Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/16/20
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
246 PM AKST Wed Jan 15 2020
.SHORT TERM...While the cold continues across Southeast Alaska
today, actual temperatures have warmed slightly across many parts
of the area, mainly due to greater mixing of the lower boundary
layer. Estimated from MDCRS soundings, some parts of the region
had a very low inversion of 300 feet, which mixed out around
midday leading to some sharper temperature rises. However, with
wind comes wind chills; thus it was still unpleasant for many
Southeast Alaskans to be outdoors for long. The wind chill warning
for White Pass still runs into tomorrow morning. If one calls 50
below wind chill a break, anyone venturing outside on the high
point of the Klondike Highway today experienced one. Despite the
respite, we leave the warning in place as we expect both winds to
rise and temperatures to fall overnight. In fact, the warning may
need to be extended into early afternoon Thursday, but we will
take a second look Thursday morning before being absolutely
certain.
Gusty high winds in Juneau continue as weak cold air advection
from Canada continues through our mountain passes. Cross barrier
flow, while not extraordinary as estimated by the models should
strengthen tonight. All high res models are supporting a sharp
rise in wind gusts late tonight into Thursday morning. Therefore,
the gusts to 85 mph for Downtown Juneau and Douglas still seem
reasonable. In fact, as the gradient responds to a low pressing up
the BC Coast from the south, we should see the tightening gradient
even further. Now heading into the weekend, a new front looks to
form out in the North Pacific. We have gale force easterlies
building over the gulf. This should support another period of
potentially high winds for Downtown Juneau late Friday into at
least Saturday night. To prepare for this, we have dried out
conditions by reducing pop markedly for the northern Panhandle
during this time, in line with temperatures still well below
normal. But we have also begun warming temperatures a bit earlier
on Sunday as we allow the precipitation bands to climb north.
Thus, late Saturday night into Sunday, we are looking for possibly
significant snow potential for the southern Panhandle but much
lighter snow for the north.
Lastly, we did nudge upward temperatures for the next 30 hours over
the Inner Channels using the HRRR which seems to be performing
far better than the NBM`s disappointing cold bias. We still left
the heavy freezing spray for Sumner Strait late tonight into
tomorrow morning, as Stikine River outflow may be pretty
impressive overnight, and temperatures in Wrangell are indeed
quite cold in the middle teens.
.LONG TERM...Change is still in the works for the next week as
the cold dry weather starts gives in to warming temperatures and
rain creeping into the forecast, perhaps even for some locations
in the northern Panhandle. Forecast confidence past the weekend
is still suffering from what the upstream upper level features
will do, but the overall message is a gradual warm up with
southerly onshore flow. Forecast confidence is moderate favoring
the WPC and NBM for updates.
&&
.AJK Watches/Warnings/Advisories...
PUBLIC...High Wind Warning until 9 PM AKST Thursday for AKZ025.
Strong Wind from late tonight through Thursday morning for
AKZ022.
Strong Wind through Thursday morning for AKZ021.
Strong Wind through Thursday afternoon for AKZ019.
Wind Chill Advisory from 9 PM this evening to noon AKST Thursday
for AKZ019.
Wind Chill Warning until 10 AM AKST Thursday for AKZ018.
Strong Wind through late tonight for AKZ018.
MARINE...Heavy Freezing Spray Warning for PKZ011-031.
Heavy Freezing Spray Warning for PKZ011.
Heavy Freezing Spray Warning for PKZ011.
Heavy Freezing Spray Warning for PKZ011.
Heavy Freezing Spray Warning for PKZ013.
Heavy Freezing Spray Warning for PKZ031.
Heavy Freezing Spray Warning for PKZ012.
Heavy Freezing Spray Warning for PKZ035.
Storm Warning for PKZ012.
Gale Warning for PKZ013-021-022-031-043-051.
Small Craft Advisory for PKZ011-032>036-041-042-052-053.
&&
$$
JWA/EAL
Visit us at http://www.weather.gov/Juneau
Area Forecast Discussion...UPDATED
National Weather Service Amarillo TX
804 PM CST Wed Jan 15 2020
.UPDATE...
Based on some 18Z models, the HRRR, TT WRF we have extended the
advisory to fill in the WRN counties. This also matches the ABQ
advisory better. NAM, HRRR and TTU WRF show a band of snow and
possibly sleet impacting the far west tomorrow morning. In fact
some suggest around 1" or slightly more snow south of DHT, which
may be overdone given we have to overcome the dry air near the SFC
initially, but it is certainly noteworthy. Given this have
mentioned more sleet and snow potential initially with the new
counties (Deaf Smith, Oldham, Hartley) but still expect
the transition to sleet. That said, still seeing a huge range in
model temperatures in the aftn with the HRRR and ECM suggesting a
break in precip and a big temp recovery to near 40 and possibly a
struggle to reach freezing again from there, while the GFS TT WRF
and NAM keep us wet bulbed down below freezing all day and even
suggest temps in the upper 20s for some which would be concerning
for greater ice potential. No reason to argue with a blend/middle
of the road approach which is basically what the current forecast
is and see no reason for more changes attm.
&&
.PREV DISCUSSION... /Issued 559 PM CST Wed Jan 15 2020/
AVIATION...
Precipitation will begin spreading north across the area in the
morning hours. Coverage will be more patchy initially but will
increase to widespread in the afternoon and evening. Freezing
rain is expected to be the dominant precipitation type, although
can`t rule out brief period of snow or sleet to start things off
in DHT and perhaps GUY. Icing on planes on the runway will be the
main concern for the TAF sites as elevated surfaces will see
greater accumulation. Believe temps may not get cold enough for
significant icing on bare ground and runways (esp if treated), but
stay tuned on that. CIGs will also fall through the day and
should reach MVFR levels in the AFTN. IFR to VLIFR CIGs appear
likely near or just after 00z Friday and visibilities will also
drop in the evening hours. There is a chance these occur before
00Z but this is not indicated in current TAF package.
PREV DISCUSSION... /Issued 311 PM CST Wed Jan 15 2020/
SHORT TERM...Today through Friday...
A developing winter system is expected to move from southwest to
northeast across the Panhandles starting mid morning Thursday and
continuing through Friday morning. The potential is there for
impacts due to freezing rain, especially Thursday afternoon
through Thursday night.
As we go into the morning hours on Thursday, a broad H500 trough
will move east across northern Mexico in-conjunction with a broad
H500 anti-cyclonic feature shifting west across the western Gulf
of Mexico. This will result in mid level flow which will funnel
right into the Panhandles from SW to NE. Closer to the surface,
good H850-800 east to southeasterly flow with upslope across the
high terrain to the west, pronounced H850-700 isentropic lift, and
lift downstream of the trough axis itself across northern Mexico
will help to spread precipitation across the region. Latest 15/12Z
model and numerical guidance continues to moisten the lowest
1kft-1.5kft AGL sooner than previous model data runs. This should
help start precipitation across the southern TX Panhandle as early
as 12Z and spread north through the morning hours. Dry air aloft
is expected, especially across the northern areas which may delay
the onset of precipitation. However, precipitation by late
Thursday morning into early Thursday afternoon is expected across
all of the Panhandles. As a result, wet bulbing will be critical
for precipitation type with freezing rain expected to be the main
precipitation type by Thursday afternoon through Thursday night.
As the main 700 hPa theta-e advection continues, this will be the
main catalyst for persistent WAA and lift for precipitation
through the overnight Thursday into Friday morning. Precipitation
rates will likely be the greatest the second half of Thursday as
the main trough continues to move into the Panhandles and provide
the main lift downstream of the axis across the region.
Eventually, the WAA should erode the sub freezing airmass across
the lowest levels of the ATM. As the main trough exits the
Panhandles to the east on Friday morning, precipitation should be
in the form of rainfall as temperatures will continue to rise on
Friday with high temperatures into the upper 50s to lower 60s.
The main precipitation type throughout the event on Thursday into
Thursday will be freezing rain with rain at times that could be
mixed in. The sfc based depth of cold air is still the tricky
aspect of the forecast. As of this current forecast, current ice
accretion amounts by Friday morning will range from a few
hundreths of an inch across the west to a tenth on an inch or
locally higher amounts across the east where the highest
probs of measurable QPF will exist along with duration of the
precipitation. Impacts, especially on elevated surface with ice
accretion are of greatest concern with elevated roadways and
powerlines that may be impacted. If colder air is entrenched,
especially off the caprock, surface based ice accretion after
sunset on Thursday may occur and could impact travel. High
temperatures for Thursday will struggle to get out of the 30s.
Meccariello
LONG TERM...Friday night through Tuesday...
Upper level storm system will move away from the Panhandles by
Friday night. Lows Friday night will fall into the 20`s and lower
30`s under mostly clear skies.
The flow aloft will remain fairly zonal and progressive through the
weekend. This flow will keep the Panhandles near normal for
temperatures. Any systems should stay well to the north of the
Panhandles as well.
A couple a cold fronts, one Friday night and another early Monday
will come through dry.
An upper level ridge will move across the Panhandles on Tuesday, so
this along with stronger downslope winds should help to push
temperatures upward.
&&
.AMA Watches/Warnings/Advisories...
TX...Winter Weather Advisory from 9 AM Thursday to 6 AM CST Friday
for the following zones: Armstrong...Carson...
Collingsworth...Deaf Smith...Donley...Gray...Hansford...
Hartley...Hemphill...Hutchinson...Lipscomb...Moore...
Ochiltree...Oldham...Palo Duro Canyon...Potter...Randall...
Roberts...Sherman...Wheeler.
OK...Winter Weather Advisory from 9 AM Thursday to 6 AM CST Friday
for the following zones: Beaver...Texas.
&&
$$
88/88
Area Forecast Discussion
National Weather Service Gaylord MI
915 PM EST Wed Jan 15 2020
.UPDATE...
Issued at 915 PM EST Wed Jan 15 2020
Low pressure center has shifted SE of Lower Michigan late this
evening...with a weak frontal boundary holding along the southern
border of our CWA. Broken area of light synoptic snow continues to
stream thru portions of our CWA...with the most persistent
snowfall occurring over the Straits area where vsbys have fallen
to around 1SM with light snow. Some light drizzle/freezing
drizzle is mixing in with the light snow from time to time...but
this mix should come to an end soon as CAA begins to activate the
lakes as we head into the overnight hours. Winds have already
begun to shift to the NW across much of our CWA. Latest RAP drops
850 mb temps into the negative teens overnight...and with the
moist layer extending thru 700 mb thru the night...conditions will
become increasingly favorable for lake snow shower production.
Will certainly keep all headlines in tact for the typical snowbelt
areas of NW/North Central Lower Michigan tonight thru Thursday
with the expectation of 3 to 5 inches of new snow within these
areas. Rest of our CWA will see generally 1 to 2 inches of new
snow. CAA will drop overnight lows into the teens to lower 20s.
&&
.NEAR TERM...(Through Tonight)
Issued at 401 PM EST Wed Jan 15 2020
High Impact Weather Potential: Moderate
...Accumulating snow this evening and overnight, followed by lake
effect. Gusty winds could create areas of blowing and drifting
snow...
A weak PV-anomaly continues to slide through the upper Mississippi
valley this afternoon, supporting a weak surface low just south of
Chicago. Some broad weak lift out ahead of the shortwave/PV-anomaly
(along with WAA east of this surface low) have continued to produce
snow showers, mainly in northern Wisconsin and Minnesota. This area
of snow have been struggling to fill in...but it is fighting dry air
near 850mb (residual from this mornings sounding). Radar echos have
been fairly prevalent across the area, but nothing has started to
reach the ground yet in our CWA. Farther to the south in downstate
Michigan, an area of rain has broken out, with temperatures in the
mid-30s. Precipitation is still expected to fill in between these
two as better lift and a corridor of mid-level moisture overspreads
our area as we head into the early evening. Snow continues
overnight, likely heaviest between midnight and 6am. Slightly wetter
snow this evening transitions to increasingly drier and fluffier
lake effect through the overnight hours. Overlake instability should
reach about 15 C, with decent omega within the DGZ. Inversion
heights rise through the night, from about 4 - 5 kft early overnight
to 5 or 6 kft in the wee hours of the morning. Total snowfall
amounts between late this afternoon through early tomorrow morning
are expected to be between 2 and 4 inches. More snow expected
Thursday in the typical northwest flow belts.
&&
.SHORT TERM...(Thursday through Saturday)
Issued at 401 PM EST Wed Jan 15 2020
High Impact Weather Potential: Lake snow showers continue into
Thursday...then potential for more widespread synoptic snow (and
maybe rain?) Saturday.
Pattern Synopsis/Forecast: Large scale pattern features shows a
strongly -PNA trough over the eastern Pacific...with generally zonal
flow across the CONUS. Strong storm system off the Pacific
Northwest coast...with a weaker short wave trough heading into the
upper Great Lakes this afternoon (and an even weaker trailing wave
back across the western Dakotas). Polar jet axis cuts right across
the Great Lakes...subtropical jet axis has lifted north into Kansas/
Missouri and extending east into the Ohio Valley. Passage of
upstream short wave trough Thursday will be followed by strong
height rises for the end of the week as ridge axis crosses Michigan
Friday. But another piece of energy gets "slingshotted" out of the
eastern Pacific long wave trough Friday and quickly moves into the
midwest Saturday. This short wave trough will provide the bulk of
the forecast issues for the short term portion of the forecast.
A couple of surface waves associated with both jet axes upstream of
Michigan this afternoon...one over northwest Wisconsin associated
with aforementioned short wave trough axis...a second broader area
of low pressure over Missouri/Illinois. Strong low level cold
advection behind the Wisconsin surface low...with subzero early
afternoon cold over the Dakotas/eastern Montana. 1047+mb Arctic
high settles into the upper Midwest during the day Thursday with
cold advection/lake aggregate troughing lying across Michigan.
Pressures then rise across Michigan as surface high splits around
the upper Lakes as winter anticyclones are wont to do. As high
moves east of Michigan by Friday evening warm advection will
commence as next system takes a run at Lower Michigan Saturday.
Primary Forecast Concerns: Cold northwest flow across the upper
Great Lakes expected to set up northwest flow lake induced
convection off the surrounding lakes. 850mb temperatures dropping
toward -15C over Lakes Huron/Michigan...and -20C over Lake Superior
will result in plenty of instability...and passage of weak trailing
short wave trough during the morning won`t hurt the cause though any
window for seeder-feeder potential appears to be short-lived. But
inversion heights not bad up around 750-800mb and inversion top
temperatures in the -20C vicinity (a little colder off Lake
Superior). Better accumulation potential looks to be around and
east of Grand Traverse Bay in northwest Lower benefitting from a two-
lake effective fetch...with a couple inches during the day with some
uncertainty regarding how persistent banding will be over a given
area. Snow showers will continue into Thursday evening but with
increasing subsidence and weakening winds as high pressure builds
into the upper Lakes should allow this activity to wind down.
Attention then turns to snow potential for weekend system. Storm
track for the time being cuts right across Lower Michigan...some
question about potential for dry slotting wrapping around the east
side of this system and getting into Lower Michigan for a time
Saturday...as well as given the storm track the possibility of a
surface based warm layer allowing precipitation to change over to
rain for a time along the southern periphery of the storm track.
Probabilistic guidance of 24h snowfall greater than 6 inches ending
12z Sunday is split between the GEFS (greatest probabilities over
northern Michigan with potential for rain along/south of M-55
Saturday) and the ECMWF ensemble (greatest probabilities south of
the M-55 corridor where higher QPF potential is in the ensemble).
Will continue to message the potential without getting bogged down
in the details for the time being...still a number of questions to
be answered. The potential for at least advisory criteria snowfall
to occur appears to be pretty decent...whether we can go above
that is still uncertain.
.LONG TERM...(Saturday night through Wednesday)
Issued at 401 PM EST Wed Jan 15 2020
Split flow ridging forecast to set up over western Canada extending
well north of the Arctic circle...which will allow an Arctic branch
of the jet to dive southward and into the upper Midwest/Great Lakes
to start next week. There is disagreement on degree of focus
temporally of cold air "firehose"...but will allow temperatures to
moderate heading into midweek.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 600 PM EST Wed Jan 15 2020
Widespread light snow will develop across Northern Michigan this
evening as a short wave slides thru the region. Colder air will
arrive overnight into Thursday behind this short wave. Widespread
synoptic snow will transition to NW flow lake effect snow
showers...targeting our typical snowbelt areas for the most
persistent snow showers thru Thursday. Expect mainly MVFR
conditions tonight thru Thursday night...with some areas
periodically dropping to IFR within some of the heavier snow
showers. Winds will shift to the NW tonight and strengthen to 15
to 25 kts early Thursday...with some higher gusts expected.
&&
.MARINE...
Issued at 401 PM EST Wed Jan 15 2020
Small Craft Advisories will be expanded tonight into most
nearshore zones...which will continue into Thursday evening before
pressure gradient flattens as high pressure builds in. Another
round of Small Craft Advisories appear to be likely Friday night
into Saturday.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 7 PM EST Thursday for MIZ021-022-
027-028-099.
LH...SMALL CRAFT ADVISORY from 4 AM to 11 PM EST Thursday for
LHZ346>349.
LM...SMALL CRAFT ADVISORY from 4 AM to 7 PM EST Thursday for LMZ323-
341-342.
SMALL CRAFT ADVISORY until 11 PM EST Thursday for LMZ344>346.
LS...SMALL CRAFT ADVISORY until 11 PM EST Thursday for LSZ321.
&&
$$
UPDATE...MR
NEAR TERM...STJ
SHORT TERM...JPB
LONG TERM...JPB
AVIATION...MR
MARINE...JPB
Area Forecast Discussion
National Weather Service Denver/Boulder CO
814 PM MST Wed Jan 15 2020
.UPDATE...
Issued at 809 PM MST Wed Jan 15 2020
Will see some increase in high level clouds overnight
otherwise no changes needed to previous fcst.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 254 PM MST Wed Jan 15 2020
500 mb height are rising over Colorado as upper ridging builds up
from the south. West-southwesterly flow aloft will be turning more
southwesterly overnight, with good warm advection spreading across
the area. Clear skies overnight will allow for good radiational
cooling over the high mountain valleys as their airmass decouples
and winds calm. Pressure gradients will be increasing over the
plains as a lee trough deepens along the urban corridor and high
pressure pushes in from the Great Plains. This will cause
southerly winds across the eastern plains as well as the Palmer
Divide to remain breezy with speeds of 10 to 20 mph sustained,
with gusts to 30 possible.
Moisture will increase from the south Thursday with thickening
high clouds through the morning. Temperatures will be about 10
degrees warmer over the mountains due to the warm advection. Over
the plains, the high surface pressure system over the Great
Plains will push cooler air into the east plains. The deepening
surface trough will continue to produce a Denver Cyclone, which
may pull in the cooler air into the northern urban corridor, while
the southwest flow flowing over the southern foothills and Palmer
Divide will bring warmer air downsloping in. Therefore the high
temperature forecast is challenging for tomorrow, as it will
depend on the location of the circulation center. Have decreased
temperatures over the eastern and northern plains for now. It will
be tough along the northern foothills where the westerly warmer
downslope winds will meet the cooler easterly winds.
Weather will remain dry over the forecast area through the
afternoon as most of the moisture will still be south of the area,
however the one exception may be Lincoln County. Some low level
moisture may move in to bring some drizzle, but low confidence in
it reaching this far north, so did not include it in the forecast.
Some model guidance has it much cooler as well, with a high in the
mid to upper 30s. Currently think the southerly flow off the
Palmer Ridge should have a warming effect, however the far
southern end of the county would be on the "upslope" side of the
ridge. If this is the case, may need to look into the possibility
of freezing drizzle. But again, low confidence on this event, so
not including it in the forecast at this time.
.LONG TERM...(Thursday night through Wednesday)
Issued at 254 PM MST Wed Jan 15 2020
...Main concern for this period will be potential for high winds
across the Front Range and all of the plains late Friday into
Friday night...and accumulating snow/blowing snow in the
mountains.
Southwest flow aloft will strengthen across the forecast area
Thursday night, but we`ll remain in between moisture streams (one
extending northeast from New Mexico into Kansas, and the other
ahead of the next system dropping in across the Great Basin).
By Friday, weather conditions will change fairly quickly with the
onset of snowfall in the mountains, and a blast of winds across
the Front Range and Plains. Snow will first develop in the high
country during the morning hours with increasing QG lift and
moisture ahead of the trough moving across the Great Basin and
into Colorado. The initial southwest flow may limit snowfall
early in this event, but we do expect a sharp uptick in snowfall
rates with the mid level cold front, switch to west/northwest
flow, and high mid level lapse rates of 7-8 C/km. Travel will
likely become hazardous by Friday afternoon along the I-70
Mountain Corridor, with a brief period of very poor visibility due
to a burst of heavy snow and blowing snow along the front. Then,
snow will taper off rather quickly Friday evening with large scale
subsidence and drying. Overall, initial indications are for
snowfall of 3-8 inches in the high country.
The cold front will push across the Front Range late in the day with
a blast of downslope wind. At this time, it`s most likely arrival
time would be mid to late afternoon. The airmass should be
adequately mixed, there`s strong downward QG forcing, and the
low/mid level pressure gradients are high. The local wind forecast
program suggests we`ll be reaching high wind criteria due to the
gradient alone. We`ll probably need a high wind watch with the
next forecast package issuance, and will do so in collaboration
with our neighboring offices. There is still some uncertainty to
the exact center of downward forcing, but if that moves across the
Front Range we could easily be looking at gusts to 75 mph or
greater in/near the foothills and 60 mph or more across the
adjacent plains late Friday afternoon through Friday evening.
By Saturday, we`ll see flat ridging build across and surface high
pressure sliding southeast through the Central Plains. That should
allow winds to decrease in all but the northeast corner of the
state. Dry conditions will prevail, although a bit of lingering
mid level moisture could keep a few flurries over the mountain
ridges. Little change is expected Sunday. Temperatures will
average closer to normal for the weekend.
By Monday, a pretty sharp ridge is advertised to pop across the
Central Rockies. This will bring warmer and a continuation of dry
weather. The next short wave will likely arrive by Tuesday with
another toward Wednesday. This would bring a return of snow
showers to the mountains, but mostly dry conditions still
prevailing on the plains with downslope flow.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 809 PM MST Wed Jan 15 2020
Winds have become southerly early this evening and should
remain so overnight. Towards 12z, the HRRR has them going
light westerly while the RAP keeps them southerly. For now will
keep them from the south.
&&
.FIRE WEATHER...
Issued at 254 PM MST Wed Jan 15 2020
Strong southerly winds will blow across the eastern plains tonight
and into tomorrow, with gusts of 35 to 45 mph possible. The
strongest winds will be found along I-70 east of Denver. Cooler
temperatures are expected now for tomorrow however, so humidities
should only get into the mid 20s. Drier humidities will be found
over the southern foothills and north of the Palmer Divide, where
wind gusts should be less than 20 mph.
Fire danger will be elevated across the foothills and plains
Friday afternoon through Friday night due to increasing winds.
Sustained speeds of 25-40 mph will be possible with gusts in
excess of 60 mph. While humidity will be increasing behind the
cold front responsible for the winds, the dry grasses will
certainly be capable of carrying fire spread given the strength of
winds.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...RPK
SHORT TERM...Kriederman
LONG TERM...Barjenbruch
AVIATION...RPK
FIRE WEATHER...Kriederman/Barjenbruch
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
934 PM CST Wed Jan 15 2020
.UPDATE...
Issued at 927 PM CST Wed Jan 15 2020
Made a few changes to the remainder of tonight and into early
Thursday morning with clouds and temps. Stratus has been slower to
clear than previously thought. Using a combination of
extrapolation trends from GOES-East Nighttime Microphysics RGB
and the RAP 950 mb RH progs, the main thrust of clearing will be
along the spine of the MS River and a good 3-4 hours slower.
Temperatures are also quite cold upstream attendant with the large
Arctic surface high. Despite more clouds tonight, pure cold
advection would argue for slightly colder overnight and early
morning temps.
Glass
&&
.SHORT TERM... (Through Late Thursday Afternoon)
Issued at 255 PM CST Wed Jan 15 2020
Early this afternoon, a flat zonal flow prevailed across much of the
CONUS. A fairly strong upper level disturbance was to our north in
southeast Minnesota, while a strong storm system was located just
offshore from the Pacific Northwest states of Oregon and Washington.
At the surface, an area of low pressure was over northwest Indiana
with a trailing cold front through central Illinois, the Saint Louis
Metro area, and into south-central Missouri. A rather stout 1043mb
area of high pressure was the airmass building in behind this front
with an even more impressive 1050mb Arctic high pressure behind
this. Skies were nearly cloudy areawide with a few breaks starting
to show, but a more definitive clearing of clouds does not occur
until eastern Nebraska and far northwest Iowa. Temperatures were
quite mild ahead of the front, with mid to upper 50s widespread, and
temperatures dropping into the lower 40s in northeast Missouri where
strong CAA began in earnest. The regional radar mosaic was largely
devoid of echo, except in Wisconsin ahead of the upper level
disturbance.
The cold front will complete its trek through the forecast area
before sunset, with the strong CAA occurring a couple hours after
accompanied by gusty northwest to north winds. Any breaks in clouds
should fill back in again this evening with clouds finally clearing
out later tonight. The Arctic airmass is expected to quickly
overtake the leading Polar airmass late tonight, building into the
Upper Midwest as a 1048mb area of high pressure by sunrise Thursday
morning. This is expected to result in temperatures dropping into
the teens for areas north of I-70, and into the low-mid 20s
elsewhere.
The strong storm system will come onshore into northern California
on Thursday, resulting in development of an upper RIDGE in the
central CONUS. Look for a dry, yet cold, day across the forecast
area with the Arctic high pressure in control from the north and
filtered sunshine from abundant high cirrus clouds. Either way, it
will be MUCH different, as we go from daytime temps 15-20 degrees
above normal today to temps 5 degrees below normal this day.
TES
.LONG TERM... (Thursday Night through Next Wednesday)
Issued at 255 PM CST Wed Jan 15 2020
(Thursday Night - Saturday)
Strong Canadian high pressure Thursday evening is expected to be
located across the Upper Mississippi Valley helping to bring
seasonably cold and dry conditions to the area. This high will slide
eastward through the period, with surface winds veering slowly from
the northeast to the east/southeast by Friday. By late Thursday
night/early Friday morning, still expecting precipitation to begin
across central Missouri due to increasing low-level warm/moist
advection, vorticity advection, and diffluent flow aloft. There is
still some uncertainty with the onset of precipitation with
different arrival times of these aforementioned forcing mechanisms
as well as how fast the very dry low/midlevels of the troposphere
become saturated. For now, continued to lean toward the faster
guidance (i.e., the NAM/NMM-East) as warm-air advection
precipitation events are notorious for beginning about three hours
faster than model consensus at this forecast timeframe.
Precipitation should overspread the rest of the area from the
west/southwest through the morning/early afternoon hours.
Precipitation is still expected to begin as snow as the atmosphere
saturates/wetbulbs. However, there is now more model agreement
depicting a faster transition to sleet, and then freezing rain
shortly thereafter. In addition, cooled surface temperatures several
degrees through the early evening hours on Friday, which is more in
line with the raw NAM/GFS output. The combination of this faster
transition to freezing rain and cooler surface temperatures has
led to an increase in ice amounts compared to the previous shift.
Widespread amounts of 0.10-0.20" are forecast, mainly in a
KCOU>>KUIN line. A light glaze up to as much as a tenth of an inch
of ice is expected further to the southeast. In terms of snow,
highest amounts are forecast to be in northeast Missouri where
temperatures aloft will stay below freezing the longest. One to
three inches of snow (which includes sleet) is forecast for these
locations. While individual wintry elements (snow/sleet/freezing
rain) should stay below warning criteria, the combination of
accumulating snow/sleet/freezing rain may warrant a warning
headline potentially for northwestern parts of the area.
Therefore, have issued a winter storm watch for these locations
from late Thursday night through Friday evening.
The entire area should transition to a cool rain Friday evening as
surface temperatures rise above freezing from southwest to
northeast. Moderate rainfall will continue overnight, before ending
late Friday night/early Saturday morning. The rain may mix with or
briefly changeover to snow before ending early Saturday but no
accumulations are expected.
(Saturday Night - Next Wednesday)
A rare period (so far this winter) of below normal temperatures is
expected for most of the remainder of the extended forecast as bi-
state area will reside beneath northwest flow aloft. Dry weather is
also favored, though we will have to watch a northwest flow
shortwave/weak clipper system for the potential for light snow
sometime Monday. Climatology however would favor any light snow to
stay mainly to the north and east of the area.
Temperatures will start off seasonably cold through Monday, with
highs generally in the teens and twenties and lows in the single
digits and teens. Wind chills Saturday night and Sunday morning
slightly below zero across northern sections of the area are also
likely. Moderating temperatures back to near or slightly above
normal is likely by the middle of next week.
Gosselin
&&
.AVIATION... (For the 00z TAFs through 00z Thursday Evening)
Issued at 543 PM CST Wed Jan 15 2020
Stratus resulting in predominately MVFR cigs/flight conditions
will prevail at the all the terminals through at least 02z.
Thereafter the stratus is expected to gradually clear from
northwest to southeast, exiting the St. Louis region
(KSTL/KSUS/KCPS) around 06z. VFR flight conditions will then
prevail through the remainder of the forecast period with
increasing high clouds on Thursday.
Northwest surface winds with occasional gusts up to 20 kts can be
expected tonight, diminishing slightly and veering to north and
northeasterly on Thursday.
Glass
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Winter Storm Watch from late Thursday night through Friday
evening for Audrain MO-Boone MO-Callaway MO-Cole MO-Knox MO-
Lewis MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
Osage MO-Pike MO-Ralls MO-Shelby MO.
IL...Winter Storm Watch from late Thursday night through Friday
evening for Adams IL-Brown IL-Pike IL.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Portland OR
315 PM PST Wed Jan 15 2020
.SYNOPSIS...A strong low pressure area will move across Vancouver
Island late tonight. The trailing cold front will slowly slide across
the forecast area tonight. Most elevations below 500 feet appear
unlikely to see much more than a brief dusting of snow before
precipitation turns to rain. More significant accumulations can be
expect in the Columbia Gorge and Upper Hood River Valley. It appears
the primary freezing rain threat area will be in the Gorge between
Multnomah Falls and just east of Cascade Locks late this evening
through Thursday morning. Areas east of Cascade Locks should see
mainly snow. A threat of lowland snow will continue late Thursday
through Friday morning. The progressive weather pattern will continue
over the weekend and into the first part of next week.
&&
.SHORT TERM...Tonight through Friday...Water vapor early this
afternoon showed a nicely developed, but compact surface low pressure
center near 45N 129W. The 3-hr NAM valid 21Z suggested a central low
pressure near 975 mb. This is slightly deeper than the 12Z model
runs. Lightning continues over the coastal waters and was within
about 30 nm of the coast at 2030Z. KLGX doppler radar indicated 75-80
kt south wind about 7000 feet MSL. It appears the tightest surface
gradient is fairly close to the low pressure center, with weaker
isobar packing toward the trough base. Buoy 46089 had a peak gust of
52 kt late this morning, but the 20Z observations have shown a
slightly decreasing trend. Still not confident the high wind warning
will verify, especially with the most recent model runs maintaining
an east component where the isobar packing is the tightest. By the
time the surface isobar orientation becomes a more favorable south
direction, which is early this evening, the gradient is much weaker.
The HRRR 80m wind product shows the strongest winds late this morning
through the afternoon over the inner coastal waters, with slightly
lower speeds along the immediate coastline.
The KTTD-KDLS gradient was -7.8 mb at 20Z and is expected to peak
around -9 mb. Gusts to 70 mph have been noted at Crown Point and 55
mph at Corbett. The 12Z NAM shows the KTTD-KDLS gradient weakening to
around -2 mb by 08Z Thu.
South surface wind already making an impact over the southern part of
the forecast area early this afternoon. K77S and KEUG were already
50 to 55 degrees as of 22Z. Even KSLE had warmed to 47 degrees at 22Z
with 30 mph southerly wind gusts. Models in general agreement showing
the cold front passing across the coast by late this afternoon and
then slowly moving inland tonight. The mid and upper level trough
will be splitting as it moves ashore. Not as concerned about
widespread or impactful freezing precipitation in the Gorge and
vicinity tonight through Thu morning. Model soundings near Hood River
would imply more of a snow sounding. The most likely area for
freezing rain and its impacts looks to be in the Gorge between
Multnomah Falls and just east of Cascade Locks. Subfreezing temps
will be stubborn Stevenson eastward, so there will be a zone east of
Multnomah Falls but west of Carson that receives icing, perhaps up
to a quarter inch. For now, we just have Winter Weather Advisories
for the Gorge and Hood River Valley, but will need to monitor
closely for the potential necessity to upgrade to a warning. Upper
portions of the Hood River Valley and eastern Skamania County will
have mainly snow from this system through Thursday morning.
Cannot rule out localized spots of freezing rain in some of the
normally colder valleys in the North Oregon Coast Range and also SW
Washington interior lowlands.
The next weather system is forecast to move across the area late
Thursday through Friday morning. Even through the gradient through
the Gorge will be neutral or weak onshore, there remains a threat of
low-elevation snow. Will go with snow levels to near 500 ft across
the north half of the forecast area, with any sticking snow confined
closer to 1000 feet, except in the Gorge, especially east of Cascade
Locks. Low-level offshore flow through the Gorge develops Fri as
another surface low heads toward the southern British Columbia coast.
Model 850mb temps gradually moderate to around -4C Fri afternoon with
south wind flow. Thus, the low-level east flow will be fairly
shallow, getting overwhelmed by the the southerly flow. This will
allow snow levels to rise to around 1000 to 1500 feet in the north to
2000 to 2500 feet in the south. Weishaar
.LONG TERM...Saturday night through Wednesday...A trailing occlusion
will likely bring a reinforcing shot of precipitation to the region
Saturday. Snow levels should gradually rise to near the Cascade
passes by the end of Saturday with another round of decent mountain
snowfall expected. Many model scenarios suggest snow levels will
rise well above the Columbia River Gorge and upper Hood River valley
elevations as well, but given the pattern, cold air will have a
difficult time retreating in these areas so have held snow levels
closer to the valley floor in these zones for this time period.
Otherwise, it looks like there should be another break in the
precipitation Sunday and/or Monday before another storm system
brings mountain snow and valley rain to the region early next week.
BPhillips/Neuman
&&
.AVIATION...A strong cold front just nearing the coast at 2 pm.
Still widespread VFR inland, with spotty light precipitation.
But, cigs lower to MVFR just ahead and along the front. This
front will push across the Willamette Valley this afternoon, and
be near the Cascades Crest by 03Z to 04Z. Will see period of
strong southerly winds with the front, mainly along the coast and
over the higher terrain, and breezy with gusts 25 to 30 kt
across interior lowlands as well into early this evening.
Air mass behind the front will be milder, but still unstable. So,
will see mix of VFR and MVFR, with plenty of showers, with an
evening thunderstorm or two along the coast. Cold air in the
Columbia Gorge will maintain areas of snow there, and over higher
terrain tonight
KPDX AND APPROACHES...VFR at moment, but will see increasing MVFR
with rain this afternoon, along with breezy east wind. Front will
push across ops area early this evening, more showery pattern
overnight. Though may see some snow mix in the rain, am not
expecting any accumulation. Temperatures stay above freezing
tonight and Thu, with just rain showers. /Rockey.
&&
.MARINE...The 21Z MSAS surface analysis showed a 979mb low
centered near 47N 128W. This low was a few millibars weaker than
this morning`s 12Z guidance. Nonetheless, a strong cold front
moved across the waters earlier today. Widespread storm force
gusts were reported by offshore buoys, with buoy 46050 peaking
near 60 kt, buoy 46089 peaking near 55 kt, and buoy 46029 peaking
near 50 kt. Seas were slow to build today, but they quickly
ramped up this afternoon with the strongest winds and are
currently running around 18 to 20 ft with dominant period around
10 to 12 seconds.
Guidance continues to show this low lifting north inside of 130W
tonight and making landfall over Vancouver Island as a 990mb low
on Thursday. As the low moves further north this evening winds to
subside. However, expect a quick uptick in the winds this evening
as the bent back occlusion finally moves across the waters with
gusts around 35 to 40 kt possible over the central Oregon waters
and gusts around 50 to 55 kt possible over the northern waters.
Based on the latest obs and guidance decided to end the Storm
Warning for the central Oregon waters at 3 PM and replace it Gale
Warning through this evening. Will maintain the Storm Warning for
the northern waters through this evening.
Expect a brief lull in the winds on Thursday with weak gradients
over the waters. Unfortunately, seas will likely remain in the
mid teens through the morning hours, but look to fall to around
10 ft by Thursday evening, then into the 7 to 9 ft range by early
Friday before another strong cold front approaches the waters
later Friday. This front will likely bring southerly gales around
35 to 45 kt Friday afternoon with seas building back into the mid
to upper teens Friday night into Saturday. The active weather
will continue through the weekend and into early next week as
additional disturbances move across the waters. /64
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 PM PST Thursday for Central
Columbia River Gorge-Upper Hood River Valley.
Winter Weather Advisory until 10 AM PST Thursday for Western
Columbia River Gorge.
Winter Weather Advisory until 4 PM PST Thursday for Northern
Oregon Cascades.
Winter Weather Advisory until 4 PM PST Thursday for Cascades in
Lane County.
Winter Weather Advisory until 4 AM PST Thursday for Coast Range
of Northwest Oregon-Lower Columbia.
High Wind Warning until 6 PM PST this evening for Central
Oregon Coast.
High Wind Warning until 8 PM PST this evening for North Oregon
Coast.
WA...Winter Weather Advisory until 4 PM PST Thursday for Central
Columbia River Gorge.
Winter Weather Advisory until 10 AM PST Thursday for Western
Columbia River Gorge.
Winter Weather Advisory until 4 AM PST Thursday for Greater
Vancouver Area-I-5 Corridor in Cowlitz County-South
Washington Cascade Foothills-South Washington Cascades-
Willapa Hills.
High Wind Warning until 10 PM PST this evening for South
Washington Coast.
PZ...Storm Warning until 9 PM PST this evening for coastal waters
from Cape Shoalwater WA to Cascade Head OR out 60 NM.
Gale Warning until 10 PM PST this evening for coastal waters
from Cascade Head OR to Florence OR out 60 NM.
Small Craft Advisory until 9 PM PST Thursday for Columbia River
Bar.
&&
$$
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This discussion is for Northwest oregon and Southwest Washington
from the Cascade crest to 60 nm offshore. This area is commonly
referred to as the forecast area.
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
708 PM EST Wed Jan 15 2020
.UPDATE...
Latest RAP model shows deep layer ridging from west to east residing
across the area overnight that eases southward Thu in response to a
cold front tracking through the Deep South and into northern FL by
late Thu.
The ridging will continue to supply a warm and moist air mass
with light winds...resulting in some low clouds and fog later
tonight. The fog will be patchy for many southern locations...
patchy to areas for central locations...and areas to widespread
in the north. The fog will begin to lift and mix out starting
around 8 to 9 AM.
&&
.AVIATION...
16/00Z. VFR gives way to BR starting around 06Z and continuing
TIL 15Z. Expect brief MVFR VSBY/CIGS at TPA/PIE/SRQ with IFR at
LAL/PGD. VFR AFT 15Z with SCT CU and SCT OCNL BKN CI. Light to
calm winds overnight pick up and beginning shifting in the
morning...becoming NW for the afternoon AOB 08KT.
&&
.MARINE...
High pressure across the waters will keep winds 5 to 10 knots for
the next day or so with a sea breeze component in the afternoon
near the coast. A dry front sliding south Fri and high pressure
behind it will tighten the gradient with winds up to 20 knots at
times for Fri-Sat. The high pressure begins to shift east Sun and
allows winds to decrease. However high pressure builds in from
the northwest for the start of next week with increasing winds and
seas.
&&
.Preliminary Point Temps/PoPs...
TPA 66 81 65 78 / 0 0 0 0
FMY 64 84 65 79 / 0 0 0 10
GIF 64 83 65 76 / 10 0 0 10
SRQ 63 82 65 79 / 0 0 0 10
BKV 58 82 62 77 / 0 0 0 0
SPG 67 79 65 78 / 0 0 0 0
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
UPDATE/AVIATION/MARINE...09/Rude
UPPER AIR...29/Delerme
DECISION SUPPORT...69/Close