Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/31/17
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
442 PM MST Sat Dec 30 2017
.AVIATION...
00Z TAF CYCLE
Dry northwest flow aloft with occasional high clouds. A modified
arctic airmass along the NM/TX border at 23Z will continue to ooze
westward thru 31/15Z with the western extent eroding somewhat
thereafter before pushing to the east slopes of the central mt chain
by 01/01Z. Attendant MVFR to IFR cigs/vsbys in br or fzfg will be
more widespread along and east of the Pecos Valley before 31/15Z, but
will eventually reach the east slopes of the central mt chain.
&&
.PREV DISCUSSION...327 PM MST Sat Dec 30 2017...
.SYNOPSIS...
An arctic airmass will dive into the eastern plains tonight
reinforcing a shallow and cold airmass already in place.
Temperatures will not rise above freezing again across parts of the
far eastern plains until Tuesday. Areas of dense freezing fog, light
freezing drizzle and snow flurries will impact much of the eastern
plains tonight through Sunday morning, and may linger across the
southeast plains through Sunday afternoon. Sunday night the focus
for freezing fog will probably shift to the east slopes of the
central and south central mountains. A ridge of high pressure will
cross the Rocky Mountain states during the middle to latter half of
the work week spreading fair and warmer weather from western areas
eastward over the plains as well.
&&
.DISCUSSION...
The shallow and cold airmass lingering over the eastern border from
the Canadian River northward should allow areas of freezing fog to
return there this evening. A persistent and moist low level south and
southeast flow over the southeast plains will probably also allow
freezing fog to develop there this evening. The area of freezing fog
is expected to become more widespread late tonight into Sunday
morning across the eastern plains as an arctic airmass arrives with a
stronger back door cold front. Areas of light freezing drizzle will
combine with the dense freezing fog and snow flurries to make travel
hazardous. The NAM and RAP models suggest patchy fog and drizzle
could linger across the southeast plains into Sunday afternoon. Will
issue a Special Weather Statement to caution travelers about these
hazards across the east tonight into Sunday. The night shift will
monitor and issue a Dense Fog Advisory when and where needed.
After some freezing fog along the east slopes of the central and
south central mountains Sunday night (and possibly on parts of the
plains), the airmass will finally begin a slow retreat on Monday;
but, much of the far eastern plains will probably remain below
freezing until Tuesday. Freezing fog may again return to parts of the
east Monday night into Tuesday morning.
Meanwhile, locations west of the central mountain chain will continue
to experience unseasonably warm and dry weather for the remainder of
the weekend as a ridge of high pressure builds over the west coast,
then through the coming work week as the ridge moves inland. Eastern
areas will join in the warmer weather during the mid to latter half
of the week, as temperatures gradually rise above normal there as
well.
44
&&
.FIRE WEATHER...
West winds and very low humidity are generating spotty critical fire
weather conditions this afternoon from the central mountains across
the eastern slopes. Critical fire weather will be alleviated as
winds taper off early this evening.
The focus the next 5 to 7 days will be widespread poor ventilation
across NM, and the timing and placement of cold frontal passages and
associated higher humidities across the east. A reinforcing shot of
cold air will slide into eastern NM tonight and lead to more areas
of freezing fog. Well below normal temperatures will continue into
Sunday behind this airmass in the east. Another reinforcing blast of
arctic air will arrive over eastern NM on New Year`s Eve. This will
bring another round of freezing fog and frigid temperatures. A gap
wind will attempt to trickle into the Rio Grande Valley through New
Year`s morning, and result in decent improvements to humidity values
through New Year`s Day. This will also trend temperatures several
degrees colder, but still above normal.
Guidance keeps cold temperatures in place across eastern NM through
Wednesday morning, while central and western NM remain above normal
and very dry. A ridge is then expected to crest eastward over NM
Wednesday through Friday and trend temperatures much warmer across
the east. Light winds will favor strong midslope inversions each
night for the central and west with very weak daytime mixing.
Guidance was starting to come into better agreement on increasing
chances for rain/snow around Sunday of next weekend, but there are
now significant differences, which does not bode well for precip.
Guyer
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Amarillo TX
924 PM CST Sat Dec 30 2017
.UPDATE...
Backed off on the expiration time of the Freezing Fog Advisory
until 12Z Sunday now. HRRR and 00Z NAM indicating that the lower
visibilities in the freezing fog should begin to improve around
09Z to 12Z Sunday. The original 16Z Sunday expiration time was
likely too long considering the rapidly improving conditions
expected by sunrise Sunday. Conditions may even improve prior to
12Z Sunday, however later shifts can cancel earlier if necessary.
Schneider
&&
.PREV DISCUSSION... /Issued 746 PM CST Sat Dec 30 2017/
UPDATE...
The HRRR has been consistent over the past few to several runs about
developing low visibilities in freezing fog mainly across the far
western Panhandles and then extending south southeast across
Dumas, Amarillo and Canyon areas into Carson and Armstrong
counties beginning around 02Z to 03Z Sunday and then lifting
around 16Z Sunday or so. The HRRR has been doing a great job of
handling the timing and coverage of the freezing fog over the past
couple of nights or so. Updated all public forecast products but
otherwise, no other changes to previous forecast.
Schneider
PREV DISCUSSION... /Issued 531 PM CST Sat Dec 30 2017/
AVIATION...
00Z TAF Cycle
VLIFR to IFR conditions will prevail at the Dalhart and Amarillo
TAF sites through about 15Z to 17Z Sunday and should become VFR
after 17Z Sunday. MVFR conditions will prevail at the Guymon TAF
site until around 14Z to 15Z Sunday and then becoming VFR after
15Z Sunday. Winds at the Guymon TAF site will be southeast 5 to 10
knots and then become northeast 5 to 15 knots after 07Z to 09Z
Sunday. Winds at the Dalhart and Amarillo TAF sites will remain
southeast 5 to 10 knots and then shift to the northeast 10 to 20
knots after 08Z to 14Z Sunday.
Schneider
PREV DISCUSSION... /Issued 418 PM CST Sat Dec 30 2017/
DISCUSSION...
Theme for this forecast package is basically cold. A cold stretch
will last for several days through the beginning of next week. We
will slide towards "warmer" temps middle of next week. A wind chill
advisory will be needed for the next couple days during the
overnight and morning hours. Monday morning we may need a wind chill
warning but winds will be the limiting factor, but for now we will
advertise just an advisory as we are borderline warning criteria
across northern areas of the forecast area.
At the surface, high pressure will continue to build in from the
north across the region through the next couple days...peaking
Monday and pushing eastward by Tuesday. Monday will be the overall
coldest day for wind chill values in the morning hours with some
locations flirting with warning criteria near 15 below zero. Wind
speeds are borderline for the needed 10 mph criteria, but the main
things is we will be bitterly cold and its also a holiday.
Also noteworthy is the chance for freezing drizzle tonight. Forecast
soundings show a very shallow moist layer near the surface. There
will be low clouds and fog around tonight into tomorrow morning.
Given the moist layer its certainly not out of the question for some
light precipitation. However, there is little to no lift in this
timeframe. Confidence is not that high for a winter weather advisory
for freezing drizzle, but will mention the freezing drizzle chances
in the weather element.
We will see a warming trend towards the middle of next week to the
end of next week. Looks like next weekend we could possibly get
above normal with highs in the 50s across the local area.
Guerrero
&&
.AMA Watches/Warnings/Advisories...
TX...Wind Chill Advisory until 10 AM CST Sunday for the following
zones: Armstrong...Carson...Collingsworth...Dallam...Deaf
Smith...Donley...Gray...Hansford...Hartley...Hemphill...
Hutchinson...Lipscomb...Moore...Ochiltree...Oldham...
Potter...Randall...Roberts...Sherman...Wheeler.
Wind Chill Advisory from 6 PM Sunday to noon CST Monday for the
following zones: Armstrong...Carson...Collingsworth...
Dallam...Deaf Smith...Donley...Gray...Hansford...Hartley...
Hemphill...Hutchinson...Lipscomb...Moore...Ochiltree...
Oldham...Potter...Randall...Roberts...Sherman...Wheeler.
Freezing Fog Advisory until 6 AM CST Sunday for the following
zones: Armstrong...Carson...Dallam...Deaf Smith...Hartley...
Moore...Oldham...Potter...Randall...Sherman.
OK...Wind Chill Advisory until 10 AM CST Sunday for the following
zones: Beaver...Cimarron...Texas.
Wind Chill Advisory from 6 PM Sunday to noon CST Monday for the
following zones: Beaver...Cimarron...Texas.
Freezing Fog Advisory until 6 AM CST Sunday for the following
zones: Cimarron.
&&
$$
11/99
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
925 PM EST Sat Dec 30 2017
.UPDATE...
Clear and cold conditions will take hold over SE Michigan tonight as
lake effect diminishes near the Lake Huron shoreline. Since the
afternoon burst of activity, additional snow bands have only brushed
Huron and northern Sanilac counties while gradually settling
offshore. The offshore drift is expected to hold as low level
gradient flow weakens slightly and nocturnal cooling over land areas
further favors the normal lake aggregate trough positioning. In
addition, larger scale subsidence under confluent flow aloft will
force shallower convective depth for any bands or clusters of snow
showers that manage to waver westward during the night through Sunday
morning. For these reasons, a late evening update will be good
timing to cancel the winter weather advisory in favor of scattered
snow showers. Elsewhere, the wind chill advisory will remain in
effect through Sunday morning.
&&
.PREV DISCUSSION...
Issued at 638 PM EST Sat Dec 30 2017
AVIATION...
The terminal corridor will be on the edge of a stratocu field
originating from Lake Huron and Saginaw Bay during the evening.
Ceiling is VFR while some light snow is reported farther east
through the interior Thumb region. Expect the clouds to brush
through FNT, PTK, and DET while struggling to reach DTW during the
evening. Otherwise, northwest wind will be around 10 knots at the
surface and a bit more due north above the surface, which is a dry
combination and is expected to maintain mostly clear conditions
overnight followed by thickening high clouds Sunday morning. Backing
low level flow then has a chance to carry some stratocu eastward
from Lake Michigan Sunday afternoon and evening.
//DTW THRESHOLD PROBABILITIES...
* None.
PREV DISCUSSION...
Issued at 237 PM EST Sat Dec 30 2017
DISCUSSION...
Surface convergence zone over Lake Huron associated with surface
trough/cold front clipped the eastern Thumb region this afternoon
with short lived heavy thunder snow (up to 3 inches reported at
Harbor Beach). Northwest-North (340 degrees) winds to follow for
this evening, and majority of guidance (NAM/RAP) keeps bulk of the
925 MB convergence/lift offshore tonight, which seems reasonable
considering the ICE cover extends past the nearshore waters of Lake
Huron. None-the-less, will maintain the advisory in case of a
wobble, or if we end up with more multi-bands as indicated by the
HRRR/ARW, which will lead to snow rates not as intense as inversion
heights lower, but at least impacting the Eastern Huron shoreline
with additional light accumulations (few inches) this evening-
tonight.
Frigid airmass working through the Great Lakes Region today as deep
upper level low center (505 DAM height at 500 MB with a temp of -46
C) resides along the Ontario/Quebec border. 12z GRB raob indicated
an 850 mb temp of -25 C and this slightly modified cold core is over
southern Lower Michigan early this evening, setting us up for very
cold night as gradient slackens and low clouds dissipate/retreat
closer to the Lake Michigan/Huron shorelines.
Planning on carrying mins of zero to -10 F, coldest readings
probably along U.S. 23, in line with Euro ensemble temps, as 12z
Regional Gem and latest RAP raw temps are even a bit colder. Wind
chills will be flirting with -15 F, as falling temps are offset by
decreasing winds, and elected to issue a marginal wind chill
advisory overnight into tomorrow morning.
More solid wind chill advisory potential over the upcoming week.
Re-enforcing shot of arctic air descending from Hudson Bay on
Sunday, swinging through the Central Great Lakes on Monday. 850 MB
temps bottoming out close to -24 C during Monday morning,
supportive of highs stuck around 10F degrees during the day. Exact
timing and extent of Lake Michigan clouds/modification early Monday
will determine our mins, but good chance for temps to sneak below
zero, with a potential wind chill advisory needed for the morning
hours of New Years day. Even with "warm" advection pattern attempting
to kick in Monday night, min temps do not look to be too far from
zero Monday evening/night. Elevated winds 10+ MPH probably enough for
wind chills to touch -15 F once again.
Extended Period - Temperatures
Little change to the extended forecast regarding temperature. A high-
amplitude longwave troughing pattern will remain in place across the
eastern-third of the U.S., bringing temperatures that will run 15 -
25 degrees below the seasonal normal. For reference, highs are
typically in the lower 30s across SE MI. Tuesday temperatures will
peak in the upper teens across Flint to Saginaw and up through the
Thumb, but will remain capped in the low to mid-teens across the
Metro region. The pressure gradient will also strengthen across the
Great Lakes throughout Tuesday due to a strong high pressure system
moving east across the Plains, producing breezy conditions for most
of the day. As a result, wind chill temperatures will start off
ranging between -20 to -10F for the morning hours, and will struggle
to peak above the 0F mark for the afternoon. After sunset, expect
wind chills to return back down to morning values. Temperatures
again will peak into the mid-teens Wednesday, but with the wind,
wind chills will reside again between the -20 to 0 F degree mark,
peaking in the afternoon. There were some thoughts yesterday that
Wednesday would have a chance to peak at or above the 20F mark,
however, confidence is increasing that we will reside in the mid-
teens for a high.
The upper-level trough will continued to amplify across
the Great Lakes and will bring even colder air to the region for
both Thursday and Friday, highlighted nicely in the 850mb thermal
temperature maps. Temperatures averaging -17 to -20C by Wednesday
afternoon will drop down to -22 to -24C by Thursday afternoon.
Taking a peak at sounding climatology for DTX, these temperatures
approach record values (~ -27C) for 12Z soundings. In any case,
confidence has increased regarding single digit temperatures highs
for both Thursday and Friday, with overnight lows dipping down into
the negative single digits to negative teens. Saturday will see
temperatures back in the teens, and while outside our official
forecast period, long-range models are showing early signs that we
will potential rebound back to seasonal temperatures by next
Sunday/Monday.
Last thing to note -- With increased confidence regarding sub-20
degree temperatures on Wednesday, Detroit will have a shot at
breaking the record for number of consecutive days where max
temperature < 20. The current record is 11 days in a row, once
achieved on 02/02/1936 and again on 02/18/1979.
Extended Period - Precipitation
The first chance for snow will move in across SE MI throughout
Wednesday afternoon as a clipper system pushes southeast across Lake
Huron and southern Ontario. As the trough deepens across the Great
Lakes and winds shift from the west to the northwest, persistent
lake effect chances will then be possible across the Thumb, mainly
for communities bordering Lake Huron. Low confidence regarding where
the band of lake effect will set up, with various models keeping the
band just onshore, while other solutions keep it just offshore
across western Lake Huron. The set-up will be something to keep an
eye on heading into next week. Lake effect chances across the
eastern portion of the thumb will be possible late Wednesday through
early Saturday.
MARINE...
The forecast period will be characterized by episodic northerly or
northwesterly gusts to near-gales as waves of strong Arctic high
pressure descend south along the Front Range of the Rockies. The
first such episode will be over the southern Lake Huron basin this
evening and will be accompanied by intense snow squalls. After winds
diminish for the latter half of the weekend, gusty northerly flow
will return Monday and Tuesday. Expanding ice cover may result in
some forecast fluctuations in wind gust intensity as affected areas
experience reduced mixing depth.
Climate...
The deep freeze continues, with no let up in site during the next 7
days. Yesterday`s high at DTW was 19, which sets us up to break the
longest stretch of days where the high temperature fails to reach 20
degrees. The current longest streak is 11 days, set in 1979 and
1936, with the end dates occuring Feb 18 and Feb 02 respectively.
For reference tonight, The record low temperatures for DEC 31:
FNT -11 (1976)
MBS -7 (1976)
DTW -5 (1976)
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Wind Chill Advisory until 10 AM EST Sunday for MIZ047>049-053>055-
060>063-068>070-075-076-082-083.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
UPDATE.......BT
AVIATION.....BT
DISCUSSION...SF/AM
MARINE.......MR
CLIMATE......SF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Wichita KS
500 PM CST Sat Dec 30 2017
.SYNOPSIS...
Issued at 354 PM CST Sat Dec 30 2017
The Arctic air officially has its hold on the Plains.
Temperatures were in the single digits to lower 20s across Kansas
which is definitely a stark contrast from the upper 30s to lower 40s
of yesterday. It is downright frigid further north with temperatures
not wind chills of -10 to -25 in Minnesota and the Dakotas. There is
a low pressure system over the Great Lakes.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 354 PM CST Sat Dec 30 2017
Forecast highlights: Dangerous wind chills tonight and Sunday night
into the morning of New Year`s Day
Wind chills or the feels like temperatures are the most significant
part of the entire forecast with values plummeting tonight and
Sunday night into Monday. The Wind Chill Advisory is on target, and
no modifications were needed. Previously there was a question if the
criteria of -25 degrees would be met for a Wind Chill Warning on New
Year`s Day. This does not appear to be the case thus the advisory
should suffice at this time. Given the holiday and respective travel
or many people heading out to celebrate, it is very important to:
bundle up, cover your extremities, avoid extended periods of time
outdoors, stay indoors if possible, have a winter disaster kit in
your car and protect your pets by either bringing them indoors or
providing them a warm shelter.
High pressure is over the area at the lower levels. A weak
trough in the mid and upper levels will move through on Sunday. This
does beg the question of flurry chances tonight as mentioned in the
previous discussion. The NAM and RAP are showing some forcing across
central Kansas, so flurries were added for tonight from 3-6AM.
Record cool high temperatures are still expected on Sunday or New
Year`s Eve for Russell and Salina. Please see the climate section
for a complete breakdown of the potential records.
.LONG TERM...(Tuesday through Saturday)
Issued at 354 PM CST Sat Dec 30 2017
In the discussion from the last forecast issuance, the wind chills
on Tuesday morning were brought into question for meeting advisory
criteria of -15 degrees for a few hours. This forecast shows a hint
of meeting this criteria in central Kansas. It is possible that an
advisory could be issued, but the decision was made to hold off at
this time given the expected coverage and day in the forecast. Wind
chills are going to be from -5 to -15 degrees which is concerning
especially with many children returning to school following their
winter breaks. Please make sure to add extra layers to them and
yourself before you head out the door.
A ridge is in place for the rest of the week. The return to above
the freezing mark for the entire area will not be until the end
of the week. Saturday is going to be refreshing comparatively
with forecast high temperatures back into the 40s. Unfortunately
precipitation does not show up in the forecast; however, there is
a hint of trough coming down from Canada next weekend with
moisture transport in advance of this system. Thus there could be
some precipitation to start the following week. It is too early to
tell though.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 457 PM CST Sat Dec 30 2017
Cold arctic air continues to move into the region this afternoon
and overnight. VFR conditions dominate the region as a result and
this is expected to continue through the night and into New Year`s
Eve. Some mid level clouds are expected to move into the region
and affect all terminals tonight and tomorrow. This cloud cover is
not expected to bring conditions below VFR tonight or tomorrow.
&&
.CLIMATE...
Issued at 332 PM CST Sat Dec 30 2017
This cold spell is challenging the current record books. New Year`s
Eve or Sunday is expected to be record breaking in terms of cool
highs for Russell and Salina. Below is a summary of the record
values and their respective forecast.
Cool high on Sunday for Russell
Record: 8 degrees in 1978
Forecast: 4 degrees
Cool high on Sunday for Salina
Record: 8 degrees in 1927
Forecast: 5 degrees
New Years Eve in Wichita and Chanute could have their coolest high
temperatures since 1973 given the current forecast. As mentioned in
the previous discussion, New Years Day could be the coldest since
1979.
This month has been dry. In fact, Wichita will tie for the second
driest December on record with only 0.03 of an inch of moisture. The
last time that it was this dry for this month was in 1996. Russell
is anticipated to tie their record for the driest December with only
a trace for the month so far. This last occurred in 1976. Our
monthly climate narrative will be issued on January 1st. Check it
out if you want to read more on a summary of this month.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 6 11 -2 12 / 0 0 0 0
Hutchinson 3 8 -5 11 / 0 0 0 0
Newton 2 7 -6 10 / 0 0 0 0
ElDorado 5 9 -4 11 / 0 0 0 0
Winfield-KWLD 8 12 -2 13 / 0 0 0 0
Russell 0 5 -7 10 / 10 0 0 0
Great Bend 1 7 -6 12 / 10 0 0 0
Salina 2 5 -7 9 / 10 0 0 0
McPherson 1 7 -7 11 / 0 0 0 0
Coffeyville 9 15 0 13 / 10 0 0 0
Chanute 6 11 -3 11 / 0 0 0 0
Iola 5 10 -4 11 / 0 0 0 0
Parsons-KPPF 8 13 -2 12 / 10 0 0 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory from 6 PM Sunday to noon CST Monday for
KSZ067>072-082-083-091>096-098>100.
Wind Chill Advisory from midnight tonight to noon CST Monday for
KSZ032-033-047>053.
&&
$$
SYNOPSIS...VJP
SHORT TERM...VJP
LONG TERM...VJP
AVIATION...ELM
CLIMATE...VJP
Area Forecast Discussion
National Weather Service North Platte NE
609 PM CST Sat Dec 30 2017
.SHORT TERM...(This evening through Sunday)
Issued at 331 PM CST Sat Dec 30 2017
The primary forecast challenges through Sunday afternoon are
temperatures and snow. Near record cold continues as the next (and
coldest thus far) polar plunge swings around the Hudson Bay low.
Meanwhile, a shortwave is currently dropping through the northern
Plains and will traverse the forecast area this evening.
Precip... The first round of flurries/light snow showers has moved
across the northern tier of the state late morning, and the next is
just north of the Neb/SoDak border as of 21z. Mid level moisture has
been present for much of today, but fgen really increases early this
evening as the wave nears. Forecast soundings suggest decent lift
sub H7, while isentropic analysis (mainly at 270-275K) also shows
upglide in a nearly saturated layer. Sfc obs and RAP mesoanalysis
suggest two layers of the temp profile in the DGZ... one from the
sfc to about H85 and another H7 to H6, with colder air in between
and the elevated warm layer (pushing -5C). In short, relatively
little of the saturation and forcing occur in the DGZ. However, with
fairly high SLR`s (20:1) and plenty of upper level support (130kt+
H3 jet overhead), kept minor accumulations (1-2") along/north of Hwy
20. Subsidence quickly takes over after 06z, essentially shutting
off precip potential. Dry air gradually entrains through the day on
Sunday, helping to clear out the stratus, mainly north. Farther
south, low level moisture and lift support brief snow showers and/or
flurries through tonight. Continued scattered flurries into Sunday
afternoon across the far southwest (mainly Perkins and Chase
counties) to account for upslope flow.
Temps... Continued the trend of using the coldest guidance for
tonight lows and Sunday highs. The 30/12z model suite is in
agreement regarding H85 temps approaching -25C across the Sandhills
(around 1%ile of climo) and a 1050mb+ sfc high pushing into the
state. Made no change to current Wind Chill headlines as air temps
alone drop below -15F tonight across the north and -5 to -10F south.
Clouds and northerly winds will do little to help temps recover
Sunday, as highs stay below zero north and struggle to reach 5 above
south.
.LONG TERM...(Sunday night through Saturday)
Issued at 331 PM CST Sat Dec 30 2017
The models, which are in very good agreement, suggest the 1045+mb
arctic high will move very slowly through the Missouri Basin Monday.
This will support subzero lows and wind chill advisories or warnings
both Monday and Tuesday morning. A blend of guidance plus bias
correction was the basis for lows of 10 below to 20 below zero
Monday morning and 5 below to 10 below zero Tuesday. Wind speeds
will be fairly light, generally 5 to 10 mph both mornings and near
calm at times in some locations. Both the NAM and GFS indicate
precipitable water between 0.10 and 0.15 inches which should support
good radiational cooling. These models show a swath of low clouds
persisting Monday morning but clear skies are indicated Tuesday
morning.
Once this arctic high moves off south and east Tuesday afternoon,
high temperatures should warm into the 20s. Arctic high pressure
will move south through the Midwest Wednesday and back into western
Neb. This high will ridge slowly south Thursday and Friday. We
should see a prolonged period of south winds recycling cold air
north. The model consensus would suggest a relatively brief period
of low clouds on the wrn flank of the high pressure system affecting
ncntl Neb. The high temperature forecast Wednesday through Friday is
for 20s and 30s.
The high pressure system ridging through the Midwest should be
across the Southeast U.S. by Saturday, well south and east of
Nebraska, and the models signal a chinook with west and southwest
winds developing next Saturday for highs in the 30s and 40s.
The forecast is dry and the temperature forecast is a blend of model
guidance data, plus biased correction. Bias correction had little
impact on the high and low temperatures but did suggest the warm up
late next week could commence as early as Friday and high
temperatures Saturday could be about 5 degrees warmer than currently
forecast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 609 PM CST Sat Dec 30 2017
Snow will be the main focus for the next day with KVTN being the
most likely to see any snowfall. Visibilities at KVTN could be
reduced to near 1 SM at times Saturday night. Snow will slowly taper
off shortly after midnight. Cloudy skies with ceilings under 5000 ft
will stick around through Sunday morning. Ceilings rise back into
VFR conditions late Sunday morning.
At KLBF, snow will mainly stay north of the terminal. However,
ceilings are still expected to fall to near 3000 feet for the
overnight and Sunday morning period. Ceilings rise back into VFR
conditions by Sunday afternoon.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory from midnight CST /11 PM MST/ tonight to
noon CST /11 AM MST/ Monday for NEZ022>025-035>038-056>059-
069>071.
Wind Chill Warning from midnight CST /11 PM MST/ tonight to noon
CST /11 AM MST/ Monday for NEZ004>010-026>029-094.
&&
$$
SHORT TERM...Snively
LONG TERM...CDC
AVIATION...Kulik
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
855 PM CST Sat Dec 30 2017
.UPDATE...
855 PM CST
Main concern is lake effect snow/mesolow trends on Sunday. Had
earlier issued a Wind Chill Advisory for portions of the CWA as
multiple sites fell below criteria due to a quick temperature drop
early this evening. Clouds from the next approaching clipper type
wave have overspread the area and resulted in rising temperatures
in some locations. Not planning any changes to the Wind Chill
Advisory at this time. Regarding the clipper type wave, light snow
or flurries remains possible with it overnight into tomorrow
morning, with a low but better chance for anything more than a
dusting (up to a few tenths or so) appearing to be mainly south
of I-80.
Turning to the primary concern, lake effect snow associated with
the prominent mesolow evident on regional radar mosaic along and
off the northern lower MI shore. Have been closely monitoring
radar and guidance trends with the mesolow. Overall trend,
including on latest HRRR runs and on 00z 12km and 3km NAM has
been a westward shift of the mesolow into Sunday morning and an
increasing chance for a period of snow clipping northeast
Illinois.
The position of the mesolow is also important with respect to
snow potential and associated impacts into northwest Indiana into
the afternoon hours. Have become more concerned for at least a few
hours of snow and some accumulation, particularly in
northern/northeastern Porter County, though north central/northeast
Lake County IN could get clipped as well. Thermodynamics will
needless to say be excellent, so more than an hour or two of snow
band residence time will increase potential for more significant
accums and impacts and midnight shift possibly needing to issue a
headline.
This forecast remains lower confidence and fraught with
uncertainty. However, for now, given what can be gleaned from
trends, will be bumping up PoPs and QPF/accums and issuing a SPS
and graphic for the web and social media to ramp up the message of
possible travel impacts on Sunday.
Castro
&&
.SHORT TERM...
224 PM CST
Through Sunday...
Cold and snow chances continue to be the focus through Sunday.Afternoon
water vapor imagery shows the large upper low continuing to spin
over eastern Canada with a secondary upper low moving southeast
out from Alberta and British Columbia. Upper ridging continues off
the west coast. Of note is a wave moving southeast across South
Dakota/northern Nebraska which is generating some snow. This wave
will move across the local area overnight. On the snow side, there
is not much moisture to work with but most guidance shows
sufficient forcing to generate some snow. However, saturation may
be an issue and the forcing is mainly above the favored snow
growth zone. In addition, guidance differs on where the best
forcing sets up over the forecast area. Radar and satellite trends
support the most organized forcing tracking over the far southern
parts of the area. Have seen some periodic expansion of radar
returns across western/central South Dakota over the last few
hours suggesting that a somewhat broad area of light snow may be
what plays out locally. Will increase pops to lower end chance
category for far southern areas mainly Livingston, Ford,
Iroquois and Benton Counties overnight and carry lower pops across
the rest of the area. Most areas, especially those south of
I-88/I-290 could see some light snow but the focus is favored
south. A dusting is possible just about anywhere and southern
areas could see even a few tenths accumulation if some persistent,
though weak, banding can continue into the area.
On the temp side, the overnight system will bring an influx of
cloud cover. Visible Satellite shows mid level clouds advancing
eastward across Iowa and these will work into areas along/south of
I-80 late this afternoon closer to sunset and into the Rockford
and Chicago areas early this evening. Have lowest temps this
evening as they will likely fall steadily for a time but may be a
little quick with the drop off given the above cloud arrival
times. Temps will then level off and probably even come up a few
degrees with the increasing cloud cover tonight. Winds will
decrease this evening and given the expected temperature trends,
expect wind chills to remain just outside of advisory criteria.
For Sunday, the system will be departing to the southeast in the
morning and some flurries may linger far southeast. Lake effect
snow potential becomes the focus as winds will have diminished
enough for a more concentrated lake influence to develop. With
winds having turned more northerly into early Sunday a convergent
band of lake effect snow will have set up over the lake. A meso
low, which may stem from the one currently moving onshore over the
central UP of Michigan off Lake Superior, is expected to be moving
southward down Lake Michigan tonight and Sunday. The big question
will be how far west the meso low will meander. Trends continue to
favor it staying offshore of Wisconsin/Illinois but will have to
watch this carefully as this is something not easily forecast.
Will continue with the thought that the lake snow band/meso low
will remain offshore of the forecast area and then possibly move
onshore across far northeast Porter County or even east of there
later Sunday afternoon. Otherwise, clouds will scatter through the
day, especially northwest and it will continue to be cold with
highs in the single digits.
MDB
&&
.LONG TERM...
224 PM CST
Sunday night through Saturday...
The initial concern will be bitterly cold air Sunday night through
Tuesday as high pressure dips into the Mississippi River Valley
and eventually moves eastward across the Ohio Valley. The area
will be within the pressure gradient on the eastern flank of the
high keeping a steady breeze in place as overnight lows fall into
the mid teens below zero away from the lake and Chicago metro and
into the minus single digits in the metro. This will result in
wind chills in the -20 to -30 range Sunday night for the Chicago
metro, and immediate surrounding areas with -30 to -35 at least
west and south of there. Will go ahead and upgrade to a Wind
Chill Warning for Sunday night and Monday morning west and south
and continue with the Wind Chill Advisory all other areas. An
advisory will be in place for all areas Monday afternoon through
Tuesday morning. Monday highs will struggle to go above zero. Lows
Monday night will be similar to Sunday night but winds will be
weaker as the high will be closer to the area so expect wind
chills to remain within advisory thresholds.
Temps briefly moderate into the teens Wednesday ahead of a low
pressure system which will need to be watched for some light snow
potential. This system will bring a push of colder air with it so
will likely return to single digit highs for a day or two.
Otherwise it appears that mainly dry weather will be in place into
early next weekend. Beyond that, models show that upper ridging
off the west coast will move eastward across North America late
next weekend and could lead to another active weather period but
also a milder temperature regime.
MDB
&&
.AVIATION...
For the 00Z TAFs...
Quiet aviation weather this evening across the region, with the
only real concern coming late tonight into Sunday morning with the
potential for a period of some light snow or flurries, mainly
south of the terminals.
Strong arctic high pressure was centered across the northern
plains early this evening, with surface ridging extending into
central IL. Very dry air mass is largely cloud free at this time,
with northwest winds around 10 kts expected to slowly diminish a
little this evening. Turning attention to the west however,
another quick-moving clipper system was emerging from the northern
Rockies onto the plains, with an area of associated light snow
developing from South Dakota into the mid-Missouri Valley. Various
model forecasts continue to develop this light snow east-southeast
overnight, with precipitation expected mainly along/south of a DBQ
to LAF line by pre-dawn Sunday. Northern IL/IN terminals along the
northern fringe of the forecast position of the light snow, which
may eventually impact the terminals. Expectation is that impacts
would be fairly minimal, with perhaps a brief MVFR vis/cig combo
Sunday morning. Have maintained going prob30 at this time,
monitoring evolution of northeast edge of precip shield to the
west this evening. In addition, area of lake effect snow is
expected to develop over Lake Michigan into Sunday, which may not
be too far off to the east of the IL shore. Once the mid- level
wave with the clipper moves through during the afternoon, VFR/SKC
conditions are expected.
Winds expected to remain 300-320 deg near 10 kts for the duration,
perhaps increasing a bit late Sunday/Sunday evening.
Ratzer
&&
.MARINE...
254 PM CST
Lake Michigan is positioned between low pressure over eastern
Canada and high pressure ridging extending from Alberta to the
lower Ohio River Valley. Steady northwest winds will ease this
evening allowing conditions to fall below small craft advisory
through the evening. A weak system will pass late tonight and lake
effect influences will take over the wind field tonight through
Sunday. Expect a meso/small scale low pressure circulation to work
southward down the lake tonight into Sunday morning creating a
challenge with the wind direction forecast. North to northwest
winds are expected across the western sections of the lake tonight
and Sunday while northeast to east winds will likely occur to the
east thanks to the meso low with south and east winds to the
southeast of the circulation. The low should meander southward to
the southern half of the lake late tonight and eventually move
eastward across the southeast part of the lake during the day
Sunday. From there gusty northwest winds will set up Sunday night
and persist through Monday before turning westerly and easing
somewhat into early Tuesday. High pressure will pass to the south
Tuesday night with a low passing to the north which will bring
increasing southwesterly winds into early Wednesday. May see a
period of gale force winds Tuesday night with a lull Wednesday and
another period of gales later Wednesday as winds shift north-
northwest. Steady northwest winds then continue through late week
with a shift to southwest winds later next weekend. Freezing spray
will be likely with each period of stronger winds as bitterly
cold air remains in place over the next few days and then again
behind the system Wednesday and Thursday.
MDB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Chill Advisory...ILZ003-ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039
until 8 AM Sunday.
Wind Chill Warning...ILZ003-ILZ004-ILZ008-ILZ010-ILZ011-ILZ019-
ILZ032-ILZ033-ILZ039...9 PM Sunday to noon Monday.
Wind Chill Advisory...ILZ003-ILZ004-ILZ008-ILZ010-ILZ011-ILZ019-
ILZ032-ILZ033-ILZ039...noon Monday to noon Tuesday.
Wind Chill Advisory...ILZ005-ILZ006-ILZ012-ILZ013-ILZ014-ILZ020-
ILZ021-ILZ022-ILZ023...9 PM Sunday to noon Tuesday.
IN...Wind Chill Advisory...INZ001-INZ002-INZ010-INZ011-INZ019...9 PM
Sunday to noon Tuesday.
Wind Chill Advisory...INZ010-INZ011-INZ019 until 8 AM Sunday.
LM...Small Craft Advisory...Winthrop Harbor to Gary IN until 9 PM
Saturday.
Small Craft Advisory...Gary to Michigan City IN until 3 AM Sunday.
&&
$$
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