305
FXUS21 KWNC 271758
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT September 27 2026

SYNOPSIS: A cold front is forecast to shift southward across the East and Gulf
Coasts early in week-2, with an elevated risk of heavy precipitation. Behind
this cold front, at least a brief period of seasonably cool temperatures are
expected to overspread much of the central and eastern Contiguous U.S. (CONUS).
Areas of frost and/or a light freeze are possible from the Upper Mississippi
Valley eastward across the northern Great Lakes and interior Northeast. A
series of low pressure systems with enhanced onshore flow results in a slight
risk of heavy precipitation and high winds for southcentral and southeastern
Alaska.

HAZARDS

Slight risk of heavy precipitation for much of the East and Gulf Coasts, and
Tennessee Valley, Mon-Wed, Oct 5-7.

Slight risk of heavy precipitation for the Florida Peninsula, Mon-Sun, Oct 5-11.

Slight risk of heavy precipitation for parts of southcentral and southeastern
Alaska, Mon-Sun, Oct 5-11.

Slight risk of high winds for coastal parts of southcentral and southeastern
Alaska, Mon-Sun, Oct 5-11.

DETAILED SUMMARY

FOR WEDNESDAY SEPTEMBER 30 - SUNDAY OCTOBER 04:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR MONDAY OCTOBER 05 - SUNDAY OCTOBER 11: The GEFS and ECENS are in good
agreement today on an amplifying 500-hPa ridge over interior western North
America during early October, which helps drive a cold front southward across
the Central and Eastern CONUS early in week-2.  A complex frontal system over
the East warrants a slight risk of heavy precipitation (3-day total of at least
one inch) for parts of the East and Gulf Coasts, and Tennessee Valley, Oct 5-7.
The ECENS precipitation Probabilistic Extremes Tool (PET) favors a maximum of
30-40% chance for this hazard over the Southeast, while the GEFS remains a bit
more subdued with its probabilities. Uncalibrated precipitation forecasts from
these same models follow a similar pattern, with the ECENS featuring somewhat
elevated probabilities over the GEFS. The slight risk of heavy precipitation
continues over the Florida Peninsula at least into the latter portion of
week-2, as front stalls across the area. This stationary front is expected to
serve as a focus for enhanced rainfall across the region. The Bay of Campeche
will have to be closely monitored for tropical cyclone (TC) development through
early to mid-October.



During the first few days of week-2, surface high pressure initially over the
Midwest is forecast to move eastward towards the Upper Mid-Atlantic coast,
accompanied by a seasonably chilly air mass. Minimum overnight temperatures
from the Dakotas and Upper Mississippi Valley eastward across the northern
Great Lakes and interior Northeast are predicted to drop through the 30`s (with
frost and/or a light freeze possible) according to the GEFS and CMCE model
ensemble means. The ECENS solution, however, is milder, with these same areas
forecasted to be perhaps 5-10 degrees warmer than the GEFS/CMCE. At best, the
GEFS PET forecasted 20% chances for much below normal temperatures in this
region, and according to the Midwestern Regional Climate Center (MRCC)
Vegetation Vulnerability map, the areas of concern are primarily limited to
Minnesota and Wisconsin. Given that the cold temperature hazard has been on the
map for several days now, the ECENS is going with a milder outcome, and the
very limited overlap between freezing temperatures with vulnerable vegetation,
it was decided that this hazard would only be listed as a text-mention, but
removed from the map itself.



A highly amplified 500-hPa trough over the northeast Pacific is likely to
promote a series of low pressure systems that track from the Alaska Peninsula
eastward to the Gulf of Alaska. Based on the enhanced onshore flow associated
with these low pressure systems, and support from the ECENS and GEFS PETs (20%
chance of 3-day precipitation amounts > 85th percentile and 2-3 inches), a
slight risk of heavy precipitation is designated from the Kenai Peninsula to
southeastern Alaska. Uncalibrated precipitation amounts from both the ECENS and
GEFS provide plenty of support as well for totals exceeding 2 inches. Since the
GEFS, ECENS, and CMCE persist the deep 500-hPa trough over the North Pacific
through early October, the heavy precipitation hazard is maintained for the
entirety of week-2. Although most of the model ensemble members only depict
surface lows of moderate strength (mostly 970-990 hPa), a slight risk of high
winds is maintained based on pattern recognition and support from the ECENS PET
wind tool. The high wind hazard is also valid from Oct 5-11.



In the Central and Eastern Pacific, the tropics remain very active with two
hurricanes (Nolo and Polo), tropical storm Odalys, tropical depression 18-E,
and a broad area of low pressure currently well east-southeast of Hawaii which
has a 80 percent (high) chance of tropical development within the next week,
according to the National Hurricane Center. Although environmental conditions
appear to be conducive for development of a tropical depression, the system is
predicted to move northeastward away from the Hawaiian Islands. This is good
news for the residents of Hawaii that have already experienced a memorable
hurricane season this year. The most immediate concern is short-term (next
72-hours), as Hurricane Nolo moves westward south of the Islands, and then
curves north-northwestward. Regarding Tropical Depression 18-E (currently about
330 miles south of Acapulco, Mexico), NHC projections  strengthen this system
into a hurricane several days from now while taking it northwestward,
potentially reaching 20N/110W by day 5 (Friday). If correct, this would be
about 150-200 miles south of the southern tip of Baja California. It remains to
be seen whether or not this system (or its remnants) brings significant
precipitation into the American Southwest in early October.

FORECASTER: Anthony Artusa

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