Area Forecast Discussion
Issued by NWS Goodland, KS

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000
FXUS63 KGLD 191439
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
839 AM MDT Tue Sep 19 2017

.UPDATE...
Issued at 839 AM MDT Tue Sep 19 2017

Update to forecast to remove mention of fog from central and
eastern zones. Latest obs from around the CWA showing 7sm or
greater under morning sunshine. High cloud currently moving
across western zones and temp trends covered well in going
forecast and made no changes.

&&

.SHORT TERM...(Today through Thursday night)
Issued at 245 AM MDT Tue Sep 19 2017

Large scale mid-upper trough is in place over the Pacific
northwest, with southwest flow deepening into the Central High
Plains. A shortwave trough will swing around the large scale upper
low and send a cold front over our CWA by late tonight. A deep
dry air mass and large scale forcing well north of the region will
keep dry conditions in place.

Ahead of this trough southwest flow and increasing deep gradient
will support unseasonably hot afternoon temperatures and windy
conditions today. If prefrontal surface trough holds west we may see
higher temps that most 2m and statistical guidance indicate, and I
couldn`t rule out some locations near 100F. Ahead of this surface
trough early this morning we may see patchy stratus and fog, but
increasing BL winds have helped mix the low levels, so mention has
been left out.

Wednesday-Thursday: Deep dry air mass and unfavorable upper level
pattern will keep dry conditions in place during these periods.
After  near seasonal temperatures Wednesday, southwest flow
redevelops. Deepening lee trough will result in unseasonal highs
and breezy conditions once again Thursday.

.LONG TERM...(Friday through Monday)
Issued at 245 AM MDT Tue Sep 19 2017

Amplified pattern will be in place on Friday as a deep H5 trough
will be situated with a north-south axis around the Great Basin. The
trough will not move much over the course of the extended period;
however, a cold front and theta-e axis will interact with fast-
moving H7 shortwaves that will propagate along the eastern flank of
the larger H5 feature. This will allow a dynamic but nearly
stationary boundary that will stretch from southwest to northeast
across the CWA Friday through Sunday before moving slightly eastward
for Monday.

Friday and Saturday: Looking at the possibility of strong to severe
thunderstorms late Friday afternoon along a pre frontal trough ahead
of an approaching cold front. CAPE will be in the 1100 to 1800 J/Kg
range with an increasing shear profile that will be favorable for
isolated stronger storms. PW values will climb to well over one
inch, approaching 1.30 inches late Friday. Due to the slow-moving
nature of this system, heavy rainfall and flash flooding will be a
concern. For Saturday, another round of strong to severe storms will
be possible as CAPE once more climbs into the 1500 to 1800 J/Kg
range mainly east of the KS/CO border. Shear will be sharply
increasing along the frontal boundary, which is expected to slowly
push to the east through the day. Much like Friday, we will see very
high PW values as high as 1.60 inches (GFS) along and just ahead of
the front/boundary. The front will become nearly stationary Saturday
afternoon, increasing our chances for training thunderstorms and
creating another day where heavy rainfall will be a concern.

Sunday and Monday: The vast majority of the CWA will be post-frontal
as we head into Sunday afternoon. The lingering theta-e boundary
will keep PoPs in the forecast through much of the day and with PW
values remaining in the 1.25 to 1.50 inch range, we could see
another day of moderate to heavy rainfall potential, especially in
our eastern counties. Instability will not be as high as in previous
days, thus I expect widespread showers and thunderstorms with a
limited potential for stronger storms. Monday, the boundary pushes
slightly eastward and begins to dissolve a bit, lowering PoPs
slightly; however, there remains a chance of showers and a few
embedded storms through the afternoon and evening.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 522 AM MDT Tue Sep 19 2017

Fog and stratus has developed east of the Colorado border between
KGLD and KMCK. IFR conditions are occurring where main area of
stratus is, but currently satellite shows this between both
terminals. I can`t rule out brief IFR conditions, and MVFR vis
continues at KGLD. Trend with satellite and high resolution
guidance has been towards this transitioning east and dissipating
before reaching KMCK as much drier air moves in from the west. I
decided to keep mention limited to 6sm for now at KGLD, and left
mention out at KMCK.

Winds will increase from the south as surface low pressure
deepens and shifts into northwest KS and southwest Nebraska by
midday, then shift to the northwest behind a cold front tonight.
There will be periods of low level wind shear at KMCK with a low
level jet axis over the terminal this morning and again tonight.


&&

.FIRE WEATHER...
Issued at 245 AM MDT Tue Sep 19 2017

Tds rapidly decrease from the west this morning through this
afternoon, and with hot temperatures expected this will support
RH values well below 15% across our CWA. Mixing heights are a
question (particularly further east) and may limit magnitude and
duration of strongest wind gusts this afternoon/early evening. At
the same time, confidence remains high that 3hr of 15% RH/25 mph
wind should be seen across our CWA (or at least come very close).
I upgraded Fire Weather Watch to a Red Flag Warning for the rest
of our CWA, and extended the duration by an hour based on latest
timing and confidence.

Low RH and breezy conditions may develop again on Thursday
afternoon, and elevated to critical fire weather conditions may
once again be an issue. Current forecast is marginal and there is
still some time to fine tune details before considering fire
weather highlights for that period.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Red Flag Warning from noon MDT /1 PM CDT/ today to 7 PM MDT /8
     PM CDT/ this evening for KSZ001>004-013>016-027>029-041-042.

CO...Red Flag Warning from noon today to 7 PM MDT this evening for
     COZ252>254.

NE...Red Flag Warning from noon MDT /1 PM CDT/ today to 7 PM MDT /8
     PM CDT/ this evening for NEZ079>081.

&&

$$

UPDATE...JN
SHORT TERM...DR
LONG TERM...TL
AVIATION...DR
FIRE WEATHER...DR



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