Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/25/21
Area Forecast Discussion
National Weather Service La Crosse WI
1056 PM CDT Sat Apr 24 2021
.SHORT TERM...(This evening through Sunday)
Issued at 240 PM CDT Sat Apr 24 2021
Main forecast concerns in the short term are on rain chances Sunday.
Cold front pushes east of the region tonight as high pressure builds
in from the west. Expect gradual clearing skies tonight as the high
builds in and this will lead to chilly overnight low
temperatures. Expect lows to fall into the 20s to lower 30s. The
coldest temperatures can be expected across central into north-
central Wisconsin, where lows could drop into the upper teens in
favored cold spots.
Clouds will then overspread the area early in the day on Sunday
as a trough dives into the pacific northwest and shunts a warm
front and warm air advection eastward into the Upper Mississippi
River Valley. Meso-models are in fairly good agreement at a band
of rain/showers will move across the area. The big question is how
far south will this activity get? The latest HRRR suggests the
bulk of it will stay along and north of Interstate 90, working
from west to east across the area. Tomorrow won`t be a washout,
but rather a 1 to 2 hour period of rain before the band shifts
north of the area. The rain will likely be on the lighter side
with rainfall amounts of a few hundredths to perhaps around 1/10th
inch possible. Expect one more cooler day on Sunday with highs
mainly in the 40s, but warmer air is on the way for the work week,
behind the warm front.
.LONG TERM...(Sunday night through Saturday)
Issued at 240 PM CDT Sat Apr 24 2021
Main forecast concern in the long term are on high temperatures and
periodic shower or thunderstorm chances through Thursday.
Temperatures will finally return to near seasonal normals, and
possibly slightly above at times next week.
Expect strong southerly winds on Monday as surface low pressure
deepens across Nebraska. In addition to the windy conditions, it
will be mild for locations south of Interstate 94, with highs
climbing into the 70s. A few showers are possible on Monday,
mainly north of Interstate 90 earlier in the day as a shortwave
moves through. A cold front then edges southeast across the area
Tuesday night into Wednesday bringing chances for showers and
thunderstorms to the area. Temperatures will then cool back to
normal for the last half of the work week as northwest flow
returns. Showers are are possible across the area on Thursday, but
the latest forecast model runs are trending drier. Some ridging
looks to build back into the region next weekend with high
temperatures possibly edging back into the 70s.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1056 PM CDT Sat Apr 24 2021
VFR conditions are expected overnight through Sunday morning. A
short wave trough will move across the area Sunday afternoon and
evening and combined with up glide in the warm air advection zone,
enough forcing should be generated to produce a line of showers
that will advance east/northeast across the area. These showers
are expected to be light so only minimal visibility reductions are
expected but they could be enough to saturate the lower levels and
produce a period of MVFR ceilings. This looks to be more likely at
KRST and have left the ceilings VFR at KLSE. These lower ceilings
should lift out of the area Sunday evening for a return to VFR
conditions.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...04
Area Forecast Discussion
National Weather Service Binghamton NY
931 PM EDT Sat Apr 24 2021
.SYNOPSIS...
Low pressure will bring periods of rain overnight into early
Sunday morning, followed by scattered showers Sunday afternoon.
A cold front moves through bringing drier, breezy and cool
weather Sunday night and Monday. Upper level ridging will bring
partly sunny skies and warmer temperatures on Tuesday.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
930 PM Update
Radar shows light rain showers heading north northeast toward
central NY and northeast PA. This precipitation was assocated with a
well defined upper level short wave moving into the Ohio Valley and
another upper feature moving across the Great Lakes. The Great lakes
wave was supporting isentropic lift across NY and PA leading to the
breakout of precipitation to the southwest of central NY and
northeast PA. The low-levels were very dry so initially much of
these radar echoes will be virga. Models including CAMs indicate
that precipitation will remain light as boundary layer moistens up.
The ohio valley upper level wave was more vigorous and will support
a surface low developing off the middle Atlantic coast by Sunday
morning. This low-level cyclone will become more dominant during the
Sunday leading to subsidence on the back side. As a result, we see a
break in the precipitation in the morning. The latest hi-resolution
CAM models including the HRRR, GEM, NAMnest all show precipitation
tapering off early Sunday morning after a quick shot of light
showers overnight. HRRR has low-level cyclone closer to the coast
leading to more QPF in the Poconos. We will use CONNSHORT for our
hourly POPS which incorporates this new guidance. Initially cut POPs
down as radar echoes on the models are overdoing the extent of the
precipitation given the dry low-levels.
By Sunday afternoon, colder air will be advecting in on northwest
winds with temperatures falling significantly at 850 mb and 700 mb
more so than at the surface. The low-levels will still be fairly
moist so we expect scattered to numerous showers to develop with the
afternoon heating Sunday. All model soundings have a strong capping
inversion between 10 and 15 KFT which will in effect preclude any
thunderstorm activity. Most of the CAPE was below the ice crystal
growth zone meaning just liquid water and less chance for
significant electrification in the clouds. We will have scattered to
likely POPs for rain showers in the afternoon. This activity will
wind down after sunset with just a few lingering showers or
sprinkles/flurries possible in our far northern Oneida County late
Sunday evening. Overnight Sunday to early morning Monday, very
strong dry advection occurs bringing surface dewpoints way down to
the low 20s or so. This will end any lingering sprinkles/light
rain/snow showers in northern Oneida County.
630 PM Update
Minor changes to grids as previous forecast on track.
345 PM Update
High clouds will continue to lower and thicken from southwest
to northeast this evening as the next weather system slowly
approaches. Light rain should hold off until around midnight
down across the Wyoming Valley region, then rather quickly
spreading north as it saturates the column, and the low level
dry air. Light rain is forecast to develop between 1 to 4 AM
tonight/early Sunday AM across most of central NY. The track of
the surface low will be to our south, across the DELMARVA then
almost dues east. Our rain will be develop due to forcing from a
weakening mid level wave/trough. PWATs do rise to around 0.75"
and surface dew points come up into the lower 40s. Cool tonight
as temperatures wet bulb out, ranging from 40 to 45 degrees by
daybreak.
The rain is only expected to last for several hours at any one
location, with the latest guidance showing it exiting east between
7AM to 10 AM Sunday morning. The rain may be moderate at times
across NE PA and the southern Catskills, with mainly just spotty
light rain or drizzle expected across our NW zones (Finger Lakes).
QPF amounts by 10 AM will range from about 1/10th of an inch across
the north/northwest, with close to a 1/2 inch across the Poconos and
Sullivan County NY. Some question on how long it takes the clouds to
scatter out late Sunday morning or early afternoon. Another weak
shortwave zips in from the Finger Lakes and combines with very
modest (and capped instability 50-100 J/Kg) to produce some pop-up,
scattered showers in the afternoon. Otherwise, it should turn partly
sunny and a little breezy as winds turn west-northwest 8-15 mph
(gusts up to 25 mph late). Still seasonably mild, with highs ranging
from the upper 50s to lower 60s (some mid-60s in the Wyoming Valley).
Cold air advections strengthens on a dry northwesterly flow Sunday
night. 850mb temperatures fall to around -7C but sounding show very
dry air in the mid levels, which should prevent a lake response.
Expect partly cloudy skies, brisk northwest winds 10-20 mph with
overnight lows dipping down into the upper 20s to mid-30s. Went
slightly below the NBM guidance for these overnight low, closer to
the bias-correct guidance.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
315 PM Update...
The short term period will be fairly quiet with mostly dry and
warming conditions through the first half of the week.
Ridge of high pressure builds overhead on Monday with very dry
conditions expected. Not much in the way of changes from the
previous forecast, except going even a few degrees cooler with
afternoon dew points as very dry air above the boundary layer
should easily mix down near max heating in the afternoon. Fire
weather conditions will likely be favorable for the spread of
brush fires, as RH values dip into the low 20s to possibly upper
teens in some areas and afternoon wind gusts will be in the 15
to 20 mph range.
The high will remain directly over the region for Monday night,
with clear skies and light winds overnight making for efficient
radiational cooling. Went well below forecast guidance
overnight, with lows dipping into the low 30s across much of the
area and possibly a few of the colder spots getting into the
upper 20s.
Ridging shifts eastward on Tuesday with warm SW`rly return flow
developing. Expecting much warmer temperatures Tuesday with
highs climbing well into the 70s across much of the region.
Dewpoints will also increase some, but relative humidity should
still manage to fall into the 30s percent range and perhaps a
few spots into upper 20s. Clouds will start to increase Tuesday
evening as the push over the crest of the ridge. This will lead
a much milder night of thickening clouds with lows of upper
40s- mid 50s by dawn Wednesday. Some model guidance is showing
the upper ridge flattening out a bit Tuesday night with a weak
short wave pushing eastward into Western NY late Tuesday night.
Still quite a bit of uncertainty here though, but decided to
introduce slight to low chance PoP for now based on a blend of
deterministic and ensemble guidance and will keep an eye on how
the pattern unfolds among the models over the next couple days.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
335 PM Update...
Made very little changes to the long range forecast, however
most changes made were in the Wednesday time frame. Pulled back
high temperatures a few degrees for now on Wednesday, as most
guidance is now indicating the ridge starting to break down
Wednesday and then several waves pushing through the region from
Wednesday afternoon through Friday. Now expecting increasing
clouds Wednesday afternoon and possibly showers/thunderstorms
developing, especially across Central NY.
Through the remainder of the week, a front remains nearly
stationary with several periods of rain showers or thunderstorms
possible. Models continue to differ on timing of each wave
moving up the front and the Euro is the most progressive in
having the front completely exit the region Thursday night. For
now, continued a blend of model guidance to populate the
forecast through this period, which keeps a chance for showers
right through Friday night.
355 AM Update...
Generally warm yet also unsettled weather is anticipated during
the second half of the week.
Things are pretty complicated for Wednesday through Friday, with
uncertainty for frontal boundary placement and thus a fairly
wide ensemble spread in temperature. Overall weather pattern
looks warmer than average, but it will just be a matter of by
how much. We get into a warm yet moist southwesterly flow,
riddled with disturbances and/or waves of low pressure. The
first low tracks to our northeast yet sends a cold front at
into the area, probably with at least some instability. There
will be a chance of showers and perhaps thunder Wednesday
afternoon-evening. Ahead of that front, though, we will be
either near or above the warmest temperatures of the year so
far. Highs of mid 70s to lower 80s are expected.
Models differ on whether to stall the front out over the area,
or to allow it all the way through Wednesday night. Regardless,
it likely kicks back Thursday-Thursday night as an upper trough
digs into the Great Lakes and initiates a bigger wave of low
pressure to move through our region. This period will pose our
best chance of rain, and again perhaps a little embedded
thunder; followed by modestly cooler temperatures into Friday
as the system begins to exit.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
While clouds continue to thicken, VFR conditions are still expected
at least through 06Z or so. After that, rain showers move in
from south to north. These showers will bring in MVFR ceilings
and visbys. MVFR ceilings are expected to lower further to Fuel
Alternate by daybreak before returning to MVFR by the
afternoon. While brief IFR conditions cannot totally be ruled
out at KAVP and possibly KBGM, did not include this in this set
of TAFs because confidence is too low. VFR conditions are
expected to return by Sunday evening.
Outlook...
Sunday night through Wednesday Midday...Dry weather and VFR
expected.
Wednesday afternoon through Thursday: Chance for rain showers
and associated restrictions.
&&
.FIRE WEATHER...
Rain showers are expected tonight through midday Sunday, but
amounts will be generally be lower than a third of an inch in
most areas. Locations that do not receive a wetting rain may be
vulnerable to sensitive fire weather conditions on Monday, with
very low relative humidity and somewhat gusty northwesterly
winds anticipated. Tuesday will also be dry with warming
temperatures.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...DJN/MJM
NEAR TERM...DJN/MJM/MWG
SHORT TERM...DJN/MPK
LONG TERM...MPK/MDP
AVIATION...BJG
FIRE WEATHER...
Area Forecast Discussion
National Weather Service Bismarck ND
954 PM CDT Sat Apr 24 2021
.UPDATE...
Issued at 953 PM CDT Sat Apr 24 2021
00Z guidance that has arrived shows a temporal delay in the onset
of precipitation across southern North Dakota until later tonight.
This trend is supported by current dewpoint depressions around 20
degrees Fahrenheit and cloud heights mostly still above 7,000
feet. Another trend in 00Z guidance is for precipitation to spread
farther into north central North Dakota on Sunday, and more
quickly. Some minor adjustments were made to precipitation
chances to account for these trends.
HRRR and RAP visibility trends have prompted the addition of
patchy fog to the forecast Sunday evening through Monday morning.
UPDATE Issued at 720 PM CDT Sat Apr 24 2021
Only minor adjustments were made to the forecast for this update.
More detail was added to precipitation chances Sunday morning and
afternoon based on recent high-resolution model consensus. We
removed any mention of freezing rain from the forecast, which
there wasn`t much of to begin with. Some model soundings do show
wet-bulb temperatures aloft approaching 0 C, but the warm layer
aloft appears very shallow and likely would not allow frozen
hydrometeors to melt. Furthermore, while near-surface air
temperatures may fall below freezing, ground temperatures will
likely stay above freezing. Some elevated surfaces may become
slippery, but that could occur with either rain or snow falling.
On the south side of the band of heaviest precipitation, a loss of
ice production may occur. But by the time that happens later
Sunday morning, ground temperatures should be well above freezing.
Several parameters still appear favorable for enhanced
precipitation rates across south central North Dakota and the
southern James River Valley late tonight through Sunday morning,
including strong mid level frontogenesis, mid level lapse rates
around 6-8 C/km, and the potential presence of conditional
symmetric instability. However, the warmer ground temperatures and
low snow-to-liquid ratios (expected to be less than 10:1) should
limit accumulations to under 2 inches on grassy surfaces for most
areas. A possible exception is from the higher terrain of western
Dickey County back to the west through McIntosh County, where
orographic forcing may further enhance precipitation rates. The
main expected impact is reduced visibility under falling snow.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 240 PM CDT Sat Apr 24 2021
A weak wave embedded within quasi-zonal flow will approach the
western Dakotas late this evening. At the surface, weak
cyclogenesis will develop a low over eastern Wyoming and western
South Dakota overnight. A narrow band of precipitation will
develop over southwestern North Dakota late this evening and lift
north and east into the central part of the state and into the
James River valley by Sunday afternoon. This band will be
associated with some enhanced low level frontogenesis and modest
synoptic scale ascent. The best forcing will remain right along
and below the South Dakota border, from south central North Dakota
into the James River valley. Portions of the far south central
and southern James River valley could end up with 1 to 3 inches of
snow by early Sunday afternoon. Areas across the south central
and southeast could see 0.20" to 0.40" of total liquid through
Sunday evening with lesser amounts as you go west and north (the
northern fringe of this system will have to fight some pretty dry
air).
The northern boundary of the precipitation shield could see some
brief freezing rain mixed in at the onset, but no ice accumulation
is expected. Snow will transition to rain once again on Sunday
afternoon as precipitation starts to diminish and move out by the
evening.
Regarding temperatures, expect lows tonight in the low to mid 30s
with Sunday highs ranging from the lower 40s to lower 50s.
.LONG TERM...(Monday through Saturday)
Issued at 240 PM CDT Sat Apr 24 2021
Flow turns southwest aloft to start the work week and another weak
wave approaches from the west. This wave will interact with a
northward drifting warm front, developing a band of precipitation
along and north of the South Dakota border by Monday morning.
This band will move north through the day, gradually diminishing
in intensity. Precipitation on Monday will mainly be light rain
and areas in and around the band could see another 0.10" to
0.30" of liquid. The exact track this band is still quite
uncertain at the moment.
After another seasonably cool day Monday with highs in the 40s, a
warming trend is expected as guidance is consistent with a ridge
building in the west through the second half of the week. NBM
temperature percentiles do begin to spread towards the weekend as
another western trough may be possible.
Various weak waves will move through mid to late week, but high
uncertainty regarding these low predictability features preclude
mention of any specific precipitation chances beyond Monday at
this point.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 953 PM CDT Sat Apr 24 2021
All terminals start off this forecast period with VFR conditions.
A west-to-east oriented band of rain and snow is forecast to
develop across southern North Dakota late tonight and drift
northward through Sunday. The greatest impacts are expected at
KBIS and KJMS Sunday morning, where snow will likely cause periods
of at least IFR visibility restrictions. There is slightly lower
confidence in precipitation falling and of what type at KDIK.
Farther north, there is greater uncertainty on the strength and
coverage of precipitation, and rain would be the most likely
type. All terminals will see ceilings lower to at least MVFR
levels Sunday morning, with IFR likely by the afternoon. Generally
expecting southeast winds through the forecast period, increasing
to around 15 kts on Sunday.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Hollan
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...Hollan
Area Forecast Discussion
National Weather Service Boston/Norton MA
1022 PM EDT Sat Apr 24 2021
.SYNOPSIS...
Cloudy with rain spreading in late tonight. A coastal storm
will bring periods of rain Sunday followed by blustery and drier
conditions Monday. Turning milder Tuesday and Wednesday, and a
few locations in interior New England may reach 80 degrees. More
unsettled moving into the latter part of the workweek with
temperatures trending closer to or just above seasonable levels.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
10 PM Update...
Already generally overcast with mid to high clouds in place per
satellite imagery, so have increased sky cover in the latest
update. Other change to the forecast was to reduce precipitation
chances toward the latest HRRRE guidance. As the previous update
stated have very dry air in the lower to mid levels. Expect it
to take a bit for things to moisten up enough to see
precipitation. Think that the HRRRE has a good handle on this,
but best shot will be across the south coast late tonight.
Adjusted temperatures as we were cooling things off a bit too
quickly given the cloud cover in place. Low temperatures will
generally be in the 40s.
735 PM Update:
High clouds continue to stream northward early this evening,
with daytime gusts now subsiding as PBL decouples. Cloudiness
will continue to gradually thicken as the evening/overnight
progresses, but will likely remain as mid to high clouds for
most of the night. RAP-based soundings show drier air winning
out and will probably hold any precip from our southern coastal
waters until early Sunday morning (thinking ~3-5 AM).
Aside from the start timing of rains, the forecast challenge
for tonight will be low temperatures. Expect at least some
radiational cooling early in the night given the cirrus
cloudiness, but eventually should slow some as thicker and
lowering cloudiness advances during the second half of the
night. May also be a period of evaporational/wet-bulb cooling
toward daybreak especially southern and coastal areas as rain
shield advances into the in-situ drier air. Given this, it`s
conceivable that southern/coastal towns may be a few degrees
cooler than further north as the HRRR suggests. Did modify lows
a bit warmer by a couple degrees but still looking at readings
in the mid 40s.
Previous discussion:
Cirrus moving up from the Mid Atlantic states will spread overhead
this evening, followed by lower clouds overnight. Rain over the
Carolinas and Srn Appalachians will move up the coast, reaching
CT and parts of the south coast late at night.
Fairly dry air in place from the afternoon with dew points in the
20s. This will change as the low level flow becomes south and
southeast, bringing in marine air with dew points in the 30s and,
eventually, the 40s. Expect min temps in the 40s.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Overview... Both northern and southern streams are at work.
Shortwave in the southern stream is supporting a surface low
entering the Southern Appalachians. Meanwhile, a shortwave in
the northern stream is driving a cold front toward the Western
Great Lakes.
Sunday...Southern stream upper low and surface low will move to the
Mid Atlantic coast tonight, then swing south of New England on
Sunday. General agreement among the models that the track will pass
just south of the 40N/70W benchmark. The supporting upper jet will
move across Eastern New England Sunday, with the right entrance
region nearby in the midday/afternoon generating an area of lift. PW
values are forecast at 0.75 to 1.0 inches, with the GFS a tad more
aggressive than the NAM. Meanwhile, much of the Vapor Transport is
aimed out to sea...although a side-lobe of transport brings 400-500
units to our South Coast. This is mediocre as transport goes, but
should be enough to generate some rain. Given the track, the best
chance will be along the South Coast with lower pops to the north
and west. Amounts look to range from 0.1 to 0.25 along the northern
MA border to 0.6 to 0.7 inches along the South Coast/Islands.
The upper jet and support move off to the east during the afternoon
and evening. Expect the rain to taper off from west to east during
this time.
Sunday night... Northern stream shortwave then drive the Great Lakes
cold front across Srn New England Sunday night. Drier air then moves
in after midnight, with dew points dropping from the 40s into the
mid 20s-mid 30s. Also expect increasing northwest wind after
midnight with gust potential of 25 kt late night. Temps fall to the
30s and lower 40s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Highlights...
* Seasonable temps with dry and blustery conditions Mon.
* Warmup Tues-Wed. Highs nearing 80 in the interior Wed.
* Cooler and more unsettled late week, but large uncertainty in rain
chances and temperatures.
Details:
Monday into Monday Night:
Closed low and associated cold pocket of air aloft will gradually
lift NE into the Maritimes through Mon nite. Though generally
pleasant weather overall, strong daytime heating and this cold pool
of air aloft should promote deep mixing, which will lead to blustery
NW wind gusts around 25-35 mph as well as dewpoints falling into the
teens to mid 20s. Given highs around seasonable levels in the 50s to
lower 60s, progged relative humidities tumble into the mid 20s to
near 30 percent in the afternoon. So while we should see lots of
sun, a window for potential fire weather concerns may exist on
Monday pending how much rain we do get from the Sunday system.
Mostly clear and dry weather for the evening with gusts subsiding
shortly after sundown with lows in the mid 30s to low 40s.
Tuesday into Tuesday Night:
We then begin a warm-up into Tuesday with 850 mb temps rising to
around +6 to +9C and sfc ridge to our south bringing SW winds to
Southern New England. Boosted highs by around 3-5 degrees over NBM
which seemed too cold given full sun, deeper mixing and SW flow.
Remains dry with highs reaching well into the 60s into the mid 70s.
A few upper 70s probably can`t be discounted either in the CT
Valley. Rather strong confidence that Tuesday is the "pick of the
week" from a weather standpoint.
Wednesday through Friday Night:
Carrying over from the overnight 00z guidance, the 12z suite of
guidance continues to display little continuity moving into the
middle to latter part of the week, with forecast confidence
dwindling significantly. This is due in part to varied handling of
interaction between northern-stream troughing moving across the far
northern Plains/Canadian Prairies and a closed upper low over the
Desert Southwest. A frontal boundary will also be lingering and/or
lying across Southern New England, a feature which may sag southward
as a backdoor front later on Wednesday into late in the week. With
anomalous 850 mb temps around +12 to +14C, it leads to substantial
uncertainty both on PoPs but also large temperature bust potential
especially in high temperatures. Encapsulating this large spread is
the 10th- and 90th-percentile NBM highs for Wed and Thurs: the 10th-
percentile values in the mid 50s to low 60s, while the near top-tail
90th-percentile highs are well in the 80s!
Wednesday could prove to be even warmer than Tuesday with highs at
least into the 70s and perhaps near 80 out in the CT Valley. Onshore
flow/sea-breeze near the coasts would keep highs closer to the 60s
here. Though the GFS/Canadian are dry, the ECMWF shows a weak area
of low pressure moving across northern MA which would bring chances
for rain and also cooler temperatures. Seems to be an outlier with
respect to other guidance and doesn`t seem to have much support from
ensembles so opted for a generally dry day and temps closer to the
milder guidance.
Thursday and Friday are when the models really begin to diverge the
most significantly due to the different handling of 500 mb features
and position of surface frontal boundaries. The GFS shows more
phasing of the Desert SW trough with northern stream troughing,
while the ECMWF/Canadian GEM keep the streams separated with a more
northern-stream dominated regime for the latter part of the week.
Though it does look more unsettled moving into the latter part of
the week, really too much uncertainty to go any higher than Chance
PoP and temperatures in the 60s.
Saturday:
Still a good amount of uncertainty for Saturday as well given
the low-predictability in the weather pattern from late in the
week. GEM and the ECMWF are drier, while the GFS maintains
unsettled conditions. Stuck fairly close to NBM for Saturday
until there`s better consensus in the pattern.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight: High confidence.
VFR with high and then mid-level cloudiness for most of the
evening/overnight. Ceilings then trend more BKN-OVC lower VFR
around 09-12z, perhaps approaching MVFR levels as rain
overspreads near the southern coast/Cape Cod. SW winds 6-11 kt
lighten and shift to S/SSE to 4-7 kt thru overnight/daybreak.
Sunday: Moderate confidence.
Conditions then continue lowering, to MVFR/IFR during the
morning. Some localized LIFR is possible across Cape Cod and the
Islands with rain. Winds shift from the E and eventually the NE
as low pressure slides by Cape Cod and the Islands. All
forecast models show a track of the storm center just south of
40N/70W. Visibility reductions from heavier precip most likely
late in the morning into the afternoon, around 1-2 nm.
Conditions improve to VFR in the CT Valley toward evening.
Sunday night...
Conditions continue to improve to VFR from west to east through
8 PM. Winds turn from the northwest with gusts to 25 kt after
midnight.
KBOS TAF...High confidence in TAF. VFR.
KBDL TAF...High confidence in TAF. VFR.
Outlook /Monday through Thursday/...
Tuesday: VFR. Breezy.
Tuesday Night: VFR.
Wednesday through Wednesday Night: VFR. Slight chance SHRA.
Thursday: Mainly VFR, with local MVFR possible. Chance SHRA.
Thursday Night through Friday: Mainly VFR, with local IFR
possible. Breezy. Chance SHRA.
&&
.MARINE...
Tonight...
West to southwest winds in the evening will turn from the south
toward midnight and from the southeast late. Speeds will
diminish to less than 10 kt. Seas will linger at 2 to 4 feet,
lower closer to shore.
Sunday...
Coastal weather system passes south of the 40N/70W benchmark
during the afternoon. Rain will move across the waters, bringing
reduced vsbys of 1-3 nm in the heavier areas of rain/fog.
Winds continue to shift, coming from the east and then
northeast during the day with speeds of 10-20 kt. Seas building
across the south and east to 4-7 ft. Seas of 5 feet are expected
on the southern outer waters, with 4 feet or less farther
north. A Small Craft Advisory will be issued for these outer
waters.
Sunday night...
Winds shift from the northwest and rain tapers off as the
offshore system heads for Nova Scotia. Winds may gust 25 to 30
kt after midnight. Seas will build to 4-7 feet on the exposed
waters. An additional Small Craft Advisory will go in effect for
most of the remaining southern waters.
Outlook /Monday through Thursday/...
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Tuesday Night: Winds less than 25 kt. Seas locally approaching
5 ft.
Wednesday through Wednesday Night: Winds less than 25 kt. Areas
of seas approaching 5 ft. Slight chance of rain showers.
Thursday through Friday: Winds less than 25 kt. Seas up to
5 ft. Chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 6 PM Sunday to 8 AM EDT Monday for
ANZ232>235-237.
Small Craft Advisory from 11 AM Sunday to 8 AM EDT Monday for
ANZ254>256.
&&
$$
SYNOPSIS...WTB/BL/Loconto
NEAR TERM...WTB/BL/Loconto
SHORT TERM...WTB
LONG TERM...Loconto
AVIATION...WTB/Loconto
MARINE...WTB/Loconto
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
720 PM CDT Sat Apr 24 2021
...New Short Term, Aviation...
.SHORT TERM... /NEW/
Update:
The inherited forecast is in good shape, with just a few minor
changes needed. I went ahead and increased cloud cover for areas
near and north of I-20 and east of U.S. HWY 287. GOES PWAT imagery in
tandem with RAP 850-925mb mixing ratio progs indicate sufficient
moisture remains on the backside of the upper trough that
continues to scoot eastward through the SE CONUS. Drier air was
noted upstream across Oklahoma and Arkansas and this, in tandem
with the loss of daytime heating, should be efficient at eroding
the stratocumulus deck over the course of the next few hours.
The other change was to explicitly mention patchy fog in the
worded forecasts and highlight the potential for reduced
visibility down to near a mile in spots in the HWO. MRMS QPE
analysis revealed that several areas along the Red River and
across parts of Central Texas received around 1-3 inches of
rainfall from yesteray`s convection. Recent rainfall in
conjunction with clear skies, diminishing low level winds and
large scale subsidence should promote an environment conducive for
radiation fog. Utilizing the UPS "crossover method" from BUFKIT in
conjunction with RAP time-lagged ensemble probabilistic visibility
guidance (through at least 0900 UTC Sunday) yielded high enough
confidence to at least highlight the fog potential across areas
that saw over an inch of rainfall yesterday. At present time, I
don`t expect widespread dense fog, though it`s not out of the
realm of possibility along the U.S. HWY 82 corridor (Bowie to
Paris) where the greatest rainfall amounts reside). We`ll monitor
visibilities and the need potentially for any dense fog headlines.
While some of the more rural parts of the D/FW Metroplex may
experience very shallow fog, the more urbanized regions will
likely remain fog-free due to the UHI.
Outside of those elements, the remainder of the short term
forecast remains largely unchanged.
Bain
Previous Discussion:
/This Weekend/
After an active Friday, the start of your weekend has been much
more quiet with partly to mostly cloudy conditions. Efficient
momentum transfer of low level northwest flow has resulted in a
breezy day with northwest winds 10 to 15 mph. A few gusts to
between 20-25 mph were being observed as well. A strong subsidence
inversion was noted above 850mb in wake of our departing mid
level trough with a relatively deep layer of moisture trapped
underneath. This has resulted in stratocu development this
afternoon across much of the region. The trapped moisture will be
eventually replaced by drier air by early evening with clearing
conditions. I did lower highs a few degrees this afternoon across
North Texas due to the aformentioned stratus and residual low
level cold air advection.
Mostly clear skies will prevail tonight with the subsidence inversion
strengthening and lowering down into the boundary layer. Decoupling
will help wind speeds to diminish below 10 mph quickly after
sunset. A broad surface high will transit readily east across the
Southern Plains and move into the Ozarks and Lower Mississippi
Valley after sunrise Sunday. Optimal radiational cooling and a
thin layer of moisture trapped beneath a strong low level
inversion should allow for patchy fog development, especially
areas that saw more significant rainfall. Lows will bottom out
tonight in the upper 40s to lower 50s.
Increasing low level warm advection and mixing will dissipate any
spotty fog by mid morning Sunday, as southeast winds increase to
between 10-15 mph. Plentiful sunshine and a relatively dry
airmass will allow high temperatures to warm quickly into the
upper 70s to mid 80s with occasional wind gusts to 20 mph possible
in the afternoon.
05/
&&
.LONG TERM... /Issued 337 PM CDT Sat Apr 24 2021/
/Sunday Night Onward/
The main highlight in the extended forecast is the return of
showers and thunderstorms across the region by the middle of the
week. We`ll have to keep an eye on the potential for strong to
severe thunderstorms, as well as the threat for locally heavy
rain. Otherwise, unlike last week, the final week of April will
feature near to above normal temperatures.
Although rain-free weather is expected across North and Central
Texas on Monday, the next upper level system should be located
over the western US and gradually moving toward the region. Breezy
southerly winds will aid in transporting moisture northward and
will result in dew point values rising into the upper 50s and low
60s by Monday afternoon. Afternoon highs in the 80s are forecast
across most of the region, but our far western counties may warm
into the low 90s. The combination of low humidity, warm
temperatures, and breezy winds may yield an elevated fire weather
threat across parts of the Big Country Monday afternoon as well.
Persistent southerly flow should result in overcast skies on
Tuesday, aiding in slightly lower high temperatures than the
previous day. Precipitation chances return by Tuesday afternoon
as the forcing for ascent associated with the upper low begins to
spread across North and Central Texas. The initial activity on
Tuesday should be limited to mostly warm advection showers and
thunderstorms.
It still seems that the highest precipitation chances will be late
Tuesday night and Wednesday as the upper low enters the West
Texas region. With high moisture content, large scale lift, and
instability in place, strong to severe thunderstorms cannot be
ruled out as a dryline/Pacific front approaches the region.
Additionally, both the ECMWF and NAEFS ensemble guidance indicate
a heavy rain potential during this time period with PW and IWT
percentiles in the 95-100 range. Rainfall accumulations of 1 to 3
inches, with locally higher amounts, look possible for most of
North and Central Texas. Details will continue to be refined over
the next few days, so check back for updates.
There are still discrepancies on the evolution of this system as
we head into Thursday and Friday, with the GFS ending rain chances
by Thursday night and the ECMWF keeping rain chances through
Friday. For now, introduced some low precipitation chances across
the eastern half of the region through Thursday night until guidance
comes into better agreement. Rain-free weather looks to return by
the weekend with slightly above-normal temperatures.
Garcia
&&
.AVIATION... /NEW/
/00 UTC TAF Cycle/
Concerns---Near term cig trends at D10 TAFs & low BR potential.
A deck of pesky MVFR cigs continues to persist and has even
expanded southward some this evening. D10 TAFs can expect at least
intermittent MVFR for the next few hours before dry air arriving
from the northeast scatters and lifts cigs...likely resulting in
near SKC. This deck of MVFR stratus is expected to remain north
of Waco.
Northerly winds near 10 knots this evening will diminish and
become more easterly around midnight such that there will be
flexibility for takeoff/landing configs for the Sunday morning
push. There is a low potential for MVFR BR thanks to yesterday`s
rainfall, but current projections are that the greater risk will
be north of D10 TAFs and generally outside of the urban landscape.
Some of the more rural D10 TAFs (GKY and AFW) along with ACT may
have a slightly greater chance for 4-5 SM vsby, but even this
potential looks low.
Any BR should dissipate quickly after sunrise Sunday with
southerly winds increasing to near 15 knots. VFR CU may bubble
Sunday afternoon but should diminish after sunset. There`s a non-
zero threat of non-convective LLWS in the 24-30 hour D/FW TAF,
but we`ll take a look at this closer in subsequent TAFs.
Bain
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 52 81 61 85 68 / 0 0 0 0 0
Waco 50 82 60 84 66 / 0 0 0 0 0
Paris 50 78 57 81 63 / 0 0 0 0 0
Denton 49 82 61 83 65 / 0 0 0 0 0
McKinney 50 79 60 82 65 / 0 0 0 0 0
Dallas 54 82 61 85 68 / 0 0 0 0 0
Terrell 50 80 58 82 65 / 0 0 0 0 0
Corsicana 52 81 58 83 66 / 0 0 0 0 0
Temple 51 82 61 84 66 / 0 0 0 0 0
Mineral Wells 49 84 61 86 65 / 0 0 0 0 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Junction CO
803 PM MDT Sat Apr 24 2021
.UPDATE...
Issued at 800 PM MDT Sat Apr 24 2021
Critical fire weather conditions have improved with sunset and a
minor recovery in humidity therefor the red flags warnings have
been allowed to expire for tonight.
&&
.SHORT TERM...(Tonight through Sunday night)
Issued at 300 PM MDT Sat Apr 24 2021
A quick-moving deck of cirrus clouds moved over a large portion of
eastern Utah and western Colorado this morning, but these clouds
have mostly thinned out and pushed off to our east as of early
this afternoon. In their wake, we have a mostly sunny sky with
just a few diurnally forced cumulus clouds developing along the
higher terrain. The increased diabatic heating is leading to
rising temperatures and strengthening mechanical mixing in
response. Combined with a weak, low-amplitude shortwave embedded
within a 40-50kt mid- level jet, strong wind gusts of 30-40 mph
will be readily brought to the surface, especially at elevation.
So expect breezy conditions through the remainder of the afternoon
along with fire weather concerns given the dry air in place. This
morning`s 12Z GJT RAOB revealed a very deep dry layer which
extended from the surface all the way up to 500mb. As this dry air
aloft mixes to the ground, relative humidities will plummet into
the single digits and low teens. Given the above, made no changes
to the ongoing Red Flag highlights which remain on track.
Within an hour or so after sunset, critical fire weather
conditions will diminish as surface winds decouple and relative
humidity recovers above criteria. Clouds will increase this
evening as the aformentioned shortwave passes through the forecast
area overnight. With a dry subcloud layer, not expecting this wave
to produce much in the precipitation department other than maybe a
few showers in the northern mountains along the Continental
Divide. This activity exits to our east by Sunday morning with
mainly dry, partly sunny weather to follow. As we head through the
day, a large trough just off the West Coast will slowly move
inland. Ahead of this feature, deep southwest flow will increase
and set the stage for another afternoon and evening of strong,
gusty winds and critical fire weather conditions. In fact, the 12Z
HRRR experimental Fire Weather Index indicates Sunday could be a
high end fire weather day with more severe conditions than
typical, especially when compared to today. So with this forecast
package, we decided to expand the Red Flag Warning northward to
include Utah Fire Weather Zone 486 below 7kft as latest guidance
points towards winds and RH meeting criteria there. We also
hoisted a Wind Advisory for northwest Colorado as winds will have
the potential to gust as high as 50 mph. Debated including more
zones farther south in the Wind Advisory, but held off for now and
will let subsequent shifts take a look at additional guidance.
Highs on Sunday will be well about 10 degrees above normal.
While winds will gradually lessen Sunday night, there`s a quite a
bit of guidance that keeps winds fairly elevated through the
overnight hours, particularly in southeast Utah and southwest
Colorado. This may allow critical conditions to linger deeper
into the night than is otherwise typical, but Red Flag Warnings
will expire by midnight.
.LONG TERM...(Monday through Saturday)
Issued at 300 PM MDT Sat Apr 24 2021
On Monday, there are still some difference between the deterministic
models regarding how much this trough closes off into a low
pressure. The ensembles are more in favor of the closed off solution
as the system moves over the Great Basin and into the Desert
Southwest. This will have implications on the speed of the front and
amount of lift provided across our area. The associated jet will
still reside overhead on Monday so the potential for strong gusty
winds is still high. The one concern will be the moisture advecting
ahead of the front in the southwest flow. Some of the models
continue to indicate isolated showers in the afternoon, but most of
the area should stay dry. This increasing moisture looks to cool the
midlevels therefore mixing might not be as deep as tomorrow. The
moisture and hopefully cooler temperatures will keep the relative
humidity from dropping too low as well. The one exception might be
the Four Corners region so red flag conditions may continue in this
area and borderline elsewhere. By Monday evening the front pushes
into northwest portions of the forecast area. Showers look to
increase in coverage as the front slides eastward. Some of the high
res models are showing pre-frontal instability and banded precip
associated with the frontogenesis. Overnight the precip will spread
across the remainder of the forecast area especially in the higher
terrain.
By Tuesday morning the front exits the area, but if the low pressure
closes off to the southwest of the Four Corners there could be some
lift that enhances the showers through out the day. Flow shifts to
the west and eventually northwest favoring those slopes. Showers
will likely also be enhanced by the day-time convection on Tuesday.
There are a few models slow to kick the low pressure out of the
Desert Southwest on Wednesday, so there is a slight chance for
showers to linger in southern Colorado. It appears most locations
will remain dry though for now. Overall the total QPF has increased
probably due to influence from the high-res model and daytime
instability. and the system closing off. The most likely time frame
for impacts from snow may be Tuesday morning mainly at pass level
unless the clouds can hang around some impacts may linger into the
day.
The new trend in the models now is to stall this low pressure over
NM and northern Mexico mid week, which is supported by roughly half
of the ensembles. This will have implications on the ridging that
attempts to build across the western CONUS and nose over us. This
may likely dictate how warm and dry we get in the later half of the
week. Unfortunately, we could be looking at another round of
elevated fire weather conditions under this ridge. Hopefully the
lacking pressure gradient will keep the winds near or slightly below
criteria. Hard to tell at this point with that stalled low pressure
around. Another strong system is forecasted to impact the Pacific
Northwest this weekend and drop southeastward towards our area early
next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 507 PM MDT Sat Apr 24 2021
VFR will continue at all sites through the forecast period. The
primary weather at all terminals will be strong winds. Westerly
gusts over 30 knots will continue this evening until after 2z. As
surface winds decrease overnight, wind shear will be present aloft
with strong west winds continuing overhead. Gusty winds will
affect all terminals once again on Sunday.
&&
.FIRE WEATHER...
Issued at 300 PM MDT Sat Apr 24 2021
Critical fire weather conditions will continue through this
evening before winds diminish and humidities recover. Red Flag
Warnings remain in effect for Sunday afternoon and evening with
southwest winds gusting 30-50 mph and relative humidity dropping
to near 10 percent. Given the strong winds and very dry air, there
is potential for Sunday to feature conditions that are more severe
than typical. Winds will remain gusty Sunday night into Monday,
but increasing cloud cover will keep critical fire weather
conditions much more localized to start the new week. Cooler and
wetter weather is expected to arrive by Tuesday as the next system
rolls in from the west.
&&
.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Red Flag Warning from noon Sunday to midnight MDT Sunday night
for COZ203-207-290-292-295.
Red Flag Warning from noon to 9 PM MDT Sunday for COZ200-202.
Wind Advisory from noon to 9 PM MDT Sunday for COZ001-002.
UT...Red Flag Warning from noon Sunday to midnight MDT Sunday night
for UTZ490-491.
Red Flag Warning from noon to 9 PM MDT Sunday for UTZ486-487.
&&
$$
UPDATE...TGJT
SHORT TERM...MDM
LONG TERM...KJS
AVIATION...MAC
FIRE WEATHER...TGJT
Area Forecast Discussion
National Weather Service Wilmington NC
943 PM EDT Sat Apr 24 2021
.SYNOPSIS...
Low pressure will move into the area from the Gulf Coast tonight,
bringing moderate rain to the region. High pressure will build
in Sunday through early next week, bringing dry air and
seasonable temperatures to the area. Another system may affect
the region late next week.
&&
.UPDATE...
No updates required to the evening forecast.
&&
.NEAR TERM /THROUGH SUNDAY NIGHT/...
It`s been a day of playing catch-up with the diminishing severe
weather threat, which has now about dwindled to nothing. This is on
account of the insolation-inhibiting cloud cover. In fact, latest
mesoanalysis shows zero CAPE across the area and thunder will now be
so hard to come by that it has been removed from the forecast for
all but our far southern zones. Now some vexing model discrepancies
remain regarding rainfall amounts, with the trend being one towards
suppression to our south. The HRRR seems to represent the extreme in
not delivering much rainfall at all and the WRF is either suffering
from convective feedback or is suggesting a healthy gravity wave
moving through our SC counties around 00Z. The latter was a concern
a few days ago and is certainly possible, though the required
ducting inversion at 8kft mixes out at that time. Regardless, a few
special weather statements may be issued later on for non-severe
wind gusts in heavier shower elements due to the strength of the low
level wind fields. Deep layer moisture pushes offshore by 06Z at
which time rain chances decline precipitously. Light rain however
will be tough to rule out until later Sunday morning due to the
lagging PVA and height falls. Strong dry advection underway by
midday Sunday. Strong southerly prefrontal winds tonight will keep
lows close to 60 whereas tomorrow`s CAA will keep highs in the low
70s and drive Sunday night lows into the low 50s.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Surface and mid-level ridging will dominate the short term. Surface
high building in from the north Mon morning slips offshore Mon
night, setting up return flow for Tue. Northeast flow Mon will keep
highs near to slightly below climo, but development of weak warm
advection Mon night should bring about the start of a gradual
warming trend. Lows will be near climo Mon night, although the
typical cold spots will likely run a little cooler. Highs near to
above climo Tue with lows above climo Tue night. Aloft the mid-level
ridge will generate subsidence and forecast soundings show a healthy
mid-level subsidence inversion. Not expecting much if any cloud
cover and no chance of rain for the start of the week.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Amplified mid-level pattern Wed through Sat will transition from
ridging midweek to troughing by the weekend. Still a lot of
uncertainty with respect to the strength and timing of the weekend
trough, but unsettled weather to end the week looks like a good
possibility. However, coverage remains a question and for now will
maintain pop in the chance range. Wed and Thu will be warm and dry
before rain chances start to increase later Fri. Trough helps push a
cold front across the area during Sat.
- Highs above climo Wed-Fri with lows well above climo.
- Rain chances return later Fri and continue through Sat.
- Temperatures near to slightly below climo Sat.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Low pressure and associated frontal passage brings gusty winds
until around sunset with lowering MVFR/IFR ceilings tonight.
Winds will shift to the northwest by mid to late morning Sunday.
Improving conditions through the day Sunday.
Extended Outlook...Flight restrictions could persist into Sunday
morning. Otherwise, VFR.
&&
.MARINE...
Through Sunday Night:
Wind and seas will continue to build ahead of approaching cold
front, both increasing to advisory levels by tonight. FROPA
around daybreak will veer winds sharply to the NW while also
allowing for a decrease in wind speeds as no large high is
forecast to build behind the front, that being more typical of
the cooler seasons. Current advisory runs through noon but it
will likely be lowered sooner than that over southern zones
whereas 6 foot seas may plague NC waters until roughly that
time.
Monday through Thursday:
Brisk northeast flow Mon morning starts to weaken by mid-
morning with winds veering to east and then southeast as surface
high shifts over the area. Gradient collapses and winds drop
under 10 kt by Mon afternoon. Light and variable winds Mon night
with the high shifting offshore Tue through Thu. Gradient
remains somewhat ill-defined into Wed before the high pushes a
bit farther offshore. Southerly flow increase to 10 to 15 kt Wed
and 15 to 20 kt Thu ahead of slow moving cold front. Seas 2 to
3 ft Mon morning will drop to 2 ft or less in the afternoon and
remain 2 ft or less into Wed afternoon. Gradual increase in
southwest flow will build seas to around 3 ft Wed night and 3 to
4 ft later Thu.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until noon EDT Sunday for AMZ250-252-254-
256.
&&
$$
UPDATE...MCK
NEAR TERM...MBB
SHORT TERM...III
LONG TERM...III
AVIATION...MCK
MARINE...MBB
Area Forecast Discussion
National Weather Service Indianapolis IN
1146 PM EDT Sat Apr 24 2021
...Updated Aviation Discussion...
.Forecast Update...
Issued at 858 PM EDT Sat Apr 24 2021
Radar loop indicates some patchy light rain lingering over about the
southeast half of the forecast area, associated with a weakening
deformation zone. Extrapolation and short term model data suggest
any lingering precipitation should exit the area by 250300Z. Will
keep some chance PoPs going over the southeast half until that time.
Clearing line currently working its way into the far northwest zones
at this time. The line should continue to progress southeast during
the course of the night, but short term model data suggests at least
some areas of low cloud cover may develop later tonight, For that
reason, will not go too optimistic on the sky cover.
&&
.Short Term...(This evening through Sunday night)
Issued at 252 PM EDT Sat Apr 24 2021
Surface analysis early this afternoon shows low pressure in place
across Central Tennessee...with cyclonic flow in place across KY and
Indiana. Radar shows widespread rain showers in place across
KY...spreading across southern Indiana. Easterly surface flow was in
place at the surface...allowing some dry air to arrive within the
lower levels.
Tonight...models suggest the surface low will push
northeast...slowly exiting the area...allowing high pressure over
the Plains states to build across the area overnight. HRRR suggests
precip will exit the area between 02-03Z. Meanwhile the forecast
soundings show deep moisture departing this evening...while keeping
some lower level saturation in place through the evening before
clearing things out overnight. Thus will trend for some low pops
this afternoon and evening as the low departs...before trending
toward a decreasing cloudiness type forecast overnight. Given the
expected clearing skies and ongoing cold air advection in the wake
of the departing low...will trend lows at or below the NBM.
Sunday...models suggest strong NW flow in pace aloft with a weak
short wave moving through the southern Great Lakes late in the
afternoon. Meanwhile cool high pressure will be building across the
surface and forecast soundings show a lack of moisture along with a
mid level inversion that should prevent any convection. Thus will
trend toward a dry...partly cloud day on Sunday...sticking close to
the NBM highs.
On Sunday night...the models suggest broad ridging building aloft
over the plains states with subsidence in place over the high
valley. Meanwhile strong surface high pressure will be pushing
across Indiana...allowing a return flow of southerly air to begin by
Monday morning. Forecast soundings remain dry through the
night...thus will trend toward a mostly clear forecast and stick
close to the NBM on lows.
&&
.Long Term...(Monday through Saturday)
Issued at 252 PM EDT Sat Apr 24 2021
Big warm up coming up for central Indiana as high amplitude upper
ridge will move across the Great Lakes and Ohio Valley next Monday
night providing subsidence, and a strengthening surface pressure
gradient will bring increasing southerly flow to the area.
Dry column and low level thermal axis pointing into the Ozarks and
Wabash Valley Monday, will be over the Ohio Valley Tuesday with 850
temperatures to 15 degrees Celsius. This combo will result in near
record high temperatures in the lower 80s by Tuesday.
After that, things will change as the ridge moves to the east and a
western trough and slowing moving frontal system approach. Gulf
inflow ahead of the front will bring deepening moisture and
increasing instability to the Ohio Valley. Meanwhile, there is the
potential for a wave or two of low pressure to move along the nearby
front. The combo of the lift, moisture and instability support the
possibility of some heavy convection midweek. Models are different
in timing, but the Wednesday and Thursday period looks to be the
best chance.
High pressure will build in next weekend and should result in mostly
dry but cooler weather. After coordinating with local offices,
lowered the guidance PoPs.
&&
.Aviation...(250600Z TAF Issuance)
Issued at 1143 PM EDT Sat Apr 24 2021
IMPACTS:
- Localized LIFR visibilities/indefinite ceilings due to fog through
about 251000Z.
- Areas of MVFR ceilings 010-015 for a period from sunrise through
late morning Sunday possible.
- Surface winds becoming 330-360 degrees at 8-12 kts towards
daybreak Sunday.
DISCUSSION: Areas of fog, with localized dense fog resulting in LIFR
visibilities and indefinite ceilings, have formed in the wake of the
clearing line pushing into southeast Indiana. These low conditions
will remain possible at the terminals until about daybreak Sunday. A
stronger wind surge is expected to begin moving into the northwest
zones over the next several hours, which should help dissipate the
fog from northwest to southeast during the course of the night.
There may be a period after the fog lifts through the late morning
hours of Sunday where ceilings 006 AGL-012 will be possible, as the
fog may temporarily mix out into a low cloud deck.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...JAS
Short Term...Puma
Long Term...Koch
Aviation...JAS
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
933 PM CDT Sat Apr 24 2021
.UPDATE...
928 PM CDT
No major updates needed to the forecast this evening. A few
more feisty showers have developed along the incoming cold front
across Chicago within a lingering sliver of marginal instability
present under 15 kft or so. These will swing south and east of the
region through the rest of the evening hours leaving us with
gusty northwesterly winds and some enhanced low cloud cover and
possible patchy fog/mist downwind of the lake overnight.
Temperatures across northwest Illinois will fall towards 33-36
degrees towards daybreak Sunday, but with the core of the surface
high still off to our northwest, thinking we`ll maintain some
occasional gusts through enough the nighttime hours to limit the
frost potential. The mention of patchy-areas of frost in the grids
covers this potential well, with no plans to hoist any Frost
headlines. Updated hourly products have been sent.
Carlaw
&&
.SHORT TERM...
303 PM CDT
Through Sunday...
The near term forecast has a couple subtle weather features, the
one most of note being a cold front late today/early this evening
bringing scattered showers for locales mainly north of I-80.
Otherwise some gusty winds behind that front and cooler highs for
most locations Sunday than today.
Earlier precipitation of a more stratiform nature is about to
depart the far southeast CWA. Associated clouds through peak
heating have limited temperatures in this area with mid 50s
prevalent, while further northwest some sun helped temperatures
into the lower to mid 60s. The cold front is just entering north
central Illinois as seen on visible satellite where it is
highlighted by a zone of more convective-ish, albeit closed-
celled, cumulus clouds. There has been a gradual uptick in radar
echoes since 2 PM with a similar trend expected the next few hours
in northern Illinois as the front approaches the Chicago metro.
Upper forcing from a parent strong short wave is much better
north of the Wisconsin/Illinois state line. Subtle PVA from this,
the surface convergence along the front, and some weak MUCAPE
around 100 J/kg are basically all these showers have going for
them. That CAPE is almost all below -10C as advertised on almost
all guidance and seen from modifying this morning`s 12Z DVN
sounding, so the lightning threat remains low. A few of the
showers in far northern Illinois may produced some 30 mph gusts
but otherwise should not be a big deal.
The front will clear the forecast area by around 9 pm, with
northwest winds becoming gusty afterward owing to 4 mb/6 hr
pressure rises. Winds will bend more north-northeast toward
morning. Some low clouds are likely, mainly between the 1,000 and
4,000 ft layer, and RAP guidance has indicated moisture through a
good part of this depth and even a couple runs with spotty QPF
(probably patchy drizzle). See that being an outlying solution,
but do think it will be cloudy to start Sunday in northeast
Illinois and far northwest Indiana.
Also for Sunday will be the cooler temperatures in part due to
those northeast winds. These will get an enhancement in the
afternoon with the density difference maximized at daytime peak
heating. This will keep highs only in the mid 40s or so in far
northeast Illinois and far northwest Indiana on Sunday. Inland
readings will extend into the 50s. Clouds look to thicken Sunday
especially in the afternoon as warm advection aloft progresses
into the Upper Mississippi Valley/western Great Lakes. Of note
with this is the potential for some light rain extending as far
south as far northern Illinois. The better jet forcing and
frontogenesis along the 850-700 mb baroclinic zone remain north
of the area. Have introduced only a slight chance of rain in the
far north for Sunday afternoon.
MTF
&&
.LONG TERM...
Sunday Night through Saturday...
246 PM...Forecast concerns include much warmer temps and windy
Monday and Tuesday then precip chances Tuesday night through
Thursday.
With a dry airmass in place Sunday evening, temps are expected to
fall quickly in the evening and possibly into the mid/upper 30s
before leveling off and then likely warming a few degrees prior to
sunrise as strong warm air advection aloft occurs Monday morning.
Confidence for these trends is only medium and with the potential
for cloud cover and winds increasing into the 10 to 15 mph range
by sunrise, frost is looking unlikely and no mention with this
forecast. There will also be a small chance for a few showers or
sprinkles both early Sunday evening and again toward daybreak
Monday morning. Maintained slight chance pops for the far northern
cwa but confidence remains low.
Monday will be much warmer and quite windy by afternoon though
there is still some uncertainty regarding just how deep the mixing
will be on Monday. However, wind gusts into the 35-40 mph range
still look possible. Wind directions may remain far enough south/
southeast for cooler temperatures along the IL lakeshore,
especially from downtown north to the IL/WI state line.
Temperatures will climb well into the 70s with upper 70s likely
across the southern cwa, perhaps a few places tagging 80. Winds
will remain breezy Monday night as low temperatures only drop into
the lower 60s. Tuesday looks windy again with winds turning more
to the southwest allowing the warmer temps to reach all the way to
the lakeshore. Highs expected to reach the lower 80s for most of
the area.
As one area of low pressure moves north of the area Tuesday night,
a cold front is expected to move into the area by Wednesday
morning. Precip chances during this time are unclear. The bulk of
the precipitation may stay north of the area, with some weakening/
decaying activity by late evening into the overnight hours. Then a
second area of low pressure is now expected to move south of the
area Wednesday night. The trend in all of the models is much
drier, especially for areas along/north of I-80. Still have quite
a bit of likely pops during the midweek time period and too early
to back off on those, but if the drier trend continues, pops will
need to be trimmed back. Temps trend back to seasonal readings
for the end of the week. cms
&&
.AVIATION...
For the 00Z TAFs...
Primary Forecast Concerns:
* Scattered showers early this evening
* Gusty NW winds behind a cold front veering north overnight
* MVFR (possible IFR) cigs for the Chicago area terminals
overnight
* Northeast winds Sunday morning with a reinforcing
lake breeze in the afternoon
A cold front is currently progressing southeast across northern
Illinois early this evening with scattered showers having
developed along it. These will continue to drift southeast slowly
with -SHRA possible between 00-03Z. Prevailing wind directions at
ORD and MDW remain out of the east in the near term but will soon
turn northwesterly with the passage of the showers and cold front.
The pressure gradient begins to tighten behind the front
resulting in increasingly gusty northwest winds to 20-25kt this
evening. Winds remain elevated but ease slightly after midnight as
they veer north to northeasterly. This will allow low clouds to
move inland off the lake with MVFR to potentially IFR cigs
expected overnight. These will begin to lift through the morning
hours and diminish in coverage.
A reinforcing lake breeze develops tomorrow and should push far
enough west to reach RFD by the end of the TAF period.
Petr
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...IL nearshore waters until 3 PM Sunday.
Small Craft Advisory...IN nearshore waters until 7 PM Sunday.
&&
$$
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Area Forecast Discussion
National Weather Service San Francisco Bay Area
857 PM PDT Sat Apr 24 2021
.SYNOPSIS...Widespread light to moderate showers are forecast for
the entire region late tonight and Sunday as a late season cold
front moves through. There is also a slight chance of
thunderstorms in the wake of the front Sunday afternoon across
portions of the North and East Bay. This front will also keep
temperatures cooler than normal. Lingering showers are possible
into Sunday evening. A warming and drying trend is then on tap
from Monday through Wednesday, followed by cooling late next week.
&&
.DISCUSSION...As of 8:55 PM PDT Saturday...A weak boundary moving
inland over northern California earlier today produced very light
rain across the extreme northern portion of our forecast area,
but otherwise the only impacts were considerable cloud cover and
temperatures remaining on the cool side of normal.
The system that is forecast to bring widespread shower activity
to our area late tonight and Sunday is still well offshore. Radar
has been showing weak returns off the North Bay Coast this
evening, but it`s doubtful we will see anything more than a few
sprinkles over the next several hours. The 00Z NAM and latest HRRR
agree that light warm advection precip will begin to overspread
our area right around sunrise on Sunday morning, which is a bit
later than models had been forecasting previously. Rainfall
intensity will remain light until the cold front arrives and helps
generate scattered moderate rain rates starting in the North Bay
a few hours after sunrise and progressing southeast through most
of the rest of the area by late afternoon. As has been the case
for much of this rainy season, the models have been trending drier
with this system and the latest model QPF is generally a half
inch or less, with most areas now likely too see only a tenth to a
quarter inch of rain by late Sunday. The bottom line is that
although much of our area will see wetting rains, this system will
not contribute in any serious way to alleviating our severe
rainfall deficits. Also, rainfall on Sunday may delay the onset of
fire season by a week or two, but won`t have any material impact
on the state of the fuels this summer.
Winds are not expected to be a factor with this system, with only
localized brief breezy south winds expected just ahead of the
cold front on Sunday, mainly near the coast.
Thunderstorm potential in the unstable airmass behind the front
looks to be waning, although it`s not out of the question that we
could see an isolated storm in the North or East Bay tomorrow
afternoon. Showers are expected to taper off Sunday evening and
mostly end by midnight.
A cool airmass will remain over our area into Monday, although
temperatures will warm a bit on Monday due to mostly sunny skies.
A robust warming trend is then forecast for Tuesday and Wednesday
as an upper ridge builds along the West Coast. By midweek we can
expect some lower 80s in the warmest inland areas. Cooling is then
on tap for late next week and into the following weekend when
longer range models bring a trough in from the west. No rain is
currently anticipated with this trough.
&&
.AVIATION...As of 5:14 PM PDT Saturday.....For the 00Z TAFs. The
cold front reached the North Bay, but west of the SF Peninsula
it`s crawling along at maybe 5 mph per extrapolating from visible
satellite imagery; this is slower than the WRF/HRRR model forecasts
are showing since these models forecasted the front to have already
reached the San Mateo Coast. Increasing clouds /MVFR/ with rain
arriving tonight and Sunday with the approaching low pressure
system.
Vicinity of KSFO...Near to slightly higher than moderate confidence
VFR continues for early to mid evening. MVFR ceiling with rain by
late evening through Sunday morning. Rain changing over to showers
Sunday afternoon. West to southwest wind 10-15 knots becoming gusty
southeast to 25 knots Sunday morning. Wind shifting to west or west
southwest Sunday afternoon and evening.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...West to northwest winds 10 to 20 knots
early this evening, becoming light southwest mid to late evening.
VFR-MVFR with rain developing tonight and Sunday. MVFR ceilings
with rain changing over to showers Sunday afternoon.
&&
.MARINE...as of 8:41 PM PDT Saturday...A low pressure system to
the north will sweep a cold frontal boundary across the waters
late tonight through Sunday morning. Winds will shift to the south
tonight and increase, becoming locally gusty along the boundary.
Winds will then shift to the northwest in the wake of the front
through the day on Sunday. The first significant southerly swell
of the season has arrived and will move through the waters over
the coming days. A shorter period northwest swell and wind waves
will also be present across the waters.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm from 3 AM
SCA...Pt Arena to Pigeon Pt 10-60 nm from 3 AM
&&
$$
PUBLIC FORECAST: Dykema
AVIATION: Canepa
MARINE: Canepa
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