Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/04/24
Area Forecast Discussion
National Weather Service Denver/Boulder CO
843 PM MST Sat Feb 3 2024
.KEY MESSAGES...
- Heavy snow is ongoing across the western half of the
metro/Palmer Divide, Foothills, and portions of the mountains
and will continue through the early evening, with significant
travel impacts at times.
- Patchy fog possible across the lower elevations tonight into
tomorrow
- Light rain showers will continue across the far northeast plains
through tomorrow, with quieter weather for the rest of the
forecast area.
&&
.UPDATE...
Issued at 830 PM MST Sat Feb 3 2024
Well that was fun...
As this headache-inducing, spring-like February winter storm winds
down, it leaves some hefty snow totals in its wake. As expected,
the more impactful accumulations occurred across the
central/southern foothills and communities immediately adjacent,
particularly from Boulder south through Golden and into the Palmer
Divide. For these areas, storm-total reports of 8-14" were
widespread, with a handful of higher totals of 12-19" across the
lower foothills.
As of 8:30PM, remaining snow showers are largely confined to the
southern foothills, where an additional inch or two may
accumulate before midnight. At the same time, we`ve also been seen
scattered convection in the plains under modest instability, but
that activity is losing steam as night falls. With all this said,
it seemed more than appropriate to drop all remaining winter
weather headlines. Of course, road conditions may still take some
time to fully improve, so it`s still recommended to check road
conditions via CDOT prior to traveling tonight.
The primary forecast concern for the overnight period transitions
to fog, which we`ve already seen develop across much of the Denver
metro and northeast plains. With weak winds tonight, combined with
warm advection over fresh snow cover and some partial clearing,
there`s a large enough potential for persistent dense fog for
these areas to warrant a Dense Fog Advisory, which was issued a
short while ago. Some question just how extensive it will be
outside of areas of fresh snow cover, and some of these lingering
convective showers in the plains could locally disrupt the fog at
times.
Otherwise, expect a cool night with lows in the 20`s for the urban
corridor, and 30`s for the eastern plains. Lowered temperatures a
few degrees based on today`s snowfall, especially for the Denver
metro and nearby areas.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 220 PM MST Sat Feb 3 2024
We`ve made it into the final stages of this winter storm. Water
vapor satellite and KFTG radar data shows the back edge of the
precipitation shield advancing west into the Denver metro this
afternoon, and this should continue to back into the western metro
over the next several hours. Meanwhile, the western extent of the
band has managed to make it into the foothills. This band still
appears to be enhanced somewhat by some additional convergence
and/or a weak barrier jet, with snowfall rates of 1-2"/hr in the
lower foothills and far western suburbs.
Guidance is in fairly good agreement that this band will start to
contract this evening as this convergence zone tightens and the
best moisture/lift depart the region. The past several cycles of
the HRRR have insisted this occurs between Estes Park and the
southwest Metro, favoring Boulder or just west into Coal Creek
Canyon/Boulder Canyon this evening. Though snowfall will quickly
diminish inside this band, guidance is in good agreement that
>1"/hr rates will be possible through the early evening hours
before the band dies off sometime this evening.
After the snow ends, patchy fog is expected to develop across the
plains due to calm winds and the anomalously high surface
moisture. We`ve added patchy fog into the grids but may need
another Dense Fog Advisory if all the ingredients come together.
Tomorrow should be much quieter across most of the forecast area
as the upper low slides into the ArkLaTex region by tomorrow
afternoon. Some wraparound moisture could be enough for some rain
showers across the far northeastern corner of the state, mainly
during the first half of the day. Temperatures should rebound back
into the upper 30s to mid 40s across the plains.
.LONG TERM...(Sunday night through Saturday)
Issued at 220 PM MST Sat Feb 3 2024
Models have upper ridging to move across the forecast area Sunday
night into Tuesday morning. Downward QG vertical velocity is in
place into Monday evening. There will be a dry airmass over the
forecast area along with warming temperatures. Increasing
southwesterly flow aloft moves in for the rest of Tuesday and
Tuesday evening ahead of the next upper trough. Upward synoptic
scale energy gets into the CWA ahead of the trough late Monday
night through Tuesday night into the extended period. Moisture
increase with the trough through the afternoon Tuesday and Tuesday
night. There should be enough moisture for light snow to develop
in the mountains by Tuesday night. Snowfall amounts will be light.
For the later days, Wednesday through Saturday, broad upper
troughing moves into Colorado later Wednesday into Thursday. Zonal
flow to weak upper ridging is in place the rest of Thursday into
Saturday morning. This is followed by another upper trough/closed
low depending on the model you choose. There is enough moisture
over the mountains for light snowfall, off and on, Wednesday
through Saturday. The deepest moisture and best orographics occur
on Thursday afternoon and evening. The alpine snows do not look
exceptional in amount. Over the plains, there will be some
10-30% chances of precipitation off and on Wednesday afternoon
into Saturday. Temperatures look to be right around normal values
for this time of year.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 434 PM MST Sat Feb 3 2024
No more snow expected for KDEN and vicinity, with only -SHSN for
KBJC for the next couple of hours. However, major concern for the
TAF period will be fog potential. Increasing likelihood of
prolonged fog with visibility 1/4-1SM (already present) extending
through the early morning hours. Still leaning on some improvement
after 08-10Z, but potential exists for these conditions to extend
closer to 15Z Sun before there is more substantial improvement.
As far as winds are concerned, anticipate direction to become more
W/SW this evening, with lights speeds generally under 8 kts. Light
SW flow may be rather persistent through the morning before a
period of SE winds later Sun PM.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM MST Sunday for COZ039>041-043-045-
050-051.
&&
$$
UPDATE...Rodriguez
SHORT TERM...Hiris
LONG TERM....RJK
AVIATION...Rodriguez
Area Forecast Discussion
National Weather Service Boston/Norton MA
933 PM EST Sat Feb 3 2024
.SYNOPSIS...
A prolonged duration of quiet weather Sunday through most of
next week as surface high pressure takes hold of the northeast.
While a cool, albeit seasonable temperatures Sunday into mid-
week, a spring- ish feel is possible by late next week.
&&
.NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
9:30PM Update...
Forecast remains stable, only minor adjustments made to
temperatures using the HRRR as winds are precluding temps from
dropping off as quickly as previously forecast.
650 PM Update...
* Dry/Seasonable tonight, lows in the upper teens to middle 20s
Previous forecast is on track. Much of the mid and high level
cloudiness this evening should dissipate overnight. A bit of
ocean effect clouds may flirt with the outer-Cape/Nantucket at
times...but otherwise skies will become mostly clear overnight.
High pressure to our north with low pressure spinning east of
the Canadian Maritimes will continue to generate a northerly
flow of dry/seasonable chilly air into the region tonight.
Winds continue to gust to between 20 and 25 mph along the
southeast New England coast overnight, but less further inland.
Overnight low temps should bottom out mainly in the upper teens
to the middle 20s.
&&
.SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY/...
Tomorrow & Tomorrow Night
Rather stagnant pattern across southern New England for at least the
next 48 hours. An upper-low meandering over Nova Scotia and an area
of high pressure over The Great Lakes/Midwest will keep southern New
England under a steady and dry north/northwest flow through the
weekend. Highs in the upper 30s to the lower 40s tomorrow
afternoon. North winds may be breezy at times near the coast
with gusts between 20 and 25 mph along the I-95 corridor and
25 to 35 mph for parts of the Cape and Nantucket. Sunny skies
are on tap for tomorrow. No signals for impactful weather
during this time frame.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Key Points...
* Extended period of quiet & mainly dry weather continues next week
* Ocean effect snow showers possible for Cape/Islands Mon night & Tue
* Seasonable temps Mon/Tue/Wed reach above normal levels Thu/Fri/Sat
Details...
Our extended period of very quiet and mainly dry weather continues
next week. We will be under the western side of a trough axis Mon &
Tue...which should result in fairly seasonable temps. Highs will
mainly be in the middle 30s to the lower 40s with the warmest of
those reading the CT Valley. The chilliest of those readings will be
towards the southeast New England coast...where high pressure over
the Canadian Maritimes will team up with a distant offshore low
pressure system. This will generate gusty N-NE winds/clouds towards
the southeast New England coast with some ocean effect snow showers
possible Mon night and Tue towards the Cape and Islands. Any
accumulations will likely just be a dusting to 1"...but clouds and
gusty NNE winds should hold high temps in the middle 30s early in
the week.
Shortwave trough over the southern Plains lifts northeast towards
the Great Lakes for the second half of the upcoming week. In
response...height fields will rise across southern New England. This
will allow for highs to reach well into the 40s Thu, probably near
50 Fri and perhaps into the 50s for Sat. Mainly dry weather persists
other than a few brief showers possible sometime Fri night/Sat with a
shortwave crossing the region...but nothing more than that is
expected.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update...
Tonight...High confidence.
VFR. Winds out of the N at 5-15 kts with gusts of 15-25 kts
across the southeast New England coast.
Sunday...High Confidence
VFR, including the Cape and Islands. N/NNW winds gusts to around
20 knots along and southeast of the I-95 corridor and up to 30
knots across parts of the Cape and Nantucket.
Sunday Night... High Confidence
VFR. N/NNW winds 10 to 15 knots.
KBOS TAF...High confidence
KBDL TAF...High confidence.
Outlook /Monday Night through Wednesday/...
Tuesday: Mainly VFR, with local MVFR possible. Windy with local
gusts up to 30 kt.
Tuesday Night through Wednesday: Mainly VFR, with local MVFR
possible. Breezy.
Wednesday Night through Thursday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Tomorrow Night
Small Craft Advisories remain in effect through early Monday
Persistent north/northwest winds over the coastal waters this
weekend with sustained winds from 15 to 20 knots and gusts between
20 and 30 knots. This wills support SCY criteria over most of the
marine zones through the weekend. Seas will be somewhat elevated in
the 8 to 10 foot range off the east facing shores. Conditions will
be more calm off the south coast where conditions should fall below
SCY criteria this evening.
Outlook /Monday Night through Wednesday/...
Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas. Chance of snow showers.
Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Areas of rough seas. Slight chance of
snow showers.
Wednesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft.
Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST Monday for ANZ231-250-251-
254-255.
Small Craft Advisory until 4 PM EST Sunday for ANZ232>235-256.
&&
$$
SYNOPSIS...Frank/RM
NEAR TERM...Frank/KS
SHORT TERM...RM
LONG TERM...Frank
AVIATION...Frank/RM
MARINE...Frank/RM
Area Forecast Discussion
National Weather Service Cleveland OH
912 PM EST Sat Feb 3 2024
.SYNOPSIS...
High pressure will remain in control through most of next week.
This high will finally move to the east coast by Friday allowing
a cold front to approach from the west.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
915 pm update...
No other forecast changes were needed at this time.
615 pm update...
We have made some changes to the near term hourly forecast from
this evening through tomorrow midday. We have backed off a
little bit on the cloudiness from the previous forecast update.
The clouds overnight should be more confined to northwest Ohio.
Previous discussion...
Very quiet conditions for mid winter are expected through the
remainder of the weekend as a broad area of high pressure at the
surface and aloft remains in control. Visible satellite and
water vapor loops this afternoon show a large Omega block
characterized by sharp mid/upper ridging from the Tennessee
Valley through the western Great Lakes with broad mid/upper lows
offshore of the Pacific Northwest and near the TX/OK
panhandles, as well as a mid/upper trough over New England and
the North Atlantic. This places the southern Great Lakes in fair
weather upper level confluence on the eastern side of the Omega
ridge allowing for strong high pressure at the surface over the
Great Lakes. This 1020+ mb surface high is centered over the
central Great Lakes this afternoon and will remain nearly
stationary through Sunday night as the associated mid/upper
ridge folds toward the central Great Lakes in response to the
southern Plains mid/upper low starting to undercut it as it
drifts along the Gulf coast. This all spells dry conditions with
temperatures slightly above seasonal levels through Sunday
night.
The only question mark of the forecast is cloud cover. Low-level
moisture trapped below the inversion associated with the building
high caused overcast skies to hold on into this afternoon,
especially in NW and north central Ohio where the easterly flow
helped to slow the clearing. Skies have finally cleared out in all
areas as of late afternoon, but most high-res guidance suggests low
clouds returning overnight tonight. NAM and RAP forecast soundings
in BUFKIT show much shallower low-level moisture tonight compared to
last night, so not sure the low clouds will be as widespread, but at
least patches of low clouds will redevelop, especially in NW and
north central Ohio away from the influence of downsloping in E to NE
flow. With this in mind, have skies becoming mostly cloudy again
overnight. Clouds will gradually erode Sunday morning allowing for a
mostly sunny afternoon.
Lows tonight will fall into the mid/upper 20s. Went slightly warmer
than NBM guidance due to the clouds expected to redevelop. Highs
Sunday will reach the upper 30s to mid 40s. It will be coolest near
the lakeshore Sunday given the NE low-level flow off the cold lake
waters.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
A ridge will remain in place across the region through the short
term period with dry weather, sunshine, and above normal
temperatures anticipated for the start of the week. High temps will
be in the 40s across most of the area each day, but the cooling
effect of onshore off Lake Erie will cause highs across the northern
zones of the CWA to remain in the upper 30s to around 40 degrees
each afternoon. Overnight lows will be in the mid to upper 20s.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
The aforementioned ridge will begin to shift east on Wednesday with
the ridge axis crossing the local area Wednesday night into Thursday
morning. Flow becomes southerly Wednesday which will result in
warming temperatures areawide; anticipate highs in the mid to upper
40s to lower 50s Wednesday afternoon. Overnight lows will warm as
well and expect minimum temps in the mid to upper 30s Wednesday
night.
By Thursday low pressure will begin to take shape over the Plains,
lifting a warm front northeast across the area Thursday. Thursday
will be the warmest day of the week with highs in the low to mid 50s
across NE OH and NW PA and the mid to upper 50s to possibly the
lower 60s across the western half of the area. The CWA should remain
in the warm sector Thursday night so don`t expect lows to drop out
of the mid to upper 40s overnight.
The low will push a cold front across the area Friday. While there`s
still a little bit of uncertainty in precip timing amongst long
range guidance, PoPs increase ahead of the front Thursday night into
Friday morning with showers continuing as the front crosses the CWA
through Friday afternoon. The best upper level support may not
arrive until Friday night into Saturday, so rain chances continue
into the start of the weekend. It doesn`t look like there will be
much cold air advection behind the late week system so above normal
temperatures continue through the end of the long term period.
&&
.AVIATION /00Z Sunday THROUGH Thursday/...
The aviation forecast doesn`t look as grim as the previous
update depicted. MVFR to IFR ceilings will be confined to
northwest Ohio tonight into early Sunday morning. The rest of
the area will be VFR through the period with high pressure
in control of the weather pattern. NE winds will average 3-7
knots through Sunday afternoon and evening.
Outlook...VFR expected through Thursday.
&&
.MARINE...
High pressure will maintain influence over the region through the
first half of next week with northeast winds remaining under 10
knots through Sunday night. Winds may increase to 10 to 15 knots
Monday night through Tuesday before flow shifts to the
south/southeast and winds diminish below 10 knots Wednesday. Waves
should remain under 3 feet for most of the week. Unsettled maine
conditions will likely return towards the end of the week as
southerly winds increase ahead of an approaching cold front.
&&
.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.
&&
$$
SYNOPSIS...Garuckas
NEAR TERM...Garuckas/Griffin
SHORT TERM...Maines
LONG TERM...Maines
AVIATION...Griffin
MARINE...Maines
Area Forecast Discussion
National Weather Service Cheyenne WY
455 PM MST Sat Feb 3 2024
.KEY MESSAGES...
- Winter Storm Warnings and Winter Weather Advisories continue
for portions of Carbon, Albany, Converse, Platte, and Laramie
counties from now until Sunday afternoon. Primarily snow
expected in the mountains and areas west of the Laramie Range
from now through Sunday morning.
- Above seasonal temperatures return for the first half of the
week for areas east of the Laramie Range and the Nebraska
Panhandle.
- Unsettled weather returns as another storm system will
approach the area Tuesday night and Wednesday. Rounds of
moderate to heavy snow will be possible across the Sierra
Madre and Snowy mountains. Rain showers transitioning to snow
showers will occur across most valley locations throughout the
day on Thursday and should become mostly snow by Thursday
night.
&&
.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 150 PM MST Sat Feb 3 2024
Currently...Surface low to our south in extreme southeast
Colorado and the Oklahoma Panhandle this afternoon. Southeast
moisture transport still evident out ahead of this low across
central Kansas into western Nebraska. Wrap around moisture
around the north side of this low and upslope flow across
southeast Wyoming. Snow has been pretty heavy across central
Laramie County to Albany County. Radar showing this band of snow
basically from Cheyenne to Laramie at 20Z. HRRR mesoscale
guidance has a pretty good handle on this band of heavy snow.
Dry slot moving into the Nebraska Panhandle this afternoon with
reports from observations showing precipitation has pretty much
ended out that way.
HRRR shows this band shifting west into Carbon and Albany
Counties this evening after 00Z and continuing overnight. Will
keep current winter headlines going as they are this afternoon
and evening.
Need to be on the lookout again this evening for another
widespread fog event. Southeast upslope flow similar to last
night expected again this evening. Did expand areas of fog
across the Panhandle into Niobrara and Converse Counties as GFS
continue to show a favorable fog profile on forecast soundings.
Concerns with ending time of precipitation Sunday that will
impact ending times of warnings and advisories. GFS forecasting
700mb low transitioning to eastern Oklahoma and western Arkansas
by 12Z Sunday. This will effectively cut off the southeast
moisture transport across Kansas and Nebraska...shifting it
further east into Missouri and eastern Nebraska. Have
precipitation ending fairly quickly Sunday morning after 15Z or
so. Decided to trim the end times of winter headlines to 18Z
Sunday. Overnight crew may need to shorten it even more.
Upper ridging returning for warmer and drier weather Monday and
Monday night. GFS 700mb temperatures back near freezing Monday
afternoon. Likely 50s returning east of the Laramie Range and
upper 40s west.
&&
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Issued at 150 PM MST Sat Feb 3 2024
After a brief break from wintry conditions, unsettled weather is
expected to make its return in the middle of the work week with
moderate to heavier snowfall across the mountains and lighter snow
possible for the valleys.
Before the onset of the next snowfall, much more pleasant conditions
are expected for areas east of the Laramie Range, with an upper
level ridge slowly migrating eastwards towards the Great Plains and
an upper level long wave trough digging from the Western Seaboard to
the Intermountain West. With this setup, above average temperatures
are expected to remain in place on Tuesday for areas to the east and
a decent cooldown with snow potentials off to the west, mainly
across the mountain zones and into western Carbon County. Consensus
for above average temperatures are gaining traction with the NAEFS
mean 700mb temperatures in the climatological 90th percentile for
areas east of the I-25 corridor in southeast Wyoming and the
Nebraska Panhandle. Therefore, started blending in higher NBM
percentiles to the current blends and thus raising temperatures for
Tuesday before the arrival of the long wave trough into the High
Plains, which is progged to occur shortly after sunset on Tuesday.
Once the upper level feature fully moves across the CWA Tuesday
night into Wednesday afternoon, precipitation chances increase from
west to east, with 30% PoPs for areas west of the Laramie Range and
upwards to 60% or greater for the mountain areas through the early
morning hours on Wednesday. 700mb flow at that time will maintain a
southwesterly flow, with the Sierra Madres generally being favored
with the majority of upslope flow shadowing the Snowy Mountains
bringing much higher accumulations for the Sierra Madres throughout
the event. Under this pattern, is likely to see further shadowing
downstream in the lower terrains off to the east as observed in
similar events, and decided to keep PoPs below 10% for the I-25
corridor throughout the morning hours. This limited precipitation
should be relatively short lived with the upper level features
continuing their tracks eastward, bringing greater than 40% PoPs for
southeast Wyoming and the Nebraska Panhandle by around sunset on
Wednesday evening. Should be interesting to see how the rain to snow
transitions take place with this event, as temperatures remain on
the warm side and very unlike typical February weather. However,
with the combined precipitation potentials and in the event colder
air moves across the region, will see the rain to snow transition
become all snow fairly quickly, especially if the column cools
enough to reach the dendritic growth zone and ultimately a much more
likely scenario for this time of year. Nevertheless, confidence
remains low at this time with the latest long range models
indicating much better moisture advection with the earlier onset of
the long wave trough, and an evident atmospheric river signal by the
elongated moisture plume from the Pacific through to Desert
Southwest and slightly extending some higher PWATs into our mountain
zones. However, as the upper level feature continues its track to
east, much of the better moisture advection gets pushed further
eastward and into the Midwest and leaving the High Plains
essentially dry. As a result, will need to continue to evaluate the
need for headlines across our mountain zone with 15:1 snow ratios
expected and around 0.5 to 1.0 inches of QPF for the Sierra Madres
and up to 0.5 inches for the Snowy Range.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 455 PM MST Sat Feb 3 2024
Storm system over the Texas and Oklahoma panhandles will continue to
bring unsettled weather to southeast Wyoming and western Nebraska
tonight with periods of rain below 5500 feet, and mostly snow above
5500 feet. Fog will likely redevelop tonight before the storm weakens
and pushes east of the southern Rockys for Sunday.
HAZARDS/WEATHER TRENDS: For southeast Wyoming, periods of snow...heavy
at times...and LIFR conditions will continue between now (00z) and 06z
tonight. Snow will gradually taper off after 03z, with improving
conditions likely after 07z. KLAR and KCYS may see VFR conditions as
early as 09z to 12z early Sunday morning due to light downslope winds.
For western Nebraska, rain will continue to become more isolated with
limited coverage tonight. Low clouds will likely linger through Sunday
afternoon. High res models are now showing the likelihood of fog
(increased probabilities of 60 to 80 percent) with VIS below 1 miles
for KAIA, KBFF, and KSNY for most of tonight and into early Sunday
morning. Fog looks less likely for KCDR as they may receive additional
rainfall after 06z, but can`t rule it out. Looks like LIFR conditions
will continue through 18z Sunday with some improvements Sunday
afternoon.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 11 AM MST Sunday for WYZ103>106-
109-111-113-115-117-118.
Winter Storm Warning until 11 AM MST Sunday for WYZ110-112-114-
116.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...MRD
AVIATION...TJT
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
332 PM PST Sat Feb 3 2024
.SYNOPSIS...Another powerful storm will bring strong gusty winds
and moderate to heavy rainfall with high elevation heavy snowfall
to Northwest California on Sunday. Wet and unsettled weather will
continue into Monday, and then ease up by Tuesday.
&&
.DISCUSSION...Another potent atmospheric river storm system
centered several hundred miles SW of Cape Mendocino outside
130W this afternoon will impact northwestern California with
strong winds and moderate to heavy precipitation late tonight
and into the day on Sunday. A warm front south of 35N and well
inside 130W will advance northeastward tonight. Moderate to
locally heavy overrunning precipitation is forecast to begin late
tonight across southern Mendocino and Lake Counties. High
resolution ensemble guidance continues to indicate mean snow
amounts of 4-6 inches per 6 hours from 10PM Saturday to 10AM
Sunday in southern Lake county, particularly above about 3000
feet. This will impact travel on highway 175 and a winter storm
warning has been hoisted. There are indications that snow
levels, based on the deterministic GFS and NAM (and BUFKIT
profiles) may start out near 2000 feet early Sunday morning in
Lake County as drier low level easterly flow ramps up. NBM snow
levels are usually too high in these overrunning set-ups. How much
snow and how quickly snow levels rise is not certain. BUFKIT
deterministic profiles indicate levels rising by late morning over
Lake county and for now will go with that until observational
data indicates otherwise. The snow will not last long and probably
melt quickly with warm air advection pushing levels up above 4000
feet by late morning.
A very similar set-up will exist in eastern-northeastern Trinty
County where low elevation snowfall (2000-3000ft) will probably
last longer before the warm air eventually mixes down and levels
rise above 3000-3500 feet Sunday afternoon and evening. Once
again, sided with the deterministic guidance for snow levels.
Additional support for deviating from NBM guidance is the high
resolution mesoscale ensemble guidance with 6 hourly means around
8 inches and 25th-75th spreads around 2 inches.
In addition to the heavy snow, strong and potentially damaging
wind gusts (~60 mph) are expected for Mendocino coastal areas as
ESE 925mb winds crank up to 50-60kt around the northern semi-
circle of the surface low which will edge toward Pt Arena by 18Z
Sunday. High resolution ensemble guidance indicates lower
probabilities for gusts to 50 mph for the higher elevations
(ridges) of southern Humbodlt. Strong winds are not completely out
of the question for Humboldt if the barotropic low track
northward. Consensus from the various models is for the low to
fill. A compact mesoscale circulation (per the HRRR) will still be
capable of strong wind gust >40 mph for Humboldt. Considerable
uncertainty remains with large spreads in the guidance and
inconsistencies in the models. Stay to tuned to the latest
forecast for updates, especially if planning to be on the water or
on Humboldt Bay.
Lastly, there is a concern for minor flooding in southern
Mendocino and southern Lake Counties on Sunday with this
latest surge of subtropical moisture (PWATS > 1 inch). The
highest influx of moist air intersecting the coastal terrain is
forecast to be highest south Pt Arena. 12Z global models and high
resolution mesoscale models have trended wetter and a bit further
north with first wave of moderate to heavy rain on Sunday. HREF 6
hourly probabilities for greater than 1 inch in 6 hours is
90-100% for Lake and SE-E Mendocino Counties. 2-4 inches of rain
in 12-18 hours are likely as the warm front lifts northward and
925-850mb winds shift to S-SW (at least on some of the models).
Also, with snow levels initially low (2000-3000 feet) in Lake
County, all the precipitation in the watershed may not fall as
rain. Considering we are in WPC`s slight risk (15% chance) for
execessive rain and the CNRFC continues to indicate sharp rises on
rivers, streams and creeks in southern Mendocino and southern
Lake Counties, we will continue with the flood watch. Chances for
flooding are lower compared to the last atmospheric river storm.
For more on this see the hydrology section below.
The upper trough complex will remain over the area on Monday for
continued wet and unsettled weather. Drier conditions are forecast
for Tue with minimal chances (10-20%) for precipitation.
Additional transient shortwave troughs in cooler NW flow will
probably bring episodes of light to moderate precipitation mid to
late week. Potential for a colder system and low elevation snow
increases toward the end of the week. There is considerable
spread and variance with rain and snow amounts at the moment.
Overall it looks cooler and calmer for much of next week. DB
&&
.AVIATION...Aside from dense valley fog this morning along the
Russian River Valley, generally unstable conditions paired with
building offshore flow has allowed for clearing skies and VFR
conditions to prevail. A storm system moving up the coast will
begin to impact Mendocino and Lake COunties early sunday morning.
This system will first bring low level windshear and gusty surface
winds near UKI, followed by rain showers and inconsistent MVFR to
IFR conditions through Sunday. Further north, terminals will
start to experience some gusty offshore wind, but generally VFR
conditions until showers arrive after sunrise. /JHW
&&
.MARINE...A decaying mid period westerly swell around 12 feet has
continued to control the seas state today. Currently gentle winds
have also begun to turn southeast ahead of an approaching storm
system.
Southeast winds will rapidly increase in the southern waters
overnight as the storm zips north along the California Coast. This
storm will bring a narrow but potent band of gale force winds
impacting the southern waters through the day Sunday. A southerly
swell will travel with the storm brining mid period seas in excess
of 12 feet. The northern waters will remain calmer though still
elevated Sunday.
Very significant uncertainty remains in the forecast Sunday into
Monday, especially for the northern waters. Some high resolution
models including the HRRR and CANSAC show the storm continuing
north, brining gale force gusts to the northern waters early Monday.
Most other models, however, do not support this with the low
stalling or weakening off of Cape Mendocino. The possible need for a
Gale Warning will need to watched closely for the northern waters
late Sunday.
In either case, the wake of the storm system will leave an
exceptionally confused sea state early next week with both mid
period northerly and southerly swells crashing together Monday
combined with chaotic short period seas. Surprisingly, there is broad
model agreement on generally calmer conditions by mid next week with
moderate northwest wind and a series of mid period northwest swells.
/JHW
&&
.HYDROLOGY...Rapid rises on rivers, streams and creeks in
response to moderate to heavy rainfall rates are forecast for
southern Mendocino and southern Lake Counties on Sunday. In
particular, Scotts Creek may flood portions of Scotts Valley road
and the Russian River at Hopland may reach flood stage of 15 feet
causing minor flooding of highway 175. The threat for rock falls
and landslides will also increase.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
Winter Storm Warning from 6 AM Sunday to 10 AM PST Monday
for CAZ107-108.
High Wind Warning from 2 AM to 7 PM PST Sunday for CAZ109.
Wind Advisory from 2 AM to 7 PM PST Sunday for CAZ110>115.
Winter Storm Warning from midnight tonight to 4 PM PST
Sunday for CAZ111-114.
Flood Watch from Sunday afternoon through Sunday evening
for CAZ112-113-115.
Winter Storm Warning from midnight tonight to 10 AM PST
Sunday for CAZ115.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory until 9 AM PST Monday for PZZ450-470.
Small Craft Advisory until 9 AM PST Sunday for PZZ455-475.
Gale Warning from 9 AM Sunday to 3 AM PST Monday for PZZ455-
475.
&&
$$
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https://www.facebook.com/NWSEureka
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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png
Area Forecast Discussion
National Weather Service Sioux Falls SD
708 PM CST Sat Feb 3 2024
.KEY MESSAGES...
- The soupy conditions will likely continue tonight as areas of
fog and patchy areas of drizzle develop across the area.
- Near record warmth continues to look possible for much of
next week. Minimum temperature may challenge some of the
warmest recorded for February.
- Confidence remains higher than normal that we`ll have
precipitation within the Wednesday-Thursday timeframe.
Confidence on locations and intensity of the system remains
lower than normal.
&&
.UPDATE...
Issued at 707 PM CST Sat Feb 3 2024
Based on automated observations and DOT cameras we have decided to
expand the Dense Fog Advisory to include Beadle, Kingsbury, Sanborn,
and Miner counties. Visibilities in this area have deteriorated to a
mile or less with pockets of 1/2 mile or less. The additional
counties will expire with the original advisory at noon Sunday.
The rest of the forecast remains on track.
&&
.DISCUSSION...
Issued at 229 PM CST Sat Feb 3 2024
Tonight-Sunday:
Another dreary and foggy day continues! Taking a look at
satellite imagery, a mix of stratus and fog continue to sit over
the area today bringing widespread reductions in visibility. As
of 18z, we`re starting to see some gradual improvements as we
finally mix out of our inversion according to the soundings.
From here, high resolution guidance is a bit split on how things
progress for the rest of the afternoon and evening. On one
side, the HRRR and HREF have the stratus lifting temporarily in
areas along and east of the James River helping visibilities
improve through sunset. On the other side, the RAP has a similar
situation to the HRRR/HREF happening. However, the RAP keeps
more patchy areas of dense fog in along a Lake Benton, MN to
Storm Lake, IA line this afternoon/evening. Given the trends
over the last few days, I would lean closer to the RAPs solution
since we haven`t seen any drastic improvements through 20z.
Nonetheless, as temperatures decrease and the inversion
strengthens after sunset; more areas of fog and stratus will
return with visibilities below a mile expected at times.
As a result, our dense fog advisory has been extended through 18z on
Sunday with most of our area (besides the upper James River Valley)
included. Expect the fog and stratus to persist through early Sunday
afternoon before dissipating at least temporarily. Taking a look
aloft, a deepening upper-level wave continues to dig into the
Rockies as a strengthening upper-level high sits over the Great
Lakes Region. The combination of both of the features along with
southeasterly flow aloft has led not only a tightening SPG for us,
but increased Gulf moisture for the region this afternoon. With this
in mind and increasing PVA ahead of the wave, a line of light to
moderate shower has formed stretching roughly from western South
Dakota to eastern Kansas. As this line continues to push to the
northwest this afternoon, expect periods of drizzle to light rain to
move through areas west of the James River with the highest chances
in our southcentral SD counties (Gregory, Charles Mix, and Brule).
However, accumulations will be on the lighter side with less than an
0.10" of an inch expected through Sunday morning. Otherwise, more of
the same is expected overnight as easterly winds becomes
northeasterly overnight as temperatures slightly decrease into the
upper 20s to low 30s for the night.
Heading into Sunday, any lingering showers will gradually dissipate
in the morning as more fog and stratus continue to sit over the
area. Looking at high resolution guidance, we`ll likely see similar
conditions to today. This was characterized by areas of dense fog
developing as the surface inversion strengthens in the morning then
visibilities gradually improving by the early afternoon as the
inversion weakens. However, while there could be some brief areas of
sunshine east of I-29; more fog and stratus likely develop in the
late-evening hours dropping visibilities back below a mile
overnight. Otherwise, the mild stretch will continue into Sunday as
highs in the low to mid 40s continue across the area which is well
above normal for this time of year. The warmer conditions will carry
over into the overnight period as overnight lows in the upper 20s to
low 30s approach record warm low territory especially at Sioux Falls
(KFSD) and Huron (KHON).
MONDAY-TUESDAY: We`ll break free from stratus and fog to start next
week, as mid-lvl and low-lvl flow turns more southwesterly in
nature. The introduction of slightly drier low-lvl air and better
mixing should lead to drier boundary layer conditions. That said,
we`ll have a bit of mid-high lvl clouds early Monday as an open
wave moves through the Northern Plains. Breaking free from the low-
lvl clouds and still under a seasonally warm low-lvl airmass will
promote even warmer temperatures given the loss of most of the snow
cover over the weekend. Given performance of model guidance last
week, have blended in some of the warmest guidance for Monday, and
especially Tuesday. This will push high temperatures into the upper
40s and lower 50s, with more widespread 50s on Tuesday.
WEDNESDAY-FRIDAY: We`ll begin to see low-lvl flow sharpen and
increase quickly late Tuesday into Wednesday in response to
troughing digging into the Southwestern CONUS. The meridional wind
component of the 850mb jet increases sharply into Wednesday morning,
approaching the 99th percentile of model climatology for early
February. This increased northerly wind will push both increased
amounts of moisture northward, but also a surge of warmer low-lvl
air. After starting Wednesday with record overnight warmest minimum
temperatures, we`ll see a high potential for temperatures rising
into the middle and upper 50s to lower 60s. In fact, temperatures
may rival some of the warmest highs on record given a trace to 1" of
snow on the ground in the Sioux Falls area. The caveat would be the
impact on any stratus that may try to form within the warm conveyor
belt northward.
By Wednesday night and Thursday, there remains more uncertainty on
just how this upper trough will pivot into the Plains. Both
GFS/ECMWF/CMC show a trough deepening as it reaches the Tri-State
area early Thursday. Given the synoptic lift ahead of the wave,
would expect some shower development into Thursday along increased
convergence of the low-lvl jet. The GFS/ECMWF also suggest a bit of
elevated CAPE, mainly through Nebraska and Iowa, so while not in the
forecast, some lightning potential isn`t out of the realm of
possibility. Also of note, is the likelihood of record high minimum
temperatures once again. Low temperatures only falling into the
lower to middle 40s will challenge some of the warmest low
temperatures on record for February especially south of
I-90. The ECMWF EFI indicates the significance of the event in
respect to climatological reforecasts, with the shift of tails
suggesting that there is considerable potential for a higher end
climatological event.
The track of the upper wave becomes more in doubt through Thursday,
with the latest ECMWF pulling the wave slightly further southeast
than the GFS. The dprog/DT of 500 mb heights from the EC/GFS
ensembles also indicate at least some trends towards a deeper wave.
The impact of this would be moreso on track of a developing
deformation band on the western/northwestern flank of the upper
trough, and if we could see any type of wintry mix late Thursday
into Friday. For now, do not have enough confidence to make any
meaningful change to PoPs or weather types.
The upper wave will pull east by late Friday into next weekend, and
temperatures should trend back downward as low-lvl cold advection
increases. NBM temperatures could be a tad high for Friday and
Saturday, but again, with uncertainty on track of the trough,
confidence is not high enough to modify lower ATTM.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 532 PM CST Sat Feb 3 2024
Widespread LIFR ceilings and visibilities this afternoon. KHON and
KSUX being the lone IFR conditions. Expect that KHON will stay there
until after noon Sunday, when clouds begin to lift and scatter out
due to day time heating. KFSD current conditions are LIFR with
visibility down to 1/4 mile. Expect conditions to improve around
midnight to IFR, and then follow a similar pattern as KHON, and
improve to MVFR after noon. Expect KSUX ceilings to degrade to LIFR
after midnight and continue through the period.
Winds are easterly at 10-15 kts, with gusts up to 20 kts. Winds will
slowly decrease after sunset and become east-northeasterly at 5-10
kts.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until noon CST Sunday for SDZ038>040-050-
052>071.
MN...Dense Fog Advisory until noon CST Sunday for MNZ071-072-080-
081-089-090-097-098.
IA...Dense Fog Advisory until noon CST Sunday for IAZ001>003-
012>014-020>022-031-032.
NE...Dense Fog Advisory until noon CST Sunday for NEZ013-014.
&&
$$
UPDATE...AJP
DISCUSSION...Dux/Gumbs
AVIATION...AJP
Area Forecast Discussion
National Weather Service Hastings NE
658 PM CST Sat Feb 3 2024
.KEY MESSAGES...
- Off and on rain continues through tonight and gradually winds
down on Sunday. A few rumbles of thunder remain possible
through this evening.
- More dense fog is possible tonight.
- Localized flooding remains possible through Sunday. The
primary threat will be from ice jams along the Loup and Platte
Rivers. Ponding and minor flooding is possible in poor
drainage areas as well.
- Dry and warming through middle of next week. Next chance for
rain is Wednesday night into Thursday.
&&
.UPDATE...
Issued at 655 PM CST Sat Feb 3 2024
Expanded the Dense Fog Advisory for a few of our SW counties
given recent automated obs and webcams at Holdrege,
Phillipsburg, and Norton. Visibilities have fallen to around 1/2
mile, or less, and are expected to continue for at least several
more hours. The E/SE side of the advisory is more marginal at
this time, and recent HRRR trends actually suggest steady or
improving conditions for these areas overnight...so may be able
to remove some counties at some point. Would like to wait and
see how things trend this evening before "pulling the plug".
&&
.DISCUSSION...
Issued at 230 PM CST Sat Feb 3 2024
East to southeasterly flow persists at the surface and aloft as
we remain north of a slow-moving cutoff low. Moisture will
continue to feed into the area, bringing additional rounds of
rain to the area tonight. Dense fog will also continue to be an
issue, especially during the breaks in rain. A Dense Fog
Advisory is in effect until noon Sunday for the northern half of
the forecast area.
On Sunday, the main area of rain will begin to focus further
west and will gradually diminish during the afternoon. Total
rain amounts (including rain from Friday night) are expected to
range from 0.10" to over 1.50" (locally as high as 2.00").
Highest total are expected to be over the southwestern half of
the area, with decreasing amounts as you move northeastward.
So far, stream gauges across the area have showed little to no
response to the rainfall. Fortunately, rain rates have been slow
enough for the partially thawed soil to accommodate it. That
said, several gauges on the Platte and Loup River systems are
showing ice movement/breakup. Locations along these rivers
should continue to monitor river levels over the next 24-48
hours. Please report any observed ice jams or elevated water
levels to local authorities and the National Weather Service.
The beginning of next week will be dry, with warming
temperatures as ridging returns to the region. Low temperatures
will be near-record warmth each night. Wednesday looks
particularly warm thanks to strong southerly flow ahead of the
next shortwave. Highs on Wednesday are expected to reach the
upper 50s and 60s across the entire area.
Chances for rain return to the area Wednesday night through
Friday as the as the aforementioned shortwave moves through.
There is a chance for a little bit of snow to mix in on the back
side, but the potential for anything meaningful is low. The
latest NBM has a less than 10 percent chance for 1" of snow.
Long-range ensembles had looked a little more favorable for
below-normal temperatures returning next weekend into the
following week, but latest runs are backing off of this a little
bit. The latest EPS ensemble actually favors above-normal
temperatures clear through the middle of the month.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 550 PM CST Sat Feb 3 2024
Significant weather: LIFR CIGs and mixed VSBYs, potentially as
low as LIFR as well.
Both terminals will remain socked in the LIFR CIGs all night,
and likely through at least Sun AM. This is a high confidence
aspect of the forecast. Some improvement is expected Sun aftn,
but the degree to which remains uncertain. Return to IFR Sun
aftn is most probable outcome at this time, but would anticipate
another round of LIFR Sun night.
VSBYs are much more uncertain and will be somewhat tied to
trends in shower intensity. In general, though, would expect a
return to at least IFR VSBYs this eve, and LIFR is a strong
possibility overnight, esp. at EAR. Dropped EAR to half mile
around midnight, and GRI to 3/4sm by dawn Sun AM, but both could
conceivably drop to 1/4sm, at times, overnight into Sun AM.
VSBYs should return to MVFR around midday Sun, then VFR Sun
aftn. Probably looking at another round of fog Sun night with
already at least a 30 percent chc of MVFR, or lower. Overall
confidence on VSBYs is low.
Winds will back from E to NE overnight, with speeds steady
around 8-12kt. Confidence in wind forecast is high.
&&
.CLIMATE...
Issued at 230 PM CST Sat Feb 3 2024
Potential Record Warm Minimum Temperatures:
Grand Island:
Feb 3: Observed 39...previous record is 37 in 1909
Feb 4: Forecast 34...current record is 36 in 1927
Feb 5: Forecast 30...current record is 35 in 2005
Feb 6: Forecast 37...current record is 34 in 2013
Feb 7: Forecast 46...current record is 35 in 2015
Feb 8: Forecast 38...current record is 35 in 1966
Hastings:
Feb 3: Observed 39...previous record is 37 in 1962
Feb 4: Forecast 32...current record is 36 in 1991/1954
Feb 5: Forecast 30...current record is 35 in 2005/1954
Feb 6: Forecast 36...current record is 35 in 1930
Feb 7: Forecast 46...current record is 34 in 2015
Feb 8: Forecast 36...current record is 38 in 1960
Hastings daily precipitation:
Feb 3: Forecast 0.68"...current record is 0.78" in 2012
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Dense Fog Advisory until noon CST Sunday for NEZ039>041-
046>049-060>064-072>076-082>084.
KS...Dense Fog Advisory until noon CST Sunday for KSZ005.
&&
$$
UPDATE...Thies
DISCUSSION...Mangels
AVIATION...Thies
CLIMATE...Mangels
Area Forecast Discussion
National Weather Service Grand Junction CO
554 PM MST Sat Feb 3 2024
.KEY MESSAGES...
- Snow tapers off over most of the southern Colorado mountains
this evening...while lingering over the central and north
into early Sunday. Difficult travel conditions over the
mountain passes remain a threat.
- After mild temperatures and dry weather tomorrow through
Monday, unsettled weather returns from Tuesday onward with
temperatures dropping back toward normal.
- Another strong atmospheric river will move across the
Southwest almost unabated to the central Rockies. The
potential of significant mountain snowfall from late Tuesday
into the late week period is high.
&&
.UPDATE...
Issued at 551 PM MST Sat Feb 3 2024
Some light snow is expected over the San Juans and Uncompahgre
Plateua this evening and early overnight hours according to the
HRRR and NAMNEST. However, guidance continues to highlight very
light accumulations which looks to be panning out according to
the latest SNOTEL and observational data. With that, allowed the
highlights for those same areas to expire.
&&
.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 216 PM MST Sat Feb 3 2024
A visually impressive cyclone on the lee side of the S.Rockies
has been pumping an equally impressive amount of moisture back
toward Colorado today. The front range has been capturing the
bulk of this moisture which is leading to heavy snowfall rates
from the foothills to the divide. The 03/12Z H500 hand analysis
map shows this stalled cyclone in the base of deep negatively
tilted trough with a tap into the GoMex. Deep lift from the jet
ejecting on downstream side of the trough helped with the
explosive ascent today to our East. Gulf moisture will continue
to impinge upon the divide through the overnight hours even
though the stronger lift will be dissipating. Broad difluent
flow and moist northwest orographics will be the main player for
our Colorado mountains through the early morning
hours...lingering farther North past sunrise. Farther West drier
air is filtering in as evidenced by the falling dew points.
This created some clearing which has filled in with convection
and in some cases isolated to widely scattered showers over
eastern Utah into southwest Colorado which should dissipate with
sunset. So winter headlines will start to drop off this evening
in the south and West and linger into morning up north with
looks reasonable. Most of the activity should be limited to the
highest elevations by then as the dendritic layer begins to dry
out and stabilize with increasing heights building building out
of the Great Basin...with the ridge axis expected to be along
the CO/UT border by late tomorrow. The ridge axis will be
sliding east tomorrow night followed by a strong increase in SW
flow aloft. This will likely be the last of high pressure over
the area for a good long time. The weather looks relatively
tranquil as we make our way through the PM hours tomorrow into
early Monday. The main concerns will be fog and stratus that
usually forms in the wake of these moist storms with ridging and
warm air advection moving in aloft. The Gunnison Basin also
looks to become strongly inverted in this pattern and trended
the daytime temperatures downward the next few days. This has
been a swing and miss on my part in the past...especially as we
get out of deep winter and just a bit a mixing can erode the
cold air...so confidence in medium. Most eyes will be upstream
along the Cali coast where another strong AR will have moved
onshore tomorrow afternoon. This moisture will keep the
snowpack trend moving swiftly upward on the SWE chart...while
lower elevations see more rainfall. More details below and in
the coming days with the arrival of this abundant moisture
source.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 216 PM MST Sat Feb 3 2024
An elongated trough will engulf the Pacific Ocean on Monday as the
upper level ridge axis overhead gets shunted to the northeast in the
morning. Strong southwest flow will advect an abundance of mid and
high-level moisture across eastern Utah and western Colorado on
Monday, seeing clouds increase in response. A quick glance at the
synoptic pattern makes it seem like widespread precipitation will
follow soon after, but the trough will actually become more
positively tilted off the coast of southern California before
finally swinging inland some 24 to 36 hours later. As a result,
mainly dry weather will prevail across the West Slope into Monday
night. Northeast and east-central Utah will be an exception as the
jet rounding the base of the trough settles overhead, providing
sufficient lift to fuel at least isolated snow showers over the
higher terrain Monday afternoon and evening. The Eastern Uintas look
to receive a couple to several inches of snow during this timeframe
with a dusting expected over the Tavaputs. By Tuesday morning the
trough axis will extend as far south as Baja, strengthening the
southerly flow and moisture advection even more. A ripple ejecting
out ahead of the parent system will swing through the Four Corners
on Tuesday, seeing showers increase across the region. Favorable
upslope flow will produce moderate rates in the southern mountains
as mild temperatures keep snow levels above the valleys.
As the trough pushes inland across the Desert Southwest on Tuesday
night and Wednesday, PWATs will increase to at least 180 to 200
percent of normal area-wide during this time, so look for plenty of
clouds and showers in response. Confidence is increasing that the
trough will push through on Wednesday afternoon as the vort max
associated with it follows suit. After the trough passes flow aloft
will switch to the northwest, advecting cooler air into the region.
Until then, snow levels will remain pretty high but, either way, 60
to 80 percent PoPs look likely for the majority of the region mid-
week. We`ll have to keep an eye on trends over the coming shifts but
the long term period looks to remain active as we head into the
latter half of the week as additional systems brew offshore. All the
same, be sure to keep an eye on the forecast, especially if planning
to travel in the high country, as significant mountain snow looks
more and more likely.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 419 PM MST Sat Feb 3 2024
Conditions are slowly starting to improve across eastern Utah
and southwestern Colorado so KVEL, KCNY, and KDRO will see VFR
conditions form here on out though midlevel ceilings will likely
persist. However, low ceilings and visibilities in snow will
persist at KHDN, KASE and KEGE until the evening and ceilings
will remain below ILS breakpoints through at least 06Z tonight
if not beyond. Fog remains a possibility overnight but still not
enough confidence to include in any TAFs. Showers will largely
come to an end after 12Z but stray light snow showers will be
possible up north into Sunday afternoon. Clearing skies will be
the rule from about 18Z onwards tomorrow.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Storm Warning until 5 AM MST Sunday for COZ004-009-010-
012-013.
Winter Weather Advisory until 5 AM MST Sunday for COZ005.
UT...None.
&&
$$
UPDATE...TGR
SHORT TERM...15
LONG TERM...MMS
AVIATION...TGJT
Area Forecast Discussion
National Weather Service Grand Rapids MI
630 PM EST Sat Feb 3 2024
.KEY MESSAGES...
- Cloud trends remain the focus tonight
- Unusual sustained warmth next week, likely rain late Thu-Fri
&&
.DISCUSSION...
Issued at 325 PM EST Sat Feb 3 2024
A difficult cloud forecast tonight as is usually the case when
we get later into the winter and the early spring. An assist
from lake moisture and subsidence inversions are usually in
play when these tougher forecasts come up. The first part of
equation is the wind direction from the moisture source (Lake
Huron and Erie). Winds tonight over Lake Huron will be more
northerly, so the source region of last nights moisture for us
will be taken out of play a bit. Winds off of Lake Erie will be
easterly which can easily push moisture into the I-94 corridor.
Subsidence inversions will still be in play tonight to aid in
trapping low level moisture. The bottom line is we will continue
to follow the HREF low level cloud forecast as it is one of the
few pieces of guidance that did well last night. Using that as
a guide we look to be a bit more partly cloudy today as compared
to last night, especially in Western Lower. Further east
towards Highway 127 there will likely be more in the way of
clouds. Given the propensity for more in the way of clearing
this evening and light winds we are thinking there are better
chances for fog tonight. So, a mix of clouds across the forecast
tonight with areas of fog forming. Not out of the realm of
possibilities that fog and temperatures dipping into the 20s
results in some icy spots.
A similar day to today on Sunday with some morning clouds and
fog giving way to sunshine once again. A repeat performance of
the clouds looks to develop once again Sunday night. The RAP
model is showing quite a bit of cloud cover pushing into the
forecast area from the north. Confidence overall is not high in
the cloud forecast for tonight, Sunday and Sunday night. In
these cases this time of year persistence is usually the way to
go, meaning clouds reforming each night.
There is quite high confidence that the area will see warm and
dry conditions persist for much of the upcoming week. That
confidence is the result of various independent ensemble means
agreeing on the details, with little to no spread.
Model ensemble means agree that we will see much of the area in the
50s by Thursday, with slight warming each day after Monday. Some
slight cooling is expected on Monday compared to Sunday with
advection of some cooler air. This trend will reverse quickly on
Tuesday through Thursday as we end up on the backside of the sfc
ridge, and return flow will advect warmer air up over the area. 850
mb temps will warm from around +4C on Monday to +10C on Wednesday.
These temperatures aloft will easily support the 50s by Thursday.
The upper ridge building to our West, and only slowly building over
the area through Tuesday will ensure plenty of subsidence and dry
air to keep any precipitation out of the area. This is expected to
last through Wednesday, with only some high clouds moving in at that
time. The model ensembles are in good agreement that any rain should
not start any earlier than Thursday morning, and will be centered
more on later Thursday and Friday with the cold front coming in as
the long wave trough lifts in.
The only uncertainty in the forecast is really how quick we see the
rain move out and temperatures cool down toward next weekend. The
spread there is in how quick the cold front can move through. This
is not a bit deal at this time with no major impacts expected. The
forecast features a cool down with diminishing rain chances by next
Saturday.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 628 PM EST Sat Feb 3 2024
Another night of potential IFR conditions as low level moisture
may result in fog or low clouds forming after midnight. Low
confidence in timing, so we will keep close continuity with the
previous forecast of MVFR/IFR conditions developing between 06Z
and 10Z and then gradually improving during the morning with VFR
conditions Sunday afternoon. WInds will continue to be from the
east to southeast BLO 10 knots.
&&
.MARINE...
Issued at 325 PM EST Sat Feb 3 2024
No marine concerns in terms of winds and waves for the remainder
of the weekend and into the early portion of the work week. High
pressure will dominate and keep winds down. Winds are expected
to remain at or below 15 knots for the most part through
Tuesday. So, no advisories are expected during that time frame.
Winds will likely push into advisory levels on Wednesday as
south winds develop ahead of our next system.
It is not out of the question that fog becomes an issue tonight
as we clear and cool. At this point confidence is low in fog
trends tonight so no advisory
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Duke/NJJ
AVIATION...Ostuno
MARINE...Duke
Area Forecast Discussion
National Weather Service Huntsville AL
938 PM CST Sat Feb 3 2024
...New NEAR TERM...
.NEAR TERM...
(Rest of tonight)
Issued at 938 PM CST Sat Feb 3 2024
Low level southeasterly flow will continue to advect better
moisture into the region, and have seen an increase in high clouds
this evening. Low level jet winds will increase overnight, but
believe these likely will not mix down closer to the sfc until
sometime tomorrow morning as near sfc gradient winds increase. The
exception overnight will be the higher terrain areas across
northeast AL and southern middle TN where wind gusts up to 30mph
will be possible at times. With these things in mind, fog should
not be an issue overnight and also do not have any current plans
to issue a Wind Advisory. Only minor adjustments were made to sky
grids and dewpoints to better match current obs, but otherwise no
changes were needed during the evening update.
&&
.SHORT TERM...
(Sunday through Tuesday)
Issued at 359 PM CST Sat Feb 3 2024
Just before daybreak on Sunday, expect more widespread rainfall
to begin to develop in northwestern Alabama and spread eastward
during the mid morning and early afternoon hours. This is in
response to isentropic lift that continues to strengthen to the
northeast of the surface low and along the earlier mentioned
stationary front as the low dives southeast into the Florida
panhandle by Sunday afternoon. PWATS climb to between 0.80 and
0.90 inches primarily during this period. Given the strong
isentropic forcing seen in models, one half to one inch of
rainfall looks very possible across much of the area. Our southern
middle Tennessee counties may see only 0.25 to 0.50 inches, as
forcing drops off to the north in Tennessee. Most models show the
strongest low level forcing south of Tennessee, so we will likely
see some wet-bulbing of temperatures closer to dewpoints early
Sunday morning in those areas. Between initial evaporative
cooling, rain, and cloudy conditions, highs will likely be a bit
cool and raw. Highs in most locations should only reach the mid
40s in many locations (this may be a tad optimistic). Our southern
middle Tennessee area will likely be a tad warmer, with highs in
around 50 degrees. Northeasterly winds will be blustery. Sustained
winds of 10 to 20 mph with some gusts to around 30 mph could
occur. NAM12 and HRRR show high gusts (slightly strong 925 mb
winds). If this materializes, a wind advisory may be needed on
Sunday. Light rain holds on in most models through Sunday night,
as the surface low hangs around the northeastern Gulf of Mexico
into Monday morning.
However, by Monday morning the center of the surface and its
associated upper level low will move far enough southeast that dry
weather should return. We likely will see cloud cover hang on
early Monday morning over most of the area, except maybe in
southern middle TN. Drier air will push into the region as an
area of high pressure builds southeast behind the departed surface
low late Sunday night. However, cloud cover and winds will likely
keep temperatures from dropping below the upper 30s to lower 40s
around daybreak.
Most models quickly push this cloud cover southeast of the area
by the mid morning hours, as the surface low pivots further east
across the Florida peninsula. Despite sunshine on Monday highs
will only climb into the upper 50s to lower 60s.
&&
.LONG TERM...
(Monday night through Saturday)
Issued at 359 PM CST Sat Feb 3 2024
Our coldest period over the next week or so will be Monday night
through Wednesday, as high pressure builds into and remains in
place over the Tennessee Valley. Good radiational cooling and
drier air will allow for highs to drop into the lower to mid 30s
again both Tuesday night and Wednesday night. This will further
temper highs on Tuesday especially. Despite abundant sunshine,
highs will likely remain in the upper 50s in most locations.
Some southerly return flow returns around the backside of the
surface high late on Wednesday into Wednesday night. At the same
time a very strong upper level ridge develops over the eastern
CONUS, as a strong longwave trough develops over the western
CONUS. This should bring the area another warming trend towards
the end of next week. Highs should climb back into the 60 to 65
degree range towards the beginning of next weekend. Unfortunately,
with the warmer weather comes more cloud cover and rainfall
though, as the longwave trough axis and associated weakening front
moves through the area. Some models hint at some elevated weak
instability, but confidence is low concerning these parameters.
&&
.AVIATION...
(00Z TAFS)
Issued at 520 PM CST Sat Feb 3 2024
VFR conditions will prevail through the overnight hours, before
rain and lower clouds reduce categories down to MVFR and IFR
Sunday afternoon. Periods of LIFR cigs/vsbys will be possible,
especially for KMSL Sunday afternoon and early evening during the
heaviest rain before conditions start to improve within the last
few hours of the TAF period. Southeast winds will pick up on
Sunday as well, with gusts up to 25kts possible at times. No
thunder or fog is expected at this time, so the main impacts will
be focused on rain, lower cigs, and increasing winds.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.
&&
$$
NEAR TERM...25
SHORT TERM....KTW
LONG TERM....KTW
AVIATION...25
Area Forecast Discussion
National Weather Service Reno NV
252 PM PST Sat Feb 3 2024
.SYNOPSIS...
A significant winter storm with widespread snow impacts moves into
the Sierra and western NV regions starting late tonight that expects
to last into early next week. Travel is not advised during this
storm due to the hazardous winter weather conditions. Following this
storm, the region sees chances for wintry precipitation throughout
the rest of the work week (especially in the Sierra portion) with
these chances expecting to lessen on Saturday.
&&
.DISCUSSION...
Rest of Today:
* Travelers are advised to get to where they wish to be within the
region by this evening as dry conditions and relatively lighter
winds are expected this afternoon and evening. By late tonight,
the latest HRRR model run shows snow chances begin in southern
portions of the CWA (Mono and Alpine counties as well as the
bordering areas of the adjacent counties) between 9-10 PM PST as
winter storm begins its approach into the region. These snow
chances are forecast to spread into the remaining portions of the
Winter Storm Warning going into early Sunday morning.
Sunday-Monday:
* MAIN POINTS: The forecast still appears to be on track with a
significant winter weather system impacting the CWA on Sunday and
Monday (possibly lingering into early Tuesday). This winter
weather is associated with low pressure just off the coast of
central CA. A Winter Storm Warning is in effect within the region
as well as a Winter Weather Advisory for northern Washoe County.
For more detailed information including the latest snowfall
forecast for this event: please refer to
www.weather.gov/rev/winter. Moderate to extreme travel impacts are
anticipated within the effected parts of the region (Refer to the
Winter Storm Severity Index (WSSI) on the aforementioned website
for a more detailed map and explanation of what the potential
winter storm impacts could be for a particular location).
* MONO COUNTY: The heaviest snowfall in the region is still
expected to impact Mono County particularly along the Sierra
crest. When viewing the latest GEFS run of the Probability of
IVT greater than 500 kg/m/s, it shows a ~70-90% probability of
this criteria being met in central CA around 10 AM PST to around
4 PM PST on Sunday. With this signal, a very good amount of
Pacific moisture looks to funnel into the county for a good
portion of the winter event and support likely snowfall rates of
3 inches or greater. Snow showers continue within Mono County
throughout Monday though intensity and rates currently are
forecast to be lower than those seen on Sunday. Portions of the
county have a very good chance of seeing greater than 1 ft of
snowfall with far western portions a good portion for more than
4 ft of snowfall during this event when looking at the latest
guidance for this event.
* TAHOE BASIN AREA: Models show chances for snow moving into the
Tahoe Basin after midnight and spread throughout the rest of the
region during the morning hours of Sunday. Snowfall is also
expected to intensify through the middle of the Sunday. Forecasted
winds gusting up to around 80-90 kts are possible which will cause
dangerous white-out conditions at times within this area during
the afternoon and into the overnight hours. Snowfall currently
looks to continue through Monday though lessen in intensity during
the later hours of Monday. Peaks of the Sierra as well as the
Sierra Passes continue to see good confidence in greater than 3 ft
of snow possible. At the Lake Tahoe level, confidence remains
pretty good for greater than 1 ft of snowfall possible.
* WESTERN NV/NORTHEAST CA: The latest model runs show the winter
weather system causing the snow chances to begin early Sunday
morning and intensifying a bit by the late morning hours. Around
12 PM Sunday, models show snow levels rising allowing for a
transition to a rain-snow mix with portions of western NV seeing
precipitation type turn to mostly rain by the late afternoon and
evening hours. The mostly snowfall P-type looks to return
overnight into Monday morning as temperatures cool. Still
monitoring for the potential "boom" scenario in case snow levels
do not rise as anticipated or if a band of convective snow occurs
on Monday morning which would increase snowfall totals and winter
weather impacts. Accumulating snowfall chances look to lessen by
the afternoon hours as intensity decreases and rain mixes in again
during the day. The chances for 4 inches of snow or greater
continue to look rather good for valley areas while areas above
5000 ft continue to see good chances for 1+ ft of snowfall.
Tuesday-Saturday:
* Accumulating snowfall chances expect to decline and depart for a
good portion of the region during the first half of Tuesday with
southern portions seeing the highest remaining chances though not
much additional snow is anticipated. By Tuesday night, the
forecast calls mostly conditions with portions of Mono County
still seeing lingering snowfall chances.
* Chances for snow showers particularly in the Sierra region are
seen through the rest of the work week with Saturday seeing the
lowest precipitation chances within the forecast period.
-078
&&
.AVIATION...
Generally VFR conditions with light and VRB winds through 6Z.
Conditions quickly deteriorate overnight. Snow levels drop down to
valley floors. Therefore, between 6-12Z expect MVFR to IFR
conditions as SHSN develop across Sierra sites. IFR to LIFR expected
after 12Z over the Sierra due to snow rates between 1-2"/hr, and
greater rates with the heaviest snowfall. SN expected to continue
through Mon. For the W NV sites, MVFR to IFR conditions with LIFR
possible during periods of heavy SN. Accumulations are still
expected to be 1-3 ft for the Sierra sites, and 3-6 inches for the W
NV sites. However, there is a 20-40% for SN amounts above 8 inches.
Snow levels increase after 20Z to 5000-6500 feet resulting in RA/SN
mix or RA for the valleys. However, convective showers may drop down
snow levels back to the valley floors. There is also a 10- 15%
chance of thunder at Sierra terminals which may result in some snow
bursts through the day.
Winds become from the east-southeast area-wide with speeds between
10-25 kts at TAF sites. However, wind speeds above 7 kft are above
30-50 kts with gusts to 80-100 mph. The strongest winds will be near
the crest. Furthermore, LLWS is expected at Sierra terminals after
9Z, and at all terminals after 00Z Mon.
-Crespo
&&
.AVALANCHE...
Following dry conditions within the region today, the most
significant winter storm of the season so far arrives tonight and
lasts into the beginning of next week.
* AFTERNOON UPDATES: No new forecast updates since the previous
discussion.
* SWE: 95+% chance of 1" SWE in 24 hours between 10 PM Saturday-10
PM Sunday along the entire Sierra crest. Storm total SWE along the
Sierra crest likely (80-90% chance) up to 4", 60-70% chance of SWE
totals approaching 5" along and west of the Sierra crest.
* SLR: Upside-down storm as temperatures warm through its duration.
12-14:1 ratios for the onset of this storm late tonight,
decreasing to 10:1 midday Sunday into Monday morning.
* Snow Rates: For the Sierra in Mono County, likely 2-3" per hour
through the storm duration, exceeding 3" per hour at times. For
the Sierra from Tahoe northward, periods of 2-3" per hour
possible. Cannot rule out thunder either with a 10-20% chance.
* Winds: Sustained ridge level winds increasing to 50+ mph out of
the SW by Sunday morning, remaining elevated into Monday morning.
Gusts upwards of 100+ mph possible along ridgelines.
-Whitlam/078
&&
.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory from 4 AM Sunday to 4 AM PST Monday
NVZ005.
Winter Storm Warning from 10 PM this evening to 10 AM PST Monday
NVZ002.
Winter Storm Warning from 10 PM this evening to 10 PM PST Sunday
NVZ001-003.
Lake Wind Advisory from 10 AM to 10 PM PST Sunday NVZ004.
CA...Winter Weather Advisory from 4 AM Sunday to 4 AM PST Monday
CAZ070.
Winter Storm Warning from 10 PM this evening to 10 AM PST Monday
CAZ071>073.
&&
$$