Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/26/18
Area Forecast Discussion
National Weather Service Columbia SC
1039 PM EDT Thu Oct 25 2018
High pressure centered over the mid-Atlantic region will extend
into the forecast area through Friday. Low pressure developing
along the Gulf coast will lift northeast tonight and spread rain
across the forecast area through Friday. Cold air damming will
result in temperatures well below normal over much of the area
Friday. The low pressure system will move northeast of the area
Friday night but a deep trough over the region will result in
below normal temperatures through Saturday with some patchy
.NEAR TERM /UNTIL 7 AM FRIDAY MORNING/...
Moisture will continue to increase tonight ahead of a low
pressure system currently centered over southern Mississippi.
High pressure over the mid-Atlantic region is resulting in the
development of a cold air damming wedge across the local area. A
strong mid-level shortwave trough in the central Plains will
cause the low pressure system to strengthen and track towards
the Southeastern States tonight. Moisture flux and isentropic
lift appears strong late tonight through Friday morning with
strong low-level east flow 35 to 40 knots in the boundary layer
above a strong surface based inversion with strong southwest
flow in the mid levels. Deep layer shear is also strong. Rain is
starting to move into the CSRA and is expect to overspread the
area by morning. As far as temperatures are concerned, there is
potential for evaporational cooling late tonight given initially
dry low levels, but dewpoints have come up since this afternoon.
Given current trends and wet bulb values, expect lows in the
mid to upper 40s to low 50s south.
.SHORT TERM /7 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
There could possibly be some heavier rain around daybreak as
well as some elevated convection, especially across the
southeast Midlands/CSRA. Models suggest wedge will be
relatively strong across the Midlands. The surface low should
stay just east of the area tracking across the coastal plain or
the coastal waters Friday afternoon. With the warm front near
the southeast Midlands there is potential for some convection,
and given strong deep layer shear a little concern for severe
thunderstorms. Hodographs suggest rotating updrafts with a
marginal damaging wind/isolated tornado threat but mainly in the
coastal plain as low-level stable air is more likely. Will keep
isolated thunderstorms in the forecast southeast of CAE. Rain
may diminish in the afternoon especially to the southwest as
isentropic downglide develops as the surface low moves rapidly
to the northeast along the coast. The temperature forecast is
tricky of course. Think MOS is too high given wedge pattern,
especially north of CAE. Prefer cooler local wedge guidance
although southeast Midlands near warm front temperatures more
uncertain. Little change in temperatures was made from earlier
forecast. Mid and upper 40s north of CAE to lower to mid 50s
central Midlands and upper 50s to low 60s southeast Midlands and
along CSRA. Categorical pops with qpf 0.5 to 0.75 inches with
heavier precip in the Piedmont where upslope stronger.
Models are in good agreement with evolution of wedge and track
of low pressure along/near the Carolina coast Friday
afternoon/evening. Any threat of severe should have ended by
Friday night as surface winds shift NW/W behind the departing
area of low pressure. Southeast will remain under the mean
trough through the period. A series of shortwaves will move
through the trough Saturday through Sunday. Main trough axis
will cross the area Saturday night but a stronger reinforcing
shortwave trough will arrive Sunday night into Monday. Model
time sections show low- level moisture lingering across the area
Friday night through at least Saturday. Will keep a chance for
light rain/drizzle Friday night then more showery type
precipitation with each passing shortwave. As systems pass to
our north, greatest chances for showers Saturday through Sunday
night will be across the northern/central Midlands. Expect
plenty of low clouds through Saturday with mostly cloudy skies
for the most part through Sunday night. With cold air aloft, any
heating will produce clouds during the day. Overnight lows will
mainly range from the middle 40s to lower 50s. Afternoon highs
will be in the middle 60s Saturday to upper 60s/lower 70s
Sunday. Some slight warming ahead of s/w approaching Sunday
.LONG TERM /MONDAY THROUGH THURSDAY/...
Trough will move off the coast Monday as surface high pressure
builds into the region from the central Plains. This will
provide pleasant fall weather through Wednesday. Both ECMWF/GFS
show another strong shortwave trough digging south/southeast
into the central Plains by Wednesday night into Thursday. The
mid/upper flow across the Southeast will become more SW from the
Gulf and rain chances will increase by late in the week. Went
with chance pops for now Thursday, but timing and pops could
change by that late in the period. Temperatures will moderate
through the period. Expect below normal temperatures Monday and
Tuesday with more seasonable/slightly above normal temperatures
for Wednesday and Thursday.
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Widespread IFR conditions will develop. There will be low-
level wind shear.
Moisture and isentropic lift will be on the increase tonight
ahead of low pressure approaching from the southwest. Ceilings
will lower into the MVFR and IFR categories. We followed the HRRR
for the timing. Visibilities will be reduced in heavier rain
and fog. A wedge pattern and strong low-level jet suggests wind
shear will be an issue. Followed the NAM and included LLWS in
the terminal forecasts. There may be elevated thunderstorms. The
models indicate cross totals in the lower and middle 20s during
the day Friday. Expect these will remain scattered with the
chance too low to include in the terminal forecasts at this
EXTENDED AVIATION OUTLOOK...Widespread ceiling and visibility
restrictions are expected through the rest of Friday night
because of considerable low-level wrap-around moisture
associated with low pressure tracking northward along the coast.
Improvement is expected over the weekend with the system moving
farther away and westerly flow in its wake. Breezy conditions
may occur Saturday.
Area Forecast Discussion
National Weather Service Green Bay WI
956 PM CDT Thu Oct 25 2018
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Friday
Issued at 201 PM CDT Thu Oct 25 2018
The latest RAP analysis and satellite/radar imagery show surface
high pressure centered over the eastern Great Lakes and a trough
of low pressure over the Dakotas. Mid and high clouds continue to
stream north into the region ahead of this trough and various
pieces of shortwave energy over the Plains. Although weak moisture
advection contributed to showers over the Upper Peninsula that
grazed the border area earlier today, most of the precip activity
remains over Minnesota and Iowa so far. As this system slowly
moves east, precip chances is the main forecast concern.
Tonight...The trough of low pressure will move into Minnesota.
Lingering dry air below 700mb will likely keep most of the area
dry during the evening hours, but progged soundings indicate that
this dry wedge will get partially eroded overnight. Light shower
chances will be highest where the dry air gets eroded the most,
mostly near the U.P. border and also from central WI into the
southern Fox Valley. Due to ample cloud cover, temps will mainly
fall into the middle and upper 30s.
Friday...The shortwave energy will outrun the trough at the
surface and proceed to move across Wisconsin. Forcing will remain
very weak in the form of mid-level convergence, but any lingering
mid-level dry air will continue to erode, which will give all
locations a chance of light showers. Saturation depth continues to
argue for the highest chance near the U.P. border and also from
central WI to the southern Fox Valley. Under cloudy skies, temps
will fall back a few degrees into the middle 40s to near 50.
.LONG TERM...Friday Night Through Thursday
Issued at 201 PM CDT Thu Oct 25 2018
Large-scale pattern evolution over the extended suggests low
predictability overall as weakly split flow over the northern
Great Lakes early in the period, gradually transitions to a trough
over the northeast CONUS and intermountain west, with shortwave
ridge in between by late Monday.
Forecast area, at least through Saturday, situated in no man`s
land with no clear-cut forcing to organize precipitation. On
Friday night, primary southern stream shortwave forecast to
continue to pass southeast of the forecast area. Meanwhile
another weak disturbance quickly dives southeast toward Wisconsin
by 12 UTC Saturday, however, the majority of the model guidance
tend to weaken this impulse during the day on Saturday with only
some light shower activity mainly west of the forecast area as
column saturation still questionable further east. Also a bit
deeper saturation near the Upper Michigan border will support a
few more showers there. This seems to be supported by latest
model blended QPF with only slight chance POPs over most of the
forecast area during the day on Saturday so will not deviate from
that. Any shower activity on Saturday will likely be light and
widely scattered especially the far northeast with minimal
rainfall amounts. Should remain mainly dry into Saturday evening
with very weak surface ridge suggested by the model guidance.
Still expect lots of clouds Saturday night as another more potent
shortwave quickly approaches Wisconsin initiating more focused
WAA. No definitive consensus from the various model guidance with
respect to location of best concentrated forcing with this system.
GFS ensemble mean and ECMWF suggest heaviest QPF will generally
track across the southwest half of Wisconsin, while the Canadian
and NAM are further north overall. Will therefore just continue
with likely POPS across the entire forecast area starting late
Saturday evening over central Wisconsin, then expand east
overnight into the first half of Sunday. Rainfall amounts
associated with this system will generally range from the around a
tenth of an inch northeast, to perhaps a quarter of an inch over
the southwest portion of the forecast area where deeper moisture
will reside. At this time it appears boundary layer temperatures
across the north on Saturday night will be too warm to support a
rain/snow mix with readings generally hovering in the middle to
upper 30s. Later Sunday afternoon, any lingering light rain or
drizzle should come to an end with CAA and mid-level drying
quickly following in the wake of this disturbance.
To start the work week, Monday still looks to be a pretty decent
day as shortwave ridge builds in. Under partly sunny skies, highs
will generally range from 45 to 50 degrees with light northwest
winds. As surface ridge passes to the east on Monday night, WAA
will be on the increase especially after midnight as LLJ kicks in
ahead of progressive shortwave trough pushing across the central
Plains. Associated surface low will likely pass well north of
Wisconsin with trailing cold pushing across the area late Tuesday
and Tuesday night. ECMWF and GFS are in the ballpark on the timing
of the fropa across the forecast area with majority of the shower
activity falling between about 00Z and 12Z Wednesday. Given
progressive nature of this system and that gulf moisture will be
somewhat limited, expect only modest rainfall amounts.
Through the extended period, temperatures will be at or perhaps
slightly below late October normals and stayed close to the
blended model guidance.
.AVIATION...for 06Z TAF Issuance
Issued at 955 PM CDT Thu Oct 25 2018
VFR conditions expected through much of this TAF issuance. An
upper - level trough will slid into the area this
afternoon/evening, leading to increasing chances of light rain
showers and potentially some MVFR to IFR ceilings. Winds are
expected to remain light through this TAF issuance.
Area Forecast Discussion
National Weather Service Miami FL
739 PM EDT Thu Oct 25 2018
Aside from a stray shower here and there throughout the day today,
not much happened weather wise. Overall, another quiet night is
forecast with a slight chance for rain showers across the east
coast and over both Atlantic and Gulf waters. HRRR and Hi-Res WRF
models are bringing swift moving rain showers from the Gulf over
inland Glades/Collier Counties around 09-12Z tonight. There is
also a slight chance for thunderstorms in the Atlantic, but
overall, convection associated with an approaching warm front and
deepening longwave trough is not forecast to spark until the mid-
morning hours. Essentially, the higher chance for convective
activity remains over the Gulf and Atlantic waters. Otherwise, the
remainder of the forecast looks to be on track with no further
updates are anticipated through midday.
.PREV DISCUSSION... /issued 736 PM EDT Thu Oct 25 2018/
AVIATION...Both Gulf/Atlantic seabreezes should diminish 02Z-04Z,
becoming light/vrb. Pre-frontal trough approaches late, with
winds becoming SSW towards daybreak. Speeds increase to 8-10kts
after 13Z, and 12-15kts after 16Z ahead of main front that arrives
after current TAF cycle. Initial trough may bring SHRA or TSRA
vcnty KAPF late tonight, but chances too low to mention currently.
Isold SHRA and TSRA threat for all sites tomorrow afternoon, may
need to be added in later TAFs.
PREV DISCUSSION... /issued 425 PM EDT Thu Oct 25 2018/
Widespread showers pestering the East Coast throughout the day
today are expected to dissipate throughout the overnight hours
before ramping up again tomorrow morning ahead of an approaching
frontal system; however, showers and potential thunderstorms over
the Atlantic will continue to persist due to warmer temperatures
over the water. Overnight temperatures will range from the low-
mid 60s in the northern CWA and upper 60s to lower 70s elsewhere.
15Z WPC analysis depicted a surface low spinning over the Central
Gulf states with a cold front extending from the south of the
feature and a warm front extended out towards the east and across
Central FL. This warm front will lift northwards overnight,
allowing for a shift in wind direction from the southwest across
On Friday, the combination between the lifting warm front and a
longwave trough deepening across the southeast CONUS will initiate
a brief surge in low level moisture and greater instability across
South Florida. Satellite derived PWAT values look to increase up
to 2.00". Not only do POPs increase, but so will temperatures
(compared to the past couple of days, anyways) as they climb into
the upper 80s across the majority of the CWA. A chance of
thunderstorms will persist across the region as well, and this
will continue into Saturday evening (after FROPA).
On Saturday, a cold front associated with the low pressure trough
is forecast to sweep through South Florida, drastically dropping
PWATs into the 0.50-0.75" range. Then Saturday night into Sunday,
after FROPA, winds shift from the Northwest and eventually from
the north. Dewpoints drop into the mid-upper 50s across most the
CWA with the occasional low 60s for coastal sites. Drier and
cooler weather conditions will continue into early next week as
high pressure builds.
MARINE...Relatively quiet southeasterly winds in the 5-10 kt
range will persist into the overnight hours across the Atlantic.
For Friday, moderate southwesterly flow is expected ahead of a
cold front with winds increasing into the 10-15 kt range for both
the Atlantic and Gulf waters. Winds are going to stay on the
breezy side for the majority of the weekend while simultaneously
shifting from the north as the aforementioned front approaches the
region. Wave heights are not expected to exceed 4 ft. Similar to
earlier today, rain chances will remain isolated to widely
scattered this evening, with an additional spread of showers and
thunderstorms with the front Friday into the early part of this
BEACH FORECAST...Moderate Risk of Rip Currents remains in effect
for Atlantic Beaches this evening throughout the day tomorrow.
Like the past several days, lunar tides will continue for
tomorrow. Tides of 1/2 to 1 foot above normal are possible for the
Atlantic beaches during this period. This could result in
localized minor flooding issues as a result. However, widespread
issues are not anticipated at this time.
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 72 89 73 87 / 20 20 20 20
Fort Lauderdale 76 88 76 87 / 20 20 20 20
Miami 74 88 74 88 / 10 10 10 20
Naples 72 86 73 84 / 20 30 40 20
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Friday)
Issued at 342 PM CDT Thu Oct 25 2018
Low clouds and widespread rain/drizzle soon come to an end, with
clearing skies and warming temperatures for Friday.
A complex upper tropospheric longwave trough with multiple
embedded shortwaves is occluding over the central U.S. this
afternoon, with the well-defined dry slot wrapping northeastward
into eastern Kansas in water vapor imagery and a subsequent
deformation zone arching from north-central Kansas into southern
Minnesota. Widespread rain transitioned into more of a drizzle
under the dry slot, with light to moderate rain noted in a wide
swath from Minneapolis to Marysville. This deformation zone should
continue to pivot and shift eastward over the next 3-6 hours,
gradually weakening as the overall mesoscale forcing wanes.
The question then turns to how quickly clouds clear out tonight.
Most short-term guidance solutions keep the majority of the area
under a broken to overcast cloud deck overnight, but there are
some indications of this cloud shield breaking up to some degree
after sunset. The RAP is the most bullish in this trend, and given
the current clearing rates in southwest Nebraska, this solution
has some merit. Such trends would clear out the stratus in north-
central Kansas before 06Z and reach Topeka before sunrise. Any
location in which the clouds clear would be susceptible to fog
formation given the light winds and recent precipitation.
Maintained mention of fog in the western CWA where the stratus has
the best chance of clearing tonight, which is supported by recent
RAP forecast soundings showing either a very low stratus deck
(which would lead to reduced visibilities in any areas with
terrain) or fog developing after 08Z.
The last clouds associated with this system depart during the day
on Friday with warming temperatures from west to east as a +8 to
+10 C H850 downslope airmass begins infiltrating into the region.
Highs should top out around 60 around the KS/MO border to near 70
in north-central Kansas.
.LONG TERM...(Friday night through Thursday)
Issued at 342 PM CDT Thu Oct 25 2018
The weekend looks to start warm, with a cold front moving through
Sunday morning keeping temps near seasonal norms into next week.
Continued advection of warm downslope air will push temperatures
into the low to mid 70s for Saturday ahead of an fast-moving
Alberta Clipper system that drops through the Dakotas Saturday
night and reaches the Mid-Mississippi River Valley by sunrise on
Sunday. The biggest impact this system would have on the local
area will be a rapid increase in winds Sunday morning behind the
barotropic cold front, with differential CAA at H850 steepening BL
lapse rates and enabling a 40 to 50 kt jet to potentially mix to
the surface. There is some disagreement amongst the medium range
solutions as to the track of this clipper and the resultant
pressure gradient over the Central Plains. The GFS/EC take the low
on a southern course and bring stronger winds to NE Kansas, while
the NAM/GEM take the low on a more northerly track that keeps the
stronger winds in Iowa. For now, have stuck closer to the GFS/EC
blend for forecast consistency.
After the passage of this system, longwave ridging builds into
the central CONUS, keeping quiet weather and seasonal temperatures
in place to start the work week. The next chance of precipitation
comes on Tuesday as this ridge shifts east and sharp H300 trough
digs into the central U.S., with a cold front advancing eastward
ahead of this trough. Surface ridging builds in for Halloween on
Wednesday, bringing with it cool and quiet weather.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 543 PM CDT Thu Oct 25 2018
For the 00Z TAFs, low stratus continues to impact the terminals
along with -SHRA becoming less common as -DZ becoming the more
predominant precip type through about 02Z at KMHK and then precip
ending later around 04Z at KTOP/KFOE. Do expect mostly MVFR CIGS
and VIS to be persistent through much of the overnight hours.
Therefore, have extended MVFR through 12Z time frame before
working a more dry airmass fully into the area. Not completely out
of the question that fog does form if clouds do actually clear
earlier than expected. This may be what models are struggling
with. However, satellite trends would indicate that clouds will be
slow to clear. So, have not gone too aggressive with the idea of
fog at this time.
Area Forecast Discussion
National Weather Service Tulsa OK
918 PM CDT Thu Oct 25 2018
Moisture wrapping around the upper-low moving into Missouri
has been resulting in patches of light rain across northeast
Oklahoma and western Arkansas, along with patches of drizzle
and fog. As the low continues east the precipitation and fog
will diminish with time. Deep-layer drying has resulted in the
clouds breaking a little this evening in Choctaw Co. Overall
the clearing will be slow to expand as area stays beneath cyclonic
We have been tweaking the forecast this evening, following
the latest trends. Another forecast tweak will be released
.PREV DISCUSSION... /Issued 627 PM CDT Thu Oct 25 2018/
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.
Areas of drizzle will remain possible for the next few hours
across NE OK/NW AR in association with upper vort max. Otherwise
IFR/brief LIFR conditions will continue overnight into Friday
morning. Ceiling heights will begin to slowly rise through the day
with VFR conditions possible in most areas by mid/late afternoon,
except far northwest Arkansas where lower clouds will likely
PREV DISCUSSION... /Issued 324 PM CDT Thu Oct 25 2018/
The main challenges in the short term will be drizzle chances this
evening, low cloud coverage thru tomorrow and then fog potential
tomorrow night. Rain/thunder chances with next week`s storm system
are another item of mention.
WV imagery and RAP analysis shows a PV max rotating around the
basal portion of an eastward progressing shortwave trough across
northern OK this afternoon. WV imagery also indicates that the air
has dried out aloft from the initial wave, with only BL saturation
lingering. Lift in advance of the northern OK PV max is bringing
another round of drizzle to NE OK attm. This area of drizzle will
slide east with time this evening into NW AR, where higher PoPs
for low QPF will be maintained.
As expected, low clouds have persisted over the region today and
will continue over the region tonight. Guidance is clearing these
low clouds fairly quickly tonight into Friday, but this is usually
too fast. For the forecast, the back edge of the higher NAM BL
moisture was used as an approximation of the low clouds. As such,
the forecast will reflect a much slower west to east clearing on
Friday. A more aggressive clearing will occur Friday night into
Saturday as the BL flow gains more of a westerly downslope
component in the wake of another subtle wave rotating down the
back side of the departing central CONUS trough. Radiational
cooling of a cool saturated airmass near the surface Friday night
west of the clearing low cloud deck should lead to some fog
development Friday night.
Used a blend of raw model and short term guidance for lows
tonight, which show temps holding in the mid to upper 40s under a
blanket of low clouds. A slower clearing of the low clouds on
Friday suggests that highs will not be as warm as previously
thought. Saturday will be the warmest day of the forecast with
downslope flow ahead of the front for Sunday. Cooling will not be
significant behind this front.
Yesterday it looked like winds would be strong and gusty on Sunday
afternoon behind said front. Today`s data has backed off from
this, mainly due to the fact that a strong shortwave trough in the
developing NW flow over the Plains will be displaced farther to
the northeast from our area compared to yesterday`s forecast. This
places the gusty NW winds farther up into MO and have thus backed
off on winds for our area.
The GFS and ECMWF now show more run to run consistency in regards
to next week`s storm system and front, showing a faster
progression thru the region. As such, will reflect higher PoPs
with the initial frontal push Tuesday and Tuesday night. What is
less certain is the amount of energy holding back in the basal
portion of the digging upper trough. The ECMWF maintains energy to
our west and has more post-frontal precip into the day on
Halloween, while the GFS dries things out. Will maintain some
PoPs into Wednesday for this reason. Moisture return will be
fairly meager with the initial frontal push, as it will be too
fast to plow thru our area before some decent moisture can return
north from the Gulf. Nevertheless, models do show some low end
instability and have thus inserted isolated thunder mention.
As for Halloween evening festivities, the potential remains for
these to be wet, especially if the ECMWF verifies, though this
potential appears to be greater across eastern and southern
portions of the forecast area versus the northern and western
areas attm. Stay tuned for updates.