Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/08/24
Area Forecast Discussion
National Weather Service Amarillo TX
513 PM CST Sat Dec 7 2024
...New AVIATION...
.KEY MESSAGES...
Issued at 231 PM CST Sat Dec 7 2024
- Snow chances are less likely but still possible across the
western Panhandles behind the front Monday night into Tuesday.
- Colder air will settle in Tuesday through Wednesday morning.
- Above average temperatures and below average precipitation
resume mid to late next week.
&&
.SHORT TERM ...
(This evening through Sunday night)
Issued at 231 PM CST Sat Dec 7 2024
Quiet weather will persist through the remainder of the weekend
across the Panhandles, as we wait for a closed low currently over
the bootheel of NM to track over the Panhandles tomorrow. In the
meantime, recent runs of the HRRR along with other model forecast
soundings hint at a very low probability that some spotty areas
of patchy fog could develop tonight, especially over the NW TX
Panhandle (10-30% chance for minor reductions in visibility).
Radiational cooling suggests it would be possible, but downsloping
SW winds overnight make for less than ideal fog conditions.
Regardless, it`s something worth monitoring into tomorrow morning.
Tomorrow will be even warmer and more beautiful than today as the
low passes overhead, favoring highs in the 60s area wide. It`ll be
noticeably breezier though, especially across the SW TX Panhandle
where a tighter sfc pressure gradient should setup. Most of the
area will have 10-15 mph winds out of the southwest, but locations
in the southwest will likely be closer to 20 mph with gusts up to
30 mph at times. Sunday night into Monday, the upper and
attendant sfc low will exit, turning winds out of the north at
5-15 mph, providing the initial signal of the colder air soon to
follow.
Harrel
&&
.LONG TERM ...
(Monday through next Friday)
Issued at 231 PM CST Sat Dec 7 2024
Cooler air will begin to infiltrate the region late Monday as a
reinforcing cold front pushes in beneath a weak, positively
tilted upper level trough. Pressure rises behind the front will
promote slightly breezier north winds of 15-25 mph, further aiding
CAA. After highs in the mid 40s and 50s, temperatures should have
no trouble dropping below freezing for most of the forecast area
overnight into Tuesday. Highs on Tuesday will struggle to get much
higher than the 40s, and we can`t rule out portions of the far NW
Panhandles staying in the 30s all day.
Moisture with this front continues to trend less and less,
especially in the lower levels. Forecast soundings show mid-level
moistening late Mon night - early Tue morning will be decent at
times across the western Panhandles, but any snowflakes will have
to survive the trip through a rather dry sfc layer to reach the
ground, even as flurries. Intermittent runs of a few global models
such as the ECMWF have shown stronger 700mb frontogenesis at
times, which could help better utilize any available moisture to
squeeze out a little more snow, rather than measly flurries. Even
if this can occur, dynamic lift from the upper trough is still
weak, and the odds of anything more than a dusting accumulating
across the far western Panhandles is less than 20%.
Wednesday morning will be the coolest of the weak, when lows in
the 20s are forecast across the CWA. The NW combined Panhandles
will even have a 20-50% chance to drop into the teens, with wind
chills solidly in the low teens. Beyond that, ensembles agree
we`ll fall back into a quiet stretch of weather under northwest
flow aloft, leading to above normal temperatures and below average
precipitation.
Harrel
&&
.AVIATION...
(00Z TAFS)
Issued at 509 PM CST Sat Dec 7 2024
Mainly VFR conditions expected to prevail across the Panhandles
over the next 24 hours. Some patchy fog may develop around KDHT
during the overnight hours. However, confidence is low for this
impacting the terminal at this time. Will be something to watch
for. Otherwise southwest winds around 6 to 13 kts expected during
this period.
36
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 36 64 34 53 / 0 0 0 0
Beaver OK 33 62 30 54 / 0 0 0 0
Boise City OK 27 64 29 47 / 0 0 0 0
Borger TX 36 65 33 56 / 0 0 0 0
Boys Ranch TX 31 63 30 54 / 0 0 0 0
Canyon TX 35 64 33 54 / 0 0 0 0
Clarendon TX 36 65 37 57 / 0 0 0 0
Dalhart TX 26 63 29 50 / 0 0 0 0
Guymon OK 28 63 29 52 / 0 0 0 0
Hereford TX 35 65 32 54 / 0 0 0 0
Lipscomb TX 36 63 34 55 / 0 0 0 0
Pampa TX 36 63 34 54 / 0 0 0 0
Shamrock TX 36 65 36 57 / 0 0 0 0
Wellington TX 36 67 37 60 / 0 0 0 0
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&
$$
SHORT TERM...38
LONG TERM....38
AVIATION...36
Area Forecast Discussion
National Weather Service La Crosse WI
552 PM CST Sat Dec 7 2024
.KEY MESSAGES...
- Above normal temperatures through Monday with highs in the 40s
to around 50 tomorrow.
- Low risk for a wintry mix in north-central WI for Sunday
evening (< 20%). Can`t fully rule out sprinkles further south,
but impacts would be negligible.
- Much colder for Wednesday and Thursday (coldest wind chills 0
to -20) with periodic flurries Tuesday night through
Wednesday.
&&
.DISCUSSION...
Issued at 155 PM CST Sat Dec 7 2024
Today - Monday: Above Normal Temperatures, Precipitation Chance
for Central Wisconsin?
Shortwave ridging remains in the region through the weekend. Warm
west to southwest flow will help to bring above normal temperatures
to the area. High temperatures for today and Sunday are between 10
and 15 degrees above normal. This translates to highs in the 40s and
low 50s today and upper 30s to upper 40s for Sunday. Given the flow
pattern continues through Sunday, there remains a medium chance (40
to 60%) that highs get into the 50s for portions of southeast
Minnesota and northeast Iowa.
Heading into Sunday evening, a shortwave trough digs down into the
Upper Midwest. This will bring rain and snow to the northern Great
Lakes region. Meanwhile, a shortwave trough will be lifting
northeast across Missouri and Illinois with moisture transport
vectors increasing in this region. The hi-resolution model
forecast soundings vary on how much low level moisture
transport will take place. The GFS/NAM have increasing RH 90%+
in the low levels, the RAP too, however the HRRR is much drier.
Looking across Texas, there is an area of stratus. This stratus
is forecast to lift north across Missouri and Illinois. The RAP
is farther west with the stratus for Sunday evening while the
HRRR scoots the low level moisture eastward. We`ll be able to
monitor the northward progression of the stratus during the day.
As the trough pushes eastward, there is a small chance (10 to
20%) of rain/wintry mix for Taylor and Clark counties Sunday
late afternoon/evening. HREF probabilities for freezing rain are
10 to 30 percent, so will continue to mention the wintry mix.
Precipitation amounts where they occur should be quite light.
Probabilities of greater than 0.01" are low; 10-30%. Should the
low level moisture materialize, some light drizzle will be
possible farther south. Did add a mention for now, but impacts
appear low due to the temperatures being above freezing.
Much colder for Wednesday and Thursday (coldest wind chills 0
to -20) with periodic flurries Tuesday night through Wednesday:
Cooler temperatures build in Monday night with reinforcing cold
air Tuesday and a stronger push of cold air Wednesday. Highs
Tuesday drop into the 20s, with single digits and teens for
Wednesday and Thursday. Tuesday night into Wednesday, flurries
and snow showers with the cold air advection can be expected.
Will need to fine tune this as we get closer, but do have a
mention in there.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 550 PM CST Sat Dec 7 2024
MVFR ceilings spread across north-central Wisconsin after 04Z,
but look to stay north of an EAU to DLL line through sunrise.
Confidence is low with how far south and west this stratus
expands during the day, but for now have kept the LSE TAF VFR.
West winds this evening decrease to less than 5-10 kts, backing
to the S/SE for the day on Sunday and increase to around 10 kts
during the afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Cecava/Zapotocny
AVIATION...Skow
Area Forecast Discussion
National Weather Service Boston/Norton MA
743 PM EST Sat Dec 7 2024
.SYNOPSIS...
An Alberta Clipper system passing across northern New England
tonight will bring minor accumulations of snow to areas north of
the Mass Pike, with coatings for the majority of our area.
Milder temperatures expected for much of next week with a period
of rain sometime Monday, and again by Wednesday. We will need to
watch for a temporary period of shallow cold air later Monday
into Tuesday with Quebec high pressure system.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
* Light snow overnight with accumulations up to an inch north of
I-90
Current forecast timing still appeared to be on track, and was
supported by the last few runs of the HRRR and RAP. Still
expecting a light snowfall across northern New England,
especially north of I-90 and northwest of I-495. No major
changes to snowfall accumulations this evening. Did bring
temperatures and sky cover back in line with latest
observations.
Previous Discussion...
A progressive Clipper system will result in several hours of
light snowfall for most of southern New England overnight.
Southwest flow will support low-level WAA over southern New
England which will be the driving for precipitation this
evening. Antecedent conditions are favorable for snow tonight as
surface temps across the region are currently in the mid to
upper 30s. Once the sun sets it won`t take long for temperatures
to dip back to freezing allowing for the warm frontal
precipitation to fall as snow, at least for areas away from the
south coast, Cape, and Islands. Recent 12Z suite of model
guidance has backed off a smidge with respect to precipitation
amounts, but we`re still expecting around a tenth of an inch of
liquid precipitation between roughly midnight and 6AM. This
will translate to a dusting to an inch of snow accumulation with
the highest amounts north of I-90 and northern Berkshires.
Expect snow to begin between 11PM and 1AM west of I-495 before
reaching areas east of I-495 between 1AM and 3AM. As mentioned
previously, this will be a progressive system, so expect snow to
be wrapped around sunrise (5-7am).
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Key Message for Sunday and Sunday night
* Gusty southwest winds Sunday morning into early Sunday
afternoon
* Milder temperatures Sunday afternoon in the mid to upper 40s
Any lingering snow showers should be tapering off around sunrise
as skies begin to clear from west to east. Thereafter, southwest
winds and low-level WAA will continue to transport warmer air
into southern New England. As this occurs, a robust low-level
jet will develop over the region and may support a period of
gusty southwest winds for the first half of the day. Areas at
elevation in the Worcester Hills may see 20 to 30 mph gusts
while The Cape and Islands could see gusts in the 30 to 40 mph
range. Elsewhere, gusts should be more modest, topping out
around 20 to 25 mph. As the gradient slackens into the early
afternoon, wind gusts will gradually diminish into the evening
hours. The milder air mass will support above normal high
temperatures in the mid to upper 40s.
Tomorrow Night
Winds become light and variable after midnight. With clear skies
overhead, this should support efficient radiational cooling. The
air mass will be relatively mild for December with 925 hPa temps
right around freezing, thus low-temps will be mild compared to
last week, but still close to normal ranging from the lower to
upper 20s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Key Messages:
* Unsettled start to the work week with mixed precipitation
possible Monday evening into Tuesday morning
* Deepening trough and its associated surface low bring
widespread soaking rain Wednesday into Thursday
* Drying out going into next weekend
Have moderate confidence in the overall synoptic pattern into
the middle of next week. Confidence drops off in the details
late next week into next weekend. Mid level pattern expected to
evolve from a nearly zonal flow to one with an amplified trough
over the central USA. This places southern New England on the
warmer side, resulting in a trend to above normal temperatures
by Tuesday, and especially into Wednesday. This is short-lived,
with below normal temperature more likely late next week into
next weekend.
At the surface, yet another low pressure should move from the
Great Lakes into southern Canada. Most of the guidance suggests
the development of a secondary low pressure towards southeast MA
Monday night into Tuesday. Otherwise, just a pair of fronts to
trigger some rainfall. There is a low chance for some snow or
freezing rain with precipitation onset Monday at the higher
elevations, but that would not last long.
Another low pressure should pass through our region from the
southwest some time from late Tuesday night into Wednesday
night. Expecting a period of widespread rainfall, with a chance
for a few thunderstorms ahead of a cold front. These
thunderstorms would be mainly towards southern RI and southeast
MA.
High pressure from the central US should begin to build towards
our region Friday, then pass offshore Saturday. Most likely
looking at a brief cool-down Thursday night into Friday, before
starting another warming trend for Saturday.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...Moderate Confidence
VFR through about 06Z with southwest winds from 5 to 10 knots. A
period of light snow is expected between roughly 04 and 10Z.
Accumulations from a dusting to an inch are possible as well as
a period of MVFR ceilings. Light snow showers should come to an
end in the 09-11Z time frame with any MVFR ceilings improving to
VFR. Gusty southwest winds up to 25 knots develop after 09Z.
Tomorrow...High Confidence
VFR. Breezy southwest winds around 12 kt with gusts to 20-25 kt
possible.
Tomorrow Night...High Confidence
VFR. Light west winds becoming light/variable.
KBOS Terminal...Moderate Confidence
Expect light snow to begin around 06Z, but could be as early as
05Z. A period of MVFR ceilings will be possible with the light
snow showers between 06 and 09Z. High confidence in improvements
to VFR by 12Z and thereafter. Winds strengthen after 09Z with
some gusts up to 25 knots possible through about 18Z tomorrow
afternoon.
KBDL Terminal...Moderate Confidence
Light snow beginning around 04Z and lasting through about
08-09Z. Some MVFR ceilings/vsbys may be possible during this
time, but generally expecting cloud bases from 040-050 feet. VFR
conditions tomorrow with steady southwest winds.
Outlook /Monday through Thursday/...
Monday: Mainly VFR, with areas MVFR possible. RA.
Monday Night: MVFR/IFR conditions possible. RA.
Tuesday: MVFR/IFR conditions possible. Chance RA.
Tuesday Night: MVFR/IFR conditions possible. Breezy. RA.
Wednesday: Mainly IFR, with local MVFR possible. Windy with
gusts up to 35 kt. RA.
Wednesday Night: MVFR/IFR conditions possible. Windy with areas
of gusts up to 30 kt. RA, chance SN.
Thursday: VFR. Breezy. Slight chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent. Medium - 30 to 60 percent. High -
greater than 60 percent.
Tonight
Light rain showers over the coastal waters tonight as a clipper
system passes to the north. Gale force wind gusts develop out
of the southwest over the south coastal waters and outer marine
zones after about 4 AM tonight. Peak gusts somewhere between 35
and 40 knots, with the strongest gusts over the southern marine
zones. Seas build to 6 to 9 feet over the southern marine zones
and are more modest over the eastern marine zones in the 3 to 6
foot range.
Tomorrow
Gale force wind gusts continue through late morning before
diminishing to Small Craft Advisory criteria by early to mid
afternoon. Southwest winds becoming more westerly, but remain
steady out of the west between 10 and 20 knots. Seas begin to
subside as well, but remain somewhat elevated over the southern
marine zones through tomorrow evening.
Tomorrow Night
Steady west winds gradually diminish to 10 knots or less after
midnight. This will be accompanied by seas subsiding below Small
Craft Advisory criteria.
Outlook /Monday through Thursday/...
Monday: Winds less than 25 kt. Chance of rain.
Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Rain.
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain.
Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Rain.
Wednesday: Low risk for gale force winds with gusts up to 35
kt. Rough seas up to 13 ft. Rain, isolated thunderstorms. Areas
of visibility 1 to 3 nm.
Wednesday Night: Strong winds with gusts up to 35 kt. Rough
seas up to 15 ft. Rain. Areas of visibility 1 to 3 nm.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Rough seas up to 12 ft. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 4 AM to 1 PM EST Sunday for ANZ231-
232-236-251.
Gale Warning from 4 AM to 1 PM EST Sunday for ANZ233>235-237-
250-254>256.
&&
$$
SYNOPSIS...Belk/RM
NEAR TERM...Belk/RM
SHORT TERM...RM
LONG TERM...Belk
AVIATION...Belk/RM
MARINE...Belk/RM
Area Forecast Discussion
National Weather Service Green Bay WI
556 PM CST Sat Dec 7 2024
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- A light mix of rain, freezing rain, and snow is possible across
the forecast area Sunday evening into Monday. The most likely
location to see any mixed precipitation will be north-central
Wisconsin.
- Warmer temperatures into early next week before arctic air
returns mid-week.
&&
.DISCUSSION...
Issued at 115 PM CST Sat Dec 7 2024
Short Term...Tonight and Sunday
Any lingering snow showers across the far north gradually came to
an end late this morning, giving way to warming temperatures and
decreasing low clouds. Increasing southwest flow then ushered in
well-above average temperatures this afternoon (upper 30s to mid
40s), the mildest temperatures we`ve seen in some time. Gusts
from 20 to 25 mph were observed along and east of the Fox Valley.
Tonight... Expect increasing low clouds to hold temperatures down
in the upper 20s to low 30s across the forecast area overnight as
a weak cold front stalls out over northern Wisconsin. Surface
winds will gradually subside overnight through tomorrow morning,
veering to west/northwest.
Mixed precip chances Sunday evening... Our next weathermaker
arrives tomorrow evening in the form of a clipper system as an
upper-level shortwave approaches from the northern Plains. Expect
precip chances to arrive to central and north-central Wisconsin
from the west tomorrow evening ahead of increasing warm air
advection. Ptype looks to be tricky as CAMs present several
different scenarios that could play out based on thermal profiles.
Model soundings across north-central Wisconsin show deep-layer
saturation Sunday evening, with temperatures hovering
near/slightly below zero. This solution would suggest the onset of
frozen precip (snow) right off the bat. However, the NAM and RAP
show a more pronounced warm nose in the low to mid levels with
saturation in the lowest 3 to 5k ft, introducing the potential for
liquid precip (freezing rain or drizzle) earlier on. Suspect that
precip will start as snow across north-central Wisconsin tomorrow
evening before warm air advection chases away colder air in the
low levels. This being said, an abrupt switch to liquid precip
looks to be in store later Sunday evening (more on this in the
long-term). All in all, forecast confidence remains on the low
end for ptype as any wobble of a degree or two in the thermal
profile could paint a completely different picture. Opted to leave
a rain/snow mix in the forecast for the time being.
Long Term...Sunday Night Through Saturday
Precipitation type on Sunday night remains a concern with a wintry
mix possible over the north. Behind this system, another push of
cold air settles across the region most of the week. Lake effect
snow showers will return to northern WI and some areas will see
sub zero wind chills Wednesday into Thursday. Upper level pattern
buckles late this week into next weekend with sudden zonal flow
taking over, leading to a warming trend, but there also may be
another chance of precipitation as that occurs.
Precipitation...
PV anomaly/shortwave crashing ashore later today over British
Columbia reaches northern plains with clipper low pressure system
by Sunday evening. As that occurs, warm front will extend east of
the low across the western Great Lakes. The low then crosses Lake
Superior Monday into Monday evening while a cold front sweeps
eastward across the Great Lakes. Warm air advection along south of
edge of more widespread precip could result in a wintry mix of
snow, freezing rain and rain Sunday night, especially into the
early morning hours. There is uncertainty on how far south the
widespread precip will extend into our northern counties and there
is also a question of degree of warmth in the lowest 3-5kft. Both
these factors result in a complicated and lower confidence ptype
forecast. Where a wintry mix or mainly freezing drizzle occurs,
untreated roads, sidewalks and parking lots could become slippery.
Winter weather advisory could be needed eventually, but it is not
clear cut by any stretch. For now, will continue to mention this
in the HWO.
Once the system shifts east, Monday looks mainly dry. Cold front
shifting through on Monday night will start up a lake effect
regime over northern WI as a sufficiently cold northwest flow
regime develops across Lake Superior. Glace at forecast soundings
point to low inversions under 5kft Tuesday through Thursday.
Normally that would result in light intensity lake effect, but
most of that lake convective layer will be in the DGZ, so higher
SLRs, fluffier snow. In addition, a shortwave working through
Tuesday night into Wednesday interacting with an already primed
lake effect setup could result in several inches of snow for Vilas
County. That shortwave could also bring snow showers or flurries
to most of the area on Wednesday, even away from the lake snow
belts of northern WI. Adjusted pops to a floor of slight chance
late Tuesday night into Wednesday and ramped them up to likely
for snow belt of Vilas County.
The next chance of precipitation arrives next weekend. A lot of
uncertainty though with this as the primary models (GFS, ECMWF,
Canadian) are much more wrapped up with a low tracking across the
region than their associated ensembles. If something closer to
the stronger ideas ended up verifying, we would be dealing with
widespread mixed precipitation and even the potential for
accumulating snow at some point next weekend. Did not mention any
freezing rain in forecast this far out, especially given the
uncertainty how the system will play out.
Temperatures...
Roller coaster fits temperature trend this week. Temps start off
mild with highs as warm as low to mid 40s on Monday, but then
tumble with highs only reaching the teens to lower 20s Wednesday
into Thursday. During this time, will see another round of sub
zero wind chills, with lowest readings expected Wednesday night
into Thursday morning. Highs become more seasonable chilly by
Friday (20s north into the low 30s east-central), then rebound
back above normal by next weekend. Though extent of that warm up
will depend on strength and location of possible low pressure
system.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 555 PM CST Sat Dec 7 2024
VFR conditions will continue this evening as some mid and high
clouds spread across the region. Then, look for IFR/MVFR ceilings
to spread north to south into central (AUW/CWA) and north central
WI (RHI) Sunday morning. It looks like the lower clouds will not
make it to the Fox Valley (ATW/GRB) and lake shore (MTW) until
late in the day. Mid-high clouds will continue to spread across
the region at times on Sunday as well.
A cold front will drop south into the state on Sunday, as a low
pressure system and warm air advection spread across the region.
These features will increase chances for light wintry precip
across central and especially north central WI. Still some
disagreement on just how saturated the low-levels will be, leading
to uncertainty on the drizzle/freezing drizzle threat. Will only
add some -RASN for RHI at this point, but some -FZDZ may need to
be added. While amounts will be light, some minor snow
accumulation and freezing drizzle could create some icy/slick
surfaces.
A period of LLWS is expected through ~07z as southwest surface
winds subside late this afternoon and evening and winds at 2000
ft remain between 35-50 kts. Winds aloft will decrease later this
evening, ending the LLWS threat. Winds will become light and
variable Sunday morning, then shift to the southeast Sunday
afternoon.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....Goodin/JLA
AVIATION.......Bersch
Area Forecast Discussion
National Weather Service Marquette MI
623 PM EST Sat Dec 7 2024
.KEY MESSAGES...
- A system moving into the Upper Great Lakes will bring
accumulating wet snow, mainly away from the lakeshores late
Sunday into Monday morning.
- Warmer than normal temperatures are expected the rest of the
weekend into early next week, but a return to below normal
temperatures is expected mid next week.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 309 PM EST Sat Dec 7 2024
Water vapor imagery and RAP analysis show mid-level ridging
extending from off of the CA coast into the Canadian Rockies and
broad troffing over eastern Canada into the ne U.S. Result is nw
flow into the Great Lakes this aftn. A couple of shortwaves are
tracking se in this flow from Manitoba to Lake Superior. At the sfc,
low pres was located to the n of Thunder Bay, ON. Strong
waa/isentropic ascent in response to the aforementioned shortwaves
and to the s of the sfc low brought a broad area of -sn across the
fcst area early today. On the back edge, the -sn mixed with and
changed to -fzra/-ra as warm nose aloft advanced eastward. Back edge
of the widespread pcpn has now pushed into the eastern fcst area,
but some spotty -ra lingers back to the nw toward the Keweenaw.
Current temps have risen into the mid and upper 30s F, but a zone of
lwr 30s extends from around Gladstone to Munising/Grand Marais. Low
clouds have cleared out over the w as drier advects eastward. Higher
up, mid clouds are also thinning over the w, allowing for a little
sun.
Aforementioned sfc low will track ese, passing just to the ne of Lake
Superior this evening. To its s, low-level drier air will continue
to push eastward, bringing an end to lingering -ra/spotty -fzra.
Cold front trailing from the sfc low will then drop s during the
night, bringing a return of low cloudiness. Spotty -ra may accompany
the front into the eastern fcst area during the evening. Otherwise,
moisture depth becomes shallow there and will be shallow westward.
So, if any pcpn does occur overnight across the n, ptype is more
likely to be just patchy -dz/-fzdz. Expect min temps in the upper
20s/lwr 30s F.
&&
.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 318 PM EST Sat Dec 7 2024
Above normal temperatures early in the extended period will allow
for wet snowfall and light rain (with perhaps a small/20% chance for
freezing rain) to make it into the forecast late this weekend before
below normal temperatures return by mid next week as Arctic air
drops down from far northern Canada. This Arctic air will result in
northwest flow lake enhanced/effect snowfall most of next week.
However, expect temperatures to return to above normal by next
weekend as warmer air from the Southern Plains/Gulf pushes into our
area. The above normal temperatures look to continue to just before
Christmas as the latest CPC 8-14 Day Outlook has us under a 70 to
80% chance of above normal temperatures the week beforehand.
Additional details follow below.
A few upslope freezing drizzle/drizzle/light snow showers are
possible to start us off Sunday morning over the north central as
the previous low continues streaking towards the Canadian Maritimes
throughout the day. With model soundings showing inversion heights
only getting up to around -4C, it`s most likely that the precip type
will be freezing drizzle or drizzle, depending on the surface
temperature. However, with the saturated layer only getting up to
around 3-4 kft, shower coverage will be pretty spotty. In addition,
no real impacts are really expected from these showers, save for
maybe a tiny glaze of ice on sub-freezing surfaces and a trace of
snowfall (if snow even occurs).
Moving into the afternoon, a Clipper low begins phasing with a
shortwave lifting off from the Northern U.S. Rockies as they both
travel eastwards towards the Upper Great Lakes. This will bring
mainly snowfall across the U.P. late Sunday into Sunday night; the
main exception looks to be Menominee County and the southern half of
Delta County, which could see a rain/snow mix early on. While warm
frontogenesis will be working to bring precipitation across the area
late this weekend, with the more southerly shortwave phasing with
the Clipper, there is some decent spread amongst the differing model
guidances as to whether we will see a transition to wintry mix
and/or rain across the U.P. late Sunday night; it could be that the
more southerly shortwave inhibits the warm air advection northward
just enough to prevent the transition over to other precip types
from snowfall. However, the warm nose of the front aloft and the
warm air advection down at the surface could be enough to have a
change over to a wintry mix followed by possibly rainfall across the
area late Sunday night into early Monday morning. Overall, it looks
like this second solution is more favorable (70% chance), although
recent model runs have abandoned the transition to a wintry mix and
instead are showing mainly just a pure snow to rain transition; only
over the far east do the most recent model runs hold a transition to
freezing rain Monday morning. While the colder first solution has
around a 30% chance of occurring, I generally went with the
second/more favorable solution and kept to the most recent runs
where there was a transition from just snow to just rain Monday.
Overall for impacts, expect to see slick roads, particularly early
in the morning; expect generally 1 to 3 inches of wet snow across
the U.P., with the Keweenaw seeing 2 to 4 inches via some slight
upslope enhancement (some light upslope enhancement is also possible
over the north central south and west of Marquette too). With the
likely (70%) changeover to rainfall, we may see the rain freeze at
some spots given the marginally `warm` temperatures above freezing
and the frigid ground temperatures still. This could cause some icy
spots along parts of the roadway across the area, save the south
central where warmer temperatures will just create sloppy, wet
roads.
As the cold front of the low works into the area, expect to see
northwest flow lake enhanced snowfall begin to pick up, eventually
becoming pure lake effect by Tuesday morning as cold air advection
continues across the area from Canada. The lake effect snowfall
could get quite heavy at times as delta-Ts get up to to around 20C;
a Manitoba Mauler low could reinvigorate the snowfall from Lake
Superior by mid next week as 850 mb temperatures as cold as -23C
roll into the western lake; this could drop high temperatures down
into the teens by next Thursday. Expect temperatures to warm as we
head into next weekend, with above normal temperatures returning by
next Saturday as warm air from the Southern Plains/Gulf slowly makes
its way into our neck-of-the-woods. The above normal temperatures
are expected to continue through much of next week weekend and the
week afterwards as the CPC 8-14 day outlook keeps a 70 to 80% chance
of above normal temperatures for that time period over us.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 612 PM EST Sat Dec 7 2024
Low-level dry air sweeping into the area s of a low pres system
passing by just to the n of Lake Superior will result in VFR
prevailing into at least the early evening at IWD/CMX/SAW. The cold
front tied to the low will then drop south across the area
tonight thru early Sun, bringing a return to MVFR cigs,
beginning first at CMX late this evening, then at IWD/SAW
overnight. Cigs will dip further to IFR early Sun morning at
IWD/SAW and potentially at CMX overnight as well. IFR may hang
on thru Sun morning at SAW and especially at IWD. The upslope
winds after low-level moisture returns may lead to some -dz/-fzdz
developing, so included a prob30 chance of fzdz at SAW from
12-16Z. Gusty westerly winds to 20-30kt at CMX early this
evening will gradually subside late evening into the overnight
hours.
&&
.MARINE...
Issued at 318 PM EST Sat Dec 7 2024
West winds of 20 to 30 knots veer to the northwest this evening,
with a few gales up to 35 knots possible over the east half tonight
as a shortwave low leaves Lake Superior for the Canadian Maritimes.
While winds weaken to 20 knots or less by Sunday morning, winds pick
back up again from the east to southeast Sunday night to 20 to 30
knots across the lake as a warm front moves in from the southwest.
As we move into the early Monday morning hours, expect southeast
winds over the east half to increase to gales of 35 to just below 40
knots along the U.S./Canada border. As the phasing low responsible
for the warm front moves over Lake Superior Monday afternoon, expect
the winds to weaken before becoming west to northwest winds of 20 to
30 knots behind the low late Monday into Monday night. As the cold
air advection behind the low weakens, expect the winds to become 20
knots or less again by late Tuesday. However, expect the winds to
pick back up from the northwest yet again by Wednesday as another
reinforcing shortwave from Canada brings winds of 20 to 30 knots
back across the lake Wednesday into Thursday. In addition to the
winds, some freezing spray could be seen across the lake due to the
frigid air and stronger winds Wednesday into Thursday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Watch from late Sunday night through Monday afternoon for
LSZ264-266-267.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...TAP
AVIATION...Voss
MARINE...TAP
Area Forecast Discussion
National Weather Service Morristown TN
957 PM EST Sat Dec 7 2024
...New UPDATE...
.UPDATE...
Issued at 943 PM EST Sat Dec 7 2024
Dewpoints have failed to recover despite the end of afternoon
mixing, thus, the main changes with the evening update was
blending NBM10th and HRRR to lower those values. Extended this
blend through Sunday afternoon and have re-sent FWF to update RHs
there. Minor tweaks to hourly temperatures to account for this dry
air as well, but no significant changes to the overnight mins
occurred. Lastly, both low and mid level water vapor imagery loops
from GOES-16 show a subtle impulse moving through the area. This
lead to the development of a relatively narrow cloud deck across
portions of the central and northern forecast area. Have reflected
this in the sky cover grids but optimistic this should be short-
lived as the impulse swings through.
&&
.SHORT TERM...
(This evening through Sunday)
Issued at 218 PM EST Sat Dec 7 2024
Key messages:
1. Breezy conditions expected tonight in the higher terrain of
our Virginia counties.
2. Much warmer tomorrow with highs in the 50s.
Discussion:
Dry weather expected this period with a weak ridge over the
Southeast and high pressure at the surface. Gusty winds will be
possible on the highest ridgetops in Southwest Virgina late
tonight as 850 mb westerly winds increase to 40 to 45 knots. The
higher terrain in Southwest Virginia may see gusts of 35 mph late
tonight through early tomorrow morning. Otherwise, a quiet night
with clear skies allowing temps to drop into the lower 30s and
upper 20s in the Tennessee Valley.
Tomorrow will be warmer as southerly flow continues to bring warm,
moist air into the region. Cloud cover will increase in the
afternoon ahead of the next system approaching from the west.
Highs will be slightly above normal in the mid or upper 50s.
&&
.LONG TERM...
(Sunday night through next Saturday)
Issued at 218 PM EST Sat Dec 7 2024
Key Messages:
1. Widespread rain will be moving into the region Sunday night
lingering through Tuesday night.
2. Light snow is possible Wednesday into Wednesday night on the
backside of the system. Cooler temps later in the week.
Discussion:
Sunday night will usher in a completely different weather regime for
the next several days. The primary forcing mechanism behind this
change will be a fast moving low/shortwave coming out of the
southern plains headed towards the Great Lakes Region to merge into
the mean flow of the northern stream. As it moves across the region
it will also help drive thorugh a cold front during the middle of
the week.
Multiple days of precipitation are expected as surface winds turn
more southerly on Sunday before the rain begins, this will draw up
warm and moist air from the Gulf of Mexico. Front edge of the
precipitation will likely move onto the Plateau and southeast TN
sometime between sunset and midnight Sunday night, spreading
northeast across the entire southern Appalachian Region before
sunrise on Monday. The initial rain will come right as the shortwave
zips across the Ohio Valley overnight... And we`ll likely get some
breaks in the precipitation during the daytime on Monday behind the
shortwave, but before the arrival of the front.
Surface low riding up along the front will reload the atmosphere
with additional warm and moist air from the GoM with Tuesday looking
like the next round of moderate to heavy precipitation with this
system. This will also be the time-frame when the warmest air is in
place with highs climbing into the 60`s for much of the Valley, and
we cannot completely rule out seeing some embedded thunderstorms
within the greater precipitation shield.
When everything is said and done, it looks likely that most places
will see at least an inch of rain between Sunday night and Wednesday
morning... and some of the orographically enhanced rainfall areas
should be able to climb above the 2 inch mark.
Rain begins to exit the area on Wednesday with some possible wrap
around showers on the backside of the low which is fairly typical
for these type of events. After the front moves through on Wednesday
temperatures will quickly drop and we`ll see about a 20 degree
difference between Tuesday and Wednesdays high temperatures. Any
lingering precipitation could come down in the form of light snow,
especially across the higher elevations of northeast TN and
southwest VA.
Remainder of the work week will remain colder and drier behind the
front with overnight lows below freezing and daytime highs in the
40`s. Another system may try to move thorugh over the weekend, but
deterministic models this far out have a LARGE array of solutions,
so confidence is very low on what the upcoming weekend will bring at
this time.
&&
.AVIATION...
(00Z TAFS)
Issued at 627 PM EST Sat Dec 7 2024
VFR conditions will prevail over the next 24 hours. Have included
a mention of LLWS at TRI given westerly low-level
flow(925mb-850mb) is expected to amplify overnight. LLWS may need
to be considered at TYS in a future amendment or TAF issuance,
however, the potential for a light surface wind leads to some
uncertainty at this time. Increasing clouds ahead of the next
system is expected throughout the day tomorrow, but conditions
will remain VFR among light westerly winds.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 30 56 46 61 / 0 20 100 80
Knoxville McGhee Tyson Airport, TN 33 58 46 60 / 0 10 100 70
Oak Ridge, TN 31 56 44 57 / 0 10 100 70
Tri Cities Airport, TN 25 55 43 56 / 0 0 100 70
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...McD
AVIATION...KRS
Area Forecast Discussion
National Weather Service Shreveport LA
956 PM CST Sat Dec 7 2024
...New UPDATE, SHORT TERM...
.UPDATE...
Issued at 943 PM CST Sat Dec 7 2024
Decreased likely rain overnight and added patchy/areas of fog.
&&
.SHORT TERM...
(Tonight through Monday Night)
Issued at 943 PM CST Sat Dec 7 2024
This initial wave of overrunning rain has largely pushed across
more than half of our region and we have lowered at least the
likely PoPs for the rest of tonight`s zones. The 00Z Nam and the
HRRR are in decent agreement on some more light rain here and
there with coverage ramping up again toward daybreak. Until then,
our temps have already dropped to a handful of our forecasted
lows, as the air is drying out a bit and we nudge down closer to
the dew point. Along with that, we added patchy fog and some areas
of fog to the remainder of tonight with a light S/SE wind or in
many cases calm. Updated zones are available and graphics will
only see subtle changes to this update as the PoP is a 12 hour
grid and we have seen the likely portion from 00-03Z factored
into the prelims. /24/
&&
.LONG TERM...
(Monday through next Friday)
Issued at 152 PM CST Sat Dec 7 2024
Dawn will break on the new work week to find most of the region damp
but free of new rainfall at first. This weekend`s weakening trough
looks to be absorbed into a deeper upper level trough far to the
north over the western Great Lakes, but a weak shortwave will ripple
across the resulting pseudo-zonal flow over the Four State Region on
Monday, stirring up another round of slight rain chances, primarily
for our Louisiana zones along and east of the I-49 corridor. These
showers may linger into the evening and nighttime hours, coming to
an end by Tuesday morning at the latest and beginning a dry stretch
for much of the remainder of the week. Highs on Monday look to be
the warmest seen in some time, ranging from the middle 60s north to
middle 70s south.
Behind the features responsible for a soggy weekend and start to the
new week, a new upper level trough will deepen over the
Intermountain West Monday before plunging south across the Plains
by Tuesday. The ArkLaTex currently looks set to receive the first
cold frontal passage early Tuesday, resulting in highs ranging
from the lower 50s northwest to middle 60s southeast. Behind the
front, lows will drop back to below normal values in the upper 20s
north to middle 30s south. Northwesterly flow aloft will sustain
near seasonable highs in the 50s and 60s and chilly morning lows
in the 20s and 30s, with Thursday morning looking to be the
coldest, before a developing ridge and returning southerly surface
flow boost temperatures and return slight rainfall chances to
close out this extended forecast period.
SP
&&
.AVIATION...
(00Z TAFS)
Issued at 546 PM CST Sat Dec 7 2024
Multiple rounds of light to moderate rain will move across the
region during the next 24 hours. The first rounds is already
affecting most of East Texas north of I-20 and will move into
Southeast Oklahoma, Southwest Arkansas, and extreme Northwest
Louisiana early in the period. Coverage of the precip may
decrease somewhat for a few hours around sunrise. However,
widespread rain is expected to affect all TAF sites from 08/12z
through the remainder of this cycle. An isolated thunderstorm or
two cannot be ruled out, but TS was not included in the TAFs.
Ceilings and visibilities will gradually deteriorate in the
MVFR/IFR range. IFR, and possibly some instances of LIFR, flight
conditions will likely prevail for much of the daytime hours of
Sunday due to the precip and low clouds.
Nuttall
&&
.SPOTTER INFORMATION STATEMENT...
Issued at 600 PM CST Sat Dec 7 2024
Spotter activation is not expected at this time. /09/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 44 62 54 74 / 70 90 50 10
MLU 44 65 58 73 / 40 90 90 20
DEQ 43 54 45 64 / 40 90 20 0
TXK 43 59 50 68 / 60 90 30 0
ELD 41 61 51 71 / 60 100 70 10
TYR 43 59 53 71 / 70 80 10 0
GGG 42 60 52 73 / 80 90 20 0
LFK 43 64 55 77 / 40 80 30 10
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
SHORT TERM...24
LONG TERM....26
AVIATION...09