Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/20/20
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1013 PM EDT Sun Jul 19 2020
.SYNOPSIS...
A few showers and thunderstorms are possible tonight as
it will remain warm and muggy. A cold front will move across the
region on Monday with only isolated shower and thunderstorm
potential. Dry and slightly cooler weather is expected on Tuesday.
The next chance for showers and thunderstorms arrives during the
middle of the week.
&&
.NEAR TERM /THROUGH MONDAY/...
A Heat Advisory remains in effect for portions of the Capital
Region, central and southern Taconics, mid-Hudson Valley,
southern Berks, NW CT and eastern Windham County of VT from 11
to 8 PM EDT Monday.
As of 945 PM EDT...Most of the convection has weakened yet still
lingering instability as seen in the 00Z sounding. Nighttime
satellite imagery reveals layers of clouds with lower stratus
developing under the canopy of high and mid clouds. Rather
chaotic H2O vapor imagery due to all of the convection so
difficult to ascertain embedded waves for future development
overnight. However, some hints within the HRRR suggest a weak
wave across western NY and Lake Ontario may touch off additional
isolated to scattered convection overnight across most of the
region. So with this update, we will taper back the higher PoPs,
leave in the mention of thunder, and adjust temperatures a bit
per observations and NY Mesonet. Overnight lows look okay at
this time as it will remain rather warm and muggy overnight as
dewpoints hang out well into the 60s and lower 70s.
Then a weak cold front will track southeast during Monday as
winds gradually back to the west then west-northwest with a
slight drop in the humidity levels from the Capital Region and
points west and north. Just to the south, another hot and humid
day where the heat advisory remains in effect. Could touch off a
shower or thunderstorm with the frontal passage as PWATs remain
around 2 inches, negative Showalter values and SBCAPES around or
just above 2000 J/Kg.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
The focus for this evening will be the advancement of showers
and thunderstorms and how intense they will be upon arrival.
Guidance continues to show a weakening trend as they move
eastward, mainly due to the loss of daytime heating and weak
upper-level forcing and shear over the area. Should storms
maintain themselves long enough, some gusty winds and heavy
rainfall will be possible to just west and north of Albany.
The Storm Prediction Center continues a Marginal Risk for
severe thunderstorms for this area with a Slight Risk clipping
far northwestern Herkimer County. Outside of this area, slight
chance to chance pops are maintained for showers. However,
850mb theta-e values remain very high overnight and PWATs rise
to 1.5 to 2 inches across the area so an isolated robust
thunderstorm with a heavy downpour is not out of the question.
With an increase in cloud cover and the continued southerly
flow, it will be a warm and muggy night with lows ranging from
the upper 60s in the higher terrain to the low to mid-70s in the
valleys.
Monday, a cold front will push eastward across the region
during the day. Latest guidance has the front clear Litchfield
County in the far southeast around 2 PM. Isolated
showers/thunderstorms are anticipated with the better chances
south and east of the Capital District (where the front will be
crossing during the late morning/early afternoon). High
temperatures will range from the upper 70s to lower 80s across
the higher terrain to the upper 80s and lower 90s in the valleys
(with the highest values in the mid-Hudson Valley). Heat Index
values between 95 and 103 are still possible from the Capital
Region and points south and east; therefore the Heat Advisory
will continue in these areas.
High pressure will then build eastward across the region with
dry weather Monday night through Tuesday. The air mass will be
a bit more comfortable than the previous days. Lows Monday night
will range from the upper 50s in the higher terrain to the low
to mid-60s. Highs Tuesday will range from the 70s in the higher
terrain to the 80s in the valleys.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
The long term period will look fairly summer-like with afternoon
highs each day in the 80s and a few chances for afternoon
thunderstorms.
To start the period, a low pressure system will track across the
Great Lakes and into New England. This will allow for a warm front
to lift north through the region Wednesday, bringing increased
humidity levels and chances for showers/storms. The low tracks
further east into western Maine Thursday-Thursday night, sending its
surface cold front through the region. This will lead to the threat
for showers and thunderstorms throughout the day Thursday with highs
reaching the upper 80s in the valleys (low 80s elsewhere). Depending
on the timing of the frontal passage, could see some of the storms
getting strong to potentially severe with ample surface based
instability and lift with the front.
High pressure builds in behind the front, bringing a reprieve to
humidity levels and above normal heat. Friday and Saturday look dry
with mostly sunny skies and highs in the upper 70s to mid 80s.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Challenging TAFs through this evening with respect to convective
potential as isolated to scattered convection on the 88D
continues to track east-southeast. We will carry TEMPO groups
through this evening to cover the potential of convection.
Overnight, subtle hints at the potential for more
showers/storms, however the coverage remains in question as we
will leave it out for now overnight and monitor upstream trends.
Some haze/mist may develop but expected to remain above MVFR
thresholds. Ceilings should also remain above thresholds with
VFR conditions anticipated.
Frontal boundary will slide southeast during Monday. This will
result in VFR conditions as winds become west-northwest with an
increase in magnitudes and a few gusts near 20kts. There also
could be a shower/storm to the south of Albany but confidence
remains low to include in KPOU-KPSF at this time.
Outlook...
Monday Night: No Operational Impact. NO SIG WX.
Tuesday: No Operational Impact. NO SIG WX.
Tuesday Night: No Operational Impact. NO SIG WX.
Wednesday: Moderate Operational Impact. Likely SHRA...TSRA.
Wednesday Night: Moderate Operational Impact. Chance of SHRA...TSRA.
Thursday: Moderate Operational Impact. Chance of SHRA...TSRA.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: Low Operational Impact. NO SIG WX.
&&
.FIRE WEATHER...
Humidity will increase to between 80 and 95 percent tonight
along with the chance for showers and thunderstorms, mainly
north and west of the Capital District. Minimum RH values Monday
afternoon will be 40 to 50 percent. RH values are forecast to
recover Monday night back to 85 to 100 percent.
&&
.HYDROLOGY...
No problems are expected on the main stem rivers in the ALY
Hydro Service Area over the next week. Forecast rainfall during
this period ranges from 0.75 to 2 inches. Isolated to scattered
showers and thunderstorms are expected tonight into Monday,
mainly north and west of the Capital District with some locally
heavy downpours possible, but not over a wide enough area to
have big impact on main stem rivers. The next chance of
precipitation will be on Wednesday. Much of the area remains in
abnormally dry to moderate drought conditions per the latest US
Drought Monitor, with streamflows well below normal.
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...Heat Advisory until 8 PM EDT Monday for CTZ001-013.
NY...Heat Advisory until 8 PM EDT Monday for NYZ052-053-059>061-
064>066.
MA...Heat Advisory until 8 PM EDT Monday for MAZ025.
VT...Heat Advisory until 8 PM EDT Monday for VTZ015.
&&
$$
SYNOPSIS...SND/BGM/Rathbun
NEAR TERM...SND/BGM/Rathbun
SHORT TERM...SND/Rathbun
LONG TERM...JLV
AVIATION...Evbuoma/BGM
FIRE WEATHER...SND
HYDROLOGY...SND
Area Forecast Discussion
National Weather Service Caribou ME
909 PM EDT Sun Jul 19 2020
.SYNOPSIS...
A cold front will approach overnight and cross the region
Monday. High pressure will build across the region Tuesday. A
weather disturbance will begin to approach from the west
Wednesday then move into the region Thursday. High pressure will
begin to build toward the region from the west Friday.
&&
.NEAR TERM /THROUGH MONDAY/...
9:09 pm update: The 00z KCAR sounding had a PWAT of 1.7" and MU
Cape of 1155J/KG. Area radars show showers & thunderstorm
moving into northern Maine from Quebec. Shear is expected to
increase with time the remainder of the night and this will keep
the threat of thunderstorms going across northern Maine
overnight. The greatest threat from the storms will be heavy
rain. The threat of hail looks relatively low due to high
freezing levels, but some gusty wind is certainly possible with
any stronger storms. Made some adjustments to the PoPs based on
the latest radar trends. The past couple of runs of the HRRR do
not appear to have a very good handle on the convection that is
now tracking across northern Maine.
Previous discussion:
An increasingly unstable environment will develop this evening
in northern zones as an MCS propagates from the Ontario and the
eastern Great Lakes region. This complex will mostly affect
northern Aroostook County. In spite of the loss of daytime
heating, SBCAPE will continue well into the night and shear will
increase in the evening. As a result, expect the complex to
hold together rather than falling apart after sunset. With PWATs
in excess of 2 inches, dew points near 70F, a deep warm cloud
layer, a strengthening LLJ and favorable Corfidi vectors, have
some concerns about heavy rainfall in the North Woods and
northern Aroostook tonight. The MCS passage will correspond with
the thermal ridge at 850 and 925mb. A second round of
thunderstorms with the cold front will reach the North Woods
early Monday morning and quickly weaken as it moves eastward
across the state Monday morning. At this point, it looks like
stabilization and dry air will kill another round of convection
towards the Downeast region for Monday afternoon...and SPC
agrees as the marginal risk has been removed from the forecast
area. Monday will be another hot day with morning lows near
70F...allowing daytime highs to push into the upper 80s to low
90s before cooler air arrives late day.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
The cold front will slide off the Maine coast Monday evening. NW
flow behind the front will bring in some cooler and much drier
air. Winds will stay up between 5 and 10 mph keep temps up
overnight w/low to mid 50s across the n while further s, upper
50s to lower 60s. Tuesday will feature high pres pressing east
toward the region. There will be NW breeze sustained at 10-15
mph. Plenty of sunshine w/seasonal temps. High pres moves
overhead Tuesday night w/winds dropping off and clear skies
leading a chilly night. Decent radiational cooling overnight
w/allow some low lying sites hitting the upper 40s especially
across the Allagash region and far NW Maine.
Wednesday will start sunny, but increasing clouds are expected
as high pres slides off to the east. The cold front sitting off
the coast is forecast to start advancing back to the n. The 12z
model guidance showing some differences in timing of rainfall
later in the day as a low pres wave lifts up along the boundary.
The latest GFS run was slower and keeps the high ridge in longer
keeping rainfall at bay. The ECMWF on the other hand is faster
in bringing rain northward w/that weak wave of low pres and
giving a good dose of necessary rainfall to the central and
downeast areas. The Canadian Global is similar to the ECMWF in
timing. Decided to blend the pops w/a lean toward the ECMWF for
the placement given its last 3 consecutive runs being
consistent in showing that wave of low pres. Plus, the last 2
runs of the Canadian Global were similar to the the ECMWF timing
and placement. Decided on showers w/some embedded tstms later
in the day across the srn 1/2 of the CWA.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
Wednesday night through Sunday...Continuing w/the blended apch,
this first batch of showers and embedded tstms is forecast to
end by later Wednesday night. A brief break in the action early
Thursday and then another round of showers and possible tstms in
the offing for later Thursday afternoon into the evening as a
cold front crosses the region. The long range guidance is
remarkably in close agreement w/the timing the rainfall and
frontal passage. Much cooler air arriving by Friday w/breezy
conditions but seasonal temps. NW winds of 10-20 mph w/some
higher gusts. Continued dry for Saturday w/a moderation in temps
as a SW flow takes hold as high pres slides off to the se.
Another frontal system is shown by the long range guidance to
approach the region on Sunday with showers and perhaps some
tstms. Given that this day at the end of the extended forecast
period, stayed w/just showers.
&&
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
NEAR TERM: Mostly VFR except from KPQI north where showers and
storms overnight may locally produce IFR/MVFR cigs following
into Monday morning. There`s also a chance of IFR conditions at
BHB overnight.
SHORT TERM: VFR Monday night through Wednesday. The exception to
this will be for KBHB as some IFR cigs/vsby possible Monday
night. SW winds becoming WNW 10-15 mph Monday night into
Tuesday. Winds will drop off Tuesday night to less than 5 mph.
Variable winds less than 10 mph will become S on Wednesday.
Wednesday night into Thursday...MVFR to IFR w/showers and
possible tstms. The bulk of the activity looks like it will be
across the KBGR and KBHB airfields. SSE winds 5-10 mph.
Thursday night into Friday...Showers and tstms into Thursday
evening w/MVFR and IFR. Improvement to VFR will be across
KBGR and KBHB Thursday evening while the northern terminals hang
on to MVFR into early Friday morning. VFR all terminals for
Friday. SSW winds 10 mph Thursday night becoming WNW 10-15 on
Friday.
&&
.MARINE...
NEAR TERM: Fog continues late this evening, but is expected to
be swept out later tonight...and then move back over the waters
Monday afternoon. Winds pick up later tonight into Monday
morning with gusts over 20 kt, but it`s not expected that an
advisory will be needed. Shorter period waves will respond to
the winds and occasionally reach as high as 5 ft by Monday
morning.
SHORT TERM: SW winds 10-15 kt Monday evening becoming WNW later
Monday night right into Tuesday. Seas 2-3 ft. Some fog is
possible early in the evening before the frontal passage and wind
shift.
Tuesday night into Wednesday...NW wind less than 10 kt becoming
S around 10 kt on Wednesday. Seas 2-3 ft.
Wednesday night into Thursday...S wind around 10 mph becoming
SW on Thursday ahead of the front 10-15 kt. Seas build to 3 ft.
Thursday night into Friday...SW wind 10-15 kt becoming WNW by
Friday 10 kt. Seas 2-3 ft.
&&
.CLIMATE...
Today was the 30th day this year with a high of 80 degrees (F)
or warmer in Caribou, Maine. This the most year-to-date on
record. The all-time record for an entire year is 51 days, set
in 1999.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...CB/MCW
Short Term...Hewitt
Long Term...Hewitt
Aviation...CB/MCW/Hewitt
Marine...CB/MCW/Hewitt
Climate...CB
Area Forecast Discussion
National Weather Service State College PA
1115 PM EDT Sun Jul 19 2020
.SYNOPSIS...
A subtropical ridge over the southern half of the CONUS and a
broad Bermuda High will continue to provide PA with hot and
humid weather for the next few days.
A weak cold front moving southeast from the Upper Great Lakes
will generate strong storms this evening.
After a few generally dry days to start the week, the risk of
showers and thunderstorms will increase next week with typical
summertime conditions across central PA.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Compact shortwave riding over the northern edge of some very
warm air aloft (+10-11C) will support a few small clusters of
showers and tsra across the NW and Ncent mtns of PA through 08z
before they weak near and to the NE and E of KIPT toward
daybreak. Past few HRRR runs have depicted the formation and
track of this convection nicely. Elsewhere it will be partly
cloudy and muggy with just a brief shower possible late.
Temps will be much warmer overnight compared to recent night,
and dewpoints stay sticky in the mid 60s to low 70s, so this
should make the conditions unbearable for many in the SE
tonight.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
The heat advy continues through Monday aftn for the SE. In
fact, the HIs Mon may even be a deg or two lower than Sunday
aftn, as dewpoints should be a hair lower. The drier air will be
more noticeable across the NW 2/3rds of the area. Temps should
also be a little cooler in the NW, too, thanks partly to some
early lower clouds and perhaps fog. Just a small chc of showers
exists Mon along the MD border.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
High heights forecast to remain in place through the long term
period with weak westerly flow aloft. Thus, the hot and
generally dry weather continues on Tuesday with little changes.
Forecast becomes a bit more uncertain beginning Tuesday night
for the rest of the week. GEFS more progressive with an
approaching trof and associated fropa then the Euro. For now,
will increase pops into Wednesday and Thursday with convective
systems moving in from the west. Subtle cooling aloft will bring
temperatures closer to average, with no significant cooling
likely. Lower pops look in good order for Friday and Saturday
behind the trof, then slowly increasing next Sunday.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
At 03z, a few lingering thunderstorms were moving across west-
central PA. Thunderstorms will likely fizzle out by around
05-06z. Some lower clouds in the NW - maybe IFR at BFD - are
expected to develop after 07z, but wind will not be light enough
for much fog. Elsewhere, conditions should be VFR with mid to
upper level clouds.
Cigs will improve to VFR in the NW by 14z and there will be a
clearing trend through the day as drier air moves in. Any chc
of a TS/SHRA Mon aftn will be along or, more likely, to the
south of the PA Turnpike (JST- LNS line)... but left it out of
the TAFs for now.
Outlook...
Tue...Mainly VFR, very hot and humid. Isold-sct PM
showers/t-storms.
Wed-Thur...Mainly VFR conditions again, but chc of
showers/storms with slightly lower temperatures & humidity.
Fri...MOrning fog poss N. Mainly VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT Monday for PAZ036-057-059-063>066.
&&
$$
SYNOPSIS...Lambert/Dangelo
NEAR TERM...Lambert/Dangelo/Colbert
SHORT TERM...Dangelo
LONG TERM...Ross/Gartner
AVIATION...Dangelo/Colbert
Area Forecast Discussion
National Weather Service Duluth MN
1004 PM CDT Sun Jul 19 2020
.SHORT TERM...(This evening through Monday night)
Issued at 346 PM CDT Sun Jul 19 2020
Gusty winds out of the west this evening with cooler temperatures
than the previous day thanks to the cold front that swept through
overnight. Another cold front is currently pushing southeast this
afternoon with some increased clouds and some light showers peppered
across the Northern MN. A few short lived thunderstorms could
populate across the Arrowhead this evening but the overall dynamics
are not favorable for any sustained convection.
Winds will taper off this evening and a weak surface high builds in
behind the front. Less windy conditions will be on tap for tomorrow
with another diurnally driven cumulus field developing over the
Northland. Temperatures will be near the seasonal averages of mid to
upper 70s.
Monday afternoon into Tuesday morning will bring the next round of
precipitation for the region. An upper level trough moves in from
the west with a surface low developing over ND and marching east
towards MN. The CAMs are currently not in good agreement with the
onset time. HRRR has the fastest progression with activity entering
the Brainerd Lake region in the afternoon, the other models have a
slower ramp up time with initiation later in the evening. Overall,
the instability at the start of the event is fairly minimal with
MLCAPES between 500-1000 J/Kg. Bulk shear is also on the lower end
of the scale around 25-30 kts. This could generate a few strong
storms but at this time severe potential is not overly favorable.
Tuesday evening shows a little more favorable dynamics for storms.
The cold front attached to the low pressure system moving through MN
swings across the region and intersects with some more favorable
instability across our southern regions. MLCAPES will have risen to
over 1500 J/Kg and bulk shear values will have increased as well.
However, these parameters are likely incumbent on how much surface
heating we can ingest into the area prior to the afternoons start
time.
.LONG TERM...(Tuesday through Sunday)
Issued at 346 PM CDT Sun Jul 19 2020
Rain showers move out Tuesday night and high pressure settles in for
the next couple days. High temperatures fluctuate around the mid to
upper 70s for Wednesday and Thursday. Model discrepancy is rather
high going into Friday and the weekend. The current consensus is
that the upper level ridge will begin to break down and give way to
a more quasi zonal flow. However, there is poor agreement on the
timing. For now, we have left the mention of POPs for Thursday but
trimmed back the percentage as there seems to be fairly higher
agreement that the upper level ridge axis will still be to the west.
As the ridge flattens out periodic rain chances will percolate
through the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 640 PM CDT Sun Jul 19 2020
Windy conditions continue at most of the terminals, but the mixing
layer near the surface will decouple in the next couple hours as
the sun sets and high pressure develops over the area, leading to
light winds less than 10 kt after 02Z and becoming calm overnight.
Several short range models continue to hint at some fog
development primarily at HIB/BRD where the likelihood is highest
for calm winds overnight. The fog will likely be patchy, and the
visibility will likely be VFR most of the night but drop to MVFR
or IFR for brief periods during the morning.
Otherwise, high pressure will keep ceilings and visibilities VFR
with light winds on Monday.
&&
.MARINE...
Issued at 1002 PM CDT Sun Jul 19 2020
Some blustery winds are continuing over the nearshore waters this
evening with post-cold frontal northwesterly flow. Most sites
are reporting wind gusts to 20 kt or less, so the Small Craft
Advisory is allowed to expire at 03Z. There may still be some
gusts to around 20 kt for the next couple hours, but the overall
trend will be for wind speeds to diminish as high pressure builds
into the region.
Light and variable winds are expected Monday and Monday night
with high pressure in place. A chance for showers and
thunderstorms return on Tuesday as an area of low pressure
develops and passes just south of Lake Superior. This will create
a period of northeasterly flow over Lake Superior which may be
breezy with gusts up to around 20 kt possible.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 54 76 57 70 / 0 10 70 80
INL 49 75 56 67 / 0 0 70 70
BRD 55 77 60 74 / 0 10 80 70
HYR 52 77 57 75 / 0 10 60 80
ASX 57 76 57 75 / 0 0 60 80
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...Small Craft Advisory until 10 PM CDT this evening for LSZ121-
140>148.
&&
$$
SHORT TERM...Britt
LONG TERM...Britt
AVIATION...JDS
MARINE...JDS
Area Forecast Discussion
National Weather Service Grand Forks ND
1002 PM CDT Sun Jul 19 2020
.UPDATE...
Issued at 1002 PM CDT Sun Jul 19 2020
A weak mid level wave is moving east along the Canadian border
with ND this evening. An area of low level convergence along a
stalled frontal boundary across eastern ND will be the focus for
an isolated shower or two this evening. Some runs of the HRRR try
to keep activity going all night, but other CAMs have been rather
quiet with it. The weak low level forcing...combined with MUCAPE
of 1000 J/kg exists...but the upper support is more to the north.
Believe a mostly dry forecast is the best route. Will update as
needed.
UPDATE Issued at 651 PM CDT Sun Jul 19 2020
A quiet night is expected tonight with a dissipating cumulus
field across much of the area. However, an area of weak low level
convergence exists from NW to SE across southeastern SK through
the Devils Lake Basin and extending through the Fargo area. Some
of the CAMs have a few isolated showers/thunderstorms in this area
this evening, but radar trends indicate this is likely overdone a
little. Still, there area a couple of weak cells in the Turtle
Mountain region and north of the Canadian border...and with 1000
J/kg of MUCAPE currently, we could see a few cells make it into
Towner/Cavalier/Ramsey counties. Impacts will likely be minimal
and confined to lightning alone.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 322 PM CDT Sun Jul 19 2020
Gust northwest winds and an extensive cumulus cloud field have
developed across the northern RRV and much of northwest MN in the
backwash of departing low pressure system, now in southern
Ontario. A brief shower or isolated thunderstorm is possible
through the remainder of the afternoon and early evening, mainly
of far northwest MN, otherwise clouds and winds should diminish
with sunset as surface high pressure settles over the area.
Fair skies and light winds are expected this evening and
overnight, though bands of thin mid to high level clouds are
moving into the area from southern MB and central ND, so this may
reduce clarity for any early evening Comet Neowise viewing. Else,
overnight low temperatures should settle into the 50s.
Monday will see light and variable winds early, with winds
turning back from the south, and increasing throughout the
afternoon. Late afternoon into the evening will see increasing
clouds across central and eastern ND, with thunderstorms likely
from late afternoon into the evening and overnight hours. Clouds
and thunderstorms will spill across the Red River corridor
through early evening, and across much of northwest and
westcentral MN through the evening and overnight periods.
Widespread wetting rains are expected across most of the area from
late Monday into Tuesday morning, with isolated strong to severe
thunderstorms possible.
.LONG TERM...(Tuesday through Sunday)
Issued at 322 PM CDT Sun Jul 19 2020
The pattern continues to be unsettled as the mean jet position
remains over the northern tier of states. This will lead to periods
of unsettled weather through the period.
For Tuesday...an upper level shortwave and associated surface low
will depart the area decreasing precipitation chances.
By Wednesday...surface high pressure remains in control. Upper
pattern shows shift toward ridge amplification and return flow will
help increase temperatures by Thursday...when another system crosses
the forecast area and chances for showers and storms increase again.
Behind the system...expect moderating temperatures and more pleasant
conditions to end the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 651 PM CDT Sun Jul 19 2020
A few dying showers or isolated thunderstorms will approach the
DVL terminal from the NW this evening. However, they`re not
expected to reach DVL. Otherwise, expect dissipating clouds across
much of the region, except we`ll see some more lingering clouds
in the DVL area than other areas tonight. Expect winds becoming
light and switching to the southeast across eastern ND by
tomorrow, but remaining light. A better chance for showers and
thunderstorms comes tomorrow by early afternoon to DVL and then
pushes east to the rest of the area through the late afternoon and
evening hours.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Knutsvig
SHORT TERM...Gust
LONG TERM...Hopkins
AVIATION...Knutsvig
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
849 PM CDT Sun Jul 19 2020
.UPDATE...
Issued at 842 PM CDT Sun Jul 19 2020
Updated the forecast tonight to slow down introduction of
convection from the west. I did leave in a slight chance for the
western half of the CWA during the evening as we got some very
small pop-up showers, which might have a stray bolt of lightning.
I did lower chances of precipitation a tad overnight, and as
mentioned earlier, brought in the higher chances later into the
night, and more likely toward dawn, especially in the eastern half
of the CWA.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 452 PM CDT Sun Jul 19 2020
Focusing on the first 5 night/day forecast periods in this
section, by far the main issues/challenges are: 1) VERY tricky-
to-pin-down rain/thunderstorm chances (PoPs)...2) A risk of severe
thunderstorms mainly for tonight, but perhaps also for Monday-
Tuesday (although these chances are still quite murky/unclear)...3)
A tricky high temperature forecast for Monday (especially by July
standards).
Briefly looking at the current/recent weather scene as of 4 PM:
As expected, the vast majority of the day has been dry across the
vast majority of the coverage area (CWA) once the overnight/early
AM thunderstorm activity faded away (most of this affected our KS
zones last night, but a separate area of isolated-scattered non-
severe storms affected areas near the I-80 corridor a few hours
either side of sunrise). Under mostly sunny to partly cloudy
skies, high temps this afternoon are on track to nearly match or
perhaps very-slightly exceed expectations from the early-AM
forecast package, with most of our CWA topping out 87-91. In the
mid-upper levels, water vapor satellite and short term model data
confirm fairly typical mid-summer, quasi-zonal (west-east) flow
over our region, with the departed subtle disturbance from the
overnight crossing the eastern KS/MO area, while more little waves
to our west are kicking off convection mainly over the High Plains
of the CO/NE/KS border area. That being said, a bit of weak
convection has recently fired up within 50 miles north-northwest
of the CWA as well, likely aided by some weak mid level warm air
advection. At the surface, breezes are generally out of the
southeast at sustained speeds 10-15 MPH/occasional gusts up to
around 20 MPH.
Now going over the basic expectations of these next 60 hours...
This evening-tonight:
First of all, want to make it VERY CLEAR that confidence in
exactly how things play out is not overly-high. While PoPs were
trended down most areas for the evening (pre-midnight) hours,
maintained some fairly high values (as high as 60-70 percent)
mainly for the late night time frame (especially in our Nebraska
zones). That being said, even at this close time range, there is
noticeable disagreement between two of the more heavily-relied-
upon shorter-term models. On one hand, the NAMNest depicts fairly
widespread coverage of rain/storms overnight, both as a
potentially-organized complex (MCS) rolling in from the west and
also perhaps activity initiating directly over the CWA within the
exit region of a modest low-level jet. On the other hand, several
recent runs of the HRRR have been less generous with thunderstorm
coverage/potential overnight, instead splitting the majority of
convective potential around/near the northern/southern and even
eastern fringes of our CWA (while largely missing some of our
driest central counties that truly need rain the most). Given this
inherent uncertainty, was not willing to raise PoPs any higher
than the 60-70 percent featured in the previous forecast, but also
did not lower them either. Just lots of question marks. Either
way, whether convection ends up being more widespread or more
spotty, at least a limited risk for severe storms exists, given
fairly healthy mixed-layer and elevated CAPE into the 2000+ J/kg
range, although deep-layer shear should be on the modest side
(only around 30KT at most). Especially if an organized complex
manages to roll in from the west, damaging winds would be the main
threat. Localized heavy rain of at least 1-2" in could also occur
overnight, but assuming that much of this would fall in our drier
Nebraska zones, am just not overly-concerned about much of a
flooding threat. Timing-wise, will obviously need to watch some of
the ongoing late-afternoon development that has sprung up near the
northwest corner of our CWA, but for the vast majority of our
area, the main potential for storms should hold off until after 10
PM (and for many after midnight). In other departments, opted to
keep any formal mention of fog out of the late night/early AM
forecast, but especially if storm coverage ends up being sparse,
at least some patchy fog probably cannot be ruled out. Low temps
were nudged up slightly, with most areas bottoming out mid-upper
60s.
Monday daytime:
As if you already haven`t read enough about forecast uncertainty
just for tonight`s period, it simply continues right on into
tomorrow. Although PoPs were trended down a bit from previous
forecast, it is likely that at least isolated-scattered convection
will continue into the first part of the day (especially eastern
zones). Could even see a few stronger storms (mainly with small
hail potential), mainly before 10-11 AM. Otherwise, while most
areas will probably be dry during the afternoon, enough
uncertainty exists that some low-confidence 20-40 PoPs were
maintained all areas. Another big question mark Monday is cloud
cover, as models such as NAM/RAP have been fairly aggressive in
lingering lower clouds across especially northern/eastern zones
much of the day, with better potential for at least partly cloudy
skies south/southwest. While feel that this cloud cover could be a
bit overdone (it`s hard to remain truly overcast all day in July
after all), the resultant temp forecast is a bit tricky. Ended up
lowering northern zones slightly and raising southern zones
slightly, resulting in a more pronounced gradient between upper
70s-low 80s north and mid-upper 80s south-southwest. But could
easily see some areas missing this forecast by 5-ish degrees
depending on clouds (or lack thereof). Wind generally easterly
around 10-15 MPH (similar to today).
Monday evening-night:
Although the entire CWA is in a Marginal Risk of severe per SPC
Day 2, the finer details of storm coverage remain quite murky, and
models such as the NAMNest are considerably drier than tonight. As
a result, held PoPs under 50 percent all areas, but of course at
least small chances for convection certainly exist. Low temps
similar to tonight, mainly mid-upper 60s.
Tuesday-Tues night:
This looks to be the last "cooler"/slightly below average temp day
of the week, as we begin a transition to slightly warmer temps
thereafter (see Long Term Below). Highs are aimed mid 80s most
areas, with any upper 80s most favored far southwest. At least
small PoPs continue through these 24 hours as we remain subject to
weak waves drifting in from the west. As is typical of mid-
summer, the seemingly better chances should favor the night hours
versus the day. At least for now, roughly the western 1/3 of our
CWA is included in the SPC Marginal risk for severe, but this is
very subject to further refinement as it gets closer in time.
.LONG TERM...(Wednesday through Sunday)
Issued at 452 PM CDT Sun Jul 19 2020
General overview of this 5-day period:
Very generally speaking, this stretch is looking mostly dry (fewer
rain chances/PoPs compared to early-week) and also continues
looking warmer than early-week, with slightly above normal
temperatures prevailing, but nothing overly/oppressively hot
either. That being said, factoring in humidity, each of these 5
afternoons could feature heat index values up to around 100
degrees in various portions of the area.
Basic weather pattern/precipitation overview:
In the mid-upper levels, the mid-week starts out with generally
quasi-zonal (west-east) flow over the Central Plains. However, by
Friday and especially into the weekend, both the ECMWF/GFS are in
relatively good agreement depicting a large-scale ridge building
northeastward out of the south-central CONUS and becoming more
centered over MO and vicinity. As a result, we will reside more on
the northwestern periphery of this ridge as opposed to the heart
of it. This means that while our rain/storm chances will not truly
be zero most days/nights, they will be overall-lower compared to
the early-mid week time frame. In fact, at least for now, the
official forecast remains dry CWA-wide for the Friday-Saturday
time frame, with only fairly spotty/low-confidence chances on
either side of this from Wed-Thurs and also by Sat night-Sunday.
Put another way, if you don`t get the rain you are looking for
prior to Wednesday, it will likely be tougher to come by from
Wednesday onward.
Temperature overview:
Overall, very little change from previous forecast here. As it
currently stands, Wednesday is a bit of a "transition day" between
the slightly cooler early-week periods, and the warmer later week-
weekend days. More specifically, highs Wed are currently aimed
upper 80s-low 90s, most areas, with low-mid 90s then more common
from Thurs-Sun. As mentioned above, while not anticipating any
need for formal Heat Advisories at this point, the combo of
slightly above-normal heat and fairly high humidity could easily
drive heat index up to around 100 degrees on several afternoons
(especially southern/eastern zones). Overnight lows are also aimed
into slightly above normal territory, with most nights expected to
hold up into the low-mid 70s.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday)
Issued at 650 PM CDT Sun Jul 19 2020
This is a low-confidence forecast largely because thunderstorm
chances are low confidence. Short term CAMs continue to diverge
with solutions. Stratus development could be greatly disrupted by
any thunderstorm activity and conditions are conducive to a
sunrise surprise thunderstorm, especially for KGRI and farther
east for Monday morning.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
UPDATE...Heinlein
SHORT TERM...Pfannkuch
LONG TERM...Pfannkuch
AVIATION...Heinlein
Area Forecast Discussion
National Weather Service Gray ME
1029 PM EDT Sun Jul 19 2020
.SYNOPSIS...
Hot and humid conditions are expected to last one more day into
Monday. A cold front will be slipping south across the region,
but ahead of it will remain well into the 90s with high
humidity. Isolated showers or thunderstorms are possible with
the front but overall dry weather will continue. More
comfortable temperatures arrive for the middle of the week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
1025 PM...Mesoscale models have actually panned out reasonable
well given where they were 3-4 hours ago, and for the most
part, convection to the west of the CWA has diminished. Still a
few SHRA and maybe some rumbles of thunder with be possible
across the Ct vly of NH, and the mtns through 4-5Z, but the
general trernd for these showers will be downward. Will see
another chc for showers and maybe a TSRA toward daybreak in SW
NH as we deal with storms forming on leftover to boundaries to
our W and shifting into the CWA.
630 PM...Forecast update mainly involves approaching convection
over NY attm. Meso models not in sync with current convection
there, with actual storms outpacing the HRRR by an hour or so.
So have adjusted POPS this evening to cover the chance of some
sct SHRA/TSRA moving into wrn NH after 00Z. All the models do
diminish the intensity and coverage by that time, but could see
a few weaker TSRA move into CT vly and then die as they cross NH
this evening. Otherwise no signif changes to the forecast, with
a very warm in store for most places.
Previously...Widespread 90s across the forecast area
today...with upper 90s over Srn NH. Dewpoints are just starting
to mix out now...so apparent temps have maxed out around 100
degrees. A little bit more of a seabreeze is keeping temps down
from PWM on N...but even PWM is sitting at 88. The real relief
is felt at RKD with a comfy reading of 78.
A well organized line of thunderstorms has formed across Wrn NY
with very isolated convection ahead of it. The question for late
this evening is how long this convection survives before
weakening. Current speed and direction would have the storms in
Wrn zones around 10 pm. However...CAM guidance weakens
convection quickly after sunset as storms outrun S/WV support.
So I have some chance PoP in Wrn zones...but very little
confidence that it extends much farther E than that. That just
leaves a sticky air mass overnight...with plenty of near 70
readings.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Cold front will settle thru the area during the first half of
the day. Again CAM guidance is very bearish on any convection
forming along the front...and SPC has removed the marginal risk
for the area. I will continue to have some isolated
thunderstorms in the forecast...but even this is very low
confidence.
Ahead of the front it will remain hot and humid. With WSW winds
it will heat up quickly...and I expect some 90s early in the day
near the coast. Heat advisory remain in effect for Srn and Ern
zones Mon.
Drier air really begins working into the area from the N
overnight...though I expect most of that to mix down Tue. But we
will see more widespread readings in the 60s than 70s for some
relief.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Overview:
High pressure moves into the area from the west on Tuesday
bringing with it drier and more seasonable temperatures. An
unsettled pattern returns for both Wednesday and Thursday as a
series of disturbances bring increased chances for scattered
showers and thunderstorms. Tranquil weather returns for Friday
before another potential disturbance arrives for the upcoming
weekend.
The long term portion of the forecast begins quiet on Tuesday as
high pressure moves into our region from the west behind the cold
front. High temperatures will be about 10 degrees cooler compared to
Monday with dewpoints also falling into the 50s to lower 60s.
The pattern then becomes a little more interesting as we head into
Wednesday and Thursday as an upper level trough moves in from the
upper Great Lakes and southern Ontario. There remains some
differences in model guidance in terms of the timing, placement, and
strength of this trough along with an expected associated low
pressure system. The greatest chances for scattered shower and
potentially thunderstorm activity will come in two waves with the
first arriving during the day on Wednesday and the second arriving
on Thursday in the form of a cold front. Depending on the timing of
this front, scattered thunderstorms will be possible, especially
across the coastal plain where the passage will likely better
coincide with peak daytime heating. A few strong to severe
thunderstorms will be possible if the front cross the area later in
the day given mid-level winds of 40 to 50 kts and decent CAPE.
This front will be affiliated with an area of low pressure which
model guidance has forming to our west on Thursday before traversing
northward towards northern Maine and southern Canada later in the
day. The eventual track, strength, and timing will play a key
role in determining both the coverage and severity of any
potential thunderstorm activity. For now PoPs were kept at
chance with thunder added for portions of south-central New
Hampshire as well as portions of the coastal plain in
southwestern Maine where the greatest instability is currently
expected to be located.
A return to quiet weather is expected on Friday as high pressure
builds to our west and the cold front moves offshore. A return to
more unsettled weather returns for both Saturday and Sunday as a
disturbance that will be located somewhere in the Northern Plains on
Friday may ride along the northern ridge axis and into our area by
Sunday. The ECMWF remains more bullish on this idea while the GFS
has this system mostly diminishing before reaching us. Nonetheless,
there will likely be enough forcing to allow for at least a few
scattered showers across the area during this time period and
therefore Chance and slight chance PoPs were left in.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Short Term...Generally expecting VFR conditions to prevail thru
Mon night. A lot of uncertainty with how long TSRA survive
across the Northeast. CAM guidance decays TSRA before they reach
the Wrn zones...and so I have no precip in the TAFs at the
moment. Guidance is also light on activity early Mon and it is
possible we see little RA.
Long Term...VFR conditions on Tuesday as high pressure moves into
the region with accompanying light surface winds. Scattered rain
showers on Wednesday may result in MVFR conditions. On Thursday
scattered showers and thunderstorms will be possible with continued
VFR/MVFR conditions expected. The greatest chance for thunderstorm
development currently looks to be across the coastal plain where the
greatest instability will be located. Confidence in forecast for
Tuesday is high while confidence in forecast for Wednesday and
Thursday is moderate to high.
&&
.MARINE...
Short Term...Increasing SW flow will allow seas to build
overnight. Some 5 to maybe 6 ft seas are expected N of Cape
Elizabeth and so I have issued a SCA for those zones. Otherwise
thunderstorm risk has decreased over the waters into Mon.
Long Term...High pressure approaches the area from the west on
Tuesday allowing for light surface winds. Southerly winds expected
Wednesday afternoon to around 10 to 15 kts before turning
northwesterly Thursday night behind a passing cold front.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Heat Advisory until 8 PM EDT Monday for MEZ018>020-023-024-033.
NH...Heat Advisory until 8 PM EDT Monday for NHZ008>015.
MARINE...Small Craft Advisory until 5 PM EDT Monday for ANZ150-152.
&&
$$
SYNOPSIS...Legro
NEAR TERM...Cempa/Legro
SHORT TERM...Legro
LONG TERM...Tubbs
AVIATION...Legro/Tubbs
MARINE...Legro/Tubbs
Area Forecast Discussion
National Weather Service North Platte NE
643 PM CDT Sun Jul 19 2020
.SHORT TERM...(This evening through Monday night)
Issued at 302 PM CDT Sun Jul 19 2020
The main forecast challenges through early week are thunder chances,
including severe potential. A warm front is bisecting the forecast
area today and will likely hang around through tomorrow, which will
help provide forcing for thunderstorms.
Synopsis/Today... As of 19z, southwest Nebraska was primarily in
southeast surface flow while the northern Sandhills were east to
light northeasterly. Significant moisture pooling was also occurring
in the Platte River Valley with dew points reaching the mid 60s.
Scattered rain showers traversed far northern Nebraska since this
morning, while bouts of clearing were experienced in the south.
This evening and tonight... Expecting some convective initiation in
the panhandle sometime around 23z near the surface low and possibly
along the warm front into the southern Sandhills. Early development
will likely be isolated to scattered in nature, with the capability
of growing into supercells. RAP mesoanalysis indicates ample
instability south of the front and decent deep layer shear to the
north. However, shear may increase this evening across the south as
a weak shortwave works off the Rockies. Forecast soundings indicate
veering winds in the lowest 3km and CAPE originating above the mixed
layer. Hail will probably be the bigger threat while convective mode
is still discrete. This also presents a non-zero tornado threat,
primarily in the far western zones. Toward sunset, cloud layer winds
become more aligned with the boundary orientation, and cells become
cold pool dominated as they progress eastward. While shear may still
be borderline for an organized widespread MCS, most CAMs are
suggesting at least a couple clusters or mini complexes. Thinking
wind and heavy rain will be the bigger threats in the latter stages,
especially as DCAPE values remain above 1000 j/kg and PWATs near
90%ile of climo. Made little change to previous forecast regarding
min temps with upper 50s northwest to lower 60s elsewhere.
Monday and Monday night... The surface low slowly meanders across
the High Plains, dragging the warm/quasi-stationary front with it.
Fairly significant discrepancies exist in the short range solutions
regarding precipitation chances during the day. Certainly can`t rule
out scattered activity, similar to the far north experienced today,
with the front providing forcing and abundant moisture still in
play. Not expecting widespread activity early on, in the wake of
tonight`s anticipated storms and instability being at a relative
minimum. Later in the afternoon and evening, when the atmosphere has
time to rejuvenate, most of the thunderstorms should redevelop. Deep
layer shear will be marginal, on the order of 30 kts, while mid
level lapse rates barely push 7C/km. The strongest forcing will be
confined to western Neb near the sfc low and where the greatest low
level upslope flow takes place. Although severe parameters don`t
appear great, agree with SPC analysis that some potential still
exists. Max temps were lowered a smidge to lower 80s north and mid
80s south to account for weak CAA at H85 and potential cloud
cover.
.LONG TERM...(Tuesday through Sunday)
Issued at 302 PM CDT Sun Jul 19 2020
Tuesday and beyond... Broad northwest flow transitions to
southwest this week as the upper ridge regains strength over the
southern and central Plains. Closer to the surface, the thermal
ridge returns to the High Plains with strong southerly flow and
H85 temps approaching 30C. So after a brief retrieve from the
summer scorcher, highs should reach the mid/upper 90s once again
to round out the week. The highest precip chances exist early in
the week during the upper ridge transition and with a surface
front in the vicinity. The next best potential comes closer to the
weekend with a weak cool front or surface trough passage.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 642 PM CDT Sun Jul 19 2020
Thunderstorms will begin to move into western and southwest
Nebraska this evening. Confidence is high enough that they have
been included in the LBF and VTN TAF`s. Thunderstorms should clear
out of the area after midnight with stratus expected to develop
behind the thunderstorm activity. Probability is fairly high that
IFR conditions will occur across portions of southwest Nebraska
including the LBF TAF. Farther north ceilings are expected to be a
bit higher with MVFR conditions expected across northern Nebraska
including the VTN TAF.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Snively
LONG TERM...Snively
AVIATION...Meltzer/Taylor
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
651 PM CDT Sun Jul 19 2020
.SHORT TERM... (Through Late Monday Night)
Issued at 210 PM CDT Sun Jul 19 2020
Cold front has now moved to near Springfield Illinois to Columbia
line. Satellite imagery is showing a well developed CU field
along and south of this front in an area where the SPC
mesoanalysis shows MLCAPES of 2500-3500+ J/kg with little CINH.
The HRRR has been consistent in developing thunderstorms along the
front between 21-23Z, so kept likely PoPs for late this afternoon
into this evening. There remains the possibility of one or two
severe thunderstorms given the amount of instability, with a wet
microburst and hail up to the size of quarters being the main
concerns.
Thunderstorms will continue through at least mid evening before they
begin to weaken with the loss of daytime heating and passage of weak
mid level vort max that is currently over eastern Kansas. Then
focus for convection will shift for additional storms developing
across western Missouri later tonight as a broad 25kt low level
jet sets up. These storms will move east into the CWA tomorrow
morning as the jet veers to the northeast. There will be some
threat for locally heavy rainfall given the PWATS around 2" and
deep warm cloud layers, particularly if any storms train.
Additional storm development is possible tomorrow afternoon along
the front in the unstable atmosphere. On late Monday night, there
will be another weak shortwave move along the front as a low level
jet sets up bringing another MCS potential.
Even though it will be humid tomorrow, expect highs to be mainly in
the 80s tomorrow with the clouds and rain potential so will not
extend the heat advisory. Lows the next two nights will be around
70.
Britt
.LONG TERM... (Tuesday through Next Sunday)
Issued at 210 PM CDT Sun Jul 19 2020
There remains relatively good agreement between the EPS and GEFS
means Tuesday into this weekend. The front will still likely be
stalled across Missouri and Illinois Tuesday into Thursday. The
front will lie beneath zonal flow with several low amplitude
shortwave troughs moving through the region. CIPS severe analogs
suggest that there will at least some chance for severe weather
during this time period given the very unstable atmosphere on the
southern edge of the westerlies. In addition, still expect the
threat of MCSs in a high PWAT atmosphere which will bring the
threat for locally heavy rainfall. By Friday, the front will move
north of the area as both the ensembles are still showing a 594dm
high building over the central CONUS next weekend. Forecast
guidance by next weekend suggest highs will be in the mid 90s.
Britt
&&
.AVIATION... (For the 00z TAFs through 00z Monday Evening)
Issued at 640 PM CDT Sun Jul 19 2020
Thunderstorms can be expected this evening from COU to the St
Louis metro area near a cold front which has dropped southward to
near the Interstate 70 corridor. These storms should dissipate by
late evening as the atmosphere stabilizes. There will be the
potential for another round of scattered storms Monday afternoon
and early evening as the front becomes nearly stationary just
south of the taf sites. Winds may be chaotic and gusty early this
evening near storms, but should become light by late evening,
mainly from a north-northeast direction.
SPECIFICS FOR KSTL: Thunderstorms can be expected this evening
from COU to STL near a cold front which has dropped southward to
near the Interstate 70 corridor. These storms should dissipate by
late evening as the atmosphere stabilizes. There will be the
potential for another round of scattered storms late Monday
afternoon and early evening as the front becomes nearly stationary
just south of the STL area. Winds may be chaotic and gusty early
this evening near storms, but should become light by late evening,
mainly from a northerly direction.
GKS
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 7 PM CDT this evening for Audrain MO-Boone
MO-Callaway MO-Cole MO-Crawford MO-Franklin MO-Gasconade MO-
Iron MO-Jefferson MO-Lincoln MO-Madison MO-Moniteau MO-
Monroe MO-Montgomery MO-Osage MO-Pike MO-Ralls MO-Reynolds
MO-Saint Charles MO-Saint Francois MO-Saint Louis City MO-
Saint Louis MO-Sainte Genevieve MO-Warren MO-Washington MO.
Flash Flood Watch until 1 AM CDT Monday for Boone MO-Callaway MO-
Cole MO-Franklin MO-Gasconade MO-Jefferson MO-Lincoln MO-
Moniteau MO-Montgomery MO-Osage MO-Saint Charles MO-Saint
Louis City MO-Saint Louis MO-Warren MO.
IL...Heat Advisory until 7 PM CDT this evening for Bond IL-Calhoun IL-
Clinton IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL-
Madison IL-Marion IL-Monroe IL-Montgomery IL-Pike IL-
Randolph IL-Saint Clair IL-Washington IL.
Flash Flood Watch until 1 AM CDT Monday for Bond IL-Calhoun IL-
Clinton IL-Fayette IL-Jersey IL-Macoupin IL-Madison IL-
Marion IL-Monroe IL-Montgomery IL-Saint Clair IL-Washington
IL.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Memphis TN
854 PM CDT Sun Jul 19 2020
.UPDATE...
A hot and muggy night across the Mid-South at this hour.
Temperatures are mainly in the mid 80s to as hot as 90 degrees.
Heat index values still range from the lower to upper 90s. The
latest GOES Nighttime Microphysics RGB imagery shows an expansive
southward advancing MCS along the I-44 corridor. This system is
progged to weaken and skirt across northern portions of the CWA
overnight. As it does, the HRRR suggests a few light showers or
isolated thunderstorms could form. Went ahead and increased POPs
to slight across this area and adjusted sky grids accordingly.
Monday morning temperatures will bottom out in the low to upper
70s across the region. Made a few minor tweaks to the forecast and
removed today`s wording in the HWO.
AC3
&&
.PREV DISCUSSION... /issued 626 PM CDT Sun Jul 19 2020/
UPDATE...
See the 00z aviation discussion.
&&
.PREV DISCUSSION... /issued 357 PM CDT Sun Jul 19 2020/
DISCUSSION...
Isolated showers and storms have developed this afternoon as a
weak perturbation moves along the weak mid-level high located
over the southeast, in addition to strong surface heating. Radar
currently shows a few showers over SW TN and far northern MS. Weak
outflows have formed over Tipton and Fayette counties in TN from
showers downstream. Goes-16 satellite imagery shows cloud tops
cooling and indicating some towering cumulus clouds are likely
located over northeastern AR and northwestern TN, just north of
the outflow - indicating that further development of showers and
storms is possible. However, coverage is expected to remain
isolated and any storms that develop will likely remain weak due
to low bulk shear. Heat Index Values have mainly behaved across
the Mid-South as we sit in the low 100s across most locations -
remaining below the 105 degree threshold that`s needed to warrant
a heat advisory. Current temperatures are in the low to mid 90s
with dew points in the low to mid 70s.
The high over the southeast will slowly push east which will
allow a stationary boundary to drag south into the lower Ohio
Valley and northern Mid-South over the next couple of days. Rain
chances will go up as the boundary pushes south with likely
outflows pushing into the MO Bootheel, eastern AR, and
northwestern TN. With the area remaining in a highly unstable
airmass as far as CAPE is concerned, showers and storms are
expected to develop, however, coverage will remain isolated to
scattered. The best chance for rain will be on Wednesday as a weak
upper-level disturbance clips the northern portions of the County
Warning Area (CWA). Storms are still forecast to be weak due to
low bulk-shear. Temperatures will remain consistent as they tend
to do during the Summer months in the Mid-South.
Rain chances will decrease as we end the week with a building
ridge from the east. Diurnally driven showers and storms will
still be possible as the heat and humidity remains. Temperatures
will be in the low to mid 90s with heat indices mostly remaining
at or below 105 degrees.
KRF
&&
.AVIATION...
/00z TAFs/
Isolated thunderstorms continue along the I-40 corridor but will
diminish by 01z. Expect dry weather overnight with mostly clear
skies. There is a potential for patchy fog, so will keep an eye
out, mainly for TUP/MKL terminals. Otherwise, expect VFR
conditions through the period with generally light south to
southwest winds. Isolated to scattered storms are possible again
Monday afternoon, but will not be included in current TAF given
anticipated limited coverage.
MJ
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Las Vegas NV
759 PM PDT Sun Jul 19 2020
.SYNOPSIS...Limited mid level moisture moving up from southern
Arizona will bring scattered clouds and a few showers and isolated
thunderstorms to the area through Tuesday. More significant
monsoonal moisture may begin to creep into the region toward the
end of the work week resulting in thunderstorm chances for at
least northwest Arizona and slight chances for southern Nevada.
Temperatures should also begin to slowly decline towards the end
of the week.
&&
.UPDATE...Isolated storms over Mohave, Lincoln, Esmeralda and
northern Inyo Counties all going to bed early this evening. We`ve
also been monitoring the Stewart Canyon Wildfire in south central
Lincoln County. Fire really got going late in day with an estimated
2000 acres burned.
HRRR and other convective allowing models look to be picking up on a
feature presently over southwest Arizona. As the feature lifts
northward tonight those models show light rain showers and
potentially embedded thunderstorms into southern Mohave County and
the lower Colorado River Valley. By late morning and tomorrow
afternoon it will be another day of isolated to scattered
thunderstorms over Inyo County, southern Nevada and northwest
Arizona. This looks to be well covered in our current forecast.
&&
.DISCUSSION...through Tuesday.
A slight chance of showers continues through the afternoon hours
across portions of Clark and Mohave counties, along the Sierra and
northern parts of Inyo County and across parts of south central
Nevada. A few embedded thunderstorm cells are possible as well
featuring brief rain and occasional lightning. The primary concern
however will be locally strong wind gusts near showers/storms.
Shower chances diminish rapidly this evening and should end by
sunset. Breezy winds 15-25 mph will push into the western portions
of the Mojave Desert late this afternoon into the evening. Shower
chances return Monday with hi-res guidance showing an uptick in
coverage and a few more robust cells. Again, locally strong wind
gusts will be the primary concern but with the potential for
embedded, potentially more robust thunderstorm cells, there could be
some areas that see brief heavy rain and occasional lightning. The
moisture profile is forecast to remain generally shallow in most
areas both Monday and Tuesday with a somewhat deeper moisture
profile forecast over Mohave County with a rise in PWATs and 850 mb
dewpoint temperatures. The activity forecast for Monday and Tuesday
is likely associated with a weak trough currently located along the
SoCal coast but forecast to move east and settle over the area on
Monday and Tuesday. Temperatures on Monday are expected to be 3-5
degrees above normal but only slightly above normal on Tuesday.
Wednesday and Thursday...A change in the weather pattern is
forecast when a weak low pressure system moves to the central
California coast. This low kicks the Mon/Tue trough east of the
area and the closed circulation associated with the low begins to
tap into deeper moisture over SW Arizona and draw it northward.
However, at the same time, shortwave ridging passes over the area
with elevated temps aloft possibly capping any convection early in
the day. Then, an increasing SW upper level flow associated with
the low is forecast to bring mid level drying in the afternoon.
Depending on how the pattern plays out, this could be a decent
setup for a more robust thunderstorm day on Thursday for Mohave
County and possibly parts of Clark County with a fairly deep
moisture profile along with modest instability and increasing
shear associated with the incoming low pressure system. Too early
to say for sure and confidence is low.
Friday through the weekend...currently looks like we will have
afternoon breezes each day with temperatures a few degrees below
normal. Looks like a down period for active weather as the deeper
monsoon moisture is forecast to be east of the area.
&&
.AVIATION...For McCarran...Isolated showers and storms should
diminish through the evening, with dry conditions anticipated
overnight. Sudden gusty winds from area storms are possible, with
gusts 35-40kts possible if any outflows get close enough to the
terminal. The risk for gusty outflows should end by 06Z, with dry
conditions and light south to southwest winds expected after that.
For Monday, a similar set up is expected to what we saw this
morning. There may be scattered precipitation around with isolated
thunderstorms, however there is low confidence that showers and
storms will impact or be in the vicinity of the terminals. If
convection is close by, more gusty winds are possible from outflow.
Outside of thunderstorm influence, light winds Monday more will
become east then southwest through the day but remaining less than
10kts.
For the rest of southern Nevada, northwest Arizona and southeast
California...Scattered showers and thunderstorms are expected nearby
BIH through the early evening, with vicinity storms potentially
causing sudden outflow winds from the northwest or west, gusting to
around 35kts. Elsewhere, isolated scattered precipitation with
isolated convection is possible through southern Nevada and western
Arizona, however activity should be waning. Outflows are possible in
this area but less likely. For tonight, any precipitation should end
around 03Z with typical drainage winds will returning through
tonight. For Monday, another round of isolated to scattered
precipitation is possible, including a few thunderstorms, with the
best chances in northern Inyo County. Winds will be light before
becoming south to southwest in the afternoon, with gusts to around
20kts possible in spots.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
UPDATE...Pierce
DISCUSSION...Salmen
AVIATION...Nickerson
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