Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/10/19
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
926 PM EST Mon Dec 9 2019
Low pressure will move from the Great Lakes into Quebec overnight,
dragging its trailing cold front through the region Tuesday.
High pressure will build into the region late Tuesday night
and remain through Thursday, before shifting offshore of New
England as low pressure develops over and approaches from the
southeastern United States.
.NEAR TERM /THROUGH TUESDAY/...
KLWX WSR-88D at 0130Z shows scattered light showers primarily
east of Blue Ridge. Short-range HREF and HRRR has these
scattered showers becoming more isolated as the overnight
continues, with the overwhelming majority of the CWA staying dry
between midnight and daybreak. Temperatures are not going to
change much overnight, as low level moist advection and
southerly flow keep pumping in warmer air. This will result in
overnight lows 5-10 deg F above average. Gusty surface winds
before midnight as evidenced by numerous surface reports
throughout the CWA at 01Z of G15-25KTS, caused by a 60KT H85
jet which was directly overhead the CWA at 10/00Z. This low
level jet will eject northeastward towards Cape Cod by
midnight, and the winds will slacken after midnight.
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
(02Z Update)...Rain showers will develop Tuesday morning,
and will be prevalent by Noon across the entire CWA, especially
along and east of Interstate 95. The cold front will pass
through the area on Tuesday afternoon, which will start to
filter in colder air. The 18Z ECMWF continues to be consistent
with its prior 4 model runs with measurable snow across much of
the CWA Tuesday night. There will be a brief lull in rainfall
late tomorrow afternoon and early evening, before the region
begins to feel the effects and influence of the right rear
quadrant of a 170KT H3 jet which will be optimally positioned
late Tuesday night providing jet induced dynamics. By 06Z Wed,
the column should be cold enough to support all snow west of a
line from Bel Air-Damascus-Sterling-Harrisonburg. Any pcpn that
falls after 06Z west of this line will likely be all snow. East
of this line, there will be a gradual transition from rain to a
mixture to finally all snow by daybreak Wednesday. Accumulations
along and east of I-95 will be limited as the race for the cold
air to arrive in time before the precipitation departs will be
There will likely be a sweet spot in this colder region north
and west of the Balt/Wash metro areas where 2-3 inches could
accumulate on grassy surfaces, i.e., near the Catoctins,
northern portions of Carroll, Baltimore, and Harford Counties,
and along the Blue Ridge. Impact-wise, I am concerned about I-70
from eastern Frederick County to Hagerstown, and the confluence
of other high-speed roads around Frederick MD, including the
I-270 corridor from Frederick to Rockville. Motorists on the
roads in these areas between midnight and daybreak will be prone
to slick roads and low visibilities. The one thing that is
working in favor of lesser accumulations on roadways is that
temps will max out at least mid-50s CWA-wide today, and along
and east of I-95 will be hovering in the lower 60s. I do think
that snowfall early Wednesday morning will make its way to the
Chesapeake, although the surface temps will still be AOA
freezing, thus very unlikely to stick on roadways. I have
updated the snow graphics reflecting grassy accumulations to
the Bay, and slightly increased snowfall totals north and west
of the major metro areas. Reminder...official NWS snowfall
forecasts are for accumulations on whiteboards/grassy areas,
and not on road surfaces./End 02Z update/
The latest model guidance has honed in on the 10:00AM to 4:00PM
window for greatest coverage of shower activity Tuesday, as low
level convergence increases along an eastward advancing cold
front and PVA associated with another mid level shortwave pivot
across. Showers will probably become a bit less widespread for a
time during the late afternoon and evening following the frontal
passage, but coverage is expected to increase again by late
evening into the overnight in concert with RRQ jet dynamics
associated with a very strong upper jet.
Since the low level front will have passed by Tuesday night,
temperatures will begin to cool. As such, rain is expected to
change to snow. There is still uncertainty in the timing of
temperatures becoming cold enough for snow, especially east of
the Blue Ridge where downsloping and compressional warming
effects tend to be most notable. Even when precipitation changes
to snow, surface temperatures will likely be near or above
freezing, so snow may have trouble sticking in the lower
elevations. Overall, the setup remains largely unchanged, with
typical run to run and model to model variability noted. The
highest confidence in snowfall accumulations will be over the
higher terrain (above about 1000 feet), with the higher
elevations of north-central/northwestern Virginia likely to see
the highest totals.
Even though boundary layer temperatures are expected to be
marginal in the lower elevations and especially in the I-95
corridor, the timing of wintry precipitation lines up with the
Wednesday morning commute, and the powerful mid/upper jet
dynamics may result in localized heavier bands of precipitation,
beneath which snowfall rates could overcome surface temps and
result in accumulation even on paved surfaces.
Precipitation should come to an end by midday Wednesday, with
gusty northwest winds ushering in an Arctic airmass in its wake.
.LONG TERM /THURSDAY THROUGH MONDAY/...
Guidance overall is in good agreement with the synoptic pattern
concerning the long term. A strong area of high pressure moves
eastward out of the Great Lakes region and extends down the
majority of the Eastern Seaboard. The resultant is dry yet
chilly conditions expected for Thursday. At the same time, low
pressure develops over the Gulf of Mexico and will begin to lift
northeastward late Thursday night into Friday.
While guidance is in better agreement about the timing of precip,
there is still some spread in regards to timing, track and
temperatures. The GFS/GEFS bring precipitation into the CWA by
Friday morning, while the ECMWF/EPS delay precip onset by about
6 hours. Interesting to note that today`s 12Z ECMWF suite
advanced the precip by about 6 hours, compared to the 12 hour
difference (from the GFS) it showed yesterday. Therefore, there
is better confidence that precip onset will occur by Friday
afternoon. With the chilly air mass in place, some wintry
precipitation (freezing rain), will be possible at the onset,
mainly near and west of the Blue Ridge. Elsewhere, mainly plain
rain is most likely.
The low will exit the region by early Saturday morning with
some partial clearing expected for the afternoon. Dry weather
persists through Monday as temperatures remain slightly on the
cooler side of normal.
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
IFR CIGS will prevail through 05Z/midnight then improve to LIFR
and remain through daybreak. Winds should start to relax too
after 05Z as the H85 ejects northeastward.
Latest guidance pegs the 15-21Z window Tuesday for most likely
showers and sub-VFR CIGs/VSBYs. A brief respite is anticipated
Tuesday evening, before precipitation re-develops and changes to
snow after midnight. The most likely terminal to see
accumulation is MRB, least likely at CHO/DCA, though there could
be a quick coating even on paved surfaces at any terminal if a
localized heavier band of snow moves overhead, overcoming
marginal surface temperatures.
VFR returns by midday Wednesday with gusty NW winds. Another
round of rain seems definite Friday afternoon into Saturday as
coastal low pressure develops to the southwest and lifts
northeast. Expect IFR conditions in moderate rain Fri night and
Saturday. Mixed pcpn possible mainly near MRB.
Winds will continue to blow SCA overnight as the H85 jet impacts
continue. There will likely be a lull in the winds Tuesday, so
the headline drops to just the lower most Maryland portion of
the Chesapeake Bay and lower tidal Potomac. Winds likely
increase in NW flow behind a cold front Tuesday night and
Winds lighten Wednesday night through Thursday night as high
pressure builds overhead.
SCA conditions possible Friday into Saturday as pressure
gradient tightens in advance of a coastal low pressure lifting
MARINE...Small Craft Advisory until 10 AM EST Tuesday for ANZ531>533-
Small Craft Advisory until 6 PM EST Tuesday for ANZ534-537-543.
Small Craft Advisory until 6 AM EST Tuesday for ANZ530.
Small Craft Advisory until 6 AM EST Tuesday for ANZ535-536.
Area Forecast Discussion
National Weather Service Memphis TN
1001 PM CST Mon Dec 9 2019
Latest surface analysis places a cold front from Camden, Tennessee
southwest back through Bolivar, Tennessee, and into Oxford,
Mississippi. North and west of the front, temperatures are in the
50s with light rain and gusty northwest winds. South of the front,
temperatures are still in the low to mid 60s with westerly winds.
Latest Hi-Res data remains pretty consistent wrt to mixed
precipitation for tomorrow morning into the afternoon hours. The
aforementioned front is expected to push completely south and east
of the area overnight, dropping temperatures into the 30s
areawide. However, the majority of the area is expected to remain
at or above freezing tomorrow.
Overrunning precipitation will develop and remain along and south
of I-40 tomorrow morning and into the afternoon hours, fed by a
southern branch shortwave. As the southern wave phases with the
northern jet in the afternoon hours, a more concentrated area or
snow in the form of a band or two may set up over northern
Mississippi by the late afternoon hours. Both the HRRR and NAM
have continued to advertise this solution for successive runs. If
a band or two can set up over an area for an extended period,
accumulations could approach an inch over portions of northeast
Mississippi. However, confidence still remains low as the cold and
dry air will likely undercut the moisture, resulting in drizzle
or nothing at all.
The current forecast captures the mixed precipitation well during
the morning hours with a changeover to mostly light snow in the
afternoon hours. Accumulations will be confined to mainly elevated
and grassy surfaces and should remain below half an inch. Unless
00Z model data or Hi-res model data drastically changes, the
impacts look to be little to non-existent as no accumulations are
expected on roadways at this time.
.PREV DISCUSSION... /issued 625 PM CST Mon Dec 9 2019/
Update for 00Z Aviation.
.PREV DISCUSSION... /issued 302 PM CST Mon Dec 9 2019/
20Z / 2 PM CST surface map showed an Arctic cold front over
southern MO. The freezing line extended from Kansas City to
Dubuque to Green Bay. GOES water imagery showed subtropical
moisture extending from a small upper low over southern AZ,
eastward across the TX and the southeast states.
The aforementioned compact upper low will track east into TX by
midday Tuesday, weakening as it phases with a longwave trof axis
extending from the upper Midwest to the southern plains. Rainfall
will expand downstream over the lower MS River valley, supported
by an elevated warm conveyor belt and isentropic lift over the
front. For the Midsouth, this main area of rain will set up along
and south of I-40 in the morning, and then translate east during
the afternoon. It is along the northern periphery of this precip
shield where thermal profiles will become favorable for mixed
(sleet/snow/rain) precip. Further north, toward the MO/KY borders,
lift will be significantly weaker, confined mainly to a narrow
band of marginally-moist isentropic upglide. Model soundings
depict less of a sleet potential from Jonesboro over across NW TN
Tuesday afternoon, with rain/snow a mixture more likely. With
surface temps above freezing across the area Tuesday afternoon,
expect snow/sleet accumulations to be light and mainly confined to
As we head into Tuesday evening, precip will end over west TN and
east central AR, leaving weakening rain/slow/sleet over north
central and portions of northeast MS. 12z models were in agreement
in ending precip over northeast MS by midnight Tuesday night,
followed by temps cooling to below freezing during the overnight.
With light winds expected Tuesday and Tuesday night, evaporation
of moisture on bridges may not complete before temps fall below
freezing. A few slick spots on bridges Tuesday night may be main
impact of this marginal winter event.
Sunny skies and temps in the 40s should follow for Wednesday, The
model depict an open southern branch upper trof passage Thursday
night into Friday. This system won`t have much moisture to work
with until it gets to the east of the Midsouth. After this system
exits, zonal flow will transition to southwesterly, setting up for
our next chance of measurable rainfall next Monday.
A sfc cold front continues to move into the Mid-South this evening
causing winds to shift NW then N. Winds are currently 8-12kts,
however, as the front passes gusts 18-21kts are possible. Cigs
have improved to VFR/MVFR for the time being but are expected to
lower to MVFR with the onset of rain showers. Rain will begin
shortly after 06Z, becoming a RA/SN mix by mid-morning and -SN by
early tomorrow afternoon. Have not included -SN at TUP at this
time based on temperatures and low confidence. Winds will remain
out of the north tomorrow generally 8-10kts and gusts possible at
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
529 PM CST Mon Dec 9 2019
.DISCUSSION...Updated for latest aviation discussion below.
00Z issuance...General VFR conditions were noted across the area
at 23Z with an area of low end MVFR CIGS along and west of Mobile
Bay. General low end MVFR conditions are expected to become IFR
with local LIFR conditions along and just north of the I-10
corridor as southerly winds over the area weakens to around 5
knots or less. Impact to operations at area TAF sites are possible
after 06Z as dense fog forms. Conditions are expected to improve
after sunrise to low end MVFR CIGS and VFR VISBYS. A slowing cold
front moves south across the area Tuesday, bringing scattered rain
showers along with drops in conditions to the IFR/MVFR juncture.
The I-20 corridor is expected to be impacted after 21Z Tuesday
afternoon. South winds 5 to 10 knots will become northerly around
10 knots as the cold front moves south across the area.
.PREV DISCUSSION... /issued 410 PM CST Mon Dec 9 2019/
NEAR TERM /Now Through Tuesday/...A CONUS-wide trough is
currently present aloft, with a prominent shortwave over the
southwest CONUS. This feature is expected to progress eastward
over the southern CONUS tomorrow and towards the southeastern
CONUS through midweek. A surface cold front will also approach
the region late tonight into early tomorrow, increasing showers
from the northwest. Model reflectivity shows showers in the form
of a line, with scattered showers ahead of the line, that will
move from northwest to southeast over the region through midweek.
Model soundings for areas near the coast and even further inland
show CAPE values generally between 200 and 700 J/kg Tuesday
morning and through the afternoon. Therefore, this combined with
frontal forcing will lead to the possibility of a few
thunderstorms as the line moves through Tuesday morning and
through the afternoon.
The other concern will be the potential for fog development
tonight into early tomorrow morning due to southerly flow leading
to increased warm and moist air. Some of this fog may become dense
towards dawn, particularly for Mobile Bay, Mississippi Sound, and
areas surrounding. Model guidance from the SREF and HRRR also
supports this. Thus, a Dense Fog Advisory was issued from tonight
through mid-morning tomorrow for Mobile Bay and Mississippi Sound
areas. Will monitor through the evening to see if the advisory
needs to be extended to the land areas as well.
Temperatures will continue to run above seasonal norms tonight,
with lows around 60 degrees further inland (SW AL and SE MS) and
in the mid 60s along and south of I-65. Highs tomorrow will be in
the upper 70s for areas south of I-65, but highs will be lower in
the interior SW AL and SE MS due to FROPA. Expecting highs to only
reach the mid to upper 60s in this region. /26
SHORT TERM /Tuesday night Through Thursday night/...A cold front
associated with an upper trough over the lower Mississippi River
Valley pushes offshore Tuesday night, ushering in a cooler and
more stable low-level airmass. Aloft, the upper trough lags to the
west, with an unsettled southwest flow continuing and showers
lingering across the area throughout the day Wednesday. Rain
chances end over inland areas Wednesday night as the upper trough
departs to the east, though a slight chance continues right along
the coast. Another trough moves east across Texas right on the
heels of this one, with southwest flow returning aloft by
Thursday night as it approaches the lower Mississippi River
Valley. Rain chances increase across the entire area Thursday and
Thursday night in response to the impinging trough. /49
LONG TERM /Friday Through Monday/...The upper trough over the
lower Mississippi River Valley continues east across the Deep
South during the day Friday. A surface low develops over the
northern Gulf as the upper trough takes on a slight negative tilt.
The low moves quickly northeast, but in doing so keeps the local
area in its northwestern quadrant and firmly entrenched in a cool
and stable airmass with daytime temps hovering in the 50s across
much of the area. Above the stable surface layer, however, south
to southwest flow prevails and enough mid-level instability
develops for a chance at some elevated convection mixed in with the
showers. Best rain chances Friday and Saturday will be over the
eastern half of the area, in closer proximity to the passing
surface low and beneath the best region of upper divergence
associated with the passing trough. Drier air finally moves into
the area Sunday and Monday, with skies clearing and temps climbing
back into the 60s. /49
MARINE...Light to moderate onshore flow will persist through
tomorrow afternoon. Areas of marine fog may restrict visibility
tonight over bays and sounds and adjacent near shore waters. Thus,
Dense Fog Advisories may be needed tonight. Winds will then shift
from onshore to offshore and increase dramatically across the
marine area Tuesday night as a cold front moves east over the
region. Thus, a Small Craft Advisory was issued and is in effect
from Tuesday night through Friday morning. Moderate to strong
easterly flow will then take hold for late week, especially over
the open Gulf waters. Light to moderate northwest flow will then
follow for the beginning of the weekend. /26
AL...High Rip Current Risk through late Tuesday night for ALZ265-266.
FL...High Rip Current Risk through late Tuesday night for FLZ202-204-
GM...Small Craft Advisory from 9 PM Tuesday to 6 AM CST Friday for
Dense Fog Advisory from 9 PM this evening to 10 AM CST Tuesday
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Area Forecast Discussion
National Weather Service Blacksburg VA
1016 PM EST Mon Dec 9 2019
A cold front approaches from the west tonight, before crossing the
Mid-Atlantic region Tuesday. A wave of low pressure is expected to
develop along the front Tuesday night before moving off the Mid-
Atlantic coast Wednesday. Another storm system will impact the
region for the end of the week.
.NEAR TERM /THROUGH TUESDAY/...
As of 1006 PM EST Monday...
Cold front was located from the Ohio/Indiana border south into
western Tennessee this evening. Aside from patchy light rain
across the area, mainly dry tonight, before better lift ahead of
the front moves in Tuesday morning. Fog will be an issue early
near the Triad, but overall mainly cloudy skies should render
less fog issues. Temperatures will start to warm overnight in
the east as flow turns more southwest.
Previous early evening discussion...
Update to increase pops over the southeast WV to Alleghanys of
VA based on radar trends. The 18z NAM/21z RAP showing this area
overall better than any of the other high-res solutions.
This precip looks short-lived but overnight expect patchy light
rain/drizzle along the Blue Ridge and east with fog. Will see
showers increasing ahead of the cold front in the mountains
Previous discussion from early this afternoon...
A cold front from the Great Lakes to the southern plains this
afternoon will move east tonight into the Ohio valley and across the
Mid-Atlantic region on Tuesday. The first batch of rain associated
with the isentropic lift and warm front aloft is lifting northeast
out of the forecast area as expected this afternoon. Lingering
showers and patches of drizzle will continue this evening into
tonight. Moisture with the approaching cold front will increase
across the mountains late tonight resulting in a redevelopment of
widespread precipitation west of the Blue Ridge toward daybreak
Tuesday. Low temperatures may occur this evening, otherwise
temperatures will be nearly steady or slowly rising overnight into
Tuesday morning. Low temperatures readings will range from around 40
degrees in the northern mountains to the lower 50s in the southeast.
A cold front will move east across the area Tuesday into Tuesday
night. Moisture associated with the cold frontal passage will linger
post surface fropa, with the precipitation not ending until the
associated 850mb cold front clears the area late Tuesday night.
There is enough cold air on the backside of the front to change rain
to snow in the mountains Tuesday afternoon. The best CAA will be
delayed several hours from the front. Through 00z Wednesday, any
snow accumulations will be light from a coating to around half inch
in western Greenbrier county in southeast West Virginia. High
temperatures Tuesday will range from the upper 40s in the mountains
to the mid 60s in the piedmont.
Confidence in the Near Term forecast is moderate.
.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 226 PM EST Monday...
The surface low along the front will be in the eastern Carolinas on
Tuesday evening as it slowly fills and moves east and offshore. High
pressure builds from the Tennessee Valley across the Mid Atlantic
region on Wednesday and Wednesday night then gets reinforced with a
1040MB high over Pennsylvania by Thursday morning. This will set up
a strong wedge for Thursday and Thursday night.
850MB temperatures begin to drop below zero on Tuesday afternoon and
will range from zero in the piedmont along the Virginia/North
Carolina border to -8 in southeast West Virginia by Wednesday
Favorable lift in the form of upper diffluence in the right entrance
region on the upper jet will cross the area mainly between 06z/1am
and 12Z/7AM Wednesday. Forecast of partial thicknesses support snow
northwest of a Buckingham to Boone line by Wednesday morning with a
transition zone of winter mix southeast between the snow and the
rain over central North Carolina. Bufkit forecast soundings show
more sleet than freezing rain in the transition area.
Models still end all the precipitation across the region by
Wednesday afternoon. But seeing no support in the HREF/SREF and
other ensembles for 4 or more inches of snow. HREF does show the
potential for over 0.25 to 0.50 inches of flat ice accumulation
along the southern Blue Ridge in the 00Z/7PM Tuesday to 12Z/7AM
Wednesday (roughly 0.20 of radial ice.) No headlines will be posted
.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 225 PM EST Monday...
The surface based wedge will remain in place Friday. Seeing
significant differences in the surface pattern between the GFS and
the ECMWF Friday night through Sunday, with the ECMWF in general
slower with the systems in the southern stream. WPC was leaning
toward the ECMWF solution in this time frame.
Southwest surface and low level winds will warm the airmass and
place the region in the warm sector Friday and Saturday. Combination
of upper diffluence, deep moisture and upslope flow Friday afternoon
into Saturday will support precipitation. ECMWF and GFS bufkit
soundings have the precipitation stating as freezing rain on Friday
then warm up the column enough for only rain Friday night and
Saturday. Leaned toward the cooler NBM temperatures for Friday. Low
clouds, snow showers and upslope remain along the western slopes of
the central Appalachians through Sunday.
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
As of 628 PM EST Monday...
Ceilings will be fluctuating from IFR or lower in the east with
wedge starting to erode to VFR in the west. A few showers will
make for sub-VFR vsbys at LWB/BLF, with MVFR vsbys in the east
Confidence is high for some improvement in the cigs out east but
not anticipating VFR if any to last very long.
Strong low level jet above surface inversion creates low level
wind shear through about 10z Tuesday. Southwest winds become
west along the front then northwest during the day Tuesday.
Expect showers to make it into BLF/LWB by 12z, reaching ROA/BCB
11-13z, and LYH/DAN by 18z. These showers will bring sub-VFR
ceilings/vsbys with some gusty winds possible in the mountains.
Colder air behind the front lags somewhat but could see some
snow/sleet mixing into BLF by the end of this taf period.
Confidence is high for most of the taf period being sub-VFR, but
not as high in the east on breakdown of wedge overnight-Tuesday
.Extended Aviation Discussion...
Expect widespread low MVFR/IFR conditions to persist through
early Wednesday areawide, mainly due to low ceilings but also
reduced visibility associated with rain/drizzle/fog, and an
eventual change over to snow across the mountains as colder air
arrives Tuesday night.
A transition to VFR is expected Wednesday afternoon into
Thursday, followed by poor flying conditions again for Friday
and into the weekend as low pressure envelops the southeast
CONUS. There is also the potential for this system to produce
freezing rain across parts of the Mid-Atlantic Friday. Sub-VFR
is possible on Saturday with precipitation and clouds.
Forecast confidence is moderate to high.
For frequently asked questions about the Area Forecast Discussion
Area Forecast Discussion
National Weather Service Tucson AZ
827 PM MST Mon Dec 9 2019
.UPDATE...Adjusted clouds, precipitation, fog, temps and dewpoints
for the overnight hours.
.SYNOPSIS...Skies will continue to gradually clear off this
evening then some valley fog and patchy very low clouds will
likely form by dawn and linger into the mid morning hours.
Otherwise dry conditions are expected Tuesday into next weekend
with a slow warming trend.
.DISCUSSION...The primary dynamics associated with the upper low
moving across SE AZ have moved off to the east and what we are
left with is the cold pool aloft and without the sunshine to
trigger the convection, it quickly died off this evening. Now we
enter the gradual clearing out phase which will be difficult with
the abundant low level moisture we have around and we will likely
end up with some fog and/or patches of low stratus clouds. With
the mid and high clouds quickly dissipating I opted to increase
the fog to "Areas" from "Patchy" for the favored valley locations
and left some clouds in the Gila valley near the NM border. The
HRRR is suggesting LIFR conditions (fairly thick fog) in many of
those valleys and it just `feels like` a fog night for many areas.
It will be interesting to see how this plays out overnight but be
prepared for the potential for fog during your early morning
At any rate, I removed the threat of showers from the forecast
from here forward and tweaked with the clouds, winds, temps and
dewpoints. The sunshine will return tomorrow and you should be
safe to wash your car once the puddles disappear as we are not
expecting rain at least into the weekend at this time.
.AVIATION...Valid through 11/00Z.
SCT to locally BKN clouds 3k-6k ft MSL through midnight then
clouds thinning out. From 10/09Z thru 10/15Z areas of valley fog
with VSBYS AOB 3SM and ISOLD-SCT stratus AOB 1k ft eastern
valleys. KOLS and KDUG terminals potentially will be impacted.
Becoming clear after 10/16Z. Winds diminishing to under 6kts by
midnight. Aviation discussion not updated for TAF amendments.
.FIRE WEATHER...Minimal fire weather concerns. Dry conditions
return Tuesday and continue into the weekend. 20-ft winds will
generally remain less than 15 mph through the forecast period.
.PREV DISCUSSION... /issued 247 PM MST Mon Dec 9 2019/
The low over central to south-central Arizona continues to bring
areas of valley rain and mountain snow showers with isolated
embedded thunderstorms. This will continue through the late
afternoon hours before ending from the west with partial clearing
overnight as the low merges into the base of the broad trough
downstream. Patchy fog possible in the early morning hours as
things clear out. We`ll probably have enough residual boundary
layer moisture and patchy cloud cover to keep from reaching the
cold potential of the airmass Tuesday morning, but still freezing
in some colder valleys east and south of Tucson.
A dry zonal flow the rest of the week with a slow warm-up into the
weekend. Another system could impact the region early next week,
but the inland trajectory looks kind of dry for our neck of the
woods. Primarily gusty winds and cooler temperatures by next
Monday or Tuesday. Still seeing some signs of an active pattern
the second half of the month with long range ensembles suggesting
low height anomalies.
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