Weather Prediction Center

National Oceanic and Atmospheric Administration

US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
429 PM EDT Fri Sep 29 2023

Valid Monday October 02 2023 - Friday October 06 2023

Hazards:
- Heavy rain across portions of the southern High Plains, Mon, Oct 2.
- Heavy rain across portions of the northern and central Plains, and into the upper Midwest, Tue,
Oct 3.
- Heavy rain across portions of the Southern Plains, Wed-Thu, Oct 4-Oct 5.
- Flooding possible across portions of the northern Mid-Atlantic and New York City vicinity.
- Heavy rain across portions of the Alaska Panhandle and southern coastal Alaska, Wed-Fri, Oct
4-Oct 6.

Detailed Summary:

...CONUS...

The deep upper-level trough/low engulfing much of the western U.S. during the short-range period is
forecast to advance progressively eastward across the mid-section of the country toward the eastern
U.S. through the work week next week. Ahead of this upper trough, at least a couple of low
pressure waves are forecast to develop and track northeastward across the northern Plains as the
upper trough interacts with a well-defined frontal boundary. An elongated zone of heavy rain is
expected to organize ahead of the trough and the front over the central Plains on Tuesday in the
warm air mass where scattered strong thunderstorms are possible. Meanwhile, an axis of heavy rain
is forecast to organize farther north over the northern Plains near the front where the low
pressure waves are expected to track across.

By Wednesday, the low pressure waves are forecast to move away into the southern Canada, leading to
a decreasing threat of heavy rain for the northern Plain, although the heavy rain threat may linger
there into Wednesday if the second low pressure wave moves slower than expected. Meanwhile, the
heavy rain potential is forecast to shift farther south into the southern Plains on Wednesday as
shortwave energy near the base of the upper trough could interact with the trailing portion of the
front where a low pressure wave could develop. By Thursday, the heavy rain threat should push
farther south into southern Texas as the front advances toward Texas' southern border. By next
Friday, the northern portion of the front is forecast to move east into the lower Great Lakes/Ohio
Valley with scattered showers and thunderstorms possibly producing an area of enhanced rainfall
across upstate New York into portions of Pennsylvania.

In addition to the above-mentioned heavy rain areas, convective-induced heavy rain could impact
portions of the southern High Plains on Monday ahead of a dry line/lee trough.

Cooler than normal conditions will remain in place over the interior western U.S. underneath
lingering upper-level troughing in the wake of the cold front. Some higher-elevation wet snow can
be expected early next week over portions of the northern and central Rockies. Subfreezing lows
are forecast for some of the valleys in addition to the higher elevations of the northern Great
Basin and Rockies, where the first freeze has already occurred.


...Alaska...

The medium-range period should begin with moderate to locally heavy rain from along the southern
coast of Alaska to the Panhandle as an old occluded cyclone weakens and dissipates in the vicinity.
Beginning on Wednesday, models are agreeing with a rather potent surge of moisture/atmospheric
river toward the Panhandle as a warm front supported by a strong upper jet lifts north toward the
Gulf of Alaska, leading to a rather strong signal for heavy rain to impact the Panhandle Wednesday
and Thursday. By next Friday, it appears that the ensemble means are agreeing with a continued
northward push of the warm front toward the southern periphery of Alaska, which would lead to
northward expansion of the heavy rain into the southern section of mainland Alaska. There is still
a fair amount of disagreement among the deterministic guidance late next week (the GFS in
particular) but the ensemble means are agreeing quite well with the aforementioned pattern late
next week along with the latest ECMWF and CMC.

Kong