Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/14/17
Area Forecast Discussion
National Weather Service Denver/Boulder CO
735 PM MDT Fri Oct 13 2017
Issued at 734 PM MDT Fri Oct 13 2017
Increased coverage of patchy fog further west and south over the
plains, with hires models showing some move in after 06z on
consecutive runs. Have also removed rain showers over the far
northeast plains as conditions are too dry.
.SHORT TERM...(This evening through Saturday)
Issued at 300 PM MDT Fri Oct 13 2017
Upper trough is presently over the northwest CONUS with a
ribbon of strong (100-140kt) southwest flow aloft stretching
from srn CA to the northern Great Lakes. RAP indicates 125-130kts
winds crossing over nrn and wrn CO. some of this high altitude
momentum has managed to mix down into the high valleys of nrn CO
where swly winds at a number of reporting sites across North and
Middle Parks have been gusting in the 20-30kt range. On the
plains, a weak cyclonic upslope flow persists, while the extensive
low cloud deck that this flow generated has all but dissipated
this afternoon with heating.
Tonight,the upper trough out west is forecast to swing down over
Idaho/wrn Wyoming/Utah, and an associated sfc cold front down
across nwrn CO/sern WY. On the plains, HiRes models show the
boundary layer saturating across the nern corner of the CWA
overnight, the product of a moist low-level sely winds. Have added
patchy to areas of fog acrs the far northeast counties after
midnight in line with neighboring CWAs. In the high country,
strengthening swly 700-500mb flow and a steady increase in static
stability will likely result in an increase in ridgetop winds
overnight. Stronger ridgetop and Front range east slope winds
likely to set up after midnight and more so near sunrise with
amplification of the mtn wave. Could see gusts on the ridges and
higher east slopes in the 40-55kt range. With the nearing trough,
could see a few light snow showers developing over the highest
ridges in the northern mtns towards morning with cold air
advection behind the passing cold front.
On Saturday, this stand-up cold front sweeps out across the plains
during the morning flattening the rise in temps. Should see gusty
west-northwest Bora-type winds of 35-65kts continuing on the mtn
ridges and east slopes for most of the day. May even see an uptick
in snowfall in the northern mtns during the morning. Snow totals
on the higher slopes probably no more than a few inches by midday.
On the plains, frontal passage in the morning will set off gusty
nwly winds areawide. But its not until late late morning when
winds are likely to be at their strongest the the back side of the
passing upper trough. Expect to see some the 45-55kt nwly 700 mb
flow mixing down onto the plains producing peak gusts in the
30-40kt range. These strongest winds are expected to materialize
east of the I-25 corridor after 17z. Fortunately, an increase in
base line RH values with cooler temperatures will reduce the
rangeland fire danger, even with the gusty winds. As a rule,
highs tomorrow will be some 8-10deg f, even with plenty of
.LONG TERM...(Saturday night through Friday)
Issued at 200 PM MDT Fri Oct 13 2017
Gusty winds will be diminishing during the early evening hours
Saturday as gradients relax and subsidence/mixing decrease.
We should see light winds in all but the higher mountains by mid
to late evening. Temperatures will drop below freezing over the
entire forecast area Saturday night, with 20s over most of the
plains and teens mountains. Freeze Warnings will no longer be
issued this season as we observed a hard killing freeze last
Monday night/Tuesday morning.
By Sunday, we`ll start a warming trend as a prolonged period of
dry, warm, westerly flow develops across the Central Rockies.
We`ll see highs push back close to normal by Sunday, and then
warm to several degrees above normal Monday through Friday. Dry
conditions will persist through Thursday. Then the next embedded
weather disturbance may reach the mountains and bring a few
showers into the picture by late Friday.
.AVIATION...(For the 00Z TAFS through 00Z Saturday afternoon)
Issued at 734 PM MDT Fri Oct 13 2017
VFR conditions expected next 24 hours. Northerly winds will trend
to the northwest over the next couple hours before going to
drainage by midnight under 10 kts overnight. An exception to this
will be near the foothills such as at KBJC where west- southwest
winds of 15-25kts could develop after 06z tonight. On Saturday, a
dry cold front is expected to sweep eastward across the Denver
metro area between 14z-16z, causing gusty west-northwest winds of
15-30kts through the afternoon. By evening, look for speeds to
decrease as winds become more northerly in direction.
Issued at 300 PM MDT Fri Oct 13 2017
On Saturday, a dry cold front will sweep eastward across northeast
Colorado during the late morning and early afternoon hours,
causing a shift to gusty west-northwest winds of 25 to 40 mph.
Strongest winds are likely to be found east of the I-25 corridor
and particularly across the northeast corner of the state during
the afternoon hours. Fortunately, relative humidities levels will
be higher tomorrow in response to anticipated cooler post-frontal
temperatures. So, no fireweather highlights are planned at this
Area Forecast Discussion
National Weather Service Cleveland OH
912 PM EDT Fri Oct 13 2017
A high pressure ridge over the Ohio Valley will weaken Saturday. A
low will move northeast across the Great Lakes Sunday pulling a cold
front through the area. High pressure will spread east over the
region Sunday night and Monday and should last into next weekend.
.NEAR TERM /THROUGH SATURDAY/...
Update...Convergence showing up as a persistent area of clouds
from Trumbull and Ashtabula county east into nwrn PA this
evening. This convergence shifts into PA early tonight and then
weakens to expect the clouds will shift east and then thin
through the overnight. Still, likely worth a mostly cloudy
forecast for PA. Also put a trend into Ashtabula sky cover. To
the northwest satellite also shows clouds across lower MI and
western Lake Erie moving southeast. These could impact north
coast into northeast OH but for now will continue with PC most
Original...Weak upper ridging will be over the area into Sat
before shifting off to the east Sat night. The models still keep
the stalling cold front far enough to the NW that conditions
may stay dry until the end of Sat night when the front will
start to get pulled SE toward the NWRN counties. Will still keep
a small chc pop in the far NW Sat as the nose of the low level
jet not that far to the north.
The other issue of concern will be the cloud cover as low level
winds from the south may not be strong enough to flush out the low
level moisture tonight, especially in the east. On the other hand,
patchy fog will probably form where the clouds clear out. On
average. Sat should end up being partly cloudy for most of the area
then cloud will be on the increase later Sat night.
Lows tonight will again be mainly in the 50s, but rebound nicely on
Sat to the mid to upper 70s. Increasing south winds and cloud cover
will lead to a warmer night Sat night with lows probably only into
the low to mid 60s.
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
Cold front will move across the region on Sunday. However the cold
front is slightly slower with the latest model runs. This may allow
for slightly better instability ahead of the front. So have added a
slight chance of thunder back to the forecast. Winds will be the
main story with gusts 35 to 40 mph possible. Cooler in the wake of
the front on Monday with some lake effect showers possible. Drier a
ir arrives on Monday as high pressure increases its influence. It
will then remain dry into Tuesday.
Sunday will see highs in the 70s. Cooler on Monday with most
locations remaining in the 50s. MOnday morning may end up being
frosty for much of the area away from the lake. Warmer on Tuesday
with 60 to 65 degrees common.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
High pressure will dominate the area throughout the long term. Highs
will be around 70 degrees each day with abundant sunshine. Lows will
start out cooler Tuesday night with temps dipping into the lower
40s, but lows will rebound to the upper 40s and lower 50s for the
remainder of the long term.
.AVIATION /00Z Saturday THROUGH Wednesday/...
A couple of aviation issues for the evening and overnight.
First, satellite shows mid deck dropping southeast out of lower
MI. This may impact KTOL 01z-02z time frame however with cig
hgts around 6 to 7kft it shouldn`t be a problem. To the east
from KYNG to KERI satellite shows a developing lower deck around
3 to 4kft supported by low level convergence shown by the HRRR
and to a lesser extend the NAM12. This hangs around into the
night especially in the KERI area although flow weakens. Will
handle tempo groups into the evening and will watch trends.
Otherwise did bring some MVFR fog back after 08z through 13Z
away from the lake. Saturday should be VFR.
OUTLOOK...Non-VFR and strong winds with a strong cold front Sunday.
Non-VFR across northeast OH/nw PA Monday.
Winds will be light on the lake tonight. Southerly winds will
increase by Saturday afternoon. As a cold front moves closer to the
area Saturday night into Sunday southwesterly winds will increase.
By sunrise SUnday morning winds may be high enough to need a small
craft advisory. Just ahead of and in the wake of the cold front
Sunday afternoon winds may increase close to 35 knot gales. This
will need to be monitored by later shifts. Northwesterly winds will
remain strong enough to likely need a small craft into mid day of
Monday. Southwesterly winds should return to the lake by Tuesday.
Area Forecast Discussion
National Weather Service El Paso Tx/Santa Teresa NM
337 PM MDT Fri Oct 13 2017
Southerly flow around a ridge of high pressure centered over the
northern Gulf of Mexico states will pull some moisture into the
area. Isolated showers and thunderstorms this afternoon will
increase in coverage during the overnight hours, with shower and
thunderstorm chances tapering off on Saturday. A strong backdoor
cold front will sweep through the area early Sunday morning,
bringing much cooler temperatures to the region. Temperatures will
climb back up above normal on Tuesday, while drier conditions
As of 3:30 PM MDT, ELP has tied the record high of 91 F last set
in 1996. Still time for it to go a little higher.
Subtropical ridge is centered over Louisiana this afternoon, while
a broad trough dominates the Pacific Northwest and Northern Plains
states. SW flow aloft over New Mexico has been slowly backing more
to the south, allowing a feed of subtropical moisture to stream
into the area. This morning`s RAOB had 1.18" PW, while G16 blended
PW product shows this may have increased slightly to around
1.30". Lack of instability and mid-level capping has been
suppressing convection over the area, which has mainly been
limited to the Sacramento Mountains, Otero Mesa, and Bootheel
regions. Here at KEPZ we can see the tops of the CBs over the
Otero Mesa, but overhead there are numerous lenticulars suggesting
the stable layer remains intact. RAP13 analysis still shows
significant are of CIN over most of the lowlands N and W of ELP.
Our main hope for precip lies in the Bootheel and southward into
the Sierra Madre, where convection has been slowly increasing over
the past hour. Several Univ of AZ WRF runs and the past few HRRR
runs suggest this activity will continue to increase in coverage
and slowly move NE, reaching the lowlands of South-Central NM and
Far West TX after 00z (and focused between 02Z - 09Z). With strong
capping in place and lack of strong upper level forcing, will keep
the PoPs in the lower end of the scale for scattered coverage.
Drier air will work in from the west tomorrow (Sat), but some very
spotty showers or a thunderstorm may persist near/east of the
A strong cold front will sweep in from the NNE late Saturday night
into Sunday morning, bringing strong winds to the west facing
slopes of area mountains. NAM and GFS show 850 mb wind max 40-45
knots centered over Southern Otero County, El Paso County and into
northern Mexico around 12z Sunday, suggesting wind gusts in excess
of 50 mph will be possible west of the Huecos and Franklins, and
possibly along the Otero Mesa.
Temperatures Sunday will drop to the mid/upper-60s over the
lowlands of Otero and Hudspeth Counties, and the lower-70s along
the Rio Grande from ELP-TCS. Normal high is around 78-79.
Temperatures will quickly recover, climbing back up to around 5
degrees above normal by Tuesday and staying that way through the
week. A fast-moving shortwave trough will pass north of the area
mid-week, but the risk of precip is minimal, with little change
in temperature expected with its passage. A more significant
disturbance may come into play next weekend.
VFR conditions will occur for most of the valid period. A plume
of moisture streaming over the area will generate areas of light
rain showers and isolated thunderstorms with periods of MVFR cigs
and vsby at TAF sites between 00Z and 12Z. Mountain areas will see
lower cigs and obscured mountain tops and increased rain coverage
overnight. Skies will be scattered to broken at 10 kft lower with
lower cigs near thunderstorms. Winds will be from southwest at 7
to 12 kts shifting to west at 5 to 10 kts after 06Z.
Moisture flowing into the local area will increase chances for
showers and thunderstorms area wide tonight and for eastern areas
on Saturday. Rain amounts will be scattered in coverage and
generally light to occasionally moderate. Dry conditions will
occur by Sunday and for much of next week with high pressure in
place over the region. A cold front will push into the area early
Sunday and generate strong easterly winds along the border region
with strongest gusts along west slopes of area mountains. Wind
gusts along the mountains in Dona Ana, Otero, El Paso and
Hudspeth counties may exceed 50 mph. Winds will diminish Sunday
night into Monday. Relative humidity values will be slightly
elevated tonight through Saturday as a result of the moist flow
pattern. Humidity values will drop after the cold front brings in
a drier air mass. Minimum humidly values will be in the lower 20s
with overnight recoveries will in the 40 to 60 percent range.
.PRELIMINARY POINT TEMPS/POPS...
El Paso 66 87 58 71 / 30 20 0 0
Sierra Blanca 61 90 54 64 / 20 20 30 0
Las Cruces 63 86 53 72 / 40 10 0 0
Alamogordo 65 85 52 72 / 30 20 0 0
Cloudcroft 50 64 36 57 / 40 30 0 0
Truth or Consequences 59 87 52 75 / 20 0 0 0
Silver City 54 81 47 73 / 10 0 0 0
Deming 58 89 54 74 / 30 0 0 0
Lordsburg 59 87 52 76 / 20 0 0 0
West El Paso Metro 67 87 59 70 / 40 20 0 0
Dell City 60 90 51 70 / 20 20 20 0
Fort Hancock 63 90 59 70 / 20 20 30 0
Loma Linda 61 83 51 66 / 30 20 0 0
Fabens 62 88 55 71 / 30 20 0 0
Santa Teresa 66 86 56 71 / 40 10 0 0
White Sands HQ 67 86 55 72 / 40 20 0 0
Jornada Range 63 86 53 72 / 40 10 0 0
Hatch 60 89 53 75 / 30 0 0 0
Columbus 60 89 56 73 / 40 0 0 0
Orogrande 67 86 54 72 / 30 20 0 0
Mayhill 54 74 36 61 / 40 30 0 0
Mescalero 52 73 37 66 / 40 30 0 0
Timberon 52 72 37 62 / 40 30 0 0
Winston 47 80 37 70 / 10 0 0 0
Hillsboro 56 85 48 73 / 20 0 0 0
Spaceport 60 87 49 76 / 30 0 0 0
Lake Roberts 46 80 35 75 / 10 0 0 0
Hurley 51 83 44 72 / 20 0 0 0
Cliff 49 86 38 80 / 10 0 0 0
Mule Creek 54 83 47 79 / 0 0 0 0
Faywood 54 84 50 72 / 20 0 0 0
Animas 61 88 56 75 / 20 0 0 0
Hachita 57 88 52 75 / 30 0 0 0
Antelope Wells 59 87 54 74 / 40 0 0 0
Cloverdale 58 84 54 74 / 30 0 0 0
25-Hardiman / 04-Lundeen
Area Forecast Discussion
National Weather Service Grand Rapids MI
1152 PM EDT Fri Oct 13 2017
Issued at 326 PM EDT Fri Oct 13 2017
Rain chances will be on the increase tonight, with periods of
showers and thunderstorms then expected through early Sunday
morning. The biggest threat with this will be heavy rain that could
cause some minor flooding, and strong winds Saturday evening through
Some lingering showers will be possible on Sunday before ending.
Cooler weather will come in for early next week along with dry
weather. Temperatures will then warm up gradually next week to above
average levels once again.
Issued at 1027 PM EDT Fri Oct 13 2017
Only change to the fcst this evening was to delay the arrival of
possible tstms to after 09z tonight and only in the southwest
corner... based on latest RAP guidance. Otherwise expect shower
coverage to gradually increase overnight and spread farther south
and east with time.
.SHORT TERM...(This evening through Sunday night)
Issued at 326 PM EDT Fri Oct 13 2017
Our main concern in the short term is dealing with all aspects of
the incoming system which will impact the area from tonight through
A quiet weather day is in progress, or the calm before the storm.
The changes are on their way, with the leading edge of these changes
making their way through central Wisconsin as of 19z. Initial
moisture advection is ongoing, and will ramp up a bit this evening
as the front to our W/NW drops into the state. The showers this
evening will move in across the NW first and gradually sink south
through most of the CWFA by 12z Sat. Thunder does not look possible
until very late tonight, and just across the far srn half of the
CWFA based on elevated instability parameters.
We may see a brief lull in the morning as the front settles a bit
south, and the the initial surge of moisture moves east. This will
be short lived, if at all before the next surge of moisture advects
in with a 35+ knot low level jet. Thunder will become a little more
likely as more elevated instability moves in. Parcels below 850 mb
remain relatively stable through 00z Sun. Heavy rain will be the
main threat with pwat`s increasing to as much as 1.75 inches, which
is almost as high as it gets for mid-October. Some training of
showers/storms will be likely with only small shifts in the
Saturday night/early Sunday morning will be when the most impactful
weather affects Lower Michigan. This is when the main wave lifts in
from the SW and brings a strong slug of moisture via a 60+ knot low
level jet in addition to the strong dynamics via the RRQ of a 140+
knot upper level jet to our NW. Instability overall will not be
impressive with only a few hundred j/kg of MU Cape available. It is
the wind fields that are concerning. If any storms are able to
organize an updraft, the 50 knots below 1000 ft and 60 knots around
1500 ft could be brought down in the downdraft and cause damage,
even with little to no lightning. The strong low level wind shear
also could cause kinks on any convective lines, that could produce a
spin up tornado. The time frame for this would be roughly from 9 pm
Sat night to 3 am Sun morning. The best sfc based instability does
stay to our S and SW, keeping the best threat there.
We then turn our attention to the frontal passage which should occur
shortly after the worst convection. The frontal passage will bring
strong cold air advection and pressure rises, which could help bring
down the strong winds, albeit a little less than earlier with the
low level jet. We are looking at wind gusts of over 40 mph likely
behind the front. This may eventually require a Wind Advisory for at
least the lakeshore counties, and maybe also further inland.
Conditions will gradually improve later Sunday as the best gradient
moves out. We will likely have a few instability showers linger on
Sunday, with some lake enhancement likely off of the lake with h850
temps dropping to -1C or so, giving delta t/s over the lake of mid
to upper teens. Moisture will not be too shabby for lake effect
purposes, since it looks to be up to around 7k feet or so.
.LONG TERM...(Monday through Friday)
Issued at 326 PM EDT Fri Oct 13 2017
Lake effect showers will diminish Monday morning as inversion
heights lower following the departure of the upper trough. Monday
will be the coldest day of the week but clouds will scatter out.
Warmer air above the surface will already be flowing back over the
area Monday night. A strengthening pressure gradient between a low
to our north and high to our south is expected to maintain southwest
winds Monday night and prevent frost.
In the third week of October, climatological normal temperatures are
considered to be highs near 60 and lows in the lower 40s. We will be
5 to 10 degrees warmer than that from Tuesday through the rest of
the week. A stubborn anticyclone will develop over the eastern US
and Michigan will be under nearly continuous southwest flow. An
upper level wave and Hudson Bay low will pass by well to the north
of the Great Lakes on Wednesday, and precipitation chances here look
quite low. Overall, this looks like a dry and milder-than-normal
week with abundant sunshine.
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1130 PM EDT Fri Oct 13 2017
Conditions will gradually deteriorate from primarily VFR to MVFR
and then IFR overnight into Saturday morning from north to south
as low clouds and rain develop. On Saturday conditions will likely
remain IFR at our northern terminals (KMKG and KGRR) while
further south and east we expect conditions to be quite variable
from VFR to MVFR through the morning and afternoon with some IFR
at times with heaviest showers.
Thunderstorms will develop mid to late Saturday afternoon and
continue through Saturday evening and result in LIFR conditions at
times in heaviest rain and thunderstorms. Prevailing conditions
most of the time will be a mix of MVFR and IFR Saturday evening.
Stronger storms will also bring potential for gusty winds.
Issued at 326 PM EDT Fri Oct 13 2017
We are issuing a Gale Watch from 00z Sun through 00z Mon for the
entire nearshore waters with this package. This Gale watch will
encompass strong winds immediately ahead of the front, likely Gale
to potential Storm force winds along the front/with convection, and
the strong cold air advection coming in behind the front. Winds and
waves will then come down Sunday night as the gradient relaxes.
Issued at 326 PM EDT Fri Oct 13 2017
We continue to expect a large area of 1 to 2 inch rainfall across
much of the forecast area with the most intense rainfall occurring
Saturday evening. There is potential for significantly greater
amounts in excess of 3 inches in spots, which could produce moderate
localized flooding. There is some disagreement about exactly where
the heaviest rain will fall.
Some of the larger scale forecast models place a broad swath of 2+
inch accumulation totals from Muskegon to Mount Pleasant, which
would mostly affect the Muskegon and Chippewa river basins. Some of
the finer scale convection allowing models place the greatest
precipitation farther south towards the I-94 corridor.
Ensemble river forecasts suggest that even with the greater rainfall
amounts, there remains a limited chance for achieving flood stage in
mainstem rivers in the affected basins. River advisories seem much
The overall environment highly favors training or back building
convection which could produce rainfall rates of 1-2 inches per hour
and totals well over 3 inches in spots. Smaller streams, basins, and
urbanized areas could see significant flooding if overlapped by
these local areas of enhanced rainfall. Another factor that may
exacerbate nuisance flooding is the falling leaves that might clog
smaller drainage systems.
LM...Gale Watch from Saturday evening through Sunday evening for
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
941 PM CDT Fri Oct 13 2017
941 PM CDT
No significant changes to going forecast this evening, other than
to add some detail to hourly pop grids through late evening per
radar and high-res guidance trends.
Cold front has sagged to just south of the I-88 corridor across
northern IL this evening, and was stalling/transition to a warm
front as it becomes parallel to deep southwesterly flow aloft. 00Z
DVN sounding depicts strong low level veering wind profile,
indicative of strong warm advection across the baroclinic zone,
complimented by 02Z RAP analysis which depicts 30 kt south-
southwest low level jet and theta-E advection from eastern KS/MO
into the IA/MO border region and an axis of 500-1000 J/kg MUCAPE.
Regional radar shows developing convective showers into southeast
IA, which high res guidance expands northeastward across the LOT
cwa overnight. Thus would expect a gradual expansion in precip
coverage from current activity along the IL/WI border, across much
of the area in the hours after after midnight. Going forecast has
this well in hand with current pops along the WI border
expanding/increasing across the remainder of the cwa through the
Otherwise, tweaked winds a bit with frontal boundary a bit further
south than previously depicted in hourly grids.
248 PM CDT
Today has been sunnier than expected leading to slightly warmer
afternoon temperatures outside of the Rockford area. Cloud cover
will increase though through this evening as a cold front over
central WI and northern IA will stall over northern IL this
evening. The front should settle just north of O`Hare to Amboy,
IL. Showers spread across areas northwest of I-55 this evening,
and a few embedded thunderstorms are possible to the north of the
front. Showers and isolated to scattered embedded thunderstorms
continue to spread across much of the forecast area overnight.
CAPE values are minimal so I have low confidence in thunder
coverage. Severe storms are not expected.
PWATs are forecast to be 1.5-1.75 inches overnight so some areas
could see upwards of a half inch of rain tonight.
The front surges north as a warm front Saturday. Morning showers
and storms should dissipate. There may be a short dry period late
Saturday morning, but kept a chance of showers in the forecast in
case scattered showers linger.
An upper level wave moves through forcing another round of showers
and storms. Models differ on CAPE location but agree that CAPE
will likely be minimal. CAPE values may be slightly higher than
currently forecast if we get peaks of sun, but I`m expecting CAPE
values to be much lower than we`d typically like for severe storms
given a cloudy forecast. Shear remains favorable at around 60 kt.
If any storms pulse up, damaging winds are the most likely hazard.
High PWATs could lead to additional heavy rain. The highest
rainfall forecasts are for areas north of I-55, which could see
another 0.5-0.75 inch of rain Saturday. Higher rainfall totals
would be north of I-88, and could be locally higher under
248 PM CDT
Saturday night through Friday...
A powerful cold front will sweep across the region Saturday night
into Sunday morning. Surface low is projected to track from eastern
Iowa Saturday evening to southern Wisconsin Saturday night with a
trailing cold front sweeping across most of the CWA overnight. Out
ahead of the low track, a strong low level jet will transport
unusually high PWat air of 1.7-1.9 inches over the local area
driving heavy rainfall. An axis of one to two inches of rainfall
appears likely with locally higher amounts plausible. Where exactly
this sets up remains a bit uncertain at this point, but somewhere
along or just north of the IL/WI state line is favored depending on
where the strongest convergence ahead of the 60kt+ LLJ aligns.
Within the warm sector, lapse rates are fairly weak and unfavorable
diurnal timing will contribute to overall weak instability. Still
guidance shows 200-300 J/Kg MLCAPE possible ahead of the cold front
superimposed by very strong deep layer shear. Despite the lack of
any appreciable instability, given the strong kinematic environment,
any convective elements would bring some risk of strong and
potentially damaging winds and bears close watching as the event
Prefrontal 850mb temps of 15-17C Saturday will fall to around -1C by
midday Sunday behind the front. The strong cold advection will
result in steep low level lapse rates. Meanwhile, as precipitation
along the front exits the CWA to the east Sunday morning, high
pressure will build across the Great Plains resulting in a strong
gradient and isallobaric response. GFS indicates a corridor of 6-
7mb/3hr pressure rises will move across northern Illinois mid to
late in the morning. This combination of factors will result in
strong and gusty winds across the region. Expect winds gusting in
excess of 30 mph Sunday morning, very gradually tapering in
magnitude through the day as the gradient relaxes and the strongest
pressure rises move to our east. In addition Sunday, expect the area
to remain locked under stratus cloud cover with moisture trapped
atop the shallow cold airmass by a strong inversion. Expect early
morning high temperatures Sunday with falling or steady non-diurnal
temperatures trends through the day.
Ridge axis will move across the local area Monday then settle to our
east Tuesday through the end of the upcoming week. Seasonably cool
temperatures on Monday will return to above normal conditions
Tuesday through the end of the week as southerly flow dominate on
the western periphery of the ridge. No significant chances for
precipitation are noted as upper ridge gradually strengthens over
the eastern CONUS.
For the 00Z TAFs...
The concerns for the Chicago area airports through Saturday are:
- Winds with mainly an easterly component likely through mid
Saturday morning, with some variance in speeds
- Showers likely by overnight with isolated thunder in the area
- Periods of showers likely again Saturday afternoon into Saturday
night, with increasing chances for thunder after dark
- Winds becoming near due south Saturday afternoon
A warm front is developing across northern Illinois with showers
traversing north of this feature near the IL/WI border through
the evening. Some of these will close in on ORD and MDW but the
best chances for those airports are overnight as an upper
disturbance moves overhead. Isolated to possibly scattered thunder
is likely in the region. Winds will likely be below 8 kt, with
some variance in direction but should be mainly if not entirely
from the eastern half of the compass.
Confidence in a minimum in coverage of showers Saturday morning is
fairly high, but there is increasing confidence in IFR ceilings
being an issue. These are likely along and north of the warm
front, which is expected to be just south of ORD and possibly MDW
too. The warm front will ease northward during Saturday and as it
passes the Chicago airports winds will turn to southerly. Speeds
will increase, especially after dark Saturday and some gusts will
be occasionally seen.
Periods of showers are favored during Saturday afternoon,
especially along/northwest of a PIA to ORD line. It is challenging
to say what thunder coverage would be in these showers as
instability is somewhat marginal. Ahead of the cold front later
Saturday evening into the early overnight, a band of convection is
likely, some of which may be gusty.
248 PM CDT
Low pressure is expected to track across Lake Michigan this weekend
bringing a period of strong gales as a trailing cold front sweeps
across the region. A leading warm front will begin to lift across
Lake Michigan this evening and tonight with strengthening
northeasterly flow expected across the northern 2/3 or so of the
lake while southerly winds overspread the south end of the lake. By
Saturday evening, expect south to southeast winds to be in place
across most of the lake, increasing to around 30 kt. A few southerly
gales are possible by Saturday evening ahead of the low, but gales
will become widespread and potentially strong Saturday night into
Sunday as winds veer around to the west and northwest behind a
trailing cold front. Expect wind gusts to peak around 40 to 45 with
the potential for a few occasional 50 kt gusts with any showers that
help mix down stronger winds aloft. A Gale Watch has been hoisted
for the open waters, though there may yet need to be refinements to
timing before the event begins. Winds should ease back below gale
force mid to late Sunday afternoon or early Sunday evening.
LM...Gale Watch...LMZ777-LMZ779...7 PM Saturday to 7 PM Sunday.
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Area Forecast Discussion
National Weather Service Lubbock TX
921 PM CDT Fri Oct 13 2017
Evening thunder has more closely followed earlier RAP projections,
thus a bit more coverage and slightly further east. All-in-all,
activity appears to have peaked and likely will be slowly
declining. But cold pool activity will continue to spread across
our northwest corner for several more hours. Updated for slightly
broader coverage and higher probability of thunder in the
northwest tonight. RMcQueen
.PREV DISCUSSION... /issued 635 PM CDT Fri Oct 13 2017/
Isolated thunderstorms that have developed to the northwest of the
terminals are not anticipated to affect any of the terminals this
evening. There is another chance of low CIGS Saturday morning but
confidence is too low to mention in the TAF at the moment.
PREV DISCUSSION... /issued 354 PM CDT Fri Oct 13 2017/
After the brief bout of low clouds and fog across portions of the
central and southwestern South Plains this morning, we have
received strong insolation with 20Z temperatures warming into the
upper 80s and lower 90s at most spots. This heat along with weak
convergence along a surface trough was supporting scattered high-
based cumulus across the northwestern zones. These clouds could
potentially bubble into a few thunderstorms through the late
afternoon and early evening hours. MUCAPE around 1000 J/kg and
0-6 km wind shear of 30 knots could support a strong storm or two,
though organized strong/severe storms are not anticipated. Even
if the late afternoon activity fails to mature, additional
convection currently forming over the higher terrain of eastern
New Mexico will have a good shot of clipping our far northwestern
zones around/over Parmer County as it translates northeastward.
Otherwise, moist southerly breezes will keep overnight
temperatures on the mild side. We could see another bout of low
clouds and fog attempt to develop toward Saturday morning, though
signals are weak and patchy ground fog and/or dew are a better
Saturday will provide another warm day as breezy and relatively
moist southwesterly winds persist. Highs will again rebound into
upper 80s and lower 90s, except perhaps across southwest Texas
Panhandle where more persistent mid-level cloud cover could keep
temperatures down somewhat. We could again see isolated convection
attempt to develop along a pre-frontal surface trough over the
Caprock Saturday afternoon, but the better chances will develop
Saturday night. This will occur as a potent upper level trough
currently over the northwestern states advances through the central
and northern High Plains. Although the bulk of the lift with this
system will pass by to the north it will propel a seasonably strong
cold front southward through the South Plains. This front should
enter the northern zones around 03Z and quickly sweep southward,
likely positioned well south of the CWA by 09Z. As the front plows
into the better moisture/instability a line of thunderstorms will
likely erupt, though how far west the line can build is still in
question. The best storm chances will favor roughly the southeast
half of the FA through the overnight hours before quickly shifting
south of the area. Both deep layer shear and instability should be
up a notch from today, so this could support several strong to
severe thunderstorms. In addition, a strong pressure gradient (and
associated isallobaric component with 3 hour pressure rises of 10-12
mb) will result in gusty post-frontal northerly winds that could
rise to advisory levels (sustained in excess of 30 mph) for a few
hours late Saturday night.
The strong winds will gradually ease through the day on Sunday, but
highs will only rebound into the 60s (maybe struggling to make 60
over the southwest Texas Panhandle) even with abundant insolation. A
surface ridge will settle over West Texas Sunday night providing
light winds and clear skies. This combined with relatively dry air
will promote near ideal radiational cooling. Given this we have
favored the cooler guidance numbers which may support a frost or
light freeze generally north and west of Lubbock.
Light southerly winds will return on Monday under dry northwesterly
flow aloft. This will allow temperatures to rebound several degrees
from Sunday`s levels. The dry conditions and warming trend will
persist into much of next week, with highs returning to the 70s and
lower 80s. The upper flow should gradually flatten by the latter
part of the week with a more significant trough potentially
affecting the region in some manner (increased wind and/or storm
chances) by Day 8 or 9 (Saturday or Sunday).
Area Forecast Discussion
National Weather Service Reno NV
758 PM PDT Fri Oct 13 2017
The latest HRRR guidance has a few showers over far northern
Washoe County and the Surprise Valley through the evening...then
clouds begin to decrease. The latest NAM guidance agrees with this
scenario. Based on the current trends in satellite imagery and
the lack of radar returns...we have opted to decrease shower
coverage over the far northern parts of the forecast area late
this evening and decrease cloud cover as well. The forecast past
tonight remains on track with low level winds shifting to the
north then east over the ridges late tonight. Updates out soon.
.PREVIOUS DISCUSSION... /Issued 244 PM PDT Fri Oct 13 2017/
Below average temperatures are on tap through Saturday as a trough
moves over the West. Strong easterly winds are likely at the
northern Sierra crest late tonight and Saturday morning as strong
surface high pressure builds into the Great Basin. Warmer
temperatures and dry conditions are expected early next week, with
the potential for cooler, wetter, and windier weather late week.
A weak cold front will drop south through the region tonight turning
the flow northerly, then easterly. The depth of the colder air is
fairly shallow, but it will be enough to bring a bit of cooling for
temperatures into Saturday. It will also limit mixing potential
Saturday with stronger inversions in place. As a strong surface high
sets up over the Great Basin tonight into Saturday, it will
strengthen the gradient, especially across the Sierra. This will
bring gusty easterly winds of 60 to 80 mph across the Sierra crest,
with western Sierra slopes likely to see breezy winds tonight into
Saturday as well. While this is only a middle of the road type of
event for strength of wind speeds, it will be enough to generate
choppy conditions on Lake Tahoe and a Lake Wind Advisory has been
issued for tonight into midday Saturday.
Upper level ridge builds across the west for the early part of next
week with warming temperatures and mostly clear skies. Winds will be
light until midweek when an approaching system will begin to
increase wind speeds. It currently looks like Thursday will be the
windiest day next week, with southwest winds gusting in valleys
possibly as strong as 40 to 50 mph and ridges gusting over 100 mph.
These winds are in response to a strong jet ushering in a plume of
Pacific moisture and a trough into the west. The Sierra and western
Nevada are on the edge of the deeper moisture, which looks to move
into the northwest. An interesting development in the most recent
GFS run is that the main low coming into the west coast absorbs a
weaker secondary low off the southern California coast. This
enhances the precipitation chances across much of Nevada and has
ensemble support from about 50% of the perturbations. The EC keeps
this piece of energy off the coast, never merging it with the main
trough, and limits precipitation chances to areas mainly north of
Highway 50. While the finer details of this system aren`t clear at
this time, what we can say is this is the best shot at precipitation
the region has seen in some time. Anyone with plans the end of next
week should anticipate the potential for windy, cooler, and wetter
Breezy northwesterly surface winds this afternoon due to a cold
frontal passage. The strongest winds will be north of I-80 where
surface gusts are likely to reach 20-25 kts. There may also be a
brief period of low level wind shear this evening as post-frontal
surface winds trend to northerly while winds aloft remain westerly
25-35 kts. By Saturday, easterly flow returns with gusts across
Sierra ridges possibly reaching 50-65 kts. JCM/Dawn
NV...Lake Wind Advisory from 2 AM to 1 PM PDT Saturday for Lake Tahoe
CA...Lake Wind Advisory from 2 AM to 1 PM PDT Saturday for Lake Tahoe
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