Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/19/22
Area Forecast Discussion
National Weather Service Boston/Norton MA
1013 PM EDT Sun Sep 18 2022
.SYNOPSIS...
A few showers or an isolated thunderstorm possible into this
evening ahead of a backdoor cold front. This front will stall
across southern New England Monday with a sharp temperature
gradient across the region and numerous showers and scattered
thunderstorms developing during the afternoon, especially
across the interior. Unsettled weather pattern continues
Tuesday, then dry and warmer conditions return Wednesday.
Another round of showers and thunderstorms is possible Wednesday
night into Thursday ahead of a cold front, followed by blustery
and much cooler weather Friday. A gradual moderating trend is
expected next weekend.
&&
.NEAR TERM /THROUGH MONDAY/...
1015 PM update...
Northern stream short wave exiting southern Quebec and entering
northern New England, triggering scattered showers and isolated
thunderstorm across northern MA and the adjacent coastal waters
this evening. This short wave is associated with a backdoor
front that just entered northeast MA, with a wind shift to the
northeast at BVY and LWM. This boundary will drive to the
southwest overnight, as the short wave continues to move ESE. As
the short wave move east of our longitude, showers and isolated
thunder will shift offshore overnight.
Mild overnight with lows in the 60s and humid out ahead of the
backdoor front, with slightly cooler and less humid behind the
front later tonight across northeast MA.
Given dew pt in the 60s overnight across CT/RI and southeast MA,
can`t rule out some patchy fog overnight.
&&
.SHORT TERM /MONDAY NIGHT/...
Highlights
* Showers and thunderstorms possible across southern New
England. Isolated strong to severe storms possible across
western MA/CT during the afternoon/evening.
* Any remains storms taper off Monday night, but there still
could be some spotty showers heading into Tuesday.
A neutrally tilted trough over the central Great Lakes lifts
into the eastern Great Lakes/Quebec and becomes slightly
negatively tilted. This trough becomes somewhat cutoff as it
lifts into New England late on Monday. Will still have the
backdoor cold front stalled over the region for much of Monday.
Anticipate a low to develop and ride along this boundary later
on Monday into Monday night. This push the backdoor front
through the rest of our region.
Main concern in the forecast for this period is the threat for
isolated strong to severe thunderstorms across far western
portions of our forecast area. Deep layer shear in the 0-6 km
layer increases to 30-45 kts. Should see roughly a few hundred
to perhaps 1000 J/kg of MLCAPE within the warm sector. The key
especially across western areas is where the backdoor cold front
has moved through. On the cool side of the front some storms
are possible, but should remain elevated in nature. May still
have some lingering stratus over the cool side. Can see this in
the low level lapse rates of 6-8 Celsius mainly across
CT/western MA. Per usual mid level lapse rates look quite poor.
Think that the SPC latest Day 2 Outlook area really highlights
the risk area well. Will have to keep an eye on if storms stay
together as they move into the cool side of the front as the
last 3 runs of the NCAR HRRR Neural Network Convective Forecast
still indicate a low risk of a wind hazard. Main risks are
damaging wind gusts and hail. May see some heavy downpours at
times as well as PWATs rise to 1.5-1.75 inches along with some
extra lift due to a 25-35 kt SW low level jet late in the day.
Timing may be another issue as the activity from NY moves in
late in the day, so instability may wane as activity moves in.
Guidance has pushed back the onset timing a bit in the latest
runs, so have reflected this in the forecast.
Confidence at this point is low to moderate when it comes to the
temperature forecast. The location of the backdoor front along
with where the stratus is socked in. At this point confidence is
highest across the CT River Valley in temps along with eastern
MA. Less certain across central MA/RI. At this point think highs
range from the mid 70s to low 80s within the warm sector and 60s
to low 70s on the cool side of the front.
Still may see some lingering spotty rain showers late Monday
into early Tuesday with the cool cutoff moving into northern New
England. Low temps range from the mid 50s to the mid 60s heading
into Tuesday.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights...
* A few lingering showers and thunderstorms Tuesday.
* Pick of the week on Wednesday, before a strong cold front brings
the chance for strong/severe storms Thursday.
* Coldest air of the season so far arrives Friday-Saturday.
Temperatures moderate towards Sunday.
Details...
A neutral tilt mid level trough should pass by our region Tuesday,
leaving our region in a brief lull ahead of a more potent mid level
trough that should arrive sometime Thursday into Friday. This second
mid level trough will one of the main factors in a significant
cooldown late this week into this weekend.
At the surface, a weak low pressure move offshore Tuesday morning,
dragging the remnants of the backdoor front with it. A little bit of
a warm-up Wednesday, before the arrival of a stronger cold front
Wednesday night into Thursday. High pressure should dominate our
weather late this week into next weekend.
Precipitation-wise, looking at a risk for showers Tuesday, mainly
across the interior. Turning drier Tuesday night into Wednesday,
before shower and thunderstorm chances increase late in the day
ahead of an approaching cold front. Will need to monitor the
potential for strong to severe thunderstorms. At this time, thinking
that not all the ingredients will be in place for severe
thunderstorms, but the timing could change to make this more of a
possibility. Turning drier into Thursday night, which continues
through next weekend.
Temperatures should start out near to slightly above normal across
the interior Tuesday, with below normal temperatures across much of
northern MA. Near to slightly below normal temperatures Wednesday
and Thursday region-wide, before turning below normal Thursday night
through Sunday.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
02z update...moderate confidence.
Scattered showers and isolated thunderstorm focused across
northern MA tonight, then moving offshore late. IFR/LIFR over
coastal NH into downeast ME, will move into northeast MA
overnight. Earlier discussion below.
=================================================================
Tonight...High confidence in trends, moderate in exact timing.
Starting off VFR. Expecting SW winds to diminish and winds shift
to the N/NE as a backdoor cold front moves across southern New
England. In the wake of this front, expect IFR stratus to
develop across NE MA and spread across E MA/central MA toward
daybreak. A few showers or and isolated t-storm possible this
evening across northern MA.
Monday...Moderate confidence.
MVFR/IFR cigs mainly confined to north central MA, eastern MA
and RI with easterly flow behind the backdoor front. There may
be some localize LIFR as well. Mainly VFR cigs elsewhere with
southerly winds from CT valley to the south coast. Numerous
showers and sct t-storms developing across the interior in the
afternoon and into the evening.
Monday night...High confidence in trends moderate in timing.
Starting off MVFR/IFR with showers/storms. Should see
thunderstorms coming to an end during the evening, but there
still may be spotty showers lingering late. Drier air punches in
and should usher in VFR conditions from SW to NE late.
KBOS Terminal... High confidence in TAF. Backdoor front with
wind shift to NE between 08-10Z. Conditions lower to MVFR/IFR
for the AM push.
KBDL Terminal...High confidence in TAF.
Outlook /Tuesday through Friday/...
Tuesday: VFR. Slight chance SHRA.
Tuesday Night: VFR.
Wednesday: VFR. Chance SHRA.
Wednesday Night through Thursday: VFR. Breezy. Chance SHRA.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence.
Backdoor cold front sliding across much of the eastern waters
tonight. May reach the southern waters toward daybreak. This
shifts winds rapidly from a W/SW direction to the NE/E. Should
see the gusty winds diminishing and anticipate the Small Craft
Advisories will be allowed to expire as winds come down. Seas
generally 2-4 ft, but the far southern outer waters may still
see some 5 ft waves late.
Monday and Monday night...Moderate confidence.
Backdoor cold front lingers nearby or over portions of the
southern waters until late. E/NE winds across the eastern
waters at 10-15 kts and S/SW at 10-15 kts for the southern
waters. Winds shift to the W/NW Monday night with speeds of 5-15
kts. Seas 2-4 ft.
Outlook /Tuesday through Friday/...
Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.
Tuesday Night: Winds less than 25 kt.
Wednesday: Winds less than 25 kt. Slight chance of rain
showers.
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers,
isolated thunderstorms.
Thursday: Winds less than 25 kt. Areas of rough seas. Chance of
rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 4 AM EDT Monday for ANZ232>235-237.
Small Craft Advisory until 8 AM EDT Monday for ANZ254>256.
&&
$$
SYNOPSIS...Belk/BL
NEAR TERM...Belk/Nocera/BL
SHORT TERM...BL
LONG TERM...Belk
AVIATION...Belk/Nocera/BL
MARINE...Belk/BL
Area Forecast Discussion
National Weather Service Cheyenne WY
544 PM MDT Sun Sep 18 2022
.SHORT TERM...(This evening through Monday)
Issued at 211 PM MDT Sun Sep 18 2022
The current weather setup includes a pleasant late summer day,
with temperatures in the 70s to low 80s, and a few areas in the
60s in the higher terrain. Mostly sunny conditions are also
present with fair weather cumulus clouds visible on GOES 16
satellite imagery. Dry conditions will prevail the remainder of
the day due to the amplifying upper level ridge present across the
Intermountain West. Overnight, we will see a battle of air masses
as the Laramie Range acts a barrier between moist and dry air.
Very dry air will be present west of the Laramie Range, and we are
likely to see fair to poor overnight RH recovery. Would not be
surprised if the higher terrain of the I-80 corridor has warmer
temperatures and poor RH recovery within the thermal
belt/inversion. East of the Laramie Range, we will see weak to VRB
winds of upslope flow. The HRRR and NamNest are showing strong
signals of decreased visibility across the NE Panhandle between
11-15Z. It could be a repeat of low-level clouds that stick around
in the central and southern tier of the NE Panhandle. There is
also a strong signal for a LLJ to kick in across the area
overnight, so that is why confidence is high in RH recovery being
poor in some regions.
Very warm temperatures aloft will be present on Monday morning,
and with stronger winds at 700-800mb, the dry air and warm
temperatures will mix easily down to the surface. A critical fire
weather regime is expected across our west and northern FWZs,
thus have gone with the issuance of a RFW for several of the FWZs.
Minimum RH values of potentially the single digits to 15% are
expected. West to southwest winds will create breezy to gusty
conditions through sunset. Afternoon highs from the middle 80s to
middle 90s east of the Laramie Range, and highs in the 70s west of
the Laramie Range are expected for Monday. The lone cool areas
will be in the mountain zones of the Snowy/Sierra Madre Ranges
will be in the 60s for afternoon highs. Dry conditions will be
expected for Monday night as seasonal temperatures will be seen
through early Tuesday morning.
.LONG TERM...(Tuesday through Sunday)
Issued at 211 PM MDT Sun Sep 18 2022
Key Impact Messages:
1) Large cooling trend starting Tuesday with Wednesday the coolest
of the week with Highs in the mid to upper 50s and about 10-15F
degrees below normal. Slow warming trend late week into next weekend.
2) Precipitation chances increase through the day Wednesday and
maximize into Wednesday night. However overall coverage could be
limited near the WY/CO and NE/CO borders where greatest moisture
will reside.
Weather Discussion: Model envelope remains in agreement with large
cut-off low off the coast of CA, a shortwave ridge over the
intermountain Rockies into the the southern Plains, and a mainstream
trough farther north in southern Canada. Tropical Storm Madeline off
the west coast of Mexico and nearby monsoonal moisture on the
southern periphery of the large cut-off low will siphon tropical
moisture across the desert SW over the next 24 to 48 hours. This
moisture will travel into UT and CO and partially into WY late
Tuesday, through Wednesday, and then start to decrease Thursday.
PWATs will be upwards of +2 to +3 standard deviation above normal
for this time of year and even higher slightly farther south over CO.
Despite this elevated moisture, the real question of what lifting
mechanism occurs comes into play to help promote precipitation. With
the slow progression of the cut-off low and weak perturbations ahead
of it with limited instability, weak forcing appears to be in place.
Secondly, the slightly earlier timing of the front Tuesday night may
place it just south in CO and that could act as a local convergence
boundary to limit precipitation farther north. GEFS and additional
model ensemble output suggests grater precipitation coverage farther
south in west CO and along the WY/CO to NE/CO border were some
upslope lift could occur. Precipitation chances have slowly trended
down for northern sections of the region with temperatures trending
lower on Wednesday with highs likely only in the mid to upper 50s.
The aforementioned cut-off low starts to rejoin the main flow
Thursday into Friday while tightening height gradients across WY
into NE. Stronger dynamic ascent will pivot through during this time
with new shower development farther north but rainfall rates will be
lower as greater moisture amounts will be shunted farther east.
Winds will increase starting late Thursday and peaking mid-day
Friday. Wind prone areas might need High Wind Watch Highlights but
overall probabilities of this occurring remain near 40-50%. None-the-
less, a breezy day is expected Friday across much of the region.
Confidence decreases next weekend with initial dry NW flow in place
but then giving way to either more of a ridge pattern or another NW
flow trough.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 541 PM MDT Sun Sep 18 2022
Wyoming TAFS...VFR. Wind gusts to 33 knots until 05Z, then gusts
to 33 knots after 15Z Monday.
Nebraska TAFS...VFR, except for MVFR at Alliance from 12Z to 16Z.
Wind gusts to 24 knots at Chadron and Alliance after 16Z Monday.
&&
.FIRE WEATHER...
Issued at 211 PM MDT Sun Sep 18 2022
Red Flag conditions expected on Monday for FWZs 417-423, 432, and 434.
West to southwest winds of 15 to 25mph will gust up to 30 to 35mph
by Monday afternoon. Minimum RH values of 10-15% are expected where
Red Flag headlines are present. Elevated fire weather conditons are
expected for all other FWZs Monday as critical minimum humidity values
will combine with breezy winds of 10 to 20mph at times. We will see a
return of moisture by mid-week to reduce fire weather concerns by
then.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from noon to 7 PM MDT Monday for WYZ417>423-432.
NE...Red Flag Warning from noon to 7 PM MDT Monday for NEZ434.
&&
$$
SHORT TERM...BW
LONG TERM...JSA
AVIATION...RUBIN
FIRE WEATHER...BW
Area Forecast Discussion
National Weather Service Des Moines IA
637 PM CDT Sun Sep 18 2022
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Sunday/
Issued at 318 PM CDT Sun Sep 18 2022
4pm Mesoscale Environment Update:
Mesoscale Update: The greater tornado threat has moved further southeast,
however a tornado threat still exists for our southeast counties.
Isolated storms/showers are possible anytime between now and 6pm.
The greatest strong supercell potential will start around 6pm,
and ramps up around 7pm. Areas east of I-35 and south of I-80 will
be the greatest concern this evening with supercell
thunderstorms. Large hail and damaging wind needs to be expected
with any supercell thunderstorms. Between 6-9pm, supercells will
carry a tornado threat. The timing of initiation of storms is
still in question. The main threat could start as early as 6pm,
but current model guidance indicates after 7pm to be the bigger
threat. A further north and northwest initiation means a greater
tornado threat for our counties, later and further southeast
initiation means greater tornado threat for southeast Iowa. For
right now, we are preparing for all modes with supercells.
We continue to see clearing across much of southern and central
Iowa this afternoon, and mixed layer CAPE values continue to
steadily increase ahead of a cold front currently positioned from
Council Bluffs to Fort Dodge to north of Mason City. There is a
weak surface low inflection centered back toward the MO River
Valley. Some surface analysis plots have a warm front that extends
along the Hwy 34 corridor, not sure I am a comfortable saying
this is truly a thermal boundary. The reason for saying the
greater tornado threat has been pushed southeast is because the
cold front appears to be forcing the surface low further south,
therefore pushing the the areas of backing surface flow further
south. RAP and HRRR runs have shown the 0-500m SRH being pushed
further south. While the surface flow itself seems weaker, low-
level storm-relative inflow looks to remain quite strong, in
excess of 25 kts. Even in areas further north where the SRH is
much lower, the storm-relative inflow could be quite strong, with
RAP soundings indicating 25 kts with a mean wind storm motion and
and near 30 kts for a right moving supercell. This will help to
promote wider updrafts in southeast Iowa, increasing the hail the
threat, and maintaining stronger rotation. Stronger mid-level
lapse rates, with drier air around 700mb above the strong moisture
advection occurring below provides a favorable thermodynamic
environment for hail as well. The most of the wind shear is
concentrated in the lowest 0-1km, but stronger flow aloft has
provided longer hodographs through 6km, and in further southeast
Iowa through 8km. Therefore, any supercells that maintain a clear
inflow may have some potential to become long tracked. This
potential though may be outside of our county warning area. The
tornado threat for our counties will be highly dependent on when
and where initiation occurs. If initiation occurs earlier and
further northwest (north of I-80), there will be decent tornado
threat between 6-8pm for our counties. Later convective initiation
will push the tornado threat to 7-9pm, and further south and
southeast. There is still some uncertainty with initiation time.
Visible satellite trends indicate the forcing is still trying to
erode some of the cap in central Iowa, which may hold initiation
back a bit. For other details, HRRR still continues to produce
convection with strong updraft-helicity tracks through southeast
Iowa this evening, with HREF probabilities over 50% for 150
m^2/s^2. This is high for September. While UH tracks do not equal
tornado tracks, it provides a good indication of how storms may
use the low to mid- level hodographs
Previous Discussion:
Key Messages:
-Strong to Severe Storms This Afternoon/Evening
-Localized Flood Risk with Storms in SE IA Tonight
-Hot to Begin the Week Then Cooling Off Late Week
Yet another shortwave is expected to track across Iowa this
afternoon and evening, bringing with it another round of strong to
severe storms in the southern portions of the state. Storms are
expected to fire ahead of and along a weak boundary moving through
southern IA this afternoon. The exact location of where convective
initiation will begin has been the challenge for the forecast,
with high resolution guidance jumping around quite a bit through
the day. A few HRRR runs have shown convection beginning as soon
as 21z in the western portions of the CWA along I80, however, the
more common solution for CI has been around 23z in south-central
IA. Given the consistency of the south central solution, would
tend to lean towards that, however, more northwestern development
still cant be ruled out. After initiation, storms will then track
east southeast through the state into an environment favorable
for all modes of severe weather. This has prompted the issuance of
an SPC enhanced risk in southeast IA.
The atmosphere is primed for severe storms this afternoon with
strong instability and shear present across southeast IA. CAPE
values over 3000 J/kg and mid-level lapse rates of 7 to 8 C/km will
combine with effective bulk shear near 50 kts and 200-300 m2/s2 of
SRH to create strong rotating updrafts with any convection that gets
going this afternoon and evening. This is reflected well in guidance
as well, with the HREF and individual CAMs painting updraft helicity
swaths across a good portion of southeastern IA where the
environment is most favorable. Given these parameters, and the
relatively low convective inhibition during the late afternoon/early
evening, it would not be surprising to see multiple supercell
storms track through southeast IA this afternoon and evening.
In addition to the severe parameters mentioned above, there also
appears to be a moderate amount of moisture available to these
storms, especially at the low-levels. The overall moisture transport
isn`t exceptional, but PWATs of 1.5 to 2" within the column are
suggestive of locally heavy rainfall rates. Storms may also begin to
train along the boundary later this evening as the LLJ kicks in and
fuels additional convection in southeast IA through the early
morning hours. Heavy rainfall rates in conjunction with storms
training over an area that already saw 3 to 5" of rain last night
has prompted the issuance of a Flood Watch in our far southeastern
counties. Rainfall last night was almost entirely absorbed by the
dry soils across this area so would generally expect that to be the
case tonight, especially with minimal response from local rivers.
However, given the above factors, we could still see some localized
flooding, especially in more urban areas.
The weather pattern remains fairly dynamic through the rest of the
week. To start it out, the building high pressure to our south will
open the state up to warm southerly flow which will launch high
temperatures into the mid to upper 80s on Monday and the 90s on
Tuesday. However, this hot air wont stick around long as an upper
level trough digs into the upper Mississippi Valley region, subduing
the high pressure and tracking a cold front through the state. This
will result in more fall-like temperatures in the low to mid 60s to
round off the work week.
In addition to the changing temperatures, rain chances return to the
forecast Tuesday night as the cold front sags across the state.
Model guidance still varies quite a bit regarding location and
intensity of this rainfall but will continue to monitor through the
week regarding any rain along this front Tuesday night through
Wednesday. Later in the week, another trough looks to pass through
the region some time Friday, with all models currently in agreement
that there will be some precipitation brought along with it. This is
still a good bit out in the forecast, but still something to keep an
eye on through the week.
&&
.AVIATION.../For the 00Z TAFS through 00Z Monday evening/
Issued at 637 PM CDT Sun Sep 18 2022
Main concern is convection this evening focused on OTM, DSM and a
lesser extent ALO. Have covered with tempo cat groups at OTM where
likelihood higher; VCTS at DSM and VCTS at ALO. Some fog possible
MCW 11-14z with lower vsby at OTM with stronger storms. Potential
strong winds gusts OTM from 02 to 05z. Most areas VFR aft 12z with
convection heading southeast of terminals. /rev
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday morning for IAZ086-097.
&&
$$
DISCUSSION...Dodson
AVIATION...REV
Area Forecast Discussion
National Weather Service Grand Rapids MI
1201 AM EDT Mon Sep 19 2022
LATEST UPDATE...
Aviation
.UPDATE...
Issued at 958 PM EDT Sun Sep 18 2022
Things are evolving upstream this evening as expected, with
strong to severe storms now impacting the Quad Cities area. These
storms will be tracking southeast along the instability gradient
and will remain south of MI. There is however other, weaker
storms, developing over srn WI and those will likely cross the
area south of I-96 overnight.
Deep layer shear ramps up to 40 kts or more over srn Lwr MI
overnight as 50 kt mid level jet streak punches in from the west.
Instability increases as well, with latest RAP showing MUCapes
rising to around 1500 J/KG south of I-96 after 06Z. Therefore a
stronger storm or two with gusty winds and/or hail still appears
possible, particularly between about 2 AM and 6 AM along the I-94
corridor.
Otherwise mainly just scattered showers expected overnight as the
sfc cold front arrives from the west with pops ranging from only
20-30 pct north of I-96 to about 60 percent along I-94.
&&
.DISCUSSION...(This evening through next Sunday)
Issued at 332 PM EDT Sun Sep 18 2022
-- Showers and Storms Tonight...especially Southern Lower MI --
A round of showers and thunderstorms is expected tonight. Storms
are expected to fire this evening in Iowa and press east towards
the Southern Great Lakes. We will follow the 12z HREF lead in that
showers and storms should be pressing across Southern Lake
Michigan as we approach midnight. Showers and thunderstorms are
then expected to move east across areas near and south of I-96
between midnight and 500am or so. MUCAPE values will likely stay
in the 1,000 - 2,000 J/KG range tonight along and ahead of an
advancing cold front. Not out of the question to see some storm
organization tonight given deep layer shear is on the order of 30
knots. Given evolution/time frame we will see the storms stronger
winds would be our main threat. Not out of the realm of
possibilities to see some 45+ mph gusts towards I-94 tonight. An
isolated severe gust is possible.
Showers and storms should clear out of the area early in the day
on Monday.
-- Occasional chances for precipitation in rest of forecast --
A fairly active pattern is in the offing for the upcoming work
week and into next weekend. There is a small chance for few
showers and storms on Tuesday with a weak warm front in the area.
The trends in the models look to be less in the way of
precipitation with this possible event on Tuesday.
Additional showers and storms will be possible Tuesday night into
Wednesday as a strong cold front sweeps through the area. This
front will plunge 850mb temps from summer type values to late fall
values (near +20C to around +2C). We will be cold enough
Wednesday night into Thursday for some lake effect rain showers.
Next weekend another trough moves through aloft with a cold front
expected around Saturday. We will have chances for precipitation
in the forecast from Friday night right through the weekend.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1200 AM EDT Mon Sep 19 2022
VFR conditions are expected at all of the terminals overnight with
some scattered showers. A few thunderstorms may develop overnight
mainly at our southern terminals which may potentially cause
brief reductions to MVFR/IFR between around 06Z and 10Z Mon.
However regional radar trends suggest that most of the storms will
stay southwest to south of our area. VFR conditions are forecast
from mid morning Monday through Monday evening with nothing more
than a few lingering showers early Monday.
&&
.MARINE...
Issued at 332 PM EDT Sun Sep 18 2022
We dropped the Beach Hazard Statement and Small Craft Advisory a
bit earlier this afternoon. Webcams and observations no longer
supported the headlines. Winds and waves look to remain below
advisory type levels tonight through Monday night. The gradient is
in the process of becoming fairly slack and that should be the
case into tonight. High pressure will be situated overhead Monday
into Monday night.
Tuesday into Tuesday night is the next time frame of concern as
strong south to southwest flow sets up. Advisory conditions look
likely at this point. The flow becomes northwest Wednesday behind
the front and at least advisory conditions should continue.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...Meade
DISCUSSION...Duke
AVIATION...Laurens
MARINE...Duke
Area Forecast Discussion
National Weather Service Lincoln IL
740 PM CDT Sun Sep 18 2022
.SYNOPSIS...
Issued at 320 PM CDT Sun Sep 18 2022
Showers and thunderstorms, some severe, are forecast for this
evening and tonight. After a warm and dry day Monday, very warm
conditions are expected Tuesday with heat index values
approaching 100 degrees. Cooler weather with occasional shower
chances is forecast for the remainder of the week.
&&
.UPDATE...
Issued at 737 PM CDT Sun Sep 18 2022
Convective initiation has occurred across portions of south
central and SE Iowa this evening and expect coverage to continue
to increase over the next couple hours as the low level jet
continues to kick in. While there remains some uncertainty in the
overall coverage and placement of storms overnight, main thinking
has not changed much. The severe threat is expected to move into
the central Illinois forecast area starting 9-10 pm and
continuing overnight before it evolves into more of a hydro threat
with training storms on the nose of the low level jet. In the
near term, latest RAP continues to show moderately strong MLCAPE
values of 1500-2500 J/kg near and north of the Illinois River
Valley. Despite loss of daytime heating, guidance suggests the
threat for strong or severe convection rooted within an unstable
boundary layer will continue through late tonight as these
stronger instability values slowly spread east ahead of an
approaching cold front. Deep layer shear continues to increase
ahead of a digging shortwave over northern IA/southern MN this
hour. In addition to deep layer shear values increasing to 40-50
kt late this evening, 0-1km SRH values of 100-200 m2/s2 continue
to point to favorable conditions for tornadoes with any
supercells. After midnight tonight, do expect the severe threat to
moderate/wane some as the storms outrun some of the stronger
instability currently in place, but an evolving hydro threat
remains plausible with training storms developing on the nose of
the veering low level jet. There is some uncertainty on the exact
axis of heaviest rain fall but some flash flooding will be
possible south of I-74 with the most likely location near a
Havana/Beardstown to Taylorville line.
&&
.SHORT TERM...(This evening through Monday)
ISSUED AT 320 PM CDT Sun Sep 18 2022
A cap near the 3000 foot level this afternoon is keeping shower
and thunderstorm activity minimal in central IL early this
afternoon, with so far just one weak shower south of Taylorville.
Meanwhile, quite a few sunny areas in northeast MO, southeast IA,
and west central IL are contributing to increasing instability,
which models anticipate should be in the 2000-3000 J/Kg SBCAPE
range by 6 pm, along with 40-50 kt sfc-500 mb shear and the
arrival of a strong upper level shortwave via the northern Plains.
Thunderstorm initiation with a preceding shortwave appears to be
taking place in southeast IA, but it appears it may take until
closer to 6 pm before convective inhibition diminishes further and
the main shortwave arrives. At that point, some supercells look to
develop close to west central IL, and could pose all severe
thunderstorm hazards including damaging wind gusts, very large
hail, and a few tornadoes. Storms could congeal into a linear
system for a time as they spread eastward into the IL River Valley
and I-55 corridor, however some CAM model solutions keep activity
more scattered. SPC indicates an enhanced risk of severe
thunderstorms from around I-55 westward, and a slight risk over
the remainder of central IL. Overnight, there appear to be two
general areas of more widespread convection. One heading eastward
between the I-74 and I-80 corridors following the upper level
shortwave, and another more slowly moving southeastward associated
with a nocturnal low level jet. This latter feature looks to be
associated with the heaviest precipitation. General expectation is
for up to around 2 inches in a corridor from west central into
southeast IL, but a couple of models depict a maximum of several
inches in this general area. WPC indicates a slight risk of
excessive rainfall in this area, and flash flooding will have to
be watched for.
Dry weather will return for Monday afternoon`s the shortwave
heads east and a large scale high pressure ridge amplifies again
into the region. Following the overnight system, a cold front will
slowly settle southward, bringing a slight cooling for Monday
with highs in the lower 80s near the I-74 corridor.
.LONG TERM...(Monday night through Sunday)
ISSUED AT 320 PM CDT Sun Sep 18 2022
Hot and humid weather will resume on Tuesday as winds shift to
southwesterly again. Expect dewpoints cracking 70 degrees along
with lower 90s for Highs, resulting in heat index around 100
degrees. The heat will be short lived, however, as another cold
front sweeps into the area late Tuesday night and pushes through
the forecast area by peak heating Wednesday. Highs should range
from 79 in Galesburg to 94 in Lawrenceville. Wednesday and
Thursday should see highs in the 60s to lower 70s, followed by a
gradual warming trend on the weekend. Precipitation chances should
accompany the Wednesday cold front, but modest CAPE and shear as
well as timing should keep severe weather threats to a minimum.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 616 PM CDT Sun Sep 18 2022
This evening, a cold front stretches from just west of Green Bay
back to north of Kansas City. Thunderstorms are developing along
the front over portions of south central Iowa this hour and are
expected to increase in coverage as they move across central
Illinois tonight. An initial broken line of storms will move
steadily west to east across the terminals late this evening and
overnight while additional storms continually redevelop behind the
main line and train across portion of central Illinois resulting
in multiple rounds of storms. The best likelihood for multiple
storms is SPI to DEC and possibly CMI while PIA/BMI should only
see the one round. The northern terminals of PIA/BMI are expected
to see MVFR or possibly IFR ceilings develop late tonight into
Monday morning. SSW winds ahead of the front will become variable
in the vicinity of and behind storms tonight, then will set up out
of the E/NE Monday.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Deubelbeiss
SYNOPSIS...37
SHORT TERM...37
LONG TERM...37
AVIATION...Deubelbeiss
Area Forecast Discussion
National Weather Service North Platte NE
704 PM CDT Sun Sep 18 2022
.SHORT TERM...(This evening through Monday night)
Issued at 324 PM CDT Sun Sep 18 2022
The forecast focus in the short term will be the potential for
patchy fog and low cloudiness later tonight into Monday morning
southwestern areas, followed by much above normal temperatures
Monday afternoon.
Tonight, a return southeast wind at the surface will bring higher
dewpoints in the mid to upper 50s to the area. The SREF
probability of fog up to 25 percent supports patchy fog possible
across the southeast panhandle into southwest NE. This also shown
by the HRRR and RAP.
On Monday, early morning stratus and patchy fog across
southwestern areas will erode by mid to late morning. Forecast
highs are the same to a degree or two less than the previous
forecast. Mixing will be limited across most of the area. Highs
around 90 most locations to near 95 far southern counties. With
boundary level moisture shallow, dewpoints will fall off quickly
across the western Sandhills into the upper 30s and lower 40s.
Afternoon humidity may fall below 15 percent in Sheridan County
combined with a southwest wind gusting to 15 mph with elevated
fire weather possible.
.LONG TERM...(Tuesday through Sunday)
Issued at 324 PM CDT Sun Sep 18 2022
The forecast focus in the long term will be an upper ridge
from the Southern into the Central Plains Tuesday, followed by a
Canadian cold front dropping through Tuesday night bringing much
cooler temperatures Wednesday and Thursday. Precipitation
chances also return Wednesday through Friday morning.
An upper ridge will be centered over north central TX into OK on
Tuesday. This continues to look like the hottest day across the
southern half of the area. Winds will shift to the north in the
afternoon as the leading edge of a cold front drops south. This
will cause compressional heating with highs approaching 100 across
the far south. A near record high of 94 at North Platte is
expected. Details found in the climate section.
Monsoonal moisture will be in place on the western side of the
upper ridge across the Four Corners Region through Wednesday. An
upper low over Hudson Bay Canada and upper trough extending south
into the Northern Plains and Great Lakes will drive in cooler air
behind the cold front Tuesday night and Wednesday.
A chance for showers Wednesday through Wednesday night. Mid level
frontogenesis is shown by the GFS and ECMWF from southwest NE into
northeast CO and northern KS. The highest POPS area across the
southwest becoming likely Wednesday night.
The GFS and ECMWF continue to depict an upper low and trough
moving from the Northern Great Basin into the Northern Plains
Thursday into Friday. This will bring another round of shower
chances with the highest POPS Thursday night. Highs only in the
60s Wednesday and upper 50s and low 60s Thursday. A warmup into
the 70s to near 80 across the west Friday and slightly warmer
Saturday and Sunday. As upper flow becomes northwest, dry conditions
are expected, although a few showers are possible Saturday night
into Sunday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 703 PM CDT Sun Sep 18 2022
For the KLBF terminal: Low level moisture will lead to the
development of stratus overnight. Ceilings will fall off to around
1000 FT AGL after 09z overnight. Ceilings will then increase to
5000 FT AGL by late morning Monday with scattered ceilings around
2000 FT AGL Monday afternoon. For the KVTN terminal: Expect mostly
clear skies over the next 24 hours with ceilings ranging from
12000 to 20000 FT AGL.
&&
.CLIMATE...
Issued at 324 PM CDT Sun Sep 18 2022
High temperatures will be well above normal Monday and Tuesday.
Temperatures will climb into the 90s for most locations,
The hottest temperatures are expected to be on Tuesday across
southwest Nebraska. Near record high temperatures are still
possible at KLBF. Monday the forecast high is 92, which is 4
degrees below the record of 96 that was set way back in 1895.
Tuesday, the forecast high is 94 which is 2 degrees below the
record of 96 set in 2016.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Roberg
LONG TERM...Roberg
AVIATION...Buttler
CLIMATE...Roberg
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
642 PM CDT Sun Sep 18 2022
.SHORT TERM...
Issued at 249 PM CDT Sun Sep 18 2022
Through Monday...
The forecast focus this afternoon continues to focus on pinning
down the primary threat areas and timing of potential severe
thunderstorms this evening.
Water vapor satellite imagery early this afternoon indicates the
presence of an eastward moving disturbance moving across central
parts of IA. Recently, this has supported some weak elevated
shower and storm development over parts of IA. Since the area this
is moving across remains north of the effective warm front, which
is now nearing the IA and MO stateline, this area remains capped
to surface based storm development. This disturbance will continue
to shift eastward into northern IL after 4pm this afternoon, and
as it does so it could produce a couple of isolated showers, but
capping will prevent any robust storm development through sunset
this evening over northern IL.
The main area we are watching for initial storm development is
over south central into southwestern IA. Low-level moistening is
occurring in this region as lower 70 degree dew point air
continues to pool near the frontal boundary, and this is really
apparent by the rapid uptick in Strato CU development over this
area over the past couple hours. The expectation is that initial
storm development will occur somewhere over south central IA after
4 PM this afternoon as the boundary layer continues to
destabilize and capping weakens. Very steep mid-level lapse rates,
associated with an Elevated Mixed Layer (EML), are also
overriding this boundary, thus continued boundary layer heating is
expected to yield rather impressive MLCAPE values in excess of
2,000 J/KG over the next couple hours. A well sheared kinematic
environment is also developing into the area, with deep layer bulk
shear increasing to in excess of 45 kt, per the last SPC RAP
mesoanalysis. A veering low to mid level wind profile will also
support supercellular storm structures, with an attendant
tornado, hail and wind risk will thus be favored into early
evening as this developing activity likely begins to shift into
west central IL. It still appears the primary tornado risk will
remain southwest of the WFO LOT CWA.
With time early this evening storm coverage will begin to
increase, which should begin to favor east-southeastward forward
propagating clusters as they approach the southwestern LOT CWA
sometime after 7 pm this evening. Strong damaging winds and some
instances of large hail are likely to become the primary severe
hazards through the evening as they track into central parts of
IL. At the present time, it appears La Salle, Livingston, Ford and
Iroquois counties in the LOT CWA and points to the south-
southwest into central IL look to be in the higher threat area for
these forward propagating severe storms this evening, roughly
between the hours of 8 and 12am.
Additional scattered thunderstorms may develop farther north
towards the I-80 and I-88 corridors mid to late this evening as
the low level jet and warm air advection ramp up over this area in
advance of the approaching cold front. While this is likely to be
the case, questions remain with the actual coverage (footprint)
of these northern storms into the Chicago metro area due to the
fact that a regenerative upstream nature to the central IL convection
may rob a good deal of the moisture and low-level jet focus for
areas to the north. We continue to advertise good chances (40-60%)
for storms into northern IL and northwestern IN later this evening
into the early overnight, but the coverage could end up remaining
more widely scattered in nature, especially as you approach the
WI state line. The best timing for these storms into the Chicago
metro area still looks to be in the 9 pm through 2 am period, when
some instances of hail and strong wind gusts will be possible.
However, the primary severe threat continues to be favored south
of I-80 towards central parts of IL through the evening.
The storm threat will gradually wane from northwest to southeast
overnight. Heavy rainfall will also accompany these storms, and
this could result in some isolated instances of flooding. However,
at this time, the primary threat area for excessive training due
to upstream regeneration looks to remain south-southwest of the
area over central IL.
Quieter and cooler weather is on tap for Monday following the
passage of tonight`s cold front. Expect northerly winds through
the day with cooler temperatures in the upper 70s to around 80.
KJB
&&
.LONG TERM...
Issued at 313 PM CDT Sun Sep 18 2022
Monday night through Sunday...
The main forecast messages for the long term forecast period are:
* Chance for showers and storms Tuesday morning and again late
Tuesday into Wednesday with a low-end potential for strong or
severe storms on Tuesday.
* After an unseasonably warm and muggy Tuesday, conditions more
fitting for fall will arrive in time for the autumnal equinox and
the latter half of the week after a mid-week cold frontal passage.
Upper-level ridging centered over the southern Plains will be in
place to start off the extended forecast period late Monday into
Tuesday. This ridging will be responsible for imposing a more summer-
like weather pattern across the central CONUS through the middle of
the week, which will manifest itself in the form of warm and muggy
conditions and possibly thunderstorms in the local area on Tuesday,
before the ridge gradually flattens over the latter half of the
workweek, giving way to a more zonally-oriented upper-level flow
pattern as we approach the first weekend of astronomical fall.
The area should remain dry Monday evening with high pressure still
exerting some influence over the area, but by daybreak Tuesday, this
may no longer be the case. The available suite of guidance is in
fairly good agreement that a mid-level impulse will work in tandem
with a 40 kt low-level jet arcing anticyclonically around the
periphery of a low-level/surface ridge to generate convection
overnight in the Upper Mississippi River Valley. The elevated
cluster of storms that comes out of this will dive southeastward
towards our forecast area, riding along a sharp MUCAPE gradient and
likely either getting near or entering our far northern CWA sometime
around or soon after daybreak before eventually decaying by the late
morning/early afternoon hours as the low-level jet loses some steam
over time. With steep 7-7.5 C/km mid-level lapse rates yielding
around 1500 J/kg of elevated instability amidst the presence of 30-
35 kts of cloud layer shear, would not be surprised to see some
transient hail cores with this activity before these storms
diminish in intensity as they lose their low-level jet support.
Some uncertainty exists in the details for the forecast for the
remainder of Tuesday as that will partially hinge upon how robust
and widespread the morning convection ends up being. At any rate,
a warm front will attempt to move from southwest to northeast
across the area on Tuesday with an unseasonably warm and humid air
mass behind it. If the morning activity doesn`t amount to much,
then temperatures should have no problem climbing into the mid-
upper 80s and even the lower 90s by peak heating during the
afternoon. Behind the warm front, dew points across much of the
area are also expected to climb into the 70s, which is a rather
uncommon occurrence for our area in mid/late September. If the
morning convection ends up being stronger and more widespread than
currently expected, then it`s possible that outflow from these
storms could hold the warm front at bay and result in a less humid
and not quite as warm Tuesday afternoon than currently advertised.
The warm front (and/or any outflow boundaries left behind by the
morning convection) could serve as an impetus for additional
convective development during the mid/late afternoon hours, though
at this point, it appears that the combination of capping, a lack
of forcing mechanisms outside of any surface boundaries, and
presence dry air aloft may prove to be too much for any new
convection to get going, so have maintained a dry forecast for
Tuesday afternoon for now. Will need to keep an eye on forecast
trends with this though as kinematic and thermodynamic profiles
appear to be favorable to support another threat for strong to
severe thunderstorms in the event that storms are able to develop.
A cold front is then expected to make inroads into the area sometime
overnight on Tuesday or early Wednesday morning. This front will be
accompanied by additional chances for showers and thunderstorms
Tuesday night into Wednesday before these chances subside by
Wednesday night as the frontal zone works its way out of our CWA.
This cold frontal passage will usher in a decidedly more fall-like
air mass into the region for the latter half of the week with cooler
and drier air being advected in by northwest/north winds in the
front`s wake. Highs on Thursday and Friday are currently pegged to
remain in the 60s with low temperatures expected fall to as low
as the low-mid 40s in many locations across our CWA Thursday night
into Friday morning. Slightly warmer temperatures then appear
favored to occur over the weekend. There`s also a signal in long
range guidance that there could be one or two opportunities for
rain sometime between Friday and Sunday, but the large spread in
current ensemble solutions lends low confidence to the specifics
of the exact timing and coverage of this precipitation at this
time.
Ogorek
&&
.AVIATION...
For the 00Z TAFs...
642 PM...Forecast concerns include...
Scattered thunderstorms later this evening/early Monday morning.
Wind shift to northeast early Monday morning.
Possible low mvfr cigs early Monday morning.
Scattered thunderstorms are developing across southeast IA early
this evening ahead of a cold front and addition development is
expected further north along the front. This activity will likely
stay scattered as it moves into northern IL later this evening
with low confidence for coverage. Current timing to rfd appears to
be around 02z and then into the Chicago terminals around/after
04z but these times may need tweaking as trends emerge. The best
potential for severe thunderstorms looks to remain well south of
the terminals where better instability exists. But any of these
storms may have gusty winds and heavy rain with brief ifr
cigs/vis. This activity is expected to move southeast of the
terminals by early Monday morning.
Winds will likely become light south/southwest this evening, then
shift to the northwest behind the storms and eventually shift to
the northeast early Monday morning. Timing will likely need some
refinement with later updates. Northeast winds will continue on
Monday, turning more east/southeast Monday evening.
There will be a period where mvfr cigs are possible Monday
morning, mainly ahead of winds turning to the northeast. Model
trends suggest this time period may be short across the Chicago
terminals and scattered mvfr cigs out after sunrise though mvfr or
even ifr cigs may persist longer south and southwest of the
terminals Monday morning. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service San Francisco Bay Area
436 PM PDT Sun Sep 18 2022
.SYNOPSIS...Showers with isolated thunderstorms the rest of today
into tonight. Shower chances stay in the forecast Monday with an upper
low offshore though no all day rain is forecast. Threat of showers
continues into Tuesday as the low stays west of San Francisco. The
low moves inland Wednesday then high pressure builds Thursday into
next weekend with a return to dry and seasonably warm weather.
&&
.DISCUSSION...as of 2:50 PM PDT Sunday...Bands of rain showers
continue to move onshore this afternoon and this trend will
continue right into tonight. As usual, its our coastal hills from
Sonoma to Monterey county that are seeing the highest totals with
2.51 inches at Oakridge RAWS in Northwest Sonoma county, 2.27
Cazadero, 1.70 Venado, 0.92 Ben Lomond and many of our gauges in
the Santa Lucia range above Big Sur are now exceeding 1 inch
rainfall amounts. Meanwhile bands of showers continue to pass
through the Bay Area this afternoon.
Lightning data and spotter reports indicate thunderstorms across
far northern Sonoma county (near Cloverdale) and into southern
Mendocino. Thus will continue the slight chance of thunderstorms
into tonight as colder air associated with the upper low will help
to steepen lapse rates as large scale ascent gets maximized with
jet energy passing overhead.
Latest HRRR and 18z NAM models indicate the period of most
widespread and heavy rain will be now through about midnight
tonight along with the best chance of thunderstorms. So if out
driving plan accordingly for wet roadways.
In addition to the early season rain we are seeing strong
southerly winds, especially along the coast and coastal hills with
frequent gusts in the 35-45 mph. As the low remains nearly
stationary at around 1000 mb located west of Pt Reyes we can
expect the gusty southerly winds to continue tonight. Current end
time of 4 am Monday still looks on track. So far we`ve gotten
reports of some downed limbs and small trees via chp reports.
Looking ahead to Monday and Tuesday the forecast details are
difficult as the upper low stays offshore and keeps at least the
threat of showers in the forecast though no all day rains will
occur. The main instability with the upper low will stay well
offshore but the southerly flow around this feature will generate
some showers Monday afternoon especially across the interior
hills. Temperatures will stay fairly mild on Monday in the upper
60s and 70s due to the moist southerly flow.
Shower threat ends Monday night as the sun goes down, however the
low stays close to keep another chance of showers into Tuesday.
Again this will be scattered with minimal impact other than we
usually we expect to see no shower activity in the month of
September.
On Weds the upper low will finally move inland and as this occurs
we could still see some rogue shower activity but nothing
widespread.
High pressure then rebuilds Thursday into the weekend with a
return to dry and seasonably warm weather as daytime highs return
to the 80s and even some lower 90s inland.
&&
.AVIATION...as of 04:35 PM PDT Sunday...For the 00Z TAFs.
Scattered showers persist over the Bay Area, but as the center of
the low has dropped south of San Francisco over the ocean, a dry
slot is moving into the area allowing for more breaks in the
clouds. Most lowest cigs are between 2500 and 3500 feet providing
an array of MVFR to VFR conditions around the region. Showers will
likely continue through the evening, but become more sporadic.
TEMPOs will be added for approximations of periods of heavier
rainfall which may lower cigs and vis through the night. Lightning
has been spotted over the northern Pacific waters as well as the
North Bay. While the slight chance for thunder will continue
through Sunday evening, the probability for it to impact terminals
is low. Winds will remain out of the south through most of the TAF
period. Stronger gusts are possible through 02Z, with winds
diminishing after that. There is a slight chance for LLWS as the
gusts end, but confidence was too low to add it to the TAF. As
the low stalls over the Pacific, VCSH will remain in the TAFs.
Vicinity of KSFO...Clouds are slowly breaking up, but cigs remain
around 2500 feet for MVFR conditions. Periods of VFR are possible
Sunday night as breaks in the rain happen, but showery actively is
expected through the night with MVFR conditions. Winds remain out
of the south, with stronger gusts possible through 03Z. Winds will
diminish overnight, but remain out of the south through 00Z
Monday before turning more west-southwest.
KSFO Bridge Approach...Similar to SFO.
Monterey Bay...Scattered showers prevail but forecast to diminish
slightly overnight with another chance for scattered showers
Monday morning. Winds remain gusty and out of the south. Gusts
should back off after sunset, but will remain out of the south
until Monday afternoon. Winds forecast for Monday has a lot of
uncertainty and will depend largely on where the center of the low
stalls. Forecasting NW winds in the Salinas Valley Monday
afternoon while most of the area will be south-southwest, but
there is low confidence. Cigs are forecast to be MVFR overnight,
then VFR early Monday morning through the end of the TAF.
&&
.CLIMATE...
Obviously, there was a big storm back in 1959 that
holds very high records for most of these places on Sept 18. One
exception is for the downtown Oakland site which didn`t start
observations until October 1, 1970. At the bottom of these stats,
we provide the Sept Climate Normal based on 1991-2020 and the
September Average based on that station`s entire period of record.
You can clearly see that we`ve been much drier in recent history.
Climate Site 9/18 record 9/18 normal
Santa Rosa 2.82" in 1959 0.01"
Kentfield 3.85" in 1959 0.00"
Napa downtown 1.87" in 1959 0.00"
Richmond 2.05" in 1959 0.00"
Livermore dwtn 0.36" in 1959 0.00"
SF downtown 2.01" in 1959 0.00"
SFO airport 2.29" in 1959 0.00"
Redwood City 3.05" in 1959 0.00"
Half Moon Bay 1.10" in 1959 0.00"
Oakland dwtn 0.13" in 2019 0.01"
San Jose 2.00" in 1959 0.00"
Gilroy 0.28" in 1959 0.00"
Salinas arprt 0.15" in 1989 0.00"
King City 0.35" in 1989 0.00"
Climate Site 9/19 record 9/19 normal
Santa Rosa 0.34" in 1959 0.00"
Kentfield 1.65" in 1959 0.00"
Napa downtown 0.51" in 1977 0.01"
Richmond 0.71" in 1977 0.00"
Livermore dwtn 1.53" in 1959 0.01"
SF downtown 0.83" in 1977 0.01"
SFO airport 0.46" in 1977 0.00"
Redwood City 0.82" in 1977 0.01"
Half Moon Bay 2.56" in 1959 0.01"
Oakland dwtn 0.59" in 2004 0.00"
San Jose 0.58" in 1977 0.01"
Gilroy 5.97" in 1959 0.00"
Salinas arprt 0.20" in 1966 0.00"
King City 0.10" in 1959 0.00"
Climate Site Sept Monthly Record
Santa Rosa 4.39" in 1904
Kentfield 3.85" in 1959
Napa downtown 4.79" in 1904
Richmond 2.05" in 1959
Livermore dwtn 5.72" in 1918
SF downtown 5.07" in 1904
SFO airport 2.29" in 1959
Redwood City 3.05" in 1959
Half Moon Bay 2.56" in 1959
Oakland dwtn 1.54" in 1986
San Jose 6.33" in 1918
Gilroy 5.97" in 1959
Salinas arprt 1.22" in 1976
King City 1.67" in 1918
Climate Site Sept Climate Normal (1991-2020) Sept Avg (all data)
Santa Rosa 0.15" 0.38"
Kentfield 0.09" 0.27"
Napa downtown 0.09" 0.31"
Richmond 0.03" 0.15"
Livermore dwtn 0.09" 0.21"
SF downtown 0.10" 0.25"
SFO airport 0.07" 0.13"
Redwood City 0.07" 0.13"
Half Moon Bay 0.21" 0.20"
Oakland dwtn 0.10" 0.23"
San Jose 0.07" 0.22"
Gilroy 0.04" 0.25"
Salinas arprt 0.05" 0.11"
King City 0.06" 0.09"
&&
.MARINE...as of 02:43 PM PDT Sunday...An early season low
pressure system is located over the outer coastal waters west of
Point Reyes. The low will become stationary over the outer waters
until late Tuesday and Wednesday when the low will begin moving
northeast away from the coastal waters and bays. A new northwest
swell arrives by Tuesday.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...Wind Advisory...CAZ006-502-503-505-509-512-529-530
SCA...SF Bay until 9 PM
SCA...Mry Bay until 9 PM
SCA...Pt Arena to Pt Reyes 0-10 nm until 3 AM
SCA...Pt Reyes to Pigeon Pt 0-10 nm until 3 AM
SCA...Pigeon Pt to Pt Pinos 0-10 nm until 3 AM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM
SCA...Pt Arena to Pigeon Pt 10-60 nm
&&
$$
PUBLIC FORECAST: RW
AVIATION: DK
MARINE: Behringer
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Area Forecast Discussion
National Weather Service Phoenix AZ
405 PM MST Sun Sep 18 2022
.UPDATE...
Updated Aviation
&&
.SYNOPSIS...
Dry conditions will continue through Monday under mostly clear
skies. There will be a gradual increase in moisture through midweek
along with a chance of showers and storms beginning Tuesday.
Slightly below normal temperatures are anticipated midweek, followed
by a warming and drying trend into the weekend.
&&
.DISCUSSION...
Latest water vapor imagery reveals a dry southwesterly flow between
a closed low off the northern California coast and a broad
anticyclone across the southern Plains. Meanwhile, latest
mesoanalysis and ACARS soundings indicate PWATs range from roughly
0.5 to 0.7 inches, which is below average for mid-September. The dry
air is also evident at the surface and dewpoints are generally in
the mid 30s to lower 40s. With the relatively dry air promoting
favorable conditions for radiational cooling, temperatures early
this morning dropped as low as mid 60s in the outlying areas near
Phoenix.
After a respite in the Monsoon the past few days, an increase in
moisture will herald a return to the threat of showers and
thunderstorms this week. The moisture is already apparent on
satellite imagery with areas of CU developing across western New
Mexico and southeastern Arizona. Latest HREF indicates the chance of
storms will arrive as early as Monday afternoon, particularly across
eastern Arizona. Although showers are generally not expected in the
Phoenix area, the extended HRRR suggests convection in Pinal and
Gila Counties could produce an outflow boundary capable of producing
blowing dust. This is an outlier though and probabilities generally
remain below 10 percent.
Models remain in good agreement the gradual increase in moisture
will continue Tuesday through Thursday, with PWATs potentially
peaking as high as 2 inches Wednesday night. This is quite anomalous
for this time of year and may approach all-time records per the SPC
sounding climatology. However, it is unlikely this will translate
into widespread, heavy rainfall given the lack of discernible
forcing or PVDs.
In the battle between the aforementioned upper low to the west and
ridge to the east, model consensus indicates the high will
predominate, resulting in somewhat above normal temperatures aloft.
This will yield weak mid-level lapse rates and generally hinder
instability. Nevertheless, latest NBM PoPs suggest most spots will
see at least some rain in the Tuesday-Thursday time frame. But given
abundant moisture, the strongest storms will also be capable of
producing localized flooding.
The cutoff low is expected to open up and eject eastward Wednesday-
Thursday per the latest NCEP cluster analysis. Drier air behind this
system will overspread the intermountain West. However, the threat
of showers and storms will linger through Friday across Arizona.
Latest ECMWF ensemble suggests the increasing insolation may
contribute to higher CAPE. The instability combined with the
residual 20 kt deep layer-shear points to the potential for strong
storms Friday, particularly from Phoenix north and eastward.
Thereafter, a warming and drying trend remains likely for next
weekend.
&&
.AVIATION...Updated 2305Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major weather issues will exist through Monday evening with only
a modest increase in mid/high cloud decks. W/SW winds should hold
longer into the evening/overnight than recent days. Light east winds
with periods of nearly calm conditions are likely Monday midday, and
the transition to the traditional afternoon west wind may not occur
particularly quickly.
Southeast California/Southwest Arizona including KIPL and KBLH:
Clear skies will persist through the period with trends in winds
nearly identical to the past 24 hours. Uncertainty becomes tied to
magnitude and persistence of wind gusts this evening at KIPL, while
somewhat weaker winds will be preferred at KBLH.
&&
.FIRE WEATHER...
Dry conditions will prevail across the lower deserts through Mon.
Although S Gila Cty will see a decent 30% chance of showers and
storms by Mon evening. Min RH in the low-mid teens today will
improve to the upper teens-20% Mon. Winds will favor familiar
diurnal patterns with overall light speeds, but with periodic
afternoon breezes to around 20 mph through Mon. A decent return of
moisture continues through at least midweek bringing good to
excellent, 40-60%, chances for showers and storms across the eastern
Arizona high terrain by Tue along with at least slight 10-20%
chances for the lower deserts. The lower desert chances improve to
decent 30% chances for Wed-Thu. Max Ts will generally run near to
slightly above seasonal normal through the week and into next
weekend. Min RH will improve to ~30% for S-Cent AZ by Wed and fall
to near 20% for late week and next weekend. Outside of storms, winds
will overall be light and favor normal diurnal slope/valley
patterns, but with somewhat higher afternoon speeds and gusts to
around 20 mph most days through the first half of the week.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...Hirsch
AVIATION...18
FIRE WEATHER...Sawtelle/Kuhlman