Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/05/19

Area Forecast Discussion

National Weather Service La Crosse WI

 1058 PM CDT Wed Sep 4 2019

.SHORT TERM...(Tonight through Thursday night)
Issued at 256 PM CDT Wed Sep 4 2019

Broad surface high pressure sits over the Upper Mississippi Valley
this afternoon. An expansive stratocumulus cloud deck has stubbornly
held together in cool northwest flow over the forecast area. This is
finally starting to erode from the west this afternoon as the
surface high begins to drift overhead and daytime heating/mixing
(meager as it is today) takes its toll. Expect the decrease in cloud
cover to accelerate over the next couple hours. Temperatures have
been suppressed due to the expansive clouds, but increasing sunshine
should still manage to push some areas into the low 70s yet by late
afternoon.

A decent setup for some river valley fog tonight with the high
sitting overhead, providing mostly clear skies and rather light
winds throughout the lowest 5000 feet or so. The only complicating
factor is a slightly drier airmass settling into the area and
whether the rate of cooling can keep up with the drying. Most model
forecast soundings show at least patchy fog as a possibility,
perhaps reducing visibility below 1/4 mile in sheltered areas. Will
continue to monitor this potential and latest trends through this
evening. Lows tonight will range from the mid 40s in the cranberry
bogs to lower 50s elsewhere.

The surface high will depart to the east on Thursday with increasing
warm air and moisture advection in its wake. Daytime highs will
bounce back into the 70s to near 80 in a few spots. Isentropic lift
through late morning may be enough to squeeze out a few sprinkles or
showers. Then a developing surface low and associated wave aloft
will drop into the area in northwest flow aloft during the afternoon
and evening. Looks like the bulk of rain will fall east of the
Mississippi River with this system. Instability will be almost all
elevated due to decent capping above 900mb, so think thunder
potential will be somewhat limited, despite favorable deep layer
shear. Forcing will push east of the forecast area late Thursday
night with cold air advection increasing behind this departing
system.

.LONG TERM...(Friday through Wednesday)
Issued at 256 PM CDT Wed Sep 4 2019

The region is generally under a northwesterly flow to end the week.
For Saturday, the flow converges over the area and with the
combination of frontogenetic forcing, some rain showers are likely
to develop. Drier air to the north will keep the main threat for
rain near and south of I-90. It should stay relatively cool and
cloudy the rest of the weekend.

Early next week, a warm front will move northward across the region.
This will bring another chance for showers and storms. After the
frontal passage, warm air will settle in for Tuesday under a more
southerly flow. Rain chances behind the front are limited as a warmer
mid-level air would hinder convection.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1058 PM CDT Wed Sep 4 2019

Still not a clear signal whether valley fog will form and impact
KLSE. The temp/dew point spread at 03Z was 6 degrees and right on
the edge of guidance on whether fog will form or not. Forecast
soundings from the 05.00Z NAM and 05.02Z RAP look a little more
favorable with both now showing saturation occurring at the
surface. Both models still suggest winds of 10 knots or higher
just above the surface for more of a stratus layer. Webcam from
the office showing a thin layer may be forming already over the
valley so have introduced a period of IFR conditions late tonight.
Still too many uncertainties to go with a dense fog event and will
let the overnight crew monitor the development and adjust as
needed. A short wave trough will move across the Great Lakes
Thursday afternoon and evening. This will push an area of low
pressure across central Minnesota and Wisconsin. A warm front with
the low will lift north across both airports allowing gusty south
to southwest winds to occur from late Thursday morning through the
afternoon. Convection with this system should stay along and north
of the warm front and thus, north of both airports.

&&

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

$$

SHORT TERM...Kurz
LONG TERM...Aufforth
AVIATION...04



Area Forecast Discussion

National Weather Service Denver/Boulder CO

 818 PM MDT Wed Sep 4 2019

.UPDATE...
Issued at 807 PM MDT Wed Sep 4 2019

Will confine the chance of thunderstorms to the northeast plains
this evening, from Lincoln County northeast into Logan County.
Otherwise just a few sprinkles possible elsewhere this evening
with some clearing overnight.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 300 PM MDT Wed Sep 4 2019

Showers and thunderstorms should be ongoing this evening, with a
favored location along and south of I-70. GOES-16 and theta-e
plots show a ribbon of moisture extending from southwest Colorado
into central Colorado. We`ve included isolated PoPs across
northeast Colorado to account for the theta-e axis extending
across the area later this evening. The HRRR continues to show a
round of showers and thunderstorms moving along the south side of
the Cheyenne Ridge. Including ~10-20 percent PoPs from 5-8 PM to
midnight to account for that. Elsewhere there is quite a bit more
convective activity this afternoon on radar/satellite, so PoPs in
general were kept elevated across the I-25 urban corridor through
7 PM or so, though coverage will still be spotty.

Showers should be ending all areas by 10 PM with the loss of
heating and drier air moving in from the southwest. The persistent
mid- and upper-level ridge of high pressure that has influenced
our weather for two months and counting builds a bit
northwestward tonight into tomorrow, pushing the best mid-level moisture
across the western half of Colorado for Thursday. With the ridge
building a bit, 700 mb temps respond by warming another degC
Thursday afternoon, to around +16degC. That is more than enough
for low to mid 90s for high temperatures across the plains and
Urban corridor, even if clouds get going early afternoon. PW drops
a quarter inch across our area vs. today, to 0.75" across the
plains and 0.5" in the mountains. Instability continues to be best
across the mountains so expect scattered showers and
thunderstorms Thursday evening, main impacts should be gusty winds
and lightning. Storms should be moving fast enough that flooding
is not a major concern. Across the plains shallow moisture near
the surface will quickly mix out into the 30s near the foothills
to mid 40s across the northeast plains. A decent surface high
across the northern plains will drive strong upslope low- level
flow in the afternoon, but the moisture doesn`t arrive until the
evening hours across the urban corridor. With pretty good upslope
flow, hot temperatures (no real cap), and storms initiating
across the mountains, can`t rule out a few storms surviving the
trek east despite initially very dry air. However, by the evening
hours much better low level moisture works westward and PW
increases well over an inch across the Plains after 6PM, and rain
chances increase. Instability and shear will both be limited so
with any storms we expect lightning and gusty winds to be the main
impacts.

.LONG TERM...(Thursday night through Wednesday)
Issued at 350 PM MDT Wed Sep 4 2019

The upper ridge is still progged to be centered over Colorado
Thursday night into Friday morning. By Friday afternoon, the upper
high center migrates south of the state. It stays this way
through at least Saturday night as an upper trough moves eastward
north of our state late Friday into Saturday. The QG Omega fields
have very weak upward synoptic scale energy over the CWA Friday
night through Saturday evening. The low level wind winds will be
upsloping a bit Thursday night, with, perhaps some normal
drainage flow by dawn Friday morning. Southeasterlies prevail on
Friday, with drainage patterns Friday night. There will be some
weak upsloping again on Saturday, then normal drainage again
Saturday night. Moisture-wise, the precipitable water values will
generally be in the 0.60 to 1.20 inch range through the periods
over all the CWA with the highest values over the plains. With the
decent moisture around, the QPF fields have measurable rainfall
over much of the CWA during the late day periods. Will leave in
the decent pops, especially over the western 3/4ths of the CWA.
There is decent CAPE over the high country and eastern border
areas for the late day periods. For temperatures, Friday`s highs
are 4-7 C cooler than Thursday`s. Saturday`s highs warm up 0-1.5 C
over Friday`s. For the later days, Sunday through Wednesday,
models have upper ridging Sunday, then an upper trough moves
across late Sunday night into Monday. The best moisture is progged
Sunday, with lesser amounts expected Monday through Wednesday.
For temperatures, readings should be around seasonal normals all
four days.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 807 PM MDT Wed Sep 4 2019

VFR over the next 24 hrs. Enhanced drainage 14-20 kts at KDEN
with lingering thunderstorms over Lincoln County this evening.
The wind should weaken a bit as things settle into a drainage
pattern later this evening. Generally dry through mid afternoon
Thursday with a chance of shower/thunderstorms developing at KBJC
by 20z as moisture increases with the onset of gusty easterly
winds.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Cooper
SHORT TERM...Schlatter
LONG TERM....RJK
AVIATION...Cooper



Area Forecast Discussion

National Weather Service Grand Forks ND

 949 PM CDT Wed Sep 4 2019

.UPDATE...
Issued at 949 PM CDT Wed Sep 4 2019

Adjusted POPs to slow progression across our area during the
06-12Z time frame. A few stronger radar returns in the northern
RRV currently are probably reaching the ground, but the main
activity will be after midnight as the main shortwave moves east.
The SPC meso page has 1000-2000 J/kg of MU CAPE over western ND,
with some 3000-4000 over SD. The RAP advects those higher values
northeastward into the RRV as the LLJ picks up. Bulk shear is very
strong, and even if the MU CAPE values we get are half of that,
it does look like we will see at least some strong to severe
elevated storms. Bumped up thunder mention a bit more and will
update HWO for isolated 1 inch hail possibility.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 329 PM CDT Wed Sep 4 2019

Much of the focus for the short term will be on tonight into
Wednesday morning. A low pressure system is located in southern
Saskatchewan and is expected to move to the southeast this evening
and into tonight. Rain chances are expected to begin near sunset
in the Devils Lake Basin and spread towards Grand Forks and
western Minnesota near and after midnight. Despite limited solar
heating this afternoon, a southerly to southwesterly low-level
jet at the 850mb level and surface to 6 km shear values of near 50
knots suggest the possibility of some storms becoming strong after
midnight. Temperatures will remain mild in the mid to upper 50s
with rain diminishing in western Minnesota by tomorrow afternoon.
Rain chances near and south of I-94 will be limited tonight into
tomorrow morning. Highs tomorrow will be in the mid to upper 60s
in NW Minnesota to the 70s across eastern North Dakota with partly
to mostly cloudy skies. Winds will become north at 10 to 20 mph
during the afternoon.

.LONG TERM...(Thursday night through Wednesday)
Issued at 329 PM CDT Wed Sep 4 2019

For Thursday night, expect to see skies clearing across North
Dakota and then in Minnesota. Lows will remain seasonal in the 50s
area-wide. Other than an isolated shower in the northern Lake of
the Woods area, everyone should remain dry.

Northwest flow aloft to prevail through the extended period with a
couple of precipitation chances over the coming week. We are still
looking at Sat and Mon as the best targets for impactful weather.
Tranquil to start on Fri before the next precipitation chance
presents on Sat. A shortwave will move southeast out of Canada with
sfc refection continuing to favor a tract from DVL to southern
valley into MN Lakes. Areas east of this line could very well remain
mainly dry during this period. The next chance, and a more robust
one at that comes on Mon, although current model blends approaching
two inches or more QPF overdone and will likely need to be trimmed
with subsequent fcst updates.

With respect to temperatures, looks like highs in the 60s through
the entire period owing to : a few bouts of cold air advection, and,
cloud cover and showers when there isn`t cold air advection. Lows
mostly in the 40s with some 30s near Intl border Sun morn, with
widespread frost holding off for the time being.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 635 PM CDT Wed Sep 4 2019

VFR conditions at all TAF sites with some cirrus moving into the
region. Showers and thunderstorms will move in late tonight into
early tomorrow morning, mainly impacting the northern sites, so
have some VCTS or VCSH at all but KFAR. Some MVFR ceilings coming
in behind the precipitation with a cold front tomorrow morning.
Conditions should improve by the end of the period over all but
KBJI. Winds will shift from the southeast to the north with the
frontal passage, with speeds mostly below 12 kts.


&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&

$$

UPDATE...JR
SHORT TERM...Godon/Wasilewski
LONG TERM...WJB/Godon/Wasilewski
AVIATION...JR



Area Forecast Discussion

National Weather Service Lincoln IL

 900 PM CDT Wed Sep 4 2019

.SYNOPSIS...
Issued at 245 PM CDT Wed Sep 4 2019

Drier air was flowing over central Illinois on Wednesday, and will
continue overnight. High pressure will drift into the region
overnight, causing some patchy fog to develop. Conditions will be
pleasant again on Thursday, with mostly sunny conditions and
highs in the upper 70s.

&&

.UPDATE...
Issued at 900 PM CDT Wed Sep 4 2019

Skies have cleared out for the most part across central Illinois.,
with the most persistent clouds in northeast Illinois. Winds have
become light and variable, under the surface high pressure. The
NAM and RAP show a shallow inversion trapping moisture and setting
the stage for some fog later tonight. The HRRR has a weaker
inversion, and no dense fog indicated. Patchy fog looks like a
plausible occurrance for areas that picked up the most precip in
the last couple of days. Not looking for widespread dense fog,
although a few pockets of dense fog could develop.

Only minor adjustments were needed to the going forecast this
evening, so no formal zone update will be necessary.

&&

.SHORT TERM...(This evening through Thursday)
ISSUED AT 245 PM CDT Wed Sep 4 2019

High pressure is expected to move over the region tonight. With
light winds and temperatures approaching the dew points, patchy
fog will be possible. Surface ridge will move over the area on
Thursday.

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 245 PM CDT Wed Sep 4 2019

The first front to reach the area in the forecast will come
through on Friday. However, with dry air in place, the system will
come through dry.

The second front will approach on Saturday night, triggering
scattered storms. The front will linger in the area through Sunday
and into Monday, before the system lefts back to the north.
Scattered storms therefore are expected into Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 710 PM CDT Wed Sep 4 2019

VFR stratocumulus clouds should dissipate this evening as we lose
boundary layer heating. High pressure will reside over Illinois
tonight providing light and variable winds under clear skies.
Residual surface moisture may increase fog potential near the
terminal sites, so have left the tempo groups for IFR 2SM fog.
GFS guidance is mainly pointing toward VLIFR fog, while the NAM
guidance shows MVFR fog at worst. Have split the difference with
IFR fog in the tempo groups.

Winds tomorrow look to remain in flux, shifting through southeast
to south directions. Once any morning fog clears, another day of
scattered mid-clouds is expected, with minimal impact to
aviation during the day.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Shimon
SYNOPSIS...Goetsch
SHORT TERM...Goetsch
LONG TERM...Goetsch
AVIATION...Shimon




Area Forecast Discussion

National Weather Service Marquette MI

 645 PM EDT Wed Sep 4 2019

.SHORT TERM...(This evening through Thursday)
Issued at 431 PM EDT WED SEP 4 2019

Water vapor imagery and RAP analysis show troffing over eastern
Canada into the ne CONUS, resulting in nw flow over Upper MI today.
Upstream, the next feature of interest is a well-defined shortwave
over sw Saskatchewan. This wave is generating sct shra and some
thunder across southern Saskatchewan with a few shra streaking
across the border into nw ND. Closer to home, although skies are
mainly sunny across the fcst area this aftn, it`s still on the cool
side for early Sept with current temps mostly in the low to mid 60s.

Sfc high pres currently over southern MN will move to Lwr MI
tonight. As a result, light/calm wind and clear skies, at least
early on, will allow for a chilly night in the interior.
Precipitable water is not unusually low to enhance the cooling
potential strongly, and column moisture will be gradually increasing
thru the night. Nonetheless, opted to lean on the low side of avbl
guidance for min temps given the cool start to the evening and
current sfc dwpts around 40F into the lower 40s. Expect temps in the
interior cold areas to drop into the mid 30s with traditional cold
spots possibly falling to freezing. Expect some frost in the
interior, but coverage, for now, seems like it will be low enough
not to warrant a frost advy. Min temps will range up thru the 40s
along the shores of the Great Lakes. Overnight, higher clouds will
begin to increase from the w as waa regime spreads e across the
Upper Mississippi Valley in advance of the aformentioned shortwave.
Not expecting any pcpn to reach Upper MI prior to 12z.

On Thu, the approaching shortwave will weaken as it shears into the
northern Great Lakes with a trailing shortwave becoming more
dominant as it moves ese into northern MN. Expect sct -shra to
spread ese across the fcst area during the day as waa/isentropic
ascent translate across Upper MI. There is a decent mid-level fgen
signature, so shra as they arrive initially may end up being
organized more so in a wnw-ese band shifting across the area rather
than shra having a broader coverage. There is some instability noted
aloft. This instability tends to lift higher in the column and
diminish with time as the shortwave approaches, so opted to leave
any mention of thunder out of the fcst for Thu. Fcst soundings
indicate zero potential of any sfc based convection. High temps will
be in the 60s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 428 PM EDT WED SEP 4 2019

Models indicate that a gradually progressive pattern will prevail. A
mid/upper level ridge from the southern Plains through the Rockies
will give way to lowering heights over the west into early next
week as a strong shortwave moves in from the Pacific this weekend.
As a result, Northwest flow through the Great Lakes with mainly
below normal temperatures will give way to southwest flow next
week bringing a warm front a more widespread precipitation toward
the region.

Thursday night, a reinforcing shortwave trough sliding from the
northern Plains toward the western Great lakes with moderate 700-300
qvector conv along with upper level div from the left exit of the
250-300 jet will support an area of showers moving through Upper
Michigan. Model differences show up in handling the placement of the
higher QPF as the high res models keep the greater amounts farther
south through WI, in line with the better elevated instability.
Nevertheless, showers should affect most of the area with forecast
MUCAPE of 200-400 J/Kg, per NAM, supporting at least some isold TS
chances.

Friday, any lingering showers over the east will depart early.
Otherwise, dry conditions with light northerly winds are expected as
highs climb into the mid 60s.

Friday night, a strong shortwave moving through nrn Ontario will
drag a weak trough or cold front through the northern Great Lakes.
Although the stronger forcing will remain well to the north, some
light rain showers or sprinkles may be possible with the front.

Sat-Sun, a secondary cold front is expected to move through the area
dropping 850 mb temps into the 2C to 4C range. With lake temps in
the 13C-15C, instability will be marginal to support any lake effect
rain given relatively low inversion heights near 5k ft. Surface high
pressure will continue to dominate through Sunday with seasonably
cool air as winds slowly veer to the northeast.

Mon-Wed, A warm front approaching the area by late Monday into
Tuesday should bring widespread rain into the region. There is more
uncertainty with the details regarding sfc low pressure development
and pcpn timing/intensity. Some thunder may also be possibly by
Tuesday as moisture/instability spreads to the northeast. Models
consensus would push the higher pcpn chances east of the area by Wed.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 644 PM EDT WED SEP 4 2019

High pres and a dry air mass settling over the area will result in
VFR conditions prevailing thru the forecast period KIWD/KCMX/KSAW.
Although a disturbance will approach on Thu, VFR conditions will
continue as low levels remain relatively dry. A few shra may move
into western Upper MI during the morning hrs.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 431 PM EDT WED SEP 4 2019

SW winds may gust to 20-25kt this evening from around Isle Royale to
the Keweenaw. Otherwise, winds will be under 20kt thru Thu morning.
Low pres tracking se across MN and WI Thu aftn and Thu night will
result in an increase in NE winds over western Lake Superior Thu
aftn/night. Gusts may reach 20-25kt at times, especially w of the
Bayfield Peninsula toward Duluth/Superior. Winds will be under 20kt
on Fri. Passage of a cold front will then bring increasing NW winds
late Fri night/Sat. Expect the strongest winds over the e half of
the lake where gusts may reach 25-30kt. Winds will diminish for Sun,
but with sfc high pres passing by just n of Lake Superior, E to NE
winds up to 20kt will be possible over far western Lake Superior.
Winds will likely be on the increase Mon/Mon night across Lake
Superior as the high pres departs and low pres emerges over the
Northern Plains.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Rolfson
LONG TERM...JLB
AVIATION...07
MARINE...Rolfson