Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/03/20
AREA FORECAST DISCUSSION
National Weather Service Albany NY
943 PM EST Sun Feb 2 2020
Some light snow showers and flurries will continue
overnight ahead of a warm front. The best chance for a light
accumulation of snow will be over the Catskills. Dry and milder
weather will follow behind this system on Monday into Tuesday. A
frontal system will bring a chance for a few rain showers on
Tuesday, followed by colder, but dry weather on Wednesday. Unsettled
weather looks likely late in the week.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
As of 943 PM EST...A warm front continues to lift
north/northeast toward the southern reaches of the forecast area
early tonight with some patchy light snow showers and flurries
impacting the Mohawk Valley and the Capital Region south. The
latest radar trends and 3-km NAM and 3-km HRRR shows the
diminishing activity, except west of the Hudson River Valley.
This is likely due to the weak forcing and a slightly drier air
mass over the ALY forecast area. The KALY sounding has a PWAT
of 0.34" some dry air below H700.
Overall, the snow will continue to weaken, as it approaches the
northern portion of the forecast area. The low-level baroclinic
zone is not as strong this far north and east. Lows tonight
will be mainly in the 20s to around 30F. Scattered light snow
showers or flurries will end in the early morning hours. The
greatest accumulations will be over the eastern Catskills and
possibly the western Mohawk Valley with a half an inch to an
inch. Expect a coating to a few tenths in most other locations.
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
Any scattered, light snow flurries will end early Monday. A much
warmer air mass over the Ohio Valley with current temperatures
above 50 as close as southwestern Pa will try to push east-
northeast toward the area Monday afternoon, but the flow pattern
does not look to support a really strong push of warm air.
Certainly Monday will be warmer than today with highs well above
normal, but at this point highs Monday afternoon look to be
mostly in the 40s. Much of the area could see at least partial
A frontal zone will organize from the northeast southwest to the
Tennessee Valley Monday night and Tuesday, as arctic high
pressure builds southeast from central Canada while warm ridging
holds over the southeast U.S. Scattered, light showers will
become increasingly likely along this boundary Tuesday and
Tuesday night. Temperatures will remain well above normal for
our area through Tuesday night with highs Tuesday once again
into the 40s and lows Tuesday night only near freezing.
Ultimately, the arctic high pressure area will manage to push
southeastward far enough to push the frontal zone south of the
area on Wednesday. Temperatures will be colder on Wednesday,
although still just near to even slightly above normal. The
chance of showers will decrease as cold, dry air will filter in
from the north. The location of this frontal zone along with
details regarding the track of a series of waves moving along
the front will make for a very difficult extended forecast
through the second half of the week.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Active weather appears increasingly likely during the long term
with the potential for rain, snow, and mixed precipitation.
Predictability continues to be rather poor, particularly in the
specific details, although confidence is moderate to high for
moderate to locally heavy amounts of QPF for Thursday into
The flow pattern will be characterized by a positively tilted, deep
midlevel trough over the Desert Southwest early in the period. The
trough will shift eastward across the CONUS during the rest of the
week, becoming increasingly negatively tilted with time and inducing
cyclogenesis. The attendant cyclone will develop northeastward
Wednesday night into Friday, but it is uncertain which side of the
Appalachians it will track. Models have trended slightly farther
south and east with the overall track, although the 12Z/02
ECMWF remains farther west with the midlevel trough axis and
resulting surface low track from the Ohio Valley to the
central/eastern NY, while the 12Z/02 GFS deterministic model and
GEFS mean have the low track closer to the I-95 corridor
(although the GEFS mean is farther north/west than the GFS,
suggesting there are several other members with a track more
north and west).
Background larger-scale atmospheric indices would seem to favor
a more inland track, given a strongly +AO/NAO persisting and
MJO remaining or entering within a weak phase 6.
The most impactful period appears to be late Wednesday night
into Friday associated with the negatively tilted trough and
surface cyclone. Model consensus supports the local forecast
area being on the cold side of the front Wednesday night. So, as
isentropic lift across the strong front ramps up late Wednesday
night into Thursday morning, there is increasing confidence in
a period of accumulating snow for at least the onset late
Wednesday night into Thursday morning. Thereafter, uncertainty
arising from differences in the low track (as discussed above)
increases. Will work a trend of snow to mix to rain from south
to north into the forecast for Thursday afternoon into Thursday
night. The ECMWF camp is warmer with the more westerly low
track and would generally support a quicker transition compared
with the GFS/GEFS mean. Timing differences arise for Friday,
with the GFS prolonging steady precip into Friday afternoon while
the ECMWF works drier air in. Some concern for icing due to a
prolonged period of freezing rain across portions of the upper
Hudson River Valley, eastern/central Mohawk Valley, southeast
Adirondacks, and portions of southern VT, as there is some
potential for shallow cold air to remain entrenched longer in
some of these areas.
So to summarize possible hazards: A widespread/prolonged event
is likely late Wednesday night into Friday, with low confidence
in precip types. There is increasing confidence for a period of
accumulating snow late Wednesday night into Thursday morning.
The snow is expected to turn to a wintry mix (sleet/freezing
rain) and plain rain over some/all of the forecast area
Thursday afternoon through Friday, with low confidence in
timing/location of changeover at this time. Precipitation may
change back to snow or snow showers Friday afternoon along with
gusty west to northwest winds in the wake of the storm system.
Early indications for Saturday are for a cooler and drier airmass
arriving, but possibly some lingering high terrain snow showers.
However, another fast moving low pressure system could bring
some snow to the region by next Sunday.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
A warm front will lift northward across the region tonight with
some light snow overspreading the region. The light snow should
taper in the early morning to flurries as weak high pressure
builds in from the south and west on Monday.
VFR conditions will lower to MVFR or spotty IFR as the light
snow moves in. The greatest threat for IFR conditions will be
KPOU in terms of cigs, and possibly KPSF between 02Z-06Z.
KALB/KGFL will have cigs lower to MVFR levels with the light
snow also moving in between 02Z-06Z/MON. The light snow will
taper to flurries between 06Z-10Z with mainly MVFR or low VFR
cigs. The cigs will gradually improve to VFR levels in the late
morning at all the TAF sites.
After 17Z/MON, expect some scattered stratocumulus and scattered
to broken cirrus to be around at all the TAF sites.
The winds will be light to calm tonight. They will increase from
the west to southwest at 4-8 kts prior to 12Z, and expect a
shift to the west to northwest at 8-15 kts with some gusts 20-25
kts at KALB/KPSF by the afternoon.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Moderate Operational Impact. Chance of RA...FZRA.
Tuesday Night: Moderate Operational Impact. Chance of RA...SN.
Wednesday: Low Operational Impact. Slight Chance of RA...SN.
Wednesday Night: High Operational Impact. Likely SN.
Thursday: High Operational Impact. Definite SN...SLEET.
Thursday Night: High Operational Impact. Definite FZRA...SLEET.
Friday: High Operational Impact. Breezy.
No hydro issues are expected through the first half of the
week. We continue to monitor trends for the later half of the
week as significant amounts of precipitation appear to be
possible, although precipitation type remains quite uncertain.
Some precipitation will occur tonight, with mainly light snow
showers or flurries. Total QPF will range from a mere few
hundredths to maybe just over a tenth of an inch in the
Catskills, where an inch or two of snow could accumulate.
A dry stretch of weather is then likely Monday into early Tuesday
before more unsettled weather returns mid week.
For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our website.
Area Forecast Discussion
National Weather Service Amarillo TX
600 PM CST Sun Feb 2 2020
.AVIATION...00z TAF Cycle...
VFR conditions are expected through the period. However, a cold
front is expected to move through the northern terminals after
12z and may produce some low ST. Confidence is not high enough to
include as of this TAF issuance, but if the trends continue
MVFR/IFR cigs may need to be introduced at KGUY for a few hours
starting around 15z Monday. The front will switch winds from
southwesterly to northerly at 10 to 20 knots, and may stall before
arriving at KAMA late Monday. Southwest winds could become gusty
ahead of the front, which would include KAMA Monday afternoon.
.PREV DISCUSSION... /Issued 334 PM CST Sun Feb 2 2020/
SHORT TERM...Tonight through Wednesday Night...
High pressure remains over the Panhandles today and for most of
tomorrow, with the next big system moving in tomorrow night. Highs
across the Panhandles on Monday should still be very mild, in the
60s to 70s across the south, and in the 50s to the north. There
is the potential that this could change but even the high
resolution HRRR model suggests that the front will stall just
south of the OK Panhandle, until after sunset and then push
further through Monday night. In the past this much cold air
typically would struggle to stop, but there is a weak shortwave
trof expected to swing through under the southwest flow and that
might be just enough to help the front stall.
Monday evening the front will continue through the Panhandles and
winds will be out of the north, with a rapid drop in temperature
along with wind chill values around 0 in the north and in the
upper teens to the south. While moisture will be limited in the
west and northwest, there will be some moving in with the
positively tilted trof and we could see light accumulations in
the 1 to 2 inch range.
The upper level trof will stall and deepen over the southern
NM/AZ border by Tuesday evening, and this will provide enhanced
moisture across the southern and southeastern Panhandles. The main
swath of moisture looks to bullseye over the Lubbock area, but
there`s a decent amount that could provide impacts to the southern
Panhandles. SREF/GEFS plumes as well as the EC and Canadian model
suggest quite a bit of snow potential for the south and
southeast, but if the system dips further south, it could dry slot
us and then we get nothing. Right now the consistency in the
deterministic EC/Canadian/NAM models suggest it will snow quite a
bit Tuesday afternoon through Wednesday morning across the
Current forecast is 1 to 3 inches with the southeast getting the
most. This is a very conservative amount, as we have quite a bit
of moisture from the Gulf overrunning the cold air, and we are
saturated up to 300mb. In addition we have decent lift, and a
700mb warm nose. The warm nose has no significance for
precipitation type however it does pose the potential for steep
lapse rates aloft and possibly convective precipitation. Yes this
would include isolated thunder, or just heavy bursts of snow. Now
onto the snowfall rates. This is another challenge as we could
have very high snow to liquid rates with surface wetbulbs in the
teens to low 20s. Our current rate is run at 18:1(1 inch of liquid
equals 18 inches of snow), typical Panhandle rates are closer to
10:1. We could very well be too low and have rates in the 25:1 -
30:1 range. So we could have some very high snowfall amounts with
future updates, and watch/warning level highlights could be
needed. Keep up with the latest forecast as changes are likely.
LONG TERM...Thursday through Saturday Night...
Between 00Z and 06Z Thursday, southwest flow aloft will quickly
turn to northwest flow aloft as the H5 trough moves east out of
the area. This will bring forth a gradual warming trend going into
next weekend. During the overnight hours Wednesday night into
Thursday morning the combined Panhandles will experience one more
night of below normal temperatures in the teens. Highs will make
it into the upper 40s on Thursday. Friday morning lows will be
near normal for the FA, with daytime highs may be 5 degrees above
normal with highs in the mid to upper 50s. Saturday will be
similar with slightly warmer lows in the southeast Texas
Winds are looking to be relatively light for Panhandle standards
during this extended forecast period. A leeside surface low could
develop in the northwest Saturday night. If this pans outs winds
could be a bit breezy Saturday evening into overnight. Mostly
clear skies until Saturday when the H5 flow becomes more zonal and
the FA could see some high clouds develop.
VFR conditions will prevail at all TAF sites with winds out of the
west southwest for the majority of the TAF period. Winds in the 10
to 15kt range expected with gusts up to 25 kts possible. Winds may
shift more westerly as we head into the end of the TAF period.
Scattered mid and high clouds possible. Cold front expected
tomorrow, but for now frontal timing looks to be after 18z.
However, would not rule out the front speeding up and wind shifts
out of the north coming sooner.
Critical Fire Weather conditions expected to continue for a few
more hours across Cimarron County as winds around 20 mph and RH
values in the single digits should start to recover after sunset.
RFTI`s look to be in the 3 to 5 range for a few more hours. No
other Fire Weather concerns for the remainder of the forecast
OK...Red Flag Warning until 7 PM CST this evening for the following
Area Forecast Discussion
National Weather Service Green Bay WI
543 PM CST Sun Feb 2 2020
Updated aviation portion for 00Z TAF issuance
.SHORT TERM...Tonight and Monday
Issued at 154 PM CST Sun Feb 2 2020
The latest RAP analysis and satellite/radar imagery show an area
of low pressure over eastern Lake Superior and a cold front
extending west from the low across central Minnesota. Relatively
shallow cold air across northern WI into Minnesota along this
front has contributed to a large area of low stratus which had
been slowly moving to the southeast earlier today. Ample dry air
on the 12z GRB and MPX soundings have halted the forward progress
of this stratus. Where sunshine has occurred for most of the day
(generally south of HWY 29), temps are close or have surpassed
records for the date. Winds have behaved themselves so far, with
only a few gusts above 30 kts. As the cold front gradually drops
south, forecast concerns may revolve around cloud cover and temps.
Tonight...The cold front will move across most of northern WI in
the evening and settle south of the area overnight. Not expecting
much further progress south of the low clouds. But in general,
think low clouds will be retreating northeast. Mid and high
clouds will likely push in from the west through the night, but a
large dry wedge between the two cloud layers will keep precip from
reaching the ground. With winds diminishing and cloud cover,
stayed close to the national blends for temps.
Monday...Mid and high clouds will continue to move overhead and
provide filtered sunshine at times. Winds will shift around from
the northwest to the northeast with weak cold advection continuing
through the day. Temps will be much cooler than today, although
with less wind, with highs ranging from the upper 20s to middle
.LONG TERM...Monday Night Through Sunday
Issued at 154 PM CST Sun Feb 2 2020
Surface and upper air patterns favor quiet weather
across northern and central Wisconsin for the rest of the week.
The upper flow remains split with the stronger shortwaves in
southern stream forecast to stay far enough away to keep significant
snow to the south.
With the storm track to our south, Gulf moisture will not be able
to get this far north. A few shortwaves in the northern stream
could bring enough Pacific moisture to produce a very small amount
of snow at times but nothing significant is expected at this
Thickness values and 925 mb temperatures suggest that it will be
above normal temperature wise except for a brief cool down
.AVIATION...for 00Z TAF Issuance
Issued at 535 PM CST Sun Feb 2 2020
Strong west-northwest winds aloft will linger into the early
evening at the eastern TAF sites, then diminish. Surface winds
will also diminish early this evening.
Stratus, with ceilings from 2000-3500 feet AGL, will persist
across northern WI this evening, but RH timesections show moisture
shallowing out later this evening or overnight. Will hold onto
MVFR ceilings at RHI until the early overnight hours. Mid and high
level clouds should prevail through the rest of the TAF period,
along with light northwest winds veering north to northeast by
Issued at 154 PM CST Sun Feb 2 2020
Lapse rates have been unable to become steep enough to
tap into the stronger winds aloft. Additionally, the strongest
winds have remained over southern WI. As a result, wind gusts
have remained below 30 kts through the day. Will therefore
downgrade the gale warning into a small craft advisory.
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
925 PM CST Sun Feb 2 2020
924 PM CST
No notable changes for the forecast into Monday. There is a low
chance for patchy shallow fog tonight over the edge of the snow
cover area and the periphery of it where temperature-dew point
spreads are the lowest. The sky looks to remain mainly clear over
this area through the rest of tonight, apart from gradually
thickening cirrus near daybreak. The 00Z DVN sounding showed
substantial dry air all the way through the boundary layer and RAP
soundings basically continue this apart from the immediate
surface, so any fog should be very shallow. Not expecting a big
deal if any were to develop.
For tomorrow, northeast winds will gradually be on the increase as
the pressure gradient strengthens. High temperatures may end up
being a little cooler than initially forecast, depending on the
thickness of the clouds, and could see afternoon readings not
climbing much at all north of I-80.
The potential for drizzle Monday night continues to look decent in
incoming guidance, namely the 00Z NAM and its preceding 21Z SREF.
Any drizzle that would have more coverage and overlap with
temperatures below freezing is still looking to be overnight and
in northern locations, especially those inland away from
locations downstream of the slightly warmer lake.
210 PM CST
Tonight and Monday...
Today`s record high at ORD that late this morning looked so
poised to fall has instead been nicely protected by a well timed
arc of opaque cirrus. Cold advection off the snowpack also has not
helped warming at ORD, but this did not seem to be a problem at
nearby Palwaukee which did reach 51 earlier. Quite a few
locations, including ORD, did at least crack the 50s. And there is
still time for a rebound at ORD where around 2pm the temperature
had briefly recovered to 50 and even touched the record of 51
after a dip back into the 40s. So we will keep watching to see if
it can indeed be broken.
Breezy west winds also underperformed just a bit today which could
be yet another reason that low level mixing and warming was not
more pronounced. These winds will veer northwesterly this evening
behind a weak front that moved through today, then flip easterly
Monday morning ahead of the next boundary approaching from the
south as a warm front. With cool and dry advection to the north of
this boundary, most of the area will be several degrees cooler
than today but should remain dry at least until early evening when
precip chances increase slightly toward the WI line. Farther
south, mainly along and south of US-24 nearer the front itself,
temperatures still should be able to climb into the 50s again
330 PM CST
Monday Night through Sunday...
A few bouts of wintry precipitation are possible this week, but
confidence is unfortunately on the lower end. There are three
primary time windows of concern in this regard. On Monday night
into Tuesday morning, there is a risk for freezing drizzle in
parts of north central and far northern Illinois. On Tuesday
evening and night, an active baroclinic zone setting up near or
just south of the CWA could bring a threat for light snow and
minor accums to portions of the southeast CWA Then on Wednesday
evening and overnight, there is a chance for accumulating snow for
more of the area depending on evolution of a southern stream wave.
Finally, with a bout of a long duration of strong northerly winds
Monday night through Tuesday night, concern is increasing for
On Monday evening and night, an inverted trough axis will stretch
northeast across the region, with expansive dry high pressure over
the northern Plains. A tight low level thermal gradient will be
in place, with gradual cooling of the column oozing from the
north. This gradient will set up good lower level frontogenesis.
In addition, in broad southwest flow aloft, we`ll be positioned
favorably in strong upper jet dynamics. These factors would argue
for the possibility of precipitation development. However, the big
question mark is the magnitude of moisture in the column. There is
strong consensus among the guidance of dry air in the ice
nucleation layer, favoring drizzle and maybe light rain if enough
collision coalescence and precip is occurring. The main
uncertainty pertains to lower level saturation, especially during
the evening hours, as there is high variance between the much more
moist NAM/WRF guidance and the ECMWF, which is much drier, owing
to a slightly farther south inverted trough axis and dry advection
from the high pressure. Given the uncertainty, we have a low
chance for drizzle mentioned during the evening hours.
Confidence increases a bit more, but still on the lower side,
overnight into early Tuesday for an increase in saturation depth
supportive of drizzle/light rain. During this period, have
higher chance PoPs. This is when surface temperatures become
critical, as they will be gradually cooling through the night.
Portions of far northern and north central Illinois, including
Rockford and the far north and northwest Chicago suburbs, could
have risk for a light glaze from freezing drizzle. Another
uncertainty, if freezing drizzle occurs in the aforementioned
risk area, is how pavement temperatures respond after being well
above freezing, which will dictate if there`s any travel impacts.
The cold and dry advection from the north will likely mostly end
any light wintry precip during Tuesday morning for northern areas.
Active baroclinic zone will remain draped near or south of the CWA
into Tuesday night. Additional short-wave energy rippling along
the brisk southwest mid and upper flow and interacting with the
baroclinic zone could bring additional light precipitation to
portions of the area. By them, DGZ will be sufficiently saturated
and temps cold enough for snow as p-type. At this time, guidance
consensus favors our southeast CWA for best chance of getting into
this precip. Certainly possible the light snow could stay south of
the CWA counties altogether, however.
After a likely dry period area wide into the daytime Wednesday, we
we turn to the next timeframe to watch, later Wednesday PM and
night. Sensible weather impacts, if any, depend on the evolution
of a southern stream wave and track of associated surface low
southeast of our area. This southern stream energy rounding the
long wave trough emerging from the Plains region could eventually
force the trough to become more neutrally tilted, with surface
cyclogenesis along the western or central Gulf Coast on Wednesday.
The ECMWF suite shifted southeast from the 00z and 06z cycles, but
remained the farthest west of the global guidance with the surface
low track across the Ohio Valley Wednesday night. Meanwhile the
rest of the globals kept the trough positively tilted for longer,
resulting in a farther east/southeast surface low track. Since
there has been high run to run variability during the Wednesday PM
into Thursday period, maintained NBM PoPs ranging from mid to
high chance to low likely from northwest to southeast. Thermal
profile would be supportive of snow.
Temperatures through the week will be generally seasonable, with
active flow pattern continuing into next weekend, so have some
periodic low PoPs.
LAKESHORE FLOODING Monday Night through Tuesday Night...
Expansive high pressure around 1030 mb centered over the northern
Plains and low pressure troughing draped south of the area will
set up a tight northerly pressure gradient. A long duration of
brisk northerly winds will result, peaking on late Monday night
into Tuesday morning, when speeds/gusts over the lake could get up
to 35 mph if not higher. Winds will stay elevated, but gradually
come down in speed later Tuesday through Tuesday night as the
surface high approaches and the low pressure trough sinks
southeast. At this time, have forecast peak waves in the 8 to 11
foot range along the Cook, Lake IN and Porter County shore. This is
close for exacerbated lakeshore flooding impacts for the hardest
hit areas from the near record lake levels. We`re headed for
needing at least a Lakeshore Flood Advisory, and if confidence
increases in a bit higher wind speeds and wave heights, a
Lakeshore Flood Watch to Warning may be needed.
For the 00Z TAFs...
Occasionally gusty west winds will continue to abate early this
evening. The next feature of interest is a cold front to our north
which is slated to bring a gradual northeast wind shift to the
area terminals later tonight. Winds look to slowly swing through
the northwest, north, and eventually northeast, and so have
indicated the most likely arrival of the more persistent
northeasterly winds in the latest TAFs. As this boundary passes,
some additional low-level moisture will start to drift northward
and, as it encounters the cooling surface, may result in the
development of some light BR. Signal for BR is not overly
impressive, but warranting of a TEMPO mention for 5sm at RFD and
DPA, and 6sm at ORD and MDW. Could also envision some splotchy
MVFR cigs developing late tonight.
Any vsby reductions and lower cigs should scatter out through the
morning hours on Monday, but do look to return during the
afternoon and evening as the lower-levels incrementally saturate
ahead of a sharpening surface trough. For the ORD/MDW extended:
there is some signal that some light precipitation/drizzle may
develop towards the late-evening hours, but confidence on this
timing is too low to warrant a TEMPO or a PROB30 mention right
now. Do think this potential will increase after 04.06z but with
winds prevailing off the relatively warm lake, current expectation
is for any -DZ to fall into above-freezing air at the surface.
This potential will be addressed in future TAF issuances, however.
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Area Forecast Discussion
National Weather Service Marquette MI
651 PM EST Sun Feb 2 2020
.SHORT TERM...(This evening through Monday)
Issued at 323 PM EST SUN FEB 2 2020
What a difference an extra day of models makes as today`s winds are
much lighter, temperatures cooler, and skies...well still gloomy. A
low stratus deck remains across all of the forecast area and extends
in northern WI as well as slightly colder air aloft has helped these
stratus stick around. Latest guidance continues to show weaker winds
aloft as RAP soundings suggest the boundary layer is still mixing
through about 3000 feet. The northern portion of Upper Michigan is
still seeing some -SHSNDZ this afternoon along a line from roughly
Grand Marais, MN through Manistique. Models suggest weak warm air
advection ongoing ahead of these showers, as the UP also remains on
the fringe an approaching broad mid-level ridge which is creating
some PVA and divergence aloft as well. As this ridge continues to
move east this afternoon, any PoPs will slowly depart from west to
east as RAP soundings show deep moisture comes to an end and
inversions falling to near 3500 feet.
Tonight, with drier air aloft moving into the region there will be a
chance for some clouds to scatter out, but generally expecting
mostly clouds skies. Winds will remain elevated through the first
half of the evening which should help keep temperatures in check.
Lows will remain in the 20s with low 20s across the western interior
and mid to upper 20s elsewhere.
Winds relax through the evening and into tomorrow morning as 850mb
temps fall to near -12C. These temps are cold enough for LES to
begin to develop...but inversion remain low with a bit of dry air
near the sfc. Winds will remain from the NW through the day as
colder air aloft continues to work its way into the region. Near the
end of the day, we may start to see some LES in the NW wind snow
belts across the west, with the eastern half remaining a touch too
warm. High temperatures remain a touch above normal with upper 20s
in the west and low 30s east and along the Great Lakes.
.LONG TERM...(Monday night through Sunday)
Issued at 433 PM EST SUN FEB 2 2020
Models suggest that a mainly split flow pattern will persist. An
incursion of colder air is expected Tuesday into Wednesday as a
slightly more amplified northern stream brings a batch of arctic air
through northern Ontario. Although a mid/upper level trough will
move into the central CONUS by Thursday, with a trend toward little
or weak phasing of the positive tilt system with the southern
stream, chances for any significant snowfall remains low.
Monday night, weak shortwaves moving into northern Ontario will help
drop an arctic cold front into the northern Great Lakes as the
northern stream trough sags into the area. CAA with 850 mb temps
dropping from -12C to -15C will provide just enough instability to
support nw TO nnw flow LES. However, only chance POPs mentioned
with any accumulations remaining at or below an inch.
Tue-Wed, With only shallow cold air (inversion heights of 3k-5k ft)
and 850 mb temps to around -20C developing anticyclonic low level
flow, nw flow LES that develops should be light. However, lake
induced CAPE increases enough with the convective layer through
the DGZ for a few inches of fluffy snow. Winds backing to west and
sw Wed should bring an end to the LES after some additional SHSN
over the Keweenaw in the morning.
Thu-Sun, the models, including the ECMWF have trended away from the
potential of any significant system snow into Upper Michigan, closer
to the drier GFS/GEFS/GEM. The pattern is expected to amplify toward
the end of the week so that an additional batch of arctic air
brushes the northern Great Lakes. 850 mb temps down to around -15C
may bring some light LES from Friday into Saturday. There is low
confidence that additional shrtwvs will bring any significant snow
through the weekend.
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 650 PM EST SUN FEB 2 2020
While MVFR cigs will mostly prevail at KIWD/KCMX/KSAW tonight/Mon,
there will be periods of VFR conditions. Gusty winds to
around 25kt are expected at KCMX thru the fcst period.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 323 PM EST SUN FEB 2 2020
NW winds with gusts up to 30 knots will develop this evening into
tomorrow morning before calming down through the day on Monday. NW
winds pick up again on Tuesday afternoon with a few gusts up to 30
knots before calming down by Wednesday morning. SW winds then pick
up Wednesday evening into Thursday with a few gusts approaching 30
Area Forecast Discussion
National Weather Service Portland OR
325 PM PST Sun Feb 2 2020
.SYNOPSIS...Showers will increase along the coast this afternoon as a
weak trough of low pressure moves onshore. Scattered showers will
spread inland this evening, but should generally decrease in coverage
overnight. Snow levels will approach the lowest elevations this
evening, so it is not out of the question that some coastal or valley
floor locations could get a dusting of snow overnight. Chilly weather
and a few showers will linger through Monday. A warm front Tuesday
will bring a return to milder weather pattern with occasional rain
for the middle to latter portion of the upcoming week, especially
.SHORT TERM...Tonight through Wednesday...Visible satellite imagery
shows a loosely organized cluster of showers near the Pac NW coast
this afternoon. These are associated with a lobe of cold air aloft,
modeled at -37 to -38 deg C at 500 mb. Despite the fairly steep lapse
rates from the surface up to 500 mb, it appears lightning has mostly
come to an end over the coastal waters. That said, cannot completely
rule out a stray clap of thunder or two along the coast or over the
The band of showers is making slow eastward progress, but the best
dynamic forcing appears to be aimed to our south, toward Del Norte
and Humboldt Counties in California. The showers off the OR/WA coast
may hold together enough to produce scattered snow accumulations in
the Coast Range above 500 feet by later this evening, but generally
only a dusting to an inch.
Aside from this band of showers, there are several small showers
scattered around SW Washington/NW Oregon this afternoon, mostly
driven by daytime surface heating and the resulting steep or even
super-adiabatic lapse rates given the much colder air just above the
surface. These showers seem to be producing mainly small graupel for
the lowlands, briefly accumulating on grassy surfaces but otherwise
not producing much of an impact.
Some higher resolution models such as the 18z NAM 4km Nest and HRRR
hint that another band of showers may form over the Willamette Valley
overnight. With the loss of daytime heating and temps beginning to
warm aloft this evening, it is difficult to see enough instability
remaining in place for convective showers east of the Coast Range
much later than 6 or 7 PM. We generally undercut model PoPs after 06z
tonight, but left a slight chance just in case the above-mentioned
models are correct in generating just enough synoptic lift to
overcome an increasingly stable environment. If this were to occur,
most of the precipitation would fall as snow, but any accumulations
would probably be light and spotty.
High pressure moves into the area Monday, but lingering moisture and
onshore flow will provide a slight chance for showers, mainly across
the higher terrain. The airmass remains cool with snow levels
800-1200 feet. Showers will end Monday night, and any clearing could
lead to freezing fog in the interior valleys through early Tuesday
A warm front is expected to bring rain and rising snow levels
Tuesday evening. The snow levels may remain low with the light rain
ahead of the front Tuesday afternoon, but rise when the steadier rain
arrives Tuesday night. The rain will persist into Wednesday night
with the snow levels up to 3500-5000 feet early Wednesday. The
Willapa hills and the north Oregon coast range could get up to 2
inches of rain Tuesday night through Wednesday afternoon. The south
Washington Cascades may see 5 to 10 inches of snow. Weagle/TJ
.LONG TERM...Wednesday night through Saturday...Models vary with the
finer details, but the overall consensus is for a very wet pattern
across western Washington for the latter half of the upcoming week,
while western Oregon sees rain at times but not nearly as much as
their neighbors to the north. A flat upper level ridge may keep the
southern portion of the forecast area mostly dry and mild Thursday
and Friday, but there is fairly good consensus that the upper ridge
will erode enough to allow a cold front to press southward across
western Oregon Fri night/Sat. Models and ensembles generally agree on
a return to seasonably cool weather behind this front next weekend.
Will need to keep a close eye on the Willapa Hills as the Grays River
has been rather sensitive to rainfall much more than 1.00 to 1.50
inch over a 24-hour period. It appears many basins are saturated from
all the rain we have received over the past month, but hopefully the
24-48 hour break from significant rainfall will raise the bar a bit
in terms of the rainfall required to push our more sensitive small
streams and rivers to flood stage. Weagle
.AVIATION...VFR conditions continue to persist through much of
the area with a veil of MVFR cigs over the northern Willamette
Valley and coast. Convective showers continue this afternoon
with some reports of small graupel or hail near the Portland-
Metro. A shortwave will move over the area Sun night after 02Z
Mon. While very isolated, the convective rain showers will
persist overnight. Cigs will also drop to MVFR, especially along
the coast, and the central and northern valley. VFR cigs return
Mon morning around 20Z.
The challenge tonight will be whether or not fog develops again.
The dewpoint depression in many places inland are within 2
degrees F and near freezing. There is also a chance for frost
development, similar to the Sun morning. Temperatures inland
will float right around freezing, but snow is not expected. At
this time, will put some localized fog into some TAFs.
KPDX AND APPROACHES...Cumulus and showers through the afternoon
ahead of a shortwave. In some of the showers, graupel has been
reported. Frost/fog is possible again tonight with temps around
freezing. VFR cigs will become MVFR overnight which may keep fog
at bay. Cigs should lift again to VFR Mon around 18Z. -Muessle
.MARINE...Fairly consistent conditions through the next week
with seas ranging from 11 to 14 ft with a 13 second period.
Winds will be 10 to 20 kt through Mon then fall below 15 kt Mon
afternoon. At that time seas will also fall below 10 ft allowing
for the small craft advisory to expire for a period. High
pressure over the Pacific will remain anchored Mon afternoon
through Wed. Overtime, this high has flattened out slightly
making the flow mostly westerly, however typical weather
associated with high pressure will remain.
By Wed night, confidence dwindles as there is a chance for a
closed low pressure system to move south from the Gulf of Alaska.
At this point, models are fairly inconsistent. A majority of
solutions are showing a less robust low moving along the coast
line, while some international models show a true closed low
moving over the state. At this time, stayed conservative with the
overall flow and thus kept seas around 15-16 ft with a 16 second
period Wed night through Thu. -Muessle
PZ...Small Craft Advisory until 10 PM PST Monday for coastal waters
from Cape Shoalwater WA to Florence OR out 60 NM.
Small Craft Advisory until 1 AM PST Monday for Columbia River
Small Craft Advisory from 8 AM to 3 PM PST Monday for Columbia
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This discussion is for Northwest oregon and Southwest Washington
from the Cascade crest to 60 nm offshore. This area is commonly
referred to as the forecast area.