Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/10/18
Area Forecast Discussion
National Weather Service Charleston SC
943 PM EST Tue Jan 9 2018
.SYNOPSIS...
High pressure will build in from the north tonight, then slide
into the Atlantic on Wednesday. A coastal trough will linger
offshore through midweek before moving inland on Thursday. A
cold front will move through the area Friday night followed by
a secondary front Saturday night. Cool high pressure will
return late in the weekend into early next week.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Nudged overnights lows up 1-2 degrees along the Georgia coastal
counties. The rest of the forecast is on track.
High pressure located over the Virginia Tidewater region will
gradually strengthen and drift to the northeast overnight. As it
does, a well defined wedge will mature across Georgia and the
Carolinas. Any larger scale forcing will remain displaced from
the region as the mid/upper level low remains well south of the
forecast area. So, the forecast remains dry through the
overnight. The main forecast issue is the potential for stratus
development after sunset. Fortunately, model soundings and time
heights show a solid low level jet with 20-25 knots of flow
beginning just a few hundred feet, so it appears that stratus
will be favored over fog for tonight. We already have a a good
amount of stratus and stratocumulus from along the Savannah
River south, so this area should just expand across the entire
forecast area through the night, so the forecast features mostly
cloudy to cloudy skies by morning. Lows will be even a few
degrees warmer than last night, with values ranging from the mid
40s around the Francis Marion to the low 50s along the
Altamaha.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Surface high pressure centered over the Mid-Atlantic and New
England regions will shift offshore Wednesday with a cold front
approaching late in the period. Meanwhile a coastal trough will
linger just offshore into Thursday before pushing inland as the
southeasterly low-level flow strengthens. There could be some
showers across the area from time to time through Wednesday
night, but the better chances will come Thursday as deeper
moisture advects in from the southeast, especially across SC.
Even better chances are expected Friday as the front, and
possibly pre-frontal trough, approach from the west. Instability
still appears to be minimal so have not added any mention of
thunderstorms yet but cannot rule out this potential. Will keep
a close eye on this though given the strengthening wind fields
that will be occurring as a wave of low pressure on the front
near the Appalachians strengthens. Sea fog could also develop
and linger near coastal areas even during the daytime,
especially beginning Thursday when winds shift more from the
east and southeast.
Temperatures will be above normal through the period,
especially by Thursday when 70s will be possible. However the
degree of warming will likely depend on how significant any low
clouds/fog will be, including possible sea fog near the coast.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A cold front and associated precipitation will quickly push
offshore Friday night/early Saturday. A secondary front will
drop south through the area Saturday night and is expected to
come through dry. Cool high pressure will build into the region
in wake of the front and will persist into early next week.
Beyond the initial shot of precipitation early in the period, no
rain is expected. Temperatures will be near or below normal.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Primary concern:
* sub-VFR cigs
VFR this evening with cigs lowering through the night. Guidance
is mixed on exactly how low cigs will get with the latest RAP
indicating VFR prevailing through the night with NAM and GFS
soundings showing IFR to MVFR cigs forming by late evening. MOS
statistical guidance is all over the place as well. Think best
chances for sub-VFR cigs will be across Southeast Georgia
including the KSAV terminal where late night isentropic assent
and lower condensation pressure deficits will be found. Will
keep cigs at KCHS VFR for now.
Extended Aviation Outlook: Flight restrictions at times through
the week, mainly each night due to low clouds/fog, then due to
showers Thu and showers and possible thunderstorms Friday into
Friday night. Breezy conditions likely Friday/Saturday.
&&
.MARINE...
Tonight: High pressure to the north of the waters will
strengthen through the night and work to increase the northeast
to southwest oriented pressure gradient. This setup will support
strengthening northeast winds that will generally top out in
the 15-20 knot range. Seas steadily increase, becoming 3-5 feet
out to 20 nm and 5-6 feet beyond late tonight. The Small Craft
Advisory for the outer Georgia waters remains in effect starting
this evening to account for 6 ft seas and the potential for
gusts to 25 knots.
Wednesday through Sunday: A coastal trough will linger over or
near the area into Thursday before pushing inland ahead of a
cold front which will move through from the west Friday night.
Winds will remain elevated but mainly stay below Advisory levels
/25 kt/. However, building seas will lead Advisory conditions
in the offshore waters Wednesday and then eventually into at
least the SC waters. Otherwise, sea fog will become likely over
the cool nearshore waters mid to late week as low-level moisture
increases across the area ahead of the cold front, especially
starting Thursday. Dense Fog Advisories will be possible for
visibilities of one half nautical mile or less.
&&
.EQUIPMENT...
The temperature/dewpoint sensor on the KCHS ASOS is still
malfunctioning, but the observer is manually augmenting the
observation until the problem can be resolved. Parts are on
order.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 5 PM EST Saturday for AMZ374.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
908 PM CST Tue Jan 9 2018
.UPDATE...
Issuing a minor update to adjust fog/drizzle wording overnight
through mid-morning Wednesday across the eastern 2/3 of the CWA.
Southerly surface winds are remaining up between 10-15 mph due to
a deepening lee-side surface low over Southeast Colorado.
In addition, VAD Wind Profile 925mb winds are remaining 20-25
knots. In addition, forecasted 1000mb-950mb lapse rates appear
pretty low on BUFKIT and RUC plan-view progs, with stratus
favored.
Where stratus is currently socked in east of a Gainesville-DFW
Airport-Corsicana-Centerville line, I have changed wording to
"patchy" drizzle and fog, though I think the latter would be
more likely. Farther west where some drier air is mixing with the
leading edge of the stratus, there`s a better potential for areas
of fog where some scattered areas of dense fog and drizzle could
occur as far west as a St Jo-Aledo-Meridian-Gatesville/Killeen
line.
Confidence on the exact areas of better formation are very low,
though I do expect at minimum some patchy areas of fog and
possibly drizzle. The western edge of the stratus where better
cooling and surface-boundary layer occurs is where I have the best
confidence on any visibility impacts by daybreak Wednesday.
05/
&&
.AVIATION... /Issued 616 PM CST Tue Jan 9 2018/
Low clouds, with IFR ceilings, held in across areas along and
east of a KGLE-KDAL-KCRS-KLHB line throughout the day Tuesday.
Expect these clouds to spread back to the west tonight bringing
IFR or LIFR conditions with low clouds and areas of fog to all of
the Metroplex TAF sites between 02z and 05z. By 16z, the fog
should dissipate and the ceilings should lift to around 1500 feet
as deeper vertical mixing occurs due to a deepening trough to our
west. Have left MVFR ceilings through the afternoon but if the
winds off the surface become a little more southwesterly than is
currently forecast, the Metroplex sites could become VFR during
the afternoon.
A similar scenario is expected for the Waco TAF site. Low clouds
are expected to spread westward into Waco 04-05z with ceilings
around 400 feet and visibility being reduced to around 2 miles
in fog. As with the Metroplex sites, the fog should dissipate
and the ceilings should lift to around 1500 feet by 16z, as
deeper vertical mixing occurs due to a deepening trough to our
west. Have left MVFR ceilings through the afternoon but if the
winds off the surface become a little more southwesterly than is
currently forecast, KACT could become VFR during the afternoon.
58
&&
.SHORT TERM... /Issued 338 PM CST Tue Jan 9 2018/
/Tonight/
The main challenge regarding tonight`s forecast is the return of
low clouds and fog, and there is significant uncertainty regarding
these trends. We continue to monitor the erosion of the low cloud
deck across the eastern half of the CWA this afternoon, and this
cloud deck will likely begin returning west as early as this
evening. Through the evening and overnight hours the low clouds
should spread across the I-35 corridor, but as of right now it
doesn`t appear they will advance into our far western counties.
Areas of fog will likely also accompany this returning cloud deck.
Some model guidance suggests dense fog may develop under the
mostly clear skies ahead of the cloud deck, and other model
guidance develops all dense fog and no returning cloud cover. The
wind speeds and quality of near surface moisture will both be
factors in the fog potential tonight.
Many of the model guidance that suggests an overnight sky void of
cloud cover are not initializing the current cloud cover very
well or at all, and thus are likely suffering with the low-level
moisture quality. With wind speeds overnight around 10 mph, and an
increasing low level jet of 20-35 mph across mainly the central
and western half of the CWA, the potential for widespread dense
fog appears low, but not zero. Also, it doesn`t appear we will get
a large influx of additional low level moisture overnight (i.e
increasing dewpoints) or we would likely have more fog if we did.
Therefore, for now will include a mention of areas of fog and
drizzle as patchy light drizzle may occur after midnight, mainly
east of Interstate 35.
For overnight lows, trended on the warmer side of guidance, due to
southwest winds aloft combined with the low cloud cover across a
large part of the region. Overnight lows should remain in the 40s,
and locations in our northeastern counties where low level clouds
will remain for the rest of today and tonight, may not see much
change in temperatures.
JLDunn
&&
.LONG TERM... /Issued 338 PM CST Tue Jan 9 2018/
/Wednesday Onward/
Wednesday will begin with a strong upper low digging eastward
through New Mexico; this feature will be our forecast focus
through the next couple of days. We`ll start the day with a
majority of the forecast area socked into low clouds with areas of
fog roughly from I-35 eastward. These conditions and how long
they persist will have a substantial effect on the temperature
forecast for the remainder of the day. Meanwhile, the approaching
upper trough will result in strong surface cyclogenesis across the
TX Panhandle region, creating a tightening pressure gradient
across our forecast area. This will mean an increase in
southerly/southwesterly winds to 15-25 mph throughout the day and
therefore strong warm advection. Our western areas that remain
clear could easily see temperatures climb into the mid and upper
70s especially as winds take on a slight westerly component during
the afternoon hours. These locations may experience a few hours
of elevated fire danger as a result. On the other hand, locations
to the east that maintain several hours of low clouds or fog could
struggle to reach the mid 50s. Locations in vicinity of I-35 have
the greatest temperature bust potential and could see highs
anywhere from the mid 50s to the low 70s depending on if or how
fast any clearing occurs. Additional moisture arriving within the
strong southerly flow could become trapped beneath a stout
inversion, causing some areas to remain overcast for much of the
day.
Wednesday night, additional low clouds and some patchy fog will be
possible ahead of the surface low`s attendant cold front. This
front will approach North Texas early Thursday morning and enter
our northwest zones by daybreak. The front will be quite strong,
and surge through the entire forecast area by noon. Along and
ahead of the front, some rain showers will be possible east of
I-35 as the front encounters more favorable moisture. In its wake,
strong cold advection fueled by gusty northwest winds will cause
temperatures to fall throughout the day. Wind speeds may push Wind
Advisory criteria with gusts of 30-40 mph possible. These winds
will also cause wind chill values to plummet into the 30s or even
upper 20s by late afternoon.
Also behind the front on Thursday, there is the potential (albeit
low) for some snow flurries across parts of North Texas. While
models do not indicate QPF in our area, the ingredients will be in
place for some light snow to occur anywhere roughly from
Stephenville to Gainesville and points northwestward. These
ingredients include some strong isentropic ascent on the 300K
surface (within the 700-600mb layer) along with some steep lapse
rates of 7-8 C/km. This will be in vicinity of some mid-level
frontogenesis steeply sloped toward the colder air along with some
weakly negative EPVs. There should also be some limited wrap-
around moisture available through the low/mid levels, which while
it`s not enough to support a lot of snow, it will be capable of at
least squeezing out a few flurries. Surface temperatures during
this time will have fallen into the upper 30s to near 40 across
the areas of concern, and no accumulation would occur. All
moisture will be scoured from the area by the evening and a cold
and breezy Thursday night will be in store.
Much cooler weather will persist from Friday through the weekend.
While highs on Friday will be capable of climbing into the upper
40s and 50s, a reinforcing shot of cold/dry air will arrive
Friday night or Saturday morning thanks to a second cold front.
This secondary surge will hold high temperatures in the 30s and
40s over the weekend with low temperatures mostly in the 20s with
even some teens possible on Sunday morning. The shortwave may be
capable of generating some light snow in parts of OK on Saturday,
but at this time do not expect there to be sufficient moisture
within our area to support any flurries. By early next week, south
winds will resume and a swath of Gulf moisture should surge
northward and collide with another cold front arriving from the
north. This will result in additional low rain chances on either
Monday or Tuesday, but some considerable timing differences
remain amongst model guidance. A few ensemble members have
temperature profiles cold enough to support some form of wintry
weather during this time, but the most likely precip type remains
liquid rain at this point.
-Stalley
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 44 62 49 51 28 / 10 5 5 10 5
Waco 44 64 51 57 29 / 10 5 10 10 5
Paris 43 58 51 55 25 / 10 10 10 20 10
Denton 44 63 47 50 26 / 10 5 5 10 5
McKinney 44 58 48 52 26 / 10 5 10 10 5
Dallas 44 61 50 53 28 / 10 5 10 10 5
Terrell 44 61 51 55 26 / 10 5 10 20 5
Corsicana 44 61 52 56 28 / 10 5 10 20 5
Temple 44 66 51 57 30 / 10 10 10 10 5
Mineral Wells 44 70 44 49 24 / 5 5 5 10 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
05/58
Area Forecast Discussion
National Weather Service Lincoln IL
913 PM CST Tue Jan 9 2018
.UPDATE...
Issued at 913 PM CST Tue Jan 9 2018
Have already made some minor changes to add some drizzle and have
issued a dense fog advisory for the entire CWA. May make some
additional adjustments to the overnight lows but with southeast
winds, thinking temps will remain fairly steady overnight or maybe
rise a couple of degrees. So, not plans for any major adjustments
but will tweak pops and wx some and send an update shortly.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 255 PM CST Tue Jan 9 2018
High pressure ridge sliding to the east today, and mostly zonal
flow aloft with warmer temperatures advecting into the region
continues the influence of a strong temperature inversion trapping
a moisture rich airmass in place. Pattern shift as the low over
the desert SW deepens and the flow across the CONUS amplifies.
Southwesterly flow modifies the thermal forecast quite a bit, and
ejects a round of short waves into the region. Several problems
in the forecast, starting with a mixed precip issue for Thursday
night into early Friday morning. Models differ greatly for the
remains of Friday... with a significant potential impact to
Central IL.
Cloudy and foggy forecast for tonight. Southerly winds are
expected to stay a little stronger through the overnight, but the
air that is moving into the region is warm and has plenty of
moisture to translate into a bit of an advection fog event. With a
slightly different mechanism to the fog, at least initially and
from a different airmass...the severity of the fog is still
problematic. HRRR and RAP/RUC, among others, drop the vis
considerably this evening and keep it down through the overnight.
Lack of confidence for severity of the fog is holding back
issuance of the dense fog advisory. Warmed the temperatures a bit
in the overnight as the clouds/fog/drizzle expected to temper what
there is of a diurnal swing. Tomorrow, similar conditions as to
grey and foggy, at least early. However, the strong warm air
advection is expected to overcome and partially clear out some of
the reduced visibilities.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 255 PM CST Tue Jan 9 2018
Wednesday night will remain warm with the temperatures almost
steady through the overnight hours. Warm air advection continues
into Thursday as the chances for precipitation continue to come
up. Very warm temperatures on Thursday will keep the precip rain
through the day, but cold air moving in with the front will bring
a precip type changeover. Some freezing rain and sleet is
indicated in forecast soundings before switching all over to snow.
Track of the next wave ejecting out from the SW starts to impact
the forecast for Friday. Basically, the ECMWF is starting to move
north of the GFS track, putting a deformation zone of a developing
low across Central IL. The differences are many at this point, and
the forecast for Friday will be coming into focus in the next few
runs. Accumulations of both ice and snow are possible for Friday,
although the location depends on a very inconsistent track. On the
other side of that, a colder airmass moves in with the shift in
flow, opening up Central IL to below normal temperatures for the
weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 553 PM CST Tue Jan 9 2018
Fog and low clouds remain over the area with only SPI the best w/
MVFR conditions. Some clearing is seen on observations to the
west with higher clouds aloft. However, winds should become little
lighter early this evening and with lots of moisture being added
to the lower layers of the atmosphere, believe clouds below 1kft
and vis below 1sm will return in 2-3 hours this evening. So all
sites will drop back down to LIFR and VLIFR this evening and
continue overnight. Vis conditions will gradually improve during
the morning but cigs will likely stay low with move low level
moisture arriving from the south. Winds will be southeast tonight
and overnight, and then become southerly with some gusts tomorrow
morning.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon CST Wednesday for ILZ027>031-
036>038-040>057-061>063-066>068-071>073.
&&
$$
UPDATE...Auten
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...Auten
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
945 PM CST Tue Jan 9 2018
.DISCUSSION...See updated information for land and marine areas
below.
&&
.UPDATE...Primary forecast challenge for the overnight period will
be focused on the potential for areas of dense fog. Surface
observations indicate that dense fog is already developing just to
our west, with sites near Hattiesburg and Meridian already
reporting visibility down to one quarter mile. The eastern extent
of this fog may already be impacting portions of our southeast MS
counties. The past few runs of the HRRR and RAP, along with the
NAM and 21Z SREF probabilities lend highest confidence to
additional areas of fog developing across portions of the
northwest FL panhandle and the I-65 corridor late this evening or
just after midnight and advecting westward and impacting much of
the rest of the western 2/3rds of the CWA overnight into early
Wednesday morning. A deck of low to mid clouds may be a
complicating factor in fog development, but most models indicate
that this deck will erode somewhat except for far eastern and
northeastern areas overnight. Thus, confidence was high enough to
go ahead and include locations generally west of a Camden to
Navarre line in a Dense Fog Advisory overnight into early
Wednesday morning. Later shifts will monitor trends closely and
will make needed adjustments to the advisory as needed. /21
&&
.MARINE...We decided to add Pensacola Bay and Perdido Bay to the
Marine Fog Advisory overnight into early Wednesday morning based
on latest guidance trends. The advisory continues for Mobile Bay
and the Mississippi Sound east of Pascagoula. 13/21
&&
.PREV DISCUSSION... /issued 552 PM CST Tue Jan 9 2018/
DISCUSSION...Updated for latest aviation discussion below.
AVIATION...
00Z issuance...Areas of dense fog will develop around the
terminals through the evening and overnight with LIFR to VLIFR
conditions possible. Low clouds and patchy fog continues into
Thursday morning. /13
PREV DISCUSSION... /issued 404 PM CST Tue Jan 9 2018/
NEAR TERM /Now Through Wednesday/...
The surface low over the central Gulf will weaken over
the next 12-18 hours as its attendant shortwave moves southeast
across the southern FL peninsula. This allows surface high pressure
anchored just off the Mid Atlantic coast to ridge southeast into the
area. Even though low clouds have mixed out over parts of the area
this afternoon, this east to southeast low level flow will result in
the redevelopment of low stratus tonight as low level isentropic
lift becomes reestablished. Areas of fog are also likely, but
confidence in dense fog for land areas is too low at this time to
issue a dense fog advisory, as the pressure gradient with the
surface ridging will maintain an east to northeast breeze through
much of the night.
Broad shortwave ridging will hold on for one more day over the
southeast with low level east to southeast flow persisting.
Therefore, expect another mostly cloudy day with warm air advection
helping highs to climb into the mid to upper 60s. The chance of
measurable precip looks low given all of the moisture is confined in
the lowest 2000-3000 ft of the atmosphere. 34/JFB
SHORT TERM /Wednesday night Through Friday night/...
With a surface high off the eastern seaboard Wednesday night,
should see steady east to southeast winds. These winds coupled
with >90% surface RH values along with sea surface temperatures
around 55 degrees in Mobile Bay and the Mississippi Sound could
promote significant advection fog development for southern Alabama
and Mississippi after sundown and overnight. A deep mid-level
trough over Texas enters the Southeast Thursday. As it enters, low
level convergence over southern Mississippi and offshore should
initiate a few showers out ahead of the trough Thursday morning.
Models show these showers increasing in coverage starting Thursday
afternoon and lasting until the late afternoon Friday.
Instability is expected to be a non-factor as an inversion near
700mb keeps thunderstorms at bay. The mid-level trough pivots
through Alabama Friday evening as the subsequent surface cold
front pushes through the central Gulf Coast. The cold front drops
temperatures overnight into the low 30s over land. DJ/17
LONG TERM /Saturday Through Tuesday/...
With the cold frontal passage, rain chances fall to near zero and
temperatures inland struggle to reach the 50s during the day
Saturday and Sunday. The overnight hours prior to sunrise weekend
could see sub 30 temperatures inland. An upper level low anomaly
develops over the Great Lakes region to start the week. This
persistent troughing translates locally to a consistent northerly
flow Monday into Tuesday. For now model guidance show max
temperatures reaching low 50s during the day with mid to low 30s
overnight however there is much variability on the tail end of
the forecast nevertheless a chilly start to next week is expected.
DJ/17
MARINE...Areas of dense fog are likely to develop over Mobile Bay,
MS Sound, and the AL near shore Gulf waters tonight given dewpoints
in the mid to upper 50s and waters temps still in the upper 40s.
Therefore, a Marine Dense Fog Advisory has been issued from 6pm this
evening until 9am Wednesday. Patchy to areas of fog are possible
further east, but extent of the fog is uncertain. Another round of
fog is likely Wednesday night as additional warm and humid air is
ushered in over the cold coastal waters.
Otherwise, a light to moderate easterly flow will persist across the
marine area through Wednesday, gradually becoming more southerly in
nature Wednesday night and Thursday ahead of the next cold front.
The front is forecast to move through the coastal waters Friday
morning, with a moderate to strong west-northwest flow developing in
its wake. A Small Craft Advisory will likely be required for
Friday/Friday night and potentially Saturday. Offshore flow
diminishes by Sunday. Seas will build to 7-9 ft beyond 20nm in the
Gulf on Friday. 34/JFB
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...Dense Fog Advisory until 9 AM CST Wednesday for ALZ051>056-059-
261>266.
FL...Dense Fog Advisory until 9 AM CST Wednesday for FLZ201>204.
MS...Dense Fog Advisory until 9 AM CST Wednesday for MSZ067-075-076-
078-079.
GM...Dense Fog Advisory until 9 AM CST Wednesday for GMZ630>634-650.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion
National Weather Service Marquette MI
634 PM EST Tue Jan 9 2018
.SHORT TERM...(This evening through Wednesday)
Issued at 352 PM EST TUE JAN 9 2018
Water vapor imagery and RAP analysis show shortwave that was over
the area 24hrs ago has shifted to New England. Upstream, a broad,
low amplitude ridge is moving out across the Plains and s central
Canada. Next feature of interest for Upper MI is the current well-
defined shortwave/mid-level low spinning along the southern CA
coast. This wave will affect the early part of the long term fcst
period as it weakens/shears ne across the Upper Mississippi Valley
on Thu. At the sfc, high pres ridge associated with upstream mid-
level ridge is now slipping e of Upper MI. Across w and central
Upper MI, the high provided a quiet morning under sunny skies and
little if any wind. Lingering clouds off Lake Superior over the e
have shifted out over the lake this aftn, but some additional clouds
off Lake MI are now pushing n into that area. Mid cloud band
associated with isentropic ascent is lifting across the w half of
Upper MI.
Main fcst issue during the short term will revolve around increasing
low-level moisture and the potential of some very light pcpn to
develop from the shallow saturated deck. Obs show some stratus and
fog lurking across portions of northern IL/IN and southern lower MI,
and VIS satellite imagery shows low clouds quickly lifting n over
southern lake MI while progress over land is being slowed. As sfc
high pres moves e quickly tonight, southerly winds will ramp up with
50+kt low-level jet shifting across the area. HRRR runs seem to have
a decent handle in showing low clouds quickly streaming n and
expanding into far eastern WI and central Upper MI during the night
under s to sse upslope flow. Initially, these low clouds and
probably some fog should be confined to roughly the area s of a
Crystal Falls/Ishpeming/Gwinn and Manistique line. With the aid of
upsloping, there is a very small chc that a little -fzdz could occur
before 12z.
Low clouds/some fog should expand across the area on Wed under
continued low-level moisture advection. Moisture depth remains
relatively shallow, suggesting pcpn, if it occurs, should be in the
form of -fzdz/-dz. Moisture depth is a little deeper over the e,
which may allow for a little -ra at times, but -dz is still the more
likely ptype. With expectation of low clouds dominating, favored the
more conservative guidance for max temps...a degree or two either
side of 35F.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 323 PM EST TUE JAN 9 2018
Upper air pattern consists of a 500 mb trough over the central U.S.
00z Thu. This trough moves slowly east and affects the area Thu into
Thu night. Strong dynamics and deep moisture also move through the
area Thu into Thu night along with cold air. Still looks like
advisory amounts of snow for the west and mixed pcpn as well.
Overall, did not make too many changes to the going forecast. Will
continue to highlight the amounts of snow and mixed pcpn in the hwo
for now. Not confident enough yet to issue advisories.
In the extended, GFS and ECMWF show a 500 mb trough with cold air
over the central and eastern U.S. 12z Sat that remains into Mon
before the cold air starts to move off to the east on Tue. This will
continue a prolonged lake effect snow event for the area along with
below normal temperatures continuing this forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 634 PM EST TUE JAN 9 2018
VFR conditions will prevail into the late evening hrs at
KIWD/KCMX/KSAW. Strengthening low-level jet will result in LLWS
developing at all terminals this evening and continuing into
Wednesday morning. The strengthening southerly flow will also
quickly transport low-level moisture across southern Lower
MI/northern IL and eastern IA northward. LIFR conditions will likely
set in overnight at KSAW. Wednesday morning, IFR conditions should
develop at KIWD and low MVFR at KCMX. Ceilings will continue to
lower at KCMX into the afternoon hours.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 352 PM EST TUE JAN 9 2018
Some periods of gale force winds expected over the next several days
with heavy freezing spray at times Thu thru Sat. Winds are currently
beginning to increase on Lake Superior as exiting high pres ridge
slips farther away. The wind will increase further tonight to 20-
30kt. Gales will likely develop over the e half overnight into Wed
morning as low-level wind max moves across the area and max 3hr pres
falls shift across northern Ontario. Winds will diminish for a time
Wed night as cold front drifts over the lake. Winds will then
increase w to e Thu as much colder air drops into the Upper Lakes
behind low pres wave that moves along the front. Gales are expected
over much of Lake Superior late Thu morning thru Thu evening. Brisk
winds, probably under gale force, will then continue into Sat,
especially over the e half of Lake Superior as arctic air mass moves
across the Upper Lakes. Winds will diminish on Sun as high pres
ridge arrives.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Warning from 1 AM to 1 PM EST Wednesday for LSZ266-267.
Gale Warning from 1 AM to 9 AM EST Wednesday for LSZ265.
Lake Michigan...
None.
&&
$$
SHORT TERM...Rolfson
LONG TERM...07
AVIATION...KEC
MARINE...Rolfson
Area Forecast Discussion...UPDATED
National Weather Service Norman OK
916 PM CST Tue Jan 9 2018
.UPDATE...
Made minor adjustments to hourly temperatures, winds, and sky
cover tonight. Added low chances (20%) for showers and
thunderstorms across northwestern Oklahoma Wednesday evening.
&&
.DISCUSSION...
Some fog may occur later tonight into Wednesday morning southeast
of an Ardmore to Seminole line.
Made minor adjustments tonight based on latest surface
observations on HRRR model guidance. It appears that low stratus
clouds will stay mainly just east of I-35. Will continue to
mention areas of fog for parts of south central and southeastern
Oklahoma where low level moisture will be deepest. Due to
stronger low level winds compared to last night, do not think
dense fog (visibilities 1/4 mile or lower) will occur in these
areas, but will closely monitor.
A few sprinkles/light high based rain showers may impact parts of
northwestern Oklahoma 4 am to noon Wednesday due to a weak impulse
combining with mid level moisture and weak mid level instability.
Did not mention thinking the air below cloud base will remain too
dry to allow for any precipitation to reach the ground.
Warm and breezy weather will elevate wildfire potential
on Wednesday. Think humidity levels will stay too high (above
20%) to warrant the issuance of a Red Flag Warning across western
Oklahoma and western north Texas.
Most latest model guidance have been depicting light
QPF/precipitation amounts mainly northwest of a Frederick Oklahoma
to Stillwater line Wednesday night. This seems reasonable due to
increasing lift from an approaching mid/upper low as well as lift
near the intersection of the surface dryline and incoming Pacific
front combining with sufficient mid level moisture. Thus, added
20% for showers and thunderstorms in these areas in the 6 pm to
midnight time frame. Model forecast MUCAPE values up to 300 J/kg
and mid level lapse rates around 7C/km support a few rumbles of
thunder. No severe storms are expected due to the weak
instability, but brief gusty winds 30-50 mph along with pea
size hail could occur with any shower/weak thunderstorm
Wednesday evening.
Colder air will move into the area on Thursday along with very
strong north/northwesterly surface winds (widespread gusts 30-50
mph between 3 am and 5 pm Thursday).
Products will be updated.
MBS
&&
.PREV DISCUSSION... /issued 540 PM CST Tue Jan 9 2018/
AVIATION...10/00Z TAF Issuance...
MVFR to IFR stratus continues to develop across portions of
eastern and southeastern Oklahoma. This is expected to build
northward through the early portion of the period, impacting TAF
cites across central Oklahoma. Gusty south winds will persist
through the period. Given shallow, overall, moisture profiles and
the winds, fog development may be difficult, and early indications
are for stratus to be the primary aviation challenge overnight
through early Wednesday. Expect far western TAF sites to remain
VFR, but this will highly depend on how far west any stratus
extends. Ceilings will improve through the later half of the
period.
Kurtz
PREV DISCUSSION... /issued 255 PM CST Tue Jan 9 2018/
DISCUSSION...
Stubborn low cloudiness will continue to hold temperatures in the
40s F across our far eastern counties into the evening. Farther
west, drier air and much less cloud cover will allow the
currently mild temperatures to drop off overnight. Southeast
surface winds will once again support the possibility of advection
fog late tonight into early Wednesday across the east.
Meanwhile, as a large storm system approaches from the west,
southwest winds will bring very warm weather (at least for
January) to our western counties again tomorrow. Moderate wind
speeds and moderately low relative humidities will cause an
increased risk of fire in the far west, but probably not enough to
warrant any headlines.
A strong cold front will then arrive Wednesday evening/night,
bringing much stronger winds and much cooler conditions. A wind
advisory appears to be a certainty for approximately the western
half of our forecast area for most of Thursday. That is a little
too far out in time for an advisory now, but the next forecast
will likely include one.
A few light showers/snow showers may also occur with this system,
but nothing of significance is expected.
Cold air will be reinforced a couple of times this weekend, and
then there will be a chance of warmer/moist air bring pushed over
the shallow cold air early next week. The latest model runs have
pushed the chance for precipitation farther south, so it looks
less likely that we will have to deal with significant ice
(freezing rain), but it is still a possibility, especially in
south-central and southeast Oklahoma.
CmS
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 42 63 37 40 / 0 0 10 10
Hobart OK 42 69 34 39 / 0 0 20 0
Wichita Falls TX 45 70 43 46 / 0 0 10 0
Gage OK 41 70 24 36 / 10 10 20 10
Ponca City OK 41 62 35 39 / 0 0 20 20
Durant OK 42 62 47 50 / 0 0 10 10
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
17/04
Area Forecast Discussion
National Weather Service Phoenix AZ
156 PM MST Tue Jan 9 2018
.SYNOPSIS...
A strong low pressure system will move through the region today
and Wednesday bringing scattered to numerous showers, possibly a
thunderstorm, breezy conditions, and much cooler temperatures. Dry
weather along with a warming trend will return Thursday and
continue through the weekend as high pressure builds back over the
area.
&&
.DISCUSSION...
Latest water vapor imagery shows the compact vort max progressing
eastward through southern CA. Meanwhile, a frontal boundary ahead
of the upper low will continue moving steadily eastward into the
Imperial Valley this afternoon. Ahead of the front, temperatures
have soared into the upper 70s and the models had suggested that
isolated showers would develop across portions of south-central
AZ. However, latest runs of the HRRR indicate this is less likely
and consequently PoPs were lowered somewhat for this afternoon.
Nevertheless, showers have developed further west across
southeastern CA, which was depicted well by the majority of
models. Latest GOES-16 imagery shows weak gravity wave activity as
well, an indication of the stronger winds ahead of the low
pressure system.
Latest convective parameters remain generally unimpressive,
though strong vorticity and jet-forced ascent ahead of the
frontal boundary will support a line of showers with embedded
heavy precipitation across western Arizona by later this
afternoon. Ahead of the line of showers, anomalously strong pre-
frontal 850 mb winds of 40+ kt have the potential to mix down to
the surface, which will produce localized dust plumes and pockets
of reduced visibilities. The stronger mean flow will also
translate into exceptionally high values of IVT as noted by the
NAEFS, particularly near the Bradshaw Mountains of southern
Yavapai County.
SPC ensemble of the hi-resolution CAMs along with the
experimental HRRR continue to identify the 7-11pm window as the
most active period across central Arizona, though global models
indicate sufficient ascent for precipitation after midnight as
well. In addition to the precipitation, conditions will be
favorable for stronger wind gusts, perhaps up to 45 mph in the
strongest storms. SREF thunder probabilities also suggest the
potential for a few lightning strikes. Convective nature of the
activity will naturally result in some variability in the rain
totals, though consensus of the ECMWF and GEFS members indicates
around 0.3-0.6 inches of precipitation for the Phoenix area. Rain
of this magnitude within short durations certainly has the
potential to produce localized flooding in the urban areas.
&&
.PREVIOUS DISCUSSION...
Snow levels will drop through the day and fall near 5500ft at
their lowest level Wednesday morning. However with the rapid
forward progression to this system and compact cold core, little
accumulating snow would be expected. The upper low will quickly
shift to the east reaching the TX Panhandle by Wednesday early
afternoon, shutting off precipitation chances all but for the
northern/eastern AZ higher terrain through midday Wednesday. A
much cooler airmass will settle over the area Wednesday allowing
below normal temperatures with highs in the low 60s and even upper
50s possible.
Thursday through Sunday:
Low amplitude ridging transitions in from the West, rapidly clearing
skies and rebounding thermo profiles. Near normal temperatures
expected for Thursday. Temperatures will gradually warm back to
above normal readings by Friday and into the coming weekend.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA, and KSDL:
Multiple types of weather impacts will make the next 24 hours
difficult for aviation interests in cntrl AZ.
1) WINDS: There is good confidence that the late morning, light east
wind will become a gusty cross-runway south wind by mid/late
afternoon. Gusts over 25kt may be common, and some suspended dust
may impact slantwise visibilities. Fropa and an abrupt wind shift to
a westerly direction should occur between 03Z-04Z (probably closer
to 04Z). Brief gusty west winds over 30kt will be likely. After
fropa, sfc winds will likely become highly variable and eventually
switch back to a S/SE direction overnight.
3) CIGS: Lower cigs will materialize with fropa and the rain bands
likely falling for a brief period into MVFR category. Lower VFR cigs
below the 6K ft layer are very likely overnight and into Tuesday
morning with isolated showers around the aerodromes. There may be
larger pockets of MVFR cigs, and low clouds hugging terrain features
will probably result in mountain obscuration through much of
Tuesday.
2) TS: A few embedded TS are possible with fropa this evening.
Coverage and time duration do not appear sufficient to include
anything more than a VC mention in the taf package.
Southeast California/Southwest Arizona including KIPL and KBLH:
A frontal boundary was passing through the SE California terminals
this afternoon leading to gusty winds, brief lower cigs, and
scattered showers. Gusty west winds over 30kt (and possibly some
blowing dust) will impact KIPL earlier and more pronounced than
KBLH. However, showers and briefly lower cigs (as low as 4K ft) will
be more probable at KBLH. The greater impact weather should exit
east of the area later tonight.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Thursday through Monday:
High pressure aloft will build back into the area Thursday through
the weekend, allowing for dry conditions and a gradual warming trend
each day. Highs will stay near normal Thursday but climb further
Friday with most of the lower deserts rising back into the 70s.
Winds each day will stay on the light side, typically favoring the
north to west each afternoon. Minimum RH values will be quite
elevated Thursday with desert readings mostly 20 to 30 percent;
expect a bit of drying Friday through the weekend with minimum RH
values dropping into the mid teens to mid 20s each day.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...Wind Advisory until 10 PM PST this evening for CAZ562.
&&
$$
Visit us on Facebook, Twitter, and at weather.gov/phoenix
DISCUSSION...Hirsch
PREVIOUS DISCUSSION...Nolte
AVIATION...MO
FIRE WEATHER...CB
Area Forecast Discussion
National Weather Service Tucson AZ
830 PM MST Tue Jan 9 2018
.SYNOPSIS...Strong low pressure will move across northern
Arizona through the day Wednesday. This system will bring valley
rain, mountain snow and gusty winds to southeast Arizona overnight
into Wednesday morning, along with much cooler temperatures. Dry
conditions and a warming trend will commence Thursday with above
normal daytime temperatures returning Friday into early next week.
&&
.DISCUSSION...
Low pressure continues to make its way through southern California
this evening, with a band of showers stretching from Flagstaff to
Buckeye to Ajo as of 03Z. The majority of southeast Arizona remains
dry this evening although area webcams showed a quick dusting of
snow on Mt. Graham just before sunset this evening. Main story thus
far has been winds with pre-frontal southwesterly winds blowing at
15-25kts. This will continue to be the story the rest of the night
with even higher speeds forecast across far southeast Arizona after
midnight. Wind Advisory looks good for these locations. Higher
elevation mountain peaks could see Advisory level winds for a brief
time coincident with the frontal passage but far southeast Arizona
will see the greatest duration of gusty winds.
Rain has been slow to arrive thus far and I trimmed back PoPs a bit
through mid evening, although looking at radar imagery it won`t be
long before areas around Tucson and points east start seeing precip.
Best timing for precip looks to be between 06Z-12Z per last few runs
of the HRRR and other hi-res short term guidance. Retained the
mention of thunder overnight as some lightning has been noted
upstream and last few runs of the RAP indicate a few J/kg MUCAPE
into the daytime hours Wednesday. Also made minor reductions to QPF
given the slower arrival but this only shaved off a few hundredths
from the storm total. Still looks like 0.10 - 0.25" across the
deserts, a bit more than 0.50" in the White Mtns. Snow amounts still
look on track with 4-6" forecast above 7000` by the time all is said
and done.
Outside of the aforementioned minor adjustments to capture current
trends, no other changes necessary.
&&
.AVIATION...Valid thru 10/06Z.
A cold front will begin to move across southern AZ with conditions
becoming SCT-BKN045-060 BKN-OVC080-100 with scattered to numerous
SHRA and isolated TSRA. Winds will increase to SW 15-30 kts with
gusts 35-50 kts ahead of and with the front then quickly decrease
behind it. The front is expected to reach KTUS around 10/07Z and
KSAD-KDUG around 10/12Z. Aviation discussion not updated for TAF
amendments.
&&
.FIRE WEATHER...A cold front will move across the area late
tonight with numerous showers and isolated thunderstorms and a 3-6
hour period of strong southwest winds late tonight into the early
morning hours Wednesday. Winds during that period will be up to
30-35 mph with gusts 40-50 mph in the windiest locations such as
from Sonoita down through Sierra Vista and into the Chiricahua
Mountains. The shower threat will end from west to east by
Wednesday evening followed by dry conditions Thursday well into
next week with above normal temperatures once again. Winds
Thursday onward will generally be typical for January.
&&
.PREV DISCUSSION...
Southerly warm air advection today in advance of approaching weather
system has led to warmer high temperatures than forecast, even with
the cloud cover across most of the area.
Mostly cloudy conditions existed across most of southeast Arizona
this afternoon in advance of an upper low that was centered near
Santa Barbara this afternoon. The associated cold front was also
moving through southeast California with showers moving up the
Colorado River. Across southeast Arizona isolated light showers and
virga has developed, mainly across the northern sections of the
Tucson metro area, far southeast Pinal and Graham counties.
The upper level low will move across northern Arizona through late
Wednesday morning. The associated cold front, which will pick up
some Gulf of California moisture where PW values west of Tucson will
briefly be as high as 1", will sweep across the forecast area
tonight into Wednesday morning with timing impacting the Tucson
metro area between 11 pm and 1 am.
Showers will be increasing west of Tucson this evening and push on
east with a few thunderstorms possible along the cold front and if
they get frisky enough, could see brief gusts of 40 to 50 mph from
these isolated storms also.
Storm total snow accumulations are expected to generally range from
4-7 inches above 7000 feet across the Catalina/Rincon Mountains, the
Pinaleno Mountains including Mount Graham, and the White Mountains
northeast of Safford. However, isolated higher amounts may be
realized across the highest peaks.
Storm total rainfall amounts in the valleys are forecast to
generally range from 0.10"-0.50", and liquid amounts perhaps
approaching 080" across the higher peaks especially NE of Tucson.
Pressure gradient increasing in advance of the cold front will bring
breezy to windy conditions tonight into Wednesday morning. Strongest
gradient gusts will be across the higher terrain across Santa Cruz
and Cochise counties, including Sierra Vista, where gusts could get
as high as 50 mph at times. A wind advisory has been issued for the
above areas starting at 11 pm.
Much cooler on Wednesday with highs, oh dare I say, below normal.
After a chilly start on Thursday temperatures will rebound to near
normal. Then the area will yet again return to well above normal
high temperatures this weekend into MLK day.
&&
.CLIMATE...Tucson has started the calender year 2018 with nine
straight days with highs in the 70`s. Only two other years started
with 9 or more straight days, 1902 with 11 and 1956 with 16. The
record is safe with forecast high near 60 on Wednesday.
After brief cool down on Wednesday, temperatures rebound quickly
to above normal levels by Friday with continued warmup into the
upcoming weekend. An oddity in the January daily record highs for
Tucson is that one day, the 13th, is the only one with the record
high being in the upper 70s. I bring this up since the forecast
high on Saturday for Tucson will be approaching the record high
of 78 degrees set in 2006.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 11 PM this evening to 5 AM MST Wednesday for
AZZ503-507-508-512-513.
&&
$$
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