Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/03/18
Area Forecast Discussion
National Weather Service Bismarck ND
944 PM CST Tue Jan 2 2018
Issued at 941 PM CST Tue Jan 2 2018
Low clouds continue to linger over western and south central
portions of the state and should continue to do so through most of
the overnight. Further east, skies have cleared out. Updates have
UPDATE Issued at 640 PM CST Tue Jan 2 2018
Scattered flurries have been reluctant to dissipate this evening
over central portions of North Dakota, so will continue the
mention of them for the next few hours. As for cloud cover, have
increased it significantly through the overnight, particularly
over the west. Low clouds have continued to expand over the past
few hours, and some high-res models have picked up on this and
continue the cloud cover through the night.
.SHORT TERM...(This evening through Wednesday)
Issued at 222 PM CST Tue Jan 2 2018
Main issue in the short term period will be flurries and blowing
snow late this afternoon and Clouds/temperatures tonight.
Shortwave trough and associated surface boundary has pushed
through the forecast area. Currently central ND is within strong
subsidence behind the exiting wave. Decent fall-rise couplet is
pushing from Manitoba into Minnesota, but grazing central North
Dakota. RAP bufkit soundings indicate strongest winds aloft are
currently over the James river valley and are expected to slowly
diminish through the afternoon. Thus we do expect a period of
strong winds this afternoon over central North Dakota. Webcams
mostly showing drifting snow across the highways, but there is
also another are of light snow/flurries within the wrap around
moisture dropping south across central ND. ASOS visibilities have
dropped into the 1-3 mile range from Minot to Rugby and south to
Harvey and Carrington. With the combination of the flurries/snow
showers and strong winds, there may be period of reduced
visibilities and some blowing/drifting snow this afternoon.
We are expected to clear out from north to south tonight as high
pressure settles over the area behind the exiting shortwave. The
high drops over central and into eastern ND Wednesday morning and
coldest overnight temperatures are expected from the Turtle
Mountains into the James River valley.
Cold and quiet east on Wednesday with highs only reaching the
single digits. Generally quiet west too but we expect increasing
clouds along a tightening baroclinic zone. Models have been
inconsistent with the low level moisture as it begins to pool over
western ND, and the potential for light precipitation breaking
out along this baroclinic zone as shortwave energy drops along it
within a northwest upper flow. Global GFS/ECMWF have backed off on
light qpf Wednesday but the NAM and mesoscale models have become
more bullish. Will keep a slight chance of light snow mainly north
central Wednesday afternoon. This meshes well with our current
consensus pops that start the long term period Wednesday night.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 222 PM CST Tue Jan 2 2018
Chances of light snow or flurries continue Wednesday night into
Thursday over eastern portions of central ND. Abundant low level
moisture remains over much of the central so probably a tricky
temperature day depending on if/when any sun breaks out on the
western edge of the baroclinic zone.
Large temperature gradient remains over the forecast area
Wednesday through Friday with highs ranging from the single digits
above zero east to the 20s southwest. Upper ridging finally tries
to push into the northern plains on Saturday but quickly gets
squashed, and northwest flow becomes re-established by late in
the weekend. Nevertheless, we may see some highs push well into
the 30s southwest, and into the 20s east on Saturday, then
trending back down into the teens and 20s Sunday and Monday, and
then possibly another shot of Arctic air by Tuesday.
As far as precipitation through the extended period, we see only
very light amounts Wed/Thu along the baroclinic zone. Once the
western ridge breaks down over the weekend we see a broad
northwest upper flow over the northern plains with models having a
hard time resolving the specifics of energy tracking across the
region. Thus we will likely see an increase in precipitation
chances early next week but at this time no big storms through
Tuesday, but will see if this changes with time.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 640 PM CST Tue Jan 2 2018
MVFR cigs will continue overnight over western North Dakota into
portions of central North Dakota. Conditions will improve
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
926 PM CST Tue Jan 2 2018
Looks like the higher reflectivity echoes (if you want to call
them that at 10 dbz) have moved east. HRRR is showing some weak
activity farther north so kept a low chance still til midnight but
think overall this is over with.
Updated for improved moisture grids, and did extended the Wind
Chill Advisory into Duval and McMullen Counties until 6 AM.
No changes to the forecast lows, but some may be a bit on the high
side if the clouds do not clear out as rapidly as first thought.
Confidence in changing this is low so kept them. Updates are out.
Extended the SCA for a few more hours over the southern bays.
Otherwise not much change there.
.PREVIOUS DISCUSSION... /Issued 740 PM CST Tue Jan 2 2018/
Some very light precipitation falling in Nueces and Kleberg
Counties. Temperatures are hovering around freezing at this time,
as temperatures wet bulbing to near freezing. Latest RAP model
data showing the isentropic pattern in the 285K-290K area ending
about 9 PM (18Z NAM about the same0. We have made a few calls to
DPS, police and a few residents and everything is OK for now. Have
issued an SPS for this on-going brief wintry mix, and for now
will hold on to this but if precipitation gets a bit more potent
we may have to issue a brief advisory.
That is all for now. Believe SPS is adequate at this time.
PREVIOUS DISCUSSION... /Issued 543 PM CST Tue Jan 2 2018/
See 00Z AVIATION discussion.
Current released sounding (going up as this is written) still is
showing the drier air near the surface with increasing moisture to
the CIGS around 2500 feet. Model soundings are handling this well
at this time, and only real concern is whether there will be
enough isentropic upglide to warrant some of the precipitation
which will fall into the dry air below and reach the ground to
get into KCRP and possibly KALI terminals before 04Z. Since the
potential is greatest for this to occur at KCRP, did include a
TEMPO -RA for this terminal but kept it out of KALI as drier air
is a bit deeper there. Light precipitation over the Hill Country
(due to upper support) should stay out of the KVCT terminal but
will monitor that, as the only model hinting at something there is
the HRRR and that can be very poor w.r.t. handling precipitation.
Otherwise, clearing gradually AOA 03Z with VFR AOA 04Z. North
winds or northwest winds mainly less than 11 knots but as usual a
bit higher at KCRP with possible gusts tonight. Winds taper off
area- wide in the afternoon but did not need another line in the
TAF to handle this now, but will do so for the 06Z issuance.
PREVIOUS DISCUSSION... /Issued 400 PM CST Tue Jan 2 2018/
SHORT TERM (Tonight through Wednesday night)...
Upper level trough axis will move east of the area tonight,
sending a reinforcing surge of high pressure southward into the
area. This will lead to a very cold night across South Texas with
low wind chill values as well.
For this evening, there remains a slight chance of light precip
mainly along the coastal counties in the form of patchy drizzle or
a light rain/sleet mix. Precip thus far today has been encountering
a dry layer below 950mb and have not received any reports of
sleet/rain. Still, will keep a low 20 pop over the Coastal Bend
with 30 pops over the Gulf Waters. There is a slight concern if
any drizzle develops this evening/tonight as temps fall below
freezing. Confidence of this occurring is low as drier air and
clearing skies will be moving into the region. Will not mention in
the forecast, but will monitor this closely. Low tonight will be
very cold and most locations will experience a hard freeze with
temps in the low 20s up north with mid/upper 20s elsewhere. A
freezing warning is in effect for all of South Texas tonight. Wind
chill values will be dangerously cold tonight with values
generally between 15 and 25 degrees. A wind chill advisory is in
effect for the eastern parts of the area where wind chill values
will be sufficiently low and winds remain elevated. The wind
chills across the Victoria Crossroads may dip slightly below 15
but this should only be for a brief period of time.
Temperatures will moderate a bit on Wednesday with more sunshine
across the area. Highs should climb into the into the upper 40s
and low 50s out west to middle and upper 40s across the east.
Another freeze is likely Wednesday night into Thursday morning
across most areas. Lows will be in the mid/upper 20s inland with
low/mid 30s along the immediate coast.
Strong north to northeast winds will continue tonight as another
surge of high pressure arrives across South Texas. A small craft
advisory will be in effect for the southern bays until midnight
and for the Gulf Waters until noon on Wednesday. Winds and seas
will gradually diminish Wednesday afternoon.
LONG TERM (Thursday through Monday Night)...
Warming trend will commence Thursday and will persist through Sunday
as weak ridge builds aloft from NE Mexico into South Texas. Daily
max temperatures will rise from the mid 50s on Thursday to above
seasonal normals (mid 70s) by Sunday as a westerly downslope flow
develops off the lee of the Siera Madre. Next potent trough moves
into the central Rockies over the weekend drawing an increasing
southerly onshore flow into South Texas. Surface dewpoints will
climb into the lower 60s by Sunday morning overriding the cold bay
and ocean waters where temperatures are in 40s. This will likely
result in another sea fog episode persisting until the next cold
frontal passage Monday morning. A few warm advection showers will be
possible on Saturday as well. SCA`s are likely in the wake of the
front Monday and Monday Night. Temperatures will drop back below
seasonable norms again for Tue and Wed of next week, but not as
chilly as this current cold spell.
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 25 49 30 53 38 / 10 0 0 0 10
Victoria 23 48 27 50 32 / 10 0 0 0 0
Laredo 28 51 29 56 37 / 0 0 0 0 0
Alice 26 50 29 54 36 / 10 0 0 0 10
Rockport 26 47 32 51 40 / 10 0 0 0 10
Cotulla 23 52 27 54 33 / 0 0 0 0 0
Kingsville 26 51 29 55 37 / 10 0 0 0 10
Navy Corpus 29 48 36 52 44 / 10 0 0 0 10
TX...Freeze Warning until 10 AM CST Wednesday For the following
Wells...Kleberg...La Salle...Live Oak...McMullen...Nueces...
Wind Chill Advisory until 10 AM CST Wednesday For the following
zones: Aransas...Bee...Calhoun...Goliad...Jim Wells...
Kleberg...Live Oak...Nueces...Refugio...San Patricio...
Wind Chill Advisory until 4 AM CST Wednesday For the following
GM...Small Craft Advisory until noon CST Wednesday For the following
zones: Coastal waters from Baffin Bay to Port Aransas out
20 NM...Coastal waters from Port Aransas to Matagorda Ship
Channel out 20 NM...Waters from Baffin Bay to Port Aransas
from 20 to 60 NM...Waters from Port Aransas to Matagorda
Ship Channel from 20 to 60 NM.
Small Craft Advisory until 2 AM CST Wednesday For the following
zones: Bays and Waterways from Baffin Bay to Port Aransas.
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
854 PM CST Tue Jan 2 2018
Forecast remains in good shape with just a few minor tweaks to
weather and MinT grids.
Cloud cover continues to clear rapidly from west to east per IR
satellite imagery. With light and variable winds expected, optimal
radiational cooling is anticipated. I`ve nudged MinT grids down
by a few degrees area wide as a result. This will mean that many
areas will fall into the middle teens to low 20s. A few spots out
across the Big Country and along the Red River Valley west of I-35
may even fall into the lower teens. With a bulk of the stronger
lift from the compact upper level trough sliding east of the
region, the already low threat for very light snow/snow flurries
will come to an end and I`ve removed this from the forecast.
Otherwise, the rest of the forecast remains on track. Updated
products have been sent.
.AVIATION... /Issued 532 PM CST Tue Jan 2 2018/
00 UTC TAF Cycle
Concerns---None major. VFR with north flow.
VFR will prevail at all TAF sites over the next 24-30 hours. A
potent upper level shortwave trough will continue to dive
southeastward through the area. While lift is impressive with this
feature, the dry air below FL050 will likely only result in a low
potential for a few snow flakes at the surface. Given this low
potential, I`ve opted to leave it out of the TAFs. Some icing is
probable within the the VFR stratus with a potential for
turbulence below cloud base. Clouds should scour out over the next
3 to 6 hours across all TAF sites with northerly winds becoming
lighter and westerly towards midnight. Northerly breezes around
10 knots will likely resume around midday Wednesday.
.SHORT TERM... /Issued 320 PM CST Tue Jan 2 2018/
A vigorous shortwave trough currently over Southern Kansas and
Oklahoma will swing southeast across the area this evening. The
best axis of large-scale ascent will move across areas from D/FW
northeast toward Sulphur Springs and Paris through mid evening.
Per 3km NAM and RUC forecast soundings, this area will have the
highest inversion and deepest amount of dry air below the cloud
layer currently centered around 7 kft. Despite frontogenetical
forcing between 850mb-700mb, sublimation and/or evaporation within
the deep dry layer should limit the amount of any light snow that
will make it to the surface. So for now, we`re only going to
advertise a chance for snow flurries through early-mid evening and
across mainly the northeast counties. No impacts to travel are
expected, as bitter cold temperatures would result in dendrites to
be very light and blown about by the expected north-northwest
winds less 10 mph. Subsidence behind the exiting shortwave will
arrive quickly by midnight and after which should break out the
current expansive cloud deck. We should see mostly clear skies
across much of the area by sunrise Wednesday. It will be another
bitter cold morning with lows in the upper teens to mid 20s and
wind chills between 5 to 15 degrees above.
.LONG TERM... /Issued 320 PM CST Tue Jan 2 2018/
/Wednesday through next Tuesday/
The shortwave currently rotating across the Southern Plains will
swing across the Southeast CONUS tomorrow, effectively deepening
the East Coast trough. This pattern will result in a reinforcing
cold front tomorrow, which will keep the cold weather in place
through the end of the work week. The good news is that
temperatures should finally climb above freezing Wednesday
afternoon as subsidence associated with a ridge over the Southwest
states noses in from the west. A weak shortwave will spread some
cloudcover over the area on Thursday, which will keep high
temperatures near (to possibly a few degrees lower) than
Wednesday`s readings. In general, temperatures will range from
lows in the 20s to highs in the upper 30s and 40s through Friday.
The Arctic airmass will begin to retreat early in the weekend as
an upper low moves into the PAC northwest and a lee-Rockies
surface trough develops. Lee-side troughing will intensify
Saturday and Saturday night as low moves southeast through the
Great Basin. The result will be strong return flow over the
Southern Plains and North/Central Texas. The quick return of
moisture over the well-cooled surface will likely lead to drizzle
two and fog formation, along with a few warm advection showers
area- wide Saturday night into Sunday.
Rain chances will increase on Sunday as the upper low continues
southeast into the Southern Plains. The main question is whether
or not convection will be part of the equation. At this time it
appears that moisture and elevated instability will be sufficient
for occasion embedded thunderstorms, especially if the ECMWF
(deeper/stronger solution) verifies. Due to the expected low
coverage, will keep thunder isolated in the current set of grids.
A Pacific cold front will sweep through the region Sunday night
along with the upper level system. Models diverge considerably
next week, with the GFS continuing to show another Arctic push
Monday or Tuesday and the upper level pattern remaining benign,
while the ECMWF keeps the Arctic air to our north and indicates a
strong upper level trough mid to late next week. The former would
bring cold and dry conditions while the latter would bring near-
normal temperatures and a round of convective weather, so we will
likely need to wait another day before getting get a more
accurate look beyond Sunday-Monday.
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 19 44 23 42 26 / 5 0 0 0 0
Waco 16 47 22 44 24 / 5 0 0 0 0
Paris 15 39 21 39 23 / 10 0 0 0 0
Denton 15 43 21 42 23 / 5 0 0 0 0
McKinney 15 42 21 41 22 / 10 0 0 0 0
Dallas 20 44 24 43 27 / 5 0 0 0 0
Terrell 18 43 21 41 23 / 10 0 0 0 0
Corsicana 19 44 22 43 25 / 10 0 0 0 0
Temple 17 48 23 45 25 / 5 0 0 0 0
Mineral Wells 16 45 20 44 23 / 5 0 0 0 0
Area Forecast Discussion
National Weather Service Hastings NE
557 PM CST Tue Jan 2 2018
.SHORT TERM...(This evening through Wednesday night)
Issued at 417 PM CST Tue Jan 2 2018
Although we have emerged from the worst of our notable Arctic
blast from the past several days (this past week was the coldest
in the Tri Cities since 1996!) and all Wind Chill Advisories are
behind us, temperatures look to remain below average/normal
through at least Friday across most of our coverage area (CWA).
Honing in solely on these next 36 hours in this short term
section, although we are expecting relatively quiet weather, there
are some subtle challenges, including: 1) Could there be some
flurries this evening mainly in our east...2) How extensive will
low clouds coming down from the north be late tonight into Wed AM?
Examining the current/recent weather scene as of 21Z/3PM...
Other than perhaps being a bit breezier and temperatures running
a touch cooler over the snow-covered areas and a touch warmer over
our mainly snow-free KS zones, today has largely followed
expectations. In the mid-upper levels, water vapor satellite and
short term model data reveal north-northwesterly flow over the
central CONUS...flowing between a large-scale ridge over
the western states and a broad trough anchored over southeast
Canada. On the smaller scale, a clipper-type disturbance is
currently diving southward into the Great Lakes and eventually
Midwest region, with its main vorticity max currently over
northern MN. Visible satellite reveals a fairly healthy band of
mid-high clouds associated with this disturbance rapidly
overtaking our local area from north-to-south, "ruining" the
pristine sunshine that dominated much of the day. At the surface,
we are in the "warm" sector of the main low pressure center over
the Upper Great Lakes, and to the north of expansive high pressure
to our south. The net result has been steady southwest winds
today, generally sustained 10-20 MPH but with occasional gusts to
around 25 MPH/slightly higher. Temp-wise, as earlier mentioned,
this is just one of many upcoming days for which our existing snow
cover gradient will have an impact. In general, most snow-covered
Nebraska zones are going to top out in the 18-21 range, while our
largely snow-free southern zones (especially KS) are more so
Now looking ahead forecast-wise through these next 3 fcst
The aforementioned clipper disturbance to our northeast will
continue diving south-southeast, with the bulk of its forcing
focused near and east of the NE-IA border. While there will be a
concentrated swath of enhanced mid level clouds swinging southward
across our CWA this evening, we are certainly not expecting
measurable precip. However, there may be an outside shot for a few
flurries mainly east of Highway 281, and this has been added to
the fcst mainly in coordination with WFO OAX. Otherwise, at the
surface, a fairly weak cold front will pass through tonight, with
the most noticeable effect being a switch to north-northwest winds
of mainly 10-15 MPH/slightly higher gusts. Late in the night,
short-term models such as the RAP are increasingly-insistent that
another band of clouds, this time much lower (based around 2,000
ft) will invade especially the northeast half of our CWA, which
seems plausible given that these lower clouds are already evident
on satellite/obs over ND. At any rate, hourly temp trends and sky
cover will be tricky, and would not be surprised to see a few
spots rise slightly warmer as the front moves in this evening than
they did this afternoon, before falling back down closer to
sunrise. At any rate, actual low temps tonight are aimed solidly
ABOVE zero for a change, mainly into the 9-14 range.
Confidence is high in a precip-free day under fairly uneventful
northwesterly flow, but there are some question marks about sky
cover and temperatures (not completely unrelated). As mentioned
above, models such as the RAP/NAM especially are really insistent
that at least a narrow (perhaps 50-100 mile wide?) band of low
clouds will be in place over the CWA at daybreak, and perhaps
linger through at least the morning before probably breaking
up/diminishing somewhat in the afternoon. However, exactly where
this cloud band sets up is in question even at this near-range,
with the RAP favoring mainly the eastern half of our CWA with more
sun west. At any rate, the effects of any low clouds along with
reinforcing cooler air from the northeast could put a damper on
much of a warm-up. As a result, nudged down highs 1-2 degrees from
previous forecast, but still resulting in a respectable gradient
from teens far northeast, low-20s central, around 30 far
southwest. Wind-wise, overall less breezy than today with north-
northwest sustained 10-15 MPH/gusting to around 20 MPH at most.
Although not nearly as cold as some recent nights, this does look
to be the overall-coldest night of the next week, thanks mainly to
very light/variable winds in the presence of surface high
pressure. That being said, there also looks to be a fair amount of
high level cloud cover at least early in the night, which could
mitigate/at least delay how far things drop. For now am aiming
lows into the single digits above zero most areas, but ranging
from near zero far northeast, to 10-12 far southwest.
Interestingly, the SREF visibility progs are suggesting some
overnight fog mainly in our western CWA, but am not ready to buy
into this just quite yet, as it seems a bit overdone and not very
supported by raw MET/MAV guidance. Would be more of a believer in
fog if more snow were expected to melt on Wednesday. Something to
keep in mind, at any rate.
.LONG TERM...(Thursday daytime through Tuesday)
Issued at 417 PM CST Tue Jan 2 2018
General overview of this 6-day period (including precip):
For most folks, by far the #1 story of this time frame will be at
least a temporary "warm up", and even the comparably colder days
will not be as frigid as what we`ve recently had. Precip-wise, the
vast majority of this time frame appears dry, but we continue to
advertise at least low chances for snow and/or rain mainly
centered on Sunday. Because this is still several days away, the
details are from set, but at least at this point this looks like a
pretty minor precip event. That being said, we will have to be
vigilant as it gets closer, as there appears to be at least subtle
hints of some light freezing drizzle/freezing rain potential.
This is one of those patterns in which although we are highly
confident that it will be warmer than our recent record/rare
frigid cold, there are still some definite question marks on just
how much we "warm" up on certain days. This is especially true as
we get into the Saturday-Tuesday time frame as model uncertainty
grows. If anything though, temps on days such as Thursday, Friday,
Monday were nudged up a few degrees from the previous forecast
(especially Monday). As it currently stands, Thursday is aimed
roughly 5-8 degrees warmer than Wednesday, with highs mainly mid
20s to near 40 (far southwest). A backdoor cold front then knocks
things down slightly for Friday, but still looking at low 20s to
mid 30s in most areas. Then, Saturday looks to be the mildest day
we`ve seen in 2-3 weeks (and also the first above-freezing day in
the Tri Cities since Dec. 21!), with highs aimed from low 30s
northeast to mid 40s southwest. Sunday is currently expected to be
similar if not slightly milder than Saturday in most areas, but
this is somewhat in question depending on the timing of the next
cold frontal passage. Getting into Monday and Tuesday of next
week, uncertainty continues to grow in the temperature details.
While we are officially advertising a modest cool-down from the
weekend (highs mainly 30s Monday and upper 20s-mid 30s Tuesday),
there is a solid 5-10 degree spread in longer-term numerical
guidance between the GFS/ECMWF. In fact, if the ECWMF verifies,
even our Nebraska zones could see highs in the 40s early next
week. Again though, uncertainty is very high and our official
forecast predictably represents a middle-ground for now.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 519 PM CST Tue Jan 2 2018
A cold front will sag south across local area overnight...
bringing occasionally gusty northerly winds at both terminals
after midnight. Ahead of this front...expect a surge in winds
aloft to result in some LLWS for several hours until surface winds
increase around 03/08Z. While there are plenty of mid level clouds
across the area this evening...CIGS are expected to remain VFR
through the period...with lower CIGS likely staying well east of
Area Forecast Discussion
National Weather Service Green Bay WI
545 PM CST Tue Jan 2 2018
Updated aviation portion for 00Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 150 PM CST Tue Jan 2 2018
The latest RAP analysis and satellite/radar imagery show Arctic
high pressure centered across the central Mississippi and Ohio
Valleys, while the next Arctic cold front is heading towards the
ND/MN/Canadian border. High clouds are already pushing across the
northwest half of Wisconsin ahead of the system, with a narrow
band of light snow occurring over eastern SD and northern MN
within a ribbon of mid-level fgen. Other scattered flurries and
blowing snow exist behind the front. As this system passes across
the area tonight, snow trends and potential impacts are the main
Tonight...A potent shortwave trough and associated cold front will
swing across the region. Snowfall is anticipated to remain
concentrated within the mid-level fgen band and ahead of the
shortwave, which will impact central and north-central WI areas
from early to mid evening, and northeast WI areas from late
evening to early overnight. Up to an inch of light/fluffy snow
will be possible, with some blowing and drifting as a result of
breezy southwest to northwest winds, particularly in the open
areas. As winds shift to the northwest, lake effect snow showers
will be ramping up in the snowbelts of Vilas county overnight.
Temperatures look too cold for dendritic snow growth, but the
small flakes could still contribute to an additional inch by
Wednesday...Arctic high pressure will be building south across the
northern Mississippi Valley. Winds will remain breezy out of the
northwest, which should continue the lake effect snow showers
across Vilas county. The snow showers should be the most intense
during the morning, before incoming dry air erodes the snow
showers during the afternoon. Elsewhere, progged soundings and
upstream obs suggest a partly to mostly cloudy day. Highs ranging
from the mid single digits over north-central WI to the mid teens
near the Lake.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 150 PM CST Tue Jan 2 2018
Bitter cold is expected to continue into the weekend, before a brief
warmup on Sunday into Monday. Indications that temperatures will take
another plunge by the middle of next week.
For Wednesday night into Friday, lake effect snow showers are expected
to continue across Vilas county. Amounts for the entire period should
be modest with a few inches expected in the snowbelt region of northwest
Vilas county. Meanwhile, bitter cold and northwest winds will create
dangerous wind chill readings of 20 below to 30 below Thursday and
Friday morning. Based on the current forecast, would think two separate
headlines will be needed for each night instead of one continuous
advisory from Wednesday night through Friday morning. This is based
on the expected afternoon wind chill readings. The shift tonight or
Wednesday will make the final decision on the headlines. Also, winds
could go calm for a few hours out west on Friday morning. If this
occurs, low temperatures may need to be lowered Friday morning out
west (away from the snowbelt region of northwest Vilas county).
Cold conditions will continue Friday. Friday night is very intriguing
as the ridge of high pressure moves across the region. Lowered the
low temperatures for Friday night, but may need be lowered even more
if winds go calm for several hours. Next clipper system will bring
a chance of light snow Saturday night into Sunday morning. The
forecast becomes muddled Sunday night into Tuesday, although the
latest thoughts is that another clipper system will bring a chance
of light snow Monday into Monday night with the return to much
colder air on Tuesday.
.AVIATION...for 00Z TAF Issuance
Issued at 545 PM CST Tue Jan 2 2018
An upper level disturbance will bring a few hours of snow showers
and MVFR conditions as it moves across the area this evening.
SNow showers should diminish by midnight, but ceilings of 2500 to
3500 feet will last through midday Wednesday. VFR weather is
likely Wednesday night and Thursday.
Area Forecast Discussion
National Weather Service Wilmington NC
1011 PM EST Tue Jan 2 2018
Low pressure will form off the Florida coast tomorrow and travel
up the eastern edge of the arctic air in place for an
accumulating snow event for the Coastal Carolinas. The frigid
air will remain in place all week with a gradual moderating
trend over the weekend and finally seasonable weather on
.NEAR TERM /THROUGH WEDNESDAY/...
As of 930 PM Tuesday...Winter Storm Warning remains in effect
with no changes to areal coverage or pcpn type for this
Changes to hourly sfc temp/dewpoints during this evening then
meshed it with the forecast after midnight. Used HRRR data with
some tweaks to the dewpoints leading up to midnight. Winds also
tweaked, mainly closer to the coast, slightly higher especially
ILM NC Coastal Counties where a Gale Warning has been raised for
the adjacent ILM NC Waters. RH and apparent temps re-calculated.
As of 300 PM Tuesday...Arctic air is expected to continue
overnight as high pressure over the Mid-Atlantic states feeds
more cold, dry air southward. Excellent radiational cooling
conditions this evening should allow temperatures to plummet
through the 20s and into the teens in some outlying spots by
midnight. A strong upper level disturbance moving through
Oklahoma this afternoon will move across the Deep South tonight,
spreading a slowly thickening layer of mid and high clouds
eastward. These should become dense enough to impede radiational
cooling between 2-3 AM Wednesday morning. For this reason my
forecast temperatures are generally 16-20 degrees for most areas
away from ocean influence, a little warmer than GFS/NAM MOS
As the upper disturbance reaches Florida around noon on Wednesday,
surface low pressure will develop across the northern Bahamas.
Large- scale ascent ahead of the trough will weaken/dissipate
the subsidence inversion that has covered the western Atlantic
since this arctic outbreak began a few days ago. What has been
widespread shallow convection/cold air stratocumulus will
blossom into deeper convection focused near and east of the Gulf
Stream off the Florida and Georgia coast. This should pull the
developing surface low northward about 200 miles east of
Jacksonville, FL, then northeastward by late Wednesday afternoon
well east of Savannah and Charleston. (It`s been interesting
watching many of the models show explosive deepening of this
system Wednesday night and Thursday as convection feeds back
into excellent dynamics aloft. Not all feedback is model
We believe the NAM is displaying a westward and warm bias,
and are following more of a GFS/Canadian/ECMWF blend for precip
amounts and type. Precipitation should begin several hours
later than was thought at this time yesterday, and will take the
form of light sleet developing during the mid-morning hours
around Georgetown, SC. Sleet and freezing rain should then
spread northward toward Cape Fear by early afternoon. A narrow
nose of warm air spreading back onshore between 1500-4000 feet
AGL should be responsible for creating this mixed bag of precip
It will take several hours for a layer of very dry air between
4000- 10000 feet AGL to moisten up, but once that happens
expect precip rates to increase substantially during the late
afternoon hours. Areas west of Elizabethtown, Whiteville, and
Conway should be west of the westernmost extent of the coastal
warm nose aloft, and any precipitation should take the form of
snow for these inland areas. Clouds and low-level evaporational
cooling should keep temperatures cooler than virtually any MOS
guidance is indicating, and we`re forecasting highs ranging from
31-32 to maybe some mid 30s in spots.
The western edge of the precip shield should line up fairly
closely with Interstate 95. Even though we are upgrading to a
Winter Storm Warning for Florence, Dillon, and Lumberton
counties, warning-level snowfall is not expected for those
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 3 PM Tuesday...Shortwave crossing the northeast Gulf of
Mexico will induce surface low off the eastern FL coast Wed.
The low will deepen as it lifts northeast later Wed into Wed
night, spreading wintry precip across the area. If thermodynamic
profiles are correct, precip would be snow across much the area
by the time the period begins. The only exception would be
along the NC coast where freezing rain/sleet cannot be ruled out
during the first hour or two of the period. Still a lot of
uncertainty with respect to the storm`s ultimate track and its
strength (both of which will play a role in how far inland
precip spreads and how much precip falls).
At first isentropic lift will be generating light precip,
which will be falling into a cool and dry airmass. Isentropic
lift gives way to frontogenesis at 850 and 700 mb with
enhancement from increasing PVA overnight. The biggest forecast
concern remains the strength of the low level warm nose and how
much sleet/freezing rain will fall before the transition to all
snow takes place. Feel confident that measurable precip will
fall across the eastern third of the forecast area and will go
ahead and raise pop for these area with gradually decreasing pop
farther west. Later Wed night the GFS shows enhanced PVA and
850 frontogenesis producing a period of enhanced snow across
portions of SE NC. Should this verify, current snowfall totals
for these areas would be too low.
Bulk of the precip Wed night ends around midnight with deep
dry air wrapping around the backside of the exiting low. Strong
cold advection will commence as the low exits. The cold
advection coupled with snow on the ground will likely result in
lows several degrees below guidance and well below climo. Strong
cold advection continues Thu with highs struggling to reach mid
30s despite mostly sunny skies. Partial thickness values point
to lows in the mid teens Thu night with continued cold
advection, although in a much weaker state, clear skies and at
least some form of snow pack across portions of the area.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...Northwest flow aloft on Friday around
huge upper low over far eastern Canada. A stream of channeled
vorticity streaks across the area as well and it is strong
enough to have a weak surface reflection. Regardless, the column
will be far too dry to support much other than a few clouds as
it does so. On Saturday enough mid level energy then digs under
the main cutoff that it eventually opens up and the pattern
turns progressive. This means that the frigid air in place will
continue to be re-enforced through Saturday and at the surface
through Saturday night. However then beginning on Sunday a
gradual moderation gets underway, though models may be a little
too quick to move the heavy cold, dense high offshore. Monday
brings a relatively dramatic warmup back to seasonable
temperatures i.e. highs in the mid to upper 50s. Cloud cover
also looks to increase in the warm advection regime especially
as a cold front approaches from the west and the gradient
tightens through a fairly deep layer. The deepening and
strengthening warm and moist advection will lead to gradually
rising rain chances Monday into Tuesday and also likely preclude
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...High pressure will remain the dominant influence
through tonight, before low pressure develops and moves north
just off the coast Wednesday. Increasing but lowering high
level cirrus will be the only sky cover overnight. Winds will
be north to northeast around 5 kts. Low clouds will begin to
overspread the terminals from south to north Wednesday, but
latest guidance has VFR through 18Z. Thus have delayed MVFR at
KCRE/KMYR until 18Z or afterward, however, some -FZRAPL could
begin to affect these terminals by mid morning. KILM should
succumb to MVFR by mid afternoon, with -RA and PL as temps hover
just above freezing. Mid to late afternoon, predominately
MVFR/mixed precipitation will turn to IFR/snow as winds back to
the NW-N at 10-20kt, highest at the coast. Highest confidence of
IFR/snow is the coastal terminals.
Extended Outlook...Potential for MVFR/IFR Wed/Wed night in
wintry precipitation. Gusty NW winds Thursday. Otherwise, VFR.
NEAR TERM /THROUGH WEDNESDAY/...
As of 945 PM Tuesday...Raised a Gale Warning for the ILM NC
Waters only at 9 am Wed. SCA to start at 6 am across all
With the sfc low progged to deepen rapidly, dropping to possibly
sub 990mb early Wed evening at which point the low is progged to
be just offshore at the 33.5 degree Latitude. Not quite a Bomb
but has the potential given the warm Gulf Stream waters feeding
this dynamic monster.
Have increased winds to sustained Gale force across the ILM NC
Waters during mid-morning Wed and kept them just under Gales
for the ILM SC Waters but wouldn`t be surprised to see gusts up
to 35 kt. It will depend on the frequency of these gusts if
Gales are needed for the ILM SC Waters. Later forecasts will
make that call. Significant seas have also been tweaked upwards
by atleast 1 foot due to hier wind speeds. Will have fetch
limitations due to wind directions, NNE backing to NW. Are range
of seas may need to expand.
As of 300 PM Tuesday...Very cold arctic air will continue
across the Carolina coastal waters overnight, driven southward
by arctic high pressure across the Mid-Atlantic states.
Attention then will shift to developing low pressure across
the northern Bahamas Wednesday morning. This low should quickly
intensify as it jumps northward to a position about 200 miles
east of Jacksonville, FL Wednesday afternoon. By early Thursday
evening the low could have a pressure below 1000 millibars as it
moves well offshore from Charleston. In addition to increasing
winds and seas Wednesday afternoon, a mixed bag of precipitation
should develop with rain, snow, or ice possible at various
distances from shore. After the Small Craft Advisories expire
early this evening, another set will need to be issued for the
Wednesday/Wednesday night event.
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 3 PM Tuesday...Increasing gradient and development of
strong cold advection in the wake of exiting low pressure will
maintain SCA conditions, with both offshore flow 25 kt and seas
over 6 ft, Wed night into Thu. Offshore flow will slowly weaken
during Thu with winds and seas dropping below headline criteria
in the afternoon. Flow remains offshore but cold advection will
weaken and the gradient starts to relax with winds dropping to a
solid 20 kt later Thu and 15 to 20 kt Thu night. Seas 3 to 5 ft
Thu drop to 2 to 4 ft by the end of the period.
LONG TERM /FRIDAY THROUGH SUNDAY/... As of 300 PM Tuesday...A
markedly weakening gradient in placed on Friday as the local
area sees a lessening effect from the huge storm affecting the
New England States. A weak surface disturbance then crosses the
waters Friday night bringing very light winds before high
pressure begins to assert itself from the NW already by Saturday
morning. This high passes by well to the north of the area
precluding much in the way of increased winds or seas.
SC...Winter Storm Warning from 6 AM Wednesday to 6 AM EST Thursday
Winter Storm Warning from 11 AM Wednesday to 6 AM EST Thursday
NC...Winter Storm Warning from 11 AM Wednesday to 6 AM EST Thursday
MARINE...Small Craft Advisory from 6 AM Wednesday to 6 PM EST Thursday
Small Craft Advisory from 6 AM to noon EST Wednesday for
Gale Warning from noon Wednesday to 9 AM EST Thursday for
Area Forecast Discussion
National Weather Service Lake Charles LA
950 PM CST Tue Jan 2 2018
Water vapor imagery from GOES 16 shows an upper level shortwave
trough progressing across the Ark-La-Tex region this evening. The
00Z KLCH sounding sampled increasing moisture content from
roughly 800-700 hPa in advance of the approaching upper level
trough. The lower levels remained very dry with dewpoints of -20C
or below from 950-900 hPa. While a loop of the past several hours
of radar imagery show increasing returns across the region, they
continue to dissipate around 3.5-4 kft AGL which corresponds to
the top of this layer of dry air.
The latest short term guidance, in particular the HRRR and RAP,
continues to indicate a slight chance for snow or frozen
precipitation to briefly reach the ground late this evening.
However, a quick look at the model soundings indicate that they
are too moist below 900 hPa compared to observation. As a result,
the very light accumulations advertised in the model output are
probably overdone. Therefore, the current forecast of only a very
slight chance of a few flurries across SE Texas late tonight
continues to be representative.
The cloud cover associated with the approaching trough has limited
cooling of temperatures across the region so far with surface
observations running several degrees above the inherited forecast
over the past few hours. Cloud cover is likely to continue to
limit any cooling and the latest model guidance is indicating
warmer overnight lows. Therefore, based on the latest observations
and guidance this update raises the overnight lows by a few
degrees. However, a hard freeze is still expected across the
region and there are no changes to the Hard Freeze Warning which
remains in effect until 10 AM Wednesday.
.PREV DISCUSSION... /issued 540 PM CST Tue Jan 2 2018/
Cloudy skies as mid lvl clouds push across the region. Moisture
has pulled off to the east as another cold front is projected to
move through tonight. Winds to swing back around to the north.
PREV DISCUSSION... /issued 402 PM CST Tue Jan 2 2018/
Surface high over the Mid-Mississippi Valley continues to ridge
into the forecast area providing very dry and cold air mass at the
surface. Active sub-tropical jet continues to bring mid and upper
level clouds across the forecast area. With the majority of the
forecast area not seeing any sunshine, temperatures have struggled
to get above the freezing mark. The left front exit region of a
jet streak is moving on out, and thus reflectivity on radar is
moving off to the east and winding down. There is still a
significant dry layer that precipitation was falling through, so
looked a lot better on radar, but only ground truth reports we got
from the platforms was a few flurries, a few light sleet pellets,
or nothing at all.
Short term forecast comes down to an upper level impulse currently
over the Southern Plains, and what impact it will have on the
sensible weather tonight, as to any precipitation and how soon
clouds will move out that will affect overnight low temperatures.
Short wave looks to be moving fairly quickly with timing from
03-06Z (9 pm to midnight) for portions west of an Alexandria to
Lake Charles line, and 06-09Z (midnight to 3 am) for areas east of
this line. Clouds should move out rather quickly in wake of this
disturbance, which will allow for a bit more radiational cooling
tonight, therefore, air temperatures will likely be a bit colder
tonight. Operational guidance has been running a few degrees too
cold lately, with high res guidance doing a better job. Therefore,
went with a blend of bias corrected mos and high res as those
readings seemed reasonable. Therefore, hard freeze conditions will
occur with lows from the middle teens in the usual cold spots of
Central Louisiana, upper teens to lower 20s elsewhere, with mid
20s along the coast.
As for precipitation, a swath of reflectivity should develop at
the base of the upper level short wave as it passes through the
region, much like this morning, although lift seems a bit more
robust with this short wave. Again, operational guidance all keep
any significant precipitation over the coastal waters, with the
latest HRRR runs the more robust in bringing activity just inland
into Southeast Texas, and then skirting the coast into extreme
Forecast soundings show a decent moistening between 70H-85H so
about 5-7k feet. However, the forecast soundings show a significant
dry layer hanging around below 5k feet to the surface. With short
wave moving quickly, may not be enough time to moisten up the low
layers enough for significant precipitation to fall through. Therefore,
best chance of rain, mixed with light sleet, or snow flurries
will be over the coastal waters, with a very low probability of
any significant snow flurries over land areas. Better chance of
getting frost bite tonight looking for snow flurries than actually
seeing a lot of snow flurry activity.
Temperatures during the daytime will be "warmer" tomorrow, as
clear skies in wave of the short wave should allow for solar
heating to take place. The cold air mass will hang around however,
through the week, with temperatures below hard freeze, or
freezing levels through Saturday morning.
High pressure will finally move off to the east over the weekend,
allow for more of a return flow off the Gulf to moderate
temperatures upward and bring back some moisture and humidity.
High pressure will continue to build into the coastal waters
bringing a very cold air mass over relatively warmer Gulf waters.
This will keep elevated and gusty winds through Wednesday. Winds
will be between 15 and 20 knots...so will keep conditions at small
craft exercise caution level. A fast moving upper level
disturbance will bring a chance for very light rain tonight. The
rain could mix with some very light snow flurries or sleet near
Moderate offshore flow will persist through the end of the week.
By the weekend, high pressure will finally move off to the east,
with onshore flow returning.
.PRELIMINARY POINT TEMPS/POPS...
AEX 19 42 21 41 / 10 0 0 0
LCH 24 42 25 45 / 10 0 0 0
LFT 24 41 23 43 / 10 0 0 0
BPT 24 44 26 46 / 10 0 0 0
LA...Hard Freeze Warning until 10 AM CST Wednesday for LAZ027>033-
TX...Hard Freeze Warning until 10 AM CST Wednesday for TXZ180-201-215-
GM...Small Craft Exercise Caution through Wednesday morning for
Low Water Advisory from 6 AM to noon CST Wednesday for GMZ430-
Small Craft Exercise Caution from 6 AM CST Wednesday through
Wednesday morning for GMZ450-452-455.
Area Forecast Discussion
National Weather Service New Orleans LA
932 PM CST Tue Jan 2 2018
Sent another update to raise the lows again for tonight. Refer to
previous discussion for reasoning.
.PREV DISCUSSION... /issued 857 PM CST Tue Jan 2 2018/
Overcast cloud cover is likely to limit the number of hours sub-
freezing and in hard freeze tonight. Hourly temperatures have been
adjusted substantially higher this evening to account for latest
trends, and have raised the lows tonight to try to match. Some
areas of the northwest near Baton Rouge and southwest Mississippi
may have a longer period of partial clearing late tonight and
around sunrise to allow the temperatures to fall faster and closer
to the forecast and MOS values while that is less likely where
less if any clearing occurs to the southeast near the coast. The
00z LIX sounding indicated some moistening in the mid levels where
clouds were observed, but very dry air continued below the cloud
Looking at satellite imagery loops, a vigorous shortwave trough
is approaching the central Gulf coast region from the Ark-La-Tex
region. Usually, a system of this strength has a way to
dynamically create and squeeze out any available moisture through
large scale lifting over the elevated frontal zone, however it
will take substantial moistening of the low levels. Have expanded
the area slightly with mention of a slight chance of snow
flurries after midnight, and there may be a narrow strip of brief
light snow/snow showers closer to the southeast Louisiana coast to
the south of metro New Orleans during the overnight hours where
less low level dry air should be in place. This narrow zone
appears to be a true "slight chance of measurable precipitation"
for a minor dusting of very light snow accumulation if no melting
occurs while the snow flurries to the north by definition are not
considered "measurable precipitation". Regardless, the main
impacts are still expected to be from the very cold temperatures
that should lead to another hard freeze. Updates have been sent.
PREV DISCUSSION... /issued 357 PM CST Tue Jan 2 2018/
DISCUSSION...It was another frigid morning but lows again did not
quite reach its potential. Clouds have been streaming in from the
west all day and have kept the southern half of the CWA from warning
with MSY still at 33 at 3pm.
Tonight 2 issues, cold temps and frozen precip. Two features which
are very evident on WV are dropping down the back side of the
trough. First one which won`t have an impact on our area is moving
through SD/MN but the one that is currently digging through OK and
into TX is the one that could cause a few small issues. The further
this s/w digs should help keep the moisture displaced south of the
region. It is also moving quickly so that would limit the time frame
for moisture to be drawn northward. This looks to be the better bet
and has agreement from the GFS, ECMWF, and NAM. With that will
continue the mention of flurries for the south shore and again can`t
rule out one or two flakes immediately along the northshore and
coastal MS however do not get excited as no accumulations are
expected. Will mention that the GEM is more bullish and seems to
have a little more moisture to work with and thus shows some
light snow over much of the area. The HRRR has trended towards a
slightly better chance of snow showers right along the SELA coast
but does not bring it inland. This will need to be watched
overnight but feel good that moisture will be lacking and
displaced. As for lows have decided to go abv mos guidance by a
few degrees as we should see rather thick cloud cover through the
night and this will definitely hurt rad cooling potential. That
said hard freeze conditions will not have a problem developing
again tonight and areas that have had heavy cloud cover through
the day have not warmed up. Places like the NO metro that are
only around 33-35 should fall below freezing rather quick this
evening. Luckily not anticipating much if any wind so will hold
off on a wind chill adv.
Reinforcing cold air will come in behind tonight`s system and
should lead to another chilly day tomorrow with another cold cold
night over the area. Hard freeze conditions may not develop over
the entire area but at the least a moderate to light freeze will
develop in the region that is not in the hard freeze warning for
Slow moderation and dry conditions will continue as we head into the
weekend with hard freeze conditions possible again Thursday night in
some areas and then a moderate to light freeze over much of the area
Saturday morning. Finally by Sunday morning we should remain abv
freezing everywhere but don`t get too excited. The next system is
quickly on the way. Another strong s/w drops out of the Pac
northwest this weekend and heads towards the mid and Lower MS valley
region Sunday night and Monday. This will bring a good chance of
showers and a few thunderstorms. This will also send another cold
front through the region cooling us back off but there is the
possibility of another Arctic high working into the MID MS Valley
and this could bring some pretty chilly conditions back to the
region momentarily. /CAB/
Winds have come down some as expected across the tidal lakes and
sounds and they will be able to let the exercise caution headlines
come down this evening for those areas. I have extended the time for
the caution for the rest of the coastal water to go through
Wednesday afternoon as another wave is expected to move across the
area and winds will increase again tomorrow. A longer period of
relatively quiet marine conditions will be from midday Thursday
through much of Saturday. Onshore winds will pick up on Sunday.
Expect VFR conditions to prevail through the TAF period. A few mid
clouds are moving across the area. There could be a chance of a
brief snow flurry or ice pellets late tonight...mainly after
midnight for a short window of time mainly south of Lake
Pontchartrain. KHUM would be the closest site to see that threat.
Not expecting any major issues if the winter precip occurs.
Otherwise VFR conditions can be expected again tomorrow as well.
DSS CODE: BLUE.
ACTIVITIES: Hard Freeze Warnings
Small Craft Adv
DECISION SUPPORT SERVICES (DSS) CODE LEGEND
GREEN = NO WEATHER IMPACTS THAT REQUIRE ACTION.
BLUE = LONG-FUSED WATCH, WARNING, OR ADVISORY IN EFFECT OR
HIGH VISIBILITY EVENT.
YELLOW = HEIGHTENED IMPACTS WITH SHORT-FUSED WATCH, WARNING OR
ADVISORY ISSUANCES; RADAR SUPPORT.
ORANGE = HIGH IMPACTS; SLIGHT TO MODERATE RISK SEVERE; NEARBY TROPICAL
EVENTS; HAZMAT OR OTHER LARGE EPISODES.
RED = FULL ENGAGEMENT FOR MODERATE RISK OF SEVERE AND/OR
DIRECT TROPICAL THREATS; EVENTS OF NATIONAL SIGNIFICANCE.
.PRELIMINARY POINT TEMPS/POPS...
MCB 21 40 19 40 / 10 0 0 0
BTR 23 40 21 43 / 10 0 0 0
ASD 24 41 22 43 / 10 0 0 0
MSY 27 40 26 43 / 10 0 0 0
GPT 25 42 24 42 / 10 0 0 0
PQL 25 43 22 43 / 10 0 0 0
LA...Hard Freeze Warning until 10 AM CST Wednesday for LAZ034>037-039-
Hard Freeze Warning from 6 PM Wednesday to 11 AM CST Thursday
MS...Hard Freeze Warning until 10 AM CST Wednesday for MSZ068>071-077-
Hard Freeze Warning from 6 PM Wednesday to 11 AM CST Thursday
Area Forecast Discussion
National Weather Service Omaha/Valley NE
519 PM CST Tue Jan 2 2018
.SHORT TERM...(Tonight through Friday)
Issued at 325 PM CST Tue Jan 2 2018
Chance of light snow through this evening and temperatures the
next few days are the main forecast concerns in the short term.
A fairly strong jet segment at 300 mb (115 knots) was punching
southeast from Alberta and Saskatchewan toward the Dakotas at 12Z
this morning. This was somewhat coincident with a strong shortwave
trough at 500 mb (12 hour height falls of up to 180 meters). At
the surface, cold arctic high pressure was over MO, but that has
been moving southeast today. Winds in our area were from the
southwest and were bringing in air that was not as cold as in the
The shortwave mentioned earlier will mainly affect parts of MN, IA
and points to the northeast. But it will drive a cold front
through the area tonight. There has been a band of light snow up
across the SD, tracking to the south/southeast. Will use some of
the most recent RAP model guidance for tonight, which tends to
bring a band of light snow/snow showers through the region. But
will only go with some POPs of 20 to 30 percent. As an area of
850 mb moisture moves down in behind the front there may be some
flurries with temperatures in the cloud layer favorable for ice
crystal development. Winds may be a bit gusty with the frontal
passage and also behind it. Otherwise a ridge of cold high
pressure should build south/southeast into the area for Wednesday
with sunny to partly cloudy skies. That sets us up for what will
probably be the coldest night of the week.
On Thursday, the high slides east and isentropic lift probably
will be enough to develop an area of light snow just east of our
area. Will monitor that and if area of lift is closer to our area
we may need to add a chance of light snow.
.LONG TERM...(Friday night through Tuesday)
Issued at 325 PM CST Tue Jan 2 2018
We should have a mainly dry period from Friday night into Saturday,
and the upper level pattern changes a bit. Model agreement is not
all that great at this point but at least temporarily our flow
become more zonal, with the coldest air shunted to our east.
Temperatures turn much warmer on the weekend, with highs mainly in
the 20s and 30s. A wave moving from the Rockies toward the
southern part of the Plains may bring some light snow or a rain
snow mix to our area Saturday night into Sunday night, but again
model agreement is not great. Temperatures are expected to turn
colder again by Tuesday.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 516 PM CST Tue Jan 2 2018
MVFR conditions possible overnight. A narrow/fast-moving band of
very light snow will pass over all sites this evening, but
question remains if anything more than flurries will reach the
ground due to dry low-levels. Did mention a 6SM -SN tempo group
for a few hours this evening at all sites, but not expecting much,
if any accumulation. Otherwise, northwest surface winds will gust
to near 20-25kts overnight for a few hours.