972
FXUS01 KWBC 151943
PMDSPD

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
343 PM EDT Sat Jun 15 2024

Valid 00Z Sun Jun 16 2024 - 00Z Tue Jun 18 2024

...Multiple rounds of locally heavy rain with the risk for flash
flooding, as well as severe thunderstorms, expected in the
north-central U.S....

...Late-season wet snow is forecast for the northern Rockies
beginning on Monday...

...A heat wave will quickly spread from the Plains Sunday into the
Great Lakes/Upper Ohio Valley on Monday...

...A plume of tropical moisture will bring the threat for heavy
downpours and flash flooding to the central Gulf Coast...


Clusters of showers and thunderstorms are forecast to develop
ahead of a shortwave and in vicinity of a warm front lifting
northward over the Upper Mississippi Valley Saturday evening. A
Slight Risk of Excessive Rainfall (level 2/4) has been issued for
the region as rich moisture moving northward with the front and
overnight low level jet may lead to some heavier downpours and
localized flash flooding. Just to the west, a deeper upper-level
low and the main accompanying surface low pressure/frontal system
will begin to progress slowly eastward through the northern Plains
and into the Upper Midwest over the next couple of days, bringing
multiple rounds of showers and thunderstorms with both the risk
for heavy rainfall/flash flooding as well as severe weather. Some
severe storms will be possible Saturday evening ahead of the cold
front over the northern High Plains where the Storm Prediction
Center has outlined a Slight Risk (level 2/5) for the threat of
very large hail, significant damaging winds, and a few tornadoes.
The front will progress southeastward through the day Sunday
before stalling out Sunday evening, with the next round of storms
expected along an axis from the Upper Mississippi Valley
southwestward into the Upper Missouri Valley. A Slight Risk of
Excessive Rainfall is in effect as clustering of storms with
repetitive motions along the stalling front with abundant moisture
available will lead to heavy rainfall rates/totals and the risk
for flash flooding. A Slight Risk of severe weather is also in
place for the threat of some large hail. Lee cyclogenesis over the
central High Plains ahead of another upper-level wave over the
West will bring strengthening southerly flow, with the stalled
front expected to begin slowly lifting back to the north as a warm
front through the Upper Mississippi Valley on Monday. A Moderate
Risk of Excessive Rainfall (level 3/4) has been introduced as
clustering/slow-moving storms along the boundary as well as still
abundant moisture and impressive upper-level dynamics will promote
more widespread, intense downpours and potentially numerous,
significant incidents of flash flooding. This risk will continue
into Monday evening/night, just beyond the current forecast
period. A Slight Risk for the threat of some large hail and
damaging winds is also in place.

Another impact from this unseasonably strong series of upper-level
systems for mid-June will be much colder air sweeping southward to
the west of the cold front, particularly into the northern
Rockies. High temperatures will be mostly in the 60s Sunday from
the Pacific Northwest east through the northern Great Basin and
into the northern Rockies. These cooler temperatures will spread
further southward in the Great Basin and into the northern Plains
by Monday. Highs for the mountain valleys of the northern Rockies
will only be in the 40s and 50s. Precipitation chances will also
pick up here Monday, with a Winter Storm Watch in effect for the
potential of several inches of snow at higher mountain elevations.
While a mostly cold rain is expected at lower elevations, a few of
the higher mountain valleys may see some snow mix in.

While conditions will be well below average for much of the West,
much above average, hot Summer temperatures over the Plains will
begin to spread eastward into the Great Lakes/Upper Ohio Valley as
an intense heat wave begins to settle in for the region. Forecast
highs Sunday will be in the mid- to upper 90s from the central
Plains into the Upper Midwest, with upper 80s and low 90s more
broadly through the Great Lakes. Highs Monday then soar into the
mid- and even upper 90s for the Great Lakes/Upper Ohio Valley
Monday as well, with numerous record-tying/breaking highs
possible. Morning lows will be just as impressive, as temperatures
remain in the mid- to even upper 70s. The combination of heat,
humidity, and little overnight relief will bring potentially
widespread, significant heat-related impacts to anyone without
adequate hydration or reliable cooling. Unfortunately, Monday will
be just the start as this heatwave is expected to continue through
this week and into next weekend as a strong upper-level high
remains stagnant over the eastern U.S.

To the south, an impressive flow of moisture from the Caribbean on
the western side of the ridge will stream into the central Gulf
Coast over the next couple of days. While there will be a lack of
upper-level forcing, the continual influx of moisture will be
enough to bring multiple rounds of convection with the potential
to produce very heavy downpours. The rather stagnant flow will
also lead to slow-moving, clustering storms, increasing the
likelihood of heavier rainfall totals. Slight Risks of Excessive
Rainfall are in place for both Sunday and Monday for the threat of
some scattered flash flooding, particularly for urban areas. The
threat on Monday may become more significant if new storms overlap
areas that see heavy rainfall on Sunday.

Putnam


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

$$