Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Hastings NE
1247 am CDT Sat Mar 15 2014
Short term...(this evening through saturday)
issued at 410 PM CDT Friday Mar 14 2014
Main forecast concerns will be rain chances for Saturday
afternoon and temperatures.
Once again satellite shows mostly clear skies across the area.
Observations have relative humidity lowering to around 20 percent
for much of the forecast area with gusty winds mostly in the
northeast part of the area.
A weak warm front will move through the forecast area tonight and
keep temperatures fairly mild during the night. Late tonight and
Saturday morning an upper level wave will approach the area. At
the surface there will be a cold front moving through the forecast
area during the morning hours. Behind the cold front winds will
turn to the northwest and increase. There will also be colder air
that moves into the area during the afternoon. Areas in the
northwest could see temperatures start to fall during the
afternoon. In addition to the winds and temperatures falling there
is a chance for some precipitation. Easily...temperatures will be
warm enough that any precipitation would be rain. Models have a
few differences in the timing of the rain into the area. The NAM
is the quickest bringing it into the area during the afternoon.
The GFS keeps most...if not all...to the northwest. Even the 4km
WRF has rain moving in very late in the afternoon. Have kept some
low probability of precipitation in the northwest during the afternoon with a few
sprinkles further southeast. Bases of the clouds should be fairly
high and if there were any rain it would be light.
Long term...(saturday night through friday)
issued at 410 PM CDT Friday Mar 14 2014
Aloft: no substantive changes to our reasoning from the previous
2 days. The flow will remain progressive with a general tendency
for a mean West Coast ridge and an eastern USA trough through Wednesday. A pattern
very familiar since Dec. Shortwave troughs will be over the region
Sat night with the next one arriving Mon-Tue...
In the 6-15 day time frame we are still looking at a pattern
change with the North Pacific trough being replaced by a ridge. This would
force the mean trough into the western USA which can be very productive
for snow/ severe thunderstorms and precipitation. The most important aspect of
this western trough will be its persistence. Do we get hit with just one
storm or multiple storms? The Gem ensemble control run is
especially threatening with multiple lows swinging through the trough.
There is a potential snag /for at least a time/ because one or
more lows will be meandering between hi and California. Dependent on its
longitude...it would induce a ridge over the desert SW. Suffice to
say the odds are increasing for some active weather and colder temperatures as
we head into the last 10 days of the month or so.
Surface: low pressure organizes over Texas and heads east into the lower MS
valley Sat night. Great Lakes high pressure briefly builds in
sun...but a warm front will be approaching from the west...in advance
of the next low moving into SW Canada. Lee cyclogenesis will occur
Monday over Mt/WY. This low will cross Nebraska Monday night along with its
cold front. Tuesday-Wednesday the low departs for the Great Lakes...with
high pressure gradually building in. The high drops into Texas Thursday. Then
uncertainty increases as low pressure organizes over the northern rockies.
This will involve the development of a Lee-side trough. So expect by
Friday we'll be in the warm sector.
Hazards: there remains some potential that a Wind Advisory may be
needed Sat night for sustained winds of at least 30 miles per hour.
Overall confidence in this forecast is average through Wednesday...then below
The daily details...
Sat night: plenty of clouds and windy. Cold air advection /caa/ will
be underway. Possibly some brief sprinkles or flurries? As stated
above we will probably need a Wind Advisory. Best chance south of
Qpf: we continued the trend of that last few shifts...being stingy
with quantitative precipitation forecast. Most models barely bring .01" into the forecast area. Like the
past few opportunities for precipitation...most locations will not measure.
Sun: clearing as the upper trough departs. Diminishing winds but
very cool...especially along and east of Highway 281. Temperatures about 7f
Mon: we are probably not warm enough! Back to the warm sector and
it will be beautiful. Another great day to be outside. For the
incredible model persistence/consistency on 850 mb temperatures...I
cannot fathom why the models are so cool. Nearly all of the very
warm days we've had this month...we and the models have not been
warm enough until the actual day arrives. The forecast was populated
with the bias corrected NAM 2m temperatures and then nudged higher east of
Highway 183. That puts most of the forecast area in the 70-75f range...
but I am convinced we need to go higher. I think reality will end
Monday night: cold frontal passage /fropa/. Cant rule out some
sprinkles or a brief shower...but dont count on it. Another dry
frontal passage for most locations.
Tue: much cooler. Back to near normal temperatures.
Wednesday-Fri: dry with a nice temperature recovery. Back into at least the
60s for all or part of the forecast area. That could be very
conservative...especially as the first Lee cyclogenesis event
Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1247 am CDT Sat Mar 15 2014
VFR conditions expected through much of the taf period...with MVFR
conditions forecast starting at 02z. Low level wind shear will
also impact gri through sunrise.
Occasional high-level clouds...near 16000ft above ground level...will remain
possible at gri through much of Saturday. Incoming stratus will
then provide a ceiling near 2500ft above ground level starting around 02z...with
this ceiling expected to decrease in height to around 1000ft above ground level
by the end of the taf period. There is a low chance of light rain
and light snow being realized at gri after 00z...but at this time
the probability of measurable precipitation being realized at gri
is too low for introduction into the taf. The surface wind will
remain from the southwest through sunrise...becoming light and
variable 13-17z...and then becoming established from the north by
17z. Once established from the north...the surface wind will
become quite strong...sustained at around 23kts with gusts to
around 32kts. An axis of strong wind just above the boundary layer
will also continue to promote low level wind shear at gri through
sunrise...and such has been presented in the taf. Visibility
restriction is not expected at gri through the next 24 hours.