Scientific Forecaster Discussion
fxus63 kgld 271917
Area forecast discussion
National Weather Service Goodland Kansas
117 PM MDT Sat may 27 2017
Short term...(this evening through sunday)
issued at 115 PM MDT Sat may 27 2017
Latest upper air analysis shows a trough axis over the northern
plains extending southwest to the central rockies. Satellite
imagery shows a defined line of clouds accompanying the trough axis
east with colder cloud tops at the base of the trough. Ahead of the
trough axis wave clouds indicated a stable environment. Latest
radar imagery showed a line of showers accompanying the trough axis
east. On the south end of the line a cluster of storms had developed
at the base of the trough axis. At the surface the cold front was
near the Kansas/OK border arcing northwest to near Denver.
Am expecting this cluster to be the focus for attention this
afternoon for the potential of strong to severe storms as the
cluster moves southeast. The better chance for severe weather will
be south of Cheyenne and Greeley/Wichita counties near the front
where the higher instability will be. Main hazard with this cluster
will be large hail up to ping-pong Ball size if severe storms
develop. Have limited optimism due to cape of 1000j/kg or less.
However effective deep layer shear is 55kts by early evening, so if
an updraft can avoid being sheared apart large hail will be very
likely. Dcape values and hrrr ensemble model runs both show a low
probability of severe wind gusts.
Tonight the threat for severe weather will be southeast of the
forecast area, if any is still ongoing. There may be some lingering
storm activity ahead of the approaching trough axis. Cloud cover
will exit ahead of the trough axis. Behind the trough axis a
surface high will move through.
Sunday will be warmer as northwest winds bring in warm air advection. Winds will
be light as a 850mb ridge moves through. A clear sky is expected
due to dry northwest flow overhead.
Long term...(sunday night through saturday)
issued at 115 PM MDT Sat may 27 2017
Sunday night: upper level ridge will build aloft bringing drier
conditions to the area. Temperatures will be near to slightly below
Monday-tuesday: cold front moves into the area during the day Monday
and becomes stalled with a northwest to southeast orientation across
the County Warning Area. Showers and a few thunderstorms will be possible Monday
afternoon into Monday night for areas southwest of the front. On
Tuesday, a shortwave trough pushes into the area from the northwest
helping to provide extra lift and giving most of the area a chance
of rain and thunderstorms. Temperatures should be close to normal.
Wednesday-thursday: models still do not have very good agreement for
this period. GFS and European model (ecmwf) have very little continuity between them.
Tended to lean towards the GFS for this time frame. Area will see a
chance of thunderstorms on Wednesday and Thursday afternoons. 12z
GFS soundings indicate that some of these storms could be strong or
Friday-saturday: this period could remain wet and/or stormy as both
the GFS and European model (ecmwf) are advertising the possibility of a negatively
tilted trough or closed low approaching the County Warning Area from the southwest.
GFS solution shows high cape values (~2200 j/kg) but low 0-6km shear
(~12 kt). One note, GFS is also showing precipitable water values around 1.25 in.
Which could result in some heavy rain through the period.
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1141 am MDT Sat may 27 2017
VFR to MVFR conditions forecast for the tafs. MVFR cloud deck has
been just west of kmck this morning. GOES-r cloud heights show the
cloud deck continuing to increase through the last hour or so, so
am expecting VFR conditions for that site. Kgld should remain in
the lower clouds until 19z or 20z. Once the cloud deck increases,
will remain VFR.