Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Lake Charles la
653 am CDT Sat Jul 4 2015
for the 12z taf package.
all sites VFR this morning...though isolated convection is already
streaming northward from the Gulf of Mexico per regional radar
imagery. Inserted vcsh at the coastal sites this morning early
this morning. Otherwise...VFR is expected to continue to prevail
amid generally light southwest winds...though more convective
activity is expected today vs yesterday. Forced by diurnal
instability and a shortwave trough prognosticated to dive NE through the
arklamiss...the timing/placement will nevertheless be driven
largely by mesoscale features such as the sea breeze or outflows.
As such...inserted thunderstorms in the vicinity at all sites late morning...with
convection ending by middle evening. VFR to prevail thereafter.
Previous discussion... /issued 503 am CDT Sat Jul 4 2015/
latest upper air analysis/WV imagery shows shortwave trough dropping southeast across
Kansas/OK into the lower MS valley...weakening the broad area of ridging
that extends from the western Continental U.S. Across the Gulf of Mexico and east
toward the Atlantic. Abundant moisture remains over the region
with precipitable water per regional soundings and satellite blended tpw near 1.8
Surface map shows a stationary front bisecting the Continental U.S. East of The
Rockies...as it stretches from OK east across Kentucky toward the East
Coast. South of the boundary...the Bermuda high ridges west across
the Gulf Coast with southerly winds maintaining a warm and moist airmass
over the region. The combination of the surface front and approaching
disturbance was producing a cluster of storms across southeast OK into southern
Arkansas this morning while closer to home widely scattered nocturnal
convection was developing over the coastal waters and streaming NE
into coastal la/southeast Texas.
a little more convective action expected today as the shortwave
digs south into the region. The surface front is expected to remain
stationary across OK and Arkansas...however the convective complex
currently located over that area will produce an outflow boundary
that will sag south toward the lakes region and cntl la later
today. The approaching shortwave will provide enough energy to
allow activity to become scattered over inland areas as daytime
heating gets underway this morning. By this afternoon...expect
increasing coverage across the northern half of the area...especially
cntl la as surface convergence along the outflow boundary combines
with difluent flow aloft. In addition...a few storms could become
strong to marginally severe during the afternoon and early evening as
lapse rates increase in response to surface heating beneath the cooler
air aloft. The primary risks from these stronger storms will be
strong gusty winds...along with frequent cloud to ground
Activity should diminish in the evening once heating
ceases...although a few showers or storms could linger into late
evening. Rain chances will decrease slightly for Sunday as the
disturbance moves further east...but scattered showers and storms will
still be possible over the eastern half of the area with lesser
coverage for locations further west.
The upper level ridge will begin to re-establish itself by
Monday...remaining over the area through the week. This will lead
to much lower rain chances...with anything that develops being isolated
at best. Meanwhile...surface pattern across the County Warning Area is expected to
remain status quo as the Bermuda high extends west across the Gulf
of Mexico. This will keep a warm and muggy airmass over the region
through the period with near normal highs and above normal lows.
With little shower activity to help cool things off...afternoon heat
indices are expected to peak in the 100 to 105 degree
range...just below advisory criteria.
a lt to modt onshore flow will prevail through next week as surface
high pressure ridges west across the Gulf of Mexico. An upper level
disturbance passing over the lower MS valley today will bring
scattered showers and thunderstorms. Otherwise...rain chances should remain on the
low side as upper level ridging becomes re-established this week in
the wake of the departing disturbance.
Preliminary point temps/pops...
aex 89 74 90 73 / 60 30 40 10
lch 88 77 89 77 / 40 20 20 10
lft 88 75 90 75 / 40 20 30 10
bpt 90 78 90 77 / 30 20 20 10