Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/16/21
Area Forecast Discussion
National Weather Service Gaylord MI
1132 PM EDT Sat May 15 2021
.UPDATE...
Issued at 1041 PM EDT Sat May 15 2021
Dry low level environment (H7 to surface on local 00z sounding)
remains stubborn to yield, with just a few light
showers/sprinkles reaching the surface in our southwest counties.
Moisture advection/dynamics remain limited tonight, suggesting any
showers that reach the surface will be scattered and very
light....with most areas receiving very little, if any.
Definitely a much milder night than the last several, with low
temperatures ranging through the 40s.
&&
.NEAR TERM...(Through Tonight)
Issued at 323 PM EDT Sat May 15 2021
...Increasing chances of showers thru tonight...
High Impact Weather Potential...None.
Pattern Synopsis/Forecast...Complex area of low pressure continues
to take shape over the Northern and Central Plains. Associated warm
front is holding from the Central Plains thru Mid Mississippi
Valley. Deep moisture surging northward ahead of this system along
with weak instability continue to generate a broken line of mainly
showers from Oklahoma thru Missouri and Illinois into Wisconsin.
Latest KAPX base ref is still showing evidence of increasing mid
level moisture across our CWA...but nothing has reached the ground
as of yet. Some significant discrepancies amoung the near term
models noted regarding POPs thru tonight. Latest NAM12 suggests an
area of showers producing a "respectable" amount of precip (both
coverage and intensity) marching across our CWA late this evening
thru Sunday morning...while the RAP is much more conservative with
both POPs and QPF. RAP also targets mainly our southern CWA for best
chances of rain. RAP seems to be a more reasonable solution given
our persistently dry low level airmass in place...which will likely
take some time to moisten for precip to actually reach the ground.
In leaning toward the RAP...will keep POPs firmly within the chance
category thru tonight...slowly marching increasing POPs from SW to
NE this evening. Eastern Upper Michigan should stay mainly dry thru
tonight...but partly to mostly cloudy. Lack of sufficient
instability will certainly preclude any chances of thunder thru
tonight. With increasing clouds combined with southerly low level
flow/WAA...temps will be noticeably more mild tonight. Overnight
lows will only cool into the mid to upper 40s.
&&
.SHORT TERM...(Sunday through Tuesday)
Issued at 323 PM EDT Sat May 15 2021
High Impact Weather Potential: Low
Pattern Synopsis:
A closed low will dip down into Baja California while ridging in the
main upper-level flow progresses across southern Canada on Sunday. A
subtle shortwave will be moving overhead Sunday/Sunday night with
only a weak associated surface response at best. Surface high
pressure is expected to dominate most of the CONUS east of the
Mississippi River through Monday.
Forecast/Details:
Scattered showers are expected to be ongoing across northern
Michigan Sunday morning, especially across southern portions of the
CWA with decreasing confidence with northward extent towards the
bridge. Off-and-on rain chances will continue through the afternoon
with the best chances coming across the southern half of the CWA.
While southerly flow will continue to advect moisture into the Great
Lakes, rather meager forcing should limit precip intensity and
coverage. Additional totals of 0.10" or less are expected.
Otherwise, already pleasant temperatures will continue to warm
heading into early next week. Highs in the upper 60s on Sunday may
climb into the mid/upper 70s on Monday underneath mostly sunny skies
to give northern Michigan a real taste of summer. Overnight lows are
expected to be in the mid 40s for most both nights, remaining well
outside of the frost/freeze range.
.LONG TERM...(Tuesday night through Saturday)
Issued at 323 PM EDT Sat May 15 2021
High Impact Weather Potential: Low for now
Amplified ridging is expected to encompass most of the eastern CONUS
throughout the period while embedded waves rotate around the
backside of the ridge over the Great Lakes at times during the week.
At the surface, high pressure should center itself off the Mid-
Atlantic coast while upper-level flow over the Rockies produces
pressure falls out west. Enhanced southerly flow between these two
features will help advect warm, moist air northward well into the
Great Lakes by the second half of the week. While details regarding
any potential systems tracking in the vicinity of the Great Lakes
remain uncertain, instability provided by this airmass looks to at
least bring the chance for showers and thunderstorms later in the
period. Summer-like highs in the upper 70s and even low 80s are
possible throughout the week, which would be around 10 degrees above
normal heading into the second half of May.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1130 PM EDT Sat May 15 2021
High and mid level clouds will continue to slowly thicken and
lower tonight, perhaps evening bringing a period of MVFR cigs to
both KMBL and KTVC this morning. Light showers possible, but not
expecting and vis restrictions. Cigs should begin to increase
later this morning and afternoon as mixing depth increases. Light
winds through the period.
&&
.MARINE...
Issued at 323 PM EDT Sat May 15 2021
Winds and waves will remain below SCA criteria thru Monday. Chances
of showers will increase tonight and will continue into Sunday as
moisture increases ahead of low pressure developing over the
Plains.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&
$$
UPDATE...MB
NEAR TERM...MR
SHORT TERM...DJC
LONG TERM...DJC
AVIATION...MB
MARINE...MR
Area Forecast Discussion
National Weather Service La Crosse WI
1037 PM CDT Sat May 15 2021
.SHORT TERM...(This evening through Sunday)
Issued at 231 PM CDT Sat May 15 2021
A midlevel shortwave trough sits over the region with water vapor
showing another ripple in the flow over northern MN poised to drop
southeast through the area late this afternoon into early evening.
Meanwhile satellite and observed winds reveal a weak wind shift
boundary stretching from far northwest IA into central WI. Surface-
based instability has been gradually building west of the
Mississippi River where sunshine has been more prevalent today.
Temperatures are climbing through the 60s to low 70s in our far west
with dewpoints around 50. Isolated storms have been developing along
the central MN/IA border within this area of ~500 J/kg MLCAPE, aided
by weak convergence along the aforementioned boundary. Persistent
low clouds across the eastern half of the forecast area have been
keeping temperatures in the upper 50s to low 60s, though dewpoints
here are also around 50.
Expect an uptick in convection heading into mid to late afternoon as
the upstream shortwave lends some support. With greatest instability
(albeit limited) and decent wind shear (30-40 knots) coinciding over
southeast MN and northeast IA through this evening, expect storm
activity and potential for any stronger storms to generally be
focused near and west of the Mississippi River. That has been the
general trend shown in CAMs today, though there hasn`t been great
agreement with timing and placement of convection, and it is still a
bit uncertain how far north storm initiation may extend. Isolated
near-severe hail or gusty winds will be the main threats with any
stronger storm. Areas east of the river aren`t entirely out of the
woods for showers and storms, but any activity would be be weaker
and more isolated.
Activity expected to fizzle out later this evening, with greater
moisture in the low-levels looking to favor some fog or low stratus
development late tonight. Have added some fog to the forecast
tonight. Lows forecast to range from the mid 40s to lower 50s.
Low clouds expected to linger through much of Sunday morning,
diminishing a bit towards midday. If we manage to build any
instability, there will again be potential for some afternoon
showers and storms with that weak boundary still across our north
and yet another weak mid-level shortwave. The HRRR is certainly on
this bandwagon. Opted to add some slight chance PoPs to the
forecast. Look for highs in the low to mid 70s, though a bit cooler
if morning clouds are slower to diminish.
.LONG TERM...(Sunday night through Saturday)
Issued at 231 PM CDT Sat May 15 2021
Another shortwave looks to pass through the Midwest Sunday night
into Monday, but most of the energy and better moisture transport
looks south of the area. The bulk of the GEFS/EPS ensemble members
would keep precipitation south of the area as well, but a small
contingent of members and some of the deterministic guidance still
suggest a few showers will be possible on the northern edge in
northeast Iowa and southwest Wisconsin. For now, will keep small
PoPs there. Farther north, drier easterly flow will tend to favor
dry conditions. As an upper level ridge builds across the eastern
CONUS Tuesday through the end of the week, the local area will be
in southwest flow aloft with embedded shortwaves bringing
occasional shower chances. Southerly flow will also help to draw
up a plume of moisture from the Gulf for late week, with
instability and thunderstorm chances also returning, mainly
late Wednesday into the weekend.
Temperature-wise, the week is looking mild, but just how mild
remains in question. The NBM deterministic output continues to
consistently track closer to its own 25th percentile, suggesting
highs in the 70s to near 80. Taking a little closer look, the NBM
generally appears to track more closely to raw model output, with
bias-corrected output favoring the warmer side of things. Would
think that the drier/better mixing at the start of the week would
favor some temperature over-performance, though increasing
moisture and rain chances lower confidence later in the week.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1037 PM CDT Sat May 15 2021
Convection has dissipated for the most part so now trying to figure
out how widespread MVFR conditions might become with low clouds and
fog developing mainly south and east part of forecast area. GOES-16
Nighttime Microphysics display really shows these areas trying to
slowly spread north and west which some of the mesoscale models
suggest too. Confidence is not great in how far that will occur but
given the higher dew points, rain across parts of the area, and
better saturation than in a long time, seems reasonable there will
be some impact and have honored that in overnight hours.
Better news is these conditions should improve and scatter out back
to VFR conditions on Sunday. Bulk of rain threat from short waves
should remain west and south of the general area with hints of drier
air advecting in from the north.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Kurz
LONG TERM...Lee
AVIATION...Shea
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
920 PM CDT Sat May 15 2021
.DISCUSSION...Convection is persisting over the Coastal Bend on
the southern end of a short wave trough moving through the
Victoria Crossroads and strong low level convergence along the
coast. Bumped the PoPs up this evening for this activity. Hi-res
models showed this activity would diminish earlier this evening
as the short wave trough lifts northeast, but the low level
convergence has maintained convection and expect it to linger into
the early overnight period. With PWAT values near 1.8 inches,
storms could produce 2-3 inches per hour leading to localized
flooding tonight.
Next round of convection over northern Coahuila is expected to
move southeast into the region during the overnight period.
Sufficient southeasterly low level flow advecting moisture inland
should keep activity going. Adjusted PoPs slightly late tonight.
&&
.MARINE...Low level flow has strengthened to SCA levels over the
Gulf waters this evening. Expect SCA conditions will linger over
the Gulf waters until 10Z Sunday. Adjusted PoPs to show better
chances for convection tonight.
&&
.PREV DISCUSSION... /Issued 630 PM CDT Sat May 15 2021/
AVIATION...00Z Update
VCT/CRP currently at MVFR with ALI/COT/LRD at VFR as initial MCS
moves off to the east. Confidence remains low in regards to
precipitation, with model runs continuing to tell different
stories for tonight into tomorrow morning. Current thoughts are
that there will be a break in precipitation once this initial
system moves offshore. Another system is progged to move into the
region from Mexico overnight tonight, bringing another round of
scattered showers and thunderstorms from west to east. Could see
ALI/COT/LRD drop to IFR ceilings periodically overnight as this
system moves through. Moderate winds out of the SE gusting to
near 25 kts will be in place for much of the 00Z period. Can
expect vsbys to drop to MVFR with shower and thunderstorms over
terminals.
PREV DISCUSSION... /Issued 403 PM CDT Sat May 15 2021/
SHORT TERM (Tonight through Sunday)...
The previous mentioned shortwave has now broadened out instead of
shifting completely east of the area. This has allowed convection
to remain nearly stationary north of our area and over Deep South
Texas around Brownsville. In the meantime, scattered showers and
thunderstorms have developed over the northern Brush Country and
Coastal Plains. Expect scattered showers and thunderstorms to
continue through tonight but confidence is very low on exactly
where, when, and how much. There are a number of meso-models that
bring a large MCS through the area tonight leading to heavy
rainfall accumulations... Although the latest 18Z HRRR shows very
little to nothing tonight (*throws hands in air*).
Here`s a look at the mesoanalysis as of 18Z this afternoon: lapse
rates are surprisingly poor, near moist adiabatic (5.5-7C/km), CAPE
ranging from 2000-3000 J/kg, DCAPE < 500 J/kg, moisture convergence
less than 15, an 850-300mb SE MCS motion, shear is relatively
weak with the exception of western Brush Country of over 40 knots
0-6km bulk shear. The BRN is greater than 40 in most areas which
tends to favor MCS development. The big concern is will there be
lift support aloft? and will convection last passing over from
Mexico? If any of these take place, our rain chances will
significantly increase. PWATs aren`t super impressive either, this
morning`s sounding recorded 1.45" (less than 75th percentile) but
most likely have increased since. Looking at the satellite
derived total precipitable water, PWATs near 2.0" may be in place
over the coastal bend. The 00Z weather balloon launch this evening
will be useful in determining the environmental conditions. SSE
winds aloft at 850mb also helps reduce the strength of the cap.
Considering all the above, there is still heavy rain potential.
Looking at the latest Flash Flood Guidance, flooding may occur with
3-hr accumulations of 3.0-3.5" across the majority of the Brush
Country and Coastal Plains, up to 4.0-4.5" over the Victoria
Crossroads. Of course flash flooding can happen more quickly over
urban areas. The SPC has included a SLIGHT severe risk over La
Salle and Webb Counties, while the rest of South Texas is under a
MARGINAL risk. In addition, the WPC has the western half of the
CWA in a SLIGHT excessive rainfall risk. The greatest threat for
tonight will be heavy rainfall, damaging winds, and large hail.
Unfortunately the uncertainty and heavy rainfall potential does not
end tonight. Many meso-models suggest an MCS over the Hill Country
associated with another shortwave, passing over the northern
counties and Victoria Crossroads Sunday morning, with most of the
activity to our east by Sunday afternoon. The SPC has majority of
the CWA, with the exception of the Coastal Bend, in a marginal risk
for severe storms. Confidence is still low as well on Sunday, kept
scattered showers and thunderstorms through much of the area with a
greater focus on the northeastern counties and Victoria
Crossroads. However, a general downward trend in convection is
likely by Sunday afternoon.
LONG TERM (Sunday Night through Saturday)...
The active pattern hasn`t given up yet. Early in the period,
quasi zonal flow in the mid to upper levels should keep things
fairly quiet Sunday night and Monday, though a few showers will be
possible around the VCT area. By Tuesday, low pressure in the
upper levels will dig a trough into the sub tropical jet while a
mid-level low also approaches the region. Shortwaves begin
affecting the region by Tuesday and will increase rain chances
once again. Best rain chances should be Wednesday into Thursday as
the mid-level low opens up and pushes more energy deeper into the
region. The pattern is very fluid and confidence in timing and
location of convection through mid-week is fairly low, but
confidence that showers and storms will happen somewhere most days
is fairly good. Rainfall totals of a couple inches area wide are
possible, which will be fine if it is spread over a few days. That
said, PWATS potentially as high as 2 inches on Wednesday would be
sufficient to produce some heavy downpours.
Near normal temperatures Monday and Tuesday should drop to below
normal with the increase in convection and decrease in 850 mb
temps mid and late week.
MARINE...
Breezy onshore flow will continue, resulting in Small Craft
Exercise Caution conditions through Sunday. Winds may briefly
touch small craft advisory conditions. Isolated to scattered
showers and thunderstorms are expected late tonight through Sunday
as mid level disturbance move across the waters. A few storms
could be strong. Chances for showers and thunderstorms will
persist through the week as a series of upper level disturbances
pass through. Moderate to strong onshore flow will lead to periods
of Small Craft Exercise Caution and Small Craft Advisory
conditions through the week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 73 82 75 85 77 / 50 50 20 10 10
Victoria 72 80 74 86 75 / 50 60 40 40 10
Laredo 73 93 75 98 76 / 40 30 10 0 10
Alice 73 87 75 90 76 / 50 50 20 10 10
Rockport 75 82 76 85 77 / 50 50 30 20 10
Cotulla 73 92 74 97 75 / 50 40 10 10 10
Kingsville 74 85 75 89 77 / 50 50 20 10 0
Navy Corpus 75 83 76 84 77 / 50 50 20 10 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...Small Craft Advisory until 10 AM CDT Sunday For the following
zones: Coastal waters from Baffin Bay to Port Aransas out
20 NM...Coastal waters from Port Aransas to Matagorda Ship
Channel out 20 NM...Waters from Baffin Bay to Port Aransas
from 20 to 60 NM...Waters from Port Aransas to Matagorda
Ship Channel from 20 to 60 NM.
&&
$$
TMT/89...SHORT TERM
Area Forecast Discussion
National Weather Service Cheyenne WY
926 PM MDT Sat May 15 2021
.UPDATE...
Issued at 923 PM MDT Sat May 15 2021
Adjusted shower and thunderstorm chances the rest of the night
based on trends, and HRRR indicating isolated to scattered showers
the rest of the night, mainly north of a Rawlins to Scottsbluff
line. Areas of fog look likely based on the trends in the
temperature and dewpoint spreads.
&&
.SHORT TERM...(This evening through Sunday Night)
Issued at 240 PM MDT Sat May 15 2021
Latest GOES-E Low Level Water Vapor scanning a deepening low
pressure system across the Sierra Nevada Mountains as a shortwave
disturbance creating opportunities for showers and thunderstorms
for the region this afternoon. Due to low clouds and persistent
fog through the morning hours, temperatures across portions of
Laramie, Platte, Goshen and Albany Counties have struggled to
reach into the mid 50s while other places across the area have
warmed into the low to middle 60s. Cloud deck over Cheyenne will
inhibit strong convection along with mid-level cap based on model
soundings. Across the Panhandle, CAPE values have risen a bit into
the 500-1000 J/kg value though the southeast flow across portions
of Cheyenne and Kimball Counties while decent moisture advection
has produced more cloud cover and limiting diurnal heating.
As the HRRR was a bit slow to rectify the cloud deck earlier, was
inclined more towards the RAP13 for applying in the short term
with regards to temperatures and storm timing. Current thinking is
for a few strong storms to form in next couple hours with a bit of
training particularly from Converse County out into Dawes County
in the Panhandle. Some strong storms are also likely to develop
across Carbon and the the Laramie Range west of Wheatland.
Strongest storms may have gusty outflow winds in excess of 50 mph
and hail along with locally heavy rainfall. Otherwise isolated to
scattered showers and thunderstorms will be possible across much
of the region aiding in much needed rainfall. Lows tonight from
the lower 40s to low 50s for many.
Sunday will be very similar to today as the low deepens into
Arizona with vorticity advection ahead of main low and a
stationary front providing ample moisture once more for showers
and thunderstorm activity. GFS and Namnest along with other CAMS
have solutions of some higher QPF amounts of concern across the
Snowy Range and the recent Mullen Fire Burnscar that will require
additional oversight and monitoring tomorrow should radar and
satellite returns have high amounts of rainfall on the hydrophobic
soil. Morning fog again will be possible and will need to see how
that will play out again for afternoon convection. Daytime highs
similar to Saturday.
.LONG TERM...(Monday through Friday)
Issued at 315 AM MDT Sat May 15 2021
Upper low centered west of the Four Corners Monday morning will track
to the east-northeast across CO/northern NM through Tuesday, then
become an open wave over the central High Plains Wednesday. A deep
closed upper low and attendant trough will move ashore into the
Pacific coast states by Thursday morning and into the Intermountain
West Friday. Moist southeasterly low level flow combined with a
series of short wave disturbances and modest instability will produce
scattered showers and scattered thunderstorms, especially during the
afternoon and evening each day. While the overall severe threat will
be low, some stronger thunderstorms may produce small hail, gusty
winds and locally heavy rainfall. Temperatures will slowly moderate
each day, with daytime highs in the 60s and 70s and nighttime lows
in the 40s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 541 PM MDT Sat May 15 2021
VFR ceilings and visibilities across southeast WY and western NE
as scattered thunderstorms move northeast across the region.
Thunderstorm activity is anticipated to increase in southeast WY
between now and 4Z. Thunderstorms are likely to persist across
western NE between now and 11Z. Patchy fog is likely in southeast
WY after 8Z and in western NE after 11Z. How long the fog will
persist is uncertain but it should lift between 15 and 18Z
everywhere except KCDR.
&&
.FIRE WEATHER...
Issued at 200 PM MDT Sat May 15 2021
Fire weather concerns expected to remain minimal through the next
several days as near-daily afternoon and evening chances of
isolated to scattered showers and thunderstorms are possible. Min
RHs expected to remain above critical levels with only main fire
weather concern to be of dry lightning out mainly across portions
of Carbon County.
&&
.HYDROLOGY...
Issued at 240 PM MDT Sat May 15 2021
Decent moisture advection continues into the region aiding in
slowly improving drought conditions across southeastern Wyoming
and the Nebraska Panhandle. With daily afternoon and evening
chances of precipitation, attention returns particularly to the
Mullen Fire Burn Area and the hydrophobic soil that will be unable
to capture and retain rainfall. Namnest and GFS along with some
CAMS having solutions of upwards of half an inch of QPF Sunday
afternoon over the burn scar that will likely create runoff
concerns along with debris flows and areas of flash flooding.
Given trends of convective nature for these storms, seems more
will be pulsing with the terrain providing a bit of topographic
upslope rainout.Precipitable water looks to be around 0.4 inches being
available to rain out over the site. At this time, confidence in
flash flooding low to moderate over the burn scare but will
continue to monitor and adjust forecast trends as new solutions
come available.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...RUBIN
SHORT TERM...WM
LONG TERM...MJ
AVIATION...LK
FIRE WEATHER...WM
HYDROLOGY...WM
Area Forecast Discussion
National Weather Service Dodge City KS
1054 PM CDT Sat May 15 2021
...Updated Mesoscale Discussion...
.MESOSCALE DISCUSSION...
Issued at 1040 PM CDT Sat May 15 2021
Key Messages...Numerous thunderstorms were ongoing across west
central, southwest, and central Kansas. Nearly all storms were
non-severe, but a few were approaching severe levels. Main risks
through 1 AM CDT will be local flash flooding and marginal severe
wind/hail (60 mph, one inch in diameter)
Technical...the nocturnal low level jet ramped up after sunset,
but 1km AGL winds were generally on the order of 25 to 30 knots
out of the due south. Hodograph shapes were kind of interesting on
the short-term NAM forecast soundings, with a narrow clockwise
hodograph in the first 2km AGL, with some of the forecast
hodograph locations showing this 0-2km portion of the hodograph in
the upper-left quadrant...followed by straight line hodographs
through or near the origin (weak ground-relative winds). The
ground-relative wind weakness was centered around 4 to 6km AGL,
and this is likely explaining why convective mode is not favoring
supercell structures, or at least only very briefly marginal
supercell structures. Thus, hail no larger than nickels or a brief
quarter can be expected through the end of the event.
The weak mid level winds are favoring storm motions of 15 mph or
less, and in some instances, chaotic at 5 mph or less, especially
near our CWA common border with NWS GLD. This is where the heavy
rain risk will continue through 1 AM CDT. Elsewhere, an
established cold-pool (from earlier Raton Mesa/Black Mesa higher
terrain storms) continued to march east along the western KS-OK
Panhandle border, but there have been no severe wind gusts
recorded since the 62 MPH wind gust at Cimarron Grasslands north
of Elkhart.
The low level jet will continue to transport fairly abundant low
level moisture northward through the night, so maintenance of
convection is expected through much of the overnight as the system
slowly transitions to the east. Thunderstorm activity may not
completely clear the NWS DDC forecast area until 12Z.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 225 PM CDT Sat May 15 2021
Models early this afternoon remain in good agreement with an area
of thunderstorms crossing southwest Kansas during the overnight
hours. Until then a few isolated to widely scattered thunderstorms
will be possible late day near a surface boundary/warm front that
will be located just north of the Garden City and Dodge City
area. Latest HRRR does suggests that the cap will erode and with
weak forcing and mid level instability being present will go ahead
and increase the chance for late day convection. These late day
storms however are not expected to be severe weak shear and high
PWATs but a few of the strongest storms could contain some small
hail and gusty winds.
The better shear late today will be over southeast Colorado and
with steep low level lapse rates and mid level instability
forecast in this area there will be a chance for some of these
storms to become severe as they march eastward towards southwest
Kansas. These storms should persist into the evening hours as they
move into western Kansas given the strengthening low level jet
and better instability. Greatest threat for hail appears to be
early with some strong winds also being possible. After sunset the
main hazards will shift to wind and heavy rainfall.
Thunderstorms should taper off early Sunday morning with a break
in the rain expected during the day on Sunday. Sunday night is
beginning to look like a report given a similar set forecast.
Biggest difference is that better shear and forcing along our
surface boundary will be present late day.
.LONG TERM...(Sunday night through Saturday)
Issued at 225 PM CDT Sat May 15 2021
Models remain in decent agreement with an upper low crossing the
four corners region on Sunday and then slowly moving east
northeast into the Central Rockies by Tuesday night. Ahead of this
slow moving upper level low, a series of upper level disturbances
will move from the base of this upper low and out into the
Central Plains. The combination of a series of upper level waves
crossing the plains over the next few days along with available
low level moisture and a surface boundary lingering in or near
southwest Kansas will result in multiple rounds of rain showers
and thunderstorms. The potential also exists that some of these
storms may be severe, especially during the overnight hours.
Exactly where the greatest potential for this severe weather will
occur in the later periods is unclear given that the storms from
the previous night will impact how storms will evolve and where it
will occur the next day. Despite this uncertainty of where severe
weather will occur it does look like all of southwest Kansas will
have the opportunity for several more rounds of widespread
accumulating rainfall.
These multiple days of thunderstorms will briefly end late week
as the upper low weakens and crosses the central and northern
Plains. The break in the wet weather pattern appears to be a brief
one given that another upper low will drop south along the west
Coast late week and moves into the southwest United States early
next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 613 PM CDT Sat May 15 2021
Thunderstorms developing over southeast Colorado late this
afternoon are expected to move into southwest and central Kansas
through the evening hours. Initially, the storms could impact the
Garden City and Liberal terminals with large hail and wind gusts
in excess of 45 knots. As the storms move/develop eastward later
into the evening and overnight, the main threat will shift to
heavy rain and small hail. Later tonight, MVFR to IFR cigs are
expected to develop.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 57 75 56 73 / 60 60 70 50
GCK 55 75 54 70 / 70 60 60 50
EHA 53 79 54 72 / 60 60 60 60
LBL 55 79 55 74 / 70 60 60 40
HYS 56 71 55 69 / 80 60 60 50
P28 60 74 59 76 / 60 60 70 40
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
MESOSCALE...Umscheid
SHORT TERM...Burgert
LONG TERM...Burgert
AVIATION...Gerard
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
709 PM CDT Sat May 15 2021
.AVIATION... /12Z TAFS/
The airmass around DRT was spared of the heavier convective activity
from earlier today, as was much of the Hill Country. The 18Z NAM and
several of the afternoon HRRR runs depict a developing complex of
storms in NW flow, and there are severe storms 15 NW of Dryden to
reflect those projections. Thus there remains a good chance for DRT
to see a nearby thunderstorm between 05Z and 09Z; we may update to
change this to prevailing thunder in the next few hours. At
SAT/SSF/AUS, the model depictions are less conclusive and there
should be some scattered activity to reach the I-35 corridor by
around 09Z. The latest runs of the HRRR have weakened the storm
complex considerably so we`ll stick with prevailing showers and VCTS
from the predawn hours through the late morning. Midday skies Sunday
may be too pessimistic of the storms maintain their intensity longer
and create more outflows over the I-35 corridor. For now we`ll look
to the more conservative GFS MOS and show some vfr skies at 21Z. DRT
should clear up much earlier and the 10Z to 16Z forecast for ifr cigs
may be too pessimistic as well.
&&
.PREV DISCUSSION... /ISSUED 420 PM CDT Sat May 15 2021/
UPDATE...
A subtle update issued for the tonight period. Main elements were to
lower early evening PoPs out west and to add higher PoPs W/Central
counties overnight with a significant increase in QPF between 06Z and
12Z. The last several runs of the HRRR as well as the NAM indicate a
strong potential for a NW flow complex of storms to form over W TX
and move into the area mainly after midnight. Hourly temperatures
were also retrended after the ongoing daytime complex of storms has
curbed MaxT over much of the area west of San Antonio.
PREV DISCUSSION... /ISSUED 220 PM CDT Sat May 15 2021/
SHORT TERM (Tonight through Sunday Night)...
In the near term moderate to heavy rainfall will continue across
Uvalde and Medina County. Rainfall estimates of 2 to 4 inches have
prompted Flash Flood Warnings across parts of Uvalde County. In
general the high resolution models keep this area and areas to the
east towards Bexar, Wilson, and Atascosa county as the main focus
areas through the mid to late afternoon. The HRRR has consistently
turned this complex southeast by late afternoon, but so far things
have remained fairly consistent to the southwest of Bexar County.
This complex is in response to a mid-level shortwave that is evident
in the morning runs of the NAM and can be seen pushing eastward on
the GOES-16 Water Vapor.
The next round of precipitation will be late this evening and into
the overnight hours along the dryline across west Texas. The large
upper level low is dropping out of California and into Arizona this
afternoon. Ahead of it plenty of moisture and instability are
building across South Central Texas. Mid-level winds will stream
over the Serranias del Burro this afternoon. Convection initiates by
mid afternoon across Mexico and West Texas, and while the HRRR
indicates that initial storms may move more to the SE parallel to
the Texas Border, but late this evening strong to severe storms
could be moving into the Rio Grande Plains. In addition the HRRR and
the NAM seem to suggest that convection across West Texas will form
into an MCS and move to the south and east through the late evening
and into the overnight hours. The model consensus is that this
convection across the Rio Grande and West Texas will come together
and push towards the I-35 corridor in the early morning hours of
Sunday. This MCS will likely be related to a second shortwave trough
shown in the NAM to move across the state during the day on Sunday.
Sunday presents some interesting forecast challenges. If the NAM and
HRRR verify the MCS will likely be moving east of I-35 by Sunday
morning. This could stabilize the atmosphere through much of the day
leading to a relatively quiet day. If that verifies than the current
forecast package is probably overdone with PoPs for Sunday. If the
MCS and storms out west tonight are weaker then there will be plenty
of instability and moisture still in play for the next shortwave to
work with. In general though, think the best chances of rain on
Sunday will be east of Interstate 35.
Lets take a deeper look at hazards. The first heavy rainfall. We
have seen that today and that threat will continue in the short
term. Model soundings show a very moisture surface and column in the
atmosphere with precipitable water values near 1.5 inches. Locally
heavy rainfall will then be possible with any slow moving storms,
like the complex we have seen today, and individual cells or
complexes like we expected this evening into early Sunday.
In terms of Severe Weather the Storm Prediction Center has most
areas west of HWY 281 in a Slight Risk for today, with a marginal
risk for the rest of the area. Sunday the whole of South Central
Texas is painted with a Marginal Risk. While decent (1500-2000 j/KG)
of CAPE will be in place, both days a capping inversion and the
previous convection may keep storms to a minimum on Sunday. Areas of
the Rio Grande have missed out on much of today`s convection so
storms coming from the west will be more primed this evening to
produce large hail and damaging thunderstorm winds. If an MCS can
form late tonight that will also increase the overall wind threat.
Many questions remain about Sunday based on the storm evolution
through the night tonight, but in general think Sunday will be a
quieter day than today and tonight have been and will be.
LONG TERM (Monday through Saturday)...
An upper level shortwave trough will move across Texas Monday and may
provide sufficient lift to generate thunderstorms over South Central
Texas. Models suggest better lift farther north and convection over
our CWA is conditional on how far south the shortwave digs. If
convection does form, there should be enough instability and shear to
produce strong to severe storms. There will be ample low level
moisture helping to increase instability. Strong southeasterly flow
will keep moisture high into Tuesday. PWs values will increase to
above 1.5 inches. A combination dryline and cold front will move into
this warm, moist airmass Tuesday and Tuesday night. Again strong
instability and moderate vertical wind shear will make strong to
severe storms possible. In addition the high PW will make locally
heavy rainfall and flash flooding possible. The upper level trough
axis will move across Texas Wednesday/Wednesday night and showers and
thunderstorms will continue. PW will remain high and locally heavy
rain will be possible. The warm, moist airmass will remain in place
through the end of the period. A series of upper level shortwave
troughs will keep convection in the forecast each day Thursday
through Saturday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 68 80 70 85 71 / 60 70 40 40 30
Austin Bergstrom Intl Airport 68 80 70 85 70 / 60 70 40 40 30
New Braunfels Muni Airport 69 82 72 88 73 / 80 60 30 30 30
Burnet Muni Airport 67 79 69 84 69 / 60 70 30 40 40
Del Rio Intl Airport 70 88 73 93 72 / 60 10 10 10 40
Georgetown Muni Airport 68 79 70 85 69 / 60 80 40 50 40
Hondo Muni Airport 68 84 71 90 72 / 80 50 20 20 30
San Marcos Muni Airport 68 81 70 87 71 / 70 70 30 30 30
La Grange - Fayette Regional 70 81 72 87 74 / 40 80 30 50 20
San Antonio Intl Airport 69 81 72 87 72 / 80 60 20 30 30
Stinson Muni Airport 70 84 73 89 74 / 80 60 20 20 20
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term/Aviation...Oaks
Long-Term...Runyen
Decision Support...17
Area Forecast Discussion
National Weather Service Goodland KS
952 PM MDT Sat May 15 2021
.UPDATE...
Issued at 951 PM MDT Sat May 15 2021
Storms are continuing to move across Cheyenne County, Colorado and
portions of western Kansas, the main hazards continue to be
heavy rain and large hail. Due to a decreasing severe threat, the
Severe Thunderstorm Watch has been cancelled for Cheyenne County
in Colorado; however, locally heavy rain may remain possible. The
watch continues for Sheridan and Graham counties along with the
Kansas counties along and south of US-40 until 12 AM MDT/1 AM CDT.
UPDATE Issued at 909 PM MDT Sat May 15 2021
Storms are slowly moving into Cheyenne County, Colorado and
across portions of western Kansas, the main hazards have become
heavy rain and large hail. Due to a decreasing severe threat, the
Severe Thunderstorm Watch has been cancelled for Kit Carson,
Sherman, and Thomas counties. The watch continues for Sheridan and
Graham counties along with counties along and south of US-40
until 12 AM MDT/1 AM CDT.
Thunderstorms are currently tracking east to northeast across
northwest Kansas this evening. Severe thunderstorms capable of
producing heavy rain with isolated flash flooding, large hail, and
damaging winds are possible, mainly south of Interstate 70
through 2 AM MDT Sunday morning.
&&
.SHORT TERM...(This afternoon through Sunday night)
Issued at 1152 AM MDT Sat May 15 2021
Overview: Modest westerly flow aloft (30-40 KT at 300-250 mb)
will prevail over the region through Sunday.. on the eastern
periphery of a modest upper level ridge over the central Rockies.
Today-Tonight: Challenging convective forecast. In a muttled
synoptic regime.. characterized by weak low/mid-tropospheric
(SFC-H5) flow.. the evolution of the low-level (SFC-H85) pattern
and majority of forcing (i.e. not directly assoc/w convection)
will largely be dictated by mesoscale features. Per 18Z visible
satellite imagery and regional surface observations.. a weak
mesoscale low was located in southeastern CO.. centered ~20 miles
SE of La Junta (KLHX). Considerable low overcast persists on the
northern and eastern periphery of this feature (in east/northeast
CO). Further downstream in northwest KS, low overcast
lifted/scattered around mid-morning.. though recent trends suggest
that, at the very least, alternating periods of cloud cover are
likely through the afternoon.
Simulated reflectivity forecasts via the HRRR and NAM NEST
suggest that several distinct areas of convection will develop
late this afternoon and evening.
(1) Scattered convection will develop on the Raton Mesa and
portions of the CO Front Range around peak heating (21-23Z)..
progressing eastward (via modest westerly steering flow) into
eastern CO after 00-01Z. With pervasive cloud cover and pronounced
convective inhibition along the Palmer Divide, it is uncertain
whether or not (or to what degree) convection emanating from the
CO Front Range will intensify. On the other hand, convection
emanating from the Raton Mesa will encounter robust insolation in
southeast CO.. and, aided by low-level convergence invof the
mesoscale low.. will likely increase in coverage and intensify,
with activity approaching the CO/KS border (south of I-70) by
01-02Z. Deep layer shear appears marginally sufficient for
supercellular organization, though such organization may be short-
lived, with activity likely growing upscale into a line or
cluster. With the above in mind, large hail and damaging winds are
anticipated to be the primary hazards, mainly in Cheyenne county,
CO and Greeley county, KS.
(2) Scattered to widespread convection (elevated in nature) is
anticipated to blossom over northwest KS later this evening
(03-05Z).. presumably in assoc/w strengthening southerly flow
/warm advection/.. perhaps augmented by storm-scale/mesoscale
forcing associated with ongoing convection approaching from the
west. Isolated instances of marginally severe hail and/or brief
downbursts up to 65 mph are possible, mainly within the first few
hours of development. Locally heavy rainfall and flash flooding
are anticipated to be the primary hazard.. particularly where
antecedent conditions are favorable (i.e. where heavy rain has
fallen the past few days).
Sun-Sun night: With little change in the synoptic pattern, expect
sensible weather conditions generally similar to today.. i.e.
every bit as challenging as today with regard to temperatures,
cloud cover, convective development/coverage/evolution/hazards.
.LONG TERM...(Monday through Saturday)
Issued at 209 PM MDT Sat May 15 2021
Next week continues to looks unsettled with temperature near or
slightly below average for this time of year to start the week. Rain
chances are dependent on the day.
The early part of the week still looks to have an upper level cut-
off low advance in the larger ridge towards the Tri-State area. Near
the surface, a broad area of lower surface pressure is still
expected to set up towards the south and west. What this means for
the area is that there will be slight synoptic lift in the area and
more moist air will be pulled north into the area. This will allow
for near constant cloud cover and rain for Monday and Tuesday with
Wednesday possibly seeing similar conditions. Currently, the
forecast has high chances for rain, but QPF remains relatively low
as it does not currently look like a widespread rain event. Will
have to monitor the next few days. Temperatures are forecasted to be
in the mid to upper 60`s.
Wednesday sees a transition in overall pattern as the cut-off low
rejoins the main flow before a ridge sets up in the Eastern CONUS
and a trough in the Western CONUS. Near the surface, the area of
lower pressure moves further southwest with high pressure moving in
behind it. Thursday and Friday, a surface low is forecasted to form
in the Northern Rockies and move out into the Plains. This pattern
looks to favor drier and warmer conditions with lesser chances of
rain and high temperatures climbing back into the 70`s and 80`s.
Storms still are possible during the afternoon and evening hours
with some possibly being severe. Will have to see how things line up
as ensemble members show a decent spread in location of the upper
features and center of the latter low pressure. With the Tri-State
area being inbetween features, the placement will be key to the
conditions we get.
Saturday on is uncertain right now, but may need to watch for
temperatures to cool down back into the 60`s and 70`s after Saturday
if the trough moves over the area and brings a cold front from the
north.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 519 PM MDT Sat May 15 2021
As showers and thunderstorms move into the area, VFR conditions
are expected to degrade to MVFR this evening. Storms are
anticipated to impact the GLD terminal beginning around 01Z until
08Z. Storms are expected to move over the MCK terminal as early as
02Z with the best chance for storms 06-09Z. After the storms move
out of the area, conditions are expected to fall to MVFR/IFR
levels due to low ceilings and possible fog development during the
early morning hours on Sunday. Aside from stronger gusts
associated with the thunderstorms, the winds are anticipated to
remain fairly light from the east at 5-10 kts for much of the TAF
period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...KMK
SHORT TERM...VINCENT
LONG TERM...KAK
AVIATION...KMK
Area Forecast Discussion
National Weather Service Huntsville AL
915 PM CDT Sat May 15 2021
.NEAR TERM...(Tonight)
Issued at 915 PM CDT Sat May 15 2021
Temperatures are currently in the the upper 50s/lower 60s in most
locations to around 70 degrees in the Muscle Shoals area. An area of
mid to high cloud cover continues to move southeast into portions of
extreme northwestern Alabama and our southern middle Tennessee
counties. RAP seems to have a good handle on this and pushes it into
the I-65 corridor around 10 PM and into northeastern Alabama shortly
afterwards before it exits into Georgia after midnight and mostly
clear skies return in Alabama. However, our southern middle Tennessee
counties will likely not get a break from the cloudier conditions.
This should help keep temperatures from dropping as much north of the
Tennessee River. Expect temperatures in cooler spots east of the
I-65 corridor and south of the Tennessee River as a result. We could
see temperatures drop into the upper 40s to around 50 degrees by 3 or
4 AM, in portions of Cullman county and valley locations such as
Fort Payne based on observational trends. In these areas, think at
least some patchy fog may occur maybe as early as around 10 PM and
continue on and off the remainder of the morning. At this point,
dense fog is not expected though. Near and north of the Tennessee
River, expect lows to be much warmer (due to more persistent cloud
cover) and drop into the lower to mid 50s, despite the very light
winds expected.
By the 3 or 4 AM timeframe, models hint at thicker cloud cover
pushing back into northwestern Alabama and sliding southeast to
affect most of the forecast area shortly after daybreak on Sunday.
This may keep lows in the upper 50s in portions of northwestern
Alabama. Despite the deeper moisture in the cloud layer, no
precipitation is expected.
.SHORT TERM...(Sunday through Monday)
Issued at 237 PM CDT Sat May 15 2021
Dry conditions will continue throughout the short-term portion of the
forecast period. Low-level southerly winds will persist throughout
the period with the surface high located just to the east but the
lack of any syntopic lift or strong moisture advection will keep a
dry forecast going. A shortwave ridge will move across the Tennessee
Valley on Sunday as the trough exits to the east. These higher
heights aloft and sunny skies will lead to high temperatures in the
upper 70s to low 80s. Overnight lows will also be on a warming trend
with lows Sunday night into Monday morning only dropping down into
the mid 50s to low 60s. Cloud cover will increase on Monday as an
mid-level shortwave trough approaches from the west. PW values will
climb to around 1-1.2 inches by the end of the day. These values are
more towards the climatological mean for mid-May. Overall, think the
best chances for precipitation will occur Monday night into Tuesday.
Despite the increased cloud cover, temperatures will warm into the
upper 70s to low 80s.
.LONG TERM...(Monday night through Friday)
Issued at 237 PM CDT Sat May 15 2021
The best chances for precipitation will occur early in the long-term
portion of the forecast. A mid-level trough will move through the
area late Monday night and into Tuesday. Concurrently, a ridge will
be developing at 300 mb across the Southeastern U.S. extending
northwards into the Great Lakes. Moisture advection never looks
overly impressive with PW values just climbing to around the 60-70th
percentiles for mid-May. Lapse rates are not very impressive with
rather low values of instability. Overall, went with low chances for
a few showers/storms late Monday night into Tuesday but overall
confidence in precipitation is rather low. Some of the models show
the forecast area remaining dry throughout the duration of the 7 day
forecast period.
A strong ridge develops throughout the remainder of the work week
with rather impressive subsidence. Temperatures will increase
throughout the week with these increasing heights aloft. Highs will
be in the low to mid 80s Wednesday through Friday with upper 80s
possible on Friday. The good news is that dewpoints do not look
excessive with values generally remaining in the upper 50s to low
60s. This drier air at the surface coupled with unimpressive mid-
level lapse rates from the high heights aloft will lead to mainly dry
conditions continuing throughout the remainder of the forecast
period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 625 PM CDT Sat May 15 2021
VFR conditions area expected throughout the TAF period. Thick enough
mid/high cloudiness should keep fog at bay at either terminal, despite
very light winds overnight. Lower CIGS, but still VFR, are expected
after 10-12Z at both terminals tomorrow.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...KTW
SHORT TERM...MA
LONG TERM...MA
AVIATION...KTW
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wichita KS
716 PM CDT Sat May 15 2021
.SHORT TERM...(This evening through Sunday night)
Issued at 259 PM CDT Sat May 15 2021
BOTTOM LINE UP FRONT: The forecast over the next several days
continues to be a messy, and lower-confidence, one. The potential
exists for multiple round of thunderstorms, some of which could be
strong to marginally severe. With each successive round of storms,
the risk of flooding will increase some, especially for areas hit
multiple times in a row.
DISCUSSION
The surface pattern is a bit more tricky/diffuse this afternoon.
However, based on satellite imagery, surface obs, and RAP analysis,
there appears to be a warm front/outflow boundary that stretches
from SE Colorado east through SRN KS/NRN OK. Meanwhile, a secondary
boundary appears to stretch west to east across NRN KS/SRN NE.
Aloft, radar shows a weak MCV treking east across southeast KS.
Through tonight, the warm front over SRN KS should slowly lift
north, especially as the low-level flow increases by this evening.
Convergence doesn`t look overly impressive along this boundary, but
daytime heating and continued low-level moistening should help erode
the cap, opening the door for convection to develop as the front
attempts to lift north. Given the lack of better low-level
convergence, it`s possible storms won`t be able to form along this
boundary, even with weaker inhibition. The other possibility is
that initiation may wait until the low-level flow increases,
leading to increasing moisture convergence. Storms may also
develop in the easterly, upslope flow into the High Plains and/or
along the boundary across NRN KS.
The flow aloft is very weak, but some improved veering with
height/shear is possible as the LLJ develops this evening. The
combination of modest shear and instability may allow a few
stronger cores/updrafts to materialize wherever storms develop.
However, the lack of better shear should keep the severe threat
from being as significant, or widespread, as it otherwise could
be. With that in mind, we`re thinking the combination of modest
instability (1000- 2000 MLCAPE) and modest shear may support some
transient supercell structures capable of strong wind gusts and
quarter to half-dollar size hail. If any storm can keep a more
sustained, rotating updraft, the hail size could end up a bit
higher. However, the threat of larger than half-dollar size hail
looks much more conditional, with the better chance across western
KS where the shear looks better. In general, storms may have a
tendency to cluster, with very heavy rain/flooding and gusty winds
the primary concerns.
Increasing warm/moist advection with the LLJ tonight may allow for
some upscale growth of convection rolling off the High Plains and/or
simply lead to a more expansive area of convection oriented west
to east along the above-mentioned SFC boundaries. For now, we`re
thinking the coverage of storms will be more scattered along the
northward- advancing boundary across SRN KS, possibly becoming
more widespread along the I-70 corridor by tonight as the warm
front stalls. Parts of the I-70 corridor were hit pretty hard
with heavy rainfall last night, which could lead to an increased
risk of hydro concerns tonight if an expansive area of convection
does, indeed, develop in that area. Please see the "HYDROLOGY"
section below for additional details.
On Sunday, a s/w is forecast to eject out of the SRN Rockies and
across the SRN Plains. This may tend to keep the greatest large-
scale forcing for ascent focused to our south. However, continued
warm/moist advection may allow some festering showers/storms across
parts of central/eastern KS, perhaps focused across southeast Kansas
where the greatest lift may be focused. The flow on Sunday looks
even weaker than today/tonight, making the threat of severe
weather all the more conditional. In the short- term period, then,
it appears the "greatest" risk of strong to severe storms will be
this afternoon through tonight.
Martin
.LONG TERM...(Monday through Saturday)
Issued at 259 PM CDT Sat May 15 2021
Early next week, and upper low will lift northeast out of the Four
Corners region and eventually cross the Central Plains (maybe
mid- week or so). A moist, unstable airmass in place ahead of this
feature should continue to keep the door open for additional
rounds of thunderstorms, probably focused in the MON/TUE
timeframe. By Wednesday, the threat of storms may lower some in
the wake of the weakened upper low`s passage through the area.
Because of the day-to-day uncertainty with convective evolution,
though, we`ll continue to run with some low pops during the mid-
week period with the moist and unstable airmass still in place.
Late in the week, an amplified WRN U.S. trough looks to setup,
with ridging anchored over the Southeast U.S. If this pans out, it
would set up a strongly meridional flow across the Plains, with
trajectories straight off the WRN Gulf. This would be a very moist
airmass characterized by 1-2" PWATs. With relatively cool mid-
level temps in place and possibly a weaker cap, it may not take
much for isolated to scattered convection on any given day late
next week. Shear looks fairly weak, though, which should tend keep
the threat of widespread severe weather lower. With continued
opportunities for storms, hydro issues may continue to be a
concern. A persistence forecast appears to be the best way to
handle temps for now, with highs generally in the 70s and lows in
the 50s and 60s.
Martin
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 705 PM CDT Sat May 15 2021
Main concern through the TAF period will be timing storms across
the area. Early this evening storms are trying to form southwest
of a line from KGBD to KICT. Early storms are struggling to stay
together but have kept the early VCTS mention across south central
KS for this threat. Later tonight there are more widespread
chances of storms especially along and west of I-135 as additional
storms are forecast to roll in from western KS overnight. A tempo
TSRA was added for this chance across central and south central
KS tonight.
Models have been handling ceilings very poorly, thus kept the
optimistic MVFR cigs tonight into tomorrow, though could see some
scattered IFR cigs.
&&
.HYDROLOGY...
Issued at 259 PM CDT Sat May 15 2021
A band of 1-3" of rain occurred over the past 24 hours across parts
of western and central KS, with an additional 1-3" of rain possible
over some of these same areas over the next 24 hours. Where the two
areas of heavy rain overlap, there will be an increased risk of some
flooding concerns. That said, flash flood guidance is around
2-3", and soil moisture remains closer to normal. Bottom line, we
continue to prime the pump, so to speak, hydro-wise, but probably
aren`t quite there yet for widespread/significant flooding
concerns. This is something we`ll be closely monitoring in the
coming days, especially with continued opportunities for
thunderstorms through early next week.
Martin
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 61 72 60 75 / 80 50 50 60
Hutchinson 60 72 58 74 / 80 50 50 50
Newton 60 71 59 74 / 70 60 50 50
ElDorado 61 71 59 74 / 70 60 50 60
Winfield-KWLD 62 72 59 76 / 60 60 60 60
Russell 58 72 57 70 / 70 50 50 50
Great Bend 59 72 57 71 / 70 50 50 50
Salina 60 72 58 74 / 70 70 40 50
McPherson 60 72 58 73 / 70 50 50 50
Coffeyville 62 73 60 76 / 70 90 80 70
Chanute 61 73 60 74 / 70 80 70 70
Iola 60 72 60 73 / 80 70 70 70
Parsons-KPPF 62 73 60 74 / 70 90 90 70
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...RM
LONG TERM...RM
AVIATION...KMB
HYDROLOGY...RM
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1157 PM EDT Sat May 15 2021
.UPDATE...
Issued at 1157 PM EDT SAT MAY 15 2021
Very light rain was affecting portions of the Cumberland drainage
basin at the end of the evening, but no measurable amounts have
been noted yet. The forecast was generally on track, and only
minor changes were made to blend obs/radar/satellite into the
overnight forecast.
UPDATE Issued at 937 PM EDT SAT MAY 15 2021
With mainly high clouds present, light winds have allowed eastern
valleys to decouple and cool down faster than was forecast. Clouds
are expected to lower during the night, and readings will probably
be more uniform by morning. Have updated the very near term based
on obs trends, but left temperatures toward morning relatively
unchanged. The high clouds look more extensive than had been
forecast, and sky cover was increased overall for tonight, and
even through the day Sunday based on latest model data.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 405 PM EDT SAT MAY 15 2021
19Z sfc analysis shows high pressure edging further east of the
area but still able to have kept the winds light through the area
today along with mostly sunny skies. Now though, low pressure to
the west, along with a developing warm front, is starting to send
more clouds into eastern Kentucky late this afternoon. Plenty of
midday sunshine helped temperatures climb into the low 70s most
places. Meanwhile, dewpoints are still rather dry - generally in
the mid 30s to lower 40s.
The models are in similar agreement aloft through the short term
portion of the forecast. They all depict northwest flow and rising
heights today and tonight giving way to a bump of a ridge passing
over eastern Kentucky for Sunday and Sunday night. The best energy,
though weak, with this evolution passes through later tonight with a
minima noted for the rest of this portion of the forecast. The NAM
is a tad stronger than the other models with this feature heading
into Monday morning. This will mainly factor into the forecast as
presenting more suppression and something for any convection to
overcome for the latter part of the short term. Accordingly, have
adjusted the starting NBM forecast more toward the quieter NAM12 PoP
and thunder forecast also in conjunction with the latest HRRR
solution.
Sensible weather will feature A milder night with plenty of clouds
and some light rain showers or sprinkles around, at times. This will
continue into the morning of Sunday as the frontal boundary better
consolidates over the southern parts of the CWA. We may see a lull
in the activity for a time that afternoon and into the evening
before another surge with the now better defined front occurs Sunday
night for primarily our northern counties. While the NBM suggests
that a thunderstorm potential exists, did not see much in the way of
instability in the forecast soundings and in light of the uptick in
mid-level heights will continue to discount the thunder chances
through Monday morning. Temperatures will be closer to normal
through the period with a moist profile keeping the nights mild with
a minimum of terrain distinctions.
Only made small spot specific adjustments to temperatures through
the period from the NBM guidance given the higher dewpoint
environment. As for PoPs - generally lowered them through through
the day Sunday more in line with the latest HRRR run and in
conjunction with the drier NAM12.
.LONG TERM...(Monday through Saturday)
Issued at 535 PM EDT SAT MAY 15 2021
The long-term period still looks a bit showery and unsettled,
particularly Monday and Tuesday, before turning very warm and
mainly dry for late week. Within the models, there is some minor
disagreement with the timing/location of the early weak warm
front/passing disturbances and resulting rain coverage; but, the
most notable model trend has been toward a warmer and drier
solution for the middle and latter portions of the week.
The latest model suite shows broad ridging over the Southeast US
Monday morning with a more pronounced finger of ridging extending
over the Ohio Valley toward the Upper Mississippi Valley. A robust
shortwave trough is noted southwest of this ridge from about
Kansas to the TX/LA border. Closer to eastern Kentucky, a more
subtle shortwave trough is noted over the Mid Mississippi Valley
while another shortwave trough will be dropping across the Mid-
Atlantic. Further to the west, a filling ~566 dam closed low is
spinning over northern Arizona. At the surface, a broad area of
high pressure is draped from the New England to north Florida
with a narrow ridge axis forking off across the Great Lakes to
near South Dakota. To the south of this ridge, a weak lee cyclone
is drifting across the Texas Panhandle while a warm front
extends NE to over the Mid-Mississippi valley an then eastward to
over the northern Kentucky.
This warm front will serve as a focus for continued rain shower
activity through the day on Monday as a subtle shortwave
approaches from the Mid-Mississippi Valley and converges with
some upper level energy from the other shortwave passing through
the Mid-Atlantic. Sfc-500 mb BWD values on the order of 20 to 30
knots suggest the potential for some semi-organized convection
during the afternoon and evening. However, instability could be a
limiting factor, depending upon how much clearing is able to occur
over Southeast Kentucky. Temperatures will be warmer than Sunday
ranging from near 70 over northeast Kentucky, near the warm front,
to the upper 70s across the Lake Cumberland Region.
The finger of upper level ridging will try to strengthen Monday
night across the Ohio Valley/Great Lakes, but the next shortwave
trough will pivot to over the Mid-Mississippi/Lower Ohio Valleys
keeping a eastern Kentucky under a weakness (or col) in the ridge
during the day on Tuesday. This will again keep clouds and showers
in the forecast during the day. Weak lapse rates and widespread
cloud cover will keep instability very limited. Temperatures will
again be seasonable ranging through the 70s Tuesday afternoon.
More significant high rises will occur Tuesday night and
Wednesday, causing the col to fill as the shortwave trough energy
is shunted north of the forecast area. Meanwhile, the closed low,
initially over the southwest US on Monday, will also fill and
move to over the Central and Southern Plains where its remnants
will be sheared to pieces in the deep southerly flow ahead of
another deep closed low dropping into the Pacific Northwest. In
previous forecast packages, these pieces of energy were expected
to bring continued daily shower and thunderstorm chances through
late week. That no longer appears to be the case as models are
now showing a much more prominent upper level high building to
590+ dam over the southern and Central Appalachians by Friday.
This will lead to strong drying and capping in the mid-levels. A
few pulse type storms will still be possible on Wednesday as the
upper level trough and lingering warm front weaken and lift
north of the area. From Thursday through Saturday, mostly sunny
and mainly dry weather is expected with the upper level high
becoming firmly entrenched overhead. A stray late-day shower
cannot be entirely ruled out near/north of I-64 where the capping
will be a little weaker but any activity would be very isolated.
Temperatures should reach the lower 80s in most locations on
Wednesday and range through the 80s from Thursday through
Saturday. Low temperatures are expected range from the mid 50s to
near 60 from Monday night through Wednesday night before
moderating to around 60 for Thursday through Saturday nights.
Some valley fog is probable in the typical locations on most
nights.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 855 PM EDT SAT MAY 15 2021
VFR conditions were present across the JKL forecast area to start
the period, but mid and high level clouds were creating ceilings
generally around 10Kft AGL and higher. VFR conditions are forecast
to last into Sunday morning. Rain will probably affect some
locations at times during the day. The extent and amount of rain
will determine conditions from late morning on. At this time, it
is a fairly low confidence forecast. The most likely places to
drop below VFR are near and north of I-64. However, in a worst
case scenario, it is possible that much of the area could even
fall to IFR at times in the afternoon. Winds will be light through
the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HAL
SHORT TERM...GREIF
LONG TERM...GEERTSON
AVIATION...HAL
Area Forecast Discussion
National Weather Service Marquette MI
628 PM EDT Sat May 15 2021
.SHORT TERM...(This evening through Sunday)
Issued at 311 PM EDT SAT MAY 15 2021
Upper level pattern today per water vapor imagery and RAP model
heights features a blocking ridge over the eastern Pacific
stretching British Columbia with a cutoff low over northern
California. Downstream of the western Ridge and cutoff low weak
ridging was over the Rockies with a shortwave trough moving
through the Midwest and upper Great Lakes. Increasing mid-level
moisture and WAA was bringing clouds to much of the central and
western U.P along with elevated showers. The dry sub-cloud layer
was limiting much of the precipitation from making it to the
ground.
Overnight, a mid level warm front will continue to push through the
U.P but not expecting much in the way of precipitation, just
cloudiness. Clouds should decrease through the day on Sunday with
another pleasant spring day expected. With the increasing low level
moisture overnight expect the cloud cover to be low and possibly
even see some fog development, especially along the Lake Michigan
shoreline. The low clouds and any fog that develops should mix out
through the mid to late morning hours.
Fire weather concerns should be lower tomorrow due to the increase
in low level moisture and light winds. RH could still fall to near
30 percent in the interior west but it will take a good amount of
the day to get there with low clouds / moisture slowing down the
mixing during the morning hours.
.LONG TERM...(Sunday night through Saturday)
Issued at 432 PM EDT SAT MAY 15 2021
Upper level ridging moves into the area on Monday and builds through
most of next week as the CONUS pattern amplifies. At the surface, a
ridge oriented east-to-west across the area will keep weather
primarily dry through early next week. This surface ridge axis
pivots to the northeast by the middle of next week with deep
southerly flow transporting Gulf moisture into our area. The 00z
NAEFS ensemble guidance indicates precipitable water values
increasing above the 90th percentile by 00Z Thursday and remaining
above the 90th percentile at least through next weekend. In summary,
Monday and Tuesday should be dry and much warmer than normal
(widespread 80s) with more cloud cover holding temperatures in the
70s for Wednesday through the end of the long-term period.
A shortwave trough passes to our north on Monday with warm air
advection increasing 850mb temps to 10-12C for Monday and Tuesday.
Model certainty tool shows a bimodal temperature distribution on
Monday with the cluster of warmer guidance indicating mid-80s are
possible across the interior west. By Tuesday, model guidance is
more normally distributed with maximum temperatures so 80s seem less
likely or at least more isolated. Cloud cover should also increase
on Tuesday as a warm front approaches from the south. A few showers
may develop along the front or low level jet, but amounts should be
light.
A prolonged period of unsettled weather is expected to close out
next week as the CONUS pattern amplifies. Western troughing and
eastern ridging results in deep southerly flow with a connection to
Gulf of Mexico moisture. As previously mentioned, NAEFS guidance
indicates pwat values above the 90th percentile through the end of
the extended. This deep moisture (Tds >60F) combined with warmer
than normal temperatures indicates thunderstorms will be possible
each day, particularly during the afternoon/evening. Overall,
widespread precipitation seems unlikely, but a general trend toward
wetter weather appears likely late next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 628 PM EDT SAT MAY 15 2021
VFR conditions will continue through this evening with only mid
clouds spreading through the area. Low level moisture will advect
into the area overnight from the southwest bringing low clouds with
MVFR conditions to KSAW and possibly KIWD later tonight. KIWD will
go back to VFR quickly while KSAW will stay MVFR through late Sun
afternoon.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 311 PM EDT SAT MAY 15 2021
High pressure will remain over the Great Lakes for the next several
days, limiting wind gusts over the lake to 15 knots or less
into much of next week. Increasing moisture could result in areas of
fog at times tonight and again mid-week but confidence is low.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...NL
LONG TERM...EK
AVIATION...07
MARINE...NL
Area Forecast Discussion
National Weather Service Paducah KY
650 PM CDT Sat May 15 2021
.SHORT TERM...(Tonight through Sunday night)
Issued at 215 PM CDT Sat May 15 2021
Showers in association with a 500mb short wave moving SE through the
NW flow aloft will continue to impact the FA into the evening hours.
The HRR, and the RAP to some degree, indicate some diminishing of
the shower activity moving across SEMO and SW IL this afternoon with
some southeastward progression of shower chances tonight. This may
be aided by a surface warm front lifting north tonight and into
Sunday. As a result, the trend will remain toward a warmer and more
moist airmass across the region. Dew points will elevate to near 60
Sunday and there should be enough instability to increasingly yield
thunder chances Sunday and Sunday, possibly even later tonight.
The warm front is expected to stall roughly in the vicinity of I-64
Sunday night or early Monday with some 500mb ridging extending north
across the FA. This will focus the better rain/thunder chances
across the northern part of the FA Sunday night, although chances
may also increase across SEMO Sunday night in response to an
approaching 500mb short wave in the wake of the eastward moving
500mb ridge.
The airmass change will yield increasingly warmer temps, closer to
normal values, with low temps around 60 by Sunday night as surface
dewpoints reach the upper 50s.
.LONG TERM...(Monday through Saturday)
Issued at 215 PM CDT Sat May 15 2021
Main adjustment to the long term forecast period was from Wednesday
on, lowering PoPs for convection considerably, especially east of
the MS River. A strengthening mid level ridge over the east U.S. and
trof to our west will ramp up meridional flow over our region and
sharpen a cutoff zone from diurnally enhanced convection over mainly
SEMO, with slight to nil chance PoPs over the rest of the area,
especially the KY Pennyrile up into southwest IN. The NBM is
typically too slow in its realization of a notable forecast
transition. The ensemble suite and latest deterministic output
suggest this trend is the right way to go. This will also place our
temperatures on the high side of guidance. The NBM actually seems to
have a good handle on highs.
For Monday and Tuesday, before the transition occurs, we will have
higher PoPs for convection Monday through Tuesday, as a wave lifts
NNE across the region. Highest PoPs Monday will be SEMO, tapering
off to nearly nothing west KY. PoPs increase area wide Monday night
into early Tuesday, then diminish by Tuesday night. Again, pretty
good clustering of model solutions on timing.
&&
.AVIATION...
Issued at 650 PM CDT Sat May 15 2021
For the 00z Sunday issuance for WFO PAH TAF sites, there will be a
gradual transition from from VFR to MVFR conditions with periodic
light rain with the passage of a warm front to the north across
the area. These MVFR ceilings will persist through 12z Sunday for
most locations before improving back to VFR conditions.
The two exceptions will be KEVV and KOWB, where the warm front is
expected to linger, with enhanced precipitation potential at these
sites. MVFR to intermittent IFR conditions will remain at these
locations through the end of the forecast period, ahead of a cold
front expected later in the next forecast period.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
AVIATION...Smith
Area Forecast Discussion
National Weather Service Pocatello ID
212 PM MDT Sat May 15 2021
.SHORT TERM...Today through Monday. An upper level low pressure
system is centered over Central CA. Moisture is moving into our
area ahead of this system. Look for mainly afternoon scattered
showers and isolated thunderstorms mostly across the Southern
Highlands, Southeast Highlands and the Eastern Highlands along
the Wyoming border. Some gusty winds around 30 mph and small hail
are possible with any thunderstorms. Thunderstorms today will be
very isolated due to the amount of cloud cover all day. The upper
level low moves east over southern Nevada and southern Utah by
Sunday afternoon. Expect another round of scattered showers and
isolated thunderstorms mainly for our Southern and Southeast
Highlands. Some high-res models suggest that isolated showers and
thunderstorms are possible for the Montana Divide and southern
Central mountains. Monday as the low moves east expect just an
isolated chance of afternoon showers and thunderstorms, mainly
over our southeast mountain areas. Today expect near normal
temperatures, if not slightly below normal. Sunday and Monday
expect temperatures 4 to 8 degrees above normal, especially if the
cloud cover clears out early in the day as expected.
Wyatt
.LONG TERM...Tue through next Sat night. Tue through Wed morning
appear dry and sunny with afternoon highs around 10 deg F warmer
than normal under a dry southwesterly flow. This changes as a
vigorous upper level closed low, which looks to have strength
usually seen only in winter, comes onshore, generating showers over
eastern Idaho as early as Wed afternoon, with deteriorating
conditions for Wed night through Sat. Cluster analysis only varies
on how deep this low will be, and maybe its north-south positioning,
but this slow moving pattern should produce some sort of moderate to
heavy precipitation event, especially Thu night through Fri night,
and a potential wind event Wed night-Fri. In fact, the heavy
precipitation is likely to be snow above 6000ft elevations for part
of the time, so this may include Winter Storm Warnings.
Precipitation production falls off considerably for Sat, but still
should be wet and likely cold with highs about 15 deg F below
normal.
Messick
&&
.AVIATION...A line of SHRA is approaching from Utah, and is expected
to combine with afternoon heating to generate ISOLD to SCTD TSRA,
with greatest coverage for the eastern airdromes of KDIJ and KIDA,
although KDIJ is the only airport where risk gets to 30 percent.
Probability barely gets to mentionable for KBYI, although they are
closest to the severe thunderstorm risk issued by SPC. Expect skies
to stay VFR however, even at KDIJ. VSBY should for the most part be
solid VFR. Showers will wreak havoc with wind, even at KSUN. There
is another surge of late evening SHRA for KSUN and KBYI, seen only
on the latest HRRR guidance, so this has to be tracked. Unknown how
the KSFX radar outage affects the HRRR solution. Expecting
more TSRA/SHRA on Sun afternoon.
Messick
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Pueblo CO
905 PM MDT Sat May 15 2021
.UPDATE...
Issued at 857 PM MDT Sat May 15 2021
...TORNADO WATCH HAS BEEN CANCELED FOR CROWLEY, OTERO, BENT, AND
BACA COUNTIES, THE TORNADO WATCH STILL REMAINS IN EFFECT FOR KIOWA
AND PROWERS COUNTIES. THE SEVERE THUNDERSTORM WATCH FOR EL PASO
COUNTY HAS BEEN CANCELED...
PoPs have also been adjusted to reflect where current areas of
convection are, and their anticipated progression for the next
few hours.
-Steward
UPDATE Issued at 537 PM MDT Sat May 15 2021
...SEVERE THUNDERSTORM WATCH HAS BEEN UPGRADED TO A TORNADO WATCH
FOR OTERO, CROWLEY, BENT, KIOWA, PROWERS AND BACA COUNTIES...
PoPs have also been adjusted to reflect where current areas of
convection are, and their anticipated progression for the next
few hours.
-Steward
&&
.SHORT TERM...(This evening through Sunday)
Issued at 324 PM MDT Sat May 15 2021
Main Forecast Concerns/Challenges:
1) Strong to severe storms remain possible along and east of I-25
through mid to late evening. Main threats are large hail and
damaging winds, though have growing concerns for the possibility of
a tornado especially across locations closer to the CO and KS border.
2) Strong to severe storms are once again possible along and east of
I-25 on Sunday. Flash flooding concerns across area burn scars will
also increase.
Convective activity has continued to increase across the area this
afternoon, with latest radar imagery showing development over the
higher terrain, just north of the Palmer Divide, and around the
Raton Mesa. However, this development has remained on the weaker
side. RAP analysis is still showing a fair amount of CIN in place
over southern CO, with a more recent AMDAR sounding out of COS still
showing a strongly capped environment. Despite being late in the
day, still expect some additional warming along with increasing
ascent that should aid in eroding this CIN late this afternoon into
early evening. I think this should occur over the next couple of
hours, upon which MLCAPE values approaching 2000 j/kg and effective
shear of 35-40 kt will support quickly intensifying scattered
thunderstorms into the early evening. Locations along the I-25
corridor still look to have the highest chances though late
afternoon, with damaging winds and large hail the main threats.
This development will likely persist and expand as it moves east
across the plains through early to mid evening. Some lower
confidence with convective mode with some CAMs showing more linear
segments with this eastward moving development. However, given the
shear, would anticipate some continued potential for supercells.
This will be something to keep an eye on as moisture, instability,
and helicity will increase further to the east this evening. In this
location/environment closer to the CO/KS border, the highest risk
for significant hail (2") will reside. Also, in this
location/environment, the highest risk for tornadic development will
reside. These latest trends are pointing towards an increased threat
of tornadic development over the far eastern plains, closer to the
CO/KS border, in the 6 to 9 pm time frame. While concerns are
growing, the uncertainty with convective mode does keep some level
of lower confidence. Nonetheless, will continue to keep a close eye
on observational and radar trends into the evening. Thunderstorms
should depart east into KS in the 10 PM to 12 AM time frame.
On Sunday, upper trough/low is expected to approach the region with
large scale setup continuing to favor thunderstorm development over
much of the area. While instability and shear may not be quite as
strong on Sunday, this instability and moisture will have the
potential to push farther west up to the eastern mountains. So, not
only will there be a continued threat of strong to severe storms
across southern CO on Sunday, do think there will be an increased
flood/flash flood threat as moist upslope flow will now be present.
This will include the burn scars as well as other locations along
and adjacent to the eastern mountains.
.LONG TERM...(Sunday night through Saturday)
Issued at 324 PM MDT Sat May 15 2021
Main Forecast Concerns/Challenges
1) Flash flood threat Monday for area burn scars
2) Active weather continues for Tuesday, and possibly into Wednesday
Sunday night through Monday...The upper low pushes into northern AZ
Sun night, then moves across the Four Corners on Mon. Surface flow
is expected to remain out of the northeast through Sun evening,
allowing lingering shower activity to persist. However, as the upper
low nears on Mon, the surface flow is forecast to turn due east,
drawing plenty of llvl moisture back towards the I-25 Corridor and
eastern mts. With about 1000 j/kg of CAPE to work with along the
eastern mts by midday, storms are expected to fire once again
along the higher terrain. The placement of the upper low will be
a crucial piece to the puzzle, however, as the steering flow will
tend to keep any storms that do initiate close to the mts.
Therefore, flash flooding of area burn scars is a definite
possibility and is of the utmost concern for Monday aftn and
evening.
Plan on lows Sun night in the 30s to around 40F for the high
valleys, and in the 40s to around 50F for the plains. High temps on
Mon are forecast to warm into the 60s for most locations, and
nearing 70F along the eastern border.
Tuesday and Wednesday...The upper low begins to weaken early Tue as
it starts to lift to the east-northeast, then tracks directly over
CO through Wed. This track presents a very broad area of lift
combined with abundant available moisture, so feel that there is a
very good chance of widespread convection both days, with greater
chances over the higher terrain and tied more to the aftn and early
evening hrs due to heating. Model CAPE is not all that robust either
day, and given the overall flow, feel that severe potential is low.
High temps both days will climb into the 60s to lower 70s.
Thursday through Saturday...Another upper low pressure system drops
down out of the Pacific NW for the end of the week, with strong
southwest flow developing across the Four Corners region. Multiple
disturbances within the flow will most likely help motivate isolated
to low-end scattered convection each aftn across the higher terrain
and high valleys. As for temps, the southwest flow aloft will warm
things up nicely across the cwa, with highs around 70F each day for
the high valleys, and in the 70s to around 80F for the eastern
plains. Moore
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 324 PM MDT Sat May 15 2021
KCOS and KPUB: VFR conditions are expected over the next 24 hours.
Thunderstorms will continue to increase in coverage and progress
eastward before diminishing late this evening. Dry conditions are
expected through the night into early tomorrow afternoon, before
thunderstorms greatly increase in coverage by mid afternoon. These
thunderstorms will have the possibility to produce strong gusty
winds and hail. These thunderstorms would drop either site below
MVFR conditions if KCOS or KPUB found themselves under one. Even if
KCOS and KPUB are not directly impacted by these thunderstorms,
outflow boundaries will likely be present, and these would shift
winds directions and increase wind speeds quickly. There is also
possibility that low clouds/fog will develop overnight, but
confidence is low in that scenario still at this time; if this
scenario came to fruition, MVFR or lower categories would be
expected.
KALS: VFR conditions are expected over the next 24 hours. An
isolated thunderstorm is possible late this afternoon and into the
the evening over KALS, but otherwise expect dry conditions through
tonight into tomorrow afternoon, before thunderstorms increase in
coverage by mid afternoon tomorrow. These thunderstorms could
produce strong gusty winds and would also drop visibilities below
MVFR conditions if KALS found itself under one.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...STEWARD
SHORT TERM...RODRIGUEZ
LONG TERM...MOORE
AVIATION...SIMCOE
Area Forecast Discussion
National Weather Service San Diego CA
818 PM PDT Sat May 15 2021
.SYNOPSIS...
Low pressure will drop southeast over the deserts of California on
Sunday, maintaining cool conditions with gusty onshore winds over
the mountains and deserts, and a deep marine layer to the coastal
mountain slopes. Some light precipitation is likely to develop at
times tonight through early Tuesday, with the best chance on
Sunday. A ridge will arrive later Tuesday, providing dry and warmer
weather through Wednesday. Another cold, upper-level trough will
develop over the State on Thursday, setting up another round of
cooling and gusty onshore winds over the mountains and deserts.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
Marine clouds were much more stubborn today over coastal areas, and
wasted no time filling rapidly inland along the coastal slopes of
the mountains late in the day. At 8 PM PDT...Clouds covered
Orange and western San Diego County, and were even seen as far
inland as Warner Springs. Our 00Z sounding had a 7.5C inversion near
3700 FT. That`s up 1100 FT from yesterday. South-southwest winds
of around 10 KTs were observed below the inversion, which is a
little ahead of schedule, based on the 00Z WRF. The sfc pressure
gradient from KSAN to KTPH was as high as 13 MBS earlier this
afternoon and remains strong this evening. Peak westerly winds of
25-35 MPH with gusts to 55 MPH have been logged near the San
Gorgonio Pass, and a Wind Advisory covers the deserts/passes.
Sunday will be the coolest day of the weekend with daytime maximum
temperatures of from 15-20F below average in the inland valleys,
while the deserts run 10-15F below average and the coastal areas run
5-10F below average. A minor forecast update was issued earlier this
evening to adjust POPS and add some fog along the mountain slopes.
The latest HRRR runs and the 00Z WRF run are looking a bit wetter
for coastal areas Sunday morning. One-quarter to one-half inch
precip amounts are forecast locally along the coastal slopes of the
mountains through Monday, while coastal and valley areas will likely
see one-tenth inch or less. Precipitation rates will be very low so
little run off is expected.
A dynamic low pressure center will track SE from Modesto CA, to
near Las Vegas by Sunday afternoon. This track will support strong
onshore flow over SoCal through Sunday, which will pull in more
moisture from the Pacific, and likely spark scattered light showers
and/or drizzle at times into Monday morning. Weak PVA and cyclonic
flow aloft will provide modest lift, while upslope flow enhances
amounts on the coastal slopes. Even as the storm center moves east
on Monday, lingering low-level moisture will be acted upon by
another weak disturbance trailing the storm in NW flow aloft, to
renew a chance for more light precip Mon night into Tue morning over
the coastal basin.
Sunday will be a chilly one for SoCal, but gradual warming will
begin on Monday as the onshore flow weakens, and some of the low
clouds break. Despite the chance for a few more light showers/
drizzle Tue morning, the warming will continue under a weak
ridge aloft and more afternoon sun.
The ridge slips by on WEdnesday as yet another cold trough deepens
along the Coast on Thursday. This will spark another round of strong
westerly winds over the mts/deserts and more cool weather to end the
work week. Some temperature moderation is likely next weekend as the
trough weakens along the Coast.
&&
.AVIATION...
160300Z...Coast/Valleys...BKN-OVC015-030 tops 050 through 23Z Sunday
with DZ/-RA after 08Z Sunday. Only partial clearing Sunday afternoon
with a deep marine layer in place.
Mountains/Deserts...West facing mountains slopes below 6,000 ft
obscd in clouds/fog tonight and Sunday with areas of DZ/-RA.
Southwest winds gusting 30-45 kt tonight through Sunday, strongest
on the desert slopes and through the San Gorgonio Pass. MOD-STG
up/downdrafts, LLWS, and rotors possible over and east of the
mountains near KPSP.
&&
.MARINE...
No hazardous marine weather is expected through Wednesday.
&&
.BEACHES...
A long period south swell from 200 degrees at 3 ft/17 sec will
produce 3-6 ft on south-southwest facing beaches of Orange County
and far northern San Diego County Sunday. Surf of 2-4 ft is expected
in San Diego County south of Carlsbad. Strong rip and longshore
currents are likely Sunday into Monday. Swell and surf lower Monday.
Another south swell arrives late Tuesday and peaks Wednesday for
another round of elevated surf and a high risk of rip currents.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 5 AM PDT Monday for Riverside County
Mountains-San Diego County Deserts-San Diego County
Mountains-San Gorgonio Pass Near Banning.
Wind Advisory until 7 PM PDT Sunday for Apple and Lucerne
Valleys-Coachella Valley.
PZ...NONE.
&&
$$
PUBLIC...10
AVIATION/MARINE...Moede