Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 281048

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
648 AM EDT Sun May 28 2017

Warm and humid air will remain over our region through at least
Monday, as high pressure settles east of the Florida coast. A cold
front will slowly approach from the northwest, but will struggle to
push through the area during the middle of next week.


As of 645 AM EDT: A broad area of showers will move east across the
area this morning, but TSRA should remain to our south.

The forecast area will remain solidly in the MCS tracks today from
convection developing from the west in the unstable elevated mixed
layer. Convection allowing models show another round of convection
crossing the area late this morning and early afternoon. Another
round may cross NC late this afternoon and early evening. Precip
will become more isolated with each round moving over. PoP has been
adjusted to reflect this. However, there is quite a bit of
uncertainty after the initial round of showers given the potential
that instability could be limited due to less heating from lingering
convective debris. Shear should be more than adequate for
organized/severe convection, if the atmosphere can become moderately
unstable once again. The best chance for organized convection will
be along and south of the I-85 corridor later this morning and early
afternoon with the forcing from the MCS to our west. The best chance
later this afternoon and early evening will be along and near the
I-40 corridor. Of course, all this is predicated on becoming
moderately unstable.

Convection should taper off later this evening with mainly isolated
convection across the mountains overnight. Highs today will be up to
5 degrees above normal with lows tonight up to 10 degrees above


As of 230 AM Sunday: A large upper low will slowly wobble/drift
eastward across the Great Lakes and then north toward Hudson Bay,
keeping a longwave trof axis across the MS to OH Valleys thru
Tuesday. There will also be a nice jet streak extending from the OH
Valey to the northern Mid-Atlantic, placing our area within the
right entrance region. Models do show periods of better upper
divergence, both on Monday and Tuesday. At the surface, a cold front
will stall just west of the Appalachians Monday, and struggle to
push across the area Tuesday. This set up should keep the forecast
area unsettled. Models agree on decent sbcape on Monday, especially
across the Piedmont, with bulk shear continuing around 40-50 kts. So
organized convection will be possible again, with the new Day 2
outlook placing a slight risk across the I-85 corridor and south,
and marginal risk to the north. On Tuesday, both the cape and the
shear look weaker. But with continued upper support and plenty of
moisture, we will probably see another round of convection, just
with a lower severe threat. Temps will continue to be above normal.


As of 300 AM Sunday: a broad longwave trough axis will finally shift
east across the CWFA on Wednesday, bringing a second cold front in
from the west. So scattered aftn-eve showers and storms are expected
again. Temps look to be slightly cooler, as thicknesses fall with
the trough. Shear looks to increase somewhat from Tuesday, but CAPE
remains muted in the guidance. So the severe threat looks low at the
moment, but may be a bit higher, if we manage to see better CAPE.

Thursday looks to be the quietest and coolest day of the medium
range, as a cold front actually pushes east of the mountains and
ushers in some drier air. This will be short-lived, however, an
upper low near Hudson Bay will rotate back south into the Great
lakes and starts to set up another shallow trough over the MS Valley
to the OH Valley. Surface high pressure will quickly exit off the
Mid-Atlantic coast, and deep-layer SWLY flow brings Gulf moisture
back in across the region. Temps warm back above normal and a return
to slightly above climo diurnal convective coverage is expected for
Friday and Saturday.


At KCLT and Elsewhere: A broad area of showers will spread across
the area this morning. Cannot rule out some MVFR, but low VFR is
more likely. After this area of showers moves through, convection
may redevelop and move east across the area late this morning and
early afternoon. Then another round may move across NC late this
afternoon and early evening. Timing is very tricky and have picked
the most likely timing, but this is subject to change through the
day. Convection ends this evening. Any fog overnight is most likely
to occur at KAVL. W to NW wind becomes SW and gusty this afternoon.
Winds turn back to W to NW and light this evening and overnight.
KAVL will see N to NW winds through the period.

Outlook: Thunderstorms and associated restrictions, mainly of the
afternoon/evening variety, as well as the potential for areas of
morning fog and/or low stratus will continue through at least the
middle of next week.

Confidence Table...

            10-16Z        16-22Z        22-04Z        04-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  83%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High  97%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:




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