Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/27/18
Area Forecast Discussion
National Weather Service Bismarck ND
1006 PM CDT Wed Sep 26 2018
.UPDATE...
Issued at 1006 PM CDT Wed Sep 26 2018
Little change with this forecast update. A cold front approaching
the US Highway 2 corridor across northwest and north central North
Dakota as of 03 UTC will continue to propagate southeast through
the night with scattered rain showers behind the boundary.
UPDATE Issued at 643 PM CDT Wed Sep 26 2018
Did add a slight chance mention of thunderstorms to the Turtle
Mountains through sunset per upstream trends across Canada.
However, this activity is quickly weakening as of 2342 UTC.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 320 PM CDT Wed Sep 26 2018
Scattered light showers will continue across the north central and
northeast for the next couple of hours. A second wave of scattered
showers will accompany a cold front that will sweep across the
state north to south overnight. Various iterations of the HRRR
have suggested an isolated lightning strike or two may be possible
with this activity around the Turtle Mountains tonight and the
latest HRRR and the RAP iterations show 0-3 km MUCAPE values
possible ranging from 100 to 250 J/kg. However, confidence is
extremely low so did not introduce any thunder in the grids at
this time.
Behind the initial cold front Thursday, expect brisk and cooler
conditions. Northwest winds will range between 15 and 25 mph, and
afternoon highs in the mid 40s north to the lower 50s south.
.LONG TERM...(Thursday night through Wednesday)
Issued at 320 PM CDT Wed Sep 26 2018
As a highly amplified upper level ridge remains firmly in place
off of the west coast, widespread sub-freezing low temperatures
will stream in from Canada Thursday night/Friday morning, ranging
from between 27F and 32F. Freeze headlines will likely need to be
issued at some point, tonight or Thursday, to reflect the
anticipated freezing temperatures Friday morning. During the day
on Friday, surface high pressure will slide into the Northern
Plains from Saskatchewan, promoting well below normal highs in the
40s, clear skies, and northwest winds around 15 mph. These
conditions will result in apparent temperatures to feel more like
the upper 30s for most of the day.
Nearly a repeat performance in low temperatures are expected
Saturday morning with lows forecast in the upper 20s to lower
30s. A slight chance of rain and/or snow showers will be possible
across the south central and southern James River Valley on
Saturday.
By the end of the weekend, global models are in good agreement
that the ridge off the west coast will begin to deamplify and
retrograde, transitioning us into a fast zonal flow aloft. With
this pattern, expect periods of potential light snow/rain showers
on and off Sunday and Monday.
After Monday, model agreement begins to break down but a
progressive northern stream trough may deepen over the pacific
northwest, transitioning us briefly into southwest flow with more
potentially active weather and near normal to below normal
temperatures through mid week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 1006 PM CDT Wed Sep 26 2018
A cold front entering northwest and north central North Dakota as
of 03 UTC will move southeast tonight with scattered rain
showers. Ceilings may fall to MVFR across southwest North Dakota
late tonight into early Thursday morning. Additional MVFR stratus
may move into far northwest and north central North Dakota and the
upper James River Valley during the morning on Thursday, possibly
impacting KMOT.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...PA
SHORT TERM...ZH
LONG TERM...ZH
AVIATION...PA
Area Forecast Discussion
National Weather Service Marquette MI
753 PM EDT Wed Sep 26 2018
.SHORT TERM...(This evening through Thursday)
Issued at 414 PM EDT WED SEP 26 2018
WV imagery and RAP analysis indicated a broad mid/upper level trough
from north central Canada and Hudson Bay through the cntrl CONUS
resulting in westerly flow through the northern Great Lakes.
Upstream shortwaves were located over srn Manitoba and nrn Alberta.
With 850/700 mb temps to around 1C/-10C, sct/isold diurnal that
developed over wrn Upper Michigan were gradually shifting to the
east.
Tonight, The diurnal -shra should continue to move off to the east
and weaken this evening as the 700 mb trough exits the area.
Expect showers over nw MN associated with 700-300 qvect conv ahead
of the Manitoba shortwave to gradually slide eastward into the
northwest half of Upper Michigan overnight. Otherwise, clouds will
increase and thicken over the rest of the area overnight. Persistent
sw winds to around 10 mph will also keep temps from dropping off too
far with readings remaining in the lower to mid 40s.
Thursday, the initial band of showers should weaken during the
morning over central Upper Michigan. As the second stronger shrtwv
moves in during the afternoon, the shower coverage will increase
over the west half by early afternoon and across the east through
the rest of the afternoon. With moderate southwest winds continuing,
highs will climb into the mid 50s west to the lower 60s south and
east.
.LONG TERM...(Thursday night through Wednesday)
Issued at 254 PM EDT WED SEP 26 2018
Upper air pattern consists of a 500 mb trough across the central
U.S. with a ridge in the desert sw and one off the sern coast 00z
Fri. There is a shortwave in the upper Great Lakes 00z Fri. A trough
remains over the upper Great Lakes through 00z Sun. Temperatures
will remain below normal for this forecast period with periods of
rain and dry weather and pretty active with weak systems moving
through. Overall, did not make too many changes to the going
forecast.
In the extended, the GFS and ECMWF show a broad 500 mb ridge across
the sern U.S. and a trough in the western U.S. with a broad trough
across most of Canada with some colder air across the northern U.S.
12z Sun. A sfc cold front moves through the upper Great Lakes on
Sun. This sfc front stalls out to the south on Mon with upper
troughing remains in the western U.S. through Tue and the ridge
remaining over the sern U.S. 12z Tue. This ridge builds on the east
coast 12z Wed with troughing digging in the western U.S. and a sfc
front still remaining over the upper Great Lakes. Temperatures look
to be mostly below normal for this forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 741 PM EDT WED SEP 26 2018
VFR conditions are anticipated to prevail through the remainder of
the evening hours, with more cloud cover expected overnight. The
primary concern for aviation interests will be a nocturnally-
driven low-level jet cranking up overnight, with wind shear
looking likely at KIWD and KCMX. The confidence of LLWS coming to
fruition at KSAW is much lower, given the placement of the LL jet,
and have therefore negated mention there for this TAF issuance.
Showers could once again pop-up as well later tonight, although
there is higher confidence in more widespread shower activity
early Thursday morning through much of the day. As the LLWS
dissipates in the early morning hours, look for an increasing
concern for reductions in ceilings as a stratus deck builds in.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 414 PM EDT WED SEP 26 2018
Tonight into early Thursday, an approaching low pressure system from
the north will allow winds to become southwesterly at 20 to 30
knots. Expect winds to die down to 10 to 20 knots during the day on
Thursday, then becoming northwesterly 15 to 25 knots Thursday night
through Friday. Winds will remain between 15 and 25 knots through
the weekend.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
Gale Warning from 10 AM to 8 PM EDT Thursday for LMZ248-250.
&&
$$
SHORT TERM...JLB
LONG TERM...07
AVIATION...lg
MARINE...JLB
Area Forecast Discussion
National Weather Service San Francisco Bay Area
549 PM PDT Wed Sep 26 2018
.SYNOPSIS...Seasonably warm conditions are expected through
Thursday. A cooling trend will begin Friday as an upper trough
passes north of the Golden Gate with a slight chance of showers in
the North Bay on Saturday. Dry and seasonable conditions expected
on Sunday. Then a possibility of rain early next week when another
upper trough moves through.
&&
.DISCUSSION...as of 12:59 PM PDT Wednesday...Satellite imagery
shows stratus has cleared back to the coast and current
temperatures are running fairly similarly to those from 24 hours
ago. Little change in marine layer depth, as well, and surface
pressure gradients remain weak onshore near the coast, and tighter
offshore with 7.6 mb between WMC and SFO. Look for another warm
day on Thursday for inland locations, but this might be the last
one for a while as the weather pattern shifts.
The approaching upper level low over the Eastern Pacific is
forecast to approach the Northern California coast by Friday, then
move inland during the weekend. Although model solutions are
still different, there is better agreement between the GFS and
ECMWF regarding shower chances across Northern California on
Saturday with this low as it moves through. Best chances would
probably be north of our CWA but the slight chance pops we have
for the North Bay continue to look reasonable. That feature will
move inland on Sunday for dry and seasonable weather for Sunday.
Early next week, the forecast gets interesting with the
possibility of moisture from now Tropical Storm Rosa getting
infused in an upper trough and upper low along the west coast
bringing better rain chances to portions of California on Tuesday
and Wednesday. There is still uncertainty with this and
everything depends on the timing of the upper low with respect to
when moisture from Rosa advects northward. Latest runs of medium
range models have slight timing and placement differences
regarding the Eastern Pacific low. The operational run of the 12Z
GFS features a low center farther south, which places most of the
rainfall over central and southern California and into Arizona.
The 12Z ECMWF has the low center farther north as it moves
eastward into California and spreads rainfall across much more of
the state. In either case, cooler temperatures will occur, with
highs in the 70s and 80s inland, with 60s along the coast.
&&
.AVIATION...as of 5:49 PM PDT Wednesday...A late afternoon
steepened ocean to land thermal contrast and a compressed marine
layer between 500 and 1,000 feet deep will usher coastal stratus
and fog inland on onshore winds through the evening. It`s LIFR-IFR
along the coastline, VFR inland. Mainly light amounts of smoke
and haze from wildfires on the CA/OR border will continue to
advect into the Bay Area tonight and Thursday according to the 18z
HRRR near smoke forecast; surface vsbys are good /greater than 6
miles/, but it does look hazy aloft on the webcams. Restricted
slant range visibilities are very likely to extend into Thursday.
Weak upper level divergence far ahead of a closed 500 mb height low
pressure center 800 miles SW of the Bay Area will continue to bring
sct-bkn cirrus clouds in tonight and Thursday. Fairly well established
lower to mid level ridging over California will undergo little change
tonight and Thursday. Lower level cooling near 925 mb begins to ramp
up Thursday night through Friday, most likely deepening and weakening
the marine layer in our forecast area.
Vicinity of KSFO...Low to moderate confidence VFR holds into the
evening, tempo bkn cig forecast 12z-16z Thursday. Westerly wind is
picking up a bit stronger per recent 5 minute observations, gusts
nearing 25 knots. VFR Thursday.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...IFR cigs developing early, IFR tonight
into Thursday morning. VFR returning either by late morning or
early afternoon Thursday.
&&
.MARINE...as of 4:50 PM PDT Wednesday...A trough of low pressure
near the coast will maintain generally weak west to northwest
winds across the coastal waters through Friday. Winds will turn
southerly this weekend as a low pressure system develops off of
the Pacific Northwest Coast. A long period southerly swell will
gradually build beginning late in the weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...None.
$$
PUBLIC FORECAST: Sims
AVIATION: Canepa
MARINE: RGass
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Area Forecast Discussion
National Weather Service Paducah KY
1019 PM CDT Wed Sep 26 2018
.UPDATE...
Issued at 1019 PM CDT Wed Sep 26 2018
00z NAM adds support to expanding PoPs for light rains farther
north into the CWFA for the late night into Thursday morning. We
made this northward adjustment and upped QPF slightly, primarily
west KY. The RAP and HRRR remain quite consistent that this light
rain event will happen. Our PoPs are still not as high as the high
res guidance. We continue to incorporate the uncertainty element
given a dry forecast was inherited. The midnight shift will have
time to make adjustments with the routine daytime forecast
issuance around 3 or 4 a.m.
CN
UPDATE Issued at 644 PM CDT Wed Sep 26 2018
Updated aviation discussion.
&&
.SHORT TERM...(Tonight through Friday night)
Issued at 200 PM CDT Wed Sep 26 2018
The surface cold frontal boundary has pushed thru the FA, but is
not too far away...stretching from eastern Ky southwestward across
central Tn. It is progged to sink very slowly to the south and
east with time. Even so, overrunning clouds may still impact,
mainly, our southeastern counties. In addition, mid to upper level
sourced moisture/clouds are possible as upper wind core steers
across the mid Mississippi river valley, as an H5 2ndary trof
makes passage during the next 24 hours. This may squeeze out an
isolated shower even, but at this writing, we`re leaning toward a
silent Pop, and leaving the forecast dry. Otherwise we see surface
high pressure take over the entirety of the lower Ohio and Mid
Mississippi river valley thru the remainder of the short term.
12z modeling of the drier air behind the front, is not as robust
with the thrust of 40s dew points into/across the area. Still, it
will be our first good taste of Fall, as 47-50F dew points have
already entered our northwestern counties. These will extrapolate
southeastward with time, as we see still mid 60s dew points
existing at this writing across our southeastern counties. By
trmw, we`ll all range right around 50F. Temps will be cool as Lows
drop to/thru the 50s each night, and Highs in the 60s/70s warm
slightly by week`s end with a little more sun on Friday.
.LONG TERM...(Saturday through Wednesday)
Issued at 200 PM CDT Wed Sep 26 2018
Good model agreement lends to high confidence to start the long term
portion of the forecast. Confidence decreases somewhat towards the
beginning of next week with greater model variability.
Starting with the weekend, dry weather is forecast to persist as an
expansive area of high pressure migrates southeast from the Great
Lakes into the Ohio Valley and Mid Atlantic. As this occurs, expect
a gradual warming trend through the period while an upper level
ridge builds across the southeastern U.S. High temperatures should
moderate from the 70s on Saturday back to near 80 Sunday and Monday
and then perhaps the mid 80s by Wednesday. Lows are forecast to warm
from the mid 50s Saturday night back into the 60s through the rest
of the period.
As southerly flow develops on the back side of the departing high,
return moisture could result in a small chance of showers and
thunderstorms early in the new week. However, models are not in the
best agreement on exactly how and when this occurs. As a result, we
will keep just a small chance across much of the area Monday into
Tuesday.
&&
.AVIATION...
Issued at 644 PM CDT Wed Sep 26 2018
VFR conditions are expected across most of the area through the 24
hour TAF period, including the TAF sites. The only possible
exception to this will be the southern Pennyrile region where cloud
bases may drop below 3000 feet in the afternoon. Some shower
activity is possible across most of western KY Thu morning, with no
significant vsby restrictions expected. Generally light northerly
winds will veer to a more easterly direction by Thu afternoon.
Increasing clouds tonight will be on the wane by Thu evening.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$