Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service New Orleans la
805 PM CDT Wednesday may 6 2015

Sounding discussion...

Routine flight terminated almost in the same location as last
nights flight...near Grand Island at the northeast end of Lake
Borgne/southwest end of Mississippi Sound. Flight terminated after
95 minutes at an elevation of 108.3k feet or 20.5 miles.

Airmass has moistened considerably...with a precipitable water
value of 1.44 inches...about a half inch increase from this
morning. This is about 125 percent of normal. No low level cap to
speak of this evening with a lifted index of -5 and about 2000
cape. Freezing level at 13.2k feet...and -20c at 23.7k feet. Wet
bulb zero was at 8600 feet. Southeast winds from launch through
about 800 mb...gradually veering to northwest by about 550
mb...and then west to northwest through 100 mb. Maximum wind 50 knots
at 30k feet. 35

&&

Previous discussion... /issued 328 PM CDT Wednesday may 6 2015/

Short term...tonight through Saturday

A very persistent weather pattern is expected across the Gulf
south through Saturday. Deep layer southerly flow will dominate in
the low and middle-levels of the atmosphere on the southwest side of
a strong ridge of high pressure over the southeastern Continental U.S.. from
700mb and above...a strong ridge axis will dominate through the
period. There will be some weak vorticity lobes riding up and over
the ridge as they eject out of the base of a trough over The
Rockies. However...the ridging and resultant subsidence and
capping aloft will be the more dominant feature. As a
result...expect to only see some widely scattered marine layer
showers develop along weak low level convergence bands through
Saturday. Convection will be most likely during the afternoon
hours when the low level instability is at a maximum. Given
this...have kept in low probability of precipitation of around 20 percent in the forecast
for each day. With warm and moist air advecting into the low
levels...and strong subsidence aloft...temperatures will remain
seasonably warm through the short term period. Highs will range
in the middle to upper 80s which is a few degrees above normal...and
overnight lows will cool into the 60s and lower 70s each night.

Long term...Sunday through Wednesday

The pattern will turn more unsettled for next week...as a series
of weak upper level vorticity lobes ejecting out of The Four Corners slides
through the lower Mississippi Valley on the northern periphery of
the a broad ridge over the eastern Gulf of Mexico. A weak front
will slide toward the area on Sunday and become stalled along the
I-20 corridor for the first half of next week. This
front...combined with the increased Omega associated with each
upper level feature will be enough to spark off several rounds of
scattered showers and thunderstorms each day. Have went with
chance probability of precipitation for the northern and western zones beginning Monday
and persisting through Wednesday. Probability of precipitation will be highest in the
afternoon hours when peak heating and the greatest overall
instability occurs. For the southern and eastern zones...have
slight chance probability of precipitation in place for each day given the weaker forcing
expected for this portion of the County Warning Area. The atmosphere will remain
warm and humid through the period...with highs in the lower to
middle 80s and lows in the 60s and lower 70s each day.

Aviation...

Aviation...VFR conditions will continue to prevail at all terminals
through 18z Thursday. Scattered to broken convective cumulus expected at around
5000 feet again on Thursday after 15z.

Marine...

Onshore flow will continue across all of the marine zones through
early next week...as the central Gulf Coast remains dominated by a
broad ridge of high pressure centered over the southeastern Continental U.S..
winds will generally range around 10 knots through the
period...and seas will generally range from 2 to 4 feet in the
open Gulf waters. Overall...a fairly benign weather regime is
expected over the coastal waters.

Decision support...

Dss code...green.
Deployed...none.
Activation...none.
Activities...none.

Decision support services (dss) code legend
green = no weather impacts that require action
blue = long fused watch/warning/advisory in effect or high
visibility event
yellow = heightened impacts with short fused
watch/warning/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 severe and/or direct
tropical threats; events of National significance

&&

Preliminary point temps/pops...
mcb 63 84 64 86 / 10 20 10 10
btr 66 85 67 86 / 10 30 20 20
asd 67 82 66 84 / 10 10 10 10
msy 69 82 69 84 / 10 20 20 10
gpt 67 81 68 83 / 10 10 10 0
pql 64 82 65 84 / 10 0 0 0

&&

Lix watches/warnings/advisories...
la...none.
GM...none.
MS...none.
GM...none.
&&

$$

National Weather Service Glossary of Abbreviations