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fxus64 kmob 250449 
afdmob

Area forecast discussion
National Weather Service Mobile Alabama
1149 PM CDT Mon Jul 24 2017

Discussion...updated for latest aviation discussion below.

&&

Aviation...
25/06z issuance...convection has ended (for the time being) across
most of the forecast area, with only a few lingering showers
noted over north central counties. Primarily mid-upper level
clouds with no restrictions to vsby expected at terminals through
into through the early predawn hours of Tuesday. Will likely see
convective redevelopment late tonight however, especially near the
coast, where ocnl IFR conditions return in and near showers and
thunderstorms by around sunrise Tuesday. Scattered convection
expected across much of the area, especially over land areas
during the day on Tuesday. Light southwesterly surface winds (3-6
knots) expected through tonight into early Tuesday, increasing
slightly during the afternoon Tuesday (8-12 knots) before
subsiding again after sunset Tuesday evening (3-6 knots). 12/ds

&&

Previous discussion... /issued 847 PM CDT Mon Jul 24 2017/

Discussion...see updated information for land areas below.

Update...updated grids and forecast products a little earlier
this evening to reflect rapidly dissipating convection. Removed
Flash Flood Watch headline from southeast MS zones, as the flash flood advisory was
allowed to expire at 7pm. Also lowered pops from likely to chance
category for overnight hours. Otherwise, no changes required for
overnight forecast period. 12/ds

Previous discussion... /issued 703 PM CDT Mon Jul 24 2017/

Discussion...updated for latest aviation discussion below.

Aviation...
25/00z issuance...convection has ended (for the time being) across
most of the forecast area, with only a few lingering showers
noted. Primarily mid-upper level clouds with no restrictions to
vsby expected at terminals through much of the evening and into
the early predawn hours Tuesday. Will likely see convective
redevelopment late tonight however, especially near the coast,
where ocnl IFR conditions return in and near showers and
thunderstorms. Scattered convection expected across much of the
area, especially over land areas Tuesday. Light southwesterly
surface winds (3-6 knots) expected through tonight into early
Tuesday, increasing slightly during the afternoon Tuesday (8-12
knots) before subsiding again after sunset Tuesday evening (3-6
knots). 12/ds

Previous discussion... /issued 551 PM CDT Mon Jul 24 2017/

Discussion...updated for latest aviation discussion below.

Aviation...
24/18z issuance update...made a few adjustments to tafs as most of
the convection has ended (for the time being), especially along
the coast and at the air-terminal forecast locations. Primarily
mid-upper level clouds with no restrictions to vsby expected
through much of the evening. Will likely see convective
redevelopment late tonight, especially near the coast, when ocnl
IFR conditions return in and near showers and thunderstorms. Light
southwesterly surface winds expected through tonight into early
Tuesday. 12/ds

Previous discussion... /issued 420 PM CDT Mon Jul 24 2017/

Near term /now through Tuesday/...an upper level trough axis
continues to extend southwest from the eastern Seaboard through
central and southwest al, southeast MS, and back into la this
afternoon. Weak impulses embedded within this larger scale feature
moving across the region, along with convergence along an axis of
deep moisture (precipitable water values locally enhanced between
2.2" and 2.4") has resulted in a training complex of showers and
thunderstorms across portions of southeast MS today, particularly
Stone County, where multiple rounds of heavy rain resulted in
rainfall amounts of 4" to 8" across much of the County and isolated
amounts approaching 12" in the far northwestern part of the County.
Farther east, convection has been more limited today given a bit
more subsidence east and south of the convection over MS. It is
interesting to note that a mesoscale convective vortex (mcv) is also
noted across Washington/Clarke counties on visible satellite and
radar imagery as of 340 PM - and lift ahead of this feature was
resulting in some scattered convective development in the far
northern and northeastern part of the area.

A challenging forecast continues across our local area through the
next 24 hours. Latest mesoscale model trends have been consistent
with gradually diminishing convection over southeast MS into the
early evening hours. Still some opportunity for lingering showers
into late afternoon/early evening and have kept pops fairly high
over southeast MS for through early evening, and more scattered
coverage farther east over the rest of the area. The upper trough
axis will hold overhead through the rest of tonight and again into
the day Tuesday. We have maintained at least a chance of
showers/storms into the local area through the night given the
presence of this feature and continued moist environment. We have
decided not to extend the Flash Flood Watch for southeast MS past 7
PM for now as convection should be diminishing in coverage. However,
will need to watch trends overnight/early Tuesday morning carefully,
as if additional convection re-develops near Stone County, it won't
take much rain to exacerbate flooding problems. The past couple of
runs of hrrr and a look at the WRF-arw are not as robust with
convective development tonight. Later shifts will monitor trends
closely.

Expect additional scattered to numerous showers and storms to re-
develop inland over the area through the day Tuesday. Given the
quality of moisture over the region, a few storms could once again
be capable of producing very heavy rainfall and perhaps localized
flooding. Lows tonight range in the lower to mid 70s inland, and mid
to upper 70s along the beaches. Highs Tuesday should range in the
mid 80s to around 90 degrees. /21

Short term /Tuesday night through Thursday night/...guidance has
come into better agreement with the handling of an upper trough
over the lower Mississippi River valley. Guidance is advertising
the upper trough stretching as it shifts southeast towards the
northeastern Gulf Coast, then the northeastern Gulf. This will
allow an upper high over the Southern Plains to build east over
the lower Mississippi River valley. A surface ridge that has built
west over the northern Gulf of Mexico gets split, leaving a
surface high centered over the western Gulf and a surface ridge
stretching west from the Florida Peninsula.

With the upper trough overhead into Wednesday, the chance of rain
remains above normal, though is decreasing. Wednesday on, with the
splitting surface ridge, northwesterly flow brings in a drier
airmass as compared to the current tropical soup over the forecast
area. Through the short term, with the Southern Plains upper
ridge building east, increased subsidence will work with the
decreased moisture levels along with weakening upper support to
decrease the chances of rain into mid week, along with increasing
temps. Overnight lows around seasonal expected (low to mid 70s,
upper 70s along the coast) with daytime highs well above seasonal
( mid 90s expected with around 90 close to the coast). With the
increasing highs, a return of high heat indices returns, with
Wednesday seeing heat indices topping out in the 102 to 107 degree
range over most of the area.

/16

Long term /Friday through Monday/...guidance is advertising
shortwave energy digging an upper trough over the East Coast. The
first round of shortwave energy moves south across the forecast
area late Friday into Saturday. A return of a bit below seasonal
temps for Sunday is expected with above seasonal chances of rain.

A second round moving southeast across the eastern conus is not so
consistently handled by the guidance Sunday on. The European model (ecmwf) keeps
it well north of the area, whilst the GFS digs it farther south,
hot on the heels of the first round of shortwave energy. Both
ultimately organize the energy into a closed low Monday, with the
GFS advertising it over the southeast, the European model (ecmwf) over the
Tennessee River valley. The quicker GFS solution also brings in a
drier airmass behind the first round, resulting in a significantly
drier forecast in the Sunday through Monday time frame. The European model (ecmwf)
solution brings a decrease, enough of a decrease in moisture to
advertise a decrease in pops, but still advertise scattered
daytime/evening shra/tsra. Consensus leans towards the European model (ecmwf)
solutions, with temps and pops around to a bit below seasonal.

/16

Marine...a ridge of high pressure will gradually build across the
central Gulf of Mexico this week. A light to moderate westerly wind
component generally prevails. Winds, waves and seas will be locally
higher with the passage of storms. Frequent lightning activity
likely in and near any of the stronger marine storms. A few
waterspouts remain possible, mainly with overnight and early
morning storms. /21

&&

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

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