Olney, Maryland 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

109
FXUS61 KLWX 052343
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
743 PM EDT Fri Sep 5 2025

.SYNOPSIS...
A strong cold front will continue to push east toward the region
tonight before crossing the area Saturday. The front will bring
strong to severe thunderstorms to portions of the area along with
another prolonged stretch of cooler weather. Canadian high pressure
builds in from the west Monday before settling to the north of the
area Tuesday and Wednesday next week.


&&

.NEAR TERM /THROUGH SATURDAY/...
Synoptically, we continue to track an area of low pressure lifting
northward through the Great Lakes toward Hudson Bay and it`s
associated cold front ejecting out of the Ohio River Valley. Showers
and thunderstorms will accompany this front eastward into areas west
of the Alleghenies tonight and into areas east of the Blue Ridge
mountains Saturday. Current satellite and radar as of 8pm show a
scattering of convection across much of northern/western West
Virginia, eastern Ohio, and western PA. This activity may slowly
slide east toward portions of western MD and eastern WV tonight, but
should remain below severe limits. Elsewhere dry conditions are
expected with mostly clear skies to start out the night and
increasing mid/high level clouds late especially in areas west of
the Blue Ridge. There still remains some uncertainty in how far east
the front makes it overnight which could play into the amount of
thunderstorm coverage/severity Saturday. Winds will remain out of
the south (less than 10kts), which will keep temperatures mild.
Overnight lows will be in the 60s for most, with lower 70s along and
southeast of I-95. Mountain locations will see lows in the upper 50s
and low 60s due in part to increased cloud cover and scattered
thundershowers.

Saturday will be a day of transition across the region and a matter
of location when it comes to the potential for severe weather. Deep
upper troughing will remain in place across much of eastern CONUS,
with the primary trough axis extending from Hudson Bay southward
through the Great Lakes and Mississippi Valley. A shortwave/mid-
level speed max will lift northeastward through the frontside of the
trough Saturday morning, tracking from the Ohio Valley toward the
St. Lawrence Valley Saturday afternoon. Locally we`ll experience
weak height falls aloft, and also become located within the
equatorward entrance region of an unseasonably strong upper jet
streak. At the surface, the system`s cold front will track
southeastward across the area Saturday afternoon into early evening.
STorms will initiate along this boundary especially in areas along
and east of I-81 early to mid Saturday afternoon (12-4pm) before
advancing toward the Baltimore/DC metros late afternoon into early
evening (3-8pm).

Model soundings show around 1000-2000 J/kg of MLCAPE and around 35-
50 knots of effective bulk shear. Well organized thunderstorms are
expected as a result, with both multicells and even a few supercells
possible. Damaging winds should be the primary threat, but an
instance or two of large hail can`t be ruled out in any supercells
that form. Hodographs are primarily straight and there also isn`t
much low-level shear present, so tornadoes aren`t expected. With the
strong flow in place aloft, storms should be rather progressive. As
a result, flash flooding isn`t expected to be a major issue.
However, a stray instance of flooding can`t be ruled out if storms
were to train over a highly urbanized location. Both SPC and WPC
have locations roughly to the east of I-81 outlooked in Marginal
Risks for severe thunderstorms and flash flooding. A Slight Risk
from SPC clips far northeastern portions of Maryland (Harford and
Cecil counties). This risk may need to be expanded further south and
east although better forcing may reside just to the north of the
area (i.e NJ/NY). Storms will clear southern Maryland by mid-late
evening (7-9pm), with just a few lingering light showers possible
overnight. Winds will shift to out of the north to northwest behind
the front, allowing cooler and drier air to filter into the region.

Location will matter a great deal Saturday with the overall
placement of the front and any residual cloud debris/shower activity
working east from the Alleghenies in the morning which could hamper
the severe threat. Overall expect highs east of of the Blue Ridge in
the mid 80s to low 90s. Locations further west will likely see highs
in the 70s and low to mid 80s. Low-level moisture will also be on
the increase to the east of the front, with dewpoints climbing back
into the upper 60s to near 70 along and east of the Blue Ridge. By
peak heating, most guidance has the front extending from north-
central Maryland southwestward through the western DC suburbs into
the Shenandoah Valley.


&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
Upper troughing will continue to make slow eastward progress on
Sunday, with a final embedded shortwave tracking from the Ohio
Valley toward Pennsylvania by Sunday evening. A mix of sun and
clouds is expected, with more clouds toward the southeast and more
sun toward the northwest. A morning shower or two could also be
possible to the southeast of I-95. Winds will be out of the
northwest, and temperatures will be much cooler, with highs in the
70s (60s in the mountains). Lows Sunday night will fall into the
upper 40s and low 50s for mots. Mountain locations and river valley
locations west of the Blue Ridge will see lows in the low to mid
40s. Some high valley locations (i.e Bittinger, MD, Cabin Mountain,
WV, and Mill Gap, VA) could see lows in the 30s.

In the wake of a cold frontal passage Sunday, expansive Canadian
high pressure is forecast to move in from the Great Lakes and Ohio
Valley. It will be another preview to Fall with highs in the low to
mid 70s. Urban locations will be a touch warmer with mountain
locations likely seeing highs in the upper 50s and mid 60s. Skies
will trend mostly sunny with ample dry air advection funneling into
the regions. Lows Monday night will fall back into the mid 40s and
mid 50s. Urban locations and locations directly along the bay will
see lows in the upper 50s and low 60s with mountain areas seeing
lows in the low to mid 40s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
The upcoming work week will provide a return to more autumnal-like
weather ahead with below average temperatures and cool mornings. In
the wake of a cold frontal passage over the weekend, expansive
Canadian high pressure is forecast to move in from the Great Lakes
and Ohio Valley. Expect mostly sunny skies Tuesday while this
anticyclone is at it`s strongest. While the ridge remains centered
over the northeastern U.S., an approaching longwave trough will
strengthen a stalled frontal zone which straddles the Carolina to
southeastern U.S. coast. Some isentropic lift atop this boundary may
even squeak out a few showers over southern Maryland on Wednesday.
However, the chances do remain low at this point, generally around
15 to 20 percent. This does introduce plenty of cloud cover for
those east of the Blue Ridge Mountains.

The amplified flow gradually tracks another reinforcing cold front
across the region on Thursday. Given very little moisture to work
with, this should prove to be a dry frontal passage. This also
allows for a return to mostly sunny skies each day to conclude the
upcoming work week.

For high temperatures, most locations can expect daily readings in
the low/mid 70s (upper 50s to low 60s across mountain locales). At
night, many periods of ample radiational cooling will draw low
temperatures into the upper 40s to mid 50s (low/mid 40s from I-81
westward). Some uptick in overnight lows are possible by mid-week
given the increased cloud cover. Additionally, the post-frontal air
mass on Thursday may yield some highs into the low 80s owing to
downsloping winds. Temperatures do cool off in the wake of this
boundary by next Friday.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions and southerly winds are expected to continue at all
terminals through early Saturday morning. Winds will remain less
than 10kts tonight while slowly turning to the southwest mid to late
Saturday morning into Saturday afternoon ahead of an approaching
cold frontal boundary. Once again expect speeds at less than 10 kts
with gusts up to 15 kts as the immediate front passes through.
Thunderstorms will also accompany the cold front as it passes
through Saturday afternoon and evening. Highest confidence for
thunderstorms appears to be at terminals east of KMRB and KSHD
mainly between 17-00z/1-8pm. Storms will work into areas around
KIAD/KCHO/KFDK between 17-21z/1-5pm before quickly racing east
toward the I-95 corridor terminals between 19-22z/3-6pm. All of the
activity should sink south and east of the corridor toward KRIC by
23-01z/7-9pm Saturday. Overall coverage appear scattered south of
KIAD given a little less forcing. More linear organization of storms
will be noted from IAD/DCA points northward toward KBWI/KPHI where
better forcing and instability reside. Damaging winds will be the
primary threat with storms Saturday along with locally heavy
rainfall and perhaps isolated large hail. VFR conditions return
Sunday as the front clears the area. A leftover shower or two is
possible over the corridor as the front slows early Sunday morning.
Winds will shift to the north and northwest behind the front with
gusts up to 15 kts.

A dry pattern is in place on Monday and Tuesday owing to broad
Canadian high pressure settling over the northeastern U.S. This will
ensure VFR conditions during this pattern shift. By Wednesday, a
coastal boundary may increase clouds east of the Blue Ridge.
However, these are not likely to cause any restrictions. Wind fields
during the period largely meander between northerly and east-
northeasterly as high pressure tracks through the area.


&&

.MARINE...
SCA conditions are expected in southerly flow through the front half
of the overnight period. There may be a bit of a lull where the
southerly flow drops below SCA levels late tonight through early
Saturday  morning, before winds potentially pick back up in
channeled southerly flow Saturday afternoon and evening. Winds may
potentially reach SCA levels during that time. SMWs may also be
needed Saturday afternoon/evening (2-8pm) as thunderstorms move over
the waters. Winds will turn out of the north to northwest Saturday
night behind a cold front and remain northwesterly during the day
Sunday. A few SCA gusts may be possible in north to northwesterly
flow Sunday as well.

In response to high pressure settling over the area, northerly winds
are expected on Monday before turning more east-northeasterly by
Tuesday. The combination of high pressure over the northeastern U.S.
and a frontal zone off the southeastern U.S. will increase overall
pressure gradients. Consequently, some marine winds could near Small
Craft Advisories levels on Tuesday.

&&

.TIDES/COASTAL FLOODING...
Minor flooding is still possible at a few locations late tonight as
southerly flow strengthens again ahead of the next front. Highest
confidence for this will be at Annapolis with the potential for
minor thresholds to be reached at Havre de Grace, and perhaps
SOlomons Island. This front will bring a wind shift Saturday which
will decrease water levels for  back half of the weekend into early
next week.


&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 3 AM EDT Saturday for MDZ008.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 3 AM EDT Saturday for ANZ530>534-
     537-539>543.

&&

$$

SYNOPSIS...EST
NEAR TERM...KJP/EST
SHORT TERM...KJP/EST
LONG TERM...BRO
AVIATION...BRO/KJP/EST
MARINE...BRO/KJP/EST
TIDES/COASTAL FLOODING...LWX