Area Forecast Discussion
Issued by NWS Birmingham, AL

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FXUS64 KBMX 192022

Area Forecast Discussion
National Weather Service Birmingham AL
222 PM CST Mon Feb 19 2018

Midday Update and 18Z Aviation.


Tonight and Tuesday.

At this writing, most locations have at least tied their record
high temperatures and we still have a few hours of heating left.
Therefore, a pretty good chance of a record sweep today. Low level
thicknesses and 850mb temperatures both increase on Tuesday. We
will start off Tuesday with some cloud cover, and expect some
patchy areas of cloudiness to hang around much of the day.
Southerly winds and high pressure anchored east of us will keep
those temperatures quite warm. The local scheme would indicate a
3-4 degree increase tomorrow, but held it around 2 degrees due to
some clouds. At any rate, another near record afternoon. Overnight
night lows will be around the 60 degree mark area wide, the normal
high temperature for mid February. The models have a small area of
lift moving south to north over Central Alabama Tuesday afternoon
and evening. Deep layer moisture is limited, but will leave a 20
pop daytime, and 20-30 pop Tuesday night.

The trend in the extended appears that it is ongoing. The NAM and
ECMWF are close with the GFS most aggressive on frontal position
and higher rain chances Wed-Thu. This is due to the handling of
our anomalous ridge east southeast blocking any front from
zipping through. We have been trending slightly lower for pops and
will hold these values steady at this time.


Previous short-term discussion:Today and Tonight.

We`re likely to see a couple of the warmest days of the week on
Tuesday and Wednesday for most of Central AL. An anomalous high
pressure is just off the coast in the Atlantic and a deep trough is
stretched through the Western US. With the high pressure to our
east, expect deep southerly flow to bring in warm/moist air off the
Gulf of Mexico. NAEFs percentiles continue to show values at max
climatology for this time of year in geopotential height,
temperature, specific humidity, and PWATs. These are running 2-3
standard deviations above the mean, so have edged our high
temperature forecast up a little to account for this. I have
included the record highs for our climate sites below this
discussion because many sites may reach or exceed record highs.


Wednesday through Monday.

Meanwhile, a surface low develops and moves northeastward into
the Great Lakes region on Tuesday and stretches a cold front
through the Midwest and into the Ozarks. This front will slowly
push southeastward towards Central AL Tuesday night through
Wednesday. The GFS has come into much better agreement with the EC
and Canadian with this front as it slows and stalls in North
MS/Western TN. The anomalous ridge to our east essentially blocks
the frontal passage and the warm air advection across the Gulf
States lifts the front northward as an effective warm front on
Thursday. Because of the better model agreement, I`ve got more
confidence in decreasing PoPs Wednesday and Thursday overall, but
keeping some chances north of the I-20 corridor on Thursday as
some isentropic lift in the warm sector may lead to rain showers
on this side of the front. Areas in the far northwest will likely
see the best chances for rain and thunderstorms on Thursday
afternoon due to proximity of the front. It`s worth noting that
areas along and south of the I-85 corridor may not see any effects
from the front, so could remain unseasonably warm all week long.

By Thursday night into Friday, expect the front to be lifted north
of the area, leaving only lower chance to slight chance PoPs across
the northern half of Central AL. As we go into the weekend, models
are in surprisingly good agreement with the next frontal system`s
initial timing. Expect the previously stalled cold front to push
into Central AL late Saturday night into Sunday morning, so rain
chances increase north of I-20 Saturday then across much of the
Central portions of the State on Sunday. How this front behaves
after Sunday is still in question as the GFS weakens the anomalous
ridge and pushes the front through, leading to a dry start to next
week. However, the ECMWF maintains the ridge and stalls that front
over Central AL, leading to continued rain chances on Monday. NAEFs
still highlights the anomalous ridge through Sunday, albeit not as
strong as earlier in the forecast period. Therefore, my thoughts are
that the ridge will hold and at least slow the front down, so have
kept at least chance PoPs in the forecast Sunday night and Monday.



18Z TAF Discussion.

Fog has cleared and clouds have lifted to VFR. Expect sct/bkn VFR
this afternoon with breezy southerly winds near 10-20kts. Sct-bkn
clouds remain for the overnight period, but not a continuous layer
across the area. As we approach sunrise, trapped low level
moisture will lift and develop an MVFR ceiling which should also
lift to VFR by afternoon. Rain changes the next 24 hours appear
too low for any mention.




Widespread rain is not expected for the next couple of days, but
unusually high humidity values are anticipated. With the higher
RHs and good overnight recovery, do not expect there to be any
fire weather concerns.


Gadsden     59  80  61  79  60 /  10  20  40  40  50
Anniston    61  81  62  80  61 /  10  20  40  40  40
Birmingham  61  82  65  81  63 /  10  20  30  40  50
Tuscaloosa  60  82  65  82  63 /  10  20  30  40  50
Calera      61  81  65  81  63 /  10  20  30  40  40
Auburn      61  79  65  79  63 /  10  20  40  30  20
Montgomery  60  83  64  82  63 /  10  20  30  30  20
Troy        60  82  63  81  61 /  10  20  30  30  10




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