Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/03/20
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1026 PM EDT Sat May 2 2020
.SYNOPSIS...
A weak disturbance and a warm front will bring some
isolated to scattered showers tonight. Above normal temperatures,
breezy conditions and dry weather will return for tomorrow
afternoon. A cold front will move through late Sunday night into
early Monday with below normal temperatures, brisk conditions and
isolated to scattered showers mainly from the Capital Region north
and west.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 1026 PM EDT...IR satellite imagery shows skies are
overcast over much of the region, as mid level clouds have
increased from the west ahead of an approaching shortwave. Radar
imagery shows some light rain showers are starting to spread
across the area, although dry low levels is allowing for some of
this activity to evaporate before it reaches the ground.
The mid level short-wave shears out, and lifts northeast of the
region. There is an increase of low to mid level warm advection
with some moisture advection for a chance of showers through the
late evening hours. We increased the PoPs to low likely and
chance values with higher values south and west of Albany. The
triple point to the weak system may move across southern and
central VT. This will be a light pcpn event based on the short
range guidance and the CAMS and we are only looking at a few
hundredths to maybe a couple tenths of an inch in a few spots.
The better chances of widespread showers will be from midnight
to 6 am across the forecast area based on the timing from the
3-km NAMnest, HRRR and ARW-WRF. A mild night is expected with
lows in the upper 40s to lower 50s valleys areas and across the
hill towns, and mid 40s over the mtns. South to southwest winds
of 5 to 15 mph are possible late.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Tomorrow...A nice close to the weekend is expected with any
isolated to scattered showers diminishing over the northern
zones including the southern Adirondacks, the Lake George Region
and southern VT. There is not any cold advection in the wake of
the weak disturbance and its weak cold front/wind shift
boundary, and the low to mid level flow remains zonal. H850
temps will actually be about +7C to +10C across the region. The
sfc to boundary layer winds shift to southwest to west with
good mixing expected to H850 or higher. We also may see some
downsloping off the Catskills/Helderbergs/eastern Adirondacks
into the Hudson River Valley/Capital Region. The west winds will
mainly be 10 to 20 mph with a few gusts around 25 mph with partly
to mostly sunny conditions. Max temps should be close to 10
degrees above normal for early May. Upper 60s to mid 70s will be
common in the valley locations and below 1000 ft. Expect upper
50s to mid 60s over the mtns.
Tomorrow Night...A southern stream system will move over the Mid
Atlantic States and pass south of the region with an increase of
clouds especially south of the Capital Region. A stronger
northern stream piece of short-wave energy will move across
southeast Canada towards the Northeast. A stronger cold front
will move southeast with limited low-level moisture to work
with. The mid and upper level trough digs southeast, and this
cold front should be moving across the region towards daybreak.
Some lake moisture could be tapped for some lake enhanced
showers. We kept a slight chance of showers for the southern
most zones for some sprinkles of light showers with the southern
stream system, and slight or low chance PoPs with the northern
stream one and its cold front northwest of the Capital District.
The cold advection will move into the region in two ribbons,
and the better surge looks again towards daybreak. Lows will
fall into the mid 30s to lower 40s over the mtns, and mainly
lower to upper 40s in the valleys.
Monday....The mid and upper level trough axis moves across the
region during the day, as the cold front clears the forecast
area by the afternoon. Brisk and unseasonably cool conditions
are expected. 500 hPa temps falls close to -25C over the region.
In the cyclonic flow and steep mid-level lapse rates some
cellular showers or lake enhanced showers are possible. H850
temps fall -1 to -2 STDEVs below normal on the latest 12Z GEFS.
The actual H850 temps on the latest GFS are -1 to -4C or so
across the region. Max temps will run at least 10 degrees below
normal. Some wet snowflakes could mix in at elevations above
2000 kft AGL. The best chance for isolated to scattered showers
will be from the Capital Region, northern and central Taconics,
and the Berkshires north and west into the southern Dacks,
western Mohawk Valley and eastern Catskills. Highs will be in
the mid 40s to lower 50s over the higher terrain, and mainly mid
and upper 50s in the valleys with a few 60F readings in the mid
Hudson Valley. Northwest winds of 10 to 20 mph with some gusts
30 to 35 mph are possible.
Monday night...The cellular showers and lake activity should
end in the evening with the upper low moving down stream and its
associated cold pool. High pressure will begin to build in from
the northwest. Enough of a sfc pressure gradient should keep
the winds up, but some decoupling is possible north and west of
Albany. Mins will fall in the upper 20s to mid 30s over the
mtns, and mid to upper 30s in most of the valley areas. We could
have some patchy to scattered advective frost in the Hudson
River Valley /including the Capital District/ and southern
Litchfield County. We do not have widespread 33-36F readings
right now, but if colder temps are realized, then we may need a
Frost Advisory where the growing season began May 1st.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
The main weather headlines in the long term will continue to center
around the transition/return to a cooler weather pattern punctuated
by a couple of precipitation chances as a series of disturbances
ride along an active west trending northwest flow aloft.
All signs continue to point to a shift in the weather pattern next
week as forecast guidances continue to advertise re-amplification of
the jet stream that will feature the re-emergence of upstream
western U.S. ridging. Additionally, the development of a high
latitude block is also with higher heights/warmer than normal
temperatures seen over Alaska and Greenland. The combination of
these weather features/signatures will support deep downstream
troughing from the poles extending southward into the eastern U.S.
giving way to a warm West U.S. vs. a cool East U.S. configuration
reflective of a +PNA/positive Pacific North American pattern, a -
NAO/negative North Atlantic Oscillation, and a -AO/negative Arctic
Oscillation. Ultimately, this will result in unseasonably cool
temperatures for eastern New York and western New England through
the extended.
The second item of concern during this period will be with regards
to precipitation chances, placement, and timing. Forecast models
continue to depict multiple impulses during the period riding along
an active west-northwest flow established between two large scale
features that could give us a couple of shots for some
precipitation. The first chance will be Wednesday PM through
Thursday with the possibility of clouds/showers lingering into early
Friday. The second shot exist Friday evening through Sunday.
During the day on Wednesday, a shortwave associated with the
northern branch will track along the southern periphery of an upper
trough and will approach the forecast area from the west-southwest
Wednesday afternoon/evening. With the past couple of ECMWF runs (00z
and 06z) from both the deterministic and ensembles coming closer in
line with the GFS suite, confidence has increased some regarding
precipitation chances Wednesday PM through Thursday. Taking a
national blend approach with heavier weight applied to the
ensembles, have maintained slight chance to chance PoPs Wednesday
afternoon/evening through Thursday.
We could get a brief reprieve late Thursday into the first parts of
Friday before a second storm system approaches from the west Friday
evening. This storm system could maintain clouds/precipitation into
Sunday with cold air advection on the backside capable of producing
a mixture of rain mixed with a few wet snowflakes in some of the
highest elevations of the Adirondacks.
High temperatures will generally run in the 50s through the extended
with lows in the 30s/40s. Normal highs for this time of year run
from 66-67F to put into perspective how unseasonably chilly it will
be this week.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Flying conditions are currently VFR with increasing mid level
clouds. Gusty westerly winds will start to decrease through the
evening with the loss of daytime heating/mixing. An approaching
shortwave trough will allow for clouds to continue to lower and
thicken this evening, with some showers possible after about
midnight or so. Within any showers late tonight, a brief period
of MVFR cigs/visibility can be expected. Winds later tonight
will be from the south to southwest at 5 to 10 kts. Any showers
should be done by sunrise Sunday.
There could be a period of lingering clouds for a few hours
after sunrise with cigs close to MVFR/VFR levels. Otherwise,
clearing will be occurring for Sunday, with VFR conditions for
all sites. Westerly winds will increase to 10 to 15 kts for all
sites, with some higher gusts (especially at KALB/KPSF).
Outlook...
Sunday Night: No Operational Impact. NO SIG WX.
Monday: Low Operational Impact. Breezy. Slight Chance of SHRA.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: No Operational Impact. NO SIG WX.
Tuesday Night: Low Operational Impact. Slight Chance of SHRA.
Wednesday: Moderate Operational Impact. Chance of SHRA.
Wednesday Night: Moderate Operational Impact. Chance of SHRA.
Thursday: Moderate Operational Impact. Chance of SHRA.
&&
.FIRE WEATHER...
West winds may gust to around 25 mph Sunday afternoon...
A weak disturbance and a warm front will bring some
isolated to scattered showers tonight. Above normal temperatures,
breezy conditions and dry weather will return for tomorrow
afternoon. A cold front will move through late Sunday night into
early Monday with brisk conditions and isolated to scattered
showers mainly from the Capital Region north and west.
The RH values will rise to 80 to 100 percent with scattered
showers tomorrow morning and then lower to 35 to 50 percent
during the afternoon. The RH values will only increase to around
70 to 85 percent Monday morning.
West winds will diminish early this evening, then increase from
the south to southwest at 5 to 10 mph overnight. Expect the
winds to increase from the west at 10 to 20 mph tomorrow
afternoon with gusts occasionally to 25 mph. The winds will
decrease to 10 mph or less Sunday night, then strengthen again
on Monday.
&&
.HYDROLOGY...
River flows will continue to lower the next few days.
A Flood Warning was issued for Mt Marion on the Esopus as it may
briefly go above its 20 ft flood stage by a few inches. It
should crest early this evening.
Most areas will see a few hundredths to a few tenths of an inch
of rain with the system tonight into early Sunday. These
rainfall amounts will have little to no effect on river levels
Dry weather will return Sunday, but another front and its
associated upper level disturbance will bring very light rain
amounts to some basins Sunday night into Monday. Dry weather is
expected to return for Monday night into the mid week with
colder than normal temps. Flows will continue to recede.
For details on specific area rivers and lakes, including observed
and forecast river stages and lake elevations, please visit the
Advanced Hydrologic Prediction Service /AHPS/ graphs on our
website.
&&
.ALY WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...None.
MA...None.
VT...None.
&&
$$
SYNOPSIS...Wasula
NEAR TERM...Frugis/Wasula
SHORT TERM...Wasula
LONG TERM...Evbuoma
AVIATION...Frugis
FIRE WEATHER...Wasula
HYDROLOGY...NAS/Wasula
Area Forecast Discussion
National Weather Service Denver/Boulder CO
842 PM MDT Sat May 2 2020
.UPDATE...
Issued at 840 PM MDT Sat May 2 2020
Main line of convection stretched along a line from Sterling down
to Castle Rock will continue to push east tonight, with strong
winds and hail being the biggest threats. A semi linear structure
is making wind more of the bigger impact and threat at this
point, but can`t rule out hail as well. HRRR has been trending
toward the Palmer Divide being more and more active with each run,
pushing into Lincoln County, where CAPE is lower but shear is
higher. Haven`t been very impressed with the HRRR today however
with it being overactive for most of the morning and afternoon.
Will continue to monitor the development of this line as it pushes
further east. One more precipitation area over the Boulder County
foothills will be pushing east across the urban corridor bringing
mostly just rain and some gusty winds, with a rumble of thunder
possible as well. Water vapor imagery showing this area
weakening, so at this time, stronger storms are becoming less
likely.
Might be seeing additional showers moving in from western
Colorado, as some of the high res models are hinting to, however
believe most of this is overdone and with loss of the sun, believe
most of these will die off. After midnight, the southeasterly
winds moving in from the eastern plains combined with a surface
low developing around Denver will draw in moist air pushing up
against the northern foothills and Cheyenne ridge. Low stratus and
possibly some patchy fog will likely spread south along the
northern urban corridor toward sunrise. Have added some fog to the
grids to account for this.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 226 PM MDT Sat May 2 2020
Strong upper level jet will continue to help spawn showers and
thunderstorms this afternoon and evening, with another round
expected on Sunday afternoon. Low clouds have hampered the
temperatures this afternoon. Showers and thunderstorms forming
over the foothills this afternoon is starting to shift east into
the I25 into northeast Larimer and northwest Weld counties. The
shear profile is not bad this afternoon with southeasterlies at
the surface and strong westerlies in the upper levels. RAP
soundings north of Denver indicate MU CAPEs around 850 j/kg this
afternoon. Marginal Risk of severe thunderstorms has been
stretched into the mountains, primarily due the strong winds
aloft. Satellite and GLM showing storms fairly active at this
time. Overall, little in the way of changes for the grids this
afternoon and evening. All this will translate eastward across the
plains this afternoon and evening, then diminish after midnight.
On Sunday, there should be less stratus around to contend with,
which will allow for temperatures to rebound into the mid to upper
70s. At the surface, southeast winds will help develop a Denver
cyclone in the afternoon, which could help kick off initiate
thunderstorms. Strong/severe possible over the northeast plains if
we can maintain dewpoints in the mid/upper 40s. MU CAPES
1100-1500 j/kg from NAM12 forecast soundings. SPC has northeast CO
under another Marginal Risk for severe thunderstorms.
.LONG TERM...(Sunday night through Saturday)
Issued at 226 PM MDT Sat May 2 2020
An upper level trough and jet embedded in the westerly flow aloft
will track across the Central Rockies Sunday night. Best lift
associated with this will be across northern Colorado and into
Wyoming. The threat for a few severe storms will linger into the
early evening before the airmass stabilizes. However, enough lift
and moisture will remain for showers and a few embedded
thunderstorms through Sunday night. The ECMWF is a little farther
south with the upper level features and shows over an inch of QPF
for far northeast Colorado Sunday night.
On Monday a weak northerly low level flow is expected to prevail
behind a cold front that pushes through early Monday morning. This
will usher in cooler air with highs in the upper 60s to lower
70s. The cooler more stable and subsidence airmass behind the
exiting system is expected to result in dry conditions. However,
the models show isolated convection will be possible. They don`t
agrees where this may occur. Will have isolated PoPs for this, but
don`t expect much for convection Monday.
A west-northwest flow aloft will prevail Tuesday as short wave
ridging takes place over the Great Basin. Drier air will be over
the area. There is a slight chance enough moisture hangs on for a
couple showers over the higher terrain south of I-70. Temperatures
will be near normal under this pattern with readings in the upper
60s to lower 70s.
For Wednesday through Saturday, models are still showing
different solutions. The general trend is a ridge over the western
states with northwest flow aloft. However, models differ on the
strength and timing of short wave troughs embedded in the
northwest flow aloft. On Wednesday, the short wave ridge slides
east across Colorado and is east of the area by late Wednesday.
This should bring warmer and dry conditions. From Thursday on,
forecast is still quite uncertain. Will continue with the trend of
near normal to slightly above normal temperatures with low PoPs.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 840 PM MDT Sat May 2 2020
Stronger northeasterly winds occurred on the backside of the line
of convection this evening. These winds are expected to transition
to southeasterly and drainage, before near sunrise a surface low
near DEN may bring in northerly winds to BJC and DEN possibly.
This could bring in low stratus and possibly fog. If this occurs,
it should only hang around ILS restrictions from the nearby line
of thunderstorms with ceilings around 4000-5000 feet agl should be
most prevalent, but could still see MVFR restrictions possible
with a stronger shower/thunderstorms. Believe most of the
terminals are now out of TS possibilities as that line moves
further southeast. Though an area moving out of Boulder County may
have a rumble of thunder or two, but this is weakening. Winds will then
back to southeast on Sunday with another chance for thunderstorms
later in the afternoon and evening.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Kriederman
SHORT TERM...Cooper
LONG TERM...Meier
AVIATION...Cooper
Area Forecast Discussion
National Weather Service Grand Junction CO
904 PM MDT Sat May 2 2020
.UPDATE...
Issued at 904 PM MDT Sat May 2 2020
Critical fire weather conditions have ceased across the lower
elevations of west-central and southwest Colorado late this
evening as winds have decreased and relative humidity has
increased. Therefore, the Red Flag Warning has been allowed to
expire.
&&
.SHORT TERM...(Tonight through Sunday night)
Issued at 219 PM MDT Sat May 2 2020
The HRRR continues to nail down the convection this afternoon. As
anticipated, storms started forming around noon in the Uinta Basin
and along the Book Cliffs where the highest CAPE was located. CAM
guidance still showing SBCAPE around 1000 J/kg over the northern
valleys so plenty of instability remains in the atmosphere for
convection. Interestingly, the HRRR has shown a second area of
stronger storms moving into our CWA in the next hour or two.
Satellite imagery and lightning detection does show a rather
disorganized cluster of convection over central Utah heading
eastward so another round of showers/storms certainly looks
possible in a few hours. Areas south of I-70 will see plenty of Cu
clouds but with no strong forcing, don`t anticipate any showers or
storms. A quick sprinkle `might` occur over the highest terrain
but that`ll be about it. Deep mixing has allowed for some stronger
wind gusts (20 to 30 mph) to reach the surface and with low
humidities in place, Red Flag conditions are being met. The Red
Flag Warnings remain in place. Most convection will die down
later this evening though a stray shower over the Divide can`t be
ruled out.
Tomorrow, a weak cool/cold front will set up just to our north for
much of the day. Some showers will form along the front over the
Uintas and just along the WY/CO border. The front will remain
fairly stationary until later in the afternoon. By 3PM, the front
will start moving and more widespread precip isn`t progged to get
going until after 9PM so with the lack of heating, any convection
looks to be fairly weak in nature. Expect some showers for the
northern mountains and surrounding foothills for the overnight
hours. Like today, areas south of I-70 will see partly cloudy
skies, some afternoon breezes in the 20 to 30 mph range and warm
temperatures.
.LONG TERM...(Monday through Saturday)
Issued at 219 PM MDT Sat May 2 2020
Another weak shortwave will be moving through our northern zones
early Monday morning through Monday afternoon. Moisture will be
lacking with this wave so we`ll see a few isolated showers,
scattered to broken skies, and that should be about it, all up
north. Maybe a rumble of thunder over the Park Range as the
mountains provide some added lift but, for now, not too excited.
Height rises then kick in as ridging builds in across the
Intermountain West.
This ridge will usher in drier air and also cause daytime
temperatures to start rising. Ahead of the ridge axis, H7 temps
range from about 3C north/7C south and as the axis passes overhead
Wednesday, H7 temps increase to 8C north/11C south. This will be
reflected in surface temps jumping back to above average values.
Statistical guidance now suggesting this jump will be short-lived,
however, as a Pacific system moves across the west. The tail end of
this system will move through our CWA Wednesday night through
Thursday morning. Unfortunately, it looks to be dry as it moves
across the CWA but some cold air advection does look to take place
and drop temperatures to at or just below average Thursday and
Friday with a small rebound expected Saturday. So a dry period in
store with high temperatures jumping around a bit. For now, the
warmest day looks to be Wednesday before dropping back down for the
end of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 542 PM MDT Sat May 2 2020
Scattered showers and isolated thunderstorms will continue across
northeast Utah and northwest Colorado through this evening. Gusty
outflow winds will be the primary threat from storms with wind
gusts of 35 to 45 kts possible. Shower activity is expected to
diminish by 06Z, though scattered to broken midlevel clouds will
persist across the north overnight. Yet another quick moving
disturbance will brush the north on Sunday with showers
redeveloping over the higher terrain by 15Z and continuing through
Sunday evening. Elsewhere, VFR will prevail with breezy
conditions.
&&
.FIRE WEATHER...
Issued at 904 PM MDT Sat May 2 2020
Warm temperatures, gusty winds, and low relative humidities will
occur across portions of west-central and southwest Colorado
on Sunday. This, combined with dry fuels, will lead to critical
fire weather conditions Sunday afternoon and evening where Red
Flag Warnings will be in effect for these areas.
&&
.HYDROLOGY...
Issued at 219 PM MDT Sat May 2 2020
Gauge reports indicate increased flows along Elkhead Creek and
Slater Fork Creek due to snowmelt. These creeks have risen above
bankfull and are forecast to fluctuate above and then below this
level over the next few days. This will allow localized low land
flooding to occur in mainly rural areas of northeastern Moffat
County and northwestern Routt County. Other small streams and
tributaries will also see runoff increased due to warm
temperatures causing an uptick in snowmelt. An areal flood
advisory has been issued through Monday afternoon to account for
this activity.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from 1 PM to 9 PM MDT Sunday for COZ207-290-292-
294-295.
UT...None.
&&
$$
UPDATE...MMS
SHORT TERM...TGR
LONG TERM...TGR
AVIATION...MMS
FIRE WEATHER...TGJT
HYDROLOGY...TGR
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1022 PM EDT Sat May 2 2020
.SYNOPSIS...
A front will move southeast into the region tonight, and will
continue moving slowly southeast into Sunday. High pressure
will build into the Great Lakes and the Ohio Valley for Sunday
night into Monday. Drier and cooler weather can be expected.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
A few echoes passed over Hardin County last hour. A few drops
of rain probably reached the ground.
Focus is really on a enhancing vort max that will swing into
the region after midnight. Low level convergence will be on the
increase with front moving across the region. The upper support
and convergence will help support the convection out in Illinois
as it moves east into the region. Best rain coverage will be
between DAY-CVG from southeast Indiana to through Wilmington-
over to south central Ohio. Some moderate to locally heavy rain
will be possible.
Bumped lows up a couple of degrees to the Lows will range from
the upper 50s in the north to the mid 60s in nrn KY.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
The cold front is expected to be near the Ohio River by Sunday
morning. The front will move slowly southeast through the day,
exiting our far southeast CWFA by mid to late afternoon. A lull
in the widespread pcpn is expected during the morning hours.
Then, another disturbance will move in during the afternoon
hours. The lift from this feature will bring likely to
categorical PoPs to the southern CWFA with only chance PoPs
across the north. Instability will be limited across the south.
There may be enough instability during the afternoon hours
across the far south/southeast for an isolated strong or severe
storm, but confidence is low. In addition, some locally heavy
rain may occur along and south of the Ohio River. Clouds and
pcpn will keep temperatures down from today`s readings. Highs
will range from the mid 60s to the lower 70s.
For Sunday night, once the disturbance exits to the east during
the early evening, pcpn will quickly taper off behind the
departing cold front. Skies will gradually clear from the north
as high pressure begins to build into the region. It will become
cooler with lows ranging from the lower 40s north to the
mid/upper 40s south.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
A persistent upper trough positioned across the Eastern CONUS will
dictate weather through the long term. We can expect periods of
unsettled weather, but severe weather appears less likely under a
cooler and more stable than normal regime.
Monday should be mainly dry with high pressure moving east, though a
few showers could move in late ahead of low pressure heading toward
Kentucky. Showers will be possible Monday night and Tuesday as the
low crosses Kentucky. A few more showers may develop Wednesday under
the axis of an upper trough. High pressure should result in dry
weather Thursday, before a cold front returns the threat for showers
Friday into Saturday. Cool temperatures and CAPE below 500 J/KG
should limit thunderstorm potential, with isolated thunder the best
bet at this point.
After highs reach the 60s on Monday and Tuesday, readings will slip
to around 60 Wednesday through Friday, then to the mid 50s Saturday
under a prolonged period of cold advection. Lows dipping below 40
next weekend may allow frost to form.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
A few light showers are moving east through northern Indiana
and Illinois attm. This is associated with a weak vort max
running through the flow. Last few runs of the HRRR and RAP have
not produced any organized pcpn with this initial lift.
Instead they are waiting until a stronger vort swings through
central Indiana between 06-09Z. Precipitation then begins to
develop along the cold front as it is forecast to drop into the
tafs later this evening. Best coverage of the pcpn is expected
between DAY and CVG/LUK, across ILN between 09-13Z. It looks
like there will be enough instability for some thunder at that
time. Looks like the lowest ceilings will be across the southern
tafs with MVFR is forecast. Also the chance of moderate to
locally heavy rain will drop visibilities to MVFR in places.
First wave of pcpn pushes east after 12Z. A shortwave will
swing across the region during the afternoon. This will
combine with the front to bring an increased chance of showers
and thunderstorms to the srn terminals. As the lift pulls east
late in the period, pcpn will come to an end.
OUTLOOK...MVFR ceilings and visibilities are possible on
Tuesday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Hickman/Sites
NEAR TERM...Sites
SHORT TERM...Hickman
LONG TERM...Coniglio
AVIATION...Sites
Area Forecast Discussion
National Weather Service Northern Indiana
600 PM EDT Sat May 2 2020
.SYNOPSIS...
Issued at 600 PM EDT Sat May 2 2020
Scattered rain showers will develop late tonight through central
Indiana and Ohio and continue into Sunday morning. The rest of the
region will remain dry through Sunday. Lows tonight will drop back
into the low to mid 50s. Highs Sunday afternoon will range from the
mid 60s to lower 70s. A prolonged period of cool weather follows
Monday through next weekend.
&&
.SHORT TERM...(This Evening through Sunday)
Issued at 336 PM EDT Sat May 2 2020
Meager moisture profiles have allowed little more than cumulus
clouds to develop along/ahead of the warm front as it moved
through earlier this afternoon. It is increasingly clear that the
cold front can pass without sparking storms for the remainder of
the daytime hours. In this morning`s forecast model soundings
(RAP, HRRR, NAM) RH profiles were meager, but perhaps acceptable
for precip. Consecutive high-resolution model runs trended drier.
Simulated reflectivity from HRRR and RAP runs back to 11z this
morning showed sparse precip coverage at best and is perhaps a
byproduct of the virga across IA (again). Perhaps the nail in the
precip coffin is that surface winds are from the NW now in NW IN,
reducing moist dew point advection. All of this leads me to the
conclusion to cut POPs until about 03z tonight.
Later on tonight this otherwise dry cold front becomes oriented
E-W across central IN and becomes the focus for rain showers;
activity is ongoing across Nebraska. Compared to yesterday, this
front is more transient, perhaps due to a progressive incoming
surface high. As a result, rain chances end quickly after daybreak
Sunday. Rainfall coverage area remains similar to previous
forecasts; roughly the southern two tiers of counties. High
pressure settles over the Central Plains Sunday afternoon, working
to increase sunshine across the area. Cold air advection keeps
high temperatures closer to normal; upper-60s near 70.
&&
.LONG TERM...(Sunday Night through Saturday)
Issued at 336 PM EDT Sat May 2 2020
High pressure tracks east Sunday night a second surge of cold air
advection pushes south as a trough slides in over the eastern Great
Lakes. This drops lows into the 40s. Highs right near 60 Monday.
A pair of storm systems track through the Midwest midweek. The first
surface low tracks along the Ohio River Valley. The second arrives
from the Northern Plains, nearly on the heels of the first system.
Compared to yesterday, it seems that the ridge over the Southeast
U.S. is forecast to be weaker. As such, I am leaning toward the OH
Valley low to pass south or clip the southern areas. Furthermore,
both the 12z GFS and 00z ECMWF depict lingering surface and
850-mb ridging over our area which could help steer that low
south. However, it appears the second low has sped up in recent
solutions, perhaps bringing precip to the northwest areas on
Tuesday.
Cool northwest flow takes over as these systems depart. A large
upper-level trough arrives and this brings 850-mb temperatures back
to about 0 degrees Celsius near 00z Thursday (compare that to
today`s 12C). This has been a consistent model signature since
roughly Thursday/Friday. As such, confidence is increasing for
cooler than normal temperatures as we near Mother`s Day weekend. It
may not be until about 5/12-5/13 that this upper-level low and 500-
mb trough are replaced by an upper-level ridge.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 600 PM EDT Sat May 2 2020
VFR through the period as post frontal high pressure builds across
the region.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SYNOPSIS...Brown/T
SHORT TERM...Brown
LONG TERM...Brown
AVIATION...T
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Area Forecast Discussion
National Weather Service Louisville KY
919 PM EDT Sat May 2 2020
.Forecast Update...
Issued at 919 PM EDT Sat May 2 2020
Expecting a pretty quiet overnight across far southern IN and
central KY as convective activity is expected to stay mainly across
central IL/IN, and into southern Ohio through the overnight. This
will occur along a W-E oriented cold front trailing from an eastern
Canada surface low. There is a chance that some of the activity
could skirt our far NE CWA up near Madison, IN or Cynthiana, KY but
most of the data supports it missing just to the north. As a result,
will keep some pops up there overnight.
Went ahead and raised overnight lows a degree or two in most spots
to account for temps running warmer than expected at this point and
a pretty steady SW surface flow overnight. In addition, more clouds
may move into the area toward sunrise. Also tightened the
temperature gradient across our CWA for tomorrow. Temps will likely
struggle to reach 70 across our northern tier, north of the
convectively reinforced boundary. In contrast, they will likely
overachieve across southern KY where clouds hold off the longest,
and a steady S flow helps push temps near 80.
Still monitoring data for tomorrow, but there continues to be
potential for strong to severe storms during the afternoon and early
evening across the region. At this time, the most likely location
appears to be south of I-64 across central KY between 1 and 8 PM
EDT, however much will depend on where convective outflow from
tonight and the eventual surface boundary end up by midday tomorrow.
The main threats look to be large hail and damaging winds in
addition to the lightning and brief heavy rainfall threat.
&&
.Short Term...(This evening through Sunday)
Issued at 300 PM EDT Sat May 2 2020
Pleasant weather is being seen across the region today, with temps
warming nicely into the upper 70s to lower 80s under sunny skies.
Gusty southwest winds of 25-30 mph have been observed across the
area and will be continue to be possible into the evening, before
diminishing towards dusk. Expect a mild night tonight as continued
southwesterly flow helps keep low temperatures in the upper 50s to
lower 60s. Precip chances will then begin to ramp up over southern
IN tomorrow morning as our next system approaches.
An upper level trough will dig across the Great Lakes region on
Sunday, while an associated surface low progresses eastward over
Quebec, dragging a trailing cold front through the OH Valley
tomorrow. In addition, a subtle shortwave will move eastward out of
the mid MS Valley and across the OH Valley. Hi-res guidance suggests
showers and storms will begin moving into southern IN by mid-morning
Sunday, and will continue to push southeastward across KY throughout
the day. Ahead of the front, expect a broad swath of higher
dewpoints (low to mid 60s) to spread across southern and central KY.
Modest shear will be in place, with Effective Bulk Shear values
reaching into the 40-45 kt range. However, despite the available
moisture and lift, severe storm potential will remain conditional on
the presence on warmer air in the low to mid levels of the
atmosphere. Some model soundings are suggesting that a layer of
warmer 700 mb temps may keep us capped and limit overall coverage of
storms and inhibit strong convective development. If temperatures
aloft end up being cooler (like the 12Z HRRR suggests), the threat
for strong to severe storms would increase. With any stronger storms
that are able to develop, the greatest threats would be gusty winds
and hail. While models vary on timing of showers and storms, the
best chance for strong to severe storms, if they occur, will be
during the afternoon hours.
.Long Term...(Sunday night through Saturday)
Issued at 300 PM EST Sat May 2 2020
Showers and storms will still be lingering across portions of
central Kentucky as a cold front advances into northern Tennessee
Sunday night. Most activity is expected to end by Monday morning as
high pressure tries to influence the region from the north.
Looks like the break from the rain should be relatively short-lived
as our next system arrives Monday evening into early Tuesday
morning. Isentropic lift ahead of the system will promote shower
development Monday night, and soundings indicate there may be some
elevated instability to support some thunderstorms. A strong cold
front (by May standards) associated with the system should sweep
through the region Tuesday afternoon and lead to drying for many.
There continues to be some uncertainty going from the Wednesday and
beyond as long range models vary on shortwave trough evolution
within a broader, elongated eastern CONUS longwave trough. As a
result, precipitation chances will be carried through much of next
week, but its unlikely every day will see rainfall. There is a very
high likelihood that temperatures will be below climatological
normals for this period in the lower Ohio Valley, as the overall
pattern supports longwave troughing over the eastern CONUS and
ridging out west.
&&
.Aviation...(00Z TAF Issuance)
Issued at 739 PM EDT Sat May 2 2020
Gusty SW winds should settle pretty quickly this evening, although
will still keep a steady prevailing SW wind through the overnight.
Otherwise, expect continued VFR with some Sct mid clouds around at
times.
A cold front will drop into our area tomorrow, bringing lower
ceilings likely in the low MVFR/MVFR range and chances for shower
and storm activity. The best chances for thunderstorms will be at
the SDF/BWG/LEX sites in the afternoon and early evening where brief
vis reductions will be possible. Surface winds will veer to the SW,
W, then NW as the front passes tomorrow afternoon and early evening,
with a quick return to VFR by the evening at the northern TAF sites.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...BJS
Short Term...JML
Long Term...DM
Aviation...BJS
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
815 PM CDT Sat May 2 2020
.UPDATE...
815 PM CDT
Made some tweaks to the forecast this evening and overnight
regarding PoPs and thunder chances south of I-80. Northern areas
are expected to primarily see some isolated sprinkles as DVN
sounding is dry below 600 mb and any high based showers will be
brief and fast moving with small footprints. Returning to areas
south, the RAP suggests a strengthening fairly narrow
frontogenesis circulation centered around 600 mb this evening,
topped by strong negative saturated EPV on cross sections. The
f-gen circulation will maximize in intensity likely just south of
the I-80 corridor to around the Kankakee River in the mid to late
evening while translating eastward then weakening and fading
southeastward overnight. Visible and IR satellite per trajectory
of ACCAS plume and regional radar trends seem to indicate that the
RAP and HRRR implied by simulated reflectivity appear to be on
the right track.
We should have a decent narrow band of showers setting up close
to described above, for which PoPs were bumped up to likely. In
addition, the negative EPV atop the f-gen circulation suggests
some slantwise instability (similar to yesterday) evening despite
ILX and DVN soundings indicating no MUCAPE, but relatively steep
mid-level lapse rates. Regional radar shows some convective cells
feeding into developing narrow band of precip. Based on the above
thinking, carrying an isolated thunder mention. Even though low
levels are quite dry, think that saturation will get low enough in
the heart of the band to support some occasional downpours,
especially in any isolated t-storms (again similar to yesterday
evening). To the south of the band of rain, should be isolated or
widely scattered showers and isolated t-storms. As the f-gen
weakens overnight, intensity of rain band should follow suit as it
sinks south across far southern CWA and then exits east-southeast.
Adjusted QPF alignment to favor slightly higher QPF in heart of
band, though high bases/dry low levels should keep things in
check. Based off more robust convection setting up in western
Illinois and likely to stay south of Ford to Benton line, it
appears heavier rain should stay south of CWA.
Looking ahead to Sunday, most areas should be dry aside from a
non-zero threat for sprinkles as another sheared disturbance
tracks overhead. The main item of note is that a pneumonia front
charging south-southwest from Lake Michigan will bring an abrupt
end to temperatures in the 70s/around 70 late in the day. Temps
may very well drop from near 70 to the 40s in well under an hour
near the lake, with a slightly slower rate of cooling with inland
extent. Brisk north-northeast winds surging inland behind the
front will add to the sudden chill. Added hourly wind and
temperature detail to the grids Sunday evening to account for
this and will be putting out a graphic to message sharp cooling.
Castro/Izzi
&&
.SHORT TERM...
248 PM CDT
Through Sunday night...
Main concerns in the short term:
* Potential for showers and isolated thunderstorms this evening,
mainly south of U.S. 24.
* Gusty winds Sunday with a backdoor cold front sweeping through
in the evening.
Currently have a few light showers moving across our western
counties this afternoon. Expect mostly virga/sprinkles out of this
early afternoon shower activity thanks to a fairly stout dry
layer in the low levels.
Temperatures have peaked in the upper 70s to near 80 across much
of the area. With increasing cloud cover and the light sprinkles,
suspect we may struggle to get much warmer. Regardless, it was a
welcome warm spring day.
A narrow corridor of instability around 500-750 J/kg extends up
into southeastern portions of the forecast area, generally south
and east of I-55. There remains a fairly decent CAP in place that
should hinder any thunderstorm development this afternoon, but as
we get into the evening hours, a few showers may be able to tap
into this instability along the surface boundary, so cannot rule
out at least a few isolated thunderstorms. Hi-res guidance is
trending down on the overall coverage of showers, so things may
be fairly spotty in nature.
High pressure approaching from our west on Sunday sets up
northwesterly flow during the day on Sunday. Another weak
disturbance will pass through during the afternoon. Given the
airmass is quite dry again, expect mostly virga showers out of
this wave, but cannot entirely rule out a few sprinkles reaching the
ground. High temperatures will a bit cooler than today, around 70.
Gusty winds may mix down to the surface at times, especially
across our northern zones. A backdoor cold front is still forecast to
ride down the lake Sunday evening with gusty winds expected along
and behind the front with a noticeable drop in temperatures as
winds quickly turn northeasterly.
Petr
&&
.LONG TERM...
149 PM CDT
Monday through Saturday...
Upper ridging looks to be in place to start the day Monday, though
the flow flattens quickly Monday and a mid-level short wave will
approach the region. This wave will be the first in a series of
disturbances to affect the area through the week, as the upper
pattern evolves toward a large scale trough over the eastern half of
the CONUS extending from a very cold upper low around Hudson Bay.
Overall, this is expected to produce a period of cooler than average
weather, with periodic shower chances through the week.
Current guidance may be a tad faster with the lead shortwave and
we could see precip by Monday afternoon in some areas, though
cooler surface high pressure and dry low levels should limit the
initial eastward extent. East-northeasterly winds will produce
cooler temperatures, especially along and just inland of Lake
Michigan. After weekend highs in the 60s and 70s, readings will be
mainly in the 50s Monday (low 60s well inland), with 40s possible
near the lake. Several shortwaves, topped off by a bit sharper
upper trough, will transit the area Monday night through Tuesday
night, increasing shower potential. Mid level lapse rates increase
late Tuesday which could support a few thunderstorms, but model
instability progs are still fairly limited thus far and feel
coverage would be quite low. As the upper trough amplifies across
the eastern half of the country, cooler air will move in aloft,
though falling surface pressures east of the region will result in
winds backing more north- northwest and easing the lake cooling
somewhat into mid- week.
Guidance generally depicts weak surface high pressure spreading
across the area Thursday, before additional energy digs across the
Great Lakes region Thursday night and Friday with a reinforcing push
of cooler air and additional shower chances. Of course various
models indicate differences with timing of individual waves so there
is generally lower confidence in timing of precip through the
period. It certainly won`t rain all week and generally appears more
dry than not , though several showery periods still appear likely.
The coldest air will arrive toward the end of the week as the cold
upper low across Hudson Bay will dive into the eastern Great Lakes.
KMD/Ratzer
&&
.AVIATION...
For the 00Z TAFs...
VFR conditions will prevail through the TAF cycle with primary
forecast challenge being winds. Weak front will move across the
terminals after midnight tonight resulting a wind shift, less than
10kt, to the northwest. Winds could veer briefly north or even
northeast early Sunday morning (11-15z time frame) at less than
10kt, before settling back to west or west northwest by mid-late
morning Sunday. Expect extensive mid-high level cloudiness Sunday
and that could limit gust potential somewhat, but still anticipate
winds to increase to 10-15kt with gusts to around 20kt fairly
common with oncl gusts up to around 25kt possible Sunday
afternoon. A strong, lake charged, cold front will come barreling
through the terminals early Sunday evening with an abrupt wind
shift to northeast. Will probably see northeast winds gusting to
between 25-30kt for a time immediately following frontal passage,
before winds gradually ease some but likely remain 10-15kt with
more sporadic gusts to around 20kt.
- Izzi
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Marquette MI
721 PM EDT Sat May 2 2020
.SHORT TERM...(This evening through Sunday)
Issued at 407 PM EDT SAT MAY 2 2020
Water vapor imagery and RAP analysis show a well-defined
shortwave/mid-level low along the Manitoba/Ontario border. Around
the s side of this feature, much drier air has been surging into the
area on gusty w to nw winds today. Sunny skies/deepening mixed layer
has recently began to cause dwpts to drop over the interior w as
expected. With temps approaching 70F and dwpts falling toward 30F,
RH is falling into 20-30pct range. With winds gusting to around
30mph, elevated fire wx conditions are ongoing and will expand in
coverage over the next few hrs until mixing diminishes with setting
sun. Over the Keweenaw, deep mixing and ideal wnw wind direction has
resulted in wind gusts approaching 50mph at KCMX in the last couple
of hrs.
Mid-level low will open up tonight as it drifts ese with shortwave
trof then passing across the area on Sun. At the lower levels,
associated sharp sfc to 850mb trof will drop s toward Lake Superior
tonight. Ahead of this feature, a dry air mass will linger across
the area, so the night should end up mostly clear though stratocu
wlll probably be on the increase late tonight across the Keweenaw.
Lows will be in the 30s with some lwr 40s s central and e. As the
sfc-850mb trof passes across the area on Sun, models indicate
increasing low to mid-level moisture. Per obs and vis satellite
imagery, there is certainly no shortage of stratocu and stratus
vcnty of the trof from Saskatchewan into northern Ontario this aftn.
With the increasing moisture and cyclonic flow/850mb thermal
troffing, Sunday should quickly become mostly cloudy to cloudy. It
will also be sharply colder compared to today as 850mb temps of 6 to
9C this aftn fall to -3 to -5C across much of the area for mid day
on Sun. With blustery nw winds, expect highs in the low to mid 40s w
and n to the upper 50s far s central. For much of the day, temps
near Lake Superior may only be around 40F. Although the increasing
column moisture and cooler conditions will help to mitigate fire
concerns, there may be enough delay in cloud cover and column
moistening over the s central for increasing winds to catch
lingering dryness to heighten fire wx concerns thru early to mid
aftn. Given the rather sharp low-level troffing/cyclonic flow,
increasing low to mid-level moisture and fairly widepsread pcpn
vcnty of the trof this aftn in Canada, opted to add a mention of
-shra/sprinkles from the Keweenaw across the n central and eastward
during Sun aftn.
.LONG TERM...(Sunday night through Saturday)
Issued at 409 PM EDT SAT MAY 2 2020
Upper level ridge over the Canadian Rockies will allow a couple
shortwaves to stream south through the Upper Great Lakes next week.
This ridge is anticipated to amplify, allowing deep upper level
troughing to establish itself over eastern Canada and the Great
Lakes toward the tail end of this period. This will usher in a
return to below normal temperatures.
Sunday night, the tail end of a cold front will swing through the
region. Late-cycle CAMS are hinting at some showers in the north
wind belts early Sunday night. Much of this would depend on timing,
as increasing subsidence may not be enough to get much going
aside from drizzle or light snow. Skies will gradually clear out
as high pressure shifts east through northern Ontario.
Monday and Tuesday, upper level ridging and height rises will
continue building in across the region while at the surface, high
pressure will build in across southern Hudson Bay and James Bay.
Overall, this will support a dry beginning to the week, with model
soundings supporting deep mixing aloft near 5k feet in the
afternoon. Despite tapping into this air aloft, winds through the
lower atmosphere look to be light, so not expecting gusty winds. The
high will begin breaking down and shifting east as a shortwave
approaches the region Tuesday from the west. Previous model runs
have shown consistency in keeping this feature south of our region,
and given the anticipated drying at the surface, trimmed back PoPs
and QPF away from the NBM and WPC. PoPs and QPF still may be on the
high side given the the preconditioning; precip may have a tough
time overcoming the dry surface air. Temperatures Monday in the
interior should climb into the 50s and stay cooler in the 40s by the
lakeshores. Dewpoints drop into the 20s and high teens putting RH
values in the mid 20s in the western interior, increasing into the
40s by the lakeshores. Overnight lows Monday will reach just below
30 for most. Tuesday should be slightly cooler, with temps topping
out near 50 in the interior and in the mid 40s by the lakeshores.
Another shortwave digs south into Ontario Wednesday swinging a weak
surface cold front through the Upper Great Lakes during the day.
Given the dry air at the surface, models aren`t showing much in the
way of precip. Following the front`s passage, winds will back
northerly. The previously mentioned amplifying upper level ridge in
the west will be established by Friday, allowing deep troughing to
descend through Canada. This will usher in a period of below normal
temperatures.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 717 PM EDT SAT MAY 2 2020
Dry air mass in place will continue VFR conditions at
KIWD/KCMX/KSAW thru much of tonight. Expect west-northwest wind
gusts of 25kt at KSAW and KIWD and 35kt at KCMX to diminish around
sunset. Early Sun morning or perhaps sooner, an approaching sfc
trof and accompanying low-level moisture will lead to MVFR cigs
developing at all terminals. Northwest winds will be gusty again
on Sun, though not quite as strong as Saturday. &&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 407 PM EDT SAT MAY 2 2020
Low pres moving across northern Ontario will swing a trof across
Lake Superior on Sun. Relatively tight pres gradient will result in
w to nw winds mostly btwn 15-25kt becoming more northerly on Sun.
Expect some gusts to around 30kt thru this evening and then Sun aftn
over only the e half of Lake Superior. Winds will diminish to mostly
under 15kt over western Lake Superior Sun aftn. High pres over
northern Ontario will then ridge s across the Upper Lakes Sun
night/Mon, resulting in winds generally under 20kt. Winds should
then remain mostly blo 20kt to mid week.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...JP
AVIATION...Voss
MARINE...Rolfson
Area Forecast Discussion
National Weather Service Nashville TN
735 PM CDT Sat May 2 2020
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
This evening, a strong southwesterly flow has set up between high
pressure that`s centered off the southeast coast and a slow-moving
cold front that has set up north of the Ohio River. So we can
expect a dry night and probably a dry Sunday morning, too. The
evening sounding from OHX is still quite dry, with a PWAT of 0.82
inches and no moist layers anywhere in the column. Of note, mid-
level lapse rates are a robust 7.0 C/km due to cold air advection
in that layer. Looking ahead, the HRRR shows only isolated cells
as far south as Kentucky by 17Z Sunday, and the latest GFS brings
the surface front and expected line of convection into Middle
Tennessee after 21Z, with slow progression southward throughout
the evening. Even though pop-up cells may develop earlier in the
afternoon in the pre-frontal air mass, we may not see many storms
of consequence until late in the afternoon. Hourly forecast grids
are holding their own, so no forecast changes are planned at this
time.
&&
.AVIATION...
00Z TAF DISCUSSION.
VFR. SKC expected overnight before clouds increase on Sunday ahead
of an approaching front. VCTS will affect CKV near the end of the
TAF period with TSRA/SHRA possible at all airports after the
current TAF period. Southwest winds will subside tonight to 5-10
kts before increasing again on Sunday morning with gusts to 20 kts
at times.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......08
AVIATION........Shamburger
Area Forecast Discussion
National Weather Service Portland OR
243 PM PDT Sat May 2 2020
.SYNOPSIS...Unsettled conditions will continue over Southwest
Washington and Northwest Oregon through Sunday night. Thunderstorm
threat continues through Sunday, mainly along the coast and northern
inland areas. Weak high pressure settles over the region Monday. A
couple of weak frontal systems brush the area late Monday through
Wednesday. A much warmer pattern is expected late in the week.
&&
.SHORT TERM...Tonight through Tuesday...Cold front moved ashore
around 1630Z and then reached the west side of the Willamette Valley
between 18Z and 19Z. Peak wind gusts so far have been 30-40 mph,
which resulted in localized power outages around Eugene. There were
also a couple of cloud flashes in SW Linn County and another one at
1945Z in central Clackamas County. At 20Z the cold front was along a
line from near KKLS to near KRBG. Rainfall has been rather impressive
along the coast and in the Coast Range and SW Washington Willapa
Hills through early afternoon. Many locations have picked up over an
inch of rain, with 1.25 to 1.5 inches in a few spots.
Water vapor imagery revealed a broad upper low pres area in the Gulf
of Alaska, with the parent 500 mb low center near 51N 139W. Water
vapor also showed a distinct dry slot at the base of the upper trough
and just off the Oregon and Washington coast. The overall weather
picture would likely have been much different, i.e. more active, had
the cold front been a couple hours later. An upper level cold air
pool is also clearly discernable on water vapor and will push into
the forecast area tonight and Sunday. GOES-17 infra-red imagery
showed the coldest-topped clouds mainly in western Washington. At 20Z
KRTX dual-pol doppler radar indicated the heaviest reflectivity
returns over the interior valleys to the Cascade foothills. There was
also a small area of 55-60 dBZ returns in NE Clackamas County between
Sandy and Welches moving rapidly northeast. This feature produced
several flashes and a few lightning strikes along the Multnomah and
Hood River County border and, eventually, in Hood River County. This
feature is associated with the leading edge of the frontal zone. The
KRTX 0.5 deg velocity data showed the frontal boundary quite clearly.
At 19Z the Astoria profiler indicated southwest wind 25-30 kt around
1000 to 1500 ft AGL. Earlier high-res model runs were a little more
robust with the low-level wind field. The latest HRRR run indicated
30-40 kt just above the profiler surface at 20Z, but then decreasing
fairly quickly late afternoon. Model soundings from the HRRR and NAM
do not look quite ominous compared to 24 hours ago. Seems the main
threat today will be strong wind gusts as opposed to organized
convection. The SREF Calibrated 12-hr thunderstorm probability
guidance maintains at least a 10 percent threat over a majority of
the CWA through tonight, with the up to 30 percent along the
immediate coast. The bulk of the upper trough dynamics move through
the area late tonight and Sunday morning. The NAM shows -28C to -30C
500 mb temps over SW Washington and far NW Oregon Sun morning.
However, 500 mb heights begin to rise Sun afternoon, which allows the
air mass aloft to moderate just a bit. Have left a mention of
thunderstorms for the entire CWA Sunday, but feel the best threat
Sunday afternoon will be north of a KSLE-KONP line.
High pressure slowly builds Sunday night and early Monday and have
lowered POPS accordingly. This transient ridge moves across the
region early Monday and will be well into eastern Oregon by Monday
afternoon. Models show the next frontal system moving inside 125W
Monday afternoon. Model time-height sections for the Willamette
Valley show increasing saturation above 500 mb 12Z Mon, lowering to
700 mb between 18Z and 21Z. Thus, have nudged max temps just a bit
lower to account for this expected cloud cover. This weak front moves
inland late Monday and then falls apart Monday night.
Southwest flow aloft continues Monday night and Tuesday. The
operational NAM, GFS and ECMWF indicate some light QPF across the
north half of the CWA Tue afternoon. Models infer the north half of
the CWA will be in a favorable quadrant of the jet stream Tuesday
afternoon. Also cannot rule out small-scale short-waves within the
southwest flow aloft moving through the area to provide additional
dynamic support for some threat of showers. Weishaar
.LONG TERM...Tuesday night through Saturday...Model solutions are
showing shortwave disturbances from the Gulf of Alaska dissipating
by Tuesday night. This will allow for the synoptic ridging pattern
over southern California to push north over the CWA. Ensemble and
deterministic solutions are showing a ridging pattern building and
staying anchored over the West Coast through the weekend.
At the surface, an inverted thermal trough will setup over the
northern California, southern Oregon coast Thursday afternoon. This
pattern will strengthen during the afternoon to early evening hours
through the weekend. This will bring gusty conditions along the
coast and easterly winds inland. Offshore winds and ridging aloft
will bring above normal high temperatures in the upper 70s, to
possibly low 80s for inland locations. -BPhillips
&&
.AVIATION...Potent cold front has moved across the forecast area,
presently crossing the Cascades as of 21z. The front was strong
enough to trigger a line of thunderstorms which has moved across
the Hood River Valley in the past hour. Plenty of rain persists
behind the front itself, with steady -RA and scattered MVFR slow
to improve this afternoon. Eventually this will transition into
a showery pattern with higher cigs, so VFR should become more
prevalent after 00z. The exception to this may be the coast,
where conditions have already generally improved to VFR. Light to
moderate low-level SW flow may allow some MVFR cigs to backbuild
from the Coast Range, potentially affecting KAST/KTMK/KONP with
another period of MVFR tonight into early Sunday.
PDX AND APPROACHES...Cold front has passed, leaving behind mostly
light rain with general VFR cigs/vsbys and SW sfc winds gusting
up to 20 kt. Pattern should transition into more of a
showery/convective mode by 00z, with bases generally 035-045 MSL.
Heavier rain showers may briefly drop conditions to MVFR, but
this would likely be brief if it occurs at all. Weagle
&&
.MARINE...Potent cold front has moved onshore and was presently
moving east across the Cascades as of 230 PM PDT. This front
brought a quick burst of winds which briefly approached gale
force, but the strongest winds with this front are over for our
coastal waters. Moderate SW winds, generally on the order of
10-15 kt, will prevail and gradually ease tonight as high
pressure builds into the region. Post-frontal W-NW swell will
keep seas near 10 ft through Sunday. Our existing Small Craft
Advisory ends shortly after midnight. Given that we were on the
fence as to whether or not the advisory should be extended, we
will allow the evening or midnight shift to make this call.
Another storm system appears likely to bring Small Craft
Advisory level winds to the waters Monday with perhaps a second
front Tuesday. High pressure appears likely to build across the
western US later next week, which should keep storms to the west
and north of our region. Weagle/Neuman
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 3 AM PDT Sunday for coastal waters
from Cape Shoalwater WA to Florence OR out 60 NM.
Small Craft Advisory from 11 PM this evening to 3 AM PDT Sunday
for Columbia River Bar.
Small Craft Advisory from 10 AM to 6 PM PDT Sunday for Columbia
River Bar.
&&
$$
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This discussion is for Northwest oregon and Southwest Washington
from the Cascade crest to 60 nm offshore. This area is commonly
referred to as the forecast area.
Area Forecast Discussion
National Weather Service Blacksburg VA
950 PM EDT Sat May 2 2020
.SYNOPSIS...
Departing high pressure will bring hold on long enough to bring
quiet weather to the Appalachians and central mid Atlantic
region tonight into Sunday. However, an approaching cold front
will bring showers and thunderstorms back to the area by late
Sunday into Sunday evening. After a brief break of quiet weather
to start the week on Monday, unsettled conditions will return
with a chance for showers and thunderstorms, along with cool
temperatures, through the middle of next week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 950 PM EDT Saturday...
Made some minor adjustments to temperatures, pops and weather
for late tonight into Sunday morning.
As of 815 PM EDT Saturday...
High pressure continues to slide east tonight into Sunday
morning. A frontal boundary will slowly drop south into our
region Sunday. The NAMnest, Hiresarw-east and HRRR showed some
scattered showers pushing into northern portions of the forecast
area between 09z-14z Sunday. Adjusted temperatures for tonight
into Sunday morning utilizing the latest surface obs, their
trends and blended in the NBM. The Day 2 Convective outlook
highlights the marginal risk for severe thunderstorms on Sunday.
More changes later tonight.
As of 130 PM EDT Saturday...
A pleasant spring day continues across the region with lots of
sunshine and warmer temperatures. Expect the quiet conditions
will continue tonight, but an approaching frontal boundary will
be slowly sinking toward the region. Expect increasing clouds
from the north along with an increasing low level jet will
inhibit formation of radiational fog. The increasing winds will
be felt mainly along the hilltops west of the Blue Ridge
tonight, and may generate some spotty upslope showers up around
western Greenbrier, but generally expect dry conditions for the
overnight period.
Sunday looks to start quiet with some gusty conditions developing as
diurnal heating mixes the boundary layer and helps bring some of the
robust low level flow to the surface. Guidance seems to be coming
around to a more consolidated solution regarding convective potential
tomorrow. Flow will be unidirectional with a brisk low level jet in
place. Expect some short wave energy will be able to combine with
marginal surface based instability and the aforementioned unidirectional
wind shear to develop some vigorous convection upstream that will slide
toward the region with the front late in the day. Storms will present a
threat for damaging winds in the west and north, then start to lose
steam as they progress deeper into the region Sunday night. Current SPC
outlook graphic depicts the situation well.
Temperatures tonight will be a good bit warmer than last night with
lows generally in the 50s, some cooler 40s in the normally colder
locations. Highs Sunday ahead of the front will warm considerably with
mid 80s east, mid/upper 70s west.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 230 PM EDT Saturday...
Surface front is progged to sink south through the forecast area
Sunday evening, passing south of the CWA by Midnight.
Expectation is for scattered to numerous showers and
thunderstorms. Strong westerly flow aloft and deep-layer shear,
in addition to cold upper level temperatures may support storms
with damaging wind and large hail. Convective allowing models
suggest the greatest threat for storms will be between 6PM and
11PM Sunday evening.
Passage of the front Sunday night will bring a break in the rain
threat for Monday, an area of High Pressure moving from the
Great Lakes to the Mid-Atlantic Coast. The same front is
forecast to come back as a warm front Monday night with clouds
and rain spreading back across the area from southwest to
northeast. Tuesday and Tuesday night are looking wet...the front
stalling across the area.
Rainfall amounts Sunday evening are expected to range from
a half to three quarters of an inch /0.50"-0.75"/ across SE WV
and a quarter to a third of an inch /0.25"-0.33"/ across the SW
VA mountains, less than a tenth of an inch east of the Blue
Ridge. An additional quarter to three quarters of an
inch /0.25"- 0.75"/ is forecast for Tuesday.
Prior to the frontal passage Sunday evening, temperatures will
be very mild. After the frontal passage temperatures to trend
cooler with highs ranging from the 60s to mid 70s Monday and
back into the 40s Monday night. Tuesday may be hard pressed to
get any higher than the 50s due to clouds and rain.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 200 PM EDT Saturday...
Progressive quasi-zonal flow is expected for the middle and end
of the week with some amplification toward the weekend. As the
flow amplifies it will result in a deeper trough in the eastern
CONUS vs. a building ridge in the west. This suggest that we
trend into a period of below normal temperatures, and an
opportunity for frost and or freeze occurrence through at least
Mother`s Day, especially across the mountains.
Within the progressive flow pattern is expected to be short
wave energy that provides opportunities for precipitation...
mostly in the form of rain showers, but mixed with snow at some
of the higher elevations. Attm, Wednesday will feature lingering
moisture in the mountains. Thursday looks dry. Friday will
feature another system with widespread wetting rainfall
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
As of 731 PM EDT Saturday...
VFR conditions will continue this evening through tonight.
Expect increasing clouds from the north along with an
increasing low level jet will inhibit formation of radiational
fog. The increasing winds will be felt mainly along the hilltops
tonight, then present a window for gusty conditions all sites
Sunday morning ahead of an approaching frontal boundary.
Believe most of the showers and thunderstorms and associated
sub-VFR conditions will not arrive until later Sunday afternoon.
MVFR/IFR showers and thunderstorms are likely Sunday night.
Medium confidence in ceilings,visibilities and winds during the
taf period.
Extended Aviation Discussion...
Expect a period of VFR conditions on Monday before unsettled weather
with sub-VFR conditions and showers/thunderstorms become more
prevalent, especially in the mountains west of the Blue Ridge, through
the middle of next week.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...MBS
NEAR TERM...KK/MBS
SHORT TERM...PM
LONG TERM...PM
AVIATION...KK/MBS