Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 240047 AAB

Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
747 PM CDT Fri Jun 23 2017

.NEAR TERM...(Tonight)
Issued at 730 PM CDT Fri Jun 23 2017

The Huntsville area is somewhat sandwiched between two convective
systems early this evening. One convective complex brought locally
heavy rainfall and some minor wind damage to the area this afternoon.
That complex has pushed off mainly into Georgia with some residual
light showers in its wake. Off to our northwest another complex of
storms was positioned from southwest Kentucky through west Tennessee
and into the northern MS Delta. Earlier this cluster brought fairly
extensive wind damage to portions of Arkansas.

The primary question in the short term will be whether this latter
complex of storms will hold together and impact the Tennessee Valley
region later this evening. Looking at surface observations there`s
still plenty of juice to work with as dewpoints have only "dropped"
into the lower to middle 70s. The boundary layer has stabilized
somewhat per the SPC mesoanalysis, especially across north central
and northeast Alabama where precipitation lingered a bit longer.
Having said that, MLCAPE values of 1 kj/kg were noted across
northwest Alabama.

Over the past hour or so the cloud tops have generally been cooling
across the southern flank (along the instability gradient) with the
eastern flank showing little intensification and perhaps some signs
of weakening. Having said that, the storm scale model guidance
indicates some regeneration betweeen 2z and 5z across NE MS/NW AL so
will adjust pops up a touch accordingly. Otherwise, not planning
too many changes to the current forecast.

Have already issued a summary local storm report from the afternoon
activity. Most reports were of the strong/marginally severe nature.
Looking at the observed gusts the maximum reported was 49 mph at an
aprs site in Madison with 45 mph also reported at KDCU.

.SHORT TERM...(Saturday through Saturday night)
Issued at 247 PM CDT Fri Jun 23 2017

The cold front is expected to be over the area Saturday morning and
a weak disturbance moving along the front out of the OK/TX area could
generate some showers and storms during the day Saturday. So, have
slowed down the removal of PoPs from the forecast at this time. But
could easily see a situation where the front pushes through and ends
up just south of the area that we remain dry tomorrow. The good news
with the front is that much drier air will be arriving Saturday and
Sunday. Dewpoints will drop into the mid 60s Saturday and then into
the upper 50s by Sunday. This will be a welcome change from the high
humidity values we have had over the past few days.

Temps remain in the low to mid 80s for highs on Saturday but
overnight lows Saturday into Sunday drop down to around 60 degrees.

.LONG TERM...(Sunday through Thursday)
Issued at 247 PM CDT Fri Jun 23 2017

A broad trough is forecast to encompass much of the Great Lakes and
Midwest on Sunday with a surface high building into the area. This
will keep temps on the cooler side for this time of year with values
only in the upper 70s and lower 80s. While the airmass over the area
is drier and a bit on the stable side, a vort max dropping out of
the northern US could spawn thunderstorms over the central US. Latest
model guidance is showing a bit more activity with this shortwave and
storms could approach the area late Monday into Tuesday. Nudged PoPs
up for the northern half of the area but due to the expected
dry/stable environment have kept PoPs below 15 percent at this time.
Will wait another run before adding PoPs back into the forecast for
Monday night into Tuesday.

The high pressure shifts off to the east of the area on Wednesday and
winds begin to switch back to the south. Gulf moisture will begin to
stream back into the area towards the latter half of the week. Temps
will be back in the mid to upper 80s by Thursday and with the
increased moisture we could see afternoon and evening thunderstorms.

Temps from Sunday through Tuesday remain below normal and with the
drier air (dewpoints <60 degrees) we could have a few cooler mornings
with lows for some portions of the area in the upper 50s.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 630 PM CDT Fri Jun 23 2017

OVC/BKN decks of low MVFR stratus will continue at both terminals
early this evening. Some breaks in the cloud cover look as if they
will occur at KMSL thanks to a pocket of drier air moving in.
However, this will be short-lived as a line of TSRA will track into
NW Alabama along a cold front between 03-05z, producing localized
gusty winds and IFR/MVFR conditions. This activity should weaken
significantly as it approaches KHSV, so have gone with a TEMPO -SHRA
there. Winds will gradually shift to the NW behind front, bringing
in some drier air and some clearing late in the period. However, low
clouds/light fog will produce prevailing MVFR to IFR ceilings and
visibilities late tonight into early Saturday morning.




LONG TERM...Stumpf

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