Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/16/17
Area Forecast Discussion
National Weather Service La Crosse WI
925 PM CDT Tue Aug 15 2017
.UPDATE...
Issued at 925 PM CDT Tue Aug 15 2017
Low-level warm front at around 850mb lies through swrn MN and
into eastern IA this evening with a well- defined moisture
gradient /3C to 10C dewpoint over a couple counties/. This area is
mildly frontogenetic and evolving northeast tonight. Moisture
transport convergence enhances and shifts through mainly the
northwest part of the forecast area from 09-15Z on the 305K
isentropic surface per the latest RAP model guidance. Have
tailored the rain chances as such with an axis lifting northeast
through the area during that time, with the highest /50-60%/
chances KAUM-KEAU. Rain chances diminish southeastward. Before 09Z
as evolution begins, some weak forcing may cause an isolated
SHRA/TSRA.
Generic storms are possible with this push as 0-3km MUCAPE begins
to climb as well with aforementioned dewpoint increase with warm
front.
Have also done some work with rain chances Wednesday. Seems that
after the morning warm front moves through, a break will occur
around mid-day with rain chances increasing, as the afternoon
progresses, from west to east. Tough call on skies tommorrow but
would think some sun is quite possible.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 233 PM CDT Tue Aug 15 2017
Water vapor satellite this afternoon shows a long wave trough over
the Rockies with downstream ridging over the Midwest. This ridging
will get pushed east of the area tonight and Wednesday morning as
the long wave trough moves out of the Rockies. The 15.12Z models
continue to suggest there will be several short wave troughs
embedded in the long wave trough and they have also trended slower
bringing the whole system into and across the region. The first
short wave trough to impact the area looks to come across the area
late tonight into early Wednesday morning. This wave will only
produce some weak pv advection but may also come in as the leading
edge of the low level moisture transport and warm air advection
starts spreading over the area. This may lead to some showers and
a few storms over the western portions of the forecast area from
overnight into early Wednesday morning. Once this wave moves past
the area, all the forcing then shifts back to the main long wave
trough which will still be well west of the area. With this slower
arrival of the main forcing, dropped the rain chances back into
the 40 to 50 percent range across the west for late Wednesday
morning into the early afternoon and also slowed the arrival of
the rain chances across the east until the afternoon.
The main short wave trough will then swing across the area
Wednesday night followed by a secondary short wave trough for
Thursday when the long wave trough will also move across the
region. As these waves move across, they should produce periods of
weak to moderate pv advection in the 500 to 300 mb layer. The low
level moisture transport will continue to slowly increase and
looks to be at a maximum Wednesday afternoon but will be focused
to the north of the area ahead of the main short wave trough. This
will then start to diminish Wednesday night as it moves off to the
east with the short wave trough. The isentropic up glide looks to
be fairly continuous Wednesday and Wednesday night and should
average 1 to 4 ubar/s on the 305K surface. As the forcing starts
to increase, will spread 60 to 80 percent rain chances from west
to east across the area Wednesday afternoon and evening and then
start to diminish these from west to east during the overnight
Wednesday into Thursday.
With the slower arrival of the system, this will give the
opportunity for more CAPE to build across the area Wednesday, if
there can be adequate breaks in the cloud cover. The GFS now
suggest a gradient of 500 to 1500 J/Kg of ML CAPE from about
Interstate 94 into northeast Iowa. The other severe parameters
really have not changed much with very weak deep layer shear and
25 to maybe 30 knots in the 0-3 km layer. This could be enough for
a few strong storms, but not expecting much severe weather. Still
looking for the possibility of some locally heavy rains as well.
Warm cloud depths look to be in the 3.5 to 4 km range with
precipitable waters approaching 2 inches. Flooding concerns remain
low thanks to the recent stretch of dry conditions and most
counties having 6 hour flash flood guidance in the 3.5 to 4 inch
range.
.LONG TERM...(Friday through Tuesday)
Issued at 233 PM CDT Tue Aug 15 2017
Northwest flow will set up over the Upper Midwest behind the mid
week system. The 15.12Z ECMWF and GFS have come into better
agreement that a short wave trough will move across the region in
this pattern for Friday afternoon and night. Still some
differences in the strength of this wave but enough there to go
with up to a 50 percent chance of rain for parts of the area
Friday night. Behind this system, a upper level low looks to form
across central Canada with nearly zonal flow over the Upper
Midwest. As of now, there is the suggestion of a weak short wave
trough moving across the region with a cold front and some rain
chances for early next week. Presently, this timing would
interfere locally with the ability to view the eclipse.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 715 PM CDT Tue Aug 15 2017
The main aviation concern this period will revolve around
SHRA/TSRA chances and associated cloud decks. At 00Z, a cluster of
showers and storms was moving east-northeast across northern
Iowa. This activity is expected to dissipate and not affect either
TAF site. Later tonight into Wednesday, a low pressure system
will bring 2 rounds of showers and storms to the region. The first
round is expected along a warm front moving through around
11-16Z. During this time period, ceilings may drop to MVFR levels,
especially at RST. Skies are expected to remain mostly cloudy
throughout the day, but ceilings should improve from late morning
through mid afternoon. Another round of showers and storms is
expected to approach the TAF sites around 17.00Z. Winds are
forecast to remain east-southeasterly around 5-10 kt through the
period, but may become gusty at RST Wednesday afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
UPDATE...Baumgardt
SHORT TERM...04
LONG TERM...04
AVIATION...Hollan/Baumgardt
Area Forecast Discussion
National Weather Service Caribou ME
1039 PM EDT Tue Aug 15 2017
.SYNOPSIS...
A cold front will cross the region tonight. High pressure and
drier air will follow for Wednesday. The dry weather will
continue into Thursday.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
1015 PM Update...
Added the mention of heavy rainfall as the latest RAP soundings
showed potential for heavy rain as storms will align w/the
steering flow from the sw. Added enhanced wording into the
Bangor region as well for winds and heavy rainfall as ML CAPE of
500 joules nosing into the region w/PWATS 1.25 to 1.3 inches.
Radar estimated some areas on north-central Aroostook County
receiving up to 2 inches per hour
Radar showed area of showers and tstms pushing e extending Van
Buren down into Bangor. Some storms across north-central
Aroostook County showed signs of rotation as initial line had
signs of a QLCS look to it. Activity will be ending by midnight
as the cold front pushes e. Cooler air will arrive behind the
front by early Wednesday morning. Hrly temps/dewpoints needed
adjustments as rain has cooled airmass down. Also added patchy
fog through early Wednesday morning.
Previous Discussion...
Cold front currently to our northwest across Quebec province.
The front will continue to move toward the region this evening
with showers and scattered thunderstorms expected in advance of
the front. The best chances for storms remain across northern
and western sections of the forecast area. Still couldn`t rule
out the potential for a gusty storm through late afternoon. Will
continue to reference enhanced wording for small hail and gusty
winds through sunset. Latest SPC meso analysis showing decent
shear in the 0-6 km layer, however, very little in the way of
surface based CAPE as of late this afternoon. Any lingering
showers and thunderstorms will wind down quickly this evening
with the passage of the front. Patchy fog will once again be
possible until the passage of the front with areas of fog along
the coast. Lows tonight wil range from the low 50s across the
north and upper 50s to near 60s downeast.
Much drier air will follow the passage of the cold front
Wednesday with gusty northwest winds and cooler temperatures.
Dew point temperatures will fall into the mid to upper 40s
across the north and low to mid 50s downeast. Expect partly to
mostly sunny skies north and mostly sunny skies downeast. Highs
will range from the upper 60s to near 70 degrees north and mid
70s to near 80 downeast.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Strong, cold upper level low pressure will pass to our
north/northeast Wednesday night and Thursday. This will lead to
breezy conditions with the breeze out of the west/northwest, and
a dry crisp airmass. Skies will be mostly clear Wednesday night
and Thursday, except partly cloudy at times over the north
closer to the upper low.
High pressure moves overhead Thursday night with cool
temperatures. The high moves east Friday and clouds begin to
increase ahead of the next system. Chance of rain Bar Harbor,
Bangor, Moosehead regions late Friday, but most of the rain
should hold off until Friday night.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Rain event Friday night perhaps into early Saturday with a warm
front moving through. Looks like more of a regular steady rain
than a showery or stormy situation. Best shot at rain appears to
be over Downeast at this time. Models coming into better
agreement on the system, though model agreement still isn`t
great. Tough call on Saturday daytime as to whether the system
will have pushed off to the east or if it will be lingering.
Some showers or possibly storms Sunday afternoon, then dry and
warm Monday through Tuesday. Next potential system around
Wednesday.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
NEAR TERM: VFR conditions this evening will give way to MVFR at
times in showers and scattered thunderstorms, mainly northern
terminals. Expect VFR early to give way to IFR/LIFR in low
clouds and areas of fog, especially KBHB. Conditions improving
conditions on Wednesday with VFR expected along with Northwest
winds gusting to 25 kt at times.
SHORT TERM: Mainly VFR Wednesday night through Friday. Can`t
rule out occasional MVFR ceilings far Northern Maine Wednesday
night and Thursday. Widespread IFR likely Friday night into
early Saturday with a warm front.
&&
.MARINE...
NEAR TERM: Winds/seas will remain below small craft advisory
levels through Wednesday. Areas of fog will once again lower
visibility to 1 nm or less at times tonight, then improve with
the passage of the front early Wednesday.
SHORT TERM: Wednesday night, long period swell arrives from
Hurricane Gert. Doesn`t appear to be too significant and
shouldn`t be enough to need any high surf advisory. It does
appear to lead to small craft level wave heights a bit above
five feet Wednesday night into Thursday. Wind gusts to 25 kt are
also possible on Thursday (not associated with Gert).
Conditions improving Thursday night into Friday, then conditions
close to small craft possible Saturday with the next weather
system.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...Hewitt
Area Forecast Discussion
National Weather Service Cheyenne WY
739 PM MDT Tue Aug 15 2017
.UPDATE...
Issued at 737 PM MDT Tue Aug 15 2017
Upon coordination with the Storm Prediction Center, we have
cancelled the Severe Thunderstorm Watch for portions of the
Nebraska Panhandle. Strongest storms have moved east of the
panhandle, with scattered showers and isolated thunderstorms
anticipated the rest of this evening.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 250 PM MDT Tue Aug 15 2017
Shortwave trough currently across southeast Utah is fcsted to swing
northeastward through the evening. Large scale ascent and
associated cooling/destabilization aloft is causing scattered to
numerous showers and storms to develop across southeast WY. With
good bulk shear (30-40 kts) and CAPE of 500-1000 J/kg, a few of the
storms could be stronger with small hail across southeast WY. Still
think that the best chance of more severe storms will be over the
southern Nebraska Panhandle in areas along I-80. This is where
instability is greatest (SBCAPE of 2000-2500 J/kg) and any discrete
storm would have the potential of producing large hail. The HRRR
has been consistent at showing widespread rain with embedded tstms
across areas much of the plains through the evening so have PoPs of
50-60 through 06Z. The strong/severe storm threat will mostly
diminish by mid evening as the activity becomes more less discrete
and more multicell.
Precip chances will diminish after 06Z as the best large scale
ascent ahead of the shortwave moves eastward into central Nebraska.
Overnight fropa will usher in cooler temps for Wednesday with highs
dropping into the 70s over lower elevations. The cool and stable
post frontal airmass will keep storm chances minimal over much of
the CWA. Warming will occur on Thursday with dry westerly boundary
layer flow across southeast WY. An isolated storm may develop in
the better instability to the east of the sfc trough across the
Panhandle.
.LONG TERM...(Thursday night through Tuesday)
Issued at 250 PM MDT Tue Aug 15 2017
Drier conditions are anticipated this weekend as the upper level
flow turns to the northwest behind a departing shortwave across
the northern Plains. This will allow for a nice warmup with
afternoon highs starting to climb into the 80s both Saturday and
Sunday. The upper level flow is progged to turn more to the
southwest early next week which will help draw some more moisture
into the area. This will make things tricky on precipitation and
cloud cover chances especially on Monday.
&&
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1200 PM MDT Tue Aug 15 2017
The main concern with this forecast package will be the timing of
the convection this afternoon.
Latest visible imagery was showing convection already developing
along the Laramie Range/Snowy Ranges, and between Rock Springs and
Wamsutter. This convection is progged to continue developing during
the course of the afternoon and move east-northeast at speeds at 15
to 20 kts. However, some of the stronger stronger storms may move in
a more easterly fashion. This convection should begin to affect the
CYS/LAR/RWL TAF sites between 20-23z. The Nebraska TAF sites may see
some stronger convection, but the convection will probably be mainly
after 22Z. We will have to keep an eye on how things evolve today
and make adjustments as necessary. Most of the convection should
clear out by around sunset.
&&
.FIRE WEATHER...
Issued at 250 PM MDT Tue Aug 15 2017
Minimal fire weather concerns through Friday. We expect good chances
for showers and thunderstorms through this evening. Some of the
storms will produce brief heavy rain and wetting rains. A warming
and drying trend will occur Thursday into this weekend. Afternoon
humidities could drop down to 15-20 percent across portions of
southeast Wyoming by this weekend.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...RUBIN
SHORT TERM...ZF
LONG TERM...REC
AVIATION...REC
FIRE WEATHER...ZF
Area Forecast Discussion
National Weather Service Duluth MN
1008 PM CDT Tue Aug 15 2017
.UPDATE...
Issued at 1008 PM CDT Tue Aug 15 2017
Latest short term hires models continue to slow down the onset of
precipitation over the forecast area. This includes the HRRR and
RAP. 00Z NAM12 has arrived and is on board with the slower onset.
Have adjusted pops/weather for the rest of tonight as well as
tomorrow morning to reflect this approach.
UPDATE Issued at 651 PM CDT Tue Aug 15 2017
Some very light rain showers have moved into Cass county.
Meanwhile, some showers have developed from near Cook to northwest
of Ely. Have updated pops/weather to account for this activity.
Rest of the forecast on track.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 314 PM CDT Tue Aug 15 2017
High pressure over the western Great Lakes region will shift to the
eastern Great Lakes into the northeastern United States and eastern
Ontario by Wednesday afternoon. Meanwhile, low pressure over the
Central and Northern High Plains will shift east into western
Minnesota Wednesday afternoon. This area of low pressure will bring
an influx of deep moisture in from the west, with precipitable water
values increasing to 1.5 to 1.75" by Wednesday afternoon. An
approaching upper-level trough from the west, as well as multiple
shortwaves embedded in the southwest flow aloft, will bring
moderate large-scale forcing for ascent across the Northern Plains
into the western Great Lakes. This forcing will develop showers and
thunderstorms and moderate, to at times heavy, rain across the
Northland. The showers and storms will spread in from the west late
tonight and Wednesday. It should take some time to saturate the
drier low levels, because of the easterly flow, so prefer model
solutions slower to bringing in the rain into the Northland, such as
the GFS and NAM. There is also considerable model disagreement on
the track and timing of the heaviest areas of rain. Think this is
because there may be too many shortwaves, and not a dominate one, so
the models have significant differences in the track of the main
surface low. Any thunderstorms should be relatively weak because of
a lack of CAPE. The thunderstorms should just produce heavier rates
of rain and some thunder.
There will be somewhat light winds and high low-level saturation
late tonight, as well as increasing mid/upper-level cloud cover from
the approaching low pressure from the west. Think the overall
potential for fog is fairly low, especially because of the cloud
cover, which will weaken radiational cooling processes. However, 5
to 10 mph easterly and very humid flow from Lake Superior could help
produce fog along the higher terrain of the Twin Ports area. The
expected increasing cloud cover aloft, though, is leading to me
believe this will more likely just be low-level stratus rather than
fog, because of the weaker radiational cooling to help lower that
stratus to the ground-level. Meaning, I kept fog out of the Twin
Ports area, but the evening shift can reevaluate. Lows should range
from the lower 50s in the Arrowhead to the middle and upper 50s
across much of the rest of the forecast area. The cloud cover and
rain will limit heating Wednesday. Highs should only be in the lower
60s across northern Minnesota, to the upper 60s to around 70 degrees
from central Minnesota into northwest Wisconsin.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 314 PM CDT Tue Aug 15 2017
The low pressure system is forecast to deepen Wednesday night as
it lifts northeast. Model consensus is for the low center to
track through southeast Minnesota into western Wisconsin by 12Z
Thursday, continuing northeast during the day and exiting Thursday
night. Plenty of moisture will be present with this system with
PWAT values from 1.5 to around 1.7 inches, well above normal for
this time of year. There remains differences in the track of the
low but despite those differences confidence remains high that
much of the Northland will receive significant rainfall from this
system. Amounts across far eastern Minnesota into northwest
Wisconsin will be from 1 to 2.5 inches with some higher amounts
likely. Several of the models show smaller areas with amounts of 3
to 4 inches but picking that area out at this time is still too
difficult. Although flash flood guidance is still fairly high over
much of the Northland, flooding will be a concern especially if
those higher rainfall amounts occur along the North Shore and
northwest Wisconsin.
The rain will end Thursday night but any drying will be short
lived as a shortwave moves through the area causing a chance for
showers and a few thunderstorms Friday into Friday night. We have
a dry forecast Saturday then have chances for more showers/storms
Sunday afternoon into early next week over parts of the
Northland.
Highs will be below normal Thursday but moderate to and then above
normal Friday into Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 630 PM CDT Tue Aug 15 2017
VFR at the start of the forecast with high pressure nearby.
Ceilings will trend into the MVFR range after 13Z as the
elongated area of low pressure moves to the Dakotas/MN border by
18Z. Showers will be in the vicinity of BRD by 07Z and INL by 15Z.
Look for the showers to overspread the terminals through the
morning and lasting through the end of the forecast as the low
pressure creeps closer to the terminals. The exception will be at
HYR which will escape the steady rain through the forecast. The
ceilings will drop into the IFR range by 16Z at BRD and 21Z at INL
with moderate rainfall.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 56 65 58 67 / 10 80 90 70
INL 58 63 56 73 / 10 90 60 30
BRD 61 70 60 74 / 30 80 70 20
HYR 58 72 62 67 / 10 50 90 70
ASX 55 71 61 66 / 0 40 90 70
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
UPDATE...GSF
SHORT TERM...Melde/Grochocinski
LONG TERM...Melde
AVIATION...GSF
Area Forecast Discussion
National Weather Service Des Moines IA
705 PM CDT Tue Aug 15 2017
.UPDATE...
Issued at 705 PM CDT Tue Aug 15 2017
Have updated the forecast to reflect the latest HRRR for
pops/storm chances tonight. Will have to monitor the eastward
progression of the line of storms moving through western IA, but
otherwise trends suggest it should begin to diminish on the
eastern edge as it continues to move ESE dying out across the
western portion of the forecast area. Otherwise much of the
south/southeast should remain dry for the remainder of the night.
&&
.SHORT TERM.../Tonight through Wednesday/
Issued at 336 PM CDT Tue Aug 15 2017
Convection over the southeast will be departing prior to 02z.
Newly developing convection over the northwest will continue to
increase this evening with the approaching short wave and zone of
warm air advection over that area. Models continue to have a
difficult time handling the northwest area of convection...though
there is a vague consensus of the area developing north/northeast
through the late evening/overnight while the main trough continues
to increase from the west. Temperatures did not recover fully
over most of the area today due to the persistent cloud
cover...though lows will manage to remain about the same as the
previous forecast due to clouds. The southwest has cleared off for
now...but should see more clouds late into the early morning.
There remains some consensus for increasing PoP/thunderstorms
during the 12z-15z timeframe...though some of the CAMS members and
NAM continue dry until mid to late morning. For now will increase
PoP to chance through 12z and gradually to likely over the
northwest/west during the morning. Confidence is somewhat low
tomorrow morning...but afternoon as the entire trough slides east
the likelihood of showers/thunderstorms will be higher...and PoPs
remain in the likely/definite category. Once again locally heavy
downpours will be possible as PWATs will increase to 1.75 to 2
inches Wednesday afternoon. Have also trimmed highs for Wednesday
across most of the area with the exception of the southeast where
afternoon highs may still make it into the mid 80s. Though
instability will not be excessive tomorrow...there is a potential
for an isolated severe storm with wind being the main concerns.
.LONG TERM.../Wednesday night through Tuesday/
Issued at 336 PM CDT Tue Aug 15 2017
Surface cold front tied to the aforementioned trough will move
across central Iowa Wednesday night with showers and storms
preceding the front. Forecast soundings show precipitable water
(PWAT) values will be well above normal between 1.75 and just over
2 inches across the area with deep warm cloud depths. As the
front moves through, drier air will follow behind with most of the
rainfall ending from west to east by sunrise Thursday as forecast
soundings show dry air in the middle and upper levels of the
atmosphere. As surface high pressure slides eastward over the
Plains, skies will become mostly sunny for Thursday with highs a
few degrees either side of 80.
By Friday, winds from the northwest will turn and blow from the
southwest as a shortwave trough drops out of central Canada through
the Dakotas toward Iowa. This will allow moisture to return back to
the state with PWATs rising from under an inch to around 1.5 inches.
This should allow for some showers and isolated storms to form and
move through later Friday into early Saturday. As the shortwave
exits the area on Saturday, very weak ridging will arrive overhead.
Kept PoPs mainly out of the area until late Sunday when moisture
will begin to move northward as a front approaches from the
northwest. This front looks to be a slow mover as the the
forcing/parent low will be over Canada. Sensible weatherwise, this
means that a mixture of clouds and sunshine with intermittent shower
and storm chances will be possible through early next week. Bottom
line for Monday`s eclipse, it`s still too early to tell one way or
the other on sky cover as timing of the front may change between now
and then.
&&
.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 705 PM CDT Tue Aug 15 2017
Area of showers/isolated storms may impact KFOD and KMCW through
the evening, with expectations of the activity across western IA
to die off before it would impact KDSM. Some fog possible again
late tonight with low CIGS possible too, could see IFR VSBYS/CIGS.
Otherwise should dry out during the morning hours Wednesday, with
storms developing and possibly impacting KFOD and KDSM by late
Wednesday afternoon.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
UPDATE...Beerends
SHORT TERM...REV
LONG TERM...Ansorge
AVIATION...Beerends
Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
756 PM CDT Tue Aug 15 2017
.UPDATE...
The passage of a mid to upper level short-wave over the Trans-Pecos
area has aided showers and thunderstorms to develop across the
western part of Val Verde county late this afternoon into the early
evening. Latest Doppler radar and satellite images indicate storms
moving to the northeast 20 to 25 mph. Also, these images reveal
that storms are decaying with the loss of daytime heating but
expected to linger around for the next several hours. Based on this
assessment, updated the weather grids out west including parts of
the southern Edwards Plateau which includes isolated showers and
thunderstorms through midnight tonight. Kept isolated showers
overnight over same area as latest HRRR model solution shows isolated
activity.
&&
.PREV DISCUSSION... /ISSUED 636 PM CDT Tue Aug 15 2017/
AVIATION...
SHRA/TSRA continue from West Central Texas to the Serranias del
Burro. Have introduced VCSH to KDRT TAF 01z-05z and will monitor for
prevailing TSRA impacts, including gusty winds. SHRA/TSRA will wane
after sunset with loss of heating, then redevelop over these western
areas on Wednesday as moisture axis and weak shear axis remains
there. Will monitor radar and model trends for later impacts to KDRT.
No impacts are expected at KAUS, KSAT, KSSF other than cirrus clouds.
VFR skies this evening. Stratus with mainly MVFR CIGs develops
overnight into morning. Stratus then lifts to VFR FEW cumulus late
morning and prevails through evening. S to SE winds 10 to 20 KTs with
gusts to 25 KTs this evening and again midday to evening Wednesday,
otherwise, 5 to 12 KTs are expected. Wind gusts to 40 KTs are
possible with the stronger TSRA.
PREV DISCUSSION... /ISSUED 312 PM CDT Tue Aug 15 2017/
SHORT TERM (Tonight through Wednesday Night)...
The early morning upper air observations show an upper trough in place
over the western U.S. with the subtropical high centered over south
Florida. A little closer to home, satellite data also shows an axis
of higher moisture in place from southwest Texas into far north
central Texas. Precipitable water values range from 1.7 to near 2.0
inches according to early afternoon data.
The above mentioned axis of higher moisture will move very little
tonight and Wednesday. This will result in a continued chance for
showers and thunderstorms across the southern Edwards Plateau. Hi-res
models show most convection will remain northwest of a Del Rio to
Rocksprings line. Coverage of showers and storms should be rather
low, so we will keep chances in the 20-30% range. We could also see
a few showers and storms develop Wednesday afternoon across the
coastal plains and Highway 77 corridor and will continue to mention
low chances (20%) in the latest forecast. Otherwise, expect another
mild night with increasing cloud cover after midnight and lows in the
70s. Another hot day is in store for Wednesday as highs once again
top out in the mid 90s to near 100. The heat combined with a
continued moist southeasterly flow in the low-levels will result in
elevated heat index values Wednesday afternoon and early evening. As
of now, it appears areas along and east of I-35 will be very close to
needing a Heat Advisory.
LONG TERM (Thursday through Tuesday)...
The forecast for the remainder of the work week into early next week
will generally be dominated by a slowly expanding subtropical ridge
axis. However, the medium range models do show some inverted
mid/upper troughs moving through the Gulf of Mexico over the next
several days. One trough is currently forecast to move into the
western Gulf by early Thursday, with another scheduled for early
Monday. The second system appears to be stronger, but there is some
disagreement with regards to where this system will move inland.
While these inverted troughs may bring a brief opportunity for
rainfall, suspect chances will remain confined to the coast.
Otherwise, it appears high temperatures will continue to remain
roughly 3-5 degrees above normal, with overnight lows a few degrees
above normal. During this period of above normal temperatures, please
continue to exercise proper heat safety.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 79 100 78 101 77 / - 0 - - -
Austin Bergstrom Intl Airport 78 99 77 100 76 / - - - - -
New Braunfels Muni Airport 76 99 77 101 75 / 0 - - - -
Burnet Muni Airport 75 96 75 97 74 / - 0 - - -
Del Rio Intl Airport 79 100 80 102 78 / 20 10 10 10 -
Georgetown Muni Airport 77 97 77 98 76 / - 0 - - -
Hondo Muni Airport 76 101 76 103 75 / - - 10 10 -
San Marcos Muni Airport 77 99 77 100 75 / - - - - -
La Grange - Fayette Regional 79 98 78 100 76 / - 10 - 10 -
San Antonio Intl Airport 78 98 78 101 77 / 0 - - 10 -
Stinson Muni Airport 77 99 78 100 77 / 0 - - 10 -
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...04
Synoptic/Grids...17
Public Service/Data Collection...Treadway
Area Forecast Discussion
National Weather Service Glasgow MT
900 PM MDT Tue Aug 15 2017
.SHORT TERM...for northeast Montana...tonight through Thu...
Main challenge tonight will be a slight return flow from the east
or southeast that will bring some moisture back into the area. The
HRRR seems to capitalize on it and hints at some low clouds and/or
fog in the central zones. The other models are keeping things
status quo with clear skies and fog just near the North Dakota
border from Richland County north. Raised Max RH for the central
zones for now, added patchy fog wording to areas near ND border
and left rest of elements alone. TFJ
Previous discussion...
A few thunderstorms beginning to develop this afternoon on the
edge of the moisture pool left from the morning fog in the
northeast. Expect some isolated storms to work east through the
remaining daylight hours but not amount to much.
Upper trof over southern Alberta/Saskatchewan will move east
overnight with weak surface high pressure and upper westerly flow
spreading into eastern Montana. Expect dry conditions and warmer
temperatures for Wednesday. Ebert
.LONG TERM...Thu night through Tue...
The extended period remains on track as described below. Two
periods of interest exist through the long range with an initial
cold front on Thursday. Most places will be dry though an isolated
afternoon thunderstorm is possible near the Montana/North Dakota
border.
A warming trend in temperatures will then persist into Saturday
ahead of the next front. Temperatures were trended a couple of
degrees higher for Saturday afternoon compared with 12Z consensus
model blends to account for potential pre-frontal compressional
warming. This should be true in particular for the Yellowstone
River Valley locations where the front will arrive later. Highs in
the 90s and low RHs along with winds shifting NW may create
elevated fire conditions at this time. Maliawco
Previous Long Term Discussion...
A shortwave trough moves through the area Thursday Night with
limited moisture that will already be east of the forecast area.
Surface high builds into the area on Friday with dry weather and
temperatures near normal.
Upper ridge moves into the area Friday Night. A thermal ridge
follows Saturday as the ridge moves to the east which will allow
temperatures to warm to near 90 degrees ahead of a cold front.
An upper level trough moves across the Canadian Prairies on
Saturday which will bring a cold front through Northeast Montana
Saturday afternoon or evening. The cold front is expected to be
dry with RH in the teens, fire weather may become a concern if NW
winds are strong enough behind the cold front.
Surface high will bring dry and cooler weather on Sunday. Models
are now pointing towards an upper ridge building over the area
early next week with dry weather continuing. Forrester
&&
.AVIATION...
Generally VFR conditions are expected through the TAF period.
Exception may be with some possible IFR/LIFR conditions in fog
and/or low clouds later tonight through early Wednesday morning
for KSDY, but will keep a close eye on things if it spreads
elsewhere.
BMickelson
&&
.GLASGOW WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
weather.gov/glasgow
Area Forecast Discussion
National Weather Service Hastings NE
636 PM CDT Tue Aug 15 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 326 PM CDT Tue Aug 15 2017
This has been a tricky forecast today. The mesoscale features will
impact thunderstorm evolution tonight. An outflow boundary kicked
out from thunderstorms overnight pushed south and reinforced the
boundary near the KS/NE border. Due to this, the boundary was
slower to retreat back to the north this afternoon. Around 3pm the
boundary has pushed north of Kearney and Grand Island, NE.
The short-term high-resolutions have struggled to grasp the slow
down of the boundary retreating back to the north and how this
will impact later convective evolution. The convection that has
developed just west of the area early this afternoon is expected
to stay just out of the forecast area. The trend this afternoon
with the HRRR and the 12z NAMnest is that convection will develop
along the main front further west and be slower to reach
central/south central Nebraska. Do not have a clear idea of how
this mesoscale boundary will impact thunderstorm development, but
am not surprised as of 3pm that some activity has developed along
it.
All of this being said, am still expecting the main front to push
eastward as the upper low lifts out and for this to be the main
focus for widespread convection into the evening and overnight
hours. Did slow down the eastward progression of the precipitation some
this evening into the overnight hours.
As has already occurred, any of this activity this afternoon and
evening could be strong to severe with ample instability and
marginal shear. Large hail and some damaging wind gusts are
possible. Additionally heavy rainfall could cause flooding. Have
opted not to issue a Flash Flood watch as I do not feel that
widespread flooding will occur. That is not to say that some areas
will not see a flood or flash flood warning with this activity,
especially if it trains over the same area. Only a couple of areas
have antecedent conditions that would result in a quick issuance
of a warning if heavy storms overrun the same areas as storms over
the weekend.
Currently expecting the main MCS to move into eastern
Nebraska/Kansas by the Wednesday morning hours. The upper
disturbance will not exit across the Central Plains until
Wednesday afternoon/evening and this disturbance will provide the
upper support for the chance for thunderstorms during the day
Wednesday. Instability is 1000-1500 J/kg, with 30 kts shear. Some
of these storms could be strong to marginally severe.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 326 PM CDT Tue Aug 15 2017
After this upper trough exits Wednesday night, Thursday looks dry
with highs in the 80s. This is an active period though, and the
dry period will not remain for long. A few upper waves will move
across the area through the weekend bringing additional rain
chances. These chances do not look to be as widespread as what is
expected today, but none-the-less a chance for precipitation.
The upper flow becomes more zonal to slightly southwesterly with
some weak ridging for the start of the work week. Temperatures are
generally warmer than we have seen for some time, but still only
near to slightly above normal for mid-August. Scattered
precipitation chances continue through Tuesday. See more details
on Monday below in the Eclipse section.
.ECLIPSE...
Total Solar Eclipse Monday August 21st around 1pm CDT
As Monday draws closer the forecast guidance is coming into
slightly better agreement, but confidence is still not overly high
on how the forecast for Monday will evolve. The GFS/ECMWF are in
fairly good agreement with a frontal boundary moving into the area
overnight Sunday into Monday from a passing upper wave moving
across the Northern Plains. They show this boundary stalling out
and being a potential focus for precipitation potential later in
the day Monday. With this, confidence on a cloud forecast is low,
but there could be at least some higher clouds around during the
day. Continue to watch this forecast as the time period nears.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 636 PM CDT Tue Aug 15 2017
The main aviation forecast concern is the thunderstorm chances
throughout the next 24 hours. Ongoing convection is just near and
to the north of the KEAR and KGRI terminals. Ongoing convection
may stay just to the north of the terminals, but new convection
and then convection along the cold front later tonight is likely
to impact the terminals. A reduction in visibilities and ceilings
is likely with any thunderstorm that develops. Some breezy winds
may accompany the thunderstorms as well. Winds will be southerly
until the front passes through and they become northwesterly.
&&
.CLIMATE...
Issued at 326 PM CDT Tue Aug 15 2017
.Grand Island falls 1 DAY SHORT of tying the record for
"Consecutive July-August days without exceeding 85 degrees"..
A warm front lifting north this afternoon allowed Grand Island
airport to exceed 85 degrees for the first time since July 25th,
thus ending a 20-day streak of high temperatures 85 degrees-or-
cooler which lasted from July 26th-Aug. 14th. Because both July-Aug
are the warmest two months of the calendar year on average, with
normal/average highs ranging mainly 84-88 degrees, this streak was
actually quite noteworthy despite falling just short of the record.
Details of the current records for Grand Island follow:
* Top-4 Longest July-August streaks without exceeding 85 degrees *
- Grand Island (records include 121 years):
21 days...Aug. 11-31, 1964
20 days...July 26-Aug. 14, 2017 (ENDED TODAY)
18 days...July 11-28, 1993
16 days...July 8-23, 1992
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
SHORT TERM...Billings Wright
LONG TERM...Billings Wright
AVIATION...Billings Wright
CLIMATE...Pfannkuch
Area Forecast Discussion
National Weather Service Goodland KS
611 PM MDT Tue Aug 15 2017
.UPDATE...
Issued at 544 PM MDT Tue Aug 15 2017
Updated forecast to refine the timing of storms for tonight based
on latest data and satellite/radar trends. Main mechanism for
storm development will be the upper level short wave trough just
west of the Tri-State Area. This trough will deepen over a dry
line/surface trough just to the west. The upper level feature
will track northeast across the northwest half of the forecast
area tonight. With the strongest lift over this part of the
forecast area, the flash flood watch looks well placed. 600-500mb
frontogenesis will be strongest of Yuma County this evening, so
would expect a good deal of storm activity as a result. The
frontogenesis does weaken through the night and doesn`t move much
further east.
Meanwhile isentropic lift develops over the east third of the
forecast area overnight ahead of the upper level short wave
trough. Models have a second maximum of rainfall over this part of
the forecast area which is outside the watch. Confidence is not
high enough right now to justify extending the watch over that
part of the forecast area. However WPC does have a slight risk for
excessive rainfall over that part of the forecast area. Will
monitor new data coming in to see if the watch needs to be
expanded.
Regarding the risk for severe weather, deep layer shear is very
similar to yesterday as is the CAPE. The lift is even stronger
than yesterday, but the nose of the LLJ is not in as favorable a
position as yesterday. The nose is mainly over the northwest half
of the forecast area this evening, so would anticipate the severe
weather to be confined there for the most part. Flash flooding
should be the main threat with a secondary threat of hail and
damaging wind gusts. Cannot rule out tornadic development due to
0-1km helicity and 0-1km shear being favorable for tornadoes. The
tornadic threat will be confined to the first few hours of the
evening.
Once the cold front begins moving through late this evening,
anticipate the storm activity to decline behind the front.
Soundings show the elevated CAPE diminishing as the front moves
through.
On a side note, near term models not very optimistic with
rainfall over the majority of the forecast area tonight, which is
odd considering the depth of the lift with the upper level short
wave trough moving through. These models keep the storm activity
mostly north of the forecast area or over the far southern
counties. Cannot rule out greater storm activity over the south
than currently forecast, based on the latest radar trends, but
confidence is not as high as over the north half of the forecast
area where the upper level short wave trough will track tonight.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 247 PM MDT Tue Aug 15 2017
Forecast issues will coverage of thunderstorms and associated
hazards. Satellite and upper air analysis show a deep moist air
mass over the region. Main shortwave trough that will help with
the lift is just to our west at this time. Frontal boundary has
retreated some to the north through the day and is now over or
near the western and northern portions of the area.
High resolution/Cams are in disagreement where to put the convective
development which has been a problem they have been having this
season. At this time radar is showing thunderstorms developing near
the surface boundary. The Rap and latest Nam12 is showing this
scenario more than the other output. So at this time will start with
the highest pops in the north and west.
Guidance differs on how long to keep this activity around. Most of
the output is clustering around thunderstorms moving slowly east and
lasting through the night. Dcape looks to be 1000 or above over the
area through this evening and do have decent directional shear at
this time. Front and/or outflow moves across the area during this
time. So do expect a chance of severe with damaging wind and large
hail the main threats. There is an outside chance of a tornado.
Very heavy rainfall causing flash flooding looks to be higher than
normal. Precipitable water values are 1 to 1.5 inches which is near
to just above 1 to 1.5 standard deviations above normal. Locations
from Kit Carson through southeast Yuma and most of Sherman counties
into Cheyenne county Kansas and eastern Rawlins counties received to
2 to 6 inches with Kit Carson having the most widespread heavier
amounts. This combined where the models have the highest qpf and
pws, chose to put a Flash Flood Watch out for the northwest third.
For Wednesday the shortwave and associated precipitation moves
across the area through day and should be east of the area by late
in the afternoon. Models show cooler for tomorrow and used a blend
to cool temperatures off.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 205 PM MDT Tue Aug 15 2017
Over the extended period there will be a change in the upper level
pattern that will keep temperatures warmer and drier than the last
few weeks over the Tri-State region. To start off on Wednesday
night, precipitation chances are low as a shortwave trough moves east
of the region. As for Thursday, this is the best day during the
period that could see precipitation and storms. There is a broad
trough over the region and then a small shortwave passes over. This
will create uplift for storms to develop.
The remainder of the period will see ridging with southwest flow.
Mostly every day are showing signatures for precipitation with
moisture from the desert southwest being pulling into the region.
Temperatures are expected to remain the 80s for the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 544 PM MDT Tue Aug 15 2017
VFR to MVFR conditions forecast for the TAFs. Main focus is storm
arrival, with timing of both sites looking very similar.
Considered placing a tempo group for KGLD, but due to the site
being just south of the area of main storm activity did not. Did
include a mention of KMCK, which will be in a much better path for
storm activity. The storm activity will continue for KMCK into
the overnight hours. Heavy rainfall may drop the visibility to
IFR, but have low confidence of this occurring so only have MVFR
visibility. Storm activity should diminish behind the cold front
that will move through overnight, which will cause winds to turn
to the northwest. MVFR ceilings will move in for both sites
potentially, but definitely for KMCK toward 12z, lifting late
morning.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Flash Flood Watch through late tonight for KSZ001-002-013.
CO...Flash Flood Watch through late tonight for COZ090-091.
NE...Flash Flood Watch through late tonight for NEZ079>081.
&&
$$
UPDATE...JTL
SHORT TERM...BULLER
LONG TERM...CLT
AVIATION...JTL
Area Forecast Discussion
National Weather Service Green Bay WI
1054 PM CDT Tue Aug 15 2017
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 233 PM CDT Tue Aug 15 2017
The latest RAP analysis and satellite/radar imagery show high
pressure centered over Lake Superior and extending southward over
the Badger State. Morning stratus has evolved into a cu field,
which remains most widespread over far northeast WI and also the
southern half of the state. The next weather system resides
upstream over the north-central Plains, and is expected to gradually
push towards the region over the next 24 hours. Precip chances
and trends with this system are the main forecast concerns.
Tonight...High pressure will be sliding east across the region
tonight. Mid and high clouds will gradually be increasing through
the night, but do not look to lower until after midnight. Otherwise,
boundary layer winds look low enough for decoupling, which will lead
to patchy ground fog developing in the cold spots of northern WI.
Lows ranging from near 50 degrees in the north to near 60 degrees in
the south.
Wednesday...High pressure will slide to the eastern Great Lakes,
while the flow aloft will turn to the south and southwest. Mid and
high clouds will continue to thicken and lower during the morning,
but dry air below 700mb should hold off precip for most of the area
except for possibly far north-central WI where some decaying showers
could sneak in from the west. Moisture will be increasing from the
west during the afternoon, though the best moisture transport will
remain well west of north-central WI. Additionally, elevated
instability and mid-level lapse rates also look rather poor. So
will show a slight increase in precip chances over western areas
through the afternoon, but will leave thunder as isolated in nature.
Temps will be fairly similar to todays readings.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 233 PM CDT Tue Aug 15 2017
First upper trough to move across the western Great Lakes region
is expected late Wednesday night into Thursday evening, with the
second system arriving Friday night into Saturday. Beyond Saturday,
500mb pattern should be fairly zonal over the United States into
early next week.
For the system Wednesday night into Thursday, latest model trends
suggests a slower arrival of the main precipitation band due to
slower arrival of system and overcoming dry air aloft. There may
be a brief period of showers early Wednesday evening across the
north with first area of showers. The main band of precipitation
is expected to arrive into the southern half of the forecast area
during the mid to late evening hours, then work into far northeast
Wisconsin after midnight. Showers and thunderstorms are expected
across the area, but the risk of severe weather is low. The
showers and thunderstorms should move east of the area Thursday
morning with additional scattered shower and thunderstorm activity
across northeast and east-central Wisconsin Thursday afternoon as
a cold front moves across the area. It is possible that a storm
could become strong or severe Thursday afternoon. Any showers will
come to an end Thursday evening.
A brief break in the rain can be expected Friday before the next
system approaches from the west. The next chance for rain will be
Friday night into Saturday. Dry conditions expected Sunday as weak
high pressure dominates the pattern. Low confidence in rain
chances next Monday and Tuesday due to uncertainty in timing of
systems through the mean flow.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1054 PM CDT Tue Aug 15 2017
Mostly high clouds around tonight. Some patchy ground
fog is possible around sunrise. Middle clouds will increase
Wednesday with a small chance of showers or thunderstorms in the
evening. Showers and thunderstorms are likely Wednesday night and
Thursday as low pressure moves across the area.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Eckberg
AVIATION.......RDM
Area Forecast Discussion
National Weather Service Houston/Galveston TX
909 PM CDT Tue Aug 15 2017
.UPDATE...
Minor changes to the forecast this evening. Adjusted temps and dew
points to account for observations, which resulted in lowering
dewpoints a degree or two in the near term. Overnight low
temperatures are still forecast to be above normal by 2-4 degrees,
lowering into the low-mid 80s closer to the coast and upper 70s
further inland.
Tomorrow`s pattern will be quite similar to today`s, as the mid-
level ridge continues to build in from the east. High temperatures
will rise up into the low 90s near the coast and upper 90s as you
move inland, actually approaching triple digits in the NW corner
of our area of responsibility. Heat indicies will still range from
104-109 across SE TX Wednesday, but will hold off issuing a heat
advisory for tomorrow to allow the next shift the chance to go
through the 00Z guidance. Streamer showers develop once again in
our eastern coastal counties early tomorrow morning, and should
eventually spread north throughout the day. The most recent runs
of the HRRR and RAP13 show coverage ranging from isolated to
widely scattered development, with most of the precip dissipating
by sunset.
Hathaway
&&
.PREV DISCUSSION... /ISSUED 820 PM CDT Tue Aug 15 2017/
AVIATION...
Isolated SHRAs along/near the coast earlier this afternoon have
all dissipated. Did keep a mention of MVFR CIGS in for the nor-
thern sites overnight tonight through early Wed morning as this
has been the trend of late. Guidance indicating a slight uptick
with PWs tomorrow morning/afternoon so no major disagreement in
keeping the mention of VCSH for sites across the southern sites
tomorrow. 41
PREV DISCUSSION... /ISSUED 321 PM CDT Tue Aug 15 2017/
Subtle differences in the atmosphere will continue to dominate
changes in the forecast for the next several days. Temperatures
and humidity will be exactly what you`d expect from Houston in
mid- August - both high. The second half of the week may see a
return of heat advisories as upper ridging builds heights over SE
Texas again, but will ultimately depend on some more difficult to
predict features that preclude a confident statement of how
necessary they will be.
NEAR TERM [Through Tonight]...
It was another warm start this morning, with a couple more potential
record warm minimums in the area hanging on temp trends through
tonight (see Climate below). The current forecast makes it likely
that those tentative records will hold thanks to the high humidity
levels. As in previous days, showers and thunderstorms have been
considerably more numerous to our east, with some bleedover into our
eastern counties. However, vertical growth of today`s cloud streets
on satellite indicate that rain chances tail off from east to west
across our portion of Southeast Texas for the rest of the afternoon.
SHORT TERM [Wednesday Through Thursday Night]...
Another warm night is expected tonight and Wednesday night.
Overnight lows will again be in the vicinity of record high values.
Rain patterns should look pretty familiar - a handful of streamer
showers early near the coast, giving way to isolated to widely
scattered showers and storms in the afternoon. The best potential
for rain, like today, is likely to be along the eastern edge of our
area of responsibility. Though the upper ridge will be trying to
build, there are indications of a very subtle upper low sneaking
across the area somewhere in this timeframe. How much this enhances
rainfall potential will be somewhat dependent on the timing and
amplitude of this low, and there`s not been a lot of real
significant run to run consistency on this. For instance, Wednesday
previously looked drier, but with only modest increases in heights
leaving a lingering weakness in the ridge and an increase in
precipitable water, it doesn`t look quite as dry now. There may be
some more small changes in thinking on this until there is more
confidence in how this transition to a stronger ridge aloft will
play out.
In the current forecast, Wednesday features maximum heat indices of
104 to 108, with isolated spots of 108-110. Thursday`s forecast is a
touch warmer, in the 104-109 range, and some localized spots
reaching 110. These grids may end up being a bit of a worst case
scenario. Am concerned that dewpoints may be able to mix out a
little more, or on the flip side, temps may not get quite as hot if
that mixing doesn`t occur. Either way, a slight shift in either way
on this sliding scale would tip the heat index calculation too far
out of balance, resulting in lower apparent temperatures. Suffice to
say, it`s going to feel hot. Whether or not it`s enough to warrant
the issuance of an advisory is less of a slam dunk.
LONG TERM [Friday Through Tuesday]...
This end of the work week into early next week will feature the
brief reign of a midlevel high, which then moves off to the west and
weakens with the approach of an upper trough. We can look for
temperatures to bounce back upwards heading into the weekend, but
then with slight cooling into early next week. Also, we should see
rain become more isolated (or even drier), with some bounce back
sometime in the back half of the weekend or early next week. As
mentioned above, while there`s been some consistency in the guidance
in showing this upper trough, there hasn`t been as much consistency
in strength or timing. As it is, the Euro keeps this trough more
constant in strength, and is a touch slower. The GFS starts out with
a stronger trough, but shears it out and makes it weaker. The
Canadian, for what it`s worth, is about half a Gulf slower than the
Euro and GFS, and considerably weaker by the time it reaches our
coastal area. That said, it still manages to generate some fairly
widespread seabreeze convection, so I`ve modestly stepped up PoPs
for early next week, but not quite to the level in the guidance, to
account for lack of confidence in the upper pattern.
As far as potential for heat advisories this weekend, much of the
same logic from the short term applies here. If the perfect balance
of temp and RH occurs, which tends to be more of the scenario
currently in the forecast, heat advisories may be needed. Tip too
far to high values in one way or the other, and the meteorology to
require it will likely limit the other too much, capping high heat
index potential.
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 78 99 77 99 77 / 10 10 10 10 10
Houston (IAH) 80 95 80 96 79 / 10 20 10 30 10
Galveston (GLS) 84 91 84 90 84 / 10 20 10 20 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 8 AM CDT Wednesday for
the following zones: Waters from Freeport to the Matagorda
Ship Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.
&&
$$
Update...08
Area Forecast Discussion
National Weather Service Wilmington NC
736 PM EDT Tue Aug 15 2017
.SYNOPSIS...
Summertime heat and humidity will build and should peak through
Friday. Although showers and thunderstorms will gradually
become fewer in number, heat index values will climb, and heat
advisories may be needed Friday. Showers and thunderstorms will
increase during the weekend as a cold front approaches from the
north. This front will stall and dissipate nearby early next
week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 730 PM Tuesday...Latest radar loops show a cluster of
weak to moderate thunderstorms about to impact the Cape Fear
region, a few spot showers elsewhere. Will tweak forecast
slightly regarding timing of these features with the next
update, otherwise no major changes anticipated. Previous
discussion follows:
A sea breeze is resulting in isolated showers thus far while a
weak trough farther west and northwest has also resulted in some
convection as well. HRRR is supportive of widely scattered
storms through the afternoon, and into the evening as a weak
impulse moves across NC. Plan on carry chance POPs as a result
with little if any chances during the early morning hours. The
weak trough will be along the coast during Wednesday and with
moderate instability and precipitable water values >2.2 inches
will maintain chance POPs. Heat/humidity issues will be a
concern Wednesday with heat indices close to advisory thresholds
each day. Low temperatures tonight will be a category or two
above normal, which has been quite common through a bulk of this
summer.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
As of 3 PM Tuesday...Low amplitude mid-level ridge axis will slowly
transition eastward from eastern TN Wednesday night, across the
Appalachians Thursday, to the near or just off the coast by 12Z
Friday. Precipitable water values look to dip just below 2 inches
Wednesday night as northwest flow aloft ushers in a bit of modestly
drier air behind a decaying frontal boundary, but will return to
around 2.25 inches Thursday and Thursday night. Convection should
remain scattered in nature under the flat ridge, with sea breeze and
Piedmont trough acting as focusing mechanisms. Heat indices on
Thursday are expected to reach into a 100-105 range. Low temps each
night will dip into a 75-79 range.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 300 PM Tuesday...Concern for the extended involves heat and
humidity Fri/Sat, followed by a cold front for the weekend and into
early next week.
Vertically stacked high pressure offshore will strengthen into
Saturday ahead of a shortwave and associated cold front dropping
into the OH VLY. This drives very warm air with high humidity into
the region, and highs Fri will climb into the 90s, with mid 90s
well inland, which combined with the high humidity will create near
heat-advisory apparent temperatures. Isolated showers and tstms are
possible Friday as well, but ridging aloft combined with lack of
significant forcing will keep coverage isolated. On Saturday, the
front will drop into the area and then likely stall as the shortwave
hangs back, the front becomes flow-parallel, and ridging persists to
the east. Convection chances will ramp up significantly Saturday,
with still good chances Sunday as the shortwave digs through the Mid-
Atlantic and offshore. Temps for the wknd will remain above climo as
well.
Concern then shifts to Monday, the day of the total solar eclipse.
Guidance has backed off on a clean FROPA, and has the front
dissipating overhead during Monday. This is much more typical for
late August. While this could create more clouds and unsettled
conditions for Monday across the area, mid-level flow does become
W/NW behind the aforementioned shortwave which brings some drier
air into the mid-levels. At this time a fairly typical August day is
expected with aftn CU and convection, especially focused along the
stalled boundary wherever that may set up. This does not suggest the
eclipse will not be visible, but may be temporarily blocked by
convection at times.
On Tuesday offshore high pressure re-asserts itself, but yet another
weak cold front will approach from the NW creating good convection
chances with continuing above climo heat and humidity.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 00Z...Main concern for aviators this evening is impending
convection that will impact ILM over the next hour or two. Have
a prevailing TSRA group to begin with followed by a tempo -TSRA
for the next couple of hours thereafter. Radar loops show a line
of convection that will move across ILM, but should miss all of
our other terminals. There is an outside chance that a shower or
weak thunderstorm could impact CRE and MYR, but confidence is
low that this will happen. Otherwise, expect primarily VFR for
the overnight period, with the possibility of isolated
convection for all sites Thursday afternoon.
Extended Outlook...A brief period of MVFR or lower conditions
can not be ruled out in isolated to scattered showers and
thunderstorms Wed through Fri. The risk for flight restrictions
due to showers and thunderstorms will increase on Sat. Low
stratus and some fog during the overnight and early morning
hours may result in flight restrictions as well each day.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 730 PM Tuesday...Latest obs continue to show the influence
of far-distant Hurricane Gert, with a 3 to 4 ft easterly swell
with SW winds of only 10 to 15 kts. Forecast in good shape with
no changes planned. Previous discussion follows:
Swells from Gert will continue tonight but they will gradually
weaken. Seas will be 3-4 ft through tonight, primarily in an E
swell, and 3 ft or less during Wednesday. S-SW winds today will
veer to an offshore direction overnight as a weak trough moves
into the vicinity. Light southerly flow will develop again
during Wednesday once the sea breeze becomes established.
SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 3 PM Tuesday...A decaying front across the waters Wednesday
night will result in light but potentially variable winds, along
with the possibility of scattered showers and thunderstorms. Latest
guidance suggests the boundary may shift just south of the waters
Wednesday night, allowing a period of NE winds before it washes out
Thursday morning. Wind direction will veer to the SE Thursday
afternoon, and SW Thursday night and Friday as a Piedmont trough and
Bermuda high reestablish.
LONG TERM /FRIDAY THROUGH SUNDAY/...
As of 300 PM Tuesday...A cold front approaching from the NW will
sandwich the waters with a pinched gradient as high pressure spins
offshore. This will drive increasing SW winds, increasing to around
15 kts by mid-Friday and persisting at these speeds into Sunday
morning. This front will stall and begin to dissipate inland from
the waters on Sunday, causing the gradient to relax and wind speeds
to fall to around 10 kts while maintaining a SW direction. Initially
seas will be just around 2 ft, but will increase steadily thanks to
an amplifying SW wind wave, becoming 3-5 ft by Saturday night.
Conditions should remain just below any cautionary statements
however. As the winds begin to ease Sunday, seas will follow, with
wave heights falling to around 3 ft at the end of the period.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...High Rip Current Risk until 8 PM EDT this evening for SCZ054-
056.
NC...High Rip Current Risk until 8 PM EDT this evening for NCZ106-
108-110.
MARINE...None.
&&
$$
SYNOPSIS...JDW
NEAR TERM...REK/SRP
SHORT TERM...CRM
LONG TERM...JDW
AVIATION...REK
MARINE...REK/JDW/SRP/CRM
Area Forecast Discussion
National Weather Service Lincoln IL
950 PM CDT Tue Aug 15 2017
.UPDATE...
Issued at 948 PM CDT Tue Aug 15 2017
Quiet weather is expected for the most part across central and
southeast Illinois overnight. Some patchy fog is expected, but
should not get terribly thick. Most of the model guidance has
backed off on the rain chances for the rest of the night, despite
the slow arrival of a warm front from the southwest. Only minor
tweaks are needed to current forecast, mainly to go dry for the
rest of the night.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 241 PM CDT Tue Aug 15 2017
Weak surface ridge stretched from the Hudson Bay southward
through the Mississippi River Valley to the Gulf Coast. A slow
moving frontal boundary draped across the northern tier of
Illinois helping to provide very weak focus for some afternoon
cumulus growth, resulting in a couple showers. HRRR for the last
few runs seems to have a good handle on the showers, but has
become more diffuse with time across Central IL. Forecast
adjustments to allow for scattered activity and keeping it into
the early evening hours. Overnight, skies become partly cloudy and
once again a little warmer than the night before. For tomorrow,
increasing clouds with a warm air advection pattern as moisture
surges into the region and showers/thunderstorms start spreading
in coverage, limiting the daytime heating.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 241 PM CDT Tue Aug 15 2017
Precip continues into Thursday with the best chances for precip in
the forecast Wed night as the storm system/front moves through the
region. Extensive cloud cover Wed night keeps the overnight lows
up...and limits the morning warm up for Thursday. Models at this
point are in surprisingly good agreement to wrap up the week and
into the weekend. Precip a little slow to diminish through
Thursday night/Friday morning. But Friday will be dry with a
return to the mid 80s, with light northwesterly winds and weak
high pressure. Both GFS and ECMWF have next wave moving through
the Northern Plains bringing in precip for Saturday and Sat
evening. However, rather progressive flow aloft will likely usher
the system out quickly and wrap up the weekend dry. As for Monday,
right now, both the GFS and ECMWF are producing a weak wave, but
keeping it northwest of ILX through the daylight hours.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 635 PM CDT Tue Aug 15 2017
Generally quiet/VFR aviation weather conditions expected across
the central Illinois terminals through the 00Z TAF valid time. A
spotty shower is possible for the next hour or two, most likely at
KBMI, but will have little impact on flight condtions. Also, some
patchy fog is possible later tonight, most likely at KCMI. The fog
may briefly reduce the visibility to MVFR levels. Scattered
showers/storms are possible Wednesday, mainly during the
afternoon, as a disturbance approaches the area. However,
confidence in coverage/timing is too low to include in the
terminals at this time.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Bak
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...Bak
Area Forecast Discussion
National Weather Service Northern Indiana
728 PM EDT Tue Aug 15 2017
.SYNOPSIS...
Issued at 718 PM EDT Tue Aug 15 2017
Dry conditions are expected overnight into Wednesday morning with
patchy fog possible. Lows tonight will drop into the 60s, with
highs on Wednesday in the low to mid 80s. A couple rounds of
showers and thunderstorms will be possible from Wednesday
afternoon into Thursday as a low pressure system tracks into the
Great Lakes region. Drier and cooler air then follows in the wake
of this system on Friday, with another low chance for rain on
Saturday.
&&
.SHORT TERM...(This Evening through Wednesday)
Issued at 253 PM EDT Tue Aug 15 2017
Isolated showers/storms will remain possible across nrn IN/nw OH
into the late afternoon and early evening near a remnant cold
front/aggregate lake breeze. Coverage/chances/intensity will be
limited by dry mid levels and warm profile.
Dry conditions are expected tonight into most of Wednesday as
shortwave ridging amplifies in advance of an upper trough ejecting
east into the Central US. MOS and SREF probabilities are relatively
aggressive with fog/stratus development overnight given light winds,
mainly clear skies and lingering near surface moisture near diffuse
boundary (best chances across portions of ne IN/nw OH).
Coverage/impact of any fog is uncertain at this range, especially in
the north as some drier air settles in post-frontal.
A few showers/storms may pop up during the mid-late afternoon hours
tomorrow along/southwest of US 30 near an instability gradient.
Lacking flow/forcing should keep any convection below severe limits.
Temperatures tonight/Wednesday are expected to be similar to
today otherwise.
&&
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 253 PM EDT Tue Aug 15 2017
Good surge of moisture and elevated instability (PWATS nearing 2"
and sfc dewpoints up near 70F) Wednesday night into Thursday morning
will set the stage for increasing rain/thunder chances. This will
occur as ramping southwest flow (in advance of the above mentioned
upper trough) forces a warm front northeast into the region, with
the best chances for precipitation likely later Wednesday night
into early Thursday. System cold front and/or pre- frontal trough
then becomes the potential trigger for additional convection
during the afternoon and evening on Thursday. 30-35 knots of deep
layer shear and the potential for a moderately unstable boundary
layer in warm sector may present a conditional severe risk by
Thursday aftn/eve, though expected cloud contamination and poor
lapse rates thanks to warm/moist profile appear to be limiting
factors for severe wx at this time. As a result have no problem
with SPC`s marginal risk.
Dry/less humid air will lead to fair weather and cooler temps post-
frontal into Friday. The next shortwave in persistent wnw flow aloft
amplifies through the region on Saturday with the next chance for
showers/storms. Dynamics with this system appear decent for August
standards, however, moisture return is somewhat limited resulting in
low chance PoPs for now. Subsidence/height rises then allow high
pressure to build in for Sunday and Monday with fair wx.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 718 PM EDT Tue Aug 15 2017
VFR this evening into the overnight hours with mostly clear skies
and light and variable winds. Crossover temps to be reached
overnight and with light wind field and residual moisture could
see some fog formation outside of typical mid summer corn canopy
ground fog. Best chances look to be southeast but HRRR and SREF
probs not as pessimistic as earlier. CONS blends still showing
areas of 2sm or less in the southeast and have kept IFR mention at
KFWA but just MVFR at KSBN. Conditions improve Wednesday after
sunrise to VFR but mid level deck and some CU possible as next
system approaches. Small chances for shra late Wednesday toward
00z but not worthy of another line in terminals given late arrival
and uncertainty.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SYNOPSIS...Steinwedel
SHORT TERM...Steinwedel
LONG TERM...Steinwedel
AVIATION...Lashley
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Area Forecast Discussion
National Weather Service Jackson MS
913 PM CDT Tue Aug 15 2017
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Not a lot has changed in the evening update, bumped up the POPs to
reflect the current conditions. Thunderstorms have been slowly
starting to dissipate and all we are left with is some moderate
rain showers. The latest HRRR shows some patchy fog developing in
the northern Delta region near Cleveland/Greenville area. If the
winds stay light and there is some breaking in the clouds, that
will hold true. /12/
Prior discussion below:
Tonight through Wednesday: Expect these showers & storms to
linger through around early evening, around 8-10pm before
dissipating. The upper 500mb ~594DM upper ridge will slowly build
west into Wednesday & increase heights in the area. In addition,
the strong surface ridging wedging into the east will help
suppress convection overall as we go into tonight & also help
winds lighten up. This will help some patchy fog & low clouds to
develop overnight around daybreak, especially in areas that
receive some heavier downpours. With lingering soil moisture, it
won`t take much to help be conducive for some patchy fog to
develop. However there could be some lingering light winds,
especially in the west, that should keep it mostly low clouds
(stratus). Lows should be warm above normal in the low-mid 70s.
As a shortwave & upper trough dig through the Plains, expect a
surface low & cold front to eject through the central Plains into
the mid-upper Mississippi Valley on Wednesday. Our area will still
be situated in the western periphery of the upper ridge while an
upper low propagates northwest across the central to northern
Gulf. This upper jet & shortwave aloft lifting north will help PWs
climb between 2-2.25 inches. This will help some spark increasing
chances of showers & storms by late morning through Wednesday
afternoon. There is some potential, with some 850mb Theta E
approaching 340-345K & efficient moisture transport convergence,
that there could be some locally heavy downpours. Not going to
introduce in the HWO for now as these storms should be moving
somewhat. In addition, lapse rates are low & not expecting much in
the way of stronger convection. Heat indices & heat stress look
to be more of an issue as lingering ground level moisture &
warming thermal profiles help promote increasing heat indices near
105 degrees. Expanded the limited into the I-55 corridor &
Jackson Metro & also the Golden Triangle as well. Updated this in
the HWO/graphics as well. /DC/
Wednesday night through Monday: Mid level ridge centered over
northern FL will continue building into the area at the beginning
of the period. This will lead to lesser convective coverage and
warmer temperatures with heat indices becoming a problem,
primarily in the ArkLaMiss Delta region Thursday.
Heights will fall over the MS valley by Friday as another potent
shortwave dives south out of the northern Plains. This will squash
the ridge a bit and increase the potential for a better convective
coverage through Saturday. Heat indices may still push 105, mainly
in the Delta region, but the duration of these oppressive values
should be limited due to the expected convective coverage.
Sunday into Monday will be a transition period as the mid level
ridge begins building again over the north and the scattered
convection begins lessening. Heat indices look to build to around
105 over northwest sections once again, but uncertain as to duration
with the still looming convection. /26/
&&
.AVIATION...
00Z TAF discussion:
A broken band of TSRA was noted along and just north of I-20 at
2330Z. This activity wl cont north this evng and dissipate by 04Z.
GTR wl likely be affected. Otherwise, VFR conds wl prevail until
11Z when MVFR/IFR cigs wl be psbl through 14Z. After 14Z conds wl
improve to VFR and cont into the aftn before sct-numerous TSRA
development affects most TAF sites. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 74 92 75 92 / 72 55 9 18
Meridian 73 92 75 92 / 70 51 12 25
Vicksburg 75 92 75 93 / 75 52 7 15
Hattiesburg 73 92 74 93 / 35 58 12 23
Natchez 73 91 74 91 / 66 63 8 24
Greenville 75 91 75 92 / 31 30 7 25
Greenwood 75 91 76 91 / 38 35 8 21
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
12
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
630 PM CDT Tue Aug 15 2017
.UPDATE...
Issued at 505 PM CDT Tue Aug 15 2017
Updated forecast to reflect severe thunderstorm watch and added
heavy rain.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 305 PM CDT Tue Aug 15 2017
The HRRR, NAM and GFS continue bounce around the prospect of a heavy
rain center developing tonight somewhere between Valentine, Thedford
and Broken Bow. This not uncommon. We probably won`t know where it
will develop until the thunderstorms begin coalesce this evening or
later.
It certainly appears conditions are favorable for storms capable of
heavy rainfall as storms began to develop late this morning. All
models indicate precipitable water increasing to 1.5 inches or
higher and remaining high overnight. A strong upper level trof
across UT/NV this afternoon will approach Nebraska overnight lowering
heights aloft, steepening lapse rates and forcing thunderstorm
development. The model consensus shows a sfc cold front drifting
southeast overnight with a large warm sector opening up across Ncntl
Neb.
The rain activity is expected to shift east Wednesday morning with
cooler temperatures and northwest winds.
Severe weather has developed and is expected to continue well into the
evening hours as a series of MCS`s move through Swrn and Ncntl Neb.
Ping pong to golf ball size hail was reported beginning around 830 am.
The HRRR is the basis for this forecast. The amazing part of this is
bulk effective shear is less than 25kt, but lapse rates below 500
mb are steep.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 305 PM CDT Tue Aug 15 2017
The upper level trof across UT/NV this afternoon moves into the midwest
Thursday morning. This will set up northwest flow aloft which would
last until Saturday. 500mb winds aloft increase to around 30kt. Return
moisture develops Thursday suggesting a chance of thunderstorms late
Thursday/Thursday night. That rain chance shifts east Friday. More
return moisture develops Saturday through Monday with additional
rain chances mainly late in the day or in the evening. The potential
for strong or severe thunderstorms will remain under review at this
point. All rain chances are 40 percent or lower and generally isolated
in terms of coverage.
A gradual warming trend develops as h700 mb temperatures rise into the
lower teens by this weekend. This would support highs in the upper 80s
to around 90.
The sky forecast for 1 pm CDT Monday: the ECM and GFS would suggest the
potential for some high cloudiness associated with subtropical moisture
streaming across the Rockies.
The GFS indicates scattered midlevel cloudiness. Both the ECM and GFS
show morning stratus associated with a cold front drifting into Neb.
Presumably these clouds would burn off by noon.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 625 PM CDT Tue Aug 15 2017
Two areas of thunderstorms will continue this evening. Storms are
capable of heavy precipitation in both areas with near zero
visibility in the vicinity of thunderstorms. A nocturnal low level
jet will develop though the evening and intensify storms with
storms along and west of a KVTN to KLBF line capable of large hail
and strong damaging winds. Storms are expeceed to congeal after
midnight central and produce torrential rain through the early
morning hours.
&&
.HYDROLOGY...
Issued at 305 PM CDT Tue Aug 15 2017
WPC suggests the eastern portion of the forecast area could experience
some level of flooding over the next 24 hours. The Flash Flood Watch
has been expanded to include a good portion of Ncntl Neb and Swrn Neb.
The RFC 3-hour flash flood guidance shows 1.5 to 2 inches in many areas
and this was the basis for the flash flood watch covering much of the
forecast area.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Wednesday morning for NEZ006>010-022-
026>029-038-056>059-069>071.
&&
$$
UPDATE...Power
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Power
HYDROLOGY...CDC
Area Forecast Discussion...UPDATED
National Weather Service Lubbock TX
816 PM CDT Tue Aug 15 2017
.UPDATE...
Overall storm coverage locally has been less than expected to this
point this evening. A large convective complex continues to dump
rain over parts of the southern Permian Basin into the Edward
Plateau and Concho Valley, though it may be interrupting moisture
advection northward to some degree. In addition, scattered
convection at least partly associated with lift from an
approaching upper level trough was stretching from the western
Panhandles into eastern Colorado, though the bulk of this lift was
skirting by to the north. Closer to home, we`ve had a few storms
over eastern New Mexico trying to make it into the western zones,
though except for the current activity moving into the far
southwest Texas Panhandle, the bulk of this activity has struggled
to maintain itself into the South Plains. Heating today was
somewhat muted by the early day convection with spots on the
Caprock only making it into the lower to middle 80s, which in turn
has allowed the CIN to remain a little stronger than the past few
days. This is likely tending to limit overall storm coverage
locally, though where convection has been able to take root,
MLCAPE values near 1500 J/kg and 30 knots of effective shear were
still capable of supporting a few stronger storms, while the
elevated moisture levels will promote locally heavy rain. Given
the trends and recent supporting runs of the RAP and HRRR we have
reduced PoPs into the slight chance category for all but the
western/northwestern zones where chance PoPs were maintained
through the evening. Slim thunder chances were also maintain after
midnight, though if the recent high-resolution NWP are correct
this may be overdone as well. Aside from the weather and PoP
grids, minor adjustments were made to several other grids in
accord with recent observations and trends.
&&
.PREV DISCUSSION... /issued 613 PM CDT Tue Aug 15 2017/
AVIATION...
Isolated showers and TS southwest of KLBB should be a non-issue.
Of greater concern is the TS across eastern NM. Model guidance is
lacking clarity although generally confirms a mainly eastward
movement favoring the Texas Panhandle closer to upper support
provided by a mid level short wave trough. Low confidence in
timing, let alone occurrence, of TS at any of the terminals will
lead to keeping mention out of the TAFs at this time. Otherwise
VFR with modest south winds backing slightly toward southwest
Wednesday morning as the upper trough swings across the High
Plains.
PREV DISCUSSION... /issued 256 PM CDT Tue Aug 15 2017/
DISCUSSION...
Model guidance has struggled with surface features in wake of
this mornings convection. NWP mostly had S-SW surface flow 10-15
knots progged this morning while we`re actually seeing S-SE flow
at 15-20 knots. As cloud cover decreases west to east with the
exiting convective system to the east, we`re seeing CAPE values
build across our western counties near the state line up between
2k/3k J/Kg. This should be enough to overcome weak capping aloft
along the state line, with convection already beginning to initiate
in the higher terrain of eastern New Mexico as shortwave energy
ejects northeastward from the base of the upper level trough axis
entering southern New Mexico as of 3pm CDT.
Most of the blended guidance had lowered POPS across our area for
the remainder of this afternoon and overnight. As a result of the
stronger SE surface flow and increasing instability to our west
we decided to keep higher POPS in place from previous forecast as
we go through the remainder of today and the overnight. The NAM
seems to have the best handle on convection moving out of New
Mexico into our western counties this evening with continued
initiation further east through the South Plains and northern
Rolling Plains through the late evening hours which the GFS and
ECMWF pick up on eventually after midnight.
Once the trough axis lifts out of southern New Mexico into the
Central Plains through the course of the day tomorrow, we`ll see
high pressure, currently across the southern Gulf States attempt
to inch westward. Continuous shortwave energy will work to
suppress height rises with slight chance to chance POPS confined
mostly to the Rolling Plains tomorrow then returning across much
of the area for late Thursday into Friday. Saturday and Sunday
look mostly dry as heights rise aloft while a Pacific trough dives
south along the California coast. Dewpoints will remain elevated
helping to keep highs right around normal despite the lack of
precip chances Saturday and Sunday. Longwave pattern change
doesn`t appear to change much in the longterm keeping temperatures
at or slightly below normal into next week while continuing to
hint at typical convection moving off the higher terrain of
eastern New mexico across the state line into our area.
&&
.LUB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
23/07
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
728 PM CDT Tue Aug 15 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 316 PM CDT Tue Aug 15 2017
An active short term period ahead with the main concern being for
locally heavy rainfall. The severe weather threat is low this for
this period, but we could see some small hail and a few of the
stronger cells produce some wind gusts.
As of mid afternoon, there was an area of showers and thunderstorms
well to our south in association with the elevated front down across
Nebraska and into Iowa. Upper level flow veers from southerly to
southwesterly, which is trying to push the aforementioned activity
toward our area. Agree with the HRRR solution in weakening and
potentially phasing this activity out over the next several hours as
it lifts north of the pool of moist and modestly unstable air to the
south. Reduced pops quite a bit this evening across the forecast
area, as the onset of precipitation has slowed across the general
model consensus which makes sense given current placement and
slower advancement of the unstable airmass into southwestern MN.
Hence, expecting showers and storms to begin developing across
southern MN primarily after 06Z in response to the theta-e
advection, but also the strengthening jet streak to our west and the
shortwave energy advecting into western MN late tonight.
Expecting the highest QPF across western MN in conjunction with
the shortwave energy. In terms of heavy rain and severe potential,
not too concerned for either tonight. Instability and shear will
be limited and forcing is not nearly as strong as it will the
following night.
For tomorrow, the main shortwave will lift out of Colorado tomorrow
morning, with surface cyclogenesis occurring as it lifts
northeast during the day. The precipitation that develops
overnight will still be lifting through early in the morning, but
there looks to be a lull in the activity from mid morning through
mid afternoon as the forcing associate with the main wave arrives
later in the day tomorrow. Dry southeasterly flow will only aid
in the drying things out somewhat by midday. But, as the system
begins taking on a negative tilt and strengthening as it
approaches tomorrow afternoon, showers and thunderstorms are
expected to quickly develop. Deeper instability with this period
justifies a marginal risk as small hail and a some gusty winds
could develop. With PWATs increasing to near 2" and deep skinny
CAPE still shown in the forecast soundings, certainly looks to be
a heavy rain threat more than anything, especially with the warm
front and surface low lifting into the area by late in the day
tomorrow. Expecting this period through tomorrow night will bring
the bulk of forecast rainfall totals.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 316 PM CDT Tue Aug 15 2017
By tomorrow evening, the surface low will have lifted into southern
Minnesota, but there has been some wobbling of this feature among
the guidance, so it certainly bears watching what changes will be
needed in the forecast between now and then. Generally expect the
low to continue lifting northeast as the upper wave strengthens
overnight, which implies very strong forcing for ascent which
should have no problem producing heavy rainfall across the area.
Depending on the track of the surface low, the warm sector could
also see slow moving segments only raising the risk of locally
heavy rain. This is due to a lack of speed and directional shear
late tomorrow night.
This system will depart to our east Thursday, but still expect some
precip on the backside of the system mainly across eastern MN and
western WI Thursday morning. This system will bring little change
in the actual thermal profile to the region, so as conditions dry
out, we should warm back up to the upper 70s.
Another shortwave looks to move through rather quickly Friday-Friday
night which will likely bring scattered showers and thunderstorms to
the area. This system will come in from our northwest and be much
weaker and faster moving than the previous system.
Temperatures look to warm into the lower 80s as we get into zonal
flow after the Friday system, with another potential quick moving
and weak shortwave for late Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 728 PM CDT Tue Aug 15 2017
Concerns are a couple rounds of precip with IFR/MVFR for much of
the period. Forecast this evening starts out with just incoming
mid and high clouds, then scattered showers begin moving in and
developing late tonight, especially over the MN sites into far
western WI. There is some thunder risk late tonight, but the main
story will be the development of IFR ceilings over much of the
area. Confidence is rather high in this regard. Ceilings should
only rise to MVFR or maybe low VFR by mid afternoon tomorrow,
since a southeast wind with continuous moisture flow along with
inversion will serve to keep MVFR ceilings tomorrow afternoon.
Then storms develop later afternoon, but placement is tough at
this point.
KMSP...
Short term models have continued the trend of delaying onset of
precip a bit, but most recent indications are that some showers
should move in around 09Z or so, with a drop to IFR a few hours
thereafter. Confidence is above average that we`ll get some
showers and IFR, but not at all sur ethat we`ll have thunder. And
confidence in the timing is only average. After showers depart
and ceilings improve to MVFR, the MVFR may well persist all
afternoon due to southeast flow and inversion.
/OUTLOOK FOR KMSP/
Thu...VFR. Wind N-NW 5-10 kts.
Fri...VFR. Chance afternoon/evening TSRA. Wind SW 5 kts.
Sat...VFR. Wind W 5 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...SPD
LONG TERM...SPD
AVIATION...TDK
Area Forecast Discussion
National Weather Service Nashville TN
815 PM CDT Tue Aug 15 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
A surface ridge extending northward from high pressure centered
near MGM has reached through Middle Tennessee. Earlier showers
have entirely dissipated across the mid state, although there is a
cluster of cells near HOP just north of the TN/KY line. HRRR
shows very little activity overnight across the region, so have
lowered POP`s to the isolated category. Other hourly grids are
holding up well, so no other changes are planned at this time.
&&
.AVIATION...
00Z TAF DISCUSSION.
Mostly VFR conditions for this TAF cycle, however light boundary
layer winds and plenty of low-level moisture spell at least a few
hours IFR vis at KCKV and KCSV tonight and Wednesday morning.
Vis should improve after sunrise for these two, but bkn VFR deck
will be possible for most of the morning.
Winds will be very light calm overnight, become southwesterly on
Wednesday.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......08
AVIATION........Unger
Area Forecast Discussion
National Weather Service Pittsburgh PA
850 PM EDT Tue Aug 15 2017
.SYNOPSIS...
Generally dry and warm weather will continue on Wednesday. Rain
is likely with a Thursday cold front.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A weak short wave has exited the northern CWA this evening,
with dissipating showers having exited likewise. Secondarily,
the lake breeze off of Lake Erie has generated another line of
showers that has pushed well inland from roughly northern
Coshocton County toward Beaver and DuBois as of 830 PM. This
activity will continue to perpetuate ESE slowly over the next
few hours and has been well handled by the HRRR to this point.
Thus, the activity nearing the Pittsburgh area, being the most
well-developed, will linger the longest. PoPs were increased
along this corridor as it slinks southeastward in the next few
hours.
With little upstream convective blow off and cumulus dissipation
after peak heating, a clear night after the shower activity
this evening looks to be in store. Elevated surface dewpoints
and calm conditions will thus result in fog, particularly in the
lower spots overnight toward sunrise. Fries
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY NIGHT/...
After the passage of today`s wave, heights will briefly build
Wednesday, allowing a dry forecast to carry through much of Wednesday.
Increasing southwesterly flow late Wednesday night into early
Thursday will lift a warm front into the area. Will keep the
area dry through the pre-dawn Thursday, but do bring some chance
PoPs in for near the Thursday morning rush hour.
The warm front will lift north of the area Thursday afternoon,
with mostly scattered showers and thunderstorms in the warm
sector. The deep parent low lifting north through the Great
Lakes will finally swing a cold front into our western zones
late Thursday night into Friday morning. While timing
differences do exist, it looks as though the broad consensus
across model guidance is for high PoPs near or after 00z Friday
with the front. If this timing holds, it is not very favorable
for strong convection along the front to make it deep into our
forecast area. For this reason, the Day 3 marginal risk outlines
just our Ohio counties, which seems prudent.
Temperatures through the period will remain near average.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
Any lingering rain showers will taper down by Saturday as high
pressure briefly builds in. A secondary wave Saturday night
could bring additional rain chances, but timing will be
unfavorable for much else. Broad high pressure will then build
into the region for Sunday and Monday. Temperatures will remain
near average, building into the middle of next week.
&&
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions are expected through the evening, though an
isolated shower is possible with a weak crossing sfc trough.
Patchy late night/early mrng MVFR fog is possible, with IFR
likely for valley ports. VFR with diurnal CU is expected Wed
under weak ridging.
.Outlook...
Widespread restriction potential returns with a Thu/Fri cold
front.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.
&&
$$
Area Forecast Discussion
National Weather Service Pueblo CO
303 PM MDT Tue Aug 15 2017
.SHORT TERM...(This evening through Wednesday)
Issued at 302 PM MDT Tue Aug 15 2017
Upper trof moving into western CO will continue to translate eastward
across CO tonight through Monday morning. Low level moisture across
the plains has been slow to erode out of the I-25 corridor
particularly from PUB northward where dew points have maintained in
the lower 50s as of 1 PM. Southern I-25 corridor has seen dew
points drop into the 40s as dry air has started to mix down.
Meanwhile...mountain areas are seeing dew points in the upper 20s
and 30s. By far the deepest low level moisture is expected to
remain entrenched to the east of LHX where dew points will stay in
the mid 50s/lower 60s. This will yield CAPE values in the 2500+ J/kg
range. With forcing from the upper trof approaching, along with
convective temperature being reached, various high res models
develop thunderstorms along the I-25 corridor which will push
eastward and intensify across the southeast plains during the late
afternoon and evening as they move into higher CAPE. Deep layer
shears are a little on the weak side, around 25-30 kts, but with the
forcing from the system and such strong CAPE, one or two severe
thunderstorms will be possible across the plains through this
evening. HRRR pushes most of the activity east of the border by 01-
02z, though northern sections of the southeast plains may see some
residual showers and thunderstorms along/behind a cold front which
will sweep through the plains tonight.
Wednesday will start out cloudy across northern and eastern portions
of the plains with a few lingering showers on the back side of the
system. Upslope flow develops behind the system on Wednesday
however dew points are not terribly high across the I-25 corridor/se
Mts. Just some limited CAPE under 500 J/kg will be available across
the southeast mountains and plains Wed aftn. Initially model
soundings look capped, however with afternoon heating the CAP erodes
across the plains, so really can`t rule out an isolated storm
anywhere across the se mts/plains, though coverage should be a lot
more limited with less forcing behind the system. Temperatures will
be a little cooler on Wednesday. -KT
.LONG TERM...(Wednesday night through Tuesday)
Issued at 302 PM MDT Tue Aug 15 2017
...Wednesday Afternoon through Wednesday Morning...
On Wednesday evening showers will continue to dissipate as the sun
sets. Dew point values should remain in the mid 50s through the
overnight. The NAM12 is suggesting small showers over the eastern
plains overnight, in response to high surface dew points and weak
easterly upslope flow.
Thursday afternoon looks to be a favorable day for severe weather
across the eastern plains. CAPE values along the Colorado, Kansas
border will range 1500-2000 J/Kg with favorable wind shear. The SPC
has issued a marginal severe thunderstorm outlook for south and
southeastern Colorado, which is consistent with our forecast,
especially three days from the event. Thunderstorm initiation should
begin in the later afternoon hours as a shortwave trough, embedded
in the upper-level west to northwest flow, propagates over the
thunderstorm conducive atmosphere. The biggest question will be the
timing at which the shortwave will move across eastern Colorado.
Thunderstorms should be into Kansas by the overnight hours. The
threat for tornadoes isn`t out of the question, but dry lower levels
and weaker low level wind shear makes the atmosphere not favorable
for them. The main concern will be strong thunderstorm winds and
large hail.
...Friday - Wednesday Morning...
The combination of an upper-level low pressure system over
California and a ridge of high pressure begins to build over central
Texas which will advect moisture over southeastern Colorado. GFS20
suggest Friday will mainly consist of mountain thunderstorms in the
afternoon hours, but should dissipate before reaching the eastern
plains. Starting Saturday, the daily pattern will consist of
thunderstorms initiating over the mountains during the early
afternoon hours, followed by the thunderstorms propagating over the
southeastern plains. Starting Saturday evening, GFS 20 outputs
precipitable water values over the eastern plains will consistently
reaching over 1.25", granted the GFS is generally more moist than
what occurs, regardless, precipitable water values should be quite
high, conducive for daily thunderstorms.
-Skelly
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 302 PM MDT Tue Aug 15 2017
Will have to watch the potential for MVFR Cigs to spread
westward into the I-25 corridor and the KCOS and KPUB taf sites
Wednesday morning, but in the mean time expect VFR conditions to
prevail. Isolated thunderstorms will develop over the mountains
this afternoon and move eastward during the late afternoon and
evening. Northern portions including KCOS may see some lingering
showers and thunderstorms as the front moves through this evening.
Otherwise, southeast winds at KCOS and KPUB will shift around from
the northwest this evening as the front moves through. Could be
some gusts to 25-30 kts with locally higher gusts possible near
thunderstorms. KCOS will see the best chance for VCTS through the
evening. KALS and KPUB will be more likely to stay dry through
tonight. For now best chance for MVFR to IFR stratus looks to stay
around LHX and eastward late tonight through Wed morning.
Winds will shift around from the east for KCOS and KPUB on
Wednesday. Another round of thunderstorms will develop over the
southeast mountains and plains Wednesday afternoon but coverage will
be sparse, with KCOS seeing the best chance for VCTS. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...KT
LONG TERM...SKELLY
AVIATION...KT