Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 191741

Area Forecast Discussion
National Weather Service Raleigh NC
140 PM EDT Tue Sep 19 2017

Weak high pressure centered over southern Quebec will extend south
into the southern Appalachians through Wednesday. Tropical Cyclone
Jose will continue to move northward well offshore of the DELMARVA
peninsula today, and off the southern New England coast on Wednesday.


As of 10 AM Tuesday...

Abrupt dissipation of stratus will result in mostly sunny skies for
the remainder of the day. Meanwhile, with low-level flow backing
from NELY to a more NWLY component, afternoon temperatures will be 2
to 3 degrees warmer than Monday, averaging in the mid 80s.

Tonight, expect mostly clear skies as the low level flow will back
to a more west-nw direction, advecting a slightly drier air mass
which should inhibit the formation of widespread low clouds and fog.
Overnight temperatures mainly in the mid 60s.


As of 340 AM Tuesday...

Wednesday, a disturbance dropping sewd across the TN Valley will
continue to gradually strengthening as it moves into the western
Carolinas Wednesday night. The lift provided by the system,
interacting with an atmosphere that will be slight-moderately
unstable, will support the development of a few showers and t-storms
Wednesday afternoon-early evening, primarily west of highway 1. Some
model guidance suggesting coverage close to 40-50 percent coverage
over the western Piedmont by late Wednesday. This seems a bit
overdone so will cap PoPs at 25-30 percent across the western
periphery for now. Strong heating Wednesday coupled with a wly low
level flow will push temperatures well into the 80s to around 90.
With dewpoints projected to be well into the 60s, it will feel very
summer-like with heat indices likely in the low-mid 90s across most
of central NC (excluding the Triad region).

The progression sewd of the upper disturbance Wednesday night will
likely maintain a slight chance for a few showers across the sw half
of central NC. The patchy cloudiness and a warm air mass will result
in min temps in the mid-upper 60s.


As of 255 AM Tuesday...

Central NC will be under the influence of high pressure through much
of the extended forecast period, resulting in a predominantly dry
forecast. A weak trough over the region could result in some showers
on Thursday and Friday, primarily in the southwest, but chances are
no more than slight. Also, expect skies to be mostly sunny/partly
cloudy through the period. Temperatures will be highest on
Thursday/Thursday night with highs in the mid to upper 80s and lows
in the mid to upper 60s. Expect gradually decreasing temperatures
thereafter as a result of increasing northerly flow and possible
advection of some cooler air. The forecast for Sunday onward remains
highly uncertain as it will depend on the track of Maria, which will
depend on what happens with Jose. As a result, very low confidence
in the forecast for Monday and Tuesday.

The more interesting features of the extended period will be the
tropics and what happens with Jose and Maria. Jose is progged to
meander off the NE U.S. coast through the week, with increasing
uncertainty through the weekend. Meanwhile, Maria will be moving
through the Caribbean, northwestward toward the CONUS. As mentioned
above, Maria`s impacts from Sunday onward are still highly uncertain
as they will depend heavily on Jose and if/how the two systems
interact with one another. The medium range models continue to have
significantly different solutions in that regard, making forecast
confidence very low.


As of 140 PM Tuesday...

Low-level flow will becoming increasingly westerly this evening and
overnight, which will inhibit the formation of widespread low clouds
and fog overnight. The exception will be at fog-prone sites like
KRWI. Isolated to widely scattered showers and possibly a few storms
will accompany an upper level disturbance moving into the area
Wednesday afternoon. Coverage/pops are expected to be too low to
mention in TAFS at this time.

Beyond 24 hours: Additional showers and isolated thunderstorms may
occur Thursday and into Friday as the disturbance stalls across
the region. Low-level easterly flow could support widespread
fog/stratus across the area late Thursday night/Friday morning.
Otherwise, dry VFR conditions are expected through the weekend.





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