous showers today.

Water Vapor has dry air on either side of this feature, but why has it formed over us? And why will it stay over us?

What frustrates me is that our local weathercasters don't point this boundary out (except Zack on FOX 8's morning weather) and just say it's because of the return flow off the Gulf that is causing our showers.  In fact, most of the noon weather programs didn't even show a satellite loop, just the damn model forecast.  Clearly, we have no fronts around as most of the nation has warmed up.

There are lower dew points to our east & west that define the surface boundary, but what is causing it, and why will it remain over us?  because the models say so!  It sure does make a difference where it sets up. Note the 80s to our west, where they have more sunshine.

There are higher rain chances later this week due to weak upper air disturbances moving through the SW flow.  On Easter Sunday, a cold front could make it a stormy day before we dry out for early next week.  Don't get me wrong, we need this rain, but will anyone try to take a crack at explaining what I'm seeing on the satellite & WV loops?  Nope, let's look at the models!  Stay tuned!

Daily Rain Chances Make 7 Day Useless, Easter Sunday looks Wet.

Back when I was on-air, I often mentioned that once we got into May, the 7-day forecast became almost useless for planning your outdoor activities since 1) we knew each day would be warm to hot, and 2) it would rain somewhere across our viewing area due to daytime heating pop-up storms.  We're still in March, and NWS indicates the upper air pattern shift will give us daily rain chances without mentioning why or which day has a better chance.  They just give each day equal chances, and the FOX 8 seven-day forecast follows their guidance.

The higher rain chances Easter weekend will be due to an approaching cold front.  What I try to do is look for reasons why our rain chances have returned.  I do it by showing you satellite features and not just showing what the models say.  Saturday's cold front stalled off our coast and moved back northward during the morning hours. We're back in the muggies, and a weak upper disturbance is passing well to our north.

But after weeks of dry weather, what has changed?  The persistent West Coast ridge and East Coast upper trough gave us a mainly dry upper WNW flow.  Now we're going back to a West Coast trough, allowing our upper flow to turn more to the SW.

Embedded in that flow are weak disturbances that are difficult to forecast.  In addition, the moisture boundary that formed over us today becomes a forecast challenge all week.  Models say it stays in place, but what if it shifts just a little bit to our east tomorrow as the weak upper disturbance passes to our north?  Most of Louisiana is enjoying bright sunshine today.

 If I were still on-air for tomorrow, I would downplay the rain chances with higher chances Tuesday & Wednesday as the next weak upper disturbance comes from the West coast.  There are no fronts around to trigger more activity.

One thing is for sure: temperatures will stay warm to hot depending on how much sunshine we get each day.  WPC's rainfall outlook has the heaviest rains far to our north, but they give us 2-3" during the next 7 days.  It's needed and welcomed by our lawns and gardens.

So will the rain chances be equal each day?  Watch your favorite weathercaster and see if they follow the NWS guidance, or maybe give you a reason why it might be different.  Bottom line, go find your umbrellas since it hasn't rained in many weeks.  Stay tuned!