Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
FXUS64 KLIX 311415
Area Forecast Discussion
National Weather Service New Orleans LA
915 AM CDT TUE MAY 31 2016
Winds light and variable near the surface with a light southerly
flow in the lower levels. A moderate northwesterly flow in the upper
levels. Marginal risk for severe storms which would mainly include
downbursts to 40 knots and marble sized hail. However, stronger
gusts above severe levels are possible in a few storms, given a
northwesterly flow and drier air aloft. Freezing level at 13.5 kft
and wet bulb zero of 12.3 kft. Convective temperature in the upper
80s will be easy to achieve by noon with abundant sunshine this
morning. Seasonal Pw of 1.55 inches enough to bring heavy rains
over isolated areas with slow moving storms.
.PREV DISCUSSION... /issued 335 AM CDT TUE MAY 31 2016/
Another round of afternoon thunderstorms expected today. The CWA
is currently under weak upper level ridge influences from high
pressure thats centered over Mexico. Separate troughs are located
over the northern Rockies and Desert Southwest. Surface high
overhead has shifted offshore into the northern Gulf of Mexico.
Convection will once again be driven by daytime heating and likely
initiate along seabreeze boundaries. Movement for the most part
will be dictated by outflow boundaries but model soundings show
there might be enough mid level wind to produce a slow eastward
movement of storms. Also of note in those soundings are a repeat
of an inverted-v in the lower levels and wetbulb height of around
11kft. Those characteristics of the sounding would suggest the
possibility of marginally severe thunderstorms with downbursts and
smaller hail to be the main threats. For actual rain chance
forecast, 2/3`s of the area have around 30% while the far western
zones are closer to 20 as those locations are closer to the ridge
and subjected to more subsidence. Above normal temperatures will
persist with highs in the lower 90s. Movement of the upper ridge
over the Gulf of Mexico will aide in "shielding" the CWA from
convection being able to initiate, at least not widespread enough
to even have any mention of rain in the forecast except possibly
on the outer fridge of the forecast area.
The southern of those 2 troughs mentioned earlier will gradually
track east across northern Mexico early this week, reaching central
Texas by Friday afternoon. It will begin to weaken the slight upper
ridge in place over the area Thursday and Friday which will result
in a noticeable increase in shower and thunderstorm activity across
the forecast area. Have slightly increased pops to 30 to 50 percent
Friday as the trough approaches. A northern stream trough will
expand southwest towards the gulf coast over the weekend which will
keep numerous showers and thunderstorms going across the region.
Thus have increased rain chances to nearly 70% on Saturday and 50s
to 60 for Sunday.
Early next week is becoming more uncertain. The GFS suggests the
broad trough passing over the southeastern CONUS will progress far
enough south to shift all activity offshore and nearly completely
absorbing the southern trough. The ECMWF keeps these features more
separate and the southern trough gets left behind which would keep
rain in place over the local area. So haven`t made any changes to
the forecast beyond Sunday.
VFR conditions are expected outside sh/ts coverage today which will
dissipate shortly after dark. Some reduced vis and lower ceilings
can be expected in rain cooled areas by Wed morning.
Weak surface high pressure over the north gulf to maintain light
winds and low seas for much of the week.
DSS code: Green.
Decision Support Services (DSS) Code Legend
Green = No weather impacts that require action.
Blue = Long-fused watch, warning, or advisory in effect or
high visibility event.
Yellow = Heightened impacts with short-fused watch, warning
or advisory issuances; radar support.
Orange = High Impacts; Slight to Moderate risk severe; nearby
tropical events; HazMat or other large episodes.
Red = Full engagement for Moderate risk of severe and/or
direct tropical threats; Events of National Significance.
.PRELIMINARY POINT TEMPS/POPS...
MCB 92 67 90 69 / 30 30 10 10
BTR 92 69 90 69 / 20 20 10 10
ASD 92 70 90 71 / 30 30 10 10
MSY 91 73 88 72 / 30 30 10 10
GPT 91 73 88 73 / 20 20 10 10
PQL 91 68 88 68 / 30 30 10 10