Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/05/18

Area Forecast Discussion

National Weather Service Wilmington OH

 1006 PM EST Tue Dec 4 2018

.SYNOPSIS...
As an upper level trough moves through the Ohio Valley,
occasional light snow will be possible through Wednesday. High
pressure will build into the southeastern states on Wednesday
night, as a cold front crosses the Ohio Valley on Thursday,
bringing another chance of precipitation.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
A weak upper level low with embedded energy rotating around its
southern periphery will move into the region tonight. As this
occurs, steep low level lapse rates will combine with the
forcing to produce scattered to likely snow showers, most
numerous along and south of the Ohio River. Latest NAM and RAP
model runs support the previous thinking, so have gone chance
PoPs north with likely PoPs mainly along and south of I-70. Snow
accumulations will generally be around a half inch, but some
local spots of near an inch can not be ruled out, especially
near the Ohio River. An SPS has been issue to cover this
scenario, which may impact the morning commute.

Though it will remain cloudy, some cold advection will allow
temperatures to fall overnight, with min temps in the middle to
upper 20s.

&&

.SHORT TERM /WEDNESDAY NIGHT/...
As forcing associated with the mid-level low moves east of the
ILN CWA on Wednesday, snow showers will fade to flurries, and
then fade to dry conditions by early afternoon. Subsidence on
the back side of the trough axis will allow for some clearing of
the persistent stratocumulus deck, though cloudy conditions were
kept around in the forecast a little longer than previously, as
these scenarios often seem to take some time to clear up. Aside
from some late day clearing, there is little reason to take the
over on temperatures, with westerly winds persisting and the
coldest 850mb/925mb air moving over the area during the
afternoon hours. Max temps will hover within a degree or two on
either side of the freezing mark.

As high pressure builds into the southeastern states on
Wednesday night, the pattern will begin a brief change over the
Ohio Valley, with winds shifting to the SSW. Ahead of an
approaching cold front (which will be discussed in the Long Term
AFD section) models are indicating a wedge of higher theta-e air
nosing into the area from SW-to-NE by Thursday morning. Looks
like min temps should arrive early on Wednesday night (perhaps
around 06Z) with values in the middle 20s, before temperatures
begin to rise heading through the rest of the overnight hours.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Mid level short wave energy will move across the southern Great
Lakes on Thursday. This will help push an associated cold front
southeast across the upper Ohio Valley through the day. An axis
of low level convergence along and ahead of the front will lead
to an increasing chance of precipitation across the northwest
through the morning and then working into the southeast portions
of our area through the afternoon. Highs on Thursday will range
from the mid 30s in the northwest to the lower 40s in the
southeast. Some non diurnal temperatures are also expected on
Thursday, particularly across the northwest where they will get
into some low level CAA on the back side of the front through
the afternoon hours. Across the northwest any precipitation in
the morning will likely be snow, before possibly mixing with
rain into the afternoon, and then changing back to snow before
ending through late afternoon. Farther to the southeast, expect
more of a rain/snow mix to rain through the afternoon, before
possibly mixing with/changing to snow in the evening, before
tapering off as drier air moves in behind the front.

Surface high pressure will build east across the southern Great
Lakes and upper Ohio Valley Friday into Saturday. This will
result in dry but below normal temperatures with highs both days
in the low to mid 30s. A developing low pressure system will
move across the southeast United States on Sunday before
shifting off of the East Coast on Monday. The 12Z deterministic
and GEFS continue to keep us on the northern fringe of any pcpn
associated with this. Will therefore continue with some lower
end pops along and south of the Ohio River later in the weekend
and into the day on Monday. Highs Sunday and Monday with be in
the mid to upper 30s. It looks like any pcpn that sneaks up into
our south would be mainly snow.

High pressure build into the Ohio Valley on Tuesday, leading to
dry conditions with highs mainly in the 35 to 40 degree range.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
A weak upper level low with embedded energy rotating around its
southern periphery will move into the region tonight. As this
occurs, steep low level lapse rates will combine with the
forcing to produce scattered to likely snow showers, most
numerous along and south of the Ohio River. This will allow
ceilings to drop back into the MVFR category. Where the most
persistent snow showers occur, ceilings will likely drop between
1000 and 2000 feet with visibilities briefly dropping into the
IFR category.

On Wednesday, upper level low will move east with snow showers
tapering off to some flurries before ending. CAA stratocumulus
will linger for much of the day with ceilings remaining MVFR.

By Wednesday night, cold pool of air centered near 850 mb will
shift to the east. WAA and drier air aloft will eventually
lift/push stratocumulus deck to the east, returning VFR
conditions.

OUTLOOK...MVFR conditions are possible Thursday with a mix of
rain and snow.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

$$
SYNOPSIS...Hatzos
NEAR TERM...Hatzos/Hickman
SHORT TERM...Hatzos
LONG TERM...JGL
AVIATION...Hickman




AREA FORECAST DISCUSSION...UPDATED

National Weather Service Jackson KY

 1102 PM EST Tue Dec 4 2018

.UPDATE...
Issued at 1100 PM EST TUE DEC 4 2018

A relative lull in the snow shower activity between waves has been
affecting much of the region over the past couple of hours. The
heaviest snow showers at this point are near the VA border though
there has been an increase in reflectivity upstream over central
and western KY. The short term model guidance continues to
indicate an uptick overnight corresponding to the next mid level
wave moving in from the west. Thus snow showers are still expected
to impact the Wed morning commute and the Winter Weather Advisory
remains in effect. Hourly pops and temperatures, etc. were
updated based on the trends noted above and recent observations.

UPDATE Issued at 725 PM EST TUE DEC 4 2018

Snow showers continue across northeastern, eastern and
southwestern sections of the CWA, but a lull in the activity has
moved into the middle of East KY. Temperatures are generally a
couple of degrees above freezing in the valleys at this time.
Ridges across the coalfields and much of the northwest part of the
area are at the freezing mark or just below. The higher ridges,
however at 2000 feet and above have dropped below 30. The snow
shower activity has been a high snow to liquid ratio event with
only a trace recorded here at JKL, but 0.2 inches of snowfall.
Within the snow showers, social media reports and webcam imagery
from KYTC and others indicates some light accumulations on ridges
in the higher elevations during the heavier showers. The dry slow
or lull in the activity should spread across the area over the
next couple of hours, with guidance suggesting an increase in
coverage toward midnight and after when all locations should be at
or below freezing. Although this next round of snow may be less
than an inch in most areas, impacts to the Wed AM commute are
expected as well as overnight travel. Radar trends will be
monitored and some fine tuning of lowering pops for a couple of
hours prior to midnight may be needed in some locations. Overall,
no substantial changes were needed at this time. The main
adjustments were to hourly temperatures and dewpoints to reflect
recent observation trends which led to slightly lower temperatures
particularly for coalfield ridges.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 325 PM EST TUE DEC 4 2018

19z sfc analysis shows low pressure southeast of the area while
northwest wind low level flow and energy moving by aloft are
maintaining overcast skies and a good amount of showers across
eastern Kentucky this afternoon. Temperatures are generally in the
mid 30s keeping the pcpn as a mixture of both rain and snow. The
showers are variable in intensity with some brief dustings of
snow possible - mainly on the ridges. Meanwhile, dewpoints are
running in the low 30s with northwest winds of 5 to 10 mph most
places.

The models are in good agreement aloft through the short term
portion of the forecast. They all depict the Ohio Valley at the
heart of a large but fairly shallow trough. Along the base of
this, essentially through Kentucky, a stream of mid level energy
will pass through keeping good lift over our CWA with an
enhancement peak expected around and just after midnight. A final
weaker wave then passes through by midday Wednesday followed by
rising heights and fast, flat flow into Thursday morning. Given
the good model agreement have favored a general blend with a
strong lean on the higher resolution near term models like the
HRRR and HREF for weather details especially tonight and
Wednesday.

Sensible weather will feature scattered to numerous rain and snow
showers through the first part of the evening before
transitioning more toward snow after sunset. Expect the snow to
become more expansive through the late evening and overnight for
the area with falling temperatures leading to more potential to
accumulate - including on the roads. Additionally, much of the
time overnight and into Wednesday morning the saturated clouds
will be cold enough to reach the favorable dendrite growth zone.
Accordingly, have gone ahead and issued a Winter Weather
Advisory for the entire CWA through 1 pm Wednesday. The snow will
likely be more variable than depicted in the forecast snow fall
accumulation maps - due to the showery nature of the snow, some
banding, and heavier batches. In general, an inch or less is
expected for the western parts of the area with 1 to 2 inches east
- highest amounts on the ridges and lower ones in the valleys.

Temperatures will settle into the mid to upper 20s by dawn
Wednesday with only a small recovery expected during the day as
the snow showers come to an end. Look for a colder night into
Thursday morning under a brief period of mostly clear skies
allowing a ridge to valley temperature split to develop with
sheltered spots likely falling to around 20 degrees by dawn
Thursday.

Used the CONSShort and ShortBlend guidance as the starting point
for the grids with some terrain based temperature adjustments -
mainly Wednesday night. As for PoPs and QPF: leaned more heavily
on the HREF through the first part of the forecast with extra
enhancement to the upslope areas.

.LONG TERM...(Thursday through Tuesday)
Issued at 412 PM EST TUE DEC 4 2018

The northern stream will begin phasing with the southern stream by
12Z on Thursday, with zonal flow expected across the region
through the remainder of the work week. Kentucky will still be
within the colder northern stream flow, however, with high
temperatures steady but below normal in the upper 30s to low 40s
Thursday through Saturday as a result. Models are continuing to
come into better agreement about an upper level low developing
across the southwest U.S. during the day Saturday. The ECMWF is
showing the low developing across the SW/Mexico border region
Friday evening/night and sustaining as it pushes eastward
throughout the weekend. Meanwhile, the GFS shows the closed low
developing later (Saturday evening) but being stronger and faster
than the ECMWF. The model solutions start to phase again as the
system moves over the state during the day Sunday, though the GFS
will keep the low slightly farther north and deeper during this
time period. This upper level low will then linger across the
region through the end of the forecast period.

So what will this system mean for sensible weather? There is
still quite a bit of uncertainty this far out in the forecast, but
generally we can expect widespread precipitation, mainly in the
form of snow. Given this is a southern stream system moving
northward into our region, we will be in the cold sector of the
system. If the GFS pans out (faster and stronger) precip could
move into the southern CWA by during the day Saturday. The ECMWF
is some 18 hours slower, not moving into the southern CWA until
Saturday night. The GFS will pull the precip across the entire CWA
and keep widespread pops across the region through Monday. The
ECMWF may keep pops across much of the CWA, but could keep some of
the northern counties dry given its more southern track. In
similar fashion, the deeper nature of the system according to the
GFS will favor more QPF. Tried to keep a blend between the two
models for the pops/QPF.

High temperatures during the daytime hours will generally be in
the upper 30s to around 40, but with nightfall temperatures are
expected to fall below freezing. This will promote snow overnight
switching back to rain during the day. Can`t rule out some mixing ice
potential as well if the GFS forecast soundings pan out, but
confidence in this is very low given how far out this is in the
forecast and the fact that the models are not in good agreement.
All things said, based on a blend of the two models, snowfall
totals may range from around an inch in the northern CWA to
between 5 and 7 inches near the VA border. Some of the highest
peaks could see locally higher amounts (Black Mountain has a
current forecast of 9 inches). That being said, this is a
cumulative total between Saturday and Monday night, and does not
take into account the changeover to rain during the day which will
likely melt a lot of the snow that accumulated the night before.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 715 PM EST TUE DEC 4 2018

Scattered to numerous snow showers will continue to move across
the area during the first 12 to 18 hours of the period, before
tapering to flurries as upper level disturbances move through the
region. With this, MVFR ceilings and VIS are expected with some
brief further reductions to IFR in heavier snow showers. Some
light accumulations are expected with this activity. Winds will
be light and generally out of the west to northwest through the
TAF period.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 PM EST Wednesday for KYZ044-
050>052-058>060-068-069-079-080-083>088-104-106>120.

&&

$$

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



Area Forecast Discussion

National Weather Service Louisville KY

 1048 PM EST Tue Dec 4 2018

.Forecast Update...
Issued at 1048 PM EST Tue Dec 4 2018

Band of snow showers stretching from southern Illinois to west
central Kentucky is a bit farther north than earlier expected, and
some showers in the band will be moving into counties just north of
the previously issued advisory. Reports from the Evansville area
indicate roughly half an inch of snow has fallen but that there have
no impacts on the roads thus far. However, as temperatures slip into
the 20s overnight, some issues may begin to develop by morning
commute time farther downstream in central Kentucky. HRRR has been
advertising a stripe of accumulating snow from Hancock County to
LaRue County. So, after collaborating with PAH, have decided to go
ahead and add one tier of counties to the north edge of the western
advisory.

Issued at 902 PM EST Tue Dec 4 2018

No changes to the current forecast. Light, wet snow has been falling
intermittently across the region this evening but road temperatures
have been in the middle 30s to middle 40s and air temperatures just
above freezing, so no significant impacts as of yet. However
temperatures will fall into the 25-30 degree range tonight and there
is a band of snow showers extending roughly from Saint Louis to
Bowling Green that still needs to move through. So, slick roads will
still be a possibility overnight and into Wednesday morning.

&&

.Short Term...(This evening through Wednesday)
Issued at 230 PM EST Tue Dec 4 2018

Certainly not the easiest of forecasts this afternoon. Despite
temperatures in the mid to upper 30s across most of the region, snow
rates across south Kentucky were enough to cause some accidents.
Traffic monitoring sites are showing slow downs across many of the
county seats down there. Any heavier showers could briefly cause
slick spots on roads, thus as we were going to issue an advisory for
this evening anyway, decided to go ahead and start it early.

The evening advisory comes as several higher-resolution models are
pegging several snow showers moving across southern KY tonight.
Gentle upslope flow in our east likely will aid shower development
as well. Expect less coverage over the Louisville metro and points
west/north, but cannot rule out a lonely shower have a streak of 1"
snowfall totals in its wake. Will continue that area with an SPS for
now. The main wave causing this snow will depart to the east as the
day continues Wednesday. Thus will have precip ending by mid morning
in the I-65 corridor and then I-75 in the afternoon.

Morning lows in the upper 20s look to cause some road issues with
the snow on the ground. Afternoon highs will not warm up too much
above freezing, if at all in the I-75 corridor. Have the warmest
highs well west of I-65, where they have the best chance for some
afternoon sunshine.

.Long Term...(Wednesday night through Tuesday)
Issued at 227 PM EST Mon Dec 4 2018

Relatively dry and calm weather will start out the long term period.
Surface flow will switch to the southwest Wednesday night ahead of a
cold front. As the cold front approaches the region on Thursday
afternoon, light precipitation should develop ahead of it in
southern Indiana, and eventually overspread central Kentucky during
the evening and overnight hours. Thermal profiles would suggest the
precipitation starting out as rain during the daytime, and gradually
transitioning to snow as we head into the evening and overnight
hours. Moisture looks to be pretty limited ahead of the front, so
any snow accumulations overnight should be light. Can`t rule out a
few slick spots in central/eastern KY where the snow falls Thursday
night. The front looks to clear the region by Friday morning,
leaving dry but cold conditions in its wake.

The forecast for the weekend continues to look unsettled and
potentially wintry, though confidence in the details remain low.
Long range guidance continues to show a southern stream trough
(currently a 500mb cut-off low west of the CA coast as of writing
this) moving across the Gulf Coast States/Southeastern US over the
weekend into early next week. The specifics regarding the track and
evolution of the upper level fields, thermal profiles, and extent of
precipitation continue to vary from model to model. Precipitation
that is thrown our way, however, looks to be wintry in nature (snow,
sleet, and/or freezing rain) at some point over the weekend and
possibly into Monday due to a strong Canadian high over the Midwest
that will help keep the cold air locked in place. Those with travel
plans this weekend should continue to monitor the forecasts closely
in the coming days given the potential for impactful wintry
precipitation.

&&

.Aviation...(00Z TAF Issuance)
Updated at 624 PM EST Tue Dec 4 2018

An elongated upper level disturbance moving along the length of
Kentucky will bring light snow showers to the TAF sites tonight,
with BWG likely receiving the brunt of the shower activity. MVFR
cigs/vis can be expected in the showers, with some sub-fuel
alternate ceilings possible temporarily in the heavier showers.

Tomorrow the upper wave will move to the east and surface high
pressure will build from the Red River Valley to the Tennessee
Valley, resulting in gradually improving flying conditions.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...Winter Weather Advisory until 10 AM EST /9 AM CST/ Wednesday for
     KYZ023-024-026>028-053-061>064-070>078-081-082.

     Winter Weather Advisory until 1 PM EST Wednesday for KYZ035>037-
     039>043-046>049-054>057-065>067.

&&

$$

Update...13
Short Term...RJS
Long Term...DM
Aviation...13



Area Forecast Discussion

National Weather Service Marquette MI

 543 PM EST Tue Dec 4 2018

.SHORT TERM...(This evening through Wednesday)
Issued at 319 PM EST TUE DEC 4 2018

WV imagery and RAP analysis indicated mid/upper level ridging
building over the northern Great Lakes with an upstream shortwave
trough from Manitoba into the northern plains. At the surface,
southwesterly flow was increasing ahead of a trough into the eastern
Dakotas. Vis loop showed clearing over much of Upper Michigan with
mainly cirrus as daytime mixing has helped scour the remaining
stratocu.

Tonight, weak 700-300 mb qvector conv, slightly deepening moisture
and CAA dropping 850 mb temps to -12C associated with the
approaching shortwave from south central Canada and the northern
Plains will help boost west-flow LES mainly late tonight across the
Keweenaw Peninsula. There is some uncertainty on how quickly the LES
will move onshore as the bands mainly just graze the western
shoreline of the Keweenaw. However, any accumulations should be
light at an inch or less. Radiational cooling should allow temps
to drop into the teens before clouds increase again.

Wednesday, As winds gradually veer from wsw to west the most
favorable low level convergence will also shift to the south through
most of northwest Upper Michigan. Deeper moisture moving in during
the afternoon will also favor increasing LES intensity. 1-3 inch
snow amounts are expected over the Keweenaw but may be locally
higher if any stronger bands linger over a particular location. The
shortwave trough will be strong enough to bring a chance of light
snow even to inland portions of the west by mid to late afternoon.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 425 PM EST TUE DEC 4 2018

No changes in thinking from previous shift. Still looking at
potential for moderate LES in NW wind snowbelts Wed night into Thu.
Could see advisory level impacts over the W during this time with
moderate accumulations possible and breezy winds near Lake Superior.

Even as cooler air to -19C moves over Thu evening into Thu night,
inversion heights decrease so impacts shouldn`t be a big issue later
Thu into Fri, even as LES continues in the W-NW snowbelts.

Lows in the single digits to low teens are expected Thu night and
Fri night, with highs in the teens to around 20 on Fri (although
winds chills should top out in the single digits to around ten).

For Sun on, temperatures will be closer to normal with minimal
chances of precip.
&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 542 PM EST TUE DEC 4 2018

MVFR conditions are expected to persist at IWD through the forecast
period and through mid afternoon at CMX before light snow moves in
and lowers them to IFR. VFR conditions at SAW will last for about
half the period and MVFR for the other half as they will be on the
edge of lake effect clouds and snow showers.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 319 PM EST TUE DEC 4 2018

Look for westerly winds of 15-25 knots tonight into Wednesday. There
may be some higher gusts near the Keweenaw where terrain convergence
enhances the wind. The next chance for stronger northerly winds will
arrive late Wed night into Thursday behind a stronger cold front
when northwest to north gale force gusts are possible. 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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLB
LONG TERM...Titus
AVIATION...07
MARINE...JLB