Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 192335 AAA

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
535 PM CST Sun Feb 19 2017

Issued at 312 PM CST Sun Feb 19 2017

H5 analysis this morning had a highly amplified pattern
across the CONUS. A closed low was noted over North Carolina with a
trough extending south into Florida. Further west, ridging aloft
extended from Louisiana north into northern Minnesota. West of this
feature, a  closed low was noted over northern Arizona with a trough
extending south into western Mexico. West of the trough, low
amplitude ridging was building into southern California with another
trough of low pressure noted upstream just off the coast of Oregon
and Washington. Across the central plains, abundant mid and high
level cloudiness continues to stream into the forecast area from the
swrn CONUS. A surface trough of low pressure has developed along the
front ranges of Wyoming and Colorado this morning and has led to
increasing southerly winds across western and north central
Nebraska. Winds were gusting as high as 35 MPH at Broken Bow. Under
mostly cloudy skies, temperatures this afternoon were generally in
the mid to upper 60s.


.SHORT TERM...(This evening through Monday)
Issued at 312 PM CST Sun Feb 19 2017

A very mild night is on tap for the region, as low level gulf
moisture continues to surge northward ahead of a developing surface
low in eastern Colorado. This area of low pressure will track
northeast tonight as a weakening upper level low also moves
northeast across the area. Despite good moisture both at the surface
and aloft, precipitation chances look small. Lift is weak throughout
the night, and some weak frontogenesis develops toward mid evening
into the early morning hours, and a few isolated showers could
develop. Most models are dry, but cannot rule out a shower.
Otherwise very mild tonight, with the cloud cover and moisture
keeping lows in the lower 50s across eastern potions of north
central Nebraska. A bit drier air in western Nebraska will allow
temperatures to fall into the mid and upper 30s. As the surface low
moves northeast into south central South Dakota by morning, a wind
shift to the northwest will occur from west to east.

Another mild day Wednesday, with full sunshine in all areas by
afternoon. Mild Pacific air and downslope northwest winds will
continue to aid the warm temperatures, with highs in the 60s.

.LONG TERM...(Monday night through Sunday)
Issued at 312 PM CST Sun Feb 19 2017

Mid range: Monday night through Wednesday: In the mid range,
temperatures are the main forecast concern. Drier boundary layer air
will continue to push into western and north central Nebraska Monday
night behind the exiting system from Monday. Light westerly
downsloping winds and a dry airmass upstream will drop temperatures
fairly quickly Monday evening. Based on the latest MET and MAV
guidance, decided to drop lows below the forecast blender based on
the degree of dry air and light westerly drainage winds. This
yielded lows in the upper 20s in southwestern Nebraska with middle
30s expected in the sandhills and portions of north central Nebraska
where winds may be slightly stronger overnight. Strong low level
warm air advection will commence Tuesday morning. By afternoon, a
surface trough of low pressure will extend from northeastern to
southwestern portions of the forecast area. INVOF of the trough
winds will be fairly light, however, clear skies, light winds and
H85 temps in the middle to upper teens, will push highs into the
70s. Some upper 70s are even possible in southwestern Nebraska where
H85 temps approach 17C around 00z Wednesday. The latest guidance
highs came in warmer this morning with even a mention of 80 for
North Platte Tuesday with the 12z MAV guidance. FWIW, the daily
record high for North Platte Tuesday is 75 while the all time record
high is 79. Right now, I feel confident in reaching a daily record
high for January 21, but think obtaining 80 degrees, may be a tad
ambitious right now. One other concern for Tuesday afternoon is fire
weather concerns, particularly across southwestern Nebraska. Right
now, widespread 10 to 15 percent minimum relative humidities, appear
on track based on the temperature forecast, however, winds will be
light underneath the surface trough and these light winds should
keep us from reaching critical fire danger criteria. The surface
trough will slide east of the area Tuesday night with a weak cool
front pushing into the forecast area on Wednesday. Highs Wednesday
will run around 10 to 15 degrees cooler than Tuesdays highs as H85
temps drop of into the single digits C.

Wednesday night through Sunday: In the extended, precipitation
chances Thursday into Friday, in association with a significant
upper level trough of low pressure, is the main forecast concern.
On Wednesday night a strong upper level trough of low pressure
will lift east of the Pacific northwest, approaching the central
Rockies by 12z Thursday. A lead disturbance will track across the
high plains Wednesday night, leading to an increased chance for
showers across northern and northwestern Nebraska. On Thursday, as
the upper level trough of low pressure will emerge onto the
central plains. At this point, colder air will work into the
system from the north, increasing the threat for snow late
Thursday into Thursday night. As was the case yesterday, the
models are having a hard time with the track and strength of the
upper level system. The GFS lifts this feature across the central
plains as an open wave while the ECMWF and Canadian close the
system off over central or eastern Nebraska late Thursday.
Regardless, high pops and strong winds continue to be in order for
this system. The main question is, whether or not the system will
close off and the degree of deformation snow that develops on the
back side of the system Thursday night into Friday. This will be
the main forecast aspect which will have to be resolved over the
next couple of days. With the wind and snow threat in the
forecast, will continue to highlight it in the HWO.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 535 PM CST Sun Feb 19 2017

VFR is generally expected overnight through Monday afternoon with
a couple of caveats.

1-MVFR cigs across KS...KGBD and KHUT...are forecast to move north
into Cntl Neb (hwy 183 and east) this evening and exit east with
the passage of a Pacific cold front Monday morning. It is possible
these CIGS will move west to KLBF and KVTN.

2. Thunderstorms are underway across Scntl Nebraska. Scattered
thunderstorms are expected this evening across Ncntl Nebraska and
tonight across Western Nebraska with the approach of a Pacific
cold front.




LONG TERM...Buttler
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