Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/07/23

Area Forecast Discussion

National Weather Service Green Bay WI

 822 PM CST Mon Feb 6 2023

New Information added to update section

.UPDATE...
Issued at 821 PM CST Mon Feb 6 2023

Precipitation has been slow to develop over the forecast area
early this evening. Band of mid-level clouds associated with mid-
level WAA has pushed into upper Michigan producing little or
nothing as RAP soundings continue to show dry layer in the 850 to
700 mb layer. Meanwhile, primary surface trough approaching the
Mississippi Valley area with a narrow band of mostly light rain
and snow showers. Downstream, over central Wisconsin, starting to
see a bit more widespread development of shallow convective
elements underneath a mid-level dry intrusion. This activity is
starting to generate some -RA over Wood and Portage counties where
surface temps have been holding in the middle 30s. Still
anticipate this activity to expand a bit more as it moves quickly
NE into central and northcentral Wiscosnin over the next couple
hours in conjuction with approaching shortwave impulse and low-
level convergence near nose of 925 to 850 LLJ.  Surface wet bulb
temperatures north of Highway 29 have been holding in the upper
20s, thus potential remains for some light freezing rain or
freezing drizzle through at least midnight as forecast soundings
seem to struggle with deep saturation and ice crystal formation.
At this time, no changes to current forecast with best chance for
some light FZRA and/or FZDZ along a corridor from Marathon County
northeast to Langlade, Menominee, western Shawano, Langlade and
northern Oconto. North of roughly Highway 8, still anticipate
mainly light snow as primary precipitation type outcome.

Latest CAMS continue to suggest that the bulk of the light
precipitation will be east of the forecast area between about 8
and 10Z.
&&

.SYNOPSIS...
Issued at 239 PM CST Mon Feb 6 2023

Wintry precipitation north and west of the Fox Valley tonight,
with another round across the area late Wednesday night through
Thursday. Temperatures remaining at or above normal, significantly
so at times.

The upper flow across North America will remain split throughout
the period. A modest northern stream will generally remain across
Canada. A highly amplified, energetic and progressive southern
stream will dominate the CONUS and support a series of strong
cyclones that will track across the country.

There will be several opportunities for precipitation. Given the
potential for the area to be affected by at least one of the
southern stream cyclones, amounts will probably end up AOA normal.
The forecast area will be dominated primarily by air masses of
Pacific origin. Outside of a brief cool down or two behind
individual cyclones, temperatures will be above to considerably
above normal.
&&

.SHORT TERM...Tonight and Tuesday
Issued at 239 PM CST Mon Feb 6 2023

The main focus of the short term forecast will be the evening to
overnight period, as a fairly decent mid-level shortwave works its
way across the area, bringing a mix of precipitation type
concerns.

So far today, winds have gradually shifted more southwards as the
departing high pressure moves off to the east. This brought some
low clouds in along the lakeshore, but further inland skies had a
chance to clear before WAA brings clouds back this evening. As a
result, surface temperatures have had a chance to get into the
lower to middle 30s under sunny skies in central WI.

Tonight, WAA will bring back cloud cover through the evening
before a shortwave trough rapidly crosses the area. This trough
will be accompanied by both a 50-60kt low level jet off and ample
moisture to produce precipitation across the area in the late
evening to early overnight. As precipitation develops in the hours
before midnight, there will a window for freezing precipitation to
develop for areas roughly between Wausau and Wausaukee. North of
this area around 1-2 inches of snowfall will cross the far north
and south of this area will see mainly rain. The bulk of the
precipitation will fall in the late evening to early overnight.
Finally, winds associated with this system will be strong enough
for a gale warning on the marine side.

The main factor in determining the impacts with this will be the
road temperatures and how quickly air temperatures rise in the
evening. One of the main changes to the forecast in this regard is
the warmer start from this afternoon thanks to the clearing
mentioned above. With highs at least 5-8 degrees above the
previous forecast issuance this afternoon for portions of the
area, reduced ice accumulations slightly and moved them slightly
further northwards. This uncertainty and slight reduction in ice
were the main considerations in maintaining an SPS rather than
using an advisory for this evening.

Some light drizzle could briefly follow the exiting precipitation
Tuesday morning, but precipitation will largely come to an end by
mid to late morning. The Tuesday that follows will be relatively
quiet, with clearing skies and daytime temperatures pushing back
into the lower to middle 30s.

.LONG TERM...Tuesday Night Through Monday
Issued at 239 PM CST Mon Feb 6 2023

The focus of the long-term portion of the forecast was attempting
to determine the impact of a southern stream shortwave/cyclone
ejecting northeast from the Southern Plains during the latter part
of the work week. Not much has been resolved regarding that
system since yesterday. The forecast track still varies from model
to model and from run to run. That said, it is increasingly
likely at least the southeast 1/2 of the forecast area will
receive significant precipitation from the system. But
considerable uncertainty exists about precipitation type. A warm
layer (T>0C) will initially exist aloft. Strong ascent is likely
to generate sufficient cooling in the heavy band of precipitation
within the deformation zone to knock out the warm layer. However,
boundary layer temperatures will also be near freezing, so
snowfall amounts are difficult to estimate. Will continue to
mention in the HWO since the potential exists for several inches
of wet snow if the various parameters come together just right.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 619 PM CST Mon Feb 6 2023

A fast moving system will bring rapidly deteriorating flying
conditions later this evening. Winds off the surface will also
become strong as a low level jet develops with wind shear around
50 to 55 kts overnight. Latest radar and surface observations
indicated band of mid-level clouds in WAA zone ahead of the
approaching system has not been able to precipitate as still dry
layer to overcome in the 850-700 layer. Primary area of
precipitation has remained west and north of the forecast area
thus far this evening. As the evening progresses, anticipated to
see column saturate sufficiently such that scattered light snow
should begin to break out north of a AUW to MNM line by around
03Z. South of this line, anticipate some light mixed precipitation
in the form of light rain showers, and perhaps some light
freezing rain or drizzle. Any ice accumulation will be very light
and be a function of surface temperatures which will be hovering
around the freezing mark at AUW and RHI TAF sites prior to 06Z.
Mainly light rain showers expected to impact GRB, ATW and MTW TAF
sites with perhaps a brief period of light freezing drizzle at
onset at ATW.

System is fast moving thus mixed precipitation should quickly
come to an end by 10-12Z followed by gradually improving
conditions from MVFR CIGS to VFR conditions after 18Z Tuesday.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE.........ESB
SYNOPSIS.......Skowronski
SHORT TERM.....Uhlmann
LONG TERM......Skowronski
AVIATION.......ESB



Area Forecast Discussion

National Weather Service Grand Rapids MI

 941 PM EST Mon Feb 6 2023

LATEST UPDATE...
Update

.UPDATE...
Issued at 937 PM EST Mon Feb 6 2023

We are issuing a Winter Weather Advisory for most of the northern
two rows of counties from 2AM-7AM due to the potential for slick
roads.

Radar shows rain showers developing ahead of a trough over Iowa.
01z HRRR shows the leading edge of the pcpn arriving at the lake
shore around 07z and moving east. Current sfc temps over the
interior portions of the northern cwa are in the mid to upper 20s.
However, warmer air is associated with this push of moisture so
we should see sfc temps increase slowly overnight...if the HRRR is
to be believed. Even so, temperatures are not going to warm
rapidly and so we`re looking at some freezing rain across the
northern cwa. Ice accumulations should be less than 0.05 inches.
Precipitation duration looks to be 5-6 hrs with most of it ending
by 12z.


&&

.DISCUSSION...(This evening through next Monday)
Issued at 234 PM EST Mon Feb 6 2023

- Risk for a short period of ZR later tonight north

Model trends and thermal profiles show a narrow window for ZR
across portions of our northern CWA including Harrison...Evart and
possibly Baldwin. The surface temperature will remain below
freezing as the precipitation moves in after midnight. The
southeast winds will veer to the south and remain gusty overnight.
This thermal advection will lead to gradually rising
temperatures. By 09Z surface temperatures are predicted to rise
above freezing for these northern communities. This scenario is in
line with the latest HRRR. We will hold off on a winter weather
advisory for now as any icing is expected to be of a short
duration and in the middle of the night.

- Onset of the precipitation Thursday may briefly be a mix, then
  heavier QPF

Surface temperatures are likely to be near or below freezing as
the precipitation moves in later Wednesday night north of a
Hesperia....to Greenville to Alma line. Thermal profiles show that
at 850 mb above freezing temperature will exist.  This will
support a potential for freezing rain. Again...the warmer air will
be advecting in...sending surface temperatures slowly above
freezing Thursday morning so the duration is projected to be
limited. Confidence on the the impacts is limited though as trends
in the models have been a little warmer. However...enough qpf may
occur in the colder air through the commute to warrant a WSW. We
will need.

Overall the guidance still warrants heavier qpf with this system.
Many of the ensemble runs and trends suggest the Grand Rapids area
will see well over a half inch of QPF. This makes sense given the
highly anomalous PWAT values of around an inch combined with the
stronger lift noted with the passage of the deepening wave. The
FGEN seen in the models will help to focus the lift and associated
qpf throughout the CWA. A mid level dry slot could work its way
into southern parts of the Lower MI during the day on Thursday. As
colder air starts to wrap in behind the departing wave Thursday
night we could see a transition back to snow...mainly for western
zones.

- A period of snow possible Friday

On Friday a northern stream mid level wave may combine with a
southern stream wave here in the Southern Great Lake Region. This
leads to steady mid level height falls here in MI Friday.  Air
cold enough for lake effect/enhancement will be dropping down from
the Canadian Prairies. Thus a period of snow with possible
impacts could occur...especially downwind of the lake. There is
still a lot of uncertainty on this scenario as there is still a
lot of spread on the track and timing of these waves. With a
period of lake effect likely...we will feature likely pops in the
favored locations for potential impacts.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 657 PM EST Mon Feb 6 2023

Low pressure over Iowa will move northeast tonight and spread some
light rain across the terminals. Model timing has been consistent
over the past few runs and brings the leading edge to MKG around
08z. At this point we think the pcpn will be rain and not freezing
as south winds will be drawing up some warmer air. Look for
ceilings to fall to MVFR a couple of hours prior to sunrise with a
chance to also fall to 900 feet for a couple of hours.

Precipitation should depart the area by 12-13z leaving MVFR cigs
for much of the day.


&&

.MARINE...
Issued at 234 PM EST Mon Feb 6 2023

Gale force winds are still expected tonight as a 50 knot low level
jet moves in ahead the the approaching cold front. The winds will
steadily increase especially with the mixing height increasing
around the frontal zone tonight. The low level jet pulls away
later tonight into Tuesday morning as the front advances east of
the zones.

Then a strong wave moves in from the southwest Wednesday night
into Thursday. Winds could increase again to gale force as a
strong low level jet moves back in.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 2 AM to 7 AM EST Tuesday for
     MIZ037>040-044>046.

LM...Small Craft Advisory until 10 AM EST Tuesday for LMZ844.

     Small Craft Advisory until 10 PM EST this evening for LMZ845>849.

     Gale Warning until 10 AM EST Tuesday for LMZ845>849.

&&

$$

UPDATE...04
DISCUSSION...MJS
AVIATION...04
MARINE...MJS