Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/02/23
Area Forecast Discussion
National Weather Service State College PA
1102 PM EDT Tue Aug 1 2023
.SYNOPSIS...
Cool temps are expected again tonight under high pressure.
Valley fog again, too. Low temperatures overnight will be
some of the coolest readings since early/mid June. Smoke aloft will
continue to create hazy skies over the southwestern half of
Central PA on Wed. The best odds for showers and thunderstorms
will be Thursday and Friday over the eastern part of the area
followed by a drying trend into the first weekend of August.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Mostly clear skies, a calm wind and dry air under surface high
pressure should result in optimal radiational cooling overnight
and the lowest min temps across Central PA since early June.
Have blended the cooler MAV guidance with the NBM, resulting in
expected lows ranging from the mid 40s in the coolest valleys
of the north, to the mid 50s over the Lower Susq Valley.
Warm river/stream waters, combined with the cool temps and a
calm wind, should promote late night fog in the deeper valleys
of the Alleghenies and near any larger bodies of water. We also
continue to monitor the plume of Canadian wildfire smoke, which
is progged to remain over the southwest part of the state
overnight. Have adjusted sky grids upward to account for this.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Rising heights and the presence of high pressure/low pwats over
the region should ensure fair weather Wednesday. RH timesections
indicate early sunshine will give way to a mix of sun and
cumulus. The latest HRRR continues to keep the plume of high
level smoke over the southwest counties through much of the day.
Have adjusted sky grids accordingly and nudged temps down
slightly across the southwest. Latest model guidance indicates
the smoke will remain aloft and not significantly affect visibility
or air quality.
Mixing down model 850mb temps of around 12C yields expected
highs Wednesday from the mid 70s over the N Mtns, to the low 80s
across the Lower Susq Valley.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
All medium range guidance tracks the upper trough and associated
cold front through Central PA Friday, accompanied by scattered
showers/tsra. Progged pwats are unimpressive in northwest flow
pattern, so NBM POPs in the 30-40pct range appear reasonable.
Ensemble mean qpf indicates most likely areal average rainfall
with the fropa will be <0.10 inches. Latest run of the NBM
tries to bump up PoPs above 50% Friday afternoon for much of
the area, but consensus continues to favor a lower chance for
rain.
The latest GEFS and ECENS both support a return to fair and
seasonable weather this weekend, as the cold front passes well
south of PA and high pressure builds in from the Grt Lks. The
chance of showers returns Sunday PM associated with a returning
warm front lifting in from the Ohio Valley. By Monday, surface
low pressure tracking over the Great Lakes will drag a cold
front through the area. A deep southwest flow preceding this
front will advect a seasonably moist air mass into the region
ahead of the front, supporting a good chance of convection.
Latest ensemble plumes suggest areal average rainfall between
0.25 and 0.50 inches is likely Sunday night/Monday, with locally
higher amounts under any stronger storms.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
High pressure will result in mostly clear skies and calm winds
tonight, allowing for valley fog formation once again across
northern and western portions of the area. VFR conditions will
prevail tomorrow once fog dissipates with light winds and partly
cloudy skies. While wildfire smoke will be present during the
day, models indicate that the greatest concentration of near
surface smoke will remain to our south and west so have not
included any mention of haze with the 00Z TAF package.
Outlook...
Thu...Restrictions possible in PM rainfall.
Fri...Restrictions will be possible in showers and
thunderstorms.
Sat...Mainly VFR.
Sun...Showers and thunderstorms may result in some restrictions.
&&
.CLIMATE...
2023 ranked as the 2nd wettest July on record at Williamsport.
Top 5 Wettest July | Williamsport, PA
1. 2018 11.99"
2. 2023 10.05"
3. 1992 9.65"
4. 1958 8.30"
5. 1928 8.02"
July 2023 also ranked 3rd wettest at Bradford (BFD), 7th at
State College COOP (STCP1), and 11th wettest at Altoona (AOO).
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Dangelo
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Dangelo
LONG TERM...Banghoff/Bauco
AVIATION...Bauco
CLIMATE...
Area Forecast Discussion
National Weather Service Cheyenne WY
832 PM MDT Tue Aug 1 2023
.UPDATE...
Issued at 827 PM MDT Tue Aug 1 2023
Current KCYS radar loop shows limited thunderstorm activity as
we`re reaching sunset for the day. Heavy rainfall associated with
these thunderstorms is much lower in coverage than this afternoon.
Therefore, have elected to cancel the flood watch due to excessive
rainfall. Will still see some widely scattered thunderstorms from
Laramie over towards Wheatland, with a second cluster forming just
south of Sidney Nebraska...but intense rainfall rates are expected
to only be brief. Another round of heavy rainfall expected
tomorrow (Wednesday), where there is another slight risk (15 to 30
percent chance) of excessive rainfall.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 245 PM MDT Tue Aug 1 2023
Severe thunderstorms and heavy rain are the forecast challenges
with this forecast package.
Currently...Stalled out stationary boundary lays across central
Colorado north...to Cheyenne to Wheatland to the
Converse/Niobrara state line this afternoon. SBCAPE from SPC`s
Mesoanalysis page showing 2500J/KG CAPE over Laramie County with a
pocket of 3000J/KG out in the northern Panhandle. Line of strong
thunderstorms has developed from Cheyenne northeast to LaGrange
currently. HRRR seems to be picking up on this line pretty
good...maybe an hour or so late on the forecast...but location
looks really good. Multiple outflow boundaries pushing to the
southeast across southeast Laramie County into the southern
Panhandle ahead of this line.
HRRR simulated radar shows storms moving out into the southern
Panhandle towards 00Z. Adjusting the timing error...may be more
like 22-23Z...pushing through Cheyenne County by 03-04Z.
Additional storms develop across the central and northern
Panhandle in southern Sioux and Box Butte/southern Dawes
Counties after 02Z. These storms will be in an area of very
unstable air...Rap showing SBCAPE 2500/3000J/KG in the Panhandle
during that time. All storms should be done after 04Z or so.
Another round of storms Wednesday with heavy rain developing
during the afternoon. Could see boundary shifting eastward into
the Panhandle that could give us more widespread storms Wednesday
afternoon.
.LONG TERM...(Thursday through Monday)
Issued at 246 AM MDT Tue Aug 1 2023
A fairly active pattern looks to remain in place through the long
term period as upper level flow begins to transition to quasi-zonal
with multiple shortwaves passing in the flow each day. PW values
look to remain over 1" for most of the CWA with a shortwave passing
northeast through central WY. This will lead to another day of heavy
rainfall and potential flash flooding as WPC has highlighted
northern portions of the CWA with a marginal risk of excessive
rainfall. Additionally, increasing mid-level flow with this system
could increase shear values enough where severe storms could be
possible for western NE.
Should see storms again Friday, especially east of the Laramie Range
into the NE Panhandle before a cold front sweeps through Saturday
leading to cooler temperatures for the remainder of the weekend into
early next week. Latest NAEFS guidance has 700mb temperatures
dropping to near climatological 10th percentile values for early
August around 6-8C. This would lead to high temperatures Sunday in
the mid-60s to low 70s, but latest NBM continues to show quite a bit
of spread. Chance of precipitation will begin to decrease headed
into early next week as the monsoonal pattern comes to an end, but
northwest flow aloft will still keep storms in the forecast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 528 PM MDT Tue Aug 1 2023
Wyoming Terminals... Isolated showers and thunderstorms are riding
the CO/WY border and may drift north and impact KCYS over the
next few hours. Outside of these storms, VFR conditions prevail
across southeast Wyoming. KCYS may see some fog develop later this
evening into the overnight hours with the additional moisture
from the thunderstorm that impacted the terminal earlier this
afternoon. Any fog that does develop should disperse by sunrise
and VFR conditions return for the remaining TAF period. Isolated
showers and thunderstorms are possible again tomorrow afternoon
and evening.
Nebraska Terminals... VFR conditions at all terminals currently,
but an isolated thunderstorm is drifting near KSNY. Additional
thunderstorm development is possible this evening, so included
VCTS for all sites. Storms should clear out by 05Z at all
terminals. There is a small chance for some light fog development
at KAIA and KSNY overnight, but confidence is low and visibility
reductions were not included. Showers and thunderstorms are
possible again tomorrow, but look to develop after the 00Z TAF
period.
&&
.FIRE WEATHER...
Issued at 245 PM MDT Tue Aug 1 2023
Monsoon moisture in place will continue high probabilities of
afternoon and evening showers and thunderstorms on a daily basis.
Afternoon humidity well above critical levels with minimum
humidity in the mid to upper 30 percent range. Fire weather
concerns minimal through the rest of the week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...TJT
SHORT TERM...GCC
LONG TERM...BW
AVIATION...AM
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
615 PM CDT Tue Aug 1 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Wednesday night)
Issued at 123 PM CDT Tue Aug 1 2023
A 597 dm H5 ridge is currently centered just to our north near the
OK/TX border, providing us with clear skies and above normal
temperatures. However, RAP analysis indicates a weak shortwave
embedded in the upper level flow just to our ENE that will rotate
around the high into our region later this afternoon. CAMS continue
to indicate the likelihood for a few showers/storms to develop this
afternoon over the east half of the region, providing some welcome
rain and brief relief to the excessive heat for a few lucky
locations. Widespread rains are unlikely.
For most locations, expect highs to range from 99 to 106 today,
except in any spots that get lucky with mid to late afternoon rains.
Similar conditions are forecast for tomorrow, though without the
relief of isolated showers. We`ll continue today`s heat headlines
for tomorrow
&&
.LONG TERM...
(Thursday through Tuesday)
Issued at 123 PM CDT Tue Aug 1 2023
Sorry to disappoint but there is not much more to report as we go
through the long term. It will remain hot and rain free as the mid-
level ridge remains supplanted from the Desert Southwest to the
Texas gulf coast. The deterministic global model guidance that has
hinted at troughing into north-central Texas during early next week
has become less pronounced and trended towards what the ensemble
means have favored over the past few days. The daily issuance of
heat headlines will likely continue with widespread highs above 100
degrees with the majority of the region ranging from 102 to 107
degrees. Humidity levels late each afternoon will continue to fall
within the 20 to 30 percent range. This helps keep the heat indices
closer to the ambient temperature but a few locales could see peak
heat indices to around 110 degrees. This low humidity and light to
moderate south-southeast to east-southeasterly winds along with dry
to extremely dry fuels will result in the continued near critical
fire weather. Humidity levels rebound after dark featuring warm
overnight lows ranging from the mid 70s into the low 80s.
&&
.AVIATION...
(00Z TAFS)
Issued at 612 PM CDT Tue Aug 1 2023
VFR conditions are prevailing across the area. There are some very
isolated showers near AUS but impacts are expected to be minimal
outside brief wind shifts. Otherwise, southeast flow will prevail
through the period with some more breezy conditions in the late
afternoon and evening periods.
&&
.FIRE WEATHER...
Issued at 123 PM CDT Tue Aug 1 2023
A Rangeland Fire Danger Statement for near critical fire weather
continues across all of south central Texas until 9 PM. Fine fuels
continue to bake across the region given the well above normal heat
and lack of precipitation. The dry fuels combined with low minimum
afternoon humidity levels from the upper teens to around 30 percent
and occasionally gusty south-southeast to east-southeasterly winds
will continue to pose conditions favorable for the spread of
wildfires. Additional Rangeland Fire Danger Statements are likely
through much of this week and into early next week as the weather
pattern remains stagnant. Residents are urged to extra care to
prevent the ignition and spread of wildfires.
&&
.CLIMATE...
Issued at 323 AM CDT Tue Aug 1 2023
(Record Highs/Year Reached)
8/01 8/02 8/03 8/04
AUS 105/2011 106/2011 105/2011 105/2011
ATT 107/2011 107/2011 107/1923 107/2011
SAT 103/2013 103/2011 103/2022 103/2022
DRT 106/2012 106/2012 106/1996 105/2022
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 79 105 78 104 / 0 0 0 0
Austin Bergstrom Intl Airport 77 103 77 102 / 10 0 0 0
New Braunfels Muni Airport 77 102 75 102 / 20 0 0 0
Burnet Muni Airport 78 103 77 102 / 0 0 0 0
Del Rio Intl Airport 80 105 80 103 / 0 0 0 0
Georgetown Muni Airport 79 104 77 103 / 0 0 0 0
Hondo Muni Airport 75 102 74 102 / 0 0 0 0
San Marcos Muni Airport 75 103 76 103 / 20 0 0 0
La Grange - Fayette Regional 76 103 77 103 / 10 10 0 10
San Antonio Intl Airport 77 102 77 102 / 20 0 0 0
Stinson Muni Airport 77 103 78 103 / 20 0 0 0
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 9 PM CDT Wednesday for Bastrop-Burnet-
Fayette-Lee-Llano-Travis-Williamson.
Heat Advisory until 9 PM CDT Wednesday for Atascosa-Bandera-Bexar-
Blanco-Caldwell-Comal-De Witt-Frio-Gillespie-Gonzales-Guadalupe-
Hays-Karnes-Kendall-Kerr-Lavaca-Medina-Wilson.
&&
$$
Short-Term...KCW
Long-Term...Brady
Aviation...29
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
1055 PM CDT Tue Aug 1 2023
.UPDATE...
Issued at 1024 PM CDT Tue Aug 1 2023
Potential has increased for heavy rainfall (1 inch + amounts) around
the highway-20 corridor tonight into tomorrow morning. A mid-upper
level wave currently by the Colorado/Nebraska border will push
eastwards overnight into parts northeast Nebraska and northwest
Iowa. This wave will intersect a theta-e boundary sitting between
850-700 mb. Convection looks to fire around 08z tonight and slowly
spread eastwards through the mid morning hours. Soundings show tall
skinny cape profiles approaching 1000-1500 J/kg of instability along
with weak deep layer shear at or below 30 knots. Given the lacking
shear, severe weather is not expected. However, PWATS will be very
moist at or above 2 inches. Hi-res guidance has a decent handle on
how this event will unfold but varies in exact location where the
heaviest rain will fall. 00z and 01z HRRR as well as the 00z ARW
keep any storms that form just south of the area. All other members
do show storms at least getting into the highway-20 corridor. While
the model consensus is decent, BUFKIT soundings also show a dry
layer between 850-700 mb. This also presents some uncertainty as
this dry layer may slow how quickly this layer saturates. Should
this layer stay drier, then little instability will be available to
work with and thus lead to lighter to possibly no rain at all. Do
think that this layer may saturate through as hi-res guidance does
show stronger 700 mb moisture transport nudging its way into the
highway-20 corridor. As such have upped PoPs to likely`s but have
left QPF as is due to uncertainty in where the heaviest rainfall
will occur tonight.
&&
.SHORT TERM...(This Evening through Wednesday)
Issued at 231 PM CDT Tue Aug 1 2023
A weak wave will move east along the Missouri River into northwest
IA this evening. Light to potentially moderate rain showers will be
possible along the track of this wave. Model soundings show fairly
weak instability so for now only an isolated lightning strike or two
is expected. For tonight better instability exists across parts of
ND as well as central and southern NE, so expect any stronger
thunderstorms to develop in these two areas. While the activity
across ND will likely not drop south into the area, some of the
activity in NE could begin to develop northward later tonight. This
is in response to a bit more robust shortwave that should move from
CO into NE. This increases the roughly 750-700mb forcing with some
elevated instability. More than likely this instability will not be
enough to allow for severe storms but some stronger storms will be
possible with patchy heavy rain the main concern, especially given
the 13500 foot freezing level.
The shortwave will be a little slow to exit with some suggestions
that it could still be lingering in eastern NE by early evening.
This will keep clouds and some precipitation chances in mostly
northeast NE and northwest IA into the early afternoon. On top of
this model soundings are indicating a decent potential for some MVFR
stratus development behind and on the north side of this wave. So,
went ahead and lowered high temperatures in these areas. So near 80
in these areas and around 90 closer to highway 14 where more sun is
expected. While heat advisory criteria is not expected to be met,
dew point temperatures in the lower 70s and highs around 90 will
yield some mid 90 heat indices.
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 231 PM CDT Tue Aug 1 2023
Wednesday night into Thursday still expected to be mainly dry as
weak ridging builds into the area. Should be fairly warm with
overnight lows in the mind and upper 60s and highs from the mid 80s
to lower 90s. Will have to keep and eye on the fog and stratus
potential with some easterly flow in the low levels and still
relatively moist lower levels. If any fog or stratus does develop
the high temperatures would likely need to come down a few degrees.
Thursday night into Friday will see low pressure develop across
western SD and gradually spread east into Friday. This will bring an
increasing threat for showers and thunderstorms. Instability and
shear are not very impressive but potentially Thursday night into
early Friday morning an isolated elevated strong to severe storm
would be possible if something can develop out ahead of the main low
pressure.
Friday night into Saturday should be the next best chance for
showers and thunderstorms. With low pressure likely overhead and
only slowly moving east an abundance of cloud cover is also
expected. Severe weather is highly unlikely. Did lower highs a bit
to account for the potential precipitation and cloud cover.
Saturday night into Sunday will see rain chances linger as the low
pressure is very slow to exit. Should see quite a bit of cloud cover
as well as gustier northwest winds. Also lowered highs a touch on
Sunday.
Sunday night into Tuesday will see mostly northwest flow aloft but
there are hints of another wave moving in later Monday night into
Tuesday, so not confidence on completely dry conditions.
Temperatures should remain below normal with lows from the mid 50s
to lower 60s and highs in the upper 70s to around 80.
&&
.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
Issued at 1054 PM CDT Tue Aug 1 2023
Current satellite shows MVFR stratus beginning to spread south of
I-90 and east of KYKN. This stratus looks to remain for the rest
of the overnight hours through mid mourning mainly at KSUX. This
stratus could sink to IFR levels but confidence is too low to
include in a TAF as of now. Fog is also possible, primarily in
southwest Minnesota. Confidence has however increased in the
potential for rain and storms around highway-20 late tonight
through about mid morning tomorrow. Have included VCTS in KSUX`s
TAF for this reason. MVFR stratus may make it up to KFSD but
confidence is too low to deviate from VFR level stratus.
Stratus should lift to VFR levels by tomorrow afternoon and break
up. Winds remain light out of the southeast through the period.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
UPDATE...Meyers
SHORT TERM...08
LONG TERM...08
AVIATION...Meyers
Area Forecast Discussion
National Weather Service Grand Rapids MI
1059 PM EDT Tue Aug 1 2023
LATEST UPDATE...
Update
.UPDATE...
Issued at 1058 PM EDT Tue Aug 1 2023
High pressure will begin to slide off to the east tonight allowing
south flow to develop. As the south flow develops a very weak
warm front will lift northward through the area. A few showers
have been occurring for a number of hours over Wisconsin and out
into Lake Michigan. These showers are forecast by high res
modeling to move into West Central Lower Michigan tonight from
roughly Holland northward. This activity is again associated with
a weak warm front which is best seen in the theta-e gradient at
850mb. We have 20-40 pops in the forecast for this area of showers
moving in. Not out of the realm of possibilities to even see a
lightning strike or two of the lake given a boost in low level
moisture from the warmer lake.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 220 PM EDT Tue Aug 1 2023
...Mainly dry through the period...
Visible satellite loop shows a well defined swath of smoke
emanating from northern Canada moving over all of Lower MI.
Despite no clouds overhead, the sky is opaque and we`ve recorded
limited sunshine minutes. The RAP Smoke model continues to show
the smoke plume moving east overnight.
Northwest flow aloft coupled with high pressure just to the east
Wednesday will result in mostly sunny skies. And, we`ll see more
of the sun since the smoke should also be east of the region.
We`ll maintain a slight chc of a shower/thunderstorm in the
northeast cwa Wednesday and Wednesday night due to minor waves
moving across the state in northwest flow. They`ll have limited
moisture to work with though and so we don`t expect much out of
them.
Temperatures will slowly climb over the next couple of days. Lows
around 60 tonight and in the mid 80s Wednesday.
.LONG TERM...(Thursday through Tuesday)
Issued at 259 PM EDT Tue Aug 1 2023
- Small chance for a Thunderstorm Thursday afternoon north
Models are showing a weakening cold front dropping down from the
north northwest mid to late Thursday afternoon. This feature will
move into our northern zones during the warmest part of the day when
the instability will peak. Ensemble surface based CAPE values from
the ECMWF, GFS and GEM all show roughly 500-1000 J/kg. This should
be sufficient to generate a few storms. Little or no mid level lift
is seen across the CWA. Also the low level convergence remains
weak. Thus as this front slips further south in the evening...as
the atmosphere stabilizes...any showers/storms should diminish. As
a result we will feature a dry Thursday evening for central and
southern zones.
- Potential for Stronger Thunderstorms Sunday Afternoon/Evening
Models are coming into slightly better agreement with the passage of
a mid level shortwave and associated jet streak Sunday afternoon and
evening here in Southern Lower MI. Ensemble 24 hr QPF trends
also show an increase in totals, supporting the increased
confidence for precipitation. PWAT values are progged
to climb up to around 1.75 inches which is well above normal for
this time of the year. Forecast soundings from the GFS show decent
instability along with elevated values of deep layer
shear. This opens up the risk for stronger convection. The 12z
GEM also supports this scenario. As result we will increase the POPs
for this potential event. The 12z ECMWF also shows this system but
would bring it into the region not until Sunday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 840 PM EDT Tue Aug 1 2023
Smoke layer remains aloft tonight and it should be moving out to
the east with time. We do not expect impacts to aviation from it.
Little to no surface obstruction to visibility has occurred
outside of 6SM and HZ at LAN.
Cirrus continues to stream into the area aloft with bases at or
above 20,000 feet. That will continue to be the case tonight.
The main item to watch and it should not be much of an issue is
the band of scattered to broken clouds around 6,000 feet that has
formed from Wisconsin to out over Lake Michigan. This is a weak
warm frontal feature that may continue to produce clouds at that
level as well as a few showers. MKG and GRR would be the two TAF
sites that could see a few showers between 08Z and 13Z.
On Wednesday, scattered to broken cumulus clouds can be expected
with bases around 6,000 feet.
Winds will be light tonight becoming southwest at 5-15 knots on
Wednesday.
&&
.MARINE...
Issued at 220 PM EDT Tue Aug 1 2023
The center of the high was over northern Indiana early this
afternoon. Winds have begun to switch to the southwest over the
lake and the winds will strengthen a bit as the high moves east.
Waves tonight will be around a foot and 1-3 feet Wednesday and
Wednesday night.
No marine headlines until perhaps Friday as north winds strengthen
behind a cold front.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...Duke
SHORT TERM...04
LONG TERM...MJS
AVIATION...Duke
MARINE...04
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1040 PM EDT Tue Aug 1 2023
.UPDATE...
Issued at 1040 PM EDT TUE AUG 1 2023
Based on trends/obs, lowered tonight`s min temp fcst for valleys
over the southwest portion of the area.
UPDATE Issued at 737 PM EDT TUE AUG 1 2023
Forecast is on track and no substantive changes were needed.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 413 PM EDT TUE AUG 1 2023
Late this afternoon, an upper level ridge was centered over the
Southern Plains with another upper level ridge centered in the
Atlantic well east of Bermuda. In between, an upper level trough
extended from eastern Canada into the Northeast Conus to the
Carolina Coast to the Bahamas. Further west an upper level trough
extended across parts of the eastern Pacific to the west of the
west coast of the Conus. At the sfc, high pressure was centered
over the eastern Great Lakes and extended into the Lower OH
Valley. Meanwhile, a frontal zone extended from the Atlantic into
the Southeast and then turned north to the Ozarks and then west to
Central Plains. At 500 mb, a trend of rising heights was noted as
the axis of the trough near the eastern seaboard progresses east.
Guidance suggests continued height rises tonight and into the day
on Wednesday as the upper level ridge builds into portions of the
Southeast/Lower MS Valley and northern Gulf of Mexico while the
trough axis moves further east of the eastern seaboard and into
the Atlantic. Height tendencies at 500 mb are progged to be nearly
neutral from later Wednesday into Wednesday evening before an
approaching shortwave leads to 500 mb height falls late Wed night.
The upper pattern will result in west to northwest flow from the
upper MS Valley/Northern Plains to the Great Lakes, OH Valley, and
Appalachians. Multiple disturbances are expected to be moving
around the ridge that eventually becomes oriented from the
Southern Rockies and Southeast Conus east to the Lower MS Valley.
Initially tonight and into Wednesday these disturbances and
associated should pass southwest of eastern KY as they interact
with the frontal zone to our south and southwest. This frontal
zone should lift north and northeast with time as a sfc wave moves
along it that nears the mid MS Valley on Wed night. To the east,
the boundary should work into the Lower OH and TN Valleys by late
Wednesday night.
Rounds of convection with some MCS activity driven by nocturnal
LLJ are expected from the central Conus and eventually into parts
of the TN and OH Valley the next couple of nights. This activity
may eventually affect portions of south central and eastern KY by
late Wednesday night. However, the greater chances for showers
and storms should hold off until early in the long term period.
Uncertainty remains in how far east and northeast the activity may
track on Wednesday night with the 18Z HRRR run keeping this
activity largely west and southwest of the area through the short
term period. The overall consensus is that chances for convection
Wed night are lowest in the north and east and a bit higher closer
to the Lake Cumberland Region/TN border area.
With dewpoints having mixed into the mid to upper 50s for most
locations with sfc high pressure and upper level ridging
dominating, at least deeper valley locations should again drop
into the 50s. Some patchy valley fog should also develop around or
shortly after midnight, with this dissipating/mixing out by
around 9 AM EDT. Otherwise, temperatures should moderate a couple
of degrees warmer on Wednesday, with mid 80s expected to be
common. Deeper eastern and northeastern valleys should cool off
more than ridgetop and open terrain locations on Wed night as well
toward the lower 60s.
.LONG TERM...(Thursday through Tuesday)
Issued at 320 PM EDT TUE AUG 1 2023
The period will begin under an amplified upper level pattern. A
broad ridge will be centered across the Southern Plains, extending
north through the Upper Missouri Valley. Troughing will generally
rule on either side of the ridge, but the pattern evolves by the end
of the work week. At the surface, high pressure will begin across
the Mid Atlantic, where a frontal boundary lies south of the area,
across the Mid Mississippi Valley to the Deep South. Return flow
will allow for the advection of moisture, where PWATs will climb to
1.75 to 2 inches. A meandering closed low across Eastern Canada will
support a surface low and associated cold front, which will begin
influencing local weather by the start of the period. With the
ridging retrograding westward into the Southern High Plains and
Southwest, this will leave Eastern Kentucky within a corridor on the
periphery of the feature. A series of passing mid-level vorts, along
with the pressing surface boundary, will result in a higher
probability of shower and thunderstorm chances through Friday. With
PWATs anomalously high and synoptic support aloft, there is some
concern for flash flooding and a few strong storms during this
period.
Extended CAMs depict the opportunity for MCS activity out of the
Midwest to Mid Mississippi Valley, with the general trajectory of
higher QPF along a line from Western Kentucky, along the southern
half of our counties and into the Tennessee Valley. Ensembles
highlight the threat for heavy rain given the slow moving boundary,
series of height falls, and moisture rich environment, with the EFI
signifying a weak signal across the south/southeast bordering
Tennessee to Virginia. There remains uncertainty in the north to
south gradient in higher QPF within ensembles members, but the
general consensus among the Euro and GEFs is on this aforementioned
idea/track. Canadian members generally veer further north and a bit
more bullish with the heavier swath of QPF with passing waves, but
given the lack of support in other data and broader member spread,
have primarily assumed this to be the outlier. Training
thunderstorms will be the biggest concern for flash flooding
potential; however, the south/southeast has fortunately been the
driest of areas in recent weeks, and thus, should help mitigate
anything more than nuisance/isolated issues as of this package.
Uncertainty then grows through the weekend and into early next week.
Deterministic data suggests the approaching cold front will sink
south of the area into the weekend, where a subsequent wave deepens
across the Midwest and a surface low drags a secondary boundary east
into early next week. Given model variations within passing
shortwaves in a general quasi-zonal flow, have veered toward the
NBM`s solution for PoPs through the second half of the period. With
the passing boundary, a drier trend (10-30%) has emerged for
Saturday into Sunday, with scattered chances then returning (30-50%)
Sunday afternoon through Tuesday with the next disturbance.
Temperatures throughout the extended will start cool, but moderate
to near average into the weekend and last into early next week.
With extensive cloud cover and PoPs, highs Thursday will top out
in the mid 70s, warming to the mid and upper 80s for the weekend,
and settling in the low to mid 80s into the new work week.
Similarly, lows should vary in the 60s to low 70s throughout the
extended.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 737 PM EDT TUE AUG 1 2023
Valley fog will develop overnight and dissipate by mid morning,
and should be most prevalent in southeast Kentucky. It will bring
IFR or worse conditions to some locations, but is expected to have
little or no impact at TAF sites. Outside of fog, VFR conditions
are expected through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL
SHORT TERM...JP
LONG TERM...BB
AVIATION...HAL
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
910 PM EDT Tue Aug 1 2023
.SYNOPSIS...
Hazy skies, low humidity, and dry conditions look to continue
through Wednesday as high pressure builds overhead. Shower and
thunderstorm chances return Thursday into Friday as an area of low
pressure and it`s associated cold front approach the region. Brief
high pressure will follow for the weekend with an additional front
early next week.
&&
.NEAR TERM /UNTIL 7 AM WEDNESDAY MORNING/...
Canadian wildfire smoke remains evident in the upper levels of the
atmosphere this evening and will likely continue into the overnight
hours due in part to light north/northwesterly flow. Conditions will
remain quiet outside of the smoke/haze with high pressure building
in. Lows tonight will remain on the cooler side of things with mid
to upper 50s for most outside the urban areas. Mountain and valley
locations west of the Blue Ridge look to see values in the mid to
upper 40s. The thin veil of smoke/haze above combined with some
passing scattered mid/high level clouds will delay the potential for
us to fully radiate out.
Even with that said, the airmass is fairly dry with PWATS per 00z
sounding at both IAD/RNK under 1.00". This will yield likely the
coolest Summer night in about a month or so across the region. Enjoy
it while it last as the warmer air and muggier conditions return
later this week.
&&
.SHORT TERM /7 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Another day of low humidity for early August standards is
expected Wednesday with Tds forecast to be in the 50s to low
60s. There may be more clouds on Wednesday given an approaching
jet streak. Highs will likely be similar to today, if not a
degree or two warmer. There is the potential for a few showers
or storms in the far southwest parts of the FA given the
moisture return, but most locales should stay dry. The other
forecasting variable will be another surge of smoke modeled by
some guidance making it to the sfc in the NW parts of the FA
Wednesday evening. Some uncertainties with respect to how much
make it to the ground exist, so have added HZ and VSBY
restrictions to the grids for now. Will let later shifts add FU
if confidence increases. Southerly flow will allow for moisture
return to continue into Wednesday night which will not allow
low temps to fall as much as tonight.
Come Thursday, a jet streak will move over the FA from the
northwest while the southerly flow continues in the low levels
advecting moisture into the area. Given these dynamics and lack
of a strong surface based forcing element, clouds will likely be
widespread, but uncertainties remain wrt the coverage of
showers and thunderstorms. Instability and mid-level lapse rates
appear to be the lesser of most variables which raises
uncertainty with intensity. Temperatures may depend somewhat on
cloud cover but most of the area will still reach the 80s.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
On Friday, an upper trough digging into southeastern Canada and
the Northeast US is expected to bring an associated cold front
through our area. Showers and thunderstorms are possible during
the afternoon as the front passes. There is some potential for
strong to severe storms Friday, but instability currently looks
modest, around or below 1000 J/kg at best, with around 30kt of
shear. We will continue to monitor, but for now isolated strong
to severe storms are possible.
High pressure builds in briefly behind the cold front on Saturday
and as the upper level pattern over the region becomes less
amplified, yielding dry conditions. Rain chances return Sunday as
the cold front from Friday is expected to lift north through the
region as a warm front and surface low pressure moves into the Great
Lakes.
A cold front is progged to approach from the west again on Monday as
a shortwave swings into the Ohio Valley, bringing increasing chances
for showers and thunderstorms.
&&
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions will prevail through Wednesday night at all
terminals. The exception to this would be in areas along and west of
the Allegheny Front from K2G4 south to KEKN where a few isolated
showers have popped up this evening. These areas may also see a
brief period of MVFR to IFR fog between 10-13z although confidence
is low given the dry air in place. Elsewhere across the region SCT-
BKN mid and high level clouds remain as high pressure gradually
builds overhead. These clouds will decrease overnight as the
high takes over. Unfortunately the thin veil of Canadian
wildfire smoke will remain in the high levels of the
atmosphere as light north to northwesterly flow continues.
Some surface based FU/HZ conditions may impact terminals
especially west of the Blue Ridge per the latest HRRR smoke
model guidance. COnfidence in this is a bit low with light
southerly flow likely forcing the smoke back to the north
Wednesday afternoon and evening. With that said, ill let future
shifts decide if they want to add restrictions into the
terminals given upstream obs and the path of the smoke plume.
There may be a slightly greater chance of valley fog Wednesday
night as low level moisture starts to increase.
Showers and thunderstorms will become possible Thursday and Thursday
night ahead of an approaching low pressure system, although coverage
may be disorganized. Sub-VFR ceilings may develop Thursday night.
VFR conditions are expected Friday and Saturday, though showers and
thunderstorms on Friday may bring brief reductions to terminals. Dry
conditions are expected Saturday as high pressure builds in.
&&
.MARINE...
High pressure will continue to build overhead
tonight into Wednesday. Light northerly winds will switch to the
northeast Wednesday morning before shifting to the east and
southeast Wednesday afternoon. Southerly channeling remains a
possibility per the latest CAM and deterministic guidance
Wednesday night into Thursday morning as high pressure pushes
onshore. Winds should remain just below SCA levels during this
time.
Winds increase amidst southerly flow Thursday into Thursday
night. Current forecast has winds of 15-25 kts which makes sense
given the low level jet moving through Thursday night. This
will likely result in SCA conditions for most of the waters.
Showers and thunderstorms may also reach the waters Thursday
afternoon into Thursday night.
SCAs will likely be needed on Friday with a passing cold front.
Winds shift out of the north and diminish late Friday night into
Saturday.
&&
.TIDES/COASTAL FLOODING...
Northerly winds today will push the anomalies down a bit, but
they will begin to increase again Wednesday as winds become east
then southeast. Stronger southerly winds will develop toward
the end of the week and could push some locations toward minor
flooding, especially Annapolis.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...EST
NEAR TERM...EST
SHORT TERM...CPB
LONG TERM...CAS
AVIATION...CPB/CAS/EST
MARINE...CPB/CAS/EST
TIDES/COASTAL FLOODING...BJL