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Area forecast discussion 
National Weather Service Birmingham Alabama
248 PM CDT Sat Jul 23 2016

Discussion...

This afternoon through Sunday, a decaying mesoscale convective vortex across north-
central Mississippi has become outflow dominant and the cold pool
is pushing an outflow boundary southeast across our western
counties and this will act as a focusing mechanism for isolated to
scattered shower and thunderstorm activity over the next few
hours. In the upper levels a shortwave is depicted in water vapor
along with in global model output across the Carolinas and this
feature is dropping south- southwest and has supported a higher
concentration of shower and thunderstorm activity across northern
Georgia and western South Carolina. Expect this feature to
continue dropping south around the periphery of a deep sprawling
ridge that is centered across the Southern Plains states. This
shortwave will help encourage shower and thunderstorm development
across our northeast counties this afternoon and evening.
Conditions aloft are supportive of isolated strong thunderstorms
with wet microbursts that can produce winds from 40 to 50 miles
per hour generally.

Temperatures will continue to climb into the mid 90's producing heat
indices between 100 and 110 today. Though most models indicate a
gradual weakening of the ridging across the area, heights will fall
slowly and the potential of heat index readings near advisory
criteria will persist tomorrow and into Monday. At this time
confidence is too low to extend the time on the heat advisory which
is set to expire tonight at 9 PM.

Expect convection to decrease in coverage and intensity overnight
followed by isolated to scattered convective development on Sunday,
especially during the afternoon and evening hours. Some low clouds
and possible patchy fog may develop across our southern counties
toward daybreak on Sunday. Expect any development to dissipate by
mid morning with daytime heating. Lows tonight will fall into the
mid 60's across the area followed by highs reaching into the mid
90's again on Sunday.

05

Monday through Saturday, the rather typical Summer time pattern
continues. The westerlies remain near the US/Canadian border while
ridging is dominant in the south. The model suite was in fair
agreement today with a decent trough riding through the flow
Monday and Tuesday. This helps deteriorate the ridge over the
southeast, putting US in that challenging "weakness" area. The
eastern ridge cell eventually works its way toward central Alabama
Wednesday and Thursday before a more significant trough develops
over the central conus next weekend.

Low level thickness values and boundary layer temperatures appear
to be a bit lower than we have seen the past few days, so near
normal Alabama Summer heat can be expected. Highs generally 90 to
95 and muggy. Maximum heat indices will be near 100 degrees each
afternoon. There is a small chance these numbers will be higher on
Monday and have re-introduced a low confidence for a heat
advisory Monday. Rain chances will also be near normal for Summer
generally in the 30 to 50 percent range and focused diurnally. It
appears the highest rain chances will be when the trough develops
towards next weekend.

At this time, thunderstorms each day do not look to be organized.
Bulk shear values are low, as would be expect with a generally
light flow through the entire layer. Cape, dcape, precipitable
water, lapse rates all would indicate moderate wet microburst
potential at best. But since these parameters are highly mesoscale
driven and changeable, will monitor strength each day. But at
this time, only general thunderstorms with a few gusts to near 30
mph, lightning and brief heavy rain.

75

&&

Aviation...
18z taf discussion.

Adjusted thunderstorms in the vicinity starting at 20z at bhm/tcl/anb/asn/eet to account
for shower and thunderstorm activity expected to develop early
this afternoon. Added tempo for thunderstorms and rain at anb/asn from 20-22z with
most likely convective initiation NE then drifting SW with time.
Uncertainty will be with storm motion as outflow will easily
overcome light low level flow. Added 5sm/br with low cig's at
mgm/toi at 08z tonight but this may be experienced further north
depending on how much rain falls across the area with today's
convection.

05



&&

Fire weather...

Scattered showers and thunderstorms are expected over the next
several days with highs in the 90s. Surface winds will be rather
light and variable. Thunderstorms may produce some gusty winds.
Since surface dew points are so high, critical fire weather
thresholds are not expected to be met with no watches or warnings
anticipated.

&&

Preliminary point temps/pops...
Gadsden 73 94 72 93 73 / 50 30 20 40 30
Anniston 74 94 72 93 73 / 40 30 20 40 30
Birmingham 76 95 76 94 75 / 40 30 20 40 30
Tuscaloosa 74 95 75 94 74 / 40 40 20 40 30
Calera 74 94 74 93 74 / 30 30 20 40 30
Auburn 75 94 74 92 74 / 20 30 20 30 40
Montgomery 75 96 75 95 74 / 20 30 20 40 30
Troy 73 93 73 92 72 / 20 30 20 30 30

&&

Bmx watches/warnings/advisories...
heat advisory until 9 PM CDT this evening for all of central
Alabama.

&&

$$

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