Area Forecast Discussion
Issued by NWS Huntsville, AL

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS64 KHUN 221459

Area Forecast Discussion
National Weather Service Huntsville AL
959 AM CDT Thu Jun 22 2017

.NEAR TERM...(Rest of Today)
Issued at 959 AM CDT Thu Jun 22 2017

Bit of a gradient across the area in terms of rainfall totals. But
that is to be expected when dealing with rainbands associated with
tropical systems. MRMS precip totals show an axis of 1-1.5 inches
pretty much along the I-65 corridor with values dropping off to the
east and west. NE and NW AL seem to have missed out on the rain so
far with only about 0.25-0.5 inches.

The first band/swath of precip is beginning to slowly push off to the
E/NE, but a more narrow rain band is moving north along the MS/AL
border. Models are still a bit up in the air where they want to take
this secondary band but believe that the almost N/S orientation of
the band may hold through the noon hour. Then it might start to
become orientated in a SW/NE fashion as now TD Cindy begins to turn
to the N/NE. If this band does end up sitting over portions of the
area for an extended period of time, flash flooding mainly in urban
areas might be possible. So, something we will need to watch closely.

In terms of thunderstorm and any severe potential today, warmer
temps and the greatest instability is forecast to remain over the
southern half of AL. We may see some limited instability (<200 J/kg)
but the constant rainfall, cloudy skies, and weak lapse rates will
be a limiting factor for thunderstorm development. However, shear and
especially low level wind shear is very favorable for rotation, we
just need a few deeper/stronger updrafts to be able to realize the
potential. If we do see instability increasing this afternoon above
100-200 J/kg, the threat for a few weak tornadoes will increase. But
again, as mentioned above, think that severe threat remains to our
south today. However, should be more of a concern during the day

.SHORT TERM...(Tonight through Saturday)
Issued at 445 AM CDT Thu Jun 22 2017

T.D. Cindy is then xpcted to turn more toward the ne later tonight
across the Lower MS Valley and into the Mid South region by Fri.
Latest model suites seem to be hinting at a little bit of a lull/or
at least a weakening trend in some of the shower/tstm activity going
into the evening hrs. The moisture fetch extending into the n cntrl
Gulf is broken up some by the tropical system moving towards NW MS/W
TN, while the progression of upper waves become more concentrated
around the inland sfc low. The shear axis actually becomes more
aligned in a ne/sw orientation, as a longwave upper trough pattern
dropping out of the Plains states moves into the Midwest/OH Valley
regions during the day Fri.

The remnants of T.D. Cindy will likely become merged with this upper
trough axis, as it continues to dive towards the se Fri evening.
With the influx of moisture converging along an approaching cold
front associated with the upper trough pattern, coupled with ample
forcing/lift provided by the front/trough axis, periods of num/wide
showers/tstms should again spread into the area from the s/w Fri/Fri
night. With the remnant sfc wave along the cold front moving ewd
across the mid TN area late Fri afternoon into Fri evening, there
remains the prob for some storms to become strong/svr in nature, as a
brief window develops where low level curvature/shear become better
maximized. Brief damaging wind gusts coupled with a few weak
tornadoes remain the two primary threats with any severe storms.
Total rainfall amounts thru Sat look to be around 2-2.5 inches with
locally higher amounts, although these numbers may change pending the
actual track of T.S. Cindy. Any Flash Flood Watch during this time
frame would again need to be evaluated later today pending any change
in the xpcted total rainfall values/developing wx pattern across the
SE states.

.LONG TERM...(Saturday night through Wednesday)
Issued at 445 AM CDT Thu Jun 22 2017

The remnants of Tropical Storm Cindy by Saturday evening should be
shearing apart across the northern Mid Atlantic and New England
region. A cold front at this time should be moving south of the
Tennessee Valley. Even though the front for the most part will be
south of the area Sat evening, decided to keep a slight chance of
thunder in for the night time. The models do keep a little post
frontal moisture across the region, especially the ECMWF in
comparison to the drier NAM.

Afterward, expect an "abnormally cool" spell in late June for the
first half of next week. Surface high pressure building to the
southeast from Canadian Rockies, will bring a respite from the usual
summer heat, and an opportunity to dry out from recent bout of
tropical rains. The surface high will coincide with rather deep
troughing for early summer across the eastern CONUS. Far as
temperatures go, highs into the middle of next week should remain
below seasonable norms. High temperatures in the lower 80s next
Mon/Tue should warm into the mid 80s by Wednesday. Normal high
temperatures on June 28th are around 90. Night time lows early next
week, especially Mon/Tue nights will cool to around 60 in the central
Tennessee Valley. Record lows are a bit cooler, in the low/mid 50s
these mornings.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 703 AM CDT Thu Jun 22 2017

Large swath of light/mod shra are now spreading nwd across much of
the TN Valley area, with lower cigs/vis now beginning to impact the
two main terminals. Prevailing MVFR conds or vis around 4-5SM/cigs
near 2-3K ft look to be the trend for the majority of the TAF period,
with a strong southerly flow extending well into the n cntrl Gulf.
Conds/vis may tempo lower to IFR this morning, and again late this
afternoon in/near heavier shra/tsra. Sfc winds are xpcted to turn
toward the se near 15-17KT later this morning, and prevail thru the
afternoon hrs, before weakening a few kts this evening.




NEAR TERM...Stumpf

For more information please visit our website
at is the U.S. government's official web portal to all federal, state and local government web resources and services.