Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 122054
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
254 PM MDT Thu Apr 12 2018

.SHORT TERM...(This evening through Friday)
Issued at 155 PM MDT Thu Apr 12 2018

Current GOES-16 WV imagery shows the jet pushing through the
region from the SW. Persistent cloud cover this morning and
afternoon delayed the onset of mixing and winds over the northern
plains and foothills. Winds are expected to steadily increase over
the next few hours with continued gusty winds over the Palmer
divide and Park county. Maintained the Red Flag Warning through 9
pm, however areas over portions of Larimer and Weld could still be
borderline with winds taking some time to reach criteria. Models
show the upper level low progressing ESE with the divergent
portion of the upper jet over the eastern plains by Friday
morning. Increased moisture embedded with the cold push from the
WNW will help to bring a chance of snow to the NE plains by Friday
morning along with increased rates in the mountains. For the
lower foothills and urban corridor NW flow is not the best for
snow accumulation thanks for downsloping. Showers will start off,
very light with little to no accumulation for most areas nearest
the foothills. Through Friday the jet will push eastward with
steady QG lift continuing into the evening. This lift and moisture
will keep snow into the overnight hours for the far NE plains. At
this time snow amounts will vary between a trace to 1 inch for
most areas along and west of I-25 and will become higher east of
I-25. The NE counties of Logan, Washington, Sedgwick and Phillips
counties will see the highest amounts with 4 to 8 inches and
locally higher amounts of up to 10 inches.

With the upper jet in place winds will continue to be a concern on
the plains with a High Wind Warning from midnight through 6 am for
the counties of Weld, Adams, Arapahoe and Morgan with speeds of up
to 65 mph possible. Further south over Douglas, Lincoln and Elbert
will see higher amounts in the 65 to 75 mph range that will last
until the overnight hours on Saturday. With the snow amounts
combined with the high winds over the far NE plains blizzard
conditions are expected through Friday. The highest impacts will
occur by Friday afternoon into the evening hours with visibilities
reaching down to a quarter mile or less at times. This will cause
impacts to travel for Friday late afternoon and evening...
especially over the Sedgwick and Phillips county areas.
Temperatures will take a large dive Friday with highs only
reaching into the upper 30s on the plains.

.LONG TERM...(Friday night through Thursday)
Issued at 155 PM MDT Thu Apr 12 2018

Strong snow and wind issues wl continue across the northeast
plains Friday night into Saturday. Mdls keep a tightly wound
vertical stacked storm system, over scentral NE/ncentral KS at
00z Saturday, and slowly shift it eastward Friday night. This will
result in a strong west-east sfc pressure gradient with a strong
northerly flow aloft over the cwa. The mdls maintain weak mid
level qg ascent over northeast CO through 06z, with mid level
subsidence developing by 12z Saturday. No changes regarding the
highlights at this time. Blizzard conditions over the northeast
corner of the state will continue through the evening, but the
snow should start to taper off by after 06z Friday night. The
wind however will continue to blast across the eastern plains
through most of Saturday, strongest east of a line from around
Sterling to Limon. By 00z Sunday an upper level ridge will move
into from the west with the flow a gusty but drier north/northwesterly
flow aloft Saturday night. The ridge axis will move across
eastern CO Sunday afternoon and Sunday night with a dry and warmer
airmass in place. Moisture will increase across western and
northern CO on Monday as another trough moves into northern CA by
00z Tuesday. Should see another chance of snow in the high country
Monday night into Tuesday. The models show increasing mid level
qg ascent with the trough axis over eastern UT by 12z Tuesday, and
over central CO by 18z Tuesday. Likely enough instability and
dynamics for showers to carryover into the northeast plains on
Tuesday. May need to increase pops over the northeast plains there
at some point. Drying and subsidence behind the trough Tuesday
night into Wednesday. Next system that may impact the area moves
into the Great Basin region by 00z Thu, and into increasing pops
across the cwa by Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 155 PM MDT Thu Apr 12 2018

Cloud cover and sfc low to the southeast of Denver has keep
lighter northerly winds at KDEN/KBJC, with gusty southwesterly
winds at KAPA. Latest HRRR/RAP not very useful so far today so
will need to interpolate from current obs. Still anticipate
northwest/northerly winds with fropa 03-06z. We may need to tone
down the winds gusts through 09z, 25-30 kt range, then the
stronger winds will develop as the sfc low quickly intensifies
along the eastern CO border in the 12-18z period on Friday. VFR
conditions overnight, then ILS restrictions bkn-ovc050-060 Friday
afternoon, with ocnl MVFR cigs bkn020-030 agl, with any developing
snow showers. Overall shower coverage, isolated to scattered.


&&

.FIRE WEATHER...
Issued at 155 PM MDT Thu Apr 12 2018

Still expect critical to extreme fire weather conditions over most
of the NE plains through the afternoon and early evening hours.
Currently winds are starting to increase with the delayed mixing
and RH values will continue to drop through the afternoon.

A strong spring storm will move into the mountains this evening
and onto the plains by Friday morning bringing a mix of rain and
snow along with much cooler temperatures to the plains.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Blizzard Warning from 6 AM Friday to 6 AM MDT Saturday for
COZ048>051.

Red Flag Warning until 9 PM MDT this evening for COZ214>216-
238>247-249.

Winter Weather Advisory from 6 PM this evening to 9 PM MDT
Friday for COZ031-033-034.

High Wind Warning from 6 AM Friday to midnight MDT Friday night
for COZ042>045.

High Wind Warning from 6 AM Friday to 3 PM MDT Saturday for
COZ041-046-047.

&&

$$

SHORT TERM...Bowen
LONG TERM...Cooper
AVIATION...Cooper
FIRE WEATHER...Bowen



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