Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 250450
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
1050 PM CST Mon Feb 24 2020

.UPDATE...
For 06Z TAFS.

&&

.NEAR TERM...(Tonight)
Issued at 803 PM CST Mon Feb 24 2020

The 00Z 300 mb analysis shows a 130-140kt jet streak diverging over
the middle TN valley this evening. A narrow dry slot has poked
through northern MS into middle TN and KY, while the larger mass of
rain has shifted into south AL/GA/Carolinas. Showers have been more
scattered in between over north AL and southern middle TN this
evening. Low clouds and patchy drizzle are also occurring. At the
surface, low pressure over southeast MO was slightly occluded now,
with a warm front draped southeast through central AL into south GA.
A narrow warm sector has poked into southwest TN ahead of the cold
front that is now just east of the MS River. A few showers continue
along the cold front, but the OHX and BMX soundings show little to no
CAPE to work with. In fact, the BMX sounding showed a warm layer
between 8-7h which should negate thunderstorm potential further. The
HRRR suggests a continued reduction in coverage of showers as this
line progresses east overnight. Have removed thunderstorms from the
forecast, but maintained the showers albeit with decreasing PoPs
going east later tonight. All rain should exit most areas before
09-10Z with a few lingering showers in the far east just before
sunrise.

.SHORT TERM...(Tuesday through Wednesday)
Issued at 310 PM CST Mon Feb 24 2020

Rain will come to an end early Tuesday morning, but expect low clouds
to remain through the morning, before some breaks develop later in
the day. With deep SW flow quickly developing ahead of the next
upper-low developing across KS/OK, do not expect much in the way of
air mass modification. Expect temperatures to surge into the lower
60s by the afternoon -- the last time our highs will be above normal
for the next 6-7 days. As the aforementioned upper-low shifts into
the Ohio Valley, a stronger, arctic front will dive through the
Tennessee Valley Tuesday night into Wednesday. Deep layer moisture
will be a little more limited ahead of this system, so expect shower
activity to be more scattered in nature and QPF a bit lighter. Colder
and drier will filter in by Wednesday afternoon, cutting off
precipitation by late in the day.

.LONG TERM...(Wednesday night through Sunday)
Issued at 310 PM CST Mon Feb 24 2020

Good arctic air being advected into the area around the backside of
the strong surface low over the eastern Great Lakes region on
Thursday afternoon will keep temperatures in the upper 30s to lower
40s, despite sunshine. Some 925 mb temperature progs suggest highs
could be a bit lower only reaching the 30s across the area. Expect
cloud cover to move into the area Thursday evening. Models keep dry
air in place near the surface late Thursday night into Friday morning
in much of the boundary layer. Also, models keep the area on the far
on the edge of the forcing swinging east from Missouri into eastern
Kentucky/Tennessee. These factors have led me to leave any
precipitation out of the forecast with this system. If this forcing
does move further south than currently forecast, then some
precipitation (partially in the form of flurries or light snow) may
need to be added to the forecast late Thursday night into Friday
morning. However enough cloud cover should keep temperatures from
tanking, keeping them in the upper 20s to lower 30s overnight.

Think we will see a break in the cloud cover during the day on
Friday. This and a bit warmer start to the morning should help
temperatures climb a bit higher. Right now, highs around 40 degrees
in higher elevations and lower to mid 40s elsewhere look reasonable.

Models are trending more towards a second stronger shortwave moving
southeast from Missouri into central Tennessee and northern Alabama
Friday evening into Saturday morning. Though snowfall amounts and
accumulations vary from model to model at this time, it is looking
like we could see a period of light to moderate snowfall shortly
after midnight on Friday into early Saturday morning. Actual air
temperatures (and possibly ground temperatures) will help to keep
accumulations very light. The exception to this may be in the higher
elevations above 1000 feet. There, these factor may not limit
accumulation as much given a weak temperature lapse rate just above
the surface. For now, though only including a trace to one quarter of
an inch of snowfall accumulation by early Saturday morning. For now
only included a 20 to 30 percent chance of this precipitation.
However, this may need to be raised if current trends hold in future
guidance. A few models do suggest that between one half of a inch to
one inch is plausible in our higher elevations, but this is too
uncertain at this time to include. Late Thursday night through Friday
morning will need to be monitored closely for possible increases in
snowfall.

Forecast sounding and RH fields suggest a clearing late Saturday
morning. This should allow temperatures to rebound well above
freezing into the 40 to 50 degree range in most areas later in the
afternoon. Saturday looks to be one more cold night, with northwest
flow aloft continuing and lows reaching the mid to upper 20s.

The good news is that by Sunday, the pattern changes as the large
area of low pressure previously hung up over the northeastern CONUS
finally moves east and well away from the northeastern seaboard.
Zonal flow aloft quickly builds into the area behind it on Sunday.
Highs should rebound back into the lower to mid 50s. As a result much
warmer and more moist air will be advected back into the region, as
a front builds up it strength over the Midwestern CONUS. This could
bring rainfall back to the area early next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1050 PM CST Mon Feb 24 2020

A cold front will push the last line of showers east of KHSV by 09Z.
Behind the front, a west-southwest flow of 5-7kt is expected with a
period of VFR conditions developing with SCT-BKN layer at 040agl at
times. Ceilings in the 010-020agl layer will arrive again by around
15Z. At KHSV, these clouds may again exit the area leaving VFR
conditions by 22Z. However, another area of lower ceilings of
010-020agl (MVFR) will swing into the area and be more persistent in
northwest AL including KMSL through the end of the period.

&&

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

$$

NEAR TERM...17
SHORT TERM...AMP.24
LONG TERM...KTW
AVIATION...17


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