Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/11/23
Area Forecast Discussion
National Weather Service Amarillo TX
709 PM CDT Wed May 10 2023
...New AVIATION...
.MESOSCALE UPDATE FOR WIND, HAIL, AND A LOW TORNADO THREAT FOR
THIS AFTERNOON THROUGH TONIGHT...
Issued at 241 PM CDT Wed May 10 2023
* Synoptic Overview: The latest 10/18z RAP H500 analysis shows a
negatively tilted trough located over the Desert Southwest and
is continuing to move east/northeast early this afternoon. Out
ahead of this feature, southerly winds continue to advect
theta-e at H700 across mainly an axis along west TX and east NM.
This can be seen in the mid level water vapor satellite band and
with some cumulus clouds developing across northeastern NM.
Moisture return would be greater across the area if low pressure
was not located to our southeast along with ongoing convection
in east and southeast TX. A subtle weak shortwave out ahead of
the main low pressure system is moving across north central NM
early this afternoon. Current expectation is that this weak
disturbance will aid in convective initiation across far
northeastern NM, as already seen by a thunderstorm developing
across the higher terrain in NM. The main event so to speak, is
expected to be during the late evening into the overnight hours
as the main upper level wave approaches the Panhandles and
provides stronger PVA. This may generate a secondary round of
thunderstorms, some of which could be severe, during the
overnight hours and could continue into early Thursday morning.
* Mesoscale: Latest 18z surface analysis shows dew points are
continuing to slowly decrease across the Southern High Plains as
daytime mixing is bringing down drier air from aloft to the
surface. A surface dry line continues to sharpen across eastern
NM and is expected to be the surface lifting mechanism to get
convection started this afternoon. This is already apparent as
of 1845z, with a shower/storm beginning to develop south of
Raton, NM. The 10/18z RAP mesoanalysis shows that there may be
a small area along the dry line that is uncapped at this time,
with MLCAPE around 1000 J/kg. This is located in the vicinity of
where the initial storm is beginning to develop. CIN will
continue to decrease through the daytime hours, but surface
moisture will also decrease which will lead to lower CAPE
values. Given the weak upper level flow aloft, any storms that
form during the afternoon into the early evening hours are not
expected to be fast moving. With that being said, effective
shear will be quite weak and may inhibit some of the severe
weather threat. As thunderstorms move into the western
Panhandles later this afternoon, the more aggressive models
suggest that 1000-1500 J/kg of MLCAPE may remain over the area
along with slowly increasing effective shear as southerly H850
winds increase to near 30 kts. The better chance of storms being
surface based looks to be in the northwest based on the more
aggressive soundings from models that have a higher moisture
bias. This initial round of storms, which looks to become linear
based on CAMs and the relatively marginal shear, may continue
across the west and potentially the central Panhandles til
midnight. A secondary line of linear storms may develop over
portions of west TX as the main upper level wave comes across
during the overnight hours. The first round of convection may
hinder how far north this secondary line is able to develop as
portions of the Panhandles could be worked over and may limit
further thunderstorm development. In any case, low level
moisture will be on the increase and surface dew points may
approach the mid to upper 50s, with low 60s further east. As
moisture increases throughout the column, long skinny CAPE
profiles look possible with CAPE values around 1000 J/kg. Cannot
rule out some of these storms potentially becoming surface
based, which would lead to a low end tornado threat given the
long low level forecast hodographs. A QLCS may develop as 0-3km
shear values are near 30 kts along and behind where the line is
forecast to develop. Several CAMs are depicting that this
scenario is possible and a brief tornado spin-up looks plausible
during the overnight hours. Will need to continue to monitor
the potential for this threat, especially since it is during the
overnight period.
* Threats: The main threats with any severe thunderstorms this
afternoon through this evening will be large hail (up to ping pong
ball) and damaging wind gusts (up to 65 mph). Given the lack of
moisture this afternoon, especially across the west, CAPE values
combined with weak shear are not overly supportive of a very large
hail threat. Even though moisture and shear will increase through
the overnight hours, as mentioned above, long skinny CAPE profiles
are possible and are not the most supportive of very large hail.
Storms are expected to become mainly elevated after sunset tonight
as we lose daytime heating and capping in the low levels becomes
prevalent. This will decrease the damaging wind threat, but if a
QLCS is able to form, some gusty winds could mix down to the
surface. The low end tornado threat is highly conditional and will
depend upon the low to mid levels cooling as the upper level wave
approaches the Panhandles. Cannot rule out a quick spin-up or two
during the overnight hours. Will need to carefully monitor the
trends through the overnight hours.
* Timing & Location: Two rounds of thunderstorms are expected over
the next 12 to 18 hours. The first round is forecast to move in
across the western Panhandles around 5 to 7 PM Central. A line
of storms may move across portions of the western Panhandles
through early evening. A secondary round of thunderstorms may
develop across portions of west TX during the overnight hours
(around 11 PM through 1 AM) and is expected to trek east. The
highest chance at seeing these storms overnight would be across
the central and/or southern TX Panhandle. These storms are
expected to be east of the area near sunrise on Thursday.
Muscha
&&
.SHORT TERM ...
(This evening through Thursday night)
Issued at 241 PM CDT Wed May 10 2023
For the severe weather threat this afternoon through early
Thursday morning, refer to the Mesoscale Discussion above.
As this event gets going later this afternoon/evening, the best
chance for initial storms would be in the NW TX and OK Panhandle,
but confidence is low on storms being that far east from 21-00z.
For this reason, have slightly lowered and trimmed back NBM POPs
for that time frame. Otherwise NBM POPs looked reasonable for
tonight and were left in as they were. Some ongoing storms may
linger in the east/northeast combined Panhandles Thursday morning
into the afternoon but should generally exit the CWA by 18z so
have lowered and confined POPs to the northeast OK Panhandle after
18z.
Low clouds associated with tonight`s system as well as breezy
southeast winds will limit radiational cooling overnight and keep
low temperatures Thursday morning in the 50s across the area. As
the upper level disturbance moves east, the pressure gradient will
tighten from a sfc low and increase winds out of the southwest.
Drier air will set in from west to east as these downsloping winds
and clear skies help most of the area warm into the 80s. A cold
front will move in behind the sfc trough Thursday night as it
moves east, bringing cooler temps and northwest winds to the
Panhandles. As a result, lows will dip to the mid 40s in the NW to
low 50s in the SE.
Harrel
&&
.LONG TERM ...
(Friday through next Tuesday)
Issued at 241 PM CDT Wed May 10 2023
Friday will be a transition day as the first disturbance moves
away from the area and the next disturbance approaches. This
should result in a mostly non-eventful day as a cool front
moves through during the daytime period. Chances for
thunderstorms will be on the increase Friday night into Saturday
as moisture attempts to surge back into the area ahead of a sub-
tropical disturbance. The question with this concerns how far
south the aforementioned front advances before it stalls. If it
stalls further south (say in Lubbock`s area), storms will be less
likely in the area until Saturday morning. If it stalls further
north, then storms would be possible (a few severe given CAPE and
marginal shear also possible) in the southern zones by Friday
evening. Right now only about 20 to 30 percent of the total NBM
membership is showing more than 400 J/kg before midnight, and only
about 10 to 15% show 1000 J/kg or more which suggests the front
may slip too far south.
Beyond Friday night through early next week, the 500mb
disturbance advances from the Big Bend region of Texas almost due
north in a weak flow regime (very reminiscent of mid to late
Summer). There are differences in exactly where the low will
track, but most ensemble members bring it right across the
combined Panhandles, if not slightly west which puts the area in
really good shape for persistent moisture advection over a long
period and synoptic lift (along with theta-E advection /
isentropic ascent). The deterministic GFS brings the wave
slightly east which is not as favorable as it brings down drier
air from the north, especially for our western zones. The good
news is that the GFS is an outlier, even to its own ensemble
suite. The GEFS mean 24 hour QPF ending Sunday morning paints a
50% to 80% chance for 1/2" across all but part the northwest
zones (which are more around 20% to 40%). PWAT values may approach
daily max values with ensemble means suggesting periods over 200%
of normal, and with the weak flow aloft storms may be slow moving
and thus a flood/flash flood risk will exist. The models continue
to pump moisture into the area early next week on the backside of
the system, so solid chances for rain continue at least through
Monday. When it`s all said and done, a good chunk of the area may
see well over 1 inch of rainfall this weekend into next week (as
long the the GFS doesn`t verify).
Ward
&&
.AVIATION...
(00Z TAFS)
Issued at 648 PM CDT Wed May 10 2023
For the 00Z TAFs, an upper level storm system will impact the
forecast area tonight and will bring a threat for showers and
thunderstorms to the terminal sites. KDHT will likely be affected
by showers and storms this evening, followed by KGUY and KAMA late
tonight. All precipitation should be east of the TAF sites by
around 10Z Thursday. A brief period of MVFR cigs is expected to
develop at KGUY and KAMA late tonight into Thursday. Southwest
winds will then increase and become gusty at the terminal sites by
around mid to late Thursday morning and continue through Thursday
afternoon.
02
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 57 85 52 87 / 50 10 0 0
Beaver OK 59 84 52 86 / 30 50 10 0
Boise City OK 52 79 46 80 / 70 20 0 0
Borger TX 60 88 54 90 / 50 10 0 0
Boys Ranch TX 57 86 50 89 / 50 10 0 0
Canyon TX 55 84 51 89 / 60 10 0 0
Clarendon TX 59 85 54 89 / 50 20 0 10
Dalhart TX 51 81 45 83 / 60 10 0 0
Guymon OK 57 83 50 84 / 60 20 0 0
Hereford TX 53 85 49 89 / 50 0 0 0
Lipscomb TX 58 85 52 89 / 20 40 0 0
Pampa TX 58 85 53 87 / 40 10 0 0
Shamrock TX 59 86 54 90 / 30 30 0 10
Wellington TX 60 87 54 90 / 40 30 0 10
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&
$$
SHORT TERM...38
LONG TERM....07
AVIATION...02
Area Forecast Discussion
National Weather Service La Crosse WI
611 PM CDT Wed May 10 2023
.DISCUSSION...(This evening through Wednesday)
Issued at 227 PM CDT Wed May 10 2023
Key Messages:
- Shower, storm chances west of the Mississippi overnight into
early Thu morning. Non severe.
- Next highest chances (up to 70%) for rain and possible
thunderstorms come Friday/Saturday.
Tonight-Thursday... Rain Chances West
Showers and a few storms ongoing across parts of NE/SD early this
afternoon, associated with an upper level shortwave trough. CAMS
models suggest this convection will get a bit more punchy this
evening as the shortwave pushes into southern MN and the low level
jet noses in. RAP shows a nose of 500-1000 J/kg of MUCAPE, aiding
storm development. Storms will likely become elevated as the evening
wears on, with RAP bufkit soundings not showing much wind shear to
help the storms along. The shortwave is slated to shift northeast
into northwest WI overnight while at the sfc a trough/warm front
shifts across IA, laying up roughly west-east across southern MN.
Showers/storms could become more associated with the boundary and
track east into the local forecast area. Most of the short term
guidance suggests something along these lines. As the convection
tracks east though, they move out of the instability plume while also
encountering drier air. Upper/mid level moisture still in play, but
not a richer moisture source. The low level jet also progged to lift
more north rather than eastward, keeping another forcing mechanism
just outside of the forecast area. Recent model trends have wanted
to bring various convective elements across western parts of the
forecast area over the past couple days, only to pull them back due
to the drier atmosphere coupled with an upper level ridge. Here
though, think the CAMS have some solid footing in bringing at least
some scattered convection across parts of MN overnight, although
should struggle to make it much farther east. 12z HRRR run paints a
30-50% for measurable rainfall overnight into early Thu morning for
southeast MN. Model blend suggest dry but other short term guidances
more favorable - and will lean more into that for rain chances. For
the moment, will hold with sub 50% for chances - but will keep a
close eye on trends and up pops if conditions warrant it.
Friday-Saturday... Additional Chances for Showers and Possible
Storms at Times
Main focus will be on Friday through Saturday with the chances for
rain showers and storms. The NBM guidance today is nearly similar to
the previous forecast for Friday & Saturday with around 50-60%
chances for locations with the higher chances south of I-94. At
times, Friday night and Saturday afternoon/evening, chances increase
to even near 65-70% for areas mainly south of I-90. A higher risk
for severe storms looks to hold further off to the southwest of the
area around central Iowa into eastern Nebraska closer where
convection is anticipated to initiate from the frontal boundary
convergence zones and greater instability. Now the question remains
is how far northeast do storms and the resulting risk extend. SPC
does bring a slight risk to brush by portions of northeast Iowa. The
CSU guidance would have this risk even further back to the southwest
of the region with the GEFS as its main input.
One of the lacking areas is the deep layer support. As the surface
low pressure system slowly lifts to the northeast, the upper level
low is anticipated to retrograde back to the west with the surface
system weakening/filling-in the further northeast it progresses.
Tomorrow night over the central plains, MSLP probabilities of 1010
mb or less show near 100% agreement among the EPS, CMC, and GEFS
ensemble members. But as the system moves to the northeast towards
northeast Iowa, these probabilities at most would be 15% by Friday
evening. On the leading edge of the surface system, a near
uninterrupted fetch of moisture from the Gulf of Mexico would bring
a more unstable airmass into the region with PWs nearing 1.25".
These values would be above the 90th percentile of the NAEFS model
climatological guidance. Global models would have MUCAPE values
around 500 J/kg edging into northeast Iowa by Friday afternoon. But
as warmer air continues to advect into the region, forecast
soundings show a capping inversion to develop around 800 mb,
limiting any surface based convection by Friday evening.
Depending on how the environment is impacted on Friday, there would
be another chance for showers/storms again on Saturday as the
filling/weakening surface low edges closer towards the Upper
Mississippi River Valley Region. Confidence is too low at this time
to determine the risk for severe storms at this time, but will
evaluate as the system draws near and how the events evolve on
Friday.
Sunday through Mid-Week... Little to no precipitation chances
Precipitation chances quickly drop off Sunday as high pressure
settles into the region and cooler conditions briefly settle into
the region. Will stick with the blended model guidance through the
extended portion of the forecast with with little to no
precipitation chances anticipated beyond this weekend through mid
next week. Any precipitation chances would likely come from weak and
quickly passing short wave troughs. Temperatures will likely be the
coolest on Sunday in wake of the passing system with afternoon highs
only reaching into the 60s. Temperatures look to rebound some for
the first half of the new work week with high temperatures topping
out in the upper 60s to 70s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 547 PM CDT Wed May 10 2023
VFR conditions are expected through the period. Watching an
increase of instability edging closer to the KRST airfield from
the west overnight to support showers or possibly a TSRA in the
vicinity by sunrise. Confidence is low on the TSRA nearby KRST (5%
chance), but will continue to monitor. A few VFR showers around
southeast MN / KRST is a somewhat higher chance of occurrence
(30%). Thus, continued VCSH in the forecast.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Peters/Rieck
AVIATION...Baumgardt
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
958 PM CDT Wed May 10 2023
.UPDATE...
Issued at 958 PM CDT Wed May 10 2023
One strong storm exists in southern Peirce County, just small hail
with that. The storm is almost stationary however so localized
flash flooding is a concern. A flash flood warning may be need in
an hour if it continues. The CAMS have really dropped the
scattered storms overnight, so it looks like the main rain event
will start Thursday morning in the south.
UPDATE Issued at 634 PM CDT Wed May 10 2023
Scattered storms are developing along a warm front extending from
the southwest to the northeast. With shear only around 20kts,
storms may grow and fall all evening as the shear won`t be able to
separate the updraft/downdraft. The severe threat is very low.
&&
.SHORT TERM...(This Evening through Thursday)
Issued at 253 PM CDT Wed May 10 2023
Expect isolated to scattered showers and thunderstorms late this
afternoon through tonight with more widespread showers and storms
developing on Thursday.
Western and central North Dakota remains under southwest flow
aloft with a deep western US trough in place to our west. As this
trough slowly moves closer to the central US, an upper low will
close off near the Colorado/New Mexico border this evening.
For the rest of this afternoon, expect neutral heights to limit
convection chances across much of the area. The one exception may
be across the far southwest or south central along an effective
surface warm front. Most CAMs still keep the entire area dry until
after 00z this evening, but a couple have been initiating
convection along this boundary over the south as early as 21z.
Better chances for storms increase along the warm front after 00z
this evening as modest height falls move in and a weak vorticity
maximum ejects into the area from the south, traversing through
the trough. A few of these storms may become strong with a non-
zero chance of a severe hail report or two. RAP soundings suggest
that MUCAPE in the vicinity of the warm front will range from 500
to 1500 J/kg tonight. However, a limiting factor for severe
weather will be relatively weak deep layer shear in the 20 to 30
knot range. Thus, we can expect some elevated pulse or multicell
structures primarily with hail to the size of quarters as the main
threat.
By Thursday, the aforementioned upper low will start to lift into
the central Plains as a surface low starts to deepen to the lee
of the Rockies. Various waves will rotate north from around the
upper low on Thursday, bringing widespread chances of showers and
thunderstorms to southern parts of the state in the late morning
or early afternoon, spreading north through the rest of the day. A
few stronger storms will be possible once again during the
afternoon across the far south, but weak shear will once again be
a limiting factor for severe storms.
With the widespread cloud cover and increasing precipitation
chances on Thursday, highs will be just a bit cooler than today,
generally in the mid 60s to mid 70s.
.LONG TERM...(Thursday Night through Wednesday)
Issued at 253 PM CDT Wed May 10 2023
Widespread rain and thunderstorms continue through at least the
first part of the weekend, followed by dry and warming conditions
through the rest of the long term.
The upper low will continue to lift from the central into the
northern Plains Thursday night into Friday. We may see a lull in
activity over southern portions of the state Thursday night before
the next wave moves in from the south on Friday. This will mean
more widespread showers and thunderstorms through at least
Saturday afternoon. The strong thunderstorm potential Friday will
be similar to Thursday with more weak instability and shear in
place. PWATS will be in the 90th to 99.5th percentile Thursday
through Friday night over much of the area with the highest
percentiles generally across the west and south, so heavy rain is
certainly a threat. When all is said and done, the NBM continues
to show widespread 48 hour percentiles for over an inch of QPF in
the 50 to 80 percent range (highest percentiles over the west and
south, maximized over the southwest). When we increase that
threshold to two inches, the highest probabilities dip into the 30
to 35 percent range over portions of the west and central. Thus,
we have fairly high confidence in widespread totals over an inch,
but confidence decreases as we move into the higher totals.
The low will continue to fill as it drifts east on Saturday with
showers and thunderstorms diminishing from north to south across
the area. Saturday will also feature the coolest temperatures in
the long term in the wake of the low, ranging from the mid 50s to
the mid 60s. However, we quickly warm back into the mid 60s to
lower 70s again on Sunday with more upper 70s and potentially some
lower 80s back in the forecast by mid next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
Issued at 958 PM CDT Wed May 10 2023
VFR through the period. Calm winds until Thursday afternoon where
winds could gust to 20 again. Widespread rain starting late
Thursday through Friday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Smith
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...Smith
Area Forecast Discussion
National Weather Service Boston/Norton MA
1025 PM EDT Wed May 10 2023
.SYNOPSIS...
Tranquil evening in store for tonight with high pressure in
control. Early summer-like warmth expected Thursday and Friday
and possibly into Saturday as well. Mainly dry weather is
expected, but we do have to watch for isolated pop-up showers or
thundershowers Thursday and Friday. A bit of a cooldown into
this weekend and early next week, but temperatures still will be
seasonable for the second week of May.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
No major changes with this update. Forecast remains on track,
with quiet weather continuing. Tweaked temperatures to reflect
observed trends.
230 PM Update:
Another mild and pleasant afternoon for Southern New England, with
westerly breezes and abundant if somewhat filtered sun by high-
altitude smoke from Alberta wildfires. Temps have reached into the
mid 60s to low 70s for most of Southern New England.
For tonight, a continuation of tranquil conditions is anticipated.
The very dry air mass in place combined with clear skies and light
winds should allow for rapid hourly temperature falls once the sun
sets. While last night was pretty chilly, especially in the outlying
valleys, temperatures running several degrees warmer than yesterday
should support lows in the low to mid 40s in eastern CT, northwest
MA and in and around I-495 in MA. Upper 40s to the mid 50s should be
more common in the urban areas.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
235 PM Update:
Thursday:
High pressure to our southwest and a broad sfc trough over the
Canada Maritimes will permit a continued westerly flow on
Thursday, with full sun, if still filtered by high-altitude
smoke being transported SE from the Alberta wildfires. Thursday
should be even warmer than today and areas away from the coasts
should reach into the upper 70s to low 80s.
Question for Thursday is the potential for diurnally-driven
pop-up showers or thundershowers in the NW flow aloft. Water
vapor imagery as of Wednesday aftn shows a notable shortwave
disturbance aloft rounding the upper-level ridge over the
western Gt Lakes region, a feature which is progged per the NAM
and GFS to dig southeast into interior western New England
during the peak heating hours. Accompanying that feature and its
mid to upper level divergence will be a plume of steeper lapse
rates between 850-500 mb around 7 to 7.5 C/km. A modest amount
of most-unstable CAPE is generated given the upper 70s to lower
80s temps, around 300-500 J/kg with lifted indices -1 to -3.
Most of the CAMs blossom at least Cu/Tcu with a varying degree
of shower/thunderstorm coverage, the coverage of which seems
slightly more than prior model cycles. HRRR generally shows the
least coverage, while the WRF solutions (NSSL, FV3 and ARW
cores) are more bullish. The biggest limiting factor is the
westerly sfc flow, which means focused sfc convergence should be
fairly sparse but also lead to low dewpoints and poor moisture.
Could see some added lift from the shortwave, but think the
lesser coverage probably wins out given the west flow and lower
dewpoints. While there probably will be at least isolated
showers or a storm to dodge, Thursday isn`t a washout by any
stretch. Timing roughly noon to 6 PM, with mention of 20% PoP
but left as isolated coverage, and that coverage diminishes with
sundown. Couldn`t rule out graupel or small hail in especially
stronger cores given the lapse rates aloft and the fairly strong
speed shear especially in mid to upper levels.
Thursday Night:
Any diurnal showers or thundershowers should diminish early Thurs
night (around sundown). Brief subsidence after the passage of the
Thursday daytime shortwave disturbance should allow for a period of
clearing skies with light west flow. However will see increased
clouds for the second half of the overnight especially across
central and northeastern areas, as the next in the parade of
shortwave disturbances aloft spreads mid to high level moisture into
New England. Lows should also be warmer than forecast lows for
Wednesday evening, with values in the lower to middle 50s.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Highlights
* Much of the extended will feature dry and quiet weather. Could
have a few showers/storms Fri afternoon/eve and on Sat.
* Temperatures starting off above normal late this week and Sat,
but become more seasonable Sun into early next week.
Friday...
Caught between a ridge over the OH Valley/central Great Lakes and a
deep trough digging into northern Quebec. We are somewhat on the
cyclonic flow side of things, so will have a shortwave trough
digging through the region on Fri. A weak surface trough in
combination with localized sea breezes may be enough to trigger a
few showers/storms.
Main change to the forecast was to increase precipitation across
southern New England through Fri afternoon into the evening. Still
have some uncertainty in the forecast as I think that any remnant
boundaries from Thu convection could impact how things evolve on
Fri. At this point appears that the risk for any shower/storms is
across RI and eastern MA. It is in these locations that there may be
enough SW flow in the lower levels to advect mid/upper 50 degree dew
points. Think the risk is lower across interior locations given the
westerly flow, which should keep slightly drier dew points. Will
note did lean away from the latest NAM12 as it appears to be much
too high with dew points, which impacts the instability over our
area. Should have roughly 7-9+ degree Celsius low level lapse rates
and a remnant EML moving through (mid level lapse rates between 6-8
degrees Celsius). Deep layer shear is in the 35-40+ kt range with
MUCAPE values roughly between 100-500 J/kg. Forecast soundings
showing a somewhat inverted-v sounding per GFS/NAM in Bufkit. Given
the elevated instability think that hail and gusty winds not out of
the question. Have held off from adding at this point, but may be
needed once we get the aid of more convective guidance. The flow is
relatively weak below 2 kft, so think that localized sea breezes may
mostly be the trigger. Had to deviate from the NBM as it does not do
well to capture these mesoscale details.
Have increased temps toward the 75th percentile of guidance given we
are in WNW to NW flow. This will keep roughly 16-20 degree Celsius
air overhead. This will translate to high temperatures generally in
the 70s along the immediate coastline and the low/mid 80s elsewhere.
Should see any of these showers/storms diminish Fri evening. Low
temps heading into Sat will be in the 50s to low 60s.
Saturday...
The trough over northern Quebec will dig into northern New England
by late Sat. In response to the trough a cold front will cross the
region earlier in the day.
Main change in the latest forecast was to significantly decrease
precipitation chances from the NBM. Given the rapid decreases of
low/mid level moisture as the front is sliding through think the NBM
is overdone. Best shot for showers is along/south of the MA Pike
especially earlier in the day. Should not be a washout with
relatively light precipitation expected.
Still anticipating that it will be mild with W to NW flow keeping
roughly 13-18 degree Celsius air overhead at 925 hPa. The result
will be slightly cooler readings in comparison to Fri, but still
mild nonetheless for this time of year. Highs generally will be in
the 70s with some 80 degree readings in the Merrimack/CT Valley.
Sunday through early next week...
Dry and quiet weather anticipated through much of this timeframe
with temperatures trending closer to normal readings for this time
of year. Will gradually see the ridge over the SE US that is nudging
into the Great Lakes breakdown. This will allow a trough/shortwave
to slide through at some point on Mon/Tue, which may bring us our
next shot for some showers.
Lots of uncertainty at this point with timing this shortwave and
shower chances into early next week. Does not appear that there
would be a washout, but given the uncertainty have just stuck with
the NBM at this point. Temperature trending closer to normal with
highs in the 60s and 70s and lows in the 40s to low 50s.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence.
VFR with W/WSW winds generally less than 10 kts. The only
exception is across the Cape/Islands where winds remain around
10-15 kts through roughly 03Z. May stay above that 10 kt speed
for BID/ACK as we head into Thu daybreak.
Thursday and Thursday Night...High confidence.
VFR through the forecast with WSW/W winds around 10-15 kts.
Could see some isolated 15-20 kt gusts during the afternoon. As
previous shift mentioned could have an isolated shower/storm
between 16-23Z. Confidence not high enough to include in the TAF
at this point. If a heavier shower/storm moves over a terminal
then could see sub-VFR conditions. Right now with this activity
think cloud bases around 7 kft.
Any showers/storms that develop are expected to diminish after
sundown. Increasing mid to high cloud cover toward Fri AM
daybreak. W/WNW winds around 5 kt.
KBOS Terminal...High confidence in TAF. Low probability of a
pop-up shower/storm 17-22z.
KBDL Terminal...High confidence in TAF.
Outlook /Friday through Monday/...
Friday: VFR. Breezy. Slight chance SHRA, isolated TSRA.
Friday Night: VFR. Breezy.
Saturday: VFR. Breezy. Slight chance SHRA.
Saturday Night through Sunday: VFR. Breezy.
Sunday Night: VFR.
Monday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
235 PM Update:
Overall high confidence.
Tranquil boating conditions anticipated for mariners through
Thursday night, with west winds around 10-15 kt (locally a bit
stronger around 20 kt near the southeastern waters). Seas mainly 3
ft or less all waters.
May be some pop-up showers late Thursday afternoon; while some
potential exists for a rogue thundershower or two over land Thursday
afternoon, greatest risk for any lightning would be over land given
cooler temps over the waters.
Outlook /Friday through Monday/...
Friday: Winds less than 25 kt. Slight chance of rain showers,
isolated thunderstorms.
Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers.
Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.
Sunday through Monday: Winds less than 25 kt.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...BL/Loconto
NEAR TERM...Belk/BL/Loconto
SHORT TERM...Loconto
LONG TERM...BL
AVIATION...Belk/BL/Loconto
MARINE...BL/Loconto
Area Forecast Discussion
National Weather Service Burlington VT
1004 PM EDT Wed May 10 2023
.SYNOPSIS...
Dry weather will continue through most of this week as high pressure
at the surface and aloft continue to build over our region. A
warming trend will last through the rest of the work week. The next
chance of rain arrives late in the week, with scattered showers
possible Thursday and Friday.
&&
.NEAR TERM /THROUGH THURSDAY NIGHT/...
As of 1002 PM EDT Wednesday...The forecast remains in good
functioning order. Just a few minor adjustments for hourly
temperature and sky trends with some thin mid to high clouds
popping up in the Northeast Kingdom. Previous discussion below.
Tonight will not be as chilly as the previous couple nights,
restricting frost potential as temperatures drop into the 40s to
lower 50s. This will result in lows 10-15 degrees higher than
last night`s lows for many, bringing us closer to average for
this time of year. Conditions will stay dry with high pressure
in the mid- Atlantic until potentially around dawn tomorrow. A
vort max will slide through the forecast area from northwest to
southeast, providing the potential for scattered showers and/or
thunderstorms. Expecting timing to be in the St. Lawrence Valley
around 06-08AM before it moves across the Adirondacks and into
south/central Vermont throughout the day tomorrow. PoPs will
remain at most 25% due to low certainty in the ability of the
vort max to provide sufficient forcing at the surface, as well
as timing variability.
The GFS and NAM3 place about 600-900 J/kg of CAPE across western and
southern zones on Thursday, but surface forcing continues to look
minimal and northwesterly flow could limit the atmosphere`s ability
to make thunderstorms. The ECMWF doesn`t seem thrilled with the
potential, while the HRRR is somewhat on board with about 500 J/kg
of surface-based CAPE, but shifts it farther northeastward,
indicating central and northern Vermont as spots for showers/storms.
Another limiting factor is that the shortwave doesn`t seem to quite
line up with the best conditions and instability for t-storms to
materialize. Tomorrow will likely be even warmer than today with
highs in the 70s under mostly sunny skies, about 5-10 degrees above
normal, which will be one thing the thunderstorm potential has going
for it. A second shortwave energy should pass through Thursday
night, increasing PoPs up to 20-30%, particularly late in the
night/early Friday morning along the international border. This will
also bring more widespread cloud cover and southerly winds advecting
in some warmer air. Because of this, lows will be even milder in the
upper 40s to mid-50s.
&&
.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 253 PM EDT Wednesday...A series of frnts wl cross our cwa
during this short term time frame, producing several chcs for
showers and embedded rumbles of thunder. First frnt is a warm frnt
lifting from sw to ne acrs our cwa on Friday morning, while embedded
5h vort slides along boundary in the nw flow aloft. Have noted some
weak elevated instability with NAM advertising 200 to 400 J/kg above
850mb, but areas of CIN near 100 J/kg near the sfc, so just schc for
thunder on Friday morning. Meanwhile, after morning scattered
showers, subsidence and drying occurs btwn 850 to 500mb, which
should allow for some breaks in the overcast. These breaks combined
with progged 925mb temps btwn 14 and 16C, should allow temps to
climb into the mid 70s to lower 80s most locations. Sfc heating wl
support additional development of instability during the
aftn/evening hours with CAPE values in the 400 to 800 J/kg, as dwpts
range in the upper 40s to lower 50s. However, forcing is very
limited with actual height rises and cold frnt with very weak sfc
convergence is not arriving until aft 00z Sat. So a few isolated to
widely scattered showers and embedded storms are possible on Friday
aftn/evening, but coverage/intensity looks minimal attm. Best
instability is central/eastern VT, while best forcing with
approaching boundary is over northern NY/SLV, so have mostly chc
pops with highest near the International Border and lowest pops acrs
southern VT zns. Also, looking at sounding data, suggests mixing of
drier air around 850mb behind initial warm frnt is possible,
lowering sfc dwpts into the mid 40s, which would result in less
instability acrs our cwa. Bottom line not anticipated any strong or
severe convection and coverage wl be limited.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 253 PM EDT Wednesday...Mid/upper lvl pattern wl feature closed
trof acrs eastern Canada, while building ridge develops over the
central Plains. This results in a mainly dry and cool northwest flow
aloft acrs the NE CONUS, as 1034mb high pres noses into our cwa. FA
is under modest caa on Saturday with nw 850mb winds of 25 to 35
knots, and progged 925mb temps btwn 11-14C, supporting highs mid 60s
to lower 70s. Soundings support good mixing thru 850mb, which wl
allow for drier air near summit level to transfer toward the sfc,
resulting in lower dwpts and min rh values in the 22 to 28% range on
Saturday aftn. Depending upon rainfall on Friday and fuel
conditions, a sps for fire wx concerns maybe needed for parts of the
NEK of VT, based on winds/rh`s on Saturday aftn.
For Sunday the primary concern wl be min aftn rh`s as dry northwest
flow prevails with cooler temps. Have continued to populate grids
with 10th percentile NBM for dwpts as a target of opportunity, which
results in min rh`s in the upper teens to mid 20s on Sunday aftn.
However, initial sounding data supports slightly less winds on
Sunday as best gradient is shifting to our east and 925mb to 850mb
flow is weakening. Progged 850mb temps are rather cool for mid May
with values near 0C, while 925mb temps warm btwn 6-8C under mostly
sunny skies, supporting highs in the mid 50s to lower 60s. The
potential for frost is challenging given the lack of strong sfc high
pres directly overhead, but feel with dry bl conditions, have
trended on the cooler side of guidance with values in the upper 20s
to lower 40s for both Sat/Sun. We will continue to fine tune lows as
confidence increases with regards to winds and placement of sfc high
pres.
By early next week flow becomes south/southwest ahead of next sfc
boundary and modest llvl waa develops. Based on warming 925mb to
850mb thermal profiles, I have temps in the mid 60s to lower 70s
Monday, before cooling back into the upper 50s to lower/mid 60s by
midweek. Sfc cold frnt with limited moisture looks to impact our cwa
late Monday into Tues with schc/chc pops for now and limited
potential for convection, given the lack of sfc heating/instability.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Through 00Z Friday...VFR to continue. Winds are currently west
to northwest around 4 to 9 knots, though with some sustained
winds to 15 knots at KMSS. Winds will gradually subside and
become terrain driven over the next few hours. Around 1500 to
2000 ft agl, there will be a pocket of 25 to 35 knot northwest
flow that moves into far northern New York and northern Vermont,
with a quick note of LLWS at KPBG, KBTV, KMPV, and KEFK between
about 03z and 07z when it dissipates. Otherwise, southwest to
west winds pick up after 14z around 7 to 10 knots. Again, KPBG
will see a southeasterly lake breeze develop, which could
quickly transition back to the west or northwest around 18 or
19z. An isolated shower is possible near KRUT around 18-21z, but
unlikely to impact the terminal.
Outlook...
Thursday Night: VFR. Slight chance SHRA.
Friday: VFR. Chance SHRA, Slight chance TSRA.
Friday Night: VFR. Slight chance SHRA, Slight chance TSRA.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. NO SIG WX.
Monday: VFR. Slight chance SHRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Storm
NEAR TERM...Haynes/Storm
SHORT TERM...Taber
LONG TERM...Taber
AVIATION...Haynes
Area Forecast Discussion
National Weather Service Duluth MN
658 PM CDT Wed May 10 2023
.DISCUSSION...(This evening through Tuesday)
Issued at 351 PM CDT Wed May 10 2023
Summary: Thunderstorm chances increase late this afternoon into
tonight, primarily near the International Border in north-central
MN. A storm or two may become strong to severe in Koochiching
County, capable of producing large hail and damaging winds. Dense
fog will be possible around the Twin Ports tonight into tomorrow
morning. An active pattern lingers through Saturday night with
additional chances for showers and thunderstorms. Drier and warmer
weather is likely next week.
Showers and thunderstorms have advected east of the CWA this
afternoon, resulting in decreased cloud cover. A diurnal cumulus
field has developed for portions of the area with temps warming into
the 60s and 70s. The primary concern for the rest of today into
tonight will be the development of isolated strong to severe
thunderstorms near the International Border. The 12z sounding from
INL revealed moderately steep mid-level lapse rates of approximately
6.5 degC/km. Model soundings from the RAP and HRRR in INL have lapse
rates increasing up to 8 degC/km by the late afternoon. When
combining these lapse rates with dewpoints in the mid to upper 50s,
MUCAPE is progged to reach approximately 800-1300 J/kg. Given the
favorable thermodynamic environment, large hail up to 1" will be the
primary hazard. If convection is able to initiate before the sfc
layer stabilizes after sunset, damaging winds may also be
possible.
The limiting factor for strong convection this afternoon into
tonight will be a weak shear environment. The forcing mechanism for
today`s convection is a weak amplitude shortwave riding over a ridge
axis centered over the north-central CONUS. A sfc warm front
associated with this shortwave will be slowly lifting northward this
evening, stalling out over far north-central MN. The winds aloft
that will be accompanying this front are fairly weak, which is
resulting in only about 25-30 knots of effective bulk shear. This
amount of bulk shear will likely result in short-lived storms,
limiting the severe potential. This limited severe potential is
reflected in the Marginal Risk outlook from the SPC over Koochiching
County and the far northwestern portion of St. Louis County. Expect
the potential for severe storms to diminish late tonight into
Thursday morning as drier air enters into the low to mid levels.
Dense fog will be possible around Lake Superior late tonight into
tomorrow morning as fog is advected onshore. A Colorado Low will
begin to slowly propagate into the upper Midwest on Thursday into
Friday. This will bring a chance for showers and non-severe
thunderstorms on Thursday and Thursday night. Precipitation chances
linger into Friday and through Saturday night for portions of the
CWA as the Colorado low becomes cutoff over the north-central CONUS.
Drier and warmer weather arrives on Sunday and continues into early
next week as ridging occurs over the CWA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 658 PM CDT Wed May 10 2023
Predominantly VFR conditions over the terminals as of issuance
time. Isolated thunderstorms along the US/Canada border may affect
KINL this evening, and have included VCTS groups but with VFR
conditions until 08z this evening and part of the overnight hours.
Light northeast winds are expected to help produce fog for KDLH
overnight and early Thursday, with fog also possible for KHIB.
Visibility should be lowest for KDLH, where IFR conditions are
possible for several hours. Lower is possible, but will have to
re-evaluate this evening. KHIB is more likely to be MVFR, with
mainly radiational fog processes. Shower chances move back into
KBRD and KHYR after 15z, and have included VCSH groups with VFR
conditions for now.
&&
.MARINE...
Issued at 351 PM CDT Wed May 10 2023
Winds will remain at or below 15 knots this afternoon into Thursday.
There will be a chance for thunderstorms this afternoon into
tonight. Fog will also be possible tonight into Thursday morning,
dropping visibility to a mile or less for portions of western Lake
Superior.
East to northeast winds will increase Friday into Saturday with
conditions becoming hazardous for smaller vessels during that time.
Small Craft Advisories will likely be needed for portions of the
nearshore waters. The main threat for hazardous wind/waves on Friday
will be from Two Harbors to the Twin Ports and from the Twin Ports
to Port Wing. Additional thunderstorm chances will occur on Thursday
and into Friday morning.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 48 73 52 63 / 10 20 30 30
INL 53 78 52 75 / 40 10 20 30
BRD 55 76 56 75 / 20 40 40 40
HYR 55 74 56 77 / 10 20 20 30
ASX 50 76 49 62 / 10 20 20 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
DISCUSSION...Unruh
AVIATION...LE
MARINE...Unruh
Area Forecast Discussion
National Weather Service Des Moines IA
644 PM CDT Wed May 10 2023
...Updated for the 00z Aviation Discussion...
.UPDATE...
Issued at 626 PM CDT Wed May 10 2023
Forecast is on track this evening. Seeing a mixture of residual
diurnal cumulus and higher clouds as of 630pm, with dry conditions
across the entire area. Still monitoring the potential for a few
thunderstorms to develop later this evening, generally after 10pm
across far northwest Iowa. This activity will be tied to a period
of enhanced moisture convergence related to the onset of the
nocturnal LLJ. Any isolated/scattered storms should remain
confined generally north of US20. While severe weather is not
anticipated, the various CAM solutions are showing modest updraft
helicity (UH) streaks. If storm rotation would occur, a few
hailers are possible. The is more uncertainty into Thu morning and
afternoon with the deterministic and CAMs all over the place on
the occurrence and placement of showers and isolated
thunderstorms. Thus, will maintain a 30-60 percent chance of
precip on Thursday.
&&
.DISCUSSION.../Tonight through Wednesday/
Issued at 241 PM CDT Wed May 10 2023
Take Home Points:
*Chances for showers/storms continue over next few days
*Window for stronger storms remains Friday evening/night
*Drier conditions likely to start next week.
Discussion:
Forecast remains on the active side with broad ridging over head and
the larger Western CONUS trough and multiple shortwaves expected to
affect the region in the coming days. There are what seems to be
never ending PoPs through the weekend. The overall pattern, while
active, remains rife with some mystery when it comes to the finer
scale details. As is the case, prior rounds of convection here and
elsewhere will, to varying degrees, affect subsequent
opportunities. The forecast likely looks wetter than will result.
Coming back to today, another day, another round of storms/MCS out
west over Nebraska driven by the LLJ. Overnight and morning CAM
guidance suggested the opportunity for activity to fester its way
eastward into the area, but reality has largely struggled to match.
The LLJ subsiding, lack of additional forcing mechanism, and
movement into generally weak/unsupportive environment has allowed
for majority of activity to subside by late morning/early afternoon.
Have trended PoPs dry this afternoon as a result, latching onto more
recent HRRR runs. With the downward trend in precip activity this
afternoon/evening, also upped temps a couple degrees over original
with more sunshine present.
As the Western CONUS trough begins to kick out, LLJ activity will
nudge eastward tonight and should initiate elevated convection over
portions of northeast into north-central Iowa. CAM guidance has
varied a bit, with recent RAP/HRRR runs a bit less robust and
further north than the FV3/ARW/NSSL-WRF 12z runs. Does appear mid-
level moisture plume is likely to reach that far north, so have
trended PoPs in the direction of RAP/HRRR guidance. Risk for severe
will be low with elevated nature, limited ability to organize, and
mainly poor lapse rates. There does look to be some risk for locally
heavy rainfall with persistent moisture transport, training
development, and HRRR and HREF PMM pockets of 2-3+" depicted. That
said, potential for water issues should be very local, especially
with green up of late.
By Thursday mid-late morning, a shortwave trough digging northward
from the Lower Mississippi Valley is expected to influence the area
with more broadscale lift and an additional push of moisture, which
will be reinforced to some degree by the Western CONUS trough
continue to kick out of the Rockies. Not much more than broader
light precipitation to occasional rumbles of thunder expected with
this push within an environment that will be unsupportive for
stronger convection.
Friday remains the window of opportunity for potential strong to
severe storms as the Western CONUS trough moves into the Plains with
attendant surface low. Some question will be how much and how
quickly conditions clear out, let alone the placement of the surface
low. All of which will factor in to strong/severe potential. Shear
depictions too remain on the lower end overall, but not completely
unsupportive. Also working against overall potential will be the
fact that the system will likely be beginning to degrade/fill.
Existing Day 3 Slight from SPC remains reasonable, especially should
timing/conditions fall into line and result in surface based
convection, with threat easing into the overnight.
Through the remainder of the weekend, upper pattern becomes messy
and muddled as the upper trough fills in over the Northern Plains
and additional shortwave activity moves northeastward out of the New
Mexico/Texas regions. At this point, details would be futile aside
from noting continued potential for periods of showers/storms.
Transition to northwesterly flow next week should result in a
quieter/drier period. All the while, expect temperatures to be
seasonable to seasonably warm.
&&
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 626 PM CDT Wed May 10 2023
VFR conditions are expected for the majority of the period. Still
expecting isolated/scattered thunderstorms to develop overnight
across northern Iowa, possibly impacting KFOD/KMCW with a brief
period of MVFR/IFR CIGs or VSBY. There is a chance for additional
showers/tstms on Thursday but low confidence on the timing,
location and impacts. Further refinements will be needed in future
TAF issuances.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Fowle
DISCUSSION...Curtis
AVIATION...Fowle
Area Forecast Discussion
National Weather Service Grand Forks ND
1012 PM CDT Wed May 10 2023
.UPDATE...
Issued at 1011 PM CDT Wed May 10 2023
The atmosphere decoupling has helped stabilize conditions. While
elevated instability (MUCAPE 1000-2000 J/KG) is lingering overall
trend has been thunderstorms to weaken within our CWA, and RAP
indicates this elevated CAPE will continue to decrease through the
rest of the evening/early morning hours). This lowers confidence
in "new" severe convection along the surface trough axis
developing locally, however the regional exception has been a
multicell complex in southern Manitoba. Radar/satellite trends
indicate this may clip our northeast (northwest MN counties along
the US/Canada border). This cluster is showing forward prorogation
and is collocated with stronger effective shear (30-40kt) and
while elevated 0-3km bulk shear is 30-35kt range orthogonal to the
orientation for the eastern part of the cluster (could help with
transferring stronger winds to the surface). All indications are
this is a severe cluster and if it moves into our CWA over the
next 1-3hr we could see impacts (60mph+ wind) and marginally
severe hail to 1".
UPDATE Issued at 654 PM CDT Wed May 10 2023
Axis of steep mid level lapse rates has supported destabilization
in proximity to a surface trough where ML CAPE in the 1500-2000
J/KG is shown to be in place by SPC/RAP analysis. Effective shear
is under 30kt, but marginally severe hail still remains possible
with stronger updrafts. At least until sunset, dry mid levels and
DCAPE over 1000 J/KG could support downburst winds to 60 mph.
Forcing is less organized with the main shortwave to our north,
but there is just enough convergence and PVA aloft to have
allowed for development to take place over our northwest. Timing
of initiation is matching the "general" picture from the last few
runs of the HRRR which shows the main area of possible
showers/storms remaining along the surface trough axis as it
shifts east-southeast across northeast ND and northwest MN (mainly
north of Hwy 2).
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 319 PM CDT Wed May 10 2023
Minor impacts are possible this afternoon and evening. A weak, and
nearly stationary boundary, will provide an axis of potential
thunderstorm development. Isolated severe thunderstorms are possible
in association with this boundary; however, instability and shear
remain separated from the primary forcing mechanism. Regarding
timing, CAMs develop sporadic t-storms along the International
Border and into the Devils Lake Basin from around 02Z onward through
09Z. SFC CAPE values upwards of 2500 J/Kg are in place across
portions of central North Dakota, but are disconnected from the axis
of strongest forcing. In the event that the boundary is able to push
further south, the current environment contains enough instability
and shear to allow for a supercell or two, with hail and wind gusts
being the primary risks.
Severe thunderstorm potential diminishes sharply after midnight,
with a period of quiet weather expected through around sunrise
Thursday.
Showers and thunderstorms are expected once more heading through the
day Thursday, with isolated severe thunderstorms during the
afternoon and evening. CAPE and shear look similar to the current
setup; however, forcing will be slightly stronger as a weakening
transverse wave lifts northward into the Northern Plains and Upper
Midwest. Wind and hail will be the primary expectation with
Thursday`s severe storms, with the best chances for severe weather
occuring mainly along and south of I-94. Areas north of I-94 could
still see strong storms; however, environmental conditions are less
favorable for severe thunderstorms. QPF up to 1.25 inches is
possible where the strongest storms track.
.LONG TERM...(Friday through Wednesday)
Issued at 319 PM CDT Wed May 10 2023
Key Messages:
-Active weather persists through the end of the week into the
weekend, with rain showers and some weak thunderstorms possible.
-Near to above normal temperatures continue across the long term
period.
Discussion...
An upper level trough ejecting out of the Rockies and into the
central Plains, will dictate the weather pattern across the region
through the end of the week and into the weekend. Cluster analysis
is in good agreement on the overall progression of this feature into
the Plains, with only minor discrepancies regarding the strength of
the troughing. Regardless, with continuous moisture transport to the
region and strong synoptic scale lift, widespread showers and
potentially some weak thunderstorms will be possible on Friday and
Saturday. Latest NBM probabilities for 24-hour QPF exceeding 0.25"
range from the 15-30% range across northwestern and west central
Minnesota into the northern Red River Valley, to the 40-60% range
across the Devils Lake basin into southeastern North Dakota.
Attendant probabilities of exceeding 1" are only in the10-20% range,
favoring the western portions of the CWA.
Moving into the weekend, a robust upper level ridge over the Pacific
Northwest and a building ridge from the southeastern CONUS will work
to retrograde the aforementioned upper trough. As this occurs,
precipitation chances will begin to dwindle as we lose synoptic lift
and moisture transport. Rather, temperatures are expected to respond
by remaining near to slightly above normal through the remainder of
the forecast period. This warming trend will be accompanied by
subsidence aloft and generally quiet weather across the northern
Plains. By midweek next week, there are some indications within
ensemble guidance that a Hudson Bay low may deepen and introduce
strong north-northwesterly flow aloft into the region. This would
result in cooling temperatures and possibly a return to a more
active weather pattern, but this is generally the 30% chance
scenario.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 654 PM CDT Wed May 10 2023
VFR conditions should prevail through most of the TAF period
across eastern ND and northwest MN. If there is enough clearing
when winds become lighter we couldn`t rule out pockets of ground
fog and brief visibility impacts in the 10-13 time period
(similar to previous mornings). This evening isolated to widely
scattered showers/thunderstorms are developing near KDVL and
should spread eastward across northeast ND into northwest MN. The
impacts are uncertain with best chances at KDVL and KTVF. Still,
some of the storms could be severe (hail to 1"/brief gusts to 60
mph). These are isolated threats though, and will be monitored.
Better chances for rain showers and thunderstorms arrive Thursday
afternoon with a more organized system approaching from the south.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...DJR
SHORT TERM...Lynch
LONG TERM...Rick
AVIATION...DJR
Area Forecast Discussion
National Weather Service Grand Rapids MI
752 PM EDT Wed May 10 2023
LATEST UPDATE...
Aviation
.DISCUSSION...(This evening through next Wednesday)
Issued at 318 PM EDT Wed May 10 2023
--Another Stellar Day Thursday--
Pattern changes little through tomorrow with upper ridging and
sfc high remaining in place, so expect another day with mostly
sunny skies, warm temps and low humidity. Temps moderate a few
degrees more with lower 80s within reach, except turning cooler
near Lk MI in the afternoon as typical springtime lake breezes
form in otherwise light synoptic wind regime.
--Rain Likely Friday, Especially South--
The TX shortwave that lifts toward srn lwr MI on Friday weakens
and eventually gets sheared out as it comes into our lingering
upper ridge overhead and related confluent flow. Nevertheless
guidance is still fairly bullish on sending a slug of rain into
the area before that happens, especially south of I-96, so likely
pops will be maintained for places like AZO/BTL/JXN. Several
ensemble members as well as the 12Z ECMWF suggest over an inch of
rain could fall south of I-96 on Friday.
A slight chance of Thunder will be kept as well as RAP guidance
brings 500-1000 J/KG of MUCape up to I-94. No severe weather is
expected since the sfc warm front remains south of MI.
The rain Friday may struggle to reach areas north of I-96 (or
only sprinkles will occur) where the dry air and ridging remains
more firmly entrenched, so only chance pops are warranted for
locations such as Ludington, Clare and Mt Pleasant. It`s possible
that a sharp gradient between rain-no rain sets up somewhere near
the I-96 corridor. High temps Friday will probably be highest up
along U.S. 10 (near 80), but only in the lower 70s in the thick
clouds and rain along I-94.
--Weekend Could End up Totally Dry Now--
Rain diminishes or ends on Friday evening as the upper wave
shears out and another installment of sfc ridging and dry air
pushes south from Canada.
We may be able to eventually remove PoPs entirely for Saturday
and Sunday as 1035 mb Canadian sfc high continues nudging
southward and ushers in dew points in the 30s again. Number of
ensemble members producing rain over the weekend continues to
drop although extent of mid and high level cloudiness still
remains in question.
--Coolish Next Week but Largely Dry and Pleasant Again--
Big upper trough digs into New England next week and sends an
impressive back door cold front through MI early in the week.
While some brief showers may occur with that feature, an overall
persistence of sfc riding and a dry/cool air mass behind that
front should result in pleasantly cool conditions with plenty of
sunshine-- for much of the week. Highs generally 65 to 70 with
lows in the 40s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 743 PM EDT Wed May 10 2023
A large area of high pressure was centered over Southern Ontario
with a very weak pressure gradient extending westward through
Lower Michigan. This fair weather system is forecast to build into
Pennsylvania on Thursday. As a result, southerly winds will
develop during the day on Thursday for the TAF sites. The pressure
gradient remains relatively weak so the winds will largely stay
under 10 knots. Mostly subsidence is seen through a much of the
atmosphere through the forecast period along with little moisture.
All this supports VFR conditions.
&&
.MARINE...
Issued at 318 PM EDT Wed May 10 2023
General light synoptic wind/wave regime continues through Friday
with sfc ridging in place. Afternoon onshore flow developing
again on Thursday due to lake breeze circulations. Much of the
coming weekend looks to feature offshore flow of roughly 10-20 kts
as next Canadian sfc high situated to our north sets up
predominantly east/northeast low level flow.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
DISCUSSION...Meade
AVIATION...MJS
MARINE...Meade
Area Forecast Discussion
National Weather Service Huntsville AL
1015 PM CDT Wed May 10 2023
...New NEAR TERM...
.NEAR TERM...
(Rest of tonight)
Issued at 1015 PM CDT Wed May 10 2023
Latest radar data suggests that the remnants of widespread
showers and thunderstorms (which impacted the TN Valley earlier
this evening) will continue to dissipate over the northeastern
portion of the CWFA late this evening. However, deep-layer south-
southwesterly flow of 20-30 knots will exist overnight to the east
of a shortwave trough lifting north-northeastward across eastern
OK/western AR, and we will need to keep our eyes on a smaller
complex of thunderstorms currently tracking northward along the
central AL-MS border. Latest guidance from the HRRR indicates that
these storms will likely dissipate as they encounter a
convectively-overturned and slightly more stable airmass north of
I-20, but we will maintain a slight chance POP through 12Z to
account for the possibility that it may survive. Otherwise, the
combination of overcast high-level clouds and light ESE winds will
lead to mild overnight lows in the m-u 60s, with patchy fog
possible in a few locations.
&&
.SHORT TERM...
(Thursday through Saturday)
Issued at 1245 PM CDT Wed May 10 2023
The upper trough/mesoscale lows now in TX into the northwest Gulf
of Mexico are forecast to shift northeast into the lower MS valley
Thursday afternoon. This will increase low level southerly flow
in advance of the wave. A convergence band will likely redevelop
additional showers and thunderstorms from middle TN through AL
into FL during the midday and afternoon hours. The exact placement
of this will be tricky, so PoPs will be more generalized, but some
areas may experience more or less activity on Thursday. Although
speed shear values will be a bit higher, the threat of severe
weather will remain low. However, a few strong storms due to
increasing CAPE values of 1000-1500 j/kg are certainly possible. A
bit more cloud coverage and the precip potential should keep highs
in the lower 80s as opposed to the upper 80s. There will still be
a diurnal component to the convection Thursday night, but will
maintain low PoPs into the evening.
The wave dampens considerably Friday, but will maintain chance to
likely PoPs given no capping inversion and ample moistures and
instability. With the mid and upper level ridge building on
Saturday over the southeast, coverage of showers and thunderstorms
will decrease with temps reaching the upper 80s to around 90
again. Chance PoPs are still indicated, especially in southern
middle TN and northeast AL given instability and moisture levels.
&&
.LONG TERM...
(Saturday night through Wednesday)
Issued at 1245 PM CDT Wed May 10 2023
Rain chances drop to 20-40% on Sunday with the building ridge
axis and highs around or into the lower 90s. The ridge will start
to break down early next week as troughing builds south through
the upper Midwest and Great Lakes. A cold front will sing south in
response to growing height falls in the region, arriving in the
TN valley on Tuesday. Rain chances are somewhat in question due to
more limited QG forcing being split west and east of our area.
Temperatures will certainly be modified a bit, with highs in the
upper 70s to lower 80s Tuesday and lows in the upper 50s to lower
60s by Wednesday morning.
&&
.AVIATION...
(00Z TAFS)
Issued at 643 PM CDT Wed May 10 2023
Thunderstorms that impacted the terminals earlier have pushed
North of both KMSL/KHSV at this hour, with light/moderate rain
occurring attm. Another round of storms will move into both
terminals within the next 2-3 hours, with gusty winds and small
hail again possible. IFR/MVFR conds will occur during any tstorm
activity, with vsbys AOB 4SM possible during this time. Storms
will gradually fall apart after this/overnight with a break
through mid-morning Thursday. More storms redevelop across both
terminals tomorrow afternoon (similar to what occurred this
aftn/evening), with gusty S/SE winds upwards of 20kts outside any
tstorm activity.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...None.
TN...None.
&&
$$
NEAR TERM...70/DD
SHORT TERM...17
LONG TERM...17
AVIATION...12
Area Forecast Discussion
National Weather Service Memphis TN
927 PM CDT Wed May 10 2023
...New UPDATE...
.UPDATE...
Issued at 906 PM CDT Wed May 10 2023
Convective activity continues to weaken this evening as
instability wanes with loss of surface heating. Showers will
continue to dissipate and the period from midnight to noon should
be mostly dry before the next upper level disturbance moves
through Thursday afternoon with another round of showers and
thunderstorms. Updated forecast to reflect current trends.
&&
.SYNOPSIS...
Issued at 317 PM CDT Wed May 10 2023
Wet and unsettled weather will continue through this weekend.
Loosely organized storms are possible on Thursday as an upper
level low lifts across the region. A couple of storms may produce
gusty winds and small hail. Hot and humid conditions will persist
through Mother`s Day with a pattern change anticipated early next
week. Drier and cooler air will persist across the Mid-South
through late next week.
&&
.DISCUSSION...
(This evening through next Tuesday)
Issued at 317 PM CDT Wed May 10 2023
Storms have easily exceeded expectations this afternoon. With over
2500 J/kg of MLCAPE available and less than 15 knots of shear, storms
have pulsed to severe limits across much of the region. Several
microbursts have occurred across the region today and have mainly
caused damage to trees and power poles. A couple instances of
large hail have also occurred. Additional instances of damaging
winds and large hail are possible through early evening along with
isolated flooding reports. Intensity of storms should subside by
sunset with the loss of daytime heating.
Another band of showers will lift across the region overnight, but
should not be a cause for concern. The next round of showers and
thunderstorms will arrive tomorrow afternoon as an upper level low
lifts across the region. A few strong storms are possible as
MLCAPE values approach 2000 J/kg once again. Convection becomes a
bit more scattered Friday through the weekend as no appreciable
forcing mechanisms will be in place across the region. The main
story will be heat and humidity. Highs will be approaching 90 each
day with overnight lows around 70F.
By early next week, the upper level pattern will shift as the
ridge sinks south and a large upper low invades the eastern half
of the U.S. This will help push a cold front through the region on
Monday. As a result, cooler and drier air will filter into the
region Tuesday through late week. Expect highs in the lower 80s
and lows in the lower 60s. The next chance of rainfall will arrive
next weekend as a cold front moves into the region.
AC3
&&
.AVIATION...
(00Z TAFS)
Issued at 605 PM CDT Wed May 10 2023
A large area of showers with a few isolated thunderstorms covers
much of the Mid-South at this time. Current HRRR model shows much
of this activity exiting the region before midnight with a period
of dry weather overnight through late morning. Another round of
showers and thunderstorms should move back into the Mid-South
Thursday afternoon. Mainly VFR conditions are expected through the
overnight hours with some MVFR ceilings moving in Thursday morning.
MVFR ceilings will also be possible in the vicinity of any
thunderstorms that develop during the forecast period.
Winds will be mainly from the east tonight at around 5 knots
before shifting to the south at 5 to 10 knots by Thursday
afternoon.
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...Flash Flood Watch through Saturday afternoon for MSZ011.
TN...None.
&&
$$
PUBLIC FORECAST...SJM
AVIATION...ARS
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
1047 PM CDT Wed May 10 2023
.DISCUSSION...(This evening through Wednesday)
Issued at 242 PM CDT Wed May 10 2023
KEY MESSAGES:
- An active pattern with daily chances for showers and storms will
continue into the first half of the weekend. Some heavy rainfall is
possible.
- Dry weather with more seasonable temperatures in the upper 60s and
70s return Sunday through early next week.
A vort max associated with a decaying MCS is clearly evident on
water vapor imagery this afternoon over South Dakota will continue
eastward tonight. Scattered showers and thunderstorms will develop
this evening across southwestern MN and spread east northeastward
through the overnight before diminishing just after sunrise Thursday.
A CAPE gradient will reside from southwest MN southward through
central IA. Repeated development may occur along this gradient and
MBE velocity less than 15 kts in the presence of high mean RH
throughout the column, and pwats north of 1.25 inches all point to a
good likelihood of heavy rainfall in spots. HREF localized
probability-matched mean QPF does advertise pockets greater than 3
inches. This seems reasonable. As storms move east of the CAPE
gradient and reach eastern MN, they should weaken. The best risk for
heavy rain will be south of the MN River, especially across the
southern two tiers of counties in MN.
Confidence in convection redevelopment Thursday is low, particularly
during the day. A warm front will likely reside across southern MN
for much of the day, but this could be modified by the overnight
convection. Some clearing may occur, but mid level lapse rates will
remain poor making instability difficult to develop. By late
Thursday or Thursday evening, a weakening of the cap and introduction
of greater moisture in the low levels should contribute to increased
instability. Scattered showers and thunderstorms could redevelop but
forcing overall remains weak. Shear is also weak, quite weak, but
greater 850 mb flow over western MN may be strong enough for a few
more vigorous storms.
The upper low will approach Friday but it won`t be until Friday night
or Saturday it is close enough to provide the best chance for showers
and a few storms. The warm front may remain just south of the IA
border making surface-based storms difficult to come by locally, but
if the front lists north a bit more we could have some severe storms
reach into southern MN. This will need to be watched.
Drier air and northwest flow will follow Sunday and into much of next
week. A tranquil weather pattern will then prevail for a while.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1034 PM CDT Wed May 10 2023
Confidence in the evolution in the area of shra/tsra in western MN is
still relatively low as models are struggling to pick up on the
forcing. A good example is the HRRR had been pretty consistent with
taking this activity east through MKT, keeping it mostly south of
MSP, but the 2z HRRR came in and shifted everything north 30 or 40
miles. Currently instability analysis shows best LIs less than zero
extending from southwest MN, southeast into Iowa. So given the
orientation of the instability, we still favor southern MN for seeing
the bulk of the activity. Given those expectations, changes from the
00z TAFs were pretty minimal. Continued to be fairly optimistic with
cigs, thinking any MVFR or lower cigs will be tied to where the most
persistent precipitation occurs, which at this point puts RWF at
having the best shot at sub-VFR cigs. MSP/AXN/STC have some MVFR
chances as well in the morning, but confidence in MVFR or lower cigs
at those airports is still too low to bring in a prevailing group of
restricted cigs. For the afternoon and evening, we`re definitely
seeing a trend toward drier weather, with it looking to be dry after
Thursday morning until the next surge of moisture arrives late
Thursday night into Friday morning.
KMSP...Confidence has increased enough in wet conditions to start
Thursday to move that prob30 -shra group up into a prevailing line.
Kept thunder out still, that that is certainly a possibility between
11z and 15z. Main reason we continue to keep it out is due to how far
southwest the MUCAPE and negative Best LIs still reside in IA.
/OUTLOOK FOR KMSP/
Fri...MVFR likely. Chc -SHRA/-TSRA. Wind SE 10-15 kts.
Sat...MVFR/-SHRA likely, chc IFR/-TSRA. Wind SE 5-10 kts.
Sun...MVFR. Chc IFR/-SHRA. Wind NE 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
DISCUSSION...Borghoff
AVIATION...MPG
Area Forecast Discussion
National Weather Service Morristown TN
932 PM EDT Wed May 10 2023
...New UPDATE...
.UPDATE...
Issued at 904 PM EDT Wed May 10 2023
Main feature of interest is the area of convection across northern
Alabama /southern middle Tennessee. This complex of storms has
produced an outflow boundary that is moving northeast into the
southern Plateau. Some widely scattered showers and thunderstorms
have developed along this boundary. Airmass across the southern
Plateau and far western sections of southeast Tennessee is
marginally unstable with MLCAPES of 500 to 800. Slowly diminishing
instability is expected over the next couple of hours but some
elevated convection possible over the southern Plateau to around
Chattanooga to around midnight.
Otherwise, upper ridging and weak pressure gradient will produces
dry conditions with plenty of CI/CS cloud cover anticipated.
Lowered Min temperatures forecast most locations a degree or so
overnight. Otherwise, current forecast looks good.
&&
.SHORT TERM...
(This evening through Thursday)
Issued at 321 PM EDT Wed May 10 2023
Key Messages:
1. Increasing chances for showers and thunderstorms Thursday
afternoon. Greatest chances will exist along and west of
Interstate 75 as well as along the East Tennessee mountains.
2. Temperatures will remain near to above normal.
Discussion:
A surface boundary remains draped across the southern CONUS to our
southwest. Recent radar imagery shows convection developing along
the boundary as surface heating increases this afternoon. HREF
members encroach this activity onto the southern Plateau and valley
locations later this evening. However, given the drier airmass in
place(current dewpoint depression of 25 degrees at CHA) and the loss
of diurnal heating, the activity will be trending downward. NBM has
populated with low-end PoPs in the aforementioned locations. Have
opted to keep it in the forecast because models such as the HRRR
have been initializing well for the most part... just behind about
an hour or so. Otherwise, conditions will remain dry for most
through the overnight with increasing clouds due to the upstream
convection.
A weak area of low pressure in the mid-levels will translate up the
Mississippi valley throughout Thursday. This will pull the front
northward and reduce subsidence aloft. As a result, the chance of
showers and thunderstorms will increase. This will follow a diurnal
trend with greatest coverage in the afternoon. Additionally, high-
resolution guidance has trended with keeping the better frontal
forcing along and w/nw of the Cumberland Plateau. This has been
reflected in the forecast by limiting chance PoPs along and west
of the I-75 corridor and into portions of the East Tennesee
mountains as well. Temperatures will remain near to above normal
Thursday.
&&
.LONG TERM...
(Thursday night through next Wednesday)
Issued at 321 PM EDT Wed May 10 2023
1. Not a washout, but chances for showers and storms each day
through early next week due to an early summer-like pattern in place.
2. Temperatures climbing into the mid and upper 80s this weekend,
with upper 70s to low 80s next week.
Discussion:
We begin the period Thursday night with high pressure just off to
our southeast. Meanwhile, an area of low pressure will be centered
across the Great Plains with an associated warm front extending
across to Western TN. Showers and storms will be occurring along the
front to our west. It`s possible that a few showers and storms may
extend far enough east to affect areas west of I-75 Thursday night
but only slight chance POP. Most areas will be dry. On Friday, the
ridge slightly weakens as the low pressure to our west moves further
northeast. The weakening ridge combined with the advancing warm
front will allow for better chances of showers and storms. The
highest chances occurring during the afternoon hours with peak
heating.
On Saturday, high pressure develops along the Gulf coast to our
southwest behind the warm front. This puts our area on the northern
periphery of the high with northwest flow in place. This pattern is
conducive for diurnal convection due to the weakened heights aloft
in combination with the strong surface heating. Saturday night into
a Sunday a cold front will approach from the north. The front is
associated with the deep low of the coast of New England. Then,
additional shortwaves follow behind the front Monday/Tuesday, which
keep slight chance POPs in the forecast.
There is model disagreement during the Tue/Wed timeframe on how
quickly the drier air moves in behind the front. The ECWF suggest
Tuesday should be dry and the GFS not until Wednesday. Regardless of
the exact timing , there is agreement that drier air moves in from
the north at some point mid-week.
Temperatures in the extended are very warm, especially this weekend
with forecast highs creeping into the mid and upper 80s in most
places- possibly crossing 90 near CHA.
&&
.AVIATION...
(00Z TAFS)
Issued at 723 PM EDT Wed May 10 2023
Generally, VFR conditions throughout the forecast for all TAF
sites. Only caveat is chance of showers at CHA/TYS Thursday
afternoon with thunderstorms possible during that time at CHA.
A line of showers and thunderstorms is located across northern
Alabama moving north/northeast along a stationary boundary. As the
storms moves farther north from the boundary into the drier
airmass across southeast Tennessee the convection will weaken.
Confidence is low that this line of convection makes it at CHA
this evening. Will monitor closely.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 65 83 64 80 / 10 40 20 50
Knoxville McGhee Tyson Airport, TN 60 81 62 82 / 0 30 10 50
Oak Ridge, TN 60 81 61 81 / 0 30 10 50
Tri Cities Airport, TN 53 82 58 81 / 0 10 10 50
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...DH
AVIATION...DH
Area Forecast Discussion
National Weather Service Pueblo CO
1003 PM MDT Wed May 10 2023
.UPDATE...
Issued at 1000 PM MDT Wed May 10 2023
Severe Thunderstorm Watch across the far eastern plains has been
allowed to expire. Strong thunderstorms are still possible through
the remainder of the night, with gusty winds and periods of heavy
rain. Moore|
UPDATE Issued at 844 PM MDT Wed May 10 2023
Updated forecast package for issuance of Winter Weather Advisory
for 4-10 inches of snow and gusty winds across zones 58 and
60...higher terrain of lake and Chaffee counties. Moore
UPDATE Issued at 750 PM MDT Wed May 10 2023
Updated forecast database for cancellation of Red Flag Warning for
the San Luis Valley, as well as portions of the Severe Watch
across the plains. Incorporated latest obs data. Moore
UPDATE Issued at 628 PM MDT Wed May 10 2023
Storms have waned over the I-25 corridor, and the Tornado Watch
for El Paso and Teller Counties has been canceled. The previous
Severe Thunderstorm Watch is still valid until 10 PM.
Showers and thunderstorms will still be possible across the area,
especially for our eastern plains. Heavy rain, hail, gusty winds,
and frequent lightning are all possible. An isolated tornado
cannot be ruled out entirely.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 355 PM MDT Wed May 10 2023
Key Messages:
1) Strong to severe storms across southeast Colorado this evening.
2) Another round of showers and storms spreading across south
central and southeast Colorado later tonight through the day
Thursday.
3) Locally heavy rainfall tonight and through the day Thursday
with light to moderate snow accumulations across the highest peaks.
Current water vapor imagery and upper air analysis is indicating
a compact upper low across east central Arizona this afternoon with
diffluent southerly flow across southern Colorado at this time. At the
surface east to southeast low level flow has kept low level moisture
in place across the plains this afternoon, with SPC meso-analysis
indicating SB CAPE of 1000-2000 j/kg at this time. This in conjunction
with the strong southerly flow aloft, has bulk shear of 40-50kts in
place, supporting severe thunderstorm development across the region
with a Tornado Watch in place through 9 pm across the Pikes Peak
region, and a Severe Thunderstorm Watch in place until 10 pm across
the rest of southeast Colorado.
Tonight and Tomorrow...Models indicate the upper low continuing to
lift north and east across north central New Mexico tonight and
into southeastern Colorado by mid Thursday morning before continuing
into northeastern Colorado Thursday evening. This will keep the
threat of severe storms across across the southeast Plains through
the evening, with the best shears expected along and north of the
Highway 50 Corridor.
A second round of showers and storms associated with the deformation
band as the upper low rotates up across area overnight, with showers
and storms developing and lifting out across the southeast mts and
plains after midnight, which continues to lift north and east through
the morning with wrap around precipitation then spreading south and
west across the Pikes Peak region and southeast mts through the
afternoon. Higher res models indicating the potential for stronger
to severe storms across the plains with MU CAPE of 1000-1500 j/kg
and strong shear continuing as the vertically stacked system lifts
out across southeast Colorado. In addition, locally heavy rainfall
will be possible as this system slowly lifts out across the plains,
with an area of concern being in the Pikes Peak region with southeast
upslope flow continuing through the morning. Light to moderate snow
accumulations 2 to 6 inches are also expected across the highest
peaks through the day on Thursday, however with the greatest amounts
being at or above 12K feet, will not issue any highlights at this time.
.LONG TERM...(Thursday night through Wednesday)
Issued at 355 PM MDT Wed May 10 2023
Key messages:
1) There will be numerous showers and thunderstorms over portions of
southeast Colorado Thursday night through Friday morning. Some snow
will be possible over the highest elevations.
2) Developing showers and thunderstorms in the afternoon on Friday
will occur mainly over the higher terrain and I-25 corridor, but
will also be possible over the eastern plains.
3) Some lingering showers and thunderstorms will be over portions of
the region Saturday morning, then become more widely scattered later
in the day.
4) PM scattered showers and thunderstorms over the higher terrain,
and more isolated over the plains, will be possible again on Sunday
through Wednesday.
6) Overall temperature trend will be cooler than average through the
next week with the coolest temperatures this weekend.
Detailed discussion:
Thursday night through Friday...
As a low pressure center associated with an exiting major shortwave
trough continues to move out of the area, there will be some wrap
around moisture with a sufficient amount of dynamic forcing and
moderate instability to allow for some showers and thunderstorms to
continue late Thursday evening and through the night into Friday
morning. Even with having a dry bias, the HRRR keeps a continuous
low level moisture feed out of the north along the I-25 corridor and
over the Palmer Divide area well into the morning hours on Friday,
even more so than the NAMNest. Some of the other higher resolution
model guidance also suggests higher amounts of QPF further south and
east over the lower Arkansas River Valley, although being that the
surface winds will be downsloping from the northwest, confidence of
this occurring is lower. Showers will likely linger over the eastern
plains and perhaps even a rumble of thunder, through the late
morning hours, and then should move off further to the east and out
of the CWA. Modified temperatures due to cloud cover and higher
level dewpoints at the surface will allow for temperatures to
steadily drop ito the mid 40s over the plains as cooler air is
advected in from the north. For high country, temperatures will cool
into the mid 20s to upper 30s for most locations.
Recycled moisture in the mid levels, along with a deepening mid
level wave developing into an upper level cut-off low to the west
over Utah will allow for some thunderstorms to develop over the
higher terrain later in the afternoon on Friday. At this time, the
Canadian model appears to be more of the outlier of having the
position of this upper level low further to the south over northern
Arizona. Some of the convection will move off over into the adjacent
plains, although given the movement of the storms primarily towards
the north, will likely not make it much further east than the I-25
corridor. As the low establishes itself, the mid-level steering flow
will take the movement of cells a little more towards the northwest
by late in the evening on Friday. Southeasterly winds will bring
some warmer temperatures in over the far southeastern plains,
otherwise it will be relatively cooler and below the seasonal
average for most locations for highs on Friday.
Saturday through Sunday...
All of the models do have the upper level low to the west
retrograding back towards the northwest. Depending on which model
resolves this feature better will determine how much instability and
moisture is advected up from the south over the area. If the
Canadian does verify with the low being a little further to the
south, there will be a better plume of mid-level moisture over the
region and likely a better chance of more widely scattered afternoon
showers and thunderstorms. Both of the ECMWF and Canadian also
depicts a developing mid level wave over western Texas that will
move up over the region throughout the course of the weekend and
greatly enhance moisture will higher instability and more numerous
showers and thunderstorms by Sunday. If this model verifies, this
will also keep temperatures much cooler with mostly overcast skies.
The GFS is the driest of all the models and becomes the outlier by
later in the weekend, with very little in the way of precip on
Sunday, and more confined to only the mountains.
Monday through Wednesday...
The deterministic models become much more diverse in terms of
solutions by this period in the forecast. The position of upper
level troughs and ridges are much more inconsistent. There will
still be some recycled mid level moisture over the region to provide
orographically induce convection over the higher terrain during the
afternoon hours. Depending on what the outcome is of the mid level
flow, some of these thunderstorms could also impact portions of the
plains by later in the day for all three days, yet it is still too
far out for there to be any certainty at this time. With an overall
ridge to the west and trough to the east showing up in the
ensembles, the overall trend is to keep temperatures on the slightly
cooler side, with only a slight rebound in temperatures towards the
mid part of next week. -Stewey
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 355 PM MDT Wed May 10 2023
Mainly VFR conditions expected at ALS over the next 24 hours,
with gusty southerly up to 40kts through the afternoon and early
evening possibly leading to reduced vis in blowing dust. Upper
low to pass just southeast overnight, with a low potential for
a few showers mainly east of the terminal, before breezy west to
northwest winds develop at the tale end of this taf period.
Mainly VFR conditions expected at COS and PUB with the threat of
severe thunderstorms developing along and north of the highway
50 Corridor this afternoon and evening. Best chances of storms
affecting the terminals will be at COS, with hail and strong
outflow wind gusts possible. A brief lull in storm activity
for the evening, with the potential for a second round of
thunderstorms possible after midnight and continue through
the tale end of this taf period.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MDT Thursday night for
COZ058-060.
&&
$$
UPDATE...MOORE
SHORT TERM...MW
LONG TERM...STEWARD
AVIATION...MW