Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/27/18
Area Forecast Discussion
National Weather Service Bismarck ND
911 PM CST Mon Nov 26 2018
Issued at 909 PM CST Mon Nov 26 2018
The short term forecast remains on track. The low stratus across
western North Dakota does not appear to be going anywhere anytime
soon. Adjusted sky grids through the night to better reflect
Made some adjustments to precipitation types for the Tuesday-
Wednesday system. Still looking like mainly snow through Tuesday
afternoon. Then warmer air aloft builds in from the west Tuesday
evening and night. Model soundings over this timeframe show a dry
warm layer with max temperatures around 2 to 4 C, and wet bulb
temperatures around 0 to 2 C. Using the wet bulb temperature would
result in partially melted hydrometeors, yielding a dominant
precipitation type of sleet. However, given increasing low-level
moisture transport over the same timeframe and a light QPF scenario,
think it is more likely saturation will occur as a result of
increasing moisture, rather than a wet bulb cooling effect.
Therefore, used max temperature aloft to calculate precipitation
types through Wednesday evening. This gives most locations an initial
period of snow, followed by a transition to freezing rain. It
still looks like a narrow band of sleet is possible between the
snow and freezing rain. This update results in forecast ice
accumulations of a few hundredths of an inch across much of
central North Dakota Tuesday evening through Wednesday morning.
The total snow forecast was relatively unchanged.
UPDATE Issued at 549 PM CST Mon Nov 26 2018
Satellite imagery shows a persistent low stratus deck draped
across western North Dakota late this afternoon. Model guidance
regarding these clouds has been poor. However, the 22Z RAP seems
to have caught on, and keeps low-level RH above 90 percent through
sunrise Tuesday morning. By that time, mid to high clouds will be
streaming across the area, so going with at least mostly cloudy
wording through the night and into Tuesday. Due to the expected
lingering cloud cover, raised low temperatures by a few degrees
over western North Dakota.
.SHORT TERM...(This evening through Tuesday)
Issued at 300 PM CST Mon Nov 26 2018
Forecast highlights/challenges in the short term period will be
lingering low level clouds today west, followed by chances for
mainly snow northwest and central Tuesday morning/aft.
Currently, northerly flow aloft with a quasi-stationary surface
ridge parked over the eastern Dakotas. Clearing of low level
stratus made it as far east as around 20-30 miles west of the
highway 83 corridor, but remains entrenched across all of western
ND. Models again have no clue. The stratus has been eroding
faster on the western edge across eastern Montana, and expect this
trend to continue into western ND with time. Did extend in time
and expand in coverage the aerial extent of low clouds based on
today`s trends. Cold arctic air associated with an upper level
low across the Western Great Lakes has made for a chilly day
across western and central ND, with daytime highs thus far from
around 10F across the Turtle Mountains to the mid 20s southwest.
For tonight, upper level ridge builds east across the Rockies
towards the northern high plains. Not seeing any reason to remove
clouds across the west though did trend cloud cover down while
maintaining `mostly cloudy` wording.
Upper low and sfc ridge very slowly move east for Tuesday, with
the arctic airmass maintaining its influence over the eastern half
of the region, keeping temperatures well below normal there.
Across the west, increasing clouds and WAA tonight into the day
Tuesday ahead of a warm front will yield warmer temperatures
though may also see some lingering low stratus. Light
precipitation is expected to develop into northwest ND Tues
morning, spreading east and south into central ND through the day,
as right entrance region jet dynamics/divergence aloft move
across our local area. At this time the main push of precipitation
looks to reside mainly within the cold air regime ahead of the
warm front, and should be mainly in the form of snow Tue
.LONG TERM...(Tuesday night through Monday)
Issued at 300 PM CST Mon Nov 26 2018
Upper level ridge moves into the Dakotas Tuesday night, though is
flattened by an incoming S/WV trough moving east out of the
Pacific NW & across the International border area. WAA spreads
east across the state Tuesday night into Wednesday, along with
moisture transport into the region under a southerly low level
flow regime ahead of a sfc low over southern Saskatchewan. Models
continue to portray a band of precipitation redeveloping across
portions of western and central North Dakota Tuesday night, then
pushing east on Wednesday. With the WAA, a mix of sleet, snow,
freezing rain is still expected. Uncertainty still in amounts and
aerial coverage. There is some indication by models the
precipitation remains more in the cold sector resulting in lesser
chances for freezing rain. Latest model guidance also favors
north central and northeastern areas for the heavier QPF and any
associated ice accumulations. Lesser amounts are advertised south.
Will continue to message the potential for mixed precipitation in
the HWO and social media for now and continue to monitor.
After mid-week, models remain in chaos with an active zonal flow
pattern. Huge differences between the 12Z GFS/ECMWF remain, with
much uncertainty regarding storm tracks and timing/placement of
embedded features in the flow aloft.
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 549 PM CST Mon Nov 26 2018
A persistent MVFR stratus deck is now expected to hold through the
night over western ND. Current trends would hold these clouds just
to the west of KMOT and KBIS, but it bears close monitoring. Mid
to high clouds will begin streaming over western ND late tonight
into Tuesday morning. Ceilings will lower to near MVFR levels from
west to east during the late morning and afternoon hours. A chance
of light snow will be associated with this lowering. KMOT is more
likely to see MVFR conditions Tuesday afternoon than other
terminals. Light winds through the night will become southerly
near 10 kts by Tuesday afternoon.
Area Forecast Discussion
National Weather Service Birmingham AL
532 PM CST Mon Nov 26 2018
For 00Z Aviation.
Broad troughing will persist over much of the eastern CONUS
through the short term period. A surface cold front moved
southeast through the forecast area very early this morning.
Expect sky cover to continue to gradually decrease from west to
east through the rest of the afternoon and into tonight. Clouds
look to be most persistent over our northeast counties tonight
and into Tuesday morning. Winds will remain breezy out of the
northwest through sunset then become lighter overnight, generally
ranging from 4-8 kts. Cloud cover and winds will hamper optimal
radiational cooling tonight but readings will fall into the mid to
upper 20s areawide with coldest readings across the far northern
counties and especially in the sheltered valley locations.
Fair skies are expected Tuesday with temperatures struggling to
climb through the 40`s. Expect highs to range from around 40 north
to the upper 40`s south. Northwest winds will range from 6-12 kts
during the daytime hours followed by even lighter winds overnight
under mostly clear skies areawide. These conditions will allow
temperatures to fall a few degrees more Tuesday night with lows
ranging from the low 20`s northeast to the upper 20`s south with a
few readings around 20 possible in the sheltered northeast
valleys and usual colder locations.
A warming trend will begin Wednesday as the airmass moderates
with the approach of a shortwave ridge aloft by the afternoon. Dry
conditions will persist with highs ranging from the mid 40`s
northeast to the mid 50`s southwest. Freezing temperatures
Wednesday night will largely be confined to areas near and north
of Interstate 22 and along and east of Interstate 65 within our
forecast area while areas to the south and west will experience
lows in the mid 30`s.
Made a few adjustments to the extended this run. It appears that
the split flow active weather pattern will persist. The models are
in relative agreement that the Friday/Saturday system will affect
us sooner. Therefore, increased rain chances Friday night and now
have likely both Friday night and Saturday. These will most
likely go up as we approach this time period. The ECMWF and GFS
disagree on the evolution/movement of the front and moisture
fields after the system occludes near the Great Lakes. The ECMWF
holds on the rain chances longer than the GFS and this has
ramifications downstream with the timing of the next system. At
this stage, will keep pops in the forecast into Sunday but this
time frame may be trimmed down in future issuances.
This system also has the chance for thunderstorms. Therefore
mentioned these chances Friday night and Saturday. With a split
flow pattern, a weak wave rides through the northern Gulf just
ahead of the weekend system. Models are subsequently allowing a
moisture return into Central Alabama. This is still questionable
on quality of air and timing. Both the GFS and ECMWF indicate
limited surface based instability at the time of greatest forcing
and winds above the surface. Additionally, some drier air mixes in
when the instability jumps. So, we are left with a limited
instability/high shear environment in the late Friday night into
early Saturday time frame. At this time, will not mention any
potential for strong to severe storms. Things just are not lining
up quite right. Will monitor the forecast solutions the next few
days for possible changes as models have a tough time with split
Tuesday through Thursday.
A general warming trend will continue to increase into Thursday,
as the surface high pressure continues southeastward and heights
rise in response to the exiting trough and a transition to
southerly winds. Looking upstream, a brief period of zonal flow is
interrupted by the next trough/Rossby Wave entering the West
Coast on Thursday. For here, the transition to southerly flow will
aid warming temperatures and maybe a few light isentropic rain
showers on Thursday afternoon/evening, especially areas north of
I-20 where better moisture availability is expected and a possible
transient shortwave passes to our north.
Friday through Monday.
Better forecast confidence was achieved tonight that supports
active weather towards the late-week/weekend period as the
downstream portion of the aforementioned trough moves into the
Great Plains by Friday morning. As such, cyclogenesis is expected
on the lee side of the Colorado Rockies and should continue an
eastward trajectory with propagation towards the Mississippi River
Valley. The trough is expected to transition to a negative tilt
(though also becomes more vertically stacked) by Saturday with
widespread upper-level diffluent flow over our region. With
consideration of synoptic dynamics/forcing with this system and
anticipated warm air/moisture advection, have placed rain chances
Friday morning through Sunday afternoon. Saturday seems to be the
most active as central Alabama will be within the warm sector of
the mid-latitude cyclone to our north with pre-frontal
rain/thunderstorms expected along a strong low-level jet axis. As
a result, have increased PoPs to 60-70% during this time, with a
general decrease in activity as the frontal boundary clears the
area to the east around Sunday morning/afternoon. Will continue to
adjust the forecast in future cycles as more specific details
become available, but still expect a busy pattern towards late-
week and into next week as the polar jet stream remains in place
across the country.
00Z TAF Discussion.
--VFR conditions tonight through Tuesday--
As of 23:30Z/5:30PM, GOES-16 showed a large swath of low-level
clouds associated with a bowling ball of wrap-around moisture
toward our north. This is the main forecasting item this go-round.
Some guidance is seemingly too aggressive in advancing this cloud
deck farther southward, based on satellite trends and trajectories
of the moist and dry air. So, have sided with the HRRR and EURO
in keeping the solid, MVFR cloud deck toward the north and
northeast of even our northernmost terminals.
So, expect VFR conditions during the period with ~northwesterly
breezes increasing a bit post-sunrise Tuesday, with some
gustiness through the day.
Northwesterly flow will provide cooler and drier conditions as
high pressure moves into the region through mid-week. Winds will
become generally less than 10 knots after sunset tonight followed
by winds ranging generally from 6-12 knots during the day Tuesday
with even lighter winds Tuesday night. Relative humidity values
will continue to remain above critical thresholds. No fire weather
concerns are expected at this time.
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 25 41 23 47 27 / 0 0 0 0 0
Anniston 25 42 23 49 29 / 0 0 0 0 0
Birmingham 27 42 25 49 33 / 0 0 0 0 0
Tuscaloosa 27 45 28 53 34 / 0 0 0 0 0
Calera 26 43 25 50 31 / 0 0 0 0 0
Auburn 28 44 26 49 32 / 0 0 0 0 0
Montgomery 29 47 28 53 34 / 0 0 0 0 0
Troy 29 47 28 53 34 / 0 0 0 0 0
Area Forecast Discussion
National Weather Service Norman OK
1003 PM CST Mon Nov 26 2018
Updated mins and hourly grids this evening.
Temperatures have cooled off quickly, especially in the northwest.
So updated the hourly temperatures closer to the HRRR overnight
which then affected forecast min temperatures - lowering them in
general, especially in the north and in sheltered areas elsewhere.
Otherwise the package appears to be in good shape.
.PREV DISCUSSION... /issued 555 PM CST Mon Nov 26 2018/
VFR conditions and a light wind will prevail through the period.
PREV DISCUSSION... /issued 325 PM CST Mon Nov 26 2018/
A mid/upper-level wave will pass over Kansas and Oklahoma on
Wednesday, but with very little moisture to work with, it will
have no significant effects on surface weather.
Later this week, a more significant system will move east from the
southern Rockies. As low-level moisture is drawn north ahead of
this system, some light rain or drizzle may occur in eastern
Oklahoma. Then, on Friday afternoon and evening, the system starts
to resemble a typical severe weather producer. At this time, it
appears that the main risk for severe weather will remain
southeast of our forecast area. However, there will be a few hours
late Friday afternoon and early in the evening when conditions
could come together for a few severe storms in our far southeast
counties. Current model forecasts suggest that instability will be
lacking for any substantial storms, however, so for now we will
expect showers with a few rumbles of thunder possible. This could
change significantly by Friday, though, since that is still
several days out.
Different models show different paths of departure for the Friday
storm system. This will affect the weather conditions early next
week. After a cool and breezy Saturday, it is unclear whether the
next couple of systems will affect Oklahoma/north Texas or not.
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 29 53 32 61 / 0 0 0 0
Hobart OK 29 59 34 62 / 0 0 0 0
Wichita Falls TX 32 62 36 69 / 0 0 0 0
Gage OK 24 54 30 56 / 0 0 0 0
Ponca City OK 24 45 29 57 / 0 0 0 0
Durant OK 29 59 36 64 / 0 0 0 0
Area Forecast Discussion
National Weather Service San Diego CA
200 PM PST Mon Nov 26 2018
Fair and very mild weather will continue through Tuesday. Locally
gusty northeast winds will occur through and below passes and
canyons through Tuesday morning. Cooling will begin Wednesday as
onshore flow strengthens and the marine air moves farther inland. A
low pressure trough speeding across the Pacific will bring rain,
snow to the mountain peaks, and gusty westerly winds. Locally heavy
rain will likely occur on the coastal mountain slopes. Another
system could bring more precipitation this weekend.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
Skies were sunny across the region with temperatures in the 70s and
lower 80s. Locally gusty winds were occurring through/below passes
and canyons from the northeast, with a few gusts over 40 MPH. These
winds should decrease the rest of this afternoon based on HRRR and
local WRF, before increasing slightly overnight, with highest gusts
to around 30 MPH. Current model guidance shows only a few low clouds
appearing near the coast of San Diego County late tonight, but most
likely the patchy stratus will stay off the coast. Tuesday night
looks better for the coastal stratus/fog as we will have a better
inland push to the sea breeze Tuesday.
The Pacific storm system is still on track to bring widespread rain
Thursday, possibly starting as early as Wednesday evening. Rainfall
amounts vary with each model, but it still looks like around or
slightly under one inch will prevail at lower elevations, though
confidence is increasing that orographic southwest-facing slopes
will receive substantially more, perhaps 3-5 inches locally, from
Wednesday night through Friday morning, as southwest flow in the 850-
700 MB will be saturated with speeds in the 20-40 knot range over
the mountains. GFS has been consistent with a weak atmospheric river
in our area, with 500 kg/m/s values during recent runs, and
saturation mostly up to 600-650 MB. Timing of the maximum moisture
and forcing along the front is likely to be late morning-early
afternoon Thursday, though probably a bit later in San Diego County.
The cold air aloft will stay mostly to the north, so snow levels
will be quite high, 8000+ feet Thursday morning, then 6500-7000
feet by Thursday evening, so snow will mostly be restricted to the
highest mountains of San Bernardino/Riverside County. With tight
pressure height gradients aloft, strong winds will occur in the
mountains and parts of the deserts Thursday/Thursday night, with
gust potential over 60 MPH.
Precip should end Friday morning, but models, somewhat
inconsistently, are showing a weaker but colder system moving
through sometime over the weekend, which could bring more rain and
some mountain snows, but probably nothing excessive.
262100Z...NE-E winds with sfc gusts 20-30 kt continue at this hour
in the passes and canyons, and will start to weaken this afternoon
and evening. Patchy low clouds and fog possible near the San Diego
County beaches tonight through Tuesday morning. Low confidence in
any CIGS at the coastal airports. Otherwise a few high clouds AOA
25,000 ft and unrestricted vis through Tuesday.
No hazardous marine weather is expected through Tuesday. Combined
seas will increase to 9-11 ft on Wednesday, followed by gusty west-
northwest winds Thursday through Saturday. This will likely generate
conditions hazardous to small craft for the latter half of the week.
A 9-11 ft swell at 16-18 seconds from 290 degrees will generate high
surf, strong rip currents, and the potential for minor coastal
flooding and minor beach erosion beginning on Wednesday and likely
continuing into the weekend. A Beach Hazards Statement remains in
effect for Tuesday afternoon through Friday evening.
Dry air will continue to spread around the region this afternoon,
dropping humidity below 20 percent in all areas except near the
coast. Northeast offshore winds will occur in the foothills, but
strongest mainly between Cajon Pass and eastern Orange County with
some gusts over 30 mph through mid-afternoon, then gusts to 30 mph
early Tuesday morning. Humidity will remain low Tuesday, but then
more humid onshore flow will return Wednesday with wetting rains
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
CA...Beach Hazards Statement from Tuesday afternoon through Friday
evening for Orange County Coastal Areas-San Diego County