Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/13/19

AREA FORECAST DISCUSSION

National Weather Service Binghamton NY

 912 PM EST Tue Feb 12 2019

.SYNOPSIS...
A storm system moving through the Great Lakes will continue to
spread mixed precipitation across NY and PA through tonight.
Another storm will pull a rain and snow mix into our region
early Friday.

&&

.NEAR TERM /THROUGH WEDNESDAY/...

The new NAM nest and HRRR are picking up well on a dry slot this
evening that will move west to east across the area. A band of
wintry mix still looks to move through the region overnight
ahead of the main cold front. Precipitation chances were
adjusted to match the latest trends.

With the early and mid-evening updates, some adjustments were
based on the latest round of mesoscale modeling. Current radar
trends have shown a dry slot this evening that is gradually
filling in. However, because of this QPF looks to be a bit less
than anticipated tonight in NE PA and the Southern Tier. Also,
the blend of mesoscale models still shows portions of the Finger
Lakes having temperatures rising to around freezing in the next
couple of hours. In these locations discussed above we have
converted the winter storm warning to an advisory given the
potential still for icing of a tenth of an inch and burst of
light snow around sunrise tomorrow.


230 PM update...

The changeover from snow to mixed precipitation arrived quicker
than expected today, but the net result was the same. While snow
totals fell, ice totals increased, creating hazardous travel
conditions.

The mixed precipitation line will force its way into Oneida
County between 4 PM and 6 PM. Elsewhere, the sleet and freezing
rain is already occurring. We expect the mixed precipitation to
continue through late tonight and taper off as snow showers
toward sunrise when the cold front arrives.

Cold air sliding across Lake Erie could produce squalls from the
Central Southern Tier and lower Finger Lakes to the I-81
corridor on Wednesday. In addition, winds will increase to 15 to
25 mph with gusts of 25 to 35 mph possible, creating blowing and
drifting snow.

A strong lake band is forecast to form over Lake Ontario
Wednesday evening and slide into Northern Oneida County. This
lake band could produce 6 to 10 inches of snow by Thursday
morning. Additional warnings may be needed.


1030 AM update...

Dual-pol radar depicts the mixed precipitation line entering
our southwestern forecast area at this time. The NamNest is
doing a good job with the changeover, and based on the latest
model output we are speeding up the changeover by 1-2 hours
across much of the I-81 corridor and areas northeastward.

The quicker changeover necessitated we lower the snowfall
amounts from the Twin Tiers southward.

The latest grids have been published.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
Thursday through Friday...

Main concerns in the short term are focused on the ending lake
effect snow across mainly Oneida County Thursday morning...the next
weak low pressure system expected to clip the region with a mix of
light snow and rain Thursday night through Friday afternoon...and
above average temperatures on Friday as well.

Exiting low pressure system over Maine will continue to have enough
cold air rotating around the back side of the system and favorable
west winds Thursday morning to trigger an additional 1 to 3 inches
of snow over portions of northern Oneida County. The period of
additional lake effect snow should be short-lived as upper level
ridging and backing winds lift any remaining snow to the north and
dissipate it through the rest of the morning. Weather conditions
will likely be fairly quiet through the rest of the day Thursday as
high pressure moves through and the next system prepares to move in
from the Great Lakes.

Temperatures on Thursday are expected to warm into the 30s and lower
40s. Winds out of the south will combine with a weak warm air
advection regime ahead of the next system to slowly warm the low
levels above freezing.

The leading edge of the precipitation Thursday evening/night will
move west to east across the region in the form of light snow.
However, the response from the warm air advecting in from the south
will push much of the boundary layer above freezing and allow the
snow to mix with rain into the morning hours on Friday. Continued
warming on Friday will turn much of the area to all rain...with the
exception to nrn Oneida and the highest elevations of the Catskills
where a mix of rain and snow may persist. Rainfall amounts will
generally range from a couple hundredths up to a quarter inch of
liquid.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Friday night through Monday...

Area of low pressure will move from the Central Great Lakes into srn
Quebec and allow a trailing cold front to sweep through the region
with a minimal amt of moisture available to produce an area of light
snow through Saturday morning. Snow amounts should be less than 2
inches.

A period of quiet weather is expected Saturday into at least early
Sunday with high pressure building across the region. Boundary layer
winds out of the nw may become favorable for lake effect snow, but
the limiting factors will be the lack of moisture and the shallow
depth of the mixed layer on Saturday. So...will continue with chance
pops Saturday and dry weather Sat night. There is some agreement
among the models for a mid-Atlantic system moving by to the south
Sunday and Sun night...which would brush the southern half of the
forecast area with a quick hit of snow. Still quite a bit of
uncertainty being 5-6 days out. Does appear that temperatures will
drop back to near normal this weekend and early next week as the jet
stream dips south. Highs in the 20s and 30s...and overnight lows in
the teens and 20s are expected.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
A wedge of fairly deep low level cold air was still hanging
tough early this evening with most of the terminals still
indicating mainly a snow/sleet mix rather than a phase of
freezing rain/sleet. The warm air aloft will continue to surge
in between 00Z-05Z thus we still expect more of an evolution
toward freezing rain. Models suggest passage of the surface
occluded front between 06Z-09Z with best precipitation forcing
moving east. At this point, really only expecting the corridor
from KELM-KITH-KSYR to experience any changeover to just rain
as surface temperatures briefly nudge above freezing. Most
lingering precipitation should be over by 09Z with only
scattered snow/rain shower activity through morning. Ceilings
should be mainly MVFR with occasional variations between VFR
and IFR. A period of IFR is possible behind the surface front
late tonight/early Wednesday. Dry air aloft will sweep over the
region on Wednesday morning with ceilings lifting and becoming
broken...then MVFR settles in on colder northwesterly flow
during the afternoon.

LLWS likely this evening, otherwise...moderate SE winds 15-30
knots become SW overnight, then WSW 20-30 knots on Wednesday
afternoon.

Outlook...

Wednesday night...MVFR. Gusty winds. Localized lake effect snow
in the vicinity of KRME.

Thursday...Mainly VFR.

Thursday night through Saturday...restrictions likely with mixed
precipitation.

&&

.BGM WATCHES/WARNINGS/ADVISORIES...
PA...Winter Weather Advisory until 7 AM EST Wednesday for
     PAZ038>040-043-044-047-048-072.
NY...Winter Weather Advisory until 7 AM EST Wednesday for
     NYZ015>017-022>025-044-045-055-056.
     Winter Storm Warning until 7 AM EST Wednesday for NYZ009-018-
     036-037-046-057-062.

&&

$$
SYNOPSIS...DJP
NEAR TERM...DJP/MWG
SHORT TERM...BJT
LONG TERM...BJT
AVIATION...JAB



Area Forecast Discussion

National Weather Service Columbia SC

 1025 PM EST Tue Feb 12 2019

.SYNOPSIS...
A cold front will cross the area tonight. High pressure will be
over the region Wednesday and Thursday with the next in a
series of systems crossing the region Friday into the weekend.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
The main line of showers ahead of the cold front has moved well
east of the forecast area. Strong gusty winds were associated
with these showers. Peak gusts were 56 miles an hour at Augusta
Bush Field and 54 mph at Columbia Metro. We sent a public
information statement with a listing of peak gusts earlier
tonight.

There will be lingering showers until drying occurs behind the
cold front. The HRRR and radar trends support showers moving
out of the area between midnight and 300 am. Winds have
diminished because of less mixing. Observation trends and the
GFS LAMP suggests gusts 15 to 20 knots and below the lake wind
advisory criteria. The temperature guidance was close with lows
in the lower to mid 40s.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
The cold front will be offshore at sunrise with high pressure
and drier air moving into the region. With a pressure gradient
remaining tight through the early afternoon winds will remain
strong and gusty. As the pressure gradient relaxes through the
afternoon expect winds to diminish and become light and
variable overnight as an inversion develops. Skies will be
mostly clear Wednesday night and combine with the subsiding
winds producing excellent net radiational cooling conditions.
Wednesday afternoon high temperatures will be in the upper 50s
to low 60s with in overnight lows in the mid 30s for most
locations.

Conditions will be similar Thursday as the high moves across
the region with skies remaining mostly clear and light southerly
winds. Late Thursday afternoon clouds will begin increasing as
the southerly flow increases and continues transporting moisture
northward. Thursday night clouds will continue increasing as
the next front moves through the TN Valley and into the Upstate
around daybreak. High temperatures Thursday afternoon will be in
the mid to upper 60s with lows Thursday night in the mid to
upper 40s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Models are in good agreement with the synoptic pattern through
the long term with some differences in timing and intensity. The
cold front will begin Friday in the eastern TN Valley with
models indicating it struggling to cross the Appalachians. As
such have adjusted pops to keep highest chance in the northern
Midlands with lower pops to the south. Systems beyond Friday
will occur in rapid succession as the longwave trough remains
over the West Coast with zonal flow over the remainder of the
US. The remains of the frontal boundary will stall over the area
Friday afternoon with another disturbance moving along the
boundary Friday night. This system will mainly stay north of the
area however with southerly flow persisting over the area
expect showers to develop over the area Friday night into
Saturday morning with clouds and frontal remains over the area
into Saturday night. The frontal remains will move south of the
area Sunday with only a brief period of high pressure building
into the area before the front returns northward on Monday with
increasing chances of rain for the early part of next week.
Temperatures through the long term will be above normal.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
The main line of showers ahead of the cold front has moved well
east of the terminals. There will be lingering showers until
drying occurs behind the cold front. The HRRR and radar trends
support the showers moving out of the area by 07z. Observation
trends support VFR ceilings along the front with clouds
dissipating in the dry air advection pattern behind the front
during the early morning hours. The GFS LAMP indicates gusts
around 18 knots through much of the 24-hour TAF period.

EXTENDED AVIATION OUTLOOK...Expect VFR conditions through
Thursday. A frontal system may bring widespread MVFR or IFR
conditions Thursday night through Saturday.

&&

.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 Detroit/Pontiac MI

 844 PM EST Tue Feb 12 2019

.UPDATE...

A region of snow now advancing across the northern half of the
forecast area is generally tied to the upper level forcing along the
lead edge of the mid level low now lifting toward Central Lower Mi.
This region of forcing will generally advance north and east of the
area later this evening into the early portion of the overnight. This
will greatly diminish the chances for much additional snow north of
the I-69 corridor after midnight.

Ongoing low level cold air advection within a moist cyclonic flow is
however supporting an uptick in the lake response across southern
Lake Michigan. With the westerly flow off the lake, convergence will
focus higher intensity snow showers across portions of Se Mi, mainly
between the I-69 and I-94 corridors. A secondary mid level impulse
pivoting around the back side of the upper low will track across far
southern Lake Mi overnight, enhancing the lake response. The snow squall
risk and potential for additional accumulations in this region
mentioned in the previous discussion remains valid. A push of mid
level subsidence and decreasing over-lake instability should diminish
the lake effect activity by early Wed afternoon, even with a boost
in the diurnal cycle.

The better downward momentum push associated with the upper wave will
occur across the Ohio Valley region tonight. The sfc low is actually
forecast to weaken as it lifts into Quebec Wed afternoon. It will
remain windy through Wed afternoon. Strong winds Wed will be mainly a
function of mixing, which may prove a struggle to get gusts over 45
MPH during the afternoon. So the best potential for wind gusts over
40 MPH across the southern portions of the forecast area will occur
tonight.

Based on the above, some adjustments will be made to the end times of
the current headlines. The winter weather advisory across the
Saginaw Valley and thumb will end at 4 AM, with Shiawassee, Genesee
and Lapeer Counties ending by 6 AM (by which time the higher
intensity snow squalls should be south) and the remainder of the
winter wx advisory counties will end at noon Wednesday as will the
wind advisory.

&&

.PREV DISCUSSION...
Issued at 613 PM EST Tue Feb 12 2019

AVIATION...

A rapid improving trend to cigs and vsby is already underway as the
sfc low is now lifting into the thumb region. This is driving a more
well mixed boundary layer into Se Mi. While this better mixed layer
is leading to some improvement in cigs/vsby, it is bringing with it
an uptick in the southwest winds. The sfc low will deepen as it
traverses Lake Huron tonight, driving colder air into Se Mi. This
will support a continued deepening mixed layer capable of providing
some continued improvement in cigs/vsby but also an increase in the
west-southwest winds through the night.

While the higher intensity precip from earlier this evening is
steadily lifting northeast of the terminals, deep layer moisture
advancing back into the region from the west will sustain snow
showers, with visibilities likely fluctuating from IFR to MVFR.
There is expected to be some disorganization to the snow shower
activity this evening into the early overnight. Optimal lake effect
processes are expected to develop a dominate band/bands of high
intensity snow showers late tonight into Wed morning. Based on the
flow these are expected to be more prevalent from PTK south through
metro Detroit.

For DTW...Southwest winds will be on the increase through the
evening with a deepening mixed layer. This mixing will actually
sustain sfc temps a couple degree above freezing until late evening
before low level cold air advection increases. There will be a trend
toward a little more west-southwest flow overnight into Wed morning,
with gusts topping 30 knots at times. There is at least a potential
for the winds to turn a little more westerly, which may result in
some crosswind concerns. Intense lake effect snow showers are
expected to impact the area late tonight into Wed morning, with the
09-13Z time frame being the most probable time period for impacting
metro.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 ft or less through the period.

* High in precip type being all snow tonight and Wednesday.

* Moderate in crosswind thresholds being exceeded late tonight
  through the day Wednesday.

PREV DISCUSSION...
Issued at 343 PM EST Tue Feb 12 2019

DISCUSSION...

Strong PV anomaly is noted at press time lifting northeast invof the
southern tip of Lake Michigan at press time. MSLP at Holland, near
the center of circulation, is down to 998mb with system-relative
pressure falls of 1mb/hr or slightly less progged to continue
through tonight as the center of circulation moves to Georgian Bay
by Wed morning. Cross-sections indicate a pronounced stratospheric
intrusion into the upper portion of the frontal zone immediately
adjacent to the cyclonic side of the upper jet. The attendant dry
air stream ended meaningful precipitation over the CWA several hours
ago.

Rain and snow showers have developed beneath the dry air over
eastern Illinois and central Indiana as mid-level PV advection ramps
up this afternoon. Locally, radar echoes have been percolating as H5-
H7 mid-level instability wakes up in advance of this leading to
scattered drizzle and freezing drizzle of virtually no impact as the
latter is falling into established snowpack. Convection will remain
tied to mid-level forcing and will become oriented increasingly
orthogonal to the thermal gradient, offering at least some potential
for fgen processes to aid in organization as the band lifts toward
the northern half of the CWA this evening where a quick inch will be
possible west of M53 in the cold air. Probability of disorganization
and/or rain as the dominant ptype along the front increases with
south and eastward extent - Detroit will see rain as this feature
moves through.

Well-mixed WSW flow will fill in in the wake of the surface low
tonight, the stronger winds filling in from south to north between
about 00z and 09z. Wind gusts to advisory criteria will certainly be
possible given borderline wind speeds within the modeled boundary
layer, dynamic forcing for descent, and augmented mixing courtesy of
the lake influence. Given the ongoing advertisement of blowing snow,
especially across the northern third of the CWA, and the potential
for lake effect snow opted to wrap a wind advisory into the WWA
product for all but the southern tier of counties. A straight wind
advisory for the southern tier is based solely on the expectation
that lake effect is either positioned to the north or is transient
in nature. See the earlier AFD for a summary of the headlines. Worth
noting that blowing of snow, except perhaps Bay, Midland, and Huron
Counties, will be solely dependent on fresh snowfall tonight as
existing snowpack will obviously glaciate after today`s partial thaw.

LES will develop after midnight tonight as theta-e lapse rates fall
as low as -4C/KM over Lake Michigan. Large scale ascent and strong
mostly unidirectional boundary layer flow will contribute to a
potential snow squall threat focused between I-94 and I-69 between
06z and 15z before surface ridging interrupts the fetch over Lake
Michigan early Wed. Favorable thermal profiles will support high
ratio snow within convection while the strong ambient wind field and
sufficiently cold surface will ensure dangerous travel (blowing
snow, covered-roads) within any stronger bands. Timing before and
during the morning commute will potentially lead to significant
impacts should the threat materialize. 18z HRRR and 18z NAM suggest
the favored corridor for convergence will be Livingston and Oakland
Counties, but given the ongoing situation with the rapidly deepening
low over the Lower Peninsula, the forecast fetch will remain subject
to refinement.

A breezy day expected Friday after a cold front ushers in a fresh
arctic air mass. High temps will be limited to the upper 20s
to mid 30s as the cold advection fights daytime heating. Some
lingering isolated snow showers will be possible early in the day,
but Friday looks mostly dry with ridging beginning to nudge in from
the south and west. Split flow developing aloft will divert the
storm track and allow for a period of relatively quiet weather
through the weekend into the early week. Temperatures will be a bit
below normal with highs in the 20s. The best chance for light snow
will come Sunday evening as a low moves through the Ohio Valley.

MARINE...

Gale Warnings remain in effect across the central Great Lakes
through Wednesday as a strong low pressure system tracks through
Central Lake Huron this evening. High end easterly gales around 40
knots are occuring over the north half of Lake Huron through this
evening, but will briefly diminish tonight as the low tracks
through. Wind turning west-northwest tonight and gusting to Gales
late tonight through tomorrow with additional snow. Inner Saginaw
has been added to the Gale warning for tomorrow. Conditions then
improve quickly with the arrival of high pressure Wednesday evening
into Thursday morning.

Another deepening low pressure system is then forecasted to track
through northern Lake Huron Thursday evening, with westerly marginal
Gales possible over northern Lake Huron on Friday as colder air
sweeps back in.

PREV DISCUSSION...
Issued at 1212 PM EST Tue Feb 12 2019

Update...

Update forthcoming to bring headlines and a fresh set of zones in
closer alignment with expectations going forward. Burst of strong
warm advection has nearly cleared the area by 11am LST this morning.
A general 3-5" of snow was observed in the warning, 2-4" accompanied
by mostly sleet and some fzra in the advisory, and around 0.3" of ice
accretion in the ice storm warning. The dry slot will overspread the
area for the remainder of the daylight hours limiting any additional
precip going forward, so the ice storm and winter storm warnings
have been cancelled.

Incoming well-mixed cold airmass tonight will bring a quick shot of
deep/strong convergence and dynamic support in the form of the
parent 400mb PV anomaly pivoting through the CWA 21-00z. A transient
burst of convective showers can be expected along the front with low
vsbys possible in its wake west of the glacial ridge where precip
will most likely be snow. To the east, including most of Metro
Detroit, rain is expected. Weak deformation will support additional
minor accums across the north tonight that wouldn`t be headline-
worthy on their own merit, especially after such a prolonged break,
but the potential for blowing snow, wind nearing wind advisory
criteria in spots (tonight thru Wed), and typical lower-
predictability lake effect response are sufficient to simply
transition the WSW to an generic WW advisory. LES potential will be
greatest in the climatological corridor which is already captured in
the existing advisory (I-94 to I-69) and will be a focus of
attention for this aftn. Poorly defined/lower probability threat
near the Ohio border lends itself to just a wind headline at this
time.

All advisories are now scheduled to expire concurrently Wed
aftn as wind guts and any blowing snow begin to diminish. Final note
on the ice storm - additional power outage potential as strong winds
develop tonight will be conditional on the degree of melting that
occurs today as temperatures rise well into the 30s in most spots.
Either complete melting of ice on power lines or even just enough
melting to allow ice to break free/fall off during wind would be
sufficient to limit impacts. The current expectation of light winds
until 00z or later and 32+F temps is therefore a rather fortuitous
outcome in terms of mitigating additional infrastructure damage.

MARINE...

Gale Warnings remain in effect across the central Great Lakes today
through Wednesday as a strong low pressure system moves through the
region. High end easterly gales around 45 knots are likely,
especially across the north half of Lake Huron where the long
easterly fetch over open water enhances the wind pattern. A brief
gust to storm force remains possible there while colder air remains
over the remaining ice free water. The center of the system tracks
across southern Lower Michigan and central Lake Huron tonight which
allows a brief decrease in wind before increasing to northwest gales
again through Wednesday as the system exits into Ontario and Quebec.
The associated cold front moves through Lower Michigan during the
evening and brings the northwest gales first to Lake Erie and Lake
St Clair which have been upgraded to a Gale Warning tonight through
Wednesday. An extensive break up of ice is expected over the south
third of Lake Huron which may help frequent gale force gusts reach
outer Saginaw Bay and the southern nearshore waters down to Port
Huron. Conditions then improve quickly with the arrival of high
pressure Wednesday night into Thursday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until noon EST Wednesday for MIZ082-083.

     Winter Weather Advisory until 6 AM EST Wednesday for MIZ060>062.

     Winter Weather Advisory until noon EST Wednesday for MIZ063-068>070-
     075-076.

     Winter Weather Advisory until 4 AM EST Wednesday for MIZ047>049-
     053>055.

Lake Huron...Gale Warning until 4 PM EST Wednesday for LHZ361>363-421-441>443-
     462>464.

     Gale Warning from 7 AM to 4 PM EST Wednesday for LHZ422.

     Heavy Freezing Spray Warning until 10 PM EST this evening for
     LHZ361-362.

Lake St Clair...Gale Warning until 4 PM EST Wednesday for LCZ460.

Michigan waters of Lake Erie...Gale Warning until 4 PM EST Wednesday for LEZ444.

&&

$$

UPDATE.......SC
AVIATION.....SC
DISCUSSION...JVC/TF
MARINE.......SF


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.



Area Forecast Discussion

National Weather Service Wilmington NC

 852 PM EST Tue Feb 12 2019

.SYNOPSIS...
A cold front will bring scattered showers to the area tonight.
Dry weather will prevail Wednesday and Thursday as high
pressure migrates across the Southeast. A warm up will occur
Thursday and Friday. A cold front should reach the area Friday
night and may linger as low pressure develops, leaving unsettled
weather for next weekend and start of next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 900 PM Tuesday...Shallow convection produced strong winds
across much of the Sandhills and Pee Dee region early this
evening. Gusts in the 30-50 mph range were common, with some
stronger winds and wind damage reported back across central
South Carolina. Surface-based instability, or more correctly the
lack of it, near and east of I-95 appears to have been the
determining factor for why the convection weakened as it moved
east. Now feeding on meager elevated instability of 500 J/kg or
less, the line should reach the Myrtle Beach metro area shortly
after 9 PM, then Wilmington close to 10 PM -- still capable of
producing some briefly gusty winds but no lightning given
radar-measured echo tops all below 20kft.

South-southwest wind trajectories have maintained dense sea fog
across the coastal waters and adjacent land areas all evening.
Webcams and airport weather obs from the North Myrtle Beach
airport have been instrumental in helping me define the areas
affected by fog this evening. Fog will clear as soon as winds
turn westerly behind the shallow convective squall line. Given
the current and forecast movement of the line I`ve added a
couple hours onto the Dense Fog Advisory for coastal North
Carolina. No other significant changes have been made to the
forecast with this evening update.

Discussion from 630 PM follows...

A shallow convective squall line across central South Carolina
is rapidly moving eastward. Linear motion estimates and the
latest HRRR model runs show this feature reaching Florence and
the I-95 corridor by 730 PM, the Myrtle Beach/Grand Strand area
before 900 PM, and Wilmington before 1000 PM. Temperatures
across much of central and southern South Carolina spiked into
the upper 70s this afternoon which produced an area of surface-
based CAPE in the 500-1000 J/kg range. Subsequent convection has
been relatively shallow with CAE radar echo tops measured near
20-25 kft. Bulk shear across the 0-6 km layer is 50-60 knots
which is helping to organize the storms into bowing segments,
some of which have reportedly produced wind damage.

With the loss of daytime heating, convective instability should
wane over the next few hours. However this may not be fast
enough to prevent strong to potentially severe storms from
impacting a portion of the Pee Dee region over the next 90
minutes. Strong wind is the primary severe weather mode
expected. Convection should weaken with time, and by the time of
the squall line makes it down to the North Carolina coast late
this evening it may not even be a solid line due to a drying
mid-level atmosphere and even less elevated instability present.

Dense fog continues to affect the coastal waters, and several
of our off-duty meteorologists have called to report dense fog
is moving inland across coastal portions of Pender and New
Hanover counties. Webcams and airport obs in the Myrtle Beach
area also confirm dense fog continues here. The squall line and
its shift to westerly winds will likely be what clears this fog
offshore between 8-10 PM.

No changes have been made to forecast lows tonight, with upper
40s to lower 50s expected for most areas. This is near the upper
end of the MOS guidance envelope due to overnight breezes
keeping the boundary layer rather well mixed.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 300 PM Tuesday...Zonal flow aloft keeps surface features
moving quickly from west to east during the period. High
pressure over the area at the start of the period moves off the
coast in the Thu afternoon. Slight amplification of the 5h
pattern later Thu into Thu night shifts the center of the high
northeast, but period of west-southwest flow aloft is limited.
Moisture return ahead of quick moving cold front and
deamplifying 5h trough is meager, and rainfall ahead of the
front Fri into Fri night is looking like less of a possibility.
Have dialed back precip chances during the second half of the
period, but further reduction may be required. Temperatures
above climo Thu and Thu night will run well above climo Fri and
Fri night as first strong warm advection kicks in and then
clouds arrive overnight.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...Progressive mid-level pattern will keep
a front stalled in the area through the weekend. Low pressure
exiting the the Mid-Atlantic coast late in the weekend will push
the stalled boundary southeast of the forecast area into the
middle of next week.

-A series of weak waves will travel northeast along the stalled
 front this weekend, maintaining elevated rain chances into Sun
 afternoon.

-Rain will be on and off through the weekend with cloudy skies
 and relatively narrow diurnal ranges. Highs will be near climo
 with lows well above climo.

-High pressure briefly builds in from the north late Sun through
 Mon night before expanding 5h ridge over the western Atlantic
 helps push the boundary back into the region. At the same time
 increasing southern stream energy taps into moisture, spreading
 rain across the area Tue.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...Currently VFR conditions inland with MVFR at ILM and
LIFR and the Myrtles, courtesy of sea fog pushing inland. Expect
visibilities at the Myrtles to be decreased next couple hours.
A line of showers associated with an approaching cold front is
moving in from the west. This line should reach Florence and
Lumberton shortly after start of TAF period, and the coastal sites
by 2-3z. Some higher gusts may be associated with the front line.
Precipitation to continue behind line for few hours. Look for
coastal terminals to improve to VFR by around 6z, with scattered
high clouds likely rest of period. Current southerly winds to
shift westerly behind front, and remain westerly around 10kts into
tomorrow.

Extended Outlook...VFR conditions will develop Wed through Thu as
high pressure ridges over the region. A warm front will push north
across the area on Fri with MVFR conditions and rain possible into Sat
and Sun.

&&

.MARINE...
As of 900 PM Tuesday...Dense fog continues to affect the coastal
waters of the Carolinas. Earlier satellite imagery showed dense
fog likely developing 10-15 miles offshore, then streaming
northward with the low-level winds. A line of showers approaching
Myrtle Beach from the west should move offshore between 8 and 9
PM, veering winds to the west and rapidly improving visibility.
Given the current and forecast movement of this line of showers,
I`ve added a couple hours onto the Dense Fog Advisory for the
coastal waters of southeastern North Carolina. Assuming my
forecasts on the movement of the showers are correct, all
locations, even those east of Cape Fear, should be clear of fog
by 11 PM.

Buoy-reported seas continue to build and are now 4-5 feet on the
CORMP/NDBC buoys near Cape Fear. Discussion from 630 PM
follows...

Webcams, late afternoon visible satellite data, and even
nearshore airport observations confirm that widespread dense fog
covers most of the nearshore coastal waters as rich subtropical
moisture touches our cold ocean waters. Fog should continue up
until the arrival of a line of showers between 8-10 PM. Gusty
west winds developing with these showers should push the fog
offshore, with rapidly improving visibilities expected
overnight. Before these showers arrive, south to southwest winds
will increase to a solid 20-25 kt with seas building to 5-7 ft.

Discussion from 300 PM follows...

Marine fog/stratus mixing out somewhat gradually. DFA has been
extended slightly in time into the evening. Mariner headaches
will not clear up with the visibility however as winds and seas
will ramp up to Small Craft Advisory levels with tonight`s
frontal passage. A sharp veer to NW will accompany the front
late tonight and then abating winds/seas slated for all of
Wednesday as high pressure builds in to our west. The center of
the high remains over GA/AL so winds may have a tough time
dropping below the 10-15kt range.

Extended period of south to southwest flow Thu through Sat as high
pressure overhead Thu morning shifts east-northeast. Light winds Thu
morning will steadily increase through the end of the week, peaking
on the high end of the 15 to 20 kt range Sat. Seas will build to 3
to 5 ft later Sat due to increased winds.

Weak cold front moves across the water Sat night and ends up
stalling over the waters briefly Sun morning. Front returns north
Sun as weak low passes to the northwest. The passage of the low
drives the front back south, across the waters, stalling southeast
of the area as the period ends. Erratic wind directions over the
weekend coupled with speeds under 15 kt Sat night through Sun night
will drop seas in the 3 to 5 ft range Sat evening to 2 to 3 ft Sun
and Sun night.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...Dense Fog Advisory until 9 PM EST this evening for SCZ054-056.
NC...Dense Fog Advisory until 9 PM EST this evening for NCZ110.
     Dense Fog Advisory until 11 PM EST this evening for NCZ106-108.
MARINE...Dense Fog Advisory until 9 PM EST this evening for AMZ254-256.
     Small Craft Advisory until 7 AM EST Wednesday for AMZ250-252-
     254-256.
     Dense Fog Advisory until 11 PM EST this evening for AMZ250-252.

&&

$$

SYNOPSIS...III
NEAR TERM...TRA
SHORT TERM...III
LONG TERM...III
AVIATION...21




Area Forecast Discussion...UPDATED

National Weather Service Baltimore MD/Washington DC

 806 PM EST Tue Feb 12 2019

.SYNOPSIS...
Low pressure and its associated cold front will
pass through the area late tonight. High pressure will build
south of the area Thursday. Another cold front will cross the
area late Friday.

&&

.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
Low pressure will move northeastward through the eastern Great
Lakes through tonight with its attendant cold front crossing the
area overnight. For most locations, widespread light to
moderate rain and drizzle will continue to move across the
region out ahead of the front. The exception will be portions
of central/western Maryland and eastern WV where temperatures
remain near or below freezing in the sheltered valleys and mid-
elevations. There, the Winter Storm Warnings were extended
until 11 PM. Also watching some convective elements developing
across central VA and southern MD, where some bursts of heavy
rain and even some gusty winds are possible. A weak convective
fine line is also possible, as currently being shown by the HRRR
and members of the HREF.

Partial clearing and increasing winds are expected overnight
following frontal passage with gusts up to about 30 mph. The
exception is over the higher elevs where 850 mb winds are
expected to increase substantially and may be able to mix down
more easily. There is potential for up to 50 kt winds at the
highest elevations of Grant and western Pendleton Counties where
850 mb winds are fcst to peak at 60 knots. This combined with
all the ice that has accumulated on trees the past two days may
cause significant tree damage and power lines to come down.

Some upslope snow showers are also expected to develop towards
morning along/near the Allegheny Front.

&&

.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Windy and mainly dry Wednesday under a tight pressure gradient.
The exception will be some upslope snow showers along/near the
Allegheny Front with a light accumulation likely. It`s also
possible some snow showers/flurries make it downwind of the
mountains across eastern WV and northern Maryland as suggested
by NAM12 Snow Squall Parameter and >2 Froude numbers. Most
gusts should stay in the 35 to 40 mph east of the Blue Ridge
with 50-60 mph at the highest elevations. Dry Wed night through
Thu evening with rain chances increasing again late Thu night
ahead of another low pressure moving through the Great Lks.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Overall, a potentially active long term period, characterized by
high forecast uncertainty.

A trough and associated area of low pressure will track across the
Great Lakes on Friday. The area of strongest forcing for ascent will
be displaced off to our north, so very little precipitation is
expected as the system passes to our north. High temperatures on
Friday will max out in the mid-upper 50s. We`ll have a largely dry
cold frontal passage Friday evening, which will allow cooler air to
filter back into the area Friday Night.

Beyond Friday Night, forecast confidence decreases. Many of the
deterministic models (12z GFS, 06z FV3, 12z Euro) produce a period
of snow during the day Saturday ahead of an approaching mid-level
shortwave/within the poleward exit region of a zonally elongated
upper jet stretching across the CONUS. However, this solution
doesn`t have much support from the EPS and limited support from the
GEFS.

Then on Sunday, the deterministic guidance has another round of snow
across the region as a second shortwave approaches from the Ohio
Valley. The GFS is currently the most aggressive in producing snow,
but the FV3 and Euro produce at least some snow as well. Again,
there is lesser (but non-zero) ensemble support for a snow event.
The pattern evolution as a whole is quite complex across the CONUS
leading up to the event, so uncertainty is still high. Drier
conditions are expected on Monday as high pressure starts to build
in from the northwest.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
IFR/LIFR conditions through 06Z tonight in rain and drizzle.
Cigs lifting rapidly after 06Z with frontal passage. Becoming
breezy with gusts up to 25 kt. Stronger winds tomorrow under
better mixing with gusts up to around 30 kt.

A few showers on Friday could produce brief and intermittent sub-VFR
conditions. Moving into the weekend, the pattern looks active, but
forecast uncertainty remains high.

&&

.MARINE...
Winds will strengthen tonight and tomorrow as they veer from NE
to WSW overnight. Gale Warning issued for upper Chesapeake Bay
waters and upper Potomac through tomorrow.

A cold front crossing the waters Friday will likely bring SCA gusts.
Winds relax Friday Night and stay low through the weekend.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Wind Advisory from 4 AM to 6 PM EST Wednesday for MDZ501-502.
     Winter Storm Warning until 11 PM EST this evening for MDZ003-
     004-501-502.
VA...Wind Advisory from 4 AM to 6 PM EST Wednesday for VAZ025-026-
     503-504-507-508.
WV...Wind Advisory from 4 AM to 6 PM EST Wednesday for WVZ050-055-
     503-504-506.
     Winter Storm Warning until 11 PM EST this evening for WVZ050-
     051-503-504.
     High Wind Warning from 4 AM to 6 PM EST Wednesday for WVZ501-
     502-505.
MARINE...Small Craft Advisory from 3 AM to 6 AM EST Wednesday for
     ANZ530>532-538>540.
     Gale Warning from 6 AM to 6 PM EST Wednesday for ANZ530>532-
     535-538>540.
     Small Craft Advisory from 3 AM to 6 PM EST Wednesday for
     ANZ533-534-537-541>543.
     Small Craft Advisory from 6 AM to 6 PM EST Wednesday for
     ANZ536.

&&

$$
SYNOPSIS...LFR
NEAR TERM...MM/LFR
SHORT TERM...MM/LFR
LONG TERM...KJP
AVIATION...MM/LFR/KJP
MARINE...MM/LFR/KJP



For frequently asked questions about the Area Forecast Discussion

visit...

 http://weather.gov/saltlakecity/general/afd_faqs.php



Area Forecast Discussion

National Weather Service Las Vegas NV

 710 PM PST Tue Feb 12 2019

.SYNOPSIS...Moisture associated with our next system
will reach the southern Sierra Nevada tonight. The moisture will
continue to stream eastward across the region Wednesday and Thursday
with good chances of mountain snow and valley rain. Additional
storms systems over the weekend will keep the region cooler than
normal along with a threat of rain and snow showers.
&&

.UPDATE...Increasing mid and high clouds are currently streaming in
off the Pacific ahead of our next weather system approaching the
area. HRRR and high resolution models suggest increasing
precipitation spilling over the Sierra crest by daybreak Wednesday,
with additional light shower activity traversing eastward through
the day. Overall, rainfall amounts look fairly light outside of the
Owens Valley/Sierra tomorrow, but moderate rainfall rates will be
possible in the Owens Valley and near Bishop through the day.

Of additional concern is rising snow levels, with forecast soundings
suggesting the snow level rising to between 8-9k feet by Wednesday
afternoon.  Periods of moderate rainfall on the substancial snowpack
in the higher terrain could lead to periods of enhanced runoff and
stream flow in the Sierra/Owens Valley and parts of the Spring
Mountains.

The current forecast is in good shape and no significant updates
have been made this evening.

-Outler-

&&

.SHORT TERM...through Friday.

The focus of the short term remains a developing atmospheric river
event, which could prove to be significant with inland penetration
across the region. Microwave satellite imagery already shows
impressive poleward transport of tropical moisture, already as far
as 30N over the eastern Pacific. Trends are expected to continue as
upper-level trough will continue to sag south out of the Gulf of
Alaska and phase with low pressure currently just east of Hawaii.
The fire hose of moisture will take aim first at Northern
California, then work southward and intensify as it does so.

Precipitation will begin in the Sierra by Wednesday morning and
intensify through the day. Wet-bulb effects might briefly lower snow
levels to around 5500` to start the event, but should quickly rise
through the day Wednesday, potentially to 9000` or above with the
heaviest precipitation. This could limit major accumulations to
above 8000` with transition zone of moderate amounts down to 7000`.
Just where that snow level ends up will have impacts on any rain-on-
snow runoff and flooding concerns, but minor flooding is possible
with over QPF amounts over an inch forecast for the Owens valley,
and in excess of 3-5" liquid/liquid equivalent in the Sierra, with
snow amounts of 1-3 feet above 8000`, and in excess of 3-5 feet for
the crest. The AR will continue to slide southward on Wednesday,
with quite a few models indicating moisture funneling inland around
the south of the Sierra and Tehachapis, producing some precipitation
chances in the southern Great Basin and local mountains on
Wednesday. Fairly low confidence for precipitation and amounts in
those areas for that time frame.

The AR continues sinking south under cyclonic flow and strengthening
Wednesday night into Thursday, and attention turns to the southern
California mountains. PWATs are forecast to be near or at records
for several hours. It looks like 18Z -00Z Thursday is the best
window for maximum precipitation for the mountains in/around San
Bernardino county, with plenty of spillover into places like
Morongo Valley and Yucca Valley. Flooding becomes a concern for
these areas and eastward with the progression of the AR Thursday.
Decided to hoist a flash flood watch for southern portions of San
Bernardino and Mohave counties for Thursday for the heavy rain and
runoff risk. General amounts across the Mojave desert look to be
around 0.25", but amounts closer to or in excess of 1" are
possible if not likely in areas of the Flash Flood Watch. Would
not be surprised to see areas like Las Vegas receive very little
rain, while the mountains receive plentiful rain. Snow levels will
likely rise above the 8000` mark on Thursday, which will limit
accumulation in areas like Kyle Canyon in the Spring Mountains.
Snow amounts there have been cut/shifted upward once again. Lee
Canyon may pick up significant snow, so current advisory still in
good shape.

Areas of concern if the moisture plume wobbles a bit further north
would be the Virgin and Muddy River basins. Anyone with concerns in
these basins are not out of the woods, and should continue to
monitor forecasts for updates.

The area really starts to shut off Thursday night and Friday as the
AR gets shoved even further southward, with only lingering shower
activity in the mountains from colder air taking back over. However,
it may take some areas several days to respond to the mountain
rainfall, like the Big Sandy River in southern Mohave county.

.LONG TERM...Friday night through Tuesday. A trough axis is forecast
to swing through our area Friday night on the southern periphery of
the big, cold low over the Pacific Northwest. This will provide
enough forcing to wring out some more precip over the Sierra and the
higher terrain of the southern Great Basin, possibly extending as
far south as northern Mohave County. It will also kick up westerly
winds, and cannot rule out needing a wind advisory for the places
prone to enhanced west winds such as Barstow. Behind the trough
axis, precip chances should mostly come to an end Saturday. The next
storm is forecast to roll southward through California Sunday,
bringing another round of precip chances to much of our area.
Depending on how quickly it moves out, precip chances should end
either Monday or Tuesday. Temperatures will be below normal through
the period under the influence of long wave troughing.
&&

.AVIATION...For McCarran...Clouds will slowly lower and thicken
through Wednesday, with ceilings possibly falling to 8000 feet or
below along with a slight chance of showers Wednesday afternoon. A
stronger storm is expected to bring worse conditions Thursday
afternoon into Friday morning, with low ceilings and visibilities
possible along with gusty south to southwest winds.

For the rest of southern Nevada, northwest Arizona and southeast
California...Precip chances will begin in the Sierra this evening
and spread across much of the area by Wednesday afternoon. Expect
lowering ceilings with mountain obscurations. After a brief lull
Wednesday night, a stronger storm will bring deteriorating
conditions Thursday into Friday morning, with widespread valley rain
and high mountain snow, leading to significant terrain
obscuration.
&&

$$

SHORT TERM...........STEELE
LONG TERM/AVIATION...MORGAN

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