Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
338 PM EDT Mon Oct 14 2024

Valid 00Z Tue Oct 15 2024 - 00Z Thu Oct 17 2024



...Wet snow over parts of the Upper Great Lakes to the Northeast and
Central Appalachians...

...Rain over parts of the Pacific Northwest and wet snow over parts of the
Northern Cascades...

...Lake Effect rain south of the Great Lakes...

High pressure over Central Canada will move southward to the Middle
Mississippi/Ohio Valleys by Wednesday. The clear sky and calm wind
associated with the high have triggered Freeze Warnings, Advisories, and
Watches over parts of the Midwest.

Moreover, an upper-level low over the Northeast to the Great Lakes will
produce lake-effect rain south of the Great Lakes over parts of the Ohio
Valley and Central Appalachians through Wednesday afternoon. Wet snow will
develop over parts of the Huron Mountains of Michigan s Upper Peninsula
through Tuesday night. In addition, rain and wet snow at higher elevations
will develop over parts of the Northeast through Wednesday evening. Wet
snow will also develop overnight Tuesday over parts of the highest
elevations of the Central Appalachians through Wednesday.

Meanwhile, easterly flow off the Gulf of Mexico will help produce showers
and thunderstorms over parts of the Western Gulf Coast on Wednesday.
Additionally, tropical moisture over the Florida Keys will keep showers
and thunderstorms in the forecast through Wednesday.

Furthermore, a front moving onshore over the Pacific Northwest late Monday
afternoon will move inland to the Northern Rockies and Northern California
by Wednesday evening. The system will produce light rain over parts of the
Pacific Northwest through Wednesday afternoon. On Wednesday, the rain will
expand into the Northern Intermountain Region. Moreover, wet snow will
develop over parts of the highest elevations of the Northern Cascades on
Wednesday.

Upper-level dynamic associate with an upper-level low over the Southwest
will aid in producing widely scattered showers and thunderstorms over
parts of the Great Basin, Southwest, and Central/Southern Rockies from
Monday into Wednesday evening.


Ziegenfelder


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

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
302 PM EDT Mon Oct 14 2024

Valid 12Z Thu Oct 17 2024 - 12Z Mon Oct 21 2024


...Overview...

Deep upper troughing with a likely closed low in the West will
lead to a cool and wet pattern there, including higher elevation
snow and frost/freeze concerns in some of the valleys. Heavy rain
chances could increase in the southern/central Plains by the
weekend. Upper ridging ahead of this trough will promote warmer
than average temperatures in the northern/central Plains to Midwest
as it gradually moves east, eventually displacing the chilly upper
trough and surface high in the East by the weekend.


...Guidance/Predictability Assessment...

Model guidance continues to be agreeable on the large scale
pattern evolution through much of the period, but some
uncertainties still in the timing and details of individual
systems. Most notable system during the medium range will be a
shortwave diving into the West early period, with models now
showing agreement on a deep closed low developing over the
Southwest by this weekend and eventually lifting north and east
early next week. Through the 00z run, the CMC was more progressive
and displaced east of the GFS, ECMWF, and UKMET, but the new 12z
run today did jump west. 00z GFS was quickest to lift the system
northward Sunday-Monday but the new 12z run did slow down. Good
agreement on an upper ridge building back in across the East again
behind a departing upper trough/low, but how far westward this
ridge retrogrades early next week is dependent on the evolution of
the western/central upper low.

WPC forecast for today preferred a non-CMC blend early in the
period, which was more west with the low and most consistent with
the previous WPC forecast. Leaned more heavily on the ensemble
means late period with lingering and increasing uncertainties.


...Weather/Hazards Highlights...

The upper trough/low pushing across the West later week will push
precipitation from the Pacific Northwest into the Intermountain
West/Rockies later week, with enhanced precipitation totals in
terrain. Higher elevation snow is likely, which will be the first
snow of the season in some locations given the warm Fall in the
West thus far. Some rain and snow could continue across the
central/southern Rockies into the weekend. Meanwhile, Gulf moisture
may stream in just ahead of the upper low for increasing rain
chances in the central/southern High Plains late week into the
weekend. While forecast details vary, recent models show some
moderate to locally heavy rain potential, particularly for
sensitive burn scar locations. Lighter rain may spread into the
north- central U.S. late week too along the front. More rounds of
precipitation are likely for the Pacific Northwest into the weekend
with additional impulses coming through.

Meanwhile, the eastern U.S. is forecast to be generally dry late
week into early next week, with the exception of parts of the
Florida Peninsula. There, return flow of moisture north of a
stationary front could increase rain and thunderstorm chances
especially for South Florida by Friday and perhaps spreading
northward into the weekend. Models continue to vary on how much
rain may fall onshore versus offshore, so no area is currently
delineated in the Day 5/Friday ERO, but there may be a nonzero
chance for flash flooding especially if heavy rain rates occur in
the sensitive urban areas.

An upper ridge aligned over the Mississippi Valley Thursday and
shifting into the East Friday will promote well above normal
temperatures in its vicinity. The biggest anomalies are forecast
across the north-central Plains on Thursday, where highs into the
70s and 80s are 15-25 degrees above average for mid-October. Cooler
than average temperatures by 10-15 degrees are expected to
continue across the eastern third of the U.S. into Thursday under
cool high pressure. Another round of chilly morning lows may cause
frost/freeze concerns from the Great Lakes region into the
Northeast/Appalachians. Gradual moderation/warming is likely there
Friday and even more so into the weekend when upper ridging comes
overhead, for temperatures around 5-10 degrees above normal in the
northeastern tier. Then the ridge rebuilding over the central U.S.
early next week will lead to warmer than average temperatures in
the northern Plains to Upper Midwest once again. On the other hand,
the upper trough and frontal surges in the West will cause below
normal temperatures spreading across the West Coast to Great
Basin/Intermountain West and Southwest particularly through late
week. These colder temperatures may also lead to additional
frost/freeze concerns for any still susceptible growing
areas/valley locations.


Santorelli/Tate


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
400 AM EDT Mon Oct 14 2024

Valid 00Z Tue Oct 15 2024 - 00Z Tue Oct 22 2024

A weak surface trough will push east to west across Hawaii through
Monday with an increase in moisture for some enhancement of
showers. Trades are forecast to strengthen around
Tuesday-Wednesday as the surface ridge to the north returns. By
Thursday or Friday the trades look to decrease once again, while a
weak upper low and perhaps a surface trough approach the state and
cause another surge of above average moisture that could enhance
rainfall amounts in favored windward locations especially.
Moisture levels should return closer to normal into the weekend.

Tate

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
753 PM EDT Mon Oct 14 2024
Day 1
Valid 01Z Tue Oct 15 2024 - 12Z Tue Oct 15 2024

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

Roth/Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
753 PM EDT Mon Oct 14 2024
Day 2
Valid 12Z Tue Oct 15 2024 - 12Z Wed Oct 16 2024

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

Bann


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

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
753 PM EDT Mon Oct 14 2024
Day 3
Valid 12Z Wed Oct 16 2024 - 12Z Thu Oct 17 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
302 PM EDT Mon Oct 14 2024


The upper trough/low pushing across the West later week will push
precipitation from the Pacific Northwest into the Intermountain
West/Rockies later week, with enhanced precipitation totals in
terrain. Higher elevation snow is likely, which will be the first
snow of the season in some locations given the warm Fall in the
West thus far. Some rain and snow could continue across the
central/southern Rockies into the weekend. Meanwhile, Gulf moisture
may stream in just ahead of the upper low for increasing rain
chances in the central/southern High Plains late week into the
weekend. While forecast details vary, recent models show some
moderate to locally heavy rain potential, particularly for
sensitive burn scar locations. Lighter rain may spread into the
north- central U.S. late week too along the front. More rounds of
precipitation are likely for the Pacific Northwest into the weekend
with additional impulses coming through.

Meanwhile, the eastern U.S. is forecast to be generally dry late
week into early next week, with the exception of parts of the
Florida Peninsula. There, return flow of moisture north of a
stationary front could increase rain and thunderstorm chances
especially for South Florida by Friday and perhaps spreading
northward into the weekend. Models continue to vary on how much
rain may fall onshore versus offshore, so no area is currently
delineated in the Day 5/Friday ERO, but there may be a nonzero
chance for flash flooding especially if heavy rain rates occur in
the sensitive urban areas.

An upper ridge aligned over the Mississippi Valley Thursday and
shifting into the East Friday will promote well above normal
temperatures in its vicinity. The biggest anomalies are forecast
across the north-central Plains on Thursday, where highs into the
70s and 80s are 15-25 degrees above average for mid-October. Cooler
than average temperatures by 10-15 degrees are expected to
continue across the eastern third of the U.S. into Thursday under
cool high pressure. Another round of chilly morning lows may cause
frost/freeze concerns from the Great Lakes region into the
Northeast/Appalachians. Gradual moderation/warming is likely there
Friday and even more so into the weekend when upper ridging comes
overhead, for temperatures around 5-10 degrees above normal in the
northeastern tier. Then the ridge rebuilding over the central U.S.
early next week will lead to warmer than average temperatures in
the northern Plains to Upper Midwest once again. On the other hand,
the upper trough and frontal surges in the West will cause below
normal temperatures spreading across the West Coast to Great
Basin/Intermountain West and Southwest particularly through late
week. These colder temperatures may also lead to additional
frost/freeze concerns for any still susceptible growing
areas/valley locations.


Santorelli/Tate

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
302 PM EDT Mon Oct 14 2024


The upper trough/low pushing across the West later week will push
precipitation from the Pacific Northwest into the Intermountain
West/Rockies later week, with enhanced precipitation totals in
terrain. Higher elevation snow is likely, which will be the first
snow of the season in some locations given the warm Fall in the
West thus far. Some rain and snow could continue across the
central/southern Rockies into the weekend. Meanwhile, Gulf moisture
may stream in just ahead of the upper low for increasing rain
chances in the central/southern High Plains late week into the
weekend. While forecast details vary, recent models show some
moderate to locally heavy rain potential, particularly for
sensitive burn scar locations. Lighter rain may spread into the
north- central U.S. late week too along the front. More rounds of
precipitation are likely for the Pacific Northwest into the weekend
with additional impulses coming through.

Meanwhile, the eastern U.S. is forecast to be generally dry late
week into early next week, with the exception of parts of the
Florida Peninsula. There, return flow of moisture north of a
stationary front could increase rain and thunderstorm chances
especially for South Florida by Friday and perhaps spreading
northward into the weekend. Models continue to vary on how much
rain may fall onshore versus offshore, so no area is currently
delineated in the Day 5/Friday ERO, but there may be a nonzero
chance for flash flooding especially if heavy rain rates occur in
the sensitive urban areas.

An upper ridge aligned over the Mississippi Valley Thursday and
shifting into the East Friday will promote well above normal
temperatures in its vicinity. The biggest anomalies are forecast
across the north-central Plains on Thursday, where highs into the
70s and 80s are 15-25 degrees above average for mid-October. Cooler
than average temperatures by 10-15 degrees are expected to
continue across the eastern third of the U.S. into Thursday under
cool high pressure. Another round of chilly morning lows may cause
frost/freeze concerns from the Great Lakes region into the
Northeast/Appalachians. Gradual moderation/warming is likely there
Friday and even more so into the weekend when upper ridging comes
overhead, for temperatures around 5-10 degrees above normal in the
northeastern tier. Then the ridge rebuilding over the central U.S.
early next week will lead to warmer than average temperatures in
the northern Plains to Upper Midwest once again. On the other hand,
the upper trough and frontal surges in the West will cause below
normal temperatures spreading across the West Coast to Great
Basin/Intermountain West and Southwest particularly through late
week. These colder temperatures may also lead to additional
frost/freeze concerns for any still susceptible growing
areas/valley locations.


Santorelli/Tate

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
157 PM EDT Mon Oct 14 2024

Valid 00Z Tue Oct 15 2024 - 00Z Fri Oct 18 2024

...Northeast...
Days 1-2...

A leading upper low tracks north over Maine this evening before
stalling over the mouth of the St Lawrence into Wednesday. The next
wave is positively tilted trough over the Boundary Waters of MN
this afternoon which will swing south into the Midwest tonight and
over the southern Appalachians Tuesday night. Steep lapse rates
should trigger some potent snow showers, especially in higher
terrain above 3,000ft. Snow showers look to linger in the northern
Appalachians until Wednesday morning when the trough axis moves
east and off the New England coast.

Additional snow over 4" should be confined to the higher
Adirondacks,
Green, and White mountains.


...Northwest...
Days 2-3...

An upper shortwave trough brings a surge in 850-700mb moisture and
associated height falls will cause snow levels to gradually drop
from around 6000ft Tuesday night to around 4000ft by Wednesday
evening over the WA Cascades. The airmass is not particularly cold
for the time of year, so this setup favors snowfall accumulation
in the Olympics and Cascades down toward the highest mountain
passes Wednesday night until Thursday morning when a reinforcing
trough crosses western WA brining and end to moderate precip rates.

This secondary wave digs down through far northern CA Thursday with
decent precip rates and height falls over the northern
Intermountain West to the northern Rockies. Day 3 WWD probs for
more than 4" are 50-80% for higher terrain of the WA/OR Cascades
and the Salmon River mountains in ID and the northern Absarokas in
MT.


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


Jackson

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
302 PM EDT Mon Oct 14 2024

Valid 12Z Thu Oct 17 2024 - 12Z Mon Oct 21 2024


...Overview...

Deep upper troughing with a likely closed low in the West will
lead to a cool and wet pattern there, including higher elevation
snow and frost/freeze concerns in some of the valleys. Heavy rain
chances could increase in the southern/central Plains by the
weekend. Upper ridging ahead of this trough will promote warmer
than average temperatures in the northern/central Plains to Midwest
as it gradually moves east, eventually displacing the chilly upper
trough and surface high in the East by the weekend.


...Guidance/Predictability Assessment...

Model guidance continues to be agreeable on the large scale
pattern evolution through much of the period, but some
uncertainties still in the timing and details of individual
systems. Most notable system during the medium range will be a
shortwave diving into the West early period, with models now
showing agreement on a deep closed low developing over the
Southwest by this weekend and eventually lifting north and east
early next week. Through the 00z run, the CMC was more progressive
and displaced east of the GFS, ECMWF, and UKMET, but the new 12z
run today did jump west. 00z GFS was quickest to lift the system
northward Sunday-Monday but the new 12z run did slow down. Good
agreement on an upper ridge building back in across the East again
behind a departing upper trough/low, but how far westward this
ridge retrogrades early next week is dependent on the evolution of
the western/central upper low.

WPC forecast for today preferred a non-CMC blend early in the
period, which was more west with the low and most consistent with
the previous WPC forecast. Leaned more heavily on the ensemble
means late period with lingering and increasing uncertainties.


...Weather/Hazards Highlights...

The upper trough/low pushing across the West later week will push
precipitation from the Pacific Northwest into the Intermountain
West/Rockies later week, with enhanced precipitation totals in
terrain. Higher elevation snow is likely, which will be the first
snow of the season in some locations given the warm Fall in the
West thus far. Some rain and snow could continue across the
central/southern Rockies into the weekend. Meanwhile, Gulf moisture
may stream in just ahead of the upper low for increasing rain
chances in the central/southern High Plains late week into the
weekend. While forecast details vary, recent models show some
moderate to locally heavy rain potential, particularly for
sensitive burn scar locations. Lighter rain may spread into the
north- central U.S. late week too along the front. More rounds of
precipitation are likely for the Pacific Northwest into the weekend
with additional impulses coming through.

Meanwhile, the eastern U.S. is forecast to be generally dry late
week into early next week, with the exception of parts of the
Florida Peninsula. There, return flow of moisture north of a
stationary front could increase rain and thunderstorm chances
especially for South Florida by Friday and perhaps spreading
northward into the weekend. Models continue to vary on how much
rain may fall onshore versus offshore, so no area is currently
delineated in the Day 5/Friday ERO, but there may be a nonzero
chance for flash flooding especially if heavy rain rates occur in
the sensitive urban areas.

An upper ridge aligned over the Mississippi Valley Thursday and
shifting into the East Friday will promote well above normal
temperatures in its vicinity. The biggest anomalies are forecast
across the north-central Plains on Thursday, where highs into the
70s and 80s are 15-25 degrees above average for mid-October. Cooler
than average temperatures by 10-15 degrees are expected to
continue across the eastern third of the U.S. into Thursday under
cool high pressure. Another round of chilly morning lows may cause
frost/freeze concerns from the Great Lakes region into the
Northeast/Appalachians. Gradual moderation/warming is likely there
Friday and even more so into the weekend when upper ridging comes
overhead, for temperatures around 5-10 degrees above normal in the
northeastern tier. Then the ridge rebuilding over the central U.S.
early next week will lead to warmer than average temperatures in
the northern Plains to Upper Midwest once again. On the other hand,
the upper trough and frontal surges in the West will cause below
normal temperatures spreading across the West Coast to Great
Basin/Intermountain West and Southwest particularly through late
week. These colder temperatures may also lead to additional
frost/freeze concerns for any still susceptible growing
areas/valley locations.


Santorelli/Tate


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