Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/22/22

See below for an aviation forecast discussion for the 00Z TAFs.



 &&

.SHORT TERM...(This Evening through Tuesday Night)
Issued at 304 PM CST Mon Nov 21 2022

As of 20Z, a surface cold front bisects the CWA, with northerly
winds and a batch of low stratus to the north, and light winds,
warmer temps to the south. The low stratus is approaching KABR,
which would impact aviation. The HREF, along with the HRRR suggests
the low clouds will drift southward some before shifting eastward
overnight as an upper level shortwave slides across North Dakota.
The shortwave may produce light snow, mainly in ND and northern MN,
with dry conditions expected in this CWA. Weak downslope winds will
be possible on the eastern side of Prairie Coteau between 10 to 15Z
Tuesday. Thankfully, blowing snow should not be an issue. Warmer
temperatures will move into the CWA behind the trough, surface warm
front on Tuesday with highs likely reaching the lower 30s, in
northeastern SD, to the upper 40s, in south central SD. Temperatures
should remain mild Tuesday night due to increasing southerly winds
and weak ridging aloft.

.LONG TERM...(Wednesday through Monday)
Issued at 304 PM CST Mon Nov 21 2022

First time range of interest in the extended period revolves around
the weak shortwave energy that crosses the Dakotas Wednesday night
into Thursday. Have slight chance POPs in the forecast now as there
is only limited support for precip within individual ensemble
members and in various precip probability output. Soundings are also
supportive of at least mentioning a slight chance. But again, a
minor system this looks to be, with little if any precipitation.

Main highlight throughout the extended forecast is the turn to
warmer temperatures, especially Wednesday, then again Friday and
Saturday. Rather mild air aloft overspreads the region Friday into
Friday evening, and NAEFS/EC ENS 850mb temps are still showing up at
the 90th percentile. There`s even some 97th percentile sneaking in
on the EC ENS Friday evening. All that said, this equates to periods
of highs in the 40s and 50s for many locations, especially where
snow cover is minimal or non-existent.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 514 PM CST Mon Nov 21 2022

Terminals KABR,KATY,KPIR,KMBG

While prevailing VFR conditions are expected through the valid
TAF period at KPIR and KMBG, low stratus (MVFR) will impact the
KABR terminal, and possibly the KATY terminal, for a while this
evening. Guidance suggests conditions will improve by late tonight
(at or after 06Z) at KABR.

&&

.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&

$$

UPDATE...Dorn
SHORT TERM...SD
LONG TERM...TMT
AVIATION...Dorn



Area Forecast Discussion

National Weather Service Grand Rapids MI

 850 PM EST Mon Nov 21 2022

LATEST UPDATE...
Update

.UPDATE...
Issued at 849 PM EST Mon Nov 21 2022

I am in agreement with the daytime forecaster that dense freezing
fog is likely tonight. My typical way to decide this has changed
some recently when I realized that when the RAP model, HRRR model
and NAMNEST all show dense fog at the same time in the same place
it just about always happens (over the past year anyway and there
have been numerous events for this). Actually every run of the
HRRR, RAP for the past 6 hours shows the dense fog in the same
place at the same time, this is from around 2 am till around 10 am
on Tuesday.

So here is the glitch, we have an area of low clouds dropping
south behind the backdoor cold front (which is now south of I-96).
The clouds are forecast to break up during the night. The models
keep forecasting this run after run. My problem is it is hard to
see a reason to believe that will really happen. So, for now, I
will leave the forecast as is. If the low clouds do not get down
to GRR (I-96) or if they do but break up quickly early Tuesday
morning we will very likely have dense freezing fog. I am just not
sure enough to issue a dense fog advisory.

So, be sure to allow extra time if you have to travel to work
during the morning commute Tuesday, you just may have some travel
delays from icy bridges. overpasses and locally dense freezing
fog.



&&

.DISCUSSION...(This evening through next Monday)
Issued at 310 PM EST Mon Nov 21 2022

- Risk for fog/icy spots tonight

Clouds will be dropping down from the north this afternoon and
evening...but are forecast to diminish overnight.  The winds will
decrease steadily this evening eventually going calm.  The melting
snow this afternoon will add some moisture to the low levels. For
the past couple of runs...the HRRR has been showing an area of
denser fog developing between Grand Rapids and Lansing later
tonight...as temperatures drop through the teens and potentially in
the single digits.  If this happens...there could be some icy spots
on the roadways for the morning commute Tuesday.  If the cloud cover
holds on longer or the wind stays up...the risk for any impacts will
be diminished.  For now we did add some fog to the forecast and
mentioned the potential hazard in the hazardous weather
outlook/social media posts.

- Weak system to bring showers to the area Thu night into Friday
night

A cold front is shown to track through the CWA during this
time frame.  Moisture will advect in from the south ahead of the
front with PWAT values shown to make a run towards an inch. There
will be some mid level lift along the frontal zone as it tracks
through Thursday night and this will support a potential for
scattered showers.  Forecast thermal profiles suggest these will be
mainly rain showers...which is what we will go with for most
locations. Around Big Rapids and Harrison...some snowflakes could
mix in given as 925/850 mb temps are shown to drop to near
freezing later at night.

The southern end of the cold front stalls out over northern IL
and perhaps southern MI Friday before lifting as a warm front
Friday night. Very little lift is seen along this frontal zone.
The DGZ is shown to be unsaturated...thus if there is any
precipitation along this front...it should be in the form of
light rain or drizzle. We will hold onto a very low POP for this
period.

- Increased potential for precipitation Sat night into Sunday AM

Over the weekend the models are in relative agreement in showing a
mid level low lifting out of the southern Rockies..up into the OH
Valley.  This track puts the CWA on the cold side of the
system....which raises some concern for a wintry mix of
precipitation.  We currently have low temperatures near or below
freezing for Saturday night. Thus there is some potential for a
wintry mix at some point Saturday night. Accompanying this system
will be stronger mid level lift and abundant moisture from the
Gulf...so the precipitation should be widespread. The latest
ensemble forecasts are also trending up with the 24 hr qpf...but
at this time most suggest values remaining under a half inch. Stay
tuned for later updates though as this system is still a ways off
and much can change concerning the track and timing.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 700 PM EST Mon Nov 21 2022

The primary threat tonight is dense freezing fog from around 3 am
till around 10 am (ish).

A weak or more so, a shallow cold front is moving due south across
lower Michigan as I write this at 645 pm. The clouds, with MVFR
cigs are just north of a line from near MKG to near MBS. That is
about 30 miles behind the surface cold front. Based on wind
directions and thermal profiles, seems the cold air is forecast to
be about 2000 ft deep as it moves over the I-96 area of Lower
Michigan while more like 3000 ft in depth near Route 10 by 3 AM.

Seems the clouds will not get much farther south than I-96 and
then quickly mix out leaving mostly clear skies in the 06z to 12z
time frame. Winds will be light and variable near the surface at
that time over our TAF sites. Add the moisture from the melting
snow and it would seem reasonable to believe dense freezing fog is
likely overnight. Most of our HI res models show this scenario.
MVFR cigs move in then mix out, shortly after that dense fog forms
within say, 30 miles of US-131 and does not mix out until mid
morning Tuesday.

So, I did not put dense fog for MKG , LAN or JXN but did at the
other TAF sites. Being November, it may take awhile to mix out the
fog but skies should clear by noon (17z).


&&

.MARINE...
Issued at 310 PM EST Mon Nov 21 2022

The winds remain at or above small craft advisory criteria along
the lakeshore...but they are diminishing quickly. We will still
hold onto the current headline...but it might be able to be
cancelled early if this trend continues. The current expiration is
set for 04z tonight.


&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 11 PM EST this evening for LMZ844>849.

&&

$$

UPDATE...WDM
DISCUSSION...MJS
AVIATION...WDM
MARINE...MJS



Area Forecast Discussion

National Weather Service Reno NV

 145 PM PST Mon Nov 21 2022

.SYNOPSIS...

Strong inversions will continue into Tuesday with haze and patchy
fog in valleys. A dry cold front will bring an increase in mountain
winds Tuesday night into Wednesday. High pressure then builds in for
the Thanksgiving holiday yielding quiet and mild weather. Potential
remains for rain, snow, and wind next week, starting as early as
Sunday, though forecast confidence is below normal.

&&

.SHORT TERM...

Another round of strong inversions today with plenty of valley
haze and light winds. One of the more notable inversions was
around Mono Lake where dense fog and pogonip were observed. AM
temps in Lee Vining were near 20 at 6700` while just a few miles
to the west it was 41 on Lee Vining Hill at 8900`.

Guidance favors more of the same tonight into Tuesday morning.
Intermittent high clouds into this evening but models showing
clearing overnight which would help haze/fog formation in
sheltered lower valleys especially around Mono Lake again and
possibly Crowley Lake. Fog at Mono Lake was slow to erode today,
with patchy low clouds even right now, so we could see a rather
quick increase in fog again tonight. Elsewhere, dry airmass with
limited humidity recoveries will help keep fog from being too
extensive.

Brush by (and dry) cold front will help increase NW winds aloft
Tuesday afternoon and evening, with some of that surfacing in the
Surprise Valley per the HRRR otherwise most valley areas remaining
light & variable. After the front sweeps through, we`re looking
to see a turn of the winds to more NE on the Sierra crest ridges
after midnight Tuesday evening into Wednesday. Not a major event
for the east side, and even the HRRR doesn`t show that flow
surfacing into normally prone areas like west shores of Lake
Tahoe.

-Chris

.LONG TERM...

The warming trend will continue through Friday as a ridge
amplifies over the western US. Warmest temperatures of the week
are expected on Thanksgiving Day and Friday, with high
temperatures around 5 degrees above seasonal normals across the
region. High pressure associated with this ridge will also allow
valley inversions to continue, with continued degradation in air
quality and hazy skies. Some improvement in mixing is possible on
Wednesday as a shortwave trough passes to our north and brings an
uptick in ridgetop winds. However, this system will not be strong
enough to completely mix out the inversion.

It looks more promising for active weather as we move into the
holiday weekend. A trough will start to deepen off the Pacific
Northwest coast on Saturday night. Gusty southwest ridgetop winds
in excess of 60 mph are expected to begin Sunday afternoon. Winds
look to remain elevated at ridge level overnight and into Monday
afternoon. Valleys will see breezy winds Sunday and Monday
afternoons. This system is expected to push a cold front through
the region on Monday morning, with temperatures diving well below
normal again for the first half of next week.

Exact details on precipitation associated with this system,
especially precipitation type and amount, remain on the lower
confidence side for now. However, blended guidance suggests good
chances for at least a trace of snow along the Sierra crest on
Sunday night. Bottom line, it will be a good idea to keep an eye
on the forecast if you have travel plans Sunday night into early
next week.

-Whitlam

&&

.AVIATION...

Robust inversions will yield light winds and valley haze through
Tuesday morning. Continued fog and low clouds near Mono Lake
today, will likely return again tonight and Tuesday morning. Can`t
rule out patchy fog near TRK but less confidence there with
passing high clouds and dry airmass. HRRR guidance not showing
signals for widespread fog.

Approaching cold front will starting kicking up the winds aloft
Tuesday afternoon and night with 700mb flow 20-25 knots out of the
NW. While not a favorable direction for mountain waves, some low
level wind shear is possible for mountain locations Tuesday
evening into early Wednesday morning.

-Chris

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$