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 231447

Area Forecast Discussion
National Weather Service Huntsville AL
947 AM CDT Fri Jun 23 2017

.NEAR TERM...(Rest of Today)
Issued at 946 AM CDT Fri Jun 23 2017

It will be an active day weather wise across the TN Valley as the
remnants of TD Cindy begin to shift E/NE across northern TN. This
morning we were dealing with a weak convergence axis that spawned
some light to moderate showers out ahead of the main band of precip
that remains off to the west. We are starting to see some breaks in
the cloud cover and as a result temps are warming into the lower 80s
across the western half of the area. The threats for today will be
tornadoes and flooding.

The warmer temps and slightly steeper lapse rates compared to
yesterday should allow for instability to range from 300-700 J/kg. In
addition to this, the strong S/SW winds out ahead of the system has
resulted in a bulls-eye of 30-40kts of effective shear and helicity
values upwards of 400 m2/s2. These values are very favorable rotation
and any stronger storms that do form will be able to tap into these
values and a few tornadoes are certainly possible later this morning
into the early afternoon hours. There is a chance that a Tornado
Watch might be needed for our area later today but we will continue
to monitor the conditions and coordinate with SPC on that.

In terms of the threat for flooding, thankfully we had a break in the
rainfall overnight, which has allowed for some recovery runoff wise.
However, the storms moving into the area later will be in an
environment where PWATs are between 2.3-2.5 inches. These storms are
going to be able to produce very intense rainfall rates over a short
period of time and that combined with the now saturated ground could
result in some instances of flooding. The only thing that might help
to limit flooding is that storms will be moving very quickly and the
intense rainfall rates may not linger over an area for very long.
Plus, the heaviest rainfall is forecast to occur in NW AL, which
missed out on the bulk of the rainfall yesterday.

Tweaked the timing of the PoPs and modified the trends in temps a bit
but otherwise the forecast hasn`t changed much. Outside of the storms
it will be windy with gusts of 25 to 35 mph possible.

.SHORT TERM...(Tonight through Sunday)
Issued at 445 AM CDT Fri Jun 23 2017

As alluded to in the last paragraph, the threat for a few strong/svr
tstms will continue into the evening hrs, as the remnant low makes
its way across mid TN, before merging with a cold front out of the nw
and lifting into the OH Valley states. This cold front should move
sewd and eventually clr the local area during the day Sat. Num/wide
showers/embedded tstms well ahead of the front tonight will become
more sct in nature on Sat, as rainfall eventually diminishes across
the cntrl TN Valley from the nw during the afternoon hrs. Cloud cover
will then begin to gradually diminish with this onset of the evening
period Sat night, as a strong dome of high pressure out of the nrn
Plains begins to build sewd into much of the SE region. With the
passage of the front and drier air mixing into the area from the n,
afternoon highs Sat/Sun look to trend slightly below normal, with
highs mainly in the lower/mid 80s, while lows Sat night fall into the
lower 60s given the diminishing cloud cover.

.LONG TERM...(Sunday night through Thursday)
Issued at 445 AM CDT Fri Jun 23 2017

At the beginning of this period, surface high pressure sprawled
across the northern Great Plains will be building to the southeast.
This area of high pressure with origins from the Yukon and Northwest
Territories will bring a cooler than normal start - temperature wise
for the Tennessee Valley. A deeper than normal eastern CONUS trough
will also be in place, helping to bring the Canadian high pressure
towards the southeast. After night-time lows Sunday night into the
upper 50s to around 60, highs later that day will only warm into the
lower 80s. Average high/low temperatures for next Monday are 90/69.

Standing record low temperatures early next week were in the low/mid
50s, and will likely survive this upcoming cool period. This trend
will continue into the middle of the week, with highs by Wednesday
rising to the mid/upper 80s - closer to seasonable norms. Dry weather
will also continue through Wednesday.

During Wednesday and Thursday, the surface high should be positioned
east of the region. This will of course result in winds returning
from the south, helping to bring a warmer trend. Along with the heat,
moisture from the Gulf of Mexico will also return. This moisture and
resulting instability could lead to isolated shower/thunderstorm
development next Thursday. Highs then will be in the mid/upper 80s.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 712 AM CDT Fri Jun 23 2017

Restricted flying conds remain in place over most of the area this
Fri morning, as light/mod shra/tropical moisture continue to spread
newd into the region. MVFR cigs prevail at both main terminals and
little change in this general trend is xpcted for most of the TAF
period. Higher prob for shra/tsra were noted mainly in the 18-22Z
time frame with lingering shra/tsra continuing just past 01Z. MVFR
vis arnd 4SM coupled with cigs near 1K ft were then included in the
late portion of the TAF period, with some break in the precip xpcted
across parts of the region.




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.