Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/19/24
Area Forecast Discussion
National Weather Service Cheyenne WY
750 PM MDT Fri Oct 18 2024
.KEY MESSAGES...
- Light rain and mountain snow tonight into Sunday morning.
- 40-60% chance for showers and thunderstorms Sunday into Sunday
evening.
- Strong winds are possible Monday, then more warm and dry
weather by mid-week.
&&
.UPDATE...
Issued at 747 PM MDT Fri Oct 18 2024
Expanded the existing Dense Fog Advisory to central Laramie
County...the eastern foothills...Arlington and Bordeaux this
evening. Getting reports of low visibility on WYDOT sensors that
should persist overnight. Updates have been sent.
&&
.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 245 PM MDT Fri Oct 18 2024
There are plenty of clouds across the region this afternoon, and
this is due mainly to plenty of low-level moisture and north to
northeasterly winds causing upslope flow against the Front Range,
but also broad synoptic lift associated with several passing short
waves aloft and frontogenesis associated with a cold front that is
passing through. Dense fog has been observed all morning around the
I-80 summit between Cheyenne and Laramie, and some dense fog between
Laramie and Elk Mountain. With short-range models suggesting it`ll
linger through tonight around the I-80 summit, we issued a Dense Fog
Advisory through Saturday morning, while the Dense Fog Advisory for
the North Snowy Range Foothills area will expire this afternoon.
There is potential that areas of dense fog could redevelop tonight
in the North Snowy Range Foothills again, but with HREF probability
not exceeding 50% at this time along the I-80 corridor, so we opt
against extending that headline at this time. HREF probabilities and
HRRR suggest dense fog may extend further north along the Front
Range into tonight as well, but these models have not handled the
evolution of fog thus far today very well, so confidence is low for
tonight. Winds may be light enough and changing from northeast to
southeast tonight that dense fog may just be patchy. We will
continue to monitor that situation this afternoon/evening and hold
off on headlines for now.
Precipitation has been under performing greatly with this cold
front so far with any notable snow accumulations across
northwest and central Wyoming. This afternoon, there really
hasn`t been any precipitation to speak of across the region, and
now we just watch an area of likely mixed convective and
stratiform showers developing around the Colorado Rockies and
moving north. Expect this to develop a little further this
afternoon and move to the north-northeast as a somewhat potent
upper-level wave kicks it downstream. Overall QPF amounts have
been slashed from previous forecasts. We might be able to
squeeze out a few tenths of an inch of rain across parts of the
NE Panhandle tonight, but otherwise expect totals less than a
tenth of an inch on the Wyoming side. As such, Winter Weather
Advisories for the higher terrain have been cancelled.
Additional snow amounts up to around an inch may be possible as
temperatures cool down and a few showers pass through tonight,
but this will be limited to the highest elevations above about 8
kft. Perhaps up to a dusting in some of the higher valley
locations west of the I-25 corridor, but expect that to be
pretty localized dependent on where showers develop. At this
point, it would be pretty unlikely that anywhere along and east
of the I-25 corridor sees any snow. Lows will probably struggle
to reach or fall below freezing for many places with clouds
around, despite some cold air advection.
The closed low remains well to our south on Saturday, and we will
probably see some ridging develop over our region come mid-day per
current model solutions. Sunshine is expected for many areas by
Saturday afternoon, and with that, we can expect a nice rebound in
temperatures into the upper 50s to around 60 for the valleys
and east of the I-25 corridor. Clouds and isolated showers may
linger around Cheyenne and points east into the southern NE
Panhandle.
Expect a mix of clouds and partially clear skies Saturday night into
Sunday night as the closed low gradually moves northeast over the
region. As the trough passes over the Rockies, a bit of convective
instability is possible that will bring about a ~40-60% chance for
scattered showers moving in Sunday afternoon and night. With up to
~500-800 J/kg of MUCAPE, some thunder is possible as well.
Winds are not expected to be high through Sunday aside from some
breezy conditions this afternoon and evening. Sunday night, some
gusty westerly winds are expected to develop as the upper level low
starts to move off to the east.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 245 PM MDT Fri Oct 18 2024
Gusty winds are expected to develop on Monday as an upper level
low departs to the east and westerly winds develop. The gustiest
winds are expected in the mountainous terrain with 30-45 mph gusts
likely. Higher gusts in the 50-60 mph range can`t be ruled out
in the usual gap wind areas. Temperatures also trend warmer with
sunshine expected for most areas, especially in the afternoon as
drier air filters in.
After the upper level low departs, the general pattern for next
week looks to be favoring a broad upper level ridge developing,
but with potential for a weak trough or two to ride along the
ridge. With that, we look forward to an overall continuation of
the warm and dry weather pattern that we`ve seen this fall.
Depending on timing of these potential weak waves, there could
be some brief chances for clouds and light rain. Otherwise, RH
values may dip into the 15-25% range by mid-week, so we will
have to pay attention to potential fire weather concerns again.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 535 PM MDT Fri Oct 18 2024
A potent weather system will be moving through the area, causing
VIS and CIG impacts at times. Fluctuations between MVFR/IFR/LIFR
are anticipated for most terminals this evening and overnight.
Gradual clearing should allow terminals to see VFR begin to
increase in coverage for terminals between 12Z and 18Z Saturday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Dense Fog Advisory until 8 AM MDT Saturday for WYZ106-110-117-
118.
Dense Fog Advisory until 9 AM MDT Saturday for WYZ116.
NE...None.
&&
$$
UPDATE...GCC
SHORT TERM...WFOCYS
LONG TERM...MN
AVIATION...BW
Area Forecast Discussion
National Weather Service Dodge City KS
508 PM CDT Fri Oct 18 2024
.KEY MESSAGES...
- Western counties are along a gradient of heavy precipitation.
- Precipitation is likely (>85%) for nearly all of SW Kansas,
but following recent trends amounts may be limited especially
east of highway 83.
- Main polar jet will remain well north of western Kansas next
week, leading to another period of above to well-above normal
temperatures and very little if no rainfall potential.
&&
.DISCUSSION...
Issued at 212 PM CDT Fri Oct 18 2024
Currently the deep trough and low pressure system has moved into
Arizona as forecasted. Parts of SW Kansas has received light showers
along a subtle boundary that runs north/south in the western zones.
Accumulations are expected to remain minimal; ensemble means have
the wettest parts of SW Kansas only receiving a tenth from Friday`s
light showers. Winds will continue to be strong Friday, although
considerably lighter than Thursday. Sustained winds are forecast to
reach 30 mph with gusts up to 40 mph. The forecast continues to
closely follow between the 75th and 90th percentiles of the NBM for
winds. That has fairly accurately captured the realized winds the
last couple days as the ensemble means continue to under do the
speeds. The fire weather risk is very limited with high RH values.
Blowing dust is less of an issue today with the lighter winds and
more moisture.
For Saturday, the primary very heavy band of projected precipitation
has been moved south slightly across many models and ensembles.
Models/ensembles also have the low ejecting much later than in
previous runs. This decreases the amount of rain SW Kansas could
have received. Even the newer 75th percentiles are much lower than
the extremely heavy 2.5"+ amounts touted as the upper-end potential.
Ensemble means are down to near 1.5" along the Colorado/Kansas
border. Even those amounts are sensitive to subtle changes that are
hard to forecast. As a result, Saturday is trending drier and drier
especially other than the western few counties. Ensembles now have
east of highway 83 at a <25% chance for precipitation from noon
Saturday to noon Sunday. Additionally, anywhere the 25% chance area
receives rainfall it is expected to be limited in amounts with
ensemble means struggling to reach a tenth. This trend is not much
of a surprise as this was a scenario outlined if the low pressure
system was more stagnant and held in place until well into Sunday.
Because of the behavior for the low, the window for most of the CWA
to see significant precipitation is getting smaller and pushed later.
Additionally, the low has not strengthened as much as even some of
the more pessimistic models. The unfavorable timing and strength has
helped further lower potential amounts. Many models (especially the
HRRR and NAMNST) had lighter precipitation developing ahead of the
line and spattering across SW Kansas, but those same models have
reeled back on this potential significantly. Most remaining hopes
rely on the long band slowly tracking over the area once the low is
ejected. Models and ensembles have been narrowing in on this
ejecting taking place later Sunday morning and entering Kansas
Sunday evening. Eastern zones are now only given a 0.5" mean
compared to the 0.75" previous runs. If the trend continues and the
outcome realizes as the later solution, the final totals could be
even much lower than the 0.5". Even with these amounts, localized
areas are inevitably going to see higher or lower than those numbers.
After Monday, once the low and precipitation has left the forecast
area, a zonal flow regime will take hold over much of the CONUS.
This will lead the CWA into another prolonged dry and uneventful
period for next week. Long ranged ensembles keep accumulation
chances below 10% for SW Kansas for the next week. The same
ensembles have higher temperatures in the 70s and pushing into the
low 80s for this temperate period.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 506 PM CDT Fri Oct 18 2024
A stationary front was positioned across southwest Nebraska ,
northwest Kansas and eastern Colorado, and is forecast to move
very little eastward over the next 24 hours. However an
increased moisture content atmosphere will lead to ceiling
development going forward as well spotty showers on Saturday.
South winds will slacken, losing gusts after about 3z, to as low
as 10 knots overnight, increasing back to the 20, gust to 30
knots area late Saturday morning.
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...KBJ
AVIATION...Russell
Area Forecast Discussion
National Weather Service Grand Rapids MI
1049 PM EDT Fri Oct 18 2024
.KEY MESSAGES...
- Roller Coaster Temps and Mostly Dry For The Next Week
&&
.UPDATE...
Issued at 1047 PM EDT Fri Oct 18 2024
The observations in the small craft advisory region indicate that
the winds have decreased to 10 to 20 knots and waves fallen to 2
to 4 feet. The latest HRRR indicates that the winds and waves will
continue to decrease through the remainder of the night. As a
result the small craft advisory was cancelled.
&&
.DISCUSSION...
Issued at 240 PM EDT Fri Oct 18 2024
Very dry soundings the next few days mean large diurnal
temperature ranges, with lows tonight dropping below freezing
across rural areas and rising 30 to 40 degrees tomorrow. This will
be especially true of areas with sandy soils where winds decouple
tonight.
Persistent southwest flow keeps temperatures increasing through
Monday. 850mb temps climb to near 15-16C by Monday which would be
near the maximum recorded this time of year based on DTX/APX
sounding climatology. This will translate into highs in the 70s on
Sunday, and well into the 70s if not near 80 by Monday! We cool a
bit Tuesday, back into the lower 70s as the core of the warm air
pulls away. Highs fall Wednesday and especially into Thursday as a
cold front passes through the region and troughing sets up
overhead. Highs Thursday are forecasted to be in the 50s, where
low temps were just 24 hours prior, with lows in the 30s.
As for precipitation, high pressure and dry air dominates through
the weekend and into much of Tuesday. Our only chance of
precipitation looks to be Tuesday night into Wednesday as a trough
from the northwest drives a cold front across lower Michigan. WPC
forecasts suggest a meager 0.1 inches of rain or less is expected
with this system, which won`t make a significant dent in our overall
dry pattern.
Confidence in the forecast is above average in the long term
forecast given the strong similarity across ensembles in forecast
outcomes. Cluster analysis shows little variability in the overall
mid-level wave pattern, with the small differences that exist
causing only small effects on temperatures or precipitation.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 746 PM EDT Fri Oct 18 2024
VFR/CLR weather continuing tonight and Saturday. Some patchy
shallow ground fog cannot be ruled out now that winds have become
light/calm, especially near/east of JXN 08Z-13Z, but the risk is
too low to include any mention of fog in the TAF at this time.
&&
.MARINE...
Issued at 240 PM EDT Fri Oct 18 2024
No changes to the SCA. South to southwest winds to 25 knots will
continue to build waves over 4 feet north of Holland through late
tonight. Winds and waves will be only marginally lower on Sunday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
UPDATE...MJS
DISCUSSION...Ostuno/Thomas
AVIATION...Meade
MARINE...Ostuno
Area Forecast Discussion
National Weather Service North Platte NE
650 PM CDT Fri Oct 18 2024
.KEY MESSAGES...
- Increasing rain and thunderstorm chances for tonight through Saturday
with potential for locally heavy rain totals (1-2").
- Another round of rain possible Sunday night into Monday as an upper-
level disturbance passes.
- Overall weather pattern next week favors above normal
temperatures and dry weather again though brief cool downs
are possible as frontal boundaries pass through.
&&
.SHORT TERM /THROUGH SATURDAY/...
Issued at 300 PM CDT Fri Oct 18 2024
Early afternoon satellite analysis depicts a mid-level disturbance
slowly tracking across the Desert Southwest. Ahead of this feature,
a plume of increased moisture is riding up and over downstream
ridging centered on the upper Ohio River Valley. Another disturbance
is beginning to encroach on the Pacific Northwest associated with a
deeper low across the Gulf of Alaska.
Today, deep low-pressure up invof the Hudson Bay will continue to
shuffle east. An attendant cold front extends south across the upper
Midwest and into the central Plains. As of 19z, this feature will
situated just south of an Imperial to Ainsworth line. Ahead of this,
moisture continues to pool as dew points have climbed into the upper
40s in moderate southerly flow. Upstream observations show low 50s
dew points in northwest Kansas and expectations are for this
moisture tongue to nose into southwest and south central Nebraska
late this afternoon and early this evening. While modest lapse rates
are already in place early today, guidance suggests these will wane
over the next 12 hours. The increasing moisture quality may overlap
enough with the lapse rates aloft to promote moderate buoyancy.
Latest RAP guidance suggests potential for even near 1000 j/kg of
SBCAPE across our far southwest zones. Shear aloft is plentiful as
h5 flow remains elevated around 30 to 40 knots. Even with southerly
flow in the warm sector, this should support deep-layer shear
magnitudes around 20 to 30 knots. Working against this, however,
will be shear vectors parallel to the draped surface front. This
suggests quick upscale growth and latest HRRR runs advertise as much
beyond the first hour or two of initiation. Storm motions should
carry storms across the boundary and onto the cool side where
instability will be nearly negligible and so any storm threat should
quickly die off as this occurs. Still though, can`t rule out some
smaller hail and gusty winds in stronger cores but severe weather is
not expected at this time. What is more concerning is quick upscale
growth of training thunderstorms may lead to localized heavy rain.
While I try to use that phrase lightly in the steadily increasing
drought conditions, consecutive runs of hi-res guidance continues to
paint increasing QPF in localized areas near if not just behind the
boundary. Forecast soundings show good saturation through the
profile and skinny CAPE profiles within anomalous PWAT values. The
12z upper air sounding from LBF sampled 0.90" PWATs or greater than
150% of normal. Though storm motion and upwind propagation vectors
suggest progressive storms, the training threat is what is necessary
to monitor. As mentioned, recent HRRR runs are now advertising 1-2"
of rain through early morning Saturday stretching from southwest
Nebraska up into the central Sandhills. Latest QPF closely matches
HREF probability-matched mean values with a slight maxima from Chase
County up through southern Brown County where amounts likely exceed
0.50". Elsewhere, most locations should remain at or below 0.25".
These peak values may fall short of what occurs though there remains
enough uncertainty in where the narrow 20 mile band sets up. Will
advise subsequent shifts to closely monitor through late this
afternoon.
Tonight, as instability wanes, storm strength should closely follow
and lead to scattered and widespread general thunderstorms. This
activity will be propelled by an increasing LLJ and modest WAA.
Convergence along the h85 front will also remain strong and as a
result fgen be a main driver. Gradual weakening of this is forecast
the closer to daybreak on Saturday we get and as such coverage and
intensity of rainfall should decrease. Maintained Chance (< 30%)
PoPs across our southern zones through the overnight with dry
conditions likely returning for most if not all locations north of I-
80. Lows as a result will vary considerably with low 30s in our
northwest and upper 40s to lower 50s for our south and east zones.
Dry conditions return to the whole of the forecast area on Saturday
as the surface boundary continues to slowly settle south. Mid-level
height rises as shortwave ridging builds will likely squash any
afternoon precipitation potential. Did boost afternoon highs
slightly along our far eastern zones as the frontal boundary may
stall in this immediate vicinity. Even still, encroaching high
pressure should allow for much cooler temperatures with many
locations likely hanging onto the 60. Only a few locations near the
boundary are likely to exceed that, perhaps into the low to middle
70s.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 300 PM CDT Fri Oct 18 2024
Sunday and Monday...our next potential for rain. Shortwave ridging
will breakdown as the deep low currently across the Desert Southwest
begins to track across the central Rockies. Broad WAA ahead of
approaching h5 low will usher warmer temperatures as a warm front
lifts north. Afternoon highs on Sunday will return to the 70s to
near 80 with breezy south winds. Increasing low-level moisture with
dew points climbing back into the 50s will offset any fire concerns
at this time. Meager lapse rates aloft should limit any threat for
severe weather with general thunderstorms expected. This activity
would favor the higher terrain before moving in late Sunday into
early Monday. In fact, some guidance suggests most if not all
activity holds off until early Monday. Will keep Slight Chance PoPs
(< 20%) to account for the limited confidence Sunday evening,
increasing to Chance (up to 50%) Monday. Main h5 low looks to track
immediately overhead with many deterministic solutions advertising
as much. This should allow for enough dry air intrusion to limit
precipitation potential and lead to a swift end west to east during
the latter half of Monday. Another day of cooler temperatures is
likely thanks to precipitation and cloud cover with forecast highs
in the 60s to low 70s.
Tuesday and beyond...following the departure of the Sunday/Monday
system, the extended period becomes more tame once again. A deeper
system within the northern stream will dive southeast into the Great
Lakes around the middle of the week. This will drag a cold front
south and into the local area sometime late Tuesday into early
Wednesday. The inherited model blend PoPs have painted Slight Chance
and Chance (up to 25%) categories for areas north of Interstate 80.
Deterministic and ensemble guidance varies considerably about this
potential with the GFS and GEFS suggesting a dry forecast while the
ECMWF and EPS advertising at least light QPF in these areas. This
will need monitored going forward. What is more probable is cooler
temperatures for a day or so in the post-frontal airmass. Ridging
looks to redevelop as ridge axis appears likely to settle either
across the central Plains if not immediately upstream. This will
support moderating temperatures with highs returning to the 70s or
nearly 20 degrees above normal for late October. This matches latest
Climate Prediction Center outlooks and NAEFS 8-14 Day mean
outputs.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 637 PM CDT Fri Oct 18 2024
Scattered rain showers and even a few isolated embedded
thunderstorms will be possible this evening into tonight across
western, southwest and north central Nebraska, including KVTN
and KLBF terminals. Cigs will lower tonight with MVFR to IFR
conditions possible across parts of the Sandhills into southwest
Nebraska, including KLBF terminal. Cigs will lift by early
afternoon and VFR conditions are expected. Winds across southern
Nebraska will continue to switch from the south to the northwest
this evening. Winds will remain breezy in the evening with gust
up to 20 kts possible. Winds will begin to diminish after
midnight to around 5 to 10 kts. Saturday afternoon winds will
switch again to the southwest around 5 to 15 kts.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Gomez
Area Forecast Discussion
National Weather Service Norman OK
1041 PM CDT Fri Oct 18 2024
...New AVIATION...
.KEY MESSAGES...
Updated at 1039 PM CDT Fri Oct 18 2024
- Elevated fire weather is possible over the next several hours in
northwestern Oklahoma.
- Low chances for rain will exist in western Oklahoma tomorrow
morning with a better chance for rain and thunderstorms occurring
late Sunday night through Monday across western and northern
Oklahoma.
- Summer-like heat returns for Tuesday and Wednesday.
&&
.NEAR TERM...
(Rest of today and tonight)
Issued at 211 PM CDT Fri Oct 18 2024
High cloud cover is expected to continue filtering into western
Oklahoma and western north Texas this afternoon on the far eastern
periphery of enhanced 500 mb flow. Sprinkles or showers this evening
can`t be ruled out in the far western part of the forecast area, but
dewpoint depressions remain in the 20+ degree range with not much
improvement foreseen. Southeast winds will continue through
sunset and slowly decrease overnight.
Rain chances will increase toward 20 percent in northwest Oklahoma
close to daybreak, fueled by increase moisture transport aloft. Even
then, most guidance suggests the best chance of rain will remain to
the north and west. Lows tonight will get toward into the upper 40s
in southeast Oklahoma and remain in the 50s elsewhere.
Meister
&&
.SHORT TERM...
(Saturday through Sunday night)
Issued at 211 PM CDT Fri Oct 18 2024
The relative peak in rain chances for northwest Oklahoma through the
next 48 hours will be tomorrow morning. This will occur within a
window of enhanced southerly flow at 700 mb aiding in isentropic
ascent, and forecast soundings from the HRRR and NAM even suggest
weak instability to generate some convective elements. Overall PoPS
will remain below 30 percent and this will occur in a limited
spatiotemporal window.
Things will begin to dry out west again in the afternoon while most
of the area has a sunny and warm day, with highs reaching into the
mid-to-upper 70s in most spots. The pattern will persist through
tomorrow night, with breezy southeast winds, lows dropping to near
50, and mostly dry weather. We`ll wrap that right into the day on
Sunday, with highs jumping up a few more degrees in most areas.
The upper-level low will begin to eject on Sunday night, but the
bulk of the rain looks to be on Monday, so the discussion of
that will be in the next section.
Meister
&&
.LONG TERM...
(Monday through next Thursday)
Issued at 211 PM CDT Fri Oct 18 2024
As anticipated, the GFS has begun to cave to all of the rest of
guidance regarding the timing of the cutoff low`s ejection. This
slowing trend can easily be picked out in model trend loops, and it
is evident in a slight delay in the greatest 6-hour PoPS in our
latest forecast. Right now, the expectation is for rain to move into
northwest Oklahoma several hours before sunrise on Monday and then
move east-northeast with the system. Rain chances will then diminish
from west-to-east before concluding in central Oklahoma a little
after midnight on Tuesday. Total rainfall amounts still look to
range from nothing near I-40 to close to half of an inch near the
Oklahoma/Kansas border. Although no model shows significant
instability yet, moisture return with dewpoints approaching 60 could
sufficient to bring about thunderstorms.
After the system passes by, ridging will build in very quickly
beginning on Tuesday. Highs will begin to approach October records,
especially across the southern half of the area. The ridge will
begin amplifying later in the week across the Intermountain West,
opening up our area to modest northwest flow and potentially one or
two weak troughs. A good bet is that Tuesday and Wednesday will be
the warmest days of the coming week, then, and that temperatures
have a fair shot of cooling off late in the week.
Meister
&&
.AVIATION...
(06Z TAFS)
Issued at 1039 PM CDT Fri Oct 18 2024
Mid to high clouds continue to build in from the west this
evening, with these clouds expected to linger into the day on
Saturday. Ceilings are expected to remain VFR through the period.
Winds will be from the south or southeast through Saturday night,
generally at 5-10 kts at most sites. A few showers remain possible
in western Oklahoma through Saturday morning, but chances remain
too low to mention in the TAF at KWWR or KCSM.
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 74 52 76 48 / 0 0 0 0
Hobart OK 76 56 79 49 / 10 0 20 0
Wichita Falls TX 78 54 80 50 / 0 0 0 0
Gage OK 74 53 76 48 / 20 10 30 0
Ponca City OK 76 48 77 46 / 0 0 0 0
Durant OK 76 47 78 46 / 0 0 0 0
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
NEAR TERM...04
SHORT TERM...04
LONG TERM....04
AVIATION...08
Area Forecast Discussion
National Weather Service Salt Lake City UT
345 PM MDT Fri Oct 18 2024
.SYNOPSIS...A slow moving low pressure system will continue to
bring valley rain and mountain snow to southern Utah through
Saturday, while the north trends drier. High pressure will build
into the area later Sunday into early next week bringing a warming
trend.
&&
.SHORT TERM (Through 00Z Monday)...A compact upper low is noted in
afternoon satellite imagery spinning across northern Arizona,
with an inverted trough axis extending across northern Utah into
western Wyoming. This low will stall out and temporarily become
cut off from the main branch of westerlies as it spins over
Arizona through Saturday night, before lifting northeast through
the Four Corners region Sunday. Vorticity lobes rotating around
this low will continue to bring periods of valley rain and
mountain snow to south central and southeast Utah through the
short term period while conditions trend drier over northern Utah
and southwest Wyoming. As such have maintained the going Winter
Storm Warning for the Southern Mountains zone, but dropped all
other winter headlines as the window for organized snowfall has
largely ended.
With this low spinning to the south of the forecast area, a
favorable setup for strong gap winds across lower Washington
County along with a somewhat less favorable setup for easterly
downslope winds along the northern Wasatch Front will become the
main concerns tonight through Saturday morning. Strong north-
northeast low level flow is enhancing cold advection across lower
Washington County presently, and coupled with a tight pressure
gradient is already producing wind gusts in excess of 58 mph
through Black Ridge Canyon along I-15. This will continue through
tonight and into Saturday morning, and a High Wind Warning remains
in effect for this area. Further north, afternoon RAP analysis
shows easterly 700mb flow is becoming established across portions
of northern Utah east of the Wasatch Crest. Model guidance has
backed off a bit in terms of the strength of the low level cold
advection within this regime, and hi-res guidance has trended
lower in terms of the overall magnitude of the easterly downslope
event. Still expect gusty easterly winds to develop along the
northern Wasatch Front this evening with gusts approaching 60 mph
still possible around the Park Lane area, so have left the High
Wind Warning in effect for this area. Peak winds look to occur mid
to late evening before diminishing overnight.
With much colder air in place and clearing skies overnight, it
still looks favorable for temperatures to fall below freeing
across outlying areas of northern Utah which have yet to
experience a freeze, and have maintained the going Freeze Warning
for Utah Valley, eastern Box Elder County as well as the western
Uinta Basin for tonight.
Temperatures across northern Utah will recover Saturday and Sunday
owing to mostly sunny skies, while extensive cloud cover and
precipitation maintains cool temperatures across the south. As
the low pulls away from the region Sunday, temperatures will
moderate across southern Utah while running near climo across the
north.
.LONG TERM (AFTER 00Z MONDAY)...The upper low near the Four
Corners area by 00z Monday will eject northeast across Colorado
through the evening hours. In its place, an upstream ridge will
shift over Utah. This will bring a drying and warming trend to the
area which will continue into late week.
However, a couple of troughs sliding by to the north will flatten
the ridge during the midweek timeframe (Tuesday through Thursday).
This will slow the warming trend and may bring some cloud cover to
the area. Still, afternoon maxes should rise to around 5-10 degrees
above normal by Tuesday or Wednesday. Overnight mins, while
generally above normal, will remain cold enough for frost or a light
freeze in some of the normally colder valleys.
The ridge axis is expected to roll over Utah Thursday or Friday
(although 32% of global ensemble members still have the axis near
the Utah/Nevada border by 00z Saturday) ahead of the next
approaching storm system. This will allow increasing southwesterly
flow to develop over the area, with breezy conditions and
potentially a somewhat stronger warming trend possible by Friday.
Most models continue to want to weaken the approaching storm before
moving it inland next weekend, although with a strong enough cold
front to bring another cooling trend to at least northern Utah.
&&
.AVIATION...KSLC...Northwest winds are expected to persist
around 10-15kts until at least 03z. Winds are likely to lighten
to around 4- 7kts overnight, but there is high uncertainty in the
direction. Winds may go light and variable at times overnight.
Northwest winds are likely to return after 17-19z Saturday. CIGs
around 6000ft AGL are likely to persist until ~03z, but could
become SCT-FEW sooner than 03z.
.REST OF UTAH AND SOUTHWEST WYOMING...Scattered showers will
continue across portions of southern UT overnight and even through
the morning and afternoon on Saturday, with snow possible above 7000-
8000ft ASL. Sites may see VIS/CIG reductions to MVFR and even IFR in
heavier precipitation. Gusty northerly winds may persist overnight
across western UT, with winds becoming more northeasterly to
easterly across northern and eastern UT. Downslope winds across the
northern Wasatch Front could produce gusty easterly winds at KOGD
and KHIF overnight, with gusts to 50-60kts possible right at the
base of the mountains (and lower gusts further away). Forecast winds
for KSGU are highly uncertain this afternoon and overnight, likely
switching between gusty northeasterly gap winds and light out of the
south.
&&
.FIRE WEATHER...An area of low pressure spinning over Arizona
will continue to bring periods of valley rain and mountain
snow through Saturday across southern Utah. Strong gusty winds
will continue through portions of lower Washington County
through early Saturday, while downslope easterly winds will
impact portions of the northern Wasatch Front tonight. As this
low moves away from the region, a warming and drying trend will
become established through early next week, with seasonal
temperatures and dry weather continuing through next week.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Freeze Warning from 8 PM this evening to 10 AM MDT Saturday for
UTZ103-106-114.
High Wind Warning until 10 AM MDT Saturday for UTZ104.
Wind Advisory until 10 AM MDT Saturday for UTZ105.
High Wind Warning until 4 AM MDT Saturday for UTZ123.
Winter Storm Warning until noon MDT Saturday for UTZ125.
WY...None.
&&
$$
Seaman/Cheng/Cunningham
For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity