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Area forecast discussion 
National Weather Service Birmingham Alabama
1150 PM CST sun Feb 7 2016

Update...
for 06z aviation.

&&

Discussion...

Cold front is currently pushing southeastward across Arkansas and
into far northwest Tennessee. Not much of a temperature difference right
along the front as it is more of a wind shift with a drop in
dewpoints also noted. Colder air is lagging behind it over
Missouri and Iowa. Not currently seeing any shower activity along
the front over Arkansas with cloud bases remaining high. The
precipitation that is along the front is in southeast Missouri and
Illinois and is moving more east than south. More rain and snow
showers are located further northwest over Missouri and Iowa
associated with the colder air aloft and lower cloud bases. Not
very confident in seeing any rain shower activity right along the
front before 12z with all models now keeping US dry through at
least sunrise. Have trimmed back the slight chance probability of precipitation across the
north but will maintain some small chances after 9z with some lift
associated with the main vorticity maximum and the front and at least some
moisture present. However think any precipitation through the
night tonight would be very light and not much more than a few
sprinkles. Low temperature forecast will be tricky tonight as
temperatures have dropped off quickly in a few locations
especially in the northeast. Have lowered lows by a couple degrees
in these locations but temperatures should overall begin to level
off or slightly rise as southwest winds begin to increase a bit
ahead of the front.

An initial look at the 00z model guidance for Monday does not
indicate any big changes to the forecast. Low-level relative humidity values will
increase by afternoon which should allow for rain and snow showers
to develop due to the very cold air aloft...though higher
resolution model guidance is slower with development. Additional
details will be discussed in the next forecast update.

32/Davis



&&

Aviation...
06z taf discussion.

Kept the same trend going as the previous forecast. VFR conditions
therefore remain predominant. Winds slowly swing around to the
southwest out ahead of a cold front. Not alot of time or moisture
to work with ahead of the front...therefore not many clouds. Will
see an increase in middle and upper level clouds as the front
approaches. This front reaches the northern terminals 12-14z. At
this point...will add ceilings 4-5k feet. The chanced of a shower
with the front is low and it will also track by
quickly...therefore no mention. Behind the front...winds will
become gusty in the 13 to 23kt range and last until just after
sunset. As the very cold air moves in aloft after 21z...expect a
few snow showers across the state. At this time...the timing and
terminals affected have too low a probability for mention.

75

&&

Fire weather...

No fire weather concerns are expected at this time. A strong upper
trough will dominate the weather across the eastern Continental U.S. Early
this week and bring much colder temperatures into central Alabama
through Wednesday. Rain chances return to portions of the area
beginning late tonight...with the system finally exiting Tuesday.
Best precipitation chances will be across the north. Rain may
become mixed with light snow by late Monday afternoon with light
snow possible Monday night and Tuesday morning.

&&

Previous discussion...
/issued 404 PM CST sun Feb 7 2016/

Vertically stacked storm system is rotating into the Great Lakes
region this afternoon...with a cold front stretching southwestward
from Lake Superior to St Louis to north central Texas. As the
upper low strengthens and drops into the Ohio River valley
tomorrow...the cold front will push through central Alabama
during the morning hours. Isolated light rain showers will be
possible...although quantitative precipitation forecast will be light. Winds will increase
tomorrow and be gusty due to a tightened pressure gradient. Wind
speeds are expected to remain below advisory criteria at this
time.

Behind the cold front...as cold air spreads southward..the airmass
column just off the surface cools quickly. So while temperatures
during the early afternoon across north central Alabama are in the
low to middle 40s...it will be below freezing as low as 1500ft above ground level.
Forecast profiles continue to show a moist column up to around
700mb/-19c...although there are differences depending on model of
choice. Lapse rates in the moist column are steep due to cold air
aloft...and convective showers will be possible...starting out as
rain and transitioning to a rain snow mix during the late
afternoon hours. Despite surface temperatures in the middle 30s...rain/snow
showers or snow showers will be possible. As the vertical column
falls below freezing entirely...a transition to all snow will
occur during the early evening hours...mostly likely after sunset.
Further to the south...moisture is lacking...although a few
sprinkles or flurries are possible.

Precipitation will likely come in bands...possibly training across
the same area at times. If precipitation rates are high
enough...snow could accumulate while surface temperatures are above
freezing on grassy or elevated surfaces. Forecasting the exact
location of these bands is nearly impossible at this point. Will
keep probability of precipitation in the slight chance to chance range since one location
could see precipitation while a few miles down the Road remains
dry all day. Generally...light and nonuniform accumulations could
be possible anywhere across the north...where better forcing and
moisture are expected closer to the upper low. Widespread snowfall
is not expected and some locations will likely not see any
precipitation fall. Light snow bands will be possible through the
overnight hours and Tuesday morning.

Surface temperatures will fall quickly Monday night...with overnight lows
in the middle 20s to lower 30s Tuesday morning. Strong cold advection
continues Tuesday and temperatures will struggle to get above
freezing across the far north and the middle 30s along the I-20
corridor. Strong winds continue...only diminishing to 8-10mph
overnight and increasing again after sunrise Tuesday. This will
bring wind chill values down into the upper teens and lower 20s
for most of the area around sunrise Tuesday morning.

Moisture pulls out of the area Tuesday evening...taking cloud
cover with it. Daytime highs will be slightly warmer
Wednesday...but overnight lows both Tuesday night and Wednesday
night will be in the 20s. Would not be surprised to see upper
teens across the far north early Thursday morning. Will need to
closely watch a system rotating through the back side of the
longwave trough Friday and Saturday. A great deal of uncertainty
exists as models have not been consistent. Depending on timing...there
could be a window of frozen precipitation on Friday. Too much
uncertainty regarding temperature and moisture though to include
anything other than light rain at this time.

14

&&

Preliminary point temps/pops...
Gadsden 30 47 27 35 23 / 20 30 30 20 10
Anniston 31 48 27 36 24 / 10 30 30 20 0
Birmingham 37 47 29 36 25 / 10 20 30 20 0
Tuscaloosa 36 48 30 39 26 / 10 20 20 10 0
Calera 37 48 28 38 26 / 10 20 20 10 0
Auburn 35 51 29 38 27 / 10 20 20 10 0
Montgomery 36 53 30 42 28 / 10 20 10 10 0
Troy 36 55 30 42 29 / 10 20 10 10 0

&&

Bmx watches/warnings/advisories...
none.

&&

$$

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