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Area forecast discussion
National Weather Service Wakefield Virginia
800 PM EDT Fri Oct 18 2019

Synopsis...
surface high pressure will build overhead tonight into Saturday
morning, then slides off the mid Atlantic coast late Saturday
into Saturday evening. Low pressure system will impact the
region late Saturday night and Sunday bringing more rain.

&&

Near term /until 6 am Saturday morning/...
as of 400 PM EDT Friday...

Late this aftn, sunny and cool conditions were prevailing across
the area with temps in the lower to mid 60s. Sfc high pressure
will build overhead tonight into Sat morning, providing another
cold night with lows ranging from the mid 30s to lower 40s over
much of the region (mid to upper 40s at the southeast coast). Patchy or
areas of frost will be likely in the colder spots of the northwest/west
Piedmont counties. So, have added eastern Louisa County, and
Cumberland, Goochland, and Prince Edward counties to the frost
advisory.

&&

Short term /6 am Saturday morning through Monday/...
as of 400 PM EDT Friday...

After a cold morning, dry wx will prevail on Sat as sfc high
pressure slides off the mid Atlc coast late Sat into Sat
evening. Plenty of sunshine expected for most of the day, with
increasing clouds from SW to NE late in the day into Sat night.
High temps on Sat will be a bit warmer in the mid to upper 60s.

Late Sat night and sun, potential tropical cyclone sixteen
currently in the central Gulf of Mexico, will then impact the
region as it tracks NE just inland of the southeast coast then off the
mid Atlc coast. Rain from this system will overspread the area
from SW to NE from late Sat evening into early Sun morning. Rain
then expected over all areas through at least midday/early sun
aftn, before pushing ewrd and off the coast late sun aftn into
sun evening, as the storm moves farther east off the Virginia coast.

At this time, a substantial rainfall is expected for most of the
region from this storm system. Quantitative precipitation forecast amounts of 1-2 inches will be
possible across srn/se portions, with .50-.75 inch possible
across nrn/NW third of the area. Dry wx and generally a partly
cloudy sky for later Sun night and Mon, as the storm moves
farther out into the Atlc and high pressure builds in from the
north.

Lows in the 50s to near 60 Sat night. Highs on sun will range
from the lower 60s NW, to the lower 70s southeast. Lows Sun night in
the upper 40s to upper 50s. Highs on Mon in the mid 60s to lower
70s.

&&

Long term /Monday night through Friday/...
as of 400 PM EDT Friday...

A closed low will be moving NE across the upper plains with a cold
front extending south to the Gulf of Mexico Monday night. The low
pressure system will continue to move north towards the Hudson Bay
as a cold front approaches the area. Second sfc low pressure system
developing in the region at the same time, bringing the next chance
of widespread rainfall for VA, MD, and NC. Timing of the frontal
passage will be Tuesday afternoon into the evening. European model (ecmwf) remains
slower than the GFS but both models moves all the rain off the coast
by sunrise on Wednesday, with dry condition expected during the day
Wednesday through the end of the work week.

Since the main area of low pressure will be moving north into
central Canada, we will not see strong cold air advection as sfc
high pressure system builds into the area behind the front, although
temperatures will be cooler. Low temperatures will be in the 40s
inland and low 50s near the immediate coast. Coldest morning for the
week will be Thursday morning as the center of the sfc high will be
over southeast Virginia/NE NC, with lows in the mid 40s (near 50 along the
immediate coast).

&&

Aviation /00z Saturday through Wednesday/...
as of 800 PM EDT Friday...

VFR conditions are expected at the taf sites tonight into
Saturday evening. Winds will be vrb 02-04 knots to calm tonight.
High clouds will move in from the SW as tropical storm nester
moves into the southeast US during the day on Saturday. Skies will be
scattered-broken 250 during the afternoon. Winds will only slightly
increase during the day to southeast 5-10 knots.

Next chance for flight restrictions will be with the remnants of
tropical storm nester after 00z Sunday. This storm is forecast
to track NE from the Florida Panhandle up the Carolina coast
this weekend, bringing rain to our area late Sat night and sun.
IFR conditions will be likely at all taf sites from very late
Sat night thru sun, especially during times of heavy rain. The
system should exit farther off the mid Atlc coast Sun night,
with mainly VFR conditions returning for Mon. A cold front will
bring additional showers and possibly lower cigs and vsbys on
Tue.

&&

Marine...
as of 400 PM EDT Friday...

Afternoon surface analysis shows tropical storm Nestor moving
northeast across the central Gulf of Mexico, with ~1018 mb high
pressure centered from the srn Great Lakes to the Ohio Valley. All
scas were allowed to expire earlier this aftn, as north-northwest winds are
only ~15 kt over the waters (still a few gusts to 20 kt at elevated
sites).

North-northwest winds diminish to ~10 kt by late tonight as the aforementioned
high slides closer to the area. Winds eventually become east-NE
Saturday morning before veering to the southeast by evening (while
remaining aob 10 kt) as the sfc high moves over the waters then
slides offshore. Meanwhile, tropical storm Nestor tracks newd across
the Gulf of Mexico before reaching the Florida Panhandle by ~12-15z Sat
morning (before becoming extratropical shortly thereafter). Latest
12z global models are in relative agreement and are forecasting the
center of the low to track just inland along the coastal Carolinas
through 12z sun before pushing off the NE NC coast by Sunday
evening. Timing is similar between the three main global models
(gfs/ECMWF/gem). The Gem has a track that is slightly further north than
the GFS/ECMWF. It is important to note that the 12z NAM has a track
that is even farther north than the GFS/ECMWF/Gem (with a low position
over the Virginia ern shore by 18z sun), but have largely discounted this
solution for this forecast package (but still a good bit of
uncertainty remains). After collab with neighboring offices, went
(largely) with a GFS/European model (ecmwf) blend. Expect winds (e-ene) to increase
to 25-30 kt (w/ gusts of 35-40 kt) over the srn Bay/coastal waters
by 12z sun. There may be a brief decrease in winds S of the Virginia-NC
border during the midday-early aftn timeframe if the low tracks
across NE NC. At the same time, east-NE winds increase to 25-30 kt
(with 35-40 kt gusts) over the lower ches Bay/coastal waters S of
the Virginia-Maryland border. Therefore, hoisted a gale watch from sun am-late
sun evening for the ches Bay S of New Point Comfort/coastal waters S
of Parramore Island. Winds turn to the north by sun evening as the low
moves offshore. There is the potential of a brief period of gale
force gusts across the Bay/coastal waters sun evening (driven by cold air advection
on the back side of the low). Seas build to 6-9 ft by late
Sunday/waves to ~4 ft (4-5 ft at the Lower Bay/mouth of the bay).
While the forecast reflects low-end gale conditions on sun in ocean
zones north of the gale watch, opted to hold off on any headlines in
these areas for now (given that it is almost 48 hours before the
potential onset of gale conditions).

Northerly winds fall below Small Craft Advisory thresholds Monday morning (although
seas may remain elevated through at least Mon aftn). Winds/seas
likely remain below Small Craft Advisory thresholds through much of Tue before
another cold front crosses the waters Tue evening-Tue night.

&&

Tides/coastal flooding...
as of 400 am EDT Friday...

No coastal flooding is expected through Saturday night. However,
water levels are expected to rise as low pressure tracks from southeast NC
to offshore of the Virginia/NC coast from sun aftn and night. Guidance
continues to show the potential for minor coastal flooding across
parts of the area by high tide on Sunday (best chances are in areas
adjacent to the lower ches Bay/James river).

&&

Akq watches/warnings/advisories...
Maryland...none.
NC...none.
Virginia...frost advisory from 2 am to 9 am EDT Saturday for vaz048-
060>062-509-510.
Marine...gale watch from late Saturday night through Sunday evening for
anz632-634.
Gale watch from late Saturday night through Sunday evening for
anz633-656-658.
Gale watch from Sunday morning through Sunday evening for
anz654.

&&

$$
Synopsis...tmg
near term...tmg
short term...cmf/tmg

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