Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/20/19
Area Forecast Discussion
National Weather Service Amarillo TX
608 PM CST Tue Nov 19 2019
.AVIATION...00z TAF Cycle...
Expect VFR conditions with increasing high clouds through the
overnight period. Cigs will begin to fall after 12z Wednesday with
overcast conditions increasing in conjunction with shower activity
from west to east. A few thunderstorms are also possible, favoring
the southern most terminal (KAMA), however thunder can`t be ruled
out at any location. Areas of MVFR cigs/vsbys will be possible
with this activity, with the main window being between 16z and
22z. After 22z, sky conditions should gradually improve from west
to east. Southerly winds will generally be around 10 knots or
less overnight, but will become more southwesterly and gusty
during the day tomorrow. A few gusts around 30 to 35 knots will be
possible. Also can`t rule out some localized wind gusts and heavy
rain associated with any thunderstorms that develop. Finally, some
marginal wind shear is possible overnight tonight at all three
.PREV DISCUSSION... /Issued 402 PM CST Tue Nov 19 2019/
Current satellite and model analysis depicts an H5 closed low
approaching the northern Baja Peninsula. This low which is cut off
from the main flow aloft, has been stationary over the past few
days. It is now showing signs of moving to the northeast like
models have hinted at. Moisture transport is apparent in the water
vapor product on the east side of the low. Moisture is moving
into Mexico and New Mexico as well as Southwest Texas and is
expected to be in the area by tomorrow. This low is progged to
move northeast and enter the FA tomorrow as a shortwave. The
combination of the shortwave and moisture will help with creating
rain showers and some thunderstorms during the day tomorrow.
Down stream from the open short wave trough the upper level jet
dynamics increase, with wind speeds reaching around 60 kts at H5,
even higher at H2, during the afternoon tomorrow. This will
increase the over wind shear available. The amount of CAPE
available for severe thunderstorms to be possible has been low.
Now some models are trending slightly higher with MLCAPE around
500 to 600 J/Kg. The overall bulk shear is approaching 50 knots
which is impressive if the instability ends up being there
tomorrow. If some more CAPE becomes available we cannot rule out
some isolated severe storms tomorrow mainly for the eastern FA.
Interestingly enough, the 15Z run of the RAP does show MLCAPE
values reaching 1200 to 1500 J/Kg for the eastern FA. It also
depicts dewpoints briefly reaching the 60s in the late afternoon.
The NAM however, only has dewpoints reaching the mid 50s and does
not have such high CAPE. The models with the lower CAPE may be
picking up on the cloud cover we could see most of the day with
all the moisture coming in. With all that said cannot entirely
rule out an isolated severe storm tomorrow, and will have to
monitor the trends in the model with next runs.
Tomorrow winds will pick up again around 20 to 25 mph as a lee
side surface low develops in southeast Colorado late morning. The
pressure gradient will be enough to drive some gusty winds. The
chances for rain will develop from west to east through out the
day with traversing of the upper level trough. The available CAPE
for thunder will probably be more in the afternoon for the south
and eastern FA. Temperatures should still be able to get into the
60s before the next cold front moves through Wednesday night.
LONG TERM...Wednesday Night through Tuesday...
Long anticipated disturbance that is going to kick out the Baja
low and evolve into a closed low in the vicinity of SRN CA is now
visible on WV near the Pacific NW. Will be interesting to see how
much model forecast may change the next couple days as the upper
air network samples these system better. For now, models are in
decent agreement on the big picture pattern that shows the low
moving ENE up through the trough axis (somewhat odd) toward a
northern stream strong s/wv that will be moving into the mid-west
on Thursday. Despite the agreement, there are a lot of
complexities with several models showing a new low center forming
further east from the original and becoming the dominant center(
also a bit odd) and am not at all confident in these solutions as
of yet. If forecasts do hold, the combination of a H250 jet
impulse and strong H5 s/wv rotating around the large system will
track mainly across the NW Panhandles. The initial fropa will have
occurred early Thursday, but a secondary surge will arrive from
NW to SE late Thursday afternoon through Friday morning.
Differences in the timing and strength of the secondary surge will
be key for snowfall potential as will the degree of dynamic
cooling produced by the storm system. Several models are showing a
H85 wave developing across the far southwest Panhandles which
increases the H85 frontogenesis and therefore QPF across the wrn
Panhandles. Again, how quickly the atmosphere cools will be huge
wrt how much snow accumulation occurs and how far southeast
accumulations occur. In general, with these dynamic systems, the
faster cooling and quicker frontal progression tends to verify it
seems and not crazy about the warm ECMWF H85 forecast. Taking
this all into account, the NW Panhandles continue to have
potential best potential for a 1-2 inch snow (possibly 1-4 if
things come together) esp NW of a Hooker to Hartley line based on
current models with lighter accumulations possible a county or
two south. There is some concern for a mix of sleet as precip
types change from rain to snow, and a mid level dry slot will
decrease the moist layer providing some potential for a mix of
light freezing rain or drizzle mainly south of the best snow area.
Can`t completely rule out a brief period of wintry precip in the
far SE, but the window appears brief and closer to sunrise Friday
and marginal temps suggest minimal to no impacts if frozen precip
does occur across the far SE. Minor changes in H5 evolution and
H85 temps can/will strongly impact snow forecast, so stay tuned.
Will remain slightly on cool side to start the weekend, but will
be near or slightly above normal wrt temps by Sunday aftn. Similar
conditions for Monday will be followed by the next cold front and
cooler conditions by Tuesday. The assoc upper level system is
forecast on vigorous side and both the GFS and ECMWF cut off the
H5 low across the Panhandles as it traverses the area, although
the ECMWF is 12 hours faster. This will bring the next chance for
rain and/or snow to the area Tuesday. Some accumulations would be
possible with GFS/ECMWF forecast and it wouldn`t take much of a
jog south, to make this system even more interesting with greater
potential for an impactful snow event.
Area Forecast Discussion
National Weather Service Green Bay WI
706 PM CST Tue Nov 19 2019
New Information added to update section
Issued at 704 PM CST Tue Nov 19 2019
Low-level moisture across the area, along with a temperature
inversion aloft, has led to increasing fog formation across
central into north-central Wisconsin. Surface dewpoint depressions
are steadily decreasing across those locations along with very
light winds, which will lead to increasingly dense fog through the
late evening and overnight hours. Hi-res model guidance continues
to indicate visibilities dropping below a half to a quarter mile
at times overnight into the early morning hours. Farther east,
confidence in visibilities dropping below a mile is much lower;
therefore, east-central and far northeast Wisconsin has not been
included in the advisory. Will monitor observation trends in those
locations for potential expansion later tonight. In addition to
the fog, surface temperatures are expected to drop to near or just
below freezing. This may lead to some freezing fog development
and may cause slippery travel on untreated and elevated surfaces.
.SHORT TERM...Tonight and Wednesday
Issued at 228 PM CST Tue Nov 19 2019
The latest RAP analysis and satellite/radar imagery show weak
shortwave energy moving across the northern Mississippi Valley
early this afternoon. Spotty light returns on area radars are
reaching the ground, primarily over north-central WI, in the form
of light snow. Little to no signs of freezing drizzle/drizzle and
visibilities have slowly improved through the day. Some of the
lowest visibilities reside within a weak surface trough over the
western part of the state. Otherwise, widespread low overcast
continues to prevail across the region and extends across
Minnesota and eastern Dakotas. As temperatures cool tonight,
forecast concerns revolve around fog/freezing fog potential,
followed by cloud trends on Wednesday.
Tonight...The weak surface trough over western Wisconsin is
expected to dissipate later today or this evening, but ample low
level moisture will remain beneath the subsidence inversion.
Forecast soundings show inversion heights falling and with
nocturnal cooling, so should see cloud heights fall as well.
Statistical and probabilistic guidance also supports falling
visibilities over central and north-central WI. Unsure if a dense
fog advisory will be needed, but with temps falling below
freezing over central and north- central WI, freezing fog onto
road surfaces may lead to slippery or even icy stretches. Will add
a mention to the hazardous weather outlook. Just like the past
several nights, temps will not fall much, and leaned on the
previous nights lows heavily once again.
Wednesday...Low stratus and fog will likely persist through much
of the morning as a surface ridge axis moves into central WI.
With daytime heating, increasing anticyclonic flow, and warming
low level temps, it`s possible that partial clearing will occur
during the afternoon. On the other hand, ample mid and high clouds
will be streaming into the region ahead of the next system, so
will likely see filtered sunshine at best where low stratus
erodes. Stayed close to the previous forecast for high temps, but
may have to be adjusted pending cloud cover. Most locations will
see highs ranging from the upper 30s to low 40s.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 228 PM CST Tue Nov 19 2019
A strong low pressure system is expected to arrive Wednesday
night into Thursday, and the GFS/GEFS/ECMWF are in very good
agreement on timing and a track through east central Wisconsin.
Low-level thermal profiles and thicknesses suggest all rain
across the forecast area Wednesday night. The rain/snow line is
expected to gradually shift southeast across north central WI
on Thursday, but the heavier precipitation should be tapering off
as this occurs. Could see 1 to 3 inches of accumulation over
Vilas county by evening, aided by lake-enhancement late in the
day. Farther southeast, a surge of gulf moisture, with PWATs
exceeding 1 inch, will lead to moderate rainfall late Wednesday
night into Thursday morning, with rainfall totals likely reaching
0.75 to 1.0 inch. With frost depths of 4+ inches over the forecast
area, runoff from the rain could cause minor flooding issues.
There is also some concern for minor lakeshore flooding and
erosion on the Lake Michigan shoreline, as 6-9 foot waves batter
the coast late Wednesday night into Thursday morning. The
locations most susceptible to flooding and erosion would be the
eastern shore of Door county, and the Two Rivers area, where wave
action will be most perpendicular to the coast. Winds will become
offshore Thursday afternoon, so impacts will lessen with time.
This event is NOT expected to be nearly as impactful as the event
on October 21st.
As the low pressure system exits, there will be potential for a
brief period of light lake effect snow showers over north central
WI Thursday night.
The weekend looks quiet, with systems tracking north and south of
the forecast area. Looks like a generally dry weekend, with
temperatures near seasonal normals.
Low pressure developing near the TX/OK panhandle early in the work
week will lift toward the region on Tuesday, bringing a chance of
rain or mixed rain/snow. Models show this system strengthening
as it lifts into the western Great Lakes region Tuesday night
into Wednesday. The current track would appear to be too far west
for a significant snowfall in GRB CWA, but we are 7-8 days out,
so significant changes are likely to occur. At a minimum, this
system should impact early travel for Thanksgiving Day.
.AVIATION...for 00Z TAF Issuance
Issued at 510 PM CST Tue Nov 19 2019
Widespread low stratus and some reduced visibility has been noted
across a large portion of the area this evening. MVFR to IFR
conditions are expected to linger through much of the TAF period
with some LIFR visibility possible across central and north-
central WI overnight into Wednesday morning. This would mainly
impact the CWA/AUW/RHI TAF sites. Some freezing fog potential is
also possible; however, not overly confident in this occurring as
temperatures are near to slightly above freezing. Otherwise, some
improvement will likely occur, especially in visibilities, during
the day Wednesday.
Dense Fog Advisory until 9 AM CST Wednesday for WIZ005-010-018-
Area Forecast Discussion
National Weather Service Hanford CA
1202 PM PST Tue Nov 19 2019
Low pressure will move into the region from the north tonight and
Wednesday bringing a chance of rain and mountain snow along with
cooler temperatures. The low will move east on Thursday with a
return to dry weather.
The focus in the short term continues to be on the two low
pressure systems along the West Coast. The southern closed low off
the coast of Baja will continue to push a surge of moisture into
SoCal and Arizona, while the northern digs south. Ahead of the
northern one is some shortwave energy which has edged the cold
front into the area. Not expecting much out of that frontal
passage, but can`t rule out high elevation snow.
The real focus is on the main low digging south as it packs a lot
more energy and will phase in the southern low overnight. Before
that happens however strong northerly winds associated with the
northern low will bring some fire weather concerns to the northern
half of the state. Though, Merced County will some breezy winds
not expecting nearly the impacts in our area due to the
orientation of the valley relative to the winds.
With respect to precipitation things should be quite benign until
the southern low gets phased into the other as this will bring
some of the tropical fetch. Still, the bulk of the moisture will
remain southeast of the area, though enough rap around moisture
will bring some mountain snow and valley/desert rain. Given the
moisture axis and upper level flow the main area for precipitation
will be along the Sierra Nevada, Greenhorn Mountains, and
Tehachapi Mountains. The western San Joaquin Valley north of Kings
County will likely be left out as the measureable precipitation
is expect east of Highway 99 for the most part.
For the extend, the jet stream remains quite wavy across the area,
though things look dry. The good news for the time being is this
keeps the eastern Pacific ridge from settling over us.
Areas of MVFR visibilities in haze can be expected
in the San Joaquin Valley with local IFR/LIFR visibilities due
to fog through 18Z Tuesday. VFR conditions will prevail elsewhere
over the central California interior during the next 24 hours.
.AIR QUALITY ISSUES...
On Tuesday November 20 2019... Fireplace/Wood Stove Burning Status
is: No Burning Unless Registered in Fresno... Kern... Kings...
Madera... Sequoia National Park and Forest and Tulare Counties.
Further information is available at Valleyair.org
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is high.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.html for additional information
an/or to provide feedback.
Winter Storm Warning from 10 PM this evening to 4 PM PST
Thursday for CAZ192-193.
Winter Storm Warning from 4 AM Wednesday to 4 PM PST Thursday
Area Forecast Discussion
National Weather Service Lincoln IL
924 PM CST Tue Nov 19 2019
Issued at 326 PM CST Tue Nov 19 2019
Widespread fog will develop across central Illinois
tonight...resulting in reduced visibilities for the Wednesday
morning commute. Once the fog dissipates, a partly sunny and mild
day is anticipated on Wednesday with afternoon high temperatures
topping out in the lower to middle 50s.
Issued at 924 PM CST Tue Nov 19 2019
Forecast looks ok for now, but thinking that dense fog is going to
develop tonight in the west and possibly spread east as low clouds
over the area push to the east. ALready seeing some indications of
fog developing in obs and satellite loops in west central IL.
Satellite also showing clouds moving east as west. Light winds
over most of the area and clear skies appear to be setting the
stage for this, along with the light precip we had today. Believe
cross-over temp is mid to upper 30s and we are forecasting
overnight lows in the lower 30s...so again another reason to think
dense fog will develop tonight. Going to issue a dense fog
advisory for tonight through 9 am tomorrow in west part of CWA.
Concern will have to expand east...but will do as needed. Update
will be coming.
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 326 PM CST Tue Nov 19 2019
21z/3pm satellite imagery continues to show overcast conditions
across much of central Illinois: however, the back edge of the
cloud cover has advanced as far east as a KBRL to KMVN line.
Based on satellite loops and HRRR forecasts, it appears skies will
clear everywhere south of the I-74 corridor over the next 3-4
hours...while skies remain mostly cloudy further northeast. With
clearing skies and decreasing winds, the potential for fog
development tonight will be high...especially given the moist
boundary layer from today`s light rainfall. RAP/HRRR/NAM/GFSLamp
all suggest fog forming west of I-55 early this evening, then
spreading eastward across the remainder of the area overnight.
Given strong signal from model guidance, have gone with widespread
fog except across the far SE KILX CWA where rain did not fall
today. Overnight lows will be in the lower to middle 30s. Once the
morning fog dissipates, a partly sunny and mild day will be
observed on Wednesday with afternoon highs in the lower to middle
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 326 PM CST Tue Nov 19 2019
The next significant storm system to impact the Midwest will come
into the picture late Wednesday into Thursday. As has been
advertised for the past several model runs, it appears the most
significant rainfall will occur across central Illinois late
Wednesday night and Thursday morning...followed by a lull in
precip chances Thursday afternoon as a dry slot works into the
region. Have carried categorical PoPs west of the I-57 corridor
after midnight Wednesday night, then everywhere Thursday morning.
Total rainfall will generally range from one quarter to one half
Once the system passes to the east, the trailing frontal boundary
will stall in the Ohio River Valley late Thursday into Friday.
Several weak impulses will interact with the front to keep precip
chances alive across central Illinois, with the best chances
focused south of I-70. The airmass will become cold enough to
support light snow or a light rain/snow mix on the northern edge
of the precip area late Thursday night and again Friday night:
however, little or no snow accumulation is expected. After that,
mild and dry conditions will be on tap Saturday through
Monday...with temperatures climbing back into the 50s by Monday.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 601 PM CST Tue Nov 19 2019
IFR cigs will remain at BMI and CMI through the night and into
tomorrow morning. DEC and PIA are MVFR but should scatter out by
3-4z...while SPI is VFR. The clearing that occurs across the area
will combine with light winds tonight, resulting in ideal
conditions for dense fog to develop across the central part of the
state and likely spread east toward morning. IFR and LIFR
conditions are also likely late tonight through tomorrow morning,
but then improving quickly during the afternoon. Winds will become
light and variable for the night and then as they increase
tomorrow to over 10kts, the direction will be southeast.
Area Forecast Discussion
National Weather Service New Orleans LA
718 PM CST Tue Nov 19 2019
Performed a gridded forecast update this evening - with the main
focus being forecast lows tomorrow morning/highs tomorrow
afternoon and dense fog potential early AM.
Taking a look at the latest 00Z HRRR guidance valid for 12Z
tomorrow morning, comparing it to what was initialized in the 12Z
run yesterday morning shows a similar overall atmospheric profile.
Only notable difference is a slightly stronger surface subsidence
inversion and a bit more of a southerly surface to low-level flow
developing (to around 1,000ft AGL). Given this, areas of dense
fog will likely develop again around the same areas as last night
(generally along/west of I-55 including the southshore and coastal
southern Louisiana). Will likely issue a Dense Fog Advisory later
tonight before 10PM to get an early heads up for those traveling
early tomorrow morning, with possible expansion where needed as
Similar to last night, blended guidance continues to come in a
bit too warm with overnight lows. Dropped temperatures slightly
(not as much as last night) with focus on area drainages from the
northshore east across the MS coast). Blended guidance still is
struggling with afternoon highs a bit, as some locations today
reached the mid to upper 70`s - which confirms this cooler bias.
Have manually bumped up highs tomorrow to a more realistic
.PREV DISCUSSION... /issued 332 PM CST Tue Nov 19 2019/
High pressure is in place and will persist through Thursday. This
high pressure is bringing drier air and a bit warmer air into the
region for the next few days. Wednesday and Thursday, winds will
primarily be southerly, bringing in some moisture from the Gulf
into the region as well.
Friday and Friday night, a low pressure system will move through
the area. Winds leading up to the event will remain southerly,
continuing to fuel moisture into the area. Some upper level
divergence will help to provide some lifting for the area Friday.
The abundant moisture presence combined with the lifting will
further be enhanced by the front, however, this front currently
seems weak, looking at the models. As a result, there will likely
be rain showers with the chance of a thunderstorm Friday and
If the front remains weak like the models show, then the threat of
severe weather would be low. The main threat if the front remains
weak would just be rain and scattered thunderstorms. In addition,
some gusty winds and frequent lightning would be a concern Friday
and Friday night as well.
Saturday through the beginning of next week, high pressure builds
in, which will help to stabilize the atmosphere. In general, this
stable air will help to dry out the area, so the rain chances are
pretty low for the beginning of next week again. MSW
Expect prevailing VFR conditions for all area terminals through
late evening/early tonight prior to 04-06Z. Main hazard to focus
on for terminals along and west of I-55 (including KNEW/KMSY) will
be patchy areas of dense fog. Primary time line will be between
06Z and 13Z, or till shortly after sunrise. Impacts to flight
categories (IFR/LIFR) can be expected in this time range before
all fog dissipates after 13-14Z returning all terminals to VFR.
Winds will be variable today, shifting to southeasterly tonight
and tomorrow and calm (<15 knots). Winds will be southerly and
light (<15 knots) through Saturday. Saturday through Sunday, winds
will be stronger (15-20 knots) and northerly. Sunday
through early Tuesday morning, winds will be northerly and calm
(<15 knots). Tuesday through Wednesday, winds will be southerly
and stronger (15-20 knots). Wave heights will correspond with the
wind speeds. MSW
DSS code: Blue.
Decision Support Services (DSS) Code Legend
Green = No weather impacts that require action.
Blue = Long-fused watch, warning, or advisory in effect or high
visibility event; Marginal risk severe or excessive rain.
Yellow = Heightened impacts with short-fused watch, warning or
advisory issuances; radar support for slight risk severe
or excessive rain.
Orange = High Impacts; Enhanced risk severe; nearby tropical
events; HazMat or other large episodes.
Red = Full engagement for Moderate to high risk of severe and/or
excessive rainfall, or direct tropical threats; Events of
.PRELIMINARY POINT TEMPS/POPS...
MCB 45 75 50 74 / 0 0 0 0
BTR 46 78 53 77 / 0 0 0 0
ASD 44 75 50 75 / 0 0 0 0
MSY 51 75 56 75 / 0 0 0 0
GPT 47 72 52 72 / 0 0 0 0
PQL 43 75 49 75 / 0 0 0 0
Area Forecast Discussion...Updated
National Weather Service Phoenix AZ
525 PM MST Tue Nov 19 2019
.UPDATE...Updated aviation discussion.
A series of strong low pressure systems will bring periods of heavy
rain with embedded thunderstorms through tomorrow evening,
especially from the Colorado River eastward. The strongest storms may
also contain gusty winds Wednesday. Temperatures will fall below
normal during this unsettled weather before clearing begins on
Friday. Moist conditions will persist over the weekend, though no
additional rain is anticipated.
Convection developed early this morning across northern Sonora and
has propagated northward into south-central Arizona ahead of a
pronounced Theta-E boundary. Latest mesoanalysis shows much of
Arizona generally lacks instability, with MLCAPEs > 500 J/kg
confined to far southern Arizona. Nevertheless, low-level dewpoints
in the 20s and 30s ahead of the boundary have helped to enhance
evaporation and downdrafts with peak gusts up to 35 mph across
Maricopa and Pinal counties, which has been sufficient to produce
areas of patchy blowing dust. Behind the boundary, conditions have
moistened considerably with dewpoints increasing into the 50s and
even lower 60s at Yuma.
Activity this afternoon generally materialized a few hours faster
than anticipated and model performance (including the HREF and
local CAMs) has struggled. In these scenarios, it is prudent to rely
on a HRRR time-lagged ensemble for the near-term, which indicates
that scattered showers will persist across south-central Arizona
through this evening. Latest IR satellite shows cooling cloud tops
across Pima County and it`s reasonable to expect this activity will
lift northward this evening around the Baja Peninsula closed low. A
Flash Flood Watch remains in effect, though the relatively fast
storm motion of the convection may limit the flood threat.
Models remain in good agreement that the focus will shift westward
overnight as vorticity and jet-forced ascent increases ahead of a
closed low diving down the central California coast. NAEFS continues
to highlight the central Colorado River Valley with PWAT percentiles
exceeding the 99th percentile. Consequently, the strongest cells will
be capable of producing a very quick 1 to 2 inches, which could lead
to flash flooding. This is reflected in the latest official
forecast, which again is weighted heavily towards the WPC QPF.
Predictability is expected to increase Wednesday as a broken line of
convection develops ahead of the aforementioned low pressure system
and migrates eastward across Arizona. A low-level jet
intensifying to 40 kt will approach an all-time maximum across
southern Maricopa County late Wednesday morning. Although the wind
profile won`t be ideal for training cells, some back-building along
and ahead of the line will enhance the threat of flash flooding.
Latest HREF also suggests the strongest storms will be capable of
producing wind gusts as high as 50 mph. General consensus is that the
line of storms will move east of Gila County Wednesday evening, with
isolated showers generally dissipating elsewhere.
GEFS ensembles continue to show the closed low filling across
northern Arizona Thursday. However, the cold pool aloft
will lead to increased instability and promote the development of
additional showers across Arizona. The low will move east of the
region Friday, though low-level moisture will linger through the
weekend. Latest ECMWF EPS suggests another upper low will be pinched
off in the eastern Pacific during the weekend along with a
propensity towards another Rex Block. This will yield a slight
warming trend across the Desert Southwest into early next week,
though temperatures will remain below normal.
.AVIATION...Updated at 0025.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
A series of weather systems will continue to bring widespread
showers, moderate to heavy at times, to the greater Phoenix area
this evening and through the day (at least) on Wednesday. In
general, we are looking at RA/SHRA to affect the terminals through
the TAF period, but there is sufficient instability to permit
isolated thunderstorms at times mainly during the evening hours
today. For now, due to model inconsistencies with timing/location of
convective cells, decided to leave thunder out of the TAFs and will
simply amend as needed should storms start to threaten the
terminals. Expect a thunder threat through at least 05z but
diminishing after that and into the morning on Wednesday. Again,
thunder might become an issue mainly Wednesday afternoon as a front
approaches from the west, but confidence in timing/location of
storms is too low to mention that far out in the TAF period.
Outside of thunder threats, 2 additional significant aviation issues
expected: CIGs and wind. Winds will stay generally southeast this
evening mostly 15kt or less, then strengthen later tonight and into
the morning Wednesday - favoring the south. Expect generally south
winds to persist for most of the day Wednesday ahead of the slowly
approaching front. Winds should turn to the southwest behind the
front but this will not likely occur til after 22z. Potential is
there for quite breezy south wind from mid morning into mid
afternoon with gusts over 30kt likely and sustained 20kt or higher
likely as well. This may pose crosswind issues, especially at KPHX.
CIGS also become an issue, dropping below 6kt feet by around 06z
this evening and becoming lowest mainly from 12z to 18z Wed. before
starting to slowly increase. CIGs may occasionally fall below 3k
feet especially during heavier showers or storms. Cannot rule out
CIGs briefly below 2k but should it happen it would not persist for
very long, especially at KPHX. Visibility may also drop below 5sm at
times under periods of heavier rain or thunderstorms. Overall opted
to paint a slightly more optimistic appraisal of the situation in
the TAFs especially at longer time ranges but know that conditions
could easily become more of a concern especially during the day on
Southeast California/Southwest Arizona including KIPL and KBLH:
Two weather systems will continue to bring showers to the southeast
California/southeast Arizona deserts this evening into the afternoon
on Wednesday. As of 5 pm convection has been very isolated in far SE
California but expect coverage to become more scattered as the
evening progresses; CIGS should drop into the 5-7k range for the
most part with locally lowered CIGs in heavier showers or storms.
Given low expected storms coverage, opted to leave out mention of
storms for now but will amend if needed. Conditions should graudally
improve during the afternoon Wednesday behind a cold front that will
be moving into the Arizona deserts. Winds will favor the southwest
to west at KIPL - especially later this evening and during the day
on Wednesday, and could become rather breezy during the day with
occasional gusts approaching 30kt. Winds to favor the south to
southwest at KBLH for most of the TAF period with breezy conditions
at times during the day tomorrow.
Thursday through Monday:
Showers will continue to percolate through the eastern districts
Thursday while drier conditions work into the western districts.
More widespread dry weather will finally spread into the region over
the weekend. Regardless, given the pronounced wet weather preceding
this period, fuels across the majority of the area will be quite
moist for an extended period. Temperatures will cool substantially
Thursday, then only rebound near the seasonal average over the
weekend while humidity levels likely will not fall below 50% for an
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
AZ...Flash Flood Watch through Wednesday evening for AZZ534-537>563.
Flash Flood Watch through Wednesday afternoon for AZZ530>533-535-
CA...Flash Flood Watch through Wednesday afternoon for CAZ564-565-
Area Forecast Discussion
National Weather Service Riverton WY
338 PM MST Tue Nov 19 2019
.SHORT TERM...(This evening through Wednesday night)
Issued at 230 PM MST Tue Nov 19 2019
Mid- and high-level clouds will continue streaming from the
southwest over the forecast area late this afternoon and
overnight. Although some models are suggesting light high
elevation showers late this afternoon, web cams and satellite
suggest otherwise. Breezy conditions with gusts over 30 mph will
continue from eastern Sweetwater county into Natrona county
through about 6pm. Strong trough in northwest flow is advancing
toward the area and will increase moisture and instability
overnight, with a slight chance of showers over YNP and the
northern Absarokas until midnight. At the same time, a surface
cold front will move southward from Montana into Wyoming. Latest
HRRR model run shows the northerly winds pushing into the northern
Big Horn Basin and northern Johnson county between 9pm and
midnight. Although the initial push makes it into central WY
before sunrise, the strength of the winds does not seems to
increase until mid to late morning when the surface pressure
gradient increases (due to the higher pressures moving into
Montana). Precipitation is likely over the eastern Absarokas and
Cody foothills as well as the northern Bighorns during the early
morning hours before spreading southward late Wednesday morning.
At the same time, models are showing moisture and overrunning
moving northward from eastern Utah and western Colorado into
Sweetwater county. By around noon Wednesday, the north to
northeast wind from northern into southern WY should increase to
15 to 20 mph with gusts over 30 mph. Moderate precipitation,
perhaps starting as rain but quickly changing to snow, will
develop over southern WY and move quickly into central WY. Surface
temperatures are expected to be at or just below freezing, so
snow should be able to accumulate during the day. The combination
of snow and wind will create hazardous blowing snow across much of
central and southern WY. This looks to be a decent ~9 hour
precipitation event with sustained overrunning and upslope. Overall,
the heavier amounts are expected to be from Lander and South Pass
eastward to Muddy Gap and Casper Mountain, then southward toward
Wamsutter. Please see the CYSWSWRIW products for more details
regarding the issued warnings and advisories. A special weather
statement also mentions snow in fringe areas for 2 to 3 inches,
though locally higher amounts of 4 inches could be seen in places
such as Meeteetse and Ten Sleep.
Models today are fairly good agreeing about the onset of
precipitation and movement of the cold air and wind. Concern is
for the duration of the event into Wednesday night and Thursday
morning. The GFS and other global models continue to show the SW
cut off low moving from Las Vegas eastward to the Four Corners
area. Combining this movement with ridging over the northern
Rockies would diminish precipitation quickly from the north early
Thursday morning. The NAM however, is taking the low center more
northeastward into central Utah. As expected, this pattern would
keep more moist easterly flow into central and southern WY. Will
have to monitor on subsequent shifts.
.LONG TERM...(Thursday through Tuesday)
Issued at 144 PM MST Tue Nov 19 2019
By 12Z Thursday, the trough responsible for the snow on Wednesday
and Wednesday night will split as the southern stream circulation
around the closed low over Vegas expands, and the northern stream
trough scoots east and away from the area across Canada, along
with the high building over the Pacific Northwest and the ridge
building in the southern plains. This will put us under a col
region and resulting diminishing snowfall Thursday. Snowfall will
be winding down from northwest to southeast Thursday morning, with
perhaps a bonus inch of snow from lingering upslope from the east
slope of the Wind River Mountains to Beaver Rim. A few flurries
will linger across the Casper area, Green Mtns, the southern east
slope of the Wind River Mtns amd Sweetwater County through
Gradual clearing will take place from north to south Thursday
night. Northern Wyoming will clear up in time for significant
radiational cooling there with some below zero readings expected
in YNP. Should see some patchy fog develop across portions of the
Big Horn Basin by Friday morning with fresh snow cover and warm
air advection from the north, strengthening temperature inversions
and supplying drier air above the inversion enhancing the
possibility of fog development..
Friday will feature dry and cold conditions with highs mainly in
the 30s. Saturday will be another dry day with highs reaching the
low 40s in many areas. Southwest winds will pick up along the
southern wind corridor from the Red Desert and South Pass to
Casper Friday, coincident with the developing sfc lee side trough.
These breezes will continue through the weekend. Temperatures
will likely be a few degrees cooler in areas where the wind does
not blow, including the western and central basins where
temperature inversions could linger through Friday given the fresh
By Sunday, the high over us that will build in from the Pacific
NW will get swallowed up in the westerly progressive flow. The
westerly flow will become somewhat difluent Sunday with snow
developing in northwest Wyoming out ahead of the next upstream
trough. The models appear to be agreeing upon the timing of this
trough coming through Monday as it digs, with most of the energy
propagating to the Desert Southwest. Monday will be the apex of
the snowfall associated with this trough with the far west
receiving the brunt of the snowfall given the upslope flow there.
Tuesday will see snowfall decreasing but lingering in the
northwest ahead of the next upstream shortwave, with the Euro the
fastest with the approach of this next shortwave.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 331 PM MST Tue Nov 19 2019
JAC/PNA/BPI...Western state locations will continue to see clouds
increase, thicken, and lower this evening as the next push of
cold air arrives. Expect rain showers in northwest Wyoming at the
lower elevations, including the vcnty of KJAC, along with snow
showers in the surrounding mountains. The front will move through
after midnight, bringing gusty north winds in its wake. Any wintry
precipitation will likely not arrive until after 12Z Wednesday.
MVFR/IFR conditions will occur in the southwest including KPNA and
KBPI through Wednesday along with mainly MVFR conditions at KJAC.
Expect mountain obscuration Wednesday.
Eastern and southern sites...VFR continues for the rest of this
afternoon for all sites, with generally light winds noted. Breezy
southwest winds increase tonight for the corridor from South Pass
to Casper, reaching 15g25kts at times. Then the front arrives.
Northern sites should see north winds arrive around midnight in
KCOD, 09Z in KWRL, reaching RIW/LND/CPR around 11Z, and passing
RKS around 13Z. Gusty north winds of 20 to 25 kts are expected
through the day Wednesday associated with the front moving north
to south. Snow will develop behind the southbound moving front,
across the north after midnight. Then snow will increase across
central and southern WY after sunrise Wednesday. MVFR/IFR
conditions and mountain obscurations expected after 12Z Wednesday
for the central and southern locations.
Issued AT 144 PM MST Tue Nov 19 2019
Warm temperatures continue for one more day, with highs in the
50s for the rest of this afternoon. Winds from Rock Springs to
Casper will reach 20 to 30 mph with higher gusts for the rest of
this afternoon. The cold front sweeps through overnight, with an
abrupt wind shift from the north at 20 to 30 mph. The front will
bring snow for most of the state, with several inches possible at
all elevations by later Wednesday. The snow will continue through
Wednesday night and then taper off from northwest to southeast
Winter Storm Warning from 5 AM Wednesday to 11 AM MST Thursday
Winter Weather Advisory from 5 AM Wednesday to 5 AM MST Thursday
Winter Weather Advisory from 5 AM Wednesday to 11 AM MST
Thursday for WYZ017-020-027>029.
Area Forecast Discussion
National Weather Service Sacramento CA
341 PM PST Tue Nov 19 2019
Pattern transitioning to breezy to windy conditions, cooler
temperatures and possible showers over mainly the Sierra Nevada
south of I-80.
The upper level trough is showing up nicely on water vapor and is
currently still an open wave along the CA coast. Over the next
few hours we will see this trough close off near Monterey and drop
south into SoCal by Wednesday mid morning. Showers have started
to develop mainly along the Sierra crest and are quickly pushing
east with the strong westerly flow. As the trough closes off
easterly flow will develop and that will favor precip on the east
slope of the Sierra. Last several runs of the HRRR show a band of
light to moderate precip pushing over I-80 and Highway 50 and
pushing down the slope to the east of Placerville and Auburn in
the 7 pm to midnight range. This is somewhat of an outlier at this
time as the HREF along with other models favor that band setting
up to the south of Highway 50. It is something that will have to
be monitored this evening as snow levels will be falling to just
below pass level. Current thinking is 1-2" will be possible over
I-80 and Highway 50 this evening into the overnight with the
higher snow totals staying to the south where a Winter Weather
Advisory is in effect.
The bigger impact from this system will be the cooler
temperatures and an increase in northerly wind that will develop
across a large part of the area overnight and continue into
Thursday as the surface gradient tighten. The period of strongest
northerly winds are expected Wednesday afternoon as subsidence
and upper level support increase. Gusts of 40-50 mph will be
possible in the Sacramento Valley and surrounding terrain north of
Shower chances will push south on Wednesday and will continue to
favor the east slope of the Sierra but light activity will be
possible in our area mainly near the crest south of 50. Snow
levels will be dropping down to around 5500 feet by Wednesday
afternoon and we could see some light accumulation down to that
elevation but it should remain minor.
Winds will die down quickly Thursday mid morning into the
afternoon and we will see an upper level low set up over the
Pacific on Friday. This will keep clouds in our forecast along
with the cooler but still a bit above average temperatures. Light
winds will continue on Friday.
.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
To start the weekend, the region will feature an eastward
extending ridge with a closed low positioned well off the southern
California coast. Perhaps a few additional clouds are possible
although this should not hinder temperatures much. Valley high
temperatures will easily reach the mid to upper 60s with even a
couple 70 degree readings in the upper Sacramento Valley. This is
still quite warm for mid-November with departures from climatology
on the order of 5 to 10 degrees. Although ridging will allow
optimal radiational cooling at night to keep readings closer to
Moving to next week, global ensembles continue to favor a ridge
centered over the east Pacific (i.e., 140W longitude) while
longwave troughing extends over the western/central U.S. Models
remain adamant about a sharpening shortwave sweeping across the
central Great Basin into the Four Corners. This pattern would
support another bout of gusty northerly winds on Monday into early
Tuesday. With extremely dry fuels in place, elevated fire weather
concerns are nearly a given if this setup were to become reality.
Looking further beyond, another trough may reach the West Coast
by mid-week although impacts remain unclear given increasing model
VFR conditions the next 24 hours with winds increasing from north
to south during the overnight hours. KRDD and KRBL can expect
northerly wind gusts in excess of 30 knots by around 12Z
Wednesday. Breezy conditions are likely over the Sacramento TAF
sites starting by 15Z Wednesday with slightly lighter winds down
into the upper San Joaquin Valley. ~BRO
Red Flag Warning from 4 AM Wednesday to 7 AM PST Thursday for
Central Sacramento Valley in Glenn, Colusa, Yuba, Northern
Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF-
Eastern Portion of Shasta/Trinity NF-Lake County Portion of Lake-
Napa-Sonoma Unit-Northern Sacramento Valley to Southern Tehama
County Line Below 1000 Ft-Northern Sierra Foothills from 1000 to
3000 Ft. Includes portions of Shasta-Trinity and Butte Units-
Northern Sierra Including Lassen NP and Plumas and Lassen NF/S
West of the Sierra Crest (West of Evans Peak-Grizzly Peak-
Beckworth Peak)-Southeast Edge Shasta-Trinity NF and Western
Portions of Tehama-Glenn Unit-Southern Sacramento Valley in Yolo-
Sacramento Far Western Placer, southern Sutter and Solano County
Below 1000 Ft.
Wind Advisory from 4 AM to 10 PM PST Wednesday for Central
Sacramento Valley-Clear Lake/Southern Lake County-Mountains
Southwestern Shasta County to Northern Lake County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Shasta
Lake Area / Northern Shasta County-Southern Sacramento Valley-
Western Plumas County/Lassen Park.
Winter Weather Advisory until 7 PM PST Wednesday for West Slope
Northern Sierra Nevada.