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afdbmx 


Area forecast discussion 
National Weather Service Birmingham Alabama 
705 PM CDT sun Mar 21 2010 


Update...aviation discussion. 


&& 


Short term...tonight through Tuesday. 


Surface cold front has pushed into east Alabama this afternoon. 
Cold front has encountered slightly more unstable air over east 
Alabama where temperatures were able to warm to near 60 degrees. 
Several lightning strikes have show up along convective line and 
also a few reports of wind gusts of 40-50 miles per hour as some of the 
stronger winds have been able to mix downward. Convective line 
should be out of Alabama by 5 PM with colder air spreading over 
all of central Alabama. The deep upper low was near the Arkansas/la/MS 
intersection and moving steadily eastward. The low may be moving 
along faster than forecast by models...which means coldest pocket 
of air may move into north Alabama this evening instead of after 
midnight. This is certainly a unique system as the low level cold 
air has pushed well east of the upper low. Also...the coldest low 
level air is located to the south and southwest of the upper low. 
Assuming upper low tracks to near or just north of Birmingham...the 
best chance of snow may be along the I-20 corridor and to the 
south. Low level thickness values support snow...but looking at 
cross sections of Omega...there is not much deep layer lift as 
upper low crosses over area. There is a huge middle level dry slot to 
the east of the upper low...and very little precipitation upstream 
over Mississippi. However...enhanced reactivities are starting to 
show up over west Mississippi just east of upper low. Light 
precipitation will continue across north Alabama on Monday on back 
side of departing upper low. The type of precipitation is 
questionable...as warming is forecast to occur as low moves east. 
Decided against Winter Weather Advisory due to warm ground 
conditions and small liquid rainfall amounts...but there could 
very well be a period when snowfall is intense enough for light 
accumulation on grassy surfaces. A Special Weather Statement was 
issued to discuss uncertainties. 


Wrap around low clouds will likely persist over Alabama Monday 
night but should see decreasing clouds from west to east after 
midnight. Some light precipitation will linger over northeast 
counties Monday evening...but low level thickness values support 
only rain. A nice day on tap for Tuesday as warmer air works back 
into area with highs 65 to 70 degrees. 




Long term...Wednesday through Sunday. 


A nice warm-up Wednesday and Thursday as upper ridge builds over 
the area from the west...with highs in the 70s both days. A weaker 
short wave trough will move into the Southern Plains states on 
Thursday and bring increasing high clouds to Alabama. The short 
wave trough will pass north of area on Friday. Very little surface 
development with this system...and no decent return flow to bring 
Gulf moisture northward. Instability will be limited and primary 
weather type will be showers. This system will pass on through 
area by Friday night with another system arriving by late in the 
weekend. 


58/rose 




&& 


Aviation...00z taf discussion. 


Heavy rainfall associated with a strong cold front has pushed east 
of central Alabama this evening. Upper level low will cross the area 
tonight and Monday...bringing the possibility of light rain and snow 
to the northern portion of the area. 


Gusty winds will continue for several hours before diminishing as 
the pressure gradient weakens. Ceilings are currently at or just 
above MVFR across the north. Scattered precipitation will move from west to 
east this evening...without much affect to aviation concerns. A more 
organized area of light rasn will push into the area after 03z. 
Ceilings will drop to MVFR...possibly approaching IFR before 
sunrise. Snow is not expected to cause a problem as no accumulation 
is expected. Will carry MVFR visible for now and monitor for updates as 
needed depending on the progression of activity upstream. Light rain 
will continue through the afternoon...with MVFR ceilings. 


At mgm and toi...cloud cover will increase overnight as the upper 
low crosses the area. Ceilings will lower to MVFR before sunrise and 
remain at that level through the forecast period. Light precipitation looks 
to remain north of these terminals...and will not include any 
mention at this time. 


14 


&& 


Preliminary point temps/pops... 
Gadsden 36 43 41 64 37 / 40 50 20 10 0 
Anniston 36 43 41 64 41 / 40 50 20 10 0 
Birmingham 35 45 42 66 44 / 40 50 10 0 0 
Tuscaloosa 35 47 42 70 42 / 40 50 0 0 10 
Calera 37 44 43 66 42 / 40 50 0 0 0 
Auburn 37 46 34 66 41 / 30 30 10 0 0 
Montgomery 38 50 42 69 41 / 30 30 10 0 0 
Troy 36 53 40 68 38 / 30 20 10 0 0 


&& 


Bmx watches/warnings/advisories... 
none. 


&& 


$$