Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/13/23
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
525 PM CST Tue Dec 12 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Wednesday night)
Issued at 253 PM CST Tue Dec 12 2023
Southeasterly low-level winds will continue to advect additional
moisture into the region through the period. This moisture will help
maintain overcast skies, and serve as the foundation for continued
rain chances.
Weak forcing, courtesy of some upper level divergence and a weak
shortwave, looks to increase rain chances tonight. GFS and HRRR runs
are continuing to focus the best rain chances along and east of I-
69C, however NAM and HRW runs push the rain chances further inland.
Conditions generally look more favorable along the coast and
offshore, where higher moisture values are present.
As an upper-level jet-streak sets up over northern Mexico Wednesday,
we will likely find ourselves under the exit region of the jet,
providing additional forcing. Some weak instability will further
increase rain chances Wednesday afternoon. Lower instability and
weaker forcing will cause rain chances to diminish slightly
Wednesday night, though a slight chance for light rain will remain.
High temperatures Wednesday will remain in the mid to low 70s, and
low temperatures tonight and Wednesday night look to fall to the low
to mid 60s.
&&
.LONG TERM...
(Thursday through next Tuesday)
Issued at 253 PM CST Tue Dec 12 2023
Deterministic models are in
better alignment with the placement and track of the extensive mid-
upper low that will be traveling through the 4-corners and Southern
Plains regions Thursday and Friday. Unsettled and wet weather days
for all of Deep South Texas persist these two days with best chance
of long-duration rainfall Thursday with the chance of rain waning
late Friday. The upper low should continue to lift northeast with a
mid-level ridge building in for the weekend and early next week
providing fair, dry and cooler weather.
East to southeast low level flow and deep southwest flow to
respectively advect abundant Gulf of Mexico and Pacific moisture
over South Texas courtesy of the large mid-upper level low pressure
area. Moisture convergence along a coastal trough and lift aided by
a 120kt jet streak within the subtropical jet overhead should
provide likely rain chances Thursday with rainfall amounts between
one-tenth and one-half inch (higher amounts near the coast). Rain
chances remain relatively high Thursday night and Friday but look to
trend downward Friday afternoon and especially night as the upper
low trough axis nears the Texas coast. Another tenth to quarter inch
of rain is possible Friday. Temperatures will continue to be mild
but with the rain and thick cloud cover expect narrow diurnal range
of highs in the upper 60s to low-mid 70s and lows in the low to mid
60s.
Atmosphere begins to dry out overnight Friday and remains
significantly dry through early next week with a deep northwest flow
over Texas as a large scale ridge slowly traverses the Rockies Front
Range and the Plains. This will provide a stable airmass Saturday-
Tuesday with fair skies and cool-mild days (60s) and cool-crisp 40-
low 50s)nights.
Along south Texas beaches and coastal locations there remains a
threat of coastal flooding and dangerous surf conditions as a long
period potential high swell developing over the Gulf. Models
continue to show a strengthening pressure gradient emanating from a
1040mb surface high over the Ohio Valley to Mid-Atlantic States.
Coastal flooding and dangerous beach conditions are looking more
likely Thursday into Friday morning as this swell train works its
ways westward. A strong north to northwest wind develops Saturday as
a potential deep surface low forms over the Gulf of Mexico which
will like maintain a high risk of rip current but should lessen the
chance of coastal flooding for the weekend.
&&
.AVIATION...
(00Z TAFS)
Issued at 523 PM CST Tue Dec 12 2023
Lowering ceilings and increasing chances of light rain is expected
through the next 24 hours. Overall, however, VFR will prevail for
the period.
&&
.MARINE...
Issued at 253 PM CST Tue Dec 12 2023
(Today through Wednesday night)... A surface high pressure system
over the eastern US looks to provide tightening pressure gradients
and moderate to strong easterly winds across the northern Gulf
through the period. The combination of stronger winds and the long
fetch length will lead to building seas through the period, likely
reaching Small Craft Advisory thresholds by Wednesday evening. Ample
low level moisture and weak forcing aloft will continue to support
the chance for some light rain through Wednesday night.
(Thursday through Tuesday)...Rough and dangerous marine
conditions are expected to be ongoing Thursday and continue through
at least Sunday morning. Initially, a long period swell train will
be in progress with potentially significant heights Thursday with
strong high pressure building across the Mid-Atlantic States
spreading over the Gulf. Winds although not that strong, Small Craft
advisories are likely to be in effect for the high seas through
Friday. Stronger winds develop Friday night and Saturday as an area
of low pressure developing over the southern Gulf strengthens
significantly and tracks northeastward. Models are suggesting a
window of strong northwest winds with the potential of gale force
gusts over portions of the Gulf coastal waters. In any case, Small
Craft Advisories are likely to continue Saturday and possibly
persist through Sunday morning for all coastal waters. Improving
conditions are scheduled for early next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
BROWNSVILLE 65 75 67 73 / 30 30 20 60
HARLINGEN 62 73 63 73 / 30 40 20 60
MCALLEN 62 74 63 72 / 20 30 20 50
RIO GRANDE CITY 62 73 63 71 / 10 30 20 40
SOUTH PADRE ISLAND 67 72 68 71 / 40 30 20 60
BAYVIEW/PORT ISABEL 64 74 64 72 / 30 30 20 60
&&
.BRO WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Area Forecast Discussion
National Weather Service Billings MT
202 PM MST Tue Dec 12 2023
.DISCUSSION...
Tonight through Wednesday night...
Persistent fog and low clouds were only slowly dissipating from N
to S over S Big Horn, S Rosebud and Sheridan Counties. HRRR had a
pretty good handle on the fog to start, but then dissipated it
too quickly. Added fog/clouds to the above areas through 21Z, then
had patchy fog over areas from KBIL E from 09Z tonight through
18Z Wednesday based on the HRRR. For the overall pattern, models
agreed on an upper low, currently over NV, swinging through the
four-corners region through Wed. night. Forecast area will be
under a dry airmass with upper ridging. PWAT`s will be less than
0.25 inches most areas. While 700 mb winds looked unfavorable for
strong gap flow, tight pressure gradient supported raising winds
above NBM values over KLVM/Nye Wed. morning. Also raised winds a
little over K6S0 due to pressure gradient. Lee trough strengthens
again late Wed. night, so raised wind speeds in gap areas, K6S0
and Harlowton. Temps will be about 10 degrees above normal on
Wednesday. Arthur
Thursday through Monday...
Through the long term, an upper level ridge will keep conditions
dry and warmer than normal. Weak shortwaves in the flow may
tighten the pressure gradient, bringing stronger winds over the
western foothills. The best chance for strong winds near
Livingston will be Friday night through Saturday as flow aloft
increases in response to a wave moving across southern Canada.
Currently, Livingston has a 40% chance of gusts over 50 mph and a
10% chance of gusts over 60 mph in this time frame.
High temperatures will be 10-20 degrees above normal, with highs
generally in the 40s to mid 50s. Saturday is expected to be the
warmest day, with highs in the 50s to near 60. Due to the extended
pattern of dry conditions and above normal temps, grass fire
concerns may be elevated on Saturday. Archer
&&
.AVIATION...
Low ceilings near KLVM and KSHR are expected to gradually clear
this afternoon. Fog is possible near KBIL, KMLS and KBHK tomorrow
morning. Otherwise, VFR conditions will prevail. Archer
&&
.PRELIMINARY POINT TEMP/POPS...
Wed Thu Fri Sat Sun Mon Tue
-----------------------------------------------------------
BIL 026/046 028/049 028/043 028/056 031/054 032/050 032/050
00/U 00/U 00/U 00/B 00/U 00/B 00/B
LVM 021/045 025/048 026/044 029/055 031/053 031/051 032/049
00/N 00/U 00/U 00/N 00/U 00/B 00/B
HDN 021/046 021/049 022/044 023/056 026/053 025/050 026/050
00/U 00/U 00/U 00/U 00/U 00/B 00/B
MLS 019/043 024/044 022/038 021/051 025/046 024/045 026/046
00/U 00/U 00/U 00/U 00/U 00/B 00/B
4BQ 023/045 028/048 026/041 024/055 028/051 027/050 028/048
00/U 00/U 00/U 00/U 00/U 00/B 00/B
BHK 016/041 022/044 018/034 015/050 021/044 021/043 021/041
00/U 00/U 00/U 00/U 00/U 00/B 00/B
SHR 018/046 023/050 023/044 023/059 028/056 027/053 028/051
00/U 00/U 00/U 00/U 00/U 00/B 00/B
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings
Area Forecast Discussion
National Weather Service Cheyenne WY
815 PM MST Tue Dec 12 2023
.KEY MESSAGES...
1) Freezing fog continues across much of Laramie Co including the
I-80 corridor leading to hazardous travel conditions into
Wednesday morning.
2) Benign weather expected late this week into the weekend with
overall drier and warmer conditions.
&&
.UPDATE...
Issued at 815 PM MST Tue Dec 12 2023
Fog has become slightly more patchy this evening across Laramie
county with webcams showing improvement over the Interstate 80
summit. However, areas of dense fog remain over central Laramie
county. Additionally, high resolution models are showing a
second push of low clouds intersecting the southern Laramie
range later this evening, starting around 10PM. Therefore,
decided to extend the freezing fog advisory once again through
9AM Wednesday morning. Use caution when traveling with locally
dense fog along with patchy minor icing through the morning
hours over Laramie county.
&&
.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 139 PM MST Tue Dec 12 2023
Latest satellite imagery shows an upper level low over central
NV digging southeast with a large cloud shield across much of
southern WY and the Front Range. Day Cloud Phase RGB hints at a
large swath of high clouds, however breaks show peeks of what`s
happening closer to the surface with widespread low clouds along
and east of the Laramie Range. Last night`s snow has moved out
of the area late this morning with KUDX showing the last few
echos near Chadron.
Freezing fog continues across southeast WY, especially throughout
Laramie Co and the I-80 corridor between east of Cheyenne and
Laramie. KCYS ASOS has recorded notable ice accumulation with 0.25"
for the day, but that seems to be mostly on elevated surfaces.
Latest RAP soundings for Cheyenne keep low-level saturation in place
into the evening suggesting visibility reduction will continue headed
towards the evening commute. Interstate webcams and visibility
observations have shown dense fog for much of the day, but portions
of the South Laramie Range have seen some localized improvements.
However, with upslope flow continuing it is difficult to believe
these improvements will be long lasting. Latest HRRR visibility
guidance also suggests a return of reduced visibilities around
00z for the I-80 Summit. Therefore, decided to extend the
Freezing Fog Advisory through the evening commute, but there is
the possibility these conditions could persist overnight.
Headed into Wednesday, the upper level low over the Great Basin will
be closed off moving into the southwest CONUS leading to south to
southwest flow at 500mb across the Front Range. An initial shortwave
energy looks to approach the I-80 corridor from Cheyenne to Sidney
in the morning with widely scattered snow showers possible before a
stronger wave with better lift passes through Wednesday evening.
Wednesday evening`s chance of precipitation in the southern NE
Panhandle (25-35%) is supported by latest hi-res guidance. EC
members are a little more bullish than the GEFS with precipitation in
the southern NE Panhandle Wednesday evening with up to 0.10" of QPF.
Elsewhere, PoP is pretty low (< 10%) Wednesday across the CWA
as temperatures will remain on the colder side with highs in the
30s.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 139 PM MST Tue Dec 12 2023
Overall, looking at a quiet long term with a gradual warming
trend through the beginning of next week.
As a closed upper-level low traverses eastward across New Mexico on
Thursday, some lingering wrap-around moisture from the system to the
south could produce areas of low stratus along the Interstate-80
corridor from Sidney to the south Laramie Range. With the low
stratus present during the morning, cannot rule out a slight chance
(15 percent) of some light showers, mainly around Sidney. As the
system pushes eastward, skies will gradually clear throughout the
afternoon.
The rest of the long term looks dry and uneventful as an upper-level
ridge builds over the Rockies through the weekend. The ridge will
help facilitate warm air advection across the region with 700 mb
temperatures rising above 0C. In fact, 700 mb temperatures could get
as high as +6C by Sunday. According to NAEFS climatology, 700 mb
temperatures Saturday through Monday will at least be in the 90th
percentile. These anomalously warm temperatures aloft will lead to a
mild weekend and start to next week. High temperatures by Sunday and
Monday will be well above average, sitting in the 50s for areas east
of the Laramie Range and 40s to the west. A weak shortwave moving
through Sunday will elevate winds across the wind prones and lead to
downslope flow, also helping keep temperatures on the mild side on
Sunday.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 419 PM MST Tue Dec 12 2023
IFR to LIFR conditions persist at KCYS, whereas at all other
TAF terminals across southeast Wyoming and western Nebraska,
conditions have returned to VFR. KLAR and KRWL may experience
reductions to MVFR/IFR CIGS late tonight, from 05Z until
tomorrow afternoon. The ending time for when those lowered CIGS
is still a bit uncertain. The Nebraska panhandle should remain
VFR with CIGS around 6-10 kft.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Freezing Fog Advisory until 9 AM MST Wednesday for WYZ116>118.
NE...None.
&&
$$
UPDATE...MN
SHORT TERM...MB
LONG TERM...SF
AVIATION...LEG
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
800 PM CST Tue Dec 12 2023
.UPDATE...
Issued at 800 PM CST Tue Dec 12 2023
A narrow band of low level frontogenesis was producing light radar
returns over northern MO this evening, though no reporting sites
have reported flurries as of 8 pm. Forecast soundings over west
central IL show a very dry airmass will remain in place below 850
mb. As the forcing moves overhead in a weakening fashion
overnight, a few flurries are possible toward the Jacksonville
area, but feel the dry air will win out. The main impact of the
warm advection aloft will be thickening mid level clouds, becoming
overcast after midnight. Where skies stay clearer later,
northeast of a Bloomington to Paris line, evening lows in the mid
20s are expected, while lows farther southwest will likely be in
the upper 20s to around 30F. High pressure nosing in from IA will
keep winds calm to light/variable overnight.
25
&&
.DISCUSSION...
Issued at 110 PM CST Tue Dec 12 2023
Despite the weak cold front which crossed central Illinois from the
northwest this morning, temperatures across the Prairie State remain
near climatological normal - with upper 30s northwest of the IL
River to upper 40s-low 50s south of I-70 at 1 pm. The closest we get
to experiencing any weather this work week will be tonight into
tomorrow morning, when 500mb winds increase in response to a
sharpening 1000-500mb height gradient across the region as a trough
over the Upper Great Lakes dives southeast into the Northeast, and
when a tiny blip of enhanced vorticity aloft translates into the
region from the west-northwest. Weakening FGEN (from ~3K/100km/3h in
southern Iowa around midnight to <1K/100km/3h by the time it reaches
central Illinois just before sunrise tomorrow, per HREF mean),
coupled with weak Q-vector convergence (uplift), should
theoretically generate some precip. However, the layer beneath the
saturated (or nearly saturated) dendritic growth zone looks to be
sufficiently dry to prevent anything from reaching the surface. The
CAMs continue to trend drier, and the more recent HRRR iterations
are scarcely showing even any simulated radar reflectivities in
our area tomorrow morning. The Localized Probability Matched Mean
(LPMM) from HREF, which was showing a splotch or two of measurable
QPF in the region in previous iterations, is completely void of
precip in its most recent (i.e., 12.12z) run. Can`t rule out a
flurry or two tomorrow morning, but there almost certainly (>99%
chance) won`t be impacts.
The deterministic models and their ensembles are in general
agreement that 500mb heights will embark on an upward journey
beginning late tomorrow and continuing into late Thursday or Friday
across the Midwest as a cutoff low drifts across the Desert
Southwest and into the Southern Plains. This means gradually
increasing temperatures for us with probabilities for highs > 50
increasing to 30-45% and 40-60% along and south of the I-74 corridor
Thursday and Friday, respectively.
Model disparities become more evident as we head into the weekend,
however, with the struggle being resolving the relationship
development between the aforementioned cutoff low in the Southern
Plains/Deep South and a northern stream shortwave. The 12.00z ECMWF
suggests the two will merge across Missouri and subsequently dive
southeast across the Tennessee Valley, with central and southeast
Illinois getting a tenth or two of an inch of precip out of it late
Saturday into early Sunday; the GFS has the two systems merging
together a little further southwest -- near the Oklahoma/Arkansas
border -- and consequently most of the precip missing us; and the
Canadian, by contrast, doesn`t fully merge the two systems, but
does suggest that the northern stream shortwave will be strong
enough over central Illinois to generate perhaps a quarter inch or
more QPF.
P-type issues would be a concern if this precipitation winds up
falling Saturday night when surface wet bulb temperatures fall to
around freezing but still over 70% of the LREF has 850mb
temperatures above 0C; this would indicate a warm nose aloft but
potential for refreezing of precipitation either just above the
surface (for ice pellets) or on the surface (for freezing rain).
However, around this time only about 20% of the LREF has precip, and
it`s likely those members that do have it are the ones with cooler
850mb temps and warmer surface temps than most of the ensemble, so
rain seems the most likely p-type at this point, with perhaps the
second most likely (or rather, least unlikely) being snow if dynamic
cooling brings surface temps down to the wet-bulb temperature. We`ll
continue to watch this one.
Because of model differences in how that cutoff low and northern
stream shortwave are handled, WPC`s cluster analysis suggests the
upper pattern becomes increasingly ambiguous by the end of the
weekend and especially heading into early next work week. For
Sunday, all three deterministic models are largely outliers from the
PC1-PC2 phase space, suggesting (a positive PC2 which represents) a
negative departure from the LREF`s ensemble mean 500mb heights
across the Tennessee Valley -- more concisely put: they each have a
deeper trough near/just south of us than the mean of the LREF system
(which features 100 models). Thereafter, the main source of
uncertainty in the LREF is how long it takes the ridge across the
west to build in and restore 500mb heights to (well) above normal
across the Midwest, with the general trend from the ensemble,
holistically, being a warming one next work week, the coolest days
likely being Monday and Tuesday. CPC continues to advertise a 60-80%
probability for above normal temperatures and 60-70% probability
for below normal precipitation for days 6-10.
Bumgardner
&&
.AVIATION... (For the 00z TAFs through 00z Wednesday Evening)
Issued at 500 PM CST Tue Dec 12 2023
A weak upper level disturbance crossing the region tonight and
Wednesday, will bring mid-level/VFR clouds to the area. Initially
bases are near 10k feet this evening, lowering to 5k feet after
09z, then diminishing Wednesday afternoon. At the surface, high
pressure currently centered over western IA, will shift east into
central IL tonight, and linger over the area through Wednesday.
This will result in light/variable to calm winds through the
forecast.
25
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
727 PM EST Tue Dec 12 2023
.UPDATE...
Issued at 723 PM EST TUE DEC 12 2023
Quick update to shift the higher snowfall accumulations in the
00-06Z period a bit northward toward Grand Marais based on radar
depiction of a relatively stationary convergent band in that area.
NAMNest has a good handle on the band, which may shift slightly
south over the next 6 hours or so. 2-5" more snow forecast in
the northeast Alger/northern Luce area through around 06Z before
models show a loss of saturation in the DGZ.
&&
.SHORT TERM...(The rest of this afternoon through Tonight)
Issued at 255 PM EST TUE DEC 12 2023
Key messages:
-West-northwest lake effect snow ongoing, with 3-6 additional
inches possible (25%-75% chance) over the eastern UP tonight
-Blustery conditions are ongoing across the UP this afternoon, with
the strongest gusts across the Keweenaw.
-Low temperatures falling into the teens with single digits likely
(~75% chance) in some interior west locations
RAP analysis shows the UP squarely between a 997mb low over the
Hudson Bay and a 1033mb high over Sioux Falls, SD. The pressure
gradient in addition to efficient boundary layer mixing up to nearly
5 kft is leading to particularly gusty winds, with high-end gales
observed on and along the shores of Lake Superior and winds gusting
to 47 mph at Freda and 56 mph at KCMX this morning. The Wind
Advisory is still in effect, but as the pressure gradient relaxes
with the high pressure approaching tonight, winds should relax to
below advisory threshold, though still high enough at the shores
to feel "blustery".
With 850mb temperatures plummeting to the mid-negative teens and
slightly cyclonic surface flow, WNW lake effect snow bands have
formed and are evident on the KMQT radar. The dominant band is
expected to be over eastern Alger County and northern Luce County
this evening, where the HREF is highlighting a small area of up
to a 30% chance of 8 inch accumulations over 12 hours ending late
this evening. However, given the sparse population in that area,
expecting that snow reports will probably fall in the 4 to 6 inch
range, which falls more in line with probability matched means
and ensemble mean snowfall totals. With impacts mostly limited to
rural areas that are already prepared for such snowfall, the
Winter Weather Advisory will be allowed to continue with little
changes made.
A general decreasing trend in the cloud cover and snowfall is
expected tonight as the surface high and supporting ridge aloft
advance towards the UP. Lake effect snow should only barely be
holding on in the east as the dawn breaks with surface level flow
becoming more anticyclonic and the boundary layer moisture
beginning to dry out. The NBM gives a 75% chance that the
temperatures in the interior west could fall to single digits
while much of the rest of the UP falls into the teens and low 20s
along the shoreline. Given the winds, the apparent temperature
could fall towards 0 degrees, so bundle up if you have outdoor
activities early in the morning.
.LONG TERM...(Wednesday through Tuesday)
Issued at 316 PM EST TUE DEC 12 2023
Key messages:
- Another surge of unseasonable warmth arrives Thursday on breezy sw
winds. High temps 15-20 degrees above normal.
- Over the next 7 days, the only potential of area-wide
precipitation occurs Fri/Fri night, and that pcpn will be light and
mostly in the form of rain.
- For the next 2 weeks, above normal temps will prevail on most
days, especially from the middle of next week onward, and pcpn will
be well below normal with no widespread, significant system
snowfalls on the horizon for Upper MI.
The last of the lake-effect snow ends over the eastern U.P.
Wednesday as ridging from a 1040mb high over the Mid-Mississippi
Valley moves over us. While there could be up to a dusting out east
in northern Luce County/far eastern Alger County Wednesday morning,
the snowfall should be over by Wednesday afternoon. While cold,
normal winter air still remains over our area Wednesday; with skies
being or becoming mostly sunny Wednesday, decided to bump up
temperatures a couple of degrees and make the highs around 30.
Moving into Wednesday night, a weak surface shortwave attempts to
move through our area while the aforementioned high strengthens to
1043mb over the Ohio River Valley. With the robust high interacting
with a vigorous low pressure over Hudson Bay, expect a tight
pressure gradient to develop over us Wednesday night into Thursday.
This brings breezy conditions across the U.P. Thursday, with wind
speeds up to 20 to 30 mph. While winds of 40 to 45 knots are just 1
to 2 thousand feet above the surface, with daylight being near the
annual minimum and warm air advection bringing a low-level inversion
near the surface, winds may have a difficult time getting higher
over the land. That being said, Thursday will be an unseasonably
warm day, with the the NAEFS and ENS showing temperatures getting to
around the 99th percentile of modeled climatology. What this
translates to is high temperatures in the 40s, with possibly a few
spots reaching 50. Therefore, I wouldn`t be surprised if much of the
snowfall we have/will receive melts Thursday. In addition, we could
see a few high temperature records tied or broken. Winds begin to
die down Thursday night as the pressure gradient slackens and the
high over the Ohio River Valley weakens.
Our next chance at precipitation looks to occur Friday as a weak
shortwave develops over the Northern Plains along the northwestern
edge of the flow of the weakening high pressure. While model
guidance differs on how long the shortwave will remain over our
area, it seems certain (99% chance) that the main precipitation type
will be rain. That being said, there is a small chance (20%) that
rain could change over to snow on the back-end of the system for a
short time; expect only a dusting at most.
While temperatures are projected to head back closer to normal late
this week into this weekend, expect above normal temperatures to
persist until Sunday at the earliest. Come early next week, we could
see another cold front push through the area and bring similar
conditions to what we have been seeing today. After that, more warm
air over the Western U.S. and Pacific looks to make its way toward
our neck-of-the-woods. Thus, above normal temperatures return as we
move through next week and head towards the Christmas holiday. With
above normal temperatures and below normal precipitation expected
(see Climate Prediction Center`s outlook) until Christmas, I`m
thinking chances are high (at least 70%) that we will see a brown
Christmas across the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 638 PM EST TUE DEC 12 2023
VFR conditions are expected to prevail through the TAF period as a
ridge of high pressure gradually builds in across the UP. At the
start of the TAF period, low VFR and a few isolated lingering lake
effect snow showers will be at CMX, with potential for brief MVFR
vsby through around 03Z or so. Winds at CMX will continue to be
quite strong with gusts around 30-35 kt continuing through around
06Z before they gradually decrease for the rest of the night into
the day Wednesday. A stray snow shower is possible at SAW for about
the first 3 hours of the TAF period, but vsby reductions are
unlikely. All of the lake effect lower VFR clouds should remain
north of IWD. Lower VFR clouds will gradually dissipate through the
night at CMX/SAW.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 316 PM EST TUE DEC 12 2023
Northwest gales of 35 to 40 knots slowly decrease late this
afternoon through tonight as the cold air advection has now ceased.
Winds become calm at 20 knots or less by around noon Wednesday as
ridging from a high over the Mid-Mississippi Valley moves across the
lake. However, the calmer winds will be short-lived as the parent
high pressure strengthens to 1043mb over the Ohio River Valley and
interacts with a robust low pressure over Hudson Bay. This brings a
tight pressure gradient across the lake Wednesday night through
Thursday, bringing southwesterly gales of 35 to 45 knots across the
west and north central lake; the highest winds are expected between
the Keweenaw and Isle Royale, where a there is a small (20%) chance
that storm force gusts up to 50 knots could be seen. In addition,
there is a chance (50%) that some gales up to 35 knots could be seen
over the eastern lake Thursday. While higher winds could be
realized, mixing may be limited due to the low sun angle, the low
amount of daylight, and a low level inversion setting up due to the
warm air advection across the region. Nevertheless, I think there
will be enough mixing to warrant Gale headlines in the future. As we
move into Thursday night and Friday, the pressure gradient over Lake
Superior slackens as the high pressure over the Ohio River Valley
weakens and a shortwave low developing over the Northern Plains
approaches from the west. This causes winds to weaken to below gales
by Friday morning, with winds weakening to 20 knots or less by
Friday night. There is a chance (50%) that some higher winds could
be seen ahead of a cold front moving down from Canada Saturday into
Sunday, with southwesterly gales up to 35 kt being possible (50%).
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory until 7 AM EST Wednesday for MIZ006-007-
085.
Lake Superior...
Gale Warning until 10 PM EST /9 PM CST/ this evening for LSZ241-
242-245>247-263.
Gale Warning until 4 AM EST Wednesday for LSZ243-244-248-264-265.
Gale Warning until 6 AM EST Wednesday for LSZ249>251-266-267.
Lake Michigan...
None.
&&
$$
UPDATE...Thompson
SHORT TERM...GS
LONG TERM...TAP
AVIATION...Thompson
MARINE...TAP
Area Forecast Discussion
National Weather Service Pendleton OR
735 PM PST Tue Dec 12 2023
.UPDATE...A narrow upper level ridge will be over the region for
the next couple of days with a shortwave trough riding over the
top into northern Washington on Thursday. The sensible weather
concern for tonight and Wednesday morning is the potential for
dense fog and whether or not there will be a need for fog
highlights. Primary area of concern appears to be the Blue
Mountain Foothills and North Central Oregon Where the HRRR has
been emphatically dropping visibilities below 1/2 mile overnight
over multiple runs. So far there has not been much fog reported
this evening at the ASOS sites and area web cams. Did increase the
fog coverage in the gridded forecast in the aforementioned areas
for the second half of tonight and Wednesday morning but will
monitor trends over the next few hours to determine if any fog
highlights are needed. 78
&&
.PREV DISCUSSION... /issued 213 PM PST Tue Dec 12 2023/
SHORT TERM...Tonight through Thursday...Satellite imagery this
afternoon continues to show much of eastern OR/WA under a stratus
layer, while higher mountain areas and portions of Crook and Grant
county have cleared out.
Through the first half of tomorrow, an upper level ridge building
over the region will continue to support and strengthen the low
stratus layer. In the overnight hours, the stratus layer is
expected to lower in altitude by a few hundred feet, which will
also increase the chances for patchy to areas of dense fog to
develop underneath. By tomorrow afternoon, the stratus layer
will once again increase in height and the fog dissipate with
slight warming at the surface.
Overnight Wednesday into Thursday, a shortwave trough passing to
the north will clip the forecast area. The persistent stratus
layer over the region is expected to weaken with this passing
system Thursday morning, with some areas seeing the stratus
break up overhead. This system will also result in chances of
light rain/snow across the WA Cascade east slopes and the OR
Cascade crest. Further east, the tail end of the system will clip
the northern Blues and Wallowas, resulting in a slight chance of a
flurry in these areas. By Thursday night, upper level ridging will
build back over the PacNW with drier conditions at the surface.
The ridge will also promote the strengthening of the stratus layer
over the eastern half of OR/WA while increasing chances of fog
development across the lower elevations and mountain valleys.
Lawhorn/82
LONG TERM...Friday through Tuesday...Dry and stable conditions this
weekend will mean that fog and low clouds are likely (60%
confidence) in the lower elevations. Models are in good agreement
advertising the high pressure aloft, and the axis of the ridge will
be positioned along the Cascades by late Saturday. This will be the
day of the strongest subsidence and warmest temperatures aloft. NBM
looks very reasonable with the forecast high temperatures in the 40s
in the mountains and the higher plateau of central Oregon and in the
30s for the Lower Columbia Basin and surrounding valleys, indicative
of the low level inversion that will be present.
Models are also in agreement that the ridge will shift eastward in
response to a developing trough offshore. However, models differ on
the strength of the trough and whether or not it will take a
negative tilt and travel north along the coast and western interior
Monday and Monday night. The ECMWF and Canadian have the stronger
and wetter solutions compared to the GFS, but they all show
increasing chance of precipitation late Monday. Forecast will show
60-70% PoPs along the Cascades, 35-50% PoPs over the eastern
mountains/valleys, and 15-30% PoPs over the Columbia Basin Monday
and Monday night. Snow levels during this time will range from 5000-
6000 feet.
A secondary trough off the eastern Pacific is handled differently by
all the models, and the confidence for the last day of the extended
period is low on the details. The PoPs and snow level forecast on
Tuesday are basically the same as Monday, therefore there is a
chance of rain and mountain snow across the forecast area on
Tuesday. The cluster analysis of the ensembles show a general
agreement that there will be a trough off the eastern Pacific and
near the coastline, but the amplitude and placement are
questionable. Wister/85
AVIATION...00Z TAFs...Stratus clouds will blanket eastern WA/OR for
the next 24 hours, as winds at the surface and aloft are weak and
subsidence is strengthening with a fairly high amplitude ridge. The
extensive stratus is evident on visible satellite, but the mountains
peaks are above the low level clouds which indicates that the
stratus is relatively shallow. All terminal airports are MVFR or
IFR at this time and will be the same or will even lower to LIFR
overnight. Confidence was high to have 1/4SM FG and FZFG at RDM, BDN
and PDT in the TAFs.
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 32 39 31 43 / 0 0 0 0
ALW 33 40 32 44 / 0 0 0 10
PSC 34 40 33 41 / 0 0 0 0
YKM 34 40 32 42 / 0 0 10 10
HRI 35 41 34 43 / 0 0 0 0
ELN 31 37 28 40 / 0 0 10 10
RDM 31 45 33 49 / 0 0 0 0
LGD 29 41 31 41 / 0 0 0 10
GCD 28 46 28 46 / 0 0 0 10
DLS 39 43 37 46 / 10 0 10 10
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...None.
WA...None.
&&
$$
SHORT TERM...78
LONG TERM....85
AVIATION...85