Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/06/17
Area Forecast Discussion
National Weather Service Binghamton NY
840 PM EST Tue Dec 5 2017
.SYNOPSIS...
A cold front will move east of the region later tonight. A
colder pattern sets up behind this front for Wednesday through
the weekend with scattered snow showers and flurries around.
Temperatures will be slightly below the seasonal average for the
rest of the week. Much colder air will be on the horizon for
next week.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
830 PM update...
Updated hourly POPs based on the latest HRRR model reflectivity
fields which have an excellent handle on the band of showers
across much of central and eastern NY and northern and eastern
PA. An upper level was moving northeast of Lake Ontario as of
this writing and was the impetus to push the cold front through
the region. This wave will lead to increased upper confluence
northeast of NY and PA and force a surface high pressure ridge
across central NY / northeast PA by late tonight. Precipitation
will rapidly exit as this wave moves away from our area between
02z and 08z. The cold air advection will be on a west to
southwest flow and lead to a slow cooling of the surface layer
overnight.
245 PM update...
A strong cold front has entered far western NY on its way east
across the area this evening. Ahead of the front is rain. Most
of this is light but Rome has gotten half an inch so far.
Amounts in Oneida under an inch with rest of area mostly under a
quarter of an inch. All this rain will do little with it being
dry of late. The front connected to a stacked low near Hudson
Bay which will move little this period. For NY/PA behind the
front will be strong cold air advection as the upper level
trough shifts east late tonight and Wednesday. It is cold enough
so that possibly snow could mix with the rain over the higher
terrain in far eastern areas of central NY. Nothing will stick.
Temperatures will stay up ahead of the front then all gradually
late tonight to the lower 30s.
For the rest of the time in a WSW flow at most levels with the
base of the trough over the western Great Lakes. This will keep
the majority of the lake effect snow well west and north of the
CWA. At the start lake effect will be weak with 850mb temps of -8C.
Probably a few afternoon flurries reach into the southern Tug
Hill and skirt the northern Finger Lakes. Late Wednesday night
the flow shifts slightly to 260 and 850 temps fall to -11C
giving the southern Tug Hill some scattered snow showers.
Accumulations will be less than an inch there. With this flow
NEPA and southern tier/Catskills of NY will be dry.
High temperatures Wednesday near normal and around 40 followed
by lows of mid and upper 20s Wednesday night.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
Mostly dry weather in the short term with a southwest flow of
seasonably cold air. Early Friday, a bit of a ripple in the flow
with an associated weak surface trof may briefly bring some of
the Erie band snow showers across the Finger Lakes and part of
the southern tier, likewise the Ontario band may drop into
northern Oneida for a time. This may result in some minor
accumulations, mainly over northern Oneida. Later Friday, the
bands weaken and lift back north in response to a system
approaching from the Great Lakes. Afternoon highs should be near
normal both days, but slightly higher on Friday.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Southwest flow continues into Saturday with seasonably cold air
and just a few snow showers around. Lake effect remains north
of the area. Digging upper trof approaching from the lakes for
Sunday. Surface simply shows an inverted trof pushing westward
from the baroclinic zone over the western Atlantic. This will
allow more widespread but light snow showers over the area into
early Sunday. Later Sunday, surface ridging will limit the snow
shower chance, but flow is more northwest aloft so scattered
activity may continue.
On Monday, clipper system running out ahead of an arctic front
will trigger snow showers across the area, with the coldest air
arriving on Tuesday.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Cold front has moved east of a KROC-KELZ line as of 05/2300 UTC
and will move into western Steuben County within the next hour.
Mostly -RA will likely continue off-and-on across most terminals
across Central NY/NE PA until passage of the front late this
evening. With the exception of Pike and Sullivan Counties, -RA
should generally end by 06/0700 UTC. Flight categories should
firmly remain in MVFR territory across most terminals until
frontal passage, with low CIGs bringing brief reductions to IFR
in any heavier downpours.
An increased pressure gradient after frontal passage will result
in several hours of gusty SW-W winds across the forecast area.
Otherwise, expect flight categories to improve with VFR
CIGs/VSBYs expected Wednesday.
Outlook...
Wednesday night-Thursday...Flight category reductions possible N
of NY-17/I-88 corridor (especially N of KHTF- KOIC) due to SCTD
lake-effect -SHSN.
Thursday night through Friday night...Primarily VFR.
Saturday-Sunday...Surface trough forecast to move across the
region and bring possibility of SHSN. Restrictions are
possible.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...DJN/TAC
NEAR TERM...DJN/TAC
SHORT TERM...DGM
LONG TERM...DGM
AVIATION...DAB
Area Forecast Discussion
National Weather Service State College PA
1037 PM EST Tue Dec 5 2017
.SYNOPSIS...
A cold front will move east of the area overnight. The weather
will turn noticeably colder as a pattern change brings a
prolonged period of winter chill. The below average temperatures
and mainly dry weather will persist into next week.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Meso anal shows the cold front is moving quickly, and just moved
east of Williamsport and east of the office here about an hour
ago. Temps have fallen below freezing over my far NW zones, but
radar shows no precip and satellite show skies have cleared, so
the usual scenario of rain changing to snow before ending will
not occur with this cold front.
The cold front will be clearing my SERN zones during the wee
hours of Wednesday. The HRRR suggests the entire CWA is dry by
around 3AM.
Lows will drop into the 20s over the north, and remain above
freezing over the SE. These will still be above normal, but the
trend over the next several days will be downward.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/...
Only some non-threatening strato cu is possible in the
Alleghenies on Wed. The sky should clear out nicely elsewhere.
The dry air and subsidence will initially make it tough for
post-frontal precip to form. The flow near the lakes will be
more from the WSW, and this would keep any bands which can form
later in the day up to our north. Will leave a tiny POP in the
far NW corner of Warren Co Wed.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Global model and ensemble guidance remains in very good
agreement on the maintenance of high latitude blocking pattern
featuring an amplified ridge-trough configuration over the West
Coast and eastern NOAM. The primary forecast issues will be
embedded shortwaves and associated surface waves/fronts, which
due to their scale and fast mean flow aloft may be difficult to
resolve until the short range time frame. There is high
confidence in a prolonged period of below average temperatures
into mid-December with a reinforcing shot of arctic air possible
next week.
The cold pattern will bring opportunities for snow; lake-effect
is inevitable mid-late week but should remain focused along the
Lake Erie shore into southwest NY given mean west-southwest low
level trajectory. One or more clipper systems are probable and
likely offer the best shot for light snow. Finally, there
appears to be multiple waves of low pressure lifting north along
a western Atlantic front from late week into the early weekend
timeframe, with guidance varying on specifics. There is a
possibility one of these waves could clip the eastern part of
the area with some light snow, but right now the mostly likely
outcome is for precip to stay east of the area or off the coast.
A reinforcing shot of arctic air is looking more likely next
week along with a more favorable northwest flow lake-effect
pattern. The core of the winter cold should grip the area during
the second week of December with some signs of moderation during
week 3.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
Bands of showers continue to move through the eastern half of
central PA this evening. Expect these showers to keep periods of
IFR at MDT and possible LNS with MVFR likely through 05Z. As the
rain moves eastward the cigs will slowly lift with MVFR likely
overnight. Cold northwesterly flow with gusty winds should
preclude any fog development. Expect skies to clear some this
evening, as dry air works into the area. VFR should dominate the
pattern tomorrow though persistent winds with gusts upwards of
25-30 mph through the daytime are possible.
Outlook...
Wed-Sat...No sig wx expected.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...La Corte
NEAR TERM...La Corte
SHORT TERM...Steinbugl
LONG TERM...Steinbugl
AVIATION...Ceru/Martin
Area Forecast Discussion
National Weather Service Green Bay WI
500 PM CST Tue Dec 5 2017
Updated aviation portion for 00Z TAF issuance
.SYNOPSIS...
Issued at 223 PM CST Tue Dec 5 2017
Seasonably cold weather with snow showers and flurries at times
is expected through at least early next week.
The large scale pattern has transitioned to having strong ridge
along the West Coast and a deep trough centered over the Great
Lakes region. Changes during the forecast period will be
confined to relatively modest fluctuations in amplitude and the
exact position of the eastern North America trough.
Temperatures are likely to run 4-8 F degrees below normal into
the upcoming weekend. A brief moderation is possible late in the
weekend into early next week as the eastern trough temporarily
loses a little amplitude. Reamplification of the trough, and a
turn to even colder temperatures, will probably occur at the end
of the forecast period and beyond.
Disturbances rotating through the long-wave trough will result in
scattered light precipitation at times. Moisture will be limited,
so the total precipitation for the period is likely to end up
below normal. The exception could be the Lake Superior snowbelt,
where the flow regime will favor lake-effect snow showers.
&&
.SHORT TERM...Tonight and Wednesday
Issued at 223 PM CST Tue Dec 5 2017
The latest RAP analysis and satellite/radar imagery show an
intense area of low pressure lifting into northern Ontario early
this afternoon. Base of the longwave trough now swinging through
the southern Great Lakes with drier air punching northeast over
eastern Wisconsin. Winds have perked up a little this afternoon
after a lull this morning, with a few gusts reaching 40 to 45 mph
from the Fox Valley to the Lakeshore. Clouds are hanging tough
over northwest Wisconsin with widespread flurries and brief snow
showers impacting central and north-central Wisconsin. Some of
these relatively stronger snow showers also brought down strong
gusty winds from Wisconsin Rapids to Wausau. Think these snow
showers will persist for the rest of the afternoon and may make a
run at the Fox Valley. As the shortwave exits by early this
evening, think snow showers/flurries will dissipate somewhat. As
for the wind advisory, gusts have been just below advisory levels
(45 mph), but its too close to take down, especially with the
sunshine over eastern WI. Will keep the advisory going, and should
see winds subside after sunset. The gusty winds and snow shower
trends are the main forecast concerns.
Tonight...The strong area of low pressure will continue to spin
over far northern Ontario. The pressure gradient will remain tight
across the region, though should see winds subside somewhat, with
gusts to around 30 or 35 mph through the night. May see a break in
the snow showers/flurries over central & north-central WI this
evening. Then the next shortwave trough over northern Minnesota
will rotate through the region from late evening through
overnight. Deeper moisture will slide from northwest to southeast
behind the shortwave, with saturation depth growing sufficiently
to support light snow showers and flurries, mainly northwest of
the Fox Valley by morning. Accumulations should remain below an
inch, but did increase precip chances after midnight. Cold and
blustery with lows ranging from the low teens north to near 20
degrees by the Lake.
Wednesday...The shortwave trough will exit eastern Wisconsin
during the morning. Though forcing will have shifted to the east,
deep cyclonic flow will remain across the region with various
layers saturated up through 500mb. This appears to be a pretty
good recipe for occasional snow showers and flurries under mostly
cloudy skies or overcast conditions. Will show the highest precip
chances over northern WI. Winds will remain breezy, with highs
ranging from near 20 in the north to upper 20s near the Lake.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 223 PM CST Tue Dec 5 2017
The overall weather scenario for the next week is fairly simple.
Disturbances rotating through the eastern North America long-wave
trough will result in periods of snow showers and flurries. They
will be most numerous/frequent in the Lake Superior snowbelt, but
will affect the entire area to at least some extent. The specifics
of timing and location are difficult to discern. At this point, it
looks like one round could occur Wednesday night, especially
across the north. Another round is possible Friday into Friday
evening, and that appears to have a better chance of affecting the
entire area.
The timing of the lake-effect in the Lake Superior snowbelt is
also tough to pin down. But the cold cyclonic upper flow and
favorable looking low-level trajectories will likely result in at
least several inches of snow in the snowbelt during the period.
Given the cold temperatures and potential for snow showers, it is
possible a light snow cover could gradually begin to become
established across the region. Guidance temperatures look okay for
now, but could require downward adjustment (especially at night)
if a snowcover becomes established.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 500 PM CST Tue Dec 5 2017
Strong west winds with gusts in the 30 to 35 knot range will
continue this evening before slowly easing through the overnight
hours. Gusts are expected to relax to 20 to 25 knots by midnight.
MVFR cigs will continue across northern WI, with some partial
clearing and VFR cigs at times across parts of central and most
of east-central and far northeast Wisconsin this evening as light
snow showers/flurries diminish. Another shortwave will rotate
through the region tonight, bringing a surge in cloud cover with
occasional flurries and light snow returning late tonight through
the day on Wednesday. Occasional IFR vsbys possible in the
heavier snow showers over northern WI.
&&
.MARINE...
Issued at 223 PM CST Tue Dec 5 2017
A Gale Warning remains in effect through midnight for the Bay and
6 am for the Lakeshore. Sustained west winds of 20 to 30 knots
with gusts of 40 knots can be expected through this evening, then
winds will gradually subside overnight. Gusts to 25 kts will
likely continue on Wed into Thu, so a small craft advisory may be
required following the end of the gale warning.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM CST this evening for WIZ022-031-037>040-
045-048>050-073-074.
&&
$$
SYNOPSIS.......Skowronski
SHORT TERM.....MPC
LONG TERM......Skowronski
AVIATION.......Kurimski
MARINE.........MPC
Area Forecast Discussion
National Weather Service Melbourne FL
836 PM EST Tue Dec 5 2017
.DISCUSSION...
Current-overnight...Western Atlc high pressure ridging extending
into the central FL peninsula continues overnight but does show
signs of getting nudged eastward as a cold frontal boundary moves
into the FL Panhandle by dawn Wed morning. The low-level flow also
begins to veer from SERLY to SSWRLY overnight, but remains light.
MOS guidance hints at fog formation late in the night and early Wed
morning with greatest threat over the interior. Local HRRR model
shows some light shower activity over the Gulf Stream overnight and
potentially an ISOLD shower along the immediate St. Lucie County and
Martin County coasts which is covered in the grids/zones. Overnight
mins in the L/M60s. No plans to update current forecast package.
&&
.AVIATION...VFR CIGs/VSBYs thru late evening, then increasing area
of fog chances late in the night/early Wed morning, especially over
the interior terminals with more patchy fog chances for coastal TAF
sites where confidence is also less. Fog could become locally dense
in spots with tempo IFR/MVFR visibilities, should they develop,
improving thru mid-morning. An ISOLD -SHRA will be possible near
KFPR-KSUA. VFR remainder of day on Wed.
&&
.MARINE...Overnight-Wed...High pressure ridging east-west oriented
will remain across the east central FL coastal waters, though on a
weakening trend as a cold front moves slowly into north FL. Wind
speeds generally no more than 10-15 kts over the open Atlc as SERLY
wind component veers to S/SSW overnight into Wed. Seas 3-4FT near
shore and 4-5FT offshore. Chc of shras in the Gulf Stream, slgt chc
over the shelf waters.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Sedlock/Volkmer
Area Forecast Discussion
National Weather Service Marquette MI
652 PM EST Tue Dec 5 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 418 PM EST TUE DEC 5 2017
WV imagery and RAP analysis indicated an amplified pattern with a
mid/upper level trough from Manitoba into the cntrl CONUS. A
vigorous shortwave/intense storm system was lifting north through
Ontario.
This evening into tonight, the tight gradient south of the 969 mb
centered west of James Bay in northern Ontario is still generating
storm force winds over much of central and eastern Lake Superior and
advisory level winds over the Keweenaw Peninsula this afternoon. As
the sfc low gradually fills and lifts slowly ne tonight expect winds
to gradually subside to gales over Lake Superior and blo wind
advisory criteria over the Keweenaw Peninsula. Have already
cancelled the wind advisory across the rest of Upper Mi as west
winds have generally subsiding blo 40 mph.
A shortwave swinging across the Upper Great Lakes will push a sfc
trough across the region late tonight and Wed morning causing winds
to gradually veer from wsw to wnw. This will bring the heavier lake
effect snow now over the Keweenaw peninsula back into Ontonagon and
Gogebic late tonight. Favorable deep moisture within the DGZ along
with 850 mb temps around -16C will support moderate to occasionally
heavy snow tonight into Wed with additional accumulations in the 6
to 10 inch range for Gogebic and Ontonagon and accumulations in
excess of a foot over the Keweenaw and higher terrain locations.
Broad upper troughing will be fully in place on Wed across the
region south of the Ontario storm system. Winds veering NW over
eastern Lake Superior and H85 temps to -16c will support widespread
lake effect into Alger, Luce and Northern Schoolcraft counties. Snow
showers will be enhanced due to widespread deep moisture to H7 or
10kft AGL and favorable positioning of DGZ within the lake
convective layer so snowfall will be efficient. Only negative for
really high SLRs toward 30:1 is mixed layer winds over 25 kts which
will fracture snowflakes. Expect WNW-NW flow areas to see moderate
to heavy lake effect into Wed evening west and over east into Wed
night. Probably looking at 12 hour snow amounts Wed of 3-5 inches
west to 4-7 inches east due to ideal placement of DGZ and higher
inversions up to 10kft. Expect winter storm warning headline over
the Keweenaw to either be extended late tonight or transitioned over
to a winter weather advisory. Have issued winter wx advisories for
the eastern counties beginning late Wed morning and continuing
through Wed night.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 324 PM EST TUE DEC 5 2017
Deep trough will be parked over the Great Lakes stretching south
through the Ohio Valley for the bulk of the extended periods.
Upstream a high amplitude ridge will remain nearly stationary,
allowing a continued northwest flow. With the locked in cold
airmass, the generation of lake-effect snow seems very plausible for
much of the extended periods. Thur the moisture availability
decreases; however, it is likely that some lake induced moisture
will persist and allow for some light snow showers in the favored
snow belts. Operational guidance continues to prog a clipper system
pivoting southeast along the western periphery of the deep trough
over James Bay late Thur. This clipper will arrive Fri across the
U.P.
With the clipper progged to arrive Fri, guidance indicates good
vertical lift of parcels within the favored dendritic growth zone.
Additionally moisture availability looks promising, which points
towards the potential for some steady moderate LES snow with this
system. Then a brief lull in the steady snow showers Sat, until yet
another clipper is progged to skirt the area late in the weekend.
Beyond the upcoming weekend, it appears the pattern will remain
locked in the northwest flow with periodic clipper systems bringing
light to at times moderate lake-effect snow showers. Temps
throughout the extended will remain in the low/mid 20s, with lows
likely falling into the teens to single digits above zero away from
the lakes.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 652 PM EST TUE DEC 5 2017
Combination of lake effect shsn and strong, gusty w winds to at
least 40kt producing blsn will result in LIFR conditions with vis at
or blo airfield mins tonight at KCMX. Worst conditions will be thru
the evening hrs. Very limited improvement will occur late tonight
thru Wed as winds diminish some. At KIWD, gradual veering of winds
from w to nw will result in increasing lake effect shsn while gusty
winds to 25-30kt create blsn. Expect prevailing MVFR conditions
initially to fall to IFR overnight and to LIFR on Wed. At KSAW,
downslope nature of the w to nw winds should result in conditions
varying btwn MVFR and VFR with -shsn/flurries at times.
&&
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 457 AM EST TUE DEC 5 2017
Active period on Lk Superior continues until further notice. Storms
expected over most of Lk Superior today into tonight. Winds diminish
to gales into Wed and Wed night. Storm warnings up at this time and
those will need to be transitioned to gale warnings later today or
tonight. Should be down blo gales by daybreak Thu as deep low
pressure in the Lk Superior region moves farther away into northern
Quebec. Winds will stay in the 20-30 kt range into Fri but a clipper
surging through may bring a brief return of N gales Fri night. Most
of weekend will stay with 20-30 kts for winds but more gales from
the NW are possible late Sun as another clipper works through. Bouts
of freezing spray are expected Today into Thu, late Fri and again
late Sun. Air temps staying mainly in the 20s throughout the
weekend should prohibit heavy freezing spray.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory from 9 AM Wednesday to 7 AM EST Thursday
for MIZ006-007-085.
Winter Storm Warning until 5 AM EST Wednesday for MIZ001-003.
Lakeshore Flood Advisory until 8 AM EST Wednesday for MIZ001>003.
Winter Weather Advisory from midnight tonight to 6 PM CST
Wednesday for MIZ009.
Winter Weather Advisory until 7 PM EST Wednesday for MIZ002.
Lake Superior...
Storm Warning until 11 PM EST /10 PM CST/ this evening for
LSZ240>248-263>267.
Gale Warning from 11 PM this evening to 1 AM EST Thursday for
LSZ244-245-264>267.
Gale Warning until 4 PM EST Wednesday for LSZ249>251.
Gale Warning from 11 PM this evening to 4 PM EST Wednesday for
LSZ248.
Gale Warning from 11 PM this evening to 7 AM EST Wednesday for
LSZ246-247.
Gale Warning from 11 PM EST /10 PM CST/ this evening to 1 PM EST
/noon CST/ Wednesday for LSZ240>243-263.
Storm Warning until 7 PM EST /6 PM CST/ this evening for LSZ162.
Gale Warning until 1 PM EST /noon CST/ Wednesday for LSZ162.
Lake Michigan...
Gale Warning until 7 AM EST Wednesday for LMZ221-248-250.
&&
$$
SHORT TERM...Voss
LONG TERM...Beachler
AVIATION...Rolfson
MARINE...JLA
Area Forecast Discussion
National Weather Service Charleston WV
631 PM EST Tue Dec 5 2017
.SYNOPSIS...
Cold front exits early tonight. Much colder air Wednesday
through the weekend. Some snow showers late Saturday. Another
round of snow possible Tuesday.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 630 PM Tuesday...Skies are clearing out a bit faster
behind the front than previously forecast, so with this update
sky cover was reduced moving west to east with the front.
As of 520 PM Tuesday...The cold front was located just to the
east of CRW and will be passing within the next 30 minutes to an
hour. Behind the front we will continue to see some gusty winds,
but not much in the way of precipitation. Have went ahead and
updated PoP based on latest radar and timing of the front over
the next few hours. HRRR ensemble looks to handling the back
edge of the rain line fairly well, so blended it with the
current forecast through the early morning hours and this speeds
up the end time of the precip by about an hours or two.
As of 150 PM Tuesday...
Cold front about to cross the Ohio River shortly, and will
continue its progression towards the mountains. No major changes
to the near term forecast with the exception of some slight
timing tweaks, but amounts are generally less than one half inch
with a couple of exceptions. Front should still be of the quick
sweeping variety, taking the low level moisture with it, so
only a little post frontal precipitation is expected with the
upper low lifting further to the north northeast. Cirrus could
take a bit more time to exit, well into the Wednesday time
period.
Frontal passage will also signify a significant airmass change
that will begin a colder period for the area.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 230 PM Tuesday...
Generally dry but chilly weather is expected for the second half
of the work week as moisture remains south of the forecast area.
There will be some upper level energy drifting by from time to
time, but moisture appears to limited to result in any
measurable precipitation. The consensus blend kept things dry,
so stayed with that. May eventually need to code up some
scattered flurries with 850mb temperatures cooling some Thursday
into Friday.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 230 PM Tuesday...
Mean upper level trough located over the eastern US through the
long term. This will keep chilly temperatures around. Dropped
high temps a bit on Saturday under the consensus blend as a
reinforcing 500mb shortwave trough rotates in. This should drive
some snow showers through the forecast area Saturday afternoon
into Sunday. ECMWF faster than the GFS in tapering off the
precip, and have trended that way with snow showers ending
across the mountains by early afternoon Sunday as the 850mb
temperature trough crosses east of the mountains.
The upper level low over Canada drifts south into the Great
Lakes region early next week. Models indicating this will help a
surface low develop over the central Appalachians and mid
Atlantic region Monday night and Tuesday with another dose of
snow.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 630 PM Tuesday...
Cold front continues to move eastward across the region this
evening. It has made it through CRW as of 6 PM and as about to
push through CRW. West of the front the weather is improving
rapidly, so possibly just a brief period left of MVFR conditions
at CKB and then EKN and BKW should improve later tonight as the
front comes through there. High pressure is moving in behind the
front, so once it clears out in the next few hours it will VFR
for the remainder of the TAF period.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z THURSDAY...
FORECAST CONFIDENCE: Medium through midnight, then High.
ALTERNATE SCENARIOS: Timing of restrictions in rainfall as the
front passes could vary.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
UTC 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09
EST 1HRLY 17 18 19 20 21 22 23 00 01 02 03 04
CRW CONSISTENCY H M M H H H H H H H M M
HTS CONSISTENCY H H H H H H H H H H M M
BKW CONSISTENCY M M M M M H M M H H M M
EKN CONSISTENCY M L H H L L M H H H M M
PKB CONSISTENCY H H H H H H H H H H M M
CKB CONSISTENCY L M H H L H H H H H M M
AFTER 00Z THURSDAY...
Widespread IFR not expected.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.
&&
$$
SYNOPSIS...MZ/26
NEAR TERM...MPK/26
SHORT TERM...MZ
LONG TERM...MZ
AVIATION...MPK
Area Forecast Discussion
National Weather Service Blacksburg VA
1058 PM EST Tue Dec 5 2017
.SYNOPSIS...
A strong cold front will move slowly southeast through the
region overnight and offshore the Carolinas Wednesday before
stalling Wednesday night. A low pressure area will then ride
northeast along the Southeast U.S. coast during the later half
of the week as a secondary Arctic cold front moves from the Ohio
Valley through the Mid- Atlantic by the weekend. This will
bring very cold temperatures to the area this weekend with a
chance for snow showers, especially in the mountains.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 835 PM EST Tuesday...
Surface cold front now entering southeast West Va should cross
the mountains in the next few hours before exiting eastern
sections well after midnight. Main batch of showers preceding
the boundary has shifted east a bit faster with northern/western
sections already seeing drying just ahead of the front. Appears
axis has slowed up some over the south where the latest HRRR
keeps rainfall going until the front gives moisture a boot
during the early morning hours. QPF so far has been around .10
to about a third of an inch in the far west. Appears another
quarter inch possible over the southeast third overnight with
only spotty added amounts elsewhere as drying aloft arrives.
Otherwise sped up exodus of steadier rainfall west of the Blue
Ridge and kept higher pops east for a few more hours with only
some lingering light showers mainly across Southside Va around
dawn Wednesday. Still appears not enough residual moisture or
cold enough temps for many western snow showers late so kept out
mention. However gusty westerly winds set to kick in overnight
mountains as the 850 mb front crosses and deeper cold advection
sets in. Upped lows some in the east per current mild readings
and less cooling behind the front until Wednesday when might
still have temps falling in the morning. Otherwise only slight
changes to lows elsewhere for now.
Previous discussion as of 247 PM EST Tuesday...
A cold front that is entering the mountains this afternoon will
travel east across the Appalachians tonight into Wednesday. Showers
associated with frontal boundary will spread from west to east
across our area this afternoon into tonight. The pace of the front
may slow as the parent upper trough across the western Great Lakes
undergoes major deepening. The timing of showers was fairly close on
the model solutions. In general, shaped pops towards blend of
Namnest and HRRR into this evening, then leaned towards combination
of NAM/GFS for tonight. The SPC DAY One Convective Outlook kept us
out of the mention of general thunderstorms because of the lack of
instability and CAPE. In any case, some beneficial rainfall expected
from around 1/2 inch in the west, with lesser amounts east of the
Blue Ridge mountains. There is a slight chance that some snow or
snow flurries may mix in with the rain across the highest elevations
Wednesday morning, if enough cold air catches the end of the
moisture. With the upper low moving northeast, any snow even in the
highest elevations will be minimal if not non-existent. However, it
may be time to find your winter coats for tonight low temperatures
will vary from the lower 20s in the northwest mountains to the lower
40s in the piedmont.
With a wave of low pressure developing along the front, expected the
boundary to slow as it moves southeast on Wednesday. Allowed for
slight to scattered pops in southeast portions of the forecast area
mainly Wednesday morning. Northwest winds will increase behind the
front and become gusty especially in the mountains. However, wind
speeds will remain below wind advisory criteria. High temperatures
Wednesday will be colder with readings ranging from the mid 30s in
Northwest Greenbrier county in southeast West Virginia to the lower
50s in the Piedmont.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 247 PM EST Tuesday...
Models close finally in showing a swath of precip extending along
the front from the Gulf Coast states to the NC coastal plains Wed
night into Thursday. As shortwave shifts across this boundary could
see enough of a pull back northwest of the precip shield to bring
some light rain toward the NW NC piedmont late Wed night, though
appears the flow aloft overall will nudge main area out to our east.
Strongest CAA is during this period as temperatures drop into 20s
west to 30s east Wed night, then only recover to the mid to upper
30s west, to 40s east Thursday.
As we head into Thu night-Friday night, some agreement into the
upper pattern as strong wave digs across the TN Valley to east TX.
This will turn flow aloft more south-southwest and as wave moves
along the front off the coast enough of lift over this boundary to
pour moisture west to the Blue Ridge. Will likely see light snow in
the east Friday morning though ground temps and intensity of snow
will limit accumulation to grassy surfaces/cars...but roads will
stay wet. At the moment expect just a dusting. As the afternoon
swings into gear. the boundary layer warms enough to have rain/snow
mix in the east, with some snow to the Blue Ridge. An inch or less
possible mainly along the Blue Ridge south of Roanoke to Boone,
however appears main shield of precip will stay east so confidence
is not high on pops greater than 30 percent.
Precip starts pulling out Friday night with limited QPF but still
snow will be seen in the piedmont. Highs Friday will range from the
lower to mid 30s mountains to around 40 east.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 247 PM EST Tuesday...
Very cold as northwest flow kicks in with stronger shortwave digging
across the southern Appalachians. Should see snow showers Sat
afternoon/evening in the mountains with some light accumulations.
Brisk late Sat night-Sunday with drier wx into Monday with slight
moderation in temps as 5h heights increase and low level flow turns
more southwest ahead of the next upstream shortwave and front. This
front will sink into the Carolinas Tuesday and as upper flow digs
across west of the mountains, should see another shot of snow
showers in the mountains, with rain changing to snow showers by
Tuesday night in the east. Both GFS and ECM agree on this system
potentially developing into a strong low off the mid-Atlantic Coast
by next Wednesday. Track and development/location of this system
could impact us with accumulating snow, if it develops sooner, so
bears watching---stay tuned.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
As of 1055 PM EST Tuesday...
Flying conditions should gradually improve overnight as a cold
front crosses the Blue Ridge around midnight before passing east
of the region by daybreak Wednesday. Will continue to see bands
of light showers primarily affect sites east of the mountains
over the next few hours before better downslope drying arrives
behind the front. Until this happens, potential for MVFR cigs as
well as brief MVFR vsbys in fog before mixing increases late.
Advection of drier air to the west behind the front should also
help elevated ceilings across the mountains with mostly VFR
expected outside of KBLF where could see sub-VFR upslope driven
ceilings persisting into daybreak Wednesday.
Winds will continue to veer around to the west/northwest and
increase behind the boundary overnight. Expecting strongest
winds over the mountains with possible gusts to 20-30 kts.
Punch of drier air will continue over the region Wednesday
following the front with mostly VFR ceilings under mid/high
clouds except for some lower strato-cu around KDAN.
Extended Discussion...
Could see a period of upslope low clouds resulting in high end
MVFR cigs at KBLF/KLWB Wednesday night with more widespread
lower cigs possible mountains Thursday into Thursday night as
colder air continues to work in. May also see sub- VFR return in
possible light rain/snow across eastern sections late Thursday
night into Friday night as weak low pressure works up the front
offshore but still iffy at this point. Otherwise better
potential for sub- VFR cigs/vsbys in snow showers continues
Friday night and Saturday across the west. Snow showers and snow
flurries in the mountains will taper off Sunday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/KK/RAB
NEAR TERM...JH/KK
SHORT TERM...WP
LONG TERM...WP
AVIATION...JH