Area Forecast Discussion
Issued by NWS Aberdeen, SD
FXUS63 KABR 200318 AAB
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
918 PM CST Thu Jan 19 2017
Issued at 906 PM CST Thu Jan 19 2017
Mid-evening update to revamp the drizzle/freezing drizzle wording
to just drizzle wording and to adjust the overnight low
temperatures to above freezing for much of the clouded over and
foggy portions of the cwa. Light south winds are a weak low level
waa wind and are drawing higher dewpoint air northward over the
snowfield covering this cwa. This will work to keep temperatures
from falling below freezing for much of the cwa that has very low
clouds over it while ensuring the dewpoint either holds steady or
gradually increases overnight as well. Areas where it is going to
be foggy overnight and the temperature remains below freezing will
get to experience freezing fog, where everything receives a
coating of frost. Also touched up the dense fog advisory to add
Traverse and Big Stone Counties in MN as well as several counties
into central/north central South Dakota, based off trends noted in
surface observations and satellite imagery. Updates are out.
UPDATE Issued at 635 PM CST Thu Jan 19 2017
See below for an aviation forecast disccusion for the 00Z TAFs.
.SHORT TERM...(This Evening through Saturday Night)
Issued at 255 PM CST Thu Jan 19 2017
Low level moisture(Fog) and mild air encompasses most of the CWA
east of the Missouri valley. Will add another dense fog advisory to
the mix as this airmass will remain in place and with diabatic
cooling, visibility is unlikely to improve overnight.
With two weak upper waves transitioning over eastern SD/western MN,
precipitation type still remains difficult to resolve, no less
complicated by temperatures above freezing but ground temperatures
in the mid/upper 20s. Profiles mainly support drizzle initially, and
may in fact still be too shallow through Saturday morning to
generate any precipitation except along eastern upslope areas -
namely the eastern Sisseton hills and around the Leola hills. If we
can get drizzle to form in that shallow a layer, expect QPF to be
Profiles show deeper saturation Saturday, with now only sporadic
ice introduction as the second wave moves overhead. The result is
more fog and drizzle, with a few hundredths QPF. Temperatures again
will be around or just above the freezing mark so impacts will
probably be minimal.
.LONG TERM...(Sunday through Thursday)
Issued at 255 PM CST Thu Jan 19 2017
A low pressure system will be exiting the region to the east when
the period begins, with some lingering light precipitation possible
across the eastern CWA on Sunday. High pressure will bring dry
conditions to the region Sunday night and Monday, then the models
continue to show slightly different patterns with respect to a
stronger low pressure system set to track across the central plains.
The ECMWF continues to be a bit more southerly with the system,
tracking the low across Kansas vs the GFS which tracks the low
across southern Nebraska. Precipitation amounts will be highly
dependent on this track, so for the time being will stick with model
consensus, which keeps pops in the slight chance/chance category,
with the higher pops across the southern CWA. Temperatures look to
be cold enough that the precipitation will be in the form of snow.
Wrap around light snow showers may linger across the eastern portion
of the CWA into the day Thursday.
Sunday will be the warmest day of the period, with highs in the 30s.
Will then see a gradual cool down each day to highs in the 20s on
Thursday. Overnight lows will be mainly in the teens to lower 20s.
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 635 PM CST Thu Jan 19 2017
KABR/KATY...IFR FG and drizzle and low CIGs will remain in place
overnight through at least Friday morning. Visbies should settle
back down to around 1/4SM overnight. CIGs are expected to remain
below 500ft also.
KPIR/KMBG...these two VFR terminals are literally right on the
edge of the IFR fog bank and low clouds. Fully expecting them to
joing the IFR conversation by 06Z and remain down in fog and low
clouds through at least Friday morning as well. If there is to
be any improvement at any of the terminals on Friday, KPIR/KMBG
would clear off into VFR sooner than KABR/KATY would.
SD...Dense Fog Advisory until noon CST /11 AM MST/ Friday for
MN...Dense Fog Advisory until noon CST Friday for MNZ039-046.