Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/26/24
Area Forecast Discussion
National Weather Service Grand Rapids MI
940 PM EDT Wed Sep 25 2024
.KEY MESSAGES...
- Small rain chances Saturday through Tuesday
- Drier and cooler mid-week next week
&&
.UPDATE...
Issued at 940 PM EDT Wed Sep 25 2024
Added patchy fog into the forecast for late tonight / early Thu
morning for parts of the area. Consensus of short-term models is
leaning toward the better chance of fog being west of US-131,
where already the Ludington and South Haven AWOSes are reporting
dips in visibility. The forecast thermodynamic soundings in the
HRRR and ARW do not seem as robust for fog as they were a few
times last week, but it will be close in spots, enough for shallow
fog patches, as forecast min temps should drop a couple degrees
below the crossover temperature.
&&
.DISCUSSION...
Issued at 258 PM EDT Wed Sep 25 2024
- Small rain chances Saturday through Tuesday
Fair weather with drier air arriving overnight through Thursday.
Confidence is increasing that we will remain dry for Friday, and
see small chances for rain showers beginning Friday night and
lasting into Tuesday.
Many of the various models and ensemble members continue to show
what is left from "Helene" will be absorbed by the Upper Low
centered near AR/TN/MS on Friday. The strength of the upper high
over our area and the upper low will wrap it back to the NW, but
keep most of the system south of the area.
What we will see from this scenario is we will see moisture advect
in from the SE, and weak short waves rotating on the northern flank
of the combined upper low complex. Much of the period from Saturday
through Monday will be dry. There will be periods when short waves
move through, combined with diurnal instability that will fire off a
few showers and even isolated storms at times. The air with this
system will not be that cold with the tropical part of this.
- Drier and cooler mid-week next week
Eventually what will happen by Monday night/Tuesday is we will see a
strong upper jet and associated upper wave dive toward the area.
This is a strong enough system that it will boot the weekend upper
low out. This system will arrive with a strong cold front, and a
chance of showers and storms. The flow ahead of the front will not
be favorable for much rain with the front.
The front is forecast to move through at some point on Tuesday. The
frontal passage looks to end rain chances at that point, and it will
cool the air down markedly as 850 mb temps drop from the low/mid
teens C, to the lower single digits C by Wednesday. This will
support highs in the 60s and lows in the 40s.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 746 PM EDT Wed Sep 25 2024
VFR expected to be prevalent tonight and Thursday although cannot
rule out some MVFR or lower vsbys in fog late tonight and early
Thursday (mainly between 08Z and 13Z). Given the low confidence in
overnight fog formation/coverage, have maintained the earlier
strategy from the 18Z TAFs of carrying a 4-5 hr period of VCFG in
most of the TAFs.
&&
.MARINE...
Issued at 258 PM EDT Wed Sep 25 2024
Winds are expected to remain below 20 knots and waves below 3 feet
into the weekend.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
UPDATE...CAS
DISCUSSION...Ostuno/NJJ
AVIATION...Meade
MARINE...Ostuno
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1103 PM EDT Wed Sep 25 2024
.SYNOPSIS...
Tropical Cyclone Helene is forecast to make landfall over the
Florida Panhandle late Thursday, with the remnant circulation moving
quickly north bringing gusty winds and heavy rainfall to our area
Thursday night into Friday. Expect a calmer weekend with
temperatures near seasonal normals.
&&
.NEAR TERM /THROUGH THURSDAY/...
As of 1055 pm...A wide band of rain continues to stream northward
in a plume of deep tropical moisture to the east of a stalled
frontal boundary over east TN. Thus, our Predecessor Rain Event
(PRE) continues, with the rain starting to soak in and run off,
already raising some streams into flood. The eastern edge of the
rain band is sort of being re-oriented on a line from Abbeville to
Spartanburg to Morganton, but that might not move much for the next
several hours. There remains some overlap on the eastern edge with
an air mass over the western Piedmont that retains 500-1000 J/kg
of sfc-based CAPE and deep layer shear of 30-40 kt. Another brief
tornado would not be out of the question, after what we have already
seen today, but the trend continues slowly downward in terms of
the severe weather threat. That being said, the flash flood threat
continues to ramp up as the rain continues to fall, mainly over the
foothills and along/near the Blue Ridge Escarpment. We are eyeing
another large area of rain and thunderstorms over central GA moving
northward in the conveyor belt. This could be the precip that puts
more streams into flood in the early morning hours. Several more
warnings should be expected overnight.
The new Advisory for Helene will keep the Tropical Storm Warnings
unchanged, while the Flood Watch also remains unchanged based on
the most recent QPF guidance. The 00Z CAMs are filtering in, and
the HRRR remains compelling with its wind gust forecast bringing
a swath of wind gusts into the region, but still not until after
00Z Friday. In other words, the wind gust potential still does
not ramp up until Thursday evening. Otherwise, all signs point to
a significant event across the western Carolinas and northeast
Georgia. Although another subtle westward shift in the track
is noted, Helene will be a large and fast-moving storm, so the
westward shift doesn`t really matter. We still expect a very rare
and significant amount of rainfall and some areas across the mtns
and adjacent zones will see catastrophic and damaging flooding. Once
the rainfall gets above ten inches of rain or more, we often see
numerous reports of landslides across the high terrain, and the
threat for landslides and debris flows will increase dramatically
Thursday night.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 130 PM EDT Wednesday: ***MAJOR RAINFALL EVENT FOR THE
SOUTHERN APPALACHIANS AND VICINITY WITH POTENTIAL FOR WIDESPREAD
FLASH FLOODING***
The predecessor rainfall event will be coming to an end by the
beginning portions of the forecast period as the initial tropical
rain bands from Hurricane Helene begins to move in from the south
as Helene will be in the midst of making landfall as a major
hurricane near the Big Bend of Florida Thursday evening. Large
amounts of rainfall will have already fallen across the Blue Ridge
Escarpment, southeast facing slopes, western Upstate South Carolina,
and northeast Georgia. Sandwiched between a closed upper low over
the mid-Mississippi Valley and an upper anticyclone over the western
Atlantic will inadvertently sling shot Helene into the Southeast
Thursday night before the storm takes on a more western track as
the closed upper low overtakes the track by Friday afternoon. The
heaviest rainfall rates will be within the tropical rainbands
and with already rising streams, creeks, and rivers, expect for
significant flash flooding to take place in locations that will get
hammered by the PRE in the near-term forecast. The areas of most
concern will be the southern Appalachians and adjacent foothills
as flash flooding becomes widespread, with locally severe and
life-threatening flooding likely. The rainfall is expected to taper
off by Friday afternoon as Helene becomes absorbed by the closed
upper low and drier air filters in. Before everything is all said
and done, 5-10" of rainfall will be possible in locations west
of HWY 321 and 10-15+" on the southeastern facing slope along the
Blue Ridge. Still expect moderate to major flooding on some main
stem rivers including: French Broad River Basin, Pigeon River and
Tuckasegee River Basin, and Saluda and Broad River Basins. These
areas are forecasted to see river floods that rival 1995 (TC Jerry)
and 2004. With the amount of rain and heavy rainfall rates, it`s
likely that numerous landslides will occur over the mountains,
especially the Blue Ridge Escarpments and result in a couple of
large, damaging debris flows/slope failures as well.
With the fast track north to the area that Helene will encompass,
the frictional force that usually derails any tropical cyclone`s
wind fields won`t have enough time to totally wipe out the strong
wind field associated with Helene. In this case, wind gusts of
40-50, some 60-70 mph will be possible in the western portions
of the CFWA Thursday night into Friday morning. In this case,
we have issued a Tropical Storm Watch for the North Carolina
mountains/foothills, Upstate South Carolina, and northeast
Georgia. The impacts will be significant from winds as soils will
already be super saturated and any strong wind gusts will easily
knock down numerous trees and lead to numerous power outages
across the locations in the Tropical Storm Watch. The tornado
threat will be the lowest concern of the big three that come with
any tropical system, but definitely nonzero, especially with the
initial rainbands that work into the region Thursday evening into
the overnight period. The biggest threat will be in locations along
and south of the I-85 corridor as better instability will become
established in this region and will be in the favorable front-right
quadrant of Helene. Most instability will diminish overnight as
more stable northeasterly flow filters in thanks to Helene. Most
model guidance lifts Helene out of the region by Friday afternoon
with conditions quickly improving. Flooding will be ongoing Friday
afternoon and evening, while mainstem river flooding may persist
into the weekend.
Saturday will be much improved and provides relief from the impacts
that will occur Thursday and Friday, with a lot of locations
cleaning up after the storm. The closed upper low is expected to
engulf Helene, but should gradually push east. This could lead
to a few showers in the mountains Saturday afternoon, but expect
for rainfall to remain light in comparison to the rainfall from
Thursday and Friday. Temperatures will be near-normal Saturday as
well in part to the lower heights and any lingering cloud cover.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 245 PM EDT Wednesday: Closed upper low is expected to engulf
the remnants of Helene, while gradually pushing across the Ohio and
Tennessee Valleys over the weekend before setting shop over the
Mid-Atlantic and Carolinas by the start of the new workweek. In
this case, showers will return back into the forecast for Sunday
and Monday as the upper low crosses the area and a moisture starved
front will swing across the region by midweek. Signs of true Fall
weather from the model guidance is evident beyond D6. Temperatures
will remain near-normal through much of the period as elevated
cloud cover and PoPs remain in the forecast.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: A main band of rain and thunderstorms has
made very little eastward progress this afternoon and evening,
as predicted, thus most terminals remain VFR at issuance time,
with the exception of KAVL. Unfortunately, it`s all downhill
from here. An area of TSRA will pass just east of KCLT over the
next hour, otherwise, we should make it thru the evening VFR there
until lower clouds develop after midnight/04Z. Elsewhere, a gradual
eastward creep in the rain band will bring the other terminals into
the restrictions associated with storms by 03Z at the latest, and
probably even before that. Ceilings drop overnight as more upslope
forcing arrives and deep tropical moisture streams up from the
south, down through MVFR to IFR through the pre-dawn hours. Once
there, we should stay down for the count in the LIFR/IFR range,
with frequent heavier showers moving through and winds becoming
gusty from the SE after daybreak. Lots of details are being left
out for brevity for Thursday.
Outlook: Helene will bring widespread low CIGs, heavy rain, strong
winds, and low level wind shear Thurs nite into Fri before moving
out of the area late Fri into Sat. Isolated to sct mainly diurnal
convection will be possible thru the weekend.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Flood Watch through Friday afternoon for GAZ010-017-018-026-
028-029.
Tropical Storm Warning for GAZ010-017-018-026-028-029.
NC...Flood Watch through Friday afternoon for NCZ033-035-048>053-
056-058-059-062>065-068-069-501>510.
Tropical Storm Warning for NCZ033-048>053-056-058-059-062>065-
068>071-082-501>510.
SC...Flood Watch through Friday afternoon for SCZ008-010>013-019-
101>109.
Tropical Storm Warning for SCZ008>014-019-101>109.
&&
$$
SYNOPSIS...DEO
NEAR TERM...PM
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...PM
Area Forecast Discussion
National Weather Service Northern Indiana
826 PM EDT Wed Sep 25 2024
.KEY MESSAGES...
* Isolated showers will continue to diminish this evening.
* Rain showers associated with a tropical system enter the
forecast late Friday afternoon through the weekend.
* Seasonable temperatures are replaced by a temporary dose of
fall by the middle of next week.
&&
.UPDATE...
Issued at 820 PM EDT Wed Sep 25 2024
High pressure across the upper Midwest and inverted sfc trough
feature across the Ohio Valley has allowed for broad weak
low level boundary in this weak low level deformation flow.
Have had a few instances this evening of some funnel cloud
development in vicinity of this boundary west of KFWA with RAP
analysis depicting weak axis of sfc vorticity. Radar trends have
been on the decline over the past hour and continued
diminishment of weak low level instability should end isolated
shower potential. Some patchy shallow fog is possible overnight,
mainly across the far northwest. No major changes made to the
forecast at this time.
&&
.DISCUSSION...
Issued at 220 PM EDT Wed Sep 25 2024
Isolated showers will remain possible near a weak trough axis across
northern IN and srn MI this afternoon given sufficient boundary
layer moisture and diurnal heating. This trough washes out tonight
into tomorrow with drier easterly winds developing on the southern
fringe of a low level anticyclone building northeast into the Great
Lakes. Clearing and winds becoming light/variable for a time later
tonight may allow for some patchy ground fog to develop across
mainly nw IN and portions of southern MI.
Main focus into Friday and the weekend will turn to Hurricane Helene
remnants being absorbed into a leftover upper low over the western
TN Valley. Friday likely remains dry with northeast winds becoming
breezy in response to the sfc low center pivot north-northwest into
Kentucky for a time. A few bands of light rain may clip the area on
the northern fringe later Friday into Saturday, best chances south
of US 30/24. Seasonable temperatures expected otherwise before a
cold front brings a shot of fall-like temps by the middle of next
week.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 800 PM EDT Wed Sep 25 2024
An upper level low center across the Mid MS Valley will continue
to slowly sag southward into Thursday. This will allow some
drier air to initially push into the region tonight into early
Thursday. A weak low level boundary and strong sheared
vorticity max east of this height minimum is aiding in some
isolated shower coverage just west of KFWA, but expecting this
isolated shower potential to be very short-lived and diminished
shortly after 01Z. At this time expecting focus for any
afternoon isolated showers on Thursday to be confined southeast
of terminals with better low level moisture residing east of the
inverted trough axis across southwest Ohio. Some patchy fog is
possible at KSBN given light flow and recent rainfall today, but
otherwise unfavorable vertical moisture profiles should limit
extent and magnitude of this potential. Light winds tonight will
become northeast around 10 knots late Thursday morning.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
UPDATE...Marsili
DISCUSSION...Steinwedel
AVIATION...Marsili
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
905 PM EDT Wed Sep 25 2024
.SYNOPSIS...
Light rain and cloudy conditions persist through today and into
tonight. Weak front arrives Thursday with mostly dry conditions
expected. Hurricane Helene moves further north into the Gulf of
Mexico and into the southern Appalachians and Tennessee River
Valley over the next several days. Widespread rainfall possible
Friday, especially across parts of Central Virginia. High
pressure builds in from the north this weekend, but rain chances
remain into next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
The 00Z KIAD sounding shows plenty of moisture near the surface
with RH values of 96 percent. This will result in low clouds
and patchy fog throughout the area. Recent model guidance has
hinted at increased precipitation totals overnight as moderate
to heavy rain is expected along and west of the Blue Ridge. The
23Z HRRR is the only guidance showing increased totals so we
will continue to monitor as the full 00Z guidance suite comes
in. Heaviest precipitation looks to remain west of the area
tonight with the flooding risk remaining low at this time.
Previous Discussion Follows: Off and on rain showers will
persist overnight with moderate to heavy rain expected along and
west of the Blue Ridge. Cannot rule out a rumble of thunder but
confidence is low in this coming to fruition locally. Rainfall
amounts of 1 to 2 inches will be possible for the aforementioned
areas through tonight. Given the ongoing drought concerns and
the more prolonged periods of rain, the flood threat should be
fairly limited and localized heading into early Thursday. For
tonight, lows will only drop a few degrees given the increased
cloud coverage across the area.
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
A brief relief from the precipitation will take place on
Thursday as southerly flow builds in and a quick break between
the departing frontal boundary and the impacts associated with
Hurricane Helene. Cannot rule out a few isolated showers
Thursday afternoon but most areas should remain fairly dry for
the majority of the day.
Per the NHC forecast, Hurricane Helene makes landfall along the
northeast Gulf Thursday evening, then moves north toward the TN
Valley / Southern Appalachians Thursday night. Deep tropical
moisture moves into our area by early Friday morning, bringing
widespread rain/showers to central/northwest VA and surrounding
highlands. Models have trended weaker with a surface low moving
south from Canada, meaning most of the area is likely to see
high rain chances Friday into Friday night. The heaviest is
going to be along the eastern slopes of ridges south of
I-66/US-48, and in Central VA where 2-4" of rain is possible
with localized higher amounts. Localized flooding is possible
but confidence is low at this time given the track uncertainty.
The main circulation of Helene retrogrades west towards the Mid-
South as it interacts with the cutoff low, keeping the better
tornado environment to the west of the forecast area. Continue
to monitor our local forecast and the National Hurricane Center
as Helene continues to move further north.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The remnants of Helene will continue to drift over the Tennessee and
lower Ohio River Valleys while being absorbed into a large cutoff
low this weekend. The cutoff upper level low will gradually fill and
weaken as over the Mid-South through early next week. With the low
nearby, and pieces of embedded energy pivoting around it, expect
increased chances for showers and perhaps a few thunderstorms
throughout the weekend into early next week. Some uncertainty
remains in regards to the placement of the cutoff low and
timing/placement of embedded pieces of energy pivoting around it.
The influence of surface high pressure over New England wedging
south along the Appalachians will play into the overall coverage of
precipitation as well. Overall not expecting any washouts this
weekend although abundant cloud cover and intermittent shower
chances will continue as remnant moisture from Helene overrides the
wedge high overhead.
The upper level low continues to fill and push to the east Monday
into Tuesday. Moist flow will likely remain with incoming troughing
and an associated cold front pushing out of the middle part of the
country. This deepening trough continues to show up on 12z
deterministic/ensemble model suites today and over past couple of
days. It`s exact amplitude, timing, and whether or not it cuts
off remains in question. Regardless, there is the potential for
a strong frontal passage during the Tuesday and Wednesday
timeframe providing additional shower and thunderstorm chances.
Drier conditions look to return wit high pressure by the latter
half of next week.
Due to the added cloud cover and cool air wedge, temperatures are
expected to remain at or below normal through Tuesday . Highs will
be around 80 Saturday with 60s and 70s Sunday into early next week.
Lows will fall into the 50s and 60s.
&&
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Sub-VFR conditions look to continue through Thursday as a
series of slow moving fronts cross the region. Still dealing
with a pseudo CAD wedge and a weak warm frontal boundary
gradually lifting north from central and southern VA. MVFR to
IFR (brief periods LIFR) ceilings will prevail through the
remainder of the day especially at terminals west of a line from
KBWI-KRIC. Light showers/drizzle will continue to work through
the corridor over the next 2-4 hours between now-21z/5pm.
Further west of KMRB and KSHD will continue to monitor the
progression of a line of moderate to heavy rain and embedded
thunderstorms working north along the incoming cold front from
the Ohio River Valley. This activity will gradually push east
later this evening and into the overnight hours reinforcing
reductions in vsbys and cigs across the area. IFR to possibly
LIFR CIGs are likely tonight into Thursday morning.
Conditions slowly improve Thursday as weak southerly flow ensue with
mid-level ridging overhead. Conditions should dry out for the
corridor terminals with perhaps a few showers and thunderstorms, mainly
at terminals along and west of a line from KMRB to KCHO/KSHD.
Ceilings should remain MVFR in these locations(IFR possible at
CHO for most of the day) with VFR further east. Winds will
remain light out of the east and southeast at 5-10 kts.
Sub-VFR ceilings are likely Thursday night into Friday as the
remnants of Helene work into the southern Appalachians. Widespread
rainfall is expected from this system with the heaviest at terminals
south of the corridor and down into southwest portions of VA.
Sub-VFR conditions are likely at times over the weekend into early
next week as remnant moisture from Helene continues to push over the
region. Wedging high pressure will keep abundant cloud cover and
shower chances in place through at least Monday. A few thunderstorms
are possible during this time.
&&
.MARINE...
A Small Craft Advisory goes into effect through this evening for the
Chesapeake Bay and surrounding rivers/tributaries, and the Lower
Tidal Potomac. Expect winds to gust up to 20 knots into tonight.
Winds will fall back below SCA levels tonight and remain at sub-SCA
levels through Thursday afternoon. The remnants of Helene approach
the area from the south late Friday into Saturday, with a surge of
east to southeast winds likely ahead of the tropical system. SCA
conditions are likely to develop Friday afternoon, and continue into
the weekend.
Depending on the evolution of low pressure approaching from the
OH/TN Valleys this weekend, onshore flow could be strong enough to
prompt the issuance of Small Craft Advisories at times. Uncertainty
is moderate to high at this time, and ranges from marginal SCA to
near gale-force.
&&
.TIDES/COASTAL FLOODING...
Decreasing astronomical tides will lead to slightly lower (though
still elevated) tides, with bouts of minor flooding likely around
times of high tide through Friday morning. The higher of the two
daily tides is during the overnight/early morning hours, and would
be susceptible to the most widespread minor to perhaps locally near
moderate tidal flooding.
By Friday, Helene will orbit around an upper low to the southwest as
high pressure holds firmly to the north. This pattern results in
enhanced onshore east to southeast flow at times through the
weekend, and has the potential to result in multiple rounds of
widespread minor to moderate tidal flooding through at least
Sunday.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until 6 PM EDT Thursday for DCZ001.
MD...Coastal Flood Advisory from 3 AM to 10 AM EDT Thursday for
MDZ008.
Coastal Flood Advisory until 5 AM EDT Thursday for MDZ011.
Coastal Flood Warning until 9 AM EDT Thursday for MDZ014.
Coastal Flood Advisory until 1 AM EDT Thursday for MDZ016-017.
Coastal Flood Advisory until 2 AM EDT Thursday for MDZ018.
Coastal Flood Advisory until 9 AM EDT Thursday for MDZ508.
VA...Coastal Flood Advisory until 6 PM EDT Thursday for VAZ054.
Coastal Flood Advisory until 1 AM EDT Thursday for VAZ057.
WV...None.
MARINE...Coastal Flood Advisory from 3 AM to 10 AM EDT Thursday for
ANZ530.
Small Craft Advisory until 11 PM EDT this evening for
ANZ531>534-537-538-542-543.
&&
$$
SYNOPSIS...ADM/KRR/EST
NEAR TERM...AVS/ADM/KRR
SHORT TERM...ADM/KRR
LONG TERM...EST
AVIATION...DHOF/ADM/EST
MARINE...DHOF/ADM/EST
TIDES/COASTAL FLOODING...LWX
Area Forecast Discussion
National Weather Service Melbourne FL
1033 PM EDT Wed Sep 25 2024
...New UPDATE...
.UPDATE...
Issued at 1030 PM EDT Wed Sep 25 2024
Local preparations ahead of Hurricane Helene`s impacts should now
be complete. Conditions are forecast to deteriorate overnight into
Thursday morning as the cyclone intensifies, moving north-
northeastward over the eastern Gulf of Mexico. Most locations have
experienced a brief break from the rain in the last hour or two,
but another outer rain band from Helene is impacting the Treasure
Coast and is expected to continue north toward the Space Coast in
the next 1-2 hours. These heavy showers will pack gusty winds of
30 to 45 mph as they quickly move from south to north. Continued
episodes of gusty rain bands, intermixed with periods of dry time,
will last through sunrise Thursday.
Deeper moisture is advecting northward and will continue to do so
tonight, as the surface pressure gradient tightens over the
Florida Peninsula. The evening XMR sounding showed quite the
increase in moisture when compared to this morning`s data (1.86"
PW at 15z to 2.25" at 00z). RAP analysis indicates MLCAPE around
1000 J/kg along the coast, and model guidance suggests this will
expand overnight as MLCIN begins to decrease. Surface- based CIN
will also erode gradually through the night, with SBCAPE climbing
to 1000-2000 J/kg along and east of Interstate 95. Hi- res
guidance depicts the highest lightning chances focused near the
coast or just offshore. Gusty winds to 45 mph and a brief
waterspout or tornado cannot be ruled out through sunrise along
the coast. Be sure to have multiple ways to receive warnings, in
the event they are issued later tonight. Conditions will
worsen on Thursday with daytime heating and increasing low/mid
level wind shear enhancing the already gusty squalls expected
across the state. The tornado threat is forecast to increase
during the daylight hours, along with the potential for locally
heavy rainfall. Continue to monitor weather.gov, NOAA Weather
Radio, and local news outlets for updated, official information on
Helene.
&&
.PREVIOUS DISCUSSION...
Issued at 224 PM EDT Wed Sep 25 2024
-Hurricane Helene will lift north over the eastern Gulf of Mexico
through Thursday and produce heavy rain, strong winds, and
possible tornadoes. Rough, battering surf will produce dangerous
conditions at the beaches.
-Preparations for Helene should be underway and completed by this
afternoon, with conditions deteriorating tonight.
-Hot and humid late week behind "Helene" as plume of deep moisture
returns and keeps a threat for heavy rain this weekend.
Rest of Today-Tonight...Any preparations ahead of Hurricane Helene
should be rushed to completion this afternoon. Conditions will
deteriorate tonight. Until then, showers and storms embedded
within the moisture plume of Helene continue across the area this
afternoon. Gusty winds have been reported along the coast, with
the St Lucie Nuclear Power Plant reporting a 47mph wind gust
earlier today along the barrier island from a storm. Expect
showers and storms to increase from south to north, with outer
rainbands reaching southern portions of east central Florida this
evening. Tropical Storm Warnings remain in effect.
Training showers and storms, along with ample tropical moisture
(2.25-2.5" PWATs) could produce locally heavy rainfall in some
locations. Given the recent heavy rainfall over several areas
earlier this month, have issued a Flood Watch for the entire
forecast area. Be sure to have multiple ways to receive warnings
overnight tonight. Increasing SRH, particularly along and north of
the I-4 corridor, will quickly increase the tornado threat into
the early morning hours. Breezy southeasterly flow will keep
overnight lows in the mid to upper 70s.
A High Surf Advisory has been issued through Friday morning, with
seas building into Thursday. If heading to the beach, be cautious of
large, surging waves in the surf zone. Do not enter the water.
Thursday-Thursday Night...Conditions will further deteriorate
through the morning hours on Thursday, as Helene makes its closest
approach to the area while forecast to be a Major hurricane.
Gusty squalls will increase in frequency into the afternoon, as
southeasterly to southerly winds increase to 20-40mph, with gusts
50-55mph. A few gusts to 60mph cannot be ruled out in the afternoon,
with 925mb winds around 50kts.The strongest winds will be along
and north of the I-4 corridor, which will be closest to the storm
itself. Models suggests periods of dry air being wrapped around
the storm at its closest approach. However, with 1-4" forecast and
locally higher amounts possible in training bands, will continue
the Flood Watch due to recent heavy rains this month. The tornado
threat looks to peak Thursday afternoon into the evening hours,
with forecast STP values around 1+ and low level SRH increases.
Temperatures look to be moderated by precipitation, cloud cover,
and a well mixed atmosphere. However, should the sun break through
in any dry slots, temperatures could reach values higher than
currently forecast. For now, have high temperatures reaching the
mid to upper 80s, as deep moisture surges heat indices to near
100. Dangerous beach conditions will persist through the impact
phase of Hurricane Helene. If heading to the beach, be cautious of
large, surging waves in the surf zone. Do not enter the water.
Conditions will begin to improve Thursday night. However, gusty
winds will persist through the overnight hours.
Fri-Tue (modified previous)...Models show a dry slot moving into
the area from the SW on the backside of Helene as it lifts
northward into GA then the TN Valley Thu night/early Fri. But, a
plume of deep moisture will remain across south FL and return
northward over central FL late Fri into the weekend. Hot, breezy
SW flow on Fri- Sat will produce max temps in the lower 90s even
at the coast. Combined with high humidity, peak heat indices will
climb to 104-108. Storm coverage looks higher on Sat, when the
deep moisture is squarely over the area, so have drawn 60 PoP
areawide. Then decreasing rain chances Sun (40-50 percent) and
Mon/Tue (30-40 percent).
&&
.MARINE...
Issued at 224 PM EDT Wed Sep 25 2024
Tropical Storm Warnings are in effect for the adjacent Atlantic
waters out to 60 nm. Hurricane Helene is forecast to continue to
strengthen over eastern Gulf of Mexico and accelerate into the FL
Big Bend late Thursday. Boating conditions will continue to
deteriorate tonight, as southeast winds increase to 25-30kts by
daybreak, then 30-40kts Thursday afternoon. Seas building 7-8ft
tonight, then peaking at 13ft offshore Volusia and Brevard
Thursday afternoon into Thursday night. Deep moisture lifting
northward will support a high coverage of showers and storms
through Thursday. Winds will become southwest Friday, decreasing
to 20-25kts and will continue to gradually decrease to near 15
knots late Friday night. Seas quickly subsiding below 5 ft along
the coast due to the offshore component but remaining 6-7 ft
offshore Friday. Flow remains offshore (W to SW) Saturday-Sunday
up to 15 knots, with seas subsiding 3-4 Saturday and 2-3 ft Sun.
There will be scattered to numerous storms pushing offshore
especially Saturday.
&&
.AVIATION...
(00Z TAFs)
Issued at 725 PM EDT Wed Sep 25 2024
Scattered to isolated showers and storms will continue across east
central Florida over the next several hours. Conditions are then
forecast to deteriorate across the terminals late tonight into
Thursday as outer rainbands from Hurricane Helene move across east
central Florida, with prevailing SHRA and VCTS forecast. Tried to
capture timing of a potential dry slot between 10-18Z across the
interior terminals and between 13-18Z across the coastal terminals
tomorrow, with the CAM guidance in decent agreement on this
timing. Additional rainbands are then forecast to set up after
18Z, with continual SHRA and VCTS through the remainder of the
period beyond 00Z. Sustained winds of 20 to 30 knots with gusts
beyond 30 knots are forecast out of the south to southeast
tomorrow. Also added in mention of LLWS after 18Z, with
FL015 reaching 45kt out of the south.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 77 88 78 92 / 60 90 60 40
MCO 77 88 79 90 / 50 90 60 50
MLB 79 88 79 92 / 60 80 70 60
VRB 78 89 79 92 / 60 80 70 70
LEE 77 87 78 90 / 60 90 60 30
SFB 77 88 79 91 / 50 90 60 50
ORL 78 88 80 91 / 50 90 60 50
FPR 78 88 78 92 / 60 70 70 70
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Tropical Storm Warning for FLZ041-044>046-053-058-141-144-154-
159-164-247-254-259-264-347-447-547-647-747.
Flood Watch through Friday morning for FLZ041-044>046-053-058-
141-144-154-159-164-247-254-259-264-347-447-547-647-747.
High Surf Advisory until 11 AM EDT Friday for FLZ141-154-159-164-
347-447-647-747.
AM...Tropical Storm Warning for AMZ550-552-555-570-572-575.
&&
$$
UPDATE...Schaper
AVIATION...Tollefsen
Area Forecast Discussion
National Weather Service Marquette MI
739 PM EDT Wed Sep 25 2024
.KEY MESSAGES...
- Dry weather is expected into the weekend.
- Temperatures trend well above normal into next week.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 307 PM EDT Wed Sep 25 2024
As low pressure has lifted into Ontario this morning, GOES-16 Day
Cloud Phase RGB imagery just shows some fair weather cu across the
central UP with a few low clouds over the Keweenaw. The RAP analyzes
a 1016 mb high centered over eastern Kansas that extends pressure of
at least 1011mb all the way from western Upper Michigan to the Rio
Grande Valley, and this broad high pressure will keep the weather
quiet through tonight. Temperatures have already reached into the
70s in some areas of the UP which is about what the high is expected
to be today.
Overnight, the warming trend in low temperatures continues with the
lowest of lows expected in the interior west around 45 degrees, with
lows up to the low 50s expected elsewhere. The main forecast
question revolves around whether or not fog will be able to form.
Blending hi-res model wind gives surface winds overnight around 5
knots, which is a bit high for radiation fog formation even with RHs
of 100% expected by the early morning hours. HREF chances of
visibility falling below 1 mile overnight are 0 for the west half
but range from 20-50% in the east half. GLAMP and Euro probabilities
of fog vary significantly by location, from 0-10% in the far west to
up to 40% in the central-to-east. Ended up going patchy fog tonight
(20%) given the uncertainty.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 224 PM EDT Wed Sep 25 2024
Upper air pattern consists of a 500 mb closed low of Hurricane
Helene in the Gulf of Mexico, a closed low over the mid Mississippi
Valley, and a closed low over southwest Quebec with a trough in the
Pacific NW and a ridge in the southern Rockies into the northern
Plains 12z Thu. The ridge builds into the upper Great Lakes Thu
night through Sat and will bring dry and warm weather to the area.
In the extended, the GFS and ECMWF show a 500 mb closed low over the
Ohio and Tennessee Valleys 12z Sunday with a trough in the Pacific
NW and ridging over the southern and central Rockies into the upper
Great Lakes. Troughing moves into the northern plains 12z Mon and
into the upper Great Lakes 12z Tue as a ridge builds into the
western U.S. Ridging moves into the southern half of the U.S. 12z
Wed. Temperatures start out above normal for Sunday and Monday and
then drop to near normal for Tuesday and Wednesday as colder air
moves in.
&&
.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 739 PM EDT Wed Sep 25 2024
With dry air dominating thru the low and mid-levels, VFR will
prevail at IWD/CMX/SAW thru this fcst period. However, given the
quiet conditions and longer nights at this time of year, shallow
radiation fog may develop once again, similar to recent nights. SAW
has the better chance of seeing shallow fog development as lake
breeze this aftn has brought higher dwpts to the terminal and vcnty.
Maintained a mention of MVFR in the 09-13z time frame, but there is
some potential of IFR as well. With sfc high pres over the area,
winds thru the period at all terminals will be light, under 10kt.
&&
.MARINE...
Issued at 224 PM EDT Wed Sep 25 2024
Upper Michigan will remain under high pressure for the duration
of the forecast period. Therefore, winds will remain at or below 20
knots through Sunday. 20 to 30 knot winds will not be until Monday
when the next system starts to enter the region.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...GS
LONG TERM...07
AVIATION...Rolfson
MARINE...07