Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Hastings NE
553 am CDT Sat Jul 30 2016
Short term...(today and tonight)
issued at 402 am CDT Sat Jul 30 2016
Difficulty continues to lie with timing and chances of precipitation.
Today will be a day of transition as the upper level flow becomes
more zonal as the subtropical high begins to build. Temperatures
today will be close to 5 degrees warmer and dewpoints perhaps a few
degrees warmer as well, compared to yesterday.
Although we do have some showers/thunderstorms kicking up in our
north/westerly this morning as a subtle perturbation slips by, it
appears that slight ridging aloft may give US a relative lull by late
morning early afternoon, but i'm not confident enough to pull pops
completely for mid-day with our given conditions in lower levels.
With increased instability and moderate bulk shear in the 40 kt
range, I would not be surprised to see a severe thunderstorm or two
pop up by late afternoon and heading into the evening, and this
looks especially true for areas southwest of the Tri-Cities.
Our best shot at rain should come overnight tonight as the low-level
jet strengthens and provides support for thunderstorm activity,
especially focused in our southeast. I could see some stronger
updrafts producing some decent sized hail, so severe weather could
occur for pretty much most of the night.
For temperatures, sky cover, and dewpoints, etc., I made very small
changes. I did increase chances of rain late tonight after midnight
due to the strengthening low-level jet.
Long term...(sunday through friday)
issued at 402 am CDT Sat Jul 30 2016
Aloft: heights will rise next week with a subtropical high
developing over the srn plains...and overtaking the srn 2/3 of the
Continental U.S.. the westerlies will retreat to the US-can border. Overall...
the mean position of the ridge will be over the nrn plains...with
trofs over the NE and northwest. Two systems will force cool fronts S into
the fcst area. The first is a low that will form today over British
Columbia. This low will head into cntrl Canada and stall. The second
will be the low currently over the Gulf of Alaska. This low will move
into the pac northwest Tue and weaken as it moves thru the nrn plains ridge
..temporarily lowering heights.
Surface: a weak warm front will be lifting thru the fcst area sun...
as low pres heads into cntrl Canada and its trailing cool front
advances thru the northwest USA. This cool front will cont east...slowly
crossing most of the fcst area late Mon night into Tue. It will
temporarily stall over Kansas and then lift back to the north as a warm
front Wed...with low pres forming over Montana and ejecting into Canada.
The cool front associated with this low should cross the fcst area
Thu before stalling along the Kansas-OK border Fri and then dissipating
Sat. Weak high pres will build in Fri...then shift east of the region
Temps: the main trend will be upward thru Wed...back into the 90s
and probably some low 100s over parts of north-cntrl Kansas. Temps then drop
Thu with frontal passage before beginning another warming trend into
Rain: the next best chance will be with the front Thu per the ec quantitative precipitation forecast
probabilities and deterministic global models. Before that...
anything will be very isolated.
Sun: sct tstms will probably be on-going at daybreak over ern
neb/KS. The wrn fringe of this activity could be affecting parts of
the fcst area east of Hwy 281 thru mid-morning...but it should be all east
of the fcst area by noon at the latest.
Mon-Tue: heat Cranks up again. Can't rule out an isolated storm or
two meandering in from the High Plains...but don't count on it.
Advection of the eml over the region combined with subsidence aloft
should keep the fcst area mostly capped.
Temps could be hotter Mon than what we've advertised. GFS/NAM cross
sections suggest a fair amt of clouds.
Thu: if the last 3 ec runs are right...this could be a very
productive front rainwise. They are fcstg a SW-NE oriented 100 kt
jet streak just ahead of the trof axis...putting the front and cntrl
plains in the favorable rrq. Slow movement of the front will also be
The ridge will resurge back into the region next week behind the
departing trof. This should cap most of the fcst area once again.
Aviation...(for the 12z kgri/kear tafs through 12z Sunday morning)
issued at 552 am CDT Sat Jul 30 2016
Main concern is thunderstorm potential, especially for late
tonight and low-level wind shear overnight as a low-level jet
develops and strengthens. Some storms could be severe, with large