Scientific Forecaster Discussion
fxus63 kgid 122117
Area forecast discussion
National Weather Service Hastings NE
317 PM CST Tue Nov 12 2019
Short term...(this evening through wednesday)
issued at 315 PM CST Tue Nov 12 2019
Main concern is potential for wintry mix Wednesday morning.
Afternoon water vapor reveals a moderately amplified pattern
across the conus, with a deep trough from the Great Lakes into
Ohio River valley and upper ridging along The Rockies. In between,
we are left with swift northwest flow. Our next disturbance can be seen
moving onshore the pac NW, and this wave will quickly translate southeast
in the fast upper flow and be the main weather maker for Wed. 20z
sfc analysis shows a tight pressure gradient across the County Warning Area due
to departing seasonably strong high pressure to the se, and
deepening Lee troughing along the High Plains ahead of our next
disturbance. As a result, have been seeing srly wind gusts around
35mph for much of the cwa, for much of the daytime hrs.
Temperatures, which have been slow to rise due to very cold start
this am, are currently in the low 30s to low 40s. Have been
monitoring rhs this aftn as some concern for near-critical fire wx
for a few hrs this aftn for areas S of a line from Phillipsburg
to Beloit. However, thus far, it seems we'll fall short of
reaching that threshold for the 3hr minimum, so do not plan on
adding mention to severe weather potential statement attm.
Tonight: dry and warmer. Combination of incr high clds and steady
S winds will keeps temps warmer overnight, likely in the low to
mid 20s. Have maintained a dry forecast as soundings indicate deep
dry air thru 12z.
Wednesday: the aforementioned clipper will move in from the northwest
Wed am, but will likely be lacking in moisture. There is good
model consensus that most, if not all, quantitative precipitation forecast will be limited to our
far NE cwa, or even further to the north and east. Forecast soundings
show significant dry air that will need to be overcome, but
moderate to (briefly) strong lift may eventually allow for top-
down saturatation for a few hrs. If this occurs, ptype could be
messy given wet bulbing effects under strongest cores competing
with low-level diurnal heating. Think very light sleet changing to
sprinkles/lt rn should be the primary transition in the 12z to
17z time frame, with any pcpn after 17z being all liquid. Do not
anticipate much, if any, negative impacts as the sleet may not
even occur at all due to the dry air, and by the time saturation
incr, sfc temps are rising above freezing. Otherwise, the most
noticeable wx imapct will be cldy skies and northwest breezes. Highs will
range from chilly low 40s NE where clds/cold air advection will be most
persistent, to relatively mild mid 50s far SW where cld cover will
Long term...(wednesday night through tuesday)
issued at 315 PM CST Tue Nov 12 2019
Extended periods appear quiet with a significant warming trend
for the weekend.
Northwest upper flow will continue Wed into Thu before bec less
amplified and more zonal for the end of the week. This will allow
for an influx of more mild air of Pacific origin and a warming
trend as we head into the weekend. 850 mb temps will rise from around
0c at 18z Thu to 6-10c by 18z Fri, and even warmer (10-13c) for
Sat. As a result, high temps on Thu will be similar to Wed (low
40s to low 50s), before rising to mid 50s to mid 60s on Fri and
Sat. Friday looks to be the pick day of the week as winds will be
relatively light (around 10-20mph) with mostly sunny skies. Sat
wont be bad either, but there could be substantially more mid to
high clds around.
The incr in cld cover Sat will be in response to our next
disturbance set to arrive from the northwest Sat night into sun. The ec
has a decent upper jet streak with this system, but its positively
tilted, lacking deep moisture, and generally deamplifying as it
moves through. Also, the system is of Pacific origin with no cold
air to work with as evidenced by positive epo/wpo. Thus,
appreciable weather impacts should be very low, likely limited to
only a slight cool down for sun.
Both the eps and gefs are in good agreement in bringing in a
nice, mild airmass for early next week, with widespread highs in
the 60s (and probably even some 70s) likely Mon-Tue. Models hint
at another trough and potential cooldown/chc for wintry pcpn
around the middle of next week, about 8-9 days from now.
Aviation...(for the 18z kgri/kear tafs through 18z wednesday)
issued at 1134 am CST Tue Nov 12 2019
Significant wx: low level wind shear (llws) this eve.
Today thru 00z: VFR with strong southerly winds sustained around
20kt, gusting around 30kt. Confidence: high.
Tonight: VFR. Sfc winds will decr around sunset, but winds will
remain SW around 40kt at just 1k ft, so low level wind shear will be a concern
through about midnight. Will see incr high clds, esp after
midnight. Confidence: high.
Wed thru 18z: VFR. Broken to overcast cigs around 10k ft expected most of
the morning, though a rapid decr to near MVFR cigs expected right
around the end of the period, 17-18z, as a cold front moves
through. Winds will start off lgt out of the SW, then veer and
incr behind the front by late morning. Confidence: high.