Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/02/21

Area Forecast Discussion

National Weather Service Denver/Boulder CO

 855 PM MDT Thu Jul 1 2021

.UPDATE...
Issued at 855 PM MDT Thu Jul 1 2021

After a very active day from a hydro point of view (we issued 8
flash flood warnings and 21 urban and small stream flood
advisories), the atmosphere has stabilized significantly. Latest
radar and GOES-16 satellite imagery have a broken line of
convection from western Logan to eastern Morgan to northwest
Elbert County. There is no development upstream of our area
either. The convection in eastern Colorado is producing some
lightning and brief heavy rain, though we do not expect any more
hydro highlights. It has been slowly weakening but expect the
convection to keep going eastward until about midnight before
weakening/diminishing and/or moving out of our CWA. With how
stable the atmosphere is behind this line, we ended the flash
flood watch ahead of schedule. Overall, the HRRR and HREF did a
nice job with the convective evolution going on right now, and
both weaken the convection by midnight and there doesn`t appear to
be any redevelopment along or west of I-25. Updates to the
forecast were generally minor, lowering min temps just a tad given
latest trends and updating PoPs to reflect current trends, namely
highest east of Fort Morgan to Agate, very low west of there, and
tapering off after midnight across far eastern Colorado. Patchy
fog may develop in Weld County where 2-4 inches of rain fell in
the Greeley area. We`ll keep an eye out to see if it becomes
widespread enough for a highlight.

&&

.SHORT TERM...(This evening through Friday)
Issued at 245 PM MDT Thu Jul 1 2021

Heavy rain and flash flooding will continue to be a concern
across the area this evening, with a focus along the I-25 corridor
from the Wyoming border towards Castle Rock. The recent slow
moving/backbuilding storm over Greeley was able to produce upwards
of 3-4.5 inches of rain within about 2 hours, which has produced
flash flooding across the city.

Not much was changed to the grid forecast for the rest of the
afternoon. Outflow from previous storms to the east of the metro
has worked all the way into the lower portions of the Foothills,
with convective activity gradually shifting eastward along with
it. An 18z sounding from Colorado State University near FNL had
MLCAPEs near 1750 J/kg... along with PWATs near 1.20 inches... and
very weak low/mid-level flow. While instability will diminish
with time, heavy rainfall will be likely until convection
diminishes just before midnight.

Tonight will see just a few scattered showers around after
midnight with continued moisture sitting around the area. There
could be some patchy fog in a few spots, especially where the
better rains fall this evening.

Conditions are largely similar tomorrow, but rainfall should be
more focused on the higher terrain. It looks like tomorrow will be
a bit warmer and drier, with a little less instability. The main
difference will be less of an upslope component to the low-level
wind, with slightly improved flow aloft. The end result should be
scattered storms with heavy rain, but with less coverage and less
intense rainfall rates. Most of our concerns will be focused on
the burn areas.

.LONG TERM...(Friday night through Thursday)
Issued at 245 PM MDT Thu Jul 1 2021

The upper level ridge pushed northwest out of the desert southwest
and into the four corners region through Friday evening with
subsidence persisting through the holiday weekend. This will help to
bring daytime temperatures closer to seasonal normals and slightly
above with highs in the upper 80s to lower 90s by Sunday. Models
show moisture moving in under the ridge with PWat values increasing
to close to an inch across the eastern portions of the state. Lapse
rates will improve by the afternoon hours with ML CAPEs from 600 to
850 that will provide the ingredients for some afternoon convection
both Saturday and Sunday. Flow aloft will be slightly faster than
previous days which will aid in keeping the storms moving but there
is still some concern for flooding under the stronger storms through
the weekend.

By Monday the upper ridge extends across most of the southwest
region with continued monsoon influence providing for elevated PWat
values. High temperatures will be above seasonal normals on Monday.
Models show a weak shortwave embedded in the flow aloft Monday night
into Tuesday with increased coverage of storms for Monday late
afternoon and evening. This will push out on Tuesday leaving
slightly cooler temperatures with highs dropping back into the 80s
on Tuesday. There is some slight model differences within the EC and
GFS suites that has surface flow a tad more east to northeast on the
EC creating some enhanced lift and more widespread storm coverage
Tuesday afternoon and into the evening. Wednesday will see increased
influence from the upper ridge with dry conditions expected and
temperatures reaching back into the 90s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 855 PM MDT Thu Jul 1 2021

Convection is well east of the terminals and we do not expect any
redevelopment tonight. Winds in general will remain light
throughout tonight, out of the south at APA and DEN and 10 kts or
less. Light and west at BJC. We are looking at the potential for
radiation fog to develop in Weld County where heavy rain occurred
today. The fog may make a run at DEN. It`s not a typical fog set
up for DEN, thus for now we are handling with a VCFG. The fog, if
it develops, and if it makes a run at the airport, should only
last a few hours, roughly 5-8AM or so.

By midday Friday winds should be southeast at the terminals and
we expect TSRA to develop near the terminals after 3 or 4 PM, and
possibly impact them like they did today, though the rain rates
are not expected to result in reduced VIS like they did today. We
expect variable wind gusts 20-30 kts associated with convection
but it`s too early to include in the TAF right now.Still

&&

.HYDROLOGY...
Issued at 855 PM MDT Thu Jul 1 2021

Elevated flash flooding danger is also expected tomorrow across
the burn areas. Moisture remains with storm motions still fairly
slow, and heavy rainfall will be possible during the afternoon
hours.

Flash flood threat will turn limited for the weekend with some
storms possible over the higher terrain for both Saturday and
Sunday afternoons.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Schlatter
SHORT TERM...Hiris
LONG TERM...Bowen
AVIATION...Schlatter
HYDROLOGY...Hiris



Area Forecast Discussion

National Weather Service Boston/Norton MA

 958 PM EDT Thu Jul 1 2021

.SYNOPSIS...
Areas of showers and scattered thunderstorms will produce
locally heavy rain tonight. Unsettled but much cooler Friday
into the Fourth of July weekend. Scattered pop-up showers each
day in the holiday weekend but not a washout in any one area.
Brief dry weather Monday with a warm front arriving Monday
night. Heat and humidity returns on Tuesday, ahead of a cold
front that offers a greater chance for thunderstorms either
later Tuesday or Wednesday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
10 PM update...

Widespread showers with locally heavy rain moving across SNE
this evening in response to large scale forcing within the
right entrance region of the upper jet and deep moist
thermodynamic profile. PWATs 1.7 to 2 inches with deep warm
cloud depths providing a favorable environment for warm rain
processes and efficient rainfall rates.

There are potentially two areas of concern for heav rainfall and
localized flooding. One area near the Mass Pike where there are
somewhat heavier rainfall rates. Weak front across northern MA
providing some low level convergence and there is enough
instability with MUCAPES around 500 J/kg to enhance rainfall
rates. HRRR and 3km NAM target this area for very heavy rainfall
through 06z. Amounts of 2-4 inches may be overdone given
current rainfall rates but could see locally up to 2 inches with
some urban and poor drainage street flooding. Rainfall rates
likely to diminish after 06z in the interior.

Second area is across SE New Eng, particularly over the
Cape/Islands as convective cluster along the nose of a
developing low level jet lifts NE along the coast through the
overnight period with a few t-storms enhancing rainfall rates.
The low level jet moves east of New Eng late tonight.

Winds will shift to the northeast and increase late tonight as
the cold front gradually moves through. This will result in
cooler temperatures. Anticipating overnight low temperatures in
the 60s across the region, but there may be a few upper 50
degree readings along northern portions of the region.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Highlights

* Fairly widespread showers across the region Friday morning
  becoming more scattered in nature during the afternoon. Scattered
  showers persist Friday night.

Trough digs into the eastern Great Lakes and Mid Atlantic on Friday
and Friday night. Should see a frontal boundary to the south as the
cold front moves offshore. Will have a surface trough extend over
southern New England on Friday from the departing broad low. Another
low rides along the frontal boundary to the south Friday night.

Friday...

Will still have a 1.5-2 inch PWAT plume over a decent portion of
southern New England Friday morning, but with the low lifting out
this plume will push offshore during the afternoon. This keeps us in
the 1-1.5 inch range for the afternoon. Still have decent warm cloud
layer depths between 3-4 km. Thinking there still could potentially
be some heavy rain in a few showers especially earlier in the day
given the proximity to the broad low. Cannot be ruled out during the
afternoon, but forcing becomes a bit more limited and activity
should be more scattered in nature.

Given the track of the low am anticipating a non-diurnal temperature
trend. Should see the warmest readings across the region during the
morning with temperatures dropping during the day. This is all due
to the northeasterly flow due to the low moving through. Aloft will
have cold air advecting in 7-10 degree Celsius 925 hPa air!
Temperatures will stay generally in the 60s, but will drop into
the 50s for some spots during the afternoon.

Friday night...

Expecting another wave of low pressure to ride along the frontal
boundary that is offshore. Given the persistent onshore flow, upper
level forcing and 1-1.5 inch PWATS could have some scattered shower
activity. Will still have persistent NE flow keeping 925 hPa
temperatures in the 8-10 degree Celsius range. The result will be
low temperatures bottoming out in the 50s across southern New
England.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Highlights:

* Unsettled and generally cloudy Fourth of July weekend, periods of
  pop-up showers but not a washout. Well below normal temps Saturday
  (upper 50s-low 60s!), and just less below-normal for the Fourth of
  July holiday.

* Warm front late Mon/Mon nite brings scattered showers, possible
  garden variety t-storms. Turning more humid Mon nite.

* Hot and humid Tuesday with mid/upper 90s heat indices; somewhat
  cooler and a little less humid Wed. Possible thunder either Tues
  or Wed depending on a cold front.

Details:

Fourth of July Weekend:

The story for the Fourth of July Weekend is the generally unsettled
weather conditions and cooler than normal temperatures for Saturday
and the Sunday Fourth of July holiday. In terms of temperatures, the
most anomalous of the two days is Saturday and for most highs may
struggle to reach the mid 60s with upper 50s to lower-mid 60s
common. Possible we could approach record low high-temperatures on
Saturday July 3rd, with temperatures more reminiscent of mid-May
than early-July. Looking at Fourth of July holiday climatology for
our four climate sites (Boston, Providence, Worcester and
Hartford/Windsor Locks)...with forecast Fourth of July high
temperatures in the upper 60s to mid 70s, it appears we are in
store for one of the coolest Fourth of July holidays since 2015; the
exception being Boston which recorded a high temperature of 70
on the Fourth just last year in 2020.

So for Saturday: upper low and associated cooler pocket of air aloft
initially near the lower Hudson Valley to migrate slowly NE across
Southern New England. Periods of light pop-up showers with better
coverage during the late-morning to mid/late afternoon will dot the
landscape and while generally unsettled, not expecting a washout
with limited QPF. That said, plenty of low-level moisture trapped
underneath a shallow inversion and when combined with northeast
onshore winds, it sets the stage for a cool July 3rd with lots of
low clouds around. Have lowered temperatures significantly compared
to the warmer NBM guidance, essentially a blend of the raw GFS and
NAM. Again looking for highs upper 50s to mid 60s for most -
definitely a long sleeve and light jacket sort of day! Periodic,
intermittent showers into Sat night, though still a rather cool
night with lows mid 50s to low 60s.

For Sunday/Fourth of July: Upper low will continue to pull away with
a renewed risk (Chance) for pop-up light showers during the morning
to early-afternoon. Initial overcast, but better odds for some
breaks in clouds during the second half of the day and night as
winds turn more light northerly/northwesterly. Won`t be fully clear
both day and night, but enough breaks for highs upper 60s to mid
70s; lows upper 50s to lower 60s. It may not be an ideal beach day,
but the prolonged onshore flow and related leftover swell from the
weekend, it`s possible there may be a need for either a rip current
statement or (less probable) a high surf advisory on Sunday
and/or Monday for east-facing coasts.

Monday:

Mid/upper flow turns more zonal by Mon, with modest height rises for
Mon afternoon. A warm front comes in for later Monday into Monday
night, associated with summerlike 850 mb air (mid-teens Celsius) in
the warm sector. This should bring a risk for showers, possibly a
rumble of thunder given some elevated instability. Highs low to mid
80s, but Monday night looks to turn muggy/humid with lows mid/upper
60s with similar dewpoints. As mentioned, we may need to consider
either a rip current statement or (less likely) a high-surf advisory
for the east-facing coasts.

Tuesday and Wednesday:

Hot and humid Tuesday (dewpoints back to the muggy mid 60s to lower
70s), though not to the extent of the stretch of hot and humid
weather experienced recently. That said, heat indices may approach
the mid to upper 90s on Tuesday depending on how much warming we do
get; it looks like we`ll fall short of one-day Heat Advisory
criteria and lower Heat Indices on Wed also make the consecutive 95+
heat index criteria less likely to be achieved as well. Nonetheless
still quite hot for Tuesday. This occurs ahead of a cold front, the
timing of which varies across most of the NWP. Potential exists for
heavy SHRA/TSRA depending on the timing. Kept a rather generic/broad
brushed Chance PoP both days until better agreement exists on the
timing of the frontal passage.

Highs Tues into the upper 80s lower 90s, with lows around 70 except
mid-upper 60s for the Berks. Somewhat cooler mid to upper 80s on
Wed, lows in the 60s.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels.

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

00z TAF Update:

Tonight: High confidence in trends/categories, moderate on
timing.

VFR/MVFR initially. General idea is for deterioration to IFR-
LIFR as sfc low moves ENE through CT-RI and SE MA through
overnight, though the timing is still no better than moderate
confidence. Initial rains now across western MA/northern CT
will spread eastward thru 03z for areas north of I-95, with VFR-
MVFR visby rains continuing thru overnight. Period of heavy
SHRA/embedded TSRA at PVD and South Coast/Cape and Islands
between 01-04z, with brief IFR to local/brief LIFR visby
possible. Left as just a 3 SM SHRA but will tempo lower category
visbys. Winds will back to E to NE/N mainly N/W of I-95, but
remain SW across Cape and Islands until a shift to NW/N around
pre-dawn.

Friday...Moderate confidence.

Widespread MVFR/IFR conditions. Showers likely at times during
the morning, but more scattered in nature during the afternoon.
NE winds at 5-10 kts. Gusts of 15-25 kt over E and NE MA with
the highest gusts over NE MA.

Friday night...Moderate confidence.

Widespread MVFR/IFR conditions across southern New England.
Scattered rain showers continue with winds out of the NE to NNE
at 5-10 kts. Could see some 15-20 kt gusts along the coastal
plain.

KBOS TAF...High confidence in trends. Moderate confidence on
timing of lower ceilings moving in.

KBDL TAF...High confidence in trends. Moderate confidence on
timing of lower ceilings moving in.

Outlook /Saturday through Tuesday/...

Saturday: Mainly VFR, with areas IFR possible. Breezy. Chance
SHRA.

Saturday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA.

Independence Day: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.

Sunday Night: VFR. Slight chance SHRA.

Monday through Monday Night: VFR.

Tuesday: VFR. Breezy. Slight chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels.

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Have hoisted a Small Craft Advisory for the Outer Waters, Cape
Cod Bay, Ipswich and MA Bay from Friday AM through Friday night.

Tonight...High confidence

Winds out of the S/SW across the southern waters at speeds of
10-15 kts. Expect the eastern waters to start off with light
winds, but shift to the E/NE late tonight and increase to 10-20
kts. Could have some gusts up to 20 kts toward daybreak. Seas
2-4 feet. May see some 5 ft seas across the outer southern
waters toward daybreak. Numerous showers with perhaps a few
embedded thunderstorms.

Friday...High confidence

Will see a period of NE winds at 15-25 kts across the eastern
waters. Gusts of 25-30 kts and there could be a few brief gale
force gusts. The southern waters will see winds shift to the
northeast as a cold front pushes through. Wind speeds increasing
to 10-15 kts late in the afternoon across the southern waters.
Seas building to 6-9 ft across E/NE waters and 3-5 ft for the
southern Waters. Have hoisted a SCA, but held off from high
surf advisories given the cool temperatures and scattered rain
showers. Seas 3-7 feet Friday night with NE winds at 10-20 kts.

Outlook /Saturday through Tuesday/...

Saturday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers.

Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance
of rain showers.

Independence Day through Sunday Night: Winds less than 25 kt.
Seas up to 5 ft. Slight chance of rain showers.

Monday through Monday Night: Winds less than 25 kt. Areas of
seas approaching 5 ft.

Tuesday: Winds less than 25 kt. Seas up to 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 11 AM Friday to 5 AM EDT Saturday
     for ANZ231.
     Small Craft Advisory from 8 AM Friday to 8 AM EDT Saturday for
     ANZ250-251-254>256.

&&

$$
SYNOPSIS...BL/Loconto
NEAR TERM...KJC
SHORT TERM...BL
LONG TERM...Loconto
AVIATION...BL/Loconto
MARINE...BL/Loconto



Area Forecast Discussion...UPDATED

National Weather Service Gray ME

 1120 PM EDT Thu Jul 1 2021

.SYNOPSIS...
A cool and wet period late this week with low pressure
amplifying south of us tonight, bringing widespread rains to the
forecast area into tomorrow morning. The system departs east
tomorrow night and gives a brief dry break in the action,
however a broad trough will persist across Northern New England
through the weekend, bringing cool conditions and showers at
times. The trough departs on Monday, and ridging returns early
next week with warmer weather. Midweek next week the forecast
become less certain, but above normal temperatures appear
increasingly likely.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
1120 PM Update: Update to Marine only...see below.

9 PM Update: Have lowered temperatures where rainfall has been
steadiest in line with evening observations. Otherwise...
forecast largely in good shape with decent rainfall rates now
reaching southern NH /0.1-0.2" per hour/. Low pressure near New
York City is moving ENE in line with current pressure fall
analysis with rainfall area expanding on it/s northern flank.
00Z GYX RAOB showed 1.45" PWATs with a deepening ENE flow in the
boundary layer. Rain will continue to expand northward overnight
with a few more hours of convective elements possible before the
deepening cold dome under strengthening NE flow will erode
remaining instability.

530 PM Update: Given increasing confidence in area of widespread
precipitation tonight..boosted PoPs in line with recent time
lagged HRRR and short term model consensus. Otherwise...going
forecast in good shape.

Previous discussion below...

The final nail in the coffin of our recent heat wave is
hammered down tonight as a backdoor cold front arriving from the
northeast partners with amplifying low pressure /a summertime
Nor`easter/ to the south... bringing widespread rains to the
forecast area starting tonight and lasting into tomorrow.
Temperatures will cool into the 50s to near 60 tonight.

A surface trough draped broadly over the forecast area is
already showing signs of organizing near the Mid-Atlantic coast
with rain picking up in coverage and intensity over southern New
England. As low pressure crosses Cape Cod tonight, rain will
overspread most of the area from the southwest with totals
ranging from AOB a quarter inch near the international border to
about an inch for southern zones. Hires guidance continues to
home in on a deformation zone draped roughly from Sullivan Co
NH across to the Midcoast... which would lead to locally higher
rainfall totals. Am not immediately concerned about flooding
issues with this deft band since lapse rates are poor which
will prevent convective rainfall rates... however if moderate
rainfall sits over the same area for a couple/few hours it could
lead to some ponding and poor drainage issues.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Friday wraps up the work week with some weather-whiplash when
compared to how it started. A summertime Nor`easter passes
through the Gulf of Maine tomorrow with rain, overcast, and
temperatures limited to the 50s and 60s. Steady rain over the
coastal plain near the low pressure center crosses during the
morning with more scattered activity underneath cyclonic flow
later in the day... the latter of which will taper off to
isolated showers overnight. Northeast winds continue into
tomorrow night with temperatures cooling into the mid-50s... to
as cool as the mid-40s for northern valleys, especially if they
can clear out.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Overview...The long term begins with widespread showers on Saturday
and Sunday, although Saturday looks like the wetter of the two. A
drying and warming trend begins on Monday with the next significant
chance for precipitation coming toward mid-week when a cold front
may cross through New England.

Impacts...No significant impacts are anticipated at this time...but
will continue to monitor temperatures and heat indices on Tuesday
for possible heat-related headlines for southern areas.

Forecast Details...The holiday weekend begins with an upper level
trough just to our west and a broad baroclinic zone with weak areas
of low pressure along it over the western Atlantic. In between,
plenty of cloud cover and a good chance for showers are on tap for
Saturday. Highs will remain similar to Friday, ranging throughout
the 60s. By Sunday morning, the trough passes overhead and looks to
be centered east of the CWA...but wraparound showers will be
possible on the backside of the trough on Sunday. Temperatures will
be warmer though, rising into the mid 60s to lower 70s.

An upper level ridge begins to build into the northeast U.S. on
Monday, bringing drier conditions and warmer temperatures; highs on
Monday will be closer to normal, ranging from the upper 70s to lower
80s. By Tuesday morning, the global models are in better agreement
in their latest runs that a cold front will drop south of out of
Canada on Tuesday, possibly bringing showers and thunderstorms to
the region Tuesday afternoon and evening ahead of it. Tuesday looks
like the warmest day of the period ahead of the front with highs
ranging from the mid 80s to near 90. Current apparent temperature
grids show some southern areas with an hour or two of heat indices
at 95 degrees...so will continue to monitor the potential for heat-
related headlines Tuesday afternoon. The front does not arrive until
Wednesday morning, allowing precipitation chances to continue into
Tuesday night and Wednesday.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Short Term...

Summary: Low pressure tracking southeast of the region will bring
deteriorating conditions tonight in rain before rain tapers to
showers during the day Friday with some improvement to
conditions by afternoon and evening before some fog/stratus
redevelop Friday night.

Restrictions: CIGS deteriorate to IFR for all but HIE overnight
(MVFR there) with some LIFR possible for coastal terminals with rain
at all sites. Rain tapers to showers with improvement to MVFR for
the day on Friday. Confidence decreases Friday night with
continued gradual improvement likely...but some potential for
MVFR stratus to continue through the night.

Winds: North/northeasterly winds strengthen to 10kts overnight
before strengthening to 10g18kts for the day on Friday.  Winds from
the north and northeast continue Friday night around 5kts.

Lightning: Very low potential for lightning through midnight for LEB-
PWM-CON-MHT-PSM...with no thunderstorms beyond this through Friday
night.

LLWS: There is some potential for 2kft winds to increase to 30+ kts
from the northeast in the 06-14Z timeframe...but confidence in this
occurrence remains too low to include in the current TAFs.  No LLWS
expected Friday afternoon and night.

Long Term...Widespread MVFR conditions on Saturday in showers
and low ceilings. Some improvement likely on Sunday, especially
for inland terminals, but showers with brief MVFR restrictions
remain possible. Widespread VFR conditions look likely by Sunday
night and continue through the remainder of the period.

&&

.MARINE...
Short Term...

1120 PM Update: With recent HRRR runs as well as new 3km NAM
continuing to support gales over the outer waters with support
from other high res models...will upgrade the outer waters to
gale warnings at this time and add Penobscot Bay to the SCA. Do
not foresee the need for additional adjustments.

9pm update: Mesoscale guidance continues to slowly increase
northeasterly wind expectations overnight with gales
increasingly likely over the outer waters towards daybreak. Have
boosted winds some and added Casco Bay to the SCA given the
trend...but will continue to watch the evolution of the surface
low before making any upgrades. Did mention gale potential in
the updated Hazardous Weather Outlook.

Previous discussion below...
Low pressure amplifies and approaches from the
southwest tonight with increasing northeast winds. Winds over
the outer waters will increase to 10-20 kts sustained with
frequent wind gusts to 30 kts. There is a small chance that Gale
Force gusts will be realized several miles from shore, but
without the confidence to upgrade to gales... if this were to
occur, this would be during the late Friday morning time frame
and be accompanied by rain. Seas will come up to 4-6 ft near
shore during this time, and will approach 10 ft for a brief time
well out over the waters. Winds will back down but remain out of
the northeast tomorrow night although seas will remain elevated
into Saturday.

Long Term...Showers will be possible Saturday and Sunday with low
pressure passing near or over the Gulf of Maine. Northerly winds
are expected through the weekend before becoming southerly
early next week.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory until 6 PM EDT Friday for ANZ151-153.
     Gale Warning until 6 PM EDT Friday for ANZ150-152-154.

&&

$$

NEAR TERM UPDATE...Arnott
AVIATION...Arnott
MARINE UPDATE...Arnott



Area Forecast Discussion

National Weather Service Phoenix AZ

 432 PM MST Thu Jul 1 2021

.UPDATE...Updated Aviation Discussion.

&&

.SYNOPSIS...
Scattered showers and thunderstorms will be common over the
higher terrain and more isolated on the lower elevations the rest
of the week. Gusty winds with localized blowing dust, and
localized heavy rain/flooding will be the main impacts. A slow
decline in storm activity begins by early next week, but daily
storm chances over the eastern Arizona high terrain should persist.
Temperatures will be near normal the rest of this week before
increasing slightly early next week.

&&

.DISCUSSION...
Convection today developed earlier than it did yesterday, by 9:30
AM across the northern AZ high terrain, White Mtns, and in
southeast AZ. However, for the most part, storms have been less
intense. More so, the coverage of strong/marginally severe storms
have been less. One factor may be slightly lower CAPE values seen
on 12Z morning soundings and RAP mesoanalysis. Steering flow is
still very week with 850-300 mb mean winds analyzed around 5-10
kts, so storms have been nearly stationary. PWAT values have
fallen slightly, but mixing ratios remain near 10-11 g/kg, so
storms have still been efficient rain producers with rain rates
upwards of 0.5-1.0"/hr. Flooding impacts over very localized
terrain areas will be possible with any storms that experience an
extended resonance times over one area before dissipating. DCAPE
is also notably lower today across southeast AZ, so the chance for
strong downburst/outflow winds is lower today in Gila and Pinal
county. HREF probability of >35 mph winds is around 20-30% chance.
Wind impacts and blowing dust potential will be slightly higher
out in the Kofas area of Yuma and La Paz counties, where DCAPE
values are higher.

While convection should dissipate after sunset, a weak inverted
trough moving northwest out of Sonora Friday morning may generate
isolated to scattered ACCAS showers. Most CAMs favor progression
of the wave, and best shower chances, through portions of
southwest AZ and southeast CA, but coverage could extend up into
south-central AZ. Forecast soundings in the Yuma area Friday
morning support embedded thunder chances as well, with minimal
elevated CAPE. Any stronger shower could produce gusty downburst
winds.

.PREVIOUS DISCUSSION...
For Friday, there are signs of a decent moisture push out of
northern Mexico early in the morning with some potential shower
activity moving into southwest and portions of south-central AZ.
This may be partially due to the inverted trough slowly moving
westward along the border, but also possibly a reflection of the
increasing broad southeasterly flow ramping up across the region
as the upper level high center shifts into the Four Corners area.
Low level mixing ratios do not really increase all that much on
Friday, but the higher values do spread westward to the Lower CO
River Valley. The HREF does show a slight increase in storm
activity for Friday across southeast AZ and the high terrain east
of Phoenix as well as overall MUCAPEs through south- central
Arizona. The slight uptick in moisture and instability on Friday
should result in a bit better chances of storms across the south-
central AZ deserts, but weak winds aloft and a very weak
southeasterly steering flow would likely again limit storm
longevity.

Storm chances will remain over the upcoming weekend with both days
showing fairly plentiful moisture, possibly even too much moisture
aloft resulting in possible issues with extensive cloudiness and
the lack of instability. GEFS shows PWATs increasing to around
1.75" by Saturday morning, likely due to a deepening
southeasterly fetch of moisture out of northern Mexico. Models
show the upper level ridge is likely to remain parked over
northern AZ over the weekend with very weak flow aloft across
southern Arizona. This scenario could mean we will be quite active
on one or both (unlikely) of the days, but it may also just result
in modestly unstable, but fairly capped environment.
Afternoon/evening storm chances will likely depend on the amount
of leftover clouds from the previous night/morning and if there is
any help from possible disturbances/inverted troughs. If there
ends up being plentiful moisture, storm threats are likely to
transition more toward heavy rainfall and localized flooding (as
long as instability is present). After near normal temperatures
through Friday, temperature guidance for Saturday and Sunday shows
a much higher spread. Highs are still most likely to reach near
normals over the weekend, but due to the higher potential for
clouds and storms there is definitely more room for highs barely
making it to 100 degrees in some areas.

A subtle southward shift in the position of the upper level high
center looks likely for early next week and this should result in
diminishing moisture and lower storm chances by Monday or Tuesday.
As of now, the first half of next week will favor storm chances
over the eastern Arizona high terrain with limited chances over
the lower deserts. Temperatures for the first half of next week
are also likely to creep upward slightly with fairly high
(40-60%) probabilities of the western deserts reaching 110 degrees
again, while Phoenix`s probability of reaching 110 degrees mostly
stays below 30%.

&&

.AVIATION...Updated at 2330Z.

South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Westerly to northwesterly winds will predominate across most of
the TAF sites through this afternoon with speeds reaching 8-12 kts
and occasionally gusting to 18-22 kts. There is less thunderstorm
activity today compared to previous days, with diminishing chances
for any storms within the terminal area (10-15%) through this
evening. However, the few distant thunderstorms that are out there
still have the potential for sending outflow winds that could
cause abrupt wind changes. Right now, one boundary is being
tracked east of KIWA but latest radar trends indicate this
boundary weakening and unlikely to reach any of the terminals.
Otherwise, a few periods of southerly to variable winds are
possible tonight a few hours after sunset as the overnight
easterly winds become predominate.

For tomorrow, there is a low chance for isolated thunderstorms
south of the Phoenix area early Friday morning, but current
forecast does not have this impacting the Phoenix area. Winds
will shift westerly again by the early afternoon as guidance
trends indicate an uptick in thunderstorm development in the
vicinity between 00/04z with the threat for multiple outflow
boundaries and wind shifts.

Southeast California/Southwest Arizona including KIPL and KBLH:
There are no major aviation weather concerns as convection should
remain east of KBLH and south of the US/MX border. Any outflow
winds from these storms will likely reinforce the predominate
winds. At KIPL, south-southeasterly winds will predominate through
the forecast while southerly winds will remain at KBLH.

&&

.FIRE WEATHER...
Sunday through Thursday:
High pressure is expected to become centered over Arizona over the
weekend. A slow decline in atmospheric moisture is also
anticipated to begin by early next week. Thus, the best potential
for storms with locally heavy rain looks to be this weekend.
Otherwise, a familiar Monsoon season pattern will be in place with
storms primarily focused over the higher terrain producing
outflows that spread to the lower deserts and in turn generate
isolated new storms. Temperatures will start off near normals
followed by slight warming early next week. Min RH values will
generally be in the 20-30% range through Sunday before decreasing
to 15-25% on Tuesday. Max RHs will be 40-60% for most areas
through Monday morning before decreasing to 30-50% starting
Tuesday. As the moisture decreases, temperatures will rise
slightly, with highs around 110 degrees by early next week. Apart
from thunderstorms, wind patterns will follow familiar diurnal
patterns.

&&

.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

DISCUSSION...Benedict
PREVIOUS DISCUSSION...Kuhlman
AVIATION...AD
FIRE WEATHER...Benedict/Kuhlman