Area Forecast Discussion
Issued by NWS Goodland, KS

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000
FXUS63 KGLD 141911
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1211 PM MST Sat Jan 14 2017

.UPDATE...
Issued at 1016 AM MST Sat Jan 14 2017

Based on the latest trends in guidance, I upgraded the winter
storm watch to a winter storm warning. The timing was also changed
to reflect a slightly later start time due to slower overall
movement of the system.

&&

.SHORT TERM...(Today and tonight)
Issued at 502 AM MST Sat Jan 14 2017

Our forecast area is still on track for winter storm, however
changes were made to ongoing forecast to reflect latest trends.

GFS/GEFS remain outliers in evolution of upper level pattern and
ECMWF/NAM and other guidance were favored for timing, blends, and
adjustments.

A dry air mass is in place over our CWA roughly below 800mb. Mid to
high level moisture is increasing across the region, but forcing
remains weak. This dry layer will be prohibitive to measurable
precipitation through at least 00Z and there are some indications
in short range and high resolution guidance that this will not be
overcome until late tonight for the majority of our CWA. In fact
consensus of short range guidance would not support measurable
precipitation until after midnight for our entire CWA and then on
the far southeast until 12Z Sunday. ECMWF still supports potential
light freezing rain as early as 00Z, but confidence is diminished
in impacts for the majority of our CWA until later.

A colder near surface layer advertised by the NAM and implied by
much colder Tw from ECMWF/ARW/NMM may support more in the way of
sleet accumulations one may areas of moderate precipitation begin to
slide across our CWA. This would obviously decrease freezing rain
accumulations and shift impacts from being primarily focused on
power outages to just travel. In any case travel will be very
difficult once this event gets underway with worst conditions Sunday
through Monday.

ECMWF/NAM both show the closed low tracking Sunday night and Monday
in such a way as to support a deformation band forming in our
central or western CWA and a complete change over to snow Monday.
Based on conservative QPF/snow ratios we could see 8" or higher.
This may be dependent on the slower upper low track of ECMWF/NAM and
slightly better snow ratios. I trended snow totals upwards as
previous blends were being influenced downward by the GFS which
likely is not handling this track very well and is a large outlier.
SREF mean is near the current forecast, however the SREF plume shows
how large the spread between various members with minimal
clustering. Heaviest band may not impact as large of an area and
there is still the possibility that sleet could diminish totals.
This large ensemble spread is reflecting this uncertainty.

Regarding highlights: As a result in the drier early trend I delayed
the onset of the Ice Storm Warning until 00Z and the Winter Storm
Warning until 10Z. I am still confident in measurable
(potentially high impact) ice accumulations where the Ice Storm
Warning is in place, though if sleet dominates our amounts may
need to be trimmed. Regarding the Warning: Increased confidence in
freezing rain and sleet/snow amounts led to the upgrade of the
watch to a warning. Recent Hi-Res guidance agrees with persistent
ECMWF solutions. Snow amounts may need to be adjusted based upon
where the band of heavier snow sets up Sunday night/Monday
morning. Generally we are looking at 4 to 6 inches of snow in the
warning area with isolated higher amounts possible due to the
system moving a bit slower with each iteration.

.LONG TERM...(Tuesday through Saturday)
Issued at 1211 PM MST Sat Jan 14 2017

For the extended period...with the upper level trough associated
with the weekend wintry wx having finally exiting the region...H5
ridging builds over the Central Plains...with lee-side trough
setting up over the front range. These will be intact until the end
of the upcoming week...as another shortwave dives into the Central
Rockies and slowly out into the Plains Region....Friday into next
Saturday.

Current model differences between the latest GFS/ECMWF exist with
GFS being a bit faster to swing system thru the area. Placement of
this system coming off the Rockies will determine P-type. Despite
these positioning differences for Friday/Saturday...the building
ridge/lee trough combo will bring another round of above normal
highs (mid 40s to low 50s) and dry conditions to the area ahead of
the end of the week system. Overnight lows midweek will range in the
20s.

Current temp trend for Tuesday may not be taking into acct the
potential wintry precip from the weekend...dampening highs for the
day with snow/sleet/ice covering the ground. A downshift in these
numbers may ensue as further model runs progress.

Overall for the next weekend system...trend is on the warmer
side(40s for highs)initially to allow for -rw to start...trending to
-sw from west to east as system lifts out of area and temps drop
towards the 20s towards sunset. Low model QPF numbers at this time
so not expecting much but maybe a few hundredths of rain...and a
dusting of snowfall. Again...subject to change if system shifts from
current track.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1028 AM MST Sat Jan 14 2017

For KGLD...mainly VFR conditions expected thru 12z Sunday with
decreasing ceilings due to approaching storm system. Looking for
ovc080-110 to drop to ovc050 during this time. Light precip will be
in the vicinity. From 12z Sunday onward...MVFR conditions worsening
to IFR by 17z Sunday. Looking for ceilings dropping from ovc030 to
ovc010...and 2-3sm in -FZRAPL. Winds...north around 5-10kts thru 22z
this afternoon then becoming ESE around 10kts.

For KMCK...mainly VFR conditions for much of the forecast period
with decreasing ceilings from ovc150 to ovc060 by 11z-15z Sunday. By
15z...MVFR conditions begin to encompass the area as light freezing
rain starts with ceilings dropping to ovc030. Conditions will worsen
after 18z. Winds...mainly light/variable thru 11z Sunday...then
becoming ESE around 5kts.


&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Winter Storm Warning from 3 AM MST /4 AM CST/ Sunday to 7 PM MST
     /8 PM CST/ Monday for KSZ001>003-013-014-027.

     Ice Storm Warning from 5 PM MST /6 PM CST/ this afternoon to 11
     AM MST /noon CST/ Monday for KSZ004-015-016-028-029-041-042.

CO...Winter Storm Warning from 3 AM Sunday to 7 PM MST Monday for
     COZ090>092.

NE...Winter Storm Warning from 3 AM MST /4 AM CST/ Sunday to 7 PM MST
     /8 PM CST/ Monday for NEZ079>081.

&&

$$

UPDATE...TL
SHORT TERM...DR/TL
LONG TERM...JN
AVIATION...JN



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