Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Hastings NE
553 PM CST Wednesday Jan 28 2015
Short term...(this evening through thursday)
issued at 408 PM CST Wednesday Jan 28 2015
The main focus is on gusty northwest winds tonight. The weather
pattern was undergoing changes today with a shortwave trough
translating along the High Plains...breaking down the upper ridge
axis. An associated surface trough and cold front advancing across the
plains will bring an end to the record January warmth of the last
couple of days. Already today...Grand Island has set a new record
high temperature of 67 degrees...breaking the previous record of 63
degrees. And temperatures can still edge up in the next couple of hours.
Hastings has tied their record of 69 degrees.
Low relative humidity values this afternoon have dropped to the low
20th percentile across portions of north central Kansas where near
critical fire weather conditions exist due to the dry conditions and
gusty winds. Will maintain mention of this in the severe weather potential statement through the afternoon.
Temperatures this afternoon are starting to level off...and more noticeably
colder air will advect in this evening/tonight mainly after 03z
behind the middle level trough axis. Northwest winds will ramp up
during the late evening hours with three hours pressure rises
averaging 6 mb behind the cold front. In a tight pressure gradient
behind the departing surface low and building surface high...wind speeds
will remain strong and gusty during the overnight hours with
forecast soundings indicating wind speeds at the top of the layer
between 40 and 45kts. Wind conditions tonight are looking very
similar to the gusty winds from last Saturday night when frequent
wind gusts over 40 miles per hour were observed. The steady/gusty winds are
expected to hold temperatures in the 30s for lows.
The surface gradient remains tight into Thursday morning...then
relaxes as the surface high settles in during the afternoon. In the
Post frontal cooler airmass on Thursday...highs should average in
Long term...(thursday night through wednesday)
issued at 408 PM CST Wednesday Jan 28 2015
To summarize these 6-days in the best way possible...although we
will certainly feel a return to more-winter like conditions...by
that same token we are not foreseeing any kind of prolonged
stretch of bitterly cold conditions either. In fact...only one of
these 6 days (sunday) is currently forecast to feature highs well
down in the 20s cwa-wide...while most other days are predominantly
30s/40s. Although still subject to plenty of modification being so
far out in time...its Worth noting that high temperatures for both
Monday-Tuesday were generally raised 4-10 degrees from previous
Precipitation/snowfall wise...cannot over-emphasize the
uncertainty regarding the weekend system. While our previous night
shift and their corresponding 00z models noted increasing
potential for possibly several inches of accumulating snow across
portions of the County Warning Area...the latest 12z/18z runs today have backed
off considerably especially within Nebraska zones...while focusing
most rain/snow potential near and south of the state line.
Although it is still 12-24 hours too early for US to "officially
advertise" a snow forecast with much confidence...very preliminary
indications are that Kansas zones may be looking at the possibility of
light amounts to around 1 inch...with most of Nebraska looking at
only around one-half inch or less potential. Again...please
realize the high degree of uncertainty here...and Don/T be
surprised if the next suite of 00z models again trend somewhat
back upward with amounts/northward in track a bit. At least for
now though...we can say that we are not expecting a "major" snow
event this weekend.
Continuing with the weekend system (the main focus of this 6-day
period)...for now have gone with a rain/snow mix much of the time
given marginal low level thermal profiles/surface temperatures...which
could also limit accumulations somewhat...but did go with "all
snow" potential Saturday night as the system departs. Although
not necessarily 100 percent comfortable with the latest default
multi-model blend pulling out all snow mention for Sunday
daytime...went ahead with it for now...thus focusing all probability of precipitation
between Friday evening and late Saturday night. Although it is
too soon to introduce any light drizzle/freezing drizzle
potential with this system...will have to keep an eye on this too
as it draws nearer.
Other than the Friday evening-Saturday night time frame...left the
remainder of the forecast period void of any precipitation possibilities
with the sole exception of a slight chance of snow in far
northeast counties on Tuesday. Could there be other periods next
week that might eventually need slight pops? Maybe...but its just
too soon to advertise any such chances yet with such low
Turning to limited forecast details now in 12-24 hour blocks...
Thursday evening/night...high confidence in dry/uneventful weather
as middle/upper level ridging sets up behind the departing shortwave
trough. Skies should start out quite clear...but eventually
realize some increasing high clouds from the southwest as the
night GOES on. At the surface...a ridge axis will transition
eastward across the area as the night GOES on...resulting in light
breezes that start out northerly but then transition to easterly-
southerly. Nudged down low temperatures 1-2 degrees in most
areas...aiming most places into the 17-20 range.
Friday daytime-night...on the large-scale...the County Warning Area remains in
between a southwestern Continental U.S. Trough and the main northern stream
jet and associated shortwaves traversing Canada/the northeast
Continental U.S.. during the day...confidence remains fairly high in dry
conditions despite increasing clouds...although some models try to
bring light precipitation near the far southwest edges of the County Warning Area late in
the afternoon. Actually beefed up southerly wind speeds about 5
miles per hour during the day...as gusts of 20-25 miles per hour will be commonplace.
Despite the clouds...these breezes should enhance mixing and
raised highs about 3 degrees all areas...putting most of the County Warning Area
in the 43-48 range. Friday evening/night...have maintained low-
end 20-30 probability of precipitation for mainly the southern 1/2 of the County Warning Area...and if the
latest models are onto anything it may mainly be Kansas zones only.
Left precipitation type as all-rain pre-midnight...while calling it a
rain/snow mix late.
Saturday daytime-night...as already covered above...confidence is
really low in the details here regarding precipitation/snow potential.
Left the highest 50-70 probability of precipitation in Kansas zones...while knocking down probability of precipitation
for the Nebraska County Warning Area about 10 percent from previous forecast but not
getting carried away yet in case things trend upward again. All in
all though...the main focus for precipitation seems to be trending south
of our County Warning Area...with maybe a separate band of light snow skirting
just north of the area in association with a southeastward-diving
northern stream wave. Only minor tweaks to high temperatures...generally
upper 30s-low 40s all areas.
Sunday daytime-night...although cannot rule out a few lingering
flurries opted to go with the default multi-model long term blend
and keep this period dry. With good cold air advection and steady
north breezes around 20 miles per hour...this looks like the coldest day of
the forecast period with highs only in the 20s cwa-wide.
Monday daytime-night...kept it dry...but could be a close call in
northern zones as some precipitation possibly tracks across northern Nebraska.
With a return to southerly winds...highs were raised 6-7 degrees
most areas...now putting most places into the 28-38 range.
Tuesday daytime-night...kept it dry all areas except the
aforementioned sliver of slight probability of precipitation in far northeast zones a
another northwest-flow wave moves across. Highs raised an average
of 4-9 degrees...with most areas 35-45.
Wednesday daytime...dry forecast at least for now although
especially the latest GFS suggests some limited precipitation potential.
High temperatures very preliminarily aimed 34-43 most of the County Warning Area.
Aviation...(for the 00z kgri/kear tafs through 00z Thursday evening)
issued at 545 PM CST Wednesday Jan 28 2015
Wind speeds will be one of the main foci as northwest wind behind
a cold front will be stiff. Eventually...MVFR ceilings are
expected behind the cold front tonight and should clear from the
west/southwest during the day Thursday.