Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 141725
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1125 AM CST Tue Nov 14 2017

.SYNOPSIS...
Issued at 354 AM CST Tue Nov 14 2017

At 09z...A surface trough extended south from western North Dakota
through eastern Wyoming into eastern Colorado. Anomalously high
dewpoints from 42 to 45 degrees resided near and east of North
Platte through Thedford and Ainsworth. This was attributing to fog
formation early this morning across a large portion of western
Nebraska. Lowest visibilities were on the western edge of the
stratus, with 1/2sm vsby at Ogallala and Imperial. Widespread vsbys
ranged from 1 to 3 miles all areas eastward.

&&

.SHORT TERM...(Today and tonight)
Issued at 354 AM CST Tue Nov 14 2017

Morning stratus and fog will be the near term concern. A dense fog
advisory will remain in effect until 16z, for areas east of Ogallala
through Mullen and Valentine. With the fog lifting, stratus will
also lift and erode from west to east, as a prefrontal trough
advances east. The stratus should push east of the forecast area by
18z with some lingering high cloudiness through afternoon. The area
of stratus this morning will have some affect on highs across the
far eastern zones, where highs were trimmed to the lower 60s. The
bulk of western Nebraska should see highs reach 65 to 70 degrees,
with the highest reading near 70 from southwest Nebraska to around
Thedford and Broken Bow in the central Sandhills. With a light
westerly downsloping wind, abandoned the cooler MET and ECS
guidance in favor of the warmer MAV guidance and also the HRRR and
RAP 2m temps.

A fairly weak upper level trough will cross the northern and Central
Plains tonight and drag a cold front through western Nebraska by
around 06z. Northwest winds will peak at 10 to 15 mph for a few
hours overnight. With clear skies tonight, winds should decouple
late tonight with lows near previous forecast from near 25 in
Sheridan county to 33 to 35 degrees east of Ainsworth through Broken
Bow.

.LONG TERM...(Wednesday through Monday)
Issued at 354 AM CST Tue Nov 14 2017

The long term period starts off with a flat ridge of high pressure
to the west of the forecast area and a weak trough to the east.
Zonal flow will largely prevail aloft on Wednesday, but cooler
temperatures at the surface are expected as high pressure and weak
CAA continues through much of the day. The flow aloft will induce a
lee sfc trough late in the day, which will kick up wind speeds for
Thursday and warm temperatures. Wind gusts to 25 mph will be
possible with highs returning into the 60s for the west, mid 50s
across the east.

Friday will begin to see the impacts of a short wave trough and
associated cold front.  Return flow in advance of the trough with
some central Pacific moisture in the mid and upper levels will work
in conjunction with increasing lift to promote precip chances for
the CWA. The problem is that the GFS and EC continue to be at odds
in timing of the eventual short wave/frontal passage. The GFS and
the NAM for that matter continue to be faster than the EC. The best
synoptic lift from the GFS targets northern Nebraska early and mid
day Friday. The slower EC seems to favor a greater influence from a
strong upper jet /left exit region/ and possibly mesoscale
influences first across northern portions of the CWA mid day Friday,
then the lift drops south with the upper jet to impact central and
southern portions of the CWA late Friday into Saturday.  The EC
would have more potential for a mix of rain/snow or a complete
changeover to all snow with the QPF falling in the evening/night
hours. At this point widespread chance wording is needed, but the
progression of upper jet will need to be monitored as areas of
banded QPF will be expected somewhere across the cwa with the
favorable position of the jet.  Some enhancement of the
precipitation would be expected in the band/s/, but all in all, this
event should only produce a tenth or two total liquid QPF at best
with most locations only seeing a hundreth or two.

Poor model agreement beyond the system yields low confidence, but
the general idea would be that northwest flow would transition to
zonal or quasi zonal late weekend or early next week.  Dry
conditions would largely be expected with a gradual warmup before
the next front arrives early next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1125 AM CST Tue Nov 14 2017

Low stratus extending from IML to LBF to ONL and points east will
continue to erode this afternoon, leading to scattered high
clouds for the remainder of the evening. IFR cigs at LBF are expected
to transition to VFR by 14/19z. A cold front will push south
across the region this evening. West/southwest winds will switch
to north/northwest and may briefly gust to 15 kts. All terminals
in western Nebraska should be VFR and have predominantly northwest
winds overnight into Wednesday morning.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SYNOPSIS...Roberg
SHORT TERM...Roberg
LONG TERM...Jacobs
AVIATION...Snively



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