Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/20/23
Area Forecast Discussion
National Weather Service Honolulu HI
404 PM HST Sun Nov 19 2023
.SYNOPSIS...
A cold front, currently near Kauai, will continue moving across
the western end of the state this evening and then stall near
Maui County by early Monday. Showery weather can be expected as
the front moves through, especially across Oahu tonight. Winds
will shift northeasterly and become locally breezy behind the
front from Kauai to Oahu, then return to moderate speeds and
fairly typical trade wind weather from Tuesday through the end of
the work week. Another front could shift winds southerly and bring
an increase in showers next weekend.
&&
.DISCUSSION...
This afternoon, a surface cold front continues to move across the
western end of the state. A leading band of locally heavy showers
and gusty winds moved over Kauai from late morning through early
afternoon, adding an additional 1 to 2 inches at many rain gauges
across the Garden Isle since 8am this morning. This brings 24 hour
rainfall totals as high as 4 inches or greater at some locations
across Kauai. Streams and rivers saw modest rises in response to
the additional rainfall today, though the band of showers pushed
across the island relatively quickly, limiting widespread flooding
concerns. As of press time, this leading band of showers has
progressed further east through the Kauai Channel, and radar
imagery shows that the showers have weakened as they approach
Oahu. Elsewhere, relatively light southeasterly flow ahead of the
front has brought a few pre-frontal showers into leeward areas,
but the islands from Molokai to the Big Island have remained
largely dry today.
Significant differences in timing of the front`s progression were
noted among the various hi-res models in the previous discussion
(with the ARW and FV3 providing a slower solution, while the HRRR
and NAM-Nest favored a faster west-to-east progression). Based on
satellite and radar trends throughout the day, the forecast for
this evening and tonight has been trended more towards the 12z HRRR,
as quicker motion has brought the main line of showers to Oahu as
of 02z. Still think that the front, which is lagging a bit behind
the leading showers and is currently located near Kauai, will
reach Maui County early Monday and then stall as it becomes
oriented more west-to-east. Both the GFS and ECMWF continue to
show the deepest moisture associated with the front remaining to
the north of the Big Island, so rather dry weather will prevail
here through Monday.
The front will gradually dissipate over the central islands
Monday night and Tuesday, with a weak ridge building in north of
the state. Moderate to locally breezy north to northeasterly
winds that will fill in following the frontal passage across the
western end of the state tonight will ease back to moderate
levels Monday night, with light to moderate trades then prevailing
Tuesday through Friday. Meanwhile, lighter winds are expected near
the Big Island. A return of more typical trade wind weather can be
expected from Tuesday through the end of the work week, with
showers focusing mainly across windward and mauka areas.
Looking ahead to next weekend, models suggest that winds could
shift southerly again as another front approaches the islands from
the north. This has the potential to increase showers again
across the western islands by Saturday.
&&
.AVIATION...
A line of prefrontal showers with a few isolated thunderstorms
made it through Kauai earlier today and is weakening as it moves
into Oahu late this afternoon. These showers will bring periods of
MVFR conditions to Oahu this evening...if the line of showers can
hold together for a little longer. The front is lagging behind
these showers and is expected to bring moderate to breezy north to
northeasterly winds to Kauai around 05-07Z, and if the current
trend holds, to Oahu sometime around 09-12Z tonight. MVFR
conditions are generally expected to persist across the western
part of the state behind the front tonight into tomorrow morning
as clouds and showers linger. The front will then stall around
Maui County by sometime tomorrow.
Otherwise, across the rest of the island chain, VFR conditions
will generally prevail, with only brief periods of MVFR in any
isolated showers as light to moderate south- southwesterly winds
continue.
AIRMET Sierra for mountain obscuration will likely remain in
effect for Kauai this evening. As showers move into Oahu later
this afternoon, AIRMET Sierra may be needed for Oahu, as well...if
cloud and shower coverage is substantial enough. AIRMET Sierra
for these locations may be needed through tomorrow morning as
clouds and showers potentially persist.
AIRMET Tango for moderate turbulence between FL250 to FL400, or
even a SIGMET for severe turbulence at these levels may be needed
beginning around 06Z tonight as a jet stream begins to move
eastward across the state.
&&
.MARINE...
Clouds and heavy showers associated with a cold front near Kauai
are rapidly weakening as they cross the Kauai Channel and approach
Oahu from the W. The front had been moving E near 25 kt, but its
forward speed is also diminishing. The front is expected to weaken
and stall as it moves over Maui County waters tonight and Monday.
A large NNW swell (340 degrees) will rapidly build overnight, and
a High Surf Warning (HSW) has been issued for shores most exposed
to the swell, with a High Surf Advisory for shores less exposed.
Part of the reason for the HSW is due to significant wave heights
at NDBC buoys 51001/51101 rose about 9 feet in two hours this
afternoon, with observed maximum wave heights near 19 feet well
above forecast guidance.
While the predominant period of the primary NNW (340 degrees)
swell train will be around 14 seconds, the proximity of gale
force winds over waters just NW of the area will introduce a wide
spectrum of wave energy extending into the shorter periods,
resulting in rough and choppy surf along exposed N facing shores.
The swell will become increasingly northerly (360 degrees) as it
gradually diminishes late Monday/Tuesday. This swell could lead to
moderate surges in Hilo and Kahului harbors.
The increasing seas will require an SCA for most waters through
Monday. Additionally, high pressure building NW of the islands
will support locally strong NE winds N of the front as it becomes
increasingly E-W oriented somewhere near Maui County tonight and
Monday. Lighter E winds are expected over Big Island waters
through the period, spreading to all waters by midweek as the high
to the distant NE weakens.
A small S swell will gradually decline over the next couple of
days. A small to moderate long-period NW (320 degrees) swell is
expected Wednesday night and Thursday, followed by the potential
for a very large NW (320 degrees) swell by the end of the week.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 6 AM HST Tuesday for north and west facing
shores of Niihau, and north facing shores of Kauai, Oahu, and
Molokai.
High Surf Advisory until 6 AM HST Tuesday for west facing shores
of Kauai, Oahu, and Molokai.
High Surf Advisory from 6 AM Monday to 6 AM HST Tuesday for north
facing shores of Maui.
Small Craft Advisory until 6 AM HST Tuesday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters.
Small Craft Advisory from 6 AM Monday to 6 AM HST Tuesday for
Kaiwi Channel-Maui County Windward Waters-Pailolo Channel-Big
Island Windward Waters.
&&
$$
DISCUSSION...Vaughan
AVIATION...Farris
MARINE...Birchard
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
750 PM CST Sun Nov 19 2023
.SYNOPSIS...
Issued at 231 PM CST Sun Nov 19 2023
A weather system will bring rain to the area for the start of the
new week. Precipitation amounts of 0.50 to 1 inch will be seen
areawide with the highest amounts in eastern and southeast Illinois.
Temperatures turn cooler late week onward.
&&
.UPDATE...
Issued at 750 PM CST Sun Nov 19 2023
While radar shows some rain as close as the Mississippi River,
this is mainly mid and high clouds. Surface obs do show some of
the rain is reaching the ground over central and western Missouri,
though. Forecast soundings through the night show a fair amount
of dry air lingering, with more recent runs of the HRRR reflecting
some of this trend in its rainfall output. Will limit overnight
mentions to about a 20% chance from Rushville to Jacksonville.
Otherwise, temperatures shouldn`t drop off too much overnight with
the widespread mid/high clouds, with lows mainly 40-45 degrees.
Geelhart
&&
.DISCUSSION...
Issued at 231 PM CST Sun Nov 19 2023
Key Messages:
* A low pressure system will bring periods of rain later Monday into
Tuesday. Amounts look to range from 0.50-1.00 inch, with the
highest amounts being over eastern and southeast Illinois.
* Another weather system may bring a quick burst of precipitation
Friday night into Saturday. There are still some uncertainties
with this, but temperatures will be cold enough to support snow.
* Cooler temperatures arrive late this week and stick around
through the holiday weekend.
Surface high pressure remains positioned over a good portion of the
Midwest late this weekend, keeping weather benign. Further west of
here, a 1002 mb surface low is positioned over the OK/TX panhandles.
Cirrus tied to this feature has spread over the western half of
Illinois this afternoon, with cloud cover expected to increase
through the remainder of the day. Overnight lows tonight will be
mild with values in the upper 30s to low 40s.
Precipitation chances increase going into Monday as the
aforementioned surface low approaches the ArkLaTex region. WAA north
of the low will overspread the region Monday morning, working to eat
away at mid to low-level dry air. Precipitation should hold off
until late morning or midday Monday and will be scattered in
nature initially. The surface low will lift northward toward the
Ohio Valley Monday night into Tuesday morning. Better forcing will
spread north as the low approaches, simultaneously as the left
exit region of a 150+ kt upper level jet works overhead.
Widespread rainfall will be common during this time (00-12Z Tue),
with the majority of our QPF falling then too. Rainfall amounts
still look to range from 0.5- 1 inch, with the highest amounts
being over eastern and southeast Illinois. The LREF (GEFS, EPS,
CMC) shows a 60-90% probability that everyone will receive at
least 0.5 inch with 50-60% probabilities of 1 inch near and east
of I-57.
Winds will be breezy on both Monday and Tuesday as the pressure
gradient tightens as the low approaches. Wind gusts each day will
peak between 25-30 mph, with easterly winds on Monday and northwest
winds on Tuesday.
We dry out going into midweek as a brief period of high pressure
grazes the area. A dry cold front will sag south through the area on
Thanksgiving day as Canadian high pressure drops into the Plains
states, bringing a period of cooler weather for the holiday weekend.
There continues to be a low chance for another shot at
precipitation Friday night into Saturday morning as a shortwave
trough lifts into the Ohio Valley. Some ensemble members (EPS,
GEFS, CMC) continue to hint at measurable snow near/north of I-72
with this feature, but the deterministic 19.12Z GFS has completely
backed off on this possibility, washing out the shortwave and
keeping any precipitation well south of here. Because of this,
the NBM has backed off some on PoPs for this period, which seems
reasonable at this point. The aforementioned surface high will
work east into the central CONUS this upcoming weekend, looking to
keep things cool and mostly dry for the remainder of the weekend.
NMA
&&
.AVIATION... (For the 00z TAFs through 00z Monday Evening)
Issued at 517 PM CST Sun Nov 19 2023
Main period for aviation concerns will be from 12Z onward, as
winds pick up and ceilings lower ahead of low pressure passing to
the south. By mid morning, east winds will begin gusting to around
20 knots in much of central Illinois, and will remain elevated the
remainder of the period. A rapid lowering of ceilings is likely
between 15-18Z as rain showers begin to lift into the area. Both
NBM and HREF probabilities of ceilings below 3000 feet increase
to 50-60% between 18-21Z, and approach 70% after 21Z near KPIA.
Geelhart
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Memphis TN
921 PM CST Sun Nov 19 2023
...New UPDATE...
.UPDATE...
Issued at 921 PM CST Sun Nov 19 2023
As on 9 PM, heavy radar returns have entered the western
periphery of the CWA. Observations depict fairly large dew point
depressions (ranging from 8-20 degrees) can suggest any
precipitation associated with these returns is likely not
reaching the surface. If any precipitation is reaching the
surface, it is likely just sprinkles.
All eyes for this forecast reside on tomorrow afternoon ahead of a
low pressure system. The greatest severe threat still resides in
the ArkLaMiss region. Typical cool season depicts limited
instability over the Mid-South, but this will be dependent on how
far a warm front will lift north to return moisture and provide
lift to the area.
No changes were made as the previous forecast remains on track and
depicts current trends well.
DNM
&&
.SYNOPSIS...
Issued at 404 PM CST Sun Nov 19 2023
Widespread rain showers and scattered thunderstorms are expected
to move across the Mid-South on Monday, mainly during the
afternoon and evening hours. A few strong to severe storms are
possible along with the potential for heavy rainfall. Showers will
linger through Tuesday with cooler and dry conditions expected on
Wednesday. A fast-moving system will bring another chance for rain
to the Mid-South Thursday afternoon and overnight.
&&
.DISCUSSION...
(This evening through next Saturday)
Issued at 404 PM CST Sun Nov 19 2023
A complex weather pattern is taking shape over the next couple of
days as a broad trough over the western CONUS gradually moves
east. A lead shortwave trough is lifting northeast across NE this
afternoon leading to a diffluent pattern from IA south through the
Ozarks. A 150-kt upper-level jet is noted on the GOES loop with the
right exit region lined up with this diffluent pattern to enhance
large-scale ascent. This could lead to a few sprinkles and/or
light showers this evening and overnight, though nothing of
consequence is anticipated at this time.
The main focus of this forecast is the potential for severe
weather Monday afternoon and evening. Increasing southerly flow
ahead of this system will enhance warm advection/isentropic ascent
and result in rapid moistening of the boundary layer tomorrow.
Dewpoints are forecast to increase into the lower 60s across north
MS, a good 35F higher than currently observed. Increasing
moisture will push precipitable water above the 90th percentile
for a brief period Monday evening, indicating plenty of available
moisture. The kinematics associated with this trough will be quite
robust, with deep-layer bulk shear well above 60 kts. Hodographs
will be quite long with a lot of cyclonic curvature in the lowest
3 km, indicating significant storm-relative helicity. Like is the
norm for cool-season severe weather, instability is the uncertain
ingredient.
CAM guidance is indicating MLCAPE increasing to perhaps as high as
300 J/kg. Anecdotal observations of these systems suggest that
instability along/ahead of the leading edge of convection is often
under-represented, but that largely depends on the area being in
the warm sector. The current track of this surface low looks to
limit the amount of the CWA that actually does see warm sector air
to northeast MS for a few hours around sunset. There is still a
potential that greater instability is realized farther north, but
confidence is very high. Areas that do not see sufficient
surface-based instability will likely experience elevated
convection with a low-end damaging wind threat. The greatest risk
for severe weather will remain in north MS with damaging wind
being the more likely hazard, followed by a potential brief, spin-
up tornado. Heavy rainfall is expected, though it probably won`t
be a drought-buster. The envelope of the 25th-75th percentile QPF
is roughly 1.0-2.5 inches through 6 AM Tuesday with the 90th
percentile at or above 3.0". This is captured well by the HREF
Localized Probability Matched Mean QPF which indicates embedded
streaks of heavier rainfall associated with more robust
convection.
This activity is expected to move east of the area around midnight
tomorrow evening with cooler air advecting into the CWA in the
wake of a cold front. Some light, wrap-around showers are
possible through Tuesday afternoon as the cold core of the upper
low moves across the region, but QPF is generally light. Benign
weather is expected midweek, though temperatures will be rather
chilly Wednesday morning with a freeze possible in some areas.
Thanksgiving Day will be a bit below normal with highs in the mid
50s area wide. A few rain showers are possible by the afternoon,
overspread the Mid-South Thursday night as a cut-off low
originating from the early week trough ejects northeast across the
Lower MS Valley. Again, rainfall amounts are expected to be
generally light.
Dry weather is currently forecast Friday through the weekend as
broad troughing results in quasi-zonal flow aloft across the
southern CONUS. Precipitation chances will be possible by early
next week, but forecast confidence is quite low given the time
frame and anticipated synoptic pattern.
MJ
&&
.AVIATION...
(00Z TAFS)
Issued at 553 PM CST Sun Nov 19 2023
No significant aviation weather impacts anticipated through 18Z.
High-based -SHRA will most likely affect JBR this evening and
early overnight. This activity is associated with a shortwave
trough lifting into western AR.
Primary impact expected Monday afternoon, with IFR CIGs occurring
north of a tropical maritime warm front over central MS, followed
by SHRA/TSRA. For the 00Z TAFs, followed the slightly faster 18Z
HRRR with respect to timing. This matches well with the Extended
TCF.
PWB
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
PUBLIC FORECAST...MJ
AVIATION...PWB
Area Forecast Discussion
National Weather Service Marquette MI
619 PM EST Sun Nov 19 2023
.SHORT TERM...(Through Tonight)
Issued at 228 PM EST SUN NOV 19 2023
Key message:
- A quiet, seasonable night ahead.
Water vapor imagery and RAP analysis show split flow becoming more
pronounced over western N America. Broad troffing covers much of the
western U.S. with shortwave energy diving se from the Pacific NW
into the southern Rockies. Ridging is over interior western Canada,
though a shortwave is cutting thru Alberta into Saskatchewan.
Downstream of the ridging, a trof is over eastern Canada into the ne
U.S. Shortwave that dropped into the trof forced cooler air across
central/eastern Lake Superior and mainly the ne half of Upper MI. An
increase in shallow low-level moisture and an increase in overlake
instability were expected to result in much more cloud cover today
over the ne half of Upper MI, but the day has turned out with
considerably much more sun, except for portions of Alger/northern
Schoolcraft and Luce counties. Even in that area though, clouds are
decreasing. Current temps are in the mid 30s to lwr 40s F. Sfc high
pres ridge currently extending from northern Ontario s across
central Upper MI is resulting in light winds this aftn.
As sfc high pres ridge drifts e tonight, it will consolidate into a
high center n of Georgian Bay by sunrise Mon. Since pres gradient
doesn`t tighten much across the area on the backside of the high,
sfc winds won`t respond much either. Thus, expect a quiet night.
Lingering stratocu over the eastern fcst area will dissipate over
the next several hrs, but will hang on longest, past sunset, close
to Lake Superior. There will be an increase in high clouds from the
w overnight. With the light winds and mainly clear skies thru at
least the evening hrs, leaned toward some of the lower min temp
guidance tonight. Low to mid 20s F will be common across the area,
except locally around 30F very close to the Great Lakes. The eastern
fcst area, closer to departing ridge and under a drier column to
enhance radiational cooling (precipitable water around 65pct of
normal), will see temps slip blo 20F. If skies remain clear longer
to the w, temps at traditional interior cold spots in the w and
central fcst area will also fall to the upper teens F. As winds
become e to se on the backside of the high pres ridge, there is some
potential of low clouds to develop late tonight into portions of s
central Upper MI as higher dwpt marine layer air upslopes into the
chilly conditions inland. Similar setup may occur across the
Keweenaw late.
.LONG TERM...(Monday night through Sunday)
Issued at 415 PM EST SUN NOV 19 2023
Key Messages:
-Temperatures average near or just above normal through Wednesday
night. Below normal temps arrive by Thursday and persist through the
end of the extended forecast period.
-Dry until Tuesday when there may be two areas of light rain/snow
mix.
-For anyone with Thanksgiving holiday travel plans, continue
monitoring forecasts for updates to potential for for several days
of possible lake effect snow.
The extended forecast has good model agreement through Tuesday night
under split flow aloft. However as we progress through next week,
uncertainty grows as guidance spreads. The extended starts
relatively quiet with near or just above normal temps. Temps drop
down below normal Thursday as upper level flow begins to merge and
northwest flow cools the region down. The middle portion of this
coming week starts of with low chances (50% or less) for synoptic
rain/snow mix followed by potential for LES behind it, however
trends in guidance have suggested a more delayed start to LES and
that light showers are the most likely solution next week.
Monday stays quiet and dry as high pressure builds southeast into
Southern Ontario and then tracks eastward; highs will reach slightly
above normal in the upper 30s to mid 40s. Light south to southeast
winds advect moisture off Lake Michigan and with upsloping support,
will develop low clouds over central Upper Michigan while high
clouds continue increasing from the southeast all day. This will
help insulate temps overnight in the upper 20s to mid 30s with
warmest temps near the lakeshores.
The dry weather ends on Tuesday with our next pair of systems. A mid
level trough traversing the northern end of the Canadian Prairie
Provinces on Monday amplifies as it digs southeast through Manitoba
into Ontario Monday night. Meanwhile, a closed low over the Central
Plains on Monday will slide over the Mid Mississippi Valley through
Monday night. As the trough continues to dig south through Ontario,
reaching over the U.P. on Tuesday, the closed low lifts northeast
over the Great Lakes Basin and phases with it. Model guidance has
greatly improved in the last 24 to 48 hours, with general trends
toward a drier solution. The consensus is that the stronger feature
is the sfc low that tracks northeast over the Mississippi Valley on
Tuesday and then over the Lower Great Lakes and Southern Ontario
Tuesday night. This keeps the more widespread synoptic precip to the
south and east of our CWA. While the latest GFS ensemble members are
tracking slightly more west and north when compared to the ECMWF
ensemble guidance, both leave the cold front as the primary forcing
for synoptic scale precip across much of the U.P. Overall, we can
expect a rain snow mix to start Tuesday that transitions to all snow
on Tuesday behind the cold front.
Tuesday night onward, snow showers will primarily depend on lake
effect development and latest model trends indicate best chances
hold until after Thanksgiving. Additionally, a clipper low looks to
swing across the region Wednesday into Thursday reinforcing the cold
air and potentially boosting the LES potential. These colder temps
over the lake will also provide periods of supportive Lake sfc to
850mb Delta-T for LES, however dry air will work against it.
Ensemble probabilities for snow accumulation >3 inches from now
through 0z Saturday remains below 40% with the only chances expected
over the east. Model guidance starts to diverge next weekend, but
around or below normal temps are expected with low, but increasing
chances for LES over the west to west-northwest wind snowbelts.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 619 PM EST SUN NOV 19 2023
VFR conditions and light winds are expected to prevail at all sites
in this TAF period. There is still the potential for southeast flow
to advect moisture into a chillier central Upper Michigan,
potentially resulting in MVFR ceilings overnight at KSAW. However,
guidance has trended this potential back, suggesting dry and clear
skies is more likely to prevail at KSAW (~90%).
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 415 PM EST SUN NOV 19 2023
As high pressure continues building south over Southern Ontario
through Tonight, winds are expected to stay below 20 kts through
Monday as they become southerly. Winds slowly veer southwest Monday
night around 10-20 kts as high pressure shifts east; strongest winds
are expected over the east. A cold front pasting over the lake on
Tuesday will yield a shift to northwest winds around 20-30 kts.
Strong cold air advection behind the front on leaves some potential
for gales, however probabilities at this time peak between 20-30% on
Tuesday and 20-40% on Wednesday, mainly over the west half of the
lake. Northwest winds around 20-30 kts backs west going into Friday,
dropping down to around 15-25 kts.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...Jablonski
AVIATION...JTP
MARINE...Jablonski
Area Forecast Discussion
National Weather Service Pocatello ID
230 PM MST Sun Nov 19 2023
.SHORT TERM...Tonight and Monday
As expected, it`s been a cloudy, wet and windy day across much of
eastern Idaho as a fast moving system pushes through the region.
Strongest winds have been confined to the Magic Valley and into the
South Hills where gusts in the 50 to 60 mph range have been
observed. To the east, winds drop off quickly but remain breezy in
the 20-30 mph range. The Wind Advisory will continue until 06Z
tonight. Rain has been the dominant precip type, thus far, below
6000 ft. This will change very shortly. Still feel NBM snow levels
are a few hundred feet too high with this event and this seems
reasonable based off surface observations and regional webcam
images. The 18Z HRRR and NAM continue to support the potential for
accumulating snow primarily focused in and around Pocatello and the
surrounding high country beginning in a few hours and continuing
until around midnight or so. This is supported by current radar
returns showing the development of a convergence band across the
Arco Desert which will head towards the Gate City later this
evening. After much debate, decided to roll with a Winter Weather
Advisory for Pocatello and the surrounding zones to highlight the
threat of accumulating snowfall. The primary focus area over the
next 12 hours or so is from around Cold Water north up to around
Fort Hall and the surrounding benches. It will take some time before
things begin to accumulate, but once it begins, effective snowfall
rates and gradually cooling temperatures should allow snow to begin
to accumulate. Current forecast now calls for 1-2 inches in the city
of Pocatello with locally higher amounts certainly possible. With
overnight lows dropping well below freezing, travel impacts will be
likely which was also taken into consideration for the advisory
issuance. Snow should be all by the time we get towards daybreak so
it`s a very short window for these accumulations.
Monday looks void of precip but it will remain chilly with daytime
highs only mid 30s to lower 40s regionwide. Skies should be mostly
clear however with high pressure building over the area. McKaughan
.LONG TERM...Tuesday through next Sunday
With a ridge axis of high pressure overhead for Tuesday, high
temperatures will see a warming trend over Monday by about 4 to 8
degrees to near normal levels for this time of year as conditions
remain dry. A return to active and colder weather is then expected
starting Wednesday night into Thursday as an upper level trough
descends out of British Columbia and the PacNW through the NRN
Rockies. Given colder, northerly flow associated with this system,
precipitation is expected to remain predominantly all snow with
limited rain mixing in with accumulating snow. While this system
will be quick moving in nature, widespread precipitation on
Thanksgiving Day may lead to travel impacts particularly in the
mountains. The latest snowfall forecast for Wednesday night
through Thursday night supports around a T-3 inches in the valleys
and 3-6 inches in the mountains with locally higher totals in
excess of 6 inches across the highest elevations south and east of
the Snake Plain. Colder, below normal temperatures will then
return to round out the week as conditions remain dry outside of
isolated mountain snow showers. MacKay
&&
.AVIATION...
For the 18Z TAFS through 18Z Monday.
As a cold front continues to work east through SE Idaho today,
widespread precipitation will support a mix of MVFR/IFR CIGS/VIS
along with gusty winds particularly at KBYI where gusts have
already been observed to around 40 to 50 kts. Rain will ultimately
transition to all snow in the valleys throughout the afternoon and
evening hours as dry conditions build in west to east during the
overnight hours. As a ridge of high pressure then builds in from the
Pacific for Monday, increasingly clear skies will follow suit as
lingering low clouds persist across lower elevations supporting
MVFR/IFR CIGS/VIS at times. Skies will ultimately clear throughout
the day Monday with increasing upper level clouds later in the day.
Patchy fog and low stratus will again be possible across the Upper
Snake Plain for Monday night. MacKay
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 11 PM MST this evening for IDZ051-055>057.
Winter Weather Advisory until 11 PM MST this evening for IDZ054-
056>058-060.
&&
$$
Area Forecast Discussion
National Weather Service Pueblo CO
348 PM MST Sun Nov 19 2023
.SHORT TERM...(This evening through Monday)
Issued at 305 PM MST Sun Nov 19 2023
Key Messages:
- A couple rounds of snow expected tonight and Monday with the
greatest impacts for the southeast mountains and adjacent Palmer and
Raton Ridges on Monday.
- Strong winds for the plains though HREF Probabilities keep risk of
high winds below 15 percent.
- Winter Weather Advisory expanded to include Teller county, but
warm temperatures may limit travel impacts for the Palmer Divide.
Upper level energy dropping through the Great Basin has spread snow
into the Continental Divide as the system carves out across
Northwest NM this evening. There have been some convective snow
bursts across western CO, but so far roads have remained clear at
Wolf Creek and Monarch. As the evening progresses and best forcing
moves in with the upper jet, expect snow will expand in coverage and
even spread eastward this evening. H7 winds will pull more
northeasterly across the plains with snow developing in the upslope
regions of the Wets, Sangres and Pikes Peak this evening, but it
will have a fairly big dew point deficit to overcome initially. Snow
levels will start out around 7500 feet this evening then drop to
around 6000 feet by Monday morning which should limit accumulations
to the higher elevations above 7000 feet initially, and models
advertise a lull in the snowfall late tonight for the Pikes Peak
region as the initial round of forcing stays too far south.
As the system ejects into the central plains on Monday, the wrap
around portion of the storm begins to affect southern CO. Northerly
winds on the back side of the system increase with the potential for
gusts to around 55 mph across the plains. The potential for high
wind gusts still look on the low side with only 15 percent or less
of members showing a very spotty potential for high wind gusts just
south of the Palmer Divide. EC and EC Ensembles keep peak wind
gusts in the 45-55 mph range, and HRRR and NAMNest follow suit with
even lighter values. Will hold off on any high wind highlights for
now. Snow levels will likely stay around 6000 ft through the day so
precipitation type will likely remain as snow for the Palmer Divide
which raises concerns for visibility impacts due to blowing snow.
However mixing warms temperatures into the mid 30s which should
bring some melting and may limit the blowing snow impacts to only
when snow is falling. In concert with neighboring offices, have held
off on spreading advisories into Northern El Paso county for now,
but this will continue to be monitored. Raton Pass could also see a
rain/snow mix with blustery north winds nearing high wind criteria,
but impacts may be restricted to only the pass level where current
advisory is in effect. The southern I-25 corridor (Colorado City to
Trinidad)and the San Luis Valley, looks too warm for much
accumulation. Otherwise, did shade temperatures down in line with
guidance but strong mixing will yield some 40 to around 50 degree
readings for the southeast plains which will keep scattered showers
as rain.
Snow along the Continental Divide will decrease through the day with
highlights coming down by 12z if not a little sooner south of
highway 50. Some scattered snow showers will linger through the
day with best chances across Chaffee and Lake counties. Any
accumulations up that way remain light and under 3 inches for the
event total.
.LONG TERM...(Monday night through Sunday)
Issued at 305 PM MST Sun Nov 19 2023
Key messages:
- Snow showers will taper off late Monday evening over the Raton
Mesa.
- Watching the evolution of a potential storm impacting the region
beginning by later in the day on Thanksgiving.
- Return of colder air late week through next weekend with unsettled
conditions possible through Saturday.
Detailed discussion:
Monday night...
The wrapped up low pressure system will continue to propagate
towards the east, with strong and gusty northerly winds on the
backside of the low continuing to weaken as the pressure gradient
loosens. Some of the high resolution model data, such as the ARW,
indicates that there could still be some snow showers continuing
over the Raton Mesa until early in the morning on Tuesday, due to
upsloping winds and weak isentropic upgliding. As winds further
weaken, these will eventually taper off, but there could be an
addition 1 to 2 inches of snow in this area before it is all said
and done.
Clouds will continue to move out and dissipate with mostly clear
conditions by daybreak. Strong and gusty winds will continue over
the eastern plains throughout the night, with temperatures
dropping to around the freezing mark or slightly below across the
plains. This will allow for some wind chill values, especially in
Kiowa County, to drop down into the mid teens. For high country,
temperatures will fall into the single digits and teens for most
locations, with even a few temps below zero for the highest
elevations. Depending on how much precip the San Luis Valley
receives, as well as some other high mountain valleys, there could
be some patchy (or even widespread areas of) fog developing
overnight for these locations.
Tuesday through Wednesday...
A ridge is going to move in behind the exiting trough with high
pressure building back in as it does. This will allow for a rebound
in temperatures and dry conditions returning to the region
throughout this period in the forecast. Highs by Wednesday will
be back above the seasonal average across the CWA for this time of
year, with max temps near 70 degrees for the plains.
Thursday through Saturday...
Deterministic models are cueing in on the evolution of a major
shortwave trough upstream over the northwest CONUS that is initially
positively tilted, but then becomes negatively tilted due to a
supergradient jet max entering the longwave trough. This will cause
the trough to become closed off at the 500 mb to be either somewhere
over the Great Basin if the ECMWF solution verifies by later in the
day on Friday, or over the Yellowstone region if the GFS verifies
by early Friday morning. This will allow for snow to possibly
develop over the higher terrain as early as late Thursday evening
if the GFS solution is correct. It does appear at this time that
the majority of southeastern Colorado will be dry for
Thanksgiving Day, although travel could potentially become tricky
if traveling back west through the mountains by later in the
evening. With the approaching trough, it will be cooler, along
with increasing clouds.
When comparing 500 mb heights, the ECMWF does keep the closed low
back over the Four Corners area through Saturday morning, although
it will be filling as it progresses further eastward. The GFS is
almost completely different, with the wave opening back up and
propagating much quicker downstream and over the plains by this
time. This is resulting in a fairly large dispersion of total
precipitation over the region with the GEFS vs the EPS ensembles,
showing that most of the precip remains further to the north and
ends by late Friday with the GEFS, while the EPS displays much
higher amounts of precip and further south, over southeastern
Colorado, and continuing on into Saturday. It is important to note
that being nearly a week out, all of this is subject to change.
It will bring in much colder air with this system, and it can be
said with high confidence that temperatures will likely be below
average by Friday, and through next weekend. Unsettled weather
appears to be more likely on Friday, but may continue into
Saturday. -Stewey
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 305 PM MST Sun Nov 19 2023
VFR cigs will continue to drop this evening with KALS seeing MVFR
cigs with -SHRASN this afternoon into the overnight hours. Cigs
could briefly hit high end IFR if a heavier snow showers impacts the
terminal, but risk for this looks low. Showers should clear to the
south by 12 to 13z with north winds increasing to 10 to 20 kts by
afternoon.
KCOS and KPUB will see dropping VFR cigs with the potential of VCSH
at KCOS Monday morning. Overall, cigs will likely stay in the VFR
category for both terminals. North winds will pick up around 12 to
14z with gusts up to 45 kts possible through the day. Can`t rule
out VCSH at KPUB but the risk looks low and precipitation type will
remain as rain. Little to no accumulation expected at either
terminal. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 AM MST Monday for COZ066-068.
Winter Weather Advisory until 11 PM MST Monday for COZ073>075-
080>082.
&&
$$
SHORT TERM...KT
LONG TERM...STEWARD
AVIATION...KT