Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 201759
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1259 PM CDT Sat May 20 2017

.SHORT TERM...(Today and tonight)
Issued at 412 AM CDT Sat May 20 2017

A slow-moving upper low will be centered near North Platte this
morning, wrapping cool and wet conditions across much of the
forecast area until the low eventually moves out of the state this
evening. The airmass is actually cold enough for some snow to mix in
this morning, how far south and east the snow mixes in will be the
main forecast challenge this morning. Some accumulation is already
evident on web cams in the Panhandle this morning. Most of the
accumulation will be on elevated surfaces, bridges, and vegetation
but some cameras are showing slushy rural roads as well. The coolest
850MB temperatures have yet to move in with the center of the low,
so the trend is expected to be for more snow mixing in with each
hour, especially as you head further west. There will be a battle
after sunrise however and given how close temperatures are hovering
around freezing, the longwave radiation with the morning sun is
expected to win out, especially as the time moves closer to noon.

Given the widespread precipitation, abundant cloud cover during the
day and cool airmass it should not be a surprise that high
temperatures will be well below normal. Very cool conditions will
continue with highs in the 40s to possibly mid 50s far southwest
Nebraska.

Skies will be on a clearing trend tonight, allowing temperatures to
plummet toward freezing for Sunday morning. Winds will also be much
lighter as the surface decouples from the moderate 10 to 20kt
northwest winds aloft. Relative humidities will remain around 100
percent as well. All of these ingredients will come together for
frost Sunday Morning, especially along river beds and low lying
areas. Take the time to cover your plants if possible. The best
chance for frost will be in low lying areas along and west of a line
from Merriman to Brady. The limiting factor for points north and
east will be those breezy northwest winds aloft.

.LONG TERM...(Sunday through Friday)
Issued at 412 AM CDT Sat May 20 2017

Amplified pattern is set to develop across the conus late this
weekend and into next week.  Strong ridging will encompass the pac
northwest south through the desert southwest.  East of the Rockies,
broad cyclonic flow will persist into the western New England
States.  Overall, the long range models are in acceptable agreement
with the large scale, but differ somewhat on the timing and strength
of several smaller scale shortwaves that are forecast to potentially
impact the cwa late Sunday and early next week.  The certainty of
the forecast lies in below average temperatures Sunday and into
Wednesday.  Thereafter there`s a general consensus that positive
heights will build across the northern/central plains from the west,
which will allow for seasonal, or possibly above average
temperatures late next week.  There`s the potential for another
round of frost impacting northwestern and far western portions of
the forecast area Wednesday morning as drier air works in from the
west just ahead of the building mid level ridge. The guidance is
suggesting mid-30s at this point for lows, will monitor. Otherwise
there`s below average certainty with the QPF/POP forecast as chances
are tied to small amplitude shortwaves passing through the mean
flow. The wave on Sunday still appears to have a greater impact west
and south of the forecast area.  Will continue to trend pops lower
and only carry a slight chance across our far southwest and south
into early Monday.  The Monday evening shortwave arrives with
greater DPVA/forcing for the forecast area, but no real source of
gulf moisture.  We should see greater shower coverage across the
forecast area, but qpf amounts should be on the lighter side.  A
general blend of the available medium range guidance suggest 40 pops
with less than a tenth of an inch qpf, impacts should be minimal.
Beyond Tuesday the next real shot at qpf arrives early Friday as
southwest flow in advance of a western conus trough directs a weak
wave across the plains.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1242 PM CDT Sat May 20 2017

Radar shows a broad swath of precipitation that continues to
affect much of western and north central NEB with the latest
surface plot and web cams showing a mix of precip types (rain,
rain/snow, or all snow). Snow or a rain snow mix appears largely
confined to higher elevations and intense bands of precipitation
that are located over the central and southeastern Sandhills.
Elsewhere, precipitation type is mostly rain. Snow is slushy on
paved roads and is struggling to stick, except on grasses, unpaved
roads, and higher surfaces with there is minor accumulations. A
change over to all rain is expected early this afternoon. Latest
surface plot shows mainly sub-VFR ceilings, mainly MVFR to IFR.
Some restrictions to visibility is taking place as well within
areas of heavier precipitation.

Current thinking is precipitation will start diminishing in areal
coverage late this afternoon with it slowly coming to an end in
far north central NEB this evening. Otherwise, ceilings will
improve mid-late afternoon to higher MVFR to low- end VFR (less
than 7 kft). Thereafter, ceilings will continue to improve with
decreasing clouds from west to east this evening with clouds
sticking around late tonight only in portions of far north
central NEB.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 3 AM CDT /2 AM MDT/ to 8 AM CDT /7 AM MDT/
Sunday for NEZ004-005-008>010-022>029-035>038-056>059-070-071-
094.

&&

$$

SHORT TERM...Allen
LONG TERM...Jacobs
AVIATION...ET



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