Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/01/24
Area Forecast Discussion
National Weather Service La Crosse WI
521 PM CST Sun Dec 31 2023
.KEY MESSAGES...
- Above normal temperatures for the start of the New Year, but
below average confidence in the cloud forecast which would
affect temperatures.
- Slight chance (15-20%) for light snow for the northern
portions of our region Wednesday.
&&
.DISCUSSION...
Issued at 244 PM CST Sun Dec 31 2023
Overview:
Water vapor satellite imagery/heights showed the closed low over.
southern Lake Michigan. A ridge aloft was noted across the Rockies
with a closed low over the state of Washington and full latitude
troughing off the West Coast. The latest metars and WSR-88D radar
show a few lingering flurries locally, some UP over central MN and
some snow showers pushing across parts of Lake Superior. Overnight
and early this morning, many locations experienced bouts of light
freezing drizzle/mist. Even small amounts on untreated surfaces
created a light glaze and slippery conditions. Snowfall amounts
were light as expected and ranged from a trace to 1.1" Here at the
NWS La Crosse, we had 0.2" of snow with a trace of icing. RST had a
trace of snow and light icing. LSE had 0.2" with a trace of ice.
4WNW of Ettrick reported 1.1" of snow, Black River Falls had 1",
4NNW of La Crescent 0.7" and Onalaska had 0.3". See our latest PNS
for more reports. The most recent visible satellite imagery showed
mostly cloudy skies across the region with temperatures in the upper
20s to lower 30s.
Above normal temperatures to start the New Year:
Through Monday, the storm system that brought the freezing drizzle
and light snow to the area will exit the region with mid-
tropospheric ridging building in for Monday. The short term models
are keen on clearing the low clouds out, however the western edge of
the stratus is not budging. Some breaks are occurring across parts
of central Wisconsin. The RAP low level moisture hangs around
through early Monday afternoon compared to clearing out this
evening. Thus went with the more pessimistic guidance of holding on
to clouds longer, although some breaks could develop across parts of
the forecast area overnight. We currently have lows in the mid
teens to lower 20s, however if the clouds break up more, they could
be colder. For Monday, have highs from 28 to 33 and those readings
are a few degrees above the normal highs of 24 (RST) and 29 (LSE).
Temperatures remain near to above average this week with slight
chances for snow Wednesday:
Temperatures will remain above normal through the middle of the week
with an upper-level ridge sliding into our region Late Monday. As a
result, can expect highs mostly in the lower to middle 30s for
Tuesday with the ridge axis firmly over our region and building
surface high pressure to the south. The next feature that
warrants watching is a small shortwave trough ejecting out of
the Canadian Plains late Tuesday and into Wednesday. Currently,
the latest NBM continues to keep precipitation chances almost
zero due to its limited QPF signal. However, there is a couple
subtle indications of precipitation Tuesday and Wednesday that
will need some monitoring. The 31.12z NAM soundings shows some
low-level saturation with a stratus deck that pushes into the
region ahead of the wave. With the lack of ice nucleation
present in this sounding, there would be some question of
freezing drizzle/mist if there is enough lift. With questions
remaining as to how large the saturated layer would be and with
the NAM being the only solution showing this, opted to keep out
any mention of precipitation Tuesday morning. Additionally,
with the 31.12z deterministic NAM and GFS forecast soundings
showing some potential for saturation in the dendritic growth
zone with some weak lift Wednesday morning, decided to nudge
precipitation chances to 15- 20% north of I-90 with snow being
the main ptype. After the passage of this shortwave, some cold
advection will work its way in allowing highs to fall down to
near average but will warm slightly once again as guidance shows
another ridge building in late Thursday into Friday.
Looking to the Weekend and beyond:
Long range guidance does show some interesting trends going into the
first weekend of 2024 and beyond. However, it is important to note
that predictability at this stage in the forecast remains low.
Deterministic guidance shows a fairly robust upper-level trough
digging down into the southern rockies Saturday morning that
ejects into the southern Plains. Intensity of this trough as it
will be key in determining its position as it moves eastbound
with the current consensus mostly keeping this system south of
our region. Consequently, probabilistic guidance, namely the
31.12z GEFS and EC ensemble, does not have high confidence in
measurable precipitation with only medium probabilities (30-50%
chance).
Guidance then depicts a secondary system early the subsequent week
that ejects into the Great Plains as well. There seems to be some
indication that there could be a more northward trajectory with
this system as it moves eastbound. As a result, probabilistics
in the 31.00z grand ensemble (EC ens/GEFS/Canadian ens) already
show very high confidence (70-90% chance) of seeing measurable
precipitation during this period. However, due to this being
pretty far into the extended forecast predictability remains
very low.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 520 PM CST Sun Dec 31 2023
Widespread MVFR ceilings persist through much of the period,
with an increasing probability (50 to 70%) of IFR ceilings west
of the Mississippi River after 06Z tonight. The cloud deck
across the region may begin to scatter out Monday afternoon, but
timing specifics are tough to pin down at this time. Current
northwest winds of 5-10 kts back to the west Monday morning and
the southwest Monday afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Naylor/Zapotocny
AVIATION...Skow
Area Forecast Discussion
National Weather Service Bismarck ND
856 PM CST Sun Dec 31 2023
.KEY MESSAGES...
- Areas of fog may possible southwest and south central tonight.
- New Year`s Day will be seasonably mild with highs ranging from
the low to mid 30 east, to the upper 30s to upper 40s west
(warmest southwest).
- For New Year`s night, expect low to medium chances (20 to 40
percent) for light snow in the general vicinity of the Turtle
Mountains.
- Low to medium chances (20 to 40 percent) for light
accumulating snow then return next weekend over much of
western and central North Dakota.
&&
.UPDATE...
Issued at 856 PM CST Sun Dec 31 2023
Expanded fog coverage southwest and also across the James River
Valley where visibility has dropped on the western edge of the
stratus over southeast ND. Also adjusted sky cover again across
the south based on latest satellite imagery and RAP guidance.
&&
.UPDATE...
Issued at 621 PM CST Sun Dec 31 2023
Main update to the forecast for tonight was to adjust sky cover
and the aerial coverage of fog.
Low stratus and fog developing northward across far southwest
North Dakota early this evening, which the latest RAP seems to
depict the best compared to other models. With time, as winds
begin to transition to more south-southwest and eventually
southwesterly, this area of stratus will begin advecting
eastward with clearing on the western edge. How far north the
low clouds and fog develop remains in question, as well as the
timing of the aforementioned eastward development and western
edge erosion. Will continue to monitor and adjust the forecast
as needed. With winds forecast to be steady at 7-9 knots through
the night, do not anticipate much dense fog at this time.
&&
.DISCUSSION...
Issued at 240 PM CST Sun Dec 31 2023
An upper level ridge axis is currently located along the
Montana/North Dakota border. At the surface, broad high pressure
was centered near the central North Dakota/South Dakota border.
As this surface high continues to slide south southeast, the
upper level ridge axis will move across western and central
North Dakota through the rest of today and tonight. The ridge
will start to deamplify as a shortwave trough and upper low
approach eastern Montana by early New Year`s afternoon.
For tonight, CAMs continue to advertise the potential for more
patchy fog, mainly over the south central. The general pattern
makes sense for some fog, given plenty of surface moisture still
hanging around and southerly surface flow. However, most
guidance has winds increasing through the night, which could
limit how much fog is able to form. For now, will just broad
brush patchy fog over the south central. Lows will be chilly
tonight, but still above normal for most, generally ranging from
10 to 20 (warmest west).
With the passing of the aforementioned ridge, New Year`s Day
should see plenty of sunshine for most and well above normal
highs, ranging from the low to mid 30s east, to the upper 30s to
upper 40s west (warmest southwest). Due to pattern recognition,
we did nudge towards the NBM 75th percentile for highs tomorrow,
but spread is very small. As an example, the NBM 75th percentile
for the high at Bismarck tomorrow is 40, the median is 38, and
the 25th percentile is 36. Thus, we trended towards the warmer
solution, but there`s really not much gap between the warmer
and cooler solutions.
On New Year`s night, the shortwave that was previously located
over eastern Montana will quickly move across North Dakota.
While most of the forcing will remain north of the International
Border, we will see at least some low to medium chances (20 to
40 percent) for light snow across the far north, mainly in the
vicinity of the Turtle Mountains.
A cold front then crosses the state from north to south on
Tuesday which will mean cooler temperatures (but still at or
above normal for most) through the rest of the work week and
into the weekend. Tuesday will see highs ranging from the mid
20s northeast to around 40 southwest. Wednesday will then likely
be the coolest day of the week (however, this is the day that
NBM temperature spread starts to increase) with highs ranging
from the upper teens northeast to the lower 30s southwest.
Through the rest of the week and into the weekend, forecast highs
will mainly range from the lower 20s northeast to the mid to
upper 30s southwest.
Regarding precipitation chances, while there isn`t anything
major on the horizon for the moment, ensembles are starting to
suggest maybe a bit more of an active pattern over the northern
Plains next weekend and potentially into the next work week.
The NBM is currently advertising widespread low to medium
chances (20 to 40 percent) for light snow accumulations (greater
than 0.01 inches), but we remain too far out for specific
details at this time. The pattern will at least be something to
monitor as we move closer.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 630 PM CST Sun Dec 31 2023
VFR conditions will prevail for KXWA and KMOT through the
period, with some increasing clouds and lowering ceilings
possible during Monday afternoon. KDIK will see IFR conditions
in low stratus this evening, before conditions improve by 06Z.
Some fog will also be possible for KDIK, but should remain above
IFR visibility. Stratus and areas of fog are then expected to
developing east later this evening into the overnight, impacting
KBIS by 06Z for several hours. KJMS is more uncertain regarding
fog and stratus at this time.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...NH
DISCUSSION...ZH
AVIATION...NH
Area Forecast Discussion
National Weather Service Cheyenne WY
722 PM MST Sun Dec 31 2023
.KEY MESSAGES...
- Areas of freezing fog will lead to reduced visibilities and
potential for slick roadways across portions of the western
Nebraska Panhandle tonight through Monday morning.
- Calm weather expected through most of the week with the
potential for mountain snow showers.
- Could see strong winds Friday night into Saturday.
&&
.UPDATE...
Issued at 712 PM MST Sun Dec 31 2023
No major changes for the evening forecast update on this New
Year`s eve period. Due to the surface high pressure, clear
skies, and snow cover on the ground, northern Dawes County has
dropped quickly for temperatures. HRRR guidance is the most
aggressive, with low single digit temperatures, and that looks
like the closest deterministic model guidance to use for trends
on the forecast. Fog and freezing fog still anticipated for the
NE Panhandle later this evening into the early Monday morning
hours.
&&
.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 136 PM MST Sun Dec 31 2023
Freezing temperatures and southeasterly flow this afternoon did
not help erode any more of the snow across portions of the
Nebraska panhandle, so there is once again potential for
fog/freezing fog tonight. The fog will likely develop in areas
that continue to have a snowpack, but HREF was also hinting at
it creeping up the North Platte River Valley into Scottsbluff
early Monday morning. Monday will look very similar to today
across areas west of Interstate-25, but is forecast to be much
warmer along and east of Interstate-25, into the Nebraska
panhandle, once the flow turns northwest to westerly. Across
southeast Wyoming, high clouds persist due to a weak shortwave
pushing through. Skies are forecast to mostly clear out later
tonight following the shortwave passage.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 136 PM MST Sun Dec 31 2023
The long term period is filled with an active pattern across the
western CONUS with multiple waves passing in the flow. This will
lead to daytime temperatures general in the 30s and low 40s with a
few dips with various frontal passages. Tuesday looks to begin with
northwest flow as an upper low well to the south pushes east giving
way to short-lived ridging over the Front Range Wednesday. This will
give way to another upper level low digging towards the four corners
region Thursday increasing PoPs over the Sierra Madre and Snowy
Ranges with favorable upslope flow Thursday afternoon. Did continue
to maintain slight chance PoPs along the I-80 corridor from near
Laramie through Sidney as numerous ECMWF/GEFS members try to bring
precipitation far enough north despite deterministic models mostly
missing these areas with a more southerly track.
The weather could turn a little more active headed into next weekend
with tightening gradients leading to the chance for strong winds
across southeast WY Friday night into Saturday. In-house random
forest guidance continues to show the possibility, but has been
slightly trending downward with high wind probabilities around 20-
40%. Then late into the weekend and early next week, another upper
low digs into the four corners region with a slightly farther north
track than the previous system leading to increasing chances for
precipitation. Latest cluster analysis shows ~40% of GEFS membership
with a wetter solution than the grand ensemble while CMCE and ECMWF
members still showing varying solutions.
Jumping well ahead into the extended, there are early indications of
a plunge of arctic air next week. Latest NAEFS guidance shows
700/500mb temps trending towards 10th percentile values for early
January. However, ~20% of of CMCE and ECMWF still show a warmer
solution with higher heights over much of the west. Will continue to
monitor trends as this still remains far out.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 445 PM MST Sun Dec 31 2023
Ridging aloft will weaken through the period.
Wyoming TAFS...Scattered to broken clouds around 15000 feet will
occur.
Nebraska TAFS...At Chadron and Alliance, areas of fog will occur
from 03Z to 14Z, with visibilities of 1/2 mile and ceilings
under 500 feet. Areas of fog will occur at Scottsbluff from 09Z
to 15Z, with visibilities near 2 miles and ceilings around
1500 feet. At Sidney, fog will be found from 12Z to 15Z, with
visibilities around 1/4 mile and ceilings near 100 feet.
Otherwise, scattered clouds near 15000 feet will prevail.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...BW
SHORT TERM...LEG
LONG TERM...MB
AVIATION...RUBIN
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
534 PM CST Sun Dec 31 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Monday night)
Issued at 1231 PM CST Sun Dec 31 2023
...Key Messages...
* There is a 50-80% chance of fog reducing visibility to 1/4 mile or
less east of the I-35 corridor around and after midnight January
1st and a 10-40% chance along portions of the I-35 corridor.
* Patchy Super Fog could form, resulting in spots of near zero
visibility again for areas mainly east of the I35 corridor.
* Be alert for rapidly lowering visibility late this New Years Eve
and into the overnight. If driving, slow down, use low beam
headlights, and leave plenty of space between vehicles.
Mostly clear skies are in place across South-Central Texas this
afternoon with southerly flow in place. This has allowed
temperatures to quickly reach into 60s as dewpoints recover into the
40s and 50s. Should see moisture continue to increase through the
remainder of the day.
This is setting the stage for some late night fog development to
ring in the New Year, ahead of an approaching weak cold front. HREF
probabilities of visibility 1/4 mile or less late tonight are 50-80%
east of the Interstate corridor, and around 10-40% along the I-35
corridor from the south side of Austin through San Antonio. Making
the issue more complex might be the potential for some patchy Super
Fog to mix in around and after midnight, similar to a situation
during the New Years Eve of 2018-2019. This scenario could be more
likely around the I-35 corridor metro areas from San Antonio to
Austin, where smoke particulates from New Years firework activity
are left trapped beneath a relatively strong inversion indicated on
NAM BUFR and HRRR forecast soundings. These smoke particulates could
serve as additional condensation nuclei in a relatively light wind
situation ahead of the cold front, creating patchy locations of fog
producing near zero visibility. The Super Fog Index (taking into
account temperature and humidity) is indicating probabilities above
70% for Super Fog should smoke particulates be introduced. We will
continue to mention fog and smoke in the forecast for areas along and
east of the I-35 corridor around and after midnight, and south of
the cold front.
The latest HRRR continues to show the front reaching the northern
Hill Country just after midnight, Austin metro area around 2-4 AM,
San Antonio metro area around 3-5 AM, and Coastal Plains around 5-7
AM. Improving visibility is expected behind the cold front. Latest
high-res models continue to show some patchy sprinkles or light rain
being possible along the front for the Coastal Plains, but overall
chances for accumulation rainfall is too low to mention in the
forecast. Breezy northerly winds and cooler conditions are expected
for New Year`s day with highs in the middle 50s to lower 60s. Cloud
cover will begin to increase Monday night ahead of the next
approaching upper trough. Lows will be in the 30s and 40s.
&&
.LONG TERM...
(Tuesday through Sunday)
Issued at 1231 PM CST Sun Dec 31 2023
Similar to the moistening on New Year`s Eve, moist Gulf return flow
will deepen and strengthen quickly as isentropic upglide develops
early Tuesday. The resulting thickening of cloudcover and eventual
development of showers will spread from the Rio Grande Plains around
sunrise to the entire area by midday. The arrival of the shortwave
trough will increase lift through a deep layer, causing the highest
chances for rain, and possibility of isolated thunderstorms Tuesday
afternoon and evening. An associated cold front should end the rain
and sweep in drier air overnight Tuesday into early Wednesday
morning.
Wednesday and Thursday will be dry with seasonal temperatures under
weak ridging between shortwave troughs. The next shortwave trough
will be sharper and further south, implying stronger deep layer lift
and shear for our area. However, moist Gulf return flow will be
limited except over the Coastal plains, so while showers are expected
areawide, thunderstorms should be confined to along and east of U.S.
77. The trough axis and associated cold front will pass through
Friday evening, bringing and end to the rain and ushering in another
round of dry air and seasonal temperatures for Saturday and Sunday.
&&
.AVIATION...
(00Z TAFS)
Issued at 535 PM CST Sun Dec 31 2023
VFR flying conditions prevail tonight through Monday evening. There
is a fairly high potential for LIFR/VLIFR CIGs/VSBYs due to shallow
lower level moisture, smoke due to fireworks, and light winds from
around Midnight into the overnight hours at the I-35 sites and have
gone with a TEMPO for said conditions from 06Z to 10Z. A cold front
moves through the area late night into early morning eroding any
reduced CIGs/VSBYs. Northerly winds develop in wake of the frontal
passage and increase to 8 to 15 KTs with a few gusts to 25 KTs on
Monday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 43 55 39 54 / 0 0 0 80
Austin Bergstrom Intl Airport 43 57 38 55 / 0 0 0 80
New Braunfels Muni Airport 45 59 41 56 / 0 0 0 80
Burnet Muni Airport 38 54 34 52 / 0 0 0 80
Del Rio Intl Airport 43 64 42 57 / 0 0 0 30
Georgetown Muni Airport 40 55 35 54 / 0 0 0 80
Hondo Muni Airport 43 62 40 54 / 0 0 0 80
San Marcos Muni Airport 43 58 38 55 / 0 0 0 80
La Grange - Fayette Regional 48 58 41 56 / 10 0 0 60
San Antonio Intl Airport 45 60 43 55 / 0 0 0 80
Stinson Muni Airport 47 62 44 57 / 0 0 0 80
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term...29
Long-Term...Zeitler
Aviation...04
Area Forecast Discussion
National Weather Service Flagstaff AZ
854 PM MST Sun Dec 31 2023
.SYNOPSIS...A more active weather pattern is in store
for the AZ High Country as we progress through the first week of
2024. The first storm system will bring precipitation chance to
the eastern Mogollon Rim and White Mountains late Monday and into
Tuesday. The second storm system is forecast to bring more
widespread opportunities for precipitation to most of northern
Arizona on Thursday. Additional storm systems are forecast to
impact the area next weekend. Stay tuned for updates to the
forecast.
&&
.UPDATE...Very few changes were made to the forecast this New
Year`s Eve. Cloud cover is beginning to clear from the southwest
and this trend will continue until early Monday morning when
additional cloud cover begins to increase. The main story for
tonight is temperatures dropping into the 20s in the mountains
with some wind chill readings dropping into the teens around
midnight. Bundle up if you plan to be outdoors.
&&
.PREV DISCUSSION /509 PM MST/...After an upper low brought some
light precipitation (mostly trace amounts of rain/snow) this
morning, we`ll see clouds hang tough into the early evening hours,
despite a shortwave ridge across the area. Tonight, skies are
forecast to clear from south to north and many will contend cold
conditions. Minimum wind chill values are forecast to fall into
the teens and twenties area wide, so consider bundling up for
those of you with with evening festivities.
There will be an increase in mid to upper level clouds across the
desert southwest on New Year`s Day. This is thanks to our next
upper-level trough advancing into our area. Point forecast
soundings indicate top-down moistening will transpire through mid-
morning Monday, with upper tropospheric saturation expected across
just about the entire area by sunset. This will translate to
mid/upper level cloud cover resulting in filtered sunshine through
the day, keeping temperatures in the 40s and 50s. As large scale
ascent infringes on the area mid to late afternoon, I would not be
surprised to see the radarscope illuminate some, but only trace
amounts of precipitation are expected and it`ll be in the form of
sprinkles or flurries through sunset.
After sundown Monday, more pronounced large scale ascent will
assert itself into the weather story across the eastern Mogollon
Rim and White Mountains area. The latest iteration of the forecast
package does feature an increase in PoPs down across the eastern
Mogollon Rim and White Mountains with PoPs now ranging between 50
and 70%, however, with a little uncertainty. Jet dynamics (exit
region of a +55 kt 500mb jet), height falls of 60 to 80 meters
overspread the area ,and 700-500mb RH approaching 90% along the
TROWAL have supported this increase in PoPs from the blended
guidance. Moreover, forecast soundings do indicate the presence of
100-250 J/kg aloft across areas south of I-40 and east of I-17.
This also warrants an inclusion of isolated thunderstorms across
the eastern rim and White Mountains late Monday into Tuesday.
While HREF means are not bullish with the probability of QPF >
0.01", recent iterations of the HRRR suggest more of a cellular/deeper
convective simulated radar scene late Monday through sunrise
Tuesday. If trends in the HRRR persist, and/or if other short-term
hi-res guidance jumps on board, not only would higher PoPs be
needed, the areal coverage of 20-30 PoPs will need to be increased
to the Chuskas, back toward Flagstaff and even central Yavapai
County. For now, I`m not compelled to make these changes, but
trends will be monitored. As it pertains to p-type, snow levels,
elevations as low as 5,500 feet will have an opportunity for
seeing a few flakes, with accumulation of up to 1" limited to
areas above 7,000 feet and closer to 2" around 8,000 feet.
Tuesday and Wednesday will feature largely quiescent conditions
across northern Arizona as shortwave ridging briefly dominates the
weather across our area. This will be relatively short-lived as
storm system #2 arrives late Wednesday into Thursday. Overall,
precip potential from this system will be more widespread,
however, there is still some uncertainty with the overall
progression of this system as it moves onshore the California
Coastline. Taking a look at the various solutions, there are some
timing discrepancies that would result in different rain and snow
amounts across the High Country. The *majority* of the ECMWF/GFS
ensemble solutions place rain and snow amounts on the higher end
of the model guidance envelope with the potential for snow amounts
of greater than 4" across the higher terrain (above 6,000 feet)
closer to 40-50%. This is a result of this subset of the larger
NWP blend having a slower evolution of the upper trough (thereby
greater moisture transport). A majority of the Canadian ensemble
system and the minority of EPS/GFS systems on the other hand has
the potential for over 4" confined to areas of the eastern
Mogollon Rim with a much faster system. With the ECMWF/GFS
ensembles dominating the NBM at this range, we will hold serve
with the larger coverage of potential snowfall as we round out the
week, but keep in mind, the speed of the trough will likely
modulate how much moisture can be drawn in from the Pacific
thereby impacting snow/rain amounts. One thing that appears highly
certain is that it`ll turn sharply colder Thursday and Friday
with temperatures 10 to 15 degrees below normal. In fact, high
temperatures may struggle to get above freezing across the
mountains later in the week (chances are only around 15-30% in
some locales).
While at the tail end of the forecast period, there remains some
potential for a third system. While there is more uncertainty in
the timing of this system, there will likely be enough cold air in
place, thanks to the passage of prior systems. The big question
will be moisture trajectories. Nevertheless, we`ll continue to
provide updates as we venture into next weekend.
From NWS Flagstaff, we wish you all a safe, and prosperous 2024!
&&
.AVIATION...Monday 01/00Z through Tuesday 02/00Z...VFR through the
TAF period as conditions improve this evening. Low clouds have
begun to dissipate and cloud bases have risen above FL050. However,
some mountain obscuration will remain overnight. Light winds
overnight will generally be out of the S-SE at 5-15 kts Monday.
OUTLOOK...Tuesday 02/00Z through Thursday 04/00Z...Mostly VFR
through the outlook period will be interrupted by periods of MVFR.
This includes on Tuesday from 03Z-18Z along and south of a KPAN-
KSJN line as SHRA/SHSN impact the area. Expect N winds Tuesday
becoming breezy S-SE Wednesday and breezy W-SW Thursday. Widespread
precipitation Thursday will bring periods of MVFR and IFR conditions
to portions of northern Arizona.
&&
.FIRE WEATHER...Monday and Tuesday...Seasonal temperatures both days
with afternoon minimum RH values between 25-55%. Rain/snow showers
are possible Monday night into Tuesday morning mainly for the White
Mountains and along part of the Mogollon Rim. South-southeast winds
at 5-15 mph Monday, becoming north at 5-10 mph Tuesday.
Wednesday through Friday...Rain/snow chances (40-80%) are forecast
from late Wednesday through early Friday. RH increases with
afternoon values between 50% and 80% by Thursday. Breezy southerly
winds Wednesday, shifting to west-northwest Thursday and Friday.
&&
.FGZ WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
PUBLIC...MCT/Bain
AVIATION...JM
FIRE WEATHER...JM
For Northern Arizona weather information visit
weather.gov/flagstaff
Area Forecast Discussion
National Weather Service Hastings NE
556 PM CST Sun Dec 31 2023
.KEY MESSAGES...
- Patchy dense fog is possible tonight.
- Seasonable temperatures for the first week of January.
- Chance for rain/snow late Thursday night through Friday.
Significant snow accumulation is unlikely.
- Stronger storm system moves through next Sunday into Monday.
&&
.DISCUSSION...
Issued at 330 PM CST Sun Dec 31 2023
Widespread stratus kept our temperatures a few degrees cooler
than forecast today. Northern portions of the area are starting
to see some clearing, these areas will likely see additional
fog and low stratus redevelop tonight. The HRRR and HREF show
the highest potential for dense fog over the western half of
Nebraska, but at least some patchy fog is possible across nearly
the entire area into Monday morning.
Temperatures for New Year`s Day (Monday) were trended downward
slightly, mainly because of the potential for lingering cloud
cover. Afternoon highs are expected to be in the 30s for nearly
the entire area, which is just a few degrees below normal for
the 1st of January.
Dry conditions continue through most of this week, but the
overall northwesterly flow pattern will keep temperatures near
to slightly below normal (high temperatures in the 30s and low
40s and low temperatures in the teens and 20s).
A weakening cutoff low is forecast to eject out of the SW CONUS
on Friday, potentially bringing a mix of rain/snow to portions
of the region. Areas to our south continue to be more favored
for any meaningful precipitation, but there has been a touch of
an upward/northward trend on the 12Z global ensembles. Both the
EPS and GEFS show 50-60% probabilities for 0.10" of QPF at least
up to the KS/NE state line. The latest NBM highlights a 10-30%
chance for 1" or more of new snowfall, which is a slight upward
trend compared to 24 hours ago.
A more significant winter storm system will potentially move
through the area late Sunday through Monday. Given that we are 8
days out, specifics are still quite uncertain. But the
potential for winter impacts appear to be increasing. The latest
EPS ensemble shows a 10 to 30% chance for over 6 inches of
snowfall portions of the forecast area, possibly with very
strong winds as well. A lot could still change, but this is
certainly a time period worth watching.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 550 PM CST Sun Dec 31 2023
Significant weather: IFR to LIFR flight categories late tonight
and through much of Monday morning.
Tonight: Deteriorating flight conditions are likely tonight, as
latest guidance calls for ~70% probs of at least IFR at EAR, and
~60% probs of at least IFR at GRI. So the question isn`t really
IF, its WHEN? Latest guidance has not handled the recent
clearing very well, with only the last run or two of the HRRR
even remotely close. This casts some uncertainty as to when the
stratus, and ultimately perhaps some FG, return to the
terminals. Feel EAR is most likely to see it return first, and
went with a blend of model guidance and forecaster intuition
which resulted in 04-06Z. GRI seems more likely to hold off IFR
through at least midnight. Lgt winds should promote build down
of stratus into fog for both sites, and again, was a bit more
pessimistic at EAR, but feel both sites should reach LIFR
category by 12Z as least NBM probs are ~50%, which usually runs
a bit low in these cases due to influence of GFS.
Confidence: Low.
Monday: Expect mainly LIFR conditions at dawn with both sites
dealing with FG and CIGs of only 300-400ft. Given weak mixing
and stout inversion, improvement will be slow Mon AM, with
return to IFR not until late morning, and MVFR or VFR until
midday-early aftn. Lgt and vrbl winds to start the day will turn
to SWrly 6-10kt, which should help erode the stratus and fog,
at least eventually. Confidence: Medium.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
DISCUSSION...Mangels
AVIATION...Thies
Area Forecast Discussion
National Weather Service Goodland KS
335 PM MST Sun Dec 31 2023
.SHORT TERM...(This evening through Tuesday Night)
Issued at 210 PM MST Sun Dec 31 2023
At the start of the short term period, the latest RAP analysis shows
an upper air ridge currently over the CWA this afternoon. Current
satellite imagery and surface observations report dry conditions
across the region with some low clouds moving into the northeastern
portions of the CWA and high clouds residing over the southwestern
half of the CWA. Models show the CWA staying underneath the upper
air ridge going through the rest of Sunday. At the surface, models
have a surface high moving into central NE by the evening and then
progressing southward into central KS overnight. With this feature
passing the CWA at the surface, winds across the region look to be
mostly light through the rest of the day. Models are also showing
potential for some patchy fog to develop this evening in areas along
and north of I-70 that may last into tomorrow morning. Better
chances look to be east of the CO border though not enough
confidence to put out a Dense Fog Advisory due to uncertainty seen
between models in fog location and intensity. Will monitor
conditions to see if this thinking changes. Overnight low
temperatures tonight look to range between the middle and upper
teens.
For New Year`s Day, the models show the axis of the upper air ridge
making its way east of the CWA allowing for a generally westerly
flow over the CWA by the late afternoon hours. Models also forecast
an upper air trough moving into the southwestern CONUS behind the
ridge during the day. At the surface, low pressure looks develop in
CO early in the day allowing for a southerly surface flow across the
CWA. Warmer temperatures expect to be ushered into the CWA with
daytime highs in lower to upper 40s range. The fog also is
expected to lift by the mid-morning hours. The CWA looks to see
low chances for precipitation on Monday as well. Low temperatures
on Monday night are forecast to be in upper teens to lower 20s
range.
On Tuesday, forecast guidance shows the axis of the aforementioned
trough passing over the CWA in the afternoon as the base of trough
travels along the southern U.S. border. An upper air ridge trails
the trough with the front portion reaching over the CWA overnight
and causing the CWA`s upper air flow to turn north-northeasterly. At
the surface, models show a possible weak cold front pushing through
the CWA early in the day causing northerly surface winds behind it.
Dry conditions are also expected to continue for another day within
the region. Daytime highs for Tuesday look to be in the lower to
middle 40s followed by overnight lows in the upper teens to lower
20s.
.LONG TERM...(Wednesday through Sunday)
Issued at 1240 PM MST Sun Dec 31 2023
Ridging looks to be present to start the extended period. A surface
high will also be in place helping to keep skies mainly clear. The
clear skies will be short lived as a progressive trough moves
towards the central Plains through the day Thursday and into Friday.
Deterministic guidance is still struggling with the track of the
system. Ensemble clustering though is however picking up on qpf
mainly south of Interstate 70 which is similar to what the latest
runs of the EPS and GEFS suggest so will continue following
ensembles for this forecast. Confidence is continuing to increase in
precipitation across the area especially for Friday mainly in the
form of light snow, although some rain may be able to mix in as
well. NBM pops have increased to around 40% for the south and
eastern portions of the area which is the area that the ensemble
clustering was picking up on so the trend of better precipitation
chances does seem reasonable. Overall light snow accumulation
currently does look like the most likely solution at this time
based on the current track which is across the OK Panhandle,
however a little bit more north, then multiple inches of snow may
be possible.. so will need to continue watching trends. As
mentioned in the previous discussion, a wet snow does seem likely
with the system. So despite winds being around 15-20 mph, the
overall wetness of the snow should help limit blowing snow
concerns.
As mentioned above, the system will be fairly quick moving. Guidance
continues to be in relatively good agreement in another, potentially
stronger system developing towards the latter portion of next
weekend into the early week. This system will also have a better tie
to colder Canadian air as well, bringing in perhaps some of the
coldest air of the season thus far. Being a week out from this
system, it`s way to early to start getting into specifics but there
is potential that it may be impactful for portions of the Plains.
As for temperatures, near normal temperatures are forecasted
Wednesday and Thursday with highs in the low to mid 40s. A decline
in temperatures then begins Friday as highs are forecast in the 30s,
but may be even colder if more precipitation can occur with the
further north track of the system. Some brief moderation Saturday
before the potential for much colder air starts to move into the
area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 328 PM MST Sun Dec 31 2023
Difficult forecast once again for the 00Z TAF period especially
for KMCK due to model disagreement with fog potential and low
clouds developing. KGLD expects to see VFR conditions throughout
the 00Z TAF period beginning with light and variable winds that
become southerly around 9 kts at 06Z through the end of the
forecast period. For KMCK, VFR conditions expect prevail beginning
the 00Z TAF period with variable winds around 5 kts. By 03Z, MVFR
ceilings develop over KMCK before lowering to 700 ft bringing
about IFR conditions at 06Z. LIFR conditions are then seen for
KMCK starting at 10Z with fog intensifying and ceiling dropping
even lower. IFR ceilings are expected to return at 12Z before VFR
conditions begin at 16Z when KMCK sees southerly winds around 9
kts through the end of the TAF period. Timing of low cloud and fog
development may change, so will continue to monitor future model
runs along with current conditions and amend TAFs as needed.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...076
LONG TERM...Trigg
AVIATION...076
Area Forecast Discussion
National Weather Service Green Bay WI
818 PM CST Sun Dec 31 2023
New Information added to update section
.UPDATE...
Issued at 818 PM CST Sun Dec 31 2023
The latest RAP analysis shows a surface ridge axis extending
across the Arrowhead of Minnesota this evening. Low overcast has
hardly budged across Minnesota, Lake Superior and Ontario so far.
Lake effect off inland lakes have also been augmenting the cloud
cover. As a result, slowed down the clearing trend by several
hours. Think some holes in the overcast will develop late tonight
as low level winds back to the northwest and downsloping occurs
over northeast WI. Have also increased low temps because of the
slower clearing trend.
Have also added flurries to northeast WI and far north-central WI
through the evening as obs are reporting sporadic light snow.
&&
.KEY MESSAGES...
- Any melted snow on roads and sidewalks will likely refreeze
tonight, and could create locally hazardous travel conditions.
- Lake-enhanced snow may bring accumulations of 1 to 3 inches to
Vilas County late Tuesday night into Wednesday.
&&
.DISCUSSION...
Issued at 219 PM CST Sun Dec 31 2023
Short Term...Tonight and Monday
Main forecast concerns to be ending the lake effect snow showers/
flurries tonight and low temperatures tonight as skies attempt to
clear late with diminishing winds.
The 19Z MSAS surface analysis showed a clipper low pressure over
southern Lower MI and high pressure over the northern/central
Plains. Somewhat of a tight pressure gradient across WI with an
occasional wind gust over 20 mph. Radar mosaic continues to
indicate snow shower activity off of both Lakes Superior and MI.
Even as the clipper system responsible for the light snow/freezing
drizzle pulls farther away from northeast WI, prevailing north-
northeast winds will keep lake effect snow showers brushing
Kewaunee/Manitowoc counties this evening before winds become
north-northwest and snow showers remain over the lake. Otherwise,
a surface ridge and upper ridge are forecast to build into the
western Great Lakes region tonight and begin to scour out most of
the clouds. Winds will also decrease through the night, thus
colder temperatures are expected. Look for readings to be in the
teens to lower 20s with the colder readings over north-central WI
(decreasing clouds first) and parts of east-central WI (where new
snow fell).
A mostly sunny start to the New Year is forecast as high pressure
ridge at the surface and aloft move into the region. Winds will
slowly back through the day and be southwest by late afternoon.
Max temperatures to be in the upper 20s to middle 30s.
Long Term...Monday Night Through Sunday
Above normal temperatures will continue through most of the
extended forecast period, and a few minor precipitation events are
expected midweek and next weekend. Of greatest concern is the
potential for accumulating snow in the Lake Superior snowbelt
late Tuesday night and Wednesday.
The main concern during the extended is precipitation chances
with a couple short-waves during the middle of the week. The first
wave looks like it will just brush through far northern WI on
Tuesday, so will only have small pops across mainly Vilas County.
The second short-wave tracks farther south and looks stronger
for late Tuesday night and Wednesday. A cold frontal passage
associated with this system will cause low-level winds to turn
NNW and over-water instability to increase (Lake-850 mb delta-t`s
of 18-20 C), leading to lake-effect snow showers in far NC WI and
northern Door County. The lake-effect will be enhanced by
synoptic forcing as the short-wave moves through on Wednesday.
Have increased pops across the CWA, and mentioned likely pops for
Vilas County on Wednesday. Early estimates point toward
accumulations of 1 to 3 inches in Vilas County, with a dusting to
a half inch elsewhere.
Models still suggest an upper trough will impact the region on
Saturday and Saturday night, but overall confidence is low,
and precipitation amounts look to be light at this time.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 514 PM CST Sun Dec 31 2023
As low pressure departs the region, sharp cyclonic flow with
north winds off Lake Superior will maintain MVFR cloud cover and
widely scattered flurries across the region through the evening.
Late overnight into Monday morning, a ridge axis will slide from
northwest to southeast across the region, leading to backing winds
to the west. The backing wind profile will promote clearing skies,
though timing is relatively uncertain given overcast conditions
prevail across northern Minnesota late this afternoon. Therefore
delayed the clearing trend by a few hours, which may need to be
delayed further in subsequent forecasts.
Once skies clear, the rest of New Years Day will bring VFR
conditions as the high pressure moves into the region. Anticipate
only some passing middle or high clouds with winds backing to the
southwest and remaining 10 kts or less.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.........MPC
DISCUSSION.....Kallas/Kieckbusch
AVIATION.......MPC
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
901 PM CST Sun Dec 31 2023
.UPDATE...
Issued at 901 PM CST Sun Dec 31 2023
Over the past hour or so the lake effect has become much less
organized and transitioned into broken dual bands, likely far
less impactful in its current state. RAP, HRRR, and NAM all
suggest convergence will strengthen some overnight, which could
allow for a reorganization of the band if that materializes.
However, ACARS soundings from ORD and MDW both show 2-3C of
warming in the low levels, centered around 875mb. The warming
noted in ACARS soundings is much more significant than the 0.5-1C
warming predicted by earlier model runs. The most recent HRRR did
initialize low level temps better and much more in line with ACARS
data, yet doesn`t show this warming extending east to over the
lake. Overall confidence is low, and given observational trends I
am growing increasingly skeptical regarding a meaningful re-ramp
up in LES intensity. The advisory is out and there is LES, so not
going to make any changes at this time, but if trends don`t
change, then oncoming midnight shift may be able to cancel the
winter wx advisory early.
Farther west across Illinois, flurries persist with regional
mosaic showing additional very light reflectivity (likely
flurries) upstream over southern Wisconsin. Have removed pops and
accumulations from Illinois and just maintained flurries
overnight. Can`t rule out a couple of lake effect snow showers
clipping the far southeast side of Chicago into Hegewisch and East
Side neighborhoods, but given the decreasing organization in the
LES, accumulations there seem pretty unlikely even if snow showers
do get that far west.
- Izzi
&&
.SHORT TERM...
Issued at 229 PM CST Sun Dec 31 2023
Through Monday night...
Key Messages:
* Lake effect snow showers develop tonight and persist through
Monday morning. Slushy accumulations away from the lakefront
with some patchy slick travel.
After a fairly prolonged period of drizzle and freezing drizzle
overnight and early this morning, cloud top temperatures have
continued to cool as saturated depths have risen steadily through
the day. Recent VAPOR AMDAR soundings show cloud top temperatures
are around -15C, which has been sufficient to inject condensation
nuclei into the cloud layer, leading to a changeover to all snow
across our area. We`re thinking that air temperatures held up just
enough last night to mitigate icing impacts. Had we been even a
degree or three colder, we likely would have seen much more
serious icing impacts in our region.
Through the rest of the afternoon, what you see is what you get.
Intermittent bursts of steadier snow will continue as several
sprockets of mid-level vorticity press overhead. Timing out one of
the last vort maxes (currently across central Wisconsin) suggests
we`ll eventually see snow coverage wind down through 6 to 9 PM
across most of the region. Can`t entirely rule out precip ending
as a little drizzle/freezing drizzle, but this should remain
pretty isolated and ephemeral. Not anticipating travel impacts
with road temperatures at/above freezing.
We`re starting to see the first signs of lake effect developing
off the Green Bay and Milwaukee radars, and this activity will
continue to expand southward through the evening and overnight.
Lake parameters aren`t particularly significant, with lake
surface-850 delta Ts around 12 C, and an incoming subsidence
inversion looks to hold equilibrium levels under about 6-7 kft.
Still, this will be sufficient to crank out some ephemeral heavier
convective elements tonight as convergence tightens up along the
lakeshore. Temperatures right at the lake will be influenced by
relatively mild (40+ F) lake air, but inland locales will likely
see temperatures hover in the 31-33 degree range tonight. This
will support some slushy snow accumulations away from the
immediate lakefront, perhaps locally up to 1-2 inches across
interior portions of Lake and Porter Counties in NW Indiana.
Cloud cover trends tonight and New Year`s Day are a bit unclear.
It`s possible we`ll see some holes develop in the cloud layer
overnight, but given how expansive the stratus deck is upstream
into Minnesota and western Ontario is, have greatly increased
cloud cover for tomorrow. With this in mind, also nudged low
temperatures up tonight and highs down tomorrow. Lake effect
precip will eventually diminish through midday Monday across
northwest Indiana.
Carlaw
&&
.LONG TERM...
Issued at 229 PM CST Sun Dec 31 2023
Tuesday through Sunday...
Key Messages:
* A brief breezy moderation in temps on Tuesday then more
seasonable thereafter, coldest on Thursday
* Chance (30-50%) of lake effect snow showers on Wednesday night
into early Thursday, primarily for northwest Indiana
* Low (~20% chance) of snow on Saturday
A fairly quiet shortened first work week of 2024 will give way to
a more active pattern next weekend and beyond. Expansive 1030 mb
high pressure will settle south Monday night as low pressure
tracks from Hudson Bay to northeastern Canada. A strengthening low
level jet in response to warm advection will result in increasing
west-southwest winds and slowly rising temps toward daybreak
following lows in the low-mid 20s outside of Chicago (upper 20s in
the city). Initial full sun on Tuesday will help mix into the base
of the departing low-level jet, yielding southwest gusts up to
25-30 mph through mid afternoon. Highs will reach the mid-upper
30s with upside potential to around 40F.
The cold front trailing from the aforementioned Canadian low
pressure system will move across the area Tuesday night with
little fanfare, other than shifting winds northwesterly on
Wednesday with fairly robust cold air advection in its wake,
resulting in highs in the lower 30s to perhaps mid 30s. While some
flurries getting wrung out of the closed cell strato-Cu deck
can`t be ruled out behind the cold front on Wednesday, most
guidance is too dry to support any explicit flurries mention.
Flow will turn north-northwesterly over Lake Michigan amidst
continued cold advection Wednesday night. GFS forecast soundings,
a decent proxy for the reasonably similar other guidance, indicate
respectable lake effect parameters with lake induced ELs peaking
at ~7,500-8,500 feet, lake surface to 850 mb delta Ts of 16-18 C,
and 250-350 J/kg of lake induced CAPE. Given a nearly full
northerly fetch, potential for lake enhanced low-level
convergence, and a mid-level trough axis providing synoptic lift,
the period will need to be watched for a period of potentially
robust lake effect snow showers. 330-350 deg synoptic flow
supports Porter and Lake Counties as the main threat zone with
PoPs peaking in the 40-50+% range. Steadily rising mid-level
heights on Thursday will quickly knock down inversion heights and
end any lingering snow showers Thursday morning.
Aside from the lake effect snow potential, the main story
Wednesday night into Thursday will be the chilly (by winter
2023-24 standards thus far) temperatures. Lows bottoming out in
the upper teens to lower 20s and steady northwest winds will
result in Thursday morning wind chills in the single digits to
lower teens. Afternoon highs will only recover to the upper 20s to
lower 30s, which may yield (remarkably) the first widespread sub-
freezing highs since late November. Following a chilly Thursday
evening, warm advection will ensue Thursday night into Friday,
bringing mid to locally upper 30s highs on Friday.
Our next chance for precipitation will arrive on Saturday as a
southern stream disturbance emerges from the Plains and tracks
east-northeast. While a distinct majority of super-ensemble
members keep the surface low pressure far enough south to likely
keep meaningful precip. south of our area, a few members are far
enough north to support slight chance (~20%) PoPs for snow.
Looking out beyond day 7, for multiple model cycles in a
row, the ensemble means have consistently depicted the ejection
of an anomalously deep western trough into the Midwest. The pieces
could thus come together to support a strong synoptic system
affecting the region (irrespective of precip. types) early in the
first full work week of January. Medium-long range ensemble
guidance also has been consistent in an active and colder pattern
continuing through mid January, so there may eventually be some
bonafide winter weather threats to track. Stay tuned.
Castro
&&
.AVIATION...
For the 00Z TAFs...
537 PM...Forecast concerns include...
Lake effect snow in Northwest Indiana.
Snow showers tapering to flurries this evening.
Gusty north/northwest winds this evening.
Mvfr cigs through Monday evening.
A band of lake effect snow will continue to affect northwest IN
this evening, and likely into the overnight hours. GYY will be on
the edge of the heavier snow, which may end up just east.
Elsewhere, current light snow/snow showers will taper off to
flurries this evening and the flurries will gradually end
overnight.
North/northwest winds may gust into the lower 20kt range this
evening and then gusts should diminish into the late evening and
overnight. Winds will turn northwest Monday morning, westerly
Monday afternoon and southwesterly Monday evening.
Mvfr cigs extend as far back as northwest MN and western IA and
this is little to support these mvfr cigs clearing before Monday
evening and mvfr cigs may persist longer than indicated. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...Winter Weather Advisory...INZ001-INZ002 until 9 AM Monday.
LM...Small Craft Advisory...IL and IN nearshore waters until 9 AM
Monday.
&&
$$
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Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
956 PM EST Sun Dec 31 2023
...New UPDATE...
.UPDATE...
Issued at 951 PM EST Sun Dec 31 2023
Showers have not materializes in eastern KY as suggested by some
of the earlier CAMS runs. The HRRR seems to be doing the best,
keeping showers north of our area, in line with current radar.
Still, as a cold front pushes through the area, and temperatures
aloft drop and steepen lapse rates, a slight increase in showers
cannot be ruled out. The PoPs in SW VA will be lowered for the
update, with just a slight chance in Wise/Russell counties
overnight and flurries elsewhere in VA and NE TN. PoPs into Monday
will be lowered as well as moisture appears too shallow for
measureable precip, but sprinkles/flurries will be mentioned.
Overnight temps will be raised a few degrees as cloud cover and
winds have kept observed temps above forecast.
&&
.SHORT TERM...
(This evening through Monday)
Issued at 332 PM EST Sun Dec 31 2023
Key Messages:
1. Mostly dry cold front passage tonight will bring light rain
mixed with snow and flurries to some of the higher elevations of
the Southern Appalachians and Southwest Virginia. Everywhere else
will remain dry with increased cloud cover.
2. Winds will be gusty at times this afternoon out of the
southwest before turning northerly with the cold front. Gusty
conditions may continue overnight.
Discussion:
A shortwave and associated low pressure system moving from the
Great Lakes to the Atlantic Coast will send a cold front our way
tonight. The core of the moisture with this system is from about
West Virginia and north, so there won`t be a lot of moisture to
work with tonight. However, flow turning out of the northwest will
aid development of showery activity along higher terrain of the
Southern Appalachians and Southwest Virginia overnight. Amounts,
if any will be very light. Some places may only see flurries. A
few soundings pulled between this time from the latest GFS and NAM
show very dry air aloft, not conducive for ice crystal
development. Not expecting any precipitation outside of the
mentioned areas, just increased cloud cover.
This afternoon may be the last we see highs in the 50s in the
Valley at least in the foreseeable future because highs tomorrow
will barely surpass 40s in the lowest elevations. Lows will be
near or below freezing.
Currently ahead of the front, expect gusts between 15 and 25 mph
across the area this afternoon and evening. Winds may persist
overnight as they turn more out of the north with the FROPA. Winds
should subside some at least in the lowest elevations tomorrow.
&&
.LONG TERM...
(Monday night through next Sunday)
Issued at 332 PM EST Sun Dec 31 2023
Key Messages:
1. Wednesday system will bring another round of precipitation with
possible light accumulations in the highest elevations.
2. Another round of precipitation expected over the weekend, and
then again early next week.
3. Temperatures look to remain below normal for the next 7 days.
Discussion:
By Monday night we`ll transition to a weak ridging pattern along
with surface high pressure which will lead to an eroding of the
cloud deck throughout the day on Tuesday... Temperatures will climb
up to right around seasonal normals for the day. The synoptic
pattern begins to change during the middle of the week as a southern
stream system tries to move into our region out of Texas on
Wednesday into Thursday. Models have continued to change their tune
on how far north the impacts of this southern stream system will be
felt, and at what point does it phase with the northern stream
system expected to be moving through the Great Lakes/Ohio Valley at
the same time. Generally the models and probabilistic guidance shows
less than a tenth of an inch of liquid precipitation, mostly
concentrated in the southern valley and the southern Appalachian
Mountains. Looks like this precipitation should predominantly fall
as liquid, with a transition to light snowfall in the peaks of the
mountains, with possibly just over an inch at the very top of them.
On Thursday the more northern system could come on the heels of the
southern one inducing a lower impact northwest flow snow event, and
again possibly bringing another light round of accumulations at the
peaks of the mountains.
We`ll get a quick ridge building in by Friday into Saturday,
bringing temperatures back up to near normal before another fast
moving system quickly zips across over the weekend. A trough/low
will come out of the southern plains towards the Tennessee/Ohio
Valleys and quickly exiting by Sunday. Once again, systems in the
day 6+ time frame do tend to change the timing/intensity as they
draw nearer, so confidence is low on precipitation type with this
system. If it comes in overnight with temperatures dropping into the
upper 20`s light snow will be possible, but a weaker system or one
that moves through during the day will much more likely bring cold
rain to the valley... At this time the mountains of southern
Appalachia look to have a good shot at some accumulating snowfall.
Another system looks to quickly move through the region again late
Monday into Tuesday.
&&
.AVIATION...
(00Z TAFS)
Issued at 622 PM EST Sun Dec 31 2023
For the first few hours of the TAF, winds will be from the SW
around 8-12 kt, with a few gusts near 20 kt possible at TYS. A
cold front will cross the area around 04-08Z, shifting winds to
N-NW and bringing broken to overcast cigs on the VFR/MVFR margins.
Confidence in MVFR conditions is highest at TRI, with lower
confidence at TYS. CHA will remain VFR. Any MVFR cigs will lift to
VFR by late tomorrow morning.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 56 33 45 28 / 0 0 0 0
Knoxville McGhee Tyson Airport, TN 53 31 41 26 / 0 0 0 0
Oak Ridge, TN 52 29 41 26 / 0 0 0 0
Tri Cities Airport, TN 49 29 37 26 / 0 10 10 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
UPDATE/AVIATION...DGS
Area Forecast Discussion
National Weather Service Phoenix AZ
442 PM MST Sun Dec 31 2023
.Updated...Updated Aviation Discussion
.SYNOPSIS...
Near to below normal temperatures along with periodic rain
chances will be noted for the week ahead. This will translate into
mostly 60s for highs through mid week, with even some cooler 50s
for highs in the lower deserts by the end of the week. The first
chance for rain will be late Monday into Monday night, mainly
affecting south-central and southeast Arizona. Any rainfall will
be light. A colder and more potent weather system will progress
across the area Thursday, bringing the potential for more
widespread light rain and high elevation snow across the entire
region.
&&
.DISCUSSION...
A progressive pattern across the southwest U.S. will persist over
the next 7-10 days as a series of weather systems move across the
area. This pattern will offer up periodic precipitation chances
and bring an overall cooling in temperatures. Ensembles have been
very consistent with timing and precipitation trends.
Weak short wave ridging in place overhead this afternoon for dry
conditions as water vapor imagery showing the next system
circulating off the west coast of CA. This system will progress
east toward the area for late Monday, tracking across southern AZ
Monday night. Not a lot of moisture transport into the area ahead
of this system with a nose of 0.50-0.60 PWATS into SC AZ, but
enough dynamics and upper diffluence to bring in some light
showers across southeast AZ where best chances for rain will
occur. Phoenix metro will be on the northern edge, but the latest
HRRR does try to bring in a few showers or sprinkles into the
valley Monday eve/night. With limited moisture, rainfall amounts
will remain light where rain does fall.
Short wave ridging Tues/Wed for dry conditions, then the next
system still on track for Thursday. This system will be a bit
stronger and more dynamic yet moisture transport still fairly
limited. The progressive pattern just too fast to pull up any
deeper moisture. Again PWATs maybe as high as 0.60-0.70 by
Thursday. However, given the stronger upper support, it is looking
like it could produce more widespread rain and high elevation
snow but amounts still on the lighter side.
Even into next weekend, the pattern persists with another system
likely by late next weekend.
&&
.AVIATION...Updated at 2345Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns are expected during the TAF period.
Winds this evening will be light and variable before becoming
established out of the E by early tonight. SCT-BKN mid and high
level clouds will decrease in coverage tonight for a brief period
before prevailing over the region once more starting early
tomorrow morning. Lowest bases will range between 12-15 kft.
Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected during the TAF period. Light
and variable winds will prevail during much the period at IPL,
with N`rly winds anticipated at BLH. SCT-BKN high level clouds
will persist this evening/early tonight before a brief period of
clearing. Considerable cloud cover will become reestablished
across the region again tomorrow morning.
&&
.FIRE WEATHER...
Cooler temperatures will settle into the region today with more
unsettled weather expected during the coming week. A weak weather
system will mostly bypass the region to the south later Monday and
Monday night, but some light showers will be possible mainly east
and southeast of Phoenix. Winds through Monday will continue to be
light, while mostly following diurnal trends. Moisture levels
will improve starting today with MinRHs staying above 40% areawide
and staying above 30% through the early part of this week. A
colder weather system is then expected to move through on
Thursday with the potential for widespread precipitation and a
30-50% CWR across south-central Arizona. Moisture levels will
remain elevated through the latter half of the week with MinRHs
mostly staying above 35-40% each day, while temperatures hover at
or just below normal readings.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Frieders
AVIATION...RW
FIRE WEATHER...Kuhlman