Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 191848

Area Forecast Discussion
National Weather Service North Platte NE
1248 PM CST Thu Jan 19 2017

Issued at 329 AM CST Thu Jan 19 2017

H5 analysis from earlier this evening had an elongated
area of low pressure which extended from northern New Mexico into
southern Nebraska. Further west, a broad trough of low pressure
extended from the Gulf of Alaska south into the eastern Pacific, off
the coast of northern California. North of the low across the
central CONUS, a low amplitude ridge of high pressure was present
across central Canada. At the surface: A weak surface trough of low
pressure extended from north central Nebraska into the southeastern
Nebraska panhandle. East of this feature, light southerly winds and
low level moisture advection had pushed into central and eastern
portions of the forecast area. West of this feature winds were
westerly and much drier boundary layer moisture was present.
Overnight, fog has pushed into portions of southwestern and central
nebraska and had become locally dense with a visibility of 1/4 of a
mile at North Platte. NDOR cams south of Arnold have indicated dense
fog as well. Temperatures as of 3 AM CST were mild for this time of
year and ranged from 21 at Ogallala to 36 at O`Neill.


Issued at 846 AM CST Thu Jan 19 2017

Low clouds continue to lift north and east with areas of dense fog
now impacts parts of Thomas and Boyd counties where a Dense Fog
Advisory is now in effect until noon CST. The westward expansion
will now slow while the areas of fog persists through 10 am CT and
lifts slowly from west to east through noon CST.

UPDATE Issued at 636 AM CST Thu Jan 19 2017

Expanded the dense fog advisory to include McPherson, Blaine,
Loup, Garfield, Rock, Wheeler and Holt counties. Highway cameras
in these locations indicate very limited visibilities. Surface obs
in these areas were running visibilities on the order of 1/4 to
1/2 mile. The ending time of the advisory remains at noon CST.


.SHORT TERM...(Today and tonight)
Issued at 329 AM CST Thu Jan 19 2017

Today and tonight: For this morning, based on the
latest WARW, SREF ensemble visibility probabilities and the latest
HRRR, will hoist a dense fog advisory for portions of southwestern
and central Nebraska this morning. Indications are that the fog will
begin to burn off by late morning. However, stratus will be an issue
in the east today given the favorable low level moisture advection.
That being said, decided to undercut guidance for highs this
afternoon in the eastern CWA. Further west, drier air and mainly
clear skies will allow temps to reach the upper 40s to lower 50s.
For tonight: The upper level low will lift into eastern Nebraska.
Underneath this feature, widespread stratus and fog will develop
once again from central into eastern Nebraska. A surface trough will
remain stationary from north central into southwestern Nebraska
overnight tonight and serve as the dividing line between fog/stratus
and clear skies. SREF probabilities for visbys under 1 mile are near
100 percent for tonight in the eastern CWA. With further support
from the WARW visby product an NAM12, went ahead and inserted areas
of fog into the forecast for tonight.

.LONG TERM...(Friday through Wednesday)
Issued at 329 AM CST Thu Jan 19 2017

Friday starts off foggy with locally dense areas. Visibilities
across south central Nebraska could drop to under a mile during the
early morning hours. Fog lifts by mid morning, giving way to a
pleasant Friday. Even with cloudy skies across much of the forecast
area, high temperatures will still be able to rise into the low to
mid 40s.

Our next system will briefly impact north central Nebraska on Friday
night. Generally, precipitation will remain east of highway 83. The
low pressure system moving across central and eastern Nebraska will
be quick moving and precipitation is expected to remain mostly all
liquid. However, some snow is possible late Friday night as
temperatures drop below freezing. At this time, little to no
accumulation is expected. The system will be well northeast of the
region by Saturday, allowing a return to dry weather.

High pressure and dry weather sticks around for the remainder of the
weekend and into the first part of next week. The next major winter
system potential arrives on Monday night and lasts through Wednesday
morning. Specific details about snow amounts and onset of
snow/timing of heaviest snow is still being worked out. It is safe
to say right now, though, that this system has the potential to drop
several inches of snow from Monday night through Tuesday night. A
added concern with this storm is the potential for gusty winds late
Tuesday which could cause blowing and drifting snow making travel
difficult. Will continue to monitor the development of this storm
over the next couple days.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1245 PM CST Thu Jan 19 2017

Forecast challenge is areal coverage of fog tonight. Model
differences creates low confidence in spacial coverage of the fog
with higher confidence along and east of a line from North Platte
to Ainsworth. A boundary will move southeast with the eventual
placement to create LIFR conditions to the east or southeast.
Further northwest to include Valentine VFR conditions will
continue. The LIFR conditions over the southeast half of the area
will begin to lift between 15Z to 18Z.




SHORT TERM...Buttler
AVIATION...Keck is the U.S. government's official web portal to all federal, state and local government web resources and services.