343 
FXUS64 KHUN 111518
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
918 AM CST Sun Feb 11 2018

.NEAR TERM...(Rest of Today)
Issued at 918 AM CST Sun Feb 11 2018

Observations and radar as of 900 AM show the cold front entering the
far NW corner of AL and extending S/SW into central MS. A batch of
scattered showers developed around sunrise and are moving through the
TN Valley currently. These appear to be connected to shortwave that
is lifting off to the NE into the eastern OH Valley. GOES-16
satellite imagery shows a subtle dry layer moving in aloft along the
cold frontal axis. However, this afternoon models are in agreement in
a low developing on the tail end of the front over LA/MS and moving 
NE into central AL. This is reflected to some degree in radar imagery
with the storms that are moving into southern MS. 

The issue for this afternoon is are we able to see any regeneration
of showers/storms along the front as it moves across the area.
GOES-16 mesosector over the area shows some patchy clearing in the
low stratus and could lead to temps warming into the mid to upper
60s. But, the low and eventual storms that move into central AL
should be sending high level clouds over the area. We may also have a
situation where the line of showers/storms that are to the south may
rob us/limit any potential instability, as well as could lead to some
downstream subsidence. Most recent RAP soundings hint at this
possibility with a weak inversion developing 

Now with all of that said, less than 200 J/kg of CAPE and 30-40kts of
shear could be just enough for an isolated thunderstorm to form along
the front. So, have kept thunder in the forecast for this
morning/afternoon. Main focus today will be rivers and flooding as
all the water starts to flow towards the TN River. Numerous Flood
Warnings are in effect for some of the tributaries to the TN River. 


.SHORT TERM...(Tonight through Wednesday)
Issued at 354 AM CST Sun Feb 11 2018

The front should be east of the region by sunset. Despite this, lots 
of post frontal clouds and light showers will continue. Additional 
rainfall amounts into Monday should range in the one to four tenths 
of an inch. 

Generally cloudy skies will continue Monday night into the mid week, 
as post frontal clouds remain. A Canadian based area of high 
pressure will build to the east, helping end any remaining light 
rain across the Tennessee Valley by Monday night. The coldest air 
associated with this high will move more eastward than to the south, 
thus temperatures here on Monday will cool down some, but not like 
they did in some instances last month. As the high shifts rapidly to 
the east, a return southerly flow will result in warmer temperatures 
on Tuesday, up into the lower to mid 60s. The southerly flow will 
also bring more moisture back to the area, and chances for showers 
for the midweek. Even with the showers, warmer than normal 
conditions are forecast with highs in mid 60s for the mid week. Not 
enough instability for thunder for Wednesday. 

.LONG TERM...(Tuesday night through Saturday)
Issued at 354 AM CST Sun Feb 11 2018

Showers look to be ongoing across portions of the cntrl TN Valley
heading into the latter half of the forecast period. Latest global
model runs are hinting at a series of weak upper disturbances out of
the wrn Gulf states traversing ewd across the region Wed night into
Thu. This looks to precede a cold front out of the OH Valley/Midwest
areas dropping swd into the region late Thu into Fri. Additional
showers are possible along/ahead of this approaching sfc boundary,
with ample moisture already in place. As sfc winds veer more to the
WSW ahead of the front, a weak upper ridge axis will remain fairly
stagnant over the Gulf region. This looks to result in unseasonably
warm conditions in place over the mid TN Valley, with afternoon highs
Thu perhaps climbing well into the upper 60s/near 70F for most areas.
This will follow unseasonably warm temps from early Thu as well, with
lows only falling into the upper 50s/around 60F.

The front does look to move swd thru the area by early Fri, thereby 
allowing some cooler air to filter into the area, as lows that 
morning fall more into the upper 40s/near 50F. High pressure will 
quickly move ewd across the region heading into the weekend period, 
while the flow pattern turns more towards the SW. This may at least 
keep some showers in the forecast on Sat, as highs both Fri/Sat trend
more seasonal in the mid 50s for most areas. The latter half of the 
global model runs are hinting at another/perhaps stronger cold front 
dropping out of the Plains states and into the region near the end of
the weekend period. This could bring additional rain chances and 
perhaps some cooler air as the weekend ends. 

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 540 AM CST Sun Feb 11 2018

A cold front will slowly transition from west to east across the
Tennessee Valley today. The passage of this front will help diminish
rain chances, as somewhat drier and cooler air filters in from the 
northwest. SW winds at the start of the TAF, should veer to the NW as
the front passes, reaching KMSL ~ 15Z and KHSV ~ 18Z. Despite 
passage of the boundary, generally MVFR CIGs (1500-2500 ft AGL) are 
expected, however reduction to IFR are possible with the passage of 
the front. NW winds in the 10-15kt range should continue for much of 
the night.


&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&

$$

NEAR TERM...Stumpf
SHORT TERM...RSB
LONG TERM...12
AVIATION...RSB


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