Area forecast discussion...aviation update
National Weather Service Mobile Alabama
635 PM CDT Tuesday Jun 18 2013
Aviation [19.00z terminal forecast discussion]...VFR conditions
will prevail through much of the period. Isolated to scattered
showers and thunderstorms will develop during the late morning and
afternoon hours on Wednesday with localized MVFR to IFR ceilings/br
possible tonight into Wednesday...particularly near shra/tsra. /13
&&
Short term [tonight through wednesday]...water vapor imagery and
RUC 500 mb analysis indicate a moist westerly flow regime is
persisting across much of the southeastern U.S. This afternoon.
Surface low pressure is meanwhile centered in the vicinity of North
Carolina/Virginia...while an associated weak frontal boundary remains
draped southwestward from this feature across northern
Georgia...Alabama and Mississippi. MLCAPES are generally ranging
between 1000-1500 j/kg across our forecast area this afternoon...
while precipitable water values are mostly averaging between 1.5 and
2 inches. This moist and unstable environment...combined with a weak
embedded shortwave impulse in the westerly flow aloft has aided in
the development of scattered to numerous showers and thunderstorms
across interior portions of southeast Mississippi and southwest
Alabama early this afternoon. The wet microburst risk remains in the
moderate category...so a few strong pulse storms will be possible
through the early evening hours.
The moist westerly flow pattern will persist across our forecast
area through Wednesday. The aforementioned weak boundary will
continue to sag southward and will become oriented near coastal
portions of the forecast area by early Wednesday morning. The deep
layer moisture axis will also continue to edge southward to near the
coast by Wednesday afternoon. We therefore expect scattered showers
and thunderstorms to continue to develop along and ahead of the
boundary through Wednesday. Precipitation chances will be maintained
in the 40-50 percent range across most locations tonight into
Wednesday. Frequent lightning...gusty winds...and very heavy rain
will be possible at times with the stronger storms that develop.
Little change was made to the temperature forecast. Lows tonight
should range from near 70 over the interior to the middle 70s near the
coast. Highs Wednesday look to mostly range from the upper 80s to
around 90. /21
Short term [wednesday night through Thursday night]...surface
trough will move toward the central Gulf Coast on Wednesday evening
and offshore overnight. It will serve as a Focal Point for convection
within a high humidity band of air...where precipitable water is
about 2 inches...aligning itself east to west along the trough axis.
Eastward passage of well defined middle level disturbances at the base
of the approaching feature will combine with thermodynamic lifting
from the surface and dynamic lifting by those upper vortlobes
mentioned. These two terms would bring scattered to numerous
showers and thunderstorms. Some will bring heavy rain and strong
gusty winds. After sunset before midnight the convection will die
down and the atmosphere will stabilize while it is recycling fallen
rainwater into water vapor. Showers and thunderstorms would increase
southward off the coast after midnight Wednesday night toward
sunrise Thursday morning with the aforementioned surface feature
being offshore and the land breeze spinning up which we believe
would both bring a greater chance of rain than after sunset. The
trough aloft should migrate east Thursday and give US a lesser chance
for rain. /77
Long term [friday through monday]...no changes. The forecast area
will remain in a generally humid middle level zonal flow through much
of the medium range with a weak surface trough present to the east.
That feature should be gone by Saturday expect to see isolated to
scattered showers/storms remaining in the outlook with slightly more
coverage during the daytime when humidity will be high
horizontally and vertically...and thermodynamic instability
increases. Dynamic forces aloft appear to be much less than they are
currently since a ridge aloft will be building over the region late
this week. /77
&&
Marine...surface low pressure will continue to move eastward to
near the eastern Seaboard tonight...while high pressure stretches
across southern Florida into the northern Gulf of Mexico. The
gradient between these two features will result in a moderate
southwesterly wind flow over the marine area through tonight. A
light to moderate southwest to northwest wind is expected
Wednesday-Thursday as a weak cold front/pressure trough approaches
the Gulf Coast region. A light to occasionally moderate
southeasterly to southerly flow pattern should develop by the end of
the week into the weekend as high pressure builds across the
southeastern states. Winds and seas will be locally higher near
isolated to scattered showers and thunderstorms. /21
&&
Preliminary point temps/pops...
Mobile 73 89 70 89 70 / 50 50 20 30 20
Pensacola 75 90 74 90 73 / 40 50 20 30 30
Destin 76 88 76 87 75 / 40 50 20 40 30
Evergreen 70 88 68 91 67 / 40 50 20 30 30
Waynesboro 70 88 65 90 65 / 40 40 20 20 20
Camden 70 88 66 91 66 / 40 30 20 20 20
Crestview 71 91 69 92 67 / 50 50 20 40 30
&&
Mob watches/warnings/advisories...
Alabama...none.
Florida...none.
MS...none.
GM...none.
&&
$$
