Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/11/20
Area Forecast Discussion
National Weather Service Bismarck ND
1013 PM CDT Fri Apr 10 2020
.UPDATE...
Issued at 1013 PM CDT Fri Apr 10 2020
Still getting scattered radar returns across northwest and north
central North Dakota, but like the previous update, no real
indication of anything making it to the surface. The closest rain
observation as of 3 UTC is in Glasgow. The Bismarck 00 UTC RAOB
showed a significant dry layer up to 600 mb, and the latest high-
res guidance seems to be picking up on that, with the 6 hour QPF
for 6 to 12 UTC tonight only one or two hundreths, mainly across
the southwest. Because of this, decided to scale back POPs some,
as well as QPF.
UPDATE Issued at 637 PM CDT Fri Apr 10 2020
Cold front is currently draped southwest-northeast from the
Williston area to the Rolla area, with some radar returns just
behind the front but no indication of anything making it to the
ground just yet. Expanded POPs to the south as some weak rain
showers popped up ahead of the front, with light rain observed at
Dickinson for about 10 minutes around 22 UTC. Otherwise no changes
to the forecast with this update.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 304 PM CDT Fri Apr 10 2020
This afternoon, North Dakota sits in the warm sector of an occluding
surface low over central Saskatchewan/Manitoba, under subtle ridging
aloft. Regional radar shows scattered rain showers trying to develop
in proximity to the surface cold front from northeast Montana into
southern Saskatchewan. Chances for rain will increase in northwest
North Dakota this afternoon as the cold front begins to enter the
state. Ahead of the front, most locations will see afternoon
temperatures in the 50s.
Chances for rain showers along the cold front will continue through
the evening as the front sags south across western and central North
Dakota. There may be some mixing of snow on the back end of the
precipitation, but it looks more likely that rain will end at any
given location for temperatures cool sufficiently for this to occur.
There could also be some gusty winds with the frontal passage, but
nothing too impactful is expected.
By Saturday morning, a deepening shortwave trough will be moving
from British Columbia into the U.S. Northern Rockies. Shear induced
vorticity ahead of the shortwave, the right entrance region of an
upper level jet, and low to mid level frontogenesis will combine to
provide enough forcing for precipitation to develop from central
Montana into western South Dakota late tonight through Saturday
morning, clipping the southwest corner of North Dakota. There has
been a slight northward shift with the 12Z model cycle, but
consensus still keeps the bulk of the precipitation along and south
of Highway 12. Interestingly, recent runs of the HRRR and RAP are
producing precipitation much farther north Saturday afternoon. It is
difficult to discern an exact reason for this, as the placement of
the baroclinic zone in these models is similar to the NAM and ECMWF
(the GFS is a southern outlier). Perhaps there is less low level dry
air entrainment occurring in the HRRR and RAP due to a more easterly
wind field as opposed to northerly. Regardless, will mostly
disregard these solutions for now.
Precipitation will continue across southwest North Dakota through
the day Saturday as the Northern Rockies shortwave continues to
deepen. Wet bulb temperature profiles suggest that most, if not all
this precipitation will fall as snow. The forecast snowfall remains
generally unchanged, with 1-3 inches expected in the three
southwestern most counties, highest south of Highway 12. Most of the
accumulation will be on grassy surfaces, but some minor travel
impacts cannot be ruled out. Elsewhere, it will be cool and breezy
with highs only in the mid 30s to lower 40s.
.LONG TERM...(Saturday night through Friday)
Issued at 304 PM CDT Fri Apr 10 2020
Well below normal temperatures are the main story for the long term
period.
Longwave troughing extending from Hudson Bay down through the
Mississippi River Valley will continue to deepen through the weekend
and into early next week. This will keep temperatures around 20 to
30 degrees below normal, with daytime highs only reaching the lower
to mid 30s Sunday through Tuesday.
There have been two notable shifts in guidance since this time
yesterday. One is that models are now much slower to dissolve the
longwave trough pattern, keeping northerly flow over the Northern
Plains possibly through the end of the work week. This would prolong
the period of below normal temperatures, though there would still be
some slight improvement as the week progresses. The other shift is
that there now appears to be more distinct shortwaves rounding the
longwave trough. While QPF is still largely absent from model
guidance, this pattern suggests the potential for periodic
precipitation chances through the long term period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 637 PM CDT Fri Apr 10 2020
Cold front will be moving southeast through western/central ND
this evening and overnight, with a slight chance of rain/snow
showers and breezy northwest winds along the front. Could see
precip at KDIK, but low confidence in this, so kept out of the TAF
for now. KDIK and KJMS could see ceilings drop to MVFR along the
front. Behind the front, expect VFR conditions and north-northeast
winds around 10 - 15 knots. There is a chance for rain/snow in
southwest ND through Saturday, potentially impacting KDIK again.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...MJ
SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...MJ
Area Forecast Discussion
National Weather Service Denver/Boulder CO
945 PM MDT Fri Apr 10 2020
.UPDATE...
Issued at 945 PM MDT Fri Apr 10 2020
Convection is waning and pushing east this evening, have adjusted
the weather grids to reflect the current conditions into the
forecasted conditions. There may be a push on wind from the north
across the I-25 corridor in the early morning, but not expecting
any sensible weather from this.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 245 PM MDT Fri Apr 10 2020
A few thunderstorms already starting to initiate over the Palmer
Divide, and over northeast Weld County early this afternoon.
Expect this trend to continue this afternoon and into the early
evening hours. RAP soundings this afternoon show modest MU CAPE in
the range of 300-400 j/kg. Gusty outflow winds to 40 mph and
brief light rain showers the main output from these storms. The
showers and thunderstorms will weaken and shift eastward this
evening, with partial clearing overnight. On Saturday, a dry
northwesterly flow aloft will be over the region in the morning.
The cold front will be over central WY by 18z Saturday, with an
inverted surface trough along the Front Range in the afternoon.
One more mild spring afternoon with highs near 70. There will
enough moisture and instability for a few showers and
thunderstorms in the afternoon. Coverage will be scattered in
terms of showers and thunderstorms along the northern tier zones,
and isolated over the southern half of the forecast area. MU CAPE
values are similar to this afternoon. Cold front will make it to
the northern border by 00z Sunday.
.LONG TERM...(Saturday night through Friday)
Issued at 245 PM MDT Fri Apr 10 2020
Weather pattern changes Saturday night bringing cold and snow for
Easter. Latest model runs have slowed the cold front arrival by a
few hours. Also, models not quite as deep with the upper level
trough as yesterday. Still, this system will bring cold and snow
for late Saturday night and Sunday. The cold front arrives in
Denver around midnight. Gusts to 40 mph, possibly a little
stronger on the plains will accompany the front. Snow will form a
little after frontal passage and spread south across the area.
Forcing associated with the front quickly shifts southeast of the
area Sunday. Because of this, expect the plains to see up to 3
inches of snow. Northeast upslope flow west of the I-25 will
provide enough forcing for snow to continue most of Sunday. Expect
2-5 inches across the Denver area with higher amounts near the
foothills. Will issue an advisory for the foothills where this
upslope flow may produce 5-12 inches of snow. In the mountains, an
unstable west-northwest flow aloft is expected to produce snow
through Sunday as well. Will also issue an advisory for 5-12
inches of snow. Light snow is expected to linger into Sunday
evening and end Sunday night. It will be very cold Sunday
night/Monday morning with lows in the teens. Single digits will be
possible where it clears out.
For next week, Monday through Friday, northwest flow aloft will
prevail through the entire week bringing a cold active pattern.
Monday will remain chilly behind Sunday`s system with highs in the
30s across northeast Colorado. A weak system embedded in the
northwest flow aloft is expected to bring light snow to parts of
the area Monday afternoon through Monday night. Accumulations look
generally light at this time, less than 2 inches. Not much
warming expected on Tuesday with highs in the mid 30s to lower 40s
over northeast Colorado. There is some weak instability, so
isolated to scattered snow showers will be possible. Expect a
slight warm up on Wednesday ahead of the next trough digging
southeast across the Rockies. Highs may approach 50s degrees
Wednesday. The upper level trough and cold front punch through
late Wednesday bringing a good chance for snow Wednesday night and
early Thursday. Models are starting to come in better agreement
with this. Warming and drying are expected for Thursday and Friday
as an upper level ridge starts to build over the western states.
Even with the warming, temperatures are not expected to top 60
degrees.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 945 PM MDT Fri Apr 10 2020
VFR expected through the period. Convection has ended and southwesterly
winds are beginning to prevail. Winds will once again come out of
the west-northwest Saturday late morning into the afternoon, with
higher speeds near the foothills.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight Saturday night to 6 PM MDT
Sunday for COZ033>036.
&&
$$
UPDATE...Kriederman
SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Cooper
Area Forecast Discussion
National Weather Service North Platte NE
654 PM CDT Fri Apr 10 2020
.SHORT TERM...(This evening through Saturday night)
Issued at 309 PM CDT Fri Apr 10 2020
Near-term concerns revolve around the potential for accumulating
snow across much of western and north central Nebraska late Saturday
through Sunday leading to travel impacts.
Overall big picture has a surface high pressure situated across the
lower Mississippi River Valley tracking south and east with
southerly flow on the back side of this feature helping bring about
warmer, more humid air into the region. A split flow pattern is set
up across the central high plains with a deep cutoff trough situated
over southern California. This feature will be slow to meander across
the desert southwest and eventually phase back into the southern
stream through the day Saturday. Prior to that, a weak shortwave
will eject ahead of this main trough and move across the Colorado
plains and into portions of southwest Nebraska this evening as a
weak low-pressure develops in response. Modest low-level convergence
will develop in response and with increasing moisture, have elected
to increase PoPs across the far southwest counties. NWP forecast
soundings in the Imperial area suggest some elevated instability,
perhaps enough to lead to a few claps of thunder, but not enough to
warrant any organized thunderstorm concerns. RAP and HRRR simulated
radar products show some weak thunderstorms moving in around 00z
Saturday but diminishing rather quickly as h85 flow quickly veers by
late evening and what little instability was there fades with the
loss of daytime heating. Expecting a fairly mild overnight tonight
as winds remain elevated and low-level moisture remains high.
Expecting values to hang onto the upper 30s to low 40s across
southwest Nebraska.
The previously mentioned desert southwest trough will quickly phase
into the upper-level flow. As this occurs, a northern stream trough
will dive southeast out of the Pacific Northwest and towards the
central Rockies by midday Saturday. As perturbations within the
southern stream flow move into the area, lee-cyclogenesis will pull
a strong cold front out of the Dakotas and into the area through the
daytime hours. This frontal boundary will likely settle south of the
area by early afternoon, with northeasterly flow at the surface
behind this feature. While a significant cooldown isn`t expected,
the area will likely see a few degrees at least knocked off Saturday
highs with values ranging from the mid 40s across the northwest
Sandhills to near 70 for areas south of Highway 23. As fgen
increases behind this front, scattered rain and some weak
thunderstorms will develop across portions of western and north
central Nebraska, initially in the far north but gradually working
south through the day. Modest elevated instability will be in place
but again, organized thunderstorm activity is not expected. As
temperatures fall by late evening, precipitation will begin to
transition to a rain/snow mix and eventually all snow. Snowfall
prior to midnight Saturday night is expected to be limited to areas
north of Highway 2 and west of Highway 7. Temperatures continue to
fall quickly Sunday morning, with a transition to snow for all
locations by shortly after sunrise Sunday morning. Latest trends
with respect to this has been to slow the sub-freezing airmass`s
progression north to south through the area. This delays the start
time of accumulating snow generally by a few hours at each location.
By this time, fgen will be strong with increasing height falls and
mid-level vorticity advection ramping up. All this combined will
allow for strong forcing for ascent and saturation of the thermal
profile. This should allow for a relatively clean transition from
rain to snow across the area and minimal if any wintry mix caught in-
between the transition. As a result we expect the heaviest snowfall
to occur during the morning hours Sunday with snowfall intensities
approaching 1" per hour, mainly across the Sandhills. Total snow
accumulations of 4-8" is expected for areas north of Highway 92
and generally 1-4" for areas south. Strong cold- ir advection will
overspread the area during the daytime hours Sunday and so little
in the way of daytime warming is expected. Have elected to go
below most guidance with high temperatures with most locations
remaining below freezing through the daytime. This should prolong
winter travel impacts essentially through the entire day. Strong
north winds off the surface will develop with h85 flow approaching
50 knots, thus have elected to bump up winds during the day with
gusts approaching 50 mph. This will lead to areas of blowing snow
during the day and significant visibility restrictions. Though
snow will gradually diminish through the day, strong winds will
still promote a blowing and drifting snow. High temperatures will
only reach the 20s to low 30s but feels like temperatures with the
strong winds will never climb out of the teens. Those needing to
be outdoors during this time should plan accordingly with the
impending hazardous weather.
.LONG TERM...(Sunday through Friday)
Issued at 309 PM CDT Fri Apr 10 2020
Beginning 00z Monday. Precipitation will be out of the area by
Sunday evening but blowing snow will persist across north central
Nebraska through the evening. Winds will be quick to diminish with
any blowing snow threat ending by midnight Sunday night. Low
temperatures Monday morning will fall into the teens to upper single
digits across portions of the eastern Panhandle. With winds
remaining fairly elevated, will see wind chills fall to near or
slightly below zero during the morning hours. Thanks to fresh snow
and mostly cloudy skies, will see another cold day for April
standards on Monday as highs range from around 30 in the Pine Ridge
and low 40s across the southern tier of counties. High amplitude
flow remains entrenched across the plains and will help to keep
temperatures below normal for much of the next work week. This
amounts to daytime highs Tuesday through Thursday. Periodic chances
for precipitation will continue across the area as multiple
disturbances within the northwest flow will dive south into the
area. Confidence in any one system is low, however, given model
spatial and temporal discrepancies so will limit PoPs in any period
to Slight Chance and Chance with the cooler temperatures allowing
daytime rain and nocturnal light snow for precipitation types.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 651 PM CDT Fri Apr 10 2020
Mostly quiet aviation conditions expected over the next day. The
only major concern will be the potential for rain to move into the
region on Saturday morning. Rain will spread north to south likely
impacting KVTN during the afternoon. Precipitation will be slower
to arrive at KLBF; however, lowering ceilings will be experienced
here throughout the day. Rain will reduce visibility to near 3
miles at times.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 1 AM CDT /midnight MDT/ to 10 PM
CDT /9 PM MDT/ Sunday for NEZ022-035>038-056>059.
Winter Storm Warning from 1 AM to 10 PM CDT Sunday for
NEZ006>010-025>029.
Winter Storm Warning from 7 PM CDT /6 PM MDT/ Saturday to 7 PM
CDT /6 PM MDT/ Sunday for NEZ004-005-023-024-094.
&&
$$
SHORT TERM...Jurgensen
LONG TERM...Jurgensen
AVIATION...Kulik
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
955 PM CDT Fri Apr 10 2020
.UPDATE...
955 PM CDT
Main updates were to bump up cloud cover and forecast low
temperatures tonight and then to bump up forecast highs and lower
PoPs slightly on Saturday. GOES nighttime microphysics shows
expansive mid and high cloud cover over the region, with a large
area of opaque mid clouds around 12-15kft from northwest Illinois
to central Indiana. This cloud cover should prevent temperatures
from dropping as much overnight.
Then on Saturday, based off satellite trends and forecast
soundings, it appears there will be a window from the mid to late
morning into early afternoon where we should see at least filtered
sun through mid and high clouds. Given southerly winds and climo
of progged 925 mb temps favoring low-mid 60s, bumped up temps into
that range, except Lake IL shore likely limited to 50s by a
southeast component to the wind. For the shower chances, a mid-
level wave will cross the MS River around 00z. With very dry
antecedent low and mid levels, much of the shower activity should
hold off until/after 21z and then spread eastward and increase
into the evening as moisture increases. This idea is supported by
the ECMWF which has been consistently slower with precip. onset,
as well as 00z HRRR and NAMnest.
Castro
&&
.SHORT TERM...
233 PM CDT
Through Saturday night...
Sprawling surface high pressure across the central US has resulted
in a pretty nice day locally, albeit just a bit below normal in
the temperature department, and a far cry from the upper 70s and
80 degree readings from earlier in the week. Things are starting
to change a bit upstairs, however, as a series of
shortwaves/vorticity maxima are inching their was eastward across
the central and northern Great Plains. The first is just now
cresting the western flanks of the aforementioned ridge and
drifting towards Iowa with an attendant increase in mid-level
cloud cover. This feature looks to simply toss additional mid and
higher level clouds our way later this afternoon and moreso
through the evening and overnight hours. Some guidance is trying
to squeeze out some very light precipitation overnight, but in
reality this would likely be no more than some sprinkles or spits
of flurries with dry air lingering under 10 kft.
Once this first wave passes our longitude late tomorrow morning,
we`ll then be turning our attention off to our south and west
during the afternoon hours as the next shortwave disturbance--
currently initiating some higher-based convection across
Colorado--approaches the area. There are some subtle timing
differences within the NWP suite regarding this feature`s arrival
and associated increases in low-level warm advection. The 15z
extended RAP was the fastest of the bunch along with the GFS,
while the ECMWF, NAM, and UKMET are all just a hair slower. For
this forecast, have sort of blended these two scenarios together,
which results in quickly increasing PoP chances mainly later
Saturday afternoon and especially during the early-evening hours
as a burgeoning low-level jet drives increasing WAA/isentropic
upglide across northern Illinois. Mid-level lapse rates don`t look
overly supportive of thunder, although suppose this threat isn`t
entirely zero across our far southwestern counties by Saturday
night. Whenever this shortwave/vort max does arrive, precipitation
coverage initially looks to be quite high and maximized
approximately from very late Saturday afternoon through the late-
evening.
As this second shortwave passes by, precipitation chances may
temporarily relax a bit overnight Saturday into early Sunday
morning as the strongest and most coherent large scale forcing for
ascent peels out of the region, although at least scattered light
showers will probably continue on an intermittent basis. Some
potential for fog development exists near the Wisconsin/Illinois
state line, although this will depend on the placement of the
surface warm front which has shown a good degree of variability in
placement among the model suite.
Carlaw
&&
.LONG TERM...
Sunday through Friday...
227 PM...Forecast concerns include rain with a chance of
thunderstorms Sunday/Sunday evening...quick mix/change to snow
Monday morning then very strong winds Monday.
Low pressure over the southern Plains Sunday morning will deepen
as it moves into the Ohio Valley late Sunday night and then
continue to rapidly deepen early Monday morning crossing near
Lake Huron as low as 974mb as shown on the 12z gfs. As this low
approaches...a frontal boundary will lay out across northern IL
and far southern WI. Much of the current 12z guidance shows this
front near the IL/WI state line early Sunday evening...keeping
much of the area into the warmer air. But only a small shift east
could have this front further southeast across the cwa and thus
cooler temps across the north. Its possible that much of Sunday
morning/early afternoon will end up dry across the area with
precip chances increasing during the late afternoon and into early
Sunday evening with the bulk of the rain falling Sunday evening.
This is also the best time period for thunder...Sunday evening.
South of the frontal boundary...temps well into the 50s are
expected Sunday into Sunday evening. And if the front does end up
further south with cooler flow off the lake...some fog will be
possible near/over the lake.
As the low shifts east of the area...a strong cold front will move
across the area early Monday morning. Winds will shift to the
northwest and become strong/gusty. Temps will quickly drop into
the 30s behind the front and while precipitation will be ending...
there is some uncertainty as to how fast precip will end and as
the colder air arrives there could be a brief mix with...or
changeover to snow by daybreak Monday morning. Even if there is a
period of snow...confidence for any accumulation is very low but
is possible on grassy/elevated surfaces. Depends quite a bit on
just how cold temps drop and lower 30s across much of northwest IL
is possible.
The strong northwest winds will continue Monday diminishing with
sunset Monday evening. Given the speed and strength of the
departing low...gusts into the 45 mph range certainly look
possible and if these trends continue a wind advisory may be
needed. Wind directions look to remain generally westerly which
should limit any potential lakeshore flooding to northeast Porter
County in northwest IN.
Colder and below normal temps are expected for all of next week
with periodic chances for light rain/snow showers or sprinkles/
flurries with various weak waves moving across the region. cms
&&
.AVIATION...
For the 00Z TAFs...
Aviation forecast concerns:
* Lake breeze passage across ORD this evening.
* Showers developing late Saturday afternoon/evening with eventual
lowering of ceilings into MVFR with some minor vis restrictions
in SHRA/BR by late evening.
Lake breeze had developed along the Lake Michigan shore this
afternoon, and moved through GYY earlier. With gradient weakening
later in the afternoon, the lake breeze boundary had pushed west
from the IL shore, and moved through MDW around 23Z. Expect it to
reach ORD around/shortly after 01Z per extrapolation of radar
depiction of boundary with further weakening of the westerly
gradient across the region. Winds expected to gradually evolve
to a light southeast later this evening, before becoming light
southwest overnight.
Mid-level disturbance approaches from the southwest on Saturday,
initially tightening up the gradient a bit with winds becoming
breezy from the south-southwest by midday. Forecast soundings
suggest some gusts above 20 kts into the afternoon. Subtle surface
warm frontal feature lifts across the area by evening, allowing
winds to back a little more south-southeast. VFR mid clouds
thicken and lower during the day, with a few light showers or
sprinkles possible during the mid-late afternoon hours as moist
ascent increase ahead of the approaching disturbance. Some model
guidance develops -SHRA across northern IL as early as 21Z, though
probability increase more rapidly during the evening. Guidance
develops MVFR ceilings and minor vis restrictions by mid-late
evening as precip coverage increases.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Marquette MI
714 PM EDT Fri Apr 10 2020
.SHORT TERM...(This evening through Saturday)
Issued at 435 PM EDT FRI APR 10 2020
WV imagery and RAP analysis indicated mid/upper level troughing over
eastern Canada resulting northwest flow through the Great Lakes. An
upstream shortwave trough was located over southern Manitoba. At the
surface, ridging extended southward from western Lake Superior while
a trough was moving through central north Dakota. Although drier air
was moving in from the west, a band of moisture/clouds through
central Upper Michigan persisted.
Tonight, expect the lower clouds to dissipate this evening with the
loss of daytime heating. However, WAA ahead of the trough supported
mid/high clouds that were advancing into the area. Otherwise, with
light winds, radiational cooing will still be favorable enough to
allow temps to drop into the low to mid 20s inland and the upper 20s
near the Great Lakes.
Saturday, Models suggest that the stronger forcing with the Manitoba
shrtwv and any associated pcpn will remain north of Lake Superior.
even with increasing mid clouds, expect enough sunshine/insolation
to boost temps into the upper 40s near the Great Lakes to the mid
50s inland.
.LONG TERM...(Saturday night through Friday)
Issued at 413 PM EDT FRI APR 10 2020
The long-term period continues to be focused on the major winter
storm which will impact most if not all of Upper Michigan late
Sunday through early Tuesday. As advertised yesterday, with the GEPS
and GEFS members consolidating on their tracks of the cyclone, some
of the ensemble cyclone strength indicators have ticked up; the 00z
NAEFS mean cyclone is now a once/10 year event relative to CFSR
climatology for the middle of April, at both 12z and 18z Monday. And
that accounts for the GEPS remaining more spread out than the GEFS.
Looking at just the 00z GEFS, its mean cyclone (973 mb over Georgian
Bay at 18z Monday) is deeper than anything in the CFSR climo (1979-
2009) for the 18z hour. In other words, this is shaping up to be a
very anomalously strong system.
What is certain is that there will be a broad precipitation region.
Even though a surface cyclone tracking across Lake Huron is
sometimes too far east for big snow in parts of the U.P., in this
case the system is still maturing as it passes by so it remains well
tilted with height. It doesn`t become vertically stacked and the low
at 500 mb doesn`t fully close off until about 00z Tuesday, by which
point it is centered about half way between Lake Superior and the
southern tip of James Bay and by which point the bulk of the storm
is over for us in the U.P. This prolonged tilt with height ensures a
broader precip region rather than trying to thread the needle with a
narrow deformation band like in some storms. Confidence is also
increased by the high degree of ensemble clustering and the run-to-
run and model-to-model consistency for the past 36-48 hours or so.
So we can say with confidence that the entire U.P. will see precip,
and most if not all of us will see at least some if not all of that
fall in the form of snow. What else is fairly certain is that the
wind will be quite strong even inland. Given the very strong
pressure gradient on the low`s western flank and pressure falls of
up to 7 mb/3hr followed by pressure rises on the back side of up to
10 mb/3 hr, felt it was more than justified to increase sustained
winds over land over the interior to get 15-25 mph sustained winds
inand and gusts as high as 40 mph. Therefore, where heavy snow falls
there could be blizzard conditions, especially along the Lake
Superior shoreline as well as potentially widespread in the
afternoon and evening as colder air aloft wraps in and the snow
becomes fluffier.
What is less certain is the precip type and therefore amounts. The
best chance of seeing rain at the onset continues to be east of a
Marquette to Iron Mountain line, with precip likely staying all snow
west of there. There are several SREF members from the 09z cycle
that produce rain rather than snow as far west as MQT, the 12z NAM
had a few hours of freezing rain sandwiched in between longer
periods of heavy snow, and the new 12z EC also gets the 850 mb
freezing line as far west as MQT. So we may not be out of the woods
quite yet when it comes to precip type even as far west as the
central U.P. This forecast relies pretty heavily on the CONSRaw for
hourly temps rather than attempting to pick a winning model this far
out. Also pushed the warmer air a bit farther inland over the blend
initialization to account for this slight trend north and west today
in the cyclone track. This results in some freezing rain in the
grids but have kept it to 0.10" or less since the story with this
event will be the snow rather than the ice. The best chance for
freezing rain right now looks to be right along the Marquette to
Iron Mountain line and east about 25-50 miles, but that may change.
Given the combination of heavy snow, blowing snow, and potentially
some ice, and with the holiday weekend upon us, have issued a Winter
Storm Watch for Alger-Marquette-Dickinson and points west for Sunday
afternoon through Tuesday morning.
Now taking a quick peak at the extended... The CONSRaw is near the
10th percentile of model guidance for highs Tuesday and Wednesday
(when factoring in bias-corrected guidance) which makes sense given
the anomalousy cold air aloft for this time of year. So took highs
down several degrees closer to the CONSRaw during that time period.
Increases POPs in the W to NW wind LES belts as well since lake-
effect snow showers will likely continue through the day Wednesday
beneath 850 mb temps around -12 to -14 C.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 714 PM EDT FRI APR 10 2020
VFR conditions will prevail through the forecast as a weak ridge
slides over the area tonight. Winds will remain light through
Saturday afternoon. With a weak surface low passing to the north of
Lake Superior...will see an increase in cloud cover but VFR
conditions will persist through the forecast.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 435 PM EDT FRI APR 10 2020
Winds will continue to diminish tonight as the pressure gradient
relaxes and a weak high pressure ridge passes through. Although a
low pres trough will pass across Lake Superior Sat night, winds
should remain mostly blo 20kt Sat thru Sun aftn. Low pres will then
organize over the Southern Plains on Sun. This low will rapidly
deepen as it crosses the Great Lakes region Sun night/Mon morning.
By Mon evening, deep low pres will be located s of James Bay. This
strong system will likely bring gales to all off Lake Superior late
Sun night through Mon evening with storm force gusts also likely
developing over the east half Monday by late morning into Monday
evening. A Gale Watch was issued for west and central Lake Superior
starting late Monday night. A Storm Watch was issued for the east
starting late Monday morning that will also preceded by a period of
gales from late monday night into Monday morning.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Storm Watch from Sunday afternoon through Tuesday morning
for MIZ001>006-009>011-084.
Lake Superior...
Storm Watch from Monday morning through Monday evening for
LSZ249>251-266-267.
Gale Watch from late Sunday night through Monday evening for
LSZ162-240>248-263>265.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...RJC
AVIATION...RJT
MARINE...JLB
Area Forecast Discussion
National Weather Service Pocatello ID
212 PM MDT Fri Apr 10 2020
.SHORT TERM (Tonight - Monday AM)...
The well advertised clash of seasons is on track to impact eastern
Idaho tomorrow late afternoon into the evening. Before this occurs
however, we have one more beautiful afternoon with mild
temperatures and mostly clear skies and only a few high clouds
streaming in from the north. Temps overnight will remain around 5
degrees or so above normal. Things change quickly tomorrow as a
potent upper-level trough will push into the area bringing a
strong cold front with it. Ahead of the front winds will increase
quickly after sunrise tomorrow and become quite windy across the
Magic Valley and Snake Plain. Sustained winds of 25-35 mph are
expected with gusts between 40-50 mph across the Magic Valley,
Arco Desert, Lower Snake River Plain, and the Southern Highlands
Saturday afternoon and evening, where a wind advisory remains in
effect. Expanded the wind advisory to include the Upper Snake
River Plain on this forecast package. Winds will be a bit lighter
in this area but still close enough to warrant adding to the
advisory especially with the likelihood of some blowing dust
across the interstate corridor between Idaho Falls and Roberts.
Additional areas of blowing dust appear likely further south
including around Blackfoot, Pocatello, American Falls and Burley.
As the front moves through the area tomorrow afternoon, will
likely see some showers perhaps a thunderstorm or two develop
ahead of and along the front. Temperatures and snow levels will
drop quickly behind the front. Does not appear that there will be
a ton of moisture with this feature but some light snow
accumulations will be possible across the higher elevations in the
1-4 inch range. Can`t rule out some snowflakes in the Snake Plain
but most of the moisture looks to be out of the area before the
colder temps push in. Temperatures Sunday will be much colder than
Saturday with highs only reaching the 30s and 40s for most. Sunday
night looks cold, perhaps nearing records in spots. Statistical
guidance is running quite a bit colder than the NBM. Given the
strong CAA expected, nudge temps down 3-5 degrees from the NBM but
my forecast remains warmer than much of the model guidance for
Monday morning so some additional downward adjustments may be
needed in subsequent forecasts. McKaughan
.LONG TERM (Monday - Friday)...
For the upcoming week, a deep longwave trough will remain firmly
entrenched over the central and eastern USA (perhaps weakening a
bit by Fri). This places SE Idaho in a NW flow regime (and
potentially active storm track) on the western edge of this
trough. That said, no significant or high-impact events appear to
be on the horizon. All of the long- range models do carry some
periodic moisture in this flow, which may result in episodes of
light snow showers over the mntns, especially each afternoon.
Accumulations should be light. An embedded shortwave may enhance
this activity Wed/Wed night, although the ECMWF is far more
amplified and wetter than the GFS/Canadian. Even if a wet solution
verifies, this trough should be fast-moving with limited impacts.
The EC/GFS try to spin off another closed low near the Pacific
coast Thurs/Fri, although it remains too early to know if this
feature will impact our CWA. Made very minimal adjustments/edits
to NBM guidance throughout the long-term forecast. Temps will
start off solidly below climo norms Mon with highs in the upper
30s to upper 40s, and then gradually trend a bit above normal over
the course of the week, back into the 50s/60s by Fri pending what
happens with the potential Pacific low. - KSmith
&&
.AVIATION...
Gorgeous VFR conditions will continue this afternoon/tonight as a
weak tongue of high pres remains sandwiched over our area between a
closed low pres center to our south over srn CA, and our next
shortwave trough loading up to our north over Canada. Skies remain
mostly clear early this afternoon per satellite imagery except a few
passing high-level clouds...matching up well with model guidance.
Sfc winds will be breezy across the ern Magic Valley/Snake Plain
terminals, albeit generally out of the SW and well aligned with the
major runways. We may see a trend from SE to WSW at KSUN later this
afternoon if MOS guidance is to be believed, and if not, winds will
certainly be out of the west just off the sfc over the airport.
Speeds will only gently increase w/ height so no LLWS concerns here.
A few high-res models (esp the HRRR and RAP) try to develop a small,
convective complex/cluster of showers/storms that track SE across
KIDA/KDIJ between 02z-06z this eve. There is PERHAPS a tiny embedded
disturbance in pres height analysis during that time, but some other
high-res CAMs don`t develop this activity and it would be well in
advance of the main trough, so this really lowers our confidence in
this occurring. For now, we have leaned dry and left this out of the
TAFs...will monitor trends for any signs of development this eve.
Forecast confidence today/tonight is high aside from that.
The trough in question drops across SE Idaho Sat/Sat night bringing
a few showers/t-storms. The best chance of anything beyond VCSH/VCTS
will be at KDIJ near/just beyond the end of the 18z TAF period, with
perhaps some cig/vsby reductions to MVFR. Otherwise/elsewhere, skies
should remain VFR and it really looks like the big impact with this
system will be winds, perhaps exceeding 25G35KT out of the SW at
KBYI/KPIH/KIDA during the afternoon/eve (lower at KDIJ). A Wind
Advisory is in effect covering all 3 terminals. Trajectories will
again align fairly well with the major runways and reduce
crosswinds, but the magnitude of the wind will still be a concern
for smaller aircraft, in addition to headwind/tailwind
considerations. We have higher confidence tomorrow in a sfc WSW wind
being established by early afternoon at KSUN at 15+ knots, so a
crosswind there. For all TAF sites you`ll see a 15-17z FM group in
the TAF ramping up the winds, but the strongest values are expected
after 19z. A cold front is also forecast to cross the region and
turn winds into the north Sat eve, with speeds dropping off pretty
progressively after sunset. - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 2 PM Saturday to 1 AM MDT Sunday for
IDZ051>057.
&&
$$
Area Forecast Discussion
National Weather Service San Angelo TX
622 PM CDT Fri Apr 10 2020
.AVIATION...
/00Z TAFS/
A few storms continue across the Permian Basin but have not made a
lot of progress east towards West Central Texas terminals. Will
leave a mention of storms out of the forecast to start with this
evening. Will continue the mention of a few storms possible across
the the central and northern terminals late tonight and into
Saturday morning, and a mention on Saturday afternoon across the
eastern terminals ahead of the dryline. Otherwise, MVFR and IFR
conditions will return across all sites late tonight and for much
of the day on Saturday, along with gusty southeast winds. Dryline
will clear the western locations on Saturday afternoon and provide
better southwest flow.
&&
.PREV DISCUSSION... /issued 336 PM CDT Fri Apr 10 2020/
SHORT TERM...
(Tonight)
..Thunderstorms...
As another minor disturbance aloft moves across West Central Texas
this afternoon and tonight, thunderstorms may develop. Short term
models present different initiation times and locations. The NAM
indicates the best location and timing are mainly after midnight,
across our western counties. The HRRR indicate mainly our southern
counties this evening. Model consensus favors more of an after
midnight and mainly western counties event. That matches our
neighbors; so, that looks reasonable. Also, a few thunderstorms
this evening may be severe. The main threats are large hail and
damaging winds. However, there is a non-zero tornado threat, for
tonight as well. The primary locations for possible severe
thunderstorms tonight is mainly along and southwest of a line from
Sweetwater to Mason.
(Saturday)
..Severe Thunderstorms...
The potential for severe thunderstorms remains the highlight for
Saturday`s forecast. The Storm Prediction Center has all of West
Central Texas in at least a Marginal Risk of severe thunderstorms.
The highest risk area (Enhanced Risk) lies mainly along and south
of a line from Brownwood, to Mertzon, to Ozona. The main threats
are large hail, damaging winds, and a perhaps a few tornadoes,
mainly after 4 PM, CDT.
LONG TERM...
(Saturday night)
..Severe Thunderstorms...
The potential for severe thunderstorms will continue Saturday
night. See the Saturday discussion above, for threats and
locations.
(Sunday)
..Dry and Breezy...
As the upper system moves east, and drier air moves into West
Central Texas, surface winds from the west will become gusty. Some
locations may see gusts in the 25 to 30 mph range.
(Sunday night through Friday)
..Dry and Much Cooler Initially...
The remainder of the long term dry conditions will dominate, with
much cooler temperatures initially. Another cold front will move
across West Central Texas late Sunday afternoon and overnight
Sunday night. This front will bring much cooler temperatures,
along with surface winds from the north. Overnight lows Monday
night may be in the mid to upper 30s; that`s much colder than
usual early April lows. Then, cooler temperatures will continue
into mid week, before a warming trend brings highs back very close
to usual early to mid April highs.
&&
.PRELIMINARY POINT TEMPS/POPS...
Abilene 57 77 54 75 / 30 60 40 0
San Angelo 61 83 53 79 / 50 30 50 0
Junction 60 80 56 79 / 50 40 70 0
Brownwood 55 75 56 77 / 20 60 70 5
Sweetwater 58 79 53 75 / 40 50 30 0
Ozona 60 83 53 78 / 50 20 40 0
&&
.SJT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
07
Area Forecast Discussion
National Weather Service Las Vegas NV
857 PM PDT Fri Apr 10 2020
.SYNOPSIS...Unsettled weather will continue into the weekend as
one system is kicked out and another grazes the area into Monday.
Dry weather with warming temperatures expected for much of next
week, with some unsettled weather potentially returning later in
the week.
&&
.EVENING UPDATE...
Precip is largely waning across the southern third of the CWA
tonight and that trend is expected to continue per that latest HRRR
runs. Did make some PoP modifications through 18Z Saturday to
capture extent of wrap around moisture and additional development
across southern Mohave. Otherwise, some slight changes to the Min T
and hourly T through the morning hours were all that was changed.
.DISCUSSION...Through next Friday.
Saturday should be the last day under the influence of the
persistent upper-level closed low that has been plaguing the
region for the last week for most. A shortwave trough embedded in
the developing longwave trough over the eastern US will kick the
southwest US trough out to the east and drag a cold front down
across the area. A fair bit of disagreement exists on how fast
this cold front dives south, as well as how far south it gets.
Synoptic models seem to be later on the timing, with frontal
passage for Las Vegas late Sunday into Monday, whereas high-
resolution models kick this through early Sunday morning. In both
scenarios, the front seems to outrun the supporting gradients, so
would expect it to wash out somewhere around the Las Vegas Valley,
with northerly winds responding down the Colorado River a few
days later as pressure gradient increases in response to high
pressure building into the Great Basin.
Of importance will be just how sharp this cold front is with all
the lingering moisture. Most of the synoptic lift from this system
will remain well north of the area, but several cold fronts so far
this season have over-performed in the precipitation department
if moisture is already in place.
There should be an extended quiet period with warming temperatures
for next week, however, the forecast becomes quite muddy after
that. In the background of a strong Pacific ridge rebuilding,
there is signal for some cutoff lows to undercut the highly-
amplified ridge by the end of next week. So far in the
deterministic models, these lows look like the worst of both
worlds...occurring in between split flow, they lack a deep
moisture connection, while also being fairly compact and likely
more barotropic than baroclinic, in which case they would not be
prolific precipitation producers for the deserts.
&&
.AVIATION...For McCarran...Some light vicinity showers are possible
through about 22-23Z this afternoon, dry conditions expected
thereafter. Ceilings are expected to remain aoa 5-7 kft through this
evening before scattering out overnight tonight, leaving FEW to SCT
aoa 10 kft through tomorrow afternoon. Winds will be light and
variable through the afternoon favoring a southeasterly direction
through the early evening before turning to more of a south-
southwesterly direction after 03-04Z. Light winds expected through
much of tomorrow afternoon because a push of southwest winds move
through the Las Vegas Valley between 22-23Z tomorrow. Expect gusts
to 20-25 knots.
For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered/isolated showers and lower ceilings are
expected to continue across southeast California, lower Colorado
River Valley and southern Mohave County through tonight. Ceilings
should generally remain aoa 5-7 kft, with locally lower ceilings to
around 3-4 kft. Ceilings will begin to scattered out overnight
tonight with FEW to SCT aoa 10 kft through tomorrow afternoon. Winds
should generally be light and variable with shower activity, though
some locally gusty winds are possible with stronger showers.
Otherwise expect winds to follow diurnal trends. Breezy to gusty
winds are expected across the tomorrow afternoon with gusts to 20-25
knots.
&&
.SPOTTER INFORMATION STATEMENT...Spotter activation is not
anticipated in the current forecast period, however, spotters are
encouraged to report any significant weather or impacts according
to standard operating procedures.
&&
$$
DISCUSSION...Steele
AVIATION...Kryston
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