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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 88 °
• Low: 73 °
• Thunderstorm

• Tuesday
• 
• High: 88 °
• Low: 72 °
• Thunderstorm

• Wednesday
• 
• High: 86 °
• Low: 68 °
• Chance of T-Storms

• Thursday
• 
• High: 86 °
• Low: 72 °
• Chance of T-Storms

• Friday
• 
• High: 90 °
• Low: 70 °
• Chance of T-Storms

Area forecast discussion 
National Weather Service New Orleans la 
910 am CDT Monday may 20 2013 


Update... 


Sounding discussion... 


No problems with the flight this morning. A very Summer-like 
morning with plenty of instability and moisture near the surface 
with a precipitable water of 1.37 inches and an Li of -8.2. A significant cap above 
850 mb...expected to keep afternoon and evening convection to a 
minimum. A moderate southerly flow in the lower to middle levels 
with a light to moderate west northwesterly flow aloft. 


&& 


Previous discussion... /issued 510 am CDT Monday may 20 2013/ 


Short term... 


Low to middle level high pressure to the east of the forecast area 
will be gradually weakening...but will continue to influence the 
weather pattern across the forecast area through Tuesday as a 
shortwave trough moves out of the southern rockies into the 
Southern Plains. Isolated /10 to 15 percent coverage/ afternoon 
showers and thunderstorms will be possible across portions of east 
central and southeast Louisiana today due to a combination of 
slightly higher temperatures than yesterday and the expected 
weakening of the strong capping inversion between 800 and 700 mb. 
This cap was maintained yesterday due to middle level subsidence in 
the wake of a potent shortwave trough that moved through...but 
that should not be a source of middle level warming today as 
persistent southerly winds are expected from the surface up to 
about 600 mb. In addition...the upper level winds will start to 
become diffluent today and especially on Tuesday between 
anticyclonic flow over the Gulf of Mexico and cyclonic flow near 
the approaching shortwave trough over the plains. Isolated 
afternoon showers and thunderstorms are again expected on Tuesday 
inland from the coast. 


Have gone slightly above the mav MOS pop guidance and blended in 
some of the European model (ecmwf) quantitative precipitation forecast which has consistently been showing some 
light precipitation. The MOS guidance has also continued to 
struggle with keeping dewpoints and the low temperatures high 
enough...so have made upward adjustments for tonight and Tuesday 
night. 


On Tuesday night and Wednesday...the shortwave trough is expected 
to gradually weaken as it moves east across the lower Mississippi 
Valley...and there is no frontal boundary to focus convection. 
However...precipitable water is expected to increase to 1.6 to 
1.9 inches across the forecast area as upper level divergence 
increases due to the right entrance region of the upper jet core 
on east side of the shortwave trough. Have trended the pop back up 
across much of the forecast area and the rain chance may have to 
be raised a bit more later if the GFS and NAM trend towards the 
wetter European model (ecmwf). Convection may focus on thunderstorm outflow 
boundaries which may result in some more organized storms capable 
of producing both strong gusty winds and hail. The Storm 
Prediction Center has the forecast area in a /see text/ or 5 
percent probability of severe thunderstorms on Wednesday...and 
this looks reasonable given the weather pattern. Will mention a 
few strong to severe storms in the hazardous weather outlook. 


Long term... 


The slower moving northern portion of the upper trough with a middle 
level low across the northern plains on Tuesday is expected to 
eventually move southeast across the lower Ohio Valley on Thursday 
and the middle Atlantic and southern Appalachians region Thursday 
night and Friday. There may be some minor effects of the northwest 
flow associated with this system that will extend down to the 
central Gulf Coast...however...low to middle level high pressure 
will be gradually be building back into the forecast area Thursday 
into Friday. There should be enough residual moisture and 
instability for isolated diurnal showers and thunderstorms into 
Friday...then it looks like there will be very little or no rain 
over the Holiday weekend as high pressure builds with the 
exception being on Memorial Day when the ridge may weaken 
slightly...but the rain chance will likely be 20 percent or less. 
22/dew point 


Aviation... 


Little change in the pattern over the last several days...and not 
much change anticipated until about Wednesday. 


As has been the case the last several nights...moisture trapped 
below the nocturnal inversion has allowed low stratus to develop 
across the area. Currently ceilings are a little more prevalent at 
terminals along and north of Interstate 12...at kasd...khdc...kbtr 
and kmcb...with scattered stratus elsewhere. Expect conditions to 
become widespread by 10z with ceilings generally in the fl005-fl015 
range. Any IFR ceilings should improve to MVFR by about 14z...and to 
fl025-fl030 by midday. Not expecting any significant convection. A 
repeat of this mornings conditions and timing is anticipated in the 
following overnight period. 35 


Marine... 


High pressure centered in the western Atlantic extends into the Gulf 
of Mexico. It will remain in place over the coastal waters in that 
fashion through Tuesday night which will keep winds southeasterly at 
10 to 15 knots...possibly a touch above 15 knots briefly in the far 
western waters. Seas through that period to be mainly in the 2 to 3 
foot range...with the exception of the western waters...where some 4 
footers are possible tonight and Tuesday with persistent winds near 
15 knots. 


Upper level trough will dig across the eastern half beginning middle 
week. This will break down ridge over the Gulf Coast and cause the 
wind field to breakdown. A weak frontal boundary will pass through 
at the end of this week. Only expecting a wind shift at this 
point...with offshore flow to begin Friday...and last through much 
of the weekend. 35 


Decision support... 


Dss code...blue. 
Deployed...none. 
Activation...none. 
Activities...slurry support. 
Monitoring river flooding. 


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 to high risk severe 
and/or direct tropical threats; events of National 
significance 


&& 


Preliminary point temps/pops... 
mcb 88 71 88 68 / 10 10 10 20 
btr 89 73 89 72 / 10 10 10 20 
asd 87 73 87 70 / 10 0 10 10 
msy 88 74 87 73 / 10 10 10 10 
gpt 84 73 83 72 / 10 0 10 10 
pql 86 68 86 68 / 0 0 0 10 


&& 


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


$$