TTCM () > WeatherTuesday, July 14, 2020
Washington DC Climate ReportDCwxWeatherSunrise: 5:55; Solar Noon: 1:14; Sunset: 8:33

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Last 72 Hours: ObservationsCurrently: 73°F  — USNO Clear Sky ChartHeavens-Above

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                VALUE   (LST)  VALUE       VALUE  FROM      YEAR
  MAXIMUM         91   3:18 PM 100    1954  89      2       91
  MINIMUM         71   4:52 AM  56    1888  71      0       73
  AVERAGE         81                        80      1       82

  TODAY            0.00          3.37 1922   0.12  -0.12     0.00
  MONTH TO DATE    2.60                      1.60   1.00     5.70
  SINCE JUN 1      6.11                      5.38   0.73     9.97
  SINCE JAN 1     23.21                     21.34   1.87    28.00

Observations Archive

Forecast updates at 6 AM ET

Today: Isolated showers between 7am and noon. Partly sunny, with a high near 90°. Northwest wind 5 to 7 mph. Chance of precipitation is 20%.

Tonight: Isolated showers before 3am. Partly cloudy, with a low around 71°. Northwest wind 3 to 6 mph. Chance of precipitation is 20%.

Tuesday: Sunny, with a high near 90°. North wind around 6 mph.

Tuesday Night: Mostly clear, with a low around 70°. Light and variable wind.

Wednesday: Mostly sunny, with a high near 92°. Calm wind becoming southeast around 5 mph in the afternoon.

Wednesday Night: Partly cloudy, with a low around 73°.

Thursday: A chance of showers and thunderstorms after 9am. Partly sunny, with a high near 91°. Chance of precipitation is 30%.

Thursday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 75°. Chance of precipitation is 30%.

Friday: A chance of showers and thunderstorms. Partly sunny, with a high near 94°. Chance of precipitation is 50%.

Friday Night: A chance of showers and thunderstorms. Mostly cloudy, with a low around 75°. Chance of precipitation is 50%.

Saturday: A chance of showers and thunderstorms. Mostly sunny, with a high near 93°. Chance of precipitation is 50%.

Saturday Night: A chance of showers and thunderstorms. Partly cloudy, with a low around 75°. Chance of precipitation is 50%.

Sunday: A chance of showers and thunderstorms. Mostly sunny, with a high near 95°. Chance of precipitation is 40%.

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ISS Sightings

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Discussion updates at 4 AM ET

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
342 AM EDT Mon Jul 13 2020

A weak front along the Atlantic seaboard will push offshore by
tonight. High pressure will then build across the area Tuesday
and Wednesday before moving offshore. A front may approach from
the north late in the week.

Weak front appears to be positioned along the Delmarva Peninsula
early this morning. A mid level trough is approaching from the
Ohio Valley. Patchy fog has developed, but convective debris
clouds are approaching from the west which may hinder it from
becoming too widespread. Precipitation extends from the
Allegheny Highlands southward toward Roanoke. While the northern
end seems to be dissipating, there is a little more instability
in southern Virginia, so areas near and south of
Staunton/Charlottesville could see some showers through the
early morning hours.

Any morning cloud cover should clear out through the midday
hours as the trough axis pushes to the east. The trend has
continued that the trough axis and surface front will be far
enough to the east/south that they will not serve as the focus
of new convection this afternoon. As a result the Marginal Risk
for severe storms has been removed. Models have turned focus for
any precipitation today to two sources of potential lift: the
higher terrain (especially near the southern Shenandoah Valley)
and a weak secondary front/moisture discontinuity dropping
southward from Pennsylvania. However, there will be a lot of dry
air aloft as well as a subsidence inversion behind the trough,
so would think most updrafts will struggle without more
organized lift. It`s not out of the question that nothing will
develop, though have added small PoPs to the forecast given
overall signal in guidance. Thunder will probably be limited
unless localized lift can instigate a stronger updraft. Some
models even keep the showers going through the night across
central Virginia/southern Maryland as the weak boundary drops
south, but have elected to decrease PoPs with the typical
diurnal cycle at this time given weak forcing and weak

Since we should see a fair amount of sun during peak heating,
most guidance is giving highs in the 85-91 range, which is a
touch higher than the previous cycle. With slightly lower dew
points behind the secondary boundary, tonight should be pleasant
by July standards with lows in the 60s to near 70.

By Tuesday, main mid/upper trough will be positioned over New
England with surface high pressure over the Ohio Valley. This
will lead to dry conditions and lower humidity (dew points
possibly mixing into the upper 50s in the afternoon). Daytime
temperatures will be near or slightly above normal in the mid
80s to lower 90s, while nighttime lows will be in the 60s to
near 70.

For Wednesday-Wednesday night, the high will translate toward
New England while mid/upper ridging builds overhead. Return flow
around the high will bring an uptick to the heat and humidity,
with high temperatures in the upper 80s-lower 90s. A southeast
surface flow intersecting the terrain near the southern
Shenandoah Valley may spark a shower or weak thunderstorm, but
the ridging should suppress convection for the most part.

Low pressure over the lower Great Lakes will move northeast into
upstate New York Thursday into Thursday night. A developing pre-
frontal trough of low pressure Thursday could generate a few
thunderstorms along and east of the Blue Ridge Mountains Thursday
afternoon. A cold front, trailing from the low pressure, will follow
the trough eastward Thursday night. Showers and additional
thunderstorms could develop Thursday evening as the front approaches
the region. Highs Thursday should be near 90 degrees.

The cold front will slowly move southeastward Friday and Friday
night. Additional showers and thunderstorm could develop along this
front, mainly across the southern half of our region. Temperatures
ahead of and along the front will reach well into the 90s,
while temperatures may hold in the 80s to the north.

Weak high pressure should nose in from the northwest Saturday and
Saturday night. As light to moderate northerly winds becoming more
easterly and southeasterly Saturday afternoon, a couple of showers
and a thunderstorm could form in the Potomac Highlands or along the
Blue Ridge Mountains due to an upslope wind and differential
heating. Temperatures will be in the lower 90s.

Weak high pressure should remain in control Sunday and Sunday night.
Most areas could be rain-free. A pop-up thunderstorm along the Blue
Ridge or a few baybreeze thunderstorms could ignite over eastern and
southern Maryland. Temperatures should be in the lower to middle

While heat indices could reach above 100 from Friday into the
weekend, there is still some uncertainty in temperatures due to
the surface front nearby.

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