Area Forecast Discussion
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FXUS61 KLWX 210117
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
917 PM EDT FRI MAY 20 2016
Low pressure will track east to North Carolina tonight before
turning up the Mid-Atlantic coast Saturday. Upper level low
pressure will persist along the Mid-Atlantic coast Saturday night
through Monday night. High pressure returns Tuesday.
.NEAR TERM /THROUGH SATURDAY/...
Low pressure now centered over west TN will be tracking NE
overnight. First lead batch of R- brought some light rain to
Waynesboro around 8 pm but that line has weakened as it has
tracked north. The significant rain extends across western NC
northward into OH. Believe this will be working into the
southwestern section of the forecast area around midnight...and
into DC around 3 am...Baltimore before sunrise.
A sharpening trough axis in the Great Lakes/Ohio Valley will
assist in transferring energy to a coastal low off the Carolinas
early Saturday. This coastal low will then head northeast up the
coast during the day. The area will have ample moisture in place,
with a conveyor coming from the Atlantic ahead of the low.
Therefore, the morning to midday hours likely to see the heaviest
rain, as the low level jet interacts with an airmass with
precipitable water above an inch. Due to the synoptic pattern,
there will be a wedge of cool air in place; am therefore going
with a forecast of steady rain.
Amounts of an inch to an inch and a half should be quite common
in central Virginia and southern Maryland by midday Saturday.
Could see some upslope enhancement along/east the spine of the
Blue Ridge, especially in central Virginia. The lowest flood
guidance values extend west of there, so after collaboration a
slight risk of excessive rainfall was painted by WPC in these
This pattern will keep the daytime hours quite cool. It may be a
struggle to see 60 degrees Saturday.
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As the low tracks north of the area by mid-late afternoon, we will
experience a greater influence from the trough axis. There will be
multiple shortwaves embedded within the flow that will cross the
area. This will last for the rest of the weekend. Therefore,
needs to continue at least a chance of showers (with mostly cloudy
to cloudy skies). Timing these vorts will ultimately determine
when the best chance of rain will be. While skill not present to
do that specifically, it would seem as though Saturday evening and
Sunday afternoon would have the best chance at additional showers.
Since Sunday looking to be cloudier/rainier, high temperatures
for Sunday have been lowered. Not much change for low
temperatures, which should be kept near or above 50 degrees due to
.LONG TERM /MONDAY THROUGH FRIDAY/...
An upper level low near the Delmarva Peninsula will gradually
pull away from the coast and move toward the northeast Monday
and Monday night. There is a chance for a couple of showers or a
thunderstorm Monday with a slight chance expected in the eastern
half of our region Monday night. Temperatures will be
slightly below normal.
High pressure will build into the region Tuesday through Wednesday.
Dry conditions and warmer temperatures expected each period.
By Thursday, a trough of low pressure will develop and bring the
next chance of showers and thunderstorms. Temperatures will be
A cold front should slowly work its way southward across the region
Friday. The threat for showers and thunderstorms will exist along
and ahead of the front with temperatures remaining above normal and
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
Rain spreads over the Mid Atlantic from southwest to northeast
tonight but won`t affect the terminals until the overnight hours.
Since winds ahead of the rain should be easterly, anticipate a
rather sudden drop from VFR to IFR. Am not certain when this will
happen, but it should be complete by Saturday morning.
The pattern will remain wet through the rest of the weekend, but
not a washout. In general, majority of the time should be MVFR.
Periods of IFR certainly possible, especially during the overnight
and morning hours. Precipitation will become more showery, which
does mean local/brief restrictions possible.
MVFR conditions possible with showers and thunderstorms around
Monday. VFR conditions possible at MRB, CHO, and IAD terminals
Monday night. MVFR conditions possible elsewhere to the east.
Winds becoming light and variable Monday night.
Low pressure will be approaching tonight, and passing east of the
waters tomorrow. Will have an increased flow ahead of this low.
Small Craft Advisories in place for the lower waters overnight and
all waters Saturday. Momentum transfer looks reasonable during the
evening hours on the Bay/mouth of the Potomac; have extended
Advisory for then. Shortwave energy will be swinging across the
waters Saturday night through Sunday, but will ample cloudcover,
mixing will be poor.
MARINE...Small Craft Advisory from 8 AM Saturday to midnight EDT
Saturday night for ANZ530>533-538>541.
Small Craft Advisory from 4 AM Saturday to midnight EDT
Saturday night for ANZ534-537-542-543.
Small Craft Advisory from 8 AM to 7 PM EDT Saturday for ANZ535-