Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/29/20
AREA FORECAST DISCUSSION
National Weather Service Albany NY
951 PM EDT Fri Aug 28 2020
.SYNOPSIS...
A frontal boundary will lift northward, as a warm front tonight
bringing some showers and isolated thunderstorms. The air mass will
become more humid with showers and scattered thunderstorms some with
heavy rainfall and gusty winds tomorrow ahead a low pressure system
and a cold front. A cooler and less humid air mass will settled into
the region for the 2nd half of the weekend into early next week with
high pressure building in.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Mid and high clouds quickly spreading east and will slow the
cooling of temperatures this evening and tonight. Some very
isolated showers are brushing the NY/PA border and could affect
the eastern Catskills. Some sprinkles and showers could form
overhead through the early morning hours as warm advection and
moisture advection increases overnight. Between midnight and
daybreak many areas could be seeing intermittent showers, maybe
even a rumble of thunder in western areas. Some patchy fog is
possible as rain increases in coverage. Just some minor
adjustments to temperatures, rain timing and sky cover through
tonight. Previous AFD has a few more details and is below...
A stationary front over the NY-PA border, northern NJ and
coastal southern New England will begin to lift northward
tonight as a warm front. The mid and upper level flow will
become zonal ahead of low pressure system moving into the Great
Lakes Region. A weak sfc high north of the warm front will
weaken and move down stream.
The low-level warm advection, as well as theta-e advection will
increase ahead of the warm front tonight. Some weak elevated
instability with mean MUCAPE values of less than 500 J/kg is
noted on the 00Z HREFS overnight. The Showalter values get into
the 0C to -2C range over most of the forecast area between
06Z-12Z on the latest NAM. Sfc dewpts start to creep up and
latest 12Z GEFS indicate PWATS start to rise to 1 to 2+ STD DEVs
above normal towards daybreak. We kept a slight chance of
thunderstorms overnight
Clouds will thicken and lower overnight with the increasing
thermal advection and we gradually increased POPS into the high
chance and likely range. Lows will be in the mid 50s to around
60F north of the Capital Region...and upper 50s to upper 60s
from the Capital Region south and east. Some patchy fog may also
develop with the showers and isolated thunderstorms.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY/...
Tomorrow...The air mass becomes very moist and humid as the warm
front lift north of the region. Some of leftover moisture from
TC Laura may be tapped, but the majority of the remnants should
remain south of the region over the northern Mid Atlantic
States. PWATS may increase to +2 to +3 STDEVs above normal in
the 1.5"-2.0" range with the higher values south and east of the
Capital Region. Sfc dewpts increase into the 60s to lower 70s.
Cloud cover will likely become an issue for widespread strong to
severe thunderstorm development. However, some of the CAMs are
indicating that some breaks may be possible towards the
afternoon ahead of a prefrontal disturbance and a cold front
approaching from the west. Locations from the Capital Region
north and west will possibly be located near an axis of better
deep shear /0-6 km bulk shear values/ 35-40+ kts and moderate
instability with mean SBCAPE values of 1000-1500 J/kg based on
the 00Z HREFS. The mid-level lapse rates are very weak /less
than 6C/km/ in the tropical like air mass, but pcpn loading
into any organized convection may yield some isolated to
scattered strong to severe thunderstorms with wet microbursts.
If we do not get the sfc heating, then this threat will be
limited to nil. Some of the CAMs like the 12Z 3-km NAMnest and
the HRRR are showing a line of showers and thunderstorms moving
through in the mid to late pm. The Marginal Risk from SPC looks
fine at this point. The elevated PWATs above normal in the muggy
air mass will allow for some locally heavy rainfall. Poor
drainage/urban flooding of low- lying areas and an isolated
flash flood will be possible.
Some locations still desperately need the rainfall
based on the latest drought monitor and DGTALY product where
parts of extreme eastern NY, and the southern Adirondacks are in
D0 /abnormally dry/ to D1 in western New England /moderate
drought/ and spotty severe drought conditions in Litchfield Co.
Temps on Saturday will be in the mid 70s to lower 80s in the
valleys and upper 60s to mid 70s over the higher terrain.
Saturday night...The showers and thunderstorms will end from
west to east quickly in the early evening, as the cold front
moving through. Cold advection will begin to spread across the
region. The mid and upper level trough axis will lag upstream
so some isolated to scattered showers are possible especially
from the Mohawk Valley/Capital Region/Berkshires northward.
Dewpts will be lowering upper 40s to 50s, as the actual lows
will get into the 50s to around 60F.
Sunday...Brisk and cool conditions, as the upper trough axis
moves through some light orographically forced showers are
possible over the western Adirondacks and southern Greens as
some Lake Ontario moisture is tapped until noontime. Brisk
northwest winds of 10 to 20 mph are possible with some gusts 25
to 30 mph. H850 temps fall to about +6C t +10C from northwest to
southeast across the forecast area. Partly to mostly sunny skies
are expected with temps running a little cooler than normal with
comfortable humidity levels. Highs will be in the upper 50s to
mid/upper 60s over the hills and mtns, and lower to mid 70s in
the valleys with a few upper 70s in the mid Hudson Valley.
Sunday night...High pressure builds in with decreasing winds and
a cool and pleasant late August night. Lows will be in the 40s
to lower 50s with near ideal radiational cooling conditions. It
will feel a little bit like early Fall.
&&
.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Dry and tranquil weather Monday with highs in the 70s but upper 60s
higher terrain. A southern stream weak upper impulse drifts north
and east out of the TN/OH Valley Tuesday and there are some
disagreements in sources of guidance and ensembles with how far
north the moisture, clouds and chances of showers spreads. Lots of
uncertainty, so including isolated to scattered showers with the
best coverage in the mid Hudson Valley and NW CT Tuesday. Highs
Tuesday in the 70s with upper 60s higher terrain.
Northern stream upper energy builds east through Canada and the
Great Lakes Wednesday into Thursday with relatively strong warm
advection and low level forcing Wednesday. One upper impulse departs
with a potential dry period sometime in the Wednesday night or
Thursday time frame. Guidance/ensembles disagree with the timing of
the exit of this upper impulse and slight cooldown and drying period.
Another upper impulse embedded in the mean upper troughing and
cyclonic upper flow in eastern Canada/North America approaches later
Thursday into Friday. Again, disagreements in guidance and
ensembles exist with the trailing upper energy in the Thursday to
Friday time frame.
So again, there is lots of uncertainty in the Wednesday through
Friday time frame. Therefore, including scattered showers and
isolated to scattered thunderstorms. Boundary layer temperatures
should be somewhat warm, so surface temperatures will potentially be
warm as well, before any cold advection spreads across our region,
which may be Thursday, Friday or beyond.
Highs Wednesday in the mid 70s to near 80 but lower 70s higher
terrain. Highs Thursday around 80 to mid 80s but mid to upper 70s
higher terrain. Highs Friday very similar to Thursday, maybe a
degree or two cooler than Thursday.
&&
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions prevail this evening with mid and high clouds
thickening into the early morning hours. A warm front will
bring increasing chances for showers to all TAF sites between
06Z-10Z with VCSH being indicated. Between 10Z-16Z VFR ceilings
and MVFR visibilities with predominant intermittent showers at
all TAF sites but there will be brief periods with no rain.
Including PROB30 for MVFR ceilings in any steadier showers with
visibilities bordering on IFR.
By 15Z-17Z, steadier showers with MVFR ceilings and visibilities
and PROB30 for visibilities and ceilings bordering IFR.
Basically, one wave of showers around daybreak to mid morning, a
possible brief 1-3 hour decrease in coverage, then another wave
of steadier showers and isolated thunderstorms in the afternoon.
Isolated nature to the thunderstorms suggests not adding to TAF
at this time but future TAFs will likely add them once we see
storms develop and can track them.
Nearly calm winds tonight will become south to southwest
Saturday morning at 10 Kt or less and continue through the
afternoon.
Outlook...
Saturday Night: Moderate Operational Impact. Chance of SHRA.
Sunday: Low Operational Impact. Breezy. NO SIG WX.
Sunday Night: No Operational Impact. NO SIG WX.
Monday: No Operational Impact. NO SIG WX.
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: Moderate Operational Impact. Isolated SHRA.
Tuesday Night: Moderate Operational Impact. Scattered SHRA.
Wednesday: Moderate Operational Impact. Scattered SHRA...TSRA.
&&
.FIRE WEATHER...
A frontal boundary will lift northward, as a warm front tonight
bringing some showers and isolated thunderstorms. The air mass will
become more humid with showers and scattered thunderstorms some with
heavy rainfall and gusty winds tomorrow ahead a low pressure system
and a cold front. A cooler and less humid air mass will settled into
the region for the 2nd half of the weekend into early next week with
high pressure building in.
The RH values will increase close to 100 percent tonight and
Sunday morning, and then only lower to 60 to 75 percent
tomorrow in the humid air mass.
The winds will become south to southeast at 5 to 10 mph late
tonight, and will be southerly at 5 to 15 mph tomorrow, and
shift to west to northwest at 10 to 15 mph tomorrow night.
Overall, a widespread soaking rainfall is possible late tonight
through tomorrow.
&&
.HYDROLOGY...
No widespread problems are expected on the main stem rivers the
next several days.
More showers and isolated to scattered thunderstorms are
expected tonight into tomorrow. High PWAT values will allow for
more heavy downpours /briefly intense rainfall rates/ and some
isolated flash flooding/urban flooding cannot be ruled out. Most
areas will see anywhere from three-quarters of an inch to an
inch and a half of rain, but some localized higher totals around
2 inches are possible. The rainfall won`t be heavy enough to
cause any issues on the larger rivers. The MMEFS guidance
continues to show no flooding on the rivers.
Dry weather is then expected for Sunday into Monday which will
allow for river and stream flows to recede. Some showers and
thunderstorms as we head into the mid week.
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...NAS/Wasula
SHORT TERM...Wasula
LONG TERM...NAS
AVIATION...NAS
FIRE WEATHER...Wasula
HYDROLOGY...Frugis/Wasula
Area Forecast Discussion
National Weather Service Binghamton NY
811 PM EDT Fri Aug 28 2020
.SYNOPSIS...
A few showers and isolated thunderstorms are anticipated as a
warm front lifts north mainly in Northeast Pennsylvania this
evening, and then across central New York later tonight. A cold
front brings more showers and thunderstorms Saturday, a few
with gusty winds and locally heavy rain. Generally dry and quiet
weather returns Sunday and Monday with cooler temperatures.
&&
.NEAR TERM /THROUGH SATURDAY NIGHT/...
630 pm update...
Just minor changes to better represent current conditions. Upped
cloud amounts into Saturday. Convection in NEPA isn`t doing much
and thunderstorms were short lived.
previous discussion...
A complex and rather complicated forecast in the near term
period. A few showers and perhaps isolated thunderstorms will
continue rolling through NE PA into this evening; mainly south
of Towanda--Montrose and Honesdale. SPC is still highlighting
this area for a marginal threat of a severe storm or
two...therefore there is a low chance for some isolated gusty
winds or hail. Further north, across all of CNY it should stay
mainly dry under partly to mostly cloudy skies this evening.
Temperatures will hold in the 70s for most locations.
Overnight: A complex forecast as we have the remnants of Laura
moving into the Ohio Valley, combining with a rather strong wave
of low pressure across the upper Great Lakes. A stationary
boundary across central PA and far southern Michigan is progged
to lift off to the northeast overnight. This will bring
increasing low level moisture and instability. CAMS and other
near term guidance is struggling with the various areas of
convection out there, and how these will move overnight. Current
and best thinking is that the chance for showers and embedded
thunderstorms really begins to increase after midnight, as a
weak wave moves through and PWATs reach 1.8 inches. Think the
RAP may be handling the overnight scenario best, so stuck close
to that guidance. The HRRR is a little slower and doesn`t really
fill in the shower and t`storm activity over our region until
after 3-5 AM.
Saturday: There will likely be a round of moderate to
occasionally heavy rain with embedded t`storms to begin the day
as the pre-frontal trough lifts through. The majority of the
remnants of Laura are progged to remain just south of our CWA,
but some deeper, tropical like moisture still gets advected
northward into our area. PWATS hold between 1.75 and 2.0 inches
through at least early afternoon areawide, and warm cloud depths
approach 12 k ft...so very efficient rain processes are
expected. There should be a small break in the showers and
perhaps even some break of sun late morning or early afternoon.
This may be enough to increase instability for our area. The 12z
NAM is showing between 1000-1500 J/kg of MLCAPE, meanwhile the
GFS is a bit lower between 700-1200 J/kg. There will be plenty
of forcing and deep layer shear around 35-45 kts. SPC currently
had much of the area under a marginal risk for severe storms,
but would not be surprise to see portions of our FA upgraded in
future updates...especially if it becomes more apparent that
there will be enough instability present. WPC also has CNY and
NE PA under a marginal risk for excessive rainfall and flash-
flooding...so this potential will also need to be watched
closely. A strong cold front then pushes through from NW to SE
during the late afternoon and evening. This will allow the
showers and storms to taper off from NW to SE starting around
3-5 PM across the Finger Lakes, and reaching I-81 in NY by 4-6
PM, and finally clearing NE PA by 6-9 PM. There could even be
some late day breaks of sun across the western areas. It will be
humid on Saturday with highs in the upper 70s to lower 80s.
Mid and upper level trough moves overhead Saturday night, with
a rather potent shortwave rotating through across Lake Ontario
after midnight. Cooler air aloft will allow for some lake
induced instability and enhanced showers in a NW to SE
flow...these showers and isolated t`storms could impact the
norther portion of our CWA, up toward the NY Thruway corridor
overnight. Further south across the Twin Tiers and NE PA is
should be mainly dry overnight and a little breezy with lows in
the 50s.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY/...
235 PM UPDATE...
Northwest flow combined with a large upper low over Quebec may
bring a few showers Sunday, mainly along and north of the I-90
corridor and into the Catskills. Showers will be supported early
in the day with a surface trough swinging through in the morning
hours, High pressure building in during the afternoon should
end most of the showers.
That same high pressure will slowly slide southeast into western
New England by 00Z Tuesday keeping the area dry for the
remainder of the short term.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
235 PM UPDATE...
No changes to the long term. Period is fairly quiet as we begin
with dry weather. Then, a southwest flow develops and gradually
brings moisture slowly increasing the chance for showers each
day. By Wednesday, a short wave swinging by will focus the
moisture and bring a higher chance for showers and thunderstorms
into Thursday.
415 AM Update...
The National Blend of Models (NBM) was used as a starting point
for the long-term grids.
The week starts out dry with high pressure over the Northeast U.S.
on Monday. The high gradually to retreat off the New England and
Mid- Atlantic coast during the middle of next week. Return
flow around the high and ahead of the upstream trough over the
central CONUS will lead to a warming trend. The forecast
includes an extended period of chance for showers and
thunderstorms for midweek but PoPs were generally kept below NBM
(20-40 percent) due to uncertainty in the forecast (with
several fast-moving disturbances rounding the base of the
upstream trough. The best chance for showers and storms will be
when the cold front moves through our region. However, timing of
the fropa is still uncertain.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Mainly VFR this evening with ceilings generally at around 5000
to 8000 ft, but a passing warm front will cause ceilings to
drop and will also bring in additional chances for showers and
mist tonight. Ceilings start dropping back to MVFR and even IFR
first at KRME, KITH, KBGM and KELM after 6Z, followed by KAVP
and then KSYR around and just after sunrise.
Chances for showers and some rumbles of thunder will be ongoing
into the daytime hours as ceilings start to slowly lift to MVFR
and low VFR. However, thunderstorms become likely from around
16Z to 20Z as a cold front moves through. Towards the end of
the forecast period, clouds begin to scatter out with a return
to VFR into the evening.
Winds turning to the southwest come in at around 5 to 10 kts
tonight, but increasing winds aloft will bring in a chance for
some low level wind shear especially at KRME tonight. For
Saturday, winds increase to around 10 to 15 kts with higher
gusts before winds start to turn calmer into the evening.
Outlook...
Saturday night...Restrictions possible in lingering showers,
otherwise mainly VFR.
Sunday through Monday night...Mainly VFR, but valley fog likely
Sunday night for at least KELM and possibly other terminals.
Tuesday...Restrictions possible with a chance for showers.
Wednesday...Possible restriction with a chance of showers and
thunderstorms.
&&
.BGM WATCHES/WARNINGS/ADVISORIES...
PA...None.
NY...None.
&&
$$
SYNOPSIS...MDP/TAC
NEAR TERM...MJM/TAC
SHORT TERM...DGM
LONG TERM...DGM/JRK
AVIATION...HLC
Area Forecast Discussion
National Weather Service State College PA
1125 PM EDT Fri Aug 28 2020
.SYNOPSIS...
Rounds of showers and thunderstorms will continue through the
first part of the weekend, before conditions dry out Saturday
night and Sunday. Additional rainfall is likely at times early
next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Anomalous southwesterly low level jet and plume of tropical
moisture will overrun old outflow boundary south of Pa overnight,
bringing additional showers to the region. Evening SPC
mesoanalysis indicates only minimal capes across the region.
However, expect increasing instability late tonight, as
southwest flow increases ahead of approaching upper trough. The
instability, combined with increasing large scale forcing ahead
of upper trough, could lead to some late night tstorms with
heavy downpours. Latest HRRR supports the possibility of spot
amounts of around 1 inches overnight. Given the recent dryness,
believe the threat of flooding is quite low.
High humidity and a southwest breeze will hold temperatures up
tonight, with mornings lows likely ranging from the mid 60s over
the northwest mountains, to the low 70s across the Lower Susq
Valley.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
A large scale upper trough is forecast to move eastward across
the Northeast and push a cold front across the Appalachians on
Saturday. Tropical moisture associated with the remnants of
Laura will be drawn north ahead of the approaching trough,
bringing a fairly widespread rain with embedded thunder over the
eastern half of the forecast area early Saturday.
Model soundings support breaking clouds by afternoon, as low
level jet and plume of tropical moisture shifts east of the
state. Trailing cold front is then progged to sweep southeast
across the region during the afternoon and early evening,
accompanied by a last round of showers or thunderstorm in some
spots. A few of the storms could be strong to severe, with the
greatest risk across the extreme southeast Pa per latest SPC
guidance. Deep-layer shear should be sufficient ~30kts for some
organization, but modest instability due to early day cloud
cover suggests a marginal severe storm potential overall.
Showers will exit the southeast counties Saturday evening with
much cooler/drier air arriving Saturday night into early next
week. Expect high temps to be more in the 70s and lower 80s
with low humidity through early next week.
High pressure will lead to generally dry weather Sunday into
early Monday, although it may be cool enough aloft on Sunday
for some lake effect rain showers to form off of Lake Erie which
could move into the northern tier of PA.
There is now increasing confidence in a period of damp weather
late Monday/Monday night, as a weak wave of low pressure rides
south of Pa. The combination of this feature and high pressure
east of New Eng is resulting in anomalous southeasterly flow in
the GEFS output and will likely result in a period of
rain/drizzle, especially over the southeast half of the forecast
area.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Low level southeast flow appears likely to persist into Tuesday,
resulting in persistent low clouds and possible morning drizzle
along and east of the Alleghenies. Med range guidance is in
decent agreement into midweek, all of which push a dying cold
front into the area Wednesday with a potential wave riding east
across Pa on the stalled boundary Thursday. Have thus kept the
chance of showers in the forecast both days, with the highest
POPs during the PM hours. Model guidance diverges a bit toward
the end of next week. However, latest ECENS and operational
Canadian support the chance for another round of showers/tstorms
with a cold front passage Friday.
&&
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
Some adjustments to the TAFS late this evening.
Some showers and isolated thunderstorms been trying to work
eastward this evening. Time of day and rain cooled air keeping
conditions better east of the higher terrain so far.
Earlier discussion below.
For the 00Z TAF package, some minor adjustments to the fcst.
Overall the earlier forecast good, especially with timing of
the cold front on Saturday.
Main changes were early on tonight and to add groups after 18Z
on Saturday.
Some high base showers this evening, with lower CIGS across
the west. Also an isolated rumble of thunder for another
hour or so.
Improving conditions from west to east on Saturday afternoon,
as winds shift to the west.
Sunday looks mainly VFR and dry. Perhaps a few lower CIGS and
a brief shower with the upper level trough and secondary cold
front moving across the far north. Main area that could see
lower clouds and a brief shower would be BFD early.
Hopefully dry weather and VFR conditions would remain into
Monday. Rather fast weather pattern for next week, with some
chance for the warm and humid conditions to move back northward
into the area by late Monday or Tuesday.
Outlook...
Sat night-Sun...VFR with no sig wx.
Late Mon-Wed...More rounds of showers and storms possible.
&&
.CLIMATE...
Summer 2020 is on track for the warmest on record at Harrisburg
with an average temperature of 78.1F month-to-date.
August 2020 currently ranks 2nd warmest on record with an
average temperature of 78.7F. 2016 holds the top spot coming in
at 79.1F.
Harrisburg has reached 90 degrees or higher 35 times since June
1st, including 1 day at 100F.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Steinbugl
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Steinbugl/Travis
LONG TERM...Fitzgerald
AVIATION...Martin
CLIMATE...Steinbugl
AREA FORECAST DISCUSSION
National Weather Service Eureka CA
254 PM PDT Fri Aug 28 2020
.SYNOPSIS...Warm temperatures will occur across the interior
during the weekend, though slightly cooler conditions will be
likely under areas of thick wildfire smoke. Otherwise, dry weather
is expected during the next seven days, with a warming trend
likely during early to middle portions of next week.
&&
.DISCUSSION...Visible satellite imagery showed areas of thick
smoke across portions of southern Trinity and much of Lake and
Mendocino counties this afternoon. Surface heating has been
reduced significantly as a result, and high temperatures were
struggling to climb out of the 80s. Expect similar smoke
conditions during Saturday afternoon, and thus reduced Saturday
highs over Mendocino and Lake counties. Otherwise, the marine
layer has mixed out across all coastal areas with the exception of
Mendocino county, where a boundary layer eddy was focusing
stratus development. Model guidance indicates stratus will
redevelop tonight from roughly Humboldt Bay southward, and then
dissipate during Saturday afternoon. Farther north, the Del Norte
county coast may remain stratus free tonight due to the occurrence
of dry northeasterly winds immediately above the surface.
Going into next week...model guidance shows upper heights building
over the West Coast. A warm deep-layer airmass is forecast to
develop over NWRN CA as a result, including in the low-levels
along the coast partially due to a slight offshore component in
boundary layer flow. Hot temperatures in the 90s to low 100s will
be probable across interior valleys, and heat risk concerns will
exist. In addition, the marine layer is forecast to become
progressively shallower during early to middle portions of next
week, such that warm coastal temperatures in the 70s will be
possible.
&&
.AVIATION...Widespread haze and localized smoke linger over the
region today, with significantly impacted visibilities in
Mendocino and Lake counties. HRRR smoke guidance is suggesting
visibilities in these areas will improve this afternoon as
afternoon onshores push the smoke off toward the east, however
somewhat impacted visibilities are expected for the remainder of
the TAF period.
Farther north in Del Norte and Humboldt counties, a smoky layer
aloft is expected to remain in place while low-level gusty north
winds pick up this afternoon, particularly at KCEC. The
combination of smoky haze and haze from sea spray should continue
keep visibilities down to MVFR through this afternoon at KCEC
while skies stay clear. HIRES guidance is indicating a southerly
wind reversal and associated northward surge of stratus this
evening as strong northerlies build offshore, which should bring
IFR to LIFR conditions to Redwood Coast tonight. /TDJ
&&
.MARINE...Northerlies continue to RAMP UP to GALE FORCE through
the weekend, strongest across the outer waters. Wind speeds are
expected to moderately step up in intensity each day as high
pressure builds over the NEPAC and the local thermal trough is
deepened by afternoon heating, both acting to tighten the
nearshore pressure gradient. The most significant step looks to
occur on Saturday afternoon, when sustained wind speeds of 30 to
40 kts with gusts nearing 50 kts are expected to develop and
persist through Sunday within the strongest wind core in the
Northern Outers. These winds will generate seas of 14 to 18 ft
across the outer waters in response, largest during the day on
Sunday. GALE FORCE winds will likely reach close to the headlands
of Point St George and Cape Mendocino, but otherwise model
guidance indicates a sharp wind gradient toward the coast with
significantly weaker winds nearshore, with HIRES guidance
indicating possible overnight southerly wind reversals along the
coast.
Steep northerly seas propagate into all zones this weekend in
response to these winds, and have lifted a Haz Seas warning for
the Northern Inners starting tomorrow afternoon through Sunday to
cover as the wind speeds and wave generation peak just offshore.
The southern inners still look sufficiently protected in the lee
of Cape Mendocino that an SCY should suffice, however steep and
hazardous seas of 10 to 13 ft will plague Cape Mendocino through
the weekend.
Conditions look to significantly improve heading into next week
as the high currently building over the NEPAC slips overhead and
the pressure gradient relaxes, possibly bringing a period of
widespread light-and-variable-mixed-with-rounds-of-southerly winds
around mid- week. /TDJ
&&
.FIRE WEATHER...Northeast winds gusting from 20 to 30 mph are
forecast to occur across exposed ridges in Del Norte county
tonight, and particularly Saturday night. Those winds combined
with moderate to locally poor overnight humidity recoveries will
aid in an elevated fire weather threat.
&&
.EKA WATCHES/WARNINGS/ADVISORIES...
CA...None.
NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory until
3 PM PDT Saturday for PZZ450.
Hazardous Seas Warning from 3 PM Saturday to 3 AM PDT Monday for
PZZ450.
Gale Warning until 3 AM PDT Monday for PZZ470.
Small Craft Advisory until 3 AM PDT Monday for PZZ455.
Hazardous Seas Warning until 3 AM PDT Monday for PZZ475.
&&
$$
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Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1102 PM EDT Fri Aug 28 2020
.SYNOPSIS...
An area of low pressure will bring beneficial rain to the area
on Saturday with a few strong storms possible. An upper level
trough will produce a few clouds and scattered showers mainly
across the higher terrain Sunday with the rest of the region
being breezy. High pressure will build in from Canada early
next week for a period of dry weather possibly followed by some
more rain midweek.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Update...Minor changes to reflect latest observational trends.
Previous discussion...At this hour, RAP analysis shows a high
pressure center shifting from Ontario into Quebec with its broad
reach providing a mostly sunny and nice day locally. Meanwhile
a northern stream trough is on its way out of the plains of
Canada and will pick up an area of low pressure over the Great
Lakes, strengthening it into tomorrow. Also of consequence is
the remnants of what was Laura, starting its march up the Ohio
Valley.
Tonight, high pressure erodes and sinks southeast across Maine into
the Atlantic as low pressure approaches from the west. Expect a
pretty quick drop in temperatures especially over western Maine late
this evening with dew points and sky cover relatively low. Clouds
will increase through the night and gradually lower as a fairly
deep layer of dry air erodes. Surface forecast charts suggest
an ageostrophic northeast wind (read: cold/dry air dam) holds
through the night roughly north of PWM which will keep PoPs low
until a stronger band of warm frontal upglide arrives in the
Connecticut River Valley in strengthening southwesterly mid-
level flow just before dawn. Low temperatures tonight shake out
to the 40s across the north to near 60 across the south.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
A complex area of low pressure containing post-tropical remnants and
an extratropical circulation crosses the Northeast and Mid-Atlantic
states Saturday, driven by a digging northern stream trough tracking
through the northern Great Lakes region. As has been discussed in
prior forecasts, CAMs and other higher- resolution models continue
to suggest poor phasing between Laura`s post- tropical remnants
and the northern stream low so while strong moisture availability
is there, focused forcing continues to be an issue. Am anticipating
plenty of haves and have-nots; rainfall rates will be relatively
good given high PWATs but substantial accumulations will only
occur where forcing, mainly in the mesoscale, can be wrangled.
The main band of warm frontal rain crosses from SSW to NNE during
the morning to mid-day hours bringing between 0.5-1" of rainfall
where it crosses...highest in the Whites/western Maine mtns where
low-level flow out of the south to southeast allows for some
upsloping, and perhaps in embedded elevated convection. Behind this
feature, in the warm sector (at least aloft), PWATs increase to 1.5-
2" but forcing remain fairly broad and unorganized. Instead,
broad baroclinicity increases over the CWA as the surface warm
front creeps north through southern New Hampshire and into
extreme SW Maine through the middle of the day... so between
surface-based instability and pockets of forcing with the
frontal system itself am expected scattered to numerous showers
and storms tomorrow afternoon with heavy rainfall. Overall am
not expecting flooding issues except for on a very isolated
basis with repeated storm activity or in areas of poor drainage.
While thermodynamics remain fairly marginal... kinematics are
fairly strong so stronger storms could produce strong, gusty
winds...also cannot rule out a tornado, especially with the warm
front.
Dry air quickly enters in behind the system and cuts heavy
rainfall threat for late evening and overnight...but showers
remain possible for a little while longer as the upper trough
rotates through. By early Sunday morning showers are relegated
to the mountains in northwest upslope flow.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Low pressure will depart to our east on Sunday allowing for cool
and breezy conditions with wind gusts around 25 knots likely in
the CAA regime. Upslope stratocu will likely be present in the
mountains, with clearer skies downwind.
Monday and Tuesday look quiet with high pressure passing through
the region from west to east.
Some 12z deterministic and ensemble information indicate some
potential for a rain event Wednesday as a southern stream wave
moves northeastward from the Mid Atlantic. Several members keep
this system far enough to our east to keep the area dry.
Therefore, low confidence exists in the midweek forecast at
this time. Thereafter, some signals point toward a frontal
boundary stalled over our region Thu and Fri with the attendant
chance for showers and thunderstorms.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Short Term...VFR prevails for the time being with gusty west
winds today relaxing and going variable late this evening. CIGs
gradually lower tonight into tomorrow morning with an
approaching frontal system. -RA/RA, and perhaps an isolated
thunderstorm, break out from the southwest by mid morning with
MVFR and locally IFR conditions expected. This band crosses to
the NE by early afternoon... then SHRA/TSRA becomes likely
during the afternoon and evening. Storms could produce strong,
gusty winds... with best probability of this occurring over
southern terminals. Conditions gradually improve from west to
east Saturday night, except for at HIE, with winds backing to
the west and northwest.
Long Term...MVFR in the mountains Sunday in stratocumulus.
Westerly gusts to around 25 kt likely area-wide. VFR Monday and
Tuesday with lighter winds.
&&
.MARINE...
Short Term...A broad area of low pressure with rain and a few
storms will cross the waters Saturday into Saturday night.
Onshore flow initially will turn offshore behind this system
with seas building to around 5 ft over the outer waters. A SCA
will likely be necessary, but it is marginal and there remains
some uncertainty in timing.
Long Term...SCA conditions increasingly possible for Sunday with
westerly wind gusts around 25 kt.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
NEAR TERM...Legro
Area Forecast Discussion
National Weather Service Houston/Galveston TX
654 PM CDT Fri Aug 28 2020
.AVIATION [00Z TAF Issuance]...
Some evening showers and thunderstorms scattered across the inland
flying areas are dissipating out now. By 01-02z, thunderstorms
activity may transition to some showers for a bit, but VFR
conditions will return across the TAF sites by 02z. Tonight may
bring in some lower ceilings but mostly looking borderline and
drier. Tomorrow will be VFR through the day with some chances of
afternoon convection but much lower chances than today. 35
&&
.SHORT TERM [Tonight Through Tomorrow]...
A trough of low pressure persists across SE TX and this feature
coupled with high PW air has allowed for scattered showers and
thunderstorms to develop this afternoon. The GFS and HRRR continue
to be aggressive with shra/tsra this afternoon into the evening
while other models are more benign. The ingredients are in place so
will maintain chance PoPs through 01z and keep slt chance going over
the W-NW zones through 03z. Activity should begin to wane once
heating ends after sunset. Speaking of heat, 850 mb temps were very
warm and cloud cover/winds last night blunted any cooling and the
warm start has allowed temperature to reach the upper 90s by 1 PM.
Dew points are not mixing out and the heat/humidity combo is
producing oppressive and dangerous heat index values. Galveston
reached a heat index value of 110 degrees by 10 AM and 114 degrees
at 2 PM. Sugar Land reached a HI of 112 degrees by 2 PM and Angleton
reached 110. Will maintain the Heat Advisory through 10 PM but the
area should fall below criteria by around 800 PM.
There should be some clearing by mid evening but more clouds will
develop prior to sunrise and this coupled with winds not fully
decoupling will yield another night of very warm temperatures. It
will probably only cool into the upper 70`s inland and lower/mid 80s
toward the coast.
On Saturday, another warm start to the day and very warm
temperatures aloft will translate to another day with oppressive
heat. Have issued a Heat Advisory for Saturday as conditions look
rather similar to today with dew points struggling to mix out
coupled with warm daytime temperatures. Max Heat Index values will
again exceed 108 degrees by late morning at the coast and by early
afternoon further inland. Max Heat Index will range from 105 to 113
degrees. PW values drop considerably but briefly peak near 2.00
inches on Saturday afternoon. Could get a few showers and storms
late but most of the area will probably remain dry. 43
.LONG TERM [Tomorrow Night Through Friday]...
The forecast trend through the remainder of the weekend and into
the beginning of next week will continue to be characterized by
hot and humid conditions with potentially dangerous heat indices
along with scattered to isolated showers and thunderstorms. Upper
ridge will continue to build into the central CONUS by late
Saturday, while broad surface high pressure across the Gulf and
low pressures over the Rockies will promote low-level moisture
advection. Global models continue to indicate a surge of higher
(1.75-2.0+ in) PWs by Sunday evening, although ECMWF solution is
more aggressive than other sources. Regardless, values should
approach 90th percentile of observed climatology for nearby
sounding sites, particularly surrounding Galveston Bay. With
daytime highs expected to approach forecast sounding convective
temps across the area, conditions will remain favorable for the
development of diurnal showers and thunderstorms into the early
part of the week. With the surge of moisture expected to peak on
Monday, have included 40-50% PoPs. Daily activity should diminish
upon the loss of daytime heating.
We`re likely going to need to continue the Heat Advisories through
the weekend, with daytime highs not expected to budge from the mid
to upper 90s and maximum heat indicies remaining around 110
through Monday. Low temperatures, particularly along the coast,
will not exceed the low to mid 80s, near daily record values.
Given that these elevated nighttime low temperatures can
exacerbate heat stress experienced during the day, it will remain
imperative to take heat precautions in the coming days.
ECMWF/GFS have come into better agreement regarding the departure
of the prevailing ridge axis and approach of an upper trough as we
head into the middle of next week with GFS now favoring the
slower EC solution. A cold front extending from the associated
surface cyclone remains on track to approach the CWA on late
Tuesday/early Wednesday. Both solutions now show the surface
boundary pushing into the northern counties, though a prolonged
wind shift/temperature drop is not anticipated. Showers and
thunderstorms associated with the approaching front could impact
areas north of I-10 through Thursday. Have maintained slight-
chance PoPs for now given current uncertainty.
Cady
.MARINE...
Falling pressures in the lee of the Rockies and building surface
high pressure over the eastern Gulf of Mexico will allow for a
moderate onshore flow tonight. The flow will slacken early Saturday
and veer to the SW as low pressure scoots across the southern
plains. Winds will back to the SE as a weak sea breeze moves inland.
The pressure gradient tightens again Saturday night into Sunday with
onshore winds strengthening. A moderate to occasionally light
onshore flow will persist through Wednesday with a lighter winds
expected Thu/Fri as weak high pressure settles over the northern
Gulf of Mexico.
Re-issued a Coastal Flood Advisory for the bay facing shores of the
Bolivar peninsula. Water was reported on a few roads in Crystal
Beach. Overall, tides have returned to within a 1/2 foot of normal
values along the coast. 43
.CLIMATE...
The day is not complete yet so this discussion is preliminary and
subject to change but the low temperature at GLS this morning was
only 86 degrees and this would tie for the all time warmest
overnight low temperature for this site (08/12/2020 and others). The
city of Houston recorded a low temperature of 83 degrees and this
would also tie for the warmest overnight low temperature for this
location (6/23/2019 and others). Late afternoon storms could bring
some rain cooled air so the low temps could change before the end of
the day. 43
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 77 101 77 100 79 / 20 10 0 10 0
Houston (IAH) 80 98 79 97 80 / 20 10 0 30 10
Galveston (GLS) 84 93 83 93 84 / 10 20 20 40 20
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Heat Advisory until 10 PM CDT this evening for the following
zones: Austin...Brazoria
Islands...Brazos...Burleson...Chambers...Coastal
Brazoria...Coastal Galveston...Coastal Harris...Coastal
Jackson...Coastal Matagorda...Colorado...Fort
Bend...Galveston Island and Bolivar
Peninsula...Grimes...Houston...Inland Brazoria...Inland
Galveston...Inland Harris...Inland Jackson...Inland
Matagorda...Madison...Matagorda
Islands...Montgomery...Northern Liberty...Polk...San
Jacinto...Southern
Liberty...Trinity...Walker...Waller...Washington...Wharton.
Heat Advisory from 10 AM to 9 PM CDT Saturday for the following
zones: Austin...Brazoria
Islands...Brazos...Burleson...Chambers...Coastal
Brazoria...Coastal Galveston...Coastal Harris...Coastal
Jackson...Coastal Matagorda...Colorado...Fort
Bend...Galveston Island and Bolivar
Peninsula...Grimes...Houston...Inland Brazoria...Inland
Galveston...Inland Harris...Inland Jackson...Inland
Matagorda...Madison...Matagorda
Islands...Montgomery...Northern Liberty...Polk...San
Jacinto...Southern
Liberty...Trinity...Walker...Waller...Washington...Wharton.
Coastal Flood Advisory until midnight CDT tonight for the
following zones: Galveston Island and Bolivar Peninsula.
GM...None.
&&
$$
SHORT TERM...43
LONG TERM...Cady
AVIATION...35
MARINE...43
Area Forecast Discussion
National Weather Service Wichita KS
627 PM CDT Fri Aug 28 2020
.SHORT TERM...(This evening through Monday night)
Issued at 258 PM CDT Fri Aug 28 2020
Tonight-Saturday:
Mainly minor tweaks to going forecast. Precipitation should
develop in central KS later this evening as front approaches.
There is a small chance for strong-severe storms, however there
are only small areas at various times throughout the night where
better wind profiles/shear and instability are co-located. Leaned
toward combo of NBM and RAP time lagged data for this period for
precipitation chances. Precipitation should slowly spread south
during the night and on Saturday morning. With extensive clouds
probable tomorrow, only modest temperature recovery, except
possibly near OK border. This will significantly limit instability
on Saturday, which was reflected in updated SPC day two outlook.
Saturday night-Monday:
Less clear how things will evolve with model consensus spreading
precipitation area wide as surface low moves northeast and some
850MB moisture works north across western KS Saturday night.
Better chances would seem more likely in far southeast KS, but
confidence anywhere is not that high. Ultimately, with the west-
north west flow aloft and return surface flow, would anticipate
weak/diffuse dryline to develop somewhere just west of the
forecast area with scattered very late night/early morning
elevated precipitation. Main cold front now looks to move through
on Monday morning, likely in the predawn hours in central KS.
-Howerton
.LONG TERM...(Tuesday through Friday)
Issued at 258 PM CDT Fri Aug 28 2020
Unsettled weather is the rule as significant upper trough slowly
moves across the area during this period. Considerable differences
in the surface front location at the onset, with 1200 UTC ECMWF
near I-40 and GFS roughly from KCNK-KDDC. Appears to be decent
chance of precipitation for most areas early in period, but am
increasing less optimistic after Tuesday, as most recent runs are
trending drier or completely dry. If the drier solutions verify,
temperatures on Wednesday-Friday would likely be a few to several
degrees warmer than forecast. Of note, initialization grids/NBM
were coldest of all solutions across central and south central
Kansas for high temperatures on Wednesday and bumped up close the
the 25th percentile. -Howerton
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 627 PM CDT Fri Aug 28 2020
A cold front will move southward across central and southern
Kansas this evening/overnight. Scattered showers and thunderstorms
are expected to develop just behind front and have indicated this
with VCTS in the terminals. Otherwise, mainly VFR conditions are
expected to prevail away from any convection.
KED
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 72 76 63 85 / 30 50 30 30
Hutchinson 69 74 59 84 / 50 60 30 30
Newton 70 75 60 84 / 50 60 30 30
ElDorado 72 76 61 83 / 30 60 30 30
Winfield-KWLD 74 82 64 85 / 10 50 40 30
Russell 66 75 59 85 / 50 40 20 30
Great Bend 67 73 59 83 / 70 60 20 20
Salina 69 77 59 85 / 50 50 20 30
McPherson 68 74 59 83 / 60 60 20 30
Coffeyville 75 84 66 85 / 0 50 50 40
Chanute 74 79 63 84 / 20 50 40 40
Iola 74 80 62 84 / 20 50 40 40
Parsons-KPPF 75 82 65 84 / 10 50 50 40
&&
.ICT WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
SHORT TERM...PJH
LONG TERM...PJH
AVIATION...KED
Area Forecast Discussion
National Weather Service Indianapolis IN
1132 PM EDT Fri Aug 28 2020
.UPDATE...
The AVIATION and Near Term Sections have been updated below.
&&
.SYNOPSIS...
Issued at 141 PM EDT Fri Aug 28 2020
Remnants of Laura will make their way across the southeast third
of central Indiana today, and a cold front will bring the threat
of isolated strong to severe thunderstorms tonight. Lingering
showers will continue through Saturday morning with a lull in
activity by Saturday afternoon except across the far southern
counties. Nonetheless, the shower and thunderstorm threat will
quickly resume again Sunday morning from the southwest as a weak
upper trough moves in ahead of some warm air advection.
&&
.NEAR TERM /Tonight/...
Issued at 700 PM EDT Fri Aug 28 2020
Forecast looks on track with scattered dying convection currently
over southern sections associated with the remnants of Laura and
upstream convection over Iowa that could make it into the Lafayette
area late this evening and overnight. The latter would appear to be
the bigger concern with 50 knot mid level jet approaching from
central Illinois and an increase in 850 millibar inflow combining
to increase wind shear.
Previous discussion follows...
Issued at 141 PM EDT Fri Aug 28 2020
The effects of Tropical Depression Laura have been minimal across
central Indiana so far as it spins into the western Tennessee
Valley. Scattered showers and thunderstorms have been drifting
through the forecast area throughout the day, but they have
remained below severe limits with the main threat being some
localized flooding.
So far, the HRRR has been spot on this afternoon in regard to the
convective trend. Showers and thunderstorms quickly spread across
the southeast third of the forecast area earlier this afternoon,
and current radar mosaic is showing some scattered activity from
bands over northern and southwest portions of central Indiana.
This, too, was well handled by the HRRR. As a result, confidence
has increased in a lull in activity this evening into early
tonight. Will not entirely pull Pops at this time, but will not
rule it out with future forecast updates.
At that point, focus then turns toward an approaching cold front
from the northwest. It`s looking like this will be the best shot
for any strong to severe thunderstorms. Without the diurnal
heating though, it is questionable whether these storms will
survive. But, if any do reach strong to severe levels, damaging
winds will be the main threat. The time frame for the frontal
passage will be between Sat 06-09Z across the northern portions of
central Indiana to Sat 09-12Z across the southern counties.
&&
.SHORT TERM /Saturday through Monday/...
Issued at 141 PM EDT Fri Aug 28 2020
Low chances for showers and thunderstorms will linger through
Saturday morning, but the afternoon will be dry across all of
central Indiana. Meanwhile, the heat and humidity will make it
feel like the mid to upper 80s. That trend will change on Sunday
though as temperatures and dewpoints drop into the 70s and 50s,
respectively.
The dry weather will continue into Sunday for most of central
Indiana, except the southern counties where some showers and
thunderstorms will start infiltrating the area. This activity is
expected to spread northeastward across the forecast area on
Sunday evening and night with higher chances for more widespread
activity on Monday. Temperatures through the period will
generally be below normal.
&&
.LONG TERM /Monday Night through Friday/...
Issued at 141 PM EDT Fri Aug 28 2020
Chances for rain will continue for much of this period as the models
suggest weak forcing features along with a warm and humid air mass
available at the surface.
ECMWF shows mainly a zonal flow in place on Monday night with a weak
short wave passing across the Ohio Valley. Moisture appears to be a
little limited as this feature passes Monday Night. Meanwhile
additional weak short wave are depicted to be ejected from a
deepening trough aloft over the western plains on Tuesday Night into
Wednesday. Again confidence in this type of forcing mechanism is
low...but low chance pops are still warranted.
Best chances for rain look to arrive on Thursday as the previously
mentioned upper trough will drift into the Mississippi Valley along
with a cold front. At this point...several days of warm and humid
southerly flow will have been in play across Indiana...providing
plenty of moisture. Thus with this more organized forcing expected
to arrive...best chances appear to be on Thursday and Thursday night
before dry weather returns with another high pressure system.
&&
.AVIATION /Discussion for the 290600Z TAF Issuance/...
Issued at 1132 PM EDT Fri Aug 28 2020
The impact of the remnants of Laura have moved off to the southeast
of the terminals. Meanwhile, a cold front will drop southeast across
the terminals 11z-15z. High Resolution Rapid Refresh and radar
suggest some a few MVFR storms may drop down southeast along and
ahead of the front. Otherwise, any MVFR ceilings will improve to VFR
behind the front.
Winds will be south and southwest less than 10 knots ahead of the
front and northwest 8 to 11 knots or so behind it.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS...TDUD
NEAR TERM...TDUD/MK
SHORT TERM...TDUD
LONG TERM...JP
AVIATION...MK
Area Forecast Discussion
National Weather Service Marquette MI
738 PM EDT Fri Aug 28 2020
.SHORT TERM...(This evening through Saturday)
Issued at 336 PM EDT FRI AUG 28 2020
A quasi-stationary front remains draped west to east across the UP
this afternoon with a well-pronounced short wave riding along it. SW
850 mb flow of around 25-35 kts nosing up to the boundary and then
backing to SE is leading to a band of low to mid-level moisture
convergence, theta-e advection, and fgen along the front. This
morning`s NAM run had some beefy rainfall totals (2-3" in many
areas) and while the instability isn`t there to support that rate of
rainfall (and upstream obs and radar rainfall rate estimates confirm
it is not happening) the NAM continues to have the best handle on
the placement of the rain, as well as on how cool the temps are
beneath this rain shield. Temps are mostly in the low to mid 60s
where it is raining and in the upper 60s where it isn`t. They`ve
likely already hit their highs for the day this morning everywhere
except Menominee County where visible satellite shows the low-level
stratus trying to erode somewhat. If it succeeds in doing so,
temps could reach the mid 70s down there.
The rest of the afternoon, the wave and associated surface low will
continue riding east along the stationary front leading to continued
moderate (occasionally heavy) rain. Relied on the experimental ESRL-
HRRR for near-term POPs over the south-central as that seemed to be
the only model picking up on the northward extent of the dry slot.
It and the regular HRRR, as well as the NAM-nest and this morning`s
NSSL-WRF, all develop thunderstorms in the clear warm sector over
northern Wisconsin over the next couple of hours and race them east
through Menominee County around 22-23z. However so far these aren`t
materializing as satellite shows low stratus stubbornly hanging on
across much of northern Wisconsin with little if any ice cloud that
would indicate the beginnings of convective growth. Therefore, did
not bite on that solution.
Tonight, the rain should be exiting the east by midnight, but
continued cloud cover and a few additional light showers will
probably keep temps from falling to anywhere near as cool as the
bias-corrected guidance advertises. After about 06z west and 09z
central and east, models indicate a brief period of clearing that,
being timed with peak diurnal cooling, could help lows get a little
lower than they otherwise might. Still, only expecting low to mid
50s, even in the notoriously cool spots.
Tomorrow a bowling ball closed upper low will dive southeastward
across eastern Lake Superior. CAA with this wave will drop 850 mb
temps to around 4-5 C by tomorrow evening which means another day of
highs mostly in the 60s to perhaps low 70s south-central. Temps
aloft are marginally cold enough to support lake-effect rain showers
across the eastern half of the NW wind lake-effect belts, especially
when combined with synoptic-scale lift from this vigorous wave
dropping through. Model profiles show saturation from generally 900-
700 mb much of the day Saturday, and CAMs unanimously have showers,
so felt confident enough to go with scattered showers across the
east for most of the day. Elsewhere downwind of the lake there will
be plenty of lake-effect clouds even in the absence of deep enough
saturation for precip. The counties bordering the Wisconsin state
line will probably be the only areas in the CWA to see much sunshine
tomorrow.
.LONG TERM...(Saturday night through Friday)
Issued at 434 PM EDT FRI AUG 28 2020
Models suggest that a progressive pattern will prevail into next
week. Mid level and surface ridging Sunday will give way to an
approaching mid level trough and cold front Monday. A large scale
trough will then linger into the north central CONUS and Great
Lakes with the potential for additional precipitation chances.
Temps near or slightly below seasonal averages are expected.
Saturday night, cyclonic low level northerly flow with abundant 850-
750 mb moisture and 850 mb temps to around 6C (lake temps to near
20C) will support additional areas of light lake effect/enhanced
rain/drizzle into locations near Lake Superior from Marquette county
eastward. Otherwise, clearing over the interior west should allow
temps to drop into the lower 40s, while readings into the lower to
mid 50s are expected near Lake Superior and east.
Sunday, any lingering light pcpn should diminish early even as
clouds persist into the early afternoon. Mid level and and sfc
ridging with low level drying and anticyclonic flow should bring
clearing as winds veer to the east. Southerly flow will take over
Sunday night ahead of the trough/front.
Mon, 700-300 qvector conv ahead of the approaching mid level trough
will support a band of rain moving through the region. Forecast
instability is marginal for tsra, but may be high enough by the
afternoon and evening over the east for a a few thunderstorms.
Tue-Fri, the GFS/GEFS were more aggressive in bringing another large
area of rain into the area supported by upper level div with the
right entrance of a developing 250-300 mb jet. The ECMWF/ECENS keeps
any pcpn with this feature farther south. As the mid level low
settles over Hudson Bay, the models suggest another significant
clipper shrtwv may drop into the area with increasing rain chances
Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 737 PM EDT FRI AUG 28 2020
As rain ends at the TAF sites and pushes east, expect IFR conditions
to remain until a cold front passes through each of the terminals
later tonight. This front will weaken as it pushes east through the
U.P., bringing the greatest amount of rainfall (and greatest effect
on vis) at KCMX, followed by KIWD. The front may weaken so much that
showers may develop and pass around KSAW later tonight. KIWD should
see showers move in from 00z to 05z; the showers should move through
KCMX between 05z and 07z, and KSAW may see showers in the vicinity
between 06z and 08z. Once this front moves through, expect
conditions to improve to VFR conditions for KIWD and KCMX. Thinking
KSAW should have some low lying stratus/patchy fog that keeps the
conditions at low MVFR until late Saturday morning. The passage of
the front will lead to gusty NW winds developing during the day
Saturday as well a return to cloud cover, but think even if there is
a cig it will stay just high enough to keep things VFR, save maybe
at KSAW, were there is a chance for some scattered showers that may
bring cigs back down to MVFR. As usual, KCMX will be gustiest of the
three terminals. Could see some 30-40 kt gusts there, especially by
Saturday afternoon. KIWD should be the calmest TAF site in regards
to winds and wind gusts.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 336 PM EDT FRI AUG 28 2020
A double-barreled low pressure system moving through the Upper Great
Lakes tonight and Saturday will lead to a period of strong winds.
Initially, E winds to around 20 kts are expected over the eastern
half of the lake this evening on the northern periphery of one of
those lows which will be passing south of the lake tonight. Then
tomorrow the other low moves southeast through northern Ontario,
just north of the lake. Cold air for this time of year with this low
will lead to stiff NW winds developing late tonight from west to
east across the lake, increasing to gale force Saturday morning on
the east half. Thus, have maintained the Gale Warnings with this
forecast package and did not need to alter the start and end times.
Gales will subside to N winds around 20 kts Saturday night then
become light and variable Sunday morning. But winds pick back up to
15-20 kts Sunday night out of the SE, veering to SW on Monday ahead
of the next frontal system. SW winds 15-20 kts look to continue into
the middle of next week behind the front.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Beach Hazards Statement from 6 AM EDT Saturday through Saturday
evening for MIZ005-006.
Lake Superior...
Gale Warning from 3 PM to 8 PM EDT Saturday for LSZ267.
Gale Warning from 10 AM to 6 PM EDT Saturday for LSZ244-264.
Gale Warning from 11 AM to 8 PM EDT Saturday for LSZ266.
Lake Michigan...
None.
&&
$$
SHORT TERM...RJC
LONG TERM...JLB
AVIATION...TAP
MARINE...RJC
Area Forecast Discussion
National Weather Service San Francisco Bay Area
900 PM PDT Fri Aug 28 2020
.SYNOPSIS...Slightly stronger onshore flow will bring minimally
cooler conditions to inland areas on Saturday, with gusty onshore
winds possible during the afternoon and evening. High pressure
will rebuild by early next week, resulting in drier and warmer
conditions. Very warm to hot temperatures are expected inland from
Tuesday onward next week. A shallow marine layer will linger near
the coast and weak onshore flow should maintain milder
temperatures near the ocean.
&&
.DISCUSSION...As of 9:00 PM PDT Friday...Coastal profiler data
indicate the marine layer depth has changed very little through
the day, with the depth currently ranging from just over 1000 feet
at Bodega Bay to around 1500 feet at Fort Ord. Evening water
vapor satellite imagery shows a cyclonic circulation centered just
west of Monterey Bay, which verifies the weak upper low models
had predicted would develop in this area. The development of the
upper low has thus far not had much impact on the depth of the
marine layer. Even if the marine layer does not deepen over the
next 12-24 hours, we will still likely see at least a few degrees
of cooling on Saturday due to an expected increase in onshore
flow. Also, the latest HRRR smoke model indicates this increased
westerly low level flow on Saturday will result in a decrease in
near-surface smoke concentrations by late afternoon.
By Sunday, the upper low off the Central Coast is forecast to
drift to the southwest as an upper ridge, centered over the
Northeast Pacific near 45N/145W, begins to expand to the ESE and
over northern California. This will likely result in the start of
a warming trend on Sunday. A gradual warming trend is then
forecast to continue through Tuesday as the upper ridge continues
to expand and strengthen over California. Look for the marine
layer to compress to less than 1000 feet early in the week, with
its depth likely decreasing to 500 feet or less by Tuesday. 90s
will become more common across inland areas by Monday and then
become widespread by Tuesday. The warmest inland locations are
forecast to reach or exceed triple digit temps by Tuesday.
The models generally agree that at least light onshore flow will
prevail throughout this upcoming warming trend. Thus, although
coastal areas will experience warming, the magnitude of warming
near the ocean is not expected to be as robust as inland areas.
Most areas close to the ocean are forecast to remain in the 70s,
although 80s are likely in some of the warmer coastal spots such
as Santa Cruz and Big Sur by Tuesday.
The center of the upper ridge is forecast to shift to our east by
midweek, but still remain our dominant weather feature through the
end of the week. As the ridge axis shifts to our east, we may see
a slight uptick in onshore flow which would cause modest cooling
near the coast during the second half of the week. But inland
areas will likely remain very warm to hot throughout the week.
Heat Risk next week is currently projected to remain in the
moderate category except for isolated pockets of High Heat Risk in
interior portions of our forecast area. Longer nights as we move
into September will allow for more overnight relief from the heat.
However, if models trend higher with daytime temperatures next
week, we will likely see greater impacts due to more widespread
elevated Heat Risk.
&&
.AVIATION...As of 5:30 PM PDT Friday...For the 00z tafs. A mix of
MVFR and VFR across terminals, with smoke and haze reducing vis
across SF Bay area. Stratus lingers along the coast and has begun
flowing into coastal MRY Bay. Marine layer has compressed a bit to
about 1300 ft AGL, as per coastal profilers. Expect continued
MVFR/VFR vis into the evening for SF Bay area as well as poor
slant range vis. Overnight into Saturday morning, expect a range
of VLIFR- MVFR in fog, stratus, wildfire smoke and patchy coastal
drizzle. Stratus should clear out a bit earlier tomorrow morning
with a more compressed marine layer. Continued onshore flow
through tomorrow afternoon.
Vicinity of KSFO...VFR conditions prevail through the evening,
with possible intervals of MVFR vis. Winds NW at 17 kt, weakening
overnight. Expecting MVFR/IFR cigs tonight after 10z, but earlier
in North Bay and East Bay terminals. Clearing tomorrow around 18z.
Continued lowered vis tomorrow morning and afternoon due to
wildfire smoke and haze.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR across KMRY and KSNS, with stratus
pushing east of the bay. IFR cigs expected across terminals after
03z. Cigs lowering to LIFR/VLIFR overnight through Saturday
morning with fog, stratus, smoke, and haze reducing vis. Cigs
should begin to lift after 17z but lowered vis may linger into
early afternoon. Winds 10-12 kt WNW becoming calm overnight.
Continued onshore flow tomorrow.
&&
.MARINE...as of 08:00 PM PDT Friday...Gusty northwesterly winds
will continue across the northern outer waters through the weekend
and into early next week. These winds will generate steep fresh
swell resulting in hazardous seas conditions, particularly for
smaller vessels. Expect generally light to moderate winds
elsewhere over the waters with winds gradually shifting out of the
west to southwest along the coast tomorrow. Mixed seas will
persist with a short period northwest swell and a longer period
southerly swell.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm
&&
$$
PUBLIC FORECAST: Dykema
AVIATION: Lorber
MARINE: AS
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Area Forecast Discussion...CORRECTED
National Weather Service New York NY
1123 PM EDT Fri Aug 28 2020
.SYNOPSIS...
A warm front moves north of the region overnight into Saturday
morning. A frontal system will move through the area Saturday into
Saturday evening. High pressure will build in on Sunday, with
high pressure remaining nearby on Monday. A weak disturbance along
with a warm front will approach from the southwest towards mid
week. A cold front will approach Thursday night into early Friday
and should clear the region in time for next weekend.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Adjusted POPs for showers, kept thunderstorms at slight chance
but shifted chance to likely POPs late overnight (after 08Z Sat)
and into early Sat Morning. This is similar to forecast
reflectivity from the HRRR model. Adjusted temperatures slightly
lower with current observed trends. Otherwise, forecast mainly
on track.
There is a better overall chance of shra and embedded tsra
activity areawide mainly overnight and into early Saturday with
the approach of northern stream shortwave and shearing post
tropical Laura energy increasing lift and theta-e advection into
the area, with focus along northward moving warm front.
Potential for isolated stronger storms in a marginally unstable
and modestly sheared environment near the coast. Will have to
watch for any storms along the front, with enhanced helicity
lending potential for rotating updrafts.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
A deepening northern stream closed low swings into the Great
Lakes on Saturday, and then into New England Sat Night. The
remnant upper level vorticity of Laura will get absorbed in the
northern stream trough and swing towards the Mid Atlantic coast
Sat afternoon. An accompanying surface low will take a similar
track, with associated warm front lifting north Saturday
morning, and then pre-frontal trough approaching Saturday
afternoon. Numerous showers and scattered tstm development
expected late Sat morning into Sat evening ahead of pre-frontal
trough, in a very moist airmass (enhanced by remnant moisture
from Laura), forced by approaching shortwave and weak llj ahead
of trough axis. Deep layer shear is moderately strong, but in a
weak skinny CAPE environment (weak mid-level lapse rates) with
limited heating potential with morning and aft/eve convection.
Overall this environment would present a potential for a few
strong to severe storms (localized strong to damaging wind gust
threat), but if we do get a few breaks of sun and better heating
in the morning, the severe threat would increase. There is a
localized flash flood threat from any training heavy
downpours/convection in a very moist airmass (2-2 1/2" PWATs)
Pre-frontal trough pushes east Sat eve, ending main shower
threat, with a few localized showers possible with cold frontal
passage passing Sat Night. Gusty NW winds and cooler and drier
airmass advects in for Sat night.
There is high risk of rip current development at Atlantic Ocean
beaches on Saturday due to building 3 to 5 ft S wind waves on
15-20 kt SW flow, and a background 1 ft se swell.
&&
.LONG TERM /SUNDAY THROUGH FRIDAY/...
The cold front should pivot through later Saturday night leading
to a drier northerly component to the flow into Sunday morning.
Thus, high pressure is expected to build for the second half of
the weekend leading to very nice weather along with lower dew
points and more comfortable conditions.
There is a moderate risk of rip current development on
Sunday.
Some uncertainty is now showing up among the global guidance
beginning Monday night and into early Wednesday. As surface high
pressure gradually retreats to the east and north the models
are starting to show disturbances in the mid level southwest
flow. The GFS is the most robust, thus it is showing more precip
generally speaking during this time frame. This may be overdone
based on potential feedback issues, as the other guidance is
hinting at precip chances although not as robust as the GFS.
Chose to go mainly on the lower end of chance POPs for Monday
night through Tuesday night.
Uncertainty still exists regarding precip and POPs for later in
the period, namely Wednesday through the day on Friday. The
upper level ridge will try to hold during this period, but the
northern branch will attempt to get through and into the
northeast at some point, more likely for late Thursday into
Friday. For now kept mainly a diurnal trend for POPs and trended
slightly higher with POPs further west and northwest.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Warm front associated with low pressure over the Great Lakes
will move north of the region overnight into Saturday morning.
The associated cold front approaches Saturday and moves across
Saturday night.
MVFR to IFR stratus has started forming for a few terminals.
Mainly VFR conditions will eventually become more MVFR to
localized IFR as rain showers return overnight into Saturday.
S-SW flow subsiding to near 5-10 kt for the rest of tonight and
into early Saturday. Winds return to a 10-15 kt S-SW flow
Saturday morning through Saturday afternoon with gusts up to 20
kt.
...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
Amendments will be possible for timing of any showers and
thunderstorms as categorical changes late tonight through
Saturday. Timing could be a few hours off from TAF.
.OUTLOOK FOR 00Z SUNDAY THROUGH WEDNESDAY...
.Saturday night...Winds becoming more W-NW 10-15kt with some
gusts to 20 kt. Showers and thunderstorms taper off and VFR
conditions eventually return.
.Sunday-Monday...Mainly VFR. MVFR possible with a chance of
showers late Monday night.
.Tuesday...MVFR possible. A chance of showers. Slight chance of
thunderstorms for western terminals Tuesday night.
.Wednesday...MVFR possible. A chance of showers and a slight
chance of thunderstorms with local MVFR.
Detailed information, including hourly TAF wind component forecasts,
can be found at: http:/www.weather.gov/zny/n90
&&
.MARINE...
Conditions stay below SCA criteria for tonight into Saturday
morning.
Seas possible to build to near 5 feet Saturday afternoon into
evening due to strengthening SW wind fetch. Winds increase to
15-20kts with occasional gusts up to 25kts Sat.
Winds shift out of the north west Saturday night into Sunday.
Marginal SCA conditions are anticipated on the ocean through
much of Sunday, especially for the eastern ocean on a northwest
wind. The winds will then turn more to the north, and eventually
northeast for Sunday night into Monday as winds and seas
diminish further. Ocean seas are then expected to climb for
later Tuesday and into Wednesday as the winds switch to the
southeast along with an increasing south to southeasterly swell.
Thus, the chances for small craft seas will increase during
this time frame.
&&
.HYDROLOGY...
A widespread 3/4 to 1 1/4 inches of rain is likely tonight into
Saturday evening, with locally 1-2 inches of rain possible in
areas affected by multiple rounds of showers and thunderstorms.
This will pose mainly a minor urban and poor drainage flooding
threat, with a localized flash flood threat with training
convection.
At this time no hydrological concerns are anticipated through the
remainder of the forecast period.
&&
.OKX WATCHES/WARNINGS/ADVISORIES...
CT...None.
NY...High Rip Current Risk from 6 AM EDT Saturday through Saturday
evening for NYZ075-080-081-178-179.
NJ...None.
MARINE...None.
&&
$$
SYNOPSIS...JE/NV
NEAR TERM...JE/JM/NV
SHORT TERM...NV
LONG TERM...JE
AVIATION...JM
MARINE...JE/JM/NV
HYDROLOGY...JE/NV
Area Forecast Discussion
National Weather Service Pueblo CO
308 PM MDT Fri Aug 28 2020
.SHORT TERM...(This evening through Saturday)
Issued at 238 PM MDT Fri Aug 28 2020
Currently...
scattered showers and a few thunderstorms were noted over the high
country at 2 pm this afternoon. Over the plains it was dry, with
quite a bit of higher clouds along the I-25 corridor and mostly
sunny out east. Temps around the region were in the mid 90s over the
far eastern plains with generally 80s along the I-25 corridor. Over
the mtns/valleys it was quite a bit cooler due to the clouds and
showers, and readings were in the 70s San Luis Valley, to 50s and
60s mtns.
This afternoon through tonight...
Main concern is flash flooding potential for the burn scars,
especially the Spring scar. Guidance continues to indicate the
potential for heavier rain over the scars, especially over the
Spring scar. Otherwise, SPC meso page is starting to show deep shear
values increase as sfc winds shift to a easterly component, however
CAPE values were meager along the I-25 corridor and mtns, with
around 500 jules over the far eastern plains.
I anticipate storms will continue to move northeast and gradually
increase in intensity as the afternoon progresses per hi res NAM and
HRRR guidance. Best overall chance for the heaviest rain still
appears to be down along the Raton Mesa (including the Spring Burn
scar area) and eastward to the KS/OK border areas. Areas N of
highway 50 east of Fowler may not see all that much precip, except
for eastern Kiowa county.
Precip is going to be slow to move out of the plains this evening
and will likely last into the early morning hours, especially over
the far southeast Plains (greater Baca county area). Although some
locally heavy rain will be possible, overall flood threat is low due
to the antecedent dry conditons over the southeast plains.
Tomorrow...
Fcst area will continue to be under the threat of locally heavy rain
and a couple of severe storms per national guidance products.
Although shear will be stronger tomorrow, best low level forcing
will over the far eastern plains by mid afternoon. so it will be
this region which will likely see the best chance of severe storms.
Overall precip chances tomorrow look quite good as guidance shows an
cluster of storms moving across the region, with areas generally
south of highway 50 having the best chances. Since areas south of
highway 50 are likely going to see the heaviest rain today,
potentially more heavier rain tomorrow may lead to local flooding
issues.
Given the better shear and CAPE projections for tomorrow over the
far eastern plains, I believe we could see some larger hail and
stronger winds then todays svr threat.
.LONG TERM...(Saturday night through Friday)
Issued at 238 PM MDT Fri Aug 28 2020
Finally, some model agreement for next week! The GFS has trended
with the ECMWF for early next week, so forecast confidence is now
increasing. It appears we will continue to have rain chances
through Tuesday before drying out later next week.
Saturday night into Sunday...an upper disturbance embedded in the
flow will be moving across Colorado Saturday evening, with
thunderstorms ongoing across the region. A few could be strong to
severe in the evening with hail to near an inch in diameter and
wind gusts to near 60 mph possible over the Plains. Locally heavy
rainfall will be possible along with flash flooding on area burn
scars and urban areas through the evening. Expect thunderstorms to
shift eastward across the Plains in Sunday morning, clearing to
the east late.
On Sunday, an upper trough is forecast to pass to the north.
Energy embedded in the flow aloft will lead to another round of
afternoon and evening thunderstorms across the region. Limited
instability should lead to less coverage and less rain efficiency.
Storms will initiate over the Mountains, and spread east into the
Palmer Divide and Raton Mesa region during the evening, before
dissipating overnight. While less rain efficiency is expected, if
a storm moves over a burn scar, especially if it receives heavy
rainfall Friday and/or Saturday, flash flooding may be possible. A
strong cold front will drop south across the Plains Sunday night
into Monday morning.
Monday and Tuesday...both the ECMWF and GFS have converged on a
solution during this time frame. Both drop a strong upper trough
south out of the Northern Rockies during this period. As the upper
storm moves across the area, continued periods of showers and
thunderstorms will be possible across the region. It would not be
too surprising if by Tuesday, a few of the Central Mountain peaks
above 13 kft have a light dusting of snow. As for the lower
elevations, storms will form over the Mountains, and spread east
across the Plains on Monday. As the upper system moves across
Colorado, more widespread light rainfall is possible through
Tuesday. One thing is for certain, it will be much cooler both
days. After highs back around the lower 90s on Sunday, highs will
fall about 20 degrees into the 70s and 80s for Monday and Tuesday.
Wednesday through Friday...the upper trough is forecast to shift
east into the Missouri, high pressure is forecast to build over
the western states. This will put Colorado in dry northwesterly
flow for the end of the week. The ECMWF builds the upper high east
into Colorado, which would lead to warmer temperatures than are in
the forecast. The GFS is less amplified with the upper high and
keeps the warmest air to the west. It does appear that we will be
dry during this period. Highs will most likely reach into the 80s
with the GFS, while the ECMWF has us back into the 90s. Mozley
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 238 PM MDT Fri Aug 28 2020
Overall, expect VFR conditions during the next 24 hours at all 3 taf
sites, KPUB, KALS and KCOS. Some TSRA will be possible at each of
the sites later this afternoon and tomorrow afternoon, with brief
mvfr possible as the storms move through. Gusty outflow winds will
be possible with any storms near, or over, the taf sites.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...HODANISH
LONG TERM...MOZLEY
AVIATION...HODANISH
Area Forecast Discussion
National Weather Service Reno NV
148 PM PDT Fri Aug 28 2020
.SYNOPSIS...
Isolated thunderstorms for eastern California and portions of
western Nevada today are expected to retreat to near the Sierra
Saturday. No storms are expected next week. Winds will remain
relatively light until northerly winds possibly increase Monday
with a dry front. Afternoon temperatures may fall to near average
early next week; otherwise, they will remain mostly above average.
&&
.DISCUSSION...
* Main forecast points:
- Periodic pushes of smoke with deteriorating air quality remains
a concern for portions of northeast CA and western NV.
- Isolated afternoon thunderstorms through Saturday, then dry.
- Near to slightly above average high temperatures to soar to
well above average, possibly near records, for late next week.
Yup, more early morning thunderstorms out in Pershing and Churchill
counties, this time east of Highway 95 and Interstate 80. Sometimes
whole years go by without non-surface based/elevated storms in the
summer and we have had at least 3 events in the couple weeks! The
main forcing ahead of the disturbance responsible for the thunderstorms
has shifted off into far northern and northeastern Nevada. However,
a low-level theta-e maximum with a weak surface trough remains in
west-central and northwestern NV, roughly along a line running from
Pyramid Lake to Lovelock to Battle Mountain. This should be a focus
for afternoon and evening showers and thunderstorms as daytime heating
maximizes instability near the theta-e ridge. Elsewhere today, models
do not have much of a signal for thunderstorms and it will mainly be
reliant on differential terrain heating; therefore, isolated coverage
at best is expected in the Sierra today with many areas not seeing
anything at all. Any thunderstorms today do not look to move much
so heavy rainfall is certainly possible along with gusty outflow
winds 30-50 mph.
As far as air quality, it has slowly improved for most spots per
sensors noted on the AIRNOW page (airnow.gov). However, with the
fresh influx of smoke particulates last night, ozone appears to be
rising this afternoon as the sun works on the particulates. That
is about all this forecaster knows about air quality science...please
refer to air quality experts for a deeper dive into the details. In
any case, HRRR simulations unfortunately continue to indicate another
push of smoke tonight between ~7-10 PM, heaviest north of Lake Tahoe
and Highway 50 in western NV. With this in mind, we have extended
the dense smoke advisory through noon Saturday, and added areas north
of Lake Tahoe, to highlight the expected degradation of air quality
again tonight.
Saturday, the focus for isolated showers and thunderstorms shifts to
the Sierra, mainly south of Hwy 50, as weak deformation aloft combines
with the standard higher terrain heating. Note that short-range, hi-
res simulations as well as the GFS/NAM show minimal chance for
thunderstorms Saturday afternoon...~10-15% at best per calibrated
and/or ensemble based guidance. Still, will leave a low chance in
there to cover any mid-afternoon to early evening pop-ups. Like a
broken record, smoke may once again roll into western Nevada
Saturday night as models show some westerly flow.
Starting Sunday and running through next week, thunderstorm chances
all but evaporate as strong high pressure over the north Pacific works
its way over California and Nevada. Sunday through Tuesday, high
temperatures look to ease down or at least remain somewhat in
check as a dry backdoor front moves through the area Sunday/Monday.
However, by mid to late next week, temperatures are expected to
heat up in earnest as the ridge dominates the region. Highs in the
90s to low 100s are expected in the lower valleys, with a few
records not out of the question. At least overnight and early
morning temperatures should drop off decently given dry air, few
clouds, and ever-lengthening nights as we move into September.
Smoke`s impact on air quality remains a wildcard next week
depending on fire activity and smaller-scale wind flow; however, a
westerly evening wind remains possible given the strong heating
in the Basin each day.
-Snyder
&&
.AVIATION...
A couple of thunderstorms may develop near the Sierra Crest today,
but the majority of thunderstorms should form out in the Basin and
Range. Chance for a storm impacting a terminal today is about 15% at
KLOL and 5-10% elsewhere. Outside of gusty outflow winds from
isolated showers/storms today, the general low level winds will be
northeast to east this afternoon with gusts under 20 kts.
Thunderstorms for Saturday will shift to along the Sierra from
Lake Tahoe south to Mammoth Lakes.
Light northeast to east winds along with increased mixing have
allowed visibility to improved somewhat this afternoon. Additional
smoke transport will result in conditions worsening overnight
through Saturday morning. -Edan
&&
.FIRE WEATHER...
A couple of storms may develop near the Sierra, but high resolution
simulations have really backed off on that possibility for today.
Better potential for isolated storms exists across the Basin and
Range, where we are concerned about erratic and gusty outflow winds
over 40 mph. Storms for Saturday will be confined mainly to the
Sierra from the Tahoe Basin southward with drier and more stable
conditions all areas by Sunday.
The primary fire weather concern over the coming days continues to
be the trough dropping down into the Great Basin and Rockies early
next week. Model scenarios are still varying enough that warrant
uncertainty with the winds, but central to eastern Nevada could see
some gusty winds starting Sunday and Monday. For now the most gusty
winds will be east of the Sierra Front, but it will likely still
impact any ongoing fires across the Winnemucca dispatch areas. We
are still keeping an eye on it as trough location could slide
farther west resulting in stronger winds, even as far west as the
Sierra. -Edan
&&
.REV Watches/Warnings/Advisories...
NV...Dense Smoke Advisory until noon PDT Saturday portions of
NV002.
Dense Smoke Advisory until noon PDT Saturday NVZ003.
CA...Dense Smoke Advisory until noon PDT Saturday portions of
CAZ071.
Dense Smoke Advisory until noon PDT Saturday portions of
CAZ072.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
AREA FORECAST DISCUSSION
National Weather Service Charleston WV
1048 PM EDT Fri Aug 28 2020
.SYNOPSIS...
Remnants of Laura pass overnight. Cool high pressure briefly
builds in Sunday before more unsettled weather returns for next
week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 1045 PM Friday...
Forecast in good shape this evening, and no changes needed at
this time.
As of 800 PM Friday...
Forecast largely on track this evening. Previously mentioned
boundary across northern WV appears to have drifted north over
the past few hours as the influence from the remnants of Laura
begin to take over. Based on recent radar trends, HRRR may be
overplaying convective development thus far this evening. As
such any flash flood threat appears to be decreasing. I still
cannot rule out an isolated threat later this evening, but
areal extent is small enough to forgo a watch. Remnants of Laura
will move across the area overnight and be east of the area
shortly after sunrise. Rainfall from the remnants should be
manageable and largely absent of convective enhancement. Low
stratus left in its wake will gradually lift and scatter as flow
picks up ahead of approaching cold front.
As of 415 PM Friday...
Quick update to decrease POPs considerably over the next couple
of hours in the wake of the activity across the northern
Lowlands. Given the interaction with a southward moving boundary
into southern PA and far northern WV, there may be additional
backbuilding straddling our border with PBZ which may lead to
isolated flash flooding over the next hour.
Thereafter, latest runs of HRRR are trying to develop
convection along the I79 corridor and points southward to the SE
WV plateau along ML CAPE axis amid increasing moisture advection
ahead of Laura, with additional development this evening along
WV portions of route 33 and expanding eastward into the northern
mountains. This corresponds where our most vulnerable counties
are for flash flooding.
I will monitor radar/satellite/HRRR trends over the next hour
to see how things start to shake out. I may need to hoist a
Flash Flood Watch for this evening across the aforementioned
areas that were hard hit yesterday.
As of 135 PM Friday...
Made some minor upward tweaks to afternoon highs, otherwise
forecast on track. Should continue to see convection blossom in
an area of moist advection coupled with decent surface heating,
mainly across southeast Ohio and north central West Virginia
over the next few hours with additional storms developing in
breaks in the clouds further south by 3-4 PM.
As of 1230 PM Friday...
Strong moisture advection into southwest Virginia, northeast
Kentucky, and southwest West Virginia will continue to generate
elevated showers and thunderstorms through the early afternoon.
Further north and east, substantial breaks in mid-level
cloudiness will allow for more substantial insolation and
resultant building of surface based instability. As more
favorable moisture advects into these areas, should see a
blossoming of surface based storms through the afternoon hours.
Deep layer shear generally at or below 25KTs across this area
will limit overall potential for storm organization with the
primary threats being localized gusty/damaging winds from wet
microbursts and locally heavy rain. Training potential is
significantly less than yesterday and storms are expected to be
moving right along with storm motions around 25-30KT. This
should help limit the overall flash flood threat and currently
appears the heaviest cores will be generally west of an area of
significantly compromised soil moisture holding capacity due to
recent rain. Did strongly consider hoisting a flash flood watch
for some of our northeast counties where 3 hr flash flood
guidance values are 1 to 1.5 inches, but do not currently have
enough forecast confidence with the aforementioned factors. Will
still need to watch these areas very closely through this
afternoon and evening.
Shower and thunderstorm chances fade through the evening hours
with steady rain associated with the remnants of Laura beginning
to move into southwestern portions of the area around midnight.
Overall, impacts are expected to be limited with an additional
half to one inch of rain coming during mainly the early morning
hours Saturday.
The main area of concern will be limited to the aforementioned
areas of low FFG with additional possible rain this afternoon.
Some higher wind gusts will be possible, 20 to 30 mph, mainly
across any more exposed ridgetops and in more favored
isentropic down-glide off the higher terrain as winds aloft
begin to shift more southerly heading toward daybreak.
Remnants of Laura will largely exit the region to the east by
mid-morning with largely dry conditions across much of the area
from morning into early afternoon. A cold front approaches
from the northwest during the afternoon hours yield a broken
line of showers and thunderstorms. Severe potential will hinge
on how quickly we can clear out and get some insolation down.
High res model consensus suggests recovering enough to yield
1500-2000J/kg MLCAPE across portions of West Virginia in an an
environment with 40KT deep layer shear which could yield some
strong to severe cells in the line.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 210 PM Friday...
Remnants of Laura and cold front will have departed with a
wholesale change in airmass filtering in with higher pressure.
After the days of unsettled conditions, a day of stable air,
slightly cooler temperatures, and dewpoints hanging out in the
50s will prevail. This will be short lived with the next upper
trough and surface low developing over the Tennessee Valley.
Surface low passes through Monday, bringing back the unsettled
conditions with chances for showers/storms in southwesterly flow
aloft.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 210 PM Friday...
Likely to get waves aloft and a stationary boundary through the
extended with another upper low digging into the lower
Mississippi Valley. The degree of activity in the pattern will
be largely dependent on the location of the stationary boundary,
which the models are not doing well in covering on a solution
yet. Expecting low level moisture to return to the region as
well as September will begin on the more active side.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
As of 815 PM Friday...
Remnants of Laura pass tonight with scattered convection this
evening giving way to a general rain overnight. Bases will lower
into MVFR and eventually IFR at most terminals. Predominately
MVFR VSBY in rain, but brief IFR VSBY cannot be ruled out.
System pulls east after 12Z with lingering low CIGS until late
morning or midday as surface flow picks up and cold front
approaches. Mountain terminals will likely hang on to low
stratus a bit later. Cold front will move across with a narrow
band of SHRA or TSRA and gusty winds in the afternoon.
FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SUNDAY...
FORECAST CONFIDENCE: Medium.
ALTERNATE SCENARIOS: Timing and extent of convection through 03Z
may be more than forecast. CIGs may not lower into IFR as the
remnants move across late tonight.
EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
DATE SAT 08/29/20
UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14
EDT 1HRLY 23 00 01 02 03 04 05 06 07 08 09 10
CRW CONSISTENCY H H H H H L H H L H H H
HTS CONSISTENCY H H H H H H H H H H H L
BKW CONSISTENCY H H H M H L M M M H H H
EKN CONSISTENCY H M H L L L L L L L M H
PKB CONSISTENCY H H H H H H H H H H H H
CKB CONSISTENCY H H H L H H H H H H H H
AFTER 00Z SUNDAY...
IFR valley fog possible Sunday morning.
&&
.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.
&&
$$
SYNOPSIS...26/JP
NEAR TERM...JP/30
SHORT TERM...26
LONG TERM...26
AVIATION...30
Area Forecast Discussion
National Weather Service Las Vegas NV
810 PM PDT Fri Aug 28 2020
.SYNOPSIS...
Increasing chances for storms can be expected for the weekend as
moisture filters in from the south across Mohave, eastern Clark,
and eastern San Bernardino counties. Strong storms which could
produce flash flooding and gusty winds will be possible. A Flash
Flood Watch has been issued for central and southern Mohave County
where more widespread flooding is expected.
&&
.UPDATE...Another tranquil evening across the region but changes are
on the horizon. A surge of moisture will work up the Gulf of
California tomorrow with shower and thunderstorm chances returning
to parts of the Colorado River Valley and Northwest Arizona. Already
seeing some mid level moisture getting entrained into the flow with
this afternoons 00z VEF sounding showing a small moist layer near
600mb. Current HRRR guidance seems a bit bullish developing some
late night shower activity out of this pocket of mid level moisture
but some virga activity may pop in the early morning hours mainly
south and east of Las Vegas. Made some small tweaks to the cloud
cover grids tonight but otherwise no major changes needed.
-Outler-
&&
.SHORT TERM...Currently, a pattern is unfolding that is supportive
of flash flood potential for areas where storms develop on
Saturday. High pressure located to our east will slowly sink
southward toward northern Mexico as low pressure continues to
spin near the central CA coast and larger trough moves into the
PacNW. In between these two features a weak jet will set up
across northwest AZ and southern NV. Add in a gulf moisture surge
fortified by Tropical Depression Hernan near the tip of Baja and
we have a portion of our area with a favorable set up for storms
capable of producing flash flooding as well as strong winds.
PWATs will increase northward going into Saturday with the 1.00 in
PWAT line cutting through central Clark into central San
Bernardino County and across the AZ Strip. The moisture gradient
will be quite tight just to the north of this boundary as PWATs
drop to around 0.5 inches across the southern Great Basin and Inyo
County. The jet will provide upper level support and a decent
amount of wind shear to work with on Saturday along with 1000-1500
J/kg CAPE values which could support some organized complexes of
storms. Best chances for storms remain across Mohave County where
we have decided to go with a Flash Flood Watch for central and
southern portions of the county. This is where moisture, forcing,
and instability will all be in place for higher coverage of flash
flood producing storms. However, strong storms producing
localized flash flooding will be possible outside of this area as
well. With upper level support and little change in available
instability, activity could continue through early Sunday morning
across Mohave County.
Storm chances will continue on Sunday but will be dependent on
what transpires tomorrow and tomorrow night. If it looks like
another active day is in store, the Flash Watch Flood may need to
be extended or expanded. As moisture increases this weekend temps
will moderate as a result, dropping a few degrees from today`s
high temps.
.LONG TERM...Monday through Friday.
On Monday, a mid-level trough will dive down from the PacNW
through the Great Basin to the southern Plains. Not much wind to
speak of with its passage but it will push moisture southward out
of the area and storm chances will be limited to the furthest
southeast corner of our area of responsibility Monday and Tuesday.
Temps will continue on a downward trend, bottoming out on Monday
with high temps right around seasonal normals which means around
100 degrees for Vegas. A strong ridge builds in behind this
trough and temps will rebound for the second half of the work
week with dry conditions.
&&
.AVIATION...For McCarran...Winds will shift from south to
southwest this afternoon at speeds of 10-15 knots gusting near 20
knots. South to southwest winds will continue overnight at 8-10
knots before becoming breezy out of the south to southwest once
again on Saturday afternoon. Storms will be possible to the east
across Mohave County and the Colorado River valley with best
chances for any outflows in the valley after 00z Sunday.
For the rest of southern Nevada, northwest Arizona and southeast
California...Breezy, southwest winds will continue through this
evening with gusts of 20-25 knots possible. This wind pattern
will again be present on Saturday. Storms will develop Saturday
afternoon with highest chances across Mohave County and lower
chances over the Colorado River Valley and the eastern half of San
Bernardino County. There are low chances for storms to directly
affect any of the terminals but outflow are possible at all
terminals less KBIH. Storms could potentially last through early
Sunday morning for Mohave County.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
SHORT TERM/LONG TERM...Guillet
AVIATION...Guillet
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