Special Weather Statement, NWS Goodland, KS

Area Forecast Discussion
National Weather Service Goodland KS
952 PM MDT Sat May 15 2021

.UPDATE...
Issued at 951 PM MDT Sat May 15 2021

Storms are continuing to move across Cheyenne County, Colorado and
portions of western Kansas, the main hazards continue to be
heavy rain and large hail. Due to a decreasing severe threat, the
Severe Thunderstorm Watch has been cancelled for Cheyenne County
in Colorado; however, locally heavy rain may remain possible. The
watch continues for Sheridan and Graham counties along with the
Kansas counties along and south of US-40 until 12 AM MDT/1 AM CDT.

UPDATE Issued at 909 PM MDT Sat May 15 2021

Storms are slowly moving into Cheyenne County, Colorado and
across portions of western Kansas, the main hazards have become
heavy rain and large hail. Due to a decreasing severe threat, the
Severe Thunderstorm Watch has been cancelled for Kit Carson,
Sherman, and Thomas counties. The watch continues for Sheridan and
Graham counties along with counties along and south of US-40
until 12 AM MDT/1 AM CDT.

Thunderstorms are currently tracking east to northeast across
northwest Kansas this evening. Severe thunderstorms capable of
producing heavy rain with isolated flash flooding, large hail, and
damaging winds are possible, mainly south of Interstate 70
through 2 AM MDT Sunday morning.

&&

.SHORT TERM...(This afternoon through Sunday night)
Issued at 1152 AM MDT Sat May 15 2021

Overview: Modest westerly flow aloft (30-40 KT at 300-250 mb)
will prevail over the region through Sunday.. on the eastern
periphery of a modest upper level ridge over the central Rockies.

Today-Tonight: Challenging convective forecast. In a muttled
synoptic regime.. characterized by weak low/mid-tropospheric
(SFC-H5) flow.. the evolution of the low-level (SFC-H85) pattern
and majority of forcing (i.e. not directly assoc/w convection)
will largely be dictated by mesoscale features. Per 18Z visible
satellite imagery and regional surface observations.. a weak
mesoscale low was located in southeastern CO.. centered ~20 miles
SE of La Junta (KLHX). Considerable low overcast persists on the
northern and eastern periphery of this feature (in east/northeast
CO). Further downstream in northwest KS, low overcast
lifted/scattered around mid-morning.. though recent trends suggest
that, at the very least, alternating periods of cloud cover are
likely through the afternoon.

Simulated reflectivity forecasts via the HRRR and NAM NEST
suggest that several distinct areas of convection will develop
late this afternoon and evening.

(1) Scattered convection will develop on the Raton Mesa and
portions of the CO Front Range around peak heating (21-23Z)..
progressing eastward (via modest westerly steering flow) into
eastern CO after 00-01Z. With pervasive cloud cover and pronounced
convective inhibition along the Palmer Divide, it is uncertain
whether or not (or to what degree) convection emanating from the
CO Front Range will intensify. On the other hand, convection
emanating from the Raton Mesa will encounter robust insolation in
southeast CO.. and, aided by low-level convergence invof the
mesoscale low.. will likely increase in coverage and intensify,
with activity approaching the CO/KS border (south of I-70) by
01-02Z. Deep layer shear appears marginally sufficient for
supercellular organization, though such organization may be short-
lived, with activity likely growing upscale into a line or
cluster. With the above in mind, large hail and damaging winds are
anticipated to be the primary hazards, mainly in Cheyenne county,
CO and Greeley county, KS.

(2) Scattered to widespread convection (elevated in nature) is
anticipated to blossom over northwest KS later this evening
(03-05Z).. presumably in assoc/w strengthening southerly flow
/warm advection/.. perhaps augmented by storm-scale/mesoscale
forcing associated with ongoing convection approaching from the
west. Isolated instances of marginally severe hail and/or brief
downbursts up to 65 mph are possible, mainly within the first few
hours of development. Locally heavy rainfall and flash flooding
are anticipated to be the primary hazard.. particularly where
antecedent conditions are favorable (i.e. where heavy rain has
fallen the past few days).

Sun-Sun night: With little change in the synoptic pattern, expect
sensible weather conditions generally similar to today.. i.e.
every bit as challenging as today with regard to temperatures,
cloud cover, convective development/coverage/evolution/hazards.

.LONG TERM...(Monday through Saturday)
Issued at 209 PM MDT Sat May 15 2021

Next week continues to looks unsettled with temperature near or
slightly below average for this time of year to start the week. Rain
chances are dependent on the day.

The early part of the week still looks to have an upper level cut-
off low advance in the larger ridge towards the Tri-State area. Near
the surface, a broad area of lower surface pressure is still
expected to set up towards the south and west. What this means for
the area is that there will be slight synoptic lift in the area and
more moist air will be pulled north into the area. This will allow
for near constant cloud cover and rain for Monday and Tuesday with
Wednesday possibly seeing similar conditions. Currently, the
forecast has high chances for rain, but QPF remains relatively low
as it does not currently look like a widespread rain event. Will
have to monitor the next few days. Temperatures are forecasted to be
in the mid to upper 60's.

Wednesday sees a transition in overall pattern as the cut-off low
rejoins the main flow before a ridge sets up in the Eastern CONUS
and a trough in the Western CONUS. Near the surface, the area of
lower pressure moves further southwest with high pressure moving in
behind it. Thursday and Friday, a surface low is forecasted to form
in the Northern Rockies and move out into the Plains. This pattern
looks to favor drier and warmer conditions with lesser chances of
rain and high temperatures climbing back into the 70's and 80's.
Storms still are possible during the afternoon and evening hours
with some possibly being severe. Will have to see how things line up
as ensemble members show a decent spread in location of the upper
features and center of the latter low pressure. With the Tri-State
area being inbetween features, the placement will be key to the
conditions we get.

Saturday on is uncertain right now, but may need to watch for
temperatures to cool down back into the 60's and 70's after Saturday
if the trough moves over the area and brings a cold front from the
north.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 519 PM MDT Sat May 15 2021

As showers and thunderstorms move into the area, VFR conditions
are expected to degrade to MVFR this evening. Storms are
anticipated to impact the GLD terminal beginning around 01Z until
08Z. Storms are expected to move over the MCK terminal as early as
02Z with the best chance for storms 06-09Z. After the storms move
out of the area, conditions are expected to fall to MVFR/IFR
levels due to low ceilings and possible fog development during the
early morning hours on Sunday. Aside from stronger gusts
associated with the thunderstorms, the winds are anticipated to
remain fairly light from the east at 5-10 kts for much of the TAF
period.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

UPDATE...KMK
SHORT TERM...VINCENT
LONG TERM...KAK
AVIATION...KMK

Hazardous Weather Outlook
National Weather Service Goodland KS
950 PM MDT Sat May 15 2021

COZ090>092-KSZ001>004-013>016-027>029-041-042-NEZ079>081-170400-
Yuma-Kit Carson-Cheyenne-Rawlins-Decatur-Norton-Sherman-Thomas-
Sheridan-Graham-Wallace-Logan-Gove-Greeley-Wichita-Dundy-Hitchcock-
Red Willow-
950 PM MDT Sat May 15 2021 /1050 PM CDT Sat May 15 2021/

This hazardous weather outlook is for extreme southwest Nebraska...
northwest Kansas and east central Colorado.

.DAY ONE...TONIGHT...

Storms are continuing to move across Cheyenne County, Colorado and
portions of western Kansas, the main hazards have become heavy rain
and large hail. With a decreasing severe threat, the Severe
Thunderstorm Watch has been cancelled for Cheyenne County in
Colorado; however, locally heavy rain may remain possible. The watch
continues for Sheridan and Graham counties along with the Kansas
counties along and south of US-40 until 12 AM MDT/1 AM CDT.

Thunderstorms are tracking east to northeast across northwest Kansas
this evening. Severe thunderstorms capable of producing heavy rain
with isolated flash flooding, large hail, and potentially damaging
winds are possible, mainly south of Interstate 70 through 2 AM MDT
Sunday morning.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH SATURDAY...

Severe thunderstorms capable of producing large hail, damaging
winds, and locally heavy rainfall are possible once again late
Sunday afternoon and evening. At this time, the relative greatest
potential for severe weather appears to be in eastern Colorado and
adjacent Kansas and Nebraska border counties.

Thunderstorms are possible during the late afternoon and evening
hours each day this week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required.

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GOODLAND KS
1017 PM MDT SAT MAY 15 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1006 PM     FLASH FLOOD      TRIBUNE                 38.47N 101.75W
05/15/2021                   GREELEY            KS   PUBLIC

            FACEBOOK PICTURE OF ESTIMATED 3-4 INCHES OF
            WATER OVER INTERSECTION OF HWY96 AND HWY 27
            IN TRIBUNE.

&&

TT

Special Weather Statement
National Weather Service Goodland KS
1120 PM CDT Sat May 15 2021

KSZ014>016-028-029-160515-
Gove KS-Sheridan KS-Thomas KS-Graham KS-Logan KS-
1120 PM CDT Sat May 15 2021

...SIGNIFICANT WEATHER ADVISORY FOR THOMAS...NORTHEASTERN LOGAN...
SHERIDAN...NORTHERN GOVE AND GRAHAM COUNTIES UNTIL 1215 AM CDT...

At 1120 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 11 miles west of Palco to 7 miles north of
Winona. Movement was northwest at 10 mph.

Penny size hail and winds in excess of 40 mph will be possible with
these storms.

Locations impacted include...
Colby, Oakley, Hill City, Hoxie, Grainfield, Grinnell and Levant.

This includes Interstate 70 in Kansas between mile markers 39 and 84.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

A Severe Thunderstorm Watch remains in effect until 100 AM CDT for
northwestern and west central Kansas.

LAT...LON 3913 10015 3912 10015 3910 10134 3949 10135
      3950 9962 3913 9963
TIME...MOT...LOC 0420Z 154DEG 8KT 3920 9978 3917 10124

JN