Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/14/23
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
612 PM CDT Thu Jul 13 2023
.SHORT TERM...(This Evening through Friday Night)
Issued at 227 PM CDT Thu Jul 13 2023
Convection has begun to develop across portions of the
CWA...particularly down towards the Pierre area, with a cumulus field
extending into the James valley. Focus areas for greatest severe
threat remains far northeast with strong unidirectional shear being
the main feature. LCLs are highest in the southwest CWA, where DCAPE
is over 1K J/KG. Thus, maintaining mostly a wind/hail threat. For
Friday, models still show some CAPE and strong unidirectional shear,
despite some weak cold and dry air advection. Additionally, smoke
moving in aloft may inhibit convection, however uncertain at this
point so will leave the chance of POPs. Additionally, added mention
of smoke as a surface obscuration with this next plume coming out of
Canada based on both HRRR and RUC guidance.
.LONG TERM...(Saturday through Thursday)
Issued at 227 PM CDT Thu Jul 13 2023
There`s good model agreement in regards to the weekend pattern,
which features cooler air filtering into the region under northwest
flow aloft. At the surface, high pressure will be nosing southward
into the region as well. As the high builds in, Saturday and Sunday
will see an increasing pressure gradient, thus resulting in
breezy/gusty northwest winds. Coolest of the air looks to be over
the eastern CWA on Monday, where 850mb temps could possibly drop
below +10C. Highs in the 70s look to be common over eastern areas
through the weekend into Monday. As a side note, could still be
dealing with smoke aloft (and possibly near-surface?) during the day
Saturday. Tuesday into Wednesday there is evidence of some energy
moving eastward across the Northern Plains, with precipitation
chances returning to the forecast after what looks to be a dry
weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 611 PM CDT Thu Jul 13 2023
Terminals KABR,KATY,KPIR,KMBG
VFR skies/vsbys are expected through tonight.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
SHORT TERM...Connelly
LONG TERM...TMT
AVIATION...TDK
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1044 PM EDT Thu Jul 13 2023
.SYNOPSIS...
A cold front will stall near eastern New York Friday with more
scattered showers and thunderstorms expected. The weather pattern
remains unsettled for the upcoming weekend with additional
showersand thunderstorms, especially Saturday night into
Sunday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 1015 PM EDT...Severe Thunderstorm Watch 481 was allowed
to expire at 10 PM. The Flood Watch for flash flooding as been
trimmed back and only remains in effect for Litchfield and
eastern Dutchess until 6 am Friday.
Convection continues to occur ahead of the cold front across the
southern portion of the forecast area where there is plenty of
instability in place. Not expecting severe but storms can still
be strong. Heavy rainfall will continue to occur with convection.
Updated forecast to better reflect current and expected coverage
storms overnight with chances continuing across the southern
portion of our forecast area overnight as the cold front stalls.
Adjusted temperatures, dew points, sky and wind parameters based
on observational data and blended with latest guidance.
PREVIOUS DISCUSSION [0749 PM EDT]...The forecast area has
endured the wrath of a QLCS that is in the process of merging
with some discrete supercellular convection that has drift
north/northeast up the Hudson River Valley. We have reports of
widespread wind damage across portions of Washington, Warren,
Saratoga and Montgomery Counties. Ground truth continues to come
in. Substantial instability remains in place and we just
coordinated with SPC for a Severe Thunderstorm Watch extension
until 10 PM. We did cancel Hamilton, Herkimer and Fulton
Counties. MLCAPES are in the 1000-2000 J/kg range along and
south and east of the Greater Capital Region based on the latest
RAP Mesoanalysis with 30-40 KT of effective bulk shear in
place. The severe threat will continue the next few hours and
diminish. We did issue a Flash Flood Warning for portions of
eastern Greene and Columbia Counties where rainfall estimates of
1-2+/hr occurred with a cluster of strong to severe convection.
No tornado reports but some mesocyclonic rotation and funnels.
Temps have rapidly cooled into the 60s with the squall line.
PREVIOUS DISCUSSION [0450 PM EDT]...KENX radar shows a line of
severe thunderstorms moving northwest to southeast across the
Western Adirondacks ahead of a cool frontal boundary set to
slowly progress through the region through tomorrow. Pop-up
thunderstorms, too, have developed out ahead of this line,
mainly in the Upper-Hudson Valley, whose conditions have
warranted multiple severe thunderstorm warnings already this
afternoon.
Severe thunderstorms embedded within the aforementioned line will
continue to progress across the region from northwest to southeast
throughout the afternoon and evening, supported through ample
instability (SBCAPE on the order of >= 2000 J/kg) and
frontogenetical forcing. Southerly flow will persist, perpetually
providing the fuel necessary to yield locally heavy downpours that
could accumulate 1-2" of rain especially in the Western Adirondacks,
Upper-Hudson Valley, southern Vermont, the Berkshires, Taconics, and
Northwest Connecticut.
Several threats and impacts can be expected with storms this
afternoon, the primary being damaging winds. This morning, the Storm
Prediction Center upgraded portions of the forecast area (Western
Adirondacks, Mohawk Valley, Upper-Hudson Valley, Schoharie Valley)
to an Enhanced Risk for severe weather due to the categorical wind
threat. Strong vertical motion (0-6 km shear increasing to ~35 kt)
paired with DCAPE values of about 1200 J/kg will support damaging
wind gusts along the storm line. Any bowing within storms (that has
been hinted at in latest CAM guidance especially in the Upper-Hudson
Valley) may very well lead to severe straight line winds. Power
outages as a result of severe wind gusts are likely.
Another threat from these storms is flash flooding. With PWATs on
the order of 1.5" to near 2", precipitation loading could certainly
play a significant role in locally heavy downpours resulting in
flash flooding especially in the areas enclosed within the Flood
Watch. Outside of the Watch, flash flooding becomes less of a
threat, though moderate to heavy rain will likely lead to poor-
drainage flooding and ponding of water especially throughout urban
areas.
The Storm Prediction Center also has an increased risk of large hail
and tornadoes. Strength of vertical ascent paired with relatively
cool air aloft have increased the threat for large hail especially
within the region of the Enhanced Risk. Tornadoes, though
probability of occurrence is much less than damaging wind and hail,
are also very possible. Elevated shear and 0-3 km SRH values of 200-
250 m2/s2 have increased the risk of some brief, spin-up tornadoes.
Any tornadoes that form are not expected to be significant.
Thunderstorms will significantly weaken with the loss of diurnal
heating, though persistence of elevated instability will sustain the
possibility of rumbles of thunder after sundown as the line moves
south and east of Albany. Convection should cease by 2 AM, but a
lingering shower or two in the Hudson Valley cannot be ruled out.
Then, sky cover will look to improve throughout the night, yielding
low temperatures in the 60s with upper 50s in the Western
Adirondacks.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Tomorrow...The cold front will still be over eastern NY and
western New England. A weak wave will be moving along the
boundary rekindling the showers and thunderstorms. PWATs will be
running 1 to 2 STDEVs above normal with values in the 1.5-2.0"
range especially south and east of the Capital Region based on
the latest NAEFS. Some of the thunderstorms could be on the
stronger side as the 12Z HREFS has mean SBCAPEs of 1000-2000+
J/kg from the Capital Region, eastern Catskills and southern VT
south and east. 0-6 km shear values of 30-35 KT are located
south and east of ALY. The severe threat will depend on the
degree of heating lingering clouds throughout the day. The
Marginal Risk looks pretty good south and east of Albany from
SPC. Isolated to scattered instances of flash flooding may also
linger with backbuilding and training showers and thunderstorms.
We may need to extend for expand the Flood Watch or issue a
brand new one after the strong to severe thunderstorms today.
Max temps will 80-85F in the lower elevations and across NW CT
and 70s to around 80F over the higher terrain. It will remain
sticky with dewpoints in the 60s to lower 70s with a few upper
50s over the southern Dacks.
The showers and thunderstorms diminish early in the evening
prior to midnight, as the weak sfc wave moves northeast and the
cold front dips to the southeast. It will be a muggy night with
a micro high/ridge moving into the region. Some patchy fog will
be possible and light rain showers may persist east of the
Hudson River Valley. Lows will be in the 60s with some upper 50s
over the southern Dacks, southern Greens and eastern Catskills.
Saturday...Persistent mid and upper level southwest flow
will continue over eastern NY and western New England on the
eastern flank of the mid and upper level trough. Another short-
wave impulse will approach during the afternoon from the lower
Great Lakes, OH and PA. Isolated to scattered showers and
thunderstorms will increase during the afternoon. It will be a
steamy day with some sunshine mixed with clouds. Highs will
range from the mid 80s to around 90F in the major valleys and
upper 70s to mid 80s over the higher terrain. The better
synoptic lift with the approaching short-wave arrives from the
southwest to northeast at night. PWATS remain above normal high
chance and low likely POPs were continued with a chance of
thunderstorms with some elevated instability Lows will be balmy
for mid July with 60s to lower 70s.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Wet conditions close the upcoming weekend, but their light at
the end of the tunnel for a period of some drier weather towards
the middle of next week.
A closed/cutoff low over southwest Ontario and the Upper Great
Lakes Region embedded in a sprawling mid and upper level trough
will continue to plague the forecast area with periods of
showers and thunderstorms to close the weekend. Strong
isentropic lift occurs ahead of a wave and warm front to close
the weekend for periods of showers and a chance of
thunderstorms. PWATS remain above normal and soils are saturated
in spots, so will have to monitor for possible flash flooding.
Max temps will be near normal with 70s to lower 80s. The cold
front moves across most of the region Sunday night with a
continued threat of scattered showers and isolated
thunderstorms. Lows fall back into the 60s with a few upper 50s
over the southern Dacks.
A secondary cold front moves moves through Monday through
Tuesday with isolated to scattered showers and thunderstorms.
Coverage looks less than the weekend. High pressure builds in
Wednesday with drier weather and slightly lower humidity levels.
Temps will be near to slightly above normal Monday through
Wednesday. Clouds increase Thu from the south and some showers
or isolated thunderstorms may impact locations south and east of
Albany. Overall...the Day 8 to 14 Temp and Pcpn Outlook from CPC
continues to call for near normal temps and above normal pcpn
for the 3rd to 4 week of July for the forecast area.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
THROUGH 00Z SATURDAY...Strong thunderstorms are still present
throughout the forecast area, though KGFL and KALB have seen the
last of their convective activity for the day. Currently, some
lingering showers and distant thunderstorms exist for these
terminals, but all precipitation will likely be over within the
next hour or two. Current radar shows KPSF currently being hit
by thunderstorms that will keep its conditions in the IFR-LIFR
category for at least the next couple hours. KPOU may luck out
without thunder, but some showers will likely grace the terminal
within the next few hours as well.
Behind the convection, skies are clearing and ceilings are
expected to dissipate overnight. However, persistence of
elevated RH, saturated soils from locally heavy rain and
decreasing wind speeds will likely contribute to some mist and
fog overnight. The more likely terminals to see mist/fog are
KGFL and KPSF, though lighter mist at KALB cannot be ruled out.
KPOU is not expected to leave the VFR threshold once showers
move through there later this evening.
Skies will remain mostly clear through tomorrow morning before
ceilings develop ahead of another possible round of showers and
thunderstorms tomorrow. Convection will not be as widespread,
however, and with confidence in spatial spread not great at the
time of this update, kept afternoon precipitation out of the
TAFs until a later update.
Winds are decreasing throughout the area now, yielding mainly
southeasterly winds on the order of magnitude of 6-10 kt. KPSF
and KPOU still have intermittent gusts upwards of 20 kt.
Throughout the period, winds will continue to decrease and turn
more northerly with sustained speeds of 3-7 kt.
Outlook...
Friday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Saturday: Moderate Operational Impact. Chance of SHRA...TSRA.
Saturday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Sunday: High Operational Impact. Definite SHRA...TSRA.
Sunday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Monday: Low Operational Impact. Slight Chance of SHRA...TSRA.
Monday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Tuesday: High Operational Impact. Likely SHRA...TSRA.
&&
.HYDROLOGY...
The Flood Watch for flash flooding as been trimmed back and only
remains in effect for Litchfield and eastern Dutchess until 6
am Friday. Heavy rainfall will continue to occur with convection
across that area overnight.
Another round of showers and storms looks to occur Friday afternoon
and evening, although this would likely be further south and
east of Thursday`s activity. High rainfall rates could lead to
some additional flooding concerns and another flood watch could
be needed for additional parts of the area.
More showers and thunderstorms over the weekend could lead to
additional hydro concerns, mainly for Sunday. This will come
into better focus over the next few days.
For details on specific area rivers and lakes,
including observed and forecast river stages and lake
elevations, please visit the Advanced Hydrologic Prediction
Service /AHPS/ graphs on our website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch until 6 AM EDT Friday for CTZ001-013.
NY...Flood Watch until 6 AM EDT Friday for NYZ066.
MA...None.
VT...None.
&&
$$
SYNOPSIS...IAA/Wasula
NEAR TERM...IAA/Gant/Wasula
SHORT TERM...Wasula
LONG TERM...Wasula
AVIATION...Gant
HYDROLOGY...IAA/Frugis/TAW
Area Forecast Discussion
National Weather Service Denver/Boulder CO
805 PM MDT Thu Jul 13 2023
.UPDATE...
Issued at 758 PM MDT Thu Jul 13 2023
Mostly quiet conditions are prevailing across the forecast area
this evening. The previous moisture boundary/outflow boundary
collision near I-25 resulted in a few brief cumulus clouds but not
enough convergence to generate any convection. Outside of a few
weak/high based showers across the high country along and north of
I-70, satellite and radar show little other activity in our area.
Any remaining showers should diminish this evening. An isolated
shower or storm cannot be ruled out over the far eastern plains,
but guidance has trended away from this solution.
The previous forecast grids were in good enough shape, and only a
few minor updates have been made this evening.
&&
.SHORT TERM...(This evening through Friday)
Issued at 241 PM MDT Thu Jul 13 2023
For this afternoon, isolated severe thunderstorms across
southeast Washington and eastern Lincoln counties. In addition,
isolated to scattered weaker high based showers/storms were
developing over the higher terrain. In between these two areas of
convection is a dry line that stretches from Longmont to Limon.
Plenty of moisture and instability east of this line for
additional severe storms which is why an addition severe
thunderstorm watch as issued to include areas north and northeast
of Denver. Drier outflow from the mountains/foothills should shift
this line eastward, but there will also be outflow generated by
the storms over Washington/Lincoln counties. SPC analysis shows
MLCAPE of 2500-3500 j/kg along and east of the dry line. Large
hail, damaging outflow winds and isolated tornados will be
possible with the severe storms possible through 9 pm this
evening. On Friday, a cold front will move into the Denver area in
the morning, around 8-9 AM, with post frontal northeast winds
expected in the through the afternoon. A moderate northwesterly
flow aloft will remain in place through the day. Isolated to
scattered thunderstorms will develop over the higher terrain and
along the northern border by late in the afternoon. NAM forecast
soundings show MLCAPE 500-1000 j/kg by 21z Friday, with the
greatest instability near the foothills/Palmer Divide. We cracked
the 90 degree mark this afternoon, but that will not be the case
on Friday.
.LONG TERM...(Friday night through Thursday)
Issued at 241 PM MDT Thu Jul 13 2023
Upper level high over the Desert Southwest will bring northwest
flow aloft through Sunday. A jet streak moves across northern
Colorado Friday night. This may trigger storms well into the
evening and overnight hours. There are some hints of this on the
GFS and HRRR models. CAPE overnight runs 500-1500 J/kg, so some
strong to severe storms will be possible. Airmass will be more
unstable and moisture increases for Saturday. ML CAPE of
1000-2000/J/kg will prevail with good shear, so severe storms will
be possible. Models tend to favor the eastern plains during the
late afternoon and evening, though the threat extends west to the
foothills. Temperatures Saturday will be on the cool side with
highs in the lower 80s over northeast Colorado.
For Sunday, the upper level high begins to intensify and drifts
eastward. This will bring warmer and drier conditions to the area.
Highs across northeast Colorado will be around 90 degrees. Very
warm and dry conditions will prevail Monday and Tuesday. Main
weather concern shifts to fire weather over the north central
mountains and mountain valleys. For Tuesday, there will be an
increase in mid level moisture, which is expected to produce high
based showers and thunderstorms. Convection is expected to be weak
with gusty outflow winds being the main threat.
Cold front pushes through Tuesday night/early Wednesday.
Temperatures fall back to the upper 80s to lower 90s. Moisture
will increase as well bringing better chances for showers and
thunderstorms Wednesday and Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 535 PM MDT Thu Jul 13 2023
TDEN shows outflow from showers west of DEN and a remnant outflow
boundary/moisture gradient east of the field. End result will
likely be a couple of hours of gusty winds, predominantly out of
the northwest. Some concern for additional TS/SHRA development
with this boundary but not confident enough to include anything in
the TAF. Once this activity clears, VFR and quieter conditions
are forecast overnight into tomorrow.
A few showers and possibly a TS will again be possible late
tomorrow afternoon or evening, with briefly variable/gusty winds
possible.
&&
.FIRE WEATHER...
Issued at 240 PM MDT Thu Jul 13 2023
Elevated fire weather concerns will remain limited on Friday to
the mountain valleys and the mountains west of the Divide. Some
cooling across the plains following the passage of a cold front
with isolated to scattered afternoon/evening thunderstorms
developing in the afternoon.
Drier air moves into the area Sunday with much warmer
temperatures accompanying it for Monday and Tuesday. Greatest fire
weather concerns will be across the mountains valleys where the
driest conditions have been. Relative humidities fall into the 5
to 15 percent range with gusty winds during the afternoon. Cold
front pushes through the area early Wednesday bringing cooler
temperatures and better moisture.
&&
.HYDROLOGY...
Issued at 240 PM MDT Thu Jul 13 2023
Isolated high based showers/thunderstorms possible this
afternoon, but no flash flood potential for the burn scars. On
Friday, scattered storm increase along the Front Range Foothills.
Limited flash flood potential for primarily Cameron Peak burn scar
but no issues elsewhere.
Scattered thunderstorms are expected for Friday evening/night and
again Saturday afternoon and evening. Best moisture will be
across the Urban Corridor and eastern plains. This will keep the
flash flood threat for the Cameron Peak Burn area low/limited with
no concerns for the East Troublesome and William`s Fork burn
areas. May be a low flash flood threat with the storms Saturday
across the places where the NAM and GFS are showing an area of
organized convection Saturday afternoon and evening.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Hiris
SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Hiris
FIRE WEATHER...Cooper/Meier
HYDROLOGY...Cooper/Meier
Area Forecast Discussion
National Weather Service Boston/Norton MA
943 PM EDT Thu Jul 13 2023
.SYNOPSIS...
Low pressure over the St. Lawrence Valley will move northeast
tonight. A line of strong thunderstorms over central New York
will move eastward into Southern New England tonight. While
isolated instances of wind damage are possible in western parts
of Southern New England tonight, heavy rain and a renewed risk
for flooding may develop tonight and Friday. Periodic showers
and thunderstorms then continue through this weekend and into
early next week with seasonable temperatures.
&&
.NEAR TERM /THROUGH FRIDAY/...
10PM Update:
Still seeing upwards of 1500 J/kg of MLCAPE in western MA and CT
helping sustain the severe thunderstorms. As storms move east,
they will start to run into more stable air with MLCAPE quickly
dropping to 500 J/kg east of Worcester. 0-6km shear also drops
off east of Worcester which will help weaken storms. Storms
have slowed down a bit since entering MA allowing for 1 hour
rain fall rates to exceed 1.5 inches. This has prompted the
issuance of flash flood warnings this evening across western MA
as 1hr flash flood guidance is only 1.5-2.0 inches.
7PM Update:
Hi-res guidance still shows the line of convection currently
across eastern NY beginning to diminish as it enters western MA
and CT. There is still a chance for severe wind gusts and
torrential rainfall mainly from the Berkshires to the CT river
valley. SPC meso analysis is still showing 1500-2000 J/kg of
MLCAPE and 30 knots of 0-6km of bulk shear. The main hazard this
evening looks to be strong wind gusts with steep low level
lapse rates nearly 10C/km per RAP/HRRR soundings. Heavy rain is
a secondary threat with PWATS near 1.5 inches and warm cloud
depths near 10kft. These cells are moving rather quickly at
about 40mph which should help alleviate flash flooding concerns
this evening. There is a low chance for a short lived QLCS
tornado as the line enters the region with STP around 1 and
0-1km SRH near 100m2/s2, however LCL heights are around 3000ft
which is very unfavorable for tornadic development.
330 PM Update:
Highlights:
* Weakening complex of thunderstorms late tonight, posing a
lightning/heavy rain and possible localized wind damage risk
for western MA and perhaps Hartford County CT thru 11 PM.
* Additional rounds of showers/t-storms possible late tonight
through pre-dawn/early Friday AM for western and central MA
into CT and RI. Localized urban and poor drainage flooding
possible. Flood Watch issued for tonight into late
tonight/early Fri AM.
Broad WSW cyclonic flow in mid-levels continues. Sfc conditions
feature a warm sector air mass which has spread across SNE,
ahead of a seasonably strong low pressure over the St. Lawrence
River. In a moderately-unstable air mass across central and
eastern portions of NY into western sections of New England,
along with increasing vertical wind shear, regional composite
radar mosaic shows an organizing cluster of strong/severe
thunderstorms near the western Gt Lakes/NY Finger Lakes
vicinity, expected to morph into a convective squall line as it
moves into eastern NY and western New England late this
afternoon into early tonight.
While the most intense thunderstorms are expected across NY,
portions of VT and western New England thru late- afternoon
(see: SPC`s upgrade to an Enhanced Risk for severe weather for
portions of eastern NY), we will have to keep close tabs on
this feature and its evolution. Typically thunderstorms tend to
weaken post-sundown, however there are indications this may not
necessarily be the case for tonight: for one, mid-level lapse
rates improve late tonight and overnight. In addition, southerly
flow will allow for rising dewpoints/precipitable water values
for the overnight, which can sustain nocturnal thunderstorms
despite surface instability dwindling. The combo of the two may
keep most- unstable CAPE values in the 1000-2000 J/kg
neighborhood well into the evening/overnight. The risk for
strong to perhaps locally severe storms capable of localized
wind damage arrives in from eastern NY and Berkshire/Litchfield
County after 7 PM this evening, mainly into Hampden, Hampshire,
and Franklin Counties in MA and Hartford and Tolland counties in
CT thru about 11 PM. In at least a loose-consensus, that seems
to be the trend across convective- permitting guidance and the
00z/12z HREF max-updraft progs. Localized heavy rain, lightning
and gusty winds are all risks as this line of thunderstorms
moves across. Certainly, the areas in western MA and northern
CT are sensitive to additional and potentially heavy rains, thus
I`ve hoisted a Flood Watch for late this afternoon into
overnight.
I`ve also added a Flood Watch mainly for urban and poor
drainage flash flooding for central MA, eastern CT, RI and into
Bristol County in MA. While this is not well agreed upon, it
appears that a boundary/wind shift left behind by the
progressive line of thunderstorms described above may trail
through northern CT, RI and SE MA for the overnight into the
early Fri AM hours. Following the conceptual model for a
convective line/MCS, it`s this trailing boundary on the
southern/southwestern periphery that can be the source of
training/heavy rain moving over the same area. If this indeed
materializes, there may be multiple rounds of showers and
thunderstorms capable of heavy rainfall, which could coincide
with the Fri AM commute into the Hartford, Springfield,
Worcester, Providence and Fall River metros. The risk for
thunderstorms is lower, shown by lower HREF max-updraft progs,
but insists on showing some t-storms tonight.
The risk further north and east into Metrowest, Greater Boston
and North Shore areas currently is low enough to preclude a
Flood Watch for now.
QPF for tonight was based off NERFC`s 12z QPF while blending in
some of the higher amts from recent HRRR guidance. In the Flood
Watch area, have shown 1 to 2 inches of rain with locally higher
amts in sustained/training t-storms, with less into eastern and
northeast MA.
Having said all this, forecaster confidence in the thunderstorm
potential and the hydro/flooding risk is rated as no better
than moderate, and is low to moderate on the overnight/pre-dawn
heavy rain risk. A lot of those details will hinge on how
tonight`s MCS/line of storms evolves, in which there is
continued variance in solutions/outcomes and where/if boundaries
left behind may reside. That will greatly influence the heavy
rain/hydrologic forecast. But hoisting the Flood Watch seemed
the smarter call in this scenario, given sensitivies to heavy
rain owing to saturated ground and urban/poor drainage areas
that are vulnerable to heavy rain in a short period of time
coinciding with overnight/Friday AM commute travel.
&&
.SHORT TERM /FRIDAY NIGHT/...
330 PM Update:
Highlights:
* Heavy rain and potential flash flooding again may re- develop
Fri and Fri night, though is currently low confidence outlook
on rain amounts and when/where.
* Existing Flood Watch may need to be expanded and/or extended
in time.
It looks to be another active day with rounds of rain and
thunderstorms. However uncertainties and forecast developments
to still avail themselves for tonight/overnight render forecast
confidence for Friday and Friday night as low.
We remain in a fast belt of WSW flow aloft and any subtle
disturbance may trigger rounds of showers and t-storms and a
warm, humid and unstable air mass. Showers and t-storms from the
overnight may be ongoing across parts of SNE to begin Friday,
though appear to weaken into the late-morning period. There is
some loose consensus in 12z NAM, 12z GFS and the 15z SREF mean
in showing a weak low pressure near eastern/northeast PA,
perhaps along some boundary that may return back NE and focus
renewed showers and t-storms for the afternoon and the evening.
HREF max-updraft progs, which tends to be a good proxy for where
thunderstorms are at least possible, show increasing
probabilities across central and western MA into northern CT
and parts of RI into the afternoon-early evening, with the risk
for the evening and overnight then shifting into eastern and
southeast MA and RI for the evening and overnight.
QPF amounts remain uncertain in a convective pattern, but the
potential exists for multiple rounds of rain on Friday. HREF
6-hourly probability matched mean QPF values indicate the
potential, which appear greater across northern CT and most of
MA along and north of the Mass Pike (around 1-2") through 00z,
then focus along southeast MA and RI later in the afternoon into
the overnight, with local amts up to 3 inches!
Will refrain from extending the Flood Watch into Friday or
Friday night until we get a better look at what fell tonight and
overnight, but if guidance and HREF solutions show consistency
in recent runs, it`s possible the Flood Watch may need to be
extended in time or area.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights...
* Little change in the overall pattern into next week
* Continued warm/humid with showers/storms at times
Ensembles favor a continuation of the blocky weather pattern that
has dominated this week, with yet another cutoff low slowly
migrating through southern Canada and Great Lakes. This will keep
our area in moist southerly flow with showers and storms at times,
especially during the afternoon and evening hours.
After Friday night, focus for more widespread rainfall appears to be
Sunday as low pressure heads toward New England from Ohio Valley.
Potential is there for another 1-2" of rain which may result in
urban/poor drainage flooding but at this point flooding of rivers
and streams seems to be less likely.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecast Confidence
Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight... High Confidence
Linear convective line pushes in from the NW after 00Z tonight.
Should maintain strength into western terminals between 03-06Z
before dissipating as moves into central MA/RI. Confidence too
low on the coverage of thunder to include it in any individual
TAF east of BDL. Heavy rain associated with these storms will
be the main concern, though gusty winds also possible in strong
cells. VFR outside of storms, but localized IFR/MVFR likely to
be associated with the convective line.
Conditions briefly improve as the line dissipates, but cigs
will deteriorate to low end MVFR across much of the area with
IFR for southern terminals especially Cape Cod and the Islands.
Friday... Moderate confidence
MVFR/VFR to start the day, but widespread downpour/thunderstorm
activity expected. While it wont rain at any terminal all day,
heavy rain is expected especially across western and
southeastern terminals. Boston and Nantucket may avoid the worst
of things. Winds will be variable in direction given stalled
frontal boundary will be centered across the region but will
range from S to NW.
BOS Terminal... High confidence.
Generally dry, VFR through the period, though cant rule out a
spot shower this evening or some more stratiform showers after
04Z tonight. S/SSW winds will increase to 10-15, gust to 20 kt.
BDL Terminal...High confidence.
Convective line approaches from the NW after 00Z, bringing
increased chances for localized MVFR/IFR in heavy downpours and
storms primarily between 03-06Z. Light winds from the SW this
morning growing to between 5-15kt this afternoon. Winds will
shift to the NW briefly behind the frontal passage early
tomorrow.
Outlook /Saturday through Tuesday/...
Friday Night: Mainly VFR, with local IFR possible. SHRA likely,
chance TSRA.
Saturday: Mainly VFR, with local MVFR possible. Chance SHRA,
isolated TSRA.
Saturday Night: Mainly VFR, with local IFR possible. Chance
SHRA, isolated TSRA.
Sunday through Sunday Night: MVFR/IFR conditions possible.
Breezy. SHRA likely, isolated TSRA.
Monday: VFR. Slight chance SHRA, isolated TSRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
This afternoon through Friday night... High Confidence.
Generally an active period, though, seas and winds remain below
advisory criteria. Seas are generally two to four feet, winds are
south/southeast less than 15 knots and occasional gusts less than 25
knots.
Frontal boundary moves from west to east across the waters late this
evening through the overnight hours, which may contain a few strong
thunderstorms. Within these storms, locally seas and winds may pose
a risk to mariners. Areas of fog possible overnight, reducing vsby
to less than a mile across eastern waters. Numerous showers and
embedded storms Friday and Friday evening as a surface low
approaches from the southwest.
Outlook /Saturday through Tuesday/...
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Rain showers likely, chance of thunderstorms.
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers, isolated thunderstorms.
Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Chance of rain
showers, isolated thunderstorms.
Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Rain showers likely,
isolated thunderstorms.
Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Chance of rain showers, isolated thunderstorms.
&&
.HYDROLOGY...
Flood Warnings remain in place for many locations along the CT
River from the MA/VT border to the Long Island Sound, except for
a small portion of the river near Springfield, MA. Many sites
along the CT River crested overnight, though it will take
several days for river levels to fall below flood stage.
Additional rainfall late this week into this weekend may
exacerbate existing flooding, or lead to new flooding elsewhere.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch until 6 AM EDT Friday for CTZ002-003.
Flood Watch until 6 AM EDT Friday for CTZ004.
MA...Flood Watch until 6 AM EDT Friday for MAZ002-003-008>011.
Flood Watch until 6 AM EDT Friday for MAZ004-012-013-017-020.
RI...Flood Watch until 6 AM EDT Friday for RIZ001>007.
MARINE...None.
&&
$$
SYNOPSIS...Loconto/JWD
NEAR TERM...Loconto/KP
SHORT TERM...Loconto
LONG TERM...JWD
AVIATION...Loconto/Dooley/JWD
MARINE...Loconto/Dooley/JWD
HYDROLOGY...
Area Forecast Discussion
National Weather Service Cheyenne WY
253 PM MDT Thu Jul 13 2023
.SHORT TERM...(This evening through Friday night)
Issued at 200 PM MDT Thu Jul 13 2023
Diurnal Cu has begun to pop up early this afternoon, along with
the beginnings of organized convection. The heavily advertised
dryline has been waffling back and forth across extreme southeast
WY through the late morning and early afternoon hours. Dew points
have shifted back and forth upwards of 10-20 degrees with the
advancement and retrograding air mass boundary. This convergence
boundary has allowed some of the first round of showers and
thundershowers to occur. SPC mesoanalysis depicts EBWD shear of
30-55 knots east of the Laramie Range, low-level and mid-level
lapse rates of 6-10 degrees C/km, and MUCAPE of 500-4000 J/kg as
of 20Z. This would be more than enough for organized convection to
develop and persist as discrete thunderstorms/supercell
thunderstorms. As such, a Severe Thunderstorm Watch through 3Z has
been issued.
Hi-res 18Z CAMs model runs depict organized convection persisting
through approximately 0Z-2Z. Damaging winds and large hail are the
primary hazards. Can`t rule out a brief tornado spin-up, but
modeled SRH from 0-1km and 0-3km aren`t too impressive. Daytime
highs in the 80s and 90s will prevail across the region, with
slightly cooler temperatures in the 70s for the higher terrain by
the early evening hours. Overall, the 18Z CAMs are hinting at an
earlier end time to the convection this evening, with slightly
elevated convection being present in the mid-levels across our
northern forecast zones and the northern NE Panhandle. Sub-severe
thunderstorm activity is anticipated with any convection that
persists during the overnight hours. With the cloud cover and
abundant moisture plume remaining present, would expect a few
areas east of the Laramie Range to struggle to decrease below
65-70 degrees for the overnight low, especially the NE Panhandle.
Friday and Friday night will be more of the same regarding
afternoon showers and thunderstorms. However, SPC Day 2 doesn`t
have a risk for severe thunderstorms highlighted in our cwa at
this time. Only a General Thunder Risk. A weak cool front will sag
to the south through the day, with weak CAA being present in the
lower and mid-level of the atmosphere across the northern Plains.
This CAA will limit daytime temperatures for most of the cwa, with
a general 5-10 degrees cooler. Middle 70s to middle lower 80s can
be expected in the lower terrain. Warm overnight lows will be
expected again across the cwa, east of the Laramie Range. Slightly
cooler temperatures can be expected west of the Laramie Range
Friday next, before the start of the weekend occurs.
.LONG TERM...(Saturday through Thursday)
Issued at 200 PM MDT Thu Jul 13 2023
PREVIOUS LONG TERM DISCUSSION FROM 12 JULY...
The medium range to extended forecast will include near to slightly
above average temperatures, and a couple of upper level disturbances
moving along a persisting upper level ridge across our cwa. The
northwest flow aloft will provide an opportunity for passing weak
wave features to bring chances of showers and isolated thunderstorms
to the cwa. As the upper level ridge amplifies across our cwa, we
can expect a much warmer trend of temperatures from Sunday to
Tuesday before we have a transition to slightly cooler temperatures
behind a weak cool frontal passage.
Saturday will bring a contrast of CAA to our northern zones due to a
passing upper level wave, and WAA for our western zones by the late
afternoon ours. The dividing feature between the two air masses will
be the Laramie Range. However, with the lower elevations seeing
decent atmospheric mixing, daytime maximum temperatures for the
eastern forecast zones will be similar to those for areas west of
the Laramie Range. The coolest temperatures are likely across the
CO/WY border for Saturday as daytime highs there will hover in the
middle to upper 70s, with the remainder of the cwa seeing daytime
maximums in the low to middle 80s. There will be an isolated chance
of thunderstorms on Saturday along the I-80 corridor from Albany
County towards the NE Panhandle, but severe weather isn`t expected.
Sunday and Monday will bring warmer temperatures to our cwa due to
the upper level ridge amplifying across the desert Southwest towards
the Central and Northern Rockies/Central Plains. The lower and mid-
levels of the atmosphere will warm considerably. 700mb temperatures
on Sunday will be 5C to 7C warmer than Saturday. This will translate
to afternoon highs being 5 to 10 degrees F warmer for Sunday
afternoon. Most locations should see middle 80s to lower 90s for
highs in the lower terrain, and slightly cooler temperatures in the
higher terrain. The axis of the upper level ridge will propagate to
the east from the Great Basin area towards the Central/Northern
Rockies by Monday. 700mb temperatures by Monday afternoon will range
from 15C to 20C, and will mix to the surface easily. Because of the
very warm temperatures being present, isolated showers and a
thunderstorm may be possible as the elevated mixed layer has weak
instability within it. Severe weather is not expected, but afternoon
and evening showers and thunderstorms can`t be ruled out. Widespread
80s and 90s can be anticipated for the lower terrain to start next
week on Monday.
Tuesday will be the warmest day of next week. Ensemble members for
daytime highs for locations east of the Laramie Range are favoring
low to upper 90s. Some cities along the North Platte River Valley
from approximately Torrington to Sidney are the highest favored for
potentially reaching the century mark for high temperatures. This
will be a little tricky to fine tune as we approach Tuesday due to
the model guidance favoring an approaching shortwave disturbance to
our north. If this shortwave disturbance treks further to the south,
then we will see a higher probability of showers and thunderstorms.
This could easily impact daytime highs by having additional cloud
cover over the area, and slightly cooler temperatures. However, have
gone with an aggressive approach to daytime highs, with several
areas seeing the highest forecast maximums of the summer period:
Widespread 80s and 90s. Have kept the century mark out of the
forecast as it is 6 days away at this time of inspection.
Wednesday has the signals to be nearly as warm as Tuesday, with
isolated chances of showers and thunderstorms as well. We
recommend paying attention to the extended forecast as it
transitions to the short term desk by early next week. There may
be a need to issue headlines due to the very warm to hot
temperatures expected by early next week.
&&
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1133 AM MDT Thu Jul 13 2023
Showers and thunderstorms remain possible again today, with a
slight risk of severe weather for the Nebraska Panhandle, and a
marginal risk of severe weather extending further westward but
staying just outside KCYS. HiRes model guidance has convection
beginning shortly after 20z today, with stronger storms developing
after 22z. All in all, will largely depend on where the dryline
sets up, with current observations showing the dewpoints in KCYS
oscillating between 34F and 45F. The HRRR has continued to show
areas in southeast Wyoming remaining much more dry with most
storms keeping into the Nebraska Panhandle where dewpoints are
much better. Main impacts to aviation will be gusty/erratic winds
and hail potentials near stronger storms, in addition to
lightning within vicinity to terminals. Will continue to be a
challenge to determine if convection will drift directly overhead
the terminal sites, with HiRes model guidance keeping most
convection just VCTS. Will need to continue to monitor throughout
the afternoon for AMDs required.
&&
.FIRE WEATHER...
Issued at 200 PM MDT Thu Jul 13 2023
Very warm temperatures are expected this afternoon, with breezy winds
up to 20-35mph west of the Laramie Range, and minimum humidity values
near 10-15 percent. Areas east of the Laramie Range will see slightly
higher minimum humidity values greater than 20 percent today. With the
extended green-up pattern in place for fuels, fire weather concerns
will remain low to elevated. A weak cool front will sweep across the
area Friday, reducing fire weather concerns to low thresholds.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...BW
LONG TERM...BW
AVIATION...MRD
FIRE WEATHER...BW
Area Forecast Discussion
National Weather Service Des Moines IA
642 PM CDT Thu Jul 13 2023
...Updated for the 00z Aviation Discussion...
.SHORT TERM.../Tonight through Friday/
Issued at 226 PM CDT Thu Jul 13 2023
Key Messages:
- Convection developing this afternoon near the Minnesota/Iowa
border and moving southeast with severe weather possible
- Frontal boundary moving through Friday leading to widespread
shower and thunderstorm chances across the state
Current satellite imagery shows a band of agitated cumulus at the
Minnesota/Iowa border. SPC currently has a slight risk of severe
weather for extreme northwest/north central areas of the CWA.
Showers and thunderstorms are starting to form here due to an area
of convergence seen near the surface. 0-6 km bulk shear per SPC
mesoanalysis reveals values of 40 kts in this area with DCAPE
values of 900 J/kg. BUFKIT soundings reveal a decent amount of dry
air in the upper levels, and combined with the DCAPE, may lead to
strong gusts with any storms that form. Small hail is also
possible. Storms will move SE over time.
Upper level data shows a zone of convergence associated with an
approaching shortwave entering western Iowa late tonight into
Friday. The HRRR model is picking up on some convective activity by
8z early Fri over western and northern IA and then moving SE while
gradually weakening, while other CAMs are not quite picking up on
this. Regardless, any storms that form could have the potential for
some strong gusts given the amount of dryness in the upper
atmosphere.
A frontal boundary will also move into Iowa from the northwest on
Friday and exit the area by Saturday. Expect to see widespread
showers and thunderstorms developing during this timeframe as the
boundary moves thru. 0-6 km bulk shear is around 30 kts across the
state again and may promote some stronger storms across northern
into NE IA given better instability seen here. PWATs are in the
range of 1.5 to 1.75 per the GFS near the boundary area, meaning
storms have the potential to efficiently produce rainfall.
Temperatures tonight will remain in the low 60s north to upper 60s
south, with highs for Friday similar to today. Friday nights lows
will be cooler in the low 60s north, and may even approach the upper
50s due to the frontal passage.
&&
.LONG TERM.../Friday night through Thursday/
Issued at 226 PM CDT Thu Jul 13 2023
Key Messages:
- Storm chances continue into the weekend. Highest chances Sunday.
Severe threat uncertain.
- Low humidity and mostly dry early next week.
Northwesterly flow around the bottom periphery a deep upper low will
stay in place through the extended forecast forecast. Chances for
showers and storms remain in the forecast through the weekend,
although the most likely time period is still focused around Sunday
into Sunday night as an shortwave trough rotates around the parent
upper low and activates a cold frontal boundary as it is pushed
through the state. Deep layer shear profiles are more than adequate
to support organized strong/severe convection, however instability
is in question since we may reside in a drier post-frontal
environment before initiation occurs.
A dry airmass pushes south behind the frontal passage, leading to
unseasonably low dewpoints in the mid 40s to mid 50s Monday and
perhaps into Tuesday. Guidance suggests parts of northern Iowa may
drop into the 40s Monday night. NBM continues to spit out low chance
PoPs as models are quick in their attempts to return moisture into
the area. Opted not to make any adjustments to the NBM PoPs at this
time, but current thinking is the NBM will trend drier as moisture
return lags a bit. Both GFS and EC show another shortwave digging
south off the Canadian prairies over the middle of next week, which
may serve as our next appreciable opportunity for rainfall.
&&
.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 629 PM CDT Thu Jul 13 2023
Primarily VFR conditions will prevail through the night tonight.
Scattered showers and thunderstorms are expected to continue in
northern Iowa over the next few hours which would lead to
temporarily reduced flight conditions if any pass over the
terminals. This will mainly affect KMCW, KALO, and potentially
KFOD. With the scattered nature of storms, confidence is low for
if and when storms will impact any given terminal. Therefore,
included periods of VCTS for when nearby storms are most likely at
KMCW and KALO, and will continue to watch storm trends through
the night for all sites.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Castillo/Martin
LONG TERM...Martin
AVIATION...Dodson
Area Forecast Discussion
National Weather Service Grand Forks ND
1026 PM CDT Thu Jul 13 2023
.UPDATE...
Issued at 1016 PM CDT Thu Jul 13 2023
The chance for strong to severe storms has greatly diminished
since last update as the mid level impulse pushes east along with
stabilizing air mass with loss of daytime heating.
A few showers and weak thunderstorms remain possible mainly within
northwest MN tonight as the surface boundary and some residual,
weak instability aloft.
While it`s a low chance, there may be some patchy fog that
develops east of the boundary within Minnesota given today`s
rainfall, higher low level moisture content and lower winds ahead
of the boundary.
UPDATE Issued at 642 PM CDT Thu Jul 13 2023
Strong to severe storms will remain possible within lakes country
of west-central MN as well as within northwest Minnesota near Lake
of the Woods region through 8 PM CDT. Numerous reports of large
hail, gusty winds, and wall clouds have accompanied strongest
storms, with some minor damage reports trickling in as well
(review LSRs for details).
While main hazards will remain hail up to the size of golf balls
and gusty winds, there is a non-zero chance for a brief tornado
given supercellular characteristics and LCLs lower than 1.5 km
despite the marginal low level shear environment. Within northwest
MN near LOW, objective analysis does show maybe some better lower
level shear both in magnitude and in terms of streamwise
vorticity.
As current convection pushes east of the area after 8 PM, there is
little chance for additional thunderstorms with subsidence behind
the current shortwave impulse moving overhead as well as a drier
low level air mass advecting in from the west.
Smoke is starting to filter in the area as well, but looks to
initially still be aloft. Better chance for smoke at the surface
still expected tomorrow.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 231 PM CDT Thu Jul 13 2023
Convective strength and smoke tomorrow will be the main issues for
the period.
Large upper low over Hudson Bay continues to spin around, with
several weak embedded vort max/shortwaves coming through the
Northern Plains. While some Canadian wildfire smoke aloft has cut
heating a bit, there has been enough to bring 1500 J/kg of ML CAPE
to eastern ND. The effective bulk shear is 30-40 kts, which in
theory would be good for supercells. However, so far convection
that is firing across the northern Red River Valley into the
Devils Lake Basin so far is multicell and not very organized, but
there is some signs of more organized cells developing along the
southern edge of current convection. HREF has some 30 to 40
percent probabilities of strong updraft helicity tracks across the
Red River Valley in the next few hours. At this point, the
messaging we have going isolated severe producing a few quarter sized
hail reports or 60 mph winds seems reasonable as we get some cells
pulsing upwards. With not a lot of upper support and no low level
jet kicking in, think convection will quickly weaken after
sunset.
Northwesterly flow aloft will continue into tomorrow, with one of
the shortwaves digging southeastward and pushing a cold front into
our northern counties by afternoon. Some instability is possible
out ahead of the cold front, but may be tempered by increasing
smoke aloft and deep layer bulk shear is a bit lower. Think there
will be some more scattered showers and thunderstorms developing
tomorrow afternoon with peak heating, but not too impressed with
severe chances at this point. The HRRR and to lesser extent RAP
both have some of the wildfire smoke getting mixed down to the
surface near the front tomorrow. Will continue to keep the smoke
mention previous shifts have put in and air quality alert has been
sent for our MN counties. The cold front will push the rest of the
way through Friday night, with precip chances tapering off after
sunset but at least some smoke lingering a bit longer.
.LONG TERM...(Saturday through Thursday)
Issued at 231 PM CDT Thu Jul 13 2023
-Smoke from wildfires may impact the region with airmass change
behind the frontal boundary late Friday into the weekend.
-Another batch of showers or storms are anticipated near the middle
of next week as a stronger wave crosses the region. Predictability
for potential severe weather is low, but general thunder can be
expected at this time.
For Saturday into Sunday: Northwest flow aloft will be the main
feature to start the period as the upper level low remains
entrenched near Hudson Bay. Expect some impulses to propagate
through the flow, but rain chances will remain minimal, except near
the Lake of the Woods region of Minnesota.
By Tuesday, the low finally begins to push east as a vigorous short
wave transits the ridge axis flattening it out. The accompanying
surface system will begin crossing the region, and return flow will
help increase low level moisture ahead of the system. Expect
sufficient dynamics in place to help trigger showers and storms
across the region. As the system exits across the Great Lakes, the
upper ridge maintains its relative strength keeping high
temperatures in the upper 70s to low 80s through the end of the
period. Otherwise, as upper level disturbance propagate through the
flow, precipitation chances continue through the end of the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 642 PM CDT Thu Jul 13 2023
VFR conditions are forecast throughout the TAF period, with some
scattered thunderstorms moving through portions of northwest and
west-central Minnesota through 01 UTC. While storms are likely,
currently not expecting any impacts to TAFs, namely KBJI. Winds
will remain light, under 10 kt, through 15 UTC before they pick up
out of the northwest to around 10 to 20 kt, perhaps gusting a
little higher through the afternoon Friday.
Smoke is also filtering into the area this evening through
tomorrow. While initially staying aloft, there is a medium to high
chance for smoke at the surface during the day Friday, likely
impacting vsby. The degree of vsby reductions is low in
confidence.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...CJ
SHORT TERM...JR
LONG TERM...Hopkins
AVIATION...CJ
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
636 PM CDT Thu Jul 13 2023
...Aviation Update...
.DISCUSSION...(This evening through Thursday)
Issued at 221 PM CDT Thu Jul 13 2023
Key Messages:
* Thunderstorms are expected to move into the area late this
evening with some risk of strong/severe storms.
* Next issue the lingering showers/storms during the day Friday.
* And, in general, the weekend weather looks drier though may not
be completely dry, and that seems to be the trend going into
next week.
Showers and scattered thunderstorms have hung around all day
across south central Nebraska mostly, but also at times north
central Kansas. The trend is waning now as expected, but the
after effects are a slightly more stable air mass across the
forecast along with more stable mid-level lapse rates due
to the cloud cover. Isolated showers will gradually wrap up
the next couple hours, and with the more stable air mass
in place, that should lead to a few hours of quiet weather
through early evening.
Eventually that will change as by late evening thunderstorms
in northwest Nebraska edge southeast into south central Nebraska,
and eventually north central Kansas, most likely after midnight.
The storms are firing in the northwest flow and will feed into
a low level jet developing across the area. Good wind shear
and acceptable instability could support a few severe
thunderstorms initially capable of producing quarter to golfball
size hail and wind gusts over 60 mph. This is very similar to
the northwest flow storms we have seen in the recent week to
10 days. The storms should weaken but still may produce locally
gusty winds (and some rain) as they traverse south into Kansas.
Friday is kind of a tough day to forecast with the potential
for another day of precipitation across much of the region
as a stronger wave aloft and surface front move through.
The front will eventually move through by mid-afternoon
but the time ahead of that could very well be mostly
wet, in terms of pretty widespread showers and scattered
thunderstorms. The potentially exists for the locally
beneficial rainfall with "limited " severe risk. The severe risk
is mostly confined to north central Kansas in the afternoon if
instability can establish itself. All of the precipitation Friday
will eventually push south with only and isolated, brief storm
possible early Friday evening. Temperatures Friday could be
a bit high side some areas especially if precipitation lingers
longer into the day.
Beyond that, the area in general will be slowly rising
upper level heights and a slightly less active northwest
flow pattern. The weekend may not be completely dry but
less widespread precipitation for sure, especially Saturday,
which is dry, and even the Sunday rain chance is 20%
or less. Otherwise, we will see sort of standard summer
weather through next week, though not overly, and only
spotty storm chances when compared to recently.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 624 PM CDT Thu Jul 13 2023
The latest HRRR model seems to be handling the convection out to
the north and west of the area this evening the best so far. There
are expected to be a couple of rounds of showers and thunderstorms
this TAF period, the first of which should move across the area
late this evening into the overnight hours. There is uncertainty
for how long this round sticks around, but put in a period of VCTS
from 03-07Z at KEAR and 04-08Z for KGRI for now...I have a little
higher confidence in the start time than the end time for this
round. The second round is expected from around mid-morning to
around mid-afternoon...with VCTS in the TAFs for this timeframe Friday.
Some model guidance indicates MVFR or even IFR CIGS from shortly
before sunrise to early afternoon Friday, mainly associated with
the potential for heavier rain Friday morning, but confidence is
low...so left VFR CIGS for this TAF issuance.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...NOAA/NWS/Moritz
AVIATION...Hickford
Area Forecast Discussion
National Weather Service Green Bay WI
1056 PM CDT Thu Jul 13 2023
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Friday
Issued at 306 PM CDT Thu Jul 13 2023
The latest RAP analysis and satellite/radar imagery show Wisconsin
positioned beneath flattened upper troughing early this afternoon.
Weak low level warm advection is occurring across much of the
state, with a semblance of a surface trough extending northeast to
southwest along the MN-WI border. Instability west of this trough
is supporting scattered shower and thunderstorm development. High
resolution models indicate that a few of these showers and storms
will make a run at central WI late in the afternoon or early this
evening. Otherwise, not expecting shower development elsewhere
this afternoon as instability is very limited. Besides the storm
threat this afternoon, forecast concerns also include storm
potential late tonight into Friday.
Tonight...Things are not entirely clear how they will evolve. Although
the weak surface trough will remain over western WI at the start
of the evening, thinking thundershower potential will end by mid-
evening as the trough becomes less defined. The weakening trough
and growing nocturnal stability should then lead to a period of
clearing skies. Then attention turns to a shortwave trough
(currently approaching the US-Canadian border from North Dakota to
Minnesota) that will move across the region after midnight. The
latest guidance point towards isolated to scattered showers and
thunderstorms moving across northeast WI after 2 am. Elevated
instability of 200-400 j/kg could lead to small hail or brief
gusty winds, but no severe weather is expected.
Friday...Any showers and storms should exit the lakeshore by mid-
morning. With partial clearing, growing instability in the
may result in scattered thunderstorm development in the
afternoon. Guidance has a wide instability range in the afternoon,
that leads to below normal confidence for thunderstorm potential.
Think there is potential for a few strong storms if instability
in excess of 1000 j/kg can develop. Deep layer shear of 25-30 kts
could lead to a small hail/gusty wind threat. Warmer highs in the
low to mid 80s.
.LONG TERM...Friday Night Through Thursday
Issued at 306 PM CDT Thu Jul 13 2023
A period of unsettled weather is anticipated for the extended
period as a broad upper level low pressure system remains
stationed to our north through the middle of next week.
Friday night into Saturday...
Isolated shower and thunderstorms activity will be possible
already Friday afternoon, continuing on into the extended period
Friday night. Any storms that develop will rely on a combination
of temperature advection aloft, shortwave energy evident in the
500mb vorticity field, and instability at the surface. That said,
the first two are relatively unfocused in any one area and the
surface instability will be somewhat spotty. Only the NAM produces
impressive low level-lapse rates and surface instability, but this
is likely due to the forecast having dewpoints into the 70s, which
would likely require an unrealistic amount of moisture transport
during the day. All considered, would not expect severe storms
Friday night but there may yet be a window for a stronger storm or
two. Although some showers may stick around into the overnight
hours, any remaining convective strength will quickly diminish as
instability decreases overnight.
Rest of the forecast...
Much of the weekend and early next week will be fairly similar,
with mild to near seasonal temperatures and scattered
precipitation during the day. A quiet period Saturday morning will
give way to a few isolated scattered showers in the afternoon as
weak CAA comes in across the region. Any precipitation will likely
diminish again overnight before repeating on Sunday. The two days
of weak CAA over the weekend will gradually drop high temperatures
from the middle 70s to middle 80s on Saturday to the lower to
upper 70s on Monday. Quieter weather then follows for middle of
next week ans the upper low finally shifts enough northeastwards
to bring and end to the daily light precipitation.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1056 PM CDT Thu Jul 13 2023
VFR conditions will continue late this evening with with a mix of
clouds mainly between 3500-9000ft, with more clouds pushing in
from the west. Question for tonight will be if/where any fog/low
clouds will form and if any showers or storms will impact the TAF
sites. Models mixed on how things will play out, leading to fairly
low confidence. First area of showers and storms just missed
AUW/CWA, but now heading toward the Fox Valley and may briefly
impact ATW/GRB. Next area over western WI and will likely spread
across much of the area tonight, but may diminish as it approaches
eastern WI. Another area of northern MN might swing across
northern WI overnight as well. Most of Friday is looking dry, but
a spotty shower or storm can`t be ruled out. Isolated to scattered
showers and storms are expected Friday evening. Some fog is
possible again tonight into early Friday where skies remain clear
and winds die off, but increasing clouds will likely limit the fog
potential. Best chance will be in central or north central WI
if/when the large cloud area pushes to the east, but will hold
off any fog mention and monitor trends. Smoke, mainly aloft, will
become more apparent on Friday as it works in from the west.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM.....MPC
LONG TERM......Uhlmann
AVIATION.......Bersch
Area Forecast Discussion
National Weather Service Grand Rapids MI
1018 PM EDT Thu Jul 13 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 1018 PM EDT Thu Jul 13 2023
Have added some low (20-30) pops to the fcst very late tonight
mainly near/west of Highway 131. Rough extrapolation of the
convection currently over MN has it arriving at the Lk MI
shoreline shortly after 4 AM. While this activity will diminish to
some extent overnight with loss of the diurnal component, any
remaining convection could impact wrn Lwr MI by daybreak. Latest
NBM PoPs support this notion, and RAP guidance shows PWATs around
1.5" and MUCapes >1000 J/KG arriving around that same time.
Any shower activity that arrives very late tonight should perk up
again by mid/late morning as instability builds and it continues
floating slowly east. Or, new development will take place along
residual mid level feature or sfc trough. It remains questionable
though whether that occurs over the GRR CWFA on Friday or over
adjacent CWFAs, and if/how quick the sct`d storms become
strong/severe. There`s been several reports of large hail this
evening with the MN convection and the same corridor of 40 kt deep
layer shear will be overhead tomorrow, so it is something to
watch.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 332 PM EDT Thu Jul 13 2023
- Relatively quiet tonight
A weak ridge of surface high pressure will move across the Great
Lakes region tonight. This afternoons diurnal CU, and perhaps some
spotty late day showers, will diminish by early this evening. This
is expected to yield clear to partly cloudy skies with lows in the
50s. That said, a few showers may sneak back into far western Lower
Michigan late tonight, thanks to brisk 500 mb flow aloft and
southerly flow /moisture advection/ over upper MS valley and western
Great Lakes.
- Potential for severe storms returns Friday and Friday night
S/SW low level flow will continue to advect respectable moisture
across the region on Friday, in advance of surface trough moving
into the western Great Lakes. In addition to some spotty
/aforementioned/ morning showers, diurnal heating will support
additional showers/storms across the upper MS valley and Great Lakes
by afternoon. Timing and location of convective initiation is highly
uncertain, and models are offering a variety of solutions. Expect
scattered showers/storms areawide on Friday, with a potentially more
organized complex of storms Friday night, as upstream LLJ veers into
the region overnight.
Some of the storms both Friday afternoon and Friday night may become
severe...per SPC Day Two Marginal risk. NBM soundings reveal MLCAPEs
Friday afternoon in excess of 2.0k J/kg, and impressive 500 mb
westerly flow approaching 50 kts. In addition to wind, the presence
of mid level dry air on soundings suggests hail may a bigger threat
than with our most recent severe weather event.
.LONG TERM...(Saturday through Thursday)
Issued at 332 PM EDT Thu Jul 13 2023
- Periodic Thunderstorms Saturday into Sunday
Most of our region is included in the SPC Day 3 Marginal Risk
area, and areas east of I-69 are in the WPC Day 3 Excessive
Rainfall Outlook. Currently the greatest threat for severe weather
on Saturday is anticipated to be east of US 131 based on upper
level forcing and low level moisture advection.
Upper troughing continues on Saturday. At the upper jet level,
divergence is shown mainly east of US 131 from 12z-18z. Lower
down, a LLJ of 20-30 kts seems better aimed at SE Lower Michigan
especially through midday/early afternoon. As the day progresses
there is some low level speed convergence over our CWA which is
not ideal for severe weather. SB CAPE values do look impressive,
however, with both the ECMWF and GFS showing potential for over
2000 J/kg. Deep layer shear is not great at 25 kts or so. Thus, it
is a mixed bag for severe weather potential but enough there to
keep an eye on things both in terms of a large hail and locally
damaging wind threat (DCAPE up to around 1000 J/kg).
In terms of a heavy rainfall risk, there may be some swaths of
0.50"-1.00" with these storms, mainly east of US 131. PWATs are
shown to reach 1.50"-1.75" but steadily decrease after 18z. It
looks like the window of time for heavy rainfall may not be quite
large enough to create an areal flood risk, but will need to
monitor for any higher amounts that may creep up toward I-96 given
recent heavy rainfall there. The observed July rainfall percent
of normal near and north of I-96 is currently in the 200%-400%
range.
Precipitation should wind down late Saturday. By Sunday, an
impressive upper low will be diving south toward Lake Superior
with a mid level jet of 40-50 kts moving overhead especially late.
However, upper level jet forcing holds off until Sunday night.
Daytime instability looks questionable, and both the GFS and ECMWF
show PWAT values actually declining during the day to less than 1"
but rebounding slightly in the 00z-06z Monday time frame. The
current thinking is shower and thunderstorm coverage will be
relatively low on Sunday with perhaps a better chance for rain
Sunday night as a cold front pushes through.
- Dry Period Likely Monday into Tuesday, Rain Possible Midweek
Dry weather is favored early next week as upper troughing moves
out and some ridging tries to develop, albeit the end result may
be more of a zonal flow pattern by the middle of next week. Models
are favoring fairly vigorous LLJ development by early Wednesday
across the central Plains and Midwest, but too soon to tell if
this would begin impacting the Great Lakes, which could bring
additional storm chances by Wednesday or Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 810 PM EDT Thu Jul 13 2023
The sct`d tstms currently impacting srn WI and nrn IL are not
expected to impact srn Lwr MI so VFR weather continuing tonight.
Can`t totally rule out some local vsby reductions from shallow
fog later tonight/early Friday morning though.
Fcst confidence remains low on shower and tstm potential/coverage
later tonight and Friday. There is some suggestion in recent CAM
guidance that the activity currently in MN could make it into wrn
Lwr MI toward daybreak Friday (if it holds together that far).
Kept the VCSH remark after 12Z at MKG and GRR to account for this
possibility but would not completely rule out a risk of thunder
or earlier arrival of sct`d convection as RAP shows MUCapes over
1000 J/KG arriving from the west after 09Z Fri.
As far as any afternoon/diurnal convection on Friday, that should
be limited to mostly ern and far srn Lwr MI (away from the lake
shadow) and some of these storms could be strong. For now will
carry VCTS at LAN and JXN after 18Z Friday and try to fine tune in
later TAF issuances.
&&
.MARINE...
Issued at 332 PM EDT Thu Jul 13 2023
Waves will likely build into the 2-3 ft range near and north of
Grand Haven Friday and Saturday as southwest winds increase.
However, we`re not yet seeing any model guidance that suggests
winds will be high enough to generate higher wave heights at this
time.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...Meade
SHORT TERM...Smith
LONG TERM...Hoving
AVIATION...Meade
MARINE...Hoving
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
913 PM CDT Thu Jul 13 2023
.SYNOPSIS...
Issued at 912 PM CDT Thu Jul 13 2023
Temperatures continue to be typical for the middle of July, with
highs generally in the 80s. Friday will be the warmest with highs in
the low 90s and heat indices in the upper 90s. A couple fronts are
expected to pass through central and southeastern Illinois in the
next couple of days. Tomorrow brings potential for some stronger
showers and thunderstorms.
&&
.UPDATE...
Issued at 912 PM CDT Thu Jul 13 2023
Thunderstorms continue to settle southward toward Stark and
Marshall Counties as a convergent boundary weeks moving southward.
These look to enter the area just after 10 pm, and have sent
updates to reflect this. Models continue to weaken this storm over
the upcoming hours as instability wanes. Currently, however, the
main storm has intensified to severe levels to the north in Bureau
County. Otherwise, have updated cloud cover to match the
approaching storm, and lows tonight still look to reach the mid to
upper 60s overnight.
37
&&
.DISCUSSION...
Issued at 315 PM CDT Thu Jul 13 2023
For the remainder of today, skies will continue to be mostly to
partly cloudy. Winds should stay light and variable. Lows tonight
hang around in the 60s across the entire CWA. Tomorrow brings more
unsettled weather.
Taking a look over the 13.12z run of the CAMs, a widespread system
of showers and thunderstorms appears to develop between 18z and 20z
Friday afternoon. However, the location is iffy. The HRW FV3 depicts
the initiation of a complex of storms to be in more north-central
Illinois then generally moving east-southeast through the CWA. The
HRRR shows it developing in southeast Missouri then extending
northward as it progresses east. The NAM Nest is the most dramatic
of the CAMs. It is showing a squall-like situation that moves east-
southeast through the CWA a little later than the rest.
There should be sufficient instability and lift for these storms to
fire up. The HREF Grand Ensemble shows a 100% chance of exceeding
1000 J/kg SBCAPE and a 60-80% chance of exceeding 2000 J/kg SBCAPE
at 18z Friday. There will be a boundary draped over far southern
Illinois before moving gradually north and eastward. SBCIN values
appear to be fairly zero for much of central and southeastern
Illinois around 18z Friday. This set up is indicating a high CAPE,
low shear situation. Bulk 0-6km shear is minimal with some
pockets of near 45 kts scattered across the area through out the
afternoon. Currently, there a marginal risk from the SPC barely
within our southwestern Illinois counties. It would not be a
surprise if they decided to extend this risk further into the CWA
on the upcoming updates. Any storms that fire have the potential
to be on the strong side but whether or not they become severe is
still in question. Based on forecast soundings, storms could be
pulsey in nature with some strong winds. The soundings were
showing a somewhat inverted-v shape and some pretty steep low-
level lapse rates, with DCAPE values just over 1000 J/kg. These
signatures suggest downbursts may be possible tomorrow
afternoon/evening.
After Friday, there are chances for showers and thunderstorms daily
through the extended forecast. Friday will have highs in the low 90s
with some heat indices in the upper 90s. Otherwise, temperatures
will continue to be what you would expect for mid July. Highs
ranging in the 80s and lows in the upper 60s to low 70s throughout
the extended.
Delaney
&&
.AVIATION... (For the 00z TAFs through 00z Friday Evening)
Issued at 606 PM CDT Thu Jul 13 2023
VFR conditions likely for most of the forecast period. Isolated to
scattered TSRA possible after 18Z, however chances are too low and
timing/location too uncertain for explicit mention at this point.
Have included VCTS starting 21Z as thunderstorm activity looks to
be high enough by that point that impacts become possible across
the area, potentially including brief MVFR cigs/vsby and strong
gusty and variable winds. Winds generally light and variable
overnight, becoming S-SW 6-10 kts by 16Z.
37
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1150 PM EDT Thu Jul 13 2023
.UPDATE...
Issued at 1150 PM EDT THU JUL 13 2023
Just a quick update to the forecast to continue the shower and
storm chances through most of the night - especially east - per
the latest radar and CAMs trends. Did also include the current obs
and trends for the T/Td/Sky grids with this update. Also fine
tuned the fog potential based on where the rain occurred this
past evening. These adjustments have been sent to the NDFD and web
servers along with a freshening of the zones and SAFs.
UPDATE Issued at 745 PM EDT THU JUL 13 2023
23Z sfc analysis shows a cold front just north of eastern
Kentucky. This has helped to spawn numerous showers and storms
that briefly dampened northern parts of the JKL CWA. An outflow
from these earlier stronger storms is now clearing sinking south
just along and south of the I-64 corridor. This may yet be a
trigger mechanism for additional strong to severe storms but
likely isolated in nature as the instability is starting to wane
even as some better upper support starts to arrive from the west.
Additional strong storm cells are noted northwest and southwest
of Lexington and moving east with more outflow potential - as well
as a healthy cell working east of Pikeville. All other activity
south of the watch has been unable to sustain itself and likely
will have to wait until that upper support gets closer to kick off
any substantial cells. The latest HRRR suggest additional
activity remains possible in the south through the night with even
another batch perhaps kicking off nearer the front in the north
towards dawn. For that reason have kept storm chances high through
the night with some adjustments per the CAMs consensus and near
term radar trends. Otherwise, temperatures in the semi-rain cooled
areas of the far north are in the upper 70s while most of the
area reports mid 80s. Stick dewpoints remain, as well, generally
in the low to mid 70s. Meanwhile, winds outside of any storms, are
generally west southwest at 5 to 10 mph - but northerly just
behind that northern outflow boundary. In addition to the PoPs and
Wx updates for the rest of the night did also include the current
obs and trends for the T/Td/Sky grids. These gridded forecast
updates have been sent to the NDFD and web servers along with a
freshening of the zones, SAFS, and HWO.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 314 PM EDT THU JUL 13 2023
13/18z analysis depicts a surface front situated along and just
north of the Ohio River, with dewpoint temperatures well into the
lower to mid 70s to the south of the front over eastern Kentucky.
At 500 mb, west-southwest flow continues with increasing winds
from south to north across eastern Kentucky. West to west-
southwest flow mostly diminishes to 5 to 10 knots near the
surface. Water vapor and visible satellite also depict a low
pressure and upper disturbance moving east across the mid-
Mississippi River Valley heading in our general direction.
Moderate instability with little in the way of a capping mechanism
makes for an environment primed for strong to severe thunderstorms
this afternoon, especially with 30-40 kts of vertical wind shear
over our northern half of the forecast area. We have noted already
the presence of splitting thunderstorm cells over our far southern
counties indicative of weak rotation, but these cells have not
even been on the strong side.
The main issue as of mid-afternoon is the lack of a widespread
forcing for ascent mechanism, but this is likely to change as the
aforementioned upper disturbance and surface low begin to trek
along the surface front, and the surface front begins to move
south toward eastern Kentucky, which is likely to be more toward
this evening. Strong to severe storms to the north and west may
also produce outflows that could also initiate convective activity
during this time.
The severe threat should wane with the loss of daytime heating
this evening, but there will be a continued chance for showers and
thunderstorms through tonight and into the first half of Friday
before the surface front moves completely through the area. Though
the atmosphere will remain weakly stable, drier air moving into
the area through the afternoon into early evening warrants a
decreasing chance of showers and storms through the daytime hours.
For Friday night into Saturday morning, shower and thunderstorm
chances increase again through the night as an approaching
disturbance pushes a warm front across eastern Kentucky.
.LONG TERM...(Saturday through Thursday)
Issued at 248 PM EDT THU JUL 13 2023
Key Points:
* A few instances of excessive rainfall and severe weather are
possible on Saturday/Saturday evening with the passage of a cold
front/weak low pressure system.
* Another weak front brings a widespread rainfall threat Monday into
Tuesday.
* Popup showers or storms are a possibility on other days of the
period, though coverage is not expected to be as widespread.
* Temperatures will remain within a few degrees of seasonal norms
while humidity levels remain muggy.
Analysis: The 13/12z analysis 500H analysis shows an ~542 dam low
over northeast Manitoba at the start of the forecast period.
Shortwave troughing, embedded within the cyclonic flow around the
low, will be oriented roughly SW-NE from the Texarkana to Great
Lakes. This shortwave will be reflected at the surface by a cold
front. Meanwhile strong high pressure ridging, centered over
central California, will dominate the Southwest US.
Much of the guidance depicts a weak surface low riding along the
boundary across the Ohio River Valley on Saturday/Saturday evening.
PWATs climbing to around 2 inches ahead of the boundary poses some
concern for hydro issues if convection repeatedly impacts a given
location. Fortunately the system as a whole does appear progressive,
which should limit the flash flood potential. Shear and instability
look to remain fairly marginal, though a stray strong to severe
storm appears possible at a few locations.
Looking ahead to the new week, the aforementioned front drops south
of the forecast area Sunday with just some low end rain chances,
mostly near the Virgina border. The next upper level shortwave,
embedded in the cyclonic flow aloft, moves into the Ohio Valley on
Monday with another round of unsettled weather, likely persisting
into Tuesday. An associated cold front will likely wash out over
our area during this timeframe. By Wednesday and Thursday, the
upper low over central Canada will have weakened and shifted into
the eastern Canadian Arctic. This will open the door for the
steamy ridging over the Southwest US to expand across the Gulf
Coast States, which will place our region in the track of
potential ridge-riding MCSs.
Temperatures won`t stray far from seasonal norms, ranging primarily
in the 80s for daytime highs and in the 60s at night. Dew points
will remain at muggy levels.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 815 PM EDT THU JUL 13 2023
The current VFR conditions could deteriorate through the evening
as scattered to numerous showers and thunderstorms develop. This
activity will encompassing much of the rest of the TAF period but
be most prevalent for the first 6 to 12 hours. Expect reductions
as low as IFR/LIFR within heavier showers/storms. Fog is likely,
especially where rain occurs and where there is any brief partial
clearing - at least for the valleys. Even if/when precipitation
begins to clear the area towards Friday morning, MVFR CIGS are
likely to only slowly lift to VFR by afternoon. Another small
chance for storm will then be around for the first part of the
afternoon. Winds will mainly be light, generally from the west, at
around 5 kts - away from any storms.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...CMC
LONG TERM...GEERTSON
AVIATION...CMC/GREIF
Area Forecast Discussion
National Weather Service Louisville KY
828 PM EDT Thu Jul 13 2023
.Mesoscale Update...
Issued at 828 PM EDT Thu Jul 13 2023
With a weakening trend being observed in current shower/storm
activity and the environment trending toward more stable conditions
in the low levels, have gone ahead and cancelled the Severe
Thunderstorm Watch a little early. Isolated storms will be possible
for the next several hours where heavy rain and perhaps an
occasional strong gust of wind will be possible.
Issued at 617 PM EDT Thu Jul 13 2023
Storms this afternoon have struggled to maintain any sort of
intensity despite being in an environment with modest deep layer
shear (25-35kts) and instability (MLCAPE +1000J/KG). A couple
possible reasons for this are that SPC Mesoanalysis data shows a
minimum of values in mid-level lapse rates (~5.5 C) over the CWA and
forecast soundings show the potential for dry air entrainment of
convective updrafts above 700mb. The aforementioned reasons could be
inhibiting the development of more robust updrafts that would lead
to severe weather. The `bigger` threat so far today has been
nuisance flooding where storms have trained along outflow or other
mesoscale boundaries. Any flooding issues that develop today should
remain very isolated.
With that being said, while the severe threat seems to be low over
the next few hours, will still plan to let the Severe Thunderstorm
Watch ride a little longer in case there are a few storms that are
able to take advantage of the shear/instability.
&&
.Short Term...(This evening through Friday)
Issued at 315 PM EDT Thu Jul 13 2023
=== Severe Thunderstorm Watch in effect until 01z ===
Strong to severe storms are beginning to fire up just north of the
forecast area this afternoon, located along the sfc frontal
boundary. With day time heating pushing temperatures into the mid to
upper 80s and sfc dewpoints in the mid to upper 70s, we are able to
realize MLCAPE values exceeding 1500 J/kg, though there is even more
instability located over Northern KY. Overall low level shear is not
very high, with the greatest deep layer shear located across Ohio,
but roughly 30-35kts of effective bulk shear across the region.
Storms currently firing up along the boundary are located within a
deep moisture convergence zone, which is expected to sag south-
southeastward as the sfc boundary approaches the Ohio River vicinity
in the coming hours.
It`s possible to see scattered showers and storms across all of
central KY and southern IN through this evening, but the best
chances for any isolated to scattered severe storms will be for
portions of the Bluegrass and Northern KY, including the I-75
corridor and eastward. Model soundings continue to indicate rather
high DCAPEs, with values generally above 1000 J/kg, along with high
PWATs near the 90th percentile of sounding climatology. With any
severe storms that do develop, damaging wind gusts and small hail
will be the main threats. Weak low level shear and relatively
straight hodographs should help keep the tornado threat on the low
side, but it`s possible that any outflow boundary interaction with
sfc rooted storms could briefing increase the tornado potential.
Again, the overall tornado threat remains low.
Our severe weather potential will diminish by tonight as leftover
sfc heating depletes and the sfc front gets hung up along the Ohio
River. Clouds should linger across central KY tonight, but we may
see some better clearing north of the boundary due to weak
subsidence. This would ultimately lead to better radiational cooling
conditions, and possibly some patchy fog development. Temps will
remain rather mild overnight, with lows only dropping into low 70s.
Areas north of the boundary could get a few degrees cooler thanks to
the clearer skycover.
For tomorrow, the sfc boundary will be dissipating, leading to a
mostly dry day with zonal flow overhead. Expect another hot and
muggy day, with temps in the upper 80s and low 90s, and dewpoints in
the low 70s. This will result in another day with heat indices in
the mid to upper 90s, potentially around 100F.
.Long Term...(Friday night through Thursday)
Issued at 245 PM EDT Thu Jul 13 2023
=========================================
Synoptic Overview
=========================================
The upper level pattern will start off the period with a heat ridge
across the desert southwest with very broad trough over eastern US.
The flow over the Ohio Valley initially will be zonal with
perturbations moving within the flow. By the late weekend, the ridge
out across the west will increase in amplitude with some model
solutions showing heights breaching 600 dm. Meanwhile, a broad
trough axis will be in place across the eastern third of the nation,
including the Ohio Valley for the first part of the new work week.
Perturbations moving through the base of the trough will bring
periods of unsettled weather the area. By mid-late week, model data
suggests that the ridge out west will slowly build eastward. Our
area will be on the northeastern periphery and may have some MCSs to
deal with. While earlier runs suggested that the ridge would
continue to build east toward the late week period, there is now an
emerging trend that the ridge may retrograde westward again keeping
our area in a northwest flow aloft with the potential for cooler
than normal temperatures along with above average rainfall.
=========================================
Meteorological Discussion and
Sensible Weather Impacts
=========================================
Friday Night through Sunday Night...
Somewhat of an uncertain forecast for Friday evening as to whether
we`ll see widespread convection moving through the region. The vast
majority of the guidance is generally dry Friday evening, though the
HRRR solutions brought a weakening MCS through the area in the
evening. The majority of the models seem to be focusing more on
convection moving in from the west late Friday night ahead of an
approaching upper level trough and cold front. Overall, the best
chances of storms Friday night would be in areas west of I-65. Lows
will be in upper 60s to the lower 70s.
MCS activity looks to move through the region Saturday morning and
into Saturday afternoon. Blended PoP guidance here is pretty high
and given the ensemble solutions, this seems reasonable as a large
number of members agree with some sort of MCS rolling through. Heavy
rainfall, gusty winds, and lightning would be possible with this
activity. Additional convective development may occur in the
afternoon in the wake of the morning convection, if the atmosphere
can recover sufficiently. Given anticipated clouds and
precipitation, have lowered Saturday`s temps down into the low-mid
80s for 80s. With the upper level wave and front to our east,
Saturday night looks to be trending much drier now with lows in the
upper 60s.
For Sunday, generally dry conditions are expected across the region.
We`ll have some chance PoPs in the early morning period across the
east, but I suspect we`ll be able to drop those in later forecasts.
Not much in the way of cooler conditions are expected here as
afternoon highs will warm into the 84-89 degree range. Lows Sunday
night will dip back into the upper 60s and lower 70s.
Monday through Thursday...
As mentioned above, an upper level trough axis is forecast to remain
centered across the eastern third of the country during this time
frame. Multiple perturbations will move through the base of the
trough resulting in periods of unsettled weather. For now, a
climatological 30-40 PoP for each afternoon will suffice. By mid-
week, the upper level ridge will attempt to expand eastward. This
will push the storm track a little further north. However,
perturbations rounding the ridge will likely result in multiple MCSs
developing and rolling southeastward. Some of these could impact
our region in the Wed/Thu time frame. Daytime highs will average in
the mid-upper 80s with overnight lows in the upper 60s to the lower
70s.
=========================================
Forecast Confidence
=========================================
In general terms, confidence in the synoptic scale evolution across
the CONUS remains medium-high through the period. Lower confidence
exists on the timing and coverage of convective systems moving
through the area. Medium-high confidence exists with respect to
temperatures through the period.
&&
.Aviation...(00Z TAF Issuance)
Issued at 701 PM EDT Thu Jul 13 2023
Scattered showers and storms are dwindling down in coverage this
evening and will continue to do so through the overnight hours. Best
odds for a TAF site to see a shower/storm is LEX near the start of
the forecast period; otherwise, chances are too unlikely or low to
mention in other spots. With increased low level moisture in the
region and the potential to clear out some behind the
showers/storms, patchy fog may develop at some TAF sites toward
dawn.
Any morning fog should quickly burn off and give way to VFR
conditions the remainder of the day along with dry conditions.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Mesoscale...DM
Short Term...CJP
Long Term...MJ
Aviation...DM
Area Forecast Discussion
National Weather Service Nashville TN
713 PM CDT Thu Jul 13 2023
...New UPDATE...
.UPDATE...
Issued at 709 PM CDT Thu Jul 13 2023
Latest radar imagery shows little activity across Middle
Tennessee this evening with just a few tiny showers in Davidson
and Williamson Counties, along with a few showers and storms west
and east of our forecast area. Newest HRRR runs are very
aggressive in developing widespread showers and storms this
evening, but this seems unreasonable based on radar and the latest
visible satellite imagery showing sparse cumulus. Therefore have
lowered pops significantly for the evening and overnight periods
to just slight to low chance. Rest of forecast remains on track
with a warm and very humid night on tap.
&&
.SHORT TERM...
(This afternoon through Friday Night)
Issued at 308 PM CDT Thu Jul 13 2023
Satellite shows a few weak outflow boundaries throughout the area
and we are seeing a few widely scattered showers and
thunderstorms but overall the radar is quiet. These outflow
boundaries don`t have a ton of lift with them and the cloud cover
today has helped to limit convection. We still could see a few
cells go up this afternoon into the evening. We will also see
scattered thunderstorms develop along a cold front/stationary
front to our north. These will push south this evening and some
could reach our area but once again forcing doesn`t look great
with it. Soundings are not overly impressive and shear is on the
low side. This will limit strong storm potential but still can`t
rule out gusty winds and heavy rain with any of the stronger
looking cells.
A few showers and thunderstorms may linger into the overnight but
it will be mainly dry, humid, and mild. Upper level pattern
Friday will be zonal over us with a strong upper level low digging
over Canada. This will provide little lift for us but a decaying
thunderstorm complex to our west will push east in the afternoon
and evening and should provide some lift for scattered
thunderstorms. Once again it`s uncertain how much lift it will
provide. Soundings tomorrow will be similar to today, not overly
impressive with marginal lapse rates and shear. Still can`t rule
out isolated stronger cells with a wind and heavy rain threat.
The thunderstorm threat may linger into the overnight mainly over
the plateau. Cloud cover has held temps down some today and that
could be an issue again tomorrow but nevertheless we will still
be looking at heat index values well into the 90s given the dew
points.
&&
.LONG TERM...
(Saturday through next Thursday)
Issued at 308 PM CDT Thu Jul 13 2023
Saturday we are looking to be under an upper-level trough with
significant rain chances Saturday morning into the early afternoon.
Max ensemble precipitation values for early Saturday go up to 0.2
inches with moderate CAPE giving way to the possibility of a couple
of strong storms with gusty winds and heavy showers. There is some
disagreement for Saturday evening showers, though most model QPFs
are lighter. The biggest talking point of next week will be the
rising heat as an upper-level ridge builds over the central plains
and starts moving towards the east. We will get a small drop in
dewpoints for Monday with dry air aloft. We start the week with
lows in mid 70s and highs in the mid 90s which steadily climb to
the upper 90s by the mid-week according to the NBM. There is
another synoptic low pressure system over in Northwestern Canada
that will begin to flatten the ridge pattern overhead around
Wednesday allowing for more short waves to predominate the upper
level flow. This will give us forcing to provide "popcorn" showers
and thunderstorms late next week. With significant day-time
heating and dewpoints in the 60s-70s, models show that there might
be enough instability mid-week for some stronger storms to pop-up
with gusty winds and localized downpours.
&&
.AVIATION...
(00Z TAFS)
Issued at 645 PM CDT Thu Jul 13 2023
VFR conditions expected for the most part. High resolution models
are hinting at some lower VIS and CIGs especially for the plateau
and near the river at CKV towards the morning hours. At this time
will go with MVFR...however if the models are correct this could
go down to IFR around sunrise and just afterwards.
During the next few hours the showers and thunderstorms in
southern KY should continue to dissipate. Have removed the VCTS
and TSRA from CSV and SRB. Will keep an eye on this just in case.
Otherwise some high clouds expected with westerly winds 10 kts or
less through the TAF period. The plateau could see some mid level
CU tomorrow afternoon. Not expecting and TSRA in or around the TAF
sites.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 75 94 74 90 / 30 20 60 80
Clarksville 73 95 73 90 / 20 20 60 80
Crossville 68 85 67 82 / 30 20 60 90
Columbia 73 92 73 90 / 30 30 50 80
Cookeville 70 88 70 84 / 30 20 60 90
Jamestown 69 85 68 82 / 30 20 60 90
Lawrenceburg 73 90 72 89 / 30 30 50 80
Murfreesboro 73 93 72 90 / 30 20 50 80
Waverly 72 92 71 89 / 30 30 60 70
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Shamburger
SHORT TERM...Mueller
LONG TERM....Mueller
AVIATION.....12
Area Forecast Discussion
National Weather Service Raleigh NC
840 PM EDT Thu Jul 13 2023
.SYNOPSIS...
A lee surface trough will extend across the Piedmont of the southern
middle Atlantic and Carolinas through the weekend.
&&
.NEAR TERM /TONIGHT/...
As of 840 PM Thursday...
A few isolated storms moving across the NW Piedmont this evening
will continue with isolated showers over the Sandhills later
tonight. Shortwave energy will proceed to move across the Mid-
Atlantic region bringing ongoing chance of isolated showers and
storms through the overnight and early morning hours.
Previous Discussion as of 239 PM Thursday...Dry weather continues
this afternoon across central NC as the cu field continues to grow.
We`ve seen modestly unstable conditions across our central to
western Piedmont where dew points have mixed out into the upper 60s.
Further south and east, better instability has developed as dew
points remain in the lower 70s. So far today, convection has been
confined to the coast (sea-breeze-induced) and over the high terrain
and foothills of SC (close proximity to the sfc trough). Guidance
continues to suggest that isolated to scattered showers/storms will
develop along the sfc trough over the NC foothills the next few
hours and trickle into our western zones through this evening.
However, this activity should fade with eastward extent into
tonight.
As we turn to the overnight hours, there is still some uncertainty
wrt to how far upstream convection over VA will extend southward
into our area. However, latest runs of the HRRR (as well as the 12Z
NAM nest) have backed off on driving this upstream convection
through our area until at least 12Z. Thus, have trended the
overnight POPs down some since this morning (still highest across
the north) for the 06 to 12Z timeframe. Still, this may have to be
updated as things evolve over the next several hours. Overall
though, linger elevated instability (with better moisture to play
with), will promote at least a slight chance for thunderstorms
overnight if convection ends up trickling into our area. Otherwise,
warm and muggy overnight lows in the mid 70s are expected.
&&
.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 239 PM Thursday...
Coverage on Friday will largely depend on the evolution of
upstream convection over VA in the pre-dawn hours Friday morning.
The latest 12Z HREF ensemble mean guidance sags this convection into
our northern/central areas by ~07Z to 12Z, decaying with southward
extent through late Friday morning. This scenario would justify
higher POPs in the 12Z to 18Z timeframe across the far north.
However, there are a few individual HREF members (e.g. 12Z NAM nest,
and to some extent the latest HRRR runs (15, 16, 17Z)) that don`t
bring any convection into our area until much later in the day.
Regardless of which scenario plays out, there will be plenty of
anomalous moisture for convection to tap into during the day/evening
hours. Thus, any heavier rain could pose a threat for isolated
instances of flash flooding in urban and low level areas (WPC has
introduced a slight risk for excessive rainfall from generally
Raleigh northeastward from 12Z Friday to 12Z Saturday; elsewhere
marginal).
Decided to lean on the HREF mean for POPs, with chance POPs early
Friday sagging southward with time through 18Z. A re-generation of
showers and storms along early morning outflow boundaries then
appears possible Friday afternoon/evening supportive of higher POPs
in this timeframe. Pinpointing exactly where the highest POPs is
difficult given it`ll be largely dependent on where the outflow
boundaries set up. However, most CAM guidance hints at perhaps
slightly higher coverage across the south and east Friday
afternoon/evening. Decided to trend my forecast that way as a
result. However, this may need to be modified later tonight from
future shifts depending on the eventual evolution of upstream
convection later tonight. Any lingering convection into the
overnight period should subside through 12Z Saturday.
High temps Friday may be a tad lower given the cloudiness and rain
peaking in the upper 80s to lower 90s. Overnight lows in the lower
to mid 70s are expected.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 345 PM Wednesday...
This time frame starts with a continuation of high shower/storm
chances, then pops start a daily downturn, with good chances Sun
dwindling to isolated by the middle of next week. Persistent above
normal temps and high humidity will pose increasing concern through
next week, with daily highs generally in the upper 80s to mid 90s
(and isolated upper 90s mid week) and lows in the upper 60s to mid
70s. Tue through Thu are expected to be the hottest days.
Sat-Sun: Friday`s high pops continue through much of the weekend,
highest in the afternoon/evening. The strong/hot Desert Southwest
ridge centered over CA/NV/AZ will further amplify, while the large
cyclone centered over NE MB, and covering a large part of central
Canada and the Upper Midwest, drops S and SE toward Lk Superior over
the weekend. The blocking pattern persist across much of NOAM and
Northeast Pacific, with a closed low off BC and an omega ridge (an
extension of the Desert Southwest ridge) over BC/AB/NT. Weak surface
troughing should persist over the W Piedmont of NC, keeping us
within a warm and stagnant air mass and a light S-SW surface flow.
Our mid level flow will remain rather modest, mostly staying around
15-20 kts, which will limit organization and strength of any
convection. But with the gradual backing of our mid level flow,
periodic jetlets of 850 mb SW flow to around 20 kts (mainly over our
E sections Sun ahead of a passing H8 wave), forecast MUCAPE peaking
at 1500-2500 J/kg each day, passage of weak mid level perturbations
across the area, and forecast PW near or over 2" (areawide Sat,
mainly E Sun) all support daily above-climo shower/storm chances.
Will carry likely pops areawide Sat, then good chance W and likely E
on Sun as some lower PW spreads into W sections behind the passing
H8 trough. With high PW Sat and a warm column with light steering
flow, meandering storm clusters may produce heavy rainfall.
Low level thicknesses will stay above normal, favoring highs roughly
a category above normal, and the tangible impacts of this become
amplified given that we`re nearing the climatological hottest part
of the year.
Mon-Thu: The blocked flow over Canada will mostly hold over NOAM
through next week. The E Canada upper low will fill a bit as it
tracks N through Quebec, while the closed low off BC holds largely
in place, as does the blocking W/central Canada ridge, although we
do see a piece of the offshore low undercut the rex block, tracking
along the US border before dissipating over the Great Lakes. There
is still little change in our surface pattern, with weak surface
troughing holding over the Piedmont and stagnant air/light flow over
central NC. PWs are projected to drop slightly to 1.25-1.75" W to E
Mon through Wed, although some rebound back to around 2" is forecast
by the op GFS/ECMWF by Thu. The Canada blocking will facilitate an
eastward expansion and spreading of the hot Southwest ridge early to
mid week toward the Gulf States and Southeast, which will result in
well above normal thicknesses, an overall downturn in cloud
coverage, and a dip in pops back to more seasonable isolated to
scattered coverage each day. As low level humidity builds and with
expected lower sky cover and lighter surface winds, we could have
several successive days of 100-109F heat index over much of central
NC (at least the Hwy 1 eastward sections). Several days of a heat
advisory (at least) are possible for a portion of central NC in this
pattern. Highs should be solidly in the low-mid (and possibly upper)
90s each day. -GIH
&&
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 815 PM Thursday...
Primarily VFR conditions are expected through tonight, followed by a
risk of IFR-MVFR ceilings, owing to an increasingly moist/humid low-
level airmass enveloping the Carolinas, Fri morning. The best chance
of a shower/storm will be from ongoing, scattered cells near and
just west of INT/GSO this evening. Thereafter, the principle feature
of interest will be a composite outflow boundary stretching this
evening from s-cntl VA wwd across the lwr OH Valley. Some forecast
guidance suggests this boundary and accompanying showers/storms will
settle as far south as the nrn NC Piedmont, including at all cntl NC
TAF sites except FAY, overnight. Such a solution would also favor a
higher probability and longer duration of the aforementioned low
ceilings in the rain-cooled air to its north early Fri.
Observational trends do not depict much southward progress during
the past several hours, however, so it seems that the boundary and
accompanying convection may instead hold to the north of cntl NC. As
such, the 00Z TAFs were sent with a more optimistic, lack of
overnight convection in cntl NC. Additional, mainly scattered
convection will otherwise develop with diurnal heating Fri afternoon.
Outlook: Seasonably hot and humid, mid-July conditions will favor a
diurnal chance of (morning) stratus and (afternoon) convection
through early next week.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...CA/Luchetti
SHORT TERM...Luchetti
LONG TERM...Hartfield
AVIATION...MWS
Area Forecast Discussion
National Weather Service Blacksburg VA
933 PM EDT Thu Jul 13 2023
.SYNOPSIS...
The region has evolved into an active weather pattern, which
will remain in place for much of the next 7 days. A frontal
boundary will sag through the area over the next couple of days.
However, more importantly is a deepening upper trough anchored
over the Great Lakes that will send a series of disturbances
through the area over the next several days. Temperatures will
be held down by cloud cover remaining near to slightly below
seasonal normals for mid-July.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 930 PM EDT Thursday...
Severe weather threat slowly diminishing. Severe Thunderstorm
Watch has expired as of 900 PM EDT. No additional watches
expected per SPC. Showers and thunderstorms will continue
overnight along the slowly southward moving front. Main concern
going forward will be heavy rain and flooding. Flash flooding
ongoing in the Lynchburg area at this time.
As of 800 PM EDT Thursday...
Severe Thunderstorm Threat Continues Through the Evening...
Very active severe weather afternoon/evening across the forecast
area with over a dozen SVRs and one FFW issued. While the severe
threat will diminish with the loss of daytime heating and as the
upper short wave responsible for the widespread convection moves
on, a lingering frontal system, abundant moisture, and a
deepening trough over the Great Lakes will continue the threat
for scattered showers and isolated thunderstorms through the
night. Activity will increase in coverage and intensity once
again Friday afternoon, especially across the southeast half of
the CWA. A few of those thunderstorms could also be strong to
severe, but upper-level dynamics and instability will be less
than that observed today. Rainfall will become an increasing
problem as the days pass with repeated rainfall.
Pops and temperatures have been adjusted accordingly to reflect
current trends. Max temperatures for Friday will be lower across
the board because of clouds and showers/thunderstorms.
As of 100 PM EDT Thursday...
Isolated severe storms possible later this afternoon into
tonight...
Main focus continues to be the threat of strong to isolated severe
convective development later this afternoon into tonight as an upper
disturbance pushes eastward across the TN and Ohio valleys ahead of
a frontal boundary. CAMs lack some consensus on coverage though
mostly agree on some initial triggering along the Blue Ridge earlier
this afternoon, which are starting to see signs of in recent radar
analysis, then a bit more organized cluster of storms by this
evening into the overnight. RAP progged SBCAPE looks to be in the
2500-3000 J/kg range for much of the area and with marginal deep
layer bulk shear of about 30-35 kts some isolated severe development
is possible with the main threat of strong to damaging wind.
Downdrafts could be aided by hydrometeor loading with increasing
PWATs of 1.75-2 inches as moisture advection kicks in from the SW.
Heavy rainfall from efficient precip producers and an isolated
flooding threat will also be possible especially if there are some
training storms which may occur given not much directional shear.
Some patchy or areas of fog may develop late tonight into Friday
morning especially where any low level moisture is increased from
what convection occurs late today/tonight and if winds lax.
Friday afternoon could have a bit more instability present, though
the bulk shear looks a bit less or more confined to the eastern CWA.
Will advertise some decent chance to likely pops for scattered
shower and storm potential with a few strong to severe possible but
not as great of a threat as today.
Forecast confidence is medium to high.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 100 PM EDT Thursday...
Scattered showers and storms possible for the weekend
with the greater chance Saturday...
We should see a diminishing trend to convection Friday night as the
front and moisture axis pushes southward, though this axis looks to
have a northward surge ahead of the next amplifying shortwave set to
influence the area Saturday afternoon into night. Have increasing
pops accordingly. As the moisture and instability could be more
limited for Sunday with the progression of the cold front, the upper
trough axis remains west of the area so we could still have weak
upper forcing to aid any diurnally driven convection and am
advertising mainly general chance pops.
Max temps for the weekend look to be generally near climo norms,
then a bit cooler in the mountains for Sunday as the aforementioned
front pushes eastward.
Forecast confidence is high.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
The weather pattern favors mainly afternoon and evening
scattered showers and thunderstorms through the weekend. Fog
development is also possible each morning through the weekend
and into early next week.
As of 1130 AM EDT Thursday...
Confidence is moderate for increasing chances of showers and
thunderstorms towards the middle of the week.
The overall synoptic pattern throughout this week will feature a
large upper level ridge in the southwestern United States and
ongoing troughs moving across southeastern Canada and the Great
Lakes. The Mid Atlantic will thus reside in a persistent west to
northwest flow aloft. With a cold front departing offshore on
Monday, that day appears to be the driest of this week as weak high
pressure crosses the Appalachian Mountains. However, another cold
front should approach by Tuesday to bring increasing chances of
showers and thunderstorms. The frontal boundary could stall across
southwest Virginia on Wednesday and linger into Thursday, which
would keep conditions unsettled with daily chances of
convection.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 800 PM EDT Thursday...
Synopsis: Weak frontal boundary will sag southward through the
area and linger for the next several days. Deepening upper
trough over the Great Lakes will dominate the area for the next
several days. Expect scattered to numerous showers and
thunderstorms, peaking in intensity and coverage during the
afternoon/evening hours. Activity will favor the north/west
tonight and more of the south/east Friday.
Ceilings...Mostly MVFR ceilings through the period with periods
of IFR-LIFR during the late night/early morning hours in dense
fog. Brief IFR conditions also possible in heavier
thunderstorms, mainly until 04Z tonight and after 17Z Friday.
Visibility...Mostly VFR except in late night dense fog,
especially in areas of wet ground/substantial rainfall Thursday
resulting in LIFR FG in the 08Z-14Z time frame Friday morning.
Brief MVFR-IFR conditions possible in heavier
showers/thunderstorms and higher elevations above 3000 ft.
tonight/Friday morning.
Winds...Highly variable through the period, favoring WSW 5-7kts
in areas outside thunderstorms and especially across the
Piedmont.
/Confidence Levels in Forecast Parameters/
- Moderate Confidence in Ceilings,
- Moderate Confidence in Visibilities,
- Low Confidence in Wind Direction and Speed.
EXTENDED AVIATION OUTLOOK...
Unsettled and active weather pattern will remain in place
through the period. Scattered to numerous showers/thunderstorms
expected each afternoon/evening with scattered showers overnight
hours. Late night and early morning fog likely in many areas
with high humidity and wet ground conditions.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...BMG/AB
NEAR TERM...RAB/AB
SHORT TERM...AB
LONG TERM...PW
AVIATION...RAB
Area Forecast Discussion
National Weather Service Springfield MO
627 PM CDT Thu Jul 13 2023
Key Messages:
1. Heat Advisory this afternoon for locations along and south of
a Fort Scott, Kansas to Marshfield, Missouri line.
2. Potential for additional thunderstorms tonight into Saturday
morning including a marginal to slight risk for severe
thunderstorms and flash flooding.
3. Slightly cooler from Friday into early next week with hot
conditions returning by the middle of next week.
.SHORT TERM...(This evening through Friday)
Issued at 236 PM CDT Thu Jul 13 2023
Synoptic Scale Pattern and Current Conditions: An upper level west-
northwest flow aloft remains established from the northern Rockies
through the Ohio Valley. There are likely multiple weak
perturbations within the flow, however they are hard to discern on
the three water vapor channels. This alone is a forecast
challenge when it comes to the potential for convection over the
next 24- hours.
At the surface, a frontal boundary has stalled out fairly close to
the I-44 corridor from southwest Oklahoma through the St. Louis
metro. Surface temperatures and dew points are fairly homogeneous on
either side of the front, with most areas seeing temperatures in the
lower and middle 90s as of mid-afternoon. Dew points are running
in the lower to middle 70s. This has resulted in heat indices
ranging from 96 to 106 degrees.
The highest temperatures and heat indices are occurring generally
south of a Fort Scott, Kansas to Marshfield, Missouri line. We
recently expanded the Heat Advisory northward another tier of
counties with it now including the Springfield area. The advisory
goes until 7 PM.
Radar across the Missouri Ozarks is fairly quiet this afternoon with
capping holding down convection, at least through the 3 PM hour.
Potential for Storms from Late this Afternoon into Tonight: There
appear to be two different opportunities for showers and
thunderstorms, primarily from extreme southeast Kansas into southern
Missouri. The first opportunity will come from late this afternoon
into early this evening as convective inhibition is eroded south of
the Highway 60 corridor. Beyond weak convergence along the front, we
are struggling to find any other notable features which would aid in
convective initiation.
With that being said, we will carry 10-20% PoPs for this potential.
If a storm can manage to develop, it will do so in a highly
unstable environment with short term ensembles progging MLCAPEs of
2500-3000 J/kg into early evening. Deep layer shear will be
marginal with 0-6 km bulk shear magnitudes of 25-30 knots. This
would support a conditional severe threat with hail to the size of
half dollars and locally damaging wind gusts being the primary
potential severe weather hazards.
The second opportunity for storms will then come later tonight,
likely after midnight. Short term ensembles are in good agreement
that a low-level jet will strengthen and nose into southeastern
Kansas and eastern Oklahoma in the 2-6 AM time frame. Isentropic
upglide will correspondingly develop in a corridor from southeastern
Kansas through southwestern Missouri.
The question then becomes whether or not this lift will be strong
enough to erode convective inhibition in the 850 to 700 mb layer.
Some members of the 12Z HREF do indeed break out elevated convection
in this corridor, while others do not. The last several runs of the
RAP have oscillated back and forth regarding the potential for
elevated convection.
Another fly in the ointment will be the potential for MCS
activity rolling off the central High Plains later this evening
and then moving across portions of southern Kansas and northern
Oklahoma late tonight. Again, some CAMs show this scenario while
others do not. If the MCS does indeed develop, it could glance
portions of southeast Kansas and southwest Missouri. It may also
dive southwest of the area and effectively cut off that low-level
jet and eventually thwart that potential for elevated convection.
With all of these potential scenarios under consideration, we
have gone with 40-70% PoPs across primarily southwest Missouri
and extreme southeast Kansas for late tonight. These PoPs will
likely have to be raised/lowered accordingly as we get a better
feel this evening for how this complicated setup will transpire.
There will again be a conditional Marginal Risk for severe storms
late tonight. If the elevated scenario comes to fruition on the nose
of the low-level jet, hail to the size of quarters would be the
primary potential severe weather hazard. If we get glanced by an
MCS, damaging wind gusts to 60 mph would be the primary hazard.
We will also have to watch for a localized flash flooding threat to
emerge over extreme southwestern Missouri late tonight. Some
locations received 2-3" of rainfall last night across McDonald
County. The 12Z HREF localized probability-matched mean product
shows a few pockets of 2-4" rainfall amounts from southeastern
Kansas through southwestern Missouri into northwest Arkansas late
tonight. If these amounts pan out over areas that saw heavy
rainfall last night, localized flash flooding would become likely.
Potential for Thunderstorms Friday: How the overnight situation
transpires will have big impacts on sensible weather for Friday.
If an MCS does indeed develop and glances southwestern Missouri,
we may see the remnants of this MCS impact southern Missouri well
into the morning. That could include showers/ thunderstorms and
abundant cloud cover. The 12Z HRW NSSL and ARW both depict this
general scenario, as do recent runs of the HRRR.
In contrast, the NAM Nest is farther south with the MCS activity,
which is common with this particular model. The operational NAM
and GFS are also drier for Friday morning. With all of this said,
we have maintained a middle of the road approach with PoPs Friday
morning with most areas in the 40-60% range. Again, adjustments
will be likely as we get a better feel for how this will play out.
Friday afternoon should then be drier across extreme southeastern
Kansas and western Missouri, especially if the atmosphere is worked
over by morning activity. The eastern Ozarks may still be in line
for scattered showers and thunderstorms, especially if there is a
remnant MCV in the area.
Due to the uncertainties in precipitation and cloud coverage, there
are high NBM spreads in potential high temperatures for Friday. If
rain and clouds are more prevalent, highs may only warm into the
lower and middle 80s. Less in the way of rain and clouds will
support highs in the lower to middle 90s. We have gone with NBM
numbers for now which is right around the 50th percentile (upper 80s
to lower 90s).
.LONG TERM...(Friday Night through Thursday)
Issued at 236 PM CDT Thu Jul 13 2023
Thunderstorm Potential Friday Night into Saturday Morning: Short
term ensembles are in good agreement that a more pronounced short
wave trough will move southeastward across the northern and
central Plains. The 500 mb feature is forecast to reach the Upper
and Middle Mississippi River Valley by 12Z on Saturday. As this
occurs, a cold front will drive southeast through the area.
Confidence is therefore increasing in yet another round of
thunderstorms from later Friday night into Saturday morning.
Inspection of SREF data reveals 90%+ probabilities of at least
1000 J/kg of MUCAPE with 50-70% probabilities of greater than 2000
J/kg of MUCAPE, especially before 06Z Saturday. With 0-6 km bulk
shear magnitudes progged to be around 40 knots, these storms will
have at least some potential to be severe. The SPC Day 2 Outlook
does have the area painted in a Marginal to Slight Risk for severe
storms. Given that a linear MCS would be the likely storm mode,
damaging winds would be the primary potential severe weather
hazard.
The threat for flash flooding will also exist with this round of
storms as PWATs are again forecast to be in the 1.8" to 2.0" range.
Thus, stronger storms will contain torrential rainfall. Given
that some locations will be saturated from previous rounds of
storms, flash flooding will be a potential hazard. WPC has the
area in a Slight Risk for excessive rainfall.
Quiet from Later Saturday into Sunday: The upper level pattern will
briefly become more amplified as strong short wave energy digs
southeast into the Great Lakes. This will put the region in a
northwest flow aloft with that surface front likely dropping south
of the I-40 corridor by Sunday morning. Dry weather is therefore
expected with temperatures returning to near normal values. The NBM
is fairly tightly clustered around highs in the upper 80s to lower
90s.
Sunday Night into Tuesday: WPC cluster scenarios hold onto a
northwest flow aloft but do start to build an upper level ridge from
the southern Rockies and Plains back towards the Missouri Ozarks.
There are some ensemble members that hint at more MCS potential as
a surface warm front gradually begins to retreat north through
the region.
Temperatures will begin a gradual warming trend with highs returning
to the lower and middle 90s by Tuesday. Confidence is increasing
that portions of southwestern Missouri and southeastern Kansas will
warm into the upper 90s on Tuesday.
Next Wednesday and Thursday: Cluster scenarios begin to flatten the
upper level flow with the upper level ridge beginning to span east
into the Lower Mississippi Valley. This will result in a continued
warming trend with NBM statistical data suggesting that high
temperatures will once again make a run at the upper 90s to around
100 degrees.
Thunderstorm chances will largely be tied to the track of potential
MCSs. Initially, the favored track would tend to be north of the
area on Wednesday. There are then some ensemble members that
shift a cold front (and corresponding MCS track) a bit farther
south to end the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 624 PM CDT Thu Jul 13 2023
Should mainly have VFR conditions through the period. There is a
period late tonight between 09-14z where some convection will be
possible at the TAF sites. Could see some MVFR or brief IFR within
any convection that occurs. Generally light winds are expected,
initially from the northeast, but switching to the south towards
morning.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 7 PM CDT this evening for MOZ077-088>096-
101>105.
KS...Heat Advisory until 7 PM CDT this evening for KSZ097-101.
&&
$$
SHORT TERM...Schaumann
LONG TERM...Schaumann
AVIATION...Lindenberg