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Area Forecast Discussion (AFD)

Issued by Huntsville, AL (HUN)

FXUS64 KHUN 161723

Area Forecast Discussion
National Weather Service Huntsville AL
1123 AM CST Fri Nov 16 2018

For 18Z TAFS.


.NEAR TERM...(Rest of Today)
Issued at 944 AM CST Fri Nov 16 2018

High pressure at the surface moving across the Gulf Coast and a 
departing system to our NE has resulted in winds shifting back to 
the S/SW. This is starting to bring back some warmer temperatures
with current values already surpassing our values from yesterday!
Temperatures should warm into the low to mid 50s by this afternoon
with a few western locations possibly sneaking into the upper 50s. 
Other than the high clouds evident out the window and on satellite we
are not expecting anything of note weather wise over the next 24
hours. Made some minor tweaks to temps trends but the rest of the
forecast is in good shape. 

.SHORT TERM...(Tonight through Sunday night)
Issued at 508 AM CST Fri Nov 16 2018

Mid and high level flow will back further to the west-southwest and 
begin to increase overnight, downstream from a well-defined vort max 
progged to drop southeastward into the northern Rockies. This feature
is expected to shift steadily southeastward into the central Plains 
by 00Z Monday, becoming increasingly sheared as it enters a region of
confluent flow to the north of the subtropical jet. Periods of high 
clouds will be possible in this regime at any time, but should 
gradually become thicker and more widespread from Saturday night into
Sunday as very weak synoptic scale forcing for ascent begins to 
overspread the region from the west. Based on expectations that high 
cloud cover will briefly dissipate after Midnight tonight, we feel 
that conditions will be favorable for radiational cooling once again,
with an attendant threat for fog (and freezing fog across portions 
of the CWFA). Thicker high clouds should limit both temperature falls
and the threat for fog on Saturday night/Sunday morning, with lows 
expected to only reach the u30s-l40s. Highs on Saturday and Sunday 
will be pleasantly warm compared to the past few days, reaching the 
l-m 60s for most of the area.

By Sunday night/Monday morning, models suggest that the mid-level 
shear axis over the central Plains will be approaching our region 
from the northwest. Although lift associated with this disturbance 
will be quite weak, it may be sufficient for the development of a few
showers along or immediately in the wake of a weak cold progged to 
enter the region during this period. Due to the weak nature of the 
lift and evidence of dry air in the subcloud layer, we have only 
included a slight-low chance POP at this point. Due to an increase in
lower cloud cover late Sunday afternoon, min temps should only reach
u30s-l40s once again Monday morning.

.LONG TERM...(Monday through Thursday)
Issued at 508 AM CST Fri Nov 16 2018

Models have changed little concerning details of the forecast on 
Monday. It looks as though a weak pre-frontal boundary ahead of a 
very weak cold front will move east into northern Alabama and 
southern middle Tennessee on Monday. Forcing along this convergence 
feature ahead of the front remains weak in most models. A fairly 
moisture starved atmosphere is in place along and ahead of it. 
However, they continue to show just enough moisture for isolated 
shower development as this boundary continues to move into locations 
west of I-65 into southern middle Tennessee Monday morning. Most 
models continue to further dry out the airmass ahead of the front and
along this pre-frontal boundary as they push the boundaries further 
east during the afternoon hours, only allowing some virga to develop.
Thus kept less than 20 pop in the forecast during that period. 
Mostly cloudy conditions are expected to occur with these features 
Monday morning through the evening hours, before starting to clear 
out towards daybreak on Tuesday. The dissipating cloud cover and 
persistent winds around 5 mph should keep low temperatures from 
really bottoming out. It does look cool though with lows dropping 
into the upper 30s.

Despite more abundant sunshine on Tuesday, some cold air advection 
behind the front should keep the high temperatures in the lower to 
mid 50s. Winds remaining around 5 mph or a little higher should keep 
similar temperature trends in the forecast, despite clear skies 
overnight. Lows in the lower to mid 30s with highs in the mid 50s 
look reasonable on Wednesday.

With a more zonal to slightly southwesterly flow developing ahead of
some upper level energy moving across eastern Texas, it should be 
warmer late Wednesday night into Thursday (lows in the mid/upper 30s 
and highs in the upper 50s/around 60 degrees). This trend continues 
into the weekend, as weather conditions change little through Friday 
afternoon. Some isolated to scattered showers may push east into the 
area ahead the afore-mentioned upper level energy as it approaches 
the area.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1122 AM CST Fri Nov 16 2018

Southwesterly winds around 6kts will continue through 23z before
becoming light and variable overnight. SCT/BKN clouds around 25,000ft
will continue through the TAF period keeping conditions VFR. Some
guidance is trying to show fog developing between 08-13z but not
confident enough to keep this in the TAFs. If fog does occur some
patchy freezing fog could occur but very low confidence in this. 




NEAR TERM...Stumpf

For more information please visit our website 
at weather.gov/huntsville.