Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/08/18
Area Forecast Discussion
National Weather Service La Crosse WI
532 PM CST Sun Jan 7 2018
.SHORT TERM...(Tonight through Monday)
Issued at 230 PM CST Sun Jan 7 2018
Water vapor imagery this afternoon capturing a mid-level closed low
along the Manitoba/Saskatchewan border with a trough extending
southward into the eastern Dakotas. Meanwhile, another trough was
pushing east across the central Plains. This was drawing milder air
into the area along with broken higher cloud cover. Will have to
watch this trough as it swings through this evening. Right now,
thinking it will come through mostly dry. A couple caveats though,
with a small chance of some very light patchy freezing drizzle for
portions of southwest/central WI. Another caveat is HRRR showing the
possibility of some light snow right along the trough axis as it
moves through. Will keep this feature dry right now but will
continue to monitor. Clearing skies expected for later tonight after
midnight as the trough exits east. Otherwise, a relatively mild
night tonight with lows in the upper teens/lower 20s.
Monday appears mostly sunny as a ridge of high pressure builds in
from the west. Look for highs in the upper 20s to the middle 30s.
.LONG TERM...(Monday Night through Sunday)
Issued at 230 PM CST Sun Jan 7 2018
Ready for the January thaw? It`s right on track for the early work
week period, but the bigger focus remains on midweek with continued
potential for a messy storm system to impact at least portions of
the local areas. Lots of questions remain about that system (more
below), but first things first, significantly warmer air still in
the works Tuesday into perhaps Wednesday as the flow regime across
the CONUS finally flattens out, with strengthening south to
southwesterly flow over the entire region expected in advance of a
stronger shortwave working into southern California (our "fun" for
midweek). Not much moisture available initially for any lower
cloud/stratus worries on Tuesday, though some passing mid clouds may
act to slightly hinder daytime highs. Still, with 900mb temps
responding to 3-6C per consensus blend (GFS by far the coldest),
don`t see any reason highs won`t rebound well into the 30s if not
even lower 40s.
Uptick in low level moisture advection by Tuesday night and
Wednesday will likely spell an increase in lower stratus, with
perhaps even a little drizzle as the cloud layer deepens within
continued broad warm advection ascent. Pending surface temperatures,
can`t rule out some freezing drizzle Tuesday night, though gut
feeling is consensus lows are likely too cold in this setup.
However, will have to watch how ground/road temps respond the next
few days with such deep frost depths noted out there (20+" in many
areas). Regardless, do expect to see highs the warmest on Wednesday
given the warmer start and core of warmest air aloft arriving, with
readings likely pushing 40+ in many areas. Get those short sleeved
shirts ready - going to feel amazing after the past 2 weeks!
Now for the challenge - Wednesday night into Thursday. A trend is
well established for a rather robust upper wave across southern
California to northward toward the area on Thursday, weakening as it
shears the north while additional energy drops into the southern
Plains. This is where the forecast challenge arrives, as a weaker
approaching system suggests a weaker surface reflection and less
warm air drawn north into the area (more of a snow or wintry mix
scenario like the GFS) while a stronger scenario draws the surface
wave farther north and places much of the area in a warmer setup
(more rain like the ECMWF). Ensembles not much help just yet as
there`s just too many pieces of energy to resolve, so a consensus
blend remains the best charted course for now.
As the system passes, regardless of the eventual outcome, an
strengthening signal is emerging among the guidance for a return to
colder temps to round out the work week and into next weekend.
Probably not looking at readings as cold as the past week or so,
though temps back below normal are increasingly likely. Ultimately,
readings will depend on whether or not we replace the snow that many
if not all areas are likely to lose over the next few days.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 532 PM CST Sun Jan 7 2018
Patchy areas of very light snow, sleet, and possibly some freezing
drizzle will move across the region this evening. That said, timing,
coverage, and intensity is uncertain and any impacts to TAF airfields
will be brief, so will keep forecast dry for now. Later this evening
and into the early overnight, some MVFR ceilings are possible at
KRST, but should remain VFR at KLSE. Late tonight through Monday
will see clearing skies and VFR conditions. Light southwest wind
will gradually turn to the west later this evening and continue
through the remainder of the period.
Area Forecast Discussion
National Weather Service Caribou ME
1052 PM EST Sun Jan 7 2018
High pressure will remain to our south tonight. Low pressure
tracking to our northwest will pull an occluded front across the
area Monday. The front will continue east Monday night. High
pressure will build in from the west Tuesday into Wednesday.
.NEAR TERM /THROUGH MONDAY/...
1050 PM Update...
Radar showed snow moving across the region. So far, snow amounts
have been on the light side w/less than one inch in the northern
locations. Activity was being fueled by a jet streak of 50 kts
at 850 mbs. A second area of enhanced snow was setting up
across the Central Highlands and interior Downeast. This area
was shown well by the latest RAP and NAM12 to expand across the
central and eastern areas overnight w/a mid level punch(55 kts)
moving across this region. This was picked up well by the 00Z
ua. Decided to increase the pops to 80% and brought the snowfall
amounts up a bit on the second area overnight. Snowfall amounts
will be an inch or so especially across the southern tier due
to that mid level punch. Temps have leveled off and actually
will slowly rise by early morning hrs w/some weak llvl
Lgt snow progged to mv into the north aft 00z. Only minor
accums ranging fm 1/2 to 1 inch thru 12z as it quickly comes to
an end shortly aft midnight in nrn areas.
Expect that lgt snow dvlps again aft daybreak as wmfnt mvs thru.
This wl allow temps to climb closer to normal values, nr 20 in the
north and m/u 20s acrs the south. Could see a quick inch or two drg
the daytime hours tomorrow.
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
The occluded front which will bring some light snow on Monday will
be pushing away to the east Monday evening. Snow will taper off
during the evening but the sky will remain mostly cloudy with low
clouds lingering. The upper trough will cross the area Tuesday
bringing a mostly cloudy sky with snow showers over the far north
and a partly cloudy sky Downeast. Gusty winds and falling
temperatures will bring a chill on Tuesday. The sky will
become mostly clear Wednesday night as high pressure builds in.
The high will slide to our southeast on Wednesday as a return
flow behind the high and ahead of a warm front brings in some
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A series of low pressure systems tracking up to our west combined
with a large high pressure system well east of the East Coast will
bring moderating temperatures Wednesday night with snow turning over
to sleet, freezing rain and then plain rain from south to north.
Some rain, drizzle and fog will continue Thursday into Thursday
night as warm moist air surges north ahead of a strong cold front.
Rain may become briefly heavy as the front pushes in on Friday. The
front will press across the area late Friday into Friday night
possibly changing rain over to freezing rain, sleet and then
snow. A secondary wave of low pressure may then lift north late
Friday night into Saturday bringing more snow north, and sleet
or freezing rain Downeast as cold air presses in from the north
in the low levels. Overall, this looks like a very complex and
potentially messy and icy scenario at the end of the week. It
should be noted, however, that the ECMWF differs considerably
from other long range models bringing Saturday`s low to our west
pulling up more warm air, rain and fog.
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
NEAR TERM: VFR with clear skies this afternoon, diminishing to
MVFR in light snow across the north after 01z. Some improvement
possible to VFR around daybreak before steadier snow moves in by
mid-late morning, dropping to MVFR/IFR at all terminals.
SHORT TERM: IFR conditions Monday evening should improve to
MVFR Downeast late Monday night but may remain IFR to MVFR
across the north. Conditions should range from MVFR across the
north to VFR Downeast on Tuesday then be VFR Tuesday night into
Wednesday in high pressure. Conditions should lower to IFR
Wednesday night and remain IFR in low clouds on Thursday.
NEAR TERM: SCA issued for all waters thru 12z Mon but will
likely need to be extended for the outer waters during the day
due to hazardous seas. Gale Watch is in effect beginning late
in the period as wind gusts look to increase to aoa 25kts late
in the day. Expect that light freezing spray will exist across
the waters into Mon afternoon before diminishing altogether as
air temperatures rise.
SHORT TERM: A gale will likely be needed Monday evening for
strong southwest winds, then again late Tuesday into Tuesday
evening for gusty northwest winds. Winds should be light on
Wednesday as high pressure moves across and then will increase
from the south on Thursday.
MARINE...Small Craft Advisory until 7 AM EST Monday for ANZ050>052.
Gale Watch from Monday afternoon through Monday evening for
Area Forecast Discussion
National Weather Service Houston/Galveston TX
733 PM CST Sun Jan 7 2018
At 00Z, the cold front was located just west of Fort Worth and
progressing quickly toward the CWA. There is already some
lightning activity in the storms associated with the pre-frontal
trough currently moving into the northern counties. Latest hi-res
models show lapse rates around 6.5 deg C/km and MUCAPE
approaching 1000 J/kg. Combined with drier mid-levels and higher
wet bulb freezing heights, the potential for isolated small hail
Biggest change is the potential for surface-based convection
along the coastal counties from approximately 10 PM CST until the
front passes just before sunrise. If the convection is able to tap
into the surface parcels, DCAPE values near 1000 J/kg allow for
isolated wind gusts. Additionally, SPC has placed coastal areas in
a 2% tornado risk, which is conditioned on surface-based
convection. With 0-3 km SRH values topping out over 250 m2/s2,
isolated rotation in some storms cannot be ruled out.
Updated PoP and weather grids to account for faster motion of front
than previously anticipated. Temperature and dew point grids are on
track. Brief fog was observed near Bolivar at 5 PM CST, so left in
mention of patchy fog in the bays and 0-20 nm coastal zones until
front passes with dew points in the 60s and SSTs in the low-50s.
.PREV DISCUSSION... /ISSUED 537 PM CST Sun Jan 7 2018/
An area of light showers is moving through KCLL now and will
likely reach KUTS and KCXO in the next couple of hours. Generally
VFR conditions are expected until a line of showers and
thunderstorms pushes through the region from NW to SE ahead of a
cold front. The timing of this line was pushed up a little from
the previous taf package, but the overall categories/impacts
should remain about the same. Showers and thunderstorms should
reach KCLL after 00Z and end by 09Z for everyone except maybe
KGLS. Gusty W winds and rain showers are expected in the wake of
the line of thunderstorms, with gusty NW winds expected as the
front itself finally pushes through. HRRR is showing some low
wrap-around ceilings in the wake of the front overnight, but if
these develop they should become VFR Monday morning. 11
PREV DISCUSSION... /ISSUED 303 PM CST Sun Jan 7 2018/
Preparing for an evening of scattered convection...mainly showers
and ordinary thunderstorms...with a moderate threat that some of
these thunderstorms could reach strong criteria. The impetus to
tonight`s more active weather will be the approach and early
Monday morning passage of a shortwave upper trough and its
associated pre-frontal surface trough/cold front. Troughing will
pull down cold enough middle layer air (near -20 deg C at 5H) to
support sfc to 6km near 6-6.5 deg C/km lapse rates. Each
successive model run leading up to this event has been slightly
stronger with the thermodynamics. Recent runs are suggesting 30
kts of inflow layer shear and SRHs in the 200-300 range. Lapse
rates producing upwards to neg 5 to neg 6 lifted indices with lift
in the upper levels from a southeastern-diving jet (LFQ)...with
general widespread increasing omega as the region falls into the
warm sector this evening...all support organized draft structure.
Strongest cells will likely put down 30-40 kt wind gusts...small
hail...and produce frequent lightning. Nothing stands out for a
significant tornado potential but higher helicity values do signal
the weak potential for rotating updrafts within the most organized
cells. As storms near the coast and better root themselves to the
surface layer (tap into the available CAPE) we will have to monitor
for a marginal threat for strong...maybe brief severe...evolution.
The main message is generally ordinary storms with a moderate
chance for isolated strong storms.
The cold front will travel across the area during the pre-dawn
through late Monday morning hours...moderate northwesterlies in
its wake. Current 7-8 C 85H temperatures are actually forecast to
warm back up to around 10 C in the post-frontal. Thus...the backing
air mass will not have any punch other than to modify the next
few day`s warming to near climate standards. As tomorrow morning`s
upper low/trough dives down across the northeastern Gulf...transitory
ridging will partially clear skies with offshore flow swinging around
the dial to southeast by late Tuesday night. Moisture advection
through mid week will take Tuesday`s near 40 F dew points back up
into the middle 50s to lower 60s early Thursday morning. A
becoming-negatively tilted upper trough will pass over the Red
River Valley Thursday...Plains high pushing a strong cold front
across the area Thursday afternoon-ish. Not much fanfare with this
front as it will be entering a moisture-challenged southeastern
Texas environment. This frontal passage will open the gates for a
bitterly cold and dry Canadian air mass to descend southeast and
spill over the U.S Midwest and clip eastern Texas. Below normal
temperatures will rule again from Friday on through next weekend.
Mornings in the 30s-40s with afternoons struggling to achieve the
lower to middle 50s. As robust northerly winds fully-decouple and
skies clear out Friday into Saturday the northern third of the
CWA will likely experience another light freeze next weekend. 31
A tightening gradient in advance of a cold front will lead to SCEC
conditions over the offshore waters this evening. Winds will
briefly drop off as the front nears but wind speeds will increase
again from the northwest in the wake of the front. Conditions are
becoming less favorable for sea fog as winds become S-SW this
evening and eventually SW. That said, sfc dew points are still in
the lower 60`s and water temps are in the lower 50`s so can`t rule
out at least patchy fog over the near shore waters.
Offshore winds will increase in the wake of the front and will
have a SCEC for the bays and near shore waters beginning around
09z. Sustained winds should reach or exceed 20 kts over the
offshore waters and will issue an SCA for the offshore waters
beginning at 09z. Winds begin to relax on Tuesday and veer to the
east and southeast on Wednesday. Another very strong cold front
will cross the coast on Thursday afternoon. Strong NW winds will
develop in the wake of the front an an SCA will be required for
the bays/nearshore waters and a Gale Watch/Warning may be needed
for the offshore waters by early Friday morning. 43
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 48 61 40 62 45 / 80 0 0 0 10
Houston (IAH) 52 64 45 65 48 / 70 0 0 0 10
Galveston (GLS) 55 60 50 60 53 / 80 10 0 0 10
GM...SMALL CRAFT SHOULD EXERCISE CAUTION from 3 AM CST Monday through
Monday afternoon for the following zones: Coastal waters
from High Island to Freeport out 20 NM...Galveston Bay...
Small Craft Advisory from 3 AM to 3 PM CST Monday for the
following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Waters from Freeport to
the Matagorda Ship Channel from 20 to 60 NM...Waters from
High Island to Freeport from 20 to 60 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION until 3 AM CST Monday for
the following zones: Waters from Freeport to the Matagorda
Ship Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.
Area Forecast Discussion
National Weather Service Wilmington OH
1039 PM EST Sun Jan 7 2018
A quick moving storm system will bring a wintry mix of
precipitation to the region late tonight into Monday. A brief
shot of cold air will return for Monday night. A much warmer
airmass will move into the region for mid week.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Temperatures continue to run warmer than most if not all
guidance including the HRRR and RAP. This makes for a
challenging forecast because while the bias is known at the
surface, it is not clear whether that cold bias exists through
the lower levels which will be crucial for determining
Currently low levels are very dry and so there should be some
decrease in temperatures due to wet bulbing. But how much will
occur is in question.
It looks like most if not all precipitation will start as
liquid, although cannot rule out some ice pellets mixing in.
Whether air temperatures are above or below freezing, the
precipitation should freeze on contact with the surface as most
road sensors indicate that the pavement is below freezing. And
the road temperature model continues to indicate that road
surfaces should come up to around freezing but not warm above
that until precipitation moves out.
Slightly cooler air working in behind a short wave could cause a
mix or change to snow in northwest counties late tonight.
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Around 12Z Monday, the base of the shortwave will be swinging
into the region. Latest model soundings are showing that as the
trof swings through during the morning, that cooler air aloft
will work into the region. This will drop temperatures in the
warm nose below freezing, changing the pcpn to mainly snow.
Pockets of freezing rain or sleet will still be possible.
Latest road temperature models are showing the sfc temps will
stay below freezing until around noon and then they jump above
freezing. If correct this should help with the evening commute.
Will leave the end of the advisory timing as is for now.
Models quickly push the backedge of the steadier pcpn e of the
region between 18-00Z. However, it looks like the low clouds
will hang around and with drier air filtering in aloft, drizzle
may form during the afternoon and will linger into Monday night.
With temperatures falling back below freezing Monday night, the
drizzle is expected to change over to freezing drizzle.
Expect highs Monday in the upper 30s. with lows back into the
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Dry conditions will be in place for the day on Tuesday. Light
moisture begins to move into the region Tuesday night. There will
be the potential on the leading edge of the precipitation that some
light freezing rain or freezing drizzle will be possible as
temperatures will be around freezing. Temperatures will warm as the
night progresses however therefore any freezing precipitation will
be changing over to rain. There will be the potential also with
lots of low level moisture for fog beginning Tuesday night through
Wednesday night. The worst and most widespread fog will be Wednesday
evening into Wednesday night. Winds will pick up for Thursday
allowing for fog to dissipate.
As southerly flow increases on Thursday temperatures will be able to
rise into the 50s and potentially into the 60s. Widespread rain will
move into the region Thursday night. There are several model
discrepancies on how quickly the cool air moves into the region
Thursday night into Friday night. This will have large implications
on precipitation type and potential weather impacts. Mixed
precipitation and snowfall will be possible during this time and
this event will have to be watched carefully as the week progresses.
By Saturday precipitation should be all in the form of snow and
there could be some banding of snow leading to additional snow
accumulations on Saturday. With winds off of the lake additional
lighter snow will be possible into Sunday. Cooler air will be in
place as the weekend progresses.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
VFR conditions will continue into the early part of the TAF
period with a 4-7kft deck eventually spreading in. Precipitation
will work across the area after 06Z. Expect this to start as
light freezing rain with the potential for some ice pellets to
mix in. Precipitation type will transition to snow at all
terminals except in the Cincinnati area. There it appears that
precipitation will remain as freezing rain or perhaps even
become rain. Ceilings will lower into MVFR and where snow occurs
visibilities will likely drop to IFR. Bulk of the precipitation
will move east between 13Z and 16Z. However, ceilings will be
lowering to IFR and in this low deck some lingering
flurries/freezing drizzle/drizzle will be possible. IFR ceilings
will likely persist until late in the TAF period. A low level
jet will translate across the area with the precipitation. This
will provide enough speed shear to warrant continuation of low
level wind shear in the TAFs.
OUTLOOK...MVFR to IFR ceilings will likely continue into Monday
night. MVFR ceilings and visibilities possible again late
Tuesday night through Friday.
OH...Winter Weather Advisory until 2 PM EST Monday for OHZ026-034-
KY...Winter Weather Advisory until 2 PM EST Monday for KYZ089>100.
IN...Winter Weather Advisory until 2 PM EST Monday for INZ050-058-
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
618 PM CST Sun Jan 7 2018
.SHORT TERM...(This evening through Monday)
Issued at 436 PM CST Sun Jan 7 2018
Upper low in northern Saskatchewan Sunday morning continues moving
southeast, with a weak short wave extending to its south. Meanwhile,
abundant mid level clouds were associated with a weak short wave
across the northern and central plains. The result is a baggy
Pacific type trough moving across the area now, with another cold
front following it. There is a somewhat large batch of low clouds in
the cold advection that have been moving into west central and
central Minnesota. These will persist through the evening but
gradually dissipate later tonight as drier air moves in and best
Flow across the forecast area will remain mostly westerly tonight,
with perhaps some northwest component as well. But the source region
is the warm air to the wnw, and lows tonight will easily be the
mildest we have seen in more than two weeks. Generally looking at
lows in the teens overnight.
Surface ridge will be over the eastern Dakotas tomorrow, with modest
west-northwest winds. 120 knot wind max is oriented from southern
British Columbia to southern Saskatchewan, and it looks like a broad
area of mid and high clouds will begin moving across MN/WI Monday as
the jet approaches. Therefore temperatures will be able to warm
about 10-12 degrees tomorrow, but that`s about all. Overall, stayed
quite close to the current forecast.
.LONG TERM...(Monday night through Sunday)
Issued at 436 PM CST Sun Jan 7 2018
The January thaw continues into mid-week as ridging aloft builds
over the eastern US. 850 mb temperatures will reach as high as
8-10C by Wednesday which, despite the snow cover, should
translate to surface temperatures reaching the upper 30s if not
40 in spots. Will likely see some fog/patchy drizzle develop
Tuesday night into Wednesday as low-level moisture increases due
to moisture advection & melting snow cover. This could result in
some slick spots on roads & walkways as ground temperatures are
still well-below freezing after the latest cold snap.
The main focus in the long term will be what impact we see in our
weather from the approaching potent upper level wave Wednesday
night into Thursday. Ensembles are highlighting the uncertainty
regarding the evolution of this approaching system, with a rather
large spread in precip amounts & members clustering rather
uniformly among these outcomes. Confidence has been increasing in
the area seeing some at least some snow Thursday & went with high
PoPs accordingly. How much snow exactly will depend on the phasing
of the upper-level low over the southern plains with the
approaching trough. Strong phasing & we may be looking at our
heaviest snowfall this season, while weak phasing will result in
the system shearing apart & giving us rather paltry amounts. As
always, keep up to date with our latest forecast as confidence in
this system`s evolution increases.
Regardless of the outcome of this system, another shot of Arctic
air moves in behind it for the weekend. Temepratures will rely
heavily on how much snow we get, but this airmass is not looking
as potent as with our last cold outbreak.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 618 PM CST Sun Jan 7 2018
Only concern this period is batch of MVFR stratus moving through
now. Going TAFs had a good handle on timing for cig onset, though
they kept these lower cigs around a little too long. Sped up the
timing of their departure, though went closer to a slower HRRR
timing than the faster LAV. There will be some variability with
heights, though between 1k and 2500 ft. Behind this stratus there
KMSP...Stratus is rapidly closing in and will be here by 1z. Will
likely see cigs drop as low as 1200 ft at times. Look for this
stratus to clear out between 5z and 7z.
/OUTLOOK FOR KMSP/
Tue...VFR. Wind SE 5-10 kts.
Wed...VFR. IFR with RA to SN likely late. Wind S 5-10 kts bcmg NW.
Thu...IFR possible with SN. Wind NNW 10-20 kts.