Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/13/23
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
633 PM CDT Sat Aug 12 2023
.UPDATE...
Issued at 630 PM CDT Sat Aug 12 2023
Showers and thunderstorms have moved into central SD a little
faster than expected so have adjusted pops accordingly through the
evening. Otherwise, best parameters for severe weather remain
along I-90 south as shortwave energy drops along a northwest-
southeast axis in western SD.
&&
.SHORT TERM...(This Evening through Sunday Night)
Issued at 153 PM CDT Sat Aug 12 2023
The forecast challenges revolve around:
1. precipitation timing/amounts/coverage
2. severe weather potential
3. temperatures on Sunday
At 2 PM CDT, skies are sunny on light northerly winds as a surface
high pressure system is over the region. Temperatures are warming
through the 70s and 80s.
There is an area of low pressure organizing over southern Alberta
that will begin extending influence over this region later tonight.
But first, there is the potential for a few thunderstorms to move
into the southwestern forecast zones this evening. Deep layer shear
is forecast to be ~40-50 knots, coupled with something on the order
of 500-1500J/kg MUCAPE. Right now, the boundary layer in South
Dakota is rather dry, but there is a slug of impressive low level
moisture (+12C to +18C 850hpa dewpoints) analyzed in the RAP model
over the central high plains region. Some portion of this low level
moisture is going to feed up into the southwestern/southern portion
of South Dakota this afternoon through later this evening to give
that needed low level moisture for strong storms a boost. If/once
(supercellular) storms start to develop over/near the Black Hills,
storm motion could take some of it east/southeast, glancing the
southwestern zones of this CWA with a hail/wind threat.
Later tonight into Sunday morning, as the brunt of the main dynamic
lift of this approaching/strengthening low pressure system reaches
north central South Dakota, there should be a pretty good WAA zone
establishing, and some fairly efficient rain-producing showers and
thunderstorms getting going. The GEFS plumes and super-ensemble
plumes are all beginning to cluster around 0.25 to 1.50inches of
rainfall and the ECMWF EFI/shift of tails is beginning to center
over north central and northeast South Dakota with this next rain
event. The probabilities of 0.50inch and 1.00inch of precipitation
are continuing to increase as well. While a couple of strong storms
cannot be ruled out heading into the early morning hours on Sunday,
the potential for any further severe thunderstorms on Sunday or
Sunday night will become highly dependent on if any daytime
heating/pockets of sunshine can happen across the southeastern
forecast zones. This is where the best low level shear/deep layer
shear couplet will reside. But, right now, MUCAPE values aren`t even
showing up (less than 250J/kg). Otherwise, the system`s TROWAL-
forcing is still expected to take over by late in the day Sunday and
persist through Sunday night resulting in PoPs increasing some,
mainly across the Prairie Coteau over into west central Minnesota
Sunday night.
Temperatures will be near normal for low temperatures tonight and
Sunday night. But, forecast guidance has been cooling off over the
past few days and now appears to be locking in on high temperatures
in the 60s to low 70s region-wide on Sunday.
.LONG TERM...(Monday through Saturday)
Issued at 153 PM CDT Sat Aug 12 2023
The extended forecast looks mainly dry after the strong wave departs
Sunday night. Temps will be on the cooler side Monday before they
start to rebound through mid week. The main feature is the northwest
flow will continue with the strong ridge to the south. This ridge
looks to continue to build through mid week. The exception is
another wave will bring a weak cold front through Wednesday
afternoon with very small chances of showers at this time.
However, after this wave passage the ridge really looks to rebound
into the weekend bringing back hot temps by the the weekend. The
ensembles are in really good agreement with the ridge developing
over the country with the ridge axis over the great lakes by
Saturday afternoon. This will place the area under warm southwest
flow with temps in the mid 80s to mid 90s most locations Friday and
Saturday. Forecast looks dry as mentioned earlier, but will have to
watch for monsoonal moisture later in the period which could trigger
some afternoon/evening storms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 630 PM CDT Sat Aug 12 2023
Terminals KABR,KATY,KPIR,KMBG
VFR conditions will deteriorate to MVFR and occasional IFR as
showers and thunderstorms spread over the region tonight and
Sunday. Winds will shift to the north and northwest behind this
system and become gusty on Sunday.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Wise
SHORT TERM...Dorn
LONG TERM...Scarlett
AVIATION...Wise
Area Forecast Discussion
National Weather Service La Crosse WI
623 PM CDT Sat Aug 12 2023
.DISCUSSION...(This evening through Saturday)
Issued at 211 PM CDT Sat Aug 12 2023
Key Messages:
- Slow moving storm system to bring widespread rain/a few storms
to the region Sunday into Monday with rainfall 1/2" to 2" with
locally higher amounts possible.
- Much cooler for Tuesday
Overview:
Early afternoon water vapor satellite imagery/heights/lightning
showed a trough over the Great Lakes with northwest flow aloft over
the local area. The mid-level ridge was covering much of the
southern U.S. with a closed low off the California Coast. Of note
in the northwest flow aloft is trough over Alberta/Saskatchewan into
Montana/Idaho/Wyoming. This will be our weather-maker to end the
week.
Ahead of Friday`s trough/cold frontal passage, temperatures warmed
into the 80s with several locations experiencing 70+ degree
dewpoints. This unstable environment combined with deep layer shear
of 45 to 55kts resulting in a line of storms that moves from
northwest to southeast across the area. Rains of .25" to 1.25"
occurred in streaks with pockets of 1.5"+. Damaging winds and large
hail occurred with winds of 60 to 75 mph. Much quieter today, but
breezy and not as humid behind the cold front.
Sunday into Monday:
Some patchy morning fog with the winds diminishing tonight, the wet
ground, and decreasing clouds. Mid clouds do begin to spread into
the area by morning.
The mid-tropospheric trough over southern Canada/MT digs southeast
into the Northern Plains/Upper Great Lakes region. Ahead of the main
shortwave trough isentropic lift/vorticity advection/increased 850mb
convergence should result in some light rain showers. In addition,
there is a shortwave passing to the south across southern Iowa and
Missouri. Several of the hi-res models have some connection to this
wave as well with an axis of showers passing across parts of Iowa.
There is dry air in place, thus low confidence in placement of where
the bands of light showers will set up. Trended with the RAP/FV3/ARW
for pops. If the initial lift is not as strong, the coverage may be
less, but have isolated to scattered showers as a starting point
Sunday morning. Instability is limited with 250 J/kg, increasing to
250-750 J/kg overnight and Monday with the main 500mb low tracking
across northern Iowa, thus predominantly showers with a few storms
embedded. Vertically stacked, the surface low is also forecast to
track from Iowa into northern Illinois. Rain overspreads the area
from the west Sunday night into Monday. There are pockets of deep
layer shear; 30-40kts, however shear is limited. Storms are
generally expected to be non-severe. The main instability axis is
over the Missouri River Valley. There are some hints of potentially
highs CAPE values across the south Sunday, so will need to assess
this in the short term. For Monday, will need to continue to assess
the NST potential. With the track of the closed low, there are some
low values of the non-supercell tornado threat across parts of
southern Minnesota and northern Iowa.
Rainfall amounts continue to range from a half of an inch to two
inches through Monday. The 12.12Z GFS/NAM show precipitable water
values increasing to around 1.50 inches with the system and forecast
soundings show warm cloud depths in excess of 4km. Storm movements
are 10 to 20kts with the system movement quite slow. While the mean
rainfall amounts range from .5 to 1" at several locations, there is
a good spread with the EC showing 14 out of 50 members with greater
than 1.5" at LSE and 10 out of 50 members at RST greater than 1.5".
The current axis of higher amounts is along and north of I90.
Recent rains over the last week have varied from .25 to 2 inches.
The current 6hr FFG shows we can take a good 3 to 4 inches at most
locations.
After temperatures in the 70s and 80s Sunday, look for much cooler
temperatures Monday with highs only in the 60s.
Tuesday through Saturday:
Ridging builds in for Tuesday, however by mid-week, there are model
differences on the next trough pushing through southern Canada; how
far south the cold front will make it. A general ridge will prevail
over the Central Plains and shortwaves in the west to east flow
could impact the local area. Our current forecast leans toward the
EC which brings a chance for rain back Wednesday night. Temperatures
look to warm back up into the 70s/80s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 623 PM CDT Sat Aug 12 2023
MVFR/IFR conditions at KLSE from valley fog remain uncertain with
soundings from the 12.18 NAM and 12.20 RAP which suggest lowering
surface winds at KLSE later this evening. However, winds aloft tend
to keep above 10 knots for a larger part of the evening just off the
deck and when considering mid-level saturation in the guidance
initially during the overnight hours, lowers confidence for valley
fog overnight. Remained with persistence in current 00z TAF but will
monitor for changes. Otherwise, expecting some mid-level clouds and light
showers building in throughout tomorrow with an approaching
disturbance from the west. Currently not expecting MVFR cigs or
visbys with onset of shower activity tomorrow at either TAF
site.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Zapotocny
AVIATION...Naylor
Area Forecast Discussion
National Weather Service Boston/Norton MA
955 PM EDT Sat Aug 12 2023
.SYNOPSIS...
A frontal system over the Great Lakes region will move into
Southern New England tonight into Sunday. While an isolated
thunderstorm or two are possible by early tonight, a greater
potential for strong thunderstorms increases later tonight into
early Sunday morning. Another round of a few strong to
potentially severe storms is possible later morning Sunday,
mainly across eastern New England. Dry Sunday night into
Monday. Next chance for rain comes Monday night through Tuesday.
The biggest threat at this time appears to be heavy rain.
Drying out Wednesday and Thursday with slight chance for rain
Friday.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
1000 PM Update
Made some minor adjustments to PoPs/weather to reflect latest
radar trends. Most of the forecast region is quiet with the
exception of western (more specifically southwestern) CT, where
a cluster of moderate to heavy showers and thunderstorms is
ongoing. Expect this activity to wane as we approach midnight
before a potential regeneration over the south coast tomorrow
morning.
Previous Discussion
345 PM Update:
Key Points:
* Other than an isolated to scattered t-storm along the immediate
south coast, mainly dry weather to prevail this afternoon into
early tonight.
* Risk for strong t-storms increases this evening in
isolated/scattered coverage, but especially into the overnight in
greater number/coverage (roughly midnight to 7 AM), mainly south
of the Mass Pike but is possible anywhere. Heavy rain capable of
street flooding, frequent lightning and locally gusty winds are
the greatest thunderstorm risks for the overnight.
Much of SNE as of early this afternoon is a relatively less unstable
air mass due to low dewpoints in the upper 50s to the low 60s, south
of a warm front which trails along the immediate South Coast of
RI/MA and into coastal southern CT, then trailing back NW into the
Tug Hill Plateau of NY. SW of the warm front, the air mass is
considerably more unstable with scattered to numerous strong storms
across central and southern NY, the mid-Atlc and Ohio Valley region
where mixed-layer CAPE values are in the 2000 J/kg neighborhood. The
area of stronger convection over the northern mid-Atlc region is
also being supported a strong WNW 500 mb jetstreak and subtle
shortwave disturbance over northern OH. Compare that mixed layer
CAPE value to the 500 J/kg or less of mixed-layer CAPE values over
much of SNE. Thus, other than a cluster of developing t-storms
riding along the aforementioned warm front/instability gradient in
coastal southern CT, which looks to graze the South Coast thru 5 PM,
its turned into a pretty decent afternoon.
It`s pretty clear that model guidance performance and trends today
have been quite poor and in some solutions (see: 16 and 17z runs of
the HRRR) are having difficulty resolving even the cluster of storms
over southern CT. Not good, frankly. Thus confidence in the
evolution and timing is pretty low and forecast details will hinge
on evolving convective developments happening across the OH Valley,
Gt Lakes into the northern mid-Atlantic region. Thus took a rather
probabilistic approach in terms of PoPs/Wx and related convective
hazards for most of the tonight into Saturday period.
A few things seem likely to occur tonight. First is that the
warm front lifts northward later this afternoon into early part
of tonight and with it will be an increase in surface
dewpoints/humidity levels toward more uncomfortable/tropical
levels (e.g. lower 70s). In an air mass where 850-500 mb lapse
rates are pretty weak and less than 6.0 C/km, this tap of higher
moisture levels often results in an increase in nighttime
convective instability. In addition to that, midlevel westerly
winds improve a bit supporting effective-layer shear magnitudes
around 30 to 35 kt. So while an isolated t-storm is possible
this afternoon into early tonight in western MA/CT, the risk
increases for strong thunderstorms during the late evening to
early morning hrs. With that said, it`s not clear when the risk
is greatest and also drilling down where the greatest threat for
t-storms may lie (though it is possible pretty much anywhere).
As mentioned model guidance has been pretty poor, but it seems
as though the greatest risk for t- storms is centered during the
overnight hrs and mainly along and south of the Mass Pike
including Cape Cod and the Islands. This is the trend indicated
by the WRF FV3/NSSL/ARW cores as well as the HRRR and the global
GFS model. To better illustrate the uncertainty, the NAM and
its 3-km downscaled version hints more at areas north of the
Mass Pike during the overnight to pre-dawn hrs. Tried to draw
PoP and Wx in such a way that PoPs are at least in the Chance
level everywhere for the second half of the night, but are in
the Likely range across CT-RI and eastern/southeast MA to focus
the better chance following the non-NAM-based consensus. Heavy
rain and frequent lightning pose the greatest t-storm risks, and
certainly street flooding in urban and poor drainage areas is a
concern, but the increase in kinematics/winds may still support
some storms reaching marginally/borderline severe levels.
Details on how the evening to early-morning evolves will greatly
influence Sunday`s forecast, but there is admittedly still a
level of uncertainty on the forecast for Sunday which should be
messaged.
Turning more humid, with muggy nighttime lows in the mid 60s to low
70s.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
345 PM Update:
Thunderstorms, some potentially strong/intense, may be ongoing from
the overnight period across RI and eastern MA with somewhat less of
a risk across central/western MA and much of northern CT. As of the
Saturday afternoon forecast issuance, there`s a couple of potential
outcomes in play for Sunday but which of them actually more closely
resembles reality will hinge on how overnight to early-Sunday
t-storms evolves, which at this point is still uncertain:
(1) If overnight to early day t-storms can clear out early enough,
such that we can destabilize, that would more or less be the worse
of the two possible outcomes. In that situation, we may have a
better potential for strong to severe storms in scattered cellular
coverage given the strong mid-level westerly flow aloft (0-6km shear
magnitudes of 40 to 45 kt) and moderately strong instability
(MLCAPEs up to 2000 J/kg); that potential seems greatest along the I-
84 corridor in CT to I-290/I-495 corridor in MA east and southward
during the late morning to mid afternoon. Any storm in that
environment would pose an isolated large hail and localized straight
line wind damage risk as storms move ESE.
(2) Storms from the overnight last well into the morning across
eastern and southeast MA, and the potential to destabilize is far
more limited by cloud cover. In that situation, we may end up with
certainly a cloudy and humid day but may end up being dry or at
worst isolated t-storm re-development and probably not reaching
strong/severe levels.
Among already mentioned uncertainties in both outcomes is that flow
aloft is westerly/veered with limited sfc convergence, and there is
also some drier air aloft that may stunt convective depth. Forecast
will show greatest PoP early to mid morning, then show more
isolated/scattered t-storm coverage reflecting lower overall chances
for showers and t-storms in the afternoon.
Highs mainly in the mid 80s but still rather humid.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Sunday Night
After the upper level trough moves north, the flow becomes more
zonal with dry post frontal airmass working in. With subtle height
rises combined with dry air aloft will allow skies to clear. Light
westerly winds and clear skies should allow for low temperatures to
drop into the low 60s with upper 50s possible in our typical cold
spots.
Monday
Upper level flow remains zonal, but impulses of short wave energy
move through the flow ahead of a strong short wave trough over the
Great Lakes. Surface flow begins to turn more southwesterly bringing
in higher surface moisture. Upper level winds remain westerly
keeping dry and warm air aloft. This should keep thunderstorms from
popping Monday with better instability and less capping remaining to
the south. Mostly sunny to start Monday, but mid to high cloud
should stream in mid to late day. Highs should only top out in the
low to mid 80s due to late day cloud cover.
Monday night - Tuesday night
The short wave over the Great Lakes begins to move east, but also
deamplifies and weakens as it does so. This will place the region in
the right entrance region of a 100+ knot jet streak helping produce
lift. A warm front will set up just south of the region Monday night
but stalls out Tuesday into Tuesday night as upper level forcing
weakens. With precipitable water values between 1.5-2.5 inches
across the region, this could set the stage for a heavy rain event.
With strong jet dynamics aloft, 0-500mb bulk shear will be rather
high in the 55-65 knots range. Even with the strong shear, the
severe thunderstorms threat appears rather low at this time due to
instability struggling to extend north of the warm front. With lots
of cloud cover and rain around during this period, high temperatures
on Tuesday likely struggle to reach the 80s.
Wednesday - Wednesday night
The short wave trough continues to deamplify, however still suck in
some cyclonic flow could allow for lingering showers during the day.
Highs jump back into the upper 70s to low 80s with partly cloudy
skies. Clearing Wednesday night as dry begins to move in from the
west.
Thursday and beyond
Confidence begins to break down in this range as the GFS tries to
begin to build a stout ridge over the SE that extends into New
England, while the EURO sends a potent short wave into the Great
Lakes region. Stuck with NBM for POPs during this time period, but
blended in some cooler guidance for highs as NBM seemed to be an
outlier among model guidance.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00Z TAF Update:
Tonight and Sunday...Low Confidence
Showers and thunderstorms should mainly stay confined to
western terminals this evening before 06Z, then push into
eastern terminals overnight. Another round of thunderstorms are
possible for eastern terminals just before day break through
mid morning before clearing out Sunday afternoon. Mainly VFR to
high end MVFR this evening with the exception of the Cape and
Island terminals where periods of IFR are possible. Most model
guidance wants to bring in MVFR ceilings across the entire
region by daybreak through Sunday morning, however confidence in
this is not high. IFR/LIFR is most likely to occur just before
daybreak for CAPE and Island terminals. Winds remain SSW at 5-15
knots.
Sunday night... High Confidence
Generally VFR, though pockets of MVFR possible across the Cape
and Islands.
KBOS TAF...Low confidence in TAF. Mainly VFR this evening.
Showers and thunderstorms may move into the terminal after 08Z
but confidence on exact timing and intensity is low. MVFR
possible tomorrow morning but confidence is also low at this
time.
KBDL TAF...Low confidence in TAF, Thunderstorms possible
through 08z, but confidence in exact timing is low. MVFR has
moved into the terminal a bit sooner then expected but should be
off and on overnight.
Outlook /Sunday Night through Thursday/...
Sunday Night through Monday: VFR.
Monday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.
Tuesday: Mainly VFR, with local IFR possible. Breezy. Chance
SHRA, isolated TSRA.
Tuesday Night: VFR. Breezy. Slight chance SHRA.
Wednesday through Thursday: VFR.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Overall high confidence.
Tonight:
Winds/seas at sub-SCA levels with south winds around 10-15 kt
with gusts up to 20 kt and seas 3 ft or less. Patchy marine fog
this afternoon into tonight, but also periods of thunderstorms.
Storms are possible on the southern waters by late afternoon,
then increase in number late tonight and overnight.
Sunday:
Ongoing showers and thunderstorms, some of which may be strong,
are likely to shift eastward into the offshore Atlc waters by
late morning to early afternoon. Another round of t-storms are
possible mid-afternoon but this isn`t set in stone. Otherwise SW
winds around 10-15 kt with seas 3 ft or less, locally higher
in/near t-storms.
Sunday Night:
Winds become W and decrease to 10 kt or less, with seas 3 ft or
less.
Outlook /Sunday Night through Thursday/...
Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Monday: Winds less than 25 kt.
Monday Night: Winds less than 25 kt. Chance of rain showers.
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain showers.
Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.
Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft.
Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft.
Thursday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...Loconto
NEAR TERM...Loconto/KP
SHORT TERM...Loconto
LONG TERM...KP
AVIATION...Loconto/KP/KS
MARINE...Loconto/KP
Area Forecast Discussion
National Weather Service Caribou ME
1004 PM EDT Sat Aug 12 2023
.SYNOPSIS...
High pressure will move east of the region overnight. Low
pressure will approach from the west tonight, then cross the
area Sunday followed by weak high pressure Monday. Low pressure
will approach Monday night into Tuesday then cross the area
Tuesday night. The low will continue east into the Maritimes on
Wednesday as high pressure begins to build in. High pressure
remains through Thursday.
&&
.NEAR TERM /THROUGH SUNDAY/...
Update...
Surface analysis shows weak low pressure north of the Great
Lakes with a warm front extending eastward into central New
England. The low will track east into Quebec province with warm
front approaching southwest Maine. As it does so, expect showers
to move in from west to east, mainly after midnight. Latest
HRRR still indicates the potential for some locally heavy
downpours in any showers. A few lightning strikes cant be
totally ruled out with some elevated instabilty, thus added
mention of isolated thunderstorms mainly west of Route 11.
Otherwise, just minor tweaks to adjust for current conditions.
previous discussion
This Evening will begin fair as a progressive s/wv ridge
moves E of the FA, then clds increase from the W as another
major s/wv ejecting from the LW trof psn ovr the Midwest arnd
90W lon begins to apch from the WSW. Shwrs/lgt rn from this
system will begin late Tngt and cont on Sun morn as a weak sfc
low associated with this s/wv apchs and moves ovr the FA
followed by aftn/eve shwrs/tstms on Sun with the upper trof
axis. Low temps ovrngt should looks to be mild.
Latest cnvctv allowing meso-models indicate the highest
sfc-mixed mean CAPE of about 1500J/kg ovr the WSW ptn of the FA
with a uniformly distributed 0-6km bulk shear upwards to 35kt.
Subsequently, some tstms Sun Aftn into Erly Eve may be
accompanied by hail, gusty winds, and heavy downpours, with
a few early discrete cells erly to mid aftn showing some
rotation with possible weak meso-cyclones then cells possibly
merging to a bowing segment(s) as they apch the NB border by
erly Sun Eve.
Although lcly hvy rnfl will possible Sun aftn/eve, overall,
PWATs look to be less, in the 1.25 to 1.50 inch range, compared
to the 1.50 to 2.00 inch range for the past couple of systems.
Subsequently, basin wide rnfl should be less, with max PoPs
reaching 80-90 percent and total rnfl for both phases of the
event msly in the 0.50-1.00 inch range. High temps Sun will be a
little below seasonal norms due cld and shwr/tstm cvrg.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
A shortwave will continue to exit east into the Canadian
Maritimes through Sunday night, with decreasing chances for rain
from south to north through the night. Increased surface
moisture from the rainfall of the last day may lead to some
patchy fog into the early Monday morning hours. Weak ridging
will return through the day on Monday, though lingering moisture
could lead to a few showers late in the afternoon due to diurnal
heating, especially across the north.
The next system to impact our forecast area will approach Monday
night through Tuesday. Though deterministic guidance have been
indicating that the low pressure system will cross the Downeast
region Tuesday afternoon, the GFS shows a weak ridge of high
pressure over the North Atlantic that could set up a weak
blocking pattern, and ensemble clusters lean heavily on a slower
solution, with the low center not crossing the forecast area
until later Tuesday night. Therefore, pulled back on precip
timing by about 6 hours with this forecast from what the NBM
originally indicated, with likely rain showers not reaching
until Tuesday evening. Even with the slower low solution,
southeast winds Tuesday afternoon may provide enough warmth and
moisture to kick off some afternoon thunderstorms, especially
into the Central Highlands and southern Aroostook regions.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
The amount of rain that falls with the Tuesday night coastal low
pressure system will greatly depend on the track of the low. If
the low crosses over the Gulf of Maine and heads towards Nova
Scotia, light to moderate rainfall at most will reach our FA,
confined mostly to the Downeast region. Should the low hug the
coast, however, rainfall may spread up through the north and
heavier rainfall could be possible. In either solution, the low
will exit over the Canadian Maritimes on Wednesday, leaving a
drier weather day in place for the day on Wednesday.
Some uncertainty remains for the pattern through mid to late
week next week. Most clusters of ensembles indicate that ridging
will return to the New England region, though the 12z
deterministic GFS does drag a shortwave across the Crown of
Maine on Thursday. For now, left the forecast with the NBM for
the end of the week to capture this uncertainty.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
NEAR TERM:
Tonight...VFR early this evening. At the Aroostook county
terminals, expect ceilings to deteriorate to MVFR after 09Z Sun
with scattered showers developing. MVFR/IFR ceilings are then
expected to continue into Sunday afternoon with scattered
showers and thunderstorms expected to affect the terminals after
20Z. South wind 5 to 10 kt.
At KBGR and KBHB, expect VFR to give way to IFR ceilings after
07Z Sun (high confidence), with possible locally heavy showers.
An isolated lightning strike is possible vicinity both
terminals 08z thru 11z IFR conditions persist into Sunday
morning then improve to MVFR with scattered showers and
thunderstorms aft 19Z, especially vicinity BGR. South wind 5 to
10 kt.
SHORT TERM:
Sunday night: VFR south, MVFR north as rain clears the area.
Winds light and variable.
Monday – Monday night: VFR. W winds 5 to 10 kts, becoming light
out of the NW Monday night.
Tuesday: VFR trending towards MVFR. Thunderstorms possible at
KGNR/KMLT/KHUL up through KPQI. E to SE wind around 5 kts.
Tuesday night: IFR with rain likely at Downeast terminals. Light
E wind.
Wednesday: Conditions trending towards VFR across all terminals.
NW winds 5 to 10 kts.
&&
.MARINE...
NEAR TERM: No hdlns anticipated tngt thru Sun with patchy marine
fog arriving overnight, becoming areas of fog by daybreak Sun
and contg areas of fog thru the rest of the day Sun. Kept close
to blended wv model guidance for fcst wv hts with emphasis on
NWPS. Wv pds from two spectral groups will be arnd 6 sec advcng
from the SSW and 11 sec from the SSE.
SHORT TERM: Wind and seas are expected to remain below SCA into
the middle of next week. Humid air over the waters will result
in fog limiting visibility at times, especially through Tuesday
night.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...TWD/VJN
Short Term...Bloomer
Long Term...Bloomer
Aviation...TWD/VJN/Bloomer
Marine...TWD/VJN/Bloomer
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
658 PM CDT Sat Aug 12 2023
...Updated 00Z Aviation...
.Discussion...
Issued at 305 PM CDT SAT AUG 12 2023
Key Messages:
- Quiet Weather Today
- Multiple Rounds of Showers/Storms Sunday
- Severe Weather Possible Sunday, Lots of Conditional Chances
Discussion:
The H5 ridge over the southern Plains has been attempting to amplify
and has resulted in subtle height rises across the lower Missouri
River Valley this morning. This has allowed a surface high pressure
to develop over the Central Plains and is moving southward in
response to a stronger PV anomaly currently over western Canada. As
a result, this has pushed the warm front back southward as a cold
front, and this southward track has also been reinforced by the
outflow boundary that emanated from the overnight convection in
northern Missouri. This boundary appears to have stalled just south
of Interstate 70, and can be seen on GOES 16 visible imagery with a
band of cloud cover from east-central Kansas across most of Central
Missouri. Based on the 12z TOP RAOB, there is still an area of dry
air between 800 and 700mb that should prevent any substantial
precipitation from developing. There is a bit more moisture
available in southwestern Missouri where showers and isolated
thunderstorms are possible, but this is outside of the forecast
area. For the rest of the day, expecting mostly clear skies across
northern Missouri, with some lingering clouds along and south of
Interstate 70.
The PV anomaly over western Canada is developing a deepening trough
with stronger jet streak that will continue to dig into the Northern
Rockies this afternoon, with the positively tilted H5 trough axis
arriving in the Northern Plains by Sunday mid-afternoon. There are
two mid-level vort maxes that progged to eject to downstream across
our region starting early Sunday morning and continuing through
Sunday afternoon. This will provide two periods of CVA and subsequent
height falls that will counter the southern ridge`s attempt to
amplify, and bring us active weather on Sunday. Current deterministic
GFS/NAM guidance depicts two area of stronger dCVA that will result
in two areas of surface cyclogenesis, on top of the area of lower
pressure over the Texas Panhandle where short-waves on the backside
of the 594dam H5 high have helped to maintain a cyclone for the past
few days. The first area of surface cyclone development is progged
to be concentrated over western KS/NE, and the second over the
IA/SD/NE area, and perhaps closer to MN. Eventually these cyclones
combine and form a broad surface low across much of the Central
Plains and Midwest as the main trough increases coverage of dCVA,
and WAA expands over much of the region. Behind the the area of
cyclogenesis, expecting a stronger trailing cold front to develop
over the High Plains into the Central Plains. Most of this will be
close to the main H5 trough axis. Ahead of this, the warm front that
has been pushed southward and is currently stalled out, likely
pushes back north a warm front as the cyclone deepens and will span
from eastern Kansas across Central Missouri. As this system evolves,
the multiple periods of dCVA will provide three periods of potential
lift, presenting three opportunities for convection Sunday across
the forecast area.
Round 1: Elevated Convection between 07z-14z, with minimal severe
threat.
Round 2: Conditional on morning activity, potential for surface
based storms between 17z-01z. Severe storms possible if storms
initiate. May just be showers with isentropic upglide with the warm
front and WAA.
Round 3: Along the main cold front. Thunderstorms possible, showers
likely, severe threat conditional. Timing uncertain, as there is
spread amongst ensemble guidance on propagation of speed of cold
front. The potential for the H5 wave to close off could also
drastically change this. Bulk of activity may be overnight.
Early Sunday morning, the first round of CVA arrives with a short-
wave trough around 06-07z timeframe, with H5 height falls starting
an hour or two before that. This will provide a modest increase in
convergence mainly above the boundary layer and increase overall
kinematic forcing. With localized mid-level jet streak, the
hodograph will lengthen through the early morning hours of Sunday,
with a mostly straight shape. 0-6km bulk shear values based on RAP
output is progged around 30 kts, increasing to 40 kts toward the end
of the morning. EBWD values are around 25 to 30 kts, with cloud
layer shear around 55 kts. With WAA starting and maximized around
850mb, would expect a warm nose to develop and provide a stronger
inversion just above surface, thus looking at parcels to start
around 1.0-1.5km. Mid-level lapse rates will be around 7.5 to 7.9
C/km. While the mid-level lapse rates and wind shear could help to
develop and organize updrafts, there will still be a dry punch of
air between 975mb and 875mb, which may result in a high amounts of
evaporation before precipitation could reach the surface. Further,
depending on which parcel is most likely to be realized, dry air
entrainment impacts could be detrimental to deep convection. Without
deep convection, it will be difficult for storms to become strong
enough to reach severe limits. Evaporational cooling may result in
some downbursts with showers, but associated wind gusts mostly
subsevere. MUCAPE off the RAP for most of the early morning hours
Sunday is only around 500 J/kg, showing the impacts to the MU parcel
from the drier air. HREF mean values for MUCAPE are also generally
around 500 J/kg, with other ensemble probabilities of exceeding 500
J/kg less than 40 percent. Therefore, the severe threat is limited,
with wind gusts and hail associated with most Sunday early morning
thunderstorms sub-severe.
During Sunday afternoon, another short-wave trough and compact vort
max ejects from the main trough over the High Plains or Central
Plains and brings another period of H5 height falls and increased
kinematic forcing. As this time, there should be stronger surface
pressure falls over the HIgh Plains located where the strongest dCVA
is at with the main H5 trough (or potentially closed low). Surface
troughing may extend eastward into the lower Missouri River Valley,
increasing both low-level and mid-level kinematic forcing. While
this is ongoing, this should start to send a warm front back
northward somewhere into Central Missouri. A warm front could
potentially be further south if surface pressure falls well west of
the area are not as rapid as currently progged, and thus flow
remains weak. Insentropic ascent through the WAA wing may force weak
rain shower activity between 16z-20z timeframe. This would actually
be somewhat beneficial to help erode the dry layer that current RAP
soundings have between 975mb and 875mb. However, further
precipitation could start to eat into available CAPE, and cloud
cover inhibiting boundary layer destabilization through insolation.
MUCAPE mean from 12z HREF has values around 1200-1500 J/kg, mainly
along and south of Interstate 70 with lesser values into northern
Missouri. SBCAPE means are around 750-1000 J/kg. RAP point soundings
throughout eastern Kansas and Central Missouri indicate rather
saturated soundings even within the boundary layer, which keeps both
boundary layer and mid-level lapse rates rather meager struggling to
exceed 6.5 C/km. This would explain the lower CAPE values. Now, if
there is any subsidence after the early morning vort max passes
through, perhaps boundary layer destabilization becomes more robust.
The other factor for Sunday afternoon convection initiation will be
outflow boundary potential, and its impact to either reinforce,
relocate, or weaken the strength of the warm front. If there is an
area of differential heating that strengthens convergence, perhaps
this forcing can help overcome the weaker lapse rates and low CAPE.
Only the HiRes-ARW seems to want to favor such as solution though,
as most other CAMs including the typically over-mixed FV3 has rather
weak convection. Most of the simulated reflectivity fields though
look more warm air advection upglide-like shower activity than true
deep convection. Given that the passing vort max is not the main
trough system, these weaker showers/storms solutions are a
reasonable forecast. Therefore, will call this a conditional threat
for stronger to severe storms, because there will be deep layer
shear still present that could organize deep convection.
Further, surface winds along the warm front and the axis of
surface troughing may increase low-level shear, with the low-level
hodographs demonstrating decent turning, though overall low-level
flow strength is questionable. Even though LCLs would be very low
assuming morning showers occur, the lower-level wind shear may
not mean much given the likely lack of instability. South of the
forecast area toward the Ozarks Region will be deeper in the warm
sector with more instability, as well as experiencing more backing
surface winds with the surface troughing stemming from the Texas
Cyclone expanding there, but not quite reaching out forecast area.
There, the forcing and instability may result in more robust
updrafts, and more likely to support supercells. Check back for
updates late tomorrow morning on how the morning convection sets
up the afternoon for our forecast area. Any clearing in the late
morning could quickly ramp up a severe threat Sunday afternoon.
Should surface based supercells develop, all hazard types could
become possible.
Finally late Sunday Night into early Monday morning, the main PV
anomaly swings the H5 trough/closed low across the area increasing
CVA across the area and more drastic H5 height falls. The surface
cyclone will also deepen and move eastward, dragging the cold front
with it across the area. With the closed low system, there is still
timing discrepancies with the propagation speed of the system.
Convergence will be quite strong along the cold front. The main
question will be what kind of airmass lies ahead of it, largely
dependent on the previous morning and mid afternoon activity. If
there is any kind of subsidence on the backside of the second
exiting vort max that allows for latter day destabilization, parcels
forced by the cold front late into the evening and overnight may
become surface based. Deep layer shear will remain robust, with 0-
6km bulk values around 40-45 kts. Further, current RAP analysis
suggests that deep layer shear vectors to be perpendicular to the
front, which could support an initial discrete storm mode with
supercells. With the approach of the surface cyclone, the triple
point may pass through the area which will back near surface flow,
and provide an increase in both speed and directional shear in the
lowest 0-1km. If there is enough instability, both mid-level and low-
level storm organization can be supported in this shear environment,
and present all severe hazards. Eventually storms would congeal, and
likely form either a line segment or a few clusters of
thunderstorms, perhaps still capable of wind. Current RAP soundings
along and just ahead of the cold front though are somewhat iffy, as
they remain largely saturated with weak low-level lapse rates. The
mid-level lapse rates will be okay, around 7.0 C/km, and with
increasing moisture with theta-e advection, overall CAPE values are
higher but is not equally distributed throughout the column. The
HRRR seems to reflect this kind of thermodynamic environment, with
storms starting to weaken along the cold front as they cross the KS-
MO stateline. Just as with the afternoon convection, will need to
monitor thermodynamic trends to see what kind of airmass the cold
front pushes up against. If the boundary layer does note
destabilize, there still could be enough convergence to support
elevated convection along the cold front late into the evening.
Hodographs will remain quite long, allowing wind shear to organize
storms with higher bases. RAP hodographs indicate a narrow corridor
setting up somewhere over Missouri where the 3-6km hodographs back,
which if elevated supercells develop could support a left-mover with
larger hail. Questionable thermodynamics though could end up
hindering such a threat. If the lapse rates are not overly great, an
elevated convection threat does have a high likelihood of
dissipating as it cross the KS-MO border for our counties. If storms
congeal over Central KS as the trough moves eastward and becomes and
MCS, that system may want to trend south of the forecast area toward
the area where there are high probabilities for greater instability.
The 12z CAMs seem to be hinting at this, and runs of the HRRR
through the afternoon do as well. If the threat for strong to severe
storms does not materialize throughout the day, most of the forecast
area still holds onto probabilities around 60 percent for at least
0.50 inches of QPF with locally higher amounts. HREF probability
matched-mean values for QPF totals for this event around 2 to 2.5
inches, which is capturing some of the members that produce stronger
thunderstorms Sunday afternoon and along the cold front into early
Monday morning. For those higher amounts captured in the probability
matched mean, would need to realize a robust thermodynamic
environment, or, have the closed low stall over the area with warm
rain processes. Areas that have had heavy rainfall recently may see
some flooding concerns if a a stronger core develops.
For the start of next week, H5 ridge over the western CONUS
amplifies while the trough works through the Great Lakes Region.
This leaves the lower Missouri River Valley in area of predominantly
northwesterly flow in the mid-levels, and will keep temperatures
cooler for the first few days. Toward the middle of the week though,
a trough over the Pacific forces the ridge axis eastward and will
send warm and humid conditions back toward the area. There are not
any overly high probabilities within the NBM for precipitation
through the middle of the weak, but it is possible for weak
perturbations riding above the ridge to move through and produce
some more activity, but likely too small of scale to be able to
resolve this far out.
&&
.Aviation...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 648 PM CDT SAT AUG 12 2023
VFR conditions are expected through much of the evening into the
overnight. A complex of showers and thunderstorms is expected to
progress across KS overnight reaching the terminals near sunrise.
Showers and thunderstorms linger through much of the morning
hours. A small break is anticipated midday; however, CIGs are not
expected to crest MVFR as another system moves through during the
late afternoon into the early evening. Some uncertainties remain
in timing of these systems as they all will influence the
environment and each other as they progress through the region.
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
MO...NONE.
&&
$$
Discussion...Krull
Aviation...Pesel
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
918 PM EDT Sat Aug 12 2023
.SYNOPSIS...
A round of thunderstorms, some strong to severe, will move in
from the west this afternoon and evening. Thunderstorm chances
return Sunday and Monday afternoons, along with hotter and more
humid weather. Monday`s heat could be dangerous in the Piedmont
for some individuals. A cold front Monday night and Tuesday will
restore milder and drier weather for mid-week.
&&
.NEAR TERM /THROUGH SUNDAY/...
Evening Update...Isol light showers will persist over the next
couple hrs before dissipating. A pretty good night for rad cooling
once the debris clouds shift east. The NC mtn valleys look to have
the best chance for dense fog formation. The NC fthills and Piedmont
are also under the gun before daybreak as well as the wrn Upstate
where pockets of 0.5 to 1.0 inches of rain has fallen earlier. Will
evaluate this threat thru the overnight and a DFA may be needed for
some areas. The widespread convec earlier has overturned the llvl
atmos with temp readings averaging abt 10 degrees below the fcst
curve. Have adj/d min temps down a a couple degrees over most areas
and this may have an effect of max temps Sun and any needed heat
advisories.
As of 230 PM EDT Saturday: Convection developing across the
Cumberland Plateau appears to be taking over as the leading edge of
a loosely organized MCS. This activity is forming in an environment
with over 2500 J/kg of MLCAPE, and 25-30 kt of effective shear with
up to 1000 J/kg of DCAPE. So the expectation now is that tstms
will probably be strong to severe as they enter the NC mountains
later this aftn. A Severe Tstm Watch 635 has been issued for the
NC mountains, the adjacent foothills and most of the Upstate and
NE GA until 00z (8 pm EDT). How much this activity will survive
further east is still a big question mark. The 17z HRRR now has
the strongest storms push SE into NE GA and the Upstate, possibly
still strong. The NC Piedmont seems the least likely to see storms,
given the lowest CAPE and some capping from NWLY downslope 850 mb
flow, but slight chc PoPs will be retained there. The main threat
will be damaging wind gusts, but isolated hail up to 1"-diameter
will also be possible.
Convection should wane this evening, as an upper-level shortwave
exits to our east. Mountain valley fog is expected, with patchy
fog possible elsewhere. Lows will be slightly above normal, mainly
in the upper 60s in the mountain valleys to mid 70s in the lower
Piedmont.
A slight building of heights from the large subtropical ridge
should help suppress convection somewhat Sunday. Low-level flow
will be weak, and generally backing to WSWLY, resulting in less
downslope. Guidance is showing less mixing of the dewpts during
the aftn, and with highs getting into the mid 90s, we could see
plenty of 105-109 heat indices across the Upper Savannah Valley
and just south and east of Charlotte. Given that just a deg or
two difference in the temp or dewpt could keep us below advisory
criteria, we will hold off on an advisory with this forecast package
and let the midnight shift assess the latest guidance. Otherwise,
expect isolated to widely scattered convection across the Piedmont
and scattered storms across the mountains, with a couple of pulse
severe storms possible.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 245 PM Saturday: Monday is looking very similar to
Sunday. We`re left with convective scraps that die off Sunday
evening while a lead short wave moves past to the north. The
upper pattern remains flat into Monday with somewhat uncertain
evolution of an MCS over the Cumberland Plateau and central
Appalachians. However, consensus is that we should be in a warm
sector of sorts with more than adequate instability to support
thunderstorms developing by afternoon. The fcst has precip probs
close to climo. The storm chances look good over the mtns, but
a cap east of the mtns on fcst soundings supports limiting to a
slight risk. The big problem for Monday will be the temps and heat
index. Altho high temps might only be on the order of five degrees
above normal...well short of records...the dewpoint climbs a bit
more into the middle 70s which suggests a good bet for at least a
Heat Advisory for a large part of the area east of the mtns. Some
places might reach Warning criteria along/S of I-85. Only concern
is how such a plan could go awry with convective debris or early
storm development keeping us from getting warm enough. That leads
us into Tuesday, when model guidance suggests a cold frontal
boundary will be dropping down across the forecast area during
peak heating. The guidance affords us an excellent opportunity to
develop an environment with sufficient buoyancy and shear to support
organized severe storms along/S of the front Tuesday afternoon/eve
east of the mtns. Temps drop off a few degrees which may take care
of the heat advisory concern at least.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 227 PM Saturday: The cold front is expected to push E/SE
of the fcst area by sunset on Tuesday, or shortly thereafter, as
a shortwave moves east and past to our north. High pressure will
build in from the northwest behind the front for the middle part
of the week, with drier and cooler air bringing some relief. The
model trend is toward temps being a few degrees below normal for the
rest of the work week as the high slides past. What is uncertain
is how quickly our usual diurnal convection returns, because
of big differences in how the guidance handles the evolution of
a mid/upper trof late in the week. The ECMWF and Canadian keep
a relatively deep trof axis off to our west through the end of
the period that keeps a west/northwest flow into the region thru
Friday that would be inhospitable to deep convection. The GFS
is more muddled and shows a weak upper low cutting off to our
west that would bring moisture back by Friday. The ECMWF/Canadian
look preferable at this point, but the forecast will end up with
an unmentionable slight risk for late week because of the model
blend. Expect changes as agreement improves.
&&
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Rain showers will affect KCLT and KHKY for a
couple hours this evening with gusty winds and lowering CIGS, yet
likely remaining low VFR. A good chance of fog overnight esp across
the mtn valleys and fthills where IFR or lower VSBY is possible thru
14z. Another round of convection is anticipated Sun afternoon
associated with a passing upper shortwave. The better thunder
chances look to occur across the NC zones where PROB30 Desires begin
after 17z/18z. Elsewhere, an afternoon VCSH has been included. Winds
remain light overnight and align w/ly to wsw/ly outside the mtns,
while winds at KAVL remain aligned nw/ly.
Outlook: Daily shower and thunderstorm chances with associated
restrictions will continue the rest of the weekend and thru the
first half of next week. Mountain valley fog/low stratus will
be possible each morning. Drier conditions expected to return
Wednesday.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...PM
NEAR TERM...ARK/SBK
SHORT TERM...PM
LONG TERM...PM
AVIATION...SBK
Area Forecast Discussion
National Weather Service Gray ME
1145 PM EDT Sat Aug 12 2023
.SYNOPSIS...
Showers and thunderstorms move into the area late today as a
cold front approaches from the west. Additional showers and
storms are possible on Sunday before the front moves through
and high pressure noses in for the beginning of the work week.
Another low pressure system moves in Tuesday as the pattern
remains active. This system slowly moves away and high pressure
builds in for late Wednesday and Thursday, and then another
system is possible for the end of the week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
1145 PM Update... Thunderstorms that have pushed across VT and
into northern NH have weakened as they moved into the area.
There is another cluster of storms in central VT that is also
expected to weaken as it pushes into NH over the next couple of
hours. The overall trend continues to be for less coverage of
thunderstorms across much of NH and SW Maine overnight with
possibly better coverage of showers with embedded thunder during
the pre dawn hours across central Maine and the Mid Coast. Have
mainly refined PoPs to capture the latest trends and refreshed
T/Tds to capture the latest observations. The threat for any
strong storms looks even lower per the latest guidance.
742 PM Update...At the regional scale, all of the convective
activity remains well west of the area across Upstate NY with
some activity weakening as it spills into VT. The overall trend
amongst 18Z guidance and recent runs of the HRRR has been to
delay the arrival of any showers and embedded thunder into the
area until 10 PM to Midnight. By this time instability will be
elevated and the trend is for less widespread convective
coverage through the first part of tonight. All of this leads
to a lowering threat for any strong storms through this evening
and tonight, while a strong to severe storm cannot be completely
ruled out. Late tonight there has been some run to run
continuity bringing some elevated convection along the coastal
plain of Maine during the pre dawn hours that could bring some
locally heavy downpours. Have mainly refined PoPs based on the
latest trends with this update.
Previously...
Cirrostratus has moved over much of the CWA with pockets of cu
in between. Hires guidance has been very inconsistent with
placement and mode of showers/storms this evening. To the west,
formation has been scattered, and confidence in strong,
organized storms reaching the CWA is low.
What can be expected are scattered showers with thunder this
evening moving into NH and then ME overnight. Believe the threat
for any strong storm formation exists between this evening and
midnight, mainly in the form of small hail and heavy downpours.
Elevated instability will be the primary driver for thunder
chances overnight, and wind gusts to the surface may be limited.
Otherwise, onshore flow should promote the development of some
fog along the coast as well as into the ME capitol region.
Typical valley locations may see fog developing after midnight
as well.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Showers may be ongoing across the area Sunday morning, along
with overcast skies. This overcast will limit how warm temps
climb in the morning, which could have impacts on afternoon
thunderstorm potential.
Not much has changed with thinking here; shear and low level
lapse rates will be in place for some organized storm
development, but deep layer moisture and instability (incl mid
level lapse rates) are lacking. Adding the potential for
lingering morning cloud cover, initiation will likely be broken
and messy. That said, for regions the break out in sun early,
the environment would be conducive for strong storms. Both
gusty winds and small hail will be possible given the earlier
afternoon initiation.
The best axis for instability in multiple guidance is from far
southern ME, between the coast and eastern NH, then north
towards the Moosehead Lake region. HREF ceiling probs begin to
decrease in early afternoon, so expect there may be some
differential heating for the beginning half of the day with much
of southern ME under stratus and parts of the mountains or
eastern NH a bit clearer.
The low responsible for the triggering of storms Sunday will
swing north in the evening, with rain chances decreasing across
the region. Overnight should be dry, with a light westerly
breeze keeping the lower atmosphere mixed. The result should be
lows in the lower 60s for much of the region outside of the
mountains.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Weak high pressure and W/NW flow ushers in drier air for Monday.
Most of the region will stay dry, but this flow pattern will
probably result in more upslope clouds and scattered showers toward
the mountains. Fairly high Froude numbers suggest more cloud cover
and a couple of showers could make it downwind of the mountains, but
again, most will stay dry. Highs will make it into the upper 70s to
lower 80s, except a bit cooler toward the north with more clouds
expected.
Like most of our dry periods lately, this one will also be short-
lived as another upper trough moves across the Great Lakes toward
New England, bringing another round of showers through the area
along with a couple of storms, although models are not showing much
instability at this point. The general trend among model guidance is
for slower eastward progression of this system, so have scaled back
PoPs for Monday night and highlighted Tuesday into Tuesday night as
having the highest PoPs of 50 to 70%...the higher of these numbers
across inland and northern areas. Ensemble means from the ECMWF
and GFS show QPF generally in the 0.50" to 0.75" range with
very low probabilities for exceeding an inch. This seems
reasonable with the limited instability and higher moisture
looking to remain south of the area.
Once the upper trough axis crosses through, high pressure will
follow for the middle of the week, although diurnal showers are
possible on Wednesday. Another trough may approach toward the
end of the upcoming week and start of next weekend, but there
are large differences in the upper air pattern. For now will
stick close to the NBM, which advertises a low-end chance of
showers for Friday and Saturday.
&&
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
Short Term...VFR this evening with isolated SHRA and TS. TS is
most likely around southern NH terminals this evening, but could
continue for much of the area sporadically overnight. Ceilings
fall overnight, to IFR in some ME locations like AUG/RKD/LEW.
Fog may also develop along the coast causing low vis
restrictions. Ceilings and vis will slowly improve during the
course of Sunday morning.
Additional chance of SHRA and TS Sunday afternoon across most of
southern ME towards the seacoast of NH.
Long Term...Mainly VFR Monday, except HIE could see MVFR ceilings
early in the day. Chances for flight restrictions then increase
generally in the Tuesday through Tuesday night timeframe as low
pressure brings possible MVFR to IFR ceilings and showers along
with a few storms across much of NH and western ME. VFR returns
Wednesday and Thursday.
&&
.MARINE...
Short Term...Below SCA conditions expected, but some gusty
southerly winds may be possible this evening and overnight.
Long Term...SCA conditions are currently not forecast over the
upcoming week. Low pressure will bring increasing chances for
showers along with a few storms over the waters in the Monday night
through Tuesday night time frame. Drier weather returns for
Wednesday and Thursday, but another low pressure could bring
increasing S/SW flow toward Friday or Saturday.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
UPDATE...Schroeter
NEAR TERM...Cornwell
SHORT TERM...Cornwell
LONG TERM...Combs
Area Forecast Discussion
National Weather Service Wichita KS
648 PM CDT Sat Aug 12 2023
.SYNOPSIS...
Issued at 311 PM CDT Sat Aug 12 2023
Key Messages:
* Severe storms will be possible across south-central Kansas tonight
and area wide on Sunday.
* Multiple rounds of storms could lead to flooding across south-
central Kansas tonight into Sunday night. A flood watch is in
effect until late Sunday night.
* Below normal temperatures are expected Monday and Tuesday before
returning to near normal temperatures.
* Seasonal temperatures return by midweek along with drier
conditions.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 311 PM CDT Sat Aug 12 2023
Multiple subtle shortwaves will move across the region tonight
through Sunday night out ahead of a more significant shortwave that
will move across the Northern and Central Plains Sunday night into
Monday. Multiple rounds of storms will move across the region
tonight through Sunday night. With these, severe storms and flooding
will be possible.
Severe storms will mainly be focused across south-central Kansas
tonight and then across the entire area on Sunday. The main threats
will be quarter sized hail and damaging winds up to 70 mph for the
storms tonight. Although CAPE values are well above 3000 j/kg,
MLCAPE values are around 2000 j/kg, and 0 to 6km shear is expected
be 35 to 45kt, model forecast soundings show a column that may be
nearly saturated. This would limit some of the hail potential in
storms, but hail up to quarter sized may still be possible. Winds
were increased to 70 mph from the previous forecast due to the
potential for wet microbursts.
The biggest concern looks to be the heavy rain potential. RAP runs
have shown PWAT values in 2.2" to 2.7" range across south-central
Kansas tonight. Mesoanalysis also shows a 700mb and 850mb front
situated east to west across southern Kansas. As the shortwave
troughs interact with these boundaries, storms would become
efficient rain makers. Flooding would be possible where storms may
train over the same areas as well. A flood watch has been issued
for portions of south-central Kansas.
The main upper level trough will send a cold front through our CWA
Sunday night into Monday bring highs in the low 80s and lows into
the upper 50s Monday and Tuesday. Drier conditions will also be in
place behind the front.
.LONG TERM...(Wednesday through Friday)
Issued at 311 PM CDT Sat Aug 12 2023
Upper flow will shift well north of the region in the extended range
as a high amplitude pattern builds in. There is some uncertainty on
whether a 594 ridge will build into the region during this period,
but a return to seasonal highs in the low to mid 90s appears likely
as well as a dry period. If higher heights do build into the region,
well above normal temperatures will be possible. For now, only the
ECMWF and EPS shows this scenario with the GFS/GEFS and
Canadian/GEPS showing a weaker ridge situated over our region. For
now, will continue to show near to slightly above normal highs
through Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 639 PM CDT Sat Aug 12 2023
Main aviation concern will be another round of storms later
tonight.
Storms that developed earlier over northeast NM and southeast CO
have developed what looks to be a fairly impressive MCV that is
tracking off the east-northeast as it moves into southwest KS.
This feature will bring another round of storms generally after
06z and will have a low end severe threat along with very high
rainfall rates. These storms should move out of KHUT-KICT-KSLN in
the 12-14z time frame and will linger at KCNU through most of the
morning hours. Strong cold front is then expected to move through
the area Sun afternoon, flipping winds around to the north. It is
expected to move through KRSL around 19z and KICT by 21z.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 72 89 64 80 / 80 40 60 0
Hutchinson 70 89 62 81 / 80 50 40 0
Newton 71 88 62 80 / 80 40 50 0
ElDorado 71 88 62 79 / 80 50 60 0
Winfield-KWLD 72 92 65 80 / 70 40 60 0
Russell 68 88 60 82 / 70 60 20 0
Great Bend 68 86 60 80 / 80 50 30 0
Salina 70 88 61 83 / 80 60 30 0
McPherson 70 88 61 80 / 80 50 40 0
Coffeyville 73 93 67 81 / 80 40 80 0
Chanute 72 88 65 78 / 80 60 70 0
Iola 71 87 64 78 / 80 70 70 0
Parsons-KPPF 72 91 66 81 / 80 50 80 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late Sunday night for KSZ067>069-082-083-
091>093.
Heat Advisory until 8 PM CDT this evening for KSZ093-098-099.
&&
$$
SYNOPSIS...CRW
SHORT TERM...CRW
LONG TERM...CRW
AVIATION...RBL
Area Forecast Discussion
National Weather Service Midland/Odessa TX
555 PM CDT Sat Aug 12 2023
...New AVIATION...
.SHORT TERM...
(This afternoon through Sunday night)
Issued at 158 PM CDT Sat Aug 12 2023
Did someone say precipitation? WV imagery places the axis of the
upper ridge from the Gulf up through Texas, keeping us under
southwesterly flow aloft. Increasing monsoonal moisture in the mid
and lower levels will be sufficient for diurnally driven storms
today, beginning in the mountains and moving northward through the
afternoon and evening. Slightly cooler temperatures expected today
with storm chances and cloud cover, but the location of the thermal
ridge along with strong southerly surface winds in response to
surface troughing should still be sufficient for most to reach
triple digits. With the slightly cooler temperatures mainly confined
to the west, a Heat Advisory is in effect for this afternoon and
early evening for the eastern Permian Basin, lower Trans Pecos, and
Big Bend region. Given the temperatures expected today and the
environmental inverted-V sounding profile, some pulse thunderstorms
are likely to bring very strong winds and brief, heavy rainfall.
Localized microbursts are not out of the question with storms today.
As the storms start to diminish late tonight, decent cloud cover and
southerly flow should keep us warm and temperatures only fall to the
upper 70s/low 80s, potentially breaking another daily record warm
low. On Sunday, the upper ridge won`t have moved much and afternoon
highs should look very similar to Saturday, with another Heat
Advisory in effect. Monsoonal moisture will still be ushered in with
the southwesterly flow, so expect another around of diurnally driven
convection mainly across the higher terrain with all the hazards
listed in the first paragraph. The thing to watch Sunday evening
will be an upper trough pushing down from the Dakotas, shooting a
cold front through Texas. Some precipitation moves into the
Panhandle early Monday morning on the heels of the front, but this
rain will struggle to make it further south given the location of
the high pressure. If anything, those in Southeast New Mexico will
likely receive some storms before sunrise Monday morning while areas
further east and to the south may miss out on this rain. Regardless,
slightly cooler temperatures as the front approaches Monday morning
will be a welcome change, and lows Monday morning may only be in the
upper 60s across the northern reaches of the CWA as this front makes
its appearance!
-Zuber
&&
.LONG TERM...
(Monday through Friday)
Issued at 158 PM CDT Sat Aug 12 2023
The upper ridge over the SE US Monday gets pushed west by a trough
sweeping down from the Upper MS Valley to the Great Lakes. By
Tuesday morning the center of the ridge will be over the Rockies
becoming more established over CO/NM and extending into TX
Wednesday. Late in the week an upper trough hits the West Coast and
pushes the ridge back to the east as it moves inland.
After a long string of 100 degree days a weak front will blow into
the area Monday knocking highs Monday and Tuesday back down into the
90s with even some 80s for the nrn CWA. The front will slowly push
south across the area during the day Monday reaching the Rio Grande
by Tuesday morning. Triple digits start to creep back into the
forecast Wednesday and become more widespread Thursday and Friday.
Lows mainly in the 70s but Tuesday morning should be the coolest
time with 60s over the mountains, SE NM, and much of the Nrn Permian
Basin.
Monday looks fairly active for showers and storms over SE NM and the
higher elevations with lower pops extending across the plains.
Tuesday rain chances shift south closer to the frontal boundary with
only the mountains looking to have a possibility of rain Wednesday
through the rest of the week.
&&
.AVIATION...
(00Z TAFS)
Issued at 551 PM CDT Sat Aug 12 2023
VFR conditions will prevail next 24 hours except in direct
convection. Current radar trends and HRRR suggest KCNM, KHOB,
KFST, and KPEQ have the best chances of convection next few hours.
Otherwise, southerly flow continues, augmented by a 30+kt LLJ
overnight. Forecast soundings develop a widespread cu field late
Sunday morning, w/bases starting 4.5-7 kft AGL.
&&
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 80 105 76 96 / 0 0 10 20
Carlsbad 75 102 73 94 / 30 30 40 50
Dryden 77 103 76 100 / 10 0 0 0
Fort Stockton 77 104 76 98 / 10 10 0 20
Guadalupe Pass 72 94 71 86 / 30 40 50 50
Hobbs 76 101 72 90 / 30 20 40 40
Marfa 65 96 64 93 / 30 30 10 20
Midland Intl Airport 80 104 76 97 / 10 0 10 20
Odessa 81 104 77 97 / 10 10 10 20
Wink 80 106 77 99 / 20 10 20 30
&&
.MAF WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 9 PM CDT this evening for Borden-Central
Brewster County-Chisos Basin-Crane-Davis Mountains-Ector-
Glasscock-Howard-Lower Brewster County-Martin-Midland-
Mitchell-Pecos-Reagan-Scurry-Terrell-Upton-Winkler.
Heat Advisory from 1 PM to 9 PM CDT Sunday for Borden-Central
Brewster County-Chisos Basin-Crane-Davis Mountains-Ector-
Glasscock-Howard-Lower Brewster County-Martin-Midland-
Mitchell-Pecos-Reagan-Scurry-Terrell-Upton-Winkler.
NM...None.
&&
$$
SHORT TERM...88
LONG TERM....72
AVIATION...44
Area Forecast Discussion
National Weather Service Memphis TN
919 PM CDT Sat Aug 12 2023
...New UPDATE...
.UPDATE...
Issued at 919 PM CDT Sat Aug 12 2023
The latest HRRR along with the 18Z NAM model depicts possible
convection that could develop on the MS/TN border tonight. This is
definitely a possibility when looking at the isentropic lift and
moisture situated over the area however other guidances shows the
region staying dry for the night. This potential is sufficient
enough to warrant a slight chance late tonight. Early morning fog
development will impact some areas in west TN, like Jackson, and
other surrounding areas.
Tomorrow morning, an MCS will enter from the NW and impact the
CWA. Heat headlines are issued for the southern half of the CWA
as convection may not impact those areas until much later. By late
evening, storms should dissipate leaving residual moisture for
another round of fog in the same areas as previously mentioned. On
Monday, a cold front starts to move across the forecast area
bringing in more potential thunderstorms and showers.
&&
.SYNOPSIS...
Issued at 317 PM CDT Sat Aug 12 2023
Another round of showers and storms will likely impact the Mid-
South overnight into Sunday morning. Outside of rain impacts, heat
will also be an issue Sunday as heat index values reach and exceed 105
degrees. By Monday, a cold front will bring cooler air and dry
conditions through the end of the week.
ANS
&&
.DISCUSSION...
(This evening through next Friday)
Issued at 317 PM CDT Sat Aug 12 2023
Prolonged showers and pop-up thunderstorms have diminished heat
impacts for portions of the Mid-South today. As such, both the
Excessive Heat Warning and Heat Advisory have been adjusted to
account for recent temperature trends. Additional showers and
storms are possible through the evening hours, with the main
threats being gusty winds and small hail.
The forecast becomes tricky overnight as a cluster of storms
enters southern Missouri, tracking eastward to the Mid-South.
Latest CAMs guidance remains in large disagreement as some models
(HRRR) depict storms dying off as they move into northeast
Arkansas, while others (NAM 3km) suggest MCS development by
mid-morning. Forecast sounding analysis shows a relatively
unstable and moist airmass over the region by the morning hours.
If an MCS does materialize, the main threats will be damaging
winds and hail.
Depending on how Sunday morning`s convection plays out, heat
impacts will vary. An Excessive Heat Warning and Heat Advisory
will go into effect for areas of north Mississippi, east-central
Arkansas, and southwest Tennessee at noon on Sunday. Areas in the
Mississippi Delta have the greatest chance of seeing heat index
values in excess of 110 F. Limit time outdoors tomorrow and ensure
you have a place to remain cool.
A change in weather patterns will occur on Monday as a cold front
moves across the region. Behind this front, rain chances will
decrease and temperatures will remain in the 80s through at least
Thursday. There exists slight model disagreement for the end of
the week as the ECMWF has an upper level trough moving over the
Great Lakes Region on Thursday. Behind this trough, the ridge
moves in and centers over the Mid-South. If this occurs, heat
headlines will likely be needed by next weekend. On the other
hand, the GFS depicts the cooler air lasting through at least
Friday before another front impacts the area. Additional updates
to the forecast regarding the end of next week will occur as more
data becomes available.
ANS
&&
.AVIATION...
(00Z TAFS)
Issued at 631 PM CDT Sat Aug 12 2023
VFR conditions are expected to prevail area wide through the
period, barring a few hours of patchy fog around MKL in the pre-dawn
hours overnight. A loosely organized MCS looks to make its way
over from southwest Missouri tomorrow morning. Impacts at each
terminal are still quite uncertain with the latest CAMs... as of
right now, it looks like JBR will likely take the brunt of the
potential TSRA in the late morning. Kept just VCTS at MEM and MKL
tomorrow afternoon since the spatial coverage of the convection
continues to be all over the place with each subsequent CAM run.
Guidance finally comes into better agreement that the convection
will start to consolidate along a boundary around TUP by late
tomorrow afternoon. Winds should be fairly light and southeasterly
tonight, picking up to 6-8 kts from the south/southwest tomorrow
morning.
CAD
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Heat Advisory from noon to 8 PM CDT Sunday for ARZ035-036-048.
Excessive Heat Warning from noon to 8 PM CDT Sunday for ARZ049-
058.
MO...None.
MS...Heat Advisory from noon to 8 PM CDT Sunday for MSZ001>006-008-
009-012>017.
Excessive Heat Warning from noon to 8 PM CDT Sunday for MSZ007-
010-011-020>024.
TN...Heat Advisory from noon to 8 PM CDT Sunday for TNZ088>092.
&&
$$
UPDATE...GNC
PUBLIC FORECAST...ANS
AVIATION...CAD
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1009 PM EDT Sat Aug 12 2023
...New SHORT TERM...
.SHORT TERM...
(Tonight through Sunday)
Issued at 1005 PM EDT Sat Aug 12 2023
The main change for the evening update will be to expand the
mention of fog. With clearing skies, calm winds, and dewpoint
dperessions in the range of 0-3 degrees already, fog looks to be a
good bet in most areas. The HRRR and LAMP are in agreement with
this, although the usually foggy NAM is not as excited. All PoPs
will be removed through tonight and tomorrow morning as stable
conditions have developed behind the earlier convection, and a
weak shortwave ridge will be over the area.
&&
.LONG TERM...
(Sunday night through next Saturday)
Issued at 114 PM EDT Sat Aug 12 2023
Key Messages:
1. Additional showers and storms are possible at times Monday and
some storms may become strong to severe. Main threats will be
damaging winds and hail.
2. Heat indices could approach 100 degrees for central and southern
portions of the area at times Sunday and Monday.
3. Cooler and drier conditions expected Tuesday through Thursday.
Discussion:
The main focus for the extended period will be Monday and Monday
night as another anomalous shortwave tracks into the Ohio Valley and
eastward. The positively tilted shortwave will result in H5 flow
amplifying upwards of 50-60kts, with southwesterly H85 winds
increasing to roughly 30-40kts per the latest NAM model run. Some
initial convection may be possible across northern portions of the
area where upper level diffluence occurs ahead the shortwave Monday
morning/mid-day. Quite honestly there still remains a bit of
uncertainty with timing and confidence in severe weather chances for
this time period. Most recent model solutions from the NAM3K and
HRRR differ significantly on the placement of this early day
convection, with the HRRR being most bullish on a potential MCS
progressing near the TN/KY/VA border. Soundings ahead of the MCS
show an unusually unstable environment for morning hours with MLCAPE
nearing 2000J/kg. If a scenario as such pans out, some strong to
severe storms may be possible early morning mid-day across northern
portions of the area, damaging winds and hail being the primary
concerns.
Storms should clear out for the afternoon with muggy and hot
conditions expected. Heat indices could approach 100 degrees for
portions of the southern and central Tennessee Valley. A cold front
is anticipated to approach the area bringing additional storm
chances late Monday potentially into early Tuesday morning. Timing
will play an important role in the severe weather chances as slower
timing could lead to increasingly diminishing instability. NAM
soundings currently continue to show MUCAPE persisting between 1000-
2000 J/kg ahead of the convection. Again, winds and hail will be the
main threats. For this Monday timeframe, isolated flooding cannot be
ruled out for areas that see multiple rounds of showers and storms
as well.
Some light lingering activity may persist early/mid-Tuesday with
wrap around moisture but the general trend for the remainder of the
week will be drier with temperatures slightly below normal. An
additional trough will dig south from the Great Lakes region late
week but plenty of model discrepancies lead to uncertainty on the
potential of returning PoP chances at the end of the extended.
&&
.AVIATION...
(00Z TAFS)
Issued at 703 PM EDT Sat Aug 12 2023
Abundant moisture near the surface left by exiting showers will
favor the development of low clouds and fog tonight at the TAF
sites. How low vis/cigs will go is uncertain, but at least MVFR
conditions are expected. If clouds clear out enough, LIFR vis will
be possible. After fog and clouds lift tomorrow morning, the
remainder of the TAF period will be VFR.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 91 73 93 75 / 50 10 20 10
Knoxville McGhee Tyson Airport, TN 89 73 89 74 / 60 10 20 20
Oak Ridge, TN 88 72 89 73 / 50 10 20 20
Tri Cities Airport, TN 85 70 85 70 / 30 10 20 20
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...DGS
LONG TERM....KRS
AVIATION...DGS
Area Forecast Discussion
National Weather Service Nashville TN
727 PM CDT Sat Aug 12 2023
...New UPDATE...
.UPDATE...
Issued at 711 PM CDT Sat Aug 12 2023
All earlier convection has departed the mid state and the 88D is
actually running in clear-air mode at the moment. We will leave in
minimal rain chances overnight just in case something else
develops in this humid air mass. It`s not out of the question with
a surface boundary so close by to our north. It is worth
mentioning the the HRRR really doesn`t develop much of anything
until sometime after 16Z tomorrow. In the meantime, we`ve added
some overnight fog to the grids given the wet ground and the
potential for radiation cooling. No other changes are planned for
now.
&&
.SHORT TERM...
(This afternoon through Monday Night)
Issued at 251 PM CDT Sat Aug 12 2023
Today`s MCS will continue moving eastward and is now exiting
the area. Boundary to remain stationary to our north through Sunday
with ample southerly low level flow working northward. Additional
MCS development is likely but the mid and upper level flow
becomes a bit more westerly with time. Thus, the better energy
will shift just to our north for the Sunday period. Models are
rather widespread on prognostications and thus pops will remain in
that 30- 50% range.
For now, it looks like MCS development to our north with middle TN
being on the southern edge through Sunday night. I`d say areas north
of I-40 will stand the best chance for activity. Although, residual
outflows could force convection chances further to the south.
Plenty of heat and humidity so instability levels will remain
high.
On Monday, we will get an actual fropa although models are tending
to shy away from any precipitation enhancement. Will still carry
some lower end pops through the day. Also, some shower activity may
linger into Monday night as some upstream troughing is observed.
For the near term temps, it will continue to be on the hot side and
quite muggy. I think the continuation of added cloudiness will keep
us out of any advisory level heat for Sunday, though it will be
close. Monday could get quite warm, as well, ahead of the
boundary with lower to mid 90s. Some sunshine will return ahead of
the boundary so our heat index values will again be in the
100-104F range. We will actually see our lows drop down to just
below seasonal for Monday night as the slightly cooler air moves
in.
&&
.LONG TERM...
(Tuesday through next Saturday)
Issued at 251 PM CDT Sat Aug 12 2023
In the extended forecast, after a brief cool down for mid week, a
pattern change does appear to be possible. However, model solutions
do differ with the GFS building an Atlantic ridge and trending
toward a more tropical scenario. Meanwhile, The Euro is building the
upper ridge across our area from the west. At any rate, the pattern
looks less active despite the GFS`s lean to a more tropical style
flow. NBE numbers are carrying just single digit pops through the
period.
For the near term temps, looking very nice for mid week with that
cool down. Then, we`ll quickly warm right back up to seasonal
levels. Those highs will only reach the lower 80s or so for Tuesday,
then approach 90 by the end of the period. Look for lows in the 60s.
&&
.AVIATION...
(00Z TAFS)
Issued at 618 PM CDT Sat Aug 12 2023
Conditions are currently VFR at all mid-state terminals, but due
to earlier rains and small dew point depressions overnight, expect
IFR or worse fog to develop at CKV/CSV/SRB by 05Z. Conditions
should improve to VFR by 14Z/Sun. Models are not in good agreement
regarding TS tomorrow. Will cover with VCTS, but these may need to
be adjusted with future issuances.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 75 92 76 94 / 20 60 20 40
Clarksville 74 90 74 91 / 30 60 50 40
Crossville 68 85 69 88 / 30 50 20 40
Columbia 74 92 75 94 / 30 40 10 30
Cookeville 71 87 72 89 / 30 60 20 40
Jamestown 70 85 71 88 / 40 50 40 50
Lawrenceburg 73 90 73 93 / 20 40 10 20
Murfreesboro 73 93 74 94 / 20 60 10 30
Waverly 72 90 73 91 / 30 60 20 30
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Rose
SHORT TERM...21
LONG TERM....21
AVIATION.....Unger
Area Forecast Discussion
National Weather Service New York NY
1051 PM EDT Sat Aug 12 2023
.SYNOPSIS...
A cold front approaches the region tonight, moving in late
tonight into Sunday. The cold front moves east of the region
Sunday night with weak high pressure building in thereafter.
High pressure pushes offshore Monday before another frontal
system impacts the area Monday night and Tuesday. High pressure
returns for Wednesday and Thursday, with a warm front possibly
lifting north Thursday night. A cold front approaches the region
Friday.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Severe Thunderstorm Watch in effect for western 1/2 of the CWA.
Widespread shower/tstm activity across Central and eastern PA
along pre- frontal trough expected to slide E/SE into the watch
area. Shortwave forcing trigger, pre- frontal trough focus,
increasing deep layer shear and steeper mid-level lapse rates
point towards isolated to scattered strong to severe tstm
activity working into areas N&W of NYC this evening. Less
confidence in how well this activity maintains it strength
towards the coastal portions of the watch area late this evening
towards midnight, with waning diurnal instability a limiting
factor. Flash flood threat in path of an W to E training
convection. This is currently favored across the mid- Hudson
valley for the next couple of hours, but could slip south into
Lower Hud and SW CT in vicinity of outflow boundaries later this
evening.
Convection should decrease in intensity after midnight as it
continues east into a stabilizing airmass.
Previous Discussion...
The main focus will be on the potential for strong and/or
severe convection, which looks to be mainly tonight when the
higher bulk shear moves in. There will be another few rounds of
showers and thunderstorms for tonight. CAMs vary with their
respective depictions of reflectivity and cell structures across
the local region so timing could vary. Challenging forecast to
pinpoint specific timing and spatial windows for each round of
convection. Generally expect the showers and thunderstorms to
encompass much of the interior going into early this evening,
getting closer to the coast and NYC by mid to late evening, and
then become more likely across Southern Connecticut and Long
Island overnight.
There will be a pre-frontal trough moving in this evening with
a cold front moving in behind that for overnight. The speed of
the thunderstorms will limit the flood threat but models
indicate high precipitable waters near 2 inches so flooding
will still be possible. Also, still a severe thunderstorm threat
with marginal to slight risk for severe thunderstorms with an
enhanced risk for Western Orange County NY. With higher wind
speeds aloft and increased storm motion, already have an
environment with relatively large shear to allow for
thunderstorms to get organized and deep vertical motion. Models
indicate bulk shear 0-6 km AGL of 35-50 kt. The instability from
CAPE for tonight, generally near 500 to 1000 J/kg, relatively
higher across the coastal regions. Overall, severe threat
highest going into early evening especially across Lower Hudson
Valley, SW CT and Northeast NJ as well as into NYC. Then, severe
threat shifts farther east across the coastal areas across Long
Island and the rest of Southern CT for late evening into
overnight. Main severe threat will be strong wind gusts but
large hail and a brief tornado will be possible especially north
and west of NYC where the probabilities for strong wind gusts,
hail and a brief tornado are relatively higher. The potential
for a brief tornado is seen from an increase in forecast low
level helicity to values near 150 to a little over 200 indicated
by the NAM and RAP models in the BUFKIT data. This is from the
low level veering of winds from S to SW and wind speeds
increasing from surface to low levels as well.
With larger scale operational models with NAM, GFS, ECMWF, and
Canadian, they mostly convey under a quarter of an inch in rain
accumulation by 8PM tonight. All of these models show more rain
between 8PM tonight and 8AM Sunday and spread across mainly the
northern half of the CWA from west to east, total run
accumulation around a half to 0.75 inch of rain. There will
likely be some higher amounts of rain. Have these higher rain
amounts closer to 1 to 1.25 inches of rain across parts of the
interior. There could even be some locally higher amounts up to
near 2 inches of rain.
Lows tonight were from NBM 50th percentile and consensus of raw
data, ranging only from the upper 60s to lower 70s for much of
the forecast region.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Mid levels show a zonal pattern but there will be some slight
ridging during Sunday. At the surface, the cold front Sunday morning
will be within the area, prolonging showers and thunderstorms
especially across Long Island and Southern Connecticut morning into
early afternoon. There will still be bulk shear 0-6km AGL near 35-40
kt, and surface CAPE reaching near near 1000 J/kg from NAM and
GFS forecast model data. Model BUFKIT soundings indicate warmer
temperatures just above 10kft acting as some convective
inhibition. Will keep thunderstorms just chance but if there are
thunderstorms, they could be strong and a very low chance (less
than 5 percent) of severe.
POPs for showers and thunderstorms will decrease substantially mid
to late Sunday afternoon with totally dry conditions expected Sunday
night.
The front shifts east of the region Sunday night, allowing for
surface winds to become more westerly, advecting in drier air.
Instability will considerably decrease and dry conditions should
prevail as weak high pressure builds in.
High temperatures forecast Sunday used a blend of NBM/MET/MAV with a
range from the low to upper 80s. The upper 80s forecast are mostly
across Northeast NJ and NYC Metro Area where there will be less
clouds and less rain. Expecting more radiational cooling Sunday
night, with not much cloud coverage and light winds and
therefore a more vast range for low temperatures, from upper 50s
to lower 70s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Weak surface ridging holds on long enough during the daytime on
Monday to keep any showers from moving in from the west as the next
storm system approaches from the Ohio Valley and Great Lakes. Highs
near normal at 80-85.
Another shortwave will approach from the Great Lakes region Monday
night, and move through Tuesday into Tuesday night. A wave of low
pressure will track along a nearly stationary cold front south of
the region Monday night. This will bring a warm front near or into
the region Monday night into Tuesday. Precipitable water values will
be increasing to 2 to nearly 2 1/4 inches Monday night, and with
forcing, instability, and surface CAPE increasing with the front,
convection is expected to develop with periods of moderate to heavy
rainfall possible. The 90% percentile from SPC`s sounding
climatology page is 1.75 inches, so very humid air will move into
there area for this time of year. WPC currently has the region under
a marginal risk for excessive rainfall, so flash flooding is a
possibility, especially if heavy rain moves in during preceding
days. There is uncertainty as to where the warm front will be, and a
track farther to the north could bring the heavier rainfall into the
region.
The frontal system will be progressive as the upper trough weakens
and passes to the east Tuesday night. A mid-level ridge continues to
build into the area Wednesday into Thursday while high pressure
builds in at the surface, keeping the region dry through the period.
Then another shortwave digs into the Great Lakes and upper midwest
Thursday night into Friday before becoming negative during Friday.
At this time there are minimal chance for precipitation Friday.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
A cold front approaches and moves across the region early Sunday.
Mainly VFR, except MVFR or lower possible in showers and
thunderstorms.
Southerly flow around 10 kt will continue to lightening (and
possibly becoming variable) overnight before becoming westerly
on Sunday. An area of showers and thunderstorms west of the
region will move across the region overnight. Will continue with
TEMPO groups til 06z, then just a chance of SHRA afterwards.
There is a chance that thunder may continue past 6z. Some of
these storms may produce locally heavy rainfall and gusty winds,
however, coverage and timing remain low confidence. Conditions
dry out and return to VFR everywhere by 12z Sunday.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Low confidence in timing and coverage of shower and thunderstorm
activity tonight. Amendments likely.
OUTLOOK FOR 00Z SUNDAY THROUGH THURSDAY...
Sunday: VFR.
Monday through Tuesday: VFR Monday, then a chance of showers and
thunderstorms Monday night and Tuesday with MVFR or lower possible.
Wednesday: VFR.
Thursday: VFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: https:/www.weather.gov/zny/n90
&&
.MARINE...
The pressure gradient will be relatively weak enough to keep
conditions on the forecast waters below SCA thresholds through
the rest of this weekend and into Monday.
With a persistent southerly flow Monday night into Tuesday,
ahead of a cold front, ocean waters likely build to around 5
feet Tuesday afternoon, then subside Tuesday night as winds
shift to the west due to a cold frontal passage. Marginal seas
possible once again for the central and eastern oceans zone for
Wednesday and Friday morning, subsiding during the afternoons of
both days. Winds should remain below 25 kt on all waters From
Monday onward.
&&
.HYDROLOGY...
Marginal to slight risk of flash flooding, layer precipitable
waters reach up to near 2 inches for tonight.
There will be potential for training of cells from parallel
flow low to upper levels, but mean storm motion judging from
looking at winds between 10 and 20 kft, stay generally in a
25-40 kt range. Individual thunderstorm complexes will be rapid
moving. It just a matter of how deep the convection gets and how
large the structure is that moves across that will be a main
factor to assess for flooding potential.
CAMs late tonight indicate in terms of structure a MCS moving
across with some variance in terms of locations within the
forecast region of where the most intense part of the MCS
occurs. Minor flooding will be likely as the MCS moves across
especially with low lying, poor drainage and urban areas with a
marginal to slight risk for flash flooding.
From Monday night into Tuesday, brief periods of moderate to heavy
rainfall may produce isolated flash flooding. The Weather Prediction
Center has placed the entire area in a marginal risk for flash
flooding. Currently, the more likely scenario is for minor urban and
poor drainage/nuisance flooding.
From Tuesday night through the end of the week no hydrologic impacts
are expected.
&&
.TIDES/COASTAL FLOODING...
There is a moderate risk for rip currents on ocean beaches Sunday
with wave heights around 3 ft.
There is a low risk for rip currents on NYC and Nassau Co beaches on
Monday with wave heights around 2 ft, and a moderate risk for
Suffolk Co beaches, where wave heights will be around 3 ft.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JM/JP
NEAR TERM...JM/NV
SHORT TERM...JM
LONG TERM...JP
AVIATION...BC
MARINE...JM/JP
HYDROLOGY...JM/JP
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Tallahassee FL
845 PM EDT Sat Aug 12 2023
...New UPDATE...
.UPDATE...
Issued at 842 PM EDT Sat Aug 12 2023
Areas of thunderstorms are currently moving into southwest Georgia
and southeast Alabama. Raised rain chances and cloud cover
throughout these areas for the next few hours. HRRR does indicate
a weakening trend towards midnight and have the grids following
suit. That area of southwest Georgia was not worked over by
afternoon convection so a few more hours of thunderstorms seems
reasonable. Although not explicit in the grids, some patchy fog
could occur in areas that received rainfall today and tonight.
&&
.NEAR TERM...
(Through Sunday)
Issued at 245 PM EDT Sat Aug 12 2023
Extremely dangerous heat is expected to continue across the entire
region on Sunday as the upper level ridge that was previously
centered over southern Alabama will settle into the tri-state region
by Sunday afternoon. Air temperatures are expected to top out in the
upper 90s, with many areas reaching triple digits through the
afternoon hours. Dewpoints are expected to remain high across the
region, with values in the mid to upper 70s, and even low 80s for
those along the coast forecast for Sunday. This will lead to quite
dangerous heat index values to 113 or higher over much of the
region. Portions of the Florida Panhandle and Big Bend might
possibly see heat index values near 120 degrees or possibly higher
for an hour or two Sunday afternoon. Given this dangerous heat
expected, the entire forecast area is currently under an Excessive
Heat Watch for Sunday.
The only reprieve some lucky few might see from the heat is with the
possibility of an afternoon shower or thunderstorm that may develop
along a weak quasi-stationary southwest to northeast orientated
surface boundary. Any storms that do develop may have the
possibility of developing strong gusty winds as DCAPE values are
forecast above 1000 J/Kg on Sunday. Much of the area has a 30-40
percent chance of seeing a shower or thunderstorm on Sunday. The
building upper level ridge over the region will likely instill
enough subsidence areawide to prevent storm initiation, which will
help us reach the dangerously high temperatures and heat index
values across the region.
&&
.SHORT TERM...
(Sunday Night through Tuesday)
Issued at 245 PM EDT Sat Aug 12 2023
No relief from the dangerous heat on Monday and Tuesday. A very hot
and moist air mass will remain. Ridging aloft begins to breakdown on
Monday with the approach of a front on Tuesday. PoPs on Monday of 30-
40 pct increase to 40-50 pct on Tuesday. Heat indices/Apparent temps
will range from 110 to 115 on Monday and 107 to 112 on Tuesday, so
dangerous heat will continue, with the likely continuation of heat
advisories and/or excessive heat warnings both days. On Tuesday, a
stronger wind field aloft and greater CAPE indicated by ensembles
will lead to the potential for strong storms.
&&
.LONG TERM...
(Wednesday through Saturday)
Issued at 245 PM EDT Sat Aug 12 2023
Lower heat index/apparent temps are expected beginning Wednesday.
A weak front will stall across the region in the Wednesday through
Friday time frame. The flow will become a bit more cyclonic aloft as
a trough develops between a ridge centered over the plains states
and the subtropical high to the east. The GFS ensembles are more
bullish on this compared to the Euro ensembles, with some showing
deep southerly flow. The most likely solution is a gradient in
moisture across the region, but there is disagreement on whether
this is more east-west or north-south oriented. For now, our PoP
forecast splits the difference, with the highest values roughly
southeast of a Tift to Panama City line. Confidence is medium at
best given the uncertainty with further adjustments likely. A less
likely solution is for more of a deep southerly flow to develop,
which would increase PoPs across much of the region. Regardless of
the scenario, there are hydrology concerns, which are highlighted
in that section below. By Saturday, ensembles indicate a seasonal
pattern developing, with PoPs reflecting this, ranging 30-50 pct.
With the front in the vicinity resulting in a wetter pattern,
heat index/apparent temperatures should decrease from mid to late
week, ranging from 100 to 105. However, values of 105 to 110 will
still be possible in the FL Counties.
&&
.AVIATION...
(00Z TAFS)
Issued at 726 PM EDT Sat Aug 12 2023
Scattered convection is occurring currently with additional
convection moving south from central Alabama towards our northern
terminals of DHN and ABY. Atmosphere over DHN is worked over but
remains conducive towards ABY. Have VCTS at ABY through 02Z. Other
areas of convection may impact ECP or TLH through 01Z. Convection
should overall decrease towards midnight. Convection chances are
lower Sunday with just a PROB30 mention at TLH and DHN later
Sunday afternoon.
&&
.MARINE...
Issued at 245 PM EDT Sat Aug 12 2023
High pressure situated just southeast of the waters will maintain
fairly tranquil conditions this weekend into the middle of next
week, with westerly winds around 10 knots and seas around 2 feet.
The exception will be locally higher winds and seas in and around
thunderstorms.
&&
.FIRE WEATHER...
Issued at 245 PM EDT Sat Aug 12 2023
High temperatures will be hot across the region, with near triple
digit highs forecast for the next several days. Although
temperatures will be hot areawide, abundant moisture is expected to
be in place, with minimum RH values only dropping into the mid 40s
during the peak of afternoon mixing. Transport winds are expected to
remain fairly light with winds less than 10 mph anticipated out of
the west/southwest for the next several days. Given the hot
temperatures, burning is discouraged; however, with abundant
moisture and light winds forecast, there are no other fire weather
concerns at this time.
&&
.HYDROLOGY...
Issued at 245 PM EDT Sat Aug 12 2023
A front will approach on Tuesday and stall near the region from
mid to late week. With the boundary in place, Precipitable Water
values near 2 inches, and slow storm motions, there is a marginal
risk of excessive rainfall from late Tuesday into Friday. Still
uncertainty on where the heaviest amounts will occur, but they`re
currently favored southeast of a Tift to Panama City line, where
isolated flash flooding will be possible.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 79 100 79 98 / 40 40 20 40
Panama City 82 95 82 94 / 20 30 20 40
Dothan 76 99 77 98 / 80 40 20 30
Albany 77 99 78 98 / 80 40 20 30
Valdosta 77 100 78 99 / 30 30 10 40
Cross City 78 98 78 96 / 20 30 20 50
Apalachicola 81 94 82 93 / 20 30 10 40
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...Excessive Heat Warning from 10 AM EDT /9 AM CDT/ to 8 PM EDT /7
PM CDT/ Sunday for FLZ007>019-026>029-034-108-112-114-115-
118-127-128-134.
High Rip Current Risk until 1 AM EDT /midnight CDT/ Sunday for
FLZ112-114.
GA...Excessive Heat Warning from 10 AM to 8 PM EDT Sunday for
GAZ120>131-142>148-155>161.
AL...Excessive Heat Warning from 9 AM to 7 PM CDT Sunday for
ALZ065>069.
GM...None.
&&
$$
NEAR TERM...Bunker
SHORT TERM...LF
LONG TERM....LF
AVIATION...Scholl
MARINE...LF
FIRE WEATHER...Bunker
HYDROLOGY...LF