Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/18/23
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
933 PM EDT Mon Jul 17 2023
.SYNOPSIS...
Warm weather will continue this week with the chance for
isolated to scattered diurnal showers and storms. A weak cold
front potentially crosses the area late Friday into Friday
night, bringing slightly cooler temperatures for the upcoming
weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
As of 930 PM EDT Monday...
Any showers and storms from earlier have largely dissipated and
will continue to do so over the next couple of hours. There is a
complex of showers and storms just west of the forecast area
(approaching Lynchburg), but these should also dissipate by the
time they make it to the forecast area. Overnight low temps
will range from the upper 60s to low/mid 70s. Lastly, wildfire
smoke has made it into portions of the area, and should persist
through tonight (especially across the NW half of the FA). As
such.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
As of 255 PM EDT Monday...
The broad upper trough is progged to shift eastward on Tuesday and
become centered over ern Canada, with the trough axis extending
southward over the Mid-Atlantic/NE CONUS. Temperatures will be a
couple degrees warmer tomorrow than they are today, with forecast
highs in the lower-mid 90s. Not expecting heat headlines to be
needed as dew points should mix out into the mid 60s-lower 70s
during the aftn. Isolated to perhaps widely scattered aftn tstms are
possible just about anywhere, with PoPs mainly 20-30%. Tuesday
will feature a fairly typical summertime setup with strong sfc
heating/modest shear. As is often the case in these types of
setups, a couple of the storms will be capable of producing
localized damaging wind gusts. SPC has introduced a MRGL Risk
for severe wx for the entire area to account for this. Diurnal
weakening should quickly occur after 00z/8 PM. Lastly, smoke
from wildfires in wrn Canada will continue to be over the region
on Tuesday as per latest HRRR guidance.
The upper trough axis moves to our east on Wednesday, allowing
the flow aloft to become NW. Guidance remains in agreement that
a fast moving shortwave trough will track near or over the area
late Wednesday. This should allow for more coverage of tstms,
mainly during the aftn and evening. There is still some
uncertainty regarding specific timing/placement of tstms, so
have capped PoPs at 40-50%. A few strong to locally severe
storms cannot be ruled out as well. Storms may last through part
of Wed night before gradually weakening late. We will also
likely see a bit less in the way of smoke aloft by Wednesday.
Forecast highs again in the low 90s with lows overnight around
70 degrees. NW flow aloft continues on Thursday with the
potential for yet another disturbance to move across the region.
Less confident in the timing and strength of this wave so will
keep PoPs aob 30% attm. High temps in the 89-93F range.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 255 PM EDT Monday...
Flow becomes more zonal/WSW on Friday as a shortwave digs south and
east across the Great Lakes. A weak surface low to our north and an
approaching front will keep slight chance PoPs in the forecast for
the afternoon and evening. Highs Friday once again in the low 90s
with low temps overnight a touch cooler, ranging from the mid 60s NW
to the low 70s SE. Slightly cooler Saturday decreased humidity
behind the weak front. Temps generally in the mid to upper 80s with
the chance for an isolated shower/tstm across the southern half
of the area. Perhaps a degree or two warmer on Sunday with the
chance for isolated showers and storms area wide.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 730 PM EDT Monday...
VFR conditions at all sites to start out the 00z/18 TAF period.
Similar to the past couple of nights, some patchy fog may try
to form at the typical sites (PHF, SBY, and ECG) early in the
morning hours. Added MVFR visbilities for now, but could see
some brief periods of IFR (low confidence). Any patchy fog
dissipates shortly after sunrise with VFR returning to all
sites. An isolated afternoon thunderstorm will be possible at
any of the sites Tuesday afternoon, potentially resulting in
brief flight restrictions.
Outlook: Prevailing conditions are expected to remain VFR
through the week. Isolated to scattered aftn/evening tstms are
in the forecast from Tue-Thu, with the highest coverage of
storms expected to be on Wed.
&&
.MARINE...
As of 210 PM EDT Monday...
Latest afternoon analysis indicates a cold front weakening along the
Atlantic coast. Winds are quite variable across the waters due to
this boundary, however, speeds are remaining around light at 5-10kt.
The seabreeze has created E/NE winds from the Hampton Roads
area down into Currituck, NC. Isolated showers are developing
along the boundary in the Lower Bay, Currituck Sound, and
immediate coastal waters early this afternoon. Generally think
the best chance for isolated showers and storms through the rest
of the evening will remain across the lower/middle Bay and down
into coastal NE NC, but there are slight PoPs across most of
the waters. Waves are around 1ft with seas of 2-3ft.
Expect this typical summertime pattern to repeat for much of the
week ahead as the Bermuda high regains control over the weather
pattern over the region. Winds increase slightly on Wednesday and
Thursday, with a prefrontal trough sharpening inland, which will
help bump up rain chances a bit each day. Waves remain 1-2 ft with
seas 2-3 ft, building the 3 to 4 ft with increasing SE swell tonight
and Tuesday.
Rip Currents: Moderate Rip Risk all beaches this afternoon with a
more shore-normal component to wave energy, and another
Moderate Rip Risk for Tuesday as well with an increasing SE
swell. Rip risk should subside to low on Wednesday.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...None.
&&
$$
SYNOPSIS...RHR
NEAR TERM...AJB/ERI
SHORT TERM...ERI
LONG TERM...ERI/RHR
AVIATION...AJB
MARINE...MAM/JKP
Area Forecast Discussion
National Weather Service Columbia SC
725 PM EDT Mon Jul 17 2023
.SYNOPSIS...
A building ridge from the west will provide drier than normal
conditions. However, this will also usher in above average
temperatures through at least Friday afternoon, with Heat Index
ranging from 100-110F most afternoons. Moisture starts to return
late week, increasing thunderstorm chances once again.
&&
.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
Lingering isolated showers near Augusta and just south of Columbia
are expected to diminish after sunset. Overnight, a weak surface
trough will remain across the region. Upper trough axis remains
well west of the area. Smoke from Canadian wildfires showing up
east of the Appalachians this evening will be slow to push out
overnight. This will keep hazy conditions, along with the potential
for patchy fog late tonight. Overnight, lows fall into the low
to mid 70s.
&&
.SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
A fairly substantial pattern change in store for Tuesday as the
broad upper low that has been over the eastern US will begin to
weaken with upper heights rising across the forecast area.
Temperatures expected to rise into the mid to upper 90s as a
result with broad subsidence over the area. Similarly low
moisture compared to average as Monday which will once again
limit convection across the area. An isolated, weak shower or
storm cannot be ruled out, especially across the NE but
otherwise expect much of the area to remain dry. HiRes guidance
does indicate that increased mixing will lead to drier air at
the surface which should keep indices below heat advisory
criteria but generally up to 105F. Increased southwest winds
overnight will keep low temperatures generally in the mid 70s.
Bit more uncertainty as to the temperature forecast as well as
convective potential for Wednesday. GFS has a fairly robust
shortwave moving through the area late in the day which would
keep highs a bit closer to normal with widespread showers and
storms, however, it does remain a bit of an outlier with much
higher deep moisture return to the area even compared to its
own ensemble members. Other global models do not dig this
shortwave quite as far south either. Likely will at the very
least be more clouds and highest chances for showers and storms
across the northern portion of the forecast area which will keep
highs closer to normal in the northern portion of the forecast
area with highs approaching 100F across the south as NAEFS
indicate that the 500mb heights are approaching the
climatological max. A bit higher dew points may push the heat
index slightly higher for Wednesday. Similar lows Wednesday
night, in the mid 70s.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
NAEFS indicates thats anomalously ridging will continue over the
forecast area into Thursday with GEFS mean indicating the
highest 850mb temperatures will be present across the area
Thursday. This along with a fairly substantial SW breeze for
this time of year will continue to support above average
temps. More consistency among both GEFS and EC ensemble members
of deep moisture increase Thursday which will increase pops.
Ensemble means generally support a breakdown of the ridge with a
deepening trough once again over the eastern US and a cold
front approaching the area. This will lead to the potential for
a relief from the heat with higher chances for showers and
thunderstorms this weekend.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Generally dry atmosphere in place with some mid level capping.
Isolated convection along a weak surface trough expected to
dissipate later this evening.
Area of smoke aloft and near the surface indicated on satellite
and surface obs, with surface VSBYS 3 to 5 miles in an area
from N GA NE across Upstate SC into W and Central NC, just north
of our TAF sites. Latest HRRR smoke model indicates the lower
near surface VSBYs to only slip slightly south this evening,
staying just north of our TAF sites. The model does indicate
that the smoke over GA could shift east into our FA late tonight
and Tuesday. So, some possibilities of surface VSBY
restrictions due to smoke/haze, but confidence on specifics too
limited to include mention at this time. Will evaluate trends
and latest guidance for possible inclusion in later TAFs.
Guidance showing only low probabilities of fog/stratus tonight,
favoring fog prone AGS and OGB, with some stratus also possible
across the coastal plain possibly getting inland as far as OGB.
Only isolated diurnal convection expected Tuesday with little
change in the atmosphere. Some upper energy will pass by to our
NE. CAMs indicating some convection over NC, well NE of our TAF
sites. So, will not include TS/SHRA mention at this time.
EXTENDED AVIATION OUTLOOK...Increasing probabilities of diurnal
thunderstorms and late night/early morning fog/stratus Wednesday
through Saturday. Smoke/Haze from distant wildfires may reduce
flight VSBYS and possibly surface VSBYs.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Caribou ME
948 PM EDT Mon Jul 17 2023
.SYNOPSIS...
An upper level trough will remain west of the area through
Tuesday, bringing a series of weak systems across northern New
England. A cold front will slowly cross the region Wednesday.
High pressure will briefly cross the region Thursday. Low
pressure will track west of the region Friday into Saturday.
&&
.NEAR TERM /THROUGH TUESDAY/...
9:47 PM Update...A Dense fog advisory remains in effect for
Coastal Hancock and Coastal Washington Counties tonight through
10am Tuesday. Visibilities have dropped to a quarter mile in
spots, including Bar Harbor. Otherwise, a few showers are moving
through Eastern Aroostoook County at this time. These will come
to an end by midnight.
Previous Discussion...
Latest HRRR & RAP near- surface smoke models are showing a
decent concentration of western Canadian wildfire smoke moving
into the area. Western New England and New York observations are
showing stronger smoke concentration that previous models
suggested. Opted to add patchy to areas of smoke into the grids
starting this evening into tomorrow. The upper level smoke is
already working into the area aloft but expecting low levels to
increase in concentration. In coordination with Maine DEP have
issued an Air Quality Alert product from 1AM tonight through
Midnight tomorrow night for particle pollution levels at
unhealthy for sensitive groups range. Otherwise expecting patchy
to areas of fog across the area with strong low-level inversion
and very moist boundary layer. Expect lows in the low to mid
60s and very muggy conditions overnight.
Tomorrow expecting the Marine layer to hang in across Hancock
and Washington counties with increasing sunshine in the morning
across the north. A strong shortwave will approach from the
west with a cold front slowly approaching from the northwest in
Quebec. Patchy to areas of smoke will make for hazy skies in
the morning in areas away from the Marine layer. Expecting some
daytime heating to help destabilize the atmosphere and
expecting the convective temperature across the North Woods to
be reached by early afternoon. Warm and muggy with highs in the
low to mid 80s away from the coast and dew points around 70F. A
lot of questions around the arrival time of forcing will
determine how strong convection may become in the afternoon. For
now not expecting anything too strong to prompt enhanced
wording for hail or gusty winds. However, SPC does have a
"marginal risk" for severe on D2 for wind and hail. At this
point cannot rule out some gusty winds and hail but holding off
on the wording for now. The bigger concern is the potential for
flash flooding especially along and north/west of Longfellow
Mtns. WPC has placed the area in a "slight risk" for D2 across
the area (see the hydrology section below).
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
A stream of heavy rain showers and thunderstorms will continue
to stream into the forecast area along a slow moving cold front
through Tuesday night. The NAM shows warm cloud thicknesses up
to 11,000 ft, tall skinny CAPE around 500 J/kg, and PWs well
over 1.5 inches that exceed the 90 percentile for 00z Wednesday
will lend to the threat for heavy rainfall with the convection
of the evening. Storms will likely train along the boundary from
southwest to northeast, so the same areas may receive extended
periods of heavy rainfall which could pose a flooding threat.
The front will continue to weaken as it slowly limps through the
forecast area Wednesday morning. Rain showers will begin to
taper off into the afternoon with skies clearing overnight
Wednesday night as brief high pressure builds into the area.
Thursday may very well be the driest day of the week with brief
high pressure overhead and mostly sunny skies. That said, rain
ahead of the next disturbance will begin to approach the area
from south to north late in the day on Thursday.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
There is good consensus among ensembles that an upper level
trough will remain over the eastern CONUS through the end of the
week with a blocking ridge centered just east of the Canadian
Maritimes. The only general variation between various ensemble
members is in the strength of the low pressure over the area,
but its position will be similar to where it has been this
entire season so far. Shortwaves will wrap around this upper
level low through the weekend, giving way to a continued
unsettled pattern with daily chances for rainfall.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: Aroostook terminals are generally VFR late this
evening. BHB at LIFR cigs and vsby with fog. BGR at LIFR cigs,
but vsby still P6SM. Expecting cigs to fall to IFR/LIFR at all
southern terminals tonight with FG developing. Generally VFR
north but BR/FG may reduce vsby at HUL, PQI, CAR late tonight
into the early AM. FVE expecting generally BCFG potentially
reducing vsby, otherwise VFR conditions through tonight.
Tomorrow generally VFR at BGR northward with MVFR at BHB after
13z. Showers & T-Storms develop tomorrow afternoon impacting
northern sites. Heavy rain may reduce vsby. Winds light &
variable tonight becoming S 5-15kts tomorrow.
SHORT TERM:
Tuesday night...Variable conditions with any fog, or showers and
thunderstorms. Otherwise VFR/MVFR, lowering to IFR/LIFR across
all terminals. Variable winds 5 to 10 knots.
Wednesday...Brief IFR possible early with any fog. A chance of
showers and thunderstorms. All terminals lifting towards VFR in
the afternoon. Variable winds 5 to 10 knots.
Wednesday night...Variable conditions with any fog. A chance of
showers and thunderstorm early. Otherwise, VFR. Variable winds
5 to 10 knots.
Thursday - Thursday night...VFR. Slight chance of an afternoon
shower. Variable winds 5 to 10 knots.
Friday...VFR diminishing towards MVFR/IFR in showers and
thunderstorms. Southeast winds around 10 knots.
Saturday...MVFR/IFR with showers and thunderstorms. South winds
around 10 kts.
&&
.MARINE...
NEAR TERM: Winds and seas below SCA through tomorrow evening.
Waves are subsiding to generally 2-4ft by tomorrow. Winds will
mostly be below 15kts. Vsby will be impacted with prolonged fog
across the waters. Vsby one quarter mile or less tonight with
dense fog.
SHORT TERM: Winds/seas below small craft advisory levels. Areas
of fog over the waters Tuesday night into Wednesday morning,
reducing to patchy fog that will last over the waters through
the next several days.
&&
.HYDROLOGY...
A slow moving cold front will approach from the northwest later
in the day tomorrow. Ahead of this front precipitable water
will increase to between 1.6-1.7 inches. Although precipitable
water isn`t as high as previous events the soils across much of
Eastern & Northern Maine are very sensitive to excessive
rainfall. 1-3hr FFG is as low as 1 inch to as most as 1.8
inches. Modeled soundings show a deep warm cloud layer of
10-11kft through the afternoon into the overnight hours. Tuesday
afternoon will feature tall skinny CAPE supporting convection
with mostly deep layer unidirectional flow ahead of the
boundary. The potential for excessive rainfall that may pose a
risk of isolated flash flooding is possible especially along
and northwest of the Longfellow Mtns into the Crown. It is here
WPC ERO is "Slight Risk" for D2 with an area of "Marginal" along
the I-95 corridor. In addition to the flash flood potential
excessive rainfall may cause rapid rises of small creeks,
streams posing the potential of washouts especially on North
Woods dirt roads. Lastly, those planning on recreational
activities across the Moosehead Region into the Baxter Region
should familiarize themselves with their surroundings. The best
chance of rapid rises on streams and creeks may occur after
dark Tuesday evening.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...Dense Fog Advisory until 10 AM EDT Tuesday for MEZ029-030.
MARINE...None.
&&
$$
Near Term...Clark/Sinko
Short Term...AStrauser
Long Term...AStrauser
Aviation...Clark/Sinko/AStrauser
Marine...Clark/Sinko/AStrauser
Hydrology...Sinko
Area Forecast Discussion
National Weather Service State College PA
1123 PM EDT Mon Jul 17 2023
.SYNOPSIS...
A weak cold front will push through Central Pennsylvania
Tuesday, then stall out just south of the Mason Dixon Line
Tuesday night and Wednesday. The frontal boundary will return
north on Thursday ahead of a shortwave tracking across the Grt
Lks. High pressure is then likely to build into the region late
week through next weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Regional radar late this evening shows convection associated
with a passing mid level vort max beginning to exit the eastern
part of the forecast area. Linear extrapolation and latest near
term model guidance support POPs falling below 10pct over most
of the region by around 06Z.
Breaking clouds and light wind behind the departing vort max
should promote areas of valley fog late tonight in locations
that received rain late today. Will also continue to carry haze
in the grids through late evening associated with Canadian
wildfire smoke. However, the latest HRRR suggests the thickest smoke
pushes east of the area late tonight.
Overnight low temps should range from around 60F across the NW
Mtns, to around 70F in the more urbanized locations of the Lower
Susq Valley.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
A weak cold front is progged to push through the region
Tuesday, accompanied by a round of showers or tsra in some
places. The latest HREF supports the highest POPs of around
50pct across the NW Mtns. Progged shear values are highest
across the eastern counties, where a late day fropa will also be
more favorable for a few strong thunderstorms. Latest SPC
outlook covers the eastern third of PA in a marginal severe
weather risk.
Large scale subsidence and the arrival of drier air behind the
exiting cold front should result in breaking clouds and the
threat of late night fog Tuesday night. Will maintain a slight
chance of showers into the late evening per NBM guidance, but
this may even be overdone.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The weak cold front is progged to stall out just south of the
Mason Dixon Line Wednesday, close enough to support a low chance
of an afternoon shower/tsra across the southern counties.
However, lower humidity and seasonable temperatures appear
likely for most of the area associated with a weak area of high
pressure passing across upstate NY.
The stalled frontal boundary should lift north into the region
Thursday ahead of a deepening upstream trough over the Grt Lks.
Diurnal heating, combined with falling heights and surging low
level moisture, should result in a good chance of showers and
thunderstorms Thursday PM. Areal average rainfall is likely to
range from 0.25 to 0.50 inches based on latest ensemble plumes.
However, locally heavier amounts of over an inch are likely with
stronger convection.
The bulk of medium range guidance supports a stretch of
relatively dry and seasonable weather Friday through next
weekend in association with a large area of high pressure
building southeast from the Grt Lks. Upper level troughing
should result in scattered, diurnally-driven showers Friday,
then mainly sunny and dry weather appears likely for the
weekend as the surface high and associated low-pwat air mass
build over PA.
Warmer and more humid conditions appear likely by early next
week with scattered diurnal convection possible, as the high
drifts off the east coast.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Showers and thunderstorms are moving through the area this
evening and are resulting in brief restrictions. This will
continue for the next few hours, with MDT and LNS being the most
likely to see lower cigs and visibilities. Outside of any
thunderstorms, visibilities will likely remain MVFR due to
wildfire smoke. Valley fog is expected to form overnight as
rain comes to an end and skies begin to clear out. It is
possible that BFD and JST also see a period of IFR/LIFR cigs
overnight.
Fog will dissipate fairly quickly after sunrise, but it remains
uncertain whether or not visibilities increase to VFR as
wildfire smoke will remain in place through most of the day.
A few showers will be possible during the afternoon across the
west, but coverage of showers and storms looks to be much lower
than today.
Outlook...
Tue Night - Sat...Sct-numerous TSRA mainly across the Central
and North Central Mtns of PA tonight and again on Thursday.
Otherwise, VFR to MVFR in periods of smoke and/or haze, that was
being transported all the way from Southwestern Canada.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...Lambert/Fitzgerald
LONG TERM...Fitzgerald
AVIATION...Bauco
Area Forecast Discussion
National Weather Service Cheyenne WY
529 PM MDT Mon Jul 17 2023
.SHORT TERM...(This evening through Wednesday night)
Issued at 340 PM MDT Mon Jul 17 2023
Current KCYS radar loop shows convection initiating across Carbon
County and also just south of Laramie along the southern Laramie
Range this afternoon. This is quite a bit different compared to
what models were showing over the last 48 hours which had
most of the thunderstorm activity well to the north. Radar loop
shows a well defined convergence boundary/dry line feature along
the Laramie Range with the best convection forming along it. HRRR
has continued to increase the coverage and intensity of
thunderstorm activity this afternoon and this evening across the
eastern plains. Dewpoints in the low to mid 60s are still being
observed across all of the western Nebraska Panhandle, with
dewpoints in the low to mid 50s across the far eastern Wyoming
plains. This has resulted in high MLCAPE between 1000 to 2000 j/kg
across most of the high plains and a risk for severe weather late
this afternoon through late this evening. Shear is plentiful with
0-6 Bulk Shear of 45 to 55 knots. Models also show a shortwave
disturbance, currently across northern Wyoming, diving southeast
across the area on the periphery of the upper level ridge axis
that extends north of the Upper level high near the four corners
region. The main forecast concern is the coverage and extend of
thunderstorms and severe thunderstorms through late this evening.
Previous models showed the shortwave feature much further
east...barely clipping east central Wyoming and western Nebraska a
few days ago. As of today, the upper level high and ridge axis
are considerably further west than previous models suggested for
this time of the day...so there is some degree of uncertainty
with how far south the strong to severe thunderstorms will
develop, especially given current radar trends this afternoon.
Agree with SPC`s slight to marginal risk across the eastern plains
along and east of the I-25 corridor. Would not be surprised to
see both the marginal and slight risk area adjusted a little
south and west this afternoon since Cheyenne has struggled to
reach dewpoints lower than 50 degrees. Continued to increase POP
between 15 to 25 percent along the I-80 corridor, and up to 50 to
60 percent further north from Lusk to Torrington and points east
of this line. Worded forecast for Damaging winds and hail,
although we believe strong winds may become the primary concern
due to straight hodographs, considerable forcing, and strong
shear.
Very warm to hot temperatures will continue on Tuesday with highs
in the 80s to low 90s. Surface winds will shift into the
northwest, allowing some drier air to move into the forecast area.
This should limit the amount of instability and CAPE, but still
expect showers and some thunderstorms to develop with a marginal
risk for severe thunderstorms east of I-25. High res models show
some convection early in the day across Carbon and Albany
counties, gradually shifting east through the day. However, models
have consistently started the day drier than expected, so there is
considerable uncertainty for Tuesday regarding the timing and
coverage of thunderstorms. Kept POP between 15 to 30 percent
Tuesday afternoon and evening due to this uncertainty. Previously,
it looked like Tuesday would be our transition day between dry and
hot and cooler and unsettled weather, but now models have trended
FROPA to Wednesday.
Cooling trend starts on Wednesday with highs mainly in the low to
mid 80s. Models show a backdoor cold front pushing south across
the plains and stalling near the mountains through the afternoon.
Thermodynamic profiles should be less unstable due to the cooler
air near the surface. However, the front is expected to stall
near the Laramie Range and expect this region to be the focus of
daytime and evening convection. Kept a solid chance of showers
and thunderstorms mainly for the I-80 corridor and more focused on
southeast Wyoming through Wednesday evening. At this time,
thunderstorms are not expected to be severe but a few stronger
storms are possible.
.LONG TERM...(Thursday through Monday)
Issued at 249 PM MDT Mon Jul 17 2023
Daily storm chances are expected for the first half of the long
term, with a chance for severe weather on Thursday. A warming trend
is expected through the long term, with a hot start for next week.
Precipitation chances come to an end by Saturday.
Thursday looks to be an active day with the potential for severe
weather across the region. An upper-level ridge begins to flatten
out Thursday as zonal flow moves over the intermountain west. Strong
cyclonic vorticity advection at 500mb begins as several vorticity
maximums move across the CWA and mid-level flow turns northwesterly
through the afternoon. A jet maximum develops into the evening
hours, providing additional synoptic lift to the CWA. 700mb flow
remains mostly northwesterly through the day Thursday with a low-
level jet maximum developing over eastern Nebraska. SBCAPE values
are marginal for Thursday, with the GFS suggesting SBCAPE values
only around 500 J/kg, with similar values of MUCAPE. The GFS
Ensemble suggests a decent, 30-40% chance, for CAPE to exceed 1000
J/kg, so there is a potential for higher CAPE values than currently
modeled. What Thursday lacks in CAPE, it makes up in shear. Bulk
shear values are forecast to be between 45 and 50 kts in southeast
Wyoming and western Nebraska, with PW values exceeding 0.9in across
southeast Wyoming and 1.00in for western Nebraska. Moisture and
shear will not be an issue for Thursday, but CAPE could be a
limiting factor. However, GFS forecast sounding show tall, skinny
CAPE profiles indicative of heavy rain producing storms. While CAPE
values are marginal, with northwest flow over the region, synoptic
lift, high shear, and higher PWs it will be possible to get
thunderstorms to initiate across the region. Trends will need to be
watched as Thursday approaches.
Northwest flow aloft continues into Friday as a ridge begins to
build over the western CONUS. Several vorticity maximums traverse
through the ridge with northwest flow over the CWA Friday allowing
for the chance for afternoon showers and thunderstorms once again. A
subtle shortwave is progged to move over the area in the afternoon
hours, providing additional lift across the region. A jet maximum
develops at 250mb, further placing the region in an favorable
location for enhanced synoptic lift. The GFS Ensemble suggests a
higher probability, 50-70%, for CAPE values to exceed 1000 J/kg
across western Nebraska. Bulk Shear values for Friday are similar to
Thursday, with 45-50 kts present across southeast Wyoming and the
Nebraska Panhandle. PWs will be significantly lower Friday,
especially across the Panhandle where PW values are progged to be
between 0.70 and 0.80in, with 0.50 to 0.60in across southeast
Wyoming. Dewpoints will also be slightly lower for Friday, but still
enough to get convective development. GFS forecast soundings show
better CAPE profiles across western Nebraska. All these factors come
together for a prime environment for storms to develop. While it is
a bit far out to determine how significant the severe threat is for
Friday, all signs point to a good environment for convective
development.
Precipitation chances come to an end Saturday as the upper-level
ridge builds over the western CONUS and shifts easterly towards the
CWA. A 500mb ridge of 594dm is firmly in place across the western
CONUS by Saturday and strengthens to nearly 600dm by early next
week. Strong subsidence under the ridge will allow for clear skies
for most of the weekend. As a result, a strong warming pattern is
expected this weekend and into early next week. Temperatures will
approach the mid-90s across the Panhandle by Sunday, with upper-90s
being possible Monday. Max temperatures for Sunday and Monday were
increased with this forecast package, as the GFS and ECMWF both
suggest a stronger ridge than is currently present across the CWA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 521 PM MDT Mon Jul 17 2023
A Severe Thunderstorm Watch is in effect until 1 AM MDT for
Converse, Niobrara, Platte and Goshen Counties in southeast
Wyoming and for the Nebraska Panhandle except for Kimball and
Cheyenne Counties.
Wyoming TAFS...A passing weather disturbance will produce isolated
thunderstorms at the terminals until 02Z, producing wind gusts to
45 knots and ceilings from 5000 to 8000 feet AGL. Otherwise
scattered to broken clouds from 9000 to 10000 feet AGL will
prevail. Winds will gust to 30 knots at the terminals after 15Z
Tuesday.
Nebraska TAFS...A passing weather disturbance will produce
isolated thunderstorms at the terminals until 05Z, with storms
capable of producing wind gusts in excess of 50 knots and ceilings
around 7000 feet AGL. Otherwise winds will gust to 30 knots at the
terminals from 01Z to 05Z. Later tonight and Tuesday, expect
scattered clouds from 7000 to 10000 feet AGL.
&&
.FIRE WEATHER...
Issued at 255 PM MDT Mon Jul 17 2023
It will remain dry this afternoon with gusty west to southwest
winds west of the Interstate 25 corridor. Although conditions are
generally elevated due to relative humidities around 10 to 15
percent, fuels remain green which will likely hinder the potential
for rapid fire growth. Further east, humidities are above 20
percent with lighter winds. Widely scattered showers and
thunderstorms are forecast to develop late this afternoon across
southeast Wyoming, and then push east into the plains as they
increase in coverage. Conditions will generally trend cooler and
wetter over the next 48 to 60 hours through the middle of the
week. Below normal temperatures and numerous showers and
thunderstorms are expected by Thursday with a good chance for
wetting rainfall.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...TJT
LONG TERM...AM
AVIATION...RUBIN
FIRE WEATHER...TJT
Area Forecast Discussion
National Weather Service Grand Forks ND
1050 PM CDT Mon Jul 17 2023
.UPDATE...
Issued at 620 PM CDT Mon Jul 17 2023
Smoke remains relatively widespread across the area this evening,
with isolated light showers near Lake of the Woods. Winds are
expected to diminish through the remainder of the evening, then
shift to the south heading into Tuesday morning. Overall, the
forecast remains on track this evening.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 257 PM CDT Mon Jul 17 2023
Key Message
-There is a threat for severe weather Tuesday afternoon and early
evening, although the exact details are still uncertain
Fairly thick cumulus still exists over most of the FA, but is
thickest to the east of the Red River Valley. Bemidji reported a
stray shower, but there haven`t been too many showers showing up
on radar or surface observations yet. Wind speeds were a little
higher east of the Valley and lower from Devils Lake to Valley
City. Moving into tonight, the cumulus will fade away and wind
speeds look to become light. It will be cooler around the Lake of
the Woods region, with exact cloud amounts being more uncertain
for other areas. The cloud uncertainty tonight revolves around the
fact that some CAMs develop showers and storms over Saskatchewan
and northwest North Dakota tonight, then show them moving as far
east as eastern North Dakota late (as they weaken). This would
spread more cloud cover across the state of North Dakota late
tonight and possibly Tuesday morning.
For Tuesday into Tuesday night, SPC has placed central North
Dakota eastward to the western edge of the Valley in a marginal
risk for severe weather. As mentioned before, the details
surrounding this are still uncertain. Some of the general
components are an approaching 500mb low, with a short wave out
ahead of it. The shear actually looks pretty good this time
around, with the potential for over 40 knots (better to the south
than the north). The HREF shows CAPE values pushing up into
central North Dakota by early afternoon, getting into our western
FA by late afternoon, then the values quickly weaken during the
early evening. The GFS ensemble shows about a 40 percent chance of
reaching 2000 J/kg of CAPE from Carrington to Jamestown at 00z
Wednesday. Do not see much of a low level jet, which could help
to sustain any stronger activity into the overnight period.
There are a couple of scenarios. First, morning cloud cover could
help to hold down the temperature rise on Tuesday. The HRRR has
been showing the overnight convection weakening over eastern North
Dakota Tuesday morning, but it also develops additional showers
and storms over the central Dakotas during the mid to late morning
hours. Don`t think that would limit the later afternoon
convection all that much though, but the first scenario would be
longer lasting clouds and the possibility for longer lasting
convection Tuesday morning. Another scenario would be that the
overnight convection dies out Tuesday morning with heating
developing through the day. Storms break out again in the 3 to 5
pm time frame from Devils Lake to Jamestown, moving into eastern
North Dakota during the early evening, producing some severe
storms. The HREF develops some UH tracks greater than 75 in that
Devils Lake to Jamestown corridor around 23z (6 pm), moving them
toward the western Valley by 03z (10 pm). We have been messaging
the 3 pm to 9 pm time frame for severe storms, and this is still
within that ballpark.
Lingering chances for showers and thunderstorms will continue into
Tuesday night, as the daytime convection continues to drift to the
east. It is possible some storms may yet be severe in the early
evening, but any of those should weaken in the later evening and
overnight. Weakening means the severe threat should end, but the
showers and storms should track through the entire area, giving most
of the FA about a 30-40 percent chance of seeing 0.25 inch
amounts.
.LONG TERM...(Wednesday through Monday)
Issued at 257 PM CDT Mon Jul 17 2023
Key Messages
-A 500mb low traverses the FA Wednesday/Wednesday night, bringing
more precipitation chances
-Northwest flow sets up Thursday through Sunday, with more subtle
waves possible (chances for precipitation) at times
The 500mb low will track across the FA Wednesday into Wednesday
night. There is a cold pool aloft, so expect some morning sun
leading to thicker afternoon clouds and the chance for showers and
storms. Severe weather does not look likely, but these lows can
produce funnels under the right circumstances. Later shifts can
take a closer look at that.
For Thursday through Sunday, as the 500mb low pushes off to the east
and ridging builds over the Rockies, flow over the FA turns to the
northwest. By Monday, the western ridge flattens, with a more zonal
pattern ensuing. The main highlights for this period will be that
any waves during this period will be more subtle, but they could
produce precipitation. Confidence is just too low to narrow that
down this far out. The other thing is that temperatures look to
return to near or slightly above normal.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1047 PM CDT Mon Jul 17 2023
MVFR conditions persist at KGFK and KDVL tonight due to low level
smoke. Other sites are currently VFR, but could experience brief
reductions into the MVFR category due to smoke, mainly this
evening and overnight. Look for winds to become southerly Tuesday,
with smoke expected to diminish slightly through the late morning
and into the afternoon. Look for a chance of isolated showers and
thunderstorms during the mid to late afternoon. Strong to severe
storms are possible for portions of the region, primarily from the
Red River Valley and points west.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Lynch
SHORT TERM...Godon
LONG TERM...Godon
AVIATION...Lynch
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
900 PM CDT Mon Jul 17 2023
.UPDATE...
Issued at 846 PM CDT Mon Jul 17 2023
The main update this evening was to expand the chances for
precipitation further southwest based on the potential for storms
to expand a little further to the south and west as they tap into
the enhanced shear and instability. Forecast soundings show a
significant amount of MUCAPE, very steep mid level lapse rates
(on the order of 8-9 degrees C/km), and ample deep layer
shear...this increases my confidence in hail sizes in general
larger than just the "basic" severe size of quarters. Thinking
potentially up to the size of golf balls in the strongest storms,
at least as they start to move into the area from the northwest
(most likely around 1 or 2AM). If these develop into a more
coherent line, gusts up to 70 mph may be possible, but currently
not confident one way or the other on that. These storms are
expected to move southeast across the area during the overnight
hours (roughly 1-5AM according to the latest HRRR run), with
perhaps another round in our far north around mid to late morning.
&&
.DISCUSSION...(This evening through Monday)
Issued at 430 PM CDT Mon Jul 17 2023
Key Messages:
* Off and on thunderstorm chances continue for the next several
days due to active zonal to NW upper flow.
* These will be hit and miss, and not everyone will see them...but
any storms that do form late tonight through Wednesday could be
on the severe side given strong instability and unseasonably
strong wind shear.
* Outside of far southern portions of the forecast area, any
really hot and humid conditions look to remain confined mostly
south of the area until perhaps the upcoming weekend.
* Smoke from Canadian wildfires has caused poor air quality today
and kept temperatures lower than forecast, but these impacts
should lessen over the next 24 hours.
Forecast Details:
Once iso-scat shwrs/storms ended this AM it`s been a pretty quiet,
and overall fairly comfortable, summer day across most of the
forecast area. Steady NE-E sfc winds have had a lot to do with
this, but so has the thick smoke from Canadian wildfires, as air
temperatures have been held several degrees cooler than forecast.
In fact, most locations along/N of Hwy 6 are still, as of 3PM,
only in the 70s. The exception to this is across far S tier of KS
zones owing to thinner smoke and pooling low level moisture where
air temps are closer to 90F, and dew points are in the lower 70s.
Heat indices may briefly touch the century mark in these areas,
but probably only for an hour, or two.
Tonight, attention turns to the next round of shwrs/storms
forecast to move into the area from the W/NW. Shortwave ridging
and large scale subsidence have kept conditions along the High
Plains quiet thus far, but this is forecast by most CAMs
(including last several runs of the HRRR) to change this eve as a
shortwave trough, currently seen on WV imagery from MT into ID,
shifts E towards the Plains. While timing of this wave is not
ideal for sfc based convection to organize into an MCS prior to
diurnal stabilization, model progs of a 35-45kt LLJ (and
associated isentropic ascent) nosing from the S Plains into KS/NE
region should still allow for continuation of at least weak to
moderate convection into the late overnight hours as the upper
level shortwave rounds the top of the ridge near the Black Hills
late this eve, then turns SE overnight. This is pretty classic
"ring of fire" effect for this region for this time of year as
convective complexes tend to track along the mid level thermal
gradient, which tonight, is a fairly impressive 10C from SW to NE
across Neb. TL HRRR and HREF suggest areas N and E of the Tri-
Cities have the greatest chcs for storms and appreciable rain
amounts. However, want to caution that if storms really tap into
the unseasonably strong upper shear (effective shear progged to be
40-60kt per latest SREF), then sometimes these complexes can take
a hard turn to the right/south, as was evident in KS last eve.
HRRR simulated refl is less than impressive with activity over
most of our CWA tonight, but am somewhat skeptical given
aforementioned features and overall pattern recognition. It is
just hard for me to ignore that kind of wind shear in July, esp.
when steep mid level lapse rates and strong MUCAPE are being
advected N/NE by a decent LLJ. So...if storms are stronger, then
Tri-Cities will be in play for decent rainfall, but it would also
probably come with incr risk for hail and/or high wind.
As for the ongoing smoke, mixing has helped vsbys to finally rise
back to the 7-10 mile range for most of the area, but there`s
still an obvious "milky/smokey" look to the air. HRRR/RAP progs
suggest continuation of this through the overnight, perhaps even
backing some to the W/SW, but then steady improvement through the
morning hours Tuesday. Reference the latest AQA for additional
information. Latest guidance suggests minimal smoke concerns on
Wed, but perhaps another round sometime late Wed night into Thu
along and behind a cold front.
Tonight`s convection should be largely E/SE of the area by sunrise
Tue with the daytime hrs likely playing out pretty similarly to
today - mix of sun/clds/haze and Erly low level flow. Most
guidance has trended a bit cooler for Tue, which makes sense given
how today has played out. This should once again limit temps and
keep any heat index concerns of AOA 100F confined to far S
portions of our KS zones. Lowered Tue highs a solid 2-4 deg and
this may not even be enough per latest NBM.
Probably looking at a repeat scenario Tue PM as convection once
again develops over the High Plains of WY/CO/W NE during the aftn,
then shift E in the quick mid-upper level flow Tue eve/night.
Guidance still suggests decent combination of effective shear and
instability, though the instability axis and magnitude may not be
as impressive as tonight. Most notably, however, is the fact the
LLJ is oriented much further S and noses primarily into the Mid MS
Valley, so convection moving off the High Plains probably won`t
be quite as organized. Nonetheless, SPC Marginal risk of severe
still looks warranted, at least for W third or so of CWA.
Next synoptic disturbance looks to come later Wed into Wed night
in the form of a decently strong cold front. Timing of the front
currently looks to be post peak-heating/instability, but suspect
decent instability/shear/mid level lapse rates will still persist
into the eve/overnight hrs, so again, the SPC Marginal risk seems
appropriate. If timing managed to speed up, then a greater risk
for severe weather could materialize.
Should get into a slightly cooler and drier airmass behind the
synoptic cold front for the end of the work week. In fact, Thu and
Fri look to be quite pleasant by late July standards with highs in
the 80s and seasonably low dew points in the upper 50s to lower
60s. Latest ensembles suggest a warming trend in time for the
weekend with highs returning to the 90s.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 629 PM CDT Mon Jul 17 2023
Showers and thunderstorms are expected in the vicinity of the
terminals overnight tonight, mainly between around 07Z and 15Z. As
far as visibility and CIGs are concerned, sticking with the 6SM
and HZ for the overnight hours due to the wildfire smoke filtering
through the area. CIGS will lower but likely still be VFR as
thunderstorms move through, but probably drop to MVFR (maybe a
brief period of IFR) in the morning after storms depart. CIGs
should improve to VFR by the afternoon. Winds will generally be
out of the east to southeast the entire period at 8-12 kts (except
gusty and variable in thunderstorms). Gusts may be 20-25 kts at
KGRI during the late morning and early afternoon hours.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
UPDATE...Hickford
DISCUSSION...Thies
AVIATION...Hickford
Area Forecast Discussion
National Weather Service Goodland KS
755 PM MDT Mon Jul 17 2023
.UPDATE...
Issued at 744 PM MDT Mon Jul 17 2023
Fairly decent signal for fog/stratus over the eastern portion of
the area starting around 09Z-14Z as moisture advection brings low
70 dew points back into the area. The only caveat to fog formation
would be if any ongoing showers/storms are occurring which would
mitigate the potential. I also added in haze into the forecast as
the HRRR Vertically Integrated Smoke Parameter has been
consistently showing smoke aloft moving into the area from the
ongoing Canadian Wildfires. I do think the haze will be a bit more
widespread than today (as McCook has been at 5sm all afternoon and
evening) as the ridge breaks down and retrogrades a bit more to
the west. I also did lower high temperatures across the east for
Tuesday due to the impacts of the haze and the potential for the
fog/stratus deck to linger for the majority of the morning.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 332 PM MDT Mon Jul 17 2023
Current visible satellite shows mostly clear skies over the area
with 500 mb analysis showing the upper high centered over the Four
Corners region and the ridge axis through eastern Montana/Wyoming.
Forecast 850 mb temperatures today to around 27-32C have us seeing
high temperatures climb into the lower 90s over northeastern
portions with lower 100s over southwestern portions. Heat indices
have been observed in the middle 90s to low 100s. As a shortwave
moves through the generally northwesterly flow aloft this evening-
tonight, may see storms from WY continue southeastward with
potential to clip north-northeastern portions of our area, between
approximately 03-09Z. If this does occur, storms could be strong to
severe with 0-6 km bulk shear 40-50 knots, modest instability, and
PWATs to around 1.25 to 1.5 inches. Overnight lows are forecast in
the middle 60s to near 70.
Going into tomorrow, the upper high slides eastward with the ridge
being deamplified by an upper low moving through Saskatchewan. Flow
aloft becomes more WNW. At the surface, flow veers to become ENE
with a surface low moving through. 0-6 km bulk shear still around 40-
50 knots, SBCAPE generally around 2000-3000 J/kg, 700-500 mb lapse
rates around 8-8.5 C/km, and PWATs increasing to around 1.25-1.5
inches allow for severe potential with storms. Approximate timeframe
for development is expected in the mid to late afternoon (~22-00Z)
west of the area, continuing into the evening hours with primary
hazards of damaging winds and large hail. Afternoon highs continue
in the low to upper 90s with overnight lows in the middle 60s to
near 70.
On Wednesday, the positively tilted trough/upper low continue
southeastward towards eastern ND/northern MN as the upper high
remains across the southern CONUS. A frontal boundary moving through
will serve as focus for convective initiation in the mid to late
afternoon. The severe threat currently looks to cover eastern
portions of the area where better instability and moisture are
available with PWATs around 1.5-1.75+ inches. A marginal risk of
excessive rainfall also exists and may lead to localized flash
flooding with storms. High temperatures climb into the upper 80s to
middle 90s followed by overnight lows in the low to middle 60s.
.LONG TERM...(Thursday through Monday)
Issued at 147 PM MDT Mon Jul 17 2023
The latest GFS/ECMWF both continue to show strong, amplified upper
ridging over the western portion of the country on Thursday, with a
slow progression eastward towards the Plains region for the latter
portion of the upcoming weekend, on into the beginning of next week.
There will be a couple shortwaves working southeast along the
eastern periphery of the ridge. Based on model track, these systems
will move through mainly western and southern portions of the CWA
for Thursday into Friday night. With the upper ridge starting to
crest over the CWA by the weekend, looking for a dry period for the
area. ECMWF a bit closer towards this versus the GFS.
At the surface, a frontal boundary will be the low level focus for
precipitation over the first 48 hours. The front is draped over the
south/southwest portions of Kansas as high pressure resides north of
there. The western portion of the front does extend back into
Colorado by Friday. This will allow easterly flow over the CWA on
Thursday to transition to more southeasterly by Friday/Friday night.
The result of this will keep a steady inflow of low level moisture
into the area as each shortwave passes through. Chances for rw/trw
will result. With high PW values over an inch to 1.5", locally heavy
rainfall will be of concern and is highlighted for excessive Day 4/5
Rainfall Outlooks from the WPC. Hydro concerns will have to be
monitored. Most of this precip will occur during the afternoon/
evening hours, so diurnal heating will create additional
instability, so can`t rule out a strong to severe storm possibility.
For temps, highs on Thursday and Friday will range from the upper
70s into the mid 80s. Coolest locales will be in the west/southwest
where best chances for clouds/precip to occur. Going into the
upcoming weekend, warmer conditions expected with no precipitation
forecasted. Looking for a range in the mid to upper 80s Saturday,
give way to lower and mid 90s for Sunday. Going into next Monday,
hot temperatures remain with mid and upper 90s on tap.
Heat indices for the the upcoming 72-hour period (Saturday through
Monday) will range at this time to near or just above forecasted
highs.
Overnight lows will have an increasing trend as well with upper 50s
to lower 60s Thursday night, give way to mid 60s west to upper 60s
east by Sunday/Monday nights. A few spots east of Highway 83 may
only drop to around 70F.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 533 PM MDT Mon Jul 17 2023
Some haze from Canadian wildfires is occurring at KMCK currently
which is causing MVFR visibilities, as the night inversion sets in
around 02Z should let VFR conditions return to the terminal.
Stratus and fog looks to develop east of the KGLD terminal
overnight and persist through sunrise. Guidance is in fairly good
agreement for KMCK to be impacted by MVFR to even IFR ceilings and
possibly visibilities through mid morning. Forecast humidity
cross sections isn`t as optimistic for fog/stratus at KGLD so will
leave out of the TAF for now and monitor. A low chance for
showers and storms exists across the area Tuesday afternoon; will
leave out of the TAF for now until exact location details become
more clear.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...Trigg
SHORT TERM...CC
LONG TERM...JN
AVIATION...Trigg
Area Forecast Discussion
National Weather Service Gray ME
1038 PM EDT Mon Jul 17 2023
.SYNOPSIS...
Somewhat unsettled weather returns on Tuesday as an upper
trough arrives resulting in a return of scattered showers and
thunderstorms some of which could be strong during the
afternoon. Localized flash flooding will be possible as well.
Drier air is expected for Wednesday Night into Thursday before
another trough arrives late week bringing chances for showers
and thunderstorms Friday into the weekend.
&&
.NEAR TERM /TONIGHT/...
1040PM Update...No changes needed to the forecast other than
massaging temps and dewpoints to match latest observations.
745PM Update...The forecast for this evening remains is in good
shape and didn`t need any changes. Going into late
tonight/early Tuesday morning, a few showers and possibly a
storm could approach far northern areas toward or just after
sunrise in response to a weak wave aloft. The HRRR has been
showing this for a few consecutive runs now, especially into
Coos county. So I did add a small shower/storm chance across
these areas starting around 09Z/5 AM. The rest of the area is
expected to remain dry with fog possible along the coast as well
as the valleys.
Previous...
Mostly clear skies continue tonight with some haze making its
way across New Hampshire and into Maine overnight. While skies
remain clear, moisture will linger at the surface with dewpoints
remaining in the upper 60s to low 70s south of the mountains.
This will allow fog to return to the coast and central Maine
tonight, likely lingering along the midcoast into the morning.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
A cold front will begin to cross the area tomorrow morning from
the west bringing another round of showers and thunderstorms.
Showers are expected to increase through the day with the
thunderstorm potential strengthening in the afternoon as
instability builds. As thunderstorms pass through, some may
strengthen to strong to severe with rainfall rates up to 2
inches per hour. While not all areas may see heavy downpours,
those that do may experience a renewal of flash flooding due to
saturated soils. Along with the flooding potential from heavy
rain, the saturated soils may cause trees to be blown over at
lower windspeeds in thunderstorms. Showers and thunderstorms
look to continue into tomorrow night, tapering off after
midnight as the cold front exits to the east.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
A trough of low pressure will exit the region Tuesday night and
Wednesday, leaving most of the forecast area with dry
conditions however there may be a slight chance of a shower over
eastern sections. It will be very warm and perhaps slightly
less humid with most locations in the 80s for afternoon high
temperatures.
A weak short wave trough is expected to cross the region on
Thursday but forcing will be weak. Therefore we expect mainly
dry weather with perhaps an isolated afternoon shower or
thunderstorm.
A deeper short wave trough approaches Friday and is likely to
aid in widespread showers and thunderstorms Friday and Friday
night. This could cause renewed flash flooding depending on how
favorable parameters line up. Leftover showers may occur
Saturday.
Better weather is then expected Sunday and Monday with weak high
pressure moving in.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Short Term...Skies will remain mostly clear tonight for western
terminals while fog returns to coastal terminals and AUG
bringing ceilings down to IFR into the morning. Ceilings will
then thicken and lower from west to east through the day
tomorrow as a cold front crosses the area bringing showers and
thunderstorms through most terminals. Showers taper off after
midnight tomorrow with conditions returning to VFR for
Wednesday.
Long Term...Mainly VFR during the daytime hours Wed and Thu with
areas of fog coming in at night. Low pressure moves in from the
west Friday and Saturday with more IFR conditions in showers and
thunderstorms.
&&
.MARINE...
Short Term...Seas will continue to subside through the short
term while winds remain primarily from the south. Coastal fog
returns tonight as moist conditions continue. A cold front
crosses the waters tomorrow afternoon bringing showers and
thunderstorms with gusty winds and high seas near these storms.
Long Term...Winds and seas will be below SCA thresholds during
the long range portion of the forecast. However, maritime fog
will develop from time to time, especially during the nighttime
hours.
&&
.HYDROLOGY...
Locally heavy rains can be expected once again Tuesday into
Tuesday evening as a trough of low pressure once again enters
the Northeast. The risk of excessive rainfall is primarily over
central and northern areas. A flooding watch has been issued,
mainly due to scattered slow-moving thunderstorms producing very
high rainfall rates.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch from Tuesday afternoon through Tuesday evening for
MEZ007>009-012-033.
NH...Flood Watch from Tuesday afternoon through Tuesday evening for
NHZ001>009-011-012-015.
MARINE...None.
&&
$$
NEAR TERM...Combs/Thunberg
SHORT TERM...Thunberg
LONG TERM...Ekster
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1031 PM EDT Mon Jul 17 2023
.SYNOPSIS...
A cold front will move southeast through the Great Lakes and
Ohio Valley tonight, bringing a chance of showers and
thunderstorms. Precipitation chances will decrease into Tuesday
as stalls out near the Ohio River. Additional chances for
showers and thunderstorms are expected Tuesday night into
Wednesday as a warm front lifts north into the Ohio Valley.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
MCS continues to push southeast across ILN/s FA into the Scioto
River Valley and northern Kentucky. These storms have a had a
history of producing large hail and strong to damaging winds
across western portions of ILN/s FA.
Radar shows a general weakening trend and the severe weather
potential diminishes as the storms encounter a less favorable
environment. However, with lingering instability continuing
across the far south and southeast -- can not rule out severe
out a severe potential through about midnight, with strong to
damaging wind being the main threat.
As storms line up across the south ahead of the surface front
that lays out in an east-west fashion - the potential for
training storms, heavy rain and localized flooding will exist
overnight.
Lows tonight will be in the low to mid 60s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/...
With the front washing/stalling out along or just to the south
of the Ohio River, will linger some slight chance pops across
mainly our southern areas during the day on Tuesday. The HRRR
smoke model is suggesting some lingering, but less concentrated
smoke across the region through the day on Tuesday. It also appears
to be pinching off the smoke somewhat, so will hold off on
including any mention of haze/smoke in the forecast for now.
Highs on Tuesday will be in the upper 70s to low 80s.
The models have trended a little farther to the southwest with
a mid level short wave/MCS moving through the lower to mid Ohio
Valley Tuesday night into Wednesday morning. As a result, will
keep pops in the chance category, with the highest pops across
our southwest. The exact timing and track of the Tuesday night
MCS may affect how things play out through the day on Wednesday.
As of now, it looks like the remnant cold front/boundary may
lift back north into our area as a warm front through the day on
Wednesday. This, combined with some additional mid level
energy, should result in some decent chances for showers and
storms, especially across our southern areas. Highs on Wednesday
will be in the 80 to 85 degree range.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
On Wednesday night, an upper level trough will be moving east
through northern Quebec, with a second upper level trough moving ESE
into the northern Great Lakes. To the south of these features, the
flow over the Ohio Valley will be pivoting from northwesterly to
westerly, as a a 700mb wave crosses through the area. A surge of
theta-e in the low levels is expected heading into Wednesday night,
though in reality, this may be disrupted somewhat by the Wednesday
morning MCS. Impacts from that MCS will have effects on the forecast
for Wednesday night and beyond, so overall confidence is fairly low.
Most models do suggest an environment that may become favorable for
additional storm development Wednesday night through early Thursday
morning, so some PoPs will be maintained.
The greatest chance for precipitation during this part of the
forecast period will be on Thursday afternoon and evening. The warm
sector will become established over the ILN CWA on Thursday, with
an area of low pressure moving across the lower peninsula of
Michigan, and a cold front trailing behind it to the southwest. This
is still a few days away, but early indications are that instability
and shear could both be just enough for some risk of strong storms.
Cold frontal passage late Thursday into Friday morning will bring in
a drier and slightly cooler air mass, with rain much less likely for
Friday and Saturday. For Sunday and Monday, confidence is very low
in the forecast specifics, but broad troughing will likely be
settling into the eastern half of the CONUS, suggesting at least
some chance for precipitation will exist.
Thursday will likely be the warmest day of the extended period, with
highs in the mid to upper 80s. Behind the cold front, Friday and
Saturday will be cooler, with highs in the upper 70s to lower 80s.
Some warming is possible thereafter.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Thunderstorms have developed across central Indiana into west
central Ohio this afternoon - in a region of low level theta-e
advection, where moderate instability exists ahead of a
southward advancing cold front.
This cold front will push southeast into the region through
this evening before stalling out near the Ohio River late
tonight into Tuesday morning.
Shower and thunderstorm will overspread the TAF sites early this
evening with strong to damaging winds possible across the
western TAF sites early. Have locally expanded the severe
thunderstorm watch.
Pcpn should then taper off through the overnight hours. Outside
of the storms, areas of MVFR haze will persist into tonight. In
addition, some MVFR cig development will be possible in the
wake of the pcpn later tonight and into Tuesday morning. MVFR
cigs will lift into VFR later Tuesday morning into the
afternoon.
OUTLOOK...Thunderstorms possible at times Tuesday night into
Thursday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...JGL
NEAR TERM...AR
SHORT TERM...JGL
LONG TERM...Hatzos
AVIATION...AR
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
909 PM CDT Mon Jul 17 2023
.SYNOPSIS...
Issued at 909 PM CDT Mon Jul 17 2023
As a cold front slips southward through tonight, the persistent
haze is expected to fade away by morning. A few showers and
thunderstorms will continue late this evening south of a
Jacksonville to Danville line, but will diminish from north to
south overnight. Additional showers and thunderstorms are
expected Tuesday and Tuesday night, but the trend for heavy rain
is focusing more on an axis from west central Illinois into
western Kentucky.
&&
.UPDATE...
Issued at 909 PM CDT Mon Jul 17 2023
Updates have been made for lingering thunderstorms streaming into
the area from the northwest west of Springfield, but otherwise the
front settling southward through the area, will bring stabilizing
conditions gradually expanding southward tonight. Currently
2000-3000 J/kg MLCAPE remain south of I-72 along with near 40 kt
effective bulk shear indicating a continued severe weather threat,
but the axis of the shortwave enhancing lift and leading to
earlier severe storms has nearly exited the area. A severe
thunderstorm watch remains in effect from Shelby to Paris County
southward until 11 PM, but current trends could lead to this watch
ending early.
Otherwise, lows still look to reach the upper 50s north of I-72,
and low to mid 60s to the south.
37
&&
.SHORT TERM... (Through Late Tuesday Night)
Issued at 317 PM CDT Mon Jul 17 2023
Main concerns in this period:
1) Convection through this evening, then MCS trends for Tuesday
2) Eventual waning of the haze/smoke layer
Early afternoon weather map shows the cold front is located
roughly from the northern St. Louis metro northeast to near
Watseka. The storms that had been tracking southeast from Iowa
have mostly skirted the forecast area, but recent development is
near Springfield/Jacksonville and also from Bloomington to
Danville. These have been robust at times, producing hail up to
walnut size at Danville, and are occurring along an axis of 3000
J/kg SBCAPE. New SPC Day1 outlook upgraded to a level 2 (slight)
risk from about I-72 southward. The trend will continue to shift
southward through the evening as the front slips to near I-70.
Trends with the Tuesday/Tuesday night MCS activity continue to
shift a bit southward, with most of the CAM`s focusing on a
corridor from near Quincy southeast into western Kentucky. This
matches up with HREF ensemble means which are showing 1.5 to 2.5
inches of rain Tuesday afternoon/night in that area. MCS`s can be
a bit finicky in their tracks, so only a small northward jog would
easily get parts of our CWA into flash flood concerns. Will
concentrate the highest PoP`s Tuesday night south of a Rushville-
Paris line, and have lowered them north of I-74.
Regarding the smoke, the ribbon of lower visibility has been
shifting closer to I-72/Danville this afternoon. Latest RAP smoke
model keeps it in this area south to I-70 through the night,
though thinning with time. Will not mention any haze at this point
for Tuesday, though there remains some concern it may still
linger in that area. The vertically integrated smoke parameter
shows the layer aloft moving out during the afternoon, and no
correction to the sky grids was made after midday Tuesday.
Geelhart
&&
.LONG TERM... (Wednesday through Next Monday)
Issued at 317 PM CDT Mon Jul 17 2023
Upper level pattern will be dominated by an amplifying ridge over
the Rockies beginning on Thursday, gradually shifting east into
early next week. This will keep us in more of a northwest flow,
though a shortwave will be dropping southeast into the Great Lakes
Wednesday night and Thursday. Longer range models suggest more of
an MCS ridge-rider pattern early next week for our area with the
amplifying high, though details this far out are sketchy.
Temperatures below normal are expected this weekend with broad
troughing over the eastern U.S., before starting to edge upward
early next week as the ridge shifts toward the Plains.
Geelhart
&&
.AVIATION... (For the 00z TAFs through 00z Tuesday Evening)
Issued at 629 PM CDT Mon Jul 17 2023
Wildfire smoke will start to clear out by later tonight. Scattered
thunderstorms over west-central IL this evening will continue to
expand east/southeast along a cold front, possibly clipping SPI,
DEC, and CMI (near/south of I-72). West-northwest winds
below 12 kts will become light overnight, gradually veering to a
southeasterly direction by midday Tuesday.
Delaney
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Indianapolis IN
935 PM EDT Mon Jul 17 2023
.Forecast Update...
Issued at 934 PM EDT Mon Jul 17 2023
Bulk of the convection was moving out of central Indiana, however
there was still a cell with rotation near Spencer coincident with
100 or so 0-1 and 0-3 km SRH, so will hold on to the Severe
Thunderstorm Watch for now. Radar trends and CAMS still suggest more
activity could move in late this evening and overnight, so will hold
on to small PoPs through the night. Would not rule out some fog,
especially in areas that saw the most precip as surface winds become
light to calm. Otherwise, temperatures have fallen through the 60s
behind the cold pool and upper 50s are possible over far northern NW
sections in the wake of the advancing cold front, currently near
the I-70 corridor.
&&
.Short Term...(This evening through Tuesday)
Issued at 307 PM EDT Mon Jul 17 2023
- Chances for showers and storms late this afternoon and evening.
- Improving Smoke conditions.
- More chances for showers and storms on Tuesday afternoon.
Surface analysis early this afternoon shows weak cyclonic flow
across Central Indiana, associated with a large area of low pressure
over eastern Ontario. A ridge of high pressure was found over the
northern plains, nosing southeast into the middle Mississippi
Valley. Aloft the broader pattern suggested a strong ridge over the
western United States while a broad trough was found from the
plains, across the Ohio Valley toward the Appalachians. A few
embedded short waves were found within the cyclonic flow, over
western KY and a second over IA, entering western IL. Skies remained
smokey across Central Indiana, as air quality was Unhealthy for
sensitive groups. PM2.5 values have improved to near 110 across
much of the forecast area per airnow.gov. However, better air was
found to the southwest with southerly winds in place.
Tonight...
The short wave over IL is expected to push across Central Indiana
late this afternoon and into the evening. It still remains unclear
if convective temps will be reached as smoke has limited max heating
today. Still, ample forcing will be available through the evening as
the short wave passes. Further forcing will be available as a weak
surface cool front approaches the area. Forecast soundings continue
to suggest a favorable column for convection, with over 1800 J/kg of
CAPE available this afternoon and evening. HRRR continues to
suggest scattered to isolated shower and storm development after
21Z, lingering through the late evening hours. Thus will continue
the ongoing forecast with dry weather expected through at least
400PM, then continuing the chance to likely pops across the forecast
area thereafter and through the evening.
Lingering fog will be possible overnight due to earlier rainfall and
dew point depressions of 2-3F overnight. Look for lingering high
clouds in the wake of any convection overnight as the enforcing
exits the area and low temperatures in the lower 60s.
Tuesday...
More showers and storms look possible on Tuesday. The upper flow
across Indiana is expected to become more northwesterly. Indiana
will be caught between strong high pressure aloft anchored over the
American southwest and a trough of low pressure aloft across eastern
Canada and the northeastern United States. Models suggest that
within this resultant NW flow a quick moving short wave will
approach central Indiana by mid to late afternoon, Once again ample
moisture will remain present with dew points in the 60s. Weak
surface convergence will be present also, as the lingering frontal
boundary from tonight/s possible storms will remain in the area.
Forecast soundings show reachable convective temps, but much
shallower CAPE on Tuesday afternoon. Overall, enough thunderstorm
ingredients appear to be present to necessitate the inclusion of at
least chance pops during the afternoon on Tuesday as the short wave
arrives in the area. Given the slightly cooler air mass in place
across the area, highs near 80s will be expected at most spots.
&&
.Long Term...(Tuesday night through Monday)
Issued at 307 PM EDT Mon Jul 17 2023
The long term will span the final days of the year`s
climatologically hottest period...yet temperatures are progged to
continue their near, to at times slightly below normal trend.
Synoptically, a rather broad H500 trough will prevail over the
eastern half of North America...while a hot upper ridge centered
near the Four Corners extends northward into southwestern Canada.
With the inflection point amid this wave hinged near Iowa, central
Indiana will generally be influenced by weak disturbances embedded
in the flow of the trough`s southwestern quadrant.
Tuesday Night through Thursday...
A more active pattern is expected for the mid-week as the upper
trough first becomes better established near/east of the region. A
more zonal pattern that should hold pronounced heat just to our
south and west...will nevertheless focus so-called ridge-riding
convective chances from the Middle Mississippi Valley towards
Kentucky. This conditional opportunity for isolated to scattered
showers/t-storms will be focused across southern portions of Indiana
where deep moisture levels will approach 2.00 inches. Convective
parameters will present conditional potential both days...with
daytime CAPE ranging from around 1000 J/kg (Wednesday) to 2000 J/kg
(Thursday)...with decent mid-level lapse rates Wednesday and
lackluster amounts Thursday...yet all while the ridge gradient`s
presence brings adequate vertical wind shear over the region both
days. Late Thursday`s storm potential could also be enhanced by the
trough`s weak wave/boundary passing just north of the region.
Marginal severe threats would be primarily wind and large hail with
limited amounts of low-level shear. The Wednesday night-Thursday
tandem are expected to be the warmest of the long term, with lows 65-
70F and highs in the mid to upper 80s...with other periods at least
a couple degrees lower amid this continued seasonable stretch of mid-
summer conditions.
Friday through Monday...
A somewhat drier column will accompany seasonably weak, yet rather
broad surface high pressure that should cross the Midwest late this
week. Guidance is continuing to show a transition early next week
as lower heights slide east and the hot, western ridge perhaps
finally builds towards the Midwest. At a first glance a few pulse
storms cannot be ruled out as a more summery pattern returns, with
what should be low-moderate levels of both instability and wind
shear. Most days surrounding this weekend are expected to bring
highs 80-85F and lows 60-65F.
&&
.Aviation...(00Z TAF Issuance)
Issued at 615 PM EDT Mon Jul 17 2023
Impacts:
- Thunderstorms accompanied by MVFR and worse conditions will likely
impact the terminals through 03z and possibly later and also after
18z Tuesday
- MVFR ceilings are possible away from thundersorms 03z-12z
Discussion:
Thunderstorms will roll across all but perhaps KLAF this evening
before the activity diminishes. More MVFR conditions are also
possible overnight away from convection. Finally, more convection
is possible Tuesday afternoon.
The storms this evening could be severe with large hail and possibly
brief gusts to 50 knots in the heavier storms.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...MK
Short Term...Puma
Long Term...AGM
Aviation...MK
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1127 PM EDT Mon Jul 17 2023
.UPDATE...
Issued at 1127 PM EDT MON JUL 17 2023
A line of sub-severe storms and showers has held together long
enough to enter the northern portion of the CWA. The line has
become outflow dominant and should begin to weaken as it
progresses southeast though the area and into a less favorable
environment. areas along the I-64 corridor and farther east near
WV are more likely to experience thunderstorms. A few sub-severe
wind gusts of around 40 mph are possible and may warrant an SPS or
two. CAMs do hint at isolated shower/storm activity farther south
and west, warranting low chance PoPs for the overnight.
UPDATE Issued at 742 PM EDT MON JUL 17 2023
Considerable uncertainty still remains in regards to the
development of showers and storms along a front that is dropping
southward through the Ohio Valley. CAMs do not show agreement for
the overnight period with the HRRR on the dry side and the NAM
Nest and ARW sending a decent MCS through eastern KY but vastly
different timing. Have kept the precipitation forecast in tact
from the day shift for now. Minor tweaks to the sky cover, T/Td,
and wind grids have been made to account for the latest
observation trends.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 326 PM EDT MON JUL 17 2023
The surface analysis shows a cold front is heading toward the
Ohio Valley. We saw some morning convection move through, and
there are some subtle outflows as a result over the far east.
Given this, we will see a few storms develop through the
afternoon. The question comes for the late afternoon and evening,
as cloud cover and some CIN have been an issue based on the latest
mesoanalysis. Given this thinking, the best chances of strong
storms would be generally north of the Mountain Parkway, and SPC
did favor this in their 1630Z update. This leads to lots of
uncertainty overnight and will be highly dependent on development
this afternoon and evening. Overall, keep PoPs maxed in the chance
range at 30 to 40 percent through the overnight given the spread
in the CAMs.
On Tuesday, the previously mentioned front will remain draped just
to our north along the Ohio River. This will allow the weather to
remain somewhat unsettled. However, we do see relatively lower
PWAT values, and CAMs suggest less coverage overall on Tuesday.
Given this, PoPs maxed out at around 30 percent through the day
Tuesday, with perhaps some convection early before renewing in the
afternoon. This will allow highs to top out in the mid- to upper
80s. By Tuesday night, guidance showed the potential for another
MCS that could slide toward the Ohio Valley, with ample moisture
in the mean PWAT values of 1.5 to 1.7 inches. There remains a fair
amount of uncertainty about where this will actually end up going,
and some of the early indications and trends in the ensembles have
been more south and west. Right now, the greatest potential for
flooding Tuesday night is across southern Illinois and western
Kentucky, as CAMs align with this idea. Right now, we will stick
with a mix of NBM and some forecaster adjustments given the recent
trends. This will lead to a 50 to 60 percent chance of showers and
thunderstorms through the night, but we could see this trending
lower depending on how this MCS tracks.
.LONG TERM...(Wednesday through Monday)
Issued at 238 PM EDT MON JUL 17 2023
A rather active period is on tap as a strong ridge of high pressure
remains in place over the Desert Southwest. While this ridge stays
in place, upper-level flow will remain largely out of the northwest.
Within the flow, multiple impulses are expected to move through the
flow bringing period of rain through the early part of the period.
The period begins with surface boundary draped over the CWA allowing
for continued threat for showers and storms. Models are largely in
agreement of multiple MCSs moving out the Central Plains riding
along along the ridging into the Commonwealth. One of those MCSs is
forecast to move through the region on Wednesday. The SPC has the
area under a Day 3 Marginal and with time, that`ll likely be
upgraded as confidence increases. Within the environment surrounding
the showers and storms, PWs are rather high with values approaching
almost 2.00" in places. If shower activity can be efficient, then
hydro issues may be arise with the expected shower and storm
activity. Fortunately, deterministic guidance has come down on
overall QPF values through Thursday. Nonetheless, WPC has placed a
large portion of the Commonwealth under a "Slight Risk" of excessive
rainfall.
A cold front is expected to move through the Commonwealth on
Thursday and stall across the Tennessee Valley. This will keep
showers and thunderstorms in the forecast through the day Thursday
into Friday with lingering chances of showers and storms into
Saturday before drying out for Sunday. However, the dry weather is
short-lived as there`s some model agreement for another system into
early next week. Nonetheless, the period will be highlighted by near
seasonal temperatures but with above average precipitation and the
potential for flooding issues through the end of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 742 PM EDT MON JUL 17 2023
There remains considerable uncertainty regarding the development
of showers and storms developing later this evening and into the
overnight as a sluggish front drops southward. For now we will
keep VCTS for the overnight hours at each of the TAF sites but
amendments may be needed. Fog will mainly be contained within the
river valleys but may impact the SME/LOZ sites before dawn. Winds
have relaxed to around 5 knots or less and will be light and
variable through the overnight before increasing to between 5-10
knots from the southwest after dawn.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...BATZ
SHORT TERM...DJ
LONG TERM...VORST
AVIATION...BATZ
...UPDATED AVIATION FORECAST DISCUSSION...
.SYNOPSIS...
Issued at 358 PM CDT Mon Jul 17 2023
Key Messages:
- Severe weather appears likely across portions of north central
and central Nebraska tonight. Wind damage is the primary threat
with the potential for very large hail across far nrn Nebraska.
- Severe weather could also develop elsewhere across western
Nebraska tonight.
- Along with the threat of severe weather tonight will be locally
heavy rainfall which could cause flooding in some areas.
- Weather conditions will continue to be favorable for severe
weather at times Tuesday through Friday.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 358 PM CDT Mon Jul 17 2023
The 12z CAMs agree on the development of an organized cluster of
storms across north central into central Nebraska. Isolated
development is possible across southwestern areas. The
NAM/NAMNest as well as the ECMWF generate heavy QPF across
portions of north central into central Nebraska tonight into
Tuesday morning. The POP forecast tonight leans toward the
NAM/NAMNest which suggests likely storms across ncntl Nebraska. A
strong disturbance is currently located from central Montana into
southern Idaho. A backed southeast low level flow is established
and SBCAPEs at 00Z this evening will range from 1500-2500 J/KG
across the western Sandhills into far eastern WY and southeast MT.
Effective bulk shear will be more than adequate to initiate
storms and sustain long lived storms. Models, including the latest
HRRR suggest isolated/scattered storms will form across eastern
WY and track into southwest SD and western and north central
Nebraska tonight.
SPC continues a Slight Risk for severe weather east of Chadron
through Broken Bow tonight with a marginal risk Tuesday morning.
The significant hail outlook includes Sheridan and Cherry County.
While large hail and damaging winds remain a threat across the
remainder of the sight risk area, it will be interesting to see
what happens in terms of hail and wind damage potential. The
severe weather will be operating in an environment rich in
moisture (PWAT 1.25 to around 1.50 inches).
Tuesday, chance to likely POPS will linger Tuesday morning across
the northeast where redevelopment behind the overnight convection
would support a few strong storms. By afternoon, the upper flow
become more zonal as an upper low moves across southern
Saskatchewan and an upper ridge centered over New Mexico. Highs
will be limited to the upper 70s to lower 80s across the east,
with the strongest heating across the southeast panhandle and
southwest with lower 90s. Isolated storms may develop across far
southwest areas late afternoon and spread across the forecast area
overnight. Models differ on coverage, with POPs limited to 20-30
percent overnight. Isolated strong storms are possible through at
least the evening hours.
.LONG TERM...(Wednesday through Monday)
Issued at 358 PM CDT Mon Jul 17 2023
Wednesday, a weak cold front will move through, with highs ranging
in the 80s. While the northwest Sandhills should remain dry, a
slight chance for showers/thunderstorms elsewhere behind the
front. Any development should be isolated, although a few strong
storms are possible due to 0-6km shear from 40-45kts.
A reinforcement of cooler air arrives Thursday with highs only
from 76 to 83 forecast. There is a good chance however that
storms will develop from southeast WY and northeast CO into
southwestern areas during the afternoon and further east Thursday
night.
Thunderstorm chances remain Friday into Friday night with
northwest flow aloft and sufficient deep layer shear.
An upper level ridge across the desert Southwest will build north
and east into Nebraska Saturday through Monday, as winds aloft
weaken somewhat. The intense heat across the Southern and
Southwestern U.S. will begin to be felt across western Nebraska
with highs reaching the low to mid 90s by Sunday and Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 627 PM CDT Mon Jul 17 2023
The main aviation concern surrounds scattered thunderstorm
potential late this evening into the overnight for much of the
Sandhills and portions of north central Nebraska, including KVTN
terminal. Severe storms are possible with this activity including
large hail, strong erratic winds, and heavy rainfall. The area of
the greatest severe risk is across the northwest into northern
Sandhills, impacting KVTN. Given that guidance continues to
suggest direct impacts to the terminal, did include a TEMPO group
from 05Z to 08Z to account for the strong wind gusts, lowered
visibilities, and +TSRAGS potential. Future refinements are
possible as the storms evolve over the next few hours.
Though the strongest of storms are anticipated to remain north of
KLBF, did include a brief mention of VCTS as guidance suggests
some activity may reach the area. Confidence is low on specific
impacts to KLBF terminal, thus future refinements and inclusion is
possible given trends in storm evolution through the late
evening/overnight.
Ceilings begin to low in the wake of the departing storm complex
around daybreak across much of the area bringing a brief period of
MVFR/IFR conditions, impacting KLBF and KVTN.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...Roberg
SHORT TERM...Roberg
LONG TERM...Roberg
AVIATION...Viken
Area Forecast Discussion
National Weather Service Morristown TN
1020 PM EDT Mon Jul 17 2023
...New UPDATE...
.UPDATE...
Issued at 1012 PM EDT Mon Jul 17 2023
Hazy conditions continue tonight and are expected to continue
across the valley until better convective mixing improves near-
surface concentrations mid-morning Tuesday. The big weather
question tonight will be if we remain dry. The 0z guidance did not
initialize well with the convective complex near the Tennessee
River in West Tennessee northward through western Kentucky. This
convective complex is moving eastward and would reach the western
edge of our forecast area at around 0730-0800z if it holds
together. We expect a general decrease in this convection and
anticipate it weakening over the next few hours as instability
wanes, but there is at least a low (20 to 30 percent) chance of
this holding together and bringing some showers and/or rumbles of
thunder to portions of the area late tonight and early Tuesday.
Model guidance continues to be very uncertain with potential
weather conditions Tuesday afternoon and evening. A lot will
depend on on-going convection to our west, residual outflow
boundaries, and the strength/exact track of remnant MCVs. Have
included low-end chance PoPs for most locations on Tuesday
afternoon into the early overnight hours.
JB
&&
.SHORT TERM...
(This evening through Tuesday)
Issued at 308 PM EDT Mon Jul 17 2023
Key Messages:
1. Hazy skies continue today and tonight from Canadian wildfires
2. Chance for quick round of storms across northeast TN and
southwest VA tonight
Discussion:
Currently hazy skies across much of the eastern Tennessee Valley as
smoke funnels into the area from the wildfires across Canada. Smoke
models are having a difficult time resolving how the smoke plumes
interact with convection and outflows across the region. Have have
gone more aggressive with haze wording in the forecast for the rest
of today and into tonight. An Air Quality Alert is in effect for
many places across eastern Tennessee for particulate matter through
midnight. Smoke will likely remain overnight and into tomorrow, but
most indicators point to conditions beginning to improve tomorrow
with smoke density hopefully decreasing from west to east during the
daytime...But still do expect another hazy/smoky sunrise tomorrow.
Another round of convection will try and move southeast from KY
tonight and possibly make a run towards northeast TN and southwest
VA. Certainty on this occurring is low due to CAMs discrepancies with
how these storms will strengthen and develop the rest of the
afternoon. Have generally kept close to HRRR and NBM output showing
that the convection strength and coverage will be limited with
decreased moisture return and storms fighting against the hazy
conditions.
&&
.LONG TERM...
(Tuesday night through next Monday)
Issued at 308 PM EDT Mon Jul 17 2023
Key Messages:
1. Active weather pattern throughout the week with locally heavy
rain possible.
2. Cooler temperatures for the weekend with very low rain chances.
Discussion:
The pattern over the eastern U.S. will be dominated by a trough
through this forecast period. The trough and associated instability
and abundant moisture will aid in thunderstorm development west of
the forecast area each afternoon through the night starting Tuesday
night. Rainfall, heavy at times, will extend into the morning hours.
The heavy rainfall could become problematic for some areas,
particularly those along and north of I-40. The PWATs are relatively
high, moisture transport will peak over these areas during the best
timing for the rain showers, and forecast soundings support
efficient rainfall. Concern for flash flooding is in the moderate to
high range for the Wed/Thu time frame. This coincides with WPC
Excessive Rainfall Outlook (ERO) coordination. Needless to say but
there will be multiple rounds of rainfall possible as wave after
wave gets driven across KY/TN through the remainder of the week. By
the weekend, the trough deepens enough to push a frontal boundary
well into Georgia and Alabama. This should not only cool things off
considerably (lower to mid 80s) but lessen rain chances through
early next week.
&&
.AVIATION...
(00Z TAFS)
Issued at 652 PM EDT Mon Jul 17 2023
Will keep prevailing smoke and haze through the night as HRRR near
surface smoke does keep similar concentrations across the valley
through about 14z Tuesday with VFR conditions and 4-5k few to sct
clouds through the afternoon at all sites. Winds begin to shift
to the WSW on Tuesday afternoon with low probs for thunderstorms
near TYS and TRI late in the day. There is still considerable
uncertainty in convective development and coverage late in the
forecast period, so have included a prob30 group for TSRA at TYS
and TRI late in the period.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 70 94 74 94 / 0 20 20 20
Knoxville McGhee Tyson Airport, TN 68 91 72 89 / 10 30 30 40
Oak Ridge, TN 67 89 71 88 / 10 30 30 50
Tri Cities Airport, TN 63 87 67 83 / 10 30 40 60
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...
LONG TERM....AC
AVIATION...JB
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 312 PM CDT Mon Jul 17 2023
Key Messages:
- There is a Slight Risk for severe weather after 1 AM tonight.
There are two potential rounds. The first could have 60-75 mph
wind gusts and large hail and should end by 6 AM. The 2nd
possible round would take place in northeast Nebraska and could
have damaging wind gusts and large hail.
- There is a Marginal Risk for severe weather on Wednesday
evening.
- Cooler temperatures are forecast to end the week.
Today and Tomorrow:
Early morning severe weather was observed in the area this
morning producing golf ball sized hail near Leigh, Nickerson, and
Arlington. The hail continued into southwest Iowa where Malvern
observed ping pong sized hail.
Severe weather will continue to be the story as there is a Slight
Risk (Level 2 out 5) for storms after 1 AM and continuing until noon
tomorrow. There is some uncertainty into how the situation will
play out during the overnight hours as there could be potentially
two rounds of storms. The first round of storms are expected to
develop in Wyoming and western Nebraska along the peak of a ridge
of theta-e. This will also be co-located with a minor disturbance
in the upper level flow. Initially, these will be capable of
producing large hail up to 2 inches (remember, that`s way out
west). CAM guidance shows these storms combining into an MCS or a
linear line and following the edge of the theta-e ridge southeast
across the state. The line is expected to maintain its strength
as it moves to the southeast and the low level jet strengthens.
Potentially significant damaging wind gusts will be possible as
runs of the HRRR show 60 to 75 mph wind gusts moving through the
area. Hail will also be possible with mid-level lapse rates
between 7.5-8.0 C/km. Confidence is higher in this first round of
precipitation. CAMs are showing potential for a 2nd round,
farther to the north as the theta-e ridge shifts to the west and
warm-air advection initiates storms. The lapse rates aren`t as
impressive farther to the north in the mid-morning hours, but
severe weather will be possible with 0-6 km shear between 50 to 60
kts. With upper level winds oriented along the elevated warm
front, there is potential for localized flash flooding if storms
train along that front. Outside of storm potential, there will be
a large gradient in temperatures across the area, especially if
the 2nd round of precipitation does materialize. The forecast is
for upper 70s in northeast Nebraska and western Iowa and upper 80s
in southern Nebraska where clearing will happen earlier in the
day.
Wednesday through Sunday:
An upper level low is forecast to trek across southern Canada. It
will bring with it a cool front which will lead to a chance for
precipitation and thunderstorms Wednesday afternoon and evening.
The NBM came in a bit low on precipitation chances so PoPs were
upped in collaboration with neighboring offices. Upper level flow
will maintain its strength. So there should be adequate shear and
instability to support a severe weather risk as evidenced by the
SPC forecast of a Marginal Risk (Level 1 of 5). Height falls at
the mid-levels and a trough building over the Ohio River Valley
will lead to cooler end to the week with temperatures in the low
to mid 80s. These days are expected to be dry with precipitation
chances remaining below 15%.
Into the weekend, a strong ridge will again build over the West
Coast which is unfortunate for residents of that area as it has
already been under oppressive heat for some time. Nebraska and
Iowa won`t see oppressive heat, but mid-level heights will
increase over the area and temperatures are forecast to return to
the 90s. At this time, PoPs are low for the weekend but with
strong northwest flow overhead, it wouldn`t be surprising to see
isolated storms as the area has observed commonly the past few
days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 626 PM CDT Mon Jul 17 2023
Main concern of the forecast period continues to be showers and
storms that become possible late this evening into the overnight
hours and tomorrow morning. KLNK has the highest potential of
seeing stronger storms that will form well to the northwest and
affect the TAF site around 09z. Both KOFK and KLNK are likely to
see two sets of showers and storms move through while KOMA stays
northeast of the initial activity. Lightning doesn`t appear like
it will be constant outside of KLNK`s initial round of storms, so
light rain may be the predominant weather for parts of the
morning. Aside from the brief dips into MVFR and potentially IFR
conditions with the stronger storms, VFR conditions are forecast
with southeasterly winds tomorrow.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
DISCUSSION...Fajman
AVIATION...Petersen
Area Forecast Discussion
National Weather Service Nashville TN
822 PM CDT Mon Jul 17 2023
...New UPDATE...
.UPDATE...
Issued at 815 PM CDT Mon Jul 17 2023
Our eyes are back to the northwest monitoring the trends with the
cluster of storms south of Paducah moving ESE. Closer to home, the
00z OHX sounding showed 1600 J/kg of MLCAPE but mesoanalysis
shows values closer to 2500 J/kg along the Tennessee River.
Effective bulk shear values are around 25-30 kts. The CAPE will
decrease as the evening continues and the HRRR insists the storms
will become disorganized and weaker as the approach the NW. I feel
fairly confident in the HRRR solution given the recent trends of
warmer cloud tops as seen on IR. A couple of storms are possible
this evening, but I think they will remain sub severe. The
forecast is on track and only minor changes were made to hourly
PoP grids.
&&
.SHORT TERM...
(This afternoon through Tuesday Night)
Issued at 214 PM CDT Mon Jul 17 2023
I don`t usually do this, but I`ve sat here for 10 minutes trying to
decide what to type. My struggles revolve around the lack of any
consistency between models when it comes to storm development and/or
evolution today. Storms that I mentioned in this morning`s update
fell apart and are barely a couple of clouds in the sky at forecast
time. That has to be related to some amount of subsidence over
central Kentucky and a good portion of Middle TN that`s being seen
right now. Based on visible satellite, there`s almost zero
cumulus development this area (though some mid-to-high clouds
exist). I have to believe this won`t be the case as we move into
the late afternoon and early evening hours. More storms are firing
up over Missouri as I type this and with general troughiness over
the TN Valley, at some point, I would expect convection to make
its way into the mid-state. I don`t think everyone sees rain
today, but we should get at least some storms. Everything I
mentioned in this morning`s update stands in regards to
environmental analysis: CAPE has climbed near 3000 J/Kg in our
west, mid-level lapse rates are creeping towards 7.0 degrees and
bulk shear values are still around 30 kts -- we just need some
lift -- and with this environment, a few storms could be strong to
severe. Damaging winds would be the main concern.
&&
.LONG TERM...
(Wednesday through next Monday)
Issued at 214 PM CDT Mon Jul 17 2023
It`s really amazing how models are holding onto this Omega pattern.
The upper level low over Canada and the strong upper ridge
stretching from California to Arklatex continue to put the
Tennessee, Mid-Mississippi and lower Ohio Valleys into this
northwest flow for most of this forecast package. This will give us
at least chance PoPs throughout and while we are still seeing a weak
frontal passage Friday, by the end of the weekend, we`re right back
into the same pattern. In the end, because of this pattern,
consistent, good PoP forecasts are going to be hard to come by. So,
I have to carry a chance PoP throughout the week and we`ll have to
see about storm cluster and any MCS development as it comes.
In regards to the heat this week, I still like the potential for a
heat advisory on Wednesday, with Heat Index values expected to be
into the triple digits for the western 2/3 of Middle TN. However,
the verification of these higher temperatures are going to hinge
greatly on timing of any storms we see this week. For instance,
there are several indications of a MCS development late tomorrow
night and into the morning hours on Wednesday. Something like this
would greatly hurt the potential for getting that warm, even though
temperature guidance has been very consistent for several days now
of showing Wednesday as the hottest day this week. In any event,
even low to mid 90s with dew points in the 70s -- while not advisory
level heat -- will still be uncomfortable.
&&
.AVIATION...
(00Z TAFS)
Issued at 625 PM CDT Mon Jul 17 2023
A complex of storms currently over Missouri and Arkansas is
steadily tracking this way. Tempos are in at all terminals for
best timing of impacts. MVFR vsbys will be possible during these
storms with wind gusts up to 25-30 kts possible. Once storms clear
terminal sites, mainly high level sct clouds expected through the
night with calm winds. Fog/haze is possible overnight at
CKV/SRB/CSV.
More storms are possible by 12Z, but confidence in storm coverage
is low, so sticking with VCTS at BNA/MQY/CKV for now. Winds will
be out of the WSW by 18Z.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 71 92 75 96 / 30 40 40 30
Clarksville 69 91 74 95 / 40 40 50 30
Crossville 62 85 67 86 / 20 40 50 50
Columbia 68 92 74 96 / 20 30 20 20
Cookeville 66 87 71 88 / 30 40 60 40
Jamestown 64 84 68 85 / 30 50 70 50
Lawrenceburg 67 92 73 95 / 10 30 20 20
Murfreesboro 68 92 73 95 / 20 40 30 30
Waverly 67 91 74 95 / 30 40 30 20
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Reagan
SHORT TERM...Unger
LONG TERM....Unger
AVIATION.....Baggett
Area Forecast Discussion
National Weather Service Raleigh NC
905 PM EDT Mon Jul 17 2023
.SYNOPSIS...
A weak surface trough will hold over the North Carolina Piedmont
through mid week, as a warm and humid air mass persists over the
region.
&&
.NEAR TERM /TONIGHT/...
As of 905 PM Monday...
Water vapor this evening depicted continued troughing along the
eastern seaboard downstream of an anomalous ridge anchored over the
southwest US. While southwest flow is present aloft over central NC,
perturbations in the flow and associated convection has been
displaced offshore. Wnwly flow is expected to continue just above
the sfc promoting dry conditions through the overnight period.
However, smoke associated with Canadian fires will continue to
envelope our area through tomorrow afternoon. Consequently, a code
orange air quality alert remains in effect for most of central NC
through Tuesday night. Otherwise, warm overnight lows in the upper
60s/lower 70s are expected tonight.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 139 PM Monday...
The mid/upr short wave trough axis currently just west of the
mountains will move east and gradually cross our area during the
late afternoon. Given the dry air that we`re currently seeing to
our west and southwest, the west to southwest flow ahead of the
trough axis won`t be advecting much moisture into our area. Still,
forecast soundings do show a gradual/modest uptick in PWAT (climbing
to around 1.4-1.5 inches by late afternoon) and sfc dwpts...with
highest dwpts across our eastern zones as is typically the case. As
such, with the arrival of the trough axis and assoc large scale
ascent, coupled with cooling aloft as noted on forecast soundings,
locations that see the highest dwpts... mainly our eastern zones...
will be able to realize building cu with max afternoon heating,
perhaps building deep enough to support a few widely scattered
showers. Across our western zones, dwpts are likely to remain just
low enough to result in thinner CAPE profiles. That coupled with the
lingering mid-level dry air should result in shallower cu and mostly
preclude the risk for shower activity. With the same airmass as
today, look for persistent highs...low-mid 90s.
By Tuesday evening the trough axis should be to our east, thus look
for partly cloudy and dry weather for Tuesday night. Lows from
around 70 north to mid 70s south.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 330 PM Monday...
Mid to late week will be hot as the upper level ridge over the
Southwest US slowly expands to the east by late week. Wednesday will
remain mostly dry before a short wave moves into the Carolinas late
afternoon early evening bringing a chance of showers and storms
across the region. Depending on timing of the developing storms,
will also depend on temperatures and how high heat indices will be.
For now, areas along and east of the US1 corridor are expected to
reach heat indices of 100 to 107 degrees Wednesday afternoon. As the
short wave moves across the region Wednesday night a Piedmont trough
develops which is will increase chance showers Thursday and Friday
afternoon/evening. Temperatures these days will range from low 90s
in NW to upper 90s SE. With dew points forecast to be in the mid to
upper 70s this will result in heat indices of 100 NW to 109 SE both
days.
Over the weekend strong surface low over the lower Great Lakes lifts
to NE with a trailing cold front over the Carolinas and into the
lower MS valley. As the front sags just to the south of the region,
slight to chance PoPs remain in the forecast for the
afternoon/evening hours with the best chance of showers and
thunderstorms in the southern half of the CWA. With the passing of
the cold front, temperatures will be just below normal with highs in
the mid to upper 80s and lows in the mid to upper 60s.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 740 PM Monday...
With very little to no clouds and dry weather dominating for the
next 24 hours, the main aviation story remains the areas of smoke
and haze that have brought down air quality and have generated MVFR
vsbys over the western and southern portions of the forecast area,
including INT/GSO, for much of the day. Output from the HRRR Smoke
model suggests that this smoke may thin/disperse very gradually
through Tue while shifting slowly eastward, but it may continue to
knock down vsbys to 4-6SM through much of Tue across E sections,
while INT/GSO should start to improve back to VFR after 14z Tue
morning. Just a few high-based cu and high thin clouds are otherwise
expected Tue. Surface winds will be light and variable through mid
morning, then be from the W then WSW and SW from late morning
through the end of the TAF period.
Looking beyond 00z Wed, a few showers and isolated storms can`t be
ruled out late Tue night in the NW (near INT/GSO) and again areawide
late Wed, but otherwise VFR conditions will dominate. Shower/storm
chances will start to increase from Thu onward, mainly late in the
day, and pockets of early-morning fog will return late in the week
as well. -GIH
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Hartfield
NEAR TERM...Luchetti
SHORT TERM...np
LONG TERM...CA
AVIATION...Hartfield
Area Forecast Discussion
National Weather Service Blacksburg VA
1003 PM EDT Mon Jul 17 2023
.SYNOPSIS...
High pressure will be shifting to the south through Tuesday. A
front pushes into the Ohio Valley and mid-Atlantic toward
Wednesday. This is going to increase the chance for storms
Wednesday into Thursday.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 950 PM EDT Monday...
Lowered probability of precipitation tonight...
Cluster of thunderstorms in the piedmont continues to weaken as
the air mass becomes more stable. Latest CONSShort and HRRR
guidance have the probability of precipitation confined to the
mountains overnight. Some of the Hi-Res models had isolated to
scattered showers and thunderstorms tracking out of the
Tennessee Valley and reaching the mountains around 09Z/3AM.
Haze was no longer in any regional observations, but expect a
brief period of fog where there was rain this afternoon and
evening. Fog will also develop along the New and Greenbrier
Rivers with visibility less than 1/2 mile in pockets after
midnight.
Only minor changes made to temperatures overnight.
Previous discussion...
The northwest upper flow has pushed smoke from western Canada
wildfires into the central Appalachians and Mid-Atlantic region.
Expect hazy skies this afternoon into tonight due to the smoke.
High pressure at the surface will be pinched southward by a
eastward moving cold front that reaches Ohio Valley by late
tonight. A shortwave will move east across the region this
afternoon into tonight.
Instability subsides tonight, but another decent wave pushes
across the TN Valley to Ohio Valley after midnight which due to
sharpness of the trough should provide showers/maybe a
thunderstorm across the mountains.
Another shortwave will rotate around the broad upper trough
Tuesday. This will result in scattered showers and thunderstorms
with the best chances in during the afternoon.
Forecast confidence is Moderate during the Near Term Period.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 200 PM EDT Monday...
Unsettled weather expected Wednesday and Thursday...
The deterministic models are in good agreement that the eastern U.S.
remains under a broad upper level trough, with embedded short waves
moving through the region. While there is some uncertainty with the
timing of these shortwaves, there appears to be at least a couple of
opportunities for clusters of storms to impact our area during the
short term period.
The first wave comes through Wednesday and with slightly above
average PWAT values and anomalously high CAPE and shear values,
mainly in SW VA/NW NC, forecast by both the SREF and the ECMWF
extreme forecast index, there is the potential for locally heavy
rain and damaging winds. This threat will continue to be highlighted
in the HWO.
A stronger signal for the potential for severe weather is on
Thursday as shown by both the CSU Machine Learning Probabilities
Prediction page and the ECMWF extreme forecast index. With upper
level winds increasing, a jump in PWAT values, and the GEFS showing
a high probability of CAPES exceeding 1000 j/kg, along with a sfc
boundary moving through, expect strong to severe storms to develop.
The day with the greatest uncertainty in the short term period, is
Friday as the deterministic models show large differences with the
amount of drying and the forecast position of the low level boundary
that pushes through Thursday. The multi-model ensemble output
suggests a deeper upper level trough and a more southern location
of the surfaced boundary is the most likely scenario, so placed
lowest POPs in the short term period on this day.
Deviated little from the NBM temp forecast with temperatures close
to normal during the period.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 200 PM EDT Monday...
Slightly below normal temperatures expected...
The long range deterministic models and ensembles show a strong
signal for a an anomalously deep upper level trough over our area with
500mb heights at least two standard deviations below normal. This
will result in lower humidity levels and below normal temperatures
through the period.
As for precipitation chances, while PWAT values will be below normal
during the period, an increasing low level easterly flow may bring
enough shallow moisture to spawn scattered showers/isolated storms
with chances increases through the long term period.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 755 PM EDT Monday...
Isolated thunderstorms were moving across southwest Virginia and
will impact KROA at the start of the TAF forecast period. Wind
gusts of 30 to 40kts have been observed upstream of the
airport. Once this storm goes east of KROA is moves into an
environment that is not as unstable. For now have no tsra in at
KLYH but will monitor.
Otherwise still some MVFR visibility with haze. Expect KLWB to
drop to LIFR overnight with fog after 07Z/3AM. KBCB will likely
also have MVFR to IFR fog tonight. Once the fog burns off in
the morning there will be residual haze but low confidence on
any MVFR visibility for Tuesday.
RAP guidance and some other Hi-Res models suggested scattered
showers and thunderstorms from the Tennessee Valley may reach
western Virginia early Tuesday morning. So have VCSH in the
KBLF and KBCB TAFs. Once again scattered thunderstorms are
expected in the afternoon. The probability is more favorable in
the mountains.
Average confidence for ceiling, visibility, and wind
EXTENDED AVIATION OUTLOOK...
The next chance for possibly sub-VFR with showers/storms will
be Wednesday-Thursday with a slow moving front. Also, late night
fog/low stratus possible at LWB and perhaps BCB. Unsettled
weather continues Friday, then drier conditions arrive for
Saturday into Sunday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...PM/WP
NEAR TERM...AMS/KK
SHORT TERM...PH
LONG TERM...PH
AVIATION...AMS/KK
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
528 PM MDT Mon Jul 17 2023
.DISCUSSION...(This Evening Through Monday)
Issued at 125 PM MDT Mon Jul 17 2023
The main forecast impacts are (1) the chance of thunderstorms,
some severe, tonight and (2) the ongoing smoky and hazy
conditions. Confidence is low in the coverage and evolution of
storms tonight, but if they do get going confidence is high that
they will be severe. Confidence is medium that the smoke will be
diminishing overnight and Tuesday, but this smoke and haze also
may return on Wednesday.
The latest water vapor images show a potent trough and jet stream
approaching the CWA, but with plenty of midlevel and upper-level
clouds ahead of it. The combination of warm midlevel temperatures
and the smoky skies (reducing insolation) has resulted in a very
strong cap, with MLCIN of -100 to -400 J/kg at 1900z. Thus, would
be very surprised to see any organized thunderstorms develop
before 22z. The most likely scenario is thunderstorms developing
over the higher terrain of MT/WY later this afternoon and moving
over the CWA this evening and overnight. Sounding profiles suggest
the storms will be mostly elevated, with large hail being the
primary threat given strong 0-6km shear and MUCAPE of 2500+ J/kg.
The convection-allowing models (CAMs) are struggling with the
evolution of the storms (likely because of the strong cap), with
the HRRR being conspicuously weak in the depiction of storms
compared to the bullish NSSL-WRF.
After the wave pushes through overnight, the thunderstorm and
severe threat (whatever that turns out to be tonight) will be much
less on Tuesday. However, as an upper low spins to our north
across southern Canada we still will have a surface trough and 50s
to lower 60s dewpoints lingering across the southern/eastern CWA,
so cannot rule out some strong storms in those areas. Beyond that
the weather will be relatively quiet Wednesday into Thursday, but
another wave in the northwest flow aloft will bring more chances
of thunderstorms later Thursday and Thursday night, especially
across the southwestern CWA.
Hazy/smoky skies will persist through tonight, but should diminish
Tuesday. RAP/HRRR smoke models then hint at more haze/smoke
moving into the CWA behind a front on Wednesday as the surface
flow turns northwest again.
Models/ensembles then suggest a ridge building more toward our
CWA late this week into early next week, which would results in
warmer and drier conditions. We might even see our first 90-degree
readings for the year at the office. However, much uncertainty in
this still exists given the relatively green conditions and
persistent upper low to our northeast.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening)
Issued At 524 PM MDT Mon Jul 17 2023
Low VFR to MVFR VSBY in smoke/haze may return overnight, with
gradual improvement expected on Tuesday. Scattered thunderstorms
currently over northeastern Wyoming will spread eastward across
western South Dakota this evening. Isolated to scattered
thunderstorms will then occur over parts of western South Dakota
until around 12Z on Tuesday morning.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION...Bunkers
AVIATION...10
Area Forecast Discussion
National Weather Service Las Vegas NV
903 PM PDT Mon Jul 17 2023
.SYNOPSIS...Showers and storms possible this afternoon for areas
along and north of the Interstate 15 corridor, as well as the
Arizona Strip. Strong outflow winds and lightning are the main
concerns. Convective activity shifts poleward tomorrow, primarily
focused in our northern areas. Outside of any precipitation,
excessive heat will continue through the week across the Mojave
Desert and northwestern Arizona.
&&
.UPDATE...The 12Z HRRR did quite well this afternoon with regard to
timing and placement of convection. A stubborn cell with multiple
updrafts, 4 Severe Thunderstorm Warnings, 1 Flash Flood Warning, and
1 Flood Advisory persisted over Black Mountain, Henderson, and
southeastern Las Vegas through much of the afternoon. Coldest
observed cloud tops were around -58C and highest thunderstorm-
related wind gust was 64 mph with heavy rain and pea-sized hail
reported. Otherwise, we had convection in San Bernardino, southern
Lincoln, and across the Arizona Strip that had sub-severe gusty
winds and cloud-to-ground lightning. In general, most storms across
the forecast area have subsided with sunset, though a line of storms
from Colorado City southeastward to the Mohave County / Yavapai
County border persists as of 2035 PDT. Tuesday, forecast HRRR
convection is fairly in-line with forecast RAP 500mb vorticity
advection - focusing primarily on the southwestern Great Basin
across northern Inyo, Esmeralda, and southern Nye counties as well
as portions of the eastern Mojave Desert in northern Mohave County.
PWATs between 0.80 and 1.00 inches paint the forecast area, with
localized flooding a potential concern with stronger cells tomorrow.
Allowed the Excessive Heat Warning for the southern Great Basin and
Heat Advisory for the Clark County Mountains expire on time this
evening. The Excessive Heat Warning will continue for the Mojave
Desert through Saturday. No changes were made to this evening`s
forecast, as it looks to be in good shape.
&&
.PREVIOUS DISCUSSION...1132 AM PDT Mon Jul 17 2023/
.SHORT TERM...Today and Tuesday.
The 500mb high has retreated into east-central AZ, allowing south-
southeasterly flow to advect in more moisture. This is not only
evident in the increased mid-level clouds, but surface observations
as well. 24-hour dewpoint changes at 16z are as high as +25 degrees
in the Las Vegas Valley. This morning`s 12z sounding recorded 0.85"
of PWAT, a jump of over 0.5" from yesterday at 12z. Increased
moisture and cooler temperatures aloft due to the retreating high
will fuel isolated to scattered afternoon thunderstorms. Model
guidance continues to show convection focused along/north of the I-
15 corridor, as well as the Arizona Strip, though I would not
completely rule out an isolated storm or two farther south. Modeled
instability wanes with northward extend, so convection in Inyo, Nye,
Esmeralda, and the northern half of Lincoln Counties should be less
robust than storms along the I-15 corridor. 12z HREF mean depicts
CAPE values of 250-750 J/kg over most of San Bernardino, Clark,
Mohave, and southern Lincoln Counties. As excessive heat continues
in the presence of modest moisture, deep inverted-V profiles with
DCAPE values around 2000 J/kg will exist across the area. This means
any shower/storm will likely produce gusty outflow winds. Given the
parameter space and expected storm coverage, the best chance of
severe thunderstorm winds is the I-15 corridor from Barstow to
Mesquite. HREF confirms this analysis by placing 10% probability of
50kt wind contours in this area. Fortunately, dry low-levels will
mitigate flash flood potential. As far as timing goes, convection is
expected to develop around 1pm, and wane around sunset. Storms are
possible once again Tuesday afternoon, but activity is expected to
be focused in the northern 1/3 of the area, as well as the AZ Strip.
Similar to today, gusty winds and lightning will be the main
concerns.
Outside of any convective activity, excessive heat will persist,
particularly for the Mojave Desert and northwestern AZ. Tomorrow`s
temperatures should cool sufficiently for the Excessive Heat Warning
to be expired in Lincoln, central Nye, and Esmeralda counties.
Elsewhere however, dangerous heat is expected to continue into next
weekend, with Major to Extreme HeatRisk lingering. As such, the
Excessive Heat Warning for these areas was extended until Saturday.
.LONG TERM...Wednesday through Sunday.
Drier southwest flow continues to look more probable over most of
our region Wednesday through Friday compared to Monday and Tuesday
as ensemble means indicate our strong ridge to shift more over
eastern Arizona/New Mexico and Texas. EC/GEFS PWAT anomalies shift
to below normal through the end of the week and begin to recover
heading into next weekend. During this time, high temperatures will
vary only a few degrees up or down, but remaining at major to
extreme heat risk levels, especially with the duration of these
above normal temperatures persisting several days. Thus, the
Excessive Heat Warning has been extended through Saturday.
Heading into late next weekend and early next week, there continues
to be little sign of significant temperature relief other than
increased moisture moving into the region. Day 8-9 cluster analysis
indicates that the western ridge will reposition itself and deepen
yet again, perhaps over the El Paso area. At the same time, PWAT
anomalies now swing to above average setting the stage for potential
monsoon activity. NBM does paint 20-40% PoPs across Mohave by early
next week as well in line with the ensemble suggestions.
&&
.AVIATION...For Harry Reid...Gusty, south to southwest winds can be
expected through this afternoon, with isolated areas of convection
possible mid-afternoon through early evening. Most of this activity
is likely to remain over the higher terrain surrounding the Vegas
Valley, but erratic outflow winds from the storms may impact
operations at the field, most likely between 3 PM and 7 PM when
gusts to 40kts are possible. Any thunderstorm activity that does
develop should end by sunset. Winds will remain southerly overnight
into Tuesday morning before becoming gusty out of the south again
Tuesday afternoon. Outside of thunderstorm activity, no significant
cloud cover is expected.
For the rest of southern Nevada, northwest Arizona and southeast
California...Isolated areas of convection are possible this
afternoon, mainly across the higher terrain north of I-15 in Nevada
and California. Gusty and erratic outflow winds to 40kts are the
primary concern with any storms that do develop. Away from
thunderstorms, winds generally less than 15kts following typical
diurnal patterns are expected, along with a few clouds AOA 15kft.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Varian
SHORT TERM...Woods
LONG TERM...TB3
AVIATION...Planz
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