Scientific Forecaster Discussion
fxus64 klix 222041
Area forecast discussion
National Weather Service New Orleans la
341 PM CDT Thu Aug 22 2019
radar coverage thusfar has been consirably less than at this time
the past few days due to lack of focusing mechanisms outside of
the typical lake/sea breeze boundaries. Meanwhile, the satellite
imagery shows increasing bulk loading of tropical moisture in the
west-central Gulf of Mexico tapping into inter-tropical convergence zone south of the
Yucatan. This will be steadily advancing northward and bring
precipitable values upward into the 2.3-2.5 inch range Friday
from the current sub-2.0 inch levels. Thes conditions linger
through the weekend with convective temperatures expected to
lower into the mid 80s so marine layer advection will likely be
enough to spark nocturnal showers in and near the coastal
locations that will efficiently penetrate inland with early onset
Gulf Breeze convergence. What typically happens in these regimes
is a short period of thunderstorms with lengthy duration anvil
and high based lighter rain. Rain rates at peak should be close to
2 inches per hour for about 30-45 minute duration each of the
next 2-3 days. Accumulations should average 1-2 inches closer to
the Louisiana coast with spotty amounts near 4 inches Friday. The
marginal risk for excessive rainfall appears plausible, though
often if the heavy rain axis is established along or just off the
coast, this could hinder deeper moisture feed farther inland,
hence the marginal risk. Temperatures should be held to slightly
below normal during the daytime due to rain and extensive cloud
cover though a brief sprint to Max temps in the late morning hours
before convection gets going in earnest.
upper pattern transitions to some amplification of higher latitude
trough to place the region into a northwest flow regime for much
of next week. It appears some semblance of a front, or at least,
some Continental influenced airmass to bring some mid level drying
to bring a return to near normal rain chances and a trend to
slightly above normal temperatures as surface high pressure builds
from the west and northwest by middle of next week. This pattern
also portend favorability of mesoscale convective system activity rolling out of the
Central Plains into the lower Mississippi Valley. Combined with
compressional and sensible heating, could evolve into better pulse
severe threat later in the week. Meanwhile, in the Gulf, the
models are hinting at a tropical wave to traverse the central Gulf
heading into next week. This is both spatially and temporally
favorable teleconnection for some developments, but may be
hampered by what should be considerably westerly shear across the
north Gulf to limit extent of any feature's developments until
reaching the westernmost Gulf waters over the Labor Day weekend.
Plenty of time to watch model trends.
general VFR conditions at all terminals outside of limited
convection this evening. Overnight hours should remain essentially
VFR though marine layer advection may cause ceilings to bounce
MVFR-VFR around scattered-bkn025 at times generally between 08-13z,
particularly at khum, kgpt and possibly khdc and kasd.
no significant issues with prevailing light onshore winds and low
seas outside of convection, which should Blossom into better
coverage heading into Friday morning. The air mass will become
increasingly more conducive for tropical funnel and waterspout
formation in the near shore waters, near shore marshes and tidal
lakes/bays Friday morning through at least Sunday.
dss code: blue.
Activities: marginal risk excessive rainfall Friday/Saturday.
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; marginal risk severe or excessive rain.
Yellow = heightened impacts with short-fused watch, warning or
advisory issuances; radar support for slight risk severe
or excessive rain.
Orange = high impacts; enhanced risk severe; nearby tropical events;
hazmat or other large episodes.
Red = full engagement for moderate to high risk of severe and/or
excessive rainfall, or direct tropical threats; events of
Preliminary point temps/pops...
mcb 72 88 72 88 / 10 70 10 80
btr 75 87 74 89 / 20 90 30 80
asd 74 89 73 90 / 30 80 30 80
msy 77 88 77 89 / 40 90 50 80
gpt 75 87 75 88 / 50 70 40 70
pql 74 89 73 90 / 30 50 20 60