Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/11/21
AREA FORECAST DISCUSSION
National Weather Service Albany NY
944 PM EST Wed Feb 10 2021
.SYNOPSIS...
A weak system passing south of the region overnight into
Thursday morning will bring some light snow with the better chance
of snow towards the Interstate 84 corridor. Otherwise, mainly dry
weather is anticipated into the start of the weekend. Temperatures
will remain colder than normal and mainly below freezing over the
next several days.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 944 PM EST...Clouds continue to increase, thicken and
lower from the south and west early tonight. High pressure
continues to move off the Delmarva Region in the zonal flow
aloft. A weak low pressure system continues to move towards the
Piedmont Region and the Mid Atlantic States. An inverted sfc
trough north of the weak cyclone will bring some light snow into
the eastern Catskills and mid Hudson valley around midnight and
expand northward towards the I-90 corridor. We retooled the
PoPs some based on the latest 3-km HRRR and NAM trends. We also
kept a few snow showers or flurries downwind of Lake Ontario
into the western Adirondacks tonight.
Snow accumulations overnight will generally be in the coating
to few tenths of an inch range, though up to an inch is possible
near KPOU and the I-84 corridor. Snow to liquid ratios continue
above the climatological numbers in the 14-20:1 range with a
dry fluffy snow. The better moisture convergence will have a
hard time expanding northward towards the Capital Region. A weak
cold front with a reinforcing short of colder air will move
across the region in the late morning with isolated snow showers
and flurries. The coating to inch of snow could produce some
snow covered roadways and slick spots on the untreated surfaces
for the morning commute especially south of I-90 in the Capital
District and Berkshires towards the I-84 corridor. Lows will be
in the teens with some single digits over the southern Dacks,
southern VT, Berkshires into the Lake George Region.
Thursday, any snow should end rather quickly in the morning
hours as skies improve. As cold advection will be underway with
sub negative teens at H850, high temperatures Thursday
afternoon likely not getting out of the 20s for most areas.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
1040MB high just to the north of the Great Lakes will extend its
influence southward Thursday night. This will keep the weather
dry and cold as skies early on should be favorable for
radiational cooling with light winds. However, clouds will be
soon on the increase as next upstream warm advection regime
commences. Overnight lows are expected to range below zero north
of I90 to single digits elsewhere.
These clouds will likely result in occasional mostly cloudy
conditions through the day Friday. Forecast soundings appear to
be too dry as we will continue with the dry forecast at this
time. Due to forecast limited insolation, we will keep
temperatures mainly into the teens and lower half of the 20s
across the region.
Friday night, the persistent warm advection and moisture aloft
will continue to increase. However, should remain dry for our
CWA at this time as low level ageostrophic flow remains from the
drier north. Overnight lows will be similar to Thursday night
lows, perhaps a degree to two `warmer`.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Model guidance has come into somewhat better agreement regarding the
forecast for over the weekend. While models and ensembles seem to
suggest that any southern stream moisture/energy remains unphased
and offshore, a period of light snow still appears likely (mainly
for Sat night and early Sunday morning). After a dry day on
Saturday, clouds will increase late in the day with some snow for
the overnight thanks to an upper level disturbance passing by to the
north. This should be rather brief and most of the area will be
clearing out for Sunday morning, with partly sunny skies returning
by afternoon. Just a few inches of snow accumulation looks to occur,
as any heavy QPF will remain offshore. Highs will remain chilly this
weekend with temps in the teens and 20s and lows in the single
digits to low teens.
There should be another brief break in the weather with shortwave
ridging for Monday, although temps will continue to remain cold and
below normal with partial sunshine. Models still suggest another
period of precipitation is expected for Tuesday into Wednesday,
although the exact evolution of this system remains uncertain. Once
again, there is the potential for both southern stream moisture and
an approaching upper level disturbance within the northern stream so
a more moderate precip event looks possible, although exact
timing/amounts are still yet to be determined. 12z GEFS shows a
wide variety of solutions regarding QPF within the Tues-Wed time
period, mainly depending on how much phasing occurs and depending on
the track/strength of any developing surface storm. With temps
looking cold, will continue to keep p-type as snow for the entire
area, with daytime temps in the 20s and overnight lows in the teens
and POPs in the high chance range.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Clouds thicken and lower tonight ahead of a weak wave of low
pressure passing south of the region near the Mid Atlantic
States and an inverted sfc trough extending northward bringing
some light snow to the region. A weak boundary moves through
late tomorrow morning into the afternoon with high pressure
building back in later in the day.
Mid and high clouds increase and will thicken and lower quickly
tonight. VFR conditions will lower to MVFR/IFR levels with light
snow moving into KPOU first between 03Z-05Z/THU, and conditions
lower to IFR between 07Z-12Z/THU. Further north, some light snow
moves into the KALB/KPSF corridor between 09Z-13Z/THU with MVFR
conditions possible and perhaps IFR vsbys at KPSF. Some light
snow or snow showers may bring MVFR cigs for KGFL. Overall, a
trend towards MVFR cigs is expected at all the TAF sites between
06Z-12Z/THU.
Conditions should quickly improve back to VFR levels between
12Z-15Z/THU, except lingering MVFR cigs at KPSF until around
noon or so. Expect sct-bkn stratocumulus 4-5 kft AGL in the
afternoon with VFR levels.
The winds will be light and variable direction at 4 kts or less
tonight. They will increase from the north to northwest at 4-7
kts in the mid to late morning, and be northwest at around 10
kts in the afternoon with a few gusts 15-18 kts at KALB/KPSF.
Outlook...
Thursday Night: No Operational Impact. NO SIG WX.
Friday: Low Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: High Operational Impact. Likely SN.
Sunday: Moderate Operational Impact. Chance of SN.
Sunday Night: No Operational Impact. NO SIG WX.
Washingtons Birthday: No Operational Impact. NO SIG WX.
&&
.HYDROLOGY...
No hydrological issues are expected through the weekend.
Temperatures will mainly remain below freezing through the
upcoming week, which should allow ice to expand and thicken on
area waterways.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...BGM/Wasula
NEAR TERM...BGM/Wasula
SHORT TERM...BGM
LONG TERM...Frugis
AVIATION...Wasula
HYDROLOGY...BGM/NAS
Area Forecast Discussion
National Weather Service Boston/Norton MA
956 PM EST Wed Feb 10 2021
.SYNOPSIS...
A weak storm system will pass by to our south overnight, but
close enough to bring flurries or a brief period of light snow
to parts of Connecticut, southern Rhode Island and the Islands.
Dry and seasonably cold weather will last into Saturday. A
coastal storm tracking south of New England may bring a period
of snow Saturday night into Sunday which could mix with rain
along the South Coast. Another storm may impact the region
Tuesday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
945 PM Update:
Overall no significant changes needed to the going forecast. Did
make some adjustments to temps and dewpoints as these were too
cold/not dry enough, using a heavy dose of recent RAP fields.
Mid/high clouds are finally starting to thicken a bit.
Examination of 00z observed RAOBs at ALB and OKX still show a
significant dry layer that will keep any flurries or light snow
suppressed for the next handful of hours or so. Moistening will
likely struggle amid drier northerly sfc flow. RAP model
soundings from HFD, IJD, GON and PVD all saturate enough after
07z to support some flake production around or just after that
point in time, though. Being so far removed from the pretty
weak forcing, wouldn`t expect anything worse than light snow
capable of a coating of new snow, though in most cases should be
more conversational flurries than anything else. Current fcst
reflects this already, with snow likely continuing into the
South Coast and Cape Cod. Flurries may make it as far north as
the Pike but no further.
Previous discussion from 645 PM:
No significant changes.
Doesn`t look like changes are needed to the forecast overnight
regarding extent of light snow/flurries across region based on
a consensus of 18z models, latest observations, and near term
guidance.
Mid and high clouds are already streaming into SNE this evening
ahead of next system. Still looks like most of the precip will
pass to our south overnight and early Thu AM. Cross sections
only show very weak lift despite moistening of column so it`s
possible we see flurries from roughly Hartford to Providence
and Cape Cod/Islands. Worst case seems to be a light coating of
snow.
Low temps are a challenge since thicker mid level clouds will
move in by midnight, but may be thin enough across northern MA
to allow for more cooling. Keeping forecast lows near 10 near
VT/NH border but mainly 15-25 degrees elsewhere, warmest near
Cape Cod/Islands.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
310 pm update...
Whatever left over flurries along the south coast/Cape and
Islands will quickly diminish. Lots of clouds across the
region, should give way to more sunshine by afternoon as the
moisture departs and dry northwest flow continues. 925mb
temperatures will be in the -8 to -10C range, which suggests
most places will not crack the 32F mark for highs.
Clear and rather cold tomorrow night. The light northwest winds
should go calm in many areas, especially inland and in protected
valleys, as the boundary layer decouples. I`ve got lots of 5-10F
lows inland, mid teens along the coast, but with the snowpack we
have, it`s quite possible we will see sub-zero readings across
those normally colder interior locations.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
310 pm update
Highlights...
* Active weather pattern continues into next week:
- Quick shot of snow Sat night/Sun as low passes to our south
- Another storm possible Tue but high uncertainty in track
An active weather pattern is expected to continue through next week
as we remain in +PNA and largely neutral NAO regime but AO is
forecast to drastically shift positive early next week. It`s often
during these phase changes when we have the potential for coastal
storms and that appears to be the case this time (although it`s far
too early to determine the details).
Saturday into Sunday:
Looks like a glancing blow from a secondary coastal low which should
track well SE of New England. As previously noted, upper flow
remains fairly flat as upper low (AKA piece of the infamous Polar
Vortex) drops south into the upper Midwest and northern Great Lakes.
CSTAR Ensemble Sensitivity plots show this feature to be the main
player, since it will eventually produce downstream ridging over
Maritimes - where this ridging ends up and how amplified it will be
will determine how much our secondary low will be suppressed.
Ensembles and today`s 12z models support this idea, though it does
look like we end up with some of the "leftovers" from the decaying
primary low over the Ohio Valley. Thinking is we`ll see some light
snow Saturday night into Sunday morning but pattern recognition says
this should be a minor event, something on the order of 1-3". This
also fits well with NBM percentiles which favor those totals but
indicate reasonable "high end" totals of 3-6" in a few locations
should things come together (i.e., lift and moisture) moreso than
what models indicate right now.
Bottom line - looks like a nuisance type snow event for SNE, perhaps
Winter Weather Advisories as a higher-end scenario.
Tuesday:
Upper flow becomes more amplified as southern stream trough lifts
through Great lakes and possibly closes off (depending upon your
model of choice). Obviously we can`t get into the details this far
out in time but with southern stream systems we can usually count on
two things: (1) plenty of moisture due to broad southerly flow aloft
and (2) possibility of milder air being drawn into the region which
can create all sorts of fun with precipitation type.
At this time range, it`s best not to focus on the individual 12z
model runs but put more emphasis on probabilities and ensembles. Low
positions from 12z GFS ensembles and last night`s ECMWF ensembles
show clustering near SE New England which overall favors a "warmer"
storm and shifts the heavier snow to our north (which agrees with
NBM probabilities). However in these setups we can also see a good
amount of snow on the front end before a change to rain (again, too
early to determine how far inland, if at all). For now, we think
it`s likely there will be a coastal low nearby, but we`ll need to
wait a couple of more days before we can start to figure out the
details in its track and strength.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z Update: High Confidence.
VFR CIGS AOA 080 develop overnight and should lower to 040-060
from roughly BAF-ORH-PYM and points S through Thu morning. Still
looks like best chance of light snow (more likely flurries as
indicated in TAFs) runs from BDL-PVD and onto Cape Cod/Islands.
Any precip ends by 14z with CIGS improving Thu afternoon, before
skies clear Thu night. Light N/NW winds across region.
KBOS TAF...High confidence in TAF.
KBDL TAF...Moderate confidence in TAF. Flurries expected 08-12z
but visibility could lower to 4-5SM as worst case scenario.
Little if any accumulation.
Outlook /Friday through Monday/...
Friday: VFR. Breezy.
Friday Night through Saturday: VFR.
Saturday Night: Mainly MVFR, with local IFR possible. Breezy.
Chance SN.
Sunday: Mainly VFR, with local IFR possible. Breezy. Chance SN.
Sunday Night through Washingtons Birthday: VFR.
&&
.MARINE...
310 pm update...
Generally light northwest winds up to 15 knots will persist
across the coastal waters overnight and all day Thursday. A
slight uptick in winds, with gusts of 20-25 knots is expected
Thursday night, mainly across the waters off the east coast of
Massachusetts and around the Cape. Given expected air
temperatures in the teens and lower 20s over the waters, and the
wind, some light freezing spray may be possible. In addition,
the winds may end up bringing seas to 5-6 feet or so, especially
further offshore. That would mean Small Craft Advisories as
well.
Outlook /Friday through Monday/...
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Friday Night through Saturday: Winds less than 25 kt.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of snow.
Sunday: Winds less than 25 kt. Seas up to 5 ft. Chance of snow,
slight chance of rain. Local visibility 1 to 3 nm.
Sunday Night: Winds less than 25 kt. Seas up to 5 ft.
Washingtons Birthday: Winds less than 25 kt. Areas of rough
seas.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Nash
NEAR TERM...Loconto/JWD
SHORT TERM...Nash
LONG TERM...JWD
AVIATION...Loconto/JWD/Nash
MARINE...Loconto/JWD/Nash
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
858 PM EST Wed Feb 10 2021
.SYNOPSIS...
A winter weather event will unfold tonight, with mixed wintry
precipitation near and south of the Ohio River and snow north
of the river. Drier conditions return by Friday with colder air
filtering into the region for Saturday and Sunday. Below normal
temperatures are expected this weekend into early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
The primary focus for increasingly hazardous conditions remains
across the southern and southeastern parts of the ILN CWA, where
a Winter Storm Warning remains in effect. The details of this
warning have been adjusted (see the 807 PM issuance) to indicate
a greater potential for significant icing in
Robertson/Mason/Lewis counties in Kentucky.
Regional mosaic radar shows that a long and generally continuous
band of precipitation extends across a wide swath of the Ohio
Valley. While there is an overall expectation that this feature
will begin a slow translation to the southeast, this has not yet
occurred. In fact, a fire hose of steady to possibly heavy
precipitation (augmented slightly misleadingly by melting /
bright banding) has been generally trained on the southeastern
corner of the ILN CWA for an hour or two. Upstream conditions
suggest this may not change for a while. Several model runs, as
mentioned in the earlier discussion, had suggested a second
wave of precipitation may slide northward to affect these
counties again during the late evening / early overnight.
Instead, it is more like the first wave has simply never come to
an end.
For much of the ILN CWA, precipitation has switched to dry
conditions or light snow, with perhaps a little bit of freezing
drizzle in some spots where cloud ice is not present. The p-type
transition across the current area of concern is obviously a
very sharp gradient -- there have been reports of several inches
of snow in places like Georgetown and Piketon, with a mix of
sleet and FZRA in Portsmouth, and all ice in Ribolt (Lewis
County KY). Unfortunately, this means that at least a portion of
the precipitation is falling as FZRA, and precipitation amounts
are getting to the point where ice accumulations are likely to
hit Ice Storm Warning criteria (greater than a quarter inch). In
fact, the most recent numbers produced locally suggest as much
as 0.4" of ice in Lewis County, which would be enough to lead to
some fairly significant problems. In collaboration with
neighboring offices, doing a headline switch from one type of
warning to another type of warning seemed likely to only add
confusion in the middle of the event, but the threat for
increased ice is being communicated within the current warning
and through other channels. There is also expected to eventually
be a transition to sleet and then snow as the precipitation
gradually winds down in the 4AM-8AM time frame.
Previous discussion (545 PM) >
An intense burst of precipitation that affected the Cincinnati
Tri-State region has now moved into the southeastern corner of
the ILN CWA, prompting additional updates to the afternoon and
evening forecast -- including the expansion of the Winter Storm
Warning to two more counties (Adams/Scioto).
In the Cincinnati area, this burst of precipitation fell mainly
as snow, producing a quick 1-2 inches in the span of an hour or
two. Dual-pol radar (CC) shows that there is definitely mixing
going on with the southern end of this area of precipitation,
which would suggest that snow rates and amounts will likely be
the heaviest near and just north of where the mix is occurring.
However, surface obs and temperatures do not suggest that a
significant amount of FZRA has entered the ILN forecast area as
of now -- perhaps just impacting the far southern areas where
observations are very sparse. The snow amounts that have
occurred made the advisory expansion into the Cincinnati area a
very good call, but the situation in NE Kentucky and south-
central Ohio is more complicated, because additional waves of
precipitation are expected tonight. Snow totals themselves may
not get to the 4" warning criteria, though obviously impact (and
the busy time of day) is a big factor in warning decisions as
well. However, for the warning areas, additional precipitation
tonight will likely bring a mix of icy conditions /on top/ of
the snow that is falling right now. The combination of snow
(with some mix) right now, in addition to additional mixed
precipitation later on, will mean that warning-level impacts are
likely in Adams and Scioto counties (in addition to those
already in the warning).
Two other counties worth noting:
1) Pike County OH may end up close to warning-level snowfall,
but without much mix, and lesser impacts from additional
precipitation tonight. The current advisory should still cover
the 3" or so in the forecast as of now, though of course this
will continue to be be evaluated.
2) Although FZRA is looking likely to be confined to the far
southern ILN border areas, this does include a sizable portion
of Lewis County. If a second wave of precipitation develops
tonight as suggested by the HRRR / 18Z 3km NAM, significant
icing (>0.25") may occur, particularly in the southern parts of
the county. The current Winter Storm Warning addresses this
threat appropriately given that snow may be the bigger issue for
northern parts of the county.
Previous discussion (246 PM) >
A break in the precipitation has occurred early this afternoon
near the Ohio River while some light snow has developed along
the I-70 corridor in an area of weak warm air advection. The
area of snow along I-70 is forecast continue into the evening
leading to an inch or two of snow accumulation. Some slick spots
may result for the evening commute. This area of snow should
then come to an end tonight when WAA degrades due to the 850 hPa
winds shifting to northerly. The biggest concern shifts south
of I-70 later this afternoon into the evening hours for a
potentially impactful round of freezing rain and mixed
precipitation in southern Ohio and especially northern Kentucky.
An area of precipitation currently over Indiana along a band of
frontogenesis at the nose of a 850 hPa LLJ is going to move
northeast into the aforementioned area around 3PM or 4PM. Relatively
heavy rain and ice accretion rates may occur as this precipitation
traverses along the Ohio River this evening along with snow in
southern Ohio. Some sleet and snow may also mix in over northern
Kentucky where the thermal profile is supportive mixed precipitation
and 850 hPa temperatures remain a degree or two cooler than
previously forecast.
Ice accumulations are expected to be highest south of the Ohio River
in the northern Kentucky counties where a Winter Storm Warning has
been issued. Storm total ice accumulations could approach 0.25 inch
or more overnight in these counties. Elsewhere, a Winter Weather
Advisory has been issued for areas where ice amounts are most likely
going to remain below 0.2 inches with snow amounts less than 2
inches. Either way, travel impacts this evening and overnight are
likely to be fairly significant in northern Kentucky and perhaps
southern Ohio regardless of whether a county is inside or outside a
Winter Storm Warning. Please use extreme caution if traveling.
Precipitation then starts coming to an end late overnight, but
lingering travel impacts will prevail. Forecast lows are in the low
teens north of I-70 and near 20 by the Ohio River.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
High pressure tries to build in from the northwest on Thursday.
As this occurs, cold northerly flow will advect cold air into
the region. Northerly flow and the high building in should keep
most chances for snow suppressed and south of the area. However
a few lingering snow showers are possible in southern Ohio and
northern Kentucky. Forecast highs range from the lower 20s to
near 30.
High pressure continues to lead to dry and cold conditions for
Thursday night.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Westerly mid level flow with a dry period expected Friday.
Temperatures look to be around 10 degrees below normal with highs
from the lower 20s northwest to the upper 30s southeast.
Lobe of polar vortex to pivot southeast into the Great Lakes with
Arctic high pressure building into the Northern Plains/Upper MS VLY
this weekend into early next week. Shortwave rotating through the
Great Lakes and another to our southeast will combine to result in a
chance of snow Saturday. Snow expected to be an inch or less with
the best chance across West Central Ohio. Cold temperatures with
lows by Sunday morning in the single digits across most of the area.
Dry but cold weather Sunday/Sunday night with Highs in the teens
northwest to mid 20s southeast. Lows Sunday night in the single
digits below zero northwest to the single digits above zero
southeast. Model solutions differences regarding the southern extent
of the cold air. Have trended these temperatures colder than NBM
solution for this period.
Wind chill readings will likely approach or reach advisory levels at
times for this period -- Sunday into early Monday.
Mid level flow backs with with moisture increasing from the
southwest ahead of a developing low pressure system Monday. This low
to lift northeast across the area on Tuesday.
Model solution differences continue on the exact track of the low
and therefore the thermal fields, which continue to make details
uncertain. There is a signal for accumulating snow in both the GEFS
and ECWMF ensemble systems. Have continued likely pops later Monday
into Monday night. Depending on how much warm air is advected into
the system -- there is a chance for a wintery mix, especially over
the southeast half of ILN/s FA.
Temperatures to moderate some with highs Monday from the mid/upper
teens northwest to the mid 20s southeast, and then from the mid 20s
to mid 30s on Tuesday.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Aviation conditions are currently rather diminished across the
area, with lots of IFR observations in snow. This may represent
the worst of the aviation conditions, with IFR expected to
continue for another few hours, before gradual improvements
begin overnight. Visibilities in snow will be the biggest issue,
with ceilings generally in the MVFR category. As snow gets
lighter overnight, visibilities will improve to MVFR, before
going VFR in the morning.
Winds will generally remain out of the N to NNE through the TAF
period, but with some gusts into the 15-20 knot range tomorrow
afternoon.
OUTLOOK...MVFR ceilings are possible on Friday. MVFR conditions
are expected again on Saturday-Sunday-Monday, with snow on
Saturday, and additional snow possible on Monday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Winter Weather Advisory until 7 PM EST Thursday for OHZ070>074-
077>080-082.
Winter Storm Warning until 7 PM EST Thursday for OHZ081-088.
KY...Winter Weather Advisory until 7 PM EST Thursday for KYZ089>093.
Winter Storm Warning until 7 PM EST Thursday for KYZ094>100.
IN...Winter Weather Advisory until 7 PM EST Thursday for INZ066-
073>075-080.
&&
$$
SYNOPSIS...Campbell
NEAR TERM...Campbell/Hatzos
SHORT TERM...Campbell
LONG TERM...AR
AVIATION...Hatzos
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
942 PM CST Wed Feb 10 2021
.UPDATE...
Midsouth ice event was underway at midevening. Heavier convective
freezing rain showers moved through the Memphis metro in the early
evening. Latest HRRR runs have cued into an elevated convective
potential evident on the 00Z LZK soundings. This convective
potential has resulted in locally heavier rain rates that will
persist through early Thursday morning - mainly along and south of
the I-40 corridor. Storm total ice accumulations to 3/4 inches
appear possible where these heavier convective showers persist.
PWB
&&
.PREV DISCUSSION... /issued 600 PM CST Wed Feb 10 2021/
UPDATE...
See the 00Z aviation discussion below.
PREV DISCUSSION... /issued 207 PM CST Wed Feb 10 2021/
DISCUSSION...
A very cold and complex forecast will prevail through the weekend
into next week. The main concern continues to ice potential
tonight through Thursday. A front will slowly move south as very
cold air from the north moves into the area. Waves will continue
to push through the area allowing precipitation to move into the
Mid-South. Soundings show a sub-freezing layer at the surface
with a pronounced warm nose overhead. This will indicate freezing
rain over the area, rather than snow. Unfortunately, models still
aren`t in the best agreement on temperatures tonight,just a few
degrees difference could dictate whether this is a significant ice
event. However, at the moment less than one quarter inch is still
expected through this evening. Amounts look lighter and more
uncertain farther south and east with impacts primarily being
slick spots on bridges and overpasses. Our northern counties
should prepare for power outages as well as undrivable conditions.
The 25th-75th percentiles ice accumulations for the whole event
range from roughly 1/4 to 1/2 inch of ice from Jonesboro to
Union City. Worst case scenario (90th percentile) has a full inch
of ice in this swath with near 1/2 inch as far south as Memphis
and Jackson. On the other end of the spectrum, the 10th
percentile calls for roughly 2/10 within the Ice Storm Warning,
mainly in our northwest corner in eastern Arkansas. Needless to
say, an inch of ice would be devastating. With all of this in
mind, the official forecast of up to 0.35 inches of ice is quite
conservative and there could be more, even though models are
hinting at lower amounts up north. The biggest change is over
Shelby County, with a much higher chance of having 0.3 inches of
ice accumulations. Thus, more counties have been added to the Ice
Storm Warning.
This system looks to move east of the area Thursday evening with a
wintry mix possible as precipitation winds down. Afterwards, very
cold air will settle over the area. We`ll see several days with
highs in the 20s/30s with lows in the teens. Wind chill readings
Friday and Saturday will be quite cold, approaching single digits
in some areas. A fast-moving trough will bring a chance for very
light snow to portions of the area Saturday evening, but no
impacts are anticipated. A reinforcing cold shot will arrive by
Sunday (and Monday), where wind chill values may fall below zero.
So, ice may have a hard time going away. With powerlines and trees
down areas could be majorly affected. Make sure you prepare!
Another deep trough is progged to affect the region early next
week, bringing another chance for snow to the into early next
week. Confidence is still low on this, but there is a potential
that we could actually see some accumulations. Will continue to
monitor.
SGW
&&
.AVIATION...
00Z TAF cycle
Temperatures are now at or below freezing at JBR, MEM, and MKL.
Thus, -FZRA will now be the predominant precipitation at these
locations through tomorrow morning. TUP remains south of the front
and is not expected to see FZRA through the period. Precipitation
will initially be scattered, but should become more steady
especially at MEM and MKL within the next couple of hours. There
is concern that a quarter inch of ice or more is possible at MEM
through tomorrow morning. Precipitation should come to an end by
early tomorrow afternoon. Winds will remain northerly 10-14 kts
overnight, relaxing slightly to 8-10 kts tomorrow afternoon.
AC3
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Ice Storm Warning until noon CST Thursday for Clay-Craighead-
Crittenden-Cross-Greene-Lee AR-Mississippi-Phillips-
Poinsett-St. Francis.
MO...Ice Storm Warning until noon CST Thursday for Dunklin-Pemiscot.
MS...Ice Storm Warning until noon CST Thursday for Coahoma-DeSoto-
Quitman-Tate-Tunica.
Winter Weather Advisory until noon CST Thursday for Benton MS-
Lafayette-Marshall-Panola.
TN...Ice Storm Warning until noon CST Thursday for Benton TN-Carroll-
Crockett-Dyer-Fayette-Gibson-Haywood-Henry-Lake-Lauderdale-
Madison-Obion-Shelby-Tipton-Weakley.
Winter Weather Advisory until noon CST Thursday for Chester-
Decatur-Hardeman-Henderson.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
535 PM EST Wed Feb 10 2021
.SHORT TERM...(This evening through Thursday)
Issued at 433 PM EST WED FEB 10 2021
Water vapor imagery and RAP analysis show a deep trof across
southern Canada from coast to coast with largest 500mb height
anomalies from Alberta to northern Ontario. This trof is situated s
of an extensive area of strong positive height anomalies in excess
of 400m across north central Canada to the N Pole (result is a
highly negative AO). Within the trof, 850mb temps are in the low to
mid -30s C from Alberta to northern Ontario. Under general wnw low-
level flow, this arctic air continues to spread into the Upper Great
Lakes today, resulting in persistent LES off Lake Superior. This LES
is largely confined to northern Houghton/Keweenaw counties. However,
very slight veering of winds has led to LES at times in Ontonagon
County along the shore and n of Mass City. Light LES is also
occurring from around Munising eastward.
Tonight and Thu, fcst soundings show little overall change from what
has been occurring. There will be a change in the winds, however.
With pres gradient weakening, winds will be slackening a bit,
allowing land breezes to have an increasing influence on the LES and
low-level convergence areas. In addition, with some building of sfc
high pres ridging to the n of Lake Superior, land breeze
strengthened northerly wind component will move farther s over Lake
Superior. This will be particularly important over the eastern fcst
area. Caribou Island recently switched from wnw winds gusting over
20kt to a nne wind. Vis satellite imagery shows enhanced LES
activity along this wind shift, and even KMQT radar is picking up
this stronger LES. Ahead of the wind shift, convergence appears to
be strengthening in the wnw flow toward Grand Marais. As the wind
shift over eastern Lake Superior continues to shift w and s,
convergence should become focused tonight from around Grand Marais
across Luce County. Painted 3-5 inches of snow in that area with
winter wx advy issued. Higher amounts will certainly occur if the
convergence zones become stationary. On Thu, land breezes off
Ontario and the far e end of Upper MI may push convergence farther
w, potentially leading to mesolow development offshore of Alger
County. While this will shift LES out of Luce County, development of
a mesolow, or at a minimum, the enhanced convergence zone shifting
westward, will focus LES into Alger County, probably somewhere btwn
Munising and Grand Marais. Always difficult to know how land breezes
will playout, so there could be some surprises later tonight and
Thu.
To the w, vis satellite imagery still shows a dominant band forming
off the Bayfield Peninsula. This band streams ene and is impacting
the area around Houghton. This band will probably waiver around
northern Houghton County this evening. Overnight, winds across
western Lake Superior will shift more to the nw, breaking down the
dominant band as it settles s. In addition, the nw flow will lead to
lighter LES into the Keweenaw Peninsula under shorter fetch. Opted
to carry the N Houghton/Keweenaw advy thru the night, but largely to
catch the heavier LES this evening under current westerly flow. The
new nw or wnw flow regime over western Lake Superior should favor
enhanced convergence in northern Ontonagon County/central Houghton
County on Thu. With gradient winds continuing to diminish, this LES
may not be well organized to support advy level snows in that area.
Away from the LES, wind chills will be the concern tonight/Thu
morning. With gradient diminishing, wind really may not be much of
an issue tonight (winds were frequently down to around calm even
last night in the interior). Closer to lakeshores, winds will remain
up a bit more, but temps will be higher in those areas than in the
interior. In any event, the light wind and temps down in the -15 to
-25F range will put wind chills down to around -30 at times. Wind
chill advy has been issued for all but nw and eastern Upper MI late
evening into Thu morning. Would not be surprised to see temps drop
into the -30s F tonight at traditional cold spots where winds fall
off to calm. High temps on Thu will be similar or just slightly
higher than today.
.LONG TERM...(Thursday night through Wednesday)
Issued at 440 PM EST WED FEB 10 2021
Models/ensembles suggest that strong positive height anomalies over
northern Canada and the polar vortex over southern Manitoba and
northwest Ontario will dissipate into next week as a ridge dominates
the northeast Pacific and a downstream trough develops over the
central CONUS. Much below average temps through the weekend should
also moderate into next week.
Thursday night into Friday, a broad shortwave lobe associated
with the mid level low is expected to rotate through the western
Great Lakes bringing more widespread light snow through most of
the region Thu night. Given the scarce moisture in the arctic air
mass, snowfall amounts should be light, generally an inch or less.
A inverted trough into the area is expected to greatly modified
by Lake MI/Superior influence with meso low(s) development,
especially over southern Lake Superior. Strong low level conv
associated with this feature is likely to support heavier snow
bands that would mainly affect the Keweenaw and locations near Big
Bay. Another Band could also move in near ISQ. Confidence in the
details with the location/strength of the low and snowbands is
still low.
Friday night and Saturday, another shrtwv is expected to rotate
through the area but with less synoptic scale snow. With general sfc
troughing remaining and the very cold air in place, continued meso
low evolution/development is also likely. Although the Keweenaw and
areas over the southeast still would see the greatest impacts.
Sat night through Sun night, as the vortex slides by to the north and
core of the lower 850 mb temps near -35C edge into or closer to the
area, models suggest a transition toward a more traditional nw or
wnw LES pattern. Severe wind chills will also prevail with values
again into the -20 to -35 range. However, if winds veer enough there
may some moderation with a larger wind component off of Lake
Superior.
Mon-Wed, LES should diminish into Mon as mid level and sfc ridging
build into the area with diminishing winds. Models/ensembles hint at
the potential for a stronger shrtwv and area of snow lifting into
the Great Lakes Tue but confidence with any details regarding the
system are low.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 535 PM EST WED FEB 10 2021
VFR conditions are expected to prevail at KIWD/KSAW until the end of
this fcst period. At KCMX, lake effect shsn will continue under
westerly winds. Conditions thru this evening will likely remain
around airfield landing mins. Later tonight into Thu, winds will
veer toward the nw, and this should result in -shsn that will be
somewhat lighter than what has been occurring and may allow
conditions to improve to IFR, perhaps MVFR.
&&
.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 409 AM EST WED FEB 10 2021
Westerly winds of 20-30kt are expected to prevail across Lake
Superior shifting northwest this evening, becoming northerly in the
east half Thursday. Some gale force gusts to 35kt can`t be ruled out
today. An area of low pressure is expected to develop over the lake
on Friday, with the effects lingering into the weekend. The ongoing
arctic airmass will continue making heavy freezing spray possible.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Wind Chill Advisory from 10 PM EST /9 PM CST/ this evening to 11
AM EST /10 AM CST/ Thursday for MIZ002-004-005-009>013-084.
Winter Weather Advisory until 7 AM EST Thursday for MIZ001-003.
Winter Weather Advisory until 7 PM EST Thursday for MIZ006.
Winter Weather Advisory until noon EST Thursday for MIZ007.
Lake Superior...
Heavy Freezing Spray Warning until 1 AM EST /midnight CST/
Thursday for LSZ162-240>251-263>267.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...JLB
AVIATION...07
MARINE...JP
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Morristown TN
951 PM EST Wed Feb 10 2021
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
The main change that is needed to the forecast this evening is to
delay the southward spread of precip chances. Based on current
radar trends and latest hi-res models, rain across KY at the
moment will make slow southeastward progress through the night. It
is expected to start to spread into the counties along the KY
border in the 06-09Z time frame, then into the TN Valley toward
12Z. After 12Z, cold advection will start to drop surface temps
near the KY border, bringing a potential for freezing rain, mostly
in Wise County VA. At this time, there are no compelling reasons
to make changes to that period, and the WSW will be continued.
DGS
&&
.AVIATION...
00Z TAF DISCUSSION.
Midlevel clouds will become broken to overcast over the next few
hours as a front and an upper level trough approaches from the
west. Through the night, cigs will lower and are expected to reach
MVFR levels around 09-12Z. Rain will be spreading into the area
around that time frame, which will further lower vis and cigs,
likely to IFR levels. Moderate rain may bring LIFR conditions at
times tomorrow.
DGS
&&
.PREV DISCUSSION...
/ISSUED 319 PM EST Wed Feb 10 2021/
SHORT TERM...(Tonight through Thursday Night)...
Key Messages:
1. Increasing clouds expected tonight with increasing chances of
precipitation.
2. Widespread showers are expected on Thursday. Freezing rain is
likely mainly along the Kentucky state line. More significant ice
accumulations are expected in Wise County, Virginia where a
quarter to four-tenths of an inch of ice is possible.
Currently...
Water vapor imagery along with RAP analysis places troughing
across the western CONUs with zonal flow across the Ohio and
Tennessee Valley. Surface observations along with visible
satellite imagery show mostly clear skies across a large portion
of the forecast area which has allowed temperatures to soar into
the mid to upper 60`s to near 70 at CHA.
Tonight...
West-southwest flow aloft continues to advect moisture eastward
while a surface trough becomes located from northern Alabama NE
through East Tennessee/Southwest Virginia. Increasing jet dynamics
aloft from an 120 knot 300mb jet will allow precipitation to expand
in coverage overnight from West/Central Tennessee and across much of
Kentucky. Believe for the most part precipitation stays to the
west and north of the forecast area through much of the night but
should be approaching the Cumberland Plateau and KY/TN state line
by morning. Lows tonight will range from near 50 across the
southern valley to the low to mid 30`s across the northern
Cumberland Plateau and portions of southwest Virginia.
Thursday and Thursday Night...
Much uncertainty still exists on Thursday regarding surface
temperatures especially along the TN/KY state line and into
Southwest Virginia. The surface trough will begin to kick off to the
east while northerly flow advects a cooler airmass southward.
Increasing upper level divergence will move overhead the region on
Thursday with showers expected area wide. Overall QPF continues to
decline and feel like any heavy rain issues will remain very brief.
Will continue to highlight the potential of localized moderate to
heavy rainfall, and isolated flooding of low lying areas.
The main concern for the Thursday time-frame will be the potential
for ice accumulations across the KY/TN state line and portions of
southwest Virginia. How much of the shallow cold air can reach
down into the CWA remains uncertain. The greatest confidence for
ice accumulations will remain across Wise County in Southwest
Virginia. Ice accumulations will likely range from a few
hundredths of an inch to a couple tenths of an inch. This
warrants the need for an ice storm warning that will go into
effect 12Z Thursday through 12Z Friday. The most uncertainty lies
across the TN counties that border KY along with Lee County.
Assuming temperatures can briefly reach 32 or lower a couple
hundredths to a tenth of an inch of ice is certainly possible in
isolated locations. Feel that a winter weather advisory would be
best to communicate the potential impacts. This advisory will go
into effect at 12Z Thursday and goes through 00Z Friday.
Precipitation finally begins to move east with brief periods of
rain or freezing rain possible on the back side as colder air
moves in. Lows Thursday night should be much cooler with area-wide
lows in the low to mid 30`s with lower 40`s possible across the
southern valley and southwest North Carolina.
Diegan
LONG TERM...(Friday through Wednesday)...
Models continue to be struggling mightily with much of the long term
period, with little consistency from run to run and poor agreement
between models. This leads to a significantly lower forecast
confidence than usual. Models are in decent agreement with the upper
level closed low that moves into the western Great Lakes Region over
the weekend before opening up and shifting northeast. They also
agree relatively well on the shortwaves that move out of Mexico into
the western GOMEX Friday, out of New Mexico into western Texas on
Saturday, and the next one that takes a similar path early Monday.
The details however, are not well agreed upon. The largest
disparities seem to be mainly with respect to the positioning of the
surface high to our north during much of the long term period, and
the resulting intrusion of cold air into our CWA. This obviously has
notable impacts on both max/min temperatures, and precip types.
Given the continued run-to-run, and model-to-model discrepancies,
have taken a similar approach as the previous shift and gone largely
with the NBM guidance.
Going into a bit more detail here, it looks like most of the area is
probably dry Friday, save maybe some lingering rain showers in the
south perhaps. However the shortwave ejecting into the western GOMEX
will likely generate some light precip across the CWA Friday night
into Saturday morning. It`s possible another round of some light
freezing rain could occur in northern parts of Scott and Campbell
counties, and maybe the same for northern Wise county. But again,
the details of the low level thermal profiles matter a great deal
here, and unfortunately those are not in good agreement. For
instance, there`s a nearly 15 degree spread in forecast highs
between the latest runs of the GFS and ECMWF for those areas. The
colder GFS says Oneida in northern Scott county barely makes it to a
high of 32 degrees, while the ECMWF highs in the low 40s are on tap.
NBM guidance is somewhat in the middle, and suggests the need for
mention of wintry mix. Have followed suite for the time being.
Influence from that first shortwave pushes east by Saturday
afternoon, yielding another dry period before the next brings the
potential for more showers Sunday afternoon/evening. This precip
should be mostly in the south. As for ptype, a middle ground
approach yields some wintry mix even in the south, but confidence is
very low. The next shortwave moves across TN Monday night into
Tuesday, but confidence is the lowest that far out given the
differences Fri-Sun time frame.
CD
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 49 55 41 51 42 / 60 90 50 20 60
Knoxville McGhee Tyson Airport, TN 44 49 39 47 39 / 50 90 60 10 60
Oak Ridge, TN 41 46 36 48 38 / 60 90 50 10 50
Tri Cities Airport, TN 41 46 38 48 37 / 30 90 70 10 50
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Winter Weather Advisory from 7 AM to 7 PM EST Thursday for
Campbell-Claiborne-Scott.
VA...Winter Weather Advisory from 7 AM to 7 PM EST Thursday for Lee.
Ice Storm Warning from 7 AM Thursday to 7 AM EST Friday for Wise.
&&
$$
Area Forecast Discussion
National Weather Service Norman OK
511 PM CST Wed Feb 10 2021
...New AVIATION...
.SHORT TERM...
(This evening through Thursday)
Issued at 1215 PM CST Wed Feb 10 2021
Impacts from freezing rain and freezing drizzle continue mainly
along and southeast of I-44. As dry air slowly moves in, we`re
seeing a transition to snow grains along the northwest edge of
precipitation (trimmed a few counties off the northern edge of the
advisory that are already well behind this transition). Expect
precipitation to gradually move out of central Oklahoma this
afternoon / evening, but persist through the night in south
central and southeast Oklahoma and parts of north Texas.
Forecasted ice accumulations have changed little from previous
forecast, remaining below ice storm criteria but still quite
hazardous for travel (with temperatures this cold, it doesn`t take
much to make roads slick).
For temperatures, followed the RAP and NBM 25th percentile fairly
closely given recent performance and alignment with a conceptual
model of little diurnal variation.
Day
&&
.LONG TERM...
(Thursday night through next Tuesday)
Issued at 313 PM CST Wed Feb 10 2021
Models suggest any brief clearing or breaks in clouds we see
Thursday afternoon will quickly fill in area wide Thursday night as
easterly or southeasterly flow returns at 850 mb. This may lead to
another round of freezing drizzle across portions of western north
TX and southern OK Friday morning. Impacts are possible but there is
uncertainty regarding how widespread the precipitation may be at
this time. During the day Friday, clouds will keep temperatures from
moving a whole lot, with highs likely to remain in the low to mid
20s for much of the area, teens for northwest OK. A weak shortwave
then approaches Friday night into Saturday, but will be weakening as
it does so. The GFS and ECM have come into better agreement now,
generating light QPF with this wave. At this point the forcing
looks too weak to produce significant precipitation, but some
light snow, potentially up to once inch, will be possible Saturday
morning across mainly western OK given very cold temperatures.
Speaking of temperatures, a renewed surge of arctic air is
expected behind this system Saturday as the center of the arctic
high presses southward a bit. Single digit lows are expected by
Sunday morning for at least portions of northern OK, potentially
even into central OK.
Attention then turns to the next system digging to our west by
Sunday. Models suggest an impressively cold airmass in place across
the area, which should keep the vast majority of the precipitation
that falls in the form of snow. Lift associated with the wave may
impact our region for an extended duration, with snow potentially
beginning as early as Saturday night and lasting into the day on
Monday as the wave finally passes to our east. QPF totals this far
out are uncertain and may change, but ensembles have consistently
suggested the potential for greater than 0.5" for much of the
area. With snow to liquid ratios likely at least 12:1 to as much
as 16:1, the potential for a significant snowfall (4"+) continues
to increase.
In addition to the snow, dangerously cold temperatures are more
certain, with lows below zero possible across northern and perhaps
even central OK Monday and especially Tuesday mornings if the
snowfall forecast pans out. Wind chill values may reach -10 to -25
in some areas on these mornings.
Models show yet another system and potential for snow in the
Wednesday timeframe, but uncertainty increases markedly during this
period. However, it does appear general troughiness and below normal
temperatures will linger into much of next week.
Ware
&&
.AVIATION...
(00Z TAFS)
Issued at 510 PM CST Wed Feb 10 2021
Continue to see widespread IFR ceilings tonight with modest north
winds. Could see a period of freezing drizzle impact SPS overnight
with remainder of sites remaining dry. Expect most ceilings to
rise into MVFR cat by Thursday afternoon and some breaks in the
clouds may occur across the west.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 18 27 16 23 / 10 0 0 0
Hobart OK 18 29 16 24 / 10 0 0 0
Wichita Falls TX 22 33 21 29 / 20 0 0 0
Gage OK 11 25 9 19 / 0 0 0 10
Ponca City OK 14 24 11 21 / 10 0 0 0
Durant OK 25 32 24 33 / 40 20 0 10
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Winter Weather Advisory until 6 AM CST Thursday for OKZ027>032-
037>042-044>046-050.
Winter Weather Advisory until 6 PM CST this evening for
OKZ022>026-033>036.
Winter Weather Advisory until noon CST Thursday for OKZ043-047-
048-051-052.
TX...Winter Weather Advisory until 6 AM CST Thursday for TXZ084>090.
Winter Weather Advisory until 6 PM CST this evening for TXZ083.
&&
$$
SHORT TERM...14
LONG TERM....08
AVIATION...30
AREA FORECAST DISCUSSION
National Weather Service Charleston WV
1035 PM EST Wed Feb 10 2021
.SYNOPSIS...
Several weather disturbances bring a mixed bag of wintry
precipitation types through Friday. Colder temperatures and
periods of snow showers will follow into the weekend.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 1025 PM Wednesday...
...Significant Icing Continues Across Northeast Kentucky and
Along and Just East of the Ohio River...
Slight warming (as in 1 degree) has crept toward the Tri-State
with many locations reporting temperatures of 31-33. Given the
precipitation rates, this may mitigate further icing over the
next couple of hours. This will be very short-lived as colder
air will filter in from the northwest with a continuation of
icing in next few hours. We have received reports of three
tenths of ice accretion across parts of Greenup County thus far
with power outages.
Colder air has made its way into northern and northwestern WV
with many locations in the upper 20s. 00Z model runs are
hinting at burst of snow in these locations in the 8-11Z
timeframe. I`ve elected to increase snowfall amounts during the
predawn on the order of 2 to 4 inches...generally between Route
33 and Route 50.
Otherwise, no other meaningful changes made to the forecast
update.
As of 700 PM Wednesday...
...Significant Icing Occurring Across Northeast Kentucky and
Along the Ohio River...
Forecast generally on track overall but the minute details are
critical as we progress through the evening. Precipitation has
expanded considerably in coverage and intensity as forcing for
ascent is being maximized on the cold side of the inverted
surface trof courtesy of increasing PVA from favorable upper jet
dynamics. Precipitation type has generally been a snow or
snow/sleet mixture across southeast OH with rates approaching
1"/hr where hydrometeors remain all snow. Given upstream reports
and robust radar returns where surface temperatures are in the
upper 20s, elected to expand the winter storm warning into parts
of southeast OH. I also added a sliver of counties in west
central WV where mainly freezing rain is falling with the
anticipation of a transition to snow overnight.
It is the 2 to 3 tier of counties southeast of that line where
significant impacts from freezing rain are expected,
particularly across northeast KY and the Tri-State area. Surface
temperatures will remain just below freezing here and slowly
fall through into the overnight hours. It is here where two to
four tenths of ice accretion is forecast. This would result in
scattered power outages in addition to hazardous travel
overnight into the morning commute. A gradual changeover to snow
will occur after midnight where an inch or snow may accumulate.
Heading farther east and south, surface temperatures are more
marginal, especially in the Kanawha Valley and extending north
along the I79 corridor. Even though some locations may be at
freezing or just below, precipitation rates will likely limit
ice accretion for a time this evening. Conditions will
deteriorate toward midnight as temperatures slowly fall with the
inverted trof becoming pinched against the windward slopes of
the mountains. As such, hazardous impacts will increase
overnight as more efficient ice accretion is realized with
amounts to two tenths possible. A changeover to snow will occur
for these locations as well with generally an inch or so in the
predawn hours.
Across the central and northern mountains, a mixture will
develop later this evening, transitioning to all snow during the
predawn hours. Generally an inch or two is expected with ice
accretions of one to two tenths on the ridges.
The forecast remains fluid and highly susceptible to location
and magnitude of inverted surface trof over the next several
hours. Errors of just 25 miles in the placement of this feature
could result in meaningful changes in precipitation type and
subsequent impacts. At this point in the game, it is surface
observations from official and private weather stations along
with reports provided to us or our partners in media that will
provide the critical data for grasping if further changes in the
forecast are needed.
As of 235 PM Wednesday...
Forecast challenges through this period continue to focus on
temperature forecasts at the surface and aloft with a very sharp
gradient in precipitation types expected late this afternoon and
continuing through Thursday evening. Substantial differences in
wintry precipitation types are likely over rather short distances
with a sharp precipitation type gradient.
In the absence of proximity soundings, have largely depicted
initial temperatures aloft based on current observed
precipitation type and radar data, blending into the 12Z NAM
and 15Z RAP as we move forward in time. Guidance has been
trending slightly weaker with the warm nose, especially across
the northern half of the forecast area heading into this evening
with a net result of less freezing rain potential and more
sleet or even snow potential. Across these areas (covered by
advisories) snow accumulations of 2 to 3 inches, ice
accumulations of a light glaze to perhaps a tenth of an inch,
and sleet accumulations of a trace to around quarter of an inch
will be possible. In our mountain zones, currently covered by
winter storm warnings, snow accumulations of 3 to 5 inches with
some locally higher amounts up to 8 inches, ice accumulations of
a light glaze to a tenth of an inch, and sleet accumulations up
to half an inch will be possible. Best chances for impactful
freezing rain tonight will be across NE KY and W WV where
guidance continues to suggest ice accumulations a quarter third
of an inch with local amounts in excess of four tenths of an
inch possible. As cold air sinks south Thursday morning these
locations transition to all snow with a couple inches expected.
Further east in the warning overall freezing rain totals have
come down slightly due to an increased sleet forecast. For the
Charleston area, now expecting a tenth to two tenths of an inch
of ice along with a quarter to half an inch of sleet followed by
1 to 3 inches of snow Thursday morning.
Father south, precipitation through much of this evening into
the very early hours Thursday will fall largely as rain. As the
aforementioned cold air continues to sink south during the
morning, will likely see pockets transitioning over to freezing
rain. Did elect to issue an ice storm warning for our SW VA
counties in collaboration with our neighboring offices for
Thursday into Friday morning. Went on the lower side of guidance
for temperatures here and confidence levels are just barely
sufficient to pull the trigger. Here, precipitation type will
either be freezing rain or a cold rain and the lack of other
wintry precipitation types is why we went with an ice storm
warning over a winter storm warning. Should the surface
temperature forecast come in as advertised, a tenth to a
quarter of an inch is expected, with localized amounts
approaching four tenths of an inch, especially across the
northwestern halves of these counties.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 145 PM Wednesday...
As the frontal boundary and inverted trough that is creating
this wintry mixed bag of weather over the area moves east
through early Thursday night, snow tapers off to just chances
across the area, with the exception of the far south where it
will still be warm enough to promote rain or freezing rain
dependent upon surface temperatures. Snow accumulations taper
off with generally around an additional 1-2 inches in the
northeast WV mountains and less than an inch on average across
the lowlands. The event ends with a changeover to freezing rain
in the higher terrain along the mountains before completely
ending by late Friday morning.
This will allow the area to endure a short break for the rest
of Friday with temperatures moderating to above freezing for
most of the area, excluding the highest elevations. Another
system, forcast to originate in the Gulf, will traverse north
across the area promoting chances of rain across the southern
half of the CWA with possible freezing rain where areas drop to
below freezing at the surface into Saturday morning. Chances
will eventually make their way up to the northern fringes of
the CWA through the daytime. This will create a setup of a
possible wintry mix precipitation regime which will transition
to an all snow regime by nightfall.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 145 PM Wednesday...
The aforementioned feature will exit Sunday morning taking any
chances of snow with it. The Euro and GFS are confident at
another system developing and affecting the area during the new
work weak, however the Canadian is struggling with timing and
location. The long range models do indicate an active period of
unsettled weather so decided to accept a blend of models which
equated to chance or better POPs for the rest of the extended
period. Good news is, that as the polar low to the north dips
south and slides east near the area, temperatures will have
dropped enough to promote all snow showers instead of the messy
wintry mix that the area will have dealt with in the previous
periods. Although temperatures will not be as cold as we
previously thought, they will be sufficient enough to make the
precipitation type easier to forecast during this period.
Temperatures do moderate at the end of this period starting
Tuesday and beyond as the polar low shifts northeast out of the
area.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
As of 700 pM Wednesday...
Freezing rain will affect most terminals this evening with the
exception of BKW where rain will be the primary precipitation
type. A transition to snow will gradually occur from northwest
to southeast overnight. Generally looking at IFR flight
restrictions with occasional drops into LIFR/VLIFR where snow
falls.
This system slides south and east Thursday morning with even BKW
transitioning to freezing rain and then snow before ending. CIGs
may rise into low end MVFR, though light snow may fall
throughout the day helping to keep IFR locked in.
Weak north-northeasterly surface winds gradually shift north by
Thursday morning.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: Weather types may differ over very small
distances tonight. Visibility reductions largely contingent on
very difficult precipitation type forecast.
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.
DATE THU 02/11/21
UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
EST 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09
CRW CONSISTENCY M M H H M H M M H H M H
HTS CONSISTENCY M M M M M H H H H H M H
BKW CONSISTENCY L H M M M M H M H H M H
EKN CONSISTENCY H M H H H H H H M M M M
PKB CONSISTENCY H H H H H H H H H L H H
CKB CONSISTENCY M M M M M M M M M H H H
AFTER 06Z FRIDAY...
IFR possible in a wintry mix through Friday morning.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...Winter Weather Advisory until 7 AM EST Friday for WVZ010-011-
016-018-020-027>032-039-040-517>522-524-525.
Winter Storm Warning until 7 AM EST Friday for WVZ005>009-
013>015-017-019-024>026-523-526.
Winter Weather Advisory until 7 AM EST Friday for WVZ033-034-
515-516.
OH...Winter Weather Advisory until 7 AM EST Friday for OHZ075-076-
084.
Winter Storm Warning until 7 AM EST Friday for OHZ083-085>087.
KY...Winter Storm Warning until 7 AM EST Friday for KYZ101>103-105.
VA...Ice Storm Warning from 7 AM Thursday to 7 AM EST Friday for
VAZ003-004.
&&
$$
SYNOPSIS...JP/JZ
NEAR TERM...JP/30
SHORT TERM...JZ
LONG TERM...JZ
AVIATION...30
Area Forecast Discussion
National Weather Service Las Vegas NV
206 PM PST Wed Feb 10 2021
.SYNOPSIS...Mild weather is expected through Thursday before the
first of two systems drops into the area Thursday night into early
Friday. This system will bring gusty winds to the western deserts,
along with cooler temperatures and a chance of rain and mountain
snow. The pattern remains active with a second system dropping into
the area over the weekend bringing more cooling along with gusty
winds and another chance of precipitation. &&
.SHORT TERM...Today through Friday.
Northwest flow overhead has allowed for mostly clear skies, light
winds, and warmer temperatures today.
Quiet weather will continue through much of Thursday before a
shortwave digs into southeast CA late Thursday-early Friday.
A vorticity band ahead of the main shortwave will move through
southern NV & southeast CA Thursday night. This band largely won`t
be impactful, and likely will only result in lower cloud decks to
around 8-10 Kft. Previous HRRR runs were indicating potentially
light precipitation associated with this band, however, latest runs
are now dry. Slightly better moisture is expected with the actual
shortwave, bringing slight chance (15-24%) and chance (25-50%) PoPs
to northwest Inyo, southern NV, and northwest AZ early Friday -
better chances are over Lincoln County. Any precipitation that
does fall, is expected to be very light mainly resulting in
sprinkles or storm totals of less than 0.20".
Impacts associated with this shortwave will primarily be in form
of winds as pressure gradients tighten ahead of the low. As the
shortwave digs into northern CA, gradients tighten across the
eastern Sierra Thursday night, resulting in gusty westerly winds.
Cross sections indicate winds are not expected to reach Wind
Advisory criteria, and downslope winds of 30-35 mph are only
expected to get down to mid slopes. Gradients will be tightest
across the western Mojave Desert/western San Bernardino County
late Thursday night into Friday. Depending on what you look at,
winds may or may not meet criteria for that area. HREF, METDAG,
and ECMWF ensemble meteograms for DAG all indicate borderline
criteria with gusts at or just above 40 mph in the Barstow/Daggett
area. Whereas MAVDAG, ECSDAG, SREF, GEFS plumes, and local hires
models indicate below criteria, with gusts only getting to around
35-38 mph at KDAG. Since the majority of guidance indicates below
advisory criteria, and the strongest winds will be overnight into
early Friday, decided against issuing a Wind Advisory for western
San Bernardino County. Additionally, if winds do reach 40 mph they
are expected to be very brief, since this low will quickly dig to
the southeast.
As the low digs into southeast CA Friday morning, west-northwest
winds will move across Yucca Valley where gusts to around 30 mph
will be possible. At the same time, a brief period of breezy winds
will spread across the Mojave Preserve and central Mohave County.
Essentially, expect breezy winds with gusts 20-25 mph south of
the I-15 corridor and along the I-40 corridor overnight into
early morning Friday. Elsewhere, winds are expected to be lighter,
generally less than 15-20 mph. Behind the low, breezy northerly
winds with gusts to 25 mph are possible mainly across central Nye
Friday afternoon.
As this system approaches the area, expect clouds to increase
with mostly cloudy conditions by late Thursday afternoon and
temperatures decrease a few degrees by Friday afternoon.
.LONG TERM...Saturday through Tuesday.
Brief shortwave ridging is expected by late Friday and overnight
Saturday before another more `potent` weather system digs into the
area over the weekend. A shortwave will begin to dig into the Great
Basin & northern NV early Saturday morning. As it continues to
deepen and dig into southern NV through Saturday afternoon, pressure
gradients will tighten across the region, resulting in widespread
gusty southwest winds. Expect widespread wind gusts to around
35-45 mph with stronger winds to 50 mph across western San
Bernardino County.
Outside of gusty winds, better moisture with this system will result
in more widespread chances for rain Saturday. With slight chances
across southeast CA, and chance to likely`s across southern NV and
northwest AZ. Though, QPF storm totals have decreased considerably
since the previous forecast, now only producing 0.25" to 0.50"
across Lincoln and Mohave counties and generally less than 0.25"
elsewhere.
Snow levels start off fairly high Saturday around 5500-6500 feet. So
much of the snow accumulations will be above 5,500-6,000 feet.
Overall, snow totals aren`t too impressive, with only 1-4 inches in
Lincoln and a little less in central Nye, the Arizona Strip, and in
the Spring Mountains and Sheep Range.
Chances decrease from west to east overnight Saturday into Sunday
morning as the low digs to the east. Northwest flow transitioning to
brief shortwave ridging Monday. Under this pattern, continued
shortwaves moving through are possible through next week. One of
which looks possible sometime Mon night - Tuesday. Confidence on the
forecast details beyond Sunday are low, so stay tuned!
&&
.AVIATION...For McCarran...Light and variable winds expected to
remain through tomorrow morning, favoring typical diurnal
directions. By late afternoon tomorrow, winds are expected to shift
to the southwest with sustained speeds around 10-12 knots. Mostly
clear skies expected through tomorrow morning before another round
of mid to high clouds move in from west to east through tomorrow
afternoon.
For the rest of southern Nevada, northwest Arizona and southeast
California...Light and variable winds expected to remain through
tomorrow morning, favoring typical diurnal directions. By late
afternoon tomorrow, winds are expected to shift to the southwest
with sustained speeds around 10-12 knots. Gusty west winds are
expected at KDAG by late tomorrow night. Mostly clear skies expected
through tomorrow morning before another round of mid to high clouds
move in from west to east through tomorrow afternoon. &&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION/AVIATION...Kryston
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