Area forecast discussion
National Weather Service Birmingham Alabama
440 am CDT Tuesday may 21 2013
Discussion...
The forecast remains largely unchanged over the next 7 days. Upper
troughing continues to dominate across the central US this morning.
Latest WV satellite imagery shows a large upper low spinning over
the Dakotas with a shortwave rotating eastward through The Four Corners
region. A line of weakening showers and thunderstorms was ongoing from
Indiana southwestward into the middle Mississippi River valley...which
is in association with what appears to be a prefrontal trough well
ahead of the actual surface front. Meanwhile upper ridging remains in
place across the central Gulf Coast states. Stratus deck can be seen
spreading northward across MS and southern Alabama at this hour and will
likely push into the south and western portions of central Alabama
over the next couple of hours. The upper ridging will keep central
Alabama dry again today with afternoon highs warming into the upper
80s and lower 90s.
Surface front currently in the Central Plains will slowly progress
eastward today before stalling west of the MS river as it loses its
upper level push. The Four Corners shortwave will eventually pick up
the frontal boundary tonight and bring it through the forecast area on
Wednesday into Wednesday night. The system should weaken as it approaches the
County Warning Area due to lack of upper/lower jet features...rather weak low level
shear and middle level lapse rates...as well as a lack of dry air in
the middle levels. Therefore still do not expect anything in the way of
severe weather across our area. Have kept probability of precipitation the highest and temperatures
a bit lower in the northwest.
Initial boundary may still be located across the southern part of
the state by Thursday which could lead to some additional isolated/scattered
activity. Best chances will be the south. The main upper trough
finally pushes through Thursday afternoon/evening bringing another weak
boundary through the County Warning Area. Models aren't showing any real quantitative precipitation forecast with this
feature as it comes through...so probability of precipitation may be a bit overdone for
Thursday if the first boundary manages to push south of the forecast
area.
Surface high pressure builds in from the north on Friday bringing a much
drier air mass into the region. Highs will be near normal with lows
in the 50s Friday night and warming back into the low 60s by Sun night.
Models diverge a bit in the extended with the European model (ecmwf) indicating a bit
more of a zonal pattern across the eastern Continental U.S. Than the GFS. The
more pronounced central US ridge in the GFS keeps any disturbances
rotating around the northern periphery of the high well to our
north. Whereas the European model (ecmwf)...with it's weaker ridge...tries to bring
a couple impulses across the northern portions of Alabama early next
week. Will go with a dry forecast for now but will keep an eye on
future trends.
19
&&
Aviation...
06z taf discussion.
The large scale communications failure appears to have been
corrected...and thus inclusion of amend not schedule in the tafs is no
longer necessary. Routine amendments have resumed.
Little change from previous tafs. VFR conditions at present.
Boundary layer moisture is expected to increase as we move through
the overnight hours with light southerly flow just aloft above the
surface. Fairly confident of MVFR visibilities but continue to not
be quite as confident on the possibility of IFR visibilities...so
only a few tempos for now. Winds aloft near sunrise may be too much
for the lower range. All locales should go back to VFR by 14/15z
with mixing expected.
08/56
&&
Preliminary point temps/pops...
Gadsden 89 66 82 66 84 / 10 10 50 40 20
Anniston 88 67 84 65 85 / 10 10 40 40 20
Birmingham 90 68 83 66 85 / 10 10 50 30 20
Tuscaloosa 91 67 83 65 86 / 10 10 50 30 20
Calera 90 66 84 66 85 / 10 10 50 40 20
Auburn 89 67 85 65 85 / 10 10 20 40 30
Montgomery 92 67 88 67 87 / 10 10 20 40 30
Troy 91 67 89 67 86 / 10 10 20 40 30
&&
Bmx watches/warnings/advisories...
none.
&&
$$
