Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/25/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
832 PM MST Sun Jan 24 2021
.UPDATE...
Issued at 819 PM MST Sun Jan 24 2021
Forecast appears to be on track this evening. Some weak showers
have drifted off the foothills earlier this evening but dissipated
as they moved into the Denver area. Additional showers upstream as
they next system moves toward the OK/TX panhandles tonight into
Monday morning. Generally light snowfall expected overnight with
the best chance of accumulating snow over the plains of ecentral
and northeast CO late tonight into Monday morning. Still do not
expect much impact from this system in metro Denver at this time,
with isolated to scattered showers overnight.
&&
.SHORT TERM...(This evening through Monday)
Issued at 229 PM MST Sun Jan 24 2021
Satellite and radar showing shallow convective showers spreading
northeast across the high country, and some virga across the
plains. One weak wave has already moved through Summit County, but
expect a couple more waves late this afternoon into early evening
per upstream observations. Accumulations of an inch or two will be
possible with these in the Summit/Park County areas. Some of the
showers will be spreading down through the foothills, and we`re
still seeing a large variation in potential for showers stretching
across the plains. At this point, think the convective allowing
models (CAMs) like the HRRR are still overdone given the dry
downslope layer just above the boundary layer, while the global
models look underdone. The 12Z NAMNEST looked most realistic with
scattered showers but not much accumulation across the plains,
although the latest NAMNEST was more bullish. In any case, it may
end up like last night where a couple spots in the lower
elevations get a quick half inch of snow, but most places would
only see a dusting or brief flurries.
Later tonight, we`ll start dealing with the effects of the main
weather system ejecting out of the Desert Southwest. QG lift will
be increasing with the best lift organizing over the eastern
plains. There has been slight trends to the northwest and a
stronger, earlier development. That will be favorable for more
snow across the plains late tonight and Monday morning. Right now,
it looks like widespread snow will stay just east and southeast
of Denver, but place like Limon and Akron to around Julesburg
should be able to pick up a couple inches of snow from this first
wave. Snow will then decrease tomorrow afternoon, except in the
mountains where another round of showers develops with sufficient
moisture and instability.
.LONG TERM...(Monday night through Sunday)
Issued at 229 PM MST Sun Jan 24 2021
Our continued long duration light snowfall will be ongoing at the
start of the forecast period. Initially, there should be two
areas of more widespread snow - over our far northeast plains, and
across most of the Front Range/Foothills on Monday night. There`s
not a ton of synoptic scale lift overnight, though there is
enough of a weak upslope component and steep enough lapse rates to
promote at least scattered snow showers through the night.
Accumulations overnight will generally be 1-3 inches in the
aforementioned locations, with little to no snowfall between I-25
and a line from roughly Sterling to Limon.
A second shortwave will swing across the state Tuesday, bringing
another round of widespread light snowfall to the area. Most
guidance is in good agreement showing increasing QG ascent and
shallow upslope flow through the day. Best timing seems to be late
morning to late afternoon for the plains, with another inch or
two likely, and the best chance of accumulating snow for metro
Denver and Fort Collins. Snow departs the area from west to east
overnight as moisture and lift rapidly shift away from the state.
The only exception to this may be over the Park Range overnight
where shallow moist layer and weak upslope flow over a deep layer
of steep lapse rates could allow for snow showers to continue
through early Wednesday morning.
By Wednesday, ridging begins to take over and a warmer and drier
trend starts. There`s still some cold air overhead on Wednesday,
and combined with a fresh (but shallow) snowpack, we probably
won`t see highs any warmer than 40F. Temperatures look much warmer
on Thursday and Friday, with highs in the low to upper 50s over
the plains. Another trough finally begins to impact the weather by
next weekend, though for now it looks like most of the impacts
would be limited to the higher terrain.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 819 PM MST Sun Jan 24 2021
Ceilings are expected to lower again through the course of this
evening. Isolated light snow showers will be possible this evening
but a trace at best. Ceiling heights are expected to lower into
the 1000-1500 foot range 05Z-09Z, but timing and certainty of
this is difficult as it revolves around evolution of the Denver
Cyclone. Latest satellite this evening show these low clouds east
of FNL and around Limon.
The cyclone should in effect pull low clouds and stratus back
southward across the Denver area TAF sites. Later tonight, there
is a chance of light snow redeveloping toward 12Z as a storm
system begins to organize to our southeast. At this time, only
expect a dusting of light snow possible once again through Monday
morning as the bulk of the snow should stay over the eastern
plains of Colorado. Expect some lifting and breaking of the
stratus deck toward 18Z Monday. Lowering ceilings and some light
snow will return to the terminals Monday evening.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Cooper
SHORT TERM...Barjenbruch
LONG TERM...Hiris
AVIATION...Cooper
Area Forecast Discussion
National Weather Service Grand Forks ND
900 PM CST Sun Jan 24 2021
.UPDATE...
Issued at 850 PM CST Sun Jan 24 2021
Light snow continues to slowly expand overcoming dry northeasterly
air. The strongest radar returns and lowest visibility this
evening have been in the Harvey to Carrington area just southwest
of the FA. Expecting that area of moderate snowfall to slowly work
to the east northeast into southern Devils Lake basin. Still
expecting 1 to 3 inches in the southern Devils Lake basin with
under an inch in the Red River valley.
UPDATE Issued at 621 PM CST Sun Jan 24 2021
Light snow beginning to develop as expected across central ND and
into the western portions of the Devils Lake basin. Accumulations
will depend on saturation with dry easterly flow slowing the
eastward progression of the snow area this evening. HRRR solns
continue to keep much of the valley dry from this easterly flow
whereas the RAP continues to bring about an inch to GF. Will need
to monitor radar trends and the CAMs this evening to refine
PoPs and snow amount for the overnight.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 237 PM CST Sun Jan 24 2021
Main focus within the short term will be snow tonight into Monday
AM within Devils Lake basin into northern/central RRV. This may
impact the Monday morning commute. Wind chills dip below -25 F for
international border counties, hence a Wind Chill Advisory has
been issued.
Forcing mechanisms that will be responsible for tonight`s
snowfall are manifesting themselves nicely on satellite, radar,
and objective mesoanalysis. Synoptic lift assoc with a subtle mid
level wave driven by entrance region jet dynamics is shown
through textured, colder cloud tops in western ND via satellite.
With the jet progressing east, synoptic lift will also trek east
into eastern ND later tonight. Ahead of the wave, low level WAA
and increasing theta-e (also apparent on satellite through
northward moving stratus out of SD) is lending to isentropic lift
already apparent over central ND through radar returns. This
initial snow is battling dry near surface layer as apparent
through virga on area webcams, but should help pave the way of
saturation for when better upper support moves over the area. As
the wave nears, snow production is expected to be near the head of
a weak but advertised H8 LLJ nosing into the Devils Lake basin by
06 UTC. This will help focus lift in the H8-H7, feeding a small
area and progressive area of fgen. Additionally, forecast
soundings suggest deep saturation within the DGZ between 100-200
mb collocated with maximum lift. This lends confidence in high
snow ratios greater than 20:1, esp with a lack of wind shear
expected. While QPF amounts will be light, this efficient snow
production should lead to a fluffy 1-3 inches of snow near the
Devils Lake basin. Lesser amounts are expected into the central
and northern RRV as synoptic lift decreases and the H8 jet
dissipates.
Most snowfall should fall within the 00 - 12 UTC timeframe Sunday
night into early Monday morning. Impacts to travel may be
possible through moderate snowfall rates leading to reduced
visibility to a half mile at times, as well as slick travel
conditions from accumulating snow. This is especially true within
the Devils Lake basin during the Monday morning commute. Winds
will be relatively light keeping drifting/blowing snow concerns
low. While accumulating snow is expected to end around 12 UTC,
lingering flurries will be possible for northern counties
throughout the day tomorrow.
Cold temps already in place near the international border will
combine with just enough of a light wind to present wind chill
values near or below -25 F. Thus a wind chill advisory has been
issued for these counties starting midnight tonight lasting
through Monday morning.
Cold conditions continue into Monday night. May need to re-
evaluate for another night of wind chill headlines for northern
counties Monday night into Tuesday morning.
.LONG TERM...(Tuesday through Sunday)
Issued at 237 PM CST Sun Jan 24 2021
The probability for weather related impacts for Tuesday through
Thursday will be minimal. Temperatures will struggle to climb out of
the single digits Tuesday and Wednesday, with low temperatures in
the single digits to teens below zero. Heading into Thursday,
temperatures moderate slightly, with near average teens for highs
and lows in the single digits either side of zero. For Friday and
the weekend, unsettled weather is possible, with a chance for snow;
although much uncertainty surrounds the exact scenario, impacts are
possible through the weekend.
Low H5 heights and 850 mb temperatures in the -22C to -12C range are
expected Tuesday and Wednesday. The biggest challenge will be the
low temperature forecast, as cloud cover will impact radiative
cooling potential. Overall, lows will fall into the -14 to -3 degree
range across the area. The lower H5 heights push to the east heading
into Thursday, with somewhat strong shortwave ridging filling into
the region late in the day. Some temperature rebound is possible;
however, with a strong southwest to northeast jet, situated across
the Central Plains, WAA will be minimal. This translates to highs
generally in the teens to middle 20s with split flow across the
Northern Plains and Upper Midwest.
As the H5 split flow pushes east, we see the upper flow turn more
southwesterly, allowing temperatures to rebound into the middle to
upper 20s Friday and Saturday. Moisture advection will also take
place, with precipitation chances increasing ahead of an upper
trough, that will move southeastward out of Alberta Saturday
afternoon and evening. As previously mentioned, confidence in this
solution remains low; however, there is growing ensemble support for
an increased chance for snow Saturday into Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 621 PM CST Sun Jan 24 2021
FAR and BJI are expected to remain VFR for the period with light
snow and MVFR CIGs expected at DVL and GFK tonight into tomorrow.
TVF may see MVFR CIGs and light snow though this location is much
more uncertain as drier easterly winds create less confidence of
snow reaching that far east.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Wind Chill Advisory from midnight tonight to noon CST Monday for
NDZ006>008-015-054.
MN...Wind Chill Advisory from midnight tonight to noon CST Monday for
MNZ004-005.
$$
UPDATE...JK
SHORT TERM...CJ
LONG TERM...Lynch
AVIATION...JK
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
929 PM CST Sun Jan 24 2021
.UPDATE...
Issued at 922 PM CST Sun Jan 24 2021
Challenging forecast for the significant winter storm expected
across portions of Nebraska and Iowa Monday and Monday night.
Influx of dry air on the northern edge is expected to produce a
very sharp gradient in snowfall totals. Previous guidance
suggested this cutoff would largely be south of our forecast area,
however a slight northward trend in the 18z guidance has
continued/maintained in the 00z guidance and leaves some doubt
that the Hwy 20 corridor will be spared impactful snowfall. 00z
HRRR and WRFs still more robust with this dry push and largely
reflect the previous forecast. 00z NAM/NAM Nest and 21z RAP/SREF
are much more concerning bringing at least Advisory level snow
into the Hwy 20 corridor in Iowa. There is also a notable trend
upward in the SREF mean plume diagram for Sioux City over the last
several runs.
Still believe a pronounced push of dry air will keep the northern
edge of the snowfall in check but confidence is far lower than it
was a day or two ago. Have increased POPs and QPF somewhat but
will wait for the full suite of 00z guidance to come in to make
any whole-sale changes (if even necessary).
&&
.SHORT TERM...(This Evening through Monday)
Issued at 221 PM CST Sun Jan 24 2021
Stratus will be the main concern for the next couple of days as a
very strong system passes to the south. Drier air still wrapped in
place across the area and will play a roll in stratus expectations
through tomorrow. Going into tonight expect the stratus near the
Missouri River into northwest IA to expand a bit north as low
pressure develops to the south. By late morning into the afternoon
low pressure will move to the southeast of the area and start to
advect this dry air more southwest. This should really eat away at
the stratus and bring improving sky conditions to many locations.
May even see some slightly quicker drying and slightly stronger
winds just west of the Buffalo Ridge where a bit of a downslope flow
develops. As for snowfall the chances are pretty much confined to
locations along and south of a Sioux City to Sioux Rapids line. The
GFS is a little farther north with saturation and lift compared to
the Nam but neither bring too much activity into the area. Overall a
chance for an inch or so along and south of that line. Low
temperatures will be tricky with clear skies in some locations
before cloud cover increases. Will go towards the 75th to 90th
percentile where clouds are expected to remain through the night and
colder in southwest MN where clouds should be last to develop. Highs
on Monday pretty cold, especially with a breezy east and northeast
wind, only climbing into the teens to lower 20s, maybe a little
warmer under the cloud cover to the south.
.LONG TERM...(Monday Night through Sunday)
Issued at 221 PM CST Sun Jan 24 2021
High pressure remains well to the north Monday night into Tuesday so
while temperatures will be on the cold side, not as cold as the
might be if the high pressure was farther south. Lows near zero along
highway 14 to around 10 above closer to the MO River into northwest
IA.Highs only in the teens to around 20 on Tuesday with cold air
locked in place.
The next system of interest will move into the area on Tuesday night
but for now not looking like much of an issue. Any lift that can
generate some snow will be fighting through some lower level dry air.
So will keep the chance for snow at slight and chance.
After this system passes through upper level ridging will build into
the area through the end of the week. This will bring temperatures
back to above normal Thursday into the weekend. Some hints of a
system moving into the area again next weekend but temperatures will
be much warmer so if precipitation can develop it would not be a
guarantee for snowfall.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 440 PM CST Sun Jan 24 2021
Arcing area of MVFR to IFR ceilings trying to fill back in on
KFSD and KHON as of late afternoon and will likely succeed over
the next couple/few hours. Could also see some fog form at the
edge of this stratus through the overnight hours although will
likely be fleeting depending on where this cloud cover ends up.
For Monday, lower ceilings will likely linger at least until the
afternoon as mid and upper level clouds also stream northward with
the arrival of a significant winter storm to our south. Latest 18z
GFS and nested NAM guidance somewhat concerning for KSUX for the
potential of impactful accumulating snow. Will monitor this trend
thru the evening as 00z guidance arrives.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
UPDATE...Kalin
SHORT TERM...08
LONG TERM...08
AVIATION...Kalin
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
952 PM CST Sun Jan 24 2021
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Regional surface analysis had a 1000mb low over west central Texas
with a warm front stretching east across the central portions of
our CWA. Lower 60F dew points have spread as far north as
Interstate 20 this evening and are progged to continue spreading
north the remainder of the night. Similar to last night,
temperatures across our northern zones will warm through the
night. Local radar shows the bulk of the measurable rain has moved
north of our CWA. Pops have been lowered significantly the
remainder of the night maintaining low pops in the northwest and
east through sunrise. Patchy fog development is likely in the east
and northwest as well but dense fog development is not currently
anticipated. /22/
Prior discussion below:
Tonight and Monday: The mid level wave responsible for the showery
activity over northeast MS continues moving east as seen in latest
WV imagery. The bulk of this activity will move into AL before
sunset. Very little precipitation noted behind the departing mid
level wave as drying/warming occuring its subsident wake.
Elsewhere, mainly just isolated light showers were observed along
the weak warm front from central MS into north LA. The boundary will
begin to gather some northward speed this evening as the mid level
system over AZ begins to lift out to the northeast. At the same
time, the coastal baroclinic zone, where dewpoints in the mid to
upper 60s exist, will begin to surge northward tonight.
While showers may become concentrated again this evening along the
warm front over north LA/south AR/northwest MS, they will not
persist as the forcing lifts northward with the boundary before
midnight.
As the mid level system ejects to the northeast and weakens, it will
drag a cold front through the area during the day Monday. The
tightening pressure gradient will increase surface wind speeds
enough to warrant a limited wind hazard in the HWO. Forcing along
this boundary may be adequate for showers, but the lack of
sufficient low level moisture (dewpoints in the lower 60s) and the
strengthening warm layer will make deep convection difficult to
materialize. The majority of the CAM data show this scenario,
although the HRRR is the only model showing convective potential and
that over southeast portions during the afternoon. HRRR model
soundings show a bit more moisture and a bit less cap compared to
others. Will have to watch this trend to see if other models catch
on to this possibility./GG/
Monday night through next weekend...
Showers and storms will be moving out of most of the area Monday
night as a frontal system moves through and stalls near the coast.
Dry weather will return to much of the area Tuesday, although some
showers and possible storms look to linger across the south in the
vicinity of the stalled frontal system. Highs Tuesday will range
from the lower 60s northwest to the lower 70s southeast. Rain
chances will return to the entire area Tuesday night into Wednesday
as a shortwave moves across the area. Highs Wednesday will range
from the mid 50s northwest to around 70 southeast. Dry weather
returns to the entire area Wednesday night through the remainder of
the week under the influence of high pressure. Temperatures will be
cooler, with highs Thursday ranging from the mid 40s northwest to
the mid 50s southeast. Highs will be slightly warmer Friday, ranging
from the lower 50s northwest to the lower 60s south. Rain chances
look to return Saturday as another frontal system approaches the
region. /27/
&&
.AVIATION...
00Z TAF discussion:
At 2330Z IFR cigs were observed in the north while MVFR cigs were
observed cntrl and south. Cigs will lower to IFR at most sites
this evening and continue until after 12Z. Cigs are expected to
improve to MVFR by 15Z and MVFR cigs are expected to prevail
through Monday aftn. A se wind will increase Monday morning
becoming sustained around 12 knots with gusts around 20 knots.
Monday aftn TSRA may come in vcty of GLH-GWO. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 63 75 51 69 / 21 66 49 13
Meridian 59 75 54 69 / 36 62 79 18
Vicksburg 63 74 49 68 / 21 70 22 10
Hattiesburg 62 77 59 71 / 18 54 74 36
Natchez 64 73 51 68 / 12 69 30 16
Greenville 55 71 46 63 / 21 73 8 3
Greenwood 58 73 48 65 / 23 77 24 4
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
22/GG/27
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
940 PM EST Sun Jan 24 2021
.UPDATE...
Issued at 940 PM EST SUN JAN 24 2021
Visibilities have gone down significantly over the past few hours
in areas north of the mountain parkway. For this reason, opted to
issue a special weather statement to cover the fog threat for the
rest of the night. The fog threat could creep farther south, but
for now, will just focus the dense fog on the areas where it
currently resides. Updated the forecast to reflect dense fog in
these areas and also to expand the drizzle to more areas.
UPDATE Issued at 848 PM EST SUN JAN 24 2021
The earlier shower activity is exiting to our southeast as the
frontal boundary continues to sag southward across the area. This
is allowing some of the lower ceilings, fog, and drizzle to build
into the area from the north. Given the trends, will cut back on
the pops through about 10z, and go with more patchy drizzle and
fog through this period. The better rain potential should begin to
push into and across the area around or after 10z with pops
quickly ramping back up. Did make some adjustments to temperatures
as we have quite the gradient over the area right now ranging from
the low to mid 30s in the north to the mid 40s in the south. As
the boundary shifts southward, we should see those cooler
temperatures also slip a bit farther south. It looks like the
prospects of freezing drizzle should remain just north of our
coverage area as Fleming-Mason airport currently sits at 33
degrees. We`ll watch it closely, but we do not anticipate
temperatures dropping much across the north tonight. It just looks
like a very cold drizzle.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 435 PM EST SUN JAN 24 2021
20z sfc analysis shows a developing area of low pressure to the
southwest as the first wave of moisture is rolling across eastern
Kentucky this afternoon. Temperatures have warmed through the
day and above freezing most places early in the afternoon ending
the mixed pcpn threat from the morning. Readings now vary sharply
across the CWA - from around 33 degrees in the northeast to the
lower 50s in the southwest. Dewpoints, meanwhile, range from the
low 30s in the southwest to the mid 20s in the northeast. For the
most part, winds have been running at 5 to 10 mph from the
southeast to southwest beneath a deck of thickening and lowering
clouds.
The models are in a bit better agreement aloft through the short
term short term portion of the forecast compared to yesterday for
the Monday time frame. They all depict deep layer southwest flow
for Kentucky atop a broad Southeast ridge while a pair of
shortwaves dig troughing in the Desert Southwest on Monday. The
lead shortwave of this will dampen as it moves into the Central
Plains tonight with some of its energy making it into the mid
level flow and riding over the Bluegrass State. A close passing of
this lead trough on Monday night will push some height falls into
our northern counties by Tuesday morning, along with more in the
way of energy. This is where the models diverge a bit with the NAM
and ECMWF quicker to take the wave east compared to the GFS.
Favored a consensus model solution with the NBM as a starting
point along with details from the HRRR and NAM12 - for the
forecast grids.
Sensible weather will feature a wet and milder 48 hours with
light rain showers around tonight along with some fog.
Temperatures will basically hold steady or slowly rise. More
substantial rain showers then arrive during the day Monday with
locally heavy rains possible across eastern Kentucky as the
system`s sfc trough kicks off some deeper convection with thunder
a decent bet for parts of the area Monday afternoon and evening.
Depending on instability, some of these storms could become
strong in the western parts of the Cumberland Valley. Winds will
also become breezy on Monday with some gusts to over 30 mph
possible in our highest terrain near the Virginia border. The
soaking rains will fall onto relatively dry grounds with
antecedent conditions nearing D0 and minimal stream flow through
the bulk of eastern Kentucky. Accordingly, have left this event as
just a mention in the HWO with not enough of flood potential to
warrant a Flood Watch at this time. Mild conditions hold through
Monday night and into Tuesday morning with pockets of light rain
around.
Made only point based adjustments to temperatures through the
period outside of the near term adjustments based on current obs.
As for PoPs: ended up generally wetter than the NBM tonight -
closer to the CONSShort values.
.LONG TERM...(Tuesday through Sunday)
Issued at 303 PM EST SUN JAN 24 2021
A few stray rain showers will be exiting far eastern Kentucky
early Tuesday morning, as a large area of low pressure continues
to move away to our east. A ridge of high pressure will briefly
move through the region Tuesday and Tuesday, and will bring a
short period of dry and warm weather to eastern Kentucky. However,
this respite will be short lived, as a fast moving area of low
pressure is forecast to move through the region Wednesday through
late Thursday morning. Precipitation with this system will begin
as rain during the day on Wednesday, as warmer air will be in
place. The rain will mix with and then change over to snow
Wednesday night, with light snow expected to linger around the
area through Thursday morning. Light snow accumulations will be
possible, especially north of the Mountain Parkway, and along the
I-64 corridor in particular.
Temperatures will start off well above normal, with highs in the
upper 50s to lower 60s on tap for Tuesday, and the mid 40s to mid
50s on Wednesday. Below normal temperatures are forecast for
Thursday, in the wake of a passing area of low pressure. Highs on
that day will likely max out in the 30s around the area. Gradual
warming is expected to begin again on Friday, and we could see
well above normal temperatures over the weekend, as another ridge
of high pressure sets up over the region, and winds swing around
to the south.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 848 PM EST SUN JAN 24 2021
Ceilings will continue to lower from the north through the
overnight hours tonight as a frontal boundary slips farther
southward. Patchy to areas of fog will be seen along with some
drizzle through the overnight hours. As the frontal boundary
begins to lift back to the north late tonight and Monday morning,
widespread rain should develop areawide and continue through the
day on Monday. A few thunderstorms may be possible very late in
the period at KSME and KLOZ as the boundary pushes north and we
get some unstable conditions to develop as milder air pushes north
into the area. We will take a closer look at this potential in
future TAF issuances.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...KAS
SHORT TERM...GREIF
LONG TERM...AR
AVIATION...KAS
Area Forecast Discussion
National Weather Service North Platte NE
531 PM CST Sun Jan 24 2021
.SHORT TERM...(This evening through Monday night)
Issued at 313 PM CST Sun Jan 24 2021
The synoptic and mesoscale models continue to converge on a storm
track for the storm system affecting Arizona this afternoon. The
system will track through the srn Rockies tonight and then through
ern Colo, KS and southeast Nebraska Monday. The model blended QPF
forecast increased liquid a few hundredths across wrn and ncntl
Nebraska which translates to a slight increase in snowfall; most
noticeable across wrn Nebraska where an upslope snow event will occur
Monday night once the upper level energy moves east of Nebraska
Monday evening. The higher snowfall amounts across southwest
Nebraska have also been shifted south toward KS slightly.
The system is now in range of the HRRR and RAP models which are only
predicting slightly more than half as much liquid as the synoptic
mesoscale model blend. Thus, there is still a fair amount of
uncertainty with the snowfall for this portion of the storm event.
The predicted snowfall across wrn and ncntl Nebraska will occur as a
result of a moist and favorable environment for snow growth with
h700mb temperatures around -13C and layer mean RH between 70 and 90
percent. Lift, however, is very modest, presumably producing light
to briefly moderate snow.
Snowfall totals of 2 to almost 6 inches are in place tonight through
Monday night affecting areas along and south of highway 2 west of
Dunning and along and south of highway 91 east of Dunning. SLR
numbers are close to climo for this event; 12 to 15 to 1 which might
be too low but out of respect for the drier RAP and HRRR models,
these SLR numbers will be used. The ECM continues to suggest strong
forcing across southwest Nebraska and continues to trend north. Just
a 50 mile error in the forecast would place parts Custer county,
Lincoln county and parts of Frontier county in a winter storm
condition.
The Winter Storm Watch will be converted to a Winter Weather
Advisory and a few counties will be added to the highlight. The
tandem storms will produce around 2 to 5 inches of snow each day
Monday and Tuesday.
The temperature forecast tonight through Monday night uses the short
term model blend plus bias correction which handles the
radiative effects of overcast skies better than the guidance
blend.
.LONG TERM...(Tuesday through Sunday)
Issued at 313 PM CST Sun Jan 24 2021
A second storm off the nrn California coast this afternoon will
swing south through the Great Basin and then east through the cntl
Rockies arriving on the ern Colorado plains Tuesday afternoon.
This system has the potential to produce a few additional inches
of snow. The models are in reasonably good agreement tracking the
h700mb low through wrn KS and southeast Nebraska Tuesday night.
Likely POPs are in place Tuesday afternoon and Tuesday evening for
this system.
Clearing skies will begin to advance east through wrn Nebraska
Tuesday night which could set the stage for subzero lows in the some
areas Wednesday morning and again Thursday morning when most of the
region will be clear. Wrn and ncntl Nebraska will still be under the
influence of arctic high pressure Wednesday and Thursday morning.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 531 PM CST Sun Jan 24 2021
An approaching winter storm will result in several aviation
weather hazards across western and north central Nebraska.
Widespread stratus is already in place with MVFR cigs, likely
lowering to IFR overnight. Snow will develop toward sunrise across
the far southwest and spread north through the day. Expect
considerable visby reductions at times during the afternoon. Wind
will primarily be from the east tonight, then northeast tomorrow.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight CST /11 PM MST/ tonight to
midnight CST /11 PM MST/ Tuesday night for NEZ022>029-035>038-
056>059-069>071.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Snively
Area Forecast Discussion
National Weather Service Marquette MI
733 PM EST Sun Jan 24 2021
.SHORT TERM...(This evening through Monday)
Issued at 212 PM EST SUN JAN 24 2021
Water vapor imagery and RAP analysis show a shortwave moving across
northern Ontario and northern Lake Superior. Additional shortwave
energy is streaking from the mid-Mississippi Valley toward the Lower
Great Lakes. In response, waa/isentropic ascent has led to a large
area of -sn across the central Great Lakes into this afternoon. Some
weak enhancement to snow appears to be occurring along Lake Mi,
but it`s hard to tell from sfc obs/webcams alone as radar is
inoperable right now. Will keep advisory going through 21Z as a
few of the models indicate isentropic ascent increasing on the
280K sfc from 18Z-21Z with the approach of the sfc-h85 trough.
Expect snow to end out east by early evening as shortwave and
associated sfc trough push east of the U.P. CAA behind the
trough/front has led to some light wnw flow LES over the western
counties late this afternoon.
Tonight and Monday, sfc high pres centered over northern
Saskatchewan will build a ridge se toward the Upper Mississippi
Valley as low-level winds veer nw tonight and then more northerly
late Monday. Fcst soundings indicate a low inversion around 3kft
setting up off western Lake Superior and 3-4kft off eastern Lake
Superior. The DGZ is favorably situated mostly within this shallow
convective layer. Thus, expect -shsn and flurries off Lake Superior
tonight into Mon morning under a nw flow and then into Mon afternoon
as flow becomes more northerly. However, only a dusting to maybe as
much as an inch of accumulation is anticipated given the shallow
convection and dry air as noted on fcst soundings with inverted-v
look toward the sfc.
As for temps, there may be enough breaks in the cloud cover to allow
min temps to fall toward zero over interior western Upper MI
tonight. Under a northerly onshore flow and mostly cloudy skies for
much of the area, Monday`s max temps will range from the upper teens
to lower 20s west half to the mid 20s east half.
.LONG TERM...(Monday night through Sunday)
Issued at 324 PM EST SUN JAN 24 2021
Trending a little warmer through the week, with a few chances for
light lake-effect snow, and nothing too significant the week. Strong
positive height anomalies across the Arctic and the Pacific, with
negative height anomalies along the West Coast and just off New
England are leading to a split flow pattern across NOAM with a more
active southern stream progged to bring much needed pcpn across the
west, though maybe too much at once, and add`l pcpn across the
southern Mississippi Valley eastward through the Ohio River Valley
and Appalachians. This southern stream will bring an active storm
track with it as troffing sets up in the west with rising heights
and weaker ridging in the east. Global ens means suggest this
pattern to continue through at least the longterm period, which is
expected to bring a slow warm up through the week, with temperatures
trending just above normal by this weekend
As a shrtwv moves through the central CONUS Monday evening through
Tuesday, high pressure drops south on the leeside of the Canadian
Rockies. With split flow in place and this high pressure influencing
much of the Northern Plains, the Central Plains shrtwv will remain
south of Upper Michigan. The shrtwv passes Tuesday evening as cooler
air slowing moves across Superior from the Canadian high pressure.
This pattern will support some light LES through Wednesday before
coming to an end by Thursday. With light northerly flow and model
850mb temps in the -13 to -16C range. A brief peek at model
soundings show rather low inversions, with an inverted V profile,
and the DGZ remaining closer to the sfc. This should keep any
accumulations on the lighter side as Arctic high pressure remains to
the north of Lake Superior. Through Wednesday night could see 2 to 4
inches total in the higher terrain of west of Marquette and across
the Porkies. The NAM has been hinting at a stronger convergence band
on Wednesday for Alger County the last few days, but sounding
profiles still don`t allow much better conditions for the usual
heavy snowfall amts seen within these bands, stay tuned.
As another shrtwv moves through the southern stream across the
Appalachians on Thursday, rising heights and SW return flow increase
Thurs aftn across Upper Michigan. This pattern will bring the end of
any LES and a slight increase in temperatures.
Another wave moving onshore across the desert SW Saturday shifts
into the central US on Sunday, which will need to be monitored over
the coming days for potential shifts in the track. Models are
trending towards wrapping up a sfc low that looks to impact the
Great Lakes region somewhere, but details have several days before
they can be ironed out.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 727 PM EST SUN JAN 24 2021
VFR conditions are expected at KIWD and KSAW until Mon morning when
north winds develop and bring MVFR cigs from lake clouds back
into the area. Onshore flow into KCMX will support mainly VFR cigs
in the dry airmass over the region. Slightly greater moisture
moving in Mon morning should also result in MVFR cigs with some
flurries.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 212 PM EST SUN JAN 24 2021
Expect w to nw winds 20-30kt in the wake of the front this evening.
High pres will then slowly build toward Lake Superior with ridge
axis crossing Lake Superior on Thu. Ahead of the ridge, expect nw
winds to diminish to 15 to 25 knots later tonight into early Monday.
Northerly winds will be mostly under 20kt into Thursday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...JAW
AVIATION...JLB
MARINE...Voss
Area Forecast Discussion
National Weather Service Phoenix AZ
410 PM MST Sun Jan 24 2021
.UPDATE...Updated Aviation Discussion.
&&
.SYNOPSIS...
An active weather pattern featuring a series of storm systems will
bring chances for rain and thunderstorms, high elevation snowfall,
and much colder temperatures over the next several days. The first
storm system will move through the area today, followed by a second
colder system Monday and Tuesday. Below normal temperatures are
expected through at least next weekend with possible freezing
conditions Wednesday morning.
&&
.DISCUSSION...
Latest water vapor imagery reveals a well-defined closed low
traversing a bit faster eastward through Arizona. Cold pool
associated with this system juxtaposed atop anomalously high moisture
has resulted in objectively analyzed area of 250+ J/kg MLCAPE. This
has lead to the development of numerous small cells across Maricopa
County, with several producing pea-sized hail. Latest consensus from
the CAMs suggests this activity will persist through this evening,
before eventually fizzling out in the ephemeral subsidence behind
the departing low.
Quick on the heels of the aforementioned low will be another
stronger low pressure system diving down the west coast with its
anomalous low height anomalies. Given the antecedent low-level
moisture, shower activity will quickly redevelop in the
orographically favored areas north and east of Phoenix after
midnight. Successive runs of the HRRR and local CAMs indicate
strong vorticity-forced ascent will then give way to a developing
pre-frontal line of showers and thunderstorms during the early
morning across southeastern California. Latest CAMs suggest this
line will become more organized as it marches eastward through
Arizona during the morning. Sufficient deep layer shear of 40 kt
will be present and insolation could yield a few hundred joules of
CAPE, per the latest HREF. Meanwhile, pressure gradient will will
be strong enough to produce breezy conditions on its own,
particularly across southeastern California and southwestern
Arizona. The line will only enhance the potential for wind gusts
up to 40 mph, as suggested by the ECMWF ensembles. Although gusts
to 40 mph are not anticipated throughout the entire day and over a
widespread area, latest HREF max ensemble hints at this threat
and a Wind Advisory has been hoisted across Maricopa County to
address the potential. Given the steep lapse rates, conditions
will also be favorable for small hail within the strongest cells.
The other noteworthy component of Monday`s low pressure system will
be the winter storm impacts. While lower desert activity will
generally taper off Monday evening, rain and snow showers will
persist across the higher terrain through Tuesday. Critical
thicknesses will be low enough to support snow as low as 2000-2500 ft
in elevation. Wrap-around precipitation Tuesday morning could very
well take the form of snow across north Scottsdale and Cave Creek,
and possibly graupel a bit lower in elevation. Across the higher
terrain north and east of Phoenix, total snow accumulations will
likely amount to 1 to 2 feet above 5000 ft in elevation and 3 to 6
inches near Globe above 3500 ft, where the Winter Storm Watch has
been upgraded to a Warning.
Considering the uncertainties often inherent with moisture
and low pressure systems, overall GEFS and ECMWF ensemble spread
remains relatively low, even with regard to total QPF. Although
amounts have trended downward, latest EMCWF ensemble mean indicates
around three quarters of an inch in the Phoenix area, while the WPC
deterministic amount is lower and closer to the GEFS mean. The
prolonged moist southwesterly flow is conducive for even higher
amounts in the foothills, where as much 1 to 2 inches in liquid or
SWE is possible. This could lead to runoff into Tonto
Creek near Tonto Basin, where increases are again forecast.
&&
.PREVIOUS DISCUSSION...
Otherwise, colder temperatures will become entrenched, save for
southeast California, which may be be fortunate enough to hold
onto the low 60s through the week. The cold air mass will cause
high temps to drop into the 50s across the lower Arizona desert
through Thursday. On Tuesday afternoon, the high in Phoenix will
struggle to reach the low 50s, potentially setting up for freezing
Tuesday night/Wednesday morning lows in many places. Fog could
also emerge as a possibility on this night, or of these nights,
after rain and modest sky clearing. By Thursday, afternoon highs
should warm nicely into the mid to upper 60s. Guidance remains
consistent portraying a quick moving weather system passing
through the Southwest late this week that could bring another
round of rain and high elevation snow.
&&
.AVIATION...Updated at 2305Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Scattered showers and isolated thunderstorms will continue through
this evening and to a lesser degree through the night as well.
The strongest storms will be capable of producing localized winds
up to 25 kt and pea- sized hail. Meanwhile, abundant low-level
moisture is resulting in CIGS of 4-6 kft. In general, CIGS should
remain in this general range through the morning, but may briefly
drop lower in any showers. Westerly winds of 8-15 kts will
gradually weaken and veer to southerly overnight as well.
Scattered showers will increase once again Monday morning. Monday
late morning (about 18-20Z) a strong line of showers and
thunderstorms will move through. Accompanying this line of showers
will be gusty southerly winds of 20-25 kts with a few gusts to 35
kts possible. Behind the band of showers, breezy westerly wind
with scattered showers will continue for several hours. CIGS will
drop to 2-4 kft with reductions in visibility also possible during
the heaviest showers, but CIGS will rise again to 4-6 kft behind
them.
Southeast California/Southwest Arizona including KIPL and KBLH:
Light westerly wind will shift to light southerly overnight with
FEW-SCT coverage near 5-8 kft. Monday morning CIGS will lower to
4-8 kft with scattered showers expected. The biggest aviation
issue will be the wind. Gusty westerly wind of 15-20 kts with
gusts to 30 kts will develop at KIPL. Expect similar windy
conditions at KBLH, but out of the south.
&&
.FIRE WEATHER...
Tuesday through Saturday:
Lingering rain and snow showers possible in the wake of a
departing weather system Tuesday and snow levels could drop below
3000 feet. Otherwise, a clearing and drying trend will begin.
Colder temperatures and lingering moisture should keep min RH
values above 25% every day. Overnight recoveries will reach the
40-80% range. Afternoon breeziness will be common, especially over
any higher terrain features. Another weather system could bring
rain chances again by Friday-Saturday.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Wind Advisory from 10 AM to 4 PM MST Monday for AZZ534-537>563.
Winter Storm Warning from 5 PM Monday to 3 PM MST Tuesday for
AZZ562.
Winter Weather Advisory until 11 PM MST this evening for AZZ557-
558-563.
Winter Weather Advisory from 5 AM to 5 PM MST Tuesday for AZZ557-
558-563.
Winter Storm Warning from 11 AM Monday to 5 PM MST Tuesday for
AZZ557-558-563.
Wind Advisory from 11 AM to 11 PM MST Monday for AZZ530>533-535-
536.
CA...Wind Advisory from 10 AM to 10 PM PST Monday for CAZ560-561-
563>570.
Wind Advisory from 10 AM Monday to 4 AM PST Tuesday for CAZ562.
&&
$$
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...AD
AVIATION...Hodges
FIRE WEATHER...AD