Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/10/23
Area Forecast Discussion
National Weather Service La Crosse WI
552 PM CST Thu Mar 9 2023
.DISCUSSION...(Tonight through Thursday)
Issued at 230 PM CST Thu Mar 9 2023
Key Messages:
- Winter storm continues to impact the region tonight, exiting east
early Fri morning. A few inches of snow still on tap
- Snow chances continue to be highlighted for Sat/Sun with a few
inches possible
- Quieter start to the new work week
* WINTER STORM CONTINUES TONIGHT: a few inches still on tap, highest
south of I-94. Exits east early Fri morning.
Upper level shortwave trough driving across IA this
afternoon/evening, exiting east across the eastern great lakes
Friday morning. The sfc low hangs farther south with a trough
running north/northwest of the low, sliding across the local
forecast area this evening. That boundary could hang around into Fri
afternoon. Good low level thermodynamics will provide much of the
lift for snow production, with latest RAP showing a lot of upglide
along the 280:295 K isentropic surfaces, shifting across
north/eastern WI overnight. Not much frontogenetic response across
the local forecast area, moreso across southeast WI this evening per
latest RAP/NAM. Perky QG convergence in the 700:300 mb layer across
the forecast area into the evening while coupled 300 mb jet
continues to enhance the overall lift.
For additional amounts, SREF and RAP bufkit soundings show DGZs from
100-200 MB thick, fairly isothermal, and through the evening hours.
Some hints of instability/convective elements in the soundings for a
few hours this evening too. Both would suggest snow ratios above
climatology. However, its fairly warm in the near sfc layer - with a
wetter nature to the snow - working to hold ratios down. Meanwhile,
the lack of much Fgen lowers confidence in enhanced banding and
locally higher amounts. Have lowered ratios closer to 10:1 for rest
of the afternoon, but ratios should see an uptick this evening with
cooler sfc temps and favored lift. Overall though, amounts continue
to trend down a bit. Mostly 4 to 7" expected. Localized higher
amounts remain possible, although maybe not as high of a threat sans
any enhanced bands.
For headlines - almost downgraded some of southeast MN/northeast IA
to advisories. Per coordination with surrounding offices will hold
the warning for now, but if lower amounts continue to realized,
maybe do that downgrade sometime this evening.
* WEEKEND SNOW: increasingly likelihood, a few inches possible
Medium range guidance has been in good agreement with sliding a
shortwave trough across the northern plains Sat morning, churning
across the upper mississippi river valley Sat aft-Sun. Swath of
north-south running low level thermodynamics leads the system across
the region, evidenced with upglide along the 280:295K isentropic
surfaces. A weak ripple in the upper level flow could precede the
main shortwave, coming up from the south and co-located with the low
level warming. Some relatively weak north-south running Fgen too.
While no tap to southerly moisture currently progged, ample
saturation with the shortwave to fuel widespread pcpn. Temperatures
locally would favor snow.
How much falls? Models have been fairly consistent with suggesting 1-
4" of snow (at 10:1 ratios), the bulk of which falls Sat aft-
evening. The DGZ is mostly 50:100 mb per latest GFS/NAM bufkit
soundings - not too deep. Some hints in the NAM that we could lose
ice in the cloud for a few hours Sat night, although the GFS
disagrees. In addition, the models are suggesting there could be a
secondary ripple dropping in behind the departing shortwave for
Sun/Sun night - running along a northwest hanging sfc front off the
exiting low. This could bring another 1-3", although more focused
north of I-94 at this time. It could push total amounts into the 3
to 6" range in the north before all is said and done...but over a 36
hour period.
Considering the length of time to accumulate these potential totals,
the need for a winter weather advisory is probably a 50/50
proposition. However, any small uptick in amounts (either more qpf
or higher snow ratios) could push that answer to a "yes". Stay
tuned...
* START OF WORK WEEK: quiet, milder air returning
Shortwave ridging on tap to slide across the region for the start of
the new work week. At the sfc, high pressure builds across the
region from the northern plains Monday, shifting east Tue night.
After a relatively cool start, southerly flow sets up Wed-Thu,
pushing milder air northward and bringing temps back to/above
normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 553 PM CST Thu Mar 9 2023
The back edge of the heavier snow will move out of KRST about
10.02z and KLSE around 10.03z. During this time frame, snow will
reduce visibilities to around a half-inch. After these times,
expect that the snow rates will dramatically decrease and
visibilities will improve. Snow totals by Friday morning will be
in the 3 to 5" range.
While visibilities will be dramatically improving, ceilings will
likely stay IFR/MVFR through this forecast period.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Warning until 6 AM CST Friday for WIZ032>034-
041>044-053>055-061.
Winter Weather Advisory until 6 AM CST Friday for WIZ029.
MN...Winter Storm Warning until 6 AM CST Friday for MNZ079-086>088-
094>096.
IA...Winter Storm Warning until 3 AM CST Friday for IAZ008-009-018-
019-029.
Winter Storm Warning until 6 AM CST Friday for IAZ010-011-030.
&&
$$
DISCUSSION...Rieck
AVIATION...Boyne
Area Forecast Discussion
National Weather Service Billings MT
239 PM MST Thu Mar 9 2023
.DISCUSSION...
Tonight through Friday...
A shortwave that was over Livingston this morning, has pushed as
far east as Billings. As it has tracked east, the light snow that
was associated with it has decrease and there are only a few weak
echos, and not much is reaching the ground. The majority of the
the remaining snow this afternoon is located in Fallon County as
the main shortwave has moved into the Dakotas. What little snow
that remains is light and the Winter Weather Advisory has been
cancelled.
Overnight, moist flow ahead of another shortwave move that will
move in from the Pacific Northwest will start to impact the
western mountains. There could There will also be a chance for
some fog west of Billings tonight, given the recent moisture and
the upslope easterly flow.
The HRRR continues to run much warmer for tomorrow than the rest
of the of the models. The majority of the ensemble members are
running in the 30s for highs. The surface low in associated with
the shortwave is much slows, so the colder air can remain in
place through the day. The HRRR however continues to push that
surface low much faster through the area allowing highs to get
into the 50s and approach 60 degrees. Have continued to run under
under the NBM to offset the influences of the HRRR solution.
As the Pacific front moves through, there will be chances for
light snow as far east as Billings. The better chances for
accumulations is around the western foothills where an inch or two
are possible and the Crazy and Beartooth/Absaroka Mountains where
amounts of 6 to 10 inches are still expected.
With the front, there will also be some breezy conditions across
the area, especially along the western foothills. However, the
latest local NBM probabilistic guidance has come down with the
chance for strong winds around Livingston with the chance for 50
mph winds only around 70 percent. The chance of Wind Advisory is
down under 50 percent.
Saturday will still a little breezy, especially from Miles City
to Alzada east. However, it should be a little warmer with highs
approaching 40s degrees, and should be dry. Reimer
Sunday through Thursday...
For Sunday cluster analysis is in good agreement the region will
be transitioning from the troughing pattern seen on Saturday to a
ridging pattern bringing warmer temperatures to the region. Monday
and Tuesday the ridge is firmly overhead bringing warm
temperatures in the 50s for most areas by Tuesday. By Wednesday
there is little agreement in the cluster analysis on the pattern,
although all show some kind of troughing returning to the region.
This troughing could create some light precipitation Wednesday and
lower temperatures. Overall, the long term looks mostly dry with
temperatures starting out cool on Sunday with 30s for most before
warming into the 50s for areas on Tuesday, then turing a little
cooler later in the week.
Torgerson
&&
.AVIATION...
The next chance of snow for the Beartooth/Absarokas arrives late
tonight. More widespread and light snow looks to move into the
region around 10Z Friday impacting mostly western areas such as
KLVM. Easterly surface winds will prolong the risk of upslope low
cloud (i.e. areas of MVFR ceilings) through tonight. There may be
a risk of fog as well, especially west of KBIL late tonight.
Torgerson
&&
.PRELIMINARY POINT TEMP/POPS...
Fri Sat Sun Mon Tue Wed Thu
-----------------------------------------------------------
BIL 018/035 022/036 016/032 017/050 036/055 031/048 029/045
12/W 60/N 10/B 00/B 02/R 32/S 22/S
LVM 018/039 023/038 017/037 022/049 036/052 029/044 025/041
37/W 80/N 10/B 00/B 14/R 42/S 22/S
HDN 013/037 017/034 010/032 010/047 025/056 026/048 024/045
01/B 60/B 00/B 00/B 02/R 42/O 22/S
MLS 012/031 019/027 009/024 007/039 023/047 028/043 024/039
01/N 41/N 00/B 00/U 01/B 21/B 11/B
4BQ 013/037 021/030 014/027 009/042 027/052 031/047 027/041
00/E 20/N 00/B 00/U 01/B 21/B 22/S
BHK 008/026 017/025 007/020 003/034 021/045 023/038 016/034
01/N 52/J 00/E 00/U 00/B 11/B 11/B
SHR 008/041 018/034 009/030 011/044 025/052 024/044 021/038
01/B 40/U 00/B 00/U 01/B 42/O 33/S
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Charleston SC
910 PM EST Thu Mar 9 2023
.SYNOPSIS...
A cold front will cross the area Friday, followed by high
pressure through Saturday night. Developing low pressure will
approach the region Sunday then will cross the region Sunday
night. This low will pull a strong cold front through the area
Monday, then unseasonably chilly high pressure will prevail
through mid week. A warming trend is expected later next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Current radar and observations trends have dictated a rather
substantial increase in pops for the late evening update. KJGX
radar shows a band of light to locally moderate rain extending
from central Georgia east to just west of the I-95 corridor
south of Savannah. The atmosphere under this band has moistened
much quicker than expected with surface dewpoints depressions at
10/02z having dropping to 0 degs at KRVJ and 2 deg at KVDI.
This has result in measurable rainfall occurring across much of
Candler, Tattnal, Evans and Bulloch Counties over the past 1-2
hours where amounts range from 0.01 to as much as 0.14",
highest in western Candler County.
Steadier rains are still expected to move in from the west
overnight as the moisture profiles moisten considerably and a
warm frontal feature moves north to near/just north of the I-16
corridor by 10/12z. Forecast lows, temporally defined from
6pm-6am LT, will likely occur this evening to around midnight
with patches of light rain aloft/sprinkles inducing at least
some degree of diabatic cooling. Temperatures will then hold
steady or slowly rise overnight as low-level warm advection
intensifies. Influences from diabatic cooling can be seen at
KMHP and KRVJ where temperatures dropped quickly with the onset
of rainfall.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Friday: All locations will receive measurable rainfall as a cold
front presses through the region, although hour by hour details
regarding coverage of showers and overall event timing remain
somewhat uncertain. Thus, while 12 hour PoPs of 100 percent are
appropriate across the region, hourly PoPs may not reflect this
degree of certainty. As opposed to a deep layered low pressure, this
event will be dominated by a channel of vorticity and moisture
transport/pockets of isentropic ascent embedded with a fast quasi-
zonal flow. This scenario could initially contribute to a relative
lull in shower coverage Friday morning, as depicted by recent HRRR
runs, followed by best coverage of showers late morning until
mid/late afternoon. in addition, fast/quasi-zonal steering flow
could support earlier drying across northern/inland counties, but
showers could persist longer, perhaps into early evening. across
southern counties as moist plume reorients parallel to the
west/northwest to east/southeast steering flow. Also of note,
elevated instability and perhaps some degree of surface based
instability - especially across southern counties - justifies a
mention of thunderstorms. Areas south of I-16 remain within a
marginal risk for severe, and high resolution reflectivity progs
depict some degree of multicell organization south of the advancing
cold front. However, the potential for isolated damaging wind gusts
appears limited as model forecasts of shear/instability remain
unimpressive for mid-March. All told, most locations should receive
0.25 to 0.50 inch of rain from this event. temperatures should top
out in the 60s north and 70s south.
Friday night, a few showers could linger south of I-16 early.
Otherwise, building high pressure will push cooler/drier air into
the the region, and by Saturday morning lows in the 40s will be
common most areas.
Saturday will start sunny and cool, then high clouds will stream
across the region from the west during the afternoon. Temperatures
should top out in the 60s most areas except around 70 near the
Altamaha River. rain free conditions will continue as late Saturday
night/early Sunday low temperatures average in the 40s inland and in
the 50s along the coast.
Sunday: Another precipitation event will commence, initially
dominated by moisture transport/pockets of isentropic ascent
embedded within a fast quasi-zonal flow regime and enhanced by
overrunning of a retreating wedge of high pressure. A few showers
could develop across inland counties Sunday morning, but
precipitation coverage should ramp up starting Sunday afternoon,
with PoPs increasing to likely across inland counties. A later
arrival of showers should allow temperatures to rise to 75-80F
across southern counties. On the other hand, across far
inland/northern counties, temperatures could remain in the 60s,
especially if showers arrive earlier. In between, expect highs 70-75
across a wide swath of the region. Also, some degree of surface
based instability could support thunderstorms Sunday afternoon,
especially inland.
Lake winds: Northwest winds could gust to 25 knots in Lake Moultrie
Friday night. Then. in the wake of a strong cold front Monday, winds
could gust to 25 knots on the lake through Tuesday. Lake Wind
Advisories could be required for these events.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Precipitation event which begins Sunday will overspread the region
Sunday night. A prominent baroclinic zone could promote surface
cyclogenesis, and this surface low could intensify mass/moisture
convergence and associated forcing for ascent as it crosses the
region. As a result, many locations could pick up another 0.50-1
inch of rain. Further, elevated instability could support at least
isolated thunderstorms, which could produce locally greater
rainfall. Monday morning should start off with lingering showers,
then intensifying low pressure tracking northeast along the coast
will drive a strong cold front and sharply drier air into the
region. High temperatures in the upper 60s to middle 70s may occur
by midday/early afternoon.
Dry and unseasonably chilly conditions will then prevail Tuesday and
Wednesday. Of greatest concern, freezing temperatures could
infiltrate areas away from the coast Tuesday night; frost may remain
a secondary concern as north/northwest winds could persist. Also,
wind chills could fall into the 20s Tuesday night.
As the air mass modifies under high pressure, temperatures should
recover back into the 70s late week.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
KCHS/KJZI: VFR this evening with deteriorating conditions late
tonight and especially Friday morning as a warm front moves
north through the two terminals. Light rain will spread in from
the west overnight with vsbys dropping to MVFR with IFR cigs
about 14-15z as the warm front approaches. There could be
pockets of lower vsbys at times, but it could be a difficult
morning, especially for general aviation. The risk for tstms is
non-zero with some elevated instability noted, but the risk
looks to low to justify a mention at this time. Rain should end
by 20z, but IFR cigs will linger.
KSAV: VFR for much of the night with conditions deteriorating
after daybreak as a warm front lifts north. An area of
widespread rain will likely brush the area by mid-morning with
the bulk of the rain remaining north of the terminal. By early
afternoon, a band of widespread rain with embedded tstms will
push through the terminal 18-21z. There will likely be pockets
of heavier rain in convective elements, but widespread MVFR
vsby and cigs are likely with occasional periods of IFR,
especially in vsbys. A TEMPO group for IFR was introduced to
account for this. Tstms were left out of the 00z TAF for the
KSAV terminal, but a few rumbles can not be completely ruled
out, especially in that 18-21z window.
Extended Aviation Outlook: Flight restrictions are likely late
Sunday into early Monday associated with showers. After a strong
cold front passes, gusty north/northwest winds should develop early
next week.
&&
.MARINE...
Tonight: High pressure will be in control of the waters, before
giving way to a warm front from the west late tonight. Easterly
winds will shift out of the SE tonight at speeds less than 15 kt.
Seas will average 2 to 4 feet through the night. Mariners can expect
showers to spread offshore into the marine community overnight,
resulting in a minor reduction in visibilities.
Friday through Tuesday: Ahead of an approaching cold front, a
tightening SW surface pressure gradient will contribute to elevated
winds. We raised a Small Craft Advisory for AMZ350 and AMZ374 as
winds should gust to 25 knots was early as Friday morning. After a
cold front crosses the region, winds will shift to the NW, and gusts
to 25 knots are likely across all marine zones. Winds should diminish
and seas should subside for a time saturday into Sunday. Then, ahead
of developing/approaching high pressure, south winds could increase
Sunday night, and Small Craft Advisory conditions will likely
redevelop most/all areas. Of greater concern, a strong cold front
will cross the waters Monday. Strong N/NW winds and at least
widespread SCA conditions will persist through early next week, and
the probability for gale force gusts/hazardous seas will increase as
cold air spreads across coastal waters and marine layer mixing
intensifies.
&&
.EQUIPMENT...
The KCLX WSR-88D will continue to be down for an important
upgrade. The radar is expected to return to service by March 20,
2023, assuming no issues are encountered. During the downtime,
adjacent radars will be available, including:
Columbia, SC (KCAE); Robbins AFB (KJGX); Moody AFB (KVAX);
Jacksonville, FL (KJAX); and Wilmington, NC (KLTX).
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory from 11 AM Friday to 11 AM EST Saturday
for AMZ350.
Small Craft Advisory from 8 AM Friday to 11 AM EST Saturday
for AMZ374.
&&
$$
Area Forecast Discussion
National Weather Service Goodland KS
548 PM MST Thu Mar 9 2023
.SHORT TERM...(This evening through Friday)
Issued at 251 PM MST Thu Mar 9 2023
Across the Tri State region this afternoon, skies are a mix from
sunny in spots, down to partly sunny as some locales are still
seeing remnants cloud cover from this morning as well as from a
front moving through the area. Temperatures as of 200 PM MST are
ranging widely and are highly dependent on how much cloud cover
remains, with upper 30s to low 50s. Winds are mostly northwest and
gusting up to 25 to 35 mph a times.
For the remainder of the afternoon, region will continue to see a
clearing skies going into the evening and overnight hours. Looking
for gradient to slacken as well as front and associated low move
away from the cwa, giving way to transient surface ridge that will
eventually set up east of the cwa going into Friday.
Going into Friday, guidance carrying upper level ridging over the
Plains, but at the surface, a strong lee-side trough sets up over
the Front Range with the aforementioned ridge remaining east of the
cwa. The resulting tight southerly gradient will bring windy
conditions to the area, along with a continued warmup. Gusts will
approach to 30-40 mph mark, especially during the afternoon hours.
Despite the expected strong winds, looking for humidity to stay well
above criteria for overall fire wx concerns. Latest SPC elevated
outlook now well south of the cwa.
Increasing cloud cover going into Friday night and carrying much of
the upcoming weekend. There will be a couple shortwaves coming
through the central Rockies and over the cwa. These will interact
with a surface boundary to create some light rain/snow for portions
of the area. The aforementioned lee-side trough settles south of the
cwa by the end of the weekend, allowing for an eventual shift to
easterly flow Saturday, over to northerly on Sunday for most areas.
Another windy day is probable for most Saturday as surface low sets
up south. The expected easterly fetch will aid in bringing upslope
moisture and some weak instability to allow for rain/snow to occur
via low cloud deck. Low qpf expected, so little to no snow accum. On
Sunday, the second shortwave will focus precip mainly along/west of
Highway 27, moving south going into the evening hours as the surface
low moves south.
For temps, highs on Friday will range from the upper 40s in the
northeast, down to the 60F mark in southern and southwest locales.
For the upcoming weekend, Saturday will have a range from the upper
40s into the mid 50s and for Sunday, mainly the 40s with warmest
areas in the east. Overnight lows will see a range mainly in the
20s, with Friday night seeing the 30s, warmest areas south of the
Interstate.
.LONG TERM...(Monday through Thursday)
Issued at 115 PM MST Thu Mar 9 2023
Upper ridge axis will be moving across the central CONUS to start
the period with dry conditions Monday and Tuesday. This will be
followed by a slow moving upper trough that moves out of the
western CONUS mid week with its axis along the length of the
Rockies by Thursday. It will bring a chance for rain and snow
mainly Wednesday night and Thursday. Snow amounts are not
particularly impressive at this time, and with temperatures
remaining above freezing until Thursday night we may be looking
at mostly rain. Model QPF is not in very good agreement, other
than showing highest amounts in northeast Colorado and lowest
amounts in eastern areas from McCook to Hill City. Breezy
northwest winds possible on Thursday as well. Temperatures will be
slightly below normal on Monday, much above normal Tuesday and
Wednesday, then dipping back to slightly below normal on Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 500 PM MST Thu Mar 9 2023
GLD: Recent runs of the RAP and HRRR suggest that IFR-LIFR
stratus (and/or fog) may develop at the GLD terminal late tonight
and Friday morning -- beginning ~06-08Z and ending ~13-15Z.
Otherwise, VFR conditions will prevail.. with increasing mid/upper
level cloud cover (ceilings 12-18 KFT agl) on Friday. Light
NE winds will become variable this evening and overnight..
shifting to the SE and increasing to 7-12 knots AOA sunrise Friday
morning. Winds will veer to the S and strengthen to 20-30 knots
late Friday morning into early Friday afternoon -- as the MSLP/H85
height gradient tightens on the eastern periphery of a developing
lee cyclone in Colorado -- decreasing to 15-20 knots mid-late
Friday afternoon.. by the end of the TAF period.
MCK: Recent runs of the RAP and HRRR suggest that MVFR ceilings/
stratus may briefly develop at the MCK terminal AOA sunrise
(12-14Z) Friday morning. Otherwise, VFR conditions will prevail..
with increasing mid/upper level cloud cover (ceilings 12-18 KFT
agl) on Friday. Light NE winds will become variable this evening
and overnight. Winds will shift to the SE and increase to 7-12
knots AOA sunrise, veering to the SSE-S and strengthening to
15-25 knots Friday afternoon.. as the MSLP/H85 height gradient
tightens on the eastern periphery of a developing lee cyclone in
Colorado.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JN
LONG TERM...024
AVIATION...Vincent
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
900 PM CST Thu Mar 9 2023
.UPDATE...
Issued at 857 PM CST Thu Mar 9 2023
Approaching the mid-evening, areas roughly near and south of I-80
have struggled to transition from rain over to snow with
temperatures still hanging onto the upper 30s in spots along the I-
80 corridor. The majority of the metro that has managed to switch
over to snow remains too warm to allow accumulation on most
roadways. Areas west and northwest of the metro as well as the far
northern suburbs are starting to see minor accumulations on roads.
Diurnal cooling is sure taking its time with the low cloud cover
overhead and we`re certainly not getting any help from continued
modest warm advection in the low levels. However, high-res forecast
soundings continue to insist upon a good deal of dynamic cooling
taking place over the next few hours. While this makes sense with
surface wet bulbs sitting closer to freezing, dynamic cooling has
been notably lagging behind from what models have been saying thus
far this evening. But with the mid-level vort max still approaching
from the west, some accelerated cooling may take place as it
propagates across the area over the next few hours. This is all to
say that we are still anticipating lighter snow coverage to
expand southward through the rest of the evening and tonight.
RAP mesoanalysis shows the prominent f-gen signature is beginning to
make its way off to our east which lines up with where we`re
currently seeing the banded precip vs lighter, stratiform precip.
That being said, it looks as though the heavier rain and snow will
be departing the area over the next hour or two. We still have a
good deal of synoptic forcing to work with for the next couple of
hours as we remain in the left exit region of a stout mid-level jet
max on top of the aforementioned low and mid level vorticity
providing ample synoptic ascent for steady precip to persist.
There is a bit of a dry slot starting to inch into parts of the
western CWA as some drier air begins to infiltrate the mid-levels
including through the DGZ. Nonetheless, light precip continues to
fall with additional snow showers wrapping around the backside of
the low and currently falling over far eastern Iowa. Light precip is
still anticipated through most of the night before departing to the
northeast through the early morning. A couple of models are
resolving one last push of light snow showers in the cold advection
regime on the northwestern periphery of the low through mid-morning
tomorrow. All in all, still expecting widespread 4 to 6 inches across
the northern CWA with a sharp gradient in snow totals likely setting
up in the neighborhood of the I-88 corridor. No changes to headlines
planned at this time.
Doom
&&
.SHORT TERM...
Issued at 252 PM CST Thu Mar 9 2023
Through Friday night...
No changes are planning to the going headlines.
The initial warm air advective surge of precipitation is quickly
shifting eastward into northern IL early this afternoon in advance
of a quickly approaching vigorous shortwave trough and associated
upper level speed max now shifting eastward over the Mid-
Missouri Valley. Forced ascent continues to be robust and is
largely being driven by rather robust low-to-mid level isentropic
upglide (warm air advection) juxtaposed beneath a region of
increasingly diffluent upper level flow associated with the exit
region of the upper level jet speed max. Given the steep lapse
rate environment, heavy precipitation intensities are occurring,
with many sites across eastern IA reporting heavy snow with 1/2 to
1/4 mile visibilities and around 1" per hour rates. Expect this
activity to steadily translate eastward into northeastern IL and
eventually northwestern IN over the next couple hours this
afternoon.
The main forecast idea with this event has not changed much,
though the heavier precipitation is arriving a few hours quicker
than originally anticipated. We generally still expect the
heaviest snow rates (1" per hour rates) to largely occur north of
the I-88/I-290 corridors late this afternoon through mid to late
this evening. However, warmer initial temperatures farther to the
south over parts of the Chicago metro area and points south and
east into northwestern IN will result in the precipitation
onsetting as rain for at least a few hours before it begins to
mix with snow as far south as the I-80 corridor later this
evening. As such, this is likely to result in a sharp snowfall
north-to-south snowfall gradient between the I-88 and I-80
corridors.
The heavier snow rates are expected to gradually abate from west
to east after midnight as the main larger scale forcing peels off
to the east. However, lingering mid-level deformation in the
vicinity of the 700 mb low track over far northern IL will likely
continue to support periods of lighter snow overnight before it
ends early Friday morning. Lake effect parameters continue to look
rather poor and largely unsupportive of any meaningful lake
enhancement to the precipitation overnight. Total snow
accumulations of 4 to 7 inches are still favored near the WI state
line, with amounts dropping to around an inch across the I-80
corridor. Farther south of I-80, especially south of the Kankakee
River Valley, rain will be the primary precipitation type.
The weather on Friday is likely to remain cloudy, and some
lingering flurries could continue into Friday evening. Otherwise,
temperatures during the day will remain in the 30s, with the
coolest locations likely to be over the snowpack. Temperatures
Friday night are then expected to drop into the 20s as a surface
ridge of high pressure builds overhead.
KJB
&&
.LONG TERM...
Issued at 252 PM CST Thu Mar 9 2023
Saturday through Thursday...
Main forecast concerns:
* Another round of accumulating snow likely Saturday night-early
Sunday
* Unseasonably chilly this weekend through Tuesday, especially
Monday-Tuesday
Surface high pressure will be in control to start Saturday, though
with mostly cloudy skies from a mix of lingering stratus east and
mid and high clouds moving in from the west. This will be in
advance of Saturday evening-overnight`s snow producing system.
Temperatures will recover to mid 30s to near 40 I-80 and north,
coolest lakeside and far north, and around 40 to lower 40s and
locally mid 40s south.
A positively tilted mid-level short-wave associated with a brisk
southern stream upper jet will eject eastward through Saturday
night and become embedded in the trough axis of a stout mid-upper
low across the northern Plains. There is variance in the model
guidance in handling the progression of the short-wave. In general,
the NCEP (GFS and NAM) guidance is slower moving and slower to
weaken the wave, with better upper jet support, while the foreign
guidance (ECMWF, Canadian, UKMET) is faster to push the wave
across and weaken it.
The above being said, there`s expected to be sufficient forcing
to bring accumulating precip. to the entire area, supporting the
NBM`s categorical PoPs. How the short-wave evolves will be more
tied to QPF and snow amount distribution, with the NCEP guidance
more broad brushed and foreign guidance favoring the western or
southwestern half of the CWA. If top-down saturation occurs
quickly enough, some light snow and rain may reach into far
western and southwestern sections late day Saturday. Most of the
precipitation, however, will fall near and after sunset (last CST
sunset until November!). Given a cold enough air mass aloft, think
the duration of any rain south should be fairly brief. Overall
moderate forcing paired with fairly steep lapse rates above the
DGZ should generate light to occasionally moderate snowfall rates,
barring a much faster weakening of the parent wave. Looking at a
typical wet, lower SLR spring snow, and for now, given the model
differences, 1-2" accumulations in the grids appear reasonable for
now. Expect the typical slushy road and reduced visibility impacts.
Some mainly non-accumulating light snow may linger into Sunday
morning. Then on Sunday afternoon-night, a vigorous clipper-like
low associated with fast southeastward trajectory of the northern
Plains upper low may bring snow showers (some robust) as strong
cold advection steepens lapse rates. After temperatures top out in
the upper 30s to near 40 on Sunday, many locations are unlikely to
get out of the low 30s on Monday (30-35F range officially) amidst
blustery north-northwest winds. Lake effect snow showers may get
going into northwest Indiana, with flurries possible inland,
though not mentioned yet.
Following chilly conditions under high pressure Monday night-
Tuesday evening, should see a warm-up (to what extent is
uncertain) during the mid week period and some threat for rain
showers.
Castro
&&
.AVIATION...
For the 00Z TAFs...
Aviation Forecast Concerns:
* Snow with IFR/LIFR ceiling/vis overnight. Brief period of
rain/snow mix at KMDW/KGYY. Snow decreases in intensity after
midnight, and lingers into Friday morning before ending.
* Breezy east winds become northeast after midnight, then gusty
from the north by midday Friday.
Evening water vapor imagery shows a compact, vigorous mid-level
wave tracking east across IA, which is evident mainly as a south
to north oriented trough at the surface. Strongest deep layered
ascent with this disturbance will persist through midnight or so,
before the mid-level trough axis shifts east of the region. Very
dry low level air has taken some time to saturate from the top
down, though have finally seen snow or a snow/rain mix develop for
the Chicago metro terminals. This should transition over to snow
fairly quickly this evening as dynamic/wet-bulb cooling persists.
Worst conditions (LIFR/VLIFR) in heavier snow are expected for
KRFD, and areas along and north of the IL/WI border, though
Chicago metro terminals (KDPA/KORD) will likely also see a period
of at least moderate snow and LIFR conditions this evening. Snow
should decrease in intensity after midnight, though light snow
will likely persist into Friday morning before ending, with IFR
cig/vis expected through mid-morning before improvement to
MVFR/VFR vis and MVFR cigs is expected.
Surface winds will be mainly east-northeasterly overnight, with
gusts into the 20-25 kt range possible at times. Winds will turn
northeasterly after midnight, and eventually more northerly by
late morning Friday. Gusts will likely be limited during the
morning in the vicinity of the surface trough, but will become
modestly gusty in the 15-20 kt range again by midday. It`s
possible winds may waffle between 350-010 degrees or so, though
confidence is low in prevailing NW or NE during the day. There may
eventually be a trend more toward NE later Friday evening as
surface high pressure ridge approaches from the west.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
ILZ010-ILZ011-ILZ012-ILZ013-ILZ103-ILZ104 until 7 AM Friday.
IN...None.
LM...Small Craft Advisory...IL nearshore waters until 9 AM Saturday.
Small Craft Advisory...LMZ743-LMZ744-LMZ745...10 AM Friday to 3
AM Saturday.
&&
$$
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Area Forecast Discussion
National Weather Service Nashville TN
856 PM CST Thu Mar 9 2023
...New UPDATE...
.UPDATE...
Issued at 846 PM CST Thu Mar 9 2023
The latest mesoanalysis shows the weak cold front approaching the
Mississippi River with moist, southerly flow ahead of it helping
to improve moisture values from 24 hours ago. This evening`s 00Z
sounding shows a much more saturated atmosphere with a PWAT of
1.11". Despite this, showers so far today have been unimpressive
with any relatively heavier activity to our south. This evening`s
update just features freshening up the PoP grids which do stay
high overnight as guidance shows shower coverage increasing ahead
of the aforementioned cold front. Precipitation tonight is still
expected to remain light, below 0.25 inches. Rain should be
winding down around sunrise with a quiet Friday on tap for the
area.
&&
.SHORT TERM...
(This afternoon through Friday Night)
Issued at 109 PM CST Thu Mar 9 2023
Intermittent showers continue to push through the area this
afternoon with steadier rain to the south. The HRRR shows a weak
cold front approaching Middle Tennessee between 7-9pm tonight
with a few rain showers possible out ahead of it. The upper levels
continue to moisten and mix down to the surface, assisting in
lower dewpoint depression and much higher RH values than we saw
yesterday. Both GFS and NAM forecast soundings feature an almost
totally saturated profile, so rain should make it to the ground
with the approaching cold front tonight. Perhaps a few rumbles of
thunder for the southernmost counties, but generally will just be
rain. QPF values range from a quarter to a tenth of an inch. The
line should exit the CWA by early Friday morning.
For the remainder of Friday, clouds will clear out during the early
afternoon and highs will be in the mid 50s, so not too shabby of
a day if you don`t mind the cooler temperatures. Winds will
steadily turn out of the north through the day, leading to a cold
night Friday with lows sitting right at or a degree below
freezing. Clear skies and calm winds could lead to a few areas of
patchy frost Friday night.
&&
.LONG TERM...
(Saturday through next Thursday)
Issued at 109 PM CST Thu Mar 9 2023
We will have a brief respite from the rain during the day
Saturday. Temperatures will be in the mid 50s with increasing
cloud coverage through the afternoon ahead of the next
disturbance. A shortwave will bring another round of light showers
to the area by Saturday night. While it`s pushing its way through
the area, an upper-level trough that is setting up over the
western Great Plains will begin tracking east, supporting a
surface low pressure system that will bring yet another round of
rain through the area. The rain associated with this system will
be more widespread. Current model soundings do not support severe
weather, but a few rumbles of thunder will be possible. With the
placement of the surface low being almost directly over the state,
southern counties will have a better chance of hearing thunder.
This front should clear the CWA overnight Sunday into Monday
morning. After that, high pressure will begin building in and the
weather will stay dry for a few days. QPF values with this system
range from 0.75-1.5 inches with the higher values confined to the
southern counties.
For Monday, clouds will clear out through the day and winds will
turn out of the north, ushering in cool, continental air. This
cool air is going to stick around for a few days with overnight
lows Monday and Tuesday night below freezing areawide.
Temperatures will still be cold going into Wednesday morning, but
a wind shift out of the south during the day Wednesday should
keep temperatures above freezing through the rest of the week. The
next chance for rain looks to be late Thursday into Friday.
Models do not have a good handle on this system since it`s still a
ways out so this is subject to change.
&&
.AVIATION...
(00Z TAFS)
Issued at 533 PM CST Thu Mar 9 2023
After a slow come down, cigs are finally starting to become MVFR.
IFR conditions are expected this evening as more rain moves into
the area and the atmosphere becomes more saturated. These should
last through daybreak Friday with cigs returning to MVFR by mid-
morning, then VFR before sunset Friday.
Winds will be relatively light and southerly tonight, then shift
to the northeast around sunrise Friday morning as a weak fropa
occurs. A few gusts of 15 to 20 kts will be possible post fropa.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 44 57 35 57 / 70 0 0 10
Clarksville 41 54 33 55 / 80 0 0 30
Crossville 43 52 30 54 / 90 10 0 0
Columbia 44 57 33 57 / 80 0 0 10
Cookeville 44 52 32 55 / 90 0 0 0
Jamestown 41 50 30 53 / 90 10 0 0
Lawrenceburg 46 57 33 58 / 90 0 0 10
Murfreesboro 44 57 32 58 / 90 0 0 10
Waverly 41 55 33 54 / 80 0 0 30
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Clements
SHORT TERM...Baggett
LONG TERM....Baggett
AVIATION.....Unger