Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/20/22
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
1023 PM CDT Fri Aug 19 2022
.UPDATE...
Issued at 1009 PM CDT Fri Aug 19 2022
Showers are diminishing across the state due to increasing
stability. Patchy fog is expected to form across the central and
eastern part of the state early Saturday morning. Fog is expected
to be interment and locally dense at times. Patchy fog could
reduce visibilities at times making the morning commute more
strenuous. Thus, fog was expanded eastward into the James River
Valley to match recent guidance.
UPDATE Issued at 640 PM CDT Fri Aug 19 2022
Wrap around precipitation will continue to move across
southeastern North Dakota this evening. Isolated thunderstorms are
possible as precipiation moves southwestward, severe weather is
not expected. Patchy fog could form tonight as low temperatures
near the dewpoint early Saturday morning. No major updates to the
current package, adjusted PoPs to match current conditions.
&&
.SHORT TERM...(This Evening through Saturday)
Issued at 227 PM CDT Fri Aug 19 2022
The main theme this evening through Saturday is a slight chance of
showers this evening in the southeast and mild temperatures.
Currently a few rain showers are making their way southwest
through portions of the central and southeast. There has been no
lightning with these, just light rain. The threat for
thunderstorms looks to be low now. Cloud cover all day has not
allowed the cap to break. According to SPC mesoanalysis CAPE
values are 500 J/kg or less, with very low shear. The surface low
is located in western Minnesota, with the upper level low slightly
farther to the east. A band of showers and a few thunderstorms in
northern Minnesota is wrapping around the low and moving
southwest into eastern North Dakota. Along this line would be our
chance for showers and thunderstorms if they either develop ahead
of that line or is the line makes it all the way to our
southeastern counties. Confidence is lower in the chance than this
morning, CAMs either don`t have this line, or clipping Dickey and
LaMoure Counties late afternoon or early this evening, which is
the mostly likely outcome.
Tonight clouds will clear out from west to east as surface high
pressure moves in from Canada. Winds over the area will be light
and variable from this, and the surface low moving out of the
area. Low temperatures tonight will be in the 50s.
Saturday morning looks to have clouds across most of the central
and eastern areas indicated by RAP relative humidity. Timing on
these clouds will be between 5am and noon CDT, then will clear out
for a mostly sunny day. Temperatures will range from the upper
70s in the north, to the lower 80s in the west. The 850mb thermal
ridge is just off to the west, nudging the west warmer than the
rest of the forecast area. Winds will also be lighter than today.
.LONG TERM...(Saturday Night through Friday)
Issued at 227 PM CDT Fri Aug 19 2022
The long term will start dry with warmer temperatures, then the
second half cooler with chances of rain.
Temperatures:
With the ridging pattern continuing, the first half of the period
will be dry, with temperatures warming back into the 90s. The
driving force behind the higher temperatures is the thermal ridge
sliding east into the western half of the state through Tuesday.
The thermal ridge is then forced south with the upper level flow
flattening. Wednesday through Friday temperatures are back into
the upper 70s and mid 80s.
Precipitation:
Upper level flow becomes more zonal in the Northern Plains
Monday. A few disturbances in the flow move through, bringing the
chance for showers and thunderstorms Monday evening through
Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
Issued at 640 PM CDT Fri Aug 19 2022
Winds will remain out of the north to east tonight across the
region. SHRA is possible for KJMS this evening with chances
diminishing later tonight. Patchy fog could form across central
and western North Dakota Saturday morning. However, confidence is
low for fog formation and will be AMDs if fog forms.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Johnson
SHORT TERM...Smith
LONG TERM...Smith
AVIATION...Johnson
Area Forecast Discussion
National Weather Service Boise ID
909 PM MDT Fri Aug 19 2022
.DISCUSSION...Showers and thunderstorms are continuing in the
w-central Idaho mountains and portions of southeast Oregon this
evening. Storms have produced gusts to 45 mph, and brief heavy
rain. Expect activity across these areas to dissipate by midnight.
An area of showers and thunderstorms propagating from east to
west will track through the western Magic Valley this evening and
overnight. Shower development is possible in the Owyhees towards
morning. Have updated the forecast to reflect shower and
thunderstorm potential through early Saturday morning.
&&
.AVIATION...VFR. Isolated showers and thunderstorms ending
overnight. Showers and thunderstorms will develop after 20/18Z,
mainly over the higher elevations of central ID. Smoke layers
reducing visibilities, especially south of KMYL. High density
altitude due to hot temperatures. Surface winds: generally
variable 10 kt or less. Gusty outflow winds up to 35kt in
vicinity of showers and storms. Winds aloft at 10k feet MSL:
variable up to 10 kt.
Sunday Outlook...VFR with mostly clear skies. Smoke layers
reducing visibilities, especially south of KMYL. High density
altitude due to hot temperatures.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Sunday night...At 2 PM MDT scattered
showers and isolated thunderstorms have developed in Owyhee and Twin
Falls Counties, with a few light showers in the mountains north of
the Snake Basin and Baker County/OR. These are the favored areas
through this evening; other areas should be partly cloudy but stay
dry. Skies will clear in Oregon overnight but stay partly to mostly
cloudy in central and south-central Idaho. Clouds will keep nighttime
temperatures warm. Greater convective development is expected Saturday
afternoon in the Boise Mountains, west central Idaho Mountains, Camas
Prairie, and near the ID/NV border, as a weak Pacific upper trough
moves through those areas. Behind the trough eastern Oregon will
be sunny and warm. The clearer skies in Oregon will advance eastward
into Idaho Saturday night, and Sunday should be mostly sunny everywhere
under a short wave upper ridge, except in eastern-most Idaho mountains
where a slight chance of afternoon thunderstorms is again forecast.
Skies will become clear in Idaho Sunday night, but the next weak
Pacific trough will bring clouds and a slight chance of showers to
eastern Oregon Sunday night. High temperatures Saturday will be
1-3 degrees warmer than today, and another 5 to 7 degrees Sunday.
Boise may break its record for the number of 100+ days for the
season. However, smoke may hinder full heating and latest HRRR
smoke model does have Sunday slightly smokier than Saturday.
LONG TERM...Monday through Friday...Upper level trough passage to
the north will suppress the ridge over the region beginning Monday.
This will lower temperatures about 5 degrees on Tuesday. Upper level
flow will remain somewhat zonal through the remainder of the period.
Moisture will remain rather limited though it`s possible moisture
will reach the Nevada/Idaho border by Friday. Temperatures will be
several degrees above normal area-wide.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
www.weather.gov/Boise
www.facebook.com/NWSBoise
www.twitter.com/NWSBoise
DISCUSSION...DG
AVIATION.....BW
PREV SHORT TERM...LC
PREV LONG TERM....JDS
Area Forecast Discussion
National Weather Service Green Bay WI
1041 PM CDT Fri Aug 19 2022
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Saturday
Issued at 246 PM CDT Fri Aug 19 2022
The latest RAP analysis and satellite/radar imagery show an upper
level low pressure system spinning over southern Minnesota early
this afternoon. Scattered light rain showers moved northeast into
central Wisconsin and parts of the Fox Valley earlier this
morning, but have since dissipated as elevated moisture
convergence weakened. Focus then turns to eastern Minnesota and
western Wisconsin where increasing instability could interact with
shortwave impulses wrapping around the parent circulation. The
most robust cu currently resides over eastern Minnesota and far
western Wisconsin where some thunderstorms have already developed.
But with further heating, it remains possible that cu over
southwest Wisconsin will develop into thunderstorms that move into
central Wisconsin later this afternoon. Deep layer shear is
rather weak (15-25 kts), but instability of 1000-1500 j/kg could
lead to a few strong pulse storms that could produce gusty winds
and heavy downpours. If storms do develop, they could approach the
Fox Valley by early this evening.
Tonight...The upper level low will move slowly south-southeast
into Iowa. As this occurs, the axis of instability over western
Wisconsin will shift east, which will prolong the chance of
showers and storms well into the evening hours across central and east-
central WI. An isolated strong storm will remain possible until
diurnal instability dissipate by around mid-evening. Activity
could remain more isolated across far northern WI so chances will
be lower there. In general, precip chances will diminish during
the late evening into the overnight hours though chances will
remain highest over eastern WI where instability will be the
highest. Short range guidance is bullish for low clouds and
fog/mist developing over central and north- central WI late. Low
stratus was plentiful over northeast Minnesota this morning, so
this is plausible.
Saturday...The upper low will continue to hang across the western
Great Lakes. The day could start off rather cool and cloudy though
some peaks of sunshine will develop with the heat of the day.
Any sunshine will help mixed layer instability grow up to 1000
j/kg by early to mid-afternoon, and therefore should see scattered
showers and thunderstorms redevelop. With shear remaining weak,
the threat of severe weather is low, but heavy downpours will be
possible in any storms. Highs in the low to mid 70s.
.LONG TERM...Saturday Night Through Friday
Issued at 246 PM CDT Fri Aug 19 2022
Medium range models are in good agreement with the
upper trough weakening and exiting the region Saturday night and
Sunday. They are also in good agreement with northwest upper flow
from Monday through Friday next week, with a shortwave tough and
surface cold front coming through Wednesday night. The upper flow
is forecast to become southwest by the Saturday and Sunday, with
southerly low level flow and and increasing chance of
precipitation. Temperatures should be pretty close to normal next
week, with the warmest day being Wednesday and the coolest next
Friday.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1035 PM CDT Fri Aug 19 2022
No significant changes to the aviation forecasts are planned for
the 06Z TAF issuance. Adding meaningful detail to the SHRA/TSRAs
fcst across the region remains difficult. Will maintain TEMPO
groups for the start of the TAFs, including TSRA over central WI
where the strongest convection was located. There is also still a
lot of uncertainty regarding stratus and fog potential later
tonight. The NW 1/2 of the forecast area is most at risk. Rain
over central WI during the evening increased the risk, though if
the showers linger and skies remain cloudy conditions probably
won`t deteriorate as much as earlier anticipated. Still plan to
bring ST/FG into the C/N-C WI TAFS late tonight.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM.....MPC
LONG TERM......RDM
AVIATION.......Skowronski
Area Forecast Discussion...UPDATED
National Weather Service Hanford CA
306 PM PDT Fri Aug 19 2022
...Updated Air Quality Issues Section...
.SYNOPSIS...Temperatures will remain well above normal through
Saturday then a slight cooling trend will take place Sunday into
early next week before another warm-up takes place later next
week. Dry conditions will continue as monsoon moisture will be
limited but some afternoon cumulus clouds are likely over the
Sierra Nevada each day.
&&
.DISCUSSION...The large upper ridge over the northern Rocky
Mountain region is shifting eastward as another large ridge
centered near 130W builds inland in CA. The building ridge will
maintain the much above normal temperatures through Saturday
before a slow cooling trend takes place on Sunday and Monday as a
negatively tilted trough impacts the PAC NW region and weakens the
ridge over CA. With daytime temperatures expected to remain well
above average on Saturday, a Heat Advisory remains in effect for
the San Joaquin Valley, West Side Hills, Lower Sierra Foothills,
and the Kern River Valley through Saturday.
Visible imagery showing some cumulus buildups over the higher
elevations of the Sierra Nevada. HRRR indicating CAPE and
instability are sufficient enough for some isolated showers and
thunderstorms this afternoon in the higher Sierra in Fresno and
Tulare Counties. Mid level drying associated with the offshore
ridge building inland will likely inhibit mountain convection on
Saturday.
Medium range ensemble members are in fairly good agreement with
dry weather continuing through next Wednesday with temepratures
remaining slightly above seasonal averages on Monday and Tuesday.
Latest NBM probabilistic guidance is indicating a better than 50
percent chance for most of the San Joaquin Valley to reach the
century mark on both day, but only a 5 to 20 percent chance of
maximum temperatures at 105 DEG F or higher.
The ridge is progged to strengthen over the region later next
week which will result in another warming trend across our area
and a possible return of dangerous heat in the San Joaquin Valley.
RH progs are indicating mid/upper might become sufficient enough
for isolated afternoon showers and thunderstorms over the higher
Sierra Nevada on Thursday and Friday.
&&
.AVIATION...VFR conditions will prevail across the Central CA
interior through at least the next 24 hours.
&&
.AIR QUALITY ISSUES...On Saturday August 20 2022... Unhealthy
for Sensitive Groups in Fresno... Kern... Madera and Tulare
Counties... and Sequoia National Park and Forest.
&&
.CERTAINTY...
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
&&
.HNX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 7 PM PDT Saturday for CAZ300>317-319-321-332.
&&
$$
public/aviation/fire wx...DAS
pio/idss...JDB
weather.gov/hanford
Area Forecast Discussion
National Weather Service Lincoln IL
810 PM CDT Fri Aug 19 2022
.SYNOPSIS...
Issued at 203 PM CDT Fri Aug 19 2022
A slow-moving weather system will bring periods of showers and
thunderstorms tonight through Sunday morning. A stretch of dry and
seasonably hot weather will then return next week.
&&
.UPDATE...
Issued at 810 PM CDT Fri Aug 19 2022
Most of the convective activity this evening has been staying off
to our northwest, with just a few showers tracking up the Illinois
River valley. Latest HRRR has been working toward taking the more
isolated supercells over southeast Iowa and forming them into more
of a line, potentially moving into areas near Galesburg toward
midnight. Some weakening should take place after 2 am or so as the
line moves more toward the I-55 corridor. Recent forecast updates
have been to work on some timing adjustments tonight and Saturday,
though more work may be needed in the very short term due to
impacts from some computer issues this evening.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 203 PM CDT Fri Aug 19 2022
A vertically-stacked, cold-core low centered over southern Minnesota
will bring forth an unsettled weather pattern to start the weekend.
At the surface, a cold front currently arcs from roughly Minneapolis
to Sioux City to North Platte. The warm sector ahead of this front
can be characterized by surface temperatures in the low 80s with
dewpoints in the mid-to-upper 60s. Plenty of solar insolation and
steepening lapse rates just ahead of this upper low has eroded
MLCINH and has helped push MLCAPE values between 2000-2500 J/kg.
A quick glance upstream reveals deep moist convection organizing
along and ahead of the cold front in southwest and south central
Iowa. There, parcels have benefited from a 40kt 500-mb speed max
that`s effectively rounded the base of the closed upper-level low
and has increased deep-layer shear.
Latest CAM guidance supports this convective activity spreading
eastward across the Mississippi Valley this evening, perhaps
losing its punch as the 500-mb speed max diminishes in the
divergent flow downstream of the upper low. Still, with a modest
LLJ veering in ahead of the surface cold front, scattered showers
and thunderstorms will likely persist into the overnight hours
across central Illinois.
While a few strong storms cannot be ruled out this evening,
weakening deep-layer shear, waning surface-based instability and
marginal MUCAPE should limit the severe weather potential.
The better chance for severe weather comes Saturday afternoon as
the cold front pushes in from the west. Model soundings around
central Illinois for tomorrow afternoon resemble similar PBL
conditions to what central Iowa has in place this afternoon. Thus,
it`s a decent proxy to what might occur across central Illinois
Saturday afternoon. With marginal CAPE/Shear profiles and a
straight hodograph, a few storms may be capable of producing large
hail and damaging winds.
Convective activity could linger through sunset tomorrow, mainly
east of the Illinois River Valley, as a LLJ again veers in ahead
of the front. Storms should lose their punch, though, as the
upper-level jet max becomes displaced south of our area and deep-
layer shear diminishes.
.LONG TERM...(Sunday through Friday)
ISSUED AT 203 PM CDT Fri Aug 19 2022
The upper-level low will begin to open and shift eastward by
Sunday morning as strong shortwave energy digs into the Hudson
Bay. With heights increasing behind the departing upper trough and
surface high pressure slowly building into the Midwest and Great
Lakes regions, a stretch of dry and seasonably hot conditions are
anticipated through late next week. NBM guidance is offering daily
highs in the lower 80s Monday and Tuesday with overnight lows in
the low 60s, and we see no reason to stray away from this
guidance. Conditions then turn slightly warmer Wednesday through
Friday as surface high pressure begins to depart and low-level
flow veers southerly. Mid 80s will be more common to end the work
week with overnight lows in the mid 60s.
&&
.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 633 PM CDT Fri Aug 19 2022
Timing of convection will be the main concern in the period through
12Z. While a few showers will be possible this evening, think the
main thunder risk will begin around 06-07Z at KPIA and then passing
KBMI/KSPI toward 09Z. Beyond that, the storms will be on a weakening
trend and TSRA chances are less certain in eastern Illinois.
Scattered storms expected to redevelop in the afternoon as an upper
low moves into Illinois.
A period of MVFR ceilings is possible near KPIA early to mid
Saturday morning, but outside of that, VFR conditions should prevail
outside of any temporary restrictions during storms.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SYNOPSIS...MJA
SHORT TERM...MJA
LONG TERM...MJA
AVIATION...Geelhart
Area Forecast Discussion
National Weather Service North Platte NE
645 PM CDT Fri Aug 19 2022
.SYNOPSIS...
Issued at 320 PM CDT Fri Aug 19 2022
H5 analysis this morning had a ridge of high pressure,
which extended from the Four Corners north into southern Alberta.
East of this ridge, closed low pressure was noted over central
Minnesota. A trough of low pressure extended to the south of this
feature into the lower Mississippi Valley. West of the ridge, a
decent shortwave was noted over northern portions of Nevada. A
second shortwave trough was noted off the coast of western
Washington State. South of this feature, high pressure was anchored
approximately 700 miles off the coast of southern California. At the
surface, low pressure was located over central Minnesota. A cold
front extended to the south of this feature into northwestern
Missouri. The frontal boundary became more westerly at that point,
extending across northern Kansas into east central Colorado. Across
western and north central Nebraska this afternoon, skies were partly
cloudy as an abundance of cumulus and altocumulus cloud had
developed across the forecast area. Cloud cover was thicker in
northeastern portions of the forecast area where clouds continued to
wrap around the low located over Minnesota. Temperatures as of 2 PM
CT, ranged from 76 at Gordon to 86 at Imperial.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 320 PM CDT Fri Aug 19 2022
Upper level low pressure will slowly track south across southern
Minnesota into northern Iowa overnight. There will be a continued
threat for isolated rain showers on the western periphery of the
low tonight. The threat will be greatest through mid evening in
our far northeastern forecast area. Not expecting much in the way
of precipitation after sunset as cooling temps should end
instability. High pressure will build into western portions of the
forecast area overnight. With light winds and dry air in place,
temperatures may reach the upper 40s in the NW Sandhills
overnight. Feel fairly confident in this forecast as the MET and
MAV guidance is in good agreement. The guidance was hinting at fog
potential in the northeastern forecast area tonight. However,
after looking at the HRRR visby product and SREF visibility
probabilities, will hold off on a fog mention for now. Will advise
the oncoming shift to watch for fog development later this
evening into the overnight. High pressure will slide east on
Saturday with light easterly and southeasterly winds developing
Saturday afternoon. Temps will be warmest in the west, where some
mid to upper 80s are possible. Highs further east will top out
around 80. Saturday night will see lows in the middle to upper
50s.
.LONG TERM...(Sunday through Friday)
Issued at 320 PM CDT Fri Aug 19 2022
Dry conditions will continue through Tuesday with ridging present
across the western half of the CONUS. Highs will gradually
increase into the lower 90s early next week. Beyond Tuesday, the
temperature forecast becomes less certain. The latest NBM
continues to be well below the latest MEX guidance and has a large
spread in its members for high temps and low temps toward the
middle and end of next week. This leads to a low confidence
temperature forecast beyond Wednesday. As for precipitation
chances, the latest NBM appears "optimistic" with its chances
Wednesday, Thursday and Friday. After looking at the latest ECMWF
and GFS solns from this morning, am more pessimistic about the
precip forecast next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 645 PM CDT Fri Aug 19 2022
VFR is generally expected across western and north central Nebraska
overnight through Saturday evening.
There is a chance MVFR ceilings will back into north central
Nebraska Saturday morning. This flight concern is expected to
remain north and east of KONL. VFR should be widespread in this
area by 16z Saturday morning.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Buttler
SHORT TERM...Buttler
LONG TERM...Buttler
AVIATION...CDC
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
900 PM CDT Fri Aug 19 2022
.UPDATE...
Issued at 859 PM CDT Fri Aug 19 2022
Broad large scale ascent in the form of warm advection is
increasing in the vicinity of the Mississippi River this evening
in response to the arrival of a stout upper vort max. An initial
batch of showers and thunderstorms is ongoing across parts of
Winnebago, Ogle, and Lee counties, and expect this mass of
convection to continue to develop and expand south and westward
into Iowa. A second area of thunderstorms has recently begun to
materialize farther west of the river within a zone of enhanced
upper divergence at the northern terminus of a modest 60 kt jet
streak. DVN radar already shows outflow racing ahead of this
arcing area of thunderstorms, but additional isentropic ascent
should provide the impetus to result in additional development as
this feature presses east towards the region. Have increased
precipitation chances after 11 PM to midnight with recent HRRR
trends not looking too unreasonable.
Currently, am not really expecting much of a severe threat as this
main batch of convection rolls across our region late tonight with
mid-level flow still being pretty weak combined with a continued
gradual loss of MUCAPE as already mushy mid-level lapse rates
trend moist adiabatic as the column saturates. Some gusty winds
and perhaps a few instances of small hail would be about the most
we expect in our area. Localized heavy rain threat certainly
exists, at least until this second wave of precip helps move
things along at a better clip. Upwind Corfidi Vectors are pretty
uniformly expected to fall under 5-10 kts suggesting regenerative
development will have the potential to train over similar areas,
and can`t discount the need for a flash flood warning west of I-39
if this activity remains entrenched. Updated products have been
sent.
Carlaw
&&
.SHORT TERM...
Issued at 308 PM CDT Fri Aug 19 2022
Through Saturday night...
A slow moving mid-level cyclone, currently over southern MN, is
expected to gradually shift southeastward into the Lower Great
Lakes by Saturday evening. As it does so, the area is likely to
experience a couple periods of showers and thunderstorms through
Saturday evening. The first wave of showers and storms is
in the process of developing now across southern IA, where
diurnal heating has resulted in an uncapped and unstable
environment in the vicinity of a surface frontal boundary. The
expectation is that thunderstorms will continue to develop across
this region eastward into northwestern IL late this afternoon into
the early evening as better upper level level diffluence within
the exit region of an upper level jet max continues to overspread
this area. These storms are expected to have an east-
northeastward movement, which should allow them to shift into
areas near and just west of the I-39 corridor after 7 or 8 this
evening. Some locally strong gusty outflow winds will be possible
through around sunset with the strongest storms, but expect this
threat to wane through the evening as the cluster of shower and
storms shifts eastward across the remainder of the area later this
evening and overnight.
Signs continue to point at a break in the activity during much, if
not all of the morning on Saturday as the initial round of
showers and storms weakens and moves eastward out of the area. For
this reason, I have lowered POPs into the lower chance category
for most areas through the morning hours, with any lingering
shower activity likely to remain isolated to widely scattered in
nature. Renewed thunderstorm development is expected during the
afternoon though as the main mid-level disturbance begins to
settle in over southern WI and northern IL. Some of these storms
could become strong/severe, particularly for areas along and
south of I-80, where the combination of better mid-level flow
around 30 kt (and shear) looks to overlap with the better
instability. The primary threat looks to be strong wind gusts,
though some hail could also be possible with any supercellular
structures. Locally heavy rainfall will also accompany these
storms into Saturday evening. The storm threat should then
gradually wane from west to east Saturday evening.
KJB
&&
.LONG TERM...
Issued at 301 PM CDT Fri Aug 19 2022
Sunday through Friday...
The main forcing with the upper-level low over the area on
Saturday will have shifted east of area by early Sunday morning,
but a secondary embedded compact wave tracking southward over
eastern Wisconsin/Lake Michigan will provide lingering mid-level
support into the area on Sunday. Weak dry air advection and
decreasing mid- level lapse rates will greatly reduce potential
coverage of showers and especially thunderstorms compared to
Saturday. At this point, isolated showers in the morning will
likely see some diurnal enhancement ahead of the approaching wave
by early afternoon, with a localized higher area of coverage
shifting south over the Chicago metro into east-central Illinois
and northwest Indiana in the afternoon and early evening.
NW/WNW flow aloft will prevail for much of next week, resulting
in generally seasonable temps for late August. A weak embedded
disturbance within a rather dry mid-level airmass may produce a
few spotty showers or sprinkles across the northern CWA on Tuesday
afternoon. Otherwise, the next chance of rain will be with a
stalling cold front over the area late Thursday into Friday.
Kluber
&&
.AVIATION...
For the 00Z TAFs...
Aviation forecast concerns:
* Multiple rounds of showers and storms through the period
- Greatest chance late eve at RFD, SAT afternoon areawide
* MVFR cigs SAT AM toward RFD, and areawide late Saturday
Showers and storms:
Occasional spotty showers are expected across the area this evening
covered by VCSH in the TAFs. A narrow axis of isolated thunderstorms
just west of the forecast area should eventually drift east toward
RFD, however eastward progress remains slow at this hour. Have
maintained a thunder mention at RFD from 3-7Z to account for this
and other activity across Iowa.
Further east it appears that lightning will be on a diminishing
trend upon their approach. For now have a TEMPO for SHRA during
the 6-12Z timeframe acknowledging there remains a non-zero threat
for a few lightning strikes.
Still think that shower coverage will diminish some Saturday morning
before additional scattered showers and storms develop in the
afternoon, covered by VCTS for the afternoon and PROB30 TSRA when
there is slightly better confidence in greater coverage of storms
near the terminals. Additional showers will remain possible at times
through the evening.
Ceilings:
CIGS are expected to remain mostly VFR through the evening and
overnight outside of any thunderstorms or heavier showers. Toward
RFD cigs will begin to decrease toward daybreak with models hinting
at low-end MVFR to near IFR possible through out the day on Saturday
there. Confidence is lower for the Chicago area terminals on CIG
trends outside of any thunderstorms. Have maintained mainly VFR
through the TAF, then trending toward MVFR Saturday evening.
Winds:
Any lingering gustiness from earlier this evening will continue to
ease with sunset. Directions will remain generally southerly (150-
210 degrees) overnight. Winds then trend WSW during the daylight
hours (outside of any thunderstorm outflow influences) with speeds
10-12kt with gusts in the upper teens to near 20kt. Winds then turn
light and variable Saturday evening and overnight as the upper low
moves directly overhead.
Petr
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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AREA FORECAST DISCUSSION
National Weather Service Morristown TN
1022 PM EDT Fri Aug 19 2022
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
No notable changes were made this evening as the forecast remains
largely on track. Coverage of showers and storms diminished fairly
quickly in our area with activity continuing to our north and to
our south. With continually decreasing instability, additional
activity is becoming less likely, which has led to a decrease in
PoPs. Also, lingering cloud cover has led to temperatures
increased slightly for the next few hours with no change to
overnight lows. Other elements were updated based on the latest
model guidance.
BW
&&
.AVIATION...
00Z TAF DISCUSSION.
Lingering showers and storms will continue to diminish this
evening with most places remaining dry overnight. Low ceilings are
expected to develop at CHA by the early morning hours with
potential for reduction to IFR. Fog is another possibility, most
likely to occur at TRI with lessened potential at TYS. Confidence
for this occurrence remains limited and could yield VFR
visibilities or reduction to below IFR. During the day on
Saturday, any lingering low clouds and/or fog should gradually
lift by closer to noon with re-development of showers and storms
anticipated again. The timing for potential impacts will be
earlier in the day for CHA and latest at TRI.
BW
&&
.PREV DISCUSSION...
/ISSUED 330 PM EDT Fri Aug 19 2022/
SHORT TERM...(Tonight and Saturday)...
Key Messages:
1. Scattered showers and thunderstorms this evening with clearing
conditions and fog late tonight.
2. Chance of additional showers and thunderstorms on Saturday
afternoon with the highest chances across the higher elevations.
3. Heavy rain rates may produce localized flooding issues.
Discussion:
Upper-level 80kt jet axis across the Southern Appalachians this
afternoon is providing favorable support for ascent within an
environment of 2000 J/Kg MLCAPE. PW values are 1.6 to 1.8 inches
which is not anomalously high, but some heavy rain rates will be
possible along cell mergers and any training. Widespread
convection is expected to continue to develop through the late
afternoon hours before decreasing this evening as synoptic upper
support shifts northeastward and instability decreases. Greatest
coverage of precipitation is expected across SE TN and SW NC and
northeastward along the Southern Appalachians. Fog and low clouds
are expected late tonight for those areas that receive afternoon
rainfall today.
We remain in a pattern of longwave troughing across the Great
Lakes and Ohio Valley on Saturday with WSW flow aloft and
southerly low-level flow. Shortwave ridging will actually build in
across our region in the wake of a departing shortwave that
enhanced precipitation coverage on Friday. The southerly low-level
flow will continue to bring an increase in boundary layer moisture
with chance PoPs for most locations. With the RAP showing PW
values increasing to around 1.8 to 1.9 inches and MLCAPE near 2000
J/Kg during the afternoon, scattered thunderstorms are expected,
especially across the higher elevations. A large warm cloud layer
depth and a nearly saturated forecast sounding will favor
additional periods of heavy rain rates within thunderstorms with
localized flooding possible.
JB
LONG TERM...(Saturday night through Friday)...
Key Messages:
1. There will be showers and some thunderstorms around at times for
the weekend into Monday.
2. Tuesday through Thursday will see drier conditions for most, but
still low chances for showers/storms mainly in the afternoons.
Discussion:
An upper level low entering the Great Lakes region will continue to
weaken and open up as it moves east, before being reabsorbed into
the westerly flow as it exits through New England into maritime
Canada. While passing our portion of the country, this upper low
will push a weak cold front through the area. Ahead of the front,
southwesterly flow will draw moisture into our area. The combo of
forcing and moisture will yield showers and storms area wide on
Sunday, with a risk for localized flooding for any area that
receives repeated rounds of rainfall through the weekend. On Monday
the rainy weather will exit as the front pushes into Georgia.
Behind the front, Tuesday through Thursday should be dry for most
locations, as drier air advects in from the north. An afternoon
thunderstorm cannot be ruled out in the afternoon each day,
especially along elevated terrain. By Friday, greater low level
moisture looks to return to give a chance for showers and storms for
more of eastern Tennessee. Start of the week will be a couple
degrees cooler than average this time of year, owing to the storms
and cloud cover. Second half of the week post-front expect
temperatures to rise back to seasonable temperatures.
Wellington
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 69 84 70 83 70 / 30 50 70 80 60
Knoxville McGhee Tyson Airport, TN 67 86 69 83 69 / 30 40 60 80 70
Oak Ridge, TN 67 84 68 82 68 / 30 40 60 80 60
Tri Cities Airport, TN 63 84 67 81 66 / 30 30 40 90 60
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
Area Forecast Discussion
National Weather Service Nashville TN
750 PM CDT Fri Aug 19 2022
...New UPDATE...
.UPDATE...
Issued at 745 PM CDT Fri Aug 19 2022
Current convective activity has diminished somewhat from earlier
coverage and intensity, but cells remain ongoing and the HRRR
suggests that we won`t be entirely free of active weather
throughout the night. Have therefore left in isolated POP`s for
the duration. Evening sounding from OHX gives us a CAPE of 1,766
J/kg and a Lifted Index of -5, so the instability is definitely
there, and with a weak upper trough hovering over the mid state,
believe there is enough impetus for the occasional cell to develop
even during the overnight period.
&&
.SHORT TERM...
(This afternoon through Sunday Night)
Issued at 145 PM CDT Fri Aug 19 2022
Longwave troughing now in place across the eastern half of the US.
An embedded shortwave axis is located just to the east of the MS
river. PVA to the east is interacting with some afternoon warmth to
promote the ongoing scattered convection across portions of the mid
state. This activity will extend into the early evening hours with
a chance of showers and tstms continuing for a few more hours.
More of the same tomorrow although coverage will be a little higher
as the low level southerly flow ramps up a touch and brings more
moisture in across the area. This is all in response to a stronger
shortwave upstream which will move across the mid state on Sunday
and bring a good chance of showers and tstms. The deeper moisture
will continue into Sunday night as well before the system pushes
south of the mid state by Monday.
Not looking for any severe wx on Sunday. However, 850 mb wind flow
amplification will match up with greater instability levels just to
our north during the afternoon. Should the mid level jet drop
further south we could see a marginal risk drop into our northern
counties perhaps. Otherwise, just a general risk for now.
For our near term temps, looks like seasonal values through Sunday
night.
&&
.LONG TERM...
(Monday through next Friday)
Issued at 145 PM CDT Fri Aug 19 2022
In the extended forecast, the aforementioned system drops to our
south with a weak frontal passage by Monday. Upper trough axis will
be oriented n-s across the mid and southern Atlantic states.
Northerly flow will extend uniformly across region so we will be
under a drier and less active regime. Convective parameters on
Monday will yield very low cape with afternoon subsidence
prevailing. By Tuesday, some afternoon capping will also emerge
and will continue into Wednesday. By the end of the week, cape to
cap ratios will become a little more favorable with slightly
higher pops at that time.
For the extended temps, we will start out near seasonal levels for
early in the week. Heights will increase with time, however, as the
troughing pattern begins to break down. Temps by the end of the week
will be running a few degrees above normal.
7 day precip totals do not look too bad. Euro and GFS blends suggest
one half inch north up to 1 1/2 inches south. Peripheral flooding
concerns are not indicated other than over Texas and the Arklatex
region.
&&
.AVIATION...
(00Z TAFS)
Issued at 636 PM CDT Fri Aug 19 2022
VFR conditions are expected at airports most of this TAF period
although patchy fog will bring MVFR vis to CSV overnight. VCSH
will be seen near BNA/MQY early this evening, then VCTS will
develop again Saturday afternoon at BNA/MQY/CSV with MVFR
conditions possible. Light southeast winds tonight will become
south to southwest at 5-10 knots on Saturday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 69 89 71 87 / 20 40 30 70
Clarksville 68 89 70 86 / 20 20 40 60
Crossville 64 80 66 78 / 20 40 50 80
Columbia 68 88 70 87 / 20 40 30 60
Cookeville 67 84 68 82 / 20 40 50 70
Jamestown 65 81 66 78 / 20 30 50 80
Lawrenceburg 68 86 69 86 / 20 50 30 60
Murfreesboro 67 88 69 86 / 20 40 40 70
Waverly 67 88 68 86 / 20 20 30 60
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Rose
SHORT TERM...21
LONG TERM....21
AVIATION.....Shamburger