Area forecast discussion
National Weather Service Mobile Alabama
322 PM CDT sun may 19 2013
Short term (tonight and sunday)...a surface ridge stretching west
over the northern Gulf of mex will continue to create an onshore flow
over the northwestern and north-central Gulf Coast. This will keep
moisture levels high with another round of stratus/fog development
likely tonight. A possible wildcard for tonight in the probability of precipitation is a
system moving south over western Georgia. Looks like any outflows will
remain east of the forecast area...and the forecast reflects this. But things
with active systems...things don't always work out the way on
intends...so feel keeping an eye on this is warranted.
Monday...the shortwave causing the Georgia system moves over NE-eastern fla
as a weak shortwave moves over southern miss in an upper ridge that
moves over the eastern Continental U.S.. soundings over the area still show a
good cap above the surface limiting convection...but less than they
were indicating for today. Feel the cap will continue to limit
convection development...but have a small pop in there just the
same. /16
For Monday night through Wednesday night...upper level riding over
the region Monday evening breaks down through Tuesday night as a
vigorous shortwave moves through the base of a trough over the plains
and advances to near the lower Mississippi River valley. A surface
ridge meanwhile remains near the coast and maintains a light to
occasionally moderate southerly flow. Will continue with a dry
forecast through Tuesday as the effects of ridging suppress
convection. An isolated thunderstorm cannot be ruled out but
coverage from any that develop is too limited to support mention of
precipitation. The environment becomes more convectively favorable over
the western portion of the area Tuesday night as the ridging breaks
down but without a forcing mechanism to generate convection...will
continue with a dry forecast for now for Tuesday night.
The strong shortwave ejects off across the southeast states
Wednesday into Wednesday night with the plains upper trough weakening
while beginning to move into the eastern states. The onshore flow
continues Wednesday then a weak surface reflection trough moves across
the forecast area Wednesday night. Model soundings show an improved
profile overall...especially over the western portion furthest
from lingering effects of ridging. Will continue with chance probability of precipitation
generally west of the I-65 corridor with slight chance probability of precipitation further
east. Slight chance probability of precipitation follow for Wednesday night for lingering
convection. Temperatures will be near to slightly above seasonable
levels through Wednesday night. Low clouds and patchy fog are
expected late Monday night. /29
&&
Long term (thursday through sunday)...HPC prefers a blend of the
00z European model (ecmwf) and GFS/European model (ecmwf) ensemble means for the long term
period...and it was noted that the 12z GFS was close to this blended
solution as well adding confidence to the period. The weakened
upper trough amplifies again while continuing eastward across the
plains states through Friday...moving off into the western Atlantic
on Saturday with drier deep layer air flowing into the region.
The weak surface trough meanders over the forecast area on Thursday
and meanwhile merges with the southernmost extension of a weak front
associated with a surface low well off to the northeast. After a
brief delay on Friday due to daytime heating and a sea breeze...the
weak front moves offshore Friday night as a large surface high
builds into the eastern states. Will continue with chance probability of precipitation for
Thursday with the presence of the weak trough/front as well as an
expected afternoon sea breeze. Slight chance probability of precipitation follow for Friday
for development along the sea breeze with convective development by
drier air moving into the area.
A large upper ridge over the plains spreads into the forecast area
this weekend with a surface ridge becoming established over the
southeast states. A northerly flow on Saturday becomes easterly by
Sunday with a sea breeze becoming more developed through the
weekend. Have continued with slight chance probability of precipitation for Saturday for
sea breeze convection with coverage again expected to be limited by
drier air flowing into the area. Even drier deep layer air is
expected to move into the area on Sunday as the ridging builds
further into the region and have continued with a dry forecast for
Sunday. Temperatures continue a similar trend from the short term
period with values slightly above seasonable levels. /29
&&
Aviation (18z issuance)...VFR ceilings/visbys across the forecast area expected
to continue into the evening hours. Guidance is advertising a
stratus deck moving inland overnight tonight...after 06z...with
ceilings/visbys dropping into IFR levels. Some local drops to LIFR
levels...especially near kmob...are likely. With daytime
heating...cigs/visbys expected to rise quickly. /16
&&
Marine...a surface ridge stretching west over the northern Gulf of
mex will keep a light to at times moderate onshore flow over the
area into Friday. A deepening trough develops over the eastern Continental U.S.
Thursday on...pushing the surface ridge west...to over the
northwestern Gulf of mex and brings a light offshore flow to the
area. A weak front will move south across the area Friday...bringing
a moderate enhancement to the now offshore flow Friday night...but
am not anticipating small craft level winds at this time. /16
&&
Fire...a moist southerly flow will remain over the area through
Wednesday with afternoon relative humidities remaining well above
critical levels through middle week. Afternoon dispersions will be
generally good with deep mixing heights...especially away from the
coast.
Fog potential and other remarks...patchy dense fog is likely late
tonight and late Tuesday night...with visibilities dropping to a
quarter mile in some locations. /29
&&
Preliminary point temps/pops...
Mobile 69 87 68 87 66 / 10 10 05 05 10
Pensacola 70 85 70 86 69 / 05 05 05 05 10
Destin 72 80 71 83 70 / 05 05 05 10 10
Evergreen 67 91 66 91 65 / 10 05 05 10 10
Waynesboro 70 90 67 90 65 / 10 10 05 10 10
Camden 67 91 67 90 65 / 10 05 05 10 10
Crestview 66 89 64 91 65 / 05 05 05 10 10
&&
Mob watches/warnings/advisories...
Alabama...none.
Florida...none.
MS...none.
GM...none.
&&
$$
