River Flood Warning 91, NWS Baltimore/Washington

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
248 PM EDT Mon Sep 17 2018

.SYNOPSIS...
The remnants of Florence will lift north through Appalachians
tonight before passing by to our north Tuesday. The cold front
associated with the remnants will pass through our area Tuesday.
High pressure will return for Wednesday and Thursday before
moving offshore late in the week. A cold front may approach the
region this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
The surface low pressure for TD Florence is currently located
near the WV/OH border this afternoon and the upper- level low
is nearby as well. The low will continue to slowly move north
just west of the Appalachians through this evening before
tracking into Pennsylvania overnight.

The dry slot has moved into the Shenandoah Valley and Potomac
Highlands, and it will continue to gradually overspread the area
through this evening. However, a plume of moisture has advected
into the area ahead of the dry slot across the Washington and
Baltimore Metropolitan areas into central Maryland. Latest
mesoanalysis shows pwats around 2 to 2.25 inches across these
areas. Showers and scattered thunderstorms will continue along
the moisture plume through this afternoon. The heaviest rain is
most likely to be east of the Blue Ridge Mountains to near
Interstate 95. Farther west, coverage will be more scattered
through this evening...but even across these areas there will
be plenty of moisture. Also, antecedent conditions are worse
given the recent rainfall. Therefore, will continue with the
Flash Flood Watch across most areas (except southern Maryland
where FFG is higher).

In addition, there are moderate shear profiles in the high
theta-e air, so some updraft rotation will be possible. Have
scattered thunder in the forecast to account for this. An
isolated tornado cannot be ruled out.

The cold front associated with the remnants of Florence will
approach from the west overnight. The upper-level low associated
with the remnants will shear apart as it shifts east into our
area. Falling heights and the boundary approaching suggests
that showers and thunderstorms are possible overnight as well.
Do think shower coverage will be scattered to perhaps numerous,
and thunderstorm coverage will be isolated since it will be
taking place during an unfavorable time.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
The cold front associated with the remnants of Florence will
slowly pass through the area from west to east Tuesday into
Tuesday evening. The upper-level trough axis will also pass
through the are during this time. Another round of showers and
scattered thunderstorms are likely, and the best coverage will
be east of the Blue Ridge Mountains where instability will be
higher (due to the front arriving later). Shear profiles will be
weaker, but there will be moderate instability so a couple
stronger storms are possible. Locally heavy rain is also
possible and isolated flooding cannot be ruled out (best chance
east of the Blue Ridge and Catoctin Mountains).

The boundary will push off to the east Tuesday night and high
pressure will build overhead for Wednesday through Wednesday
night. Dry and less humid conditions will return due to a
northwest flow.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
High pressure overhead Thursday will become elongated from New
England to the Carolinas Thursday night. Dry conditions will
continue Thursday and Thursday night.

As the high moves offshore Friday, a cold front will sag southeast
across the eastern Great Lakes and move close to our northwestern
zones of western Maryland and eastern West Virginia by Friday
night. Dry conditions will continue Friday with a chance of a
few showers in our northwestern zones Friday night. Temperatures
will be warmer Friday.

A cold front will slide southeast across our region Saturday into
Saturday night, bringing an increased chance for showers and
thunderstorms across much of our region. At this time, it appears
that most activity will be isolated since much of the upper level
support will have left the region and moved well to the northeast.

The front could stall across southern parts of our region or
perhaps reach the Virginia and North Carolina border Sunday
and Sunday night. Additional showers or perhaps a thunderstorm
could form along and just north of the front. Slightly cooler
temperatures near the Mason-Dixon region.

Weak high pressure will try to nudge farther south into our CWA
Monday, but it may have trouble with its push since the stalled
front could hold its ground in southern parts of Virginia.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
A southerly flow will continue through tonight. MVFR cigs are
most likely this afternoon due to the deep moisture in place,
although a few VFR conditions cannot be ruled out. Low clouds
will return later tonight and IFR cigs are likely. Cigs will
lift later Tuesday morning into Tuesday afternoon.

Showers and perhaps a thunderstorm are possible through Tuesday
afternoon. The most widespread coverage will be this afternoon
across the eastern terminals. Even across these areas, thunder
may be more isolated. Localized IFR conditions are possible in
any showers that develop due to tropical moisture in place.

A northwest flow will develop for Tuesday night behind a cold
front and VFR conditions are expected for Wednesday. Patchy fog
is cannot be ruled out overnight Tuesday into Wednesday morning.

VFR conditions expected Thursday through Friday night with high
pressure in control across and to the east of our region. Winds
northeast becoming southeast 5 to 10 knots Thursday and Thursday
night. Winds becoming southwest around 10 knots Friday and Friday
night.

&&

.MARINE...
Southerly winds will continue over the waters through tonight.
An SCA remains in effect. There may be a lull in the winds later
this evening and overnight over the upper Tidal Potomac River
and northern Chesapeake Bay. A cold front will approach Tuesday
before passing through late in the day into Tuesday evening. An
SCA is in effect for portions of the waters ahead of the front
through midday Tuesday, and for all the waters behind the front
Tuesday afternoon into Tuesday night.

High pressure will build toward over the waters Wednesday
through Wednesday night. An SCA may be needed for portions of
the waters Wednesday.

No marine hazards expected Thursday through Friday night. Winds
northeast becoming southeast 5 to 10 knots Thursday and Thursday
night. Winds becoming southwest 10 to 15 knots Friday and Friday
night.

&&

.HYDROLOGY...
The dry slot has moved into northern and central Virginia and
for locations along/west of the Blue Ridge Mountains. However, a
moisture plume continues to advect through the Washington and
Baltimore Metropolitan areas. Widespread showers continue across
these areas, but convection is isolated to scattered behind the
dry slot. The most widespread heavy rainfall will be over the
metro areas through this afternoon, perhaps toward the Blue
Ridge Mountains. Additional rainfall totals of 1 to 2 inches are
possible. Farther west, scattered showers/isolated thunderstorms
are expected to develop through this evening. Locally heavy rain
is possible. Did continue with the Flash Flood Watch since
antecedent conditions are highly favorable across the west and
the heaviest rain is still occurring in the east.

Rainfall totals will be around 1 to 2 inches for
most areas with locally 3 to 6 inches near the Blue Ridge
Mountains in central Virginia. Locally higher amounts are
possible elsewhere as well due to the convective nature of the
precipitation.

River flooding is possible along the Shenandoah and Potomac
River Basins.

&&

.TIDES/COASTAL FLOODING...
A stronger southerly flow has developed and it will continue
through tonight before gradually turning to the southwest
Tuesday morning and the northwest Tuesday evening.

The southerly flow has caused anomalies to increase, and this
trend will continue through tonight. Have issued Coastal Flood
Advisories for most areas along the western shore of the
Chesapeake and the Potomac River. A Coastal Flood Warning is in
effect for Anne Arundel County during this time. Will have to
watch the anomalies due to the stronger southerly flow. It is
possible that water levels could approach moderate flood
thresholds in Washington DC and St Marys County, but confidence
is too low for a warning at this time.

Minor flooding is possible during the high tide cycle Tuesday,
then the northwest winds should cause anomalies to decrease
Tuesday night.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flash Flood Watch through late tonight for DCZ001.
     Coastal Flood Advisory until 7 AM EDT Tuesday for DCZ001.
MD...Flash Flood Watch until midnight EDT tonight for MDZ501-502.
     Flash Flood Watch through late tonight for MDZ003>006-011-013-
     014-016-503>508.
     Coastal Flood Advisory from 7 PM this evening to 4 AM EDT
     Tuesday for MDZ016.
     Coastal Flood Advisory until 1 AM EDT Tuesday for MDZ017.
     Coastal Flood Advisory from 7 PM this evening to 2 AM EDT
     Tuesday for MDZ018.
     Coastal Flood Advisory from 1 AM to 9 AM EDT Tuesday for
     MDZ508.
     Coastal Flood Warning from 9 PM this evening to 6 AM EDT
     Tuesday for MDZ014.
     Coastal Flood Advisory from 10 PM this evening to 7 AM EDT
     Tuesday for MDZ011.
VA...Flash Flood Watch until midnight EDT tonight for VAZ025>027-
     029-036>040-503-504-507-508.
     Flash Flood Watch through late tonight for VAZ028-030-031-
     050>057-501-502-505-506.
     Coastal Flood Advisory from 7 PM this evening to 4 AM EDT
     Tuesday for VAZ057.
     Coastal Flood Advisory from 11 PM this evening to 7 AM EDT
     Tuesday for VAZ054.
WV...Flash Flood Watch until midnight EDT tonight for WVZ050-055-
     501>506.
     Flash Flood Watch through late tonight for WVZ051>053.
MARINE...Small Craft Advisory until 9 AM EDT Tuesday for ANZ530>532-535-
     536-538>540.
     Small Craft Advisory from 4 PM Tuesday to 2 AM EDT Wednesday
     for ANZ532-540.
     Small Craft Advisory from 4 PM to 10 PM EDT Tuesday for ANZ530-
     531-535-536-538-539.
     Small Craft Advisory until 2 AM EDT Wednesday for ANZ533-534-
     537-541>543.

&&

SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...KLW
AVIATION...BJL/KLW
MARINE...BJL/IMR/KLW
HYDROLOGY...BJL
TIDES/COASTAL FLOODING...BJL

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
110 PM EDT MON SEP 17 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1151 AM     FLOOD            1 NW STANARDSVILLE      38.31N  78.45W
09/17/2018                   GREENE             VA   DEPT OF HIGHWAYS

            OCTONIA ROAD FLOODED AND CLOSED NEAR SOUTH RIVER ROAD.
            ENTRY RUN ROAD AND ROUTE 634 ALSO FLOODED AND CLOSED IN
            THE AREA.

&&

EVENT NUMBER LWX1802042

JE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
113 PM EDT MON SEP 17 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1124 AM     FLOOD            ETLAN                   38.53N  78.26W
09/17/2018                   MADISON            VA   DEPT OF HIGHWAYS

            MULTIPLE ROADS FLOODED AND CLOSED IN THE ETLAN AREA.

&&

EVENT NUMBER LWX1802043

JE

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
117 PM EDT MON SEP 17 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0111 PM     FLOOD            CHURCHVILLE             38.23N  79.16W
09/17/2018                   AUGUSTA            VA   DEPT OF HIGHWAYS

            NUMEROUS ROADS REPORTED CLOSED IN THE CHURCHVILLE AREA,
            AS WELL AS MORE THROUGHOUT AUGUSTA COUNTY.

&&

EVENT NUMBER LWX1802044

JE

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