Scientific Forecaster Discussion
fxus64 kmob 241122 aaa
Area forecast discussion...updated
National Weather Service Mobile Alabama
622 am CDT Wed may 24 2017
Discussion...updated for latest aviation discussion below.
12z issuance...cigs/visbys range from VFR along to the coast to
low end MVFR/IFR north of Highway 84. An upper system spinning
over the mid Mississippi River valley will push east today through
tonight, bringing continued MVFR/IFR ceilings/visbys along with light
shra to areas along and north of Highway 84, with general MVFR to
Previous discussion... /issued 414 am CDT Wed may 24 2017/
Near term /now through tonight/...
shortwave energy sweeping around the base of a southward moving
upper low located over eastern portions of the Central Plains pushes
a front (currently located along the lower Mississippi river) across
the forecast area today. Looking at the regional radar loop, the
bulk of of the rain is located closer to the upper low (read
northwest of the area), leaving a more isolated to scattered
coverage to our west to move over the area this morning. The current
activity over the land and marine portion of the forecast area
should be along our eastern border by the time the current package
comes into effect. As the day progresses, guidance is consistent
bringing a few isolated rain showers to northern portions of the forecast
area later today into tonight as the upper system transitions
from southward moving to eastward moving and opens, passing just
north of the area in the process. Am putting highest chance of
rain over eastern portions of the forecast area, mainly this
morning, with a few light rain showers hanging on over northern portions
into this evening as a result.
Cold air will move over the area behind the front, though with the
south to eastward movement transition of the upper system, am
expecting the initial northwest winds late afternoon to early
evening to transition to westerly, lessening the cold push. With
southeast portions of the forecast are seeing the cooler air last, a
northwest to southeast gradient with respect to highs is expected
today. Highs ranging from mid 70s northwest to low 80s southeast
are expected. Tonight, the cooler air overspreads the entire
forecast area, with overnight lows dropping into the well below
seasonal low to mid 50s.
Short term /Thursday through Friday night/...
the storm system which has plagued the forecast area for the past
several days will finally move east of the region Thursday. A
northwesterly flow aloft in wake of the system will Herald a drier
airmass into our area as ridging, both at the surface and aloft,
moves into the forecast area. The result will be drier and slightly
cooler conditions for the 36-48 hour time period.
Shortwave ridging aloft should dampen as it heads into the eastern
United States Friday. The surface high should correspondingly move
east, resulting in a gradual return of low-level moisture to our
corner of the world Friday afternoon. Even so, precipitable water
values should remain below 1 inch, which is below climatological
means for this time of year. With no synoptic scale forcing present,
weather conditions should remain dry, although it'll likely feel a
little more humid. /02/
Long term /Saturday through Tuesday/...
our next storm system will start to take shape Saturday, as a
shortwave trough tries to amplify heading into the plains. The
associated cold front should push into the lower Mississippi Valley
Sunday, then inch its way toward our forecast area for Monday and
For Saturday, most of the low-level moisture is expected to pool
along the surface front extending from the midsouth into the
arklatex. And while precipitable water values approach seasonal
values for our area, any convective development will be due to
mesoscale processes. Because of the very limited nature of any
convective development, the odds of seeing showers/thunderstorms
will remain below 15% Saturday.
Things change for Sunday through Tuesday as the front approaches and
subsequently stalls. At least a scattered coverage of showers and
thunderstorms is expected through the period, with a weakening
diurnal trend anticipated by Tuesday. /02/
strong westerly winds will transition to north-westerly, then ease
into Thursday night as surface high pressure moves toward and
over the area. Light to moderate onshore flow returns by Friday
as the surface high moves east of the area. A passing upper system
will bring a temporary increase in the onshore flow Saturday into
Saturday night, but by Sunday, the flow returns to a light
Alabama...high rip current risk through this evening for alz265-266.
Florida...high rip current risk through this evening for flz202-204-206.
GM...Small Craft Advisory until 1 am CDT Thursday for gmz650-655-670-