Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
FXUS64 KLIX 201003
AREA FORECAST DISCUSSION
National Weather Service New Orleans LA
403 AM CST Mon Feb 20 2017
Surface observations across the area show low level moisture has
been steadily increasing from south to north as a warm front lifts
north. Warm temperatures above the boundary layer have led to a
strong inversion and subsequent areal fog. Winds just above the
surface are right at the cusp of being too strong from dense fog.
This will result in intermittently dense fog conditions. Temperatures
will being to rapidly rise this morning after fog lifts and before
thicker cloud deck moves in from the west. Expect highs to top 80
degrees across much of the CWA, which is 10 to 15 degrees above
An elongated upper level trough that stretches from the northern
Rockies to West texas will be moving east towards the region today.
A few showers and isolated thunderstorms ahead of this system may
nudge into the western forecast zones before 00z. So have upped pops
to around 30% for those areas. Otherwise, just expecting increasing
clouds throughout the day.
The trough will slowly progress east across Texas tonight. A wide
swath of showers and embedded thunderstorms will move into the
forecast area. Model soundings show precip water values moving up to
over 1.5" tonight. Although that value may not seem very high for
the local area, it is near the daily maximum from a climatology
perspective. A completely saturated atmosphere through the night
suggest very efficient rain producing cells can be expected. Do have
some concern for flash flooding, but attm feel warnings will be
adequate to address those specific situations vs a flash flood
watch. In addition, event totals looking like a mainly up to 2
inches in general with isolated 3 to 4 inches.
Heavier convection will shift east Tuesday morning and into the
afternoon hours. The GFS is quicker than the ECMWF, but kept the
forecast closer to the slower ECMWF for now. Scattered showers
wrapping around the base of the upper low will be possible across
the area Tuesday night as the low passes overhead.
The rest of the week looks be fairly quiet as the upper low ejects
east and weak ridge passes through. Upper 70s to lower 80s for highs
along with near 60 degree lows can be expected during that period.
Models show a weak frontal boundary swinging through Friday night as
a quick moving trough races across the northern Mississippi Valley.
Although isolated showers could develop on the boundary, the
coverage appeared to be too low to have any mention in the forecast.
This front will knock down temperatures by 5 to 10 degrees and keep
the region rain free through most if not all of the weekend.
Low level ceilings and varying vis will remain through most of the
morning. Prevailing ceiling heights will be shown at BKN005 with
ceilings above that at OVC250. This will all lift and clear after
sunrise but decks will invade once again late this
afternoon/evening. A prevailing deck around OVC040 should move
through the region and affect each terminal from the west. A TEMPO
deck at BKN003 may show again tonight especially when the sh/ts
begin to move through BTR around 10pm and into GPT by about 5am. The
line of sh/ts will move slowly through the area and may stall for a
while Tuesday after this taf pack.
Patchy dense fog will affect the nearshore and protected water areas
this morning. The fog should not be widespread and will be very
transitory as winds bring the fog in and out. This will a little
different in the Mississippi River as wind will be able to pack fog
banks in the river turns with the levees holding the fog in place
Tightening pressure gradient between high pressure to the east and
lowering pressure to the west will cause a gradual increase in winds
to 15-20kt today after noon. This will prompt the issuance of a
small craft caution statement for this afternoon over all waters.
The caution statements will be extended through tonight as well but
there is a possibility of this being upgraded to an advisory by
tonight into Tuesday.
Numerous sh/ts will be associated with a broad, slow moving inverted
trough, with a possible embedded surface low, as it meanders
southeast to the central Gulf Tuesday into Wednesday. This will
cause a shift in wind to a northerly direction in western waters
Tuesday night with a more easterly wind elsewhere. A high pressure
ridge is expected to rebuild along the central Gulf coast Thursday
into Thursday night with a return of southeast winds in 10-15kt
range. Another cold front will move through the northern gulf Friday
DSS code: Blue.
Activities: Dense Fog Advisory late tonight through mid morning
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 81 61 71 52 / 10 80 80 40
BTR 81 63 71 55 / 30 80 80 40
ASD 79 66 71 55 / 10 70 80 40
MSY 78 64 71 58 / 20 70 80 40
GPT 73 67 69 58 / 10 60 80 40
PQL 78 65 71 58 / 10 50 80 40
LA...Dense Fog Advisory until 9 AM CST this morning for LAZ034>037-
MS...Dense Fog Advisory until 9 AM CST this morning for MSZ068>071-