Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 191405

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1005 AM EDT Thu Apr 19 2018

Dry and cool high pressure will build in from the northwest today,
bringing very pleasant conditions for the weekend. Another system
will approach the area late Sunday, with cool and wet conditions
expected early next week.


1000 AM Update...area temperatures have remained rather high
overnight due to good mixing and even with the FROPA taking place
right now...expect max temps to reach arnd a cat or so abv the fcst
due to very good insol and deep layered subs. Thus...the max temp
grid has been adj/d accordingly.

As of 625 AM EDT Thursday: the line of showers associated with the
approaching cold front moved into the NC Mountains over the past hour
or so with very little fan fare. As it did, most of the precip dried
up. At present, the RADAR mosaic is showing very little if any returns.
Cloud cover has also been less than previously expected over the higher
terrain, thus sky cover has been reduced with this latest update.

Otherwise, the parent sfc low will move off the Atlantic Coast today
and tonight as very broad sfc high pressure overspreads the region
from the northwest. This high will dominant the synoptic pattern well
into the weekend and keep things dry. We can expect mostly sunny skies
today with brisk SWLY winds becoming NWLY this afternoon in the wake
of the fropa. Gusts between 20 and 25kts are expected again today with
values in the 30 to 40kt range across the higher terrain. Our northern
mountains will likely see even higher gusts, hence a Wind Advisory
remains in effect until 6pm. While temperatures will be notably cooler
today, mixing should be sufficient to bring dewpoints below 25 percent
in localized areas. This combined with the wind gusts warranted a Fire
Danger Statement to be issued again for NC today.


As of 215 AM EDT Thursday: Quiet through the short term. High
pressure over the Upper Midwest will slowly translate east as an
upper ridge over the Plains is forced eastward by an incoming
midlevel closed low over the Four Corners working its way toward the
Plains. Mean troughing in place along with the post-frontal cool
airmass will lead to below-normal temps (by a handful or so degrees)
into the weekend, finally getting a few days of March-like spring
that we never really got. It`s possible we may see some frost issues
across the southwest mountains Saturday morning, but that would be
the only potential headline through the period.


As of 230 AM EDT Thursday: The former Midwest surface high will be
over the Great Lakes at the start of the extended, ridging across
the Central Appalachians and beginning to dam down the eastern
slopes of the Southern Appalachians. Meanwhile the Plains low will
push toward the Lower MS Valley, with strong moisture advection into
the Deep South ahead of the surface low. Northeastward progress of
the moisture advection will be halted by the developing wedge front,
though isentropic upglide will contribute to increasing sky cover
early Sunday. The surface low will dive SE toward the northern Gulf
Coast as the upper low begins to fill and slowly phase with another
shortwave diving out of the Northern Rockies. The surface high will
move offshore Tuesday, but residual cool pool will remain locked in
across our area.

As for sensible weather impacts, have delayed onset of pops on
Sunday but overall trend is still similar with highs progged a good
10 or so degrees below normal with the damming in place Monday into
Tuesday. Have once again trended pops higher during the event with
likely pops Monday and Tuesday, with guidance in better agreement on
timing and extent of precip with the 00z runs. Overall QPFs are down
a tad but it still looks like a good soaking early next week though
certainly not a gullywasher, generally a good 2-3 inches across the
favored upslope areas of the southwest mountains and a little less

The Northern Rockies shortwave works toward the Great Lakes and
drags a front with it, serving to scour out the damming on Wednesday
and resulting (as is typical) in slightly warmer temperatures with
decreasing clouds. However, the progressive pattern remains in place
with yet another system gearing up over the Desert Southwest at the
end of the period.


At KCLT and elsewhere: expect VFR conditions to prevail thru the 12z
taf period. No significant changes were needed from the previous TAF
issuance with gusty W to SW winds giving way to NWLY winds in the wake
of a dry fropa later this morning. Winds will shift to NWLY first at
KAVL, and then elsewhere by the early afternoon. The front will be
accompanied by shallow moisture, however most of the MVFR to low-VFR
cigs should remain confined to the western slopes of the NC mountains.
Some bkn low-VFR cigs are possible over KAVL late this morning, but
shouldn`t linger for more than a few hours. Elsewhere, only sct to few
clouds are expected thru the period. In the wake of the front, wind
speeds will increase again along with higher gusts. Speeds should
weaken a bit later tonight as the pressure gradient weakens and high
pressure begins to spread over the area.

Outlook: broad high pressure will overspread the region on Friday
leading to lighter winds and pleasant conditions through Saturday.
Restrictions may develop late Sunday and into Monday as a warm
front lifts northward over the area, bringing deeper moisture up
from the Gulf of Mexico.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
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:


Cooler and much drier conditions expected through the end of the
work week. RH values will slowly drop today to around 30 percent,
with locally drier RH as low as 20 percent possible. NW winds today
will combine with the drying airmass and will result in elevated
fire danger across the area again. Winds will decrease on Friday
below critical thresholds but will have to be monitored, since RH
values will remain critically low.


GA...Fire Danger Statement until 7 PM EDT this evening for GAZ010-
     Freeze Warning from midnight tonight to 9 AM EDT Friday for
NC...Fire Danger Statement until 7 PM EDT this evening for NCZ033-
     Freeze Warning from midnight tonight to 9 AM EDT Friday for
     Wind Advisory until 6 PM EDT this evening for NCZ033-049-050.


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