Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/15/20
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
607 PM CDT Sat Mar 14 2020
.SHORT TERM...(This evening through Sunday)
Issued at 315 PM CDT Sat Mar 14 2020
Aloft: Feel like a broken record the last few months. The
longwave pattern is the same old longwave pattern we`ve seen since
late Nov: an E Pac ridge...Wrn USA trof ...Ern USA ridge. WSW
flow was over the Plns. RAP tropopause analyses showed the shrtwv
trof that brought the snow Fri and last night was over IA/MO and
moving away. Heights were already rising and becoming
anticyclonic. Anticyclonic WSW flow will remain over NEB/KS thru
tomorrow as the ridge axis will be over the Plns.
Surface: A cool front was stationary along the Gulf Coast...acrs
TX and then banked up against the Rckys over NM/CO/WY. Very strong
1052 mb high pres was over Wrn Canada and it encompassed most of
the Cntrl/Ern USA. A piece of this high will break off and head E
acrs Srn Canada thru tomorrow. As this occurs...winds here will
shift from E to SE.
Rest of this afternoon: Cldy with patchy fog/drzl. E winds 10-20
mph. Temps hold steady in the low-mid 30s.
Tonight: Same but with winds diminishing to around 10 mph and
becoming SE. Fog should become widespread. Not sure how bad it
will get...but given that no clearing/radiating is
expected...believe CIGs will just lower. Am not expecting dense
fog to develop (1/4 mi or less)...but it can`t be completely ruled
out.
Confidence is drzl and espcly frzg drzl is extremely low. This is
not the most favorable setup in this fcstrs opinion...but it
can`t be completely ruled out either.
Sun: Cldy widespread fog becoming patchy after midday. Some
patchy drzl (or frzg drzl forenoon) possible. Continued cooler
than normal temps.
.LONG TERM...(Sunday night through Saturday)
Issued at 315 PM CDT Sat Mar 14 2020
Aloft: Split flow will cont over the CONUS...with the CWA
dominated by the Srn stream next wk. Anticyclonic WSW flow will
basically cont Mon-Wed before turning cyclonic and SW Thu. The
cut-off low off the W coast of CA will eject a shrtwv trof into
the Desert SW and that should induce lee cyclogenesis Thu. After
that low (or trof) goes by...low-amplitude W flow will prevail
over NEB/KS Fri-Sat and becoming increasingly anticyclonic. The
mean trof will still remain along the W coast.
Surface: Sun night a wk cool front will form over the Nrn Plns
and it will cross the CWA Mon. Nrn Rckys high pres will quickly
follow and slide by Tue. Low pres will then begin to form over CO
Wed. The prvs front will lift back into KS as a result. The CO low
could then deepen to about 990 mb Thu. The warm front should
stall near the NEB/KS stateline...and the temp grad will
strengthen as a cool front drops out of Canada and merges with the
warm front. Based on the 12Z/13 and 00Z/14 runs of the EC...this
low should begin to fill as it heads E along the front Thu night.
The 12Z/14 EC run came in with an open wave aloft and weaker at
the sfc. It looks like an outlier run. The low is then fcst to
rapidly weaken Fri as it heads into IL. FWIW...the last couple CMC
/GFS-FV3 runs are quicker to eject the low...and quicker to
weaken it. As usual...prefer to ride the EC. Very strong (1040+)
Arctic high pres will come out of Canada Fri and overtake the Plns
into Sat.
Temps: This fcst will be dominated by clds until Sat. Temps will
be cooler than normal Mon-Tue. Should return to normal Wed...then
above normal Thu. Turning much colder Fri-Sat. There is a high
probability that our fcst is not cold enough.
Precip: Lots of uncertainty. Mdls are generating a lot of very
low QPF due to the lingering stratus thru Tue. It is likely that
much of this won`t materialize. It is probably overdone. Would
prefer that it wasn`t even in the fcst as conds are not favorable
for much with no ice in the clds. A few low-top shwrs could skirt
the SE 1/3 of the CWA Mon night...and then over parts of the CWA
Tue night-Wed morning. The highest-confidence precip event will be
Thu-Fri. Rain with embedded tstms psbl. It`s psbl the wraparound
snow could move thru before precip ends. Some accum is on the
table.
Thu the EC is fcstg dwpts in the 50s to wrap into the NW corner of
the warm sector which will be over N-cntrl KS. If the EC is right
with the sfc low...and if some sunshine occurs...some svr tstms
can be ruled out near the triple pt. The EC has a SBLI of -2 to
-4. This potential will need to be watched.
Incrsd winds Thu-Fri in collab with neighboring offices.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 601 PM CDT Sat Mar 14 2020
Low clouds/stratus will hold firm through the TAF period with
cloud cigs at IFR or LIFR. Visibility is expected to vary with
periods of reduced visibility in fog and areas of dense fog
(visbility 1/4 mile or less) is possible. While not widespread,
cannot rule out the potential for drizzle or freezing drizzle,
especially towards Sunday morning and will monitor.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Fay
Area Forecast Discussion
National Weather Service Goodland KS
734 PM MDT Sat Mar 14 2020
.UPDATE...
Issued at 725 PM MDT Sat Mar 14 2020
Latest GOES-16 IR data indicates large area of stratus in the
supercooled water range (< -10C) across the entire area. While
dewpoint depressions have managed to hold around 2 degrees, this
will likely decrease as fog develops across most of the area.
Soundings indicate a little bit of surface instability should
things saturate, which will lead to spotty/showery periods of
freezing drizzle. These will be transient and will likely not
bring the accumulations that occurred last evening, with ground
temperatures also limiting the overall impact on the surface. Not
planning any major changes to winter weather advisory tonight.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 300 PM MDT Sat Mar 14 2020
Low level upslope across the central plains has resulted in
persistent low clouds through the day. Temperatures have risen
only a few degrees from morning lows and dew point depressions
remain low. No change in the pattern is expected tonight or
Sunday, with an upslope component to the wind direction forecast
to persist. The HRRR and RAP show widespread fog developing this
evening and continuing through the overnight hours and into Sunday
morning. Temperatures are already at or just above freezing, so
expect freezing fog and freezing drizzle to quickly become
predominant. Given all of this, felt best course of action was to
issue a winter weather advisory for tonight through Sunday
morning. Roads are already slick and the freezing fog/drizzle will
only exacerbate the situation. Fog will be dense at times. Low
temperatures will not vary much from current temperatures, upper
20s to lower 30s.
Sunday may very well be a repeat of today. One exception will be
far western portion of the forecast area in northeast Colorado,
where surface front will creep just far enough eastward to allow
winds to go south southwest and allow some afternoon clearing.
Elsewhere, expect to be stuck in the clouds all day with areas of
fog and drizzle and temperatures going nowhere. Expecting highs in
the 30s in most locations, but far western areas may actually
manage to reach the 40s/50s if clearing materializes early
enough.
Sunday night...may see the fog redevelop early once again with no
real change in the pattern and persistent upslope component to the
surface winds. Temperatures are forecast to remain in the lower
to middle 30s, which may minimize the chances of freezing fog, but
it depends on how much warming actually takes place during the
day. After 06z, a weak shortwave trough comes up in the southwest
flow and brings a chance for light rain to southeastern areas.
.LONG TERM...(Sunday night through Saturday)
Issued at 312 PM MDT Sat Mar 14 2020
An active forecast period is expected for this run of the long-term
forecast. The main concerns will be another period of freezing
drizzle possible Monday night into Tuesday, continued precipitation
chances through Wednesday with perhaps a few thunderstorms, and then
ending with a potential winter system Thursday into Friday. I will
break up this discussion to cover each threat one at a time.
The first threat to begin the long-term forecast period will be a
chance for freezing drizzle Monday night into Tuesday morning.
During this time frame, a strong upper level trough will be located
along the Pacific Coast, extending into the desert southwest. Ahead
of this system, a shortwave trough should move across the Plains.
This trough, in combination with flow from east to west across the
forecast area, should provide enough lift behind a cold front for
precipitation formation. Looking at forecast soundings and moisture
aloft, there should be some dry air above the surface so thinking
most of the area would not see ice crystals in the column. The lone
exception may be along the Kansas/Nebraska border and points north
as there may be sufficient moisture aloft to have ice crystals. The
reason having ice crystals in the column is important is because
this will be the difference between light snow occurring (with
crystals) and light freezing rain or freezing drizzle occurring
(without crystals). For most of the area, expect to see some
freezing rain/drizzle and perhaps some fog. Light ice accumulations
of a few hundredths would be possible under this scenario, perhaps
causing a few issues on area roadways.
From Tuesday night into Wednesday, a warm front is expected to move
across the forecast area. In addition, another shortwave trough
should move through. However, the main brunt of the forcing should
remain south. Therefore, with the warm front in the area and weak
forcing aloft, a few showers will be possible. There could certainly
drizzle too with a dry airmass above the boundary layer. One thing
to note...initial guidance was quite cool with temperatures. Given
the warm air advection and expected cloud cover, I do not see
temperatures falling too much. The current forecast does call for a
rain snow mix but with warmer temperatures forecast, the chances of
any wintry impact Tuesday night into Wednesday will be low. Most
precipitation should be in liquid form.
During the day Wednesday, the aforementioned longwave trough will
begin spreading east over the Four Corners region. A more powerful
shortwave will eject ahead of this trough, bringing a chance for
showers and thunderstorms to the High Plains. Moisture return and
warmer temperatures are anticipated, and even some instability.
MUCape increases to around 200-700 J/kg depending on what model you
prefer along the warm front. What is also interesting is that the
shear is fairly high...0-6 km bulk shear is around 50-60 kts and a
few guidance members suggest helicity up to 300 m2/s2. Model
soundings indicate a stout inversion north of the warm front where
storms would be likely to develop. Given that detail, and the fact
instability isn`t the best, currently do not anticipate severe
weather with these storms although it isn`t out of the realm of
possibilities. If anything, storms will be elevated and therefore
not a significant threat. This will need to be monitored though for
our potential first round of storms this Spring.
Finally, models continue to be in fairly decent agreement with a
more vigorous low pressure system moving through Thursday into
Friday. A strong surface low should develop and pass through or just
south of the forecast area. A strong cold front will move through
from the north Thursday night, bringing much colder temperatures.
Banded precipitation is also expected on the northwest side of the
low as it moves through. With added frontogenesis, lift from the
low, and upper level support, this has the makings of a winter
system to monitor. In addition, winds should be stronger with this
system which makes one ponder if a blizzard may be possible. Still
many details to work out with this system...but it has the potential
to bring an unwelcome reminder that we are still in blizzard season
across the High Plains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 512 PM MDT Sat Mar 14 2020
...Persistent and widespread IFR or less conditions prevail...
Widespread easterly flow has helped maintain a large area of
moisture across the area, resulting in ceilings at or below 1000
feet across much of northwest Kansas and nearby areas. Expect to
see ceilings and visibilities lower through the evening, with
values approaching airport minimums for a time between 06 and 13
UTC. GOES-16 data indicates current clouds are supercooled water
and given temperature profile will see periods of freezing drizzle
as fog develops.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...Winter Weather Advisory until 9 AM MDT /10 AM CDT/ Sunday for
KSZ001>004-013>016-027>029-041-042.
CO...Winter Weather Advisory until 9 AM MDT Sunday for COZ090>092.
NE...Winter Weather Advisory until 9 AM MDT /10 AM CDT/ Sunday for
NEZ079>081.
&&
$$
UPDATE...JRM
SHORT TERM...024
LONG TERM...RRH
AVIATION...JRM
Area Forecast Discussion
National Weather Service Northern Indiana
734 PM EDT Sat Mar 14 2020
.SYNOPSIS...
Issued at 334 PM EDT Sat Mar 14 2020
Snow will end by early tonight with an inch or less accumulation,
especially from near Monticello to Portland. The snow may be
mixed with rain at times. After tonight, conditions should be
mainly dry through Wednesday. Cold tonight into Sunday night, then
moderating temperatures. Highs will be mainly in the 40s Monday
through Wednesday.
&&
.SHORT TERM...(This Evening through Sunday)
Issued at 334 PM EDT Sat Mar 14 2020
A highly proficient banding type of event associated with
frontal/genetic forcing and helped by the right entrance region
of an upper level jet was able to bring up to 4 inches of snow
along and south of a line from Monticello to Portland. The forcing
was weakening although some lighter snow was upstream with some
heavier bursts of snow occurring over northeast Illinois. The
HRRR has been handling this event well and brings some heavier
snow bursts into northern Indiana from late this afternoon into
the evening. The upper level system will move east rapidly early
tonight, and will bring an end to the snow. Up to an inch of
additional snow accumulation is possible from these heavier snow
bursts as well as from lingering snow from Monticello to Portland.
Highs Sunday should be from 40 to 45, except near 40 over
remaining snow covered areas.
&&
.LONG TERM...(Sunday Night through Saturday)
Issued at 334 PM EDT Sat Mar 14 2020
Conditions should be mainly dry through Wednesday with seasonably
cool conditions with highs in the 40s as a large surface high
pressure area tracks north across southern Canada into New
England. Warmer and more unsettled condition are ahead late in the
week as moisture returns.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 732 PM EDT Sat Mar 14 2020
an area of 700 mb fgen forcing is creating a 1 to 3 hour period
of snow at SBN and a 2 to 5 hour period of snow at FWA during the
first part of this TAF period. Am expecting little in the way of
accumulations with this as a result of poor dynamics and warm
antecedent conditions leading up to this event. Flight conditions
are expected to drop into MVFR with the occasional IFR condition
while the snow is occurring.
Models don`t have a good handle on how the conditions will play out
after the snow moves out, between 6 and 12z. Expect the fgen forcing
and associated low-mid level vort max to push out by 6z, which lends
to dissipating clouds and eventual VFR conditions as high pressure
moves in. Should BKN-OVC clouds linger, there may be a time period
of MVFR conditions as low level moisture does appear to linger in
model time sections at FWA. At any rate, do expect clouds to
dissipate at least by 12 to 14z allowing for VFR conditions for
the rest of the TAF period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&
$$
SYNOPSIS...Skipper
SHORT TERM...Skipper
LONG TERM...Skipper
AVIATION...Roller
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Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
913 PM CDT Sat Mar 14 2020
.UPDATE...
913 PM CDT
Evening Update...
Going forecast in pretty good shape this evening. Have updated
mainly to remove evening snow, which has moved out of the area.
Evening GOES vapor imagery depicts mid-level short wave trough
axis now east of the forecast area, and substantial mid-level
drying spreading across the region. This drying, in combination
with the initiation of large scale subsidence within the area of
negative differential vorticity advection in the wake of the
departing disturbance, has allowed a rapid erosion to the trailing
edge of the eastward moving precipitation shield and an ending of
light snow across the cwa. Low level cloudiness persists however,
as evident in the GOES-16 nighttime microphysics RGB imagery.
Northeast low-level winds on the southern periphery of a sprawling
area of surface high pressure building southeast across Ontario
and the northern Lakes will bring drier air into the region,
though colder air aloft will induce steep low level lapse rates
over Lake Michigan waters which will maintain a source of low
level cloud cover which is expected to linger across a good
portion of the IL part of the forecast area into Sunday. This
cloud cover will be relatively shallow, with equilibrium levels
generally below 5000 feet, though may be just deep enough to
produce a few flurries at times for counties adjacent to the lake
overnight into Sunday morning. Otherwise, skies will gradually
become partly cloudy into Sunday, as continued subsidence and
advection of drier low level air continues.
Northeast flow off the lake will limit warming near the shore, and
further inland into northeast IL. Despite sunshine increasing by
afternoon, temps look to range from the upper 30s near the Lake
Michigan shore, to the lower 40s inland. Warmest areas will be
parts of east central IL and northwest IN, where a combination of
a lack of fetch off of the lake and longer duration of sunny skies
will occur.
Going forecast has these trends well in hand, so other than tweaks
to allow precip to exit stage right this evening, no changes
needed.
Updated digital/text forecast products already available.
Ratzer
&&
.SHORT TERM...
241 PM CDT
Through Sunday...
Snow will be winding down for good in the area early to mid
evening giving way to mainly quiet but cool weather to round out
the weekend.
The last in a series of mid-level perturbations today, and the
primary synoptic wave itself, is across eastern Iowa into northern
Missouri this early afternoon. This will move across the area
late this afternoon and early this evening. With assistance from a
125 kt upper let jet streak, the precipitation across eastern
Iowa and northwest Illinois (mainly snow) should spread east-
northeast over the CWA. There may be some eroding as it interacts
with drier air in northeast Illinois and far northwest Indiana,
but the synoptic signal for forcing is stout enough that we
envision one more three hour period or so of light to moderate
snow across the area. The moderate snow may be confined more to
north central and far northern Illinois, with upstream visibility
of 3/4 to 1 1/2SM in eastern Iowa. Because of a limited time
duration of this snow as well as warm pavement temperatures, we
anticipate minimal impacts, but will still highlight with Special
Weather Statement and Graphical NOWcast messaging. Snow should
end from west to east across the area during the 7-9 p.m. time
frame.
Northeast winds will increase somewhat into early this evening as
the pressure gradient across the area is "squeezed" from an
expansive 1047 mb high pressure across Ontario. Some gusts to 25
mph near the lake are likely with sporadic 20 mph gusts inland.
With the cooler temperatures in the boundary layer coming out of
today, the low-levels are somewhat primed for lake effect clouds
to develop and most guidance does do that. The RAP and NAM produce
low-level CAPE from the lake around 100-150 J/kg. So despite the
shallow cloud depth under 3,500 ft, do see flurries or possibly
sprinkles occurring in lake adjacent counties through Sunday
morning. With the marginal parameters, don`t envision any of this
becoming more than flurries.
Into Sunday the northeast winds will continue and eventually drier
advection. What time this brings clearing is of low confidence,
though there seems to be a guidance trend toward early-mid
afternoon. Temperatures look to be a few degrees shy of normal,
with lakeside areas to not climb but a couple degrees.
MTF
&&
.LONG TERM...
245 PM CDT
Sunday night through Saturday...
Model/ensemble forecast guidance continues to favor positive
upper-level height anomalies persisting through the forecast
period across the northeast Pacific and Alaska. This in turn will
induce a split upper-level flow pattern downstream across North
America. The northern stream portion of this pattern is expected
to largely remain over Canada, at least through later next week.
However, the southern stream pattern will be of high interest
through the week for much of the central and eastern CONUS as it
locks into a pattern favoring active weather for much of the
central CONUS. Specifically, this pattern will feature a large
upper trough/low over California and much of the southwest CONUS,
with downstream ridging dominating over the southeast CONUS. Large
scale patterns like this are favorable in steering several
moisture laden impulses east-northeastward across our region.
While more active weather is looking likely, especially mid to
later in the week, the period will start on the quiet side for
Monday. Temperatures on Monday should warm well into the 40s with
southwesterly surface winds. An approaching cold front is expected
to push across the area Monday night. This could result in a
period of light showers over the area Monday night, but with
moisture lacking, this is likely not to be much of a
precipitation event for our area.
Following a dry Tuesday with seasonable temperatures, attention
will then turn to our first of possibly several upper level
impulses likely to impact the area later in the week. This
feature looks to provide the area with the next best chance of
rain on Wednesday. However, a more substantial storm system looks
to develop over the Plains on Thursday in response to a more
substantial mid-level impulse ejecting out of the southwestern
trough. While the specifics with the evolution of this storm
system will need to be ironed out over the next few days, there
are strong signs that another period of rain (possibly heavy in
some areas with thunderstorms) will impact the area late Thursday
night and on Friday. This will be a system to keep an eye on as we
get closer.
A period of cooler weather may then shift over the area in the
wake of this system into next weekend as the northern stream
disturbance digs over the Great Lakes Region.
KJB
&&
.AVIATION...
For the 00Z TAFs...
Aviation forecast concerns:
- Light snow ending quickly by early evening. MVFR ceilings
improve to VFR.
- Northeast winds persist through the period. Occasional gusts
generally less than 20 kt.
- Likely redevelopment of MVFR ceilings late evening and overnight
with winds off Lake Michigan. Expected bases 1500-1900 feet. A
few flurries possible. Gradual lifting Sunday, with VFR
conditions by early afternoon.
Last in a series of mid-level disturbances was transiting the area
as we approach 00Z. Light snow associated with this feature has
ended at KRFD, and should end shortly at KDPA, KORD and KMDW as
depicted by trailing edge of weak radar returns now near a KVYS to
KDKB and KUGN line. KORD/KMDW 1-minute ASOS data indicating some 1
1/2SM to 3SM visibility, which should improve very quickly as in
addition to a quick eastward movement to the precipitation, mid-
level drying is also working to erode precip from the west.
Current radar trends indicate light snow may linger at KGYY for a
couple of hours before similar improvement occurs. Expectation is
that MVFR ceilings will linger briefly with the end of precip,
but improve to VFR for a time this evening (KRFD already VFR where
precip has already come to an end).
A sprawling area of strong surface high pressure will build
southeast across Ontario and the northern Great Lakes region
through Sunday, allowing northeast winds to persist through the
forecast period. Sustained speeds of 10-12 kts with occasional
gusts 15-20 kt are expected, with a gradual decrease in wind
speeds by Sunday afternoon as the gradient weakens slightly.
Cool northeast flow off of Lake Michigan will likely support
redevelopment of MVFR stratocu by late this evening, with model
guidance depicting bases from 1500-1900 feet. A gradual lifting of
MVFR ceilings to above 2000 feet is likely by midday Sunday,
before drier air spreads in from the east and allows for
scattering of clouds early Sunday afternoon.
Ratzer
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...IL nearshore waters until 1 PM Sunday.
Small Craft Advisory...IN nearshore waters until 10 AM Sunday.
&&
$$
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Area Forecast Discussion
National Weather Service Mobile AL
957 PM CDT Sat Mar 14 2020
.NEAR TERM /Now Through Sunday night/...For the remainder of
tonight will continue to monitor the fog potential, but thus far
this evening fog has been slow to develop. Only just in the past
half hour or so some fog has been noted around Gulf Shores, but
all other observations and traffic cams are not indicating much in
the way of fog at all. Some high level clouds streaming east
across the area are making it difficult to use the satellite fog
channels. Latest HRRR model visibilities are not very aggressive
with the development of dense fog overnight, and then mainly only
near the coast. So we will continue to monitor trends and hold off
on issuing a Dense Fog Advisory for now. Otherwise forecast for
the remainder of tonight looks to be in good shape.
For Sunday and Sunday night, don`t expect any changes to forecast
from previous package. Mid and upper ridging weakens slightly as flow
becomes a little more zonal, and surface high pressure ridge
weakens slightly and drifts east of the area by late Sunday
afternoon and Sunday night. This will allow the frontal boundary
that has been nearly stationary to the north of our forecast area
to sag southward, approaching or perhaps entering the far northern
portions of our area by late Sunday night. Even with this, mid
levels of the atmosphere remain very dry, and not much in the way
of precipitation is expected and a mostly dry weather pattern will
persist through the near term period. Only a small portion of our
extreme northern zones have a small chance of a light shower late
Sunday afternoon into Sunday evening as the frontal boundary drifts
down into our area. Patchy fog is a possibility yet again Sunday
night with the main focus over the southern half of the area. There
is again the potential that some of the fog could become locally
dense, especially near the coast. High temperatures on Sunday will
mainly be in the low to mid 80s (with warmest temps east of I-65
in south central Alabama and over interior portions of the Florida
panhandle). Mid to upper 70s expected along the immediate coast.
Sunday night low temperatures should range from the mid and upper
50s over far northwestern counties (behind the front), to the
lower 60s across most of the remainder of the area. /12
.PREV DISCUSSION... /issued 638 PM CDT Sat Mar 14 2020/
AVIATION...
15/00Z issuance...VFR conditions prevail over most locations
through mid evening, then a return of low ceilings and potentially
some dense fog is expected again late tonight into early Sunday
morning. This area of low clouds and fog late tonight and early
Sunday is most likely across southeast MS, portions of southwest
AL (especially near the coast) and possibly extending eastward into
coastal areas of northwest FL. Light and variable winds for most
locations tonight, then becoming primarily light southerly on
Sunday. /12
PREV DISCUSSION... /issued 338 PM CDT Sat Mar 14 2020/
NEAR TERM UPDATE /Now Through Sunday/...A dry weather pattern
will persist through Sunday afternoon as upper ridging remains
over the northern gulf and deep south. Only a small portion of our
extreme northern zones have a small chance of a light shower late
Sunday afternoon as a quasi-stationary frontal boundary north of
the forecast area drifts down into the area. The pattern remains
favorable for additional patchy to areas of fog development along
the coast and eventually inland overnight tonight. It currently
appears that the best chance for dense fog development tonight
will be across portions of southeast MS into coastal southwest AL,
and possibly into a small portion of coastal northwest FL.
Additional advisories may become necessary again tonight.
Temperatures will remain well above normal for this time of the
year. Lows tonight primarily in the upper 50s across the area,
with a few locations in the lower 60s. Highs on Sunday should
again reach into the lower to mid 80s over the interior, and in
the upper 70s along the beaches. /22
SHORT TERM /Sunday night Through Tuesday night/...The persistent
upper level ridge over the Gulf continues to control the local
weather to open up the new work week. It appears the better
moisture for better rain chances will be aligned within the
northern periphery of the upper ridge from northern TX, eastward
to northern GA through Monday. Expect the southern zones to remain
rain-free. May just be enough environmental moisture in place
along and north of US Hwy 84 though to support a small chance of
showers mainly Monday afternoon. Upper flow flattens briefly by
Tuesday then shows a gradual increase in geo-potential height
rises over the deep south Tuesday night as Gulf upper ridge re-
amplifies. With the flattening and weakening of the Gulf ridge
influence Tuesday, a slightly higher rain chance is presented
mainly for areas along and north of I-10. Perhaps a few
thunderstorms over the interior as well. Pressure ridge (Surface
and aloft) migrating to the east brings an unseasonably warm,
spring-like pattern for the first half of the upcoming week.
Patchy fog is a possibility yet again Sunday night and Monday
night with the main focus over the southern half of the area.
There is potential that fog could become locally dense. /10
EXTENDED TERM /Wednesday Through Saturday/...Will begin the
medium range with a pattern that shows more amplitude in the
height field aloft. A large nearly cut-off upper low migrates
eastward over the southwest US causing short-wave upper ridge to
amplify over the southeast US. The upper low opens up and ejects
more rapidly to northeast while phasing with the northern stream
Thursday and Friday. As this occurs, the axis of the upper ridge
over the southeast US is pushed southeastward across the FL
Peninsula the latter end of the week and flattens over the Gulf
Saturday.
There is a question on rain chances into the middle of the week as
a more amplified response of the Gulf ridge would favor more
subsidence and a net reduced rain chance for the coast. Although
forecasters carry PoPs over the interior, for perhaps diurnally
driven showers Wednesday and Thursday, considering the ridge
aloft have also lowered chances in the blends by about 10 to 20%.
late Friday and into Saturday, a cold front approaches the deep
bringing with it a better chance of showers and a few storms.
Daily highs and lows to remain well above climatology through
Friday. /10
MARINE...Main impacts to commercial and recreational boating will
be fog over bays and sounds. Fog could be locally dense with
restrictions to visibility to a mile or less. A weak front will
move over the near shore waters Sunday night before retreating
back to the north early next week. This pattern will result in a
brief offshore flow early Monday followed by a light east to
southeast flow into midweek.
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&
$$
This product is also available on the web at:
http://weather.gov/mob
Area Forecast Discussion
National Weather Service San Francisco Bay Area
847 PM PDT Sat Mar 14 2020
.SYNOPSIS...Significantly cooler and wetter conditions will
continue through the remainder of the weekend as a slow moving
weather system moves gradually south along the coast. Unsettled
weather will likely continue through the middle of next week.
Another weather system will then possibly bring more precipitation
by the end of next week and into the following weekend.
&&
.DISCUSSION...As of 8:45 PM PDT Saturday...Satellite and radar
show a nearly stationary cold frontal boundary across the
southern San Francisco Bay Area, Santa Cruz County, and far
northern Monterey County. The boundary is drifting very slowly to
the southeast, but hasn`t moved much since mid afternoon. Rain
rates have been mostly light to moderate, but some locations in
the Santa Cruz Mountains have picked up between 1.0 and 1.5 inches
of rain in the past six hours. The 00Z NAM and latest HRRR agree
that the boundary will continue to move very slowly to the
southeast through late this evening, but then progress more
quickly to the southeast late tonight as the next organized line
of shower activity approaches from the northwest and begins to
spread precipitation into the North Bay. All thunderstorm activity
has remained well to our north and east today and it appears
unlikely we will see thunderstorms in our area overnight, at least
not with this initial boundary.
Southerly winds ahead of the boundary have been gusting as high as
40 mph across isolated locations in the higher hills. The local
WRF has been forecasting strongest winds to occur across western
Monterey County overnight and a Wind Advisory is in effect from 9
pm this evening until 5 am PDT Sunday for the Big Sur Coast and
Santa Lucia Mountains. Wind speeds as forecast by the 00Z WRF are
not quite as strong compared to the 12Z run, but still strong
enough to warrant maintaining the Wind Advisory.
Snow levels are currently above most Bay Area Peaks, but are
expected to drop as low as 2500 feet in the North Bay by late
tonight as the next, colder, boundary moves in.
From Previous Discussion...For Sunday - the slow moving cold
front will finally exit to the south late morning. In its wake
another low pressure system and upper trough are projected to
drift southward along the coast. The atmosphere looks to have a
little more instability associated with round number two on
Sunday. Have increased coverage/chances for thunderstorms mainly
north of the Bay Bridge in the afternoon/evening on Sunday.
Coverage also fits with SPC Day 2 outlook for a general mention of
thunderstorms. Given the colder air aloft on Sunday small hail
will once again be possible. The second low will pinwheel/wobble
southward Sunday through Tuesday keeping convective showers in
place. Precip appears to come through in waves as the low moves
south. Have not included a mention for thunder on Monday, but
something to keep an eye on. Snow chances over higher elevations
will also increase Sunday and Monday as snow levels drop over
southern peaks (ie Santa Lucias). Would not be surprised if 3-6
inches of snow fell over the highest peaks by Tuesday.
Wednesday and Thursday will see an overall drying trend. Longer
range models show the storm door remains open with another low
pressure moving into the region next Friday/Saturday. The GFS/ECM
shows this will be another low dropping down the coast. Still not
an AR, but need precip nonetheless. Stay tuned.
&&
.AVIATION...as of 05:35 PM PDT Saturday...For 00Z TAFs. Latest
KMUX radar imagery shows primary frontal precip band now extending
through Monterey Bay northeastward across the Santa Cruz
Mountains and Santa Clara Valley, and into central and eastern Alameda
and Contra Costa counties. It`s very slowly progressing to the
southeast. Reflectivity returns have ramped up a bit over the past
hour indicating associated showers are getting a bit heavier.
Winds are generally out of the southwest, and on the strong and
gusty side around the Monterey Bay region as it approaches. Behind
it there`s a mix of clouds and showers which will be moving
through this evening and overnight, resulting in potentially
rapidly changing ceilings and visibilities at the terminals. A
second frontal boundary then looks to approach late tonight and
Sunday morning with winds again picking up out of the southwest
and another round of rain.
Vicinity of KSFO...Rain has diminished a bit as the primary
frontal band continues to slowly progress farther southeastward,
but showers will persist on and off through the evening and
overnight hours as moist and unstable onshore flow continues.
Winds are projected to increase out of the south southwest late
tonight and Sunday morning with the approach of the next frontal
boundary.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...The primary frontal boundary is presently
moving onshore, and is accompanied by gusty winds out of the south
southwest. As it moves through, it will bring periods of rain
along with ceilings lowering to near or into the MVFR range. Behind
it, look for partial clearing but with showers remaining in the
area. Another boundary will arrive Sunday afternoon.
&&
.MARINE...as of 02:03 PM PDT Saturday...A large disturbance moving
down the coast of California will bring strong conditions to the
area waters. Near gale conditions are expected around Point Sur
tonight. In addition, expect rain and possible thunderstorms with
hail associated with this disturbance. Conditions will ease during
the first half of the work week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...Wind Advisory...CAZ517-530
SCA...Mry Bay
SCA...Pigeon Pt to Pt Pinos 0-10 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm from 9 PM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pt Reyes 0-10 nm from 9 PM
SCA...Pt Reyes to Pigeon Pt 0-10 nm from 9 PM
SCA...SF Bay from 3 AM
&&
$$
PUBLIC FORECAST: Dykema/MM
AVIATION: Blier
MARINE: BFG
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Area Forecast Discussion
National Weather Service Phoenix AZ
446 PM MST Sat Mar 14 2020
.UPDATE...Updated aviation discussion.
&&
.SYNOPSIS...
A few showers may develop today mainly north and west of Phoenix.
Overall, drier and somewhat warmer conditions can be expected
through the day time Monday. Another weather system will affect
the region in the Monday night through Thursday time frame. The
most active period is expected to be Wednesday afternoon and
night. However, this system will not produce as much rain as the
one we just had though snow levels will be significantly lower.
&&
.DISCUSSION...
Visible satellite imagery from early this afternoon reveals
lingering moisture in the afternoon in the form of cumulus clouds.
Some of those clouds have more depth to them and have been
showing up on radar over northern AZ due to some minimal
precipitation sized particles present. There is still a
possibility of that happening (sprinkles/very light showers) in
isolated spots over our forecast area. Hi-res guidance has been
depicting this over La Paz County and western Maricopa County
(though recently the HRRR has trended down). This scenario is
driven not only by left over moisture, but a weak disturbance
embedded within the broad cyclonic flow aloft. Models also depict
another very weak disturbance this evening. Some of the hi-res
guidance actually depicts a few weak showers this evening over
Imperial County. Not confident enough in that scenario to mention
any precip chances.
The next system of interest is centered off the Oregon coast.
Models show this system slowly tracking southward over the next
few days. Meanwhile, high pressure centered over the Gulf of
Mexico expands eastward a bit leading to some amplification of the
flow. The moisture content over the forecast area slowly declines
as well. During this time temperatures increase but not
dramatically.
The Pacific system begins making its presence felt beginning
Monday night as a frontal zone enters far southeast California.
The front appears to stall out/weaken over western Arizona
Tuesday. The low appears to take on something of a dipole
configuration Tuesday night and Wednesday with the southern end
being deeper/colder. There is good model agreement on that portion
of the storm swinging through southeast California and Arizona
Wednesday afternoon and night. In fact, the whole system moves
inland as well and transitions to an open wave. That is when
dynamical forcing looks to be best. GEFS SBCAPE peaks during that
time as well. Thus, at this time, that is when the most active
weather period is anticipated. This system will be much more short
lived than the previous one since it is expected to exit AZ during
the day Thursday. The moisture plume will not be as robust over
our area either. Thus, the precip totals - especially over
southeast CA - will not be as great as with this past system.
But, it will be colder and in that respect have more precip
efficiency. At this time, accumulating snow looks to be limited to
elevations above 5000 ft. There are indications of yet another
system affecting the region next weekend.
&&
.AVIATION...Updated at 2345Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
SCT clouds around 6-7kft will continue to thin this evening, but
will linger through the overnight hours. Potential for brief
periods of BKN but overall SCT will predominate. High clouds AOA
20kft will also increase through the overnight hours. Winds from
the west will persist into the overnight hours, with easterly flow
developing later than usual. Expect the usual westerly winds to
redevelop for Sunday afternoon.
Southeast California/Southwest Arizona including KIPL and KBLH:
Mostly clear skies expected with a few clouds near 6-7 kft and
increasing clouds AOA 20kft. South to westerly winds will persist
through the overnight hours. By Sunday afternoon, could see a few
wind gusts in the mid teens develop, especially around KBLH.
&&
.FIRE WEATHER...
Monday through Friday: Drier conditions will move on Monday before
wetter and more unsettled weather is expected into the middle part
of next week, beginning later on Tuesday. Humidity levels will stay
elevated through the period with minimum readings generally 25-40%.
High temperatures will stay near seasonal normals through Monday
followed by cooling with well below normal temperatures likely by
Wednesday and Thursday. Winds will be breezy at times through
much of the period, especially during the daytime hours. Gusts
will mostly reach into the 20-25 mph range.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...AJ
AVIATION...Iniguez
FIRE WEATHER...Kuhlman/CB