Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/18/22
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1049 PM EDT Wed Aug 17 2022
Scattered showers and isolated thunderstorms will
diminish in coverage early this evening with just a few showers
possible overnight, mainly north and east of Albany. Tomorrow will
be warmer with morning clouds giving way breaks of sun with
scattered afternoon showers and isolated thunderstorms. Friday and
Saturday turn dry with above normal temperatures returning as high
pressure dominates the Northeast.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
.UPDATE as of 1045 pm EDT...Low pressure remains near the Maine
Coast with the H500 low capturing the wave and it will occlude
and become vertically stacked overnight. Scattered to numerous
showers continue mainly from the Capital Region north and east
and we increased PoPs into the likely range in these areas. An
inverted sfc trough rotating around the sfc low is helping focus
the showers. PWATS remain in the 1-1.2" range based on the SPC
RAP Mesoanalysis page with some rainfall rates still in the
0.25-0.50"/hr range with some of the showers. Decent rainfall
efficient processes are ongoing and the rainfall should help
some of the areas with large rainfall deficits that are in
various drought levels across the forecast area. The latest CAMS
have the showers lifting out faster but based on the radar
trends we have opted to linger them longer.
We increased the POPs overnight and slowly decreased south and
west of Albany. We also removed the slight chance of
thunderstorms with little to no instability left. It will
remain humid tonight with the rainfall but temps should still
cool into the 50s to lower 60s. Clouds will linger most of the
night except south towards the mid Hudson Valley/eastern
Catskills and NW CT where a trend towards partly cloudy
conditions may occur.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Morning clouds tomorrow should break for some afternoon sun,
especially along and south of Interstate 90 as the coastal storm
in New England exits into the Canadian Maritimes and high
pressure from the Ohio Valley builds northeastward. The pressure
gradient between the departing low and incoming high looks to
tighten enough to result in somewhat breezy northwest winds
tomorrow afternoon with sustained winds reaching 8 - 15mph and
gusts up to 20mph. The increased winds should lead to deeper
boundary layer mixing resulting in sfc temperatures likely
warming back into the upper 70s to low 80s with even mid-80s
possible in the mid-Hudson Valley. Dew points should still be in
the upper 50s to near 60 with guidance also indicating that mid
and upper level temperatures are still somewhat cool. Both of
these factors combined with increased sun and warm sfc
temperatures should result in diurnally driven isolated to
scattered showers due to steeper low-level and mid-level lapse
rates. While mid-level lapse appear to range 5.5 - 6C/km,
overall instability is still mediocre on the latest high res and
HREF guidance which suggests surface based CAPE only ranges 500
to 1000 J/kg. However, this is still enough to maintain slight
chance to chance wording for thunderstorms in the forecast. We
limited thunderstorm wording to areas along and south of I-90
where more breaks of sun are expected and closer to where a
differential heating boundary could set-up between increasing
sun to the south and cloudier skies north. The height of
updrafts should still be limited so not expecting any severe
weather and SPC maintained its "general thunder" outlook for the
Diurnally driven showers and storms diminish with the lose of
daytime heating tomorrow night as riding and subsidence builds
aloft. Skies should gradually clear overnight as well with
temperatures cooling into the mid to upper 50s with some areas
in the Hudson Valley only falling to near 60.
Expect a very pleasant end to the work week on Friday as high
pressure builds overhead with morning sun mixing with some
diurnally driven cumulus clouds as we hit the convective
temperature. Southwest flow aloft will advect in a warm air
mass with 850hPa isotherms warming back up to +14C to +16C
resulting in afternoon highs rising into the mid to upper 80s
with mid to upper 70s in the higher terrain. Dew points will
still be somewhat elevated so it will feel like summer once
again due to the humidity. Otherwise, expecting a dry day.
Staying dry and a bit muggy into Friday night with some clouds
increasing towards sunrise. Increased clouds should keep
temperatures warm overnight with lows only in the low to mid
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The extended forecast opens with high pressure and weak mid and
upper level ridging over the region with above normal temps. A slow
moving upper level trough approaching from the western Great Lakes
Region and Midwest will increase the threat for showers and isolated
thunderstorms late in the weekend into the middle of next week.
Temps will run above normal with higher humidity levels. A weak
cold front may move across the region late Tuesday into Wednesday.
Sat-Sun...High pressure will build in over NY and New England to
open the weekend with the mid and upper level flow transitioning
from zonal to southwesterly late SAT. H850 temps run above normal
by about a standard deviation or so based on the latest NAEFS with
the actual H850 temps in the +15C to +17C range. Max temps in the
upper 80s to near 90F will be common in the valleys with upper 70s
to mid 80s over the hills and mtns. A weak disturbance passing to the
south of the region may bring a few showers south and west of the
Capital Region. Humidity levels start to increase Sat night into
Sunday with dewpoints rising into the upper 50s to mid 60s. Lows
will be mild in the mid 50s to mid 60s. The mid and upper level
trough reaches the west-central Great Lakes with a weak impulse in
southwest flow potentially bringing isolated to scattered showers a
few thunderstorms Sunday afternoon. Max temps will be similar to
Sun night to Wed...The positively tilted mid and upper level trough
remains upstream of the forecast area heading into early next week.
The closed H500 circulation opens on Monday with embedded short-
waves in the southwest flow tapping into the muggy air mass for
rounds of showers and isolated thunderstorms Monday into Tuesday
with some timing differences between the latest GFS/ECMWF and the
Ensembles. We stayed close to the NBM with high chances of showers
and possibly thunderstorms in the sticky air mass Monday and Tuesday
afternoon. The showers/isold thunderstorms should diminish at night.
A cold front and the upper level trough axis may not clear the
forecast area until Wed. We maintained a chance of showers this
Max temps will generally be in the lower to mid 80s across the lower
elevations and 70s to lower 80s over the higher terrain, and upper
50s to mid/upper 60s across the region each night. Cloud cover may
impact temps early next week. Temps should continue to average
above normal heading late into the week and into next weekend based
on the long range guidance.
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Through 00z Friday...Bands of scattered showers continue across
eastern NY and western New England early this evening. VFR
conditions prevail early on with scattered low clouds with decks
of mid and high clouds associated with the upper low and the
coastal wave near Maine. Some of the showers may impact the TAF
sites prior to 04Z/THU. A prevailing VCSH group was used at
KGFL/KALB/KPOU/KPSF with a TEMPO 00Z-04Z for MVFR vsbys and low
VFR cigs. Brief IFR reductions may occur with any of the
showers. The showers should diminish around or shortly after
04Z/THU based on some the high resolution model guidance. There
is a chance some may linger near KGFL/KPSF/KALB and VCSH groups
were continued overnight here.
Lingering mid level clouds should persist the rest of the night
with VFR conditons. Expect a gradual clearing KPOU northward in
the late morning into the afternoon. KGFL will likely have a
stratus deck around 5 kft AGL with a few residual showers as a
VCSH group was continued, but expect a transition to scattered
stratocu and some mid level clouds in the afternoon. Midlevel
clouds will linger near KALB/KPSF into the afternoon with some
high clouds near KPOU. Overall, VFR conditions are expected from
the late morning through the afternoon.
The winds will be light and variable in direction at 5 kts or
less overnight. They will shift to the west to southwest at 5-10
kts after 12Z, and become west to northwest at 8-12 kts in the
afternoon with some gusts 15-18 kts at KALB/KPSF.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: No Operational Impact. NO SIG WX.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Moderate Operational Impact. Chance of SHRA...TSRA.
Sunday Night: Moderate Operational Impact. Chance of SHRA.
Monday: Moderate Operational Impact. Chance of SHRA
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
1004 PM CDT Wed Aug 17 2022
Issued at 959 PM CDT Wed Aug 17 2022
Scattered thunderstorms continue across the area. The first area
to the east continues over south central North Dakota just to the
south of Interstate 94 which have developed along a rather staunch
outflow boundary. This area of storms have produced 60 mph wind
gusts. The second primary area is along and ahead of a modest cold
front over western North Dakota. These storms have in the past
produced strong wind gusts, but have tamed down some. With
instability to work with, expect storms to pulse around for the
next few hours before completely taming down.
UPDATE Issued at 646 PM CDT Wed Aug 17 2022
Main concern right now is a group of storms, one supercellular,
over northeast Montana moving into northwestern North Dakota along
and ahead of an advancing cold front. These storms are moving into
a somewhat more unstable environment with marginal instability.
Reports of 60 mph wind gusts have occurred in far Northeast
Elsewhere, some showers and a few thunderstorms continue to move
mainly through south central North Dakota, but these continue to
remain on the tame side.
.SHORT TERM...(This Evening through Thursday)
Issued at 231 PM CDT Wed Aug 17 2022
Key messages for the short term forecast are as follows:
- Scattered showers and thunderstorms this afternoon and tonight,
with a few strong storms possible, but only about a 5% risk of
a severe storm at any given location. Precipitation will become
more widespread north and east by late tonight/Thursday morning
- Cooler temperatures beginning Thursday, with forecast highs in the
70s to around 80 F, but potential for them being even cooler in
some areas if cloud cover is significant enough
Early this afternoon, a broad, broken band of convection extends
from north central ND southwest into southwestern ND and eastern
MT, along and ahead of ascent related to a middle- and upper-level
shortwave trough. Moisture channel imagery shows the cyclonic flow
with that shortwave trough well, and implies that while its band of
forcing for ascent extends southward all the way into northern WY.
The boundary layer is destabilizing away from existing cloud decks
and convection, with steep midlevel lapse rates sampled by the 12
UTC Bismarck RAOB sufficient for around 1000 J/kg of MLCAPE given
surface dewpoints in the mid 50s to lower 60s F. There is a bit
of uncertainty in the magnitude of lingering inhibition, but
observed soundings suggest it is becoming negligible with
temperatures nearing 90 F. Given that and the approaching band of
ascent seen on water vapor imagery, we expect a continuation of
the broken band of convection, with additional and potentially
stronger development in western and central ND the rest of the
afternoon and evening. We are continuing to message the potential
for a few strong storms, supported by the thermodynamic setting.
Deep-layer shear on the order of 25 kt will marginalize, but not
negate, the risk of severe storms. The CAPE-shear setting favors
multicellular convection, with potential transient updraft
strengthening in favor of a low, approximately 5% probability of
severe hail or wind at any one location. The boundary layer is
well-mixed with steep lapse rates, and forecast soundings display
some "inverted-v" type structures along with DCAPE on the order of
1000 J/kg, which may favor wind gusts of 45 mph to locally 60 mph
associated with collapsing or outflow-dominant storms, though
again in a disorganized fashion due to the lack of stronger deep-
layer shear. The favored area for any strong or severe storm risk
is likely over southwestern and south central ND before 03 UTC
where the boundary layer will be the most well-heated and buoyant,
though the risk could extend into northwestern ND by early evening
if the boundary layer can destabilize after clouds shift eastward.
Otherwise, moisture channel imagery this afternoon also suggests the
primary vorticity maximum and related strongest forcing is located
over southern Saskatchewan. Extrapolating the latter feature favors
north central ND into the James River valley for the highest chance
(50 to 70 percent probability) of showers and storms overnight and
into Thursday. That precipitation will likely come from additional
development as the shortwave trough and vorticity maximum moves into
the area, but the timing of that is somewhat uncertain and could be
as early as mid evening if sufficient destabilization occurs in the
wake of the ongoing clouds and convection (similar to some HRRR
cycles), or as late as sometime after 06 UTC if destabilization is
delayed sufficiently (similar to the 12 UTC NAM Nest simulation).
During the day Thursday, showers and thunderstorms remain possible
in central and eastern ND, with the probability ranging from roughly
40% from Bottineau and Minot to Bismarck and Linton, to 70% from the
Carrington area south to Jamestown and Ellendale. This scenario is
the result 1) the early-day passage of the initial shortwave trough,
2) lingering cyclonic flow in its wake, which could favor scattered,
low-topped convective development as early as midday, and 3) forcing
associated with another shortwave trough approaching from the north
by late in the day. A strong storm is also possible given weak to
moderate CAPE, but the lack of shear will once again minimize the
severe-storm risk. This scenario also lends itself to a much cooler
day, with forecast highs in the 70s to lower 80s. However, if cloud
cover or precipitation is more significant in any one area, then
highs could held be several degrees cooler.
.LONG TERM...(Thursday Night through Wednesday)
Issued at 231 PM CDT Wed Aug 17 2022
Key messages for the long term forecast include:
- Cool weather, breezy winds, and precipitation chances on Friday,
especially in eastern areas
- Confidence in a warming and drying trend beginning Sunday and
continuing through early next week, with some uncertainty in the
forecast evolution by the middle of next week
Global ensembles favor a low aloft forming over the eastern Dakotas
or Minnesota by Friday morning, and then a gradual south-southeast
motion of that feature by Saturday morning. We expect the potential
for a more stratiform-type shield of rain on the west side of this
low, and 60-80 percent probabilities of this are focused over the
James River valley where odds are highest of the low being in close-
enough proximity for precipitation. Suffice to say, small changes in
the placement of the upper-level low remain possible, and both that
and the potential for diurnal convection in the broadly cyclonic flow
are why we have 20-40 percent chances of precipitation as far west as
central ND Thursday night into Friday. The surface pressure gradient
will tighten in this scenario, too, likely leading to breezy north
winds centered on the Friday daytime time period.
Middle and upper-level ridging is then expected to begin building
into the area this weekend, and ensemble clusters display high
confidence in that ridge yielding a dry and warmer period from at
least Sunday through Tuesday. Spread in temperatures from NBM
members is only about 5 degrees F from Friday through Tuesday, which
raises our confidence in the deterministic forecast that calls for
highs warming from the 70s F Friday to mostly the 80s F from Sunday
through Tuesday. By the middle of next week, there is suggestion
that the ridging aloft will dampen, but the manner in which it does
is uncertain, with one outcome (with about 30% odds) favoring a
shortwave trough directly crossing the area with renewed chances
of precipitation. The other outcomes mainly favor a more gradual
dampening of the ridge and perhaps some cooling temperatures, but
with a drier northwest flow pattern taking hold instead by next
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 646 PM CDT Wed Aug 17 2022
Scattered thunderstorms will continue this evening into the
overnight hours over most locations, with the exception of
western areas where thunderstorm chances will wane this evening.
Chances will linger through the day on Thursday over parts of
central North Dakota, affecting the KJMS terminal.
Area Forecast Discussion
National Weather Service Boise ID
837 PM MDT Wed Aug 17 2022
.DISCUSSION...Showers have formed over southeast Oregon, mostly in
Harney County, and have been producing wind gusts around 30 mph.
These are expected to diminish after sunset. Otherwise, we are
experienced smoky skies over much of southwest Idaho, and this is
going to continue into tomorrow. The excessive heat warnings and
heat advisories will expire at 9 PM MDT / 8 PM PDT. All this is
well-handled by the current forecast, and no changes are planned
at this time.
.AVIATION...Isolated showers and thunderstorms this evening, and
again Thursday afternoon and evening, mainly in southeast Oregon
and south of the Snake River Valley in Idaho. Elevated smoke
layers over central and southwest Idaho. High density altitude due
to hot temperatures. Surface winds: variable 10 kt or less,
except gusts over 30 kt possible near showers and storms. Winds
aloft at 10k feet MSL: E-SE 5-15kt.
SHORT TERM...Tonight through Friday night...Near-surface smoke
has become thick enough to slightly moderate the afternoon heat
in western Idaho. Latest HRRR smoke model keeps smoke there
through Thursday but clears it out from south to north Thursday
night and Friday. Smoke will continue north of Ontario/OR to
Stanley/ID as the Four Corners Fire continues to burn near
Cascade, ID. Monsoon moisture has been spreading northward into
central Oregon and is expected to begin high-based thunderstorms
in western Harney County/OR late today, then across southern-most
Oregon and Idaho Thursday afternoon and night. Isolated thunderstorms
will develop in the Boise Mountains and West Central Idaho Mountains
Friday afternoon as a Pacific upper trough moves inland north of
that area. Owyhee and Twin Falls Counties will still have a slight
chance of thunderstorms Friday and Friday night as the monsoon
surge shifts slowly eastward. Max temperatures will be slightly
lower Thursday and again Friday, but still slightly above normal.
LONG TERM...Saturday through Wednesday...A transient ridge will
build ahead of the next upper level low pressure system on Sunday.
The low will weaken as it moves inland on Monday but should be
sufficient along with lingering moisture to support thunderstorm
development across the higher terrain of Southwest Idaho. This
system will move north of the region Tuesday as the next upper
level ridge builds off the West Coast. Ensemble guidance favors
dry northwesterly flow across the area through Wednesday.
Temperatures will be at or slightly above normal through the
ID...Heat Advisory until 9 PM MDT this evening IDZ012-014>016-028>030.
Excessive Heat Warning until 9 PM MDT this evening IDZ033.
OR...Heat Advisory until 9 PM MDT this evening ORZ061>063.
Excessive Heat Warning until 9 PM MDT this evening ORZ064.
PREV SHORT TERM...LC
PREV LONG TERM....JDS
Area Forecast Discussion
National Weather Service Gray ME
1018 PM EDT Wed Aug 17 2022
The coastal storm continues to head inland tonight with rainfall
continuing into tomorrow. Near the storm center will have the
greatest potential for drought relieving rainfall, but otherwise
showery conditions will gradually add up to around a quarter to
half inch of rain for most. The storm will also bring gusty
northeast winds for much of the area. The storm will slowly
drift northeast through early Friday before conditions improve.
While it will be more reminiscent of fall to end the week,
summer returns for the weekend with widespread temperatures in
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
1015 PM Update...Forecast remains in good shape overall, but for
now have raised PoPs to 90-100% over the next few hours
basically across the northern half of western Maine based on
radar trends and short term guidance.
Update...As the previous discussion alluded to, there has been a
bit of a surge in winds over the past hour or two across
portions of the Maine Coast and inland here at the GYX office
and over toward Augusta and Waterville, where a few gusts have
approached 30 kt. So have bumped up the winds just a tad over
the next few hours across these areas based on what we`re
Models doing a good job at this point handling synoptic scale
features of this low, as it tracked N through the Gulf of ME
today, and will then shift NW toward upper low tonight, crossing
the ME coast around or east of Pen Bay. System has
underperformed forecast a bit in winds, but may see a surge over
the next several hours as it changes direction and intensifies
slightly. As for precip, I think we’ll see several clusters of
moderate to heavy rain move through /as the HRRR suggests/, but
I think widespread rain amounts will tend to come in three
quarters of an inch to an inch with 1-2” amounts more localized
from Casco Bay east along the coast and into interior parts of W
and Central ME as well as into Coos county NH. Central and
southern NH, will likely be limited to half inch or less, and
parts of southern NH, may only end up with closer to a tenth of
an inch. Lows will fall off a few degrees as driers air moves in
behind a winds shift to the NW later tonight, and drop into the
upper 50s to low 60s.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
On Thursday the low will be moving NE, and should see rain chances
diminish from SW to NE with, with mainly dry conds in central
and southern NH, and SW ME and showers in the morning along the
ME coast. Showers should continue through most of the day in
the mtns as wrap around moisture works in from the NE.
Clearing and the lack of showers in the S will allow temps to
rise into the mid to upper 70s in the S NH, but only in the mid
to upper 60s in the mtns.
Some lingering showers in the mountains continue Thu evening,
but drying and clearing will be the trend most everywhere else,
with lows in the mid 50 N to around 60 in the S.
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
A general region of high pressure will set in Friday through the
weekend as weak ridging builds in aloft. Clearing skies and warming
temperatures set in with highs reaching up into the mid 70s in
the north to the upper 80s in the south Friday afternoon. Highs
Saturday and Sunday will reach into the 80s with some parts of
southern NH reaching to around 90 on Saturday. Increasing clouds
Sunday will keep temperatures a few degrees cooler but still
remaining in the 80s. Low pressure passing nearby to the south
on Sunday could bring some higher winds and waves to the
waters, however only the GFS is showing the stronger winds at
the surface so I haven`t bumped them up yet.
A weak shortwave will slowly make its way across the Great Lakes and
into New England on Monday. Guidance suggests that this SW will
bring generally unsettled conditions to the area for the first half
of next week. By the time the SW reaches New England, the main
trough axis will be lifting out which could keep the surface
reflection fairly progressive as it passes through. Uncertainty in
the strength and track of weak shortwaves like these is quite large,
especially in the warm season, so further details will have to come
as the system draws nearer.
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Short Term...Despite the rain, drier low levels are keeping
cigs at VFR at many terminals this afternoon. I think there will
a period of MVFR overnight at all but KHIE and KLEB, and some
IFR at KRKD and KAUG. Expect improvement to VFR at all nut
KRKD/KAUG in the morning, but those two terminals should see VFR
during the afternoon. VFR is expected at all terminals Thu
night, but valley fog is possible at KHIE/KLEB.
Long Term...VFR conditions prevail through the weekend with
some lingering MVFR ceilings at KHIE Friday morning. Some valley
fog may develop Friday and Saturday nights, otherwise VFR
conditions prevail through Monday before another chance of
precip moves in midweek.
Short Term...SCA now in effect in all but Casco Bay into
Thursday morning, as winds should come up a bit this evening,
but stay below gales, before diminishing late tonight. Seas will
stay up into Thursday morning, but will slowly subside as well.
Long Term...Winds and seas will gradually subside to 1-2 ft for the
weekend with winds mostly from the west. Low pressure will track
nearby Sunday which could bring some higher winds and waves over the
outer waters before another chance of precip moves in midweek.
MARINE...Small Craft Advisory until noon EDT Thursday for ANZ150>152-
Area Forecast Discussion
National Weather Service Louisville KY
738 PM EDT Wed Aug 17 2022
...Updated Aviation Discussion...
Issued at 542 PM EDT Wed Aug 17 2022
Visible satellite imagery shows a relatively small area of taller cu
generally along the I-64 corridor. Weak moisture convergence and
very steep low level lapse rates (8.5 C/km) are apparently
sufficient for very isolated light showers. MLCAPE is around 500
J/kg according to the 21z SPC RAP analysis.
10-15% coverage looks reasonable for this activity as it continues
to drift south into northern portions of central KY early this
evening. The probability for a thunderstorm is less than 10%.
.Short Term...(This evening through Thursday)
Issued at 305 PM EDT Wed Aug 17 2022
North to northwest upper flow is pushing a surface high, currently
centered over southern Wisconsin, towards Ohio. This high pressure
system is extending it`s influence to the south over the CWA,
limiting weather to scattered cumulus. A few of these scattered
cloud decks could spit a few sprinkles here and there, but that will
be very isolated. Heavier rainfall isn`t expected.
Tonight, skies will begin clearing as winds drop to near calm. This
will allow for radiative cooling as model soundings show a
subsidence environment with a near surface inversion. This will
cause some areas to reach their dew point, allowing for patchy fog.
Areas that hold on to cloud cover will see less fog. Most areas will
see lows in the low 60s. The cooler valleys will likely see the
upper 50s, and those in Louisville will only reach the mid 60s.
Tomorrow, expect more of the same. Light northeast surface winds
will remain as the aforementioned surface high cuts across central
Indiana. Skies will begin mostly sunny, but will see cumulus form
during the afternoon hours. High are expected to reach into the low
to mid 80s.
.Long Term...(Thursday night through Wednesday)
Issued at 310 PM EDT Wed Aug 17 2022
General troughing over the eastern half of the US will be sinking
southward at the beginning of the long term, resulting in height
falls and a change in upper flow from northwesterly to more
westerly. As the stacked New England low departs further off to the
northeast, another shortwave will be diving out of Canada and
towards the mid-Mississippi River Valley. With us placed in between
waves, it should be a relatively quiet end to the work week. Some
northward surge of moisture associated with a frontal boundary
across the Deep South will result in some lower chance PoPs, but the
best chances remain east of I-65. Temps rising back into the mid to
upper 80s will support some instability and steeper low level lapse
rates, but overall weak shear will keep convection less organized.
With the upper flow becoming more southwesterly during the weekend,
temps are expected to rise back to near normals. Mid to upper 80s
are expected for Saturday, and slightly cooler for Sunday. The
southward-diving shortwave will close as it tracks over US soil, and
eventually will pivot to the east once it approaches the Great
Lakes. Our highest precip chances come Sun and Mon as an associated
sfc boundary cuts through the Ohio Valley and provides greater lift
and moisture. Model soundings show rather saturated profiles, along
with enough instability and effective shear to support thunderstorms
and maybe a few more organized cells. Overall severe threat remains
low with this FROPA.
.Aviation...(00Z TAF Issuance)
Issued at 737 PM EDT Wed Aug 17 2022
Prevailing VFR conditions are likely through much of this forecast
period. Rogue isolated showers from earlier in the evening have
dissipated, and tonight looks dry.
Mainly clear skies and light winds are forecast overnight, allowing
the temperature to drop near the crossover temperature at LEX and
HNB. Forecast minimum temp at HNB is -2 from Tx, so went with tempo
IFR fog early Thursday. Confidence is lower at LEX, but think at
least brief MVFR fog is possible. Fog is expected to be fairly
prevalent in the valleys over the eastern half of KY.
High pressure continues to sink southeast over the Ohio Valley for
Thursday. Expect light northeast winds and a SCT diurnal cu field.
Area Forecast Discussion
National Weather Service Sacramento CA
131 PM PDT Wed Aug 17 2022
Hot temperatures continue through Saturday with a slight cool down
Thursday. Monsoon moisture will bring showers and isolated
thunderstorms tonight over the Sierra and higher terrain of Shasta
County increasing fire risk through midnight.
Extensive cloud cover keeping temperatures down today in central
valley. Always a threat with monsoonal surges like this. Rain
activity has remained stratiform for the most part so far today
with only a few strikes mainly in the Bay area and a few in far
northern Shasta county. HREF and HRRR have been doing pretty well
with this moisture and activity and do suggest an uptick this
afternoon continuing through early morning with main risk of
lightning over northern zones where current Red Flag Warning is
posted. Still thinking lightning should mainly be isolated as
models not showing much organization to the convection and flash
density forecasts from HREF/HRRR and EC still on the low side. All
this activity shifts north through the night and should clear the
area by sunrise.
Friday looks like there should be a slight cool down but may end
up being a warmer day with no clouds. Temperatures should
basically be from 100 to 105 across the valley. Much drier air
will be over the area but still some lingering moisture and lift
over eastern Shasta county for chances of thunderstorms. Heights
raise a bit and temperature should rebound a bit again and thus
will keep the heat advisory going.
Saturday...some slight cooling as we begin to be under the
influence of a large trough in the Gulf of Alaska. This trough
will keep any monsoonal moisture shunted off to the east.
.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...
Sunday ensembles suggesting influence from Gulf of Alaska trough
lingers around with onshore flow keeping us mainly in the upper
90s. Ensembles also in good agreement that this influence start to
diminish early next week with more ridging in place but not seeing
any monsoonal type flow setting up. Rasch
VFR conditions over interior Northern California over the next 24
hours. Isolated thunderstorms are possible until 06z tonight,
mainly over the mountains. Surface winds mainly at or below 12 kts
except in the vicinity of the Delta, where gusts to 25 kts are
Red Flag Warning until midnight PDT tonight for Burney Basin and
Northeast Plateau in Shasta County Including Northwest Lassen NF
north of Lassen NP-Eastern Mendocino NF-Eastern Portion of
Shasta/Trinity NF-Northern Sierra Including Lassen NP and Plumas
and Lassen NF/S West of the Sierra Crest (West of Evans Peak-
Grizzly Peak-Beckworth Peak)-Northern Sierra Including the Tahoe
and ElDorado NF/S West of the Sierra Crest-Southeast Edge Shasta-
Trinity NF and Western Portions of Tehama-Glenn Unit.
Heat Advisory until 8 PM PDT Friday for Carquinez Strait and
Delta-Central Sacramento Valley-Motherlode-Mountains
Southwestern Shasta County to Western Colusa County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Northern
San Joaquin Valley-Southern Sacramento Valley.