Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Israeli-owned oil refiner Alon USA Energy (NYSE: ALJ) are sinking today, ripped away by the swelling tide of a rain-gorged Mississippi River.

So what: Heavy flooding in the American Midwest has "shut Ohio River terminals, limited barge movements and threatened to disrupt refinery operations along the Mississippi River to the Gulf of Mexico," according to the AP. And while Alon is the smallest refiner affected (with an estimated 80,000 barrels per day of refining capacity), its stock is getting harder hit than Valero (NYSE: VLO), Marathon (NYSE: MRO), or Exxon Mobil (NYSE: XOM).

Now what: It doesn't seem fair. After all, these three oil majors have much more refining exposure to the flood-struck states than do Alon. So why is Alon the biggest recipient of Mother Nature's wrath? The answer could be as simple as investors worrying that the gains Alon got from last week's earnings news are fleeting, and soon to be replaced with losses. When you've got chips on the table, and the flood water's rising, a prudent investor just might want to pocket the money … and retreat to higher ground before counting.

Want to learn more about Alon USA Energy? Add it to your watchlist.

The Fool owns shares of Exxon Mobil, but Fool contributor Rich Smith does not own shares of, nor is he short, any company named above.  The Motley Fool has a disclosure policy. Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.