Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Birmingham Alabama
351 am CST Friday Nov 27 2015
today and tonight.
Central Alabama and a majority of the southeast will remain fairly
quiet once again today with the large surface ridge dominating the
eastern Seaboard. The ridge has prevented the eastward movement of
the current trough over the center of the center of the country.
With not much movement and a subtropical jet pouring in moisture
from what will be left over from Sandra in the Pacific...locations
over the Southern Plains and Midwest will see flooding concerns from
heavy rainfall over the next several days.
With the ridge in place in our neck of the Woods we'll see dry and
very warm temperatures for this time of the year. Current infrared
satellite as of 3am presents increasing high cirrus clouds over the
western half of the state and that will continue throughout the day
today. The high cirrus will be the only impact from the system to
our west for today...and we'll be able to get temperatures rising
well into the 70s once again for most locations. We underestimated
highs yesterday by about 2-3 degrees in some spots...and with low
level thickness values a bit higher today have revamped highs by at
least 3-4 degrees across the board. The thicker cirrus clouds coming
in may help to mitigate insolation a bit for western and northwest
locations...but at least low to middle 70s should be observed across
the board. Clouds will continue to be on the increase overnight
tonight but still no precipitation anywhere close to central Alabama just
yet. Overnight lows will remain quite mild with the cloud cover and
be very similar to what we're seeing now ranging from the lower 50s
east to the upper 50s west.
Saturday through Thursday.
An upper ridge across the western Gulf of Mexico and extending
into the central Gulf Coast region will keep the bulk of the rain
northwest of central Alabama Saturday and Saturday night. Another
mild day on Saturday with highs in the 70s. A slow moving cold
front will stall out across western Tennessee and southeast
Arkansas Sunday and Monday as the main upper level flow remains
fairly flat or zonal on the bottom side of a deep upper low over
the western United States. As the upper low moves into the
northern plains states early next week...the surface cold front
will finally get nudged southeastward on Tuesday. Before
Tuesday...several waves of upper level energy will ride along the
frontal zone...with the best chances of rain staying north of
I-20. There may very well be a prolonged period of light to
moderate rainfall across the northern portions of central
Alabama...but the lack of heavy rainfall should hinder any
flooding issues. The surface front will slowly sink southward
through central Alabama Tuesday night and Wednesday as the main
upper low passes to the north of Alabama...and rain chances will
decrease from north to south.
The long range models are handling the residual moisture
differently on Wednesday and Wednesday night. The GFS clears out
the rain early Wednesday and then increases rain chances Thursday
as another short wave trough approaches the area from the west. The
European model (ecmwf) model also shows the Thursday short wave trough...but keeps
the rain in across the area Wednesday and Wednesday night due to
prevailing southwest flow aloft. Will keep small rain chances in
for Wednesday and Wednesday night...and increase rain chances
across the southeast counties on Thursday as the short wave trough
approaches the area.
06z taf discussion.
Very similar setup to last night across central Alabama. No clouds
developed at all last night while several MOS/soundings develop them
again tonight. Kept the mention of MVFR ceilings for a few hours
around sunrise for all but mgm/toi...but confidence remains rather
low and kept the tempo at this time. Not seeing a huge increase increase
in moisture content. Precipitation water, mixing ratios, specific
humidities all indicate little change. Isentropic lift is weak at
best. But there is a small possibility that some lower clouds may
develop and enter the picture more toward 12z. Some clouds are
still pooling along the southern Appalachians and these clouds
could slip this way. Otherwise...high cloudiness begins moving in
from the west. Winds will keep a light easterly component
overnight and become southeast around 9kts on Friday.
Mild and dry conditions for much of the area through Saturday.
Rain chances will arrive Saturday night in the extreme northwest
part of the state...expanding slowly through all of central
Alabama on Sunday and Monday. There are no fire weather concerns.
Preliminary point temps/pops...
Gadsden 72 49 70 53 65 / 0 0 10 10 30
Anniston 71 49 70 52 68 / 0 0 0 10 10
Birmingham 73 53 72 55 69 / 0 0 10 10 20
Tuscaloosa 74 54 73 56 71 / 0 0 10 10 20
Calera 73 53 72 55 70 / 0 0 0 10 10
Auburn 71 52 71 53 71 / 0 0 0 0 0
Montgomery 76 52 73 52 75 / 0 0 0 0 0
Troy 76 52 73 52 73 / 0 0 0 0 0