Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Huntsville Alabama
920 PM CDT sun Jul 27 2014
adjusted probability of precipitation to account for upstream thunderstorms. Small
adjustments to dew points and overnight temperatures.
thunderstorms have developed just along/ahead of a
cold front moving southward through the Ohio/Tennessee Valley region. The latest
surface analysis indicates the front is nearing the Kentucky/Tennessee border. Surface
convergence in associated/west the front and instability/lift provided by a
digging middle-level short wave will likely maintain shower/storm
production through the evening hours. Although surface solar heating has now ceased, continued boundary layer Theta-E advection from the west-SW will likewise continue to feed instability into the area and allow for storm development. The latest hrrr/rap models suggest this is a reasonable scenario and probability of precipitation were increased for parts of the area. There is a potential limit of development to the SW...and probability of precipitation were lowered just a little for far southwestern portions of the area.
Fairly steep middle-level lapse rates in conjunction with a very moist
boundary layer indicate parcels will have quite a bit of bouyancy
once aloft...with ml convective available potential energy ~2-3 kj/kg and MUCAPES ~3-4 kj/kg. Shear
will be strongest in the northeast...closer to a middle-level jet
maximum...and may be supportive of a stronger storm or two in southern
Tennessee and northestern Alabama. Damage wind gusts would be the most likely threat,
although small hail and very frequent lightning would accompany those storms. Due to a sifniciant middle-level cap ~750 mb, storms are likely to be confinued to a fairly narrow corridor just along/ahead of the front. The latest timing estimate places storms in our Tennessee counties around midnight-1 am, in Huntsville/Shoals/Scottsboro around 1-2 am and Cullman/Albertville by about 3-4 am CDT.
Updates out momemtarily.
/issued 700 PM CDT sun Jul 27 2014/
for 00z tafs...VFR conds likely to continue through ~05-06z at
khsv/kmsl until a broken line of rain showers/thunderstorms and rain arrive in the area. Coverage
of rain showers is expected to be scattered with the extent of thunderstorms and rain perhaps only
isolated. Thus...kept VFR prevailing conds at taf sites for now. If a
strong cell impacts a taf site however...expect IFR/MVFR visible in heavy
rain cores. Thunderstorms and rain will be more likely in northestern Alabama...and was included
in khsv taf. SW winds ~10-15kt will continue at khsv/kmsl until
~05-06z...with wind shift in associated/west cold front ~07-08z.
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