Weather

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fxus64 kbmx 061138 
afdbmx 


Area forecast discussion 
National Weather Service Birmingham Alabama 
635 am CDT Monday Oct 6 2008 


Update...for aviation. 


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Short term...today and tonight. 


Today and tonight will be the transition periods for the pattern 
shift that will begin on Tuesday...but more on that below. Middle level 
clouds have developed this morning across southeastern portions of 
central Alabama...generally south of I-85. This will slide a little 
farther north...but not much more as the clouds will hit a drier 
airmass in place across the rest of central Alabama. By this 
afternoon...look for scattered cumulus clouds...with the highest 
concentration across the southeast. Highs will be in the middle 80s. 


Tonight...clouds will be on the increase across the south...as more 
moisture moves north into the area ahead of the approaching cold 
front. GFS keeps the area dry through sunrise. However...the NAM 
paints a more moist picture over the area tonight...with a 
developing warm front moving through the area. Current soundings are 
quite dry and feel that the NAM is trying to moisten up the airmass 
a little quickly. With that said will continue with dry forecast as 
deep layer moisture and lift are expected to be fairly limited 
through sunrise. Overnight lows will be mild with the increase in 
cloud cover expected. 


16 


Long term...Tuesday through Sunday. 


Deep southerly flow quickly develops over central Alabama on Tuesday 
as short wave trough approaches Mississippi River. Expect low cloud 
deck to spread rapidly north just before sunrise with cloudy 
conditions continuing throughout the day. Strong warm air advection 
will likely kick off some showers across West Alabama Tuesday 
morning with showers and thunderstorms increasing in coverage during 
the afternoon as warm front lifts northward. Most of the activity 
will occur west of I-65 in area of better lift and instability. 


A fairly active period of convection expected Tuesday night 
through Wednesday night as a deepening upper low will move across 
the lower Mississippi River valley region. A track this far south 
is quite unusual so early in the fall season. Cloud cover and 
saturated moisture column will limit intensity of thunderstorms on 
Tuesday...but some middle level drying on Wednesday may provide enough 
downdraft potential for some stronger storms. However...extensive 
cloud cover will limit heating and will hold off including any 
strong wording in the hazardous weather outlook at this time. 


GFS model continues to be the faster of the models with regard to 
eastward progression of short wave trough...and will take a slower 
approach with rain lingering across area through Wednesday night. 
Most of the convection should be east of Alabama by sunrise Thursday 
as upper trough axis will be over east Alabama by this time. Gradual 
clearing on Thursday as weak subsidence moves in behind trough axis. 


Rain free conditions on Friday and Saturday as upper trough moves away 
from Alabama and airmass dries out from the top down. Another 
strong short wave trough will dig southward across the Southern 
Plains states over the weekend and moisture will quickly move back 
into central Alabama on Sunday. 


58/rose 


&& 


Aviation...12z taf discussion. 


Middle level cloud deck continues to push through toi and mgm. 
Beginning to see some few clouds as far north as eet and tcl. Expect 
these clouds to spread out a little more across the south as the 
morning progresses...so went with scattered at 7 kft for mgm and toi. The 
decks will be a little lower this afternoon around 4 to 5 kft...with 
a broken deck around 7 kft. Overall forecast will be for increases in 
cloud cover and lowering of ceilings over the 24 hours. At this time do 
not expect many impacts to terminals over the next 24 hours. With 
toi the only exception. Model soundings indicate clouds could be 
scattered around 2500 feet by 9z. Will keep broken deck above 
5000ft...so only marginal MVFR expected there. 


16 


&& 


Bmx watches/warnings/advisories...none. 
&& 


$$