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FXUS61 KLWX 191429

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1029 AM EDT Sat Oct 19 2019

High pressure will move offshore today while Tropical Storm Nestor 
makes landfall over the Florida Panhandle. The remnants of 
Nestor will move into Georgia tonight, across the Carolinas 
Sunday, then offshore of the Outer Banks by Sunday evening. A 
cold front will approach from the Ohio Valley Monday, then cross
the region Tuesday. High pressure will follow for Wednesday 
through Friday before another cold front approaches by Saturday.


High pressure sitting atop the region this morning under sunny
skies and temperatures rising into the 40s and lower 50s. We did
see widespread freezing conditions earlier this morning across 
portions of the Potomac/Virginia Highlands and eastern West 
Virginia, effectively ending the growing season there. We will
be following up with a PNS today to indicate the areas where 
frost/freeze headlines will cease the remainder of the year.

Cirrus clouds on the far northern periphery of Tropical Storm 
Nestor are creeping northward across southern and southwestern 
VA this morning. These clouds will continue to increase over 
our area throughout the day as Nestor comes ashore over the 
Florida Peninsula, tracking northeastward as the aforementioned 
high shifts off the Mid- Atlantic coast. Dry conditions and near
normal temperatures in the mid to upper 60s are expected 
through this afternoon as a light southerly flow develops. No 
updates needed to the current forecast package. 

Previous discussion follows:

Overcast conditions are expected over the entire area by shortly
after midnight, with clouds lowering and thickening as the
remnants of Nestor move from Georgia into the Carolinas.
Increasing moisture and lift along a developing frontal zone
north of the low center should result in rain over much of the
area by daybreak Sunday, with the steadiest most likely east of
the Blue Ridge and south of US-50.


The remnants of Nestor are forecast to move offshore of the
Outer Banks of North Carolina by Sunday evening. To its north,
an arc of rain is expected, forced by a strengthening low- to 
mid-level frontal zone. Nestor will be post-tropical by this
time, driven by temperature gradients and acquiring frontal
characteristics as it makes its closest approach.

Regardless of its structure, rain and a northeasterly breeze will
continue for much of the area Sunday. The NAM is the northern 
most piece of guidance as of early this morning, and although a 
steadier, heavier rain can't be completely ruled out as far west
as the eastern foothills of the Allegheny Highlands or as far 
north as the Mason-Dixon line, it appears most likely that the 
axis of heaviest rainfall will remain across southern and 
eastern Virginia into southern and southeastern Maryland.

Rain should begin exiting the region pretty quickly by or
shortly after midday as the best lift/convergence rapidly moves
offshore. Residual low-level moisture may result in a few
lingering showers or spotty light rain, but overall the
steadiest rainfall should be focused during the first half of
the day. Drying northerly winds increase on the backside of the
low and could gust 20 to 30 MPH near the Chesapeake Bay.

With the rain and cloud cover around, high temperatures may
struggle to get much above 60 for most of the area (a few
degrees warmer outside the steadiest rain over portions of
eastern West Virginia and western Maryland).

Surface high pressure will ridge briefly back over the area
Sunday night. If clouds clear quickly enough, fog may develop.
Southerly winds increase Monday ushering in warmer air with
highs nearing 70, but clouds will increase quickly Monday night
ahead of the next approaching cold front, with showers possible
by daybreak Tuesday.


On Tuesday, a strong mid/upper trough will be sliding east out of 
the northern/central Plains into the Midwest/Great Lakes. The 
associated surface low pressure system will be occluding over 
southern Ontario. The cold front associated with this system 
will push through the area Tuesday morning, with showers likely 
across the entire forecast area. Doesn't look to be an 
excessive rainfall event, but could see a quarter to half an 
inch. High temperatures will be seasonable in the low to mid 
60s. Overnight lows Tuesday night will be about 10 degrees 
cooler than Monday night, with lows in the low to mid 40s. 

Surface high pressure will build over the region out of the 
southeast, resulting in dry weather with seasonable temperatures for 
the remainder of the week. Highs each day will reach the low to mid 

The next chance for some potentially heavier rainfall appears 
to be next weekend, but too far out for exact details at this 
point in time.


VFR with light S or SE flow expected through most of tonight, 
before lower CIGs and rain develop after 08-10Z. Steadiest rain 
and highest potential for IFR appears to be southeast of a line 
from CHO to DCA Sunday morning. Winds increase out of the east
especially near and east of I-95 Sunday, then switch to
northerly Sunday afternoon with a few gusts of 20 kts possible.
VFR will likely return by late Sunday afternoon as CIGs lift,
but fog may develop late Sunday night into early Monday morning.

Mainly VFR expected Monday into Monday night on a light S wind.

VFR conditions expected throughout the long term period for the most 
part. A frontal passage Tuesday morning will likely lead to some 
brief CIG/VSBY restrictions with some showers. After that, 
though, high pressure builds into the area, keeping things dry 
through the end of the week. Additionally, no high wind 
concerns at this time.


High pressure will move offshore today as Tropical Storm Nestor
approaches from the south. The post-tropical remnants of Nestor
will then pass offshore of the Carolinas Sunday. Light 
southeasterly flow is expected today into tonight, increasing 
out of the east and then north on Sunday. SCA conditions are 
likely over much of the waters by early Sunday afternoon, with a
period of gale conditions possible over the lower tidal Potomac
River and Chesapeake Bay south of North Beach Maryland on 

Winds will subside Sunday evening, then flip back to the south
ahead of an approaching cold front Monday into Monday night.

SCA conditions possible mainly Tuesday night into Wednesday
behind a cold front pushing through the area. Southerly winds 
ahead of the front could come close to SCA criteria, especially 
in the Bay, but low confidence at this time.


Light onshore flow is expected to develop today into tonight.
Snap-ex guidance has been insistent on near minor flooding at
Annapolis with this evening's high tide cycle, but that would
require tidal anomalies of about a foot which seems unlikely.
Sided with CBOFS which is in between the more conservative
ETSS/ESTOFS and more aggressive Snap-ex through tonight, before
leaning on a blend of ETSS/ESTOFS through the end of the weekend,
which are very similar holding higher water levels near the 
mouth of the Chesapeake Bay in northeast flow. This should keep
the flood risk at a minimum for the tidal Potomac and western
shore of the Chesapeake Bay north of Smith Point Virginia.

Those higher water levels will likely linger in some form in the
Virginia side of the Chesapeake Bay, however, and then return
northward as winds go light and switch to the south late Sunday
night into Monday. There's a pretty substantial spread in the
guidance as it remains to be seen just how much water is left
piled up at the bottom of the bay, but for now running with a
1-1.5 foot anomaly early next week which results in minor flooding.


MARINE...Small Craft Advisory from 10 AM to 6 PM EDT Sunday for ANZ531-
     Small Craft Advisory from 1 PM to 6 PM EDT Sunday for ANZ530-
     Small Craft Advisory from 7 AM to 6 PM EDT Sunday for ANZ532-
     Small Craft Advisory from 4 AM to 6 PM EDT Sunday for ANZ534-
     Small Craft Advisory from 10 AM to 4 PM EDT Sunday for ANZ536.



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