Area Forecast Discussion
Issued by NWS North Platte, NE

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261
FXUS63 KLBF 180427
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1127 PM CDT Tue Apr 17 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 256 PM CDT Tue Apr 17 2018

Tonight and Wednesday. There remains good agreement on the track and
timing of the next winter system that is scheduled for tonight and
tomorrow.  The GFS, ECMWF and NAM have all increased QPF amounts
across northern Nebraska with the latest consensus around a third of
an inch across our northern tier and ALL keep trending south with
the axis of precipitation.  Across the Sandhills, QPF amounts of up
to two-tenths of an inch are possible. The onset of the
precipitation continues to slow with the various model camps as well
indicating the bulk of the QPF after 03z this evening. The trough
responsible for the QPF is rather sharp, so we would expect a fairly
progressive nature, but it does close off of low to our east and
takes on a slight negative tilt, so precipitation may linger over
our far northeast into late morning.

Warm air advection and strong dynamics are the primary player of the
precipitation process, though some convective element is anticipated
as the latest solutions show an area of neg EPV.  With that, we are
a bit concerned that a brief period of wintery mix may accompany the
precipitation across our north and Sandhills overnight, due to the
warm layer/air advection, but this should be short.  Initially
thermal profiles will support rain that will change to snow late
overnight.  Latest SLRs are indicative of late Spring, so below
average.  An inch or two may accumulate with the heaviest
anticipated over northern portions of Keya Paha and Boyd Counties,
so **IF** an eventual winter headline is needed, those counties
would be the likely candidate.  At this point the accumulations and
timing would suggest no headlines are needed, and since winds will
largely be below 20mph during the peak intensity of QPF, blowing
snow is not anticipated.

Southwest of the main precipitation area winds will be elevated
through much of the overnight as a tight surface pressure gradient
develops in post frontal conditions.  Wind gusts in excess of 30-40
mph are possible overnight, especially across southwest Nebraska.

Again the system is fairly progressive with shortwave ridging
building to our west on Wednesday.  Increasing subsidence will be
offset by low level CAA with a modified Arctic/northern Pacific high
to keep temperatures cool Wednesday.  So after lows in the 30s
overnight, we should see 40s and low 50s for highs Wednesday.  This
is below normal.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 256 PM CDT Tue Apr 17 2018

Mid and long term solutions in fair agreement. Timing issues and
amount of cooler air remains in question. Upper low moves to the
east Wednesday night with the possibility of some isolated showers
across northeast Nebraska. Ridge moves east behind the exiting
system and decreasing clouds over night will see lows in the upper
20s. Temperatures rebound into the 50s over most of the forecast
area on Thursday as upper low approaches from the west. Gulf opens
Thursday night as upper low approaches the four corners region.
Continued dry over western Nebraska.  Through the day on Friday
upper low over the four corners region takes a southeast trajectory
into the Texas Panhandle as a stronger northern stream dominates.
This would leave best chance for precipitation over southwest
Nebraska. Some mixed precipitation occurring over the Sandhills
through the morning Friday changing to all rain as the temperatures
rise to around 50. Best forcing with strong low level jet and 700mb
mid level forcing along the inverted trough will bring moderate rain
to southwest Nebraska north to Highway 2 through the evening. Then
you can expect a mix through the early morning hours through the
early morning hours Saturday. Precipitation forecast erodes from
north to south through the day on Saturday as the upper support
pulls away. Ridge and warmth rebound Sunday and Monday with
temperatures topping out in the 60s and dry. Monday night clouds
increase from the west with light rain through the evening and a
change over towards sunrise.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1051 PM CDT Tue Apr 17 2018

Local radar display shows a swath of precipitation covering much
of the area outside the southeast Panhandle moving gradually east.
Rain has changed over to snow across northwestern NEB into the
central Sandhills, elsewhere rain is predominant. Latest surface
obs show IFR ceilings in northwestern NEB and MVFR/low-end VFR
(less than 6 kft) ceilings elsewhere. Rest of tonight, precip is
expected to continue to push east moving out of southwest NEB
during the small hours. Thereafter precip is expected to affect
mainly north central NEB late tonight into early morning tomorrow.
Of which, rain will changeover to snow across the remainder of
the Sandhills and northern NEB the next couple hours. Winds will
remain elevated rest of tonight, mainly out of the northwest, with
some gusts up to 40 MPH possible across parts of southwest NEB
overnight. Looking ahead, skies will be clearing late tonight
into early tomorrow morning across southwest NEB and the eastern
Panhandle with clouds then decreasing over the Sandhills tomorrow
afternoon. Otherwise, sub-VFR ceilings are expected to linger
across parts of north central NEB during the day.

&&

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

$$

SHORT TERM...Jacobs
LONG TERM...Power
AVIATION...ET



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