Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/11/21
Area Forecast Discussion
National Weather Service La Crosse WI
938 PM CST Wed Mar 10 2021
.UPDATE...
Issued at 927 PM CST Wed Mar 10 2021
The line of showers and a few storms continues to move across far
eastern Iowa and parts of western and central Wisconsin. Over the
last hour, we have seen an uptick in gusty winds in southeast
Minnesota 45 to 50 mph at RST/TOB. Decided to extend parts of the
wind advisory until 09Z as it looks like the winds may hang on a
little later.
&&
.SHORT TERM...(Tonight through Thursday)
Issued at 200 PM CST Wed Mar 10 2021
SEVERE THREAT THIS EVENING: decent clearing has developed ahead of
an area of low pressure currently pushing into western IA, although
has filled in somewhat with cu. Upper 60s temps and mid to upper 50s
dewpoints were located in the warm sector, working northeast ahead
of the low/sfc cold front. RAP SBCAPE results in a thin ribbon of
+1000 J/k by 00z along the western edges of the forecast area,
quickly falling off as the storm system moves east/loss of daytime
heating. Shear is...robust. 30-40 kts of 0-1km shear with plenty of
turning in that layer. Shear continues into the 3-6 km layer, but
not as impressive as in the low levels. If there was more
instability, this would get ugly awfully fast. As it stands, a few
strong potential severe storms are possible, with SE MN/NE IA
holding the higher threat (more instability). Overall timing roughly
4 to 10 pm, with the severe threat probably more so 4 to 7. Isolated
tornadoes highlight the hazards, with winds then perhaps a bunch of
small hail. Not sure the instability/low level lapse rates (and
somewhat skinny cape profile) will be enough for inch plus hail.
Updraft strength could be an issue. Not saying "no" though. In
addition, RAP KRST showing a relatively healthy cap to deal with.
Another issue to overcome. Overall, will be watching radar closely
and don`t be surprised to see a few warnings.
WINDS: After the storms sweep through by mid evening, the parent low
pressure system tracks from southern MN into northern WI, exiting
overnight across the northern great lakes. Strong winds a loft/near
sfc with +60 kts 850 mb jet streaking ahead of the sfc low and
tightening sfc pressure gradient on the southern/western side of it.
RAP bufkit soundings suggest mixing down upwards of +40 kts at KRST
while 50 kts hangs out just under 2 kt. Inversion/time of day will
work against working down the strongest winds but gusts upwards of
45kts look reasonable for the open areas west of the Mississippi
river, potentially across northwest WI. Will continue Wind Advisory
in its current configuration with this mind (modify if becomes
necessary).
.LONG TERM...(Friday through Wednesday)
Issued at 200 PM CST Wed Mar 10 2021
After the passage of the storm system later thu, quieter and cooler
air will settle in for the weekend as a sfc high meanders overhead.
Temperatures still looking to be above normal though.
Winter hasn`t left quite yet though as the next storm system takes
aim on the region for Sun night-Mon. Upper level shortwave trough
slated to swing out of the desert southwest Sat, lifting northeast
toward the eastern great lakes (but on a weakening trend). Sfc low
holds well south of the region but with good west-east frontogenetic
banding north of the low - across the local area. Decent fetch of
850 mb moisture transport will feed this lift, with some enhancement
from the left exit region of a 300 mb jet max. Overall, the GFS and
EC have been fairly consistent with placement/timing of this next
pcpn maker across the area for the past several days. Bulk of the
ensemble members support accumulating pcpn for the local area
too. Bigger questions lie with what would fall.
Colder temperatures will already be in place by the time this trough
works into the region. Time/height x-sections via the GFS and EC
(along with some sounding data) point to above zero sfc/near sfc
temps and colder aloft - suggestive of more a rain/snow question
rather than mixed (at least at this time). Currently, the GFS is
the more aggressive with considerably more snow but a wide variety of
outcomes (per GEFS ensembles). The EC would drop a few inches of
snow, but much less. With a wide range of potential outcomes,
confidence is pretty low in how it plays out. Pcpn looking likely,
but amounts and exact layout are uncertain. Something to watch for
sure...
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 540 PM CST Wed Mar 10 2021
Broken line of showers has pretty much cleared through RST at this
hour and now sits on LSE doorstep. Thunder chances are very low
and confined more to our north and south. Breezy southerly winds
will quickly shift to the southwest this evening behind a passing
front. Despite the gusts this evening, winds at 2000 ft will
approach 50 kts so still expect up to a few hours of low level
wind shear. Winds then ramp up behind the front with gusts
of 25 to 35 knots, perhaps a bit stronger at RST. Satellite shows
widespread MVFR to IFR cloud cover just off to the west, which
will spread into the TAF sites later this evening. Strong winds
gradually become more westerly overnight, slowly relaxing late
tonight into Thursday morning. High pressure then gradually builds
into the area on Thursday, ushering in a clearing trend towards
midday and a return to VFR.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Advisory until 3 AM CST Thursday for WIZ017-029-032>034.
MN...Wind Advisory until midnight CST tonight for MNZ094-095.
Wind Advisory until 3 AM CST Thursday for MNZ079-086>088.
IA...Wind Advisory until midnight CST tonight for IAZ008-009-018-019.
&&
$$
UPDATE...Zapotocny
SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...Kurz
Area Forecast Discussion...Updated
National Weather Service Billings MT
607 PM MST Wed Mar 10 2021
.UPDATE...
Updated forecast to expire Winter Weather Advisory for NE Bighorn
Mountains. Light snow showers will continue over the mountains
through around 03Z based on latest HRRR, but accumulations will be
light. Other snow showers over the Beartooths/Absarokas and
adjacent foothills will die out this evening due to loss of
insolation. Lapse rates of 8 deg C/km were indicative of an
unstable airmass, but lift was very weak and mainly orographic. A
few other snow showers had formed E of KBIL, so had low PoPs in
through 03Z for these. Also latest HRRR continued to bring patchy
fog S behind a cold front later tonight. Stratus was visible
behind the front in Canada in surface obs and on IR satellite.
Fog/stratus looked to start around 08Z so pushed back start time
in grids. Otherwise, forecast was in good shape. Arthur
&&
.DISCUSSION...
Tonight through Thursday Night...
Satellite imagery shows a shortwave over SD/NE moving east, and a
low off the coast of northern CA, leaving us under a broad region
of below normal heights and weak flow aloft. 500mb temps to -35C
in central MT allowing for instability snow showers to form over
our mountains and adjoining foothills. Some of this shower
activity could be briefly heavy but otherwise it will not be
organized. A winter weather advisory remains in effect til 6 pm
for the NE Bighorn Mountains, and while synoptic snowfall has
pretty much ended, a couple more inches of snow is possible w/ the
showers over the next few hours. Overall, snow showers will taper
off during the evening.
Looking to the north, there is a cold front moving into north
central MT, supported by a Canadian shortwave and trailed by an
area of stratus in southern Alberta into Saskatchewan. As this
front moves south, we could see some low clouds and perhaps
localized fog eke into our cwa beginning around 10z tonight
(mainly KBIL north and eastward). The fropa may be followed by
some flurries but otherwise better forcing and potential for snow
showers looks to stay to our north. As the Canadian wave moves off
to the east, warming temps aloft will reduce the instability and
should prevent any diurnal showers tomorrow afternoon. Thursday
night will be dry under rising heights within col region.
Temps will be seasonable over the next 36 hours, with lows mainly
in the 20s and highs in the 40s.
JKL
Friday through Wednesday...
Mainly dry conditions and above normal temperatures are forecast
Friday through the weekend with high pressure over the Northern
Rockies, while a cut-off low to the south tracks from Arizona
to southeast Colorado. There is a chance the cut-off low pushes
some moisture far enough north to affect Sheridan County and some
areas along the Montana/Wyoming border by Saturday night and into
Sunday. This could bring some snow accumulations, but most of the
area will be dry through the weekend.
High levels of uncertainty remain with regards to what happens
early next week. Latest trends are for the cut-off low to move
east into the central plains, with upper troughing moving into the
West. How these interact with each other will dictate our
weather. There remains quite a bit of spread in temperatures and
precipitation, with ensembles showing a variety of solutions. That
being said, it looks like cooler and more unsettled weather are
possible over the area early next week with chances for rain/snow
showers. Highs temperatures are forecast to range from the 40s
and 50s Friday, to mainly 50s for the weekend. Highs in the lower
40s to lower 50s for early next week. Low temperatures in the 20s
to lower 30s will be common for the extended period. STP
&&
.AVIATION...
Snow showers will frequently obscure mountains late this afternoon
and evening, while VFR prevails across lower elevations tonight.
Early Thursday (08z-16z), there is potential for localized fog
and broken MVFR ceilings from KBIL to KMLS and KBHK. Otherwise,
VFR will prevail tomorrow. Arthur/JKL
&&
.PRELIMINARY POINT TEMP/POPS...
Thu Fri Sat Sun Mon Tue Wed
-----------------------------------------------------------
BIL 025/047 026/053 028/053 033/055 031/053 031/048 029/047
10/U 00/U 00/U 10/B 11/B 23/O 21/B
LVM 019/043 021/046 024/050 030/051 030/050 030/046 028/045
20/U 00/U 00/U 00/B 11/B 33/S 21/B
HDN 022/046 022/054 026/055 030/055 029/053 027/049 028/047
20/U 00/U 00/U 11/B 12/R 23/O 21/B
MLS 022/043 023/053 027/056 029/054 029/050 026/045 026/044
01/B 00/U 00/U 00/B 11/B 11/B 11/B
4BQ 024/046 023/051 028/052 030/050 028/048 026/046 026/044
00/B 00/U 01/U 21/B 11/B 12/S 11/B
BHK 020/042 020/052 024/054 026/051 025/046 022/043 022/042
01/B 00/U 00/U 01/B 11/B 11/B 11/B
SHR 020/043 019/046 023/045 026/046 023/046 022/043 023/043
21/B 01/U 12/O 32/O 12/O 23/S 22/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Cheyenne WY
522 PM MST Wed Mar 10 2021
.UPDATE...
Issued at 517 PM MST Wed Mar 10 2021
Let the Winter Storm Warnings and Winter Advisories expire this
evening as most of the snow has ended with the first shortwave
moving into the northern plains. Will send out updates to POP,
temperature, and winds over the next few hours once the snow
showers or flurries end shortly. Winter Storm Watch in effect for
Friday and this weekend with the most severe conditions likely
Saturday, Saturday night, and Sunday morning.
&&
.SHORT TERM...(This evening through Friday)
Issued at 300 PM MST Wed Mar 10 2021
...One winter event winding down this afternoon.
Another...potentially historic event taking shape for Friday
through Sunday....
Currently...Surface low near Wheatland this afternoon with cold
front extending southwest into northwestern Colorado. Snow band
continues across the northern Nebraska Panhandle westward to
Converse County. Still getting snow reported on mountain SNOTELS
in the SNowy and Sierra Madre Ranges as well as Metars up near
Douglas and Chadron. Decided to clear out most of the advisories
across the southern CWA with the exceptions of the Snowy and
Sierra Madre Ranges and Converse/Niobrara and northern Panhandle
where warnings will be allowed to continue through 5PM. Off to our
west across central California...our next low pressure system is
moving on shore.
Evening shift will need to monitor for fog development this
evening as the snow that fell today had quite a bit of moisture
content to it. Would say the lower elevations of the Panhandle and
maybe Laramie would be the prime areas for fog tonight.
Mainly dry Thursday for most of the day...but guidance begins to
hint at qpf developing across our southwestern counties late
Thursday afternoon. Upper low moves into southern Nevada and
northern Arizona Thursday evening with difluent upper level flow
over southern Carbon and Albany Counties. NAM...SREF and GFS all
showing widespread QPF Thursday evening into Friday morning in
this diffluent flow. ECMWF showing similar placement...but much
less QPF. Given the pretty good agreement from the GFS...NAM and
SREF QPF...decided to start a Winter Storm Watch for our western
counties after 00Z Friday...spreading east to the Panhandle by 12Z
Friday.
.LONG TERM...(Friday night through Wednesday)
Issued at 300 PM MST Wed Mar 10 2021
Key messages...Heavy snowfall is likely starting Friday afternoon.
Prepare for impossible travel conditions starting Saturday morning into
Sunday evening. Protect livestock, people, property, and pets.
IMPACTS...Whiteout conditions, low visibility levels, and possible
power outages. Blizzard conditions are possible starting Saturday
afternoon into Sunday evening for the Nebraska Panhandle and
Albany, Laramie, Platte, and Goshen counties.
Saturday and Sunday`s snowfall will bring major impacts to the
entire CWA across southeastern Wyoming and the western Nebraska
Panhandle. Forecast confidence is medium with placement and duration
of the low pressure system hovering in Colorado. The uncertainty
continues for exact snowfall amounts and intensity of this system
due to the forecast concerns of varying dynamics and the
possibility of a barrier jet forming. Although it is still early,
this system shows tight gradients and strong winds aloft will
support strong surface gusts up to 35-40 MPH for the Nebraska
Panhandle and southeastern Wyoming. A possible jet could develop
along the Rocky mountain ranges which could enhance snowfall
development especially with most models showing cold air aloft.
Snowfall ratio were too high with the GFS so using a NBM/ECMWF
blend, I created a sweet spot ratio across the CWA ranging from
11:1-8:1. If this set up continues on track, this will lead to
record-breaking snowfall across the region. Potential 3-day storm
total snow forecasts are significantly above maximum 3-day records
for Cheyenne and Scottsbluff including the March 2003 snowfall
event.
In addition to snowfall and strong winds, temperatures continue below
freezing in southeastern Wyoming and hover in the upper 30s for
the Nebraska Panhandle into next week. Skies will remain overcast
into Tuesday afternoon. A piece of energy cuts off the same low
pressure system from the weekend which may lead to light snowfall
again Tuesday although upper level moisture is not present at this
time. Mild conditions are possible mid next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 420 PM MST Wed Mar 10 2021
Snow has started coming to an end for the southeastern Wyoming
terminals, and is expected to continually diminish this evening
for the Nebraska Panhandle. Will still see some lingering show
showers over the next few hours for the KCYS and KRWL terminals.
Otherwise, KCDR should begin to lift from a IFR to VFR this
evening as snow pushes out of the region, with mostly MVFR and VFR
expected for the remaining terminals. Current HRRR forecast
soundings do indicate a potential for some low-level fog with the
widespread melting snow moistening up the atmosphere for KLAR and
the Nebraska Terminals. However, confidence remains low with a
lack of clear skies to promote good fog development. Went ahead
and lowered visibilities for the time periods expected, and will
continue to monitor current conditions for any corrections needed.
&&
.FIRE WEATHER...
Issued at 300 PM MST Wed Mar 10 2021
Minimal fire weather concerns as we have seen widespread snow and
are looking at another widespread heavy snow event Friday through
the weekend.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Watch from Thursday evening through late Sunday
night for WYZ101>103-106>108-116>119.
Winter Storm Watch from Thursday afternoon through late Sunday
night for WYZ104-105-109-110-113>115.
NE...Winter Storm Watch from late Thursday night through late Sunday
night for NEZ002-003-019>021-054-055-095-096.
&&
$$
UPDATE...TJT
SHORT TERM...GCC
LONG TERM...AW
AVIATION...MD
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Des Moines IA
540 PM CST Wed Mar 10 2021
...Aviation Update...
.DISCUSSION.../Tonight through Wednesday/
Issued at 137 PM CST Wed Mar 10 2021
145 PM CST Update on Severe Weather:
SPC has issued an MCD recently, so will not provide a lengthy
update here but just hit the highlights for this AFD issuance.
Instability continues to build across central Iowa, and day-cloud
phase satellite imagery is showing a cumulus field attempting to
develop across central Iowa. As of 1930z, there were some weak
radar reflectivities in northwest Iowa. Lapse rates continue to
steepen, maintaining an a favorable thermodynamic environment. The
MCD at 1933 UTC from SPC states a watch may be needed this
afternoon. The next section will repeat the 1741 UTC AFD update
from today.
Previous AFD Update from 1141 AM CST Today:
Short-wave trough and deepening surface cyclone continue to move
northeast, currently located over eastern Nebraska. Pre-frontal
surface troughing extends from northwest Iowa into southern and
southeastern Minnesota as of 1715z. As was noted overnight by GOES-
16 visible satellite imagery, a prominent dry slot has been moving
through over the warm-sector of the cyclone. Visible satellite
imagery shows mostly clear skies for southwest Iowa, with cloud
cover diminishing across central and northern Iowa. With this
clearing, insolation will allow the convective boundary layer to
destabilize ahead of the convergent boundary in an area of stronger
convergence. At 1715z, SPC mesoanalysis depicts a bullseye of SBCAPE
of 1000 J/kg in west-central Iowa, with 500-750 J/kg expanding
toward the northeast within the pre-frontal surface troughing
region. With insolation and the continued push of rich theta-e air,
expect SBCAPE values continue to rise and spread eastward over the
next few hours ahead of the convergence. 14z-15z runs of the HRRR
favor SBCAPE values reaching as high as 1500-1750 J/kg over the next
few hours, and this trend seems reasonable. This is higher than what
the HREF mean had been depicting over the past 24 hours. Dewpoints
have also been steadily rising from the mid 40s into the mid and
upper 50s. There was some concern earlier that robust mixing with
the gusty winds may create too dry of an environment, but as the
convective boundary layer evolved this afternoon moisture does not
appear to be in short supply. The vertical wind shear environment
remains strong, this was never in question as is typical with early
spring convective developments. 0-6 km bulk shear ahead of the
convergent boundary is 50-60 kts. RAP and HRRR analysis indicate 0-1
km SRH for right moving supercells to be in excess of 200 m^2/s^2
ahead of the boundary, and 0-500m SRH around 100 m^2/s^2. Given this
environment, all severe threat types are possible this afternoon and
early evening, from hail, damaging winds, and a tornado or two could
spin up in this environment. As for timing of initiation and
eventual evolution, this is still a bit hard to pinpoint at the
current moment. Recent runs of the HRRR have initial development in
the far northwestern portion of the forecast area between 18-19z,
but quickly move these storms into southern Minnesota. If updrafts
do go at this time, the environment is there to help get them
spinning and could produce hail and maybe a brief spin up. The
window though for this happen in areas such as Emmet, Palo Alto, and
Kossuth Counties will be narrow. Later this afternoon then,
convergence increases across central Iowa along much of the
Interstate 35 corridor. Recent runs of the HRRR over the last couple
of hours have pulled initiation further north and west, and about an
hour earlier to around 23z. With the instability that has developed
in the strong shear environment, a couple of discrete supercell
thunderstorms are possible in central and east-central Iowa this
afternoon into the early evening. Again, all severe threats are
possible close to the initiation time of thunderstorms. But, deep
layer shear by early evening begins to align more parallel to the
convergent boundary, and as noted in most of the CAMs since 12z
develops more into a broken squall-line. As this evolves into a
squall-line, the hail and tornado threat will decrease, but still
could result in severe wind gusts through the evening in east-
central Iowa, and perhaps southeast Iowa. The 1630z SWODY1 from SPC
highlights this with the expansion of the slight risk. With strong
flow, these storms and the eventual linear system will move rather
swiftly, in excess of 50 kts. Over the next few hours, will continue
to monitor the moisture transport, the surface wind field, and the
instability. The areas of interest in the middle of the afternoon
will be the far northwest Iowa, and then late afternoon early
evening for central and east-central Iowa.
Thursday and Beyond:
Short-wave trough moves away from the region, while deeper trough
develops into a broad closed low at H5 in the western CONUS. Weak
ridge develops across the central Plains to just west of the Great
Lakes Region, which will allow surface high pressure to build
Thursday into Friday. The center of it will move through Thursday
Night into Friday morning. This will clear skies out, and bring in
slightly cooler temperatures with light north to northwest flow.
There is another wave within the flow that moves across Missouri
that may generate some precipitation there, and may just clip the far
southern counties Friday Night. However, with the high pressure
developing, there is decent probability this forcing gets pushed
even further south. Do not anticipate much in the way of
accumulation if precipitation does occur in far southern Iowa Friday
Night. Ridge amplifies some as the closed low slowly propagates
eastward. Expect clouds to be on the rise advecting from the bigger
system out west. By Saturday evening, precipitation shield will
start working toward the region, which may bring rain showers to
southwest and west-central portions of the forecast area. This will
increase in coverage Sunday into Monday as this system moves into
the central Plains and upper Midwest. Models again are not showing
the best agreement with the timing and track of this closed low
system, and within the ensemble members QPF placement is not
consistent. Accumulating snowfall could be possible if the
deformation zone aligns favorably, by the end of the weekend and
start of the work week. After the passage of this system, colder air
will move into the region, and expect temperatures for much of next
week to be below normal. The good news is that it is March below
normal, not February, thus although temperatures will be colder they
will not necessarily be brutal cold. The overall pattern is still
somewhat active through next week, expect multiple periods of
precipitation.
&&
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 536 PM CST Wed Mar 10 2021
Main concerns will revolve around lingering convective activity
the over the next couple of hours and then transitioning over to
MVFR/IFR stratus potential. The main convective threats will be a
KALO and KOTM. The primary MVFR/IFR stratus potential will be
KFOD/KMCW with lesser opportunity at KDSM/KALO. Winds will also
remain gusty, to 25 to 30 kts or greater out of the west, across
the northern TAF sites much of this evening and into the
overnight before easing early Thursday and settling out of the
W/NW.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 8 PM CST this evening for IAZ033>039-046>050-
059>062-072>075-083>086-094>097.
High Wind Warning until 8 PM CST this evening for IAZ044-045-057-
058-070-071-081-082-092-093.
Red Flag Warning until 6 PM CST this evening for IAZ057-058-070-
071-081-092.
Wind Advisory until midnight CST tonight for IAZ004>007-015>017-
023>028.
&&
$$
DISCUSSION...Krull
AVIATION...Curtis
Area Forecast Discussion
National Weather Service Quad Cities IA IL
555 PM CST Wed Mar 10 2021
...00z AVIATION UPDATE...
.SYNOPSIS...
Issued at 214 PM CST Wed Mar 10 2021
A wind advisory remains in effect until 8 PM this evening. MSAS,
surface analysis showed a surface low in northwest ILlinois with a
stalled front stretching northeastward from the surface low
towards MSP. A cold front stretching from the surface low
southwestward into south central Nebraska. A dryline stretched
southward along the Iowa and Nebraska border then is turns
southwestward into Kansas then into southwestern Oklahoma and into
West Texas. Across the local area, temperatures ranged from the
lower 60s along the Highway 20 corridor to the upper 60s south of
Interstate 80. KMLI was the warm spot at 70 degrees. Strong
southerly winds sustained at 20 to 30 MPH with gusts up to 40 MPH.
Skies were clearing ahead of the dryline across central Iowa with
temperatures in lower 70s.
&&
.SHORT TERM...(This Evening through Thursday)
ISSUED AT 214 PM CST Wed Mar 10 2021
The main forecast concerns have been winds and the potential for
severe weather. Models are in good agreement but CAMs have a
better handle on the severe weather potential for today.
Models are in good overall agreement that the surface low
currently in northwest Iowa will track northeastward and into
southwestern Ontario by 12 UTC on Thursday. This will drive a cold
front across the area tonight. Models prog the cold front moving
across eastern Iowa, northeast Missouri, and northwest Illinois
between 00 UTC and 06 UTC. Ahead of the front, warming as clearing
spreads into eastern Iowa and northwest Illinois late this
afternoon and into this evening before sunset will allow for more
mixing and may increase winds slightly this afternoon and into
this evening. Model soundings show the potential for mixing higher
winds down to the surface so wind gusts up to 45 MPH are possible
before gradually decreasing behind the front with the pressure
gradient decreasing in the wake of the low during Thursday
morning. Temperatures on Thursday will be noticeably cooler.
Expect thunderstorms to develop late this afternoon ahead of the
front and continue across the area this evening with most storms
exiting the far eastern end of the CWA in the 6 to 9 UTC
timeframe. Please see the previous update issued earlier.
Previous Update
Guidance and obs are pointing to a better environment for HSLC
severe threat this evening across the area. Insolation and breaks in
the clouds in the clear slot are leading to the development of
surface instability. With the system already shear heavy the
environment is supportive of a conditional severe threat.
While it looked like the main threat was winds earlier, the threat
for tornadoes appears to be increasing for the following reasons.
1). CAPE that develops is concentrated in the lower levels of the
atmosphere. As a result of this, the updraft will be shallower and
will have the bulk of the llvl shear to tilt. This shear will lead
to updraft rotation in the llvls increasing convergence in the
lowest levels. There is also 0-3km CAPE that would be supportive of
tornado development 2). The shear is impressive and the H85 LLJ
strengthens across the area from 00z to 03z. This strengthening of
the LLJ will increase shear and subsequent storm updraft and
intensity. This will only aide in convergence at the sfc. The 0-
0.5km shear of near 30knots is impressive and will help to create
frictionally generated vort in the low levels. If the HRRR is
correct and we stay S at the sfc with winds, we will have more than
sufficient directional shear for a tor. Even so, if we have a long
lived mesovort with less directional shear that could pose a tor
threat as well. Regardless, these storms will pose a damaging wind
threat across the area. Any mesovort that develops will bring
chances for winds up to 70 mph.
The HRRR is the most aggressive with storms, yet has been extremely
consistent for the last 7 to 8 runs, increasing confidence in its
solution. The tornado threat, while increasing, is completely tied
to the sfc wind direction and mesovort longevity. The wind threat
continues to be the main threat from these storms.
.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 214 PM CST Wed Mar 10 2021
Key messages:
1. Active period with cooler temps through the long term period.
Discussion:
Active period as a cutoff upper low across the SW US eventually
ejects across the Plains through the weekend. As this feature
shifts east with time, additional shortwaves advect into the
backside of the trof and provide chances for pops through the
extended. This large trof will bring cooler temps to the area and a
chance for mixed precip this weekend. A lot is still unknown with
the thermo fields for this weekend so confidence in Ptype is low.
With the highly energetic momentum fields, expect forecast skill to
be low, so while there are chances for precip, exact timing and
intensity will likely change through the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
ISSUED AT 548 PM CST Wed Mar 10 2021
Strong LLVl wind fields and turbulent airmass continues in place,
and will time a short 1-2 hour tempo window at each site this
evening for walking through a line of thunderstorms along an
incoming front. CIGs may still stay VFR as these storm pass by or
brief bouts of MVFR, but rain or wind blown rain reduced VSBYs
may go to passing bouts of low MVFR or even IFR at times. Then
behind the storms, a temporary dry slot clear window with sfc
winds going west-southwest and still gusty to at least 25 KTs.
Hopefully no gravity wave rear storm-line enhancement boosting
winds even higher. Will go brisk variable winds of 25-30 KTs and
gusts to at least 38-40 KTs in the TEMPO groups with the stronger
passing storms, but they may be higher. Later tonight with some
decrease in west winds, will have to watch for a wrap around
post-frontal MVFR stratocu deck getting into at least the CID and
DBQ sites for at least Thu morning. CIGs should trend VFR by Thu
afternoon. ..12..
&&
.HYDROLOGY...
Issued at 315 PM CST Wed Mar 10 2021
Moderate within bank rises continue on area rivers as snowmelt
from far northern Iowa and Wisconsin works its way south.
A flood warning continues for the Wapsipinicon river near Dewitt.
More tributary rivers are forecast to approach flood stage
from the snowmelt late this week and over the weekend before
falling early next week. Those locations are;
Cedar river at Cedar Bluff and near Conesville
Iowa River at Marengo, Columbus Junction, Wapello, Oakville and
near Lone Tree
Maquoketa river at Manchester
Pecatonica river at Freeport
Rock river at Como, Moline and near Joslin
Ensemble runs suggest the Mississippi river may begin to approach
flood stage due to snowmelt after March 15th.
Weather prediction models continue to trend lower with the predicted
rainfall through Thursday. Most of the area now looks to see 0.1
to 0.2 inches of rain which will soak into the ground. The heavier
rainfall now looks to occur from central Missouri into the
southern half of Illinois.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Wind Advisory until 8 PM CST this evening for Benton-Buchanan-
Cedar-Clinton-Delaware-Des Moines-Dubuque-Henry IA-Iowa-
Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-Linn-Louisa-
Muscatine-Scott-Van Buren-Washington.
IL...Wind Advisory until 8 PM CST this evening for Bureau-Carroll-
Hancock-Henderson-Henry IL-Jo Daviess-McDonough-Mercer-
Putnam-Rock Island-Stephenson-Warren-Whiteside.
MO...Wind Advisory until 8 PM CST this evening for Clark-Scotland.
&&
$$
SYNOPSIS...Cousins
SHORT TERM...Cousins/Gibbs
LONG TERM...Gibbs
AVIATION...12
HYDROLOGY...DC
Area Forecast Discussion
National Weather Service Lincoln IL
809 PM CST Wed Mar 10 2021
.SYNOPSIS...
Issued at 312 PM CST Wed Mar 10 2021
Gusty south winds linger into this evening, with gusts up to 45 mph
possible. Rain showers and some storms spread in from the northwest
overnight into Thursday. Overnight lows will be mild with values in
the middle 40s to upper 50s. Some stronger storms capable of
producing small hail and gusty winds are possible across southeast
Illinois on Thursday.
&&
.UPDATE...
Issued at 808 PM CST Wed Mar 10 2021
South half of the wind advisory has been canceled early, as gusts
in this area have dropped off to less than 40 mph. Still seeing
some stronger winds across the north, especially along I-74 with
recent gusts near 45 mph at Peoria and near 50 mph at Bloomington.
HRRR drops off these higher gusts from southwest to northeast the
remainder of the evening.
Line of showers and thunderstorms currently extends from northeast
Iowa into south central Kansas, just ahead of the cold front.
Latest high-res model runs bring it to near Peoria toward
midnight, with some breakup in the line as it approaches the I-55
corridor. RAP model shows 300-400 J/kg of MUCAPE lingering
through the night with this line, though, so will keep a mention
of some thunder continuing. Temperatures to remain very mild over
most of the CWA overnight and may struggle to drop below 60 before
sunrise, while upper 40s/lower 50s come into the Illinois River
valley.
Updated zones/grids have been sent.
&&
.SHORT TERM...(This evening through Thursday)
ISSUED AT 312 PM CST Wed Mar 10 2021
South winds gusting to 45 mph continue across the area, with a few
50+ mph gusts being reported in east-central Illinois where winds up
to around 850 mb are mixing down. An area of surface low pressure
located over western Iowa this afternoon will continue to lift
northeast into the Great Lakes Region, bringing us our next shot of
precipitation later tonight through Thursday night. A cold front
will approach the area from the northwest late tonight, spreading
widespread rain showers and scattered storms southeast through
the area. Winds look to remain pretty gusty ahead of the front`s
arrival with the LLJ enhancing itself this evening. Winds should
lessen as the front moves through/LLJ backs down going into
Thursday morning. Rainfall amounts look to be heaviest across
areas along/south of I- 72, where 1.00 to 1.50" are expected,
though locally higher amounts are possible where storms occur.
This will likely result in rises on rivers across the south, with
the Little Wabash River near Clay City forecast to reach flood
stage by the end of the week.
Not expecting any stronger storms late tonight, but as the front
slides into central and southern parts of the forecast area come
Thursday morning/afternoon, a few stronger storms are possible. CAPE
looks to be very marginal with MUCAPE values generally less than 500
J/kg, but with the front present, around 50 kt of shear with decent
turning looks to set up over far southeast Illinois. This paired
with steep lapse rates will lead to a marginal threat for small hail
and gusty winds in any stronger storms.
&&
.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 312 PM CST Wed Mar 10 2021
The front sags south of the CWA going into Friday as high pressure
builds in from the north, drying things out for a short period.
Temperatures will be cooler, yet still warmer than normal on Friday
with values in the 50s. Precipitation chances increase across
southern counties Friday night into Saturday as a surge of WAA
interacts with the stalled front over the Ohio River Valley/an
approaching system`s warm front. Precipitation amounts with this
wave will be on the lighter side and should remain confined to areas
south of I-70.
The next chance for precipitation for the entire area looks to
spread in late Saturday night/Sunday morning as an upper low across
the southwest CONUS tracks into the middle Mississippi River Valley.
Differences in track and timing still exist with this system, but
additional rainfall is expected. Temperatures in the long-term
period will return back to seasonable values.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 534 PM CST Wed Mar 10 2021
Area of MVFR ceilings is impacting portions of east central
Illinois early this evening, and ceilings will fluctuate around
3,000 feet through the evening. Wind gusts have begun to subside a
tad, but will still gust at or above 30 knots a good portion of
the evening. Some LLWS will still be an issue as the winds settle
down a bit. A narrow line of showers/storms will approach KPIA
around 06-08Z and KSPI/KBMI around 08-10Z. Storms should be in a
weakening state, so did not mention thunder at KDEC/KCMI at this
time. With the rain, ceilings around 1500 feet should become more
widespread, lingering into Thursday afternoon as a cold front
pushes across the area.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until midnight CST tonight for ILZ027>031-036>038-
040>048-053.
&&
$$
UPDATE...Geelhart
SYNOPSIS...NMB
SHORT TERM...NMB
LONG TERM...NMB
AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
919 PM CST Wed Mar 10 2021
.UPDATE...
907 PM CST
The strong low level jet core has shifted over northeast IL and
northwest IN this evening, thus while some areas have slightly
decoupled, area temperatures in the lower 60s has maintained
mixing even into the evening hours. Sustained winds in excess of
30 mph continue to be reported at times and Chicago Midway just
recently had a 49 MPH gust. Therefore we will continue the wind
advisory through the evening hours ahead of the approaching cold
front in spite of numerous areas holding winds in the 35-45 mph
range.
The compact upper low is across MN with a strong PV anomaly nosing
into it across the plains. This vorticity max is driving and area
of showers and embedded thunderstorms ahead of the cold front in
Iowa. The stronger forcing is nosing into MN and thus radar echoes
have been less deep and a noted lowering of dbZ core at -10C has
occurred and thus a significant drop off in lightning. This lines
up well with RAP guidance indicating some weakening of the CAPE
axis. Still, DVN Oz sounding does have some elevated instability
above a 800 mb inversion and lapse rates approaching 8 C/km. Thus
it is conceivable that this line holds at least a few rumbles of
thunder as it moves into the remainder of the area late this
evening, and may actually see an uptick along and SE of Chicago as
the upper jet noses in overnight. ILX also has some elevated
instability to higher based air parcels.
KMD
&&
.SHORT TERM...
337 PM CST
Through Thursday night...
We`ve got ourselves another balmy mid-March afternoon out there
today with mid-afternoon temperatures across the area mainly in
the mid and upper 60s with even a few 70s here and there. This is
unfortunately as warm as we are going to get for a while as a cold
front will come through tonight and bring temperatures back down
a bit with highs expected to stay in the 50s and lower 60s
tomorrow. Prior to that though, we`ll all but certainly break two
more records today with the March 10th record high minimum
temperatures for both Chicago and Rockford on track to fall when
the clock strikes midnight tonight. The record high (maximum)
temperatures for both cities are also in jeopardy of at least
being tied, but it`ll be a close call to see if both cities can
reach 70 in the next hour or two before temperatures begin to
descend later this afternoon. More information about today`s daily
climate records can be found in the Climate section of the AFD
further below.
While the temperatures are certainly headline-worthy, its been the
winds today that have been the main story for us so far. A tight
surface pressure gradient associated with a deepening low pressure
system currently over northwestern Iowa has allowed sustained winds
of 20-30 mph to be a common occurrence across the CWA, and with
skies having cleared a bit to allow solar insolation to aid in
surface heating, we`ve been seeing wind gusts starting to pick up
over the past few hours with several 40+ mph gusts already clocked
at some of our observations sites south of I-80. In fact, just
south of our CWA, Champaign Airport (KCMI) reported a recent peak
gust of 52 kts (60 mph)! The stronger 40+ mph gusts will spread
northward into the Chicago metro later this afternoon and evening,
with at least sporadic 50+ mph gusts appearing quite achievable
as well given the observations that we have already seen and that
the low level jet won`t really get cranking for a few more hours
here. The greatest likelihood for 50+ mph winds will generally be
concentrated southeast of I-55 where steeper low-level lapse rates
will be present. Winds will gradually cease through the evening
and will turn more westerly by tomorrow morning in the wake of
tonight`s cold frontal passage.
The aforementioned potent low pressure system will continue to churn
its way off to our northwest as we head into tonight. The cold front
draped off to the southwest of the surface low will eventually
encroach upon our area tonight, bringing some rain showers with it
as well as a good chance for many to experience their first
thunderstorm of the calendar year. The actual cold frontal passage
won`t occur until around midnight for our western counties and
will come closer to daybreak Thursday for our southern and eastern
counties. Convergence along the frontal boundary will be the
primary forcing mechanism at play, allowing for convection to
bubble up over Iowa later this evening and track eastward into our
area along the cold front. However, with the left exit region of
the southern stream jet beginning to nose its way over the area
and additional confluence expected out ahead of the front amidst
plentiful moisture within a climatologically high 1.0-1.4" PWAT
plume, additional showers could also sprout out ahead of the main
line of showers and thunderstorms tonight, mainly southeast of
I-55.
MUCAPE up to around 500 J/kg and decent deep layer shear should
allow for some degree of organized thunderstorm activity tonight
through tomorrow afternoon. Some thunderstorms could feature gusty
winds and maybe even some small hail, but should remain below
severe limits. As the front becomes more west-to-east oriented
across our southern CWA, we`ll also need to watch the potential
for training thunderstorms, which could potentially produce a
swath of 1-2" or so of rain somewhere south of I-80 if things
align favorably for that, but overall potential for flooding
remains fairly low given that we`ve melted just about all of our
snowpack and that the soils across the areas with the greatest
potential to see heavier rainfall are fairly dry (D1 drought stage
has lingered around and just south of the Kankakee River Valley
for several months now).
Any lingering showers across our far south should cease by
Thursday evening. High pressure will build in from the north and
keep us dry into the night while overnight temperatures drop
generally into the low-mid 30s.
Ogorek
&&
.LONG TERM...
202 PM CST
Friday through Wednesday...
The main focus of interest during the period will center on the
evolution of the large upper low expected to shift from the
southwestern CONUS out over the central Plains later this weekend.
This system could impact our area later in the weekend into early
next week, with rain and possibly even some wintry weather as
well.
At the start of the period on Friday, a surface high is expected
to shift into the western Great Lakes. This should result in a
fairly quiet weather day across the area. High temperatures should
top out in the middle 50s inland, but due a northerly wind likely
shifting off the lake during the day, much cooler conditions (in
the low to mid 40s) are expected near the lake. The period of dry
weather looks to continue on Saturday as the surface high settles
over southern Lake Michigan. Dry low-level east-northeasterly
flow, emanating from this surface high, should hold any
precipitation well to our southwest through at least Saturday
evening. Expect temperatures on Saturday to once again be the
coolest along the lakeshore due to onshore winds.
Our next period of potential inclement weather looks to be
sometime Sunday through Monday as the aforementioned upper low
shifts eastward across the central Plains. Forecast guidance
continues to suggest that this system will be in a weakening
state into Monday as it approaches the lower Missouri River
Valley. This adds uncertainty to the the extent of precipitation
the area will experience, particularly later Monday into Monday
evening. Traditionally the evolution and track of upper lows can
be difficult to pin down beyond a couple of days, so we will have
to continue to monitor model trends with this storm system.
As of right now it appears our best potential period of
precipitation from this system will be sometime later Sunday
and on Monday. This appears to be the period in which the
weakening systems moist conveyor belt converges over the area.
The main uncertainty for this period is if any lingering dry low-
level air acts to inhibit precipitation from making it into
northern IL. With this possibility, I did not stray from the NBM
blended guidance for the probability of precipitation, which is
generally in the change range (30-50%) for this time period.
Precipitation type could become tricky into Monday, especially if
the forcing for ascent continues to be adequate during the day.
Thermal profiles indicate that snow, and or a wintry mix could
occur over parts of the area as the column cools overhead with
the approaching upper system. The threat for any decent snow will
be conditional on there being some heavier precipitation rates,
and at this time, the chances for this remain unclear due to the
weakening nature of the larger scale storm system.
KJB
&&
.CLIMATE...
A very mild air mass will be over the region through tonight.
Here is a look at record temperatures at Chicago and Rockford for
Wednesday, March 10.
Wednesday March 10th
....................
Record High for Chicago: 70 in 1955 (upper 60s forecast)
Record High for Rockford: 70 in 1955 (mid-upper 60s forecast)
Record High Min for Chicago: 52 in 1876 (lower 50s forecast)
Record High Min for Rockford: 44 in 2010 (lower 50s forecast)
&&
.AVIATION...
For the 18Z TAFs...
The main aviation weather concerns through this evening are wind-
based, with a high likelihood of crosswind impacts on E-W
runways. This will be followed by a brief window for precipitation
late tonight.
Surface observations late this morning have begun to show an
uptick in gustiness across central Illinois where clouds are
scattering and where the strongest low-level flow currently
resides. Anticipate stronger south-southwesterly gusts developing
early this afternoon as a result as this clearing continues to
work eastward. Guidance suggests that winds at the top of the
mixed layer are approaching 45 kts or so, and with some enhanced
mixing, the latest thinking is we`ll start transporting some of
this flow to the surface in the form of near 40 kt gusts towards
19-20z. By early this evening, there is a potential for winds to
more routinely gust to near and above 40 kts, but the main
question revolves around just how decoupled the near-surface layer
becomes. Given the rather strong model agreement indicating
increasing gusts this evening, have elected to prevail these
stronger gusts until the front passes. Winds will favor a 190-200
direction this afternoon, and may veer slightly to 210-220 this
evening which will likely continue notable crosswind impacts on
E-W runways.
Winds will subtly shift with the passage of a cold front late
tonight. A narrow line of showers is likely to develop ahead of
this. At this time, it looks like this activity will begin to
outpace the main reservoir of better moisture and instability as
it starts to enter the C90 TRACON and have refrained from a
thunder mention as a result. The TS threat at ORD/MDW is non-zero,
mainly during the 7-9z window, but is too low to justify an
explicit mention. The TS potential RFD stands a somewhat better
chance of TS--at least in the vicinity--and have maintained the
PROB30 there as a result.
Additional showers and embedded storms are likely to re-develop
towards early Thursday morning, with increasing coverage south of
MDW/GYY. Surface winds will veer northwesterly with time through
Thursday afternoon, with gusts to 25-30 kts continuing.
Carlaw
&&
.MARINE...548 AM CST
A Gale Warning remains in effect from 9 AM CST this morning
(Wednesday) through early Thursday. Deep low pressure will track
to the upper MS Valley by Wednesday evening, putting southern Lake
Michigan in the windy warm sector of the storm system.
Very mild air temperatures well in the 60s will lead to
increasingly stable conditions over the lake. However, in these
setups, the strong winds over land typically mix out into at least
the first 1-3 miles of the nearshore waters. Current forecast has
peak speeds up to 40 kt, but with forecast soundings on land
pointing toward potential for occasional gusts approaching 45 kt.
Thus continued to mention 35-40 kt prevailing speeds/gusts and 45
kt gale gust potential in the text of the nearshore, with areas
over/closer to open waters remaining lower. Strong southwest winds
will continue until cold front trailing the surface low sweeps
across the area Thursday morning, with 25-30 kt speeds pre-dawn
through mid morning. Hazardous speeds from a westerly direction
may continue behind the front on Thursday afternoon.
Castro
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108 until
midnight Thursday.
IN...Wind Advisory...INZ001-INZ002-INZ010-INZ011-INZ019 until
midnight Thursday.
LM...Gale Warning...nearshore waters until 4
AM Thursday.
&&
$$
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Area Forecast Discussion
National Weather Service Marquette MI
1027 PM EST Wed Mar 10 2021
.UPDATE...
Issued at 1026 PM EST WED MAR 10 2021
Water vapor imagery and RAP analysis show a well-defined shortwave
lifting ne across e central MN. At the sfc, associated sfc low is
over the Twin Cities. The more widespread shra activity has lifted n
of Upper MI recently. Hvy downpours have accompanied some of the
shra with rainfall rates of around 4 in/hr, though those high rates
only lasted for a few minutes given small cells and quick movement.
Scattered shra and some isold tsra are now spreading ne into the
area ahead of the low pres tracking ne toward western Upper MI.
Opted to carry a schc thunder mention into the central fcst area
over the next several hrs as a weakening area of elevated mucape
shifts ene. Should see some very brief hvy downpours with some of
this activity. Temps over the far w high elevations are flirting
with the freezing mark. May see some minor ice accumulations on
trees. Fortunately, heavier, steadier pcpn has passed. Once the low
passes, colder air will switch pcpn to snow over the w late
tonight/early Thu morning. A brief period of lake enhanced snow
under cyclonic flow/deep moisture will be possible during the
morning over the w as 850mb thermal trof with temps down to -12C
moves across western Lake Superior. Attm, only an inch or 2 of snow
is expected. Last concern for late tonight/Thu morning is the
potential of high winds over the s central into especially the
eastern fcst area. Sharp caa will drop 850mb temps from around 10C
to 0C btwn 09z and 12z, and there will be a favorably oriented pres
rise/fall couplet (+2 to +3 mb/3hr and -5 to -7mb/3hr) to the
gradient wind to provide isallobaric enhancement. HRRR and RAP have
been the most concerning, indicating potential to mix to 50kt
winds. There has only been a slight decreasing trend in this
potential over the last several hrs of model runs. For now, have
increased gusts to the 40-45mph range across the e late
tonight/early Thu morning. Will need to monitor upstream trends
over the next several hrs to see if the area of gusty winds to
around 40kt in IA progresses ne without losing intensity. Right
now, those strong winds are occurring just ahead of a 6mb/3hr pres
rise.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 420 PM EST WED MAR 10 2021
Light to moderate rain spread from SW to NE across the CWA this
morning within a robust warm air advection regime. Persistent WAA
kept morning minimum temperatures well above freezing with
existing snow cover becoming ripe for melting. Fog developed
quickly after rain began falling on the ripe snow pack.
A negatively tilted shortwave trough over the Northern Plains
produced a strengthening 994 mb low near Souix Falls, SD as of 20Z.
This low is expected to continue deepening as it approaches and
then passes over western Upper Michigan overnight. The expected
surface low track is farther west than most of yesterday`s model
guidance, which reduced icing concerns for our CWA. The current
forecast calls for less than 0.1" of ice accretion except for the
Porcupine Mountains and higher elevations of the Keweenaw, which may
get up to 0.25" by Thursday morning. The more western low track
allowed for more elevated instability to work into the area with a
small area of thunderstorms about to cross into MI from WI. This
area of thunderstorms appears to be associated with frontogenesis on
the nose of the 850 mb low level jet with a broad dry slot apparent
immediately to the south. The dry slot should result in several
hours of drier conditions for central and eastern zones ahead of the
cold front moving through overnight.
Visible satellite shows an second area of more surface-based showers
developing near the cold front that is draped across Iowa this
afternoon. This line of showers is expected to expand as it tracks
northeast toward southeastern Upper Michigan. Decided not to include
thunder in the grids, but several hundred J/kg of MUCAPE may be
enough for a few rumbles of thunder across southern and eastern
zones between 03-06Z on Thursday. By 06Z the surface low will be
tracking across the U.P. with a secondary cold front bringing
substantially colder air into western zones. This air mass appears
cold enough to change remaining precipitation to light snow with up
to an inch of snow. Winds become southwesterly behind the
initial cold front and then westerly behind the secondary
cold front. Eastern zones look particularly breezy Thursday
afternoon with efficient mixing up to 4-5 kft supporting gusts into
the low to mid 30s.
.LONG TERM...(Thursday night through Wednesday)
Issued at 357 PM EST WED MAR 10 2021
Thursday night will begin with the departing weather system to the
northeast and away from the Great Lakes region. Low chances of
precipitation may linger in the easternmost areas of the Upper
Peninsula Thursday evening as this happens, but impacts look to be
marginal at best from the falling precipitation. However, with
temperatures hovering near the freezing mark near 0Z Friday that
will decrease quickly overnight, there could be some standing water
from the recent rainfall we will have received that may cause some
slick spots on on roads and sidewalks. Having mentioned the
decreasing temps, a quick look at 850mb temperatures shows a drop of
approximately 10C overnight. This will be in response to not only
partially clearing skies overnight, but an additional shortwave
advecting colder temperatures aloft into the region. While the main
energy at the surface will stay to the north of Lake Superior for
the most part, the surface cold front will cause temperatures to
stay chilly for most of the northern half of the Upper Michigan
area. This shortwave will quickly move to the east on Friday, but
the effects at the surface will respond to 850mb temperatures down
to -18C by 18Z with a lingering chance of light snow showers. Most
locations will struggle to get out of the middle to upper 20s with
the subsidence and CAA occurring. The only areas that will be less
impacted with chances of PoPs and elevated surface temperatures are
expected to be in Menominee and Dickinson County where weak WAA will
still be somewhat present. The progressive shortwave will propagate
out of the Great Lakes region by Friday evening toward the New
England area, thus limiting the duration of snow showers and
flurries to a short time period.
From late Friday night into the early portion of next week, there
will be split flow jet energy aloft. The polar jet stream will
advect multiple shortwaves via nw flow aloft along a building ridge.
Saturday looks to be the nicest day of the weekend with the ridge
axis building slightly to the east, and over our CWA. Temperatures
could very easily reach the middle 40s to lower 50s as sw flow
increases in coverage over the area by early Saturday afternoon. As
the weak embedded shortwaves ride along the upper level ridge, they
will remain close enough to the periphery of the Lake Superior and
north Upper Michigan regions to affect our temperatures by Sunday
and Monday. This will be a slight change compared to Saturday as
daytime highs will be impacted with more cloud cover anticipated,
lowering by perhaps 10 degrees across the region. The subtropical
jet stream will stay primarily far south of our region as well for
the weekend, with an occluded upper level low slowly propagating
from the 4 corners region and heading east by Monday of next week.
We will need to continue to monitor the medium to extended range
guidance as some of the forecast models are showing the northern
fringe of this occluded surface low energy making it toward Lower
Michigan and southern WI by late Monday of next week. The most
likely scenario to play out is that the southern stream of jet
energy may amplify the upper level wave and assist with it evolving
into a weather system to the south of the Great Lakes region.
Tuesday and Wednesday of next week are signaling toward a trend of
another upper level ridge building across the central and northern
CONUS. This would cause temperatures to increase as warmer air would
then be advected into the region. I have increased forecast highs
for Tues/Wed of next week up by a few degrees in our southernmost
areas in response to this feature showing up in the guidance. If
trends continue, this would likely assist with most areas seeing
afternoon highs through the middle of next week once again in the
low to mid 40s, which would put the area into above average
temperatures for mid-March.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 654 PM EST WED MAR 10 2021
Low pres near the Twin Cities will lift ne, crossing western Upper
MI during the night. Ahead of the low, -SHRA, BR/FG and LIFR
conditions will generally prevail at KIWD/KCMX/KSAW thru the
evening. Colder air is currently pushing s into nw Upper MI, and it
will probably lead to temps falling to around freezing at KCMX. So,
-fzra is expected to develop there during the mid evening hrs. As
the low moves across western Upper MI and then out to the ne
overnight, pcpn at KIWD/KCMX will switch over to -sn late tonight
into early Thu morning. Winds will also become gusty to 25-35kt at
all terminals. Prior to that occurring, low-level jet will shift
across central Upper MI, resulting in a period of LLWS mid evening
until later in the night. KIWD/KCMX will improve to VFR Thu aftn as
drier air arrives. Improvement to MVFR will occur late tonight at
KSAW, but it may not be until late Thu aftn that conditions improve
to VFR.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 420 PM EST WED MAR 10 2021
An area of low pressure tracking northeastward over Lake Superior
tonight will lead to periods of gales this evening, overnight, and
tomorrow. NE gales are expected on the west half of the lake this
evening with a brief period of gusts to 40-45 kts. Upgraded the
Gale Watch to a Warning for eastern zones on Thursday afternoon
where WNW gales are expected as the low pressure exits to the
northeast. Strong winds around 25 kts west half to 30 kts east half
are expected again on Friday with another shot of cold air, as well
as some patches of heavy freezing spray. However, winds are
currently expected to stay below gale force. Winds will then remain
around 20-25 kts across the lake through Sunday morning.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Lakeshore Flood Advisory until noon EST Thursday for MIZ014.
Lake Superior...
Gale Warning from 7 AM to 8 PM EST Thursday for LSZ249>251-266-
267.
Gale Warning until 4 AM EST /3 AM CST/ Thursday for LSZ162-
240>244-263-264.
Lake Michigan...
Gale Warning until 9 AM EST Thursday for LMZ248-250.
&&
$$
UPDATE...Rolfson
SHORT TERM...EK
LONG TERM...BW
AVIATION...Rolfson
MARINE...EK