Forecast Discussion
004
FXUS61 KLWX 140106
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
906 PM EDT Thu Mar 13 2025
.SYNOPSIS...
A front will waver near the Mid-Atlantic through Friday night
before retreating back to the north as a warm front Saturday. A
stronger cold front will cross the area Sunday. High pressure
will build in from the west early next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
With persistent moist flow off the cold Atlantic, Tds have risen
~5-12F compared to this time last evening. Overall, forecast
remains on track, but did increase the mention of fog south of
US-50/the forecast stratus deck. This deck may come in rather
quickly, and is already evident on satellite imagery across
Delaware and New Jersey. Otherwise, previous discussion
follows...
A stationary front has sagged southward to the NC/VA border,
then arcs back up the Appalachians. The front will push
farther south tonight as the high expands southwestward. This
means stratus will likely spread or redevelop across much of the
area, although there could be some fog especially in southern
areas (i.e. south of US-50). Lows will range from the upper 30s
to mid 40s overnight.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
Conditions will remain largely the same through early Saturday.
This means bouts of low clouds, fog, and drizzle can be expected
during the late overnight to morning hours, with the chance of
drizzle highest Saturday morning.
Thereafter, strong low pressure across the Midwest will lead to
increasing isentropic lift across the region late Saturday into
Saturday night. Shower activity may break out as early as the
afternoon on Saturday west of I-81, with chances increasing
further east through the night. Winds over the higher elevations
will increase out of the south Saturday night as a strong LLJ
develops overhead.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
By Sunday, a potent low pressure system will be exiting the central
CONUS into Canada. However, along the trailing cold front, another
potent low develops as a deep upper trough traverses the center of
the country. A potent shortwave embedded within this trough
will provide ample energy for a powerful storm system to move
through the Great Lakes region into Canada Sunday afternoon. The
cold front associated this system will be powerful as well as
it traverses our forecast area on Sunday, likely sparking off
heavy showers with some embedded thunderstorms. Ahead of the
actual frontal passage, strong southerly to southwesterly flow
develops across the region due to a tight pressure gradient
between the strong low and a high pressure positioned offshore.
Winds could gust into the 20 to 30 mph range ahead of the
frontal passage as a result (stronger at higher elevations).
This will also usher in plenty of warm and moist air ahead of
the frontal passage. High temperatures will be in the upper 60s
to mid 70s across the area with higher elevations staying in the
50s. This will also be our first real taste of a humid air mass
this year, as dew points rise into the low 60s.
A lot of the talk with this system has largely been related to
severe weather risk across the region, and that still remains a
possibility. However, it is going to be very dependent on us being
able to break out during the mid-late morning and develop some
instability ahead of the cold front. While that is possible, it
doesn`t appear overly likely at this time. In fact, the majority of
ensemble members only have a 100-200 J/kg of CAPE developing. While
the wind field remains impressive, not sure we will tap into it to
create a significant severe threat. That all being said, SPC
maintains a 15% highlight in the day 4 outlook, and for good reason.
If we do manage to trend upwards in our instability numbers and are
able to tap into the wind field aloft, we could see a pretty
impressive squall line. We will continue to monitor this threat as
it comes closer into focus.
Additionally, given the anomalous PWATs that will likely be in place
(3 to 4 sigma), heavy rain is likely with whatever line of
shower/storms that does move through on Sunday. Antecedent dry
conditions should help to mitigate a true flash flooding threat, as
will the speed of the line moving through. However, brief heavy
rainfall rates seem plausible, which could become an issue for more
sensitive areas (urban/poor drainage, steep terrain, etc.). The
Weather Prediction Center has much of our area in a Marginal Risk
for excessive rainfall to highlight this risk, which is certainly
plausible.
The cold front will push east by Monday morning, ushering in a much
cooler, but still near normal, air mass into the region. High
temperatures will be noticeably cooler with temperatures in the 50s
to low 60s (40s mtns). Expect a brisk northwest wind Monday
afternoon in the wake of this front, with gusts around 20 to 25
mph. We will also dry out significantly, with RHs dropping back
towards the 20s and 30s. No fire weather concern at this time,
unless we somehow miss out on rain this weekend, which just
doesn`t seem a very likely scenario.
High pressure will then build to our south and eventually push
offshore Tuesday into Wednesday as a strong upper-level ridge builds
overhead. This will put temperatures well above average on both
days, but especially on Wednesday. Highs on Tuesday jump to the mid
to upper 60s, while highs on Wednesday will be well into the
70s area-wide. It wouldn`t surprise me if someone pushed for 80
on Wednesday if this all pans out. One notable thing to watch
for will be the really dry air and gusty southerly flow on
Wednesday. This could bring about some fire weather concerns
(see more on that in Fire Weather Discussion below).
&&
.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
A weak backdoor cold front will gradually drift south of the
terminals through Friday. The main concern through this period
will be low ceilings due to marine stratus. IFR CIGS may
develop at all terminals, although recent guidance shows a drier
NE push that could keep BWI/MTN MVFR. This situation will
repeat Saturday morning as well. There are mixed signals for
fog/reduced visibility, although Friday night seems to have the
highest chance of drizzle/mist. Winds will vary from NE to SE
during this time, generally staying at 10 kt or less.
Low ceilings will eventually lift Saturday as the warm front
lifts back north. As it does, southerly winds will steadily
increase, with gusts of 20-25 kt persisting into Saturday night.
Any showers during this time will be isolated to scattered, with
the highest chance at MRB.
Gusty Southerly to southwesterly winds are expected ahead of a
frontal passage on Sunday. Wind gusts could approach 30 knots
in the afternoon across all terminals ahead of the frontal
passage. Rain showers are expected with thunderstorms possible
in the afternoon and into the evening. Damaging wind gusts and
heavy rainfall are the main hazards possible with any convection.
During showers and thunderstorms, reduced CIGs and VSBYs are likely.
Winds shift to northwesterly Sunday night in the wake of the frontal
passage with VFR flight conditions expected on Monday as precip
moves out of the area. Winds will remain gusty on Monday, but more
in the 15 to 20 knot range.
&&
.MARINE...
A backdoor cold front will gradually drift south of the area
through Friday night. At this time, winds are forecast to remain
below advisory thresholds, with direction fluctuating between
NE and SE. Patchy fog and drizzle could reduce visibility Friday
night into Saturday morning however.
The front will eventually lift north of the area Saturday.
Advisory conditions will eventually become likely as southerly
flow strengthens heading into Saturday night.
Small Craft Advisory winds are likely on Sunday ahead of a frontal
passage in strong SW flow. Winds may approach gale force, however
think the very warm air moving over comparatively cold waters
will make that a very difficult task outside of convection. As
showers and possible thunderstorms move across the waters Sunday
afternoon and evening, Special Marine Warnings are possible due
to gusty winds. South/southwest winds on Sunday shift to
northwesterly on Monday, with SCA conditions expected Monday
morning before gradually diminishing by Monday evening.
Given the forecast for warm temperatures early next week, it is
likely that there will be a large increase in mariners on local
waterways. However, remember that just because the air is warm, it
doesn`t mean that the water is warm. Mariners should be aware of the
threats of boating in cold water and take the proper precautions to
protect yourselves and your passengers. Visit
weather.gov/safety/coldwater for more info.
&&
.FIRE WEATHER...
Dry conditions will continue in most areas through Friday night,
although a few showers are possible in the Appalachians this
afternoon, and some patchy drizzle could occur Friday and Saturday
mornings. With a stalled front gradually settling to the south,
easterly winds will bring an increasing marine influence with more
clouds and higher humidity today, especially along and east of the
Blue Ridge.
The main exception will be for portions of the Allegheny Highlands,
where RH may still drop to 25-35 percent this afternoon with more
sun, but winds will generally stay less than 10 mph.
Increased humidity will envelop the entire area by Friday, although
winds will start to increase along the terrain by Friday night and
Saturday. While showers are possible Saturday, a more significant
wetting rain remains likely Sunday as a strong frontal system pushes
through the area. Thunderstorms and strong gradient winds are also
possible Sunday. At any rate, fire danger is not expected to be very
high any of these days.
The potential for hazardous fire weather conditions Monday to
Wednesday next week will be directly correlated to rainfall
received from the weekend storm system. I don`t see it as a
likely scenario to get missed by a substantial wetting rain.
However, if we do manage to get missed by substantial rain,
Monday through Wednesday next week will be quite dry. We will be
in a post-frontal gusty wind pattern Monday, then warm and dry
Tuesday and especially Wednesday. Wednesday will also come with
an uptick in winds, not dissimilar from what we saw earlier this
week. So, will have to monitor this threat closely. One thing
to also consider is that green-up is starting to occur, so this
will help more and more with each passing week as the tree
canopy returns.
&&
.TIDES/COASTAL FLOODING...
Strong southerly channeling ahead of a cold front will lead to
rising tidal anomalies this weekend. Sensitive tidal locations such
as Havre De Grace are forecast to hit minor flood stage during the
high tide cycle Saturday afternoon. Other locations, including
Baltimore, Annapolis, and Washington DC SW Waterfront will
reach Action Stage during high tide on Saturday afternoon.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.
&&
$$
SYNOPSIS...DHOF
NEAR TERM...DHOF/CPB
SHORT TERM...DHOF/CPB
LONG TERM...CJL
AVIATION...DHOF/CJL/CPB
MARINE...DHOF/CJL/CPB
FIRE WEATHER...CJL
TIDES/COASTAL FLOODING...LWX
