Scientific Forecaster Discussion
fxus63 kgid 231133
Area forecast discussion
National Weather Service Hastings NE
633 am CDT Sat Jun 23 2018
..significant svr wx and flash flooding possible for parts of the
fcst area sun into Sun night but uncertainty remains high on the
Short term...(today and tonight)
issued at 353 am CDT Sat Jun 23 2018
Aloft: rap analyses and 00z radiosonde observation data cont to depict an unusual
split flow pattern over North America with the polar jet far to the north
over Canada and a weak branch of westerlies over the srn USA with
a stream of slow-moving lows and trofs in the weak flow in
between. One such trof was overhead...moving thru the cntrl/nrn
plns and one such low was over Montana. The trof will exit the rgn this
morning followed by a shortwave ridge tonight while the Montana low
digs into Wyoming.
Surface: a weak pres pattern was over the cntrl plns. A weak low
was over South Dakota with a trof extending S into cntrl neb and northwest Kansas. This
trof will dissipate today leaving the weak pres pattern. An
inverted trof will form sun...arcing from OK-SD.
Overnight patchy area of -ra occurred over S-cntrl neb east of Hwy
183 with a couple embedded tstms. This area has decreased markedly
Now thru sunrise: the back edge of this decreasing area of rain
was collocated with the shortwave trof and it should be east of the
County Warning Area by dawn. Clds will be decreasing as well. With light winds and
low T/TD depressions...some patchy fog will probably form.
Today: variable between M/sunny and M/cldy this am. Should see
transition to or development of extensive stratocu late am but
increasing subsidence after midday should result in M/sunny west and
S of the Tri-Cities and p/cldy north and east.
Can't completely rule out an isolated shwr or tstm north and east of the
Tri-Cities this afternoon during peak heating. Temps in the low
80s with dwpts in the mid 60s will result in MLCAPE around 1500
j/kg. With 0-6 km shear near 30 kt...can't completely rule out an
isolated svr tstm.
Tonight: any isolated shwr/tstm activity north and east of the Tri-
Cities will rapidly die by sunset. M/clear to start then
increasing clds as tstm activity fires well to the west. Tstms could
move in after midnight mainly west of Hwy 183. This is discussed more
below...but there is considerable uncertainty in the fcst
location of tstms.
With 2000 j/kg of MUCAPE...effective deep layer shear near 30
kt... and the strength of the forcing...it is entirely possible
these tstms could be svr.
Be sure to follow our latest fcsts/posts to social media and Storm Prediction Center
outlooks. Changes and refinements to the fcst are likely over the
next 24 hrs.
Long term...(sunday through friday)
issued at 353 am CDT Sat Jun 23 2018
Aloft: the Wyoming low will slowly inch along neb/South Dakota border sun-Mon
and into srn Minnesota by 12z/Tue. A potent shortwave trof sweeping
across Canada will kick the low into the gtlks Wed establishing
consolidated zonal flow across the nrn USA. Thu-Fri a pattern chg
will occur with a broad wrn trof/ern ridge developing...with a hot
subtropical high over the ern USA. This pattern will amplify at
times but persist into early Jul.
Surface: low pres will form over OK sun eve and cyclonically
rotate thru ern Kansas/neb into South Dakota Mon. Very weak high pres will build
over neb Tue as this low then heads for the upr Midwest. High
pres over the Atlc will take over Wed-Fri with return flow over
the plns. The tail end of a cool front will drop to the neb/Kansas
border Wed...then lift back north was a warm front Thu before the next
weak cool front arrives Fri.
Temps: sun-Mon enjoy the comfortable temps...but the humidity
will be creeping up...espcly from the Tri-Cities north and east. The
change in flow aloft will allow summertime heat to return Tue and
remain thru at least Fri. The cool fronts will barely put a Dent
in temps. Their only impact will be to keep temps from being as
hot as they might be without them. Bottom line is temps will still
be above 90f.
Precip: a comma-shaped arc of shwrs/tstms will be form sun am
over wrn neb/northwest Kansas due to the strong forcing associated with the
approaching low. There is tremendous uncertainty on how precip
chances evolve sun into Sun night due to the wildly varying model
qpfs. One thing seems fairly certain...there will be more than one
episode of heavy rainfall.
What happens to the sun am tstm activity will play an important
role in how additional tstms develop and evolve Sun afternoon/eve.
Does the daytime tstm activity diminish the svr tstm potential in
the afternoon due to the suppressing effects of cloud cover and
cooler temps? Wherever this cluster of tstms is in the afternoon
..it is likely to intensify and become svr. Present indications
are that these storms will slide southeast across Kansas and that is why the
Storm Prediction Center has an enh risk of svr there. If this occurs as some models
depict...it really casts doubt on what happens further north over neb.
One would think that the persistent qg forcing/lift associated
with the low should initiate tstms there as well...but have seen
many times when one big cluster of storms robs nearby areas which
see little or nothing. Stay tuned.
Please follow Storm Prediction Center outlooks for more details.
Qpf: there is a decent chance much of the County Warning Area will measure at
least 0.50-1.00". There is a smaller chance for narrow swaths of
3-4" and locally higher in a small portion of the County Warning Area.
The slow movement of this low and potential for repeated tstm
activity could eventually require we issue a Flash Flood Watch...
espcly for Nuckolls/Thayer/Smith/Jewell counties which have moist
soils from the 3-7" of rain that fell last Tue eve. These counties
will be particularly susceptible to quicker run-off.
Let's hope everyone gets the rain we need sun-Sun night because
once the low GOES by...it's back to Bone dry. The fcst does
advertise a chance of tstms Wed night into Thu...but don't bet on
it. The atms is likely to be capped with the ec fcstg 700 mb temps
Aviation...(for the 12z kgri/kear tafs through 12z sunday)
issued at 633 am CDT Sat Jun 23 2018
Significant wx: a bit of ground fog early this am.
Today: a little ground fog until 13z...possibly reducing the visibility
to MVFR at gri. Otherwise VFR. Scattered stratocu should form around
2500 ft 15z-16z and then lift to 5-6k ft this afternoon. Lgt/vrbl
winds become SW 8-14 kt. Confidence: high
Tonight: VFR cigs at or above 10k ft invade from the west after 06z.
There is a low probability IFR tstms could be moving in or near
after 09z. Winds diminish below 10 kt and shift to southeast...then
become lgt/vrbl. Confidence: medium