Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/02/21
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
555 PM MDT Wed Sep 1 2021
00Z TAF CYCLE
Showers and embedded thunderstorms will continue through the evening,
then slowly dissipate after 06Z. Isolated showers may linger through
12Z. Periods of MVFR conditions and mountain obscurations are likely
with the heavier downpours. Low clouds and fog are possible later
tonight/Thursday morning between 09Z and 15Z, with the best chances
being at KFMN and KGUP as the sky tries to clear later tonight.
Friday`s crop of thunderstorms will favor the south and east, with
much less coverage elsewhere as dry air works in from the northwest.
.PREV DISCUSSION...417 PM MDT Wed Sep 1 2021...
Dropped the Flash Flood Watch for west central and southwest portions
of the area as the heavier rain has moved east of the watch area and
little to no redevelopment is expected. The watch continues for the
.PREV DISCUSSION...212 PM MDT Wed Sep 1 2021...
After a fairly wet period through tonight with numerous showers and
scattered thunderstorms, some producing heavy rainfall, a return to
more normal late Monsoon season conditions is forecast from the end
of the work week through the weekend. High pressure will dominate the
region next week, with temperatures trending above normal and daily
rounds of showers and storms trending down.
SHORT TERM...(TONIGHT THROUGH THURSDAY NIGHT)...
Showers and thunderstorms have been ongoing west of the central
mountain chain, with some activity beginning across the eastern
plains. ABQ`s 12z sounding showed PWAT at 1.06" (within the 90th
percentile). The daily record for Sept 1st is likely to be broken,
as tropical moisture from remnants of Hurricane Nora continues to
filter in. A weak disturbance crossing to the north will also aid in
lift for these storms. A few stronger storms may be possible across
the eastern plains, with MLCAPE ranging from 500-1000 J/kg, as this
morning`s partly cloudy skies allowed for heating and
destabilization. Elsewhere across western and central NM, it`s been
mainly stratiform rain up to this point, with the cooler
temperatures and cloud cover putting a damper on destabilization.
The HRRR and HREF show several rounds of precipitation continuing
through the evening, particularly across the Luna and Medio fire
burn scar areas. At this time decided not to include the south
central mountains in the Flash Flood Watch as the event is already
unfolding, but the issuance of Flood Advisories in the area are
likely especially after heavy rainfall several days prior.
Precipitation will taper off across western and central areas this
evening, becoming more focused across the eastern plains by late
evening. Any remaining convection will shift eastward into TX/OK by
early Thursday morning. Left mention of patchy fog in the forecast
package across western areas as skies begin to clear out, but some
low clouds/fog will be possible across the east as well.
The high will remain to our east on Thursday, as it elongates over
the Ark-La-Tex region. As drier air filters in, areas across the
northwest will miss out on most of the precipitation. Locally heavy
rainfall and flash flooding will once again be possible from the
south central mountains into the east central plains, with PWAT`s
exceeding 1.2-1.5". High temperatures will generally be a few
degrees warmer across the state, with the exception being the areas
with continued precipitation.
LONG TERM...(FRIDAY THROUGH WEDNESDAY)...
The upper high will be over the ArkLaTex on Friday and we`ll remain
on the periphery of the circulation with a Monsoon moisture plume
directly overhead. Given some destabilization from daytime heating, a
healthy round of storms is forecast Friday afternoon/evening, with
the potential for locally heavy rainfall across the southwest and
south central mountains. Same story for Saturday as the upper high
begins to establish a second center over the region, but the
addition of a backdoor front will increase chances for storms across
the northeast and east central plains during the afternoon/evening
The upper high is then forecast to build-up over the Great Basin
from Sunday through Tuesday and expand over much of the Desert
Southwest and southern/central Rockies. This development will lead to
a warming/drying trend that will bring above normal daytime
temperatures and a gradual downtrend in daily rounds of storms,
especially across northern NM.
As remnant moisture from Hurricane Nora streams into the state,
widespread showers and thunderstorms will continue through the
evening hours and focus mainly across eastern New Mexico after
sunset. Locally higher rainfall amounts of 1" or more will be
possible across the the Sangre de Cristos. Drier air will begin
filtering into the northern part of the state Thursday and Friday,
with the larger wetting footprints focused over south central and
eastern New Mexico. Overnight humidity recoveries will be excellent
overall. High pressure will shift and build over the Great Basin
region late into the weekend and over the Labor Day holiday,
decreasing storm coverage and returning temperatures to above normal.
Isolated showers and thunderstorms may focus across southern New
Mexico during this time.
Flash Flood Watch until midnight MDT tonight for the following
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1015 PM EDT Wed Sep 1 2021
Periods of moderate to heavy rain will impact the region
from near Interstate 90 southward tonight before ending early
tomorrow morning. Rainfall rates exceeding one inch per hour at
times will increase the potential for both river and flash flooding.
Then, Canadian high pressure takes control of the area resulting in
a stretch of dry and fall-like temperatures the rest of the
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
.A Flash Flood Watch remains in effect for the mid-Hudson
Valley, Berkshires and Litchfield Hills from until 2 PM
.A Flash Flood Watch remains in effect for the Schoharie Valley
to portions of the Capital District and into southern Vermont
from until 11 AM tomorrow...
As of 1015 pm...forecast remains on track with heavier rainfall
rates about to move into southern portions of Dutchess and
Litchfield Counties. Added slight chance of thunder to
Litchfield. Tweaked PoPs but remainder of the forecast remains
unchanged. Additional details below.
As of 800 pm...the center of the remnants of TC Ida are located
near Wilmington, DE. Rainfall associated with isentropic
lift/midlevel Fgen continues over much of the region south of a
line from Ft. Plain to Glens Falls. The rain shield should
likely not expand further north and west than this. Rainfall
rates have generally been around 0.2-0.4"/hour over our southern
two tiers of counties and should continue to increase over the
next several hours. Looking upstream, intense rainfall rates of
1-3"/hour have been observed over portions of eastern
PA/northeast NJ. This is associated with intense 1000-925mb
Fgen. CAMs in the 18Z HREF suite as well as more recent HRRR
runs suggest the 2-3" hour rates remain just south of our CWA
border, but the 18Z HREF does have high probabilities of 1"/hr
and 3"/3hr scraping southern portions of Dutchess/Litchfield
Counties 03-08Z. This is where and when the concern for
significant flash flooding is highest. Even outside of this
area, flash flooding remains possible as NYSM sites in southern
Ulster/Dutchess are already up to 2-3" for the storm total and
rates will only continue to increase over the next several
hours. It appears we will stay out of the warm sector, so the
threat for severe thunderstorms/tornadoes is basically nil.
Overall, no meaningful changes needed to the forecast.
As of 5 pm, moderate rain associated with the incoming remnants
of Ida has brought about 1 to 1.50 inches of rain to the mid-
Hudson Valley, eastern Catskills, and Litchfield County, CT so
far today with a rather sharp northward cut-off heading towards
I-90 where rain amounts have only accumulated up to 0.25 to
0.50. Areas just north of this interstate have only just started
to rainfall over the last hour or two and therefore have only
received a few hundredths.
With the low now tracking across the Mason Dixon Line towards
NYC, its associated warm front is lifting northward which is
allowing the area of moderate to heavy rain in the cool air
wedge within the deformation zone to push northward as well. As
a result, parts of Litchfield County could see rain turn light
at times through the evening commute with rain inching into
Glens Falls. Even with this northward push, the dry air ahead of
the precip shield looks to stand tough and prevent rain from
advancing much beyond Warren, Washington County into southern
parts of Herkimer and Hamilton County through tonight.
Upstream, the strong southerly mid-level jet ahead of the
surface with winds ranging 40 - 50kts is pushing through
eastern PA and NJ. This has resulted in very high rainfall
rates up to 0.50 inch at times. As the low advances towards NYC,
such high rainfall rates are expected to spread into our
forecast area. The period from 00 UTC (8PM) to 09 UTC (5AM) is
still the main window of concern where very high rainfall rates
ranging 1 to 2 inches per hour are possible again primarily for
the eastern Catskills, mid-Hudson Valley and NW CT. Efficient
warm rain process in place combined with high moisture flux in
the 925 to 850 hPa layer coincident with strong omega and
additional synoptic lift from a favorable 300 hPa jet position,
means rates exceeding 2 inches per hour at times is in the realm
of possibilities. Such high rainfall rates increase concerns
for both flash and river flooding in this region. Total storm
total rainfall amounts of 3 to 6 inches is still predicted but
isolated higher amounts are possible. 1 to 3 inches is expected
from the Capital District into Schoharie County and southern
VT. See hydro discussion for more details on river flooding. The
one saving grace is convective elements should be at a minimum
as our region remains in the cold air wedge ahead of the warm
Moderate to heavy rain should quickly exit by 06 - 12 UTC from
northwest to southeast with most rain out of western New England
by the morning commute. In fact, skies should turn clear for
areas north and west of the Capital District by sunrise. Winds
look to also turn breezy overnight with gusts up to 25 - 30 mph
possible and sustained winds reaching up to 10 to 20mph. Areas
with especially saturated soils could become more susceptible
to smaller/weakened trees falling, mainly in the mid-Hudson
Valley, NW CT and eastern Catskills.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Fall-like temperatures will occur the rest of the week as an
upper level trough digs into the Northeast Thursday into
Thursday night with Canadian high pressure building at the
surface through Friday.
The rather tight pressure gradient between the incoming high
and departing remnant tropical cyclone will result in breezy
conditions tomorrow morning with gusts up to 25mph possible.
Northerly flow will usher in cooler and drier Canadian air
tomorrow preventing temperatures from warming up too much.
Expect highs to only max out in the upper 60s to low 70s with
most reaching their respective convective temperature during
afternoon peak heating. This will allow morning sunshine to mix
in with afternoon fair weather cumulus clouds.
Partly cloudy skies stay in place Thursday night as the base of
the trough swings through the region. Even still, temperatures
should turn cool dropping into the 50s throughout the region
with a light breeze still in place.
The Northeast will remain under the influence of the upper level
trough most of Friday so some cloud coverage looks to linger
with even a few isolated showers not ruled out as the upper
level cold pool moves overhead. However, skies gradually clear
later in the afternoon as high pressure finally takes control.
Despite improving conditions late in the day, high temperatures
should be well below normal with most only rising into the mid
to upper 60s making it feel fall. Skies become clear overnight
allowing temperatures to turn quite cool dropping into upper 40s
to low 50s.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Closed off upper level low will be exiting eastern New England and
moving across Atlantic Canada for Saturday. As this feature
departs, rising heights will allow for a weak shortwave ridge to be
in place over the area for Saturday. This will result in a partly
to mostly sunny sky and seasonable temps, with valley highs in the
This shortwave ridging will quickly be departing, as a large upper
level trough north of the Great Lakes over Ontario starts moving
southeast. This may allow for a few passing light showers and
possibly a thunderstorms for late Saturday night into Sunday, mainly
for areas north and west of the Capital Region. Temps should be
similar to Saturday with valley highs in the mid 70s, although
dewpoints will be rising from the 50s into the low to mid 60s by
As the upper level disturbance sits and spins across Ontario and
Quebec, we will keep slight to low CHC POPs across the area for
Monday through Wednesday, especially during the diurnally favored
afternoon hours. The best chance may wind up being on Monday ahead
of a frontal boundary, but can`t rule it out for Tues/Wed as well.
Any precip looks fairly scattered in coverage and mainly brief in
duration. Temps will remain seasonable, with valley temps still
reaching into the mid 70s for daytime highs. Dewpoints look highest
in the low to mid 60s for Monday ahead of the weak boundary and will
fall off into the upper 50s for Tues/Wed.
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
As of 2330Z Wednesday...Rain shield associated with the
remnants of TC Ida continues to envelope most of the area, with
KGFL on the outer edge. KGFL expected to remain VFR through the
rest of the night as the low levels likely remain unsaturated.
Elsewhere, conditions should continue to deteriorate over the
next few hours as rain becomes heavier. Worst conditions should
exist at KPOU 02-06Z and KPSF 05-08Z where LIFR conditions are
possible. Rain will be less heavy at KALB, but an interval of
IFR conditions are possible roughly 04-08Z. Conditions should
improve fairly quickly as the storm pulls away from west to east
especially after 08Z. VFR conditions are expected for much of
the daylight hours Thursday with SCT-BKN cu developing in the
Winds will be from the north to northeast at around 10 kt, with
gusts to near 20-25 kt at times at KPSF/KPOU overnight. Winds at
2kft may increase to 40-45 kt 02-12Z at KPOU so LLWS was
retained. The winds will become north to northwest at around 10
kt with occasional gusts near 20 kt during the afternoon on
Thursday Night: No Operational Impact. NO SIG WX.
Friday: Low Operational Impact. Slight Chance of SHRA.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Moderate Operational Impact. Chance of SHRA.
Sunday Night: Moderate Operational Impact. Chance of SHRA.
Labor Day: Moderate Operational Impact. Chance of SHRA.
Periods of rain, heavy at times, associated with former tropical
cyclone Ida will impact eastern New York and western New England
through tonight. High pressure builds in tomorrow morning through
the afternoon with cooler and drier conditions. Fair and dry weather
will continue into Saturday.
The RH values will be close to percent tonight, and then lower to 50
to 65 percent Thursday afternoon. The RH values will recover to 90
to 100 percent Friday morning.
The winds will be north to northeast at 5 to 15 mph with some gusts
20 to 30 mph south and east of the Capital Region. The winds will
be northerly at 5 to 15 mph Thursday afternoon, and will be become
light from the northwest at 10 mph or less.
The period from 8PM to 5AM tonight will likely feature periods
of moderate to heavy rain for areas from Interstate 90 southward
especially in the mid-Hudson valley, eastern Catskills and
Litchfield County, CT. During this window, the remnant low of
Ida will track near or just south of NYC with very efficient
rainfall processes coincident with strong synoptic forcing which
will likely result in high rainfall rates exceeding one to
possibly even two inches at times. The latest guidance
positions the region of highest 925 - 850 hPa moisture flux
overlapping very strong omega just north of the system`s warm
front which looks to track across southern New York. There is
still some uncertainty on the exact position of these
ingredients and should they line up just south of our area, we
could miss out on the highest rainfall totals. However, the high
resolutions guidance including the 3km NAM, HREF and HRRR still
suggest this overlap will track in our southern zones including
Litchfield, Ulster and Dutchess county mainly from 8PM to 5AM.
With storm total rainfall amounts expected to range 3 to 6
inches (locally higher up to 7 inches possible), both flash and
river flooding in this region is expected. The latest guidance
from the Northeast River Forecast Center places forecast points
along the Esopus, Rondout, Wappinger Creek and the Housatonic
River in flood stage. While the current forecast points to most
rivers only reaching minor flood stage, a few near moderate
flood stage. According to MMEFS this is possible depending on
which river basins receive the highest rainfall amounts.
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.
CT...Flash Flood Watch through Thursday afternoon for CTZ001-013.
NY...Flash Flood Watch through Thursday afternoon for NYZ058>061-
Flash Flood Watch through Thursday morning for NYZ047-051>054.
MA...Flash Flood Watch through Thursday afternoon for MAZ001-025.
VT...Flash Flood Watch through Thursday morning for VTZ013>015.
Area Forecast Discussion
National Weather Service Billings MT
149 PM MDT Wed Sep 1 2021
Tonight through Thursday night...
Satellite imagery shows a deep low over southern Alberta, and a
moist monsoonal wave lifting thru the 4-corners area. Confluent
southwest flow aloft and lee side surface ridging (along with both
high cloud and smoke cover for much of our cwa) are limiting
surface heating and instability behind last night`s cold front.
There were some showers that clipped southern Carter county this
morning, otherwise it`s been a dry day. Upstream radar shows some
showers from Casper to south of Gillette.
The main surge of moisture from the southwest, and thus the
heaviest precipitation over the next 24 hours, will be south and
east of our forecast area...and of that we have high confidence.
There is a weak shortwave lifting out of northern UT and southwest
WY that could bring some showers to our far east tonight into
Thursday morning. Recent HRRR runs develop some convection near
Sheridan and Lame Deer this evening, but feel that there is not
enough moisture and instability that far west for showers.
Something to watch.
Trof over the PacNW will track slowly eastward bringing ascent
and a good chance of showers beginning Thursday night. This
feature will tap into a little monsoon moisture before it arrives.
Temperatures tomorrow will be a few degrees cooler than today,
with highs in the upper 60s and 70s. Southwest flow aloft will
bring us another day of lofted smoke. Surface winds out of the
NE-E should keep lower elevations fairly clear of smoke.
Friday through Tuesday...
A trough will move through the area on Friday with showers and
thunderstorms across the area. Areas near Billings could see
around 0.05 inches while areas in the far southeast corner could
see upwards of a half inch or more. To the west of Billings will
miss out on rain. As the trough shifts to the east, ridging will
build over the four corners. This will bring drier and warmer
weather concerns back to the southeastern Montana through early
next week. It looks like the pattern could change around midweek
but it is too early for details.
High temperatures will be in the 60s and 70s Friday, warming into
the 70s and 80s on Saturday. Sunday into the middle of next week
will have temperatures in the 80s.
High cloud cover will continue over much of the area today before
clearing out from west to east overnight. Gusty west winds to
20 knots will continue at KLVM through the afternoon. Otherwise,
winds remain relatively light throughout the area. There is a
slight chance of brief showers in the vicinity of KSHR-KMLS late
this evening. While near-surface smoke concentrations remain low,
expect reduced slant range visibility due to high smoke
.PRELIMINARY POINT TEMP/POPS...
Thu Fri Sat Sun Mon Tue Wed
BIL 050/072 050/068 049/081 053/087 056/087 055/085 055/084
00/H 44/W 10/U 00/U 00/U 00/U 01/B
LVM 039/074 044/071 043/080 047/086 050/086 050/085 051/084
01/H 33/W 10/U 00/U 00/U 00/B 11/B
HDN 049/076 051/068 046/081 049/087 053/087 053/085 054/086
01/H 55/T 10/U 00/U 00/U 00/U 01/B
MLS 055/077 052/070 048/078 051/085 054/084 054/084 054/084
11/H 44/W 10/U 00/U 00/U 00/U 00/U
4BQ 057/077 054/066 049/076 051/083 055/083 054/083 054/084
11/H 66/T 20/U 00/U 00/U 00/U 01/U
BHK 057/076 050/068 047/076 049/082 053/082 052/081 052/082
22/T 35/W 20/U 00/U 00/U 00/U 00/B
SHR 047/077 048/068 044/079 047/086 051/086 051/085 051/086
12/T 56/T 10/U 00/U 00/U 00/U 01/U
Area Forecast Discussion
National Weather Service Columbia SC
747 PM EDT Wed Sep 1 2021
A cold front crosses the area from the west tonight. Dry weather
will then prevail through the weekend under the influence of
high pressure. Small rain chances will return early next week as
moisture increases and upper level troughing develops over the
.NEAR TERM /TONIGHT/...
Radar showing patchy light showers across parts of the northern
Midlands, with its development aided by a passing short wave.
Drier air aloft farther south should keep the rest of the
forecast area rain-free. Showers will then generally be on a
diminishing trend through this evening.
Drier air will filter into the area tonight in wake of the
passing cold front, with dew points falling through the 60s
during the overnight hours. Some additional clearing is expected
tonight as well. Temperatures should fall to lows in the 65-70
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
By early Thursday, the trough associated with the remnants of
Ida will be crossing the forecast area. A quick shift from
southwesterly to north-northwesterly flow aloft and at the
surface will occur between 06z and 12z. Strong ridging will fill
in behind the trough passage and help drive some very
impressive dry air advection all the way down to the Gulf coast.
Dew points and PWATs will fall steadily throughout the day
Thursday across South Carolina and Georgia, from the mid-upper
60s to the mid 50s and from over 1.5 inches to under 0.75
inches, respectively. Compared to the dry air advection,
temperature advection will not be quite as impressive and we
will still reach the upper 80s across much of the area thanks to
abundant solar heating with limited cloud cover expected. With
the dry air in place, Friday morning will likely be our coolest
in some time. Exactly how much we cool will primarily depend on
whether we can decouple the boundary layer. Winds may remain up
enough thanks the pressure gradient along the leading edge of
the surface ridging to prevent completely decoupling.
Regardless, temperatures Friday morning will fall into the mid
or low 60s.
The story remains much the same for Friday as the dry air continues
to be reinforced with persistent northwest flow aloft and
northerlies at the surface. Dew points will bottom out in the upper
40s Friday afternoon with PWATs falling near or below 0.5
inches; NAEFS shows low level moisture and PWATs both in the 1st
percentile climatologically for Friday and early Saturday.
Winds will gradually weaken throughout the day as the surface
ridge sinks a bit south. High temperatures will again be just
few degrees below average thanks to ideal solar heating.
Radiational cooling Friday night and Saturday morning will be
close to maximized with clear skies, light or no winds, and far
below average moisture from the surface to upper levels.
Guidance is likely under-doing the cooling at this time, but is
still showing low 60s everywhere. So given the trends and
anomalously dry airmass, lows will likely near 60 or possibly
the upper 50s in spots.
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The long term will primarily be a gradual return to more
typical early September conditions across the forecast area. Below
average surface dew points and PWATs will remain in place Saturday.
NAEFS shows near average moisture and temperatures returning by late
Sunday. The surface ridge begins to shift offshore by late Saturday,
and along with a strengthening trough to our west, allows
southerly flow to kick back up across the southeast. This will
gradually allow moisture to return and bring back near normal
dew points and PWATs by Sunday. All ensemble guidance shows the
trough and associated low pressure center to our west swinging
up through the northeast by late Sunday. However, the trailing
front will weaken and stall before it truly reaches the area as
the flow aloft and near the surface becomes nearly uniformly
zonal. With the weak forcing, precipitation chances consequently
remain only around slight as the front weakens, with only a few
members of blend and ensemble guidance showing any accumulation.
Ridging to our west then fills in through mid-week and returns
near normal temperatures and moisture for early September.
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR conditions will remain outside of a brief shower across the
Midlands this evening. Otherwise after 03z, vfr conditions
Narrow band of showers in the northern Midlands is being shown
on radar slowly moving southward towards CAE/CUB this evening.
There does remain some uncertainty as to whether these will hold
together over the next few hours. However the hrrr does show
this band passing through CAE/CUB this evening. Timing off of
radar doesn`t bring this activity in until near 01z, then passes
it through by 03z. Have gone ahead and included vcsh between
those hours, with a tempo group for mvfr visibilities in
rainfall. Do not think this will hold together as it approaches
OGB, so have not mentioned anything there at this time.
Outside of these showers, vfr conditions expected, although
ceilings will remain broken for a good portion of the night.
Skies scatter out Thursday morning as drier air pushes into the
Winds start off out of the west, then gradually turn northwest,
then north through the night. Speeds should remain around 5
knots through the period.
EXTENDED AVIATION OUTLOOK...VFR with drier conditions through