Turner Downs Forecast Discussion

FXUS62 KRAH 210300

National Weather Service Raleigh NC
1100 PM EDT Tue Oct 20 2020

High pressure sticks around into Thursday, before weakening
offshore. A front arrives Saturday with limited moisture.


As of 1100 PM EDT Tuesday...

High pressure ridges remains along the southeastern United States
coast. Two layers of clouds can be seen on satellite, with low
clouds moving from east to west while high clouds move from south to
north. Once again models are indicating low clouds and fog will
develop once again. Thickest fog should be along the I-95 corridor,
with visibilities higher on either side. The cloud cover will help
keep temperatures warm, from the mid 50s to mid 60s.

Wednesday will see the low clouds/fog erode again toward mid-late
morning, but may be slower given surface inversion and lack of
mixing. Coastal flow weakens over the coastal plains, north of I-40,
but showing some influx of moisture toward Clinton/Fayetteville. Am
leaning toward a dry forecast, but cannot rule out isolated showers
popping up east of Fayetteville in the afternoon. Highs again
running 5-10 degrees above normal, with mid 70s to around 80.


As of 200 PM EDT Tuesday...

High pressure surface/aloft remain stuck across the coast into
Thursday, locked in place by TS Epsilon east of Bermuda. Meanwhile,
another upper trough works underneath this ridge across southern
Georgia/Florida. At the surface the ridge will maintain mostly dry
conditions as deeper Atlantic moisture stays south of North Carolina.

Thursday night into Friday, the upper shortwave across Georgia
weakens but heads northward toward the Carolinas, while northern
stream energy digs across the upper Midwest. This will act to
squeeze the upper ridge offshore between Epsilon and the trough to
the west. As such likely will see increasing mid and high clouds,
but overall appears mainly dry. Temperatures will continue to run
above normal with highs in the 70s, and lows in the upper 50s to
lower 60s.


As of 200 PM EDT Tuesday...

Upper ridge heads offshore and weakens with flow becoming more
zonal, with one front and upper trough working in Saturday, followed
by high pressure late Sunday-Monday, before another wave approaches.
Overall, this first front is limited in moisture, so pops
overall will be on the low side. Latest data suggest the next
trough will have a bit more depth too it, with southwest flow
aloft. Given some differences kept pops in the low chance range
Tuesday, but trends are for an uptick in shower chances by the
middle of next week.


As of 805 PM Tuesday...

Little change in the overall pattern with southeasterly low-level
flow bringing in moisture for stratus/fog development. Like this
past morning, feel the favored areas for fog will be RDU/FAY/RWI and
more stratus at GSO/INT. Expecting partial clearing of the low and
high-level cloudiness after 04Z, resulting in another favored period
of fog. Opted to keep RDU/FAY at IFR after 06Z, though guidance
suggests visibilities lowering to 1/4 SM. Confidence in this
solution is not high at the moment. VLIFR expected again at RWI.
Fog/stratus should lift similar to the past few mornings with
diurnal heating around 15-16Z, though opted to keep MVFR ceilings at
GSO/INT with deeper low-level moisture shown in model soundings.
Winds will be light and variable once again.

Outlook: The pattern for the remainder of the week will continue to
support sub-VFR stratus and fog potential during the early morning
hours. A frontal boundary approaching over the weekend may result in
a slight chance of showers.





NWS RAH Office Area Forecast Discussion