Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/09/24
Area Forecast Discussion
National Weather Service Amarillo TX
516 PM CST Sun Dec 8 2024
...New AVIATION...
.KEY MESSAGES...
Issued at 329 AM CST Sun Dec 8 2024
There is a slight chance for light snow accumulations generally
less than 1/2" across the western Panhandles.
Colder airmass will lead to below normal temperatures Monday
night through Wednesday morning.
Temperatures will warm to slightly above normal values by the
weekend with dry weather persisting.
&&
.SHORT TERM ...
(This evening through Monday night)
Issued at 142 PM CST Sun Dec 8 2024
Initial wind shift associate with a cold front will occur late
this aftn through the overnight hours. A second cold air push
will occur on Monday with stronger CAA occurring Monday afternoon
through evening. Despite the unfavorable positive trough axis
orientation, models do indicate decent lift per H7-3 Q-Vector
convergence Monday evening/night and this will combine with a
band of H7 frontogenesis to provide at least some precipitation
potential. Moisture will be a limiting factor in 2 ways: 1) Deeper
moisture will be limited in the wake of an upper level low
currently exiting the area into OK, and 2) There is a layer of
near surface dry air that will quickly have to be overcome given a
short window for precipitation. So, how much snow do we lose as
virga before the SFC moistens up remains a big issue. The trend
in 12Z models has been toward a little strong convergence along
the H7 boundary and POPS have started to trend back up slightly.
CONSShort POPS showed an agressive increase in response to NAM
and 12Z HRRR while NBM has only slightly increased. Didn`t want to
make too agressive a change in case this is a one run wonder, but
decided to start with a slightly tweaked down 12Z CONSALL as a
starting point. For now limited POPS to 20 percent with highest
chances along the western counties. Also expanded the flurry
mentions much further east to include even the entire western half
of the Panhandles.
It should be mentioned, this still is a low ceiling event
seemingly without potential for a multi-inch snow accumulation
event, but if the recent more agressive solutions pan out, we
could have minor impacts on the Tuesday morning commute for the
WRN half of the area given plenty cold SFC temps. The 12z 3 PM NAM
is probably close to a reasonable worse case scenario as it
generated a narrow band of snowfall accumulation of around 1/2"
to 1 1/2" near DHT and it even generated very modest accumulations
near and west of AMA. NBM probabilities of even just 1/10" snow
remain extremely low (10% mainly far NW), but these aren`t being
influenced by CAMs just yet. This will change by late tonight.
WRT temps, we will see several days of below normal temperatures
with the coldest day being Tuesday (highs 40s areawide). Expect
20s for all but the SE Tuesday morning and the coldest readings
should occur Wed morning when the entire area will reach well into
the 20s with a few teens possible. The wind chills are expected
to bottom out near 10 across the NW early Wednesday.
Gittinger
&&
.LONG TERM ...
(Tuesday through next Saturday)
Issued at 142 PM CST Sun Dec 8 2024
After a cold start in the morning with lows in teens and 20s and
wind chills in the teens and even a couple single digits in the
NW, a warming trend begin and continue through the weekend. This
will be aided by low level WSW flow as the cool SFC high tracks
all the way to the Lower Rio Grande Valley through Wednesday
before rapidly shifting east across the Deep South. Upper level
flow will become relatively zonal as Great Lakes trough progresses
east early in the period. There was terrible agreement between
the 00Z operational ECMWF and other major 00Z ops models wrt a fat
moving trough within the zonal flow. There are a couple LREF
ensemble members producing prospection associated with this
trough (or a following trough) between Friday and Sunday, but
their are so few that the NBM is not producing any POPs over 5
percent through this period. For now, the main key message is the
anticipation of above normal temperatures next weekend and likely
beyond into next week.
Gittinger
&&
.AVIATION...
(00Z TAFS)
Issued at 508 PM CST Sun Dec 8 2024
VFR conditions will prevail at all TAF sites over the next 24
hours. Variable winds will transition to more northerly with the
cold front passage. Winds will pick up around 15-18z as the colder
push of air behind the front makes its way into the Panhandles.
Mostly clear skies, with a few high clouds possible.
Weber
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 35 54 29 45 / 0 0 10 10
Beaver OK 32 54 25 46 / 0 0 10 0
Boise City OK 30 47 22 42 / 0 10 20 0
Borger TX 35 56 30 48 / 0 0 10 0
Boys Ranch TX 31 54 29 46 / 0 0 20 0
Canyon TX 33 55 29 45 / 0 0 10 10
Clarendon TX 38 58 31 46 / 0 0 10 0
Dalhart TX 29 49 23 43 / 0 0 20 0
Guymon OK 30 51 24 45 / 0 0 10 0
Hereford TX 33 54 28 45 / 0 0 10 10
Lipscomb TX 35 55 29 46 / 0 0 10 0
Pampa TX 36 54 29 45 / 0 0 10 0
Shamrock TX 37 59 32 47 / 0 0 0 0
Wellington TX 38 59 34 49 / 0 0 0 0
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&
$$
SHORT TERM...88
LONG TERM....88
AVIATION...89
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
524 PM CST Sun Dec 8 2024
...New AVIATION...
.SHORT TERM...
(Tonight through Monday night)
Issued at 256 PM CST Sun Dec 8 2024
Southwesterly flow aloft will gradually give way to west-
southwesterly over Deep South Texas throughout the short term as a
series of shortwaves pass over the region ahead of a mid-to-upper
level trough digging and deepening southeastward through the Pacific
Northwest and Rocky Mountains. Closer to the surface, a weak
stationary front, extending southwestward from a low pressure over
Louisiana, will lift northward overnight tonight as the low tracks
northeastward.
Short term guidance indicates that moisture associated with the
boundary will continue to keep overcast skies and low clouds
throughout the rest of this afternoon and overnight with light
southerly winds. A blend of the NBM and HRRR models yields a 15 to
near 20% chance of brief light showers possible overnight across the
mid and upper RGV, northern Ranchlands, Kenedy and Willacy counties,
with chances diminishing towards sunrise. A light shower or two is
also possible elsewhere through tonight. Went with CONSShort for
overnight minimum temperatures with lows ranging from the mid to
upper 50s across the upper RGV, the Rio Grande Plains and western
portions of the northern Ranchlands as well as low 60s for points
south and eastward with mid 60s at the beaches.
As the boundary and associated low level moisture lifts out by
tomorrow morning and a dry line across central Texas extends
southward across the Sierra Madre and close to the northwestern
fringes of our County Warning Area (CWA) by tomorrow afternoon and
evening, clouds are expected to dissipate across the northern
Ranchlands, Rio Grande Plains and upper RGV as drier air is filtered
in via northwesterly winds aloft. Meanwhile, scattered to broken
skies are expected to linger across much of the RGV, especially
closer to the coast and over the beaches. Combined with the
influence of southerly surface winds and downsloping effects from
the Sierra Madre, decided to go with a blend of NBM and CONSShort,
which progs highs to reach into the mid 80s across the Rio Grande
Plains, northern Ranchlands and the mid-to-upper RGV, while low
80s are anticipated east of I69C. Mid 70s are expected at the
beaches.
Winds remain out of the south for most of Monday night. In the early
morning pre-dawn and dawn hours, winds will begin to shift from the
west ahead of an advancing cold front. More details can be found in
the long term forecast. Kept with the NBM forecasted minimum
temperatures of mid to upper 50s across the northern Ranchlands, Rio
Grande Plains and upper RGV while 60s are expected for the rest of
inland Deep South Texas. Lows will fall to the lower 70s along the
barrier islands.
A moderate rip current risk is expected at the beaches throughout
the short term period.
&&
.LONG TERM...
(Tuesday through next Sunday)
Issued at 256 PM CST Sun Dec 8 2024
Key Messages:
- A cold front will arrive on Tuesday, bringing well below normal
temperatures Tuesday night through Thursday morning.
- There is medium to high confidence for Small Craft Advisory to
Gale Warning conditions over the Gulf waters late Tuesday
afternoon into Wednesday evening. This may also result in
hazardous beach conditions.
- Warming trend for the rest of the week and into the weekend,
with low precipitation chances returning over the weekend along
the coast and Gulf waters.
The most notable change with the long term forecast update this
afternoon is the expected frontal passage timing of a strong cold
front on Tuesday across Deep South Texas. Although we`ve been
advertising a frontal passage of late Tuesday afternoon over the
past several days, the latest suite of high res guidance,
including the NAM12 (which handles cold air masses fairly well),
continue to support a faster frontal passage timing. HREF members,
including the HRRR and NAM12, suggest the cold front will be
knocking on the doorstep of the Northern Ranchlands by early
Tuesday morning, pushing across the Rio Grande Valley by late
Tuesday morning.
While we`ll still have to keep an eye on downslope warming ahead
of the cold front across portions of the Rio Grande Valley as
winds shift to the west/southwest ahead of the boundary Tuesday
morning, the earlier time of arrival should limit temperatures
from warming above the low to mid 70s. Additionally, high res
guidance suggests 850MB temperatures will range from 15-16C
Tuesday morning, falling to around 12-14C by Tuesday afternoon
with the earlier arrival of the colder airmass. After coordination
with several Texas offices to our north, Tuesday`s high
temperatures have been adjusted to reflect a faster frontal
timing, with highs ranging from the mid 60s across the Ranchlands
to low to mid 70s across the Rio Grande Valley. It is likely,
based on the current guidance, temperatures will fall into the 60s
across the Rio Grande Valley by late Tuesday afternoon as cold
air advection arrives. We`ll still need to keep an eye on the
frontal timing trends and adjust the temperature forecast as
needed over the next day or so. Given the presence of high
moisture content ahead of the cold front, isolate showers cannot
be ruled out over the Lower Rio Grande Valley and Gulf waters late
Tuesday morning into afternoon, but should come to an end as
northerly winds usher in a cooler and drier airmass.
Persistent cold air advection will result in some of the coldest
low temperatures of the season heading into Tuesday night and
Wednesday night across the region. Both deterministic and
probabilistic guidance indicate low temperatures should fall into
the upper 30s across the Northern Ranchlands to low to mid 40s
across the Rio Grande Valley each night. I did blend closer to
the NBM 50th percentiles for low temperatures each night to
account for these trends. There is a low chance (10% or less) of
temperatures falling below 32 degrees across the Northern
Ranchlands Tuesday night into Wednesday morning, and a low to
medium chance (10-40%) of temperatures falling below 32 degrees
across the Northern Ranchlands Wednesday night into Thursday
morning. There is a slightly better chance of a light freeze over
the Northern Ranchlands early Thursday morning as high pressure
settles in with light wind and mostly clear skies.
Wednesday will feature high temperatures in the 60s region wide,
around 10 degrees below normal for early to mid December. Brisk
northerly winds will have fallen below 10 MPH by Wednesday morning
along/west of I-69, but should remain elevated through late
Wednesday evening along/east of I-69. With the return of low level
southerly flow, expect a warming trend Thursday through the
weekend with highs warming into the 70s each afternoon. Low rain
chances return Friday and into the weekend, but the best chances
look to be along the immediate coast and over the Gulf waters.
&&
.AVIATION...
(00Z TAFS)
Issued at 517 PM CST Sun Dec 8 2024
VFR conditions are expected to largely persist for the next
several hours until closer to midnight tonight. After which MVFR
conditions will become the prevailing category for the TAF sites
for the rest of the overnight hours. The next big change will
occur during the morning hours as the low-level clouds are
expected to mix out and result in VFR conditions returning to the
region. Winds are expected to be light and out of the south for
the TAF period. There were some model guidance that IFR
conditions could return for a short period at HRL and MFE during
the overnight hours, but confidence was not high enough to include
in this TAF package.
&&
.MARINE...
Issued at 256 PM CST Sun Dec 8 2024
Tonight through Monday night...Light to moderate southerly winds
and slight to moderate seas (3 to 4 feet) are expected throughout
the short term. Chances of showers tonight will diminish
throughout the day Monday.
Tuesday through next Sunday...Adverse marine conditions will
prevail through at least Wednesday evening in response to the
passage of a strong cold front on Tuesday. There is a high chance
(60% or greater) of Small Craft Advisory conditions as early as
Tuesday afternoon as northerly winds increase with the arrival of
the cold front, a medium to high chance (60% or greater) of Gale
force wind gusts late Tuesday night into Wednesday morning, and a
high chance (70% or greater) of Small Craft Advisory conditions
continuing through Wednesday evening. Conditions should begin to
improve Wednesday evening and night, with favorable marine
conditions continuing into the weekend. Low precipitation chances
exist along the cold front on Tuesday, and return once again Friday
into the weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE 63 81 68 72 / 10 0 0 20
HARLINGEN 61 83 63 69 / 10 0 0 10
MCALLEN 61 86 65 72 / 20 0 0 0
RIO GRANDE CITY 59 85 57 73 / 10 0 0 0
SOUTH PADRE ISLAND 66 77 70 71 / 10 10 0 30
BAYVIEW/PORT ISABEL 63 81 65 70 / 10 10 0 20
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
SHORT TERM...65-Irish
LONG TERM....22-Garcia
AVIATION...64-Katz
Area Forecast Discussion
National Weather Service Glasgow MT
234 PM MST Sun Dec 8 2024
.DISCUSSION...
KEY MESSAGES:
- Headlines:
* High Wind Warning:
SW Phillips/Petroleum Counties
thru 5 PM Today
* Blizzard Warning:
McCone, Richland, Prairie, Dawson and Wibaux Counties
thru 4 AM Monday
* Winter Weather Advisory:
North of Missouri River, Petroleum
and Garfield Counties thru 5 PM Monday
- A transition to all snow expected by tonight. Totals range from
2-4 inches along the higher terrain of the Big Sheeps, western
Garfield and Wibaux Counties through Monday evening. Isolated
higher amounts in strongest snow bands.
WEATHER PATTERN OVERVIEW:
This morning`s precipitation generally fell as rain as we had a
bit of a warm nose thru at least 850 hPa. A secondary area of
precipitation is starting to gain steam across the NW`ern zones.
Of the HREF members, the NamNest was the best at depicting this
morning`s precipitation, so gave more confidence in it`s
interpretation for the near-term forecast. RAP mesoanalysis shows
that this melting layer will quickly wet-bulb evaporatively
cooling erode this warm layer. Surface winds are broadly gusting
as high as 55 mph, though some locations are easily gusting as
high as 65 mph.
This in combination with light to moderate snowfall rates will
bring periods of near-whiteout conditions for locations under a
Winter Weather Advisory and in whiteout conditions in areas under
the Blizzard Warning. At this time, didn`t feel it`d be
appropriate to upgrade any of the advisories to Winter Storm
Warnings (given plenty of near 60 mph wind gusts but minimal
snowfall accumulation). Impacts may justify the issuance of this
but will discuss with the evening crew.
After the system winds down on Monday, we`ll remain under near
northerly flow aloft, allowing daily chances of light snow showers
through Friday.
FORECAST CONFIDENCE & DEVIATIONS:
Of the HREF members, the NamNest was the best at depicting this
morning`s precipitation, so gave more confidence/weight in the PoP
blend for the near-term forecast.
- Enriquez
&&
.AVIATION...
LAST UPDATED: 2130Z
FLIGHT CAT RANGE: VFR becoming IFR through Monday AM.
DISCUSSION and Wind: Snow bands are setting up across NE MT. This
and in combination with a broad area of 30-40 kt WNW wind gusts
(isolated areas gusting as high as 55kts). Blowing snow and
moderate snowfall will bring visibilities down to a 1/4SM or less
near KGDV and KSDY through early Monday morning. Snow and wind
taper off gradually through the rest of Monday.
- Enriquez
&&
.GGW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM MST Monday for Central and
Southeast Phillips-Central and Southern Valley-Daniels-Eastern
Roosevelt-Garfield-Northern Phillips-Northern Valley-Petroleum-
Sheridan-Southwest Phillips-Western Roosevelt.
High Wind Warning until 5 PM MST this afternoon for Petroleum-
Southwest Phillips.
Blizzard Warning from 6 PM this evening to 4 AM MST Monday for
Dawson-McCone-Prairie-Richland-Wibaux.
Winter Weather Advisory from 4 AM to 5 PM MST Monday for Dawson-
McCone-Prairie-Richland-Wibaux.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Goodland KS
421 PM MST Sun Dec 8 2024
.KEY MESSAGES...
- Cold frontal passage tonight will yield below normal
temperatures through mid week.
- 15-24% chance of light snow for east Colorado Monday. Little
to no accumulation is currently forecasted.
&&
.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 104 PM MST Sun Dec 8 2024
A complicated setup is currently ongoing across the area with many
features impacting the weather for the next 24 hours. Currently
watching two surface lows; one across the Sandhills and another
developing low across southeast Colorado along with a more
pronounced mid level low ejecting into eastern Kansas
currently. The two surface lows are leading to a tighter
pressure gradient across northeast Colorado with wind gusts
around 30 mph currently. RAP suggests an 850-700mb jet
associated with cold front in the Black Hills will break apart
and move towards the northwest portion of the area (Yuma, Dundy
counties) which will then support the potential for some 40-45
mph winds through the remainder of the area. A corridor of lower
dew points in the mid teens have developed across northeast
Colorado as well (interestingly enough under cirrus), the
combination of this along with the breezy to gusty winds will
promote near critical to locally critical fire weather through
the afternoon. The overall duration of the critical fire weather
does look to be short enough as the cirrus is impacting
temperatures that sites that are currently in the upper 60s will
fall into the low 60s which is forecast to help keep the
combination of sub 15% RH values and breezy winds to an hour or
two so am not leaning towards issuing a Red Flag Warning.
Through the remainder of the night, guidance wants to create a
period of light and variable winds this evening which I`m not
currently buying as pressure rises looks to occur during this time
frame which is forecast to yield winds around 10-15 mph sustained.
If the light winds do end up verifying then temperatures may quickly
fall due to the dry incoming air which would then support
radiational cooling. The focus will then turn to a modest cold
front and increasing low to mid clouds which interestingly
enough may actually warm temperatures a little bit due to
continued mixing and less radiational cooling. At this time
forecast lows are in the mid 20s across the west to near
freezing across the east.
Monday, the cold front will move slowly south across the area along
with a persistent cloud cover through the day is forecast to
see most areas struggle to warm much leading to near normal
temperatures. Some guidance does suggest that the cloud cover
may be thick which if is the case along with 850mb temperature
from 2 below to zero may lead to colder temperatures than
currently forecast with mid 30s for highs being tough to
realize. As for precipitation chances will maintain a 15-24%
chance of light snow across mainly Kit Carson and Cheyenne (CO)
counties through the day as a 700mb frontogenesis (FGEN)band
will be in place and align with the best mid level moisture. The
concern is if to much dry air will be in place at the surface
which may lead to flurries or even virga. The reason I leave the
snow chances in for Colorado is due to elevation reasons as
there is lesser chance for the dry air to have as much of an
impact on evaporating the snow. I did extend the mention of
flurries further east into Gove county Monday afternoon due to
the overlapping nature of the best mid level moisture and FGEN
band. Overall though, it doesn`t appear there is going to be
much if any snow accumulation or impacts in general with this
system.
Monday night and into Tuesday morning, continued cold air advection
is forecast to continue into the region so have trended temperatures
a little cooler despite breezy NW winds and cloud cover as
temperatures are currently forecast in the teens to 20s across the
area.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 104 PM MST Sun Dec 8 2024
Northwest flow continues on Tuesday and through the end of the week
before some hints, most specifically the ECMWF of a pattern change
into next weekend. Temperatures for the extended period are forecast
to range from near normal to slightly above normal with some
potential variations depending on the positioning a very cold air
mass currently favoring the Ohio Valley region. A slight westward
shift which some ensemble members do suggest will lead to colder
temperatures for the week especially for eastern portions of
the area whereas a more eastward placement of this cold air mass
would lead to the continued mild temperatures for the Tri-State
area. For Tuesday nearly all guidance has trended with colder
850mb temperatures with the RAP being the coldest at 5 below at
18Z. A decrease in cloud cover through the day may help
temperatures warm an extra few degrees during the afternoon but
if the clouds do hold then temperatures may struggle to get
above freezing. A quick warming trend on Wednesday is forecasted
before another cold front moves through the region on Thursday.
This cold front again looks to be dry along with the continued
dry trend forecasted through next weekend at this time.
There is however potential for a pattern change with more quick
moving systems according to the ECMWF and ensembles that may
give some portions of the forecast area some slightly better
precipitation chances although still not slam dunk setups. It is
worth noting as well that the GFS and GEFS keep NW flow and the
same continued pattern that we have been in during this
timeframe as well. Overall though there is not enough
consistency with guidance to lean one way or the other.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 418 PM MST Sun Dec 8 2024
For KGLD & KMCK... VFR conditions are expected through the
period. The main changes will be in the winds, with winds
generally from the north/northwest but varying in speeds. Winds
have already lightened to around 10 kts and will likely stay
between 5 to 10 kts overnight. However, LLWS is forecast to
develop as a trough axis swings through and is forecast to
increase winds a few hundred feet above the surface to around
30kts. This should last to near sunrise and then fade. During
the day tomorrow in the wake of the front, winds should increase
to around 15-20 kts with gusts to 30 kts through the day. Winds
should then die off around 23Z, similar to what they did this
evening.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...None.
CO...None.
NE...None.
&&
$$
SHORT TERM...Trigg
LONG TERM...Trigg
AVIATION...KAK
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
737 PM CST Sun Dec 8 2024
.KEY MESSAGES...
- Rain is likely tonight east of I-55, with around a half inch of
rain expected south of I-70. Amounts will decrease further to
the north and west, with only a slight chance (20%) of rain west
the Illinois River Valley.
- Mild conditions continue through tomorrow, then a multi-day
cooldown is expected during the middle of the week, with high
temperatures falling into the teens to 20s Thursday. Wind chill
values are forecast to drop near to below zero Thursday
morning.
&&
.UPDATE...
Issued at 737 PM CST Sun Dec 8 2024
Radar mosaics show the rain shield has roughly reached I-70 this
hour, with more scattered (but increasing) activity over central
Missouri. High-res models show a rapid increase over central
Illinois through the next couple hours, though the HRRR is backing
off a bit in coverage, especially west of I-55. A rapid
diminishing in rain is expected from west to east after midnight,
as the upper trough currently along the western borders of
Missouri and Arkansas pushes across Illinois.
Recent forecast updates were mainly to update the PoP trends
through early Monday morning.
Geelhart
&&
.DISCUSSION...
Issued at 238 PM CST Sun Dec 8 2024
Highs yesterday really overperformed with the WAA and clear skies in
place. Highs for today have been increased, and it appears they are
once again. We are seeing upper 50s to low 60s across the CWA so
far today. Perfect weather to get out and refresh before the cold
weather comes back Tuesday. The upper low bringing us the clouds
and rain is moving up out of the Texas panhandle. The cloud deck
will lower ahead of the rain system this evening.
The rain should start impacting the southeastern counties by 00z
this evening. The northwest extent of the showers is uncertain. The
previous model run over the last few days, the precip kept shifting
eastward. Today, the deterministic are showing the showers
further west again. Amounts with this system aren`t all that
impressive. North of the Illinois River Valley will remain dry
through this event. The highest amount will be south of I-72.
There is a 50-60% chance of 0.1 inches of rain from a Springfield
to Champaign line. South of I-70 have a 90-100% chance of seeing a
quarter of an inch and a 20-40% chance of half an inch. These
probs came from the 12z.08 HREF. The rainmaker should be out of
the CWA between 12-15z tomorrow morning.
A cold front is set to move through Monday evening, which will start
to drop the temperatures again. CAA will set up over the CWA as
another cold front prepares to pass through overnight Tuesday. This
front will act as a reinforcing boundary, tanking the temperatures
even more. Highs on Wednesday will struggle to see the 30s. The
coldest day of the week is now Thursday, with highs only getting to
the upper teens north of I-72 and to upper 20s south of I-70.
This CAA regime (along with some influence from a tighter pressure
gradient) will increase the wind gusts. They don`t look to be as bad
as it was with the last wind event but the NBM has a 20-40% chance
of wind gusts of 30 mph for Wednesday afternoon. Some snow flurries
are possible during this time of higher winds. Wind chills will be
an issue late Wednesday night into Thursday morning. Apparent
temperatures are forecast to be near to below zero.
There is another system on deck for next weekend, but most of our
focus is on tonight`s rain and Thursday`s cold. After Thursday,
temperatures will rebound into the 40s for the weekend.
Copple
&&
.AVIATION... (For the 00z TAFs through 00z Monday Evening)
Issued at 521 PM CST Sun Dec 8 2024
Ceilings expected to rapidly deteriorate from southwest to
northeast early this evening, as an area of rain lifts into
central Illinois. Probabilities of IFR ceilings increase to 60-80%
at KDEC/KCMI as early as 02-03Z. It appears KPIA has a decent
chance of staying above 1000 feet, though some briefer IFR periods
can`t be ruled out between 06-08Z. By 12Z, lingering sub-1000 foot
ceilings should be closer to the Indiana border, as a steady
improvement sweeps from west to east across central Illinois.
Southerly winds will be gusty at times this evening, mainly in
eastern Illinois, before trending more toward the west in the
09-12Z time frame as the rain and low clouds exit the region.
Geelhart
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
654 PM EST Sun Dec 8 2024
.KEY MESSAGES...
- Wet snowfall tonight will result in slippery road conditions
across much of the area. In general, widespread 1 to 3 inches
of snow is expected, mainly away from the lakeshores. Higher
amounts up to 3 to 6 inches expected for the high terrain of
the Keweenaw Peninsula.
- Southeast gales of 35 to 40 knots over central and eastern
Lake Superior late tonight through early Monday afternoon,
especially closer to the International Border.
- Several inches of very fluffy lake enhanced/effect snow is
expected to fall over the northwest to north-northwest wind
snow belts Tuesday through Thursday.
- A return to below normal temperatures is expected by the
middle of this week. But above normal temperatures look to
return by this upcoming weekend.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 420 PM EST Sun Dec 8 2024
Water vapor imagery and RAP analysis show mid-level troffing over sw
Canada into the Pacific NW and northern Rockies. In response to the
trof, one sfc low pres is over se Saskatchewan with a second over
eastern SD. Fairly strong waa/isentropic ascent is developing ahead
of the trof, and in particular ahead of the SD low pres. Result is
an arc of pcpn spreading across northern MN into NW WI/western Lake
Superior. Closer to home, areas of very light snow/flurries have
been occurring in n central Upper MI today. That pcpn is the remnant
of the wider coverage of pcpn that developed late last night.
Current temps across the fcst area are in the upper 20s to mid 30s
F, coolest across the high terrain of the Keweenaw into n central
Upper MI.
Mid-level troffing will progress out across the Northern Plains and
toward the Upper Mississippi Valley tonight. The low over
Saskatchewan will move to nw MN while the SD low becomes ill-defined
as it lifts ne, resulting in a rather sharp sfc troffing extending
from nw MN ese along the vcnty of the MI-WI stateline by 12z Mon.
Isentropic ascent will be a main driver of the pcpn that will
continue to advance from MN and nw WI and spread ene across the fcst
area in roughly the 22z-06z time frame, lasting roughly 2-4hrs for
most locations. Duration will be shortest near the WI-MI stateline.
In fact, Menominee may not see much, if any pcpn, as column
saturation is less likely that far s. Steadier pcpn will linger
longest across the Keweenaw, aided by easterly upslope flow off of
Lake Superior. Most of the initial pcpn should be in the form of
snow with snow/rain more likely near Lake MI and in the far west
around Ironwood. Overnight, isentropic ascent lingers, but the
combination of the continued waa and mid-level drying will aid a
transition to -ra/-dz after the main push of snow under the
strongest isentropic ascent exits. While temps will slowly rise
during the night, readings may hold just blo freezing interior e
thru 12z, so a bit of -fzra/-fzdz could occur there late tonight.
Snow ratios are expected to be on the low side, generally 10 to 1 or
lower, so this will be a wet/dense snow that will make for especially
slippery road conditions where snow does accumulate on the roads.
With the aid of upsloping, northern Houghton/Keweenaw counties will
see the most snow, ranging from 2 to 6 inches, greatest in the high
terrain. Accumulations will range down thru 1 to 4 inches across the
rest of the n and down to less than 1 inch toward the WI-MI
stateline and e along Lake MI. That all lines up decently with
utilizing isentropic ascent for snow accumulations - the duration of
best forcing on ~295k sfc (700-750mb) and the mixing ratios of 3-
4g/kg that are avbl. So, winter wx advy for northern
Houghton/Keweenaw counties is in good shape. A quick check of the
recently arrived 18z NAMnest and HRRR show an increase in qpf, so
trends will need to be monitored this evening for the potential of
more snow accumulation than currently anticipated.
Temps will remain steady or fall back to around freezing for most
areas this evening, then temps will very slowly rise overnight. By
12z, most of the fcst area should be at least slightly above
freezing except for the far e where easterly flow will help hold
temps back a bit. Late tonight, some fog will probably develop, and
it may become locally dense in the higher terrain central and across
the Keweenaw under e to se upsloping winds.
&&
.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 313 PM EST Sun Dec 8 2024
The above normal temperatures Monday give way to below normal
temperatures by Tuesday through the mid-week as Arctic air drops
down overhead and brings lake enhanced/effect snowfall over the
northwest to north-northwest wind snow belts; we may see several
inches fall over these snow belts during the middle of this week.
Moving late into this upcoming weekend, temperatures return to above
normal as warmer Gulf air moves in from our southwest. Additional
details follow below.
As the phasing low moves into Lake Superior Monday, the dry slot of
the low moves over most of the area throughout the day. As the
precipitation ends, expect any of the remaining precipitation to be
generally light rainfall across the area, with two exceptions.
First, a wintry mix of snow, sleet, and freezing rain is possible
over the far east Monday morning before transitioning to pure
rainfall ahead of the precipitation ceasing Monday afternoon.
Second, the Keweenaw could hold out and remain pure snow,
particularly north of the airport. That being said though, impacts
from any of the remaining precipitation on Monday will be very
minimal, limited to maybe a glaze of ice/dusting of snow in the east
and up to a sloppy wet inch of snow in the Keweenaw.
Moving into Monday evening, the cold front of the low pushes in a
band of snow showers from the northwest that could leave a dusting
up to an inch of wet snow across the west and central is it pushes
southeast throughout the early overnight hours. Behind this, as cold
air advection continues across the Upper Midwest, expect lake
enhanced snowfall to start up over the northwest wind snow belts
late Monday night, becoming pure lake effect by Tuesday morning.
This lake enhanced snowfall could bring a couple of inches over
mainly the west near Lake Superior as the lake enhanced snowfall
becomes pure lake effect over Monday night. The northwest-flow lake
effect snow continues through Tuesday.
The next time period worth looking at is around Wednesday, when a
Manitoba Mauler low moves through the Upper Midwest. While the axis
of coldest air and the low`s center are currently projected to miss
us to the west, we are still on track to get reinforcing cold air
and the transition back to lake enhanced snowfall over generally the
northwest to north-northwest snow belts. We could see several inches
of fluffy 20-30+:1 SLR snow fall across these snow belts from
Wednesday into Thursday. What`s interesting is that the Canadian
model suite shows a significant convergent band in the winds
occurring over Marquette County Wednesday. Should this suite be
verified, we could easily see a foot or more fall within Marquette
County between sunrise and sunset. However, confidence in this
solution still remains rather low at this point (I`d say a 30% or
less chance); it is more probable that a convergent band sets up
over western Alger County given the north-northwest flow, with
similar snowfall amounts expected (I`d think no more than 40%
chance). Regardless, should this convergent band occur, expect heavy
lake enhanced/effect snowfall that quickly accumulates on roads. In
addition, with winds being rather gusty from the nearby low, expect
blowing snow to be a problem along all of the Lake Superior
shoreline. Therefore, visibilities are expected to be rather poor
for driving on Wednesday; I wouldn`t be surprised if we issued
winter weather headlines across much of the northwest to north-
northwest wind snow belts due to the impacts of the passing low.
Expect the snowfall to transition back down to pure lake effect by
Thursday, and to back to the west wind snow belts throughout the
day. The last of the lake effect looks to end over our area by
Friday as warmer air begins pushing in from the southwest. However,
before the warmer air starts returning, expect high and low
temperatures during the middle of this week to be well below normal,
with Thursday and Thursday night being the coldest time period
(expect highs in the single digits to teens and lows in the single
negative digits to single positive digits).
Expect a warming trend this Friday through this upcoming weekend as
warmer air from the Gulf slowly pushes in from the southwest with
time. While there is significant model spread amongst the differing
medium range guidances, it does look like there is a chance to see
some precipitation this upcoming weekend. As for the precipitation
type, that is still up in the air and will be dependent on how fast
the warmer air creeps in and the tracks of any incoming shortwaves;
we could see the gambit between rain, snow, and anything else in-
between this upcoming weekend.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 650 PM EST Sun Dec 8 2024
Approaching low pres system will spread snow into Upper MI this
evening. The snow will mix with rain and even change to rain for
some areas. With the arrival of the pcpn this evening, expect
conditions to deteriorate thru IFR to LIFR at CMX/SAW tonight.
Conditions are more likely to fall to airfield landing mins at
CMX, but there is some potential for CMX or SAW to fall to blo
landing mins late tonight or during Mon morning due to upslope
flow, diminishing pcpn and thickening fog. At IWD, don`t
anticipate conditions falling to blo IFR tonight due to
downsloping southeasterly winds. Little/no improvement is
expected at any of the terminals until maybe late afternoon
Monday, and even then, LIFR/IFR conditions will be expected.
&&
.MARINE...
Issued at 313 PM EST Sun Dec 8 2024
East winds of 20 to 30 knots over the western lake this afternoon
veer to the southeast and strengthen to gales of 35 to 40 knots
along the International Border tonight as warm frontogenesis
strengthens and slowly pushes northwards across Lake Superior. As
the phasing low moves into Lake Superior by Monday afternoon, expect
the winds to weaken from west to east ahead of the low`s center,
before picking back up again from the north and eventually northwest
to 20 to 30 knots across the lake late Monday through Monday night.
While the winds do look to weaken to 20 knots or less Tuesday due to
the low lifting away, expect the winds to restrengthen to at least 20
to 30 knots from the northwest Wednesday into Thursday as a Manitoba
Mauler low digs into the Upper Midwest just west of the lake towards
the Lower Great Lakes; the NBM currently has around a 20 to 30%
chance of seeing low-end gales during this time period. In addition
to the strong winds, expect to see at least moderate freezing spray
over the open waters Wednesday into Thursday; I wouldn`t be
surprised to see this upgraded to heavy freezing spray in the future
with the inclusion of more higher-resolution models. As we head into
this upcoming weekend, expect the winds to weaken to 20 knots or
less by Friday as warmer air from the Gulf tries to advect in from
the southwest.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory until 7 AM EST Monday for MIZ001-003.
Lake Superior...
Gale Warning from 1 AM to 1 PM EST Monday for LSZ244-245-251-
264-266-267.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...TAP
AVIATION...Voss
MARINE...TAP