Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/10/23
Area Forecast Discussion
National Weather Service Amarillo TX
716 PM CDT Sat Sep 9 2023
...New AVIATION...
.SHORT TERM ...
(This evening through Sunday night)
Issued at 246 PM CDT Sat Sep 9 2023
High pressure continues to shift westward over the Desert
Southwest into portions of Mexico and the Pacific Ocean. This is
leading to the FA being under northerly to northwesterly flow
aloft and allowing for some slightly cooler high temps today.
Slight chances for rain late tonight into the overnight period
will exist with the possibility of some help from upper level
disturbances in the flow. Overall, CAMS are on a downward trend in
activity tonight, with the best chances for some thunder showers
happening in the far southwest TX Panhandle as activity travels
southeast from portions of eastern NM. H7 theta-e advection is
lacking today but is expected to improve going into tomorrow.
Forecast soundings depict some modest CAPE of around 500-1500 J/kg
of CAPE this evening with lapse rates around 8 to 9 C/km in the
east. However, this is long before any shortwave comes to help
with lift. Although severe storms cannot be completely ruled out,
it is not looking very promising for the perfect conditions to
come together, therefore a severe storm is not guaranteed to
happen.
Tomorrow, increased moisture flux as seen in H7 theta-e advection
will increase PoPs especially going into tomorrow evening. PWATs
are only expected to be around 0.9" tonight, with an increase to
around 1.5" tomorrow for comparison. This increase in moisture
will also be accompanied by better dynamics with increased PVA. An
expected cold front late tomorrow night may also help with some
lift into the overnight hours. With this said, PoPs will be
increasing through out the day tomorrow and maxing out around 70
to 80 percent after 7 PM tomorrow evening.
Early on in the afternoon tomorrow, thunderstorms my have some
better chances to become severe with large hail and damaging winds
the main threat. However, the overall potential for hail growth
will be conditional on what happens tonight into tomorrow morning.
Depending on how much cloud cover is present early on in the day
could limit overall instability and hail growth potential. The
HRRR that has little to no activity in the morning will allow for
uncapped SBCAPE values upwards of 2000 to 2500 J/Kg, with the
potential for hail up to 1.75". However, overall bulk shear is
still not looking the greatest. On the other hand the RAP keeps
things a bit more capped at the surface as early day activity
keeps storms a bit more elevated with MLCAPE values a modest
1000-1500 J/Kg, with hail most likely topping out around 1.25" in
diameter. As coverage increases going later into the evening
forecast soundings start to become more tropical in nature. This
will increase the possibility of some flooding issues as well,
especially if areas see prolong periods of heavy rain.
36
&&
.LONG TERM ...
(Monday through next Friday)
Issued at 246 PM CDT Sat Sep 9 2023
SUMMARY...The long term outlook still appears favorable for solid
rain chances and fall-like temperatures to be on the way most of
next week! As of the current forecast, by next Thursday, everyone
in the Panhandles will have had at least a 30% chance for
measurable rain. While this won`t be a constant, widespread,
drenching rain, there will be multiple opportunities for
scattered to numerous showers/storms to reach a majority of the
area at some point or another. Temperatures will be much cooler
with daytime highs remaining below 80 degrees for most of the
Panhandles throughout the period.
DISCUSSION...Deterministic and ensemble guidance are in agreement
that northwest flow aloft in conjunction with deep layer moisture
(PWATs of 1.0-1.5") will have an extended stay over the
Panhandles through at least Wednesday. Stronger cold fronts
moving in Monday as well as Thursday, along with multiple
shortwaves (assuming they track favorably) should provide ample
large scale lift for rounds of showers and storms. Our first
front pushes in as early as Monday morning based on more
aggressive guidance, perhaps perpetuating lingering overnight
convection. Another shortwave looks to slide off the Rockies later
in the afternoon/evening for additional storm chances before
briefly washing out moisture from the area. Majority of Tuesday
could turn out to be a recovery day as southeasterly winds work to
replenish moisture, but any disturbance that finds its way into
the area may induce some convection for the southern Texas
Panhandle where best moisture will remain.
Things could get interesting Wednesday as latest trends indicate
the possibility of a stronger, slightly more amplified trough
digging into the southern plains. This could depend heavily on
the effects of a lead shortwave overnight Tuesday into Wednesday
however. If this main trough times out well and ample
destabilization can occur, sufficient shear could lead to at least
some severe weather risk. Again, this would be a conditional
threat, but with stronger dynamics in play especially whenever the
next front moves in, Wednesday may become a day requiring further
attention. Thursday and beyond, POPs begin to decrease as models
diverge on quality of available moisture, but northwest flow aloft
will persist. Realistic rainfall totals across the Panhandles
after midweek of a quarter to half inch may be commonplace, with
totals over an inch certainly plausible. Depending on which areas
receive these higher amounts, localized flooding could very well
become a concern.
Harrel
&&
.AVIATION...
(00Z TAFS)
Issued at 643 PM CDT Sat Sep 9 2023
VFR conditions expected throughout the 00Z TAF period. A very low
chance of a shower or storm for KAMA through 06Z, not high enough
to include in TAF at this time. Winds will be out of the south and
southeast at 10-20 kts with higher gusts at times, especially
during the day on Sunday.
Meccariello
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 65 91 61 73 / 20 40 60 50
Beaver OK 61 86 57 71 / 30 50 90 70
Boise City OK 59 88 56 68 / 20 30 70 50
Borger TX 67 94 64 75 / 20 50 70 60
Boys Ranch TX 64 93 61 74 / 20 30 60 40
Canyon TX 64 91 61 75 / 20 40 60 50
Clarendon TX 67 89 64 76 / 20 50 70 60
Dalhart TX 59 88 56 70 / 20 30 60 50
Guymon OK 60 89 58 70 / 20 50 80 60
Hereford TX 64 93 61 76 / 30 30 50 40
Lipscomb TX 61 88 59 73 / 20 50 80 70
Pampa TX 64 88 61 72 / 20 50 80 60
Shamrock TX 64 89 62 77 / 20 40 80 70
Wellington TX 66 92 64 78 / 20 30 70 70
&&
.AMA WATCHES/WARNINGS/ADVISORIES...
TX...None.
OK...None.
&&
$$
SHORT TERM...36
LONG TERM....38
AVIATION...29
Area Forecast Discussion
National Weather Service Cheyenne WY
530 PM MDT Sat Sep 9 2023
.SHORT TERM...(This evening through Sunday)
Issued at 335 PM MDT Sat Sep 9 2023
Current satellite imagery is beginning to show a Cu field
developing west of the Laramie Range where more instability
continues to persist early this afternoon. MSAS Frontal Analysis
depicts the stationary cold frontal boundary saddled across the
higher terrain of the South Laramie Range upstream toward west
central WY. Further downstream, the cold front boundary remains
sagged across the northern Front Range and northeast CO toward NE.
A surface trof remains present based off the 21Z surface weather
observation analysis along a line going north to south near the
WY/NE state border. Radar returns are also beginning to pop up as
of 21Z along the stationary frontal boundary of southeast WY near
the North Laramie Range. Breezy winds of 15-25mph have been
present through the majority of the day for southeast WY and the
NE Panhandle.
As the day presses on, it will be a tricky forecast to pin down
due to multiple weather factors being at play. While there is
sufficient instability and wind shear combined with moisture and
lapse rates for rain showers to develop across southeast WY this
afternoon, the best jet dynamics/kinematics won`t arrive until
this evening. Unless there is a surface convergence boundary that
becomes present this afternoon and evening similar to that of our
typical "Chugwater Cyclone," any other surface forcing will have
difficult time in sustaining convection until later tonight. The
HRRR is the most aggressive with convective initiation becoming
potential long-lasting supercells between 3Z-7Z. The NamNest
advertises similar long-track thunderstorms being present. The
"x-factor" will be whether the nocturnal inversion sets up after
sunset near 2Z-3Z this evening in time before the approaching 70+
jet streak aloft arrives over our cwa. This would inhibit boundary
layer mixing due to higher amounts of CIN becoming apparent across
the cwa. Have gone with a more conservative forecast this evening
with a majority of the thunderstorm activity remaining near and to
the north of the North Platte River Valley. Also, we will begin to
see an upslope wind pattern late this evening set up. The longer
fetch of moisture combined with the upslope winds will create low
CIGs and patchy to widespread dense fog will become present. Have
held off on any Dense Fog headlines at this time, but would not be
surprised to see visibility reductions less than 1 mile along the
I-80 Summit occur as early as 6Z tonight.
Sunday will see well below temperatures as the upslope regime of
steering flow, cloud cover, and cool temperatures aloft will cause
temperatures to struggle to reach 60 degrees for several portions
of our cwa east of the Laramie Range. Instability will be slightly
better west of the Laramie Range on Sunday afternoon due to the
frontal boundary remaining stationary across the western forecast
zones. An upper level shortwave will swing across the region by
Sunday afternoon, and this will trigger scattered to widespread
showers and thunderstorms from Sunday afternoon into the early
morning hours of Monday. Localized heavy rainfall and/or flooding is
possible due to the multiple rounds of rain shower activity
expected over similar trajectories. Rainfall amounts in excess of
0.5 inches to 1.0+ inches may occur in localized areas.
Additionally, we will see the persistent moisture and upslope flow
create more widespread fog by early Monday morning.
Well below normal temperatures will occur once again on Monday for
several areas across the cwa. The outliers will be western Carbon
County, and areas across the extreme northern tier of the Nebraska
Panhandle north of Hwy 20. Temperatures will approach 70 degrees
in these areas, but the remainder of the cwa will see daytime
highs in the 50s to middle 60s. We will finally begin to see
clearing occur by Monday night. Radiational cooling will come into
play by early Tuesday morning, and we could see the valley regions
of Albany County see patchy frost, in addition to the higher
terrain of the Snowy/Sierra Madre mountains. The active weather
pattern will trend towards a more quiet regime to start Tuesday,
before additional opportunities later in the week keep the area
cool.
.LONG TERM...(Sunday night through Saturday)
Issued at 335 PM MDT Sat Sep 9 2023
The weather pattern from Tuesday onward features several weak
impulses of energy and moisture that will skirt the southeast
Wyoming and western Nebraska areas. A weak inverted trough will pass
through the Four Couriers region on Tuesday, bringing several
waves of precipitation to areas just south of the Wyoming-
Colorado border. Both EPS and GEFS ensemble members keep most of
the moisture south of the border, however mid and upper-level
clouds look fairly abundant along the I-80 corridor given elevated
RH values aloft. By Wednesday morning, this system will eject out
into the central and southern high plains as a shortwave trough
approaches through the northern Rockies. The approach of this
shortwave trough in the north appears much more consistently
mottled in ensemble guidance over the past 12 hours of guidance
cycles. It is likely that the best forcing for showers and
thunderstorms with this system may remain far enough to the west
on Wednesday afternoon, keeping most locations in southeast
Wyoming and west Nebraska fairly dry. By Thursday, the trough axis
pivots through southeast Wyoming, with guidance trending toward a
more wet forecast area-wide on Thursday. Forecast guidance begins
to diverge notably by this point, with the GFS supporting a more
progressive wave and the ECMWF a more broad, diffuse trough moving
south and stalling. Forecast confidence decreases markedly from
Thursday onward as a result, with dry northwest flow supported by
one cluster of ensemble guidance and a wetter, monsoon-transition-
type pattern supported by another cluster of ensemble members.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 521 PM MDT Sat Sep 9 2023
A cold front will bring cooler and wetter conditions to the
terminals tonight and Sunday.
Wyoming TAFS...Scattered to broken clouds from 10000 to 12000 feet
AGL will occur until late tonight, with ceilings lowering to 5000
feet AGL at Rawlins and Laramie late tonight, and lowering to 1500
feet AGL at Cheyenne after 10Z. Sufficient gradients will produce
wind gusts to 23 knots at Laramie and Cheyenne until 06Z. Showers
will be in the vicinity of Laramie and Cheyenne after 10Z Sunday.
Nebraska TAFS...Scattered to broken clouds from 5000 to 8000 feet
AGL will occur this evening, with showers and thunderstorms in the
vicinity at Chadron, Alliance and Scottsbluff later this evening.
Ceilings will lower to 1000 to 1500 feet AGL after midnight with
areas of fog and showers reducing visibilities to 3 miles. Winds
will gust to 22 knots at Sidney until 03Z.
&&
.FIRE WEATHER...
Issued at 235 PM MDT Sat Sep 9 2023
Below normal temperatures and wetting rainfall is expected to
minimize fire weather hazards the remainder of this weekend into
early next week. Gusty and erratic winds are possible late this
evening as thunderstorms move from north to south. Very good
overnight humidity recovery will be present the next couple of days.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...BW
LONG TERM...MAC
AVIATION...RUBIN
FIRE WEATHER...BW
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1201 AM EDT Sun Sep 10 2023
.AVIATION...
A moist low level environment maintained under pervasive north-
northeast flow will continue to support the development of low
stratus through Sunday. Cloud trends likely to prove challenging
overnight, as some pockets of clearing expand in coverage per latest
satellite trends. Current trends point to a higher coverage of
stratus existing across the Detroit corridor, although a window of
clear sky may yet emerge prior to 12z. Those areas of clear sky
become most susceptible to dense fog development, with MBS/FNT
favored in this environment. Renewed westward advection of moisture
late tonight will then solidify another round of diurnally enhanced
stratocumulus on Sunday, perhaps entering as a brief high MVFR cig
before lifting into lower VFR.
For DTW...Upstream satellite trends still suggest the possibility
for a brief period of clearing overnight. This could introduce some
visibility restriction in shallow fog. Any clearing likely
relatively brief, with stratus again expanding in coverage Sunday.
.DTW THRESHOLD PROBABILITIES...
* Moderate in ceilings tonight and Sunday.
&&
.PREV DISCUSSION...
Issued at 345 PM EDT Sat Sep 9 2023
DISCUSSION...
Dry weather can be expected across southern MI through the rest of
the weekend as surface high pressure slowly drifts across the area.
The high is stretched out from SW to NE and the ridge axis is
currently NW of the region leading to continued northeasterly flow
into SE MI. Though the ridge offers some drier air, satellite shows
clouds locked in across the eastern CWA. The northeasterly flow in
between the ridge and troughing over the east coast is continuing to
pull boundary layer moisture back into the region with a good
coverage of stratus. Though some models want to keep offering the
drying trend they`ve been showing for the last 24 hours, RAP shows
the clouds sticking around through much of the night across the east
with some drying over Mid MI in the drier air. This is supported by
the pair of strong inversions in place in the model soundings and
12Z DTX sounding. Will hedge more pessimistic tonight with clouds,
which means also nudging min temps up a degree or so. Expect highs
on Sunday to slowly moderate but will be very dependent on the
degree of cloud cover and location of said clouds.
The ridge axis will pass on Sunday night allowing for the return of
southerly flow into the region ahead of an approaching trough. The
positively tilted trough will dig into the Midwest Sunday and Monday
pushing a weak front toward lower MI. In the upper levels, the
parent upper low will be well to the north over northern Ontario
with a jetlet diving into the base of the trough. This will cause
deepening of the trough while the parent low pushes off to the east
resulting in a cutoff upper low spinning over the Great Lakes
through mid week. Precip chances are expected to start increasing
late Monday as initial mid level moisture only acts to saturate the
deep dry layer above 850mb. A wet period looks to be Monday night
through Tuesday as a combination of the upper low, developing
surface low, and attending cold front pass over the area. The
positively tilted cold front will have support from the nocturnal
low level jet pumping addition moisture into the area. PWATs will be
steadily around 1 inch through Sunday night before climbing to
around 1.5 inches during that period. WPC still has us in Marginal
Risk of excessive rainfall for that period. Current QPF is for
around 0.50 to 0.75 inches over 24 hours but expect this to
change as we are still 3 days away.
With the upper low overhead Tuesday and Wednesday we can expect fall
like conditions with plenty of low cloud and suppressed temps in the
60s. High pressure will slide back in for the end of the work week
but there are already signs of the next trough moving in for the
weekend.
MARINE...
High pressure over the moving over the region this weekend will
result in favorable marine conditions. Wind direction will be
generally out of the northwest to northeast through this period as
the high pressure moves through. Stable conditions over the lake
will limit any gust potential with only 10 to 15 knots possible in
across southern Lake Huron Sunday afternoon. A stalled frontal
boundary across the northern Great Lakes will provide a focus for
some isolated shower activity across northern Lake Huron Sunday
night as troughing drops south out of Canada. As greater troughing
develops arrives Monday across the Great Lakes, the frontal boundary
will slide south as a cold front and bring the next chance for more
widespread showers and thunderstorms. The cold air advection with
this system will also bring an environment that may be favorable for
waterspout development Monday and Monday night. Continued troughing
and greater cold air over the region will bring unsettled marine
conditions Tuesday through midweek with gust potential up to around
25 knots across Lake Huron.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....MR
DISCUSSION...DRK
MARINE.......AA
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Goodland KS
540 PM MDT Sat Sep 9 2023
.SHORT TERM...(This evening through Sunday night)
Issued at 220 PM MDT Sat Sep 9 2023
Synoptic Overview: A pronounced upper level ridge, presently
centered over the Desert Southwest, will recede southward to
Mexico late this weekend.. as an amplifying upper level trough
over central/interior Canada digs southward into the Upper
Midwest, Upper MS River Valley and Upper Great Lakes.
Today-Tonight: WNW flow aloft (on the northeastern periphery of
the aforementioned ridge) will persist. Current observational and
mesoanalysis data indicate [1] a broad surface to 850 mb (SFC-H85)
trough extending NNE from eastern Colorado into west-central
Nebraska, invof a line extending (roughly) from La Junta (KLHX) =>
Wray (K2V5) => Ogallala (KOGA) and [2] a broad, ~1022 mb surface
high centered over IA-MN-WI.. and an associated surface ridge
extending southwestward into central-western Kansas (where it was
locally enhanced/reinforced by early-morning convection). The most
proximate forecast concern revolves around whether or not in-situ
convective development will occur invof the aforementioned
surface trough /dryline/ in northeast CO and adjacent KS-NE border
counties late this afternoon. Simulated reflectivity forecasts
via the 18Z HRRR and 12Z NAM NEST suggest that development will
not occur. The 15Z RRFS, on the other hand, suggests that isolated
development may occur invof Wray, CO ~21-22Z. As of 1945 UTC,
little if any Cu was present in Yuma County (per visible
satellite).. where a pronounced elevated mixed layer (~8.5 C/km
H7-H5 lapse rates) is present and considerable (50-150 J/kg)
convective inhibition persists. Based on observational/
environmental trends thus far.. and that forcing is almost
entirely relegated to low-level convergence invof the dryline..
deep, sustained convection is presently not anticipated. The
majority of convection allowing guidance does suggest that ongoing
deep convection north of I-80 (invof Broken Bow, NE) will
propogate southward (along a narrow, N-S oriented plume of low-
level moisture / axis of moderate instability) this evening,
possibly reaching Red Willow/Hitchcock counties by 02-04Z.. when
strengthening low-level southerly flow in western KS might
aid/assist further development that persists well into Sunday
morning.
Sun-Sun night: Flow aloft will back from WNW to W and strengthen
in this period.. as an amplifying upper level trough over
central/interior Canada digs southward into the Northern Plains
and Upper Midwest, suppressing the aforementioned upper ridge
south toward Mexico.. tightening the H5-H3 height gradient over
the Central/Northern Plains. With more favorable upper level
forcing, expect a greater overall potential for convection. Given
that environmental conditions may highly depend upon convective
evolution tonight and Sunday morning.. considerable uncertainty
exists with regard to convective evolution late Sunday afternoon
into Sunday night.. convective coverage, in particular.
.LONG TERM...(Monday through Saturday)
Issued at 112 PM MDT Sat Sep 9 2023
For the long term period, there is the possibility for storms most
days in the period with temperatures forecasted to generally remain
below average.
The long term is largely dominated by northwest to laminar flow
aloft which will allow for chances for shortwaves/troughs to move
through the area. Near the surface, relatively cooler air and higher
pressure are forecasted to accompany the upper disturbances.
Dewpoints are also forecasted to generally be in the 50`s and 60`s
at times short of Tuesday where some drier air may briefly move into
the area in the wake of the initial disturbance that changed the
pattern.
For the area, all of this will allow for cooler temperatures and a
few more chances for storms compared to the prior week. High
temperatures are forecasted to generally be in the 60`s and 70`s
with the cooler temperatures on Monday (if the cloud cover holds)
and Wednesday (if a larger wave moves through the flow as suggested
by guidance). For precipitation, chances look to be the best on
Monday and Wednesday with the main disturbances. Drier air on
Tuesday, may inhibit storm development while later in the week may
be inhibited by relatively high surface pressure over the area.
Severe weather could be possible on Wednesday with effective shear
forecasted to be around 30kts, but chances look to be low with cloud
cover forecasted to build in overnight Tuesday which would inhibit
heating.
Flooding is not currently expected with any of the days as ensembles
suggest most storms that would form would be unorganized and/or
lacking instability for higher rain rates.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 530 PM MDT Sat Sep 9 2023
KGLD...VFR conditions are currently expected through the period. A
southeast wind flirting around 12kts at taf issuance is forecast
to continue through tonight. On Sunday, winds will back to the
east then northeast at speeds up to 11kts through the day.
Regarding shower/thunderstorm possibilities, confidence is rather
low in areal coverage and intensity of rainfall at this time with
the emphasis of higher confidence and coverage to the east of the
terminal. Presently, any shower/thunderstorm mention wont be until
after 17z Sunday. Amendments will be made in the short term if the
threat arises.
KMCK...VFR conditions are currently expected through 20z Sunday.
Southeast winds around 10kts at taf issuance will back to the east
this evening and continue overnight. On Sunday, east to northeast
winds at speeds up to 11kts are expected. Regarding
shower/thunderstorm possibilities, immediate concern will be for
thunderstorms (currently one county north of Red Willow) to likely
impact the terminal in the 01z-03z timeframe with gusts up to
40kts and possibly heavy rainfall and hail. The rest of the period
will have likely chances for showers and thunderstorms. Cigs fall
to MVFR category after 21z Sunday with continued chances for
showers and thunderstorms.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...Vincent
LONG TERM...KAK
AVIATION...99
Area Forecast Discussion
National Weather Service Gray ME
1041 PM EDT Sat Sep 9 2023
.SYNOPSIS...
Showers and thunderstorms are expected this weekend along with
cooling temperatures, as a slow-moving boundary moves across the
Northeast. A low then moves in from the Great Lakes and brings
widespread rain and thunderstorms to the region on Monday.
Mostly cloudy but drier weather is expected on Tuesday before
another low comes down from Canada towards the second half of
next week, bringing more showers and thunderstorms.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
1040 PM Update...Mainly dry across the forecast area at this
time. However, weak ascent in a moist airmass with a weak SFC
front moving southward through the area may support widely
scattered showers and thunderstorms overnight. In fact, as of
this writing, one small storm has popped up near Biddeford ME.
Any storm will have the potential to produce heavy rainfall
overnight.
655 PM Update...Pretty much dry across the forecast area as of
this writing except for a couple of weakening thunderstorms
across southern NH. The main question for the remainder of the
evening is if the more widespread thunderstorm activity over MA
and CT will form a bit of a cold pool and advance northward into
portions of southern NH. It`s possible but the various CAMs are
unclear. Will keep chance PoPs going this evening. If more
organized convection can move in or develop over the area, then
heavy rainfall will be the biggest issue. Rainfall rates with the
storms to our south have been very high.
Previously...
Modest CU has blossomed across the area, most notably along a
convergence zone from southern Oxford County towards Waldo
County. Latest radar shows some small showers within this
convergence zone with the last few runs of the HRRR suggesting
this will be the likely area for additional showers and
thunderstorms into this evening. Latest RAP analysis shows
around 2000 J/kg of SB CAPE with around 25 kts of deep layer
shear, so storms that can form may produce some gusty winds to
around 40 mph and a severe storm cannot be ruled out. A second
area of storms to watch has developed across southern New
England, although these storms are currently moving very slowly
to the northeast and not well captured by latest CAM guidance.
Current storm motion suggests these storms are several hours
away from approaching the NH/MA border.
The last several runs of the HRRR and some other CAMs suggest
that eventually an area of showers and thunderstorms will
lift northeastward across the NH/MA border into central NH and
SW Maine late this evening into early Sunday morning. CAMs
indicate there will sufficient instability for convection
through tonight while much of this instability will be elevated.
This elevated instability combined with PWATs around 1.75
inches will bring the threat for localized heavy rain tonight.
The 12Z HREF is highlighting southern New Hampshire into York
County as the area with the greatest risk for heavy rain from
around 8 PM to 4 AM tonight. However, there are some members of
the HREF that have very little if any thunderstorm activity
during this time leading to low confidence in the forecast. At
any rate, there is a non zero threat that storms developing
late this evening into early Sunday will bring an isolated risk
for flash flooding with parts of southern New Hampshire seeing
upwards of 3 inches of rain yesterday. Given that instability
looks elevated the threat from storms to reach severe thresholds
tonight looks low. With a humid airmass in place, there will
likely be areas of fog tonight with lows in the 60s.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
An approaching shortwave will start to spread better forcing
for ascent over the area Sunday afternoon. PWATs will be
approaching 2 inches by Sunday afternoon across southern NH and
the coastal Plain of Maine. There again looks to be sufficient
instability for thunderstorms while the threat for severe storms
looks low. HREF members show a fair amount of variance in the
timing and coverage of showers and thunderstorms. The HRRR has
been favoring showers and storms through much of the day while
other members favor Sunday afternoon and evening. Have generally
followed the HREF mean for PoPs with PoPs increasing west to
east late morning into the evening.
The 12Z HREF 3 hour max QPF shows pockets of 2-3 inches of rain
in a 3 hour period scattered throughout NH and western Maine
suggesting this is the high end amount of rain in a 3 hour
period Sunday afternoon. The HREF 3 hour mean is much lower
with pockets upwards of 0.75 inches in a 3 hour period. After
multiple rounds of of isolated heavy rain, will have to watch
for an elevated risk of flash flooding late Sunday morning into
Sunday night. Given there is wide spread in coverage and timing
amongst guidance confidence is not yet there to warrant a flood
watch.
Ample cloud cover will limit temperatures to the 70s for highs
Sunday while it will remain humid with dewpoints in the upper
60s. The upper wave will remain to the west through Sunday night
maintaining chances for showers and thunderstorms to continue
into Monday morning. Areas of fog will be likely again Sunday
night with lows in the 60s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
We will continue to reenter a wet pattern as a large scale,
upper level trough approaches from the Great Lakes region to
start out the work week. Showers and a few thunderstorms will
cross the region on Monday. The atmosphere will remain quite
saturday with patchy fog and surface dew points approaching 70
degrees. The abundant cloud cover will keep temperatures in the
70s for highs.
Tuesday will be predominately dry as some weak ridging develops
over the region. However, a brief shower could form over
interior locations during the afternoon.
12Z operational models and ensemble solutions suggest the
precipitation will become more widespread once again on
Wednesday. Low pressure will approach from the west increasing a
moist, southerly flow over the region as height falls continue
over the Great Lakes region associated with the upper level
trough. Slightly drier air will enter the region on a westerly
flow on Thursday. However the upper trough may allow for a brief
shower.
Hurricane Lee will move north and northeast Friday and into the
weekend, remaining well off the coast. Long period swells will
likely impact the region.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Short Term...Lowering cigs and fog will likely bring IFR to LIFR
conditions tonight and a few TSRA cannot be ruled out across
southern New Hampshire into central Maine. Cigs may lift to IFR
to MVFR Sunday morning with additional rounds of SHRA and TSRA
possible late Sunday morning into Sunday night. IFR to LIFR is
likely again Sunday night.
Long Term...IFR and LIFR conditions in precipitation and fog
Monday, improving Tuesday before lowering to IFR/LIFR once again
Wednesday into Thursday.
&&
.MARINE...
Short Term... A stationary front will remain NW of the waters
tonight through Sunday night with winds oscillating from SE to
NE back to SE. Winds and seas will remain below SCA thresholds
while fog will be likely and chances for thunderstorms tonight
and again Sunday afternoon into Monday morning.
Long Term...Winds and seas will start out remaining below SCA
thresholds Monday and Tuesday. Seas build with an increasing
southerly flow on Wednesday. By late in the week, long period
swells may impact the region from Hurricane Lee.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.
&&
$$
SYNOPSIS...
NEAR TERM...Ekster/Schroeter
SHORT TERM...Schroeter
LONG TERM...Cannon
AVIATION...
MARINE...
Area Forecast Discussion
National Weather Service Northern Indiana
722 PM EDT Sat Sep 9 2023
.SYNOPSIS...
Issued at 311 PM EDT Sat Sep 9 2023
A mix of clouds and some sun toward far northwest Indiana
transitions to mostly sunny skies Sunday morning. Patchy fog is
possible early Sunday morning where skies have cleared. Rain
arrives over northwest Indiana on Monday, slowly reaching
northwest Ohio late Monday night. Cool and damp through midweek.
&&
.SHORT TERM...(This Evening through Sunday)
Issued at 311 PM EDT Sat Sep 9 2023
Like yesterday`s showers, stratus is slow to move out of the greater
US 24 corridor as of this midday writing. A cut-off low is present
at 700mb and is forecast to slowly drop south the Ohio River Valley,
on the eastern fridge of a persistent southwest US ridge. This
lingering cloudiness does pose a challenge for tonight`s previously
advertised fog concern. RAP guidance suggest low-level RH (clouds)
hang on over northwest Ohio much of tonight. Therefore, have
increased cloudiness there while omitting fog. Elsewhere, patchy is
fog is expected toward dawn due to cross over temperatures, low dew
point depressions, and the fact that fog was present over northern
IL and southern WI Saturday morning.
More sun than clouds on Sunday as the aformentioned low continues is
southward slide. Therefore, warmer as well with highs in the mid-to-
upper 70s.
&&
.LONG TERM...(Sunday Night through Saturday)
Issued at 311 PM EDT Sat Sep 9 2023
The primary item of long term interest is an incoming cold front
Monday, followed by cool, damp and dreary conditions lingering into
Wednesday.
A positively-tilted trough and surface cold front approach northwest
Indiana Monday morning presenting a high likelihood of showers and
perhaps a thunderstorm. The elongated northeast to southwest
orientation of the cold front suggests that most of the day will be
dry in eastern IN and northwest Ohio, as rain perhaps holds off
until Monday night.
The upper-level trough aloft becomes pinched against a strong ridge
of the Atlantic, which nearly cuts off the low over the eastern
Great Lakes. The result is likely cloudy skies with drizzle Tuesday
and Wednesday. Neighbors suggested several adjustments to POPs and
skycover Monday through Wednesday, trying to speed up arrival time
on Monday and lingering clouds and showers through Wednesday. I
personally think a slow southeast progression is most likely through
Monday night due to the steep NE to SW orientation of the system. A
dryslot may slip in at some point as this upper-level low wraps up,
while scattered showers loom otherwise.
A gradual warming trend follows as the upper-air pattern amplifies,
but next weekend is uncertain with notable differences in the
intensity of an incoming trough. Will keep an eye on the 500mb
ensemble EOF (Empirical Orthogonal Function) Pattern.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 721 PM EDT Sat Sep 9 2023
(Still some low level moisture remains. Now the question will be how
much clearing of cloud cover occurs, which may allow for the
formation of fog overnight into Sunday. Either way, cross over
temperatures may be reached, with the best chance of this occurring
being at FWA, and winds go light. Model soundings hint that a
subsidence inversion may form, but this would be contingent on
losing the clouds. Additionally, aviation guidance does bring MVFR
VISBY to both TAF sites with the SREF VISBY percentages also
introducing the potential for fog. Despite having these in play, am
still leery of cloud cover hanging tough overnight so will
continue the 3SM tempo group at FWA with SBN potentially narrowly
missing its cross-over temperature despite some lean towards
clearing of clouds. SBN will have to be watched in future
issuances for its own flight conditions that still might crop up
should the cross- over temperatures become achieved.
Winds become north-northeasterly Sunday still with some potential
for cloudiness to be around, but will keep things in VFR during the
day.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SYNOPSIS...Brown
SHORT TERM...Brown
LONG TERM...Brown
AVIATION...Roller
Visit us at www.weather.gov/iwx
Follow us on Facebook...Twitter...and YouTube at:
www.facebook.com/NWSNorthernIndiana
www.twitter.com/nwsiwx
www.youtube.com/NWSNorthernIndiana
Area Forecast Discussion
National Weather Service North Platte NE
629 PM CDT Sat Sep 9 2023
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 254 PM CDT Sat Sep 9 2023
Key Messages:
- Increasing chances of rain and thunderstorms through late
tonight with some strong to severe thunderstorms possible
capable of large hail, damaging wind gusts, and locally heavy
rain.
- Decreasing rain and thunderstorm Sunday afternoon into Monday,with
much cooler temperatures for the first half of next week.
- Temperatures rebound for the late week, returning to more
seasonable values.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 254 PM CDT Sat Sep 9 2023
This Afternoon/Tonight...isolated showers and thunderstorms have
been prevalent through the morning and early this afternoon across
portions of central and north central Nebraska. These are being
driven by the arrival of a strong cold front from the north,
encountering a moderately humid and unstable airmass across much of
western and central Nebraska on the nose of a narrow instability
gradient. Aloft, enhanced h5 flow overtop southerly low-level flow
is leading to a moderately sheared environment with 0-6km BWD values
of 30-40 knots. Latest 19z obs places the surface boundary near a
line from immediately south of ONL to immediately north of OGA. With
this southwest to northeast orientation of the boundary and
orthogonal shear vectors, expecting largely isolated convection this
afternoon. Forecast soundings show deep inverted-v profiles largely
due to dew point depressions nearing 30 degF. Steep mid-level lapse
rates will continue to advect in from the west and this will factor
into MLCAPE values hovering in the 1500-2000 j/kg range through
early this evening. Expectations going forward are for additional
thunderstorm activity to develop through early this evening as the
capping inversion weakens over time. Though DCAPE values in excess
of 1000 j/kg will support a damaging wind threat the main concern
will be large hail, perhaps exceeding golf ball size. This is due to
effective shear supporting multicell and perhaps brief supercellular
storm modes, strong mid-level shear with 2-7km BWD values exceeding
35 knots, and SHIP values from forecast soundings exceeding 1.0. As
storms merge and grow upscale in part from a growing cold pool,
expect the threat to transition to largely gusty winds. Given weak 0-
2km shear and LCLs exceeding 2000 meters AGL, believe the tornado
threat to be fairly low. That said, should a storm manage to latch
onto the boundary, a non-zero tornado threat will be present. CAMs
have been poor to handle ongoing convection early today, but believe
evolution of afternoon and evening activity they suggest is the
likely scenario...initial development early this afternoon
gradually increasing in coverage with a slight southeasterly
track. Believe storms will lose strength this evening as capping
increases. Some locally heavy rain is possible Most activity
should exit to the south and east by Midnight tonight. Attention
will then turn to activity moving off the higher terrain of
Wyoming and southwest South Dakota. Latest HRRR suggests multiple
discrete storms working in after Midnight into the western
Sandhills. Believe this activity will be weakening with time again
due to increasing capping with time. Though mid-level lapse rates
may remain favorable so cannot rule out a couple hail reports in
the early morning hours.
Sunday/Sunday Night...surface cold front will continue to shift
south through the area, settling near an Imperial to Ord line.
Modest southerly flow ahead of this feature will continue to usher
in theta-e rich air into the convergent zone. This will help bolster
increased coverage of rain and thunderstorms for our southern zones
early in the day. Expecting renewed development to favor areas east
of Highway 83 and generally south of Highway 2. Cannot completely
rule out a few hail reports with steep mid-level lapse rates of 7-8
degC/km and 2-7km BWD values of 30+ knots. Recent HREF guidance is
fairly muted with limited probabilities though this may be largely
explained by low precision within individual members. With PWAT
values hovering around 1.0" in the pre-convective environment,
will need to monitor potential for some locally heavy rain.
Limiting this concern though will be fairly progressive storm
motion and limited training of storms. Further northwest, stronger
mid-level convergence in association with an approaching
shortwave disturbance will bring increased rain and thunderstorm
probabilities in the post- frontal airmass. A few NWP solutions
depict fairly heavy rainfall in raw QPF output, notably the
NAM/Canadian solutions, so this potential will need to be
monitored. Meanwhile, the ECMWF is not as bullish and the GFS even
less so. Because of this, not overly confident that we see these
rainfall amounts in our northern zones during this period. Drier
air will begin to work in by the evening hours and this combined
with decreasing lift will allow precipitation chances to wane in
the evening. Surface high pressure will settle in during the
overnight hours, allowing winds to go light and temperatures to
fall into the low 50s and even the low 40s.
.LONG TERM...(Monday through Saturday)
Issued at 254 PM CDT Sat Sep 9 2023
Monday-Tuesday...expect the bulk of any precipitation to be out of
the area by early Monday. The exception to this would be portions of
the eastern Panhandle into southwest Nebraska. Dry air intrusion
will continue to push PWAT values well below 0.75" for much of the
area with considerable mid-level dry air overspreading the area by
the afternoon. This will support gradually clearing skies from north
to south. With h85 temperatures settling to around 10-12 degC, will
see a much cooler day again with highs only slightly warmer than
Sunday ranging in the 60s to low 70s. Large scale troughing across
the Great Lakes will continue to shift east with mid-level heights
filling in behind this feature. Resulting subsidence will keep the
forecast dry for Tuesday with only modest increases in afternoon
highs, creeping into the low to middle 70s.
Wednesday and beyond...ridging across southwest Canada will begin to
amplify during the late week. While this will slowly bleed east with
increasing mid-level heights as well, the biggest local impact will
come via amplified northwest flow aloft. Though no large-scale
system is appearing on the horizon, a weak disturbance around the
middle to latter half of the week may reintroduce some low-end PoPs
to the forecast. Though the greatest upper-level dynamics looks to
remain south of the forecast area, a trailing frontal boundary may
be the main lifting mechanism locally. NBM and EPS/GEFS
probabilities don`t signal widespread wetting rain event, but
details are murky at range so continue to monitor later forecasts
for the latest. For now, have greatest PoPs inherited from the model
blend Wednesday evening and again Thursday evening, but limited to <
30% either of the days. Ensembles also continue to highlight
anomalously cool temperatures in the low and mid-levels. This likely
explains the only modest warm-up for the latter half of the week as
highs only manage to climb into the upper 70s to potentially the low
80s by Friday and the weekend. This should keep temperatures closer
to seasonable norms and limit any threat for a return to well above
normal values.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 629 PM CDT Sat Sep 9 2023
A few different aviation weather concerns exist through the
forecast period, including thunderstorms, gusty winds, and low
ceilings. Current (as of 10/00z) thunder activity slowly exits
KLBF range, but gusty winds in the wake should wane after sunset.
A new wave of precipitation is expected to exit the Black Hills
and move into western Nebraska late tonight. Tempo visby
reductions are likely with that activity, then a stratus deck
builds in toward dawn. Most terminals should drop to MVFR by
daybreak and could spend most of the daylight hours in it as well
as scattered rain showers move through the area.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...NMJ
SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Snively
Area Forecast Discussion
National Weather Service Las Vegas NV
242 PM PDT Sat Sep 9 2023
.SYNOPSIS...Moisture drawn off Tropical Storm Jova will increase
overnight into Sunday and then linger through Tuesday resulting in
a chance of showers and thunderstorms over the southern Sierra
and east across parts of southern Nevada. Chance increase across
Mohave County on Tuesday. Expect a cooling trend to return
temperatures to around normal by Tuesday. Dry conditions and
seasonal temperatures are expected mid to late next week.
&&
.DISCUSSION...Through Tuesday.
Moisture from Tropical Storm Java is being directed into our area
by an upper level jet associated with troughing off the west
coast. This initial injection of moisture precedes the deeper
moisture that is forecast to move across our central and southern
areas later tonight and Sunday. Jet dynamics will aid shower and
thunderstorm development this afternoon over Esmeralda, Nye, and
Lincoln counties where enhanced lift and shear are present.
Further south, moisture is more limited but still sufficient
when combined with orographic lift and daytime heating to drive
shower and storm development over the mountains this afternoon.
Lower elevation sites may see virga or possibly even sprinkles as
showers move off the mountains and over the valleys.
The northern portions of our area in Nye and Lincoln counties will
see nocturnal shower and storm activity tonight thanks to
continued upper level support. Elsewhere, showers/storms are
likely to die off shortly after sunset when conditions become
stable. Expect clouds to increase overnight into Sunday with
skies become mostly cloudy as a deeper batch of moisture from
Jova moves over the area.
The HRRR is forecasting a new round of shower/storm activity over
the Sierra and northern Inyo County around 3 am Sunday which then
moves across southcentral Nevada during the morning hours. PWATs
are forecast to be 1 to 1.5 inches across much of our area on
Sunday but the moisture will be primarily in the mid to upper
levels. Mostly cloudy conditions in our central and southern
areas Sunday afternoon will keep temperatures around 3-5 degrees
cooler than today which should limit instability in these areas
and result in more light showery type precipitation. Less cloud
cover and better instability across our northern areas will
result in more convective type activity with a better chance of
thunderstorm development. With moisture limited to the mid and
upper levels on Sunday, the higher terrain will be favored for
shower and storm development with little to no rain accumulations
in the lower elevations.
Moisture is forecast to linger across the area Monday and Tuesday
a chance for shower and thunderstorms continuing across our
northern areas as well as in Mohave County.
Wednesday through Saturday...More benign weather conditions are
expected mid-late in the week. A trough is forecast to pass
across the northern Great Basin on Wednesday helping to sweep
moisture to our east - diminishing the moisture profile as PWATs
drop below an inch area wide and remain there into next weekend.
Temperatures mid to late in the week are forecast to remain fairly
steady at or slightly below normal.
&&
AVIATION...For Harry Reid...Winds will remain relatively light,
10 knots or less, and will tend to follow typical diurnal
direction trends through this evening. A couple of high resolution
models continue to show the potential for the terminal to see
northerly outflow winds from storms in Lincoln County later this
evening. Should these winds make it to the terminal area, it would
likely be between 05Z and 08Z. Other than these outflow winds,
winds during the overnight period will be light and variable.
Vicinity showers and thunderstorms will be possible tomorrow
morning and afternoon. Gusty outflow winds will be possible with
this convection.
For the rest of southern Nevada, northwest Arizona and southeast
California...Winds at the Las Vegas and Colorado River Valley TAF
sites will generally follow typical diurnal trends with winds of 10
knots or less through the afternoon and into the evening hours.
Northerly outflow winds from storms in Lincoln County may impact the
Las Vegas TAF sites between 05Z and 08Z. As these winds funnel down
the Colorado River Valley, there is a 40-60% chance that KIFP will
see 25+ knot gusts during the early morning hours. KDAG will favor a
westerly direction with sustained winds around 8-12 knots. Vicinity
thunderstorms may put out gusty outflow winds capable of impacting
KDAG. However, confidence in this occurring is low. KBIH will follow
typical diurnal trends with sustained winds of 10 knots or less.
Vicinity thunderstorms are expected in the White Mountains of Inyo
County, but these storms are not expected to impact the terminal
directly.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
DISCUSSION...Salmen
AVIATION...Stessman
For more forecast information...see us on our webpage:
https://weather.gov/lasvegas or follow us on Facebook and Twitter