Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/06/21
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
927 PM CDT Mon Jul 5 2021
.UPDATE...
Issued at 924 PM CDT Mon Jul 5 2021
Forecast appears to be in fine shape, with agreement from latest
HRRR model runs, so no major changes expected. Temperatures look
about right. Showers/thunderstorms should continue to move across
the CWA overnight as system aloft moves east/se over the region.
&&
.SHORT TERM...(This Evening through Tuesday Night)
Issued at 350 PM CDT Mon Jul 5 2021
Main challenges during the short term revolve around thunderstorm
activity, both ongoing and anticipated, in terms of severe potential
and QPF. The most intense thunderstorms this morning and afternoon
have been in the vicinity of a stationary front, across south
central South Dakota, where SBCAPE of around 3000 J/kg has combined
with just enough deep layer shear for some pulsing multicell storms.
Slow storm motions have led to locally heavy rain and potential
flooding as well. This activity is expected to track southeast into
areas of higher instability along the stationary front.
Stronger forcing in the form of a shortwave aloft and a trough of low
pressure at the surface is expected to trigger additional convection
beginning around 6pm along and west of the Missouri River. While
effective bulk shear will be in the 35 to 40kt range across north
central SD, instability may be a bit lacking given prior convection
(still have marginally steep mid-level lapse rates). A couple
stronger storms certainly have the potential for large hail and
damaging winds.
By tonight, a widespread area of showers and thunderstorms is
expected to track from west to east across the area. Southerly flow
will continue Mean PW values of 1.5 to 1.75in are in the 97.5 to
99.5 percentile for this time of year, which aids in confidence for
at least locally heavy rain potential. Ensemble guidance continues
to highlight the northern CWA as having the greatest potential for
the highest QPF, where over an inch could fall in some areas.
Further south, a quarter to half an inch of rain plus is more
likely. Precipitation will exit to the east of the forecast area
Tuesday afternoon, leaving much cooler temperatures in its wake with
highs in the low to mid 70s.
.LONG TERM...(Wednesday through Monday)
Issued at 350 PM CDT Mon Jul 5 2021
The main highlights in the out periods surround precipitation
chances mainly Thursday afternoon through Saturday, as well as
temperatures throughout the period.
The next low pressure system to potentially impact some of most of
the CWA is progged to enter the scene from the northwest, with a
notable surface low pressure reflection developing into Thursday
while low to mid-level waa is taking shape. When the main upper
level low pressure circulation works through the region Friday into
Saturday morning, additional lighter precipitation amounts will be
possible. Beyond that, much of the rest of Saturday through next
Monday should be dry while high pressure at the surface and aloft
take up residence across the region.
For much of the extended forecast period, the CWA should be
experiencing temperatures near normal for early July. Perhaps the
western third of the CWA (Missouri River valley westward) ends up
running above climo normal Wednesday, Thursday and early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
Issued at 619 PM CDT Mon Jul 5 2021
Terminals KABR,KATY,KPIR,KMBG
Coverage of showers and storms will gradually increase from west
to east this evening and overnight. After midnight, IFR cigs are
expected to develop across the area, and then linger through
Tuesday morning. Some improvement in cigs will come in the
afternoon.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...TDK
SHORT TERM...Lueck
LONG TERM...Dorn
AVIATION...TDK
Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
257 PM AKDT Mon Jul 5 2021
.SHORT TERM.../Through Wednesday night/...Most of the panhandle
enjoyed a nice sunny day today as the marine layer clouds
retreated a bit allowing Angoon, Hoonah, Gustavus, and Sitka to
get in on the sunshine. The only exception is Yakutat, which
remains in the marine layer with off and on drizzle and mist.
Typical afternoon breezes of around 15kt formed as expected
across the region, with Cross Sound a little stronger. Some folks
may have noticed that the blue skies aren`t 100% blue, with a
haze across the region. The HRRR Vertically Integrated Smoke
product shows some smoke advecting into the region from fire
activity in B.C. and Washington state. The smoke is high in the
atmosphere, so not expecting any health or visibility impacts at
the surface.
An area of vorticity near Hyder and the Misty Fjords is on track
to cross the border this evening. That combined with the heat of
the day (Stewart B.C. is 81 currently) means that the convective
potential is elevated in this area this evening. The 12z sounding
from Annette this morning does show an area of CAPE above 7000
feet that any thermals off the higher mountains of Misty Fjords
could tap into this afternoon. In light of this, the area of
showers and slight chance of Thunderstorms for this afternoon and
evening remains unchanged. Satellite has registered a few strikes
about 50 miles to the east of Hyder, so this forecast seems on
track.
Overnight tonight, the marine stratus layer and ares of drizzle
are expected to encroach into the inner channels again. The clouds
should reach as far east as Chatham Strait before retreating again
tomorrow. Any thundershowers that develop in the Hyder area are
expected to dissipate toward sunset.
Change starts to creep into the forecast for Tue night as the
surface ridge that has been keeping most of the rain well west of
the area starts to break down. Overall flow starts to become more
SW rather then the NW it has been and a weak front advances on the
northern gulf coast. Yakutat will see its drizzle become a chance
of rain as early as Tue afternoon with the northern panhandle
starting to see some chance of rain by Wednesday. The initial
feature is rather weak however so any rain the does fall is
expected to be rather light.
The forecast changes today included fine tuning the sky cover and
chance of thunderstorms in the Hyder area, matching the min/max
temperatures up with the cloud cover (or lack of) and updating the
drizzle and low stratus chances along the coast. Models are in
good agreement with the synoptic setup for throughout the short
term forecast period, but there are differences in the timing of
when and how much precipitation will fall after the ridge breaks
down.
.LONG TERM...Models are in good agreement for an upper-level low
that will support pushing moisture to Yakutat at the start of the
long term. The timing of this wave of precipitation is on track to
reach the northern half of the panhandle on Wednesday. Light
rainfall is expected at this time, with total amounts remaining
under a quarter of an inch. Confidence is increasing in the timing
and location of this band of precipitation.
A second band of precipitation Thursday looks like a repeat of
Wednesday, but is expected to reach the southern panhandle this
time around by late Thursday. The southern panhandle will likely
dry out quickly, but may see a slight chance of precipitation from
Friday to Saturday as onshore flow remains. The Climate
Prediction Center has near-normal temperatures and below-normal
precipitation in the southern panhandle and slightly below-normal
temperatures and near normal precipitation in the northern portion,
which matches what guidance is predicting.
For the extended long term grids starting on Saturday, nudged the
WPC towards the ECMWF to keep the chance/slight chance for
precipitation in the forecast due to the high uncertainty. The
next system in question is a surface low in the Gulf moving
towards the panhandle at the start of the week after next. Low
confidence in timing and the strength of the low.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...None.
MARINE...None.
&&
$$
BFL/KRT
Visit us at http://www.weather.gov/Juneau
AREA FORECAST DISCUSSION
National Weather Service Albany NY
1028 PM EDT Mon Jul 5 2021
.SYNOPSIS...
A warm and humid airmass will return for Tuesday and Wednesday.
Showers and thunderstorms will be likely at times, and some may
be strong in the afternoon and evening. It will not be as warm
Thursday with rain expected.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
.UPDATE...Area of convection has moved into the western part of
the St Lawrence River valley late this evening. The main cluster
of stronger storms has a bowing structure near the Jefferson/St
Lawrence border and has had a history of producing 30-45 mph
winds. It appears the apex of the bow will pass by to the north
of Herkimer County, but additional cells have developed farther
south along the outflow boundary and may move into the western
Adirondacks and western Mohawk Valley. SPC Mesoanalysis and 00Z
KALY sounding showing around 500-1000 J/Kg of MLCAPE in our
forecast area with fairly weak low level lapse rates, so expect
an eventual weakening trend. Increased POPs in these areas to
account for activity developing upstream. Brief wind gusts
around 30 mph and downpours/lightning will remain possible.
Chances for convection decrease for areas farther south/east,
but will still maintain slight chance if a few remnant showers
or storms last well into the overnight hours with favorable
environment aloft.
.PREVIOUS [0757]...Made just some minor adjustments based on
obs and trends this evening. Watching a cluster of convection
north of Lake Ontario moving eastward. This activity is
associated with a short wave trough tracking into the lower
Great Lakes. Best instability expected to remain to our west, so
activity should generally weaken as it approaches. However,
still expecting scattered showers and thunderstorms to move
across the western Adirondacks late this evening into the
overnight hours. Will continue to monitor this evening.
Upstream shortwave trough over Lake Superior is generating a
loosely organized area of convection over Lake Huron/Georgian
Bay. These storms are occurring within an area of steep midlevel
lapse rates (e.g., 7.7 K/km on the 12Z KAPX sounding) in a
pocket of 1.5-2.0 inch PWATs. This area of convection is
expected to continue moving eastward tonight, likely moving into
portions of the southern Adirondacks after midnight. There is a
chance a couple of these storms could be on the stronger side
as some of the steeper midlevel lapse rates fold into the area,
leading to around 1000 J/kg MUCAPE. Stronger storms could
contain hail, although fairly weak deep-layer shear of around 25
kt should limit the threat. An isolated gusty wind or two is
possible as well despite the storms likely remaining somewhat
elevated. Elsewhere, a moderate southerly wind will keep temps
considerably milder than previous nights, with lows mainly in
the 60s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Heat Advisory in effect for Mid-Hudson Valley 11 am to 7 pm
Tuesday...
An active weather period is in store in the short term with a few
rounds of convection possible along with heat concerns. Tuesday, a
few showers/storms may linger in the morning mainly north of I-90
associated with the midlevel impulse discussed in the near term
section. This activity is expected to weaken as the wave exits. Warm
advection overnight will have boosted 850 mb temps into the mid to
upper teens. Southern zones, more removed from the morning
clouds/showers and next round of convection, will likely be able to
mix to this level, supporting high temps in the low 90s. Dewpoints
may lower somewhat, but are likely to remain at least in the upper
60s, yielding heat index values of 95-100 over the Mid-Hudson
Valley, prompting a Heat Advisory. Southern Litchfield County will
be close to criteria Tue/Wed, but we opted not to include them in
collaboration with WFOs BOX/OKX.
Strong surface heating, moist low levels and respectable midlevel
lapse rates are expected to combine to result in SBCAPE of 1500-2500
J/kg roughly from the Mohawk Valley/Capital District/southern VT on
south during the afternoon. Point soundings off the HRRR and NAM3
indicate potential for DCAPE around 1000 J/kg as low levels steepen
as well. Also, despite deep layer shear being weak at around 20 kt,
there is a belt of 25-35 kt of 850-700 mb flow. These factors
suggest a damaging wind threat in any stronger updrafts. However,
both low and midlevel forcing are weak, and it is unclear how or if
morning activity will impact the convective environment in the
afternoon. CAMs show a variety of solutions with respect to how the
afternoon will play out, but current thinking is that storms may
form in the early afternoon along possible convergence due to an
outflow boundary from the morning convection or differential heating
boundary. Some CAMs suggest storms congealing into bowing segments
and pushing south into the better instability, although it is
unclear if this will occur in our area or to the south. Bottom line
is that there is enough evidence in a damaging wind threat to
upgrade the convective outlook to SLGT from the Mohawk
Valley/Capital District/southern VT on south in collaboration with
SPC and neighboring offices. Main threat period is 1-8 pm. Otherwise
it will be a bit breezy, very warm and humid with southwesterly
winds gusting to 25 mph at times.
Subsidence is expected to build in Tuesday night with zonal flow
overhead. Lows expected to be fairly mild mainly in the 60s.
Wednesday into Wednesday night, midlevel flow strengthens and backs
a bit in response to increased troughing in the Upper Midwest. Low
confidence with how this period will play out. It does look like
another hot and humid day from I-90 south, and additional Heat
Advisories are possible. The atmosphere will again become very
unstable from I-90 south. North of I-90 will be where the best
chance of precipitation will be in the morning hours along a fairly
tight low level baroclinic zone and beneath an equatorward entrance
region of the upper jet. High pressure to the north will allow
cooler air to filter in from the north, with the 12Z.05 NAM12 quite
aggressive with this scenario, dropping temps 10 degrees at ALB from
18-21Z. Think this is probably overdone, but highs north of I-90 are
expected to be cooler than Tuesday with lower humidity. Along and
south of I-90 in the unstable airmass, a convective trigger is a
question mark, but could be along the leading edge of the low-level
cooler air advancing from the N/NW. MRGL risk for severe in effect
which seems fine at this point until more certainty can be gained.
Wednesday night, PWATs increase ahead of the approaching midlevel
trough as 850 mb inflow increases modestly. Somewhat of an
overrunning signal as well, and will message scattered to numerous
showers and possibly an isolated thunderstorm. Lows expected to
range from the upper 50s to upper 60s.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
The main focus for the long term will be on the Thursday into Friday
time frame when moisture streaming northward from the Gulf of Mexico
and Tropical Cyclone Elsa could interact with an incoming trough and
jet streak to produce periods of widespread rainfall. Improving
conditions are expected over the weekend as the trough gradually
exits the region and high pressure builds overhead. However, yet
another warm front looks to return early next week increasing
chances for precipitation. Read on for details.
We begin the long term on Thursday with the latest guidance in good
agreement that a broad shortwave trough from the Midwest will be
heading eastward and southwesterly flow developing in response
downstream over the Northeast. During this period, Tropical Cyclone
Elsa, according to the latest National Hurricane Center forecast, is
expected to be tracking through or exiting off the coast of the
Southeast U.S. While the center of Elsa should still be far to our
south, the deep south-southwest synoptic flow could help advect
tropical moisture northward. Guidance also shows an anticyclonic
curved jet streak in place across southern Canada, placing the
Northeast in the right entrance. The combination of tropical
moisture in the presence of synoptic forcing has increased
confidence that periods of moderate to even heavy rainfall could
result Thursday into Thursday night. Therefore, we continue to show
likely and even categorical POPs throughout the region for this
period with some enhanced wording to highlight the potential for
heavy rain at times. Some hints of a PRE (Predecessor Rainfall
Event) are also in place but it is too early to make this
distinction at this lead time.
Favorable conditions for steady rainfall continue into Friday as our
broad trough will still be upstream over the Great Lakes/southern
Canada and Elsa, as per the latest NHC forecast, continues to track
near or just off the NJ/Long Island coast. Depending on how much the
incoming trough amplifies the downstream ridge over the western
Atlantic will determine if the trough will capture Elsa and steer it
closer to the coast or if Elsa will outrun it and escape out to sea.
The GFS is still the most progressive, suggesting Elsa is near Cape
Code and the islands by 12 UTC Friday while the CMC and ECMWF are
slower and only show it off the NJ coast at this time step. However,
all three pieces of guidance suggest Elsa will be close enough to
the coast that strong southerly flow will be able to advect tropical
moisture through at least parts of eastern NY and western New
England on Friday. In addition, a cold front will be gradually
pushing through the region at this time which could help focus the
rainfall where there is the best low level convergence.
By Saturday, Elsa should finally be out to sea, however, our broad
trough looks to be overhead. West to southwest winds in place could
still provide enough support for some diurnally driven showers and
storms. This is why we continue to carry slight chance and chance
POPs Saturday afternoon. Outside of any precipitation, temperatures
should be seasonable with dew points still a bit elevated making it
still feel a bit muggy.
Improving conditions finally arrive Sunday as high pressure looks to
build overhead and we lowered POPs compared to the blended guidance.
There is a warm front positioned to our south but recent trends keep
this boundary to our south until the new work week begins.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Mainly VFR conditions expected to prevail tonight, although a
brief period of MVFR cigs is possible at KPSF over the next 1-2
hours and overnight at KGFL. Otherwise, high and mid level
clouds will gradually increase ahead of a convective complex
approaching from just north of Lake Ontario. Showers and storms
will likely not hold together long enough to reach the TAF sites,
although a leftover shower may get close to KGFL/KALB so have
mentioned VCSH there.
Any BKN-OVC stratus clouds should dissipate to scattered
coverage during the morning, with some possible mid level
convective debris clouds around. The main concern for the
afternoon to early evening hours is the potential for strong to
severe thunderstorms. Since they are expected to occur during
the last 6 hours of the TAF period, will mention PROB30 for now
and can be refined in subsequent forecasts. Brief MVFR or even
IFR conditions will be possible with any TSRA, as well as
downpours and strong gusty winds.
Winds tonight will be southerly around 5-10 kt, becoming
southwest and increasing to 10-15 kt by early Tuesday afternoon
with occasional gusts of around 20-25 kt.
Outlook...
Tuesday Night: Low Operational Impact. Slight Chance of SHRA...TSRA.
Wednesday: Moderate Operational Impact. Chance of SHRA...TSRA.
Wednesday Night: Moderate Operational Impact. Likely SHRA...TSRA.
Thursday: High Operational Impact. Likely SHRA...TSRA.
Thursday Night: High Operational Impact. Likely SHRA...TSRA.
Friday: Moderate Operational Impact. Chance of SHRA...TSRA.
Friday Night: Low Operational Impact. Slight Chance of SHRA.
Saturday: Moderate Operational Impact. Chance of SHRA...TSRA.
&&
.FIRE WEATHER...
A very warm and humid airmass will be in place Tuesday and
Wednesday with minimum RH values mostly in the 50 to 60 percent
range. Scattered showers and thunderstorms are possible at times
through this period, although it will not be a washout. Breezy
southwesterly winds are likely on Tuesday. Rain will become more
widespread Thursday.
&&
.HYDROLOGY...
Scattered showers and thunderstorms are possible tonight through
Wednesday with typical summertime downpours possible and no
widespread hydro issues anticipated.
Rain is expected to be more widespread Thursday into Thursday
night as an approaching trough interacts with tropical moisture.
Urban and poor drainage flooding along with isolated flash
flooding will be possible. According to MMEFS data, main stem
river flooding is unlikely at this time, but this will continue
to be monitored.
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...Heat Advisory from 11 AM to 7 PM EDT Tuesday for NYZ059-060-
064-065.
MA...None.
VT...None.
&&
$$
SYNOPSIS...Thompson
NEAR TERM...Thompson/JPV
SHORT TERM...Thompson
LONG TERM...Speciale
AVIATION...JPV
FIRE WEATHER...Thompson
HYDROLOGY...Thompson
Area Forecast Discussion
National Weather Service Boston/Norton MA
952 PM EDT Mon Jul 5 2021
.SYNOPSIS...
A warm front moves through tonight followed by hot and humid
conditions Tuesday and Wednesday with scattered afternoon and
evening showers and thunderstorms. Some of the storms on Tuesday
will likely be strong to severe with damaging wind gusts and
torrential downpours. A cold front will stall south of Southern
New England Thursday and Friday with more showers and
thunderstorms, then Elsa or its remnants is expected to track
south of New England Thursday night into Friday. the front then
moves through late Friday or Saturday, then stalls to our south.
Expect scattered showers/thunderstorms to move along the front.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
950 pm Update...
Warmer and more humid tonight compared to previous nights, as
southerly flow advecting dew pts in the 60s across the region.
Given the increased moisture, be alert for areas of fog
overnight into early tomorrow morning. Scattered showers and
thunderstorms currently from just NW of Albany, to northern NY
state, is associated with mid level warm front. This shows up
nicely on SPC mesoanalysis with good thermal packing at 850 mb
and tight PWAT gradient across New England into NY. A few of
these showers/T-storms may enter our region overnight,
especially across northern MA. Previous forecast captures this
nicely, thus no major changes with this update.
Previous Discussion...
High pressure will continue to move east and further away from
the region tonight. The result will be a moist southerly low
level flow of air along with a scattered to broken deck of
clouds. Dewpoints of 60+ will result in milder temperatures than
the last few nights. Overnight low temps will bottom out mainly
in the middle/upper 60s.
While there is a modest LLJ that develops overnight it will be
somewhat veered out. This coupled with a shortwave and its
associated forcing passing well to our north should result in dry
weather dominating overnight. That being said there is some modest
elevated instability and a few brief showers along with the low risk
for an isolated t-storm or two is possible. Opted to cover this with
just low pops in the grids for now.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Highlights...
* Scattered strong-severe thunderstorms between 1 & 8 PM Tuesday
* Strong to damaging wind gusts are the main risk
* Brief torrential rain/localized street flooding a secondary concern
Tuesday...
1) Heat & Humidity:
A return to very warm/hot & humid weather arrives on Tuesday.
Southwest flow around a ridge of high pressure will result in 850T
climbing to around +18C. This coupled with good mixing should yield
afternoon high temperatures in the upper 80s and lower 90s, except
upper 70s to the middle 80s along the immediate south coast, Cape &
Islands. Dewpoints near 70 will result in Heat Indices in the middle
to upper 90s in many areas away from the south coast. Later shifts
will have to consider Heat Advisories given the potential for these
values to be reached again on Wed. The one thing that will take a
little bit of an edge off the humidity om Tuesday will be gusty SW
winds. Bufkit shows excellent mixing with southwest wind gusts of 20
to 30 mph and perhaps near 35 towards the southeast New England
coast and the typical spots near Falmouth.
2) Severe Weather:
The main concern will revolve around the likelihood of scattered
strong to severe thunderstorms; roughly between 1 and 8 PM on
Tuesday. This a result of an approaching shortwave in westerly flow
aloft. Given heat & humidity; the SPC SREF indicates modest
probabilities of MLCapes exceeding 2000 J/KG across a good portion
of the region. Guidance is also forecasting steep low level lapse
rates with a ribbon of 30-40 knots of flow in the 850-700 mb layer.
The one limiting factor is weaker winds in the 500-600 mb layer,
which keeps effective shear values lower than we normally want to
see for a severe weather event. That being said, high resolution CAM
simulations are pretty aggressive with impressive 2-5 KM updraft
helicity swaths depicted by the 3 KM NAM and even the 18z HRRR to
some extent. The 4 hour max updraft product is lit up quite a bit on
the HREF too across southern New England.
So in a nutshell, scattered strong to severe thunderstorms are
expected to sweep across the region from northwest to southeast
between 1 and 8 pm Tuesday. Steep low level lapse rates along with
modest DCape values > 800 J/KG suggest strong to damaging wind gusts
are the main threat with this activity. While storms will be moving,
PWATs near 2 inches also support brief torrential rain/localized
street flooding particularly if activity moves across urban centers.
Lastly, we can not rule out an isolated large hail report or two
given even modest steep ML Lapse rates. We opted to included
enhanced wording in the forecast.
Tuesday night...
Lingering convection should come to an end by early-mid evening even
along the south coast. Otherwise, dry and somewhat muggy weather is
expected Tuesday night with low temperatures only dropping into the
upper 60s and the lower 70s.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Big Picture...
Zonal flow across the Northern USA while a 594-Dm upper ridge sits
over the Desert Southwest. One shortwave in the zonal flow moves
east over New England Thursday night/Friday, turning our upper flow
more from the southwest. This may also affect the track of Tropical
Storm Elsa as it passes offshore. After the shortwave moves past,
the flow briefly turns from the northwest. West Atlantic upper ridge
then builds over Srn New England Sunday and Monday.
Contour heights at 500-mb are approaching their climatological max
values, in the upper 570s Dm to low 580s Dm. Values are forecast to
remain in that range Wednesday through Saturday, then increase to
around 590 Dm by Monday. Expect seasonably warm temps during the
week, except closer to the average as the trough and Elsa move past.
Relatively good agreement in the mass fields through Saturday. Even
after that, fair agreement on Sunday and Monday, including an
approaching weather system later next Monday. Overall confidence is
moderate-high, except just moderate for Sunday and Monday.
Details...
Wednesday...
Offshore high pressure continues to bring very warm humid air into
SRn New England. The airmass remains quite unstable with CAPE of
around 1500 J/Kg and LI values of minus 3 to minus 5. PW values of
1.5 to 1.8 inches. Expect scattered showers/thunder, some with local
downpours. Dew points will be upper 60s and lower 70s, so expect
high to oppressive humidity. The mixed layer reaches to near 800-mb,
with temps of 14C at that level, equiv to 19C at 850-mb. Expect max
temps of 90 to 94, cooler South Coast.
Based on the temperature and dew point, expect Heat Index values 90
to 95 most places, but potentially 94 to 98 in CT and parts of RI.
Will hold back on a Heat Advisory for now, but will be monitoring.
Thursday-Friday...
Tropical air remains in place as the approaching shortwave turns the
upper flow from the southwest. Cold front stalls north and west of
Srn New England, but is close enough that it could generate a few
thunderstorms, especially in Nrn Mass. A few local downpours are
possible due to the tropical air.
Meanwhile, Tropical Storm Elsa or its remnants will move up the East
Coast, but looks to pass well offshore of Srn New England Thursday
night..and even southeast of the 40/70 benchmark. This path, and
geographical suggestions that it will be starting a mid-latitude
transition, point to winds mostly on the southeast side of the
system while heavy rain will be mostly on the northwest
side...catching Srn New England. Expect local downpours Thursday
night and Friday morning.
The weekend and Monday...
The stalled cold front moves south through Srn New England and then
stalls again, this time offshore. Upper ridge from the ocean will
maintain little push to move the front onward. Jet segments moving
through the upper flow may generate showers of and on through the
period. Temperatures will remain warm in the 80s. Dew points will
drop back a little, but values will remain in the 60s so expect the
humidity to remain noticeable.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
02z update...
Showers and T-storms currently across NY state will mainly
track across central and northern NY overnight, weakening with
time as well. Some of the activity may track as far south as
northern MA. This is consistent with previous forecast, so no
major changes with this forecast update. Earlier discussion
below.
=================================================================
Tonight...Moderate Confidence.
VFR conditions likely dominate. There is a chance for a period
of MVFR ceilings, especially eastern New England. But areal
coverage and duration of any low clouds remains uncertain.
A few brief showers with the low risk for a rumble of thunder
are possible, but mostly this will be north of Massachusetts. The
vast majority of the night will feature dry weather and VFR.
South to Southwest winds 5 to 10 knots, but may become a bit
stronger after midnight in the high terrain and southeast New
England coast.
Tuesday...High Confidence. Mainly VFR conditions in the morning.
Scattered strong-severe thunderstorms are expected to sweep across
the region from northwest to southeast...roughly from 17z through
00z. Localized brief strong wind gusts and torrential rainfall may
result in a short period of IFR-LIFR conditions at some terminals.
Otherwise, VFR conditions dominate during the afternoon but with SW
wind gusts of 20 to 30 knots developing. The strongest of those wind
gusts will be across southeast New England.
Tuesday night...High Confidence. Any lingering showers/t-storms
will depart the south coast by early-mid evening. Otherwise,
mainly VFR conditions with WSW wind gusts generally less than 10
knots except a bit stronger across the Cape/Islands.
KBOS TAF...High Confidence in TAF. Biggest concern is a cluster of
strong-severe thunderstorms in the vicinity of and/or crossing the
terminal between 18z and 22z on Tuesday.
KBDL TAF...High Confidence in TAF. Biggest concern is a cluster of
strong-severe thunderstorms in the vicinity of and/or crossing the
terminal between 18z and 22z on Tuesday.
Outlook /Wednesday through Saturday/...
Wednesday: VFR with local MVFR. Chance SHRA, isolated TSRA.
Local downpours.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, isolated TSRA.
Thursday: Mainly VFR, with areas MVFR possible. SHRA.
Thursday Night: Mainly VFR, with areas IFR possible. SHRA
likely.
Friday: Mainly VFR, with local IFR possible. Chance SHRA.
Friday Night through Saturday: Mainly VFR, with local MVFR
possible. Chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High Confidence. High pressure moving east of the
waters will generate SW winds of 10 to 15 knots tonight. We may
see some 20-25 knot gust develop toward daybreak along with
some marginal 5 foot seas across our southern waters. Overall
though expect winds and seas to generally remain below small
craft thresholds tonight.
Tuesday...High Confidence. A modest low level jet coupled with
excellent mixing over the land will generate SW wind gusts of 20 to
30 knots developing Tue morning and continuing through the
afternoon. The strongest of the winds will be near shore and
especially towards the southeast New England where some marginal
near shore Gale force gusts can not be ruled out for Buzzards Bay
and Nantucket sound areas. Regardless, small craft headlines are
posted for all waters and mariners should expect gusty SW winds and
choppy seas.
Also, scattered strong thunderstorms during the mid-late afternoon
and early evening hours may impact the waters. Frequent lightning
and strong winds may impact pose a risk to those on the waters as
well...especially across our near shore waters north of the Plymouth
area.
Tuesday night...High Confidence. Any remaining convection should
dissipate/weaken across the southern waters by mid-evening. Small
craft wind gusts should also diminish, but lingering 4-6 foot seas
may persist across our southern outer-waters.
Outlook /Wednesday through Saturday/...
Wednesday: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.
Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.
Thursday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.
Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Rain
showers.
Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers.
Friday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers.
Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert from 11 AM to 11 PM EDT Tuesday for
CTZ002>004.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 AM to 8 PM EDT Tuesday for
ANZ230>237-251.
Small Craft Advisory from 5 AM Tuesday to midnight EDT Tuesday
night for ANZ250.
Small Craft Advisory from 5 AM Tuesday to 8 AM EDT Wednesday
for ANZ254>256.
&&
$$
SYNOPSIS...WTB/Frank
NEAR TERM...WTB/Frank/Nocera
SHORT TERM...Frank
LONG TERM...WTB
AVIATION...WTB/Frank/Nocera
MARINE...WTB/Frank
Area Forecast Discussion
National Weather Service Burlington VT
1012 PM EDT Mon Jul 5 2021
.SYNOPSIS...
A warm front will produce scattered showers with a few embedded
thunderstorms overnight across northern New York with the activity
decreasing in areal coverage over Vermont by Tuesday morning. A
warmer night with some patchy fog is possible in eastern Vermont, as
temperature cool into the upper 50s to upper 60s. After a few
lingering morning showers, intervals of sunshine will develop as
temperatures warm back into the 80s. A few additional showers and
storms are possible on Tuesday afternoon. Forecast continues to
support a widespread rain event on Thursday into Friday.
&&
.NEAR TERM /THROUGH TUESDAY NIGHT/...
As of 1002 PM EDT Monday...Watching closely a cluster of
showers/tstorms over Saint Lawrence County. KTYX sampling
inbound winds 45+ knots at around 5000 ft just to the south of
Saint Lawrence County, however RAP soundings indicating
inversion below 3000 ft preventing the momentum aloft from
reaching the surface. Thus, still thinking severe threat remains
minimal...though some gusts up to around 30 knots and some pea
sized hail are possible within the cluster. Complex will
continue to weaken as it progresses eastward and instability
continues to wane. Previous discussion follows.
Fcst focus overnight wl be potential for convection acrs
northern NY into VT, along with impacts clouds/winds have on
temps. Water vapor/satellite and radar show complex showers with
thunderstorms over the northern-central Great Lakes. This
activity is progged to angle east-southeast toward northern NY
btwn 03z-06z and into the CPV after 06z. Still some question
about how well complex holds together acrs VT, so have continued
with likely pops northern NY, tapering off to chc pops in VT.
Have noted SPC place SLV into marginal risk overnight for svr.
Feel the risk for severe is very low, but not zero, given axis
of elevated CAPE of 700 to 1000 J/kg with 0 to 6 km shear of 25
to 30 knots, associated with developing 850mb to 700mb jet of 35
to 45 knots. Best potential for a stronger storm, which may
require an spc would be over the SLV btwn 04z-07z tonight. The
instability/shear and dynamics for weakening s/w is less acrs
VT, so mainly anticipating showers with an embedded rumbles of
thunder. Have noted soundings at VSF showing a shallow/sharp
llvl thermal inversion developing below 925mb this evening, with
nearly saturated bl conditions, supporting the idea of patchy
fog btwn 03-09z, before high clouds and winds increase toward
sunrise. Have patchy fog in the CT and Passumpsic Valleys. Sfc
dwpts already in the lower 60s SLV and southwest winds,
expecting lows near 70F SLV/CPV with coolest values in the
mid/upper 50s acrs eastern VT, including the NEK.
Tuesday best short wave and axis of better 850 to 700mb moisture is
east-southeast of cwa by 15z, resulting in large scale
subsidence/drying aloft. Soundings show a very deep dry layer btwn
850-500mb developing, with some mixing of drier air toward the sfc,
lowering dwpts back into the 60s. Many of the CAM models show
favorable sfc based cape profiles in the 1800 to 2400 j/kg range,
while axis of best 0 to 6 km shear of 25 to 35 knts is either
displayed to our north our southeast. Furthermore, sfc convergence
with boundary is minimal, so general idea of decreasing pops into
the 15 to 25% range on Tues aftn looks good. Tuesday wl not be a
washout with very limited areal coverage of showers/storms expected.
Given instability cannot completely rule out a stronger storms, but
with minimal upstairs support probability is low.Temps wl warm back
into the upper 70s to mid/upper 80s. A spot 90F is possible with
better mixing profiles in the aftn here at BTV. Tues night wl be
quiet with any showers/storm dissipating by sunset. Lows generally
in the mid 50s to lower 60s.
&&
.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
As of 316 PM EDT Monday...Main focus on Wednesday will be on a
shallow W-E oriented cold front that is expected to bisect the North
Country throughout the daylight hours. Light north to northeast
surface winds and abundant low clouds are expected across the
northern half of the forecast area, yielding well-below normal
daytime high temperatures - only in the mid-upper 60s near the
International Border, and only in the lower 70s across most of
the Champlain Valley. May see a few showers within the frontal
zone, but overall forcing is limited for much rainfall. Limited
QPF to 0.05" or less across northern areas on Wednesday.
Meanwhile, appears portions of s-central VT will remain south of
the cold front, with partly sunny conditions and better surface
heating. Should see south-central VT valleys warming into the
upper 70s to lower 80s based on present indications. Given
frontal location and strong differential heating, can`t rule out
isold thunderstorm development across Rutland/Windsor counties
Wednesday afternoon. Best instability mainly expected to remain
south of our forecast area. As such, not expecting much of a
severe tstm threat attm.
Should see mostly cloudy and cool conditions continue into Wednesday
night as sfc frontal zone shifts southward and stalls across e-
central NY into central New England. Lows generally expected in the
50s areawide. Winds above the shallow frontal zone, in the 950-800mb
layer, begin to veer south to southeasterly toward daybreak
Thursday, and may begin to generate a few showers toward
sunrise with isentropic ascent across the frontal sfc. The
majority of the rainfall is expected to hold off until the
daylight hours Thursday, but there is an increase to 30-50%
PoPs, especially southern areas, after 09Z Thursday.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 316 PM EDT Monday...A widespread rainfall is still expected
Thursday into Thursday night, with rainfall amounts perhaps
exceeding 1" across portions of the Adirondacks and central/srn VT.
Per NHC guidance, as Elsa tracks newd across the southeastern
US and Mid-Atlantic coast, the global NWP guidance is consistent
in showing aspects of a Predecessor Rain Event (PRE) well
removed and to the NW from the tropical system. Our rainfall
will be driven by right entrance region of a strong 250mb jet
juxtaposed with the lingering low-level frontal zone and a
850-700mb deformation zone that is forecast to intensity during
the daytime hrs. Both the 12Z GFS and NAM indicate elevated
instability in the frontal zone, so may see some embedded
convective elements within larger swath of precipitation
expected across nrn NY and VT. In additional to 80-90% PoPs,
included chance of thunderstorms for Thursday afternoon into
Thursday evening given CAPE for parcels rooted near 850mb.
Mesoscale details aren`t clear yet, but appears enough
ingredients in place for an axis of rainfall amounts 1-1.5"
across portions of the CWA. Overall, a much needed rainfall
given antecedent conditions, and don`t foresee any flooding
threat attm with generally light to moderate rainfall rates.
We`ll monitor for any locally heavier rainfall rates in
aforementioned convective elements, but with 6-hr flash flood
guidance expected in the 2.5-3" range, will take a lot to yield
any flood threat. High temperatures on Thursday generally
expected in the upper 60s to lower 70s, with lows Thursday night
55-60F. Best large-scale forcing shifts to our east Friday
morning, with decreasing chances for showers through the day,
and partial clearing expected from west to east. Should see mid-
late afternoon high temperatures in the mid-upper 70s.
Should see near normal mid-July temperatures for the weekend
into early next week. Weak surface high pressure generally in
place, but with modest mid-level trough across sern Ontario into
northern New England, did maintain roughly 30-40% PoPs for
possible shower activity - especially afternoon periods -
Saturday through Monday.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Through 00Z Wednesday...Widespread VFR conditions to start the
TAF period will deteriorate through the evening/night as an
approaching shortwave spreads mid and low-level clouds through
the area along with some rain/tstorms. As of 00Z, the
rain/tstorms are just approaching northern NY from the west,
poised to move through the Saint Lawrence Valley between 00Z and
04Z, and through the northern Adirondacks between 02Z and 06Z.
The storms will generally weaken through the night as they
progress eastward into Vermont. Not expecting any severe weather
associated with the storms, but they may contain some gusty
winds and lightning, especially at KMSS and KSLK. Have not
specifically included mention of TS in TAFs due to weakening
nature of the system, but will be watching closely and amend if
needed. A period of MVFR ceilings/visibilities is expected
overnight at most TAF sites as the precipitation moves through.
Conditions will trend towards VFR after 15Z behind the departing
shortwave.
Winds will be from the south/southwest overnight with some
gusts 15 to 20 knots possible. In addition some low level wind
shear is expected overnight as a 35 to 45 knot low level jet
develops. During the day Tuesday, winds will be from the
southwest/west with gusts to 20 knots.
Outlook...
Tuesday: VFR. Chance SHRA, Chance TSRA.
Tuesday Night: VFR. Slight chance SHRA.
Wednesday: VFR. Chance SHRA.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, Slight chance TSRA.
Thursday: Mainly VFR, with areas MVFR possible. Chance SHRA,
Slight chance TSRA.
Thursday Night: Mainly IFR, with local MVFR possible. Likely
SHRA, Slight chance TSRA.
Friday: Mainly MVFR, with areas IFR possible. Chance SHRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Taber
NEAR TERM...Duell/Taber
SHORT TERM...Banacos
LONG TERM...Banacos
AVIATION...Duell
Area Forecast Discussion
National Weather Service Caribou ME
1132 PM EDT Mon Jul 5 2021
.SYNOPSIS...
High pressure will crest south of the region this evening. A
warm front will approach tonight and lift north through the area
Tuesday. A cold front will cross the area early Wednesday then
stall offshore on Thursday while low pressure approaches. Low
pressure will pass south of the area Friday and pull away from
the region Saturday.
&&
.NEAR TERM /THROUGH TUESDAY/...
11:30 PM Update: Sky remains mostly clear except for some low
clouds/fog moving in near the coast. Adjusted temps over western
areas where the valleys have cooled into the upper 50s.
Otherwise, no major changes this hour.
Previous discussion:
Clear skies this evening as high pres ridge moves across the region
w/winds becoming light. As this ridge shifts to the east, S winds
will set up later tonight w/increasing dewpoints and llvl moisture.
Mdl soundings from the NAM, RAP and GFS show llvl moisture being
trapped under an inversion below 1500`, which could allow for some
low clouds and fog to develop. Some of the CAM guidance such as the
NAMNEST support this set up. Therefore, decided to show low clouds
moving from from s to n w/fog development expected as far Caribou
and Presque Isle. The Bangor and Downeast region could see some
dense fog setting up w/vsbys dropping below 1 mile by early Tuesday
morning. This region did get heavy rainfall and w/clear skies and
light wind, and also some cooling, fog a good bet. Attm, did not
have the confidence to go w/any Dense Fog Advisory. The evening crew
can assess this potential further when the updated guidance arrives.
For Tuesday, low clouds and fog should lift and burn off w/some
sunshine available for heating and the destabilization of the
atmosphere by late morning, especially across the Maine Central
Highlands. Temps across the CWA by early afternoon will reach
into upper 70s to lower 80s. GFS and NAM/NAMNEST show CAPE
potential of 800-1200 joules in the aforementioned area w/some
decent shear of around 30 kts at 0-6km to allow some convection.
Mid level lapse rates of 6.5 c/km progged to set up by early
afternoon to allow for good updrafts and potential for organized
convection. Given the shear and some divergence aloft, thinking
that some stronger wind gusts are possible, again mainly for the
Maine Central Highlands and the Bangor region and interior
Downeast. PWs are forecast to be in the 1.5 to 1.8 inch range
leading w/a warm cloud up through 11k and dewpoints in the
mid/upper 60s for heavy rain. Coordinated w/GYX to include heavy
rainfall and gusty winds in the forecast. Further n of the
Millinocket-Lincoln region, lapse rates were not impressive at
all w/values < 6.0c/km keeps updrafts to a minimum. Therefore,
just went w/general tstms and no enhanced wording. The later
shifts can assess this potential and make adjustments as needed.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
The cold front will gradually cross the area overnight. Some
thunderstorms are possible before midnight ahead of the front
and maintained mention of a slight chance. The cold front looks
stronger than it did in the charts a day ago and have lowered
low temps to the lower 50s in the Saint John Valley and mid 60s
for Bangor and Downeast. It will still be a humid night for
Bangor and Downeast with dew points also in the mid 60s and not
falling until Wednesday morning. Steadily drier air filters in
Wednesday and have reduced highs to the upper 60s to around 70F
in northern Aroostook County to around 80F for Bangor and the
coast. The coast will be the warm spot in the forecast area
with the offshore flow. The biggest challenge for later
Wednesday into early Thursday will be whether a wave of low
pressure can maintain itself as it moves from the Great Lakes
region towards Maine along the stalled frontal boundary. Most
model guidance has backed off PoPs on this feature compared to
yesterday...except ECMWF. This is mostly due to the expectation
that the cold front is stronger and pushes further south than
yesterday`s expectation. The wave then tends to fizzle out as it
moves into dry air and the only affect is high clouds rather
than precipitation. Based on that scenario, reduced PoPs and
clouds in the forecast for later Wednesday into early Thursday.
The stalled front will lift northward as a warm front on
Thursday with thickening clouds and steadily increasing PoPs
through the day. The cooler air behind Tuesday night`s cold
front will be entrenched in the area by Thursday with highs only
reaching the upper 60s.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Heavy rainfall is possible Thursday night into Friday night as
low pressure from the Great Lakes region moves northeastward
along the stalled frontal boundary. The associated upper level
shortwave will amplify and help pull in the remnants of Tropical
Storm Elsa northward towards eastern Maine. With deep moisture,
elevated instability and PWs over 1.75 inches, it`s certainly
possible most of the area could see an inch or two of rainfall
or more. The low pressure system will exit later Friday night.
Drier and seasonable cool air is expected for next weekend and
into Monday as cool Canadian high pressure builds. A blend of
models leads to increasing PoPs again by later Monday into
Monday night.
&&
.AVIATION /04Z TUESDAY THROUGH SATURDAY/...
NEAR TERM: VFR late this evening. Conditions will likely lower
to IFR from KHUL south overnight into Tuesday morning in lower
clouds and fog. Conditions should improve from north to south
late morning and into the afternoon. VFR at the terminals from
KPQI to KFVE with the outside chance of a little late night fog
that could briefly lower conditions. Isolated to scattered
thunderstorms Tue PM with brief IFR/MVFR. Light SW winds 10 kts
or less becoming S. Strong and erratic wind gusts possible
in/near any thunderstorms Tue PM.
SHORT TERM:
Tuesday night...Fog may be an issue for BHB...and more likely
towards Eastport, Machias and Princeton. Otherwise VFR
conditions are expected with a slight chance of a thunderstorm
Tuesday evening.
Wednesday into Thursday...VFR with just a small chance of a
brief period of MVFR cigs north of HUL on Wednesday morning.
Thursday night into Friday night...IFR cigs and tempo IFR vis in
heavy rain. Embedded thunderstorms possible.
Saturday...VFR outside of a chance of MVFR cigs north of HUL in
the morning.
&&
.MARINE...
NEAR TERM: No headlines expected through Tue. SW winds 10 kt
increasing to 10-15 kt from the S on Tue. Gusts to 20 kts are
expected. Seas 3-4 ft gradually building to 4-5 ft Tue
afternoon. Highest seas over the outer zones. Areas of fog
through the day lowering vsbys to < 1 NM.
SHORT TERM: No advisories are anticipated. Did adjust winds and
seas down for Tuesday night due to stability. Fog remains the
big concern Tuesday night into early Wednesday morning before
the front pushes it out. The next round of fog appears likely
Thursday night into Saturday morning. Have started with mention
of patchy fog, but with the very humid remnants of TS Elsa, it
could end up being dense on Friday. Elsa could also bring high
surf and heavy rainfall Friday.
&&
.CAR WATCHES/WARNINGS/ADVISORIES...
ME...None.
MARINE...None.
&&
$$
Near Term...CB/Hewitt
Short Term...MCW
Long Term...MCW
Aviation...CB/Hewitt/MCW
Marine...CB/Hewitt/MCW
Area Forecast Discussion
National Weather Service Corpus Christi TX
642 PM CDT Mon Jul 5 2021
.AVIATION...
Latest radar shows storms north and west of COT moving toward COT.
Weak showers are also present across the eastern TAF sites. Weak
isolated showers are expected to continue through early evening
across VCT, ALI and CRP TAF sites, while sct thunderstorms
continue across LRD and COT. Convection is expected to wane by
late evening for a few hours, then increase to numerous once again
overnight into Tue morning. Models indicate that rain chances
will decrease across the northern areas by Tuesday afternoon, but
remain numerous across LRD, ALI and CRP TAF sites into Tue
evening. A mix of VFR and MVFR conditions will prevail tonight
through Tuesday with periods of LIFR/IFR due to convection.
&&
.PREV DISCUSSION... /Issued 348 PM CDT Mon Jul 5 2021/
SHORT TERM (Tonight through Tuesday Night)...
Surface analysis at 3 PM consisted of a broad, circular outflow
boundary expanding west into the Brush Country and north into the
Victoria Crossroads, with generally light SE winds and quiescent
conditions elsewhere. Convergence along the outflow should be
greatest on its northern end for the next hour or two where the
greatest PoPs remain focused, while much of the Coastal Bend
remains more stable behind the outflow.
A bit of a wild card exists this evening and early tonight across
our western zones as storms currently over the Edwards Plateau
continue trekking south in weak NW flow. Most models (including
the HREF and TTU WRF) dissipate and shift this activity west of
Cotulla and Laredo overnight, but the most recent HRRR has trended
farther east which seems plausible. Opted to show 40-50% PoPs in
our western counties tonight; however, certainty increases toward
daybreak as we expect at least two larger clusters of convection
to evolve - one over the western Brush Country tied to an
approaching MCV, and the other near the Upper Coastal Bend
courtesy of enhanced speed convergence along the coast. This
latter area is favored by most CAMs to dominate the scope of our
CWA by midday as outflows congeal and potentially lead to a
diffuse MCS that drifts south. With PWATs around 2.4", weak
steering flow, and deep warm layer rain processes, the stage is
clearly primed for some heavy rain. Opted to hold off on flood
headlines given rather high flash flood guidance values of 2-4",
although localized flooding is likely at some point during the
day tomorrow. By late Tue afternoon, conditions look to be too
worked over/stabilized in the wake of these storms and this should
extend into the first half of the night before another round of
coastal speed convergence yields late night/early morning
convection near the coast.
NBM`s high temps for Tuesday look too warm for the degree of
thicker clouds and widespread precip, so nudged temps lower and
more in tune with the CONSSHORT output.
LONG TERM (Wednesday through Monday)...
Significant moisture remains in place across South Texas with PWATs
ranging from 2.0-2.5" through Friday before decreasing to near 2.0"
this weekend into early next week. Low to mid level support seems to
be the most driving factor for convective development compared to a
potential limiting upper level setting. At 250mb, the GFS has high
pressure over the Gulf of Mexico push further inland over the
Coastal Plains, inducing ridging by separating troughs from Mexico
and the AR/LA/TX border. However, there are model disagreements as
the ECMWF and CMC deepen the trough over South Texas keeping the
high pressure well east over the Gulf. The latter would lead to an
environment more favorable for convective development through upper
level divergence. Models are in fair agreement with a mid level
trough axis spanning from Deep South Texas into South Texas
Wednesday through Thursday night. In addition, cyclonic flow will
also be present down to the surface with speed convergence evident
and greatest along the coast.
Considering all the above, scattered to numerous showers and
thunderstorms are expected Wednesday through Thursday night, then
decrease to scattered on Friday as ridging approaches from the east.
Heavy rainfall and localized flash flooding will also be possible
through this time period as moisture remains near or above the 99th
percentile, CAPE generally less than 1500 J/kg, and cloud layer mean
wind remains slow at less than 15 knots. The WPC has all of South
Texas in a marginal risk of excessive rainfall on Wednesday.
Therefore, have included heavy rain for Wednesday through Thursday
when conditions are most favorable. Storm total QPF through Friday
ranges from 2 to 6 inches with locally higher possible. Expect the
greatest coverage and rainfall over the waters, Coastal Bend, and
Victoria Crossroads.
High pressure from the Gulf begins to push westward into South Texas
heading into the weekend, with the trough or developing closed mid-
level low (ECMWF hinting) over northeast Mexico, west of the CWA,
persisting into early next week. This push will likely focus rain
chances to this mid-level disturbance, outside of the CWA, as
ridging builds over South Texas. The GFS sticks out as an outlier
this weekend as it keeps the high pressure over the north Gulf of
Mexico with the mid-level trough draped over South Texas. Due to the
close proximity of the disturbance, uncertainty, and high PWAT
values above the 75th percentile, kept 20-40% PoPs for diurnally
driven showers and thunderstorms Friday night through Monday.
Tropical Storm Elsa may increase wave heights to near 7 feet and
swell periods to 6-8 seconds Thursday into Saturday. This increase
in swells with P-ETSS guidance indicating tide levels near 1.5 ft
above MSL, could cause waters to reach the dunes as well as an
increase in rip currents. High temperatures will remain below
normal, ranging from the mid to upper 80s through Friday before
gradually increasing through the weekend. Lows remain in the mid to
upper 70s.
MARINE...
Light to moderate onshore flow continues tonight through Tuesday
night. Scattered showers and thunderstorms this evening should
expand and become numerous during the pre-dawn hours on Tuesday
and continue through much of the day, before diminishing in
coverage Tuesday night. Weak to moderate onshore flow will
continue through Thursday before strengthening to moderate
Thursday night through the weekend. Swells from Tropical Storm
Elsa will likely move into the region and increase wave heights
Thursday through Saturday. This may lead to periods of Small Craft
Advisory conditions at times, particularly over the offshore
waters. Numerous showers and thunderstorms Wednesday through
Thursday, will decrease to scattered Thursday night. Rain chances
will decrease to 20 to 40 percent Friday into early next week as
an upper level ridge builds west into the region.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 77 84 74 85 75 / 50 90 80 80 70
Victoria 75 85 74 84 74 / 70 80 80 80 60
Laredo 77 86 75 87 74 / 70 80 70 70 50
Alice 75 84 73 85 73 / 50 90 80 80 60
Rockport 77 83 76 86 77 / 70 90 80 80 70
Cotulla 76 88 74 88 75 / 70 70 70 70 50
Kingsville 76 85 74 85 74 / 50 90 80 80 70
Navy Corpus 78 83 77 86 78 / 60 90 80 80 70
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
TE/81...AVIATION
Area Forecast Discussion
National Weather Service Cheyenne WY
530 PM MDT Mon Jul 5 2021
.SHORT TERM...(This evening through Thursday)
Issued at 200 PM MDT Mon Jul 5 2021
Leeside low east of the Laramie Range this afternoon. Southerly
winds east of the low with dewpoints in the mid 50s to 61 at
Torrington east of the Laramie Range. West of the Laramie
Range...winds out of the north and 1PM dewpoints in the mid 40s.
MUCAPE of 1000 to 2000 J/KG east of the Laramie Range. Starting to
see convection developing along the Laramie Range and out across
Albany County. To our north...a cold front is being analyzed
across southern Montana near the Wyoming state line.
Latest HRRR guidance showing showers and storms increasing in
coverage by mid afternoon west of the Laramie Range and along the
Laramie Range. Storm motions less than 10kts for the remainder of
the afternoon...so we need to be watching for flash flooding. WPC
does have a Marginal Risk for Flash Flooding across much of our
CWA this afternoon.
Shear begins to increase after 00Z that will help with the flash
flood threat...but then we will be dealing with severe
thunderstorms with the additional shear. Surface based CAPE of
2000-2500 J/KG across the northern Nebraska Panhandle...west to
Lusk this evening. Would anticipate a busy evening for the evening
folks.
Upper shortwave associated with the surface front very slow to
move through tonight. Looks to be near the northern Panhandle by
12Z Tuesday. SREF QPF coming more in line with the ECMWF in
holding QPF across our southeastern zones through Tuesday
afternoon. Will continue to keep chance PoPs going for that time.
Warming and drying for Wednesday with the departure of that
shortwave. High pressure builds back into the area with warmer
temperatures and increased concerns for critical fire weather.
WIll probably need some fire headlines for Thursday as GFS 700mb
winds increase to 25-30kts west of the Laramie Range and afternoon
humidity falls to the low teens.
.LONG TERM...(Thursday night through Monday)
Issued at 200 PM MDT Mon Jul 5 2021
Friday...Somewhat cooler in the wake of a cold frontal passage
associated with a shortwave trough passing across the Northern
Plains states. The front looks rather dry, though we may see
isolated late day thunderstorms.
Saturday...Even cooler and more stable in the relatively dry air in
the wake of the cold front passage. With minimal low and mid level
moisture, it looks dry.
Sunday-Monday...Mostly dry with a warming trend as the ridge aloft
builds overhead. Ridging aloft breaks down slightly on Monday as a
shortwave trough moves overhead, perhaps spawning isolated late day
thunderstorms due to an increase in low and mid level moisture and
convergence along a north to south oriented surface trough.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 520 PM MDT Mon Jul 5 2021
KRWL will continue with MVFR conditions until 01Z. Thunderstorms
moving northeast across the region will impact all TAF sites this
evening until 15Z Tuesday morning. KCYS and KLAR will drop to MVFR
starting 0Z for KCYS and 02Z for KLAR with cloud bases trending
BKN at 4k ft. Sites across the Nebraska Panhandle will experience
thunderstorms until 10Z along with BKN clouds at 5k ft. There is a
possibility of fog tonight for KCYS starting 07Z thus MVFR
conditions are possible until 12Z.
&&
.FIRE WEATHER...
Issued at 200 PM MDT Mon Jul 5 2021
Minimal fire weather concerns today through Tuesday as a slow
moving low pressure system moves through southeast Wyoming. This
low will bring widespread chances for wetting
rains...thunderstorms and cooler temperatures. We begin to dry out
Wednesday and especially Thursday as high pressure builds in from
the south. Critical fire weather conditions looking likely
along/west of the Laramie Range Thursday with afternoon humidity
falling below 15 percent and westerly wind gusts of 30 to 35 mph
expected. These critical conditions could continue for Carbon
County FWZs into Friday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...AW
FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Des Moines IA
624 PM CDT Mon Jul 5 2021
...Updated Aviation...
.DISCUSSION.../Today through Sunday/
Issued at 218 PM CDT Mon Jul 5 2021
Forecast Highlights:
-- A few storms possible over northern Iowa this afternoon/early
evening
-- Scattered showers and storms Tuesday night into Wednesday
-- Cooler and turning dry later Wednesday into Thursday
-- Growing confidence in strong to severe storm chances including
locally heavy rain in the region Friday perhaps into Saturday
Details: For this afternoon into early this evening, 18z SPC
mesoanalysis shows over 2000+ J/kg of MLCAPE with deep layer shear
less than 25 knots with a weak boundary around the Iowa/Minnesota
border. There are weak perturbations in the mid-level flow, but this
weak lift is displaced from the instability axis. The NAM, RAP, and
HRRR forecast soundings show a weak warm layer that persists through
daytime heating that will likely limit convection this afternoon. 1
minute GOES-East visible imagery has shown this cap in the way of
developing cumulus over eastern Hamilton County that were showing
slight vertical development. However, a short time later these
clouds were suppressed. Examining the 5/00z and 5/12z HREF members,
the ARW has been the most aggressive with storm development this
afternoon. However, the NSSL WRF and FV3 show less storms than 24 or
even 12 hours ago and even the ARW has backed off, perhaps owning to
better resolving the cap and weak forcing. SPC morning update
removed the marginal and all guidance here is supportive of such
removal. Any storms that do form will be isolated, but could pose a
risk of downburst winds given inverted V soundings and perhaps hail
in the updraft stage of a storm. Any storms would diminish shortly
after sunset.
With the boundary being pushed back northward tonight, Iowa will be
well within the warm sector on Tuesday. As a shortwave trough moves
across the Dakotas and into Iowa by later in the day, this will
bring the boundary/front into the state. Timing continues to look
late in the afternoon if not the evening hours for reaching our
northwestern forecast area. Most of the scattered storms will be
behind the surface front and instability is lowering into the
overnight hours. The deep layer shear is better than this afternoon
so a few strong storms may result late in the afternoon or evening
hours. Precipitable water values around 2 inches will pool near and
behind the slow moving boundary, but the 850-300mb flow is not
parallel to the boundary. While storms may be slow moving, not
seeing a concern for flash flooding with 3 hour flash flood guidance
values around 2 inches and expected rain amounts. The scattered
showers and storms will push through by later Wednesday afternoon
with cooler air arriving. Temperatures Wednesday afternoon and
Thursday morning will average 5 or so degrees below normal with
highs in the 70s to around 80 degrees and lows in the 50s to around
60 degrees with the lowest of those temperatures in northern Iowa.
The lower temperatures will be accompanied by lower dewpoints for a
short period late Wednesday into a good portion of Thursday.
Attention will turn upstream as a strong shortwave trough will be
arriving over the Pacific Northwest and British Columbia province of
Canada Wednesday and moving over the Canadian Rockies later
Thursday. Another shortwave will undercut this shortwave and phasing
of these two is being shown in both the ECMWF and GFS. This would
help to strengthen and could cause the merged shortwaves to close
off and slow down as it moves southeastward toward the upper and
middle Mississippi Valley. Storms may arrive overnight Thursday into
early Friday into parts of the state, but later Friday is when there
is likely to be favorable instability and deep layer shear. This
environment would be supportive of strong to severe storms chances
somewhere in the region later in the day. 5/00z CIPS analog has a 50-
60% of at least 1 severe report over much of western into portions
of central Iowa and points immediately west of Iowa with the recent
12z run focusing these probabilities farther southwest with the 12z
GFS track of the shortwave farther southwest. Indeed, the idea of a
severe risk is also being highlighted in SPC`s day 5 outlook. If the
slower solution results, then portions of our forecast area may have
another round of storms on Saturday and with the closed low nearby,
this could result in a favorable environment for tornadoes northeast
of wherever the low moves.
There is also a signal for heavy rainfall as the ensemble mean
precipitable water values from the GEFS and EC ensemble show over
1.75 to at times above 2 inch values with favorable warm cloud
depths for efficient rainfall later Friday into Saturday. The 850-
300mb flow at this time looks a bit on the fast side for ideal
training storms, but given the high PWs, locally heavy rainfall
looks possible in the region. 5/00z CIPS top 15 analogs for the
period ending 10/00z shows over an inch in portions of the state
with the more recent 12z run shifting the heavier rainfall into
southwestern Iowa and adjacent areas of neighboring states.
Meanwhile the 5/00z WPC cluster analysis shows a half an inch over
southern Minnesota. While a half an inch is not impressive, it is
the mean of 100 members from the deterministic and ensemble
solutions of the CMC, GFS, and ECMWF. Subjectively examining the
ensemble members, there are more members that have around or more
than 2 inches amounts than yesterday. Deterministic solutions, of
course, can have higher 6 hour maximums, though not as extreme as
one solution from yesterday`s 12z run. Further looking at
deterministic solutions as they relate to the 100 year annual return
interval, the GFS and ECMWF extreme precipitation forecast table
highlights areas of Minnesota into parts of north central or
northeastern Iowa Friday night into Saturday with generally 30 to
50% for 6 hours and about 20 to 30% higher for the 24 hour period.
While rainfall deficits are greater over northern Iowa looking at 30
and 60 day departures and soil moisture percentile, as we saw in
southern Iowa a few weeks ago this does not preclude water issues.
Indeed, yesterday`s and today`s National Water Center`s prototype
National Hydrologic Discussion mentions the medium range forecast is
signaling bankfull and rapid onset flooding on Friday or Saturday
possible in parts of the region. An important note is that the
National Water Model`s precipitation is driven by a single model
(GFS) so that signal in the medium range will shift with the
deterministic weather model.
All of this said about the heavy rainfall and severe potential late
this week into perhaps the first part of this weekend will hinge on
if the shortwaves merge, if they close off, if they slow down, which
has an impact on timing and placement of key features. While
confidence is growing in severe weather and heavy rainfall later
Friday into Saturday in or around Iowa, the details and what that
will mean for a certain area or city will remain in flux for at
least several more days.
&&
.AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/
Issued at 623 PM CDT Mon Jul 5 2021
VFR conditions prevail through the current TAF period. Isolated
TSRA likely in north central Iowa this evening. Coverage should
remain sparse enough to not warrant mention in the forecast.
Additional TSRA late day Tuesday should hold off until around or
after 00z.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Ansorge
AVIATION...Martin
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
630 PM CDT Mon Jul 5 2021
.AVIATION...
The bulk of the thunderstorm activity has shifted west of the I35
sites, with moderate rainfall and some thunder continuing at DRT.
Things should slowly calm down through the night, but some of the
high-res model guidance shows a bit more overnight activity than
previous nights especially for the San Antonio sites. Will hold onto
a VCSH group there overnight. Another round of afternoon storms
appears likely for tomorrow and will handle that with a -SHRA VCTS
group for now. Some MVFR ceilings will be possible overnight.
&&
.PREV DISCUSSION... /ISSUED 208 PM CDT Mon Jul 5 2021/
SHORT TERM (Tonight through Tuesday Night)...
Widespread showers and thunderstorms are already ongoing across
South Central Texas this afternoon as a mid-level impulse works its
way south into the the Southern Edwards Plateau. This, combined with
the effects of convective outflow boundaries as a result of the sea
breeze, will result in locally heavy rain and occasional cloud to
ground lightning. Showers and storms that have formed east of I-35
and the I-37 corridor are mostly multicellular in nature, with
little in the way of deep layer shear to work with. Given this lack
of meaningful shear with height, expect storms to be very pulse-like
in nature, and with PWATs in excess of 2" across the board, along
with sfc dewpoints well into the 70s, it`s no wonder rainfall rates
could exceed 1-2" per hour at times with the heaviest cells. Some
brief gusty winds are possible as well along any outflow boundaries,
but the bigger threat for perhaps an isolated wind gust to 50mph
will be out west over the Rio Grande Plains and Southern Edwards
Plateau, where some shear will be present this afternoon and
evening. Along with the mid-level impulse and MLCAPE of 2000-3000
J/kg, 0-6km bulk shear will actually be in the 20-25 kt range,
leading to the slight possibility of a couple gusty winds from
storms. Storms should push southward towards Del Rio this evening
posing the risk for some gusty winds and locally heavy rainfall.
Storm coverage should decrease after sunset out west, but hi-res
guidance, in particular the HRRR and TT WRF, are indicating that
showers and perhaps a rumble of thunder could develop over the
Coastal Plains and the I-35 corridor after midnight. Have bumped up
PoPs to the high chance threshold in anticipation of this threat.
Tuesday will be yet another active day, however, more diurnally
driven storm activity is once again expected, as the lack of a mid-
level shortwave disturbance will result in chaotic storm motion and
outflow boundaries by mid-afternoon. With PWATs still nearly off the
charts for this time of year in the 2.1-2.3" range, along with sfc
dewpoints in the 70s, expect yet another shot at locally heavy rain
to continue with any storms that can sit over any location for more
than 30 minutes. While the flash flooding threat will be very
localized, it is not out of the question that we could start seeing
more flash flooding threats, especially in locations that have
received 1-3" or more in the last couple of days.
LONG TERM (Wednesday through Monday)...
Overview: The well advertised cool, wet pattern will continue mid to
late week with a slight southward trend noted in the guidance for
the best rain (and particularly heavy rain) chances Wednesday
through Friday. Considerable uncertainty remains in the forecast
this weekend into early next week but some rain chances will
continue for at least portions of the area.
Details: Wednesday morning, the tail end of available high
resolution guidance paints a picture that the "center" of the
somewhat disorganized upper level height falls will be to our south
or southeast with a potential surface reflection noted in the model
pressure and wind fields centered over deep south TX. Rain chances
in the morning will thus be higher across our southern counties,
especially the Coastal Plains as increased onshore flow/convergence
seems likely. Rain chances will spread northward through the day,
and although coverage will diminish overnight as usual, some
lingering isolated activity may remain. A very similar story is
forecast Thursday. Locally heavy rain could occur anywhere within
the CWA these days, but probabilities are notably higher south of I-
10/US-90.
As we head through Friday and beyond, the global models begin to
disagree significantly as they have the past several model cycles
with little signs of converging on any one solution. The Euro
continues to shift the main area of energy to the west into Mexico,
then northward along the terrain which would allow for our
northeastern areas to see much lower rain chances while our western
counties would become the focus area for convection. The GFS and its
ensemble members are generally less defined with any system
organization and keep the primary POPs closer to the Gulf Coast. And
the Canadian continues it`s way-out-there high QPF over south-
central TX through the weekend. While the amounts can certainly be
discounted, the potential for a wetter solution than the GFS/Euro
are currently spitting out cannot. It remains to be seen how this
will play out but we will have to remain cognizant of continued low
risk for locally heavy rain through the rest of the long term.
Hopefully additional clarity will come over the next 24-36 hours.
PREV DISCUSSION... /ISSUED 1248 PM CDT Mon Jul 5 2021/
AVIATION (18Z TAFS)... /NEW/
Bottom line: Widespread showers with isolated thunderstorms are
expected to continue over the next 24-30 hours, making this a rather
difficult forecast. Trying to pick out and decipher any particular
prevailing weather will be tough given a moist and unstable airmass
with very weak steering flow leading to chaotic storm motions and
storm interaction. Expect CIGs to fluctuate between MVFR and VFR
throughout the day at all sites, most notably AUS/SAT/SSF. Have gone
with a TEMPO group at those three sites for early afternoon to early
evening for thunderstorms with visibility and ceilings down to IFR.
Meanwhile at DRT, a complex of storms looks to be organizing to the
north and should arrive between 22Z-02Z, hence the TEMPO for that
time period. Overnight, rain chances continue, but the thunder threat
should be reduced with rain showers possible at all sites through
tomorrow. IFR ceilings are expected to form after 09Z at all three
I-35 sites and continue through 15Z.
Morris
PREV DISCUSSION... /ISSUED 414 AM CDT Mon Jul 5 2021/
SHORT TERM (Today through Tuesday)...
Another active day is in store with scattered to numerous showers
and thunderstorms expected mainly this afternoon and evening.
However, we could see some showers and maybe an isolated
thunderstorm before noon across the Coastal Plains and the northern
part of the Hill Country.
For this afternoon and early evening, the weather scenario looks
interesting as an upper level impulse pushes down into our area.
This feature is forecast to generate showers and thunderstorms as it
moves into the Hill Country and Edwards Plateau. A second feature
that is forecast to play a big role on today`s weather is the
seabreeze. Between these features, in addition to outflow
boundaries, the combination brings the potential for localized heavy
rain.
Why heavy rain? First, dewpoint temperatures are likely to range
from the mid to upper 70s under a rich tropical airmass in place.
Second, PWATs are likely to range between 2.1 to 2.25 inches based
on GEFS and as high as 2.5 inches per GFS. These values are between
+2SD and +3SD for this time of the year. Third, mean wind flow is
expected to be around 10 mph allowing storms to slowly move forward.
All of these components when put together bring the potential for
impressive rain rates and therefore the potential for minor flash
flooding. For the past two days, localized rainfall amounts of 3 to
4 inches have occurred and today will be another day for some areas
across the Hill Country, Edwards Plateau, along I-35 and/or the
Coastal Plains to experience these types of isolated rainfall
amounts. Therefore, average storm totals rainfall amounts for today
are one tenth to one inch over most areas with maximum values of 3 to
5 inches. The Weather Prediction Center Excessive Rainfall Outlook
for Day One has areas along and north of Highway 90 under a slight
risk of rainfall exceeding flash flood guidance. As a friendly
reminder, 6 inches of fast moving water can knock an adult off their
feet and 12 inches of rushing water could carry away most cars. Turn
Around, Don`t drown if flooded roadways are encountered.
Shower and thunderstorm activity is expected to decrease late
tonight into Tuesday morning. Then the activity picks up in the
afternoon once again with the western half of South Central Texas
favored for pockets of heavy rains in the afternoon.
LONG TERM (Tuesday Night through Sunday)...
A broad mid and upper level low/trough is forecast on Wednesday to be
positioned from Deep South Texas northeast up the Texas coast. The
focus for the heaviest rainfall should remain over the Coastal Plains
on Wednesday. Nevertheless, southeasterly boundary layer flow will
maintain elevated precipitable water values across the region
Wednesday, especially the southern half of the area, and there should
be a diurnal pattern of scattered showers and thunderstorm
development inland through the afternoon and early evening. There
are indications that the trough will shift slightly west and inland
on Thursday, potentially bringing some higher rain chances farther
north into the CWA.
Beyond Thursday there are some significant differences in the upper
level pattern between the 00Z operational runs of the GFS, ECMWF, and
CMC. The ECMWF and CMC close and tighten the upper level low up and
drift it northwest Friday through Saturday, with the CMC bringing it
into western areas of the CWA and the ECMWF into Coahulia, Mexico.
Both also have a surface low reflection. A scenario like this could
bring much greater rain chances Friday into the weekend than are
currently advertised, especially across the southwest and western
CWA, which would include nocturnal convection. Some may also
continue to notice the very high run total QPF from the CMC and
ECMWF solutions. While these are currently outliers, they can`t be
completely discounted in terms of the general potential for pockets
of higher QPF amounts Friday into the weekend. With respect to the
operational run of the GFS, this solution maintains a broad trough,
but does shift it northwest indicating continued broad rain chances.
With that said, in general 2-4" of rainfall is advertised this week
across the CWA, favoring southern and western areas. Pockets of
higher amounts up to 6" inches are likely, and a caveat that if GFS
and the GEFS trend toward the ECMWF and CMC then the pockets could be
even higher. These isolated pockets could occur in a short period of
time. Thus, we will continue to advertise a threat for localized
flooding concerns through the week.
With respect to temperatures, forecast max temperatures will continue
to remain below normal for this time of year, welcome news for most
given it`s July.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 73 87 72 88 73 / 50 70 40 60 20
Austin Bergstrom Intl Airport 72 87 71 87 71 / 50 70 30 60 20
New Braunfels Muni Airport 74 87 72 87 72 / 60 70 40 70 20
Burnet Muni Airport 71 85 71 86 71 / 50 60 30 50 20
Del Rio Intl Airport 75 88 74 91 74 / 60 70 40 50 50
Georgetown Muni Airport 72 86 72 87 71 / 50 60 30 60 20
Hondo Muni Airport 73 85 72 86 71 / 60 70 50 70 40
San Marcos Muni Airport 72 87 72 87 71 / 50 70 40 70 20
La Grange - Fayette Regional 75 87 74 89 73 / 50 70 40 70 20
San Antonio Intl Airport 74 84 73 86 73 / 60 80 50 70 20
Stinson Muni Airport 76 86 74 87 74 / 70 80 50 70 30
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term/Aviation...Hampshire
Long-Term...YB
Area Forecast Discussion
National Weather Service Grand Forks ND
934 PM CDT Mon Jul 5 2021
.UPDATE...
Issued at 934 PM CDT Mon Jul 5 2021
A nearly stationary W-E oriented frontal boundary has sagged
south of the Highway 2 corridor this evening... with showers still
trying to inch eastward along that line. Deeper convection now
increasing in western SD is associated with a deepening surface
low there... and should continue to track east-northeastward into
s-cntrl and eastern ND during the overnight... effectively pushing
that frontal boundary back north a bit, before it finally slides
through the area on Tuesday. Lots if players in this game
tonight, with southeastern ND and west-central MN likely to be
the biggest precipitation winners. Still expect some frontal
overrunning precip up into the Highway 2 corridor and GF areas as
well.
The latest 00z and 01z RAP13 runs support this, though the recent
23z, 00z, and now 01z SPC HRRR runs are still quite variable
convection evolution. Long story short... not planning any
significant changes to the current evening and overnight forecast
package.
UPDATE Issued at 715 PM CDT Mon Jul 5 2021
An updated Aviation Discussion is attached below.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 319 PM CDT Mon Jul 5 2021
The showers moving east thru the far northern parts of ND continue
to weaken as they move into Cavalier-Langdon-Cando. Main focus
will be the coverage of showers and thunderstorms tonight and
rainfall amounts. Next wave over northern Wyoming and south
central Montana will move east and be in the Aberdeen/Jamestown
area 12z Tuesday with sfc low just a tad south of this. 850 mb low
tracks along the SD/ND border and best warm advection and
isentropic lift looks to be south of Hwy 200 overnight peaking
prior to 12z. PWATs near 1.50 inches so some good rainfall rates
seem likely in this zone. Average amounts look to run around
1.25-1.50 inch near the SD border thru 12z Tues then a bit more
after before it ends. Farther north rainfall amounts will be less
as sfc pressure rises as high moves south into central Manitoba.
This will limit how far north rain will get overnight and amounts.
Clearing will work quickly southeast behind the system Tuesday,
with last area for rain to end and skies to clear being west
central MN by late aftn. Cooler Tuesday with highs mid 60s to low
70s.
Skies mainly clear Tuesday night in the mid 40s to low 50s.
.LONG TERM...(Wednesday through Monday)
Issued at 319 PM CDT Mon Jul 5 2021
Wednesday into early Thursday...surface high pressure continues
to retreat and return flow will bring warmer temperatures and
breezy conditions ahead of the next system. Energy aloft will
propagate through the flow helping to trigger showers and storms
by Thursday and Friday bringing another round of measurable
precipitation.
The system will reorganize farther south late Friday and Saturday
resulting in drier conditions over the area...with continued
seasonal temperatures. Pleasant conditions will persist through the
end of the forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Update at 934 PM CDT Mon Jul 5 2021
Generally VFR conditions across the FA with sct rainshowers and
isolated thunderstorms moving eastward into eastern ND along a
nearly stationary W-E oriented frontal boundary laying currently
lying along the Highway 2 corridor. An approaching low pressure
system will bring areas of showers and scattered MVFR CIGS and
VSBYS in thunderstorms into eastern ND from 05z through 11z...
becoming more numerous and overspreading northwest and westcentral
MN through 14z. Conditions will improve from the north from 16z
through 20z as the frontal boundary sags further southward.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...Gust
SHORT TERM...Riddle
LONG TERM...Hopkins
AVIATION...Gust
Area Forecast Discussion
National Weather Service Goodland KS
934 PM MDT Mon Jul 5 2021
.SHORT TERM...(This evening through Wednesday night)
Issued at 140 PM MDT Mon Jul 5 2021
Satellite and 500 mb RAP analysis showed near northerly flow aloft
this afternoon, with the region on the eastern side of an area of
high pressure. A shortwave trough could be seen rounding the
northern periphery of the high, exiting the Great Basin. Skies were
clear across the western CWA; however, fields of cumulus were
billowing into the region from the southeast. No thunderstorm
development was associated with these clouds at this time. At 1 PM
MT, temperatures ranged from the low 80s to the low 90s, with
southeast winds at 10 to 15 mph.
Thunderstorms developing along the Front Range this afternoon are
expected to push east into the evening hours as the upper trough
approaches the High Plains. This disturbance brings a slight chance
for showers and thunderstorms to areas west of a line from Stratton,
NE to Sharon Springs, KS late this evening. At this time, confidence
in storms making it to the region before dissipating is quite low,
resulting in the lowering of precipitation chances for tonight. If
activity does make it into the area, severe weather is not
anticipated. Otherwise, temperatures fall into the 60s region-wide.
Tuesday looks to be a bit more active in terms of storms. The cold
front associated with our aforementioned disturbance pushes across
the region throughout the day, becoming a focus for thunderstorm
development as early as the morning hours. Of course better chances
come in the afternoon and evening as daytime heating cranks things
up (highs in the 80s/low 90s) and storms increase in coverage. It
appears that a likely scenario is one or two linear clusters form
and track across the area from northwest to southeast. Again this is
just one scenario, and where such storms would set up is uncertain.
Moisture will be plentiful, with PWATs near 1.5" by the afternoon.
Additionally, moderate instability, lapse rates of 6-7C/km, and
shear maybe up to 30 knots suggests that a few strong to severe
thunderstorms will be possible (mainly in the afternoon and
evening). Primary threats with these storms include damaging winds,
large hail, and locally heavy rainfall which could create flash
flooding issues. Storms should exit the region to the southeast
overnight as temperatures fall into the upper 50s to mid 60s.
Thunderstorms pass to our east Wednesday morning while drier air
moves into the High Plains. Quiet weather is anticipated, with highs
in the 80s behind Tuesday`s cold front as ridging builds east across
the western CONUS. Temperatures fall into the upper 50s to low 60s
under clear skies Wednesday night.
.LONG TERM...(Thursday through Monday)
Issued at 123 PM MDT Mon Jul 5 2021
The extended period begins with high pressure located over the Four
Corners region and a trough located over the Great Lakes. The
majority of the day Thursday is expected to remain dry. I have
introduced low end pops for areas north of Highway 34 as a subtle
shortwave emanates off the Rockies in northern Colorado/Southern
Wyoming. The better forcing may remain north of the CWA in the
Nebraska panhandle but felt it was worth addressing the potential.
High temperatures for the day will be in the 90s across the area
with lows in the mid 60s to low 70s.
Friday, a ridge begins to take shape over the western CONUS as an
upper level low moves southeast from the northern plains into the
Great Lakes. A cold front will be associated with the upper level
low and is currently forecasted to move through the CWA during the
afternoon to late evening. Before the cold front arrives, warm to
hot temperatures are expected with daytime highs in the in the low
90s across Colorado to approaching triple digits to the east,
some heat indices could approach 100 degrees during the afternoon.
Regarding the timing of the cold front, model discrepancies exist
with either a afternoon passage or a late evening passage which
could have an impact on how warm it will actually get. Showers
and storms appear possible during the afternoon and evening as
well with the better chances currently looking to be south of
Interstate 70. Some guidance has been hinting at gusty to perhaps
strong winds with the passage of the front, confidence is not high
enough currently to raise wind gusts but is something that will
continue to be monitored.
Saturday and Sunday, will be relatively cooler in the wake of the
cold front passage as afternoon highs in the 80s are expected. Low
temperatures each morning will be in the mid 50s across east
Colorado to the mid 60s across eastern portions of the CWA.Saturday
will feature a low chance for afternoon showers/storms as a weak
disturbance moves down the eastern periphery of the ridge still
situated over the western CONUS; however the better forcing looks to
remain off to the east across central Kansas.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 934 PM MDT Mon Jul 5 2021
VFR conditions will prevail at KGLD and KMCK terminals through the
forecast period. Southerly winds around 6-10kts will transition
to the west overnight and into tomorrow morning. Winds will shift
to the northwest as a cold front moves through the region. Showers
and thunderstorms will be possible in the vicinity of the
terminals by 18Z, tapering off by 00Z.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JBH
LONG TERM...TT
AVIATION...AW
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
923 PM CDT Mon Jul 5 2021
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
This evening`s shower and thunderstorm activity has mostly faded
after the sea breeze storms` outflow boundary reached just north
of the I-20 corridor. A cluster of storms near Meridian is about
all that is left to wind down, but can`t rule out a few stray
showers overnight. An area of upper-level low pressure is centered
over the central Gulf Coast tonight, and this should help to
steer more moisture and wrap rain chances farther across our
forecast area by tomorrow afternoon. Updated POPs and weather
through the afternoon tomorrow to account for trends in latest
short-term guidance. The first showers and storms of the day will
likely be in the Pine Belt again, which should keep temperatures
from climbing too quickly there. Otherwise, most locations should
see a range of normal lows tonight and normal highs tomorrow. /NF/
Prior discussion below:
Tonight & Tuesday...
Tonight: With showers moving to the NW closer to I-20 corridor & a
little better moisture, any remnant showers/storms will wind down
within an hour or so after sunset. The boundary is progged to
continue lifting N, bringing increasing moisture depth & in the
boundary layer. This will help more cloudiness to spread N overnight
& higher sfc dewpoints in the low 70s. Lows will remain near normal
in the low 70s.
Tuesday: Tropical Storm Elsa will be moving off of N Cuba by Tuesday
morning & will straddle the western FL Peninsula but will remain no
threat to the N Gulf Coast. As the front stalls, deeper moisture
near 2 inch PWs will advect NW. A broad upper low over the TX coast
& areas of PV in the region will help convection to spread W-NW.
Coverage will be more scattered-numerous along & S of the I-20
corridor & highest in the Hwy 84 corridor. Shear will be subtle but
500mb temps could be slightly cooler, leading to a little better
lapse rates. Some strong storms are possible but severe looks
unlikely. Light backbuilding flow will bring some potential for
quick heavy downpours. Heat will be a little less due increasing
convective coverage, but warmer in the west. /DC/
Tuesday night through early next week:
By Tuesday night into Wednesday morning, an upper trough will have
begun ejecting Tropical Storm Elsa north and east, which should let
it go away from the area with very little local effect. Afternoon
isolated to widely scattered showers and thunderstorms will be
possible each day this week, though the best chances may come
Wednesday and Thursday afternoon and evening when an upper trough
glances by to the north. Temperatures will also begin to warm and
moisture increases through the week: Lows warm from the lower 70s F
by early week into the middle 70s F by late week while highs will
rise from the middle 80s F into the lower and middle 90s F. By
Friday, the upper trough responsible for the scattered showers
earlier in the week will be just east of the area, placing the
ArkLaMiss under convergent upper flow and increasing upper heights.
This will dramatically lower rain chance as we head into the weekend
with only isolated showers and storms in the evening. An additional
upper trough will approach the area by late in the day Sunday which
should bring increased rain chances and perhaps a marginal reduction
in afternoon high temperatures to close out the week. Day 7 and
beyond, we venture a bit into the unknown as a complex pattern could
evolve with an upper low in retrograde or stalled across Texas which
could block the pattern somewhat with flow to the north of the cut
off low becoming zonal or a bit ridged. This will likely lead to
near or above average temperatures and near to slightly below
average rain chances as we start next week with the late-Sunday
trough lifting out to the east. /86/
&&
.AVIATION...
00Z TAF discussion:
Mainly VFR conditions reported in the short term...with a broken
line of thunderstorms lifting through JAN/HKS this afternoon.
Showers and thunderstorms will be ending soon...and dissipating
as they move northward. Llvl moisture will contribute to LIFR cigs
in PIB/HBG...and IFR for HKS/JAN/MEI/GTR in the overnight. SREF
and HRRR as well as other guidance is in good agreement about the
northern extent...if not necessarily about the magnitude. However,
persistence will side on LIFR in the southeast in the predawn
hours. Another day with showers and thunderstorms and light se
winds for tomorrow.
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 72 88 72 86 / 24 73 46 82
Meridian 70 85 69 86 / 29 82 46 81
Vicksburg 73 90 72 88 / 18 68 45 79
Hattiesburg 72 85 71 86 / 29 86 50 82
Natchez 72 88 71 85 / 26 77 53 82
Greenville 71 89 71 88 / 11 32 28 73
Greenwood 71 90 71 88 / 11 43 31 74
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
NF/HJS/DC/LP
Area Forecast Discussion
National Weather Service Pendleton OR
814 PM PDT Mon Jul 5 2021
.SHORT TERM...It was another hot and dry day with highs in the
mid-80s to mid-90s for most of the forecast area--95 to 100 over
the Lower Columbia Basin. Temperatures today were very similar to
the highs observed on the 4th. Tuesday will likely be several
degrees warmer as the inverted surface thermal trough strengthens
east of the Cascades, and heat risk graphics place the area under
moderate to high risk for those sensitive to heat. Since this is
a one-day advisory situation, and people know it`s hot, I will
not issue any Heat Advisories for tomorrow. The focus will be fire
weather and the probability of new fire starts due to lightning
as well as the increasing wind Tuesday night and Wednesday. Fire
Weather Watches were issued for the forecast area from Tuesday
afternoon through Wednesday evening.
There are a lot of challenges with the upcoming shortwave trough
late Tuesday and Wednesday. The center of the trough is currently
about 500 miles west of the northern CA coast and will weaken as
it lifts northward along the OR coast on Tuesday. This will force
the upper level ridge and inverted surface thermal trough
eastward. The breakdown of the upper ridge will increase
instability. However, cooler marine air with a strengthening
onshore flow will provide some stability at the surface Tuesday
night and Wednesday. The instability will be aloft. The question
is the amount of moisture which is quite limited. For Tuesday
night, some of the CAMS models (particularly HRW) advertise weak
radar reflectivity over Grant, Union, and Wallowa Counties.
Thunderstorms will mostly be isolated Tuesday night. On Wednesday
morning, as the upper level trough tracks northeast across WA,
the upper level dynamics will play a role in high based
thunderstorms over south central WA. Models show very little to no
QPF which is disconcerting when looking at the elevated
instability. Those in the Lower Columbia Basin and surrounding
valleys could wake up to several hours of thunderstorms and
possible new fire starts. Confidence isn`t high at this point, so
will keep the watch going for now and see what future CAMS models
have in store. The marine push will improve humidity values but
winds will cause problems for fire spread on Wednesday.
Wildfires have increased in numbers since Thursday night storms.
The upper flow from the southwest will push smoke from fires in
northern CA over central and southeast OR, but the HRRR and USFS
Blue Sky show this as more elevated smoke and not extensive at the
surface. Air quality monitors for both eastern WA and OR remain
good. Current forecast indicates haze for our eastern OR zones,
and patchy smoke was added to the John Day Basin where the Dixie
Creek, Lewis Rock, Bologna, and Lovlett Corral are in the
vicinity. Wister
&&
.PREV DISCUSSION... /issued 420 PM PDT Mon Jul 5 2021/
LONG TERM...Thursday through Monday...Deterministic and ensemble
guidance are in good agreement through the extended period and
continue to indicate that the hot and dry trend will persist into
the weekend.
Thursday, guidance depicts a second, weaker, shortwave trough
moving across the forecast area, and exiting by the evening.
Though weaker, the shortwave trough will reduce temperatures
another 1 to 3 degrees compared to Wednesday, and likely bringing
the coolest day over the next week with highs in the upper 80s to
90s. At the surface, tight cross Cascade pressure gradients with
a mid- level jet will produce another day of breezy winds across
the forecast area, especially through the Gorge and the Kittitas
valley. Behind the departing shortwave trough, upper level ridging
will build back over the region while the thermal trough pushes
north into southeast Oregon. Conditions will continue to be dry
across the forecast area with warming temperatures under the ridge
and thermal trough while winds will mostly be light with an
occasional light breeze in the Gorge and the Basin. Saturday,
ridging over the area will be muted and a westerly flow aloft
setups as a shortwave trough dropping out of the Gulf of Alaska
into central BC suppresses the upper high pressure over the
Southwest. Meanwhile, the thermal trough centered over central NV
will support a warming trend Saturday, with temperatures across
the Basin likely breaking the triple digits in the afternoon.
Breezy westerly winds will develop as well in the afternoon and
evening Saturday as surface pressure gradients tighten across the
Cascades.
Sunday and beyond, deterministic and ensemble guidance begin to
come into a strength and timing disagreement with the next
synoptic feature to impact the area. The general trend amongst
guidance is that the shortwave trough moving into central BC will
clip the forecast area. The GFS deterministic and ensemble mean
depict the shortwave trough strengthening and shifting south,
producing breezy conditions through the Cascade gaps and cooler
temperatures Sunday afternoon. However, ECMWF deterministic and
ensemble mean shows the feature weaker and further north, which
would still result in low end breezy conditions, but not as great
of a cooling trend. Confidence is moderate that the feature will
produce breezy conditions and a slight cooling trend, however,
the intensity of each brings low confidence, so have elected to to
keep NBM temperatures as it falls between the ECMWF and GFS
outcomes and have increased winds for Sunday. Lawhorn/82
AVIATION...00Z TAFs...Clear skies will prevail at the terminal
airports through Tuesday afternoon, but high-based cumulus buildups
will develop after 21Z. Bases around 12K-14K expected. Winds will
primarily be light and terrain driven, although there will be
evening gusts at 15-20 kts. Wister
FIRE WEATHER DISCUSSION...Upper ridge building over the region
tonight into Tuesday. Meanwhile an upper low will be approaching
the California coast. This low will move across Oregon into
Washington Tuesday night and Wednesday. Thunderstorms are expected
to develop over central Oregon Tue afternoon and evening, then
move across northern Oregon into southern Washington overnight and
Wednesday morning. Gusty westerly winds will then develop as this
system departs on Wednesday. It will remain breezy into Thursday.
FIRE WEATHER WATCH IN EFFECT FROM LATE TUESDAY AFTERNOON THROUGH
WEDNESDAY EVENING FOR ABUNDANT LIGHTNING FOLLOWED BY WIND AND LOW
RELATIVE HUMIDITY FOR FIRE WEATHER ZONES OR610, OR611, OR639,
OR640, OR641, OR642, OR643, OR644, OR645, WA639, WA641, WA643,
WA645, WA675, AND WA681.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 60 99 66 92 / 0 0 20 20
ALW 65 102 70 94 / 0 0 20 20
PSC 66 102 67 97 / 0 0 20 20
YKM 60 100 68 94 / 0 0 20 20
HRI 63 103 70 96 / 0 0 20 20
ELN 61 98 65 87 / 0 0 20 20
RDM 54 98 55 89 / 0 10 20 10
LGD 59 97 61 89 / 0 0 20 20
GCD 61 98 61 90 / 0 10 20 10
DLS 64 100 67 85 / 0 0 20 20
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Fire Weather Watch from Tuesday afternoon through Wednesday
evening for ORZ610-611-639>645.
WA...Fire Weather Watch from Tuesday afternoon through Wednesday
evening for WAZ639-641-643-645-675-681.
&&
$$
SHORT TERM...85
LONG TERM....82
AVIATION...85
Area Forecast Discussion...UPDATED
National Weather Service Portland OR
852 PM PDT Mon Jul 5 2021
Updated Aviation discussion
.SYNOPSIS...Typical summer weather pattern prevails, with only minor
changes expected over the next week. Onshore flow will maintain
coastal low clouds, which will spread inland to varying degrees each
night and morning before clearing back to the coast for sunny
afternoons inland. Temperatures remain near to above normal, with
little to no precipitation expected. Tuesday appears to be the
warmest day this week, followed by a cooldown Wednesday and Thursday
as a weak upper trough moves onshore and deepens the marine layer.
&&
.SHORT TERM...This evening through Thursday...With little changing in
the synoptic pattern, the coverage of stratus tonight and early
tomorrow is likely to be similar to today. The main difference will
be the depth of the marine layer, which should be a little lower
tonight thanks to a weaker gradient across the area. Observations
last night revealed a +6-8mb pressure gradient from Spokane to North
Bend, while forecasts (which, of course, are just that - imperfect
attempts to ascertain the future) from the GFS and NAM for tonight`s
gradient are slightly weaker at around +4-7mb. As a consequence, the
tops of clouds, which (according to approximations based on current
Satellite) are around 2,500-3,000 ft, should be slightly lower
tomorrow. To account for this, tomorrow`s cloud forecast was made to
be essentially a repeat of this morning`s forecast, minus elevations
over around 2,000 ft (which, being above the marine layer, are
expected to remain cloud-free).
Heights continue to rise across the area through tonight as a strong
ridge builds to our southeast across the Great Basin and Desert
Southwest. The GFS, ECMWF, NAM, and UWWRF agree that thereafter a
shortwave trough and its associated vorticity maximum will approach
the Oregon and Washington coasts from the southwest. This feature
bears watching to evaluate thunder potential for the Tuesday night
timeframe.
Several high resolution models - including the NAMNest, HRW, and
HRRR - depict composite reflectivities indicative of elevated
convection impacting areas (which vary from one model to another)
from the central Willamette Valley north and east into the north
Oregon and south Washington Cascades from about 10 p.m. Tuesday to 6
a.m. Wednesday. Forecast soundings from various models suggest the
presence of elevated instability, which, if recognized, could prove
sufficient for convection capable of lightning. Because this highly
elevated (NAM soundings suggest the LFC is at upwards of 14,000
feet) instability is above a deep layer of convective inhibition,
lifting parcels to this level of the atmosphere is a challenge. If
the LFC should be lower than what models suggest, orographic forcing
may be sufficient to trigger free convection; if not, storms are
less likely, but still possible via another mechanism. The NAM and
GFS are both portraying a lowering of the dynamic tropopause ahead
of the approaching trough. If this materializes, the mass of stable,
sinking air may serve as a wedge to lift air parcels into the
unstable tier of the atmosphere. With the freezing level present in
this unstable layer, a mix of liquid and frozen water droplets would
result - yielding sufficient charge separation for a few lightning
strikes. Given this (low, but not nonexistent) chance for thunder,
along with SPC`s addition of a thunder outlook for the northeastern
third of our CWA, we have decided to include a mention of it in our
forecast for parts of the area.
By mid-morning Wednesday, any remaining convection will have exited
our area to the northeast. In west-southwesterly 500hPa flow behind
the trough, and with a strengthening gradient across the area, a
strong marine push will likely overspread the region with clouds and
result in some drizzle along the coast. However, the next system,
right on the heels of its predecessor, will swing ashore Wednesday
night and cross the area early Thursday. This system is currently
progged to be dry, but will serve to keep the entire area seasonably
cool Thursday with highs in the low 80s across the Willamette Valley
and 60s along the coast. /Bumgardner
.LONG TERM...Thursday night through Monday...In the wake of the
aforementioned low, heights begin to rise Thursday night into Friday
before another low approaches from the Gulf of Alaska. Deterministic
runs of the GFS, Euro, and CMC each depict this system, but differ
considerably on its shape, size, location, and timing of possible
arrival. Interestingly enough, WPC cluster analysis solutions, while
not all the same, are not drastically different from one another -
the general trend being for weak ridging to zonal flow over the
area. The shortwave trough depicted by the deterministic models
might be getting washed out by the cluster analysis trends, but
regardless the chances for seeing precipitation (especially wetting
precipitation) seem low at this time. /Bumgardner
&&
.AVIATION...At 0345Z Tuesday, marine stratus remained over the
south WA/north OR coast and the Willapa Hills. Stratus was also
beginning to push into KONP. Expect stratus to continue along
the coast through 18-19Z Tuesday before scattering out. The
exception to this will be at KAST, where stratus will have the
potential to linger through the day like it has the past couple
of days. That said, model guidance does suggest there will be a
brief break at KAST between 21-00Z before stratus moves right
back in. Confidence is low that this break will actually materialize,
so for now will assume stratus will last through the day since
the overall pattern will be very similar to the past couple of
days.
Similar to last night, stratus will once again push down the
Columbia River into Clark County and the northern Willamette
Valley towards 12Z Tuesday. This should affect KPDX and KTTD, but
is not expected to affect KHIO or KUAO. KSLE and KEUG should also
remain clear tonight. Stratus should scatter out by 16-17Z for
inland locations.
For detailed regional Pac NW aviation weather information, go
online to: https://weather.gov/zse
KPDX AND APPROACHES...Expect marine stratus to return around 12Z
Tuesday with cigs around 1100-1400 feet, before scattering out
around 16Z. -TK
&&
.MARINE...Will continue to see high pressure centered offshore
combine with low pressure will inland to result in a general
northwest to north wind across the waters. Strongest winds will
occur inside of 30 NM and over the central coastal waters this
afternoon and evening. Otherwise, pressure gradients will ease
for the next couple days with winds gusting 15-20 kts, strongest
in the afternoons and early evenings.
Seas are generally expected to remain in the 4 to 6 ft range
with a dominant northwesterly fresh swell component. Choppy seas
can be expected at times, especially during the afternoons and
evenings as wind waves build. /JBonk
&&
.PQR WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
PZ...Small Craft Advisory until 7 AM PDT Tuesday for Waters from
Cascade Head to Florence OR from 10 to 60 NM.
Small Craft Advisory until 11 PM PDT this evening for Coastal
waters from Cascade Head to Florence OR out 10 NM.
&&
$$
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Area Forecast Discussion
National Weather Service Phoenix AZ
410 PM MST Mon Jul 5 2021
.UPDATE...
Updated Aviation
&&
.SYNOPSIS...
Drier conditions will settle into the area, likely persisting
through the majority of the week. Daily isolated storms will still
be likely across the eastern Arizona high terrain, while the lower
deserts will mostly remain dry. Temperatures will warm to a few
degrees above normal for much of the coming week with highs mostly
in a 109 to 112 degree range across the lower deserts. A slight
boost in moisture is likely later this week, but this alone is not
likely to be enough to bring back rain chances for the lower
deserts.
&&
.DISCUSSION...
Latest water vapor imagery reveals drier air aloft overspreading
the Desert Southwest, however conditions remain quite moist in the
lower levels with dewpoints in the 50s and even lower 60s. Total
PWATS are near 1.5 inches in Phoenix but are steadily decreasing.
Meanwhile, RAP streamline analysis indicates the Monsoon High has
taken up residence near the Four Corners, while the 700 mb ridge
is positioned across southwestern Arizona. This is resulting in a
weak north-northwesterly steering flow across the higher terrain
well east of Phoenix, where there is more instability and convection
is more likely to initiate. Consensus from the CAM ensemble
indicates only isolated storms will develop across Gila County this
afternoon, before drifting southward. There is also a very low
probability of an outflow boundary with gusty winds reaching the
Valley this evening.
NBM PoPs remain less than 5 percent across the Valley this evening,
owing to widespread convective inhibition. This is largely due to a
well-defined subsidence inversion around 800 mb evident on the
latest ACARS sounding. Latest HREF depicts debris clouds lingering
overnight, which will likely result in temperatures a few degrees
above normal.
&&
.PREVIOUS DISCUSSION...
Looking at the large scale pattern throughout the coming week, model
ensembles have shifted the positioning of the building ridge.
Currently, the upper level (250/300mb) ridge center is situated just
south of Arizona. There is now better agreement in this ridge slowly
shifting to the northwest late this week while strengthening,
becoming another anomalously strong ridge over the Western U.S.
Previous runs were fairly similar, but there was at least a strong
sign of a moist easterly return flow later in the week. This is
still somewhat true, but a likely stronger ridge and a subtle shift
in the winds will likely only give us a brief window of moisture
return, mostly involving shallow Gulf of California moisture surges
Wednesday into Thursday. After limited storm chances over the
eastern Arizona high terrain through Wednesday, Thursday could
possibly bring a few isolated storms to the south-central Arizona
deserts with the help of the GoC surge, but it is looking much less
likely due to the lack of deeper moisture. Friday is likely to be
similar to Thursday, but NBM PoPs continue to back off on rainfall
chances over the lower deserts (now at 10% for Phoenix, down from
20%). PoPs for next weekend are also considerably lower than the
previous few forecast packages as the shift in the high center to
our west northwest is likely to bring more pronounced northerly dry
flow. We will have to wait and see if the potential moisture return
later this week will be enough for a return of storm chances for
some of the lower deserts.
A warming trend is definitely on the way over the next couple days
as the boundary layer dries out. Highs are still forecast to warm
to around 110 degrees across the western deserts today and then over
the south-central Arizona deserts starting Tuesday. From Tuesday
through the coming weekend, NBM guidance shows little variability in
forecast highs mostly ranging from 109-111 degrees across the
Phoenix area to 110-113 degrees across the western deserts. As the
ridge strengthens later this week, these temperatures will mostly be
dependent on how much boundary layer moisture is present. If we end
up being drier than forecast, temperatures very well could reach
excessive heat levels in some areas. The highest probabilities of
this occurring looks to be during the Friday-Sunday time period when
the ridge is likely peaking in intensity.
&&
.AVIATION...Updated at 2310Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Westerly winds will weaken this evening with speeds falling below 10
kts. Guidance shows easterly winds struggling to take hold overnight.
Chances for convection in Phoenix this evening is low (< 10%) and
model guidance do not support outflows reaching the terminals. West
winds should return quickly be late Tuesday morning. FEW-SCT clouds
aoa 10 kft are forecast through the period.
Southeast California/Southwest Arizona including KIPL and KBLH:
Mostly clear skies are expected through the TAF period. South winds
will be expected at KBLH with NBM showing speeds as high as 12kt.
West winds at KIPL should become SE again Tuesday morning with NBM
showing a few gusts up to 20kt this evening.
&&
.FIRE WEATHER...
Thursday through Monday:
Somewhat drier than normal conditions will generally confine the
threat of storms to the higher terrain north and east of Phoenix.
Strong high pressure affecting the region will also result in
slightly above normal temperatures. Min RH values will generally be
in a 15-20% range over the lower deserts and 20-30% across the
eastern Arizona high terrain. Max RHs will recover into the 35-45%
range for lower deserts locations to 50-60% across the high terrain.
Wind patterns should follow diurnal patterns for much of the period
with daily afternoon gusts to around 20 mph likely.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Excessive Heat Watch from Saturday morning through Sunday
evening for CAZ560-561-570.
&&
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Kuhlman
AVIATION...Smith/18
FIRE WEATHER...Kuhlman/Hirsch
Area Forecast Discussion
National Weather Service Pueblo CO
904 PM MDT Mon Jul 5 2021
.UPDATE...
Issued at 901 PM MDT Mon Jul 5 2021
The Flash Flood Watch has expired. There is still a chance for
some lingering showers this evening, but severe and flash-flood
potentials have dwindled significantly.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 328 PM MDT Mon Jul 5 2021
1) The threat for heavy rain and flash flooding across the burn
scars continues this evening, along with the potential for scattered
strong to severe storms along and west of I-25.
2) More widespread showers and storms are expected across the
eastern mountains and plains on Tuesday, with the flash flood risk
for area burn scars along with the potential for strong to severe
storms also returning.
Showers and thunderstorms continue this afternoon, continuing to
focus over and near the mountains. The main hazard so far this
afternoon has been heavy rain with possible flash flooding across
the burn scars. Radar trends along with short term guidance all are
pointing toward an increase in coverage of storms around the burn
scars here in the near term, and likely persisting through mid
evening. Given these trends, have not made any adjustments to the
current Flash Flood Watch in effect. Still anticipate thunderstorm
development away from the mountains towards the I-25 corridor this
afternoon into early evening, with the potential for some of these
to become strong to severe. Once again, no change in this thinking,
but do think the severe threat may be more isolated. Latest RAP
analysis showing weakening trends with instability and shear, and
with short term guidance indicating this might continue into the
evening. So, while storms will remain possible along the I-25
corridor into this evening, think only a few storms will be strong
to severe.
Overall coverage of showers and storms will diminish by mid to late
evening, with the threat of heavy rain/flash flooding lowering.
However, weak west/northwest flow aloft will remain in place along
with the potential for some weak mid level waves to move overhead.
This may keep the precip development occurring across Lake and
Chaffee counties, but think the intensity of any additional showers
or a few storms will be much lower. So, have not extended the Watch
for this area at this time.
With this northwest flow remaining in place on Tuesday, a boundary
is expected to push south across CO early Tuesday. This setup and
boundary along with a steady and deep push of east northeast winds
will help support thunderstorm development across the plains and
eastern mountains on Tuesday. This support will be in place rather
early in the day, and expect thunderstorm development to be early in
the day across both the mountains and plains. Instability and shear
expected to increase in the afternoon, supporting a risk for strong
to severe storms over much of the plains. Additionally, persistent
and strong focus across the eastern mountains will support another
day of higher potential for burn scar flash flooding.
.LONG TERM...(Tuesday night through Monday)
Issued at 328 PM MDT Mon Jul 5 2021
...On Tuesday, a chance of thunderstorms will be possible over most
of the CWA during the afternoon and evening afternoon and evening,
some of these storms could become severe, especially over the
central and southeast plains.
On Wednesday, slight chance of a thunderstorm during the morning
hours over the far southeast plains. Isolated thunderstorms will be
possible later in the day, mainly during the afternoon, over the
mountains.
On Thursday...a slight chance of thunderstorms will be possible
during the afternoon and evening over the mountains.
On Friday and Saturday, thunderstorms will be possible over the
mountains and plains, with the best chance being over the southern
Sangre de Cristo Mountains, Raton Mesa, and southeast plains in the
evening for both days.
On Sunday and Monday, thunderstorms will be possible in the
afternoon for both days, with a better chance on Monday...
Tuesday...
A weak perturbation in the longwave pattern overhead to the north
coupled by some monsoonal flow around the plateau high with the
upper level ridge in place over the southwest CONUS will allow for
there to be some moderate instability over the area a bring a chance
of thunderstorms over most of the CWA, with a possibility of strong
to severe thunderstorms over the plains. Greatest areas that there
looks to be a severe potential will be over the I-25 corridor and
over the central and southeast plains, due to a weak convergence
boundary and also the possibility of a weak lee-side meso-low
cyclogenesis over the southern I-25 corridor as some models are
indicating. MLCAPE and MUCAPE values are appearing to be highest
over the central and eastern plains, with an area of relatively high
CAPE right along the I-25 corridor of more than 1500 J/kg, although
this is all relatively skinny CAPE, whereas the values of over 2000
J/kg over areas of the eastern plains yield a little more fatter of
a CAPE in the profile sounding, along with some helicities between
150 and 200 m^2/s^-2 showing up on the ARW and WRF models, which
will give this area more of a favorable environment for rotating
updrafts. The NAM 3km does have an area of very strong bulk sheer
with most of this being between 0-3km and values in excess of 55 kts
over the central portion of the I-25 corridor at around 1600L, this
area is just southeast of the Wet Mountains and if this model holds
true, there could also be potentially severe storms forming in this
region as well. Main threat due to the CAPE being more of a skinnier
profile, would be strong downdraft winds, but there could also be
some hail of 1 inch or greater and a very slight chance of a weak
tornado, yet the greater chance of an isolated tornado occurring
would be over the central and southeast plains. Storms are likely to
develop elsewhere and could possibly still become strong to severe,
especially over the southern Sangre de Cristo Mountains and Raton
Mesa area. Burn scars will could also experience flash flooding as
well, yet if there is enough shear in the mid levels, it could help
to prevent the storms from becoming too stationary and hopefully
bring down the risk, yet with heavy rain in a brief period of time
associated with some of these thunderstorms, even the storm not
being stationary could still have an impact. Winds will become
predominantly out of the northeast later over the plains and cooler
as well tomorrow with the trough overhead, with high temperatures
around 5 degrees cooler than the seasonal average for most
locations. Rain showers and some thunderstorms will continue into
the evening hours and overnight for the southeastern portion of the
CWA. Only some clearing will take place further west and lows for
Tuesday night will fall into the mid 50s to low 60s for the plains,
to the 40s and low 50s for the mountain valleys and generally the
40s for the mountains and 30s for the highest peaks.
Wednesday and Thursday...
The upper level ridge axis over southwest CONUS is going to continue
to slightly propagate further west and become squished by a trough
deepening over the northwest in the longwave pattern, this will
allow for relatively cooler and drier air to move in from the west
over the Pacific upstream, and help to dry out of mid level
monsoonal moisture for both of these days and hinder much in the way
of thunderstorm development for both of these days. There will be a
slight chance due to some residual moisture along a weak boundary
associated with the trough downstream for there to be a few morning
shower or thunderstorms over the southeast plains, otherwise only
some isolated thunderstorms will develop during the afternoon and
early evening over the mountains on Wednesday. On Thursday, isolated
thunderstorms will be possible again over the mountains, with the
central mountains having the best chance for this day. The troughing
upstream will enhance the mid-level flow out of the west with an
adiabatically warming downsloping wind, coupled with southerly flow
over the plains, will result in hot and dry conditions for most of
the region and above the seasonal average high temperatures for most
locations on Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 328 PM MDT Mon Jul 5 2021
VFR conditions will be predominant throughout the forecast period
for all TAF sites, CIGs will remain fairly high based although they
could come down a bit in SHRA or TSRA in the vicinity of all
terminals for the rest of this evening. Keep in mind that
outflows can also cause wind shifts to occur in the vicinity of
anyone of these terminals. Some of the higher wind gusts in the
lower levels near KALS later in the day could also result in some
light to moderate CAT near the surface.
Winds at KALS will be primarily light and variable and then
become NW`ly and then back to the NE and increase a little with
some gusts as high as 22 kts, they will weaken later in the
evening and become East to SE`ly and return to light and variable
by tomorrow morning. At KCOS and KPUB, SE`ly winds will
eventually shift out of the NW later this evening and then remain
from that direction throughout the rest of the forecast period.
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GARBEROGLIO
SHORT TERM...RODRIGUEZ
LONG TERM...STEWARD
AVIATION...STEWARD