Area Forecast Discussion
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FXUS61 KLWX 180130
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
930 PM EDT Sun Jul 17 2016
Weak high pressure will remain over the area through Monday
morning. A cold front will approach from the northwest late Monday
and cross the region on Tuesday. High pressure will build in
Wednesday and remain in place through Saturday. A cold front may
cross the region Sunday.
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
While the theme of the night is high pressure centered offshore,
there are a couple weak boundaries across the area: a weak front
which has slipped into the NW, and another boundary pushing
northward from central VA. However, these are generally dew
point/subtle wind shift boundaries, as the 00Z IAD raob indicates
a stable and dry environment. For the rest of the night, some
cirrus will continue to spill in from the west, but otherwise
mostly clear skies are expected. Patchy fog is possible,
especially south of the southern boundary where dew points are
highest. Temperatures appear to be on track at this time to lows
in the 60s and lower 70s.
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
Things look more active on Monday but much uncertainty remains.
Front pushing southeast from Canada looks to move through early
Tuesday...a bad time if you want convection. What most likely
would happen is that storms well ahead of the front develop in
association with a weak leading shortwave and surface trough.
Higher resolution models (NSSL/ARW/NMM WRFs, NCAR Ensemble, NAM,
HRRRX) indicate the trough activating with at least scattered
storms near the I-81 corridor around 16-18Z, pushing to the
southern MD Bay by evening (GFS/ECMWF remain relatively dry).
Thought this warranted a little bump in POPs as well as a faster
arrival time. There is 25-35 knots of 0-6km shear and decent CAPE,
so a few strong/severe storms not out of the question...but there
are also hints of a westerly flow which may try to suppress
convection. There`s lesser agreement on whether upstream storms
propagate into NW zones later in the evening. Bottom line...not
a lot of confidence in potential thunderstorms on Monday aft/eve
but potential definitely exists especially in our NW zones. With
the SW to W flow ahead of the front, temps should spike into the
mid 90s in our warmer locales. Heat indices will be in the upper
90s to possibly just above 100 for most locations east of the Blue
On Tuesday...any showers/storms depend on just how fast the front
moves through...as well as a push of drier air aloft. Right now
have them mostly in our southern zones...which makes sense given
expected frontal position. Temps will be on their way down.
Tuesday night into Wednesday...Canadian high pressure will provide
a cooler and drier air mass with sunshine. Lows in the 50s and 60s
with highs in the 70s and 80s.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As high pressure remains in the area Thursday expect dry and
comfortable weather, with near seasonable temperatures (M/U 80s),
and relatively low humidity (dewpoints U50s/L60s).
We turn hot (highs in the M90s) but stay dry Friday. Though,
humidity gradually increases as southwest flow develops, which
will make it begin to feel slightly more uncomfortable.
Cold front then approaches the area next weekend. Still some
uncertainty with how far the front pushes through the area. Current
forecast has chance pops returning Saturday and Sunday afternoon
with front nearby and hot/humid atmosphere.
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
VFR and dry conditions through this evening. Some patchy fog
possible again late tonight, but coverage appears to be less than
Sunday morning. CHO area may be most favored with highest dew
points, but there may also be some gradient wind. Therefore have
left mention out of TAFs for now.
Next chance of showers/thunderstorms will arrive
Monday afternoon through evening with next frontal system.
Reductions below VFR possible along with potential for strong wind
gusts. The best chance may be at MRB, but scattered storms will be
possible across much of the area. TAF mention will be included as
period draws closer and details refined. A stray storm may pop up
Tuesday but odds are low.
VFR conditions prevail Wednesday through Friday under high pressure.
Winds are now turning SW/S this evening as a weak boundary pushes
north. Seeing some 10-15 kt obs. Will have to monitor these, as
channeling could develop on the Bay as the night progresses, but
confidence low on which, if any, areas reach SCA criteria.
Southerly flow increases Monday with marginal SCA conditions
expected late Monday into Monday night out ahead of next frontal
system. Isolated to scattered showers/thunderstorms also possible
Monday into Tuesday. NW flow behind front Tuesday- Tuesday night
may also bring SCA conditions with northerly channeling.
High pressure builds in Wednesday then remains through Thursday.
Winds should gradually increase Friday as southerly flow
redevelops over the area.
Anomalies are still near astronomical normals this evening but
could increase a bit as southerly flow develops ahead of the next
front. Sensitive sites (Annapolis) may briefly reach minor
thresholds on Monday.
MARINE...Small Craft Advisory from noon to 9 PM EDT Monday for