Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
258 PM EDT sun may 19 2013
Synopsis...
a warm front will slowly lift north of the area tonight into
Monday morning. A weak middle-level trough will move through Monday.
High pressure builds over the western Atlantic Tuesday and
Wednesday...with southerly return flow providing warm temperatures
to the region. A cold front will approach from the Great Lakes
late this week.
&&
Near term /through tonight/...
the quasistationary fnt alng the Virginia/NC brdr has begun to creep back northward again
as a warm front...especially in vicinity of the Delaware-Maryland-Virginia. Still wedging in the shen
valley to I-95. Air mass north of boundary still stable...as evidenced by the lack of
radr rtns as well as the low clds/cigs. Meanwhile...numerous thunderstorms and rain across
NC/southern wva should advect northward and override the stable llvls. Therefore...
am keeping low likely probability of precipitation for the lt afternoon-Ely evening...and scale back
from there.
Model soundings depict a satd layer sfc-h9...especially during the overnight hours.
Therefore think that dzfg will once again be an issue tonight. The warm front
will likely continue to inch northward...but west/ little wind and no blyr rooting...
it/ll be hard to tell.
&&
Short term /Monday through Wednesday/...
low clouds and fog will continue to be a factor into the morning hours.
However...the may sun angle will gradually erode the satd layer...permitting
the fnt to jump north of area by the afternoon. South of this front...a
warm and a modestly humid airmass will be in place. Maximum temperatures in
the 80s each day although clouds may inhibit temperatures from reaching
80f in some locations on Monday.
NAM/GFS/ECMWF forecast a middle-level shortwave trough to mv through the middle-
Atlantic region on Monday. Lift/moisture ahead of the trough in conjunction
with daytime heating will support diurnal convection over the County Warning Area.
Probability of precipitation highest toward central Virginia/southern Maryland but still in chance range.
Middle-level ridge builds overhead Tuesday and Wednesday after the shortwave
trough exits the area. Coverage of showers and storms will be low
Tuesday and Wednesday due to an absence of organized lift and a strengthening
subsidence inversion. Mav/met diverge here. Kept forecast dry for most
of the I-95 corridor and chesepeake Bay as weak steering flow will
limit how far east convection propagates once initiated over the
mts.
&&
Long term /Wednesday night through Sunday/...
shortwave trough and associated cold front will approach from the
Great Lakes/Midwest regions Wednesday night and Thursday before passing through
the area on Friday. Chances for showers and storms will accordingly
increase late in the week and will be highest with frontal passage. Above
normal temperatures ahead of the cold front will trend much cooler in
wake of frontal passage Friday into the weekend.
&&
Aviation /18z Sunday through Friday/...
flgt restrictions remain...but impvmnt beginning. IFR hanging on metropolitan
balt as well as cho and mrb. Ceilings at iad/dca have risen to MVFR. Have
fllwd lamp guidance which has good performance today. While flgt cats
should reach MVFR elsewhere taftn...dont forsee VFR anywhere. Sch rain showers
possible...but covering lmtd/brief.
After dark...the trend should reverse...once again per lamp. Llvls saturate
and winds light. At or below IFR expeceted overnight.
IFR conditions likely to start the day Monday before morning stratus/
fog mix out from west to east. Predominately VFR conditions expected Monday
afternoon although brief restrictions in rain showers/thunderstorms and rain are possible.
Diurnal fog/low clouds possible at night and early in the morning each
day in the midweek. Chances for rain showers/thunderstorms and rain will be low during this
time.
&&
Marine...
Maryland Bay/tidal ptmc on the stable side of a warm front at this time. Mixing poor
and winds at or below 10 knots. However this fnt slowly working northward again. Small Craft Advisory GOES
into effect for Middle Bay and lower ptmc at 3pm...and for Bay Pooles
isl-nbeach at 6pm. Suspect this is a bit fast...and dont have a
good feel whether spds will reach Small Craft Advisory criteria at all or be trapped
above an invsn. Will maintain status quo for now.
Light southerly flow Ely in the week will strengthen later in the week.
Small Craft Advisory conditions possible by Thursday...when a cold front approaches from
the northwest.
&&
Tides/coastal flooding...
departures continue to decrease today...now all less than a half-foot.
No tidal flood issues expected in the near future /tngt or even
tomorrow/.
Water levels should tick upward Ely next week with southerly flow
persisting and a waxing gibbous moon. This far out...still some
uncertainty if positive anomalies increase enough to reach minor
threshold.
&&
Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory from 6 PM this evening to midnight EDT
tonight for anz531-532-539-540.
Small Craft Advisory until midnight EDT tonight for anz533-534-
537-541-543.
&&
$$
