Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
405 PM EDT Wed Oct 09 2024

Valid 00Z Thu Oct 10 2024 - 00Z Sat Oct 12 2024

...Major Hurricane MILTON is expected to make landfall along the
west-central coast of Florida overnight Wednesday...

...There is a High Risk of excessive rainfall over parts of the Florida
Peninsula...

...There is an Enhanced Risk of severe thunderstorms over parts of the
Florida Peninsula...

Major Hurricane MILTON continues to advance across the Gulf of Mexico and
is forecast to move northeastward and make landfall along the west coast
of Florida late Wednesday/early Thursday. Expected impacts include a large
area of destructive storm surge, with highest inundations of 10 feet or
greater, and devastating hurricane-force winds along portions of the
west-central coast of Florida. Milton is expected to remain a hurricane
while it crosses the peninsula, bringing life-threatening hurricane-force
winds, especially in gusts inland. Preparations to protect life and
property, including being ready for long-duration power outages, should be
rushed to completion as winds and rain will begin to pick up rapidly
through Wednesday as the storm approaches.

Moreover, heavy rain will be associated with MILTON. Therefore, the WPC
has issued a High Risk (level 4/4) of excessive rainfall over parts of the
Florida Peninsula through Thursday morning. Severe, widespread flash
flooding is expected. In addition, areas that normally do not experience
flash flooding will flood. Lives and property are in great danger.

Further, several tornadoes, including a few strong tornadoes, are likely
this Wednesday afternoon and night across parts of the central/southern
Florida Peninsula in association with Hurricane MILTON. Therefore, the SPC
has issued an Enhanced Risk (level 3/5) of severe thunderstorms over parts
of the Florida Peninsula through Thursday morning. The hazards associated
with these thunderstorms are frequent lightning, severe thunderstorm wind
gusts, a few tornadoes, and minimal threat of hail.

The threat of excessive rainfall continues over the eastern portion of the
Florida Peninsula. Therefore, the WPC has issued a High Risk (level 4/4)
of excessive rainfall over parts of the eastern portion of the Florida
Peninsula from Thursday through Friday morning. Severe, widespread flash
flooding is expected. In addition, areas that normally do not experience
flash flooding will flood. Lives and property are in great danger.

However, the threat of severe weather has decreased yet continues.
Therefore, a brief tornado or two remains possible during the late morning
Thursday along the east-central to northeast Florida coast. The threat of
excessive rainfall and severe thunderstorms will end by Friday.

Meanwhile, an upper-level low over Southeastern Canada/Northeast U. S.
will produce light rain over parts of the Northeast through Friday
morning. Moreover, another area of upper-level energy over parts of the
Central/Southern Plains will trigger scattered showers and thunderstorms
over the region through Friday.

Furthermore, on Wednesday evening, a front extending from the Northern
Rockies to the Great Basin and then into Northern California will move
slowly to the Upper Great Lakes to the Central Plains and then into the
Northern Intermountain Region by Friday. Associated upper-level energy
will aid in producing scattered light rain over parts of the Pacific
Northwest through late Wednesday night. Overnight Thursday, as the front
moves into the Upper Great Lakes, showers and thunderstorms will develop
over parts of the Upper Great Lakes.


Ziegenfelder


Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 PM EDT Wed Oct 9 2024

Valid 12Z Sat Oct 12 2024 - 12Z Wed Oct 16 2024

...Desert Southwest record heat moderates/lingers into Saturday...


...Overview...

Guidance continues to show development of an amplified ridge-trough
pattern over the lower 48, downstream from a deep system just
south of Alaska. A shortwave diving through the north-central U.S.
this weekend will begin the process of amplifying eastern U.S.
troughing and support a Northeast surface system, with multiple
trailing impulses helping to reinforce the trough. Much below
normal temperatures and frost/freeze may be a concern over some
areas from the Plains into the East. The front leading the colder
trend should suppress this weekend's central-southern U.S. heat
that may challenge daily records at some locations. The upper ridge
over the Rockies will support persistent warmth over the Interior
West and Rockies, focusing more over the northern Rockies/High
Plains toward the middle of next week. Expect the leading edge of a
Pacific trough to push a front and some accompanying rainfall into
the Northwest by next week.

...Guidance/Predictability Assessment...

Comparisons of latest dynamical and machine learning (ML) guidance
show good agreement for the large scale pattern evolution overall,
with the most prominent uncertainties being the specifics of
surface low development over the northeastern quadrant of the lower
48 around Sunday-Monday and how energy evolves within the eastern
U.S. upper trough by next Tuesday-Wednesday.

Solutions have been waffling for precise strength and track of the
Sunday-Monday surface system, with sensitivity to details aloft. At
the very least, ML solutions offer good support for more of a
closed upper low and better defined surface system than what
multiple CMC runs have been depicting. GEFS/ECens means have been
tilting toward a more occluded system reaching New England than
depicted in the 00Z ECMWF or past couple UKMET runs, but the ML
model spread includes the range of dynamical model details. The
dynamical model average has weakened the surface low somewhat
versus the prior 12-hourly cycle, with the average of ML models
fairly close to the dynamical guidance.

Later in the period, model/ensemble spread develops regarding
whether an upper low could form within the eastern U.S. trough. For
now such an upper low is a minority solution, so the deterministic
preference continues to be the open trough per a blend/ensemble
mean approach. There was hardly any guidance support for the
Midwest upper low in the 00Z CMC, while the 12Z CMC has at least
trended eastward with it toward the 00Z GFS (which was still a bit
on the western side among the subset of guidance that had a closed
low). On the other hand, the new 12Z GFS becomes more progressive
with the trough versus the majority.

Latest consensus has the Pacific upper trough axis reaching just
offshore the West Coast by early next Wednesday. ML models show
similar or slightly faster timing, but multi-day trends have been a
little slower--favoring the dynamical guidance for the time being.

Guidance considerations led to starting the early-middle part of
the forecast with a blend of the 06Z GFS, 00Z and 12Z/08 ECMWF, and
a small weight of 00Z UKMET. Then the blend added in some of the
06Z GEFS/00Z ECens means by next Tuesday-Wednesday with the
increasing detail uncertainty.

...Weather/Hazards Highlights...

A large part of the lower 48 will see fairly dry weather for a
majority of the period. A compact eastern Pacific upper trough/low
may bring a brief period of mostly light rainfall to the central
West Coast into Saturday, with a little light precipitation
possibly reaching farther eastward into the West thereafter. Then a
front approaching the Pacific Northwest may bring some moisture
and light to moderate rainfall into the region by the start of next
week. The amplifying upper trough and accompanying surface system
affecting the East late this weekend into early next week should
produce some areas of locally enhanced rainfall across parts of the
Great Lakes/Northeast. Little if any instability and fairly modest
moisture anomalies even on the higher side of the spread suggest
that short-term rain rates will likely not be high enough to pose
a flash flood threat. Therefore the Days 4-5 Excessive Rainfall
Outlooks continue to show no risk areas.

An upper ridge aligned over/near the Rockies for most of the
period will maintain well above normal temperatures over the
Southwest/Interior West into Rockies, and extending into the
northern High Plains toward midweek as the ridge shifts eastward a
little. The central/southern Plains will also have a very warm
start to the weekend before northern stream troughing and a cold
front suppress above normal readings to the south/southeast.
Greatest anomalies of plus 10-20F should be over the northern
Rockies multiple days and eventually the northern High Plains, as
well as the southern Plains during the weekend. Daily records will
be possible from the Southwest through the southern Plains this
weekend. Meanwhile, the East should see some near to slightly above
normal temperatures this weekend followed by a colder trend toward
highs 5-15F below normal next Monday-Wednesday underneath
amplified upper troughing. Morning lows next week may be a tad less
anomalous but still cold enough to raise some frost/freeze
concerns from the north-central U.S. through the Midwest/Great
Lakes and Northeast/Appalachians.

Rausch/Santorelli


Additional 3-7 Day Hazard information can be found on the WPC
medium
range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw

Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
318 AM EDT Wed Oct 09 2024

Valid 00Z Thu Oct 10 2024 - 00Z Thu Oct 17 2024

An upper trough over Hawaii will weaken as it ejects northeastward
with upper ridging becoming reestablished the rest of this week
and lasting well into next week. This should allow for a more
stable weather pattern and moderate to locally breezy trades.
Showers should generally favor windward locations. A cold front
approaching and dissipating north of the islands late this week
and into the weekend should allow some weakening again of the
trades before trades trend stronger next week with surface high
pressure building to the north.

Santorelli

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
825 PM EDT Wed Oct 9 2024
Day 1
Valid 01Z Thu Oct 10 2024 - 12Z Thu Oct 10 2024

...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
CENTRAL FLORIDA...

...WIDESPREAD AND NUMEROUS INSTANCES OF FLASH FLOODING ARE
EXPECTED WITH LIFE-THREATENING AND CATASTROPHIC FLASH FLOODING
PROBABLE...

...01Z Excessive Rainfall Discussion Update...
With Milton's eyewall getting close to the FL west coast near
Sarasota-Venice, the latest observational trends and recent
guidance (especially HRRR and HREF CAMs) show the heaviest rainfall
axis on the north side of Milton's track. Therefore with this
update we trimmed the outlooks on the southern periphery
(especially the High and Moderate), while also extending the High-
Moderate-Slight areas a little farther north along the east coast.

Given the estimated rainfall that has fallen thus far (using MRMS
QPE), along with the expected additional rain between 00Z Thu-00Z
Fri, we now expect 10-14 inches across much of the High Risk area,
with localized totals around 18 inches.

Hurley


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
825 PM EDT Wed Oct 9 2024
Day 2
Valid 12Z Thu Oct 10 2024 - 12Z Fri Oct 11 2024

...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL FOR THE ORLANDO METRO
AND PORTIONS OF THE FIRST AND SPACE COASTS...

...WIDESPREAD AND NUMEROUS INSTANCES OF FLASH FLOODING WITH LIFE-
THREATENING AND CATASTROPHIC FLASH FLOODING WILL LIKELY BE ONGOING
THURSDAY MORNING...

2030Z UTC Excessive Rainfall Discussion Update...
Maintained the High Risk for a portion of the central Florida
peninsula as rainfall associated with Milton should still be
falling as the Day 2 period begins at 12Z. There was a shift
towards a faster solution in the morning guidance...so trimmed a
bit of the areal coverage of various outlook categories. There
were few other changes needed.

Bann

0830 UTC Excessive Rainfall Discussion...

A High Risk area was introduced with this update in coordination
with MLB/Melbourne, FL forecast office. Almost no changes were made
to the other ERO risk areas.

Unfortunately, guidance continues to very gradually slow the
forward speed of Milton as it completes its track across the
Florida Peninsula and exits out into the Atlantic on Thursday. As a
result there was a small increase in the forecast rainfall after
12Z/8am Thursday from Orlando east up I-4 to the Atlantic coast.
The introduction of the High Risk for this area was much more the
result of expected continued catastrophic impacts from widespread
power outages and around a foot of storm total rain which will
continue into Thursday morning and perhaps a portion of Thursday
afternoon. Along the immediate coast, onshore flow at the time of
high tide may also hamper any drainage into the ocean by the local
streams, creeks, and rivers. Overall, with 3-5 inches of rain
expected after 8am Thursday in the High Risk area, which will be on
top of previous rainfall and likely the heaviest intensity of the
entire storm, it's likely the widespread impacts indicative of a
High risk will continue into the day Thursday.

The rain will quickly end from west to east Thursday morning for
west Florida and Thursday afternoon for east Florida. Thus, all of
the ERO risk areas are likely to be downgraded long before the 12Z
Friday end of the period. Since there remains some uncertainty,
especially around Tampa, as to what the nature of any lingering
rainfall will look like, the area remains in a Marginal Risk.

Wegman

Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
825 PM EDT Wed Oct 9 2024
Day 3
Valid 12Z Fri Oct 11 2024 - 12Z Sat Oct 12 2024

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Bann

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 PM EDT Wed Oct 9 2024


A large part of the lower 48 will see fairly dry weather for a
majority of the period. A compact eastern Pacific upper trough/low
may bring a brief period of mostly light rainfall to the central
West Coast into Saturday, with a little light precipitation
possibly reaching farther eastward into the West thereafter. Then a
front approaching the Pacific Northwest may bring some moisture
and light to moderate rainfall into the region by the start of next
week. The amplifying upper trough and accompanying surface system
affecting the East late this weekend into early next week should
produce some areas of locally enhanced rainfall across parts of the
Great Lakes/Northeast. Little if any instability and fairly modest
moisture anomalies even on the higher side of the spread suggest
that short-term rain rates will likely not be high enough to pose
a flash flood threat. Therefore the Days 4-5 Excessive Rainfall
Outlooks continue to show no risk areas.

An upper ridge aligned over/near the Rockies for most of the
period will maintain well above normal temperatures over the
Southwest/Interior West into Rockies, and extending into the
northern High Plains toward midweek as the ridge shifts eastward a
little. The central/southern Plains will also have a very warm
start to the weekend before northern stream troughing and a cold
front suppress above normal readings to the south/southeast.
Greatest anomalies of plus 10-20F should be over the northern
Rockies multiple days and eventually the northern High Plains, as
well as the southern Plains during the weekend. Daily records will
be possible from the Southwest through the southern Plains this
weekend. Meanwhile, the East should see some near to slightly above
normal temperatures this weekend followed by a colder trend toward
highs 5-15F below normal next Monday-Wednesday underneath
amplified upper troughing. Morning lows next week may be a tad less
anomalous but still cold enough to raise some frost/freeze
concerns from the north-central U.S. through the Midwest/Great
Lakes and Northeast/Appalachians.

Rausch/Santorelli

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 PM EDT Wed Oct 9 2024


A large part of the lower 48 will see fairly dry weather for a
majority of the period. A compact eastern Pacific upper trough/low
may bring a brief period of mostly light rainfall to the central
West Coast into Saturday, with a little light precipitation
possibly reaching farther eastward into the West thereafter. Then a
front approaching the Pacific Northwest may bring some moisture
and light to moderate rainfall into the region by the start of next
week. The amplifying upper trough and accompanying surface system
affecting the East late this weekend into early next week should
produce some areas of locally enhanced rainfall across parts of the
Great Lakes/Northeast. Little if any instability and fairly modest
moisture anomalies even on the higher side of the spread suggest
that short-term rain rates will likely not be high enough to pose
a flash flood threat. Therefore the Days 4-5 Excessive Rainfall
Outlooks continue to show no risk areas.

An upper ridge aligned over/near the Rockies for most of the
period will maintain well above normal temperatures over the
Southwest/Interior West into Rockies, and extending into the
northern High Plains toward midweek as the ridge shifts eastward a
little. The central/southern Plains will also have a very warm
start to the weekend before northern stream troughing and a cold
front suppress above normal readings to the south/southeast.
Greatest anomalies of plus 10-20F should be over the northern
Rockies multiple days and eventually the northern High Plains, as
well as the southern Plains during the weekend. Daily records will
be possible from the Southwest through the southern Plains this
weekend. Meanwhile, the East should see some near to slightly above
normal temperatures this weekend followed by a colder trend toward
highs 5-15F below normal next Monday-Wednesday underneath
amplified upper troughing. Morning lows next week may be a tad less
anomalous but still cold enough to raise some frost/freeze
concerns from the north-central U.S. through the Midwest/Great
Lakes and Northeast/Appalachians.

Rausch/Santorelli

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
209 PM EDT Wed Oct 9 2024

Valid 00Z Thu Oct 10 2024 - 00Z Sun Oct 13 2024

The probability of significant snow and ice across the CONUS is
less than 10 percent.

Fracasso

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 PM EDT Wed Oct 9 2024

Valid 12Z Sat Oct 12 2024 - 12Z Wed Oct 16 2024

...Desert Southwest record heat moderates/lingers into Saturday...


...Overview...

Guidance continues to show development of an amplified ridge-trough
pattern over the lower 48, downstream from a deep system just
south of Alaska. A shortwave diving through the north-central U.S.
this weekend will begin the process of amplifying eastern U.S.
troughing and support a Northeast surface system, with multiple
trailing impulses helping to reinforce the trough. Much below
normal temperatures and frost/freeze may be a concern over some
areas from the Plains into the East. The front leading the colder
trend should suppress this weekend's central-southern U.S. heat
that may challenge daily records at some locations. The upper ridge
over the Rockies will support persistent warmth over the Interior
West and Rockies, focusing more over the northern Rockies/High
Plains toward the middle of next week. Expect the leading edge of a
Pacific trough to push a front and some accompanying rainfall into
the Northwest by next week.

...Guidance/Predictability Assessment...

Comparisons of latest dynamical and machine learning (ML) guidance
show good agreement for the large scale pattern evolution overall,
with the most prominent uncertainties being the specifics of
surface low development over the northeastern quadrant of the lower
48 around Sunday-Monday and how energy evolves within the eastern
U.S. upper trough by next Tuesday-Wednesday.

Solutions have been waffling for precise strength and track of the
Sunday-Monday surface system, with sensitivity to details aloft. At
the very least, ML solutions offer good support for more of a
closed upper low and better defined surface system than what
multiple CMC runs have been depicting. GEFS/ECens means have been
tilting toward a more occluded system reaching New England than
depicted in the 00Z ECMWF or past couple UKMET runs, but the ML
model spread includes the range of dynamical model details. The
dynamical model average has weakened the surface low somewhat
versus the prior 12-hourly cycle, with the average of ML models
fairly close to the dynamical guidance.

Later in the period, model/ensemble spread develops regarding
whether an upper low could form within the eastern U.S. trough. For
now such an upper low is a minority solution, so the deterministic
preference continues to be the open trough per a blend/ensemble
mean approach. There was hardly any guidance support for the
Midwest upper low in the 00Z CMC, while the 12Z CMC has at least
trended eastward with it toward the 00Z GFS (which was still a bit
on the western side among the subset of guidance that had a closed
low). On the other hand, the new 12Z GFS becomes more progressive
with the trough versus the majority.

Latest consensus has the Pacific upper trough axis reaching just
offshore the West Coast by early next Wednesday. ML models show
similar or slightly faster timing, but multi-day trends have been a
little slower--favoring the dynamical guidance for the time being.

Guidance considerations led to starting the early-middle part of
the forecast with a blend of the 06Z GFS, 00Z and 12Z/08 ECMWF, and
a small weight of 00Z UKMET. Then the blend added in some of the
06Z GEFS/00Z ECens means by next Tuesday-Wednesday with the
increasing detail uncertainty.

...Weather/Hazards Highlights...

A large part of the lower 48 will see fairly dry weather for a
majority of the period. A compact eastern Pacific upper trough/low
may bring a brief period of mostly light rainfall to the central
West Coast into Saturday, with a little light precipitation
possibly reaching farther eastward into the West thereafter. Then a
front approaching the Pacific Northwest may bring some moisture
and light to moderate rainfall into the region by the start of next
week. The amplifying upper trough and accompanying surface system
affecting the East late this weekend into early next week should
produce some areas of locally enhanced rainfall across parts of the
Great Lakes/Northeast. Little if any instability and fairly modest
moisture anomalies even on the higher side of the spread suggest
that short-term rain rates will likely not be high enough to pose
a flash flood threat. Therefore the Days 4-5 Excessive Rainfall
Outlooks continue to show no risk areas.

An upper ridge aligned over/near the Rockies for most of the
period will maintain well above normal temperatures over the
Southwest/Interior West into Rockies, and extending into the
northern High Plains toward midweek as the ridge shifts eastward a
little. The central/southern Plains will also have a very warm
start to the weekend before northern stream troughing and a cold
front suppress above normal readings to the south/southeast.
Greatest anomalies of plus 10-20F should be over the northern
Rockies multiple days and eventually the northern High Plains, as
well as the southern Plains during the weekend. Daily records will
be possible from the Southwest through the southern Plains this
weekend. Meanwhile, the East should see some near to slightly above
normal temperatures this weekend followed by a colder trend toward
highs 5-15F below normal next Monday-Wednesday underneath
amplified upper troughing. Morning lows next week may be a tad less
anomalous but still cold enough to raise some frost/freeze
concerns from the north-central U.S. through the Midwest/Great
Lakes and Northeast/Appalachians.

Rausch/Santorelli


Additional 3-7 Day Hazard information can be found on the WPC
medium
range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw