309
FXUS63 KABR 100521
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
1221 AM CDT Wed Jul 10 2024

.KEY MESSAGES...

- Chances for thundershowers mainly east of the James River to
  diminish through the early morning hours.

- Hazy conditions continue through Wednesday night as north-
  northwest flow brings periodic waves of smoke from Canadian
  wildfires. Much of this is expected to remain aloft, with little
  to no reductions in visibility at the surface.

- High confidence in hot and muggy conditions for the extended
  period. High temperatures will be in the 90s (5-10 degrees above
  average) Friday through Sunday along with dewpoints in the mid
  to upper 60s. This combination will result in "feels like"
  temperatures ranging in the mid and upper 90s with a few spots
  to 100F each afternoon.

&&

.UPDATE...
Issued at 920 PM CDT Tue Jul 9 2024

Still some thunderstorm activity going on east of the Missouri
River, with more approaching the northeastern CWA from North
Dakota. Have seen some large hail and gusty winds with a few of
the storms. No changes made to winds or temperatures at this time.

&&

.SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/...
Issued at 331 PM CDT Tue Jul 9 2024

As shown by several CAMs earlier, isolated showers have developed
over far eastern SD into western MN. Air mass out that way is
characterized by around 1500 J/KG SBCAPE, but not much to speak of
in terms of shear. Mid-level lapse rates are also rather poor in
terms of supporting any robust convection. So, the trend through
this evening will be for these isolated/widely scattered showers to
persist, and perhaps even persist into the overnight a bit as there
is a vort noticeable on satellite imagery moving south across
central ND. Some CAMs keep additional development going through 06Z
right in the vicinity of the vort center. Did convey this thinking
through PoPs, with some higher 40-60% values in the vicinity of the
expected vort path.

Otherwise, other issue to watch will be the smoke moving southward
across the region from Canadian wildfires. HRRR/RAP smoke products
suggest mainly smoke aloft being the issue here as concentrations
increase towards morning. In fact, there is some noted increase in
near-surface smoke potential by 12Z Wed in the HRRR output.
Overnight shift may want to consider adding smoke to the wx grids
if, in fact, vsby start to drop across the region towards morning.
Confidence wasn`t high enough that these modest smoke concentration
increases would be enough to affect vsby, so mention of it was left
out for the time being. Although, with the expected increases in
smoke aloft, did bump up the sky grids just a bit.

Any afternoon pop-up showers on Wednesday look to be confined to
around the I-29 corridor and points east, which is where current
PoPs are evident in the forecast. Again, severe parameters are
lacking, so not expecting severe storms at this time. As for
temperatures, fairly similar to today, with highs rising into the
80s to around 90 degrees over central SD.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 331 PM CDT Tue Jul 9 2024

Main highlight for the long term will be the increase in
temperatures/dewpoints across the CWA for the end of the week and
especially this weekend. Clusters indicate the 500mb ridge`s axis
over the Rockies with the mid level high continuing over the
southwestern US for Thursday. This pattern continues Friday through
the weekend (the ridge becoming more broad) with the mid level high
expanding over much of the Rockies and into the western Plains where
it starts to de-amplify early next week. Across Canada, several
shortwaves will push west to east, disrupting the northern edge of
the ridge`s axis. It does become more amplified again over western
Canada by early next week, shifting east through the midweek.

High confidence exists on Friday through Sunday being the hottest
period with Sunday the hottest day of the week. Mean ensemble 850mb
temps are forecasted to range between 22-26C Friday afternoon, 23-
27C Saturday afternoon, and up to 29C Sunday! To put this in
perspective this is above the 90% average, per KABR sounding climo
page. NAEFS indicates the 850mb temps range from 90-97.5% above
average and 700mb temps 97.5-99.5% above climo average by 00Z
Monday. So daytime heating and mixing and a higher/stronger sun
angle will allow surface temps to warm up quickly into the 80s and
90s for the end of the week. By Saturday, temps over the entire CWA
will be in the 90s to even some lower 100 readings, mainly in south
central SD on Sunday. At this time, prob of 100 degrees for Sunday
ranges from 30-50% over south central SD. EFI has a value of 0.9 for
for Max T this day, however, NDFD Forecast Records do not show
anything for the CWA in terms of MaxT records for now. The overall
spread between the NBM 25-75th is pretty thin, ranging from 3-5
degrees. Little bit more of a spread on Sunday with a max difference
of 5-8 degrees over north to central SD, with the spread increasing
further out in time next week over the CWA.

Not only will it be hot, dewpoint values will range in the mid to
upper 60s Friday into this weekend making it muggy! This will put
heat index readings across the CWA well into 90s with even lower
100s, especially across central SD. So NWS Heat Risk does highlight
a major risk for of heat related impacts for Saturday across our
northern and northeastern CWA and more widespread for Sunday. The
good news is a cold front is forecasted to push through early next
week with cooler air behind it that will move in from the northwest
bringing relief.

Convection wise, NBM has occasional slight pops chances (15-20%)
over the CWA Friday evening into early next week associated with
these Canadian shortwaves (ridge runners!). CSU does highlight
low chances (15% and under) of severe probabilities Days 4-7.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1221 AM CDT Wed Jul 10 2024

Terminals KABR,KATY,KPIR,KMBG

Showers and thunderstorms will affect the eastern part of the
area (mainly ATY) until between 07-08Z Wednesday. Periods of MVFR
vsbys are likely with the thunderstorms. The entire region will
see VFR conditions once the storms exit the area. Smoke aloft will
occur over the region on Wednesday, but at this time do not
expect it to reduce surface vsbys.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Parkin
SHORT TERM...TMT
LONG TERM...MMM
AVIATION...KF