Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/23/23
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
909 PM CDT Mon May 22 2023
.UPDATE...
Issued at 907 PM CDT Mon May 22 2023
Some weak shower and thunderstorm activity that developed over the
past couple of hours over eastern Spink county has now dissipated.
With the loss of daytime heating, do not expect any additional
development. No changes made to winds or temperatures at this
time.
&&
.SHORT TERM...(This Evening through Tuesday Night)
Issued at 211 PM CDT Mon May 22 2023
Smoke, pcpn chances and temperatures remain the biggest challenges
for the short term. Per current sat pix, elevated smoke continues to
pretty much cover the entire Northern Plains. The latest RAP data
suggests this will likely occur at least through Tuesday. The bigger
if is whether or not the smoke gets thick enough in the LL to cause
vsby reductions. Here the RAP still highlights the western Dakotas
into the overnight hours. For Tuesday am not confident in the amount
of LL smoke, so will leave out of the grids for now. For this
evening will continue mention of spkls. Soundings indicate elevated
CAPE late this afternoon and evening, but moisture is pretty scant.
An isolated shower/storm isn`t entirely out of the question. For
Tuesday and Tuesday night a back-doorish looking front will slide
toward the northern/ne CWA. This system is expected to stall out
near the SD/ND border area. A few showers/storms are possible near
this boundary, particularly late afternoon/night across far northern
SD. Temperatures will remain warmer than normal for the period as
H850 temps continue in the 15-20C range.
.LONG TERM...(Wednesday through Monday)
Issued at 211 PM CDT Mon May 22 2023
An unsettled blocky weather pattern continues for the long term with
ongoing warm temperatures. GEFS/ENS ens agree on the amplified ridge
with the crest well into Canada and the Northern Plains under the
ridge Wednesday morning. At the same time, a high pressure system
will be to our northeast. This ridge will become more positive
tilted as it pushes east. This is due to a low pressure system over
western Canada/Pacific Northwest along with the troughing pattern
over the western US. This low will push north and reattach to the
main flow well north to us in Canada. By the end of the week, this
deep trough remains fairly stationary over the western US into the
weekend. This will provide southerly/southwesterly winds aloft
Thursday through the weekend. With this setup, several shortwave
pulses will move northeastward along the right side of the trough,
creating this unsettled weather. The shortwave for the end of the
week looks to affect more western SD/NE and Rockies area. More of
the shortwave energy will move east over our area for the weekend.
Cluster ensembles are in good agreement with location and intensity
of this trough/ridge setup and the split flow pattern for day 3/4.
Onward, clusters disagree on the ridge/trough intensity. The good
news is once our winds aloft turn southerly/southwesterly, this will
help alleviate the smoke aloft! Gusty winds (up to 35-40kts) returns
to the area Wednesday/Thursday afternoons on the backside of a high
and in between the low causing steeper pressure gradients.
Looking down at the surface, ensembles plus deterministic agree on a
surface low and trough, but timing is still off a bit between the
models. We really see the CWA in the warm sector between the warm
and cold fronts next weekend into Monday. Most of the action stays
to our west Wednesday and models have backed off on the eastward
movement. As this low moves east, spotty chances of pops (15-35%)
periodically for Thursday west of the Missouri and a gradual
increase eastward Friday into the weekend, each afternoon per
NBM/ECMWF Ens. ECMWF/GFS ensembles indicate PWAT>1 inch increases
Friday-Saturday with 80-100% west of MO river to 20-90% east of
Missouri river. CIPS Prob Severe Day 5-8 really keeps most of the
severe chances out of the CWA with 10% prob mostly in Rapid City WFO
area being hail the main concern. ECMWF/GEFS prob of CAPE>1000 is
between 10-40% east of the Mo and up to 60% west river
Wednesday/Thurs evening. Even looking into the weekend, CAPE and
bulk shear values are not too impressive over the area. For example
GFS MUcape up to 1500 which creeps into the area Friday-Sunday
afternoons over the CWA. Better chances for higher CAPE look to
occur early next week.
With dewpoints increasing on Friday-weekend into the 50s and maybe
into the lower 60s, along with lift from the boundaries, and some
CAPE, thunderstorms are possible. No organized severe weather
expected at this point due to the lack of instability. However,
isolated severe could be possible if a few storms extend upward
enough for some hail/gusty winds.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 623 PM CDT Mon May 22 2023
Terminals KABR,KATY,KPIR,KMBG
VFR conditions will prevail across the area tonight and through
the day Tuesday. Elevated wildfire smoke from Canada will remain
over the region through the TAF period.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Parkin
SHORT TERM...TDK
LONG TERM...MMM
AVIATION...Parkin
Area Forecast Discussion
National Weather Service La Crosse WI
1005 PM CDT Mon May 22 2023
.DISCUSSION...(This evening through Monday)
Issued at 246 PM CDT Mon May 22 2023
Key Messages:
- Hazy skies expected again tomorrow across portions of the
forecast area.
- Low humidity is the biggest concern in the extended forecast with
multiple days of very dry air in place.
- Forecast continues to trend dry through Sunday with no clear
signal of when precipitation will return.
HAZY SKIES CONTINUE:
The RAP smoke model continues to show the presence of smoke aloft
over most of the forecast area through tomorrow night. The
concentration of smoke in the vertical column is forecast to slowly
decrease over time, but some obstruction is expected to continue.
WARM AND DRY THROUGH THE WEEKEND:
A longwave ridge amplifies over the central CONUS this week bringing
a pattern of high pressure to the region. This will lead to light
winds, warm temperatures, and low relative humidities. Wednesday is
the exception with an 850mb temperature gradient setting up
somewhere across the forecast area from a trough passing by to the
northeast.
An early look at model soundings for later in the week shows a very
dry layer of air above the surface. This dry air will mix down to
the surface, especially during the afternoon hours. As a result,
minimum relative humidity values could bottom out in the teens and
low 20s. Light winds will help mitigate the fire risk some and most
places are further along in the green-up process, but with the dry
air lack of recent rainfall fire conditions could become elevated.
In previous forecasts there was a question about precipitation over
the Memorial Day weekend, but the most recent deterministic and
ensemble guidance have trended drier with upper-level ridging
holding in place.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1005 PM CDT Mon May 22 2023
CIGS: smoke from Canadian skies will continue to make for milky
skies through Tue. Could see a few afternoon cu. Will continue to
cover smoke with SCT250. Models then point to a backdoor front
slipping in Wed morning, potentially bringing in a few hour period
of lower VFR cigs.
WX/vsby: some potential for MVFR FU vsbys Tue, but not high enough
to include in the forecast.
WINDS: staying light, mostly from the south.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...KAA
AVIATION.....Rieck
AREA FORECAST DISCUSSION
National Weather Service Bismarck ND
914 PM CDT Mon May 22 2023
.UPDATE...
Issued at 914 PM CDT Mon May 22 2023
Various observations across the forecast area continue suggesting
near-surface smoke is reducing visibility to between 6 and 9
miles in some locations. Otherwise, a quiet evening continues
before shower and thunderstorm chances work into the area
Tuesday.
UPDATE Issued at 637 PM CDT Mon May 22 2023
Smokey conditions continue, especially in the west where
visibility has dropped to as low as 5 miles from near-surface
smoke. The only other update at this time was to remove sprinkles
in the south central. Any diurnal cu is east of the forecast area
and is not producing any radar returns. With lots of dry air
remaining off the surface and dewpoint depressions in excess of 30
degrees, it would be extremely difficult for any unorganized
precipitation to reach the ground at this point in time.
&&
.SHORT TERM...(This Evening through Tuesday)
Issued at 259 PM CDT Mon May 22 2023
An upper level ridge over the Northern Rockies continues to bring
weak northwest flow into the Northern Plains. Therefore, elevated
smoke from the fires up in Canada continues to move through the
region resulting in hazy skies. Near surface smoke has cleared out
of western and central North Dakota for the moment. The RAP Near-
Surface Smoke does increase smoke coverage across the west this
evening as an inversion sets up. Therefore, patchy smoke remains
in the grids through 12Z Tuesday. Southeasterly surface winds
could limit near surface smoke across central North Dakota tonight
maybe keeping smoke out over the west.
The upper level ridge is going to settle over the Northern Plains
tomorrow leading to temperatures in the mid 80s to lower 90s. The
low level thermal ridge will span across south central North
Dakota where the warmest temperatures are expected. A warm front
will lift through the region tomorrow causing thunderstorms out
west. A lack of shear and the storm motion will result in slow
moving storms that could cause localized flooding. In addition
PWATs are going to be over an inch increasing likelihood of heavy
rain. The CSU severe weather machine learning has highlighted a
chance for hail across much of North Dakota. Due to the lack of
shear storms will pulse up and remain unorganized making the hail
potential low. A back door cold front will move in tomorrow
evening bringing breezy winds and maybe initiating convection in
the evening.
.LONG TERM...(Tuesday Night through Monday)
Issued at 259 PM CDT Mon May 22 2023
An unsettled weather pattern will return Wednesday through the end
of the week.
Troughing across Western CONUS will continue to bring in
southwesterly flow aloft to the Northern Plains. A back door cold
front could keep initiating storms Wednesday morning. Much of
Wednesday the area will remain dry with a few showers and
spattered around. Thursday thunderstorm chances increase as
another short wave moves across the western half of the state.
PWATs are still forecast to remain above an inch continuing the
heavy rain potential for western and central North Dakota. Another
wave is forecast to move through the state Friday evening through
Saturday morning. The active pattern will continue into the
weekend with increased chances out west. Temperatures are forecast
to sit slightly above normal in the upper 70s to lower 80s for
the remainder of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 637 PM CDT Mon May 22 2023
Near-surface smoke is reducing visibility to as low as 5 SM in
western North Dakota. Generally speaking though, visibility
remains at 6 SM or greater. Therefore, while MVFR visibility from
smoke is possible at KDIK or KXWA, VFR visibility is expected to
prevail. A couple showers or thunderstorms may develop in western
North Dakota late tonight and into the morning hours.
Precipitation chances then increase mid to late afternoon Tuesday.
For the most part, left precipitation chances out of TAFs for now
due to uncertainty in both timing and location of any shower and
thunderstorm development.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Telken
SHORT TERM...Johnson
LONG TERM...Johnson
AVIATION...Telken
Area Forecast Discussion
National Weather Service Denver/Boulder CO
800 PM MDT Mon May 22 2023
.UPDATE...
Issued at 800 PM MDT Mon May 22 2023
Scattered showers and thunderstorms are expected to linger another
hour or two before they dissipate for the night. Small hail, gusty
outflow winds, and brief heavy rain have accompanied the strongest
storms. Going forecast is on track and don`t anticipate any big
changes.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 245 PM MDT Mon May 22 2023
Weak convection continues to slowly develop, with limited strength
and organization limited by the lack of any wind shear. We did get
a few storms out around Limon earlier than expected as dew points
rose into the 50s. There is a boundary moving northeast from that
area that could generate more storms further west, but they should
continue to be disorganized and the strength should be limited by
cloud cover. We just added isolated storms from Lincoln county
west to Douglas county through this evening.
For Tuesday, there`s very slight warming and also probably a
little less smoke, so slightly warmer temperatures look good.
There`s still very little wind through the depth of the
atmosphere, but probably a little tendency towards and eastward
drift later in the day. We trimmed back PoPs a little in the
gradient east of the mountains again. There may be a better chance
of something drifting off the mountains in the evening.
.LONG TERM...(Tuesday night through Monday)
Issued at 245 PM MDT Mon May 22 2023
Key Messages:
1) Gradual improvement in smoke Wednesday
2) Increasing chances & coverage of showers and storms by Weds
3) Potential for locally heavy rainfall and severe storms later
this week
Into Wednesday, the upper level pattern transitions to SW flow
aloft as an amplified 500 mb trough moves into the western CONUS.
As the previous ridge pushes eastward, ensemble guidance
indicates a plume of anomalous moisture (~145% of normal) moving
into Colorado. An embedded shortwave in the flow will provide some
upper level support for ascent thus helping initiate storms
across the region in the afternoon after instability develops.
MLCAPE builds with values in the 600-1100 J/kg range. With
sufficient shear around (0-6 km bulk shear 20-30kts), a couple of
strong storms will be supported, potentially even severe. These
stronger storms may be capable of producing small hail, gusty
outflow winds and localized heavy rainfall.
More numerous showers and storms Thursday and Friday. In a typical
pattern, the trough to the west would have moved across Colorado;
however, a blocking pattern will likely slow this progression down
as an upper low retrogrades back into the Tennessee Valley. This
will amplify the ridge centered east of Colorado. Above normal
moisture continues to shift across the mountains and into the
plains. Within the SW flow aloft there will be bulk shear values 20-
30 kts with a good amount of instability forming ahead of a few
embedded waves with MLCAPE 1000-2000 J/kg. This will support
afternoon showers and thunderstorms with a chance for severe storms
as well. Given the anomalous moisture in place and fairly weak flow
aloft, slower moving storms are possible and with the capability of
producing locally heavy rainfall.
Into the weekend, confidence in the upper level pattern decreases
given the uncertainty in the progression/evolution of the blocking
pattern. WPC cluster analysis shows some eastward progression of the
ridge by Sunday which would push the trough across Colorado.
Overall, looking at an unsettled pattern with scattered to numerous
showers and thunderstorms across the region each day. For much of
the long term period, highs stay close to normal across the urban
corridor/plains in the mid to upper 70s.
Although this pattern calls for the threat of severe storms and
local heavy rainfall/flash flooding potential, flow aloft should
gradually push the wildfire smoke out after mid-week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 535 PM MDT Mon May 22 2023
Main aviation issue will continue to be smoke from the wildfires
in Canada. Visibility should stay above 5sm through Tuesday, but
enough smoke should be around to impact arrival slant visibility
at KDEN. The southeast winds will increase a little around 02Z as
outflow winds arrive from earlier storms that were off to the
southeast. Winds then settle south to southwest direction around
06Z. Weak winds to prevail Tuesday morning and then become light
out of the northeast around 18Z.
For Tuesday afternoon/evening, the HRRR model shows westerly
outflow winds from convection moving through around 00Z and
triggering a few storms. This is the only model showing convection
near DEN, so will leave the mention of thunder out of the TAFs
for now.
&&
.HYDROLOGY...
Issued at 245 PM MDT Mon May 22 2023
For this evening and Tuesday afternoon, scattered slow moving
storms are expected over the mountains. The strength and
organization of the storms will keep the burn area flood threat
low, but if one of the heavier storms does occur over a sensitive
area there could be some flooding.
There is a trend of increasing moisture, shower/storm coverage and
strength mid through late week. Flow aloft will be on the lower
side, supporting slower moving storms. Above normal precipitable
water values will support storms capable of producing localized
heavy rainfall. As a result, there will be at least a limited threat
for flash flooding over the burn areas each day with even a threat
over portions of the plains towards the latter end of the work week.
An elevated threat is becoming likely over the burn areas Wednesday
given slow storm motions and above normal moisture. For the
remainder of the week, at least a limited threat with more
confidence in an elevated risk for Cameron Peak Thursday and Friday.
A lot of this will depend on the how the upper level pattern
progresses. If it is slower to progress eastward and weaker flow
remains, there may be an extended elevated threat through the
weekend.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Meier
SHORT TERM...Gimmestad
LONG TERM...Mensch
AVIATION...Meier
HYDROLOGY...Gimmestad/Mensch
Area Forecast Discussion
National Weather Service Des Moines IA
1027 PM CDT Mon May 22 2023
...Updated for the 06z Aviation Discussion...
.DISCUSSION.../Tonight through Monday/
Issued at 242 PM CDT Mon May 22 2023
Key messaging highlights:
* Little change anticipated through the week
* Mainly dry and warm through at least the weekend
Our current weak northwest flow pattern will give way to central
CONUS upper level ridging over the next few days keeping our
weather warm and dry through at least the weekend. The ridging
will be persistent with little sign of breaking down until
possibly early next week. A weak, compact PV anomaly continues to
drift across IA this afternoon, but with limited forcing or
moisture the result has been nothing beyond some mid/high level
cloudiness with higher based cumulus underneath.
The small short wave should drift into MO tonight with two
features of note into tomorrow, upper level ridging well through
the Plains into Canada, and a progressive long wave trough
clipping the Great Lakes. The former feature will keep our
forecast dry for at least several days, but the latter will drive
an airmass change, especially in terms of moisture. The trough
passage will produce a noted backdoor cool front Wed night into
Thursday. Temps will drop back some, but still remain in the 70s
and just above normal. The most sensible change will be
significant drying through the entire column late week. Dewpoints
should dip into the 30s to end the work week, and precipitable
water values may reach anomalously low values for late May per
NAEFS and EPS percentiles with plenty of sunshine. A bit of the
guidance suggests light precip potential with the backdoor front,
but confidence is certainly low and the forecast remains dry.
Regarding smoke, satellite imagery shows the highest
concentrations north and west of IA, and the latest RAP extension
(15Z) suggests this should remain mainly north of IA. There are
higher concentrations drifting northward from MO in the model,
but this appears to be over-initialized.
The only real forecast question will the re-introduction of
precip. The latest deterministic and ensemble guidance continues
to be less bullish, lowering PoPs and/or pushing things back in
time. A pseudo Omega block, some form of Appalachian or OH Valley
low and ridging topping it to the north, will follow the trough
and keep our dry pattern locked in through at least the weekend.
Low level trajectories will struggle to move beyond SSE keeping
any appreciable low level moisture return at bay. Ensemble
guidance does suggest some potential for better moisture and the
far eastern fringe of the weak Plains southwest flow to barely
nudge enough to the MO Valley to get some precip here late in the
period. Would not be surprised to see the late holiday weekend
chances diminish with time however if present trends continue.
Recent GEFS/EPS guidance yet to be ingested in the NBM suggests
the holiday weekend will mainly be dry.
&&
.AVIATION.../For the 06Z TAFS through 06Z Tuesday night/
Issued at 1027 PM CDT Mon May 22 2023
Few changes needed to going forecast. VFR conditions expected with
winds generally below 10kts. Sct to broken mid level cu expected
aft 15-17z with possible more widespread deck of 150-180kft aft
01z. Otherwise, smoke aloft and sfc restrictions not expected.
/rev
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Small
AVIATION...REV
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Mon May 22 2023
.AVIATION...
Light southeast to south flow around high pressure will maintain dry
conditions. Wind speeds will remain generally under 10 knots with a
gradual veering to a more southerly direction into Tuesday night.
DTW THRESHOLD PROBABILITIES...
* None.
&&
.PREV DISCUSSION...
Issued at 312 PM EDT Mon May 22 2023
DISCUSSION...
Enhanced boundary layer convergence extending from the Tri Cities
down to Port Huron is shown in the recent sfc observations. The
moisture depth is quite shallow, which will likely inhibit any
evening convection. The most recent RAP solution for vertically
integrated smoke suggests the high altitude smoke overhead will
remain quite thick through the night, thinning toward daybreak. The
weak gradient flow and relatively dry air in the boundary layer will
still offer enough radiational cooling opportunity to support min
temps in the 50s.
Subtle mid level height rises and a lack of moisture will ensure dry
conditions on Tuesday. Sfc high pressure will become centered along
the coast of New England with light southerly return flow developing
over Se Mi, driving 925MB temps up toward +19C. Model soundings show
mixing depths up to 6-7k feet which will support afternoon highs
into the low 80s.
Amplification of a mid level trough axis moving from northern
Ontario into upstate New York/Quebec Tues night into Wednesday will
drive a cold front south across the Great Lakes region. Deep layer
FGEN will support widespread showers as this system enters the
northern Great Lakes Tuesday night. The upper jet support and region
of mid level height falls will track largely east of Lake Huron Tues
night/Wednesday. This will result in a weakening of the deep layer
FGEN as the front moves south across the forecast area Wed morning.
Per the 12Z model suite, moisture depth and forcing look adequate to
support a chance of showers early Wed morning across the thumb and
Saginaw Valley. The FGEN is then forecast to quickly fall apart,
leaving just a low level and shallow frontal circulation by the time
the front passes south of metro Detroit. There will be a respectable
push of cold air in the wake of this front, modified by the cold
waters of Lake Huron. 925mb temps are forecast to plunge into the
single digits on Wednesday. Even with a late May sun angle, high
temps will most likely occur Wed morning, with afternoon temps likely
falling/holding in the 50s or low 60s.
The strength of the subsidence in the wake of this mid level wave
will allow strong high pressure to expand across the northern Great
Lakes by Thursday. A cool and very dry (continental polar airmass)
will reside across the area through the end of the work week. Medium
range model solutions are suggesting a rex block becoming
established by this weekend, with Lower Mi under the ridge. This
will ensure continued dry conditions. Modification of the airmass
will allow warmer temperatures to return, leading to a warm and dry
holiday weekend.
MARINE...
A washed out cold front retreats back toward Canada tonight as
mild/weak return flow off eastern high pressure seeps into the
central Great Lakes tonight and into Tuesday providing favorable
marine conditions. Benign weather wanes Tuesday night as a cold
front tracks due south along the long-axis of Lake Huron. It will
take some time before the upper level trough forces the front across
the southern waterways Wednesday, but expect prevailing winds to
become uniform in the frontal wake, organizing out of the north
with a modest uptick in speeds as the gradient responds. Potential
continues to increase regarding the development of Small Craft
Advisory criteria waves and gusts, especially for the Huron
nearshores, Wednesday afternoon and early evening. Ridging then
reestablishes over north-central CONUS late week supporting
diminished wind/wave response into the weekend.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....DG
DISCUSSION...SC
MARINE.......KGK
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
640 PM CDT Mon May 22 2023
...Aviation Update...
.DISCUSSION...(This evening through Monday)
Issued at 355 PM CDT Mon May 22 2023
Key Messages:
* Mainly dry with mild temperatures through midweek.
* Better chances for showers and thunderstorms may arrive Thursday
and continue into the weekend. However, latest model trends are
for majority of activity to remain W and SW of the Tri Cities -
over/along the High Plains. The latest forecast for the holiday
weekend likely sounds worse/wetter than what will happen, and
risk for organized severe weather appears low at this time.
* Smoke for Canadian fires will impact the region again this week,
but latest indications are that it should remain mostly elevated
and not be as impactful at the surface as last week.
Forecast Details:
Latest WV and upper air analysis reveals more of a summer-like,
split flow/weak pattern in place across the CONUS relative to a
"normal" mid-late May pattern. The primary belt of westerlies runs
from a trough in the Pac NW then well N into Canada due to strong
upper ridging across the N Plains, with any other subtle
enhancements due to small/compact perturbations and/or vorticity
maxima. One such vort max can be seen clearly on regional sat/rad
over SW KS. Another vort max is apparent on WV along IA/MO border.
Subsidence behind this wave is making it tough for more than high
clouds to advect northward from the KS wave. As a result, appears
most convective chcs tied to this wave will remain S/SW of the
CWA. However, did maintain some slgt chc PoPs in our KS zones due
to band of agitated CU beneath a swath of implied weak ascent
denoted by cirrus. This probably won`t develop into anything
given aforementioned battle with incr mid level dry
air/subsidence, but if we do get anything this eve, this is where
it would be. CAPE/shear are far too limited for anything severe.
Other than the KS vort max "washing out" and drifting SE, the
overall pattern changes little Tue into Wed as upper ridging
dominates majority of central/northern Plains into Upper MS Valley
and Great Lakes region. Thus, expect similar conditions to this
aftn to persist - highs in the upper 70s to 80s, lows in the 50s,
and just some aftn fair wx cumulus. Only modest S/SE sfc wind
should make for very pleasant wx by mid/late May standards. Fires
continue to burn over portions of Canada (quite intensely, in
spots) and generate plentiful smoke. Fortunately, latest RAP
forecast smoke output continues to indicate that while smoke will
be noticeable visually next couple of days (at least), the impacts
at the surface to visibility and health look to be minimal...or at
least significantly less than compared to last week (Thu).
Pattern could trend "more active" as we head into the upcoming
Memorial Day holiday weekend...however want to emphasize that the
weekend does not appear to be a "washout" as there will be plenty
of dry time and current forecast may sound worse than what will
really occur. Overall predictability on day-to-day
details/features is fairly low - owing to aforementioned summer-
like pattern and weak mid to upper flow - but it appears that
convection will be a daily occurrence over the High Plains where
there is a favorable combination of E/SE upslope sfc flow and weak
capping. This type of pattern tends to favor diurnally driven
convection that peaks in coverage/intensity W of our CWA, but can
occasionally still make it in during the late eve and overnight
hrs, particularly with the help of a robust MCV. These features
are notoriously difficult to predict beyond 12-18 hrs, but would
tend to favor W/SW/S zones given placement/proximity of main
instability axis. And even if robust convection develops over the
High Plains, progged weak 0-3km and 0-6km shear vectors argue for
lack of organization and declining intensity with eastern extent
during the eve/night hours. Further illustrating this point is
distinct trend in last few deterministic EC runs of placing sharp
drop-off in QPF from W to E across KS/NE...such that NE/E zones
could see very little to no appreciable QPF through the weekend.
Not good for drought stricken areas locally, but at least those
just S/SW of here should see some much need relief from ongoing
drought in those areas. Perhaps this could pave the way for better
moisture return later in the spring/early summer.
Otherwise, temperatures look to remain quite steady through the
weekend and not too dissimilar to the next couple of days.
Perhaps additional cloud cover over the weekend could knock a few
deg off, but not expecting substantial low level cloud cover at
this time.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 637 PM CDT Mon May 22 2023
VFR conditions persist at both terminals through the forecast
period. Expect a few mid-level clouds this evening and into
tonight, with ceilings expected to lower, but remain at VFR levels
around midnight. Southeasterly winds 5-10kts this afternoon become
southerly tonight. Southerly winds persist through the rest of the
TAF period, increasing to around 10-15kts by mid-morning. There
will be a chance of a few thunderstorms across north central
Kansas tomorrow afternoon, but these are not expected to reach
impact either TAF site.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...Thies
AVIATION...Wekesser
Area Forecast Discussion
National Weather Service Grand Junction CO
545 PM MDT Mon May 22 2023
.SHORT TERM...(Tonight through Tuesday night)
Issued at 235 PM MDT Mon May 22 2023
Rinse and repeat story today as widespread, anomalously high
moisture has led to another round of scattered to numerous showers
and thunderstorms. Coverage has been enhanced by the passage of a
weak, midlevel low pressure system across the southern tier of our
forecast area this afternoon. Dynamics associated with said low
has led to some slightly stronger storms across the Four Corners
region with SBCAPE sitting near 1000 J/kg. However, weak shear has
prevented storms from being long-standing and, while it`s not quite
the "pop-and-drop" variety, the lifespan has been relatively short.
Precipitable water (PWAT) values remain elevated at 150 to 200%
of normal across the region with localized areas approaching 250%
of the norm in southwest Colorado. As has been the trend the last
several days, brief heavy rain will be the primary threat from any
stronger storms with secondary threats of gusty winds to 40 mph
or less as well as small hail. The midlevel wave will exit east of
the Divide tonight, seeing convection largely dissipate by 9 PM,
though the HRRR in particular is pinging on some lingering showers
over the central mountains through midnight or so.
Tuesday will see the upper level trough centered over the Pacific
Northwest elongate along the West Coast. Meanwhile, a ridge of
high pressure will build over the Great Plains. As a result, look
for flow aloft across eastern Utah and western Colorado to shift
to the southwest on Tuesday. Additional moisture will advect into
the region ahead of the trough in this pattern shift, seeing PWATs
reach 180 to 200% of normal (or more) by the afternoon. A weak
ripple in the flow also looks to quickly slide overhead across
eastern Utah and far western Colorado on Tuesday. The uptick in
moisture paired with weak support from this shortwave will result
in more widespread showers and thunderstorms Tuesday afternoon and
evening. Given the earlier days of moderate to heavy rain, most
notably down south, localized runoff concerns will be possible if
any stronger convective cells develop. Drier air will begin to
infiltrate the Four Corners late Tuesday evening and overnight as
the Pacific trough dives farther south towards Baja. The originally
projected cutoff low over California is not as favored in the
latest models but, regardless, dry air will spread northeast in
the southwest flow. In response, showers over the southern zones
will come to an end earlier than previous evenings with activity
gradually tapering off elsewhere into the midnight hour. Partly to
mostly clouds skies will persist into Wednesday.
High temperatures on Tuesday will moderate by a couple of degrees
compared to today`s values. Overnight lows both tonight and Tuesday
night will follow suit. Either way, low temperatures will sit 4
to 8 degrees above normal while Tuesday`s highs will trend 3 to 6
degrees above normal across eastern Utah and northwest and west-
central Colorado. The southern zones will sit a couple degrees
below normal due to increased clouds and showers.
.LONG TERM...(Wednesday through Monday)
Issued at 235 PM MDT Mon May 22 2023
Models still struggle to handle the complex weather pattern with
little jet support to steer the systems, so there is low confidence
in the extended forecast. That being said, the latest runs have a
low over eastern Montana with deep troughing down into the Great
Basin, a high over the Northern Plains to the Great Lakes and a
low over the southeastern US in a weak omega block that hangs
around into Friday before the Arctic jet drops down into the
Pacific Northwest to eject the Montana low and Northern Plains
high east, setting up a longwave trough across the Western US.
With troughing in the Great Basin and ridging over the Central
Plains, look for breezy southwest winds Tuesday, peaking Wednesday
and tapering off going into the weekend pulling a drier, near
seasonal normal airmass up from the southwest. Through the weekend
into early next week, a couple shortwave systems track across Utah
and Western Colorado with a return of a moister airmass and
unsettled weather to the Utah and Colorado mountains.
The weather across the region will have continued widespread afternoon
and evening showers and thunderstorms across the higher elevations
of Colorado and northern Utah Wednesday. Beyond Wednesday, the
dry air intrusion will reduce the convective activity to isolated
to scattered showers and thunderstorms over the northern Utah
mountains, and along and east of the Divide in Colorado. Sunday
into early next week will see scattered showers and thunderstorms
slowly creep back south and west across the region as the longwave
trough allows shortwave systems to pass over the region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 540 PM MDT Mon May 22 2023
Scattered showers and thunderstorms will persist this evening.
Storms will fire on the terrain and drift into adjacent valleys.
Terminals will remain mostly VCTS with these storms. A few may
make it into the valley with a brief heavy shower and strong
outflow gust, as well as brief reduction of visibility thanks to
rainshowers. Showers will subside after sunset and quiet
conditions should prevail into tomorrow morning. This pattern is
expected to hang on another day and storms should initiate again
by lunchtime Tuesday across the region with similar impacts as
today: small hail, lightning, gusty outflows, and brief heavy
downpours.
&&
.HYDROLOGY...
Issued at 235 PM MDT Mon May 22 2023
Daily showers and thunderstorms blossoming atop mountain peaks will
continue to influence snowmelt and a limited threat for flash flooding
across saturated or impervious terrain. Stronger storms are capable
of producing periods of heavy rainfall, thus, accelerating runoff
in very localized basins. Determining which basin is still difficult
to pin point each day, so there remains that window of uncertainty
in terms of spikes in river forecasts.
However, the next system driving into the Great Basin tomorrow will
result in a shift in weather patterns through the holiday weekend.
Deep troughing over the western CONUS will set up southwest flow
upstream the Four Corners Tues night into Wed, and essentially nudge
the moist airmass overhead out of the forecast area. As a result,
this will reduce storm coverage spatially and temporally through the
latter half of the week. Flashy spikes in water levels will be
reduced in tandem, however, spring runoff season is in full
swing, and clearing skies with warm/dry southwest flow will still
efficiently melt snow via radiational processes. Forecast hydrographs
continue in an upward fashion for many of the main stems across
the Western Slope. Be sure to keep an eye on river conditions and
updated forecasts this week, especially if holiday weekend plans
involve close proximity to these swift moving channels. Campground
closures are probable, if not already in effect, as well as several
road closures due to inundated crossings or damaged roadways.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&
$$
SHORT TERM...MMS
LONG TERM...DB
AVIATION...LTB
HYDROLOGY...ERW
For this long-term forecast discussion, an active weather pattern is
still anticipated across the Tri-State Region, beginning Wednesday and
going into the holiday weekend. It wouldn`t quite be Memorial Day
around here without the threat of thunderstorms, including some strong
to severe. However, there is some uncertainty with this forecast as the
overall upper level pattern just isn`t terribly conducive to larger
thunderstorm events yet most forecast guidance continues to provide
high chances for precipitation and also the potential for heavy
rainfall for some of the forecast period. Early in the forecast period,
it is also difficult to identify the potential locations of the surface
features the storms will fire upon, so that is another point of
uncertainty...exactly where storms will fire and who will be under the
highest threat. Either way, the key message for this forecast period is
that a prolonged threat for thunderstorms, including potential severe
storms and heavy rainfall, is expected Wednesday into the holiday
weekend.
To begin, the upper level pattern should remain consistent through this
stormy time period. A large ridge of high pressure is projected to
build across the Great Plains, bordered by troughs of low pressure on
either side...one situated over the eastern third of the United States,
and the second centered along to just onshore from the Pacific Coast.
Into the weekend, the trough of low pressure slowly advances east
across the Rockies, and several spokes energy ejecting over the Plains
during that time frame. This energy, in the form of shortwave troughs,
are what will support the development of precipitation/thunderstorm
activity each afternoon and evening. One thing to note about this
entire forecast period is that the mid-level winds are fairly week,
which should limit the maximum magnitude of available wind shear each
day for storms to work with. This may limit the potential severe
weather events compared to many others observed in the month of May.
As for the surface pattern, consistency is also anticipated here.
Initially, southeast flow, bringing in warm, moist air from the Gulf of
Mexico, is expected to extend all the way to the Rockies for at least
Wednesday and perhaps Thursday as well. As the upper level low slowly
migrates east, a surface trough of low pressure should form in lee of
the Rockies. This should help bring in some drier air into the Front
Range region, which will serve to sharpen a dryline in eastern Colorado
for Friday into the weekend. There may also be a temperature
gradient/pseudo-frontal boundary for Wednesday and Thursday in the
region, likely stemming from temperature differences caused by
persistent cloud cover in some areas versus breaks in the cloud cover
further west.
Starting with Wednesday, overall it appears that the severe weather
potential may be limited to parts of eastern Colorado, or as currently
highlighted by the marginal risk issued by the Storm Prediction Center
this morning. A shortwave trough will move over the plains, but with a
surface pattern that does not contain an easily identifiable feature
for storms to fire, i.e. a dryline, it`s quite possible that this may
be one of the days where we watch storms fire on the Rockies and await
their arrival in the High Plains later that evening. Storms are
certainly possible to fire in our area within the warm sector,
especially on any thermal boundaries that form. Instability seems to be
limited, generally 750-1250 j/kg of SBCape and poor lapse rates ranging
from 5-7 C/km. Shear is also poor for most of the region, although
guidance is coming into agreement that winds should strengthen over
east central to more southeast Colorado, resulting in up to 35 kts 0-6
km bulk shear. Based on all of this, think we`ll see storms potentially
fire in the warm sector over our area, but more likely along the
Rockies, slowly moving east over the plains and possibly entering
southwest portions of the forecast area (Cheyenne County Colorado, and
Wichita and Greeley counties in Kansas). Severe weather would be
possible, although there`s always the question of how long storms will
maintain their intensity after sunset. Overall, it does appear probable
that widespread non-severe thunderstorm activity may be realized across
the area, which will help start to saturate the soils for future
thunderstorm days and potential flash flooding.
On Thursday, a more favorable setup for thunderstorm activity is
anticipated, including one that favors severe storms. Winds increase
enough at the lower and mid levels to cause shear to become relatively
impressive considering the pattern, topping out at 40kts 0-6 km bulk
shear in some guidance members. Further, a notable uptick in
instability is also anticipated with SBCape increasing to 1500-2500
j/kg for a large portion of the area, and lapse rates climbing into the
6-8 C/km range. Forecast guidance indicates there may be two areas of
storms that impact the area...the first forming right over us in the
High Plains, and the second in the form of an MCS moving into the
region later that originally formed on the Rockies. With multiple
rounds of rain and slow storm movement anticipated, the flash flooding
risk should ramp up for Thursday as well, especially if widespread rain
is received on Wednesday. One concern with Thursday`s forecast, in
addition to the previously mentioned concerns with the general pattern,
is that rising heights aloft may be realized, which means that upper
level support isn`t the best for thunderstorm initiation. This may
serve to keep thunderstorms more scattered than widespread, at least
initially until a potential MCS is able to develop.
For Friday, yet another shortwave looks to move out over the High
Plains. Further, this is the first day with some semblance of a
sharpening dryline to the west. The question remains of how much will
the environment be altered from the previous day`s storms. It does seem
like instability will build once again along the dryline, so feeling
comfortable in continuing precipitation/storm chances but wondering if
they may be currently overdone. As mentioned yesterday, it can be
difficult to get multiple days of higher-end severe storm days in a row
without a significant upper level pattern causing it, and we just don`t
have that for these potential events.
Going into the weekend, the pattern remains fairly consistent with a
dryline sharpening over eastern Colorado, serving as the focus for
storm development as shortwaves move out over the Plains. Model
differences are causing issues with the projections on instability and
wind shear, and when those would be maximized. However, that being
said, it currently appears that we no longer can expect a front moving
in from the north. Instead, any potential front would stall well to the
north, or arrive early to middle of next week, therefore no longer
being a concern for this long-term forecast period. Therefore,
confidence is growing in the surface pattern that should be
anticipated, and therefore once minor model timing/location differences
are resolved, we`ll be able to more comfortably and confidently provide
a holiday weekend severe weather outlook. For now, the key
message/takeaway for the weekend forecast is that there remains
potential for strong/severe storms and heavy rainfall throughout the
weekend, so those with plans, particularly outdoors, should keep a
close eye on the forecast and outlooks.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 531 PM MDT Mon May 22 2023
For KGLD, VFR through 06z Tuesday, then conditions drop as fog
develops. Ceilings will drop to less than OVC010 through 17z then
MVFR. Visibility in fog will range mainly 3-6sm but a period down
to 2sm or less is possible. Winds mainly south-southeast around
10kts. Light/variable possible 06z-17z Tuesday.
For KMCK, mainly VFR conditions for much of the forecast period.
Several hours of MVFR/IFR ceilings around BKN009-015 are possible
from 11z-18z Tuesday. Winds, mainly southeast around 10kts.
Light/variable possible from 02z-18z Tuesday.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...JN
SHORT TERM...076
LONG TERM...RRH
AVIATION...JN
Area Forecast Discussion
National Weather Service Marquette MI
1200 AM EDT Tue May 23 2023
.SHORT TERM...(Through tonight)
Issued at 1238 PM EDT MON MAY 22 2023
A 1028 mb surface high in southern Quebec is downstream of broad
ridging over the central CONUS today, leading to mostly clear skies
with the exception of some midlevel cu over northern Lake Superior
due to a subtle shortwave. This afternoon, the NAM 4k, WRF FV3 and
NSSL WRF have convection popping up across northern WI and the
interior of the UP, though the low level and upper levels struggle
to saturate per BUFKIT soundings and GOES-16 water vapor imagery.
With the majority of other CAMs not showing convection, limited PoPs
this afternoon to only sprinkles mentions. SPC RAP Mesoanalysis
shows 500 J/kg of SBCAPE over the central UP, so it isn`t out of the
realm of possibility if enough moisture is present and convection
initiates that some thunder is possible, but left it out of the
grids due to the high uncertainty in initiation. Sustained warm
advection in the low to mid levels will help temperatures recover
into the 70s today despite sustained smoke aloft from wildfires in
Canada. RH`s fall into the 30s and upper 20s especially across the
interior west, though sustained winds around 5 mph and gusts up to
10-15 mph should keep fire weather concerns mostly limited.
Overnight, skies should remain mostly clear besides a few clouds
over Lake Superior and the far east and the ever-present smoke,
allowing temperatures to fall to near 50. Winds over Lake Superior
do begin to increase ahead of an approaching front from the north,
but widespread PoPs do not enter the region until Tuesday.
.LONG TERM...(Tuesday through Monday)
Issued at 255 PM EDT MON MAY 22 2023
Upper air pattern consists of a 500 mb trough on the west coast, a
trough over Hudson Bay and a broad ridge over the northern and
central plains 12z Tue. The ridge amplifies over the plains 00z Thu
while troughing amplifies in the western U.S. and troughing moves
onto the east coast and the pattern changes little through 00z Fri.
Cold front moves through Tue night with a narrow band of moisture
and 850-500 mb q-vector convergence. Tue night looks to be the only
chance for rain for this forecast.
In the extended, the GFS and ECMWF shows 500 mb troughs in the
western and eastern U.S. and a ridge across the plains into the
upper Great Lakes 12z Fri. The ridge remains over the upper Great
Lakes 12z Sat with a rex block setting up 12z Sun with the ridge
still over the upper Great Lakes and a closed low in the sern U.S.
which remains into Mon. Temperatures look to be above normal for
this forecast period. One problem with temperatures though will
continue to be smoke from fires in western Canada and this could
knock temperatures down a few degrees. Will continue dry for this
forecast.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1200 AM EDT TUE MAY 23 2023
VFR will prevail thru this aftn at IWD/CMX/SAW as dry air lingers in
the lower levels. A cold front will then drop s into Upper MI late
aftn/evening, followed by low MVFR cigs. IFR is possible, mainly at
SAW where postfrontal nne winds will be more directly upsloping at
that terminal. A few -shra will also be possible after fropa at all
terminals during the evening hrs. SW to W winds ahead of the front
will shift to n to ne after fropa. The westerly winds today at CMX
will be gusty to around 20kt, and postfrontal n to ne winds will be
gusty to around 20kt at all terminals this evening. An elevated
smoke layer, probably at around 10kft, originating from forest fires
in western Canada will persist thru today.
Expect rapidly improving conditions to VFR at all terminals just
beyond this fcst period as much drier air arrives.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 255 PM EDT MON MAY 22 2023
Winds will remain below 20 knots through Tue morning. Behind a cold
front late Tue afternoon, north to northeasterly gusts at up to 25
to 30 knots Tuesday evening through Wednesday afternoon with the
highest winds mainly over the west half of Lake Superior. Ridging
settling over the area and then the lower and eastern Lakes will
keep winds below 20 knots from Thursday through the Holiday weekend.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...GS
LONG TERM...07
AVIATION...Rolfson
MARINE...07
Area Forecast Discussion
National Weather Service San Francisco CA
851 PM PDT Mon May 22 2023
...New UPDATE, MARINE...
.SYNOPSIS...
Issued at 1229 PM PDT Mon May 22 2023
Warm temperatures today inland as highs in the interior valleys
reach into the 80s. Coastal areas remain cool with stratus at the
immediate coast. Cooling starts tomorrow as an upper level trough
builds, with temperatures slightly below seasonal averages for the
end of the work week before a slight recovery for the beginning
of next week.
&&
.UPDATE...
Issued at 850 PM PDT Mon May 22 2023
The North/South pressure gradient continues to diminish, now below
6 mb heading toward below 5 mb. The ocean is once again free of
clouds west of the Sonoma Coastline, while the Monterey Bay is
under a heavy swath of stratus clouds with bases just over 600
feet. Winds remain onshore and breezy around 10 mph.
The longwave trough moves southward from the Pacific Northwest on
Tuesday and takes of residence for the better part of the week.
With it, cold air advection will help cool temperatures compared
to the weekend. With its onset on Tuesday, a very weak boundary
will pass over the Bay Area. Its strongest signal is in the NAM,
but even the most recent HRRR run shows a very, very weak tuft of
potential for rain Tuesday morning. There is still low confidence
in rain materializing, if it does it will most likely be a drizzle
or a sprinkle, and accumulations will be limited. Otherwise, the
forecast listed below will persist.
DK
&&
.SHORT TERM...
(This evening through Tuesday)
Issued at 1229 PM PDT Mon May 22 2023
Coastal stratus lingers in patches on the Marin coast and across the
coast south of Half Moon Bay, including extensive inland coverage in
the Monterey Bay region. Clearing will continue across the region
for the rest of the day, but any clearing near the immediate coast
will be short lived with stratus building once again this evening,
with stratus expected to return quite far inland overnight.
The early clearing will enhance daytime heating, and for the last
day in the foreseeable future, temperatures will reach the low to
mid 80s for the inland valleys, with the most interior areas seeing
highs close to 90 degrees. The coastal regions will see highs in the
low to mid 60s with the San Francisco Bayshore and higher elevations
reaching into the low 70s.
An upper level trough starts building along the coast on Tuesday,
causing a mild cooldown across the region. Tomorrow`s high
temperatures drop to the mid 70s to lower 80s in the inland valleys,
with temperatures at the Bayshore dropping to the mid 60s to lower
70s and remaining at the low 60s along the coast. Tonight`s lows
will be from the upper 40s to the lower 50s, dropping to the mid 40s
in the higher elevations.
Model output today shows a very slight chance for convection over
the northern reaches of Napa and Sonoma Counties later this
afternoon, and again Tuesday afternoon. The NAM has been the most
potent model in terms of convection potential with surface cape
values in northern Sonoma and Napa counties reaching 1000-2000 J/kg
or above. However, the NAM is alone in reaching such elevated
values. ECMWF and GFS output suggests that CAPE values will struggle
to exceed 500 J/kg. In addition, all models suggest that dry
conditions aloft and at the surface will inhibit convective
activity. Based on those factors, the likelihood of any convection
is limited. At most, a 5-10% probability of convection on both days
near Mount Saint Helena and the mountains of far northern Napa
County.
&&
.LONG TERM...
(Tuesday night through next Sunday)
Issued at 1229 PM PDT Mon May 22 2023
The upper level trough continues to build throughout the week with a
continued cooldown in temperatures as a result. By the end of the
work week, high temperatures should bottom out at or slightly below
the seasonal averages. Expect highs around the upper 50s to low 60s
along the coast, and the upper 60s to mid 70s inland. Then a modest
rebound could see highs in the interior valleys climbing to the
upper 70s by the beginning of next week.
For the next week, CPC outlooks suggest that, while the signals are
weak, the signals we do have suggest a lean towards lower
temperatures and higher precipitation than seasonal averages,
keeping in mind that for this time of year, climatology would
dictate that any measurable precipitation would effectively be above
average for our area. The European, American, and Canadian ensemble
model outputs all suggest that the trough pattern could persist well
into the first week of June.
&&
.AVIATION...
(00Z TAFS)
Issued at 507 PM PDT Mon May 22 2023
The marine layer depth has compressed a bit since this morning and
is now around 1300 feet at Bodega Bay to 1600 feet at Fort Ord
per profiler data. With that compression coupled with the
northerly pressure gradient increasing again, we`re seeing a
thinning out of stratus north of Half Moon Bay airport to the
Golden Gate Bridge with no stratus along much of the North Bay
coastline.
With the incoming trough on Tuesday, there`s a bit of a challenge
on timing and height of the lowest cigs overnight. The hi-res
NAM model indicates some patchy drizzle possible, primarily along
coastal areas including SFO, OAK, MRY, and SNS overnight into
Tuesday morning.
Vicinity of SFO...VFR expected this evening. As the upper level
trough arrives tonight, the marine layer should deepen and bring a
return of MVFR stratus arriving sometime between 06-10z then
continuing through about 21z...although cigs will gradually
increase on Tues morning. Expecting VFR Tuesday afternoon and
evening.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...MVFR Stratus persists near MRY and
lingers just north of SNS. Forecast is for cigs to impact SNS
sometime between 03-06z and then both airports will have
persistent MVFR into Tuesday afternoon. Patchy light drizzle
possible.
&&
.MARINE...
(Tonight through next Saturday)
Issued at 841 PM PDT Mon May 22 2023
Continued gales impact the northern waters with breezy to gusty
winds elsewhere including across the bays each afternoon and
evening. Hazardous seas for small craft due to wind driven waves.
A series of southerly swells continue, with heights of 2 to 3
feet and periods of 14 to 16 seconds until mid week. Upper level
troughing moves into the region tonight and lingers for much of
this week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 9 AM to 9 PM PDT Tuesday for PZZ530.
Gale Warning until 3 AM PDT Tuesday for PZZ540.
Small Craft Advisory until 3 AM PDT Tuesday for PZZ545.
Gale Warning until 3 AM PDT Wednesday for PZZ570.
Small Craft Advisory until 9 PM PDT Tuesday for PZZ575.
&&
$$
SHORT TERM...DialH
LONG TERM....DialH
AVIATION...JBB
MARINE...JBB
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Area Forecast Discussion
National Weather Service Tallahassee FL
1003 PM EDT Mon May 22 2023
...New NEAR TERM, MARINE, AVIATION, HYDROLOGY...
.SYNOPSIS...
Issued at 418 PM EDT Mon May 22 2023
A stationary front will continue to support an abundance of shower
and thunderstorm activity through Tuesday. The front will start to
push south on Tuesday evening, with showers and thunderstorms
lingering over the southeast Big Bend on Wednesday. The air mass
will be dry enough areawide on Thursday for little if any shower
activity. Over Memorial Day weekend, a drier air mass and
northeast winds will support little if any rain, and temperatures
should run a little below normal, especially at night.
&&
.NEAR TERM...
(Through Tuesday)
Issued at 1004 PM EDT Mon May 22 2023
Over the past few hours, we have watched easterly surface winds
spread all the way west through the Alabama Wiregrass and
Northwest Florida. We now have shallow cool air in place.
Is interesting to watch the multi-cell cluster of thunderstorms
now crossing I-65 between Evergreen and Greenville Alabama. EOX
radar shows broad rotation around the 10,000-foot level, which
could help sustain this during the late evening and overnight
hours as it cross Southeast Alabama and makes headway into
Southwest Georgia. Am reluctant to trim back the Flood Watch until
we have a chance to see how this round of convection will behave
overnight. Though recent runs of the HRRR show it weakening in the
hours ahead, am reluctant to bit off on that given the mid-upper
level support.
By Tuesday afternoon, a stronger push of high pressure down the
coastal plain of the Carolinas and Georgia will finally start to
push the back door front more squarely south through out Florida
counties and into the Gulf on Tuesday evening. The sharpening
of the front as it crosses our FL counties will support the
heaviest rain there on Tue afternoon. After pockets of heavy rain
today, our FL counties will be the focus of flash flood concerns
by Tuesday afternoon. Meanwhile to the north over Alabama and
Georgia, the push from the northeast will start to advect a deeper
layer of drier and somewhat cooler air. Rain chances will be in
the process of dropping north of U.S. 84 on Tue afternoon.
&&
.SHORT TERM...
(Tuesday night through Wednesday night)
Issued at 418 PM EDT Mon May 22 2023
A stationary back door cold front is currently located from near
Eufaula AL to Camilla GA to Lake Park GA. On Tuesday evening, this
boundary will start to push south, driven south in part by
developing surface low pressure off the Southeast U.S. coast.
After another active day of convection on Tuesday, Precipitable
Water (PW) values will start a sustained drying trend on Tuesday
evening, falling in most places below 1.5 inches by sunrise
Wednesday. The main exception will be over the SE Big Bend, where
that will take until about Wed evening. So the SE Big Bend is the
one place where convective coverage on Wednesday will continue to
warrant likely PoPs. Elsewhere to the northwest, rain chances will
drop off into the 20-40 range for Wednesday. As drier air finally
makes it to Cross City on Wed evening and surface dewpoints
areawide drop into the 55F-65F range, rain chances will diminish
further.
&&
.LONG TERM...
(Thursday through Monday)
Issued at 418 PM EDT Mon May 22 2023
A blocking pattern will hold a 500 mb low over the Tennessee
Valley from Thursday through Sunday, then wandering east across
the southern Appalachians on Memorial Day. 500 mb heights over the
tri-state area will hover in the 5740-5800 meter range. For
reference, 5790 meters is in the 10th percentile of the moving
average for this week of the year in the SPC Sounding Climatology.
So upper heights will be unseasonably low, and mid-level temps
will be cool. We will be under cyclonic flow aloft for most of the
weekend. However, the air mass will be fairly dry, with PW values
hovering in the 0.8-1.2 inch range. This is typically not high
enough to support deep, moist convection, but the low heights and
cyclonic flow make it impossible to rule out a weak, low-
topped shower, especially in the afternoon hours. Will hold onto
chicken 10-15 PoPs for the afternoon hours through the weekend.
However, the main message for Memorial Day weekend will be how
pleasant it will be. Temperatures will run a couple degrees below
normal, especially at night given the drier air mass. Sunshine and
fair weather cumulus will dominate the days, with little more than
a stray, weak shower.
&&
.AVIATION...
(00Z TAFS)
Issued at 1004 PM EDT Mon May 22 2023
Overnight, heavy rain over southwest Alabama may move east and
affect the DHN terminal. Shallow cool air near the surface will
set the stage for low stratus overnight areawide, likely with IFR
cigs and possibly with fog. Drizzle is possible at VLD. After
sunrise, low clouds will start to lift, albeit more slowly than
usual due to northeast winds at the surface. Thunderstorms will
develop as soon as late morning and coalesce into clusters during
the afternoon.
&&
.MARINE...
Issued at 1004 PM EDT Mon May 22 2023
Buoys over the northeast Gulf are observing light breezes and seas
of less than 1 foot. Over the next 24 hours, the main concern will
be strong thunderstorm outflow wind gusts on Tuesday afternoon,
particularly closer to shore.
From CWF synopsis...A nocturnal surge of moderate easterlies is
spreading across Apalachee Bay this evening. Late Tuesday, a back
door cold front will spread across the waters. Following the
front, low pressure off the Georgia and Carolina coast will
maintain moderate northeasterly breezes through Friday night,
occasionally becoming fresh during nighttime hours.
&&
.FIRE WEATHER...
Issued at 418 PM EDT Mon May 22 2023
A very wet pattern is expected through Tuesday night with widespread
showers and thunderstorms throughout the day and into the evening.
Storms could produce erratic gusty winds along with lightning and
locally heavy rainfall. Gradually improving mixing heights and
transport winds will lead to fair dispersions in our AL and GA
districts but, will remain low for the FL districts during the day
Tuesday. As rain chances decrease during the day Wednesday, it
appears that dispersion indices will begin to increase by the end
of the term as the mixing heights are also expected to increase.
&&
.HYDROLOGY...
Issued at 1004 PM EDT Mon May 22 2023
Many pockets of heavy rain occurred on Monday. Overnight and early
Tuesday morning, the main focus for heavy rain will be across
Southeast Alabama into Southwest Georgia, generally west of
Albany.
By Tuesday afternoon, the heavy rain threat will focus further
south... over our Florida and far southern Georgia counties. More
pockets of 2-4 inch rainfall can be expected, with flash flooding
being a concern.
Thunderstorms should settle down on Tuesday night and Wednesday.
By Wednesday night, a turn to mostly dry weather will occur, with
no additional hydrologically significant rain through Memorial
Day weekend. Heavy rain will not be widespread enough for river
flooding, through rises within river banks can be expected over
the next couple days.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 69 79 65 79 / 50 80 40 40
Panama City 71 82 65 80 / 40 60 30 30
Dothan 68 73 61 76 / 70 70 30 30
Albany 67 72 61 76 / 70 70 40 30
Valdosta 68 77 63 77 / 80 70 40 40
Cross City 69 84 66 80 / 50 70 40 70
Apalachicola 74 81 68 78 / 50 70 40 40
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through late Tuesday night for FLZ007>019-026>029-
034-108-112-114-115-118-127-128-134.
GA...Flood Watch through late Tuesday night for GAZ120>131-142>148-
155>161.
AL...Flood Watch through late Tuesday night for ALZ065>069.
GM...None.
&&
$$
NEAR TERM...Haner
SHORT TERM...Haner
LONG TERM....Haner
AVIATION...Haner
MARINE...Haner
FIRE WEATHER...Montgomery
HYDROLOGY...Haner
Area Forecast Discussion
National Weather Service Las Vegas NV
802 PM PDT Mon May 22 2023
.SYNOPSIS...Showers and storms focus on our northern areas the
next couple of days before dry conditions return everywhere on
Thursday. An area of low pressure will bring stronger gradient
winds to the area on Tuesday and Wednesday. Above normal
temperatures will continue through midweek then become more
seasonal for the end of the week.
&&
.UPDATE...Thunderstorm activity continues to diminish this evening,
with most of the activity confined to areas north of I-15. The
remaining storms will continue to decrease through the evening and
should end by midnight. Scattered thunderstorms are expected
tomorrow, although coverage should be less than what was seen today
and be mainly over northern and far western areas of the CWA. The
current forecast looks good, and no updates are needed to the
forecast grids this evening. &&
.PREV DISCUSSION...
318 PM PDT Mon May 22 2023
.DISCUSSION...Tonight through Wednesday.
An elongated area of low pressure over Washington State evolves
into 3 separate disturbances by early Tuesday. Tonight, the low
over Washington is forecast to lift northward into Canada while a
second shortwave moves south on the backside of this initial low
and into Oregon Tuesday morning. A third weaker disturbance is
forecast to be near the central California coast by midday
Tuesday. While the 2 northern most systems remain nearly anchored
in their respective places into Tuesday night, the southern most
disturbance is forecast to move into central California and then
could combine with a secondary feature spinning off the low over
Oregon. This combined system/trough determines weather conditions
over the Southwest through the rest of the work week although
uncertainty increases as we approach next weekend.
Models maintain a connection between the anomalous moisture over
our area and a pool of anomalous moisture along the southern
California coast. This moisture connection remains continuous over
the next 48 hours although the breadth of the connection shrinks
as the trough, as a whole, moves east. So what does this actually
mean? Well, officially the thunderstorm coverage area for Tuesday
is limited to the far northern fringes of our CWA. However, the
HRRR is forecasting showers and possibly a few isolated
thunderstorms developing Tuesday afternoon across Death Valley
and in parts of western San Bernardino County within this
aforementioned moisture band. Officially, showers are not
in the forecast for these areas but this will need to be looked
at when the 00z model data suites arrive. Especially if the
vorticity max moving into California near Point Conception
Tuesday afternoon can act as a forcing mechanism in these areas.
By Wednesday, models forecast the connection between these 2
anomalous moisture regions thinning or separating. The southern
most moisture band is still forecast to have PWATs of 120-150% of
normal over the Colorado River Valley and Mohave County. The
difference being there are no discernible sources of forcing to
lift the moisture.
Winds are the primary concern for both Tuesday and Wednesday and
it needs to be determined whether they will be strong enough to
warrant headlines. It`s apparent from the 12z data that widespread
windy conditions will develop on Tuesday with gusts in the 20-40
mph range. Wednesday is similar but areas covered by stronger
30-40 mph gusts expands. For either day however, areas where
gusts meet or exceed 40 mph remain very localized. Based on the
current data, neither day would require a headline. Otherwise,
temperatures both days change little compared to what we see today.
&&
Thursday through Monday...
Very large differences remain in the model forecasted pattern
evolution during the long term, especially heading into the
weekend. The NBM has temperatures cooling Thursday into Friday
with Friday being the coolest day. A minor warming trend is
then forecast over the weekend into the beginning of next week.
This trend is largely unchanged from what I was looking at
yesterday. Apparently, there wasn`t any clear signal to move away
from the previous forecast.
&&
.AVIATION...For Harry Reid...Prevailing southwest winds are expected
for the remainder of the afternoon with speeds generally between 10-
20 kts. There will be isolated thunderstorms, mainly over the higher
terrain, through the afternoon which could potentially bring varying
outflow winds into the valley with gusts up to 30 kts possible. It`s
also not out of the question that a thunderstorm could pop over the
valley between 21-23z this afternoon, but confidence is too low to
include in the TAF. Convection is expected to diminish after 01z
with FEW clouds around 10k feet. Thunderstorm coverage Tuesday is
expected to be less than today with most of the activity remaining
north of the Las Vegas Valley.
For the rest of southern Nevada, northwest Arizona and southeast
California...South-southwest breezes, primarily for areas along and
south of I-15. This results in drier conditions for the Colorado
River Valleys. Here, afternoon breezes are expected to be around 10-
15 kts from the south, with gusts of 15-20 kts possible. Isolated
thunderstorms are possible elsewhere through the afternoon with
gusty outflow winds up to 35 kts and FEW-SCT clouds around 8-10k
feet. Otherwise, typical diurnal winds are expected at these sites,
with gusty west-southwest winds at KDAG this afternoon. Thunderstorm
coverage will be less Tuesday with areas across Nye and Lincoln
Counties seeing the better chances.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Planz
DISCUSSION...Salmen
AVIATION...Gorelow
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