Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/20/19
See below for an aviation forecast discussion for the 00Z TAFs.
&&
.DISCUSSION...
Issued at 309 PM CDT Mon Aug 19 2019
A weak shortwave passes through parts of the Dakotas this evening.
While a couple showers or thunderstorms may affect the northwestern
CWA tonight off this wave of energy or via daytime heating alone,
confidence has been decreasing that anything will develop. A better
chance for precipitation occurs tonight as a low-level jet sets up
over eastern South Dakota, but even then the best forcing looks to
be mostly south of the CWA. Nevertheless, ensemble PWATS are about
1.25 standard deviations above climatological normals for eastern
South Dakota as southerly winds help draw in low-level moisture. In
addition, very good instability and moderate shear would indicate
that if thunderstorms do develop, they would be able to sustain
themselves and potentially become severe.
High pressure builds into the region Tuesday and looks to keep
things mostly dry through the day Thursday. Thursday night through
the weekend will likely be more active. Models are in pretty good
agreement and suggest a bit more potent shortwave working its way
through the region Thursday night and through the day Friday
followed by a second shortwave Sunday.
High temperatures this week look to be seasonably cool overall
with Tuesday being the warmest day besides this afternoon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 655 PM CDT Mon Aug 19 2019
Probably looking at VFR conditions for the next 6 hours. However,
there is a notably moist airmass advecting northward over the
region right now, and some of it hasn`t mixed out completely.
There could be some 3500 to 5000 ft agl bkn cigs at times through
this evening at any of the four terminals, before cigs begin to
lower. If KMBG sees a thunderstorm this evening, it`s mainly
between 03Z and 05Z. If KATY sees a thunderstorm, it`s mainly
between 09z and 13Z. RAP model guidance still supports sub-VFR
stratus forming, mainly over the KABR/KATY terminals between 06Z
and 12Z, and likely sticking around for a few hours on Tuesday
until dry air advection and daytime heating have a chance to mix
the lower cigs out.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Dorn
DISCUSSION...Telken
AVIATION...Dorn
Area Forecast Discussion
National Weather Service La Crosse WI
1043 PM CDT Mon Aug 19 2019
.SHORT TERM...(Tonight through Tuesday)
Issued at 150 PM CDT Mon Aug 19 2019
Upper level shortwave trough slides east across the northern plains
this evening with the low level jet/850 mb moisture transport nosing
into the shortwave by 09z as it shifts across northern IA.
Convection should take off in earnest as this occurs, and meso
models show just that with rapid development between 06-09z over
northwest IA, dropping southeast into western IL toward 12z. Despite
overnight timing, there looks to be some elevated instability to
work on along with favorable shear, moreso in the 0-3 km layer.
Expect some strong to severe storms across IA overnight. Current
location would keep the bulk of this threat just southwest of the
local forecast area. Certainly a scenario that bears a close watch,
especially for northeast IA.
As the MCS exits southeast, some models (esp RAP) hang an inverted
trough/piece of upper level energy northwest of MCV. In those
scenarios, enough low level saturation also hangs back, providing
ingredients for cont shower/isold storm chances across the south
into the afternoon. Don`t anticipate any strong/severe threat with
any of this activity. Will hold small pops for now.
Another bit of upper level energy looks to slip east/southeast
across northern MN Tue morning, into northern WI by the evening.
Differences in timing between the variety of models...with latest
HRRR about 12 hours quicker on bringing in convection north of I-94
compared to the 12z NAM12. That said, many of the other models only
produce a smattering of showers/storms. Going against the convection
is no/little tap to gulf moisture (focused south with that exiting
MCS), cloud cover across the south from the MCS (how extensive,
thick), and bufkit soundings suggest capping that could/will need to
be overcome (either warming or by the front/shortwave). What does
get going will have some instability to work with - RAP suggests
upwards of 2500 J/kg of SBCAPE over northern WI by 00z Wed and
potentially +30 kts of effective shear. If that manifests, enough
support for some stronger/isold severe storms. A lot of "ifs" though
for Tue afternoon/evening...and confidence is not high at this time
with how it will playout.
.LONG TERM...(Wednesday through Monday)
Issued at 150 PM CDT Mon Aug 19 2019
Models in good agreement with the overall, big picture for the last
half of the week.
Upper level shortwave trough slated to drop southeast across the
great lakes Wed/Wed night. Little saturation to work on though -
most of that will be cleared south/southeast with the Tue system. A
sfc high then progged to build in from the west for Thu/Fri while
the axis of an shortwave ridge a loft treks east across the northern
plains. Should see a dry end to the work week, with temps likely a
few degrees below the late Aug normals.
The ridge quickly shifts east for the weekend, allowing for a
shortwave trough to nudge in from the west. Showers/storm chances
will accompany the trough and its associated sfc front. Should also
see a bump up in temps as winds turn more southerly.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1043 PM CDT Mon Aug 19 2019
Patchy to areas of valley fog are possible at KLSE tonight then
MVFR stratus could impact the TAF sites from mid Tuesday morning
into Tuesday afternoon. Mid to high level clouds blowing off of
thunderstorms over northwest and central Iowa will create
increasing clouds at the TAF sites tonight and should keep the
valley fog from going dense at KLSE. The storms then push
southeast of the region Monday morning and stratus could develop
along moist air pushing north into the area in the wake of the
morning storms. A cold front then approaches the region from the
northwest Tuesday afternoon and storms could develop along it and
impact the TAF sites, especially KLSE, late Tuesday afternoon into
Tuesday evening.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Rieck
LONG TERM....Rieck
AVIATION...Wetenkamp
Area Forecast Discussion
National Weather Service Denver/Boulder CO
901 PM MDT Mon Aug 19 2019
.UPDATE...
Issued at 848 PM MDT Mon Aug 19 2019
The forecast is generally on track. With dew points in the low 70s
across the far northeast corner along with weak upslope flow, fog
will likely develop after around 3am and continue into the mid
morning hours. Therefore, fog was added to the grids over Morgan
County and areas to the north and east. I wouldn`t be surprised if
Denver made it into the upper 90s tomorrow so I bumped the high up
a degree or two.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 237 PM MDT Mon Aug 19 2019
The record high of 97 has been broken with the max at 98 so far.
There is still enough time to add another degree or two the
record. If it reaches 100, that would be the latest for so late in
the year. Generally light winds across the forecast area this
evening. Too much of a mid level cap around 500 mb to produce
thunderstorms, only chance could be over the far northeast corner
with ML 100 CAPE around 1000 j/kg over the far northeast plains at
00z so will add isolated thunderstorms there until around 02z.
Latest HRRR suggests the cap could be broken with the potential
for one or two strong storms between 23-02z. The upper level ridge
will bring another day of hot temperatures to the region on
Tuesday. In the mountains, dry conditions will persist with rh
values in the teens North and Middle Parks. Across the northeast
plains, low level moisture will gradually increase from east to
west as a weak front pushes into the urban corridor and northeast
plains late in the afternoon. The forecast soundings keep much of
the Front Range dry for most of the day with ML 100 mb CAPES
around 200-300 j/kg. The instability will increase dramatically
over the northeast plains with the NAM12 indicating ML 100 mb
CAPES over 4200 j/kg with precipitable water values around 1.35
inches. SPC has the northeast corner under a slight risk, so
strong to severe will be possible after 22z.
.LONG TERM...(Tuesday night through Monday)
Issued at 237 PM MDT Mon Aug 19 2019
The threat for storms will continue through Tuesday evening and
even after midnight. Easterly low level flow behind the cold front
will continue to transport moisture westward. A short wave trough
will be tracking over the ridge and will help produce storms
through the evening hours. Storms will likely survive after
midnight as they slowly track east across the Colorado. Increasing
easterly winds over northeast Colorado may result in enough shear
for severe storms over northeast Colorado. Heavy rain, large
hail, and strong winds will be possible with the storms over the
northeast plains through the evening hours.
Cooler airmass will be over the area Wednesday with highs in the
80s across northeast Colorado. Airmass will be moist with
precipitable water values around an inch across northeast
Colorado. Surface based CAPE climbs to 1200-2200 J/kg. Winds aloft
will be weak, so there is uncertainty if there will be enough
shear for severe storms. Heavy rainfall will be the main threat if
there isn`t enough shear. Because of the weak winds aloft, storms
will be slow moving.
On Thursday and Friday, the upper level ridge will be over the
Southern Rockies. This will result in a westerly flow aloft across
Colorado. A lee side surface trough will act as a dry line. This
is expected to be set up near the foothills on Thursday and keep
the chance for thunderstorms in the forecast for much of northeast
Colorado. The surface trough shifts eastward on Friday, reducing
moisture over the and the chances for thunderstorms.
For the weekend and next Monday, models still having issues
resolving the large scale patterns. The GFS shows the upper level
ridge remaining over the Central Rockies. The ridge retrogrades
over the western U.S. if the ECMWF pans out. Will keep the
forecast mainly dry with temperatures above normal. If the ridge
retrogrades to the west, northwest flow could bring cooler air and
low level moisture to eastern Colorado.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 848 PM MDT Mon Aug 19 2019
VFR conditions will continue through tomorrow. A weak boundary is
pushing through DEN this evening which will turn the winds more
northeasterly with a few stronger gusts possible. Once this
boundary washes out, drainage is expected. Storms will develop to
the east of the airports tomorrow afternoon/evening and may push
an outflow boundary westward to the airports. With flow already
being from the east, the boundary`s affect will probably be to
increase wind speeds.
&&
.FIRE WEATHER...
Issued at 210 PM MDT Mon Aug 19 2019
On Tuesday, fire danger will remain elevated in the high country
especially North and Middle Parks. RH values will drop below 15
percent but only light winds expected. Not as hot over the
northeast plains but will still be in the low to mid 90s. Low
level moisture however will improve from east to west in the
afternoon behind a cold front that will start to push into
forecast area late in the afternoon.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Danielson
SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Danielson
FIRE WEATHER...Cooper
Area Forecast Discussion
National Weather Service Cheyenne WY
1001 PM MDT Mon Aug 19 2019
.UPDATE...
Issued at 916 PM MDT Mon Aug 19 2019
Though pretty dry right now...dewpoints are beginning to increase
in the Panhandle this evening with southeast winds. Td at Alliance
up to 66...Scottsbluff 62 and Sidney 64. Southeasterly winds
continue this evening through Tuesday morning. HRRR and SREF
hinting at low clouds and fog moving in after 09Z. Decided to add
fog to the forecast tonight through 15Z Tuesday.
UPDATE Issued at 803 PM MDT Mon Aug 19 2019
Area observations have been showing a down trend on wind speeds
and a slow uptick in humidity this evening. Went ahead and let the
Red Flag Warnings we had out...expire on time at 8 PM. Updates
have been sent.
&&
.SHORT TERM...(This afternoon through Tuesday night)
Issued at 230 PM MDT Mon Aug 19 2019
A upper level ridge dominated the south-central CONUS with warm
and dry zonal flow aloft. 700mb temperatures in the mid-upper teens
Celsius and gusty downsloping westerly winds pushed the mercury
into the 90s east of the Laramie Range. Cheyenne eclipsed its daily
record high temperature of 92 degrees in 2001 with 95 degrees.
Visible satellite imagery revealed a scattering of cumulus clouds
across much of the Cowboy State. The combination of warm temperatures,
gusty winds and low humidities was creating critical fire weather
conditions across portions of south-central and southeast WY this
afternoon. Dry and mild weather will prevail tonight under partly
cloudy skies.
A cold front poised just north of the Canadian/US border is forecast
to progress southward into western NE and eastern WY plains Tuesday
afternoon, shifting winds into the east. Low level easterly upslope
flow will introduce cooler temperatures, increasing moisture and
instability east of the Laramie Range during the afternoon and
evening. NAM sounding profiles are progging MUCAPEs upwards of
3000-4000 j/kg with bulk shear values of 40-50 kt. The SPC Day2
Outlook includes much of the NE Panhandle in a Slight Risk for
severe thunderstorms, with a Marginal Risk extending west to the
I-25 corridor. The primary hazards will be hail (ping pong ball
size or larger) and damaging downburst winds of 60-70 mph. With
precipitable water values rising to 1.25 inches across the plains
Tuesday evening, will also be concerned with locally heavy rainfall
and minor flooding. Models have been consistent with convection
lasting into the late night hours east of the Laramie Range.
.LONG TERM...(Wednesday through Sunday night)
Issued at 335 AM MDT Mon Aug 19 2019
Showers and thunderstorms will continue Wednesday and possibly
Thursday ahead of a slow-moving Pacific system which will push
east along the Canadian/US border through the middle of the week.
Some stronger storms are possible Wednesday afternoon, but with
the lack of decent 0-6km shear near the upper level ridge axis
any concerns are limited at this time. Once this Pacific system
moves east, drier air will filter into southeast Wyoming and
western Nebraska for next weekend. Extended forecast then becomes
uncertain into the last week of August as some models are hinting
towards the first polar cold front of late summer moving southward
out of Canada and into the northern Great Plains. The GFS and
Canadian both show this cold front moving across the Front Range
and bringing much cooler temperatures. but this feature is still
8 to 10 days out.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 958 PM MDT Mon Aug 19 2019
Wyoming TAFS...VFR. Thunderstorms in the vicinity at Laramie and
Cheyenne after 01Z. Wind gusts to 23 knots from 15Z to 01Z.
Nebraska TAFS...VFR, except for IFR from 09Z to 15Z. Thunderstorms
in the vicinity after 01Z. Wind gusts to 27 knots from 15Z to 01Z.
&&
.FIRE WEATHER...
Issued at 143 PM MDT Mon Aug 19 2019
Elevated to critical fire weather conditions will continue this
afternoon across much of southeast Wyoming due to warm temperatures,
gusty winds and low humidities. A cold front is forecast to move
south across the plains Tuesday and stall along the Front Range
through Thursday. Areas along and east of the Laramie Range can
expect cooler temperatures with scattered showers and thunderstorms
from Tuesday afternoon through Wednesday night. A few strong to
severe thunderstorms will be possible. Areas west of the Laramie
Range can expect mainly dry and warm conditions.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...GCC
SHORT TERM...MAJ
LONG TERM...TJT
AVIATION...RUBIN
FIRE WEATHER...MAJ
Area Forecast Discussion
National Weather Service Dodge City KS
806 PM CDT Mon Aug 19 2019
......
.SHORT TERM...(This afternoon through Tuesday night)
Issued at 1145 AM CDT Mon Aug 19 2019
Remaining stratus is burning off late this morning along the I-70
corridor, leaving behind scattered cirrus and rapidly building
instability in a very moist boundary layer. Widespread dewpoints
in the 60s currently, will only mix out to the upper 50s/lower
60s this afternoon. As SE winds increase to 15-25 mph this
afternoon, convergence along the lee trough/dryline is expected to
allow at least isolated convection to develop across the
western/SW zones this afternoon. With limited forcing, coverage
will not be widespread, and with instability/shear both far less
than impressive, convective expectations through this evening are
rather low. Marginal 5% wind probability from SPC basically west
of US 283 is justified, given inverted-V soundings, a hot boundary
layer, and well-mixed subcloud layers. It won`t take much to get
a downburst wind gust of 50-60 mph, with the area most likely to
see such activity along an Elkhart-Ashland line near the Oklahoma
border, as shown by the latest several HRRR iterations. Any
convection will dissipate rapidly with the loss of daytime
heating, leading to a quiet warm night with an elevated south
breeze near 10 mph. Most locations will hold easily in the lower
70s through Tuesday. With the loss of upslope flow, fog and/or
stratus is not expected to redevelop through Tuesday morning.
The heat will continue on Tuesday, with no change in airmass. Most
locations will end up within a couple degrees of 100. Most of the
daylight hours Tuesday will remain dry courtesy of strong upper
level ridging aloft. That said, both 12z NAM/GFS generate
scattered convective QPF late Tuesday afternoon/Tuesday evening
across SW KS, apparently in response to weak shortwaves embedded
in the anticyclonic circulation aloft. Wind shear will be weak to
non-existent, with convective organization expected to struggle.
Kept inherited 20-40% pop coverage for late Tuesday. Clearly, the
more organized severe wind/hail threat Tuesday PM will remain
focused on the frontal boundary well to the north of SW KS, mainly
in Nebraska.
.LONG TERM...(Wednesday through Monday)
Issued at 217 PM CDT Mon Aug 19 2019
Stationary frontal boundary near the Kansas/Nebraska border early
Wednesday is expected to receive a shove southward into SW KS and
vicinity Wednesday night/early Thursday, in response to a strong
upper trough swinging through the Great Lakes. 12z NAM depicts the
cold front making steady southward progress through SW KS daylight
Wednesday. The addition of the boundary will no doubt increase
shower and thunderstorm coverage across Kansas late Wednesday
through early Thursday, as the boundary acts as a trigger in a
moist unstable airmass. While mesoscale placement/details are
unknown, the NBM pop grids of 50-60% (into the likely category,
which matches 12z MEX guidance) for late Wednesday/early Thursday
were accepted in the grids. Locally heavy rainfall and strong
storms are both possible, per SPC Day 3 marginal 5% wind/hail
probabilities. One or two MCSs are expected in this type of
pattern, but the locations in Kansas that receive them will be
resolved in later forecasts.
Convection will encourage the boundary further southward on
Thursday, and this is the day when most of us have the best chance
of remaining below 90 degrees. If cloud cover can hold north of
the front stalled along the Kansas/Oklahoma border as 12z NAM
suggests, then the going forecast temperatures for Thursday will
be too warm. Northern counties may easily hold in the 70s for some
free air conditioning.
A warming trend through the 90s is expected each afternoon Friday
through Sunday. Rain chances will dwindle over the weekend period,
with most locations remaining dry.
12z ECMWF depicts a strong trough swinging through the northern
and central plains next Monday, a sign that autumn is inevitably
approaching. Strong convection is probable on the frontal
boundary Monday afternoon/evening, followed by much cooler
temperatures Tuesday Aug 27th.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 800 PM CDT Mon Aug 19 2019
Showers and thunderstorms at the beginning of this TAF period were
on a weakening trend and only affecting the LBL terminal through
the 01-02Z time frame. VFR flight category will prevail through
this period. A warmer airmass in place late tonight and early
Tuesday will prevent development of low level stratus and fog.
South to southeast winds will prevail through this period as well
with strongest winds 14 to 17 knots sustained mid to late
afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 74 101 71 93 / 10 10 30 30
GCK 71 100 67 95 / 10 10 30 30
EHA 70 99 68 95 / 10 10 20 20
LBL 71 100 68 96 / 30 10 30 20
HYS 72 98 68 89 / 10 10 40 40
P28 75 102 73 93 / 10 0 30 30
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Turner
LONG TERM...Turner
AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Duluth MN
926 PM CDT Mon Aug 19 2019
.UPDATE...
Issued at 843 PM CDT Mon Aug 19 2019
Due to the Day 1 severe weather outlook over the northwest corner
of the forecast area being upgraded to a slight risk, have added
some severe wording to the forecast. If any severe storms occur,
they will be closer to 2 am at the earliest. Made some other minor
adjustments, especially to cloud cover.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 336 PM CDT Mon Aug 19 2019
A cold front will approach from the north tonight with scattered
showers and storms developing along and ahead of the front,
lingering through the day Tuesday. The cold front then exits from
north to south on Tuesday afternoon leading to clear skies and below
normal temperatures for Tuesday night. Total precipitation amounts
will vary, and not all locations are expected to experience
precipitation. There is a very low chance for a few strong to severe
storms being possible in north-central Minnesota this evening, but
generally storms are not anticipated to be severe.
On the synoptic scale a fairly zonal flow pattern exists across the
Canadian Prairie, the northern Great Plains, and the Upper Midwest.
At low levels a weak cold front is moving south across southern
Manitoba, tracking southeast towards the Northland tonight into
Tuesday. While the area of high pressure behind the front will bring
cool and dry air to the region, along and ahead of the front showers
and storms are expected. Specifically, across the central and
northern Great Plains rich low level moisture is surging northward,
evident even in the visible satellite imagery as stratus advects
across the Missouri River valley in south Dakota. While the
mid/upper level is generally zonal, a weak mid-level impulse will
move across southern Saskatchewan towards North Dakota this evening.
The strong warm air advection combined with the weak approaching
impulse will result in relatively strong broad-scale lift across the
eastern Dakotas, with an elevated mixed layer with steep mid level
lapse rates also advecting into this area. While capping should
prevent any surface-based storms from developing this afternoon,
this evening an increasing low level jet is expected to kick off
scattered to widespread thunderstorms across the eastern Dakotas.
These storms will then track eastward late tonight into early
Tuesday morning, possibly in two clusters - one along the actual
cold front near the international border and another cluster moving
across central Minnesota. These storms could be capable of producing
severe weather given around 2000 j/kg MUCAPE and 40-50 knots of deep-
layer shear, mainly in the form of speed shear. The main threat from
the strongest storms will be large hail given the elevated nature of
the storms, with the best chance for severe storms across north-
central Minnesota.
As storms evolve east-southeastward and the cold front moves from
north to south, showers and storms will linger into Tuesday morning.
It is uncertain if storms will maintain their momentum after moving
out of a better low level wind field on Tuesday morning, but there
will remain both rich low level moisture and probably a decent EML
to support convection if any is ongoing. The most likely scenario is
that storms will fizzle out as they move into northeast Minnesota
Tuesday morning and transition to more showers with embedded thunder
as they get into northwest Wisconsin Tuesday afternoon, but there is
a chance storms can sustain and remain strong, producing lightning
and heavy rain across much of the Northland. This probability is
low, but given the trends observed in both model guidance and
current surface observations, the environment may support storms
lasting well through the morning hours.
On Tuesday afternoon, assuming the morning storms eventually fizzle
out, there may be a second round of showers and storms that develop
ahead of the cold front as it moves from north to south through
northeast Minnesota and into northwest Wisconsin, resulting in
isolated showers/storms through Tuesday afternoon in northwest
Wisconsin. These storms would likely not be severe. Otherwise skiEs
will already begin clearing out of north-central Minnesota by mid
afternoon, clearing out across the rest of the Northland by the late
evening hours. Highs Tuesday will range from the low 70s in north-
central Minnesota to the upper 70s to near 80 in northwest
Wisconsin. Lows Tuesday night in the 40s to low 50s.
.LONG TERM...(Wednesday through Monday)
Issued at 336 PM CDT Mon Aug 19 2019
Quiet conditions will be in place for the first part of the extended
before turning more active for the weekend. High pressure will build
in across the Upper Midwest for Wednesday and Thursday bringing
clear skies and highs in the upper 60s and lower 70s. The high will
then shift to the east on Friday setting up southerly flow across
the Northland. This will bring in some warmer air along with an
increase in moisture ahead of a shortwave trough moving into the
Northern Plains. The ECMWF is much more organized with this trough
with an upper low moving into eastern Saskatchewan and western
Manitoba. Rainfall from this trough is expected to hold off until
Friday night or early Saturday morning, mainly for western areas.
This wave doesn`t look to move across the Northland as the upper
level support weakens and leaves a boundary draped across the
region. This will keep chances for showers and storms in place for
Saturday and Sunday. Models diverge for the weekend with the GFS
keeping zonal flow in place while the ECMWF transitions from
northwest flow to southwest flow. With southwest flow persisting at
the surface, this will keep the flow of moisture in place. Questions
remain this far out as to the mesoscale and thermodynamic features
that will be be in place for the weekend, but there are hints that
some strong or severe storms may be possible at some point,
especially if timing of energy aloft lines up favorably with daytime
heating. Highs for the weekend will be in the 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 716 PM CDT Mon Aug 19 2019
VFR conditions are expected through around 09Z. Clouds will start
to move in from northwest to southeast late tonight as a cold
front moves through Tuesday morning. This will bring showers and
thunderstorms, which will bring terminals to MVFR and possibly IFR
ceilings and visibilities. A brief period of fog is possible at
HIB before clouds move in during the early morning, but it is
possible that clouds could prevent it from forming. Winds are
expected to become northwesterly through the afternoon, but should
remain between 5 and 10 kt. There is a slight concern for some
brief LLWS as the cold front moves through between 12Z to 15Z per
NAM and RAP guidance, mainly at INL and HIB, but confidence is not
high enough to mention it in the TAFs at this time. Clouds will
gradually begin to clear out during the afternoon with most sites
returning to VFR, possibly remaining MVFR for much of the
afternoon at HYR.
&&
.MARINE...
Issued at 926 PM CDT Mon Aug 19 2019
A cold front will move through around midday that will bring
showers and storms along with a wind shift to the northwest at 6
to 12 knots. A few of the storms may be strong, to near severe,
with gusty winds and some hail, heavy rain and frequent lightning.
Northwest winds will then continue on Wednesday at 6 to 12 knots
with a few gusts to around 15 knots. Waves will be 2 feet or less
through the period outside of any thunderstorms.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 61 77 51 72 / 10 60 0 0
INL 57 72 44 68 / 80 90 0 0
BRD 62 78 50 74 / 10 60 0 0
HYR 57 79 50 74 / 0 50 30 0
ASX 59 80 54 74 / 0 40 30 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...GSF
SHORT TERM...JJM
LONG TERM...BJH
AVIATION...JS
MARINE...GSF
Area Forecast Discussion
National Weather Service Des Moines IA
944 PM CDT Mon Aug 19 2019
.UPDATE...
Issued at 942 PM CDT Mon Aug 19 2019
The active night still appears to be on target with little change
from previous thinking. 4-5K j/kg MUCAPEs are present along the
NE/IA border in the projected genesis area with 40-45kts of
effective shear. The only concern may be slightly delayed timing
and onset. 00z soundings and the latest model guidance do not
depict the strongest low level jet with RAP 305K inflow into the
base of the effective layer only 20kts or so. Nevertheless, once
it goes it may go quickly with fresh 00z CAMs all still depicting
a significant wind producing MCS NW-SE starting 06-09z and not
exiting southeast sections until 12z or so. If this caliber of MCS
develops as expected, it will be somewhat rare in magnitude
reflecting the infrequency of overnight Enhanced Risks in IA.
Possibly reminiscent of significant wind events in 2008 or 2010.
&&
.DISCUSSION.../Tonight through Monday/
Issued at 309 PM CDT Mon Aug 19 2019
High pressure remains ridged into central Iowa this afternoon with
return flow beginning to develop into far western Iowa and into
Nebraska and Kansas. The return flow will increase this evening as
the High departs to the east. The low level jet will form and
increase to 35-40kts between 03-06z and will bring a strong push of
theta-e advection into central Iowa. This combined with steepening
mid-level lapse rates will lead to moderate to highly unstable
environment with MUCAPEs exceeded 3500 J/kg. Expect thunderstorms to
develop across portions of northwest to west central Iowa around
midnight then roll southeast down the instability gradient. Severe
weather and heavy rain fall will both be concerns with this activity
overnight. Initial storms will be elevated with a few supercells
capable of large hail possible. The initial cells should congeal
into an MCS and propagate southeast with an attendant damaging wind
threat into central and southeast Iowa. In addition, an isolated
tornado or two may be possible given the amount of low level SRH if
the 0-3 km shear vector can orient correct in time. This would be
contingent on potential for increased mixing ahead of the line can
help erode the low level inversion and allow for low level vortex
stretching. A few areas of wind driven hail may occur given the
maintaining instability and potential for cold pool development.
The potential for heavy rainfall is increasing as the increasing
instability within a moisture rich atmosphere with good warm cloud
depths near 15 kft aiding in the efficient rain process. A rainfall
band of 2 to 4 inches is possible and cannot discount a heavier
localized band in excess of 5 inches. The intense rainfall amounts
will cause significant ponding in urban areas. If a 5 inch band does
develop, the threat may translate to a flash flooding threat given
the rates and amounts.
Warm advection following the the morning MCS will create a
significant elevated mixed layer that will lead to a significant cap
across the state. Convective debris looks like it will eventually
clear out over parts of the state. The biggest challenge will be how
much of the state will recover from the morning outflow. Have the
warmest temperatures over central and western Iowa with high
temperatures approaching 90 degrees and heat index values in the 100
to 105 degree range. Not anticipating any heat headlines at this
point especially considering uncertainties given the recovering.
Have lowered chances for thunderstorms Tuesday afternoon and
evening. A greater threat for storms will late Tuesday night into
Wednesday morning over as storms move east out of Nebraska.
Little change to the remainder of the forecast with cooler
temperatures Thursday through Saturday then a transition to more
westerly flow by Sunday into early next week. This will lead to
seasonal temperatures and a few more chances for precipitation.
&&
.AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/
Issued at 637 PM CDT Mon Aug 19 2019
There is high confidence in VFR conditions into the evening, but
also at least medium confidence that a significant thunderstorm
complex will develop into portions of central IA during the early
morning hours. Have VFR VCTS mention for now, but there will
likely be a period of lower conditions for at least one of the
TAF sites overnight. No mention until timing and location
confidence increases however. Some lingering stratus is possible
after the precip, but confidence is medium to high that VFR
conditions will return by Tue afternoon.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Small
DISCUSSION...Donavon
AVIATION...Small
Area Forecast Discussion
National Weather Service Pueblo CO
255 PM MDT Mon Aug 19 2019
.SHORT TERM...(This evening through Tuesday)
Issued at 245 PM MDT Mon Aug 19 2019
Area of isolated convection developing at mid-afternoon over the far
southeast plains, where weak convergence along a rather diffuse
surface trough was providing some modest lift near the wrn edge of
the moist/unstable air mass near the KS border. Expect these storms
to move into KS by late afternoon as trough drifts east, with HRRR
suggesting all activity will be out of CO by 00z. Suppose there
could be some briefly strong/gusty winds with storms given rather
wide t/td spread, with perhaps a more organized outflow pushing
westward across the plains this evening. Elsewhere across the
region, dry and hot conditions persist, with record high already set
at Pueblo (102f so far), while readings still a have couple more
degf to go to break the the record (94f) at Colorado Springs.
Overnight into Tue, upper level high pressure center remains just to
our south, with weak sly flow bringing a modest influx of mid level
moisture into the region by Tue afternoon. At the surface, pre-
frontal trough turns winds on the plains ely through the day, while
main cold front hangs back in nern CO until sometime Tue evening.
Overall, most of the mountains should see a modest upturn in
convection by Tue afternoon, though with dry low levels precip will
be spotty and light. Activity on the the plains should stay fairly
sparse, with perhaps a few cells along the NM border and up near the
Palmer Divide. Max temps will continue on the unseasonably warm side
Tue afternoon, with readings within a degf or two of Monday`s hot
numbers.
.LONG TERM...(Tuesday night through Monday)
Issued at 245 PM MDT Mon Aug 19 2019
A boundary bringing in somewhat cooler air will arrive at the
beginning of this long term period and bring relatively cooler air
to the region (and a chance of storm) Wednesday and Thursday.
Temperatures will warm up again and it will dry out from late in the
week into Sunday. Cooler weather will likely return for the new
workweek.
An initial boundary will likely be on the Palmer Divide early
Tuesday evening. This may spark a thunderstorm or two along the
divide, otherwise it will remain dry over the region.
Wednesday morning, a 2ndry surge of cooler air will backdoor into
the region from the east and this will cool the plains down 10
degrees or so compared to Tuesdays max temps. With increasing
upslope and a more unstable environment in place, the chance of
showers and storms along the plains/mtns interface will increase,
with a good chance of storms possible during the afternoon and
evening time period. Given sufficient CAPE and marginal shear in
place, a few marginally severe storms will be possible, and SPC has
all of the plains in a marginal risk for severe storms for this day.
Burn scar flooding may also be an issue on this day.
For Thursday, upslope will continue although flow will be a bit more
southerly and flow aloft will be a bit weaker (although still
northwesterly). This should decrease the showers and storms over the
plains this day, with the best chance over the mtns/plains interface
and over the far se plains. Max temps should be a degree or two
cooler than Wednesdays max temps.
For Friday into the weekend, it will dry out area-wide with only
isolated pops expected, and temps will return into the mid 90s/L100s
across the plains. By late in the weekend into early next week
another cool front should move into the region/ although long term
guidance is not in good agreement when this front will move into the
region.
Looking a bit farther out, there is some agreement that a stronger
cold front will move down the plains, and this could knock temps
several degrees below normal by mid week next week. /Hodanish
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 245 PM MDT Mon Aug 19 2019
VFR conditions expected the next 24 hrs at all taf sites with usual
overnight diurnal wind cycle. On Tue, slight increase in convection
expected across the region, though with moisture still rather
shallow, expect most activity to be weak, high based and tied mainly
to the higher terrain.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...PETERSEN
LONG TERM...HODANISH
AVIATION...PETERSEN