Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 190130
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
730 PM CST Wed Jan 18 2017

.SHORT TERM...(This evening through Thursday)
Issued at 328 PM CST Wed Jan 18 2017

The main forecast challenges during the short term... through
Thursday afternoon... are temperatures and fog potential.

Went with a general blend of the MET, MAV, and ECS for tonight`s
lows, giving teens in the panhandle and western Sandhills and 20s
elsewhere. A weak trough at H85 approaches the CWA overnight and
stalls across the panhandle during the day Thursday. This leads to
weak downslope across the west and southerly flow and temps 4-6C at
H85 across the east. Moisture content is rather impressive to the
south and east with dew points in the 30s and 40s, and south winds
will keep drawing that air ahead of the trough. SREF guidance is
showing high probabilities of stratus and/or fog generally east of
U.S. Hwy 83 tonight into Thursday morning, and forecast dew point
depressions are 3F or less. Expanded mention of fog west from
previous forecast, essentially lining up with Hwy 83.

For Thursday, bumped max temps up a degree or two across the west to
account for continued downslope flow and mostly sunny skies. Made
little change across the east, where stratus will likely hold on for
much of the day. NAM soundings show near saturation in the lowest
100-150 hPa at KBBW and KONL. Cannot completely rule out drizzle,
but with lift being marginal at best, held off on any mention
through the 00z period.

.LONG TERM...(Thursday night through Wednesday)
Issued at 328 PM CST Wed Jan 18 2017

The GFS...NAM and ECM all show stratus Friday morning from near
highway 83 east through Ern Neb. The models show these low clouds
lasting most or all of the day Friday which would certainly disrupt
the heating cycle. None of the models suggest any gradient in the
forecast high temperatures because of an increase in midlevel
cloudiness from the west. The low clouds hold lows Thursday night to
the lower 30s east of highway 83 with teens and 20s across a clearer
area over Wrn Neb.

There is little change in the forecast for the weak disturbance
lifting through Ern Neb Friday night and Saturday morning.
Temperatures support a mixed rain and snow event. The GFS suggests
there could be a sliver of freezing rain along the transition line
from rain to snow. This feature was not shown by the NAM because it
is a very dry solution and just shows rain with no transition to
snow. The ECM was also very dry like the NAM and shunted nearly all
of the precipitation east of Ncntl Neb.

The ECM and GFS have lessened wind speeds Sunday to northwest at 15
to 25 mph. H850mb winds are running about 30kt-35kt in both models
with 500m AGL winds around 20kt...about 20 mph at the SFC.

The GFS and GFS ensemble trended north a bit with the big storm
heading for the Cntl/Nrn Plains Tuesday suggesting Nrn Neb would
experience the best forcing for significant snowfall. This might not
be important since both models show the H700mb low over Nrn KS and
this is very favorable for snow along Interstate 80 and north.

Meanwhile the ECM breaks the system into 2 staggered disturbances
which is a big change over the previous model run. This would cut
snow chances way down. A check on the Gridded MOS from MDL indicates
heavy snow Tuesday across the Dakotas with light to moderate
accumulations across Wrn Neb.

There is significant variability in the model suite. By virtue of a
calculated model consensus...POPs have been lowered slightly to 50
to 70 percent and shifted north away from scntl Neb. Snow chances
operate from Monday night through early Wednesday morning and the
model consensus suggests this could be a 24-hour event in some
areas.

The temperature forecast Thursday night through Wednesday follows a
blend of model data plus bias corrected guidance. This suggested
about a 1 degree increase in high temperatures. It also lowered min
temperatures across Western Nebraska but tended to increase lows a
degree or so across Ncntl Nebraska. Highs mostly in the 40s to near
50 are expected Friday through Monday. 30s should continue across
the northwest where snow is on the ground. 20s and 30s are expected
Tuesday and Wednesday. The storm system next week will be tapping
Pacific high pressure which tends to produce mild weather.

Lows fall into the teens and 20s with lower 30s in the moist air
east of highway Thursday night and Friday night.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 730 PM CST Wed Jan 18 2017

Stratus and fog, possibly dense, will develop tonight and persist
into Thursday morning across the southeastern half of the forecast
area. The area looks to be east of a line from North Platte
through Bassett. Have lowered the visibility to 1sm from 10z-16z
along with sct003. will need to monitor closely, with LBF
potentially falling to LIFR or even VLIRF conditions.

&&

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

$$

SHORT TERM...Snively
LONG TERM...CDC
AVIATION...Roberg



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