Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/19/23
Area Forecast Discussion
National Weather Service Burlington VT
1053 PM EDT Mon Sep 18 2023
.SYNOPSIS...
Unsettled, cool weather over northern New York and Vermont will
take place into Tuesday as a deep upper level trough and
developing coastal low pressure system will bring periods of
light to moderate rain. High pressure returns for Wednesday and
dominates the region`s weather through the upcoming weekend with
dry conditions and slightly above normal temperatures expected.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
As of 1047 PM EDT Monday...Rain has finally ended in St
Lawrence County but continues across southern Vermont and in
parts of Eastern Vermont. Winds are very light and ceilings
remain pretty low. Expect slow improvements overnight, and
especially during the daytime hours on Tuesday. No big changes
for the evening update, mainly adjusted pops to reflect current
radar trends. Previous discussion follows.
Surface observations suggest that the surface low that we`ve
been tracking is nearing Long Island. Precipitation is expanding
north and west as the surface low deepens. Increasing low-level
convergence and modest frontal forcing will produce moderate
rain east of the Greens, especially between 6 PM and about 2 to
4 AM, then taper off as the surface low lifts north. West of the
St. Lawrence River, we continue to see a slow moving cold front
produce scattered convection, with a few flashes of lightning
here and there. Eventually, the front will completely stall and
then get absorbed into the northwesterly flow imparted by the
coastal low, and the exact placement of convection when that
happens is somewhat up for debate. Noting the HRRR is suggesting
it makes it east of the St. Lawrence River and nudged things in
that direction this evening given present radar imagery.
Rainfall amounts over the next 24 to 36 hours will be greatest
in eastern Vermont at 0.75" to 1.50" and more scattered
0.10-0.50" forecast west of the Greens.
Temperatures have been very cool this afternoon, except some
upper 60s to lower 70s in parts of northern New York where the
Sun has broken out. Elsewhere, upper 50s to mid 60s has
prevailed. Despite increasing northwest winds, cold air will lag
behind for sometime before a reinforcing trough shifts east
Tuesday. So overnight temperatures aren`t going to budge very
much, mainly in the 50s.
On Tuesday, a reinforcing trough and a vort max working through
the upper trough will swing east. With some diurnal instability
and plenty of moisture, anticipate scattered showers to
numerous up north. Orographic enhancement on the northwestern
slopes will likely keep areas like Jay Peak showery all day. By
evening into the overnight hours, moisture will begin to depart.
Cold advection will make for another cool day, with upper 50s
to mid 60s, except some readings near 60 in the lower
Connecticut and into parts of far western Rutland or Addison
County. Continued cold advection will result in a cool night
with temperatures in the 40s to lower 50s near Lake Champlain.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 320 PM EDT Monday...Surface high pressure centered over
the Great Lakes will gradually move eastward. Some lingering
cloud cover in the morning should dissipate, bringing some
sunshine to the region for a majority of the day. Daytime highs
will be pleasant and seasonable, generally in the mid to upper
60s. With the high pressure building overhead, there will be a
favorable set up for fog development in the favored valley
locations, especially with the recent rainfall across the
region. With clearing skies, overnight lows will be quite cool
with temperatures dipping into the 40s.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 320 PM EDT Monday...The aforementioned surface high
pressure will continue to build overhead, bringing a pleasant
stretch of weather through the end of the work week into the
start of the weekend. As the week progresses, there will be a
gradual warming trend, with highs reaching the mid 70s by
Friday. Overnight lows will be more seasonal as clear skies will
allow temperatures to drop, generally into the 40s.
Heading into the later half of the weekend, a plume of maritime
moisture will move northward along the Atlantic Coast, however
at this point there are still a number of disagreements across
deterministic guidance, so the forecast relies on the NBM and
blended guidance. Currently expecting an increase in cloud cover
and some possible showers across the forecast region,
particularly the southern portions for Sunday into next week.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...Currently, conditions are VFR over New
York and BTV while they are IFR over the rest of Vermont. These
restrictions are mostly due to low ceilings, but there are some
temporarily reduced visibilities in the heavier showers over
Vermont. The rain will slowly shift north and east and become
lighter during the night. This should cause visibilities to rise
above 5SM where they are currently lower. However, there will
be very light boundary layer flow for much of the night so low
level moisture will remain in and the ceilings will likely
remain low. A cold front will move through the region later in
the night and begin to slowly increase the winds and cause them
to turn northwesterly. Ceilings are forecasted to lower in SLK
and MSS after it passes through as is typical in northwesterly
flow. However this wind should eventually scour out some of the
low level moisture, especially in the valleys in Vermont, so
ceilings should rise to at least MVFR at all locations by 15Z.
Outlook...
Tuesday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Wednesday: VFR. NO SIG WX.
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.
&&
.EQUIPMENT...
The KCXX radar will be down for radome repairs, with a return to
service around September 20th.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Haynes
NEAR TERM...Haynes/Neiles
SHORT TERM...Kremer
LONG TERM...Kremer
AVIATION...Myskowski
EQUIPMENT...WFO BTV
Area Forecast Discussion
National Weather Service Des Moines IA
700 PM CDT Mon Sep 18 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Monday/
Issued at 249 PM CDT Mon Sep 18 2023
Key Messages:
- Scattered showers and thunderstorms expected this evening and
overnight; No severe weather anticipated
- Warmer tomorrow with lingering, sporadic precipitation chances
south; Highs returning to the 70s rest of the week
- Larger scale system on the horizon for Friday into the Weekend
In wake of the upper level trough that moved through this last
weekend, we see surface high pressure departing with the trough to
the east and low pressure filling in behind. This, in conjunction
with the weak shortwave moving through, has resulted in a tightening
pressure gradient and strong southerly flow over the western half of
the state today, causing breezy conditions with gusts over 25 mph
this afternoon. A developing low level jet this evening will combine
with warm air advection and increasing moisture to produce scattered
showers and isolated thunderstorms over portions of central and
eastern Iowa tonight. These look to first develop shortly after 00z
at the leading edge of the LLJ in our far east and northeast before
zippering southwest back into central and south central Iowa.
Confidence is low in how far south and west precipitation will
develop tonight into the early morning hours, as soundings indicate
a drier profile over this region compared to those further north and
east. However, better instability will be present further south and
west, and if a storm could tap into some of that, the dry air would
likely be overcome. Therefore, have included some isolated storm
chances further south and west to account for any updrafts that can
overcome the drier profile. That being said, even with the 35 to 40
kt LLJ producing decent shear profiles, the instability values still
struggle to exceed 1000 J/kg for much of the area tonight into early
tomorrow morning, making the chances for severe storms fairly low.
The RAP and HRRR show these sporadic showers and storms lasting over
southern Iowa through much of the day Tuesday and even lasting into
Tuesday night as the layer continues to warm and moisten. These two
models are outliers through tomorrow and drier air at the surface
will continue to inhibit rainfall, but with increasing surface
dewpoints, can`t rule out precipitation festering through the day.
This trend of sporadic precipitation continue this week as lobes of
forcing propagate through the agitated, quasi-zonal flow. This has
resulted in a prolonged period of low-end precipitation chances over
southern Iowa in the NBM. However, this should be interpreted as
brief, occasional showers over the area rather than rain falling
during this entire period. In addition to occasional
precipitation chances, surface high pressure begins to leak back
into the state Wednesday, resulting in slightly cooler
temperatures than Tuesday and highs falling back into the 70s and
low 80s through the rest of the week and into the weekend.
Looking ahead to the weekend, we continue to watch an approaching
upper level trough that will develop off the west coast before
making its way east into the midwest by late week and into the
weekend. Time of arrival varies slightly among current guidance,
with the GFS being slightly faster than the Euro and Canadian. There
is also some discrepancy on its departure as well, with the
Euro/Canadian having the system linger overhead through Sunday
but the GFS completely departed by this time. This has resulted in
a smearing of precipitation chances from the NBM through the
entire weekend. Needless to say, this likely doesn`t represent the
actual timing of rainfall, but, depending on the evolution of the
low, there may still be a decent period of rain falling this
weekend. It`s a bit too early to get locked down into any specific
details such as precipitation amounts or exact severe parameters,
however, severe weather does look possible as the cold front
first arrives on Saturday. The most likely location at this time
would be over the western portion of the state where the better
instability resides, but this is subject to change through the
coming days. Colorado State Univeristy`s machine learning
algorithm also highlights most of the area with severe
probabilities on Saturday and CIPS Analog guidance pings the
western half of the state as well. This will be the system to
watch through the week and will continue to update as new
information becomes available.
&&
.AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/
Issued at 641 PM CDT Mon Sep 18 2023
Forecast remains on track from previous issuance with LLWS and
isolated to scattered showers or thunderstorms developing later
tonight and continuing overnight. Confidence in shower to isolated
storms remains highest over eastern sites (KALO/KOTM), though some
VCSH remains plausible at all sites. Kept with shower to VCSH
mentions due to isolated coverage of any thunderstorms and will
adjust mentions if needed later on. Generally expecting VFR
conditions to prevail though won`t completely rule out a temporary
categorical reduction if a stronger shower/storm is to occur over
TAF site. A few showers/storms may bring some gusty conditions but
overall the breezy south winds from this afternoon are expected
to decrease tonight resulting in the LLWS potential overnight.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Dodson
AVIATION...KCM
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
315 PM PDT Mon Sep 18 2023
.SYNOPSIS...Isolated to localized scattered thunderstorm development
across portions of Trinity and Northeastern Mendocino County will
end this evening. Dry and locally breezy conditions are then
expected Tuesday through Thursday. Cooler weather will arrive late
week, with a wetter pattern developing over the weekend and
especially next week.
&&
.DISCUSSION...Afternoon visible satellite imagery depicts a band of
mid to high level clouds associated with a weak front draping down
from the north. RAP mesoanalysis showed surface cape values around
500 J/kg around Trinity County early this afternoon, as the
cloudcover thus far had only a moderate optical thickness.
Thunderstorms are beginning to fire up along the leading edge of
the front in SE Trinity County. Confidence is highest for further
convection in this area through the Trinity Horn.
Breezy north winds will occur in the wake of the front, particularly
during Wednesday, with gusts from 20 to 30 mph possible across
exposed terrain. A deepening, cold trough will dive from the north
through S Oregon Wednesday through late Thursday. This will bring
gradual cooler temperatures and the chance for very light
precipitation. Some weak, elevated instability may clip E Trinity
County late Wednesday, but probabilities for thunderstorms are very
low at this time. Can not rule out nocturnal convection given the
forcing from the trough.
A second cold upper trough will drive into the Pacific Northwest
from the west this weekend. This will be followed additional
troughing and then potentially an additional stronger trough with an
associated IVT plume early next week. There is much uncertainty on
the strength and timing of the system early next week, but high
confidence remains on the pattern change and opportunity for early
season rainfall.
The probability for a wetting rain over a tenth of an inch has
constantly ranged from 10 to 15% through the weekend, mostly for the
northwest portion of the region. The probability for over a quarter
inch of rain quickly increases early next week to 25 (south) to
45% (north), but there is still a high degree of run to run
variability.
&&
.AVIATION...A deep marine layer for the coastal terminals will meet
inversion sooner at KCEC than KACV. Deeper and longer lingering low
level moisture at KACV will keep ceilings 1500 to 2000 feet
overnight. Expect an inversion to lower at KCEC by midnight,
although it could be scattered and broken to overnight, post frontal.
Otherwise. Models show moisture upstream as another deep upper level
low approaches. Expect IFR conditions in the morning at the coastal
terminals during early sunrise.
&&
.MARINE...Northerlies are expected to quickly ramp up in the
northern outers and spread to the southern outers, continuing to
accelerate tonight with gusts nearing Gale Force offshore of Pt St
George by early Tuesday morning. Northerlies continue to accelerate
during Tuesday, likely reaching Gale Force in the outer waters by
afternoon and evening. Winds further strengthen Wednesday then trend
weaker Thurs and Fri. Short period seas quickly respond to the
increasing winds, spreading to most zones by Tuesday, and possibly
the southern inners as well on Wednesday. A more significant NW
swell is expected to quickly fill in late this evening and tonight,
currently forecasted to peak early Tuesday morning around 9 ft at 15
seconds, and likely leading to a chaotic sea state through much of
the work week. This looks to be reinforced Wednesday night by
another NW swell, peaking around 7 ft at 15 sec.
&&
.FIRE WEATHER...Isolated to localized scattered thunderstorm
development across portions of Trinity and Northeastern Mendocino
County will end this evening. Storms will move slowly, which will
yield wetting rains beneath storms. However, lightning will pose
at least a slight risk for additional fire starts. Otherwise, a
dry cold front will move south across the region during Monday
night. A dry airmass will spread south across northern California
behind the front, and periods of breezy north winds gusting from
20 to 30 mph across exposed terrain will be probable, especially
over interior portions of Del Norte County during Wednesday.
Elevated fire weather conditions will occur as a result, but a
fire weather watch has not been issued due to marginal min
forecast RH values in the 30s.
&&
.BEACH HAZARDS...A moderate threat for sneaker waves will
extend through this evening. Long period Northwest Swell can set in
suddenly, surprising beachgoers or recreational aquatic enthusiasts
near jetties or near shore. The timing of this event is during
daylight hours when a majority of people are out and about. Please
be aware as calm conditions can fool you into complacency. This is
when tragedy strikes. Do not turn your back to the ocean and keep
your distance as large objects, logs specifically, can be lifted and
propelled onto beaches.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...
Beach Hazards Statement until 8 PM PDT this evening for
CAZ101-103-104.
NORTHWEST CALIFORNIA COASTAL WATERS...
Small Craft Advisory from 9 AM Tuesday to 1 PM PDT
Wednesday for PZZ450.
Gale Warning from 1 PM Wednesday to 9 AM PDT Thursday for
PZZ450.
Gale Warning from 4 PM Wednesday to 9 AM PDT Thursday for
PZZ455.
Small Craft Advisory from 7 PM this evening to 7 AM PDT
Tuesday for PZZ470.
Gale Warning from 7 AM Tuesday to 9 AM PDT Thursday for
PZZ470.
Small Craft Advisory from 7 PM this evening to 9 PM PDT
Tuesday for PZZ475.
Gale Warning from 9 PM Tuesday to 9 AM PDT Thursday for
PZZ475.
&&
$$
Visit us at https://www.weather.gov/eureka
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For forecast zone information
see the forecast zone map online:
https://www.weather.gov/images/eka/zonemap.png
Area Forecast Discussion
National Weather Service Goodland KS
511 PM MDT Mon Sep 18 2023
.SHORT TERM...(This evening through Thursday Morning)
Issued at 206 PM MDT Mon Sep 18 2023
Shortwave is currently moving into eastern Colorado where a
noticeable uptick in cumulus has developed over the past hour. At
the surface a trough is located across the area with light and
variable winds along the axis and breezy winds gusting 25-30 knots
ahead and behind it. RH values across the NW portion of the area
have fallen to around 12% as of 1pm MT, as soundings support the
potential for wind gusts up to 30 mph if enough mixing can occur
have messaged near critical fire weather conditions for the
remainder of the afternoon.
For thunderstorm potential, dry line is currently placed near
Highway 83, is overall not the strongest dry line at this time which
may overall limit any additional ascent for storm development, this
may be the reasoning as well that CAMs have backed off on initiation
this afternoon. As a result of this have lowered overall pops down
to 15%. If a storm were to initiate however given RAP forecast
soundings of shear around 25-30 knots, MUCAPE of 1000-1300 j/kg
and steep lapse rates, hail up to quarter size and 60 mph winds
would be the primary hazards along with lightning.
Tonight another round of mid level moisture moves off of the Palmer
Divide in the form of mid level clouds, given the dry nature at the
surface don`t think any precipitation should be observed other
than some spotty sprinkles at best. Temperatures should remain a
bit warmer than the previous nights in the low 50s to low 60s.
Tuesday, some guidance tries to show showers or sprinkles across the
area during the morning, however think given the drier air at the
surface sprinkles or just mainly virga will be what occurs. Warm
temperatures again are forecasted with low 80s across east
Colorado to the low 90s across the east. During the afternoon
another wave moves across the Plains leading to some showers and
storms along and south of Highway 96. Severe storms aren`t
currently anticipated with this activity as cloud to ground
lightning would be the primary hazard.
Wednesday, riding briefly again develops across the area ahead of
a developing trough over the west. Temperatures will again be
warm in the 80s to 90s. Winds will be out of the NW for the
majority of the day before switching to a more southerly component
as the effects of the developing trough a felt. Moisture ramps up
from the south as well overnight so upcoming shifts may need to
keep an eye on status or fog potential.
.LONG TERM...(Thursday through Monday)
Issued at 100 PM MDT Mon Sep 18 2023
Will start the long term with southwest flow aloft ahead of an
upper low in the Great Basin. That system will evolve into an
open wave as it ejects into the northern plains Friday night and
Saturday. Ridging then follows for Sunday and Monday.
Precipitation chances on Thursday will be east of Highway 25
where instability axis will set up and weak wave in southwest flow
will provide lift for convection. Instability of up to 1500 j/kg
is currently forecast with deep layer shear around 30 kts, which
should be sufficient for a marginal risk of severe storms. Timing
looks to be the typical mid afternoon initiation, peaking during
the evening, then moving east and out of the area during the
overnight hours. Highs will be in the 80s and lows Thursday night
mainly in the 50s.
On Friday, the western system will begin to move out of the
Rockies. The local area appears to be dry slotted with the
northerly track, with instability swept out of the area by Friday
afternoon. If that verifies, may see only gusty westerly winds
and a risk for critical fire weather conditions as relative
humidity drops below 20 percent, especially in western areas. Cold
front moves through Friday night, but moisture appears to be very
limited and may see a dry frontal passage. High temperatures look
to be at least in the mid to upper 80s, perhaps warmer with the
downsloping surface winds. Lows Friday night will be in the 40s
and 50s, coolest in Colorado.
Main upper trough axis moves through on Saturday. Models suggest
perhaps some light wraparound type showers, but instability is
basically zero. May see gusty northwest winds, with ECMWF showing
gusts in the 40-45 mph range, a bit lower in the GFS at 35-40 mph.
Low level lapse rates are best early in the day for blowing dust,
less favorable in the afternoon. Relative humidity forecasts are
currently above 20 percent the entire day. So, a breezy day with a
few isolated showers and marginal conditions for blowing dust
and/or fire weather. Highs will be in the 70s and lows Saturday
night in the 40s.
For Sunday and Monday, dry conditions are expected with upper
ridging. Highs will be in the 70s both days and lows in the 40s.
Relative humidity forecast to be above 20 percent both days and
wind gusts less than 25 mph, so not expecting any fire weather
concerns.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 511 PM MDT Mon Sep 18 2023
VFR conditions with generally light winds are expected throughout
the period for both KGLD and KMCK. Mid-level showers and low end
thunderstorms are moving through the region currently, with a second
wave of showers possible in the early morning hours tomorrow.
Confidence is very low that they will impact flight categories at
either TAF site. KGLD could see some near 20 kt gusts from the
northwest around 9Z as the second wave comes through. Gusts are
expected to die down around 14Z. There is another chance of showers
and thunderstorms tomorrow evening to impact the area.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...Trigg
LONG TERM...024
AVIATION...CA
Area Forecast Discussion
National Weather Service Gray ME
1145 PM EDT Mon Sep 18 2023
.SYNOPSIS...
Widespread rains continue tonight with locally heavy rain
possible. Some showers may linger in the mountains and northern
areas tomorrow as high pressure begins to build in through the
end of the week. Northwesterly flow brings dry air with
seasonable temperatures through midweek with nighttime valley
fog possible. Another chance for rain looks possible late in the
weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
1145 PM Update... No significant changes to the going forecast
with only minor refinements of PoPs and QPF based on incoming
00Z guidance. The focus from now through the next 4 to 6 hours
will be a band of moderate to heavy rain forming on the NW side
of low pressure now in the Gulf of Maine. This band looks to
set up from south-central NH where both MHT and CON have
reported bouts of heavy rain into the White Mountains and will
pivot through western Maine over the coming hours. Instability
is lacking although around 100 J/kg of MU CAPE has built into
southern NH with a few instances of lightning as of this
writing. Much of the area has seen a good soaking rain up until
now with spots having 3 hour flash flood guidance drop below 2
inches. As this band will be capable of producing 1 to 2+ inches
of rain over the coming hours will be watching portions of
east-central NH into western Maine for any flood issues through
tonight.
810 PM Update...Low pressure is currently just south of Cape
Cod and will continue to deepen over the next several hours as
it tracks northeastward through the Gulf of Maine. An area of
moderate to heavy rain associated with Fgen forcing on the
northeast side of the low has pushed through Cape Cod with
observed rainfall rates around one inch per hour. Hi res
guidance has been fairly consistent in keeping this area of
moderate to heavy rain offshore as the low moves through the
Gulf of Maine lowering flood concerns near the Mid Coast,
although it will be close enough to keep an eye on. Another area
of moderate to heavy rain looks to develop across central New
Hampshire around midnight and pivots through western Maine
through the pre dawn hours. Overall, rainfall rates with this
second area look to top out around 0.75 inches per hour. So far
area gauges suggest 1 to 1.5 inches has fallen throughout the
past several hours. Have mainly refined PoPs and QPF with this
update with an additional 1 to 1.75 inches forecast across east
central NH into western Maine. Will continue to monitor the
development of the second band of rain around midnight for
potential flood concerns.
Previously...
The phasing is occurring at 500 MB attm and the trough is
showing neg tilt, so the sfc low, now south of Cape Cod is
deepening, and will continue to do so through this evening as it
track across Cape Cod and into downeast ME by morning. There is
some good mid level FG out ahead of the low and this will drive
an increase in rainfall rates this evening, and into the
overnight, although rain begin to shut off in the S by late
evening. An then into the N and E zones during the pre-dawn. The
first round of the heavier rains cross SE New England attm, and
could just stay offshore as it passes early this evening, or
perhaps move into the mid coast. A second round of heavy rain,
as predicted by the last few HRRR runs comes around the west
side of the deepening in the fairly deep FG on the CAA side of
the storm, and this looks to move through srn NH and SW ME later
this evening and into central around midnight or shortly
thereafter. If we see rain rates of an inch an hour or more,
this will be the most likely time and area. The rain should
taper off quickly to scattered showers behind this feature, and
will likely be over before sunrise across all but the NE zones.
May see a brief burst of W winds behind this feature, but should
settle back until daylight really breaks the inversion. Lows
will be mostly in the 50s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Tuesday should be mostly dry outside the mountains ans a brisk
WNW flow will downslope S and E of the mtns, while we see our
first decent upslope event of the season in the mtns, although
it will be RA at all elevations /OK, guess I can’t rule out some
graupel on MWN./ Highs range from the the low to mid 60s in the
mtns, and 70-75 in the S. Also it will be breezy with winds
gusting to around 25 mph at times.
Tuesday night should see enough pressure gradient to keep some
light W flow at all but the sheltered locations, so rad cooling
will be limited. Clouds will linger in the mtns through the
evening before they start to clear after midnight. Lows range
from the upper 40s N to the mid 50s S.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The extended period starts off relatively quiet as high
pressure builds in at the surface through the end of the week.
Northwest flow sets up behind exiting low pressure Wednesday and
Thursday bringing dry air from the north and sunny skies with
seasonable temperatures. As winds calm and decouple overnight,
radiational cooling sets in bringing overnight lows into the
40s across the area with valley fog possible.
While the surface stays quiet, the upper levels remain active
through the week as the polar and sub-tropical jets diverge around
building high pressure over the East Coast. The ensemble suite has
shown good temporal and model-to-model consistency of a trof
emerging out of the southern Rockies before dipping south and
strengthening as it crosses the southeast US. Eventually, all the
ensembles take this trof up the east coast from the Florida
peninsula with most uncertainty lying in the northward speed of this
system. As this happens, the polar jet begins a ridging pattern
with several shortwaves passing along its north side. The ensemble
suite has larger uncertainty in the strength and position of this
ridge, possibly due to the complicated pattern of shortwaves in this
timeframe. Eventual this ridge breaks down late in the week as
the southern trof pushes up the East Coast with a tightening
pressure gradient across the northeast for the start of the
weekend. How this phases with the shortwaves within the polar
jet is still largely uncertain, however a period of rain
sometime this weekend looks possible whether it be from the
shortwave to the south or the west.
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
Short Term...Terminals remain variable in terms of flight
restrictions, as most are varying between MVFR and IFR, mainly
die to cigs. KRKD should drop to MVFR or IFR shortly, and KHIE
may bounce around for a few hours before they go to IFR, along
with all the other terminals around or just after sunset. Should
see some improvement to MVFR after sunrise Tuesday as the wind
pick and mixing begins, and eventually to VFR by late morning at
all but KHIE, which will stay MVFR in upslope flow.
Long Term... High pressure will dominate through the end of the
week keeping terminals at VFR with a northwest wind. Nighttime
fog is possible mid to late week before ceilings thicken over
the weekend.
&&
.MARINE...
Short Term...Low pressure moves through the Gulf of Maine
tonight and produce SCA conditions. Thereafter, gusty NW winds
and seas will remain above SCA levels into Tuesday evening.
Long Term... Seas are expected to stay below SCA thresholds through the
end of the week with a few hours of 5ft swells building in Thursday
afternoon. Winds start out of the northwest before becoming
light and variable Thursday. Southwesterly flow then builds in
Friday as low pressure begins approaching from the south
bringing SCA conditions back for the late weekend.
&&
.HYDROLOGY...
A general 1 to 2 inches of rain is expected through tonight in
the flood watch area, however mesoscale banding, convection, and
upslope winds could allow for local amounts of up to 3 inches.
Localized instances of flash flooding will be possible along
with a good chance of poor drainage flooding and small stream
rises.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch until 11 AM EDT Tuesday for MEZ007>009-012>014-
019>022-024>028-033.
Flood Watch until 5 AM EDT Tuesday for MEZ018-023.
NH...Flood Watch until 11 AM EDT Tuesday for NHZ002>006.
Flood Watch until 5 AM EDT Tuesday for NHZ008>010-012>015.
MARINE...Small Craft Advisory until midnight EDT Tuesday night for
ANZ150>152-154.
Small Craft Advisory until 4 AM EDT Tuesday for ANZ153.
&&
$$
UPDATE...Schroeter
NEAR TERM...Cempa
SHORT TERM...Cempa
LONG TERM...Thunberg
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 333 PM CDT Mon Sep 18 2023
Key Messages:
- Continued well above normal temperatures early in the week,
trending to cooler than normal this weekend and early next
week.
- Chance of showers and storms tonight, sporadic chances mid
week, but showers/storms becoming likely by Friday/Saturday.
Hot, breezy conditions this afternoon with southerly winds 20 to
30 mph and temperatures in the mid 80s to lower 90s, well above
normal.
There is a weak, slow moving disturbance moving through Central
NE, and this could trigger isolated showers/storms tonight.
Latest HRRR suggests this could be in the 1-3z timeframe in
northeast NE, with continued development through the night as
activity pushes east southeast through daybreak. And then a few
models continue to show a chance of showers/storms along/south of
I80 on Tuesday. All of this activity doesn`t look particularly
strong with SPC outlooks only forecasting general thunder. And
there could be additional slight chances of showers/storms south
of I80 Tuesday night. Otherwise, it looks like another hot day
Tuesday with well above normal temperatures again in the mid 80s
to around 90.
And then Wednesday/Thursday look mainly dry, but model blends have
sporadic slight precip chances here or there, but it`s probably
more dry than wet midweek. Highs still above normal Wednesday, but
just slightly cooler, and then then near normal on Thursday with
highs in the upper 70s to lower 80s.
We definitely begin a transition to a wetter and cooler pattern
for the end of the week into the weekend. A strong, closed low
develops across the western CONUS. Diffluent flow aloft ahead of
the trough leads to increasing rain chances by Thursday night, and
especially into Friday as southerly flow draw surface moisture and
instability northward. SPC hasn`t highlighted any severe
probabilities in the Days4-8 outlook, but CSU machine learning
algorithms suggest some low end severe probabilities to our west
on Thursday, but then highlights the mid Missouri Valley region
Friday, and then possible along/east of the Missouri River for
Saturday for stronger and possibly severe storms. Still lots of
time for things to change though, so it`s just a could be scenario
a this time. Pattern recognition certainly suggests a severe
threat somewhere on the Plains Friday, this would be as the upper
low and attendant surface low/triple point move through the
region.
The NBM is pretty aggressive on 60-70% Pops Friday through
Saturday, but there could be a dry slot Saturday as well, which
could lead to precipitation chances trending significantly down,
while we wait for wraparound precipitation to move in from the
northwest by Saturday evening into Sunday. And that wraparound
precipitation could certainly be out of the area by Sunday too.
So there still is quite a bit of uncertainty in the details of the
upcoming weather toward the end of the week through the weekend.
It certainly looks breezy and increasingly cooler by the weekend,
as southerly winds Friday become west and then northwest. Highs
Saturday could struggle to reach the lower to mid 70s, and then
highs Sunday mostly in the upper 60s to around 70, certainly well
below normal, with the cool weather continuing into Monday.
Fall is definitely a season of sharp transitions. The first day
of astronomical Fall is Saturday, September 23. The cooler weather
is right on schedule apparently.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 607 PM CDT Mon Sep 18 2023
Latest CAM output suggests the potential for isolated to widely
scattered storm development between 01-03z in the KOFK vicinity
with additional storms possible closer to KOMA and KLNK after
about 04z. Confidence in the terminal sites being affected
remains low, so TSRA will not be included in this forecast. As
such, VFR conditions will prevail with gusty south winds
diminishing this evening. Sustained winds are expected to remain
at or above 12kt at KOMA and KLNK tonight. Additionally, LLWS will
affect all sites tonight into Tuesday morning.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...DeWald
AVIATION...Mead