Area Forecast Discussion
Issued by NWS Aberdeen, SD
FXUS63 KABR 031736 AAC
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1136 AM CST Sat Dec 3 2016
Issued at 1042 AM CST Sat Dec 3 2016
An upper level shortwave over South Dakota could bring light pcpn
to the eastern portion of the CWA later this afternoon. Based on
current trends and short range models, could either go with a high
pop/low QPF or no pops with non-measurable weather. Thinking no
pops with non-measurable weather is the way to go this afternoon.
Will make additional adjustments once obs in southern SD,
northeast NE start reporting pcpn.
.SHORT TERM...(Today through Monday Afternoon)
Issued at 337 AM CST Sat Dec 3 2016
Stratus continues the rather rapid retreat with 925mb winds shifting
to the south/southwest. Clearing has resulted in localized pockets
of dense fog, mainly downwind of the Missouri river. A surface
trough will move across the western Dakotas today, with a warm
advection push that will result in increasing low to mid clouds,
with weak lift of 3-5 microbars generating light snow/sprinkles.
There will also be some light precipitation that follows the upper
trough as it moves overhead Saturday night, and mid level
temperatures cool slightly.
The post frontal airmass will be milder than ahead of the trough as
a modified Pacific airmass moves into the Dakotas. Westerly winds
will also enhance mixing - with mixed temps around 40F. Snow cover
will probably have less impact on these readings due to the
favorable mixing direction and ample sunshine compared to the
readings expected for Today. Mild air will remain across the area
early Monday though a surface low is expected to develop and track
across the forecast area during the day. While the cold front will
move across the area during the morning, 925mb readings start
quite mild, from -1 to +4C at 15Z, resulting in highs above
average for the day but likely falling in the afternoon as 925mb
readings drop to 0 to -6C by 00Z Tuesday. Also anticipate
precipitation on the northwest side of the surface low as
temperatures within the profile cool.
.LONG TERM...(Monday Evening through Friday)
Issued at 337 AM CST Sat Dec 3 2016
Not a lot of change to speak of in the out periods this morning,
compared to yesterday morning. Still dealing with a low pressure
system early next week that, arguably, could be producing a decent
band of snow in some strong wind somewhere over the northern plains.
Available deterministic/ensemble guidance still seems to be pinging
North Dakota for placement of most of the precipitation potential
Monday/Monday night with this system, but this system is still being
watched closely. A shift of just 50 miles to the south, and this
band of snow is creating hazardous traveling conditions across, at
least, north central South Dakota!
The rest of the 7-day is dry except for Thursday and Saturday. For
two consecutive mornings, the ECMWF brings a slug of saturated
conditions between 850-700hpa southward through the eastern Dakotas
and much of Minnesota, when SnowRatios are quite possibly between 18
and 23:1 over the region. There could be up to an inch of light
fluffy snow falling over the region east of the James River valley.
The 00Z GFS/ECMWF are also still highlighting some waa-forced
precipitation chances on Saturday as another Pac-NW shortwave sweeps
through the Dakotas.
Lastly, given past run-ins with 925hpa thermal progs as low as
-20C, and 0.5km wind progs as high as 25 to 30 knots, considering
whether wind chill values will be lower than advertised -10F to -20F
w.c. values currently showing up in the forecast database between
Tuesday and Friday. Perhaps a target of opportunity for refinement
over the next few days.
.AVIATION...(For the 18Z TAFS through 18Z Sunday Afternoon)
Issued at 1134 AM CST Sat Dec 3 2016
VFR conditions are expected to prevail through the period. KATY
would be the most likely site to see some MVFR cigs and vsby
toward morning. However, confidence is not high enough for a
mention at this time.