Friday, May 02, 2008

Severe weather on the horizon

Last night the moderate risk issued by the SPC seemed to be spot on. As of this morning the SPC received 19 reports of tornadoes. Tornadoes were reported in Iowa, Missouri, Kansas, and Oklahoma. I happened to catch a few minutes of the video taken in Oklahoma after the boys and I finished watching one of my favorite movies of all time, "Hoosiers". One of the tornadoes appeared to be large and was impressive looking as it was back-lit by lightning.

Today, the SPC has progged much of the Mississippi Valley for a moderate risk of severe weather. There may be a few significant (EF2 or greater) tornadoes today in places such as the eastern half of Arkansas, western Tennessee, northwestern Mississippi, and/or northern Louisiana.

Tomorrow things get interesting for those of us in the great state of Alabama. Almost the entire state has been under a slight risk since five days out. The latest outlook expanded the slight risk outward into surrounding states.

There may be two bands of storms. The first may come overnight tonight as the "leftovers" from today's severe weather to our west. This will probably be in the form of a line and may contain some heavy rain and strong storms. Depending on the timing of this initial band of storms, and how much the atmosphere can destabilize afterwards, Alabama may be in for a round of strong to severe storms tomorrow. If the sun comes out tomorrow morning the atmosphere will be much more likely to destabilize.

The factors I'll be watching include: the severity of today's storms in the moderate risk area, the timing of the first band of storms in Alabama overnight tonight, the ability of the air to destabilize tomorrow morning, whether we have sunshine or overcast skies tomorrow morning, the dewpoint, the amount of shear.

Here is an excerpt from this mornings AFD (area forecast discussion) by the NWS Birmingham:

EXPECT CONVECTIVE LINE TO ENTER THE NORTHWEST AROUND THIS
TIME TOMORROW MORNING. POTENTIAL STRENGTH OF THIS LINE OF
STORMS IS AN IMPORTANT QUESTION. EARLY MORNING TIMING WOULD
SUGGEST THAT THE STORMS WOULD BE AT THEIR WEAKEST PART OF THE
LIFE CYCLE. BUT EVEN THEIR WEAKEST COULD MEAN VERY STRONG TO
POETNTIALLY SEVERE. WILL HAVE TO WATCH HOW THINGS DEVELOP/
TRANSPIRE THIS EVENING AND EARLY SATURDAY MORNING.

GFS AND NAM CONTINUE TO DIVERGE ON WHAT HAPPENS AFTER THE
FIRST CONVECTIVE LINE MOVES THROUGH DURING THE DAY SATURDAY.
GFS STILL SWEEPS THE RAIN RIGHT ON THROUGH AND BRINGS THE DRY
AIR RIGHT IN BEHIND IT. THE NAM HAS THE RAIN OUTRUNNING THE
FRONT...SO THATTHERE IS A WINDOW OF OPPORTUNITY OF THUNDERSTORM
REDEVELOPMENT SATURDAY AFTERNOON. THE FORECAST WAS LOOSELY
BASED ON THE GFS'S PLACEMENT AND TIMING OF THE MAIN CONVECTIVE
RAIN BAND...BUT STILL KEPT OPEN THE POSSIBILITY OF THE NAM'S
REDEVELOPMENT.

ANY STORMS THAT WE DEAL WITH ON SATURDAY...BE THEY ALONG THE
MAIN LINE OR IN A REDEVELOPMENT ZONE BEHIND IT...WILL HAVE TO
BE WATCHED FOR SEVERE POTENTIAL. INSTABILITIES ARE FORECAST TO
BE SUFFICIENT FOR STRONG/SEVERE STORMS...ESPECIALLY IF THE SUN
COMES OUT AT ALL SATURDAY AFTERNOON. SPC HAS THE ENTIRE CWA
OUTLOOK FOR SEVERE ON SATURDAY...WITH THE PRIMARY THREAT BEING
DAMAGING WINDS.
This is still severe weather season in Alabama. Every Alabamian should pay close attention to the weather during the next 36 hours!

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