Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/14/17
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
900 PM CST Mon Nov 13 2017
Issued at 857 PM CST Mon Nov 13 2017
No major changes planned this evening. Ifr cigs/fog are expected
to gradually develop over the region through the night.
Temperatures look okay for now.
.SHORT TERM...(This Evening through Tuesday Afternoon)
Issued at 228 PM CST Mon Nov 13 2017
Forecast challenges include fog/low stratus potential tonight and
their impacts on temperature.
Currently, except for a small portion of northeast South Dakota into
west central Minnesota where some sct/bkn coverage of low clouds
continues, the region is experiencing full sunshine. Southerly
breezes are occurring over the eastern third of the forecast area
while the western two-thirds of the region are characterized as
light and variable. Temperatures are warming through the 40s and 50s
and in some areas into the low 60s.
The forecast is a dry one tonight and Tuesday. Behind a cold frontal
passage on Tuesday, it`s debatable whether or not an isolated shower
or two may be working its way east-southeastward across the cwa. The
atmosphere is pretty dry to support precipitation. The most note-
worthy aspect of the short term forecast period is the potential for
fog and low stratus to develop. The table is set for excellent
radiational cooling conditions on (at least) the front end of the
tonight period. Ample surface moisture (surface dewpoints at or
above 36F) to start things off this evening when the sun sets at
appx 5 PM CST. Rap soundings in BUFKIT support a fog/low stratus
sounding, particularly for the KABR and KATY areas. It`s entirely
possible that foggy conditions develop/spread as far west as the
Missouri River valley. But confidence in that scenario unfolding is
still a bit low at this point. Higher confidence in fog/stratus
developing over the eastern half of the forecast area.
Numerical/aviation guidance supports fog formation over the Prairie
Coteau and in the James River valley as well. If fog/low stratus
materializes overnight, areal coverage/depth of fog and low stratus
will play a large role in how much temperatures can fall overnight
tonight, as well as how quickly temperatures can recover on Tuesday
(time needed to mix out/dissipate fog and stratus). A couple models
are hinting at temperatures warming the most on Tuesday once the
surface cold frontal passage occurs and better northwesterly mixing
.LONG TERM...(Tuesday Evening through Monday)
Issued at 228 PM CST Mon Nov 13 2017
A cool snap for Wednesday, strong winds Thursday into Friday and
relatively dry conditions are the main highlights of the extended.
Will start with a shortwave crossing the northern plains Tuesday
night. The mid/surface low will have already passes into far western
Ontario, and a weak surface trough will have already crossed the
CWA. Northwest flow and a weak surface ridge will keep us mixed
overnight. The cold push of air that follows is delayed until 09-12Z
with 925mb temperatures falling from a peak of around +6C to a range
of +1 to -5C by mid day from south to north across the state. This
suggest temperatures will stall and possibly fall in the afternoon
for northern parts of the CWA.
Southeast flow develops for Thursday early, becoming more southerly
during the day with warm advection. The gradient increases to around
20mb across the state, with pressure falls of 9 to 12mb in 6 hours.
That strong gradient pushes into Minnesota by the evening but
pressure rises behind a front, along with low level westerly flow
will keep us mixed Thursday night. Breezy conditions will redevelop
for Friday thanks to the westerly component and favorable mixing
conditions, with a shot of Canadian air coming in late in the day.
As for precipitation, blended guidance supports some low chances for
Friday, however the deterministic GFS depicts best forcing splitting
the CWA. BUFKIT shows a warm/dry layer below any mid clouds and
forcing so while I decided it best to maintain blended low POPs/low
QPF, anticipate little moisture reaching the area.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 531 PM CST Mon Nov 13 2017
Ifr cigs/vsbys are expected to gradually form over or move into
the region later tonight, and then linger into mid morning on
Tuesday. The wind will be fairly light through tonight.
Area Forecast Discussion
National Weather Service La Crosse WI
530 PM CST Mon Nov 13 2017
.SHORT TERM...(This evening through Tuesday)
Issued at 312 PM CST Mon Nov 13 2017
At 3 PM, southerly winds were advecting warm air into the
Upper Mississippi River Valley. The coldest temperatures (mid-30s)
were found in north-central Wisconsin (due to snow cover) and
southwest Wisconsin (due to dense fog earlier in the day).
Elsewhere, temperatures ranged from the upper 30s to mid-40s.
The 285K isentropic surface shows that the lift and moisture
transport will increasing as warm air advection develops across
the region. The HRRR, NAM, and RAP soundings show that the low
level moisture will increase into the 1 to 2 km range by late
evening and then continue into Tuesday. As this occurs, drizzle
will develop. This should occur along and west of the Mississippi
River between 8 PM and midnight. Temperatures will initially fall
into the mid-30s and then slowly rise. As a result, not seeing any
threat for any icing threat.
Meanwhile, in central and north-central Wisconsin, the drizzle
will be develop between midnight and 6 AM. Temperatures at this
time will be likely near 30 with dew points in the upper 20s. This
provide up to a 3 hour period in which freezing drizzle may occur
before the temperatures and dew points rise above freezing; thus,
ending the icing threat. The highest potential for any icing will
be in Clark, Jackson, and Taylor counties. Thought about issuing
a Winter Weather Advisory for this freezing drizzle threat, but
the threat is such a short period decided to go with a Special
Weather Statement instead and monitor how things evolve.
Besides the freezing drizzle threat, another potential threat will
be the development of dense fog. With the SREF not hitting this
hard; thus, confidence was not high enough to add it to the
forecast at this time. This will just be another thing that we
will have to monitor tonight.
The final concern for tonight is whether we are too cold with the
low temperatures along and west of the Mississippi River. Dew
points have been slowly increasing to our south this afternoon and
these higher dew points along with LIFR/IFR clouds will be moving
into this area during the evening. This will limit the cooling.
As a result, expect that our low temperatures will occur this
evening and then they will slowly rise through the remainder of
On Tuesday, the drizzle will continue as synoptic lift continues
to produce omega in the saturated low levels of the atmosphere.
.LONG TERM...(Tuesday night through Monday)
Issued at 312 PM CST Mon Nov 13 2017
From late Thursday night into Saturday, the 13.12z models
continue to struggle with evolution of a low pressure system that
will be affecting the Upper Mississippi River Valley. The GFS is
faster with its southern stream short wave; thus, more phasing
occurs. As it result it is the fastest at developing its surface
low, producing more QPF, and bringing cold air into the region.
Meanwhile, the Canadian and ECMWF do not have these two waves
phasing until it is well to our southeast. This result in the
colder air moving into the region slower and lighter QPF.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 530 PM CST Mon Nov 13 2017
Cigs/Vsby/WX: low level saturation continues to increase across the
region, with responding cigs from ifr to lifr. Once these move in,
they should hold through Tue night. Fog is accompanying the lower
cigs - generally MVFR. That said, as the saturation deepens it will
start to touch low level warm air advection/isentropic
upglide...resulting in areas of drizzle. Deeper cloud mass suggests
a change over to mostly rain or a ra/dz mix...but will leave dz for
simplicity for now. Mostly 1-2SM vsbys with the pcpn. This too
should hold across the region into Tue night.
Wind: will stay southerly through tomorrow, taking a turn to the
northwest with a frontal passage late Tue night.
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
703 PM EST Mon Nov 13 2017
Weather throughout the taf period will be influenced by expansive
surface high pressure that is in place from James Bay clear down to
the Gulf coast. The surface ridge axis will slowly push through
southeastern Michigan tonight, setting up over the central and
eastern Great Lakes later Tuesday. Surface ridge will result in very
weak and variable surface winds with little to no tangible
advections. High confidence in clouds holding tonight as a slowly
lowering stratus deck. While some very light haze could be possible
at daybreak with center of surface ridge, not really seeing the
potential for any significant fog late for a couple of reasons. The
first is that plan view perspective of moisture on isentropic
surfaces offers focus that the Nam moisture profile is way overdone
owing from over moist boundary layer scheme. Rap soundings are
vastly different there, much more subsaturated. Two, forecast
soundings remain overwhelmingly mixed just off of the surface with
little support for impactful fog in latest HRRR surface condensation
pressure deficits. Models sounding do support a lowering of the
inversion heights which should cause cig heights to drop MVFR.
Little change tomorrow, expecting stratus.
//DTW THRESHOLD PROBABILITIES...
* High for cig aob 5kft through tonight. Low Tuesday morning.
Issued at 326 PM EST Mon Nov 13 2017
NEAR TERM / TODAY THROUGH TONIGHT
As of 325 PM EST...A dreary and cool, but dry, day continues across
the region, despite high pressure ridging into the region and
currently centered over Illinois. A sharp subsidence inversion around
850 hPa continues to trap boundary layer moisture, leading to the
persistent stratus deck seen throughout the day. Enough daytime
mixing has allowed for a few peaks in sun from time to time, and even
some more substantial clearing across western Michigan over the past
few hours. High temperatures have reached into the lower 40s for
most places, although a few readings in the upper 30s were noted in
Heading into tonight, there continues to remain some doubt as to the
potential degree of cloud clearing, especially after midnight.
Current thinking is that any clearing that does occur late this
afternoon will fill back in with stratus after sunset and loss of
daytime mixing. The degree to which the subsidence inversion erodes
remains in question, as the ridge axis will be directly over
southern areas overnight, with enough drier air potentially pushing
in closer to Saginaw Bay to allow for some eroding of the stratus.
Latest probabilistic guidance supports these observations, which
will play a critical role in fog formation later tonight. Boundary
layer analysis supports more of a low stratus event tonight for most
areas, but have gone with patchy fog in the grids as there will
likely be areas where visibility gets down into the 2-5 SM range. As
of now, the best shot at seeing more substantial fog appears to be
west of US 23 and north of I-69, where dense fog may be a
possibility. Any fog that does form will be a result more of
advection rather than radiation, as low-level warm air advection
begins late tonight and moves over antecedent coldish ground.
Low temperatures will also be dependent on degree of cloud cover,
with upper 20s to lower 30s where stratus persists, but any clearing
towards daybreak could allow lows to dip into the mid 20s. Will need
to monitor fog potential trends closely this evening into tonight.
SHORT TERM / TUESDAY THROUGH WEDNESDAY NIGHT
Dry weather will continue into Tuesday as the surface high exits off
to the east. High temperatures will be a few degrees warmer than
today in the increasing low-level warm air advection regime, with
highs into the mid 40s for most places, and even some upper 40s
possible from the Detroit metro and points south.
Heading into Tuesday night, upper-level shortwave energy will eject
out of the northern Plains, following a similar wavetrain pattern
exhibited over the past several weeks. Modest dip in northern stream
PV looks to enhance the upper-level jet as a cold front approaches
the region. Modest isentropic ascent will preclude the arrival of
the front, with rain showers on the increase primarily across
northwestern areas by early Wednesday morning. Thermal profile is
generally warm enough for all rain at the onset, although cannot
rule out a few wet snowflakes mixing in where low temps (mid to
upper 30s) are closer to the mid 30s and enough evaporational
cooling in the preceding dry midlevels can cool the column enough.
Wednesday will feature the cold front moving across the region, at a
relative quick pace and exiting eastern areas by late Wednesday
evening. A warm front looks to also lift north through the region
placing all areas in the warm sector and for a rain frontal passage.
Rather impressive height fall field will accompany the frontal
passage and help to steepen midlevel lapse rates. Although moisture
will generally be limited with the shower activity (only around a
quarter of an inch anticipated), enough dynamical forcing looks to
be in place coupled with surface temps approaching 50F that a slight
chance of thunder has been added across far southern areas for
elevated thunderstorms Wednesday afternoon.
Good shot of cold air advection will occur behind the frontal
passage, with 850 hPa temps falling to -5 to -8 C after peaking
around 5 C earlier in the day. Another quick-moving impulse will
dive southeastward behind the cold front across northern areas,
helping to spark some additional rain/snow showers mainly across
Lake Huron. Low temperatures Wednesday night will be in the 30s.
LONG TERM / THURSDAY THROUGH SUNDAY
Dry conditions expected Thursday as a ridge of surface high pressure
moves eastward through the Great Lakes. High temperatures look to be
seasonably cool in the low 40s. Return southerly flow and warm air
advection to commence Friday ahead of the next approaching low
pressure system. Moist air and a series of shortwaves moving into
the region will also lead to a chance of showers that will increase
in coverage from scattered Friday morning to widespread in the
The strongest forcing for this system will arrive Saturday as the
low deepens thanks to favorable left exit region of upper jet and
mid level PVA. The low is still progged to pass directly over lower
MI Saturday morning, which will lead to a prolonged period of
precipitation. Looking like an all rain event Saturday as SE
Michigan should stay on the warm side of the low, though snow
showers have the potential to mix in Saturday evening after the cold
front pushes through. The deepening low will lead to gusty
conditions from late Friday through Sunday, and 850 mb temps of near
-10C settling in will make for a cold Sunday with some flurries
lingering over the area. High pressure building in the wake of this
departing system will result in drier and calmer conditions for the
first part of the next work week.
Modest northwest winds will decrease tonight before shifting to
southwesterly Tuesday morning as high pressure slides east of the
region. South winds will then increase to 15 to 20 knots Tuesday
afternoon ahead of a cold front. South winds will further strengthen
to 20 to 30 knots Tuesday night into Wednesday, especially across
the open waters of central Lake Huron where waves will approach 8 to
10 feet. A period of showers will be likely as the cold front pushes
through on Wednesday before winds shift to the west on Wednesday
evening. Moderate northwest winds of 15 to 25 knots will then
develop in the post-frontal environment Wednesday night into
Thursday allowing waves to grow to 6 to 8 feet across southern Lake
Huron on Thursday. This will lead to small craft advisory conditions
for the nearshore waters of Lake Huron on Thursday.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online
Area Forecast Discussion
National Weather Service Shreveport LA
952 PM CST Mon Nov 13 2017
To sky and pop/weather for the overnight hours.
Skies are fair over our East, but increasing clouds West with warm
air lifting North. New guidance is showing some light QPF down
into NE TX around 09-12Z, so we have added pops over this area as
GFS and HRRR both are very similar for the pre-dawn hours. Amounts
will be light and there could be some patchy fog farther North in
parts of Oklahoma. Meanwhile NE winds East under the fair skies
should allow for dew points to fall with no changes to our
overnight low grid needed at this time. /24/
.PREV DISCUSSION... /issued 553 PM CST Mon Nov 13 2017/
Low MVFR cigs persist across the Wrn sections of E TX this
evening, but should see a gradual improvement later this
evening/overnight, although high based MVFR cigs will spread back
NE across much of NE TX/extreme SE OK from N TX after 06Z, before
eventually reaching adjacent sections of SW AR (including TXK)
by/after 12Z Tuesday. Elsewhere, VFR cu cigs will persist tonight
as well over extreme SW AR/Wrn LA/Deep E TX, with elevated AC
cigs likely this evening across Scntrl AR/Ern sections of Ncntrl
LA (including ELD/MLU) before clearing. The higher based MVFR cigs
Tuesday morning across NE TX/SW AR should eventually lift/become
VFR by midday/early afternoon, giving way to VFR conditions
areawide even as the extensive cu field spreads back NE into
Scntrl/Cntrl AR. Should also see an increase in low AC cigs as
well Tuesday with the passage of a weak mid level shortwave, which
may result in isolated -SHRA development late tonight/Tuesday
over portions of extreme NE TX/SE OK/adjacent sections of SW AR,
mainly W of N of the TXK terminal. Given the isolated nature of
any -SHRA, have omitted VCSH mention in the TXK TAF. ENE winds
5kts or less tonight will become ESE around 5kts after 15Z. /15/
PREV DISCUSSION... /issued 407 PM CST Mon Nov 13 2017/
A rich plume of moisture continues to stream over the area around
the northern periphery of an upper level ridge over the Gulf of
California. This stream moisture will remain over the area for the
next few days, so plenty of cloud cover is expected. With
abundant moisture in place, some weak ascent just above the
surface ahead of a shortwave trough moving across the Plains may
be enough to generate some scattered showers along and north of
Interstate 30 overnight tonight and into late Tuesday morning.
Rainfall amounts are expected to remain fairly light with any
activity that does develop. Otherwise, daytime temperatures will
remain on a warming trend as southerly surface flow returns to
On Wednesday, a weak cold front will move into the region, but
will stall near Interstate 20. Large scale forcing will be far
removed to the east of the region. However, some weak isentropic
ascent north of the front should be able to tap into the abundant
deep layer moisture to develop scattered showers north of a line
from Jacksonville to El Dorado. Chances for convection should be
better Wednesday night through much of Thursday as a surface low
in North Central Texas ejects and the old cold front moves back
Attention turns to the strong upper trough moving across the
country Friday and into the weekend. The trough will drive a
strong cold front through the region. The latest models are a bit
slower now bringing the front through during the day Saturday.
However, the GFS is considerably quicker than the Euro. Therefore,
considerable uncertainty exists regarding rain chances. It appears
the best chances for convection will be overnight Friday night and
into the day Saturday, with rain chances ending by 00z Sunday.
While instability remains meager, shear profiles are quite strong
and the upper trough is progged to be very robust. A couple of
severe storms cannot be ruled out. If severe weather develops,
damaging winds and large hail should be the primary threats. Ahead
of the front on Friday, strong southwest winds and compressional
warming will lead to very warm temperatures areawide. Daytime
temperatures on Friday will likely be near or over 80 degrees F
Behind the front, colder and drier air will filter into the
region. Cool nights and moderating temperatures during the day can
be expected for Sunday and into early next week. /09/
.PRELIMINARY POINT TEMPS/POPS...
SHV 51 73 54 73 / 10 10 10 10
MLU 45 70 48 71 / 0 0 10 10
DEQ 50 64 53 66 / 20 20 10 30
TXK 49 66 53 69 / 10 10 10 20
ELD 44 67 49 68 / 0 0 10 10
TYR 55 72 57 73 / 10 10 10 10
GGG 53 73 55 75 / 10 10 10 10
LFK 55 76 56 77 / 10 10 10 10