Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/15/23
Area Forecast Discussion
National Weather Service Cheyenne WY
442 PM MST Thu Dec 14 2023
.KEY MESSAGES...
- Pesky freezing fog continues this afternoon and could persist
into the overnight hours across the Panhandle and here at
Cheyenne.
- Well above seasonal temperatures expected across the region
through much of next week.
- Low confidence/low impact wind event may develop across the
wind prone regions late Monday night into Tuesday.
&&
.SHORT TERM /THROUGH SUNDAY/...
Issued at 130 PM MST Thu Dec 14 2023
Discussion: Freezing fog continues this afternoon in and around
Cheyenne. Looking at WYDOT webcams...fog is confined to the
Interstate 25 corridor from the Colorado state line to mile
marker 16 and Interstate 80 in Cheyenne to mile marker 357 west
of Cheyenne. Let the Freezing Fog Advisory expire on time at 11
AM this morning and replaced with an Special Weather Statement
that expired at 1PM.
On the surface...we have a surface low analyzed across southern
Platte County with southerly wind flow still over the area that
still has low clouds and fog. Do not really see a change in the
winds for tonight. HRRR and HREF shows low clouds and fog
returning tonight after 03Z...so went with a persistence
forecast for tonight on low clouds and fog. Basically from
Cheyenne east into the Panhandle. West of the Laramie
Range...winds do become more westerly...so held off on fog.
Upper shortwave forecast to move through overnight after 09Z and
through the Panhandle after 12Z. Westerly winds for Friday
morning expected to scour out low level moisture.
Winds pick up after 12Z from the northwest with clearing skies
and warmer temperatures finally. Breezy conditions Friday
afternoon as GFS 850mb winds 20-25kts and 700mb winds 25-30kts.
Upper ridge builds over the CWA Saturday with 700mb temperatures
+1 to +3C. Expecting to see afternoon highs in the low to mid
50s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Issued at 130 PM MST Thu Dec 14 2023
Overall the main impactful weather in the long term forecast remains
on track from the previous forecast package. A continuation of dry,
quiet and warm conditions are expected to prevail through the
weekend and into much of next week, with temperatures climbing 10-
15F above seasonal normals across much of the region. We are still
tracking the potential for an elevated to high wind event to develop
across the wind prone areas late Monday night into Tuesday as a weak
shortwave trough passes overhead and brings better 700mb winds and
subsidence to the regions in question. Not one model or in-house
models are particularly bullish on this event so we will continue to
advertise ad low confidence/low impact forecast regarding this
possible wind event.
.PREVIOUS LONG TERM...
All Long Range models show a benign and quiet weather pattern
for late this weekend and through early next week, with little
if any impacts expected. Northwest flow aloft will continue over
southeast Wyoming and western Nebraska Sunday and Monday, ahead
of the high amplitude ridge axis slowly drifting east across the
Great Basin Region. A weak backdoor cold front is forecast to
quickly push south and west across the high plains on later on
Sunday, which should lower temperatures a few degrees with some
mild to high cloud cover. Temperatures on Monday will still be
10 to 15 degrees above normal behind the front with even warmer
temperatures expected on Tuesday as the upper level ridge axis
finally pushes over and east of the region. May see a few record
high temperatures on Tuesday with forecast highs in the mid 50s
to low 60s along and east of the Interstate 25 corridor...with
the warmest temperatures across western Nebraska.
The only minor forecast concern and general uncertainty is the
potential for gusty winds across the wind prone areas Sunday,
with another potential minor event late Monday and into Tuesday.
Not very impressed with the set up on Sunday once the front
moves southward into the northern and central plains. Winds do
increase a bit, but it looks mainly driven by low level gradient
with winds aloft well below critical thresholds. In-house winds
models are also not very impressive and have backed off
considerably compared to a few days ago. Monday night and
Tuesday looks a little more interesting with a weak upper level
shortwave pushing east across the area and better low level
subsidence and 700mb flow. Other than that, mountain snowfall
will be the primary impact from this next round of Pacific
energy as models indicate a pattern shift across the eastern
Pacific Ocean mid to late next week.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 430 PM MST Thu Dec 14 2023
SE WY: While KRWL and KLAR have returned to VFR and will likely
remain VFR through the TAF period, LIFR CIGS and VIS are sticking
around KCYS for at least the next two hours. As the next system
pushes through, winds will turn NW and clear out the FZFG. Gusty
winds possible 20 to 30 knots beginning early tomorrow morning.
W NE: MVFR to IFR CIGS will persist until 07-09Z, until the
winds turn NW and push the CIGS and FZFG east. Gusty winds 20 to
30 knots possible as early as 14Z, and continuing through the
afternoon.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...AW
AVIATION...LEG
Area Forecast Discussion
National Weather Service Peachtree City GA
825 PM EST Thu Dec 14 2023
...Evening Update...
.UPDATE...
Issued at 753 PM EST Thu Dec 14 2023
The ridge of high pressure will continue to build in overnight
before weakening and sliding off to the east of the Appalachians
tomorrow. Will hold off on issuing a Fire Danger Statement this
evening as uncertainty lies in the spatial extent of relative
humidities reaching criteria, but one is likely warranted for a
large portion of the CWA Friday. The short term forecast remains
largely on track despite some tweaks to the temperature and
dewpoint grids in the immediate near term. Additionally, sustained
wind speeds were adjusted over the next few hours as observations
across central Georgia have been lighter than advertised.
&&
.SHORT TERM...
(This afternoon through Friday)
Issued at 251 PM EST Thu Dec 14 2023
Key Messages:
- Gusty winds through today. Windy tomorrow, but not likely as
strong.
- No rain expected. Dry airmass in place has lead to Fire Danger
Statement for this afternoon across North GA. Another statement
may be needed tomorrow.
Forecast:
Huge surface high is parked over the central Appalachians that
covers much of the country east of the Rockies. This high is
dominating our weather tonight through tomorrow, bringing mostly
clear skies outside of some cirrus and a dry airmass filtering in
from the northeast. High will slowly weaken through Friday thanks to
decreasing convergence aloft and slide to the east ahead of our
weekend system, but rain chances through Friday Night will remain
near zero. With weakening surface high pressure, high temperatures
increase a bit on Friday but remain within a few degrees of
climatology in the 50s and lowers 60s. Winds should also decrease a
bit thanks to weakening of pressure gradient, though some of this
may be offset by beginning of surface low development in the gulf.
For dewpoints tonight into tomorrow, ran a local blend of
statistical models with HRRR and NBM10 to account for mixing of dry
air aloft down to the surface. These are very close to criteria for
another fire danger statement across much of north Georgia, so
expect the potential for one with forecast package update tonight.
Lusk
&&
.LONG TERM...
(Saturday morning through next Wednesday)
Issued at 251 PM EST Thu Dec 14 2023
A change in the pattern will be ongoing as the extended period
begins on Saturday. The upper ridge and associated surface high will
be shifting northeastward towards the Mid-Atlantic coast as deep
troughing digs into the southern Great Plains. A lobe of shortwave
energy will swing around the southeastern periphery of this trough
and through the northern Gulf of Mexico over the course of the day,
which will lead to the development and intensification of an
surface low in the central Gulf. This low is anticipated to move
northeastward towards the Florida coast Saturday and Saturday night.
Much uncertainty and run-to-run inconsistency remain with respect to
how far north or south this low will track. For example, the latest
GFS solutions brings the low onshore into the Big Bend region of
Florida while the latest ECMWF brings the low on shore near Tampa by
Sunday morning. While these tracks continue to shift from run to
run, ECMWF was been fairly consistent in indicating a more southward
track and slightly weaker surface low overall. In any case, another
wet weekend is on tap as scattered showers are forecast to spread
into central Georgia by Saturday afternoon on the north side of the
low, then increase coverage northward Saturday night into Sunday as
the low gets closer.
PoPs and rainfall amounts will be contingent upon the track the low
takes, with more northward tracks favoring more widespread coverage
of showers and higher rainfall totals. Coverage is expected to be
best on Sunday as the low continues to move northeastward towards
the mid-Atlantic coast. At this time, rainfall amounts are forecast
to range from 2 to 3 inches roughly south of the I-85 corridor and 1
to 2 inches to the north. Some locally higher amounts will be
possible in southeast portions of the forecast area closest to the
low. A tight pressure gradient in the vicinity of the low will also
lead to strong winds across the area on Sunday into Monday. Gusts of
30-35 mph will also be possible across the majority of the forecast
area. Isolated thunderstorms will be possible across portions of
east-central Georgia on Sunday. One variable to keep an eye on will
be a trough digging from the High Plains towards the Midwest
Saturday night into Sunday, which is anticipated absorb the first
trough mentioned, deepening into a cutoff low. The behavior of this
feature and how far south it plunges will have a major influence on
the evolution and movement of the Gulf low, which will warrant
monitoring.
After the system moves away to the northeast, gusty winds will
likely persist until Tuesday or Wednesday as a result of the
pressure gradient on the back side of the high. The upper level
trough axis will also swing through Georgia by Monday morning, which
would set up northwesterly flow aloft and push dry air back into the
region. Another trough will swing through Monday night into Tuesday
morning, bringing another shot of cool and dry air. This will help
drop low temperatures into the upper 20s and low 30s on Tuesday
morning. Highs on Tuesday will rise into the upper 40s to mid 50s,
then begin to moderate underneath another upper ridge and surface
high pressure during the mid-week.
King
&&
.AVIATION...
(00Z TAFS)
Issued at 641 PM EST Thu Dec 14 2023
VFR conditions throughout TAF cycle at all terminals. NE winds from
8 to 12 KT expected though the end of the period. As moisture
increases tomorrow evening, expect to see FEW/SCT250 return to most
terminals at the end of the forecast period.
//ATL Confidence...00Z Update...
High confidence on all elements.
KAL
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 30 56 35 55 / 0 0 0 20
Atlanta 34 56 39 54 / 0 0 0 20
Blairsville 30 55 33 51 / 0 0 0 10
Cartersville 31 57 37 56 / 0 0 0 10
Columbus 37 60 44 60 / 0 0 0 30
Gainesville 33 55 37 51 / 0 0 0 20
Macon 33 59 42 59 / 0 0 0 30
Rome 29 59 35 58 / 0 0 0 20
Peachtree City 31 57 39 57 / 0 0 0 20
Vidalia 36 61 45 65 / 0 0 0 30
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...KAL
LONG TERM....King
AVIATION...KAL
Area Forecast Discussion
National Weather Service Indianapolis IN
937 PM EST Thu Dec 14 2023
.Key Messages...
- Light QPF rain chances Saturday night through early Sunday
- Windy with isolated flurries/snow showers possible Monday
- Otherwise, mostly dry and mild weather through the next 7 days;
Drought conditions expected to continue
&&
.Forecast Update...
Issued at 937 PM EST Thu Dec 14 2023
Good radiational cooling conditions have allowed temperatures to
fall quickly this evening, especially in favored cold areas. Lowered
hourly temperatures as needed based on latest trends seen in
observations.
Given these trends, have also lowered low temperatures some as
needed across the area. Otherwise, forecast is in great shape.
&&
.Short Term...(This evening through Friday)
Issued at 252 PM EST Thu Dec 14 2023
Strong surface high pressure (1040mb) remains over the region this
afternoon with large-scale subsidence, resulting in clear skies and
calm winds. Boundary layer mixing has allowed for a rather wide T/Td
spread, with RH values once again dipping to near 30 percent. Model
soundings indicate less dry air in the near-surface layer, however,
and dew points are not nearly as low as they were yesterday. This
trend should continue into tomorrow as low-level moisture gradually
increases.
Ideal radiational cooling potential is expected tonight. Lows will
dip into the 20s, like last night, with widespread morning frost.
Given the aforementioned conditions, will plan on adding additional
weight to the HRRR which better captures terrain effects on
temperatures. Lower elevations and sheltered areas should see cooler
(by a few degrees) readings than elsewhere.
Increasing heights associated with upper-level ridge building is
expected into Friday, and will lead to generally warmer highs than
what we saw today. Additionally, the center of the surface high
slides eastward allowing winds at the surface to gain a southerly
component. Clear skies early on and light winds should allow for a
quick temperature recovery after sunrise. Increasing high clouds in
the afternoon may temper this somewhat, but not prevent highs from
climbing into the 50s.
&&
.Long Term...(Friday night through Thursday)
Issued at 252 PM EST Thu Dec 14 2023
The primary forecast challenge through the long range will be the
upcoming storm system slated to arrive Saturday evening. Ahead of
its arrival, departing high pressure will lead to generally quiet
conditions with increasing cloud cover. High clouds begin to
increase during the day on Friday, becoming a thick overcast by
Saturday morning. A few scenarios exist regarding this system and
its eventual evolution, and these will be discussed below.
THIS WEEKEND`S RAINFALL POTENTIAL
First, an overview on the overall synoptic set up. A rather
complicated flow pattern aloft exists over the CONUS, which can be
described as split flow in the northern jet along with a potent
quasi-zonal subtropical jet. Vort maxes in each (one embedded in
each branch of the northern jet, and one within the subtropical jet)
are set to interact with one another...eventually phasing into a
potent low that rides the eastern seaboard.
Scenario 1: The northern branch vort maxes (one currently in the
Texas Panhandle and one diving south out of Montana) phase over
Missouri. Should a more complete phase occur, forcing will be
maximized over Illinois and Indiana before energy is eventually
transfered to the coastal low. The deterministic ECMWF depicts such
a scenario, and generally has higher QPF amounts compared with less-
phased models/runs.
Scenario 2: Phasing occurs, but is less `complete` and/or delayed
slightly. The deterministic GEM depicts such a scenario. Generally
lower QPF amounts are shown in guidance with such an evolution.
Given the complicated nature of the upper-level flow pattern and the
tendency for phasing to fail during El Nino seasons...will lean more
towards this scenario for now.
Scenario 3: A third scenario exists, but is lower probability than
the first two. This depends on the vort max embedded within the
subtropical jet (over the Gulf of Mexico), which interacts with the
northern stream vort maxes sooner. This then allows the developing
east coast low to be further inland and occlude further south,
allowing TROWAL/Wrap-around precip to extend as far west as Indiana.
The 00z deterministic GFS depicts such a scenario, but recent runs
have trended away from this and more towards the ECMWF/GEM.
Regardless of which scenario plays out, another factor needs to be
taken into account - namely, a rather dry antecedent air mass. Model
soundings indicate this air mass, centered around 850mb, lingering
through much of the day on Saturday. Moisture return ahead of the
northern stream system (phased or not) may be limited by the
developing surface low over the Gulf of Mexico. This, combined with
our preference for scenario 2, brings forecast QPF amounts under
what blended guidance suggests.
Should everything go right (phasing), and moisture advection end up
greater than currently anticipated...the reasonable worst-case
scenario still only ends up with QPF amounts under an inch, falling
more around the 0.5-0.75 inch range (mainly south/east Indiana).
This would be ideal, given our ongoing drought. Conversely, total
amounts as low as 0.1 inch are not out of the question if everything
goes wrong (no phasing, too much dry air).
THE REMAINDER OF THE LONG RANGE
Beyond this weekend, the deepening coastal low will allow troughing
to prevail into the upcoming week. Most guidance shows a potent vort
max diving southward on the back side of the deepening trough.
Enough moisture and forcing may be present for flurries/light snow
on Monday as a result. Additionally, a strong MSLP gradient could
lead to Monday being quite windy as well. With strong cold air
advection behind the departing low, scattered flurries/snow showers,
and gusty winds...Monday could end up being the most winter-like day
of the period.
Surface high pressure arriving will allow for a few nights with
ideal radiational cooling potential (Mon night and Tue night). As
the high slides eastward, ensembles suggest a quick return to dry
and seasonably warm conditions through the end of the period.
&&
.Aviation...(00Z TAF Issuance)
Issued at 553 PM EST Thu Dec 14 2023
Impacts:
- No impacts expected.
Discussion:
High pressure will continue to provide VFR and dry conditions. Winds
will be light and somewhat variable tonight then become south to
southeast at less than 10kt Friday. High clouds will increase during
the day Friday.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...50
Short Term...Eckhoff
Long Term...Eckhoff
Aviation...50
Area Forecast Discussion
National Weather Service Marquette MI
939 PM EST Thu Dec 14 2023
.UPDATE...
Issued at 939 PM EST THU DEC 14 2023
Strong winds have been observed in the Keweenaw Peninsula overnight.
For the most part, sustained winds of 30 mph have resulted in wind
gusts near 40 mph at KCMX, but occasionally winds have been observed
at 45-50 mph. Recent HREF and NBM runs of mean winds at 10m AGL is
capturing this well and continues these stronger winds overnight
through at least 9z. Additionally, multiple power outages have been
observed north of Calumet. With this in mind, opted to hoist a wind
advisory.
Elsewhere, winds have been light save for occasionally 20-30 mph
gusts near Lake Michigan and Superior. Temps have also been mild so
far, with most sites still in the 40s as of this writing.
&&
.SHORT TERM...(Through Tonight)
Issued at 253 PM EST THU DEC 14 2023
Key Messages:
-Gusty west-southwest winds over the UP today
-Temperatures remain well above normal this afternoon into tonight
Latest RAP analyses show deepening low pressure over northern Hudson
Bay, and sprawling high pressure centered over the Ohio Valley. The
resulting tight pressure gradient between these features has yielded
gusty w-sw winds across the fcst area today. Gusts have typically
been in the 20-25 knot range this afternoon although some gusts
around 35 knots have been realized at KCMX. Under mostly sunny skies
and a 850 mb thermal ridge moving over the area, temperatures have
risen into the mid 40s east and into near-record warm upper 40s to
lower 50s elsewhere across the U.P. this afternoon.
Wind gusts should fall back later tonight with a slackening gradient
and the core of 50+ kt LLJ winds sliding eastward. Clouds spread in
from the west late tonight with the approaching shortwave rounding
the mid-level ridge and the associated cold front sagging se from
Ontario. Models indicate some light rain could reach into western
counties of the U.P. just before sunrise. Expect temperatures
tonight to stay quite mild with the warm airmass and increasing
cloud cover. Lows will generally range from the lower 30s south
central and east to the mid 30s west and north central.
.LONG TERM...(Friday through Thursday)
Issued at 308 PM EST THU DEC 14 2023
Key messages:
- Rain showers move in Friday, turning to wet snow Friday night over
the interior west. Mainly around an inch or less of wet snow is
expected, but the WI border counties have about a 30% chance of
seeing up to 3".
- Periods of lake effect snow are likely (60% chance) in the NW to N
lake effect belts Sunday night into Monday along with a brief cool-
down to near normal temperatures.
- For the next 2 weeks, above normal temps will prevail on average
with no widespread, significant system snowfalls on the horizon for
Upper MI.
Polar jet stream displaced northward compared with normal resulting
in positive 500 mb height anomalies encompassing much of the CONUS
to start the period. The associated unseasonably warm airmass will
continue to be in place over the local area to start out Friday
morning, with temps starting out likely in the mid-30s to low 40s.
Meanwhile, confluent 300 mb flow over Ontario will support high
pressure building in to our northwest through Friday. Ascent tied to
the equatorward entrance region of this jet, reflective of a
midlevel frontogenetic circulation, will spread into the area on
Friday. This will allow rain to move into the area from northwest to
southeast through the morning and into the afternoon hours. The
incipient low-level front tied to weak troughing crossing Ontario
will stall over our area as it connects to a surface low drifting
gradually east into Minnesota during Friday night. This will allow a
band of precipitation to remain fairly stationary over at least
portions of the area Friday night. Where exactly is still a
question, as drier air supplied by the aforementioned high to our
north may result in a sharp cutoff to the northern edge of the
precip. Highest probabilities of precipitation (>80%) exist over the
WI border counties Friday night, tapering off to ~40% near Lake
Superior. Where the steadiest precip occurs is where evaporational
cooling and latent cooling due to melting may support a changeover
to wet snow. Probabilities of snow >3" along the WI/MI border have
increased to 30-40% on the latest HREF. However, that`s at 10:1 snow
ratios, and actual ratios may be less than that. Bottom line,
official forecast shows around an inch near the MI/WI border, but
locally higher amounts up to around 3" will be possible (~30%
chance) where the most persistent bands are located.
For Saturday, the f-gen band lifts northward through the day, with
rain or a rain/snow mix. It`s unlikely that we see any impactful
accumulation during the day (>70% of less than an inch). It should
be mild still as the frontal boundary washes out/lifts back
northward, with the mild airmass remaining in place Sunday in
advance of a diving trough. Highs mainly in the mid-30s to low 40s
both days. Sunday should be mainly dry.
Only other period of impactful weather may be in the Sunday night
into Monday timeframe. High confidence that the east coast cyclone
and anomalous moisture plume will remain east of the local area, but
light snow is expected to move in ahead of a digging positively
tilted northern stream trough Sunday night. 850 mb temps falling to
around -15C will support lake enhancement, transitioning to pure
lake effect Monday morning. Probability of measurable snow has been
increased to 50-70% chance in the NW to N snow belts Sunday night
into early Monday.
After the shot of cold air associated with the trough for Monday,
ensemble guidance favors a return to ridging, with slightly above
normal temperatures returning into midweek. Climate Prediction
Center`s 8-14 day outlook continues to predict a 70-90% chance of
above normal temperatures continuing in the 8-14 day outlook (Dec.
21-27), and a 70-75% chance of near to below normal precipitation.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 620 PM EST THU DEC 14 2023
A strong low level jet will continue to support low level wind shear
underneath clear skies overnight. At the surface, gusty winds are
also expected, particularly as mixing changes. Gusty winds,
upwards of 40 kts, are expected at KCMX overnight while KSAW and
KIWD decouple and find themselves removed from the stronger winds
aloft. The jet will exit and winds at the surface will also
lighten Friday morning as a cold front moves into the region and
stalls out overhead. This will support rain spreading over all
terminals in the morning hours. Additionally, the stalled boundary
will result in ceilings falling to IFR.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 308 PM EST THU DEC 14 2023
Southwesterly gales of 35-45 kt continue into tonight for the
western and central part of the lake before diminishing late tonight
into Friday. A few storm force gusts to 50 kt still cannot be ruled
out through this evening from the tip of the Keweenaw north to the
Canadian border. After a relatively calm period Friday night into
Saturday morning, southeasterly winds will increase to 20-25 kt over
the central and eastern lake Saturday afternoon and evening. The
next gale potential looks to be Sunday night into Monday as a brief
shot of colder air invades the region on northerly winds.
Probabilistic guidance shows a 50-80% chance of gales during this
time.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Wind Advisory until 5 AM EST Friday for MIZ001-003.
Lake Superior...
Gale Warning until 10 PM EST /9 PM CST/ this evening for LSZ162-
245-246-248-265.
Gale Warning until 4 AM EST /3 AM CST/ Friday for LSZ241>244-263-
264-266.
Lake Michigan...
None.
&&
$$
UPDATE...JTP
SHORT TERM...Voss
LONG TERM...Thompson
AVIATION...JTP
MARINE...Thompson
Area Forecast Discussion
National Weather Service Phoenix AZ
405 PM MST Thu Dec 14 2023
.UPDATE...
Updated Aviation
&&
.SYNOPSIS...
Temperatures will continue to trend upward through the rest of the
week with highs climbing well above normal this weekend. Saturday is
expected to be the warmest day with highs in the mid to upper 70s to
near 80 degrees across the lower deserts. Dry conditions will
continue into early next week before a more unsettled pattern sets
up, bringing chances for rain to the region for the latter part of
next week.
&&
.DISCUSSION...
Visible satellite and WV imagery show clear conditions across much
of Arizona this afternoon as dry, subsident northwesterly flow aloft
prevails on the back side of a departing low pressure system. RAP
analysis showed this area of low pressure centered over New Mexico
this afternoon as it continues to move away from the region. This
system brought slightly cooler temperatures to the area and some
chilly morning lows in some of the colder, sheltered locations.
Morning observations recorded lows in the lower 30s along parts of
the Lower Colorado River Valley as well as areas around Casa Grande
and Arizona City.
Going forward through the weekend, an amplified ridge of high
pressure will build in across the western CONUS, causing
temperatures to rebound to well above normal readings. Saturday is
forecast to be the warmest day as the ridge axis moves through
Arizona. Ensemble guidance shows 500 mb heights Saturday climbing up
to around 582-585 dm, which is above the 90th climatological
percentile. This will translate to daytime highs rising upwards of
nearly 15 degrees above daily normals in some places where
temperatures will be flirting with 80 degrees. The latest NBM has
probabilities of reaching or exceeding 80 degrees up to around 25-
35% across Phoenix Saturday. Well above normal temperatures in the
mid to upper 70s across the lower deserts will continue into the
start of next week with the high for Phoenix Monday forecast to come
within a couple of degrees of the daily record (79 degrees in 1950).
Aside from the unseasonably warm temperatures, a tightened gradient
will bring some breezy winds across parts of central Arizona
Saturday with the strongest winds remaining confined to the higher
terrain/ridgetops east of Phoenix.
While much of the west will be under the influence of ridging this
weekend, a potent cutoff low will set up in the eastern Pacific.
This system is expected to bring heavy rainfall to the West Coast
for the start of next week, while dry conditions are favored to
continue across our CWA. Ensemble guidance show this low becoming an
open wave and ejecting northeast into the Pacific Northwest early
next week. Meanwhile, a shortwave that will be near the Aleutian
Islands will dive southward in the eastern Pacific while developing
into a closed low. Ensemble cluster analysis reveals much better
agreement amongst members compared to prior runs in recent days
regarding the overall evolution of this system. Ensemble guidance
favor this low pressure system positioning itself off the coast of
California, though uncertainty remains around the magnitude of this
low along with the amount of moisture it will pull into the region.
This unsettled weather pattern will bring the potential for rainfall
across the Southwest along with cooler temperatures. Forecast
uncertainty is reflected in NBM temperatures where a 10 degree
spread in the interquartile range for highs by next Thursday. The
unsettled pattern will be getting into the holiday timeframe, so
stay tuned as details become more clear.
&&
.AVIATION...Updated at 2305Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather impacts will exist through Friday afternoon as FEW-
SCT cirrus decks move into the region. Confidence is excellent that
light west winds will quickly revert to easterly (and in some cases
nearly calm) mid/late evening across the Phoenix metro. Other than
low chances of a few isolated gusts above 10kt late Friday morning,
light east winds should prevail later into the afternoon than is
usual before obtaining a light westerly component. Across SE
California, light north or west winds below 10kt will be preferred
with extended periods of nearly calm conditions.
&&
.FIRE WEATHER...
Temperatures will continue to rise over the next several days, with
well above normal temperatures expected over the weekend. As the
latest weather system exits the region, RH`s will trend drier, with
overnight recoveries degrading going through the weekend. Winds will
favor typical diurnal patterns over the next couple of days.
Enhanced breeziness is expected Friday night into Saturday as high
pressure builds into the region. Otherwise, dry conditions will
continue with skies remaining generally mostly clear to, at worst,
partly cloudy through the weekend. A more active weather pattern may
be in store for the middle portions of next week.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Smith
AVIATION...18
FIRE WEATHER...Young