Special Weather Statement, NWS Goodland, KS

Area Forecast Discussion
National Weather Service Goodland KS
712 PM MDT Mon Aug 6 2018

.UPDATE...
Issued at 700 PM MDT Mon Aug 6 2018

Overview: Westerly flow aloft will prevail through tonight. A
potent shortwave located invof Rapid City SD at 00Z will track
E/ESE to Sioux City by 12Z Tue. In the lower levels, a SW-NE
oriented SFC-H85 thermal/moisture boundary extended from Johnson
City--Garden City--Hill City.

00-04Z: Radar trends, SPC mesoanalysis data, observations, etc.
suggest that the relative best potential for isolated severe
thunderstorms this evening will largely be confined to eastern CO
and southwest NE. In particular, a long- lived supercell tracking
SSE through western NE (approaching Ogallala at 0030Z) could
impact portions of Hitchcock/Red Willow counties in the 04-05Z
time frame. Whether or not this updraft will persist for several
more hours is difficult to ascertain, though the downstream
environment appears more than supportive (7.5C/km H7-H5 LR, 2500
MLCAPE, 40-50 KT EBWD).

04-12Z: Simulated reflectivity forecasts from the HRRR and NAM
NEST suggest that convection will develop over northwest KS
between 03-06Z and gradually progress E-SE into central/southern
KS between 06-12Z. With plentiful moisture (PWATs 1.3" to 1.5"),
moderate to strong instability (2000-3000 J/kg MUCAPE), and
strengthening low-level warm advection/frontogenesis invof the
H85 thermal/moisture boundary after sunset, the aforementioned
scenario appears quite reasonable. Updrafts developing invof the
SFC-H85 TMB in northwest KS are likely to interfere with one
another as coverage increases late this evening, however, with
moderate instability and effective deep layer shear on the order
35-45 knots, a few instances of large hail will be possible in
association with the more robust updrafts (or transient
supercells) during the 04-08Z time frame. Otherwise, the primary
hazard associated with post- sunset convection will be heavy
rainfall /isold flash flooding/, particularly invof the SFC-H85
TMB (along/east of Hwy 83).

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 247 PM MDT Mon Aug 6 2018

Main concerns for the short term period are potentially severe
storms this evening and fog overnight.

Currently, KGLD is showing some precipitation echoes in the
eastern half of the CWA. Expecting shower activity to increase
from the eastern Colorado / Kansas border. SPC has since backed
off on the severity of the majority of the CWA, but some cells
could still become severe this evening. If the cooler stable
airmass that's moved over the area can get sufficient heating, we
may see multiple rounds of supercellular clusters bringing
damaging winds and large hail. Upslope flow will help aid in
supercells training and will help to pose flash flooding risks.

Target area will be the extreme southwestern half of our CWA
around the Colorado/Kansas line. Effective bulk shear values are
expected to be in the 40 to 50 knot range around peak afternoon
heating. SFC CAPE will be sitting in the 2500 to 3000 range, so
expecting large growth for the cells that do break the cap
creating potentially large hail. DCAPE values are lower than the past
couple of days, but it's still sitting around 1000 this afternoon
which will be more than enough to bump winds to severe criteria.

Today's highs are still on track, despite the impact of light to
moderate showers impacting the eastern half of the CWA. Tonight's
lows may vary lower than previously forecasted by 5 to 10 degrees
across the Tri-State area depending on extent of showers tonight
and where the gradient sets up in relation to the prevailing
cooler prefrontal airmass. Expecting mid 50s to low 60s.

Overnight, winds are expected to relax and become light and
variable across the Tri-State area. This, in conjunction with the
cooler moist airmass, will allow radiation fog to develop.
Confidence on extent and timing is still a little uncertain, but
hanging on to persistence from this morning's fog event for the
northeastern portion of our CWA to drop again, since it is even
more favorable tonight.

Tomorrow, expecting seasonably average highs in the mid 80s with
slight chances of precipitation in the evening.

.LONG TERM...(Tuesday night through Monday)
Issued at 303 PM MDT Mon Aug 6 2018

Main forecast issue will be for thunderstorm chances from Tuesday
night into Thursday night. Satellite showing an amplified pattern
from the eastern Pacific into western North America. Pattern is
being dominated at this time by large cutoff low off the Pacific
northwest. Broad troughing/faster westerly flow is over the eastern
portion.

Tuesday night...Area will be in easterly upslope flow at the
surface. Right rear quadrant of the jet will affect the south and
southwest third of the area through the night. At 500 mb there is
shortwave trough that moves through in northwest flow aloft. However
at 700 mb there is actually a shortwave ridge in place.

Looks like thunderstorms develop over the higher terrain to the west
of our area. Question becomes how far east does that cluster of
thunderstorms get. Mean wind is 5 to 10 knots and starts out north
and turns to the west. Per the reasoning above will keep the
thunderstorms confined to the western portion of the area and that
fits with the blend. The threat will have to watch for is locally
heavy rainfall. Precipitable water values are not as high before but
could get some decent rainfall amounts out of this.

Wednesday/Wednesday night...There looks to be linger rainfall in the
morning. Weak right rear quadrant moves across the area during the
afternoon and evening hours. Shortwave trough moves through in the
north to northwest flow aloft. There looks to be a rather strong Eml
in place and am wondering how much can develop. For now I am siding
with being slightly wetter than the output. Per the above reasoning
above and collaboration with neighbors, will insert slight chance at
this time.

Thursday/Thursday night...Weak right rear quadrant affect the
northern area Thursday afternoon and the entire area through the
night. At the same time, a shortwave trough moves through in
northerly flow. Forecaster builder gave me some slight chance pops,
and considering the weak lift those seem reasonable and will keep.
Temperatures look reasonable.

Friday through Monday...Models in good agreement through the period.
Amplified ridge is over the western portion of the area  at the
beginning with north to northwest flow in place through Friday. Then
the ridge gets shoved slowly east as it becomes positively tilted
from the desert southwest into the north central portion of the
country. This is the result of trough off the Pacific Northwest
coast moving east and deamplifying.

For Friday and Friday night...Heights continue to slowly rise and
the flow becomes more northeasterly. This flow aloft usually means
much drier air and that is shown well by the output. Temperatures
are rather cool for this time of year. There is a weak shortwave
trough coming through. However considering the weak lift and rather
deep dry layer, am fine with a dry forecast.

For the remainder of the period. Ridge stays in about the same place
through this time with anomalous northeast flow aloft. This continue
to bring very dry air aloft with continue shortwave troughs in this
flow. Most of this period looks dry with a small chance possible on
Monday. Different/tricky flow that will just have to watch closely
for any subtle changes that could bring precipitation. Again what
the forecaster builder gave me looks reasonable and will keep.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 545 PM MDT Mon Aug 6 2018

Scattered thunderstorms are expected to develop over the Tri-State
area this evening/tonight. Either terminal could be affected, with
the relative best chance expected between 03-06Z at MCK and
03-08Z at GLD. MVFR conditions associated with stratus or fog
cannot be ruled out between 10-14Z (AOA sunrise) at either
terminal, though confidence is too low to warrant explicit mention
with the 00Z TAF issuance. Otherwise, expect VFR conditions and
light (5-10 knot) E/NE winds to prevail.

&&

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

UPDATE...VINCENT
SHORT TERM...EV
LONG TERM...BULLER
AVIATION...VINCENT

Hazardous Weather Outlook...UPDATED
National Weather Service Goodland KS
531 PM MDT Mon Aug 6 2018

COZ090>092-KSZ001>004-013>016-027>029-041-042-NEZ079>081-072345-
Yuma County-Kit Carson County-Cheyenne County-Cheyenne-Rawlins-
Decatur-Norton-Sherman-Thomas-Sheridan-Graham-Wallace-Logan-Gove-
Greeley-Wichita-Dundy-Hitchcock-Red Willow-
531 PM MDT Mon Aug 6 2018 /631 PM CDT Mon Aug 6 2018/

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

.DAY ONE...THROUGH TONIGHT...

Isolated severe thunderstorms capable of producing large hail and
damaging winds will be possible between 7 PM and Midnight MDT,
primarily in eastern Colorado and southwest Nebraska. Isolated flash
flooding will be possible in northwest Kansas late this evening and
overnight, primarily east of Highway 83.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH MONDAY...

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required

Vincent

Special Weather Statement
National Weather Service Goodland KS
813 PM CDT MON AUG 6 2018

KSZ015-016-070145-
Sheridan KS-Graham KS-
813 PM CDT MON AUG 6 2018

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN SHERIDAN AND
SOUTHWESTERN GRAHAM COUNTIES UNTIL 845 PM CDT...

At 813 PM CDT, Doppler radar was tracking a strong thunderstorm 6
miles east of Hoxie, moving east at 30 mph.

Nickel size hail will be possible with this storm.

Locations impacted include...
Morland, Penokee, Tasco and Studley.

LAT...LON 3929 10043 3947 10040 3947 9990 3920 9994
TIME...MOT...LOC 0113Z 277DEG 26KT 3937 10032

DDT