Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/29/21
Area Forecast Discussion
National Weather Service La Crosse WI
535 PM CST Thu Jan 28 2021
.SHORT TERM...(This afternoon through Friday)
Issued at 1242 PM CST Thu Jan 28 2021
At 18Z, surface high pressure was over the area with light winds
and broken sunshine. Further west, over western MN/IA, a sharp
increase in the pressure gradient is causing some blowing snow
with gusts to 30 mph in SW MN and visibility reductions. Low
clouds are streaming northward along a moisture axis from eastern
KS into this same area, converging into trough/wind shift across
southern MN. While temperatures at the surface dont exhibit this,
aloft a warm front and warm advection is occurring west of I-35.
Morning RAOB temperatures at 850mb of -11C/-1C at MPX/ABR indicate
the strong front in place. This entire area of warm advection,
convergence, and cloud will translate east overnight to about the
Miss river with about 1-1.5 km of low-level saturation. Most of
the warm advection is centered near 850mb and remains west of the
Miss river, strongest around midnight and weakening into the
morning per RAP analysis. Both the latest RAP and NAM have this
same suggestion and do dribble some light QPF out...mainly
flurries or drizzle.
Forecast soundings would suggest temperatures in the near-ice
nucleation region of -10 to -12C but warming overnight in the warm
advection. Thus, flurries look to be mainly the type should enough
lift occur along the warm front in eastern MN/IA overnight. Worst
case scenario some patchy freezing drizzle occurs. At this time,
it appears FZDZ is too low a probability outcome to include in the
forecast. But, will add flurries west of the Miss river and
monitor this evening and overnight.
.LONG TERM...(Friday night through Thursday)
Issued at 206 PM CST Thu Jan 28 2021
Model solutions continue to settle down and offer similar
solutions for the upcoming weekend system. Good consensus now that
the system will track from the Texas Panhandle northeast to the
lower Great Lakes/Ohio River Valley area from Saturday morning
through Sunday. This will take the strongest forcing from the
short wave trough by just to the south of the area, but still
close enough that there will be plenty of lift that spreads across
the area. As the system approaches, a general 2 to 4 ubar/s of up
glide on the 290K isentropic surface will spread over the area to
help form the initial precipitation Saturday afternoon. Looking at
forecast soundings for this period, there will initially be some
dry air to overcome which could lead to a short period of some
freezing drizzle before the column saturates deep enough for a
change over to all snow. This change over will be aided by the
development of a mid level frontogenesis band that develops on the
north side of the surface low Saturday evening but moves pretty
quickly off to the northeast overnight into Sunday morning. This
signal for some mixed precipitation continues to be seen in some
of the 28.06Z GEFS members as well.
Once the precipitation switches over to snow, the various ensemble
members have settled in to showing about 3 inches up into the
Interstate 90 corridor with around 5 inches for the far southern
sections of the area. This looks to be a pretty solid advisory
with the small threat of some warning criteria snows across the
south. The ECMWF EFI continues to be between 0.8 and 0.9 with this
system suggesting most of the members indicate a decent system,
but likely not strong enough to make it significant with
widespread warning criteria amounts. This seems reasonable with
the 28.00Z NAEFS holding steady with precipitable water amounts
about 1 standard deviation above normal with amounts above 0.5
inch but less than 0.75 inch. Based on this assessment, not
planning for any headlines with this system at this time.
Looking out past the weekend system, there appears to be another
on the horizon for the middle of the week. Initial indications are
this may be a stronger system than the upcoming weekend one but
also take a more northwest track. This could mean more of mixed
precipitation scenario. For now, will let the model consensus
grids do their thing with this system.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 535 PM CST Thu Jan 28 2021
Feed of moisture ahead of low pressure over the High Plains will
produce widespread MVFR/IFR stratus at the KLSE/KRST sites
later tonight int Friday (KRST after 04z/KLSE after 07z). A few
flurries will be possible as well mainly at KRST from 04-14z but
no reductions in vsby expected.
Area Forecast Discussion
National Weather Service Dodge City KS
531 PM CST Thu Jan 28 2021
.SHORT TERM...(This evening through Friday)
Issued at 248 PM CST Thu Jan 28 2021
The trend is for much warmer air over the extreme southwest counties
late this afternoon, much like the HRRR model output. Highs can
reach the low 60s over the Cimarron grasslands...and still only to
just above the freezing point north of the K-96 corridor. The
breezy conditions will likely slack off with the the diurnal
trend. However the southerly winds will persist overnight. The
surface high pressure center and axis of coldest air this evening
will be centered over northcentral/northeast Kansas. This will
leave southeasterly winds early , becoming more southerly
overnight. The models that can produce visibility fields are all
in agreement on a layer of freezing fog in the BL basically
centered over northwest kansas. The uncertainly lies in if the fog
develops as far south as the KS/OK line as the WRF models
suggests (unsupported by the HRRR/RAP).
Overnight lows again spatially look to be most mild over the red
hills and south central Kansas counties, , generally in the upper
20s...with more variability in the upper teens and low 20s across
west central Kansas (Hays-Dighton-Syracuse).
.LONG TERM...(Friday night through Thursday)
Issued at 248 PM CST Thu Jan 28 2021
Friday will be a challenging afternoon for the temperature forecast
with downsloping wind becoming more pronounced and the large area
of snow cover needed to melt away to achieve maximum temperatures.
Windy conditions are expected on Saturday as a front swings though
the area in the morning with a decent gradient over western
Kansas through the day. Not necessarily a perfect high wind
scenario, however the GFS and ECMWF at this time have solid 30 to
35 knot winds in the 850 mb layer at 18Z Saturday. A decent belt
of warm advection precipitation out ahead of the developing
surface low will offer a chance for rain over just about anywhere,
but even a few thunderstorms the farther southeast toward the OK
A very amplified system, tapping arctic air comes out of the west
next week, shown by the Canadian/GFS/ECMWF. This will develop an
intense cyclone over the central plains, leaving large uncertainty
at this time yet where the main axis of wintry impacts will be.
The one constant for our area of Kansas looks to be strong to high
winds (if dry slotted), which very well could be the case, the
GFS is showing at this time.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 525 PM CST Thu Jan 28 2021
VFR flying conditions are expected this TAF period for all
terminals except HYS which could drop to MVFR/IFR owing to fog
development roughly in the 05-11Z time frame. Low level wind shear
is also expected to impact all terminals overnight as a 35-45 kt
southwesterly low level jet overspreads southwest Kansas. Winds
will stay light to moderate roughly out of the south, but could
become gusty at times at DDC and LBL.
.PRELIMINARY POINT TEMPS/POPS...
DDC 28 54 35 49 / 0 0 10 30
GCK 22 53 31 49 / 0 0 0 10
EHA 34 66 36 56 / 0 0 0 0
LBL 29 62 35 56 / 0 0 10 10
HYS 22 41 28 38 / 0 0 0 30
P28 29 55 41 54 / 0 0 20 60
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
611 PM EST Thu Jan 28 2021
MVFR to lower VFR stratus will persist overnight, but trend from OVC
to BKN with time as drier low level air works gradually into the
area as a ridge of high pressure settles into the central Great
Lakes. This trend will continue into Friday with SCT conditions
developing. A weak pressure gradient associated with the high will
also favor light winds under 10 knots this forecast with a slow
backing from NW to WNW/W.
For DTW...This will remain aob 5kft tonight, but scatter out on
Friday as high pressure builds into the area. WNW winds under 10
knots will prevail for the forecast period.
DTW THRESHOLD PROBABILITIES...
* High in ceilings at or below 5000 feet through this evening.
Moderate tonight and low Friday morning.
Issued at 433 PM EST Thu Jan 28 2021
Meridional surface pressure ridge axis (+1032 mb, 90th
climatological percentile per NAEFS/ECMWF climatology...per
overnight afd last night) is in place from Far-Northwestern Ontario
southward through Lake Superior to Wisconsin. The position of the
surface high is leading to cold north gradient flow across Southeast
Michigan. The surface ridge is forecasted to hold position through
the next 24 hours. 850mb temperatures this afternoon are running at
-17 to -18C and has activated high amount of lake effect
stratocumulus downwind of the Lake Superior and the N. Lake Michigan-
Huron aggregate. Boundary layer depths are running some 3.5 kft this
afternoon which is extending into -12C to -14C isotherms for ice
nucleation. Latest radar imagery depicts light returns across the
forecast area, flurries are expected to persist throughout the
remainder of this afternoon and into the evening. The question for
tonight centers on the cloud forecast. Uncertainty exists with the
typical moist NAM holding saturation sub 4.5 kft agl base. On the
other hand, the RAP is drier at the top of mixed layer after 09Z
bringing a clearing trend particularly across the southern cwa
daybreak Friday morning. Pattern recognition of cold northerly flow
sides with a more pessimistic forecast which favors the inherited
cloudy forecast. Do actually favor more clearing for late Friday
afternoon as models show a very aggressive increase in anticyclonic
flow trajectories late afternoon with very efficient dry isentropic
downglide. The inherited forecast has this clearing forecast for
late Friday well in hand.
The focus of the Medium Range is centered on the accumulating snow
potential early Sunday morning through Monday/Mon evening.
Remarkable intra-model/run-to-run continuity has existed with
regards to both the low pressure track and the axis of heaviest
precipitation. No real surprises with the 28.12Z deterministic
solution output with heaviest precipitation axis remaining south and
west of Lower Michigan.
From a big picture dynamic view, rapid cyclogenesis will be
supported in the lee of Rocky Mountains/Central Plains as dynamic
Potential Vorticity anomaly ejects rapidly out of the 4 Corners.
Very favorable upper level left exit region jet dynamics will
support sub 998mb surface cyclone across Missouri and western IL Sat
night. The low is then forecasted to weaken rapidly as it crosses
the Mississippi River. Sharpness to the composite trough is lost
with the upper level low closing off and becoming vertically
stacked. Main dynamical reasoning is that trough remains fairly
progressive and gets caught up within a very impressive zone of
upper level confluence off of preceding jet max. Given the setup and
separation between the upper level jet cores there is high
confidence in this weakening and zonal track of the low pressure
Sunday. In fact, there is a very low amount of variance that is
depicted in the Ensemble Cluster EOF technique. So the questions for
Southeast Michigan are: 1. How progressive will main warm advection
snow be after 09Z Saturday night (Important for both the start time
of accumulating snow and how far north the accumulating snow will
make it on the front end.) 2. How formidable will the dry air feed
be funneling directly into Southeast Michigan from the east Sunday
(Given the strong east to west gradient flow any more weakening of
the barotropic low should significantly undercut the northward
transport of moisture, i.e. increase in bust potential here
locally). With that stated the heaviest QPF placement is immediately
south of the forecast area so margin of error is less for Monroe and
Given a survey of EPS members along with latest Probabilistic
forecast information offered by NBM, favor a solution that calls for
categorical/likely PoPs for accumulating snow late Saturday night
and Sunday. Highest confidence exists in accumulations of a couple
of inches or more south of 8 mile. Given forecast soundings and plan
view of thermals, higher than normal confidence exists that all
precipitation will fall in the form of snow with this event.
Another uncertain aspect of this event is whether or not the
potential for accumulating light snow may extend into and throughout
the Monday/Monday evening timeframe. Models are showing that
absolute vorticity energy may consolidate on back edge of the trough
and lead to a persistence of inverted troughing northward through
western Lake Erie back into far eastern Lower Michigan. It is always
difficult forecasting exact absolute vorticity energy and deep
moisture/saturation evolution at these timescales within broad
troughs. The potential is certainly there for grinding out light
snow through Monday evening. This would most likely be east of U.S.
23. Given Southeast Michigan`s proximity along the northeast fringe
of precipitation swath, did want to refrain from getting too
specific in messaging today.
Elongated high pressure moves over Lake Michigan tonight with
northwest wind around 15 to 20 kt, gusts 25 to 30 kt over Lake
Huron, continuing into Friday. Extended the Small Craft Advisory
around the Thumb into Friday with wave heights reaching near or just
above 4 feet expected to persist across the nearshore waters. The
high pressure slowly drifts east over the central Great lakes by
early Saturday with winds then becoming light and variable. Low
pressure then moves from the mid-Mississippi Valley into the Ohio
Valley by Sunday, shifting winds from the east and northeast by late
Saturday. Winds will remain below gales but the easterly trajectory
brings onshore wave activity that will likely necessitate another
round of Small Craft Advisories beginning early Sunday. The system
brings a good chance for a period of snow across Lakes Erie and St.
Clair for Sunday into Monday.
Lake Huron...Small Craft Advisory until 4 PM EST Friday for LHZ421-441>443.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
522 PM CST Thu Jan 28 2021
.DISCUSSION...(This evening through Thursday)
Issued at 316 PM CST Thu Jan 28 2021
Fog from this morning was slow to clear, but has largely mixed out
as of this afternoon. Stratus remains in place across most of the
area (except for our southern most KS counties). As a result,
temperatures have struggled to rise any higher than the low to mid
20s for most locations. A few breaks in the clouds are possible
late this afternoon and evening, but additional low stratus and
fog is expected to redevelop again tonight. The HRRR and RAP show
the thickest fog developing over northwestern portions of the
area. Therefore a dense fog advisory was issued for this area.
Dry conditions are expected on Friday, but lingering fog and cloud
cover will make for another cold day. Temperatures were nudged down
several degrees, and many locations will remain below freezing.
Friday night, a quick moving shortwave trough will push across the
southern Rockies, lifting towards local area early Saturday morning.
This will bring a chance for precipitation to the area during the
day on Saturday. Most models continue to show the bulk of the QPF
remaining largely east of the local area. Even still, we could still
see some light freezing drizzle at the onset, followed by flurries
or light snow/sleet, and then possibly another round of light
freezing drizzle on the back side of the system. This may be just
enough to lead to spotty slick roads across the area.
In addition, northwest winds will also pick up on the west side o
the system on Saturday. While not excessively strong, we may have
wind gusts up to 35 MPH at times. The concern here is that some
locations (especially the west) will remain cold enough that the
existing snowpack will not have an opportunity to crust over.
Therefore some patchy blowing snow was added to the grids.
Mid and upper level ridging will return for early next week. This
will lead to a bit of a warming trend, but this will be rather slow
given the deep snow cover. High temperatures are forecast to return
to the high 30s to low 40s on Tuesday.
The next storm system is forecast to impact the area late Wednesday
into next Thursday. While this has the potential to be a
significant winter storm, model ensembles have actually backed
off on its strength over the past couple model cycles.
Nevertheless, this will be something to continue to monitor over
the coming days.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 518 PM CST Thu Jan 28 2021
Cigs continue to flirt the line between MVFR and IFR but should be
improving more solidly to MVFR over the next few hours. Fog is the
main concern again tonight, especially for KEAR where fog is
expected to be dense at times during the early morning hours and
possibly into the mid morning. KGRI will likely see fog as well,
though visibilities are likely to be slightly better than KEAR.
Fog will likely linger again through a good part of the day as it
NE...Dense Fog Advisory from 9 PM this evening to noon CST Friday for
Area Forecast Discussion
National Weather Service Las Vegas NV
656 PM PST Thu Jan 28 2021
.SYNOPSIS...Heavy snow will continue in the eastern Sierra through
the evening hours. Rain and mountain snow will spread across the
Mojave Desert and southern Great Basin late tonight and into the
afternoon on Friday. Drier conditions expected over the weekend with
Plume of moisture that brought significant amounts of rain and snow
to portions of California has started to pivot east this evening. So
far, precipitation has remained west of the Sierra Crest, but over
the next couple of hours snow will once again start increasing
across the Eastern Sierra Slopes. This will lead to a few more
inches of snow in places like Aspendell where they have already
received around 40 inches of new snow. With the warmer air that has
advected into the Owens Valley, snow levels are currently around
5000 feet. As the precipitation moves into the area, we don`t see
those snow levels falling very much, at least initially. By the time
temperatures drop to allow for snowfall in the Owens Valley most of
the precipitation will have moved east. However, it is still
possible that places like Bishop could see some snow accumulations
up to an inch or two in the morning.
Very little change with the timing of the precip as it moves through
the CWA Friday. Latest HRRR showing rain moving into western San
Bernardino County around midnight and then working east and arriving
in Las Vegas just before sunrise with widespread light rain expected
for the morning commute. Most areas below 5500 feet will see rain as
this main band pushes through. The main band of precip looks to push
east by late morning, but as the base of the trough moves overhead
we could see additional showers develop with snow levels dropping to
around 4000 feet in the afternoon. This could potentially bring some
snow accumulations to Mountain Springs and Mountain Pass. We will
also have to watch for the potential of thunderstorms Friday
afternoon across far southern NV and Mohave County as strong
dynamics associated with the low interacts with afternoon heating.
Current forecast on track and no evening updates needed.
115 PM PST Thu Jan 28 2021
.SHORT TERM...through Sunday night
Latest satellite imagery continues to show the plume of moisture
into central California. This plume will continue to become more
north to south oriented during the course of the afternoon. Steady
southerly winds continue to funnel up the Owens Valley with gusts
generally in the 30-40 mph range. That has increased temperatures
and snow levels to above 5000 feet. As the trough begins to push
across Inyo County overnight snow levels will drop again but any
snow accumulation in the Owens Valley is expected to be less than an
inch. The heaviest snow in the eastern Sierra will begin to diminish
toward midnight, but lighter snow will continue into Friday.
The latest, 12Z runs of the HREF as well as the HRRR show the
progression of the band of rain and snow showers pushing south and
eastward overnight. Expect the leading edge to reach the Barstow
area around midnight, Mountain Pass and the Spring Mountains between
2 and 4 am, and into the Las Vegas Valley by daybreak. Snow levels
will initially be around 5500 feet and then fall to around 4500 feet
during the morning. Mountain Pass is expected to initially start out
as rain but transition over to snow with the potential to receive a
quick couple of inches of accumulation. The winter weather
advisories across southern Nevada remain in place. The latest HREFs
have trended upward somewhat with the snow amounts in the Spring
Mountains and the latest forecast reflects this.
Elsewhere, the biggest change in the forecast is the issuance of a
Winter Weather advisory for the higher terrain above 5500 feet in
Mohave County from 5 am Friday through 5 pm where 3 to 6 inches can
be expected. Snow levels will fall to around 4000 feet during the
afternoon, but accumulations in the 4000 to 5500 foot elevation
range should be no more than an inch or so. Lastly, the EMC HREF is
indicating sufficient CAPE and instability to produce some shower
activity behind the main precipitation band and underneath the cold
core of the trough. This will also provide some isolated lightning
strikes in far eastern San Bernardino and Clark Counties as well as
across Mohave County on Friday afternoon.
The trough axis will push to the east on Friday night with a
shortwave ridge building into the area for the weekend. This will
provide some drier conditions, although temperatures will remain at
or slightly below the climate normals.
.LONG TERM...Monday through Thursday
The next trough of low pressure will begin to approach the area on
Monday with southwest flow beginning to increase. Precipitation will
begin to move into the eastern Sierra by Tuesday morning with the
trough axis approaching the northern and central California
coastline. The 00Z WPC Clusters are showing one scenario where about
20 percent of the ensemble is indicating a tap of moisture into
southern California and southwestern Arizona. None of the members
were from the GEFS, but the 12Z GFS does indicate that potential as
their is a plume of 200-300 units noted. I suspect with the 12Z
Clusters we will see an increase in the probabilities somewhat. At
this point no significant changes were made to the forecast during
this period. Widespread PoP chances are in the forecast area wide on
Wednesday. As the trough exits on Thursday there is the potential
for some stronger northerly winds, particularly down the Colorado
.AVIATION...For McCarran...Ceilings will remain aoa 15 kft
through about midnight. More uncertainty regarding the wind
forecast. Wind speeds expected to remain below 10 kts, however some
guidance suggests several hours of a southeast wind direction late
this afternoon into early evening. If that does not materialize the
direction looks to stay favorable today before shifting to the
typical downvalley direction this evening. Period of light rain,
lower ceilings and visibility making for MVFR conditions for the
morning push Friday morning. Visibilities could lower 3SM in
moderate rain with ceilings 2-3 kft between 13Z and 19Z Friday.
Turbulence forecast below 18 kft along with mountains obscured.
Conditions will improve Friday afternoon as the weather system moves
For the rest of southern Nevada, northwest Arizona and southeast
California...Tonight and Friday, a storm system will move east
across the region bringing with it lower cigs/vsby and widespread
rain and snow to the mountains. Snow could mix with rain for a
period tonight at KBIH. Otherwise, MVFR conditions with ceiling 1-3
kft AGL and vsbys falling to 3SM in light to moderate rain.
Turbulence for below 18 kft with mountains obscured. Conditions will
improve from west to east throughout Friday as the system moves
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
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