Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 220849

Area Forecast Discussion
National Weather Service Aberdeen SD
349 AM CDT Fri Jun 22 2018

.SHORT TERM...(Today and Tonight)
Issued at 348 AM CDT Fri Jun 22 2018

Low pressure over eastern MT early this morning is responsible for a
few clusters of showers and thunderstorms over northwest SD and
northeast WY. Some of this activity may push as far east as the far
western CWA later this morning so have included small POPs for this
potential. Otherwise, main precipitation chances will be later this
afternoon and overnight as the low pressure system advances further
east. Not much in the way of instability to work with as CAPE is
generally less than 1000 J/KG with shear somewhat lacking as well.
Synoptic scale lift though should be enough to get some showers and
thunderstorms going by late afternoon and early evening over
western/central SD, with activity continuing into the nighttime
hours as activity approaches the James Valley by 12Z Saturday.
Although, CAMs indicate a decrease in areal coverage by that time.
Will keep POPs in the chance category at this time for late this
afternoon through the overnight.

Temperatures today look to rise into the low to mid 80s for most
areas, with the warmest readings right around Aberdeen once again
where conditions have been the driest over the past month or so. 850
mb temps are fairly similar to yesterday, so feel highs today may be
close or even a few ticks warmer thanks to a bit more sunshine.
Soundings do indicate some afternoon cumulus development across most
of the CWA.

One note on winds today - they were increased a bit, especially over
central SD where the pressure gradient looks to bring breezy
conditions. Went with more of a CONSMOS feel which usually does
better with wind speeds anytime there is somewhat of a decent
pressure gradient. Even went a couple knots higher than CONSMOS over
central SD.

.LONG TERM...(Saturday through Thursday)
Issued at 348 AM CDT Fri Jun 22 2018

Not much change to the overall extended with the evenings
deterministic guidance. The main features we are tracking are 1) a
weak circulation that will come out of the northern Rockies and
pivot over the Dakotas Saturday and Sunday and 2) a more impressive
upper trough that will absorb feature number 1 between Sunday PM and
Monday, vigorously ejecting towards the western lakes region Monday-
Tuesday. Flow aloft after that becomes more zonal and typical for
late June/July.

Thunderstorm chances increase with the approach of the first wave,
mainly as a result of increased low level humidity on light south
winds. Profiles become unstable with very little cap, and skinny
CAPE. Additionally, wind shear is weak with peak 0-6kt shear only
about 25kts. The result is pulse convection along a series of
convergent boundaries that will have some minor thermal/dewpoint
discontinuity as well as any outflow boundaries. Will limit POPs to
around 40-50 percent given the small scale/short duration nature of
convection suggested by CAMS and supported by the storm mode.

A deeper, more organized surface low is associated with wave number 2
and develops in the Central Plains Sunday night. This feature will
lift northeast towards Omaha/Sioux Falls, then pull back to the
northwest and into the CWA Monday night, before lifting northeast
Tuesday. There is limited CAPE in the profiles with this system as
well, with some localized higher areas of shear but generally a weak

Generally this flow and chances for moisture, as well as an amoebic
thermal pattern supports near average temperatures for the next few


.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
Issued at 1234 AM CDT Fri Jun 22 2018

VFR conditions are forecast to prevail through the TAF forecast




LONG TERM...Connelly
AVIATION...TMT is the U.S. government's official web portal to all federal, state and local government web resources and services.