Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/14/20
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1151 PM EDT Tue Oct 13 2020
.AVIATION...
Light west-northwest flow will develop behind a weak cold front
overnight. Mainly clear skies will be replaced by increasing mid
level clouds on Wednesday as a warm front lifts into the area. Winds
will become south/southeast with the passage of this front as well.
.DTW THRESHOLD PROBABILITIES...
* None.
&&
.PREV DISCUSSION...
Issued at 359 PM EDT Tue Oct 13 2020
Anticyclonically bifurcated flow with sfc-850 high pressure center
will move east of Southeast Michigan during the mid to late
afternoon hours. Ribbon of modest 925-675mb thetae is poised to
track into the forecast area as moisture transport increases behind
the departing anticyclone. Satellite trends have been very bullish
with altocumulus-altostratus in advance of weak shortwave within
favorable corridor of system relative isentropic ascent. The clouds
will march across the area through roughly 02Z. With regards to
precipitation potential, consensus of model solutions keeps
saturation above 10.0 kft agl through this evening. The RAP
soundings do suggest that some moisture aoa 6000 ft agl will be able
to provide for some convective instability and free lift mainly 00-
02Z for the Saginaw Valley and Saginaw Bay region. Upstream
observations are lacking with any midlevel moisture/clouds. Will not
be introducing PoPs this forecast package.
Deep potential vorticity reservior with strong left exit region
dynamics will result in low pressure across the Northern Great Lakes
Wednesday. Thermal ridge amplification downstream of the wave will
lead to organizing elevated warm front/warm advection beginning
midday Wednesday. A strong signal exists in veil of high cloud
overspreading the area by 18Z. High confidence in dry air mass sub
10.0 kft agl for southeast Michigan with bulk of lead wing
isentropic lift occurring north of the forecast area. Dry
environment brings some question for surface wind gusts potential
during the daylight hours. Current messaging supports 15 to 25 mph
during the afternoon with residual subsidence inversion at a fairly
low 4.5 kft agl limiting mixing heights.
Main baroclinic zone/composite cold front will push into Lower
Michigan late Wednesday night and for the daytime Thursday. Main
forecast item to watch for will be enhanced/deep moisture that is
expected to eject northeastward out of MO/Mid Mississippi River
Valley and ride along the cold front as a frontal wave. Deep fgen
response is being forecasted under change in upper level jet
dynamics due to jet streak. Both cloud cover, development/coverage
of stratiform precipitation, and frontal timing will impact
temperatures Thursday as surface cold front will be east of the
area. Current high temperatures forecast is likely for 12Z timing
with holding/falling temperatures during the day. A considerable
amount of uncertainty exists with the magnitude of isentropic ascent
aloft, some solutions are very lean on precipitation. Late afteroon
boundary layer destabilization with cold air/instability showers may
end up being the greatest precipatation potential after 18Z.
Deep cold air aloft will be firmly entrenched across Southeast
Michigan Friday. Automated guidance is likely too optimistic, highs
will likely struggle to climb above 50 degrees. Persistent cool
weather is being advertised for next weekend with highs in the lower
50s.
MARINE...
Passage of a cold front late tonight will increase instability
slightly over the lakes and will result in a brief period of
elevated winds between 20-25 knots. Diminishing winds then expected
late Wednesday morning as the northern periphery of a high pressure
system slides into the Great Lakes. Lighter winds will be short-
lived as low pressure travels from Minnesota into Ontario late
Wednesday into early Thursday which will increase the pressure
gradient over the Great Lakes as a strong low-level wind field
develops aloft. This will result in the likely issuance of Small
Craft Advisories for the nearshore zones. Some brief gales will be
possible across Lake Huron, specifically around central and southern
Lake Huron, but will preclude the issuance of a Gale Watch as the
duration of potential gales will be to or below the three hour
threshold. Otherwise, a moderate pressure gradient will hold over
the Great Lakes through Thursday which will result in
continued elevated winds and waves.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 4 PM Wednesday to 4 PM EDT Thursday for
LHZ421-422-441>443.
Lake St Clair...Small Craft Advisory from 4 PM Wednesday to 4 PM EDT Thursday for
LCZ460.
Michigan waters of Lake Erie...Small Craft Advisory from 4 PM Wednesday to 4 PM EDT Thursday for
LEZ444.
&&
$$
AVIATION.....DG
DISCUSSION...CB
MARINE.......AM
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Goodland KS
916 PM MDT Tue Oct 13 2020
.UPDATE...
Issued at 904 PM MDT Tue Oct 13 2020
Update the forecast mainly for the area of possible frost early
Thursday morning and Thursday night into Friday morning. Strong
winds during the day on Wednesday ahead and behind of a cold
front will subside Wednesday night from north to south across the
area. The far northern sections of the forecast area extending
eastward along US Hwy 34 from northern Yuma county in far
northeast Colorado through far southwest Nebraska to the McCook
area could see temperatures around freezing along with light winds
and partly cloudy skies that will have diminishing sky cover, all
of which increase the possibility of frost across that area.
Thursday night into Friday morning, much of the forecast area will
see temperatures below freezing as another surge of colder air
moves into the region.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 205 PM MDT Tue Oct 13 2020
500 mb RAP analysis and water vapor imagery showed northwest flow
over the region today, with an upper trough entering the Pacific
Northwest. Skies were sunny to mostly sunny across the area, as east
winds shifted to the south at 10 to 15 mph. At 1:30 PM MT,
temperatures ranged in the upper 60s and low 70s.
Temperatures fall into the upper 30s to upper 40s tonight as dry
weather prevails. A surface trough moves across the region, shifting
winds from south to west. Meanwhile, the Pacific Northwest
disturbance pushes further onto the northern and central Rockies.
On Wednesday, a cold front is expected to push through the High
Plains, entering the northern portion of the region by the early
afternoon. As a result, high temperatures range from the upper 70s
to low 90s from northwest to southeast. Gusty north winds will push
through the region from north to south behind the front during the
afternoon and early evening. Current thinking is gusts up to 50 mph
will be possible, but this will need to be monitored. With relative
humidity values of 10 to 15 percent throughout the majority of the
region, have issued a Red Flag Warning in effect from 11 AM MT to 8
PM MT. In addition to fire weather concerns, there is also a
potential for blowing dust which could reduce visibilities.
The cold front continues across the southern portion of the area
Wednesday evening where winds will continue to be gusty.
Temperatures fall into the low 30s to low 40s with the coldest
temperatures in eastern Colorado. A frost/freeze highlight will
likely be needed.
.LONG TERM...(Thursday through Monday)
Issued at 316 PM MDT Tue Oct 13 2020
At the start of the forecast period, model guidance shows the CWA
underneath the back part of the base of the trough associated with a
Hudson Bay low giving a west-northwesterly flow aloft on Thursday.
Going into Friday, the flow over the CWA changes more northwesterly
as the back part of the trough moves over the CWA. Starting
Friday going into Saturday, the trough begins to move eastward
away from the CWA causing a transition to a more zonal westerly
flow aloft. Models continue to diverge with their solutions
beginning late Saturday. The GFS shows a trough developing as the
Hudson Bay low moves southward placing the CWA under the base of
the trough by Sunday and staying there into Monday. The ECMWF
shows the Hudson Bay low remaining stationary developing a trough
with a base in the Northern Plains area keeping the westerly flow
over the CWA on Sunday and Monday. This situation will be
monitored to see if future models come into better agreement.
At the surface, the Tri-State area expects to see temperatures
getting colder along with possible chances for precipitation
starting over the weekend. The CWA may see a hard freeze overnight
Thursday into Friday morning for areas along and west of a line from
Tribune, KS to McCook, NE. Saturday sees potential for possible fire
weather west of KS-25 with area RH values forecasted below 20%.
However forecasted wind gusts below 25 mph for these areas do not
support fire weather at this time. A cold front is expected to pass
through the CWA late Saturday giving the very northern parts of the
CWA a slight chance for rain transitioning to snow into Sunday
morning. Areas north of I-70 may also see a chance of rain on Sunday
evening that will transition to snow in the early Monday morning
hours.
The Tri-State area expects to have high temperatures in the lower to
upper 50s on Thursday with Friday`s highs reaching the lower to
middle 60s. High temperatures on Saturday increase to the middle to
upper 70s followed by highs dropping to the lower 50s on Sunday and
Monday. Tri-State overnight lows for Thursday and Saturday expect to
drop to the middle 20s to lower 30s. Overnight lows on Friday are
forecasted to range from the upper 30s in the western portion of the
CWA to the lower 40s in the eastern portion. Overnight lows in the
middle 20s are expected across the Tri-State area for the remainder
of the forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 541 PM MDT Tue Oct 13 2020
Conditions will remain VFR at MCK and GLD through the 00Z TAF
period. Mostly clear skies are expected with a few high clouds.
LLWS is also expected at MCK between 04-10Z with southwest winds
above the night time surface inversion at around 40kts. Light
south surface winds at both locations will turn southwest after
08Z and then northwest following the passage of a cold front
around 18Z. Northwest to North winds will continue to increase
with the following the passage of the front with wind speeds of
20-25kts gusting to 35kts.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Red Flag Warning from 11 AM MDT /noon CDT/ to 8 PM MDT /9 PM
CDT/ Wednesday for KSZ001>004-013>016-027>029-041-042.
CO...Red Flag Warning from 11 AM to 8 PM MDT Wednesday for COZ252>254.
NE...Red Flag Warning from 11 AM MDT /noon CDT/ to 8 PM MDT /9 PM
CDT/ Wednesday for NEZ079>081.
&&
$$
UPDATE...LOCKHART
SHORT TERM...JBH
LONG TERM...076
AVIATION...LOCKHART
Area Forecast Discussion
National Weather Service North Platte NE
648 PM CDT Tue Oct 13 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 330 PM CDT Tue Oct 13 2020
The main concern in the short term will the strong winds Wednesday
afternoon and fire weather concerns Wednesday afternoon as well.
Winds are expected to be strong Wednesday, with the strongest wind
gust in the afternoon. Forecaster confidence is moderate to high
in the wind forecast, the one concern is that winds will be even
higher than anticipated. Increased winds higher than most of the
forecast models to better handle stronger winds aloft and deeper
mixing level. Looking at bufkit soundings there will be very
strong winds aloft that will mix down and some soundings suggest
wind gust as much as 50 to 55 mph but was not confident enough
to put wind gust above 50 mph at this time, as that looks to be
mostly sporadic, mainly across the northwest CWA.
As for fire weather concerns, recovery overnight will be poor with
RH ranging from 35 to 65 percent, with the lowest RH across
southwest Nebraska. A poor recovery in combination with strong
gusty northwest winds has led to a concern in elevated to near
critical conditions across much of the Sandhills and near
critical to critical conditions across portions of southwest and
north central Nebraska. Did trend dewpoints tomorrow towards the
RAP as this model did fairly well with this afternoons dewpoints,
however this was a lower trending model for dewpoints. The main
concern, thus creating low to moderate confidence in min RH for
Wednesday afternoon will be cloud coverage. Models have suggested
cloud coverage during a majority of the day across portions of
north central Nebraska and the Sandhills. If we remain cloudy
during the day this could have an impact on temperatures and min
RH would be higher than anticipated. Across southwest Nebraska
confidence is a little better and can moderately expect min RH
around 20 percent, possibly lower, as the likelihood of cloud
coverage is much less. The main driving force for issuance of the
fire weather watch is the continue dry conditions, anticipated
warmer temperatures and near critical humidity in combination
with very strong northwest winds. Will continue to monitor and
will likely upgrade the fire weather watch.
.LONG TERM...(Thursday through Tuesday)
Issued at 330 PM CDT Tue Oct 13 2020
With the passage of the cold front Wednesday temperatures will be
below normal Thursday and Friday with highs in the upper 40s to
low 60s. Temperatures then rebound back into the 70s across the
southern CWA which could cause elevated fire weather concerns.
Then another cold front will push through Saturday night bringing
colder temperatures for Sunday with highs only in the 40s. There
will also be a possibility of precipitation in the form of rain,
rain/snow mix or possibly snow showers with the cold front passage
Saturday night, however at this time precipitation amounts look to
be low.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 648 PM CDT Tue Oct 13 2020
Skies will be mostly clear over the next 18 hours with some
scattered high clouds expected overnight. Some mid level
cloudiness will impact the KVTN terminal Wednesday afternoon. Low
level wind shear is expected overnight tonight at both terminals
with speeds of 45 to 50 KTS expected. Wind shear levels will range
from 1000 to 1500 FT AGL. On Wednesday afternoon, a strong cold
front will pass through the area. this will lead to gusty
northwesterly winds which may reach 30 to 40 KTS late Wednesday
afternoon.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Wednesday afternoon through Wednesday
evening for NEZ209-210-219.
&&
$$
SHORT TERM...Gomez
LONG TERM...Gomez
AVIATION...Buttler
Area Forecast Discussion
National Weather Service Marquette MI
821 PM EDT Tue Oct 13 2020
.SHORT TERM...(This evening through Wednesday)
Issued at 355 PM EDT TUE OCT 13 2020
Latest RAP analysis and Hi-res guidance is showing a broader
shortwave that will track over the northern part of Lake Superior
throughout the day. This shortwave is part of a mid to upper-level
low seen at 500mb, that is located near the James Bay and will
likely stay in place through this forecast period. This low has a
negative tilt to it and will be responsible for this shortwave and
another shortwave that will come Wednesday with a good rush of caa
moving into Upper Michigan, beginning of a cooling trend. Both
shortwaves will bring more chances of showers and windy conditions
but better rain chances and breezy winds will come with the
Wednesday shortwave.
With this shortwave moving through the cwa today, some showers have
developed with a little bit fgen as a forcing mechanism ahead of the
cold front. Latest runs did show LI values as low as -4 and some
decent bulk shear of up to 50 kts, which has triggered a few
isolated thunderstorms, mainly over the east half. Have tweaked PoPs
and PoTthunder to reflect this change since previous runs did not
catch this. Even if a thunderstorm occurs, will not be a washout
like yesterday with most areas that see rain, only receiving up to
0.05" QPF. Once front passes on through, conditions will dry out
and skies will turn mostly clear to start before the next
shortwave moves in Wednesday morning. There will be better fgen
forcing and dynamics will be better than today`s shortwave, which
means widespread rain is likely again. Rainfall totals will be
between 0.5-1.0" in most spots. Best chances of seeing heavier
rain will be over the north and less to the south. With this fall
pattern, continue to count on breezy conditions through the rest
of the afternoon and early evening. Did decide not to issue a wind
advisory for the Keweenaw Peninsula, even though there have been
a few gusts near the 45mph range but still think this won`t last
all afternoon. Like last night, winds will subside again tonight
and then increase again with decent mixed layer just above the
surface.
Temperatures this afternoon should reach the mid to upper 50s with
those southerly winds, aiding in waa ahead of cold front. Once front
passes, caa will start to work in and with clear skies to start,
lows should drop in the 30s in most spots with a few upper 20s in
the more favorable cool spots over the interior west. Went with the
25th percentile for highs Wednesday as this will begin the stretch
of some strong caa taking hold over the cwa.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 427 PM EDT TUE OCT 13 2020
The extended fcst for much of the next week will be generally
highlighted by below normal temperatures as models and ensembles
advertise an amplified blocking pattern setting up and a broad, cool
and persistent trough enveloping much of central North America.
Models indicate positive 5H height anomalies developing over the
eastern Pacific into the Gulf of Alaska and over the North Atlantic
into Greenland by late week into early next week. The 500 mb height
anomalies become abnormally strong this weekend over the North
Atlantic into Greenland where heights become more than 3 standard
deviations higher than normal. These amplified ridges will force
a broad and amplified mid-upper level trough to develop and
persist across central North America through the period, including
the Upper Great Lakes region. The result will mean much blo
normal temperatures beginning by Thu and continuing for the most
part into the early part of next week with fairly peristent lake
effect rain and snow showers for the w-nw wind belts downwind of
Lake Superior.
Beginning Wed night into early Thu, as a sfc low lifts e-ne
across north central and eastern Lake Superior into Ontario Wed
night, the dry slot associated with the low will move into sw and
central sections of the U.P. with mostly dry conditions there.
There could be some scattered evening showers along the cold front
over the eastern counties, but then mostly dry conditions after
that. The best coverage for showers will be over the western
counties where wraparound moisture, cyclonic upslope nw flow and
some lingering enhancement at least into the evening (with lake
delta-t around 10C) will aid with some lake enhanced/lake effect
showers. With web bulb zero heights most places staying at or
above 2 kft, expect pcpn mostly as rain. KIWD NAM sounding does
however show WB zero heights lowering near 1 kft just before
sunrise as CAA increases, so maybe some light snow
showers/flurries could mix in with rain far west just before
sunrise into late Thu morning. Tightening of the pres gradient on
the backside of the system and 5-6 mb/3hr pres rises with ensuing
CAA will likely result in a period of 35-40 knots nw gales over
central and eastern Lake Superior late Wed night into Thu morning.
A brief period of advisory criteria gusts to 45 mph may also be
possible along the eastern Lake Superior shore from Munising to
Whitefish Point early Thu morning. Otherwise, expect breezy
conditions elsewhere during the day on Thu.
By late Thu into early Sat, this looks like it will be the start of
a sharp cool down where 850 mb temps drop to around -7 to -9 C by
Thu afternoon and remain in that range into Sat morning. Light lake
effect rain and snow showers generated by the cold flow across Lake
Superior will be mostly over the nw wind lake effect belts of Lake
Superior on Thu and then should be mostly confined to the Keweenaw
Peninsula Fri. Models do indicate a shortwave moving across the area
on Fri which could aid isolated diurnal shower development for the
rest of Upper Michigan, and perhaps provide enhancement to lake
showers over the Keweenaw.
Late Sat-Sat night, models now in agreement that a Pac NW Coast
shortwave and deepening storm system will track southeast through
the Northern Plains on Sat then round the base of the long wave
trough and track northeast through the Upper Great Lakes Sat
night/early Sun. Models still differ somewhat on the strength and
track of the storm system, although a blend of the 12Z GFS and
UKMET and 00z ECMWF would appear to converge on a track of the
storm through the Dakotas and southern MN and then tracking
northeast through northwest WI into western Upper Mi. This sfc low
track solution would be too far north for any notable wintry
pcpn, with the most likely 850 mb low track going across the
Apostle Islands and then western and north central Lake Superior.
Still, it`s not impossible that some of the WAA precip Saturday
evening at the onset could end up as light snow or a light
rain/snow mix as temps on Saturday are only expected to make it
into the low 40s before the precip arrives.
Expect gusty southerly winds, perhaps gale or near gale force over
northern Lake Mi and the east half of Lake Superior late Sat into
Sat evening. Might also be some lakeshore flood issues along Lake
Michigan during this period.
I`m discounting the latest 12Z ECMWF solution as an outlier at
this point as it tracks the storm system on an IMT-MQT path
through the U.P. Obviously this will be something to watch though,
as this scenario would probably yield a few inches of
accumulating snow for the western cwa Sat night.
Sunday, as the low departs expect another round of blustery NW
winds, CAA, and lake-effect rain/snow chances in the west and west-
northwest wind lake-effect belts. Models bringing 850 mb temps right
back down to around -5 or -8 C for Sunday means another day with
highs ranging from the mid 30s west to mid 40s east. If the deeper
00Z ECMWF solution verifies then advisory wind criteria would be
likely over at least the nw U.P. with nw gales over much of Lake
Superior.
Monday into Tuesday, model solutions become a bit more muddy out
beyond Sunday. The ECMWF shows a baroclinic zone setting up just se
of the Upper Mi for early next week where the se fcst area could get
brushed with light mixed pcpn during the period. Meanwhile, the GFS
and CMC show no evidence of this boundary, just spawling high
pressure from the mid-Mississippi Valley into the Lower Great Lakes
as our region maintains a cool nw to w flow with light lake effect
pcpn downwind of Lake Superior. Since ensembles show less support
for the ECMWF, will lean more toward the GFS and CMC at this time
and maintain chc pops for nw-w flow lake effect rain and snow
showers downwind of Lake Superior along with cooler than normal
temps.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 821 PM EDT TUE OCT 13 2020
VFR conditions tonight into Wednesday morning will give way to
deteriorating conditions as a low pressure system moves into the
region. The increased low level moisture inflow along with rainfall
will drop cigs to MVFR during the afternoon. There may also be
period of IFR vsby with any heavier showers. Southerly winds will
increase and become gusty during the afternoon.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 355 PM EDT TUE OCT 13 2020(For the 4 PM Lake Superior forecast issuance)
Issued at 406 PM EDT MON OCT 12 2020
Well, the active weather pattern is here to stay, at least through
this forecast period. Current gales will linger over the east half
of the lake through this evening while dropping over the west half.
duration will be shortest over western Lake Superior. Winds will
briefly drop under 20 kts overnight tonight before ramping back to
20-30 kts from the southeast ahead of next shortwave approaching
from the Dakotas. Would not be surprised at all if there were
some gale force gusts to 35 kts, especially over the east half.
Behind the shortwave, winds will turn to the north and northwest
with winds increasing to gales to 35 kts across the lake early
Thursday. Could have some high-end gales to 45 kts, especially
over the central and eastern parts of the lake. Winds finally
diminish to under 20 kts by late Thursday into Friday. Winds will
increase again Saturday ahead of next system.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Warning until 10 PM EDT this evening for LSZ250-251-265>267.
Lake Michigan...
None.
&&
$$
SHORT TERM...JH
LONG TERM...Voss
AVIATION...JLB
MARINE...JH