Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 221951

Area Forecast Discussion
National Weather Service Huntsville AL
251 PM CDT Sun Apr 22 2018

.NEAR TERM...(Tonight)
Issued at 250 PM CDT Sun Apr 22 2018

The upper level low is located over northern AR based on latest WV
imagery and will be ever so slowly moving east towards the area
overnight. WV imagery also indicates very dry air streaming in on the
southern flank of this system, which corresponds with the upper level
jet. To the east winds remain out of S/SW and continue to advect deep
moisture into the region. A batch of moderate to heavy rain that has
been stagnant over central MS for much of the morning has quickly
moved east. These also appear to be aligned with what a MCV evident
in radar and a few surface obs. So, we could see some enhanced
rainfall rates on the northern side of this MCV, which is currently
tracking N/NE and should move across the TN Valley. At this time LAPS
and RAP soundings suggest very limited instability due to a moist
adiabatic profile but the lift associated with the MCV and gradually
increasing shear could allow for a few rumbles of thunder. But
believe that based on current environment any storms will be elevated
and might be able to produce a few stronger gusts. The real severe
weather threat will remain well to our south over southern AL where
the better instability is located. Rainfall totals through tonight
are upwards of 2-3 inches of rain and could cause minor flooding
especially in urban areas and along river and streams.

Based on the current movement of showers/storms and latest hires
guidance think the main line will be east of the area by 07-09z
tonight. Lapse rates steepen behind the line but as mentioned above
the drier air moving in aloft should really limit convection due to
dry air entrainment.

Models continue to show a strong LLJ (50-60kts) moving across the
eastern half of the area and have kept the Wind Advisory going. The
stronger winds should begin to subside by 06z as this LLJ moves off
to the N/NE. Temps tonight should remain in the 50s.

.SHORT TERM...(Monday through Tuesday)
Issued at 250 PM CDT Sun Apr 22 2018

As the upper low and vort max move over the area on Monday we can
expect a few isolated to scattered showers and storms to develop.
Models over the last 24 hours have shifted the low track a bit more
to the north and have adjusted PoPs in that direction. Could be a
situation where the further south you are on Monday the lower the
PoPs and higher your chances for a few peeks of sunshine. Temps will
end up a few degree warmer Monday compared to todays values with
highs in the mid to upper 60s.

The low begins to pull away from the area on Tuesday but some
lingering wrap around moisture could allow for a few light showers
and have continued lower end PoPs through Tuesday afternoon. Highs on
Tuesday end up close to Mondays values.

.LONG TERM...(Tuesday night through Saturday)
Issued at 250 PM CDT Sun Apr 22 2018

Weak CAA on the backside of the departing system could allow for a
shallow inversion to develop Tuesday night and with the recent rains
could support some fog potential. Don`t have anything in the forecast
at this time but something to keep an eye on. Tuesday night through
Wednesday afternoon will be one of the few dry periods in the
forecast. A weak trough is forecast to drop S/SE out of the northern
Plains towards the Gulf Coast. Models differ on just how far south
to dig this feature and could be the difference between only a few
light showers Wednesday night/Thursday to more scattered to
widespread rain on Thursday. Because of this uncertainty have kept
PoPs more broad brushed but tried to show some gradient north to
south in PoPs.

Beyond Thursday models begin to diverge on another trough that is
forecast to drop SE out of the northern Plains. The GFS has the core
of the trough over the OH Valley with the TN Valley remaining dry.
The GEM has the trough moving across the TN Valley bringing another
round of showers on Friday. The ECMWF on the other hand is between
these two solutions with only a few light showers. Ensembles are also
not very supportive to any of these solutions and have just slight
chance PoPs for Friday afternoon to account for these differences.
Winds remains out of the N/NW through the extend period and should
allow for a few cool mornings with the colder morning likely
occurring Saturday morning. Clearer skies over the weekend would
support temps in the 70s despite the weak CAA.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1223 PM CDT Sun Apr 22 2018

The earlier line of showers/storms has lifted to the north leaving
mainly light rain and MVFR cigs between 1,000-2,000ft. An upper level
system to our west will push east through the afternoon/evening and
bring a batch of moderate to heavy rain across the terminals. IFR
cigs/vis are possible with the heavier showers, otherwise expect MVFR
conditions. Winds increase out of the E/SE as the low nears the area
with gusts of 25-30kts possible from HSV east towards GA. The KMSL
terminal may see gusts up to 20-25kts. A cold front will lower rain
chances from west to east late tonight into early Monday morning.
However, scattered light rain could continue for much of Monday.

Have kept thunder out of the TAFs at this time as we haven`t seen any
lightning activity to our S/SW recently. Plus any storms that do form
will be embedded in the heavier rain and thus likely elevated.


AL...Wind Advisory until 1 AM CDT Monday for ALZ006>010-016.

TN...Wind Advisory until 1 AM CDT Monday for TNZ076-096-097.



NEAR TERM...Stumpf
LONG TERM...Stumpf

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