Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 192131

Area Forecast Discussion
National Weather Service Aberdeen SD
331 PM CST Sun Nov 19 2017

.SHORT TERM...(This Evening through Monday Afternoon)
Issued at 331 PM CST Sun Nov 19 2017

Quite a bit of cirrus streaming southeast across the area, with more
upstream. The high cloud cover should keep temps fairly mild
overnight as we keep a light breeze as well. Although valley areas
such as Aberdeen may cool off more than surrounding areas if any
clearing can occur with the light winds.

Very mild air will stream across the area on Monday, with 925mb
temps getting rather warm for this time of year. Question was just
how warm to go with highs tomorrow given the good mixing and warm
air mass. Although, will have to watch cirrus potential on Monday
which could hold temps back a touch. For right now went pretty
optimistic on highs and leaned towards warmer end of guidance. If it
begins to look like there will be some thicker cirrus over the
region on the overnight shift, we may need to scale back a couple

A side note on winds late tonight through Monday morning as it looks
like there will be a bit of a downslope event across the Coteau
region. Sided with the models that pick this up rather well in the
wind grids, such as NSSLWRF.

.LONG TERM...(Monday Evening through Sunday)
Issued at 331 PM CST Sun Nov 19 2017

Mostly dry forecast with a few wild temperature swings continues
into perpetuity with a few minor exceptions. Precipitation chances
are "best" with a push of mid level warm advection Wednesday PM. GFS
BUFKIT soundings show some run to run consistency - depicting a deep
saturation layer with only weak lift - generally less than 10
microbars. It will be a complex scenario with the sounding initially
representative of snow, before becoming warm enough aloft for some
melting with a near surface sub freezing layer potentially deep
enough for re-freezing. Then we may loose saturation in the
dendritic growth zone for some drizzle, but this will also have to
overcome a dry subcloud layer, which will probably limit any ice
accumulation while surface temperatures slowly warm above freezing.

The rest of the extended mainly concerns temperatures. Initially we
will be in a cold advection regime. Mixing will limit temperature
falls Monday night, but restrict high temperatures for Tuesday.
Surface high pressure moves overhead Tuesday night for ideal
radiational conditions. We begin to see the warm advection push
Wednesday but there is some inconsistencies between deterministic
guidance on the degree and speed of warming. The weak system that
initiated this warm advection will also cause the arctic front to
wobble back into the northeast CWA but a second warm push will re-
organize for Thursday. That warm air persists into Friday. 925mb
temperatures Friday are 2 standard deviations above climo. Mixing
from 900/850mb yields highs in the mid/upper 60s which is well above
blended guidance. There is a front to the north and the degree of
high clouds is indeterminate at best this far out - so will remain
pessimistic but there potential to break some high temperatures


.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 1122 AM CST Sun Nov 19 2017

VFR conditions will prevail through the TAF forecast period, with
just some passing high clouds.




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