Area Forecast Discussion
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FXUS61 KLWX 231911
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
311 PM EDT Sun Apr 23 2017
High pressure near the Jersey Shore will slide out to sea
tonight. Low pressure in Georgia will very slowly move
eastward, reaching the South Carolina coast on Monday, the North
Carolina coast Tuesday, and moving east of Mid-Atlantic on
Wednesday. A cold front will reach the region late Thursday or
.NEAR TERM /THROUGH MONDAY/...
Latest surface analysis depicts low pressure over Georgia, with
a stationary front extending eastward towards Wilmington, NC and
a cold front extending south into the Gulf of Mexico. To the
north, high pressure is centered near the Jersey Shore and over
the southern Great Lakes, with another center in the central
Plains. Aloft, we have a closed low over western Tennessee, with
a shearing shortwave over southern New England and another ridge
over the southern Plains.
This closed upper low will be moving at a snails pace over the
next few days, and its associated surface features will do
likewise. Overall, this is acting like a mid-winter storm,
except that its too warm for any snow. Other than the lack of
snow, the cool northeast wind, minor coastal flooding and long
period of precipitation also reflect its rather winter-like
Another element of similarity will be the excruciatingly slow
progress of the precipitation into our area. As the low pushes
east tonight, the confluence over our region will only very
slowly give way tonight and Monday, and the drier air in place,
fed into the region by the elongated high pressure ridge
(classic banana ridge often present on the northwest side of
winter storms) will continue to feed dry air into it. Guidance
has been slowing the advance of precip into the area through the
day, with latest estimate having an arrival in the DC metro
after midnight, and waiting until after dawn around Baltimore.
This might be optimistically fast, given trends. However,
certainly by mid-late day Monday, rain will have overspread the
region. As the best forcing stays south, significant heavy rain
is generally not expected across the region, so no flood
watches have been issued, though if any were needed, it would be
in central VA near the Blue Ridge where the upslope flow and
upper level forcing is maximized. Lows tonight will be in the
40s with highs generally in the 50s on Monday.
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
The slow moving low will only reach Cape Hatteras on Tuesday and
won`t even make its closest approach to the region until Tuesday
night, though at that point it should be starting to weaken with
diminishing precip across our region. Bottom line is that we`ll
continue to see periods of rain through Tuesday evening, which
should then diminish later Tuesday night. Northeast winds will
continue and temperatures will stay in the upper 40s to mid
50s. A period of heavier rain is possible late Monday night into
Tuesday as the low lifts northward and forcing increases, by
which time the dry air feeding into the system from the north
should be mostly eliminated, but again, no flood watches, as
uncertainty about placement and timing remains rather
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A cut off low moves from the Mid-Atlantic coast into the NE,
and away from the coast on Wednesday. Some isolated to scattered
showers possible, mainly to the eastern half of our CWA on
Wednesday. High pressure builds Wednesday night into Thursday
before a cold front approaches from the west. This front is
expected to stall over or near our CWA Friday and into Sunday
keeping warm and humid conditions over our region, allowing for
showers and maybe thunderstorms at times.
Temperatures will be above normal during this period, with highs
reaching the 70s and 80s, lows in the 50s and 60s.
.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
VFR now, but deteriorating slowly tonight and Monday as low
pressure moves slowly toward the region with rain, a northeast
wind, and lowering CIGs and VIS. Generally expect IFR by this
time on Monday, though it may take until then for it to happen
in the northern terminals. IFR likely to continue at times
through Monday night and Tuesday as the low continues slowly
moving northeast up the coast. Some improvement likely to start
Tuesday night as the low starts heading into the Atlantic.
Sub-VFR possible for the terminals early on Wednesday before
VFR conditions return on Wednesday night as low pressure moves
away. VFR conditions continue into Thursday, and sub- VFR
conditions possible Friday with a lingering front nearby.
Mostly below SCA right now, but expect widespread SCA by Monday
afternoon as a slow moving low moves its way up the eastern
seaboard. Right now not expecting gales, but could be close in
the middle bay. Winds may start diminishing by Tuesday night.
Isolated to scattered showers possible early on Wednesday
before dry conditions return Wednesday night as low pressure
moves away. Dry conditions continue into Thursday, and showers
and maybe thunderstorms possible on Friday with a lingering
front nearby. Wind gusts should remain below the small craft
A persistent onshore flow will continue over the waters through
Tuesday. Elevated water levels are expected during this time. The
onshore flow will strengthen a bit for Monday through Tuesday.
Minor flooding is possible near times of high tide. The flow
should gradually turn north Tuesday night into Wednesday as the
low moves away from the area. Water levels should decrease
during this time.
MARINE...Small Craft Advisory from 6 AM Monday to 6 AM EDT Tuesday for
Small Craft Advisory until 6 AM EDT Tuesday for ANZ534-543.
Small Craft Advisory from 6 PM this evening to 6 AM EDT
Tuesday for ANZ533-537.