Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/08/20
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
620 PM EST Tue Jan 7 2020
.AVIATION...
Passage of right entrance region over southern parts of the area
later this evening continues to show some promise for a several hour
window of enhanced snow shower activity mainly KPTK south, but will
back off timing of TEMPO group to 03z-05z. Main cold front pushes
through the area behind this feature with a wind shift from SW to
NW. Wind gusts overnight will top 25 knots within CAA behind this
front. Cigs are problematic into Wednesday with a general lower VFR
deck in place off/on into midday Wednesday with clearing late in the
forecast. Winds will also diminish late in the day Wednesday and
become basically calm by evening. There will likely be snow flurry
activity late tonight into Wednesday morning, but signal for any
more significant snow shower activity does not support a mention in
the forecast ATTM.
For DTW...Concern is brief IFR snow shower later this evening with
wind gusts 25 knots or more overnight into the first part of Wed
morning as direction veers to WNW.
DTW THRESHOLD PROBABILITIES...
* High for ceilings aob 5kft later this evening again and late
tonight into Wed morning, low confidence by midday Wednesday.
&&
.PREV DISCUSSION...
Issued at 333 PM EST Tue Jan 7 2020
DISCUSSION...
Latest water vapor imagery shows large upper level low over northern
Ontario with deep southwest flow over the Central Great Lakes,
resulting in another mild day as temperatures have reached into the
upper 30s to lower 40s. Radar activity over Lower Michigan matching
up nicely with lead 850-700 MB Theta-E/Specific Humidity (up to 2
g/kg )/pre-frontal trough. This narrowing moisture axis and activity
will slide east around 23Z. Additional snow shower activity expected
to move in later this evening with the help from Lake Michigan.
Quick glancing blow of cold air to track through the Central Great
Lakes tomorrow morning, as 850 MB temps around -20 C extend to
Saginaw Bay, with -18 C extending toward the Ohio Border. Westerly
flow this evening veering around to the unfavorable northwest flow
tonight for lake effect, coupled with very dry nature of the Arctic
airmass and crashing inversion heights to limit activity to mostly
flurries on Wednesday, with a decent amount of sunshine even likely.
As the arctic front passes through late this evening, there are
still plenty of indications (ARW/Regional GEM) there will be a quick
burst of snow along the front. Note the clouds/radar returns near
the Quad Cities which may be able to provide the favorable backdrop
of 700 MB support/left exit region of the upper level jet (>110
knots), although the bulk of the forcing looks to be tracking just
south of the Michigan border through this evening, with the
aggressive mid level dry slot then taking hold after midnight over
southeast Michigan. Still, various soundings, RAP for instance, do
show a brief window of good supersaturation with respect to ice and
capes (50+ J/kg) intersecting the DGZ late this evening/around
midnight, and still favor localized accumulations of a dusting to 1
inch. As the colder and dry airmass takes hold tonight, the modest
cape/supersaturation with respect to ice looks to reside mostly
above/colder than -15 C isotherm, and thus probably looking at
mostly flurries around Wednesday morning with the dry sub cloud
layer around 2 kft. Despite the lack of snow cover in place, the
deep/cold airmass should hold maxes in the mid/upper 20s, in line
with the latest guidance.
Broad longwave troughing over western half of North America
Wednesday night, with one piece of upper level energy/surface low
pressure tracking through the Midwest on Thursday, and through Lake
Superior Thursday evening. A decent Pacific Moisture plume/PW Values
up near 0.75 inches to track through southeast Michigan during the
evening. The low level moisture advection/isentropic ascent coming
over the cold ground should be enough to generate light rain
showers, as strong southwest low level jet brings 5-8 C (925 MB dew
pts) into southeast Michigan Friday morning. Frontal boundary looks
to be stalling out as 500 MB heights rise in response to summer-like
upper level ridge (591+ DAM at 500 MB) center building near the
Bahamas. Sprawling Bermuda surface high (1040+ MB) will be pumping
Atlantic and Gulf of Mexico moisture north on Friday as a strong
storm system exits the Four Corners region. Meanwhile, northern
stream/arctic airmass will be tracking through the northern Plains,
and the race will be on to get to the Great Lakes Region, determining
our precip type. With the unusually high moisture content for January
standards, even if we do end up on the mild/rainy side (which is
looking more likely, supported by 12z Euro and ICON), could have some
flood issues with potential 3+ inch total rainfall, followed by some
very strong wind as the cold advection/dry slot kicks in on Sunday.
MARINE...
Passage of a clipper system traveling across the southern Provinces
of Canada will allow an Arctic front to travel across the Great Lakes
late this evening through late Wednesday morning. Post-frontal
northwest flow will hold mixing depths and will tap into stronger
winds aloft, allowing 25-30 knot gusts to persist across the open
waters and nearshore zones now through Wednesday morning. Strongest
winds are expected across northern and central Lake Huron during the
mid and late morning hours on Wednesday, where near-gales to low-end
gale force winds (around 35 knots) will be possible. Have decided to
preclude the issuance of a gale warning at this time as the window
to see persistent gale force winds is short. Small craft advisories
are in effect for all nearshore zones. Additionally, prolonged
northwest flow will activate lake effect snow, especially along the
arctic frontal boundary, where snow squalls are expected given the
instability in place over the warmer waters relative to the air
mass. All of Lake Huron and the Saginaw Bay will have the best
chance to see squalls late tonight and overnight, where brief but
drastic reductions to visibilities will be expected with squall
activity. Snow squall threat and associated winds will diminish by
Wednesday afternoon as instability over the lakes decreases, with
freezing spray holding through the bulk of Wednesday.
A strong warm front is then forecasted to push north into the Great
Lakes Thursday morning and afternoon, which will bring the next
chance for strong winds across the lakes. Much higher confidence
regarding gusts between 35-40 knots across Lake Huron on Thursday
given the impressive low-level wind field that moves in. A gale
watch remains in effect for Lake Huron.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Advisory from midnight tonight to 4 PM EST
Wednesday for MIZ049.
Lake Huron...Gale Watch from Thursday morning through Thursday evening for
LHZ361>363-441>443-462>464.
Small Craft Advisory until 10 AM EST Wednesday for LHZ442-443.
Small Craft Advisory until 5 PM EST Wednesday for LHZ421-441.
Small Craft Advisory until 10 AM EST Wednesday for LHZ422.
Lake St Clair...Small Craft Advisory until 10 AM EST Wednesday for LCZ460.
Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EST Wednesday for LEZ444.
&&
$$
AVIATION.....DG
DISCUSSION...SF
MARINE.......AM
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Rapids MI
929 PM EST Tue Jan 7 2020
LATEST UPDATE...
Update/Marine
.SYNOPSIS...
Issued at 307 PM EST Tue Jan 7 2020
-Lake effect snow showers into Wednesday Morning; slick
Wednesday morning commute possible
-Heavy Rain Threat Thursday Through Saturday Night
-Potential travel impacts over the weekend from freezing rain,
sleet and snow mainly north
&&
.UPDATE...
Issued at 929 PM EST Tue Jan 7 2020
The shortwave that caused the area of snow showers to cross
Southwest Michigan between 7 pm and 9 pm is exiting the area now.
So there will be a quiet period in terms of snow showers until
the arctic front reaches this area. Currently front can be seen as
a band of west to east clouds from near GRB to TVC (just south of
both at 920 pm actually). There is a band of snow showers on the
radar associated with that too. That band will move south and be
in our area (I-96) by midnight or so. After that moves through
temperatures will fall down into the teens north and lower 20s
south. Snow showers will become widespread west of US-131 but due
to the shallow depth of the inversion, will not be heavy enough to
result in more than 1 to 2 inches of snow. The will likely be
some blowing and drifting even so due the gusty northwest winds.
Still I do not see this getting nasty enough to put out a headline
UPDATE Issued at 645 PM EST Tue Jan 7 2020
The snow showers are already developing, more in line with the NMM
than the HRRR so I believe once again the models are underplaying
this event. There are two snow shower events actually, the one
associated with the cold front (which is what we are seeing now)
and the one associated with the real lake effect in the deep cold
air. That moves in around midnight and should last until the back
edge of the upper jet moves over this area, taking us out of the
deep cold air. I did not change our overall forecast, 1 to 2
inches for a max snowfall makes sense given the short duration of
the event and the inversion heights only to 5000 ft to 6000 ft
over night. That being said, our high res models do suggest the
strongest lift centered in the DGZ toward morning, so there could
be some decent snow showers around even so.
All of this should slowly weaken during the mid to late morning
Wednesday as the deep cold air moves out of the area.
&&
.DISCUSSION...(This evening through next Tuesday)
Issued at 307 PM EST Tue Jan 7 2020
-Lake effect snow showers into Wednesday Morning; slick Wednesday
morning commute possible
A brief but sharp cool down occurs tonight into Wednesday. Lake
effect snow showers will be on the increase as a result.
Inversion lower considerably to around 5K ft from 06z to
18z...which should limit the impacts risk. The DGZ is show to be
moist so high pops are warranted. Surface temperatures are
projected to fall through the 20s tonight.
-Heavy Rain Threat Thursday Through Saturday Night
There has been a trend in many of the models towards a warmer
scenario. Based on the latest runs...less in the way of snow is
expected. With a more northern track of the low along the
baroclinic zone...greater amounts of Gulf moisture are projected
into the region...becoming very anomalous. At this time...most
models are showing several inches of precipitation...which will
need to be monitored very closely given the potential impacts.
-Potential travel and power outage impacts over the weekend from
freezing rain, sleet and snow mainly central and north
Tough call this far out how this one will go down. Stay tuned as
there is still a fair amount of uncertainty on the storm track. We
know the precipitation will be heavy at times. The type of
precipitation is the challenge. Looking at trends...the warmer
scenario is pushing the main snow risk further north...and could
support a band of heavier freezing rain just to the south of the
heavier snow area. There are concerning ingredients showing up.
Shallow cold air will be advecting in as the main wave will be
lifting up through the region. This would raise the risk for a
swath of heavier freezing rain somewhere in the CWA. To the north
of the elevated warm layer...mainly snow would be expected. The
freezing rain risk looks the greatest over central parts of the
CWA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 645 PM EST Tue Jan 7 2020
The snow showers are already developing, more in line with the NMM
than the HRRR so I believe once again the models are underplaying
this event. I have some IFR conditions in our TAF sites near and
west of US-131 tonight and MVFR on the more eastern TAF sites.
Even so do not be surprised if briefly we have visibilities going
down to near a one mile at times between 03z and 12z at the more
western TAF sites. Ceiling should become MVFR by 06z or so as the
colder air comes in.
With the upper wave that brought in the cold air moving out so
quickly Wednesday I believe skies may actually clear or at least
become scattered by 21z at most of the TAF sites on Wednesday. It
will be breezy tonight into midday Wednesday as the core of the
cold air moves in. Winds let up by midday Wednesday as the deeper
cold air moves out of the area.
&&
.MARINE...
Issued at 929 PM EST Tue Jan 7 2020
We continue to see gale force wind gusts in the near shore and
with the passage of the arctic front around midnight, there is a
second maximum in the wind, which of course is what is helping to
bring in the arctic air. So I (after coordinating with near by
offices) extended the gale warning till 9 pm Wednesday. I did not
change the coastal flood advisory. That seems fine as is.
&&
.HYDROLOGY...
Issued at 307 pM EST Tue Jan 7 2020
All rivers have now fallen below flood stage, although the Grand
River at Robinson Township remains very high as gusty west winds are
pushing some water back up the river mouth.
Attention now turns to the growing possibility of widespread very
heavy rain across parts of our area late this week and into this
weekend. There has been a very concerning trend among the models in
the last 24 hours toward the possibility of incredibly heavy
rainfall for our area for this time of year. Guidance is suggesting
much of the area (I-96 and southward) could see 2 or even 3 inches
of rain in the Friday/Saturday timeframe. Needless to say, with
soils saturated and river levels already high, this has the
potential to produce more significant river flooding than we`ve seen
at any other point in the last year.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Advisory until 11 AM EST Wednesday for MIZ037-
043-050-056-064-071.
LM...Gale Warning until 9 AM EST Wednesday for LMZ844>849.
&&
$$
UPDATE...WDM
SYNOPSIS...MJS
DISCUSSION...MJS
AVIATION...WDM
HYDROLOGY...AMD
MARINE...WDM
Area Forecast Discussion
National Weather Service Lincoln IL
920 PM CST Tue Jan 7 2020
.SYNOPSIS...
Issued at 330 PM CST Tue Jan 7 2020
A weak cold front will move southeast through the region tonight
before high pressure builds back into area during midday
Wednesday. Dry weather is expected to continue across the area
through early Thursday. A series of storm systems are then
expected to eject northeast across the area from Thursday
afternoon through Saturday evening, potentially bringing 2 to 5
inches of rain to central and southeast Illinois from Thursday
night through Saturday. This will be followed by a wintry mix with
some accumulating snowfall possible for parts of central and
especially northwest IL overnight Friday night and Saturday.
&&
.UPDATE...
Issued at 915 PM CST Tue Jan 7 2020
A weak cold front passing through Illinois tonight will trigger a
wind shift from SW to N-NW. Gusty winds could develop behind the
front for at least a few hours after midnight tonight. Gusts back
in Iowa are up between 20-25 mph at times. No precipitation will
occur with this FROPA due to an abundance of dry air below the
cloud bearing layer (10K FT). All radar returns have not resulted
in any precip in our area as a result. Cold air filtering into
Illinois behind the front will push lows down into the low 20s in
our northern counties. The gusty winds will put wind chills into
the single digits above zero late tonight and early Wednesday
morning.
Cool high pressure will settle into the area tomorrow, with north
winds shifting to the E and SE by the end of the day. Our coolest
highs of the next 7 days will come tomorrow, with readings topping
out in the lower 30s north of I-74 to the low 40s south of I-70.
The current forecast database has a decent handle on the short-
term forecast, and no formal update will be needed this evening.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 330 PM CST Tue Jan 7 2020
Mid afternoon surface map shows 1028 mb high pressure over east
Texas and ridging into the mid MS river valley. A cold front was over
over central WI/IA/KS and associated with a weak short wave. This
feature was spreading broken to overcast mid/high clouds at or
above 10k ft over northern 1/3rd of IL including northern CWA.
Mostly sunny skies still prevailed over rest of central and se IL
at mid afternoon. Breezy west winds 10-18 mph and gusts of 18-25
mph prevailed over central IL, with temps mostly in the low 40s
central IL and mid 40s in southeast IL. Cooler upper 30s in
cloudier areas of Knox, Stark and Marshall counties with Lacon 38
and Galesburg 39.
The cold front will track se thru central IL this evening and
southeast IL overnight and should pass thru dry, with flurries
possible in northern IL this afternoon/evening. Mid level clouds
will decrease later this evening and overnight with fair skies by
daybreak Wed. WSW winds diminish early this evening and veer NW
behind the cold front overnight. Lows tonight range from upper
teens to near 20F northern CWA to the mid 20s in southeast IL.
High pressure over the Dakotas settles into the upper MS river
valley Wed and ridges across IL, bringing ample sunshine and
lighter winds tomorrow. Cooler highs Wed in the mid to upper 30s,
ranging from lower 30s north of I-74 to lower 40s in Clay,
Richland and Lawrence counties.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 330 PM CST Tue Jan 7 2020
High pressure ridge exits east over the eastern Great Lakes and
mid Atlantic States overnight Wed night with a warm front lifting
northward over central IL. Evening lows Wed night in the upper 20s
and lower 30s (coolest ne CWA) then slowing rising overnight Wed
night with increasing southerly flow. Stronger south winds on Thu
bring milder highs in the lower 50s, with some mid 50s over sw CWA
and se IL. Most areas should stay dry Thu morning, then see a good
chance of light rain showers developing during Thu afternoon in
strong warm air advection pattern and cold front approaching nw IL
by sunset Thu.
1st wave of widespread rain showers to occur Thu night into Friday
as cold front slowly moves into heart of central IL by midday Fri.
Mild lows Thu night in the mid to upper 40s, except upper 30s and
lower 40s nw of the IL river behind cold front. Mild again on Fri
with highs ranging from 45-50 nw of the IL river to the upper
50s/lower 60s in eastern/se IL.
2nd wave of heavier rain showers to eject ne over area Fri night
and Saturday as more energy ejects ne from the southern plains
toward the southern Great Lakes. Models have trended further nw
with heavier qpf and also have lower snowfall amounts with slower
changeover to snow overnight Fri night and Sat. The heaviest qpf
appears to be Fri night and Sat over central and se IL and between
3-5 inches of rain expected by early Sat evening over se half of
CWA (highest se of I-70), with 1.5-3 inches of rain from I-55 nw.
Rain to chance to snow over the IL river valley late Fri night and
Sat, and changeover to snow as far east as I-55 on Sat, then
turning to light snow over rest of central IL Sat evening in
deformation zone, while se IL likely stays rain into Sat evening.
A couple inches of snow possible late Fri night and Sat along and
nw of I-55 with little or no snow accumulations in eastern/se IL.
Temps likely slipping during Sat with increasing cold air
advection on back side of storm system. Still some model
difference with track of heaviest rain and ending during Sat
night. Issued ESF for se half of CWA for 3-5 inch rain expected and
flooding potential Thu night thru Saturday. This rainfall could
reach near or even above our normal January precipitation in just
a couple days.
Dry weather returns late Sat night and Sunday as weak high
pressure settles into the area. Models show a weak northern stream
system clipping nw/northern IL Mon while a southern stream system
mainly se of the Ohio river. Much of area has little or no qpf on
Mon and Mon night. Ecmwf then spread qpf ne over area on Tue
while GFS and GEM are dry. Stayed close to consensus/blend for
forecast next work week which keeps lows pops in there especially
se IL though confidence is low. Cooler highs Sunday in the mid to
upper 30s central IL and low to mid 40s southeast IL. Temps
moderate into the 40s Mon/Tue with lower 50s in southeast IL. So
overall above normal temperatures look to continue across the area
into next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 546 PM CST Tue Jan 7 2020
VFR conditions are forecast to continue across the central IL
airports through 00Z/6 pm on Wed. Overcast to broken mid/high
clouds generally at or above 10k ft will push across all terminal
sites this evening, due to a weak shortwave in the upper level
flow. Skies will clear out from NW to SE by midnight. A weak cold
front over far nw IA into se Nebraska will slide se to the IL
river valley by late this evening, and thru DEC and CMI during
early overnight. W-SW winds at 5-8KT will veer to the NW after
cold FROPA tonight. HRRR is indicating some gusty NW to N winds
will develop in the wake of the front, with sustained speeds of
10-14KT and gusts possibly between 20-25kt. Those gusts should
subside by morning on Wednesday, as winds shift through the
northerly directions to E-SE Wednesday afternoon.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SYNOPSIS...07
SHORT TERM...07
LONG TERM...07
AVIATION...Shimon
Area Forecast Discussion
National Weather Service North Platte NE
636 PM CST Tue Jan 7 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 242 PM CST Tue Jan 7 2020
A 1032 mb high pressure center will cross North Dakota this evening
and be centered across central Minnesota by Wednesday morning. This
will drive a cold front southward into the area tonight. The front
will stall from southeast to northwest across the area late tonight.
Low-level moisture will pool and expect an area of low stratus
clouds to develop along and north of the front across the Sandhills
and north central Nebraska. Also added some patchy fog as the RAP
and HRRR hint at low visibility in spots, mainly across the
Sandhills after midnight.
The front will attempt to lift northward as a warm front Wednesday.
South to southeast low-level flow will keep low-level moisture in
place with the potential for low clouds to linger across north
central Nebraska most of the day. Have limited highs to mid 30s in
that area, with lower and mid 40s across western and southwest
Nebraska.
.LONG TERM...(Thursday through Tuesday)
Issued at 242 PM CST Tue Jan 7 2020
Thursday into Friday a long wave trough will be digging across the
western CONUS. This is forecast to dig into the Southern Plains
and bring a round of heavy rain and T-Storms to the Mississippi
Valley region during the weekend. Still appears that our area may
see some light snow Thursday night into Friday as the upper trough
passes, but some uncertainty remains here as strong northern
stream energy will be approaching at the same time. This could
shunt much of the moisture south and east of the area. The NAM and
ECMWF are a bit slower with the northern stream and allow for a
period of light snow before it arrives. The GFS remains quicker
and keeps much of the precipitation southeast of the region. Will
increase pops a bit with agreement between the NAM and ECMWF.
Regardless only around an inch or so of snow is expect at this
time as the northern stream will quickly shut down the snow when
as it arrives.
Arctic air that dives south into the area Friday behind a cold
front, with highs only reach the upper teens across portions of
north central Nebraska. Temperatures will moderate some over the
weekend, with high temperatures back into the 30s all areas by
Sunday. Southwest flow aloft develops during the weekend as
another long wave trough digs southward through the Pacific
northwest toward the central and southern Rockies. Temperatures
will moderate some with highs back into the 30s most areas by
Sunday.
We are monitoring the potential for some fairly cold air to move
south into the region later next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 607 PM CST Tue Jan 7 2020
A weak cold front currently roughly bisects the area from
northwest NEB to south central NEB and will become stationary
tonight. Otherwise, latest satellite imagery shows passing high
clouds across western NEB with lower ceilings, albeit still VFR,
across central and eastern SD. Concerns turn to stratus and patchy
fog potential. Current thinking is ceilings dropping to MVFR,
perhaps even IFR, late this evening across parts of the Sandhills
towards central NEB. Patchy fog will then be concerned as well,
however, thinking visibility restrictions will be 1/2 mile at
worst. While conditions improve early tomorrow, mostly cloudy
skies will prevail along with increased southerly winds. Gusts up
to 25 mph Wednesday, highest across northern NEB.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Taylor
LONG TERM...Taylor
AVIATION...ET
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 345 PM CST Tue Jan 7 2020
Overview:
Warmer than normal temperatures through Thursday. The forecast
becomes more complex for Friday with a potential winter
storm/accumulating snow that develops over parts of Nebraska and
there is a transition zone to rain/mix near the Kansas/Missouri
border.
Tonight through Friday:
The latest surface analysis shows an area of surface low pressure
over Iowa with surface winds veering from the west to northwest and
north with a cold frontal passage. The brunt of the cold air will
remain well to the east of the area across parts of MN into the
Great Lakes, although some cooling is expected for tonight into .
Wednesday. A persistent area of clouds has developed with the
isentropic lift/h85/h7 warm air advection near ONL into parts of
northeast Nebraska. A 40kt low level jet strengthens tonight and
continues Wednesday through parts of the Central Plains. We don`t
have any precipitation forecast with this feature beyond clouds. RAP
RH progs show a band of clouds may persist through tonight with mid
clouds displaced a little more northward overnight
Southeast surface winds strengthen to 10 to 20kts and gusty
Wednesday with high temperatures in the 30s and 40s.
A mid-level trough over the Rockies swings eastward Wednesday night.
Brisk south flow and patchy clouds should yield warm minimum
temperatures Thursday morning. We currently have lows in the lower
to mid 30s. Temperatures are forecast to drop below these levels
Thursday night by midnight. Something to watch-the record warm
minimum are around 35 Thursday. Highs Thursday are expected to top
out in the 40s and 50s.
The surface low/initial mid level trough swings through Thursday and
taps into moisture south of the forecast area. This will be a big
weather maker for much of the U.S. to our east into the weekend.
Friday...a north to south mid-level trough combined with a strong
upper level jet will begin to spread snow from CO/WY into parts of
Nebraska and South Dakota. Farther south, rain will re-develop,
lifting northward over the front across Kansas and Missouri.
There is still decent model disparity in how strong the forcing will
be across KS and Nebraska into Iowa and thermal fields/resultant
QPF/snow/mix. There is general agreement with a precipitation
signal (NAM/EC/CMC/GFS/SREF) for precipitation south of a line
from the Platte River to Little Sioux Iowa southward and
especially I80 southward. The GEFs plumes have a spread of an inch
or 2 to 9 inches of snow. The NAM is the most robust of the
deterministic models with snow accumulations Friday afternoon into
Friday night, lasting into Saturday morning. The warmer air does
make it farther north with the transition in southeast Nebraska
and southwest Iowa. The GFS is more all snow and on the lighter
end of accumulations. Our current forecast has a couple of inches
of light snow.
Friday Night through Monday:
Surface high pressure builds in for Saturday and have lowered highs
to the teens and 20s. Near or below normal temperatures are forecast
in the 20s and Thursday Sunday Through Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 539 PM CST Tue Jan 7 2020
VFR conditions will prevail over the region through 00Z Thursday,
with cloud bases AOA 8,000 ft and unrestricted visibility. Winds
will become gusty out of the east/southeast (15 to 20 kt, gusts
20 to 30 kt) by mid morning Wednesday (15Z) and continue through
00Z Thursday. All of the TAF sites (KOMA, KOFK, and KLNK) will see
impacts from the winds.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Zapotocny
AVIATION...Albright
Area Forecast Discussion
National Weather Service Reno NV
328 PM PST Tue Jan 7 2020
.SYNOPSIS...
A couple of weak weather systems will bring breezes and chances
for light snowfall tonight through Thursday. Temperatures will
cool to near average. Additional storm systems this weekend into
next week could bring increased snow amounts, especially for the
Sierra, along with below average temperatures.
&&
.SHORT TERM...
The main adjustments in the short term were to hoist a lake wind
advisory for Lake Tahoe through tonight and slightly increase
snowfall amounts in west-central NV Thursday morning.
Winds have picked up (gusts 20-35 mph) this afternoon for many
spots across eastern California and extreme western Nevada as low
pressure nears the Pac NW coast. The lower valleys of western
Nevada have been slower to pick up wind-wise as full mixing has
been slower there despite sustained winds around 50 mph over the
Sierra ridges. Winds could pick up for more locations along the
Sierra Front/Hwy 395 corridor into this evening as a cold front
nears the area, with isolated gusts 40-45 mph possible in wind-
prone areas as indicated in the latest HRRR guidance.
Scattered to numerous snow showers will break out in the northern
Sierra into northeast California late this evening and overnight
as the aforementioned low pressure moves over northern CA and NV.
Snowfall is expected to remain light with only up to around 2
inches expected near the crest. As the system`s cold front is
expected to push out ahead of the main forcing tonight, deep
forcing (especially east of the Sierra) looks limited with
spillover expected to be light and hit or miss into western
Nevada with little or no snowfall acccumulation.
Although a few snow showers could linger across northeast CA and
the northern Sierra Wednesday, minimal additional accumulations
are expected.
Wednesday night and Thursday morning, attention turns to a bit
more potent disturbance set to move over the Sierra in a slider-
like fashion. The national blend of models (NBM) continues to
indicate a good chance for at least a dusting to 0.5" for many
areas across western NV, with probabilities good for an inch or
two across far northeast CA (including Surprise Valley) and
perhaps 2-4" for the northern/central Sierra near the crest.
With all this in mind and the favorable track for at least some
accumulating snow in western NV, POP was raised further for
Thursday with snow likely in most areas. This could certainly
cause issues for the Thursday morning commute in western and
west-central NV given the typical traffic volume, especially if
the heaviest snow showers hit between 6-8 AM. All we can say is
be ready for a slick morning commute Thursday and don`t wait until
the last possible minute to leave for work as travel speeds my be
significantly affected.
Thursday`s wave exits in the afternoon for a rapid shutoff to snow
showers. Friday will be another break between systems with dry
conditions and temperatures topping out near average. -Snyder
.LONG TERM...Friday evening through mid-January...
No major changes to the overall forecast thinking in the long term
as a large area of low pressure slowly deepens over the west coast
through mid-January. The evolution remains a bit chaotic with
multiple short waves digging the trough deeper and farther west for
about the next 10 days or so. This will most likely allow a decent
winter storm into the region...eventually.
The first couple waves this week are relatively fast moving, mainly
nuisance waves, dropping into the region from the northeast. This
angle of attack doesn`t allow for much moisture into the systems and
gives them less then ideal orographic potential. Nevertheless these
waves will create increased winds (especially along the higher
terrain), bring chances for light snow accumulation, and begin to
usher in more winter-like temperatures into our region that has been
5-10 degrees above average to start 2020.
The next wave is expected Friday night into Saturday with current
projections starting to spread snowfall into the Sierra early
Saturday morning, so travel over Sierra passes on Friday evening is
currently forecast to by dry. Cold air dropping in from the north
should keep precipitation in the form of snow at all elevations, but
overall amounts are expected to be pretty meager, mainly in the 2-6"
range in the Sierra with another possibility of a dusting to half an
inch in western Nevada.
Chances for stronger storms increase next week as the longwave
trough is forecast to continue to deepen and shift west. There
remains significant inconsistencies in timing and overall strength of
a more significant storm next week, however, we can say there is
increasing chances for stronger storms through next week. Currently
it looks like there are two time periods of possible for a stronger
storm, early next week and again closer to the MLK weekend. -Zach
&&
.AVIATION...
Winds have picked up over ridges (gusts 40-50 kts) this afternoon
ahead of the next quick moving disturbance, with peak ridge gusts
60-70 kts expected tonight. Valley surface winds have become
breezy in northeast CA and into far western NV as well, with peak
gusts to around 25 kts expected for terminals through tonight.
There is also a 30-40% chance for gusts 30-40 kts in Mono County
including KMMH (as indicated in HRRR simulations). While this
isn`t a significant winter storm, there is potential for mountain
wave turbulence as well as local areas of LLWS through tonight.
For NE CA and Tahoe terminals, light snow showers are most likely
from 06-12Z tonight into early Wednesday, producing periods of IFR
conditions and up to 1" of runway snow accumulation at KTRK-KTVL
and possibly a dusting at KSVE. Elsewhere, nothing to a trace
amount of snow is expected tonight through Wednesday.
Another round of light snow could bring IFR conditions and up to
2" of runway snow accumulation to the Sierra terminals early-mid
morning Thursday, with smaller snow amounts (possibly to 1/2" or
so) for western NV terminals including KRNO-KCXP-KMEV. There is a
chance that higher amounts to an inch or two could fall out into
west-central NV including KLOL and KNFL; however, where the
heaviest bands of snow will wind up are highly unpredictable at
this time with low confidence in the location. -Snyder/MJD
&&
.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 4 AM PST Wednesday for Lake Tahoe in
NVZ002.
CA...Lake Wind Advisory until 4 AM PST Wednesday for Lake Tahoe in
CAZ072.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno