Scientific Forecaster Discussion
fxus64 klix 201307
Area forecast discussion
National Weather Service New Orleans la
807 am CDT Thu Jul 20 2017
Building high pressure aloft has modified the airmass since just
yesterday morning. Precipitable water is much lower at 1.64 inches, which is below
average. Drier air especially above 850 mb will allow for little
cloud cover today. 500 mb height is up to 595 dm, which is the Max
for today in the Storm Prediction Center climatology. Heights at the 850 and 700 mb
levels are also at the Max this morning. A subsidence inversion
has developed in the 700 to 650 mb layer. These factors should
allow for only isolated storms today if any, mainly over cities
or near the lake boundary.
Previous discussion... /issued 339 am CDT Thu Jul 20 2017/
expansive stacked high over the interior will remain for the next
few days causing heat levels to remain high especially over the
central portion of the nation. Around this feature, the infamous
"ring of fire" rotates in a clockwise fashion. Convective temps
will climb into the mid 90s today through Friday as precip water
values also fall to less than 2". This will help cause a
noticeable decrease in sh/ts coverage through Friday. But will
also cause an increase in temps and heat index values through
Friday. Oppressive heat is expected to affect the area but should
remain just under heat advisory criteria, although a few isolated
locations could actually reach 108 with no cloud cover.
Thunderstorms numbers will be at a minimun through at least
Friday. An upper low will retrograde from the South
Carolina/Georgia coast and begin to affect this area Friday night
into Saturday. By Sunday, rain chances fall back to normal levels
for this time of year.
Each day will present a potential for strong thunderstorms. The
greatest chance out of the next several days will be as the upper
low begin to swing through Saturday.
VFR conditons will be the rule for this 12z taf pack. Some early
morning br restricting vis to 4sm may be found over the usual
terminals such as hum and mcb, otherwise no issues with the
exception of high density altitude implications.
winds will be lighter and more variable through Friday with
landbreeze/seabreeze cycles dominating the wind flow pattern.
Offshore winds can be expected in the morning before switching to
an onshore component in the afternoon both today and Friday. This
weekend and early next, the pressure gradient will increase
slightly. Expect to see a prevailing onshore wind of around 10
knots develop and persist from Saturday through Monday. Seas of 1
to 2 feet can be expected through the period.
dss code: green.
Activities: monitoring convective trends
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 95 75 92 73 / 20 10 40 30
btr 95 76 94 75 / 20 10 40 20
asd 95 76 92 75 / 20 20 40 20
msy 94 77 92 76 / 20 20 40 20
gpt 94 77 92 77 / 20 20 40 20
pql 94 75 92 74 / 20 20 40 20