Scientific Forecaster Discussion
fxus64 khun 230052 aaa
Area forecast discussion...updated
National Weather Service Huntsville Alabama
752 PM CDT Thu Jun 22 2017
issued at 744 PM CDT Thu Jun 22 2017
The remnant low (artist formerly known as cindy) was located
near the arklatex with a rather tight surface gradient positioned to
the east across Mississippi and into Alabama. Temperatures were in
the lower 80s to middle 70s this evening but most notable was the
very high dewpoints in the middle 70s in most areas. The 00z
radiosonde from kbmx showed a precipitable water of close to 2.3
inches with near saturation up to 200 millibars.
Looking at the regional radar and infrared loops there has been some
decrease in the overall convective activity in the past couple of
hours. However, multiple convective bands were still noted from
central Georgia through southern Alabama and Mississippi back to the
aforementioned low center. The primary question for the overnight
period is the precipitation potential for the Tennessee Valley.
Given the loss of daytime heating, one would expect the
precipitation maxima to contract to near the low/remnant circulation
center. This is also projected by the most recent runs of the hrrr.
Based on current radar trends and consensus of the high resolution
model guidance will likely keep in chance/scattered type pops for
the overnight period. There is enough remaining instability to
support isolated convection so will maintain some thunder in the
forecast as well. Given the very moist atmosphere in place don't
expect temps to move much the rest of the night.
Looking briefly at tomorrow's weather, things look to be rather
active by midday to early afternoon. The low will be approaching from
the west. As such, the combination of increased low level shear and
sufficient instability along with very high pwats should set the
stage for isolated to scattered strong/severe thunderstorm
development. Model soundings would support rotating/discrete cells
for at least a period of time after initiation. More details to
follow on the midnight shift.
Short term...(friday through Saturday night)
issued at 326 PM CDT Thu Jun 22 2017
For Friday, dew point Cindy is expected to weaken to a Post-tropical
cyclone as it moves further inland. The current forecast track will
take it through western Tennessee Friday morning and then up across northern
Tennessee/southern Kentucky during the day. We can expect winds to be a bit higher
on Friday as we are closer to the center of the system and gusts up
to 30 mph are possible. Wouldn't be surprised to see a few isolated
reports of 35-40 mph in a few locations tomorrow.
With the storm to our north during the day we can expect partly
cloudy skies, which should allow for temps to warm into the mid 80s.
Those values combined with dewpoints remaining the low to mid 70s
should be more than enough for the development of strong to severe
storms on Friday. While the shear vectors and overall low level
helicity values won't be as strong as this afternoon, the potential
for more vigorous thunderstorm development should allow for an
increased threat for severe storms. Tornadoes, damaging wind gusts,
and flash flooding will be The Hazards with storms tomorrow. We
remain in a slight risk via Storm Prediction Center and that is warranted based on the
parameters expected tomorrow.
The only good news in terms of flooding threat is that the areas that
received the heaviest rain today are expected to see lower values on
Friday and the areas that haven't seen much will get the brunt of the
rainfall tomorrow. With quantitative precipitation forecast values forecast to remain below flash
flood guidance for much of the area have held off on issuing any type
of Flash Flood Watch for tomorrow as well. Will be mainly concerned
with any type of banding/training of storms tomorrow.
The remnants of Cindy will be pushed off to the east by a cold front
that is expected to drop into the area behind the departing system.
Models have delayed the arrival of the front a bit compared to
previous guidance and don't move it completely through the area until
Saturday afternoon/evening. So, adjusted pops a bit to leave them in
a bit longer on Saturday. Drier air in the lower levels will be quick
to rush in during the day Saturday and likely keep any activity
limited to showers. By Saturday night all precip will be south of the
area and much cooler air spreads in with overnight lows Saturday into
Sunday will be in the low to mid 60s. This will be a welcome change
from the high humidity values we have had the past past few days.
Long term...(sunday through wednesday)
issued at 326 PM CDT Thu Jun 22 2017
Dry conditions will persist through the long term period, as surface
high pressure slides southward into the region. Temperatures will be
on the "cool" side for late June, given a broad upper level trough
that will remain anchored over the eastern Continental U.S.. high temperatures
will generally remain in the lower 80s on Sunday through Tuesday,
with a gradual warming trend beginning Wednesday. Under good
radiational cooling conditions, overnight lows will cool into the
upper 50s each night.
Aviation...(for the 00z tafs through 00z Friday evening)
issued at 600 PM CDT Thu Jun 22 2017
Large expanse of rain/embedded convection associated with remnants of
Cindy continue to move off to the northeast early this evening. Thus
expect a general lull in the precipitation for most areas across
north Alabama through the overnight hours, though will maintain
vicinity shower wording for occasional light/scattered development at
both taf sites. Pressure gradient will remain rather tight due to
associated low pressure system and kept gusty winds in the forecast
through the period. Based on movement of the remnant low and a rather
unstable atmosphere expect an abundance of shower/thunderstorm
development during the midday/afternoon hours on Friday and trended
tafs as such. Otherwise, the very moist/tropical environment will
maintain fairly low ceilings and kept predominant MVFR ceilings in
through the period.