Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 170732

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
232 AM EST Fri Feb 17 2017

A warming trend continues as southerly flow returns to the area
underneath a strong ridge of high pressure. A weak upper low will
cross the Tennessee Valley and Carolinas over the weekend, bringing
chances for light rainfall to the area. Another upper low will move
across the Gulf Coast mid to late next week with another round of
light rainfall possible. High temperatures will stay 10 to 15
degrees above normal through the period.


As of 228 AM EST: Water vapor satellite imagery shows a closed upper
level low pressure system lifting slowly northeast across west
Texas. IR imagery shows cirrus over the northern tier of our area
embedded in the deep layer NW flow on the east side of the
downstream ridge. This ridge axis will build over the southern
Appalachians today and any lingering cirrus should thin as the ridge
moves east to not otherwise mar a very good insolation day. MOS
guidance has been notoriously cool on these good insolation days
with some measure of 850 mb westerly downsloping and general
southwest low level return flow. Will thus feature maxes some 3 to 4
degrees above MOS throughout, which will be some 15 degrees or so
above climo.

The H5 ridge axis will progress eastward tonight as the TX low
pressure system continues to open up and lift east over the
Mississippi River Valley. Any deeper returning moisture ahead of
this system should remain southwest of the forecast area through
daybreak Saturday. Min temperatures should rebound 1 to 2 categories
over Friday morning mins as mid and high level clouds return
overnight from the southwest.


At 200 AM EST Friday...An upper level trof approaches the SE states
Sat. Good agreement is had btw the models with the timing and
placement of the stronger vort lobes, which look to cross south of
the FA. Mid-level difl does increase over the FA however and this
forcing along with sw/ly mech lift will be the main drivers for
precip...mainly across the wrn zones. Not expecting deep showers nor
tstms as instability remains quite low due to fairly low sfc td/s
and warm mid levels. The column moistens up throughout the day, but
enuf insol shud be had by the afternoon along with continued sw/ly
flow to generate max temps about 10 degrees above normal. The trof
axis shifts east early Sun and enuf model support is had for the
continuation of weak nw flow -shra till daybreak. Strong ridging
develops quickly to the west and a well defined subs inversion
lowers across the area. Low-level winds will shift west to nw/ly
during the day...however no sigfnt airmass change will occur to
offset max temps reaching the L70s non/mtns and M60s mtn valleys.
Mins will remain about 10 degrees above normal each morning as well.


As of 130 AM EST Friday:  Medium range starting Monday morning with
a huge upper ridge axis extending from Florida to the western part
of Hudson Bay in Canada.  A surface high centered over Quebec moves
east with flow into our region from the Atlantic coming up against
the southern Appalachians which will at times produce some upslope
enhanced showers. All models keep our area mostly dry at least until
Wednesday. The GFS then brings in some rain as a wave on the back
side of the flattening ridge crosses TN and dissipates as it gets to
the western Carolinas.  The closed 500mb low over the Texas coast
early Tuesday moves east and weakens possibly even opening up (on
the GFS) as it crosses Florida Thursday into Friday. The result of
all considered models and their general agreement is slight to low
chance POPs in the Wed to Thursday night timeframe.  As mentioned
before, even though this is still winter, we will be way too warm to
have any precip other than rain. The southern stream low which opens
up into a wave will move east of Florida Thursday night with weak
high pressure controlling our weather until another closed upper low
crosses the Mississippi Valley with preceding cold front getting to
our region next weekend.

Temperatures will be about 15 degrees above normal Monday through
Wednesday then slightly cooler only 10 to 15 degrees above normal
Thursday as the ridge breaks down with more cloudiness.


At KCLT and elsewhere: Expect some lingering cirrus aloft in the
deep layer NW flow early today, but with high clouds thinning and
departing east through the day as ridging builds in from the west.
Low level flow will become more southwesterly with time, except for
continued NNW flow in the French Broad Valley at KAVL. Some low end
gusts will be possible this afternoon during the period of best
mixing, but these should be too infrequent and of low enough
magnitude to avoid mentioning in the TAFs.

Outlook: Spotty showers may move through the region Saturday into
Saturday night, but with the chance of restrictions highly
questionable. After that, expect dry and VFR conditions through
early next week.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     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:


Max temperatures have been raised about 3 degrees above MOS in most
areas for this afternoon, while dewpoints have been dried out a bit
during the period of best mixing. This will lead to plenty of
afternoon RH values in the upper teens and lower 20s. Given the dry
air and fuels, a Fire Danger Statement will be issued for northeast
Georgia with several hours of RH in the 20 to 25 percent range and
fuel moistures below 8 percent.


GA...Fire Danger Statement from 10 AM EST this morning through this
     afternoon for GAZ010-017-018-026-028-029.


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