Forecast Discussion
673
FXUS61 KLWX 091412
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1012 AM EDT Fri May 9 2025
.SYNOPSIS...
A cold front will slowly move through the area today as low
pressure moves northeastward from the Mid Atlantic coast. High
pressure will prevail through the weekend. Low pressure will
approach from the southwest toward the middle of next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
A dual area of upper lows are situated across southeastern
Ontario and western Pennsylvania, respectively. The mean trough
axis connecting these features extends southward from western
New York down to the Central Appalachians. There is quite a
moisture gradient as noted in the GOES-19 multi-channel water
vapor imagery. Much drier air looms off to the west, while
extensive cloud cover and showers persist across the Mid-
Atlantic region. More specifically, multiple clusters of showers
continue to pivot east-northeastward across the area,
particularly east of the Alleghenies and north of I-66. Although
moisture is relatively anomalous in nature, a lack of
instability has generally held 3-hour rainfall totals to around
0.10 to 0.25 inches.
For the rest of the morning into the early afternoon, waves of
showers will persist given the wavy stalled frontal zone
extending across St. Marys County through southern Delaware. Any
threat for isolated thunderstorm activity would be along that
mentioned moisture gradient seen on water vapor imagery. High-
resolution models remain at odds with one another on whether
such a threat will materialize. Will withhold mention of
thunderstorms until confidence increases. Even if such storms do
form, the instability should be shallow which suggests any
storms likely will not get too strong.
Skies start to clear from the southwest during the afternoon
while showers become less widespread. Locations that get some
sun could pop into the upper 60s to near 70s, while the rest of
the area will remain in the lower to mid 60s.
Any precipitation should end by this evening as the surface low
moves farther up the coast and dry air advects into the area.
For most of the area, cold advection will drop lows into the
40s. Some of the deeper western valleys could decouple, though
there is some uncertainty with how low temperatures can get as
winds aloft will likely remain elevated. Have issued a Frost
Advisory for locations where valleys are most likely to approach
freezing, with some potential for future expansion.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
High pressure will slide southwest of the area Saturday. Dry
conditions will prevail, but it will be a bit breezy with a
lingering gradient to the low over New England. Near normal
temperatures are expected with highs in the lower to mid 70s and
lows Saturday night in the mid 40s to mid 50s.
A weak front will drop into the area Sunday but dissipate as it
does so. High pressure will quickly build in from the eastern
Great Lakes, with little effect on the tangible weather. Since
heights will be rising, temperatures will be warmer despite the
front, with highs in the mid to upper 70s and lows in the 50s.
Dry weather will continue, but some cirrus may intrude from a
cut off low over the southern states.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
H5 pattern reveals large cut-off ULL across Louisiana to start the
period. This feature will eject northward into the Mid-Atlantic
through the early parts of the week as UL ridging over the southwest
US kicks it east and ridging over the Atlantic steers it north. At
the surface, high pressure will reside over the area Monday before
shifting eastward into Tuesday. Late Tuesday into Wednesday an area
of low pressure will move up the coast bringing a soaking rain.
Ensemble probabilities for 1" of rain range from 30-60% across the
area, so something to keep an eye on 5-6 days out. Thereafter, the
long term looks to remain somewhat unsettled with multiple
shortwaves moving through later next week bringing renewed chances
for rain showers.
In terms of temperatures, generally within a few degrees of climo
norms. Tuesday and Wednesday look to be the coolest in terms of high
temps due to rain and clouds. Moderating slightly by the end of the
week.
&&
.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
Light to moderate rain showers continue to pivot toward the
east-northeast this morning. Consequently, ceilings remain along
the fringes of IFR to MVFR. However, most recent trends have
pulled ceilings to around 1,200 to 1,500 feet. As showers pass
through, these could briefly lower at times.
Some improvement is expected by midday/early afternoon as
steadier rain exits. However, VFR may not completely return
until late afternoon. A few northwest wind gusts to 20 kt could
occur, but winds should generally be light. CHO may clear out
this afternoon, offering an opportunity for heavier showers or
thunderstorms to develop, but confidence in direct impact
remains low at this time.
VFR conditions will prevail tonight through the weekend.
Northwest winds may gust 20-25 kt Saturday, especially in the
morning. Lighter north winds are expected Sunday.
VFR conditions Monday with light winds out of the southeast.
Restrictions possible heading into Tuesday and Wednesday as low
pressure and corresponding rain/clouds move through. Winds generally
southeast Tuesday into Wednesday with gusts to 15 kts.
&&
.MARINE...
Winds may be somewhat variable through the day as a front pushes
through and low pressure moves up the coast. One surge of winds
may affect the waters from late morning through early afternoon,
then there could be a bit of a lull. Winds will pick back up
tonight, especially along the bay. Have issued a Small Craft
Advisory for the wider waters today and tonight to account for
these scenarios. Confidence is lower on the western tributaries,
but some occasional gusts can`t be ruled out. A few
thunderstorms may affect mainly the southern Maryland waters
early this morning and again this afternoon.
Confidence is higher for gusty winds on all waters Saturday,
with a Small Craft Advisory in effect for that period. Winds
will become lighter Saturday night. A weakening front will shift
winds to the north Sunday, but advisories are not expected at
this time.
Winds could flirt with SCA criteria Tuesday into Wednesday depending
on low track.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Small Craft Advisory until 6 PM EDT Saturday for MDZ008.
VA...Frost Advisory from 2 AM to 8 AM EDT Saturday for VAZ503-504.
WV...Frost Advisory from 2 AM to 8 AM EDT Saturday for WVZ501-505-
506.
MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ530-531-
539.
Small Craft Advisory until 6 PM EDT Saturday for ANZ532>534-
537-540-541-543.
Small Craft Advisory from 8 AM to 6 PM EDT Saturday for ANZ535-
536-538-542.
&&
$$
SYNOPSIS...ADS
NEAR TERM...ADS/BRO
SHORT TERM...ADS
LONG TERM...CPB
AVIATION...ADS/BRO/CPB
MARINE...ADS/CPB
