Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/10/18
Area Forecast Discussion
National Weather Service La Crosse WI
557 PM CDT Tue Oct 9 2018
.SHORT TERM...(This evening through Wednesday night)
Issued at 210 PM CDT Tue Oct 9 2018
Water vapor satellite this afternoon shows the trough over the
Rockies deepening with an upper level low forming over southern
Colorado. The low will continue to deepen and become closed over
the Dakotas tonight and remained closed as it moves northeast
across Minnesota Wednesday. As the low moves northeast, a strong
short wave trough will move over the region and is expected to
produce strong pv advection in the 500-300 mb layer as moves
across late tonight into Wednesday morning. The surface front
currently extends from southwest Iowa into northern Wisconsin and
will not move much tonight and then get pushed east of the area
Wednesday. The short wave trough will push a surface low along the
front that is expected to move across the area overnight and
Wednesday morning. As these features approach the area, the low
level jet will crank up ahead of the surface low and should be
focused on the area this evening before becoming focused farther
to the north overnight. As the nose of the low level jet works
into the area, should see showers and some storms rapidly
redevelop over the area late this afternoon into the evening. The
latest set of hi-res meso scale models then suggest there could be
a break from the late evening into the early overnight until the
surface low and short wave start influencing the area with more
activity expected to form along the front and then work east
through the late overnight into Wednesday morning. All the
activity should then taper off from southwest to northeast late
Wednesday afternoon through the evening with just some lingering
precipitation chances into Wednesday night across the far north
in the cyclonic rap around flow.
With the front bisecting the area this afternoon, the areas east
of it are warming up with temperatures well into the 70s. Dew
points in the warm sector are in the middle to upper 60s yielding
ML CAPE values of 500-1000 J/Kg over northeast Iowa into southwest
Wisconsin. The 09.17Z RAP holds this CAPE in place in the warm
sector through the evening with just a slight decrease expected
from the loss of daytime heating. Plenty of shear will be in place
with 30 to 40 knots in the 0-3 km layer and up to 30 knots in the
0-1 km layer. This continues to suggest a severe potential through
the evening hours with damaging winds the main threat. There will
also be a tornado threat if any storms can remain discrete and
latch onto a boundary to maximize the turning in the low level
wind field.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 210 PM CDT Tue Oct 9 2018
Once this system moves past the area, much cooler air will spill
in behind it. The entire area looks to have low temperatures below
freezing Thursday night and headlines will be needed to highlight
the end of the growing season. The next chance of precipitation
will be from Saturday night into Monday as the western long wave
trough finally looks like it will become progressive and should be
moving east across the central part of the country.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 557 PM CDT Tue Oct 9 2018
Messy and poor aviation weather with wave and associated surface low
moving through region next 24 hours. Conditions vary from VFR in
warm sector, to LIFR near and just northeast of surface bounary. As
this low tracks northeast, these split conditions will pretty much
stay as is with our area straddling these conditions. TAF sites will
stay IFR to LIFR just on north side of front with occasional
convection moving through.
As system pulls east tomorrow, have introduced wind shifts and
should begin to see some drier air moving in with gradual shift back
to MVFR conditions at least late in forecast.
&&
.HYDROLOGY...
Issued at 210 PM CDT Tue Oct 9 2018
No changes will be made to the ongoing flood watch. Conditions
remain favorable for more heavy rain through the overnight. As
mentioned above, the low level moisture transport will strengthen
and become focused on the area this evening before focusing
farther north overnight. Precipitable water values in the warm
sector will remain in the 1.75 to 2 inch range with warm cloud
depths around 3.5 km. With the repeated rounds of showers and
storms tonight into Wednesday morning, another 1 to 2 inches can
be expected to fall on grounds that are already saturated. Rivers
and streams will continue to rise with numerous river flood
warnings already issued and more expected to be issued tonight and
Wednesday. See the latest river flood warnings and statements for
specific river information or consult our hydrology web page at
water.weather.gov/ahps2/index.php?wfo=ARX.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Flood Watch through Wednesday morning for WIZ017-029-032>034-
041>044-053>055-061.
MN...Flood Watch through Wednesday morning for MNZ079-086>088-094>096.
IA...Flood Watch through Wednesday morning for IAZ008>011-018-019-029-
030.
&&
$$
SHORT TERM...04
LONG TERM...04
AVIATION...Shea
HYDROLOGY...04
Area Forecast Discussion
National Weather Service Charleston SC
933 PM EDT Tue Oct 9 2018
.SYNOPSIS...
Hurricane Michael will move north across the Gulf of Mexico
before making landfall along the Florida Panhandle Wednesday.
Michael will then weaken to a tropical storm as it moves
northeast across Georgia and South Carolina Wednesday night
into Thursday. Cooler high pressure will then build in through
early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
The band of light to moderate rains has finally made it into the
Charleston metro area, with it`s westward extent into areas of
Dorchester to Jenkins, and it`s southern extent to near the
Savannah River. Further south across the bulk of Georgia, the
rain is more scattered. We have adjusted PoP based on radar
trends, and since we lapse rates are poor and there is only
minimal instability, we have removed mention of thunder prior to
midnight. We remain on track for possible record high minimums
at all 3 Climate sites. Since we are just past high tide, given
the ongoing rains in downtown Charleston could certainly
complicate the flooding situation.
Previous discussion...
A single wide band of moderate to locally heavy rainfall has
setup from Metter and Millen east to Beaufort. Vsbys have been
as low as 1/4 mile in the heavy rain. Could see a quick 1-2
inches of rain with this band as it moves slowly north, likely
reaching the Charleston Metro area by 10 PM or so. Adjusted near
term pops to reflect 100% pops for in the Millen-Charleston-
Savannah-Metter corridor. While low, there is a non-zero tornado
risk along the Georgia and far southern South Carolina coast.
GOES-E visible imagery shows a ribbon of tropical moisture
arcing from Southeast Georgia to offshore of the eastern
Bahamas into the central Caribbean Sea. RAP and satellite
derived data suggest PWATS of 2.25-2.50 inches are embedded in
this tropical connection and is helping to support several large
bands of heavy rainfall from southern Georgia and offshore of
the Florida east coast. The band will slowly propagate north
through the night as Hurricane Michael moves north across the
eastern Gulf of Mexico and several mid-level perturbations
embedded in the southeast-northwest oriented flow between
subtropical high pressure moving farther offshore of the North
Carolina Outer Banks of Hurricane Michael cross the area.
Southeasterly low-level jetting as high as 35-40 kt will remain
in lace through much of the night so any shower activity will
have the potential of producing localized wind gusts of 40-50
mph. Otherwise, breezy conditions will continue at the beaches.
Overnight pops will range from 70-100% along with a "rain heavy
at times" qualifier. The risk for any freshwater flooding will
be highest across the coastal counties, especially during the
evening high tide. Widespread flash flooding is not expected
through sunrise, thus a Flash Flood Watch will not be issued for
this time period.
It will be a warm and humid night for early October with lows
ranging from the mid 70s inland to around 80 at the beaches. The
record high minimum temperatures at all three climate sites
could be challenged. See the climate section below for
additional information on the records.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
On Wednesday the main feature will be the weak inverted trough
off to the northeast of Hurricane Michael. The center of this
trough will be along the SC/GA coastline at daybreak Wednesday,
then move north-northeast through early afternoon. We expect
numerous heavy showers with isolated tstms across the area during
the morning with the greatest coverage and intensity over
southern SC closer to the trough. Unseasonably high PWATs in
excess of 2.1" will support torrential rainfall at times. During
the afternoon the best convergence associated with the trough
are is forecast to move north of the area though we then expect
some outer rain bands from Michael to start rotating through the
area.
A bit of a lull is possible Wednesday evening, then the rain
shield associated with Michael is expected to move into interior
southeast GA with some outer bands farther to the north and
east. The brunt of the torrential rainfall associated with
Michael`s circulation will move through on Thursday with the
greatest effects over our inland zones. Latest storm total QPF
shows 2-4 inches across coastal sections and 3-5" inland. The
strongest winds will begin in southeast GA late Wed night and
affect most of southern SC during the day Thursday.
An enhanced tornado threat appears likely from Wednesday
afternoon through at least Thursday morning based on model progs
for low-level helicity and surface-based instability.
Slightly cooler and drier weather expected late Thursday night
into Friday.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Late this week, surface high pressure will build back into the
region behind departing TC Michael. Precipitation potential is
looking rather low Friday and Saturday as a dry column sits
overhead, then rain chances will increase with increasing moisture
levels ahead of an approaching cold front Sunday into the first part
of next week. Temperatures look to remain above normal.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
A band of moderate to heavy rain will move north into the KCHS
terminal by late evening and persist through about 07z. Expect
vsbys as low as 1/2 mile at times with this line, but vsbys
should generally average 2-3SM. Other banks are likely to
develop overnight and impact both KCHS and KSAV. High resolution
guidance supports such a line reaching KSAV 07z and lingering
through about 10z. Again, prevailing vsbys should be MVFR and as
low as 2SM at times. Rain should move out the terminals by 10z
and expect mainly dry conditions to prevail for the remainder
of the 00z TAF period. Steadier rains associated with Michael
should hold off until after 00z, although it will be close at
KSAV. Gusty winds will persist through the night and increase a
bit Wednesday afternoon.
Extended Aviation Outlook: MVFR or lower conditions likely at
both terminals Wednesday afternoon through Thursday night as
Hurricane Michael moves west of the area. The greatest chance
for IFR ceilings and/or vsbys will be late Wednesday night
through Thursday afternoon due to moderate to heavy rain.
&&
.MARINE...
Tonight: Nasty marine conditions will continue across all waters
tonight with winds 20-25 kt with gusts to 30 kt. Shower activity
will be capable of producing localized wind gusts to 40-45 kt.
Seas will build through the night, reaching 5-8 ft nearshore
waters and 9-11 ft offshore waters.
Wednesday through Saturday: The impacts of Hurricane Michael
are obviously the main concern with this package. Marine
conditions will become increasingly treacherous during the day
Wednesday with the strongest winds and largest seas Wednesday
night into Thursday. Improving conditions Thursday night into
the weekend as high pressure builds in.
Rip Currents: A high risk for rip currents continues into
Wednesday due to persistent, strong onshore wind, some swell
and astronomical influences. The rip current risk will remain
elevated through the week.
&&
.TIDES/COASTAL FLOODING...
Coastal Flooding: The decision was made locally to issue a
long-duration Coastal Flood Advisory for all coastal zones,
excluding Tidal Berkeley, to cover all high tides through the
duration of Michael. Minor to locally moderate coastal flooding
is expected through the period. At this time, levels are not
expected to reach Coastal Flood Warning criteria for either Fort
Pulaski or Charleston Harbor with average inundations above
ground level expected to stay 2 feet or less. This will be
watched carefully and warnings will be issued if needed.
High Surf: Expect breakers of 5 to 8 feet to impact the surf
zone before winds turn offshore in the wake of Michael. A High
Surf Advisory has been posted for all beaches.
&&
.CLIMATE...
Record high minimums for 9 October:
KCXM: 77/2017.
Record high minimums for 10 October:
KCHS: 75/2017.
KCXM: 78/2017 and previous.
KSAV: 75/2017.
Rainfall record for 10 October:
KCHS: 1.82/1990.
KCXM: 2.13/1990.
KSAV: 5.68/1990.
Rainfall record for 11 October:
KCHS: 4.48/1990.
KCXM: 5.46/1990.
KSAV: 4.43/1885.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Tropical Storm Warning for GAZ087-088-099>101-114>119-137>141.
High Rip Current Risk through Wednesday evening for GAZ117-119-
139-141.
High Surf Advisory until 8 PM EDT Thursday for GAZ117-119-139-
141.
Coastal Flood Advisory until 2 PM EDT Thursday for GAZ117-119-
139-141.
SC...Tropical Storm Warning for SCZ040-042>045-047>052.
High Rip Current Risk through Wednesday evening for SCZ048>051.
High Surf Advisory until 8 PM EDT Thursday for SCZ048>051.
Coastal Flood Advisory until 2 PM EDT Thursday for SCZ048>051.
MARINE...Tropical Storm Warning for AMZ330-350-352-354-374.
&&
$$
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...
CLIMATE...
Area Forecast Discussion
National Weather Service State College PA
1054 PM EDT Tue Oct 9 2018
.SYNOPSIS...
A strong ridge of high pressure will remain parked off the Mid
Atlantic coast through Wednesday. A cold front will move through
the area Thursday. Hurricane Michael is expected to hit the
Florida Panhandle tomorrow and then turn sharply northeastward
on a track off the east coast south of Pennsylvania. Cooler and
drier conditions will arrive for Friday and the upcoming
weekend.
&&
.NEAR TERM /UNTIL 8 AM WEDNESDAY MORNING/...
Evening GOES-16 IR FOG product (10.3-3.9um) shows a fair amounts
of cirrus spreading NE across the region with several areas of
shallow stratocu clouds across our far eastern zones, where mean
sfc-925 mb streamlines were advecting moisture with u60s to l70S
DEWPOINTS off the Western Atlantic and Chesapeake Bay.
lATEST 09/23z RAP LLVL RH fields shows stratocu deck lowering
into a stratus deck and spreading north-northwest across our the
region to blanket most of the CW outside of portions of Mckean
and Warren counties, and Cambria/Somerset counties west of
Laurel Ridge.
With the return of the low clouds overnight, we could see some
patchy drizzle develop over eastern sections, but no real
measurable precipitation is expected at this time.
The clouds and light southerly flow at the sfc will create another
muggy night. Lows in the 60s will average around 20 deg above
normal. Some maxi min records in the upper 50s to mid 60s are
on target to be broken. The record warm low at KBFD of 57F looks
to be the most susceptible to be broken, considering the current
dewpoint of 64F there, and a fcst min of only 61F.
&&
.SHORT TERM /8 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
Wednesday looks like it will be very similar to the last several
days. Morning clouds and patchy fog burning off to a partly
sunny afternoon.
Highs once again will range from the mid 70s to the lower 80s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
*Heavy downpours and localized flooding possible Thursday
*Significant cool-down expected by Friday as a more typical
fall weather pattern finally takes hold into next week
Periods of locally heavy rain are likely on Thursday as a cold
front crosses the Appalachians and interacts with tropical
moisture from Michael. PW values are forecast to reach 1.5 to
2.0 inches which is well-above normal for early/mid October.
Blend of NBM/WPC QPF yields 1-2 inches over the southeastern 1/3
of the CWA falling mainly in the 12-hr window ending 00Z
Friday. Very soggy soils and swollen streams from relentless
rainfall over the last several months will make this area
susceptible to potential flooding concerns. The WPC D3 excessive
rainfall outlook (ERO) places southeast PA in a marginal risk.
The models are in general agreement in keeping the heaviest
rains directly associated with Michael from the NC piedmont
across southeast VA to the Delmarva Peninsula Thursday night
into Friday. There is some uncertainty in the max QPF location
and timing with at least some risk that it could track or shift
farther north, but for now the most likely outcome is a
southern track with the main impacts staying south/east of
central PA.
A significant pattern change is expected to follow in the wake
of Michael as it accelerates away from the southern Mid Atlantic
coast on Friday. The extended summer pattern will come to an
end with all signs pointing toward noticeably cooler, more
typical fall weather lasting into next week. After one of the
warmest starts to October on record, the upcoming period of
seasonably cooler weather with near to below average
temperatures will feel rather chilly this weekend and next week.
Parts of the northwest Alleghenies may see frost Sunday
morning. Sub-zero air at 850mb crossing the lower lakes should
result in rain showers (perhaps the seasons first flakes?) over
the NW Allegheny Plateau and Fri-Sat. Model consensus shows the
next rain-maker impacting the area early next week.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
VFR areawide this evening under influence of high pressure
(centered off to our east). Expect to see a return of low
clouds and areas of patchy fog overnight in anomolously high
dewpoint air and southerly flow, with much of central PA
becoming MVFR then IFR for several hours centered around
sunrise. Could see development of some dense fog over the Susq
Valley around this time as well. Restrictions expected to last
through mid morning Wednesday.
As like the past several days, conditions will improve by
Wednesday PM.
.Outlook...
Thu...MVFR-IFR cigs/LLWS early becoming MVFR/VFR.
Showers/isolated T-storms accompanying a cold front. Post-
frontal low cigs developing northwest mtns Thursday night-Friday
morning.
Fri...MVFR cigs possible NW. Wind gusts 20-25kts from NW.
Sat...MVFR cigs possible NW.
Sun...No Sig Wx.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...La Corte/Lambert
NEAR TERM...La Corte/Lambert
SHORT TERM...La Corte
LONG TERM...Steinbugl
AVIATION...RXR
Area Forecast Discussion
National Weather Service Cheyenne WY
557 PM MDT Tue Oct 9 2018
.SHORT TERM...(Tonight - Wednesday)
Issued at 304 PM MDT Tue Oct 9 2018
A broad swath of snow has developed across much of western/central
Nebraska this afternoon. The western extent of this activity as of
21z was approximately along and south east of a line from Kimball-
Alliance. This activity is associated w/ an impressive TROWAL that
has taken shape on the back side of a strong upper-level shortwave
currently lifting into the Central Plains, along with an excellent
fetch of moisture contributing to deep saturated profiles. QPF via
several high-resolution models including the HRRR & HREF continues
to suggest the potential for snowfall accumulations in excess of 3
inches, potentially as high as 6 inches although snowfall rates do
not appear high enough to overcome warm ground temperatures. Rates
have been increasing over the last few hours though, w/ visibility
finally falling below 1 SM at Sidney recently. We would anticipate
seeing some accumulations shortly, especially on grass or elevated
surfaces. Winter Wx Advisory looks to be in good shape through the
midnight hour, although later shifts may consider extending if any
road issues linger into the night. Accumulating snow should end by
06z or so as sounding profiles quickly dry out.
A second disturbance was observed over the Intermountain West this
afternoon per GOES-16 Water Vapor imagery. This system will follow
very quickly in the footsteps of the ongoing weather maker, likely
resulting in snow across much of Carbon County by 09-12z. Mountain
areas may receive 6 to 12 inches, while lower elevation areas will
have a good chance to see a general 2-4 inches of snow through Wed
afternoon. The system will be weakening, so just how far east snow
accumulations will extend is uncertain at this time. It`s possible
the I-80 summit may be impacted as well though. The Laramie Valley
will likely be shadowed by low-lvl easterly flow regardless, so do
not expect to see much in the way of snowfall there. We went ahead
and issued a Winter Wx Advisory for far western areas for the time
being, and later shifts can expand eastward if necessary.
.LONG TERM...(Wednesday Night - Tuesday)
Issued at 304 PM MDT Tue Oct 9 2018
Warmer and mostly dry conditions prevail moving into the end of
the week as a southerly flow affects the region. However, by
Saturday night, the next strong system looks as though it will
drop out of the north, bringing the next round of cold
temperatures to the region and the next shot at decent precipitation.
For now, the remnants of Hurricane Sergio look like they will
stay south and east of the region, but should the moisture track
change and push further north, this system may spell another
story for the region. This will need to be monitored as we move
towards the end of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 551 PM MDT Tue Oct 9 2018
Band of light to moderate snow over the Nebraska Panhandle will
continue moving to the east northeast over the next few hours.
This should keep MVFR to IFR conditions in play for SNY and AIA
through later this evening. Low ceilings will remain in place
dropping further overnight as upslope flow continues overnight.
Expect LIFR in some spots as additional snow showers develop over
the high terrain to the west and spread east. Light to moderate
snow will continue tomorrow bringing reduced visibilities to many
southeastern Wyoming and Western Nebraska Terminals. Aviators use
cation and stay updated on weather conditions through out the
area as snow and icing could impact safety.
&&
.FIRE WEATHER...
Issued at 242 AM MDT Tue Oct 9 2018
A cold and active pattern will continue over the next week,
significantly limiting fire weather concerns and aiding in fire
containment issues. The next best chance of measurable
precipitation across the mountains will arrive Wednesday.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from midnight tonight to 6 PM MDT
Wednesday for WYZ109>114.
NE...Winter Weather Advisory until midnight MDT tonight for NEZ021-
055.
&&
$$
SHORT TERM...CLH
LONG TERM...AB
AVIATION...AL
FIRE WEATHER...AB
Area Forecast Discussion
National Weather Service Dodge City KS
712 PM CDT Tue Oct 9 2018
...updated aviation section...
.SHORT TERM...(This evening through Wednesday)
Issued at 123 PM CDT Tue Oct 9 2018
The synoptic trof that has brought days of rains with significant rainfall
has finally started to move out of the region. Rain and clouds will
exit the FA through this evening from the south to the north. A ridge
of high pressure will build in its wake. There will be weak cold air
advection associated with this. Do have a freeze warning for 4 counties
across the NW. Main fly in the ointment for this is cloud cover. Models
do show partial clear and with weak CAA in place, temperatures could
get near freezing. The area that is in the freeze warning is just climo
for their first freeze and along low lying areas such as near the Ark
river basin. Otherwise, lows to the east should be warmer with additional/lingering
cloud cover. For Wednesday, high pressure will be in control and the
area should dry out. Highs should be mainly in the 50s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 123 PM CDT Tue Oct 9 2018
Will have to watch for the freezing potential for Thursday morning.
High pressure is just to our north and winds are weaker. In addition,
not much in the way of clouds are expected through the overnight period.
A large area of the NW and N zones may get close to freezing. Will
defer a headline for now as we have hydro concerns and freezing concerns
already during the short term period. The GFS and EC disagree with
the slight chance of showers on Thursday. A better chance at precip
is still indicated by long range models next weekend. Here the synoptic
wave driving the weather is strong than compared to the Thursday system.
In addition, there is more in the way of boundary layer moisture as
well. The EC does have cold enough 850-hPa temperatures for some mixed
precipitation and even snow on Sunday. Confidence in the thermal fields
is low at this point. The EC is still advertising cold air moving in
the wake of the system and a freeze or even a hard freeze may be possible
Monday morning for much of the FA.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 642 PM CDT Tue Oct 9 2018
Marginal ceiling improvement is forecast by the HRRR over the
next few hours, generally through mid evening - however little
improvement over that will be seen until well after midnight.
Therefore we can expect the IFR category ceilings through around
03 UTC with rain showers dwindling as the Missouri Valley surface
low lifts northeast and MVFR category ceilings. An intrusion of
drier air aided by downslope will lead to removal of the
widespread stratus during the overnight with some scattered
1500-3000 ft clouds lingering mainly in the HYS area by 12 UTC.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 35 55 35 53 / 10 0 10 0
GCK 34 53 33 50 / 20 0 10 10
EHA 33 56 35 55 / 20 0 10 20
LBL 34 56 34 54 / 10 0 10 10
HYS 36 52 31 50 / 40 0 0 0
P28 41 58 40 57 / 10 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 2 AM CDT /1 AM MDT/ to 10 AM CDT /9 AM MDT/
Wednesday for KSZ043-061-062-074.
Frost Advisory from 2 AM to 10 AM CDT Wednesday for KSZ044-063-
075>077-084>087.
&&
$$
SHORT TERM...Sugden
LONG TERM...Sugden
AVIATION...Russell
Area Forecast Discussion
National Weather Service Grand Forks ND
1008 PM CDT Tue Oct 9 2018
.UPDATE...
Issued at 1004 PM CDT Tue Oct 9 2018
No big changes needed. Updating grids to show advance north of the
rain area. Just arrived in Fargo between 2-3z and timing would
bring it to Grand Forks 07z or so. HRRR cools 925 mb layer to snow
levels 09z-12z period. Incoming NAM shows about the same ideas as
past runs with snow band near mid level def zone with higher rates
of snow in NW MN later Wed into Wed eve vs more Wed morning-midday
in Jamestown/Valley City area.
UPDATE Issued at 630 PM CDT Tue Oct 9 2018
Rain area on its way northward and updated timing of rain arrival
as it spreads north. Timing of rain to snow changeover is the main
fcst issue with the idea of it doing so in the 09z-13z period
across the area for most. Snow amounts of 3-6 inches look good for
the advisory area...though as usual some slight differences in
exact heavy snow placement. NAM and RAP are more JMS-GFK-ROX vs
GFS seems to target more FAR-TVF-BDE.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 300 PM CDT Tue Oct 9 2018
Snow totals and winter headlines will be the main headaches for
the period.
Water vapor loop shows the main upper trough over CO/NM, with a
kicker system digging down through OR/ID that will help push the
more southeasterly trough into the Northern Plains by Wednesday
afternoon. The surface low is still well to our south over KS, but
will move quickly northeastward tonight into IA/southern MN and
then into the Great Lake for tomorrow. There will be plenty of
synoptic lift from the trough as it lifts into our area, and the
models continue to indicate strong 700mb frontogenesis setting up
over our area tonight into tomorrow. Rain currently moving through
eastern SD will enter our southern counties this evening, pushing
northward throughout the night. The main deformation band will
continue over the central CWA for much of the day tomorrow, before
weakening and pushing eastward during the late afternoon and
evening.
The biggest question is not if we will get rain and snow, which is
yes, but how much snow will accumulate and what the impacts will
be. GEFS plumes are still all over the place with snow amounts,
ranging from less than an inch of accumulation to near 10 inches
at KBDE. There will be a decent amount of cold air coming down the
backside of the low pressure system, along with strong northwest
winds. However, quite a bit of the QPF will be falling during the
daytime hours, and there should be at least some melting as snow
falls. With the melting and compaction of wet snow, think that
even with 0.5 to 1.5 inch of QPF there will be a pretty broad area
of 3 to 6 inches. The exception of this will be where any
mesoscale banding sets up, the exact location still unknown. Could
see more than 6 inches to even warning level snow amounts in that
band, but again, do not know the exact location at this point.
Thus, will put out a broad winter weather advisory, and highlight
in the wording there will be a narrow band of heavier snow.
Visibilities will also be reduced within that narrow band,
although with the wet snow it will be more splattering on north
facing surfaces vs blowing.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 300 PM CDT Tue Oct 9 2018
Potent storm affecting the forecast area on Wed will see snow
gradually taper off from southwest to northeast during Wed night
into Thu morning, ending over north central MN by early Thu morning.
Cool and breezy, but drier weather will move back into the region
for Thu as temperatures remain solidly in the 30s. Zonal flow and
modest warm air advection will result in some warming into the 40s
on Sat as a clipper system moving out of Canada brings rain and snow
chances to northeast ND and northwest MN. Overall winter weather
impacts are expected to be minimal at this time. Any residual pcpn
will move east during Sun with temps dipping well below average once
again. Another clipper offering chances for mixed pcpn is scheduled
for Tue with some hope for moderation in temps maybe to near normal
by the end of next week or next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 630 PM CDT Tue Oct 9 2018
Conditions will go downhill thru the night with majorty of the
areas in IFR conditions for vsby and ceilings. North winds will
increase to 15 to 30 kts highest in the RRV.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Winter Weather Advisory until 1 AM CDT Thursday for NDZ008-016-
024-026>030-038-039-049-052>054.
MN...Winter Weather Advisory until 1 AM CDT Thursday for MNZ001>009-
013>017-022-023-027-028.
&&
$$
UPDATE...Riddle
SHORT TERM...JR
LONG TERM...WJB
AVIATION...Riddle
Area Forecast Discussion
National Weather Service North Platte NE
629 PM CDT Tue Oct 9 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 333 PM CDT Tue Oct 9 2018
The models continue to track a closed h700mb low northward through
ncntl Nebraska tonight. Last night`s heavy snow discussion from WPC
indicated the low was closing off faster than previously forecast by
the models. This faster intensification process would likely cause
snow to develop farther south and indeed, snow is underway this
afternoon across southwest Nebraska and northeast Colorado. In fact,
cameras throughout ncntl Nebraska have shown a mix of rain and snow
this afternoon. Boundary layer heating is holding up the changeover
process to all snow. As sunset approaches this evening, the heating
process will cease and a rapid changeover should occur, especially
across western Nebraska where winds will become northwest.
The forecast snowfall amounts, up to 7 or so inches, uses an
aggressive approach which is appropriate for the strength of the
upper level disturbance. The forecast uses a blend of the HRRR, RAP
and HREF models as a basis for snowfall. The forecast places the
area along and west of a line from Hayes Center to Newport in a
winter weather advisory. A winter storm warning is in place for
Cherry county.
The snow should become moderate to heavy this evening in some areas.
The models show a convectively enhanced rain-snow line setting
up from roughly Hayes Center to North Platte to Ainsworth. Just west
of this line, a period of heavy snow should develop with 1 inch per
hour accumulations possible.
The disturbance and the snow should exit ncntl Nebraska Wednesday
morning. A period of light non-accumulating snow is possible across
the eastern Panhandle in the afternoon associated with a disturbance
following quickly on the heels of tonight`s storm.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 333 PM CDT Tue Oct 9 2018
Rather unsettled during this period, but no major storms are
expected. First will be the cold temperatures expected Wednesday
night into Thursday morning. High pressure will build in during
this time, and with light winds and clear skies, a widespread
freeze can be expected.
A strong shortwave trough will cross the area Thursday night into
Friday morning as flow aloft transitions to northwesterly. Mid level
frontogenesis increases Thursday evening and persists into Friday
morning. Appears to be cold enough for a light rain/snow mix during
this time, but little accumulation is expected. Another disturbance
drops quickly southeast Saturday night into Sunday. A few showers
may accompany this, but available moisture looks quite limited by
this time.
As the northwest flow becomes established, several cold fronts will
accompany the disturbances, which will keep temperatures below
normal. Sunday appears to be the coldest day, with highs only in the
30s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 628 PM CDT Tue Oct 9 2018
We continue to see widespread MVFR and lower ceilings/visibility
across west central Nebraska, this trend will continue through
much of the forecast period as a strong upper low lifts north into
the northern plains. The precipitation will be heavy at times
before ending south to north on Wednesday. Snow accumulations are
possible, especially across north central Nebraska, including
KVTN. AT KLBF, we will see a change over to snow later this
evening, which will lower visibility. This should occur before
06z. Otherwise, northerly surface winds will prevail, with gusts
in excess of 20kts for most terminals through the forecast period.
At KLBF, winds will fall below 15 kts overnight.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 9 AM CDT /8 AM MDT/ Wednesday for
NEZ004-006-008-009-022>026-035>037-056>059-069-070.
Winter Storm Warning until 9 AM CDT /8 AM MDT/ Wednesday for
NEZ005-094.
&&
$$
SHORT TERM...CDC
LONG TERM...Taylor
AVIATION...Jacobs
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
721 PM CDT Tue Oct 9 2018
.SHORT TERM...
210 PM CDT
Through tonight...
Isolated to scattered showers and storms are expected this
afternoon. The only forcing is surface heating so widespread
storms are not expected. The latest RAP analysis shows up to 2000
J/kg of CAPE and 25-35 kt of shear. DCAPE values are 800 J/kg or
less. While a storm or two may pulse up close to severe limits,
the vast majority of storms will not be severe. Main threats will
be gusty winds, heavy rain, and lightning. Convection will
diminish after the sun goes down and forcing eases.
I kept a chance of showers and storms west of a McHenry to
LaSalle line this evening as guidance suggests a few showers or
storms may percolate there ahead of the main cold front. Speaking
of the cold front currently over central Iowa, it will slowly
march east tonight. Showers and storms are expected ahead of it,
and will mainly impact areas along and west of I-39. I have low
confidence in the number of showers and storms tonight because
forcing will be mainly tied to the front. A couple transient
vorticity streamers may help force precipitation, but the
streamers are not forecast to be very strong.
Due to cloud cover tonight, low temps should be mild in the upper
60s.
JEE
&&
.LONG TERM...
252 PM CDT
Wednesday through Tuesday...
A pronounced pattern change will occur during the beginning of
this period, with the transition time providing gusty
showers/storms on Wednesday and then prevailing wind gusts 30-35
mph Wednesday night into Thursday. This will be followed by the
likelihood for frost Thursday and Friday nights if winds can
diminish enough.
The well-defined closed upper low over southeast Colorado this
afternoon will eject across the Upper Midwest tomorrow, with
guidance in good agreement on a deepening surface low to just
below 1000 mb near La Crosse WI by mid-afternoon. With the
negative tilt to the ejecting wave, strong forcing for ascent will
be overriding the deep moisture plume and pre-frontal
convergence, all a recipe for widespread showers.
The instability in the column becomes quite narrow, not that
atypical for ahead of an autumn cold front especially one with
deeper warm cloud processes such as this. But given the negative
tilt to the wave, can see embedded thunderstorms being present.
Lightning or not, the unidirectional strong southwest winds in
the column provide the potential for downdraft-driven gusty
showers. In any more well-defined arcs of convective activity,
mainly any that are not far ahead of the front in the afternoon,
the potential for isolated severe gusts will exist. Some members
of the higher-resolution guidance family try to key in on higher
reflectivity/deeper updrafts moving to the east-northeast across
the area in the afternoon, but others do not. While there is ample
low-level shear, the orientation of the deeper shear vectors to
the boundary is not ideal for discrete activity, and this pre-cold
front is not an ideal setup for a tornado threat. But surface
winds are backed to around due south, so if mode can be more
discrete immediately ahead of the main convective line/semi-line,
that may not be ruled out.
After a mild and humid day with highs in the 70s, the cold front
will sweep through Wednesday evening. With the strong isallobaric
response and steeping low-level lapse rates in cold advection,
westerly winds behind the front will sharply increase. Gusts
immediately behind the front may reach 40 mph, with regular gusts
of 30-35 mph expected into the day Thursday. Temperatures by
daybreak Thursday look to be lower 40s. Despite a mainly sunny
sky on Thursday, the northwest winds will keep highs from
rebounding much, with highs generally around 50 (around 35 degrees
colder than today).
Surface high pressure around 1021 mb is forecast to build into the
Mississippi River Valley Thursday night. It is likely that some
northwest wind will be maintained through the night in our area,
at least given current forecasts, though challenging to say if
enough to mitigate frost. With the low starting point in
temperatures going into the night, readings will likely dip to
around freezing in north central Illinois and continue frost
mention in the forecast.
The Friday forecast became a bit more tricky, as the 12Z EC
shifted north with the Pacific-hybrid system moving quickly across
the region, and places that more over our area. This would bring
light rain potential. Even with that forecast, the quick
progression would likely favor a clear sky Friday night and a
frost threat and depending on wind speeds again, possibly a
freezing threat into north central Illinois.
The weekend, especially the latter weekend into Monday, look
unsettled in global guidance, but a wide disparity between models
and between runs on how the pattern will evolve. This is increased
by the fact the flow is split with a phasing potentially
over/near the Great Lakes. Chances for rain have been increased
within blended model guidance, but apart from that it is presently
difficult to give more details in coverage/timing than that. The
pattern favors cold advection undercutting the backside of
precipitation, but right now the chances for some flakes of snow
before ending look to be north in Wisconsin. Highs on Monday are
only forecast to be in the mid 40s in the northern CWA and could
end up being a little cooler than that in time.
MTF
&&
.CLIMATE...
305 PM CDT
Records for today, October 9:
Record High Record High Minimum
------------------------------------------
Chicago: 86 (1949) 68*(1879)
Rockford: 84 (1920) 67 (1949)
* With Chicago not having dropped below 70 this morning, the low
for the calendar day today may remain 70 or above. This will be
only the 7th time that has happened in October, and the 2nd latest
after October 21, 1979.
MTF
&&
.AVIATION...
For the 00Z TAFs...
The main concern for the period will be timing and coverage of
shra/tsra spreading across the region tomorrow.
For the remainder of the evening and overnight, expect relatively
quiet conditions at the terminals. Much of the sct shra/tsra
moving through the area this afternoon was either diurnally driven
or associated with a weak mid-level impulse. This mid-level
impulse has moved north onto Wisconsin and both the diurnally
driven cu and shra have dissipated with sunset. Under a moderate
southerly gradient, expect that winds should remain generally
southerly at 5-10 kt through much of the night. The pressure
gradient is expected to strengthen late tonight as low pressure
over the Upper Missouri Valley deepens while tracking newd and an
associated cold front pushes east through Iowa.
Expect that the potential for shra/tsra will rapidly increase
through the morning hours as the cold front pushes east through
the day. Much of the activity should be along and ahead of the
front in an area of strong continued warm, moist advection. With
instability increasing through the morning, scattered shra/tsra
should develop, but the more organized, widespread convection will
be more closely associated with the frontal zone. The general
trend of precipitations should be in the form of rounds of
showers with embedded thunder until the cold front finally pushes
through the area. Latest guidance suggests that the fropa may not
occur until close to 00z tomorrow evening at RFD and 02Z or so at
the Chicago area terminals. So, given some uncertainty with the
fropa timing, have not included the fropa details in the RFD/DPA
TAFs just yet and introduced the fropa timing of 02z at ORD/MDW,
though that exact timing will be subject to adjustment in later
updates.
&&
.MARINE...
305 PM CDT
A strong weather system will move across the region Wednesday
into Wednesday night. In response to this, south winds on Wednesday
will be near Small Craft Advisory, and there could be some gusty
showers and storms as well, especially in the afternoon. A strong
cold front will pass Wednesday evening. Behind this there will
likely be wind gusts nearing gales and potentially to frequent
gales along the Illinois nearshore. This is especially true further
from the immediate shore given lake-induced instability. The gusts
should slowly ease after midday Thursday.
MTF
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...LMZ742-LMZ743-LMZ744-LMZ745...9 PM
Wednesday to 10 PM Thursday.
Gale Watch...LMZ740-LMZ741...9 PM Wednesday to noon Thursday.
&&
$$
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Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
707 PM CDT Tue Oct 9 2018
.SHORT TERM... (Through Late Wednesday Afternoon)
Issued at 336 PM CDT Tue Oct 9 2018
Main concern in the short term continues to be the strong cold front
that will slide through the region late tonight through Wednesday.
Latest HRRR is beginning to come into better agreement with what is
actually happening over region as of 20z. Ahead of system, scattered
showers and thunderstorms are developing in a moderately unstable
environment with surface based CAPES in excess of 1500 J/kg and
effective bulk shear 30+ kts over portions of central/northeast
Missouri as of 20z. This initial round of activity is more diurnally
driven so should see showers and storms diminish a bit towards
sunset. However, the break in activity will not be long as more
significant storms develop along prefrontal trof over central
Missouri after 02z Wednesday and track east through forecast area
during the late evening and early morning hours. There will be
plenty of instability and shear late into the evening for a few
strong to severe thunderstorms over portions of central/northeast
Missouri as well as west central Illinois. SPC has kept this area in
a slight risk with the main threat being damaging winds, though
isolated tornadoes and large hail are possible.
Then another round of activity to fire along main cold front after
08z Wednesday over western Missouri and track eastward through
forecast area during the day on Wednesday.
With progressive nature of system, rainfall amounts will remain
below flash flood criteria, though could see between half an inch
and an inch of rainfall through Wednesday afternoon before system
exits region.
As for temperatures, another mild night tonight with lows only in
the mid to upper 60s. On Wednesday, highs will be in the upper 60s
to upper 70s, with steady or falling temperatures during the
afternoon hours most locations.
Byrd
.LONG TERM... (Wednesday Night through Next Tuesday)
Issued at 336 PM CDT Tue Oct 9 2018
Strong surface ridge to build into region Wednesday night with
scattered showers exiting region. Ridge will usher in much colder
air with lows in the upper 30s to upper 40s Wednesday night. Highs
on Thursday will only be in the low 50s to low 60s, which are 10
to 15 degrees below normal for this time of year.
By Thursday night, even colder temperatures can be expected with
lows in the mid 30s to low 40s. This cold air combined with little
or no winds and clear skies could allow for the formation of patchy
frost across northern portions of forecast area. However, confidence
is low as a quick moving shortwave to approach region towards
daybreak on Friday, so should see increasing clouds. Left out
mention of patchy frost for now.
Upper level shortwave to slide through region on Friday undercutting
surface ridge. Even though moisture will be limited, isolated/
scattered showers will develop by midday and slide quickly east
through forecast area, exiting by early Friday evening.
Beyond that, better chances of rain will move into the region
Saturday evening and persist through Sunday night before exiting
Monday morning. Still some differences in timing, strength and
duration of the rain for the weekend as a southern stream shortwave
slides through region just south of forecast area Saturday night
through Sunday morning and a northern stream system slides through
region Sunday night. No major changes to ongoing forecast at this
time. Below normal temperatures to persist through remainder of
forecast period.
Byrd
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 646 PM CDT Tue Oct 9 2018
Low pressure over the eastern Plains will strengthen and move
northeast tonight and Wednesday. This will push a cold front east
through Missouri into Illinois through Wednesday afternoon. Expect
waves of showers and thunderstorms ahead of the front tonight
into Wednesday, with the first wave moving through central and
northeast Missouri this evening. While prevailing conditions this
evening and into the early overnight hours should stay VFR, any
shower or thunderstorm will be capable of producing lower ceilings
and visibilities in heavy rain. There will be a general lowering
of ceilings and also expect an increase in coverage of showers and
thunderstorms Wednesday morning as the cold front moves into
central and eastern Missouri. Expect widespread MVFR ceilings and
visibilities, and some IFR is also expected with the showers and
storms. Some lingering MVFR ceilings and showers will likely
persist behind the front Wednesday, but there should be a general
improving trend after the front passes during the afternoon. Wind
should shift sharply from the south to the west as the front
passes.
SPECIFICS FOR KSTL:
Expect VFR flight conditions to prevail at Lambert through the
evening and into the pre-dawn hours of Wednesday morning. Most
model guidance holds the bulk of the rain back until after 10Z
Wednesday morning, but I cannot totally rule out a few showers or
thunderstorms before that. Expect ceilings to drop ahead of the
front on Wednesday morning when most of the rain rolls in. Current
thinking is prevailing low end MVFR ceilings with occasional MVFR
visibilities in the heavier showers or storms. There is a
possibility that ceilings could drop to IFR, but confidence is low
at this time so did not go that low in the TAF. Latest model
trends are pushing the front through Lambert around 18Z on
Wednesday. Should see a general decrease in precipitation and
rising ceilings after the front moves through. Wind will turn
sharply from the south-southwest to the west when the front passes
through the terminal.
Carney
&&
.PRELIMINARY POINT TEMPS/POPS...
Saint Louis 70 76 46 60 / 60 90 5 0
Quincy 66 70 41 54 / 90 90 5 0
Columbia 64 68 40 56 / 90 80 0 0
Jefferson City 67 70 42 58 / 90 80 0 0
Salem 68 79 48 59 / 40 100 20 0
Farmington 68 76 45 61 / 40 90 5 0
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Blacksburg VA
1121 PM EDT Tue Oct 9 2018
.SYNOPSIS...
High pressure over the western Atlantic will begin to lose
influence over the region late tonight into early Wednesday. A
surge in subtropical moisture banked against the Blue Ridge will
lead to a period of steady rains Wednesday. Hurricane Michael
is expected to progress through the southeast US Wednesday into
Thursday. Moderate to locally heavy rain in association with
Michael`s closest passage is expected to begin Thursday across
the southern half of the region. A cold frontal passage late
Thursday evening is expected to usher in a more seasonable air
mass into the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 1000 PM EDT Tuesday...
Latest updates remain minor, basically modest adjustments to
rain chances through midnight based on the HRRR rapid update
weather forecast model, as well as hourly temperatures.
Overall, the afternoon forecast package remains on track.
As of 205 PM EDT Tuesday...
A persistent and stout anticyclone, both at surface and aloft is
centered off the mid-Atlantic coast, which is extending a ridge back
westward into the Appalachians. This has led to a persistent east to
southeast fetch across a large part of the Appalachians and VA/NC
Piedmont region. Partly to mostly cloudy skies exist across the
region this afternoon and will continue to be the case at least for
the first part of the evening. Widely scattered showers in this
regime across northern/central NC will continue to progress westward
and ascend upslope against mainly the southern Blue Ridge through
mid-evening, as reflected in most finer-resolution guidance. While
southeast upslope will continue, as we progress deeper into the
evening, model guidance QPF becomes more nebulous and spotty but
again is largely along or east of the Blue Ridge. Forecast BUFKIT RH
profiles again show re-development of lower stratus with any cloud
breaks filling in overnight, as was the case last night. As this
moisture is quite shallow - a mostly unsaturated moisture profile
above 850 mb - suspect that only drizzle or light rain would
predominate again through the bulk of the overnight. Overall through
overnight, rain amounts are pretty minimal and are generally a few
hundreths of an inch or less, but amounts up to a tenth possible
along the southern Blue Ridge from Carroll County southwest into
Watauga County. Turbulent mixing from a continued southeasterly wind
around 5-10 mph should keep mist from developing in most areas,
though there could still be some patches at times into the Blue
Ridge. Lows again on the whole similar to last night in the 60s,
again quite unseasonable for this time of year.
Wednesday is shaping up to be a pretty wet day, as we begin to feel
the fringe effects of Hurricane Michael in the form of elevated
tropical precipitable water values (GFS depicts values rising to on
the order of 2"+). While still some minor timing differences exist
between available 12z models, they each show a band of what is
likely to be a period of moderate to locally at-times heavy rain
showers progressing from south to north from around mid-morning
across the NC Blue Ridge/foothills through early evening. This
steady rain shield is the one currently affecting portions of
northeast FL into coastal GA/SC, this rain enhanced by subtle vort
energy in the weakness in the large high over the western Atlantic
seaboard mentioned above. As a southeasterly low-level jet to the
tune of 30-40 kts will be occurring, expect there to be some
significant upslope enhancement to rainfall totals on the lee of the
Blue Ridge and into the foothills with notable rain shadowing and a
relative minimum in PoPs/QPF as one progresses further northwest
across part of the New River Valley/Mtn Empire region into southeast
WV. There`s also a small amount of CAPE to the point where I did
include a few possible rumbles of thunder for areas within or close
to the Blue Ridge into the Piedmont. This will only serve to enhance
rainfall totals, which through Wednesday afternoon should range from
about a half to three-quarters of an inch from the NC foothills,
Roanoke valley area into part of Southside, to locally near an inch
along the escarpment of the Blue Ridge into Ashe and Watauga
Counties. Otherwise, rain amounts taper to a quarter to a third of
an inch in the New River Valley to less than a quarter inch into
southeast WV and the Mtn Empire in the rain-shadowed area...with
amounts of a quarter inch or so in the southern Shenandoah Valley
area into central VA. This will set the stage for additional
rainfall coming later Wednesday evening and particularly Thursday,
in association with the approach of Michael. Coordinated with NWS
Greer on a Flash Flood Watch which has been posted for the NC
Mountains counties (Wilkes, Alleghany, Ashe and Watauga Counties)
beginning at 2 pm Wednesday, ending early Thursday evening. Highs
mainly in the low to mid 70s.
Forecast confidence is moderate.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 400 AM EDT Tuesday...
Primary focus is the track and anticipated rainfall footprint
from Hurricane Michael.
In general, model guidance is in reasonable agreement, featuring
a highly amplified upper air pattern with an anomalous
subtropical ridge of high pressure off the Mid-Atlantic Coast,
and a deep longwave trough over the southern Plains. Caught in-
between is Hurricane Michael over the eastern Gulf of Mexico
which is forecast to gain latitude in a proverbial sling shot
between the two upper air features. Latest track guidance
suggests the center of Michael will bisect the Florida Panhandle
Wednesday afternoon/evening then trek northeast across south
central GA and into the Carolinas Wed-night and Thursday.
A generous amount of moisture is forecast into our forecast area
Thursday as the center of the system passes to our southeast...
an axis of heavy rainfall occurring within the northwest
quadrant of the storm where the low level winds converge with
the increasing westerly winds aloft. Attm we are forecasting a
general 1-3 inches of rain across the forecast area with the
higher amounts along and east of the Blue Ridge. There are two
areas which may see locally higher amounts... one being the Blue
Ridge Parkway southwest of Roanoke into the NC high country
where the southeast upslope wind component will be a premium
before the storm arrives. The second area to watch will be over
the NC/VA Piedmont on the northwest side of the storm track
where convergent flow will be maximized...CLT-GSO-DAN corridor.
If all comes to fruition, watershed within our CWA which will
have the most impact from runoff would be the Dan River Basin.
Wind impacts for our County Warning Area (CWA) from this system
may be felt more so on the back side of the storm as it exits
the region Thursday night and Friday. Direct impact from core
tropical storm strength winds will occur along the central track
of the storm (southeast of our CWA). However, as the storm
moves rapidly to the northeast and away from the area Thursday
night, pressure rises in the wake of the system across our
mountains, in addition to the passage of a surface front will
bring strong cross barrier flow with 85h winds of near 40 kts.
This will result in gusty surface winds, similar to a strong
frontal passage, across our CWA Thursday night and Friday with
gusts of 20 to 30 mph.
A noticeable airmass change will take place Thursday night into
Friday. A surface front associated with the upper trough to our
west will finally makes its entrance, northwest winds quickly
introducing an airmass change that will reflect much lower
dewpoints and cooler temperatures. These temperatures/dewpoints
will be a seasonal eyeopening change, more of a reflection of
what mid October should actually feel like weatherwise.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 400 PM EDT Tuesday...
Upper level pattern will deflate over the weekend and into the
following week as the Bermuda high becomes a summer ghost. One
last surge of higher dewpoint air will try to work back into the
area Sunday into Monday ahead of what will be the remnants of
Hurricane Sergio, which is expected to get drawn into the
southwestern CONUS from the Pacific Saturday, then into the
base of the central CONUS long wave trough. Attm it appears the
energy associated with this feature will pass through the OH
valley Sunday with showers primarily to our northwest. However,
with the passage of this feature it will open the door for a
pattern change with the northern jet stream making a dive into
the central and eastern CONUS, a feature that will favor below
normal temperatures across much of the central and eastern U.S.
by the middle of next week.
As for the details, the upcoming weekend as a whole does not
look that bad...featuring dry conditions and near seasonal
temperatures. Near seasonal temperatures however, means
temperatures at night will be in the 40s, so it will feel
noticeably cooler compared to our extended summer-like nights.
By Monday, showers associated with the deepening upper level
trough to our northwest are expected to move across the area.
After that...it dries out for the middle of next week, but
expect much cooler nights with the potential for frost in some
areas toward 18th of the month.
&&
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
As of 738 PM EDT Tuesday...
Poor flying conditions expected tonight into Wednesday with
areas of rain, drizzle and fog. Southeast upslope flow will
continue areas of rain, drizzle and fog tonight into Wednesday.
Conditions will drop to MVFR/IFR in pockets of rain and fog.
The general VFR conditions will lower to MVFR and IFR overnight
into Wednesday. The more persistent MVFR/IFR will prevail along
or near the Blue Ridge. Expect ceilings to at least partly
obstruct the Blue Ridge ridgetops. Southeast winds again remain
around 6-10 kts. Toward early Wednesday morning, an increased
southeasterly jet of 35-40 kts will likely contribute to
development of choppy conditions and mechanical turbulence near
ridgetop level along the southern Blue Ridge south of Roanoke,
and into the hilltops of southeastern WV and the New River
Valley.
Worst flight category conditions anticipated on Wednesday.
Guidance shows good consistency in progressing a band of what
should be moderate to potentially heavy rain at times from south
to north along the spine of the Blue Ridge between 11-18z (and
continuing into the late afternoon and evening hours). Expect
ceilings to lower to MVFR- IFR category with visbys largely VFR-
MVFR, though will tend IFR at times in the steady and at times
heavy rain.
Confidence is average for the entire period, though is lower
than average on ceilings and placement of dense fog for the
overnight period.
Extended Discussion...
Showers are expected to increase in coverage by Wednesday night and
Thursday as tropical moisture shifts northward ahead of
Hurricane Michael and a cold front moving in from the west. Rain
may be heavy at times Thursday. Conditions will improve back to
VFR on Friday behind the front, then VFR over the weekend.
&&
.HYDROLOGY...
As of 1100 PM Tuesday...
An inflow of deep tropical moisture will introduce the
possibility of both flash flooding and, later, river flooding in
the Wednesday afternoon through Friday time frame.
A first round of heavy rain is expected to affect the Blue Ridge
and foothills region on Wednesday afternoon/evening as winds
shift southeasterly across the mid-Atlantic, carrying very deep
moisture into the mountains. Two to three inches, with locally
higher amounts, are expected along the crest of the Blue Ridge
and may result in flash flooding in spots by Wednesday evening.
A flash flood watch has already been issued for this region.
After a brief decrease in rainfall on Wednesday night, rainfall
coverage and intensity is expected to increase again on
Thursday late morning/early afternoon with the approach of what
is expected to be (by that time) Tropical Storm Michael. Weather
forecast models are still indicating a variability of rainfall
amounts depending on the track and speed at which the storm
pushes across the Carolinas, but the most likely scenario
indicates 2 to 4 inches across the Southside of Virginia and the
Piedmont of North Carolina, where a flash flood watch has been
posted. Convective bands with high rates of rainfall within a
tropical environment will obviously present an enhanced flash
flood threat, with the Weather Prediction Center calling for a
slight to moderate risk of excessive rainfall during the
Thursday to early Friday timeframe, mainly across the southeast
one-third of our forecast area.
The Dan and lower Roanoke river basins will be most heavily
affected by rainfall from Michael, and it appears reasonable
that points these rivers will experience at least minor
flooding...again: all dependent on where the heaviest rainfall
occurs. Lesser amounts are expected to the northwest to
include the Greenbrier and James River basins, which should
limit the flood threat there.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Flash Flood Watch from Thursday morning through late Thursday
night for VAZ032-043-044-058.
NC...Flash Flood Watch from Thursday morning through late Thursday
night for NCZ003>006-020.
Flash Flood Watch from Wednesday afternoon through Thursday
evening for NCZ001-002-018-019.
WV...None.
&&
$$
SYNOPSIS...AL
NEAR TERM...AL/KK/NF
SHORT TERM...PM
LONG TERM...PM
AVIATION...AL/KK
HYDROLOGY...NF/PC