Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/09/18
Area Forecast Discussion
National Weather Service Bismarck ND
911 PM CST Thu Nov 8 2018
.UPDATE...
Issued at 911 PM CST Thu Nov 8 2018
Snow is beginning to wind down across southwest ND as anticipated.
Still have Hettinger at 1 1/2 mile visibility as of 03Z, but have
seen improvement at other stations and on webcams. Elsewhere,
GOES-East satellite imagery shows bands of lake-effect snow
streaming off of Lake Sakakawea, particularly south of Van Hook
Arm over northeast Dunn County. This may continue into the
overnight as low-level winds remain northerly. Very localized snow
accumulations of 1 to 2 inches are not out of the question.
Decreased low temperatures by a few degrees from northwest into
central ND, as some stations were already approaching forecast
lows. However, given scattered clouds moving across the region,
expect to see up-and-down temperature trends through the night.
UPDATE Issued at 556 PM CST Thu Nov 8 2018
6.95 and 7.34 micron GOES-16 water vapor imagery show a mid-level
disturbance moving over southwest ND early this evening. This is
reflected well in the RAP 700 mb vorticity and 925 to 850 mb
frontogenesis fields. Periods of moderate to heavy snow have been
observed across southwest ND late this afternoon, with surface
stations and webcams showing visibility below a half mile at times
at Dickinson, Belfield, Beach, and Amidon. The 22Z RAP moves the
best forcing to the south and east, exiting ND around 03Z. Until
then, expect these conditions to continue, gradually migrating
southeastward over time.
Will have to keep an eye on cloud cover trends through the
evening, which may impact low temperatures. Even with scattered
clouds, still expecting widespread lows in the single digits above
zero with wind chills approaching -15.
&&
.SHORT TERM...(This evening through Friday)
Issued at 308 PM CST Thu Nov 8 2018
Its a rather messy precipitation forecast this afternoon and evening
with fairly widespread flurries/snow showers within a cold upper
trough. Then a short wave trough will move through the upper
trough across the southwest later tonight. And mixed in with this,
there should be some lake effect snow with Lake Sakakawea
temperatures in the 40s and air temperatures in the teens.
NAM Model soundings support flurries or light snow showers well
into the night, with low level supersaturation and weak vertical
motion supporting them. So we were slow to clear the precipitation
tonight, carrying flurries/light snow through midnight most areas
central and west, and through the night south central. The best
chance for accumulating snow will be southwest with the short
wave, but this should be an inch or less.
Model consensus depicts a 1040 surface high pressure moving into
western North Dakota tonight. this should be a very cold night
with a few readings below zero west and north. Along with this
expect wind chills of 15 below, perhaps a few 20 below zero chills
Friday morning.
The clouds will clear Friday, but highs will only be in the
teens.
.LONG TERM...(Friday night through Thursday)
Issued at 308 PM CST Thu Nov 8 2018
The main concern for the long term will be some accumulating snow
Saturday, and cold temperatures Monday and Tuesday. This will be
followed by a gradual warming trend by the end of the week.
Model consensus supports one to 2 inches of snow Saturday, with
the best chance for 2 inches of snow northwest. At this time, will
keep the weather messaging high confidence of minor travel
impacts.
A second push of cold air will arrive Sunday night through
Tuesday. Will see lows in the low single digits above zero both
days, with highs Monday in the Teens most areas. This will then
be followed by a dry warming trend, but not quite to above
normal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 556 PM CST Thu Nov 8 2018
Expect snow causing LIFR to IFR visibility reductions and MVFR
ceilings to continue at KDIK through around 01Z, with conditions
improving by 02Z. Otherwise, mainly VFR conditions are expected,
though a brief period of MVFR ceilings cannot be ruled out into
Friday morning at any TAF site. North to northwest winds around
10-15 kts through the night will become light and southerly Friday
morning and afternoon.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Hollan
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Des Moines IA
612 PM CST Thu Nov 8 2018
...Updated Aviation Discussion...
.SHORT TERM.../Tonight through Friday/
Issued at 359 PM CST Thu Nov 8 2018
Main concern over the next 24 hours will be snowfall associated with
a shortwave trough sweeping across the northern Great Plains and
Upper Midwest. Strong PV anomaly will provide widespread ascent
across most of the CWA, with the vertical profile becoming more
saturated as it digs southward across Iowa before lifting northeast
into the upper Great Lakes Region. With northwesterly to northerly
low-level flow, a shot of cold air has made it into the area. Model
soundings favor temperatures below freezing through much of the
profile. With increasing saturation through 20 kft, there should be
plenty of ice introduction to keep the precip type all snow this
evening and overnight, allowing for healthy dendritic growth. Main
challenge regarding snowfall amounts has been QPF, with some spread
between model guidance. The higher amounts are favored south of
Interstate 80 this evening. One to one and half inches is likely
along the Iowa-Missouri border up to around U.S. Highway 34
corridor, while half of an inch to one inch favored for central and
northern Iowa. The bulk of these snow showers should move out of the
CWA by 9 UTC.
Friday afternoon, there are two concerns. The first, will be another
surface feature development on the backside of the PV anomaly
moving across the area that will likely produce snow showers,
especially in western Iowa and possibly southern Iowa. RAP and NAM
model soundings indicate lapse rates that would be favorable for
snow showers to be more convective in nature. Most likely timing for
this short round of snow will be between 12 and 20 UTC. Depending on
how quickly this feature moves through, this could drop another half
to one inch in western and southern portions of the CWA, though
there is a possibility this could be less. The other concern Friday
afternoon will be gusty winds, as a strong pressure gradient
develops across Iowa as surface high pressure over the Plains slowly
shifts eastward into Iowa. These winds could present some visibility
issues during times of snowfall, but overall is not anticipated to
be a hazardous issue at this time. Following the winds, colder air
will begin to settle in.
.LONG TERM.../Friday night through Thursday/
Issued at 359 PM CST Thu Nov 8 2018
Key Points:
Very cold temperatures expected Saturday, Monday, Tuesday.
No high-impact/hazardous precipitation impacts forecast at this
time.
Gradual warm-up towards the end of next week.
This Weekend...
Very high confidence in strong CAA behind the tonight/Friday
system described above in the short-term AFD. 850mb temps drop
from around the -4C to -6C range they were this morning to the
-13C to -15C range Friday night. CAA aided by a very fast-moving
sfc high that should be near the IA/NE border by 06z Sat... and
into south-central Illinois by 18z Sat. As this sfc high pushes
east/southeast, a weak wave will push eastward across Minnesota
into Sunday, bringing a brief warm-up for Sunday, before cooler
temperatures return to Iowa for Monday and Tuesday.
Digging into details a little further, Saturday morning`s lows will
likely be impacted by cloud cover as it appears high to mid-level
clouds will be entering Iowa from west to east from around 06z Sat
through Saturday. These clouds can be traced back to the Pacific NW
in advance of the aforementioned wave above. So, it will not be a
purely radiational cooling night. Regardless, forecast
temperatures are within a few degrees of record lows at almost all
major climo sites in our area (exception at KMCW). Given the wind
chill values slated to be in the single digits, plus the fact
this will be the first surge of "very cold" air this season, plus
outdoor activities likely Saturday morning, worth heightened
messaging for this cold weather.
Am watching northern Iowa Saturday afternoon for the slight
potential of some light snow/flurries in the northern two or so
tiers of counties. In short models are converging on a solution
where an upper wave/impulse leading the main "trough" propagates
eastward through Minnesota Saturday PM. There is decent 500mb-300mb
Q-vector convergence ahead of this impulse, and models show a broad
area of 850mb moisture flux convergence plus a band of 850mb theta-e
advection that is well phased with this impulse. Looking at KMCW
forecast soundings, the snow growth zone looks saturated where
the 850-700mb level ascent processes are occurring. Challenge is
sfc dwpts in the single digits... so obviously a lot of sub-cloud
dry air to contend with. For now, have precip formally out of
forecast, but may need to add these flurries in next update. With
forecast winds in the 10 to 20 mph range, any uptick in intensity
beyond flurries could lead to reduced vsbys and slight travel
impacts.
Monday and Tuesday...
An upper low at the heart of the longwave trough in terms of
impacting the Midwest passes on the Canada side of the Great Lakes
region Monday through Tuesday. Models in good agreement with
keeping associated forcing, moisture, etc. north and east of Iowa.
Concurrently, a 1040mb or so sfc high builds off the Rockies and
heads towards the Dakotas. This synoptic combination/setup will
put Iowa back into strong CAA for Monday and Tuesday. 850mb temps
once again drop to the -13C to -17C range by 12z Tue. With slight
pressure gradient in advance of sfc high, winds may be in the
10-15mph range Tuesday morning, which would yield wind chill
values near to slightly below zero as far south as Highway 30.
Wednesday and Beyond...
A huge thermal ridge that is forecast to build over the
Intermountain West on Monday and Tuesday, is slated to come
crashing down over Iowa Wednesday into Thursday. Long-range models
show the 850mb temps making it roughly into the +4C to +7C range
at 12z Thu... which would obviously be a stark contrast from their
12z Tue values. Per usual a this range out, long range models in
some disagreement with handling a few Alberta clipper-type systems
that look to stay north and east of Iowa. What is noteworthy, is
the northward retreat of the polar jet. Initial impressions are
that Iowa could return a prolonged period of at least near-normal
temperatures.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 610 PM CST Thu Nov 8 2018
Light snow continues to spread over central and southern Iowa.
Currently, visibility remains VFR but expecting some MVFR and
possibly brief IFR visibility restrictions later tonight as the
peak of the snow gets going. Confident in the MVFR ceilings
through tomorrow morning, once they set in. Added a break in the
light snow towards Friday morning before the second round comes
in past 12-15z. This should likely have some MVFR visibility with
the stronger winds associated with this shortwave.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Krull
LONG TERM...Kotenberg
AVIATION...Podrazik
Area Forecast Discussion
National Weather Service Grand Rapids MI
825 PM EST Thu Nov 8 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 249 PM EST Thu Nov 8 2018
A weak area of high pressure will track eastward through Lower
Michigan providing the region with dry weather to start the night.
A storm system begins to move in from the west later tonight
spreading light snow into the area. As this storm system tracks
through Friday into Saturday additional snowfall is forecasted at
times. The cold weather then persists right through Sunday.
&&
.UPDATE...
Issued at 825 PM EST Thu Nov 8 2018
The forecast is largely on track with not much changed in
expectations over the next 24-36 hours. No changes to headlines
will be introduced for the evening update. However, there are a
few things we are monitoring closely:
1). The potential for a north/south oriented band of heavy lake
effect snow to come ashore around the noon hour with associated
impacts. Should this occur, quite a bit more snow may fall west
of US-131 Friday than currently reflected in our forecast before
the well-advertised lake- effect snow event begins Friday
evening. Note that the latest few runs of the HRRR would be a
worst-case scenario with such a band making it through nearly our
entire area of responsibility.
2). The potential for areas of blowing snow and significantly
reduced visibilities Friday night as the lake-effect snow ramps up
and westerly winds gust upwards of 40-45 mph, especially along
the lake shore.
We will obviously be taking a closer look at the aforementioned
concerns for the 3:30 AM forecast package. Updated products will
be sent out soon.
&&
.DISCUSSION...(This evening through next Thursday)
Issued at 249 PM EST Thu Nov 8 2018
The main challenge in the forecast deals with the potential impacts
from the storm system Friday into Saturday.
Models are in relative agreement in tracking and deepening a
surface low from Central Appalachians northward into Ontario
Friday into Saturday. This is an unusual track for the region.
This system will provide the region with several opportunities for
precipitation, most of which will be snow. Initially with warm
and moist air advection arriving later tonight then through the
morning commute...some snow is expected. Overall the lift is shown
to remain weak, but the moisture is forecasted to be relatively
deep, through the DGZ. So it looks like light snow will occur
that moves in just before or during the morning commute. With
surface temperatures starting the day near or just below freezing,
this is expected to support a period of slick conditions for the
morning commute, especially on elevated surfaces. If surface
temperatures end up a few degrees warmer, not much in the way of
impacts would occur. Guidance has lately been showing a stronger
band of snow over Lake MI during the morning that moves onshore
around noon. It appears that temperatures during the middle part
of the day will be above freezing...but any steadier/heavier band
of snow could lower values back down to near freezing. We will
keep the headlines going. After this band tracks eastward through
the region...a lull in the snow may occur mid to late afternoon.
The second round of snow develops most likely Friday evening. This
is when the shortwave that digs down into the area evolves into a
rather deep mid level low. Beneath this feature deep cyclonic
flow with temperatures supportive of lake enhancement suggests
widespread snow showers some of which could be heavy. Couple that
with deeper mixing and stronger wind fields not too far off the
ground and you have impacts. We may need to extend the Friday
night advisory further inland if these strong winds do draw the
snow bands into the central part of Lower MI.
Low level ridging moves in Saturday afternoon with an area of high
pressure moving up the OH Valley. Thus much less in the way of
precipitation will be around. Well below normal temperatures will
continue.
Snow and rain showers return by Monday as a weak low pressure
system moves in from the west. This system then transfers it
energy to another low riding northward up the east side of the
Appalachians on Tuesday. This system then bombs out on its way to
Eastern Quebec. The result of this for our CWA will be for
stronger cold air advection to develop that draws down another
arctic surge of air. Lake effect snow showers can be expected.
With more of a northerly component, highest POPs will be for the
lakeshore.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 743 PM EST Thu Nov 8 2018
There is little question a significant winter storm will move
through the Great Lakes tonight into Saturday. The first phase
will be the warm advection precipitation event. That will be from
around 09z to around 18z. For the most part this should be snow
but in the I-94 TAF sites it may be mixed with rain when the
precipitation is not moderate or greater. Once this moves out
there may be a period of drizzle or mixed flurries or drizzle.
Finally the cold air comes in by mid afternoon and that will push
a band of heavy snow showers on shore. The band will weaken as it
moves on shore but MKG and possibly GRR will see 1 to 2 hours of
heavy snow as that moves through.
Clearly this means IFR conditions across the TAF sites from
around 09z on into Saturday. There will be very strong winds
Friday evening, gusting over 35 knots so expect considerable
blowing snow on landing in GRR or MKG after 03z Saturday.
Given this will bring snow into the area expect moderate in cloud
icing tonight through Saturday morning. Also expect moderate
turbulence above 9000 ft tonight into Friday.
&&
.MARINE...
Issued at 249 PM EST Thu Nov 8 2018
With a relatively weak pressure gradient in place through tonight
the winds and resulting waves will be limited. As the storm
system moves in for Friday into Saturday the winds will increase
considerably with gales looking likely to develop Friday night.
That combined with strong cold air advection will result in big
waves out on Lake MI. The hazardous conditions will likely persist
through Saturday.
Will need to monitor the potential need for a lakeshore flood
headline given the risk for big waves Friday night to Saturday.
&&
.HYDROLOGY...
Issued at 942 AM EST Thu Nov 8 2018
River levels are generally above normal for the time of the year
with most sites nearing or already past their crests due to recent
rainfall. No rivers are expected to rise to flood stage.
Lake-effect showers will occur into the weekend with fairly light
precipitation amounts. We will see some snow accumulations Friday
and Saturday. This should have little impact on area rivers, and
temperatures will not yet be cold enough to worry about rivers
freezing or ice jam formation.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 1 AM Friday to 7 AM EST Saturday
for MIZ037-038-043-044-050-056-057-064-065-071>073.
Winter Weather Advisory from 1 AM to 7 PM EST Friday for MIZ039-
040-045-046-051-052-058-059-066-067-074.
LM...Gale Watch from Friday evening through Saturday morning for
LMZ844>849.
Small Craft Advisory from 7 AM to 7 PM EST Friday for LMZ844>849.
&&
$$
UPDATE...Borchardt
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...WDM
HYDROLOGY...63
MARINE...MJS
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
949 PM EST Thu Nov 8 2018
.SYNOPSIS...
A cold front will move through the Carolinas tomorrow, with cool and
dry Canadian high pressure spreading back over the southeast for the
weekend. Expect the coldest night so far on Saturday night. Next
week will be chilly and unsettled, with numerous rainy systems
moving through.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 945 PM: The latest RAP runs have nicely captured a passing 500
mb vorticity lobe moving northeast across piedmont sections
southeast of I-85 this evening. This appears to be associated with
the better showers and rainfall rates observed on regional radars.
The next in the series of upper waves in the southwesterly flow will
likely not arrive until daybreak across the southwest zones.
However, coverage should still increase overnight, even if rates
diminish a bit, as isentropic lift increases and moisture deepens in
the profiles. A cold air damming wedge should get established
overnight with the surface high center setting up over eastern PA
and precipitation increasing in the nose of the surface ridge across
the western Carolinas. Will also likely see some low end gusts as
the CAD gets firmly established. Lows will be 5 to 10 degrees above
normal.
The upstream upper trough axis moves toward the area Friday pushing
a cold front into the region. This brings deep moisture and synoptic
scale lift into the area. The CAD remains locked in through much of
the day, but does begin to erode from the south and west late in the
day as the cold front begins scouring the CAD. Surface CAPE should
be nil, however muCAPE increases to around 500 J/kg southeast of I-
85 with non-zero amounts elsewhere. Therefore, maintained slight
chances of thunder across the far southern CWFA as the front moves
in. Also kept the character of precip as showers instead of rain and
drizzle as would be expected in a classical CAD. This also means
some heavier QPF values, especially across the mountains. However,
the flood threat remains low. Did keep highs in a CAD configuration.
This means highs 10 to 15 degrees below normal with only a small
diurnal curve.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 100 PM EST Thursday: Guidance has dried out considerably
Friday night, resulting in what will likely only be light isolated
shower activity in the eastern half of the CWA by the time the short
term period picks up at 00Z Saturday. The area will dry out through
the balance of the evening, with just very light NW flow snow
possible in the higher elevations of the NC mountains through
Saturday morning behind the passing surface front. Saturday morning
will be chilly, with lows ranging from the high 20s in the mountains
to the high 30s elsewhere. Saturday will be generally clear as dry
surface high pressure slips eastward, though persistent cold air
advection through the day will keep max temperatures about 10
degrees below average.
Sunday morning will likely be the coldest morning so far this year,
with the center of the surface high parked just to our north over
the Virginias. Anticipate a widespread freeze across the whole CWA,
so freeze products will probably be raised in the next few days.
Despite plentiful insolation on Sunday, max temps will be more on
par with early January averages than mid-November, close to 15
degrees below climo.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 300 PM EST Thursday: Beginning Sunday night, the medium range
forecast period kicks off dry, with overnight low temperatures above
normal, as sfc high pressure meanders in place across the Mid-
Atlantic and down into the Carolinas through early Monday. As this
feature retreats off to the northeast, in true long-term forecasting
fashion, the temporal and spatial details of the next approaching
system vary. But overall consensus continues, thus have kept with
the general trend of increasing chances for precipitation from SW to
NE beginning Monday ahead of an approaching cold front, progged to
push eastward through the area Tuesday morning, and a trailing
deepening upper trough.
A plume of moisture is expected to infiltrate into the Carolinas for
the early part of the week, bringing the potential for rainfall
amounts around 1 to 2 inches, with higher amounts possible over
portions of the southern mountains through Tuesday overnight. With
temperatures around or just below freezing before to around daybreak
on Monday, would entirely not rule out showers mixed with light snow
across western NC and areas north of the I-40 corridor,
transitioning to all rain as temperatures warm. Overnight Monday
into Tuesday, any mix of snow with rain will remain confined to
areas along the TN border. Into Tuesday afternoon, periods of
overlapping colder air and rainfall may allow for an additional mix
of rain with light snow before tapering off behind the cold front.
Any light snow accumulation will remain confined to the western NC
mountains, but even then, confidence remains low attm given how far
out this system is and will continue to monitor as the system nears
the area. Behind the front, arctic high pressure will build in,
leaving conditions dry with below normal temperatures Wednesday and
Thursday, as latest guidance even progs low temperatures Thursday
morning below freezing across the entire FA.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Cold air damming continues to get slowly
established across the region, with high pressure setting up to the
north, northeast winds increasing, and precipitation coverage
becoming more widespread as ceilings lower. Expect a steady
transition down through lower VFR ceilings into the MVFR range circa
midnight and then on toward IFR by daybreak. The wedge should be
locked in through most of Friday as a cold front approaches from the
west. Mainly IFR or less cigs will continue with intermittent rain
and generally MVFR vsby in fog. Any improvement will only occur late
in the period as the front moves through and winds turn NW with
fropa.
Outlook: Rain and restrictions will come to an end Friday night as a
cold front moves east. Dry and generally VFR conditions will
continue through the weekend, but yet another storm system will
likely bring a round of rain and restrictions early in the work week.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 84% High 98% High 89% High 82%
KGSP High 97% Low 48% High 88% Low 59%
KAVL High 84% Med 60% Med 64% Med 70%
KHKY Med 79% Med 75% Med 60% Med 70%
KGMU High 97% Low 56% High 88% Med 63%
KAND High 93% High 91% High 88% Med 74%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...Carroll
NEAR TERM...HG/RWH
SHORT TERM...Carroll
LONG TERM...SGL
AVIATION...HG/RWH
Area Forecast Discussion
National Weather Service Wilmington NC
910 PM EST Thu Nov 8 2018
.SYNOPSIS...
Skies will remain cloudy with occasional light rain and drizzle
overnight. Cool high pressure to the north will build south
over the Carolinas into Friday. Colder and drier conditions will
arrive over the weekend, with frost possible early Sunday.
Another pool of chilly air may migrate into the region during
the middle of next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 915 PM Thursday...Areas of light drizzle falling from
widespread low stratus clouds are being supplemented by showers
across eastern South Carolina falling from deeper clouds up
above the frontal inversion in the southwest flow aloft. Models
continue to indicate low potential for measurable rain
overnight. For the overnight period forecast PoPs range from
20-30 percent from Bennettsville and Lumberton to Whiteville, up
to 40-60 percent across Williamsburg County to Conway and
Georgetown. But even here rainfall amounts of only one or two
hundredths of an inch are expected.
Temperatures at 8 and 9 PM were running a couple degrees higher
than most models had indicated. I`ve adjusted hourly readings
upward through about 1 AM, but still believe we`ll see lows
reach the mid to upper 50s by morning as cooler air entering
northeastern North Carolina is pulled southward.
The HRRR was the primary model used to tweak PoPs, temperatures,
and dewpoints for this evening update.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM Thursday...A light southerly flow will increase
slightly as it veers around to the SW to W ahead of a cold front Fri
eve. May see some breaks in the clouds along the coast, but inland
should see wedge hold on with fairly steep low level inversion
maintaining moisture and low clouds below 1500 ft. Overall expect
more in the way of stratiform pcp inland up through FROPA which
should come around midnight inland and toward daybreak along the
coast. Soundings show some elevated instability with pcp water
values reaching up near 1.7 inches and dewpoint temps in the mid 60s
just ahead of the front Fri eve. Have left out thunderstorms along
the coast for now. Any lingering pcp will clear the coast shortly
after daybreak with clearing skies behind cold front with plenty of
cold and dry air advecting in. Temps will drop behind the front,
with overnight lows down below 50 west of I-95 and closer to 55 near
the coast.
Cold and dry high pressure will build in through Saturday with pcp
water values just under an inch along the coast by Sat morning but
near a quarter of an inch inland. Expect sunny but chilly weather
with gusty northerly winds on Saturday. Temps will not increase much
from morning lows in deep CAA with max temps in the mid 50s to
around 60 along the coast.
Clear skies and very light winds will prevail Sat night with frost
or freeze a possibility. Light northerly winds may prevent ideal
radiational cooling as the center of the high moves east and should
reach the VA/NC border by Sun morning. Soundings do not look like
atmosphere will decouple completely, but wind sheltered areas should
drop out. The light winds and very dry air mass in place may also
prevent frost with temps not quite making it down to dewpoint temps
in the mid 20s. Places closer to the coast should see higher NE
winds and should help keep temps up a bit more. Overall expect
possible frost or freeze in spots with temps near freezing inland
and closer to 40 right along the coast. Confidence is not high
enough to include any frost in the forecast at this time.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 300 PM Thursday...Flat mid-level flow on Sun will quickly
shift surface high from the Mid-Atlantic to the Northeast as
weak coastal trough develops. Resulting wedge will keep the
region cool Sun and Mon. Pattern aloft starts to become more
amplified Mon as shortwave drops south across the central part
of the country. Southwest flow aloft slowly spreads Gulf
moisture over the southeast, as clouds late Sun and Sun night.
Isentropic lift taps into the increasing moisture and precip
chances increase Mon with the best chances Mon night and Tue.
Disagreement over the handling of the surface wave/low
developing along the Gulf Coast front continue between the
GFS/ECMWF. Concerning rainfall both solutions are wet with
similar timing and amounts. The main difference concerns
temperatures. GFS has a coastal low which keeps areas away from
the coast below climo early next week while the ECMWF has the
low tracking inland, with the entire forecast area rising above
climo early next week. Confidence is low so for now will stay
with the cooler/inherited solution to avoid jumping back and
forth.
Strong cold front crosses the area Tue night, bringing about a big
airmass change. Strong cold advection on Wed will likely result in
morning highs with temps falling during the afternoon. Lingering low-
level moisture behind the front keeps low cloud hanging around
through Wed and Thu may end up turning cloudy in the afternoon with
some heating. Partial thickness suggest highs will struggle to reach
mid 50s Wed and 60 on Thu. Lows will be in the mid 30s with
potential for upper 20s to lower 30s inland Wed night if winds are
light.
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 00Z...A cold air damming pattern will persist overnight and
begin to relinquish tomorrow afternoon. Except for potential IFR at
KCRE/KMYR until 01-02Z, MVFR cigs will be predominate, lowest around
12Z. Best chance of light showers will be through 06Z at the coastal
terminals. Northeast winds will persist overnight and become more
variable to light south tomorrow afternoon.
Extended Outlook...Brief clearing later Friday before another cold
front passage late Friday and high pressure will build into Sunday
before a coastal trough/cold air damming pattern develops Monday and
Tuesday. MVFR/IFR possible Monday into Tuesday.
&&
.MARINE...
NEAR TERM /THROUGH FRIDAY/...
As of 915 PM Thursday...Small Craft Advisory conditions are
close to developing across the outer portions of the Cape Fear
coastal waters as winds reach 25 knots in gusts and seas are
approaching 6 feet. Models indicate the highest winds should
occur now through about 2 AM Friday before diminishing slightly
by sunrise Friday. Seas, currently ranging from 4 feet at the
nearshore Cape Fear buoys to almost 6 feet out at the Frying Pan
Shoals buoy, should build by another 1 or 1.5 feet overnight in
response to the steady northeast winds. Winds and seas over the
South Carolina coastal waters are inferred to be 5 knots and 1
to 1.5 feet lower than over the North Carolina waters, and an
`exercise caution` headline should cover anticipated conditions
overnight. The HRRR, GFS and NAM models were blended to create
wind speed/direction forecasts for the overnight period.
SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM Thursday...Lighter winds Fri eve with winds coming
around to the south and increasing slightly ahead of a cold
front. Winds do not look very impressive ahead of the cold front
remaining 5 to 10 kts until winds shift to the W-NW after
midnight with cooler and drier air making its way over the
waters heading toward daybreak Saturday. May see a slight
increase in winds and seas at that time, but initially winds
will be off shore.
High pressure will build down across the waters through Saturday
with decent N-NE winds up to 20 kts developing. Expect a well mixed
marine layer heading into Sat night as cold air rushes over the
relatively warmer waters. Expect seas to rise through Saturday up to
3 to 5 ft with precautionary headlines and then SCA thresholds
reached for a brief period overnight Sat into early Sun in stronger
NE flow.
LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 300 PM Thursday...Weak coastal trough develops Sun as
high pressure to the north retreats northeast for Mon. Northeast
flow around 20 kt at the start of the period weakens late Sun
and Sun night as the trough develops. East-southeast flow starts
to increase late Mon into Mon night as surface wave moving
northeast from the northern Gulf of Mexico develops into weak
low pressure. Strong southwest flow develops in the wake of the
low Tue as a cold front moves into the region. Seas 3 to 5 ft at
the start of the period will drop to 2 to 3 ft later Sun and
Sun night. Increasing winds Mon into Tue build seas with 3 to 5
ft likely by the end of Mon and 4 to 7 ft on Tue.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until noon EST Friday for AMZ250-252.
&&
$$
SYNOPSIS...III
NEAR TERM...TRA
SHORT TERM...RGZ
LONG TERM...III
AVIATION...MRR
Area Forecast Discussion
National Weather Service Jacksonville FL
705 PM EST Thu Nov 8 2018
.UPDATE...Have had to update hourly POP/Weather grids over the
past few hours for evolution given radar showing large area of
showers and a few t-storms over n-ctrl FL with dry conditions
further north. As shown by the HRRR, expect current area of
showers to gradually diminish over the next few hours, with an
isolated shower or two possible further north later Tonight.
Latest HRRR and SREF guidance suggests potential for areas of fog
and low clouds to develop later Tonight and have maintained this
in the forecast. Low temperature forecast supported by latest
consensus guidance.
&&
.AVIATION...Areas of MVFR CIGs this evening, with latest guidance
suggesting potential for IFR CIGs and areas of fog to develop
late Tonight. Latest TAFs reflect this potential. Area of showers
around KGNV should diminish next hour or two.
&&
.MARINE...A weak frontal boundary across the area waters will lift
north of the waters as a warm front Friday. A cold front will pass
through Friday night with high pressure building to the northwest
then north over the weekend. A period of exercise caution appears
likely offshore with advisory conditions possible during the weekend
in the wake of the cold front. Another strong cold front will
approach the waters Tuesday with winds veering and increasing to
exercise caution and possibly to advisory criteria.
Rip Currents: A moderate risk anticipated for the Ne Fl beaches and
low risk for the Se Ga beaches for Friday.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 66 79 53 65 / 30 40 40 0
SSI 68 78 58 67 / 20 30 30 10
JAX 67 83 59 70 / 10 30 20 10
SGJ 68 82 63 72 / 30 30 20 10
GNV 67 84 61 73 / 50 20 10 10
OCF 66 85 63 76 / 30 10 10 10
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Wolf/Bricker
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
831 PM CST Thu Nov 8 2018
.UPDATE...
Issued at 811 PM CST Thu Nov 8 2018
The forecast looks to be generally on track this evening. Have had
many reports of light snow accumulations on elevated surfaces
ranging from a dusting to around an inch on the west side of
Columbia Missouri. Not much more than a dusting yet on the ground
outside of grassy surfaces, and wet roads except for a dusting on
the roads reported earlier in Monroe City Missouri. Still think
the primary accumulations will be on elevated and grassy surfaces.
The 2 inch soil temperature at the NWS office in Weldon Spring was
47 degrees, and at 4 inches it was 48 this evening. Think snowfall
rates will have to be truly heavy to overcome that amount of heat
in the ground. There could certainly be slick spots on bridges and
overpasses, but I don`t think there will be anything widespread
until temperatures fall below freezing.
RAP is indicating that we are likely seeing the heaviest
precipitation now, and that it will last until between 11 PM and 1
AM. Low level warm advection weakens substantially after that, and
the low level frontogenesis also weakens/moves southeast away from
us. At the very least, the snowfall should rapidly diminish as
this occurs as the frontogenesis is what`s likely producing the
heavier snow bands that we`re seeing right now. Ending times of
precipitation still look good as well, going from southwest to
northeast from central and northeast Missouri around 200 AM, and
east central Missouri between 400-500 AM and then our south
central Illinois counties by around 800 AM. Highest accumulations
of 1-2 inches still look good from central into northeast Missouri
and west central Illinois, with lesser amounts further to the
south and east...again, mainly on elevated and grassy surfaces.
Carney
&&
.SHORT TERM... (Through Late Friday Afternoon)
Issued at 307 PM CST Thu Nov 8 2018
Focus thru the period will be the two different snow events.
The first snow event is falling into place. The upper trof is
approaching the region bringing with it a large area of rain and
snow. Current observations show that 34 degrees F is the magic
temperature at which the rain switches to snow. With wet-bulb temp
above the shallow boundary layer well below freezing, see no reason
this will change tonight. The uncertainty in the forecast thru
tonight will be where and when the temp will cool to 34 degrees due
to wet bulb effects. Given the dry air across the area, much of the
region north of roughly KVIH to KSTL to K3LF, may not see any rain
and precip simply begin as snow.
Have increased snow amounts slightly from roughly KCOU to KPPQ as
models have come into better agreement with slightly higher QPF
amounts. While this results in snowfall amounts of up to 2 inches in
this area, the overall impact is still expected to be minimal. This
is due to both the timing of the snow as well as the warm ground
which should keep the roads generally clear. However, bridges and
overpasses may become slick, especially across northern portions of
the CWA where temps will be cooler. The precip should be east of the
CWA by sunrise on Friday, but have kept some low PoPs in far eastern
counties to account for some timing uncertainty.
Focus then turns to the second event, occurring on Friday. This
event, due to a clipper digging the main trof into the region, is a
more classic setup for convective snow showers with deep cyclonic
flow and steep low level lapse rates. The main question with this
event will be coverage, but also snowfall amounts with the heavy
snow bursts. Given these showers are quick hitting and short lived,
amounts where these showers hit are expected to be less than an
inch. However, snowfall rates will be high within these showers.
Also of concern is the anticipated timing of these snow showers.
Since more of this is discussed below, will omit it here.
As for coverage, models generally agree with the highest coverage
being northern and into western portions of the CWA, which will
gradually transition to northeastern portions of the CWA...areas
along and downshear of the main vort. However, isolated snow showers
are possible across much of the area. With high confidence in
occurrence, have chosen to use coverage wording over chance. Believe
that most of the precip with these showers will be snow given the
thermal profile and expected convection. However, some light showers
may be rain.
Strong and gusty nwly winds and much cooler temps will also
accompany this clipper.
Tilly
.LONG TERM... (Friday Night through Next Thursday)
Issued at 307 PM CST Thu Nov 8 2018
Main concern for Friday evening will be during the early evening
hours as scattered snow showers and bursts continue across
portions of the area. Highest chances of snow showers will start off
centered near the St. Louis metro area and shift southeastward
through late evening along/ahead of a secondary cold front. These
snow showers may be moderate to heavy at times, with low
visibilities a concern for the conclusion of the evening rush hour.
Breezy northwest winds will only help decrease visibility further.
In locations that do see some of these heavier bursts of snow,
accumulations up to a half inch are possible. While total
accumulations of snow will likely be on the light side, impacts to
the evening rush hour in the St. Louis metro area could be high due
to the aforementioned low visibilities within the heavier snow
showers/bursts.
The loss of daytime instability is expected to lead to lessening
coverage and intensity of snow showers by mid evening. Very cold
arctic air will be the main story for the remainder of Friday night
as cloud cover decreases and a strong surface high pressure center
heads toward central Missouri. Lows should drop into the mid teens
to low twenties across the area, which should be the coldest night
so far this young winter season. To put these readings in more
perspective, lows Friday night will be about 20-25 below normal and
may threaten record lows for the date. Record lows for Saturday
11/10 at KSTL (18F/1973), KCOU (18F/1926), and KUIN (14F/1950) are
all within reach, but most likely to be broken at KCOU.
Well-below normal temperatures will continue through the weekend
along with a period of dry weather. Highs on Saturday will only
reach into the 30s across the area, but look for moderating
temperatures back into the 40s is likely on Sunday ahead of the next
cold front.
There is still a fair amount of uncertainty with early next week,
but general indications are still for a shortwave trough to eject
out of the south-central Plains on Monday. The interaction (or
lack thereof) with a northern stream shortwave is one of the main
sources of uncertainty. The 12Z deterministic GFS remains the dry
holdout Monday/Monday night due to a weaker ejecting shortwave
trough out of the south-central Plains and a further south placement
of the low-level baroclinic zone. Believe the ECMWF/CMC probably has
more of the right idea with a round of light rain/snow mix ending as
snow across the southeastern 1/2 of the CWA. In actuality, the
possible Monday/Monday night event may turn out to be very similar
in many respects to tonight`s forecast, just moved to the southeast
about 100 miles. While still about 4 days out, it appears there is
the potential for a couple of inches of snow across northwestern
portions of the precipitation shield.
Main story from Tuesday through the remainder of the forecast will
transition back from the potential of wintry precipitation back to
very cold air. While probably not record breaking due to some very
cold daily records, temperatures 15 to 25 degrees below normal are
once again likely during this period. The airmass coming in on
Tuesday actually appears to be more impressive than expected early
this weekend as evidenced by 850-hPa temperatures which are forecast
to drop into the -10 to -15C range. Coldest daytime highs are
forecast to be on Tuesday, with readings struggling to even hit the
freezing mark. Coldest morning will likely be on Wednesday morning
with low temperatures dropping into the teens.
The arctic high pressure center is forecast to slide into the Ohio
Valley through Wednesday night with strong warm air advection
at low levels on its western flank. Moderating temperatures are
expected for the middle of next week as high temperatures reach back
into the upper 40s to low 50s on Thursday.
Gosselin
&&
.AVIATION... (For the 00z TAFs through 00z Friday Evening)
Issued at 533 PM CST Thu Nov 8 2018
Light rain and snow is overspreading the forecast area from the
west. Expect precipitation to begin in central Missouri within the
next hour and into eastern/northeastern Missouri and west central
Illinois by 02Z. Temperatures are borderline for snow, but think
most of the precip will be snow in central and northeast Missouri
as well as west central Illinois. Further south...still think
there will be a period of rain-rain/snow mix this evening changing
to all snow between 05-07Z. Flight conditions will start out VFR,
but should deteriorate to low MVFR/IFR as rain changes to snow.
Low MVFR and IFR will continue to prevail after the snow ends
early Friday morning, but should be improving during the late
morning and early afternoon. Scattered snow showers are expected
across the area on Friday afternoon. Any snow shower will be
capable of briefly reducing flight conditions to IFR.
SPECIFICS FOR KSTL:
Still expecting precipitation to start at Lambert between 02-03Z.
Temperatures in the area of the terminal are right on the edge
between rain/snow...so initially I think there will be a period of
rain, then a mix before finally going over to all snow between
05-07Z. Precip should be light, but anytime you have snow in the
mix the visibility and ceiling will deteriorate pretty quickly.
Think low end MVFR and IFR are likely, especially after the rain
changes totally over to snow. IFR ceilings will likely prevail
through the early morning hours Friday, increasing to MVFR by 12Z
or within an hour or two thereafter. Scattered snow showers are
likely to be in the vicinity on Friday afternoon. Any snow shower
that hits Lambert will be capable of briefly reducing flight
conditions to IFR.
Carney
&&
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 32 36 22 36 / 90 50 50 0
Quincy 29 33 17 34 / 100 50 5 0
Columbia 29 35 16 36 / 100 30 20 0
Jefferson City 30 35 16 37 / 100 20 20 0
Salem 34 39 22 36 / 60 20 30 0
Farmington 33 39 20 37 / 60 20 20 0
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
627 PM EST Thu Nov 8 2018
.SHORT TERM...(This evening through Friday)
Issued at 311 PM EST THU NOV 8 2018
...Areas of heavy snow expected...
WV imagery and RAP analysis indicated a broad mid/upper level trough
through the central CONUS. A vigorous shortwave trough and 120 knots
250 jet was diving se into eastern Montana. At the surface, a weak
ridge sliding through the northern Great Lakes bringing an end to
the lingering LES over eastern Lake Superior. 700-300 mb qvector
conv ahead of the mid level trough axis supported a developing area
of light snow from srn MN into wrn WI.
Tonight, expect the area of snow to continue to expand into west and
central Upper Michigan as the forcing strengthens ahead of the nrn
plains shortwave trough with general accumulations of around an inch.
The light wind field with mid level forcing will also favor Meso-low
development over central into western Lake Superior. 850 mb temps
around -10C will provide enough instability for heavier snowbands
that are expected to affect mainly the nrn portion of the Keweenaw
Peninsula by late this evening. However, there is still uncertainty
with the duration and location of this feature. By late tonight, a
mid lake snow band is also expected to move from Lake Michigan into
portions of the se cwa, likely in an area from the Garden
peninsula to Seul Choix Point.
Friday, Although there is uncertainty on how the Lake Superior meso-
low will evolve, as the trough axis moves onshore across the west
periods of heavy snow and strong winds will develop from closer to
KIWD in the moring through the rest of the Lake Superior counties in
the west, mainly during the afternoon. The Lake Michigan snowband
should still bring moderate to heavier snow to the southeast.
There will likely be a lull in the snowfall through much of
central Upper Michigan.
Friday night, A burst of heavy lake enhanced snow should move into
north central Upper Michigan btwn 00z-03z/Sat. However, some models
have trended slower with this feature more toward the GEM/ECMWF
which have shown a slower progression with the 500 mb low. Since
there is higher uncertainty with the timing, an SPS rather than
winter headline remains in effect for the north central cwa.
However, once the trough moves on shore by late evening or even
overnight, a period of heavy lake enhanced snow and strong winds
will result in very difficult travel.
.LONG TERM...(Friday night through Thursday)
Issued at 355 PM EST THU NOV 8 2018
With significant weather in the short term, spent much of the day
assisting with efforts related to that. Long term can be summarized
by continued cold conditions with occasional chances for snow. Most
notable potential impacts are the potential for SE wind lake
enhanced snow over the eastern U.P. Sun into Sun night and potential
for moderate to heavy NW wind LES Mon night into Tue night. For the
Sun-Sun night snow, there is uncertainty with the duration and amount
of snow, but does not look too significant at this time. The NW
winds LES event is handled well by blended initialization. There is
uncertainty with the magnitude and location of the coldest air and
enhancing forcing from a shortwave, so can`t get very specific at
this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 611 PM EST THU NOV 8 2018
Lake effect snow band over the Keweenaw brushing KCMX with IFR
vsbys at present will weaken and lift out over Lake Superior this
evening as conditions improve to MVFR. A low pressure trough over
the lake will begin to move onshore late tonight and Fri lowering
conditions back down to IFR and possibly LIFR in moderate to
possibly heavy lake enhanced snow at KIWD/KCMX. Expect mainly
MVFR conditions until heavier lake enhanced snow band associated
with the trough moves onshore Fri night lowering conditions to
IFR/LIFR.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 355 PM EST THU NOV 8 2018
As a low slides over western Lake Superior tonight, expect NE winds
to increase to 25 kts over portions of the lake late tonight. As the
low and associated trough slide drop across Lake Superior and Upper
Michigan Fri, expect N gales to 35-40 kts to develop over much of
Lake Superior. Gale warnings have been posted. Possible that gales
may end up stronger to 40 kts Fri aftn into Fri evening, especially
central sections. NNW gales to 35 kts finish up on Sat morning over
eastern sections. Winds rest of weekend into early next week should
stay 25 kts or less.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory from 5 AM Friday to 3 AM EST Saturday
for MIZ007-013-014-085.
Winter Storm Warning from 10 PM this evening to 7 AM EST
Saturday for MIZ001-003.
Winter Storm Warning from 7 AM EST /6 AM CST/ Friday to 7 AM EST
/6 AM CST/ Saturday for MIZ002-009.
Lake Superior...
Gale Warning from 7 PM Friday to 4 AM EST Saturday for LSZ266.
Gale Warning from 7 PM Friday to 1 AM EST Saturday for
LSZ245>248-265.
Gale Warning from 1 PM Friday to 1 AM EST Saturday for LSZ244-
264.
Gale Warning from 1 PM EST /noon CST/ to 11 PM EST /10 PM CST/
Friday for LSZ241>243-263.
Gale Warning from noon EST /11 AM CST/ to 9 PM EST /8 PM CST/
Friday for LSZ162.
Lake Michigan...
Gale Watch from late Friday night through Saturday morning for
LMZ221-250.
&&
$$
SHORT TERM...JLB
LONG TERM...Titus
AVIATION...Voss
MARINE...Titus
Area Forecast Discussion
National Weather Service Nashville TN
820 PM CST Thu Nov 8 2018
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
As of now, the 88D shows a dearth of activity across Middle
Tennessee. An inverted trough is in the process of developing
across the mid state, and this will provide the impetus for
widespread rain, mainly after 06Z. The HRRR has been consistent in
bringing precipitation into the mid state between 06Z and 18Z, so
the best POP`s are being held off until the overnight period.
Current forecast appears to be on track, so no changes are planned
at this time.
&&
.AVIATION...
00Z TAF DISCUSSION.
BNA/MQY/CKV/CSV...The evening begins with VFR wx across the mid
state. During the next several hours, a surface low will develop
along an inverted trough that is currently digging into Middle
Tennessee, and widespread rain and MVFR/IFR ceilings will settle
in after 06Z. Drier air will move in behind this system from west
to east during the day Friday.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 11 PM Friday to 11 AM CST Saturday for
Bedford-Cannon-Cheatham-Clay-Coffee-Cumberland-Davidson-De Kalb-
Dickson-Fentress-Giles-Grundy-Hickman-Houston-Humphreys-Jackson-
Lawrence-Lewis-Macon-Marshall-Maury-Montgomery-Overton-Perry-
Pickett-Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-
Trousdale-Van Buren-Warren-Wayne-White-Williamson-Wilson.
&&
$$
DISCUSSION......08
AVIATION........08
Area Forecast Discussion
National Weather Service Blacksburg VA
1106 PM EST Thu Nov 8 2018
.SYNOPSIS...
A warm front lifts north tonight. A strong cold front will
approach from the west Friday, sweeping through the area Friday
night. High pressure will settle across the area for the
weekend, but wet weather is expected to return by Monday as an
area of low pressure moves northeast along the Atlantic coast.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1100 PM EST Thursday...
Rain starting to pick up in coverage across the area, but still
more in a scattered nature. Low pressure sits over the middle TN
Valley with inverted trough extending northeast into the
southern WV mountains, while wedge of high pressure situates
itself over the piedmont. The theme overnight will be increased
chances of rain, but appears most of it will be on the light
side, with steadier to more moderate showers arriving with the
front Friday.
Otherwise not too many changes to the forecast with cloudy skies
and temperatures not falling too much with 40s most places
overnight.
Previous discussion from early evening...
Radar showing higher dbz over southside VA into the NC piedmont
but surface obs only showing light rain. This should help
moisten the low levels, while at the same time we are seeing the
wedge work in from the northeast. Forecast on track for seeing
patchy light rain over the area toward late evening with drizzle
and fog possible as well.
Previous discussion from 4pm...
Stream of moisture continues to advect northeastward from the
Deep South, this moisture advection occuring atop a residual
surface high pressure which is wedging down the Carolinas into
the southern Appalachians. Visible satellite reveals this
moisture manifesting as a shield of low to mid-level cloud cover
which will continue to advance northeastward through the rest
of the afternoon. Current radar mosaic shows some intermittent
light showers in the western NC mountains but it`s unlikely this
is reaching the ground as the air mass below cloud base is
still rather dry. Most synoptic scale and higher-resolution
convection-allowing guidance generate isentropically driven
precip falling into the wedge for tonight but given the dry air
in place, it likely will take some time for the column to
saturate. Think radar echoes we do see this evening will likely
be more virga at least through midnight - in fact the HRRR is
dry until early Friday morning. Will therefore show very light
rain or drizzle in the forecast, along with areas of mist. Best
surge of warm advection occurs after midnight, which should help
to produce a steadier light rain. Despite the nocturnal
increase in clouds and an 850 mb southerly/southeast jet of
40-45 kts which would normally keep temps from falling much,
think temperatures tonight should show some slow diurnal cooling
trend given evaporative/wet bulb cooling helping offset the
above factors. Shown lows in the 40s areawide for tonight,
though upper 40s across the Piedmont and Southside. Also trended
QPF down towards a few hundreths to no more than a tenth of an
inch, given evaporation effects and expected very light nature
to rain intensities, with the best chance of measuring being
early Friday morning.
Overcast wedge conditions with intervals of mist/fog and light rain
should be ongoing early on Friday, which will help keep temperatures
from climbing much from overnight lows. We`ll then await the
approach and eventual passage of a strong cold front which will
herald a change toward a much cooler air mass. Today`s model
guidance have slowed the front`s eastward passage some, closer to an
16-00z passage areawide, when compared to earlier model runs. We
should start to see a period of steady light to moderate-intensity
rain (with Categorical PoPs) between 11-1 pm in southeast WV and
into Bland/Tazewell Counties, toward early to mid afternoon across
the mountains of NW NC up through the Blue Ridge/NRV and southern
Shenandoah, and toward late afternoon in the foothills, Piedmont and
Southside. Forecast sounding show a limited amount of instability
elevated over the wedge inversion, which may only go to augment rain
rates. Have currently downplayed the threat of thunder, but if we
can realize the elevated instability, a few rumbles within the line
itself not out of the question. Shown total rainfall amounts from a
third to half inch generally, but with amounts from two thirds to
0.80" across the northern and western third of the forecast area.
Amounts this much are not expected to result in hydrologic issues,
but localized ponding or nuisance issues from storm drains clogged
from leaves I suppose could be a possibility. Opted for a non-
diurnal temperature trend, which will show temperatures rising very
little if at all given persistent cloud cover and at least off and
on rain for a good part of the day. May see temperatures rise into
the 50s across Smyth and Tazewell, but otherwise looking at
temperatures in the mid/upper 40s.
Forecast confidence is high, though is moderate on rainfall amounts
and lower confidence on coverage of thunder, if any, on Friday.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 349 PM EST Thursday...
A significant shot of cold air lies behind the cold frontal passage
late Friday into early Friday night - expected to be the coldest
shot of air yet experienced to this point in Fall - and cold
advection should begin in earnest areawide into Friday evening. Main
potential weather-related impacts of note this period are gusty to
potentially strong northwest winds Friday night into Saturday for
our Blue Ridge counties, and rain changing to a period of light
accumulating wet snows in the higher elevations from western
Greenbrier County down into the mountains of northwestern North
Carolina Friday night.
On the wind threat, most areas in the western CWA should at least
see breezy conditions with gusts at times up to 30 mph. However, 850
mb jet maximizes to near 50 kts near the Blue Ridge overnight which
should support gusty northwest winds at least through the southern
Blue Ridge from Watauga County through Roanoke starting overnight
into early Saturday morning. A couple potential hindrances to
potential for Wind Advisory level gusts include really high
inversion heights (above 4000` in most western locales from the 12z
GFS), and the likelihood for post-frontal clouds/precip. Best
pressure rises occur more on Saturday with breezy conditions
developing into the Piedmont to around 25 mph, even as the low-level
jet begins to weaken. It`s still not certain we`ll see Advisory-
level wind gusts from this event, but I did bump wind gusts in the
southern Blue Ridge to near-Advisory level (around 45 mph).
Best cold advection occurs tomorrow night into early Saturday, with
850 mb temperatures by 12z Saturday expected to plunge to values
from near 0C in our northern NC Piedmont counties, to -6 to -9C from
the Blue Ridge west. Expect a rather quick transition of mountain
rain to snow showers before midnight in western Greenbrier County,
and then into the overnight across the mountains of northwestern NC.
Cold advection is so strong that even areas from the New River
Valley and southeastern WV may see their first snowflakes since last
winter overnight. Soundings at Elkins and Beckley show some level of
shallow instability that could help bump snow accumulations to some
extent in western Greenbrier County, but do expect snow ratios
to be better than 10:1 (up to 13:1) at these elevations
overnight. Overall looking for a few to several flakes from the
New River Valley west, with expected accumulations of a dusting
to an inch towards Mt Rogers and the mountains of northwestern
North Carolina. Up towards western Greenbrier, amounts there of
around 1 to as much as 2". In terms of temperatures, looking at
lows Friday night into the mid 20s to lower 30s, while highs on
Saturday should range from the lower-mid 30s in the higher
elevations in western Greenbrier and the mountains of
northwestern NC, the upper 30s to near 40 in the New River
Valley, and into the 40s across the eastern half of the area.
Cold, dry high pressure settles overhead Saturday night leading to
overall dry weather. It will be quite cold given near ideal
radiational cooling Saturday night. 850 mb temperatures should be
sub-zero (-2 to -4C) in most locations with good conditions for
early-season snowmaking for the ski areas in northwest NC and the
mountains in WV. Should see widespread lows in the mid 20s, with mid
to upper teens in the western mountains and the New River Valley.
Confidence is high on the cooler weather pattern ahead, but is
low to moderate on mountain snow amounts and on peak wind gusts
overnight into Saturday morning.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 349 PM EST Thursday...
Deep synoptic scale trough will develop over the central United
States Sunday and Monday. Spread in solutions between the models
gets larger and larger after Monday night.
Starting out at the surface with high pressure centered over
Virginia Sunday morning. Then southwest flow and warm air advection
Sunday, Sunday night and Monday. Cold front will move through
Tuesday night and lead in 850MB temperatures in the -6 to -10 range.
Air mass moderates Wednesday and Wednesday night. Deep moisture
returns to the Mid Atlantic region throughout the day Monday. May
take until Tuesday night to clear out the upslope clouds on the
western slopes of the central Appalachians. Rest of the area will
clear out on Tuesday. High pressure builds in for Thursday.
Wednesday and Thursday are much more uncertain. Some suggestion that
a coastal low may bring widespread precipitation to the area by
Thursday.
Confidence is average for all elements until Wednesday, then below
average.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
As of 554 PM EST Thursday...
Expect broken to overcast VFR ceilings through this evening,
then should see lower cigs as we head into overnight with patchy
light rain/drizzle and MVFR fog.
Ceilings/visbys should then begin a steady lower to sub-VFR as
warm frontal precip overspreads the TAFs atop wedge conditions early
Friday morning. Look for areas of 5-6 SM rain with mist/fog
through the early to mid-morning Friday hours, with ceilings
lowering to a widespread MVFR-IFR range. A strong cold front
will likely introduce a period of steady moderate-intensity rain
for western terminals by 13-15z, then east by 17-19z, with rain
dissipating to light rain or nothing toward the end of the taf
period.
While surface winds should be variable under 5 kts at
most sites (except southeast at Bluefield 6-10 kts) in the pre-
frontal air, a strong south- southwest jet of 45-50 kts within
the temperature inversion around 4000` could lead to choppy
conditions for small aircraft flying in the western slope of the
Appalachians.
Forecast confidence is high for through the evening, then medium
overnight into Friday.
Extended Discussion...
A Cold front will shift east of the region Friday night. Expect
sub-VFR in the mountains with upslope rain/snow showers with
improving conditions east.
High pressure and mainly VFR conditions return to the region
Saturday night into Sunday.
Clouds and light precipitation will be on the increase again
during the day Monday thanks to a southern stream system
approaching the Carolinas. Expect an increase in sub-VFR
conditions as the day progresses, especially during the late
afternoon, with sub-VFR continuing into Tuesday as the storm
system moves overhead.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...AL/PM
NEAR TERM...AL/WP
SHORT TERM...AL
LONG TERM...AMS
AVIATION...AL/PM/WP
Area Forecast Discussion
National Weather Service San Angelo TX
503 PM CST Thu Nov 8 2018
.AVIATION...
/00Z TAFS/
IFR/LIFR ceilings will continue at all sites through the overnight
hours. Ceilings will begin to lift into the MVFR category by mid
morning Friday, with VFR ceilings returning by mid to late
afternoon. Scattered showers along with areas of drizzle will be
possible overnight. In addition, patchy fog will be possible,
especially at KABI, this evening. North to northeast winds will
increase to 8 to 14 knots, with higher gusts, this evening and
continue into the morning hours. Winds will decrease to near 10
knots by mid to late afternoon.
&&
.PREV DISCUSSION... /issued 406 PM CST Thu Nov 8 2018/
UPDATE...
Issued a Dense Fog Advisory for the Big Country until 9 PM. The
current visibilities are 1/4 to 1/2 mile from Abilene to
Sweetwater. The latest HRRR Hi Res model has visibilities less
than 1/2 of a mile through 6 PM, and will keep an eye on
surface observations. 21
PREV DISCUSSION... /issued 254 PM CST Thu Nov 8 2018/
SHORT TERM...
(Tonight and Friday)
The cloudy skies and patchy mist and drizzle will continue into the
evening. A slow moving frontal boundary located across the northwest
portions of the area will continue its slow march to the southeast
through the evening. We are going to watch our southeastern
counties, primarily; Mason, Kimble and San Saba counties for the
potential for some convective activity to develop late this evening.
Upper air SKEW-T soundings show a pronounced low level inversion
across these areas. Just above that inversion, CAPE values are
running in the 1000 J/kg range suggesting that elevated convection
will be possible as the frontal system moves into the area. The
window for thunderstorm development will be a couple of hours at
best with the threat of any of the storms becoming severe is very
low. There could be isolated cases of a storm or two producing small
hail. Behind the front, continued overrunning will over the shallow
cold airmass in place will keep skies overcast through the night.
Temperatures will drop 5 to 8 degrees from where they are right now.
Overnight lows will be in the upper 30s across the Big Country, with
40s across the rest of the region.
By tomorrow a tightening pressure gradient will increase the
strength of the northeasterly winds. Winds will increase to 15 mph
with gusts up to 25 mph possible. Drier air moves into the region
and the clouds will finally begin to dissipate and bring an end to
any lingering rain showers that may develop during the early morning
hours. Skies will begin to clear out by the late morning and perhaps
we could see some peaks of sunshine by lunchtime. With the winds
still out of the northeast and a cold, dry airmass in place,
temperatures will remain cool across the area on Friday. Expect
highs only in the upper 40s to low 50s.
LONG TERM...
(Friday Night through Wednesday)
It will be cold again for Friday night but due to some increase
in cloud cover, temperatures should remain above freezing across
the area. Could see a few readings near 32 degrees towards
daybreak over the northern Big Country but most of the area will
see lows in the mid and upper 30s. Should see a fair amount of
cloud cover on Saturday, which will keep temperatures on the cool
side, with highs in the lower 50s. Warmer temperatures are on tap
for Sunday ahead of a strong cold front approaching from the
north. Skies will be partly cloudy, with light south winds and
afternoon highs in the lower and middle 60s.
A strong upper level shortwave will move across the Plains Sunday
night and Monday, with an associated strong cold front moving
south across the area. The front is expected to clear far southern
counties by the mid morning hours on Monday, with much colder
temperatures following the front. High temperatures in the 40s
will occur early on Monday, with temperatures likely falling into
the upper 30s across the northern two thirds of the forecast area
by afternoon. Blustery north winds will also follow the front on
Monday, with wind chill readings possibly in the upper 20s and
lower 30s by afternoon. There will also be a chance for some
rainfall behind the front as the upper trough moves across West
Texas. Latest model guidance indicates that temperatures may be
cold enough to support a rain/snow mix across the Big Country on
Monday but confidence remains low at this time. The first freeze
of the season will likely occur next Monday night, with temperatures
falling into the upper 20s and lower 30s. Freezing temperatures
are also possible again Tuesday night, with forecast lows in the
30s.
&&
.PRELIMINARY POINT TEMPS/POPS...
Abilene 38 52 34 52 / 40 5 0 10
San Angelo 41 53 37 54 / 60 10 10 10
Junction 46 54 40 53 / 70 30 10 10
Brownwood 42 53 36 52 / 60 5 5 10
Sweetwater 37 49 35 52 / 40 5 0 5
Ozona 42 50 40 51 / 50 20 10 10
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 PM CST this evening for Callahan-
Fisher-Haskell-Jones-Nolan-Shackelford-Taylor-Throckmorton.
&&
$$
Daniels