Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/02/21
Area Forecast Discussion
National Weather Service La Crosse WI
1025 PM CDT Sat May 1 2021
.SHORT TERM...(This evening through Sunday)
Issued at 215 PM CDT Sat May 1 2021
Still could see a few showers develop late this afternoon and
continue into the early evening in the Interstate 90 corridor across
western Wisconsin. The RAP continues to suggest some weak
frontogenesis in the 850-500 mb layer across this area combined with
some convergence at 850 mb as the moisture transport begins to
increase ahead of an approaching short wave trough. These should
then move out of the area early this evening with much of the rest
of the night expected to be dry.
The rain chances will then increase Sunday, especially in the
afternoon. The upper level flow will turn to the southwest ahead of
an approaching trough in the northern stream. The models have been
consistent in showing this to be a rather dirty flow pattern with
several smaller embedded short wave troughs versus a single stronger
one. As a result, the pv advection in the 500-300 mb layer never
looks to be all that impressive, but it will be rather persistent
once it starts. A cold front will ever so slowly move into the area
and looks to have good low level forcing along it. The RAP suggests
there will be 4 to 6 ubar/s of up glide on the 305K surface in the
warm air advection right ahead of the front. This lift looks to be
augmented by a zone of weak to moderate frontogenesis in the 850-700
mb layer. This should allow showers to develop pretty quickly in the
afternoon over the northwest sections of the forecast area. Around
750 J/kg of ML CAPE should be in place in the warm sector to support
some rumbles of thunder as well. The chances for any severe storms
looks very low as the shear in the baroclinic zone looks to only be
around 20 knots or so.
.LONG TERM...(Sunday night through Saturday)
Issued at 215 PM CDT Sat May 1 2021
Slightly southwest flow aloft with several embedded waves, combined
with the sluggishly progressing surface front, will result in
periods of showers and storms Sunday night and into late Monday when
the front finally exits. Quasi-zonal flow will persist through the
middle of the work week, giving way to slightly more amplified
northwest flow as we head into next weekend. The next notable chance
for rain is Thursday as a weak trough and surface cold front passes
by. Otherwise, generally cool temperatures will continue through the
extended portion of the forecast.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1025 PM CDT Sat May 1 2021
Cigs: sct-bkn mid level vfr deck persists into Sunday morning, with
an increase in low level saturation then expected into Sunday night.
MVFR still looks likely, but how soon those lower cigs move in is
the big question. NAM/GFS suggest sub 3 kft will build in by 18z
now. RAP and SREF would hold off until closer to 00z. For now, will
continue to hold with bringing the low cigs in later, with the
expected pcpn. Trends will have to be monitored closely. Once the
cigs settle in, they will look to hold into Tue morning.
WX/vsby: latest RAP/HRRR a bit quicker with pcpn onset at KRST/KLSE,
although still mostly tied to the cold/warm fronts. SHRA/TS looking
more likely by 00z Mon now, but could be a tad earlier too.
Expecting widespread shra/ts for the evening, becoming scattered
overnight.
Winds: mostly southerly through Sun afternoon, roughly around 10
kts. LLWS a concern for both sites tonight with +40 kts by 2 kft.
Should improve by 08-10z. Warm front slated to sag south to around
the I-90 corridor. As (if) it does, winds should become a tad
lighter and more east/northeast. Going to lean the forecast this
way.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...04
LONG TERM...DMD
AVIATION...Rieck
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
646 PM CDT Sat May 1 2021
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...A mix of low and mid level clouds and light winds
prevail across deep south Texas early this evening. Ceilings are
expected to improve somewhat through late this evening as some
drier air starts to filter into the area from the W-SW. However,
short term guidance continues to suggest ceilings at HRL and BRO
may drop to MVFR/IFR levels overnight into Sunday morning. Otherwise,
VFR conditions are expected for the next 24 hours. Light and
variable winds tonight will increase and become southerly on Sunday.
&&
.PREV DISCUSSION... /issued 256 PM CDT Sat May 1 2021/
SHORT TERM (Now through Sunday Night): The latest KBRO reflectivity
indicates that the conv coverage continues to decrease steadily
across the region with the bulk of the ongoing conv located offshore
over the lower TX Gulf waters. The big question is whether or not
there will be any last minute development as the 500 mb closed low
over the Big Bend region starts lifting NE allowing a drier and more
subsident flow aloft to spread over the region. The latest vsbl satl
imagery shows there is some orographically driven conv firing over
the higher terrain in NE Mex. Since some of this may hold together
long enough to move into the RGV, will leave some mention of low end
pops in place for one more period this evening. However, the latest
HRRR and RAP is pretty pessimistic that much more significant
rainfall will occur this evening and tonight across the region. The
HRRR shuts us out completely from the conv while the RAP13 does try
to bring a few cells right over the Cameron County area later
tonight.
Outside of the shorter range conv models, the NAM/GFS and ECMWF
models are all consistent in lifting the Big Bend 500 mb low out to
the NE later tonight and Sun moving it into the ARK/LA/TEX area
tomorrow.
As the 500 mb low moves out of the area and the moisture levels
decrease across the region, high temps will be on the increase
tomorrow as the daytime heating increases. The short temp guidance
reflects this warmup pretty nicely and will opt for a general blend
of the model temps throughout the short term.
Since the pops will be decreasing this evening and the heavy rain
threat appears to be fading, will cancel the FFA for the Coastal
areas of Cameron/Willacy and Kenedy Counties.
LONG TERM (Monday through Saturday): Weak mid level ridge of high
pressure across the Gulf of Mexico gets pushed a bit further south
next week by a shortwave as it sweeps through TX on Tuesday. A
stronger 500mb high builds through the end of the week. Low
pressure across the Plains will strengthen the pressure gradient
on Monday, bringing another windy day across the lower Texas
coast. A Wind Advisory may be needed. A dryline works into the
western CWA on Monday as well, allowing temperatures to spike and
humidity values to crash. The lower humidity and higher winds may
just miss each other across the CWA, to fall short of any Fire
Weather criteria.
A weak frontal boundary approaches on Tuesday and stalls just south
of the border on Wednesday, before dropping further south through
the remainder of the week. Low pressure returns to the Plains
next weekend, likely strengthening the PGF and bringing more
breezy to windy conditions to the lower Texas coast. The best POP
will remain Tuesday evening into Wednesday morning, mainly across
the ranchlands and coastal counties. Kept light POPs in along the
southern border and offshore into Wednesday afternoon near any
remaining frontal boundary convergence.
Highs on Monday could range from 81 to 88 along the coast and 97
to 104 across western counties. Expect 90s again on Tuesday before
the front brings highs back toward normal or slightly below on
Wednesday. The remainder of the week looks close to normal.
MARINE (Now through Sunday Night): The PGF will remain pretty weak
for tonight and Sun allowing for pretty low winds and seas to
persist. Another 500 mb short wave digging across the Southwestern
States will result in a pretty strong surface low spinning up over
the South Central Plains States Sun Night into Mon morning. This may
result in some SCEC conditions for both the Bay and Gulf waters.
Monday through Saturday: High pressure across the Gulf edges
further eastward as low pressure deepens across the Plains. The
pressure gradient strengthens along the coast on Monday, with SCEC
conditions on the Gulf and potential SCA on the bay due to winds.
Persistent southeasterly swell is expected to build or maintain
elevated seas Tuesday into Wednesday as a weak cold front arrives
and gradually slows or stalls south of the Rio Grande. SCEC to SCA
are possible late Tuesday into Wednesday. High pressure builds
through the remainder of the week, allowing marine conditions to
improve. As low pressure returns to the Plains, expect another
breezy to windy day on Saturday.
&&
.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL 69 88 74 88 / 20 0 0 0
BROWNSVILLE 70 90 76 91 / 20 0 0 0
HARLINGEN 67 92 74 94 / 20 0 0 0
MCALLEN 68 96 74 97 / 20 0 0 0
RIO GRANDE CITY 65 101 73 103 / 20 0 0 0
SOUTH PADRE ISLAND 71 79 74 82 / 20 0 0 0
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
63-KC
Area Forecast Discussion...CORRECTED
National Weather Service Cheyenne WY
959 PM MDT Sat May 1 2021
.UPDATE...
Issued at 951 PM MDT Sat May 1 2021
A fairly active late afternoon and early evening as scattered
high-based showers and thunderstorms developed and moved east-
northeast across the CWA. The primary threat with the showers
and storms has been strong and gusty outflow winds. Peak wind
gusts were 60 mph at KRWL and 64 mph at KDGW, with numerous 50
to 60 mph gusts along portions of I-80 between Cheyenne and
Rawlins.
Isolated thunderstorms are still possible until midnight, with
scattered rain showers overnight. Precipitation amounts will
be light. Adjusted PoP, sky and weather grids to match trends.
Updates sent.
&&
.SHORT TERM...(Tonight - Monday)
Issued at 215 PM MDT Sat May 1 2021
Scattered to numerous showers & perhaps a weak thunderstorm can be
expected across much of southeast Wyoming and the western Nebraska
Panhandle through this evening. This activity will be mainly high-
based with very limited low-level moisture, so generally expect to
see virga showers for most areas. Inverted-V profiles & high DCAPE
values around 1000 J/kg will support occasional wind gusts near 50
MPH with some cells. Scattered showers will continue overnight for
many areas, but potential for strong wind gusts should diminish by
03z or so. Low-level moisture return becomes more established late
tonight and early Sunday as an upper level short wave digs south &
and east into the 4 Corners. Increasingly difluent flow aloft will
support widespread convective development after 18z on Sunday. Dew
points near 50 F, coupled w/ steep mid-level lapse rates may prove
supportive of SBCAPEs up to 1200 J/kg. 0 to 6 km shear of 40 to 50
knots may support a few organized updrafts capable of severe hail/
wind along the I-80 corridor east of Cheyenne. The 12z installment
of the HRRR did show several helicity tracks in/near the CWA. MRGL
Risk from SPC on DY2 looks good. In the meantime, convection along
with some orographic support will yield a period of heavy mountain
snow especially in the Snowys. Models have trended lower with QPFs
over the high country, but the potential does exist for 12+ inches
above 10k feet from Sunday afternoon through Monday. Have issued a
Winter Storm Watch for the Snowy Range. Advisories could be needed
for the Sierra Madres and perhaps the I-80 summit by Sunday night/
early Monday.
.LONG TERM...(Monday Night - Saturday)
Issued at 215 PM MDT Sat May 1 2021
Unsettled weather continues Monday evening as a shortwave moves east
through southeast Wyoming and western Nebraska bringing more rain to
lower elevations and snow to the mountains. There`s a brief settling
of the weather Tuesday during the day, then by Tuesday night another
shortwave disturbance will pass through southeast Wyoming and
western Nebraska bringing rain to lower elevation areas and snow to
higher elevations and the mountains through Wednesday night.
Thunderstorms are possible Wednesday afternoon in far southeast
Wyoming and western Nebraska as this disturbance moves east. Thursday,
a strong ridge will build in with above normal temperatures and
dry conditions through Friday. Possible precipitation returning to
western Nebraska Saturday as a brief disturbance passes through,
breaking down the ridge.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 520 PM MDT Sat May 1 2021
Latest KCYS radar scanning scattered showers and thunderstorms
across southeastern Wyoming. Brief gusts up into the 40s and 50s
may be possible in strongest decaying thunderstorms. VFR conditions
should return for all sites after 09z in WY with last showers ending
late Sunday morning for NE. Models are trending in response to
frontal passage and upper trough moving in for lower CIGS after 18z.
&&
.FIRE WEATHER...
Issued at 304 AM MDT Sat May 1 2021
Relative humidities will be quite low today across the entire
region with values ranging from 10 to 15 percent. It will also be
quite breezy over the Wyoming plains, but fuels are not ready in
this region yet. East of the Laramie Range wind speeds will be
lighter at 10 to 15 mph. This area is leaning a bit towards more
critical fire weather conditions. These near critical fire
weather conditions will be short-lived after the front moves
through the area on Sunday and brings more rain and snow to the
region through midweek.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Watch from Sunday afternoon through Monday
afternoon for WYZ114.
NE...None.
&&
$$
UPDATE...MAJ
SHORT TERM...CLH
LONG TERM...LK
AVIATION...WM
FIRE WEATHER...REC
Area Forecast Discussion
National Weather Service Dodge City KS
625 PM CDT Sat May 1 2021
...Updated Aviation Discussion...
.SHORT TERM...(This afternoon through Sunday night)
Issued at 1230 PM CDT Sat May 1 2021
Starting off May with a near perfectly clear sky across all of SW
Kansas as of midday. 12z NAM deepens the lee cyclone to near
992 mb near Limon, Colorado by 7 pm, which will act to keep
pressure gradients tight for the remainder of the day. South to
southwest winds will routinely gust 30-35 mph through sunset, with
afternoon temperatures in the 80s.
South winds will remain elevated tonight, averaging 10-20 mph,
facilitating moisture return and dewpoints climbing back into the
50s. Moisture advection will allow stratus to spread northwestward
into at least the eastern half of SW KS tonight, most likely along
and east of US 283. Some uncertainty exists on how far west
stratus will advance tonight, with some drizzle possible in the
deepest moisture across the southeast zones. Most locations will
hold in the 50s through sunrise Sunday.
Closed low over Texas Saturday afternoon will finally eject to the
Mississippi valley Sunday afternoon, as shortwave energy begins to
approach from the west. The vast majority of Sunday will be dry,
with elevated and gusty S/SE wind in response to strong low
pressure developing near the NW panhandles. Models show little if
any cooling versus Saturday, so expect lower to mid 80s to again
prevail Sunday afternoon. NAM develops CAPE of 2000+ J/kg Sunday
afternoon and early evening, east of the dryline, with isolated
thunderstorms possible across the western/NW zones toward sunset.
12z NAM and the latest HRRR iterations agree, suggesting an
organized thunderstorm complex will develop near the Palmer Divide
Sunday evening, and then advance eastward into NW Kansas Sunday
night. Current model trends suggest this complex may only graze
the northern zones, with a strong capping inversion discouraging
convection further south. Inherited likely pops Sunday night, but
it is probable these are overdone south of K-96, and pops will
likely need to be lowered if trends continue. Damaging
winds and marginally severe hail would be a risk from any
organized complex, and SPC`s 15% wind/hail probability mainly
north of K-96 is warranted. Outflow from any mesoscale convective
system in NW KS will help propel a strong cold front through SW KS
Sunday night/early Monday, with a period of strong north winds.
Trended wind/wind gust grids toward the stronger 12z MET guidance,
especially along the preferred US 83 corridor.
.LONG TERM...(Monday through Saturday)
Issued at 220 PM CDT Sat May 1 2021
A big change to a windy, wet and raw day on Monday behind the cold
front. North winds will be quite strong in response to surface low
pressure sliding east through Oklahoma, and increased the NBM wind
and wind gust grids by several mph. Cold advection will drive
850 mb temperatures down to the 3-5C range by late afternoon, and
coupled with an expected overcast, temperatures will struggle
through the 50s. Reduced NBM`s max T grid 1-2 degrees, but it may
be cooler than that. 12z ECMWF remains consistent spreading the
best opportunity for measurable rain into SW KS Monday afternoon,
as forcing for ascent ahead of the approaching shortwave
increases. Instability is essentially wiped out by Monday, so
thunder will be hard to come by. 12z ECMWF suggests 0.25-0.50 inch
of rain Monday, with heavier amounts favoring the southern zones
adjacent to Oklahoma.
Subsidence behind the exiting wave will provide much improved
weather Tuesday, although temperatures will still be several
degrees below normal. Sunshine, much lighter winds, and afternoon
temperatures in the 60s.
A shortwave embedded in the NWly flow aloft will pass through the
region Wednesday and Wednesday night, providing a chance of
showers and thunderstorms in the region. Accepted NBM`s pops for
now, but will need to rearrange these as the wave approaches and
any instability is ascertained.
12z ECMWF builds a strong ridge axis through the Great Basin on
Thursday, and then slides the ridge axis to the spine of the
Rockies on Friday. More dry quiet NW flow aloft will result with a
warming trend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 615 PM CDT Sat May 1 2021
Gusty south southeast winds at around 15 knots will continue
overnight. These winds will draw increasing low level moisture
back into southwest Kansas with ceilings falling into the 2000 to
3000ft level in the Dodge City area after 06z Sunday. Ceilings as
low as 500 to 1500ft AGL will be possible between 10z and 15z
Sunday. Hays will also have a high probability of lowering
ceilings overnight with the lowest ceilings occurring between 12z
and 18z Sunday. HRRR and NAM late this Saturday evening suggesting
these low clouds will stay east of Garden City and Liberal areas
but confidence is not high that this will occur so did include a
tempo group of low clouds in these locations also. Also overnight
the winds in the 1500 to 2000ft AGL level will increase into the
40 to 45 knot range so did include a wind shear group at all four
TAF sites late tonight.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 57 81 52 59 / 0 10 60 70
GCK 53 82 49 57 / 0 30 70 80
EHA 52 88 48 56 / 0 20 20 80
LBL 53 87 49 58 / 0 10 30 70
HYS 58 80 51 62 / 0 20 80 60
P28 59 80 57 68 / 0 0 30 60
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM CDT /7 PM MDT/ this evening for
KSZ061-062-074-084.
&&
$$
SHORT TERM...Turner
LONG TERM...Turner
AVIATION...Burgert
Area Forecast Discussion
National Weather Service Grand Forks ND
956 PM CDT Sat May 1 2021
.UPDATE...
Issued at 956 PM CDT Sat May 1 2021
Frontal boundary pushing through Fargo area, with wind shift to
the north northeast. The front will continue to move south through
the rest of the evening. Adjusted winds as well as the sky cover a
bit for mid-level clouds near the front. Temps still seem on
track to slowly fall into the 40s overnight.
UPDATE Issued at 640 PM CDT Sat May 1 2021
Still very warm across the region with temps in the 80s across
much of our central and southern counties. Cold front pushing into
the Highway 2 corridor has shifted wind to the north-northeast and
started to drop temps back into the 70s. Used HRRR for wind
shift position as it seems closest to reality this evening.
Decreasing temps and lower winds should allow us to drop the Red
Flag when it expires at 8 PM. Cold front will continue to push
southward this evening.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 232 PM CDT Sat May 1 2021
Fire weather remains the main concern in the short term, and that
will be discussed in the fire weather section below.
Although there are some bands of cloud cover across the FA, it
remains mostly sunny this afternoon. Temperatures have risen into
the upper 70s and 80s, as expected. At Fargo and Grand Forks,
this is the first 80 degree day since late last September. Winds
are from a variety of different directions and speeds, and they
will stay that way into the evening. Speeds should decrease
somewhat overnight, but it will stay relatively mild. Another
decent temperature day is anticipated for Sunday, although cooler
than today. It does look to be cooler across the Devils Lake
region and warmer elsewhere. Winds also look breezy again,
especially along and west of the Red River Valley. However, rain
should begin to spread into the FA, especially by the afternoon,
which will decrease the fire weather threat. Rain chances continue
into Sunday night as well.
.LONG TERM...(Monday through Saturday)
Issued at 232 PM CDT Sat May 1 2021
Impactful weather during the extended forecast period is not easy to
find, with chances for mainly light rain presenting during midweek
and perhaps at some point next weekend.
Pcpn will be heading out of or have completely cleared the area as
Mon dawns, with brisk north winds sustaining at 20 to 25 mph. The
best opportunity for QPF comes Wed/early Thu with a transient wave.
Colder early AM temps would make some snowflakes possible, offering
insignificant impacts, except to one`s psyche! The amplified upper
structure during the mid week period is likely to see the ridge
begin to break down with the flow becoming flatter and more zonal
heading toward the weekend. This would allow for some Northern
Rockies moisture to move toward our area. The likely result would be
surface high pressure in place Thu/Fri yielding to pcpn chances over
weekend, although the lion`s share would appear to remain south of
the forecast area.
The temperature regime will remain below normal during the upcoming
week, as 850 mb temps stick close to 0 C translating to overnight
lows around freezing with daytime highs only in the 50s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 640 PM CDT Sat May 1 2021
Winds will be the main issue with VFR conditions for most of the
period. Cold front coming down has shifted winds to the north-
northeast for all but KFAR which is still northwesterly and
gusting to around 20 kts. The cold front will continue to drop
down this evening, and winds will decrease overnight. Some picking
up again during the day tomorrow to the 10 to 15 kt range with
gusts to 20 kts, still mostly from the northeast. Showers and
possibly some MVFR ceilings will be possible in the KDVL area
towards the end of the period. For now kept just VCSH and lower
VFR as most model solutions are not consistent on bringing
ceilings down below 3000 ft.
&&
.FIRE WEATHER...
Issued at 232 PM CDT Sat May 1 2021
Interesting fire weather day to say the least. The gustiest winds
(from the west-northwest) have generally been south of the
highway 2 corridor so far. The driest dew points have west and
southwest of Jamestown ND. A thin corridor of fairly light winds
yet have stretched from Langdon to Grand Forks to just north of
Bemidji. Just to the north of this, north winds at 15 to 25 mph
are occurring. Temperatures have risen quite nicely, with most
locations closing in on the 80s. So critical fire weather
conditions will continue into the early evening, when the Red Flag
Warning is set to expire at 8 pm. Rain should begin to move into
the area Sunday, lessening the fire weather threat.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...JR
SHORT TERM...Godon
LONG TERM...WJB
AVIATION...JR
FIRE WEATHER...Godon
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
717 PM CDT Sat May 1 2021
.SHORT TERM...(This Evening through Sunday)
Issued at 229 PM CDT Sat May 1 2021
As of mid afternoon, surface observations show temperatures have
skyrocketed into the upper 80s to mid 90s. Humidity levels have
dropped to the teens and 20s, with fire danger being exacerbated
across northwest Iowa where warm air advection ahead of the
stationary front has combined with deep boundary layer mixing to
produce gusts up to 40 mph. Scattered cirrus and cumulus may help
taper high temperatures a bit, but overall hot and dry as
expected.
Cloud cover will increase across the region tonight, in advance of
an approaching mid level shortwave. In response to the resident dry
air and height falls aloft associated with the departing upper
ridge, temperatures will drop dramatically overnight, reaching the
50s by early Sunday morning.
A mid level shortwave brings scattered showers and maybe a brief
rumble of thunder to areas in south central and southeast SD late
tonight and through Sunday. Rain chances will spread east of I-29 in
southwest MN early Sunday morning. Model soundings suggest it may
take up to a few hours for lower levels to saturate with this weaker
disturbance so expect meager rainfall amounts only up to a few
hundredths of an inch at most sites. Up to a tenth of an inch of
rain is possible along and west of the James River Valley. There`s a
prolonged period of rain chances given lower confidence in location
of off/on showers scattered across the region on Sunday, but the
majority of Sunday should be dry for most.
Cooling aloft combined with cloudiness and the lingering stationary
front bisecting the region will mean Sunday`s highs should be 10 to
20 degrees cooler than Saturday`s. Increased dew points will make
for higher humidity levels Sunday, and highs should still reach the
70s, cooler further north behind the stationary front.
.LONG TERM...(Sunday Night through Saturday)
Issued at 229 PM CDT Sat May 1 2021
Showers and storms are likely to develop Sunday late afternoon and
night as a stronger mid level trough tracks through in southwest
flow aloft and interacts with the stationary boundary draped across
northwest IA and eastern NE. There is disagreement on timing the mid
level wave and cap erosion, but most guidance supports a line of
storms popping up along the front in western IA. A second area of
scattered showers and isolated weaker storms is possible further
west across the rest of the forecast area Sunday night, prompted by
the approaching upper longwave trough. In northwest IA along and
ahead of the front, HREF guidance of SBCAPE 1000-1750 J/kg and mid
level lapse rates 7-8 C/km are supportive of storm development and
small hail, but deep layer effective shear is weak at 20-25 kts and
the overall wind profile remains unimpressive. Although today`s 12z
HRRR paints a robust picture of a line of storms from SPW to SUX and
southwest, the severe threat is quite low unless the front stalls
further west than currently expected and is able to interact with
stronger deep layer shear. The more likely scenario is to see
scattered storms initiate in northwest IA Sunday night with perhaps
a stronger storm or two with gusty winds and small hail.
Cooler, near normal air moves back in for Monday and Tuesday as
highs return to the 50s and 60s in the vicinity of a passing upper
longwave trough. Most of the region will see lingering cloud cover
and rain chances continues for parts of northwest IA on Monday. A
breezy north wind will make Monday feel even cooler as the Northern
Plains remains squeezed between the departing sfc low and
approaching high. Drier air and weaker winds spread in with sfc high
pressure Tuesday.
Widespread rain chances and breezy conditions develop for Wednesday
through Thursday as a strong clipper system tracks through the
Northern Plains in northwest flow aloft. At this point, there is low
confidence regarding the exact track and how much rain we could see,
but the latest guidance does still support the better chance of rain
being Wednesday afternoon and evening. Beyond this system, late week
looks mainly dry with near seasonal average temperatures continuing
through Thursday - highs in the 50s to 60s and lows in the 30s to
40s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 715 PM CDT Sat May 1 2021
Frontal boundary sagging through KFSD at time, but most winds
are starting to decouple pretty well in the vicinity of the
boundary. As winds weaken toward/after sunset, low-level wind
shear conditions will develop again during the overnight ahead of
the front, including the KSUX area. This front will focus the
better chances for precipitation by late in the TAF period, but
hard to mention much in the way of chances past a couple hours at
this point. There may also be some weakening showers moving
through KHON after 09z. Otherwise, there is a non-zero threat that
some stratus could move north and get close to KSUX toward 12z,
but the focus at this point seems far enough eastward to not
mention more than a hint with a few/sct layer for the morning.
&&
.FIRE WEATHER...
Issued at 229 PM CDT Sat May 1 2021
As of mid afternoon, temperatures have risen in the mid 80s to mid
90s. With dew points in the 30s and 40s, this has fueled very dry
conditions with humidity levels dropping as low as the teens
across northwest Iowa. The area in the Red Flag Warning is also
seeing gusts above 20 mph, occasionally as high as 40 mph, making
for extreme fire danger. Elsewhere, fire danger remains very high
due to dry conditions and hot weather. We strongly encourage
avoiding burning if possible through tonight, even if your
location is not included in critical conditions due to having lighter
winds. Low humidity levels combined with dry fuels may still
support rapid spread of wildfires. After sunset, falling
temperatures and weakening winds will reduce fire danger.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&
$$
SHORT TERM...BP
LONG TERM...BP
AVIATION...Chapman
FIRE WEATHER...BP
Area Forecast Discussion
National Weather Service Reno NV
151 PM PDT Sat May 1 2021
.SYNOPSIS...
A cold front will bring a few showers and thunderstorms to the
region late this afternoon and tonight. Breezy winds and cooler
temperatures Sunday, will be followed by another warmup through
mid week as high pressure overspreads the west. Pacific low
pressure will bring increased winds Thursday and Friday along with
cooler temperatures into next weekend, but unfortunately little
to no precipitation.
&&
.DISCUSSION...
* Cold front dropping through the Great Basin will bring breezy
winds through tomorrow along with isolated-scattered showers and
thunderstorms this afternoon and tonight. No significant changes
to the ongoing forecast with respect to these items. Latest NAM3
and HREF guidance shows sufficient instability along and north
of a SVE-RNO-NFL line to produce a few t-storms but nothing
overly strong with basically zero updraft helicity noted in
HREF. HRRR produces outflow gusts in model convection to about
30-40 mph, so that coupled with brief heavy rains and lightning
are the main hazards.
* Breezy W/NW winds today will transition to more N/NE tomorrow
in the post-frontal airmass. Not an overly impressive wind
scenario but gradient is sufficient for winds to remain gusty
even overnight tonight, with some stronger N winds possible
along Hwy 95 and the Eastern Sierra valleys tomorrow. Typical
travel and recreation impacts expected. Localized fire weather
concern in lower elevation areas with dry fine fuels and limited
greenup.
* After a cooler and more seasonable day Sunday, temperatures
warm well above normal by Wednesday. Small chance, but not zero,
we approach record highs at least at RNO on Wednesday with NBM
75th percentile max temp of 87 - a record tie.
* Ensemble guidance from both GEFS and ECMWF showing a decent
Pacific trough working towards the west coast late week. This
one unfortunately does not have much if any moisture to work
with. There does look to be potential for another couple breezy
days Thursday-Friday per latest NBM and ECMWF EPS guidance. Most
EPS members show 30-40 mph type stuff with 1 in 4 chance of
seeing widespread winds 40-50 mph with more appreciable travel
and fire weather impacts. For Thursday the latest Hot Dry Windy
Index based off the GEFS is up into the 95th percentile for
this time of year.
* Upper low settles into the Great Basin next weekend and that
could be enough to generate a few instability showers. Ensemble
guidance is quite noisy so there`s low confidence on those
shower prospects. Week two outlook has potential for some
showers if that upper low lingers around, but only a small
fraction of ensemble members produce any meaningful
precipitation. Drought continues.
-Chris
&&
.AVIATION...
Southwest wind gusts generally in the 20-30 kt range will
continue for area terminals through this evening. Showers and
thunderstorms will develop north of I-80 this afternoon and
evening with some small hail possible. These showers weaken and
move south overnight, with showers chances south of I-80 and east
of highway-95 through Sunday morning. Winds will shift to the
north Sunday with afternoon gusts again in the 20-30 kts range.
Expect lighter winds Monday through Wednesday but strong winds,
mtn wave turbulence and LLWS are possible for the Thursday through
Saturday period. JCM
&&
.FIRE WEATHER...
Dry and breezy conditions will continue through this evening with
critical conditions for wind prone areas, especially in the
Lahontan Basin, Sierra Front, Southern Sierra Front, and Southern
Mono County. Breezy north winds to follow tomorrow, but RH will
trend a bit higher than today (likely 15-20% tomorrow afternoon).
Showers and thunderstorms north of I-80 could bring some spotty
wetting rains this afternoon, and outflow wind gusts up to around
40 mph. These showers may shift south overnight, reaching Mono and
Mineral Counties by tomorrow morning. There could also be some
buildups and isolated showers over the Sierra crest tomorrow
afternoon.
A low-pressure system forecast for the second half of next week
looks to be fairly dry and windy. The timing is uncertain, but at
this point Thursday through Saturday are the days with potential
for critical conditions due to gusty winds and low RH. JCM
&&
.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 11 PM PDT this evening for Pyramid Lake
in NVZ004.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Topeka KS
1107 PM CDT Sat May 1 2021
...AVIATION UPDATE...
.DISCUSSION...
Issued at 349 PM CDT Sat May 1 2021
1. Increasing Clouds--Still a Pleasant Weekend:
Another gorgeous, albeit breezy day was in progress this afternoon
as the pressure gradient gradually tightens on the backside of our
departing ridge. A southern stream cutoff low is slowly working
eastward across Texas this evening and will start to eject
northeastward tonight ahead of the next main shortwave moving into
the Pacific NW. High cirrus were already overspreading the forecast
area ahead of this low and clouds should continue to thicken
through the afternoon and evening.
Lower clouds spread northward overnight and may linger through
the morning on Sunday based on a number of shorter range
solutions. We may see some breaks in the afternoon, but expect
more clouds than sun. Highs will be tempered a bit by the clouds,
but with a similar lower-tropospheric airmass in place, readings
will still be above average for this time of year. The threat for
showers and storms has decreased for the day on Sunday with
forcing still weak and increasing inhibition noted on forecast
soundings. Trimmed PoPs for the daytime hours to just the far
east/SE forecast area.
2. Unsettled Start to the Week
Medium range solutions have slowed the eastward advance of a cold
front Sunday night into Monday, bringing it through mainly after
06Z. Convection developing off the High Plains may congeal into an
MCS and propagate eastward within a corridor of higher theta-e air
resulting in 1500-2000 J/kg of MLCAPE/MUCAPE. The lack of deep shear
may keep the system from maintaining severe winds for long (cold
pool quickly working ahead of the line) and this idea is well-
reflected in the 12Z members of the HREF.
There still remains some uncertainty in how far eastward the cold
front and resultant severe weather threat will push before peak
heating on Monday. The general concensus is that the boundary and
warm sector will be nearly completely out of the forecast area by
this time. The evolution of the Southern Plains lee cyclone during
this time will also drive the potential for precipitation in the
warm conveyor belt region of the system for Monday night into
Tuesday. The EC ensemble members remain slower and wetter than their
GEFS counterparts and in general have kept with the NBM PoPs for
that timeframe.
3. Pleasant Middle to End to the Week
Broad cyclonic flow will persist in the wake of our early week
convection, which will keep temperatures seasonal with periods of
sun and clouds. The medium to longer range guidance shows one
disturbance working through on Thursday, thus have maintained some
slight chance PoPs for that period.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday)
Issued at 1107 PM CDT Sat May 1 2021
It appears the stratus may be slower than models earlier progged.
The stratus has developed over western KS and the 02Z RAP appears
to have the better depiction of this. And the RAP is slower to
advect the low clouds into the terminals. But there remains a
consensus for the low clouds to move in with CIGS hanging in
across eastern KS well into the afternoon. They should improve to
VFR as the boundary layer deepens Sunday afternoon. Otherwise the
terminals look to remain between the upper low lifting across the
Ozarks and the frontal system moving in from the northwest late
Sunday night so will keep the forecast free of precip.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Skow
AVIATION...Wolters