Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/14/17
Area Forecast Discussion
National Weather Service Bismarck ND
1002 PM CDT Sun Aug 13 2017
.UPDATE...
Issued at 1002 PM CDT Sun Aug 13 2017
T/Td spreads nearing or at zero southeast. HRRR also continues to
advertise widespread fog development across the James River
Valley, patchy areas elsewhere overnight. Thus maintained fog in
the grids and will monitor overnight for possible statements.
UPDATE
Issued at 705 PM CDT Sun Aug 13 2017
Forecast is in good shape for this evening and the overnight.
Expect clouds to clear most areas with the removal of daytime
heating. Lingering showers over the James River Valley will
diminish now through mid evening. Fog remains a possible impact
for the James Valley tonight.
&&
.SHORT TERM...(This evening through Monday)
Issued at 250 PM CDT Sun Aug 13 2017
Latest suite of satellite imagery shows a mid/upper level low
circulating over southeast ND, with one last 500mb-300mb vorticity
lobe swinging into the James River Valley this afternoon. With
this vort passage, the mid/upper low will shift east this
evening, as a brief mid level shortwave ridge migrates into
western ND by 12z Monday. Will continue to mention isolated
showers far southern James River Valley through the afternoon.
With mixed layer cape between only between 250 and 500 J/Kg, weak
lapse rates and no shear, feel the threat for thunder will be too
minimal to mention at this time.
For tonight, dry weather will commence as a mid/upper level ridge
transitory ridge shifts from eastern MT into western ND by 12z Monday.
Despite light northerly to northeasterly winds/drier air in the
boundary layer tonight across the southern James River Valley,
enough low level moisture remains per BUFKIT soundings for some
fog formation. This trend continues in the HRRR/RAP13 surface
visibility forecast. Have utilized these models which produce an
area of fog based on expected visibility reductions from 06z-15z
Monday. Future shifts can monitor/adjust as we get closer and fog
develops.
Otherwise, the mid level transitory ridge quickly loses its
identity as southwest flow begins to impinge into western ND
Monday morning, with the approach of our next mid level shortwave
trough. NAM/GFS show the strongest synoptic scale ascent shifting
from Alberta into Saskatchewan Monday, with weaker lift extending
into western/central ND. Have collaborated with SPC on the
Marginal Risk for Severe Thunderstorms Monday through Monday night
across southwest ND. A lack of strong forcing, mixed layer/most
unstable CAPE close to zero, along with weak/marginal mid level
lapse rates of 6C to 6.5C/Km, will hinder and limit severe
thunderstorms. This despite decent 0-6km Bulk Shear of 25kt to
40kt. Thus, have gone with the gridded solution which just barely
nudges a mention of thunderstorms in Bowman County Monday
afternoon and evening. This thunderstorm mention is highly
dependent on the SREF model, which also keeps the threat for
thunderstorms/and severe thunderstorms south of our border
Monday/Monday night - per 15Z SREF Calibrated Thunderstorms.
.LONG TERM...(Monday night through Sunday)
Issued at 250 PM CDT Sun Aug 13 2017
Scattered showers expected Monday night with the initial shortwave
mentioned from the short term period. The next shortwave arriving
from the Great Basin will have stronger synoptic scale ascent,
which overspreads western/central ND Tuesday. It also appears to
have a stronger mid level low associated with it, but placement
varies between the NAM/GFS/ECMWF. Overall though, Tuesday represents
a more widespread shower/thunderstorm day then Monday/Monday night.
The SREF 3hr Calibrated Severe Thunderstorm indicates that on
Tuesday, there is some potential for severe thunderstorms in far
south central ND, closest to the ND/SD border. The SPC Day
3/Tuesday Convective Outlook portrays a Marginal Risk for Severe
Thunderstorms mainly in the James River Valley. Showers exit the
James River Valley Wednesday morning, with dry/clearing weather
elsewhere . A quasi zonal flow then ensues through the weekend
with periodic fast moving shortwaves and chances for showers/thunderstorms.
At this time, it appears that Thursday and Friday would support
some chances of showers/thunderstorms while the weekend looks dry.
Given the fast flow and timing of shortwaves, expect changes
throughout the upcoming week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 705 PM CDT Sun Aug 13 2017
High pressure will drift southeast tonight with a southerly
return flow developing. Another round of IFR ceilings and fog is
expected for south central and southeastern parts of North
Dakota. KJMS looks to have the highest probability for this to
occur, lesser so for KBIS. Confidence in low ceilings and fog low
for KDIK, KISN and KMOT.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...NH
SHORT TERM...KS
LONG TERM...KS
AVIATION...NH
Area Forecast Discussion
National Weather Service Columbia SC
944 PM EDT Sun Aug 13 2017
.SYNOPSIS...
A moist atmosphere will remain over the region through much of
the forecast period. A dissipating frontal boundary remains
over the area. A surface low developing in the lower Mississippi
Valley will move along the front and into the area on Monday.
This will bring unsettled weather and chances for showers and
thunderstorms through mid week. Expect near or slightly below
normal max temps. An upper ridge will build over the region late
in the week with warming temperatures.
&&
.NEAR TERM /THROUGH MONDAY/...
Regional radar this evening shows most of the shower and
thunderstorm activity has shifted toward the coast while
isolated showers and thunderstorms remain across the area. A
frontal boundary will remain stalled in the area through Monday
morning. The HRRR shows isolated coverage of showers and storms through
tonight which aligns well with radar trends, so have lowered
pops to slight chance for most areas. Precipitable water values
remain relatively high at or above 2 inches. Showers and storms
have contained heavy downpours, but storm movement has been
sufficient enough to preclude significant flash flooding. It
will remain warm and humid overnight with lows in the mid 70s.
Patchy fog and stratus is likely by Monday morning.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
Weak surface front will remain stalled out over portions of the cwa
through the period. High Pwat values will also be across much
of the area, with higher amounts over 2 inches across the east.
Models still indicating a few weak shortwaves moving through the
flow aloft. Still expecting the development of scattered
showers and thunderstorms by late morning, lasting into the
early evening each day. Activity becomes more isolated during
the overnight hours. Biggest issue with these showers and storms
will continue to be the threat for brief heavy rainfall,
especially with the training storms and the high moisture
content in the air. WPC keeps eastern portions of the cwa
outlooked in a marginal risk of excessive rainfall. Conditions
will remain hot and sticky each day, with afternoon high
temperatures around 90 and overnight lows in the 70s.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Both the GFS and ECMWF in general agreement with the main upper
pattern across the southeast through the period. Upper pattern
does flatten out some through the longer term period, with some
weak ridging possible Thursday and Friday, then a weak upper
trough/weakness develops in the ridge into the weekend. Models
keeping general diurnal showers/storms in the forecast each day.
Temperatures will be on the increase, with readings rising into
the middle 90s each afternoon. With the expected moisture and
high rh values, heat index values will range from 100 to 105
each afternoon.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
The main concern will be stratus and fog late tonight and Monday
morning. There will also be scattered showers and thunderstorms
mainly during the afternoon and evening.
Moisture will be high tonight because of convergence along the
front. Also, recent showers have occurred at the terminals. The
moisture and nocturnal cooling should help support stratus and
fog development as indicated by the HRRR, NAM and GFS MOS, plus
many SREF members. Heating and mixing should lead to general
improving ceilings and visibilities later Monday morning. Mainly
followed the GFS LAMP for the timing of greatest restrictions.
There will be scattered thunderstorms mainly during the afternoon
and evening but these were not included in the terminal forecasts
because of timing uncertainty.
EXTENDED AVIATION OUTLOOK...A stalled frontal boundary will
linger during much of the period. Widespread restrictions are
likely especially due to stratus and fog during the late nights
and mornings. There will be scattered to numerous showers and
thunderstorms especially during the afternoons and evenings.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
Area Forecast Discussion
National Weather Service Dodge City KS
650 PM CDT Sun Aug 13 2017
...Updated Aviation Section...
.SHORT TERM...(This evening through Monday)
Issued at 114 PM CDT Sun Aug 13 2017
The main focus for the short term will be a convective risk this
evening though around midnight. A trough extending from south
central Nebraska into northeast New Mexico will be the focus area
for discreet to clustered convective elements originating near
the front range to spread east and southeast this evening. Earlier
runs of the WRF ARW/NMM cores have backed off the large heavy
rain and wind producing organized mcs, in favor of much more
discreet storms, and much less coverage across southwest Kansas.
The HRRR however remains the more aggressive model as of midday,
with widely scattered convection much farther east as well. The
latest 1630 SPC update continued the slight risk over much of the
western 1/2 of the area, and certainly mesoscale parameters
support general severe, i.e large hail up to 2 inch and damaging
wind. Another consideration for this evening will be the
relatively low flash flood guidance generally west of the highway
83 corridor to the Colorado line. Most storms that would impact
the area should be progressive enough to not pose a flooding
threat.
.LONG TERM...(Monday night through Sunday)
Issued at 114 PM CDT Sun Aug 13 2017
There were no significant changes made to the extended forecast
period. An upper trough is slowly carved out across the Great
Basin/Intermountain West regions which will provide the set up
for some vigourous shortwaves to move out into the northern and
central Plains regions by Tuesday night and beyond. Temperatures
remain on the cool side of climatology Monday, while warming a
little closer to normal for the rest of the week (close to 90
degrees). Additional enhanced chances for thunderstorms exist
Thursday night and Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 645 PM CDT Sun Aug 13 2017
Some variation of a south wind will prevail through the forecast
period. Speeds of 12 to 15 knots early this evening will drop off
to 6 to 9 knots tonight, which will continue through at least the
late morning hours Monday. Speeds will probably pick back up to
around 12 knots by afternoon, although that is not currently
reflected in the latest TAF given some uncertainty in pressure
gradient strength. As far as thunderstorm chances go at the
terminals, only GCK has enough of a confidence (barely) to include
a 2-3 hour period late tonight. We will continue to monitor
convective trends after sunset in northwest KS should a mesoscale
convective system become organized more than what convective-
allowing models are showing.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 64 87 68 92 / 30 10 20 30
GCK 63 87 67 91 / 30 10 20 30
EHA 63 86 65 92 / 30 20 20 20
LBL 64 87 67 93 / 20 20 20 20
HYS 64 88 68 91 / 20 10 30 20
P28 66 87 70 93 / 20 30 30 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Green Bay WI
553 PM CDT Sun Aug 13 2017
Updated aviation portion for 00Z TAF issuance
.SHORT TERM...Tonight and Monday
Issued at 208 PM CDT Sun Aug 13 2017
The latest rap analysis and satellite/radar imagery show upper level
low pressure spinning over the eastern Dakotas and western Minnesota
early this afternoon. Showers and storms continue to develop ahead
of the low, but remain mainly west of the MN/WI border. Some decent
cu has popped over north-central WI, and could see an isolated
shower develop over Vilas County later this afternoon into early
this evening. As low pressure moves closer to the region, precip
chances and trends are the main forecast concerns.
Tonight...The shortwave trough will slowly move east across the
northern Mississippi Valley. With mid 50s dewpoints all the way
south into northern Missouri and central Illinois, moisture will
take some time to move into the region. As a result, will see
increasing clouds above 8-9kft from west to east tonight, but precip
chances are likely to hold off until after 09z tonight across
central and north-central WI. More clouds will call for warmer
lows, with temps ranging through the 50s.
Monday...The shortwave trough finally moves into the state and will
see the threat of precip increase from west to east through the day.
Slowed down the timing slightly from the previous forecast, as
indicated by the mesomodels. Will see better mid-level moisture
transport and weak instability develop in the afternoon, so no
reason to downgrade the chance of thunder. Due to the slower arrival
time, will increase temps a degree or two over the east.
.LONG TERM...Monday Night Through Sunday
Issued at 208 PM CDT Sun Aug 13 2017
Low amplitude flow aloft should prevail across the northern CONUS
during this part of the forecast, with several shortwave trofs
moving through the region.
Monday`s precipitation will linger into the evening. Weak shortwave
ridging will dry things out until Wednesday when approaching shortwave
trof and associated surface system brings chance for showers/storms
to the area. ECMWF has been a bit weaker/faster than GFS with
system, resulting in less QPF/deep convection for NE Wisconsin.
Will continue blend of models until we get closer to mid-week.
Another mid level trough will bring chances for showers late in
the week.
Temperatures should generally be near or a bit above normal.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 553 PM CDT Sun Aug 13 2017
An upper level disturbance will move slowly across
Wisconsin Monday and Monday night, while a weak surface low moves
across the southern part of the state. the air near the ground is
dry, so little or no rain is expected through midday Monday. There
is a good chance of showers and thunderstorms and MVFR ceilings
moving in to central and northcentral Wisconsin Monday afternoon
and into the eastern part of the state Monday evening. IFR conditions
are possible across some of the area by late Monday night.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......JKL
AVIATION.......RDM
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
617 PM CDT Sun Aug 13 2017
.SHORT TERM...(This evening through Monday)
Issued at 305 PM CDT Sun Aug 13 2017
The NAM and HRRR/HRRR EXP models have been persistent showing storm
development across the central Sandhills this afternoon and this
evening. This is related to a weak frontal boundary drifting south
through the region. Winds aloft at 500mb strengthen a bit to 35kt to
perhaps 45kt this evening. Instability, 2500-3000 J/KG MLCAPE should
be sufficient for supercell development. Temperatures at H700mb have
warmed to near 10C across Srn Neb and this could be a capping
mechanism as activity moves south toward I-80 this evening. The
models show storm activity breaking up and becoming scattered or
even isolated.
A second disturbance across the cntl Rockies this afternoon should
move east into Wrn Neb late tonight. The showers and thunderstorms
may dissipate as they move through Wrn Neb. The models suggest they
will encounter rain-cooled and more stable air.
POPs for tonight are limited to 40 percent given the limited
coverage shown by the HRRR models. Storm activity should diminish
Monday morning. Isolated showers and thunderstorms are in place
Monday afternoon. The forcing for storm development Monday is highly
uncertain but the instability and cape are favorable.
The SREF was the basis for the fog forecast Monday morning. The RAP
and NAM models maintain a moist layer at h700mb. This should prevent
dense fog from forming. The SREF and MET guidance suggest fog will
form and the forecast is for patchy fog.
The temperature forecast uses blended guidance plus bias correction
for lows in the 50s and 60s with highs in the 80s Monday. A weak
frontal boundary should be draped across Ncntl Neb keeping highs
across Ncntl Neb near 80 while highs rise toward 90 across the
Southwest.
.LONG TERM...(Monday night through Sunday)
Issued at 305 PM CDT Sun Aug 13 2017
The GFS and ECM suggest any storm development Monday afternoon would
grow upscale across ncntl Neb Monday evening. Winds aloft at 500mb
decrease to 25-30kt suggesting the severe weather potential will be
lower. SPC is favoring the Black Hills for genesis and awarded the
Hills a 5 percent severe chance.
Two other significant rain chances develop Tuesday and Thursday and
instability returns Saturday for what could be a third rain
event/opportunity. A broad upper level trof will migrate through
Canada furnishing jetlets of wind speed maxima aloft and an
occasional lowering of heights across Nebraska appear to be the
foci for storm development.
The situation late Tuesday has been advertised for several model
runs now and ambient precipitable water increases to over 1.5 inches
Tuesday afternoon. Winds at 500mb are 25-35kt perhaps suggesting a
HP multicell environment. POPs are 60 percent for this event and SPC
has a 5 percent severe chance covering much Cntl and Swrn Neb.
Moisture returns Thursday and another disturbance moves through.
Winds aloft increase to 25-35kt once again and precipitable water
increases to 1.25-1.50 inches. The model consensus shows h700mb
temperatures falling to around 8C presenting a weak cap.
A similar set up is in place Saturday with warmer temperatures at
700mb.
Highs in the 80s are expected this week and a gradual warming trend
develops Thursday through Saturday. This supports increasing
instability and a strengthening cap at 700mb which could limit
storm coverage.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 616 PM CDT Sun Aug 13 2017
Isolated to scattered storm coverage is underway and should
generally continue as depicted by the HRRR model which shows the
storms exiting south around 03z.
A second disturbance across the Laramie range this evening should
move east into Wrn Neb later tonight. The showers and
thunderstorms may dissipate as they move through Wrn Neb. The
models suggest they will encounter rain-cooled and more stable
air. Any storm activity should diminish Monday morning.
The MET guidance, NAM and SREF models suggest MVFR/IFR cigs/vsby
will develop tonight. The SREF was the basis for fairly widespread
stratus developing.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...CDC
Area Forecast Discussion
National Weather Service Louisville KY
1146 PM EDT Sun Aug 13 2017
.Forecast Update...
Issued at 1145 PM EDT Sun Aug 13 2017
Upstream radar echoes getting a tough time going with the first wave
moving through the TN Valley at this time. That wave however has
set the stage for the second shortwave trough moving in from the
southern IL/MO border to set off some light rains across the region
toward daybreak Monday. Have continued the trend of raising
pops...with perhaps some rumble of thunder along and south of the I-
64 corridor. Cloud cover likely will delay heating for the day
tomorrow, so lowered highs a little as well.
Issued at 715 PM EDT Sun Aug 13 2017
Trend in model data continues to show some rains moving into the
region from a disturbance currently over Arkansas. Have trended the
rain chances up, in response to these changes. Updated products will
be out shortly.
&&
.Short Term...(This evening through Monday night)
Issued at 300 PM EDT Sun Aug 13 2017
High pressure this evening will give way to a shortwave moving
northeast along an inverted trough late tonight into tomorrow
morning. The NAM and WRF models have come in more robust with
precipitation associated with this feature while some of the other
global models remain weaker and further suppressed. Felt enough of
a trend was there in the NAM/WRF and very end of the HRRR to add
POPs late tonight (20% after midnight in the S.) and increase them
slightly for tomorrow (20-30% central KY). Storms look to be mainly
elevated in nature providing a decent rain for locations that
receive a storm. Overnight lows look to range through the 60s.
For Monday, expect isld-sct showers/storms mainly over central KY
with the best chances over south central KY as the shortwave passes
through. Precipitation should decline toward evening. Highs on
Monday look to range through the low to mid 80s. The warmer area
will be southern Indiana where no rain is expected.
.Long Term...(Tuesday through Sunday)
Issued at 315 PM EDT Sun Aug 13 2017
Tuesday - Thursday...
Mid week we`ll remain in an active pattern as multiple shortwaves
move through the Ohio Valley ahead of an approaching cold front
progged to move through Thursday. Tuesday will remain mainly dry
except for far south central KY which may be close enough to a
southerly shortwave to see a stray shower/storm. Temps will increase
into the mid to upper 80s for highs Tues.
A better shortwave looks to bring scattered showers/storms to the
area Wed and then the best chance for precip will be Thu as the cold
front moves through the area. Strong storms may be possible by Thu.
Temperatures will increase ahead of the front with highs in the
upper 80s both Wed/Thu and maybe reaching 90 in some locations over
south central KY Thu.
Friday - Sunday...
The pattern looks to remain a bit unsettled as we head into the
weekend with a slight chance of storms possible. There is low
confidence in precipitation chances/timing with this pattern
however. Temperatures look to be near normal for this time of year.
&&
.Aviation...(00Z TAF Issuance)
Issued at 715 PM EDT Sun Aug 13 2017
Models continue to trend wetter for Monday morning, because of a
system now over Arkansas. We do have a fairly dry airmass in place
over us, so still not overly confident in restrictions occurring
with this rain. Think the best chance for restrictions is at BWG, so
have a PROB30 group for MVFR conditions there, but lesser vicinity
wording at SDF/LEX. Expect light and variable winds through the
period.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...RJS
Short Term...AMS
Long Term...AMS
Aviation...RJS
Area Forecast Discussion
National Weather Service Morristown TN
930 PM EDT Sun Aug 13 2017
.DISCUSSION...
Latest radar indicates end of convection across all but extreme NE
TN at this time. Approaching shortwave over West TN now, is
producing some pcpn in that area but remainder of Middle and East
TN expected to be dry through the first half of tonight. Decreased
POPs slightly through late tonight, in agreement with latest
radar trends and HRRR model. Otherwise tweaked temperatures and
cloud cover in line with observations/satellite respectively. No
other changes needed at this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 74 87 73 87 / 20 70 40 40
Knoxville McGhee Tyson Airport, TN 72 84 71 86 / 20 70 50 40
Oak Ridge, TN 71 84 71 86 / 20 70 50 40
Tri Cities Airport, TN 67 83 67 85 / 20 70 40 50
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...None.
TN...None.
VA...None.
&&
$$
EJH
Area Forecast Discussion
National Weather Service Pittsburgh PA
1040 PM EDT Sun Aug 13 2017
.SYNOPSIS...
Seasonable temperatures and dry weather are expected for most
locations through Wednesday, although showers will be possible
in the Morgantown and Latrobe vicinities on Monday.
&&
.NEAR TERM /THROUGH MONDAY/...
Changes for the overnight period included a fog coverage
reduction as mid and upper clouds will be on the increase with
the advance of a shortwave in wsw flow aloft.
That shortwave may support some weak convection in vicinity of
MGW and LBE and points east as per low level moisture convergence
into the ridges and a weak inverted surface trough. Have
structured POPs for scattered convection using the latest HRRR
and incoming NAM depictions.
Temperature near the seasonal averages continue.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
An isolated shower could persist across the ridges Monday night
and Tuesday with encroachment of an upper trough sliding over
the Great Lakes. Otherwise dry conditions are expected with
high pressure across the eastern Great Lakes. Rising heights via
shortwave ridging support a dry and warmer Wednesday forecast.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Daily rain chances are projected to return for the second half
of the week as a series of disturbances in general zonal flow
crosses the Great Lakes and Upper Ohio Regions. Temperature
under this pattern will remain near the seasonal averages.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Mainly VFR conditions are expected through the TAF period as sfc
high pressure slides E, though late night/early morning MVFR to
IFR valley fog is expected to affect a few ports. A weak
shortwave tracking NE from the TN valley should bring an
increase in clouds Mon, along with shower chances toward MGW.
.OUTLOOK...
Localized erly mrng fog psbl thru the week. 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
904 PM MDT Sun Aug 13 2017
.UPDATE...
Issued at 903 PM MDT Sun Aug 13 2017
Updated for cancellation of a portion of the Severe Thunderstorm
Watch and current pcpn trends.
&&
.SHORT TERM...(This evening through Monday)
Issued at 344 PM MDT Sun Aug 13 2017
...Severe Thunderstorms for the Southeast Plains through this
evening...
Next upper wave evident in WV pics was moving through northwest CO
early this afternoon will be tracking across eastern portions of the
area through this evening. Meanwhile...dew points in the 60s still
reside across the southeast plains...though as one goes westward
into the mountains dew points fall off into the 40s and 30s. Main
concern this afternoon and evening will be potential for severe
thunderstorms as model soundings show rather high CAPE across the
plains...particularly east of a line from La Junta to Kim. Values in
this area will be running in the 2000-3000 J/KG range. Low and mid
level winds look rather weak but do shift around from the southeast
in the afternoon especially across southeast portions of our area.
Overall this will yield 0-6km shears in the 30-40kt range. HRRR
model runs suggest an early show for the mountains with
thunderstorms developing around noon. These will be high based
initially, however as they roll off the eastern mountains into the
plains and tap richer low level moisture, heavy rain, very large
hail and damaging wind gusts will be possible. Although low level
helicities are not all that great, any storms which can tap local
vorticity along surface boundaries could quickly spin up a non-
supercell tornado...so this potential will have to be watched
closely today as well. Satellite imagery reveals a boundary across
northeast Las Animas, northern Baca and southern Bent and Prowers
counties.
Activity decreases quickly this evening so have tailed down pops a
bit sooner than previous couple nights. Flow aloft on Monday
becomes more southwesterly as the upper ridge axis shifts eastward.
Still sufficient moisture for another round of isolated to scattered
thunderstorms across the mountains and plains...though it appears
there will be less forcing on Monday. CAPEs will still be on the
high side across the southeast plains so will have to watch for the
potential for a strong storm or two along the dry line...but deep
layer shears will be weaker which should result in a lower threat
for severe weather than today. -KT
.LONG TERM...(Monday night through Sunday)
Issued at 344 PM MDT Sun Aug 13 2017
Will keep discussion brief due to ongoing active conditions.
Primary meteorological concerns during the longer continue to be
pops, temperatures, heavy rain/localized flash flood issues and
the potential for intense storms at times.
Recent longer range PV analysis, forecast model soundings and
computer simulations suggest that generally drier conditions
should be noted over the forecast district this week(when compared
to the past few weeks) with increasing atmospheric moisture
then anticipated by next weekend.
Overall, expect isolated to scattered primarily afternoon into
nighttime shower and thunderstorm activity during the balance of
the longer term with precipitation generally favoring higher
terrain locations.
Still anticipate that some of the stronger storms will be capable
of generating heavy rain and localized flash flooding concerns
and storms may also be intense at times.
Also, well-behaved gradient winds and low-grade fire weather
issues are expected to continue into next weekend in combination
with maximum and minimum temperatures running near mid-August
climatological averages.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 344 PM MDT Sun Aug 13 2017
Isolated to Scattered thunderstorms will be possible at the
terminals through 01-02z...producing erratic gusty winds up to 30
kts (or stronger should a storm make a direct hit) along with VFR
Cigs/Vis. KCOS and KPUB will have the risk for GS/GR in addition to
locally heavy rainfall. However appears the greatest risk for
severe thunderstorms with large hail and damaging winds will be east
of KLHX through this evening. Thunderstorms should wind down for
all areas by 06z with VFR conditions expected tonight. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...28
Area Forecast Discussion
National Weather Service Seattle WA
345 PM PDT Sun Aug 13 2017
.SYNOPSIS...Onshore flow and a typical pattern of night and morning
clouds and near normal temperatures will extend through at least mid
week. An offshore upper level ridge will shift onshore Thursday
resulting in a warming trend Thursday and Friday. A weak system may
brush the area Saturday likely resulting in cooler temperatures and
increased clouds.
.
&&
.SHORT TERM...Showers have further tapered off this afternoon.
Low level convergence remains fairly weak. Expect mostly cloudy
skies will linger through the central Puget Sound and Cascades
tonight with Partly cloudy skies over the north and south interior.
Onshore flow overnight will reinforce marine stratus with mostly
cloudy skies lingering through Monday morning and afternoon clearing
to partly to mostly sunny skies. High temperatures will be a bit
below normal, reaching into the low to mid 70s over the central and
south interior and mid to upper 60s over the coast, strait and north
interior. The onshore pattern will continue into Wednesday with
temperatures rising to normal levels by Wednesday.
.LONG TERM...The broad upper level ridge over the Gulf of Alaska and
Eastern Pacific will begin to shift eastward Wednesday afternoon as
an upper level trough begins to dig into the Gulf of Alaska from the
Bering Sea. Heights will begin to rise across Western Washington
Thursday or Friday as the ridge is nudged east. The GFS solution
remains the more aggressive with this shift, with 500-mb height rises
reaching to over 580 DAM by Thursday afternoon, while the ECMWF
remains a bit weaker with the ridge as it shifts onshore. The
current forecast continues to reflect the resulting warming and
drying Thursday into Friday with high temperatures reaching into the
low 80s over parts of the interior and upper 60s to low 70s along
the coast.
Medium range models also remain in general agreement on a weak upper
level trough moving mainly into British Columbia later Saturday. The
current forecast reflects this primarily with increased cloudiness
and cooler temperatures.
&&
.AVIATION...A somewhat broad upper level trough will remain over
western WA through 06Z then move over E WA by 12Z. Westerly flow
aloft this evening will become drier NW flow later tonight and
Monday.
Gradual drying has taken place around W WA this afternoon with
cloud layers lifting to VFR conditions with most stations
reporting a BKN040-050 CIG. A convergence zone formed earlier over
central Puget Sound but showers have been rather sparse this
afternoon. W flow through the strait has been weaker than expected
so the convergence zone seems to have stalled over North Puget
Sound. Per the latest hourly HRRR model the convergence zone may
end up staying north and not producing much more showers.
The BKN040-050 CIG should hang around the interior through most of
tonight but may end up eventually dissipating early Monday
morning. The models indicate that an MVFR stratus layer will form
early Monday morning, the dissipate as usual around midday for
good VFR conditions Monday afternoon.
KSEA...The terminal has been in a little hole in the cloud cover
so the SCT040-050 layer will become BKN at times through 06Z. The
convergence zone looks like it will stay north of the terminal
with little shower activity expected. Surface winds have shifted
to northerly at KBFI but winds at KSEA will probably remain
westerly through about 00Z. Winds should still shift to NW-N 5-7
KT sometime 00Z-03Z.
Stratus is expected to form around 12Z for MVFR conditions until
18Z or so. Kam
&&
.MARINE...Westerly onshore flow will weaken overnight. Onshore
pressure gradients have not been increasing much this afternoon as
expected and the gale warning for the central and east Strait of
Juan De Fuca is in doubt, although winds have reached SCA levels.
Still there is a chance that the onshore flow will increase
enough over the next 6 hours to reach borderline gale levels. So,
the gale warning and the SCA for adjacent waters will remain in
place. Winds will diminish as expected after midnight.
A surface ridge will continue to rebuild over the WA offshore
waters tonight, and will remain in place through this week. The
resulting W-NW onshore flow over W WA will be in the weak to
moderate range with SCA winds expected in the strait during most
evenings. Kam
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Gale Warning until 11 PM PDT this evening for Central U.S.
Waters Strait Of Juan De Fuca-East Entrance U.S. Waters
Strait Of Juan De Fuca.
Small Craft Advisory until 11 PM PDT this evening for Admiralty
Inlet-Northern Inland Waters Including The San Juan Islands.
&&
$$
www.weather.gov/seattle
You can see an illustrated version of this discussion at
www.wrh.noaa.gov/sew/gafd/latest_webafd.html
Area Forecast Discussion...UPDATED
National Weather Service Shreveport LA
1030 PM CDT Sun Aug 13 2017
UPDATE... For the 10 PM CDT set of data lowered the chance of
showers and thunderstorms for all the forecast area for the rest
of tonight.
DISCUSSION...
New short range model data from rap13 and hrrr and nam along with
the current doppler radar trend indicated a need to lower the
chance for the overnight period with the exit of an upper level
short wave across the region. This along with the loss of daytime
heating. Kept the higher chances for the North and into the
Northeast zones with next in a series of upper disturbances moving
through the nearly zonal flow in the middle levels. Did not make
any significant changes, other than minor wind speeds for early
Monday, in and beyond the second period of the gridded data. Much
of the current dew point forecast and resultant relative humidity
levels will result in heat indices across areas along and South
of Interstate 20 of 105-108 degrees for Monday and Tuesday. This
could require a heat advisory unless the values lower, so will
allow the next two shifts look at model outputs from 14/00Z and
make needed adjustments or determine if an advisory is needed.
/06/
PREV DISCUSSION... /issued 711 PM CDT Sun Aug 13 2017/
AVIATION...
Scattered shwrs/tstms continue across the region this evening, and
will likely do so through 06Z. Picture somewhat uncertain
thereafter, but expecting a lull in convection until after sunrise
Monday. Otherwise, some mainly MVFR BR/stratus will be possible
around sunrise, but should diminish by mid morning. Tstms will be
possible again during the day Monday, but have refrained from
including in TAFs attm due to uncertainty of coverage/location.
/12/
PREV DISCUSSION... /issued 245 PM CDT Sun Aug 13 2017/
DISCUSSION...
Weak surface boundary extending along I-20 from Tyler to Monroe to
be the trigger for convection this evening. Latest radar imagery
already indicating thunderstorms approaching Canton and moving
east toward Mineola and Lindale. HiRes models suggest convection
to continue across northeast Texas and north Louisiana through
late this evening. Some storms could produce rainfall totals as
high as 3 to 5 inches by mid-evening. At this time, not expecting
widespread flash flooding with this round of storms due to their
movement across areas that have reported only 2 inches or less
over the past 24 hours. However, cannot rule out locally heavy
rainfall producing ponding of water on roadways along with gusty
winds and frequent cloud to ground lightning.
Weak disturbances in upper-level zonal flow to maintain a chance
for afternoon showers and thunderstorms through Monday. Upper-
level ridge to build west across the region through the work week
allowing for only isolated to widely scattered afternoon showers
and thunderstorms each day. However, upper-level ridging will
support much warmer temperatures with highs climbing back into the
mid 90s. With sufficient low-level moisture in place, afternoon
heat index values on Monday will climb to around 105 degrees with
some areas in deep east Texas approaching 107 degrees. Will likely
issue a heat advisory for Monday but will hold off until after
the 14/00Z model runs come in. By Thursday, with the upper-ridge
fully established across the region, the entire ArkLaTex could be
facing heat index values of around 107 degrees. Otherwise, hot and
humid conditions with a a chance for afternoon showers and
thunderstorms expected from late in the week into the weekend.
/05/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 76 93 77 94 / 20 20 10 20
MLU 75 90 76 93 / 30 30 20 30
DEQ 72 87 74 92 / 40 50 30 20
TXK 74 89 76 93 / 40 40 20 10
ELD 73 88 75 93 / 40 40 20 30
TYR 76 94 78 94 / 10 10 10 10
GGG 76 94 77 94 / 20 20 10 10
LFK 77 95 77 95 / 10 10 10 20
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
06/12