Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/22/17
See below for an aviation forecast discussion for the 00Z TAFs.
&&
.SHORT TERM...(This Evening through Friday Afternoon)
Issued at 336 PM CDT Thu Sep 21 2017
High pressure has now slid well off to the east, with low pressure
centered over Colorado, with a boundary extending from it northward
over western South Dakota. This boundary will push very slowly
eastward tonight to becoming situated from northwest Minnesota to
south central South Dakota. Instability looks to increase across the
far eastern CWA and into Minnesota later this evening into the
overnight hours, along with a developing 45-55 knot LLJ. May see
some strong thunderstorms develop at this intersection, mainly over
the far northeastern CWA around or after midnight. Quiet conditions
are expected during the daytime hours on Friday as the LLJ
diminishes and the shear weakens.
Will see a decent temperature gradient both tonight and Friday, with
much cooler air behind the front. Lows tonight will range from the
upper 40s over north central South Dakota, to the upper 60s over
east central Minnesota. High temperatures on Friday will range from
the upper 50s over north central South Dakota, to the upper 80s over
northeastern South Dakota and west central Minnesota.
.LONG TERM...(Friday Evening through Thursday)
Issued at 336 PM CDT Thu Sep 21 2017
Fairly good agreement over the long term pattern which features a
western CONUS upper low/trough and an eastern CONUS ridge. This puts
us in southwest flow aloft with several distinct waves lifting into
or just southeast of the CWA before the upper low opens and lifts
over the area Monday. In the low levels at the start of the period
we should be on the northwest side of the surface trough. That means
each wave will generate generally overrunning precipitation so have
minimized the mention of thunder for the most part, outside the
initial round of severe weather that develops friday night. 850mb
temperatures remain between +6 and +14C for the extended, so high
temperatures will be stuck in the 50s and 60s for the next few days.
There does looks like, with high pressure overhead and despite a
trough overhead, no waves passing through, that we will see ideal
radiational conditions Wednesday morning. Thus, lowered
temperatures a notch below blended guidance. Otherwise no
significant changes over blended guidance within the extended.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 631 PM CDT Thu Sep 21 2017
VFR conditions expected to persist into the overnight hours before
the potential for sub-vfr stratus (perhaps even some areas of fog)
sets up. Remarkably high dewpoint air exists at the surface from
the James River valley eastward into MN. Once the surface
trof/cold front begins to slow down over central/northeast South
Dakota tonight and surface low pressure begins to deepen along
it, the potential for low level saturation really ramps up, per
the latest RAP Refresh output. For now, have introduced a low
cloud deck at all four terminals late tonight/early Friday
morning.
There is also the potential for isolated/scattered elevated
thunderstorms tonight at or after 06Z which may travel over/near
the KATY (lesser chance at KABR) terminal before convective
potential refocuses east into MN Friday morning. Low level wind
shear potential exists tonight, as well, at the KATY terminal,
where the nose of the low level jet will be focused.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
&&
$$
UPDATE...Dorn
SHORT TERM...Parkin
LONG TERM...Connelly
AVIATION...Dorn
Area Forecast Discussion
National Weather Service Bismarck ND
1019 PM CDT Thu Sep 21 2017
.UPDATE...
Issued at 1012 PM CDT Thu Sep 21 2017
CAMs pushed up the timing of possible convection closer to 12Z so
POPs were adjusted for this. SREF t-storm probs continue to depict
thunderstorm potential increasing after 09Z across southern ND
then expanding northward with time. Shear profiles within the
elevated instability ranges from 50-65Kts. Would not be surprised
to see a few stronger storms near warning-worthy given all the
ingredients in place. Time will tell. Products were updated to
increase the t-storm potential wording.
UPDATE
Issued at 705 PM CDT Thu Sep 21 2017
Forecast through this evening remains on track.
For the overnight period (after midnight), models are showing a
band of precipitation forming across southwest and south central
ND 9-12Z as a ribbon of instability lifts north along the
frontogensis zone north of the surface low across SD. Modified
POPs to better reflect this. SREF thunderstorm probs start to ramp
up as well after 09Z and remains rather high through the day
Friday. Coupled with SPC having the entire state in at least the
general t-storm outlook, I spread isold thunder across the board
Fri aft. Will take a closer look at the nocturnal showers as I
may need a mention of thunder as early as 9-12Z if model MUCAPE
projections are accurate. ESRL HRRR and NAMNest also trigger
convection early Friday morning. The ESRL HRRR as early as 1145Z
and the NAMNest 14Z. Right now I have isold thunder in the
forecast starting at 15Z for the southwest and south central.
&&
.SHORT TERM...(This evening through Friday)
Issued at 307 PM CDT Thu Sep 21 2017
An upper level trough over the western U.S. into southern Canada
will influence the weather over the northern plains over the next
several days. Tonight, jet energy propagating through broad
southwest upper flow will continue to produce an area of light
showers/virga extending from south central MT into northwest and
far north central ND. Associated surface low pressure from central
North Dakota into southwest South Dakota will push slowly east.
Strong southerly winds over the James River Valley, ahead of the
surface trough, will diminish late this afternoon and evening.
Capping over this same region is expected to inhibit any
afternoon/evening convection despite a moderately unstable
atmosphere.
Moderate to strong 700-500mb frontogenesis develops tonight over
a good portion of central and northwest ND north of the surface
trough. Although synoptic scale forcing is not strong, it does
persist over this same area. Global models have been persistent
the last couple of runs in developing a band of light
precipitation over western and central ND late tonight into friday
morning, which is handled well with the current forecast.
Continued surface and mid level forcing along the surface front,
combined with upper level divergence over the region, will
support an area of thunderstorms Friday, but most likely just to
the south and east of the forecast area. Although we will need to
monitor the southern James river valley for possible thunderstorm
activity in case there is some north and/or westward shift to the
surface boundary. Most of the CWA will be cooler on Friday (50s
and 60s) but the southern James River Valley could see some
readings near 80.
.LONG TERM...(Friday night through Thursday)
Issued at 307 PM CDT Thu Sep 21 2017
Cool and showery weather remains through the upcoming weekend and
into early next week. Highs mainly in the 50s and lows generally
in the upper 30s to mid 40s. Substantial cloud cover should
inhibit any widespread frost, but will certainly have to monitor
the western half of ND in case we would happen to clear out more
than expected.
Precipitation chance wane as we head into the middle of next week
but we remain at or below seasonable normals.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 705 PM CDT Thu Sep 21 2017
MVFR ceilings will lift northward into North Dakota after 12Z
Friday bringing MVFR ceilings to KJMS and KBIS by 15-18Z. MFVR
ceilings will also be possible for KDIK and KMOT after 18Z.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...NH
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...NH
Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
729 PM MDT Thu Sep 21 2017
.UPDATE...
Issued at 729 PM MDT Thu Sep 21 2017
Winds are dropping off as the boundary layer decouples most
locations. With diminishing winds and humidity rising with cooler
temps, have allowed the Red Flag Warning to expire on time. No
other changes at this time.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 248 PM MDT Thu Sep 21 2017
Main forecast concern through the aftn will continue to be the
critical fire weather conditions across lower elevations of
southeast Wyoming. Deep southwesterly flow and very dry midlvls is
causing dewpoints to drop well below the consensus guidance, with
the HRRR really the model to capture the very low RH values (8-12
percent). The Red Flag Warning is in good shape with even some
extreme Red Flag conditions to the west of the Laramie Range where
gusts to 30-40 kt are occurring. Highly amplified upper trough
will remain rather stationary on Friday with the axis across the
Great Basin. Temps will be around 10-15 degrees cooler on Friday
over the CWA, ending fire weather concerns. With increasing large
scale ascent ahead of the trough during the aftn/evening,
scattered showers and isolated thunder will be possible over
mainly southeast Wyoming. The models continue to show excellent
upper level divergence and overrunning over the llvl front by
Saturday afternoon/evening. Raised PoPs to above 60 percent on
Saturday aftn with the good model agreement. Wet bulb zero heights
through 00Z Sunday stay mostly above 11000-11500 ft, so only the
higher peaks of the Sierra Madre and Snowy Ranges will see any
chance of snow through 00Z Sunday.
.LONG TERM...(Saturday night through Thursday)
Issued at 248 PM MDT Thu Sep 21 2017
Closed mid/upper level low will be located over southern Utah
early Saturday night. To the east a broad area of upper diffluence
combined with a low level frontal zone over our Panhandle
counties will contribute to widespread moderate rainfall
especially over the plains. Best forcing for ascent will push
north and east of the area by Sunday morning with some drying
aloft noted on forecast soundings. With the low level NE flow and
weak overrunning, Sunday should be a cloudy and cool day with
little temperature recovery continued the trend of undercutting
MOS guidance a bit.
Models have come into a bit more agreement in the mid level low
weakening and moving to the north and east directly over central
Wyoming Sunday night through Monday. This track is not typically a
good one for low elevation snow in SE Wyoming. Models have
continued the trend of keeping the colder air at bay to the west
until the precipitation rates begin tapering off late Sunday night
and Monday morning. So while a period of accumulating snowfall in
much of the Snowy and Sierra Madre ranges is likely Sunday into
Sunday night, accumulating snowfall in the lower elevation is
becoming less likely. Still expect some rain/snow mix or maybe a
brief period of all snow for the higher valleys west of the Laramie
Range late Sunday night into early Monday morning but the steadier
precipitation should be ending by that time and boundary layer
temperatures would be marginal for much accumulation.
Tuesday through Thursday look basically dry and seasonable as the
upper trough pushes east and some ridging rebuilds along the west
coast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 729 PM MDT Thu Sep 21 2017
VFR expected overnight with winds dropping off to less than 20 kts
most spots with the exception of the usual late dropoff at Rawlins
and the overnight increase we have been seeing the past several
nights at Chadron where gusts around 25 kts will continue well
into the late evening. We brought in some vicinity mention for
Rawlins tomorrow afternoon for showers as the southwesterly upper
flow moistens across the western zones.
&&
.FIRE WEATHER...
Issued at 248 PM MDT Thu Sep 21 2017
It will continue to be a warm, very dry, and breezy afternoon over
much of southeast Wyoming. A Red Flag Warning remains in effect
through the early evening for Fire Weather Zones 304, 306, 308, 309,
and 310. Fire weather concerns will be minimal after this
afternoon. Cooler temperatures on Friday will cause RH values to
stay mostly above 25 percent. It will turn much cooler over the
weekend with good chances for widespread precipitation.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...JG
SHORT TERM...ZF
LONG TERM...DEL
AVIATION...JG
FIRE WEATHER...ZF
Area Forecast Discussion
National Weather Service Grand Forks ND
717 PM CDT Thu Sep 21 2017
.UPDATE...
Issued at 712 PM CDT Thu Sep 21 2017
HRRR had indicated a few cells developing in NW MN at 00z... and
there was one shower nr Waskisk that formed nr 23z. Otherwise have
considerable high based stratocu in warm advection zone over the
fcst area. Quite strong low level moisture push early this evening
with 60 dew pts into Fargo and 70 dew pt into Elbow Lake. For
Fargo this is a good 15 deg rise in the last few hours. Actual
frontal boundary east of Langdon to Crary ND to Carrington and
moving southeast. Low level moisture will stream northward ahead
of this boundary. Low level jet cranks up 06z-09z period with nose
of the jet into WC/C MN. HRRR indicates some thunderstorms in far
NE SD into WC MN 08z time period...moving quickly ENE. This
conforms to the fcst for now so will not change.
&&
.SHORT TERM...(This evening through Friday)
Issued at 330 PM CDT Thu Sep 21 2017
A couple areas to watch for potential pcpn tonight. One area will
be mainly over northwest minnesota early this evening in zone of
enhanced warm advection ahead of approaching surface boundary
which will reach the northwest by early evening. Appears to be a
weak impulse from water vapor over sw ND which may also assist in
upper support. Convective parameters weak so may be mainly shra vs
T. Of more concern will be later tonight initially over the far
south spreading e-ne during the early morning. During mid- late
evening a low level jet will strengthen with favored convergence
vcnty tri-state border region. This area will also be under zone
of maximized warm advection. Capping may initially retard
development however cap weakens during the late evening. Although
storms will be elevated cannot rule out a few storms reaching
severe limits. Minimum temperatures will remain mild overnight
over all but the far nw with thermal ridge axis in place, warm
advection and low level moisture flux.
On Friday, the frontal boundary will drift to a BDE-ABR line. As a
mid level impulse lifts northeast during the day an associated
surface low will propagate ne along the front reaching the tri-
state border region by evening. Unsure at this time how much
convection will be occuring during the day. Current guidance
hinting that most pcpn during the day will be on the cold side of
the boundary. By late afternoon with approaching wave convection
should initiate vcnty boundary. Convective parameters sufficient
for severe storms and with approaching surface low/triple point
over the far s/se cannot rule out a tornado.
.LONG TERM...(Friday night through Thursday)
Issued at 330 PM CDT Thu Sep 21 2017
Storms which develop Friday afternoon should propagate e-ne
through the evening as the surface low continues to lift along
boundary. With front nearly stationary and precipitable h2o values
of 1.5 inches or greater will have to watch for heavy rainers in
addition to severe.
On Saturday/Saturday night boundary sags to the far s-e forecast
area. Another surface low and upper wave will lift northeast
bringing a continue threat for rain mainly over the southeast half
of the fa.
The upper level low centered around the four corners region will
keep the Dakotas largely in southwest flow aloft continuing to draw
moisture up from the south. Mid level waves of energy will ride
within the southwest flow over the region utilizing the available
moisture. In the low levels, a southwest-northeast oriented stalled
front draped over Minnesota will serve as a focal point for
moisture to overrun upon. Steady rainfall will be possible for west-
central and northwestern Minnesota as well as within southeastern
North Dakota Sunday with a gradual tapering off of rainfall chances
from north to south Monday. The upper level low is then progged to
shift eastward over the region bringing another wave of energy over
the area towards Tuesday, although moisture return will not be as
great as Sunday`s forecast. Conditions finally start to dry around
Wednesday into Thursday as a high pressure builds into the region.
With the forecast area expected to remain on the northern side of
this front along with northerly flow, cool and cloudy conditions are
expected through at least Tuesday with highs remaining largely in
the 50s. Somewhat milder temperatures return Wednesday and Thursday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 712 PM CDT Thu Sep 21 2017
Issue this period is wind shift with cold front sagging
southeast...and development of likely low clouds overnight into
early Saturday ahead of front into Fargo-Bemidji eastward.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&
$$
UPDATE...Riddle
SHORT TERM...Voelker
LONG TERM...CJ/JK/Voelker
AVIATION...Riddle
Area Forecast Discussion
National Weather Service Green Bay WI
1059 PM CDT Thu Sep 21 2017
Updated aviation portion for 06Z TAF issuance
.UPDATE...
Issued at 932 PM CDT Thu Sep 21 2017
Updated forecast grids to include widespread dense fog over the
east, lake and bay. This matches the dense fog/marine dense fog
advisory areas. Also downplayed the PoPs for at least the next
several hours.
&&
.SHORT TERM...Tonight and Friday
Issued at 258 PM CDT Thu Sep 21 2017
A warm front was lifting into southern MN and southwest WI
this afternoon. A band of low clouds was persisting north
of this boundary, and moving northward through GRB CWA.
Temperatures were in the low to mid 70s within the cloud band, but
in the upper 70s to lower 80s where there was sunshine. Despite
SBCAPE of 1000-1500 j/kg across the region, CINH of 75-100 j/kg
was capping off any convection.
The warm front is expected to lift north across the region tonight
and Friday morning. The front, combined with a developing 30-35 kt
low-level jet, should trigger isolated elevated thunderstorms
north of the boundary, as H8 LI`s of -3 to -5 C advect into the
region. Storms may be a bit more numerous over north central WI,
as some weak short-wave energy and the RRQ of 50-60 kt jet brush
past later tonight. SPC still has a small part of north central WI
in the Marginal risk for severe storms tonight, and this seems
reasonable, as deep-layer shear is strongest there (around 30
kts). Have added patchy fog across most of the region overnight,
with areas of fog in far northeast WI and on Lake Michigan, where
marine fog is already occurring.
The warm front will lift into the Upper Peninsula of Michigan
on Friday, ending the threat of thunderstorms. The resulting
clearing and gusty southwest winds will lead to strong heating,
with mixing through 900-875 mb supporting high temperatures
in the middle 80s to lower 90s, much above normal.
.LONG TERM...Friday Night Through Thursday
Issued at 258 PM CDT Thu Sep 21 2017
An amplified pattern will be in place for the conus until early next
week, thanks to a deep trough over the western U.S., and a ridge
over the east. The pattern does translate east, which will signal a
pattern change by the middle of next week across the region.
Although there are some timing differences in regards to when this
pattern change occurs, models are generally in good agreement this
far out, so will continue to use a multi model blend for this
forecast.
Friday night through Sunday...With a cold front nearly stationary
over Minnesota, and a warm front extending east over Lake Superior,
the entire region is expected to be located in the warm sector
during this period. With mostly clear conditions and a breezy south
wind, temperatures will likely range from 15 to 20 degrees above
normal. Saturday should be warmer than Sunday, when a few 90s are
possible in the warm spots. Heat indices in the low to mid 90s on
Saturday will fall back to the upper 80s on Sunday.
Rest of the forecast...Sunday night continues to look quiet and
warm. Then precip chances will gradually increase from west to east
on Monday and Tuesday when a cold front drifts closer to the region.
Storm chances look the highest on Tuesday along this front, but its
too early to assess a severe threat. More seasonable temps return
behind the front for midweek.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1059 PM CDT Thu Sep 21 2017
Plenty of issues just in the short term make this a low confidence
forecast. Rain that most of the synoptic scale models had reaching
the area by 06Z at the latest, has not yet developed. HRRR had a
few specs in central/north central Wisconsin on the simulated
reflectivity product, but just for a couple of hours and then
nothing moves in until around 14Z when showers and storms reach
Vilas County. In the mean time mostly clear skies prevailed, but
dew points were well into the 60s and it will not take much for
temperatures to drop enough for fog development. IFR/LIFR
conditions in dense fog prevailed close to Lake Michigan and the
fog could advect farther inland overnight.
Will go with mostly MVFR and/or IFR conditions in fog at most
locations overnight. Some low ceilings may also develop. Plan to
bring showers and storms in during the morning and continue them
east into the afternoon.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CDT Friday for WIZ022-040-050.
&&
$$
UPDATE.........MG
SHORT TERM.....Kieckbusch
LONG TERM......MPC
AVIATION.......MG
Area Forecast Discussion
National Weather Service San Joaquin Valley - Hanford CA
230 PM PDT Thu Sep 21 2017
.SYNOPSIS...Scattered showers will continue over the mountains
through this evening as an upper trough to our east keeps
unsettled conditions over the area. Winds will also be strong and
gusty through and below the mountain passes into this evening.
Temperatures will be cooler than normal across the area through
the upcoming weekend as the trough remains over the Great Basin. A
slow warming trend will take next week as highs pressure slowly
builds inland into the region.
&&
.DISCUSSION...Cold front pushed through central CA earlier today
and brought widespread precipitation to our area overnight and
this morning. Several locations in the Southern Sierra Nevada
picked up between half and inch to an inch of rainfall with a few
locations in and near Yosemite Park picking up over an inch of
rain. The precipitation mainly fell as snow above 11000 feet, but
the snow level lowered to 7000 feet by daybreak in the cooler
post-frontal airmass. In the San Joaquin Valley a few locations
measured close to 0.40 inches, but most locations picked up a
tenth of an inch or less. Although the front has now moved out of
our area, radar composites are indicating scattered instability
showers have developed over the Southern Sierra Nevada this
afternoon. Isolated thunderstorms will also be possible in the
Yosemite Park area as the HRRR is showing CAPE and instability are
sufficient for thunderstorm development today. The main concern
through through this evening will be strong winds over the ridge
tops and below the passes in the Kern County Mountains and Deserts
where gusts up to 75 mph will be possible through this evening. A
High Wind Warning remains in effect for these area through 1100
pm PDT this evening. Breezy conditions are also expected along the
I-5 corridor and below the passes along the west side of the San
Joaquin Valley through this evening as well and a Wind Advisory
remain in effect until 1100 pm PDT for the west side of the San
Joaquin Valley.
WRF indicating a deep upper trough will remain situated over the
Great Basin tonight through Satruday with a cyclonic flow aloft
prevailing over Central CA through Friday Night. This will result
in much below normal temperatures across our area on Friday. Other
than some upslope clouds on the valley facing slopes of the
mountains skies should be mostly clear on Friday. There will be a
slight chance of afternoon and early evening showers over the
Southern Sierra Nevada on Friday as instability remains
sufficient.
An upper ridge will begin to push inland on Saturday and bring
about a slow warming trend across our area over the weekend.
However temperatures will remain below seasonal normals as a cool
northerly flow prevails over Central CA as we remain situated in
between the trough over the Great Basin and the ridge off the CA
coast.
The medium range models are in good agreement with the ridge
building inland next week as the the trough finally moves east
toward the central CONUS. Rises in heights and thicknesses will
result in a warming trend with temepratures rising to above normal
levels by next Tuesday and continuing to rise through the
remainder of next week. High temperatures in the San Joaquin
Valley, lower foothills and the Kern county desert will be in the
90s during the second half of next week while the nights will be
relatively cool (mid 50s to mid 60s). RH progs are indicating no
signs of significant moisture impacting our area next week and as
a result a dry forecast will remain in place.
&&
.AVIATION...Scattered showers will produce areas of MVFR and
local terrain obscurations over the southern Sierra Nevada through
03Z Friday, while lingering upslope clouds will persist along
north and west facing slopes of the Kern County Mountains through
12Z Friday. Winds will gust near 35 knots along the west side of
the San Joaquin Valley and near 50 knots over the Kern County
mountains and deserts through 06Z Friday. Areas of MVFR and local
IFR visibilities will be possible in blowing dust from the gusty
winds. VFR conditions are otherwise expected over the Central CA
interior during the next 24 hours.
&&
.AIR QUALITY ISSUES...None.
&&
.CERTAINTY...
The level of certainty for days 1 and 2 is medium.
The level of certainty for days 3 through 7 is medium.
Certainty levels include low...medium...and high. Please visit
www.weather.gov/hnx/certainty.php for additional information
an/or to provide feedback.
&&
.HNX Watches/Warnings/Advisories...
High Wind Warning until 11 PM PDT this evening ABOVE 1500 FEET
FOR CAZ095-098-099.
Wind Advisory until 11 PM PDT this evening CAZ089-091.
&&
$$
public...DS
avn/fw...Bean
synopsis...DS
weather.gov/hanford
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
907 PM CDT Thu Sep 21 2017
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Extended pops in the Golden Triangle area for another hour as
showers continue to slowly dissipate in that area currently.
Otherwise, the 00z sounding showed a decrease in precipitable
water and so do not expect fog to be as widespread as past
mornings. /10/
Prior discussion below:
SHORT TERM...Tonight through Friday...
Latest RAP satellite imagery showed the area showed the region under
an upper ridge which extended through the Lower Mississippi Valley
as well as under a shear axis over the southern areas which extended
from an upper trough over the eastern seaboard. Also a weak
shortwave was pushing across the region from the east. This combined
with some cooling aloft and some low level moisture had triggered
isolated showers and thunderstorms across the south. With 6-7c lapse
rates we may see a few strong storms with some gusty winds for the
remainder of the afternoon. Expect the weak shortwave to exit the
region by late tonight. The isolated showers should dissipate by 00z.
For later tonight expecting another round of patchy fog prior to
dawn across the northwest delta and the south which will lift by
14z. Another weak shortwave will push through on Friday. Return flow
ahead of this feature will trigger isolated to scattered showers and
thunderstorms mainly during the afternoon. Lapse rates look a little
weaker as far as strong strong potential is concern.
As far as temperatures are concern readings will continue to be
above normal. Lows will be in the upper 60s to lower 70s. Highs will
be in the lower 90s. Heat indices will range from the middle to
upper 90s./17/
Friday night through mid week next week...
Not much change in the forecast is expected over the next several
days as temperatures in the region will remain above their late
September averages under a humid airmass. The chances of diurnal
thunderstorm activity will also be present each day during the
period. There will only be slight changes in the upper level
pattern over the weekend with the deep troughing over the western
CONUS and ridging over the east. A broad, weak upper low will
begin to develop underneath the ridge, becoming centered over the
northern Gulf Coast by Sunday. At the surface, the ArkLaMiss will
remain on the western periphery of a broad surface high that will
encompass the eastern half of the CONUS. Pwats will range between
1.3"- 1.9" through the period. Long term models suggest a front
will finally sweep through region late next week bringing with it
organized chances of rain/storms and cooler temperatures in its
wake.
&&
.AVIATION...
00Z TAF discussion:
Vcty SHRAs were noted at GLH at 2315Z and a few SHRAs wl come in
vcty of GTR before dissipating by 01Z. VFR conds wl prevail at
most sites tonight. The exception wl be in the south where MVFR
vsbys wl be psbl 10Z-13Z. After 13Z VFR conds are expected to
prevail Fri until around 20Z when isold TSRA activity may come in
vcty of cntrl and s TAF sites. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 70 93 70 89 / 7 32 12 18
Meridian 70 92 69 89 / 10 34 16 18
Vicksburg 71 92 70 91 / 4 24 9 17
Hattiesburg 69 92 69 89 / 7 33 18 21
Natchez 71 92 69 89 / 5 31 13 18
Greenville 70 93 70 91 / 3 9 4 17
Greenwood 70 93 70 90 / 7 11 4 17
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
918 PM CDT Thu Sep 21 2017
.UPDATE...
918 PM CDT
Going forecast largely on track with just some mainly cosmetic
changes.
Did nudge temps up just a hair tomorrow. Forecast thermal profiles
tomorrow are actually similar, to if not a hair warmer than,
today. Cloud cover won`t be an issue over western CWA tomorrow, so
look for highs several degrees warmer than today. Eastern half of
the area, including Chicago area should see temps similar to
Thursday if not a degree or so warmer. Afternoon lake breeze
should provide some cooling near the lake in the afternoon, but
highs away from the lake should climb into the mid 90s, likely
breaking another record and tallying up another day in the ongoing
streak of consecutive 90 degree days.
- Izzi
&&
.SHORT TERM...
224 PM CDT
Through Friday...
Late September heat remains the main focus of the forecast in the
near term. New record high temp already set today at O`Hare with
a 94 degree reading there.
Midwest remains along the periphery of highly amplified upper
level ridge axis, downstream of a deep long wave trough across
western NOAM. 12Z RAOB from DVN indicated 850 mb temp of +20C, and
a 925 mb temp of +26C, resulting in low-mid 90 degree temps across
the region. Residual high cloud cover from decaying MCS over
southeast IA/northeast MO has kept temps slightly lower across
western parts of the cwa, though a decrease in the denser cirrus
has temps approaching 90 there as well this afternoon. Of course
the weak surface pressure gradient in the vicinity of the
stationary front just north of the cwa has allowed a lake breeze
to push inland across far northeastern IL, keeping temps in the
mid-upper 80`s for areas near the lake.
Recent runs of the HRRR indicate the potential for isolated
thunderstorm development across mainly the southern parts of the
cwa late this afternoon. Experimental ESRL HRRR also hints at this
though with much lower coverage. It appears these models may be
focusing on a remnant MCV from the IA/MO convection, though no
distinct circulation is noted in water vapor imagery. While
current RAP mesoanalysis depicts 3000 J/kg of MLCAPE and little
cin across the southern tier of cwa counties, weak flow and
fairly shallow cu field per GOES-16 vis imagery suggests these
models may be quite overdone with thunderstorm potential.
Maintained less than 20 percent pops through sunset, but may have
to add an isolated mention if cu field becomes more impressive or
something pops.
Another mild night is in store for the region with persistent
light south winds and unseasonably high dew points. Overnight mins
should remain in the 70`s in most locations, which will also give
a warm head start for temps on Friday. Less cloud cover and
similar low level thermal field should allow highs in the low
90`s in most spots again Friday afternoon, again at or near record
levels for September 22nd. (records for tomorrow are 92 for
Chicago, 93 for Rockford) Weak southeasterly lake breeze should
again keep temps in the 80`s right along the lake.
Ratzer
&&
.LONG TERM...
Friday night through Thursday...
218 pm...The models continue to show slight thermal cooling this
weekend but this will likely have little if any noticeable
affects as overnight lows remain in the 60s...low 70s
downtown...and highs in the upper 80s/near 90 Saturday/Sunday.
Bumped temps up a few degrees to near current guidance values.
Lake breezes are possible both days which will keep the immediate
lakeshore areas cooler but confidence is low regarding how strong
these lake breezes may be and how far inland they will move.
Forecast highs are cooler near the lake but trends will need to be
monitored as these time periods approach. Highs may still reach
the upper 80s before temps cool and winds shift off the lake.
There is still some potential that the models are cooling the
airmass too fast and if that were to occur...highs could still be
a few degrees warmer than currently expected this weekend.
However by early next week it does appear that the entire airmass
will cool enough for highs to remain in the 80s. Additional cloud
cover...perhaps a more broken afternoon cu field...may also help
put a lid on high temps...keeping them in the 80s.
A cold front will move across the area Tuesday night into
Wednesday next week. While an isolated shower is possible any
afternoon from Sunday onward next week...this front will be the
next best chance of rain for the entire area. However...not
confident on how widespread precip will become and its possible
just scattered precip in a narrow time window moves across the
area ahead of the front. Though a slower front...that arrives
later into Wednesday could allow for more daytime heating and
thus better precip coverage. This front will allow much cooler air
to spread across the area with highs back into the 70s. A second
push of colder air is possible late next week. cms
&&
.AVIATION...
For the 00Z TAFs...
Lake breeze came close to ORD, but has begun to retreat and no
longer poses much of a threat of making it through this evening.
Will probably be another lake breeze tomorrow, but opting to go
with persistence for now and not include a wind shift at the
terminals. Otherwise, other than possibly some patchy ground
fog/MVFR VSBY at DPA early Friday morning, not anticipating any
significant weather at the terminals through this TAF cycle.
- Izzi
&&
.MARINE...
218 pm...A weak cold front has stalled over south/central
portions of Lake Michigan this afternoon. This front will lift
back north as a warm front tonight...shifting light winds back
southerly. A large trough of low pressure will remain nearly
stationary over the plains through early next week maintaining
southerly winds over the lake. This trough/front will move across
the Great Lakes region Tuesday night into Wednesday shifting winds
northwest with a period of 15-25 kts expected. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Midland/Odessa TX
600 PM CDT Thu Sep 21 2017
.AVIATION...
00Z TAF issuance
Convection across the area will diminish over the next hour. VFR
conditions will prevail through most of tonight before low cigs
move in across the Permian Basin. Have included FM groups and
tempos for MVFR and IFR conditions everywhere except KCNM and
KFST. VFR conditions will return late Friday morning along the
gusty southeast winds.
&&
.PREV DISCUSSION... /issued 204 PM CDT Thu Sep 21 2017/
DISCUSSION...
Mid level flow across the desert SW continues to back in response to
an approaching trough. Meanwhile across W TX/SE NM se surface winds
have been increasing on the periphery of the mid level height falls.
Increased moisture is evident on 12Z MAF soundings with a 24hr
change in PW from .84" to 1.1". Still low level moisture is shallow
and even though the instability axis will be farther w today there
will be some CINH to overcome. 12Z NAM12 is downplaying convection
while HRRR does show diurnally driven initiation across PB from
around Girvin-ODO/MAF-Lamesa around 21Z, which we tend favor with
T/Td (M90s/N60). A few strong storms are again possible. By Fri PM
SW mid level flow will have pulled up a theta-e ridge axis which
will become increasingly rich. Showers/storms will light up within
this axis Fri, especially from GDP Mtns-Eddy Co Plains and they
will have a good chance to persist into the morning. Local heavy
rain will be possible there. Into the Sat the mid level
flow/theta-e ridge will have an especially long fetch while edging
farther e to encompass much more of the Trans Pecos/SE NM, which
will be the favored area for rain, again some heavy rain even thru
thru Sat night. Sunday with mid level moist plume now stretching
from the BB Region thru the Panhandle the PB have much a better
chance for rain. PWs within the moist axis will be +1 to +2
standard deviations and heavy rain will be possible, if not
favored and flash flood watches are likely to eventually be
warranted? The slow movement of the moist axis will favor the
interaction with a cold front that is expected to arrive late Mon
PM or early Tue AM. Even the ECMWF which typically doesn`t produce
much nocturnal precip is very wet Mon night/Tue AM. On Tue there
is the potential for very favorable positioning of the upper jet
to exacerbate heavy rain/flooding concerns. Of course hard to say
just where that precip will be maximized, but SE NM-SW parts of
the S Plains-PB are all in the mix. By Sunday the recent hot spell
will be a distant memory and high temps will be normal to below
normal into next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
Big Spring 72 92 70 88 / 20 0 10 20
Carlsbad 68 93 66 86 / 10 30 50 70
Dryden 74 92 72 89 / 20 0 10 10
Fort Stockton 71 93 70 88 / 20 10 10 30
Guadalupe Pass 67 87 64 81 / 10 30 50 50
Hobbs 66 90 64 84 / 10 10 20 50
Marfa 60 90 61 85 / 20 20 10 50
Midland Intl Airport 72 92 70 88 / 20 0 10 20
Odessa 71 92 70 88 / 20 0 10 30
Wink 71 95 69 89 / 20 10 10 40
&&
.MAF WATCHES/WARNINGS/ADVISORIES...
NM...None.
TX...None.
&&
$$
99/99/29
Area Forecast Discussion
National Weather Service Medford OR
804 PM PDT Thu Sep 21 2017
.DISCUSSION...
Forecast is on track with isolated showers still lingering from
what KMAX can see. The more tricky part of tonight`s forecast is
the possibility of fog in the valleys. There appears to be
sections of clearing given what the infrared satellite was
showing near the Willamette valley. However, latest guidance
suggests that the dew point depression, difference between
temperature and dewpoint, will just be too large to support
shallow fog. Part of this is probably because of the high level
clouds lingering around. Because of this, we removed fog from the
forecast.
Other than the fog, models show showers still lingering on the
east side tonight. It`s looking very isolated as there appears to
be broad atmospheric decent in northern Oregon at the moment.
See previous discussion for more information on the upcoming
weather pattern change. -Smith
&&
.AVIATION...21/18Z TAF CYCLE...VFR will prevail into late this
evening and partial terrain obscurations will persist and local MVFR
is possible in rain showers. IFR/MVFR ceilings and visibilities will
be possible tonight but confidence is not as high as previously
thought due to persistent cloud cover tonight. If IFR cigs do
develop late tonight, they are expected to lift quickly to VFR by
mid Friday morning. -FB
&&
.MARINE...Updated 730 PM PDT Thursday, 21 September 2017... Steep
seas will return this evening for areas beyond 10 nm of the coast.
Winds will be light today as weak low pressure drifts southward
through the coastal waters bringing with it more showers. Late
Friday afternoon and evening, north winds and seas will begin to
build with small craft advisory level conditions expected for much
of the area south of Cape Blanco by Friday evening. This will begin
a prolonged period of northerlies that will maximize in strength
each afternoon and evening as thermal troughing returns. /FB
&&
.PREV DISCUSSION... /Issued 500 PM PDT Thu Sep 21 2017/
DISCUSSION...The upper trough axis is east of area which has
allowed things to quiet down considerably compared to this time
yesterday. However, there is a weak disturbance that is moving down
along the coast. Most, if not all the precipitation should stay
offshore, but could not rule out isolated through this evening. The
HRRR high res model does not much of anything through this evening.
Therefore we`ll keep isolated showers in the forecast with very
light QPF amounts. Plenty of cloud cover remains and that will be
the case through this evening. If we don`t get any breaks in the
cloud cover, there`s a chance we could set a new record for the all
time record low max temperature which is 61 set back in 1945. Right
now were at 58 degrees.
Most locations and hours will be dry tonight. Cloud cover should
dissipate some, but not a lot. Despite the cloud cover, were still
expecting temperatures to drop near or below freezing tonight
east of the Cascades and a freeze warning and frost advisory remains
in effect. Also could not rule out patchy fog in some westside
valley locations late tonight if there`s enough clearing.
Friday will be a transition day as the upper trough shifts east
with a dry northerly flow. Still could not rule out a few showers
along the northern Cascades and eastside, but they should be the
exception. Another cold night is expected Friday night east of the
Cascades and there will be less cloud cover and wind. So a freeze
watch and frost advisory will be issued, but this time it will only
be for southwest Klamath County, northeast Siskiyou and northwest
Modoc counties. Please see NPWMFR for details on the locations of
warnings, advisories and watches for tonight and again Friday night.
Dry and warmer weather returns this weekend as an upper ridge builds
over the eastern Pacific. At the surface, a thermal trough will
develop with increasing offshore flow in Southeast Oregon and
Western Siksyou County.
Confidence is high we`ll remain dry for all of next week with above
normal temperatures. The upper ridge is expected to gradually move
over our area Tuesday through Wednesday with continued dry weather
and max temperatures averaging close to 10 degrees above normal.
The models are in general agreement showing the ridge axis shifting
east late next week with some cooling as a weak front approaches the
coast. -Petrucelli
FIRE WEATHER...Updated 200 PM PDT Thursday, 21 September 2017....
The cold upper level trough that brought the wet, unsettled
weather over the area earlier this week will gradually move into
the Great Basin and the Intermountain West over the next 24-
48 hours. Mostly light to moderate northerly flow will persist on
the back side of this trough, and while this is generally a dry
flow for the area, isolated to scattered showers will persist.
Showers will be most numerous near the coast, inland west of the
Cascades, and in southern Lake and Modoc Counties through this
evening, then tend to diminish after midnight. Isolated
showers are still possible Friday and Friday evening, but any
amounts will be very light.
Meanwhile, high pressure offshore will begin to build into the area.
This will result in a thermal trough developing along and near the
coast. Light northeast winds associated with the development of the
surface thermal trough may begin as early as late tonight/early
Friday morning over the SW Oregon coast range and western Siskiyou
County mountains, but humidity recovery should again be very good.
The thermal trough will strengthen this weekend and result in east
to northeast winds each night and morning through at least Tuesday.
Nighttime humidity recoveries will gradually worsen and afternoon
humidity will likely lower to 20-30% across most of the forecast
area. Temperatures are expected to be 5 to 10 degrees above normal
and warmth will likely reach all the way to the coast (mainly south
of Cape Blanco) each afternoon.
With recent rainfall, models may be somewhat overdoing the amount
of drying, at least initially. So, for this weekend we`ve leaned
toward the consensus guidance rather than seeking the drier
solutions (as we were doing prior to the significant rainfall). We
have lowered minimum RH values slightly across the area early
next week.
At midweek, the thermal trough is expected to weaken and move
north/inland. As such, the northeast winds will abate and we`ll
expect more of a marine influence along the coast Wednesday onward.
It will remain dry and warm inland. Extended model guidance is
hinting at a potential (mostly dry) frontal passage late next week,
which could result in stronger afternoon winds, especially over the
east side. We`ll continue to monitor this for any trends.
CPC`s 8-14 day outlook as well as weeks 2-4 on the CFSv2 continue to
indicate enhanced probabilities of above normal temperatures and
below normal precipitation. So, a steady and long-duration warm and
dry period is expected, albeit tempered by the declining sun angle
associated with the changing of the seasons. Spilde/BTL
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...Frost Advisory from 2 AM to 9 AM PDT Friday for ORZ029>031.
Freeze Warning from 2 AM to 9 AM PDT Friday for ORZ029>031.
Frost Advisory from 2 AM to 9 AM PDT Saturday for ORZ029.
Freeze Watch from late Friday night through Saturday morning for
ORZ029.
CA...Frost Advisory from 2 AM to 9 AM PDT Friday for CAZ084-085.
Freeze Warning from 2 AM to 9 AM PDT Friday for CAZ084-085.
Frost Advisory from 2 AM to 9 AM PDT Saturday for CAZ084.
Freeze Watch from late Friday night through Saturday morning for
CAZ084.
Pacific Coastal Waters...Small Craft Advisory for hazardous seas until 11 AM PDT Friday
for PZZ370-376.
$$
CZS/MAP/FJB
Area Forecast Discussion
National Weather Service Melbourne FL
925 PM EDT Thu Sep 21 2017
.DISCUSSION...
Tonight...The models show a weak inverted trough over the Atlantic
pushing west and reaching the coast late. Low level northeast flow
is forecast to become more easterly while a band of higher moisture
pushes ashore. The HRRR model has been showing a batch of showers
arriving in the pre-dawn hours. The GOES total precipitable water
product does show this ribbon of higher moisture, but is followed by
an area with lower values. The 18z GFS actually did a fine job in
depicting this scenario and only generates sparse coverage while MOS
has a max of 20 PoPs along the coast. Don`t plan to make any
changes to our 30 PoPs for the coast though, as the GFS shows the
bulk of precip after 09z and the next forecast package can account
for higher rain chances.
Prospects for higher coverage look to be a good bet on Fri as a
trough aloft dropping into the northeast Gulf of Mexico provides
destabilization while east flow spreads deeper moisture across the
entire area.
&&
.AVIATION...Generally VFR conditions expected outside of isolated/
scattered showers approaching coastal terminals from the Atlantic
through the overnight hours. Friday looks like a more active day
for convection, with scattered showers and isolated storms. Coastal
terminals would have the main chances in the morning and early
afternoon, then inland terminals should have the highest chances in
the afternoon.
&&
.MARINE...
Tonight-Fri...The pressure gradient will continue to tighten between
high pressure over the eastern U.S. and Hurricane Maria which will
be gaining latitude near the 71W longitude line. Northeast-east
winds 10-15 knots should become easterly closer to 15 knots Fri
afternoon. The exercise caution threshold probably won`t be met
overnight, but will leave statements in the forecast since we`re on
the doorstep of a long period of small craft advisory conditions
from Maria swells and peripheral winds, starting by Friday night.
There will be an increase in showers on Fri and also expect isolated
storms.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Lascody/Sedlock/Combs