Area Forecast Discussion
Issued by NWS Goodland, KS
FXUS63 KGLD 100835
Area Forecast Discussion
National Weather Service Goodland KS
135 AM MST Sat Dec 10 2016
.SHORT TERM...(This evening through Saturday)
Issued at 159 PM MST Fri Dec 9 2016
Main forecast concerns will be fog coverage through tomorrow morning
and high temperatures tomorrow. Fast west to northwest flow aloft
continues across the area. At the surface, arctic high pressure has
pushed off to the east as a strengthening lee trough has developed
to our west. This has tightened the pressure gradient allowing
southerly winds to increase low level moisture over the western
portion of the area, especially over the snow field.
Models having a little difficulty in the handling of the low level
moisture and cloud fields today. The Nam tends to be overdone and
the Gfs is too dry and does not have enough cloud cover. The Sref
seems to have the best handle. High resolution guidance, including
the Nam, brings in stratus once again tonight with the main question
of how much if any fog.
The Nam does have a bad habit of overdoing fog in this scenario. It
did get the stratus right from yesterday. However because of the
increase of low level moisture already in the west and the other
high resolution guidance showing fog developing during the night in
the same place as the current higher dewpoints, although some models
develop the fog faster than others, believe some mention of fog is
warranted. Even though the models differ on timing of fog
development they do agree on the area. So was confident enough to
add patchy fog, freezing due to much below 32 degree temperatures,
for along and east of the Colorado border from late this evening
into tomorrow morning.
The next question will be how fast does the cloud cover decrease.
Some cloud cover does hang on into the afternoon the east and
northeast portions of the area. At this time went with a blend with
the warmest temperatures along and west of the Colorado border and
the coolest in the far northern and eastern sections. However am
uncertain on this.
.LONG TERM...(Tuesday through Saturday)
Issued at 134 AM MST Sat Dec 10 2016
Zonal pattern remains entrenched across the Central Rockies and
Central High Plains regions through Thursday night. A large scale
upper low over southern Canada will keep sending reinforcing shots
of colder air into the plains Tuesday through Thursday, so despite
the zonal pattern passing shortwave troughs and a stalled cold
front south of our CWA will keep below normal temperatures in
GFS and ECMWF have both trended slightly higher on H85 temps, but
still show values in the -10-13C range. Thick cloud cover and
insulation could limit diurnal heating Tuesday and Wednesday, and
lead to "warmer" lows due to insulation. I could see highs being a
little lower, but current consensus lows in the single digits seems
reasonable. Better radiational cooling at night certainly would
support negative lows, but that doesn`t seem to be the trend in the
models at this time.
This pattern does tend to keep better deep layer moisture out of our
area to the north, and most embedded shortwave troughs track north
of our area. We could see light measurable snow chances but the
precip signal is weak, and both 00Z GFS and 00Z have trended
northward. Best moist advection along elevated frontal zone occurs
late Tuesday night and Wednesday, but even then there is enough of
a dry sub cloud layer to lower confidence in both occurrence and
type. It is possible that with better BL moisture advection in
easterly low level flow we could see freezing drizzle or a light
overriding light snow event, but confidence isn`t high.
Friday-Saturday: Large scale troughing develops across the
intermountain west Friday into next weekend, and arctic air begins
to dig back into the plains by next weekend. Consensus H85 temps
are around -21C by Saturday, which for reference is 4-6C colder
than the last arctic air mass to impact our CWA. Accumulating snow
chances could be increasing as SW flow ahead of large scale trough
overrides arctic front bringing deep layer moisture along with
strong large scale forcing Friday into Saturday. Saturday is
beyond the current valid forecast period, but I wanted to draw
attention to this due to reasonable agreement.
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1024 PM MST Fri Dec 9 2016
For KGLD...mainly VFR conditions thru the period...w/ MVFR
fog/ceilings 10z-15z. Will see near 3sm in visibility and bkn020
during this time. Winds...SSW around 10kts.
For KMCK...VFR conditions thru 10z...then MVFR thru 23z. Looking
for ceilings bkn-ovc015-030 and visibility down to 3sm at times.
Winds...Lgt/var thru 10z then becoming ENE around 10kts. By 14z
SSE around 10kts.