Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 161510

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1010 AM EST Fri Feb 16 2018

Warm high pressure will move out over the Atlantic today as a cold
front crosses bringing much cooler air to start the weekend. A wave
of low pressure will develop along the front over the weekend,
keeping rain in the forecast Saturday and Saturday night. The next
cold front will arrive in mid week bringing some thunderstorms.


As of 1055 am Friday: The leading edge of a frontal zone and
accompanying narrow shower band currently extends from Middle TN,
across extreme southeast Kentucky, and into southwest Virginia. This
will continue to move steadily SE with a weakening/dissipating
trend anticipated within the trailing stratiform precip region, as
it moves away from the better upper-level support while also
encountering westerly downslope flow downstream of the Blue Ridge.
As such, the highest pops this afternoon will continue to be
advertised across the mtns, particularly the northern mtns. However,
guidance remains consistent in depicting resurgence of low level
convergence and the narrow shower band along the boundary (as well
as some very weak instability) across the NC Piedmont late this
afternoon, so will allow solid chance pops to continue roughly
along/east of I-77 during that time.

In the interim, another very warm day is already well underway
southeast of the front, with temperatures already in the 70s in
moist locations south of I-40 and southeast of the Blue Ridge. Max
temps should easily reach the mid/upper 70s in these areas, and
there will likely be some 80 degree readings across the southern
Piedmont before all is said and done. Record maxes are well within
reach at all sites, and will likely be broken at KCLT. Highs will be
cooler across the mtns/I-40 corridor, where the front should pass by
late afternoon, but northern Piedmont/foothills and most mtn valley
locations should still see maxes in the 70-75 range.

Otherwise, gusty SW to W winds continue through the day ahead of the
front, quickly turning to the NW and remaining gusty (esp across the
mtns) behind the front. Showers end early in the evening as the
front moves southeast of the area taking the deep moisture and
forcing with it. There may be a few lingering showers across the
mountains in the lingering low level moisture and developing NW
flow. Rain returns toward daybreak as a cold air damming high builds
in from the north and southerly low level flow develops. Low level
moisture and isentropic lift increase by daybreak bringing a chance
of rain across most of the forecast area. Temps drop behind the
front as a relatively cold air mass moves in. Lows will still be 10
to 15 degrees above normal which is significantly cooler than the
previous 2 mornings. Temps do drop to near freezing over portions of
Avery county and the northern Blue Ridge. However, do not expect any
freezing precip at this time. A deep warm nose remains in place
precluding any snow.


As of 330 AM EST Friday: A hybrid/in-situ cold air damming will
dominate the weather on Saturday, with strong isentropic lift atop
the CWFA. The parent high will quickly translate east and a weak low
will streak along the wedge front, then deepen over the Mid-Atlantic
coastal waters Saturday night. This will bring the low-level flow
around out of the NW and cut off PoPs by daybreak Sunday. The
rainfall shouldn`t be too heavy, with the axis of highest QPF across
the TN Valley, where the upper divergence will be strongest. The
SWLY to WLY upslope areas will see the most rain with locally 1-2"
possible. Most of the area will see just less than 0.5". Temps will
be held down by the CAD, mainly in the 40s to mid 50s, then cool
into the 30s to lower 40s Saturday night.

Sunday still looks like a dry day with guidance even trending a
little less cloudy. So we should see a little more sun than we`ve
seen in a few days with a weak, transient high pressure crossing the
area. Temps rebound to the 50s to mid 60s, which is a couple
categories above normal.

The upper flow starts to amplify Sunday night, with low pressure
deepening over the Central Plains. Meanwhile, high pressure will
exit off the East Coast, allowing return flow to spread moisture
back into the area. Guidance is in good agreement on light precip
breaking out before daybreak Monday, as a weak in-situ CAD develops.
Temps will be held up well above normal overnight by the increasing
clouds and LLVL WAA flow.


As of 130 AM EST Friday...The extended begins at 12Z Monday with
500mb high centered east of the Bahamas and trough over the West.  A
low level southerly flow will enhance showers in upslope areas from
NE GA over toward Caesars Head area.  This upslope flow should be
maintained into Tuesday night then 925mb wind becomes more parallel
to the mountain range.  The cold front should extend from Kansas to
the Great Lakes early Monday and crossing KY and TN Tuesday night.
The front will slow down quite a bit going into Wednesday as waves
of low pressure move NE along the front from the northern Gulf. Also
instability will increase ahead of the front. GFS has CAPE values
over 500 Wed PM over the lower piedmont and the ECMWF has 1000 CAPE
south of I-85 same time. The front should clear the mountains early
Thursday then CAPE values in lower piedmont rise above 600 for
Thursday afternoon. The front moves south of our area on Friday and
we get into a cooler and more stable airmass with a high to our NE
for a wedge configuration. Max Temps in the lower 70s Tuesday,
Wednesday and Thursday. Min Temps well above normal due to the cloud
cover not getting near normal until Thursday night north of the
front over NC.


At KCLT and elsewhere: Gusty SW winds continue this morning ahead of
the approaching cold front except for a brief period of NW wind at
KAVL. Winds will turn NW late this afternoon or early evening as the
front moves through. Winds then diminish overnight and turn N to NE.
MVFR clouds this morning will lift to low VFR by afternoon as
heating develops. Latest guidance still shows best precip chances at
KAVL with KCLT second. Have included VCSH these areas but chance too
low to include elsewhere. Low VFR continues overnight with MVFR
possible toward daybreak as precip chances increase.

Outlook: The weather will remain periodically unsettled, with
periods of restrictions likely into at least early next week.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       Med   77%     High 100%     High 100%     High 100%
KGSP       Med   75%     High 100%     High 100%     High 100%
KAVL       High 100%     High  89%     High 100%     High  97%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       Med   77%     High 100%     High 100%     High 100%
KAND       Med   77%     High  93%     High 100%     Med   60%

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:



  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      72 2001     18 1958     51 1990      2 1905
   KCLT      76 1976     28 1969     60 1990     11 1905
   KGSP      80 1911     32 1958     59 1990      9 1958




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