204
FXUS63 KABR 181146
AFDABR

Area Forecast Discussion
National Weather Service Aberdeen SD
646 AM CDT Mon May 18 2026

.KEY MESSAGES...

- Light rain showers mid day today through this evening. Rainfall
ranges from a tenth to a quarter inch.

- Colder air for the first half of the work week. Lows Tuesday
morning close to freezing, but with clouds and a stiff northwest
breeze temperatures should stay above 32. Much better setup for
widespread frost/freeze conditions Wednesday morning with clear
skies and light winds.

&&

.UPDATE...
Issued at 646 AM CDT Mon May 18 2026

UPDATE for 12Z Aviation discussion.

&&

.DISCUSSION...
Issued at 128 AM CDT Mon May 18 2026

Next wave coming up from the southwest brings in moisture mid-day
today through the early overnight. Still mainly light rain/showers.
QPF is just a tenth or two.

For Tuesday morning, we are faced with the prospect of cold
advection enhanced winds, shallow cloud cover and NBM guidance
proposing temperatures down to the freezing mark. Clearly not a
setup for frost, but with 925mb temperatures around +1 to +2C
between deterministic models, which is in alignment with the
HREF mean that should put temperatures into the low/mid 30s.
That said, the NSSL WRF, NAM NEST and HRRR have 925 temps down
to 0C for various parts of the CWA. Latest NBM is a little
warmer for lows, and now has just about everyone at 33F and
warmer. No headlines/frost mention for Tuesday morning but it
will get quite close to the freezing mark. Frost caddishness
negated by these winds and clouds however.

Much more impactful drop in temperatures will be noted for Wednesday
morning. During the day Tuesday, daytime driven cumulus evident in
NAM BUFKIT profiles. While this is shallow (~5kft), cant rule out
light rain showers/sprinkles. Regardless, cloud cover during
the day will limit heating. Loss of daytime driven convection
with temperatures only into the 50s and dewpoints in the low/mid
30s and surface high pressure overhead will leave us with a
good setup for frost. 25th range across the CWA is 29-32 while
the upper range is 32-35. Keeping frost mention at this time but
still too early for any headlines.

The upper pattern features the current upper trough departure, with
a second trough over the intermountain west. That puts us under a
ridge for Wednesday - early Thursday. There`s a negative tilt trough
passage for Friday. Aside from the precipitation associated with this
wave/surface low, there is a wide range in temperatures with a 10
degree spread in the 25th/75th for highs so a low confidence
forecast to close out the work week. After that its zonal flow
across the northwestern CONUS into the northern plains.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 646 AM CDT Mon May 18 2026

Terminals KABR,KATY,KPIR,KMBG

IFR to low end MVFR ceilings will continue through the next 24
hours. 2-5SM visibility in fog will remain near ATY through
14Z. Light rain will dominate the afternoon hours. Expect winds
to remain out of the north to north-northwest with gusts of
20-30kts. Look for improving conditions from west to east
overnight, with VFR ceilings returning to PIR by 08Z Tuesday.

&&

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

&&

$$

UPDATE...10
DISCUSSION...07
AVIATION...06