Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/23/23
Northern Alaska Forecast Discussion
National Weather Service Fairbanks AK
304 PM AKDT Sat Apr 22 2023
.SYNOPSIS...
A potent cold front that pushed across much of northern Alaska
yesterday continues to push south of the Alaska Range today.
Widespread snow occurred across much of northern Alaska overnight
and widespread blowing snow is occurring in the wake of the
frontal passage. Gusty northeasterly winds will remain strong
through the next several days as the pressure gradient remains in
place.
.DISCUSSION...
Upper Levels...Powerful upper level features are dominating the
weather across much of the state of Alaska. An omega block upper
ridge stretches across a swath from northern Siberia to the
Chuckchi Sea and towards the Kuskokwim Delta. A Dynamic low sits
to the northeast of Banks Island in the far northeast Beaufort
Sea. An associated upper level vorticity anomaly surges southward
towards the Gulf of Alaska. This will rapidly intensify into an
upper level low as it reaches the Gulf of Alaska Overnight. This
intrusion of stable air associated with this anomaly, and
intensifying gradient will support widespread mountain waves and
gap winds across the Alaska Range.
Analysis...Widespread high pressure dominates the northern Bering,
the Chuckchi Sea and western Beaufort Seas today. A weakening low
pressure system lingers in the eastern Gulf of Alaska. The
pressure gradient between these two features is causing gusty
winds in local gaps. A low pressure system will rapidly develop in
the western Gulf of Alaska overnight, which will result in even
greater pressure gradients and stronger winds overnight across the
Kuskokwim, Tanana and Yukon Valleys. Expect strong winds through
these areas throughout Sunday as the surface low only gradually
moves eastward and relaxes the pressure gradient into late Sunday
and early Monday.
MODELS...
With its higher resolution, the HRRR model is most accurately
capturing the local wind gusts through gaps across the Yukon
river and Tanana valleys. The HRRR continues to show gusty winds
through typically sheltered locations such as McGrath and as a
result both the HRRR and NAM were the models of choice for
wind guidance. Models were in strong synoptic agreement for the
short term so a general blend of models was used.
Central and Eastern Interior...While most of the snow has ended
across much of the region, snow showers are lingering in the
eastern portions of Fortymile Country and Upper Tanana Valley as
well as near Denali due to light upslope. Elsewhere, widespread
gusts are occurring behind the front, particularly in locations
that are usually sheltered during gusty winds. These gusty winds
are kicking up recently fallen snow and resulting in reduced
visibilities especially through passes.
West Coast and Western Interior...
Wind gusts will increase tonight especially within the gaps of the
western interior with northeasterly flow. Wind gusts will
increase along the coast as well Sunday and especially sunday
night as the pressure gradient across the region increases.
Blowing snow and reduced visibilities are possible.
North Slope and Brooks Range...With high pressure dominating
across the Beaufort Sea, generally dry conditions and below
normal temperatures are expected over the short term. Gusty winds
due to the strong pressure gradient across the Brooks Range should
generally limit stratus and fog development over the next few
days. However localized low clouds and fog are possible near ice
leads due to consistent northeasterly wind.
Coastal Hazard Potential Days 3 and 4...None.
&&
.FIRE WEATHER...Heavy snow pack remains over the area so no fire
weather concerns at this time.
&&
.Hydrology...Rivers and lakes remain ice covered, with areas of
overflow and open leads. Caution should be used when traveling on
rivers or lakes. Temperatures falling well below freezing through
the middle of next week. The chance of breakup and snow melt
flooding are above normal this spring over Eastern Alaska with the
continued cold temperatures and above normal snowpack. The latest
breakup information is available at www.weather.gov/aprfc/breakupMap.
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
AK...Wind Advisory for AKZ215-216-227.
Winter Weather Advisory for AKZ219>222-224-226.
Winter Weather Advisory for AKZ227.
Winter Weather Advisory for AKZ206.
PK...Brisk Wind Advisory for PKZ803.
Brisk Wind Advisory for PKZ804-811-852-857.
Brisk Wind Advisory for PKZ805-806.
Brisk Wind Advisory for PKZ807.
Brisk Wind Advisory for PKZ812-858.
Brisk Wind Advisory for PKZ817.
Brisk Wind Advisory for PKZ851.
Brisk Wind Advisory for PKZ854.
&&
$$
Area Forecast Discussion
National Weather Service Boston/Norton MA
940 PM EDT Sat Apr 22 2023
.SYNOPSIS...
Widespread showers with heavy rainfall and perhaps a few
embedded thunderstorms will overspread our region tonight into
Sunday. The steadier rainfall tapers off from west to east
Sunday afternoon. Unsettled, with daily opportunities for
isolated to scattered rain showers, through the upcoming week.
Temperatures will be near normal.
&&
.NEAR TERM /THROUGH SUNDAY/...
930 PM Update:
Early update to address developing pre-frontal thunderstorms
extending from the Hartford/Windsor Locks CT metros on southward
into Long Island NY vicinity and into the adjacent SWrn waters.
00z/23rd OKX RAOB shows an environment of modest to moderate
elevated instability above stable sfc layer, characterized by
most-unstable lifted indices of -3 units and most-unstable CAPE
values cited at around 833 J/kg. In addition to that, we have a
rather considerable amt of effective shear in the elevated-convective
layer with about 41 kt of shear, this owing to stronger mid to
upper level SSW flow. A few of these thunderstorms have become
locally strong, with recent SPS for some of the western suburbs
of Hartford. The main risk with these is lightning and heavy
rain, but stronger cores will pose a risk for small sub-severe
hail; severe hail is not likely but can`t rule out an especially
strong or intense storm producing hail up to 1 inch in diameter
given the combo of effective shear (stronger mid/upper winds)
and a fair amt of elevated instabiilty.
It`s not clear how long this risk may last, however RAP
soundings suggest at least a continued thunder risk into the
overnight mainly W of Worcester, as elevated instability does
weaken with time but still is enough where at least some rumbles
of thunder are plausible. The main risk for the overnight would
turn to more local downpours and training of downpours that
could support isolated poor-drainage flooding/ponding issues.
Previous Discussion
Not much change to the overall forecast this afternoon, as the
synoptic pattern remained rather stagnant. The focus of this
forecast will be on abundant clouds, and rainfall overspreading
southern New England later tonight. The brunt of this rainfall
should be after midnight.
Instability is on the weaker side, and elevated. Even the mid
level lapse rates are not all that supportive of thunderstorms.
That said, it is a non-zero probability, especially across
interior southern New England. Not concerned about the risk for
severe weather, just the enhanced rainfall rates which could
result. We have been rather dry for some time, so we can handle
a decent amount of rainfall. The greatest risk for flooding will
be the poor-drainage/low-lying areas.
Above normal temperatures tonight, as we will not be able to
radiate, and we will remain on the warm side of an approaching
cold front.
&&
.SHORT TERM /SUNDAY NIGHT/...
Not much change to the forecast heading into Sunday. Expecting
widespread showers Sunday morning, which gradually diminish
from west to east into Sunday evening.
Total rainfall amounts between 0.75 and 1.50 inches still seem
reasonable for much of southern New England, with localized 2+
inch amounts possible should thunderstorms develop. The greatest
risk for the higher rainfall amounts look to focus across the
interior, particularly along the east slopes of the Berkshires
and Worcester Hills due to upslope flow enhancement given SSE
flow. Another area to watch is in the vicinity of the surface
wave of low pressure, where some low level convergence may also
enhance rainfall totals.
Showers continue to diminish/move into northern New England
Sunday night. Should be dry for most, with the greatest risk fro
lingering showers along and north of Route 2 in MA and out over
the eastern coastal waters.
Not much temperature change Sunday, with above normal high
temperatures mainly in the 50s. Turning colder, and closer to
normal for late April, Sunday night as a cold front slowly
approaches the coast.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Highlights
* Seasonable temperatures from day-to-day next week
* Wet and unsettled with shower chances each day
Monday through Friday
A broad upper-level low is expected to meander over the
Northeast for much of next week thanks to a downstream blocking
pattern. This will support seasonable temperatures from day to
day this week with highs in the upper 50s/low 60s during the day
and lows in the upper 30s/low 40s overnight. Furthermore, a
series of embedded short-waves will support cloudy/unsettled
weather with daily shower chances over southern New England each
afternoon. No washouts are expected, but scattered showers
producing less than a tenth of an inch of precip will be
possible throughout the week. Given the expected isolated to
scattered nature of any showers that develop, details are vague
with respect to where/when showers will be.
Next Weekend
Broad cyclonic flow pattern may break late week/early next
weekend with a possible mid-level ridge building over the east
coast. However, a more robust short-wave may traverse across the
Midwest and bring an opportunity for substantial rainfall at
some point next weekend. Stay tuned for more details later this
week.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight and Sunday...High Confidence.
Low end MVFR-IFR, with localized/brief LIFR conditions,
dominating tonight into Sunday. Scattered showers this evening
will give way to widespread showers from west to east late
tonight into Sunday morning. A period of heavy rainfall, and
even the low risk for an embedded thunderstorm or two exists.
Confidence still not high enough to include a thunder mention in
the TAFs, but may be needed with later updates. The heaviest
rain will shift into eastern New England by mid Sunday
afternoon. E winds 10 to 15 knots will shift to the N across
parts of western MA and CT by Sunday. Gusts of 20 to 30 knots
are expected along the coast.
Sunday Night...Mainly MVFR, with some VFR possible late along
and south of the MA Pike. Local IFR towards NE MA.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF.
Outlook /Monday through Thursday/...
Monday: Mainly VFR, with local IFR possible. Chance SHRA.
Monday Night: VFR. Slight chance SHRA.
Tuesday: VFR. Breezy. Chance SHRA.
Tuesday Night through Wednesday Night: VFR. Slight chance SHRA.
Thursday: Mainly VFR, with local MVFR possible. Chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Low clouds persist this evening, with showers and fog developing
after midnight on most waters. Also a very low risk for a few
thunderstorms. Expecting poor visibility less than 1 NM at
times. Gusty SE winds also develop overnight and continue into
Sunday. A cold front should approach the eastern waters/cross
the southern coastal waters late Sunday night. The timing of
this front is not certain. Small Craft Advisories extended into
Sunday night for some waters.
Outlook /Monday through Thursday/...
Monday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers.
Monday Night through Tuesday: Winds less than 25 kt. Areas of
seas approaching 5 ft. Slight chance of rain showers.
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Wednesday through Wednesday Night: Winds less than 25 kt.
Thursday: Winds less than 25 kt. Slight chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 4 AM to 8 PM EDT Sunday for ANZ230.
Small Craft Advisory until 11 PM EDT Sunday for ANZ231.
Small Craft Advisory until 8 PM EDT Sunday for ANZ232>235-237.
Small Craft Advisory from 4 AM to 4 PM EDT Sunday for ANZ236.
Small Craft Advisory until 8 PM EDT Monday for ANZ250-254.
Small Craft Advisory until 4 AM EDT Monday for ANZ251.
Small Craft Advisory until 8 PM EDT Monday for ANZ255.
Small Craft Advisory until 8 AM EDT Monday for ANZ256.
&&
$$
SYNOPSIS...Belk/RM
NEAR TERM...Belk/Loconto/RM
SHORT TERM...Belk
LONG TERM...RM
AVIATION...Belk/Loconto/RM
MARINE...Belk/Loconto/RM
Area Forecast Discussion
National Weather Service Quad Cities IA IL
627 PM CDT Sat Apr 22 2023
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 302 PM CDT Sat Apr 22 2023
Snow/rain showers and even some graupel were reported today. A
vigorous shortwave moved across the area leading to these showers
and gusty winds today. Temperatures this afternoon struggled to
make it out of the 30s. This upper level low will move through
the area in the short term.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 302 PM CDT Sat Apr 22 2023
Key messages:
1. Showers again are possible Sunday but with a more limited
coverage.
2. Freezing temperatures expected again tonight.
Discussion:
The upper level trof will move east through the area and will be
more east of area tomorrow. Surface lapse rates will increase but
not be as strong as today. This set up suggests a return of
rain/snow showers, but in a lower coverage and mainly along and
east of the Mississippi River. Winds will stay up in the 5-10kt
range and gust near 20kts, lower than today. Little to no impacts
are expected with these showers.
Tonight, temperatures are expected again to drop near or below
freezing area wide. Even though winds are up, below freezing temps
will be able to damage sensitive vegetation. As such, a freeze
warning has been issued for the entire area. The HRRR has some
areas in the mid to even low 20s, so could see pockets of temps
even lower than forecast.
.LONG TERM...(Sunday night through Saturday)
Issued at 302 PM CDT Sat Apr 22 2023
Three main things in the long term, first another freeze headline
is expected Sunday night into Monday where lighter winds and
clearing skies may lead to better chances for widespread freezing
temperatures. We currently have a freeze watch for the area.
Another is that the rest of the week looks rather quiet for with
the exception of light precip to start the week. Towards the end
of the period, a stronger system may bring more precip to the
area. This rainfall could affect the Mississippi River flooding.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 625 PM CDT Sat Apr 22 2023
A mix of MVFR/VFR conditions will slowly improve to VFR through
12z/23. Isolated sprinkles or flurries are possible through
15z/23. After 15z/23 VFR conditions are expected with isolated to
scattered SHRA/SHSN. Brief MVFR conditions are possible in the
stronger showers.
&&
.HYDROLOGY...
Issued at 1140 AM CDT Sat Apr 22 2023
The 2023 Spring Snowmelt Flood will continue to work its way down
the main stem Mississippi River over the next couple of weeks.
All points on the Mississippi River continue to rise. Major Flood
stage is forecast over the next week along stretches of the
Mississippi River. Additional rises are expected beyond the 7-day
forecast. With the rises at Gregory Landing on the southern
stretch of the Mississippi, that site may have to join the flood
warning group by as early as tomorrow(Sunday).
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
Benton-Buchanan-Cedar-Clinton-Delaware-Des Moines-Dubuque-
Henry IA-Iowa-Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-
Linn-Louisa-Muscatine-Scott-Van Buren-Washington.
Freeze Watch from late Sunday night through Monday morning for
Benton-Buchanan-Cedar-Clinton-Delaware-Des Moines-Dubuque-
Henry IA-Iowa-Jackson-Jefferson-Johnson-Jones-Keokuk-Lee-
Linn-Louisa-Muscatine-Scott-Van Buren-Washington.
IL...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
Bureau-Carroll-Hancock-Henderson-Henry IL-Jo Daviess-
McDonough-Mercer-Putnam-Rock Island-Stephenson-Warren-
Whiteside.
Freeze Watch from late Sunday night through Monday morning for
Bureau-Carroll-Hancock-Henderson-Henry IL-Jo Daviess-
McDonough-Mercer-Putnam-Rock Island-Stephenson-Warren-
Whiteside.
MO...Freeze Warning from midnight tonight to 8 AM CDT Sunday for
Clark-Scotland.
Freeze Watch from late Sunday night through Monday morning for
Clark-Scotland.
&&
$$
SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Gibbs
AVIATION...08
HYDROLOGY...12
Area Forecast Discussion
National Weather Service Lincoln IL
917 PM CDT Sat Apr 22 2023
.SYNOPSIS...
Issued at 314 PM CDT Sat Apr 22 2023
Well below normal temperatures continue through the weekend.
Additional scattered light rain or snow showers are possible
during the day Sunday north of I-74. Near freezing low
temperatures will threaten sensitive vegetation tonight and Sunday
night. Temperatures warm a bit for the work week, but remain
below average, with highs in the low 60s.
&&
.UPDATE...
Issued at 917 PM CDT Sat Apr 22 2023
Between a 1000 mb surface low near the Ontario/Quebec provincial
line and a 1027 mb surface high spilling onto the northern Plains,
west/northwest breezes continue across central Illinois this
evening and are forecast to persist through the overnight hours.
In addition, extensive cloud cover persists, with substantial
clearing not seen until areas west of I-35 in Iowa. CAMs indicate
that we should see patches of clearing overnight, with most of
them not sustained aside for perhaps areas south of I-72 well
after midnight. The cloud cover and wind argue for not dropping
temperatures too much. However, dew points in the mid 20s and 850
mb temps around -6 C are concerning. CAM forecasts vary from
several degrees below to several degrees above freezing. For now,
we`ll maintain a temperature forecast touching right close to
freezing for an hour or two around sunrise before warming up.
Additionally, some adjustments were made to precip chances
tomorrow to boost the coverage of rain/snow showers. We expect
these showers to be of a similar character to today`s, though
perhaps centered a bit farther east.
&&
.SHORT TERM...(This evening through Sunday night)
ISSUED AT 314 PM CDT Sat Apr 22 2023
<<<<<<< Key Messages >>>>>>>
1. Scattered rain/graupel showers continue through early evening,
primarily north of I-72. Additional daytime showers are possible
on Sunday, mainly north of I-74.
2. Well-below average temperatures are expected through the
weekend. Areas near or below freezing temperatures will threaten
sensitive vegetation tonight and Sunday night.
Weather across the Midwest continues to be dominated by an upper
low that was swirling over northeastern IL as of Sat afternoon.
Steep low-level lapse rates and around 100 J/kg of instability
have led to widespread shower development. That instability
combined with cloud layer temperatures below freezing has resulted
in lots of graupel mixing in this afternoon, giving the
appearance of snow showers despite sfc temperatures in the low
40s. These showers will follow a diurnal trend, diminishing into
the evening, though scattered flurries and sprinkles should
persist across the northern half of the CWA tonight. Into the day
on Sunday, a relatively similar setup will exist, though with
lesser instability and weak large scale ascent as the upper low
starts to move away from the region. Kept a mention of showers in
for areas along and north of I-74, but think they`ll be less
widespread than today. Winds will also become lighter on Sunday as
sfc high pressure nudges into the region.
A challenging low temperature forecast (and associated headline
decisions) for tonight. The upper low will be lifting away to the
northeast across the Great Lakes region overnight, but will remain
close enough that most guidance keeps mid/high clouds present across
the northern half of the CWA. Winds become lighter, but won`t be
calm (forecast to be sustained around 8-10 mph). So it`s not a great
radiational cooling setup or overly favorable for frost development
across the northern half of the CWA. However, low temps across our
northern counties ended up being several degrees cooler than
forecast Fri night/Sat morning, and with lows forecast to fall near
32-33F tonight, am weary that temps slip below 32, especially if
lows end up a degree or two cooler than forecast again.
CAMs are split on the freezing temp potential, with most runs of
the HRRR showing several hours of sub-freezing temps, while the
NAMNest keeps most of the northern CWA a few degrees above
freezing. Given the uncertainty, leaned on the HREF probabilities
in making headlines decisions. The highest probs of below freezing
temps tonight were along/west of the IL River. Accordingly, those
areas were upgraded to a freeze warning (if they were not already
in the warning). The existing frost advisory still seemed
reasonably placed, as it covers the counties where cloud cover and
wind speeds are expected to be lower. For the counties with no
headlines tonight, I am more concerned that temps fall below
freezing than I am about frost development.The probability of
sub-freezing temps is lower than the areas to the west, though,
and any sub- freezing temps should be short-lived, thus the lack
of headlines for those areas.
Ultimately, these headline decisions are being driven by small
differences in the forecast. The reality is that temperatures will
be near-freezing tonight, and I`d still recommend bringing in or
covering any sensitive vegetation.
Confidence is higher in a freeze occurring Sunday night into Monday.
As sfc high pressure builds into the area, it will result in a
mostly clear night with lighter winds. HREF probabilities suggest a
greater than 50% chance that temps fall below freezing, while NBM
probabilities of below freezing temps are even higher, above 60%
north of I-70. Added a freeze watch along and north of I-70 for
Sunday night into Monday.
.LONG TERM...(Monday through Saturday)
ISSUED AT 314 PM CDT Sat Apr 22 2023
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 653 PM CDT Sat Apr 22 2023
VFR conditions are expected (90% chance) to persist at all TAF
sites through at least around 12z or so on Sunday morning. Though
a VFR ceiling between 5-9 kft may persist through most of the
overnight hours north of a KSPI-KCMI line, surface visibility
should remain above 6 miles. As cloud cover increases once again
after sunrise, probabilities of ceilings below 3 kft increase to
the 30-50% range north of a KPIA-KCMI line until afternoon. Brief
rain or snow showers may occur in the vicinity of KBMI and KCMI
after 15z Sunday.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 1 AM to 9 AM CDT Sunday for ILZ027>031-036-
037-040-041-047-049-050.
Freeze Watch from late Sunday night through Monday morning for
ILZ027>031-036>038-040>057-061>063-066>068.
Frost Advisory from 1 AM to 9 AM CDT Sunday for ILZ048-051-052-
054-056-061>063-066>068-071>073.
&&
$$
UPDATE...AAT
SYNOPSIS...Erwin
SHORT TERM...Erwin
LONG TERM...Erwin
AVIATION...AAT
Area Forecast Discussion...UPDATED
National Weather Service New Orleans LA
843 PM CDT Sat Apr 22 2023
...NEW UPDATE...
.UPDATE...
Issued at 836 PM CDT Sat Apr 22 2023
Now that sunset had taken place, the question of whether or not
we`ll decouple has been answered. Most local observations over the
last hour or so has indicated winds have become calm across the
board. This will allow for radiational cooling to take shape and,
indeed, temperatures have dropped from the upper 70s and lower 80s
to the upper 50s and lower 60s just prior to 9pm. Overall, think
the overnight lows are in decent shape with the drainage areas
being the coolest locations. Day shift did take the cooler route
and will continue that overnight tonight. Otherwise, no changes
anticipated at this juncture to the ongoing forecast outside of
lowering the surface winds through the overnight. (Frye)
&&
.SHORT TERM...
(This evening through Sunday night)
Issued at 244 PM CDT Sat Apr 22 2023
Now if the weather outside isn`t perfect, I dont know what is
because it`s absolutely gorgeous today. Barely a cloud in the sky
with a nice N to NE breeze and temperatures in the upper 70`s to
a few flirting with 80. A recent frontal passage has introduced
much noticeably drier air to the area. HRRR soundings for this
afternoon going into this evening illustrates the bulk of the
driest air in the troposphere to be within the strongly mixed PBL
to around H7, with total column PW very low in the 0.4-0.5" range
(in fact, closely flirting with the daily record minimum for 00z
according to KLIX Sounding Climatology) so clearly, an
anomalously dry airmass is in place. Applied adjustments to the
dewpoints to account for such strong PBL mixing given just how dry
the lower tropospheric airmass is, with the bulk of the direst
air generally along and west of I-59. Otherwise, clearly evident
backing low-level wind profile following the aforementioned cold
front passage will keep drier air filtering into the area via CAA,
and will remain nice and calm going into tonight. Only two points
of interest which we`ll hit both at the same time. Discussing the
potential for winds to remain "high" enough to reduce radiative
cooling processes albeit strong subsidence in the vertical.
Guidance suggests winds to remain in the 04-08kt range at times as
the surface high center placement is to our north over the
central US, with a noticeable SLP gradient in place meaning
complete decoupling might not fully occur. Having said that
however, it doesn`t take much for a temporary slow down of the
winds to near calm in protected areas like the Pearl River and
Pascagoula drainage basins to drop temperatures right at daybreak
thus, am going with 25th percentile areawide with emphasis on
slightly cooler basins. Not a detrimental impact, but leaning in
the right direction given the meteorological setup.
Going into Sunday, going to start out with a zoomed out synoptic
overview. Main story is a mostly quasi-zonal flow dominating the
southern/southeastern US. Next feature to monitor will be a
subtle mid-level impulse igniting convection late today along the
remnant front draped west into Texas. This convection won`t go
far, pressing south into far southern Texas and attempts (as some
HREF members depict) to become deep enough to translate into a
cold-pool propagated MCS pressing into the NW and W GOMEX early
Sunday. As for us, what is left of the mid to upper-level cirrus
anvil canopy being stretched out along the quasi-zonal westerly
flow spreads east across our area. Did notice some CAMs try to
hint at some weak simulated reflectivity returns, and a closer
investigation at model soundings pinpoint a very dry low-level
tropospheric profile situated in place, meaning most returns that
will be noticeable on radar tomorrow will be in the form of
virga. But, can`t rule out some heavier returns attempting at
making it to the ground through this dry airmass leading to some
patchy drizzle/light showers. Targeted mainly along/south of
I-10/12 and for western areas across the Atchafalaya basin, with
coverage moreso largely depending on how deep convection can
become to our west and southwest with deeper mid/upper-level
blow off. Felt obligated to atleast mention it for now as this
always causes a surprise in our forecast and typically makes it
down to the ground atleast briefly. But again, will closely
monitor.
&&
.LONG TERM...
(Monday through Friday night)
Issued at 244 PM CDT Sat Apr 22 2023
Monday, zonal flow will continue to dominate the upper level
pattern, while northwesterly surface winds continue to bring dry
air into the area. Rain chances will be low on Monday.
Tuesday through Thursday, a shortwave trough is expected to move
through the area, enhancing the chances for rain mid-week.
Easterly to southerly surface winds will help to advect some warm
air and moisture into the area. Scattered to numerous showers and
storms will be likely Tuesday into Wednesday. Shear at the moment
will be generally low. So, there could be a strong to severe
storm, but looking at the models, widespread severe potential is
not expected for now. But, there will be the potential for
localized flash flooding with these storms. It is still too early
to tell the strength of the system and specific timing, due to a
decent lack of model consensus especially regarding some of the
timing. We will keep monitoring this system as it develops. MSW
&&
.AVIATION...
(00Z TAFS)
Issued at 604 PM CDT Sat Apr 22 2023
VFR conditions should prevail through this cycle. Perhaps an
increase in mid/upper level clouds during the day on Sunday.
Otherwise, winds becoming light and variable tonight with
generally light winds expected again through Sunday. (Frye)
&&
.MARINE...
Issued at 244 PM CDT Sat Apr 22 2023
Breezy offshore flow will persist this evening with winds of
10-15kt mainly for Gulf zones. Winds will remain in the 5-10kt,
occasional 15kt gust range tonight with high pressure well inland
int the central US causing a tight pressure gradient. On Sunday,
guidance indicates the potential for a complex of severe
thunderstorms to press well south of coastal SE LA marine zones,
but might spread gusty winds and moderate rain during the day.
Beyond sunday, several rounds of showers/storms with upper-level
impulses will be possible throughout the week, with mainly calm
seas and occasionally breezy winds at times.
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 51 74 49 69 / 0 10 10 0
BTR 56 78 56 74 / 0 20 10 0
ASD 52 81 54 76 / 0 0 10 0
MSY 61 78 60 74 / 0 10 10 0
GPT 53 79 55 74 / 0 0 10 0
PQL 51 81 54 76 / 0 0 0 0
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&
$$
SHORT TERM...KLG
LONG TERM....MSW
AVIATION...RDF
MARINE...KLG
Area Forecast Discussion
National Weather Service Las Vegas NV
705 PM PDT Sat Apr 22 2023
.SYNOPSIS...Warming temperatures through the weekend with minor
breezes and a chance for some showers and thunderstorms across
south-central Nevada this weekend. A passing system to the
northeast should bring another round of minor wind and a brief
cool down to the area mid week, but temperatures should rebound
again by the end of next week back to well above normal.
&&
.UPDATE...Quiet weather persisted across the region this evening as
northwest flow continued to dominate the weather pattern. An area of
clouds over southeast San Bernardino County and southern Mohave
County continued to shift southeast as a weak impulse in the mean
flow dove south. Otherwise, skies were clear across the region.
Northerly breezes of 20 to 25 MPH late this afternoon diminished as
the sun began to set this evening with the only area with lingering
breeze to around 20 MPH this hour being down the Colorado River
Valley. Temperatures were about 5 degrees cooler than this time
yesterday as cool air rushed into the region on the northerly winds
today.
No changes were made to the overnight forecast as quiet weather with
persist tonight with light winds and mostly clear skies. Lows
tonight will run about 5 degrees cool than yesterday.
--Nickerson--
&&
.PREVIOUS DISCUSSION...113 PM PDT Sat Apr 22 2023.
.SHORT TERM...Today through Tomorrow Night.
A cold front passage early this morning has resulted in northerly
breezes across the region with some minor gusts. The surface
pressure gradient will begin to relax this afternoon, reducing the
gust potential through the rest of the afternoon leaving a pretty
pleasant afternoon and evening in store.
12Z HREF means show some minor shower activity on the west side of
the Sierra, mostly due to the FV3, which is quite a bit more
robust with convection in the marginal instability and very weak
upslope environment there. The rest of the hi-res models are
minimal in that regard. Left sub 10% PoPs there as the NBM
suggests.
Moving into tomorrow, a much more broad area of instability
develops across eastern California and much of Nevada. This, plus
a brief period of elevated moisture and orographic lift in Nye and
Lincoln counties should be enough to spark some showers and
thunderstorms. Again, the FV3 seems to overconvect in this
marginal environment but several other HREF members produce some
convection in these areas Sunday afternoon and evening.
Nevertheless, HRRR soundings in Lincoln indicate a 3km inverted V
profile so any storms that indeed develop off the high terrain
could produce a downburst gusts over 35 mph. In fact, the HREF
highlights a 50-60% chance for this across much of Lincoln county
between 00Z-06Z.
.LONG TERM...Next Week.
Heading into next week, the main focus for the first half of the
week is a passing disturbance originating from the Pacific NW. As
mentioned in the last couple discussions, the trend continues to
be a less windy/cool solution due to the more northeast track of
this low per ensemble clusters for Day 3. As expected, wind fields
in the NBM have notably backed off Monday through Wednesday with a
less amplified surface response across the Great Basin and Mojave
Desert. At this point, the only place that could come close to
advisory levels are western San Bern and the southern Sierra,
where a secondary jet streak comes across the high terrain. As of
now, it isn`t enough, even in the more windy FV3 to reach advisory
criteria (40+mph gusts) but that could change as this period
enters the HREF domain.
Moving into the latter half of the week, a broad trough is progged
to develop over the north-central US out of Canada and there was
initially some question on how far west that would develop as it
pushed south, but the 12Z cluster analysis shows agreement across
all clusters that the low center should stay east of the Rockies.
So now the question at this point is the rate of our warm up
through the latter half of the week and how far east the ridge
axis across the Pacific moves inland. NBM deterministic
temperatures have not varied much compared to yesterday, still
showing about 10-12 degrees above normal heading into the weekend.
Looking long term...CPC 6-10 day outlook shows a high probability
for above normal temperatures through next weekend but a possible
change of pattern in the 8-14 day.
&&
.AVIATION...For Harry Reid...Northeast winds varying between 030-070
will continue through mid afternoon with wind speeds generally
between 12-20 kts. After 22z, look for winds to diminish and
generally become more easterly between 050-090 with speeds around 10
kts. Light and variable winds this evening and overnight. FEW clouds
12-14 kft AGL today with broken cirrus. Although we will see a
decrease in wind speeds Sunday, they are expected to remain
northeast around 7-10 kts between 030-060 mid morning through the
afternoon.
For the rest of southern Nevada, northwest Arizona and southeast
California...Prevailing north-northeast winds 10-20 knots will occur
across most of the region today with stronger winds gusting 25-30
knots along the lower CO River Valley from KIFP-KEED-KHII. Winds
will gradually decrease in the afternoon but still remain gusty at
times down the Colorado River Valley. Winds speeds will generally be
around 8-15 kts most areas Sunday with a southwest to west
direction.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...TB3
AVIATION...Gorelow
For more forecast information...see us on our webpage:
https://weather.gov/lasvegas or follow us on Facebook and Twitter