Ashburn, Virginia 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

532
FXUS61 KLWX 141411
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1011 AM EDT Sat Jun 14 2025

.SYNOPSIS...
A stalled frontal boundary will continue to oscillate over the
region through the weekend bringing increased chances for showers
and thunderstorms. Thunderstorm activity will be tied to the
afternoon and evening hours with flash flooding and locally damaging
winds as the primary threats. The front lifts north as a warm front
Tuesday into Wednesday with a strong cold front expected to cross
late next week. Temperatures will remain at or above average through
the period.

&&

.NEAR TERM /THROUGH TONIGHT/...

A stationary front is currently positioned over the northern DC
metro. This boundary will become the focus for the development
of heavy showers and thunderstorms late this afternoon and into
this evening. Based on morning HiRes guidance, we have expanded
the Flood Watch for flash flooding to the NE to include parts
of the Baltimore metro along with parts of northern MD and
eastern panhandle of WV. The environment this afternoon and into
afternoon will be favorable for efficient rainfall with PW`s
approaching 2 inches this afternoon and saturated through much
atmospheric column. This environment will be favorable for
hourly rain rates between 2 to 4 inches being possible with
instantaneous rain rates approaching 6 inches per hour
possible.


.Previous Discussion.

Not a washout this weekend with plenty of dry times especially early
in the day. Location will matter though for convective
development. Continue to monitor a stalled frontal boundary
draped over the region. Shortwave energy will once again
traverse this boundary from west to east later on this afternoon
and evening sparking off another round of heavy showers and
thunderstorms. Current 00Z CAM guidance once again focuses on
areas south and east of the Potomac River (i.e Washington DC
metro, central VA, southern MD, and eastern VA) for the heaviest
convective development. Similar to yesterday expecting
convection to fire across the Alleghenies and Blue Ridge mid-
afternoon before pushing eastward into the I-95 corridor and
points east late afternoon into the early evening hours. Timing
wise things look to be a bit earlier with a focus on convective
initiation between 16-19z/12-3pm along and west of the Blue
Ridge before pushing east of the Blue Ridge and into the metros
between 20- 00z/4-8pm. Beyond 00z/8pm, convection slowly wanes
with the loss of daytime heating although passing showers and
areas of drizzle/fog may remain given the moist airmass in
place. Primary threat with storms today will be localized flash
flooding. PWATS remain between 1.5 to 2 inches with FFG guidance
in a large chunk of the area running between 1-1.5 inches in
both the 3-6hr period. MUCAPE values will sit between 500-1500
J/KG with 0-6 KM shear values sitting between 25 to 35 kts. This
should yield multicellular clusters and the possibility of
training with rain rates of 1-2"+/hr. For that reason, have
hoisted a Flood Watch from 2pm today through this evening for
the DC Metro, southern MD, and northern/central VA. This watch
may need to be expanded further west into the Allegheny
Highlands given the antecedent conditions and placement of the
front.

High temperatures today will be slightly cooler given the placement
of the front and added cloud cover. Locations along the PA/MD border
into the mountains will see highs in the mid to upper 70s. Areas
further south toward the front (i.e the Baltimore/DC metros and
central VA will see highs in the low to mid 80s. Mostly cloudy
skies are expected with a few breaks of sun later this morning
and into the early afternoon hours.

Passing showers will likely linger into tonight with activity
diminishing around midnight. Areas of drizzle and fog will be
leftover as onshore flow increases across the region with the
front sagging a bit further south of the region. Lows tonight
will fall back into the mid to upper 60s for most with low 60s
north of the I-70 corridor.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Not much of a change in the forecast as a pesky stalled front
remains nearby. The good news is that Sunday appears drier
although cloud cover will remain due in part to onshore easterly
flow from strengthening high pressure off the New England
coast. This high pressure system looks to force the frontal
boundary further south into central and southwest VA Sunday
morning into SUnday midday. Subsidence behind shortwave low
pressure from Saturday evening will also promote a decrease in
PoPs as well for at least 2/3rds of the forecast region. Even
with that said, the risk for showers and thunderstorms will
still remain from the far western portions of the Alleghenies
south and east into central and eastern VA. This lines up with
both 00z CAM and synoptic guidance very well with the front
subdued to the south as jet max energy squirts east and high
pressure wedges in from the north. Once again, flash flooding
will be the primary concern with any showers and thunderstorms
that develop given the antecedent conditions. Locally damaging
winds cannot be ruled out as well with SPC maintains a Day 2
Marginal Risk for portions of the VA Piedmont mainly along and
south of I-64. Highs Sunday will push into the upper 60s and low
70s with easterly flow on the sable side of the boundary.
LOcations along and south of I-64 will sit in the mid to upper
70s to around 80 degrees.

The boundary works slowly back to the north Monday bringing
continued chances for showers and thunderstorms. Severe weather
does not appear to be an issue as stable marine air will be
slow to erode over the region. Highs Monday will remain in the
upper 60s and low to mid 70s with the influence of high pressure
along the New ENgland coast still wedging south and the front
slowly push back north from central and southern VA. Overall
coverage of showers and thunderstorms will be scattered with a
focus mainly south and east of metro areas. Convection chances
increase again Tuesday as warmer air works back into the region.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
The surface boundary that will have lingered over the area for
several days will finally start to dissipate and lift north of the
area on Tuesday. Meanwhile, a weak upper trough will approach from
the Ohio Valley. Showers and thunderstorms are expected to form
during the afternoon hours within a very humid airmass (surface
dewpoints around 70). High temperatures on Tuesday are expected to
be reach into the upper 70s and lower 80s for most.

High pressure will strengthen offshore moving into the middle of the
week, leading to south to southwesterly low-level flow and
increasing heat and humidity locally. Temperatures should reach into
the 90s on both Wednesday and Thursday. When combined with dewpoints
in the lower 70s, heat indices may approach 100 on Thursday.
Thunderstorms appear possible both days, but the greater coverage
should be on Thursday as an upper trough tracks off to our north
across the Great Lakes, with its associated cold front approaching
from the west. Current model guidance suggests that ample
instability and shear may be present on Thursday, so some storms may
be on the stronger side. Upper troughing is expected to dig in from
the Great Lakes on Friday. Cooler and drier conditions are expected
locally in the wake of the system`s cold front.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...

IFR/MVFR ceilings are being observed for much of the region this
morning with periods of brief improvement. I`ve tried to
highlight lower restrictions that keep jumping around with
tempos and sticking with the consistent ceilings in the
prevailing lines.


.Previous Discussion.


Scattered showers, low clouds, fog, and
drizzle continue across the terminals this morning as a stalled
front sits nearby. The corridor terminals as of 08z continues to
bounce between MVFR to IFR with IFR conditions across the
Shenandoah Valley and Alleghenies. MVFR to IFR cigs and vsbys
can be expected through at least 15z amongst the terminals with
subtle improvement into the mid-afternoon hours. Onshore flow
and a moist marine airmass look to linger throughout the day and
into the first part of next week. BKN-OVC MVFR TO IFR cigs are
expected this afternoon and evening with the front wavering
nearby. Another round of showers and thunderstorms will also
follow with MRB and CHO seeing activity begin between 16-20z/12-
4pm before an advancement eastward toward IAD/DCA/BWI between
20- 00z/4-8pm. Locally heavy rainfall will be the biggest threat
with storms today which will reduce vsbys. Gusty winds also
cannot be ruled out along with frequent lightning. ANy
convection will slowly wane after 00z/8pm with passing showers
and drizzle/fog leftover during the overnight hours. IFR/sub-IFR
cigs/vsbys are expected across all terminals tonight into early
Sunday morning as onshore flow increases. Winds today will
remain light out of the north at 5- 10kts before turning east
Sunday. Additional periods of sub-VFR conditions are likely to
continue for both Sunday and Monday. Shower and thunderstorm
chances will remain during the afternoon and evening hours
especially at terminals south and east of KCHO. Areas further
north will remain in a marine airmass with persistent low clouds
and areas of fog/low clouds during the overnight/early morning
periods.

Sub-VFR conditions may be possible Tuesday morning, but improvement
back to prevailing VFR conditions is expected Tuesday afternoon
through Wednesday. Temporary drops to sub-VFR conditions may be
possible in thunderstorms both Tuesday and Wednesday afternoon.

&&

.MARINE...
A stalled front will remain draped across the waters through tis
evening. Winds today will switch from the south this morning to the
north and east later this afternoon into tonight. Some marginal
SCA northerly channeling is possible in the northern and middle
part of the bay later this afternoon and evening, but
confidence is low. Shower and thunderstorm chances are expected
once again later this afternoon and evening (mainly after
20z/4pm). Some storms may warrant Special Marine Warnings with
gusty winds and locally heavy rainfall as the primary concerns.
Any convection will wane over the waters after 00z/8pm with
passing showers, low clouds, and fog leftover overnight. Less
shower and thunderstorm activity can be expected Sunday and
Monday. Winds will remain out of the east on both days at less
than 15 kts.

Sub-SCA level southerly winds are expected over the waters on both
Tuesday and Wednesday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flood Watch from 2 PM EDT this afternoon through this evening
     for DCZ001.
MD...Air Quality Alert until midnight EDT tonight for MDZ008-508.
     Flood Watch from 2 PM EDT this afternoon through this evening
     for MDZ003>005-013-014-016>018-503>506.
VA...Flood Watch from 2 PM EDT this afternoon through this evening
     for VAZ025>031-036>040-050-051-053>057-501-502-505>508-
     526-527.
WV...Flood Watch from 2 PM EDT this afternoon through this evening
     for WVZ053.
MARINE...Air Quality Alert until midnight EDT tonight for ANZ530.

&&

$$

SYNOPSIS...EST
NEAR TERM...JMG/EST
SHORT TERM...EST
LONG TERM...KJP
AVIATION...KJP/JMG/EST
MARINE...KJP/EST