Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/19/21

Area Forecast Discussion

National Weather Service Amarillo TX

 632 PM CDT Mon Oct 18 2021

.AVIATION...

For the 00Z TAFs:

VFR conditions are expected at all three terminals throughout this
TAF cycle. The main item of concern for this period will be the
potential low level wind shear overnight. A jet around 1,000 to
1,500 ft AGL could reach speeds of 50-60 knots from the
south/southwest. Otherwise, we are expecting plenty of sunshine
and--at times--breezy winds through the next 24 hours.

Guerrero

&&

.PREV DISCUSSION... /Issued 253 PM CDT Mon Oct 18 2021/

SHORT TERM...Tonight through Tuesday Night...

Warm and dry conditions expected to continue through Tuesday, prior
to a cold front arrival Tuesday night.  Upper level trough currently
east of the Reno NV area is expected to track towards the Salt Lake
area this evening.  In general warm and dry southwest flow out ahead
of this trough is expected.  However, just enough mid level moisture
around 600-700mb will be advected over the southern Panhandles later
this afternoon to early evening.  As a result there might be just
enough instability to get a shower/isolated storm to develop.  The
layer below is pretty dry so doubt there will be much precipitation
involved, if anything there might just be some breezy winds out of
it as evaporative cooling will take place under the cloud bases.
While a couple deterministic models as well as the HRRR model hint
at these showers, the confidence still remains low, and thus only a
10 pop isolated rain shower will be noted at this time. Breezy south
winds 15 to 25 mph with gusts up to 30 mph will continue through
sunset across the Panhandles.  Might be just enough for elevated
Fire Weather conditions in the Cimarron County area.  Winds are
expected to stay up overnight and will likely keep the temperature
well mixed and limit the radiational cooling.  As a result lows
tonight look to be in the 50s across much of the area.  With the
warmer start to the day on Tuesday and continued south to southwest
flow highs will likely be in the upper 70s to mid 80s.  Most of the
moisture should be east of the area on Tuesday and thus do not
expect any isolated shower activity at this time.  Winds will shift
out of the north and a cold front is expected to move through after
midnight Tuesday night.  As a result morning lows will be much
cooler with mid 30s in the northwest and mid to upper 40s in the
southeast.

Weber

LONG TERM...Wednesday through Sunday...

Following the cold front Tuesday night, Wednesday will be a bit
cooler with temperatures slightly below normal. West northwesterly
flow will build in aloft as the low pressure system pushes farther
east towards the Great Lakes and a ridge builds into the western
CONUS. Temperatures will remain in the 70s through the remainder
of the week with mostly light southwest surface winds. Winds may
turn to the north briefly Friday morning, but will remain light
throughout the day. Saturday, the flow aloft becomes westerly
with the GFS/Canadian hinting at a few disturbances in the flow
and more southwesterly flow aloft. Along with the disturbances
aloft, the GFS/Canadian form a lee low off the Rockies in east
central Colorado with breezy southwest winds possible Saturday
afternoon through Sunday. Meanwhile, the EC keeps the westerly
flow aloft with no surface low formation. If the weak disturbances
come to fruition, there is a chance for some light shower activity
across the east and southeast Panhandles Saturday night into
Sunday.

Rutt

&&

.AMA Watches/Warnings/Advisories...
TX...None.
OK...None.

&&

$$



Area Forecast Discussion

National Weather Service Grand Forks ND

 1016 PM CDT Mon Oct 18 2021

.UPDATE...
Issued at 1014 PM CDT Mon Oct 18 2021

Wind shift/cold front moving into Brandon MB and into far NW ND.
It is moving SSE and track would have wind shift into GFK around
09-10z. Clouds to follow about 2 hours later. Upstream cloud cover
and heights are not extensive so far but something to watch as
short term models insist on bringing in a larger MVFR deck behind
front.  More of an aviation issue than public.

UPDATE Issued at 701 PM CDT Mon Oct 18 2021

High clouds over the area this evening, but thin. Mild out there
after a very warm day. Will be watching cold front drop south-
southeast from Canada overnight into Tuesday AM. HRRR has it
entering NE ND around 06z and near GFK 09z.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 321 PM CDT Mon Oct 18 2021

Impacts in the short term will be minimal, though temps much cooler,
with a dry cold frontal passage expected to bring much cooler
weather to the area tomorrow. A quiet and warm evening will be the
last of the warmth for awhile with north winds greeting the morning
as gusts behind the front set to be 30 to 40mph based on the Bufkit
soundings depicting mixing to 950mb of the 30 to 35kts within the
blyr CAA and with pressure rise couplet moving down the valley in
the wake of the front offering efficient mixing of the downward
momentum transfer.

Cloudy and much cooler than today with highs 20 to 30 degrees cooler
Tuesday, in the 40s and 50s. Late overnight some light rain will
attempt to lift into SE ND with the passage of an upper wave across
the central plains with most of any accumulation holding off until
Wednesdays time frame, covered in the long term section below.

.LONG TERM...(Wednesday through Monday)
Issued at 321 PM CDT Mon Oct 18 2021

Highlights of potentially impactful weather within the long term
period mainly revolve around the region`s first widespread hard
freeze of the season likely (70-90%) starting Wednesday night as
a seasonable polar air mass moves over the area. Impacts however
are likely mitigated by this event`s late season occurrence.

A progressive Colorado low is still favored to move into the
Central Plains of SD/NE east into the Upper Midwest of MN/IA/WI
Wednesday. This track slides the northern deformation zone precip
shield across southern portions of the FA, with the southern
Valley into west-central MN favored for most precip. While there
is some signal for maybe some fgen, the overall progressive nature
of the low and generally lower amount of available moisture
content will limit amounts to the 0.10-0.50 inch range, with some
higher amounts in smaller locations likely given signal for fgen
within the def zone forcing. Temps are currently forecast to be
warm enough to negate general concern for ptype issues, in
addition to the precip zapping effects of expected very dry air
filtering in behind the low. However, there still may be just
enough overlap towards the northern and western edge of the precip
shield to mix in some snow flakes, however no impacts are expected
given very light amount of snow (if any) and warm ground temps.

The seasonably cold, polar air mass behind Tuesday`s cold front
continues into the Northern Plains fed by northwesterly flow
behind the exiting Colorado low, with even perhaps a backdoor cold
front its parent upper low into the Great Lakes region late in
the week to reinforce this colder air. This air mass along with
favorable synoptics to promote radiational cooling within a very
dry air mass are driving the likely chances of temperatures at or
below 28 degrees during the overnights and mornings of Wed night-
Sat morning. While this isn`t unusual for this time of year, it is
the region`s first widespread coverage and multiple days of hard
freeze criteria. Given such a late occurrence in this fall season,
area agricultural impacts should be mitigated, or rather not
unexpected.

Getting into next week, clustered ensemble guidance hints at more
upper ridging which may help bring temps back to above seasonal
averages. NBM is picking up on this with 75th percentile high
temps back into the 60s for some locations within the FA.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 701 PM CDT Mon Oct 18 2021

After several days of clear weather, will watch cold front drop
south across the area late tonight into Tuesday. Short term models
all bring a deck of MVFR cigs southward behind the front 1-2 hours
after passage. From satellite however, that would seem fast. But
short term models have done pretty well in the past with these
lower clouds moving in so left its thinking for the TAFs. Gusty
north winds 20-30 kts Tues esp E ND/NW MN, much less BJI-FFM areas
which will hold onto the south winds into the aftn.


&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$

UPDATE...Riddle
SHORT TERM...JK
LONG TERM...CJ
AVIATION...Riddle



Area Forecast Discussion

National Weather Service Gray ME

 1108 PM EDT Mon Oct 18 2021

.SYNOPSIS...
Upper level low will continue chances for showers primarily in
the mountains through Tuesday. Above normal temperatures return
Wednesday into Friday followed by another cool down over the
weekend. Chances for widespread precipitation through the end
of the week are low as the next low pressure system passes to
our northwest. There will be chances for showers across the
north Thursday with a warm front with additional chances Friday
with the passage of a series of cold fronts.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
1105 PM Update...
Have trended temperatures and dew points lower in the forecast
this evening. Webcams and surface observations from northern
New Hampshire indicated some snow across the higher terrain late
this evening. Have also upped pops for the next couple hours per
latest radar imagery and the latest HREF and HRRR solutions
across northern areas. Otherwise, just minor adjustments to
winds across the forecast area.

615 PM Update...
Made some adjustments to PoPs based on radar imagery and near-
term forecast guidance such as the HRRR and HREF. The
convergence band of rain that has been over portions of extreme
southeastern Cumberland county and York county, ME continues to
move offshore and weaken. The expectation is that areas south of
the mountains will begin to clear out as these showers end but
across the north and mountains additional upslope rain and snow
showers will continue through the overnight. Other than some
minor adjustments to temperatures, dewpoints, and sky cover the
rest of the forecast remains on track.


Previously...
Northwesterly flow around an upper level low to our northeast is
dominating the weather this afternoon. This has resulted in
generally widespread cloud cover, with the exception of downwind
of the higher peaks where we see some clearing. Showers are
widespread across the higher terrain, with rain at lower
elevations and snow on the summits both being observed. Downwind
of the mountains a nice convergence pattern has also resulted
in some enhanced showers into York county ME.

Through evening, expect much of the showers to decay as they are
supported by mostly diurnal instability. With that clearing
temperatures across the coastal plain will drop rapidly under clear
skies, and expect pockets of frost to develop, which could be the
first of the season for some of these areas. Further north the
mountains will also see temps drop into the mid 30s but with cloud
cover.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Tuesday will see a continuation of the NWly flow, although not quite
as windy as today as the pressure gradient and upper level low moves
off to the east. A few gusts to 20mph are possible. Again
expect a diurnal increase in showers across the high terrain,
with rain the valley and snow on the summits. While the overall
QPF amounts are quite light the continued upslope flow will
amount to a few inches of snow accumulations on the peaks.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The extended forecast period will start out with northern New
England on the northeast periphery of a surface high over the SE
CONUS with a belt of strong northwest flow aloft exiting the region
into the Atlantic. Ridging aloft will build in on Thursday followed
by an area of low pressure passing to our NW through Quebec. The
bulk of the precipitation with this area of low pressure is
projected to pass to our NW, although a series of cold fronts will
cross the area Thursday night into the weekend. These cold fronts
will bring chances for showers along with reinforcing shots of
cooler air. Temperatures will start the period above normal
Wednesday into Friday followed by temperatures dropping below normal
Saturday into early next week.

Wednesday will mark the beginning of a stretch of warmer weather
after a cool start to the week. Temperatures will climb into the
upper 60s to near 70F across southern areas with 50s for high
across the north. A departing belt of strong mid to low level
winds may lead to a fair amount of clouds to start with
clearing skies in the afternoon. An inversion will keep strong
winds associated with the enhanced mid to low level flow from
reaching the lower elevations although winds will be quite
strong in the mountains.

Wednesday night into Thursday low pressure will be taking shape
over the Great Lakes while ridging aloft crests over New
England. This low will lift a warm front through the area
Thursday with models suggesting precipitation will be limited
with this front. Temperatures will be slightly warmer Thursday
than Wednesday with partly to mostly cloudy skies. Thursday
night through Friday low pressure will be tracking through the
St Lawrence Valley. Current guidance suggest that this low will
drag a couple cold fronts through the area Friday into Saturday
with organized precipitation along the fronts washing out as
they approach the area. Thus, prospects of widespread
precipitation are low with some areas downstream of the
mountains likely not seeing any precipitation through the
forecast period. Cooler weather is expected over the weekend
withs high relegated to the 50s and 40s by Sunday.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Short Term...MVFR will hold through the mountains over the next 24 to
36hrs as NWLy upslope continues. Snow showers aloft and Rain showers
in the valleys will be most widespread late afternoon and wane with
the sun. Elsewhere partly sunny skies with VFR continuing under NWLy
flow.

Long Term...Mainly VFR is expected Wednesday through the end of
the week. Low pressure passing through Quebec may bring periods
of MVFR Thursday night into Friday.

&&

.MARINE...
Short Term... Winds and seas will be low SCA thresholds
Wednesday into Thursday. Southerly winds ahead of a series of
cold fronts may approach SCA criteria Thursday night into
Friday.

Long Term... NWly flow will persist for the next few days with marginal
SCA conditions continuing. Best chance for strong winds will be
tonight as the pressure gradient

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 8 PM EDT Tuesday for ANZ150-152-154.

&&

$$
Cannon/Tubbs



Area Forecast Discussion

National Weather Service North Platte NE

 631 PM CDT Mon Oct 18 2021

.SYNOPSIS...
Issued at 347 PM CDT Mon Oct 18 2021

H5 analysis from earlier this morning had a closed low
just north of Reno Nevada. A trough extended south of this feature
into southern California. Downstream of this feature, ridging
extended from the Ozarks north into western Ontario. Downstream of
this feature, closed low pressure was noted over eastern Quebec with
a trough extending south into New England. At the surface, a weak
surface trough was present from sw Nebraska south into sern
Colorado. Winds across central and eastern Nebraska were gusty this
afternoon, while lighter winds were present along and west of
highway 83. Skies were partly cloudy in the west and mostly clear in
the east this afternoon and 2 PM CT temperatures ranged from 63
degrees at Imperial and Ogallala to 77 degrees at Valentine.

&&

.SHORT TERM...(This evening through Tuesday night)
Issued at 347 PM CDT Mon Oct 18 2021

The main forecast challenge will be precipitation and weather
impacts with the approaching H5 low (currently near Reno Nevada).
This feature will track east, approaching far northwestern
Colorado by 12z Tuesday. Downstream of this feature, surface low
pressure will quickly deepen over northeastern Colorado. Winds
will increase east of this feature, leading to a fairly mild night
across the area. With the combination of winds and increasing
high cloudiness, lows will be in the lower to middle 40s. The
upper level low will track east, approaching the western Nebraska
panhandle by 00z Wednesday. Downstream of this feature, surface
low pressure will track into central Nebraska at the same time. A
strong cold front will be oriented south to southwest of this
feature with a warm front extending northeast of the low. An
inverted surface trough will extend north of the low into north
central Nebraska and central South Dakota by 00z Wednesday. Light
precipitation will develop in the northwestern forecast area
Tuesday afternoon as isentropic lift increases quickly across
northwestern Nebraska. Temperatures will remain warm enough to
support all liquid precipitation thorugh 00z- 03z time frame.
Temperatures do cool enough to support all snow in the northwest
after 03z, however, isentropic lift will lift quickly north into
South Dakota by late evening, shifting the bulk of pcpn north of
the area. One caveat here however, is the 12z nam soln from this
morning. It develops some convective pcpn along the NE/SD border
late Tuesday evening. If that were to come to fruition, we could
see a quick burst of convective snow along the border mid to late
evening Tuesday. This is advertised by the NAM12 soln, however it
is not advertised in the GFS soln. The HRRR soln from 12z this
morning develops some convective elements just over the border
into South Dakota. With the bulk of broad scale isentropic lift
being north of the area during the late evening and overnight
hours, not anticipating much in the way of snow accums. Tuesday
night. For now, I have a stripe of 1 to as much as 2 inches of
snow in the Pine Ridge of northern Sheridan and far northwestern
Cherry county. Another aspect keeping snow accumulations on the
lower end are SLR ratios which are running in the 5 to 7 inch
range. Further south and east, we could see a skiff of snow,
however, almost all pcpn should fall as rain as temperatures
remain in the middle to upper 30s through 09z Wednesday. As
mentioned earlier, isentropic lift will shift north of the area by
late evening, bringing a quick end in precipitation over north
central Nebraska overnight.

.LONG TERM...(Wednesday through Monday)
Issued at 347 PM CDT Mon Oct 18 2021

Temperatures will be very chilly on Wednesday behind the exiting
system. H85 temps will range from -3C in the north to 6C in the
southwest. Highs will struggle to get out of the lower 40s in far
northern Nebraska where persistent cloud cover is expected, while
highs will reach into the lower 50s mainly south of I-80.
Temperatures will slowly begin to moderate upward to more seasonal
levels toward the end of the week. Northwesterly flow aloft will
persist through Friday, followed by a ridge building east of the
Rockies Saturday into Sunday. Highs will be mainly in the 60s
toward the end of the week with some lower 70s possible in SW
Nebraska Sunday and Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 631 PM CDT Mon Oct 18 2021

VFR is expected throughout wrn and ncntl Nebraska tonight and
Tuesday morning. Thereafter, a storm system over the cntl Rockies
this evening will begin spreading MVFR/IFR conditions in -RA and
low ceilings across wrn Nebraska affecting areas north of highway
2 and west of highway 83 (Sheridan and western Cherry counties).
VFR is expected elsewhere during this time.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC



Area Forecast Discussion

National Weather Service Portland OR

 319 PM PDT Mon Oct 18 2021

.SYNOPSIS...After a brief break in the wet weather through Tuesday,
expect a very active weather pattern to bring valley rain
and high mountain snow every 12-24 hours through early next week.


&&


.SHORT TERM...THIS EVENING THROUGH THURSDAY...Clouds have been
slow to erode in the southern Willamette Valley and Cascades so far
this afternoon, and it`s doubtful whether they`ll clear before the
day`s over, but the radar remains clear and observations have been
coming in dry across the board the past several hours. The next
timeframe that area-wide rain will be likely begins tomorrow
evening. Between now and then, on the back side of the cut-off low
that brought rain to parts of the region yesterday, the overall
pattern is tranquil in nature, with weak pressure gradients that
will favor light winds. The area is likely to be cooler than normal
today with highs generally in the 50s across the board in the
lowlands. It will be a little warmer tomorrow in warm air advection
ahead of the next approaching trough, though there is some
uncertainty in how warm due to uncertainty in how cool it will get
tonight. Sky guidance is overwhelmingly indicative of clearing late
this evening through the overnight, with hints that radiational fog
and/or low stratus will develop in the early morning - mainly across
the central and western Willamette Valley. If this does occur, the
very presence of fog would imply maximum surface cooling overnight -
with temperatures falling to the dewpoints (currently forecast to be
in the 30s early tomorrow morning) in a layer at/very near the
surface. But then the fog/low stratus itself could hinder surface
heating for part of the day, depending on the depth of this
saturated layer (the deeper it is, the longer it takes for the sun
to "burn" it off), and a later burn off time means surface heating
starts later; this, in turn, means that there is less time for the
surface to heat before the sun begins to go down and outgoing
longwave radiation from the surface becomes greater than the
incoming shortwave that it`s receiving; all this is to say
forecasting tomorrow`s high is tricky.

What`s a little easier is assessing the time of arrival for
precipitation, which looks to arrive first in the Florence area
during the 4-7 PM timeframe tomorrow before quickly overspreading
the remainder of the area over the successive several hours. A weak
surface low will then move along the coast, dragging with it a cold
front that will bring an end to the steady rain and introduce a
threat for showers - especially along the coast and in the Coast
Range - Wednesday. NBM continues to suggest the possibility of
thunder over the waters Wednesday morning, and the SREF doesn`t
disagree, so for now that has been left in the forecast. The low
will also yield some gusty winds Wednesday morning. As is usually
the case in these scenarios, the coast and Coast Range will receive
the brunt of the impact from these gusty winds, but the interior
lowlands and even the Cascade Foothills are looking gusty too. The
latest runs of the HRRR and ARW are suggestive of gusts to around 35
to 40 mph (perhaps higher in spots) in the southern and central
Willamette Valley, 40 to 45 mph in the Coast Range and Cascade
foothills, and 45 to 50 mph along the shoreline (with gusts in the
high Cascades at least that high). For now, the forecast is a
conservative blend of high resolution models, but it could certainly
be a bit gustier if the higher end of guidance shakes out.

The most favored timeframe for a break in precipitation looks to be
late Wednesday evening through around lunchtime on Thursday.
Thursday evening an occluded front from the bombed out low in the
Gulf of Alaska nears the area to bring another round of widespread,
gentle rain to all of NW Oregon and SW Washington from Thursday
evening through Friday night. -Bumgardner


.LONG TERM...FRIDAY THROUGH SUNDAY...If the ECMWF and GFS
are right, the deep cut-off low in the Gulf of Alaska gets picked up
by another upper trough swinging down from the northwest, and
subsequently merges with another surface low which will bring in
another cold/occluded front during the Saturday/Saturday night time
period. Ahead of the front, the area should experience another round
of rain; behind it, the pattern turns showery again.

Forecasting becomes exceptionally difficult beyond Saturday, as the
pattern stays active, but each ensemble member seems to have a
different depiction of the placement and strength of any storm
system to approach our area on and beyond Sunday. In the left exit
region of a ~150 knot 200-300mb jet extending across central/
northern CA into northern NV, strong cyclogenesis is possible
in/near the Pacific Northwest and the adjacent eastern Pacific
between Saturday night and late Monday. If an intense enough system
can approach our area with the proper orientation of its pressure
field, a high wind event could unfold, but given the model
disparities at this time range it just wouldn`t make sense to make
consequential changes to what the NBM has populated in its forecast.
Models` forecasts of dynamic processes favored for cyclogenesis
(including 500mb vorticity advection; thermal advection; adiabatic
cooling and heating due to vertical motions; diabatic heating and
cooling provided by earth`s surface, solar heating, and latent heat
release by condensation in clouds; etc.) will be analyzed in the
coming days to determine whether anything consequential will arise
from this pattern. -Bumgardner


&&


.AVIATION...Dry southerly flow aloft as high pressure builds
across the region. Generally broken lower VFR clouds are
expected to clear by 02Z this evening according to HREF guidance.
VFR conditions will likely persist through the period ending 00Z
Wednesday. Light offshore flow develops tonight so may see
patchy fog in the valley later tonight. MOS guidance suggests
most likely locations for brief IFR conditions will be at KEUG,
KSLE, and KHIO between 10Z-15Z Tuesday.

For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse

KPDX AND APPROACHES...VFR to prevail through Tuesday afternoon.
Light onshore flow will turn easterly around 04Z Tuesday. /DH

&&

.MARINE...High pressure will push inland tonight with winds
becoming southeasterly across the coastal waters. A strong front
will approach the region later Tuesday into Wednesday. Expect
winds to gradually increase ahead of the front overnight. Winds
will continue to increase Tuesday as the front enters the coastal
waters with a period of Gale force winds expected mainly for the
outer waters Tuesday afternoon through Tuesday night. The
strongest wind is expected west of about 35 NM. Expect periods
of enhanced southerlies to then persist through the end of the
week as another front moves through the waters Thursday into
Friday.

Meanwhile, seas will be dominated by a decaying westerly swell
through the beginning of the week as it subsides from around 10
feet this afternoon to 5-6 feet on Tuesday morning. The next
front will bring an uptick in short period seas Tuesday into
Wednesday, peaking around 12 ft nearer to shore and 20 feet
beyond 35 NM early Wednesday. Seas settle some later Wednesday to
around 8 to 10 ft as a fresh westerly swell arrives. DH/MH

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory from 11 PM this evening to 11 AM PDT
     Tuesday for coastal waters from Cape Shoalwater WA to Florence
OR from 10 to 60 nm.

     Gale Warning from 11 AM Tuesday to 5 AM PDT Wednesday for
     coastal waters from Cape Shoalwater WA to Florence OR from 10 to
60 nm.

     Small Craft Advisory from 8 PM Tuesday to 5 PM PDT Wednesday
     for coastal waters from Cape Shoalwater WA to Florence OR out 10
nm.


$$



Area Forecast Discussion

National Weather Service Pueblo CO

 941 PM MDT Mon Oct 18 2021

.UPDATE...
Issued at 934 PM MDT Mon Oct 18 2021

Given recent trends, have decided to issue a High Wind Warning for
the southern Sangres for late tonight through midday Tuesday.
Previously mentioned mountain wave setting up tonight should yield
southerly gusts up to around 75mph later tonight, with HRRR
continuing to show this possibility at this time. Would not be
surprised to see a few higher gusts to 80-85mph Tuesday morning,
before winds diminish by late morning into midday.

UPDATE Issued at 715 PM MDT Mon Oct 18 2021

Update this evening was to expire the Red Flag Warning which was
in effect for eastern Huerfano, Las Animas and Baca Counties.
Gusts may continue this evening, though RH values will continue
to improve. A Red Flag Warning remains in effect from Noon until 7
PM MDT Tuesday for strong winds, low relative humidity and dry
fuels, that includes Fremont, southern El Paso, Pueblo, Huerfano,
Las Animas, Crowley, Otero, Bent, Prowers, Kiowa and Baca
Counties.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 306 PM MDT Mon Oct 18 2021

...Critical Fire Weather Conditions on the Plains Tuesday...

Upper level low moving through the Great Basin this afternoon, while
lee surface trough deepens on the plains. Tightening pressure
gradient and deeper mixing ahead of the low have led to gusty winds
across much of the area, with patchy Red Flag Conditions along the
Raton Mesa eastward into Baca County. Upper low moves quickly
eastward into nwrn CO overnight, then pushes eastward along the
CO/WY border through the day Tue. Models suggest brief band of snow
showers spreading across the Continental Divide toward 12z as main
lift with the low/trough comes across, then mainly scattered snow
showers through the day Tue, especially in nw flow enhanced
locations in Lake County around Leadville/Fremont Pass. Not
expecting much more than a dusting to an inch of snowfall across
most of the Divide, though higher peaks of the Sawatch could see an
inch or two if they`re lucky. Surface winds over much of the area
will remain breezy overnight, with perhaps some strong gusty winds
in the lee of the eastern mountains, especially the srn Sangres,
where HRRR shows some gusts over 50 kts, as brief mt wave sets up
09z-15z before forward shear increases by late morning. For Tue,
upgraded the Fire Weather Watch to a Red Flag Warning, as deep
mixing and increasing downward vertical motion should enhance winds
along and east of the mountains through the day, while dewpoints
drop off into the teens, which should more than offset any cooling
in surface temps. Maxes should end up about 8-10 degf cooler at most
locations as mid level temps fall behind the departing upper trough.

.LONG TERM...(Tuesday night through Monday)
Issued at 306 PM MDT Mon Oct 18 2021

Tuesday night...The upper low pressure system will be exiting the
region Tue night, producing some lingering snow showers over the
central mts through around midnight, as well as push a weak cold
front south across the state during the overnight hours. Additional
snow accumulations of up to an inch are expected as the shower
activity wanes. Expect minimum temps overnight to drop into the 20s
to around 30F for the high valleys, teens for the heart of the San
Luis Valley, and 30s across the plains.

Wednesday through Saturday...The story for the rest of the week and
into the weekend is a ridge of high pressure, producing dry
conditions, lighter winds and warming temps. Overnight low temps are
forecast to be in the 20s to around 30F for the high valleys, and
30s to around 40F for the plains. Highs will be slightly cooler for
Wed due to the cold front, in the upper 50s and 60s for most areas,
then 60s for the high valleys and 70s for the plains for Thu through
Sat.

Sunday and Monday...Long range models are still indicating a Pacific
longwave trough will move onshore over the weekend, approaching the
region and introducing some isolated pcpn chances along the
Continental Divide starting Sunday. There are some timing and
strength differences between models, so confidence is low at this
time on what this next pattern shift will actually mean for south
central and southeast Colorado. Stay tuned. Moore

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 306 PM MDT Mon Oct 18 2021

VFR at all taf sites the next 24 hrs. S-SW winds will gust 20-25 kts
into the evening at all terminals, then decrease slowly after
sunset. W-SW winds will increase again Tue morning at all sites,
with gusts 20-25 kts from mid-morning into the afternoon.


&&

.PUB WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from noon to 7 PM MDT Tuesday for COZ222-
227>237.

High Wind Warning from 3 AM to noon MDT Tuesday for COZ074-075.

&&

$$

UPDATE...RODRIGUEZ
SHORT TERM...PETERSEN
LONG TERM...MOORE
AVIATION...PETERSEN