Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/09/18
Area Forecast Discussion
National Weather Service Bismarck ND
945 PM CST Thu Feb 8 2018
.UPDATE...
Issued at 941 PM CST Thu Feb 8 2018
Extended the Winter Storm Warning and Winter Weather Advisory
through 08 UTC across southwest and far south central North Dakota.
Although snowfall intensities have decreased, accumulations will
slowly continue. A Wind Chill Advisory may need to replace
portions of these headlines once they expire.
UPDATE Issued at 600 PM CST Thu Feb 8 2018
Very little change in expectations the remainder of the night from
the previous forecast as Arctic high pressure builds in tonight,
forcing the low level baroclinic zone and the associated band of
snow across western and south central North Dakota as of 00 UTC
south through the late evening and overnight. Dependent on how
fast clouds can clear, widespread -20s readings may be possible
northwest and central Friday morning.
&&
.SHORT TERM...(This evening through Friday)
Issued at 239 PM CST Thu Feb 8 2018
The main forecast issue in the short term period will be our current
Winter weather hazards and Wind Chills highlights.
Currently, widespread snow extends from north central MT into far
southeast ND and western SD. Latest RAP analysis is showing strong
2D frontogenesis remaining over southwest ND through early this
evening. However, the best Deformation and steeper lapse rates are
confined to mainly far southeast MT and northwest SD, but do clip
the far southwest portion of Bowman County. No snowfall reports as
of yet but with snow expected to continue into the early evening, we
will leave hazards alone. Evening shift may be able to cancel if
thing wind down early this evening.
Focus then shifts north and east overnight as settles over North
Dakota and helps to clear things out. Very cold low temperatures
expected again tonight and utilized some of the lower guidance. Lows
tonight generally 10 to 20 below zero, except for the far south,
which near 10 below. Will need to monitor the southwest and far
south central. If skies clear here quicker than expected, the new
snowfall may help quicken the temperature drop once things clear
out.
Will need a wind chill advisory this evening through Friday morning.
We don`t include the southwest and far south central but evening and
overnight shift will need to monitor.
A cold quiet day is expected on Friday with sunny skies north and
east. Lingering clouds along the baroclinic zone remain over the
southwest. Another wave propagating through the deep upper trough
does clip the far southwest. The latest NAM brings a chance of
snow a little farther north into Slope and Adams counties, but
will keep the current forecast, which just barely brushes
southwest Bowman county, thinking the Arctic air will win out
here. Either way it would not mean anything more than trace
amounts of liquid.
.LONG TERM...(Friday night through Thursday)
Issued at 239 PM CST Thu Feb 8 2018
Dangerous wind chills to near 35 below zero can be expected for just
about all of western and central North Dakota Friday night into
Saturday morning.
A quick clipper/cold front will shift through late Saturday night
through Sunday morning but not have much impact in terms of
precipitation.
A fairly active week upcoming with the long standing stationary
Hudson Bay low remaining in place. Continued northwest flow will
push systems through North Dakota just about every other day.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 941 PM CST Thu Feb 8 2018
MVFR to IFR conditions in snow will continue late this evening
across southwest and far south central North Dakota. This band of
snow will slowly sink south through overnight. However, snow is
likely to continue most of the night far southwest. MVFR ceilings
may continue across southwest North Dakota through Friday
morning. Otherwise, VFR conditions developing northwest and
central tonight and Friday with Arctic high pressure.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory until noon CST /11 AM MST/ Friday for
NDZ001>005-009>013-017>023-025-034>037-047-048.
Winter Weather Advisory until 2 AM CST /1 AM MST/ Friday for
NDZ031>033-041-042-044-045.
Winter Storm Warning until 1 AM MST Friday for NDZ040-043.
&&
$$
UPDATE...PA
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...PA
Area Forecast Discussion
National Weather Service Cheyenne WY
207 PM MST Thu Feb 8 2018
.SHORT TERM...(This evening through Saturday)
Issued at 157 PM MST Thu Feb 8 2018
Tonight...Shallow and cold Canadian air expected to sweep southward
across our eastern counties overnight and stall near or just east of
Cheyenne. Light precipitation will develop from Douglas to Alliance
with weak lift, and soundings indicate that some freezing drizzle
may occur there along with light snow. With possible freezing
drizzle and snowfall amounts of 2 to 4 inches possible through
Friday afternoon, we have hoisted a Winter Weather Advisory for
Niobrara County as well as northern Sioux and Dawes Counties, which
meshes up well with the advisory bordering our counties.
Will continue with our High Wind Warnings through 10 pm based on
current observations and the forecast Craig to Casper 850/700 mb
height differences. Stronger winds should end across Platte County
late this evening as the the cold front eases southward across this
area. High Wind Warnings will continue for the Laramie Valley and
I-80 Summit until 2 am.
Friday...Quite a start contrast in high temperatures on either side
of the Canadian cold front with maximum temperatures in the 30s to
lower 40s west of the cold front, and only in the teens and 20s east
of the cold front. The cold front will slowly sag southward across
the eastern plains in the afternoon with chances for light snow
spreading southward along the baroclinic band. Total snowfall
accumulations of 1 to 4 inches anticipated north of a Douglas to
Alliance line.
Friday night...Snow chances will decreases as the lift decreases,
though continued upslope will help generate light snow along the
I-25 corridor.
Saturday...Stronger lift moves into Colorado with the upper trough,
though still decent chances for light snow along the Colorado state
line from the Snowy Range to Cheyenne. Quite cold with maximum
temperatures in the teens to lower 20s with 700 mb temperatures near
-15 Celsius.
.LONG TERM...(Saturday night through Thursday)
Issued at 157 PM MST Thu Feb 8 2018
Sunday...The flow aloft turns zonal, west to east, with the cold
airmass modifying and a warming trend for our counties. Dry
conditions with lack of low and mid level moisture.
Monday...Next shortwave trough aloft and its associated cold front
move across our counties producing a chance of rain and snow.
Tuesday...Drying out as much of the low and mid level moisture is
shunted into Colorado.
Wednesday...Warming trend develops with zonal flow aloft as our
counties are in the warm sector ahead of the next approaching cold
front from the north.
Thursday...Next Canadian cold front pushes southward across our
counties with a shortwave trough passage aiding in chances for snow,
although uncertainty in the progressive pattern is great for day 7.
&&
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 157 PM MST Thu Feb 8 2018
The main concern during this TAF issuance is the timing and
position of the arctic front tonight into tomorrow.
Latest surface analysis was showing the arctic air slipping down
to the Pine Ridge around Chadron. The position of this boundary
seems to be handled best by the latest HRRR which keeps this
boundary in place through much of the afternoon. We did hang on to
the LIFR ceilings at CDR through at least 20z, but it is possible
it could hang on a bit longer if the boundary does not budge.
Through the remainder of the day and this evening, we will
continue to see the arctic air sliding south through the Nebraska
Panhandle. We are anticipating LIFR/IFR ceilings to develop behind
this boundary across KAIA and KCDR this evening and KBFF and KSNY
overnight. As the column saturates we may be looking at a brief
period of freezing drizzle mainly in Chadron and Alliance before
turning to snow after midnight. KCYS will be really tricky on
where that boundary may end up tomorrow morning. The NAM/GFS/HRRR
tries to push it to the northeast by mid to late morning, but we
are not real confident in this scenario.
&&
.FIRE WEATHER...
Issued at 157 PM MST Thu Feb 8 2018
No concerns based on expected winds and humidities.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from 6 PM this evening to 6 PM MST
Friday for WYZ102.
High Wind Warning until 10 PM MST this evening for WYZ106-107-
110.
High Wind Warning until 2 AM MST Friday for WYZ115>117.
NE...Winter Weather Advisory from 6 PM this evening to 6 PM MST
Friday for NEZ002-095.
&&
$$
SHORT TERM...RUBIN
LONG TERM...RUBIN
AVIATION...REC
FIRE WEATHER...RUBIN
Area Forecast Discussion
National Weather Service Northern Indiana
1000 PM EST Thu Feb 8 2018
.SYNOPSIS...
Issued at 630 PM EST Thu Feb 8 2018
A winter storm will impact the region tonight and Friday, with
the most significant accumulations expected along and north of US
6. Light to moderate snowfall is expected elsewhere. Expect
hazardous travel for the morning and evening commute Friday.
Otherwise, more accumulating snow is likely over the weekend as
the weather pattern remains active and cold temperatures persist.
Highs will be in the 20s. Lows tonight will be in the teens and
20s.
&&
.UPDATE...
Issued at 947 PM EST Thu Feb 8 2018
Still some concerning trends in hourly runs of hires guidance this
evening with uncertainty continuing on southern extent of heaviest
snow axis. HRRR and RAP had trended southward earlier this evening
along with some 18z guidance. Latest trend has been a shift back
north with the southern periphery of heavy qpf/snow axis. Only
change made to evening update was to add Defiance and Henry
counties to advisory to match update with CLE to the east. Also of
concern is trend of hires guidance to now rotate dry slot north
and keep pcpn north in the afternoon, not allowing a transition
back southward as previous guidance had indicated. Will have to
monitor latest 00z guidance and additional hires to see if these
trends continue. Snow still expected to expand eastward overnight
with several inches by rush hour creating issues.
&&
.SHORT TERM...(Tonight through Friday night)
Issued at 239 PM EST Thu Feb 8 2018
12Z model suite has done little to resolve critical placement of srn
edge of heavy snow band this period. However better consensus seen
tonight within downstream warm advection wing with earlier start
time of mod-hvy snow development and born out with rapid upstream
expansion ese ongoing. This is not suprising given sharp frontal
slope and rapid/deep insentropic lift that develops underneath
intensifying upper jet streak across the srn lakes.
Thereafter uncertainty jumps per specific deterministic model
placement of low level baroclinic zone. NAM continues to lead
leftmost and pivots this well north into srn MI with remaining
guidance trailing swd to some degree. Blended solution provides path
of least regret and better yet retains greater continuity to going
fcst across nrn zones. Primary dilemma continues to be with srn band
edge counties. 12Z trends, including experimental highres guidance,
would bend snow band hard north Fri morning and bring accumulating
snow to a halt south of highway 6 for an extended time before
dropping back south mid-late aftn timed with passage of weak sfc
frontal wave seen in much of the highres guidance. However even in
this scenario noteable qpf values (0.20-0.40") indicated through nrn
portions of marshall-noble counties by 12Z which still yields bulk 3-
6" accums. Confidence zooms farther north invof the IN/MI stateline
where axis of heaviest qpf stripe still indicated from ne IL through
far nw IN/sw MI. Expect max point accumulations near 14" here.
Thereafter follows the period of greatest model based uncertainty
tied to how/if low level frontal zone deflects north in face of
intense low level warm advection. 12Z camp, like yesterday, is again
split although larger percentage of solution scope lies south versus
north. Can not ignore nam projection along with some similar highres
support but even these collapse south into the highway 30 corridor
later Fri aftn.
Given potential lull in accumulating snowfall and temps warming to
above freezing along srn edge of snow gradient, have leaned toward
an advisory. Although with that said, this same area could be
upgraded to a warning should it become clear that snow band will not
shift north out of the area Fri morning.
Sfc trough edges eastward Fri night with corresponding weakening
thermal/moisture advections and diminishing snow. Will hold with
prior 05Z Sat ending timing.
&&
.LONG TERM...(Saturday through Wednesday)
Issued at 239 PM EST Thu Feb 8 2018
Short term system is followed by another robust warm advective push
Sat night through Sun cwa wide, ahead of secondary sw disturbance
spinning up through swrn periphery of large scale trough across the
plains Sun. 00-12Z trends in guidance quite a bit more robust with
snow late Sat night/early Sun morning and bump pops/qpf accordingly.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 630 PM EST Thu Feb 8 2018
Quickly deteriorating conditions this evening as warm air
advection snow upstream across IL quickly expands east. Latest
hires RAP and HRRR in decent agreement with pcpn onset at
terminals. Question will be how fast cigs and vis crash and have
kept similar timing to previous terminals. LIFR with 1/4sm S+
expected for prolonged period at KSBN with 0SM not out of question
at times given expected snowfall rates of 1 to 2 inches per hour.
After initial snow, warm front may push north of KFWA leaving a
period of little to no snow at airport while heavy snow continues
not too far north of airport. This very uncertain and will be
watched.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Storm Warning until midnight EST /11 PM CST/ Friday night
for INZ003>007.
Winter Weather Advisory until midnight EST /11 PM CST/ Friday
night for INZ008-009-012-014-016.
MI...Winter Storm Warning until midnight EST Friday night for
MIZ077>081.
OH...Winter Storm Warning until midnight EST Friday night for OHZ001-
002.
Winter Weather Advisory until midnight EST Friday night for
OHZ004-005.
LM...NONE.
&&
$$
UPDATE...Lashley
SYNOPSIS...MCD
SHORT TERM...T
LONG TERM...T
AVIATION...Lashley
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Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
813 PM CST Thu Feb 8 2018
.UPDATE...
813 PM CST
No big changes planned to the overall forecast for the storm,
however, will likely move up the end time of the warning Friday as
the brunt of the snow will likely have fallen by mid-late morning
Friday in the warning.
Regional radar composite shows a long band of mostly light to
moderate snow extending from northern IL WNW into SD. A short wave
trough over the Dakotas early this evening shows up fairly well
on GOES-16 differential water vapor RGB. This shortwave is
forecast to shear quickly into the western Great Lakes Friday
morning, shearing out/weakening as it translates eastward.
Primarily light-moderate snow will continue this evening as
thermally direct circulation in the right entrance region of
120kt+ 250mb jet supports continued low-mid level frontogenesis
over about the northern 2/3rds of the CWA. As the Dakota`s
shortwave translates eastward, guidance suggests a strengthening
of the lower level f-gen and a resultant uptick in the UVVs over
northern IL.
Forecast vertical cross sections through the frontal band are a
bit worrisome for our double digit snowfall forecast amounts. The
last several runs of the RAP and 18z run of the NAM show virtually
no negative saturated EPV, which indicates that the atmosphere is
progged to be relatively stable and not primed for narrow intense
banded snow. In addition, guidance suggests that areas of stronger
f-gen will be somewhat transient in nature. While these factors
are concerning, short range high-res guidance continues to
advertise very beefy QPF values overnight into at least the first
part of Friday morning, so not planning any changes to our
forecast snowfall totals at this point.
There has been a pretty consistent signal across the spectrum of
model guidance suggesting that the meaningful snowfall will shift
mainly south of the winter storm warning area between 12-18z
Friday as shearing out shortwave passes east and associated height
falls nudge the upper jet and associated entrance region a bit
farther south. Given the expectation that snowfall across much of
the warning area will waning prior to 18z, think that for
messaging purposes an earlier end time to the warning is
justifiable. Latest guidance suggests that additional snowfall
accumulations beyond late morning would be somewhat trivial where
the warning is in effect.
Working on some fine tuning to grids and will have an updated WSW
and grids/derived products out shortly.
- Izzi
&&
.SHORT TERM...
250 PM CST
Through Friday...
Main forecast concerns/challenges are with the likely significant
snowfall totals expected this evening through Friday evening. No
changes made to the current Winter Storm Warning in effect.
However, did increase storm total snowfall amounts, with highest
amounts of 8- 14 inches possible across portions of northern
Illinois and northwest Indiana.
In the near term, mainly flurries falling over much of the area
as the anticipated snow is still just to the west of the area.
However, expect this to change over the next 2-3 hours as
isentropic ascent further ramps up ahead of approaching shortwave
energy. Current snow over Iowa will spread east southeast late
this afternoon through early this evening. Expect this initial
snow to spread over areas along and north of I-80, with the
majority of this snow staying in the light to moderate range.
However, there is currently some embedded areas of moderate to
heavy snow, and will need to monitor for more heavier snowfall by
early this evening.
No big change in the thinking regarding the overall synoptic
pattern with this event, with mesoscale features once again
playing a large role with this snow and likely higher snowfall
rates. Uncertainty in place regarding these mesoscale factors has
lowered, with confidence greatly increasing for a band of moderate
to heavy snow impacting many locations north of I-80 in northern
Illinois and northwest Indiana during the overnight hours tonight
thru Friday morning. Most guidance focusing the already present
fgen right within the current Winter Storm Warning area later
tonight, pivoting across the area tonight into Friday morning.
This strong fgen along with the presence of negative EPV and
steeper mid level lapse rates will help take the light to moderate
snow this evening quickly to more moderate to heavy snow tonight.
As was mentioned in the previous paragraph, will need to monitor
for a quicker transition to this heavier snow across the Warning
area earlier in the evening. Then anticipate a potentially longer
duration of moderate to heavy snow from around the 2 AM to 8 AM
CST time frame, that could support snowfall rates in the 1-2 inch
range. This heavier snow will provide greatly reduced visibility
of one quarter mile or less, and with snow likely quickly
accumulating on area roadways. Under these conditions, travel will
become very hazardous, with Friday morning`s and afternoon`s
commute being significantly impacted. Location of greatest ascent
and higher snowfall totals will be right along the I- 88 to I-80
corridor. Snowfall totals north and south of this location will be
lower, however, the greater difference will be noticed to the
south where snow totals will quickly fall owing to a likely sharp
cutoff. A southeastward trend with this snow would be favored into
midday and the afternoon, with snow then exiting by late Friday
afternoon and Friday evening.
South of I-80, mainly along/south of the Kankakee River Valley,
confidence does lower with snow totals owing to the nature of this
banded snow but also given that it likely won`t snow too much
until Friday. Also, thermal profiles do begin to warm enough that
some sort of wintry mix could be observed for a time later tonight
into Friday and will need to monitor this potential as well. Just
right south of the current Winter Storm Warning, could see the
need for an advisory as snow totals could be in the 3-5 inch
range. With confidence low, have not issued any headline for this
area at this time. Overall, expect winds tonight into Friday to be
relatively lighter. Later tonight into Friday, winds could pick
up out of the north on the back side of this system, possibly in
the 10 20 MPH range.
Rodriguez
&&
.LONG TERM...
207 PM CST
Friday night through Thursday...
The active weather pattern during the short term will continue
into the weekend as the baroclinic zone remains in place across
the area. Overall, this will result in a couple additional periods
of accumulating snowfall late Friday night through Sunday morning.
Additional waves of energy are likely to shift across the region
into the weekend, each of which will likely result in more snow
across the area. While the snow amounts Saturday into Sunday
morning do not appear to be anything nearly as heavy as Fridays
snow, the accumulation of a few more inches will be possible
during this period. This very active weather pattern will finally
begin to wane across the area by later Sunday morning as the
last in a series of disturbances shifts across the area.
A surface ridge of high pressure will build over the area Sunday
night into Monday marking the end of this very active streak. With
fresh snow on the ground and light winds under the high, expect
low temperatures Sunday night to fall below zero in most areas.
While I did lower temperatures a bit Sunday night, even colder
conditions then currently forecast are certainly possible.
After a couple days of quiet but cold weather early next week,
expect temperatures to moderate mid to late week. The next chance
of precipitation looks to be late Wednesday into Thursday as
another weather system approaches the region.
KJB
&&
.AVIATION...
For the 00Z TAFs...
Aviation forecast concerns focus on high potential for a period of
moderate/heavy snow across terminals tonight/early Friday morning.
Snow was already developing across IA/IL and expanding eastward
late this afternoon, per regional radar mosaic. Forcing for
ascent will increase in response to a strengthening upper jet
and tightening of the lower to mid-level thermal gradient across
the area, with conditions expected to deteriorate fairly quickly
this evening. While moderate snow will likely lower vsbys to less
than a mile at times by mid-evening, the period after midnight
through about sunrise looks to have the most persistent mid-level
forcing, and thus the greatest potential for heavy snow with
significant accumulation. High-res model guidance then suggests
the main area of heavier snow will shift south/east of the
terminals mid-morning Friday, with improvement in cigs/vis and
lighter snowfall rates expected into the afternoon. Several
models depict another wave which passes across the forecast area
Friday evening, which may briefly result in moderately lower vis
for a time after 01-02Z Sat.
Ratzer
&&
.MARINE...
218 PM CST
Relatively quiet conditions will persist over the lake for the
next several days. A weak trough of low pressure will track south
of the lakes region Friday and Friday night as high pressure
begins to build over the northern Plains. This will set up a
period of northerly winds on the lake into Saturday, though wind
speeds should generally remain in the 10 to 20 kt range. The
winds on the lake are then expected to gradually back west-
southwesterly for a period on Sunday as the surface ridge of high
pressure settles over the Upper Midwest and lower Missouri
Valley. Winds will turn south-southeasterly on Monday as the high
pressure moves east and a trough of low pressure approaches from
the Plains. Very low temperatures will remain in place through the
weekend, so expect continued ice development in the nearshore
waters.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Storm Warning...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ019-ILZ020-ILZ021 until 6 PM Friday.
Winter Storm Warning...ILZ006-ILZ013-ILZ014-ILZ022 until 9 PM
Friday.
IN...Winter Storm Warning...INZ001-INZ002 until 9 PM Friday.
LM...None.
&&
$$
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