Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/21/21
Area Forecast Discussion
National Weather Service Goodland KS
949 PM MDT Wed Oct 20 2021
.SHORT TERM...(This evening through Friday night)
Issued at 256 PM MDT Wed Oct 20 2021
Across the region this afternoon, skies are sunny as the remnants of
morning cloud cover north from exiting low pressure system have
moved away from southwest Nebraska locales. Winds are still gusting
up into the 25 to 35 mph range, with temps ranging from the mid 50s
to around 60F.
Forecast concerns in the short term revolve around the potential for
frost over the CWA with a drop in temps as surface ridge traverses
the area. As mentioned from previous forecast, the concern for
increasing cloud potential could hamper overnight lows. This
continues to hold as the latest HRRR guidance shows increasing
clouds late in the overnight period towards morning. This combined
with a switch to warm southerly flow will keep the majority of the
Freeze Watch above hard freeze numbers. As a result have changed the
Watch to a Frost Advisory with same timeframe as the current one(14z
Thursday ending). Some isolated spots along/north of Highway 34
could see upper 20s, but the areal coverage not enough to warrant
Freeze Warning at this time.
The passage of the surface ridge to the east, combined with
approaching upper ridge from the west, will afford the CWA an upward
trend in temps with decent WAA on southerly flow at the surface and
west-northwest flow aloft.
While temps at night will afford some more mention of frost, the
areal coverage will be much lower than tonight. Dry wx conditions
expected thru Friday night as a result. These dry conditions will
allow for fire wx concerns to crop up yet again, especially on
Friday when upper teens for good portion of area along/west of
Highway 27 expected. Gusts below criteria.
For temps, an upward trend is expected in the short term period with
high pressure building over the region. Thursday`s high will range
from the mid 60s to around 70F. On Friday, lower to mid 70s.
Overnight lows will see a warming trend as well with lower and mid
30s to start off tonight. A few isolated spots along/north of
Highway 34 could see upper 20s. By Thursday night, mainly mid 30s.
Going into Friday night, upper 30s west and north, to the lower and
mid 40s for southern and eastern locales.
With the expected overnight lows tonight, and expected winds, the
area will see wind chill readings drop into the mid 20s to lower
30s. Coldest readings will occur mainly in northeast Colorado and
southwest Nebraska.
.LONG TERM...(Saturday through Wednesday)
Issued at 246 PM MDT Wed Oct 20 2021
The main concern for the extended forecast is the potential for some
fire weather concerns, a slight chance of precipitation and frost
issues.
The extended forecast begins with a deamplifying ridge coming over
the Tri-State area with near-zonal flow becoming southwest as a
trough treks across the Four Corners region. Through the day and
into the overnight hours, the trough lifts to the northeast,
reaching the forecast area by Sunday morning. A few rain showers
may develop in the morning, particularly for areas along and east of
a line from Benkelman to Oberlin. Temperatures will be slightly
cooler Sunday afternoon than the previous day, ranging from the mid-
60s to low 70s. Lows will fall into the mid-30s to mid-40s. Any
chances for frost will be limited to eastern Colorado and will be
dependent on cloud cover. Clouds are expected to increase through
the night, which could eliminate the chances for frost in the
western portions of Cheyenne, Kit Carson and Yuma counties.
An amplifying ridge comes over the High Plains and Central High
Plains. Southerly winds will help bringing in the warmer air and
felt that model guidance was forecasting afternoon temperatures a
little on the cool side. Brought temperatures up a few degrees to
account for this, particularly in the western CWA. Expected highs
will range from the low to mid-70s across the region.
Tuesday, the ridge pushes to the east and a trough is expected to
enter the region. Temperatures are expected to reach into the 70s
in the afternoon with breezy conditions. Minimum relative humidity
values will fall into the mid-teens to low 20s along and west of
a line from Leoti to Atwood to Palisade. Wind gusts are expected
to reach into the low to mid-20s, particularly in eastern
Colorado. Elevated to near critical fire weather conditions are
expected. Those with fire interests will want to continue to
monitor the forecast over the coming days, particularly as there
is potential for a cold front to move through during the day. With
the FROPA potential, this could limit the amount of time where
our stronger winds and lowest RH values coincide with one another.
Tuesday evening a few rain showers are expected to develop and move
into the region. Right now, the best chance for any showers remains
limited to areas along and north of the Kansas-Nebraska border.
Areas in eastern Colorado will dip into the mid to upper 30s while
most our Kansas and Nebraska areas are expected to stay in the 40s
overnight.
Conditions remain dry on Wednesday with cooler temperatures expected
as the trough moves out. Afternoon highs will range from the mid-
60s to low 70s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 949 PM MDT Wed Oct 20 2021
The 06Z TAF period features VFR conditions for KMCK and KGLD. Winds
look to be light from the NNW before switching to the SSW just after
06Z at KGLD; whereas for KMCK winds will be light and variable
through the majority of the night before being from the SSW mid
morning Thursday. Mid to high clouds are expected to move west to
east across the area tonight and throughout the day Thursday as
conditions are expected to remain at VFR. Between 10Z-13Z there
may be a brief period of low stratus and/or patchy fog around the
KMCK terminal hinted at by some guidance and forecast soundings
moving in from the Nebraska Sand Hills where the greatest
potential for visibility restricting fog/stratus looks to develop
due to a warm front draped over the area. At this time low chance
for MVFR conditions but confidence is to low at this time to be
mentioned in the TAF but will be monitored overnight for any
potential amendments.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Frost Advisory from 3 AM MDT /4 AM CDT/ to 8 AM MDT /9 AM CDT/
Thursday for KSZ001>004-013>016-027>029-042.
CO...Frost Advisory from 3 AM to 8 AM MDT Thursday for COZ090.
NE...Frost Advisory from 3 AM MDT /4 AM CDT/ to 8 AM MDT /9 AM CDT/
Thursday for NEZ079>081.
&&
$$
SHORT TERM...JN
LONG TERM...AW
AVIATION...TT
Area Forecast Discussion
National Weather Service Marquette MI
826 PM EDT Wed Oct 20 2021
.SHORT TERM...(This evening through Thursday)
Issued at 457 PM EDT WED OCT 20 2021
Water vapor imagery and RAP analysis show split flow continuing
across much of N America. In the southern stream, the well-defined
shortwave that was over the central Rockies 24hrs ago is now
centered near Sioux Falls, SD. Wave that was in the northern stream
over western Hudson Bay 24hrs ago has separated out from that flow
and is now a well-defined mid-level low centered over far sw Hudson
Bay. Cold front associated with the latter wave swept s across the
fcst area last night/early this morning, and it is now running from
southern Quebec across northern Lower MI to low pres (associated
with the former wave) over far s central MN. In the wake of the
front, low-level moisture/upslope flow has led to considerable low
cloudiness across much of the fcst area today. Air within that
shallow moist layer has cooled sufficiently for an added lake
moisture component as well. Result has been some -dz closer to Lake
Superior, especially earlier today in the higher terrain favored by
upsloping n to ne winds. In the confluent flow btwn the 2 waves, the
resulting upper jet streak has led to right entrance upper
diffluence over the area today. Along with some increase in low-mid
level fgen and modest isentropic ascent, -shra are spreading into
south central Upper MI with more notable development to the wsw
across northern WI into central MN.
Shortwave near Sioux Falls will weaken as it moves to Lower MI by
Thu aftn then to the Lower Lakes Thu evening. Associated sfc low
will track e across northern Lower MI Thu morning. Upper
diffluence/modest isentropic ascent and broad low-mid level fgen
should support upstream -shra spreading across the fcst area this
evening, except for the Keweenaw. MUCAPE of a few hundred j/kg in
the 1-3km layer will skirt s central Upper MI, and with some
lightning noted this aftn in the pcpn across WI, will include a
mention of thunder in Menominee County. Shra will end far w late
tonight then quickly from w to e across the rest of the fcst area
during Thu morning. The one exception will be across n central Upper
MI due to potential lake effect. 850mb temps across Lake Superior
roughly around 0C at 12z Thu will fall to -4 to -5C by late aftn.
Sfc water temp of Lake Superior is roughly around 12C with higher
values present. With the increasing overwater instability,
inversions at around 3kft Thu morning do increase to 5-6kft in the
aftn. Across western Lake Superior subcloud layer remains quite
dry (inverted-v). This is quite reasonable given the early
season/still relative high sun angle which leads to well-mixed
boundary layer air advecting over the lake, a notable negative for
lake effect pcpn. As a result, do not expect any lake effect shra
to develop off western Lake Superior on Thu. Across eastern Lake
Superior, conditions should be different. Lake effect clouds are
evident off Lake Nipigon today under 850mb temps around 0C. On
Thu, 850mb temps will be around -7C across Lake Nipigon. As low-
level flow realigns, this preconditioned air will stream across
Lake Superior to Marquette/Alger counties in the aftn. Combined
with the cooling air mass and rising inversion, low chc pops
appear warranted by late aftn in that area. Leaned toward some of
the cooler guidance for max temps on Thu under caa and with
expectation of considerable stratocu development. Expect highs
from the lwr 40s to around 50F, warmest s central.
.LONG TERM...(Thursday night through Wednesday)
Issued at 344 PM EDT WED OCT 20 2021
An active weather pattern will continue for the start of the
extended forecast. The departing shortwave on Thursday evening
will continue to trek to the New England coast, while an ULL at
500mb will remain nearly stationary for a majority of Friday
through Sunday near the James Bay region. This ULL will have
numerous ripples of shortwave energy embedded within the flow as
jet energy treks from west to east across the Northern
CONUS/Hemisphere. The ULL maintaining its stationary presence over
the James Bay region will result in north to northwest flow aloft
across the Great Lakes. The north to northwest steering flow and
colder air aloft will mix down to the surface, and result in
cooler temperatures at the surface, and lake effect precipitation.
At this time, it looks to remain as a cold rain shower activity
over the area from Friday through most of Sunday. Overnight lows
going below freezing are plausible, so a rain/snow mix at times
will be possible also. Another shortwave will approach the UP by
Monday, but this time it will be from the south. Deterministic
output at this time shows the weak shortwave remaining to our
south, with a slight chance of showers over the south central tier
of Upper Michigan.
The remainder of the week will teeter totter from above average
temperatures back to near normal temperatures as the progressive
weather regime returns to the CONUS. Upper level ridging on Monday
through early Wednesday will cause above average temperatures and
mainly dry conditions. Wednesday into Thursday will bring the next
wave through the area, with precipitation and cooler temperatures.
Lake effect rain showers could also return to the area. Overall,
autumn conditions will become more present across Upper Michigan,
with precipitation opportunities on the rise as well.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 820 PM EDT WED OCT 20 2021
LL stratus deck remains fixed in place across Upper Michigan with
some hints that it attempts to break up in the vicinity of KIWD
and KCMX as Thursday progresses. However, no such luck at KSAW
through this TAF period as the wind shift from NNE to NNW becomes
favorable for an enhanced moisture feed to set up across Lake
Superior right into the KSAW vicinity, with an additional
connection to Lake Nipigon in Ontario. Winds will also be on the
increase tonight into early tomorrow as the pressure gradient
tightens overhead.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 457 PM EDT WED OCT 20 2021
NE winds gusting up to 30kt over far western Lake Superior should
diminish to 20-25kt during the night. Otherwise, gusts in the 15-
25kt range should be the rule tonight on Lake Superior. While wind
gusts will fall back to 15-20kt over western Lake Superior on Thu,
wind gusts will tick back up to 20-30kt over the e as increasingly
colder air moves over the lake. Winds will then diminish Thu night,
and for Fri/Sat, expect gusts mostly under 20kt as high pres ridge
moves closer to the lake. High pres will then settle over northern
Ontario Sun and Mon. Winds will increase a bit into Mon, depending
on the strength of low pres tracking e to the Ohio Valley.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...BW
AVIATION...lg
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Phoenix AZ
439 PM MST Wed Oct 20 2021
.UPDATE...
Updated Aviation discussion.
&&
.SYNOPSIS...
Dry tranquil conditions are expected over the next several days
with temperatures warming to around normal starting Thursday and
lasting through the weekend. A slight cool down and breezy
to possibly windy conditions will be likely early next week as a
strong low pressure system tracks mostly to the north of our
region. This system may also bring a chance of precipitation to
the region at some point early next week, but chances may be
limited to higher terrain areas.
&&
.DISCUSSION...
Weak quasi-zonal flow is in place across the area with passing
high clouds. Aircraft and RAP soundings show a few degrees of
warming below 700 mb from this time yesterday, which should result
in afternoon highs a few degrees warmer than yesterday. Height
rises over the region, as ridging amplifies downstream of an
active trough pattern in the northeast Pacific, should yield
another few degrees of warming through Thursday. NBM MaxTs for
both Thursday and Friday are in the upper-80s across the lower
deserts with 20-40% chance of reaching 90 degrees each day most
places. Conditions will also remain dry with light winds through
the end of this week as well.
Around midday Friday the first of a couple of strong and dynamic
troughs will move inland in the PacNW. While this first wave will
remain well north of the local area, heights will be suppressed
slightly which should lead to a few degrees of cooling heading
into the weekend, along with some breezier conditions. NBM
forecast MaxTs for this weekend are in the mid-80s across the
lower deserts both days. The second, more prolific trough will
take shape late this weekend and begin pushing inland in the
northwest CONUS late-Sunday into Monday. Greatest impacts from
this trough are still expected in the coastal states through early
next week. WPC cluster analysis still shows moderate variance
among global members mostly in terms of how far south the trough
will dig and timing. Models continue to support a strong
atmospheric river with this trough, so the amplitude of the trough
will certainly have an influence on precipitation chances for the
local area. It is still too early to say with confidence what the
chances are, but latest NBM still has a 10-20% chance for rain in
south-central AZ, favoring high terrain, around Tuesday. In
addition to the rain chances, this trough will also likely result
in breezy conditions across the region. There is still
uncertainty in magnitudes, but the ECMWF EFI is showing the
potential for unseasonably high winds Monday into Tuesday mainly
north of the local area. Lastly, much cooler temperatures will be
possible with the magnitude of cooling again dependent on the
evolution of the trough.
&&
.AVIATION...Updated at 2339z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:
Light winds surface and aloft (favoring westerly directions above
Fl120 and south/southeasterly below that) will continua through
Thursday except for some modest strengthening above FL210. Surface
winds will be light and follow familiar diurnal patterns overall.
But, there may be a period this evening over the Phoenix area
with light northerly directions during the transition between
early evening westerly and late evening onset of downvalley/drainage
winds (favoring easterly directions). Skies will be mostly clear
tonight followed by another batch of cirrus during the day
Thursday.
&&
.FIRE WEATHER...
Friday through Tuesday:
High pressure in place early in the period will shift to broad
troughing early next week as a strong low pressure system impacts
most of the Western U.S. Moisture levels are likely to increase
modestly late in the weekend into early next week with the weather
system, but precipitation chances are likely to be very limited
for the lower deserts to slightly better over the high terrain.
Near normal temperatures are expected for the bulk of the period
with light winds on Friday becoming breezy during the daytime
hours over the weekend. Even stronger winds will be likely for
Monday when widespread gusts of 20-30 mph will be possible. Min
afternoon RH values will improve through the period starting out
in the teens on Friday, rising to 20-30% for Sunday-Tuesday.
Overnight recoveries will mostly reach between 35-60% through the
period.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Benedict
AVIATION...17
FIRE WEATHER...Kuhlman