Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/05/17
Area Forecast Discussion
National Weather Service Gaylord MI
1010 PM EST Sat Feb 4 2017
.UPDATE...
Issued at 1010 PM EST Sat Feb 4 2017
Synoptic snow has been rather slowly invading northern MI this
evening. Antecedent dry air below 700mb (see 00z APX sounding,
though some of the dry air had eroded by then), and a generally
unimpressive system, account for this. However, significant lake
enhancement has been evident on radar, both in individual elements
moving ne-ward over northern Lake MI, and the broader tendency for
better returns to hang back across the east half of upper MI.
Upstream reports are supportive of western Mack Co already in the
2-4 inch range. Outside of eastern upper, vsbys (and thus snowfall
intensity) have generally not tanked to any great deal, except
over Beaver Isl and just recently at PLN. So lake enhancement to
starting to be a bigger factor along the nw lower MI coast, as
surface low moves from MN to Superior and 1000-850mb winds veer a
bit.
Will kick snowfall totals higher in eastern upper, especially
Mack Co west of I-75, where 4-6 inch totals are reasonable. Will
also push Emmet Co a touch higher, which is just enough to kick
them into advisory territory. Rap runs have been consistently
targeting them to see healthier see, especially with the 2nd batch
of forcing which is now pushing into far nw WI and arrives here
late in the overnight.
No other major changes for now, though will be cautiously
watching the rest of the nw lower coastal counties.
&&
.NEAR TERM...(Tonight and Sunday)
Issued at 331 PM EST Sat Feb 4 2017
High impact weather potential: More accumulating lake enhanced snows
for primarily eastern upper. Some blowing snow.
Pattern synopsis and forecast:
Sfc high pressure was settled in over mid Atlantic states while a
sfc low pressure/clipper resided in South Dakota. This clipper was
associated with a shallow/weak mid level wave, possibly also tied to
a positively tilted wave coming through Manitoba. DPVA, low level
convergence and some right entrance region upper divergence was at
play in helping develop some light snows across the Dakotas. There
is also another weak mid level trough working across Wisconsin with
low to mid level WAA being that primary forcing mechanism to produce
another area of light snow. Across nrn Michigan, some of this WAA
has taken it`s toll on the lake effect light snows/flurries from
earlier this morning, with no snows or even low level clouds seen on
satellite/area observations. Rather, just a thickening of mid and
upper level clouds this afternoon. Highs have made it into the
middle 20s to even a few lower 30s.
Kind of a tricky forecast as there are some things at play that
complicate matters. The first mid level trough and WAA spread across
nrn Michigan through this evening bringing what could be the first
of two rounds of synoptic light snows. Earlier data hinted at this
first round of snow resulting in some dynamical cooling that would
have resulted in the redevelopment of lake effect in SW flow
regimes. This does not look as prolific, with only some very low end
12-13C delta t`s. Regardless, all data sets still suggesting
re-energizing lake effect processes while the light synoptic snows
overspread the north woods. There may be something of a break in the
action, outside of the lake enhancement, until the second mid level
trough arrives late this evening/overnight and beefs the lake
response up again. This batch of forcing and deeper moisture slides
by shortly after daybreak, and by the time all is said and done,
still looking at 3-5 inches along the immediate NW lower lakeshore
and eastern upper, with the higher amounts west of Interstate 75 in
eastern upper. The advisory looks solid for eastern upper, but will
continue to leave the NW lower counties out of any headline, as it
may be confined to just the immediate lakeshore. Winds will be
decently gusty coming off the lake too, so areas of blowing snow can
be expected.
The system cold front follows through morning, with H8 temps falling
to -12C to -16C. While moisture is fairly scant, feeling pretty good
about the development of light lake effect snows in NW flow regimes.
Snowfall with this activity expected to be a half inch or less.
Lows tonight not going very far, in the lower to middle 20s. Highs
Super Bowl Sunday, in the middle 20s to lower 30s in downsloping
areas of NE lower.
&&
.SHORT TERM...(Sunday night through Tuesday)
Issued at 331 PM EST Sat Feb 4 2017
...More light snow Sunday night into Monday; stronger system arrives
Tuesday...
High Impact Weather Potential...A couple rounds of light snow are
expected...the first Sunday night into Monday across the north and
the second on Tuesday. Some freezing drizzle/rain will be possible
Monday night into early Tuesday.
Pattern Synopsis/Forecast...Low level northwest flow will back to
southwest Sunday night as high pressure dives south of northern
Michigan. This will bring an end to any lingering lake effect snow
showers early Sunday night. A northwest-southeast oriented
baroclinic zone then develops along a surface trough over northern
MI early Monday morning, with snow overspreading eastern Upper and
Tip of the Mitt before daybreak in response to WAA and frontogenetic
forcing...with some additional support coming from the right
entrance region of a 300mb jet streak. Only light amounts of snow
expected from this activity with 1 to 2 inches possible across far
northern Chippewa County. Forecast soundings show the column drying
out somewhat above 800mb for the first half of Monday night, which
will translate into a loss of ice in the clouds and hence the
possibility of some freezing drizzle.
Attention then shifts to the probable phasing of two systems over
the Midwest Monday night into Tuesday. A digging northern stream
shortwave will quickly move from the Pacific Northwest into the
Upper Midwest during this timeframe while a southern stream
shortwave lifts from the Central Plains into the Great Lakes region.
At the surface, this will translate into a rapidly deepening low
that will track from northern IL Tuesday morning through the Thumb
by Tuesday evening. Max wet bulb temps from 0-3km will start to rise
Monday night from south to north, with our southern two tiers of
counties ranging from 1 to 3C by 12Z Tues. The initial lack of ice
early Tuesday morning will spell a chance of freezing drizzle/rain
as precip with this system overspreads the area. But once the column
saturates aloft around daybreak Tuesday, expect the precip to
transition over to snow across most of the area. Forecast soundings
show only a slight warm nose aloft, so at this time am not sold on
much in the way of sleet or freezing rain during the day across our
south. The potential for a wintry mix is there for our south, but
its looking like more of a transition to mainly snow across the
north and rain across our far south (where temps will climb into the
mid 30s). Snowfall amounts on Tuesday will generally range from 1 to
3 inches mainly north of M-72. Wind not expected to be an issue on
Tuesday, as the pressure gradient will not be too strong with the
center of the low passing just to our south.
Primary Forecast Concerns...First, there is some question as to how
long Monday`s snow will linger over the northern half of the
forecast area. The NAM/CMC remain the progressive solutions,
carrying the best forcing east of the area by early afternoon. On
the other hand, the GFS/ECMWF are much slower to lift the best
forcing northeast of the area, with light snow lingering into the
evening across eastern Upper.
Being 2 to 3 days out from Tuesday`s system, general model consensus
is decent enough for handling this outside-climatological-norms
(MSLP +2 to 3 sigma) system. However, there is still considerable
spread in the possible track between deterministic models as well as
the GEFS, CMCE, and ECWMF ensemble members. The GFS and ECMWF push
warmer 850mb temperatures (0C or warmer) all the way to the Straits,
while the NAM and CMC are a tad colder. Of course, this will have
ptype ramifications and will need to be pinned down by upcoming
shifts.
.LONG TERM...(Tuesday night through Saturday)
Issued at 331 PM EST Sat Feb 4 2017
After a prolonged period of well above normal temperatures, there
looks to be a pattern change taking shape through the extended
period. Temperatures will still be above normal going into mid-week,
but the broad riding setup across much of the southern CONUS will
begin to shift westward as height falls work their way from the
northern Plains and through the Ohio Valley. By the end of the
extended period, there will be noticeable troughing through the Great
Lakes and into the Tennessee Valley, with amplified ridging spanning
from the desert SW through the Great Plains. This should help to get
temperatures back into more normal ranges as we go into the weekend.
With shortwaves moving through the pattern, wouldn`t be surprised to
see some scattered to isolated showers through the week but nothing
that looks to be producing large amounts at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 702 PM EST Sat Feb 4 2017
Snow slowly advancing into northern MI this evening, ahead of low
pressure in MN. Transition to IFR conditions expected to occur
shortly at PLN/TVC/MBL, later on at APN. Snow will be less
heavy/briefer at APN, due to lack of enhancement from Lake MI.
Duration will be lengthier near Lake MI, with one wave of snow
this evening and another late tonight. Snow-liquid ratios around
16-1 are expected. Improvement to MVFR and then VFR expected
during the day Sunday.
Ongoing south winds will veer sw tonight, and nw Sunday afternoon,
remaining somewhat brisk throughout.
&&
.MARINE...
Issued at 331 PM EST Sat Feb 4 2017
Gusty SW winds may tap low end gale force along the Lake Michigan
shoreline, especially through the Manitou Islands this evening. Have
opted to just mention isolated gales in the forecast rather than
issue a Gale Warning. These wind swing around out of the W/NW late
tonight into Sunday behind an area of low pressure and cold front.
SCA conditions continue Sunday/Sunday evening.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 7 AM EST Sunday for MIZ008-015.
LH...SMALL CRAFT ADVISORY until 6 PM EST Sunday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 6 PM EST Sunday for LMZ323-341-342-
344>346.
LS...NONE.
&&
$$
UPDATE...JZ
NEAR TERM...SMD
SHORT TERM...MEK
LONG TERM...ALM
AVIATION...JZ
MARINE...SMD
Area Forecast Discussion
National Weather Service Columbia SC
1054 PM EST Sat Feb 4 2017
.SYNOPSIS...
A cold high pressure center will move off the Virginia and
North Carolina coast tonight. Pressure ridging will extend along
the Gulf Coast Sunday and Monday. An approaching cold front
Tuesday will move into the forecast area Tuesday night or
Wednesday. Air mass modification and the southerly flow ahead of
the cold front will bring warmer weather.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Surface high pressure in the mid-Atlantic will move offshore
tonight allowing moisture to spread steadily inland in the form
of low clouds. Mostly clear skies across the central and
northern Midlands earlier tonight has allowed temperatures to
drop below freezing. How far northwest the stratocumulus will
push is uncertain. In addition, models suggest increasing mid-
level clouds early Sunday morning as a mid-level trough
approaches. These trends in cloud cover may mean the central
Midlands has already reached its low for the night as net
radiational cooling is hindered.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Weak surface high pressure will move off the coast Sunday.
A deep westerly flow from the surface to aloft develops with
increasing thickness values. This will lead to a warming trend
with highs in the upper 50s and lower 60s for Sunday.
Surface high pressure over the upper Midwest will bridge with
a suppressed high along the Gulf Coast states providing dry
conditions Sunday night.
Another cold night expected Sunday night with lows in the 30s
although increasing clouds may impact overnight lows and will
provide a gradient in temps with warmer values in the CSRA and
southeastern Midlands. Sunday will be slightly warmer than
today as the air mass modifies and surface high weakens.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Progressive 500 mb upper flow pattern expected through the
extended forecast period leading to fast moving disturbances
across the region with lower than normal confidence in timing.
Broad surface low development will occur over the northern
Plains while the surface ridge over the forecast area shifts
offshore and the Gulf of Mexico opens to southerly flow. This
will allow moisture to increase across the area again with
precipitable water values pushing over an inch by Monday
evening. Isentropic lift also increases late Monday and Monday
night as warm advection develops to our west and shifts over
the area Monday evening and continues into Tuesday as the
surface low deepens as it moves into the Great Lakes region. A
positively tilted digging upper trough will drive a cold front
through the forecast area Wednesday. Will carry gradually
increasing pops across the region Monday night through Tuesday
with the highest pops mainly Tuesday night ahead of the front.
Surface high pressure will build over the region behind the
front Wednesday night and remain over the forecast area
Thursday providing dry weather. Reasonable agreement from the
medium-range models showing a fast moving clipper system diving
through the western Ohio Valley Thursday and crossing the
forecast area Thursday night into early Friday. Moisture may be
limited with this system but temperatures may be cold enough to
support a few flurries especially across the northern counties.
However, this scenario is not a favorable one for accumulating
precipitation. Temperatures through the period will be above
normal through Wednesday, near normal Thursday, below normal
Friday, then back above normal by the weekend.
&&
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
A dry high pressure center will move off the Virginia and North
Carolina coast tonight. The high will maintain dry conditions
and VFR conditions at the terminals through most of tonight. As
the high shifts eastward an onshore flow will bring increased
moisture into the forecast area late. The near-surface layer
should remain too dry for fog. However, most of the guidance
indicated a VFR ceiling developing before 12z. Some of the
guidance such as the NAM MOS had MVFR ceilings developing
mainly at the southern and eastern terminals. This may be
correct because satellite displayed moisture not far to the
southeast across southern Georgia and near the South Carolina
Coast. The HRRR displayed MVFR ceilings remaining south and east
of the terminals. Based on the initial dryness and model
forecast of little isentropic lift and h85 westerly flow we
leaned toward the more optimistic guidance. Followed the NAM and
GFS MOS for the wind forecast with wind light and variable
tonight and west-southwest near 10 knots Sunday.
EXTENDED AVIATION OUTLOOK...Restrictions possible Monday night
through early Wednesday. Strong/gusty winds possible Tuesday
night into Wednesday as a cold front crosses the region.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
Area Forecast Discussion
National Weather Service Grand Forks ND
931 PM CST Sat Feb 4 2017
.UPDATE...
Issued at 928 PM CST Sat Feb 4 2017
Light snow has diminished over southeastern zones and will be removing
POPs after 04Z. Clearing over the northeast is resulting in latest
HRRR guidance dropping overnight lows to near 10 below across
Towner County, which seems reasonable given the lightest winds
across the CWA. Will adjust temps per latest hi-res model guidance
and find tune sky cover grids for clearing ahead of more clouds
cover coming from upstream, per latest 3.9 micron imagery.
UPDATE Issued at 648 PM CST Sat Feb 4 2017
Skies are clearing over the northwest and snow has pushed just
east of the valley. The clearing will be filled back in by the
late evening hours as more mid clouds move into northwest ND from
eastern MT. Have adjusted sky/POP grids accordingly.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 314 PM CST Sat Feb 4 2017
Next short wave which was not advertised too well is moving into
eastern ND at mid aftn. Area of snow with this feature moving
quickly east likely producing 1 inch or less of snow. Did up pops
for this feature. After this system a break as colder air moves
back south later tonight into Sunday morning. Next system to
spread some light snow into DVL basin Sunday aftn. 120kt 300 mb
jet in place so systems are moving quite fast.
.LONG TERM...(Sunday night through Saturday)
Issued at 314 PM CST Sat Feb 4 2017
Main concern throughout the period will be the winter storm
potential with the late Monday night/Tuesday system and associated
impacts.
Yet another shortwave embedded in the relatively zonal upper flow
will keep light snow chances lingering across northern portions of
the area Sunday night and into early Monday. The strongest forcing
and associated area of precipitation continues to be generally along
the international border with maybe an inch or two of accumulation.
The region should then see a brief break for the daytime hours on
Monday as low pressure begins to organize east of the Rockies.
Models continue to be in pretty good agreement with the late Monday
night/Tuesday system with the main low pressure center situated near
the Iowa/Missouri border by 06z Tuesday. As this system deepens and
propagates towards the lower Great Lakes, the main inverted trough
axis will slowly shift from west to east across the region. A broad
area of accumulating snow looks likely with some fine tuning still
needed to amounts. GEFS plumes continue to show a fairly large range
of possibilities regarding QPF but have generally been pretty
consistent with the highest amounts across the north. Lastly, as the
low deepens and high pressure noses into the western Dakotas behind
it, a fairly tight pressure gradient will persist across the region.
Although winds don`t look to be incredibly strong for a long period
of time, there should be enough to blow things around, both while
snow is falling and possibly for a time after the heaviest snow has
ended.
Colder air will then return as surface high pressure briefly builds
in midweek. Temperatures look to struggle to get above zero on
Wednesday with wind chills dropping back into the -30s during the
nighttime and early morning hours. The cold blast will be short
lived, however, as 850 mb temperatures look to warm to above zero by
the end of the work week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 648 PM CST Sat Feb 4 2017
Clearing skies over northeast ND prompted early amendment to
GFK/DVL as cleaning came across the area quicker than expected.
VFR deck will fill area back in later this evening. MVFR shall
improve across southern valley and northwest/west central MN as
well, so expect more AMDs expediting this over the next couple of
hours. Models too aggressive holding on to MVFR throughout the
night, so hopefully 00Z runs will have a better handle on latest
trends.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Speicher
SHORT TERM...Riddle
LONG TERM...Lee
AVIATION...Speicher
Area Forecast Discussion
National Weather Service Lincoln IL
905 PM CST Sat Feb 4 2017
.UPDATE...
Issued at 905 PM CST Sat Feb 4 2017
A band of mid clouds associated with the approach of a weak
trough will continue to quickly advance across central and eastern
Illinois this evening. The back edge of the clouds has already
reached near the I-55 corridor as of 9 pm. Timing tools show the
clearing should reach the Indiana border toward midnight. Have
updated the sky grids to account for this faster clearing.
The surface trough passage will lag the clouds by 8 to 10 hours
per the latest HRRR and RAP output. That will delay the wind shift
from south winds to west winds until later tonight. Winds in a few
areas have remained gusty as the cloud band has worked its way
eastward, but additional weakening should develop the rest of the
night as the trough nears the area. With weakening winds expected
later tonight under clear skies, have trimmed a degree or two from
forecast lows since we are only 3-4 degrees above those numbers
already this evening, in some areas.
Looking at a sunny and pleasant day to finish out the weekend,
with warmer temps than Saturday.
Updated forecast info will be available shortly.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 247 PM CST Sat Feb 4 2017
Brisk southerly winds will continue into this evening as the
pressure gradient between a high over West Virginia and a low
tracking across South Dakota remains tight. The gradient will relax
later tonight as a trailing surface trough approaches from the west,
leading to decreasing winds overnight. Skies will initially be
overcast: however, a rapid clearing trend will be noted from west to
east across the area this evening. Based on satellite timing tools,
think the entire KILX CWA will be clear by midnight. Due to
southwesterly flow, overnight lows will be several degrees warmer
than last night...with readings remaining in the upper 20s and lower
30s. Once the trough passes, light W/NW winds will be noted on
Sunday, which should act to mitigate the warming trend. Despite
full sunshine, have gone a couple degrees below guidance for
highs...with afternoon temps mainly in the lower to middle 40s.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 247 PM CST Sat Feb 4 2017
High pressure ridging will move off to the east Sunday night and
allow southerly winds to return to the area and bring waa and
moisture advection back into the CWA, just ahead of the next system
coming in for the beginning of the work week. The models continue to
differ on the timing of the start of the precip in the area Monday,
but consensus is that the chance of precip will begin Mon afternoon
and then quickly increase for Monday night. Though the mid level
flow remains fast zonal, the surface low begins to deepen just west
of the area Monday night and continues this trend into Tuesday. The
associated cold front with this system will quickly move through the
CWA either Monday morning or afternoon...depending on which model is
looked at. Showers and possible thunderstorms should develop ahead
of this front in the warm sector, beginning Monday night. SPC Day 3
outlook suggests a marginal risk of severe weather in southern IL,
that does include most of southeast IL, but remains south of a
Taylorville to Paris line. The main threat would be Monday night and
just be hail due to the steep lapse rates forecast by both the GFS
and NAM during this time period. As the system deepens, the threat
of storms will shift north for Tue morning and include the entire
CWA...based on the instability parameters in the models. This area
of convection will begin to shift east as the front moves through
the state. Again, SPC is indicating the possibility of some severe
storms on Tue, but mainly in the TN and OH valley areas due to the
timing of best instability during the day just ahead of the front.
The only area that could see some severe storms early in the day
would be in southeast IL before the front moves through. So, have
thunder mentioned in the forecast for Monday night over the whole
area, and then Tuesday in the east and southeast. After this system
passes the area and the low pressure area moves off into the Great
Lakes region, wrap around moisture will advect into the area, but
only in the northern parts of the CWA. Pops across this area will
mostly be in the slight chance range, which will not get mentioned
in the worded forecast this afternoon.
Cooler and dry weather will then follow this system through
Wednesday night as a high pressure builds into the area for the
middle of the week. Some of the ensemble models are trying to bring
precip/light snow into the area Thursday, but given that a large
high pressure area should be over us, think the chance of precip is
going to be small...so will not see any precip mentioned in the
forecast for Thur. This dry weather will continue through Friday
evening as this high pressure settles into the southeastern US
Friday. Models then having issues with trying to bring more precip
in for Friday night and Sat. This seems unlikely as the next weather
producer should be north of the area, but given this is 7 days out,
will let the ensemble forecast ride for now; it will likely change a
few more times before then anyway.
Temps will get quite warm for Monday and Tue ahead of the next
weather system, then cooler for Wed and Thur, quickly followed by
warmer temps for Fri and Sat. Given the fast zonal flow pattern we
are currently in, these type of temp swings are not uncommon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 600 PM CST Sat Feb 4 2017
There is a high likelihood that VFR conditions will prevail
through the entire 00z TAF period. A weak disturbance will
continue to bring low VFR clouds to the central Illinois
terminals early this evening. Latest HRRR suggests the potential
for MVFR ceilings as the back edge of the clouds progresses
across Illinois. However, no MVFR ceilings currently exist
upstream across eastern Iowa/Missouri into western Illinois.
Based primarily on satellite timing tools...have lowered ceilings
to 5000ft for this evening. After that...it appears the clouds
will depart from west to east across the area by mid to late
evening, with mostly clear conditions expected overnight into
Sunday morning. Winds will initially be quite strong from the
south this evening...with occasional gusts to 25kt. Winds will
gradually veer to the west and and remain 10-15kt later tonight,
as a trough of low pressure approaches from the Plains.
Winds will veer to the NW later Sunday morning with speeds holding
in the 10-15kt range. Little in the way of cloud cover is expected
on Sunday.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...Shimon
Area Forecast Discussion
National Weather Service Jackson MS
912 PM CST Sat Feb 4 2017
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Clouds continue to increase late this evening, with some light rain
falling across portions of the northwest. Expect chances for light
rain later tonight across much of the area, with low temps in the
40s. The only change to the current forecast was to adjust pops for
this evening based on latest HRRR and radar trends. /27/
Prior discussion below:
Tonight and Sunday...Cloud cover to the west has been slow to make
much progress east today due to the substantial dry airmass in place.
Still, continued isentropic ascent will eventually win out and
provide enough moisture/warm air advection for some light
precipitation to break out over northern portions by midnight and
increase southward toward dawn.
Though baroclinic setup north of the LA/MS coastal frontal boundary
looks sufficient for isentropic ascent Sunday, relatively weak wind
fields in the saturated layer looks to only support a light
rain/shower event. This is seen readily in the HRRR reflectivity
guidance and with the light QPF in the GFS and NAM.
Temps overnight will not be as cool as last night due the increased
cloud cover, however, boundary layer cooling from the introduction
of moisture should be sufficient to cool most areas back at least
into the 40s. As the warm front moves northward Sunday, maximums in
the 60s look possible over the southern half where otherwise a cool
day (as will be the case in the north) would have been in store./26/
Sunday Night through Saturday...For the start to the new work week,
focus will be on a sequence of shortwaves moving eastward across the
country and the chances for severe weather that may accompany them.
Sunday night into Monday, showers with perhaps a few rumbles of
thunder will be focused primarily along a lifting warm front in the
northern portions of our forecast area. Expect temperatures to warm
into the low to mid 70s during the day Monday with continued
southerly flow at the surface. Chances for thunderstorms will
gradually increase across the region throughout the day and into
Monday night ahead of the first approaching shortwave. Modest mid-
level height falls should spread eastward into the overnight hours,
while at the surface a low deepens and lifts from the central High
Plains toward the Midwest. Instability will increase along a corridor
just west of the forecast area as warm, moist air is drawn northward
Monday night. Most thunderstorm activity late Monday night should
therefore be confined to parts of Arkansas and far northern
MS/western TN.
Model guidance presents a slightly faster scenario with this first
wave than was apparent over the last few cycles, but the consensus
still indicates a window of opportunity for severe thunderstorms to
develop in our forecast area on Tuesday. A faster timing for this
shortwave would limit the peak heating and instability available to
storms firing earlier in the day Tuesday, while a slower wave passage
would keep storms capped until greater instability could be achieved.
MLCAPE values between 500 to 1000 J/kg are expected during the day,
with 50-60 kts of 0-6 km shear helping to organize and sustain
updrafts. Mid-level lapse rates near 7 to 8 C/km early in the day
will be tempered somewhat with weak height rises and warming on the
backside of the shortwave by the afternoon. 0-1 km shear of 25-35
kts and SRH of 200-300 m2/s2 suggests a possible threat for
tornadoes, particularly if storms are ongoing early Tuesday morning
when LCL heights are lower. Increasing LCL heights instability with
daytime heating suggests more of a hail and damaging wind threat
during the afternoon hours. Will keep mention of a Limited severe
and tornado threat in the Hazardous Weather Outlook for an area along
and north of Interstate 20 Tuesday into Tuesday night.
A cold front will push into the forecast area by Tuesday night,
bringing drier air and an end to shower and storm chances from north
to south. Showers may linger across southern portions of the forecast
area into Wednesday, but the remainder of the week should be dry. It
looks like moisture will be limited before another quick moving
shortwave slides across the country Thursday into Friday, but its
passage should keep temperatures from warming too far above normal by
the end of the week. /NF/
&&
.AVIATION...
00Z TAF discussion: VFR conditions were observed at all TAF sites at
2330Z but cloud cover wl cont to increase from the west with a
gradual lowering of cigs. Cigs will lower to MVFR at most locations
between 06Z and 09Z, with HBG remaining VFR. Some -shra will begin
spreading in vcty of the TAF locations after 06Z with -ra expected to
cont through Sun. Cigs wl remain MVFR over the se Sun but lower to
IFR category elsewhere by 17Z and cont Sun aftn. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 44 64 54 76 / 36 53 47 12
Meridian 42 59 51 75 / 29 50 48 16
Vicksburg 45 65 56 75 / 40 50 47 13
Hattiesburg 44 67 54 77 / 10 35 20 11
Natchez 48 67 58 76 / 32 50 28 11
Greenville 43 57 52 71 / 49 58 65 24
Greenwood 42 60 52 72 / 50 57 68 26
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1055 PM EST Sat Feb 4 2017
.UPDATE...
Issued at 1055 PM EST SAT FEB 4 2017
Based on the latest HRRR and some virga returns showing up on
radar with more to the southwest have updated the PoPs and Wx
grids to allow for more drizzle and freezing drizzle deeper into
the CWA through dawn. Also adjusted temperatures through the rest
of the night not expecting much more drop off with a mid level
deck of fairly thick clouds in place. Accordingly, have updated
the ZFP to adjust for the Wx and T changes for the remainder of
the night. The grids have been sent to the NDFD and web servers.
UPDATE Issued at 745 PM EST SAT FEB 4 2017
00z sfc analysis shows high pressure off to the east of the state
with low pressure moving into the Central Plains. This has set up
good conditions for a ridge to valley temperature split this
evening and we can see that showing up in the latest obs as upper
20s are noted in the eastern valleys while mid 30s exist on the
ridges. Winds have swung to the southeast but remain light.
Meanwhile, dewpoints are still quite dry mainly in the single
digits and teens. Passing high clouds will not slow the
temperature difference this evening - and not until lower clouds
arrive in the early morning hours are they expected to mix out.
This is also the time frame for any potential freezing drizzle -
mainly south of the Mountain Parkway - as supported by the latest
HRRR. Will continue to monitor this concern going forward, but for
this update have just made adjustments to the near term grids to
account for the latest obs and trends. These have been sent to the
NDFD and web servers.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 313 PM EST SAT FEB 4 2017
Cirrus continues to stream in north of Mountain Parkway this
afternoon ahead of a subtle upper level trough moving across the
upper Midwest into the western Great Lakes. Surface high pressure
will slide east into the mid-Atlantic, allowing winds to veer
south/southwesterly through tonight, maintaining a warming trend.
While temperatures will top out in the mid-upper 30s north of the
Interstate 64 corridor this afternoon, the western fringe of the
aforementioned surface ridge will likely hold influence long enough
for at least the more sheltered valleys of far eastern Kentucky to
decouple preceding a period of increasing winds/lowering clouds this
evening/tonight. This will set the stage for a period of below
freezing temperatures tonight into early Sunday morning before warm
air advection brings all of eastern Kentucky above freezing within
an hour or two after sunrise. A layer of saturation just off the
deck to about 850 mb near the 0C isotherm will lead to patchy
freezing and liquid drizzle late tonight into Sunday morning, with
all freezing drizzle expected to end by mid morning. Not expecting
any measurable precipitation given this shallow saturation and
rising heights aloft taking place by early morning with passage of
the anemic trough axis. However, a light glaze will be possible in
areas that do receive freezing drizzle.
Southwest winds will become gusty later Sunday morning through the
afternoon as a surface low deepens across Ontario and Quebec.
Continuing warm air advection will warm temperatures further,
although lingering low clouds should limit highs to the mid-upper
40s in the Bluegrass and generally upper 40s to lower 50s across the
remainder of eastern Kentucky. Weak shortwave ridging will keep the
warm air advection regime in play Sunday night while weak surface
ridging provides for a subtle ridge/valley temperature split with
valleys dropping into the low-mid 30s while ridges remain closer to
the mid 30s.
.LONG TERM...(Monday through Saturday)
Issued at 313 PM EST SAT FEB 4 2017
Period will begin with surface high pressure parked along and near
the Mid Atlantic Coast, with SW flow kicking in on the back side.
Meanwhile a front will stall out along and near the Ohio River and
this will interact with gulf moisture to bring overrunning precip
to the region through the afternoon on Monday. That said, thought
the model consensus seemed reasonable keeping the best chances
along and north of the Mountain Parkway. A deeper long wave trough
across the central US will eject east and deepen a surface low
across the northern Ohio Valley and Great Lakes. The trailing cold
front will be the lifting feature of concern here in eastern KY
Tuesday into Tuesday night. Some of the mass fields in the various
guidance products govern some differences in relation to timing
and evolution, and did lean to the blend for this period. Even so
did feel categorical POPs were not out of the question and
therefore made some adjustments in that direction. The guidance
does continue to pick up on some modest instability Tuesday
afternoon and evening with 300 to 400 J/kg of MUCAPE. Also the
wind fields remain strong with 850mb jet approaching 70 knots and
part of this wind energy could be mixed down along the front and
with any showers and thunderstorms that develop. Therefore main
threat with the storms at this stage of the forecast process will
be strong gusty winds.
The issues mentioned before about timing/evolution differences
will continue to present additional problems with guidance in the
remainder of the long term period. This is leading to overall less
confidence with regards to increasingly amplified trough that digs
into the SE US by Thursday into Friday. There have been wholesale
differences from run to run with embedded shortwave that quickly
moves SE out of the Pacific NW. The blend is all over the place
given the uncertainty and introduces ribbons of POPs with each
guidance idea. Given the lack of return flow seen having a
difficult time buying into the QPF suggested by the GFS/Canadian.
Right now leaning to the 12Z ECMWF solution which is dry and
therefore would be more in line with the lack of return flow and
increasing subsidence. The pattern presents us with another system
by next weekend and for now will leave as is with relation to
blended POPs.
This period we will be presented with more a roller coaster effect
temperature wise. That said, the temperatures climb into the low
to mid 60s for highs by Tuesday and in the wake of a a cold front
temperatures drop into the upper 30s to lower 40s for highs
Thursday. The high amplitude trough will move east quickly and
return flow will bring high temperatures right back into the upper
50s by next Saturday. Coldest nights will be Wednesday and
Thursday night with potential for a temp split if clouds clear. At
this point, will keep blends temps with uncertainty on clouds.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 720 PM EST SAT FEB 4 2017
VFR conditions to continue through this evening and most of
tonight ahead of a period of top-down moistening. Mid level
ceilings will be on the increase this evening, further lowering to
MVFR criteria around daybreak Sunday morning. Patchy freezing
drizzle will be possible early Sunday morning, although no more
than spots of light glazes are in the offing. Nonetheless, a
small potential for slick spots on area runways will exist prior
to temperatures quickly warming above freezing at all terminals
within an hour or two after sunrise. MVFR ceilings will likely
remain in place through 00Z Monday while southwest winds increase
toward 10 knots - becoming gusty Sunday afternoon.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...GUSEMAN
LONG TERM...DJ
AVIATION...GREIF
Area Forecast Discussion
National Weather Service Memphis TN
834 PM CST Sat Feb 4 2017
.DISCUSSION...Water Vapor satellite trends this evening indicate a
subtle but weak 700 mb shortwave trough moving through the Lower
Mississippi Valley this evening. This has resulted in the
development of rain showers across much of the area into the
evening hours. KNQA WSR-88D radar trends show most of the rain
showers have shifted south to areas mainly south of I-40. Latest
00Z WRF and HRRR suggest this activity will gradually shift
southeast overnight into Sunday morning. Will make some
adjustments to rain chances for the remainder of tonight and
adjust any other elements as needed to account for short term
trends.
CJC
&&
.PREV DISCUSSION... /issued 520 PM CST Sat Feb 4 2017/
UPDATE...
Updated to include the 00z aviation discussion.
PREV DISCUSSION... /issued 302 PM CST Sat Feb 4 2017/
DISCUSSION...
Clouds are quickly invading the Mid-South from the west this
afternoon. This has hindered temperatures from getting out of the
40s across portions of Northeast Arkansas. Winds have turned
around to the south this afternoon as surface high pressure has
shifted east. Expect low temperatures to occur this evening and
hold nearly steady overnight thanks to the cloud cover and warm
air advection. Also, expect some light showers to begin developing
generally along and south of Interstate 40 thanks to the warm air
advection.
Shower activity should diminish during the morning hours.
Although, portions of North Mississippi may continue to see small
chances for light showers throughout the day as a secondary warm
front moves into Central Mississippi. Clouds should clear over
northern portions of the area while conditions will remain mostly
cloudy over North Mississippi. Expect highs in the mid to upper
50s.
The secondary warm front will move northward Sunday Night through
most of the Mid-South. Chances for showers and a few embedded
thunderstorms will increase across the area. Lows Sunday Night
will likely occur in the evening as well as temperatures will warm
behind the front. The warm front should clear the Mid-South by
mid-day Monday. Expect clouds may scatter out behind the front
which may help highs get into the lower 70s across portions of the
area. Dewpoints will also climb to around 60 degrees.
An upper trof will begin to move into the Mid-South Monday Night
ahead of a developing low pressure system over Kansas. Models are
a tad further north with the track of the low pressure system and
a little weaker with the strength of the upper trof. Showers and
thunderstorms will begin to spread into the Mid-South late Monday
Night into Tuesday. Can`t rule out a few severe storms developing,
but the threat doesn`t look as high as it did 24 hours ago. Most
of the shower and thunderstorm activity will be east of the CWA
before the trailing cold front even enters the CWA. Thus expect
temperatures to possibly warm into the lower to mid 70s behind the
convection Tuesday afternoon.
The cold front will move through the Mid-South Tuesday Night.
Can`t rule out an isolated shower developing along the front.
Otherwise, cooler temperatures will begin filtering into the area.
The GFS continues to be consistent on the 12Z runs of bringing
another upper trof into the region late Wednesday Night into
Thursday. With colder air in place, any precipitation that
develops with the trof will fall as snow. Have added 20 POPS back
into the forecast for northern areas of the Mid-South.
High pressure will settle over the area on Friday. The high will
quickly shift east allowing winds to turn around to the south by
Friday Night. Another cold front will begin to approach the
Mid-South on Saturday. Have introduced a 20 POP for light showers
that may develop ahead of the front. Highs will back into the 60s.
KRM
&&
.AVIATION...
/00z TAFs/
Scattered, light rain showers will continue across the Mid-South
this evening, eventually shifting south of I-40 by 06z. Ceilings
are currently between 4000-6000 ft and are forecast to gradually
lower to around 1500-2000 ft by 09-10z. Ceilings are expected to
improve during the mid/late morning hours along/north of I-40 but
are expected to lower further to IFR category at KTUP. Winds will
be from a general south to southwest direction, generally under 8
kts.
Johnson
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
905 PM EST Sat Feb 4 2017
.SYNOPSIS...
High pressure centered over the area will shift off the coast
tonight and Sunday as a trough of low pressure develops along
the Carolina coast. A weak cold front will move through Sunday
night. A stronger frontal system will move through the area
Wednesday.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 905 PM Saturday...High pressure will gradually shift off
the coast overnight with a coastal trough developing along the
SE coast near the Gulf Stream. The coastal trough may briefly
move inland along the immediate NC coast late tonight/early
Sunday before moving offshore later Sunday. Clear skies and
light winds this evening have allowed temperatures to quickly
fall into the mid and upper 20s both inland and along the north
coast. The models continue to show increasing clouds with patchy
light WAA rain moving in off the waters late tonight into
Sunday morning in response to convergence along the coastal
trough as well as a weak upper level disturbance moving through
the flow aloft. The best chances of precip will be along the
coast near the trough after midnight but several models
/especially the higher resolution models/ are indicating light
qpf pushing inland across much of eastern NC as well. Latest 00Z
MHX sounding indicates very dry air below 500 MB and this could
impede the inland penetration of moisture. Indeed the 00Z HRRR
has backed off on precipitation occurring over the coastal plain
and develops it all east of Highway 17. The 12Z ECMWF and
12/18Z GFS models were also dry. The wettest models inland were
the CMC and NAM.
The main forecast concern overnight remains the threat of light
freezing rain/freezing drizzle across inland areas as
temperatures, while are expected to gradually increase after
midnight in response to increasing cloud cover, could remain at
or below freezing deep inland as much of the guidance is
indicating this through around 12z. The most challenging part of
the forecast is just how much precip reaches inland areas as it
will have to overcome a very dry airmass in place before the
column becomes saturated. Will follow a blend of guidance for
PoPs which gives slight chance across the inland tier to chance
near the sounds and coast late tonight. The moisture remains
shallow, mainly below 800 mb, with most of the saturated profile
above freezing so only expect light precip to fall, and to fall
as liquid, but if the surfaces are below freezing a light glaze
could develop. The main impacts will be the potential for icing
on bridges and overpasses making for hazardous driving
conditions. We have issued a SPS to address this as confidence
remains low as whether precipitation develops where the coldest
surface temperatures are expected overnight. Expect a non-
diurnal temp curve overnight, with lows dropping into the mid to
upper 20s by midnight, then becoming steady or slowly rising
after 06Z with increasing cloud cover.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
As of 2 PM Saturday...A weak area of low pressure will develop
off the Southeast coast along the coastal trough and lift NE
across the offshore waters Sunday. Precip chances continue in
the morning but move offshore during the afternoon with skies
clearing from west to east. The freezing rain/drizzle threat
should end quickly, by 9 am at the latest, with temperatures
rising into the low to mid 50s during the afternoon.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
As of 250 AM Saturday, A warming trend will develop through midweek,
before a strong cold front brings a threat of rain and much cooler
temperatures for the end of next week.
Sunday night through Tuesday Night...high pressure will set up
shop along the NC/VA coast Monday before moving offshore
Tuesday. This will lead to increased southwest winds, especially
later Tuesday into Tuesday night. This will enhance the warm
advection driving high temperatures into the upper 50s to lower
60s Monday, then into the lower 70s inland with low/mid 60s
Outer Banks on Tuesday.
Wednesday through Friday...Trends over the past several runs of
the Medium-Range models has been faster with the strong cold
front and association area of precipitation Wednesday. It now
appears the rain will begin early in the day and mostly be
offshore during Wednesday afternoon. Strong gusty Southwest
winds with keep low temperatures in the mild 50s with highs
again into the lower 70s away from the water Wednesday. Given
the quick movement of the system, rainfall amounts will be
limited to one- quarter inch or less. Rapid clearing is likely
for Wednesday night as dewpoints crash, dropping from the 50s to
the 20s by Thursday morning. High temperatures for Thursday
will be some 20 degrees colder across the CWA. Strong high
pressure will build down the east coast into Friday. The GFS has
trended much drier for Friday, versus the 00Z run from
yesterday, while the ECMWF builds strong high pressure down the
coast. Will continue dry trends through late week with below
normal temperatures expected through Friday.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Short Term /through Sunday/...
As of 620 PM Saturday...High confidence in VFR conditions
through 06Z with to mostly clear skies. Clouds then increase
after midnight with MVFR conditions mainly in ceilings developing
late tonight into Sunday morning. A few showers may move inland
from the coast and there is a slight chance of light freezing
rain or freezing drizzle at the terminals from around 06-14z
Sunday but confidence is low at this time and will not mention
in the TAFs. The moisture quickly move offshore Sunday afternoon
with skies clearing and VFR conditions returning by 18Z.
Long Term /Sunday night through Wednesday/...
As of 3 AM Saturday, VFR conditions should prevail through much
of the period. High pressure and fairly low dewpoints should
keep VFR conditions in place through Tuesday. Periods of MVFR
ceilings will be possible as a strong cold front crosses the
area Wednesday with areas of showers expected.
&&
.MARINE...
Short Term /through Sunday/...
As of 905 PM Saturday...High pressure building in from the west
is allowing the winds and seas to diminish across the waters
this evening. N/NE winds 10-15 kt this evening will shift to E
overnight. A coastal trough will move into the southern and
central waters late tonight with winds becoming SE around 15-20
kt east of the trough. A weak low will lift NE along the trough
Sunday with winds across the waters becoming W to NW around
10-15 kt. Seas around 3-5 ft across the waters early this
evening are expected to subside to 2-4 ft after midnight and
continue in this range through Sunday.
Long Term /Sunday night through Wednesday/...
As of 3 AM Saturday, low pressure will pass east of the area on
Sunday night with west winds around 5-15 knots and seas at 3-5
ft. Some gusts to 20 knots will be possible Sunday night before
subsiding to 5-15 knots again Monday from the WNW/NW. No
advisories are expected on area waters until Tuesday night and
Wednesday as strong gusty SW winds develop ahead of a strong
Canadian cold front. Gale force winds appears likely starting
late Tuesday night with sustained winds to near 35 knots with
seas building to as high as 8 to 9 feet, especially over the
central waters.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...Small Craft Advisory until 10 PM EST this evening for AMZ152-
154.
&&
$$
SYNOPSIS...SK/CQD
NEAR TERM...SK
SHORT TERM...SK
LONG TERM...CTC
AVIATION...CTC/SK
MARINE...CTC/SK
Area Forecast Discussion...CORRECTED
National Weather Service Reno NV
323 PM PST Sat Feb 4 2017
.SYNOPSIS...
A series of storms will impact the region this coming week with a
mix of wind, snow, and heavy rainfall. The first storm Sunday
night into Monday will bring strong winds areawide along with
mountain snow. A second storm Tuesday into Wednesday is likely to
bring heavy mountain rainfall and a risk for flooding of streams
and poor drainage areas. A third storm Thursday into Friday
doesn`t appear as strong but could bring more rain and snow to the
region.
&&
.SHORT TERM (until daybreak Tuesday)...
* Strong ridgetop winds have been more persistent today than
expected. Sierra Crest sensors still hitting gusts over 100 mph
with "more reasonable" 60 mph gusts on W Nevada ridgetop sites.
700mb flow really isn`t that strong so not sure what is going on
here. 19z HRRR trends suggest that these strong ridge winds
would continue into the evening before diminishing some
overnight.
* General lull in precipitation through Sunday afternoon as ridging
works into the area. Just a few upslope showers near Tahoe right
now but those should dissipate soon after sunset. This would be a
good period for travel, outdoor activities, or pre-storm
preparations for the coming week.
* First in a series of storms rolls in Sunday night through
Monday. This one looks to be a solid wind maker in response to
deepening low pressure inland over the Pac NW. Strong surface
gradient with approaching cold front coupled with fast flow
aloft (150 kt jet stream) should yield widespread gusts over 55
mph in the valleys with downslope wind prone areas over 70 mph.
Sierra ridges could see 120+ mph. This has the potential to be
one of the stronger wind events we`ve seen this season, so extra
attention should be paid to weakened trees and unsecured outdoor
objects. High wind watches have been posted.
* The other issue, more prickly from a forecast standpoint, is
snowfall potential in the mountains. Precip with this storm is
modest due in part to a fairly weak AR signature. Guidance
consensus has snow levels around 5500-6500 feet with variations
+/- 500 feet. This of course places many of our mountain
communities around Truckee-Tahoe-Lassen in that "uncertainty
zone" where snowfall could go big (8-12") or go home (0-2")
depending on how snow levels pan out. At pass elevations and in
Mono County we`re more confident in seeing appreciable snows due
to higher elevations. In the end we posted a winter storm watch
to cover both snow potentials and strong winds for the Sun eve
through Monday period. -Chris
.LONG TERM...Tuesday through Saturday...
Overall forecast remains on track with active weather pattern from
Tuesday through Friday, then a possible break by next weekend.
For Tuesday, the first storm system will begin with increasing
moisture with the arrival of a moderate intensity atmospheric
river. Warm air advection will bring a rapid rise in snow levels
across the Sierra and far western NV during the morning. Farther
north (roughly from Susanville-Lovelock northward), there may be a
short period of light snow or a rain-snow mix Tuesday morning,
while for the Surprise Valley and far northern Lassen County, a
couple inches of snow could accumulate before the changeover to
rain later in the day.
The main concerns and impacts with this storm will occur later
Tuesday afternoon through Tuesday night, when the peak rainfall
intensity is accompanied with snow levels rising to near 8500-9000
feet. While the guidance remains consistent with the heavy rain
potential for the Sierra and northeast CA, it still shows some
uncertainty for where the heaviest rain occurs. Previous guidance
had favored northeast CA, but in the latest guidance/ensemble data,
the highest rain totals (2-4" with locally higher amounts) could
range anywhere from Plumas County to northern Mono County. Farther
east. rainfall amounts could exceed 1 inch in the western NV
foothills and in eastern CA west of US-395, with 0.25 to 1 inch
across the Reno-Carson Minden vicinity and less than 0.25 inch
across West Central NV. In higher peaks (mainly above 9000-9500
feet) where precip remains as snow, a few feet of snow could
accumulate by Wednesday morning.
The combination of the warmer air mass and the higher elevation rain
falling on existing snow pack will lead to rises on area rivers,
with potential for localized flooding along smaller creeks/streams
and in poor drainage areas.
The heavier precip is likely to diminish on Wednesday, with leftover
lighter showers possible Wednesday night into early Thursday. There
could still be a moderate amount of additional rainfall during the
day Wednesday near a portion of the Sierra during this wind-down
phase.
The next storm then arrives on Thursday, possibly starting by late
morning for northeast CA, then spreading southward along the Sierra
from Thursday afternoon through early Friday. This system will begin
with high snow levels above 8500 feet, then drop to near 5000-5500
feet for northeast CA, near lake level for Tahoe and 6500-7000
feet for Alpine/Mono Counties by early Friday. Small stream
flooding concerns and rises on area rivers will continue with this
storm, especially if the midweek storm meets or exceeds the
advertised rainfall amounts. The forcing along the cold front
Thursday night could produce precip rates even greater than the
midweek storm, although for a shorter duration.
For western NV, winds will increase Thursday afternoon and evening,
followed by a short period of rain overnight associated with the
trough/cold front passage. Some partial spillover moisture could
enhance rainfall totals a bit in foothills and western portions of
Reno-Carson ahead of the front.
For Friday, a weaker shortwave brushing across northeast CA could
bring light showers near the Sierra and in western NV north of I-80.
Then by next weekend, we should have a break in the action as a
ridge builds into CA/NV. While our current forecast favors an inland
ridge with temps near average, some scenarios set up the axis near
or off the west coast. If this occurs we could see max temps 5-10
degrees colder with possible very light snow showers. MJD
&&
.AVIATION...
Light -shra/-shsn could bring MVFR cigs/vsby until around 03z for
KTVL/KTRK Otherwise VFR conditions will prevail thru Sunday. Some
mountain top obscurations will continue this evening near KRNO-KCXP.
With gusty ridge winds continuing through early Sunday, turbulence
will continue to be an issue across the Sierra and western NV.
Significant weather-related impacts to aviation will begin early
Monday as strong winds begin in higher elevations then spread to
lower elevations during the day--leading to periods of LLWS,
mountain wave turbulence, and rotor activity. MJD
&&
.REV Watches/Warnings/Advisories...
NV...High Wind Watch from late Sunday night through Monday evening
NVZ003-005.
Winter Storm Watch from Sunday evening through Monday evening
NVZ002.
High Wind Watch from Monday morning through Monday evening
NVZ001-004.
CA...High Wind Watch from late Sunday night through Monday evening
CAZ070-071.
Winter Storm Watch from Sunday evening through Monday evening
CAZ072-073.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Blacksburg VA
912 PM EST Sat Feb 4 2017
.SYNOPSIS...
High pressure shifts east and offshore overnight. A weak cold
front approaches Sunday before stalling across the Ohio Valley
Sunday night into early Monday. Strong low pressure passing well
to the northwest Tuesday will propel a cold front through the
region during midweek.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 900 PM EST Saturday...
Evening soundings along with surface observations show very dry
air remaining in place tonight per PWATS of a tenth of an inch
or less and dewpoints still in the single digits. This under
clear skies has again allowed temps to fall off quickly this
evening despite some lingering light southerly mixing. Given
upstream mid deck associated with return moisture still west of
the mountains, have lowered lows a few degrees across the east
as well as the deeper valleys. This still will put most in the
low/mid 20s before rising under increasing clouds after
midnight. Did bump up lows on the ridges a category or so where
expect weak warm advection, per increasing westerly winds at
elevation, to steady readings out shortly before rising as the
cloud canopy arrives.
Precip chances still looking quite small late over the far west
given the westerly trajectory and current split look to
upstream echoes this evening. However the latest HRRR continues
to show a quick surge in moisture advection just west of the
region before daybreak, while attempting to drive some light
precip into the I-77 corridor. Thus left in very low snow pops
over the western mountains for now.
Previous update as of 636 PM EST Saturday...
Expansive Canadian surface anticyclone over much of the mid-
Atlantic and southeast CONUS is beginning to gradually build
east. Clear skies and lingering very dry air mass still remain
in place and will continue to do so through midnight. That
should allow for temperatures to really plummet fast over the
next 4-6 hrs, particularly in areas that can stay
decoupled/calm. We`ll then watch low/mid cloud shield, now
extending across the Ohio and Mississippi River Valleys, advance
across the central Appalachians after midnight and into the
Virginia and North Carolina Piedmont into Sunday morning. No
changes to PoPs at this time. However, with only little moisture
recovery tonight it may be difficult to generate much of any
wintry precip. Seems that only the SREF /NAM-based solutions
generate any precip, with latest 18z GFS keeping our forecast
area entirely dry. For this update, I`ve mainly blended in
colder hourly temperature guidance into the grids to account for
a likely sharp fall in temps through midnight, and then rising
after midnight.
Previous near-term discussion issued at 315 PM Saturday
follows...
Canadian high pressure over our region this afternoon will drift
east this evening reaching the coast and push into the Atlantic
ocean tonight. A northern stream shortwave will move across the
Great lakes Sunday and then into the Northeast By early Monday. This
system has a trailing warm front and cold front associated with it.
A weak frontal system will move across our area late tonight into
Sunday morning with a slight chance of precipitation.
Very light precipitation will begin to develop across the western
mountains just before daybreak from weak upper forcing and warm
advection. With surface temperatures below freezing, a brief period
of snow/sleet/freezing rain will be possible, but with QPF near
zero, this is not expected to pose any winter weather problems
across the forecast area. Precipitation will not reach areas east of
the Blue Ridge. For PTYPE utilized the Topdown Procedure with the
NAM temperature profiles for tonight into Sunday. Used a non-diurnal
temperature curve for tonight with warm advection and clouds. Low
temperatures tonight will range from around 20 degrees in the
mountains to the mid 20s in the Piedmont.
Light wintry mix Sunday morning will transition to some upslope
sprinkles/drizzle by Sunday afternoon. Expect winds to become quite
blustery behind the front Sunday afternoon into Sunday night.
High temperature on Sunday will vary from the mid 30s in the
mountains to the mid 50s in the Piedmont.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 315 PM EST Saturday...
You can expect a transition to milder temperatures this period as 5h
heights build and 8h temps rise in advance of next upstream trough
moving into the central U.S. Monday. Decided to keep isolated snow
showers in western Greenbrier County Sunday evening, but overall
shallow moisture is expected so nothing of consequence. A little
brisk early in the evening before high pressure builds overhead
late. Lows Sunday night will be in the upper 20s to lower 30s.
Monday will be mostly sunny as winds shift to the south.
Temperatures will rise to the 50s for highs.
Monday night will see increasing moisture as a warm front traverses
the Appalachians. Appears models agree on higher threat of rain over
the mountains mainly from the Mountain Empire north to the
Alleghanys, with limited threat of measurable over the NC piedmont.
With southwest flow increasing aloft and clouds, temperatures stay
on the mild side for lows, with most in the 40s.
Tuesday best lift shifts north with the warm front with our area
becoming more entrenched in a showery regime. Sfc low moves from the
midwest Tuesday morning to the lower Great Lakes by dusk, with cold
front advancing east to a Louisville to Memphis line. Models are
adamant on keeping skies overcast but think some area east of the
mountains could see a few breaks. Temperatures should pretty warm
for early Feb with breezing southwest winds of 10 to 20 mph, with
highs ranging from the lower 60s west to upper 60s/near 70
southeast. Some record highs may be approached, especially Bluefield
which has a record high for Feb 7th of 63 set in 2005. Forecast
showing 62. Best lift stays west but showers will nudge east to the
mountains by afternoon.
Tuesday night the low level jet shifts east across the area with
strong lift with front. The 12z ECMWF showing rainfall amounts of
over an inch in the NC mountains. At the moment given speed of
system appears some of this is true as sfc low moves northeast
allowing the front to slow some with unidirectional flow aloft. At
the moment leaving thunder out of the forecast as timing overnight
this time of year favors less threat, but will have to watch winds
with line of showers given models forecasting an 8h jet of 45-60kts.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 200 PM EST Saturday...
Some change this period mainly early as models have sped up colder
air and drying behind the cold front. As such have slight chance to
low chance pops mainly in the morning. Airmass dries a bit quicker.
Another issue we have been highlighting in the Hazardous Weather
Outlook is the winds along/behind the front. Models per forecast
soundings have toned down the strength of the winds post frontal and
with sfc low track further north and its direction of movement,
climatologically we do not see a lengthy period of advisory level
winds. However, with still 40-50kt jet Wednesday afternoon and 4-6mb
pressure rises in 6 hours we will may mix some gusts close to
advisory levels over the higher ridges, so will keep in the HWO, but
back off on area covered by this to more of the mountains.
Temperatures drop in the west late in the afternoon to the lower to
mid 30s after starting the day in the 40s.
Appears mainly dry and seasonal Wednesday night into Thursday though
both the GFS/ECWMF showing an upper level system moving across in
the Thu-Thu night time frame but overall moisture seems scarce and
any precip will be light with very low pops advertised over the
mountains.
High pressure overhead Friday with warming trend next weekend. Model
timing different with ECMWF bring next rain threat late Saturday
through Sunday, while GFS keeps it dry.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
As of 635 PM EST Saturday...
VFR SKC conditions through 06z, then trending VFR low/mid
clouds (bases 060-090) after midnight from west to east.
Potential for an MVFR ceiling at LWB and BLF overnight into the
first part of Sunday but with upstream ceiling trends mainly
VFR, confidence wasn`t high enough to include. Spotty, light
wintry mix possible at these same two TAF sites but chances were
too low to include in the TAF as well, with dry conditions
prevailing otherwise.
Light southeast winds (though up to 8 kts at ROA initially)
begin a steady veer to southwest with speeds increasing to 8-12
kts after midnight. Winds turn gusty as a front moves across
the area through the first part of the day on Sunday, with gusts
as high as 25 kts at BLF and LWB.
Medium confidence in ceilings, visibilities and winds
throughout the TAF valid period.
Extended Aviation Discussion...
VFR/at times MVFR conditions for LWB and BLF, with VFR
elsewhere Sunday afternoon into early Sunday night. Gusty west
winds should begin to subside Sunday night, along with clearing
of lingering cloud cover. Weak high pressure follows this system
briefly for early next week with mainly VFR conditions expected
Monday. Conditions will deteriorate Monday night as warm
advection rain showers advance northeast into the region
resulting in lower cigs and spotty sub-VFR vsbys espcly
mountains.
A strong area of low pressure will develop across the Midwest
early next week promising to bring a longer period of sub-VFR
conditions to the area starting Monday night and especially
Tuesday into Wednesday with widespread rain and fog along with
low clouds. Generally MVFR, but with periods of IFR expected. A
strong cold front approaches from the west Tuesday night and
crosses the area on Wednesday. After the front passes, expect
improving conditions east of the Blue Ridge by Wednesday
afternoon as showers along the front shift east. However
lingering sub-VFR likely across the mountains for much of the
day behind the front, with upslope low clouds and spotty
rain/snow showers persisting under very strong post frontal
northwest winds.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH
NEAR TERM...AL/JH/KK
SHORT TERM...WP
LONG TERM...WP
AVIATION...AL/KK