National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS64 KHUN 201940
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
240 PM CDT Sat Apr 20 2024

...New NEAR TERM, SHORT TERM...

.NEAR TERM...
(Remainder of today and tonight)
Issued at 240 PM CDT Sat Apr 20 2024

There have been no significant changes to forecast reasoning for
the remainder of the afternoon (since the update earlier this
morning), as the combination of moderately strong NNE low-level
flow and abundant stratus clouds have held temps in l-m 60s.
Although only a few light showers are currently noted across
northwest AL, we still expect a broader area of rain and some
embedded thunderstorms (currently over the Arklamiss region) to
spread northeastward into the TN Valley, warranting an increase in
POPs from SW-to-NE between 21-00Z. Guidance from the 12Z CAMs and
global models now suggest that this second wave of precipitation
will provide the most widespread coverage of light-occasionally
moderate rain (and perhaps a few lightning strikes) across our
CWFA, likely during the mid-evening hours.

A third and final round of rain, associated with a slightly
stronger disturbance in the subtropical jet may build
northeastward into the local area closer to sunrise, but recent
trends in high-resolution model data indicate that this may only
briefly clip the southeastern half of the CWFA between 9-12Z, with
little to no risk of thunder. QPF guidance from WPC suggests that
storm total precipitation amounts will be rather light, ranging
from 0.05-0.10" (NW) to ~0.25" (SE). Low temperatures should
generally be in the m40s due to a combination of light
precipitation, low stratus clouds, and elevated northerly winds.

&&

.SHORT TERM...
(Sunday through Tuesday night)
Issued at 240 PM CDT Sat Apr 20 2024

Present indications are that light rain (associated with the
third/final wave discussed above) will be ending rather quickly
from W-to-E between 12-18Z Sunday, with partial clearing expected
to occur for many locations tomorrow afternoon. However, due to
weakening but persistent cold advection in the boundary layer,
highs should still only reach the u50-l60s. A broad ridge of high
pressure at the surface will begin to shift eastward across the
southern Plains on Sunday night, but the pressure gradient to the
east of the ridge`s center will likely maintain at least some
mixing in the lower troposphere locally, and this along with some
high clouds related to the passage of a longwave trough axis may
reduce impacts from radiational cooling with dewpoints in the l-m
30s. Although this scenario would lower concern for frost
development early Monday morning, a patchy coverage of frost will
still be possible (mainly across southern Middle TN, where lows
are forecast to be in the m-u 30s).

The center of the surface ridge will shift eastward across the TN
Valley and into the central Appalachians on Monday, before
building further northeastward and off the northern Mid-Atlantic
coast on Monday night. This will provide a period of clear skies,
light winds and dry conditions, with highs returning to the m-u
60s Monday before falling back into the u30s-l40s Monday night.
Southwesterly return flow will become established on Tuesday and
Tuesday night as a weakening northern stream trough and surface
low track southeastward across southern Ontario and the Great
Lakes. This will allow for a gradual increase in both dewpoints
and temperatures, but mostly clear skies and dry conditions will
prevail through 12Z Wednesday.

&&

.LONG TERM...
(Wednesday through Friday)
Issued at 303 AM CDT Sat Apr 20 2024

Afternoon Update: Based on the 12Z suite of global models, all
thoughts mentioned in the extended discussion (below) remain valid
this afternoon.

High pressure will get squeezed to the southeast mid to late
week, with a couple of weak impulses pushing across the area each
day. However, very limited moisture will keep the forecast dry,
with only scattered to broken bands of cloud cover being the main
impact. Temperatures each day will peak in the low to mid 70s,
with lows in the upper 40s to lower 50s. A pronounced longwave
trough over the western United States will slowly progress
eastward late this week into the weekend. This will be the next
feature to watch as it may bring our next decent chances for
showers/storms by next weekend.

&&

.AVIATION...
(18Z TAFS)
Issued at 1229 PM CDT Sat Apr 20 2024

The band of showers/elevated thunderstorms which impacted the
region earlier this morning has dissipated across northwest GA.
However, an additional round of rain (and perhaps a few embedded
lightning strikes) will spread northeastward from the Lower MS
Valley this aftn, reaching MSL/20-24Z and HSV a couple of hours
later. Although coverage of this activity may be inhibited by a
separate region of convection developing along a stalled frontal
boundary (well to our south) we have placed TEMPO groups in the
TAFs for this activity. Precipitation coverage will increase later
this evening as a second/stronger upper-air disturbance lifts
northeastward into the central Gulf Coast, and cigs should descend
to 3500-5000 ft as this occurs (but remain VFR) while vsby may
occasionally fall to 5SM. Rain will quickly end from W-to-E btwn
12-18Z Sunday, with cig/vsby conds improving during this
timeframe. Sfc winds will remain from NNE at 10G18 kts this aftn,
but should weaken overnight and veer to NNW by the end of the
period.

&&

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

&&

$$

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