Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Goodland Kansas
1158 PM MDT Monday Apr 20 2015
issued at 534 PM MDT Monday Apr 20 2015
During the evening and into the overnight hours a weak upper level
short wave trough moves across the area. Currently there could be
two possible areas for some rain to develop...if it develops. The
first is from Yuma southeast to Colby and Hoxie. The second area
is over Greeley and Wichita counties. Both locations have low
condensation pressure deficits and 700-500mb frontogenesis.
However the southern area has more frontogenesis and most of the
models seem to agree with rainfall developing over the southern
two counties...if it develops.
While condensation pressure deficits are low...they are not as
low as for the area further north. Am thinking this are is tied to
the light reflectity showing up on radar near the southwest part
of the area. Will monitor to see if changes will be needed to the
forecast or if the rain will remain just south of the area. If any
rain does fall...will most likely be less than .1 inches.
Short term...(this evening through tuesday)
issued at 111 PM MDT Monday Apr 20 2015
Benign weather is expected through Tuesday.
The Central High plains region will remain dry through Tuesday as
the region will be between weather producing systems. Overnight
temperatures will be cool again with some areas expected to be
near freezing around sunrise. Daytime temperatures on Tuesday will
continue to warm into the lower 70s ahead of the next cold front
expected to push into the area by Tuesday evening.
Long term...(tuesday night through monday)
issued at 125 PM MDT Monday Apr 20 2015
Weak back door front drops down Tuesday night with low level
easterly winds behind it. Models not doing much with clouds or fog
as dew points behind the front in the 20s. They do however show
some light precipitation along the southern fringes of the
forecast area overnight with a weak shortwave in the southern
stream interacting with the shallow frontal boundary. At this time
think the precipitation will stay south of the area assuming the
front clears as scheduled.
Southeasterly return flow gets underway in the low levels
Wednesday with increasing clouds. Cannot rule out an isolated
shower/thunderstorm Wednesday afternoon with the increasing
moisture and a weak shortwave trough topping the southern ridge.
Better chances will occur Wednesday night when another piece of
energy comes out of central Colorado and across the forecast area
with scattered showers and perhaps a thunderstorm with low values
of elevated cape.
Moisture continues to advect in from the south on Thursday with
southwesterly flow aloft developing ahead of the next upper low
digging into The Four Corners. By Thursday afternoon models
showing a narrow band of SBCAPE up to 1500 j/kg near the Kansas
and Colorado border and deep layer shear of 40-50kts. Weak
shortwaves ejecting out of the base of the western low should be
enough to initiate convection...some of which could be severe
with the amount of shear in place. The main low will eject
northeast across eastern Colorado and western Kansas on Friday
with better chances for rain and thunderstorms. GFS shows cool
northeasterly surface winds which could inhibit instability and
severe threat...while the European model (ecmwf) shows southerly flow due to slower
movement of the upper system and more of a severe threat.
Weekend continues to be unsettled with wraparound precipitation on
Saturday followed by another shortwave trough Saturday night and
Sunday with models trying to phase the jet streams. Might not be
enough time to get moisture return between systems for much of a
severe threat and GFS has only minimal SBCAPE Saturday night or
Sunday. Front sweeps through Sunday afternoon and night with
precipitation chances ending and a period of windy conditions.
Early next week looks dry and warmer as a high amplitude ridge
builds over The Rockies.
Aviation...(for the 06z tafs through 06z Tuesday night)
issued at 1144 PM MDT Monday Apr 20 2015
VFR conditions expected for the 6z tafs. Main issue early in the
taf will be low level wind shear. The wind shear monitor was indicating some
moderate shear occurring at kgld. Once again model soundings were
not catching the stronger winds just off the surface. Since the
sounding is very similar at kmck have added a mention of low level wind shear
there as well with the same speed. Low level wind shear will turn to the west for
kgld and to the northwest for kmck for the first couple hours of
the taf. Otherwise winds will be light through the rest of the
night then gradually strengthen during the day. For kmck winds
will become breezy during the afternoon ahead of a backdoor cold
front that will move through during the evening. Expect winds to
strengthen further just ahead of the front for kmck and possibly
for an hour or so behind the front as the stronger winds are able
to mix to the ground.