Area Forecast Discussion
Issued by NWS New Orleans/Baton Rouge, LA
FXUS64 KLIX 051002
Area Forecast Discussion
National Weather Service New Orleans LA
402 AM CST Mon Dec 5 2016
Latest surface analysis revealed a 1007 millibar low just east of
Brownsville with a warm front extending to the mouth of the
Mississippi river to Florida Panhandle. Surface winds were
generally light northeast over land forecast area and east flow
over Louisiana coast and coastal waters near the boundary. Upper
air analysis and infrared satellite imagery showed a cyclonic
circulation just south of Texas Big Bend and southwest flow over
east Texas to Mississippi. Precipitable water values on a planer
view showed the moisture axis values around 1.8 inches from the
surface low to Louisiana coast to Florida Panhandle.
Surface low to our southwest will track northeast to southwest
Louisiana coastal waters by this afternoon. With the low taking
some time before reaching 30N, the warm front will remain nearly
stationary. Rainfall could be heavy at times with amounts
approaching 1 to 3 inches south and southwest of Lake
Pontchartrain today, other areas receiving generally around an
inch with isolated higher amounts.
Low level southeast flow near and north of the warm front will
increase 0-3km helicity values around 300m/s this afternoon.
Surface base convection along and south of the front may become severe
with one or two rotating storms northeast and south to southwest
of Lake Pontchartrain and Mississippi coast. Damaging winds will
accompany the isolated severe thunderstorms in the same area.
As the low moves northeast this afternoon and evening, the warm
front will lift north placing the forecast area in the warm
sector. GFS and Euro show the cyclonic circulation opening and
lifting east then northeast across east Texas this afternoon,
north Louisiana this evening and Mississippi early Tuesday
morning. The deepest moisture and best instability will reside
across the east half of the forecast area. SPC continue to include
a 15% severe weather risk area for this afternoon and this
evening. This risk area currently encompasses Lake Pontchartrain,
northeast and south to southwest of Lake Pontchartrain,
Mississippi coast and coastal waters.
The surface low will continue to track northeast over northern
Alabama early Tuesday morning dragging the cold front across the
area. We should see a lull in the rain chances Tuesday through
Wednesday evening before a reinforcing front brings another shot
of rain across the area Wednesday night through Thursday. With
little instability in place, we should only see rain showers
ahead and along the front and have maintained chance POPs. Behind
this second front, we will likely be in for the coldest air mass
of the season with temperatures well below normal Friday morning
through Saturday afternoon.
Most shower activity has waned for the moment but that will change
before long. In the meantime, light to moderate fog along with low
ceilings will result in IFR to VLIFR conditions. Showers and
thunderstorms will begin moving in across area from west to east
beginning not too long after sunrise. All terminals should be
impacted by around 18Z. Periods of moderate to heavy rainfall will
be possible along with gusty winds. Convection will be shifting
eastward this evening but not looking like ceilings will improve
before the end of the period.
A developing surface located over the far western Gulf of Mexico
will move northeastward towards SW Louisiana and central
Mississippi. Easterly flow around 15 to 20 knots should be
maintained through around 18Z as the low moves across the
northwestern Gulf. They will begin to shift to a southerly direction
as the low moves inland. Will headline most offshore coastal zones
during that period for the 15 to 20 knot winds. A frontal boundary
appendant to the low will swing through the coastal waters this
evening and overnight. Winds will abruptly shift to the west and
increase into the 20 to 25 kn GFS
and Euro show the cyclonic circulation lift east then northeast
across east Texas this afternoon, north Louisiana this evening
and Mississippi early Tuesday morning.ot range. Thus have issued a small
craft advisory for tonight over all coastal waters. At this time, it
appears that strong winds will be a relatively short period as the
pressure gradient weakens quickly. Therefore, have the SCA expiring
by mid morning Tuesday. Expect this lighter wind field to remain in
place through Wednesday before a very strong cold front marches
through Thursday morning. A few gusts to gale force will be possible
with this frontal boundary. Small craft conditions could last
through Friday before beginning to relax Friday night high pressure
center moves closer in to the region.
DSS code: Blue.
Activities: Monitoring convective and heavy rainfall trends through
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 64 52 61 44 / 100 70 10 0
BTR 67 52 64 46 / 100 60 10 0
ASD 68 54 65 47 / 90 70 10 10
MSY 70 58 65 53 / 90 70 10 10
GPT 68 57 66 49 / 90 70 10 0
PQL 68 58 66 49 / 80 70 10 0