773
FXUS64 KHUN 052044
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
Issued by National Weather Service Morristown TN
344 PM CDT Thu Jun 5 2025

...New NEAR TERM...

.NEAR TERM...
(Rest of Today and Tonight)
Issued at 344 PM CDT Thu Jun 5 2025

There have been no significant changes to the near term forecast
since the previous update, with latest radar data suggesting that
a few showers/thunderstorms will continue to drift eastward into
the forecast area late this afternoon. The convection is
originating in the vicinity of a cold front positioned to our
northwest and will be moving into an increasingly less favorable
environment with eastward extent. Nevertheless, a few strong wind
gusts (up to 40-50 MPH) and lightning will possible until
dissipation occurs between 2-3Z. In the wake of any evening
precipitation, we expect dry conditions to persist through 12Z
Friday, although a few showers and thunderstorms may develop
across the Mid-South region late tonight as the low-level jet
strengthens downstream from a large MCS spreading southeastward
over the southern Plains. Lows will be in the u60s-l70s, with
development of patchy fog possible in a few locations by sunrise.

Previous Discussion:
Light WNW flow aloft of 15-25 knots will persist across the TN
Valley throughout the near term period, as the region will remain
along the northeastern flank of a subtropical high (centered over
the Lower Rio Grande Valley) and to the west of a weak 500-mb
trough along the southeastern Atlantic Coast. At the surface, a
lengthy cold front extends from central TX northeastward into the
western Mid-Atlantic states/New England, and this boundary will
serve as the closest focus for showers and thunderstorms to our
CWFA today, as convection related to the southeastern CONUS mid-
level wave and diffuse surface trough should remain displaced from
the region. Although the cold front is expected to move little
(if at all) over the course of the day, a couple of showers/storms
may impact the far northwestern corner of the forecast area very
late this afternoon or early this evening before largely
dissipating with the onset of the nocturnal cooling cycle. As
temperatures rise into the m-u 80s, dewpoints in the u60s-l70s
will support MLCAPE of 1500-2500 J/kg, which could yield a couple
of cells capable of producing gusty outflow winds (up to 40-50
MPH) in spite of weak tropospheric flow/shear profiles.

Overnight, the subtropical high to our southwest will begin to
strengthen, although mid-level flow across our region will
initially remain weak as the southeastern Atlantic Coast trough
drifts slowly eastward and offshore. In the absence of any
meaningful synoptic scale forcing for ascent, any lingering
afternoon convection will likely dissipate within an hour or so of
sunset, with development of patchy fog possible in our normally
fog-prone locations early Friday morning as temperatures descend
into the u60s-l70s beneath mostly clear skies.

&&

.SHORT TERM...
(Friday through Sunday)
Issued at 1152 AM CDT Thu Jun 5 2025

Latest short range model solutions still suggest that the
convective pattern across our region will become substantially
more active during the short term period, largely due gradual
strengthening of WNW flow aloft that will begin tomorrow as the
mid-level subtropical high (to our southwest) continues to
intensify while an amplifying northern stream trough digs across
Ontario. Embedded within this flow, an organized complex of
thunderstorms (originating from afternoon convection today both
across the higher terrain of CO and along the southern High Plains
dryline) will spread southeastward overnight, reaching
northeastern OK/northwestern AR/southwestern MO by 12Z Friday.
Although the core of the original MCS may tend to dissipate as it
spreads east-southeastward across the Ozarks during the day,
development of new convection along both outflow and differential
heating boundaries is expected to occur by late tomorrow morning
in the undisturbed downstream airmass across a broad region from
the Mid-South eastward across much of KY/TN and perhaps extending
into northern portions of MS/AL/GA. In the presence of
strengthening WNW flow aloft (to 30-35 knots), this activity may
have a tendency to organize into a southeastward-moving MCS during
the afternoon, but this system may miss our region to the
northeast, while another MCS (originating from additional storms
related to the remnant MCV) may miss our region to the southwest.
Even with uncertainties regarding storm coverage in our forecast
area, the increase in mid-level winds within an environment
featuring CAPE of 1500-2500 J/kg will support locally damaging
winds up to 50-60 MPH and hail up to 1" in diameter with the
stronger cells.

Present indications are that the cold front to our northwest
(initially oriented in a SW-to-NE fashion) will become more
zonally oriented on Friday night and begin to shift southward as a
surface high spreads from the northern Plains into the Great
Lakes (in the wake of the Ontario trough). Thus, after afternoon
convection dissipates early Friday evening, we will need to
monitor the progression of frontal convection that will spread
southward through the OH Valley and into northern TN during the
late evening, perhaps reaching our area by sunrise Saturday
morning. Meanwhile, in similar fashion to what will occur late
tonight, another MCS is predicted to evolve out of afternoon
convection across the southern Rockies/High Plains and spread
east- southeastward across northern OK and into the western Ozark
Plateau vicinity by 12Z Saturday. Due to processes similar to what
will occur tomorrow, renewed development of convection is once
again anticipated to occur in the downstream airmass (across the
TN Valley) by late Saturday morning, with higher confidence in a
greater coverage of storms (particularly during the afternoon) as
the synoptic cold front will likely be a bit closer to our region.
With mid-level WNW winds predicted to strengthen further (into
the 35-45 knot range) as more compact northern stream trough digs
across the Canadian Prairie provinces, the kinematic environment
will be more conducive for severe convection featuring a risk for
damaging winds/large hail (presuming that CAPE can climb into the
2000-2500 J/kg range). Although westerly flow in the low-levels
may increase into the 20-25 knot range, the risk for low-level
mesocyclone development appears very low.

By Saturday evening, a weak area of low pressure is likely to
develop across the OH Valley in conjunction with a mid-level
vorticity/speed maxima shifting eastward through the Mid-MS
Valley. Thunderstorms are expected to develop along the length of
the trailing cold front Saturday evening (extending southwestward
from the low into the Red River Valley) with several small MCSs
predicted to evolve out of this activity and track southeastward.
Thus, the spatial coverage of rain and thunderstorms will remain
very high across the region from Saturday evening through Sunday
morning, and although storm intensity may become limited by
extensive convective overturning, the risk for flash flooding will
increase considerably during this period given the potential for
multiple preceding rounds of heavy rainfall and PWAT values
perhaps exceeding the 1.6-1.8" range. Precipitation will gradually
end from NW-to-SE by late Sunday morning/early Sunday afternoon
as the cold front slips southeastward, with afternoon highs
reaching the u70s-m80s.

&&

.LONG TERM...
(Sunday night through Thursday)
Issued at 837 PM CDT Wed Jun 4 2025

Upper level troughing will plague the long term with wet and
potentially stormy conditions as the aforementioned front
continues to linger near the TN Valley. The uncertainty regarding
rain and storm chances on Sunday will continue into the long term
as our weather will entirely depend on the southeastward
progression of the front. Long range models currently suggest the
front will slowly sag south each day from Monday through Wednesday
placing at least a portion of our area under the gun for
additional rain and storms through mid week. Additional days of
rain and storms raises the alarm for flooding concerns. LREF
guidance indicates widespread 2-3 inches of rain from Friday
through midweek, with higher end values of 4-5 inches possible.
This will likely result in rises on rivers, creeks, and streams
along with the potential for urban street flooding and isolated
flash flooding. This threat through mid week will be dependent on
the location of the front. As for severe, LREF guidance indicates
decent CAPE each day of a few hundred J/KG. This paired with 20-40
KTS of bulk shear will be supportive of strong to severe storms
with the only question mark being the location of the front. If
the front moves SE of the CWA this will result in a lower chance
of strong to severe storms and heavy rainfall. If the front
remains NW of the CWA or bisects a portion of the CWA this will
favor strong to severe storms and heavy rainfall through mid week.
We will be monitoring model trends closely to refine the location
of the front each day and subsequently refine our forecast for
heavy rainfall and strong to severe storms.

&&

.AVIATION...
(18Z TAFS)
Issued at 140 PM CDT Thu Jun 5 2025

VFR will be the prevailing condition at the HSV/MSL terminals
this forecast period, and although a few SHRA/TSRA may move off of
a cold front to our northwest and sneak into the northwest corner
of AL very late this aftn/early this evening, chances for impacts
at MSL are too low to include in the forecast attm. Otherwise,
sct-bkn Cu (based in the 2.5-5 kft range) will begin to dissipate
shortly before sunset, and with mostly clear skies and light winds
overnight, patchy BR/FG may develop in a few locations early Fri
morning. Development of sct Cu is expected once again by 16Z, with
initial formation of afternoon convection possible during this
timeframe as well. However, with the greatest coverage of storms
expected to occur during the aftn (and beyond the end of this TAF
period), we will not mention PROB30 groups attm. Sfc winds will
remain from SSW-SSE, with sustained speeds of 5-10 kts.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.

&&

$$

NEAR TERM...70/DD
SHORT TERM...70/DD
LONG TERM...RAD
AVIATION...70/DD