517
FXUS63 KABR 112308
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
608 PM CDT Tue Jun 11 2024

.KEY MESSAGES...

- There are slight chances to chances (15-45%) of showers and
thunderstorms tonight through Wednesday night. The precipitation
chances Wednesday afternoon look to remain along and east of the
James River Valley. Some storms may become strong to severe.

- High temperatures on Wednesday are forecast to warm into the upper
80s to mid 90s, which is 10 to 15 degrees above normal.

- A storm system Friday night through Saturday night and early
Sunday will bring a 30-60% chance of showers and thunderstorms. The
storm system may produce locally heavy rainfall over eastern SD and
western MN.

&&

.UPDATE...
Issued at 602 PM CDT Tue Jun 11 2024

The ongoing forecast remains on track, with few changes
anticipated this evening.

&&

.SHORT TERM /THIS EVENING THROUGH WEDNESDAY NIGHT/...
Issued at 228 PM CDT Tue Jun 11 2024

At 2 PM CDT, skies are sunny and temperatures are warming through
the 70s and 80s on a 10 to 20 mph west-northwest wind, including
gusts up to 35 mph at times.

Surface high pressure is over the region, while mid/upper level
heights continue to rise. These height rises will stall out
overnight as an upper level low pressure system currently moving
into B.C. (Canada) and the Pacific NW scoots across the
international border overnight and out over the northern plains on
Wednesday. The attendant cold front is forecast to progress across
the CWA on Wednesday, potentially reaching the James River valley as
peak-heating kicks in. More surface high pressure and low level
dry/cold air advection is chasing this frontal boundary through the
CWA. By 10pm-ish Wednesday evening, the frontal boundary should be
clear of the far eastern CWA. Throughout the day on Wednesday,
though, toasty warm air that will have been advected into the
boundary layer over the CWA will help to support high temperatures
well above normal, into the 90s over much of the CWA.

There will be a low level jet developing over the region overnight,
along with a decent mid-level WAA event on top of it. A glance
through model soundings in BUFKIT indicates there is potential for
ample low/mid-level moisture return/advection into this region
overnight into Wednesday morning, when the higher-octane low-level
moist air collecting down over southern Nebraska and on down into
Kansas gets transported up into this region. If there is a time when
the cross-hairs of mid-level WAA, nose of the low-level jet and
leading edge of the best low/mid-level moist air advection all align
over this CWA, expect late night/early Wednesday morning isolated
(15%) to scattered (40%) coverage elevated showers and thunderstorms.

After the low level jet dissipates, convective potential settles
into whatever (if anything) can develop along the cold front. By
early afternoon, a fairly modest warm layer aloft will be serving as
a thermal capping inversion. NAM soundings are probably a tish
overdone on moisture/instability (~3500+J/kg CAPE), generating "fat
CAPE" large hail soundings; hail CAPE at or above 1000J/kg) and
meaningful straight-line hodographs (50knots of deep layer shear).
It`s going to boil down to whether or not there is actually enough
boundary layer moisture around for storms or if the capping
inversion along the boundary will hold, keeping robust updrafts at
bay. Leaning toward little to no convection across the eastern zones
on Wednesday. But, if sustainable convection were to occur,
supercells would be the mode, supporting some rather large hail,
potentially, and strong wind. Eventually, convection could start to
line out, given forecast 0-3km shear heading into the evening hours.
But, thinking is that by then, storms are expected to be departing
this CWA, taking any sort of severe threat with them. While surface
high pressure is trying to build into the CWA Wednesday night, the
gradually southward-shifting mid-level baroclinic zone trailing the
surface frontal boundary will move over the CWA, creating elevated
night-time shower potential over the CWA.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 228 PM CDT Tue Jun 11 2024

The main challenges in this period will be precipitation chances
returning late in the week and temperatures during the course of the
upcoming weekend into early next week. Beginning Thursday morning,
sfc high pressure will be building into the Dakotas from the
northwest. We may see a lingering shower early in the morning,
otherwise anticipate dry conditions will the rule through the day
and into Friday morning. Temperatures will remain seasonal for this
time of year with overnight lows in the 50s and highs in the
upper 70s to mid 80s.

The pattern will quickly shift back into active mode by Friday
afternoon and Friday night. By then, the next storm system will
already be taking shape across the southwest CONUS. An upper trough
is progged to dig into the PacNW toward the end of the week. A low
amplitude shortwave ridge across the Northern Plains and Great Lakes
Thursday will shift east and our region will get into southwest flow
aloft. An upper level wave across the Desert SW/Four Corners Region
will shift northeast into our region by late Friday into Saturday.
More rounds of showers and thunderstorms will be possible by the end
of the work week into the weekend. Best opportunities for precip
still remain concentrated more across our eastern forecast area from
late Friday night through late Saturday night where a 40-60 percent
chance exists. There could be some pockets of moderate rainfall with
this system across our east. WPC`s excessive rainfall outlook pegs
our eastern zones with a marginal risk for seeing heavy rain. At
this point, NBM`s probabilities for reaching or exceeding a half
inch of rainfall in a 24 hr period ending at 7 AM Sunday is 40-50
percent across northeast SD and west central MN. Temperatures look
to remain relatively mild through the weekend into early next week.
The only caveat right now in the analysis is it`s a bit difficult to
nail down exact values due to the prolonged unstable flow pattern
will be in early. Thicker clouds and rainfall versus areas of
sunshine will be the driving factors in how warm daytime readings
get.

Another disturbance is progged by guidance to shift through the
region early next week as the upper trough axis remains anchored
across the western CONUS. There is some uncertainties in timing and
placement of the wave by the deterministic and ensembles, so have
continued the trend with a 40-50 percent chance for showers and
storms Monday into Tuesday.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 608 PM CDT Tue Jun 11 2024

Terminals KABR,KATY,KPIR,KMBG

VFR conditions are expected to continue over the next 24 hours,
outside of any thunderstorms that could move over a TAF site. At
this point the potential for thunderstorms at any 1 location at a
certain time is too low to include in the forecast.

&&

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

$$

UPDATE...KF
SHORT TERM...Dorn
LONG TERM...Vipond
AVIATION...KF