Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 270902

Area Forecast Discussion
National Weather Service North Platte NE
402 AM CDT Mon Mar 27 2017

.SHORT TERM...(Today and tonight)
Issued at 358 AM CDT Mon Mar 27 2017

Main sensible weather concerns in the short term package include:
fog this morning and rain chances spreading across western NEB
mainly after midnight. 11-3.9 micron satellite imagery shows
stratus/fog spreading slowly westward across north central NEB
into the central Sandhills. Mostly clear skies are evident across
southwest and parts of the eastern NEB Panhandle. Latest surface
plot shows visibilities have been reduced at KTIF, KANW, and KBBW
between 1/2SM and 13/4SM. Areal coverage of fog appears to be
patchy at this time based on viable web cams and surface obs.

Fog will be a threat across much of western and north central NEB
given the moisture in the boundary layer and low dew point
depression. Further fog formation is expected this morning along
with the westward expansion of fog/stratus given light winds,
variable or calm, that are present. Across southwest NEB
favorable radiation cooling conditions are present as well. A
challenge will be how prevalent visibility 1/2SM or less will be.
Current thinking is the areal coverage of sub-1SM visibility will
likely be over a larger area than yesterday. However, don`t think
a headline is necessary based on SREF probabilistic products,
latest deterministic guidance, and given previous episodes. Though
will need to monitor it this morning. Low clouds and visibility
are expected to see improvement with lift and dissipation
beginning near mid morning across much of the area.

Latest water vapor imagery shows multiple disturbances, of which
upstream a northern and southern stream trough are located
offshore the Pacific Northwest and entering California,
respectively. Meanwhile, a short wave ridge is tracking into the
Central High Plains. The positive PV anomaly moving into
California will track into the southwest US today and phase with
the northern stream trough. Thereafter a closed low is expected to
develop over the Four Corners region late tonight/early tomorrow
morning. In the meantime, the 500 hPa pattern aloft will be
becoming more amplified today with the ridge moving into the Lower
and Middle Mississippi Valley. Southerly flow will develop this
afternoon with warmer temperatures being drawn northward into
western with 850 hPa temperatures increasing to 6-13 C, warmest
from west to east. As southerly flow takes hold tonight, moisture
will be transported northward with precipitable water values
increasing to near 0.75 inches across western NE late tonight
precipitable water % of normal will be increasing to 150% in the
central Sandhills to near 200% over far southwest NEB. As the
system moves eastward and forcing for large scale ascent spreads
with an enhanced zone of mid tropospheric deformation,
precipitation chances are expected to increase over western NEB
after midnight into early morning Tuesday. Of which, the greatest
chances are expected over far southwest NEB and the eastern NEB
Panhandle after midnight.

.LONG TERM...(Tuesday through Sunday)
Issued at 358 AM CDT Mon Mar 27 2017

The major story for the extended period will be the developing low
moving across the region on Tuesday through Thursday morning.
This system will bring some much needed rain to the forecast area.
Current thinking is that precipitation will remain mostly all
rain as 850 mb temperatures will range from 0 to 5 degrees C. A
few isolated chances exist where some wet snowflakes could mix in
with the rain. These chances will mainly be in the early morning
hours on both Wednesday and Thursday. However, even if snow can
make through the relatively warm boundary layer, snow will have a
difficult time accumulating on the wet ground from the rain and a
fairly warm surface. Therefore, no accumulations are expected. The
rain/snow mix would be short lived as temperatures quickly warm
after sunrise.

Precipitation will slowly migrate southeastward on Wednesday
evening as the low moves off to the east. Expect precipitation
to move entirely east of the forecast area by 12-15Z Thursday. A
brief dry spell returns to north central Nebraska as upper level
ridging returns to the central US. Dry conditions will last
through Friday.

The next chance for precipitation will arrive next weekend as
another low develops off the Rockies and moves across Kansas.
Again, precipitation should be mostly rain, but there`s a chance
on Saturday morning that some snow will fall. It`s too early in
the forecast to determine if any accumulations are possible. Will
have to monitor this system over the coming days as a shift in the
track will change the precipitation type significantly.

For temperatures, the start of the long term (Tuesday) will begin
cool (highs in the upper 40s to low 50s). High temperatures
return to the mid 50s for Wednesday through Saturday. Low
temperatures start off in the mid to upper 30s on Tuesday night
before dropping into the low to mid 30s through the remainder of
the week and into Saturday night.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1225 AM CDT Mon Mar 27 2017

Stratus trying to move west late tonight. Stratus has made it as
far west as KBBW to KANW line. Skies clearing out west of this
line with a few mid cloud decks. A range of dew point spreads
across western Nebraska - ranging 10 degrees. Some stratus and
patchy fog expected over western Nebraska as temperatures cool
towards sunrise but not as widespread as expected before. Skies
will be clear over western Nebraska Monday with winds below 10




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