Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/29/20
Area Forecast Discussion
National Weather Service Bismarck ND
1010 PM CDT Wed Oct 28 2020
.UPDATE...
Issued at 953 PM CDT Wed Oct 28 2020
With this update we trimmed up PoPs and adjusted precip type based
on 00Z forecast soundings and new high-res guidance coming in.
Overall the changes made resulted in a slightly slower onset time,
especially in the southern half where forecast soundings are slow
to saturate until around 18Z or after. Additionally, recent
forecast soundings show a relative clean transition from snow to
rain for most areas. The exception being the northwest, with RAP
soundings showing a brief period of overlap between possibly
enough saturation and a lingering warm nose to produce some very
light freezing rain around 12Z to 15Z. This is also supported by
the incoming 00Z HREF precip type product.
Stratus across central has expanded southeast into James River
Valley area, though eroding on the west edge. We bumped up lows
slightly in the north-central where stratus should persist the
longest. Additionally, with the surface high stretching over
eastern North Dakota fog may develop where there is still snowpack
in southeast North Dakota. With the expansion of stratus into
this area there is enough uncertainty to leave out fog for now,
but this will need watching.
UPDATE Issued at 637 PM CDT Wed Oct 28 2020
Updates were made to extend sky grid coverage for persistent
stratus across northern North Dakota, which guidance is handling
relatively poorly. This may impact lows tonight, with forecast
lows around or below currently observed surface dew points. We`ll
continue to monitor sky cover trends in the near term before
beginning to adjust temperatures tonight. No adjustments needed at
this time to tomorrow`s precipitation.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 220 PM CDT Wed Oct 28 2020
At the surface, a backdoor cold front will continue to drift
slowly south and west through the rest of the day before
stalling/washing out and becoming more of a stationary front. This
will setup a weak baroclinic zone from the far northwest corner of
the state, southeast along the Missouri River and then east to the
southern James River Valley. North and east of this boundary will
see slightly cooler temperatures through the short term than west
and south.
Subtle ridging will quickly move across the state tonight embedded
within northwest flow aloft ahead of an approaching weak
shortwave/Alberta Clipper. As this system approaches, clouds will
once again be on the increase and precipitation chances will start
to develop across the far northwest Thursday morning (mainly as
light snow) as the wave interacts with the baroclinic zone. This
baroclinic zone will transition back to more of a warm frontal
zone and will start to drift north and east as the precipitation
spreads south and east along it. As we move into the afternoon,
temperatures will warm enough to change precipitation to a mix of
light rain and snow before transitioning briefly to a wintry mix
of light rain/snow/freezing rain/sleet across portions of the
Turtle Mountains and James River Valley before it exits the area
tomorrow evening. Along and east of the baroclinic zone, expect a
trace to maybe a little over an inch of snow accumulation with the
highest totals across the Turtle Mountains and the James River
Valley. QPF will generally range from a trace along the western
edge of the precipitation to a couple tenths of an inch east.
Temperatures will be a bit cooler on Thursday than today almost
everywhere except for the far west central and southwest (on the
warm side of the boundary) but weak warm air advection will once
again be on the increase through the day. Clouds may start to
decrease overnight Thursday night as upper level ridging and high
pressure starts to nudge in.
.LONG TERM...(Friday through Wednesday)
Issued at 220 PM CDT Wed Oct 28 2020
Dry conditions, warmer temperatures, and a windy Saturday
highlight the long term forecast period.
An upper level ridge axis moves overhead on Friday, bringing with
it more warm air advection and a mostly sunny sky over all but
the Turtle Mountains and James River Valley. High temperatures
will range from mid 30s northeast to near 50 across parts of the
southwest. Expect breezy southerly winds Friday afternoon ahead of
another Clipper and shortwave trough/cold front.
The cold front will sweep across the state overnight Friday into
Saturday morning as the surface low remains north of the
International border. All guidance continues to keep the passage
of this front dry, but wouldn`t be surprised if we end up seeing
some spotty light rain and/or snow showers by the time it gets
here. After the Clipper passes, gusty winds will develop out of
the northwest on Saturday. At the moment, sustained winds up to
30 mph and gusts to 45 mph seem reasonable and the expectation is
that we will at least need a Wind Advisory at some point in future
forecast shifts. With evening forecast temperatures to range from
the mid 20s to lower 30s on Saturday, this will lead to apparent
temperatures dipping into the upper single digits above zero
north to the teens elsewhere. Thus a brisk and chilly Halloween
evening is likely across all of western and central North Dakota.
We will go ahead and start messaging the potential of wind
headlines in the Hazardous Weather Outlook.
Its likely to remain a bit breezy in places overnight into Sunday
morning but winds will likely shift to the west/southwest and
relax during the afternoon as warm air advection once again moves
across the state. Thus, temperatures will rebound slightly on
Sunday before warming more for the start of the work week, with
forecast highs in the widespread 50s Monday through Wednesday.
CIPS analogs would suggest that 60s may also be possible across
much of the west and central during this time frame but its still
a ways out for high confidence and quite a bit of spread remains
among the various ensemble members of the GFS and ECMWF.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 637 PM CDT Wed Oct 28 2020
Generally VFR conditions this early evening, before increased low
level cloud cover is expected with a clipper arriving Thursday.
Mostly widespread MVFR with pockets of IFR ceilings expected,
especially at KMOT-KBIS-KJMS. Rain or snow is expected to develop
between 15Z to 18Z at KMOT and possibly between 12Z to 15Z at
KXWA, though less certain. Light rain and snow transitions east
after 18Z. Breezy winds, gusting up to 25 kts, shift from south
to west through the afternoon and evening.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AE
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...AE
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
248 PM PDT Wed Oct 28 2020
.SYNOPSIS...Dry weather is expected through early next week. Above
normal afternoon temperatures are expected each day, after chilly
mornings and patches of early morning frost in some of the interior
valleys. Skies will generally remain clear except for occasional
coastal clouds and possible fog through the weekend.
&&
.DISCUSSION...Upper level ridging will dominate through Friday.
Above normal afternoon temperatures are expected in the interior
for at least one more day. The dry air mass and clear skies will
allow temperatures to fall into the mid 30`s in some of the valleys
of southern Humboldt and northern Mendocino again tonight. A frost
advisory has been issued for these colder valleys. It will be
colder in Trinity county valleys, however many sites have already
seen a season ending freeze. Frost advisories and freeze warnings
will no longer be issued for Trinity county until Spring.
A transient shortwave disturbance will move across the Pacific NW
on Friday and temporarily flatten the ridge. This shortwave will
likely induce a low level push of higher humidities for coastal
areas and adjacent river valleys as high pressure rebuilds
offshore behind the disturbance. Satellite imagery has already
been showing low clouds and possible fog forming offshore and
along the southern Mendocino coast this afternoon. The offshore
gradients tonight will likely keep the bulk of the low clouds
over the coastal waters. BUFKIT time-height sections for coastal
land sites were not showing a considerable increase in low level
humidity and low clouds tonight and Thu. Just offshore, profiles
moisten up tonight and Thu, suggesting a greater potential for low
cloud cover along the Mendocino coast through Thursday.
Otherwise, inland areas will remain quite dry through the weekend.
A few upper level stations were still reporting 5 to 10% RH`s
today. The RH`s were higher, 15-25%, at stations with stronger
winds, gusts from 20 to 30 mph. Locally critical fire weather
conditions are expected for the windier sites, due to the very low
RH`s. Widespread and long duration red flag conditions are not
expected, however. A marine push may result in higher RH`s this
weekend, however the highest mountain peaks will probably not see
any significant RH increase. The ridge aloft will spring back up
quickly this weekend, for generally warmer daytime temperatures in
the interior. Another transient shortwave will move into the
ridge early next week, around Tuesday. Rain appears unlikely,
however will leave a 15-20% chance for a few hundredths.
&&
.AVIATION...Visible satellite imagery continues to show some
stratus developing off the Mendocino coast and more off the SF Bay
area. Winds are expected to remain light through the period. Late
tonight the HREF is showing some stratus near the coast of Humboldt
and Del Norte counties. HRRR has been progressively brining more
stratus closer to the coastal terminals in the early morning hours
with local southerly return flow in recent runs. However, the
airmass is still relatively dry with light offshore flow expected at
times. Nevertheless, the 0Z TAFs may need more stratus.
&&
.MARINE...Winds and seas continue to relax, with the remaining Small
Craft Advisory in the Northern Outer Waters now expired. Light
northerlies will settle in for most of the remainder of the week,
with periods of coastal southerly return flow. Small mid-period NW
swells will linger in the waters until a longer period NW swell
builds in beginning early Saturday morning. Forecast data continues
to trend a little higher with it, to likely reach 7 feet at 11
seconds on Saturday. The northerlies will pick back up starting
Friday, and potentially remain elevated Saturday. Late Sunday
afternoon a long-period WNW swell will begin filling in, and will
build to around 4 to 5 feet at 16 seconds by Monday morning. This
could pose a sneaker wave threat depending on how strong the winds
and short periods waves are at this time.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...Frost Advisory from 3 AM to 8 AM PDT Thursday for CAZ104-106-110-
111.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until 3 PM
PDT this afternoon for PZZ470.
&&
$$
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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png
Area Forecast Discussion
National Weather Service North Platte NE
728 PM CDT Wed Oct 28 2020
.SHORT TERM...(This evening through Thursday night)
Issued at 315 PM CDT Wed Oct 28 2020
Main concern tonight through Thursday morning will be the
development of stratus and patchy fog. Surface high pressure will
become centered over western NE tonight as stratus develops
westward over the area overnight. Light winds and weak cold air
advection, with residual near surface moisture from today`s snow
melt will contribute to fog formation. This is supported by the
latest 15Z SREF, but not well supported by the latest HRRR and RAP.
That being said, limited mention of fog to patchy. Stratus looks
much more prevalent than the fog at this time.
On Thursday, surface low pressure will develop across the western
Dakotas and Nebraska panhandle. The stratus and patchy fog will
lift from west to east during the morning. Southwesterly winds
will also develop for areas near and west of Highway 83. Areas in
the northeast will clear out last, with poor mixing. Highs will
range from the low 40s northeast to the low 50s west.
A weak cold front will move in Thursday night with clear skies.
.LONG TERM...(Friday through Wednesday)
Issued at 315 PM CDT Wed Oct 28 2020
Dry conditions Friday through next Wednesday. An upper trough will
move through the Northern and Central Plains Friday night through
Saturday. This will bring a cold front through the area on
Saturday. Highs Friday and Saturday will mostly range in the upper
40s to mid 50s, then slightly cooler in the mid 40s to lower 50s
Sunday.
Monday through Wednesday, an upper level ridge across the western
U.S. will flatten out and move east. Geopotential heights at
500mb will remain above normal around 580dm. The Polar front will
also retreat well north across the northern Canadian Prairies
during this time. the NBM forecasting highs in the 60s to low
70s, with the latest GFS and ECMWF suggesting further upside into
the 70s possible.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 721 PM CDT Wed Oct 28 2020
Low ceilings (MVFR/IFR) are expected to develop after midnight
tonight and last until about mid morning Thursday. This is
primarily expected to be along and east of HWY 83. VFR is expected
all areas by Thursday afternoon. Winds will be light, generally 10
kt or less.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Roberg
LONG TERM...Roberg
AVIATION...Taylor
Area Forecast Discussion
National Weather Service Marquette MI
634 PM EDT Wed Oct 28 2020
.SHORT TERM...(This evening through Thursday)
Issued at 342 PM EDT WED OCT 28 2020
Latest RAP analysis, and GOES Satellite show a weak, closed surface
low of about 1003mb over southern Ontario from this morning and will
continue to move across Ontario throughout the day, which will ease
the tight pressure gradient from last night that brought the gusty
southwest winds. So far, drier low level air mass is keeping any
precipitation from reaching the ground but as we continue into the
rest of the day, low level moisture will increase, mainly across the
north and western parts of Upper Michigan with another shortwave
moving through today and tonight. This shortwave will have just
enough lift and fgen to produce showers across the north half but
can`t rule out an isolated shower or two across the south. Behind
the shortwave, winds will turn to the north and having 850mb temps
falling to about -10C, which will help initiate some lake-effect
snow over the north wind belts. Not expecting much in the way of
accumulation with maybe an inch at most in spots. Lingering light
snow showers will continue through Thursday afternoon before
clearing out by Thursday night.
Light rain showers, mixing in with snow over the Keweenaw, have
begun to move in over the western UP this afternoon and will spread
east through the rest of the evening, mainly across the north. These
light rain showers will transition over to snow showers and with
winds turning more northerly late tonight, lake-effect will take
place over the north wind belts. These should not reach far inland
as winds won`t help to sustain long LES bands and as mentioned from
previous discussion, did cap ProbIce at 85 to keep mentions of
freezing drizzle out of grids. In regards to the Lake-Effect snow
potential late tonight into Thursday morning, a few of the Hi-res
models, with the 12z GFS hinting that this as well, are hinting at a
long fetch band setting up from about Nipigon Bay towards the
Keweenaw Peninsula. If a band does set up, this could bring a couple
inches of snow to the higher terrain areas over the north wind belts
but not highly confident in this but worth mentioning. Winds will
become light by Thursday night with precip clearing out.
Temperatures this afternoon may be close to reaching maximum for the
day but did blend in official and latest obs to better reflect
temperatures this afternoon. Still thinking mid to upper 40s for the
far south central. Thinking cloud cover will hang around and not
have many breaks which will keep temperatures from falling too much
tonight and have lows in the 20s in most spots and low 30s along the
lakeshores. Behind shortwave, highs Thursday will be in the 30s with
maybe a 40 near Menominee.
.LONG TERM...(Thursday night through Wednesday)
Issued at 404 PM EDT WED OCT 28 2020
Thursday night will usher in some pretty chilly overnight low
temperatures, especially across the inland higher terrain where lows
could easily dip below 15 degrees based off the radiational cooling
from clear skies. Moderated temperatures along the lakeshores can be
expected with temperatures staying 7 to 10 degrees warmer compared
to the elevated terrain. Upper level ridging pattern begins to take
hold over the CWA from Friday afternoon through Saturday. Dry
conditions are anticipated at this time with the warming air mass
aloft and subsidence down to the surface. Afternoon highs in the mid
to upper 30s for Friday should be a nice temporary change of pace as
the sun should make an appearance over the region by late afternoon
across a majority of the region. Building clouds on Saturday will
limit temperature maximums despite warm air advection pushing the
afternoon highs approximately 10 degrees warmer compared to Friday.
Temperatures at 700mb level on Saturday approach 0 to -2 Celsius.
The main story for this Halloween weekend will be the shift from a
warmer Saturday afternoon to a strong upper level shortwave trough
impacting the weather Saturday night through late Sunday afternoon.
At this time of analysis, tightening pressure gradients will enhance
wind speeds across Lake Superior inland to the lakeshore areas
upwards of 45 knots. Additionally, the lake effect regime will
really come into focus as northwest winds will cause 1 inch per hour
or higher snowfall rates in the most intense snow bands. The first
period for snowfall will begin 6z-12z Sunday. Beach erosion looks
plausible as the high end gale scenario unfolds from late Saturday
night through Sunday.
As the strong upper level shortwave trough pushes further east, a
secondary upper level disturbance will create the opportunity for
snow showers across the CWA again on Monday. Upper level ridging
looks to take hold over the region allowing for moderated
temperatures near 50 degrees by the middle of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 634 PM EDT WED OCT 28 2020
A shortwave will move through Upper Michigan this evening. This will
bring mostly light rain showers around IWD & SAW with a mix of ra/sn
to CMX this evening. Winds will gradually transition from westerly
to northerly by tonight in the wake of the passing shortwave with
-sn developing at CMX and SAW with lake-effect taking shape. MVFR
conditions will continue through most of the forecast period, but
there will be times at IWD and CMX overnight that will be IFR/LIFR
with some upslope flow.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 342 PM EDT WED OCT 28 2020
Winds will continue to diminish through the rest of the afternoon,
heading into Thursday and Friday mainly below 20 knots. Pressure
gradient will ease as well with mostly westerly winds continuing
over the lake heading into Saturday. Then attention will turn to
Saturday afternoon into Sunday. Confidence has continued to increase
with the potential for a high-end gale event with southerly gales to
35 knots over the east half Saturday afternoon first, then winds
backing to the northwest with gales to 40 knots over the west half
Sunday morning and high-end gales to 45 knots with a window of storm
force gusts for several hours over the east half Sunday afternoon.
Waves between 14-19 ft are certainly possible, given how long the
storm force gusts last Winds will diminish to 20-25 knots by Monday
morning.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JH
LONG TERM...BW
AVIATION...07
MARINE...JH
Area Forecast Discussion
National Weather Service Springfield MO
1057 PM CDT Wed Oct 28 2020
...Updated for 06Z Aviation Discussion...
.SHORT TERM...(This evening through Thursday)
Issued at 227 PM CDT Wed Oct 28 2020
..A Flood Watch is in effect until Thursday Evening..
Current GOES 16 WV satellite imagery depicts an upper-level
closed low spinning into the Red River Valley of Texas. Meanwhile
along the northern Gulf Coast, Hurricane Zeta is making landfall.
A steady rain has lifted into southern Missouri this afternoon and
will persist through the overnight hours as the upper- level low
pivots into the Ozarks and a moisture-rich air mass glides
isentropically into the region on a deep Gulf fetch.
In glancing at the latest NBM probabilities and HREF runs, our
confidence remains high that a swath of 1-3 inches of rainfall
will spread across the entire area this evening into Thursday
afternoon, with the higher amounts along and south of I-44. Some
of the more recent runs from the HRRR and RAP suggest some
isolated 3-5 inch maxima occurring somewhere along
Missouri/Arkansas border. This should not be discounted given the
anomalously moist airmass in place. Per climatology (GEFS
M-Climate output), this airmass ranks above the 99th percentile
for available moisture for this time of year.
We are less confident in the impacts this heavy rainfall event
will have. Despite a very dry summer and early fall, antecedent
conditions have been wetted by rainfall that occurred this past
Monday in locations south of I-44. With incoming rain expected to
fall over a similar footprint, rises to creeks, small streams and
low-water crossings could lead to some flooding. If nothing more,
this rainfall event will alleviate the current drought
conditions.
Otherwise, synoptic wind gusts will increase late tonight into
early Wednesday as Hurricane Zeta makes its extra-tropical
transition and begins to phase together with the departing upper-
level low. Occasional gusts to 35 MPH will be possible, mainly
along the Ozark plateau.
Rain will gradually end from west to east by Thursday evening as
the upper-level low opens up and translates across the Tennessee
Valley and a ridge begins to build into the region.
.LONG TERM...(Friday through Wednesday)
Issued at 227 PM CDT Wed Oct 28 2020
The pattern turns quiet by Friday as upper-level flow becomes
zonal across the Plains. Temperatures should rebound to nearly 60
degrees as compressional warming across the front range advects
into the area.
Shortwave energy will dig into the Great Lakes region later this
weekend. This will help drive a dry cold front through the Ozarks
late Saturday night. Temperatures will be a little cooler on
Sunday behind the frontal passage, but generally speaking,
temperatures into next week look seasonal with daily highs near 60
degrees and overnight lows near 40 degrees as an amplified ridge
builds across the Plains.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1057 PM CDT Wed Oct 28 2020
Widespread rainfall will continue through the overnight hours
along with widespread IFR to LIFR flight conditions in both
ceilings and visibilities. In addition northerly winds will pick
up between 06Z-09Z with some gusts as highs 35 knots through the
morning hours. These will begin to diminish by late morning.
Flight conditions will also improve from west to east as the
afternoon wears on eventually into VFR conditions by late
afternoon.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch through Thursday evening for MOZ082-083-088-090>098-
101>106.
KS...Flood Watch through Thursday evening for KSZ097-101.
&&
$$
SHORT TERM...Albano
LONG TERM...Albano
AVIATION...Raberding