Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/24/17
Area Forecast Discussion
National Weather Service Dodge City KS
549 PM CST Thu Feb 23 2017
...Updated aviation discussion...
.SHORT TERM...(This evening through Friday)
Issued at 305 PM CST Thu Feb 23 2017
Our area is in the middle of 2 competing airmasses this
afternoon. A cool airmass to the north is holding off the further
advancement of higher terrain dry downslope air that has made it
into Elkhart, Hugoton and Liberal by early this afternoon. The
HRRR and RAP13km models showed a narrow area of convective
development anywhere from Dodge City eastward through
Stafford/Great Bend and northward, corresponding to a band of
moderate CAPE values ahead of the warm front and frontal forcing
zone. Given the environmental parameters, a brief marginally
severe hail storm couldn`t be ruled out in this area during the
very late afternoon. Meanwhile, the wave responsible for
developing the large scale lift and winter storm across Nebraska
will continue lifting northeast, with some potential for rain and
snow showers to clip the northern sections of our area (namely the
I-70 corridor and the Wakeeney and Hays area). Little more than a
dusting to a half inch of snow looks possible form the most
optimistic model runs.
The area will remain under the influence of cold northerly surface
winds through the day Friday. Low level overcast clouds should
influence central Kansas through the day, however sun should be
returning from southwest to east through the day. Much of the area
won`t exceed the mid 30s for afternoon highs.
.LONG TERM...(Friday night through Thursday)
Issued at 305 PM CST Thu Feb 23 2017
Much colder temperatures returning by Saturday morning, as cold
surface high pressure settles over the area. The entire area could
be in the the teens, with low teens in the extreme western counties.
Models indicate a slow moderation in temperatures through the early
part of next week, with a couple of westerly waves along the way
bringing outside chances for precipitation, Sunday night and Tuesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 549 PM CST Thu Feb 23 2017
Strong low pressure system moving out of southwest into south
central Kansas early this evening. North winds gusting to 35-40
knots at the beginning of this period should diminish somewhat
after sunset but will continue at 15-25 knots overnight. MVFR to
occasional IFR cigs are expected at the terminals overnight but
should improve to VFR by Friday morning. In addition, snow showers
will be possible around the Hays terminal later this evening.
&&
.FIRE WEATHER...
Issued at 130 PM CST Wed Feb 22 2017
It will be tough to see true red flag conditions across the extreme
northern sections of the warned area, like Scott County, northern
Finney and Lane. However farther south the conditions will easily be
met with stronger winds than forecast earlier and the latest HRRR
model runs taking the windy dry conditions across the entire
southern tier to Barber county. Lane and Scott counties dropped
from red flag.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 27 41 17 46 / 10 0 0 0
GCK 26 38 16 46 / 10 0 0 0
EHA 27 42 19 48 / 10 0 0 0
LBL 29 44 19 47 / 10 0 0 0
HYS 29 34 18 44 / 40 20 0 0
P28 34 46 21 47 / 10 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM CST this evening for KSZ063-064-
074>080-084>090.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Gerard
FIRE WEATHER...Russell
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
924 PM CST Thu Feb 23 2017
.UPDATE...
Southeasterly flow off the Gulf of Mexico has returned faster this
evening bringing higher dewpoints to across the I-35 corridor and
Escarpment. HRRR and RAP indicated this better than the other models
and have updated to generally follow their trends. Stratus has also
developed near the Coastal Plains. Expect it will push further to the
northwest and may approach the I-35 corridor overnight. Then, a
Pacific cold front will surge east pushing this deeper, yet shallow
moisture back to the Coastal Plains early in the morning. Otherwise,
no significant changes to the South Central Texas forecast.
&&
.PREV DISCUSSION... /ISSUED 531 PM CST Thu Feb 23 2017/
AVIATION DISCUSSION...FOR 00Z TAF PERIOD...
VFR conditions expected to prevail through midnight. An approaching
cold front may result in some BR prior to frontal passage forecast to
reach the I-35 terminals just before dawn. Then winds will shift to
the northwest becoming gusty in the afternoon. May cause some impacts
to north/south oriented runways.
PREV DISCUSSION... /ISSUED 252 PM CST Thu Feb 23 2017/
SHORT TERM (Tonight through Friday Night)...
Upper air analysis this morning showed nearly zonal flow across the
southwestern US with a trough over the northern Rockies. At the
surface, high pressure was centered over the Gulf and winds were from
the southeast to southwest. The upper level trough over the northern
Rockies will swing down through the southern plains. A cold front
will move through north Texas tonight and our CWA Friday morning. The
atmosphere is still very dry and the front will not generate any
precipitation. Behind the front, drier air will move in with breezy
northwesterly winds. Temperatures will be cooler behind the front,
but still above normal.
LONG TERM (Saturday through Thursday)...
Dry weather will continue Saturday. Low level winds will become
southeasterly bringing moist air back to the region. Sunday there may
be sufficient moisture and isentropic lift to produce showers and
thunderstorms. Monday another cold front will move through the region
bringing a chance for showers and thunderstorms Monday and Tuesday.
High pressure will build back in behind the front with dry weather
through the remainder of the period.
FIRE WEATHER...
Relative humidity will drop below 20 percent across all of our CWA
Friday afternoon. Breezy northerly winds between 10 and 15 mph will
lead to near critical fire weather conditions.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 57 80 42 65 45 / - 0 0 0 0
Austin Bergstrom Intl Airport 56 80 41 65 43 / - 0 0 0 0
New Braunfels Muni Airport 56 82 42 66 45 / 0 0 0 0 0
Burnet Muni Airport 52 75 37 61 42 / 0 0 0 0 0
Del Rio Intl Airport 54 80 44 74 51 / 0 0 0 0 -
Georgetown Muni Airport 55 77 39 62 42 / 0 0 0 0 0
Hondo Muni Airport 53 83 41 70 46 / 0 0 0 0 0
San Marcos Muni Airport 56 81 41 65 44 / - 0 0 0 0
La Grange - Fayette Regional 59 81 43 66 45 / - 0 0 0 0
San Antonio Intl Airport 56 83 44 67 47 / 0 0 0 0 0
Stinson Muni Airport 57 83 45 69 48 / 0 0 0 0 0
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...TB3
Synoptic/Grids...04
Public Service/Data Collection...Williams
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
844 PM CST Thu Feb 23 2017
.UPDATE...
844 PM CST
Primary change to going forecast this evening was to sharpen up
the temperature gradient across the area tomorrow. Strong warm
front is looking increasingly likely to make it as far north as
about I-80, with areas north of the front likely to see low
clouds, fog, drizzle, and occasional showers with stiff northeast
winds likely to hold temps in the upper 30s or lower 40s. GFS and
NAM have been consistent their past few runs with this, though
RAP and HRRR are a bit more gung-ho on bringing the front a bit
farther north, especially given the tendency for the cold lake to
retard northward advancing warm fronts this time of year.
To the south of the boundary temperatures should climb well into
the 60s with 70 not out of the question far south if the sun
breaks out. Big question convectively for tomorrow is how far west
will initiation occur. Impressive EML advecting into the area
should provide for a strong capping inversion that will take some
work to overcome, though strong forcing and heating in the warm
sector should eventually cause cap to break, just a matter of
whether it is over our eastern CWA or just to our east. Unusually
strong instability for this time of is progged tomorrow with very
strong shear as well, leading to the potential for supercells and
damaging wind producing line segments. At this distance, too hard
to say exactly where initiation will take place, so no changes
made to that aspect of the forecast this evening.
Continued isentropic ascent tonight should lead to continued
development of scattered showers and eventually some thunderstorms
too as steeper lapse rates advect north and lead to increasing
elevated instability. Overall, forecast for tonight appears to be
in good shape. Did add some fog to the forecast for late tonight
and especially Friday morning north of the warm front, where some
locally dense fog could form, especially north of the warm front
close to the surface low.
Izzi
&&
.SHORT TERM...
230 PM CST
Tonight through Friday...
Several forecast concerns through the short term period, including
large north-south temperature gradient, locally heavy rainfall,
timing/extent of thunderstorms, and the potential for severe
weather Friday afternoon across the southeastern parts of the cwa.
Deepening surface low pressure was over far southwestern Kansas
this afternoon, with a nearly stationary frontal boundary
extending northeast into central IL and IN. This low is expected
to propagate to near far southern Lake Michigan by mid-afternoon
Friday, in response to a strong mid-level short wave ejecting from
the central Rockies. Isentropic upglide was already developing
into the region this afternoon, as indicated by rain spreading
into western IL per regional radar mosaic. Increasing south winds
above the warm frontal inversion into this evening will support
strengthening moisture transport, and an increase the coverage
and intensity of showers/rain. Guidance focuses the greatest pops
and rainfall amounts generally along/north of the I-88 corridor
across northern IL, with high-res members eventually shifting
focus mainly across and north of the IL/WI border area early
Friday morning. Forecast soundings depict precipitable water
values approaching 1.00" late tonight, with blended guidance QPF
of 0.75-0.95 inches north of I-88 indicated through Friday.
Thunderstorm potential appears fairly high for late February, with
a plume of steep mid-level lapse rates (700-500 mb >7.5 C/km)
atop 40-50 kt southwest low-level jet late this evening into early
Friday morning. Forecast soundings depict anywhere from 150-450
J/kg of elevated mucape which should support embedded thunder
especially across the aforementioned area overnight.
The surface low is progged to be over far northeast MO/western IL
near Quincy by 12Z Friday, with general model agreement in taking
it across the southern parts of the Chicago metro/far southern
Lake Michigan during the mid-late afternoon hours. With the mid-
level dry slot spreading across the cwa from the southwest during
the afternoon, the focus for surface-based thunderstorm
development is across the southeast parts of the cwa, especially
east of I-55 and along/south of I-80 (with much of the high res
CAM guidance highlighting areas from I-57 east). SPC has
appropriately tightened up the western part of the day 2 slight
risk a little further east of their previous outlook. WRF and GFS
soundings indicate fairly substantial capping around 750 mb,
though large scale height falls associated with ascent with
approaching mid-level wave, divergent left exit region of upper
jet and surface cold front should be enough to force a narrow
band of convection along/just ahead of the front during the
afternoon. While mlcapes are fairly week (<500 J/kg for the most
part), 40-50 kts of effective shear will support storm
organization. While some supercell structures are possible, the
primary severe threat should be damaging winds from convection
within gusty southwesterly 25-35 kt background wind field. Storms
should exit the cwa prior to sunset. Back to the west, the
southeastern periphery of the synoptic deformation precip should
spread in during the afternoon, but should remain all liquid
through sunset. Occasional light rain/drizzle is possible earlier
in the day as well across much of the area as low levels remain
moist beneath the mid-level dry slot and increasing deep layer
ascent.
Temperatures will continue to depict a large north-south variance
across the forecast area. Cool northeast winds north of the warm
front and low track will produce temps mainly in the 30s and 40s
this evening, but will slowly rise into the 40s-50s by Friday as
the low approaches. Farther south 50s overnight will warm to the
60s Friday before colder air surges in late.
Ratzer
&&
.LONG TERM...
Friday night through Thursday...
214 pm...Main forecast concern is the potential for accumulating
snow early Saturday morning...mainly across the northern half of
the cwa...along with much colder temps. Active pattern next week
with various systems but with low confidence.
Much if not all of the convection is expected to be east of the
area by early Friday evening as colder air spreads across the
region and a dry slot moves across the area in the evening. Wrap
around moisture on the back side of the departing low will move
across the area late Friday night into Saturday morning. Qpf
amounts by Saturday morning could approach a tenth of an inch
across the north...lowering to trace amounts across the south.
With the colder air arriving a bit faster...precip should
transition to mainly snow by late evening and continue through mid
morning on Saturday. While snow amounts have gone up...generally
around an inch north of I-88...trailing to a few tenths along
I-80...there is still quite a bit of uncertainty as to how much
snow may accumulate on pavement. While the ground will be warm...
air temps will be falling into the mid/upper 20s by sunrise
Saturday. If the snow is able to fall quickly and heavy enough...
there could be some accumulation on pavement but confidence is
low from this distance. Northwest winds will become strong/gusty
Friday night and continue into Saturday but there remains
differences as to how strong winds will become. Gusts into the
30-35 mph look reasonable currently with speeds/gusts diminishing
with sunset Saturday evening as a ridge of high pressures moves
across the area Saturday night.
Southerly winds could become breezy/gusty Sunday as the gradient
tightens between the departing ridge and a trough moving across
the western Great Lakes with low pressure moving from the southern
plains Sunday to the Ohio Valley Monday...as it weakens. The Ecmwf
remains dry with system while the Gfs lifts precip into the
southern cwa and maintained chance pops for this potential. And if
precip did materialize...it could be a mix of rain/snow but
confidence remains low.
Another ridge of high pressure moves across the area Monday night
as the next low moves from the central plains Monday night to the
upper Great Lakes Wednesday though the Gfs favors a weaker low
tracking through the Ohio Valley. Trended more toward the Ecmwf
which would suggest mainly rain Tuesday/Wednesday with precip
ending before colder air arrives. Confidence remains low with this
system as well. Both models then show a clipper system moving
across the area Thursday night and from this distance...are in
fair agreement. Thermal profiles would support mainly snow with
this clipper. cms
&&
.AVIATION...
For the 00Z TAFs...
Multiple potential weather related aviation problems over the next
24 hours. First, SHRA will continue to develop and move across the
terminals this evening. MVFR CIGS partially a result of the lake
should hold and eventually develop farther inland and build down
to IFR this evening. Isolated to scattered thunderstorms expected
to develop later this evening and there`s a reasonably good chance
that SCTD TSRA will affect or be close to the terminals at times
tonight. Latest high-res guidance would continue to support most
likely timing for potential thunder in the late evening/early
overnight timing from the previous TAFs.
Continued moistening of the low levels and slowly approaching
warm front favor lowering CIGS and VSBY, with cold wind off the
lake further favoring very low CIGS and potential for dense fog
Friday morning as warm front attempts to lift north. For now, kept
the denser fog potential in a PROB30 group due to inherent
uncertainties in forecasting fog, however synoptic pattern quite
favorable for dense fog north of a strong warm front and MOS
guidance is hitting the threat fairly hard as well.
Latest guidance would support surface low tracking just south of
the terminals, except perhaps GYY could pop into the warm sector
Friday. North of the surface low track, very little improvement in
CIGS expected and dense fog potential could even linger into the
afternoon until winds back to northwest later in the afternoon.
Largely followed the trends of previous TAFs which showing
improvement in the afternoon, but feel this is an optimistic
solution assuming the sfc low tracks to our south. Winds should
swing around to the west or northwest late in the afternoon or
early in the evening, but stronger/gustier winds will likely hold
off until later in the evening with the better push of cold air.
Izzi
&&
.MARINE...
214 pm...Low pressure over the south/central plains will move
northeast to the southern tip of Lake Michigan Friday evening and
then into Quebec Saturday. Strong northeasterly winds will
increase to gale force tonight as the gradient tightens ahead of
this approaching low. While gales will diminish Friday evening...
speeds will remain in the 30kt range and then as colder air
spreads across the region and the gradient tightens...northwest
gale force winds are possible from early Saturday morning through
Saturday afternoon. A ridge of high pressure will move across the
southern lakes region Saturday night with winds shifting southerly
Sunday and a period of 30 kts is possible especially on the
southern half of the lake. Another strong area of low pressure may
move across the upper midwest and northern lakes region Tuesday
into Wednesday next week. cms
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...Small Craft Advisory...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 3 PM Friday.
Small Craft Advisory...LMZ741-LMZ742-LMZ743-LMZ744 UNTIL 9 AM
Friday.
&&
$$
VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)
FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
816 PM CST Thu Feb 23 2017
.UPDATE...
Issued at 815 PM CST Thu Feb 23 2017
Will downgrade northern portions of the headlines shortly. Now
that the event is underway and hi-res models are getting a
relatively good handle on the dry air and where the snow shield
will advance, feel confident on tightening the PoP, QPF, and snow
amount gradients. Global model resolution is too coarse to resolve
the ridiculously tight gradient expected which results in bleeding
the snow too far northward. This means locations like Redwood
Falls and the Twin Cities proper may not see a flake. The 00Z NAM
has shifted south slightly again which confirms this idea.
As for the area that will see snow, we are still not seeing
widespread steady snow, and it appears the models are too eager to
break things out this evening, particularly the NAM. However, it
is still expected to become intense tonight near the Iowa border.
Visibilities are 1/4 mile in several locations of northwest Iowa
and thunderstorms are breaking out just south of there so a
maturing snow shield is under development. Expecting this snow
shield to shift mostly east northeastward tonight, then pivot more
northeast Friday. Amounts on the northern periphery of the
Blizzard Warning may be a little high if the HRRR was to verify,
but can`t get too cute.
This southward shift in the past couple days has been a little
surprising to say the least considering the monster totals
advertised on all the models and their ensembles at one point.
Suspect this is due to the very large upper low over Florida which
deamplified the eastern ridge and resulted in a flatter pattern,
sending the low eastward and taking a more southerly track. The
mid level features aren`t as strong and compact either and
are instead more sheared which will prevent the monster totals
(15-18"+) from falling where the heavy band does set up.
The WSW and the rest of the product suite will be issued shortly.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 342 PM CST Thu Feb 23 2017
Surface analysis this afternoon shows development of a classic
mid-latitude cyclone over the TX/KS panhandles with an extended
surface front from the center of this system ENE into lower MI and
a trailing cold front over NM/AZ. Aloft, a large longwave trough
which moved onshore the lower CA coast has shifts atop the
central-southern Rockies. The upper trough is expected to deepen
over the central-northern Plains during the day tomorrow through
tomorrow night, helping add plenty of energy to the developing
surface low. The surface low will shift across KS tonight and over
northern MO tomorrow morning, on its way to lower Lake Michigan by
tomorrow evening then Lake Huron by Saturday morning. Deep Pacific
moisture will accompany this system, so much so that QPF amounts
for southern MN look to range 1.00-1.50" by the conclusion of this
system. Though there continues to be good model agreement (outside
of the NAM which has and remains a significant outlier) that SE MN
will be in the crosshairs for the highest snowfall totals, the
consensus track took another slight shift to the SE, thus lowering
the snow amounts and hence the impacts mainly N and W of the Twin
Cities metro. As such, some minor reconfiguring of the headline
products were made but the point must still be made that there
will be a very tight NW-SE gradient of snow amounts just to the
south of the Twin Cities metro. As an example, counties like Le
Sueur or Nicollet or Dakota or Brown could see as much as a 6"
difference in snow totals from NW to SE across each respective
county.
Snow has commenced in far SW MN this afternoon and snow will
gradually spread mainly E and slightly N as the overnight
progresses. There may even be a slight mixture with rain at the
immediate onset but any mixture of precipitation will have a short
duration before become all snow. As the surface low shifts ENE
and the upper level trough pivots to help enhance the surface
feature, snow coverage and intensity will increase during the
early morning hours, likely with rates increasing to 1-2"/hr for
several hours in far southern MN and into SW WI. The morning
commute for southern/eastern MN into western WI will likely have
ongoing snow then the snowfall will steadily diminish as the day
progresses. However, strong winds for much of the region will
contribute to the blowing snow issues, making for hazardous
travel conditions for much of southern MN. Another concern is
isolated thunderstorms could develop over far southern MN into
southwestern WI. Instability levels are not entirely zero given
the antecedent moisture levels plus the incoming surge and that
additional lift will be created by the pivoting upper level
trough. Confidence not high enough to include mention at this
point but some thunder cannot be ruled out.
Precipitation will end from west to east late tomorrow afternoon
through tomorrow night and the wind speeds will decrease as well,
resulting in partly to mostly cloudy skies for the start of the
weekend. As for temperatures, once temperatures drop below
freezing later this evening, they will remain below freezing
throughout the duration of this event. Lows tonight to highs
tomorrow will have a very small diurnal range, potentially 5
degrees or less from tonight through tomorrow. As colder air wraps
around this system as it departs, lows will drop into the teens
tomorrow night, temperatures this area has not seen in some time
but will be actually right on par with climatological norms.
.LONG TERM...(Saturday through Thursday)
Issued at 342 PM CST Thu Feb 23 2017
Temperatures will warm through early next week. A fairly large
storm will develop over the Upper Midwest, but thermal profiles
should be warm enough to have mostly rain, especially if the
system translates westward with time.
A weak clipper system will sweep through the region on Sunday and
could bring some snow across MN/WI. On Monday the southern stream
will develop a storm to the southeast over the Ohio river valley.
This will be followed by a third system Tuesday into Wednesday.
This mid-week storm will have a favorable temperature gradient
to work with and should develop strong cyclone. However, there is
a lot of warm air with this storm, so the primary p-type will be
rain, with perhaps some snow mixed in. There is still uncertainty
with this storm, but as of now it appears that the chance is quite
low for this system to develop into a winter storm for the Upper
Midwest.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 553 PM CST Thu Feb 23 2017
There have been rather significant changes to the 00Z set of
TAFs. Per a plethora of latest guidance, the northern edge of the
snow will be very sharp and may miss KRWF, KMSP, and KRNH
entirely. Unfortunately each of these locations is on the edge and
it can shift either way so wasn`t confident in completely
removing the snow but it is possible that will need to be done in
the next several hours. Outside of the snow, VFR conditions will
prevail through the period.
KMSP...As discussed above, KMSP will be on the northern fringe of
the snow later tonight and Friday. Depending where it does set up,
further adjustments to the TAF may be necessary.
/OUTLOOK FOR KMSP/
Sat...VFR. Wind NW 10-15 kts becoming W.
Sun...VFR. Chc MVFR/-SN. Wind SW-W 5-10 kts.
Mon...VFR becoming MVFR. Chance afternoon -RASN. Wind S 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until 6 PM CST Friday for WIZ015-023.
Winter Storm Warning until 6 AM CST Saturday for WIZ016-024>028.
MN...Winter Weather Advisory until 6 PM CST Friday for MNZ063-069-070.
Winter Weather Advisory until noon CST Friday for MNZ067-073.
Blizzard Warning until 6 AM CST Saturday for MNZ074>078-082>085-
091>093.
&&
$$
UPDATE...BORGHOFF
SHORT TERM...JPC
LONG TERM...JRB
AVIATION...BORGHOFF
Area Forecast Discussion
National Weather Service Marquette MI
943 PM EST Thu Feb 23 2017
.UPDATE...
Issued at 943 PM EST THU FEB 23 2017
Due to the very dry llvl airmass shown on local 00Z raobs as well as
general diffluent llvl flow associated with weak sfc rdg axis over
the Upr Lks, removed the potential for any lk effect pcpn near Lk
Sup. A quick look at the incoming 00Z NAM and 01Z RAP shows sn
spreading into the scentral cwa late tngt, so wl maintain the 09Z
start to the advy time for that area.
&&
.SHORT TERM...(This evening through Friday)
Issued at 341 PM EST THU FEB 23 2017
The main forecast concern through Friday evening will be the arrival
of system snow across the area on Friday, with the potential for
upslope/lake enhancement snow in the northeast wind snow belts
Friday afternoon/evening. The initial system snow looks like it
will be on the wet and heavy side, especially across central and
eastern portions of the area. In the afternoon hours, the snow is
expected to transition over to a mixture of freezing drizzle/ice
pellets across the east.
Afternoon water vapor imagery shows a strong, deep upper-level
trough beginning to lift out of the southern Rockies with a
strengthening lee cyclone developing in far southwest
Kansas/southeast Colorado. Tonight, expect mid and upper level
clouds to stream back northward as the above mentioned system begins
to lift northeast towards the Great Lakes region. Do not expect any
precipitation tonight; however, through the early morning and
morning hours as surface to 850mb flow veers to the north-northeast
expect light lake effect snows to develop in the north and northeast
wind snow belts. 850mb temperatures do not look terribly cold and
the inversions are quite low, so not expecting much in the way of
lake effect accumulations across the north through the early morning
hours on Friday. However, further south across south central
portions of Upper Michigan were 850-700mb warm air advection begins
to lift north through the early morning hours, a fairly strong mid-
level front will strengthen and may allow for a quick 1 to 2 inches
of wet, heavy snow to fall through the early morning hours.
As we progress through the mid-late morning through the afternoon
hours, the models are fairly consistent with the warm air advection
wing to lift north across the area allowing system snow to spread
north across the remainder of Upper Michigan. Temperature profiles
are on the warmer side of things, especially across eastern and
central portions of the area, so the snow should keep wet and heavy
characteristics. As we progress through the afternoon hours, the
models are fairly consistent with a dry slot moving over at least
eastern portions of the area. Forecast soundings show cloud ice
dissipating within the dry slot; however, given the depth of the low-
level cold air would not be surprised the freezing drizzle is able
to refreeze before reaching the ground. Therefore, may see a mixture
of freezing drizzle/ice pellets. Further west across central and
western portions of the area through the afternoon hours, things
are a bit more uncertain. The GFS would favor a much drier
solution and would hold off additional precipitation chances until
the evening hours, but given the onshore flow and cooling 850mb
temperatures behind the system tend to favor the high-res models
guidance that favor higher QPF, especially across the higher
terrain in the northeast wind snow belts.
.LONG TERM...(Friday night through Thursday)
Issued at 406 PM EST THU FEB 23 2017
Beginning Fri night, 4 km NAM and CMC regional soundings still
indicate mid-level drying into at least the east half of Upper Mi
through much of Friday night which could cut off ice nucleation
until cold advection at lower-levels reintroduces ice back into the
cloud for some lake enhanced snow. For now, fcst will continue to
reflect some mix with -fzra, more likely just -fzdz, which will cut
down snow accumulations over the e half to just 1-3 inches Fri
night. If the mid level moisture does not cut out, snow
accumulations will be higher than currently fcst Fri night. To the n
central and especially w, the air mass will be cold enough to
support lake enhancement as winds back more northerly. However, the
far w will be near the edge of deep layer moisture with the system,
making for a challenging fcst. The 4km NAM and Canadian sounding
maintain deeper moisture near KIWD through much of Fri night while
the GFS sounding shows deeper moisture cutting out already by late
Fri evening. This model difference could range from 6-12hrs of heavy
snow to mainly just light snow. Will continue to lean toward the
more conservative side with fcst for the n central and w with snow
accumulations Fri night in the 3-6 inch range.
System will exit on Sat with a transition to light LES from w to e.
Finally, gusty winds up to 30mph, higher at times in exposed areas
near Lake Superior, will lead to blsn, mainly Fri night into
early Sat afternoon.
As it appears now, the potential for snowfall amounts to reach 12 or
24hr warning criteria is limited so will go with winter weather
advisories at this point, highlighting a period of wet moderate
system snow Fri morning and then the potential for moderate to
possibly heavy lake enhanced snow late Fri into Fri night. Will
continue advisories over the ne counties through Sat for combination
of light les and blsn as northwest wind gust at or above 30 mph.
Some light les could linger for the west to northwest wind snowbelts
Sat night into early Mon as h85 temps hover around -14c through much
of the period.
The only other fcst item of note occurs during the midweek period
next week. Shortwave dropping down the W Coast Sun/Mon is fcst to
shift e and ne to the Great Lakes midweek. GFS is weaker and much
farther se than the 12z run yesterday. The CMC/ECMWF remain more
amplified and stronger with sfc low that will lift into the Great
Lakes, and suggest a low track far enough n for mixed pcpn or even
just rain for a time for at least the southeast parts of the fcst
area. Majority of CMC ensembles favor a warmer look, and fcst will
continue to include mixed pcpn. Thus will definitely be a system to
monitor for next week. After this system departs late Wed, models
suggest that at a clipper system will move through the Upper Lakes
region on Thu with the potential for some more light system snow.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 643 PM EST THU FEB 23 2017
There wl be some lo clds/MVFR cigs at times at the TAF sites this
evng, but overall coverage wl be limited by a llvl acyc flow/dry
air. As a lo pres to the sw moves toward the area later tngt, more
widespread MVFR cigs wl overspread the area along with incrsg chcs
for -sn. Although there is still some uncertainty on the track of
the sfc lo/overall sn coverage, incrsg ne winds along with some
sn/blsn wl incrs the potential for IFR/perhaps LIFR vsbys thru Fri.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 406 PM EST THU FEB 23 2017
NE to N gales to 35-40 kts are expected over much of Lake Superior
Fri morning into Fri night and NW gales to 35-40 knots are expected
for much of central and eastern Lake Superior Sat into Sat evening.
Some heavy freezing spray is possible Fri night into Sat, but
coverage will be limited to mainly the shoreline areas along north
central Upper Mi.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory from 7 AM EST /6 AM CST/ Friday to 7 AM
EST /6 AM CST/ Saturday for MIZ001>005-009-084.
Winter Weather Advisory from 7 AM Friday to 7 PM EST Saturday
for MIZ006-007-014-085.
Winter Weather Advisory from 4 AM EST /3 AM CST/ Friday to 1 AM
EST /midnight CST/ Saturday for MIZ010>013.
Lake Superior...
Gale Warning from noon Friday to 10 PM EST Saturday for
LSZ264>267.
Gale Warning from 7 AM EST /6 AM CST/ Friday to 1 AM EST
/midnight CST/ Saturday for LSZ162-263.
Lake Michigan...
Gale Warning from 7 AM to 7 PM EST Friday for LMZ248-250.
&&
$$
UPDATE...KC
SHORT TERM...Ritzman
LONG TERM...Voss
AVIATION...KC
MARINE...Voss
Area Forecast Discussion
National Weather Service Omaha/Valley NE
935 PM CST Thu Feb 23 2017
.UPDATE...
Issued at 922 PM CST Thu Feb 23 2017
Overall going forecast in good shape tonight. Strong ascent
associated with CDPVA in the 700-300 mb layer coupled with weak
static stability to some upright instability has led to an area
of moderate to occasionally heavy precipitation from northern KS
into eastern NEb/western IA. Models are consistent that this area
of lift will shift north and east over the next several hours
with mid-level dry intrusion working into the southern 2/3 of the
FA. This will likely shut off precipitation for a time overnight.
For precipitation type so far we have seen snow in northeast NEb
with some moderate accumulations to this point. Within the
strongly forced band we have seen some thunderstorms with a mix of
hail/sleet and some snow on the northwest edge.
Late tonight as the mid-level cyclone center works east across
NEb we will see the deformation band sink to the southeast
associated with moderately strong thermal advection with
associated frontogenetic circulation. This should be an all snow
band as it drops to the southeast with snow moving back into the
I80 corridor around 09-10Z. The snow is then expected to continue
in northeast NEb/w-central IA down to the I80 corridor and a bit
south into Friday afternoon. The precipitation intensity will be
much lighter late tonight and through the day on Friday as the
static stability increases as mid-level lapse rates decrease, but
snow ratios will also be increasing. One concern for accumulations
along the I80 corridor is the increasing sun angle and generally
light nature to the snow on Friday may limit to some degree the
impact on roadways, but a good deal of uncertainty remains on how
that affect the impacts of the storm. This concern is less over
the northern CWA where much of the heavy accumulations will be
overnight. Otherwise snow amounts from previous series of
forecasts looks on track and no changes to those or the headlines
are anticipated at this time.
&&
.SHORT TERM...(tonight through Sunday)
Issued at 220 PM CST Thu Feb 23 2017
...Major winter storm still on track to affect the region through
Friday...
Forecast overall remains on track for a major winter storm to
affect the region tonight into Friday. Some complications for the
expected weather include a chance of thunderstorms this evening
across southeast Nebraska and southwest Iowa, which will include a
severe threat with some hail possible. Second compounding factor
will be a changeover from rain to snow, where that initially sets
up, and how fast it moves southeast through time. Northeasterly
winds will continue to increase to 20 to 30 mph through time, with
gusts 30 to 40 mph possible. One of the major changes that we
have made with the upcoming package is to include a slightly
faster changeover from rain to snow based pm Rap model trends.
A couple of notes regarding QPF, the GFS model came in a little
lower, while the SREF and NAM models perhaps a little higher,
which both indicate up to 12 inches or more from northern NE
through northern IA. The ECMWF as not as high, similar to the GFS.
Blending all of that together, combined with input from WPC.
Overall, forecast snowfall amounts have not changed significantly
from the previous package. We are still forecasting 6 to 10 inches
for the northern half of the forecast area, from 2 to 5 along and
either side of Interstate 80, and an inch or less in southeast
Nebraska.
Concerning our current package of winter weather headlines, we
anticipate no major changes with this package, although we may
adjust the start time of the last group of headlines. We feel the
the overall alignment and message of expected impacts looks good
with current products in effect. We do have very strong winds
forecast with this system, and will continue to mention near
blizzard conditions expected with 1/2 mile visibility along with
blowing snow and possibly drifting. However, just not confident
we`ll see widespread 1/4 mile visibility for 3+ hours, thus have
no plans to upgrade any of the area to a blizzard warning at this
time.
Snow accumulation rates will be winding down significantly Friday
afternoon, tapering to flurries, and ending altogether before
midnight. Due to recent warmth, soil temperatures are running in
the mid to upper 40s. This will easily be overcome by expected
rates.
Impacts to travel will eventually develop. Near blizzard
conditions are expected across northeast NE and northwest IA.
Travel may eventually become impossible over parts of of the area.
Quiet weather expected on Saturday. Another weather system brings
a chance of small snow and rain south of I80 on Sunday, with the
GFS a little more robust than the ECMWF.
.LONG TERM...(Sunday night through Thursday)
Issued at 220 PM CST Thu Feb 23 2017
Another quick moving weather system moves through the region on
Tuesday. Again, the GFS is more robust with this than the ECMWF,
but we will have a chance of snow and rain in the forecast. And
one more system may graze our northern counties on Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 555 PM CST Thu Feb 23 2017
Precipitation has switched over to snow at KOFK, and periods of
moderate to heavy snow are expected to continue through the
evening with gusty north and northeast winds. Lighter snowfall and
some blowing snow is then expected late tonight and into Friday
with IFR conditions continuing. Scattered TSRA are still expected
at KLNK/KOMA this evening, with some possibility of a sleet and
rain mixture near the end around 06Z. We then expect a dry period
into the night with continued IFR conditions. The snowband is
likely to move into KLNK/KOMA around 08-10Z and continue through
the day on Friday with IFR conditions expected through the day.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Storm Warning from 3 AM Friday to midnight CST Friday
night for NEZ034-044-045.
Winter Weather Advisory from 3 AM Friday to midnight CST Friday
night for NEZ050>053-065>067.
Winter Storm Warning until midnight CST Friday night for NEZ015-
032-033-042-043.
Winter Storm Warning until midnight CST Friday night for NEZ011-
012-016>018-030-031.
IA...Winter Storm Warning from 3 AM Friday to midnight CST Friday
night for IAZ043-055.
Winter Weather Advisory from 3 AM Friday to midnight CST Friday
night for IAZ056-069-079.
&&
$$
UPDATE...Boustead
SHORT TERM...DeWald
LONG TERM...DeWald
AVIATION...Boustead
Area Forecast Discussion
National Weather Service Spokane WA
745 PM PST Thu Feb 23 2017
.SYNOPSIS...
A cool and unsettled pattern will continue over the Inland NW
right into the weekend and into early next week. The main
precipitation threat will be mainly mountain based snow showers,
but a stronger system on Sunday may bring minor snow accumulations
to the valleys and Basin. Temperatures will be cooler than normal
for this time of year with overnight lows in the teens and 20s
and daytime highs only in the 30s. A gradual warm up is forecast
by the middle of next week.
&&
.DISCUSSION...
Small update this evening to remove snow showers in the Camas
Prairie, adjust sky cover, and lower temperatures in the Blue
Mtns. There has been no snow observed on the area cams and models
are in good agreement that the dendritic layer is dried out over
the Camas Prairie. There is still some cloud cover wrapping into
the area from the storm system well to the south however any
precipitation that falls from this deck will be in the form of
flurries. A better chance for a light snow showers will exist
across far SE Shoshone County not really impacting any populated
areas.
It will be a chilly night with overnight lows in the teens and
twenties. Areas of freezing fog expected to develop but confidence
is not stellar if it will be as widespread as this morning with
HRRR indicating only very shallow activity and far less coverage.
This makes sense as nearly all ASOS sites are 4 to 9 degrees drier
than this time last night. /sb
&&
.AVIATION...
00Z TAFs: Fog and stratus development are expected tonight over
the KGEG...KSFF and KCOE TAF sites as the cold air mass decouples
overnight. Overrunning clouds from a weak system off the coast may
help break the stratus between 16Z and 18Z into MVFR stratocumulus
ceilings with a small chance of -SHSN during the afternoon hours.
It is uncertain and low confidence forecast for a return of
stratus to KPUW overnight tonight with the favorable upslope
westerly winds expected to weaken and shift more southerly
overnight which would favor less of a threat for IFR conditions by
Friday morning. KLWS is expected to remain VFR overnight as is
KMWH and KEAT. During the day Friday upslope low level flow into
the Cascades will allow thickening and lowering ceilings at KEAT
and may deteriorate to MVFR during the afternoon with -SHSN
developing near the TAF site. /MJF
&&
.PRELIMINARY POINT TEMPS/POPS...
Spokane 18 34 19 34 24 34 / 0 10 10 10 30 60
Coeur d`Alene 17 34 16 34 22 34 / 0 10 10 10 50 60
Pullman 20 36 20 36 25 36 / 0 10 10 20 30 60
Lewiston 25 40 25 41 27 40 / 0 10 10 20 20 60
Colville 18 35 18 35 24 35 / 0 20 10 10 30 60
Sandpoint 19 33 17 34 23 33 / 0 20 10 20 50 60
Kellogg 19 33 18 33 23 33 / 0 20 10 20 50 70
Moses Lake 18 35 19 35 25 36 / 0 10 10 0 20 30
Wenatchee 20 32 19 34 24 35 / 0 20 10 0 30 40
Omak 19 32 19 32 24 33 / 0 20 10 0 40 50
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...None.
WA...None.
&&
$$
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Friday)
Issued at 245 PM CST Thu Feb 23 2017
The short-term period will consist of precipitation chances along
with a return more seasonable February temperatures. As of Thursday
afternoon a deepening surface low was situated over southwestern KS.
An east to west oriented warm was located over the southern CWA. Mid
level lapse rates continue to steepened in response to the upper
level low progressing from northern Colorado into western Nebraska.
The biggest question mark through the evening hours is whether the
EML will hold across northern KS. Latest 00Z-03Z forecast soundings
from the RAP and HRRR suggest a stronger EML than previous runs.
Sufficient large scale forcing is expected as a upper level short
wave will move across north-central KS and south-central KS. Modest
isentropic lift within the 300-305K will remain across the area
through 06Z. If parcels were able to break the cap, around 500 J/KG
of MUcape and 40-50 knots of effective shear would be available.
With this potential for supercells, SPC has upgraded portions of
north-central KS to a slight risk with the primary hazard being
large hail.
We then transition back to typical winter conditions overnight into
Friday. As the surface low pushes east of the area overnight, CAA in
response to gusty northwest winds will cool temperatures
throughout the day on Friday. High temperatures for Friday will
occur at midnight, with afternoon temperatures ranging from the
low 30s in the north to low 40s in the southern areas. The bulk of
precipitation associated with upper level low in Nebraska is
expected to stay north of the area. However, sufficient low level
moisture may exist for light wintry precipitation, mainly along
the KS/NE border, possibly as far south as I-70 throughout the day
on Friday. Forecast soundings suggest a brief period near dawn
across far north-central KS, where only low level saturation
exists. With surface temperatures hovering near freezing, I have
introduced a couple hours of light freezing drizzle. Pavement
temperatures are well above freezing across the entire area,
therefore expect minimal accumulation and impacts to roads.
.LONG TERM...(Friday night through Thursday)
Issued at 245 PM CST Thu Feb 23 2017
Lingering deformation zone on the backside of our departing system
may continue to bring light snow to portions of far NE Kansas early
Friday night, but little to no accrual is expected. Surface ridging
will build in overnight Friday into Saturday morning resulting in a
gradual decrease in winds and cloud cover. The progressive zonal
flow pattern behind the departing trough will allow the 1026 mb high
to slide through the region through the afternoon on Saturday and
set the stage for our next system on Sunday. Medium range solutions
are struggling with how this upstream wave will interact with a
cutoff low NE of Hawaii, which is having a direct impact on the
timing and location of the wave as it translates ESE on Sunday. The
GFS solution brings out a more amplified H500 wave for Sunday, which
in turn brings more precip to the area. Continued using a blend of
the GFS/ECMWF for POPs through this period, with confidence in this
portion of the forecast lower than average. Temperatures for the
weekend will linger around climatological average for this time of
year with a slight warming trend for Sunday as weak WAA takes place
behind the departing ridge.
An active pattern will continue into mid week as a longwave trough
slides east across the CONUS. This will likely bring another round
of precip (mostly in the form of rain) to the area on Tuesday into
Wednesday, but as with the Sunday system, confidence in the
placement of the precip is lower than average. Highs on Tuesday will
likely rebound back into the 60s ahead of the approaching frontal
boundary, falling back into the 40s and 50s for mid to late week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 527 PM CST Thu Feb 23 2017
A surface cold front will push southeast across the terminals this
evening and switch winds to north at 14 KTS with gusts to 22 KTS.
There may be a chance for showers at MHK this evening...and
possibly some isolated showers at KFOE and KTOP late this evening.
Low stratus of 1000 to 1500 feet will move southeast across the
TAF sites during the early morning hours of Friday. The ceilings
may gradually rise above 2,000 feet during the late afternoon
hours of Friday. There may also be some isolated to scattered
showers Friday afternoon.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Baerg
LONG TERM...Skow
AVIATION...Gargan