Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/10/18
Area Forecast Discussion
National Weather Service Albany NY
955 PM EST Fri Mar 9 2018
A persistent upper level trough will keep chances for snow
showers and snow flurries in the forecast through Saturday. High
pressure will finally build in on Sunday bringing a break from
the snow along with near normal temperatures.
.NEAR TERM /THROUGH SATURDAY/...
Winter Weather Advisory in effect until 5 AM Saturday for the
As of 955 PM EST...A rather organized and intense lake effect
snow band developed this evening across central NY and has
extended eastward into Schoharie and the southwest half of
Albany county. Radar reflectivity of around 30-35 dBZ indicating
1-2 inch per hour snowfall rates are occurring with this
transitory band. Have updated the forecast to reflect the snow
in this area, with a quick 1-3 inches of accumulation expected.
Steep 0-3 km lapse rates still evident on the 00Z KALB sounding
indicates environment supportive convective lake plumes with
intense snowfall rates. Hi-res model guidance such as the HRRR
and 00Z Nam 3km now picking up on this activity, which should
start to fragment as it shifts southeast within the next few
hours. The cellular snow showers from early this evening have
dissipated, with the lake effect and upslope the main mode
through the rest of the night.
Cyclonic upper level flow and troughiness will continue to dominate
the weather across the area through Saturday. Snow showers will
continue, mainly over the higher terrain, with persistent
cloudiness. Best chances for snow showers with some additional
light accumulations will be across the Adirondacks, Mohawk
Valley and southern Green mountains of Vermont into Saturday
with some lake effect and upslope snow enhancements.
Overnight lows will generally be in the low to upper 20s with
mainly overcast skies. Temperatures Saturday afternoon will
likely remain near freezing in the high terrain but into the
upper 30s to near 40 degrees in the valleys.
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
A trough of low pressure swinging across northern portions of
the region will keep a chance of snow showers going across
the western Adirondacks Saturday night. By Sunday high pressure
will be building into the region bringing fair weather which
will last through Sunday night. Expect a good deal of sun on
Sunday followed by partly to mostly cloudy skies Sunday night.
Lows Saturday night will be in the 20s with highs on Sunday in
the upper 20s to mid 40s. Lows Sunday night will be in the upper
teens to upper 20s.
.LONG TERM /MONDAY THROUGH FRIDAY/...
We may experience a near-miss with the storm early next week,
but a frontal boundary sinking out of Canada behind it will
provide abundant cloudiness, with enough mid-level atmospheric
moisture to produce light snow shower and flurry activity,
throughout the region for the first 48 to 72 hours of the
extended, as the front morphs into a persistent inverted trof
across New England and northern New York to the northern Great
Accumulations will be light during the night, with little or
none during the daytime periods as the precipitation will be
mixed at times, or most of it will just melt on impact with the
comparatively warm March ground. Indeed most locations outside
the higher elevations will climb above freezing each day, and on
Friday, many Hudson Valley and southern zone locations will
reach well up into the 40s. But by then, the trof will be long
gone, and high pressure will be ridging in from the deep south,
beginning a period of fair weather with a warm-up.
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Some additional snow showers will occur this evening, mainly
affecting the KGFL/KPSF terminals with possible MVFR conditions
or even very brief IFR. Then, overnight into Saturday snow
shower activity should be confined mainly to higher terrain
areas, so will limit mention of VCSH to KPSF. Conditions will
generally be VFR except within any snow showers. Skies will
remain bkn-ovc through 00Z Sunday.
Winds will be westerly around 5-10 with some occasional gusts
near 20 kt tonight, especially at KALB/KPSF. Winds on Saturday
will remain westerly and increase to around 10-15 kt with gusts
of 20-25 kt.
Saturday Night: Low Operational Impact. Breezy NO SIG WX.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: Low Operational Impact. Slight Chance of SHRA...SHSN.
Monday Night: Moderate Operational Impact. Chance of SHSN.
Tuesday: Moderate Operational Impact. Chance of SHRA...SHSN.
Tuesday Night: Moderate Operational Impact. Chance of SHSN.
Wednesday: Moderate Operational Impact. Chance of SHRA...SHSN.
Snow showers will linger across the area through tonight. Some
locations in the Adirondacks could see up to an additional few
inches of snow accumulations through this time. However, no
impact is expected on the area rivers, creeks and streams.
Heading into next week there will be a chance for some more snow
showers Monday into Tuesday with perhaps some rain showers in
the valleys on Tuesday. No significant river rises are
anticipated at this time through the middle of next week.
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.
NY...Winter Weather Advisory until 5 AM EST Saturday for NYZ032-033-
Area Forecast Discussion
National Weather Service Columbia SC
950 PM EST Fri Mar 9 2018
Expect warming conditions Saturday ahead of a surface boundary
approaching from the north. The next chance for rain will be
Saturday night and Sunday, followed by a dry and cool pattern
for early to mid next week.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
First patch of cirrus clouds moving through the northern FA is
thinning as it slides east southeastward. This allowed temps to
drop a few degrees quicker than anticipated there, so I made
some adjustments to the forecast grids for the next few hours to
accomodate the current conditions. Another batch of cirrus
should move in later tonight on the back side of the progressive
jet streak moving through...although its thickness is in
question as this evening GOES-East water vapor loops indicate a
lack of upper level moisture immediately upstream.
Despite temps bottomoing out in the mid to upper 30s, it would
not surprise to see some morning frost on rooftops and other
elevated surfaces in our usually cold and sheltered locations as
the dew point readings are climatologically favorable. However,
I don`t think it widespread enough to warrant a last minute
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Surface high will shift east offshore Saturday remaining to our
S/SE, and a surface boundary will slip south and set up just to
our north Saturday and may provide focus for a slight chance of
showers across the northern Midlands by afternoon. SW low-
level flow around the high and ahead of the front to provide
warming temps Saturday. Upper energy will shift east across the
SE ahead of a northern stream upper trough diving SE into the
central CONUS. Surface low to develop to our west and begin
intensifying and tracking east towards our region Sat/Sat night.
POPs on the increase across the area Sat night. GFS and NAM
models have some differences with the evolution of the system,
with questions regrading the track of the low or possibility of
the low occluding and secondary low developing near the coast.
This will have an impact on many elements including max temps,
thunder potential, and wind Sunday. For now, will generally take
a model blend and continue to include slight chance thunder
mention for our central and southern forecast area to accompany
the model consensus categorical POPs. Highs Saturday ranging
from the mid 60s north to the lower 70s south, and upper 50s
north to near 70 south on Sunday. Lows Saturday night will be in
the upper 40s to the lower 50s.
.LONG TERM /MONDAY THROUGH FRIDAY/...
Surface low and greatest moisture to shift to our E/NE late
Sunday night and Monday, but main upper system to come through
Monday and may provide some continued precip potential
especially N/NE. Latest model consensus has slight chance to low
chance POPs Monday. Otherwise, indications of upper trough E
CONUS reinforced by upper trough and surface boundary coming
through Wed/Wed night with limited moisture will provide us
with a cool dry pattern early to mid week, with possibilities of
near freezing temps again. Temperatures moderate a bit for
Friday with dry weather continuing.
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions will occur through the 24-hr TAF period.
High pressure will be shifting farther off the Southeast Coast
through Saturday. Some moisture increase will occur in the
southerly flow and ahead of a cold front but significant
moisture should hold northwest of the area through the 24-hour
TAF period. The especially dry conditions initially plus some
mixing associated with a low-level jet should help prevent fog
during the early morning hours. The NAM and GFS MOS plus HRRR
and SREF guidance maintain VFR conditions. The low-level jet may
become strong enough to reach low-level wind shear criteria
mainly over the northern terminals where the pressure gradient
will be stronger farther away from the ridge axis. The NAM
indicates 2000-foot wind increasing to around 30 knots by 12z.
We included low-level wind shear during the early morning hours
at CAE and CUB. Increased mixing associated with diurnal heating
will help cause developing breezy conditions Saturday. The NAM
and GFS average wind in the mixed layer plus GFS LAMP suggest
gusts 15 to 20 knots.
EXTENDED AVIATION OUTLOOK...Widespread MVFR or IFR conditions
may occur Saturday night, Sunday, and Monday associated with an
area of low pressure in the region.
Area Forecast Discussion
National Weather Service Lincoln IL
921 PM CST Fri Mar 9 2018
Issued at 912 PM CST Fri Mar 9 2018
A weak upper level disturbance over southern Iowa and northern
Missouri this evening was tracking southeast. Mid level clouds
ahead of that feature in our area while further south, closer to
a frontal boundary south of the Ohio River, thicker cloud cover
and some light rain has developed over the past several hours.
The latest short term models suggest areas along and especially
south of the Interstate 70 corridor may see some light rain,
possibly mixed with a little snow late tonight, but any
precipitation over extreme southeast IL will be on the light
A stronger shortwave seen on the water vapor loop was tracking
southeast out of western Montana and will continue to push
southeast into the Plains on Saturday. The latest NAM model has
trended weaker and further west with the upper wave (more of an
open wave rather than a closed 500 mb low), very similar to what
the 12z ECMWF model was indicating with the rain and snow
associated with the surface wave and inverted trof further west
as well late Saturday night and Sunday.
The current forecast has a good handle on the late evening and
early morning trends with the precip associated with the first
wave remaining over far southeast IL, warranting only low chance
POPs for the early morning hours. Further north, clouds will
decrease late tonight across the north as the wave shifts away
from the area with another chilly night in store as early morning
lows dip into the low to mid 20s north to around freezing in far
southeast Illinois. No ZFP update will be needed at this time.
.SHORT TERM...(This evening through Saturday)
ISSUED AT 246 PM CST Fri Mar 9 2018
Short-wave trough evident on 20z/2pm water vapor imagery over
eastern Nebraska is providing enough synoptic lift to create an
area of mid/high clouds from Iowa/Missouri southeastward into the
Ohio River Valley. Earlier today, regional radar mosaic showed a
narrow band of snow immediately ahead of the wave across
central/western Iowa: however, reflectivity has steadily
diminished within this band as it has pushed into west-central
Illinois. Will continue to monitor radar and local surface obs,
but do not plan on adding sprinkles/flurries to the forecast late
this afternoon. As the short-wave tracks further southeastward, it
will interact with a frontal boundary extending from Nebraska
into western Kentucky to produce some light precip across
southeast Illinois this evening. Based on latest HRRR forecast,
think rain showers will develop between 00z and 03z, with the
light rain gradually mixing with and changing to snow before it
ends overnight. With surface temps only dropping to around
freezing south of I-70, little or no snow accumulation is
expected. Elsewhere around the area, cloudy and dry conditions are
anticipated tonight. Once the wave exits, skies will become
mostly sunny on Saturday...with high temperatures topping out in
the upper 40s and lower 50s.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 246 PM CST Fri Mar 9 2018
The next short-wave of interest is currently noted over western
Montana...and this feature will bring clouds and precip back into
the area Saturday night into Sunday. 12z Mar 9 models are in poor
agreement with the track of the wave and its associated precip,
with the NAM and GFS featuring a closed 500mb low that tracks
further east than previous runs. Meanwhile, the ECMWF/GEM both
show an open wave generally tracking W/SW of Illinois. Am not
ready to completely buy into the GFS solution just yet, but think
its wise to bring precip chances into at least the western half
of the KILX CWA. With easterly boundary layer flow preceding the
system, it will have quite a bit of dry air to overcome before
producing measurable precip. Therefore think Saturday evening
will remain mostly dry, with PoPs spreading as far east as a
Bloomington to Shelbyville line overnight.
The wave and its associated surface inverted trough will pivot
E/SE on Sunday, resulting in widespread precip across western and
southwestern Illinois. Still plenty of questions as to how far
east the precip will spread, but based on model consensus...think
locations along/northeast of a Champaign to Paris line will stay
dry. Further west, enough evaporational cooling will occur to
support a period of wet snow Sunday morning before the atmosphere
warms sufficiently for the snow to mix with or change to rain by
afternoon. Model guidance indicates high temperatures in the lower
to middle 40s, but have dropped them into the middle to upper 30s
due to the aforementioned evaporative cooling. Further east closer
to the Indiana border where little or no precip will be occurring,
highs will reach the 40s. Light precip will linger into Sunday
evening before tapering off and coming to an end by midnight.
Snowfall totals will be greatest across west-central Illinois,
where 2 to 3 inches will be possible along/southwest of a
Galesburg to Jacksonville line. As much as 1 inch will be possible
as far east as a Peoria...to Lincoln...to Taylorville line.
Once the wave departs, quiet weather will prevail for the balance
of the extended. Thanks to northwesterly flow around a prevailing
upper trough over eastern Canada, cool/dry weather will be the
rule across central Illinois through Wednesday. After that, the
trough will lift further northeastward as upper ridging builds
into the Midwest by the end of the week. As a result,
temperatures will rise back above normal into the upper 50s and
lower 60s by Friday.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 553 PM CST Fri Mar 9 2018
VFR conditions expected this forecast period. A weak weather
system will track well south of the TAF sites later tonight
keeping the lower clouds and any precip out of the area. Some
broken lower (5000-8000 ft) VFR cigs expected at times this
evening with mainly sct-bkn cirrus clouds across most of the
area after Midnight. Light easterly flow expected tonight and
east winds expected on Saturday with speeds of 10 kts or less.
Area Forecast Discussion
National Weather Service Lake Charles LA
950 PM CST Fri Mar 9 2018
Regional 88Ds show scattered showers ahead of a weak shortwave
advancing across srn TX beginning to move off the middle/lower TX
coast and into the nwrn Gulf. This activity will begin to approach
the swrn portions of the CWA later tonight, although it will have
to overcome some drier air aloft first per 00z KLCH sounding.
Latest runs of the HRRR have been in solid agreement with
inherited POP grids for the overnight hours...thus will not make
any changes to rain chances for the rest of the night.
Sfc obs indicate that temps have already reached projected mins in
several spots, thus have updated overnight min/temp grids to
account. Don`t suspect we`ll see too much more falling in the
temps with serly winds now generally re-established.
Update out shortly.
.PREV DISCUSSION... /issued 550 PM CST Fri Mar 9 2018/
Two VFR cloud decks streaming across the area this evening...the
first a low level deck around 035kft streaming out of the gulf,
the second at 070kft streaming west to east out of Texas. Both of
these will persist through the night. A weak upper trough will
swing across the area early Saturday in advance of an approaching
cold front sparking scattered showers and perhaps a thunderstorm
or two. The precipitation is expected to increase in coverage from
early to mid morning along with a lowering of ceilings to MVFR
with periods of IFR. The precipitation will become more isolated
Saturday evening. Winds will remain southerly to southeasterly
through the taf period as the cold front will not move through the
area until sometime Sunday.
PREV DISCUSSION... /issued 125 PM CST Fri Mar 9 2018/
Latest wx map shows surface high over the SE U.S. with a return
flow becoming fully established over SE TX/LA. Vis satellite and
sfc obs showing mid level BKN layer ~6500-8000 ft advecting over
SE TX/W LA this afternoon, with temperatures in the upper 60s to
The main weather system this forecast period will be the upper
level disturbance to move through the region Saturday. This will
initiate across the coastal waters during the pre-dawn hours as
the warm front moves back north. This will continue to ramp up
precip chances for the remainder of the morning across SE TX/W LA, and
across C and SC LA for the afternoon hours.
SPC has most of the area roughly from JAS to LFT northward in a
marginal risk for severe thunderstorms, with a sliver of NE
Rapides included in the slight risk. The main concern: as the
front moves northward during the late morning/afternoon hours
across C LA, moderate mid-level flow expected to increase along
with some low-level veering/shear. This could result in some brief
strong to severe thunderstorms along the warm front, with a brief
tornado or two possible. The big question will depend if we can
clear out enough for enough low level instability to develop by
late morning into the afternoon hours.
Showers and thunderstorms expected to end by Saturday night into
Sunday morning. The cold front is not expected to move through
until late Sunday morning into the afternoon hours.
A fairly deep layer trough over the Central U.S. is expected to
persist for most of next week, which will keep cooler and dry
Southerly winds will continue through Saturday. An upper-level
disturbance will generate scattered to numerous showers and
thunderstorms Saturday morning, diminishing by the afternoon and
evening as the upper level disturbance move further east of the
area. The probability for widespread hazardous weather is low,
however, cannot rule out a few strong to possibly severe marine
thunderstorms Saturday morning. A cold front will bring moderate
to briefly strong offshore flow for Sunday and Monday, where Small
Craft Advisories will likely be required.
.PRELIMINARY POINT TEMPS/POPS...
AEX 54 74 60 71 / 40 80 60 20
LCH 59 75 65 74 / 60 80 30 20
LFT 56 75 64 74 / 30 80 40 30
BPT 60 77 66 75 / 60 70 20 10
Area Forecast Discussion
National Weather Service Louisville KY
846 PM EST Fri Mar 9 2018
Issued at 845 PM EST Fri Mar 9 2018
Early evening radar imagery shows a band of precipitation extending
from near French Lick southeast through the Lexington Metro area.
This precipitation is being forced by increasing frontogenetical
forcing as upper level jet streak pivots into the region. Low-level
jet axis continues to push moisture into the region. Wetbulbing is
taking place across the east-central sections of Kentucky, mainly in
the corridor from just northeast of Louisville down the I-64
corridor into the Lexington metro region. KY mesonet readings show
temps already in the lower-mid 30s from Shelbyville eastward towards
Winchester. Already have received some rain/snow reports out toward
Lexington. Current thinking is that a switch to mainly snow is not
all that far off.
Latest HRRR runs have continued to back off the snow amounts in the
southern edge of the advisory area. In fact, watching the last 4-5
hours of HRRR runs show the accumulating snow band slowly shifting
northward with each run. However, much of the accumulations are
still solidly in the advisory area. Much of this forecast snowfall
will occur later this evening and overnight as upper jet core pivots
more into an east-west direction leaving much of central KY in the
right entrance region of the jet. Low-level SW flow from the
nocturnal jet will continue to feed into the region and will allow a
stronger thermal gradient to develop, not only at the surface but
also aloft. Resultant frontogenetical forcing will lead to the
development of a narrow band of enhanced precipitation. With
wetbulbing and some draw down of colder air aloft, along with some
dynamical cooling, a narrow band of heavy wet snow still looks good
for portions of central KY.
Current thinking is that this band will probably fall right along
the I-64 corridor. The consecutive HRRR runs would favor the
northern side of the I-64 corridor, but some dynamical cooling may
offset that resulting more snow south of the corridor. Really think
that area from Shelbyville to Frankfort and into the Lexington Metro
may get in on the heaviest snow accumulations in this event. There
is less certainty further west into the Louisville metro and areas
north and west of Louisville. Will have to watch upstream obs and
reports later tonight in those areas.
For now, the current advisory will not be changed. However, it is
possible that the southern tier of counties could be trimmed off if
the low-level thermal gradient stays warmer than currently forecast.
Have made some slight tweaks to the snowfall forecast and the new
forecast will feature a general 1-4 inch snowband from eastern
Louisville east through Lexington. The heaviest axis of snow right
now may be from Mercer/Anderson/Franklin counties eastward through
Fayette/Jessamine/Clark and into northern Madison. This band could
be narrow enough that significant differences in accumulations could
be seen over less than one mile in differences. It will really come
down to meso-beta scale temperature gradients and precipitation
rates which are very difficult to forecast even a few hours into the
.Short Term...(This evening through Sunday Night)
Issued at 300 PM EST Thu Mar 8 2018
...Slushy Snow Accumulations Expected Tonight...
A 110 knot upper level jet is currently entering the mid Mississippi
River Valley, with the left exit region of this feature expected to
overspread our CWA later this evening. It`s going to take a bit to
saturate the column as T/Td spreads are currently around 20 degrees.
By sunset, expect light rain to start over central Kentucky, with
areas along the TN border likely staying mostly dry. As the initial
band of light rain spreads eastward, it will start to shift north.
This will occur as the center of the jet core slides through the area
and pivots to a more E-W oriented axis. From that point,
precipitation will be driven by the right entrance region of the
upper jet, with good moisture transport in the low to mid levels as
the low level jet responds. This setup will create the potential for
some persistent frontogenetical banding running along and on either
side of the I-64 corridor. Best timing for the heaviest
precipitation looks to be in the 5 to 11z time frame. We could lose
some ice aloft right at the end of the event, but with temps likely
warming a degree or two after heaviest precip ends, think it would
just be drizzle (not freezing drizzle) and inconsequential.
Precipitation type will likely start out as some rain through the
evening hours, although our northern and eastern CWA could start as
snow and stay that way through the event. Don`t expect any accums
with this initial wave. As we move into that period around midnight
and after, expect the column to dynamically cool to the point where
temps stay at and just above freezing. Given the banding potential
and moderate to briefly heavy rates, think we will be able to
accumulate with temps at and just above freezing, especially with
the sun being down. Accums will mainly be on grassy surfaces, but
rates should be strong enough to create some slick spots on roadways
Still like the idea of the heaviest snow falling east of Louisville
into the Bluegrass region where 1 to 3 inches will be possible.
Locally higher amounts aren`t out of the question, but should be
localized in nature. Plan to expand the Winter Weather Advisory back
to the west through Louisville as some of the latest data shows a 2-
3 hour period of light to moderate snow between 7-10z. HRRR shows a
real nice temp drop as the heavier precip arrives, adding confidence
that the column should dynamically cool down to the point of
supporting snow. In the western portions of the Advisory, expect up
to around 1". Will also start the Advisory a bit later than
previously thought as the most impactful time should be late evening
into the overnight. New start time will be 04z.
Have seen a slight shift to the north in the latest heavier precip
band, so am becoming a bit more concerned about some of the counties
on the southern tier of the Advisory. In reality, southern portions
of these counties may see mostly rain with no accumulations, while
northern parts of the counties pick up light accums up to 1".
The rest of central and southern KY should see all rain or only a
very brief mix of snow with no accumulations. In general, a quarter
to a half an inch of rainfall is possible in these areas. The lowest
amounts of a tenth of an inch or less of rain should be along the TN
Saturday - Saturday Night...
Precipitation should quickly exit the east around sunrise with high
pressure centered to the north briefly taking hold. Not much cold
air associated with that feature so temps should still be able to
recover into the upper 40s and low 50s over most of the CWA. Could
even see mid 50s down near BWG. Tried to highlight an area of cooler
temps where an expected light snow pack will be.
Saturday night should be mostly dry, but some overrunning light
precip could begin to move into southern and western portions of the
CWA by dawn on Sunday.
Sunday - Sunday Night...
Still a lot of questions for the Sunday - Sunday night system as
models continue to have trouble. In general, a strengthening surface
low should scoot across the mid south, with overrunning precipitation
expected mainly along southern KY. This initial precipitation should
be light rain, unless the precipitation shield extends up into
northern KY or southern IN. Then, some mixed precipitation is
possible. Highs should mostly be in the mid to upper 40s during the
day, but with steady cold advection toward the surface low to our
south, temps quickly drop to the upper 20s and low 30s by Sunday
night. At this time, a second system drops into the area from the NW
where any light rain could change to snow. Some light snow
accumulations are possible, but too early to nail down details. The
latest trend is most of the data is to keep the two systems just
separated. There is still potential for it to become phased to the
point that more snow later Sunday into Sunday night would be
possible. Will keep an eye on it, but for right now it looks to be
.Long Term...(Monday through Friday)
Issued at 245 PM EST Fri Mar 9 2018
A north to northwest mid-level flow pattern will exist across the
Ohio Valley during much of the forecast period as a deep trough
swings across the northeastern U.S. during the first half of the
week. This pattern will keep cooler than normal weather across
central KY and south-central IN from Monday through Thursday
morning, coolest on Tuesday and Wednesday as a reinforcing surge of
Canadian air swings across the area. As this occurs, models suggest
there could be at least some snow flurries across eastern KY, but
our current forecast remains dry for this period over central KY.
Highs Monday through Wednesday should range through the 40s, with
only lower 40s (perhaps a little colder) over parts of south-central
IN and east-central KY Tuesday and Wednesday. This would be around
(at least) 10 degrees below normal. Expect low temperatures Tuesday
through Thursday mornings in the 20s.
On Thursday, the deep trough over the northeastern U.S. should start
pulling away allowing heights aloft to rise over the Ohio Valley.
This will create a warming trend by afternoon, with highs closer to
normal in the lower to mid 50s. Moderation continues Friday with
highs in the upper 50s to mid 60s. It will be dry late week.
Just beyond the current forecast period, models show a return to a
southwest flow pattern aloft Saturday, with increasing moisture and
lift resulting in showers and perhaps a few thunderstorms. Models
vary on the strength of this system at this time.
.Aviation...(00Z TAF Issuance)
Issued at 631 PM EST Fri Mar 9 2018
Widespread mid level clouds are across the region this evening. The
radar is currently showing quite a few returns. However, little of
this is reaching the ground at this point as there is plenty of mid
level dry air.
The atmosphere will continue to saturate through the evening and a
band of rain will set up across north central KY with more scattered
showers across south central KY near BWG. The atmosphere will cool
tonight with some of the rain changing over to snow. The best chance
for snow tonight will be at SDF and LEX. This snow could become
heavy at times during the 06-10Z time frame. The highest confidence
in the heavier snow is at LEX with a slightly lower confidence at
SDF as it is nearer to the rain/snow line. Will continue to carry a
mix of rain and snow at HNB and all rain at BWG. This precipitation
will quickly come to an end from west to east near dawn tomorrow
Ceilings will continue to lower through the evening into the
overnight hours. Fuel alternate MVFR looks likely at all sites late
tonight with IFR expected at SDF, LEX, and for a brief period at
HNB. Ceilings are expected to improve by late morning tomorrow and
scatter out in the afternoon. Visibilities will be reduced at times
tonight, particularly with the heavier snow.
IN...Winter Weather Advisory until 7 AM EST Saturday for INZ090>092.
KY...Winter Weather Advisory until 7 AM EST Saturday for KYZ029>031-
Area Forecast Discussion
National Weather Service Reno NV
332 PM PST Fri Mar 9 2018
Light rain and higher elevation snow late Saturday and Saturday
night, mainly south of Highway 50, will be followed by drier
conditions Sunday into Monday. A stronger system is expected to
bring gusty winds with rain and snow Tuesday and Wednesday.
Temperatures near or slightly above average through early next
week will fall below average late in the week.
MAIN FORECAST CHANGES THROUGH MONDAY:
- precipitation amounts/snowfall have been lowered by 30-50%
Saturday night and Sunday morning in the Sierra.
A few showers are moving across Lassen and northern Plumas Counties
this afternoon as weak, fast-moving low pressure tracks along the
Oregon-California border. All shower activity will cease this
evening as the low weakens and moves into southwest Idaho.
Elsewhere, no precipitation is expected with mainly high clouds
noted. Breezy conditions are expected to taper off overnight as a
surface high builds into northern NV, with generally light winds
expected for valleys on Saturday.
By late on Saturday and for Saturday night the next wave passes
by, mainly to the south of the region. Most simulations including
the GFS, NAM, EC, and the last couple runs of the SREF have come
in farther south with an incoming moisture slug for late Saturday
and Saturday night. This trend is best explained by Murphy`s
Facetious Weather Law, which states that the minute projected
precipitation amounts are raised (yesterday) simulations start to
dry out. The 12Z experimental HRRR does still show potential for
higher snowfall amounts in the Mono/Alpine County Sierra (comparable
to yesterday`s forecast); however, this is a higher-end outlier.
With all the above factors in mind, precipitation amounts/snowfall
have been lowered by 30-50% Saturday night and Sunday morning in
the Sierra, with a draw-down of precipitation chances north of
Highway 50. Still, Saturday night could bring light snowfall
accumulations to Highway 395 in Mono County, mainly above about
Sunday and Monday, an upper ridge axis slowly advances from northern
California into eastern Nevada. Chances for rain and high elevation
snow slowly increase for northeastern California and the northern
Sierra later on Monday and Monday night as a system over the
Pacific approaches. Temperatures Monday are expected to rise into
the 60s for the lower valleys of western and west-central Nevada,
with some chance for a few spots east of Reno to near 70.
.Long Term...Tuesday through Friday...
Stormy pattern remains likely next week as large scale low pressure
moves into the western U.S. bringing periods of rain and snow back
to the region. The midweek event we have been watching continues to
get closer in time, but the message remains the same. Predictability
in the lee of the Sierra remains low, and the forecast on the east
side of the crest into the Tahoe Basin and western Nevada remain
much more uncertain than it is on the west slopes of the Sierra.
Why? The potentially cutoff nature of this system leads to the
possibility for this system to slide south along the California
coast, driving the best moisture and dynamics into southern
California. This also increases the chances for the cold front to
either get hung up along the Sierra or allow the coldest air to
split south around the region. While many model runs still show
the low coming directly over the central Sierra, some of the GFS
runs over the past few days hint at the possibility that the low
could split south as it moves in.
This system is going to continue to be a challenge to forecast for
the lee of the Sierra crest, including the Tahoe Basin. It is
likely we are going to get rounds of rain and snow in the Sierra
and chances for colder storms continue as the week go on; however,
spillover precipitation and the rate at which the snow levels
fall are still quite uncertain through the first few waves of this
storm. Right along the crest there is a good chance to see 1-3"
of QPF, but how much of that precipitation makes it past the crest
and how much snow is able to accumulate at the lower elevations
has a very wide spread.
With all that said, if you are traveling over the Sierra Tuesday
through next weekend, watch the forecast carefully and expect to
encounter winter driving conditions. -Zach
Most of Saturday will be VFR with light winds...but another weak
system is shown by model guidance passing to the south Saturday
evening into early Sunday morning. This is likely to bring light
snow to the central Sierra with lower cigs/vsbys south of Highway
50, and possibly as far north as Interstate 80 in the Sierra.
Any accumulations for northern Sierra/Tahoe terminals Saturday
night are expected to remain very light (less than 1 inch), with
terrain obscuration and possible sub-minimum VIS in -shsn for KTVL
the main concerns. Farther south around KMMH, major reductions in
CIGS/VIS in -sn are expected...with up to 2 inches of snowfall
For western NV and northeast CA terminals Saturday night, no
major concerns with mainly VFR cloud decks north of Walker Lake;
however, there is a low-end chance for MVFR decks with a period of
-shsn for KHTH and K043 (Yerington).
Ridging rebuilds briefly for Sunday into Monday before a return
to unsettled weather through much of next week. -Snyder/XX
For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Blacksburg VA
847 PM EST Fri Mar 9 2018
An upper disturbance pushes across the area late tonight, with
a frontal boundary situated across the Tennessee valley into the
central Plains. Low pressure will move from the Gulf Coast
States and Tennessee Valley Sunday across the Carolinas and off
the coast into Monday.
.NEAR TERM /THROUGH SATURDAY/...
As of 840 PM EST Friday...
Evening soundings continue to show dry air from the surface to
7h this evening with very low dewpoints lingering per observations
showing values in the teens. This ahead of deepening moisture
to the west with initial return flow along a surface warm just
west of the mountains. However expect most of this initial
precipitation to remain aloft with gradual moistening of the
column from west to east overnight. This depicted well by the
latest HRRR that keeps most snow to the west until after midnight
when the main wave aloft arrives. Guidance continues to differ
on snowfall amounts across the far west and then whether or not
any snow crosses out east early Saturday. Since appears that a
band or two could work farther east over the west and along
Route 460 out east, included perhaps a coating of snow toward
morning in these spots. Otherwise slowed onset of pops up some
this evening given dry air and left totals in the 2-3 inch range
where the advisory continues. Lows mostly 20s west to 30s east
although may take until light snow arrives to get that cold
under increasing cloud canopy espcly during the early morning
Previous discussion as of 320 PM EST Friday...
A mid-level disturbance/clipper will track over Kentucky this
evening, then moves over the southern Appalachians late tonight into
Saturday morning. Increasing warm air advection aloft, jet dynamics
and backing low levels winds will help produce light snow across the
mountains from midnight tonight until noon tomorrow. This
disturbance will exit the area by early afternoon as snow changes to
rain but precipitation chances will be diminish by then. Backing winds
ahead of this disturbance may also bring a small chance for snow
east of the Blue Ridge Saturday morning. However, warm ground and
warming temperatures, not much if any will accumulate.
We currently have very dry air (dew points in teens) over the region
this afternoon. Saturation of the atmosphere will take some time,
but eventually snow will move into the area. Models are focusing
highest snowfall totals from Mercer County WV to Ashe County NC
where 1 to 3 inches are possible, local higher amounts possible on
ridgetops such as Mount Rogers and Whitetop. In this area we will
keep a Winter Weather Advisory up through Saturday morning. Areas
just east and south of the advisory (New River Valley to the NC High
County) a dusting to an inch of snow is expected.
Skies have cleared this afternoon and should be able to maintain
into this evening. With a dry environment, temperatures will drop
quickly into the 20s across the mountains and into the low to middle
30s east this evening. Temperatures will begin to creep up as high
clouds and southwesterly flow enter the area. With the system
exiting the area during the afternoon, high temperatures Saturday
will range in the 40s west to the lower 50s east.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 230 PM EST Friday...
Upper pattern this morning showed that the 12z GFS and CMC
initialized slightly better than the ECMWF. Still there is much
uncertainty with the track and strength of the low that affects us
late Sat night through early Monday. The GFS has shifted weaker with
the low which is different from the last 2-3 runs. The GEFS mean has
been more consistent taking the low from the TN/AL border Sunday
morning to off the NC/SC coast by evening, then turning the low
Questions also arise in temperature profiles, where the 8h zero line
is and amount of precipitation.
Leaning toward a blend of the ensemble with the GFS and ECM, but
again at this point still looking at potential for several inches of
snow, especially the higher elevations. Will still have to see how
the upper system migrates southeast from the northern Rockies and
how far away the downstream low over Nova Scotia moves, along with
another shortwave diving into the Great Lakes by late Sunday and how
it interacts with the wave over the Gulf Coast states.
With a low confidence forecast, no headlines will be issued, but
maintain in the HWO. The snow to liquid ratios (SLR) will be a big
player and if its warmer, it will be harder to more accumulation,
unless the rates are higher. For now leaning toward a general 1 to 3
inch snow in the mountains, then north of a Roanoke River to
Lynchburg line. Locally higher amounts to 5 inches on the higher
If you have colder air to keep the SLR around 10 to 12 to 1, then
may see potential for 5 to 8 inches.
Detailed wise, look for mainly rain to move into NC after midnight
Sat night, reaching a Marion, VA to Chatham, VA line by dawn, with
chance of rain/snow mix to the north. Temps warm as we head through
the day Sunday, but not too much. Precip may actually hold temps
down lower than forecast, but looking at temps from the mid 30s toe
around 40 in the mountains, and north of the Roanoke to Charlotte
Court House line in VA, with lower to possibly mid 40s over
southside VA into the NC foothills/piedmont.
Temps fall Sunday night as winds turn more north and expect a
deformation zone to bring the best threat of snow to along/west of
the mountains, to north of Stuart to Appomattox. Snow will taper off
by late Monday morning with residual rain and snow showers into the
afternoon. Highs Monday will be in the mid to upper 30s west, to
lower 40s east.
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 1235 PM EST Friday...
Looking past the exiting storm system Monday, strong low will hang
around New England in omega blocking pattern, with a strong
shortwave swinging into the area midweek. At the moment expect snow
showers in the mountains through midweek with potential for flurries
as far east as the Blue Ridge, especially Wednesday. Will gradually
see upper ridge slowly shift east into the MS Valley by Thursday-
Friday with a moderating trend in temps along with dry weather.
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
As of 610 PM EST Friday...
VFR conditions will prevail into this evening before ceilings
quickly lower to MVFR over far western sites after midnight and
then east to the Blue Ridge before daybreak. This will also be
followed by a swath of snow that will result in vsbys lowering
to MVFR or worse west of the Blue Ridge by dawn Saturday. Some
of this precipitation along with MVFR ceilings may spill east of
the mountains with patchy light rain possible at KDAN and
perhaps a brief rain/snow mix at KLYH early Saturday. All
precipitation should transition to rain across the region by
mid to late morning Saturday before ending in the afternoon.
This may also allow cloud bases to lift to VFR at most sites
excluding KBLF where upslope flow in the wake of the exiting
system looks to keep at least MVFR in place.
VFR trend should continue Saturday night with western locations
hanging onto periods of MVFR, while ceilings may lower back to
sub-VFR across southern sections late ahead of the next low
Extended Aviation Discussion:
A stronger winter storm system looks to bring widespread sub-
VFR and wintry precipitation late Sunday through Monday night
pending the track and strength with later model runs.
Storm system exits on Monday night with VFR returning outside
of lingering upslope low clouds and flurries over the mountains
where MVFR conditions could occur. Added upslope snow showers
will then likely cause sub-VFR to linger mountains into Tuesday
and Wednesday where aided by another round of northwest flow
into the middle of next week.
As of 800 PM EST Friday...
The Mount Jefferson NWR remains off the air due to a power
outage that damaged some electrical equipment. This equipment
is not expected to be fixed until this weekend or Monday.
The Richlands NWR is also off the air this evening likely due to
a phone line problem.
VA...Winter Weather Advisory until 8 AM EST Saturday for VAZ007-009-
WV...Winter Weather Advisory until 8 AM EST Saturday for WVZ042.