Area Forecast Discussion
Issued by NWS Huntsville, AL
FXUS64 KHUN 290744
Area Forecast Discussion
National Weather Service Huntsville AL
244 AM CDT MON AUG 29 2016
Water vapor imagery this morning has a few noteworthy features, the
stagnant high pressure to our north, low pressure off the TX/LA
coast and another low spinning just east of the GA/SC coast. In
between these features there is an axis of low/mid level convergence
that as of 07Z extends from around the Tallahassee region NWwrd
towards Memphis, TN. This boundary was one focus for the development
of convection yesterday and will likely be again today. However,
there is a region of subsidence between the high and the low off the
GA/SC coast that coupled with some dry air at the surface prevented
storms from firing yesterday.
For today, believe that we will see some influence from both the
convergence boundary and the drier air to the east. Models keep the
high to our north for the most part in place today but do bring some
of the subsidence and drier air westward towards NE AL. While I`m
not buying into some of the guidance dropping dewpoints into the
low/mid 60s out east, I think mid/upper 60s are more reasonable. This
would still leave some CAPE for the eastern areas around 500 J/kg.
Areas west of Huntsville will continue to see dewpoints in the lower
70s with CAPE this afternoon around 1500 J/kg. Forecast soundings
should be similar to what we saw out of the 00Z BMX/OHX soundings and
would suggest the potential for microbursts again today. However, the
upper level support will be lacking for any substantial development
like we saw yesterday. So, have kept only isolated showers and
thunderstorms in the forecast for this afternoon with convection
quickly tapering off by early evening.
The high starts to get suppressed to the SW on Tuesday. There is a
region of weak upper level energy that has been stuck along the
eastern periphery of the high and will be dragged SW with the high.
While this will provide very minimal lift, if any, models do keep
some surface convergence over the NW half of the area on Tuesday. An
isolated storm or two may form along this boundary on Tuesday but for
the most part expecting a dry day on Tuesday.
On Wednesday a trough digging south out of Canada into the Great
Lakes is forecast to send a pre-frontal trough towards the TN Valley.
Guidance continues to differ on the strength and timing of trough
but do expect the lift associated with the trough to be enough to
generate isolated thunderstorms. The best chances will likely be to
our north in TN but have kept low end PoPs in the forecast for much
of northern Alabama.
The actual front will drop south through the area Thursday afternoon
and evening. While the main upper level energy with the system
remains to our NE there will be enough lift along the front to spark
another round of isolated showers and thunderstorms Thursday
afternoon. The good news with the front is that it will send drier
and slightly cooler air into the TN Valley just in time for the
Labor Day weekend.
The forecast for the weekend up until this point has remained a bit
of a question mark as models have had a terrible time with the
handling of Tropical Depression Nine (Invest99L). But a large
percentage of the latest guidance has started to cluster around the
idea of the system entering the central Gulf of Mexico Tuesday into
Wednesday. Then the system takes a right turn towards northern FL and
moves west to east across northern FL. This path will keep any
rainfall associated with the system well to our S/SE. While there
might be subtle changes to the path, confidence is increasing that
any impacts associated with the system will remain south of the area.
Temperatures Monday through Wednesday will be on the warm side of
normal with highs in the mid 90s and heat index values around 100
degrees. The cooler and drier air arriving Thursday/Friday will send
temps back to normal/slightly below normal as we head into the
(Issued 1153 PM CDT SUN AUG 28 2016)
For 06Z TAFs: With high pressure in place at the sfc and aloft over
the OH Valley region, VFR conds are generally xpcted through the
period. Only exception may be some -br/MVFR vis during the early
morning hrs. Iso shra/tsra are also possible during the afternoon
period, but the prob is too low to warrant any mention in the TAFs at
.PRELIMINARY POINT TEMPS/POPS...
Huntsville 94 71 94 71 / 20 10 20 10
Shoals 94 71 94 71 / 20 10 20 10
Vinemont 92 70 92 71 / 20 10 10 10
Fayetteville 91 69 92 70 / 20 10 20 10
Albertville 91 70 92 71 / 20 10 10 10
Fort Payne 91 68 91 69 / 20 10 10 10
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