Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/22/23
Area Forecast Discussion
National Weather Service Birmingham AL
1002 PM CDT Fri Apr 21 2023
...New SHORT TERM...
.SHORT TERM...
(Tonight through Saturday)
Issued at 951 PM CDT FRI APR 21 2023
/Ongoing showers and storms vacate the region early Saturday/
The 00Z BMX sounding was fairly close to RAP analysis in showing
1,200 J/kg of SBCAPE, bulk shear of ~40 knots, and 100-200 low-
level SRH this evening. These parameters, alongside lift from a
shortwave just the west, was enough to sustain convection of
which produced gusty winds and a likely brief tornado in Fayette
County, between the towns of Fayette and Berry. A few storm
segments are in the vicinity of the 65 corridor but are less-so
co-located with a narrow SRH axis, now mainly ahead of the
convection given the line orientation. Storms will mainly produce
heavy rain, frequent lightning, and instances of non-severe gusty
winds in the near-term.
Spotty showers will trail the main line of rain and storms
overnight, but all activity is expected to exit by early Saturday
morning. A clearing sky is expected thereafter with a northwest
breeze throughout the day as high temperatures top out in the 70s.
89^GSatterwhite
&&
.LONG TERM...
(Saturday night through next Thursday)
Issued at 255 PM CDT FRI APR 21 2023
Not much has changed since the previous long term update. Cold
advection and high pressure will bring a cooler and drier airmass
to the region Sunday and Monday. This will set the stage for
increasing isentropic as surface winds shift to the east ahead of
an approaching shortwave. Rain is expected to overspread the
region late Tuesday into Wednesday and could continue into
Thursday and Friday as the active and anomalously suppressed
pattern persists.
87/Grantham
Previous long-term discussion:
(Saturday through Thursday)
Issued at 244 AM CDT FRI APR 21 2023
Sunday through Monday.
An upper low will be over the Great Lakes Region with a negative-
tilted trough extending southeast over the Mid Atlantic while a
zonal flow will over our area. Expansive surface high pressure
across the Northern and Central Plains will continue to build into
the area from the northwest.
Skies will range from mostly sunny further southeast to east
while more clouds will exist across the west due to a few weak
shortwaves that will ripple over the area from the west. Dry
conditions in the low and mid levels will keep conditions dry.
Lows will range from the low 40s far north to around 50 far
southeast. Highs will range from the mid 60s north to the mid to
upper 70s far southeast.
Tuesday through Thursday.
Global model solutions have improved over the past few days in
the handling of a shortwave diving southeast over the Central
Rockies early on Tuesday but some timing differences persist,
largely due to if/how fast a closed low aloft develops. Closer to
home, depictions of a few shortwaves continue to be present that
will move over the area early Tuesday followed by a stronger
impulse on Wednesday. Surface high pressure will move northeast of
the area early Tuesday while low pressure develops across the
Central Plains. A coastal/marine warm front will advance northward
across the Central Gulf Coast on Wednesday as surface low
pressure moves east along the boundary. Persistent strong high
pressure across the High Plains through the Midwest and into the
Ohio River Valley looks to help keep the warm sector suppressed
across the southern portion of the forecast area through Thursday.
While global model solutions have become a bit more consolidated
in the synoptic pattern, timing and intensity of finer-scale
features remain less correlated, resulting in lower
confidence/more uncertainty. Sky/PoPs are more broad-brushed with
an approach using deterministic temperatures that are generally
below the blended means with value spreads from 9 to 12 degrees at
times.
Expect increasing clouds with isolated showers arriving from the
southwest during the day on Tuesday. Shower activity will increase
on Wednesday with some thunderstorms near the U.S. Highway 80
corridor and further south as the warm front nears from the south.
Chances for showers with a few thunderstorms southeast will
continue into Wednesday night while reduced shower activity is
expected across the west. Unsettled conditions continue into
Thursday with low end PoPs areawide. A moderating trend is
expected with lows from the mid 40s north to low 50s south Tuesday
morning to readings from near 50 north and mid 50s south
Wednesday and Thursday mornings. Highs will actually decrease
through the period due to increased clouds and higher rain
chances. Expect highs from upper 60s north to the upper 70s south
Tuesday then ranging from the mid to upper 60s north to the mid
70s south on Wednesday into Thursday.
05
&&
.AVIATION...
(00Z TAFS)
Issued at 637 PM CDT FRI APR 21 2023
/Showers and storms now arriving, will exit early Saturday/
As of 23:37z, a band of showers and storms was located from
Decatur, AL to Jackson, MS. This activity will move across central
Alabama through the course of Friday night with any trailing
showers likely to exit by 12z Saturday. A few terminals could
briefly observe TSRA during the evening as the leading edge of the
complex arrives, excluding MGM-TOI where activity looks to be
more spotty and later. The sky will clear by 15z Saturday as a dry
northwesterly flow takes hold. Surface winds will turn from
southerly Friday evening to northwesterly on Saturday and we may
need to add some ~20 knot gusts to the TAFs for the afternoon
hours.
89^GSatterwhite
&&
.FIRE WEATHER...
Rain will move into the region late this afternoon and continue
into early Saturday morning. This will be followed by decreasing
clouds and drier conditions Saturday afternoon. Dry conditions and
northerly winds will continue into Sunday and Monday with
afternoon minimum RH values in the 25-30 percent range.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 48 71 44 70 / 100 0 0 0
Anniston 50 72 46 73 / 100 0 0 0
Birmingham 50 74 48 72 / 100 0 0 0
Tuscaloosa 48 75 48 73 / 100 0 0 0
Calera 51 73 49 73 / 90 0 0 0
Auburn 57 74 50 75 / 40 10 0 0
Montgomery 56 76 50 77 / 40 0 0 0
Troy 58 77 51 79 / 30 10 0 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...89^GSatterwhite
LONG TERM....87
AVIATION...89^GSatterwhite
Area Forecast Discussion
National Weather Service Columbia SC
836 PM EDT Fri Apr 21 2023
.SYNOPSIS...
A cold front will move across the Southeast tomorrow, bringing
showers and a few thunderstorms along with it. Behind that,
cooler temperatures return for Sunday into early next week. The
weather pattern then turns more unsettled from the middle of
next week onward.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Moisture will increase over the region tonight ahead of an
approaching cold front. An upper shortwave will move over the
forecast area late tonight/early Saturday morning as PWAT values
increase to over 1 inch. The cold front will remain to our west
through sunrise keeping surface forcing limited. Warm, moist
advection over a weak surface ridge and upper level support
suggests scattered showers developing after midnight through
early Saturday morning. There may be an isolated thunderstorm as
well with muCAPE values ranging from 250 to 500 J/kg. However
the threat of severe weather is low due to a surface inversion
keeping thunderstorms elevated. Temperatures will be mild due to
the increasing moisture and cloud cover. Expect lows in the low
60s.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...
Saturday and Saturday night: To start off the day, the main cold
front is expected to be just off to the west of the forecast
area. Moisture coming inland from the Atlantic ahead of the
front should be producing some light rain/sprinkles across the
eastern counties, possibly moving further into the Central
Midlands through the morning. The main cold front is forecast to
be moving into the western Midlands by late morning, then
quickly push into the central and eastern cwa by the afternoon
hours. Most guidance indicates the front should be east of the
cwa sunset Saturday evening. Ahead of this front, both showers
and thunderstorms are possible, especially right along the
leading edge of the front. There may be a modest amount of CAPE
across the eastern half of the cwa by the afternoon hours, with
values around 1000 j/kg still being indicated. Due to the
afternoon passage of the front, can not rule out a few stronger
storms, with small hail and strong winds being the primary
threats. SPC continues to have the eastern half of the cwa in a
Marginal Risk, with a Slight risk just brushing the eastern most
portions of the cwa, mainly east of I-95, on Saturday. Outside
of any storms, the surface wind will increase through the day.
Models have trended slightly lower with the wind speeds, and at
this time it appears as if winds over area lakes should remain
below Lake Wind Advisory criteria. However, would still expect
some small wave action to occur on the bigger lakes, and choppy
conditions could be encountered through the day. Saturday night
will see drier air enter the forecast area behind the exiting
cold front. Both daytime highs and overnight lows are forecast
to be a little cooler. Due to cloud cover, highs will only reach
the upper 70s to lower 80s. Clearing skies and a cooler airmass
leads to overnight dropping down into the upper 40s to around
50.
Sunday and Sunday night: Little change to this period. Dry high
pressure will settle into the region. Plenty of sunshine and
only weak cold advection should still help to produce
comfortable afternoon temperatures. Highs in the low to mid 70s
expected, with overnight lows Sunday night back down into the
40s again.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
Work week starts off cool and dry again, but by Tuesday moisture
will begin to increase and a few weak upper level shortwaves
move across the area through mid-week. This will bring a return
of unsettled and wet conditions, especially from late Tuesday
night through the end of the week.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions through much of the period with restrictions
expected Saturday morning ahead of cold front.
High pressure shifting offshore. Mainly mid and high level
clouds through 06z. Low level moisture will increase toward
morning. Guidance has been suggesting at least a chance of MVFR
ceilings 09z-15z. The lamp guidance is trending less threatening
especially at AGS. However, GFS/Nam model time-height
sections, and the HRRR continue to suggest low clouds late
tonight. This seems reasonable as low level south jet
strengthens during the early morning. So, continued from
previous forecast MVFR ceilings late tonight into Saturday
morning. A cold front will move through the region around 18z or
a little later to the east of CAE. A few showers and
thunderstorms are possible ahead of the front but confidence is
low for any impacts at terminals at this time. High probability
of VFR after 18z as cold front pushes toward the coast. Winds
will be south-southwest ahead of the front 10 to 15 knots then
shift to west-northwest behind the front with gusts to near 25
knots.
EXTENDED AVIATION OUTLOOK...Restrictions possible late Tuesday
and Wednesday as moisture deepens across the region and weak low
pressure approaches from the Gulf coast region.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Charleston SC
954 PM EDT Fri Apr 21 2023
.SYNOPSIS...
High pressure will weaken across the area overnight. A cold
front will move through Saturday, followed by cool and dry high
pressure through early next week. A storm system is expected to
bring impacts to our region during the middle of next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Based on recent trends we have had to lower temps some more in
Berkeley County, now showing lows in the upper 50s in the
Francis Marion and closer to the Santee River. Just about
everywhere else will be in the lower and middle 60s. We did slow
down the increase in cloud cover a bit from earlier, but no
other major changes.
The HRRR has been trending with a bit slower onset of showers
and t-storms overnight, and it now looks like the most likely
timing would be about 1-2 hours later than previously mentioned.
This would be 12-6 AM in Georgia and after 3 AM in South
Carolina. However, we`re not inclined to lower PoPs.
Previous discussion...
The influx of higher dew points, PWat and higher theta-E air
into the area will have forcing for ascent associated with a
short wave that approaches, resulting in the formation of
isolated to scattered showers and t-storms. The most likely
timing would be from 11 PM to 5 AM across our Georgia counties,
and from 2 AM through 6 AM and beyond over the South Carolina
counties. While there is 25-35 kt of 0-6 km Bulk Shear, MLCAPE
is mainly 500-1000 J/kg and lapse rates are that impressive.
Thus the risk for severe weather is non-zero, only because
DCAPE is more than 1000 J/kg. So we`ll need to watch for the
potential for locally strong winds in any t-storm. No major
changes to temps, except to lower them about 1-2F in Berkeley
County as they`ll have a longer period of time before cloud
cover increases.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Saturday: The mid-levels will consist of a large trough extending
from the Great Lakes region into the Deep South during the morning.
The trough will take on a negative tilt as it gradually shifts
eastward through the afternoon and into the overnight. Large-scale
forcing for ascent will be prominent across the area in the morning
lending to showers and perhaps a thunderstorm across the forecast
area, but most of the energy will then shift to our north as the
trough axis tilts. At the surface, a cold front will be located
along the Appalachians at daybreak and will approach our area during
the day. PWATs look to peak around 1.4" as southerly flow ushers
ample moisture into the area. Models show a second "round" of
rainfall occurring in the afternoon associated with the front. For
the most part, there looks to be indication of a weakening line of
broken showers and thunderstorms crossing into the forecast area
around mid-afternoon. However, a few storms could be severe
depending on a few factors. Given mostly cloudy skies and showers in
the morning, areas of partial clearing in the late morning/early
afternoon will allow for the environment to destabilize. Models have
MLCAPEs peaking between 1100-1300 J/kg along/east of I-95, and 800
J/kg inland. 0-6 km bulk shear should be in the 30-40 kt range, but
0-1 km and 0-3 km SRH appears to be marginal. Damaging wind gusts
followed by large hail are the primary hazards. Flooding is not a
concern given the progressive movement of the storms. The overall
threat for severe weather has shifted a bit north from the previous
forecast, where the greatest forcing lies, and SPC has limited the
Slight Risk for severe thunderstorms to just the Charleston Tri-
County. Any storms should come to an end by early evening, with
showers ending by midnight, which is around the time the cold front
moves through our area. The front will then move offshore overnight,
with drier air and clearing skies moving in from the west. Highs
could be tricky, with our current forecast showing max temps
reaching the low 80s most places and upper 70s along the beaches.
Low temperatures will dip into the upper 40s well inland and low to
mid 50s elsewhere.
Sunday and Monday: A mid-level trough will remain primarily to our
north, with nearly zonal flow across our area. At the surface, high
pressure originating from the Northern Plains Sunday morning will
build towards the OH/TN Valleys by late Monday. The periphery of the
high will bring our area dry conditions with mostly sunny/clear
skies on Sunday, followed by a gradual increase in clouds from the
south on Monday. Plummeting dew points could raise concern for fire
weather both Sunday and Monday, as min RH values drop below 25%
inland. Lighter winds and perhaps some wetting of the soils could
offset the need for a Fire Danger Statement (see Fire Weather
section below). The combination of some downslope flow and the
plentiful sun will offset the cold air advection across the region
on Sunday. High temperatures will still be cooler, generally in the
upper 70s. Lows Sunday night will range from the low to mid 50s.
Highs will be a few degrees cooler on Monday, generally in the low
to mid 70s.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Mid-level zonal flow will be over the Southeast Monday night. The
pattern then diverges Tuesday through Thursday, with signs pointing
towards a potent shortwave passing above the area. A storm system
originating along the Gulf of Mexico will likely impact our region
towards the middle of the week, bringing showers and thunderstorms.
Temperatures during the long term will be slightly below normal.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
KCHS and KJZI: VFR much of the night, before the potential for
some MVFR conditions between 09Z and 14Z due to scattered SHRA
and at least isolated TSRA moving through. This would be in
response to energy aloft moving in and higher moisture and
instability from off the ocean. VFR will then prevail through
from late Saturday morning until late in the afternoon, before
the next chance of SHRA/TSRA and flight restrictions occur
with a cold front.
KSAV: VFR early tonight, before the potential for some MVFR
conditions between 06Z and 10Z due to scattered SHRA and a maybe
a few TSRA moving through, caused by similar conditions to those
at KCHS and KJZI. VFR will then prevail much of Saturday, until
maybe some late day SHRA and TSRA moves in with a cold front.
Latest indications are that the higher probabilities though will
stay north of the terminal.
Extended Aviation Outlook: VFR returns late Saturday night and
will prevail through Tuesday.
&&
.MARINE...
We maintained the philosophy that a few strong winds in
isolated to scattered t-storms can occur overnight. Marine
Weather Statements and/or Special Marine Warnings could still
be required.
Previous discussion...
Tonight: High pressure extending across the western Atlantic will
dominate the weather pattern locally through late evening, but
should gradually retreat late with the approach of a cold front
Saturday. Conditions are expected to remain well below Small Craft
Advisory levels through the first half of the night, with east-
southeast winds generally no higher than 10-15 kt and seas no larger
than 2-4 ft. However, there could be a slight uptick in southerly
winds along with building seas late tonight, with gusts up to 15-20
kt and seas of 3-5 ft (strongest/largest well offshore) within a few
hours of daybreak.
Saturday through Wednesday: A cold front will approach from the west
Saturday, causing a southerly moderate breeze during the afternoon.
As the front moves offshore overnight, winds will shift out of the
north and briefly increase again. Gusts could exceed 20 kt beyond 15
nm, but should stay below 25 kt. Seas should peak around 4-5 ft,
thus not warranting Small Craft Advisories. Behind the FROPA, weak
high pressure will build into the region Sunday. Winds will begin to
ease Sunday afternoon, then remain 15 kt or less through Tuesday
with seas 2-4 feet. By Wednesday when the next storm system
approaches our region, models indicate building seas and strengthening
winds. Small Craft Advisories could be needed for most of the
marine zones as early as Tuesday night through Wednesday.
&&
.FIRE WEATHER...
A cold front will move through the region on Saturday, followed by
dry high pressure through early next week. Afternoon RH values are
expected to drop to 21%-26% Sunday and again Monday, in areas away
from the immediate coast. Rainfall associated with the front will
wet the fuels, limiting the fire potential. However, areas in
southeast GA could see very little rainfall (less than 0.1 inches)
which could provide little to no help in keeping soils damp. Winds
will remain on the lighter side, no more than 10 mph with occasional
gusts up to 15 mph.
&&
.TIDES/COASTAL FLOODING...
Based on latest trends it appears that tides in Charleston
Harbor will reach near or just above 7.0 ft MLLW with the 10 pm
high tide. We`ve issued a Coastal Flood Statement, as any
coastal flooding, should it occur, will be very minor and would
last no more than about 30 minutes. No concerns for coastal
flooding elsewhere along the coast.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
FIRE WEATHER...
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Des Moines IA
618 PM CDT Fri Apr 21 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Friday/
Issued at 250 PM CDT Fri Apr 21 2023
Key messaging highlights:
* Mixed precip showers diminishing early this evening
* Freezing temps tonight and especially Sat night
* Precip chances early next week, and again late
* Some temp moderation later next week
It`s been a fairly miserable day across the northwest half of the
state with intermittent rain/snow/graupel showers, brisk winds,
and below normal temperatures. The combination of steep low level
lapse rates and a lobe of differential cyclonic vorticity
advection south and east of a well defined short wave across
southwest MN per water vapor imagery has been very efficient at
producing weak convection, which should persist until dissipating
with the loss of insolation. Initialized RAP soundings have
depicted very deep mixing preceding these showers, up to 9,000 ft
at times, with atypical dendritic growth zone depths ~2km above.
They are very transient, but these conditions have been able to
produce quick bursts of <=1/2sm visibilities NW per obs and
webcams during the heavier showers. The brief nature of the
showers, warm ground temps, and road temps in at least the 40s
have precluded any significant travel impacts however. The most
significant snow showers have struggled to get too far into our
forecast area. The stratus is expected to linger into tonight with
temps hovering around the freezing mark south. The headline is
marginal, but will keep the Freeze Warning intact south where
growing season impacts would be more prevalent.
Little if any precipitation is anticipated tomorrow, but the
brisk winds and cool temperatures will continue with most highs
again no better than the 40s. Looking into Saturday night,
conditions are somewhat more favorable for a hard freeze with
decreasing winds as surface high pressure approaches the MO
Valley. Low level relative humidities do diminish somewhat, but
confidence is only medium that skies will fully clear and better
support radiational cooling. Have min temps a bit lower through
the guidance spectrum to account for this, and kept Freeze Watch
in place unchanged, but the degree of clearing will need to be
watched per cloud trends.
Looking ahead to next week after the upper low departs, another
cycles through and keeps IA influenced by the long wave trough.
Eventually this will move sufficiently for the baroclinic zone to
move into the MO Valley again bringing rain chances back into the
forecast early next week with warm advection returning, at least
aloft. Weak northern stream ridging above the NM upper low will
keep surface high pressure influence into midweek, but eventually
low level return flow does develop by Thu before another frontal
passage and upper level closed low maturation gets us fairly close
to where we are today with the influence of a large, cool upper
low.
&&
.AVIATION.../For the 00Z TAFS through 00Z Saturday evening/
Issued at 615 PM CDT Fri Apr 21 2023
VFR conditions currently prevail at all terminals. Scattered
rasn shower activity will continue into the evening and overnight
hours, however the vast majority will not result in any
categorical restrictions. Model guidance in strong agreement that
cigs will lower to MVFR by overnight into early Saturday morning
and will prevail through much of the day. Some improvement to VFR
is possible at times with a SCT deck, or possibly rising above
3000 feet by late afternoon.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 1 AM to 9 AM CDT Saturday for IAZ044>050-
057>062-070>075-081>086-092>097.
Freeze Watch from Saturday evening through Sunday morning for
IAZ044>050-057>062-070>075-081>086-092>097.
&&
$$
DISCUSSION...Small
AVIATION...Martin
Area Forecast Discussion
National Weather Service Riverton WY
427 PM MDT Fri Apr 21 2023
.DISCUSSION...(This evening through Friday)
Issued at 228 PM MDT Fri Apr 21 2023
Energetic northwest flow continues to stream over western and
central WY today, aided by a 120+ knot jet directed NW to SE over
the state. As expected, snow started and increased during the
morning hours across western WY with some moderate to heavy snow
showers also impacting areas further east such as Sweetwater
County and the Absarokas. Most areas east of the divide saw a cool
front move in yesterday, and that weak east-northeast flow
continues. Meanwhile, breezy and gusty west-northwest wind picked
up mid-morning west of the divide and continues this afternoon.
Snow will continue over the far western WY mountains through the
evening before decreasing, and accumulate in the valleys as well,
especially Star Valley. Higher mid-level NW flow will follow the
wave across SW WY and northern UT through the day. Models are
still indicating convective showers setting up from the NW WY
mountains southeast across the central basins and Sweetwater
County late this afternoon and evening, as is evident in the Day 1
Convective Outlook from SPC showing a low chance of thunder from
NW to SE WY. Can`t rule out some quick one inch accumulations
with about 0.10" of precipitation before midnight in some areas.
Several high- resolution models are favoring some enhanced
convection and weak upslope in the Wind River Basin between 10pm
and 3am as the backside of the instability moves through the area.
Temperatures remain on the cool side this afternoon and expecting
min temps overnight to be about the same as this morning, and
evening 3-5 degrees cooler in the western snow-covered valleys as
skies clear out after midnight.
The unstable northwest flow will continue on Saturday, keeping
lower elevations temperatures in the 30s and 40s as 700mb temps
remain in the -6C to -10C range. Some models are showing a weak
shortwave trough moving from western MT into western WY during the
afternoon, which would enhance convective showers across the
mountains and western WY. The GFS is the most bullish with the
showers, but a couple of high-res models like the HRRR and HiRes
FV3 indicate more shower activity than some others. Winds look to
be weaker Saturday than the past couple of day, with weak
northerly flow east of the divide and breezy northwest winds west
of the divide.
A weak dirty ridge looks to build in late Saturday into Sunday
morning, keeping a low chance of light showers over the western
and northwest mountains. The more westerly mid-level and upper-
level flow however should warm temperatures throughout the column,
leading to the lower elevations getting back to the 50s to near 60
east of the divide, and upper 30s to mid 40s west of the divide. A
large trough then moves into the Pacific Northwest Sunday, kicking
an initial shortwave trough in westerly flow toward WY late
Sunday into Monday morning. This will increase moisture and clouds
into western WY Sunday night, with light snow over the western
mountains early Monday morning. This initial system then moves
over the rest of the area Monday, with little chance of showers,
but should serve to increase the southwest winds and keep
temperatures more seasonable. Medium-range models then bring the
strong trough SE into the Great Basin. The GFS is now closing the
low off and swinging the center down through Idaho into northern
Utah on Tuesday, significantly increasing moisture and chances for
precipitation over the most of the area. With this pattern, looks
like a good amount of snow in the mountains, especially the Wind
Rivers, with a rain/snow mix in the lower elevations. Gusty north
winds should enhance favored upslope areas east of the divide. The
ECMWF keeps taking the low farther and farther south, with the
primary impact over southern WY and less of an impact over
northern WY. Still expecting cooler air with northerly flow, but
with the lack of consensus, can`t say where the heaviest
precipitation will be late Monday into Tuesday. Both solutions
move the system to the southeast on Wednesday as weak northwest
flow moves back over the area. Temperatures should rebound and
winds pick up again on Thursday under mostly clear skies.
Amazingly, both models are in good agreement with a strong
shortwave trough dropping south out of Alberta into Montana and WY
late Thursday night into Friday morning. Cold air will move in
along and east of the divide to bring a good chance of rain/snow
for parts of northern and central WY. Unfortunately, cool
northerly flow looks to continue next weekend for below normal
temperatures.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 425 PM MDT Fri Apr 21 2023
West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals
Most snow shower activity will end early this evening, but lingering
isolated snow showers remain possible. MVFR conditions may occur off
and on at all terminals through around 06Z as snow showers remain in
the vicinity, but VFR conditions should generally prevail. There is
potential for some fog development at these terminals Saturday
morning, but due to continued OVC to BKN sky cover, confidence is
not high enough to include in any TAFs at this time. Mountain
obscurations will occur through the TAF period. Isolated snow
showers will again be possible Saturday afternoon, but confidence is
not high enough to include at any Terminals.
East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals
Snow showers continue across the region this evening. It continues
to look likely that there could be a period of steady light to
moderate snow across the Wind River Basin, impacting KLND and KRIW
terminals between 04Z and 10Z tonight. IFR conditions are likely
during much of that time for those terminals. All terminals are
expected to return to prevailing VFR conditions by 14Z Saturday.
Mountain obscurations will occur through the TAF period. Isolated
snow showers will again be possible Saturday afternoon, but
confidence is not high enough to include at any Terminals.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.
&&
.FIRE WEATHER...
Issued at 1244 PM MDT Fri Apr 21 2023
Unsettled and cool northwest flow will continue over western and
central WY today and tomorrow, with below normal temperatures and
good chances of rain/snow showers over much of the area.
Accumulating snow is ongoing over far western WY with snow showers
spreading eastward through the rest of the afternoon and evening.
NE flow will continue east of the divide through the day, while
gusty northwest winds will continue through early evening west of
the divide. There is a 15-20 percent chance of thunderstorms this
afternoon and evening with the convective activity that stretches
from NW WY to SE WY, including the central part of the state. Some
of the snow showers could be heavy early this evening before
diminishing. A similar pattern continues on Saturday with slightly
warmer temperatures and less chances of snow showers, though
western WY and the mountains still have a 25-50 percent chance of
showers. Winds will be lighter on Saturday as well. Some warming
and clearing can be expected on Sunday as the flow turns more
westerly, with only light snow showers possible over the NW WY
mountains. Heads up: there is potential for a moderate storm
Monday afternoon into Tuesday across much of the area.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 PM MDT this evening for WYZ012-
023-024.
&&
$$
DISCUSSION...McDonald
AVIATION...Hensley/Rowe
FIRE WEATHER...McDonald