Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Mobile Alabama
457 am CDT Sat may 30 2015
Short term...(today through monday)...for today through tonight...
a broad middle level trough is located across the central
part of the nation early this morning while a broad ridge of high
pressure extends from the western Atlantic Ocean to the eastern
Seaboard and southeast states. A south to southwest flow pattern
aloft prevails across our forecast area between these features. A
persistent surface ridge of high pressure meanwhile extends from the
western Atlantic and eastern Seaboard to the north central Gulf.
Mostly clear skies are in place across the region early this
morning...with patchy fog development noted over a few locations.
A moist southwest flow pattern will persist across the forecast area
today as the mean upper trough approaches the Mississippi Valley
region and ridging remains in place from the western Atlantic to the
Gulf of Mexico. A shortwave trough will lift northeastward toward
the middle Mississippi Valley region and upper Midwest today...while a
cold front also approaches the Mississippi Valley from the plains.
Deep layer moisture and lift will be maximized from Texas to the
arklatex region/Mississippi Valley ahead of the approaching frontal
boundary today. While forcing overall will remain weak over our
area...we will carry a low chance of convection over southeast MS
and interior southwest Alabama today where MLCAPE values range between
500-1000 j/kg and precipitable water values will average between 1.5
and 1.75 inches. We will keep convective coverage more isolated over
the remainder of the forecast area. The mean upper level trough axis
will become located over the Mississippi River tonight...while the
frontal boundary pushes southeastward into south central la...
central MS and the Tennessee Valley region. Deep layer moisture and
weak lift will be sufficient to keep isolated to scattered showers
and storms in the forecast over southeast MS and interior southwest
Alabama through tonight. Highs today will generally range from the middle to
upper 80s...while lows tonight once again range from the middle to
upper 60s over the interior...to the lower 70s near the immediate
The wet microburst risk for today is low.
Sunday through Monday...an upper trough moves over the miss River
Valley to over the eastern Continental U.S....pulling a weak front across the
forecast area. With the weak boundary comes a focusing mechanism for precipitation
development...thus probability of precipitation above seasonal. With the slow eastward
movement of the upper dynamics...thus surface bondary...the boundary
enhancement will be over western portions of the forecast area...then forecast area wide
for Monday. East of the boundary...temperatures above seasonal
expected...around to a bit below seasonal along and west.
Along and east of the boundary...with temperatures above seasonal...
guidance is advertising mu-convective available potential energy rising to around 2000j/kg...more
than enough for some thunderstorms to become strong to severe.
Looking at the wind-shear part of the severe equation...wind-shear
will be limited...generally less than 30m^2/s^2. The result is a very
low probability of supercells forming. All in all...if any storms do
become strong to severe...it is expected to be of the pulse-
type...with damaging winds and hail the primary threats. Also...with
instability in any storms over the water generally in the low
levels...waterspouts are likely.
Long term...(monday night on)...Monday night through Wednesday...the
upper trough stalls over the southeastern Continental U.S....then organizes into
a closed low over the northeastern Gulf of mex. The GFS is quicker to
organize the low than the European model (ecmwf)...but by Wednesday evening...both
show the low. With the surface boundary stalled over northern
Florida...low level flow over the southeastern Continental U.S. Is generally weak
and variable. Resultant text guidance is temperatures and probability of precipitation a bit above
seasonal. Both European model (ecmwf) and GFS text products are with a degree of each
other...along with the GFS ensemble mean. With guidance is pretty
good agreement...haven't deviated.
Wednesday night into Friday...the GFS and European model (ecmwf) diverge with the
handling of the closed low. The European model (ecmwf) has a loosely organized low
meandering slowly east over the Florida Peninsula to over the Florida Atlantic
coast. The GFS on the other hand...deepens the low and meanders it
northeast along the Atlantic coast...to over the Georgia/SC line by Friday
evening. The GFS also is advertising this low developing a surface
low off the Yucatan coast...then taking it northeast before stalling
it with the upper low over the Georgia/SC state line. In both
scenarios...the forecast area comes under dry northerly flow...with a dry period
Friday into Saturday and temperatures dropping to around seasonal levels.
30.12z terminal forecast discussion...mostly VFR
conditions are in place early this morning...though patchy MVFR to
IFR ceilings and fog could occasionally impact some locations through
the early morning hours. VFR conditions should prevail through the
day...except near isolated to scattered shra/tsra. The best
convective coverage today is expected over southeast MS and interior
southwest Alabama. /21
Marine...a ridge of high pressure will generally maintain its
position from the western Atlantic to the northern Gulf through the
middle of next week. A light to occasionally moderate southeasterly
to southerly flow will persist each day with light offshore flow at
night through Wednesday. Winds and seas will be locally higher near
isolated to scattered showers and thunderstorms. /21
Preliminary point temps/pops...
Mobile 86 68 87 68 86 / 20 10 30 30 50
Pensacola 85 71 87 70 86 / 20 10 30 30 30
Destin 85 74 86 73 84 / 20 10 20 20 30
Evergreen 88 66 90 65 87 / 20 10 30 30 50
Waynesboro 86 66 86 65 86 / 30 30 60 40 40
Camden 87 66 90 66 87 / 20 20 30 30 50
Crestview 89 66 91 66 90 / 20 10 30 20 40