Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/18/20

Area Forecast Discussion

National Weather Service La Crosse WI

 1053 PM CDT Sun May 17 2020

.SHORT TERM...(This evening through Monday)
Issued at 345 PM CDT Sun May 17 2020

At 3 PM, the deformation rain had moved north of Interstate 94.
With moderate 850 mb moisture transport and precipitable water
values between 1 and 1.25 inches, there will still be possibility
of some localized heavy rain at times into the early evening.
This band will then pivot back into southeast Minnesota and east
across the area into Monday. As this occurs, the rain showers will
become more scattered. As a result, only expecting up to a quarter
of an inch through Monday.

Soundings continue to show strong winds aloft (up to 40 mph).
However, the rain-cooled air has stabilized much of the boundary
layer. As a result, we are only on occasion seeing wind gusts up
into the 30 to 40 mph. The strongest winds through this evening
will remain mainly along and north of Interstate 90.

Another thing we are watching this afternoon is a convergent band
located over northeast Iowa. Every once in awhile, the meso models
will try to bring this band northward into Fayette and Clayton
counties in northeast Iowa and Grant County in southwest
Wisconsin. RAP surface-based CAPES have climbed up to 750 J/kg and
occasionally there has been an increased chances of enhanced
stretching potential. This could have result in the potential of
NSTs. However, with said the HRRR has weakened both of these
parameters and kept it south of our area.

.LONG TERM...(Monday night through Sunday)
Issued at 345 PM CDT Sun May 17 2020

On Monday night, the closed low pressure area will continue to
move slowly southeast away from the region. It will still be close
enough for the potential of some evening rain in southwest and
central Wisconsin. Low temperatures will be in the mid and upper
40s,

On Tuesday, an upper level ridge will slowly build across the
region. Like yesterday, it looks like the clouds will linger into
the day, so lowered the high temperatures into the mid- and upper
60s which is much closer to the NAM MOS guidance than the GFS MOS
guidance.

From Tuesday night into Thursday night, the upper level ridge
portion of the rex block will be located over the region. This
ridge will provide weather through at least this time period and
possible even the early portion of the upcoming holiday weekend.
High temperatures will be mainly in the 70s.

From Friday into Memorial Day weekend, we will be located on the
western side of the upper level ridge. This will allow even warmer
air into the region. High temperatures will be around 80. Like
yesterday, the models continue to struggle on the speed of the
cold front moving out of the Northern and Central Plains. This
will impact precipitation chances.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1053 PM CDT Sun May 17 2020

Low pressure will continue to meander slowly south of the region
the next 24 hours, providing continued low clouds and periods of
mainly light showers and some drizzle. IFR conditions should be
dominant at RST overnight, lifting to MVFR through the afternoon
hours, while LSE holds mainly MVFR, with ceilings perhaps dipping
a bit again by Monday evening and night. Winds will remain
steady-state from the northeast, generally 10-15 knots with gusts
to around 25 knots, gradually diminishing into Monday evening.

&&

.HYDROLOGY...
Issued at 345 PM CDT Sun May 17 2020

The heavy rain (2 to 4+ inches) will cause in-bank rises along
Turtle Creek, Cedar, Zumbro, and Whitewater rivers. With only up
to an additional quarter inch of rain expected from this system
through Monday, not anticipating any flooding to occur along these
rivers and creek.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...Lawrence
HYDROLOGY...Boyne



Area Forecast Discussion

National Weather Service Twin Cities/Chanhassen MN

 706 PM CDT Sun May 17 2020

.UPDATE...
Issued at 648 PM CDT Sun May 17 2020

Updated to include 00z aviation discussion below.

&&

.SHORT TERM...(This evening through Monday night)
Issued at 225 PM CDT Sun May 17 2020

Not too much new left to say about today`s system, it`s obviously
been a soaker across the area and has a bit of time left before it
departs. Latest water vapor imagery shows an excellent circulation
centered just to our south, slowly making its way southeastward.
The main flow of good moisture from the Gulf has shifted east, but
we continue to see come cold conveyor belt moisture works westward
across the forecast area. RAP PV analysis show the upper anomaly
dipping down to below 500 mb, which is definitely helping to
enhance a deep zone of upper level divergence as well as a
persistent area of low- to mid-level frontogenesis. All of this
will shift east tonight, with rain ending from northwest to
southeast. Clouds will stick around through the night for most of
the area, then slowly work out through the day on Monday. Knocked
down temperatures some for Monday given the overall slower
progression of the system.

.LONG TERM...(Tuesday through Sunday)
Issued at 225 PM CDT Sun May 17 2020

The expected trend toward a slower overall evolution of the large
scale pattern has persisted in the guidance for this week. With
the flow becoming more amplified some slowing was to be expected.
And with the upper low currently near us cutting off over the Ohio
and Tennessee valleys (south of the larger scale ridge), the
pattern will be fairly locked up for the week. In terms of the
forecast, the main impact is to slow the arrival of warmer
temperatures, with any 80 degree readings looking like they will
hold off until at least Friday or Saturday for most locations. In
addition, precipitation will have a tough time working back into
the area as we see successive impulses eject from the western
trough and shear out as the try to move eastward into the large
scale ridge. Most of the area probably won`t see any meaningful
precipitation return until the weekend, but did start to bring
chance PoPs back in as early as Thursday night across the west to
account for some significant differences in the GEFS and EPS
members (which are inherently accounted for in the NBM solution
which was generally followed).

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 68 PM CDT Sun May 17 2020

Persistent rain shield over the past nearly 24 hours is finally
diminishing and should come to an end at all sites by 04z. That
said, low stratus (MVFR range) is expected to settle in through
the overnight hours and much of Monday morning, especially for
southern/eastern MN into western WI. VFR is expected for KAXN-KSTC
and this will slowly spread east mid-to-late day tomorrow so by
late day tomorrow into tomorrow evening, all sites will be VFR or
close to it. Breezy/gusty NE winds this evening will settle down a
bit overnight then pick up once again after daybreak Monday and
persist through the day.

KMSP...Specific timing of ceilings continues to be the trickiest
element of the forecast. While VFR ceilings have returned for
initialization, they are not expected to last. Some bouncing
between VFR/MVFR can be expected through the early evening before
persistent MVFR ceilings settle in overnight through the first
half of Monday. That said, am expecting ceilings to remain above
1700ft and visibilities to remain VFR with no precipitation beyond
the first few hours of this TAF.

/OUTLOOK FOR KMSP/
Tue...VFR. Wind E 5-10 kt.
Wed-Thu...VFR. Wind SE 5-10 kt.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&

$$

UPDATE...JPC
SHORT TERM...
LONG TERM...
AVIATION...JPC



Area Forecast Discussion

National Weather Service Marquette MI

 743 PM EDT Sun May 17 2020

.SHORT TERM...(This evening through Monday)
Issued at 427 PM EDT SUN MAY 17 2020

WV imagery and RAP analysis indicated a mid/upper level low over
Iowa which supported a large shield of rain from southern MN through
much of WI into lower Michigan. At the surface, easterly flow was
strengthening between a trough extending from central IA into
northwest IL and high pressure from James Bay through northern
Ontario. Strong 300k-305k isentropic ascent and moisture advection
associated with the 850-700 mb warm front supported moderate to heavy
rain fall through much of central and eastern WI. Otherwise, the dry
east low level flow through Upper Michigan has limited the
northward progress of the rain.

Tonight into Monday, the models suggest that although the mid
level low will will slowly slide to the southeast, thee zone of
stronger 850-700 fgen/def and isentropic ascent (upstream 850 mb
dewpoints to around 12C) will very slowly lifts to the north.
This will put areas mainly south of US-2 in line for the potential
of heavy rain. Although the NAM has been an outlier with ery high
QPF amounts, the CAMs and other short range guidance has also
focused on this area. Although there is still uncertainty with how
the system will evolve and with the overall rainfall amounts,
confidence was high enough for at least a couple inches of rain
over southern Menominee county to issue a flood watch. Consensus
guidance has amounts of over 2.5 inches by 00z/Tue. Farther north,
confidence is lower with the rainfall amounts and the northern
extent of the pcpn as a sharp northern boundary is still likely
given the continued easterly dry low level flow. Expect areas
along and north of LNL-SAW-ERY will see little if any rain.

.LONG TERM...(Monday night through Sunday)
Issued at 422 PM EDT SUN MAY 17 2020

The highly advertised blocked upper-level pattern has yet again
slowed things down. Thus, the majority of time was spend looking
Monday night/Tuesday time frame as lingering rain across the south-
central could cause some flooding concerns and strong onshore east
to northeast winds look to cause lakeshore flooding concerns early
on. The main area of concern looks to be across Menominee County,
where the focus for persistent rain and onshore flow remains. In
coordination with the short-term forecaster, have issued a Flood
Watch for Menominee County, as upwards of 3 inches of rain look
possible for southern portions of the county by Tuesday morning. The
localized higher rainfall will allow rivers, streams, and creeks to
rise and could cause minor flooding concerns for low-lying areas.
Lakeshore flood advisory was extended into Tuesday morning. Given
the longevity of this onshore wind event, those who have lakeshore
property should prepare for possible lake inundation. Will be a time
period where water levels will need to be monitored closely.

Monday Night/Tuesday, as cutoff energy progged to be over central
Illinois slowly drifts south towards Kentucky/Tennessee, southern
parts of Upper Michigan will remain under the main axis of better
moisture transport and theta-e advection funneling in from the east,
on the norther side of the upper-level low. Overnight, the main
focus is from the east, but as Tuesday progresses flow veers more
southeasterly as the upper low drifts south and ridging starts to
build across the Upper Mississippi Valley. This will allow any
lingering rain/moisture to slowly lift more northward during the
first half of Tuesday across the central and east. By Tuesday
afternoon, conditions should start to dry out as a weak shortwave
drop south across the region, ushering in a drier, post-frontal air
mass with the western edge of high pressure building into the
region. Of course, all of this is subject to change if thing slow
down even further...as is the remainder of the forecast!

Through the middle of the week, the forecast continues to look dry
as a rex block develops across the region with upper-level ridging
builds northward under the pesky upper-level low parked over
Tennessee and Kentucky. This will keep the region under the
influence of high pressure. We should see a day or two with good
mixing, and comfortable humidity levels. Above-normal temperature
are expected, with daytime highs climbing into the mid to upper 70s
inland from the Great Lakes.

Towards the end of the week into next weekend, the above-normal
temperatures will continue with increasing humidity levels. A lead
shortwave embedded within persistent longwave troughing over the
western CONUS looks to lift across the Plains, and eventually the
Upper Great Lakes. Moisture returning ahead of this wave looks to be
enough for some chances for rain, and possibly some thunderstorm
activity.
&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 742 PM EDT SUN MAY 17 2020

Rain associated with low pres well to the s will stay s of
KIWD/KCMX/KSAW. This will leave dry air to persist in the low-
levels, maintaing VFR conditions at all terminals. LLWS is expected
late tonight into Mon morning at KIWD/KSAW as easterly flow
increases atop a more stable layer closer to the surface.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 427 PM EDT SUN MAY 17 2020

Low pressure passing by well to the south of Lake Superior is
expected to maintain northeast winds to around 25 kts through
Monday, especially over the western portion of the lake. Otherwise,
winds of 20 kts or less are expected through at least the middle of
the week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Flood Watch through Tuesday morning for MIZ012.

  Lakeshore Flood Advisory from 10 PM this evening to 7 AM CDT
     Tuesday for MIZ012.

Lake Superior...
None.
Lake Michigan...
  Gale Warning from 8 AM Monday to 8 AM EDT Tuesday for LMZ221-248-
     250.

&&

$$

SHORT TERM...JLB
LONG TERM...Ritzman
AVIATION...Rolfson
MARINE...JLB



Area Forecast Discussion

National Weather Service San Francisco Bay Area

 833 PM PDT Sun May 17 2020

.SYNOPSIS...Another round of widespread shower activity will
develop overnight and continue into early Monday. Scattered
showers are forecast for the rest of Monday and Monday evening.
There is also a slight chance of thunderstorms on Monday. Drier
conditions will develop Tuesday, although isolated showers may
linger. High pressure builds Wednesday into the Memorial Day
weekend, with dry weather and seasonable temperatures expected.

&&

.DISCUSSION...As of 8:30 PM PDT Sunday...The frontal boundary
that brought rain to much of our region of the past 24 hours,
especially to our coastal mountain ranges, dissipated across the
southern portion of our forecast area late this afternoon. Current
radar shows only isolated light showers lingering behind the
frontal boundary this evening. Taking an wider look, satellite and
radar reveal an area of widespread shower activity approaching
from offshore. This activity is associated with a shortwave trough
to the south of the upper low center. This shortwave is forecast
to approach our area later tonight. The 00Z NAM and 01Z HRRR agree
reasonably well in tracking a line of showers across our area
from about midnight tonight through sunrise Monday morning.
Indications are that some of these showers will produce brief
heavy rain and small hail. Isolated thunderstorms are possible
too, although lightning detection networks are not currently
detecting strikes offshore.

After the early morning line of showers passes through, it looks
as though we will see diminished precipitation activity for the
rest of the morning. But then showers and isolated thunderstorm
will become more likely in the afternoon as the unseasonably cold
upper low drops to the southeast and lapse rates steepen over our
area. Thunderstorm potential is highest across the northern
portion of our forecast area which will be in closest proximity to
the upper low.

Models indicate mostly dry conditions Monday night and Tuesday as
the upper low moves to our east, although isolated showers are
still possible, mainly over the hills on Tuesday afternoon.

Dry weather is expected to return to all areas by Wednesday and
warmer temps will develop by Thursday as a weak shortwave ridge
temporarily builds over California. This warming trend will be
short-lived as an upper trough is forecast to swing through
northeast California on Friday and cools temps back a bit.

Dry and warmer weather is forecast over the Memorial Day weekend
as a ridge develops near the West Coast.

&&

.AVIATION...as of 7:30 PM PDT Sunday...For 00z tafs. VFR except locally
MVFR, a break in showers early tonight. Showers and lowering ceilings
to more widespread MVFR with local IFR later tonight and persisting
into the Monday morning.

Vicinity of KSFO...VFR to MVFR conditions with showers forecast tonight.
Southwest wind occasionally gusty.

SFO Bridge Approach...Similar to KSFO.

Monterey Bay Terminals...VFR to MVFR conditions with showers forecast
tonight. Southwest winds 10 to 15 knots.

&&

.MARINE...as of 1:54 PM PDT Sunday...A cold front will continue
to sweep through the coastal waters this evening and early
tonight. Behind the cold front southerly winds will gradually
become more west to northwest. Thunderstorms will be possible on
Monday, mainly across the northern waters. Mixed seas will persist
with a longer period west to northwest swell along with a longer
period southwest swell.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .Tngt...None.

$$

PUBLIC FORECAST: Dykema
AVIATION: Canepa
MARINE: MM

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Area Forecast Discussion

National Weather Service Portland OR

 856 PM PDT Sun May 17 2020

Updated aviation discussion.

.SYNOPSIS...A vertically stacked low continues to slowly move inland
near the Oregon/California border tonight. This large low will
continue slowly progressing eastward over the next few day. This will
keep the area in a showery pattern through Wednesday. Towards the
later part of the week, two opposing systems will develop but will
maintain the showery pattern across the area. Friday an upper level
ridge looks to develop and usher in a drier pattern for the weekend.

&&

.SHORT TERM...Tonight through Wednesday...For the remainder of today
there is a slight chance for some thunderstorms to develop in the
Willamette Valley and the Cascades. Some of these thunderstorms will
also have the potential to produce small hail.

The drivers for this convective weather is a rather large vertically
stacked low currently located between 130W the Oregon/California
coast. Models are in good agreement that the low will continue to push
east through Monday.

Current satellite imagery is showing some convection along the Coast
Range and towards Eugene, which is moving in a northeasterly
direction. CAM and non-CAM models show peak CAPE values happening
around now, which means that the best chance for thunderstorms will
happen over the next few hours. Lapse rates from 3km to 6km remain
around 7.0 C/km to 7.5 C/km, which will aid in some hail growth.
However, hail growth will be stifled by limited CAPE within the hail
growth zone. There is the chance that some of this instability could
persist into the night around the Eugene area, but areas north of
Corvallis will lose most convective potential as the evening
approaches. The reason for the loss of instability north of Corvallis
is the seabreeze pushing inland, which will provide a stabilizing
force for the area. Combining that with the loss of daytime heating
and large temperature/dew point spread will aid in this stabilization effort.
This process is supported by the latest HRRR run.

A decreasing shower threat continues into Monday as the upper low
passes to the south. While SREF and NBM guidance is suggesting a
thunder threat over the area Monday, have chosen to remove the threat
as diffluent flow aloft will be minimal, model soundings show weak
winds throughout the lower and mid levels of the atmosphere, and
substantial temperature/dew point separation. What this means is that
while active cell development could happen, the updraft of the cell
would be choked out by the subsequent downdraft, leaving little time
for development of any cell to occur.

However, some ensemble and deterministic models are suggesting the
low elongates as it passes over the Pacific NW which will keep the
threat of afternoon and evening showers in the forecast through
Tuesday. A weak front will start to move into the area on Wednesday,
bringing the next threat of light rain across the CWA. Temperatures
are expected to remain near seasonal normals through the start of the
week. /42

.LONG TERM...Wednesday night through Sunday...Ensemble and
deterministic solutions are showing the CWA positioned between two
opposing pressure systems Wednesday night into Thursday. To the
northeast a Canadian low will deepen over Alberta, while to the
southwest the Pacific high will strengthen and move east. This will
tighten the pressure gradient across the area resulting in strong
northwesterly flow across the coast which will immediately be pulled
northeast creating strong winds across the Cascades. Onshore
moisture flux coupled with weak disturbances separating from the
Canadian parent low will keep chances of showers through late
Thursday into Friday morning.

Throughout the day Friday a strong Pacific low to the west of the
ridge will push northeast towards the Canadian coastline, swinging
around into the Gulf of Alaska. The low will ride over the top of
the ridge causing it to weaken and deforming the ridge axis
northeast. There is fairly good agreement between models that the
ridge axis will be pushed over the CWA reducing chances of showers
Friday evening.

Moving past Friday night the models begin to diverge on the
positioning and strength of a shortwave that forms in the warm front
of the dying Pacific low. Models agree that this shortwave will
bring enough energy to flatten the ridge but whether or not
precipitation makes it to the coast and over the CWA is not known at
this time. The 12Z GFS shows precipitation returning to the area
Saturday night and the 12Z ECMWF keeps most of the precipitation
offshore.

Thursday and Friday will see cooler daytime highs as persistent
northwesterly flow brings a cool airmass over the area. Temperatures
may trend up into the 70s by the weekend if the ridge holds over the
location.  -BPhillips


&&

.AVIATION...The forecast area will be centered between a
vertically stacked low off the southern Oregon coast and a weak
surface low in the Columbia Basin of eastern Washington overnight.
This will leave the area susceptible to a few lingering showers
under a regime with light winds in the low levels of the atmosphere.
As a result, there is a decent chance that a few locations,
particularly along the coast and within the Willamette Valley, could
eventually deteriorate into MVFR and IFR thresholds between 09-15z
Monday.

The low pressure system off the coast will move south and weaken
along the northern California coast. As it does the low level flow
will turn more onshore. This will likely support showers through
Monday afternoon with most interior sites remaining low VFR. Coastal
locations though will mainly see MVFR conditions persist through the
day.

KPDX AND APPROACHES...Weak low level winds with a few lingering
showers possible tonight. This could result in conditions
deteriorating into MVFR and IFR thresholds between 10-15z Monday.
Showers will likely redevelop after 15z with cigs lifting from MVFR
to low VFR after noon. Expect showers to diminish by 02z.
Hartsock/Neuman


&&

.MARINE...Seas will gradually subside over the next 24-48 hours
into the mid single digits. The waters will likely be entering a
period of quieter weather this upcoming work week. A weak surface
low pressure will slowly track southeastward towards the southern
Oregon and northern California coast through Monday. This storm
system will be weak enough and will remain far enough away that few
impacts are expected across our waters. Broad, but weak high
pressure over the northeast Pacific should then keep winds at bay
for much of the upcoming work week as a light northwesterly wind
pattern takes hold. A weak front or two sliding out of the north-
northwest could temporarily enhance or turn winds more
southwesterly, but these appear weak at this point. /Neuman

&&

.MARINE...Seas will gradually subside over the next 24-48 hours
into the mid single digits. The waters will likely be entering a
period of quieter weather this upcoming work week. A weak surface
low pressure will slowly track southeastward towards the southern
Oregon and northern California coast through Monday. This storm
system will be weak enough and will remain far enough away that
few impacts are expected across our waters. Broad, but weak high
pressure over the northeast Pacific should then keep winds at bay
for much of the upcoming work week as a light northwesterly wind
pattern takes hold. A weak front or two sliding out of the
north-northwest could temporarily enhance or turn winds more
southwesterly, but these appear weak at this point. /Neuman

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...None.

&&

$$

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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.