Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/15/18
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1046 PM EDT Fri Sep 14 2018
Florence will continue to track inland through the Carolinas this
this weekend and weaken. This will result in an increasing threat
for widespread flooding later this weekend into early next week.
Drying will occur across the forecast area as Florence pulls away
from the southeast early next week.
.NEAR TERM /THROUGH SATURDAY/...
As of 1045 PM EDT: A few elongated bands around the outer reaches of
the circulation of Florence have been slicing quickly southwestward
across the western Piedmont of the Carolinas this evening. Stronger
winds have been mixing down to the sfc in and around these bands,
and that should continue through the early morning hours. Elected
to begin the Wind Advisory over the wrn Piedmont and metro CLT
to account for this. Precip chances look like they are in good
shape with the steadier tropical rain area making some westward
progress toward metro CLT. Precip prob was bumped up over the wrn
Piedmont/Charlotte metro to account for radar trends and to match
with neighbors. Temps look ok.
Latest satellite imagery continued to show mid and high level
clouds spiraling into the piedmont of the Carolinas from the
west out ahead of Florence. According to the NHC, Florence will
continue to drift westward through the Carolinas this weekend
before lifting north of the region early next week. This will
bring increasing rainfall chances mainly to eastern portions of
the Carolina piedmont through tonight with light to occasionally
moderate rain likely near and to the east of I-77. Dense overcast
cloud cover is expected to drastically limit any instability and
associated thunderstorm threat across this area. The RAP model
shows modest CAPE values this afternoon focused across the SW NC
mountains where isolated showers or thunderstorms will continue
to be possible through this evening. Rain coverage and intensity
will increase from the east Saturday. There is also the slight
chance of thunderstorms along and east of the I-77 corridor. The
greatest risk with thunderstorms looks to be heavy rainfall,
although an isolated weak and brief tornado cannot be ruled out
given the potential for moderate wind shear up to 850 mb.
Tightening sfc pressure gradients ahead of the storm have already
led to increasing northerly winds across the region, especially
across far eastern portions of the CWA where peak winds briefly
gusted to 35 knots at Charlotte/Douglas International Airport this
morning. Winds are expected to gradually increase for many areas
through this afternoon before leveling off overnight. However,
winds are expected to generally remain well below advisory levels
through this evening. Winds late tonight may approach advisory
levels for areas near and east of the I-77 corridor and higher
elevations of the Blue Ridge mountains. These gusty winds will
likely continue if not increase Saturday into Saturday evening.
Increasing cloud cover tonight will assist in maintaining well
above normal low temperatures again tonight. A moderate temperature
gradient will likely set up across the forecast area Saturday
with highs only into the 70s along and east of the I-77 corridor
warming to near 90 across far western portions of the Upstate of
SC into NE GA.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 330 PM EDT Friday: A Flash Flood Watch remains in effect for
Upstate SC and the NW Peidmont for Saturday morning though late
Monday night. Florence will present multiple hazards across the
region with very heavy rainfall, gusty winds, and even a threat of
isolated tornados. Some uncertainty remains with dependancy on exact
track of Florence.
Heavy rain from Florence will continue to push west Saturday night
as Florence moves NW and is expected to weaken to a disturbance on
Sunday. While the winds of Florence will be generally decreasing as
the system moves more inland, very heavy rainfall amounts will
continue to be the main threat. High rainfall amounts atop already
saturated soils are expected to produce flash flooding, significant
river rises/possible river flooding, and isolated land slides
Expect areas of heavy rain to continue Sunday night into Monday
before Florence (or the remnants thereof) lifts NW towards the Ohio
Valley. As this happens, expect precipiation to lift generally south
to north bringing an end to rainfall across upstate SC late Monday.
CLT metro area continues to be area of most concern with high
rainfall amounts in the urbanized area. While, upslope component of
the wind flow could result in enhanced rainfall amounts across the
mountains. Those areas in which landslides have occurred recently
will be more susceptible to additional landslides. For river
flooding, the river flood potential continues to increase for the
Catawba, Yadkin, and Broad watersheds.
Storm total rainfall (Friday night through Tuesday) amounts ranging
from 10 to 15 inches extending just west of I-77 eastward to the
Charlotte-metro area. Further west, QPF amounts decrease to about 5
to 10 inches extending west of I-77 to Greenville. QPF amounts for
areas south and west will taper off to about 2 to 4 inches.
Strong gusts will still be possible as models continue to show 40-
50kts at 925mb, especially on the northern side of the system.
Another area of concern will be leeward side of mountains, leading
to possible downslope acceleration of winds on Saturday night into
Sunday. Late Sunday into Monday, expect Florence (or remnants) will
lift NW toward the Ohio Valley. The combination of heavy rainfall
and gusty winds on top of already saturated soils could lead to
isolated fallen trees.
As Florence drifts inland, embedded circulations within
thunderstorms could allow for a brief, isolated tornado. SPC
continues to have a a General Thunderstorm risk for most of the FA
.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 330 PM EDT Friday: A few showers could affect the Peidmont NC
area as the remnants of Florence continues to move out of the area -
being picked up by the upper level west to east flow. High pressure
will build into the region for the rest of the work week with mostly
dry conditions which will help alleviate flooding and high river
flows from Florence. Temperatures remain in the 80s during the day
and upper 60s to low 70s overnight.
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Expect a slow decline in flight conditions
over the next 24-30 hours as Florence spins westward over the
Carolinas. Already seeing some very gusty winds at KCLT with
brief MVFR/IFR restrictions as the first outermost band moves
through. Expect several breaks in the action overnight, but suspect
we will settle in with an MVFR ceiling prevailing from mid-evening
onward, with strong and gusty N/NNE winds overnight. LLWS could be
a problem if the boundary layer decouples in the pre-dawn hours, but
that is not anticipated at this time. The steadier rain should move
in before the start of morning ops, along with gradually lowering
ceilings. Started IFR in the late afternoon...20Z Saturday...but
that could easily begin temporarily several hours earlier if
heavier showers move through, but such details were left out for
brevity at this time. By sunset Saturday, we should lock in IFR
ceiling/vis in a steady moderate rain. Very strong winds aloft
will result in LLWS from afternoon onward. All other TAF sites are
some variation of this scenario, with appropriate later timing,
even though IFR will not reach them until after the 24 hour period.
Outlook: LLWS concerns may expand to other terminals along and east
of the Appalachian mountains Saturday night into early Sunday.
Expect intermittent MVFR or IFR flight restrictions with periods
of moderate to heavy rain into early Monday as the remnants of
Florence move across the western Carolinas. Flight conditions
improve later on Monday and into Tuesday.
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 91% High 100% High 89% High 86%
KGSP High 100% High 100% High 91% High 88%
KAVL High 100% High 87% Med 78% Med 76%
KHKY High 97% High 87% High 95% High 96%
KGMU High 100% High 100% High 94% High 92%
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:
GA...Wind Advisory from 6 AM Saturday to 8 AM EDT Sunday for GAZ010-
NC...Wind Advisory from 6 AM Saturday to 8 AM EDT Sunday for NCZ033-
Flash Flood Watch from 8 AM EDT Saturday through Monday
evening for NCZ033-035>037-048>050-052-053-056-057-059-
Wind Advisory until 8 AM EDT Sunday for NCZ035-068-502-504-506-
Wind Advisory until 8 AM EDT Sunday for NCZ036-037-056-057-
SC...Wind Advisory from 6 AM Saturday to 8 AM EDT Sunday for
Flash Flood Watch from 8 AM EDT Saturday through Monday
evening for SCZ001>014-019.
Wind Advisory until 8 AM EDT Sunday for SCZ004>008-010>013-019.
Wind Advisory until 8 AM EDT Sunday for SCZ009-014.
Area Forecast Discussion
National Weather Service Melbourne FL
910 PM EDT Fri Sep 14 2018
Tonight...Rather warm temps aloft (minus 5-6C at 500mb) and a weak
sea breeze (surf temps around 85F) yielded low coverage of afternoon
showers/storms. This was despite rather high precipitable water
values, 1.8 inches in the north and around 2 inches in the south.
Radar showed the east and west coast sea breeze boundaries pushing
inland, but they became indistinct after sunset. The HRRR has been
showing some convection developing several hours after sunset across
the south half, but coverage was trending less and less. We doubt
there will be convective initiation so late, but with it so moist
across the south, will wait until late evening to remove PoPs.
VFR conditions should prevail overnight. The GFS shows high PoPs in
the south (>60%) on Sat afternoon. Temps aloft are still shown to
be quite warm, so we just have 30-40% there with vicinity thunder
KMLB-KSUA. Moisture is forecast lower across the north and both the
GFS and ECMWF have low PoPs (20%).
Tonight-Sat...A south southwest wind flow will continue over the
waters as Tropical Storm Florence moves slowly over South Carolina.
The pressure gradient should support 10-15 knots in the north and
around 10 knots in the south. Seas will continue to be from
lingering swell generated by Florence, but with the system moving
inland, would expect steady or slowly falling wave heights. The
Wave Watch actually shows a slight rise due to an east swell on Sat.
Won`t change our current forecast which has seas 3-4 feet near
shore, and up to 4-6 feet seas offshore on Sat.
The Saint Johns River remains in Action Stage just south of Lake
Harney near Geneva. The river level at Astor lingers near flood
stage of 2.3 ft and a river flood warning for this area remains in
effect. The St Johns will remain nearly steady or begin a slow
fall into the weekend and early next week.
Area Forecast Discussion
National Weather Service Marquette MI
757 PM EDT Fri Sep 14 2018
.SHORT TERM...(This evening through Saturday)
Issued at 319 PM EDT FRI SEP 14 2018
WV imagery and RAP analysis indicated sw mid/upper level flow from
California through the Northern Plains between a trough from north
central Canada through BC into the Eastern Pacific and a ridge from
New England to the Southern Plains. A shortwave trough and
associated sfc low moving across northern Ontario into northern
Quebec has pushed a frontal boundary into nw WI and western Lake
Superior this afternoon. Mid clouds and isolated showers have been
focused along this frontal boundary this afternoon and some clouds
have spilled into the western half of the U.P.
Into this evening, models indicate frontal boundary moving into
the nw portions of Upper Mi. With MLCAPE values at or above 1k
J/Kg, the boundary could provide the focus for isold/sct
shra/tsra. The limiting factor for convection is that several
model soundings show some capping around 700mb which may inhibit
initiation. However, if any tsra develop 0-6km shear to 35-40
knots and steep mid level lapse rates of 7.5C and PWAT values of
1.4 inches could support a few strong storms with heavy rain and
Late tonight tino Sat, any lingering convection will weaken late
evening with the loss of daytime heating. Models suggest that the
front will then lift back to the north with the stronger low level
moisture inflow and 850mb theta-e advection shifting into northern
MN and nw Lake Superior. This should keep the higher shra/tsra
chances mainly over nw Lake Superior and northwest portions of Upper
Michigan. With models forecasting MUCAPE values near 1k j/kg, deep
layer shear near 40 kts and PWAT values of 1.5-2.0 inches, stronger
storms with a potential for heavy rain would not be out of the
question for the nw fcst area. Increasingly anticyclonic flow and
rising 5h ridge heights should keep the rest of Upper Mi mostly dry
tonight into Sat with continued above normal temps. Expect min temps
tonight in the lower 60s with max temps Sat in the upper 70s to
.LONG TERM...(Saturday night through Friday)
Issued at 246 PM EDT FRI SEP 14 2018
Upper air pattern consists of a 500 mb ridge over the central and
eastern U.S. with Florence over the Carolinas and a trough on the
west coast 00z Sun. The remains of Florence slowly head northwest
into the Ohio Valley by 00z Tue while the ridge remains over the
central U.S. Temperatures will stay above normal for this forecast
period and will stay humid as well. Did not make too many changes to
the going forecast.
In the extended, the GFS and ECMWF show a 500 mb ridge across the
southern U.S. with a trough in the ern U.S. 12z Tue and a trough on
the west coast. A sfc front is south of the area on Tue and
continues to move south. The trough on the west coast digs further
to the southeast on Wed and then moves into the Rockies on Thu and
into the upper Great Lakes late Thu into Fri. Temperatures will
remain near normal for this forecast period.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 757 PM EDT FRI SEP 14 2018
Cold front that has drifted into nw Upper MI will move little over
the next 24hrs. This front may serve to generate shra/some tsra at
times, but potential of KIWD/KCMX being impacted appears low attm.
Thus, only VCSH was included in fcst at both terminals. Cigs should
tend to lower, especially at KCMX under light flow off Lake
Superior. Expect cigs to fall to MVFR with some MVFR vis in fog as
well, but should rainfall occur out over central and eastern Lake
Superior, IFR conditions would be more likely late tonight into Sat.
KIWD should also fall to MVFR for Sat. At KSAW, VFR conditions will
mostly prevail. Some fog, MVFR vis, should develop for a time late
tonight/early Sat morning. Not out of the question that vis could
fall to IFR.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 319 PM EDT FRI SEP 14 2018
Northeast winds to around 20 knots are expected late tonight and
Saturday over western Lake Superior as low pressure develops over
the Plains. Winds will diminish Saturday night into Sunday but
increase again Sunday night as low pressure moves into northern
Ontario. Otherwise, winds will remain below 20 knots through the