Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/31/17
Area Forecast Discussion
National Weather Service Albany NY
1047 PM EDT Wed Aug 30 2017
A cold front will approach from the northwest overnight,
and move across the region during the late morning into the early
afternoon. Moisture will be limited, so only isolated to scattered
showers are expected with the front. Unseasonably cool air will pour
into the region behind the front for Thursday night into Friday. A
frontal system, combined with remnant moisture from Harvey, may
bring clouds and rain for late Saturday into early Sunday.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 1046 PM EDT...A weak sfc high continues to pass south of
the region this evening. A cold front continues to approach from
from just north of the St Lawrence River Valley. A few isolated
showers continue across southeast Ontario and southwest Quebec.
The skies are mostly clear or clear ahead of this front, as the
winds have gone light to calm and temps are falling into the
50s and lower 60s with a few upper 40s over the southern
Adirondacks. The temps will likely level off over the next few
hours, as mid and low level clouds approach the northwestern
zones in the early morning hours. There is a lot of low-level
dry air ahead of this boundary, as evident with the 00Z KALY
raob profile, and a PWAT of 0.76". The clouds will continue to
increase quickly in the early to mid morning hours.
We retooled the timing a bit more with this update based on the
latest 3-km HRRR for the arrival of isold-scattered showers
north and west of the Capital Region between 07Z-10Z. Some
patchy fog was kept in for the CT River Valley near eastern
Windham CTY overnight before the clouds increase.
Lows tonight will be in the 50s with some mid/upper 40s across
portions of the southern Adirondacks and southern Greens.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Thursday, a cold front will sweep south and east across the
region between mid morning and early afternoon. Moisture and
instability will be quite limited, with forecast MUCAPES mainly
below 300 J/Kg, greatest across far southern areas. Will keep
mention of isolated thunder across the mid Hudson Valley and NW
CT for a brief time late Thursday morning into early Thursday
afternoon, with generally just some spotty light showers or
sprinkles elsewhere. Clearing is expected in the afternoon,
initially in valley areas, and last across higher elevations.
Max temps may only reach the mid/upper 50s across higher
elevations of the Adirondacks before falling in the afternoon.
Elsewhere, expect highs to reach upper 60s to mid 70s, with
perhaps upper 70s across the mid Hudson Valley. It will become
quite breezy in the afternoon in the wake of the front, as cold
advection and deeper mixing develop, with some gusts possibly
reaching 25-30 mph at times by mid to late afternoon.
Thursday night-Friday night, some lingering clouds/isolated
showers could persist Thursday evening across portions of the
southern Adirondacks and southern VT. Otherwise, generally fair
and cool through the period. Thursday night low temperatures
could reach into the mid/upper 30s across portions of the
western Adirondacks, the eastern Catskills and Schoharie CO,
with some wind. Elsewhere, expect mainly 40s. Highs Friday
should reach the lower/mid 60s in valleys; with mainly 50s
across higher elevations. For Friday night, frost potential will
be greater across portions of the southern Adirondacks, eastern
Catskills, and higher elevations of southern VT, with lows in
the mid 30s possible. Elsewhere, expect mainly upper 30s to mid
40s. However, thickening high clouds could prevent temps from
falling off as much as currently indicated.
Saturday, 12Z/Wed model trends are a bit quicker with clouds
increasing from the southwest, as remnant moisture from Harvey
potentially advects northeast ahead of a digging shortwave
trough approaching from the Great Lakes. The 12Z/ECMWF and GEM
seem to phase these two systems more aggressively, while the
GFS, NAM and most GEFs members keep them more separate. Either
way, it appears that clouds will increase Saturday, with little
sunshine expected. Some showers or light rain may even develop
by late afternoon, especially for areas south of I-90. Expect
highs to reach the mid 60s to lower 70s, although if clouds
thicken more quickly, even cooler max temps are possible.
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The remnant energy of Harvey will phase with an upper-tropospheric
trough Saturday night into Sunday resulting in a low pressure system
and a good batch of needed rainfall. Long term guidance is
suggesting an inch plus of rainfall for Sunday as the tropical
airmass passes through our region.
Monday...Brief upper ridging will be in place Monday resulting in
broad surface high pressure and primarily dry conditions. With a
piece of energy to the North, there could be a passing light shower
during the afternoon.
Tuesday through Thursday...A cold front will pass through the region
on Tuesday bringing a chance for showers yet again. GFS/ECMWF both
suggest that the SW-to-NE oriented front stalls out and becomes
quasi-stationary over the SE portion of our region on Wednesday into
Thursday. As a sharp upper trough swings into the region,
cyclogenesis should commence and a low pressure system will ride
along the frontal boundary bringing another batch of heavy rain.
High temperatures will moderate Sunday into Tuesday with highs in
the low 70s, upper 70s, and approaching 80, respectively.
Temperatures will drastically cool after the passage of the front
with highs in the lower to mid 60s on Wednesday/Thursday. Lows
throughout the period will be in the mid to upper 50s.
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
High pressure will briefly build in early this evening, then a
cold front will approach from the St Lawrence River Valley after
midnight, and move across the region by the late morning into
the afternoon with some isolated to scattered showers and breezy
VFR conditions will prevail most of the night with mostly clear
skies and light to calm winds early on. A band of clouds ahead
of the front will move towards KGFL/KALB/KPSF between 08Z-11Z
from northwest to southeast. The quickly approaching clouds
should prevent radiational fog or mist formation at KGFL/KPOU.
The moisture is fairly sparse with the front, but VCSH groups
were mainly used in mid to late morning at KGFL /08Z-15Z/, and
KALB /12Z-16Z/, and late morning to early pm at KPSF /13Z-17Z/
with some brief MVFR cigs around 2.5 kft AGL at KALB/KPSF.
Overall bases should be in the 3.5-5.0 kft AGL range. Further
south a VCSH group was used at KPOU with a later frontal passage
in the 16Z-21Z timeframe with VFR conditions.
Expect all TAF sites to be in the VFR during the mid to late
afternoon with sct-bkn cigs in the 4-5 kft AGL with some cirrus
The winds will increase from the southwest to west at 5-10 kt
shortly before or just after sunrise, and shift to the
northwest at 10-15 kts in the afternoon with a few gusts around
20 kts at KALB/KPSF in the wake of the front.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: Low Operational Impact. Slight Chance of SHRA.
Friday Night: High Operational Impact. Likely SHRA.
Saturday: Moderate Operational Impact. Chance of SHRA.
Saturday Night: Low Operational Impact. Slight Chance of SHRA.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: Low Operational Impact. Slight Chance of SHRA.
Labor Day: Moderate Operational Impact. Chance of SHRA.
Wind gusts of 25-30 mph possible Thursday afternoon...
A cold front will approach from the northwest late tonight, and
pass across the region Thursday. Moisture will be limited, so
only isolated to scattered showers are expected with the front.
Unseasonably cool air will pour into the region behind the front
for Thursday night into Friday. A frontal system, combined with
remnant moisture from Harvey, may bring clouds and rain for
late Saturday into early Sunday.
RH will recover to 90-100 percent tonight, with areas of dew
formation likely. RH should drop into the 45-55 percent range in
valleys, and 55-70 percent across higher elevations for Thursday
afternoon. RH will then recover to 80-95 percent Thursday night.
West to northwest winds of 5-15 mph will become light/variable
after sunset. Winds will then become west to northwest at 5-15
mph Thursday morning, then shift into the northwest to north and
increase to 10-20 mph Thursday afternoon, with some gusts of
25-30 mph possible. For Thursday night, winds will remain from
the north to northwest and decrease to 5-15 mph.
A cold front will bring isolated to scattered showers on
Thursday, but basin average amounts will generally be fairly
light, generally under one tenth of an inch, and will have
minimal impacts on rivers/streams.
Dry weather will then return behind the front for Friday and
most of Saturday. The next chance of rainfall arrives Saturday
night into Sunday. By then, rain will be needed as it will have
been over a week since the last widespread measurable rainfall.
With limited amounts of rainfall expected, river and stream
levels will remain fairly steady through Saturday.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
The KENX radar is back up and all the bull gear work is
completed. The radar is back in full service.
Area Forecast Discussion...Updated
National Weather Service Billings MT
920 PM MDT Wed Aug 30 2017
A few thunderstorms continue mainly Powder River County. The HRRR
continues to show this activity drifting east overnight. The
current PoPs cover this activity. Updated the rest of the
forecast with the latest obs but no major changes. Expired the Red
Flag Warning as winds are starting to decrease and relative
humidity values are increasing. While winds across southeastern
Montana will continue to be gusty overnight, the relative
humidities are already above 20 percent. Reimer
.SHORT TERM...valid for Thu and Fri...
Height falls across the region continuing ahead of an approaching
upper-low. Ahead of the low, strong southeasterly winds are
ongoing across much of easternmost Montana.
Isolated thunderstorms will continue to develop along the
foothills and mountains late this afternoon and evening. After 6
PM isolated thunderstorms will push off the foothills and into the
central and eastern Plains. Hi-res models indicate increasing
coverage late in the night through morning over easternmost
Thursday, surface front pushes into eastern Montana with
scattered thunderstorms east of the front in the early afternoon and
isolated thunderstorms possible west of the front in the late
afternoon/evening. Generally westerly winds aloft behind the front will
push more smoke from fires over the Pacific Northwest and western
Montana into the area.
Our chance for rain is long gone by Friday as ridging settles in
over the Mountain West. Highs will be a touch cooler but still in
the upper 80s, with clear but still smokey skies.
Fire weather...Red Flag Warning continues this afternoon and early
evening from Rosebud county east. We have already seen some
impressive fires show up as hot spots on satellite in Custer and
Powder River counties this afternoon. Also, winds have been
gusting 20 to 30 mph over the eastern Plains since late morning
with humidity values ranging from the teens west to low 20s east
. This evening, isolated thunderstorms begin to move onto the
Plains bringing the potential for new starts and locally
gusty/erratic winds. Walsh
.LONG TERM...valid for Sat...Sun...Mon...Tue...Wed...
High pressure ridging builds across the forecast area Saturday
and Sunday before a strong cold front sweeps across the forecast
area late Sunday. It is still a bit far out in time on the exact
arrival of the front but right now it looks to arrive during the
late afternoon/early evening hours on Sunday. Conditions look to
be hot and dry for the weekend with temperatures approaching or
exceeding records for some locations on Sunday.
Sunday will be the warmest day in the extended due to pre-
frontal warming. Guidance continues to warm temperatures for
Sunday, and given history of pre-frontal mixing, I have raised
temperatures a few more degrees across the forecast area
especially for the more favored hot locations. Although the GFS
brings some shower/thunderstorm activity into the area Sunday
night into Monday morning, the ECMWF keeps the area dry. For now,
we will continue to leave a dry forecast and see how the next few
model runs handle this. Temperatures to start next week will be
much cooler than we have experienced the past few weeks with
readings at or even below normal. Normal for early next week is
about 80 degrees. Hooley
Isolated showers and thunderstorms expected through the rest of
the evening in Eastern Montana and near KMLS/KBHK. VFR conditions
will prevail though can`t rule out gusty 30 kts winds and brief
periods of MVFR in any heavier showers. Elsewhere only a stray
shower or two is possible until midnight and then conditions will
begin to clear. VFR conditions expected through the night with
light 5 to 10 kt winds. Dobbs
.PRELIMINARY POINT TEMP/POPS...
Thu Fri Sat Sun Mon Tue Wed
BIL 066/089 059/089 059/093 061/099 058/080 053/080 052/084
21/K 20/K 00/U 00/U 00/U 00/U 00/U
LVM 058/089 050/089 050/093 050/098 050/083 044/082 044/084
22/T 20/K 00/U 00/U 00/U 00/U 00/U
HDN 063/090 056/090 056/095 057/097 055/082 050/081 050/085
22/T 10/K 00/U 00/U 00/U 00/U 00/U
MLS 068/090 061/089 059/093 059/100 056/080 050/079 048/084
23/T 20/K 00/U 00/U 00/U 00/U 00/U
4BQ 064/090 059/089 056/094 057/099 054/081 050/078 049/083
33/T 20/K 00/U 00/U 00/U 00/U 00/U
BHK 063/089 058/087 055/092 055/095 052/077 047/075 045/080
34/T 30/K 00/U 00/U 01/U 00/U 00/U
SHR 060/085 053/087 052/092 053/099 052/080 046/078 045/083
23/T 10/K 00/U 00/U 00/U 00/U 00/U
MT...Red Flag Warning in effect until 9 PM MDT Thursday FOR ZONE
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
938 PM CDT Wed Aug 30 2017
Experimental GOES1-16 IR and water vapor imagery showed Tropical
Depression Harvey centered over west central LA, lifting slowly
NNE. An E-W oriented outer band of showers with isolated thunder
was lifting north through central MS, on the nose of a midlevel
RAP model depicts SFC-1km storm relative helicity increasing to
300 m2/s2 over north central MS by sunrise. Will need to monitor
this area closely for quick spin-ups, but marginal instability
should limit tornado threat. A few hours into daytime heating,
maximum low level shear will shift into northeast MS.
Latest short range models and early looks at 00Z guidance suggest
no major changes need for the forecast. Thursday will be a windy
and very wet day, with the risk of flash flooding maximized
immediately north and west of Harvey`s surface low pressure
On another note, KNQA radar`s Z/R (reflectivity/rainfall)
relationship has been adjusted to tropical settings. This will
help legacy (non dual-pol) precip algorithms better estimate
rainfall. In addition, the number of supplemental low level cuts
have been increased, giving better temporal resolution to help
detect possible shallow short-lived tornadic circulations.
.PREV DISCUSSION... /issued 715 PM CDT Wed Aug 30 2017/
Updated to include 00Z Aviation Discussion.
PREV DISCUSSION... /issued 406 PM CDT Wed Aug 30 2017/
.Potentially Life Threatening Flash Flood Event Anticipated
Across the Mid South Thursday into Thursday Night...
Tropical Storm Harvey is moving slowly north-northeast across
western Louisiana this afternoon. This system will continue to
move towards and across the Mid South tomorrow through Friday.
This system will likely bring a variety of weather hazards to the
Mid South including potentially life threatening flash floods,
strong winds, and severe weather.
Harvey will likely transition from a tropical system to an
extratropical cyclone as it traverses across the forecast region.
This should occur as the tropical feature begins to interact with
the westerlies further north as strong surface high pressure
builds south across the Great Lakes. As this occurs, the
extratropical cyclone should actually deepen as it crosses our
region. In addition, isallobaric pressure differences should
become enhanced as the surface cyclone deepens. This should allow
for a developing baroclinic zone to strengthen from east Arkansas
and northwest Mississippi northeastward across much of west
Tennessee. This should provide a focus for excessive rainfall with
life threatening flash flooding possible. Rainfall totals along
this axis are likely to range from 4 to 8 inches, with a few
locations exceeding 1 foot. This area includes areas from the
Memphis Metropolitan Area northeastward across Jackson, Tennessee,
to Paris, Tennessee. Conditions will likely become dangerous
across these areas where the greatest rainfall totals occur.
Anticipate widespread flash flooding and local rivers and creeks
quickly rising out of their banks.
In addition, the enhanced isallobaric pressure differences will
result in strong winds developing by early Thursday morning and
persisting through Friday morning. Sustained winds during this
period will likely range from 25 to 35 mph, with frequent gusts in
excess of 45 mph. There may be some gusts in excess of 50 mph as
the extratropical cyclone advances across west Tennessee. This
will likely lead to a few downed trees and power lines along with
scattered power outages.
The next threat associated with Harvey will be the potential for
severe thunderstorms across the eastern half of the region. A
Slight Risk for Severe Thunderstorms now exists from late tonight
through Thursday night across northeast Mississippi into southern
west Tennessee near the Tennessee River. A Marginal Risk for
Severe Thunderstorms exist across the remainder of northwest
Mississippi and west Tennessee. The primary risk will be for fast
moving short-lived tornadoes and localized wind damage.
Rainfall will gradually end from southwest to northeast on Friday
but the damage will be done as the remnants of Harvey lift off to
the northeast. High pressure will build in behind Harvey with a
return to dry and seasonably cool weather into the weekend.
Dry weather will continue into early next week before a strong
northern stream shortwave drops south and pushes a cold front into
the area. Another tropical system near the upper Texas coast may
spread enhanced moisture northward into our region ahead of the
front. Showers and thunderstorms will again be possible with the
frontal passage. Below normal temperatures should continue through
much of the extended forecast period.
As of 00Z, Tropical Depression Harvey is located 10 miles SW of
Alexandria Louisiana. It is expected to gradually track NE
across North Mississippi Thursday afternoon into Thursday night.
Winds at JBR,MEM,MKL anticipated to be NE/E through much of the
period and at TUP starting out NE then gradually veering SE then
south towards Thursday afternoon. Gusty winds expected at times. VFR/MVFR
conditions will gradually deteriorate to MVFR/IFR conditions overnight
into Thursday with convective coverage increasing throughout the
AR...Wind Advisory from 7 AM Thursday to 1 AM CDT Friday for Clay-
Flash Flood Watch through Friday morning for Crittenden-Lee AR-
Flash Flood Watch through Friday evening for Mississippi.
MO...Wind Advisory from 7 AM Thursday to 1 AM CDT Friday for Dunklin-
Flash Flood Watch through Friday evening for Pemiscot.
MS...Wind Advisory from 7 AM Thursday to 1 AM CDT Friday for Calhoun-
Flash Flood Watch through Friday morning for Alcorn-Benton MS-
Wind Advisory from 1 PM Thursday to 7 AM CDT Friday for Alcorn-
Benton MS-Chickasaw-Itawamba-Lee MS-Monroe-Pontotoc-
TN...Wind Advisory from 7 AM Thursday to 1 AM CDT Friday for Fayette-
Flash Flood Watch through Friday morning for Fayette-Hardeman-
Flash Flood Watch through Friday evening for Benton TN-Carroll-
Wind Advisory from 1 PM Thursday to 7 AM CDT Friday for Benton
Area Forecast Discussion...CORRECTED
National Weather Service Phoenix AZ
308 PM MST Wed Aug 30 2017
Above normal temperatures will continue this week but will very
slowly trend downward. Thunderstorm chances will remain very limited
across lower desert communities through the rest of the week with
activity focused mainly over mountain areas. Moisture and humidity
will begin to increase over the weekend leading to at least slight
chances across the region early next week.
Even less storm activity over the higher terrain early this
afternoon than 24 hrs ago. An exception is southern California
with storms over the San Bernardino and San Jacinto Mountains and
even some over eastern Riverside County including Joshua Tree
National Park. Some of the CAMs are indicating at least some weak
convection lingering in that area overnight and Thursday (possibly
aided by an upper trough centered near the Pacific Northwest
coast). Earlier versions of the HRRR even had showers popping up
as far south as Imperial County. They are also indicating late
night/early morning convection development over southern Yavapai
and Mohave Counties which brushes La Paz County. As for temperatures,
they will remain above normal but will trend down slowly. So, the
Excessive Heat Warning will be allowed to expire this evening.
Overall, storms over the lower deserts will be even harder to
come by over the next couple days as precipitable water over
southern Arizona and southeast California trends down. There will
be enough lingering moisture over northern Arizona for an ongoing
opportunity for storms there. However, the steering flow changes
a bit as the high weakens and sags south (due to a trough passing
far to the north) which leads to and east-southeasterly direction
as opposed to a northeasterly direction.
An increase in moisture is anticipated to begin over the weekend
as a tropical storm (currently centered south-southeast of Cabo
San Lucas) tracks northward and gradually pushes deeper moisture
north and into the lower deserts. The GFS is slower with the
arrival than the ECMWF. It is important to note that the system
overall will stall and then push westward into the Pacific as the
upper high reforms over the great basin with the high setting up
again to the north of Phoenix. Thus the system will not bodily
move north of the border. Despite the moisture increase, CAPE
does not get excessive and with high temps falling, monsoon storm
chances remain on the low side. Again, even the rather bullish
NAEFS POPs guidance mostly keep POPs in the slight chance category
for our area this weekend into early next week. MEX MOS numbers
are also surprisingly low, mostly in the single digits for Phoenix
this weekend and then rising into the teens or 20s early next
week. Thus we will keep the rather low grade monsoon conditions in
place for the extended period, with a rather broad- brush
forecast in place. Overall very little change has been made to the
POPs/Weather/Sky elements over the 7 day forecast period.
Temperatures will near to slightly above normal over the weekend and
early next week.
South-Central Arizona including KPHX, KIWA, and KSDL:
Isolated thunderstorm activity is expected to remain relegated to
the higher terrain north and east of Phoenix this afternoon and
again Thursday. The probability of an outflow boundary from these
storms reaching the Phoenix area is quite low. Otherwise, winds
will generally remain out of the east with speeds less than 10
Southeast California/Southwest Arizona including KIPL and KBLH:
Latest model guidance suggests a low probability of thunderstorms
overnight at KIPL and KBLH. Will keep the mention of VCTS out of
the TAFs for now, but this bears watching. Winds will generally
remain light, except in the vicinity of thunderstorms.
Aviation discussion not updated for amended TAFs.
Saturday through Wednesday...
Conditions will generally remain drier than normal as high
pressure becomes reestablished across the intermountain West.
There will be a below normal chance of thunderstorms and wetting
rains, however latest model guidance suggests a slight potential
for tropical moisture reaching the Desert Southwest around Sunday
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
AZ...Excessive Heat Warning until 8 PM MST this evening for AZZ530-
CA...Excessive Heat Warning until 8 PM PDT this evening for CAZ561-
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