Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 200548 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1248 AM CDT Mon Aug 20 2018

Issued at 1239 AM CDT Mon Aug 20 2018

Aviation discussion updated below for the 06Z TAFs.


.SHORT TERM...(This Evening through Monday)
Issued at 158 PM CDT Sun Aug 19 2018

Forecast challenges revolve mainly around precipitation
coverage/timing tonight into early Monday morning, as well as

Currently, under a cloudy sky, temperatures are holding in the 60s
to lower 70s on north-northeasterly breezes. The warm conveyor belt
on this large synoptic-scale low pressure system, per satellite
imagery, continues to lift/advect semi-saturated air northward into
this cwa (mainly along and south of an Ortonville to Faulkton to
Mission Ridge line), while an ill-defined and broad deformation zone
continues to put the squeeze on clouds/precipitation across the far
north central/northeastern sodak forecast zones (mainly north of a
Sisseton to Hoven to Kirley line).

Comparing where it has rained (last night) and is currently raining
with where/how much the models (yesterday and the day before) were
saying it would rain, seems the models/qpf guidance has been way
over-doing it w.r.t. precipitation amounts and coverage with this
system. Makes trusting anything the models/qpf guidance says for
tonight/Monday a little tough to stomach. Nevertheless, can`t argue
with synoptic-scale meteorology and accompanying conceptual model.
Hi-Res CAMs and 12Z GSM output for the most part seems to be
behaving/falling in line with where/when deformation zone-forced
precipitation should occur tonight/early Monday morning and seem to
have backed off some on forecast precipitation amounts. Forecast low
and high temperatures tonight and Monday remain relatively unchanged.

.LONG TERM...(Monday Night through Sunday)
Issued at 158 PM CDT Sun Aug 19 2018

Canadian high pressure will be the dominant weather feature Monday
night through Wednesday. The high pressure will produce below normal
temperatures, along with dry conditions. With the center of the high
over the CWA Tuesday night, low temperatures could range in the 40s
and low 50s. Warm air advection will develop on Wednesday with high
temperatures warming into the lower 80s for most locations. Warmer
temps are expected on Thursday ahead of a potent shortwave. The
shortwave, along with a 40 knot LLJ should produce showers and
thunderstorms over the eastern half of the CWA Thursday night into
Friday morning. Models diverge beyond Friday, leading to a low
forecaster confidence for the weekend.


.AVIATION...(For the 06Z TAFS through 06Z Monday Night)
Issued at 1239 AM CDT Mon Aug 20 2018

MVFR/IFR conditions will persist at KATY through much of the
overnight and into the Monday morning hours before gradually
improving to VFR. -RA and BR will also persist, with -RA ending
prior to 12Z. Elsewhere, VFR conditions are expected through the
TAF forecast period.




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