Scientific Forecaster Discussion
fxus64 kbmx 201049
Area forecast discussion
National Weather Service Birmingham Alabama
549 am CDT Tue Aug 20 2019
for 12z aviation.
/updated at 0333 am CDT Tue Aug 20 2019/
today and tonight.
A warm and humid airmass will be in place once again. With the
combined increase in dewpoints and mid to even some upper 90s in the
northwest, heat index values will creep up to the 105 to 107 range.
Therefore have issued a heat advisory for the northwest, including
the Birmingham Metro. Use caution if you will be outdoor for a long
duration. As we move into the afternoon, rain chances will be on the
increase. The main axis of showers and storms will be along the
southern third of the area. Activity will then spread northward as
the outflows continue to spread from the initial convection. While
the peak of the activity will be late afternoon, activity should
continue through 10pm with fairly significant coverage across the
central sections of the area. After 10pm, activity will begin to
dissipate in coverage. Could be some patchy fog depending on the
amount of coverage this afternoon/evening. Look for highs to be in
the low to mid 90s in the east to mid to upper 90s in the west. Lows
will be in the 70s areawide.
/updated at 0333 am CDT Tue Aug 20 2019/
Wednesday through Monday.
Surface ridging over Alabama continues to weaken on Wednesday.
However, we should have less focus for convective development
outside of diurnal heating. The upper trough over the southeast
U.S. Is expected to weaken and be absorbed in the mean flow.
By Thursday, we have a more weak but open flow of moisture off of
the Gulf of Mexico. This will give US a slightly better than
normal diurnal afternoon convection chance for Thursday into
Friday. We could use the rain. As a second bonus, our high
temperatures should be a couple of degrees lower to more normal
highs for this time of year. However, we will still be in a humid
airmass just not quite as hot as what we have seen lately. At the
same time Thursday, guidance is developing an upper low pressure
over the southwestern Gulf of Mexico and dragging it northward
toward the Texas/Louisiana coast by Friday. Thankfully, at this
time, there is no indication of any significant surface feature to
accompany it. That will be something that will bear watching over
the next couple of days.
By the weekend, guidance is in fair agreement bringing this upper
low around the ridge and onto the Louisiana/Mississippi/Alabama
coast. This low should eventually get absorbed into the mean flow
across most of conus during Sunday. At the same time over the
weekend a surface front will be attempting to make progress
southward. The question is how much influence will the upper low's
timing have on the mean flow thus affecting the southward
progression of the surface front. This front should stall
somewhere across Alabama Sunday into Monday. Regardless of where
the surface front stalls, we remain in an overall moist airmass
with rain chances continuing through the extended part of the
forecast thanks to the upper low then lingering trough across the
12z taf discussion.
Low clouds in place at toi will dissipate after 14z, then we will
see 3 to 5 kft cumulus clouds begins to increase from south to
north through the afternoon. Rain chances will begin to increase
as well after 18z. Looks like best chances after 18z through 01z
will be in the south at mgm and toi. Between 22z and 3z rain
chances will be best in the north. Started prob30s in the south
after 21z/ending by 01z and the north after 23z/ending 03 to 04z.
May see a storm between 19 and 21z at toi so included thunderstorms in the vicinity at
this site. Rain chances end after 6z with possible fog/low clouds
at toi and mgm. Did not include at any other site for now, but
will need to be monitored after any rain accumulation.
Increased rain chances continue each day this week, with scattered
to numerous mainly afternoon showers and thunderstorms. Localized
fog is possible each morning, but locations will vary depending on
the previous day's rain coverage. Temperatures will gradually
return to normal levels by mid week as relative humidity values
continue to rise.
Preliminary point temps/pops...
Gadsden 94 71 94 71 92 / 50 40 40 30 60
Anniston 94 72 93 71 91 / 50 60 40 30 60
Birmingham 97 74 95 73 93 / 50 60 40 20 60
Tuscaloosa 96 73 94 73 92 / 40 60 40 20 60
Calera 95 72 94 71 93 / 50 60 30 20 50
Auburn 89 71 91 71 91 / 70 40 40 20 50
Montgomery 94 73 94 72 93 / 70 40 40 20 60
Troy 90 71 91 71 91 / 70 30 40 20 60
heat advisory from noon today to 9 PM CDT this evening for the
following counties: Bibb...Blount...Fayette...Jefferson...