Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 231330 AAB
AFDHUN

Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
830 AM CDT Wed May 23 2018

.NEAR TERM...(Rest of Today)
Issued at 829 AM CDT Wed May 23 2018

Stratus remains hugged atop the Cumberland Plateau at this hour, with
patchy fog in portions of southern middle TN and northwest AL. Short
range HRRR guidance suggests afternoon convective development will
occur along a NW-SE convergence zone from northwest AL through
central and southeast AL. Have readjusted today`s PoP to remove it
this morning and to align the greater chances along the convergence
zone in our southwest forecast area. MLCAPE values could reach
1500-2000 j/kg given dew points around 70 degrees and forecast maxes
in the upper 80s. Slow moving thunderstorms could drop locally heavy
rainfall much like Tuesday along with brief gusty winds.

.SHORT TERM...(Tonight through Friday night)
Issued at 405 AM CDT Wed May 23 2018

Showers that form today should dissipate in the evening, mainly from
a loss of daytime heating and instability. More patchy late night fog
is possible, but did not put it in given uncertainties on how much
and where it will rain. Another mild night with lows in the mid 60s.
A rinse and repeat forecast for Thursday and Friday - with daytime
instability and available moisture will lead to more isolated to
scattered showers/t-storms. Precip water amounts per model soundings
should be in the 1.5 inch range on Thursday, but increase into the
1.7 inch range on Friday - with higher PoPs in the forecast. Highs
for the rest of the work week should rise into the mid/upper 80s;
trending a tad cooler on Friday given more clouds and higher rain
chances.

.LONG TERM...(Saturday through Tuesday)
Issued at 405 AM CDT Wed May 23 2018

If you were hoping to find a day without a chance of rain in the
extended, you won`t find it in this forecast package. The much talked
about upper-low moving up through the Gulf of Mexico will bring
soggy conditions through Memorial Day Weekend and into next week.

On Saturday, weak high pressure in the Atlantic will keep winds
southeasterly allowing moisture to stay in place. As the upper-level
low and sfc low lift through the Gulf of Mexico, there will be an
increase of tropical moisture streamed into the region. Forecast
soundings show PWATs increasing to 1.8" on Saturday and 2" on Sunday
which is reaching our climatological max. These values will also
carry into next week. Given the plentiful amount of moisture, heavy
rainfall will definitely be the highest threat throughout the
extended, however with the weak wind profiles, will not rule out the
potential for hydrological concerns.

The one caveat to this forecast is the model discrepancies. The GFS
continues to be the outlier, WPC agrees, thus was not favored in this
forecast. Models agree on the development of the upper-low and sfc
low moving through the Gulf this weekend. However, the disagreement
is with the track of the upper-level trough, the track and strength
of the sfc low. This will have an effect on the POPs and QPF. The
Canadian has a stronger sfc low that tracks more northerly bringing
more precip into the forecast area while the ECMWF is weaker with the
sfc low and tracks more to the west with the upper trough.
Regardless, it looks like scattered to numerous showers and
thunderstorms are expected through the extended. So if you have any
outdoor plans, stay tuned to the lastest forecast.

The increase in cloud cover and precip will at least give us a
little bit cooler temps. Highs will be in the low/mid 80s and lows
will stay in the mid/upper 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 625 AM CDT Wed May 23 2018

At the terminals, VFR weather should continue into the late evening.
A weak frontal boundary will approach the region from the north and
become stationary. This boundary could serve as a focus for isolated
to scattered showers and thunderstorms, mainly this afternoon. Given
that rain chances remain low, did not include VCSH or TS in the TAF.
Convective activity should dissipate in the evening with a loss of
daytime heating and a more stable atmosphere. Patchy late night fog
is possible, especially in/near areas that receive wetting rainfall.


&&

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

$$

NEAR TERM...17
SHORT TERM...RSB
LONG TERM...JMS
AVIATION...RSB


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



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