Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/15/21
Area Forecast Discussion
National Weather Service Denver/Boulder CO
757 PM MST Tue Dec 14 2021
.UPDATE...
Issued at 753 PM MST Tue Dec 14 2021
Everything looks on track based on current data. There is some
potential for snow squall activity, over the I-70 Mtn Corridor
involving the rush hour Wednesday morning, as a band of heavier
snow moves across.
As for winds, HRRR continues to be consistent in showing very
strong/damaging winds developing by mid to late morning and
continuing thru mid to late Wed aftn. Strongest winds will focus in
and near the foothills and over the Palmer Divide.
&&
.SHORT TERM...(This evening through Wednesday)
Issued at 156 PM MST Tue Dec 14 2021
Main concern revolves around the high wind event for Wednesday
across the Front Range foothills and extending out over the
northeast plains. There will also be short period of moderate to
heavy snow possible over the mountains for late tonight and early
Wednesday morning.
The culprit is a strong system which will intensify across it tracks
from southwest Colorado and into east central Colorado by noon
Wednesday and then rapidly out into the central plains during the
afternoon. Weather parameters are coming together for a significant
high wind event for the foothills and plains. The track of the
low has shifted slightly southward over the past few runs so have
taken wind speeds down slightly over the northeast plains but
still high winds up to 65 mph on the plains. QG fields showing the
strongest downward ascent will be over southeast Colorado with
over 100mb/hr descent but weaker subsidence further north. Still
the surface gradient expected to tighten with surface gradient of
20-25mb across the state. In addition, cross sections showing
50-70kt cross barrier flow and a mean state critical layer
developing at 18z, also spells strong winds over the foothills/base
of the foothills up to 75kt.
Overall, have increased wind speeds in/around the foothills,
including western portions of the Denver area. Strongest winds
look to be from mid morning to late afternoon as the system
rapidly moves east of Colorado.
In addition, could see a brief period of moderate to heavy snow over
the mountains later tonight and early Wednesday morning with steep
lapse rates and strong QG forcing developing on the leading edge
of the storm system. Snow fall rates of 1-2 inches of snow are
possible for a short period of time, most likely from 4 am to 7
am. Expect lighter snowfall after the main frontal passage. Therefore
have issued a winter weather advisory for 3 to 7 inches for snow
coupled with the strong winds for late tonight through early
Wednesday evening.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 156 PM MST Tue Dec 14 2021
Wednesday night, the potent upper level storm system that brought
windy conditions to the forecast area will move into the Upper
Midwest with a moderate westerly flow aloft over Colorado. Winds
should be decreasing through the evening with still some wind gusts
to 60 mph in the foothills and gusts to 45 mph over the far
northeastern plains. There may be enough available moisture
combined with orographic lift to produce isolated to scattered
light snow showers over the high country, mainly over the higher
peaks.
On Thursday, a broad upper trough covers the western half of the
U.S. with a strong zonal flow over Colorado. Models are showing
moisture increasing across the mountains during the afternoon with
scattered snow showers developing by late in the day. Further east
across the plains, dry conditions are expected due to downsloping
flow. In addition, this pattern should result in breezy conditions
across the higher mountains and foothills with gusts to 40 mph.
Gusty winds to 30 mph will also be possible from the Southern
Foothills eastward across the Palmer Divide and into Washington
County.
The chance of snow is expected to increase across the Northern
Mountains Thursday night into Friday as the upper level trough moves
across the Central and Northern Rockies and moisture deepens. The
orographics with this system are somewhat weak, therefore snowfall
amounts are expected to be generally light. Best guess is that
amounts will range between 1 and 5 inches, heaviest over the
Northern Gore and Park Ranges. Across the plains, dry, cooler and
breezy conditions (northern and eastern sections) are expected on
Friday behind the passage of a weak cold front.
Dry and breezy weather along with slightly warmer temperatures
are expected over the weekend as a flat upper level ridge of high
pressure moves over the region. An upper level shortwave skirting
Colorado to the north may produce a few light snow showers over
the Northern Mountains on Sunday, mainly over the higher peaks.
Early next week, upper level high pressure is progged to build
over the Rocky Mountain Region with dry and warmer weather
expected. The higher mountains and foothills should be windy
with breezy conditions across the Cheyenne Ridge and Palmer
Divide.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 753 PM MST Tue Dec 14 2021
Winds have become southerly. A quick band of showers will move
across between 12z and 15z with winds becoming southwest at 20 to
30 mph with gusts up to 40 mph. By mid to late morning winds will
become more westerly with speeds in the 30 to 40 mph range with
gusts to 60 mph possible through 21z. After 21z winds should
decrease with speeds in the 20 to 30 mph range with gusts to 50
mph thru 23z from the WNW. Blowing dust will also be possible with
visibility down to 3 miles at times.
&&
.FIRE WEATHER...
Issued at 156 PM MST Tue Dec 14 2021
Decided to issue a red flag warning for the Front Range foothills...Palmer
Divide and portions of the plains on Wednesday for the strong winds.
The humidity levels are more marginal as the Wednesday afternoon
humidity levels will be in the 17-25 percent range, but feel the
winds will trump all. Even today we had several small fire starts
with marginal red flag conditions.
The continued mostly dry and breezy to windy conditions may result
in elevated fire danger through much of the period across across
portions of North Central and Northeastern Colorado. At this
time, the greatest risk for fire danger looks to be on Thursday
and Sunday from the Southern Foothills eastward across the Palmer
Divide into the adjacent plains.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 8 AM to 5 PM MST Wednesday for COZ035>051.
Red Flag Warning from 8 AM to 5 PM MST Wednesday for COZ215-216-
238>241-243>247-249.
Winter Weather Advisory from 2 AM to 8 PM MST Wednesday for
COZ031-033-034.
&&
$$
UPDATE...RJK
SHORT TERM...Entrekin
LONG TERM...jk
AVIATION...RPK
FIRE WEATHER...Entrekin
Area Forecast Discussion
National Weather Service Charleston SC
944 PM EST Tue Dec 14 2021
.SYNOPSIS...
Dry high pressure will prevail through much of the week before
a cold front arrives over the weekend.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
The sfc pattern will feature ridging high pressure across
eastern SC and GA with a broad trough near the coast. Rounds of
low cloud cover may develop over the forecast area tonight. In
fact, recent runs of the HRRR has been consistent with the
development of isolated showers across the outer GA waters late
tonight. The forecast update will feature increased cloud cover
with SCHC PoPs for showers across the outer GA waters between
midnight and sunrise. Temperatures appear on track to reach the
low 40s inland to near 50 along the coast.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
The axis of an upper ridge aloft will shift over the Eastern CONUS
and then offshore by Friday. Strong sfc high pressure wedging into
the Appalachians will gradually shift into the Atlantic late week.
Dry, rain-free conditions are expected nearly each day through the
remainder of the week with partly sunny conditions. The development
of a coastal trough Thursday could bring isolated showers to the
southeast Georgia coastal waters, mainly where H85 southerly flow
advects slight moisture in from the Gulf. Model soundings however,
keep solid low and mid-level dry in place over the coast, thus
keeping showers from developing over the land areas. Temperatures
Wednesday will average in the mid 60s to low 70s across the forecast
area. Overnight lows will dip into the mid to upper 40s, with low to
mid 50s across the coastal counties and south of I-16. Notable llvl
WAA will increase Thursday and high temps will rise to the low to
mid 70s, with highs a couple degrees warmer on Friday. Thursday
night lows will remain rather mild as well, with lows in the 50s.
High temperatures Friday could rival record temperatures (see
Climate section below).
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
High pressure will weaken on Saturday in advance of an approaching
cold front. Most of the day will be dry, then rain chances will
increase late evening into Sunday as the front pushes across the
area. Large differences in model solutions exist thereafter with the
GFS solution showing slightly less precipitation compared to the
ECMWF. High pressure will try to build inland before low pressure
possibly develops over the Gulf and shifts over the Southeast coast
early next week. Forecast details will certainly need to be refined,
however this system will keep healthy rain chances in the forecast.
Warmer than normal temperatures over the weekend will return to more
seasonable, or even cooler levels early next week.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Early evening IR satellite indicated a few patches of MVFR
clouds across the Coastal Plain. Restrictive ceiling may occur
from time-to-time over KSAV and KJZI this evening, highlighted
with a TEMPO from 0-4Z. Otherwise, VFR conditions are expected
across the terminals through the 0z TAF period.
Extended Aviation Outlook: Brief flight restrictions are possible
this weekend within showers associated with a cold front.
&&
.MARINE...
High pressure will prevail to the north as a coastal trough lingers
offshore. Northeast winds will be slightly elevated, with occasional
gusts to 20 knots. Seas will be 3 to 5 feet.
Wednesday through Sunday: Northeast winds around 15 knots will
decrease to less than 10 knots and shift predominately out of the
east. Winds will increase Saturday ahead of a cold front as
transient southwesterly winds shift back out of the northeast by
Sunday as the front moves offshore. Gusts around 20 to 25 knots are
possible Sunday and Small Craft Advisories could be needed across
portions of the waters mainly over the Charleston County nearshore
waters. Seas will average 2 to 4 ft in the nearshore waters out
20nm, and 4 to 5 ft in the Georgia waters from 20 to 60 nm.
&&
.CLIMATE...
12/17 Daily Record High Temperatures
KCHS: 78 (1971)
KCXM: 78 (1924)
KSAV: 80 (1924)
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...NED
SHORT TERM...BRM
LONG TERM...BRM
AVIATION...NED
MARINE...BRM
CLIMATE...
Area Forecast Discussion
National Weather Service Green Bay WI
537 PM CST Tue Dec 14 2021
Updated aviation portion for 00Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 250 PM CST Tue Dec 14 2021
The latest RAP analysis and satellite/radar imagery show a potent
storm system moving onshore into California, and broad ridging
downstream east of the Rockies. A large blanket of cirrus
continues to spill over top the ridge and across the western Great
Lakes. These clouds have slowed the temperature rise today, with
many temps remaining in the middle 30s over north-central WI.
However, surface dewpoints are considerably higher than they were
24 ago, with some help from moisture fluxes off Lake Michigan.
Patches of low stratus have held on over parts of central WI into
early this afternoon, but the main surge of low level moisture is
pushing north across Missouri. As a warmer and more humid airmass
moves into the region, potential for dense fog and drizzle,
followed by record highs are the focus in this part of the
forecast.
Tonight...Low level moisture will continue to surge into the area
thanks to broad southerly flow over the Mississippi Valley.
Forecast soundings show saturation increasing below 800mb from the
late evening into the overnight hours, leading to increasing
chances of fog and drizzle. Think visibilities will be good
through the evening for the most part, then visibilities fall
relative quickly overnight. Dense fog is possible, particularly
north and west of the Fox Valley. But with the late potential for
the fog, will let the next shift take another look to see if a
dense fog advisory is needed. Temps will remain steady or rise
slightly overnight with lows mainly in the middle to upper 30s.
Wednesday...Low pressure will be moving across the central Plains,
while southerly flow strengthens across the western Great Lakes.
These south winds will push a warm front into east-central
Wisconsin into the afternoon. Raised temps slightly in the Fox
Valley. However, the rest of the area will be north of the warm
front for most of the day, and shrouded in low overcast and
drizzle. As a result, remained conservative with temps as they
should be slow to rise across north-central WI where there is deep
snow pack. High temps at many locations may not occur until
Wednesday evening. Despite the low overcast, these highs will
likely break records at many locations.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 250 PM CST Tue Dec 14 2021
The extended period will once again be fairly front loaded, as the
exceptionally strong winter system crosses the region Wednesday
night into Thursday.
Wednesday night into Thursday...This will be the main period for
to watch intense winds as an intense negatively tilted trough
lifts through Wisconsin Wednesday evening. Soundings with this
system have been consistent in bringing some truly impressive wind
speeds through aloft with the strong WAA. Wind speeds up to 60-75
knots between 900-800mb have been pretty consistent for the
overnight period, with even higher winds further aloft. The main
question that remains is: how much of this wind will make it to
the surface? The fairly robust snowpack, especially across the
north, would typically help keep a fairly stable layer in place
near the surface especially given that we have WAA advection aloft
which would typically not aid in mixing. That said, with how
close the winds are to the surface, it won`t take much momentum
transfer to bring them down. Further complicating things, meso
models also develop a few showers and storms along the leading
edge Wednesday, which would certainly have the potential to mix
down wind gusts with precipitation loading. With potentially
record breaking warmth (for December) the day before and the
impressive dynamics at play, some storms ahead of the system won`t
be impossible and may indeed be the greatest threat, as
precipitation loading will enhance any wind reaching the surface.
Any precipitation will likely be short- lived, before CAA begins
on the back end of the system. Once again, winds may reach the
surface and gusts may be more widespread overall, as CAA typically
brings more favorable boundary layer mixing, however, winds aloft
will fortunately lack much of the strength they had 12 hours
prior, with gusts back down to 35 to 45 mph by Thursday afternoon.
When all is said and done, went with a High Wind Watch to
highlight the potential for strong synoptic winds reaching the
surface, which may need to be refined in future forecasts. Any
convection will need close watching, and may lead to a few wind
based severe warnings, and a wind advisory could follow for
portions of Thursday.
Rest of the forecast...Quieter and colder conditions follow for
the rest of the work week, with dry conditions at least through
Friday afternoon. The next chance for some light snow then arrives
Friday night, as a weak clipper type system grazes the area. This
could bring a quick light snow overnight, before clearing out on
Saturday. High pressure then returns for the weekend. High
temperatures will still be in the lower 30s to lower 40s on
Thursday, before dropping fairly quickly back into the lower to
middle 20s for the weekend. A few temperatures in the lower 30s in
the warm spots near the lake could return by early next week.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 536 PM CST Tue Dec 14 2021
VFR cigs will start the TAF period, with thickening and lowering
clouds through tonight into Wednesday as cigs lower to MVFR then
IFR/LIFR as low level moisture increases across the region. In
addition, vsbys will fall later tonight with fog/drizzle down to a
mile or less. The lowest conditions are expected where the deepest
snowpack is in place from the previous snowstorm across north-
central and central Wisconsin. Once the low conditions are in
place, they are expected to remain low through Wednesday.
KGRB VWP shows some LLWS in place across the Fox Valley as well as
central and north-central Wisconsin. LLWS will ramp up Wednesday
as winds increase just off the surface.
Surface winds will increase on Wednesday as a powerful low
pressure system organizes over the Plains, gusting to around 20
knots during the day.
&&
.CLIMATE...
Issued at 250 PM CST Tue Dec 14 2021
Record high temperatures are expected on December 15th. The
records are: Antigo 43 in 1894 and 1913, Appleton 52 in 1920,
Green Bay 49 in 1998, Manitowoc 52 in 1979, Marshfield 47 in
1997, Merrill 51 in 1998, Oshkosh 51 in 1984, Rhinelander 48 in
1993, Stevens Point 53 in 1998, Sturgeon Bay 51 in 1998, Wausau
48 in 1997 and Wisc. Rapids 49 in 1923. Current record highs are
in the middle 40s to lower 50s. Forecast highs are in mainly in
the 50s to around 60. A few record high temperatures are also
possible on December 16th depending on how much cooler air works
into the region at midnight.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Wednesday evening through Thursday morning
for WIZ005-010>013-018>022-038>040-048>050-073-074.
High Wind Watch from Wednesday evening through late Wednesday
night for WIZ030-031-035>037-045.
&&
$$
SHORT TERM.....MPC
LONG TERM......Uhlmann
AVIATION.......Kurimski
CLIMATE........Uhlmann
Area Forecast Discussion
National Weather Service Phoenix AZ
415 PM MST Tue Dec 14 2021
.UPDATE...
Updated Aviation
&&
.SYNOPSIS...
A low pressure system and attendant cold front will quickly sweep
eastward through Arizona this evening, bringing strong winds,
showers, and areas of blowing dust. Much cooler temperatures are
expected Wednesday, with a slight warming trend thereafter though
the weekend. Another less impactful storm system will move into the
Southwest this weekend, but most areas are expected to remain dry.
&&
.DISCUSSION...
A powerful upper level trough and associated PV max are located
south of KMRY this afternoon. Water vapor imagery clearly depicts
all the classic features associated with this system, with a mid-
level dry slot longitudinally oriented across southeast California
and western Arizona. The bulk of significant moisture advection and
rainfall is being absorbed by the coastal ranges in California,
where widespread showers have been occurring for most of the
morning. The most impactful part of this storm system continues to
be the potential for strong winds. SPC mesoanalysis shows 850-mb
winds of 30-50 kt in place across southern California, which will
contribute to increasing winds from west to east through this
evening. Already, localized gusts to 50 mph have been observed at
JTNP, where a High Wind Warning is in effect. This trough is
forecast to accelerate eastward this evening and be accompanied by a
110-120 kt 500-mb jet streak moving directly across south-central
Arizona. Most forcing for ascent accompanying the trough will remain
focused across northern Arizona, but significant low-level
frontogenetical forcing will likely result in a shallow convective
frontal band quickly advancing eastward this evening. HREF and HRRR
timing suggests a 10 PM to 1 AM time frame for this to affect the
Phoenix area. Along this band, strong winds, showers, and
potentially a few embedded thunderstorms are likely, with enhanced
wind gust potential possible given the very strong kinematic profile
in place. Most areas across the lower deserts are forecast to
receive between 0.10" to 0.25", but NBM the percentile QPF values
are close to 0.50" across the Phoenix area. Areas north and east of
Phoenix could potentially receive localized totals up to 1", which
could cause minor flooding issues. Tonto Creek is forecast to
briefly rise above action stage this evening. A dusting of snow is
also possible in parts of JTNP and southern Gila County as snow
levels fall from around 8000 feet down to around 4000 feet in the
wake of the cold front amidst lingering light precipitation.
However, any accumulations outside of the highest peaks should
remain at 1 inch or less.
The aforementioned storm system will rapidly advance eastward on
Wednesday morning and give way to a quieter, quasi-zonal westerly
flow pattern over the Southwest. Significant cooling will take
place, with temperatures expected to run about 10 degrees cooler
than Tuesday. In fact, the official forecast has most areas
(including Phoenix) staying in the upper 50s for highs. Another
concern will be the potential for freezing temperatures on Thursday
morning. NBM probabilities of temperatures below 32 degrees are
highlighting potential freezes in parts of Yuma and La Paz Counties,
the lower Colorado River Valley, and southeast California. Will have
to assess the potential for a Freeze Watch or Warning for this time
period in later shifts.
By this weekend, a weak trough will develop again over the
Southwest, but will have little to no impact on weather given the
lack of moisture in place. It will at least keep the well above-
normal temperatures at bay. Ensemble guidance is showing a more
significant storm system potentially bringing rain back to the
region late next week.
&&
.AVIATION...Updated at 2315Z
South-Central Arizona including KPHX, KIWA, KSDL, KDVT:
The passage of a strong cold front late this evening will be the
main weather hazard through Wednesday afternoon. Timing of the front
and greatest impacts at KPHX still appears to align around 06Z
(possibly as early as 0530Z or as late as 0630Z). Southerly cross
runway winds will remain an issue until fropa with gusts potentially
nearing 25kt on occasion through this evening.
An abrupt wind shift with westerly gusts near or exceeding 40kt will
be likely along this strong cold frontal passage late this evening.
A fine line of showers coincident with blowing dust, and cigs
falling towards MVFR thresholds are depicted by all models; however,
the duration of these lower flight categories should only last
around an hour or less. Gusty west winds and lofted dust impacting
slantwise visibilities should persist into the overnight and early
morning hours, though wind speeds will quickly weaken towards
sunrise, then actually switch to an easterly direction mid/late
morning.
Southeast California/Southwest Arizona including KIPL and KBLH:
A strong cold front will bring significant weather impacts to SE
California this evening with conditions rapidly improving by
Wednesday morning. Timing of the frontal passage still appears
around 01Z at KIPL and 02Z for KBLH. With frontal passage, an abrupt
wind shift will occur with wind gusts quickly increasing above 40kt
(even a brief gust to 50kt is possible). Surface blowing dust and
restricted visibilities may be an issue immediately behind the front
with a tendency for the dust and impacts to be more lofted as wind
speeds decrease overnight. There is a chance of lower cigs and
showers with this cold front, but confidence is too low to include
in TAF package with wind impact overwhelming any possible
rainfall/cig impact.
&&
.FIRE WEATHER...
Thursday through Monday:
Cool, dry weather is forecast. Winds will be light and diurnally
influenced. MinRH each afternoon will be 20-30% in most areas.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Blowing Dust Advisory from 6 PM this evening to 5 AM MST
Wednesday for AZZ540-542>544-546-548-550-551-553-554.
Wind Advisory from 6 PM this evening to 5 AM MST Wednesday for
AZZ537-540>544-546-548>555.
High Wind Warning from 7 PM this evening to 8 AM MST Wednesday
for AZZ545-557-558-563.
Wind Advisory from 7 PM this evening to 8 AM MST Wednesday for
AZZ547-556-560>562.
Blowing Dust Advisory from 5 PM this afternoon to 3 AM MST
Wednesday for AZZ530>533-535-536-538-539-559.
Wind Advisory from 5 PM this afternoon to 3 AM MST Wednesday for
AZZ530>536-538-539-559.
CA...Blowing Dust Advisory until 1 AM PST Wednesday for CAZ563>567-
569-570.
Wind Advisory until 1 AM PST Wednesday for CAZ563>567-569-570.
Wind Advisory until 1 AM PST Wednesday for CAZ561-568.
Blowing Dust Advisory until 1 AM PST Wednesday for CAZ562.
High Wind Warning until 1 AM PST Wednesday for CAZ562.
High Wind Warning until 8 PM PST this evening for CAZ560.
Wind Advisory from 8 PM this evening to 1 AM PST Wednesday for
CAZ560.
&&
$$
DISCUSSION...Rogers
AVIATION...18
FIRE WEATHER...Heil