Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 092327
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
527 PM CST Sun Dec 9 2018

.SHORT TERM...(Tonight through Wednesday)
Issued at 255 PM CST Sun Dec 9 2018

Main weather story is the system which is well off to our east,
affecting parts of the east coast. In our area, there was a closed
low dropping south through the region, but it did not generally
have moisture deep enough for precipitation.

Somewhat tricky forecast for tonight into Monday morning in
regards to potential for low clouds/fog and the overnight low
temperatures. Surface analysis at 2 pm showed a low pressure
trough stretching southward from a weak low over southwest MN into
southwest IA and northeast KS. Dewpoints were mostly in the upper
teens and lower 20s, but there was some slightly drier air
upstream in north central NE and southern SD. We are forecasting
lows quite a bit lower than current dewpoints.

Low clouds currently across parts of eastern SD and northwest IA
will tend to drop south/southeast this evening and tonight. This
is expected to be most problematic across western IA but also
parts of eastern NE. It could be one of those cases again with fog
depositing rime on exposed surfaces if the fog becomes dense.

Fog and or stratus that develop tonight should mix out by mid to
late morning Monday, with some mid and high clouds the rest of
the day. Will generally be conservative with afternoon high
temperatures, staying below MOS guidance. Expect highs mainly from
around 30 to the mid 30s. The airmass should then tend to slowly
moderate through the week, with highs Tuesday in the 30s except
some lower and mid 40s near the KS border. By Wednesday it may be
just a bit cooler with highs mostly in the 30s. The NAM hints at
potential light precipitation Tuesday morning between Sioux City
and Omaha, but no other model does. If something develops, it
could be light freezing drizzle. The ECMWF and GEM suggest some
light precipitation for parts of the area Tuesday night, but the
GFS is dry. Will leave the forecast dry for now and monitor for
possible changes with later updates.

.LONG TERM...(Wednesday night through Sunday)
Issued at 255 PM CST Sun Dec 9 2018

A moderately strong shortwave trough should affect the region
Wednesday night into Thursday. The GFS is generally the most
aggressive with coverage of light precipitation and it seemed
reasonable. Will carry some low POPs for a good part of the
forecast area late Wednesday night into Thursday. The rest of
the long range period looks mainly dry with a slight warming
trend into the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 527 PM CST Sun Dec 9 2018

Latest surface observations indicate a cyclonic wind shift
stretching from central MN to west IA. Of concern for this
forecast is a relatively small stratus deck situated along and
immediately to the west of the wind shift over east SD into
southwest MN and northwest IA. METAR data within the cloud deck
indicate IFR to MVFR ceilings and fog with visibilities as low as
2 1/2 SM. Latest model guidance indicates that the stratus and
patchy fog will continue south overnight, potentially impacting
KOMA by 3 or 4 AM. Proximity of the surface wind shift and
resultant light winds over west IA could yield local visibilities
falling to less than a mile. For now, we will indicate a period of
MVFR conditions late tonight into Monday morning at KOMA, though
confidence in the degree of visibility restriction remains low.
Elsewhere, a brief period of low clouds could impact KOFK prior to
midnight.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Mead


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