Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/28/22

Area Forecast Discussion

National Weather Service Cheyenne WY

 755 PM MDT Wed Apr 27 2022

.UPDATE...
Issued at 755 PM MDT Wed Apr 27 2022

Early evening WV/IR imagery showed a couple of shortwave troughs, one
moving into the central and southern High Plains accompanied by strong
convection, and the second moving through central MT to northwest UT.
A cold front stretched from northwest WY into southern NV, with a surface
trough through southeast WY and far northeast CO. Some showers were
developing in the vicinity of the trough over southeast WY, however
very dry low levels (inverted-v sounding profiles) resulted in virga
and locally gusty winds up to 45 mph. These showers will eventually
dissipate with more concentrated shower activity spreading northeast
across northern and northeast WY for the next several hours with the
passage of the shortwave trough. The current forecast is on track,
so no changes are anticipated this evening.

&&

.SHORT TERM...(This evening through Friday)
Issued at 345 PM MDT Wed Apr 27 2022

The weather pattern remains active for the next several days. The
main concerns in the short term forecast are as follows:
* Potential for showers and thunderstorms to develop mainly along
  and east of the Laramie range Thursday afternoon through the
  overnight hours, with a possibility for isolated severe storms.
* A strong cold front will push through Friday morning, and we may
  be looking at yet another strong wind event for parts of SE
  Wyoming.
* Elevated fire weather concerns continue. More details can be
  found in the fire weather section below.

Currently, GOES satellite shows mid to high level cloud cover near
the area associated with two weak upper level shortwaves shifting
to the northeast amid SW flow aloft. Our area is sandwiched
between the two disturbances, one of which is located over east
central Colorado, while the other is located near the Yellowstone
area. Elevated moisture has crept up as these systems pass by, but
the lower levels remain very dry. Thus, even though some light
precipitation echoes are visible on radar, this is expected to
remain largely virga.

A stronger system approaches on Thursday as a vigorous 500-mb
vorticity maximum pushes onshore near the CA/OR border. Diffluent
flow aloft on the downstream flank of the shortwave will help to
support the development of some weak surface cyclogenesis in
central Colorado. Pressure drops in this area will enhance the low
level jet over the plains and allow for increased boundary layer
moisture advection from the southeast into the western Nebraska
panhandle and far eastern Wyoming by Thursday evening. Low level
easterlies underneath strong mid to upper level southwesterlies as
the trough pushes overhead will lead to increasing deep layer
shear across the high plains. Forecast soundings show steep mid
level lapse rates resulting from the cold air aloft. Thus, the
possibility remains for the development of afternoon convection as
vorticity advection aloft provides some enhanced lift by late in
the day on Thursday.

The SPC has included the Nebraska panhandle in a marginal risk
for severe thunderstorms tomorrow, with wind and hail being the
main threats. The boundary layer remains fairly dry, exhibiting
some inverted-Vs in the forecast soundings for tomorrow. The main
source of uncertainty is the extent of the instability, even
amongst the hires models. The HRRR is quite a bit drier in the low
levels along with decreased CAPE compared to the more moist hires
NAM. Thus, the HRRR only develops isolated convection, while more
widespread thunderstorms are shown in the 3km NAM solution. We
will continue to watch this over the next 24 hours, but at least
for now, isolated to scattered thunderstorms look likely along and
east of the Laramie range starting late Thursday afternoon through
the overnight hours.

The cold front will push through Friday morning. Increasing 700-mb
height gradients across our area behind the front may lead to
another round of high winds for the wind prone areas, as early as
Friday morning for some locations. Did not have the confidence to
go with a watch at this time, but later shifts will need to
monitor this. Strong cold air advection aloft is expected during
the day on Friday as the upper level trough passes overhead. Some
wraparound moisture could bring appreciable precipitation to the
Nebraska panhandle, especially further north, on Friday. Some weak
instability remains through the day on Friday, so there could be
rumbles of thunder. Uncertainty remains quite high in this phase
of the event, which will carry into the long term period outlined
below.

.LONG TERM...(Friday night through Wednesday)
Issued at 345 PM MDT Wed Apr 27 2022

Main forecast concern in the Medium to Long Range is the evolution
and movement of the Pacific upper level trough which will initially
move across the northern Rockys as a progressive open wave; but
recent models indicate the gradual formation of a closed low across
the western Great Plains region. For now, will just monitor the
evolution of this system with all models onboard...showing the
surface low developing over Kansas and central Nebraska. This is a
bit too far east to result in significant precip/impacts across
southeast Wyoming and most of western Nebraska. However, the
northern and central panhandle of NE seem to do pretty well on the
backside in the TROWAL/wrap around moisture region. Kept POP highest
(~70 percent) near Chadron and Alliance Nebraska with some snowfall
possible Friday night. Elsewhere, not expecting all that much due to
the northern trajectory of the system over Wyoming, resulting in
downslope westerly winds across most of the area outside of the
mountains. Very windy conditions are expected on Saturday behind the
system, especially if the surface low develops quicker and
intensifies rapidly. High Wind criteria are possible, especially for
the Wind Prone areas and the High Plains east of Interstate 25 into
western Nebraska. Increased winds near HWW criteria for these areas
early Saturday morning through the afternoon hours.

For late in the weekend and through the middle of next week, models
show a progressive pattern with increasing jet energy near the
Colorado and Wyoming border along with the western third of the
United States. Expect Pacific energy to quickly move across the
Great Basin Region and into the Rockys every 36 to 48 hours.
The main Pacific system to watch during this time period is on
Tuesday, but models are in poor agreement with the position of the
upper level low. The Canadian is slower and well to the north,
showing the system in Montana by late Tuesday while the GFS is much
more progressive but shows a similar track compared to the Canadian.
The ECMWF digs this upper low into the eastern Great Basin region
and is much slower, still showing it west of Salt Lake City Tuesday
evening. The ECMWF solution bares watching, but will not go too
aggressive at this time due to poor support from other deterministic
models and most ensemble forecasts. Kept temperatures near or
slightly below normal for this time of the year with highs in the
50s and 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 540 PM MDT Wed Apr 27 2022

VFR conditions expected through the night with some mid- to high-
level clouds. Some virga showers possible during the evening, with
wind gusts up to 30 kts. Winds overnight and into the morning hours
will be light.

&&

.FIRE WEATHER...
Issued at 345 PM MDT Wed Apr 27 2022

Elevated to near critical fire weather conditions are present this
afternoon especially along and south of the I-80 corridor, where
RH has dropped to near 15%, but winds remain on the light side.
With light winds expected to continue overnight, we should cool
down well overnight leading to good humidity recoveries. Another
round of elevated to near critical fire weather is expected
Thursday. Winds will be stronger than Wednesday with gusts 20 to
25 mph possible east of the Laramie range, and up to 35 mph in
parts of Carbon county. However, dewpoints will creep up compared
to Wednesday which should prevent RH from dropping below critical
thresholds. Isolated to scattered showers and thunderstorms are
expected to develop Thursday afternoon through the overnight
hours with the best probabilities along and east of the Laramie
range. A strong cold front pushes through Friday morning, with
strong winds and cooler temperatures likely by the afternoon.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

UPDATE...MAJ
SHORT TERM...MN
LONG TERM...TJT
AVIATION...SF
FIRE WEATHER...MN



Area Forecast Discussion

National Weather Service Des Moines IA

 644 PM CDT Wed Apr 27 2022

...Updated for the 00z Aviation Discussion...

.DISCUSSION.../Tonight through Wednesday/
Issued at 333 PM CDT Wed Apr 27 2022

Key Messages:

-Increasing threat for scattered showers and storms tonight into
Thursday
-Main swath of showers and thunderstorms expected Friday night into
Saturday

A warm front is bisecting the state this afternoon from west central
Iowa to the southeast.  Relatively strong east flow north of the
boundary has produced somewhat brisk conditions with temperatures
mostly in the 50s.  South of the boundary, readings have climbed
into the 70s with readings approaching 80 in the southwest corner of
the state.  Moisture remains lacking near the front, hence only high
clouds passing over the state at this point.  Theta-e advection and
moisture transport increases into this evening and overnight which
eventually leads to the development of scattered showers and storms
in portions of the state.  CAMS have indicated development this
evening near the 850mb boundary across the northeast with the
activity persisting overnight. In fact, both the HRRR and RAP show
backbuilding across the far northeast overnight with moderate to
locally heavy rainfall grazing the extreme northeast edges of the
forecast area. Otherwise, there are varying solutions for scattered
showers/storms overnight across mainly the west and south in the
axis of low level flow into the state.

The somewhat unorganized lift persists into Thursday and Thursday
night with scattered precipitation continuing during these periods.
The main shortwave ejects into the Plains on Friday with more
organized forcing.  Convection is expected to develop in eastern
Nebraska and Kansas by late afternoon/evening and then press
northward ahead of the upper low.  The best low level instability
remains in southwest Iowa where the slight risk is currently places.
Elevated instability extends farther north and both GFS and Euro
lift the convection into the state overnight Friday night with some
threat of severe weather, mainly in southwest. Good moisture
transport into the system should assist with locally heavy rainfall
as well.  The convection moves northeast into Saturday morning
across central Iowa with diurnal weakening.  There remains some
small threat of marginally severe weather into Saturday afternoon
across the far east and northeast portions of the forecast area
where instability wraps back northwest toward the surface low.
However any convection that does fire should quickly exit the
forecast area to the north and east.  The deformation zone of the
system does wrap into the northwest half of the forecast area on
Saturday night/Sunday morning with some scattered showers and
cool/breezy conditions.

The pattern remains relatively active into next week although timing
difference are quite apparent between the medium range models.
However, there does appear to be some threat of precipitation later
Monday into early Tuesday with a surface low passing south of the
state.  Temperatures appear to remain at or below normal for much of
the period with thermal trof to the north and east of the state and
cloudiness as well.

&&

.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 644 PM CDT Wed Apr 27 2022

A warm front bisects the state this evening with easterly winds
across northern Iowa and southerly winds across southern Iowa. In
fact, though KDSM has south winds our office a few miles north is
10 degrees cooler with east winds. The front will move little
overnight and showers/thunderstorms will develop over northern
Iowa late tonight into Thursday across northern sites KMCW/KALO
and perhaps into KFOD. Further south at KDSM/KOTM spotty showers
may develop but thunderstorms are not anticipated. Precipitation
will linger into Thursday morning. While cigs will initially
remain VFR, degradation to MVFR and perhaps IFR is possible
moving later into Thursday.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...Cogil
AVIATION...Hagenhoff



AREA FORECAST DISCUSSION

National Weather Service Hastings NE

 641 PM CDT Wed Apr 27 2022

.DISCUSSION...(This evening through Wednesday)
Issued at 517 PM CDT Wed Apr 27 2022

-- Highlights/primary concerns of the entire 7-day forecast in
 chronological order:

1) Spotty strong to PERHAPS severe storm potential both this
evening and then again late Thursday afternoon-evening:
While am not overly-concerned about truly severe storm tonight,
Thursday is a bit more of a "mystery" unfortunately, and depending
on how model solutions trend, would not be surprised to see later
SPC outlooks expand the official Marginal Risk to more of our our
coverage area (CWA).

2) A seemingly more "synoptically-evident"/pronounced risk of
severe storms Friday afternoon-evening:
A fairly stout upper level low pressure system and associated
surface low swings through the region, driving a strong cold
front/dryline through in the process. SPC`s Day 3 outlook (issued
early this AM) placed most of our CWA in a Marginal-Slight risk of
severe, with the northwest edges of Enhanced Risk (level 3 of 5)
clipping our extreme southeast zones. Although still plenty of
"finer details" still need to be worked out, and obviously there
are still 2 more days of SPC outlook refinements to come, the
overall-scenario still seems to be supported. Based on various
12/18Z models, the southern half of the CWA appears overall-most
favored for surface- based severe storms/possible supercells in
closet proximity to the surface low, with a more
multicell/slightly- elevated storm threat extending farther
northward into the CWA, where plentiful cloud cover is more
favored to keep temps and resultant low-level instability down a
bit more. Although it`s simply too soon to "bank on" any one model
solution or buy too much into details, it is worth noting that the
latest NAMNest depicts a somewhat "messy" storm mode (even in our
south), and the 15Z SREF shows an interesting lack of fanfare over
our CWA in its "Significant Tornado Ingredients" parameter. So
the bottom line is that while a severe storm threat certainly
exists, it`s important not to get too carried away with its
magnitude just yet.

3) Strong northwest gradient winds on the back-side of the system
late Fri night and especially Saturday daytime:
Confidence continues to grow that Saturday will be the overall-
windiest day of the next week, with sustained speeds commonly at
least 25-35 MPH/gusts 40-55 MPH (overall strongest in our western
half). EPS ensemble continues to suggest that at least limited
potential for High Wind/severe-criteria gusts of 58+ MPH could
ultimately clip especially our far western CWA, but the overall-
strongest gusts should favor areas to our west-northwest within
western/north central NE.

4) Although things "settle down" a bit beyond Saturday, it`s odd
to say that Sunday is truly the only "guaranteed dry" day in the
forecast, as at least small-medium rain chances/PoPs re-enter the
picture by Monday and linger through mid-week. That being said,
the ECMWF/GFS models have a LOT of disparity in especially the
timing of upper waves and resultant rain chances early-mid next
week, so plenty of adjustments will likely be necessary.

-- Other items of note/interest:

1) In a BIG change from recent weeks, we actually are NOT talking
about any upcoming days with truly-concerning fire weather
potential! While the threat will certainly not be "zero"
(especially the main windy day such as Saturday), various factors
such as increasing rain chances, most days not looking overly-
windy (except Saturday) and no truly hot days will keep fire
parameters at least somewhat in check compared to lately.

2) Finally some MUCH-NEEDED, more widespread rain? Although
amounts will surely vary considerably within the CWA, WPC is
currently calling for most of our CWA to measure somewhere between
0.50-1.50" over the course of the next week (most of which would
likely fall Thurs-Sat). If anything, our north would be more
favored for the higher amounts than our south, but as it turns out
our far northern zones (Valley/Greeley area) have truly been among
the overall-driest the past several months, so hopefully some
decent amounts indeed materialize there.

-- With the "big picture" and most important points covered, will
conclude with some fairly brief day-to-day comments/additional
details (including temperatures), focused mainly shorter term:

- Current/recent weather scene as of 430 PM:
No big surprises today, although if anything fairly decent
coverage of high-level cirrus looks like it will help limit most
of especially our northern/western zones to high temps only mid-
upper 70s, while southern/eastern zones have managed greater
coverage of low-mid 80s. As expected, the overall-strongest
southerly wind today have affected our southeast 1/3 to 1/2 of the
CWA (gusts commonly 25-35 MPH), while much lighter winds
(generally sustained no more than 10-15 MPH) have prevailed in
northern/western zones closer to this trough axis.

- This evening-overnight:
Have held off any mentionable (20+ percent) chance of convection
until at least 7 PM this evening, and have overall-decreased POPs
slightly from previous forecast. While modest instability/CAPE
(RAP mixed-layer CAPE up to around 1000 J/kg in our southern zones
this evening) will be present, the overall coverage of convection
looks rather spotty per latest HRRR/NAMnest runs, with better
potential for scattered storms/perhaps a loosely-organized MCS
tracking to our south (mainly near/south of I-70 in KS). That
being said, will maintain a mention for the possibility for a few
stronger storms in our Hazardous Weather Outlook (HWOGID), mainly
near/south of the state line. Although most areas north of the
state line are likely dry through the night, very spotty weak
convection within a modest low level jet axis cannot be totally
ruled out and thus have slight PoPs going all but far northern
zones. Steady south to southeast breezes most areas overnight will
keep low temps well into the 50s most areas (Ord area most favored
for upper 40s).

Thurs-Thurs night:
For only being 24 hours out, honestly plenty of question marks
regarding thunderstorm chances. While most of the area is covered
with low-end PoPs especially during the afternoon-evening, models
show widely varying solutions on coverage/likelihood. Of greatest
concern is the last few HRRR runs, which depict a broken line of
storms developing mainly in our northern CWA along a weak frontal
boundary. Should this occur, at least a limited severe threat
seems plausible given MLCAPE progged around 1500-2000 J/kg along
with 30-40KT of deep layer shear, but overall upper forcing
appears fairly weak and other models (NAM/NAMNest) are mostly dry.
Something to watch. In other areas, generally south-southeast
winds of 10-20 MPH through the day. Temps a little uncertain
depending on how efficiently (or not) any lower level clouds
vacate, but have them aimed from mid 70s east to low 80s west.
Lows Thurs night again well into 50s most areas.

Fri-Fri night:
See paragraph above for various comments on the
thunderstorm/severe potential. Certainly the potential for some
severe, but how much so still in question. From a large scale
perspective, at least ECMWF/GFS/NAM all in pretty good agreement
on strength/track of upper system and associated surface low. High
temps Friday again vary dependent on low cloud trends any
clearing south into a possible dry slot, but for now upper 60s far
north to mid 80s far south.

Sat-Sat night:
Not a very nice day, especially given aforementioned strong
northwest winds with widespread gusts at least 40-55 MPH (highest
west), along with a decent chance for wrap-around rain showers
especially north of I-80. Most areas roughly 20 degrees cooler
than Friday (low 50s far north to low-mid 60s far south). Lows Sat
night as cold as mid-upper 30s, but winds likely well too strong
for frost concerns.

Sun-Sun night:
Pretty high confidence in a dry day with brief ridging in between
systems and lighter winds (compared to Saturday anyway). High
temps mainly 60s. Already Sunday night though, small PoPs return
to the area as the next quick-moving disturbance approaches. Lows
again possibly as cold as mid-upper 30s, but frost concerns fairly
minimal mainly due to increasing clouds.

Mon-Mon night:
Either another good chance of rain (mostly without thunder
potential due to lack of instability) per ECMWF, or a mostly dry
day most areas per GFS solution. Question marks abound. Temps
aimed around 60.

Tues-Wed:
Various small PoPs continue here or there, but timing differences
abound, with GFS favoring Tues-Tues night and slower ECMWF more so
favoring Wed daytime. At least for now, instability appears fairly
limited. Temps remain fairly seasonable if not a touch- cool for
early May, with highs aimed into the 60s both days.



&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 636 PM CDT Wed Apr 27 2022

VFR conditions prevail through the early evening at KGRI and KEAR
terminals. Winds will be from the southeast for much of the
evening at 5-10kts. A few scattered showers and thunderstorms will
be possible in the vicinity of the terminal this evening with
chances decreasing toward sunrise. Ceilings are expected to lower
to MVFR around 12-15Z. Areas receiving rainfall overnight may
experience some patchy fog, however confidence in this solution
remains low for the time being due to lack of widespread coverage
of rain. Conditions improve late tomorrow morning at KEAR with
ceilings returning to VFR.



&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&

$$

DISCUSSION...Pfannkuch
AVIATION...Wekesser



Area Forecast Discussion

National Weather Service Grand Junction CO

 804 PM MDT Wed Apr 27 2022

.UPDATE...
Issued at 804 PM MDT Wed Apr 27 2022

The Red Flag Warning has been allowed to expire at 8 PM MDT.
Winds have subsided for most locations while relative humidity has
recovered above critical levels thereby ending the threat of
extreme fire behavior.

&&

.SHORT TERM...(Tonight through Thursday night)
Issued at 144 PM MDT Wed Apr 27 2022

Both the HRRR and NAMNEST did a great job today picking up on the
convection. Both models showed some minor convection firing just
before noon, which it did, and then continuing over the San Juans
and shifting a bit north over the central mountains. Did see a few
lightning strikes near Crested Butte so, all in all, a good show
by those models. This convection is in response to a shortwave
that is moving overhead with the support of a weak 70kt jet
streak. This support, along with some midlevel instability, was
enough to get this convection going. Satellite and radar imagery
show this convection shifting to the Front Range though the
NAMNEST is highlighting some weak returns across central portions
of CO through about 6PM. Might see a quick sprinkle from a
stronger cell but with such dry lower levels of the atmosphere in
place, this will be few and far between. Deeper mixing has also
allowed some gusty winds to mix to the surface with gusts of 25 to
35 mph being common across the CWA. Red Flag Warnings remain in
effect for the combination of gusty winds, low humidities and
critical fuels (for those areas where fuels are deemed critical).

Expect some high clouds overnight ahead of the next system,
especially for UT and far western CO, where they`ll be under some
weak upper level support. Heading into Thursday proper, a trough
will be just to our west and while the best support and moisture
remains to the north, we`ll still feel the effects in the form of
gusty winds and continued warm temperatures. With increasing
southwesterly flow and a tightening surface pressure gradient
ahead of the trough, gusty surface winds will form again and look
to be stronger than those seen recently. Gusts look to range from
30 to 40 mph across the region with stronger winds north, less so
south. While we will see variable cloudiness throughout the day,
some spotty showers are also possible but these look to be very
isolated in nature. In fact, the NBM is only highlighting some
light precip over the Uintas and Park Range and is in agreement
with the NAMNEST and other models for tomorrow afternoon and
evening. However, chances will start to increase early Friday
morning as the base of the trough and associated cold front
starts to move through...more on that below.

.LONG TERM...(Friday through Wednesday)
Issued at 144 PM MDT Wed Apr 27 2022

The system that dived out of the Pacific Northwest will begin to
impact eastern Utah and western Colorado on Friday as it scoots by
to the north across the northern Rockies and Intermountain West.
At the surface, a strong cold front will surge in from the west
late Thursday night and early Friday morning. Aloft, a 110 knot
250mb jet coupled with a sharp shortwave will punch in from the
northwest. Large scale forcing for ascent will increase as a
result, particularly within the left exit region of the jet over
northeast Utah and northwest Colorado. Moisture with this system
isn`t all that impressive with progged PWAT anomalies only near or
slightly above normal. That said, the frontal forcing and
dynamics aloft combined with the meager moisture will be enough to
squeeze out some showers for mainly the higher terrain in the
northern half of the forecast area. Most of this shower activity
will subside by midday, but orographic upslope showers will likely
linger across the central and northern Divide mountains through
the remainder of the day and possibly night. All in all, QPF/snow
amounts look light and sub-advisory with 1 to 3 inches expected in
the highest elevations.

Other than precip, the other big weather stories on Friday will be
the cooler temperatures (by as much as 10 to 15 degrees), gusty
winds and fire weather. While highs on Thursday will be in the 70s
and 80s for the lower desert valleys and in the 50s and 60s in the
mountain towns and high valleys, highs will only reach the mid 60s
in the lower valleys, 30s & 40s in the mountain towns and 50s for
the high valleys. Quite a stark contrast from just the day before.
Gusty winds up to 40 mph and fire weather are also concerns,
especially south of I-70. As mentioned above, PWATs across the north
will only be nearly or slightly above normal. The opposite is true
across the south where PWATs are near 50% of normal. Where fuels are
critical (CO fire zones 290, 292 and 207 below 7000 feet), we have
another Fire Weather Watch in effect. Similar to how things were
handled on day 3 yesterday, we`re going to let that ride for now and
let the midnight shift make the decision to upgrade to a warning.
More details can be found in the Fire Weather discussion below.

Beyond Friday, a transient ridge builds in across the Great Basin
and Four Corners on Saturday. This will lead to a dry and mostly
sunny day with less wind and slightly warmer temperatures. Dry
weather lingers into Sunday, but another quick-moving and shallow
storm system will be on the doorstep Sunday afternoon. Southwest
flow will increase out ahead of this system, so we may have
additional fire weather concerns. Showers likely develop Sunday
afternoon and evening especially in the higher terrain. Most showers
will end Monday morning, but a few may linger way up high. After a
brief reprieve Monday afternoon through maybe Tuesday morning, yet
another system is in the pipeline for later Tuesday into Wednesday.
Details on this system are still fuzzy given a lack of model
agreement, but regardless, it`s still looking like an active start
to the week, especially, again, in the higher terrain. Drier weather
then likely returns to round out next week with temperatures
hovering near seasonal norms.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 532 PM MDT Wed Apr 27 2022

Instability showers over the central and southern Colorado
mountains may bring strong and unpredictable wind gusts to
adjacent TAF sites through 02Z. Aside from wind, this convective
activity will not degrade VFR conditions prior to dissipating
later this evening. Drainage winds become established by midnight,
though deep mixing during the afternoon will bring another round
of gusty southwest winds to TAF sites across the region on
Wednesday.


&&

.FIRE WEATHER...
Issued at 144 PM MDT Wed Apr 27 2022

Gusty southwest winds have combined with low relative humidities
and caused critical fire weather conditions to occur across many
of the lower elevations of eastern Utah and western Colorado today.
This trend looks to continue each afternoon through the end of
the week. However, as most fuels are not deemed critical, fire
weather highlights are only in effect for portions of southwest
Colorado.

Red Flag Warnings remain in effect for today and tomorrow while the
Fire Weather Watch also remains in effect for Friday. Above
normal temperatures will persist through Thursday. Cooler
temperatures are expected Friday behind a cold front that will
also bring scattered showers, mainly across the north, Friday into
Saturday.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from noon to 9 PM MDT Thursday for COZ207-290-
     292.

     Fire Weather Watch from Friday morning through Friday evening
     for COZ207-290-292.

UT...None.
&&

$$

UPDATE...NL
SHORT TERM...TGR
LONG TERM...MDM
AVIATION...NL
FIRE WEATHER...TGJT



Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

 620 PM CDT Wed Apr 27 2022

.SHORT TERM...
Issued at 301 PM CDT Wed Apr 27 2022

Through Thursday night...

This evening will be another cool one with temperatures dropping
into the 30`s area-wide by around midnight, but likely much earlier
for those in the Chicagoland metro. A fair breeze will pull wind
chills down into the 20`s and lower 30`s for the latter half of the
evening, being especially cool closer to the lake as onshore flow
will persist through the night. By early tomorrow morning,
temperatures across the CWA will have fallen into the middle and
upper 30`s. Just about everyone should remain above freezing,
perhaps with the exception of some more open and rural areas.

Meanwhile, a few showers are attempting to fall just west of the
CWA, but a lack of low level moisture won`t allow them to reach the
surface just yet. However, a plume of moisture advancing down the
lee side of a midlevel trough sitting just to our west will continue
to advect beds of altocumulus and altostratus clouds into the CWA
from the northwest. This means the majority of the sunshine will
continue to be obstructed for the remainder of our Wednesday.
Moderate low level moisture advection thanks to a low level high to
our SSE, with the help of some evaporating rainfall, will work to
moisten up the low levels over the next several hours making it
possible to see some rain later this evening. The rain chances will
move in from the west as early as 7-8 PM and continue through the
night while being primarily confined to areas north of I-80. There
is a good chance that light rain may even become mixed with some
snowflakes as temperatures cool through the night, though no
accumulations are anticipated.

Heading into late tomorrow morning/early afternoon, more rain
showers are expected to pop up to our southwest along a quasi-
stationary frontal boundary and advect into the CWA. The chance for
on and off showers and sprinkles will then last through the
remainder of tomorrow and into Friday morning. Guidance doesn`t have
the greatest grasp on the exact coverage of the rainfall, but it
should be scattered enough to where some spots may not see any
rainfall tomorrow while other may see rain come and go for several
rounds. Additionally, the occasional moderate shower is just about
as heavy as the rain is expected to get. As far as tomorrow`s
temperatures go, the outlying areas should be similar to today with
highs in the middle and upper 50`s. This lake-effect cold pool we`re
seeing today shouldn`t be nearly as prominent come tomorrow.
Therefore, the metro, especially areas near the lake, will see a
notable warmup with highs in the middle 40`s to lower 50`s.
Efficient low level warm air advection overnight, along with
overcast skies, should keep conditions relatively mild with Friday
morning highs expected to be in the middle to upper 40`s.

Doom

&&

.LONG TERM...
Issued at 243 PM CDT Wed Apr 27 2022

Friday through Wednesday...

As noted in the previous discussion, this period is looking to be
fairly active with a progressive flow pattern setting up into
next week. Upper ridging will be cresting the mid and upper
Mississippi River valley and amplify as it does so thanks to a
trough moving east into the Rockies. With the mid level thermal
gradient tightening between the amplifying ridge and the
approaching trough, persistent isentropic ascent/warm advection
will set up and gradually spread northeastward through the day.
Waves of scattered showers in the southwest part of the area to
start the day will spread northeastward through the afternoon with
the greatest coverage across the southwest half or so of the
area. Warm advection and southerly winds will help highs to
moderate with readings in the upper 50s to around 60, though the
Illinois shoreline will likely be cooler thanks to an easterly
component to the south wind. Moist ascent persists Friday night
with the low level flow increasing as the advancing low closes off
over Nebraska. This will provide more support for showers and
possibly some thunderstorms as elevated instability spreads north
and east toward or into the area.

By Saturday, the surface low associated with the upper low is expected
to be slowly moving from northern Nebraska into southwest
Minnesota. An associated cold front will move eastward and looks
to occlude through the day as it does so. At this point its
tough to say how far north the warm sector of the system will
spread, at least in terms of one being clear enough to realize
more than limited instability. It will be something to keep an eye
for potential severe weather which at this point would be favored
south of the area. Otherwise, periods of showers/rain are
expected. Expect warmer conditions across the area, though an
easterly wind component may remain in place keeping northeast
sections of Illinois int the 50s with mid 60s to near 70 degree
temps spread elsewhere.

Another trough digging into the west will help the closed upper
low over the local region eastward Sunday and Sunday night.
Modestly cooler air will spread in as this occurs and there will
likely be enough ascent for scattered showers Sunday, mainly
across northern sections of the area. Beyond that, several more
systems look to cross the area through midweek bringing periodic
shower and maybe thunder chances. Temperatures look to remain on
the cool side of normal with highs in the 50s and 60s depending on
the day.

MDB

&&

.AVIATION...
For the 00Z TAFs...

Primarily VFR conditions are expected to prevail through the TAF
period.

As warm air advection increases atop a stalled frontal
boundary draped across central Iowa and northern Illinois this
evening, showers will blossom and regenerate more or less in the
same place through late Thursday morning. At least some convective
processes may occur with the showers as well mainly toward the
northwestern ZAU airspace, given RAP 700-500 mb lapse rates
exceeding 7 K/km, "bumpiness" in visible satellite imagery, and
recent convective-looking radar returns near KDVN. However, closer
to the Chicago terminals, a dry low-level airmass from about
3500-10000 feet (as sampled by a recent descending flight into
MDW) may chew away raindrops as they fall toward the ground,
keeping radar echoes as largely virga through the night. Chances
for rain to reach the surface should increase toward and
especially after daybreak as the frontogenetical forcing and low-
level WAA peaks in intensity. For now, opted to maintain the
inherited TEMPO groups this evening and introduce a PROB30 group
at the Chicago terminals after daybreak, though in reality
raindrops may hit the ground really anytime from sunset through
noon tomorrow. Cigs and visbys are expected to remain above 3000
feet and 6 miles, respectively, in the showers so no impacts
beyond wet runways are anticipated. Coverage of showers should
wane tomorrow afternoon as frontogenetical forcing decreases,
leaving behind a BKN080 cloud deck. Winds through the TAF period
will maintain an easterly component, first out of the east-
northeast this evening and the east-southeast tomorrow.

Borchardt

&&

.MARINE...

Opted to hoist a small craft advisory this morning through mid
evening. Unseasonably cold air mass resides over the lake with a
couple of ship obs well offshore reporting air temps in the mid
30s. Water temps have warmed well into the 40s, resulting in a
rather unusually unstable marine boundary layer for this time of
year. As high pressure moves east the strengthening synoptic
pressure gradient should be strengthened by the lake-land breeze
circulation today. Only ran the small craft advisory through 02Z,
but it is possible winds and/or waves are slower to come down
than forecast and the advisory may need to be extended.

- Izzi

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...nearshore waters until 9 PM Wednesday.

&&

$$

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Area Forecast Discussion

National Weather Service Lubbock TX

 607 PM CDT Wed Apr 27 2022

.AVIATION...
VFR conditions will prevail at all terminals. There is a very slim
chance for a shower or thunderstorm to impact PVW and/or LBB
between 11 PM and 1 AM tonight, but confidence is extremely low at
this time. There is also a slight chance for MVFR CIGs at CDS
around sunrise, but confidence is low and will also be kept out of
this TAF cycle.

&&

.PREV DISCUSSION... /issued 220 PM CDT Wed Apr 27 2022/

SHORT TERM...
18Z upper air analysis depicts a shortwave trough beginning to eject
across the west-central Great Plains with a corresponding baroclinic
leaf present over eastern Colorado and western Kansas. A pair of
mid/upper-level cyclones were located over the Pacific Northwest and
northeastern U.S., resulting in weak blocking of the low-amplitude
ridge encompassing most of the central Great Plains. At the surface,
lee cyclogenesis is underway across southeastern Colorado with a
diffuse dryline extending south-southwestward which is draped across
east-central New Mexico/along the Sangre de Cristo and Sacramento
Mountains and a secondary surface trough arcing southeastward into
the Texas Panhandle and Rolling Plains, evident from recent METAR
and West Texas Mesonet data. Pressure falls were weak across the
CWA, near -1 mb/3 hr to locally -2 mb/3 hr as the cyclone gradually
deepens with a current pressure near 1008 mb based off nearby METARs
fixed to the low center. This has resulted in breezy, southerly
winds between 15-25 mph area-wide as the pressure gradient begins to
tighten. Cyclogenesis is expected to continue through the rest of
the afternoon as the shortwave trough ejects north of the CWA,
though deepening will continue to be gradual as it rotates through
the low-amplitude ridging overhead. The southerly fetch has advected
heavily modified moisture from the Gulf of Mexico into the region,
characterized by surface dewpoints in the lower-middle 50s across
the Caprock an/99/99d Rolling Plains, respectively. A
differential diabatic heating boundary, oriented in a north-to-
south direction and juxtaposed to the diffuse surface trough, was
also analyzed across the east-central Rolling Plains based off of
visible satellite imagery and theta-e advection magnitudes on the
West Texas Mesonet.

Diurnally-driven convection has formed along the immediate leeward
side of the mountains in New Mexico as the shortwave trough nears
and as convective temperatures have been reached amidst minimal
mixed-layer convective inhibition, which was observed on the 27/12Z
RAOBs from ABQ and EPZ. Weak geopotential height falls will continue
to contribute to the advection of a tall and skinny EML over the CWA
as mid-level lapse rates steepen to near 7.5 deg C/km, with around
1,000 J/kg of CAPE for surface-based parcels evolving later this
afternoon across the western South Plains/TX PH based off of recent
RAP analysis which is further confirmed by the observed RAOBs this
morning. As multi-cells near the TX/NM state line, the initial storm
movement governed by advection may transition into a spatiotemporal
window for discrete propagation as straight hodographs and effective
bulk wind differences (EBWDs) near 30 kt to locally 35 kt support
the potential formation of weak, mid-level mesocyclones for left-
and right-moving supercells. A dry, well-mixed sub-cloud layer with
LCLs near 700 mb across the western South Plains/TX PH will
facilitate cold downdrafts with wind gusts up to 60 mph possible
beneath the deepest cores. A hail event or two up to 1 inch in
diameter will be possible as well; however, the weak EBWDs and
skinny updrafts should limit the potential for severe-caliber hail.
There exists uncertainty on how far east cells will propagate, and
coverage will be limited to a few cells with the best potential
mainly west of the I-27 corridor. Thunderstorm coverage will wane
altogether after dark as MLCINH increases and the boundary-layer
stabilizes.

Surface winds will gradually veer overnight while remaining breezy
as the cyclone drifts towards the Raton Mesa and OK/TX PH region,
resulting in boundary-layer moistening once again as the low-level
jet (LLJ) strengthens to near 35 kt beneath the dampening shortwave
trough over central Kansas. The development of a low stratus deck
will be possible prior to sunrise Thursday, especially across the
Rolling Plains owing to the terrain-influenced, deeper PBL as T/Td
spreads near 0 deg near the top of the LLJ with decreasing potential
for saturation with westward extent onto the Caprock. After sunrise,
intense dry-bulbing and vertical mixing is expected as the dryline
mixes eastward into the eastern Rolling Plains as large-scale
forcing for ascent gradually increases compared to today due to a
shortwave trough pinching off and digging southward from the parent
mid/upper-level cyclone over western Canada and the Pacific
Northwest. Temperatures will soar into the middle 90s across most of
the CWA, excluding the extreme southwestern TX PH where temperatures
in the upper 80s are expected, in wake of the dryline. Breezy,
southwesterly winds between 15-25 mph are expected despite vertical
mixing heights ascending into the mid-levels in the dry sector as
the jet streak remains displaced over the southern Great Basin. The
dryline is forecast to stall while also sharpening (i.e. a dewpoint
gradient of nearly 20 deg F over >=30 miles depending on various
locales) across the western vicinity of the 100th meridian, keeping
the far eastern Rolling Plains from near Childress southward to
Aspermont in the moist sector. Vertical thermodynamic profiles in
the moist sector will be similar to today with straight hodographs
favoring an initial multi-cellular storm mode with the potential for
discrete propagation for left- and right-moving supercells fostering
the possibility of low-end, severe-caliber hail and wind reports
before convection moves east of the CWA.

Sincavage

LONG TERM...
Increased fire weather concerns will occur later this week with a
chance of widespread thunderstorms late in the weekend. The
increased fire weather concerns will come on Friday. An upper trough
centered over the central Rockies on Friday morning will emerge onto
the Central Plains Friday afternoon and will sharpen up as this
occurs. The upper level jet streak associated with this short wave
will track close to the 37th parallel keeping any large scale ascent
well north of the region. The rapid movement of the system onto the
Plains Friday afternoon will easily shove a dryline east of the
Rolling Plains with strong lee surface cyclogenesis in western
Kansas. Winds directly overhead will not be that impressive on
Friday during the daytime. However, the approach of the short wave
will allow the surface pressure gradient to tighten significantly
which will bring strong westerly winds and warm temperatures. A cold
front will follow late Friday into early Saturday. This will bring
temperatures closer to seasonal averages for Saturday. Short wave
ridging will be moving overhead in advance of the next short wave to
affect the area on Sunday.

Return flow will be quick to establish itself beginning early Sunday
in advance of this short wave moving across the Great Basin region.
An upper level jet streak will be more squarely overhead providing
better large scale ascent on top of a sharp dryline near the
Texas/New Mexico state line. However, at this forecast range the
devil is in the details with regards to any minor short waves in the
flow and there remains much uncertainty. Analog guidance indicates
the potential for severe storms on Sunday afternoon and evening over
a widespread area of West Texas.

FIRE WEATHER...
Critical fire weather conditions are expected across the Caprock,
particularly along and west of the I-27 corridor, tomorrow
afternoon. A Red Flag Warning is in effect between noon and 9 PM
CDT. Breezy, southwesterly winds between 15-25 mph with gusts up to
35 mph will combine with hot temperatures and very low relative
humidity, resulting in favorable conditions for the growth and
spread of fires. Southwesterly breezes will persist overnight but
decrease to around 10-15 mph with RH recovery near 100 percent
across the region.

&&

.LUB WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Friday morning through Friday evening
for TXZ021>044.

Red Flag Warning from noon to 9 PM CDT Thursday for TXZ021>023-
027>029-033>035-039>041.

&&

$$

51



Area Forecast Discussion

National Weather Service San Diego CA

 855 PM PDT Wed Apr 27 2022

.SYNOPSIS...
Cooler weather with a greater influence from the marine layer is
expected through Thursday. Gusty westerly winds across the
mountains and deserts will be boosted by a trough of low pressure
moving through the region. Low clouds and fog will spread inland
to the mountains tonight into Thursday, including patchy drizzle
early Thursday. As the trough departs a weak ridge will help
temperatures rebound into Saturday. More troughs of low pressure
appear early next week, for occasional winds and cool weather.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Update:

Marine layer low cloudiness lies along all but parts of the
northern Orange County coast this evening. However, this likely
will fill in this evening and move well into the inland valleys
overnight. Patchy drizzle is even possible overnight through
Thursday morning given the deepening marine layer. The forecast
has this handled well, so no changes to the forecast were needed
this evening.

Previous Discussion:

.SHORT TERM...(Today through Saturday)...
A coastal eddy continues to spin over the California Bight, where
clouds have eroded away off the coast. An approaching trough off the
Pacific will enhance the marine layer, where it will become deepest
tonight this week. Most areas west of the mountains will see low
clouds filter in later this evening through tomorrow morning. HRRR
picking up possible drizzle late tonight into Thursday morning for
areas west of the mountains. The marine layer will be deep and
saturated to support this. This pattern will also bring much cooler
weather and windy conditions. NBM/HRRR/WRF blend depicts desert
slopes gusting 45 to 55 MPH Thursday afternoon and night, while
deserts will gust near 30 to 40 MPH at times. Gusty winds and
blowing dust will be a concern for drivers out on the roads during
this time.

A weak ridge will come into the area by Friday, introducing less low
cloud coverage west of the mountains, warmer temperatures, and less
wind. Saturday will see further warming for all areas.

&&

.LONG TERM...(Sunday through Tuesday)...
Models diverge a bit on what will happening by Sunday and early next
week. A trough will enter the Pacific Northwest on Saturday.
Depending on the strength and position of this feature, will
determine how cool and windy we get next week. ECMWF/Canadian are
more aggressive with the system as the GFS shows it a bit weaker.
Model clusters still uncertain, but consensus leans toward zonal to
a slight troughing pattern, which would lead to near or slightly
below average temperatures with continued dry weather.

&&

.AVIATION...
280310Z...Coast/Valleys...BKN/OVC low clouds will spread farther
inland overnight with current bases of 1500-2000 ft MSL eventually
rising to 2000-2500 FT MSL, and tops to 3500 ft MSL with areas of
higher terrain obscured in clouds, and local vis 2-4 miles in BR in
the valleys. Most areas will clear by 18-19Z Thu.

Mountains/Deserts...Mostly clear skies with mostly unrestricted VIS
will continue through Thursday. Areas of west surface winds will
continue through Thursday from the mountain crests east through the
desert slopes and into the deserts with gusts 25-35 knots, locally
35-45 knots Thursday afternoon, along with areas of strong
up/downdrafts, LLWS and local vis restriction below 3 miles in
blowing dust.

&&

.MARINE...
Wind gusts of 20 knots, locally greater, are likely Thursday through
Thursday evening, especially in the outer coastal waters. Local seas
of 6-8 seconds with a period around 8 seconds will create choppy
seas in the outer coastal waters at times through Thu night.

&&

.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory from 1 PM Thursday to midnight PDT Thursday night
     for Riverside County Mountains-San Diego County Deserts-San
     Diego County Mountains-San Gorgonio Pass Near Banning.

PZ...NONE.
&&

$$

PUBLIC...Gregoria (Update)/APR (Previous Discussion)
AVIATION/MARINE...Adams



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