Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/26/17
Area Forecast Discussion
National Weather Service Hastings NE
539 PM CST Mon Dec 25 2017
.SHORT TERM...(This evening through Tuesday)
Issued at 238 PM CST Mon Dec 25 2017
No huge changes are anticipated to this forecast. Overall issue
will be snowfall in mainly the first period from a couple of
quick- moving upper level jet streaks.
Looks like the HRRR has a pretty good grip on the first round of
light snow this afternoon associated with the 150 KT jet streak.
Still looks like the expected lull will be realized by this early
evening, and then another weaker jet streak will pass through to
give us light now/flurries overnight into Tuesday morning.
Although there should be a short lull at some points, the
separation between the two jet streaks will be minimal, so we will
likely have snow on our radar through the night. Trends are for
slightly higher amounts of snow, especially west. This looks
realistic, considering the cold temperatures and deep dendritic
growth zone. We should generally see one to two inches on the
Nebraska side, with perhaps some three inch amounts, especially
toward our western CWA in Dawson County and areas nearby, as a
snow to liquid ratio of over 20 to 1 is expected. The Kansas side
should have around an inch or less.
I went a tad cooler for highs Tuesday with fresh snow on snow and
plenty of sky cover for most of the day, expecting highs near 10
for most of the area.
.LONG TERM...(Tuesday night through Monday)
Issued at 238 PM CST Mon Dec 25 2017
Pattern is stuck with arctic temperatures and northwest flow
aloft and occasional low-amplitude waves or jet streaks giving us
a small chance of light snow from time to time during the long
term, but mostly staying north/northeast of us. Expect highs
mostly in the teens and 20s, perhaps some single digits for the
weekend with a reinforcing shot of cold air.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday)
Issued at 520 PM CST Mon Dec 25 2017
MVFR CIGS and IFR VSBYS will continue off an on again at both GRI
and EAR for the next couple of hours...with VSBYS improving mid-
evening as there is expected to be a notable break in light snow.
Snow is expected to increase again around midnight...and while
there may be some IFR conditions returning...opted to only
reintroduce prevailing -SN with MVFR CIGS/VSBYS for the time
being. Conditions will then slowly improve around daybreak...with
some stratus lingering through the day around 5 KFT and continued
northeasterly winds around 10 KTS.
&&
.CLIMATE...
Issued at 238 PM CST Mon Dec 25 2017
..Longest sub-freezing stretch in the Tri Cities in nearly 4 years?..
For the majority of our coverage area, we appear to be in the midst
of at least a 10-day stretch of sub-freezing temperatures (it began
Saturday Dec. 23 and looks to continue through at least Jan. 1).
Specifically at our official Tri Cities airport sites (GRI/HSI/EAR),
it`s been almost FOUR YEARS since we`ve seen a longer streak than
this: 12 days from Jan. 31-Feb. 1, 2014.
The only day between now and Jan. 1 that could come somewhat close
to "ruining" our ongoing sub-freezing streak is Thursday (Dec. 28),
but at least for now high temperatures in the Tri Cities on Thursday
are only projected to reach the mid-20s.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
SHORT TERM...Heinlein
LONG TERM...Heinlein
AVIATION...Rossi
CLIMATE...Pfannkuch
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
918 PM CST Mon Dec 25 2017
.UPDATE...
Issued at 918 PM CST Mon Dec 25 2017
Water vapor imagery is showing a weak upper level disturbance that
is moving quickly across the area. There have been a few reports
of snow across western Missouri, but low levels are very dry with
this airmass. The RAP is showing some additional mid level
forcing moving into the area overnight which will to bring some
snow to the area. There a more impressive vort max currently over
the central High Plains which will move across the CWA on Tuesday
morning. The RAP has been consistent since this afternoon at
bringing another round of accumulating snow across the central
part of the CWA during the morning and early afternoon hours with
the potential for up to around 1". Have upped PoPs and increased
snowfall amounts based on these trends.
Britt
&&
.SHORT TERM... (Through Late Tuesday Afternoon)
Issued at 327 PM CST Mon Dec 25 2017
Conditions continue shape up for some light snow tonight and
Tuesday. A vortmax is moving east through Colorado this afternoon,
and it will move east-southeast into the Mississippi Valley this
evening. This wave is forcing weak cyclogenesis over the Great
Plains and turning the flow between 925-850mb around to the south-
southwest. The resulting warm advection and low level
frontogenesis producing clouds and a lot of light radar returns
over Nebraska, Kansas and northern Oklahoma. Some of the precip is
reaching the ground as well...mainly over southwest Nebraska. This
frontogenetical forcing will move east into our area this evening.
Meanwhile, the southeast end of the Arctic High over the northern
and central Plains will nose into our forecast area. Temperatures
will fall into the teens and single digits which should should
tighten the boundary layer temp/dewpoint spread enough for
precipitation to reach the surface. Most short range guidance shows
at least 2 f-gen bands developing this evening and persisting into
the predawn hours of Tuesday. The best chance for accumulating snow
will probably be along and south of the I-70 corridor...and some of
the latest guidance is hinting a little further north into Audrain
and Monroe Counties in central Missouri. QPF is very light...only
0.01-0.02, but S/W ratios should be between 18-23:1 so any snow that
falls will be very light, fluffy, and pile up pretty quickly. Think
this will generate a dusting up to about an inch for areas where the
snow bands linger.
Another weak wave will ripple across the Mississippi Valley on
Tuesday spreading more low level frontogenesis into our area.
However, the f-gen and warm advection associated with this wave does
not look as strong as with tongight`s system in most of the
guidance. The simulated precip in the HRRR/ESRL HRRR/and NSSL WRF
models is also not nearly as robust on Tuesday. There is an
exception though...the latest runs of the RAP are stronger than the
other NCEP models. F-gen on the RAP is pretty impressive across
northern into central Missouri on Tuesday morning with a wide swath
of accumulating snow moving into west central Missouri by 14-15Z.
This may be partially in response to enhanced upper level divergence
and ageostrophic circulations induced by a backbuilding upper level
jet. The 18Z NAM and the GFS have some flavor of this forcing as
well, but they`re not nearly as robust with the QPF. For now, will
keep the light QPF and high chance PoPs with another dusting to
possibly an inch in the forecast for Tuesday. Will make sure the
evening shift is aware of my concerns for a potentially stronger
system and the possibility of needing to increase PoPs/QPF.
Carney
.LONG TERM... (Tuesday Night through Next Monday)
Issued at 327 PM CST Mon Dec 25 2017
The MEAN large scale pattern will change little into early next week
with a broad deep longwave trof dominating most of the CONUS to the
east of the Rockies. This will result in a continuation of below
normal temperatures through the end of 2017. There continue to be
differences/variability among the models with:
1) the weak fast-moving low amplitude disturbances/short-waves
within the fast cyclonic flow
2) stronger digging short waves, and their impact on the overall
depth of the large scale trof and associated timing/intensity of
reinforcing cold air surges
3) any chances for snow, although any amounts would be light
(Tuesday night - Wednesday)
A large 1040+ mb surface high will settle east-southeastward from
the northern Plains into the upper/mid MS Valley on Tuesday night.
This will bring the coldest air we have seen yet this winter to the
region. The evening will begin with extensive clouds remaining from
just north of I-70 through southern MO/southern IL. Attendant with
these lower clouds will be a chance of flurries through the evening,
with the threat shunting southward as the lower clouds clear
southward on Tuesday night. Meanwhile the progressively colder air
will invade from the north/northwest with temperatures falling below
zero across portions of northeast MO and west central IL. Wind
chills overnight into early Wednesday morning will be in the -10 to -
15F range, and that will be driven largely by the cold ambient air
temperature rather than robust winds. Should the temps be a bit
colder or winds a bit stronger a wind chill advisory may be
necessary.
The surface high will remain dominant as it slowly retreats to the
east with the axis extending from the Great Lakes through the
western OH Valley by early evening. The very cold air mass along
with an increase in clouds during the afternoon will suppress highs
with readings averaging 20 degrees or so below normal.
(Wednesday night - Thursday night)
The region will remain under the influence of western fringes of the
retreating surface high on Wednesday night with clouds increasing in
advance of the next short wave trof moving through the Plains. The
models vary with the strength and depth of this short wave and it
moves into the upper/mid MS Valley on Thursday. The GFS is the
strongest/deepest model with more southward extent of weak forcing,
and suggests potential for some light snow generally across northern
MO/west central IL down to around I-70. Alternatively both the NAM
an ECMWF are weaker and dry. I would say at this time that
confidence is rather low and there are better odds the snow will
remain to the north of the CWA, however given the variability in
models and recent performance we will have to watch closely.
(Friday - Monday)
Confidence during this time frame in any one model solution is
rather low, especially considering the long range model performance
over the last 10 days or so. Both the GFS and ECMWF suggest
additional surges of colder air, first late Friday-Saturday and then
again Sunday into Monday. The timing and intensity of the colder air
varies however, but there is at least a trend showing that the air
mass Sunday-Monday may be coldest yet. The GFS also suggests a band
of snow may accompany one of the surges and attendant short wave
Saturday-Saturday night. We will keep watching these systems closely
and hoping for less variability/spread and more consistency.
Glass
&&
.AVIATION... (For the 00z TAFs through 00z Tuesday Evening)
Issued at 548 PM CST Mon Dec 25 2017
A couple of weak upper level disturbances will move across the
area over next 24 hours which will produce some occasional light
snow at the terminals. Initial VFR ceilings are expected to fall
to MVFR overnight as the atmosphere moistens with falling snow.
Visibilities will fall to MVFR or possibly IFR depending on how
heavy the snow is in the snow bands. Snowfall will be up to inch
or possibly greater depending if the heaviest snow lingers over
any one of the terminals. Temperatures are expected to fall into
the single digits and teens tonight and remain in the teens
tomorrow.
SPECIFICS FOR KSTL:
While a couple of periods of snow with reduced visibilities are
expected after 06Z as weak upper level disturbances move across
the area. Initial VFR ceilings will fall to MVFR with the first
snowfall and then stay MVFR through most of Tuesday. Visibilities
will fall to MVFR or possibly IFR depending on how heavy the snow
is in the snow bands. Temperatures are expected to fall into the
teens tonight and remain in the teens tomorrow.
Britt
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Memphis TN
849 PM CST Mon Dec 25 2017
.UPDATE...
Looking at the latest images out of KPAH radar, a band of light
snow or flurries may be occurring from near Malden, Missouri
southeastward to near Paris, Tennessee. Clouds have kept
temperatures in the lower to mid 30s thus far, but some clearing
is expected by sunrise. Temperatures will plummet into the mid 20s
once this occurs. Updated earlier to add 20 to 30 pops for light
snow showers. No further updates are expected.
KRM
&&
.DISCUSSION... /issued 338 PM CST Mon Dec 25 2017/
Cold temperatures and uncertainty with regard to a couple of
potential rounds of Wintry weather are the highlights of this
forecast update.
Current temperatures are in the low to middle 30s across the
Midsouth. We briefly saw the sun earlier today...but clouds have
returned area wide. As a result...most of the area has likely
already reached daily highs. The ECMWF as well as the HRRR still
show a weak disturbance moving across East Missouri into Middle TN
overnight. WPC seems to favor this solution as well. Will
maintain slight chance pops in northern portions of TN, and the
Missouri bootheel. Moisture is not particularly abundant...so will
just advertise flurries for now.
A very broad trough is currently in place across the entire
United States, centered over the Mississippi River. North to
Northwest flow across West Canada into the Northern Plains can be
traced all the way to the North Pole. If Santa would have made a
direct flight into the Central US he would have a great tailwind
for the entire flight. This pattern will remain largely unchanged
for the upcoming work week into next weekend. However, a series of
disturbance moving out of the Northern Plains across the middle
Mississippi River valley will result in a couple of rounds of
potential Wintry weather.
A reinforcing Arctic cold front will move across the Midsouth
tomorrow ushering in a bitterly cold Arctic Airmass. Dew points
will be in the single digits to teens across much of the region in
the wake of this front. Meanwhile along the Gulf coast into South
Texas the subtropical jet will become invigorated. A band of rain
and or snow showers will likely develop somewhere between the
Northern Gulf Coast and North Mississippi. While most of the
precipitation is expected to our South...it is difficult to ignore
guidance and leave out any mention of wintry weather early
Thursday over North Mississippi. Temperatures are expected to warm
to near 40 Thursday afternoon, so any lingering precipitation
should change back to rain.
Another cold front is expected Saturday resulting in bitterly cold
temperatures Sunday into early next week. Portions of the Midsouth
may struggle to warm above freezing Saturday with widespread
temperatures in the teens Sunday and Monday mornings. Uncertainty
is high but we could see additional Wintry Weather late Saturday
into Sunday.
30
&&
.AVIATION...
VFR conditions with periods of mid and high clouds. Can`t rule out
a snowflake in KJBR or KMKL this evening. Expect light ENE winds
through Tuesday morning gradually increasing to 8-10 kts as
another reinforcing cold front drops south into the region.
SJM
&&
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
657 PM EST Mon Dec 25 2017
.SHORT TERM...(This evening through Tuesday)
Issued at 401 PM EST MON DEC 25 2017
WV imagery and RAP analysis indicated a broad trough from nrn
Ontario and Hudson Bay through much of the nrn CONUS resulting in
cyclonic wnw mid/upper level flow through the nrn Great Lakes. At
the surface, arctic high pressure from wrn Canada into the plains
was bringing very cold air (850 mb temps to -35C upstream of Lake
Superior) through the region on wnw winds. Multiple wind parallel
LES prevailed into the nw cwa. A dominant band still lingered into
the ne cwa but had lifted slowly northward this afternoon.
Although the LES was not as heavy over the west, low vsbys with
small snowflakes and blsn have lingered with at least moderate
accumulations. Otherwise, temperatures remaining in the -8F to 7F
range with gusty winds to 20-30 mph has dropped wind chills into
the -10 to -30 range.
Lake Effect Snow:
Very high instability with lake induced CAPE values to around 1k
J/Kg will support moderate to occasionally heavy LES where a few
stronger bands develop. Otherwise, mainly just light LES will
continue but with low vsby. High res models suggest that the
strongest low level conv and probability for heaviest LES bands will
remain into the far ne CWA, especially the ne portion of Luce. A few
heavier bands could also develop to just east of Munising.
Additional snow amounts of 5 to 10 inches will be possible east and
about 3 to 6 inches west.
Predominant 300-310 flow over Lake Superior continues with land
breeze and lake induced convergent areas info the far ne cwa and
near M-38 and nrn Ontonagon county. Heavy accumulations will be most
likely over the northeast where the warning for LES continue.
Although some bands may affect M-28, most of the heavier snow will
remain to the north.
Wind Chills:
With temps dropping into the -6F to -18F range and
winds remaning around 10 mph, expect wind chill values to drop into
the -25 to -35 range over most of the cwa tonight into Tuesday
morning where advisory have been posted. The lowest values to near
-35 are expected from IWD to IMT.
.LONG TERM...(Tuesday night through Monday)
Issued at 238 PM EST MON DEC 25 2017
Overall, we`re looking at lingering lake effect snow mainly across
west wind snow belts early on, and then these snow showers are
expected to push offshore as southerly flow develops ahead of an
approaching waves from the west through the end of the week. As this
wave tracks across the region, it will bring chances for widespread
snow followed by another shot of colder, arctic air and the return
of lake effect snow into early next week. Temperatures during this
time period will remain 10 to 20 degrees below normal for this time
of year, if not a bit colder early on this week. A brief "warm up"
into the teens is possible on Friday, otherwise afternoon highs in
the single digits and overnight lows for the most part are expected
to remain around to below zero, expect across the Keweenaw and near
the Great Lakes where temperatures will remain modified a bit. Given
the magnitude of the cold air, certainly wind chills below zero are
expected through much of the time period.
Tuesday night through Friday: Wednesday morning definitely looks to
be the coldest day in the extended as overnight lows across the
interior west and central plunge into the negative digits. The
coldest temperatures are expected near the Wisconsin/Michigan
border, where overnight lows should easily drop to around -15,
possibly as low as -20 in some locations. Elsewhere temperatures are
expected to drop below zero, but lake effect snow/clouds should help
moderate temperatures a bit across the west wind snow belts. While
the winds won`t be terribly breezy, at those temperatures it won`t
take much for wind chill values to drop to around or just below -25.
Therefore, it may warrant an expansion of headlines for the tail-end
of the bitter cold down the road. Similar conditions are possible on
Wednesday night, but with thickening clouds overnight this will
likely complicate diurnal cooling trends.
Lake effect snow will continue to impact the west to northwest wind
snow belts through Wednesday before gradually shifting offshore as
flow backs to the south in advance of an approaching system from the
west. Quite a bit of uncertainty exists in regards to the strength
and speed of this wave ejecting out of the northern plains, but the
resulting warm air advection should be sufficient for the production
of at least light system snow across the area. Depending on the
track of the system, some areas may see some lake enhancement off of
Lake Michigan and Lake Superior. However, as the
track/speed/strength of this system continue to be fine-tuned, as
will the details.
Friday night through Monday: This main upper-level trough associated
with the above mentioned system continues to dig across the eastern
Great Lakes, another reinforcing shot of arctic air will allow for
moderate to heavy lake effect snow to kick back in and linger into
early next week. Right now, models diverge on what snow belt regions
will see the most impacts from this round of lake effect snow, as it
will depend highly on the track of the exiting 850mb low and
subsequent flow on the backside, so confidence in where higher-end
travel impacts may felt later this weekend/early next week are
uncertain at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 657 PM EST MON DEC 25 2017
Bitterly cold air mass over the Upper Great Lakes will continue to
generate widespread lake effect shsn off Lake Superior under w to nw
winds. Under these winds, KCMX will be significantly impacted. Due
to the very cold air, snowflake size will be small and extremely
effective at reducing vis, and winds will easily blow around the
snow. As a result, expect LIFR conditions to prevail at KCMX thru
this fcst period with vis at or blo airfield landing mins. At KIWD,
the southern edge of lake effect shsn streaming off Lake Superior
will frequently be just n of the terminal. Conditions will likely
fluctuate btwn VFR and MVFR thru the fcst period. However, if winds
remain backed sufficiently, VFR will prevail, and conversely if
winds veer a bit, conditions will fall to IFR or lower. At KSAW,
westerly winds will not be favorable for lake effect snow. Expect
VFR conditions thru the fcst period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 401 PM EST MON DEC 25 2017
Winds of 25-30 kts will persist over Lake Superior into Tuesday as
arctic air sweeps across. Best chance for some gale gusts will be
over east half through this evening within vicinity of stronger lake
effect snow showers. Winds diminish to 25 kts or less for rest of
the week. The arrival of the arctic air mass will also result in
periods of heavy freezing spray late tonight into mid week.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory until 1 PM EST Tuesday for MIZ002-004-
084.
Winter Storm Warning until 7 PM EST Tuesday for MIZ006-007-085.
Winter Weather Advisory until 1 PM EST Tuesday for MIZ001-003.
Winter Storm Warning until 7 PM EST this evening for MIZ001-003.
Wind Chill Advisory until 1 PM EST /noon CST/ Tuesday for MIZ005-
009>011.
Wind Chill Advisory until 1 PM EST /noon CST/ Tuesday for
MIZ012>014.
Lake Superior...
Heavy Freezing Spray Warning until 1 AM EST Wednesday for
LSZ249>251-266-267.
Heavy Freezing Spray Warning until noon EST /11 AM CST/ Tuesday
for LSZ241>245-248-263>265.
Heavy Freezing Spray Warning until 7 AM EST /6 AM CST/ Tuesday
for LSZ162-240-246-247.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...Ritzman
AVIATION...Rolfson
MARINE...JLB