Damaging Winds and Lightning Strikes in Alabama, July 17, 2017

Area Forecast Discussion
National Weather Service Birmingham AL
106 PM CDT Mon Jul 17 2017

.UPDATE...
For 18Z Aviation.

&&

.SHORT TERM...
Today and Tonight.

This AM at the surface, a weak lingering stalled surface boundary is
stretched across the northern fringes of Alabama into N GA and into
VA. In the upper levels the upper low over the Great Lakes is
expected to begin to weaken, open up, and push to the northeast
through tonight. While the continued northerly flow could allow what
is left of the boundary to sink a little further south before it
fizzles out, it is not looking promising of any significant effects
from it. We will have more effects from the shortwave activity,
extra cloud cover, and rain today. As the trough weakens through
tonight, we should begin to see upper ridging over the mid section
of the U.S. begin to expand eastward which could help to see our
rain chances decrease some as we head into tomorrow and hint at a
warming trend. So, we will look at one more above normal rain chance
day and not quite as hot temperature day before a change in the
pattern.

08

.LONG TERM...
Tuesday through Monday.

On Tuesday, the upper low and trough begin to shift eastward as
upper-level ridging builds in across the Great Plains. We could see
some scattered shower/storm activity in the southern counties thanks
to some lift from whatever is left of the weak frontal boundary by
the time Tuesday afternoon rolls around. Have only mentioned roughly
30% coverage, but it's possible that we could see less.

A high pressure system remains in place through the upcoming week
and only slides eastward slightly by the upcoming weekend. Since
there won't be much of a pressure gradient across the region, expect
winds to remain fairly weak. The upper level ridging builds eastward
through the Plains and into Western TN by Thursday before being
directly over Northern AL by Friday afternoon. Expect the synoptic
scale subsidence to limit convection across the area, helping high
temperatures warm well above normal. NAEFS, GEFs, and ENS all point
to an anomalous pattern moving through the region. 1000-850mb
thickness values in both the GFS and ECMWF are in the 1440-1445m
range, which would support air temps in the upper 90s, approaching
100 on Thursday, Friday, and Saturday. The GFS has highs reaching
triple digits while the ECMWF is somewhat lower, "only" putting
highs in the upper 90s. The good news is that the abundant soil
moisture area-wide could help moderate the temps slightly, but
unfortunately, that won't help the heat indices, which could exceed
105 in some areas. I have the forecast highs reaching upper 90s,
which is more in line with the EC and is better supported given the
thickness values. Have increased confidence in the HWO for heat risk
on Friday due to the upper-level ridge becoming more centered over
us. Have also added a low confidence mention in the HWO for
Saturday in addition to Thursday, which is already mentioned.

The upper and lower level ridging shifts eastward Sunday into
Monday, lowering the thickness values to a more typical range.
Expect near normal highs to return in the second half of the
weekend.

25/Owen

&&

.AVIATION...
18Z TAF Discussion.

Convection today should be more typical of a summertime pattern.
An upper trof was located near the I-85 corridor, but little
forcing was evident ahead of the trof axis, just deeper moisture.
Best chance of storms this afternoon will be at KTOI and included
a tempo group for tstm. Elsewhere, handled convection with VCTS.
The surface pressure pattern is very weak and surface winds will
be variable at less than 5 knots during the day and calm at night.
Tstms should dissipate by 03z. Forecasting low clouds during the
late night and early morning hours has been difficult in this
pattern. Models suggest low level moisture will be highest across
south Alabama tonight, and forecast IFR cigs only at KMGM and
KTOI.

58/rose

&&

.FIRE WEATHER...

Isolated to scattered summertime showers and thunderstorms are
expected this afternoon into tonight with best chances in the
southeastern counties. Rain chances decrease towards the middle of
the week. There are no fire weather concerns at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Gadsden     71  91  71  92  70 /  20  20  10  10   0
Anniston    71  89  72  91  72 /  20  20  10  10   0
Birmingham  72  90  74  92  74 /  20  20  10  10   0
Tuscaloosa  73  92  74  93  74 /  20  20  10  20  10
Calera      72  90  73  92  73 /  20  30  10  20   0
Auburn      71  87  73  90  73 /  30  30  10  20  10
Montgomery  73  91  74  94  75 /  30  30  10  20  10
Troy        71  89  72  92  72 /  30  40  10  20  10

&&

.BMX WATCHES/WARNINGS/ADVISORIES/...
None.

&&

Hazardous Weather Outlook
National Weather Service Birmingham AL
414 AM CDT Mon Jul 17 2017

ALZ011>015-017>050-181215-
Marion-Lamar-Fayette-Winston-Walker-Blount-Etowah-Calhoun-Cherokee-
Cleburne-Pickens-Tuscaloosa-Jefferson-Shelby-St. Clair-Talladega-
Clay-Randolph-Sumter-Greene-Hale-Perry-Bibb-Chilton-Coosa-Tallapoosa-
Chambers-Marengo-Dallas-Autauga-Lowndes-Elmore-Montgomery-Macon-
Bullock-Lee-Russell-Pike-Barbour-
414 AM CDT Mon Jul 17 2017

This Hazardous Weather Outlook is for the counties served by the
National Weather Service office in Birmingham.

.DAY ONE...This Afternoon and Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

High temperatures are forecast to be in the mid to upper 90s on
Thursday, Friday, and Saturday. Heat indices could exceed 105 across
western Alabama.

.SPOTTER INFORMATION STATEMENT...

Activation of storm spotters and emergency management is not
anticipated at this time.