Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/03/17
Area Forecast Discussion
National Weather Service La Crosse WI
630 PM CDT Wed Aug 2 2017
.SHORT TERM...(This evening through Friday)
Issued at 302 PM CDT Wed Aug 2 2017
A weak cold front has settled south of the area, although with
little change in airmass. With MLCAPEs of 1000-2000 J/kg and
minimal capping, scattered showers and storms will continue to
develop this afternoon, highest chances in central/western
Wisconsin. With shear very weak, storms will remain disorganized
with severe storms unlikely. A few showers/storms could linger
tonight with increasing southerly flow and warm advection.
Of more significance will be an intense upper shortwave trough
approaching on Thursday. Initially as stronger deep layer forcing
increases Thursday morning, a band showers/storms from overnight may
make it eastward into the area, although high-res guidance differs
somewhat on the timing of this precip, a line of showers/storms
may progress into the area by around sunrise. With little capping
in place, additional showers/storms are expected at times
Thursday along and ahead of the front. With potential for
widespread clouds, the degree of destabilization remains a
question mark. However, deep layer shear increasing to around 40
kts combined with the strong forcing could result in some strong
to severe storms ahead of the front, with winds/hail the primary
threats. A tornado could not be ruled out near the surface
low/warm front. The magnitude of the severe threat will depend on
whether any clearing occurs within the warm sector, how far north
the warm sector/surface low reaches, and the timing of the front.
At this time, southwest Wisconsin appears to have the greatest
chances for severe storms. However, there are still some
differences in the low track, with the GFS farthest south, and the
ECMWF/GEM maintaining a more northerly track across central
Wisconsin. The strongest forcing/deformation zone looks to remain
north of I-90, where the more widespread rain is forecast, with
amounts of 1-2 inches possible in some areas. See the hydro
section for more details.
Cool and showery weather is expected behind the front tomorrow
night. Friday will be more fall-like with breezy northerly winds and
temps likely holding in the 60s to low 70s. Some showers could
linger into Friday behind the departing surface low. Clearing is
possible through the day as subsidence develops behind the upper
trough, but it may be tough to scour out the residual lower level
moisture/clouds.
.LONG TERM...(Friday night through Wednesday)
Issued at 302 PM CDT Wed Aug 2 2017
A seasonably cool period will persist this weekend into next week
under northwesterly flow aloft with chances for scattered showers
or storms as upper level energy rotates through the broader
trough. The 02.12Z GFS is deeper and farther south than the
ECMWF/GEM with an upper low dropping across the region later
Sunday/Sunday night, so details remain unclear.
Some gradual warming is expected early next week, but temps should
remain near to slightly below average. Although timing of the
embedded waves becomes more uncertain by early next week, a period
of drier weather is expected early next week under surface high
pressure. Additional showers/storms are possible by the middle of
next week with models suggesting another upper low and cold front
approaching the region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 630 PM CDT Wed Aug 2 2017
The remaining convection this evening should remain to the east of
both airports before is dissipates after sunset. An area of MVFR
ceilings formed last night over the U.P. of Michigan and has
survived through the day over northeast Wisconsin but with
ceilings coming up to VFR. This area of moisture is shown by the
23.18Z NAM and 23.21Z RAP to work west through the night and
expand underneath the inversion that will form after sunset. This
is expected to bring the clouds with MVFR to IFR ceilings into
both airports overnight. Some slight improvement in ceiling
heights should occur Thursday morning, but look for the MVFR
conditions to remain through the rest of the day. Showers and a
few storms expected to move in Thursday morning and then continue
for most of the day as a short wave trough over North Dakota drops
southeast across the area. The instability looks very limited for
both airports so should primarily be showers with a few embedded
storms. Some of the hi-res models are suggesting a band of showers
and isolated storms could move through early Thursday morning
followed by a break with more activity for the late morning and
afternoon. If this continues to be a trend, will attempt to detail
it with later forecasts.
&&
.HYDROLOGY...
Issued at 302 PM CDT Wed Aug 2 2017
A strong low pressure system will bring periodic showers/storms
later tonight into Thursday night. Rainfall amounts of 1 to perhaps
2 inches are possible, mainly near or north of I-90, where
precipitation may be more widespread. However, locally heavy rain
could also occur farther south with any more persistent
thunderstorms. However, at this time, flood risk still appears low
given the expected progressive nature of the storms.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...JM
LONG TERM...JM
AVIATION...04
HYDROLOGY...JM
Area Forecast Discussion
National Weather Service Taunton MA
1007 PM EDT Wed Aug 2 2017
.SYNOPSIS...
Scattered shower and thunderstorm activity will continue
through the remainder of the week. A cold front will cross the
region Saturday that may bring another round of scattered
showers and thunderstorms. A few strong storms are possible.
Behind the front, expect beautiful late summer conditions on
Sunday with low humidity. Unsettled weather may return early
next week in the form of more scattered showers and
thunderstorms.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Current trends are on the quiet side as any leftover
thunderstorms have dissipated due to the lost of heating. Still
cannot rule out a few spot showers but believe that over trend
is low and thus have gone towards dry pops for now. Believe the
latest HRRR is to aggressive in regenerating precip.
Otherwise the focus turns towards the fog potential for tonight.
Cloudy skies currently, will eventually clear out over the next
several hours. This will result in radiational cooling as winds
will be light. Locations where the heavy rain has fallen, as
well as higher dewpoints will have the best shot for lower
vsbys. Will have to watch closely for dense fog.
Aside from a few minor adjustments, the overall forecast
remains on track for this evening.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Thursday...
Scattered showers and thunderstorms mainly over N/W MA and CT.
Low clouds and fog dissipating during the morning hours with the
early-August sun. Anticipating the burn-off towards the SE coast,
low clouds lingering the longest in and around the Newport RI to
New Bedford MA region. Heights rising within the mid-upper levels
out ahead of a stronger vortmax in associated with deeper mid-
level troughing across the Great Lakes region. A bit more of a
cap across the region, limiting shower and thunderstorm
activity, however given the moist, unstable environment still in
place, some activity is expected, the area of greatest threat
to the N/W away from the more onshore, stable marine air, mainly
atop the high terrain with anabatic, convergent flow up the
slopes. Heavy rain the main threat given the weak shear and mean
wind profile. Storms likely once again to be the pulse-type and
slow moving given the weak steering flow.
Thursday night...
Convection dissipating again, expect the return of low clouds and
fog. Clearing into the evening, anticipating that all the low clouds
along the S-shore dissipated or become scattered, given the low
level moist profile and nocturnal cooling, low clouds and fog develop
once again. Higher dewpoint air over much of the region, feel there
is a risk of low clouds and fog over a majority of S New England.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Highlights...
* Typical summer warmth and humidity Friday and Saturday
* Scattered afternoon and evening showers/thunderstorms Friday
* Another round of showers/thunderstorms with a cold front during
Saturday, a few may be strong
* Heat and humidity break Sat night into early next week
Overview...
Main H5 steering pattern across continues to signal an eastern
Pacific/Alaska high amplitude ridge with responding downstream
trough from broad cutoff H5 low across Hudson/James Bays through
Ontario to the mid Mississippi valley. Will start off with S-SW
winds and warm, humid conditions. With cold front well W of the
region, may see diurnal showers/thunderstorms during Fri across
central and western areas. The upper pattern remains relatively
progressive, so models continue to signal cold front moving
steadily E during Sat, but appears most of the energy will
remain N of the region as the short wave swings NE across
upstate NY into Quebec.
As the short wave lifts out of the region late this weekend,
generally a mainly zonal flow will bring dry and briefly cool
conditions. Another short wave may push E-NE across the Great
Lakes early next week. A weak surface reflection may push E, but
timing and track are in question due to wide model solution
spread. Overall, however, pattern looks to remain progressive
through the middle of next week.
Details...
Friday...
With broad, diffluent SW flow aloft, the cold front should
remain well W of the region closer to the mid level trough. Also
noting low pressure off the mid Atlantic coast which should
slowly pass well SE of the region. With general instability
across the region, expect scattered afternoon/evening showers
and thunderstorms to develop. PWATs generally 1.5 to 1.7 inches,
so may see some locally heavy downpours. Scattered showers may
linger Fri night across central and western areas ahead of
approaching front.
SW winds gusting up to around 20-25 mph along the S coast. Away
from the S coast, temps will top off in the lower-mid 80s.
Saturday-Saturday night...
Cold front steadily pushes E during this timeframe. Best shot
for showers/thunderstorms will occur during the day Sat,
especially across western areas where likely POPs remain in
place, with scattered activity further E. Good instability
noted, with SLIs from zero to -2 and K indices in the lower 30s.
Also noting PWATs in the 1.7 to 1.8 inch range across western
areas, so may see spotty heavy downpours during the day.
Back edge of precip should push E starting Sat evening across
the CT valley, with a few lingering thunderstorms through around
midnight across the E. Expect improving conditions after 06Z-
08Z across E Mass/RI as drier air works in.
Sunday-Monday...
Cold front well offshore by Sunday morning, then broad high
pressure works in. This will be cooler conditions especially
across the interior. H85 temps will be down to +10C to +12C
Sunday morning, coolest across the E slopes of the Berkshires
where high temps will only reach to around 70 (about 10 degrees
below normal). Temps will range to 75-80 across the coastal
plain.
On Monday, the high will shift offshore in fast nearly
progressive mid level flow. Some question on timing of next
approaching low, with leading edge may push into western areas
Mon night.
Tuesday-Wednesday...
Low confidence for Tuesday as low pressure may pass across the
region. Carrying chance POPs for now with timing and exact track
issues in place. Low may push offshore by Tue night, then
another high may approach Wed. For now, have continued with
below normal temps both Tue and Wed.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Thursday Night/...
Tonight...Moderate confidence.
SHRA/TSRA dissipate after sunset. VFR mostly however expect
IFR-LIFR CIGs and VSBYs to develop once again. Higher confidence
for the lower CT River Valley and interior SE New England
terminals. Light S winds overall.
Thursday...Moderate confidence.
IFR-LIFR CIGs and VSBYs erode towards the S-coast, lingering
possibly into the midday hours for places like UUU-EWB. SCT
SHRA/TSRA develop over the N/W interior, mainly across the high
terrain. TEMPO MVFR-IFR with any wet-weather. Otherwise VFR with
breezy S winds, gusts up to 20 kts.
Thursday night...Moderate confidence.
SCT SHRA/TSRA dissipate into evening. VFR initially again but
expect IFR-LIFR CIGs and VSBYs to develop, more widespread over
S New England terminals into Friday morning. Light S winds.
KBOS Terminal...VFR through the night. May have to watch for
MVFR cigs.
KBDL Terminal...VFR to start. Anticipate patchy fog and MVFR to
brief IFR VSBYS in vicinity of terminal from around 09Z through
12Z.
Outlook /Friday through Monday/...
Friday...High confidence.
Mainly VFR. May see sct SHRA/TSRA across N central and western
areas Fri afternoon/evening, then taper back to SHRA across the
CT valley Fri night. Patchy late night/early morning fog with
local MVFR-IFR VSBYS.
Saturday...Moderate to high confidence.
Sct-numerous showers/sct TSRA with local MVFR-IFR conditions.
Some +SHRA possible over central and western areas through early
afternoon. Leftover patchy early morning fog. Light S-SW winds
shift to W across central and western areas Sat afternoon.
Saturday night-Sunday...Moderate confidence.
Leftover SHRA/TSRA over central and eastern areas Sat evening,
should push offshore by 04Z-05Z. Otherwise, VFR conditions. W-NW
winds 5-10 kt.
Sunday-Monday...Moderate confidence.
VFR conditions Sunday. Scattered showers move from W-E during
Monday, but timing in question. Local MVFR CIGS/VSBYS.
&&
.MARINE...
FORECASTER CONFIDENCE LEVELS...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Thursday Night/...High confidence.
Small boats along the S waters should tread cautiously for the
next few days as likely with daytime mixing and subsequent sea
breezes, winds especially within bays and sounds will likely
gust 15 to 20 knots with sustained winds around 10 to 15 kts.
Seas remaining below 4 feet but expect 2 foot seas within the
inner harbors and bays.
Tonight...
Storms dissipated. Some low clouds and fog conditions are
possible along the near shore waters. Otherwise light S winds.
Thursday into Thursday night...
Breezy S winds up to 20 kts during the day. The return of low
clouds and fog along the near-shore possible overnight.
Outlook /Friday through Monday/...
Friday...High confidence.
May see S-SW wind gusts up to 25 kt and seas to 4 ft east of
the Merrimack River Fri afternoon/evening. Otherwise expect
winds and seas below small craft criteria. Locally reduced
visibilities in patchy late night fog.
Saturday...Moderate confidence.
S-SW winds will shift to W-NW Sat night. Gusts up to around 20
kt. Scattered showers/isolated thunderstorms possible Sat
afternoon/evening. Conditions should improve around or after
midnight. Locally reduced visibilities in patchy late night fog.
Sunday-Monday...Moderate to high confidence.
Dry conditions Sunday. Light W-NW winds. Remaining dry Monday
morning through midday, then scattered showers move across from
W-E through Monday night. Local visibility restrictions in
showers and patchy fog.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Sipprell/EVT
NEAR TERM...Dunten/EVT
SHORT TERM...Sipprell
LONG TERM...EVT
AVIATION...Sipprell/EVT
MARINE...Sipprell/EVT
Area Forecast Discussion
National Weather Service Burlington VT
735 PM EDT Wed Aug 2 2017
.SYNOPSIS...
Above normal temperatures and deeper moisture will set the stage
for isolated to scattered afternoon and evening showers and
thunderstorms today and Thursday. Better chances for showers and
thunderstorms will exist Friday into Saturday as an upper level
trough of low pressure slowly moves across the region. Cooler
and drier weather is expected on Sunday.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 630 PM EDT Wednesday...The forecast remains in overall
good shape as we progress into the evening hours. With
relatively high freezing levels (12-13 kft) and weakly forced
flow aloft, convection today was unorganized and pulse in nature
with a few briefly stronger updrafts that plausibly led to
gusty winds and some small hail here and there - nothing too
much above "garden variety" stuff. With loss of heating activity
is steadily on the downturn and have leaned in the direction of
hourly HRRR pops through 9-10 pm or so, after which we should
see a mainly dry overnight period. Most concentrated lingering
activity through sunset should be across the Adirondacks where a
brief heavier downpour will remain possible. Some variable high
clouds from this afternoon`s convection continues to float
around here and there, but this should trend bodily toward
partly cloudy/mostly clear skies later tonight along with patchy
fog in favored locales - all covered in current forecast quite
well. Have a great evening.
Prior discussion...
Still dealing with an environment conducive to pulse storms
late this afternoon with temperatures in the 80s and dew points
in the lower to mid 60s. This combined with 850/500 millibar
lapse rates approaching dry adiabatic and we have enough
instability for isolated pulse storms. Flow aloft is very weak
and thus as we get to sunset...we lose the instability and any
showers or storms come to an end. Should be quiet overnight with
some fog forming in the favored valley locations. Lows will be
in the 60s with some 50s in the mountains.
Thursday is looking very similar to today. Highs in the
80s...dew points in the 60s...and steeper mid level lapse rates
to produce sufficient instability for pulse storms to develop.
Activity will be terrain driven and any mesoscale boundaries.
Flow aloft remains weak and once we lose the daytime
heating...showers and storms will come to an end. Will continue
to word the activity as isolated to scattered showers and
storms. Brief heavy downpours and gusty winds would be the main
threat if any of the storms get organized...which has a low
likelihood.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 337 PM EDT Wednesday...Thursday night will be similar to
Wednesday night with any convection quickly coming to an end and
clear skies and light winds allowing for some fog in the
favored valley locations. Composite analysis of the convective
potential for Friday looks different than Wednesday and
Thursday. Upper trough moves across the Great Lakes but still
remains well west of the area. This will keep more favorable
deep layer shear out across the eastern Great Lakes and into
western New York and parts of northern New York. At this time
feel in our area the Saint Lawrence Valley will see sufficient
deep layer shear moving over the top of the favorable
instability that is expected to develop with highs in the 80s
and dew points once again in the 60s. Could see some organized
storms late in the day and will have to keep an eye on this
situation as there may be an increased hail and wind threat.
This upper trough is slow to move east so we lose the
instability Friday night when the stronger shear finally moves
over the area. Feel the threat for showers and some storms will
exist...but stronger convection may be limited.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 352 PM EDT Wednesday...Trends in the long term continue to
slow the timing of the front that comes through the weekend. I
trended the forecast towards the EC supporting showers across
the eastern Dacks Saturday morning and then brings the showers
into Vermont later in the day. The PWATS do surge but there`s a
only small window in which we could see convection. However the
forcing isn`t collocated in with the axis of heaviest precip so
I`m not too bold on the idea of significant weather.
High pressure builds into the region for Sunday leading to
cooler and drier conditions which brings our temperatures back
to near normal. With northwest flow I did keep the idea of some
lingering showers as there may be some orographic lift helping
showers to stick around.
Towards Monday afternoon, an upper level low will dig into the
the Great Lakes region and bring an surface low pressure system
up the Saint Lawrence valley. This should bring widespread
showers and thunderstorms Monday into Tuesday.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Through 00Z Friday...Isolated storms, mainly in northern NY
winding down this evening and have TAF sites dry through the
overnight hours. Expect KMPV/KSLK to fog in again tonight as
last night with good radiational cooling in light winds and
clearing skies, and dewpoints in the mid 60s. More of a LIFR fog
threat at KSLK where a brief thunderstorm this afternoon dropped
a quick 0.17 inch of rain to wet the ground. Any LIFR fog &
stratus to dissipate around 12z. Thursday afternoon similar to
today with moist unstable airmass and weak forcing, focusing
afternoon thunderstorms again mainly in the higher terrain. Went
predominately with VCSH for now with chances in the outer period
of the TAF. Light southerly wind to become near calm overnight
except KRUT where nocturnal drainage wind from the southeast
sets up.
Outlook...
Thursday Night: VFR. Isolated SHRA...Isolated TSRA...Patchy FG.
Friday: VFR. Breezy. Scattered SHRA...Scattered TSRA...Patchy FG.
Friday Night: VFR. Breezy. Scattered SHRA...Isolated TSRA.
Saturday: VFR/MVFR. Breezy. Likely SHRA...Slight Chance TSRA.
Saturday Night: VFR. Slight Chance SHRA...Slight Chance TSRA.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Monday: VFR. Chance SHRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Evenson
NEAR TERM...Evenson/JMG
SHORT TERM...Evenson
LONG TERM...Deal
AVIATION...Hanson
Area Forecast Discussion
National Weather Service Cheyenne WY
907 PM MDT Wed Aug 2 2017
.UPDATE...
Issued at 901 PM MDT Wed Aug 2 2017
Latest radar loop was showing a few showers and isolated
thunderstorms developing in southwest Wyoming. These showers
appear to be weakening, but should continue their trend east-
southeast through midnight before dissipating as the main upper
level jet energy tracks southeast into northern Colorado.
Meanwhile, the low level flow is progged to turn east tonight
which will allow for the low level moisture to increase along the
foothills and higher elevations tonight. Both the HRRR and NAM3km
are indicating this potential. As a result, we introduced some
areas of drizzle, low clouds and fog in the morning. The main
concerns will be along I-80 near the summit to near Cheyenne.
UPDATE Issued at 715 PM MDT Wed Aug 2 2017
Latest satellite loop was showing the clouds clearing out over the
forecast area due to good subsidence building in. As a result, we
removed much of the POP`s and cloud cover from the forecast this
evening.
&&
.SHORT TERM...(This evening through Friday)
Issued at 240 PM MDT Wed Aug 2 2017
Just a few showers along with a weak storm or two over the higher
mtns so far this afternoon. Cold front now over east-central Wyo
into the northwest Neb panhandle is moving south and should clear
southern parts of the CWA by early this evening. See little
convection now with less instability and with better convergence
pushed east along a pre-frontal trough over western Neb. Best area
late this afternoon looks to be over my southeast Panhandle
counties. Could still see some showers later tonight across
southeast Wy as a shortwave moves southeast over the area and
interacts with some surface upslope flow. Some fog also possible
later tonight into Thursday morning over far se Wy near the
Laramie Range.
Thursday looking mainly dry and cooler after some lingering
morning showers near the Colorado border. Max temps should be in
the 60s and 70s with plenty of cloud cover especially near the
Laramie Range. The surface high moves into the southern plains
Thursday night into Friday with return flow allowing for warmer
temperatures. Some convection possible Friday afternoon as
instability increases and another shortwave approaches from the
northwest.
.LONG TERM...(Friday night through Wednesday)
Issued at 240 PM MDT Wed Aug 2 2017
Strong shortwave trough in NW flow aloft will track across the
area Friday night into early Saturday. Good moisture return ahead
of the wave along with steep lapse rates aloft will likely lead to
convection developing and possibly continuing into the night time
hours Friday night. One or two strong storms are possible with
hail/gusty winds with deep layer shear around 40kt Friday evening
and overnight. Area remains in cool NW flow aloft through early
next week. Models indicate various disturbances tracking SE
through the area during this time which will maintain chances for
afternoon and evening convection. Temperatures will be a bit on
the cool side of normal especially Sunday with 700mb temps around
2 std deviations below normal per the NAEFS.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 528 PM MDT Wed Aug 2 2017
High pressure will continue to build south through the northern
Plains tonight into tomorrow. This will bring quite a bit cooler
conditions to the area. Cannot rule out an isolated storm or two
along the Laramie Range, but this activity should diminish before
sunset. Otherwise, there is some potential for mvfr ceilings to
develop across some of the taf sites late tonight with the best
chance of low ceilings near CYS and LAR.
&&
.FIRE WEATHER...
Issued at 240 PM MDT Wed Aug 2 2017
Decent cold front for this time of year will move south across
much of the area through this evening with some showers and maybe
a couple storms behind it. Much cooler over the plains Thursday
then warming back up Friday into the weekend. Overall fire weather
concerns will remain low though it may be a bit breezy out west
Friday afternoon with min humidities around 20 percent.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...REC
SHORT TERM...RE
LONG TERM...DEL
AVIATION...REC
FIRE WEATHER...RE
Area Forecast Discussion
National Weather Service Hastings NE
710 PM CDT Wed Aug 2 2017
.UPDATE...
Issued at 710 PM CDT Wed Aug 2 2017
Just published a substantial fcst update to drastically cut POPs
(chance for tstms) tonight and decrease cloud cover. All the QG
forcing is with the upr trof over the Dakota`s. So that leaves
tstm development solely tied to daytime heating and the weak
convergence associated with the sfc trof that extends from Wrn Neb
into Ern CO. It just isn`t enough to initiate many tstms.
Therefore...they can`t form a common cold pool and perpetuate
themsevles into the night.
The 22Z HRRR finally has a better handle on this situation. There
could be a few isolated small shwrs (possibly with some thunder)
that develop overnight...but only need a 20% POP to cover that.
Most locations will remain dry this eve and tonight.
UPDATE Issued at 632 PM CDT Wed Aug 2 2017
We cont to monitor tstm potential as we head into the evening hrs.
Convective mode has been cellular out to the W. That is not good
for seeing widespread tstms (and needed rain). This could turn out
to be a hit-or-miss event with only a small number of small
storms (with most getting missed). This is also bad for rain as
isolated storms have a better potential to die off with loss of
heating vs. a squall line with a well-established cold pool that
can perpetuate itself.
If more storms don`t form (and form quickly)...this could be a
disappointing event for those that want/need rain. Most locations
E of Hwy 183 will remain dry...and even those W of Hwy 183 will
only see an isolated storm or two.
Suffice to say we may be overdone on pcpn chances this evening/
tonight. If current trends cont...some substantial changes will be
needed.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 352 PM CDT Wed Aug 2 2017
The main forecast concerns for the short term is the cold front
moving through and the associated precipitation chances.
Cloud cover has increased associated with a MCV moving across
central Nebraska. This cloud cover has kept temperatures a bit
cooler in central Nebraska. Embedded in this cloud cover is a few
light rain showers. Further west, skies have cleared and a few
storms have developed and could develop over the next few hours.
The high-resolution short-term guidance has been fairly consistent
with this light activity this afternoon and the secondary more
potent thunderstorm activity along the cold front this evening.
Taking an average of the guidance timing, think the best chances
will be for the convective line to approach the west/northwest
portions of the area around 23-01z and move southeast from there.
The line is then expected to move into KS and out of the area by
Thursday morning. With modest instability and shear, some storms
could be strong to severe with the main threat being damaging wind
gusts to 60 mph and quarter size hail.
After the line of storms moves through, winds will switch to the
northwest and skies will clear. Overnight lows will be low 60s and
highs on Thursday, as surface high pressure builds in, will be in
the 70s.
.LONG TERM...(Thursday night through Wednesday)
Issued at 352 PM CDT Wed Aug 2 2017
Northwesterly flow persists through the remainder of the forecast.
Surface high pressure will slide eastward on Friday, and high
temps will stay in the below normal 70s. The next more potent wave
will approach on Saturday which increases precipitation chances
for Saturday and Saturday night. There are some discrepancies in
how this wave/front will move through the region which could push
some of the precipitation into the Sunday time frame as well.
High Pressure will build in again behind this wave for the work
week. With an upper disturbance rotating around north of the
Great Lakes the upper flow will become more zonal and another
front threatens the area with a chance for precipitation on
Wednesday.
Highs will be cooler than normal, in the 70s and 80s through the
remainder of the forecast.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 632 PM CDT Wed Aug 2 2017
Significant Wx: Potential for brief IFR +TSRA 02Z-06Z then MVFR
CIGs Thu AM.
Tonight: VFR except during a window when +TSRA are possible from
02Z-06Z could result in brief IFR VSBYs. The amt of cloud cover
and CIGs behind the TSRAs is uncertain...but VFR conds are
expected. Lgt and vrbl winds except near TSRAs. Confidence:
Medium
Thu: MVFR CIGs should invade around sunrise with bases gradually
lifting to 4K by midday. NNW winds 11-16 kts. There could be some
gusts up to 25 kts...but that`s uncertain due to model
disagreement. Confidence: Medium
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
UPDATE...Kelley
SHORT TERM...Billings Wright
LONG TERM...Billings Wright
AVIATION...Kelley
Area Forecast Discussion
National Weather Service Houston/Galveston TX
900 PM CDT Wed Aug 2 2017
.DISCUSSION...
Overall radar imagery shows a smattering of showers around and
lingering light rain. This is expected to continue overnight as
jet streak over N Texas on water vapor imagery moves towards E
Texas tonight. CAMs and even synoptic models show another round of
convection along the Upper Texas Coast around 08Z to about 16Z
Thursday morning. Latest HRRR runs keep most of the convection off
the coast but still leary of synoptic models showing precip
developing fairly far inland. Trough axis is not expected to push
through until late morning to early afternoon so quite possible to
have thunderstorms re-develop given precipitable water values
around 2 to 2.4 inches. That kind of moist airmass does not take
long to recover as long as there is at least some day time heating
with breaks in the clouds. Heavy rainfall threat will still be
there given the amount of moisture but will require these isolated
stronger storms that can utilize 1500 J/kg of CAPE to produce the
higher rain rates. Overall activity tomorrow should be less in
coverage than today, but still expecting scattered coverage by
late afternoon with enough recovery.
Overpeck
&&
.PREV DISCUSSION... /ISSUED 628 PM CDT Wed Aug 2 2017/
AVIATION...
All remaining thunderstorms have pushed off to be over the
nearshore Gulf waters, leaving patches of showers across Southeast
Texas. New TAFs reflect this downturn in activity, gliding
showers at area sites through the evening. Overnight, the guidance
hits ceilings relatively hard, but given the very early start to
new showers overnight even far inland, think the models are being
a bit aggressive. I keep SCT decks at MVFR heights, but think
ceilings will remain higher at this time.
Tomorrow, the base of the upper trough will be swinging through,
giving us another chance at showers and storms. Given model
trends, have delayed the onset of VCSH and VCTS slightly, but
still hold onto potential for another less intense round of
cells to fire.
Luchs
PREV DISCUSSION... /ISSUED 305 PM CDT Wed Aug 2 2017/
DISCUSSION...
Scattered to numerous showers and thunderstorms moved across SE TX
today and for the most part, the storms behaved themselves with
locally heavy but not excessive rainfall. PW values remain high
tonight with values remaining around 2.00-2.20 inches. There
should be break in the precip this evening but some regeneration
looks likely between 09-12z as another vort lobe moves into SE TX.
Upper level winds remain diffluent but not quite as strongly as
today. Fcst soundings look to be most saturated Thursday morning
with some drying noted in the aftn with even some weak capping
developing over the NW part of the area during the aftn. Will
taper PoPs lower over the NW and higher toward the coast/southern
half. On Friday, a weak cold front will inch its way toward the
northern half of the region but probably stall just north of the
area. The feature looks strong enough for showers and storms to
develop especially over the northern half of the area Friday
afternoon. Further south, fcst soundings show some drier air in
the 850-700 mb layer and a weak cap near 800 mb. The weekend is
showing some mixed signals as PW values remain 2.00 inches but
convective temps warm into the lower 90s. Upper level winds not
looking quite as diffluent so other than daytime heating and a
weak sea breeze, not seeing a well defined trigger to increase
PoPs.
PW values perk back up next Monday with values once again
exceeding 2.20 inches. Despite the higher PW air, fcst soundings
show dry air in the 850-700 layer and also below 850 mb. A well
defined upper level disturbance over North Texas will provide a
glancing blow to the region but again, having trouble finding a
trigger for widespread shra/tsra. Will maintain chance PoPs but
confidence is low. Upper level ridging will try to expand into
Texas from the east next Tues-Thu with a weak inverted upper
trough sliding westward beneath the ridge. It looks like this
feature will remain south of the HGX CWA but it could bring some
isolated shra/tsra to the region as moisture levels briefly
increase. 43
MARINE...
Mainly light south winds (sometimes more variable and
stronger in/around shower and thunderstorm activity)
can be expected through the end of the week. A better
onshore flow with south winds generally in a 10 to 15
knot range and increasing seas are anticipated over
the weekend and into the start of next week under a
slightly tighter pressure gradient. At this time, both
winds a seas are expected to remain under caution
levels. 42
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 74 91 75 95 77 / 40 40 20 30 20
Houston (IAH) 75 90 78 94 77 / 30 50 20 40 20
Galveston (GLS) 79 87 82 89 82 / 40 60 40 40 30
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...39
Area Forecast Discussion
National Weather Service Huntsville AL
908 PM CDT Wed Aug 2 2017
.NEAR TERM...(Tonight)
Issued at 908 PM CDT Wed Aug 2 2017
Quiet weather prevailed across the greater Tennessee Valley this
evening. Showers and storms that impacted parts of northwest Alabama
in the mid afternoon have long since faded. The only activity within
the 124 nmi range ring (where rain is measured) was occurring across
portions of middle Tennessee, west of Nashville and mostly north of
I-40.
The infrared satellite view from GOES-16 indicated the higher
altitude clouds moving in a SW-NE manner from northern Lousiana to
the Carolinas and Virginia. Lower clouds with bases in the 10-12kft
above ground level were scattered from the northwest Mississippi
Delta, across northwest and north central Alabama, to western and
middle Tennessee. Those clouds, and forecast soundings from the RAP
and HRRR suggest they should thin somewhat during the overnight,
maintaining partly cloudy skies.
Deeper moisture present, and especially from the recent
shower/thunderstorm activity, along with slightly longer nights that
August offers, should be favorable for patchy fog formation. Given
that NW Alabama had the most rainfall around the region (some
mesonet sites recording over 1.5") those spots would be more likely
to experience fog, along with areas near bodies of water and in
sheltered spots. As such, have left this possibility in the forecast
for the late night. The moisture should make for slightly warmer
night time lows over NW AL - so made minor adjustments in this area.
The rest of the forecast for the night time looks to be in fine shape
at this time.
.SHORT TERM...(Thursday through Friday)
Issued at 249 PM CDT Wed Aug 2 2017
Not a whole lot of change in the short range models since yesterday.
General trof position at 500 mb will remain over the southeast U.S.
through Friday night. Minor waves will continue to track from the
southern Plains into the Gulf South. A small wave is still progged to
move east through AL and far southern TN on Thursday. Will maintain a
low chance of showers/thunderstorms, with best chances still in our
southeast counties in closer proximity to the higher vorticity in the
wave. Cloud cover and temperatures will vary depending on precip
development, but will stay the course with upper 80s to around 90
once again (warmest west including HSV and MSL). With the shortwave
departing east and loss of solar heating, convection should die off
quickly by around sunset. As a vigorous shortwave digs into the
central Great Lakes on Friday, the trailing trof axis will move
through the OH and TN valleys Friday and Friday evening. The
associated cold front will slowly drop south through Friday evening.
The highest chances of precipitation will be during the day Friday
ahead of the front coinciding with peak heating. CAPE values of
1500-2500 j/kg and 30kt of 6km bulk shear will be sufficient for
strong thunderstorms. However, activity will struggle to remain
organized with weakening QG forcing and convergence along the front
Friday evening.
.LONG TERM...(Friday night through Tuesday)
Issued at 249 PM CDT Wed Aug 2 2017
The front that will bring showers and thunderstorms on Friday will
be to our south on Saturday but will slowly push back northward by
Sunday. The southerly winds behind the front will pull back in
plentiful moisture of dewpoints ~70 degrees and PWATS ~2 inches. An
upper-level trough develops in the North Plains on Sunday and a
series of disturbances in the base will lift up into the TN Valley
Sunday and Monday. This will result in scattered to numerous showers
and thunderstorms across the area capable of producing locally heavy
rainfall. As the system progresses towards the Great Lakes, it will
send a weak cold front to the area Monday night/Tues keeping a chance
of storms through the extended forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 618 PM CDT Wed Aug 2 2017
VFR conditions are expected to prevail across N AL/S middle TN for
the next 24 hours with a couple of exceptions: 1) reduced
visibilities due to fog (3-5 SM), especially close to KMSL between
10Z-13Z, and 2) additional storm development that is possible late
in the period. Any storms that develop may cause IFR-MVFR drops in
VIS/CIGS mainly south of the TN River near K4A9, K8A0, KCMD, K4A6.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...RSB
SHORT TERM...17
LONG TERM...JMS
AVIATION...SL.77
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wilmington NC
947 PM EDT Wed Aug 2 2017
.SYNOPSIS...
Moisture will slowly increase over the next few days, bolstered
on Friday by the approach of a cold front. This front will
weaken over the weekend to our west but ample moisture will
linger for unsettled weather into early next week. Another cold
front will approach the area from the northwest on Wednesday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 930 PM Wednesday...A slight update to the near term as
now the NAM and HRRR are indicating that a disturbance rotating
around the bottom of the large trough over the eastern U.S. will
transport moisture into the region towards daybreak along the
coast. I have upped the pops along the SC counties into
Brunswick, New Hanover, Columbus and parts of Bladen and Pender
as the moisture rides up the coast. The timing of the
precipitation will begin along the southern portions of the cwa
mainly an hour or two before sunrise to about an hour or two
after sunrise as you move form south to north. The best chances
of precipitation will be along the coastal areas and less
chances farther north and inland.
The the return of a light easterly flow have increased the low
level moistures will moderate the low level temperatures are
expected to fall into the upper 60s to the lower 70s. Highs on
Thursday will be in the mid to upper 80s.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
As of 300 PM Wednesday...An area of tropical moisture in the GOM
today will lift NE and drive at least a wave of low pressure up the
coast Thursday night into Friday. This wave is forced to eject NE
thanks to a deepening longwave trough dropping across the Southeast,
and the question will be how close to the coast will this feature
pass, and how much moisture will accompany it. ECM/NAM are much more
robust with this feature bringing a closed surface reflection right
along the coast with heavy rainfall, while the GFS is a bit weaker
and drier. Current satellite imagery and presence of offshore
stalled boundary suggest the wave will travel just east of the CWA,
with highest POP across SE zones and into Cape Fear. Still some
uncertainty into how much QPF will occur across the CWA, but with
PWATs climbing above 2 inches Thursday night, WPC QPF seems
reasonable with up to an inch far SE zones, and very little NW of i-
95. have tried to mimic this in the QPF forecast with LKLY POP east,
SCHC west.
This feature will lift NE away from the area Friday, but as the
trough axis stays west of the coast, strung out vorticity, continued
moist advection, and relatively lowered thicknesses will keep the
potential for unsettled weather with showers and tstms through
Friday night. Do not see any significant surface features during
this time, and mid-level forcing is weak and strung out so while
showers are possible all day Fri/Fri night, do not expect
significant QPF or an all-day rainfall.
Clouds and rainfall will keep highs below climo Friday, mid 80s near
the coast and upr 80s well inland, with weak diurnal ranges
producing mins only around 72-75 Friday night, a few degrees warmer
than Thursday night.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 3 PM Wednesday...The area will remain between a west
Atlantic ridge and a Great Lakes trough through the period.
Separate cold fronts will drop into the area over the weekend
and again on Wednesday. The net result will be an unsettled
period with a chance of showers and thunderstorms each day
though the greatest likelihood for rain should be the weekend
and again Wednesday. Temperatures through the period will
generally run in the mid to upper 80s by day and drop to the
lower to middle 70s overnight.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
As of 23Z...VFR conditions to continue across the terminals through
06 utc when BR formation is possible. previous discussion cited
guidance hinting IFR is likely at KFLO and MVFR at all other
sites. Left br in tafs except for KCRE as south to se wind
should mix it a bit to keep br from developing. Winds will be
generally less than 8 knots becoming east to south along the
coast and lighter at inland taf locations. Chances for
precipiation and increase in clouds begin to appear shortly
after daybreaks on NAM and Euro models mainly along the coast
decided to included vcts at coastal terminals. Better chance of
pcpn moving across the terminals after 21z as models develop
low across the SE and move it across the region by evening. NAM
is the wettest model with GFS and Euro less either way looks
like the chance of pcpn increases late day.
Extended Outlook...Possible periods of MVFR/IFR Thursday night
through Sunday as chances of showers and thunderstorms increase
at area TAF sites.
&&
.MARINE...
NEAR TERM /THROUGH THURSDAY/...
As of 930 PM Wednesday...with that area of weak low pressure
moving up the coast overnight into Thursday winds will become
southeast 10 to 15 knots. showers and thunderstorms chances
increase during the day on Thursday starting around sunrise
across the SC waters slowly progressing to just after sunrise in
the NC coastal waters. Seas will run 2 to 3 feet with a slight
increase to 4 ft by late Thursday.
SHORT TERM MARINE/THURSDAY NIGHT THROUGH FRIDAY NIGHT/
As of 300 PM Wednesday...High pressure offshore will expand through
late week ahead of a cold front approaching very slowly from the NW.
This front will not reach the area this period, and instead function
to tighten the gradient across the waters driving SW winds up from
10-15 kts Thursday night, to 15-20 kts Friday night. A 2ft/9sec SE
swell will exist through the period, but become increasingly masked
by an amplifying 5-6sec SW wind wave which will grow towards 5 ft
late. This will create significant seas of at least 3-4 ft late
Friday, with some 5 fters possible, up from 2-3 ft Thursday night.
LONG TERM /SATURDAY THROUGH MONDAY/...
As of 3 PM Wednesday...Expect southwest winds 10 to 15 KT Saturday
to weaken slightly to about 10 KT Saturday night and continue through
Sunday night before increasing to 10 to 15 KT again Monday. Seas
should run 2 to 3 FT though a few 4 footers are possible Saturday.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...RAN
NEAR TERM...MAC
SHORT TERM...RAN
LONG TERM...MBB
AVIATION...MAC
MARINE...MAC/RAN
Area Forecast Discussion
National Weather Service Wilmington OH
953 PM EDT Wed Aug 2 2017
.SYNOPSIS...
Showers and thunderstorms will continue to weaken this evening
as the sunsets with showers and thunderstorms expected again
Thursday. More storms can be expected as a cold front moves
through the area on Friday. High pressure will build in for the
weekend.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
During the day Thursday a closed low pressure will be located
over Minnesota and be slowly pushing southeast. Ahead of the
closed low a jet streak will extend across Illinois into
Michigan. This puts the favorable position for shower and
thunderstorm coverage more towards Indiana now. Latest HRRR runs
also tends to indicate better coverage out west. Still though,
both NAM and GFS forecast soundings both destabilize tomorrow
afternoon with mean flow very weak. This again supports
scattered thunderstorm coverage in the afternoon.
Prev Discussion->
Scattered storms will continue through the late afternoon and
diminish with the loss of heating early this evening. Locally
heavy rainfall and gusty winds with minor downbursts will remain
possible. Beyond early evening, expect little to no activity
with partly cloudy skies. Lows will be a bit warmer than last
night.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Weak troughing will persist across the region with minor
disturbances moving through it. This will result in additional
scattered showers and thunderstorms, primarily in the afternoon.
However, there is the possibility of some activity lingering
into the night in the northwest counties. Weak wind fields will
result in unorganized storms with locally heavy rainfall and
gusty winds the primary concern. Highs should be close to
persistence. Lows will be in the mid to upper 60s.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
A fairly strong mid level short wave embedded in a broader upper
level trough will pivot east across the southern Great Lakes Friday
into Friday night. This will help drive an associated cold front
east across the upper Ohio Valley through the day on Friday. The
last couple of model runs have trended somewhat slower with the
frontal passage and as as a result, our area will be in a somewhat
more favorable position for thunderstorm development. As we
destabilize ahead of the front through late morning and into the
early afternoon, expect to see an increase in coverage along and
ahead of the front across our area. Precipitation should then taper
off fairly quickly from west to east through the mid to late
afternoon hours as the front moves east. Mid and deep layer shear
will be on the increase along and ahead of the front as wind fields
increase ahead of the short wave. This will combine with the slower
timing of the front to increase our severe threat, particularly
across our eastern areas where the better instabilities should
exist through mid afternoon.
High pressure and a cooler, drier airmass will build in behind the
front for the weekend. Highs on Saturday and Sunday will mainly be
in the mid to upper 70s with morning lows in the mid to upper 50s.
The 12Z GFS has trended faster with the approach of the next trough
axis early next week but it is still slower than the past several
runs of the ECMWF. As a result, will speed up pcpn chances heading
into Sunday night and then linger a chance through the day on
Monday. With the faster timing, will also go ahead and dry us out
Tuesday into Wednesday. High temperatures will remain in the mid to
upper 70s through mid week.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Scattered convection continues this evening and should decrease
in activity over the next couple of hours as the sunsets.
Overnight weak southwest flow will continue with some VFR
clouds. High res models do show a weak signal of some patchy
ground fog, but think chance is limited mainly to the river
valleys.
Thursday morning cumulus will quickly develop as moisture
remains abundant across the area. During the afternoon scattered
showers and thunderstorms will again be possible as forecast
soundings quickly destabilize (both GFS and NAM). Coverage on
high res models looks slightly better west towards the upper
level support. For now have just added a vicinity thunder into
the TAFs as the atmosphere again looks to destabilize.
OUTLOOK...Thunderstorms are possible Thursday evening through
Friday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Haines
NEAR TERM...Haines
SHORT TERM...
LONG TERM...JGL
AVIATION...Haines
Area Forecast Discussion
National Weather Service Jacksonville FL
935 PM EDT Wed Aug 2 2017
...PERIODS OF HEAVY RAINFALL ACROSS NORTHEAST FLORIDA TONIGHT
AND SOUTHEAST GEORGIA ON THURSDAY...
.UPDATE...Deep layer moisture over the area combined with shortwave
trough over northeast FL and far southeast GA, and a weak frontal
boundary over northeast FL continues to produce showers and a few
embedded thunderstorms. With loss of heating, all convective
activity is trending to a weak phase this evening. However...activity
over the northeast Gulf of Mexico will be activity overnight due to
abundant moisture and low level moisture flux convergence. This
activity should keep the Suwannee Valley area, including
Gilchrist, Alachua and western Marion county as well in a flux of on
and off showers and a few storms. Locally heavy rainfall is the main
concern here. Have updated the forecast to reflect current trends
and leaned toward latest HRRR runs for POP forecast. Min temps
tonight in the lower to mid 70s.
Thursday...deep southwest flow with very moisture environment with
PWATs of 2 to 2.4 inches and mid to upper level troughing over the
southeast states will produce scattered to numerous showers and
storms. Periods of heavy rainfall expected. Highs may be held in the
mid 80s...possibly some upper 80s over far southeast zones.
Flooding/flash flooding remains the primary concern this period, and
excessive rainfall will continue on Thursday. Widespread
totals of 1 to 2 inches are expected, with localized areas receiving
much higher amounts in training showers and thunderstorms.
&&
.AVIATION...VFR at this time with multilayered clouds overnight
but chance of MVFR cigs later on tonight. Showers and
a few storms expected to decrease in chance overnight except for
GNV. Have continued TEMPO group for GNV tonight. Any lower CIGS down
to IFR seemed to be most probable away from terminals over inland SE
GA and perhaps over parts of the Suwanee Valley. High rain chances
for Thursday with showers and thunderstorms expected with MVFR and
IFR restrictions expected at times.
&&
.MARINE...No major changes tonight with southeast winds over the GA
zones near the front and south winds over NE FL waters. Winds
should turn south over all waters by early morning. Winds about
10-15 kt. Seas mainly 2-3 ft outside of thunderstorms.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 73 86 73 86 / 20 80 40 60
SSI 76 85 76 86 / 80 70 30 40
JAX 74 86 75 89 / 60 60 10 30
SGJ 74 87 74 89 / 30 50 20 40
GNV 72 85 72 90 / 60 70 10 40
OCF 74 87 73 91 / 50 50 10 40
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Shashy/Zibura/Corless
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
938 PM CDT Wed Aug 2 2017
.UPDATE...
Issued at 938 PM CDT Wed Aug 2 2017
The forecast for late tonight through Thursday remains largely on
track. One important trend to keep an eye on is a southward trend
in the CAMs and now even the NAM with the surface cyclone across
far southern MN closer to the ECMWF. This could focus the
deformation band of heavy rain further south as well. Latest RAP
and HRRR are more widespread with the 1+ inch totals and have
several pockets of 2-3+ inch totals across the southern half of
MN through mid afternoon. This is in stark difference to that of
the GFS and 12Z runs of the NMM/ARW which kept most of southern MN
dry from mid morning onward following brief a line of storms with
the cold front. This evolution will ultimately depend on the
interaction with the upper low now dropping south into north
central North Dakota, clearly evident on water vapor imagery.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 420 PM CDT Wed Aug 2 2017
Weather in the short term will be dominated by an anomalously
strong storm system, bringing with it a chilly & damp Thursday
that will feel more like October than early August. A potent
shortwave continues to dig over the Dakotas with a widespread
shield of precipitation continuing to move off to the east. This
precipitation is only expected to become more widespread into the
evening as a surface low deepens over SE SD. Models this afternoon
have come into general agreement with bringing the low a little
further south, tracking generally along I-90. Not often you get to
talk about deformation bands in early-August but expecting the
heaviest precipitation to fall along the axis of greatest
deformation, more typical of something we`d see with a winter
storm. The track of the low along I-90 places this axis along a
Fargo-Brainerd-Hayward WI line where a widespread 1.5-2" of
rainfall is expected. Flooding is not anticipated to be an issue
with this system as we`re expecting a steady rain falling over a
long enough time frame where basins should have no problem handling
this extra water.
Rainfall is expected to begin around 10pm this
evening across far-western MN, and continue to spread east across
the state, reaching the Twin Cities around 3am & eventually into
west-central WI towards sunrise. As noted earlier the band of
heaviest rainfall will set fall over central MN but the rest of
southern MN & west-central MN can still expect close to 1" of rain.
In addition to the steady gray rainfall, Thursday will feel even
more raw with temperatures close to 20 degrees below normal. The
forecast high of 64 at MSP is more typical for October 1st or 2nd!
Highs will likely come just after midnight & struggle to warm
during the day with the consistent rain & cloud cover. Areas in
central Minnesota under the main axis of precipitation will even
struggle to make it out of the 50s. Precipitation will taper off
Thursday evening from west to east across the area & should be off
into central Wisconsin by sunrise Friday. Clearing skies &
northerly winds behind this system will bring another fall-like,
but much more pleasant, day for Friday.
.LONG TERM...(Thursday night through Wednesday)
Issued at 420 PM CDT Wed Aug 2 2017
The dominate theme for the long term will be northwest flow and a
prolonged period of below normal temperatures. Our best chances for
rain look to be primarily diurnally driven showers this weekend and
then tied to a frontal passage Tuesday night/Wednesday next week.
We should start the long term off fairly benign as high pressure
slides across the area in the wake of Thursday`s system. We`ll have
skies clearing from west to east with light winds. H85 temps of 10-
12C though will ensure highs are 5-10 degrees below normal.
For the weekend, we get stuck in a wavy northwest flow, with cool
temepratures aloft promoting steep afternoon lapse rates and the
threat for showers. Think the GFS is way overdone with the strong
system and washout it brings to the area Sunday, so stayed closer to
a ECMWF/Canadian blend for the weekend. We did knock back precip
chances quite a bit for Saturday, with the likelies in western MN
now down to chance pops as the ECMWF and Canadian show the shortwave
driving precip from central SoDak Friday night down into Iowa
Saturday afternoon. For the MPX area it`s diurnal instability driven
showers that will be our threat, though the ECMWF shows the greatest
instability axis existing from northern WI back through northeast
MN, so we may not see all that much activity locally.
Sunday looks to be more of the same as we stay in a pocket of
relatively cool air aloft. Again ignoring the 12z GFS (which has a
washout similar to what we are expecting Thursday), we expect
scattered afternoon activity, though no severe weather is expected.
We finally get rising heights on Monday, which will push the cold
pool aloft off to our east, ending the threat for diurnal showers.
However, there will be another strong shortwave dropping through
south through central Canada. This wave will drive a seasonably
strong cold front across the area Tuesday night/Wednesday. This will
offer us our warmest day of the long term and only opportunity for
warming into the 80s in the southwest low level flow ahead of the
front Tuesday. Behind the front, h85 temps drop down to around 8C,
so we`ll be struggling to get much past 70 at the end of next week,
even with full sunshine.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 725 PM CDT Wed Aug 2 2017
Conditions will deteriorate from west to east tonight into
Thursday. Rain will gradually build eastward overnight, with the
heaviest rain likely across central/eastern MN into western WI, or
roughly along and north of I-94 late tonight and Thursday.
Widespread MVFR cigs expected by morning, but some IFR cigs are
also expected across western WI Thursday. Winds will become north
and gust as high as 25-30 kt behind the low Thursday afternoon.
KMSP...MVFR cigs and -shra will arrive after 09Z, with heaviest
rain expected Thursday morning and cigs approaching IFR levels.
/OUTLOOK FOR KMSP/
Fri...VFR. Wind NW 5-10 kts.
Sat...VFR. Chc MVFR/-SHRA late. Wind light/variable.
Sun...VFR. Chc MVFR/-SHRA. Wind NE 5 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
UPDATE...BORGHOFF
SHORT TERM...ETA
LONG TERM...MPG
AVIATION...BORGHOFF
Area Forecast Discussion
National Weather Service Omaha/Valley NE
721 PM CDT Wed Aug 2 2017
.SHORT TERM...(Tonight through Saturday)
Issued at 255 PM CDT Wed Aug 2 2017
The primary forecast issues in the short term and precipitation
chances from tonight into Thursday morning, and then also again
from late Friday night into Saturday.
Taking a look at the current situation. A cold front extended
from a low pressure center that was just east of Phillip, SD at
2 pm. The atmosphere over eastern NE has destabilized, with MLCAPE
values mainly 1000 to 2500 J/kg. Sfc to 6 km bulk shear is not
impressive, generally 30 kts or less. There is an axis of higher
downdraft CAPE though, upwards to 1000 or so centered along
highway 81. The highest risk of severe storms is to our west, but
there does appear to be some risk of gusty winds and maybe some
hail in parts of our area until 9 pm or so. That would be mainly
northwest of a line from about Pender to Seward. Did give the
convection allowing models (CAMs) a bit more weight for this
evening - compared to the parameterized models which are slower to
bring storms into our area.
Tended to favor a blend of the 12Z NAM, 15Z SREF, the 12Z ECMWF
and recent RAP runs for later tonight. The RAP however seemed too
wet and thus did give its QPF much weight. That surface low and a
cold front will continue to move east through the region during
the overnight hours, but the strongest QG forcing remains to our
north. So that is probably where the heaviest QPF will be.
Additional showers and storms, at least scattered coverage,
should develop with the frontal circulation overnight.
Precipitation will likely move out of southeast NE and southwest
IA by late Thursday morning, but it seems possible that some
instability showers may develop in the afternoon. That would
mainly be across the northern half of the forecast area. Coverage
seems like it would be very isolated, so will not include in
official forecast at this point. Highs will be cooler than today,
in the 70s.
Cool high pressure will build over the area Thursday night, with
lows expected to be mostly from 48 to 52. The high moves east on
Friday and return flow starts to strengthen. Temperatures will
start out cool though and mostly reach 75 to 80 in the afternoon.
Will keep chance POPs going in our western counties for late
Friday night and then chances mainly 30 to 60 percent Saturday.
.LONG TERM...(Saturday night through Wednesday)
Issued at 255 PM CDT Wed Aug 2 2017
Timing the ending of precipitation chances ending is not clear for
the rest of the weekend, so will keep some chance of showers and
storms into Sunday. A pretty cool airmass will likely get pulled
down into the area Sunday night and Monday but fairly deep mixing
with northwest winds in the afternoon should offset the cooling.
Temperatures then moderate a little toward the mid part of next
week but only to the lower 80s, still a bit below normal. More
rain chances return for Tuesday night and Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 644 PM CDT Wed Aug 2 2017
A couple of rounds of showers and thunderstorms will push through
the area tonight initially through northeast Nebraska then
spreading southeast through 11Z. Due to the spotty nature of the
thunderstorms will include showers/vcts. Behind the cold front
surface winds strengthen out of the northwest to 15 to 25kts after
11Z. Some MVFR cigs may move into northeast Nebraska Thursday
morning for a few hours.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...Zapotocny
Area Forecast Discussion
National Weather Service Nashville TN
726 PM CDT Wed Aug 2 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Upper divergence appears to be quite weak overnight. The upper
shortwave energy will be strongest way upstream as well as across
portions of the deep south. Hrrr indicates that the ongoing
convection should die out by 04z-05z. However, will opt to
increase the pops into the chc category for this evening across
northwestern areas, prior. Otw, will add some patchy across the
area for late tonight. Current dewpoint depressions are rather
low and numerical guidance does support lower vsbys, especially
for the southeast half. Furthermore, partial clearing is expected
overnight. Min temps still look to be on track as fcst mins are
close to current dewpoints. Update out shortly.
&&
.AVIATION...
00Z TAF DISCUSSION.
CKV/BNA/MQY/CSV...Other than light shwrs CSV that may persist
until 03/02Z, convection potential ended terminals this evening.
Some MVFR fog possible terminals 03/08Z-03/14Z. Otherwise per
above mentioned sfc/upper level pattern, iso/sct shwrs/tstms
once again possible 03/17Z-03/24Z per moist/unstable atm
continuance. Can not precisely forecast terminal timing/impacts
shwrs/tstms during this period, but certainly potential
development/moving into vcnty possible.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......21
AVIATION........31
Area Forecast Discussion
National Weather Service New York NY
951 PM EDT Wed Aug 2 2017
.SYNOPSIS...
High pressure will remain over the Western Atlantic through
Thursday, stretching into the Northeast. Low pressure then moves
through the Great Lakes Region on Friday and sends a cold front
through the local area on Saturday as it is passes to our north.
High pressure then builds in on Sunday, followed by another low
pressure system early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Showers and thunderstorms have ended across the entire CWA, so
lowered POPs to reflect current observations. The only thing
that needs to be watched is the line of showers and
thunderstorms over central Pennsylvania. It is currently
weakening, but the HRRR model does show some precipitation from
this feature moving into western portions by 2 am and
thereafter, continuing to weaken as it moves through. However,
there is very little surface instability to work with, so kept
precipitation out of the area overnight. Otherwise, made updated
forecast to reflect current observations.
Convection will continue into early evening before weakening after
sunset with loss of heating and with best shortwave forcing passing
to the NE. The threat of at least minor urban/small stream flooding
remains with the slow motion of the storm cells. Localized
flash flooding cannot be ruled out either. Otherwise, remaining
mostly cloudy for the overnight with sufficient moisture aloft.
Patchy fog is also expected away from the NYC metro.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Broad upper troughing continues on Thursday with a weak surface
trough probably developing nearby during the afternoon, but there
does not appear to be any well defined shortwaves. So the surface
trough plus any weak shortwave, seabreeze or outflow boundary will
act as the focus for convection. Will cap PoPs in the chance
category with a focus in the afternoon as convection will be mainly
diurnally driven. The steering flow remains weak, so locally heavy
rainfall is possible as any storm would be slow-moving.
Near seasonable high temperatures are forecast on Thursday.
The flow aloft becomes more anticyclonic Thursday night. This
combined and with the loss of daytime heating would serve to lessen
the coverage of showers/storms, however both NAM and GFS seem to
indicate weak shortwave and isentropic lift shifting through during
the night, so will go with some form of PoPs for most areas through
the night.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
The region then remains under SW flow aloft Friday-Friday
night, and with no notable shortwave progged through the area,
would expect mainly pulse diurnally driven convection, mainly
over the interior into Friday evening, as onshore flow will
enable local marine influence to serve as a limiting factor for
coastal zones. An approaching cold front could trigger some
showers/storms late Friday night over far western zones, so have
slight chance pops to reflect this.
The axis of a closed upper low over SE Canada moves into the region
on Saturday, this should trigger some scattered showers and
thunderstorms with its passage. With CAPEs forecast to be around
1000-2000 J/kg (mainly over W 1/2 of CWA) and the region being in
the right rear quadrant of an 85+ kt 300 hPa jet, there is some
potential for some strong to possibly severe storms, mainly across
NE NJ/Lower Hudson Valley/SW CT and possibly into remainder of the
NYC metro.
The trough axis lifts to the NE Saturday night, but other than maybe
some lingering convection over SE CT early, it should be dry.
SW flow aloft Sunday and Sunday night with no shortwaves of note
embedded in the flow should allow for both periods to be dry, with
not to much in the way of cloud cover.
Models then differ on handling of a northern stream shortwave trough
early next week. The ECMWF is more progressive, while the GFS/CMC
are slower and a bit stronger. The net result should be the same,
with a low riding along a frontal boundary stalled to our south. The
main issue is timing of precipitation, and amount. Both models have
been consistent in their solutions, so have gone with a compromise
between the two camps given the inherent uncertainty this far out.
For now, limit chance pops to W zones Monday afternoon, then have
everywhere Monday night. For now only have slight chance pops on
Tuesday, but if slower solutions are right, could be a rainy Tuesday
as well. High pressure otherwise builds in for Wednesday with
dry weather.
Temperatures should be near normal Thursday night-Saturday, then
below normal Saturday night-Sunday. Lows Sunday night and Monday
night should be near normal and highs Monday-Tuesday below
normal.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
VFR now that tstms have ended. May have to watch KSWF for a
brief round of additional showers after midnight, otherwise will
then have to watch from about 08Z-13Z mainly there and out east
at KGON for development of IFR conditions. KEWR/KTEB and also
KISP/KBDR/KHPN could briefly be on the edge of some of these
lower conditions.
Light/variable flow should settle in on a S-SE direction
overnight, followed by coastal sea breeze development in similar
fashion to previous days.
Scattered afternoon tstms are possible mainly NW of the NYC
metros in the afternoon, with overall coverage/impact likely to
be less than that of today.
...NY Metro Enhanced Aviation Weather Support...
Detailed information, including hourly TAF wind component fcsts,
can be found at: http:/www.weather.gov/zny/n90
KJFK TAF Comments: No unscheduled AMD expected.
KLGA TAF Comments: No unscheduled AMD expected.
KEWR TAF Comments: AMD possible for lower flight cat overnight
into early Thu morning.
KTEB TAF Comments: AMD possible for lower flight cat overnight
into early Thu morning.
KHPN TAF Comments: No AMD scheduled.
KISP TAF Comments: AMD possible for lower flight cat overnight
into early Thu morning.
.OUTLOOK FOR 00Z FRIDAY THROUGH MONDAY...
.THURSDAY NIGHT...Areas of mainly MVFR fog/haze late at the
outlying terminals.
.FRIDAY...Isolated afternoon TSRA inland. S-SW wind 10-15 kt.
G20KT possible late day along the coast.
.SATURDAY...Scattered tstms possible.
.SUNDAY...VFR.
.MON...Becoming MVFR-IFR with increasing chances of rain. SE
winds 15-20 kt.
&&
.MARINE...
A relaxed pressure gradient over the region through Monday will
limit winds to around 10 kt or less, except up to 15 kt in
seabreezes in the NY Bight area Thursday and Friday afternoons.
Given these relatively light winds and no significant swell,
seas/waves will remain well below small-craft levels through
Monday as a result.
&&
.HYDROLOGY...
Locally heavy rainfall is possible with any stronger convection
through Saturday, with nuisance flooding of urban/poor drainage
areas the main threat. There is at least a low chance of localized
flash flooding into this evening. Otherwise, no significant
hydrologic impacts are expected through at least Monday morning.
There is some potential for widespread rainfall from Monday possibly
into Tuesday. At this time, it is to early to specify any amounts or
impacts during this time frame.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JC
NEAR TERM...JC/JP
SHORT TERM...JC
LONG TERM...Maloit
AVIATION...Goodman
MARINE...JC/Maloit
HYDROLOGY...JC/Maloit
Area Forecast Discussion
National Weather Service Pueblo CO
345 PM MDT Wed Aug 2 2017
.SHORT TERM...(This evening through Thursday)
Issued at 344 PM MDT Wed Aug 2 2017
Upper wave rotating around the ridge and over CO this afternoon with
line of rather fast moving tsra dropping south across the region.
Mesoscale models, including the HRRR, looking a little underdone
with CAPE, as SPC and LAPS mesoanalysis suggest values well over
1000 J/KG over much of the eastern plains, which is a few hundred
J/KG more most models. As a result, convection has started slightly
earlier and is a little more vigorous than model forecasts,
especially over the eastern mountains and I-25 corridor. For the
rest of the afternoon and evening, expect isolated to scattered tsra
over much of the area, with eastern mountains and far eastern plains
favored for best convective coverage. Given rather large instability
(CAPE 2000 J/KG) over the far ern plains, some concern for strong
convection building south along the KS border this evening, with
HRRR hinting at this scenario as well. Convection over the mountains
will begin to diminish by late evening, but may linger much of the
night on the plains, as pre-frontal trough drops through by
midnight, followed by the main cold front around sunrise.
On Thu, cold front exits the area to the south by mid to late
morning, with models suggesting at least a few -shra on the plains
along and behind the boundary through midday. By afternoon,
mountains destabilize with rather widespread convection developing,
especially along and west of I-25 where upslope flow aides in
development. There will be a threat for a few stronger storms over
the srn Sangres/srn I-25 corridor and along the NM border given 30-
40 kt 0-6km shear, along with the potential for heavy rain over
eastern mountain burn scars. Would expect least coverage of storms
over the eastern plains/lower Ark Valley, as air mass may be too
cool/stable for much in the way of convection. Max temps behind the
front over the eastern mountains and plains will run 10-15f cooler
than Wed maxes, with more modest cooling of 2-4f farther west over
the remaining mountains and interior valleys.
.LONG TERM...(Thursday night through Wednesday)
Issued at 344 PM MDT Wed Aug 2 2017
The general synoptic scale pattern over the majority of the extended
forecast period includes shortwave troughs propagating over the
region and an upper level ridge consistently over northern Mexico.
The NW flow will limit the amount of monsoonal moisture available,
but thunderstorms will still be possible with the shortwaves
developing over the region.
Thursday evening will consist of showers and thunderstorms overnight
with post frontal winds conducive to upslope flow over the Raton
Mesa and the Palmer Divide in unison with CAPE values ranging from
1200 - 1500 J/kg. During the overnight hours, the energy in the
atmosphere diminishes, cutting off thunderstorms. Friday will have a
chance for thunderstorms, but a well capped atmosphere will limit
initiation towards the latter parts of the day. The storms that do
develop will initiate strongly, but timeliness of development and
lack of strong shear, will limit the storm`s life cycle.
The next cold front will propagate over the region during late
morning hours on Saturday and stall through the afternoon and
evening hours. The post frontal winds will be conducive for upslope
flow, enabling showers and thunderstorms during the overnight hours.
Sunday and Monday will be cooler, post cold front, but upslope flow
is still conducive for thunderstorms, particularly over the SE
mountains.
The next cold front and it`s associated shortwave trough will begin
to develop over the region Tuesday into Wednesday, with showers and
thunderstorms possible during the afternoon and evening hours.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 344 PM MDT Wed Aug 2 2017
Will carry a VCTS mention at all terminals into the evening , and
some MVFR conditions may be possible under some of the stronger
storms. Cold front will drop south through KCOS and KPUB after 06z,
leading to a period of gusty N-NE winds some isolated -shra until
mid-morning Thu. May also see some areas of MVFR cigs develop after
10z on the eastern plains, possibly impacting KCOS and KPUB through
the morning. Tsra will become widespread over the mountains Thu
afternoon, with storms possible at all taf sites after about 20z.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...PETERSEN
LONG TERM...SKELLY
AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service Blacksburg VA
952 PM EDT Wed Aug 2 2017
.SYNOPSIS...
Weak high pressure resides across the region into Thursday. A
cold front approaches Friday, moving across Saturday before
stalling across the Carolinas over the weekend. The front then
lifts back north by early next week ahead of another cold front
arriving from the west.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 945 PM EDT Wednesday...
Precip still remains clear of the forecast area. Some showers to
the west are struggling to make it across the mountains and are
not expected to impact the forecast area. Still an area of
clearing skies making its way into the piedmont now, however
model guidance does suggest that clouds to the west will manage
to make for at least partly cloudy skies over the course of the
evening. Due to this area of clearing, temperatures are dropping
a bit faster than originally forecast through the mountains,
therefore adjusted the overnight lows slightly down through
those elevations. Whether or not this comes to fruition will be
a fight against higher than expected dew points. As it stands,
no significant changes have been noted to any overnight fog
forecast earlier.
As of 730 PM EDT Wednesday...
Current radar shows that precipitation has ended for now in and
around the forecast area. Current HRRR guidance does indicate a
small chance that some light showers may be possible in parts of
the piedmont and Southeast WV the next couple of hours. However
that seems unlikely now that we are nearing sunset and storms
and showers to the west are beginning to dissipate. PoPs have
been adjusted accordingly.
METSAT indicates that there is some clearing moving in from the
west therefore sky conditions have been adjusted accordingly.
As of 300 PM EDT Wednesday...
Forcing for this afternoons current storms has been weak but
relying on differential heating and some low level convergence.
Models still have hard time with placement, but still advertise
better coverage later this afternoon across our NC mountains in
association with shortwave moving across northeast GA into
central NC. Persistent high clouds has kept instability limited
with MLCAPEs under 500 J/KG, but DCAPES are running close to a
1000 J/KG. Will have to watch for any isolated storms to pulse
to strong to severe levels with a downburst the main threat.
Still threat is very low, so no mention in the HWO.
Will see activity across the mountains into the foothills in a widely
scattered to isolated fashion fade by mid evening. Skies overnight
should clear some, but a few models are hinting at more high clouds
streaming across the southern CWA after midnight. Will limit fog to
the valleys for now.
Lows close to normal with upper 50s to lower 60s mountains, to mid
to upper 60s across the piedmont to Roanoke.
Thursday upper pattern unchanged with axis of 5h trough across the
TN valley and southwest flow aloft. Sfc pattern stays the same as
well, and models advertise again a shotgun pattern for
showers/storms during the afternoon, mainly over the ridges and
adjacent areas. Looks like better deep convection associated with low
off the coast of NC will become widespread along the NC coast. Could
see a minimal amount of showers/storms if we get more into the
subsidence zone with this system. High temperatures running from the
upper 70s to mid 80s over the mountains, valleys, to mid 80s to
around 90 east including Roanoke.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 400 PM EDT Wednesday...
Northern stream trough will amplify enough on Friday to push a
cold front through the area late Friday or Friday night. While
there are still some questions on exact timing, trend will be
greater shower and thunderstorm coverage.
For the weekend, the front is forecast to sag just south of the
forecast area before stalling across the Carolinas... suggesting
a 24-36 hour period of drying before the front returns north as
a warm front the first part of next week.
Warm temperatures and pooling of dewpoints ahead of the front
Friday will support scattered to numerous afternoon and evening
thunderstorms, with marginal risk for severe. Somewhat cooler
temperatures are expected behind the front Saturday.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 400 PM EDT Wednesday...
A strong northern stream shortwave trough is forecast to move
east through the Northern Plains and southern Canadian Border
Sunday, amplifying as it moves into the Great Lakes Monday. This
pattern suggests old frontal boundary to our south will move
north as a warm front as the wind flow backs ahead of the
approaching upper level trough...the return of warm moist flow
resulting in a renewed daily threat of showers and thunderstorms
for the first half of next week. Temperatures look to be pretty
close to normal...maybe a degree or two under normal if we end
up with more cloud cover due to proximity of the front.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
As of 800 PM EDT Wednesday...
Main issue during the forecast period will be the onset of fog
for locations in the valleys overnight, particularly at LWB
where LIFR conditions appear the most likely. IFR conditions
should also set in at BCB for a couple of hours before sunrise.
Some light fog is also possible at LYH as they will fall to the
crossover temperature tonight. Otherwise, VFR conditions and
light to calm winds due to high pressure are expected for the
forecast period.
Tomorrow afternoon may again feature terrain induced showers
and thunderstorms. However due to little to no larger forcing
mechanisms they look to be rather isolated in nature at this
point.
Extended Aviation Discussion...
Mostly VFR conditions are expected to continue through late in
the week as a large area of high pressure lingers across the
region, while gradually weakening. Some late night/early
morning fog will be possible in the mountain and river valleys
each morning. Next chance of reduced visibilities in isolated
convection may occur Thursday afternoon over the mountains. A
cold front will move into the area late Friday into Saturday
with perhaps a round of sub- VFR ceilings and visibilities in
showers and thunderstorms espcly Friday evening. Front stalls
just south of the area by Sunday with possible clouds/showers
and sub- VFR conditions returning north into southern sections
by late in the day.
&&
.EQUIPMENT...
As of 1040 AM EDT Tuesday...
The radar will be down most of the time through Wednesday due to
an upgrade on the signal processor. If the upgrade goes well,
the radar may be intermittently available Thursday and back to
continuous operation Friday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JH/WP
NEAR TERM...JR/WP
SHORT TERM...PM
LONG TERM...PM
AVIATION...JR/WP
EQUIPMENT...WP
Area Forecast Discussion
National Weather Service Shreveport LA
1024 PM CDT Wed Aug 2 2017
.UPDATE...
Lowered pops and kept E TX and LA southern tier of parishes.
&&
.DISCUSSION...
Lots of stars in place this evening with lower to mid 70s, more
like September than July. We have lowered pops to pretty much
where the showers are decaying in place. Our VAD is showing
shallow SE flow to 2kft and wind quickly backs to E/NE up to
10kft. 00Z Nam and HRRR agree for a quiet night. /24/
&&
.PREV DISCUSSION... /issued 630 PM CDT Wed Aug 2 2017/
AVIATION...
For the 03/00Z terminals...VFR ceilings this evening will
gradually degrade to MVFR/IFR. Could see brief LIFR conditions
across some terminals around daybreak. Conditions to gradually
improve to VFR by 03/18Z with VCTS conditions possible around LFK
thereafter. Otherwise, light and variable winds tonight to become
east at around 5 knots on Thursday. /05/
PREV DISCUSSION... /issued 401 PM CDT Wed Aug 2 2017/
DISCUSSION...
Widespread area of rain continues to move east-southeast across
much of East Texas and portions of Louisiana south of Interstate
20. Farther north, more isolated convection has been developing in
the very moist and unstable environment. Convective coverage
should gradually diminish later this evening, but an upper trough
slowly moving through the region will continue to provide a source
for vertical ascent and more convective development. A old frontal
boundary near the Gulf coast should keep most of the showers and
thunderstorms south of Interstate 20 tonight. The overall synoptic
setup for Thursday should be fairly similar to today. The coverage
of precipitation should be somewhat lower on Thursday, however.
On Friday, an upper trough moving across the Upper Midwest and
across the Great Lakes will push a cold front across the area.
This front will provide an additional focus for convection across
the entire area on Friday. During the weekend, the front will move
back north as a warm front while yet another shortwave trough pass
over the Southern Plains. This will lead to more showers and
thunderstorms during the weekend. Unsettled weather will continue
into early next week as another potent shortwave trough moves
across the Midwest and another surface cold front moves southeast
into the region. Rain chances appear to be a fixture in the
forecast through at least Tuesday.
The atmosphere will remain quite moist and unstable for the next
several days. Precipitable water values are progged to be between
1.75 and 2.00 inches through at least Saturday night. This
suggests that convection may continue to be efficient rain
producers. I would not be surprised to see my forecast rainfall
amounts be underestimated for many locations over the next several
days. Unfortunately, in this type of pattern, forecasting where
the bands of heaviest rain occurs is very difficult as the biggest
factors are typically driven by mesoscale and micro scale
processes, and where mesoscale boundaries become established each
day.
This remains a highly anomalous pattern for this time of year.
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 71 89 73 92 / 20 30 20 40
MLU 70 90 72 91 / 20 30 20 50
DEQ 67 88 69 87 / 20 20 20 40
TXK 69 88 71 89 / 20 20 20 40
ELD 68 89 71 90 / 20 20 20 40
TYR 70 87 73 91 / 30 20 20 40
GGG 70 88 72 91 / 20 30 20 40
LFK 71 89 73 92 / 40 40 20 40
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
24/05/09
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