Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/24/23
Area Forecast Discussion...UPDATED
National Weather Service Albuquerque NM
511 PM MDT Wed Aug 23 2023
...New AVIATION...
.SYNOPSIS...
Issued at 116 PM MDT Wed Aug 23 2023
More widespread cloud cover with showers and thunderstorms over the
region through Friday will bring cooler temperatures along with much
needed rainfall in some areas. Widespread moderate to heavy rainfall
is not likely but a few locations may pick up over an inch where the
heavier thunderstorms occur. Temperatures will warm up again through
the weekend as high pressure builds into NM once again. Fortunately,
a couple backdoor cold fronts may shift into eastern NM with more
moisture and continued chances for showers and thunderstorms. This
activity will be very slow moving so more locally heavy rainfall is
possible through the weekend and early next week.
&&
.SHORT TERM...
(This evening through Thursday night)
Issued at 116 PM MDT Wed Aug 23 2023
The remnant low and moisture associated with what was once Tropical
Storm Harold is moving northwest around the upper high circulation
and impacting NM with increasing PWATs and improving chances for
showers and storms through Thursday. The 12Z KABQ upper air sounding
showed a PWAT of 1.09" and the 12Z models forecast a rise to over
1.20" tonight, which is well above normal. A 24hr change plot of
surface dewpoint temperatures show positive values across the area,
but especially across southern NM as the moisture continues to
advect north into central portions of the state. Extensive
cloudiness as kept a lid on differential heating and is limiting
instability so far today, although showers have increased in
coverage and intensity over the past hour. Lightning so far has
been limited and will likely continue to be limited today. A Flash
Flood Watch continues this evening and overnight for the south
central and southwest mountains, including the San Agustin Plains,
where the greatest QPF is depicted by the NAM12, HRRR and HREF
and given burn scar sensitivity in those forecast zones.
Otherwise, any rain today and tonight will be beneficial with
little flooding concern. The remnant circulation will move from
eastern AZ to over the Four Corners tomorrow and a south to north
steering flow will develop across the area in what should be a
fairly rainfall productive crop of storms. Storm motion will
decrease in the south central mountains tomorrow and the latest
NAM is lighting that area up, so another Flash Flood Watch may be
required, especially given potential for grounds to be saturated
by that point. Tomorrow`s crop of convection should follow a
fairly normal diurnal downtrend by evening as any remaining
forcing from the remnant low moves into southwest CO. High temps
on Thursday will be similar to today`s and generally below normal
central/west and near to above normal east closer to the upper
high.
&&
.LONG TERM...
(Friday through Monday)
Issued at 116 PM MDT Wed Aug 23 2023
Cloud cover over the region from Thursday night will lead to a slow
start on Friday with limited heating and cooler max temps. There is
still a fair amount of uncertainty with regard to the coverage of
showers and storms Friday afternoon due to airmass instability and
location of remnant boundaries from any convection the day before.
The latest WPC QPF trended significantly lower for Thursday and
Friday. This is in opposition to trends from yesterday so overall
forecast confidence remains low to moderate. The latest NBM 72hr
probabilistic QPF has a dramatic range of values btwn the 25th and
75th percentiles with a mean notably higher than current WPC QPF
across western NM. Given the well-above normal PW airmass over
the region the bottom line is that any storms that do form will be
capable of very heavy rainfall with some flash flooding possible,
especially near burn scars. Storm motion will be toward the north
and northeast with training along the high terrain possible. Max
temps will be slightly below normal for late August across central
and western NM and slightly above normal across the east where high
pressure still dominates the region.
For Saturday thru Monday, the upper level high is expected to drift
west over NM with warmer temps areawide. Several convectively-aided
backdoor frontal boundaries may shift south and west into eastern
NM each day which would reinforce low level moisture across the
region. Very slow storm motion beneath the upper high helps with
locally heavy rainfall, especially near the high terrain. Forecast
confidence is still only low to moderate given the waffling of
extended range models with the location of the upper high and
strength of backdoor surface boundaries.
&&
.AVIATION...
(00Z TAFS)
Issued at 510 PM MDT Wed Aug 23 2023
Remnant Harold circulation located vicinity southwest NM at 23Z to
move northwestward into east central AZ by 24/09Z and over the
Four Corners around 24/23Z. Sct to nmrs showers and a few tstms
over western and central NM to persist through 24/15Z. Brief mt
obscurations possible in the stronger cells as well as gusty
erratic winds to around 40kt. An area of MVFR cigs and mt
obscurations possible along the Contdvd from near KGNT swd as well
as around the KSRR vicinity possible aft 24/06Z and this may
expand northward from K4CR toward KCQC by 24/12Z.
&&
.FIRE WEATHER...
Issued at 116 PM MDT Wed Aug 23 2023
Humidity and chances for wetting rain are on the uptrend across
central and western NM as remnant moisture associated with what
remains of Tropical Storm Harold moves northwest across the area.
Good chances for wetting rain, especially in the mountains, will
persist into the weekend as moisture lingers over the area and
despite the upper high moving west back over NM. The upper high will
move west of the area early next week, which may shut down storms
across western NM, but allow good chances to continue along and east
of the central mountain chain thanks to moisture getting recharged
by a backdoor front. High temperatures will trend back up above
normal most areas by the weekend, then trend down below normal east
of the central mountain chain early next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Farmington...................... 63 84 62 85 / 40 60 60 30
Dulce........................... 52 82 53 79 / 40 50 70 50
Cuba............................ 57 78 56 81 / 40 50 60 40
Gallup.......................... 56 77 55 82 / 70 60 40 30
El Morro........................ 53 75 52 78 / 80 60 60 50
Grants.......................... 54 79 51 82 / 70 60 50 50
Quemado......................... 54 76 54 79 / 80 60 50 60
Magdalena....................... 59 78 59 79 / 80 60 50 50
Datil........................... 56 75 54 76 / 80 60 50 60
Reserve......................... 55 80 54 82 / 80 60 30 60
Glenwood........................ 62 84 62 87 / 70 50 30 50
Chama........................... 49 78 50 74 / 30 60 70 70
Los Alamos...................... 62 79 61 80 / 40 50 40 60
Pecos........................... 60 79 58 80 / 40 50 40 40
Cerro/Questa.................... 47 81 47 78 / 20 40 40 70
Red River....................... 45 74 46 73 / 10 50 50 70
Angel Fire...................... 42 75 43 74 / 10 50 40 60
Taos............................ 54 82 53 81 / 20 40 30 50
Mora............................ 52 79 53 78 / 20 50 30 50
Espanola........................ 63 86 60 88 / 30 40 30 40
Santa Fe........................ 63 80 62 81 / 40 50 40 40
Santa Fe Airport................ 63 83 59 85 / 40 40 30 30
Albuquerque Foothills........... 67 84 66 85 / 50 50 30 30
Albuquerque Heights............. 68 85 65 87 / 50 40 30 20
Albuquerque Valley.............. 66 87 64 89 / 60 40 30 20
Albuquerque West Mesa........... 68 85 66 88 / 50 40 30 20
Belen........................... 65 87 62 91 / 80 40 30 20
Bernalillo...................... 67 86 65 89 / 50 40 30 30
Bosque Farms.................... 62 86 60 89 / 70 40 30 30
Corrales........................ 68 86 65 89 / 50 40 30 30
Los Lunas....................... 63 87 60 90 / 70 40 30 30
Placitas........................ 66 83 64 86 / 50 40 40 30
Rio Rancho...................... 68 85 66 87 / 50 40 30 30
Socorro......................... 65 85 63 89 / 80 40 20 40
Sandia Park/Cedar Crest......... 59 78 60 81 / 50 50 40 40
Tijeras......................... 62 81 61 85 / 50 50 40 30
Edgewood........................ 59 81 58 84 / 60 50 30 30
Moriarty/Estancia............... 57 83 53 85 / 50 50 30 30
Clines Corners.................. 57 79 56 82 / 50 50 30 30
Mountainair..................... 59 81 58 84 / 70 50 30 30
Gran Quivira.................... 60 80 59 84 / 70 50 30 40
Carrizozo....................... 65 83 64 85 / 50 50 20 40
Ruidoso......................... 58 75 56 79 / 80 70 40 50
Capulin......................... 58 83 58 83 / 10 20 10 50
Raton........................... 56 87 56 86 / 10 20 20 50
Springer........................ 58 88 57 89 / 10 20 20 40
Las Vegas....................... 56 82 57 84 / 30 40 20 40
Clayton......................... 66 90 66 91 / 10 10 10 10
Roy............................. 63 86 62 87 / 10 20 20 30
Conchas......................... 66 93 67 95 / 20 20 20 10
Santa Rosa...................... 66 88 65 92 / 30 30 20 20
Tucumcari....................... 66 94 67 96 / 10 10 10 5
Clovis.......................... 67 91 65 95 / 10 10 10 0
Portales........................ 68 93 66 96 / 20 20 10 0
Fort Sumner..................... 68 91 66 95 / 30 20 10 5
Roswell......................... 73 93 70 97 / 40 20 10 5
Picacho......................... 64 85 62 88 / 60 40 30 20
Elk............................. 59 82 58 83 / 70 50 30 30
&&
.ABQ WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 3 AM MDT Thursday for NMZ208-226-241.
&&
$$
SHORT TERM...11
LONG TERM....42
AVIATION...99
Area Forecast Discussion...Updated
National Weather Service Billings MT
835 PM MDT Wed Aug 23 2023
.UPDATE...
Much quieter evening compared to the last two. Dry air aloft was
preventing convection as layer of moisture was very shallow,
leading to flat cumulus with little vertical extent. A few weak
showers and thunderstorms were over the Park earlier this evening
(well south of the forecast area) but have since dissipated.
Another weak shower moved north of Livingston (more likely nothing
more than a cloud deck) and this has since dissipated as well.
Cleared the area of all PoPs the rest of the night. TWH
&&
.DISCUSSION...
Tonight through Thursday night...
Upper air southwesterly flow will facilitate isolated showers and
thunderstorms over and near the mountains this afternoon into the
evening. A lack of moisture aloft should inhibit showers/storms
from moving onto the lower elevations. In addition, low-level
steep lapse rates are also facilitating wind gusts to 20-30 mph
reaching the surface this afternoon and then should diminish early
this evening. Otherwise, a weak, dry cold front will then cross
the area this evening with light northerly winds behind it.
Thursday into Thursday night, an upper ridge will move eastward to
the Northern Rockies with mainly dry conditions across our area. A
few isolated showers and thunderstorms are possible (20% chance)
in far southeastern Carter County in the vicinity of a surface
trough Thursday afternoon as a weak shortwave trough moves
eastward along the MT/Canadian border. CAPE looks low so we are
not expecting any severe weather from those storms.
Smoke: 12z HRRR model shows that smoke will move back into our
area overnight tonight and linger into through at least Thursday
night.
Low temperatures will generally be in the 50s and 60s tonight then
50s Thursday night. High temperatures Thursday will mainly be in
the 80s. RMS
Friday through Wednesday...
Main forecast concerns are on occasional chances for showers and
thunderstorms as monsoonal moisture pushes back into the region
going into this weekend.
WPC clusters show high confidence in ridging persisting over the
region this weekend. Monsoonal moisture increases over the area
Friday into Saturday with precipitable water values increasing to
around 1 inch over southern Montana and northern Wyoming. Forcing is
weak this weekend but thunderstorms could (30 percent chance)
develop over the higher terrain of south central Montana and north
central Wyoming, moving off of the terrain by the late afternoon
hours. High temperatures will be near normal going into this weekend
but then are expected to warm to above normal values Tuesday into
Wednesday. At KBIL the NBM is indicating a 76 percent chance of high
temperatures exceeding 90 degrees on Tuesday and a 68 percent chance
of exceeding 90 degrees on Wednesday.
&&
.AVIATION...
Wildfire smoke will reduce slantrange visibility overnight into
Thursday night. Otherwise, VFR will prevail. RMS/TWH
&&
.PRELIMINARY POINT TEMP/POPS...
Thu Fri Sat Sun Mon Tue Wed
-----------------------------------------------------------
BIL 060/089 057/083 060/089 061/086 058/087 058/093 063/094
10/U 00/U 11/U 21/U 10/U 00/U 11/U
LVM 052/086 051/080 054/086 054/084 051/086 053/091 057/089
10/H 01/U 23/T 23/T 10/U 01/U 11/U
HDN 057/088 054/084 057/089 059/087 054/088 054/093 058/096
10/H 00/U 11/U 21/U 10/U 00/U 10/U
MLS 063/089 056/081 061/088 061/087 056/085 056/091 062/095
10/H 00/U 11/U 11/U 00/U 00/U 10/U
4BQ 064/090 058/082 061/086 061/086 056/085 055/091 062/096
11/U 00/U 11/U 21/U 10/U 00/U 00/U
BHK 061/089 053/078 055/082 057/083 053/079 053/085 058/090
01/U 00/U 11/B 21/U 00/U 00/U 00/U
SHR 057/087 054/080 056/085 057/083 052/083 053/089 057/094
00/U 01/B 22/T 23/T 10/U 00/U 11/U
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Cheyenne WY
526 PM MDT Wed Aug 23 2023
.SHORT TERM...(This evening through Friday night)
Issued at 245 PM MDT Wed Aug 23 2023
Forecast concerns deal with increasing chances for showers and
storms as well as heavy rain chances Friday into Saturday.
Currently...Remnants of Tropical Storm Harold currently in
western New Mexico this afternoon. 700 and 500mb upper high
centered over Missouri this afternoon. Remains of Harold tracking
along the western periphery of this high. Layered PWATS from the
GFS showing near 1 inch in the Nebraska Panhandle and .75 inch out
by Rawlins. At the surface...dewpoints range from the upper 50s in
the Panhandle to mid 40s west of the Laramie Range. Starting to
see a few convective cells on radar along the south Laramie Range
and southern Albany County moving north to north northeast.
HRRR and RAP simulated radar shows convection persisting along the
Laramie Range through 04Z to 05Z this evening...before
dissipating. HRRR holds onto convection a little longer...so
evening and mid shift may be dealing with some late night storms
through after midnight.
By Thursday morning 12Z...remnants of Harold near the 4 corners
area. PWATS increase over current values by tomorrow morning.
Layered GFS PWATS up to 1.10 inch in the Panhandle to 0.90 inch
in Carbon County at 12Z. By the afternoon...PWATS well above 1
inch CWA wide. Low from Harold approaches northwestern COlorado
Thursday night. Look for an increase in showers and storms
Thursday afternoon that will continue overnight into Friday
morning.
Guidance coming into better agreement Friday with ECMWF/NAM/GFS
and SREF all showing widespread light to moderate rainfall across
the western CWA. ECMWF continues to be the most bullish on QPF and
have followed its guidance on POPs and QPF. Did go over latest NBM
QPF across the board as it still seems low.
Going to need to nail down zones for possible Flash Flood Watch
over the next 12-36 hours. Collaborating with Boulder and North
Platte...we all agree that a watch may be needed and have decided
to allow one more model run for the mid shift to decide which
zones to include. WPC maintains a Slight Risk area for excessive
rainfall from Sidney to Laramie on Interstate 80 and most of
northern COlorado to Wheatland on Interstate 25. PWATS well above
1.25 inches across the CWA by Friday afternoon. Good easterly
upslope flow will aid in storm development along the Laramie
Range. Forecast storm motions under 10kts...so slow moving heavy
rainfall looking likely.
.LONG TERM...(Saturday through Wednesday)
Issued at 245 PM MDT Wed Aug 23 2023
Cool and wet conditions continue through Saturday as a shortwave
ejects along the edge of a ridging pattern through southeast Wyoming
and western Nebraska. The ridge amplifies northward and wiggles west
so the ridge axis is positioned over the PACNW, contributing to
potentially warmer and drier conditions. However, due to southeast
Wyoming and western Nebraska being in the boundary between the upper
level ridge and a closed low dropping south into the central CONUS,
any shift of this pattern east or west would result in either much
warmer and drier conditions or cooler and wetter conditions,
respectively. Tuesday, the GFS shows the upper level ridge shifting
east and starting to flatten, leaving southeast Wyoming and western
Nebraska in a mostly zonal, warm, dry, downslope flow. Expect
temperatures Tuesday into Wednesday to start creeping back into the
80s and 90s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 514 PM MDT Wed Aug 23 2023
Current radar imagery has a line of showers and thunderstorms
traveling to the northeast across Goshen county and moving into
the Nebraska Panhandle. Have seen some heavier rainfalls and some
decent lightning within this line producing visibility drops in
the northern portions of the city of Cheyenne with gusty and
erratic winds near the stronger portions of the storm. As this
line continues traveling into the Nebraska Panhandle, expecting
similar conditions as the storms travel across KCDR, KBFF, and
KAIA. Therefore, included TEMPO groups for the chance of IFR
conditions for those terminals. After sunset, should see
conditions improve across southeast Wyoming and the Nebraska
Panhandle. Into tomorrow, isolated to widely scattered afternoon
showers and thunderstorms return with plenty of moisture advection
across the region. HiRes model guidance is picking up on this
afternoon activity primarily after 20z through the evening hours.
&&
.FIRE WEATHER...
Issued at 245 PM MDT Wed Aug 23 2023
Another hot day today with temperatures in the mid to upper 90s in
the Nebraska Panhandle and upper 80s and low 90s in southeast
Wyoming. Monsoonal moisture is on the increase this afternoon as
it streams into the area from the south and southwest. This
increased moisture will keep afternoon humidity above critical
levels as well as kick off scattered to widely scattered afternoon
and evening showers and storms. Expect increasing coverage of
storms Thursday and especially Friday and Saturday as the remnants
of Tropical Storm Harold moves across southeast Wyoming Friday.
Widespread heavy rains possible Friday and Saturday...before
decreasing in coverage Sunday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...LEG
AVIATION...MRD
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1003 PM EDT Wed Aug 23 2023
.UPDATE...
A Slight Risk of severe thunderstorms and a Marginal Risk of
excessive rainfall remain in place for nearly all of SE Mi tonight,
mainly from midnight to 6 AM. Large hail and damaging wind are the
higher probability hazards but also with a low tornado risk given
the warm front draped across Lower Mi. Torrential rainfall capacity
has already been demonstrated by the early day storms and remains
likely tonight with localized flooding possible.
The scenario is still very conditional, or at least subject to lower
spatial and temporal predictability, due to strong capping above the
boundary layer while the larger scale storm environment is very
supportive of organized convection. The 00Z DTX sounding nicely
shows the strong cap around 750 mb, 700-500 mb lapse rate on the
steep end of the spectrum at 7.3 C/km, and also PW of 2.0 inches. A
plenty energetic wind profile is sampled as well with a deep layer
of 45 knot NW flow translating into about 35 kts of effective bulk
shear. These parameters are shown to mostly hold through the night
while CAPE remains surface based and in the range of 1000-3000 J/kg
along and south of the warm front. Elevated instability in terms of
850 mb LI is also shown to start out in the -4 to -7 C range and
hold at least -4 C during the late night as an additional measure of
mid level lapse rate. This leaves the scenario dependent on the
surface wave inbound from WI and its ability to boost the low level
jet just enough to initiate storms along and ahead of its track
along the front. Hi-res model consensus favors central Lower Mi as a
region of convective initiation but with a wide spatial range.
Ongoing showers and storms backbuilding from southern Ontario into
the northern Detroit suburbs are getting picked up by the 00Z HRRR
and 4km NAM which may continue toward central Lower Mi as the low
approaches. Cap level moisture transport helps break through the cap
and into the steep mid level lapse rate environment. Discrete cells
with supercell potential is the preferred mode initially and capable
of large hail. Some upscale growth into multicell clusters is then
possible for more of wind hazard. The tornado risk will be present
throughout the event until the surface low carries the bulk of
activity into Canada by sunrise.
&&
.PREV DISCUSSION...
Issued at 705 PM EDT Wed Aug 23 2023
AVIATION...
A warm front made steady progress to the north and east across SE Mi
during the afternoon and has since stalled near MBS early this
evening. It separates borderline IFR/MVFR ceiling to the north and
VFR south through metro Detroit. The front is expected to remain west
to east between MBS and FNT as low pressure from WI ripples along it
through Lower Mi late tonight and Thursday morning while initiating
another round of thunderstorms. Predictability remains low on
specific location and duration, however ongoing activity makes the
Thumb region a target area for new storms with development also
possible farther west into central Lower Mi as the low slides
eastward. There is then a chance of activity sliding NW to SE toward
the DTW area near midnight and thereafter. Storms remain in the
aviation forecasts due to the close proximity of new development
which could occur overhead or just east of the terminal corridor. The
bulk showers and thunderstorms moves out of SE Mi by sunrise with
the front remaining the dividing line between IFR/MVFR ceiling to the
north and VFR to the south through Thursday morning. Yet another
wave of low pressure is then projected to slide along the front
Thursday afternoon with another round of thunderstorms mainly south
of FNT.
For DTW... SW wind has swept warm sector VFR conditions into the DTW
area this evening. A mention of thunderstorms remains in the
forecast by midnight and thereafter as new activity near MBS has a
chance to spread toward DTW during the late night. Further
adjustments to timing are expected in later updates.
DTW THRESHOLD PROBABILITIES...
* Moderate to low for thunderstorms late evening and overnight.
* Low for ceiling at or below 5000 ft this evening, moderate
overnight and Thursday morning.
PREV DISCUSSION...
Issued at 329 PM EDT Wed Aug 23 2023
DISCUSSION...
Persistent convection centered over the northeast quadrant of the
forecast area has set up a substantial baroclinic zone along the
western edge of the region with a large area of 70 degrees or less
over the Thumb and much of Metro Detroit abutting temperatures in
the upper 80s from Adrian north-northwest to Jackson and Lansing.
Expect the large outflow boundary that is causing this gradient to
remain either quasi-stationary or perhaps drift slowly east into
this evening as additional showers and thunderstorms fire as the
very warm, moist southwesterly flow overrides this cooler airmass in
place over much of the forecast area.
The degree of convection does remain in question into the evening
and overnight hours, but generally expect scattered to occasionally
numerous showers/storms to percolate this evening with a gradual
trend overnight to shift the best coverage of this activity to the
south and southeast. Confidence in the exact timing/coverage does
remain rather low even within this 12-18z hour window, but suspect
periods of scattered convection will impact parts of the forecast
area at times into early Thursday morning. Some of this activity may
be marginally severe given the degree of elevated instability that
will be available along the edge of the upper ridge. In addition,
very heavy rainfall will be a concern, especially where convection
trains over the same area (which is definitely a potential in this
setup).
The extent of convection later this evening and especially overnight
will play a large part in just now hot and humid conditions become
on Thursday. At this time, will be issuing a Heat Advisory for the
southernmost 4 counties in SE MI as this area seems to be the most
likely to see a persistent push of temperatures into the lower 90s
with dew points in the middle 70s by midday Thursday. If convection
remains relatively tame tonight, this advisory may need to be
extended to several other counties as the expanse of hot/humid air
should theoretically be more substantial from mid/late morning into
the afternoon if west-southwesterly flow into the region remains
unimpeded.
A shortwave topping the upper ridge will drive a cold front through
the area Thursday evening with another round of showers and storms
possible. Temperatures will settle back into the 60s Thursday night
in the wake of this front with highs only in the upper 70s to lower
80s Friday. The overall upper level pattern will transition to a
cooler one this weekend with this basic pattern holding into early
to mid next week as the strong upper ridge to the west/southwest
retreats back to the southwest/south central CONUS and upper
troughing amplifies from eastern Canada into the Great Lakes and
northeast CONUS. High temperatures will largely range in the 70s
during this period with 50s common for low temperatures.
MARINE...
A stretch of unsettled conditions is expected today and tomorrow
across the central Great Lakes as energetic flow continues around
the upper ridge while a low pressure system and associated frontal
boundary move through. Showers and thunderstorms, some of which may
become strong to severe, will be the main concerns. Widespread
coverage of showers and thunderstorms early today has decreased with
some lingering activity across southern Lake Huron. There will be a
chance for a resurgence of activity tonight into tomorrow morning
that would impact portions of southern Lake Huron south to Lake
Erie. There remains some uncertainty in overall coverage of this
activity. However, strong to severe storms will be possible where
initiation can occur. The Small Craft Advisory across Saginaw Bay
will be allowed to expire as southeast winds of 15-20 knots will
push the higher waves into the northern half of Lake Huron. A cold
front will then move southward tomorrow afternoon bringing another
round of possibly strong to severe thunderstorms. Strongest storms
will more likely be focused across far southern Lake Huron to Lake
Erie. Winds will back from east-southeast to northerly Thursday
evening behind the front and maintain this direction through Friday.
Wind gust potential looks to remain below 20 knots Thursday and
Friday. Another cold front will push greater cold air advection into
the region on Saturday resulting in strong northerly flow and a
possible return to Small Craft Advisory conditions, especially
across the Lake Huron zones.
HYDROLOGY...
Additional showers and thunderstorms, some strong, will be possible
this evening into the overnight hours. Confidence remains low as to
the exact timing and coverage of this activity. However, prolific
rainfall will be possible under any activity. Additionally, while
the chances remain low, thunderstorm training cannot be ruled out,
which may bring multiple rounds of thunderstorms to the same area
within a short window.
Highly localized rainfall totals will be possible if thunderstorms
develop across SE MI. Any thunderstorm training can easily bring 2+
inches of rainfall within a short 1-2 hour window. Please stay up to
date with the latest forecast as adjustments to storm potential can
be expected into Thursday.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory from 8 AM to 8 PM EDT Thursday for MIZ075-076-082-083.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
UPDATE.......BT
AVIATION.....BT
DISCUSSION...DG
MARINE.......AA
HYDROLOGY....DG
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Forks ND
1011 PM CDT Wed Aug 23 2023
.UPDATE...
Issued at 1011 PM CDT Wed Aug 23 2023
We`ve maintained the stable/capped layer over our area, and the
upstream activity is remain rooted closer to the theta-e
axis/main ML CAPE axis to our west. As a result any updrafts that
moved east quickly fell apart and with this pattern not shifting,
even the strongest storms that hold together are more likely to
become weaker as they move towards our southwest CWA (as indicated
by past few HRRR runs). The main mid level laves are still moving
over our CWA and with enough elevated instability we could still
have a few showers/elevated (non severe) storms. The threat for
severe storms though has diminished even more than earlier though.
While it isn`t zero in our southwest (if one of these upstream
storms just barely holds together before weakening), it is
unlikely we see more than elevated/non severe storms the rest of
the night. Guidance still shows the potential for fog development
in the 07-15Z period, so I am holding firm with the earlier
update. I may ultimately expand fog coverage depending on trends.
UPDATE Issued at 654 PM CDT Wed Aug 23 2023
One pocket of light showers quickly progressed across our area
(still lingering over Beltrami) otherwise we are mainly just
seeing the prevalent stratus deck persist. Initially there were
signs of that this may have been eroding, but recent trends have
show new stratus development within the stable region over our
CWA. This persistent stable layer has limited local initiation of
deep convection, and any chances are now dependent on upstream
activity to the northwest holding together as they spread east, or
another impulse in SD initiating new activity later this evening.
RAP/HRR trends still support the idea of limited/elevated
instabilty and deep layer shear possibly being in place in our
west in a few hours, so there is still a small window for a
strong/severe storm to briefly hold together. However, that`s
based on guidance trends that have been playing catch up with the
very stable ML in place over our CWA and stable satellite
indicators lower confidence further. At this point I`m not ready
to give the all clear on severe potential as upstream activity is
still organizing and a slight shift in the elevated instability
axis eastward within that 2-3hr window would still support a
marginally severe hail risk.
Other concern during this update is the potential for fog once
again, with CAMs showing potential dense fog development in our
west. I do not have high confidence in the evolution of the BL
conditions this evening, but less overnight. However, the
overlapping signal is there and with light winds/potential for
pooling low level moisture near the eastern part of the surface
trough we have a window. I added patchy fog mention for now and
will monitor trends.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 213 PM CDT Wed Aug 23 2023
Satellite shows a MCV entering Manitoba currently, and a nice tongue
of drier air to our west in eastern Montana. Though the bulk of the
MCV will stay in Canada this evening, some convection flowing into
the MCV in the Devils Lake Basin and into the Red River Valley is
possible. Currently, initiation looks to be restricted by cloud
cover but lower stratus is beginning to clear out in the Devils Lake
Basin. Then comes the question of will it be able to warm enough to
hit convective temperature? This is a bit harder to tell, but highs
are not forecasted to reach convective temperature in the initiation
area. However, we do have a suspected cold front in eastern Montana
with the dry air intrusion that could provide the forcing to
overcome the cap for convection in the Devils Lake Basin. That and
the presence of instability (MLCAPE >500 J/kg) and decent shear (sfc
- 6km shear around 40+ knots) leads to a possibility for severe
weather in the Devils Lake Basin this evening. Storms that reach
severe criteria will be isolated, but hail up to quarter size and 50-
60 MPH wind gusts are possible with the severe storms, with hail
being the biggest threat. QPF is uncertain because of the
instability component, but main accumulation of precipitation will
be areas underneath the thunderstorms.
Temperatures will stay in the low to mid 80s for highs throughout
the area and lows in the 60s.
.LONG TERM...(Friday through Wednesday)
Issued at 213 PM CDT Wed Aug 23 2023
Key Messages:
1) Temperatures will work their way back closer to seasonal
averages.
2) Several shortwaves will pass through our area, but the likelihood
they bring significant moisture or impactful weather is low.
The heat across our region associated with the strong central US
ridge will start to wane as the ridge itself sinks further south. In
return, this will place our area under zonal flow by late this week
into the weekend. Within this flow, a couple of shortwaves will be
embedded. The first shortwave on Friday will have moisture origin
monsoonal in nature. This is not a good setup for widespread or
heavy rainfall across our area. Probabilities reflect this, with
odds of more then 0.25 of precipitation only around 30% near the
Canadian border, with the rest of the area under much lower odds.
Consistency in a widespread light rain event occurring are highest
north of highway 200. Sunday another chance for rain comes in the
form of a trough with weak synoptic forcing and some instability
present. Guidance is not certain about the moisture with this system
either, so 10 - 20% are the current probabilities for >0.25 inches
in 24 hours.
The flow turns more northwesterly by Monday, bringing in CAA at
850mb through the end of the period. With this, Temperatures will
not present the extreme gradients seen over the past several days.
We should continue to see temperatures generally remain near to a
couple of degrees below average.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 654 PM CDT Wed Aug 23 2023
Persistent MVFR stratus has eroded enough for "holes" of VFR
conditions over part of eastern ND and northwest MN, however
confidence in prevailing conditions in the first 6hr is low. By
06Z stratus should begin to fill in again, and there is potential
for fog development by 12Z, especially over the KDVL region (less
confidence in fog farther east. Other than a cluster of light
showers near KBJI conditions are currently dry, with focus on any
shower/ thunderstorm potential later this evening as upstream
activity eventually moves east and weakens. Confidence in TS
impacts at terminals has diminished (outside of the KDVL
vicinity), though isolated-scattered showers remain possible
through the night. After VFR is shown to prevail (finally) by late
Thursday morning the main aviation impact will then be related to
shower/thunderstorm chances in the late afternoon (20-40%), with
CU expected but coverage uncertain at TAF sites.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...DJR
SHORT TERM...AK
LONG TERM...AK/BR
AVIATION...DJR
Area Forecast Discussion
National Weather Service Green Bay WI
1021 PM CDT Wed Aug 23 2023
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Thursday
Issued at 241 PM CDT Wed Aug 23 2023
The latest RAP analysis and satellite/radar imagery show a
relatively stalled cold front located from near Green Bay to
between Tomahawk and Merrill early this afternoon. A radar fine
line shows this front has moved through most of Menominee,
southern Oconto, and northern Brown counties. Will therefore
cancel the heat advisory for Menominee and southern Oconto
counties. Under mostly clear skies, very warm temperatures and
high humidity has lead to heat indices from 100 to 110 degrees
south of the boundary. Meanwhile, north of the front, widespread
low stratus exists within a shallow, colder airmass where winds
are north to northeasterly and temps are in the low to middle 70s.
Forecast concerns mainly revolve around temp and sky trends
through Thursday.
Late This Afternoon and Tonight...With passage of a weak shortwave
aloft, the cold front is expected to surge south and southwest
across northeast Wisconsin and reaching central Wisconsin by mid
to late evening. Areas over the northern Fox Valley and east-
central WI lakeshore should see a relatively quick temperature
drop into the mid or upper 70s by early this evening. With passage
of the front, low clouds should surge south as well, with a low
overcast deck spreading across the forecast area. Models indicate
increasing boundary layer moisture across far northern Wisconsin
late tonight that could result in patchy drizzle.
Thursday...Weak high pressure over the Lake Superior region will
continue to funnel in cooler air via north winds across northeast
Wisconsin. Widespread broken to overcast skies are expected in the
morning, which should gradually retreat north over the course of
the day. The drizzle/light showers should continue for much of the
morning over far northern WI. High temps have continued their
cooler trend, which makes sense given the cloud cover. Highs will
range from the lower to middle 70s near the U.P. border to the
upper 80s over central Wisconsin.
.LONG TERM...Thursday Night Through Wednesday
Issued at 241 PM CDT Wed Aug 23 2023
The next chance of showers and storms will arrive on Friday as a
shortwave trough drives a cold front southeast across the region.
Dynamics are decent aloft with this system thanks to 100 kt jet
energy moving across the Lake Superior region and the right rear
quad of this jet streak passing across northern WI. Instability
will be a limiting factor, however, as guidance generally
indicates 500-1000 j/kg of most unstable cape. But given the wind
fields and upper support, strong storms appear possible on Friday
afternoon.
After high pressure brings seasonable and quiet conditions during
the weekend, another front is due to move across the region on
Monday which could provide some rain and storms. Temps will be
near to below normal this weekend into the middle of next week.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1011 PM CDT Wed Aug 23 2023
NE-E winds continued to push low stratus westward across the
forecast area this evening, and widespread IFR ceilings already
covered eastern and parts of northern WI. Expect IFR ceilings to
return to most of the forecast overnight, with fog and LIFR
conditions developing over northern WI and near Lake Michigan.
Conditions will slowly improve from south to north during the day
on Thursday, with VFR returning to the southern TAF sites in the
late morning/early afternoon, and at RHI by mid-afternoon. It is
possible that local MVFR conditions may linger over the far north
into the late afternoon and evening, but overall confidence is low
in the details at this time.
A few light showers may move through northern WI late tonight into
Thursday morning, but should have minimal impact if they occur.
NE-E winds will continue overnight into Thursday morning, then
become northerly in the afternoon.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM.....MPC
LONG TERM......MPC
AVIATION.......Kieckbusch
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1144 PM EDT Wed Aug 23 2023
.SYNOPSIS...
Hot and humid conditions persist for much of the area through Friday
afternoon. Some chances for storms accompanies the heat.
Temperatures cool back toward seasonal averages this weekend into
next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Updating to include a flood watch for four counties in central
Ohio. Confidence is medium to high that thunderstorms with
heavy rain will get into central Ohio in the next few hours.
Confidence is much lower for additional storm propagation beyond
that point, perhaps impacting areas further south and west in
the ILN forecast area. Will look to refine the forecast and, if
necessary, expand the flood watch as the scenario comes into
clearer view.
Previous discussion >
A complicated and low-confidence forecast for tonight is slowly
starting to come into slightly better view. The ILN CWA is
currently on the southern periphery of a very potent 925mb
theta-e advection regime, with high theta-e values extending
from the middle Mississippi Valley region through Lake Erie on a
generally WSW-to-ENE trajectory. This is currently feeding the
severe storm near Cleveland, which has exhibited reflectivity
thresholds typical of a severe storm in a near-advisory-criteria
heat type of environment (50dBZ to 50kft, for example).
Over the next few hours, this feed of theta-e will gradually
shift southward, and it appears likely that the continued
propagation of this feature (and possible upscale growth into an
MCS) will eventually track the feature into central Ohio. At the
very least, it seems that convection will get into the
northeastern fringes of the ILN CWA (near and northeast of
Columbus). The challenging part of the forecast is looking at
the potential for further propagation to the south and west,
which has been suggested by several models, but very
inconsistently in terms of severity and westward extent.
Further eroding forecast confidence is the fact that recent HRRR
runs have not had a monopoly on either consistent signals for
how long the storms will propagate, or even where the current
storms are located. The 00Z run seems to have initialized
poorly, with real-life storms further west than the model has
depicted.
The broader model signals would suggest that the
storms will hold together as they continue to propagate, but
where and when that propagation occurs is something probably
better answered by mesoscale analysis. Right now, the location
of the instability gradient and the overall wind flow would
suggest the ILN CWA will not be unscathed by this activity.
Thus, there is medium confidence that central Ohio will be
impacted by these storms, and then low confidence in further
southward and westward propagation from there. Yes, it would be
unusual for storms to move from northeast to southwest, but the
vector of the flow of instability into the storms would suggest
it is possible.
Wherever these storms end up, there is plenty of heat and
humidity in the atmosphere to work with -- resulting in threats
of damaging wind, large hail, and heavy rainfall / flash
flooding. HWO has been updated to reflect higher confidence in
this scenario for a handful of central Ohio ILN counties. PoPs
have also been increased.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
While the synoptic setup remains fairly certain with a low northwest
of the Ohio Valley, mesoscale uncertainty from tonight extends into
tomorrow (Thursday). If the area remains dry overnight (no MCS
diving in from Michigan), Thursday likely features highs reaching
into the 90s along with dew points in the lower to middle 70s
everywhere. This combination of temperatures and dew points would
easily support the heat index reaching over 105 which reaches
Excessive Heat Warning Criteria. However, if the dry forecast
does not work out and a MCS dives south from Michigan overnight,
the rain-cooled air and cloud cover in the wake of the MCS
could limit daytime highs to near 90 in certain locations. Wet
scenario probabilities increase further east of I-75. The wet
scenario would still likely feature hot conditions by the
afternoon with the heat index reaching up to 100 which reaches
advisory level criteria. Either way, the main takeaway for
Thursday is hot and humid conditions are expected during the
afternoon. Whether the heat index reaches 100 (Heat Advisory) or
105 (Excessive Heat Warning), the risk for heat related illness
will likely be elevated. An Excessive Heat Watch remains in
place where the greatest uncertainty regarding convection is. An
Excessive Heat Warning in now in place where confidence is
highest regarding the heat index reaching 105 or above which is
along and west of I-75. The watch will be adjusted in the future
when the nature of possible convection is clearer.
Another 30-50% chance for convection exists once again Thursday
night since the Ohio Valley remains near the upper level ridge axis.
Details regarding this chance for convection will be dependent on
how he forecast evolves over the next 24 hours or so. Forecast lows
are in the middle 70s.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
East-west oriented boundary will extend across the area at the
beginning of the period and sag south through the day. At this
stage, 12Z guidance is not too enthused with convective
potential, but it is there. So will just keep lower chance PoPs
in southern counties. It looks like there will be a reinforcing
secondary front that will pass through the region on Saturday,
and this could also be a focus for some showers and
thunderstorms.
Cooler, drier high pressure will then build in with the center
of the high tracking east across the upper Great Lakes. Another
cold front will push through the region on Tuesday as the mid
level pattern amplifies with energy dropping southeast out of
the Canadian Plains. This will result in another chance of
showers and storms. Dry conditions will return on Wednesday as
high pressure builds in the wake of the cold front.
It will still be quite warm on Friday, although below the peak
heat from Thursday, with heat indices ranging from the mid 90s
in west central Ohio to near or above 105 in northern Kentucky.
Air temperatures will be about 5 to 7 degrees cooler on Saturday
with another 5 to 7 degrees of cooling for Sunday. Temperatures
will then remain slightly below normal through the rest of the
period.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
VFR conditions are generally expected through the TAF period,
but showers and thunderstorms remain a possibility.
Tonight, mostly clear skies are expected, with generally SW
winds at 10 knots or less. By early morning, after 08Z, there
will be a chance that some showers and storms could move into
the area from the north. The timing and location of these storms
are very difficult to pinpoint, so for now, a VCSH will be kept
in the KCMH/KLCK TAFs with no mention elsewhere. However, these
forecasts may need to be significantly changed overnight if
thunderstorms do develop and move into the area.
Aside from thunderstorms, winds should remain generally out of
the southwest tomorrow, with values of around 10-12 knots.
OUTLOOK...No significant weather expected.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Excessive Heat Warning from noon to 9 PM EDT Thursday for
OHZ034-035-042-043-051-060-061-070-071-077-078.
Excessive Heat Watch from Thursday afternoon through Thursday
evening for OHZ026-044>046-052>056-062>065-072>074-
079>082-088.
Flood Watch until 11 AM EDT Thursday for OHZ046-055-056-065.
KY...Excessive Heat Warning from noon to 9 PM EDT Thursday for
KYZ089>096.
Excessive Heat Watch from Thursday afternoon through Thursday
evening for KYZ097>100.
IN...Excessive Heat Warning from noon to 9 PM EDT Thursday for
INZ050-058-059-066-073>075-080.
&&
$$
SYNOPSIS...Campbell
NEAR TERM...Hatzos
SHORT TERM...Campbell
LONG TERM...
AVIATION...Hatzos
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
810 PM CDT Wed Aug 23 2023
.SYNOPSIS...
Issued at 809 PM CDT Wed Aug 23 2023
Hot and humid conditions will continue across central Illinois
through Friday, then a cold front will settle south across the
region Friday and Friday night ushering in a more comfortable air
mass for the weekend. For today and Thursday, expect highs in the
mid to upper 90s with a few spots tagging 100 degrees Thursday
afternoon. Heat indices will peak between 105 to 115 degrees.
&&
.UPDATE...
Issued at 809 PM CDT Wed Aug 23 2023
It would appear the shields remain up and intact, as no
reflectivities have popped on radar nor vertically developed clouds
appeared on satellite to indicate parcels have risen through the
strong capping inversion around 850mb. This is very fortunate given
our 6357 J/kg of SBCAPE is the 16th highest ever observed in central
Illinois, according to climatological records dating back to 1949.
We`ll still keep an eye out for something tomorrow given a couple of
the CAMs have the outflow boundary originating from this evening`s
storms over northern Ohio tracking all the way east into western
Indiana or eastern Illinois by early tomorrow afternoon. However,
thinking really hasn`t changed a bunch given there`s still expected
to be some capping tomorrow and hence PoPs were left silent.
One small change to the forecast was the rising of dewpoints
overnight to match better with current observations, which are
overachieving (about 5-7 degrees higher than even the HRRR and
NAMNest) due to agricultural evapotranspiration. Given the
oppressive dewpoints in the low 80s, it`s tough to think we won`t
wind up with some patchy fog tonight (especially after the past two
nights of it), so that was added to the present weather forecast as
well. Otherwise, the main weather story will just be a continuation
of the advertised heat for another couple days.
Bumgardner
&&
.SHORT TERM... (Through Late Thursday Night)
Issued at 210 PM CDT Wed Aug 23 2023
An anomalously strong upper ridge remains centered over the Great
Plains this afternoon with the high spanning from the Rockies to
the Appalachians. This pressure cooker will continue to result in
dangerously hot and humid conditions through at least Thursday
for all of central Illinois. At the surface, weak and disorganized
area of low pressure is in place across the northern Great Plains
into the Upper Midwest this afternoon and will gradually shift
into the Great Lakes Thursday. Breezy SW winds will occur across
central Illinois ahead of this feature. While a few sporadic gusts
are possible through this evening, gusts to around 20 mph will
become more frequent Thursday afternoon. The stronger winds and
deeper mixing Thursday will help mix down dew points slightly from
the 80s today with mid 70s more common Thursday. Temperatures
will be able to achieve a few extra degrees as a result, and many
areas will top out right around the 100 mark with resulting heat
indices again in the 105-115 degree range. An Excessive Heat
Warning remains in effect for all of central Illinois through
Thursday evening. SPC has reintroduced a marginal risk for day 2
which clips our far northern CWA (parts of Knox, Stark, and
Marshall counties). While moderate instability (1500 J/kg MLCAPE)
will be present, deep layer shear should remain modest (<20 kt)
under the weaker flow of the ridge and forcing will be negligible.
If we reach convective temps and are able to fire off an isolated
storm or two, steep low/mid level lapse rates would be conducive
to strong wind gusts. Overall confidence in this scenario is low
and PoPs remain "Silent" at around only 10-13 percent Thursday
afternoon.
Deubelbeiss
.LONG TERM... (Friday through Next Wednesday)
Issued at 210 PM CDT Wed Aug 23 2023
Friday and Friday night, a shortwave trough is progged to dig
across the Upper Midwest into the Great Lakes region while at
the surface, an attendant cold front will push across central
Illinois late Friday into Friday night. A very strong cap will be
in place with H85 temps still in the ball park of 24-25C. This
should keep the area dry despite frontal passage. Surface temps
will be well into the 90s again Friday ahead of the front, but the
mid to upper 90s will be shunted south of I-72 while cloud cover
further north keeps temps in the lower 90s. Heat indices will
continue to run in the 100 t o115 range and an Excessive Heat
Warning was extended into Friday for areas along and south of a
Canton to Decatur to Paris line, but conditions will be close
further north.
Relief from the heat and humidity arrives over the weekend with
highs in the mid to upper 80s Saturday and lower 80s Sunday while
dew points ease back into the 60s. Cold front will settle south of
the Ohio River Valley while central Illinois falls under the
influence of high pressure centered over the Great Lakes providing
light northeasterly flow locally.
Early next week, models indicate that another cold front will
sweep across the region. At this distance, there are still
sizable timing differences but this could bring the next chance
for showers and thunderstorms to central Illinois either Monday or
Tuesday. High pressure will build back across the region behind
the front bringing more mild temperatures and dry weather.
Deubelbeiss
&&
.AVIATION... (For the 00z TAFs through 00z Thursday Evening)
Issued at 637 PM CDT Wed Aug 23 2023
VFR conditions should be predominant throughout the bulk of the
forecast period, however given (1) dewpoints in the low 80s and
(2) the past couple days of AM fog such was added in a tempo for
MVFR visibilities during the 10-13z (5-8AM CDT) timeframe. There
is a small (about 10-15%) chance for a thunderstorm during the
evening Thursday, but most likely it will be dry as strong capping
prevents clouds from rising very deeply through the atmosphere.
Bumgardner
&&
.CLIMATE...
Issued at 341 AM CDT Wed Aug 23 2023
Record High Temperatures for Climate Sites:
Peoria Springfield Lincoln
Wed 8/23 101 (1947) 101 (1936) 100 (1936)
Thu 8/24 102 (1936) 101 (1947) 101 (1936)
Record Warmest Low Temperatures for Climate Sites:
Peoria Springfield Lincoln
Wed 8/23 75 (1936) 79 (1947) 75 (1936)
Thu 8/24 74 (1947) 78 (1947) 75 (1998)
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 10 PM CDT Thursday for ILZ027>031-
037-038-043>046.
Excessive Heat Warning until 10 PM CDT Friday for ILZ036-040>042-
047>057-061>063-066>068-071>073.
&&
$$
Area Forecast Discussion
National Weather Service Louisville KY
933 PM EDT Wed Aug 23 2023
...Forecast Update...
Issued at 931 PM EDT Wed Aug 23 2023
Quiet evening in progress with just some cirrus spreading southeast
across south-central KY. Warm and humid tonight with light winds.
Will need to keep an eye on convection to the north overnight. Deep
convection is ongoing over Lake Erie and northeastern Ohio in a warm
advection regime. Convection has recently been building westward
into a MUCAPE maximum, with new development now in southeastern
Lower MI. Latest hi-res CAM guidance suggests a MCS could evolve
south through a significant portion of Ohio. Went ahead and bumped
up sky cover a bit Thursday morning into early afternoon, especially
east of I-65. Still agree with the previous forecast that the
probability is quite low that we`ll see any shower or thunderstorm
activity tomorrow in our CWA. But at this point, certainly cannot
rule out a scenario where weakening showers and storms spread into
northern and northeastern KY. May need to bump up sky cover a bit
more overnight, which could play a role in limiting sfc heating on
Thursday (especially east of I-65).
.Short Term (Now through Thursday)...
Issued at 335 PM EDT Wed Aug 23 2023
---------------------------------------------------------------------
Key Message...
- Hot conditions continue with increased humidity values leading to
the return of dangerous heat indices
---------------------------------------------------------------------
Across the region this afternoon, temperatures are as warm if not
warmer than the past few days, with latest mesonet/AWOS/ASOS obs
showing readings in the upper 80s and lower 90s. However, the heat
is slightly less impactful thanks to dewpoints "only" in the low 70s
along and east of I-65. Scattered cu field extending from the Ozarks
into central Indiana reveals where the highest dewpoints are this
afternoon, with the higher moisture air mass gradually working its
way south and east this afternoon and evening.
Tonight, expect temperatures to fall more slowly than last night as
the more humid air holds temperatures up. Surface pressure ridging
south of the Ohio River this afternoon will continue to slide
farther south tonight, allowing enough of a pressure gradient for a
light southwesterly breeze overnight tonight. Mostly clear skies are
expected tonight (and whatever cloud cover exists should be 20+ kft
off the ground); however, the aforementioned breeze will promote
weak warm advection near the surface and should keep most spots from
decoupling such that fog develops. Nevertheless, some patchy fog may
briefly develop near sunrise tomorrow across the Lake Cumberland
area and in the deepest river valleys, though confidence in this is
low.
Tomorrow, the large omega ridge across the central CONUS will begin
to retreat westward as NW flow aloft begins to move closer to the
Ohio Valley. Stronger NW flow aloft will be reflected in the low
levels, helping to advect warmer air into central Kentucky and
southern Indiana from the west. Slightly increased 850 mb
temperatures in model guidance would suggest that we could add a
couple degrees onto high temperatures from today. Expected highs on
Thursday should range from the low-to-mid 90s in rural areas to the
mid-to-upper 90s in urban areas. Alas, what will be more impactful
to heat indices and human health will be the resurgence of high
dewpoints. West-southwest flow in the sfc-925 mb layer should advect
the higher moisture air west of the Mississippi River into our area
tomorrow. With temperatures in the 90s and expected dewpoints
generally in the mid-70s, heat indices should range between 105-115
tomorrow afternoon. As a result, the excessive heat warning looks
well placed to coincide with where the highest T/Tds overlap.
Farther east, slightly lower dewpoints and temps would suggest heat
indices around 105 across the western KY Bluegrass counties. As a
result, have added a heat advisory for this swath of counties for
tomorrow (as well as Friday). Farther south and east, where the
lowest dewpoints are expected, will continue without a headline due
to low confidence in reaching criteria; however, later forecast
packages may deem an eastward expansion in the advisory area
necessary.
One low-probability spoiler east of I-65 to the high heat and
humidity would be the effects of a decaying MCS approaching the
Bluegrass in the late morning and early afternoon hours. The hi-res
NAM continues to depict this solution, though the HRRR and RRFS have
backed off more bullish forecasts from 00Z to 12Z. Tend to agree
with this trend which would keep MCS activity farther east as a
pretty stout capping layer between 925-700 mb continues to be
evident in most forecast soundings tomorrow morning. Even if the MCS
subsided before reaching the area or tracked off to the east, some
convective cloud debris or rain-cooled outflow could complicate
temperature forecasts, although this is a highly unlikely solution.
Nevertheless, thought this possibility should be mentioned to
highlight a bust potential for heat headlines east of I-65 tomorrow.
.Long Term (Thursday night through Tuesday)...
Issued at 327 PM EDT Wed Aug 23 2023
---------------------------------------------------------------------
Key Messages:
- Heat wave reaches its zenith on Friday
- More seasonable temperatures and drier air arrive by Sunday
- Minimal chances for rain over the next several days
---------------------------------------------------------------------
The large upper ridge that has brought us the hot weather this week
will hang on for one more day into Friday. Went slightly below
guidance for temperatures, but we should still end up with afternoon
readings in the middle and upper 90s. Even with mixing afternoon dew
points, heat indices will reach into the 100-110 degree range. While
record highs on Friday are probably safe (Louisville will come the
closest), warm nights may threaten record warm lows Thursday night
and Friday night.
A cold front will approach from the north on Friday, but its forward
motion will be quite slow as it weakens while drifting southward
through the region Friday night into Saturday morning. This boundary
may spark a few thunderstorms, but mid-level warmth, a weakening
trigger, weak-moderate shear, our location still on the edge of the
dominant upper ridge, and the system`s upper support weakening as it
slides from the Great Lakes to the Potomac Valley will keep any
thunderstorm activity widely scattered. Yet, this may be our best
shot at rain for the next several days.
The front will, however, bring in a much more tolerable air mass
with high temperatures Sunday through Wednesday around normal in the
80s. Dew points will mostly be in the 60s...dropping into the 50s by
mid-week. As for precipitation, the Gulf and Atlantic coasts will be
where much of the country`s rainfall will be located. The best
chance for us appears at this time to arrive Monday night into
Tuesday as a relatively sharp 5H shortwave trough digs into the Ohio
Valley with a weak surface cold front.
&&
.Aviation (00Z TAF Issuance)
Issued at 751 PM EDT Wed Aug 23 2023
Another warm, humid night is expected with mostly VFR conditions.
TEMPO MVFR fog looks quite possible at HNB, given the smaller
dewpoint depression at that terminal. Light southwesterly winds are
forecast overnight, along with FEW-SCT cirrus. Southwesterly winds
increase after sunrise on Thursday. SCT-BKN cirrus is likely to
spread in from the northeast Thursday morning.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Excessive Heat Warning until 10 PM CDT Friday for KYZ023.
Heat Advisory until noon EDT /11 AM CDT/ Thursday for KYZ024>034-
038-045-053-061>063-070>074.
Excessive Heat Warning from noon EDT /11 AM CDT/ Thursday to 11
PM EDT /10 PM CDT/ Friday for KYZ024>034-038-045-053-
061>063-070>074.
Heat Advisory from noon Thursday to 11 PM EDT Friday for
KYZ035>037-039>041-046>048-054-055.
IN...Excessive Heat Warning until 11 PM EDT /10 PM CDT/ Friday for
INZ076-077-083-084-089.
Heat Advisory until noon EDT Thursday for INZ078-079-090>092.
Excessive Heat Warning from noon Thursday to 11 PM EDT Friday
for INZ078-079-090>092.
&&
$$
Update.........EBW
Short Term.....CSG
Long Term......13
Aviation.......EBW