Area Forecast Discussion
Issued by NWS Sterling, VA
FXUS61 KLWX 160802
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
402 AM EDT Sun Apr 16 2017
High pressure will sit to the southeast today, pumping a very
warm air mass into our region. A cold front will move through
Monday. High pressure will pass to the north Monday night into
Tuesday before another system moves in Wednesday and Thursday.
.NEAR TERM /THROUGH TONIGHT/...
Southwesterly flow will dominate today now that the warm front
has cleared the region. Warm advection is bringing some rather
toasty temperatures into the region aloft and with good mixing
expected under mostly sunny skies this morning, we should rise
quickly into the 80s across the region. A few of the warmest
spots could flirt with 90, but generally think mid-upper 80s
will be the rule by early afternoon. With the mixing and the
cold front approaching, should have a gusty southwest breeze
with winds gusting up to 25-30 mph.
This afternoon, a prefrontal lee side trough may form just east
of the Appalachians, which given just enough moisture and
instability, could result in a few isolated showers or
thunderstorms which could then advect into the metro. Do not
expect storms to be severe, but a gust to 40 or 45 mph would not
Any afternoon storms should diminish early this evening, and
with the front now looking slower, expect most of tonight to be
dry with only a slight chance of showers in the metro. Greater
odds exist further west where some remnant showers from storms
which will develop closer to the front may move in before
dissipating. Lows will remain mild tonight, with 50s and 60s
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Guidance has slowed the front and many models now want a wave of
low pressure to ride eastward along it on Monday as it crosses
the area. This is increasing the risk of showers on Monday. So
far, have only gone chance in central/western VA/WV and mainly
slight chance into the metro and MD, but these odds may
increase. Will need to watch this potential closely. Some
guidance shows significant rain, while others just a few
showers, but certainly not the dry forecast we were thinking a
day or two ago. Highs will be lower with the clouds and frontal
passage, with 70s common.
Front slides south Monday night as high pressure to the north
builds down the east side of the mountains. Skies should try to
clear and lows will drop into the 40s in most areas, 50s warmest
Tuesday looks benign with the high nudging its influence into
the area still even as it starts to pull away to the northeast.
Easterly flow will develop so temps will cool a bit further than
Monday despite more sunshine.
Warm front begins to move back towards the region Tuesday night,
with more clouds and a developing chance of showers late. Lows
will be in the 40s to lower 50s.
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Low pressure weakens as it shifts east from the northern Great
Lakes Wednesday enhancing southerly flow over the Mid-Atlantic.
Little in the way of forcing, so will lower PoPs Wednesday from
likelies over most of the area to chance.
A stronger low tracks east over the Great Lakes Thursday into
Thursday night. Fewer lingering fronts in the area mid to late week
than last night. More periods with slight chance or less PoPs. No
severe weather threat apparent in long term, just general convective
showers/diurnal thunderstorms in 00Z GFS/ECMWF.
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
Patchy fog is a concern early this morning in locations where
showers occurred late yesterday. Otherwise, VFR should prevail
this morning. By this afternoon, a few isolated showers and
thunderstorms may develop mainly west of the I-95 corridor,
which could then move east toward I-95 toward evening. While
chance of impacts are low, they are not zero. Overnight tonight,
it should be generally VFR out of a lingering shower drifting in
from the remnants of storms which will develop well northwest
earlier in the day.
Cold front slides south on Monday as a wave of low pressure
moves east along the front. This could result in some rain with
sub-VFR cigs and vis. Uncertainty remains high but it would
appear the threat of impacts is growing, if still rather small.
Should go back to VFR Monday night (assuming we ever leave VFR)
and remain so Tuesday into Tuesday night.
Southerly flow Wednesday and Thursday with two low pressure
systems passing to the north. Cold front looks to cross the area
Thursday night or Friday as low pressure passes north of the
area/over the Great Lakes.
Gusty southwest winds ahead of an approaching cold front will
result in widespread SCA today, with max gusts likely this
afternoon especially near shore. Winds may be a bit lighter in
the open bay due to the cooler water. Other concern today is for
an isolated gusty thunderstorm advecting over the waters, which
might necessitate a special marine warning this afternoon or
early this evening.
Winds will only slowly diminish tonight. Cold front will cross
the waters on Monday, but right now winds do not look gusty
with it. Should remain sub-SCA behind the front Monday night
and Tuesday as high pressure passes to the north. However, they
may begin to return to SCA levels Tuesday night as a warm front
Southerly flow increases Wednesday with low pressure to the
north. May need an SCA for southern channeling that evening.
Next notable cold front crosses the area Friday.
MARINE...Small Craft Advisory from 9 AM this morning to 6 AM EDT Monday
Small Craft Advisory until 6 AM EDT Monday for ANZ532>534-537-
Small Craft Advisory from 9 AM this morning to midnight EDT
tonight for ANZ535-536.