Area Forecast Discussion
Issued by NWS Goodland, KS
FXUS63 KGLD 171627
Area Forecast Discussion
National Weather Service Goodland KS
1027 AM MDT Mon Apr 17 2017
Issued at 1007 AM MDT Mon Apr 17 2017
Made minor adjustments to timing of PoPs this afternoon/tonight
and added mention of severe with thunderstorms in the
afternoon/evening. Also made adjustment to fog coverage this
morning and late tonight/Tuesday morning.
Still not a lot of confidence in coverage of fog tonight/Tuesday
morning or location where fog may develop. On back side of
departing trough/mid level cloud deck moisture is shown to pool
within BL and high resolution guidance continues to show pockets
of low visibility developing. This is an inconsistent signal and
not a slam dunk fog set up due to more of a northerly BL flow, but
I felt comfortable expanding patchy fog mention to cover
Regarding severe threat this afternoon/evening: Besides a weak
(questionable) precip signal through the early afternoon in our
south, guidance continues to show main potential in our northwest
spreading east through the night. Moderate instability is shown by
RAP/NAM along the CO border by the late afternoon correlating
with decent shear (30-45 kt bulk effective and 300 m2/s2 0-3km
helicity). If we can get a thunderstorm to develop and move into
this area we could see rapid intensification/organization.
Hail/wind may be the primary threat, but good low level veering
profiles along surface trough could support tornado potential (at
least before sunset and low levels stabilize). Coverage is a
question, but severe potential is there and was worth adding to Wx
.SHORT TERM...(Today through Wednesday night)
Issued at 341 AM MDT Mon Apr 17 2017
Forecast issues will be periodic chances for
precipitation/thunderstorms through the period along with regular
bouts of stratus/fog. Satellite showing an amplified flow into
western North America where it then the flow flattens out and
speeds up. Also flow becomes more split over the country.
At jet level...models started out well. At mid levels...Only subtle
differences seen with the Canadian and Nam doing slightly better.
The Gfs looked to be doing a little better on the low level thermal
Today/tonight...Initial problems will be extent of fog, and if the
stratus will hold on long enough to affect temperatures
significantly. Fog looks to burn off through mid morning. However
the stratus looks to last most of the day. Surface winds will remain
from an east to south southeast direction with a weak inversion
remaining aloft through the day. So am thinking there will not be
much sun which the newer numerical guidance would support. So
lowered the maxes a little but it is still possible I am a little
too warm still.
Surface focus remains out to the west of the through the day along
with most of the mid and upper lift/moisture. So pulled what pops
there are a little further west. This would especially be true if
low level cloud cover hangs on longer and holds back instability.
Weak right rear quadrant affects the northwest portion of the area
during the last half of the night. Also during this time the
shortwave will move through along with the surface boundary. So late
in the evening through the overnight hours should be when the
highest pops occur as they progress from west to east. Not sure how
the precipitation is going to work out so right am thinking will
have mostly stratus instead of fog around after midnight.
Tuesday/Tuesday night...Lift and precipitation should be done by the
beginning of the day. Also lift through the day along with a drier
air mass looks to be in place through the rest of the day, and will
keep the rest of the day dry. Does not look like a lot of fog in the
morning but could have a decent amount of stratus around
especially along and east of the Colorado border.
It looks like the cloud cover will clear faster than todays cloud
cover. However the wind field looks to be mostly light and upslope
except maybe for the far southwest. Made some minor adjustments to
the temperatures based on expected cloud trends.
Upper jet looks to stay near to just northwest of the area through
the afternoon with the left front quadrant affecting the northern
third of the area during the last half of the night. Shortwave also
moves through at the same time. Forecast blend kept pops in the far
north and see no reason to make any major deviation from that. Again
there looks to be a lot of low level cloud cover behind the boundary.
Wednesday/Wednesday night...Some differences on the jet position
occur during this period. Above mentioned left front quadrant of the
jet and shortwave trough continue to affect the northern portion of
the area in the morning. So lingering morning precipitation can be
expected and that is what the builder gave me so made no changes.
General consensus is that the left front quadrant of a northwest to
southeast jet will be affecting the northeast half of the area
during the afternoon. The best mid level lift looks to be in the
same area as a result of strong system moving across the north
central portion of the country. Forecast builder only has pops in
the far northeast portion. Since it is still far out, it is my first
night on, and that most of the guidance supports the above, will
keep what the builder gave me. Also looks pretty stable so will keep
thunderstorms out of the forecast.
During the night, the left front quadrant of the jet moves north
during the evening. However a rather strong right rear quadrant of
the jet starts affecting the entire during the last half of the
night. At the same time there is a shortwave trough moving across
with a mid level baroclinic zone that coincides with the jet above
it. Also the next surface boundary starts moving through. Forecast
builder gave me a small area of slight chance pops during the last
half of the night. All of this makes given the above. It could be
possible that the pops may need to be expanded. Also there looks to
be some elevated cape around during this time so have thunderstorms
with this forecast.
.LONG TERM...(Thursday through Monday)
Issued at 225 AM MDT Mon Apr 17 2017
During the extended period a major system looks to move through the
Central High Plains Thursday-Saturday and produce much needed
precipitation for the region. Looking at the ECMWF, GFS and NAVGEN
the pattern for the most part are the same. The system lifts out of
the four corners region and moves across the High PLains. However, I
see the ECWMF and NAVGEN showing the system as an open wave while
the GFS has is as a close low. In the big picture this is really a
subtle difference as this system will produce widespread precip
through Saturday afternoon/evening with limited instability, so no
thunderstorms are forecasted. We may see a mix of rain/snow on back
side of the upper low; however, did not put this in the forecast at
this time, but it is something we will keep a close eye on.
Saturday night the system will continue to move out of the region
and be replace by high pressure ridge. This will produce dry
conditions for the remaining of the extended period.
.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 540 AM MDT Mon Apr 17 2017
Complicated and uncertain forecast in the first half, especially
in the first six hours since model output, mainly high resolution
guidance is struggling capturing reality on the stratus and fog
field this morning. For Kgld...at this time vfr conditions are
expected at the start with ifr and occasional mvfr conditions
through 16z. From 16z until 01z, mvfr conditions are expected.
Early in the afternoon, south winds will increase to near 19 knots
with gusts up to 28 knots. Vfr conditions will return at 01z with
mvfr conditions once again beginning around 07z.
For Kmck...at this time, vfr conditions will begin the period with
mvfr conditions beginning around 14z. These conditions will
continue until 21z when vfr conditions will return. From 21z to
07z southeast winds will be near 14 knots. At 07z south winds of
near 12 knots develop. Also at 07z ifr conditions will develop and
continue through the end of the period. From 07z to the end of the
period there will be a threat of thunderstorms in the area. Since
this is toward the end of the period, chose to put in vcts at this