Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 112347 AAB
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
547 PM CST Thu Jan 11 2018

.SYNOPSIS...
Issued at 332 PM CST Thu Jan 11 2018

H5 analysis from this morning had a broad trough of low
pressure across the central CONUS. This trough extended from the
northern plains, south into southern Texas. Within this trough of
low pressure, several embedded disturbances were noted. One over
eastern Kansas, a second over southern Texas, and a third over
eastern Montana. Ridging was present from the Eastern Pacific north
into northern California, while a second ridge extended up the east
coast of the United States. Upstream of the western CONUS ridge, a
strong shortwave was present off the coast of Washington state and
showed up nicely on WV immagery this afternoon. At the surface: High
pressure was anchored across the northern plains today with it
centered over eastern Montana. Low pressure was located over the UP
of Michigan with a cold front extending ssw into the Ozarks and
eastern Texas. Gusty northwesterly winds were present across western
and north central Nebraska this afternoon, and have only recently
begun to diminish across the west. Temperatures were cold this
afternoon with readings ranging from 9 at O`Neill to 22 at Ogallala
and Imperial.

&&

.UPDATE...
Issued at 543 PM CST Thu Jan 11 2018

The rapid refresh models are a few hours slower with the onset of
snow Friday morning; suggesting an arrival time around 12z-15z. A
new forecast is in place for this feature which uses a blend of
the previous forecast, the 18z GFS and NAM, the rapid refresh
models and the ARW/NMM models. This increases snowfall amounts a
few tenths of an inch for accumulations of 1 to 2 inches across
ncntl Neb.


&&

.SHORT TERM...(This evening through Friday)
Issued at 332 PM CST Thu Jan 11 2018

The primary forecast challenge through Friday revolves around a
shortwave and lee side low sliding southeast off the Rockies,
bringing a reinforcing shot of cold air and light snow.

This evening and tonight... Mostly clear skies will continue through
the evening as breezy northwest winds slowly wane. Clouds return
after midnight as the shortwave approaches the area. In the
meantime, conditions along with the fresh snow pack will be
favorable for a period of decoupling and efficient cooling. Lowered
min temps slightly, resulting in lower teens far west to just below
zero north central. Wind chills are not a major concern as winds
will be rather light. Slowly increased PoPs after 06z near the Pine
Ridge and expand east across the Sandhills toward 12z, which is the
optimistic approach to the higher resolution solutions.

Friday... Expect the area of light snow to be underway across the
northern Sandhills by mid-morning and north central Neb in the
afternoon. This time period lines up with the best fgen and highest
moisture in the mid levels and proximity to the low at the sfc (in
eastern CO). The most consistent signal of lift and saturation
(which are also colocated in the DGZ) is across the northern half of
the CWA, hence the likely PoPs. The overall moisture content is much
lower with this system compared to last night`s (Td`s a good 20F
lower), so kept accumulation light. However, given greater SLR`s and
efficient dendrite production, raised totals a little to around 1
in. north of Hwy 2 and up to 1/2 in. south. Winds will remain under
15 mph, so not expecting much blowing snow. Highlighted this event
in the HWO. For max temps, guidance came in much cooler as the
Arctic high tries to nudge into northern Neb. H85 temps fall from -
7C at 12z to -15C at 00z. Went with a general blend, resulting in
single digits in north central Neb, teens across the heart of the
Sandhills, and 20s southern panhandle/far SW.

.LONG TERM...(Friday night through Thursday)
Issued at 332 PM CST Thu Jan 11 2018

Friday Night through Sunday...High pressure will build
south southeast across North Dakota into nern South Dakota Friday
night with the core of the coldest arctic air sliding just to the
east of the forecast area. Regardless, with fresh snowcover and
clear skies, hedged the forecast toward the cooler MET guidance.
This yielded lows from -6 in the northeast to around 5 above in the
southwest. Winds are expected to be minimal overnight so no wind
chill concerns are expected attm. High pressure will build southeast
into northern Iowa on Saturday. Southerly winds will increase across
the forecast area Saturday afternoon, recycling arctic air into
central and eastern portions of the forecast area. Further west,
warmer air will try to push into the eastern panhandle where highs
may reach the lower 30s. Elsewhere, highs will struggle to get out
of the teens. A weak disturbance will track from the Dakotas into
northeastern Nebraska. A weak clipper will track from western South
Dakota into northern Nebraska overnight. Am expecting lows to be
reached Saturday evening with readings actually warming overnight,
as guidance depicts. As the clipper slides southeast, the threat for
snow will increase overnight from north central into northeastern
portions of the forecast area. With good timing and low track
agreement noted between the NAM and GFS solutions, decided to
increase pops over the superblend and go low end likely pops in the
far northeast. Qpf will be fairly light with this system and any
snow accums will be an inch or less. Westerly winds will push into
the western forecast area Sunday behind the exiting clipper. This
will temporairly warm temps into the 40s. An approaching arctic
front Sunday afternoon will push into far northern Nebraska with a
slight chance for light precipitation during the late afternoon
hours.

Sunday night through Thursday: An arctic cold front will dive
south across Nebraska Sunday night with an increased threat for
light snow. Again, any accums will be light with only a dusting to
a half an inch expected attm. Temperatures Monday will be in the
teens to lower 20s. Monday night, arctic high pressure will build
into the eastern Dakotas. Lows will range from around 5 above in
the far southwest to -10 in the northeast. Wind chills attm are
forecasted in the -20 to -25 degree range across the northeastern
forecast area and will continue to hit the threat in the HWO. The
arctic high will slide slowly southeast into the mid week with a
slow warmup expected. After highs in the teens and 20s Tuesday,
readings will reach the 20s, 30s and 40s Wednesday, followed by
30s and 40s for Thursday. Dry conditions are expected in the
remainder of the forecast period as a more zonal pattern aloft
settles in.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 503 PM CST Thu Jan 11 2018

VFR is expected all areas tonight through 12z Friday morning.
Thereafter, the disturbance moving the Pacific Northwest this
afternoon will move thorugh wrn and ncntl Neb producing fairly
widespread MVFR/IFR cigs and vsby in snow. These conditions should
last through 00z Friday evening.


&&

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

$$

UPDATE...CDC
SYNOPSIS...Buttler
SHORT TERM...Snively
LONG TERM...Buttler
AVIATION...CDC



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