Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/21/17
Area Forecast Discussion
National Weather Service Bismarck ND
737 PM CST Fri Jan 20 2017
.UPDATE...
Issued at 735 PM CST Fri Jan 20 2017
Quick update to expand the Dense Fog Advisory into McLean, Mercer
and Oliver counties per webcam trends through 0130 UTC.
UPDATE Issued at 608 PM CST Fri Jan 20 2017
Based on surface observation and webcam trends through 23 UTC,
issued a Dense Fog Advisory for much of the James River Valley and
portions of south central North Dakota through 18 UTC Saturday.
Will continue to monitor trends through the evening for a
potential expansion of the advisory.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 216 PM CST Fri Jan 20 2017
A continuation of low clouds/fog/areas of light freezing drizzle
across mainly central North Dakota is the theme for the short term
period. Far western North Dakota will mostly be detached from the
worst of the fog and any freezing drizzle threat at this time.
Latest water vapor imagery shows an upper low circulating over the
far southern James River Valley, with a 994mb surface low over
Mobridge South Dakota. The RAP13 is slightly too deep with the
surface low, while the NAM/GFS are both a bit too weak as compared
to the current surface observations. However the main message is
for a near vertically stacked system to emerge over south central
North Dakota Saturday. Surface convergence right over central ND
with northwest winds across western ND, and southeast to east winds
in central ND. The result will be for more of the same with
clouds/areas of fog and light freezing drizzle initially. The HRRR
visibility product maintains a wides swath of fog continuing
through tonight in central ND. BUFKIT soundings indicate
supercooled water droplets in the saturated layer with enough
vertical motion for light freezing drizzle. Not a lot of change
until Saturday night before soundings begin to moisten through the
column. High temperatures Saturday will be similar to Fridays,
especially with the low cloud canopy remaining overhead.
.LONG TERM...(Saturday night through Friday)
Issued at 216 PM CST Fri Jan 20 2017
The vertically stacked system from the short term period gets
nudged eastward late Saturday night. Sounding profiles moisten up
through the column allowing for a transition from light freezing
drizzle/light freezing rain to light snow Saturday night into
Sunday. However vertical motion remains weak behind the departing
system, and despite a chance of pops in the forecast, actual
amounts of liquid precipitation will remain very little, up to a
hundredth or so. Thus, despite a chance of pops, only a few spots
will receive a tenth of an inch of snow Saturday night.
Shortwave ridging Monday will be followed by a chance of snow
Monday night through Tuesday. A low ejecting northeast from the
Great Basin and into the northern high plains will provide for a
chance of snow mainly confined to southern North Dakota. Pops are
mostly delineated along and south of Interstate 94. At this time,
both the GFS and ECMWF keep the bulk of snow south of North
Dakota. Forecast snow amounts of between 1 and 2 inches possible
in far southern North Dakota Monday night through Tuesday. Along
with the snow in the far south, some potential for blowing snow
with boundary layer winds from the north between 10 and 20 mph.
Wednesday through Friday, overall a cyclonic north to northwesterly
flow dominates with mainly dry weather and highs in the 20s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 735 PM CST Fri Jan 20 2017
Widespread LIFR/VLIFR conditions in fog and stratus will continue
across central North Dakota tonight through Saturday. Patchy
freezing drizzle is possible. Fog is expected to spread into
northwest North Dakota tonight, with the far southwest the one
area that may remain VFR for the 00 UTC TAF cycle.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon CST /11 AM MST/ Saturday for
NDZ019>023-025-036-037-047-048-050-051.
&&
$$
UPDATE...AYD
SHORT TERM...KS
LONG TERM...KS
AVIATION...AYD
Area Forecast Discussion
National Weather Service State College PA
1046 PM EST Fri Jan 20 2017
.SYNOPSIS...
Relatively mild, but cloudy and unsettled conditions will
persist through the weekend before cooler air makes a return
next week.
A complex and slow moving storm system is expected to move
across the deep south then swing northeast along the
Appalachians Sunday afternoon and night. The storm will then
exit off the Mid Atlantic coast Monday and Tuesday and bring
rain and perhaps a return of wintry weather. Much colder
temperatures will arrive at the end of next week.
&&
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Current Obs and gridded LAMP and HRRR vsbys point twd the need
of a Dense Fog Advisory over the NW Mtns and numerous SE
counties and Schuylkill cty overnight through 13Z Sat. Sent out
a recent collaboration message to surrounding WFOs regarding
this.
A few dwindling areas of light rain were drifting across the
northern mtns of PA this evening. Elsewhere, skies were mostly
cloudy to overcast with nothing more than some patchy light
drizzle and areas of fog.
A warm front close to the I-76 corridor in southern PA will lift
slowly north across the forecast area overnight and Saturday.
increasing dewpoints (into the lower 40s) over the colder,
moist ground will allow fog to gradually thicken up to between
1/2SM and 1SM in many locations.
Should any clearing occur, vsbys could quickly dip to AOB 1/4SM.
In that case, consideration will have to be given for a Dense
Fog Advisory.
The temps will be nearly steady in most areas overnight, ranging
from the upper 40s to around 50F across the Laurel Highlands,
the lower to mid 40s across the Southern Valleys and NW mtns,
and mid to upper 30s in the Central Valleys and Middle Susq
Valley.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
Some fog and drizzle will linger in the morning, and even into
the afternoon on the ridges. Few if any breaks in the clouds are
expected outside the far lower Susq as the lowest 3kft remain
nearly saturated. Maxes are a tough call with lots of cloud
cover, but an 8-12F rise is feasible. Will run with maxes just a
hair under MOS blend. The central counties will probably top out
in the m-u40s, but most other places will. 60F is possible, but
not likely, in the Laurels and Warren Co.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
As the upper ridge is forecast to re-establish itself over the
eastern U.S. early in the period, a very complex storm system is
now forecasted to be settling over the Southwestern US by
Saturday evening. This southern stream low should continue to
track through the southern states before turning northeast over
the eastern US Sunday night into early next week. The mid to
long range models continue to trend warmer Sunday night into
Monday. 850mb and 925mb Temperatures continue to be above 0C
though a snow/rain mix remains possible in the higher
elevations. Have rain as the main precipitation type. The
forecast question through this period is QPF amounts. Based on
latest models, blends, ensembles and national guidance, have
increased QPF slightly based on PWATS, the moist southerly
flow. One limiting factor could be probability of snow/rain mix,
so higher QPFs are possible in the southeast. There remains a
fairly large spread in QPF amounts in the plumes so will
probably need to adjust amounts for later runs.
Snow is possible beginning Monday across the Laurels within the
region of greatest thickness cooling, then later Monday into
Tuesday across the northern mountians and toward the Western
Poconos. The combination of A backdoor Cfront sliding SWWD from
New England and increasing baroclinicity as the deep low
approaches the Mid Atlantic Monday night into Tuesday will allow
the low to maintain its intensity and pull colder/sub-freezing
air back into the NE and NCENT mtns.
Most signif snow in oour CWA appears to target the Laurels and
perhaps Sullivan and Tioga ctys in the NE.
Any high pressure over the region will be short lived as a
upper level low will settle over Eastern Canada. That system is
progged to drag a cold front through the mid Atlantic Wednesday.
After our early week storm system, the eastern ridge is made to
make a rapid rebound, even if for just a short time around
midweek. A fast moving shortwave quickly chews the top off the
ridge with cyclonic westerly flow by week`s end. Colder air
looks to advect into the region bringing in more winter like
temperatures late next week.
&&
.AVIATION /04Z SATURDAY THROUGH WEDNESDAY/...
IFR/LIFR stratus/fog covers nearly all of central Pa this
evening northeast of a stalled warm front, which runs from
western Pa southward along the spine of the Appalachian Mtns.
Model soundings support continued low CIGs/fog overnight
northeast of this stalled boundary. Exception may be at JST,
which is straddling the warm front and is VFR at 03Z. A very
close call here, as even a slight retrogression westward of
front could lead to a return to IFR at JST overnight.
Little improvement expected east of the Appalachians on
Saturday, as models continue to show persistent low level
moisture trapped beneath inversion to the northeast of stalled
warm front. Best conditions will almost certainly be at JST,
where VFR conditions appear likely west of front. Elsewhere,
some modest improvement appears possible by afternoon, but
IFR/low MVFR CIGs appear likely to persist through the day.
Outlook...
Sun...Low CIGs likely. Rain advances from S-N late.
Mon...Rain/low CIGs likely.
Tue...AM rain/snow and low CIGs possible.
Wed...Reduced CIGs/showers possible NW.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Dangelo/Lambert
NEAR TERM...Dangelo/Lambert
SHORT TERM...Dangelo
LONG TERM...Lambert/Ceru
AVIATION...Fitzgerald
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
838 PM EST Fri Jan 20 2017
.UPDATE...
Minor update to remove evening wording and adjust timing for fog
trends. While mid level cloud banding and weak southern gradient
flow has slowed (and in some locations reversed) the formation of
dense fog, will maintain the Dense Fog Advisory overnight into
early Saturday morning as conditions still appear favorable for
the expansion of fog. HRRR trends suggest the weak surface front
will stall near the M-59 corridor, so area of most substantive fog
may end up along and north of this boundary where light easterly
flow becomes established. Will monitor this trend the remainder of
the evening and adjust the southern edge of advisory northward if
needed.
&&
.PREV DISCUSSION...
Issued at 607 PM EST Fri Jan 20 2017
AVIATION...
Low vsbys/cigs will dominate the forecast into Saturday morning with
slow improvement thereafter. The small area of improving vsbys that
worked north into the southern zones near surface front has already
begun to fade with nightfall and the loss of any minimal mixing. So,
any vsbys above 1/4SM should reverse over the next few hours and in
general expect 1/4SM or less vsbys and ceilings in the 100-300 foot
range much of the time from mid evening into mid Saturday morning.
For DTW...Vsbys may start out around 1SM or even slightly higher,
but a trend back to 1/2SM and eventually 1/4SM is anticipated this
evening. These conditions, along with cigs around 200 feet should
then predominate into Saturday morning.
//DTW Threshold Probabilities...
* High for cigs below 5000 feet through the TAF period
* High for cig/vsbys aob 200ft and 1/4SM much of time from roughly
03z-15z.
PREV DISCUSSION...
Issued at 420 PM EST Fri Jan 20 2017
DISCUSSION...
Fog, periodic chances of light rain, and waves of drizzle are the
primary forecast items for a good chunk of this upcoming weekend.
Air mass to changeover beginning Sunday with shrewd easterly winds
developing late.
A very convoluted upper level pattern exists over much of North
America with as many as 4 separate jet impulses aloft providing an
influence. The impetus behind the noisy pattern has been the
reintroduction of the massive early week, southwestern US closed low
system back into the mean flow. That massive upper level low has
been able to hold on and maintain some integrity over the upper
Midwest. The circulation is resulting in a larger influence of
cyclonic flow within the heart of a much larger amplitude/wavelength
upper level ridge. This initial upper level low and synoptic scale
forcing is fading by the second and is currently undergoing an
tremendous amount of shearing. As a result, forcing now has
collapsed down to just last gasps of stretching deformation. This
has played out with the band of rain that lifted northward today
with nothing much left then a few pockets of light rain near the
area around Saginaw Bay.
Tonight...The narrative for the rest of the weekend will be one
revolving around a slow to develop upper level trough over the
eastern United States. What this means for tonight is a straight
persistence forecast. Virtually zero mixed flow exists overhead
behind the earlier band of precipitation under calm winds (nil
pressure gradient) and surface T/Td depressions at a degree C or
less. Surface observations the past hour have taken a concerted
movement in the negative direction and traffic cams across all of
southeastern Michigan show a shroud of fog hanging in the air. Given
the structure of the near surface inversion forecasted tonight...the
decision was made to issue a dense fog advisory that will be in
effect for all of southeastern Michigan between 00Z this evening and
15Z Saturday morning.
Another jet exit region aloft will push toward the state overnight
from the mid Mississippi River Valley. Just enough larger scale
support will exist with this feature to support another spoke of
midlevel convergence and thermal, theta e advection lifting into the
area. The nam suggests that frontogenetical support with this
activity will be much lower in the column which could yield more
drizzle activity than rain showers. Timing of this chance pops is
across the Ohio state line near Toledo just before 09Z...along M59
corridor...just before 12Z...and the northern cwa and Thumb by 15Z.
Saturday...Another grungy day of persistence from a cloud
perspective. Model data continues to support a very saturated near
surface air mass that will be supportive of reduced visibilities
right until the noon hour. However, the big difference will be
surface temperatures as the slowly developing cyclonic flow will
support increased low level theta e advection with a burgeoning warm
sector. Latest guidance suggest a warm front becoming draped across
the northern cwa with middle 50s in place over southern 2/3rds of
the cwa. Definitely have some reservations about getting there with
all this cloud in January. However, middle to upper 50s are in
place across southern IN and OH today. It will not take much at
all to get those readings here.
Sunday...A very dynamic and perfectly configured upper level jet
structure will scream across the southern United States Saturday.
Very strong upper level jet dynamics will then lead to a high end
cyclogenesis event over the southeastern United States, Tennessee
River Valley Sunday. Southeastern Michigan will remain well enough
to the north that predominately dry weather will be experienced
Sunday and Sunday night. What will happen is a steadily increasing
easterly pressure gradient that will ratchet up winds particularly
heading into Sunday night. The feeling is that the available
guidance may be too mild both late Sunday and Monday. What is
becoming more into focus is that categorical rain may be likely for
Monday as deformation forcing increases substantially and a slug of
deep moisture is forecasted to backdoor into the state from Ontario.
Mild, unsettled weather will continue through mid-week, as a series
of surface and upper level waves rotate through the region. Chances
of rain or rain/snow mixed will generally persist, barring a brief
break in conditions scheduled for Tuesday. Temperatures will remain
above average through Thursday with the warmest temperatures
occurring during the overnight hours. During the day on Thursday, a
decent cold front pushes through; dropping the temperatures through
the day. By Friday, weak chances for snow return, along with
temperatures more in line with January norms.
MARINE...
Broad low pressure will bring light winds through Saturday night.
Warmer air funneling into the region behind a warm front will
promote the development of fog, however. East winds will strengthen
on Sunday and Monday as a stronger area of low pressure tracks
through the Ohio and Tennessee Valleys. The persistent easterly flow
will allow wave heights to grow, potentially necessitating small
craft advisories for any ice-free areas by Sunday night.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Dense Fog Advisory until 10 AM EST Saturday FOR MIZ047>049-053>055-
060>063-068>070-075-076-082-083.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
UPDATE.......DG
AVIATION.....DG
DISCUSSION...CB/DE
MARINE.......CB
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Sioux Falls SD
946 PM CST Fri Jan 20 2017
.SHORT TERM...(This evening through Saturday)
Issued at 350 PM CST Fri Jan 20 2017
The biggest concern continues to be the persistent fog/stratus
threat across the region. Low visibility and ceilings have gradually
improved for areas west of the James River as clouds eroded
northward; but still they are struggling east of the I-29 corridor.
A thick cloud deck layer persists along and east of the James River;
therefore keeping mild temperatures, and a wealth of low level
moisture (fog) in the area. With this low level moisture, light
winds, and no changes in the airmass, dense fog is likely to
redevelop tonight into early Saturday morning. Models differ in some
in terms of fog coverage. HRRR and NAM suggest widespread low
visibilities to less than a quarter mile this evening and over the
nighttime hours. While the RAP only shows patchy fog across this
time frame. Given that discrepancies our confidence in low
clouds/visibility is not high for areas along and west of the I-29
corridor. At this point decided to extend the dense fog advisory for
areas along the Buffalo Ridge and portions of northwest Iowa, where
stratus on the ground will continue. A new advisory may be needed
for portions of the I-29 corridor later this evening.
The other issue is a shortwave lifting northeast tonight into
Saturday morning bringing a chance for light rain-snow. Profiles
support deeper saturation in the low-level combined with decent PVA
forcing at 500mb. There is a warm layer of air near the surface that
will keep most of the precipitation as rain. This layer is less
pronounced near the Highway 14 corridor, and may result in a little
bit of snow mixed in with the rain. Any snow accumulations are
expected to be very minor. The heaviest QPF with this system is
expected closer to the center of the upper level disturbance, down
in northwest Iowa.
On the backside of this system, there is a trough that sweeps
through the area resulting in a wind shift near the surface. While
the winds become northwest, moisture has a hard time scouring out,
and have therefore kept skies cloudy with small diurnal range.
.LONG TERM...(Saturday night through Friday)
Issued at 350 PM CST Fri Jan 20 2017
Not too much going on the second half of the weekend. Residual low
level moisture will linger over many areas. The moisture is deepest
through the lowest kilometer in southwest MN where a bit of freezing
drizzle or drizzle could linger. This area is aided by some speed
convergence just off the surface and a subtle surface wind shift
aiding in ascent. But no accumulations of freezing drizzle are
expected late Saturday night or early Sunday in that zone.
With a stout northwest flow, would not be surprised to see the low
clouds scour out Sunday afternoon as suggested by the various
models, only to be replaced by fairly thick mid and upper level
clouds. Still, it will be seasonably mild Sunday and Monday.
After that, all eyes are focused on the next storm system. The
various deterministic models between the 12Z GFS, ECMWF and GEM
global have actually come around in pretty good agreement with its
track in both space and time. The low is rather positively tilted and
sheared, therefore the event looks like a prolonged precipitation
event but one that lacks a lot of intensity. It looks like the type
of event of a typical 3 to 6 inch snow event on average through the
forecast area, but will monitor of course over the coming days.
Precipitation type is a bit tricky on Tuesday from near Vermillion
SD, to Sioux City, to Storm Lake IA. Temperatures off the surface
are near zero celsius in these areas which could result in a rain or
snow mix. The superblend highs on Tuesday looked a bit warm however
in our southern zones south of I 90 due to precip anticipated and a
lot of cloud cover. Therefore blended in some raw model values
especially from the ECMWF which cooled highs down a category.
Followed this same trend on Wednesday as once again, superblend
highs looked a bit too warm through our entire forecast area. It
will be quite windy throughout the forecast area after the surface
lows moves east Tuesday night and Wednesday and bumped up the all
blend winds.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 944 PM CST Fri Jan 20 2017
Widespread IFR and LIFR conditions will persist in most area
through the night. Conditions will slowly improve from southwest
to northeast across the area as winds turn westerly and help bring
in some drier air. Temporary improvement may also be found in the
light rain moving through far southeast SD into northwest Iowa and
southwest MN through about 10z.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until 9 AM CST Saturday for SDZ040-056.
MN...Dense Fog Advisory until 9 AM CST Saturday for MNZ071-072-080-
081-089-090-097-098.
IA...Dense Fog Advisory until 9 AM CST Saturday for IAZ001>003-013-
014-021-022-032.
NE...None.
&&
$$
SHORT TERM...05/BT
LONG TERM...MJ
AVIATION...08
Area Forecast Discussion
National Weather Service Hastings NE
624 PM CST Fri Jan 20 2017
.UPDATE...
Issued at 556 PM CST Fri Jan 20 2017
Updated the forecast to include the mention of lower visibilities
in the forecast as well as to issue a dense fog advisory through
midnight tonight. So far...we have seen numerous sites at least flirt
with dense fog criteria for the past couple of hours...and with
the HRRR showing this fog not going anywhere for several more
hours...thought it would be sound to have an advisory out to at
least cover the evening hours. This fog should diminish in
coverage and intensity from west to east late in the night as the
low level flow begins to shift and become westerly...so may need
to fine tune the advisory later as some western areas clear
out...with eastern areas of the advisory possibly in need of an
extension for a couple of hours.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 326 PM CST Fri Jan 20 2017
Visibility is extremely variable across the forecast area this
afternoon with some sites still below a mile while others are over
six miles. Clouds are consistent across the area.
The main concerns for the short term is the fog for tonight and
chances for some light precipitation.
An upper level wave is moving through the area this afternoon and
tonight with that will be a chance for mainly light precipitation.
In this case, the temperatures are warm enough this afternoon and
into the evening that it will be rain, but as the temperatures cool
during the overnight hours, there will be some rain/snow mix.
Precipitation will be ending during the overnight hours. The south
winds across the area continue to bring in moist air into the area
and as the temperatures cool during the evening there is a better
chance for some fog again. The fog will continue into Saturday
morning. At this point the winds from the west should keep the
visibility from getting as low as it has the past couple of nights,
but will have to see if it is strong enough to keep the visibility
from dropping. On Saturday the clouds will linger in the morning and
even some patchy fog, but by afternoon there will be some clearing.
.LONG TERM...(Saturday night through Friday)
Issued at 326 PM CST Fri Jan 20 2017
The biggest concern during this period continues to be the winter
weather potential early to mid week next week.
Saturday night through Monday will be fairly mild and quiet weather.
There is a surface high that moves through the area. Temperatures
will be in the 40s to lower 50s for highs and lows will be mostly in
the 20s.
The main interest will be during the Monday night to Wednesday
morning time frame. An upper level low moves into the plains states
Late Monday night and finally moving out of the area Wednesday.
Models continue to have different paths for the system. The GFS has
been further to the north than the ECMWF. With the further north
track, there would be little precipitation for the north central
Kansas portion of the forecast area. The ECMWF solution gives a
little more precipitation to areas south in the forecast area.
Continue to go with something in between and still have
precipitation across the entire area, but the best chances will be
in the northern part of the forecast area. The next concern will be
precipitation type. As the precipitation gets started Monday night,
the temperatures are cool enough that snow should be possible.
During the day, most of the snow should mix with or change to rain
for much of the forecast area. The far northwest may still have a
mix during the afternoon. Then, as temperatures cool off during the
evening the rain mixes with and changes to snow across the area.
With the different tracks of the low, the timing for moving
precipitation out of the area is also in question. Have kept some in
the north and east during the morning, but that should remain snow.
Wednesday afternoon through Friday should be another quiet period,
but temperatures will be a bit cooler than this weekend. There will
be northwest flow across the area and some in and out clouds. Highs
will only be in the 30s with lows in the teens.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday evening)
Issued at 556 PM CST Fri Jan 20 2017
Generally poor conditions will persist at the terminals through
much of the overnight hours...although there should be some minor
improvement late in the night as the low level flow shifts more
westerly and subsequently visibilities begin to improve. By
daybreak...expect CIGS to also begin to lift...with VFR
conditions likely at both sites by late morning.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Dense Fog Advisory until midnight CST tonight for NEZ039>041-
046>049-061>064-074>077-085>087.
KS...None.
&&
$$
UPDATE...Rossi
SHORT TERM...JCB
LONG TERM...JCB
AVIATION...Rossi
Area Forecast Discussion
National Weather Service Lincoln IL
851 PM CST Fri Jan 20 2017
.UPDATE...
Issued at 844 PM CST Fri Jan 20 2017
Tricky overnight cloud forecast, which will have an impact on
additional fog potential. Satellite loops had clearing surging
toward the area from Missouri earlier this evening, and last
several runs of the HRRR suggesting this clearing would quickly
spread across the forecast area. However, more recent satellite
loops has shown low clouds redeveloping back toward Missouri. A
warm front still lies across northern portions of the forecast
area, with more significant low clouds/fog/drizzle along and to
the north of this boundary. Still expect this boundary to push
north of the area by morning, and drier low-level air to the south
of the boundary should allow the upstream clearing to gradually
make its way north. Have updated forecast to be a little more
optimistic with sky condtions overnight. Otherwise only minor
hourly tweaks were needed.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 245 PM CST Fri Jan 20 2017
Warm front continues to take shape near the I-72 corridor this
afternoon. Temperatures closing in on 60 degrees over the far
southeast CWA this afternoon with mid-upper 40s north of the
boundary. Some of the fog has redeveloped near the boundary,
although visibilities mainly in the 2-4 mile range.
The inversion around 850 mb will continue to hang on for the first
part of the evening, before finally breaking down as the front lifts
further north. Short range models continue to hint at some
development by late afternoon, lifting northward with the front this
evening. With very dry air above the inversion, thinking that any
precipitation will be in the form of drizzle, and have continued
with the associated low PoP`s this evening, although diminishing
from south to north with time. Have maintained a mention of fog in
the forecast, but this would become less of a threat with time as
the front lifts north. Temperatures not expected to change too much
tonight, ranging from the mid 40s near Galesburg, to the lower 50s
from about I-72 southward.
Nice southerly flow will bring 850 mb temperatures into the 8-9C
range on Saturday. With the soundings suggesting partly sunny
conditions developing, it looks like the majority of the CWA should
reach into the 60s for highs, with upper 50s across the north. This
would be close to records in a few areas (see climate section
below).
.LONG TERM...(Saturday night through Friday)
ISSUED AT 245 PM CST Fri Jan 20 2017
After an unseasonably warm day on Saturday, models continue to
indicate a weak cool front will push across the area Saturday night
into Sunday morning. Rather steep lapse rates on soundings from 800-
500 mb with Most Unstable Cape values ranging from 700 to 900 J/KG
late tomorrow afternoon and night. It appears as a southern stream
shortwave and surface low track well to our south later Saturday
evening into Sunday morning, a large complex of showers and
thunderstorms will develop over the lower Mississippi Valley which
may effectively hold back any deep moisture transport north into
our area along the slow moving boundary. Will continue to carry
low chance POPs Saturday with the highest chances east of
Interstate 55. Another warm night for January with Sunday morning
lows forecast to be some 5 to 10 degrees above normal highs for
the middle of January with readings ranging from the middle 30s
northwest to close to 50 in far southeast Illinois.
The stronger southern stream system will continue to stay well south
of our area on Sunday keeping the heavy rains and thunderstorms
away from the forecast area. Low chance POPs will be along and east
of the I-57 corridor than translating into southeast Illinois by
afternoon as the surface low tracks further away from the Midwest.
Although not as warm as Saturday, Sunday`s highs will once again
be well above normal with readings in the upper 40s northwest to
around 60 over far southeast Illinois. As the deep upper and surface
lows slowly track north up the East Coast early next week, weak upper
level ridging will build over the Midwest bringing quiet weather to
start the new work week off with. Will still have the threat for
some lingering light rain over far east central and southeast
Illinois Monday morning, but for the most part, the bulk of any
significant rainfall early next week will be well of to our east and
southeast. Another day with above normal temperatures as highs top
out in the low to mid 40s.
Due to the slow movement of the upper low to our east and shortwave
ridging across our area early next week, models have trended a bit
slower with our next chance for precip as another storm system
develops across the Central Plains on Tuesday. We will still have
low chance POPs over our far west and northwest counties by late
Tuesday afternoon, but it appears any rainfall with this system
will hold off until Tuesday night into Wednesday with our north
having the higher chances during this time frame. A fairly decent
warm axis seen just ahead of the storm system Tuesday afternoon
may help to push temperatures well into the 40s with 50s not that
far to our south. Once the storm system tracks to our north on
Wednesday, we should start to see a gradual cooling trend set in for
the latter half of the week with temperatures returning closer to
where they should be for late January.
Medium range models today not showing much agreement with respect to
how deep the trof strengthens over the Great Lakes with the latest
ECMWF backing off considerably from what we saw 24 hours ago, while
the 12z GFS continues to indicate a rather deep trof over the lower
Great Lakes by the end of the month resulting in below normal temps,
a solution currently supported by the 12Z GEFS ensembles. Current
forecasts suggest temperatures by the end of this forecast period
will return to more normal levels. At this point, we are not seeing
any solid model consensus of any significant upstream blocking or
buckling of the Polar jet, which would allow more of a cross polar
flow to develop, which would bring some of that very cold air
currently bottled up in northwest Canada and Alaska southward
with 850 temps ranging from -25 to -30C this morning.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 525 PM CST Fri Jan 20 2017
Conditions have started to improve across the central Illinois
terminal area as a frontal boundary shifts north of the area.
There remains some question regarding how quickly improvement will
take place tonight. Recent satellite loops suggest a nearly
complete clearing may occur tonight, but most forecast guidance
does not support this. While it is pretty hard to argue with
satellite trends, have kept forecast closer to the more
pessimistic model consensus for now. However, a significant
forecast update this evening seems possible. A near total clearing
may also result in additional stratus fog development as the
atmosphere cools tonight. Will continue to monitor trends closely.
&&
.CLIMATE...
Issued at 245 PM CST Fri Jan 20 2017
Record highs for Saturday:
Bloomington............ 62 (1906)
Champaign.............. 62 (1906)
Decatur................ 69 (1906)
Galesburg.............. 66 (1957)
Lincoln................ 60 (1964)
Olney.................. 68 (1986)
Peoria................. 62 (1957)
Springfield............ 63 (1986)
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak
CLIMATE...Geelhart
Area Forecast Discussion
National Weather Service Seattle WA
309 PM PST Fri Jan 20 2017
.SYNOPSIS...A broad upper level trough will remain over the
offshore waters through the weekend. A series of systems rotating
around it will bring showers and breezy conditions at times to
Western Washington along with seasonable temperatures. By early
next week, a ridge of high pressure will build into the Pacific
Northwest for the possibility of several dry days.
&&
.SHORT TERM...I have added a chance of showers back into the north
interior since the latest HRRR runs have shown light showers for
that area tonight and the latest radar data shows showers
approaching the area.
The pressure gradients across the Cascades are dropping again and
breezy conditions over the Cascade foothills and passes should
subside. The Seattle to Wenatchee gradient has dropped below 6 mb
as of 3 PM PST.
A broad upper trough and its associated stacked surface lows
continue to spin offshore through late Sunday, bringing showers
into the area. I have added a slight chance of thunderstorms into
the coastal waters for Saturday afternoon since there looks to be
a decent amount of energy as well as upper level support. Any
thunderstorms will be short lived. Sunday will bring the best
chance for steadier precipitation as a frontal system associated
with one of the surface lows moves through the area.
On Monday the upper trough will move south into the California
coastal waters and any lingering showers will dissipate over
Western Washington. I have removed precipitation from many areas
for Monday since models have been consistent in showing a drier
trend. JSmith
.LONG TERM...A ridge will begin to build in over the area late
Monday through at least Wednesday. Beyond that, model solutions
diverge with the GFS showing a drier solution continuing and the
ECMWF showing a few systems moving through the area bringing
showers. The GEM shows precipitation on Thursday but then a return
to dry conditions in its seemingly usual middle-ground stance.
JSmith
&&
.AVIATION...An occluded front will spread light rain to the area
this evening, mainly the coast and southwest Washington. The flow
aloft is southerly. Surface flow is E/NE and ceilings are mainly
VFR. Patchy fog may form in south sound overnight. An upper level
trough will maintain showers as it moves inland on Saturday. 33
KSEA...N/NE surface flow with VFR conditions. Light rain in the
vicinity this afternoon and evening. 33
&&
.MARINE...An occluded front with bring easterly Small Craft
Advisory winds to the Coastal Waters and Strait of Juan de fuca
tonight. Meanwhile, west swells will rise to 16-22 ft, peaking on
Saturday. A 960-965 mb surface low will track along 130W late
Saturday night with another occluded front moving inland on
Sunday. This front may produce gale force winds over the Coastal
Waters. The flow over Western WA will turn offshore early next
week as the surface low weakens and drifts south offshore. 33
&&
.HYDROLOGY...The Skokomish River continues to recede and is
expected to fall below flood stage this evening. No additional
flooding is expected at this time with only showers in the short
term forecast and then a switch to drier conditions starting
Monday. JSmith
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...High Surf Advisory from midnight tonight to 6 PM PST Saturday
for Central Coast-North Coast.
PZ...Small Craft Advisory until 4 PM PST Saturday for Central U.S.
Waters Strait Of Juan De Fuca-Coastal Waters From Cape
Flattery To James Island 10 To 60 Nm-Coastal Waters From
Cape Flattery To James Island Out 10 Nm-Coastal Waters From
James Island To Point Grenville 10 To 60 Nm-Coastal Waters
From James Island To Point Grenville Out 10 Nm-Coastal
Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-
Coastal Waters From Point Grenville To Cape Shoalwater Out
10 Nm-East Entrance U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory for rough bar until 4 PM PST Saturday for
Grays Harbor Bar.
Small Craft Advisory for hazardous seas until 4 PM PST Saturday
for West Entrance U.S. Waters Strait Of Juan De Fuca.
&&
$$
www.weather.gov/seattle
You can see an illustrated version of this discussion at
www.weather.gov/seattle/gafd/latest_webafd.html
Area Forecast Discussion
National Weather Service Shreveport LA
550 PM CST Fri Jan 20 2017
.AVIATION...
VFR conditions prevailing to begin the 00z TAF cycle but this will
be changing overnight with upper level disturbances pivoting our
way from SE TX. Regional radar mosaics showing the leading edge of
some elevated convection just 50 miles or so southwest of the LFK
terminal already this evening with this convection moving
northeast near 45 mph. Latest progs and HRRR showing this
convection in the vicinity of the LFK and MLU terminals in the
00z-06z timeframe with IFR/LIFR ceilings quickly filling in behind
the convection overnight. After 08z or so...we should transition
into more of a scattered light rain and/or drizzle scenario with
strong isentropic lift continuing to go along with the low
ceilings. By mid morning through the afternoon hours...we
transition into more scattered convection as the parent shortwave
begins to influence the region from the west. By that
time...ceilings should rebound from LIFR/IFR conditions to MVFR
conditions.
13
&&
.PREV DISCUSSION... /issued 355 PM CST Fri Jan 20 2017/
DISCUSSION...
Well overcast now in Shreveport with high clouds at peak heating
has busted our update. It will be a mild night with a chance for
thunderstorms, mainly over our SE corner, but from Hemphill to
Natchitoches and Monroe keep an eye to the sky spotters with a
slight risk. Rapid development could bring down some wind damage
or tornado and or hail this evening and some of the overnight.
This impulse tonight is over the Rio Grande now and will race
Eastward. Some sort of watch may be issued before midnight.
The big kicker in the long wave pattern is over S CA/AZ and will
be here overnight Saturday into early Sunday, again poised for
perhaps organized thunderstorm action late tomorrow, mainly for
a hail threat under the core of the parent low. Models crop up
some scattered activity during the day with divergence aloft and
while still warm, tomorrow with more clouds and less wind may be
a tad cooler. The rest of the is dry with our next slight chance
mid to late week with a weak front. /24/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 56 73 50 64 / 20 40 50 30
MLU 56 74 53 65 / 50 20 60 30
DEQ 48 71 46 60 / 10 30 60 30
TXK 53 72 49 61 / 20 30 60 30
ELD 54 72 50 62 / 20 40 60 30
TYR 55 72 49 63 / 10 40 40 20
GGG 54 72 49 63 / 10 40 40 20
LFK 57 75 51 65 / 40 20 40 10
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
24/13
Area Forecast Discussion
National Weather Service Las Vegas NV
312 PM PST Fri Jan 20 2017
.SYNOPSIS...A potent storm system will impact the region tonight
with widespread rain...gusty winds...and significant mountain snow.
Locally heavy rain may cause flooding concerns across parts of
Northwest Arizona and the Colorado River Valley. Drier conditions
are expected Saturday before another powerful Pacific system brings
more rain and mountain snow to the region Sunday into Monday. Dry
and cool conditions last Tuesday through the end of next week.
&&
.SHORT TERM...through Monday.
Busy day with events unfolding about as expected. Radar detecting
highest rainfall rates with showers and embedded thunderstorms
moving through southern California currently. HRRR shifts this area
east through the remainder of eastern San Bernardino County late
this afternoon...then across the Colorado River Valley and southern
Mohave County this evening. Precipitation from this second event
will start tapering off tonight...some showers will linger in
eastern Lincoln, eastern Clark and Mohave Counties through Saturday
morning.
Attention then turns to system number 3. Precipitation from this
system will already be spreading into California Saturday
night...possibly as far east as the Spring Mtns by daybreak Sunday.
The only addition to our vast array of hazards was to go ahead and
issue another Flood Watch for northeast Clark, northern Mohave, and
Lincoln County based on the potential of more localized higher QPF
amounts.
&&
.LONG TERM...Tuesday through Friday.
Cool and drier conditions will settle in Tuesday through Friday as a
broad trough sits over the central Rockies. This will keep
temperatures below normal, but generally dry and sunny. Gusty north
winds are likely to make another visit to the Colorado River valley
Wednesday and Thursday.
&&
.AVIATION...For McCarran...CIGs will be holding fairly steady
between BKN020-025 through 03z with the steadier rain before lifting
to or above 5k by 06z. Widespread mountain obscuration is expected
through tonight. Winds have not materialized during the afternoon
but expected to develop toward the end of the rain. Gusty south
winds are likely overnight. Showers will continue in the Peach
Springs and Mormon Mesa corridors overnight. Another round of lower
CIGS and rain expected on Sunday and Monday.
For the rest of southern Nevada...northwest Arizona...and southeast
California...Storm system to continue through the evening in most
locations and across Mohave County tonight with widespread rain and
mountain snow...mountain obscurations...and low ceilings. Heaviest
rain will move from west to east across the Mojave Desert through
early evening. Embedded thunderstorms can be expected along with
pockets of severe turbulence. Improving conditions expected late
tonight after 6z in many locations as the front pushes east and CIGs
and weather improves. Low clouds and patchy fog will remain possible
however across areas mainly north of I-15.
&&
.SPOTTER INFORMATION STATEMENT...Significant rain and mountain snow
is possible through the weekend. Weather reports of flooding...high
winds...and accumulating snow is requested. Any additional weather
reports related to rainfall...road conditions...or low visibility is
also encouraged.
&&
$$
Short Term...Pierce
Aviation...Czyzyk
Long Term....Outler
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