Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/16/23
Area Forecast Discussion
National Weather Service Amarillo TX
651 PM CDT Mon May 15 2023
...New AVIATION...
.SHORT TERM ...
(This evening through Tuesday night)
Issued at 210 PM CDT Mon May 15 2023
The light rain that persisted through the morning has come to an
end and no additional rain is expected this afternoon. A modified
cold front will approach the Panhandles from the north later this
afternoon into the evening, pushing out the low-level moisture
that`s been prevalent in the area over the past several days.
Tonight will be dry and low temperatures will only be slightly
cooler than average. Some fog will be possible across the area from
around 4am to 8am due to weak winds and wet soils/evapotranspiration
from recent rainfall. RAP and HRRR are more aggressive about the fog
potential, but the models that are typically more aggressive with
low-level moisture... 12km NAM/3km NAM... are less certain about if
and where fog may occur. Therefore, will leave fog out of the
forecast but will have to be monitored this evening and tonight.
The Panhandles will be on the northern periphery of the surface high
pressure tomorrow, which was associated with the aforementioned cold
front, and it will keep winds around 5-10 mph. Toward the late
afternoon/evening hours, a shortwave trough embedded in the
northwest flow aloft will approach the Oklahoma Panhandle,
contributing to around 30 kts of 0-6km shear. Around the same time,
a plume of modestly steep mid-level lapse rates... 7 C/km to 7.5
C/km... will be advected into the Oklahoma Panhandle. However, with
surface dew points only in the upper-40s to low-50s and surface
temperatures in the low-80s, SBCAPE should remain around 500-1000
J/kg. Therefore, if thunderstorms can develop, the primary threat
they would pose is strong winds. Thunderstorm development would also
be possible in the western half of the combined Panhandles with a
weak Pacific front that is expected to try to move through at least
a part of the Panhandles. The prospect for strong winds/small hail
with these thunderstorms is even more marginal than in the Oklahoma
Panhandle due to weaker mid-level lapse rates lower surface dew
points, and weaker winds aloft.
Thunderstorms may linger into the overnight hours across the area.
If this occurs, they would be elevated with a chance for small hail.
Expect lows to be in the low to mid-50s.
Vanden Bosch
&&
.LONG TERM ...
(Wednesday through next Sunday)
Issued at 210 PM CDT Mon May 15 2023
Rain chances continue to be present and spread out through the
extended period. At this time strong to severe thunderstorms
cannot be ruled out for Wed and Thu, but confidence remains
somewhat low. High temps on Wed and Thu are progged to be near
normal in the 80s. For Fri, temps are progged to be slightly
cooler behind a cold front. The NBM has since trended warmer with
daytime highs for Fri into Sat with temperatures in the mid to
upper 70s. Previous runs of the NBM were giving temps more in the
upper 60s to lower 70s.
Despite a mid to upper level ridge over much of Western CONUS, a
cutoff low is progged to develop over Baja, California. This low
is expected to help supply some Pacific moisture to the area for
the rain chances through the early part of the extended period.
With the ridge over the Intermountain West, northwest flow is
expected to persist Wed through late Thu. Late Thu an upper level
low is progged to drop down out of Manitoba into the Upper
Mississippi River Valley. This digging trough will transition the
flow aloft to a more zonal orientation, and also send a cold front
down from the northeast on Fri.
Wed, models are hinting at the possibility of convective temps
being reached during the afternoon. Not only that but some
residual surface boundaries may exist from storms that are
expected tomorrow afternoon. Confidence in coverage and where
storms will be located Wed afternoon is low at this time. However,
models do suggest some good instability, around 1500-2500 J/Kg
with bulk shear values around 25-30 kts. This could lead to some
severe thunderstorms for Wed afternoon. With inverted V soundings
severe wind gusts may potentially be a threat on top of hail
around inch to an inch and half possible with afternoon storms.
Going into the late afternoon/evening hours, disturbances in the
northwest flow aloft may be present and aid in further development
of storms going into the overnight hours. During which storms may
become more elevated but potentially pose a low end severe risk
still.
Thu, with ample moisture ahead of an approaching cold front, the
FA may see additional thunderstorms. Severe storms may be possible
depending on cloud cover during the afternoon and if convective
temperatures can be reached. Confidence is low at this time on the
intensities of storms possible due to it being day 4. Also,
depending on storms Wed some residual boundaries may be left in
the wake. PWATS do increase late Wed well into Thu with values as
high as 150% to 250% above normal. Additional perturbations in the
northwest to zonal flow off of the mountains could add some lift
for storms as well. Going into the overnight hours Thu, showers
and thunderstorms are expected to continue especially as the front
gets closer. At this time it is unclear about the strength and
the extent of the front over the FA going into Fri. This also has
temperatures in question for Fri. Between the NBM 5th percentile
and the 95th percentile, there is a 20 degree temp difference for
the high on Fri and on Sat. Evidence suggest a gradual warming Sat
onward, with lower 80s possible on Sun. Additional precip chances
continue through next weekend as well.
36
&&
.AVIATION...
(00Z TAFS)
Issued at 641 PM CDT Mon May 15 2023
For the 00Z TAFs, lower clouds will continue to decrease this
evening across the terminal sites, leaving behind just some high
level cloud cover. There is some concern for potential fog
development late tonight or early Tuesday morning. However,
forecaster confidence is low on that scenario, which precludes
mentioning at this time. No precipitation is expected through late
Tuesday afternoon.
02
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 50 83 56 83 / 0 10 20 40
Beaver OK 48 81 53 83 / 0 0 20 20
Boise City OK 47 81 51 80 / 0 10 20 40
Borger TX 52 85 58 87 / 0 10 20 30
Boys Ranch TX 50 85 55 86 / 0 10 20 40
Canyon TX 50 83 54 83 / 0 10 20 50
Clarendon TX 52 80 56 81 / 0 10 20 30
Dalhart TX 47 83 51 82 / 0 20 20 50
Guymon OK 47 83 52 83 / 0 0 20 20
Hereford TX 50 84 54 84 / 0 10 30 50
Lipscomb TX 48 81 53 82 / 0 0 20 20
Pampa TX 49 82 56 82 / 0 10 20 30
Shamrock TX 52 81 55 81 / 0 0 20 20
Wellington TX 53 82 56 83 / 0 0 20 20
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&
$$
SHORT TERM...52
LONG TERM....36
AVIATION...02
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
948 PM CDT Mon May 15 2023
.UPDATE...
Issued at 948 PM CDT Mon May 15 2023
Once again only minor changes were made with this update. The dry
air mass and light winds will allow for a cool night, and smoke
aloft does not impact radiational cooling, so we may end up with
some locations dropping below forecast lows. However, the air mass
has warmed slightly since yesterday, so we made little change to
the low temperature forecast at this juncture.
UPDATE Issued at 626 PM CDT Mon May 15 2023
No significant changes were needed with this update, with ridging
both at the surface and aloft leading to quiet weather tonight.
All we did with this update was blend observed trends and recent
NBM guidance into the evening hourly forecast elements.
&&
.SHORT TERM...(This Evening through Tuesday)
Issued at 239 PM CDT Mon May 15 2023
Quiet and seasonably warm weather highlights the short term
period.
An upper high extends from across southern Saskatchewan into
North Dakota early this afternoon, with a broad surface high
centered over South Dakota but extending across the entire
Northern Plains. This has resulted in a quiet weather day across
the area, with sunny skies, light winds, and high temperatures in
the 70s.
There is a small amount of smoke aloft this afternoon, although
not enough to have any forecast implications. GOES GeoColor shows
thicker smoke just to our east, in northeast North Dakota into
northern Minnesota. This is coming from ongoing wildfires across
the northern Canadian Prairies. The latest RAP vertically
integrated smoke forecast shows that this will likely get thicker
overnight and into tomorrow, which could give a milky appearance
to the sky.
With the surface high still in place tonight, expect a quiet and
clear night, with lows in the mid 40s to lower 50s.
The eastern edge of a much warmer 850mb air mass moves into the
forecast area on Tuesday, while upper flow becomes more northerly.
Highs will be slightly warmer today, in the mid 70s to lower 80s,
with mostly sunny skies except for any smoke that moves in.
.LONG TERM...(Tuesday Night through Monday)
Issued at 239 PM CDT Mon May 15 2023
A cold front will bring chances for showers and thunderstorms
starting midweek, with cooler temperatures to end the work week
before warming up again this weekend.
Ensemble guidance is in fairly good agreement on a closed low
dropping south from the Canadian Prairies through the middle and
end of the work week, bringing multiple cold front passages and
chances for showers and thunderstorms. The initial front is
expected on Wednesday, with blended guidance producing 40 to 60%
PoPs from northwest to southeast through the day and Wednesday
night. Highs will be in the lower 70s to lower 80s on Wednesday,
with locations in the northwest likely seeing highs earlier in the
day, depending on the cold front timing. The frontal passage will
also bring breezy northwest winds. Southerly low- level flow
ahead of the front is forecast to bring a somewhat narrow area of
500-1000 J/kg of MUCAPE along and ahead of the front, although
weak shear will limit severe thunderstorm potential.
A secondary cold front will move through on Thursday, bringing a
more substantial pool of cooler air, as well as additional
chances for showers. Highs on Thursday and Friday will generally
be in the upper 50s to 60s, with continued breezy north/northwest
winds.
As the upper low finally exits to our east, ridging will be
building back across the western CONUS, with NBM trending
temperatures warmer starting Saturday and continuing into the
start of next work week. There is high confidence in highs being
back in the 70s by Saturday, with some 80s likely on Sunday. No
strong precipitation signal so blended forecast keeps the weekend
dry.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 948 PM CDT Mon May 15 2023
VFR conditions and light winds will be the rule across western
and central ND through the 00 UTC TAF cycle thanks to high
pressure both at the surface and aloft. Some high-level smoke is
expected at times, though.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CJS
SHORT TERM...Jones
LONG TERM...Jones
AVIATION...CJS
Area Forecast Discussion
National Weather Service Duluth MN
642 PM CDT Mon May 15 2023
.DISCUSSION...(This evening through Sunday)
Issued at 353 PM CDT Mon May 15 2023
Summary: Warm, dry, and sunny conditions continue this afternoon.
Smoke from western wildfires has been impacting portions of northern
MN, causing a milky-appearance in the sky. This smoke is expected to
continue into tomorrow, resulting in reduced air quality across
northeast MN. Near-critical fire weather conditions continue
today and are expected for portions of the area tomorrow. Our next
chance for showers and thunderstorms arrives Wednesday night into
Thursday.
High pressure continues to be in control of the pattern over the CWA
as a rex block persists over the western CONUS. The lack of rainfall
combined with low relative humidity has been creating near-critical
fire weather conditions across all of the CWA today. Another round
of near-critical fire weather conditions are likely tomorrow for
interior portions of MN that won`t be affected by a lake breeze.
Northeast winds will result in cooler temps and increased RH for
areas in the lee of Lake Superior, lessening fire weather concerns
on Tuesday.
The other near-term forecast concern besides fire weather is
wildfire smoke from western North America entering the CWA. As of
this afternoon, this wildfire smoke is expected to remain aloft
above the mixing layer. However, air quality concerns enter the
picture tomorrow following a cold frontal passage. The HRRR smoke
model has been performing poorly with this smoke, especially in
comparison to the Canadian smoke model. Due to a cold fropa tomorrow
mixing down lingering smoke to the sfc, an Air Quality Alert has
been issued for all of the northeast MN CWA on Tuesday.
Conditions on Wednesday are expected to follow the trend of the past
few days, with dry conditions and warm temps. A change in pattern
comes on Thursday as a trough that is currently traversing the rex
block arrives into the region. Ensemble guidance has some
disagreement between the global models regarding the onset time of
showers and thunderstorms on Wednesday evening/night. However, there
is still high confidence that widespread showers and storms will
propagate through the CWA on Thursday along a cold front. Severe
storms are not expected on Thursday, as instability and mid-level
lapse rates will be marginal at best.
Showers with an isolated thunderstorm or two linger into Friday
before precip comes to an end by Friday evening. High pressure is
likely to redevelop this upcoming weekend, resulting in limited
precip chances, warm temps, and sunny skies.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 642 PM CDT Mon May 15 2023
A backdoor cold front will move through the Northland later
tonight through Tuesday afternoon switching winds from westerly to
east to northeast for most areas. There was plenty of smoke aloft
over the region this evening from fires in Canada but few other
clouds. Gusty westerly winds will subside through the evening.
Winds will increase through the day Tuesday, especially around
Lake Superior as a lake breeze strengthens. There are some
indications some lower clouds will accompany the cold front but we
don`t expect widespread coverage and just have a non-ceiling
based mention for now.
We don`t anticipate significant reductions in the visibility from
the smoke and left that out of the forecast for now.
&&
.MARINE...
Issued at 353 PM CDT Mon May 15 2023
High pressure persisting over the region combined with an
approaching cold front will result in elevated winds this afternoon
and evening. A few gusts of 20 to 25 knots will continue to be
possible this afternoon, with waves up to 4 feet along the North
Shore from Grand Marais to Grand Portage. A Small Craft Advisory
remains in effect until 7 PM for portions of western Lake Superior.
Wind and waves will subside tonight. Winds become northeasterly
tomorrow and Wednesday, strengthening in the southwest arm of
Lake Superior. Another round of Small Craft Advisories will likely
be needed due to elevated winds and waves.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 52 67 38 62 / 0 10 0 0
INL 52 71 44 74 / 0 0 0 10
BRD 52 82 47 76 / 0 10 0 10
HYR 49 73 40 71 / 0 0 0 0
ASX 49 65 36 64 / 0 0 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 7 PM CDT this evening for LSZ140>143-
146-147-150.
&&
$$
DISCUSSION...Unruh
AVIATION...Melde
MARINE...Unruh
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
801 PM CDT Mon May 15 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Tuesday night)
Issued at 216 PM CDT Mon May 15 2023
A slow moving/stalled frontal boundary is draped across the Edwards
Plateau this afternoon, with a relatively ill defined upper pattern
consisting of a weak (and weakening) high to our east and a more
notable trough to it`s north across eastern Canada that will dig
southwards through the short term. This will in turn help push a sfc
high south through the Plains that will help usher the frontal
boundary southwards late tonight into tomorrow.
Scattered thunderstorms developed this morning and continue at this
hour, generally drifting northward at 10-20 mph. Isolated 30-35 mph
wind gusts and pea size hail have been possible in the strongest
storms, but locally heavy rains remain the primary concern due to
high PWATS near 1.5" and slow storm motions. Coverage of this
activity should gradually diminish this evening, but some of the
more recent HRRR runs suggest some isolated to potentially scattered
storms could continue through much of the night over central and
western areas. Isolated additional rainfall totals of 1-2" are
possible, with the potential for Advisory-type minor flooding
concerns, but most areas will just see some beneficial rains and
lightning.
Where it has rained, temperatures have been kept down significantly.
Only in the upper 60s and low 70s around San Antonio to San Marcos
at 1PM. But it reached the mid 80s under more sun in portions of the
Austin area already.
The cold front will drift slowly south tomorrow and should serve as
the focal point for additional scattered storm development during
the daytime. Likely will see lower storm coverage than today, but
isolated 1-3" rains will again be possible. A marginal Risk of
excessive rain thus remains in the day 2 ERO. The best chances for
any renewed flooding concerns will be across the areas that are
already saturated from the past week. Look for another day with
highs in the upper 70s to mid 80s.
&&
.LONG TERM...
(Wednesday through Monday)
Issued at 216 PM CDT Mon May 15 2023
Upper level ridging dominates the local area for the Wednesday and
most of Thursday periods. Therefore, dry weather conditions are
expected for the local area for that time frame with high
temperatures in the mid to upper 80s across most locations. By
Thursday night into Friday morning, an upper level short wave is
forecast to push across the local area. Shower and thunderstorm
activity is expected to develop along and ahead of the dryline and
moves to the east. GFS brings the activity over the Rio Grande and
southern Edwards Plateau on late Thursday afternoon into the evening
hours but ECMWF stays dry. So, going with a 20 to 30 percent as a
blend solution. By Friday afternoon, upper level flow changes to the
northwest while surface southerly flow stays through the period. By
late Friday into Saturday morning, a frontal boundary is forecast to
push from the north into our local area bringing chances for showers
and thunderstorms mainly to the northern part of South Central Texas
with less activity expected to the southern part. By Saturday
afternoon, chances for showers and storms are forecast to
concentrate but not limited to the Rio Grande Plains and southern
Edwards Plateau. A little change in the weather pattern is expected
with another chance for showers and storms to develop across the Rio
Grande and southern Edwards Plateau on Sunday. High temperatures in
the 80s and lows in the mid to upper 60s and low 70s for the
upcoming weekend.
&&
.AVIATION...
(00Z TAFS)
Issued at 714 PM CDT Mon May 15 2023
An outflow boundary moving southward out of the Hill Country may help
a few showers develop over the next 1-2 hours. With coverage expected
to be limited, we will only mention VCSH at the I-35 sites.
Otherwise, we should see VFR conditions tonight as plenty of mid and
high clouds continue. Low cloud development looks favored at AUS as
the leading edge of a cold front works southward into the region. DRT
may also be favored for low clouds and will mention a brief period of
MVFR between 09-14Z. Additional convection is expected to develop
Tuesday afternoon with peak heating. For now, we will mention VCSH at
AUS and hang on to the PROB30 groups for TSRA at SAT and SSF.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 83 67 84 65 / 50 30 40 10
Austin Bergstrom Intl Airport 83 66 83 64 / 50 30 40 10
New Braunfels Muni Airport 81 67 83 64 / 50 30 50 20
Burnet Muni Airport 82 65 81 63 / 50 50 40 10
Del Rio Intl Airport 83 69 86 67 / 60 40 40 10
Georgetown Muni Airport 83 66 82 62 / 60 30 40 10
Hondo Muni Airport 82 66 82 64 / 60 30 40 20
San Marcos Muni Airport 81 66 83 64 / 50 40 50 20
La Grange - Fayette Regional 81 67 82 65 / 60 20 40 20
San Antonio Intl Airport 81 67 83 64 / 60 40 50 20
Stinson Muni Airport 81 68 83 67 / 60 30 50 20
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term...Platt
Long-Term...05
Aviation...Platt
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1048 PM EDT Mon May 15 2023
.UPDATE...
Issued at 1048 PM EDT MON MAY 15 2023
A minor update to the forecast was necessary this evening. The obs
database was out of whack again, so had to make a few tweaks to
the hourly and forecast low temperatures for tonight to get things
back in line and looking good. Also made some adjustments to cloud
cover and PoPs for this evening and tonight, based on the latest
satellite and radar trends and the most recent run of the HRRR
model. All in the forecast is similar to before, with a few minor
changes here and there. The updated zone forecast text product has
already been issued. The updated forecast grids have been saved,
published, and sent NDFD and the remote web farms.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 439 PM EDT MON MAY 15 2023
Most the excitement in the short term will come tomorrow. Currently
there is a low pressure system over Southwest Missouri and it will
continue to track eastward overnight, making it into western
Kentucky by early Tuesday morning. Attached to this low pressure
system will be a warm front, which will extend eastward from the low
and then southeastward. This will be the epicenter of convective
development this evening and through the overnight, though generally
west and south of JKL. That behind said, models are continuing to
peg some additional convection on the lee side of the mountains,
going into RLX and MRX`s area. There is quite a bit of uncertainty
with these storms, as most models show them developing and moving
just outside of the JKL CWA. However, a few also show some showers
and potential thunderstorms developing right along the border and
impacting into JKL`s area as well. Because of this, did leave in
some low end chances of convection along the border into the
overnight.
By early Tuesday morning, with the low center shifting east into
western Kentucky, the warm front will also shift eastward and into
the JKL CWA. Expect the expansion of showers and thunderstorms
throughout the day along this warm front. Furthermore, the low will
eventually move into eastern KY during the late afternoon and
evening. All together, the set up looks good for strong storm
development in the afternoon and evening, especially right along
the warm front and near the center of the low pressure (the closer
to the intersection of the two the better). SPC has included
everywhere generally south of I-64 in a slight risk for severe, since
the warm front and low pressure system should not lift above this
point. Ample amounts of moisture will be able to advect into the
region ahead of this system, especially just south of the warm
front. PWATs from the GFS are over 1.5 inches every 6 hours, and
soundings look pretty saturated. In other words, these will be
efficient rain makers, and could also lead to a large amount of
lightning. If multiple storms train over the same location, it
could lead to some high water or flash flooding concerns. Because
of this WPC has also placed us in a slight risk of excessive
rainfall, with forecasted storm total amounts of 0.5 to 1.75
inches (highest amounts again through the central part of the CWA
in line with the warm front).
Winds will be backing through the morning, but will become more
SWrly in the llvls by the afternoon as the warm front moves through
or close by. The loss of directional sheer in the low levels for
most points may deter best tornado development. However can`t
rule up an isolated spin-up, mostly likely closer to the stronger
cyclonic flow of the low pressure center (better directional
sheer) and where it meets the warm front (to add some extra
instability/lift). There could also be a short-lived increased
llvl jet during the afternoon/early evening. If this increase in
winds lines up just right with the tract of the best circulation,
this could also enhance tornado potential. There is still just a
lot of uncertainty and ifs in this. The more evident concerns
(outside of heavy rain) look to be wind and hail. CAPE values will
top out over 2000 J/kg in the late afternoon along and south of
the warm front, indicative of some potentially large updraft
strengths and hail development. Conversely, the heavy rain could
advect down some stronger winds aloft, leading to some instances
of wind damage. With all storm modes on the table, this will
definitely be one of the most active severe weather days we`ve
seen so far this spring.
By Tuesday evening the low pressure center will be over far eastern
Kentucky exiting into WV overnight. This will also drag a cold front
through the far southeast portion of the state during the first part
of the overnight. After this moves through, drier air behind should
begin to cut off best precip chances. All rain should have exited
the CWA by early Wednesday morning, though clouds may stick around a
wee bit longer. Because of the lingering cloud cover during the
overnight hours, did not include much in the way of ridge/valley
splits for temps.
Speaking of temps, the cloud cover and increased southerly flow
should keep conditions quite mild tonight, with lows only in the
upper 50s to low 60s. Temperatures tomorrow will be a tale of warm
front vs. north of warm front. Locations in the north may only top
out around 70 degrees. However, the far SE will likely by in the low
80s. Once the system moves out Tuesday night and winds become more
northerly, temperatures should cool compared to tonight. That being
said, cloud cover will help temps to not plummet. Tuesday
night/Wednesday morning lows should settle in the upper 40s to mid
50s.
.LONG TERM...(Wednesday through Monday)
Issued at 322 PM EDT MON MAY 15 2023
The period will begin on the backside of a cold front, where a
secondary front is expected to pass through into Wednesday morning.
Aloft, broad ridging encompasses the northeastern USA, where a
subsequent trough sits across Central Canada. Further west, a dome
of ridging will sit entangled across the Central Rockies. At the
surface, low pressure will be well to the southeast of the area,
where weak high pressure is expected to sink south from Ontario to
the Mid Atlantic. As the upper Northeast trough pulls east through
Wednesday, rising heights across the Tennessee and Ohio Valleys will
aid in suppressing PoPs through Thursday morning. Low end PoPs
remain in the forecast during peak heating Thursday, as a rounding
shortwave progresses through southern stream flow across the
Tennessee Valley. Temperatures will stay near seasonal norms, as
flow will remain out of the north to northeast Wednesday and
Thursday. Highs both days will vary between the low to upper 70s,
with the warmest values closer to the Tennessee border.
A digging closed low and positively tiled trough then set up late
week into the weekend, with considerable model spread. The
deterministic GFS continues to be the outlier in suggesting the most
progressive solution. This is well depicted within cluster analysis,
with 57% of GEFS members suggestive of the trough axis aligned
across the Upper Great Lakes compared to no agreement in the
Canadian or Euro ensembles. That said, over half of Euro and a
quarter of Canadian members agree on a slower progression, with the
5H wave highlighted across the Northern Plains during this time.
Have favored this slower progression as a result, with the highest
PoPs Saturday afternoon/evening ahead of an approaching cold front.
with cloud cover, rain cooled air, and then followed by a post
frontal airmass, temperatures will fall back down closer to seasonal
norms, ranging in the 70s this weekend into early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 755 PM EDT MON MAY 15 2023
VFR conditions will prevail at the TAF sites to begin the period.
BKN to OVC mid-level clouds will be in place across most of the
area, with bases at 12K. The cloud bases will gradually lower
overnight, and should fall to between 2 and 3K by 12 to 14Z on
Tuesday, making for IFR CIGs at the TAF sites at times. Rain
showers will begin moving into the area again between 10 and 12Z,
and will increase in coverage through out the day on Tuesday, as
a surface front, with areas of low pressure moving eastward along
it, begins to move into southern Kentucky. The rain will persist
through the day on Tuesday, as low pressure moves across the
state. The rain should begin to taper off late in the day Tuesday
and Tuesday night, and should be out of the area by early
Wednesday morning. Thunderstorms will also occur on Tuesday,
especially during the afternoon and early evening hours, as a warm
front and area of low pressure both move through the area. A few
of the storms could be strong to severe, with damaging winds and
locally heavy rain the primary threats. Any thunderstorms could
product MVFR or worse conditions at times. Winds should be light
and variable tonight, but will shift to the south and southwest on
Tuesday as the warm front moves in from the south. Winds north of
the boundary will remain out of the north or northwest. Winds
will then shift to the west and northwest across all of eastern
Kentucky by 0Z Wednesday, as low pressure moves through. Sustained
winds of around 10Kts are expected, along with gusts of 15 to
20Kts outside of any showers or storms.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...AR
SHORT TERM...JMW
LONG TERM...BB
AVIATION...AR
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
848 PM CDT Mon May 15 2023
.UPDATE...
Issued at 848 PM CDT Mon May 15 2023
No significant changes to going forecast this evening, other than
to lower pops across far southern cwa late tonight/early Tuesday
to just slight chance. Otherwise, forecast is in good shape.
Evening surface analysis places west-east high pressure ridge
from Nebraska eastward across the IL/WI border into southern lower
Michigan. Northeasterly low level winds have brought much drier
air into the forecast area since yesterday`s cold frontal passage,
with dew points ranging from the teens/low 20s along the North
Shore north of Chicago, to the mid-upper 40s across the
western/southwest parts of the cwa. More humid conditions have
pushed well downstate. A low-amplitude mid-level short wave is
progged to track across central IL later tonight into early
Tuesday, though the WFO LOT cwa looks to be on the far northern
fringe of any precip associated with this disturbance. High-res
guidance trends keep measurable QPF south of the forecast area
across central IL/IN, and in collaboration with our southern
neighbors have decreased pops to only slight chance along our
southern border early Tuesday morning.
Otherwise, going forecast appears to have things well-handled
into Tuesday, with mainly mid and high level cloud cover and a
brief warm up tomorrow ahead of an approaching well-advertised
"pneumonia front" later in the day.
Ratzer
&&
.SHORT TERM...
Issued at 305 PM CDT Mon May 15 2023
Through Tuesday night...
Key Forecast Message and Concern:
* Timing of lake enhanced "pneumonia" front passage Tuesday PM and
associated sharp temperature drop and quick uptick in winds
Weak surface high pressure ridging will bring light winds
overnight tonight, and if high clouds aren`t too thick, will
enable lows in the mid-upper 40s in favored cool spots near and
north of I-80. A short-wave passing to our south will fight a dry
antecedent air mass and decreasing forcing with northward extent
to possibly bring spotty light rain/showers to areas near and
south of US-24 overnight into Tuesday morning.
Partly cloudy if not mostly sunny skies, especially north, deep
mixing, breezy northwest winds, and dew points mixing out will
support highs reaching the mid 70s to around 80F/low 80s Tuesday
afternoon, warmest I-80 and north. Sharp land-lake thermal gradient
will probably enable a weak lake breeze to slip inland and bring
modest cooling near the immediate IL and IN shore prior to the
much sharper temperature drop pegged for the late afternoon-early
evening.
Regarding the "pneumonia" front, no big changes in thinking,
though the exact timing is medium confidence. The HRW CAMs and
NAMnest feature an earlier frontal approach and passage timing
than the HRRR and RAP by a couple hours. Conceptually these fronts
verify in line with faster timing, so hedged that way (maybe
officially a hair slower than previous fcst), and we`ll be able to
refine the exact timing with radar and observational trends on
Tuesday. Northwest winds will quickly shift to north-northeast and
gust up to 25-30 mph, and possibly briefly stronger up to 35 mph
near the immediate shore. Breezy north-northeast winds should
continue into the evening behind the inland surging front, though
will decrease in magnitude with time.
Temperatures will drop from the 70s to 50s within 1-2 hours of
frontal passage with several miles of the lake, quickest closer
to the shore, with a slower but steady fall farther inland. Expect
lows in the 40s to around 50 Tuesday night, coolest and possibly
right down around 40F far north. Finally, the short-wave and front
may team up for a few light showers or sprinkles behind the front
Tuesday evening, favored over inland northern Illinois, where the
front aloft will be undercut later than near the lake by the
surging lake enhanced front. Most locations will remain dry, and
kept PoPs in slight chance range. No thunderstorms are expected.
Castro
&&
.LONG TERM...
Issued at 223 PM CDT Mon May 15 2023
Wednesday through Monday...
The latter half of the week comes in quietly with rising heights
aloft and a surface high positioned over the Great Lakes. With
northeast flow off the lake around the base of the high, areas near
the lake on Wednesday likely will not climb out of the 50s.
Locations elsewhere should see mid 60s to lower 70s. A transition
then begins toward the end of the week as the upper ridge moves to
our east and low level flow turns southerly and southwesterly ahead
of an approaching frontal zone.
The main question for this period remains the timing of the
frontal passage sometime on Friday, with an associated band of
rainfall and possible thunderstorms. Given the uncertainty at this
time range, the northwest half of our CWA will start with slight
chance to chance POPs for the predawn hours Friday, with the
entire area moving into the chance range for the daytime hours. It
is also possible, though less likely at this point, that the
front slows down considerably and does not move through until
sometime on Saturday. For this reason, both days will carry the
chance of showers, but trends appear to be pointing to Friday -
perhaps late Friday - as the most likely period to see rainfall,
with most of the weekend looking cooler and hopefully dry. In
other words, expect to see the period of higher POPs tightened up
as the week goes along.
Even with areas near the lake experiencing lake breeze effects and
staying in the 60s, Thursday and Friday are looking to be the
warmest days of the extended period, with highs in the mid and upper
70s away from the lake. That could change, especially for areas
northwest, if the front pushes through sooner and brings rainfall
and cooler northwest flow earlier on Friday than currently
expected.
Lenning
&&
.AVIATION...
For the 00Z TAFs...
The primary forecast concern through the TAF period are winds.
With a surface high overhead, winds will become light and variable
overnight before settling on a northwesterly direction toward
sunrise Tuesday. Wind magnitudes should range between 10-15 kt
with occasional gusts to 15-20kt through the afternoon. A cold
front is expected to sweep off Lake Michigan during the evening
with an abrupt northeasterly wind shift and gusts at or above
25kt. Based on an ensemble of high resolution model guidance and
collaboration with CWSU ZAU, opted to advertise an arrival time of
00Z at ORD and 01Z at MDW. Adjustments are all but likely as the
front materializes and can be tracked tomorrow afternoon. Various
VFR cloud decks will stream overhead through the TAF period.
Borchardt
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742...4 PM Tuesday to 7
AM Wednesday.
Small Craft Advisory...LMZ743-LMZ744-LMZ745...7 PM Tuesday to 7
AM Wednesday.
&&
$$
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Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1049 PM CDT Mon May 15 2023
.UPDATE...
Issued at 1045 PM CDT Mon May 15 2023
Compact, mostly elevated MCS continues to track east across the
far southern portion of our forecast area. This is the bulk of the
rain that`s going to fall tonight, especially of the heavy
variety. Will maintain the Flood Watch for now, but the threat has
decreased considerably for the northern portions of it. Further
north, some lighter rain is likely to develop along and north of
the 850MB front which is still a good ways north of the surface
boundary, oriented a little north of St Louis. While there`s rain
chances just about everywhere for the remainder of the night, the
heaviest rain will be in the southern 3 counties where the cluster
of storms moves through.
Kimble
&&
.SHORT TERM... (Through Late Tuesday Night)
Issued at 241 PM CDT Mon May 15 2023
A west to east oriented cold front has been sinking south through
the CWA today. Behind the front, temperatures have been cool with
many locations only reaching the mid-60s by 2 pm. Ahead of the
front, namely in southeast Missouri, temperatures and dewpoints are
much higher. This has resulted in increased instability in this
area, with mean SBCAPE values of up to 2500 J/kg this afternoon. A
series of vorticity maxima entering southwest Missouri is providing
upper level ascent for convective initiation along the 925 front.
This band of scattered thunderstorms will move northeast into the
southern CWA through the afternoon.
Thunderstorms are expected to line the upper front and lift
northward through the area this afternoon. Another round will
enter southeast Missouri this evening with the arrival of
additional upper level forcing in this area. Most thunderstorms
associated with both rounds will remain sub-severe. For the few
that are able to become severe, damaging winds will be the primary
threat.
The larger overall threat with the showers and thunderstorms moving
through tonight will be the potential for heavy rain leading to
flash flooding. Although the first two rounds of showers and
thunderstorms will be capable of producing locally heavy rainfall,
the majority of the heavy rain will be associated with a third round
of more widespread showers moving through after midnight.
Conditions will be conducive for heavy rainfall this evening.
Precipitable water values will be upwards of 1.75 inches exceeding
the climatological 97.5th percentile. RAP soundings in southeast
Missouri and southern Illinois show warm cloud depths greater than
10 kft, supporting the potential for efficient rainfall. Moisture
convergence along the 850 front extending through southeast Missouri
and southwest Illinois will be strong as well. With these
ingredients in place, there is high confidence in heavy rainfall
falling in a corridor extending from Crawford-Reynolds counties in
Missouri to Fayette-Marion counties in Illinois. HREF members have
been closing in on this axis in recent model runs. Its LPMM shows
rainfall amounts of 2-4 inches in these locations, which seems
reasonable given the environmental conditions. Although there is
high confidence in a corridor of heavy rainfall in this general
area, wavering in the low-level boundary could shift this axis north
or south.
Showers will be exiting to the east by 18z tomorrow as upper level
forcing leaves. Stratus will persist through the morning, clearing
from north to south through the afternoon and evening. Because the
northern CWA will have the influence of insolation, highs tomorrow
will be able to reach the low 70s in these areas, whereas a large
portion of the rest of the CWA will be confined to the upper 60s.
Jaja
.LONG TERM... (Wednesday through Next Monday)
Issued at 241 PM CDT Mon May 15 2023
A backdoor cold front will enter the CWA Tuesday night into
Wednesday morning, but the passage is expected to be dry. The only
impact of the front will be a weak temperature gradient over the CWA
on Wednesday, with warmer temperatures to the west (ahead of) the
front and cooler temperatures in the east (behind). These will
likely all be around average, with average temperatures expected
through Friday.
The influence of surface high pressure centered over the Great Lakes
will keep the Mid-Mississippi Valley dry and quiet for Wednesday and
Thursday. On Thursday night, low-level moisture and warm air
advection will increase ahead of the next cold front. Guidance
varies concerning the timing of the frontal passage, with models
showing time of arrival anytime from Friday morning to Friday night.
The timing of the front will impact the chance for thunderstorms in
this timeframe. A faster passage will eat into the amount of
instability that can accumulate ahead of the front. A Friday night
passage could preclude the potential for stronger thunderstorms as
it avoids peak heating. We`ll continue to monitor the potential for
thunderstorms over the coming issuances.
There`s high confidence in the front knocking temperatures below
average for the weekend, though not unpleasantly so. The NBM 25th to
75th interquartile range stays narrow through early next week as
temperatures moderate.
Jaja
&&
.AVIATION... (For the 06z TAFs through 06z Tuesday Night)
Issued at 1045 PM CDT Mon May 15 2023
Widespread MVFR to occasionally IFR conditions are expected
overnight in a post frontal air mass. Some showers or even drizzle
is possible as well. Heavier thunderstorms will stay south of the
terminals, but some rumbles of thunder may extend northward into
the St Louis metro in the coming few hours, so VCTS has been
maintained in the TAF there. Ceilings should lift through the day
tomorrow, with clearing arriving from north to south in the
afternoon or evening.
Kimble
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch until 10 AM CDT Tuesday for Franklin MO-Jefferson MO-
Saint Louis City MO-Saint Louis MO.
Flood Watch until 7 AM CDT Tuesday for Crawford MO-Iron MO-
Madison MO-Reynolds MO-Saint Francois MO-Sainte Genevieve
MO-Washington MO.
IL...Flood Watch until 10 AM CDT Tuesday for Bond IL-Clinton IL-
Fayette IL-Madison IL-Marion IL-Monroe IL-Randolph IL-Saint
Clair IL-Washington IL.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
1151 PM EDT Mon May 15 2023
.SHORT TERM...(Tonight)
Issued at 327 PM EDT MON MAY 15 2023
Water vapor imagery and RAP analysis show a shortwave trough digging
gradually south fron northern Manitoba and northern Ontario. This
shortwave and the associated sfc trough/cold front ahead of it has
pushed a 850 mb thermal ridge into the area while also tightening
the pressure gradient. The resulting west winds have gusted near 20
mph across much of the area this afternoon with higher gusts of 25
mph or more over the Keweenaw. Diurnal mixing and heating have
brought drier and warmer air to the surface resulting in widespread
temps in the 70s, dew points over the interior in the lower 20s and
widespread min RHs in the teens. The ongoing SPS for elevated fire
weather still looks spot on and it will be continued into the early
evening (9 pm EDT). Burn restrictions remain in effect across Upper
MI.
Tonight, As the shortwave and sfc cold front to the north continue
to drop southward through Ontario and towards the Great Lakes.
Westerly gradient winds will keep low levels well mixed and should
keep temps warmer despite mostly clear skies through a good portion
of the night. There could be an increase in clouds toward sunrise
and a isolated shower isn`t out of the question as the cold front
arrives, although given the very dry air mass in place have stayed
with a dry fcst. With the winds staying up tonight, RH recovery will
continue be poor across much of the area, probably failing to get to
60 percent at most locations. Look for min temps dropping close to
50F with a few readings dipping into the upper 40s.
.LONG TERM...(Tuesday through Monday)
Issued at 343 PM EDT MON MAY 15 2023
Key Messages:
-Cold front Tuesday mostly dry brings more normal temps
-Frost potential overnight
-Quiet Wednesday, marginal fire weather concerns
-Precip arrives Thursday
-Complex weekend forecast
Tuesday, the surface high that brought clear skies today weakens and
sags south. A shortwave trough is expected to pass north to south
through the region Tuesday morning, though it will quickly be
replaced by a high pressure in its wake for Wednesday. CAM guidance
is showing precip of some sort progressing through the region,
though the coarser resolutions of models show much lower chances for
precip. Ended up taking PoPs out of the land grids and putting some
slight chances over the water as the dry conditions over the land
are likely too much to overcome for any precip that is formed. The
cold fropa will bring Tuesdays high temperatures down significantly
from today`s highs, bringing highs back in line with the
climatological averages, perhaps even cooler than average in some
maritime locations. With temps being cooler, RH`s look to be more
moist than the critical fire thresholds, a welcome break from the
dry weather preceding it. Additionally, with the cold fropa and
expected clear skies for radiational cooling, lows Tuesday night
could reach sub-freezing in some interior locations, leading to
frost potential.
A dry Wednesday is expected as ridging will dominate the forecast
before the next 500mb trough digs southeast through Ontario and the
Upper Great Lakes vicinity Thursday. Regarding fire weather, the
forecast values are similar to Sunday where RH`s fall to around 20
percent but the winds are fairly light. The intriguing fire weather
concern may be Thursday morning and midday as the pressure gradient
tightens significantly ahead of the precipitation, leading to a
window of wind gusts over 30 mph with RH`s dipping below 30 percent.
There is still some considerable uncertainty regarding the trough
passage timing as the 12Z GFS is the fastest solution followed by
the 12Z ECMWF and then the Canadian-NH. The GEFS has at least slowed
down the progression of the precipitation from run to run, with May
13th and early 14th runs starting precip around 00Z Thursday and the
later May 14th and early May 15th runs have it as late as 18Z
Thursday. As far as total rain goes, ensemble means are around a
half inch to 3/4 of an inch of QPF with a few members going as high
as an inch, so with rivers having receded after recent snowmelt,
flooding concerns should be minimal, and thunder should be fairly
isolated.
A few ensemble members have wraparound moisture and precip lingering
in the UP into Saturday despite an upper 1020s mb high approaching
from the Plains. While the GEFS shows the low departing to the east,
the Euro ensemble tells a different tale, with many ensemble
members keeping the low around through the remainder of the
weekend, blocked by a high over the Atlantic. With widely
different solutions ensemble to ensemble, member to member, and
run to run, uncertainty is high at this time period. The good
news: NBM Snow Ptype values are below 2 percent through the
period!
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1150 PM EDT MON MAY 15 2023
Generally VFR conditions except for some MVFR/IFR cigs at SAW and
CMX later this morning with frontal passage, will highlight with a
TEMPO. Meanwhile, west/northwesterly winds will strengthen at CMX
and SAW closer to daybreak along with a LLWS threat at SAW.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 343 PM EDT MON MAY 15 2023
An approaching cold front from the north is bringing southwest winds
up to 30 knots, especially north of the Keweenaw. Gale conditions
may be briefly observed southwest of Michipicoten Island tonight.
Winds remain around 25 knots as winds shift to be northerly behind
the front Tuesday morning, falling below 20 knots Tuesday afternoon.
With ridging over the Upper Great Lakes Wednesday, winds remain
below 20 knots until a low pressure approaches Wednesday evening,
bringing southeasterly gusts to 20 to 25 knots over the north
central lake. Thursday, southerly gusts around 25 knots are expected
before the low passes early Friday, bringing westerly gusts around
20 knots. There is high uncertainty regarding the track and
intensity of the pressure systems for the weekend, which will
determine how high wind gusts are for the weekend.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...GS
AVIATION...TDUD
MARINE...GS
Area Forecast Discussion
National Weather Service Raleigh NC
933 PM EDT Mon May 15 2023
.SYNOPSIS...
A cold front will approach the area on Tuesday, bringing showers and
thunderstorms to the area later in the day. Cooler and drier weather
will return for the middle of the week as high pressure returns to
the area.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 933 PM Monday...
Downstream of an amplified upper ridge over the deep south, water
vapor imagery this evening depicted continued nwly flow over central
NC. Multi-layered clouds associated with a sheared lobe of
vorticity just to the north will continue to thicken into the
overnight hours. At the sfc, high pressure just off the Carolina
coast will turn sfc flow more sely overnight. This, coupled with the
extensive cloud cover should keep lows tonight a bit warmer than
last night in the upper 50s to lower 60s.
Weak isentropic upglide has produced some isolated pockets of light
rain the past few hours across our northern tier of counties.
However, given a relatively dry sub-cloud layer, most of the
generated precipitation has fallen as virga in our area. While sfc
dewpoints are expected to increase overnight, forcing will continue
to be weak overnight. Thus, outside of some isolated pockets of
light rain or sprinkles across the far north the next several hours,
the rest of the overnight forecast should remain dry.
&&
.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 142 PM Monday...
The flow aloft will gradually turn more zonal in nature during the
morning hours and a weak shortwave trough will move through TN into
NC by mid afternoon. A surface wave should develop in the process
with a line of showers and thunderstorms forming along the attendant
cold front. Decent thermodynamic profiles will reside ahead of the
front with MLCAPES ranging from 1000 J/KG in the east and upwards of
1500 J/KG in the western Piedmont. While there is some curvature in
the winds with height, shear vectors are largely unidirectional and
the primary threat with storms tomorrow afternoon/evening will be
damaging straight-line winds and hail. There are some model timing
differences with respect to when storms will form and move through
the area, with some of the latest 12Z guidance holding back the main
line of convection until closer to 21Z in the western Piedmont and
not until closer to 00Z-03Z in the east. The HRRR remains the
fastest and brings things through several hours earlier but it is
the outlier. Given the threat of severe weather, the forecast area
is covered by SPC MRGL and SLGT risks tomorrow with the exception of
southern Sampson County where BL stabilization may preclude a severe
threat by the time storms arrive by late evening. While flooding
won`t be the primary threat tomorrow given the relatively fast-
moving nature of the storms, areas with training cells could see
localized flooding.
Showers will linger into the evening and early overnight hours, then
gradually end from west to east closer to daybreak Wednesday.
Temperatures within the pre-frontal warm sector should easily reach
the low to mid 80s, with upper 80s possible in the southern Coastal
Plain. Cooler air drier air will not arrive coincident with the
passage of storms Tuesday evening and as such, temperatures will be
quite mild Tuesday night with readings ranging from the mid 60s in
the Triad to the lower 70s in the Southeast.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 225 PM Monday...
While the deterministic models are quicker in moving Tuesday`s cold
front south of the region on Wednesday, the ensembles are a bit
slower in moving the precipitation to the south. While the SREF is
always quite generous in its precipitation coverage, the GEFS
matches it fairly well, especially showing a tight gradient for
precipitation across southern counties Wednesday afternoon. So the
updated forecast is drier than the previous forecast, but not as dry
as deterministic models would go with. After a brief respite
Thursday morning, the front could still remain close enough to the
region to spark some additional showers Thursday afternoon across
southernmost counties.
While there is some broad agreement between the GFE/GEFS/ECMWF in
developing a low off the coast of the Carolinas Thursday night,
right now it appears that nearly all of this precipitation should
remain to the southeast of central NC, although a slight shift in
the models could bring a chance of showers back into the forecast.
There is quite a bit of uncertainty for the timing of any
precipitation over the weekend. While both the GFS and ECMWF show an
upper level low moving across the Great Lakes into the Northeast,
with an associated surface low and cold front extending to the
south, the GFS is nearly 24 hours faster with this system than the
ECMWF. Will stick close to the NBM through this part of the
forecast, which shows chance pops through much of the weekend.
Temperatures should be within a few degrees of normal. Thursday and
Thursday night look likely to be the coolest 24 hour period, while
Sunday or Monday will be the warmest part of the forecast.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
As of 702 PM Monday...
There is high confidence that VFR conditions will start the TAF
period. Radar continues to show some very light sprinkles or rain
drifting southeast over the northern terminals (GSO/INT/RDU/RWI).
Most of this activity will continue to evaporate as it falls into a
dry sub-cloud layer, so no restrictions are expected for the
overnight period. A northward moving warm front and return southerly
flow and moisture overnight will warrant a chance of some brief MVFR
CIGs at the Triad terminals (GSO/INT) Tue morning. These sub-VFR
conditions should lift by late-morning at the latest as southwest
winds ensue at all sites by the afternoon, with gusts upwards of 15-
22 kts. No sub-VFR conditions are forecast at RDU/FAY/RWI. An
approaching pre-frontal trough and cold front will continue to favor
an increased threat of showers/storms in the late afternoon and
evening/night into Wed. However, model guidance continues to vary
quite a bit on timing and coverage/placement. The highest confidence
for any storms exists at GSO/INT toward the end of the TAF period.
Outlook: Sub-VFR conditions are likely at times Tuesday afternoon
and night within a line of showers and storms. Dry weather returns
Wednesday but cool northeasterly surface flow could result in
periodic early-morning MVFR ceilings area-wide (especially at the
Triad sites). VFR conditions should close out the week, but a return
of sub-VFR weather is possible this weekend with another cold
frontal passage.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Leins
NEAR TERM...Luchetti
SHORT TERM...Leins
LONG TERM...Green
AVIATION...Kren/Leins
Area Forecast Discussion
National Weather Service Las Vegas NV
1205 PM PDT Mon May 15 2023
.SYNOPSIS...A ridge of high pressure across the west will
continue to bring above normal temperatures to the area this week.
Beneath the ridge, above average moisture will remain in place
across the desert southwest, providing opportunities for isolated
thunderstorms each afternoon through next weekend with the main
concern being strong outflow winds and lightning.
&&
.DISCUSSION...Today and through this week.
A pattern that could be, at a glance mistaken for a monsoonal
pattern, will be in place through the course of the week that will
introduce the prospect of isolated thunderstorms each afternoon
through likely next weekend.
What`s left of a rex block setup over the western CONUS will
deteriorate and give way to high amplitude ridging over the west
through much of the week. Also, weak low pressure off the coast of
Baja will strengthen throughout the week and set the stage for
above average PWAT across the desert southwest. The moisture from
Baja streams up and into the Colorado River Valley this afternoon
through tomorrow, raising surface Tds from the upper 30s and lower
40s this afternoon to mid to upper 40s tomorrow afternoon. Thus,
surface based instability increases for much of the region, but
mostly for northwest Arizona Tuesday. It is there that convection
over higher terrain could become robust enough to produce some
strong storms with some heavy rainfall, but this would be mostly
just east of the Mohave County area. The more likely impact for
Mohave looks like outflows from the resultant activity farther
east and/or more minor thunderstorms producing their own outflows
across Mohave County.
While this will be the case this afternoon through much of the
week, the best conditions look to come together Tuesday as some
weak upper level diffluence at 250 mb and slightly higher surface
Tds result in marginal but deep instability and lifting from
about 650mb to the EL. According to HRRR soundings at KIGM, this
enables about 500 j/kg of SBCAPE which is on the higher end of the
HREF PDF, but all inputs are about double the surface based
instability tomorrow afternoon compared to today. NBM also shows
this trend in both PoTThunder and CAPE. After tomorrow, these
conditions ebb and flow to a lesser degree compared to Tuesday,
with Tds retreating somewhat at least through Friday.
Thus, it looks like an isolated chance for thunderstorms will
exist for mostly Mohave County today, but the thunderstorm
probabilities will increase for much of the CWA tomorrow
afternoon (albeit low probabilities), and retreat again for the
latter half of the week, staying more confined to northwest
Arizona. Of the suite of possible thunderstorm impacts, the two
most concerning will likely be gusty outflow winds and lightning
given the instability and inverted V setup, but secondarily brief
heavy rainfall and hail could be on the table with the more robust
updrafts should the right conditions come together. If they did,
they`d likely be rooted to high terrain.
&&
.AVIATION...For Harry Reid...Light and variable winds early this
morning will become light east-southeast after 18Z with speeds
increasing slightly during the afternoon and occasional gusts around
15 knots. Light south-southwest components will develop 1-2 hours
after sunset and continue tonight. Increasing clouds above 15 kft
this afternoon and tonight.
For the rest of southern Nevada, northwest Arizona and southeast
California...Light and variable winds this morning will increase
from the south-southeast 10-20 knots across much of the region this
afternoon followed by light winds tonight. Scattered-broken clouds
with bases generally above 15 kft MSL will increase in coverage this
afternoon and tonight.
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...TB3
AVIATION...Adair
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