Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/24/21
Area Forecast Discussion
National Weather Service La Crosse WI
945 PM CST Tue Feb 23 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 211 PM CST Tue Feb 23 2021
Water vapor satellite early this afternoon shows a positive tilt
short wave trough from western North Dakota back into Montana. This
wave will continue to move east/southeast through the night,
crossing over Minnesota and Wisconsin. With the positive tilt, the
strongest forcing will be on the poleward extent of the wave and the
17Z RAP shows up to moderate pv advection in the 500-300 mb layer
crossing over central Minnesota into northern Wisconsin with just
weak advection farther south. At the surface, an area of low
pressure has been reorganizing and is expected to take shape over
southern South Dakota and then move along the Iowa/Minnesota border
into southern Wisconsin with the short wave trough. As the area of
low pressure approaches, decent isentropic up glide will overspread
the area early this evening with the RAP suggesting 6 to 8 ubar/s on
the 285K surface. However, both forecast soundings and condensation
pressure deficits show a lot of low level dry air has to be overcome
and this lift should result in mainly cloud cover and possible some
sprinkles at best. A band of frontogenesis in the 650-750 mb layer
is helping to support some precipitation over North Dakota at this
time but the RAP has been suggesting for much of the day that this
becomes less organized and weaker as the system approaches before
coming back together over northeast Wisconsin after passing by. So
while there will be forcing from this system, overall, it looks to
be on the rather weak side but enough to produce some light
precipitation across areas mainly along and north of Interstate 94.
Most of this precipitation should fall as some light snow, but
forecast soundings have been consistent in showing the potential for
a loss of ice in the clouds for a while overnight for the
possibility of some light freezing rain or drizzle. Not expecting
much ice accumulation, but cannot rule out the possibility of a very
light glaze. As for snow amounts, there looks to be a pretty tight
gradient on the south side of the snow band with amounts ranging
from about an inch near Wisconsin State Highway 29 across northern
Clark County up to 3 inches for the northeast corner of Taylor
County. No plans at this time to issue a winter weather advisory for
this system.
The cold front that sweeps through with this system will bring in
some slightly cooler air for Wednesday, but it will still be mild
compared to the recent cold snap. Look for high temperatures to
range from the lower to upper 30s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 211 PM CST Tue Feb 23 2021
Northwest flow aloft develops over the Northern Plains and Upper
Great Lakes region Wednesday night into Thursday. The 23.12z GFS/NAM
show a weak shortwave trough embedded in the northwest flow aloft.
The deterministic models indicate weak lift/forcing in association
with the weak shortwave trough. Bufkit soundings from both of the
NAM/GFS suggest atmosphere does not saturate completely across much
of the forecast area. Precipitation could be sprinkles or flurries
with very little or if any accumulation. Introduced sprinkles or
flurries Wednesday night into early Thursday morning.
Surface ridge builds east of the area Thursday night into Friday.
Southerly winds on the backside of ridge will allow for continuing
mild temperatures across forecast area Friday. High temperatures
will warm into the middle 30s to lower 40s across much of the region.
Main forecast concerns are periodic precipitation chances through
the period. The 23.12z GFS/ECMWF/GEM are in ok agreement in breaking
down upper level trough over the High/Northern Plains states and
develop west to southwesterly flow aloft over the central United
States through the period. Timing and placement of embedded pieces
of energy in the flow aloft will be the biggest issue through the
period...especially the potential Tuesday system. The first pieces
of energy this weekend will provide precip chances across the
forecast area. Then focus turns to the next piece of energy ejecting
out of the Rocky Mountains Tuesday. The 23.12z deterministic ECMWF
has trended further south than previous run. This is in agreement
with the 23.06z GEFS...which suggest a couple of members to be a
stronger system. However...there are some members with track of
system further south per 23.12z ECMWF/GFS and produce no precip over
the forecast area Tuesday. Confidence is low for Tuesday and will
continue with small precip chances. High temperatures through the
period will remain near or slightly above normal...with highs mainly
in the middle 20s to around 40 through the period.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 945 PM CST Tue Feb 23 2021
An area of low pressure will continue to push through the area
and bring a band of rain/snow to areas north of I-94 tonight.
Can`t completely rule out a few sprinkles sneaking into the TAF
sites, but guidance continues to show a fair amount of dry air in
the low levels that is never quite overcome for precipitation.
Ceilings will gradually decrease and eventually get to MVFR as a
cold front passes through, though still some questions on exact
timing. Still plenty of guidance suggesting IFR will be possible
and upstream observations do show some patchy IFR upstream, but
confidence isn`t super high, so covering with a TEMPO mention at
RST for now. Also including mention the typical visibility
decrease we see when ceilings go IFR at RST. Clouds should
eventually scatter out by early Wednesday afternoon giving way to
VFR conditions through the remainder of the period. Otherwise,
winds will begin as southerly/southwesterly near 10 kts before
increasing and becoming northwesterly as the low and cold front
slide through. Could see some gusts around 20 kts at both sites
through the morning hours before they subside a bit and eventually
become more westerly later in the period.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...04
LONG TERM...DTJ
AVIATION...CA
Area Forecast Discussion
National Weather Service Cheyenne WY
513 PM MST Tue Feb 23 2021
.UPDATE...
Issued at 512 PM MST Tue Feb 23 2021
High Wind Warnings were allowed to expire at 5 PM MST. Cold front
was located along the I-80 corridor and moving slowly southward.
Winds were shifting from west to north-northwest with the frontal
passage. Post-frontal snow showers may deposit up to an inch of
snow during the next few hours along the US Highway 26 corridor,
including Wheatland, Torrington and Scottsbluff. PoPs and weather
grids were updated per latest radar trends.
&&
.SHORT TERM...(Tonight - Wednesday Night)
Issued at 150 PM MST Tue Feb 23 2021
High Wind Warnings remain in effect across much of southeast Wyo &
the western Neb Panhandle until 5 PM MST. Widespread wind gusts of
60 to 70 MPH have been observed w/ a few gusts in excess of 80 MPH
in the Arlington area around Cooper Cove. Strong low-level mixing,
coupled w/ enhanced mountain wave activity should support a threat
for high winds over the next few hours given the presence of 55-65
knots at 700-800 millibars. Low-level gradients will diminish very
rapidly over the next few hours, so winds are expected to decrease
below warning thresholds by 00z. Not as much wind for Wednesday in
the post-frontal air mass, with cooler highs 25 to 35 degrees. The
next short wave will sweep across the central Rockies Wed night or
early Thursday, with modest dynamic support & weak low-lvl upslope
potentially supporting some minor snowfall accumulations along and
south of I-80 between Laramie and Cheyenne.
.LONG TERM...(Thursday through Tuesday)
Issued at 111 PM MST Tue Feb 23 2021
A high pressure sets in on the Wyoming/Colorado border Thursday
bringing drier conditions to SE Wyoming and the Nebraska
Panhandle. It also brings tight gradients as a shortwave moves
through for a period between Friday evening and Saturday which
will likely bring strong winds to the wind prone areas around
Bordeaux and Arlington, but they could spill out into surrounding
areas, especially the Laramie Valley. The energy and moisture from
this shortwave will also likely bring some light snow to the
Snowy and Sierra Madre Mountain Ranges Friday. Then, as the
shortwave interacts with a cold front just east of the
Wyoming/Nebraska border starting as a rain/snow mix becoming snow
will impact the Nebraska Panhandle Sunday into Monday. Conditions
clear up Tuesday, except for a chance of snow in the Snowy and
Sierra Madre Mountain Ranges.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 426 PM MST Tue Feb 23 2021
Trended conditions for KBFF based on obs at nearby KTOR, satellite
and HRRR model for light snowfall and reduced conditions into IFR
early this evening. Conditions to improve around 03-04z. Introduced
some VCSH for some of the other NE terminals based on the HRRR
guidance but overall story will be the diminishment of winds in
the next couple hours after quite a blustery day. Looking at winds
generally lessening from west to east with gusts overnight into
the 20kt range. Wednesday diurnal increase in winds for the
afternoon period.
&&
.FIRE WEATHER...
Issued at 230 AM MST Tue Feb 23 2021
Another widespread strong wind event today with wind warnings for
much of southeast Wyoming and Nebraska Panhandle. Cold front will
be moving through the area today with winds becoming more
northerly after 1700. This should bring an end to the strong winds
behind the front. Colder Wednesday before strong winds return
Thursday afternoon ahead of next low pressure system. Afternoon
humidities well above critical levels through the week...so fire
weather concerns minimal.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...MAJ
SHORT TERM...CLH
LONG TERM...LK
AVIATION...WM
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Duluth MN
531 PM CST Tue Feb 23 2021
.DISCUSSION...(This evening through Monday)
Issued at 339 PM CST Tue Feb 23 2021
A low pressure system will move eastward through the region this
afternoon and overnight and will bring light snow or a wintry ix
of rain and snow to portions of the Northland. There will be a few
more chances of snow during the extended. Temperatures generally
remain near to above normal until the weekend and then trend below
normal for Sunday and Monday.
An area of low pressure centered over the central Dakotas this
afternoon will progress generally eastward to southern Ontario by
18Z Wednesday. Light snow is forecast to spread eastward across
central and portions of northern Minnesota into northwest
Wisconsin this afternoon and evening. With very warm surface
temperatures across the region this afternoon, precipitation may
begin as a rain/snow mix before changing over to all snow. Thermal
profiles lack warm air aloft, so any melting which occurs will be
in the lowest thousand to 1500 feet as the snow encounters the
warm boundary layer air. Snow reports upstream over north-central
and northwest North Dakota of more than 5 inches have been
received. There is a ribbon of strong frontogenesis along and
north of the low center which is expected to propagate across
eastern North Dakota and into central Minnesota this afternoon and
evening and east into northwest Wisconsin after 00Z. The RAP and
GFS hold this band of FGEN together as it transits the Northland
while the NAM takes on a more fractured FGEN structure by this
evening.
Have maintained the trend of lower snow totals inherited from the
mid shift with a swath of 1 to 4 inches of accumulation expected.
The highest totals will likely be over Ashland, Iron, and Price
Counties as omega and the strong FGEN will extend through the
dendritic growth zone longer than areas farther west. With the
upstream reports of over 5 inches of snow, there is at least a
possibility that the going forecast undercuts the efficiency of
snow production within the FGEN band. I would not be surprised if
there were a few reports around 5 inches by tomorrow morning. Will
keep the current suite of advisories in place with this update.
Would like to see a few hours of snowfall before making any
headline changes, so will leave that up to the next shift. The
snow and wintry mix may make roads slippery for the evening
commute, mainly over central Minnesota.
With overcast skies and precipitation falling tonight, I have
raised low temps across the area by several degrees compared to
the earlier forecast. Clouds should clear out quickly as the
system departs late tonight, so areas in north-central Minnesota
should see the coldest temperatures in our area. With mainly clear
skies expected for Wednesday morning and early afternoon, have
raised temps toward the 75th percentile of the NBM guidance.
Strong albedo effects were observed over portions of the Northland
this afternoon which resulted in temperatures rising well into the
upper 30s to upper 40s. While 850 mb temps will be cooler for
Wednesday, I think the albedo effects of our forested areas will
push temps warmer than the NBM output indicates. I may yet be too
cool by several degrees, especially over northwest Wisconsin and
portions of east-central Minnesota.
Another weak wave will propagate eastward through the region
Wednesday afternoon and evening. Deep moisture is meager but lift
should be sufficient to squeeze out a few flurries or snow
showers. Have added a slight chance of snow to the forecast with
this update to account for that potential. Thursday and Friday
morning are shaping up dry with an upper-level ridge progressing
eastward. A shortwave trough and associated surface low will scoot
eastward across the southern Canadian Prairies and into northwest
Ontario by Friday evening. A cold front will trail the surface
low to the southwest and a second low center is forecast to
develop along the boundary over eastern Montana and the western
Dakotas by Saturday evening. That secondary low will advance
eastward across Minnesota and northern Wisconsin overnight. Warm
air advection ahead of the low and falling heights aloft should
provide enough lift for widespread cloud cover and at least a
slight chance of snow. NBM guidance this morning was trending POPs
lower, so blended in a bit of CONSAll to raise POPs Friday
afternoon through Saturday morning in collaboration with
neighbors. Snow amounts of 1 to 3 inches seem probable during that
time. Moisture is limited with those low pressure systems as of
this morning`s runs. Small shifts in moisture field or timing
would result in higher or lower amounts for our area. Keep up with
the forecast through the week as details are refined.
Saturday afternoon and beyond trends quieter and colder as high
pressure slides down the spine of the Rockies and into the
Northern Plains and Upper Midwest through Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 529 PM CST Tue Feb 23 2021
Low pressure over the Dakotas will move eastward to southern
Ontario by 18Z Wednesday. Snow has been slow to move into the
Northland this afternoon. Still expecting a period of light snow
to spread across the terminals this evening with a period of IFR
conditions at DLH, BRD, and HYR. Recent runs of the RAP seem to
place the heaviest snow a bit farther north than earlier
forecasts. That northward shift increases the potential for HIB to
experience IFR conditions this evening or early Wednesday
morning. Have kept them MVFR for now, but later updates may need
to lower categories. Still expect clouds to scatter out as system
pulls away tonight and Wednesday morning. Another weak wave will
move through the Northland Wednesday afternoon and evening, which
may bring another period of MVFR conditions and light snow after
25.00Z.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 21 31 14 29 / 80 10 20 0
INL 13 27 5 30 / 10 20 30 0
BRD 20 33 16 33 / 100 10 20 0
HYR 24 34 14 31 / 100 10 20 10
ASX 25 33 16 31 / 90 20 20 10
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 5 AM CST Wednesday for WIZ001>004-
008-009.
MN...Winter Weather Advisory until midnight CST tonight for MNZ025-
033.
LS...None.
&&
$$
DISCUSSION...Huyck
AVIATION...Huyck
Area Forecast Discussion
National Weather Service Grand Forks ND
935 PM CST Tue Feb 23 2021
.UPDATE...
Issued at 934 PM CST Tue Feb 23 2021
Heavy snow band continues to progress southward along axis of mid
level frontogensis and steep mid level lapse rates, while
dry/stable air ins working southward into our northern CWA.
Reports reflect possible 1"/hr rates and totals 3-5" this evening
where it has now tapered off. It is hard to say at this point
whether the band holds together all the way into our far south,
but from a forcing/pattern standpoint RAP still shows support for
this holding together until main shortwave axis shifts far enough
south and east. Where it tracks/hold together 1-3" additional snow
will I adjusted the Winter Weather Advisory to include our
southern counties, cancelled the northern tier where it`s improved
and set the expiration to Midnight for the remaining counties.
UPDATE Issued at 642 PM CST Tue Feb 23 2021
East-west orientated band of organized snow extends from
Cooperstown to Mayville ND to Lake Itasca MN and is showing signs
on University of North Dakota radar of speeding up its north to
south progression. Under this band snow rates of 0.5 to 1" per
hour are likely occurring based on measured obs at NWS Grand Forks.
Elsewhere lighter snow is continuing but obs and regional
composites support the back edge of lower visibilities/measurable
snowfall spreading southward. Trends had been slower and I had to
make adjustments extend the duration of our western advisory to
03Z (9PM). By that point RAP is still indicating mesoscale forcing
(positive 700MB frontogenesis) transitioning to the southern RRV
and my midnight out of our CWA. Snow totals for most are likely
going to fall in the 1 to 3 inch range, with higher amounts where
organized band lingers for a longer duration (afternoon totals
under the band in the western Devils Lake Basin were in the 5 to
6" range).
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 309 PM CST Tue Feb 23 2021
The main focus in the short term is the wave today, and now a
secondary one on Wednesday/Wednesday evening.
Starting off with the first wave, the snow has been pivoting
steadily around the Minot area all day. NWS Bismarck reports over
6 to 7 inches out there. Moving into the Devils Lake region, had a
new report of 2-4.5 inches there, webcam at Rugby shows a few
inches, and a light dusting now into the Grand Forks area. Fargo
has had a rain/snow mix, but the steadier band still stretches
from Minot to west of Devils Lake. Quite a few of the high
resolution models are showing this band from Minot to west of
Devils Lake holding for another hour or two, then it begins to
slowly sag southeast. The 700mb wave is still forecast to track
through the FA with frontogenesis, but the surface low that is
now between Minot and Bismarck is expected to drop much further
southward than earlier anticipated, with 3 hour pressure falls
showing a track into northeast South Dakota. So really think the
heavier snow will linger for a few more hours, then lessen as it
falls apart somewhat as it tracks east-southeast. So the highest
totals should be around and to the south of Devils Lake through
4-5 pm, then not as much heading into the central Valley and west
central Minnesota this evening. No changes planned to current
headlines.
Models now show a secondary wave on Wednesday/Wednesday evening.
This will bring another shot of light snow to a good portion of
the area, but low end amounts (a dusting to an inch or so). Wind
speeds may be a bit higher on Wednesday, but still nothing too
high. Depending on where and how much snow falls with the first
wave (today into this evening) could impact high temperatures on
Wednesday. Tried to indicated some slightly lower highs on
Wednesday from Devils Lake to Hillsboro to Park Rapids.
.LONG TERM...(Thursday through Tuesday)
Issued at 309 PM CST Tue Feb 23 2021
Overview...
Impactful weather in the long term period is expected to be minimal,
with a smattering of light snow chances on Friday, Saturday, and
Sunday respectively. Ensemble guidance indicates that the upper
level pattern will remain progressive with transient periods of
troughing and ridging across the region. Aside from the
precipitation potential, above normal temperatures may remain in
place through the end of the week, although Tuesday snowfall will
ultimately impact the potential for warmer temperatures. Otherwise,
a cool down to the teens is expected on Saturday before a gradual
warm up to near normal moving into next week.
Thursday through Saturday...
Upper level ridging and a breezy west-southwesterly wind will see
temperatures rising back up above normal into the mid 30s on
Thursday. The warming trend should continue into Friday with the
persistent warm air advection, although a shortwave will bring the
possibility of light snow to portions of the northern forecast area.
Current ensemble guidance is in generally good agreement with this
system primarily impacting northwestern MN and LOW area with light
snow. Following the Friday system, a surface northerly wind and a
southward plunge of 850 hPa temperatures in the negative teens will
see highs on Saturday drop into the teens to low 20s. Another
shortwave is expected on the heels of the Friday system and is
currently progged to bring the next round of light snow to areas
generally north of Highway 2. The probabilities of 24 hour snowfall
greater than 1 inch, however, are in the 10 to 20% range at this
time. As a result, impacts are expected to be minimal.
Sunday and Monday...
Some relief is on the way as surface high pressure looks to build
into the region following the passage of the Saturday shortwave. An
attendant gradual warming trend should accompany the surface feature
as temperatures climb back up to near normal on Sunday and slightly
above normal by Monday. Late Sunday into Monday will also see some
precipitation potential for areas primarily south of I-94 as a low
pressure system moving across the central Plains tracks to the
northeast. This system may clip our southeastern CWA, but there is
still a great deal of variability with its eventual progression and
evolution and this system will continue to be monitored moving
forward.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 555 PM CST Tue Feb 23 2021
Band of moderate (locally heavy) snow is transitioning south and
southeast with broader areas of light snow across eastern ND and
northwest MN. IMpacts range from MVFR to localized LIFR where
greater snow rates are occurring. Trend should be for snow to end
this evening, however flight conditions may remain MVFR due to
lingering stratus or flurries through tonight into Wednesday. Wind
are shifting to the north and should generally prevail less than
12kt through Wednesday morning. A shift to the west and southwest
is expected during the afternoon.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Winter Weather Advisory until midnight CST tonight for NDZ024-
028>030-038-039-049-052-053.
MN...Winter Weather Advisory until midnight CST tonight for MNZ002-
003-015>017-022>024-027>032-040.
$$
UPDATE...DJR
SHORT TERM...Godon
LONG TERM...Godon/Rick
AVIATION...DJR
Area Forecast Discussion
National Weather Service Indianapolis IN
1043 PM EST Tue Feb 23 2021
.UPDATE...
The Aviation section has been updated below.
&&
.SYNOPSIS...
Issued at 350 PM EST Tue Feb 23 2021
A few light rain showers and patchy fog are possible Wednesday AM
before generally dry conditions and seasonably chilly readings
prevail through Saturday. The remainder of the period will see
near normal to above normal temperatures. Chances of rain,
possibly mixed with snow are expected Sunday-Monday...before
chances of rain and snow Tuesday.
&&
.NEAR TERM /Rest of Today and Tonight/...
Issued at 1023 PM EST Tue Feb 23 2021
Have slowed increase in cloud cover per satellite imagery and obs.
Temperatures began dropping steadily after sunset but have come up
in the last hour in response to ample ongoing low level warm
advection. Have bumped min temps up, somewhat substantially in
some areas, particularly northeast. Expect that temps will remain
somewhat steady and perhaps even warm a bit later tonight as the
warm advection continues. Removed patchy fog from grids as temp
trends and steady winds overnight suggest fog will be hard to come
by. This is supported by LAMP guidance and HRRR visibility progs.
Previous discussion follows.
Issued at 345 PM EST Tue Feb 23 2021
A touch of early spring was felt across much of central Indiana
today, with mostly sunny skies bringing temperatures back to at
least the low 50s for most of the region...although the slowly-
melting snowpack has limited warming across northern counties.
High pressure well to our south has continued to build in from the
south today, diminishing westerly winds to lighter breezes. The
next, rather weak weather system crossing the northern Plains
today, will promote a return to scattered clouds this
evening...courtesy weak warm advection aloft as it enters the
upper Mid-West. A stray sprinkle cannot be ruled out tonight,
but the potential for widespread fog will be the main story
as winds turn southerly, holding dewpoints >32F over remnant
snowpack along/north of the I-70 corridor. Fog may be mitigated by
more cloud cover or winds...as well as noticeably lower dewpoints
across southwestern counties which plummeting well below guidance
during this afternoon`s warm-up.
&&
.SHORT TERM /Wednesday through Thursday Night/...
Issued at 345 PM EST Tue Feb 23 2021
The region will be in the warm sector of the next, relatively weak,
system...as its low pressure center crosses the Great Lakes during
the AM hours Wednesday. Today`s guidance still indicates more of a
broad H700 dry conveyor at this time than any substantive fetch of
low-level moisture from our south...courtesy the mid-level`s
predominant zonal flow preventing good PVA south of Michigan. So
kept the slight chance POP/very low QPF confined to the southeastern
half of the CWA Wednesday morning where the system`s passing cold
front could shake out a few brief rain showers. Also, any pre-dawn fog
may last several hours after sunrise Wednesday, especially over
eastern counties, prior to the mixing and lower dewpoints that
will follow the system`s frontal passage.
The second half of the period will then see the next dome of Pacific
maritime high pressure slowly advance into the Mid-West from west to
east. Moderate northwesterly breezes Wednesday afternoon will bring
readings back to near normal before diminishing to light northerly
winds Wednesday night. Thursday will be seasonably chilly, yet
pleasant under partly cloudy skies and only light westerly breezes.
Thursday night is forecast to be the coldest of the entire forecast
period...with skies clearing and winds becoming light and variable
as the center of the high settles over Indiana.
Max temperatures will trend downward from the 45-55 range Wednesday
to the low to mid 40s on Thursday...overnight lows are expected to
be in the mid to upper 20s Wednesday night, and low to mid 20s
Thursday night. The normal max/min for the period is 44/27.
&&
.LONG TERM /Friday Through Tuesday/...
Issued at 209 PM EST Tue Feb 23 2021
Confidence is low in this forecast. ECMWF shows high pressure
departing the area on Friday while a surface warm front surges
northward into the Ohio valley...moisture appears limited and NBM
responds with low chc pops as a weak surface low passes across
the Tennessee Valley. Little to no upper support is available.
On Saturday and Sunday southwest flow looks to be in place aloft
as the ECMWF suggest a couple of weak short waves being ejected
toward Indiana ahead of a broader trough aloft over the Rockies.
The ECMWF shows a broad area of low pressure moving from OK to
the Great lakes along a poorly defined warm front boundary. Thus
have included some low chc pops for now. More chances for precip
appear on Sunday night as a stronger trough aloft is suggested to
drop out of the northern plains and cross Indiana.
More chances for precip appear possible on Tuesday as yet another
upper trough looks to push across Indiana from the northern
plains.
&&
.AVIATION /Discussion for the 24/06Z TAFs/...
Issued at 1043 PM EST Tue Feb 23 2021
*IMPACTS: Expect some low level wind shear during the first
several hours of the period, with surface winds becoming gusty
out of the south/southwest near daybreak Wednesday. MVFR ceilings
may also develop near or just after this time as weak low
pressure moves through the Great Lakes.
*DISCUSSION: Low level wind shear will move into the area early in
the period as winds strengthen ahead of an approaching cold
front. Surface winds will become gusty to around 20KT around or
just after daybreak. Expect ceilings to deteriorate as the cold
front approaches as well, with MVFR the most likely category.
Some fog and precipitation cannot be ruled out but are too low
probability for explicit mention at this time.
*CONFIDENCE: Moderate-high confidence in low level wind shear and
subsequent surface gustiness. Moderate confidence in MVFR
conditions tomorrow.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS...AGM
NEAR TERM...AGM/Nield
SHORT TERM...AGM
LONG TERM...Puma
AVIATION...Nield
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
559 PM CST Tue Feb 23 2021
.SHORT TERM...(This evening through Wednesday night)
Issued at 308 PM CST Tue Feb 23 2021
Radar returns have been mostly virga so far this afternoon, but
Cambridge recently reported light rain which may be a sign the lower
atmosphere is beginning to saturate. Light rain showers, possibly
mixed with light snow, should continue developing across western
Wisconsin before lifting north and focusing more over northern
Wisconsin and the northern half of Minnesota for the evening. This
does include the northern quarter of the CWA (north of a line from
Morris to St. Cloud and New Richmond). Temperatures will remain mild
enough to keep snow ratios low. Some rain may mix in at times too,
especially early in the evening. Only expecting around an inch in
those areas. Low pressure will track east across southern Minnesota
through late evening. As it heads into Wisconsin, the weakening band
of precipitation will wrap around to the southeast and give most
areas a shot at some light snow or flurries overnight before ending
late.
Skies will clear quickly Wednesday morning, but clouds will begin to
increase again by afternoon across western Minnesota ahead of a small
disturbance. Most operational guidance shows a cluster of snow
showers pushing across southern Minnesota Wednesday night. QPF is
actually kind of impressive for such a small feature. Forecast
soundings indicate mid level lapse rates of 7-7.5 C/km and impressive
Omega centered in the layer of the DGZ. Convective snow showers
could be supported in this environment and is likely why some models
generate two tenths of an inch of QPF in a narrow swath. Added 20-40
PoPs across the CWA, with the best chances centered along the MN
River.
.LONG TERM...(Thursday through Tuesday)
Issued at 308 PM CST Tue Feb 23 2021
Ridge of high pressure will slide east Thursday and winds will become
southerly by Thursday night. The pressure gradient will increase
substantially Friday as trough approaches from the northwest. Wind
throughout the profile just above the surface is rather impressive
with roughly 50 kts at the top of the boundary layer. Forecast
soundings don`t quite show a completely mixed profile due to snowpack
and warm air advection. It is not an unstable boundary layer scenario.
This could also be why winds are so strong aloft, a slight inversion
keeping the surface friction nil. Nevertheless, if mixing does become
fully dry adiabatic, there could be impressive wind gusts in the 40
to 50 mph range. Increased gusts a little to about 30 kts (~35 mph).
The fast flow will bring deeper moisture northward. This moisture
will begin to interact with the approaching trough as it heads across
the Upper Midwest. Precipitation may break out across eastern MN and
WI Friday evening, but the trend has been drier and drier as time
goes on. Kept low PoPs in place east of I-35, but they may eventually
be removed if the trend continues.
Predictability decreases this weekend and next week with split flow
developing once again. Phasing of the two streams would increase our
storm chances early next week with a cut off low over the
southwestern U.S. ejecting eastward to the Plains Monday and Tuesday.
Right now it appears phasing will not occur, keeping the system
across the southern states.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 559 PM CST Tue Feb 23 2021
Main change with the TAFs was to continue delaying the arrival of
MVFR cigs, pushing timing out toward the RAP, which hasn`t changed
much in the last 24 hours. Some uncertainty with just how low cigs
will be. Lots of IFR cigs to the northwest, but they`re seeing an
intensity of snow that we won`t. For this reason, stuck with low
MVFR cigs, but some IFR cigs are possible. Current thinking is we`ll
see a narrow band of stratus with initial push of CAA, but forecast
soundings from the RAP would support potential for diurnally driven
MVFR strato-cu on Wednesday. Snow potential this evening looks to be
tied to that stratus threat with initial CAA push, but rates look
very light with vsby restrictions between 2sm and 4sm if snow is
observed.
KMSP...High confidence in snow timing, though we could see some
variance by an hour on the front and back end. Most models show rapid
clearing of stratus happening between 10z and 12z, though there is
some concern that MVFR strato-cu develop mid morning as mixing grows
and a diurnally driven stato-cu field tries to develop.
/OUTLOOK FOR KMSP/
Thu...VFR. Wind WSW 5-10 kts.
Fri...Mainly VFR. Slgt chc MVFR/IFR with evening -SN. Wind SW 15G25
kts.
Sat...Chc MVFR cigs. Wind NW 5-15 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
SHORT TERM...Borghoff
LONG TERM...Borghoff
AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
1011 PM EST Tue Feb 23 2021
.UPDATE...
Issued at 1009 PM EST TUE FEB 23 2021
No major changes have been made to fcst for the overnight into Wed
morning snow event. Based on overall model trends from 00z guidance,
lowered snow accumulations over the Keweenaw (may not be much more
than a dusting there) and slightly increased amounts across the s
central and se fcst area. With forcing still working to overcome
antecedent dry air mass as noted on 00z KGRB sounding, have
slowed onset of snow, but it will eventually develop fairly
quickly from wsw to ene over the next several hrs.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 402 PM EST TUE FEB 23 2021
WV imagery and RAP analysis indicated nearly zonal mid/upper
level flow through the northern CONUS with a vigorous shortwave
trough over western North Dakota. Mild westerly low level flow and
sunshine has boosted temps to around 40 north and the mid to
upper 40s over southern Upper Michigan. Light rain and snow has
developed upstream from northern MN into nw WI with the developing
WAA pattern.
Tonight, as the northern Plains shrtwv approaches expect the pcpn to
quickly expand toward Upper Michigan and move into the west this
evening and around or after midnight over the northeast half. Wet-
bulb temps are low enough so that any rain will quickly change to
snow. A period of stronger 800-600 mb fgen and 290k-295k isentropic
lift with 3 g/Kg available may support a brief period of heavier
snow with snowfall rates up to an inch per hour. Overall QPF in the
0.20-0.40 inch range with SLR values around 12/1 support amounts in
the 2 to 5 inch range. Although the higher res models suggest the
heaviest snow will move through southern Upper Michigan, confidence
in the location of the the heavier amounts is still limited.
Wednesday, the snow will taper off quickly from west to east in the
morning as the shrtwv and sfc low depart. However, accumulating snow
may linger north central where northerly flow orographic enhancement
lingers even though 850 mb temps around -9C will be marginal for
significant lake enhancement. Otherwise, relatively mild conditions
will continue with highs into the lower 30s north and mid 30s south.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 346 PM EST TUE FEB 23 2021
A weak shortwave will approach the region via nw flow aloft bringing
the chance for light snow across the CWA Wednesday night before weak
LES occurs over the w and wnw wind snow belts on Thursday. A cold
FROPA will sag southward over the Keweenaw Peninsula, and CAA will
occur, resulting in surface temperatures being slightly cooler once
again for Thursday in that area. This won`t be for the entire CWA
however, so the southern tier of the Upper Peninsula adjacent to the
WI border and Lake Michigan will still see afternoon high
temperatures near 30 degrees. The remainder of the region will see
average temperatures for the high on Thursday. Any residual LES from
the departing shortwave on Thursday will push to the east by the
evening toward Sault Ste Marie.
A building ridge aloft will propagate toward the region Thursday
night, causing a shift in wind direction at the surface to the sw.
The sw winds will be accompanied by a 50 knot LLJ by Friday morning,
enhancing surface warming over the CWA. This warming trend will
persist throughout the day as 850mb temperatures warm by 10C to 12C.
The mixing of the strong winds aloft down to the surface will create
some downslope effects over areas that are known to have terrain
enhancement of wind speeds. This will create temperatures in the
upper 30s to low 40s over localized areas. We will be in the warm
sector of a developing surface lo over Ontario as the day
progresses. The temperature/pressure gradients associated with the
surface lo to our north will cause breezy to gusty winds over a
majority of the areas, with near gale force gusts over Lake Superior.
From Friday night into Saturday morning, upper level dynamics
further downstream of the surface lo will begin to assist with
precipitation developing over the Upper Midwest and into the Upper
Peninsula. The surface lo over ontario will likely occlude by Friday
evening. Several vort maxes, surface convergence, and diffluent flow
aloft will occur to eventually create a new triple point axis at the
surface for cyclogenesis over the Great Lakes region. Between Friday
night and midday Saturday, the extended range models begin to
diverge with the deterministic solutions. The GFS is the most
robust, with precipitation persisting over the area with rain/snow
throughout the day, but the Canadian and ECMWF have the main swath
of precipitation quickly moving to the east by Saturday night.
From Sunday into Monday, extended guidance is trending toward two
different solutions to end the weekend. A cut off upper level low
developing over the 4 corners region as it is sheared off from the
main longwave trough, bringing the chance of light precipitation
over the area as the base of the shortwave trough axis propagates,
over the Great Lakes, and the second possibility may be the longwave
trough evolves and brings the potential for more widespread
precipitation over the Great Lakes. The models diverging with
varying solutions for the Sunday/Monday system leaves the forecast
at a low confidence threshold. 850mb temperatures are progged to be
near -30C per the 12Z GFS, which would bring back Arctic
temperatures temporarily for the area if the weather changed that
drastically. Canadian, UKMET, and ECMWF are all "slightly" warmer
for 850mb temperatures on the order of +10C to +20C by Monday
morning. Trended toward slightly colder temperatures for Monday and
Tuesday for afternoon highs due to the GFS being the outlier thus
far.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 649 PM EST TUE FEB 23 2021
VFR conditions will continue for the next few hours at all the TAF
sites. Then later this evening, snow will spread into the U.P.,
beginning in KIWD. Expect conditions to become IFR late tonight via
low visibilities at all the TAF sites. Conditions should begin
improving Wednesday morning, starting with KIWD. Expect conditions
to gradually improve to MVFR during the morning, becoming VFR late
in the afternoon tomorrow. KSAW should hold onto MVFR conditions
the longest Wednesday.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 402 PM EST TUE FEB 23 2021
Northwest winds to 25 knots over the east will diminish and become
northerly tonight before increasing to 30 knots on Wed across the
eastern half of Lake Superior. Winds diminish Wednesday night
through Thursday night before southwesterly increase to 30 knots
again on Friday. A few gale force gusts may also be possible. The
wind then dies down to 25 knots out of the northwest on Saturday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory until 10 AM EST Wednesday for MIZ006-013.
Winter Weather Advisory until 10 AM EST Wednesday for MIZ007-014-
085.
Winter Weather Advisory until 7 AM EST /6 AM CST/ Wednesday for
MIZ002-004-009-010-084.
Winter Weather Advisory until 11 AM EST Wednesday for MIZ005.
Winter Weather Advisory until 8 AM CST Wednesday for MIZ011-012.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
UPDATE...Rolfson
SHORT TERM...JLB
LONG TERM...BW
AVIATION...TAP
MARINE...JLB