Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion...updated 
National Weather Service Birmingham Alabama
100 PM CDT Tuesday Apr 28 2015

for 18z aviation.



Low pressure system and associated rainfall a little slower to
arrive into central Alabama. cover is also slower and
temperatures are much higher that previously forecasted as a
result. Have upped afternoon high temperatures around 5 degrees.
That may not have been enough...but will go with that for now.
Clouds are increasing from the west on satellite...but only
slowly. With that said...although I have not lower probability of precipitation...I have
pushed back the best chances for today until after 21z.
However...that will not help with the temperatures as the damage
there will already be done. Update already out.



18z taf discussion.

Rain showers are slow to push in today with most expected to hold
off until later in the afternoon with the exception of maybe a
little earlier at tcl as showers are attempting to push into the
state now but are rather sparce. When the main activity gets going
as the low pressure system nears...expecting mainly rain showers
and only low thunder chances. Therefore...will leave thunder
mention out of tafs for now. Ceilings should lower in the late
afternoon into the overnight hours as the system approaches with
MVFR this evening and possibly a few spots with IFR in the late
night hours into the morning as the low traverses across the Gulf
Coast states.



Previous discussion...
/issued 420 am CDT Tuesday Apr 28 2015/

The cool and dry airmass remains in place across central Alabama
early this morning...with mainly 40s north to the 50s south observed
through 3am. Precipitable waters on the 00z sounding from yesterday evening
measured a meager 0.55 inches. We'll have to moisten up
significantly during the day today before any precipitation is even allowed
to reach the surface. So the question to answer is when exactly will
the atmosphere begin to moisten? Looking out the window this
morning...a large cluster of showers and storms continues across the
central Gulf Coast. Those storms actually originated from along the
Louisiana coastline yesterday afternoon and are continuing to
progress eastward along the now stalled surface front. That
convection has cut US off from any further development early this
morning...and i've taken out all mention of probability of precipitation through 7am. The
latest trends this morning hold off on any widespread development
of showers and storms until later this afternoon and into the
evening hours. The hrrr for later today is certainly not very
bullish at all on shower development...with only scattered showers
across our southwest counties at best by 21z. Therefore...i've
lowered probability of precipitation a good bit for the northern half of central Alabama
to only chance...with likely probability of precipitation for the southern half. This may
need to be lowered even further later on today based on the latest
trends. So...the bottom line is that most of the day today looks
much drier than was previously anticipated.

As the very dynamic closed low moves eastward across the arklamiss
later today...isentropic lift and upper level dynamics should
finally help to trigger numerous showers with a chance for a few
storms across the southern counties later on this evening. Meanwhile
the surface low along the Gulf Coast will remain well to our
south...with all of central Alabama in a more stable easterly
surface flow. Before the closed low becomes more of an open wave on
Wednesday...we could see the development of additional showers due
to what appears to be a trowal setting up on the northwest side of
the deepening surface low across Florida. If those showers and
clouds linger...we could be looking at a fairly cool day for most
locations with temperatures not getting out of the 50s for our
eastern counties. Southern and western counties will see the better
shot of rising into the middle and upper 60s.

The deepening longwave trough across the eastern Continental U.S. Is still
expected on Thursday and Friday with a few showers possible on
Thursday due to a potent jet streak and shortwave pushing southward
into the southern Appalachians. Cooler air will continue to filter
southward as well...and widespread 40s are now expected Friday
morning. I wouldn't be surprised to see a few upper 30s in those
cooler valley locations if the clouds are allowed to clear. A
prolonged period of dry days are being advertised in the long term
on Friday and into the weekend as northwest flow aloft begins over
the southeast. Upper level ridging is also being advertised to help
moderate temperatures on Saturday and Sunday. It appears that we
shouldn't see any significant rainfall chances at least through the
middle of next week.



Preliminary point temps/pops...
Gadsden 52 60 47 68 44 / 90 70 20 20 0
Anniston 53 60 48 68 45 / 90 70 20 20 0
Birmingham 54 61 49 69 46 / 90 60 10 10 0
Tuscaloosa 55 64 50 71 46 / 70 50 10 10 0
Calera 55 61 50 69 45 / 80 60 10 10 0
Auburn 55 61 50 69 47 / 90 60 20 10 0
Montgomery 58 63 51 71 48 / 60 50 10 10 0
Troy 60 65 52 71 48 / 60 50 10 0 0


Bmx watches/warnings/advisories...



National Weather Service Glossary of Abbreviations