Scientific Forecaster Discussion
fxus63 klbf 052358
Area forecast discussion
National Weather Service North Platte NE
558 PM CST Thu Dec 5 2019
Short term...(this evening through Friday night)
issued at 234 PM CST Thu Dec 5 2019
Impacts/highlights and confidence: the main sensible weather
highlight is fog/stratus tonight-early morning. Confidence high
for stratus. Moderate confidence in fog with thinking time frame
of concern will be late tonight-early morning along and west of
Highway 83. Nbm and sref show some of signal, stronger in the
former with deterministic guidance supporting the main risk area
of the eastern Panhandle east to Highway 83.
Discussion: latest water vapor imagery show a mid-level shortwave
trough near The Four Corners region moving east and a long wave
trough downstream extending south across the northeast Continental U.S..
latest radar display shows weak returns across southwestern NE
west and south with precipitation near the Front Range. Recent
surface analysis shows broad surface low pressure to the east with
a central pressure of about 1005 mb in the northern Texas Panhandle
that extends northeast to northern WI. Low stratus has increased
and has spread across western and central South Dakota today per daytime
snow-fog imagery, and is now onto the Nebraska-South Dakota border.
The aforementioned shortwave trough/positive pv anomaly will track
east across the southern High Plains early tonight moving into the
lower Mississippi Valley tomorrow morning. Otherwise, cold air
moves in as surface high pressure evolves from the Canadian
prairies into the eastern Southern Plains by late tonight. This
sets the stage for low stratus to spread tonight. Low stratus is
anticipated to stretch area-wide before midnight CST. Concerns
turn then to fog potential with some uncertainty associated with
coverage and magnitude. Turbulent mixing will be a concern but
winds slack off late tonight. Thinking though somewhat mild
temperatures today combined with residual moisture, snow melt, and
little change in the hydrolapse late tonight-tomorrow morning per
soundings will promote patchy/areas of fog. Current thinking is
greatest coverage will be in far western NE and generally along
and west of Highway 83. Skies clear tomorrow with a ridge aloft
building in over the central-northern rockies.
Long term...(saturday through thursday)
issued at 234 PM CST Thu Dec 5 2019
Impacts/highlights and confidence: highlights include chances for
precipitation Sunday night-Monday, albeit of low impact, and
colder air Monday through Thursday. Confidence is low-moderate for
the aforementioned precip chances. Impacts from cold look to be
limited given magnitude and forecast temperatures, but highs
still below seasonable temperatures.
Discussion: low amplitude ridge in place over the central Continental U.S.
Centered over the northern-central rockies early Saturday. High
temperatures peak Saturday and Sunday as the ridge dampens and
zonal flow develops overhead Saturday and Sunday. Next upper level
trough off the West Coast early Saturday is expected to move into
the central Great Basin Sunday and will move into the region
Sunday night. That said, thinking best chances for precip lies
Sunday night across northern neb, albeit still low elsewhere.
Upper level trough is then expected to persist and extend from
western Ontario to the lower Mississippi Valley by Tuesday. A cold
front late Monday night will bring chilly temperatures into the
area for Tuesday. Highs Tuesday are forecast generally 8-18
degrees below seasonable temperatures with colder than seasonable
temperatures forecast through Thursday. That said, latest naefs
and European model (ecmwf) ensemble guidance showing the forecast isnt that cold
with respect to climo with colder air more apparent to the
northeast. Lows Tuesday and Wednesday morning are forecast near
seasonable to as much as 10 degrees below normal.
Aviation...(for the 00z tafs through 00z Friday evening)
issued at 548 PM CST Thu Dec 5 2019
Lower ceilings will continue to spread across the forecast area
this evening bringing IFR conditions. Areas of fog will develop
overnight generally along and west of Highway 83 which will affect
kvtn and klbf. By mid-morning fog and stratus will lift and
conditions will become VFR by early afternoon.