Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Mobile Alabama
422 am CDT Thursday Jul 30 2015

Short term [today through Friday night]...upper energy sweeping around
the base of an upper low near Hudson Bay will deepen an upper trough
over the East Coast of the Continental U.S.. this energy will also help to push
a drier airmass from over the tenn River Valley to the northern Gulf
Coast later tonight into Friday...merging with a surface trough
expected to develop over the northeastern Gulf Coast today.

With the surface trough developing today...and a very moist airmass
over the forecast area at this time...am expecting another round of thunderstorms and rain to develop
today...with likely probability of precipitation. With greater cloud cover and rain
coverage...have leaned towards the cooler side of guidance...in this
case...more in line with the European model (ecmwf) numbers.

With rain expected to begin developing at noon-time...feel there
will be enough time for heat indices to rise into the 104-108 degree
range before increasing cloud cover cuts off incoming insolation.
Also...with the hot/moist airmass in place over the forecast area (capes
generally rising into the 3000-4000j/kg range)...some of the
thunderstorms may become strong to severe...with damaging downburst
winds possible.

Tonight...drier air to the north is expected to overspread the area with
clearing skies coming with the end of the thunderstorms (plus what
does form is expected to head south of the fa)...temperatures cooler than
previous nights expected...especially over northern regions of the
forecast area.

There is a high risk of damaging downbursts across the area today
into tonight...with highest across northern parts of the area. /16

Friday and Friday night...eastern nose of upper ridge begins to break
down over the southeastern Continental U.S. As trough sets up from the eastern
Great Lakes...southward into the Appalachians. The evolving upper
level pattern allows a weak surface pressure trough/front to settle to
the central Gulf Coast...becoming quasi-stationary. This presents a
challenge for the forecast of showers/storms as the boundary will be
the dividing line of the deeper moisture. Higher moisture along and
southeast of I-65 and less available moisture to the northwest of the
Interstate. This is the general scenario advertised in the latest
weather models...so with the boundary being the focus for lift...the
official forecast calls for a chance of seeing showers/storms from
the southern portions of interior southeast Mississippi to along and
southeast of I-65 on Friday. Over the far northern zones...north of
the boundary...will only have a slight chance. A slight southward
shift and lower chances of showers/storms exists for Friday night.

High temperatures on Friday look to be somewhat closer to seasonal
for the last day of July...near 93 over the interior. Upper 80s to
lower 90s closer to the coast. For Friday night lows...possibly upper
60s over the interior...while numbers remain muggy along the coast in
the upper half of the 70s. /10

Long term [saturday through wednesday]...heading into the
weekend...there is very little change in the high level flow. Trough
over the eastern to southeast US and deep layer ridge over the
southwest. The weak surface pressure trough from the southeast to the
central Gulf Coast and weak waves of frontal low pressure sliding
east northeast along it will continue to prove a challenge for the
placement of rain chances over the weekend. Given the deep layer
moisture axis staying in a nearly fixed position...have the higher
chances of showers/storms along and southeast of I-65 with the far
northwest zones rainfree. Light wind pattern will be highly variable
with the surface trough meandering over the area. Moving into the
first half of next week...middle level impulses caught up in the high
level north to northwest flow between the trough to the east and the
ridge to the west...will interact with deep layer moisture. Although
the coastal surface boundary is forecast to become more diffuse
during the early half of next week...dynamic lift with the passage of
energy aloft suggests maintaining small chances of showers and
storms...mostly along the southeast half of the local area.

By Wednesday...the GFS shows another weak surface boundary/trough
setting up from the Carolinas to across Louisiana while the European model (ecmwf) is to
the northwest with its boundary...moving east over the middle
Mississippi to Red River valleys. Have followed the European model (ecmwf) solution
with a light south to southwest flow setting up late in the outlook
with surface high being more dominant over the Gulf.

High temperatures in the middle 90s over the interior...upper 80s to
lower 90s coast. Lows lifting into the middle 70s interior with little
change over the beaches...upper 70s to lower 80s. /10

&&

Aviation...
30.12z issuance...general VFR through the forecast. Exceptions being
MVFR to IFR ceilings/visibilities in scattered to numerous rain showers/thunderstorms and rain expected
to develop over southern Alabama mainly in the afternoon hours. A
drier airmass will move over the area tonight...bringing a less humid
airmass and small chance of localized fog development. /16

&&

Marine...a surface trough is expected to develop along the eastern
Seaboard to the northeastern Gulf Coast today...pushing a surface
ridge stretching west over the Gulf of mex south through tonight. A
surface boundary moving across the forecast area tonight into Friday
stalls...creating a variable flow over mainly offshore coastal waters
of the forecast area. This trough/boundary is expected to mix out Sunday into
Monday...with the Gulf of mex surface ridge regaining control and
bringing back a west to southwest flow. /16

&&

Preliminary point temps/pops...
Mobile 96 77 93 71 93 / 60 30 30 20 20
Pensacola 95 77 91 75 92 / 70 50 40 20 20
Destin 91 78 89 79 91 / 70 60 40 20 30
Evergreen 96 72 93 69 94 / 60 30 30 10 20
Waynesboro 96 70 94 70 94 / 50 30 20 10 10
Camden 96 71 93 69 94 / 60 30 20 10 10
Crestview 96 75 93 71 94 / 70 40 30 20 30

&&

Mob watches/warnings/advisories...
Alabama...none.
Florida...none.
MS...none.
GM...none.
&&

$$

National Weather Service Glossary of Abbreviations