Scientific Forecaster Discussion
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Area forecast discussion
National Weather Service Omaha/valley NE
626 PM CDT Wed Oct 23 2019
..updated aviation forecast discussion...
issued at 305 PM CDT Wed Oct 23 2019
Tonight through Thursday night:
Early-afternoon water vapor imagery depicts an active mid-level
pattern over the northern plains into mid MO valley. A lead
vorticity lobe was translating east along the Minnesota-Iowa border while
a stronger upstream perturbation was digging through central South Dakota.
The latter feature will continue southeast through the mid MO
valley this evening in tandem with a surface cold front. Steep
lapse rates and forcing for ascent associated with that system
will support isolated showers or sprinkles across mainly our
western counties through the remainder of the afternoon into
A weak surface ridge will build through the area on Thursday,
yielding dry and cooler conditions with highs in the mid to upper
Friday through Saturday night:
A split-flow, mid-level pattern will evolve, featuring a
subtropical branch low tracking from the Southern Plains into the
Ozarks. Meanwhile, a more prominent polar-branch trough will
amplify over western Canada into the northern rockies. The polar-
branch regime will encourage the advance of another surface cold
front through the northern plains on Saturday. Ahead of the front,
a persistent low-level warm advection pattern will promote highs
in the mid to upper 50s on Friday, and upper 50s to mid 60s on
Sunday through wednesday:
By late this weekend into the middle of next week, we begin to
see growing model spread in the handling of the upper-air pattern.
The 12z run of the European model (ecmwf) and Canadian models depict a continued
split-flow pattern through Monday before forming a large trough
over the western and central U.S. On Tuesday and Wednesday. In
contrast, the 12z run of the GFS deterministic and gefs ensemble
mean indicate a much quicker transition to the large-scale trough
over the central U.S. On Monday. While both scenarios indicate
the movement of the above-mentioned northern plains cold front
through the area on Sunday, timing of a secondary, more
substantial surge of colder air remains more in question. The GFS
solution would indicate the secondary cold air intrusion occurring
Monday and Monday night along with some light precipitation.
However, the European model (ecmwf) and Canadian models delay the secondary front
until Monday night or Tuesday, and indicate considerably more
precipitation, some of which could be snow.
What we know is that it's going to turn colder. Highs in the 40s
and 50s on Sunday will fall back to largely 40s on Monday. And
while we will indicate largely 40s on Tuesday and Wednesday, it's
quite possible that temperatures will be colder than that. There
will also be a chance of precipitation. Specific type and amounts
remain uncertain at this time, but some snow is possible.
Aviation...(for the 00z tafs through 00z Thursday evening)
issued at 617 PM CDT Wed Oct 23 2019
A surface trof is keeping winds out of the north this evening and
producing a broken to overcast deck around 2000ft above ground level moving in
from the northwest. Expect MVFR conditions to persist through
about 07z Thursday morning before the deck breaks and clears.