Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 191750 AAC

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1150 AM CST Thu Jan 19 2017

Issued at 1135 AM CST Thu Jan 19 2017

Aviation discussion updated below for 18z TAFs. Have also
cancelled the Dense Fog advisory. Will continue to monitor next
slug of moisture moving up from the south for potential dense fog
issues later this afternoon into the overnight hours.

UPDATE Issued at 844 AM CST Thu Jan 19 2017

Dense fog is advecting across the northwest portion of the James
valley so have extended Dense Fog Advisory through noon. Other
areas have cleared so Advisory has been allowed to expire.
Advection fog moving out of Nebraska into southeast South Dakota
will move into eastern counties by mid day so have expanded fog
mention across the east.


.SHORT TERM...(Today through Saturday Afternoon)
Issued at 328 AM CST Thu Jan 19 2017

Yesterday`s snow melt and moisture advection has produced areas of
dense fog over the eastern half of the CWA. A few obs are showing
visibility of a half mile or less at times. Several webcams are also
showing areas of dense fog. Thus a dense fog advisory has been
issued for the eastern half of the CWA.

An upper level low over the nation`s midsection will slowly lift
northeast and weaken over the 36 to 48 hours. This system will bring
moisture into the eastern half of the CWA later today through
Friday. Specific humidity at 850 mb will increase substantially by
18Z along and east of the James River Valley. The NAEFS return
interval suggests the moisture at 850 mb occurs once every two to
five years. This LLM, but lack of lift will likely result in low
stratus and fog over the eastern half of the CWA this afternoon
through Friday. With the clouds and abundance of LLM, have increases
lows tonight by a few degrees. While both NAM and GFS buffer
soundings indicate pcpn, mainly on Friday, preferred non-measurable
drizzle. Soundings moisten better Friday night into Saturday thanks
to a secondary upper level low pressure system. The drizzle should
transition over to rain/snow. With CAA pushing into the CWA from the
northwest, pcpn should become all snow by Saturday evening. Warm
surface temps and lack of good lift will limit snowfall amounts.

.LONG TERM...(Saturday Evening through Wednesday)
Issued at 328 AM CST Thu Jan 19 2017

Weak sfc low pressure with a remnant inverted sfc trough on Sunday
will keep some slight pops in the forecast across the north on
Saturday night and Sunday. There is a brief break in the action
Sunday night through Monday before the precip forecast becomes more
challenging. Models have lost their internal run-to-run consistency
on the system over the Plains on Tuesday. The ECMWF and GFS have
flipped their solutions with the EC now running dry across northeast
SD, though the Missouri River is still affected, and the GFS
plastering the entire forecast area with QPF as the stacked low
moves through southern NE and IA. Due to the extreme uncertainty,
stuck with consensus slight chance to chance pops Tuesday through
Wed night.

Temperatures will remain above normal in the extended but will see a
slow cooling trend through the week.


.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
Issued at 1135 AM CST Thu Jan 19 2017

KABR/KATY...FG/BR and low CIGs will move back into the terminals
this afternoon and remain in place overnight through Friday
morning. VSBY below 1SM is likely with 1/4SM VSBY possible as
well. CIGs are expected to be below 500ft also.

KPIR/KMBG...VFR conditions will prevail this afternoon. This
evening, BR is likely to develop over central SD, along with areas
of lowered CIGs. Confidence in areal coverage of lower VSBY and
CIGs, as well as how low the VBSY and CIGs get is lower over
central SD compared to eastern areas. For right now, have inserted
some lowered VSBY in BR across these two terminals beginning this
evening and lasting through Friday morning.





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