Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/24/20
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
601 PM CST Thu Jan 23 2020
Issued at 600 PM CST Thu Jan 23 2020
Snow has ended across much of the area, and where light snow
lingers, it is expected to end in the next hour or two. Have
allowed the remainder of the Winter Weather Advisory to expire on
.SHORT TERM...(This evening through Friday)
Issued at 334 PM CST Thu Jan 23 2020
Aloft: Moderately-amplified flow was over the CONUS per RAP
tropopause analyses and aircraft wind data. A fairly deep/narrow
troff extended from the Can Prairies to LA with a newly-developed
low over Ern KS. A ridge was progressing thru the Wrn USA. The KS
low will E into the OH Vly thru tomorrow. NNW flow over NEB/KS
will become NW turn more anticyclonic.
Surface: Wk 1014 mb low pres was near MCI and moving SE away from
the rgn. 1033 mb high pres was over ONT. A piece of this high
will break off and expand N-S acrs the Plns from ND-OK tonight and
Rest of this afternoon: Skies will remain cldy over most of the
CWA as a shield of snow conts over S-cntrl NEB. The Wrn and Srn
fringes of the precip shield were falling as -RA. Some peeks of
sun will be psbl along the Wrn border of the CWA. This precip
shield will cont to drop S along with the newly-formed upr low. So
precip will gradually decrease in intensity and/or end...espcly N
N-NNW winds will cont to gust 20-30 kt.
The Winter Wx Advy will expire at 00Z and given that main roads
are primarily wet.
Tonight: Whatever -RA/-SN is over the CWA (primarily over the SE
1/3 of the CWA) will quickly come to an end early this eve. Low
clds will remain over the majority of the CWA (along and E of Hwy
183). W of Hwy 183 skies will be more variable... and partly-
With the extensive cld cover...did not go as cold as NBM. Kept
lows toward the higher end of the guidance spread.
Fri: Finally a breather! This will be the 1st day of at least 4
without any wintry precip.
Multi-model low-level RH progs and vertical cross sections
suggest much of the day will remain cldy for most of the CWA.
After 18Z we should see the back edge of the clds move E into the
CWA...as low-lvl winds back from NW to W and the thermal trof gets
shoved E and weak WAA develops. Mdl consensus brings the clearing
line up to Hwy 183 by 21Z and Hwy 281 by 00Z. So locations E of
Hwy 281 will stay cldy all day.
Extensive cloudiness will keep temps fairly cold tomorrow. From
GRI N and E...temps will not get out of the 20s.
.LONG TERM...(Friday night through Thursday)
Issued at 334 PM CST Thu Jan 23 2020
Aloft: The wk shrtwv trof that will be moving thru the Wrn USA
tomorrow will cont E and cross NEB/KS Sat-Sun. A shrtwv ridge will
move thru Mon behind that trof. The global mdls cont to fcst the
next Wrn USA shrtwv trof to head into the Srn Plns. There conts to
be considerable uncertainty/mdl spread with its evolution. The EC
runs cont to be the most aggressive...closing off a low.
Meanwhile...the GFS runs have a decent trof but it remains open
and more progressive. There is so much spread in the EC ensemble
that the mean is not very supportive of the deterministic runs. So
the fcst is highly uncertain next Tue-Wed.
The 12Z EC run is the first one in the last svrl days that came in
not closing off a 500 mb low and keeping the trof open. That has
substantially cut its QPF.
Surface: High pres will drift E of the rgn Sat...with a lee trof
moving E into cntrl NEB/KS. That trof will dissipate Sun with a
new lee trof forming in the lee of the Rckys. A wk cool front will
be advancing thru the Wrn USA (associated with the shrtwv trof).
This front will cross the CWA Mon night while wk low pres forms
over the Srn Plns. This low will stay well S of the CWA Tue-Wed.
Temps: Overall...temps will average near normal Sat-Thu. Sun
should be the warmest day.
Precip: With the EC now coming into agreement with the past svrl
GFS runs...precip is looking pretty meager. In fact...most of
these time periods will be dry. There could be some trace amts of
precip Sat night with that trof moving thru. A touch of -RA/-SN is
psbl Mon night into Tue. Multi-model QPF is less than 0.10". So
it will be a light/minor event for area that see precip. Best
chance will be S of I-80.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 515 PM CST Thu Jan 23 2020
Not an easy forecast tonight as ceilings vary across the area.
Current thinking is that GRI will be more uniform in cloud
coverage with ceilings around 1k and will lower this evening to
IFR. EAR ceilings maybe VRB tonight as the clearing line is near
Gothenburg. For the EAR TAF have kept ceilings a little higher and
drop them to IFR after midnight. Thinking that EAR could SCT out
around mid-day. Thinking VIS will be VFR, but will vary this
evening as a little BLSN could impact the TAF sites. Winds
expected to taper down this evening.
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
907 PM CST Thu Jan 23 2020
.DISCUSSION...See updated information for land areas below.
.UPDATE...Have adjusted pops for the rest of the evening to keep
high pops mainly over the western Florida panhandle and south
central Alabama where numerous showers will continue to shift
eastward. Rain chances taper off overnight with dry conditions
expected for the entire area by early Friday morning. Made
adjustments to temperature trends and also added patchy fog,
which may become dense in some locations. /29
.PREV DISCUSSION... /issued 547 PM CST Thu Jan 23 2020/
DISCUSSION...Updated for latest aviation discussion below.
00Z issuance...Scattered to numerous patches of rain over much of
the area move off to the east overnight into early Friday morning
leaving dry conditions over the area. Expect to see patchy fog
develop over portions of the area overnight which dissipate by
early Friday morning. Southeast winds 5 to 15 knots diminish and
become west to northwest around 5 knots overnight, then increase
to near 10 knots on Friday. IFR to MVFR ceilings prevail overnight
followed by clearing Friday morning. /29
PREV DISCUSSION... /issued 343 PM CST Thu Jan 23 2020/
NEAR TERM /Now Through Friday Night/...A broad upper level
trough continues to advance eastward across the Plains states
early this afternoon, with an increasingly moist southwest flow
aloft spreading over our forecast area ahead of this feature.
Regional radar imagery shows widespread light to moderate rain
showers spreading across southeast MS and adjacent southwest AL
in association with a short-wave impulse in the southwest flow
aloft. We increased POPs to 90-100% this afternoon into this
evening as the large scale ascent spreads over the region. A weak
area of surface low pressure over southern LA this afternoon is
forecast to advance eastward to near the MS/AL/northwest FL coast
this evening. Weak low level warm advection ahead of this
approaching feature may allow surface dewpoints to briefly rise to
the upper 50s to near 60 degrees near the immediate coast late
this afternoon into this evening. The latest short range model
guidance continues to show very weak instability near coastal
portions of the CWA, mostly less than 300 J/KG, though the higher
resolution guidance, including the NAM-12 and RAP do attempt to
bring slightly higher MLCAPE values of 300-600 J/KG near immediate
coastal portions of northwest FL later this evening. However,
guidance is showing a fairly weak low level jet on the order of
20-30 knots now. Given the weak jet dynamics and limited
instability, the general risk of thunder through tonight remains
appropriate. Patchy fog could develop this evening into late
Rain chances should taper from west to east late tonight into
early Friday morning as a cold front moves across the region. A
much drier airmass will spread into the region Friday into Friday
night on the base of the larger scale trough axis. Mostly clear
skies are anticipated for Friday and Friday night.
Lows tonight range from the lower to mid 40s over western
portions of our area to the upper 40s to lower 50s across most
places roughly along and east of the I-65 corridor. Highs Friday
should range in the upper 50s to the lower 60s around the area.
Cooler temperatures follow for Friday night with lows in the mid
to upper 30s over the interior and in the lower 40s near the
immediate coast. /21
SHORT TERM /Friday night Through Sunday night/...Surface high
pressure builds into the region supporting a rain-free pattern
through Saturday. Upstream, a short-wave mid-level trof dives
southeast over the Red River Valley of TX/OK Saturday night
causing an area of mid-level height falls to spread eastward over
the deep south and northern Gulf. Net result is the formation of a
surface low off the TX coast Sunday morning which from there
tracks east or slightly south of due east across the central Gulf
through Sunday night. On this track, the low stays well south of
our coastal waters. An area of moisture and lift moves across the
area Sunday, enough that forecasters will call for a high chance
of showers. The highest coverage of rain though stays out over
the Gulf, closer to the low track. Little change in highs for
Saturday with Sunday`s numbers looking to hold mostly in the mid
to upper 50s. Overnight lows will be cool but gradually moderate
with each night.
LONG TERM /Monday Through Thursday/...A short-wave upper level
ridge translates eastward over the area Monday and Monday night
favoring a return to a rain-free weather pattern. Heading into
Tuesday, the extended range global spectral models shows next
southern stream energy approaching the Lower MS River Valley.
Timing differences are seen with the operational GFS much faster
and more bullish with its solution of measurable rain Tuesday than
the 23.12Z ECMWF outcome which is slower and not bringing in rain
until Tuesday night. The National Blends came out completely
rain-free Tuesday and have tweaked to add a small PoP by Tuesday
afternoon to account for the slower ECMWF but also the GFS. The
mid-week feature kicks out across the southeast Wednesday. There
are differences in the height fields with the handling of next
upper level storm system diving through the Plains beyond
Wednesday, but an assessment of forecast moisture fields which are
low favors a lowering in PoPs Wednesday night and Thursday.
Daytime highs upper 50s to lower 60s Monday gradually lift into
the lower to mid 60s mid week which trends a few degrees above
seasonal. Overnight lows to gradually moderate into the mid to
upper 40s interior to lower half of the 50s coast by the middle of
the week. /10
MARINE...A moderate to occasionally strong southeast wind flow
will become southerly this evening as a cold front approaches from
the west. The Small Craft Advisory for the Florida coastal and open
Gulf waters remains in effect through 9 PM this evening as well. The
cold front will progress across the Gulf coast late tonight into
tomorrow morning, followed by a light to moderate northwest to north
flow through the remainder of the week. A light to moderate easterly
wind flow is then expected by late weekend as an area of low
pressure moves eastward across the Gulf. This will persist through
early next week. /26
AL...High Rip Current Risk through Friday afternoon for ALZ265-266.
FL...High Rip Current Risk through Friday afternoon for FLZ202-204-
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Area Forecast Discussion
National Weather Service San Francisco Bay Area
948 AM PST Tue Jan 21 2020
.SYNOPSIS...Rain is forecast to spread from north to south across
our area today as a weak weather system moves into northern
California. Rainfall amounts will be light to locally moderate,
with no significant weather impacts expected. Mostly dry and
warmer conditions are then expected for the remainder of the work
week, with rain likely to return over the upcoming weekend.
.DISCUSSION...as of 8:33 AM PST Tuesday...Radar reflectivity
indicates some light rain this morning impacting parts of the
North Bay, the San Francisco Peninsula, and the East Bay. Stations
in the North Bay have registered anywhere from a few hundredths
of an inch up to several tenths through 8 am PST. Periods of
light and perhaps briefly moderate rain will continue off/on
through the day, spreading from north to south as the day
progresses. Main impacts will be the wet roadways during the
commuting hours. Total rain amounts will be generally between 0.25
and 0.50 inches on average with higher amounts in the North Bay
Mountains and Santa Cruz Mountains and lower amounts for locations
south of Santa Cruz as well as in the rain-shadowed Santa Clara
No major changes have been made to the short-term grids. For
additional forecast details, please refer to the previous forecast
.PREV DISCUSSION...As of 3:00 AM PST Tuesday...Primary short-term
forecast concerns are potential impacts from the incoming weather
system. Given that precipitation will be mostly light and winds
won`t be a significant factor, the primary impacts will be wet
roadways during the morning and afternoon/evening commutes.
Current radar shows light rain just now beginning to move onshore
in Sonoma County. This initial rainfall is associated with warm
advection out ahead of the primary front that is still a ways
offshore. Based on the latest HRRR and NAM, light rain will remain
confined to the North Bay through the morning commute, and roads
should remain dry from San Francisco southward through at least
The primary frontal rain band is expected to arrive in the North
Bay by mid morning, causing rain rates to increase somewhat. Rain
will then spread south through most of the rest of the SF Bay
Area during the late morning and afternoon hours as the front sags
south. Light rain will finally reach the Monterey Bay Area by
early evening. Areas that will most likely experience wet roadways
during the afternoon/evening commute are the central and southern
SF Bay Area as well as locations near Monterey Bay.
The NAM indicates that a couple of weak waves will develop
offshore along the frontal boundary by late afternoon and early
evening. This will result in the frontal boundary stalling across
the South Bay and Monterey Bay Area from late afternoon through
much of the overnight hours, and perhaps even until a few hours
after sunrise Wednesday. However, the front is forecast to
gradually dissipate overnight and so rain will mostly end by
Rain totals through tonight are forecast to be a half inch or less
in most areas. The North Bay Mountains and Santa Cruz Mountains
could see locally up to an inch of rain.
Dry conditions are forecast from Wednesday through Friday as upper
level ridging over California deflects incoming Pacific systems
to our north. The second half of the work week will also feature
warming temperatures as H5 heights increase to 576 dm. High
temperatures are forecast to be mostly in the 60s by Thursday and
Friday. However, if persistent low clouds and fog develop around
the Delta and locally into the North and East Bay Valleys, similar
to what occurred over this past weekend, temperatures in those
areas would remain in the 50s.
The consensus of longer range deterministic models, as well as
model ensemble means, is for the next system to bring rain to the
northern portion of our forecast area on Saturday and then south
through the rest of our area by Sunday. This weekend system looks
slightly stronger and wetter than today`s system, but will not
likely to have significant impacts. Dry weather is then expected
to return by early next week.
.AVIATION...as of 9:48 AM PST Tuesday...For 18z TAFs. A weak
frontal boundary slipping through the area today will bring a mix
of low cigs and/or vsby to area terminals during passage, along
with some light rain. Current satellite imagery is showing
widespread overcast conditions throughout the Bay Area and
increasing clouds for the Monterey terminals. STS is already
reporting 2sm with cigs down to 600 feet. Winds ahead of the front
will likely have some light to moderate wind shear, as the
surface winds will generally be out of the south while winds up
about 2000 feet will be from the southwest and gusting into the
mid 30 knot range. Therefore, wind shear remains in the tafs for
STS, OAK, and SFO.
As this frontal boundary slips out of the area, high pressure will
be building quickly in its wake. This could trap some of the low
level moisture that the front is leaving behind which could yield
some low vsby issues at many of the Bay Area terminals overnight.
The main culprit will be STS. Otherwise clouds will be clearing.
This really boils down to a timing issue as to when the ridge
takes hold behind the front. Most tafs do show some kind of
reduction in vsby and it may need to be drop even further in later
Vicinity of KSFO...MVFR is expected to remain through the day with
a possible brief drop to IFR as the front passes between about
02Z-06Z. Confidence is low with any drop to IFR (no matter how
brief) and is not reflected in the taf at this time. This will
need to be monitored to see if the front comes in any stronger to
SFO than forecast. At this time, it is expected to break up to a
degree over the coastal range. Regardless, look for some small
drops in vsby and cigs during the core of frontal passage. Winds
will come around from the south to a more north to northeasterly
direction behind the front and are forecast to be light. This may
cause some radiational fog to develop. As it stands right now,
but post sunrise on Wednesday conditions look to be improving
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR-MVFR. Light SE winds this morning.
Showers to arrive in the early evening with MVFR cigs. Only a
slight drop in vsby is expected as showers limp through the area.
Otherwise, look for VFR to prevail again by this time on
.MARINE...as of 09:31 AM PST Tuesday...Expect moderate to locally
breezy southerly winds through this morning as a cold front
approaches and moves through the waters during the remainder of
the day. A longer period northwest swell will build today before
peaking midweek generating hazardous seas conditions for smaller
vessels. Another long period northwest swell will then arrive
later this week.
.Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 3 PM
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm
PUBLIC FORECAST: Rowe/Dykema
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