Lexington Weather

Lexington, Massachusetts, USA

54°F
6/16/2024 3:58am 
  • Lexington Conditions: Clear
  • Temperature: 54.0°F / 12.2°CColder 1.6°F than last hour.
  • Dew Point: 45.1°FDecreased 0.9°Fsince last hour.
  • Relative Humidity: 72%Increased 2.0% since last hour.
  • Wind: Calm, 10-min avg: Calm, gust: None
  • Barometer: 30.12 in Steady
  • Visibility: 10 miles
  • Rain Today: 0.00 in
  •   
Southeast Middlesex County, MA - Excessive Heat Watch
 - SEE ALL NEARBY ALERTS -

National Short Range Forecast Discussion 

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