Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/06/18

Area Forecast Discussion

National Weather Service La Crosse WI

 551 PM CST Wed Dec 5 2018

.SHORT TERM...(Tonight through Thursday Night)
Issued at 115 PM CST Wed Dec 5 2018

Loop of GOES water vapor imagery showing a mid-level trough dropping
southeast across northern MN into the Dakotas. Surface analysis has
the associated surface cold front stretching from the arrowhead of
MN through eastern SD...into western NE. Temperatures this afternoon
across the forecast area ranged from the middle 20s to the middle
30s.

Look for that mid-level trough to drive the surface cold front into
the area this evening. RAP shows increasing/strong low-level
frontogenetic forcing with the passage of the front which is expected
to squeeze out around 1/2 inch of snowfall mainly between the I-
90/94 corridors. This could create some slick travel and will convey
messaging as such. This light snow looks to exit the area by
midnight. Mostly cloudy skies are expected in the cold front`s wake
with lows tonight falling into the teens on northwest winds of 10 to
20 mph. Mostly cloudy skies will be seen through Thursday morning as
well but then high pressure is expected to scatter them out during
the afternoon. Plan on highs only in the teens to lower 20s.

Frigid conditions expected for Thursday nigh as cold canadian high
pressure builds overhead. Clearing skies and snow cover will produce
ideal radiational cool with lows bottoming out in the single digits
above and below zero.

.LONG TERM...(Friday through Wednesday)
Issued at 115 PM CST Wed Dec 5 2018

Quiet and cold through the weekend as high pressure holds over the
area. Despite mostly sunny skies, highs will only be in the
teens/lower 20s for Friday, and in the 20s Saturday and Sunday. Plan
on overnight lows Friday/saturday night in the single digits above
zero.

Monday through Tuesday look to be quiet as well with reinforcing
mid-level ridging building in from the Plains.

There will be a slight chance of light snow late Wednesday as a weak
trough of low pressure moves into the region. Warming ahead of this
wave Wednesday should get most of the area into the 30s for highs
-or- right around normal.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 551 PM CST Wed Dec 5 2018

Watching a band of light snow over eastern Minnesota that was
sliding east/southeast in a band of weak frontogenesis. Expecting
that this snow will stay just to the north of both airports but
could be close enough to generate some flurries and possibly bring
in some MVFR ceilings for a short period. Once the snow moves off
to the east later this evening, expecting VFR conditions for both
sites for the most part. The one concern with this is the area of
MVFR conditions over northern Minnesota and North Dakota. The
05.18Z NAM suggests this area of moisture will break into two
sections and for the most part bypassing the area to the northeast
and west. Confidence is rather low in this solution and will
include a period MVFR for KRST Thursday morning just in case these
do get into the area.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...DAS
LONG TERM...DAS
AVIATION...04



AREA FORECAST DISCUSSION

National Weather Service Kansas City/Pleasant Hill MO

 834 PM CST Wed Dec 5 2018

.Update...
Issued at 834 PM CST WED DEC 5 2018

Have updated the forecast to adjust precipitation chances upward
and further west. The RAP, NAM, NAM NEST, and HRRR have all been
trending to bringing in some light snow developing over the
forecast area and spreading to the southeast through tomorrow
morning. The main uncertainty is with the very dry air noted of
the 00Z TOP sounding. Forecast soundings show strong omega setting
up in that dry layer, helping it to saturate. Just how quick is
the question. Feel that we should see snow develop early in the
morning, probably a few hours before the morning commute. Despite
there only being a dusting by sunrise, that may be enough to
slicken roads up. Overall, it looks like around half an inch is
possible through the metro area with a little more to the south
and east.

&&

.Discussion...
Issued at 314 PM CST WED DEC 5 2018

Southerly winds today making for a warmer day across the region.
Near normal temperatures with highs today in the middle to perhaps
upper 40s are a result of a deepening surface low just to the west
of the area. The trough will gradually sink to the south in
response to a fairly potent surface ridge, which will nose into
the area tonight into Thursday morning. Along the leading edge of
this strong ridge will be a cold front, which will not only usher
in an unpleasant mass of cold air, but also bring a chance for
some light precipitation along the leading edge. Most hi-res
models indicate the best chance for accumulating precipitation
will be along and south of I-70 and likely east of the KC Metro,
across central Missouri. There will still be a small chance for
some light rain sprinkles or light snow flurries along the I-70
corridor in the KC Metro, but we are not expecting much if any
accumulation. Even parts east the Metro will likely only see a
dusting to perhaps an inch of the light snow. Mid level support
for this event is also a bit lacking, however within the
northwest flow aloft a glancing blow from a shortwave trough may
offer at least a little mid level support for precipitation in far
northern Missouri, but this interaction will be a bit detached
from the better low level support along the cold front. This cold
front will usher in another round of well below normal
temperatures for the next several days.

With the strong surface ridge in place, it`s unlikely that the
weekend southern stream mid level wave will impact much if any of
the forecast area. Expect the majority of the impacts from
Friday/Saturday system to remain well south of the region, given
the buffer of cold and dry air provided by the strong surface
ridge. There is some signal that a very small amount of moisture
will make its way northward and affect portions of the area south
of I-70 with perhaps some light snow Saturday into Saturday night.
Once again, not anticipating much, if any, accumulation with this
system, however the cool/cold air will remain in place through at
least the beginning part of next week. With regional normals
roughly in the middle 40s, the upcoming stretch of lower to middle
30s represents a departure from normal of around 10 to 15 degrees.
By mid week next week there should be a rebound from the cold
temperatures, as the surface ridge moves east and southerly winds
can recommence. Mid level ridging in the wake of the departing
weekend low and in advance an another upstream trough will also
help in the warming trend for next week. That being said, only
expect a modest warm up, more on par with normal temperatures for
early to mid December. Next weather maker appears sometime late
next week, but as per the usual much needs to be ironed out
between now and then.

&&

.Aviation...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 513 PM CST WED DEC 5 2018

Conditions look to be VFR across eastern KS and western MO through
this forecast. However, light precipitation may move into the
terminals. Models are hinting at some light snow developing over
the area late tonight and tracking away from the area tomorrow
morning. Temperatures may initially support a light rain/snow mix
before cooling down and changing things over to just a few hours
of light snow. Confidence is medium in this actually occurring as
the best chances for precipitation look to be south and east of
the terminals. But it can`t be ruled out entirely based the latest
trends. Southerly winds this evening will shift to the north
behind the cold front. Winds will generally be less than 10 to 12
kts through the forecast.


&&

.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&

$$

Update...CDB
Discussion...Leighton
Aviation...CDB



AREA FORECAST DISCUSSION

National Weather Service Jackson KY

 1104 PM EST Wed Dec 5 2018

.UPDATE...
Issued at 1104 PM EST WED DEC 5 2018

Temperatures are plummeting in valleys where clearing has
occurred. Have updated to go for cooler readings in valleys as
skies clear.

UPDATE Issued at 828 PM EST WED DEC 5 2018

Clearing progressed eastward into the SW part of the forecast
area around KSME and KEKQ early this evening. The forecast has
been updated based on latest satellite trends and model
comparisons. Clearing is expected to make its way east across all
of the JKL forecast area by around 2 AM.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 350 PM EST WED DEC 5 2018

20z sfc analysis shows high pressure more effectively moving into
Kentucky from the southwest cutting off the cyclonic low level
flow and bringing in drier air for our region. This is helping to
diminish the snow showers as they exit to the southeast. Even some
breaks are starting to show up in the clouds on the visible
satellite images. Temperatures are pretty much holding steady in
the lower 30s this afternoon with dewpoints in the low to mid 20s.
Meanwhile, winds are from the west to northwest at 5 to 10 mph
with a few higher gusts.

The models are in good agreement aloft through the short term
portion of the forecast. They all depict the remnants of the
southern extent of the deep North American trough whisking off to
the northeast tonight as heights climb through the Ohio and
Tennessee Valleys. Any energy associated with the initial node of
the trough departs the area this afternoon. The pattern then
flattens out again on Thursday with another mid level trough axis
approaching later that night along with more energy streaming west
to east through the Ohio Valley into Friday morning. Given the
agreement have favored a general model blend with a strong lean
toward the higher resolution HRRR and NAM12 for details.

Sensible weather will feature some of the low clouds breaking up
tonight allowing for partly cloudy skies and a potential small
ridge to valley temperature difference setting up as
temperatures slide through the 20s. More high clouds arrive
quickly on Thursday slowing the temperature recovery back to the
lower 40s. A weakening and drying cold front will then slip
through Thursday night with some light snow possible, but little
to no impacts are anticipated due to its scattered nature and
minimal QPF.

Again used the CONSShort and ShortBlend as the starting point for
all the grids with a small adjustment to temperatures tonight for
terrain differences. As for PoPs did not tweak them much except to
linger some flurries in the eastern higher terrain into the first
part of the evening.

.LONG TERM...(Friday through Wednesday)
Issued at 435 PM EST WED DEC 5 2018

The big story during the extended portion of the forecast will be
the potential winter storm that will impact the region Saturday
night through Monday. Models continue to come into better
agreement concerning this system in the upper levels, however with
air temps still expected to hover near or just above freezing,
there is still quite a bit of uncertainty with the potential
snowfall accumulations.

Zonal flow is still expected to be in place during the day Friday
as the northern stream phases with the southern stream aloft. The
GFS is starting to come into better agreement with the ECMWF, with
both now showing similar placement of a developing closed low
Saturday afternoon across northern Texas. They will then follow a
similar track east-northeast towards Kentucky Saturday night into
Sunday, with the GFS still slightly farther ahead (though less so
than previous models). This low will then settle across the state
through the remainder of the weekend and into Monday, weakening
as high pressure builds north of the Ohio River. This high
pressure could play some role in impacts at the surface as well,
as subsidence across the north could suppress best precipitation
in our far northern counties.

The latest GFS, being slightly faster than the ECMWF, brings the
front edge of the precip into the southern CWA by 0Z Sunday, while
the ECMWF lags behind by about 6 hours. Either way, this is still
much more agreement than previous runs. They also both agree that
precip will overspread the entire CWA, and much of the state by
Sunday afternoon. However, as noted above, there could be a quick
cut off of QPF across the far northern portion of the state with
surface high pressure located just to the north. There is also
good agreement that best QPF will occur within our CWA, mainly
across the southern and far eastern portions. With a slightly
faster GFS, the ECMWF will keep higher precip lingering across
the CWA several hours longer, with precip finally pulling out of
the region Monday afternoon for the GFS and Monday evening/night
for the ECMWF. Increasing heights and high pressure will then take
hold to finish out the extended portion of the forecast.

As for precip types and snow amounts...this is where the largest
uncertainty lies. The airmass leading into this system will be
unseasonably cool, but air temperatures, especially in the
southern extent of the state will be well above freezing (upper
30s to near 40) for highs on Saturday as this system approaches.
With increasing cloud cover and the onset of precipitation in the
south, temperatures will not drop very much overnight, generally
to around the freezing mark if not a degree or two lower.
Meanwhile, temperatures in the northern extent of the CWA will
fall into the upper 20s. In other words, where the heaviest precip
will exist, so too will the warmest temps, with surface/road
temperatures likely lagging a couple hours behind the air
temperatures. This will result in an onset of likely a rain/snow
mix, possibly mixing in with ice pellets, then quickly changing
over to snow, but not able to accumulate until a couple hours
later unless snow falls at such a rate as to overcome the warmer
ground. Either way, this should limit amounts at the onset
Saturday night. For late Saturday night, there is general
agreement of QPF between the neighboring offices, with generally a
quarter of an inch or higher south of the Mountain Parkway. This
could result in accumulations of over an inch in most locations
where temperatures have fallen below freezing.

Temperatures will not rebound much on Sunday, but will likely
still rise into the upper 30s, which would change snow back over
to rain briefly, or at least a rain snow mix. Any rain will
likely eat away at previous snow accumulations during the day,
even if for a short period of time. Precip will then transition
back to snow for Sunday night with generally around an inch or
less of accumulations expected (though locally higher amounts are
possible, especially in the high terrain). QPF and snow amounts
will then taper off Monday, especially as temps rise above
freezing again. All together, total snowfall amounts for this
system still range from around 1 to 3 inches in the north, to 4 to
7 inches in the far east, and locally higher amounts on the high
terrain. Did cut down fairly significantly on the snowfall amounts
across the far south, now with between 1 and 2 inches forecast.
However, it should be noted that even a degree or two variation in
temperatures at any point in this forecast could have high
impacts on the expected snowfall amounts.

Given this is still several days out in the forecast, and there is
still quite a bit of uncertainty, no headlines were warranted or
discussed between the neighboring offices as of yet. However, will
continue to mention in the HWO and start to highlight more in the
weather story, while still stressing the uncertainty.

Skies will begin to clear out heading into Tuesday, with
temperatures increasing a few degrees as high pressure and upper
level ridging move overhead. Radiational cooling will keep
overnight temps low, however, with Monday night and Tuesday night
still forecasted to fall into the low to mid 20s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 828 PM EST WED DEC 5 2018

A high end MVFR and low end VFR ceiling covered most of the
forecast area at the start of the period. However, clearing was
making its way in from the west, with the back edge of the clouds
at 00z extending from a little west of KCVG, south through KSME
and on into TN. The clearing skies will continue to progress
eastward tonight, with the ceilings expected to exit east out of
the state by around 07Z. This will leave VFR conditions through
the remainder of the period. Ceilings in the 10-15K foot range are
expected to develop during the late morning and early afternoon
hours on Thursday.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...HAL
SHORT TERM...GREIF
LONG TERM...JMW
AVIATION...HAL




Area Forecast Discussion

National Weather Service Los Angeles/Oxnard CA

 441 PM PST Wed Dec 5 2018

.SYNOPSIS...05/1243 PM.

Light to moderate rain and mountain snow is expected through
Thursday evening, as low pressure system moves across the region.
Additional showers are possible through early Friday. Temperatures
will remain cool through the end of the week, but dry and warm
conditions are expected over the weekend.

&&

.SHORT TERM (TDY-SAT)...05/128 PM.

Fairly quiet day with scattered light showers that will continue
into the evening. The upper low that is currently about 350 mi
west southwest of Pt Conception will move closer to the coast
tonight and Thursday and move onshore somewhere between Pt
Conception and the Mexican border. As it gets closer to the coast
the expectation is that shower coverage will ramp up, especially
in LA County where there will be a little bit more instability and
moisture to work with. Both the GFS and NAM keep shower intensity
pretty light through Thursday morning, then indicate an increase
Thursday afternoon in southeastern LA County with the upper low.
The ECMWF and HRRR models are faster showing an increase this
evening but in the same area. Given the current position and speed
of the upper low a slower solution would seem to be better. Still
not particularly confident we`ll see amounts that the NAM and GFS
are going with as we`ll still have decent easterly flow at that
time that will continue to be a source of significant drying at
the lower levels. Might see small pockets of higher rates but not
widespread. So am keeping the forecast as is for now with high
probabilities of showers in all areas through Thursday but rates
generally under a tenth of an inch per hour and no concerns for
burn areas. Models still showing some instability offshore and to
the south and will opt to keep thunderstorms out of the forecast
at this time. Additional rainfall amounts most areas should be a
quarter inch or less, but locally up to a half inch in LA County.
A few inches of snow possible in the higher mountains but not
expecting significant impacts to the major roads.

Precip expected to exit the area Thursday night with dry and
warmer weather Friday and through the weekend as a ridge
develops and light offshore flow continues.

.LONG TERM (SUN-WED)...05/149 PM.

Dry and mild Sunday with temps at or slightly above normal. Models
have generally scaled back on a potential weather system for early
next week. The ECMWF has completely dried out as it no longer
shows any energy dropping south into California whereas the GFS
still shows the trough digging off the coast but with minimal
moisture and mainly northwest flow. There are still enough GEFS
ensemble members supporting at least a little rain across the
Central Coast Monday into Monday night but there`s very little
support for rain chances south of Pt Conception so precip has been
removed from that area. Temperatures will cool off Mon/Tue as we
briefly turn onshore and clouds increase. Then trending a little
warmer around mid week.

&&

.AVIATION...06/0040Z.

At 2350Z, there was no marine inversion at KLAX.

Overall, moderate confidence in 00Z TAF package. Moist and
slightly unstable air mass will keep threat of light to moderate
showers for TAF sites through much of the TAF period, with
MVFR/VFR cigs. There is a 10 percent chance of heavier showers or
thunderstorms at any of the TAF locations south of Point
Conception tonight through Thursday as the colder and more
unstable air approaches the region. Easterly offshore wind
component will remain across most TAF sites through much of the
period, strongest south of Point Conception through this evening,
and again after sunrise on Thursday.

KLAX...Moderate confidence in 00Z TAF. Threat of light to moderate
showers through Thursday, generally associated with MVFR cigs.
However there is a 10 percent chance of brief heavier showers or
thunderstorms tonight into Thursday. Moderate to high confidence
of east winds around 10 knots or greater through this evening, and
again on Thursday morning, with occasional gusts over 15 knots.

KBUR...Moderate confidence in 00Z TAF. Threat of light to moderate
showers through Thursday, generally associated with MVFR cigs.
However there is a 10 percent chance of brief heavier showers or
thunderstorms tonight into Thursday.

&&

.MARINE...05/1212 PM.

For the Outer Waters, high confidence in current forecast. Small
Craft Advisory (SCA) level southeast winds will diminish this
evening. For Thursday through Sunday, winds and seas will remain
below SCA levels. On Monday, there is a 60% chance of SCA level
winds developing again.

For the Inner Waters north of Point Sal, high confidence in
current forecast. Winds and seas will remain below SCA levels
tonight through Sunday. On Monday, there is a 30% chance of SCA
level winds in the afternoon/evening hours.

For the Inner Waters south of Point Conception, high confidence in
current forecast. SCA level southeast winds will diminish this
evening. For Thursday through Monday, winds and seas are expected
to remain below SCA levels.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...Small Craft Advisory in effect until 9 PM PST this evening
      for zones 650-655-670-673-676. (See LAXMWWLOX).

&&

.HAZARD POTENTIAL OUTLOOK (SAT-WED).

No significant hazards expected.

&&

$$

PUBLIC...MW
AVIATION...Gomberg
MARINE...RAT
SYNOPSIS...Delerme

weather.gov/losangeles



Area Forecast Discussion

National Weather Service Marquette MI

 639 PM EST Wed Dec 5 2018

.SHORT TERM...(This evening through Thursday)
Issued at 352 PM EST WED DEC 5 2018

WV imagery and RAP analysis indicated a mid/upper level trough from
Hudson Bay into the northern Plains. One weak shortwave trough
moving through northern Great Lakes has brought scattered light snow
showers through Upper Michigan with minimal accumulation. An arctic
cold front was diving toward the area associated with another
upstream shrtwv over nw Ontario. Winds veering from sw to w over
western Lake Superior combined with deep moisture and 850 mb temps
to around -13C has brought an increase in LES into the Keweenaw this
afternoon.

Tonight, expect the heavier LES bands to move through the rest of
western Upper Michigan reaching IWD this evening. As the deeper cold
air moves in the 850/700 mb temps dropping to -16C/-24C and
equilibrium heights climbing to around 10k feet the LES will
increase for nw flow favored locations. including IWD and from Alger
county eastward. Snowfall amounts in the 3 to 5 inch range are
expected. As the arctic front moves through late tonight winds
will veer toward the nw-n resulting in stronger low level conv
with the heavier bands moving into Marquette.

Thursday, as the winds and stronger bands move into north central
Upper Michigan including Marquette in the morning, the combination
of winds and snow will result in difficult travel conditions. So,
the advisory was expanded to include Marquette county even with
modest overall snow totals in the 2 to 4 inch range. The LES will
diminish during the afternoon as inversion heights quickly drop to
around 4k ft with slowly backing winds.

.LONG TERM...(Thursday night through Wednesday)
Issued at 237 PM EST WED DEC 5 2018

Thur ngt-Fri: Trough axis over the Great Lakes region will begin to
pivot east, but the cold airmass is poised to linger through Fri
before some moderation to surface temps. Surface ridging will be
centered well to the southwest of the Upper Peninsula, which will
keep winds oriented from the northwest across Lake Superior and
likely maintain some snow showers for the typical snowbelts. The
thermal profile continues to support LES; however, the depth of
moisture may not be completely saturating the dendritic growth zone,
leading to anticipate only minor accumulations. Thur ngt a few spots
could clear out with the drier air aloft away from the lakes,
allowing temps to radiate down to the single digits above zero or a
few sites falling just below zero. Closer to the lakes clouds may
help to keep temps slightly warmer but not much. Fri highs will
still be unseasonably cold, only reaching the teens to possibly
lower 20s closer to the Lake Superior shore.

Sat-Wed: The medium/longer range forecast continues to provide a
changing pattern, with the departure of the trough and heights
rising well into Canada and a split-flow developing for the Central
CONUS. This will likely slow the departure of the surface ridge and
could provide an extended period of drier and more seasonal airmass
to the Upper Peninsula for the periods of Sun-Wed. Current forecast
is for a dry stretch from Sat ngt through possibly Wed, when
ensemble members begin to diverge from each other and bring a return
to a few weak systems later next week. Overall expect temps in the
longer periods to return to the mid/upr 20s to possibly lower 30s by
Wed.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 638 PM EST WED DEC 5 2018

A trough is over the area and will move SE tonight, with snow along
that trough. Cold air moving in behind the trough will continue to
bring snow to all TAF sites as lake effect kicks in. Mostly expect
MVFR conditions, with shorter spans of IFR or possibly LIFR possible
at times.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 352 PM EST WED DEC 5 2018

Westerly winds of 15-25 knots will veer northwesterly tonight. AS a
cold front crosses the Lake tonight ushering very cold air into the
Upper Great Lakes...winds will continue to veer to the northwest and
increase to 20 to 30 knots into Thursday morning. Northwest to west
winds diminish back down to 15-25 knots Thu night into Fri as
another high pressure ridge passes through the Upper Great Lakes.
Winds may get a little gusty out of the southwest over the weekend
but will remain below gales.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 7 PM EST Thursday for MIZ006-007-
     085.

  Winter Weather Advisory from 1 AM to 4 PM EST Thursday for
     MIZ005.

  Winter Weather Advisory until 1 PM EST Thursday for MIZ001>003.

  Winter Weather Advisory until noon CST Thursday for MIZ009.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLB
LONG TERM...Beachler
AVIATION...Titus
MARINE...JLB