Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/25/24
Area Forecast Discussion
National Weather Service La Crosse WI
610 PM CST Sun Nov 24 2024
.KEY MESSAGES...
- Drizzle for many areas tonight, transitioning to snow towards
morning from northwest to southeast before ending. Most
locales should see minimal snow accumulation, but cannot rule
out a quick 1 to 2 inches north of Highway 29 (20-30% chance).
- Temperatures steadily cool through the week. Highs by Friday
will struggle to reach the low to mid-20s. Overnight lows next
weekend fall to the single digits with wind chills below zero.
- Confidence remains low in the snow forecast for mid-week and
beyond given that subtleties in the weather pattern will play
significant roles in snow amounts and timing.
&&
.DISCUSSION...
Issued at 230 PM CST Sun Nov 24 2024
Tonight - Monday: Drizzle, Transitioning to Snow
An elongated 1002-mb surface low was positioned over eastern
Kansas early this afternoon with an attendant warm front arcing
NE to E across central Iowa into north central Illinois. The
surface warm front advances slowly northward this afternoon and
tonight, but stays south and east of the forecast area. A moist
easterly fetch under the 800-700-mb warm front will saturate the
lowest 6-7 kft of the troposphere across the region tonight,
with modest 280-290K isentropic ascent through this cloud
shield--a classic drizzle setup. Given the light QPF and
resultant lower PoPs in the NBM, did manually increase PoPs to
the 50-80% range, values more reasonable for the sensible
weather impacts. The drizzle looks to set in around 00-03Z and
last through 09-12Z before the low passes to the south and cold
air advection ensues.
The main question in the forecast revolves around snow. The
broad and rather disorganized nature of the cyclone does not
lend us any favors in pinning down the rain/snow transition
times and snow amounts. The thicker clouds today kept
temperatures a few degrees cooler than earlier thought across
central Wisconsin, Given the shallowness of the above freezing
near-surface layer, snow is expected to begin 6 hours sooner
north of Highway 29 and amounts over Taylor County have been
increased to 1-2 inches. There is some concern that we may tap
into the secondary dendritic growth zone with a 200-300-mb
isothermal layer in the 0 to -5C region, so also increased snow
ratios to factor in this possibility. Roughly 20% of the HREF
members have 3-4 inches of snow in northern Taylor County.
Attention then turns to the backside of the system Monday
morning as sub-freezing air arrives. While the vast majority of
the short-range guidance have minimal precipitation/snow
amounts, the RAP has been the rouge outlier in strengthening the
low to mid-level frontogenesis band and bringing a quick period
of accumulating snow to the region, mainly north of I-90. Given
the shorter duration of the band, amounts should be limited.
Other convective models are warmer and weaker with the forcing,
but the steadfastness of the RAP does give one pause and
warrants further scrutiny tonight.
Monday Night - Next Weekend: Colder, Low Potential for Snow
The first surge of colder air drives southeastward during the
day on Monday with lows Monday night falling well into the
teens. Did trend cloud cover higher for Monday night given the
cyclonic flow pattern in place and early signal from the
RAP/HRRR long range runs that stratus may linger well into
Tuesday. Tuesday will be quiet and cool as a low-amplitude
shortwave ridge slides through. The main question will be cloud
cover, which is very difficult to ascertain at this range. The
LREF members still differ substantially on how far south the
upstream shortwave pivots with the GEFS and EPS still aligned in
their respective camps, but it is worth noting that the
operational 24.12Z EC has come into agreement with the 24.12Z
GFS in taking the surface cyclone over Missouri and Arkansas,
leaving the local forecast area dry. Will have to assess how
other ensemble members sort themselves out over the next 24
hours, but the forecast for Wednesday is trending drier.
This midweek wave ushers a reinforcing round of polar air
southward as highs slide further into the teens and 20s for the
end of the week. The operational NBM lows fall into the single
digits above zero for the weekend, with a 20% chance of lows
below zero, primarily west of the Mississippi River. The
northwesterly flow pattern for late week and the weekend makes
it difficult to nail down any snowfall potential at this range,
but there is a hint that we could see a clipper wave on
Saturday. Roughly 50% of the LREF members have this snow band,
but placements differ by several hundred miles. Have at least
brought PoPs to mentionable values in the forecast, but much can
change over the next six days.
Looking farther ahead, there is some hope for a rebound in
temperatures after next weekend, but there still exists a 10-20
degree spread in the guidance and most members keep temperatures
below climatological normals for this time of year.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 553 PM CST Sun Nov 24 2024
VFR/MVFR ceilings blanketed the area and will continue to see
more widespread MVFR ceilings develop this evening as a
shortwave trough moves into the area. Conditions will continue
to deteriorate with forecast soundings showing low level
saturation with IFR/Patchy LIFR conditions with drizzle and
light rain overnight into Monday morning. The forecast soundings
vary on the extent that the rain will mix with/change over to
snow with the seeding of snow from aloft,the low level -3 to
minus 5 deg C thermal layer, steep lapse rates, strength of
frontogenesis and how much dry air there is in the mid levels.
For now did mention a mix at KRST and could see a changeover for
parts of southeast MN into WI. Some minor accumulations are
currently forecast for Taylor Co., where surface temperatures
will be colder. Will need to monitor this though. Light east and
northeast winds shift around to the northwest after 07Z and
increasing 15 to 20kts with gusts 25 to 30kts.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Skow
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Columbia SC
704 PM EST Sun Nov 24 2024
.SYNOPSIS...
The air mass across the region will continue to moderate through
early in the week with temperatures rising to above normal. A
cold front with limited moisture will move through the area
Tuesday with a few light showers. A stronger cold front will
move through the area Thursday to Thursday night with scattered
to numerous showers. Below normal temperatures expected next
weekend as the coldest air mass of the season moves into the
region.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Key Message(s):
- A cool night ahead with some patchy fog along area rivers.
High pressure is steadily shifting east of the area, allowing
boundary layer flow up through 850mb to increase slightly. This
will allow for just enough turbulent mixing overnight to prevent
ideal cooling and decoupling like we had the last couple
nights. But moisture is still limited, so lows will still fall
to around 40F with good agreement across guidance. Some river
fog looks possible again since the mixing will be light, but the
airmass remains too dry away from rivers & lakes for fog.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
Key Message(s):
- Warmer weather through Tuesday ahead of a cold front.
- Isolated light showers Tuesday associated with the front.
Monday and Monday night...Low amplitude upper trough over the
northern Plains will move toward the Great Lakes region. This
trough will drive a weak cold front toward the Carolinas and
Georgia by Monday night. The surface ridge will be southeast of
the area with low-level flow increasing from the southwest.
This will lead to warmer temperatures due to warm advection and
continued weak subsidence and a modest increase in moisture
with precipitable water increase to above an inch overnight,
near 1.30 inches in the Piedmont. Highs around 70 and warmer
overnight lows due to an increase in clouds after midnight, low
to mid 50s.
Tuesday and Tuesday night...Timing differences remain with the
frontal passage as the ECMWF upper trough is more progressive and
the front clears the area early in the afternoon. The GFS appears
to hang it up through the afternoon. The grand ensemble mean
favors the faster solution. The models continue to suggest weak
forcing and limited low level convergence as low-level flow
appears westerly. Any qpf will be quite light. The probabilistic
QPF guidance remains fairly bullish on the probability of
measurable rainfall, especially in the western portion of the
forecast area. Amounts will be limited, however, with even high
end (10% exceedance) values less than a tenth of an inch. The mos
consensus suggests slight chance. If the front hangs up, light
showers could linger in the east later in the afternoon, so kept
pops up there. Warm day though with highs around 70 despite
clouds. Dry high pressure building east from the Plains, modifying
and setting up north of the area. Weak cold advection mainly
during the evening, lingering clouds until after midnight. Lows
mainly in the 40s, except upper 30s in the north Midlands closer
to the ridge.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Key Message(s):
- Scattered to numerous and isolated embedded thunderstorms
for Thanksgiving with breezy winds.
- Significantly colder weather late week into next weekend.
High pressure over the area Wednesday with seasonable
temperatures and air mass dry. A stronger and more potent upper
trough is expected to develop in the eastern CONUS by Thursday
into Friday. There remains significant synoptic differences
among the deterministic and ensembles. Low pressure is expected
to develop along a front in the Tennessee Valley Wednesday
night. ECMWF ensemble is stronger with the surface low
development and more progressive since the upper trough has more
amplification than the GFS and GEPS ensembles. The NBM highest
pops are Thanksgiving day through the evening then lower by
Friday afternoon as the front moves off the coast and upper
trough follows. Kept scattered to likely pops with ensemble qpf
around 0.5-0.75 inch with heaviest rain in the Piedmont. There
is potential for more widespread showers across the area through
Thanksgiving. Thunderstorms will be possible with some
instability noted especially over the southeast Midlands and
CSRA where surface CAPE may exceed 500 J/kg. 850mb south-
westerly winds may be near 50 kts. Strong gusty winds possible,
the ECMWF EHI CAPE and wind are elevated for Thursday.
Significant airmass change behind the cold front with NAEFS mean
indicating that 850mb temps will be below the tenth percentile.
Blended guidance likely not capturing the extent of this cold
air with bias correction indicating the blended highs and lows
are above the 75th percentile of the distribution. So lowered
temps over the weekend, especially min temps.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Low level moisture will increase tonight supporting patchy fog
development tonight. MOS and the HRRR suggest VFR through the
period but similar to the previous night we should at least see
fog near area rivers, including AGS. Therefore we added a TEMPO
group for AGS to cover the typical shallow fog that the site
observes frequently. Fog at the other terminals is less likely.
Winds will pick up out of the SW around 15Z Monday ahead of an
approaching front. No rainfall is expected through 00Z Tuesday,
however with moisture increasing ahead of the front, there may
be some low clouds and ceiling restrictions that develop near
the end of the 24 hour TAF period. At this point confidence is
too low to include in the TAFs.
EXTENDED AVIATION OUTLOOK...LLWS conditions will be possible
Monday night ahead of the approaching cold front. The front will
move through the area Tuesday with light showers possible. A
stronger front will move through the area Thursday to Thursday
night with thunderstorms and gusty winds possible.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...None.
GA...None.
&&
$$
Area Forecast Discussion
National Weather Service Dodge City KS
1003 PM CST Sun Nov 24 2024
.KEY MESSAGES...
- Gusty north winds and temperatures falling back into the 20s
tonight will result in wind chill values in the teens early
Monday morning.
- light rain showers or snow flurries are possible Wednesday
night, with no significant precipitation expected.
&&
.DISCUSSION...
Issued at 208 PM CST Sun Nov 24 2024
Short term models this morning are in good agreement and
consistent with previous runs, showing gusty north winds
developing early tonight as colder air moves into southwest
Kansas. The combination of cold air advection forecasted by CAMS
and a 5080% chance from the HREF of wind gusts exceeding 30
mph overnight will result in wind chills dropping into the teens
early Monday morning. A few locations along the I-70 corridor,
as well as areas west and north of Garden City, may even
experience wind chill values between 10 and 15 degrees (with a
2040% chance).
These unseasonably cool conditions will persist through Monday
night as a surface high builds across western Kansas. As the
surface high begins to settle into the region on late Monday,
gusty north winds will decrease, and lighter winds near the
center of the high will lead to chilly temperatures Monday night
into early Tuesday morning. CAMS remain in good agreement in
positioning the center of the surface high over south central
Kansas between 3 am and 9 am Tuesday, creating ideal conditions
for radiational cooling under clear skies. As a result, will
favor the cooler 10th to 25th percentile for lows Monday night
east of Highway 283. Further west, developing south winds in
response to falling pressures over eastern Colorado due to
improving westerly flow across the Rockies will keep
temperatures slightly higher, with lows still in the 20s but
warmer than those expected across south central Kansas.
The focus now shifts westward to the next upper level trough,
which ensemble clusters continue to show on track to cross the
Central Plains midweek. While ensembles still show some
differences in the strength and timing of this upper wave, there
is general agreement that the trough will move through the
Central Plains between Wednesday night and early Thursday
(Thanksgiving).
The 24 hour QPF differences from the ensemble mean suggest that
5060% of the clusters favor a wetter solution compared to the
grand ensemble as this system moves through midweek. However,
despite indications of a better chance for precipitation, the
progressive nature of the system still favors a low accumulation
precipitation event. This scenario is supported by ensemble
clusters 24-hour QPF probabilities, with the latest data
showing only a 20% chance of precipitation exceeding 0.1" from
this event and confined to west central and north central
Kansas.
Regarding snowfall amounts, it is too early to provide
specifics due to uncertainty in how quickly the atmosphere will
cool and the exact location of where the better forcing will be
when the rain transitions to snow. Current ensembles continue to
suggest that if any accumulating snow occurs, it will be north
and west of Dodge City, with little if any accumulations. The
NBM currently shows less than a 20% chance of snowfall totals
exceeding 0.5" along the I-70 corridor and across portions of
west central Kansas (west and north of Garden City).
Bottom line is this system midweek is a low confidence forecast
for any accumulating snow but warrants ongoing monitoring due
to holiday travel and the small potential for minor accumulating
snowfall. Latest probabilistic WSSI from WPC has only a 5-10%
for minor winter weather impacts along the I-70 corridor and
across west central Kansas.
Once the upper level trough passes, another shot of colder air
will move into southwest Kansas. This will keep temperatures
below seasonal averages, with highs in the 40s and lows in the
20s, through next weekend. Wind chills as low as 10 degrees will
be possible (20-40%) Friday morning in some areas of west
central and north central Kansas around Thanksgiving.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 957 PM CST Sun Nov 24 2024
Amended TAFS for current trend is stratus that is spreading
from north central Kansas southward. Current HRRR model would
suggest 1000 to 2000 ft ceilings would spread south impacting
terminals HYS and DDC, possibly GCK as well before clearing out
during the middle of the overnight. Gusty winds up to 30 knots
will persist during the period.
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Burgert
AVIATION...Russell
Area Forecast Discussion
National Weather Service Hastings NE
531 PM CST Sun Nov 24 2024
.KEY MESSAGES...
- A few flurries possible this evening mainly north and west of
the Nebraska Tri-Cities. No accumulation is expected.
- A light dusting of snow is possible on Wednesday. The chance
for 1" or more of snow is unlikely, with probabilities only
10-30% for an inch or more of snow (highest north of
Interstate 80).
- Well below normal temperatures arrive Thanksgiving weekend.
Single digit low temperatures are possible, and daytime highs
may remain below freezing in spots. Despite the much chillier
airmass, these temperatures are still 10-15 degrees warmer
then record cold temperatures for the date.
&&
.DISCUSSION...
Issued at 217 PM CST Sun Nov 24 2024
A cold front tracked southeast across the local area this
morning. This front...accompanied by gusty northerly winds...
helped to break up the dense fog that formed in spots, with
mostly sunny skies being observed by mid-morning for most
locations. Clouds have since started to filter in from the
north, rapidly approaching the I-80 corridor this afternoon.
Expect this cloud cover to eventually encompass the entire
forecast area by early evening, with even a few flurries
possible mainly north of the interstate as the associated upper
level wave tracks by. As of this afternoon, some very light
returns can be seen on radar across northeastern Nebraska, but
thus far, flurries have not moved into the local area. If they
do, it will likely be during the early to mid-evening hours as
depicted in HRRR and other meso-scale models.
While cloudy skies and breezy north winds will continue across
the local area overnight...expect clearing skies during the
morning hours to allow for ample sunshine to return again Monday
afternoon. Despite the sunshine, cold air advection behind the
aforementioned front will make for a seasonably cool afternoon,
with many locations likely struggling to reach 40 degrees. At
the same time, winds should be on the decrease through the
afternoon hours as the pressure gradient continues to weaken
across the local area in response to high pressure pushing in
from the northwest.
Behind todays cold front and associated upper level shortwave,
brief ridging aloft is expected for Tuesday, which should allow
afternoon temperatures to climb to near 50 degrees across the
local area, or about 10 degrees above normal for late November.
This will likely mark the warmest day of the stretch, as yet
another cold front will bring a small chance for snow and cooler
temperatures back to the area on Wednesday. This does not look
like a significant snowfall event, with very meager chances for
even a dusting of snow across much of the local area.
Thereafter...northwesterly flow will establish itself aloft
across the center of the county with a cold Canadian airmass
forecast to slide into the plains late next weekend. While again
the chances for precip look minimal, much cooler air will
filter in across the local area with high temperatures possibly
not climbing above freezing next Sunday with lows both Sunday
and Monday morning potentially falling into the single digits.
Thanks to the mild temperatures to start November (through the
23rd of the month, average temperatures for the month are about
5 degrees above normal), this will likely feel quite cold,
despite being a far cry from record cool temperatures for the
date.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 522 PM CST Sun Nov 24 2024
For KGRI/KEAR Airports:
Stratus clouds are expected to persist over the area this
evening and into the overnight hours as steady northerly flow
advects cloud cover south, with MVFR CIGS around 1.2 KFT to 1.5
KFT. CIGS should improve during the early morning hours Monday
with VFR conditions returning by around 25/10Z at both
terminals, and clear skies by 25/15Z. Winds will be from the
north to northwest through the period...remaining steady above
15 kts with gusts of near 25 kts overnight. Winds will
eventually decrease to around 8 kts during the afternoon hours
Monday.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
DISCUSSION...Rossi
AVIATION...Hickford
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
955 PM CST Sun Nov 24 2024
...New MESOSCALE UPDATE, AVIATION...
.MESOSCALE UPDATE...
Issued at 954 PM CST Sun Nov 24 2024
Rest of tonight...
Warm, moist southerly flow will keep a warmer night in store for
the Gulf Coast region. Low level flow is on the uptick, with
nearly 20kts at 925mb. HRRR fcst soundings around daybreak Monday
indicate an uptick in low-level moist advection, indicative of
saturation of the boundary layer & light sfc flow, while stronger
to the west. HREF probs of 40-60% indicate potential for lows
reaching near or even super-saturation. HREF/HRRR & other
aviation guidance indicate river valley fog formation. Radiative
cooling will be efficient, with HREF probs sfc dewpoints (Td)
above 60F & lows falling below that threshold, some 4-6F below
(53-55F). This could support at least some patchy to at times
patchy dense fog. Forecast was mostly on track, other than to add
some patchy dense fog & HWO graphic for late tonight into early
Monday morning. Lows will be seasonably warm (10-20F above) in
the mid-upper 50s (56-60F) west of I-55 & low-mid 50s (50-55F) to
the east. Updates are out. /DC/
&&
.DISCUSSION...
Issued at 252 PM CST Sun Nov 24 2024
Through Tonight:
Warm, moist return flow on the backside of departing surface high
is evident in afternoon cumulus field spreading north and east
across portions of LA and far southern MS this afternoon. The
returning moisture will boost overnight humidity levels and could
be a concern for patchy fog especially where winds go light to
calm by early Monday morning. Latest HREF probabilities for fog
development favored the Pine Belt and areas northward into east
central Mississippi, where currently clear skies would support the
best potential for radiational cooling and moisture advection to
overlap. Added patchy fog wording to the river valley areas east
of Interstate 55 overnight, but may have to upgrade fog messaging
if confidence in dense fog increases.
Monday through Sunday:
An upper-level short-wave trough moving east from the Plains on
Monday will bring the next cold front into our area late Monday
afternoon into the overnight, though moisture return should be
minimal enough to limit thunderstorm potential. Can`t rule out a
few rumbles of thunder overnight with weak elevated instability,
but mostly a mundane frontal passage is expected.
What will have more significance is the next shortwave crossing
the Rockies Wednesday into Thursday. This wave should spin up a
low pressure system in the Southern High Plains that quickly moves
east along the Interstate 40 corridor, with more moisture
recovery and warming occurring over our area in advance of its
arrival. Latest model guidance remains in poor agreement with the
timing of this low-amplitude wave, but a corridor of warm, moist
advection along the Mississippi River Valley will increase
instability Wednesday into Thursday regardless. While the wave
will be positively-tilted and low-level flow will become more
south-southwesterly ahead of the approaching system`s cold front,
a strengthening upper-level jet streak associated with the system
will intersect the developing warm sector along the Gulf Coast.
Modest wind shear and decent instability will likely support at
least a Marginal chance for severe thunderstorms as the system
moves through our area late Wednesday into Thursday. This does
include the Thanksgiving Holiday, so area residents and visitors
should pay attention to changes in the forecast and updates to
timing for best thunderstorm chances.
Potentially stronger high pressure arriving behind the cold front
should give us another chance for frost and freeze conditions
heading into next weekend. While there is less confidence than
usual for the Wednesday/Thursday pattern, more substantial
disagreements with trajectory and strength of arctic air mass
coming south out of Canada introduces even more uncertainties for
our region next weekend. Peaking a little ahead into early the
following week, this signal for potentially cold air mass
affecting the region persists for a few days. Will keep an eye on
the trends regarding freeze potential in the region. /NF/
&&
.AVIATION...
(06Z TAFS)
Issued at 954 PM CST Sun Nov 24 2024
VFR flight categories prevail, with sfc winds winding into the
evening. Southerly sfc winds will linger at northwest sites of GLH
& GWO while light in southeast MS TAF sites (I-59 & Hwy 84
corridors). In addition, low-level wind shear (LLWS) >30kts can`t
be ruled out at GLH & GWO, persisting through daybreak. Light
winds & moisture advection, especially nearby river valley
corridors, could lead to some MVFR patchy to areas of fog/BR to
even locally patchy dense fog. Can`t rule out brief sub IFR vsby
or stratus/ceiling near daybreak. These flight restrictions last
through mid-morning 25/14-16Z Monday. Southwesterly sfc winds
will be predominant after 25/15-17Z Monday, sustained up to 20mph
& gusts around 25mph. Low probs of light rain showers will build
in northwest TAF sites near the end of the 06Z TAF period, so
added some showers after 26/03Z Tuesday. /DC/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 56 78 52 65 / 0 10 80 10
Meridian 52 75 52 64 / 0 0 60 10
Vicksburg 58 80 49 64 / 0 10 50 0
Hattiesburg 53 79 58 69 / 0 0 50 10
Natchez 58 79 53 65 / 0 10 40 0
Greenville 58 77 44 59 / 0 20 40 0
Greenwood 57 77 46 62 / 0 20 60 0
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
DC/NF/DC
Area Forecast Discussion
National Weather Service North Platte NE
554 PM CST Sun Nov 24 2024
.KEY MESSAGES...
- Light snow will spread into northwest Nebraska this evening,
tapering off through midnight. Little to no accumulation is
anticipated.
- A colder airmass settles into the central US by the middle to
end of Thanksgiving week bringing a threat for wintry
precipitation Wednesday. However, any snow accumulations look
to be light at this time, from a dusting up to a half inch.
- Dry and turning colder for Thanksgiving Day into the holiday
weekend with highs in the 20s and 30s and lows in the single
digits and teens.
&&
.SYNOPSIS...
Issued at 235 PM CST Sun Nov 24 2024
Recent GOES-16 WV imagery and RAP 500-mb analysis showed a trough of
low pressure centered over the Canadian Maritimes. Just to the west
of this feature, upper-level ridging extended along the Mississippi
River Valley. An upper-level low pressure system was apparent over
southern Saskatchewan with a trough extending south-southwest along
the northern Rockies, approaching the northern Plains. The stubborn
upper-level low continues to spin off the coast of the Pacific
Northwest with an upper-level ridge building in just to the east
over the Intermountain West. All of these features combined has
resulted in southwesterly flow across western and north central
Nebraska. At the surface, the cold front that swept through the
local area this morning was continuing its southward trek across
Kansas with stout high pressure building in behind it. Northwest
winds have strengthened behind the front with 3 to 4mb/3 hour
pressure rises and cold air advection (CAA) increasing over the
local area. Recent area observations show widespread gusts of 20 mph
with peak gusts nearing 30 mph at VTN and BBW. Mid to high-level
clouds continue to move into the area with a stratus deck pushing
southward out of northern Nebraska into central Nebraska. Given the
cloud cover, temperatures have trended cooler across northern
Nebraska as compared to southwest Nebraska with 2 PM CT temperatures
ranging from 28 degrees at Gordon to 51 degrees at Imperial.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 235 PM CST Sun Nov 24 2024
A band of mid-level frontogenetical forcing over southeast Wyoming
into southwest South Dakota has tapped into increased moisture which
has resulted in the development of light snow/flurries this
afternoon. Forcing will gradually push east into the local area this
evening and tonight as the upper-level shortwave trough axis bisects
the northern Plains by 06Z Monday. This will allow for the light
snow/flurries to shift into northwest and north Nebraska this
evening, tapering off through midnight tonight. Although little
to no accumulation is expected, roads may be slippery at times
where snow has fallen. Breezy winds will persist overnight with
gusts of 25 to 30 mph as pressure rises and strong CAA continues
across the region. Our first of a series of cold air intrusions
expected through the week will certainly be felt tonight as
temperatures fall into the teens. These temperatures combined
with the breezy winds will result in brisk single digit wind
chills for Monday morning. If you don`t get your winter coat out
of storage for Monday morning, the opportunity will present
itself later this Thanksgiving week. Temperatures will struggle
to get out of the low 30s to low 40s on Monday, however,
southerly return flow will allow temperatures to rebound into
mid to upper-40s on Tuesday. Surface high pressure over the
region will allow for dry conditions to return Monday and
Tuesday.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 235 PM CST Sun Nov 24 2024
The main focus in the long term revolves around the next system
ejecting out of the Rockies mid-week, potentially impacting
Thanksgiving holiday travel across the region. As a heavily
tilted upper-level trough extending from the northern Rockies
into northern California advances eastward into the Plains
through Wednesday, a lee-cyclone will develop across southeast
Colorado driven by mid-level height falls and upper-level
divergence. The main surface low will track southeast into the
Oklahoma/Texas Panhandles, remaining well south of the area.
Despite this, a cold frontal passage will bring increased mid-level
forcing, resulting in a threat for light snow across western
and north central Nebraska. Although discrepancies exist
amongst deterministic guidance, 50% or more of the GFS and ECMWF
ensemble members highlight the potential for light snow,
accumulations of a dusting to 1". This fast moving system will
likely limit any significant snowfall accumulations across our
area, however, guidance continues to highlight greater winter
weather impacts further south and west in Colorado. Thanksgiving
travelers should continue to stay up to date on the latest
forecast and be prepared to make adjustments to your plans if
needed, especially those who may be headed to Colorado.
Dry and cold conditions settle in for Thanksgiving Day,
continuing into the holiday weekend as northwest flow aloft
increases. Temperatures will fall into the 10 to 15 degrees
below normal range during this period. Highs will struggle to
get out of the 20s and 30s with lows falling into the single
digits to teens each day through the weekend. This is caused by
a ridge developing over Alaska and northern Pacific, favoring
surface high pressure to build southward into the central CONUS
by late next weekend, continuing into the 7 o 10 day range.
Fortunately this cold snap doesn`t appear to stick around for
long as ensemble guidance suggests an upper-level ridge will
slide into the western CONUS allowing temperatures to climb back
into seasonal values (low 30s) for the start of December,
perhaps even above normal for western portions of the state.
This is highlighted by the 8-14 Day CPC Temperature Outlook
favoring above normal to near normal temperatures across western
and north central Nebraska.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 554 PM CST Sun Nov 24 2024
There will be a threat for MVFR ceilings, mainly this evening at
both the KLBF and KVTN terminals. Look for ceilings to improve
by late evening, then scatter out overnight. Skies will be
mainly clear on Monday with only a few to scattered clouds
possible above 20000 FT AGL. Northerly winds will be gusty this
evening with speeds around 20 to 25 KTS, diminishing to 10 to 15
KTS Monday morning.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Viken
SHORT TERM...Viken
LONG TERM...Viken
AVIATION...Buttler
Area Forecast Discussion
National Weather Service Marquette MI
937 PM EST Sun Nov 24 2024
.KEY MESSAGES...
- Light to moderate snow spreads northward into the UP after
midnight, continuing through Monday evening. Some rain will
mix in with snow closer to the Lake Michigan shorelines.
- Snow accumulations of 3 to 6 inches expected for much of the
interior UP through this evening, with lower totals along the
Great Lakes shorelines.
- A Winter Weather Advisory has been issued for late tonight
through Monday evening. Slippery travel conditions are
possible for the Monday morning commute.
- Temperatures will become below normal for this time of year
by late this week.
&&
.UPDATE...
Issued at 936 PM EST Sun Nov 24 2024
Persistent onshore flow and steep low-level lapse rates/weak
instability continues to result in lake effect snow showers over
Marquette County this evening. Models are struggling to depict this
activity, with moisture likely a bit deeper than models are
indicating. Although just a dusting is expected before the main
system arrives later tonight, temps are getting cold enough for it
to stick to untreated roadways, so some locally slippery conditions
are possible.
Otherwise, the leading edge of the synoptic-scale precip has made it
into Menominee County, where temps are warm enough for rain. Made
slight adjustments to PoPs but overall the forecast remains on
track. Did make a few headline adjustments: 1) extended advisory for
western/central UP through 00Z Tue (7 pm EST Mon), and 2) issued
advisory for Alger, northern Schoolcraft, and Luce, from 09Z tonight
through 06Z Tue (4 am tonight through 1 am Tue EST). That should
cover the synoptic system, but lake effect will continue for the NW
snow belts, so some headlines may need to be extended.
&&
.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 304 PM EST Sun Nov 24 2024
Weak ridging extending southward from surface high pressure over
Ontario and Manitoba is turning winds easterly this afternoon, with
lingering spotty lake effect snow showers over the north-central UP
shifting westward in response. With limited moisture aloft as
inversion heights continue to lower, it is not out of the question
that we see some freezing drizzle mixing in with these before we dry
out completely, but impacts will be limited. Otherwise, much of the
UP remains under a blanket of low stratus, with some breaks in the
cloud cover across the west and south-central. This is helping to
limited temperatures to the lower to mid 30s across most of the UP.
Meanwhile, water vapor imagery and RAP analyses reveal midlevel
shortwave action over the Canadian Prairies and the Rockies. These
two features phase this evening and swing into the Upper Midwest,
with a surface low closing off and heading towards southern Lake
Michigan by early Monday morning. Resulting isentropic ascent will
kick off a round of precipitation across central WI late tonight
that will work northward into the UP. Simulated reflectivity
continues to favor onset time more towards 06Z in the southern UP as
midlevels moisten up, with precipitation continuing to spread
northeast through sunrise. Ensembles show a widespread 0.10-0.20in
of QPF across the western and central UP from 06-12Z, with higher
totals near a quarter-inch closer to the WI border. Soundings
generally favor a wet snowfall, though warmer (if still below-
freezing) profiles, especially in the south-central UP, would
indicate a better potential for some sleet to mix in. Some NAM
profiles do continue to show a weak above-freezing warm nose aloft,
so some freezing rain would not be out of the question. However, will
note that the more northerly NAM track (which brings warmer air into
the UP) remains an outlier among the guidance. With SLRs up to 8-
10:1 across most of the UP, and below 5:1 closer to Lake Michigan, a
slushy 1-2in of snowfall is expected across the western UP by
sunrise Monday, with higher amounts up to 3in possible. East of M-
95, expect to wake up to an inch or less of snow. With more snowfall
on the way after 12Z Monday (discussion continues below), a Winter
Weather Advisory has been issued for the western half of the UP.
&&
.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 416 PM EST Sun Nov 24 2024
The work week starts off with snow over much of the UP with a wintry
mix of rain and snow (possibly including sleet in Menominee and
Delta counties) hugging the shores of Lake MI Monday morning. This
stratiform precip continues lifting north into the afternoon hours
as the sfc low over southern Lake MI moves northeast toward the
thumb of Lower MI. SLRs are likely to hold around or below 10:1 with
the system snow as sfc temps begin to warm back up. The highest snow
ratios are expected in the north and west due to close proximity
with the colder airmass accompanying the mid level trough. Some lake
enhancement off northern Lake MI is also possible Monday morning,
given the southeast winds aloft and 850 mb temps around -1C to -2C
over the warm waters of 10-12C. This lake enhancement is being
picked up by the 11/24 12Z NSSL/HRRR and 18Z HRRR, but weakly noted
in the last few RAP model runs with a lower magnitude. They place a
small corridor of up to around 4-6" of snow over Menominee and into
the lakeshores of Delta county through ~18-20Z Monday. This
enhancement has some bust potential given the placement of the sfc
low and the circulations aloft, but will monitor it with upcoming
forecast packages. Around 0.2 to 0.4" of additional QPF associated
with the synoptic precip is likely during the day on Monday.
The 11/24 12Z HREF probabilities of at least 4" of snow through 18Z
Monday (10:1 SLR) are between 40-80% over the west and 20-50% over
the east. Also with the latest GFS/ECMWF/Canadian ensembles, there
is ~50-80% chance for at least 3" or more over the west; about a 10-
20% increase from previous ensemble runs. Given the QPF and SLRs,
the forecast total is between 2-4" of wet snow with potential for
localized totals up to 6". This would create some slippery roadways
affecting the Monday morning commute; hazardous conditions may
continue into the afternoon and evening hours with a transition over
to LES. Opted to hoist a Winter Weather Advisory for travel impacts
as well as wet snow accumulations Marquette and Dickinson counties
westward. Eastern counties may be added and/or advisories may be
extended in future forecast packages.
As we move to Monday evening, the sfc low will be tracking through
Lower MI and the mid level trough will begin swinging through the
Upper Great Lakes. This will begin to usher in a much colder airmass
that continues through the extended forecast period. Northwest flow
brings 850mb temps down to around -8C by Tuesday morning with as low
as -12C possible over the far western waters of Lake Superior. Given
the anomalously warm Lake Superior sfc temps ~8C, this will be more
than sufficient for LES. This pattern of west-northwest to northwest
LES is expected to continue over the CWA through the rest of the
forecast with 850mb temps gradually lowering to -12C to -14C across
the region by next weekend. A period of weaker LES is likely
Wednesday and Thursday as weak ridging moves through the Upper
Midwest. LES then should be re-invigorated moving into next
weekend/early the following week as broad troughing over the Great
Lakes sends multiple shortwaves down through the region. This snowy
pattern should result in several inches of snowfall over the course
of the extended forecast, impacting holiday travel plans into early
December. Otherwise, temps trend to below normal by late this week.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 708 PM EST Sun Nov 24 2024
VFR/MVFR conditions continue through the evening with light lake
effect snow showers at SAW, however, deteriorating cigs/vis are
expected at all TAF sites overnight into Monday morning as low
pressure moving through Lower Michigan overspreads wet snow across
the UP. Snow will spread north overnight, beginning at IWD first
around 06z, then at CMX and SAW closer to 09z. IFR conditions are
expected to begin (>80% chance) shortly after snowfall arrives.
Confidence is also high (>80%) that visibilities at all sites will
fall through the early morning, lessening to 3/4SM around ~15z and
persisting through the rest of the day. Winds will be light, gusting
to near 10 knots out of the east/northeast.
&&
.MARINE...
Issued at 416 PM EST Sun Nov 24 2024
East winds up to 20-25 kts over the far western third of the lake
diminish this evening. Meanwhile, northeast winds over the east half
of the lake veer east for tonight as a Colorado low pressure system
approaches from the southwest. Winds then remain 20 kts and less
tonight through most of the day Monday as the Colorado low begins
moving over the Great Lakes, phasing with another low coming from
the northwest. As the newly phased low moves through Lower MI Monday
afternoon into Monday night, winds do gradually back north. Winds
then re-invigorate up to 20-30 kts Monday night through Tuesday
evening behind a cold front. A few gale force gusts up to 35 kts are
possible on Tuesday, but only a low chance (25% or less) is noted on
internal probabilistic guidance between Marquette, Stannard Rock,
and Grand Marais. Overall, strongest winds are expected over the
southern half of the lake. Expect the winds to gradually weaken
Tuesday night as weak ridging moves through the Upper Midwest, with
winds becoming 20 kts or less again by Wednesday morning. However, a
shortwave dropping down from Canada on Friday brings additional
potential for winds to increase into the 20-30 kt range.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory from 1 AM EST /midnight CST/ to 7 PM
EST /6 PM CST/ Monday for MIZ001>005-009>011-084.
Winter Weather Advisory from 4 AM Monday to 1 AM EST Tuesday
for MIZ006-007-085.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
UPDATE...Thompson
SHORT TERM...LC
LONG TERM...Jablonski
AVIATION...BW
MARINE...Jablonski
Area Forecast Discussion
National Weather Service Phoenix AZ
421 PM MST Sun Nov 24 2024
.UPDATE...Updated 00Z Aviation Discussion.
&&
.SYNOPSIS...
Temperatures will remain above normal across the region through the
next week, with dry conditions prevailing and periods of mostly
cloudy skies. A weather system will pass the Desert Southwest to the
north during the middle of the upcoming workweek, but precipitation
chances should remain confined to northern Arizona.
&&
.DISCUSSION...
The region still finds itself between a broad area of negative H5
height anomalies over the Pacific Northwest centered offshore, and a
broad area of positive height anomalies centered over Baja
California and into Sonora. The resultant tightened pressure
gradient aloft has led to stronger zonal flow, with 500 mb RAP
analysis showing speeds between 50-65 kt over the forecast area.
This strong, zonal flow will continue to bring moisture-laden air
in the middle and upper levels inland, increasing cloud cover
over the course of the day that should persist through Monday.
Thanks to the increased cloud cover, highs today across the lower
deserts should be a few degrees cooler than what was observed
yesterday, mostly in the middle 70s, and overnight lows will be a
few degrees warmer. Similar highs are forecast Monday as well.
Quasi-zonal flow should persist over the region through much of the
upcoming workweek, though with slight variations in heights aloft,
the strength of the flow, and moisture aloft. Ensembles are in
excellent agreement that H5 heights will build during the latter
portion of the day on Monday into Tuesday, peaking around 582-585
dam over southern AZ. This will shift the stream of moisture further
north, temporarily clearing skies, and likely causing the warmest
afternoon highs of the next 7 days to occur on Tuesday, in the upper
70s to around 80F, followed by the warmest overnight lows Wednesday
morning. Latest NBM output shows widespread lower desert lows in the
50s Wednesday morning, with a 40-60% chance of temps staying at or
above 60F overnight in the typically warmer locales.
On Tuesday night, the return of thick cloud cover above the 500 mb
level will also be a factor in keeping overnight lows relatively
mild. Cloud cover will return as the Pacific Northwest low finally
moves onshore, suppressing heights aloft, once again tightening the
pressure gradient overhead, and thus drawing upper level moisture
back over the region. This weak shortwave will cause little in the
way of sensible weather impacts, though widespread breezy conditions
may develop behind a dry cold front that is expected to pass over
the area. Highs should drop a few degrees Wednesday, and flow aloft
will shift out of the northwest in the wake of the shortwave trough
as it passes north of the Desert Southwest.
Cluster analysis shows decent agreement between ensemble membership
even beyond midweek. All clusters depict a ridge over the
Northeastern Pacific, undercut by a closed low well offshore
centered approximately along 30 degrees north. Both features
approach the west coast late week. With continued quasi-zonal flow
during the latter half of the upcoming workweek, and an upstream
source for moisture aloft (the aforementioned closed low), GFS bufr
soundings indicate fairly persistent cloud cover. Latest NBM
deterministic output reflects this, as forecast temperatures stay
quite stable Thursday onward, with highs in the low to mid 70s and
lows in the upper 40s and 50s for the lower deserts. These forecast
temperatures are still around 5 degrees above average. Whether the
closed low can bring appreciable precipitation chances to
portions of the region next weekend is still a key forecast
uncertainty. As of now, PoP remain low next weekend, mostly below
20% across the forecast area.
&&
.AVIATION...Updated at 2320Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:
Winds will continue to follow their typical diurnal pattern with
speeds generally remaining aob 8 kt. Extended periods of light and
variable to calm winds can also be expected, especially during
wind shifts. High cirrus clouds will continue with a SCT layer of
clouds around 15 kft and a BKN-OVC cloud layer around 20 kft.
&&
.FIRE WEATHER...
Dry and warmer than normal conditions will persist across the
region for the next several days. Winds will follow generally
light and diurnal tendencies through Tuesday before some areas,
mainly across parts of the Arizona high terrain and Lower Colorado
River Valley, pick up some marginal breeziness Wednesday and
Thursday. Regional moisture content will be on the increase today
with MinRH values between 25-35% across the western districts.
Values across the eastern districts will only be 15-20% this
afternoon, but will increase to 20-25% by Monday afternoon. Fair
to good overnight recoveries can be expected through the middle
portion of the week.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Whittock
AVIATION...Berislavich
FIRE WEATHER...RW
Area Forecast Discussion
National Weather Service Pueblo CO
508 PM MST Sun Nov 24 2024
.KEY MESSAGES...
- Cold front drops through the plains this evening.
- Snow picks up over the Continental Divide this evening,
leading to wintry mountain conditions and cooler temperatures
across the area for Monday.
- Precipitation returns late Monday through early Thursday,
with snow for the mountains and mixed precipitation modes
elsewhere.
- Quieter weather returns Friday into Saturday.
&&
.UPDATE...
Issued at 502 PM MST Sun Nov 24 2024
Have allowed the high wind warning for Huerfano County to
expire, as observed winds were below criteria, and HRRR shows a
rapid drop-off in gusts this evening.
&&
.SHORT TERM /THROUGH MONDAY/...
Issued at 219 PM MST Sun Nov 24 2024
An upper-level low is currently moving along the Canadian border,
heading eastward. As it moves, the upper-level flow will shift, and
a fast-moving trough will pass over our area Today and Tonight,
leading to some changes to our weather. Main concern for the rest of
today will be gusty west winds coming off of the mountains. Gusts
over 30 mph will be frequent over the higher terrain through this
afternoon, and areas just east of the mountains on I-25 could be
seeing some gusty winds as well. Highest probabilities of gusty
crosswinds will be over the southern I-25 corridor, mostly around
gap flow areas.
An influx of moisture and orographic lift will bring snow showers to
the Continental Divide, starting this afternoon and lasting into
Monday. Accumulations will be highest over the west and northwest-
facing slopes, but even then total snowfall amounts look minor at
this time, with 3-5 inches or so at most by Monday afternoon.
Meanwhile, a cold front is expected to pass south across the eastern
plains later today, cooling down temperatures for tomorrow. Monday`s
highs will be in the 40s across most of our area tomorrow, with
cooler temps over the mountain peaks.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Issued at 219 PM MST Sun Nov 24 2024
Monday Night - Thursday: For much of the week, active weather is
expected for portions of south central and southeastern Colorado.
Zonal flow will be in place for Monday night into early Wednesday,
with an embedded shortwave pushing over the region throughout the
day Wednesday and exiting late Wednesday into Thursday. With the
zonal flow and wave, persistent orographic forcing is expected along
the mountains, with broader synoptic ascent/support increasing with
the wave passage. In addition, an atmospheric river will extend well
inland from the Pacific, bringing a surge in moisture. With the
increased forcing and moisture, precipitation is expected for much
of the region, favoring the mountains and valleys through most of
this timeframe, but expanding to the plains during Wednesday into
Thursday. With that all said, precipitation for the higher terrain
will remain all snow throughout this period, whereas the valleys
will have periods of snow and rain/snow mix and the plains will have
rain and rain/snow mix during the day Wednesday transitioning to all
snow Wednesday night into Thursday. As of right now, any major
impacts to travel are expected to remain along the mountains where
the heaviest and most persistent snow will fall, though some minor
impacts to travel will possible elsewhere given the rain/snow and
snow during cooler periods of the days. While some precipitation is
expected to extend into Thursday morning, most precipitation present
is anticipated to dissipate during the day. Beyond all of that,
breezy winds and mostly cloudy to cloudy skies are expected for much
of this timeframe, with lighter winds and clearing skies for
Thursday. Looking at temperatures, Tuesday will be the warmest day
and above seasonal values ahead of the more inclement pattern. Then
for Wednesday and Thursday, a cool down to below seasonal
temperatures is expected given a cold front passage Wednesday.
Friday - Saturday: For the end of the week, quieter weather returns
for south central and southeastern Colorado. Flow will become more
northwesterly behind the inclement pattern earlier in the week.
Given the lack of major forcing and decreasing moisture, dry
conditions are expected to prevail. The exception to this will be
isolated snow showers along the mountains given at least modest
orographic forcing persisting. Otherwise, relatively light winds and
periods of mid to high level clouds are anticipated for south
central and southeastern Colorado. As for temperatures, cool and
below seasonal values remain thanks to the northwesterly helping to
slow any warming.
&&
.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 433 PM MST Sun Nov 24 2024
For KCOS and and KPUB..VFR conditions are expected for the next
several hours, before MVFR and IFR ceilings become possible at both
stations. A cold frontal boundary is currently pushing through KCOS
as of 2330Z, and is expected to reach KPUB by 01Z. North winds
gusting from 25kt to 28kt are expected along and behind this
boundary this evening, and will likely persist through much of the
overnight hours. As winds begin to weaken and shift more easterly
and southeasterly, low-level cloud will increase over both stations,
with MVFR and IFR ceilings possible from 10Z through around 15Z
tomorrow morning. Some light snow or rain/snow mix will be possible
through the overnight hours as well, especially at KCOS, though
chances were too low to include in the TAF at this time. Sky
conditions improve after 15Z tomorrow, with weaker southeasterly
winds persisting through the remainder of the period.
For KALS..VFR conditions are expected to prevail throughout the TAF
period. Low and mid-level cloud cover will decrease through the
overnight and early morning hours. Winds will remain mostly
westerly and southerly throughout the period, with gusts
remaining below 15kt after 02Z this evening.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from late Monday night through late
Wednesday night for COZ058.
Winter Storm Watch from Monday evening through late Wednesday
night for COZ060-066-068.
&&
$$
UPDATE...PETERSEN
SHORT TERM...GARBEROGLIO
LONG TERM...SIMCOE
AVIATION...EHR