April 21, 2021
Washington DC Climate Report
Solar Noon: 1:07;
Last 72 Hours: Observations
...THE WASHINGTON NATIONAL DC CLIMATE SUMMARY FOR APRIL 20 2021...
WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST
VALUE (LST) VALUE VALUE FROM YEAR
MAXIMUM 76 3:14 PM 94 1941 68 8 64
MINIMUM 47 5:53 AM 28 1904 48 -1 52
AVERAGE 62 58 4 58
TODAY 0.00 1.71 1940 0.10 -0.10 T
MONTH TO DATE 1.33 2.04 -0.71 3.44
SINCE MAR 1 5.13 5.52 -0.39 5.75
SINCE JAN 1 11.72 10.95 0.77 11.75
Hazardous Weather Outlook
Today: Isolated showers before 11am, then scattered showers after 1pm. Increasing clouds, with a high near 68°. Breezy, with a south wind 10 to 20 mph becoming west in the afternoon. Winds could gust as high as 32 mph. Chance of precipitation is 40%.
Tonight: Mostly clear, with a low around 37°. Breezy, with a northwest wind 11 to 20 mph, with gusts as high as 37 mph.
Thursday: Mostly sunny, with a high near 56°. West wind 7 to 16 mph, with gusts as high as 32 mph.
Thursday Night: Mostly clear, with a low around 39°. West wind 6 to 11 mph, with gusts as high as 24 mph.
Friday: Sunny, with a high near 66°. West wind 6 to 10 mph, with gusts as high as 18 mph.
Friday Night: Mostly clear, with a low around 45°.
Saturday: Showers likely after 3pm. Partly sunny, with a high near 69°. Chance of precipitation is 70%.
Saturday Night: Showers. Low around 52°. Chance of precipitation is 80%.
Sunday: Showers before 9am. High near 66°. Chance of precipitation is 80%.
Sunday Night: Mostly clear, with a low around 44°.
Monday: Sunny, with a high near 68°.
Monday Night: Mostly clear, with a low around 48°.
Tuesday: Sunny, with a high near 75°.
Baltimore/Washington Forecast Office
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Time and Date
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
353 AM EDT Wed Apr 21 2021
A strong cold front will cross the area today. Canadian high
pressure will build to our west tonight through Thursday before
settling to the south late in the week. Low pressure may will
likely pass through the area this weekend before high pressure
returns early next week.
.NEAR TERM /THROUGH TONIGHT/...
A potent upper-level trough will dig overhead through tonight.
The surface low associated with this will strengthen and track
to our north while a cold front passes through our area
today before moving offshore Wednesday night. A few showers are
possible this morning into early this afternoon along and ahead
of the cold front, with highest confidence for precipitation
being near and east of Interstate 95 and also along/west of the
Allegheny Front (upslope component to low-level flow). The
forcing along the front will be strong, so a line of gusty
showers and perhaps a severe thunderstorm is most likely to
setup to our east where instability will be higher due to the
later time of the frontal passage. However, there still is an
isolated threat for a severe storm in our area anywhere from
near I-95 to the Bay.
A mild southerly flow ahead of the cold front will give way to
sharply colder conditions (temps will fall from the 50s and 60s
to the 40s and 50s quickly with the frontal passage) and gusty
northwest winds of 25 to 40 mph. The cold front will move east
of the Allegheny Highlands by 8 AM, then through the I-81
corridor to the Blue Ridge Mountains between 8 AM and 11 AM,
then through the metro areas between 11 AM and 1 PM, and
clearing extreme southern MD and the nearby water zones between
2 PM and 4 PM.
The upper-level trough will remain overhead tonight allowing
for blustery and cold conditions for this time of year. A Freeze
Warning is in effect for northern MD and locations near/west of
the Blue Ridge Mountains where the growing season is in effect.
It will be close in the valleys with temperatures around 32
degrees. There is a possibility that wind and some clouds may
keep temperatures up, but the air aloft will be quite cold and
there may even be a little break in the winds toward sunrise.
Therefore, a Freeze Warning has been issued. Temperatures in the
ridges will be well below freezing.
For locations along and west of the Allegheny Front, the strong
cold advection and upslope flow will result rain showers
changing to snow showers later this morning into this afternoon.
Scattered snow showers will continue tonight. There will be some
instability, and that is causing elevated numbers in the snow
squall parameter. Heavier bursts of snow are likely especially
this afternoon and evening. The warmer ground and antecedent
conditions will limit snowfall accumulations, but 1-2" are
possible for the higher ridge tops above 3kft through tonight. A
few rain or snow showers may even spill east of the mountains
due to the high inversion and instability. However, any
precipitation will be light.
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The upper-level trough will remain overhead Thursday while low
pressure slowly tracks into the Canadian Maritimes. Gusty
northwest winds are expected and it will be quite chilly for
this time of year. A few snow showers are expected along/west of
the Allegheny Front and a rain/snow shower could spill east of
the mountains as well. Winds will diminish Thursday night as the
upper-level trough departs and high pressure builds nearby to
the south and west. More chilly conditions are expected and
frost/freeze headlines may be warranted.
High pressure will build to the south for Friday and Friday
night, and a return flow will allow for more seasonable
conditions along with some sunshine for Friday.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
Conditions will start out dry on Saturday, but rain is expected to
overspread the area from southwest to northeast during the
afternoon and evening hours as an area of low pressure
approaches from the southwest. There are some subtle differences
in the track of the low amongst model guidance, but little
sensible differences in terms of impact, with nearly all
deterministic and ensemble solutions showing a soaking rain
across the area Saturday afternoon through Saturday night. With
the low tracking nearby and a large shield of stratiform shield
of precipitation preceding it, we should be stable. As a result,
severe thunderstorms shouldn`t be a concern. Flooding isn`t
expected to be a concern either, with dry antecedent conditions,
and precipitation totals generally under an inch.
The aforementioned area of low pressure and its associated
shortwave trough will progress off to our east on Sunday. This
should lead to clearing skies throughout the day. The main
weather feature of note on Sunday will be winds. Gusts of 30-40
mph appear possible at times in northwesterly flow behind the
departing area of low pressure. Temperatures on Sunday are
expected to max out in the 60s for most.
The mid-upper level flow pattern across the CONUS is expected to
amplify early next week as a trough digs into the western US.
Heights will rise downstream of this trough, with a ridge
building over the Great Lakes for Monday and Tuesday. This will
place us in northwesterly flow aloft, which will encourage the
maintenance of high pressure at the surface and quiet weather
conditions. Sunny skies are in the forecast for both Monday and
Tuesday, with a moderating trend in temperatures anticipated.
Highs will reach well into the 70s by Tuesday.
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