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Area forecast discussion 
National Weather Service Birmingham Alabama 
358 am CDT Thursday Mar 18 2010 


Discussion... 


Remember the song...the sun will come out tomorrow. Well that is the 
forecast currently in play. After quite some time with little to no 
sun at all...there is some light in the future. But first we have to 
deal with these shortwaves rotating around each other on the base of 
the long wave trough over the eastern Continental U.S.. these shortwaves and 
even the mean trough are forecast to finally exit stage right 
late afternoon and evening. Clouds will finally break up closer to 
sunset...or what we believe is the new time for the sun to set 
during daylight time. Since we actually have not seen much of the 
sun since the time change. Areas in the northwest may actually see 
a little bit of sun by late afternoon...but for the most part 
mostly cloudy skies. For the most part clear skies overnight. 
Friday and Saturday may even feel Spring-like with highs in the 
lower 70s. Hard to imagine with below normal temperatures for 
today. 


This Spring weather will end quite abruptly with the next storm 
system that will move into the area late Saturday/Sunday. What 
seemed pretty definite yesterday...was made a little more difficult 
today. That fact remains it will rain with thunderstorms overnight 
Saturday into Sunday morning. Questions with the models continue to 
be the timing. Looking at all the sref and Canadian models...one 
would come with the consensus of starting the showers and 
thunderstorms early Saturday evening. The GFS is a touch slower and 
begins late evening. Meanwhile the slowest model...the Euro begins 
after midnight. With all this being evaluated...will continue with 
the ongoing forecast...closer to the Euro...but a touch faster. MOS 
numbers are having a hard time with the dewpoints...while the Euro 
is advertising the low to middle 50s for the south...which agrees with 
the graphical representation of the GFS. We may even see these 
numbers higher as the system approaches the area. 


These dewpoints are important due to the potential for severe 
weather. Storm Prediction Center does have the western half of the area outlooked for 
day 3 (saturday night/Sunday morning). There will be quite a bit 
of forcing and vertical shear with this system. The big issue is 
whether or not we can get the most unstable airmass in place 
before the system works in. If the models continue to trend to the 
slower solution then there just may be enough time. Strong to 
severe storms will continue to be possible along the line as it 
moves through the area Sunday morning. Stay tuned for the latest 
updates. 


Another issue the timing of the system is causing concerns the lows 
Sunday morning. Have opted to go with the higher numbers 
representing the Euro...which is quite a bit higher than the MOS 
guidance with the GFS. Expect the GFS MOS numbers to increase over 
the next few periods...as the ensembles show quite a spread...with 
the highest Standard deviation all week. 


Temperatures will remain cool once again on Monday...so undercut 
guidance by a few degrees. For Tuesday and Wednesday we will see 
some warming each day ahead of the next system due in by next 
Thursday. 


16 


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Aviation...06z taf discussion. 


Upper low which affected central Alabama Wednesday is currently 
rotating eastward...moving off the Carolina coast as the second 
upper low is moving southward across OK/AR. This second upper low 
will rotate across the northern Gulf Coast Thursday afternoon. 
Between these two systems...cloud cover will remain across the area. 
Heights have increased over the last several hours...but are 
expected to fall before sunrise to MVFR heights. There is a small 
chance that isolated areas of IFR ceilings/fog could develop across the 
far south and east before sunrise given these areas received light 
rainfall yesterday. 


There is a small chance of light rain tomorrow with the second upper 
low...but chances are too small to include at this time. As the low 
moves to the east...some clearing is expected tomorrow afternoon 
across the west. 


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Preliminary point temps/pops... 
Gadsden 61 42 71 44 71 / 20 0 0 0 10 
Anniston 60 40 71 43 71 / 20 0 0 0 10 
Birmingham 62 40 72 44 71 / 20 0 0 0 10 
Tuscaloosa 64 41 72 45 72 / 20 0 0 0 20 
Calera 62 42 72 45 71 / 20 0 0 0 10 
Auburn 62 41 72 43 72 / 20 0 0 0 10 
Montgomery 63 43 73 47 72 / 20 0 0 0 10 
Troy 62 43 72 45 72 / 20 0 0 0 10 


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Bmx watches/warnings/advisories... 
none. 


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$$ 


16/14