Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/14/17

Area Forecast Discussion

National Weather Service Denver/Boulder CO

 657 PM MST Wed Dec 13 2017

.UPDATE...
Issued at 645 PM MST Wed Dec 13 2017

Satellite showing a trough in the northwest flow aloft diving
southeast over eastern Idaho and western Wyoming. The trough will
continue to move southeast and lift ahead of the trough will
spread over most of Colorado tonight. Some echos are starting to
show up on radar. The lower levels of the airmass are still dry,
so most of this is likely virga. As the airmass moistens from the
top down, snow is expected to increase this evening over the
mountains and spread onto the Front Range late tonight.

The biggest change to the forecast was to add an inch or two of
snow to Park county where the HRRR is showing more than the other
models. Expected southeast surface winds should support slightly
higher snowfall totals here. Otherwise, only other changes were to
line up with the current trends.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 243 PM MST Wed Dec 13 2017

North and northwesterly surface winds are covering the plains
right now. The radars and satellite pictures upstream show some
precipitation to our northwest in Wyoming, Idaho and Utah. The
water vapor pictures show the upper trough pushing southeastward
over eastern Idaho. Models show this trough to move across the CWA
tonight. Strong northerly flow aloft moves into Colorado on
Saturday. The is a shot of upward vertical velocity on the QG
Omega fields this and overnight, with weak downward motion on
Thursday. Models show northerly low level winds this evening. They
become northwesterly out on the eastern plains after 06z, but
stay almost due north over the western plains. For moisture, cross
sections have deep moisture over the CWA from about 06Z tonight
through 15Z Thursday morning. The mountains have pretty decent
moisture this evening already. On Thursday, moisture decreases
quite a bit, but there is still some over the mountains and
plains in the afternoon. The QPF fields on the NAM/GFS/ECMWF are
in some agreement concerning precipitation amounts for the CWA
later tonight into Thursday morning. Even the snowfall amount
agree pretty well. Will leave the current, "likely" pops going
tonight into Thursday and will also keep accumulations light. No
highlights, but at least we should get a bit of moisture. For
temperatures, Thursday highs look to be 3-6 C cooler than this
afternoon`s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 243 PM MST Wed Dec 13 2017

By Thursday evening the upper trough that brought snow to the region
will move SE. Increasing subsidence behind it will help to clear out
the snow and the evening hours with overnight lows dipping into the
lower 20s on the plains. Directly along the foothills however,
models show an increasing lee side low that will help to keep lows
slightly warmer due to downsloping winds. Friday will see increased
ridging with clearing skies and highs reaching back into the mid to
upper 50s.

Over the Pacific NW a positively tilted trough will move eastward to
bring the region another round of snow. Models are still in
disagreement with the path and timing of the system with the GFS
creating a cut off low but moving the main branch of energy over CA
and the Gulf. The EC has a similar feature but separates it with an
open wave over the four corners. This in combination with a surface
cold front Saturday afternoon will bring increased chances of snow
to the mountains and foothills early Sunday. Increased upslope and
cooler temperatures behind the frontal boundary will play a large
part in how the amounts will shape up so will resist from giving any
numbers here. Will keep a high chance in the mountains with a chance
along the urban corridor and a slight chance further east.
Temperatures will drop slightly on Saturday with highs in the 40s
dipping into the teens and low 20s overnight into Sunday. With snow
and cloudy conditions temperatures will not recover with highs only
getting slightly above freezing.

With the western ridge breaking down NW flow will start to turn more
westerly and help to create a more active pattern.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 645 PM MST Wed Dec 13 2017

East/northeast winds 6-8 kts expected through 04z with prevailing
VFR conditions, ocnl ILS conditions with cigs around 050 kft agl.
MVFR cig/vsby restrictions developing 05z-15z period with
north/northwest winds 8-14 kts following fropa. Localized IFR
cigs/vsbys possible under any developing snow bands. At this time
expect light snow with a chance of brief moderate snowfall. Snow
showers will diminish after 15z with ILS cigs until 17z then VFR
returning by late Thursday morning/afternoon.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Meier
SHORT TERM...RJK
LONG TERM...Bowen
AVIATION...Cooper



Area Forecast Discussion

National Weather Service State College PA

 1029 PM EST Wed Dec 13 2017

.SYNOPSIS...
An Alberta Clipper will track across southern Pennsylvania
overnight. Behind this system, a ridge of high pressure will
slide across the region Thursday and Thursday night with cold
but mainly dry conditions.

Another clipper will move north of the region overnight Friday
and Saturday morning with limited moisture.

High pressure will build across the area early Sunday with
a brief moderating trend.

A series of cold fronts will move across the area late Sunday
into Wednesday. Windy and colder temperatures will follow for
Tuesday into Wednesday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
An Alberta Clipper, located over northwest Ohio at 03Z, will
streak ESE through southern PA overnight and off to our east by
early Thursday. An impressive mid level jet streak is progged to
dive through the Ohio Valley and just south of the MD border
overnight, placing the region in the favorable left front
quadrant of the jet. The low level response will be a
strengthening southerly flow and a period of strong warm
advection and isentropic lift centered over central PA.

Light snow has overspread nearly the entire forecast area at
03Z and expect strongest WAA at nose of low level jet to move
from the Laurel Highlands at 03Z to the Susq Valley around
05Z-06Z. Many areas will likely see snow diminish after 06Z, as
low level jet shifts east. However, 00Z HREFV2 suggests a moist
upslope flow into the the Laurels/Central Mtns should keep the
accumulating snow going in that area until almost dawn.

As expected with a clipper, model omega/temp time-sections
indicate fairly high snow/water ratios. Close to 20:1 expected
across northern Pa, where max lift if progged to occur within
the best dendritic growth zone. Across the southern counties,
indications are for slightly lower ratios with some riming
likely based on profiles of temp and lift.

Model blended qpf, including contributions from latest HRRR and
00Z runs of the HREFV2/NAM, support storm total snowfall
ranging from less than an inch from Chambersburg and York
southward, to around 6 inches across Cambria and southern
Clearfield counties. Considered upgrading to an warning for
Cambria, didn`t see much to be gained by upgrading one county
for what would be a borderline, low end warning.

Strong wind gusts across southwest Ohio have caught my eye this
evening. Although not anticipating the 47kts observed at KILN,
do expect winds to become gusty late tonight across portions of
Somerset County, as this area briefly breaks into the warm
sector south of sfc low. Bufkit soundings support gusts to
around 25kts down there by around 09Z.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
The snow should have ended by dawn over nearly the entire
region, as fast-moving clipper passes off the NJ coast. High
pressure will build in during the day leaving little more than
some scattered snow showers over NWRN sections and possibly the
Laurel highlands.

Highs ranging from the upper teens across the northern tier to
around freezing in the far SE will average about 10-15 deg
colder than normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
A few snow showers for Thursday evening, then clearing and
quite cold conditions for overnight under the center of high
pressure. Min temps will vary from the single digits over the NW
mtns, to the teens throughout the Susq Valley and Southern
Tier.

A mid level wind max will drop southeast Friday night and
early Saturday. Some snow showers expected, mainly across the
west. I did up POPS some.

For the first part of the weekend, did lower temperatures some
more.

Still looking mainly dry later Saturday into the first part of
Sunday.

A complex pattern will prevail after Sunday, with some energy
from the southern branch of the westerlies becoming more active.
Moisture from the Gulf of Mexico will be limited, with a ridge
in place.

Expect colder and more in the way of wind by later Tuesday into
Wednesday.

Overall, minor changes to the package.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
* Cloud/Ceiling info will be missing at KBFD until new part can
  be installed *

Most terminals are VFR as of early afternoon, the exceptions
being the usual higher elevation culprits from JST north into
Northern Mountains where there remains some residual lake
effect snow showers.

The near term guidance shows the snow showers over the north
dwindling over the next few hours, just in time for a larger
area of snow to begin overspreading the western part of the
flying area between about 22-00Z. The snow will reach eastern
areas before 02Z.

Expect the brief improvement this afternoon to deteriorate once
again with widespread IFR being the predominant condition
overnight. MDT/LNS being on the southern edge of the expected
snow shield could waver between MVFR and VFR.

The snow will taper off quickly in the pre-dawn hours with rapid
improvement setting in as the storm moves east of the area. The
higher elevation terminals could remain MVFR for a good part of
Thursday, but elsewhere airports should become VFR by mid
morning and continue throughout the day.

Outlook...

Thu-Sat...Scattered snow showers and local restrictions
NW/Laurels.

Sun-Mon...Mainly VFR.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 8 AM EST Thursday for PAZ004>006-
010>012-017>019-024>028-033-034-037-041-042-045-046-049>053-
056>059.

&&

$$
SYNOPSIS...Fitzgerald/La Corte
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/La Corte
LONG TERM...Martin
AVIATION...La Corte



Area Forecast Discussion...UPDATED

National Weather Service Green Bay WI

 829 PM CST Wed Dec 13 2017

New Information added to update section

.UPDATE...
Issued at 818 PM CST Wed Dec 13 2017

The two lake-effect bands over the far southeast part of the
forecast area merged into a single band, which has now shifted
southeast of the area. There are some indications the band may be
developing back to the north some out over the lake, but it`s
current movement suggests it is unlikely to produce an additional
accumulation over the lakeshore counties. As far as the winds go,
the flow has backed more northerly, which has allowed gusts to
settle back into the 20-25 kt range.

Although it`s still going to be a rough night to travel across
east-central Wisconsin, conditions should gradually improve from
here. So, will allow the remaining headlines to expire as
scheduled at 900 pm.

UPDATE
Issued at 523 PM CST Wed Dec 13 2017

Will Extend the southern Marinette/Oconto and Brown county
warnings to 03Z to match the lakeshore. Snow will be ending, but
it is very windy near the lake and bay, so travel will be very
slow to improve. Will also extend the advisory for the Fox Valley
and areas just to the NW. The remainder of the advisory will be
allowed to expire at 600 pm as scheduled. Coding is as shown
below.

The HRRR indicates a lake band will still be over Manitowoc
County at 03Z, so we may need to revisit the expiration time there
later this evening. But there is always uncertainty in the
location of lake bands, so we`ll see how things evolve before
making any decisions on extending there.


UPDATE
Issued at 433 PM CST Wed Dec 13 2017

Some headline decisions will need to be made soon. Have not
reached any final decisions yet, but feeling is that the warning
for Brown and the advisory for the rest of the Fox Valley will
need to go past scheduled expiration at 600 pm. Conditions look
like they will probably ease enough to allow the advisory for
central/north-central Wisconsin to expire as scheduled. The
Oconto/Marinette county area may the toughest call. Looks like a
bit more of a lake/bay influence there now with some transverse
banding on the radar. That`s dropping south, but still 1/2SM vsby
on the Washington Island AWOS. Winds are strong in this area too.
Looking to have final decision on headline changes by 530 pm.

UPDATE
Issued at 342 PM CST Wed Dec 13 2017

Travel conditions, which weren`t very good to begin with, are
likely to become very difficult in east-central Wisconsin for the
next couple hours.

A small-scale frontal boundary extends from near KPCZ to KATW to
KSBM. Increasing northeast winds north of the boundary were
meeting more northerly/northwesterly flow on the other side of
the boundary, leading to strong convergence near the frontal zone.
Radar returns northeast of the boundary have been increasing, and
local mesoplots showed a significant deepening of the dendritic
growth zone across the area. The result should be a period of
heavy or very heavy snowfall, with rates AOA 1 inch per hour.

In addition, winds above the surface were increasing and backing,
and will come through 040 in the 925-850 mb layer in the next few
hours. That will likely lead to some gusts over 30 mph near Green
Bay and along the lakeshore. Near whiteout conditions with very
low visibilities are likely at times.

Already sent an SPS highlighting the short-term situation, and a
graphical Wx story is on the way. Will be updating the WSW next to
adjust snowfall wording.
&&

.SHORT TERM...Tonight and Thursday
Issued at 251 PM CST Wed Dec 13 2017

The latest RAP analysis and satellite/radar imagery show low
pressure moving into north-central WI early this afternoon. The
coldest cloud tops and heaviest snowfall rates are occurring over
northeast WI where visibilities are down to 1/4sm at times. East
winds are increasing along the Bay and Lake with gusts to 35
mph. As snow continues to pile up over northeast WI and winds
shift to the northeast, expect blowing and drifting snow to impact
areas into the Fox Valley this afternoon. Added Manitowoc County
to the warning, given a report of 5 inches so far at Mishicot and
winds gusting up to 30 kts on the lakeshore. No additional changes
expected as the snow and snow/blowing snow should keep roadways
in poor shape through the evening commute. The worst conditions
should occur over far northeast WI. Snow/wind trends are the main
forecast concern.

Tonight...Low pressure will continue to move southeast towards
northern Ohio this evening. Hi-res models indicate that snow will
be ending over northeast WI by mid-evening. Winds will remain
gusty through midnight over eastern WI though, so roads may will
likely be slow to improve. Additional accums are projected to be
less than an inch this evening, highest over the lakeshore areas.
Models then insist on rapid clearing taking place from the north
behind the system, particularly for central and east-central WI
overnight. But with winds onshore from Lake Superior there is
potential for clouds to remain broken for the entire night. Lows
ranging from the mid single digits to mid teens.

Thursday...The next clipper will pass across the region, though it
will be considerably weaker and have less moisture to work with
than todays potent system. Still though, should see clouds
increase again in locations which saw clearing tonight. In
addition, moisture looks deep enough for flurries and light snow
showers from mid morning over central WI and midday over eastern
WI to the end of the afternoon. Some areas could see a dusting.
Seasonable with highs ranging from the upper teens to mid 20s.

.LONG TERM...Thursday Night Through Wednesday
Issued at 251 PM CST Wed Dec 13 2017

A weak upper level disturbance will track across the area Thursday
night into Friday, bringing snow showers and flurries to much of
the area, but accumulations will be under a half inch for all but
far north central WI where an inch or two is possible as some lake
effect/enhancement from Lake Superior is expected. Friday looks to
be the coldest day in the period, with highs struggling to get
into the teens in the Northwoods and into the lower 20s in the Fox
Valley.

The chance for flurries or snow showers will continue Friday night
into Saturday, especially across northern WI, as another
shortwave rotates along the western edge of a upper low sitting
over northeast Ontario. Most persistent and heaviest activity will
remain over north central WI as Lake Superior continues to aid in
the snow shower development. Some dry air will get into the mid-
levels on Saturday, leading to the chance of some freezing
drizzle, but confidence not high enough that precip will actually
occur to add to the forecast. Friday night looks to be the
coldest night in the period, with lows below zero possible across
north central WI and single digits above zero across the rest of
the area, away from Lake Michigan.

Models bring another shortwave into the area this weekend, now
focusing more on Sunday, but model differences are significant,
especially between the GEM/ECMWF and the GFS. Models handle both
the system crossing the northern Plains and another system
tracking NE from the southern Plains. The interaction of these two
systems will determine what, if any, precip chances will occur
this weekend into early next week. Temperatures look to return
closer to normal on Saturday, then slightly above normal Sunday
into early next week as the flow turns more W/SW.
&&

.AVIATION...for 00Z TAF Issuance
Issued at 523 PM CST Wed Dec 13 2017

Meteorological conditions will improve as the storm system exits
the area. But winds will remain strong over east-central
Wisconsin, so drifting snow will likely continue to be a
consideration for airport operations for the rest of the night.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 9 PM CST this evening for WIZ020-
021-031-037-038-048-049.

Winter Storm Warning until 9 PM CST this evening for WIZ022-039-
040-050-073-074.
&&

$$

UPDATE.........Skowronski
SHORT TERM.....MPC
LONG TERM......Bersch
AVIATION.......Skowronski




Area Forecast Discussion

National Weather Service Wilmington NC

 752 PM EST Wed Dec 13 2017

.SYNOPSIS...
Temperatures will return to normal Thursday and Friday as a
pool of cold air aloft moves away to the northeast. Another cold
front will reinforce dry and cool weather this weekend. Low
pressure approaching from the Gulf will bring an increasing
chance of rain, and a warming trend through early next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 8 PM Wednesday...Temperatures appear to have stabilized
and are even rising a bit over our western counties as warm
advection in advance of the next front takes hold. Dewpoints are
making an even more robust recovery and are now in the 20s and
lower 30s. This is all according to plan and have not needed to
make any major changes to the forecast. Previous discussion from
this afternoon follows:

Single digit dew point values are certainly a rarity in this
part of the world, but the `Carolina Desert` appears to be in
place today with widespread dewpoints of 8-12F and RH below 30
percent. This certainly is an indicator of the dryness of the
airmass, echoed further by examination of the WV imagery, and
RAP soundings depicting PWATs around 0.25 inches. Temps have
rebounded better than forecast, approaching 50 in many spots
thanks to full sunshine, but temps will drop quickly after
sunset thanks to good radiational cooling in the dry column.

However, the temp and wind forecast tonight is less than clear-cut.
Warm advection will begin in earnest this evening as high pressure
ridges northeast from the Gulf Coast, and a clipper-type low
pressure moves through the Great Lakes creating a brief warm sector
across the Carolinas. While this regime will be short lived, it will
be quite strong, with 850mb winds forecast to exceed 40 kts, driving
surface winds through the overnight. Still expect a surface
inversion to develop, especially early, which will at least limit
gust potential overnight, but do forecast an increase in winds after
midnight and towards Thursday morning, with speeds of 10-15 mph
likely. If the inversion doesn`t materialize, it could be a very
windy night, but at this time think there will be enough of a lag in
the LLJ development after sunset to permit an inversion first. As
winds pick up, temps will likely level off or increase the latter
half of the night, so mins in the low to mid 30s are expected early.

On Thursday, the aforementioned clipper will swing across the Mid-
Atlantic and drive a weak cold front into the Carolinas. Ahead of
this feature, temps will climb to seasonable norms in the upper 50s
to around 60, with continued nearly cloudless sky conditions in deep
westerly flow. The surface front, which has little to no temp
gradient across it, will swing across the region late in the period
with a wind shift to the NW at the surface but little other
fanfare.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 330 PM Wednesday...The deep east coast trough that has
been in place for some time now will relax a bit during the
short term period but not abate completely. A very broad trough
will develop out west and sink down into the area by Saturday
morning with an essentially dry frontal zone at the surface.
After a brief period of weak warm air advection Friday 850mb
temperatures will dip once again to near freezing or below by
Saturday morning. This will lead to surface temperatures at or
near freezing for most of the area for lows.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 330 PM Wednesday...The primary caption for the extended
period, `Seasonably Cool and Dry This Weekend, Milder and
Wetter early Next Week`. In wake of a dry cold frontal passage
late Friday, a mainly fair and seasonably cool weekend appears
to be shaping up, before the onset of a warming trend into early
next week, as ridging aloft ensues. GFS and ECMWF differ on
timing and strength of ejected Baja short-wave Sunday, but both
agree on a milder and wetter pattern after the weekend. The
first chance of rain by Sunday night, as this features ejects
offshore early Monday. Despite ECMWF/GFS differences even into
Tuesday, it seems we can infer a mild pattern prevailing and
rain chances ahead of an upper trough, that in both models
appears along the east coast next Wednesday.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
aS OF 00z...Quite an airmass turnaround through the overnight hours
with dewpoints rising as much as 30 degrees. A southwest low level
jet sets up and should break the inversion sometime around midnight
with winds increasing and becoming gusty. Temperatures may rise 5 to
10 degrees. Thursday, VFR with more of a westerly wind as clipper
moves through the Great Lakes.

Extended Outlook...VFR.

&&

.MARINE...
NEAR TERM /THROUGH THURSDAY/...
As of 8 PM Wednesday...Advisory conditions have not yet
developed but winds are now increasing from the SW at 10 to 15
kts and seas are up around 2 to 3 ft. Still expect conditions
to deteriorate overnight as SW winds increase in advance of the
next front. No major changes with the latest update. Previous
discussion from this afternoon follows:

Westerly winds across the waters will transition to SW this
evening as WAA begins ahead of a cold front dropping across the
Great Lakes. This will drive increasingly strong SW winds,
reaching up to 40 kts aloft, which will manifest at the surface
as 20-30 kt winds this evening into Thursday, even with the cold
ocean temperatures. For this reason the ongoing SCA remains
unchanged into Thursday morning for these winds driving seas up
to 4- 7 ft. The weak front will cross offshore during Thursday
bringing a wind shift to the NW and speeds dropping to 10-15
kts, which combined with the offshore component help drop seas
to 2-4 ft.

SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 330 PM Wednesday...Somewhat light wind fields for the
first part of the short term period as a weak boundary will
bisect the waters. Expect northeast winds to the north of the
front with west to southwest winds to the south. Later Friday
afternoon a more consistent southwest flow develops with
stronger magnitudes, 15-20 knots. This direction will be short
lived as a northwest flow develops late Friday maintaining the
15-20 knots. Significant seas will be 2-4 feet through the
period with some five footers possible later across the outer
waters.

LONG TERM /SATURDAY THROUGH MONDAY/...
As of 330 PM Wednesday...A manageable marine period over the
weekend with moderate offshore winds in wake of a dry cold
frontal passage Friday night. As a result, inshore seas will
have limited fetch length for growth, but notably larger seas
will prevail offshore, although no advisories are expected as
weak high pressure passes over then offshore on Sunday. SW-W
winds expected Monday as high pressure settle offshore and SE
of the waters.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until noon EST Thursday for AMZ250-252-
     254-256.

&&

$$

SYNOPSIS...99
NEAR TERM...REK/JDW
SHORT TERM...SHK
LONG TERM...MJC
AVIATION...DL
MARINE...MJC/REK/JDW/SHK




Area Forecast Discussion

National Weather Service Lincoln IL

 911 PM CST Wed Dec 13 2017

.UPDATE...
Issued at 910 PM CST Wed Dec 13 2017

The 995mb surface low will continue to weaken and pull away to the
east of Illinois the rest of the night. The low has reached NW
Ohio as of 9 pm. However, trailing energy behind the low is
combining with low level moisture to produce scattered flurries
this evening. Strong winds from this afternoon and early evening
will continue to diminish as pressure rises weaken and the
pressure gradient becomes less compact. Therefore, the Wind
Advisory was allowed to expire at 9 pm. Some clearing in the
clouds could develop after midnight, and satellite loops show
holes in the cloud shield developing in northern Illinois already.

Low temps will occur at sunrise, once winds weaken and the cold
air plummets into the area. Most areas should see the low to mid
20s.

The updates this evening were to add flurries and adjust cloud
cover to expected trends. The remainder of the forecast looked on
track.

&&

.SHORT TERM...(This evening through Thursday)
ISSUED AT 308 PM CST Wed Dec 13 2017

A 992 mb low is centered near Milwaukee this afternoon and a cold
front trailing from the low southwestward through roughly the I-55
corridor, pushing southeastward. Brisk winds were gusting up to 40
mph well ahead of the front, with a short lull in winds until behind
the cold front where gusts to around 45 mph are prevalent, with the
winds shifted to WNW. Expecting the strongest winds to push east to
the IN border by around sunset, then winds will begin to taper off a
few hours after sunset across central IL as the parent low moves
rapidly east and the strongest winds aloft and surface pressure
gradients shift east. A wind advisory remains in effect until 9 p.m.
for most of central Illinois except for Richland, Lawrence, and
Crawford Counties. Light showers can also be expected along the
front this afternoon, with little or no measurable precipitation.
Overnight, winds will gradually decrease as a high pressure ridge
approaches from the west. Winds will end up light WNW only around 5
mph during the day Thursday as a result of the ridge. Expect lows
tonight back down to the low to mid 20s as cold post-frontal air
moves back in from the northwest, with highs Thursday only in the
low to mid 30s.

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 308 PM CST Wed Dec 13 2017

The next weather system will arrive early Friday morning as a
shortwave trough arrives from the northwest. Models produce only
scattered and very light precipitation with this feature, however it
will likely be able to produce some flurries north of I-70. After
this, the pattern begins to shift as the large-scale eastern
trough/western ridge move east with ridging and southerly flow
developing into the central U.S. bringing warmer temperatures
reaching the 40s in central IL through early next week. A
disturbance embedded in the southwesterly flow aloft will provide a
chance of rain Sunday, potentially beginning as light snow early
Sunday morning. After that, models disagree on timing and track of
precipitation, however general trends in the pattern suggest
precipitation gravitating toward the southeast U.S. early next week
as the west coast ridge and eastern trough re-establish.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 600 PM CST Wed Dec 13 2017

A deep surface low just east of Chicago will continue to pull away
to the east this evening. An expansive area of MVFR clouds are
expected to rotate through central Illinois behind the low. HRRR
is optimistically showing ceilings improving to VFR toward 06z,
but confidence on that is low. HRRR is also showing clearing in N
Illinois expanding toward our I-74 TAF sites after midnight. PIREPs
are showing the cloud thickness to be about 2,000 feet, which is
thick enough to reduce the chances of the cloud layer thinning out
overnight. Have kept MVFR conditions through 06z, but may need to
extend later.

Strong W-NW winds will continue this evening. Mixing heights will
lower after 03z, which will help gusts diminish by midnight. By
sunrise, the pressure gradient and height rises will weaken enough
for sustained winds below 10kt.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 9 PM CST this evening for ILZ027>031-036>038-
040>057-061>063-066-067-071.

&&

$$

UPDATE...Shimon
SHORT TERM...37
LONG TERM...37
AVIATION...Shimon




Area Forecast Discussion...UPDATED

National Weather Service North Platte NE

 527 PM CST Wed Dec 13 2017

.SHORT TERM...(This evening through Thursday)
Issued at 332 PM CST Wed Dec 13 2017

The primary forecast challenges through Thursday afternoon concern
a shortwave crossing the northern Plains and its associated
precip chances. As of Wednesday 21z, Nebraska lies in the wake of
one surface cold front that has moved into Kansas and in the path
of another dropping south through the Dakotas. The main shortwave
was located in Montana with a cirrus shield extending into Wyoming
and SoDak.

This evening and tonight... The gusty winds will subside around
sunset as the pressure gradient relaxes, H85 flow weakens, and
an H5 shortwave currently over the Upper Miss Valley slides east
toward the Great Lakes. Despite the weakening winds and some CAA
overnight, temperatures will remain above normal. Generally split
the guidance due to increasing cloud cover, but lowered min temps
slightly in the Platte River Valley to account for lighter winds
and in case the cigs are slower to drop.

Thursday... The northern Rockies shortwave quickly drops onto the
Plains, crossing the Sandhills by early afternoon. Have adjusted
PoP accordingly, introducing likely across the far north during
the late morning and maintaining chc for most of the forecast area
through the afternoon. The potential exists for a short-lived
deformation band developing in southern SoDak and drifting south,
hence the higher PoP north of Hwy 20. Forecast soundings also
indicate better lift and less dry air in the low levels than
southwest Neb. The precip should turn more showery in nature
during the afternoon as drier air works into the area but weak
lift remains in the low levels. This is suggested by the higher-
res solutions such as SPC HREF, NCAR ensembles, and RAP as well as
folded theta-E in NAM X- sections. Temperature profiles favor
snow for most of the event, although a brief switch to rain is
possible during peak heating as highs approach 40F. Did increase
snow totals slightly north of Hwy 20 up to 0.5 inches for the
morning. Can`t rule out light accumulation as lift and saturation
coincide with the DGZ, but the speed of the system and limited
coverage of the precip will alleviate big impacts. Winds will be
quite gusty once again, especially as a PV anomaly helps mix 50kt
flow at H5 and 35kt at H85. The snow should remain light enough
and spatial extent low enough to limit blowing snow potential.

.LONG TERM...(Thursday night through Wednesday)
Issued at 332 PM CST Wed Dec 13 2017

Low sensible weather concerns in the long term period. Primary
weather highlights include: cooler air filtering in early on with
near-normal highs expected Sunday, increased precipitation
chances late Saturday-Saturday night, and highs rebounding Monday
on.

High temperatures ramp up Friday compared to Thursday`s highs as
winds change from north northwest to westerly Thursday night aloft
in the lower-levels and at the surface. 850 hPa temperatures
increase to near 5-8 C aloft by tomorrow. In addition, modest
downsloping winds are anticipated that should promote drying and
warming. BUFKIT soundings show decent mixing and this with
sufficient insolation/mostly sunny skies should be conducive for
highs mainly in the lower to mid 50s. Meanwhile, afternoon minimum
humidity is expected to lower into the mid-upper teens in the
southeast Panhandle and far southwest NEB. This combined with
light breezes will support elevated fire weather conditions there.

Large scale pattern early Thursday night features an upper level
ridge across the Pacific offshore waters near CA extending across
the Pacific Northwest to the Northwest Territories. The mid-level
ridge aloft will then brake down through Friday as a trough moves
over the top and south into the Pacific Northwest-Northern
Intermountain West by Friday evening. Thereafter deterministic
guidance begins to show more spread with respect to the evolution
and track of this feature Saturday-Sunday. This affecting the
possible impacts across the area, primarily precipitation chances.
Specifically, the GFS in comparison to the ECMWF and CMC wherein
the former has lower QPF and PoP chances across the local
forecast area. The ECMWF appears move progressive moving the
trough eastward steadily during the Sat-Sun timeframe. Of which,
the GFS develops a modest closed low near the Sonoran desert late
Saturday that then tracks into the Southwest US Sunday. As such,
continued slight chances-chances for PoPs given the forecast
envelope and overall confidence with the best chances falling
Saturday night at this time. Highs are expected to trend
downward with near seasonable normal values anticipated Sunday.
Thereafter highs are expected to rebound to above seasonable
normal values Monday and continue through Wednesday. Of which,
a broader upper-level ridge is expected to build and be
positioned across much of the western CONUS by Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 526 PM CST Wed Dec 13 2017

An upper level disturbance across Saskatchewan will move south and
spread MVFR/local IFR in snow and low CIGS across ncntl Neb
Thursday. This would include the wrn Sandhills north of Highway 2.
The models suggest the MVFR will last all day. VFR is generally
expected south of highway 2.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...Snively
LONG TERM...ET
AVIATION...CDC




Area Forecast Discussion...UPDATED

National Weather Service Memphis TN

 944 PM CST Wed Dec 13 2017

.UPDATE...
Clear skies and light southwest winds prevail over the Midsouth at
midevening. Temps prevailed in the 40s.

Looking upstream, an approaching cold front had progressed to
southern MO. Similar to the last cold front a few evenings ago,
little to no cooldown was evident behind the front, with 40s
temps extending into northern MO. The lack of significant cooldown
may be aided by extensive cloud deck around 3000 ft AGL. Latest
guidance from HRRR and NAM models depict these clouds dropping
southeast overnight and scattering out east of the Midsouth.

Current forecast on track, with minor updates to hourly temps and
overnight sky condition.

PWB

&&

.PREV DISCUSSION... /issued 522 PM CST Wed Dec 13 2017/

UPDATE...
Updated to include 00Z Aviation Discussion.

PREV DISCUSSION... /issued 335 PM CST Wed Dec 13 2017/

DISCUSSION...

A dry cold front will continue to move across the Mid South from
late this afternoon through late evening. Critical fire weather
conditions will continue through early evening but should
gradually improve as relative humidity levels rise. The fire
danger should be lower on Thursday as relative humidity values,
lighter winds, and colder temperatures are expected. Blowing dust
west of the Mississippi River and gusty southwest winds should
begin to diminish by early this evening. High temperatures will
remain in the 40s on Thursday under sunny skies. Dry weather
conditions should persist through Saturday with slowly warming
temperatures through the first part of the weekend.

Models have come into better agreement regarding significant
shortwave pushing through the region late in the weekend into
early next week. Rain will develop late Saturday night and
continue through Sunday night. Rain will linger into Monday across
eastern portions of the area. Overall rainfall totals do not look
overly impressive, especially across areas west of the Mississippi
River where drought conditions are worst. Expect only around one-
third of an inch in those locations, with up to one inch possible
in eastern areas. Temperatures should remain seasonable through
the weekend with highs mainly in the 50s and lows in the upper 30s
to middle 40s.

For the extended forecast period, including the early to middle
part of next week, model guidance remains inconsistent. The
latest forecast for this time period will lean towards the latest
ECMWF which are supported best by the longer range model ensemble
guidance. Therefore, at this time, will keep weather conditions
dry along with warmer temperatures into the middle of next week.
It appears that a pattern change towards wetter and colder
conditions can be expected as we get towards the Christmas holiday
and beyond. Stay tuned.

JLH

&&

.AVIATION...
00Z TAFs

Cold front will move trough TAF sites tonight. Gusty SW winds will
diminish this evening, veer W then NW/N with passage of front. Winds
will average between 7-11 kts on Thursday then become light
towards late Thursday afternoon. Potential will exist for MVFR
conditions to develop at MKL/TUP on Thursday. Otherwise, VFR
conditions expected to prevail through the period.

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&

$$




Area Forecast Discussion

National Weather Service Marquette MI

 545 PM EST Wed Dec 13 2017

.SHORT TERM...(This evening through Thursday)
Issued at 427 PM EST WED DEC 13 2017

WV imagery and RAP analysis indicated a mid/upper level ridge over
wrn North America and a trough from north of Hudson Bay through the
ern CONUS. A vigorous shortwave torugh that has produced a swath of
moderate to heavy snow from nrn WI into srn upper MI, extended from
se WI into wrn IN. At the surface, a 992mb low was located over srn
Lake Michigan resulting in cyclconic ene to ne flow across the cwa.
Lake enhanced snow (850 mb temps near -17C) into n cntrl Upper
Michigan was transitioning to LES with an area of moderate to heavy
snow.

Tonight: Expect the clipper system snow to slowly taper off into
this evening, per usptream obs over most of nrn WI with lingering 1-
2sm vsby. With amounts up to 8 inches already observed near
Menominee to Stephenson, the winter weather advisory was upgraded to
warning given potential for a few more inches, including some lake
enhancement. In addition to the snow, considerable blowing and
drifting snow will lead to to very poor driving conditions during
the evening commute.

Expect the initial burst of heavier snow around KMQT to also give
way to weaker multiple parallel band LES as subsidence moves in
and the 850-700 mb moisture moves out of the area with weakening
low level convergence. In addition, winds will also steadily back
to nrly this evening and to the nw overnight, shifting the focus
of any heavier bands.

Thursday, As another shrtwv drop toward the area out of Manitoba,
winds will continue to back from nnw to wnw. Even with 850 mb temps
remaining near -17C, inversion heights at or falling below 5k ft
will limite LES intensity. Only 1 to 3 inch amounts are expected for
nw flow favored areas with the greatest amounts from Munising
eastward.

.LONG TERM...(Thursday night through Wednesday)
Issued at 303 PM EST WED DEC 13 2017

...Lake effect Thu night into Fri then warmer late this weekend into
early next week...

Upper troughing and cold continues into first part of weekend. Could
be brief relaxing of upper trough to more of a WNW flow aloft late
this weekend into early next week which may allow us to see temps
push above normal into the lower 30s on Sun-Tue. Primary long range
models (GFS, ECMWF, GEM) along with associated ensembles and recent
runs of longer range CFS indicate any warm up will be brief with
persistent pushes of cold air dropping through again later next week
and on into the rest of the month. Signal continues that it could
get very cold (sub zero lows and single digit highs) just beyond the
end of the long term toward the holiday weekend. We`ll have to wait
and see on that though.

Main weather issue for the long term is bout of moderate to heavy
lake enhanced snow expected Thu night into Fri for the northwest
wind snow belts near Lk Superior. Strong shortwave trough digs down
across Lk Superior and Upper Michigan late Thu evening through early
Fri morning. Similar to recent trends it seems, could see light snow
arriving just in time for Fri morning commute away from the lake
effect areas. Additional shortwave energy drops across Fri morning
through late Fri afternoon but moisture with that wave is less than
the earlier morning wave so probably will not see much widespread
light snow but could see some more flurries. Lake induced troughing
helps low pressure over far eastern Lk Superior deepen from 1013mb
late Thu night to around 1008mb Fri morning. Subtle deepening of the
low, but this will only increase low-level convergence with the lake
effect.

Soundings over west and northwest show lake induced troughing to at
least 10kft AGL with strong lift well within DGZ. Winds in blyr less
than 20 kts into Fri should allow snow to be quite efficient with
SLRs 25-30:1 at least. Winds do look to shift some from W to NNW and
back to NW as the shortwaves move through. Overall, expect moderate
to heavy lake enhanced snow over west and northwest Thu night into
Fri morning. Meanwhile, over the east the low and sfc trough could
disrupt the lake effect over the east with main area of heavier lake
effect possibly shifting out over Lk Superior late Thu night or more
so Fri morning depending on where main center of low ends up. 12z
GEM shows such a scenario while most other higher res guidance still
keeps heavier snow showers in over northeast forecast area. Will
need headlines for this event. At this point, winds and blowing snow
does not look to be big factor. Snow could be very fluffy though so
should see solid advisory but if snow showers can stay anchored
later Thu night into Fri morning certainly a potential for isold
warning amounts of 8"/12 hours. Too much uncertainty where focus for
heavier snow will be to go with a winter storm watch for lake effect
attm, especially since the wind/blowing snow should not be too big
of an issue.

Beyond the lake effect late this week, weekend looks pretty quiet
other than some snow that develops as warmer air works in. Stronger
upper level waves that could focus stronger low pressure systems
remains well to south as it looks now, so think we will be okay in
terms of staying away from stronger low pressure/widespread heavy
snow that can sometimes come with switch from colder pattern to
warmer one. Cold front charging in Tue/Wed of next week will
bring next better chance of widespread snow with more lake effect
by Wed as colder air returns.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 545 PM EST WED DEC 13 2017

As winds back to nrly, lake effect snow showers will return to all
terminals at times with MVFR ceilings and variable reduced
visibilities. Lake effect snow showers will end by afternoon at KIWD
and KCMX and by morning at KSAW.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 427 PM EST WED DEC 13 2017

Winds will remain at or below 25 knots through Thursday night as the
pressure gradient relaxes across Lake Superior. Winds will increase
to 20 to 30 knots late Thursday night through Friday evening as the
next low pressure system develops and strengthens over eastern Lake
Superior. Winds will then remain in the 15 to 25 knots range through
the beginning of the work week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 1 AM EST Thursday for MIZ005.

  Winter Weather Advisory until 7 PM EST /6 PM CST/ this evening
     for MIZ010-011-013.

  Winter Storm Warning until 6 PM CST this evening for MIZ012.

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

$$

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



Area Forecast Discussion

National Weather Service New York NY

 1015 PM EST Wed Dec 13 2017

.SYNOPSIS...
Strong low pressure continues moving into the Canadian Maritimes
tonight as a Clipper low approaches from the west. This low
quickly moves south of Long Island Thursday morning and offshore
Thursday afternoon. High pressure builds from the west Thursday
night. A series of weak low pressure and frontal systems will
pass through Friday through early next week, with high pressure
building between each.

&&

.NEAR TERM /THROUGH THURSDAY/...
Minor updates were made to reflect the latest conditions. Onset
of light snow across the area looks to be toward midnight across
the western half of the forecast area, overspreading the
remainder of the area during the early morning hours. Closest
reports of snow at this time are across central PA and
northeast MD.

Unseasonably cold weather will continue with our next
accumulating snow occurring late tonight into Thursday morning.

A winter weather advisory remains in effect for Long Island
beginning 3 AM and ending at 10 AM on Thursday. A special
weather statement has been issued elsewhere, which highlights
lower snow accumulation. Some impacts to the morning commute are
anticipated, especially in the advisory area as temperatures
during the early morning hours will be in the upper teens inland
and lower to middle 20s closer to the coast.

Winds will be subsiding this evening has the pressure gradient
weakens between low pressure systems. Mostly clear skies will
start the night, but will quickly become mostly cloudy to
overcast as the clipper low fast approaches from the west.
Already beginning to see light echoes in western PA as warm
advection commences there. This warm advection is progged to
to start in the middle levels after 03z west of the Hudson River
and 05-06z east of the Hudson River. Light snow will overspread
the region from west to east with this warm advection. Main vort
max associated with the clipper will swing around the base of
the mean upper trough and enhance lift, especially 09z-12z. The
surface low translates south of the area during this time,
which could help to enhance snowfall on Long Island. These
features quickly translate east as the upper trough, vort max,
and surface low move offshore 13-15z. Lift all also be
maximized in the dendritic growth zone between 750 and 900 mb
from around 09z to 13z across eastern Long Island.

Models have continued to come into better agreement with the
above scenario with the biggest uncertainty lies within the
mesoscale details, mainly across Long Island. Latest thinking is
for around a tenth of an inch of liquid across the interior,
increasing to around two tenths across Long Island. There may be
a shadow effect over NYC and NE NJ as the surface low moves
downslope of the higher terrain to the west.

For snowfall accumulation, 2 to 3 inches are forecast in the
advisory area across Long Island with 1 to 2 inches elsewhere.
There could be locally higher amounts with any enhancement or
banding on Long Island, so it would not be surprising if a few
spots reach closer to 4 inches. SREF plumes, NAM, NAM-3km, and
HRRR all support this forecast thinking. The snow should be a
higher ratio, powdery snow, potentially around 15:1 near the
coast and 17-18:1 across the interior.

The snow ends on the east end around 15z with skies quickly
clearing from west to east. It will become breezy as high
pressure builds in from the west Thursday afternoon. Highs well
below normal in the upper 20s and lower 30s are forecast.

&&

.SHORT TERM /THURSDAY NIGHT/...
High pressure settles over the Tri-State Thursday night. With
light winds, mostly clear skies, cold airmass, and some snowpack
on the ground, temperatures should bottom out in the lower teens
inland and middle and upper teens elsewhere.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
First upper shortwave in a progressive pattern dives across the
Great Lakes region Friday. Sfc low passes across the Great Lakes
region as offshore low develops well southeast of the area late
Friday and Friday night out ahead of the shortwave energy.

Some light snow is possible, with the bulk of the associated QPF
remaining offshore, and to our NW, closer to the inland parent low.

This shortwave passes Saturday as ridge builds, and remains in
control through much of the weekend.

Thereafter, the forecast is much more uncertain. Downstream
shortwave begins to make eastward progresses as ridge flattens. Weak
PVA noted in fast zonal flow approaching area Sunday night, which
could trigger some light precip. Then, operational ECMWF remains a
fast and stronger outlier as this mid west shortwave moves east.
This would result in higher precip chances Monday when compared to
GFS and Canadian NH.

For Tuesday, northern stream shortwave approaches, with GFS picking
up the mid west shortwave as well, about 24 hours after ECMWF. All
in all, minimal chance for precip is forecast Monday through
Tuesday, and possibly into Wednesday, but still plenty of time to
iron out the details.

Chilly temperatures Friday and Saturday gradually warm closer to
normal as zonal flow or weak ridging develops.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
VFR initially but MVFR/IFR in snow overnight into mid morning
Thursday with clipper low passage just south of Long Island. VFR
then returns for Thursday afternoon into Thursday evening.  Snow
accumulation is expected to be 1-3 inches overnight into mid morning
Thursday.

W winds diminishing with still some gusts to 20kt. Expecting gusts
to drop off overnight. Winds will back to SW ahead of clipper low
overnight and then return to westerly Thursday behind the low with
gusts redeveloping in the late morning and afternoon to 20-25kt.
Wind direction could become quite variable early Thursday with low
center in close proximity.

.OUTLOOK FOR 03Z FRIDAY THROUGH MONDAY...
.Thursday night-Friday...VFR.
.Friday night...VFR. W winds G15-20KT develop towards early Saturday
morning.
.Saturday-Saturday night...VFR. WNW winds G20-25KT daytime and G15-
20KT evening.
.Sunday...Mainly VFR.
.Sunday night and Monday...MVFR or lower flight cat possible in
snow/rain.

&&

.MARINE...
All Gales have been converted to SCA, which will come to an end
across Eastern LI Sound and Peconic and Gardiners Bays during
the early morning hours. Seas though will stay up on the ocean
through at least Thursday. Gusts should increase again on
Thursday behind departing Clipper low. SCA gusts are possible on
the ocean.

On Friday, high pressure builds and passes east. Light winds and
tranquil seas are expected as a result. Low pressure develops Friday
night just east of the waters and deepens as it departs Saturday,
with increasing westerly winds, and building seas expected behind it.

Winds abate and seas subside as high pressure builds Saturday night
through Sunday.

Some uncertainty in the forecast exists for Monday as a frontal
system could impact the waters. However, will forecast sub SCA winds
this time frame as this scenario remains in question. Seas remain
under 5 ft.

&&

.HYDROLOGY...
No significant hydrologic impacts expected.

&&

.EQUIPMENT...
NYC NOAA Weather Radio Station KWO-35 (162.55 MHz) is off the
air for an extended period of time.

&&

.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...Winter Weather Advisory from 3 AM to 10 AM EST Thursday for
     NYZ078>081-177-179.
NJ...None.
MARINE...Small Craft Advisory until 3 AM EST Thursday for ANZ330-340.
     Small Craft Advisory until 6 PM EST Thursday for ANZ350-353-
     355.

&&

$$

SYNOPSIS...DS/PW
NEAR TERM...DS/DW
SHORT TERM...DS
LONG TERM...PW
AVIATION...JM
MARINE...DS/DW/PW
HYDROLOGY...DS/PW
EQUIPMENT...//




Area Forecast Discussion

National Weather Service Blacksburg VA

 946 PM EST Wed Dec 13 2017

.SYNOPSIS...
Increasing clouds expected tonight ahead of an Alberta Clipper
system. This storm system moves across the region overnight,
producing a period of light accumulating snow and strong gusty
northwest winds overnight into early Thursday. High pressure
then returns Thursday afternoon through the weekend with dry
conditions and temperatures trending above normal.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 946 PM EST Wednesday...

Wind advisories remains in effect until noon along and adjacent
to the southern Blue Ridge Mountains.

Alberta Clipper will move across the region overnight into
Thursday. Winds are starting to increase across the higher
terrain tonight as the pressure gradient tightens ahead of an
approaching cold front. Wind advisories look good tonight into
Thursday morning. May have to monitor later tonight for possible
expand of wind advisory further north, but window of
opportunity short and limited areal coverage because of cloud
cover. Made some adjustments in temperatures this evening into
tonight.



As of 630 PM EST Wednesday...

Raised pops in the west for this evening into tonight closer to
a blend of the HRRR, ECMWF and NAM to capture the light chances
in the northwest portion of forecast area and to add scattered
snow flurries further south highlighted on WSR-88d images.
Adjusted temperatures with last surface obs, their trends and
shaped towards GLAMP. More changes later this evening...


As of 324 PM EST Wednesday...Potent 500 mb shortwave trough and
associated 992 mb Alberta Clipper low centered near the Chicago
area is trailing a surface warm front southeastward from it
into the western Appalachians. Currently the central
Appalachians to the mid-Atlantic region is in a southwesterly
warm advection pattern, in the warm sector of the cyclone.
This clipper will be the primary weather maker for the region`s
weather over the next 24 hours, producing another round of light
accumulating upslope snow showers in southeast WV and into the
mountains of NC late tonight, and another burst of strong
northwesterly winds overnight into Thursday.

Due to the potential for gusty to strong northwest winds, I`ve
issued a Wind Advisory with this forecast, taking effect at 7 PM
tonight and lasting through noon on Thursday for areas along and
adjacent to the southern Blue Ridge and the Interstate 81 corridor
near/south of Roanoke.

Will be looking at a general deteriorating trend through tonight,
with clouds on the increase and pre-frontal southwesterly
winds/gusts increasing in lockstep. Southwest wind gusts project to
be as much as 40 mph at elevations above 3000`, but it will be
relatively breezy in most areas through the first part of the night.
Would expect temperatures to fall slowly if much at all through
midnight given warm advection, blanket of clouds and breezy
conditions. Moisture into the clipper system will be very slow to
recover, as dewpoints in the warm sector air mass in the Deep South
are only in the low 20s. Thus expect any precip with the cold
frontal passage to probably evaporate. Despite being well-developed,
the clipper system is really fast-moving, and the entire forecast
area should be post-cold frontal by the pre-dawn hours. Look for
light snows to once again develop into the favored northwesterly
upslope areas in southeast West Virginia into Tazewell County after
midnight tonight. There may also be periods of light snow showers or
flurries into the Blue Ridge and NW North Carolina mountains into
the early morning hours, as indicated by the past several cycles of
the HRRR and 3-km NAM. But bear in mind this is not the same
situation that we saw unfold yesterday. Though low level instability
is present given sharp cold advection, we simply don`t have the
Great Lakes moisture connection, the progressive nature of the
system limits storm total QPF/snow amounts, and poor dendritic snow
growth microphysical conditions to produce the near-whiteout
conditions we saw at times Tuesday. Snow should come to an end in
the early-morning Thursday hours. So from an accumulations
perspective, showed an coating to a inch from Lewisburg to Boone
northwest, 1-2" in Summers and Mercer Counties to 2-3" in the
favored western Greenbrier mountains.

Northwesterly wind gusts are the more notable aspect of the clipper.
850 mb northwest winds increase to around 55 kts behind the cold
front during the after-midnight/pre-dawn hours, while the strongest
6-hourly pressure rises occur essentially during the Thursday
morning commute. Local wind guidance research indicated marginal
Advisory criteria conditions for the southern Blue Ridge given those
conditions. Given the timing of the strongest winds being around the
morning commute with some potential travel impact, and in
collaboration with surrounding WFOs who already have wind headlines
in effect, opted to issue for areas along/adjacent to the Blue Ridge
and along I-81. I-77 in the Carroll County/Fancy Gap area and along
the Parkway may encounter some difficult travel as well. Peak gusts
should top out around 55 mph, with a better likelihood of achieving
gusts this high being at elevations above 3000`. As low-level jet
eases, should see northwesterly winds begin to ease up into the
afternoon hours.

Lows tonight in the upper 20s to near 30, while forecast highs
Thursday are in the low 30s to mid/upper 40s.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 324 PM EST Wednesday...

More in the way of zonal flow will develop Thursday night in advance
of the next complex of both northern/southern stream energy that
will approach and pass across the region on Friday. These continue
to remain out of phase with deeper moisture remaining to the east
Friday with a surface wave offshore, while just ahead of the
northern shortwave trough. Guidance showing lots of mid/high clouds
from later Thursday night through much of Friday but with little
precip. Thus leaving it dry for now Thursday night and Friday
followed by spotty upslope snow showers far northwest sections
Friday night, but only 20ish pop for now given lack of moisture with
this system. Otherwise expecting another cold Thursday night under
lighter winds with lows mostly upper teens to mid 20s pending how
fast clouds arrive. Went below Mos on Friday given progged clouds
for much of the day which should hold the mountains in the 30s and
low 40s east.

Fast west/northwest flow to continue behind this system into the
weekend with slowly building heights by Saturday as the 850 mb cold
pool starts to lift out. This warm advection wont deepen enough to
be realized at the surface until Saturday with sunshine helping to
push highs into the 40s to perhaps around 50 southeast. Some
increase in high clouds possible Saturday night but likely thin
enough to still allow lows to reach the 20s to around 30.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 324 PM EST Wednesday...

Warming trend will continue late in the weekend into early next week
as weak southeast ridging keeps a more zonal trajectory in place
until Wednesday when a passing trough aloft digs back into the
region. However with the warm advection will see moisture return
perhaps by late Sunday but moreso Sunday night into early Monday
with a residual upper low ejecting northeast across the Gulf states.
Appears much of this precip would be light and mostly liquid given
westerly flow and well above freezing 850 mb temps. Models then
diverge on whether or not this feature helps develop a weak low
offshore, aided by yet another shortwave headed out of the
southwest states, or things remain more progressive and drier
into Tuesday. Given somewhat wetter trends will continue chance
pops Sunday afternoon into Monday while leaving in low pops
northwest Monday night/Tuesday for showers ahead of the next
front and over the south per lingering shortwave energy. Drier
and colder air should follow the front for Wednesday as deeper
northwest flow kicks in. Otherwise looking at highs rebounding
to above normal Sunday-Tuesday and well into the 50s east for
early next week.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
As of 636 PM EST Wednesday...

VFR conditions will prevail this evening into tonight. After
04z, aviation conditions begin to deteriorate particularly for
the western mountain terminals, due to northwesterly upslope
snow showers and snow flurries, low ceilings and strong post-
frontal northwest winds. Though VFR conditions should
predominate Lynchburg, Danville and Roanoke through the TAF
period, should see ceilings drop to MVFR at Bluefield and
potentially at Lewisburg and Blacksburg. Lower confidence in
overnight ceiling forecast for Lewisburg and Blacksburg. Will
see most persistent snow showers with highest confidence mainly
on the West Virginia side and in the southern Blue Ridge in
North Carolina, but there may be periods tonight especially
between 09-14z with potential snow showers/flurries as far east
at Lewisburg, Blacksburg and Roanoke. Snow showers and snow
flurries look to abate by noon Thursday, with ceilings also
trending VFR. Northwesterly winds become gusty post-frontal
overnight lasting into midday Thursday, though the core of
strongest winds should be between around 07-13z offering
potential for low- level wind shear and turbulence along the
spine of the Blue Ridge.

Medium confidence in ceilings, visibilities and winds through
04z.


Extended Discussion...

Looking at VFR conditions with abating wind speeds/gusts
Thursday afternoon and evening. Other than an outside shot of
MVFR/VFR ceilings and possible upslope snow showers at Bluefield
Friday night, VFR conditions should prevail until Sunday night.
A better shot exists for sub-VFR conditions from a system system
forecast to emanate from the mid-Mississippi Valley Sunday
night into Monday.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Wind Advisory until noon EST Thursday for VAZ009-012>017-022.
NC...Wind Advisory until noon EST Thursday for NCZ001-002-018.
WV...None.

&&

$$
SYNOPSIS...AL/KK
NEAR TERM...AL/KK
SHORT TERM...JH
LONG TERM...JH
AVIATION...AL/KK