Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/03/23

AREA FORECAST DISCUSSION

National Weather Service Bismarck ND

 1006 PM CDT Thu Nov 2 2023

.UPDATE...
Issued at 1005 PM CDT Thu Nov 2 2023

There has been a slight uptick in radar returns across western North
Dakota over the past few hours, but there is no evidence that any
rain is reaching the ground. Do not think recent snow reports from
METARs at the Williston and Minot Airports were accurate.
Temperatures aloft are well above freezing, and for any snow to
reach the ground, it would have to be falling at a much higher
intensity than the 9 miles of visibility that had been reported in
order for wet-bulb cooling to occur.

Given the continued presence of mid to high level clouds and a
decreasing signal in rapid-refresh guidance, the areal coverage of
the patchy fog mention in the forecast has been greatly reduced
through Friday morning, and is now primarily limited to northern
parts of our forecast area. Have not made any changes to the low
temperature forecast, but satellite trends suggest at least mostly
cloudy skies could continue through much of the night. If these
trends do hold, forecast lows will likely be too cold, especially
across the north.

UPDATE Issued at 643 PM CDT Thu Nov 2 2023

Some minor adjustments were made to the forecast for this update
based on observed and latest model trends. A deep layer of dry air
above the surface that was recently sampled by the 00 UTC
Bismarck RAOB seems likely to limit chances for any measurable
precipitation through tonight to southwest parts of the state,
where surface temperatures are more likely to remain above
freezing. The latest update still contains some low chances for
rain (no higher than 20 percent) where forecast temperatures are
slightly below freezing. But the expected light intensity of any
rainfall and relatively warmer ground temperatures should limit
any impacts to minor at worst should freezing rain occur.

The development of fog tonight remains more uncertain than
previous nights, although visibility has already lowered into the
3 to 6 mile range across parts of north central North Dakota.
Near-surface relative humidity has remained high through the day,
but extensive mid to high clouds could prevent fog from becoming
more widespread, or at the very least from becoming dense. In
addition, consecutive runs of the HRRR and RAP this afternoon
have shown weak run-to-run consistency in the placement and timing
of fog. Therefore, we will continue to mention only patchy fog in
the forecast for now.

&&

.SHORT TERM...

Key Messages:

- There is a 30% chance in light freezing rain overnight tonight
  into early Friday morning within portions of western and south-
  central North Dakota. Should freezing rain develop, a glaze of
  icing will be possible leading to hazardous travel conditions.

- There is a 60% chance fog will develop again overnight tonight
  through Friday morning within portions of western and central
  North Dakota. Fog may be dense at times, although confidence in
  density and coverage of potentially dense fog is low at the
  moment.

Discussion:

Water vapor imagery this afternoon reveals a notable shortwave
trough over the Pacific Northwest into British Columbia. A plume
of Pacific moisture feeding into this shortwave is also being
noted via satellite. Latest guidance suggests this shortwave will
breakdown as it migrates eastward over the Rockies into the
northern High Plains, de-consolidating into multiple subtle, low
amplitude waves. These pieces of energy aloft and moisture will
push into western ND as early as late tonight, continuing as late
as Friday.

Latest CAMs suggest mid-upper level forcing and moisture will be
sufficient to produce rain showers into western North Dakota and
south-central North Dakota. With a near surface air mass still
near or below freezing ahead of this precip, freezing rain leading
to light icing may be possible during the overnight to early
morning hours of Friday. However, confidence is low in this
potential mainly due to uncertainties revolving around the
juxtaposition of freezing temperatures and fall rain. Forecast
soundings also present a potential scenario where low level dry
air may diminish hydrometeors from reaching the ground, although
conditional instability may help hydrometeors survive this dry
layer. Additionally, this dry layer may allow freezing rain to
occur despite temps being in the mid 30s due to wet-bulbing.

Due to these factors, confidence is degraded in potential for
light icing and impacts. However, wouldn`t be surprised if
hazardous travel conditions develop within portions of western and
south-cental ND overnight tonight and Friday early morning. There
is currently around a 30% in this occurring. Choosing to message
this potential in the AFD and HWO.

With the cool air mass in place, and increasing low level
saturation from weak temperature advection, fog is forecast to
develop over the region, with a 60% chance of occurrence tonight
through Friday morning. However, confidence in location, coverage,
and density is low at the moment.

.LONG TERM...

The main highlights of the long term will be a brief warmup
through the upcoming weekend, with occasional chances for rain and
snow showers associated with fast moving clippers thereafter.

There is growing confidence in a slight warmup through the start of
the long term period, with ridging across the southwestern CONUS
subtly building into our southwest through the weekend. Daytime
highs in the upper 40s to lower 50s across the south are currently
in our forecast, which is trending towards being more in line
with the NBM 50th percentile MaxT`s rather than the 25th
percentile. Almost our entire area will have highs above freezing
on Saturday and Sunday, which should accelerate the snowmelt,
especially across the south and southwestern portions of North
Dakota. However, overnight lows will largely remain below freezing
during this time, potentially refreezing some of the melted snow
and ice overnight. Conditions late Friday night through Saturday
should largely remain dry and cloudy.

Sunday morning will bring us our next chance (20 to 30 percent
southwest, 40 to 60 percent north central) for some rain and snow
showers with the passage of a rather quick moving clipper. Most of
the precip that falls from this system during the day Sunday should
be rain, given the temperatures in the 40s to low 50s, however some
areas of the far north may see some mixed precipitation or straight
snow. As the system departs the area late Sunday night, much of this
precip should transition to a wintry mix or snow, with surface
temperatures dropping below freezing. Accumulation of snow, if any,
is anticipated to be minimal. Northwesterly flow and subtle ridging
will return on Monday, bringing a brief break in the chances for
precipitation. Mostly cloudy skies are expected during this time.

Details become a bit murky following Sunday`s clipper, with some
models suggesting another clipper on Tuesday, and others suggesting
continued northwesterly/westerly flow aloft. Further west, some
clusters are favoring a very prominent, high amplitude ridge across
the upper Pacific Northwest and British Columbia, while other
clusters favor a more modest ridge across the PNW and more zonal
flow across the Northern Plains. With a setup similar to that of the
higher amplitude ridging across BC, enhanced troughing downstream
may bring a more unsettled pattern across North Dakota, with
multiple chances for rain and snow showers through the middle of
next week. Will have to wait and see how this setup pans out over
the next few days, but for now we have a slight chance (namely 15 to
25 percent) for precip across western and central North Dakota on
Wednesday and Thursday, anticipating the flow aloft to be somewhat
unsettled during this time.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 1005 PM CDT Thu Nov 2 2023

VFR conditions are likely to prevail through tonight, with some
light rain possible near KDIK. MVFR to possibly IFR ceilings are
forecast to develop across western and northern North Dakota
Friday morning, spreading into south central North Dakota in the
afternoon. There is lower confidence in MVFR ceilings settling
over KJMS, so amended the forecast there to SCT010 for this TAF
cycle. In addition to the lower ceilings, fog/mist could reduce
visibility to MVFR or IFR levels, but confidence in the timing of
reduced visibility at any given location is low. If fog does
develop late tonight into Friday morning, there is a lower
probability of it becoming dense compared to earlier today.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Hollan
SHORT TERM...CJ
LONG TERM...Besson
AVIATION...Hollan