Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/13/18
Area Forecast Discussion
National Weather Service La Crosse WI
530 PM CST Mon Nov 12 2018
.SHORT TERM...(This evening through Wednesday night)
Issued at 144 PM CST Mon Nov 12 2018
An upper level trough and embedded short wave trough moving south
across the region this afternoon will drop south of the area
tonight. This will push the remaining snow showers and flurries
out of the area late this afternoon and do not plan to carry any
mention of precipitation into tonight. The concern then becomes
when will the clouds break up. Water vapor satellite shows decent
subsidence in the wake of the upper level trough but visible
satellite and observations indicate the clouds are holding on back
across Minnesota into North Dakota, although there are some holes
developing. Both the 12.12Z NAM and 12.17Z RAP hold a lot of
moisture over the area at 925 mb through the evening. The NAM then
pushes this out to the east as low level ridging builds in the
west/southwest. The RAP is slower to push it out and suggest it
may take into Tuesday after sunrise before it exits the region.
However, looking at forecast soundings from the RAP, it does not
show the moisture getting trapped underneath the inversion, so for
now, will continue with the trend of the clouds clearing
overnight but did slow it down some from the previous forecast.
The ridge axis will slide southeast of the area Tuesday night
allowing southwest flow to set up over the region. This will allow
warmer air to start returning to the region with highs Wednesday
to be above 32 for the entire area with a few spots topping the 40
degree mark.
.LONG TERM...(Thursday through Monday)
Issued at 144 PM CST Mon Nov 12 2018
The next chances for any precipitation look to be from Thursday
night through Friday night. Northwest flow aloft looks to be
setting up over the Upper Midwest for late in the week which will
allow some short wave troughs to move across the region. These
waves will push a cold front into the region with one area of low
pressure expected to move by the area to the north Thursday night
that could bring some light precipitation to parts of northern
Wisconsin. Another area of low pressure could then develop along
the front farther south and move across Iowa into Illinois Friday
and Friday night possibly bring some precipitation to the southern
parts of the area. Thursday looks to be the warmest day this week
ahead of the cold front with highs reaching 30s and 40s. Cooler
air behind the front will push highs back into the 20s and 30s for
the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 530 PM CST Mon Nov 12 2018
The widespread stratus that has plagued the area for the past few
days finally has a back edge just northwest of the area. Per
current trends, it appears mainly VFR stratus (with a few possible
breaks) will hang tight through the evening and early overnight
hours, with erosion from the west occurring roughly around 07Z for
RST and 09Z for LSE, though would expect some adjustment to those
times as we go into the evening and peruse the latest satellite
data. Ceilings could briefly slip to MVFR at RST, though that
should be temporary, with high pressure building into the region
and (hopefully) ensuring a return to clearer conditions into
Tuesday. Winds will remain from the northwest either side of 10
knots tonight, gradually shifting westerly Tuesday afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...Lawrence
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
536 PM CST Mon Nov 12 2018
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...Increasing winds and lowering cloud decks are expected
through much of the next 24 hours due to the passage of a cold
front. KBRO Doppler radar shows light precipitation beginning to
stream northeast out of neighboring Mexico, and the HRRR model
suggests this will continue through late Tuesday afternoon. Pure
VFR will be difficult to find through the next 24 hours.
&&
.PREV DISCUSSION... /issued 246 PM CST Mon Nov 12 2018/
SHORT TERM (Tonight through Tuesday Night): The highly advertised
strong cold front is currently making it`s way through the northern
Ranchlands of Deep South Texas, at least at the time of this
discussion. The front will continue to slide southward through the
afternoon and evening. You will likely know when the front moves
through as winds increase dramatically. Ahead of the front, some
light and scattered drizzle/shower activity has developed. We had a
few thundershowers earlier across Hidalgo and Kenedy Counties,
however, much of the convection resides offshore this afternoon.
Overall, models showed some QPF, but nothing to write home about.
For sure the biggest story will be the winds and cool down behind
the frontal boundary. Winds will be the strongest along the coast,
however, as high pressure moves southward even inland locations will
experience gusty conditions. Decided to extend the advisory west for
all of coastal counties and issued SPS this AM to cover the I69C
corridor. The highest wind gusts without a doubt will be right along
the coast. In fact, Padre Island may experience some gusts close to
50 mph at times.
With the increase in winds and dramatic drop in temps there comes
some problems with wind chill values. Tuesday AM expect most areas
to experience wind chills in the lower 30s, perhaps briefly lower.
This of course brings higher concern for exposure. Temperatures on
Tuesday do not get out of the 40s across the eastern CWFA. That
said, if we are able to clear out the Ranchlands may break 50
degrees. Regardless temperatures will remain well below average.
In fact, overnight lows Tuesday night and into Wednesday will be
near freezing for much of the interior.
LONG TERM (Wednesday through Monday): Freezing to near freezing
temperatures Wednesday morning will quickly warm into the 40s by mid
morning. Mostly sunny to partly cloudy skies will prevail Wednesday
as surface high pressure settles across deep south Texas. High
temperatures Wednesday will be in the 50s with light to moderate
northwest to north winds. The combination of light winds and clear
skies should provide good radiational cooling conditions Wednesday
night. Low temperatures Wednesday night are expected to be about the
same as Tuesday night, with lows in the 30s. Another freeze watch
may be needed for Wednesday night as some locations may drop to
around freezing Thursday morning. Record low temperatures for
Thursday morning at Brownsville is 28 degrees and 38 degrees at
McAllen. Also, wind chill values may still reach advisory criteria
for a few hours Thursday morning as winds may remain around 5 mph or
so.
Surface high pressure across the area on Thursday will gradually
move east Friday into Saturday. Temperatures will slowly modify over
time, allowing for a modest warming trend. High temperatures will
generally warm into the 60s on Thursday and the 70s Friday and
Saturday. Moisture will begin to increase and pool across the region
Saturday night as another front pushes south. Reinforcing high
pressure may arrive for next Sunday or Monday.
MARINE: (Tonight through Tuesday Night): Conditions are already on
the decline across the marine zones. Buoy 42020 is already hitting
Small Craft Advisory criteria. Given this, decided to go ahead and
start the Gale Warning now as just up stream Gale conditions are
being realized. Gale force winds and very hazardous seas are
expected through Tuesday evening. Can`t rule out SCA conditions
continuing through the overnight Tuesday through the end of the
period. Simply put, extremely hazardous boating conditions through
the short term can be expected for both the Laguna Madre and
adjacent Gulf waters of Deep South Texas.
Wednesday through Saturday: Strong north winds and elevated seas
will support Small Craft Advisory conditions on Wednesday. Marine
conditions quickly improve Wednesday night into Thursday as winds
and seas steadily decrease as high pressure spreads over the area.
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Wind Advisory until 6 PM CST Tuesday for TXZ251-254>257-351.
Freeze Watch from late Tuesday night through Wednesday morning
for TXZ248>254-353.
GM...Gale Warning until 6 PM CST Tuesday for GMZ130-132-135-150-155-
170-175.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
Area Forecast Discussion
National Weather Service Grand Rapids MI
1001 PM EST Mon Nov 12 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 252 PM EST Mon Nov 12 2018
An area of low pressure will track northeastward through
the Central Appalachians tonight. This system will spread
light snow into much of Southern Lower Michigan. This area of snow
will diminish later at night but a colder airmass will be drawn
down from the north for Tuesday and that should lead to lake
effect snow showers mainly along the coast. High pressure moves in
for Wednesday which will support dry conditions.
&&
.UPDATE...
Issued at 1000 PM EST Mon Nov 12 2018
Forecast is on track, with no planned changes to the ongoing
headline. Synoptic snow is moving through at this time with
accumulations that should be on the order of an inch or two at
most. Flake size has been small and road surface temperatures are
still slightly above freezing along and south of I-96. The
synoptic snow should wind down between 1am and 4am, so we are
looking at 3-6 more hours of light snow.
Lake effect snows will continue to affect the lakeshore with a
marked increase in intensity around 4am. Heavier snow is expected
along the lakeshore south of Holland between 4am and noon Tuesday.
The RAP shows strong convergence between 1000-900mb during much
of that time. Travel along I-96 south of Holland and on I-94 west
of Paw Paw late tonight and Tuesday morning will feature very low
visibility at times due to heavier snow.
&&
.DISCUSSION...(This evening through next Monday)
Issued at 252 PM EST Mon Nov 12 2018
The main challenge in the period deals with the potential impacts
tonight and whether headlines are needed.
Models are in relative agreement in showing a band of synoptic
snow arriving this evening from the southwest. Any accumulations
from this area of snow should remain to the southeast of a Grand
Rapids to Alma line. Mid level FGEN coupled with deep moisture
through the DGZ does support the potential for minor
accumulations. To start the temperatures this evening will be a
little above freezing and values are not forecasted to fall below
freezing until closer to midnight. Thus we are not thinking
headlines are needed before midnight as most roads should remain
wet. This area of snow moves out closer to midnight and that is
when the lake effect snow risk rises. Based on a mainly north
northwesterly flow it does look like the area south of Holland
will see a potential for more impactful impacts. The snow showers
should persist through the morning commute. With temperature
predicted to fall several degrees below freezing later tonight a
risk for an icy commute looks likely to happen. Thus we will issue
a winter weather advisory for Allegan and Van Buren counties.
These snow showers do move inland Tuesday morning. They are
forecasted to weaken as they do...so we will not issue any winter
headlines east of the initial headline. That being said...there
is potential for localized slick spots away from the lakeshore on
Tuesday.
Guidance shows high pressure moving for Wednesday so we are
looking at a dry day. Subsidence and an airmass favoring less in
the way of lake effect clouds will allow for a decent amount of
sunshine.
Another southern stream storm system could clip parts of Southern
Lower Michigan mainly Thursday night with some snow/rain. Less in
the way of cold air moves in behind this system so we are not
expecting a repeat of tonights lake effect snow showers.
The next storm system that may lead to impacts is show to move in
on Saturday with snow. There is some lift and deeper moisture
shown with this weak storm that tracks eastward through the state.
Thus an increased risk for impacts exists. Temperatures will fall
steadily behind this departing system for Saturday night into
Sunday. Based on the forecasted winds behind this system the lake
effect impacts could be aimed toward the southern end of Lake MI
Saturday night into Sunday. We will need to monitor this closely
in the coming days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 725 PM EST Mon Nov 12 2018
Snow is beginning to spread into southern portions of the state
at 00z. The snow will reduce visibilities into the 3-5sm range at
TAF sites to the south and east of KGRR with 1-2sm visibilities
for a time as well. Ceilings will be widespread MVFR through the
night. The snow will taper off after 08z or so from west to east,
but lake effect snow will begin to push in off of Lake Michigan
after that time. The lake effect snow showers will be most
prominent at KMKG and KAZO during the 12z to 18z time frame. On
Tuesday, the MVFR ceilings in the morning lift to VFR late in the
afternoon. Winds will be northerly tonight shifting to the
northwest on Tuesday.
&&
.MARINE...
Issued at 252 PM EST Mon Nov 12 2018
The strengthening northerly flow on the backside of the departing
low pressure system will support increasing northerly winds
tonight. That coupled with cold air advection will generate larger
waves out on the lake. Thus the small craft advisory will be
allowed to continue for tonight through Tuesday night. With the
arrival of high pressure for Wednesday...the winds will be
weakening and shifting during that time.
&&
.HYDROLOGY...
Issued at 952 AM EST Mon Nov 12 2018
Rivers are mostly above normal for this time of year, though they
are below bank full and levels are steady or falling. Most of the
precipitation we will get over the next week will be frozen and
fairly low-moisture, so rivers will continue to fall. Despite the
cold weather, freeze-up ice jams are not a concern, as water
temperatures in the main-stem rivers are still well above
freezing.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 11 AM EST Tuesday for MIZ064-071.
LM...Small Craft Advisory until 7 AM EST Wednesday for LMZ844>849.
&&
$$
UPDATE...Duke
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...Duke
HYDROLOGY...63
MARINE...MJS
Area Forecast Discussion
National Weather Service Lincoln IL
856 PM CST Mon Nov 12 2018
.UPDATE...
Issued at 845 PM CST Mon Nov 12 2018
ILX radar indicates the main band of frontogenetical forcing was
shifting southeast along the I-72 corridor this evening. This
lines up well with the latest RAP forecast in taking the better
area of lift to the southeast with time this evening. Snowfall
amounts have generally been trace amounts across the far north
to a half inch to 1 inch across central into east central IL.
We expect the main area of lift to push into far southeast IL late
tonight and then east out of our area during the early morning
hours.
Forecast soundings continue to suggest a loss of ice crystals as
deep layer moisture decreases with time late tonight, especially
along and southeast of the I-70 corridor. In addition, time-height
cross sections indicate some weak lift lingers in the low to mid
levels of the atmosphere which may bring about a brief period of
snow which will mix with or change over freezing drizzle before
the precipitation moves off to our east by Tuesday morning.
Further north, much colder air will filter southeast into the
region with early morning lows dropping into the low to mid teens
with wind chills in the single digits.
Tuesday should be quiet with sunshine and temperatures well below
normal for the middle of November as highs struggle to reach 30
degrees (normal highs for Nov 13th should be in the low to mid
50s). The current forecast has a good handle on the forecast for
the remainder of the evening and overnight hours. As a result, no
ZFP update is needed at this time.
&&
.SHORT TERM...(This evening through Tuesday)
ISSUED AT 304 PM CST Mon Nov 12 2018
A surface cold front has pushed south of the Ohio River with
temperatures leveled off since late morning today, poised to drop
sharply overnight as cold air to the northwest continues to push
into the area. Meanwhile, bands of weak frontogenetical forcing
aloft continue over central IL producing light snow over most
areas from I-72 northward, which should be shifting southeastward
through the late evening. South of I-72, a mix of rain and snow
looks likely this afternoon, with mostly rain south of I-70. This
evening into the early morning hours, some mix of freezing
drizzle and snow is possible mainly south of I-70 as temperature
continue to cool off but cloud ice crystals diminish as moisture
depth decreases. Ground temperatures are still slightly above
freezing with air temperatures hovering near the freezing mark
limiting accumulations so far, however heavier snowfall rates and
cooling temperatures should allow accumulations to start this
afternoon and continue into the evening. Expecting around 1 inch
throughout the I-72 corridor which looks to be the best
combination of cooler temperatures and heavier snowfall rates,
with lesser amounts to the north and south, generally little or no
accumulation most areas northwest of the Illinois River and south
of I-70. Lows tonight are expected to reach 15 in Galesburg
ranging up to 26 in Lawrenceville. Wind chill temperatures by
morning should range from lower single digits northwest of the
Illinois River to the teens south of I-70.
Breezy, cold, and clear conditions are expected Tuesday as
northwest winds 10-15 mph combine with highs in the upper 20s and
lower 30s, as the current weather system moves off to the east.
Wind chill temperatures will be in the teens to low 20s or lower
through the day.
.LONG TERM...(Tuesday night through Monday)
ISSUED AT 304 PM CST Mon Nov 12 2018
The upper level trough over the intermountain west looks to slowly
progress eastward and close off over the southern Plain midweek,
eventually developing precipitation associated with a deformation
zone as it merges with the main large scale trough over the
northeastern U.S. Progression of this feature will still be
subject to some timing and track adjustments, however models are
in relatively good agreement with the 12Z cycle that this precip
should target areas from around I-72 southeastward early Thursday
morning into Thursday night, possibly as far northwestward as the
Illinois River. Temperatures will be cool enough for snow or a mix
of rain and snow over the area. Light amounts to perhaps a couple
inches are possible depending on timing of the system and whether
snow falls in the day or nighttime. Expect highs mainly in the
30s and lows in the 20s Wednesday night through Thursday night,
after one more cold night Tuesday night with temperatures dropping
into the upper teens most areas.
Another cold front looks to push across the area from the
northwest over the weekend, bringing a period of light rain or
snow, as well as dropping temperatures again, from highs in the
40s Friday, back down to the 30s Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 522 PM CST Mon Nov 12 2018
The weather system producing the snow across the TAF sites early
this evening is expected to push off to our east late this evening
with the snow ending and the IFR/MVFR cigs becoming VFR from
northwest to southeast in the 00z-05z time frame. Vsbys will
occasionally lower to 3/4sm in snow for a few hours early this
evening, especially in DEC and CMI before conditions start to
rapidly improve in those areas. VFR conditions will prevail on
Tuesday. Northwest winds are expected during this forecast period
at speeds of from 10 to 15 kts.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Smith
SHORT TERM...37
LONG TERM...37
AVIATION...Smith
Area Forecast Discussion
National Weather Service Northern Indiana
647 PM EST Mon Nov 12 2018
.SYNOPSIS...
Issued at 307 PM EST Mon Nov 12 2018
Light snow will spread across most of the region this evening
with up to an inch of accumulation in many areas by daybreak.
More concentrated snow amounts are expected closer to Lake
Michigan where 2 to 4 inches of lake effect snow may fall with
locally higher amounts possible through Tuesday afternoon. Below
normal temperatures will continue this week into the upcoming
weekend. There is another chance for rain or snow Thursday
afternoon and evening.
&&
.SHORT TERM...(This Evening through Tuesday)
Issued at 307 PM EST Mon Nov 12 2018
Area of precipitation continues to expand from across NW parts of
our area southwest into IL and MO. Have been seeing periodic
reports of drizzle or light rain and expect this to expand through
the remainder of the afternoon. As we get towards evening, falling
temperatures will allow more of a mixture and eventually
transition to all snow. While it may start to accumulate on grassy
areas, will need to wait till closer to 6Z for at/below freezing
temps to let road impacts start. Main axis of concentrated precip
seems to be favoring more NW (which seems on track considering
blossoming area over the NW) where cross sections show good
isentropic lift and alignment of omega. These do stay below
favorable snow growth zones which will limit flake size and
accumulation potential. Have increased pops further NW late
afternoon into tonight but for now not increased QPF a lot. By
evening, may be a dusting or so in grassy areas with up to an inch
of snow across the area during the evening as large area of light
snow moves through in response to deepening low pressure to the
east of the area. Locally higher pockets of accums will occur as
noted by several upstream sites occasionally dropping to 1/4-1/2
SM. Greater amounts will occur from formation of mesobanding this
evening and then lake effect across Berrien and LaPorte county
later tonight into Tuesday. After collaboration with GRR, opted to
hoist Winter Weather Advisory for Berrien county from 5Z tonight
through 15Z to cover greatest impacts during morning rush hour as
1-3" of snow may have fallen by this point to make for slick
spots. While no other areas will be included in headlines, the
lighter snow amounts may raise havoc as well as melting and re-
freezing of snow occurs and causes patchy black ice.
Snow showers will continue into Tuesday morning before tapering
off. Another inch or 2 is possible with NW alignment of lake
effect across Berrien and La Porte counties as well as somewhat
inland. By afternoon majority of snow will come to an end.
&&
.LONG TERM...(Tuesday Night through Monday)
Issued at 307 PM EST Mon Nov 12 2018
Piece of energy from departing shortwave will quickly cut-off
Tuesday night over Texas, ejecting northeast into Kentucky by
Thursday night. While much of the energy will be transfered to rapid
cyclogenesis on the east coast a period of wrap-around/deformation
precipitation will expand across the northern Ohio Valley and back
into portions of the area mainly Thursday night. Specifics remain to
be determined, but much like today an area of light mixed precip
should arrive Thurs afternoon and then quickly transition to all
snow Tuesday night with potential for around a quarter inch or so of
QPF. Despite some mesoband potential, thermal profiles not stellar
for good accumulation potential with ratios of less than 10:1
possible. Some chance for lake effect will move in for the weekend,
but lack of better moisture will likely limit anything substantial.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 636 PM EST Mon Nov 12 2018
Conditions will continue to deteriorate this evening as light snow
spreads across the area. VFR will drop to MVFR early this evening
with pockets of IFR at times within heavier areas of snow. Should
see improvement in visibility toward 06z as fast moving system
departs and synoptic snow diminishes. Quick transition to lake
effect snow expected for overnight and first part of Tuesday. As
always, difficult to nail down band location and timing at KSBN.
Models still have some differences on band orientation but favored
HRRR model in depicting potential restrictions at KSBN near
daybreak with a shore parallel band coming south.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...Winter Weather Advisory from midnight tonight to 11 AM EST
Tuesday for MIZ077.
OH...NONE.
LM...Small Craft Advisory until 4 AM EST Wednesday for LMZ043-046.
&&
$$
SYNOPSIS...Lashley
SHORT TERM...Fisher
LONG TERM...Fisher
AVIATION...Lashley
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AREA FORECAST DISCUSSION
National Weather Service Jackson KY
948 PM EST Mon Nov 12 2018
.UPDATE...
Issued at 946 PM EST MON NOV 12 2018
Rain is starting to fill back in across the northern portion of
the CWA, and latest radar trends show a slight uptick of radar
returns elsewhere that would support rain continuing to fill in
over the remainder of the CWA as well. Made some minor adjustments
to the pop forecast, but otherwise, the forecast seems to be in
good shape. Also loaded in the latest observations for temps and
winds to make sure the near term grids were on track with the
current conditions. Reworked a portion of the overnight diurnal
curve as well based on the current temperature trends. All updates
have been published and sent to NDFD/web. Another refresh of the
temps and winds, along with a resent of the forecast package will
be done once the obs are available just after 10pm.
UPDATE Issued at 557 PM EST MON NOV 12 2018
Some dry air has moved into the region behind an exiting cold
front, cutting off the precip across much of eastern Kentucky from
west to east. Precip is expected to fill back in overnight as a
secondary boundary moves eastward through the region, but even
this should remain quite light and could be patchy in some
locations. Given the considerable downward trend in pops late this
afternoon/early this afternoon, redid the pops through this time
period to better reflect the current radar trends as well as the
latest high-res models. Kept likely pops in for the late
night/early morning as this second system moves through, but since
some of the Hi-res models are showing some patchy coverage, did
not feel confident enough to go categorical. Also loaded in the
latest observations for the temps and winds to make sure the near
term grids were on track with the current conditions. This
resulted in some minor updates to the overnight diurnal curve as
well, though did not make any changes to the overnight low
temperature for now. All updates have been published and sent to
NDFD/web. A new forecast package was also sent out to reflect
these changes.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 335 PM EST MON NOV 12 2018
20z sfc analysis shows low pressure coming out of the northern
Gulf riding northeast south of Kentucky as a cold front approaches
from the northwest. This system has pushed a chilly rain shield
into eastern Kentucky today steadily moving north out of
Tennessee. The clouds and rain have kept temperatures from
climbing much today with mid afternoon readings in the upper 30s
north to the low 40s in the south. Dewpoints are in lock step with
the temperatures for the south and in the mid 30s north. Winds,
meanwhile, are light and generally from the northeast to east.
The models remains in decent agreement aloft through the short
term portion of the forecast. They all depict the continued
evolution of the troughing over the Southern Plains as it remains
unphased with the northern stream and proceeds to cut off over
the lower Mississippi Valley by Wednesday morning. Meanwhile the
northern stream trough works quickly east through the Great Lakes
with minimal height falls across Kentucky, but an ample stream of
energy from the southern closing off trough will ride overhead in
fast southwest flow. A few periods of stronger upper level
divergence can be expected during the short term - especially this
afternoon and late tonight - as a strengthening 300mb jet streak
develops southwest to northeast across the Ohio Valley. Given the
good agreement and steady trends have favored a model blend but
with a strong lean toward the higher resolution NAM12 and HRRR for
details.
Sensible weather will feature chilly rains - of some significance
in the south - running through the evening and into the overnight.
The duration will lead to some healthy totals of an inch or so in
the far south to around a quarter of an inch in the northwest.
This will be the main weather from this particular system that had
much promise last week for bringing the area some early season
snow. As such, cold air will now trail the rain`s departure
Tuesday allowing it to stay liquid as it ends for most places,
though some mix of wintry weather will be possible at the highest
points in the southeast for Tuesday evening. Most likely this will
be just some flakes but limited ice crystals in the column could
produce pockets freezing rain - though measurable chances are very
small so have kept it out of the grids and zones for now. A very
cold night follows into Wednesday morning with lows down in the
mid to upper 20s from the arriving Canadian high pressure system
and its CAA.
Again started the grids with the CONSShort and ShortBlend ones
with some minor adjustments to point temperatures through the
period. As for PoPs, beefed them up through the overnight period
and held them up in the higher terrain of the far east Tuesday
afternoon and evening.
.LONG TERM...(Wednesday through Monday)
Issued at 310 PM EST MON NOV 12 2018
A shortwave trough will push across east Kentucky Wednesday night
and Thursday, bringing another round of wet weather to the area.
Temperatures on Wednesday will struggle to reach 40 as clouds
increase ahead of the approaching system. How much temperatures
cool into Wednesday night will be the biggest question mark
impacting this forecast package. Temperatures will likely fall to
around freezing during the evening hours as precipitation starts
to spread in from the south. A strong warm nose aloft will be
present supporting mainly liquid through the event. Thus, the
question will reside around surface temperatures. Its possible
valley locations could decouple into Wednesday evening, allowing
them better potential to start off at or below freezing. The
better shot for freezing rain may be from the Cumberland plateau,
northward into central and northern Kentucky. Southeast Kentucky
may stay just above freezing, but again, this will be a complex
temperatures forecast and early wet bulbing could help to push the
surface temperatures cooler at the onset of this event. For now,
main threat appears to the freezing rain as the warm nose aloft
will prevent much snow or sleet. Will introduce the freezing rain
threat into the HWO this afternoon as the primary threat. As we
head into the overnight and Thursday morning hours, temperatures
will start to warm as we see latent heating with the falling rain
and warm air advection developing with the warm sector of the
system.
A cold front will then sweep across the area Thursday
afternoon/evening, bringing a cool surge of air back into the
region. This may allow lingering rain showers to mix with and
change over to snow. Fortunately, the better lift will be
departing as the colder air arrives, so limited precipitation
rates and warmer ground should limit any potential snow
accumulations.
Upper level pattern will become more zonal as the shortwave trough
departs by Friday. With surface ridging spreading across the area,
quiet weather will be seen from Friday through Saturday night.
Uncertainty increases by late next weekend as a clipper type
system could impact the area by late Sunday or Sunday night.
However, models are all over the place with various scenarios, so
stayed very close to the blended model guidance this afternoon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 723 PM EST MON NOV 12 2018
After a cold front and associated rain moved through this
afternoon, some dry slotting has now taken hold, with only
isolated to scattered showers present across much of eastern KY. A
secondary system will move through later tonight, with rain
expected to spread across the TAF sites once again. This rain
should be light, but may still drop VIS to MVFR at times. Tried to
time out onset of rain and associated impacts for each TAF site.
CIGS are currently variable across the CWA, with some sites
reporting below airport mins, and others, like SYM who are MVFR to
VFR. As such, expect CIGS to fluctuate somewhat overnight, but
the general trend should be towards LIFR or IFR, especially as
the second wave of moisture moves in. Rain will taper off after
daybreak Tuesday as this system moves east of the state, allowing
a much drier airmass to take hold from the west. This will
quickly cut off rain chances, though MVFR clouds may stick around
through much of the day. Winds will generally remain light and
variable overnight, becoming north between 5 and 10 knots through
the day Tuesday.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JMW
SHORT TERM...GREIF
LONG TERM...KAS
AVIATION...JMW
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
828 PM CST Mon Nov 12 2018
.UPDATE...
Issued at 817 PM CST Mon Nov 12 2018
The back edge of the snow is lingering longer than expected. While
the snow is pretty light, it is accumulating. We picked up about a
.2 inch here at the forecast office in Weldon Spring since 00Z.
The RAP keeps insisting that the low level frontogenesis will
continue to push southeast of the I-70 corridor down into
southeast Missouri over the next hour or two, and there is a
general decreasing trend on radar and a slow southeast movement to
the back edge of the snow. Am therefore leaving the northern
portion of the winter weather advisory as is with the expectation
that this trend will continue. However, there is plenty of
frontogenesis lingering over southeast Missouri into the overnight
hours. With that in mind, have extended the advisory for our
southeast Missouri counties until 200 AM.
Carney
&&
.SHORT TERM... (Through Late Tuesday Afternoon)
Issued at 227 PM CST Mon Nov 12 2018
System to exit region late tonight. In the meantime, ongoing snow
will persist, gradually tapering off from west to east. Model
soundings, especially over portions of southeast Missouri and
southwestern Illinois, still indicating loss of ice crystals aloft,
so could still see some very light drizzle/freezing drizzle, in
this area with a light glazing possible. Storm total snowfall of 1
to 2 inches with locally higher amounts still looks good for
forecast area by the time this comes to an end. Kept Winter
Weather Advisory going til 9 pm. As for low temperatures, they
will be in the teens to low 20s.
On Tuesday, sunny skies return to the region. Despite this,
temperatures will remain below normal with highs only in the upper
20s to low 30s.
Byrd
.LONG TERM... (Tuesday Night through Next Monday)
Issued at 227 PM CST Mon Nov 12 2018
(Tuesday Night - Wednesday)
Very cold night is in store on Tuesday night as ridge of arctic high
pressure remains anchored across the bi-state area. Combination of a
clear sky and a light/variable wind should promote nearly ideal
conditions for radiational cooling. There could also be just enough
snow cover across parts of south-central Missouri to help cool
temperatures another few degrees if these locations can manage to
keep a sufficiently deep snow cover through the day on Tuesday.
Regardless, most of the arctic airmass itself is cold enough to
yield low temperatures in the teens areawide. Leaned at or below the
cooler MET guidance for lows across parts of south-central and
southeast Missouri and near model consensus for the rest of the CWA.
While temperatures are expected to moderate slightly on Wednesday
into the mid to upper 30s, this is still about 20 degrees below
normal for the date.
(Wednesday Night - Thursday)
All eyes for the Wednesday night and Thursday time period will be on
mid/upper level cutoff low that forms near the Arklatex region. As
alluded to yesterday, these cutoff lows are typically very difficult
to forecast in terms of both track and timing. Compared to
yesterday, there is however more confidence in this system impacting
the CWA with the potential for significant snowfall (3+ inches).
However, even a slight shift in when the cutoff low ejects out and
its eventual track could have very large ramifications on sensible
weather output.
Currently, based on the track of this upcoming system, it appears
that portions of southeast Missouri and southwest Illinois would
have the highest chances at seeing the most snowfall. While there
are still some concerns about precipitation type, it does appear
that the dry/cold antecedent conditions associated with the previous
arctic air mass and dynamic cooling should yield mostly snow
wherever the deformation zone moves through.
Speaking of the track of the system, model consensus of the 850-hPa
low tracks is roughly from KMEM late Wednesday night into the lower
Ohio Valley late on Thursday. Previous research (Browne and Younkin -
1970) has shown the heaviest snow axis to be approximately 90
nautical miles (~105 miles) to the left of the track of the 850-hPa
low. Given the strength of this system and the fact that it
continues to deepen into the day on Thursday, this may be a case
where the heaviest axis of snow is just a bit further to the
northwest (say closer to 120-130 miles). This would favor the
heaviest snow axis in the CWA roughly from KFAM to just northwest of
KSLO.
An early look at NWP soundings show a classic heavy signature with
maximum lift centered in a saturated dendritic growth zone (-12 to -
18C). Elevated instability is also noted in this same layer very
late Wednesday night into Thursday morning as isentropes fold over
or decrease with height. Below the ice crystal growth zone, there is
a deep isothermal layer around -5C from the surface to near 700 hPa
which suggests dendrites would tend to aggregate. To top
it all off, wind speeds are fairly light throughout the column to
prevent fracturing of snowflakes. In summation, snow-to-liquid
ratios may be fairly high (above 12:1) which would help to increase
snowfall totals.
(Thursday Night - Next Monday)
Behind this next system, northwest flow aloft will establish itself.
A cold front is still expected to move through the region on Friday
night into early Saturday. Temperatures should reach into the upper
40s on Friday ahead of the cold front. While this likely will be the
warmest day of the extended, those highs would still be some 5-10
degrees below normal. Slightly cooler weather is then favored behind
the aforementioned cold front for this upcoming weekend as another
strong surface high settles into the region. Forecast high
temperatures this weekend should be mainly in the 30s before a
slight moderation occurs next Monday as high pressure settles into
the lower Mississippi Valley with southerly return flow returning to
the bi-state area.
Gosselin
&&
.AVIATION... (For the 00z TAFs through 00z Tuesday Evening)
Issued at 525 PM CST Mon Nov 12 2018
The storm system moving across the region is winding down at this
time. Most locations are already reporting VFR visibility with a
few patches of left over MVFR. Visibility should continue to
improve through the evening, though MVFR ceilings will likely
persist for several more hours from central into eastern Missouri
and southwest/south central Illinois. There will also be some
lingering light snow/flurries or possibly some patchy freezing
drizzle. The clouds should lift across the area from northwest to
southeast through the late evening into the early overnight
hours, and then scatter out before sunrise Tuesday. VFR flight
conditions are expected thereafter.
SPECIFICS FOR KSTL:
Think accumulating snow is mostly over for the St. Louis area.
However, occasional light snow or flurries, and perhaps a brief
period of freezing drizzle is still likely into the early evening
hours. MVFR flight conditions with cigs below 2000 feet are likely
to prevail for the rest of the evening. Latest radar trends may
indicate a little increase in the snow intensity over what is in
the TAF, so MVFR visibility for the first hour may need to be
extended. The precipitation is still expected to end by mid
evening, and flight conditions should improve to VFR overnight.
VFR conditions are expected to prevail thereafter.
Carney
&&
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 20 30 20 38 / 80 0 0 0
Quincy 15 28 17 39 / 5 0 0 0
Columbia 15 30 15 39 / 30 0 0 0
Jefferson City 17 31 14 39 / 60 0 0 0
Salem 24 31 19 38 / 90 0 0 0
Farmington 20 30 16 37 / 90 0 0 0
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Weather Advisory until 2 AM CST Tuesday for Crawford MO-
Iron MO-Madison MO-Reynolds MO-Saint Francois MO-Sainte
Genevieve MO-Washington MO.
Winter Weather Advisory until 9 PM CST this evening for Boone MO-
Callaway MO-Cole MO-Franklin MO-Gasconade MO-Jefferson MO-
Lincoln MO-Moniteau MO-Montgomery MO-Osage MO-Saint Charles
MO-Saint Louis City MO-Saint Louis MO-Warren MO.
IL...Winter Weather Advisory until 2 AM CST Tuesday for Randolph IL.
Winter Weather Advisory until 9 PM CST this evening for Calhoun
IL-Jersey IL-Madison IL-Monroe IL-Saint Clair IL.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Medford OR
806 PM PST Mon Nov 12 2018
.DISCUSSION...Current satellite imagery is showing some high
cirrus clouds moving over southern Oregon and northern California
from west to east. Overall, the airmass will be persistent to what
occurred last night, and temperatures will be very similar to what
occurred last night across the area. The only question will be
whether or not the cirrus clouds will move slow enough to keep
temperatures a bit warmer than last night. Have dropped
temperatures a little bit tonight from the day shift, but not as
low as they were last night due to these clouds. Otherwise, the
forecast is on track, and am not making changes. -Schaaf
&&
.MARINE...Updated 800 PM PST Monday 12 November 2018...Southerly
winds will continue through Wednesday as a weak front approaches.
This front will very slowly move into the area and thus sub-advisory
south winds and seas continue through Tuesday. The front finally
moves onshore Wednesday, and we`re not expecting any significant
impacts to the coastal waters until late Wednesday night or Thursday
morning when a steep westerly swell around 10 feet moves in behind
the front.
A thermal trough and northerly winds develop Wednesday night into
Thursday. Steep combined seas are possible on Thursday due to a
combination of west swell and wind seas. Small craft advisory level
winds are also possible on Thursday, mainly south of Cape Blanco in
the waters beyond 10 nm from shore. Steep seas and areas of gusty
northerly winds may persist into Friday as the thermal trough
remains in place along the coast. -CC/Keene
&&
.PREV DISCUSSION... /Issued 405 PM PST Mon Nov 12 2018/
DISCUSSION...A high pressure ridge is in place today bringing
warm daytime temperatures and dry conditions. A weak front will
approach the area tonight and Tuesday, then weaken further as it
moves inland on Wednesday. There is only a slight chance for light
rain along the coast. Elsewhere expect dry weather to continue
and the front will only bring some clouds into the area Wedensday.
Of note, ahead of the front expect southerly winds to develop over
the area Tuesday. This may result in some patchy smoke moving into
the area from fires to the south. Current high resolution
forecasts from the HRRR indicate smoke expected to move into
Siskiyou and Modoc counties during the day Tuesday, then patchy
smoke or haze may spread into portions of southern Oregon Tuesday
afternoon and Tuesday evening. Winds become more westerly on
Wednesday though so any smoke that moves into the area may shift
east on Wednesday.
Behind the front, a high pressure ridge will rebuild over the
region Thursday into the weekend. This will bring continued warm
daytime temperatures and dry weather to the area through at least
Sunday.
AVIATION...For the 13/00Z TAFs...VFR will prevail across the
forecast area, outside of the Umpqua Basin, for the next 24 hours.
Shallow moisture in the Umpqua Valley will likely bring local
IFR/LIFR ceilings/visibility back to Roseburg again late
tonight/Tuesday morning. These IFR/LIFR conditions will improve to
VFR by late Tuesday morning. Keene/Spilde
FIRE WEATHER...Conditions will remain critically dry through
Wednesday morning, then improve. But, humidities will not be high
and no rain is expected over the next 7 to 8 days, through Tuesday.
East to southeast winds have decreased today. They will increase
slightly at inland locations tonight and continue at 5 to 15 mph
into early Tuesday morning, while southerly winds develop at the
coast and continue into Tuesday evening. These weak to moderate wind
speeds will not reach Red Flag Warning criteria, but relative
humidity recoveries both tonight and Tuesday night will be poor to
moderate again over the higher terrain across the region.
Recoveries will be worst in Siskiyou County.
The improvement in conditions on Wednesday will be due to a very
weak front that will bring a slight chance of very light rain to the
coast then pass through the area late Tuesday in Wednesday. Despite
the improvement, conditions will still be drier than normal. Mild
and dry weather will persist through the forecast period, with light
east winds returning Wednesday night. East winds will continue
through the weekend. Strength of winds later in the week through
early next week is uncertain, but they are unlikely to be as strong
as during this past weekend`s episode. The pattern may finally
change and bring a chance of rain beyond day 7. -DW
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
Pacific Coastal Waters...None.
$$
Area Forecast Discussion
National Weather Service Paducah KY
554 PM CST Mon Nov 12 2018
.UPDATE...
Issued at 553 PM CST Mon Nov 12 2018
Updated aviation discussion for 00Z TAFs.
&&
.SHORT TERM...(Tonight through Wednesday)
Issued at 227 PM CST Mon Nov 12 2018
Initial reports out of southeast Missouri (mainly Butler and
Carter counties), indicate some sleet falling in the narrow
precipitation band moving into southwest Illinois. Surface
temperatures are in the lower 40s with surface dewpoints in 25 to
30 degree range. The RAP soundings and cross sections through this
area suggest a saturated sub-freezing layer above 800 mb with a
drier layer below 800 mb. Ice crystal and snow aggregation above
800 mb is allowing precipitation to fall through a sub-freezing
layer near 2kft agl (with some loss in size of due to
evaporation). Some sleet development is occurring in the lowest
2kft over southeast Missouri. As boundary layer saturates and wet
bulb values increase, some of the precipitation will change over
to rain during the evening. As the evening progresses, we will a
loss of moisture from the dendritic snow growth layer, leading
toward a combination of sleet, then freezing rain through
midnight over southeast Missouri and southwest Illinois. The best
lift moves east of southeast Missouri and southwest Illinois prior
to midnight, reducing any substantial lift through the moist
layer.
With surface temperatures and road temperatures expected to be in
the upper 30s to lower 40s, most of the wintry precipitation
should run off as liquid through at least 9 pm over southeast
Missouri and southwest Illinois. Subfreezing temperatures will
moving southeast from the foothills of southeast Missouri and into
southwest Illinois beginning around 10 pm CST, working toward the
Ohio River and the Confluence of the Mississippi and Ohio River
by 3 am CST. By the time the sub-freezing temperatures move south
of the Ohio, nearly all of the precipitation will be gone from
the WFO PAH forecast area.
Will update the Special Weather Statement and Hazardous Weather
Outlook this afternoon to reflect a better timing and coverage
area of the wintry precipitation for later this afternoon and
tonight.
.LONG TERM...(Wednesday Night through Monday)
Issued at 227 PM CST Mon Nov 12 2018
Fairly high confidence in a storm system moving through Mid week.
Timing and the amount of Precipitation as well as type still remain
a little in question.
One thing is consistent and that is a low over the southwest will
lift northeast into the lower Ohio Valley. This has been persistent
over the last several days. The exact path and timing has been in
question but the model solution continue to close the gap on the
solution and timing. The latest model runs show the GFS has slowed a
bit bringing it closer to the ECMWF/Canadian solutions. The exact
path still remains in question with the GFS taking a sudden shift to
the east as it enters our cwa. In contrast the ECMWF takes it right
through the center of the forecast area. The path of the Canadian is
a little in between with the path of the low. We will likely start
out with a wintry mix Wednesday night and slowly change over to
mainly snow. Temperatures will warm during the day Thursday to the
upper 30s to lower 40s. This will change any thing that falls over
to liquid/rain. Thursday night as temperatures begin to fall the
rain will likely change back over to snow. However it should also be
departing the area with little additional impact. The main impact
would likely be the morning commute Thursday morning as temperatures
will still remain below freezing. This could result in hazardous
driving conditions...especially on any untreated roads as well as
any bridges or overpasses. The area should dry out Friday and into
the weekend. However we will be in a northwest flow aloft with a
weak cold front set to move through Saturday. So we could see some
precipitation. However the forecast sounding indicate a very dry air
mass over the area. So anything that does fall will have little if
any impact. As we head into next week a surface high will be moving
through the gulf states and finally return a warmer southerly flow
to the area. There is another perturbations in the northwest flow
Sunday into Sunday night but again forecast soundings have a very
dry air mass over the region so little impact expected then as well.
We will encounter a little warmer temperatures toward the end of the
week with high well into the 40s and approaching 50 in some
locations. This will still be below normal temperatures. Normals
range from the middle 50s for highs and the middle 30s for lows and
should not reach those values.
&&
.AVIATION...
Issued at 553 PM CST Mon Nov 12 2018
Scattered to numerous light rain showers will continue across the
region through the evening. Some of the rain may be mixed with
light snow or light sleet at times, especially over portions of
southeast Missouri and southern Illinois as temperatures cool. The
loss of ice nucleation around midnight will transition remaining
precipitation to drizzle. While not included in the current TAF
forecast, there remains a small chance of freezing drizzle after
midnight as temperatures drop below the freezing mark. Primarily
VFR ceilings will lower to MVFR through the evening and hold there
through Tuesday morning. A gradual west-to-east improvement to VFR
is expected from mid morning through early afternoon with partial
clearing. Prevailing north winds around 10 knots will gust to 20
knots at times.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...RyanP
SHORT TERM...Smith
LONG TERM...KH
AVIATION...RyanP
Area Forecast Discussion
National Weather Service Blacksburg VA
659 PM EST Mon Nov 12 2018
.SYNOPSIS...
Low pressure from the Gulf will track over the region tonight,
reaching the New England coast Tuesday. Meanwhile, a cold front
entering the Ohio Valley will move east and stall along the
coast Tuesday night. Low pressure will develop along the front
over the southeast United States Wednesday night and track
through the Mid Atlantic region Thursday.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 642 PM EST Monday...Falling into an in-situ wedge, a
shield of steady moderate to at times heavy stratiform rains
continue to advance across the eastern two-thirds of the
forecast area. Other than potentially at Boone where radar may
be underestimating somewhat, hourly rain rates from mesonet and
ASOS sites have been almost half as much as what surrounding
radar accumulations are indicating, a consequence of
overestimation from bright banding. Most of these hourly
accumulations have been to the tune of a quarter to at most a
third of an inch. Look for rains to continue to progress
east/northeast as the evening progresses, with a general
decrease in ongoing rains from west to east through 04z/11 PM.
As reflected in the HRRR and some of the 18z forecast guidance,
next round of steady light to moderate rains should progress
into areas along/east of Highway 29 into the overnight hrs,
while areas further west, from the Blue Ridge westward, should
see more intermittent light rains at worst. These trends already
reflected well in the forecast.
As of this writing, already starting to see a turn made toward
gradual rises along gaged points on the Dan River, but still
well below action stage levels. A continued gradual rise can be
expected on most main stem rivers, though the Dan is at risk of
experiencing the greatest forecast rises. Will continue to
monitor.
Otherwise, have used a blend of most raw 2m temperatures into
the going forecast to essentially show temperatures showing
little up-or-down trend through midnight, before warm advection
induces a slow rise in most locales overnight.
Previous discussion from 232 PM Monday follows...
The wedge of cooler air remains over the area and has
strengthens some due to adiabatic (easterly upslope) and
diabatic (evaporative) cooling processes. Unfortunately,
temperatures will not make it out of the 40s with some mountain
valleys remaining in the 30s.
The big ticket item for today will be how much rain the area
will see into tonight. With warm moisture air advecting over the
wedge, strong isentropic lift and channel vorticity will result
in around an inch of rain along and south of the VA/NC border
this afternoon. Along the highway 460 corridor, a half to three-
quarters /0.50-0.75/ of an inches is expected. A range of a
quarter to a half /0.25-0.50/ of an inch is possible across the
Greenbrier Valley to the Alleghany Highlands.
The wedge may still be in play this evening and will erode once
a surface low develops over the coastal piedmont of North
Carolina and tracks to the Virginia coast overnight. PWATS
increase to 2-3 standard deviations above normal this evening as
the original disturbance brings Gulf moisture, then adds a
strong fetch from the Atlantic. Heavy rain potential remains
over the northwest North Carolina and Southside Virginia this
evening with another inch of rain is possible. Amounts taper
overnight heading west to a half to three-quarters /0.50-0.75/
of an inches towards the Blue Ridge and a quarter to a half
/0.25-0.50/ of an inch across the Bluefield area and
southeastern West Virginia. The moderate to heavy rain will move
east of the area through the early morning hours as the low
quickly races northeast of the area. If 2-3 inches or more of
rain falls over the area, areal flooding of creeks and streams
is possible, river flooding is likely to follow within 12-24
hours along the Dan River, maybe the Roanoke River. Rainfall
rates and amounts will determine if areal flood warnings are
warranted this evening. The main area of concern will be along
the VA-NC border.
The surface low tracks off the Delmarva Coast Tuesday morning.
A weak cold front will then slide across the region, bring
additional light rain showers to the area. Rain will taper off
from west to east in the afternoon as the front moves to the
coast. Overcast skies will likely remain through the day with
high temperatures recovering into the mid to upper 40s across
the mountains and lower 50s east.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 245 PM EST Monday...
Tuesday evening the far southwest portion of the area will be
receiving the tail end of the exiting line of showers associated
with the departing cold front. Western Greenbrier County will
start to experience northwest upslope flow, residual moisture
and falling temperatures to yield some isolated snow showers.
Both regions of light precipitation are expected to end by
midnight.
Dry high pressure will make a brief visit to the area Wednesday
morning. By the afternoon, light precipitation will start to
overspread this high pressure from the south. This
precipitation, in the form of light rain, will primarily only
impact the Northern Mountains of North Carolina through sunset.
Wednesday night into Thursday, precipitation will continue to
overspread the area on the eastern flanks of an area of low
pressure moving eastward through the mid-Mississippi River
Valley. A strong, deep, southeast fetch of moisture off the
Atlantic will develop. This moisture will only help to enhance
the nose of high pressure east of the crest of the Blue Ridge,
helping to keep surface temperatures on the cool to cold side,
all while bringing a nose of warmer air over the region not too
far off the surface. The result will be about an 18 hour period
where a decent portion of the forecast area will be receiving
freezing rain to at least some accretion. Highest amounts are
expected to be along and near the crest of the Blue Ridge thanks
to enhanced precipitation totals here where the effect of a
southeast upslope flow will maximize precipitation totals.
Given how far out in time this event still is, will be using a
fairly conservative 33% ice versus WPC QPF totals. Even doing
this results in some storm total ice amounts at or a little
above the quarter-inch threshold in the aforementioned favored
areas, with at least a few hundredths of an inch for a vast
majority of the forecast area save parts of Southside Virginia
and north central North Carolina, and far southwest Virginia
towards Richlands. This trend upward in ice totals matches well
with the trend offered by WPC as reflected in their most recent
3-day ice accretion totals.
While we are forecasting for the early part of Thursday rain
versus freezing rain, sleet could also be falling over parts of
the area currently forecast for freezing rain. To keep the
forecast simple that far out, we try not to offer more than one
winter weather type at a time in the forecast, but either
freezing or snow. With the warm nose in place, freezing rain,
where warranted, is the better choice of the two. However, as we
get closer to the date in question, and sleet looks more
probable where freezing rain currently is forecast, this
alteration would lower the currently forecast ice accretion
totals. By Thursday afternoon, the entire region looks warm
enough for plain rain, albeit a cold rain.
Thursday night, the parent upper low is expected to be moving
along the Mason Dixon line, bring its associated trough axis and
cold front through our region. This transition will shunt the
warm nose to our east as cold air advection streams into the
area on progressively gusty northwest winds. This will result in
a transition to scattered rain/snow showers across mainly
western sections of the area.
During this portion of the forecast low temperatures will
average around normal. However, high temperatures will be about
10 degrees below normal on Wednesday, and about 15-20 degrees
below normal.
Forecast confidence is moderate on the general transition of
the weather patterns during this portion of the forecast.
However, confidence regarding the specific precipitation types
and amounts Wednesday night into early Thursday are still in
question and likely will flucuation between now and then. What
is of high confidence is some type of wintry mix other than just
rain versus snow is expected during this time period, raising
the flag for the strong potential for a Winter Weather headline
for portions of the area.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 1230 PM EST Monday...
Friday morning an upper low will be making headway eastward
through the Upper Ohio River Valley with its associated trough
axis extending southward into a portion of our forecast area. A
timing challenge within the models exists to pinpoint just where
this axis will be at the start of the day. However, the general
trend of the day will be for any lingering precipitation in the
east from the Thursday/Thursday Night system to be exiting the
region, or to dissipate thanks to increasing northwest,
downsloping, winds across the eastern parts of the area. Across
the west, these same gusty northwest winds will allow for a
period of upslope scattered snow/rain showers across portions of
southeast West Virginia.
Heading into and through the weekend, a general northwest flow
pattern will continue across the area, but but with notably
weaker speeds. Very isolated lingering rain/snow showers will be
possible across parts of southeast West Virginia Friday night
through Sunday.
Sunday night into Monday models vary as to the degree which a
cold front will impact our region. Our latest forecast will
reflect a consensus of the guidance which yields isolated
rain/snow showers from roughly the Blue Ridge and points west
Sunday night and isolated rain showers across the southeastern
sections of the area on Monday.
Temperatures during this portion of the forecast are not
expected to show a lot of variation, although there will be a
slightly trend lower by the second half of the weekend post-cold
front. Readings on average will be just a few degrees below
normal.
Forecast confidence is highest on Friday, at moderate
confidence, and trends downhill heading into Monday.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 659 PM EST Monday...
Aviators can expect poor flight conditions through early Tuesday
morning due to sub-VFR ceilings/visbys, mountain obstruction
and areas of wind shear above wedge inversion around 3000 feet.
Steady, at times heavy rain with mist producing visbys commonly
in the 2-5 SM range will continue to progress across the
eastern two thirds of the airspace. As initial frontal wave low
moves northeast, this rain should begin to decrease in
intensity from west to east through about 04z, though fog/mist
and low ceilings (IFR to LIFR at times) likely to persist until
early Tuesday morning. Winds mainly northeast at 3-8 kts, though
increasing southerly low-level jet and directional shear through
the 925-700 mb level indicates potential for wind shear in the
Piedmont/foothills for late evening and overnight. Already some
instances of light/moderate shear being reported in PIREPs
across the Piedmont of central/southern NC.
Should see MVFR-IFR ceilings continuing into Tuesday morning as
the next weak wave of low pressure brings renewed chances for
MVFR-VFR rains. Looks like areas along/east of the Blue Ridge
stand the greatest potential for rain through mid-afternoon.
While winds likely tend variable for the first part of Tuesday,
as this secondary wave exits, look for a wind shift to
northwest late in the TAF period to around 4-8 kts.
Forecast confidence is high on poor flight conditions and
categories, but is moderate to low on timing category changes.
Extended Discussion...
Look for ceilings to trend VFR from the Blue Ridge eastward
thanks to downsloping winds overnight, but lingering sub-VFR
ceilings along with intermittent upslope snow showers possible
between KBLF-KLWB.
Another area of low pressure develops along the front on
Wednesday and brings deep moisture back into the Mid Atlantic
region later Wednesday into Thursday. Sub-VFR possible in rain
and areas of wintry mix Wednesday night into early Thursday
espcly across the mountains. This storm system is expected to
exit the region by Friday with conditions returning to VFR with
the exception of residual upslope snow showers on the western
slopes of the central Appalachians.
Forecast confidence above average Tuesday and average Wednesday
through Friday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...RCS
NEAR TERM...AL/RCS
SHORT TERM...DS
LONG TERM...DS
AVIATION...AL/RCS
Area Forecast Discussion
National Weather Service Sacramento CA
225 PM PST Mon Nov 12 2018
.SYNOPSIS...
Dry weather continues with cool nights and near to above normal high
temperatures through the week. Diminishing winds ease critical fire
weather conditions this week, but widespread smoke from the Camp
Fire will continue to impact the area.
&&
.DISCUSSION...
Ridge axis along the coast shifts inland tonight as a weakening trof
moves into the mean ridge position. High cloudiness forecast to
drift inland over Norcal on Tue, exiting the area on Wed. The cloud
cover will likely not impact min temps significantly as the dry air
mass will result in strong radiational cooling. Also does not appear
the smoke layer is having too much of an impact especially as it
shifts gradually overnight with the downslope/drainage winds. RHs
recovered very well from MYV-MOD and with similar conditions
expected this coming night from last night, expect some dew/frost
may form in this area again by Tue morning. Otherwise the dry air
mass will preclude widespread heavy dew/frost, although there is
some moisture in the ground from local watering.
Persistent upper ridging over Norcal will result in light/lighter
winds over Norcal and limited mixing heights (1 kft - 1.5 kft), due
to the time of the year, will tend to keep persistent smoke over a
large portion of the CWA for the next couple of days. Satellite
indicates some improvement on the east side of the CWA with the help
of downslope flow overnight. But during the day, with light winds,
upslope flow may carry some smoke back to the east again through
evening. Smoke may also spread towards RDD per the HRRR smoke loop
through this evening.
With no major changes in the wx pattern during the short term,
little change expected in the forecast. Smoke might help to keep
temperatures cooler the next couple of days, otherwise they will
continue to run above normal, especially in the far Nrn portion of
the CWA where they are less impacted by smoke. High temps will be in
the 60s to mid 70s for the Central Valley, with mostly 50s to 60s
for the foothills and mountains. Cold overnight temperatures are
expected mainly over the Central Sacramento Valley southward, with
lows in the 30s to low 40s. Lows will be in the teens to mid 20s
across mountain basin locations. JHM
&&
.EXTENDED DISCUSSION (Friday THROUGH Monday)
Broad upper ridge forecast to continue across the region later in
the week maintaining dry weather with mild days and cool nights,
and no strong wind events are expected. Forecast guidance is
indicating the possibility of a pattern change as an upper trough
approaches the area early next week. Big question is will the
cut-off low approaching the region next week bring any chance of
rain to Norcal. 12/12z GFS weaker and farther south than the
12/00z ECMWF Mon/Tue next week, and the 12/12z ECMWF following
suit, but also showing a Nrn stream trof bringing precip to Norcal
next Tue. These differences yield low confidence in model solutions
at this time. JHM
&&
.AVIATION...
Widespread MVFR likely the next 24 hours across the entire
Sacramento Valley with local IFR for the southern terminals due to
smoke from the Butte County wildfire. Northerly winds under 10
knots.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$