Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/23/19
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1040 PM EDT Wed May 22 2019
.SYNOPSIS...
Clouds will thicken and lower overnight with some
isolated to scattered showers possible with a weak disturbance this
morning mainly from the Capital Region south, as a low pressure
system approaches from the Great Lakes region. A frontal system
associated with this low will bring humid conditions for Thursday
along with some showers and scattered thunderstorms, mainly during
the afternoon and evening. Seasonable temperatures and breezy
conditions will return for Thursday night into Friday. Another
frontal system approaching from the west could bring some showers by
late Saturday afternoon.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 1040 PM EDT...The sfc anticyclone continues to move
east/southeast of Long Island at 02Z. The mid-level ridge axis
is over NY and New England border based on the latest RAP13. Mid
and high clouds have increased across the region ahead of a
weak disturbance running into the ridge. Some light pcpn echoes
continue on the KENX radar mainly north and west of Albany. Most
of this is virga due to the dry low-levels with dewpts in the
20s to lower 40s and the very dry 00Z KALY sounding below 700
hPa.
The best warm advection ahead of the weak short-wave rounding
the ridge is approaching the Tug Hill Plateau and western NY. We
retooled the PoPs based on the latest 3-km HRRR and NamNest with
the best forcing settling south and east of the I-90 corridor in
the early morning hours. Most of western New England and the
Lake George Region/Capital Region may remain dry. The isold-
scattered showers will likely be the most persistent over the
eastern Catskills/mid-Hudson Valley. A rumble of thunder may
graze the Catskills, but the probability looks low with a pocket
of elevated instability.
Lows tonight will range from the mid 40s to lower to mid 50s,
and temps may steady or slightly rise in the early to mid
morning hours.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Morning showers across southern areas should depart by mid
morning, with a relative lull in precipitation until early
afternoon. However, models suggest quite a bit of mid level
clouds persisting in most areas during this time, limiting
heating, and also dewpoints are forecast to only slowly rise
into/through the 50s.
By afternoon, showers and thunderstorms are expected to develop
across western/central NYS, closer to greater mid level height
falls and low level forcing ahead of an approaching
cold/occluded front. Mid level wind fields are expected to
increase dramatically Thursday afternoon, with H700-H500 winds
reaching 50-60 KT or slightly higher by late afternoon. So,
kinematics will be very strong, but it remains questionable
whether enough thermodynamics will be present to create
sufficient updrafts to work in tandem with the strong deep
layered shear and allow for any discrete storms to become
supercellular. It appears that instability will remain weak,
with MU CAPES likely only reaching several hundred J/kg across
the western Mohawk Valley/SW Adirondacks, and less farther south
and east. The weaker instability may not be enough to overcome
the strong mid level wind fields, and could result in highly
tilted updrafts with any discrete cells that can form.
Showers and some thunderstorms will likely move into the region
from the west during the mid to late afternoon, some of which
could contain strong wind gusts if they become tall enough
and/or organize into a line. The best chances for this may be if
discrete cells upstream of our region form into a QLCS, which
could then propagate into the Mohawk Valley/SW Adirondack region
and possibly points immediately south and east, potentially
mixing down strong winds from aloft due to momentum transfer.
Again, this is a possibility, but not certain, but should this
mode develop, then a better chance for damaging wind gusts would
occur across the Mohawk Valley/SW Adirondack region and perhaps
as far S/E as the greater Capital Region of NY and into southern
VT. As for any discrete cells, this potential, albeit small,
would mainly be areas west of the Hudson River across the SE
Catskills and perhaps western mid Hudson Valley region. SPC has
trimmed the Slight Risk area westward from earlier issuances
(now only covering extreme western Mohawk Valley and SW
Adirondacks) with Marginal Risk also trimmed back farther west,
extending to just east of the Hudson River.
High temperatures Thursday may reach the lower/mid 70s in some
valley areas, especially across the Mohawk Valley, Schoharie
Valley and Capital Region, with mainly 60s to around 70
elsewhere. Gusty south winds will also develop later in the day,
with some gusts possibly reaching 25-35 mph in some north/south
valleys including portions of the Capital Region.
For Thursday night, showers and scattered thunderstorms may
linger into the evening hours, before ending from west to east
before midnight. Breezy and cooler conditions will then filter
into the region behind an occluded front, with some spotty
showers/sprinkles possible across the southern Adirondacks and
southern VT. Lows mainly in the 50s, with some 40s possible
across higher terrain of the southern Adirondacks. Strong
west/northwest winds may reach 25-35 mph later at night behind
the front, especially within the Mohawk Valley/Capital Region
and Berkshires.
Friday-Friday night, breezy and cool for Friday, with clouds and
some showers/sprinkles possible across northern areas due to the
passage of main upper level trough/cold pool. Better chances for
clearing will be across southern areas. Highs mainly in the 60s,
although some lower 70s could occur late in the day in some
valley areas, while some higher elevations across the
Adirondacks and southern VT remain in the 50s. Gusty
west/northwest winds may reach 25-35 mph. Clearing for Friday
night, and cool with lows mainly in the 40s to lower 50s. Some
30s could occur across the SW Adirondacks and eastern Catskills
if skies remain clear long enough.
Saturday, the next fast moving frontal system will approach from
the Great Lakes region later in the day or at night. Expect
increasing clouds during Saturday, with chances for showers
increasing in the afternoon. Some thunder could also occur,
although initial instability parameters look fairly limited
through sunset. Highs mainly in the mid 60s to lower 70s,
although could be warmer if more sunshine occurs through the
morning hours.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The extended forecast period begins unsettled for the middle portion
of the Memorial Day holiday weekend, but high pressure looks to
build in late Sunday pm into Monday. If the ridge holds on, then
fair weather may continue into early Tuesday before unsettled
weather returns for the mid-week.
Saturday Night into Sunday...A prefrontal sfc trough and a cold
front will bring an increase of showers and thunderstorms
across the forecast area Saturday night. The better instability
looks to be from the Capital Region north and west early in the
evening. A slight to low chance of thunderstorms was kept in
until midnight. The higher PoPS were maintained from roughly the
Capital Region north and west. Lows Sat night will be on the
mild side with 50s to around 60F. The latest medium range
guidance has the cold front moving through the forecast area in
the late morning into the early pm. We kept a slight chance of
showers with perhaps a thunderstorm over the higher terrain in
the pm especially over the southern Greens and southern
Adirondacks. Overall, we will favor a clearing trend for the
afternoon and lean towards the latest 12Z ECMWF and WPC
guidance. Highs will be close to normal with mid 70s to around
80F in the lower elevations, and mid 60s to mid 70s over the
hills and mtns.
Sunday night into Monday...High pressure builds in from the
southeast Ontario and the central and eastern Great Lakes Region
with west to northwest flow aloft. A cool and pleasant night is
expected with lows in the upper 40 to upper 50s. The weak sfc high
settles over NY and New England by Memorial Day. H850 temps will be
near normal based on the latest GEFS guidance, and will be in the
+13C to +15C range with highs in the mid and upper 70s over the
valley locations, and mid 60s to lower 70s over the higher terrain.
A weak warm front starts to move towards the region late in the day
ahead of a quick moving short-wave trough. The latest 12Z EC keeps
the sfc ridge in control, while the latest GFS has a few showers
over the southern Adirondacks. We placed a slight chance of showers
from the Hudson River Valley eastward for the afternoon, and a very
low chance to west. This short-wave does not have a lot of low-
level moisture to work with, so an increase of clouds may be all
that occurs during the day.
Monday night into Tuesday...A weak sfc anticyclone may settles back
in across the region in the wake of the short-wave trough and weak
cold front late Mon night. A low chance of showers was kept in the
forecast early in the evening. The question will be how quickly a
warm front and strong low pressure system approaches from the Upper
Midwest and Great Lakes Region. The 12Z GFS is more aggressive than
the latest 12Z ECMWF, with some spread in the Ensemble guidance
brining showers back into the region by Tue pm. Low confidence
forecast here with the better chance of showers from the Capital
Region north and east. Lows Monday night will be in the 40s north
and west of Albany, and upper 40s to lower 50s south and east. Highs
Tuesday will depend on the amount of sunshine and placement of the
warm front. We did not stray too far from the superblend with 60s
to lower 70s over most the region.
Tuesday night into Wednesday...A strong subtropical ridge attempts
to build in centered over the Gulf of Mexico and Florida. Mid and
upper level heights try to increase over NY and New England. If the
warm front lifts through the entire area quickly, then we could be
in a warm and more humid air mass that the latest 12Z ECMWF
MOS/MEXMOS, as well as the 12Z GEFS /850 hPa temps +1 to +2 STD DEVs
above normal/ are indicating. We kept a slight or low chance of
showers in across the region with the highest PoPs over the northern
most zones. We went a little higher than the Superblend with upper
70s to around 80F in many of the valley areas, and mid/upper 60s to
lower/mid 70s over the higher terrain. Sfc dewpts increase into
the mid 50s to lower 60s.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
High pressure continues to drift east of NJ tonight. A warm
front will be approaching from the lower Great Lakes Region and
the Mid Atlantic States overnight into tomorrow morning. The
warm front and a mid level disturbance will bring some showers
and isolated to scattered thunderstorms during the afternoon
before the cold front moves quickly through in the early
evening.
VFR conditions are expected most of the night time period as mid
and high clouds continue to increase and lower. A weak
disturbance ahead of a warm front may bring some isolated to
scattered showers from KALB/KPSF south and west to KPOU between
09Z-14Z. We placed some VCSH groups in with the greatest threat
for KPOU and lowered clouds bases to 3.5-5 kft AGL. The low-
levels remain very dry, so we did not include MVFR cigs at this
time.
The warm front struggles to move through the region, and an
increased threat of showers and isolated to scattered
thunderstorms is possible by the afternoon. The instability
looks limited due to lack of sfc heating with abundant cloud
cover. We placed PROB30 groups in from 19Z/THU to 00Z/FRI for
all the TAF sites, and we included a thunderstorm threat for
KALB/KPOU. Conditions were lowered to MVFR in terms of
cigs/vsbys with the threat of showers/thunderstorms. MVFR cigs
were include at KPSF during the mid afternoon with the
increasing low-level southerly flow.
The winds will become light and variable in direction at 3 or 4
kts early this evening, and then calm. They will increase first
at KALB from the south at 5-10 kts between 09Z-12Z/THU, and
then expect southerly winds of 10-15 kts at all the sites by the
late morning through the afternoon. The winds may gust around
20-25 kts at KALB during the afternoon due to the funneling
effect up the Hudson River Valley. Some stronger wind gusts may
be possible with any thunderstorms.
Outlook...
Thursday Night: High Operational Impact. Breezy Likely SHRA...TSRA.
Friday: Low Operational Impact. Breezy NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: Moderate Operational Impact. Breezy Likely SHRA...TSRA.
Saturday Night: Moderate Operational Impact. Breezy Chance of SHRA...TSRA.
Sunday: No Operational Impact. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Memorial Day: Low Operational Impact. Slight Chance of SHRA.
&&
.FIRE WEATHER...
Wind gusts of 25-35 mph possible Thursday...
Clouds will increase tonight with some showers possible late as
a low pressure system approaches from the Great Lakes region. A
frontal system associated with this low will bring humid
conditions for Thursday along with some showers and scattered
thunderstorms, mainly during the afternoon and evening.
Seasonable temperatures and breezy conditions will return for
Thursday night into Friday. Another frontal system approaching
from the west could bring some showers by late Saturday
afternoon.
RH values will climb to 70-90 percent tonight, then fall to
55-65 percent Thursday afternoon.
Winds will become light/variable after sunset, then become south
to southwest and increase to 10-20 mph by Thursday afternoon,
with some gusts of 25-35 mph possible.
Spotty showers will develop after midnight, with a better chance
for showers and scattered thunderstorms Thursday afternoon and
evening as a frontal system moves across.
&&
.HYDROLOGY...
Some showers will develop late tonight, with showers and
scattered thunderstorms expected Thursday afternoon and evening
as a frontal system moves across. Total rainfall amounts for
late tonight through Thursday night are expected to range from
one quarter to one half inch for most areas, except up to three
quarters of an inch across portions of the Mohawk Valley and
southwest Adirondacks. Rainfall amounts may remain under one
quarter of an inch across portions of the mid Hudson Valley and
NW CT.
This rainfall should not have significant impacts on
rivers/streams. However, brief heavy downpours could lead to
temporary ponding of water in poor drainage/urban and low lying
areas.
Additional showers and embedded thunderstorms are possible late
Saturday into Saturday night with another fast moving frontal
system passing through.
Please visit our Advanced Hydrologic Prediction Service /AHPS/
web page for specific area rivers and lakes observations and
forecasts.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...KL/Wasula
NEAR TERM...KL/Wasula
SHORT TERM...KL
LONG TERM...Wasula
AVIATION...Wasula
FIRE WEATHER...IAA/KL
HYDROLOGY...IAA/KL
Area Forecast Discussion
National Weather Service La Crosse WI
1101 PM CDT Wed May 22 2019
.SHORT TERM...(This evening through Thursday)
Issued at 252 PM CDT Wed May 22 2019
Latest 19z surface analysis shows low over Minnesota and South
Dakota border. With tight pressure gradient and winds mixing down
aloft out ahead of the low pressure system has produced windy
conditions across the area. Latest metars over southeast Minnesota
and northeast Iowa are indicating wind gusting up to 30 to around 40
knots with wind speeds 20 to 25 knots.
Tonight into Thursday...upper level/surface low lifts north into
southern Ontario Canada and the Upper Great Lakes Region tonight.
Then...upper level/surface ridge builds into the Northern Plain
states Thursday. Due to daytime loss of heating and gradient
slackening over the area this evening...winds will diminish across
the area this evening and tonight. The 22.12z GFS/NAM suggest
stratocumulus deck of clouds advect into the northern half of the
forecast area Thursday morning...with ridging building over the
area...these clouds will erode late morning to early afternoon. With
partly to mostly sunny skies by afternoon across much of the
forecast area...high temperatures are expected to rise into the
lower 60s to middle 70s.
.LONG TERM...(Thursday night through Wednesday)
Issued at 252 PM CDT Wed May 22 2019
For Thu night thru Sat night: main fcst concerns this period are
SHRA/TSRA chances Thu night/Fri and potential rain amounts.
Model runs of 22.12z in good agreement for the shortwave ridging
aloft from Thu to be rather transient. This as the mid level low
over the Rockies lifts into the northern plains as a strong piece of
shortwave energy rotates around its east side Thu night, then toward
Man/western Ont Fri. Overall trend is a bit slower than the earlier
runs with these features Thu night/Fri. Good agreement for the
trough to continue filling/weakening as it passes north of Lk
Superior Fri night with rising hgts/westerly flow over the region
Sat/Sat night. Thu night thru Sat night fcst confidence is generally
good this cycle.
Slowing trend of the models Thu night/Fri delays the arrival of the
deeper moisture/saturation and lift into the overnight hours of Thu
night, with Thu evening continuing to trend dry across most if not
all of the fcst area. PW values of 1.25 to 1.5 inches (around 2 std
deviations above normal - NAEFS) progged to spread across the area
late Thu night/Fri morning as deeper layered forcing/lift and some
MUCAPE spreads in as well. Most if not all models spreading some
SHRA/TSRA NE into/across the fcst area later Thu night/Fri morning,
just differing on the details of where the stronger, more persistent
convection may be during the period. Consensus rain chances in the 50-
80% range spreading NE across the fcst area later Thu night/Fri are
reasonable. See hydro section below for the rain/QPF details. Models
hold the moisture plume over the SE side of the fcst area late
Fri/Fri evening. This as hgts aloft would be falling, the sfc front
would be approaching and some sfc-700mb thermo-dynamic forcing
continues. Models differ on the NW extent of convection Fri
afternoon/evening, with GFS further NW than the others. If GFS is
more correct, SWODY3 may have to be shifted to the NW as CAPE/shear
over the SE side of the fcst area may well support a few strong/
severe storms a few hours either side of 00z Sat. Consensus is for
the sfc front to be south of the area Sat/Sat night with quiet
westerly flow aloft and weak high pressure building in. GFS again
slower with front and brings a weak impulse or 2 thru the flow for
Sat and would spread precip chances across the south half of the
fcst area. Some small consensus SHRA/TSRA chances across NE IA/far
SW WI Sat afternoon/evening OK until the details sort themselves
out. Blend of guidance highs closer to normal Fri then even above
normal for Sat appear well trended for now.
For Sunday thru Wednesday (days 4 to 7): main fcst concerns this
period are SHRA/TSRA chances Mon thru Wed and potential rain amounts.
Medium range model runs of 22.00z/22.12z in reasonable agreement for
one shortwave trough to pass north of Lk Superior Sun/Sun night
while troughing/a mid level low deepen over the southwest CONUS.
Detail difference increase for Mon/Wed but overall trend is for the
southwest CONUS troughing to lift NE into/across the central CONUS
Mon into Wed, potentially phasing with northern stream energy over
the mid/upper MS valley by mid-week. Day 4-7 fcst confidence is
generally average this cycle.
Area to be between systems Sun, one north and one well west. Sunday
trends quiet under westerly flow aloft and weak sfc high pressure
drifting across the region. By Mon (Memorial Day) lead energy out of
the western CONUS troughing develops low pressure into the central
plains with increasing lower level moisture/lift ahead of it quickly
spreading NE into the Upper Midwest and SHRA/TSRA chances back in
the fcst already by Sun night. This wave/energy to pass Mon, with
the main portion of the trough, sfc low and its SHRA/TSRA chances to
lift toward/across the region Mon night/Tue. Potential phasing of
this troughing and northern stream energy dropping out of CAN would
drive a stronger cold front across the region Wed, for continued
SHRA/TSRA chances. Blend of the guidance highs near the late May
normals for Sun, then below normal with more clouds and the
SHRA/TSRA chances Mon-Wed reasonable at this time.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1101 PM CDT Wed May 22 2019
The main concern with this set of forecasts is whether MVFR
ceilings are going to move in late tonight or not. The area of low
pressure at the surface has moved into north-central Minnesota and
still has some MVFR ceilings around it. However, on the south and
west side of the low, some improvement in the ceilings has
occurred with primarily VFR conditions now. The RAP through the
evening has trended toward the ceilings being VFR for both
airports when the clouds come in late tonight and have moved both
forecasts that way as well. These clouds are still expected to
scatter out by late morning/early afternoon. Still enough gradient
to produce some wind gusts to around 20 knots for much of the day
Thursday.
&&
.HYDROLOGY...(Thursday night/Friday)
Issued at 252 PM CDT Wed May 22 2019
Area shaping up to get another round of 1/2 to 1 inch of rain Thu
night/Fri. This on top of soils already wet/saturated from the
recent rains of Sat night/Sun and Tue night, with potential for this
round of rain to produce more runoff and rises on area streams and
rivers. Models at odds on where the heaviest rains may fall, some
north of I-90, some south, but with PW values progged into the 1.25
to 1.5 inch range, potential is certainly there for any TSRA to be
efficient rain makers. Will issue an ESF for the more widespread
rains and river rise threat late in the week into the weekend.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...DTJ
LONG TERM....RRS
AVIATION...04
HYDROLOGY....RRS
Area Forecast Discussion
National Weather Service Des Moines IA
640 PM CDT Wed May 22 2019
.DISCUSSION.../Tonight through Wednesday/
Issued at 321 PM CDT Wed May 22 2019
Broad upper level low is spinning near west central Minnesota as
seen on GOES-East Clean IR imagery early this afternoon. The
pressure gradient remains tight across the state between the upper
low`s associated surface low over northeast South Dakota and high
pressure over the Southeast US. This has resulted in sustained winds
of 25 to 35 mph with gusts topping 40 mph in a few spots over
northern Iowa late this morning and early this afternoon. Otherwise,
in the Day Cloud Phase Distinction RGB, scattered cumulus clouds
denoted by the cyan/blueish coloring are rotating cyclonically
around this low over northwest Iowa. Farther south, thin areas of
high clouds denoted by a pinkish color extend from the Four Corners
Region into northern Illinois. This lines up well with the jet
location per hand analysis of the 12z 250mb upper air map that had a
130 knot jet over southwest Kansas. This jet is over southeast
Nebraska and entering southern Iowa early this afternoon per GOES-
East derived motion winds between the 250mb and 350mb level. As this
jet continues to lift northeastward, Iowa will be under the right
entrance region of this jet. With a weak baroclinic boundary over
southeast Iowa and warm air advection passing over the area late
this afternoon into this evening, this phasing of thermodynamic and
kinematic forcing will foster thunderstorms to develop. Morning
trends in high resolution guidance suggest that the best chance will
be over our far southeast forecast area such as Davis County and
less so with Appanoose and Wapello Counties. This is where the best
instability will lie and points to the south with 1000 to 1500 J/kg
of CAPE and deep layer shear at or above 60 knots from a variety of
CAMs such as recent runs of the HRRR, the 12z Texas Tech 42 member
WRF ensemble, and the 00z NCAR Ensemble. HRRR updraft helicity
tracks have trended out of our forecast area with the 00z NCAR
ensemble and the 00z and 12z runs of the HREF having updraft
helicity tracks over just far southeast Davis county. Given the
instability and shear, if storms do develop and track over our
southeast forecast area, they will have the potential of large hail
and gusty winds primarily.
As a weak ridge axis passes over the the region, this will provide a
quiet day across the state. This will be short-lived as the
baroclinic zone south of the state begins to lift northward as a
warm front late Thursday into Thursday night as a shortwave trough
lifts northeast out of the western US trough. As the low level jet
strengthens mid-evening and overnight and instability bumps up
slightly, will see storms spread northeastward across the state.
Moisture will also return back to the state with the warm front
lifting into Iowa with the precipitable water values peaking between
1.5 to 2 inches from Thursday night through Friday night. Severe
storms in the way of hail and gusty winds Thursday night are
possible given the strong deep layer shear. In addition, heavy
rainfall is likely with 1 to 2 inches and locally 3 inches of rain
possible Thursday night into Friday morning in a narrow corridor.
Models at this juncture do not have a good handle on exact location
with the NAM/GFS favoring central into northern Iowa, the CMC
regional over southern Iowa, and CMC hemispheric and ECMWF over
northwest Iowa. While flash flood guidance at 3 hours and 6 hours is
2 and 2.5 inches respectively, isolated flash flood is possible if
higher end amounts come quickly. More concerning is that this will
further prime corridors for flash flooding in the coming days.
Instability and deep layer shear will remain sufficient on Friday
into Friday night for storms including strong to severe ones,
especially over the southeastern 2/3rds of the states that are in
the warm sector. This will also be the location where the heaviest
rainfall is expected Friday afternoon and night. The boundary will
push through the state on Saturday, but hang up just south of Iowa
later this weekend into next week. Instability and deep layer shear
will continue to be over the region so there will be chances for
thunderstorms in the favored later afternoon and overnight hours
through early next week. While locations may change depending on the
location of the boundary, southern Iowa at this point looks most
favored for thunderstorms chances through early next week.
&&
.AVIATION.../For the 00Z TAFS through 00Z Thursday evening/
Issued at 640 PM CDT Wed May 22 2019
Gusty winds to diminish this evening and turn more westerly
tonight into Thursday. Winds will pick up a bit Thursday before
becoming more northwesterly late in the forecast period. Clouds
likely to diminish this evening as well with some mid/high clouds
possible Thursday. An shower or storm may impact KOTM this
evening.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
DISCUSSION...Ansorge
AVIATION...Beerends
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1158 PM EDT Wed May 22 2019
.AVIATION...
Right entrance region dynamics will support a zone of frontogenesis
that will lift out of the mid Mississippi River Valley and into the
Central Great Lakes Thursday morning. Frontogenesis aided by
nocturnal low level jet will lead to significant 875-575mb theta e
advection directly through Southeast Michigan in the 09-13Z time
window. High degree of warm air and moisture advection will support
MVFR to potential IFR cig during the precipitation. Given VWP, added
a time period of non convective low level wind shear. Hi res
consensus continues to highlight a potential for thunderstorm
activity, some of which could be robust given impressive forecast of
900-700mb lapse rates. Strong convection is not guaranteed because
of very dry air in the 7000-12000ft layer and likely active
subsidence at and below 5000 ft agl. Projected warm temperatures off
of the deck ensures very stable conditions in the lowest 2000 ft
agl. Well mixed west winds are forecasted Thursday afternoon 25 to 30
knots.
For DTW...Shower and potential thunderstorm time window at DTW is set
for 09-13Z.
.DTW THRESHOLD PROBABILITIES...
* Low to moderate confidence in thunderstorms impacting terminal
Thursday morning.
* Medium confidence in cigs aob 5000 overnight
* Low potential to reach crosswind thresholds Thursday afternoon.
&&
.PREV DISCUSSION...
Issued at 316 PM EDT Wed May 22 2019
DISCUSSION...
Mid level drying has been expanding across Se Mi in the wake of the
earlier showers. Some afternoon destabilization may occur along the
back edge of the mid level moist axis. Recent hi res guidance
suggests that any convective initiation off this will be comfortably
south and east of the forecast area. Otherwise, the mid level dry
air advection this evening will continue to support full to partial
clearing. Strengthening low level southwest flow during the night
will help drive the surface warm front now lifting toward NW Indiana
across Srn Mi. Ongoing low level warm air advection and clearing
skies will support late day max temperatures in the 60s, pushing low
70s across the south. Low level warm air advection within the
southwest gradient tonight will limit the degree of boundary layer de
coupling, leading to a relatively mild night with mins in the upper
50s to low 60s.
The upper low and associated sfc low now rotating into Minnesota
will traverse Lake Superior late tonight/Thurs morning, driving a
cold front into Lower Mi late Thurs morning. A strengthening low
level southerly jet (near 60 knots) will transport a plume of mid
level moisture and elevated instability into nrn Illinois and Lake
Mi/wrn Lower Mi overnight. This is expected to result in convective
initiation in these regions. There is actually fairly good agreement
that this convection will support development of a meso scale
convective vorticity max(s) set to traverse Se Mi early Thurs
morning. This will also allow the low level jet to veer toward Se
Mi, transporting the mid level theta e plume and instability axis
into Se Mi. This will warrant a good chance for
showers/thunderstorms in the 09Z to 14Z time frame Thurs. Although
any storms early Thurs morning are not expected to be rooted in the
boundary layer, steep mid level lapse rates will support fairly good
cape density aloft. The RAP actually brings 0-3km MU CAPE up to 1500
j/kg in by 12Z Thurs. So can not rule out the possibility of a few
stronger storms capable of gusty winds and small hail.
The passage of the sfc cold front by early Thurs afternoon will
drive the better instability to the east, with slightly colder and
drier air advecting in from the west during the afternoon. A
deepening daytime mixed layer will offset the cold air advection to
a degree, supporting high temps well into the 70s; possibly a few
low 80s. 30+ knot winds within the mixed layer will support a rather
windy afternoon on Thursday, gusts likely topping 30 MPH at times. A
building mid level ridge across the Great Lakes will drive sfc high
pressure into Se Mi Thurs night into Friday, supporting cooler and
dry conditions.
A cold front moving through the Great Lakes on Saturday will lead to
a likely chance for showers and storms through much of the day.
Ahead of frontal passage which currently looks to occur during the
evening, gusty southwest winds will develop given a decent gradient
in place between low pressure over Ontario and high pressure over
the SE CONUS. A deep mixed layer and 850mb temps around 15C will
elevate highs to the upper 70s and lower 80s. There will be a chance
of strong storms in the afternoon and evening with just enough shear
and instability in place.
The front will stall over the Ohio Valley Sunday into Monday as high
pressure builds into the Great Lakes. There will be a chance of
showers and storms over the southern counties as a series of weak
shortwaves moves over the frontal surface, otherwise mostly dry
conditions are expected. The better chance for rain across all of SE
Michigan comes late Monday into Tuesday as a low pressure system
lifts through just northwest of us and pushes the front back
northward as a warm front. Another chance for rain on Wednesday as
another low lifts through. The early to mid week will see highs in
the 70s and lows in the 50s.
MARINE...
Southeasterly to southerly flow to hold through the afternoon and
evening as a warm front continues to push across the Great Lakes.
Wind direction to veer overnight through Thursday afternoon, turning
southerly and eventually southwesterly as strong low-level winds and
diurnal mixing acts to bring breezy conditions to the marine areas.
As a result, a series of small craft advisories will be in effect
for tonight and tomorrow. Small craft advisories for outer Saginaw
Bay and the northern Thumb start tonight, tied to the southeasterly
flow which will act to increase wave heights towards the three foot
mark. The advisory is then expanded for all of the Saginaw Bay and
all of the Lake Huron shoreline as the increased mixing depths allow
wind gusts up to 25-30 knots to persist late Thursday morning into
the evening, the strongest of which will be seen over the Saginaw
Bay. In addition to the small craft advisories, showers and
thunderstorms tied to the cold front are expected overnight into
daybreak, which has the potential to produce gusty winds. High
pressure will then expand across the Great Lakes late Thursday into
Friday which will relax wind speeds and will allow the advisories to
drop-off.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory from 8 AM to 10 PM EDT Thursday for LHZ422-442-
443.
Small Craft Advisory until 10 PM EDT Thursday for LHZ421-441.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
AVIATION.....CB
DISCUSSION...SC/TF
MARINE.......AM
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Lincoln IL
934 PM CDT Wed May 22 2019
.UPDATE...
Issued at 923 PM CDT Wed May 22 2019
Area of storms continuing to develop and move into Central IL
mostly NW of the IL River valley this evening. Ongoing potential
severe weather the main concern, and only minor updates to the
forecast are required at this point.
To the severe threat, an area of instability out ahead of the
advancing storms providing a little bit of fuel...when able to
lift through the mixed layer cap. Plenty of shear in place, bulk
shear in the 50-60kts, to assist in the development and counter
any suppression of the storm genesis. Threat will remain in place
for damaging winds and isolated tornadoes through the evening in
the watch area.
&&
.SHORT TERM...(This evening through Thursday)
ISSUED AT 251 PM CDT Wed May 22 2019
Although not much evidence in wind field, nice moisture
discontinuity evident across northwest Missouri into western
Wisconsin with dew points generally in the 50s and temps in the
70s to the southeast and 40s to near 50 dewpoints and temps in the
50s and 60s northwest. This boundary will shift southeast in
response to surface low over southwest Minnesota pulling quickly
out to the northeast. As the boundary moves southeast it will
encounter an increasing unstable environment.
One missing factor that is currently not evident is convergence
along the discontinuity. 12z models suggest a low-level jet will
develop this evening and the interaction of the jet with the
boundary will be sufficient to focus moisture and enable the
development of convection which will tap into the instability.
The LLJ will also provide a good source of shear producing
effective SRH around 300 m2/s2 this evening.
The intensity of the convection and the speed at which the
boundary can move southeast overnight depends on the strength and
organization of the cold pool. Initial threat this evening to the
northwest of the Illinois River will likely be large hail,
localized gusty winds, and possibly a tornado. As the system
becomes better organized the main threat of straight-line damaging
winds will become the primary threat. Late tonight the instability
should diminish and the storms should weaken.
Models do differ on the level of organization and therefore how
far the line gets overnight. This will have a bearing on whether
any residual threat remains for Thursday. If the front stalls as
expected in the southeast forecast area some threat of storms
refiring in the afternoon south of I-70 will be possible. If a
cold pool doesn`t push the storms southeast, development on
Thursday could be further north across the heart of the forecast
area. Location of the boundary will also have implications as to
the temperatures tomorrow. May be a significant gradient between
upper 70s north to approaching 90 in the southeast.
.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 251 PM CDT Wed May 22 2019
Overall pattern changes little into next week with occasional
waves riding along the downstream side of the long-wave trough
over the Great Basin and southwest U.S. Models in decent agreement
with the general pattern. With the boundary oscillating across
the area in response to the waves. Blend of medium-range models
keep at least a chance of rain in some part of the forecast area
through the period. WPC 7-day QPF suggests highest rain threat
will be in the Illinois Valley where 3 to 4 inches of rain will be
possible between now and mid-week next week.
With split flow and northern stream remaining mostly north of the
Canadian border, temps should be above normal for the end of May.
There is some indication that phasing may be possible by the end
of the period and some cooler air may advect into Illinois, but
the solution envelope is all over the place as evidenced by the
latest 12z GEFS suite showing anything from mid-80s to mid-60s
next Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 650 PM CDT Wed May 22 2019
Scattered thunderstorms have developed from east of KMLI
southwestward to near KMCI early this evening. Models have been
consistently showing the cells forming into a line this evening,
then shifting toward the I-55 corridor by midnight. Based on radar
trends and latest HRRR forecast, have included TEMPO group for
thunder at KPIA between 03z and 06z...and further southeast at
KDEC/KCMI between 07z and 09z. Once the convection exits, a
period of showers will persist for a couple of hours before the
precip comes to an end from northwest to southeast overnight.
Winds will initially be S/SW with gusts of 20-25kt early this
evening, then will veer to the W by Thursday morning.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...HJS
SHORT TERM...Barker
LONG TERM...Barker
AVIATION...Barnes
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
711 PM CDT Wed May 22 2019
.MESOSCALE DISCUSSION...
711 PM CDT
A few showers and storms developed a bit earlier across portions
of northeastern Missouri, but have struggled to maintain intensity
as they progressed into northern Illinois, likely as they outran a
narrow plume of increased low-mid level moisture. With limited
instability present across our region, think the severe threat in
the immediate term (over the next hour or two) appears fairly
low although a stronger storms will be possible across our
northwest.
However, strong flow in the 850-700 mb layer will continue to
transport a higher theta-e airmass into the region over the next
several hours along with an associated uptick in elevated
instability. Based on the most recent guidance, it appears as if
the most favorable axis of moisture and instability will develop
essentially across the southeastern half of the CWA (perhaps from
a La Salle to Midway line). Farther to the north and west of this
line, increased westerly flow aloft should drive a drier airmass
eastward, reducing the amount of instability available to support
more robust thunderstorm development.
The kinematic environment will be favorable for severe storms,
with deep layer shear values pushing 50-55 kts at times. Recent
point soundings reveal a lingering layer of warm air in the mid-
levels centered around 500 mb, which will limit the overall amount
of instability this evening, but steep lapse rates do exist in
narrow layers under 500 mb which, when combined with the
aforementioned robust deep layer shear, will support rotating
thunderstorms with a potential for large hail (quarter to golf
ball sized based on SHIP parameters). In addition, recent CAM
guidance suggests a propensity for storms to quickly grow upscale
into a surging MCS later tonight, which could deliver an
increasing threat for strong to locally damaging wind gusts
potentially for locales along and east of I-55 later tonight.
Current thinking is the main window for severe weather across our
region will be during the 9 PM to 3 AM timeframe or so.
While plenty of clockwise curvature is noted in regional
hodographs this evening, we believe the tornado threat will remain
tempered somewhat by a lack of truly surface-based instability as
the low-levels begin to decouple with the loss of daytime
heating. That said, if a surging line of storms can get going, any
segments that orient in a more NW to SE manner would have access
to ample low-level shear for a spin-up QLCS tornado, once again
mainly for locales east and south of I-55.
Finally, while a threat for heavy rainfall exists, the push of
westerly momentum aloft should keep things moving along tonight--
especially if a MCS materializes as many of the CAMs indicate. As
a result, while locally heavy rainfall will be possible but this
threat should remain fairly localized and there are no plans to
hoist a Flash Flood Watch at this point.
Carlaw
&&
.SHORT TERM...
206 PM CDT
Through tonight...
Massive long wave trough covering about the western 2/3rd of the
U.S. has multiple smaller scale circulation pivoting within the
broad upper trough. Pronounced upper low evident on water vapor
imagery is beginning to shear out over the upper Mississippi
Valley and northern Plains early this afternoon. Water vapor
imagery does show jet streak nosing east from the central High
Plains to the mid-Mississippi Valley early this afternoon, which
is resulting in strong kinematic fields for mid-late May over the
region. At the surface, warm and moist air is surging north on
gusty southerly winds across the region with a cold front laid out
from Iowa south to southeast Kansas.
On GOES-16 differential water vapor imagery, there does appear to
be a subtle shortwave trough on the southern periphery of this
jet. Numerical guidance seems to be keying in on this relatively
subtle looking disturbance as the impetus for widespread
convective development, initially over Ozarks, then continuing to
develop northeastward ahead of the cold front into northern and
central IL this evening. Convective allowing models are
forecasting a fairly high coverage of storms, however, this
activity is progged to be well ahead of the front, so given the
somewhat nebulous forcing could see more discrete or semi-discrete
convection initially before activity likely begins to congeal
into a more linear feature late this evening into the overnight
hours.
There could be a short window early in the event where we could
see a supercellular tornado threat in our southwest CWA before
boundary layer cooling leads to convection becoming rooted above
the boundary layer. However, the greater threat will likely be
from large hail and damaging winds. Given the very strong shear
profiles (0-6k bulk shear values 50-60kt) and MUCAPES progged to
increase to over 2000 j/Kg, am quite concerned with the large hail
and damaging wind threat tonight.
While storm motion tonight should be such that there doesn`t look
to be a threat for training cells, RAP and NAM forecast PWATS
approaching the 99th percentile for mid-late May with values
progged to approach 2". In addition, high freezing levels (>13kft)
should allow for deep warm rain processes, meaning storms tonight
could be very efficient rain producers. One and three hour flash
flood guidance is generally between and inch to an inch and half,
which storms tonight potentially reaching those values. Considered
a flash flood watch, particularly for southern and eastern
portions of the area, but given the threat for training not
looking particularly high, opted to hold off for now. Thinking any
flash flood threat tonight will be on the lower end of the
spectrum and fairly localized, with greater chance of urban &
small stream flood advisory type minor flooding.
Convection should begin to weaker overnight as low level jet
veers and atmosphere slowly stabilizes, with storms likely moving
out toward or just past 12z Thursday morning.
- Izzi
&&
.LONG TERM...
250 PM CDT
Thursday through Tuesday...
The theme of the extended will be several days of more
spring/early summer-like temperatures, occasional periods of
showers or storms (though not a total wash out), then a return to
seasonal or slightly cooler conditions to wrap up the holiday
weekend.
We should be able to wring out a pretty nice day on Thursday. Most
of the convective activity will be finished by daybreak tomorrow,
possibly a few lingering showers east of the Chicago area. In
spite of having a frontal boundary clip the area, fairly warm
airmass will remain in place across the region and we should have
plenty of sunshine. Therefore expect another warm day with
readings in the lower to mid 70s north to low 80s north.
An upper ridge will slide overhead tomorrow night, and this will
shift surface high pressure off to our east. The effective front
will lift back north as a warm front late tonight into Friday.
This will bring convective chances back to the lower Great Lakes.
The stronger low level jet will focus along the Mississippi Valley
and points east, but the warm front will not completely clear the
area, some of this activity will sneak into our area, especially
for areas north and west. With the frontal position fairly
close by, there could be at least showers with this initial wave
Friday morning.
The ridge will flatten Friday night into Saturday and place the
effective front, and northern periphery of the ridge, in a more
precarious position for increased shower and thunderstorm
concerns. While it does not appear it will be raining all the
time, those with outdoor plans should keep an eye of the weather
as the airmass will be fairly moist (PWATs above 1.5" at times)
and subtle waves can easily produce heavy rainfall and lightning
and may be tough to time, through most of the holiday weekend.
The first period of concern will come late Friday into Saturday
where severe storms may be possible upstream toward the
Mississippi River, but could still pose some risk in our area
Friday night. Corfidi vectors suggest some training storms in a
very high PWAT airmass again of 2" or more, or near highest values
for late May, will pose a heavy rainfall/flooding threat before
the forcing weakens. After this, model placement of the effective
front is a bit more nebulous, but this will play a significant
role in precip chances through the weekend.
It will also remain mild through Saturday, though Sunday model
guidance does shove the front a bit farther south leading to a
likely cooler day Sunday with more of a northerly wind, and cooler
onshore flow at the lakefront also. Challenging to get into
specifics, but this same theme of seasonal temperatures and
chances of storms still hold for Memorial Day and even into mid
week.
KMD
&&
.AVIATION...
For the 00Z TAFs...
Main concern is thunderstorms this evening/tonight, which will
affect all the terminals eventually. South-southwest winds are
still gusting to around 30 kt approaching 00z, but gust magnitude
should come down with sunset. Regarding TSRA trends, SHRA and
isolated TSRA over northwest IL should affect RFD over the next
few hours. Coverage of actual lightning activity is quite low
right now, so held with a VCTS and temporary SHRA at RFD for the
first couple hours of the TAF. Instability is expected to increase
with time this evening, with a corresponding increase in coverage
of TSRA, including the potential for strong to severe storms. Did
not make any changes to timing for the Chicago area terminals,
with best window appearing to be between 05z and 09z, latest at
GYY. Latest thinking is that best chance for severe criteria
storms capable of large hail and/or damaging winds is
approximately south of a VYS to MDW line. The risk is certainly
not zero north of that line, with near severe storms still
possible. Maintained mention of gusty southwest winds in the
TEMPO TSRA and if trends suggest likelihood of higher speeds than
that at any of the sites, will update as needed.
After the TSRA exit east later tonight, cold front will approach
the area. Can`t rule out a small window of MVFR CIGs in the early
morning, but it would be brief if it occurs, with VFR the rest of
this 24-30 hour TAF cycle. Cold front will move across the area
by mid to late morning Thursday, shifting winds to west and then
west- northwest with time. Soundings support gusts into the 20-25
kt range during daytime hours, and possibly briefly higher at
times. On Thursday evening, winds will shift to northeast in
response to low pressure lifting north over the Plains and a
backdoor front. Will have to monitor for any earlier timing of
this northeast wind shift. After the end of the ORD/MDW 30-hour
TAFs, there may be low clouds and/or FG/BR drifting in off Lake
Michigan.
Castro
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...nearshore waters
until 9 PM Wednesday.
&&
$$
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Area Forecast Discussion
National Weather Service Paducah KY
840 PM CDT Wed May 22 2019
.UPDATE...
Issued at 840 PM CDT Wed May 22 2019
A large mesoscale convective system is organizing over western and
northern Missouri. Once this system acquires an organized cold pool
as it moves into central and northern Illinois, there will be at
least a small southward component of motion. Corfidi vectors are
directed almost due southeast after midnight, however speeds become
less than 10 knots by morning. The hrrr model brings the leading
edge of the mcs nearly to Interstate 64 by morning, with isolated
activity developing along the Ohio River Valley.
Given the large reservoir of very moist and unstable air feeding
northward into these storms on a 30 to 40 knot flow at 850 mb, the
convective system should remain fully intact through the early
morning hours. The forecast will maintain chance pops after midnight
for much of southern IL and sw Indiana, with slight chances down to
the Ohio Valley and parts of se Missouri. Some strong or even
possibly severe wind gusts cannot be ruled out in association with
the leading edge of the convective outflow.
&&
.SHORT TERM...(Tonight through Friday night)
Issued at 253 PM CDT Wed May 22 2019
Convection across the KHOP area will continue to shift east late
this afternoon. Upper air model data indicates subsidence across
the rest of the area, that should generally suppress any
additional development into this evening. Meanwhile strong to
severe thunderstorms can be expected to our west and north into
tonight. Later in the night, remnant activity could make its way
into the northern 1/2 of our area as it weakens. We will have some
low PoPs in to account for this. In whatever form this takes on,
any boundaries left over into Thursday could serve as a focal
point for convection. Again, best chances seems to be central and
northern sections, north of the Ohio, though isolated activity
cannot be ruled out any location. A few strong to isolated severe
storms cannot be ruled out. But this is highly conditional on
development. The NAM shows little if any activity, while other
CAM`s models and the GFS are more bullish on convection. For now,
we do not have any PoPs lingering into the evening. But the mid
shift might want to consider lingering a chance longer as the
latest data is trending that direction.
Thursday night through Friday night should be mainly free of
convection. With the area well in the warm sector, only convection
will have a potential impact on temps in the short term.
Otherwise it will be quite warm and muggy, more typical of mid
July norms vs. what we should see approaching the Memorial Day
Weekend.
.LONG TERM...(Saturday through Wednesday)
Issued at 253 PM CDT Wed May 22 2019
The forecast confidence associated with this forecast package is
higher than average(60-65%), despite the complex interplay among the
1)multi-low western U.S. trough and timing of systems from the
eastern Pacific injecting into the trough, 2) the closed lows and
transformation of systems across the Great Lakes and southeast
Canada, and 3) the broad southeast U.S. ridge.
The WFO PAH remains along the gradient between the thermal/pressure
ridge to the southeast and the baroclinic zone to the north and
northwest. The ECMWF since earlier this week has been keeping the
ridges influence more dominant over the WFO PAH forecast area versus
other numerical models in recent days. However, latest runs tend to
support a dryer (PoP-wise) solutions for most of the WFO PAH
forecast area with the wettest time periods Sunday and then again
late Tuesday night and Wednesday.
With most of the precipitation expected to fire as MCS (Mesoscale
Convective Systems) along a stationary front (embedded in a narrow
baroclinic zone along the periphery of the southeast U.S. ridge
("ring of fire") to the north and western quadrants outside the WFO
PAH forecast area. Anticipate any convection that moves into the WFO
PAH forecast area will be along the edges of southeast Missouri and
southern Illinois (along the I-64 corridor) from decaying MCS and
outflow dominated thunderstorm clusters that move tangential from
the mean propagation pathways of the MCS`s. The time of day, as
well as cloud cover, differential heating, and storm scale
thermal/vorticity eddies aloft will determine the southward extent
of convection into the WFO PAH forecast area. On days where the
southeast U.S. retrogrades northwest in response to the movement of
the western trough and Great Lakes lows, some showers and
thunderstorms may track southeast over parts of southeast Illinois,
southwest Indiana, and northwest Kentucky.
For Memorial Day weekend there will be higher than normal chances
for southern counties of the WFO PAH forecast area (especially those
counties along the TN/AR/MO/KY borders to remain drier versus
further north.
Temperatures will remain normal through the extended period. Heat
indexes during the warmest time period should not rise much above
the lower 90s.
&&
.AVIATION...
Issued at 635 PM CDT Wed May 22 2019
Southerly surface winds less than 12 knots overnight are forecast to
shift to a more southwesterly direction on Thu, and possibly gust
above 20 knots in the early afternoon. Meanwhile, cigs/vsbys are
forecast to remain VFR through the 24 hour TAF period, although
there is a small possibility of vsby restrictions with showers or
thunderstorms that may creep into the i-64 corridor overnight as
part of a decaying mesoscale convective system. VCSH was mentioned
at KMVN for now. Much like Wed, there should be a scattered to
broken cumulus deck during the daylight hours.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...MY
AVIATION...DB
Area Forecast Discussion
National Weather Service Phoenix AZ
610 PM MST Wed May 22 2019
.UPDATE...Updated aviation discussion.
&&
.UPDATE...Fire Weather Discussion.
&&
.SYNOPSIS...
Another unusually cool weather disturbance will pass through the
region today and Thursday resulting in temperatures some 15 to 20
degrees below normal along with light showers affecting portions
of southern California and Arizona. Winds will also continue to be
breezy to windy at times, especially near higher terrain features.
Temperatures will rapidly warm into the coming weekend, though
readings will still remain slightly below seasonal normals. Yet
another weather system will move into the area early next week
providing the next bout of cooler weather.
&&
.DISCUSSION...
A blocked hemispheric flow pattern will persist into early next
week ensuring deep negative height anomalies and unsettled weather
remain entrenched over the western Conus through at least the
Memorial Day holiday weekend. Even beyond the weekend, some
measure of troughing may linger over the region into late next
week further extending the string of cool weather. While scattered
showers will be common over parts of the forecast area later
today into tonight, the anomalously cool weather will be one of
the more obvious impacts with afternoon highs today 20F below
normal and 15F below normal on Thursday.
Outside of the temperature anomalies, winds will be the other
primary impact from this stalled pattern. With one shortwave
lifting through the Central Plains and another diving south along
the Sierra ridge, a pronounced quasi-zonal jet core has settled
across the Southwest. Wind advisories continue over portions of
SE California into this evening, focused across the western half
of Imperial County. Elsewhere, winds today will be markedly
lighter then yesterday, but still quite breezy.
Latest high-res HRRR and NAM 3km model output continues to show a
vorticity lobe moving into the region ahead of the main upper low,
as it moves across SE CA into SW AZ. The combination of lift ahead
of the vort lobe, very cold air aloft (500mb temps in the -20C to -
23C range, which is very close to record low values for this time of
year), and decent moisture (PWAT`S in the 0.50 to 0.5 inch range) is
expected to produce some light shower activity across northern
Riverside county in SE CA this afternoon/evening and across south-
central AZ later this evening/overnight. A few thunderstorms are
possible as mid-level lapse rates steepen, but TS development will
likely be limited by the fact that the coldest air aloft will lag
behind the area of best lift/moisture. Most locations that do
receive rain will only see very light amounts (less than 0.10 inch),
but areas that do get TS could see a bit more. Any thunderstorms
that do develop could produce locally gusty winds as well.
The deep closed low will quickly shift north-northeastward on
Thursday leaving behind a very pleasant air mass. The low center
is forecast to be over northern Utah by Thursday afternoon, but
the trough axis will become stretched well to the southwest
keeping upper level heights over the Desert Southwest well below
climatological normals. Although the trough axis will persist
through Friday, heights aloft will gradually rise allowing decent
warming. Highs by Friday will warm back into the upper 80s, before
topping out in the lower 90s on Saturday. The next deep trough is
shown diving down the West Coast Saturday into Sunday before
taking an eastward turn through the Desert Southwest late Sunday
into Monday. This will bring another cool down for our area into
early next week, but little if any chance of rainfall. Thereafter,
the synoptic pattern looks to become a bit more normalized
allowing a gradual increase in temperatures through next week.
By late next week, temperatures look to be back to around seasonal
normals.
&&
.AVIATION...Updated at 0100 UTC.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Cloud coverage has increased, with BKN-OVC around 8-9 kft, and
wind gusts have subsided in response. Though, W/SW winds aob 10
kts will continue through most of the night. Scattered showers are
expected to spread east into Maricopa county this evening,
reaching the metro area after 3Z-4Z. Evaporative cooling in the
vicinity of showers should lower CIGs to around 6 kft with FEW
possible to 5 kft. The showers may also lead to some gusts up to
20 kts. An isolated storm with gustier winds and a few flashes of
lightning cannot be ruled out between 8Z- 12Z. As showers exit
after 11Z- 12Z, winds may see a brief shift to the E or SE and
then return to the SW by late Thursday morning, with speeds still
aob 10 kts.
Southeast California/Southwest Arizona including KIPL and KBLH:
A weather system pivoting through the Desert SW will keep westerly
winds breezy at KIPL, with gusts up to 30 kts for the next few hours
before dropping off and becoming more isolated around 20-25 kts
through tonight. Winds will be lighter at KBLH, around 12 kts or
less sustained. Vicinity showers to KBLH are expected through 5Z,
with a few flashes of lightning possible, before shifting off to the
east. Clouds scatter through early Thursday morning and winds will
be lighter Thursday at both terminals, sustained around 10-14 kts
with gusts up to 20-24 kts in the afternoon.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Saturday through Wednesday:
Temperatures will warm closer to normal over the weekend before
another weather disturbance moves across the districts during the
first half of next week providing another period of cooler,
unsettled weather. Winds will be fairly typical early in the weekend
with typical upslope gustiness while locally windy conditions
develop during the latter half of the holiday weekend. Wetting rains
are very unlikely, though a scattered passing light shower is
possible late in the weekend. Afternoon humidity levels in a 10-20%
range early in the weekend will increase towards a 15-25% level
later in the weekend with the cooler airmass while overnight
recovery will be fair to good. Warmer temperatures and drier
conditions will then return during the middle part of next week.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard operating procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory until midnight PDT tonight for CAZ562-566.
Wind Advisory until 9 PM PDT this evening for CAZ563>565-567.
&&
$$
DISCUSSION...MO/Kuhlman/Percha
AVIATION...Benedict
FIRE WEATHER...MO/Percha