Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/11/18
Area Forecast Discussion
National Weather Service Columbia SC
1033 PM EST Sat Mar 10 2018
.SYNOPSIS...
Chances for rain increase Sunday ahead of an approaching low
pressure system which will cross the area Monday. Forecast event
total rainfall through Monday will be around a half inch to 1.2
of an inch. Cooler and dry weather expected Tuesday through
Friday with temperatures slightly moderating by Friday. More
frost or freeze concerns will occur during the middle of next
week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Very little change with this update. Hi-Res model soundings
still showing quite a bit of low level dry air this evening,
which has cause any precip that attempts to enter the CWA to
evaporate before reaching the ground. Moistening of that layer
will only occur gradually, so rain chances won`t materially
increase until daybreak Sunday.
I made some very slight adjustments to temp.dewpt/wind grids to
account for current conditions, but nothing that would alter the
main forecast premise for the remainder of the night.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
The next chance for significant rain will arrive on Sunday as
moisture increases over the region ahead of an approaching
upper trough that will dive southeastward into the Mississippi
Valley. In situ cold air damming develops on Sunday with
surface winds shifting to a northerly direction as deep
southwesterly flow atop the wedge results in isentropic lift
and widespread precipitation across the forecast area Sunday
into Sunday night. The flow at 500mb becomes a bit diffluent
late Sunday through Sunday night which will provide additional
upper forcing to enhance precipitation. The best moisture
transport into the region occurs Sunday evening corresponding to
an increase in precipitable water values over 1 inch. The bulk
of the rainfall is expected to fall Sunday/Sun night with around
0.75 to 1 inch of rainfall possible. Instability is basically
non-existent on the cold side of the wedge boundary so severe
weather is not expected and chance of thunder appears minimal as
LI values remain above zero.
Latest GFS shows a dry slot moving into the forecast area
around 12z Monday just ahead of the upper trough axis as deeper
moisture shifts south and east of the region, therefore will
have a period of lower pops Monday morning. A surface low will
track across the forecast area generally along the wedge
boundary, as the upper trough crosses Monday afternoon, and
expect additional showers enhanced by steep lapse rates.
Temperatures on Sunday will range from the mid 50s northern
Midlands to mid-upper 60s in the southeast Midlands and lower
CSRA. As the wedge becomes stronger and more entrenched Sunday
night, overnight lows will fall into the 40s. Cooler on Monday
with highs mainly in the 50s. Another night of possible
freezing temperatures in some locations across the area Monday
night with cold advection as high pressure builds in. Winds
should stay up though preventing a frost threat due to increased
pressure gradient.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Cool and generally dry conditions expected in the extended
forecast period as an upper trough will remain over the eastern
part of the country Tue/Wed with a secondary shortwave rotating
through the upper trough on Wednesday before shifting offshore
of the Mid- Atlantic coast Wed night. Surface high pressure will
become centered over the southeastern states on Thursday and
then shift off the southeast coast on Friday with an upper ridge
to the west of the forecast area de-amplifying and 500mb flow
becoming zonal. Dry weather expected through the extended
period. GFS showing a cold front approaching the TN Valley by
late Saturday but due to low confidence in timing of the front
this far in advance, will keep forecast dry for Saturday as
well.
Temperatures will be below normal through midweek with highs
generally in the 50s and lows in the 30s with additional
frost/freeze concerns each night through Friday morning. High
temperatures will moderate late in the week with highs back
near normal in the 60s Thursday and Friday and rising into the
70s on Saturday.
&&
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
VFR conditions will likely continue through tonight but
restrictions will develop Sunday.
Moisture will be on the increase tonight in the southerly flow
on the backside of offshore high pressure and along a cold
front sinking southward and into the forecast area. Moisture
will become high Sunday with low pressure tracking eastward
along the front just to the south of the terminals. Expect a
lowering ceiling tonight. The near-surface layer will likely
remain too dry for fog. Based on the initial dryness and good
agreement of the GFS and NAM MOS plus SREF and HRRR guidance we
believe it will remain a VFR ceiling tonight. Continued
isentropic lift should result in lowering ceilings Sunday.
Developing rain and fog should also bring visibility
restrictions. The guidance was not consistent with the timing.
We used an average of the guidance with developing MVFR
conditions during the middle of the day and ifr conditions late
in the afternoon. Confidence is low on the timing because of the
model inconsistency. The GFS and NAM display no surface-based
instability with the main surface boundary setting up south of
the terminals and widespread cloudiness. The models also
indicate little upper instability. The thunderstorm chance is
too low to include in the terminal forecasts.
EXTENDED AVIATION OUTLOOK...Rain with IFR or MVFR restrictions
will likely continue through much of Monday with low pressure in
the region.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
554 PM CST Sat Mar 10 2018
.AVIATION...
VFR conditions will prevail through this evening. At 23z, a
dryline extended southward from a surface low southwest of KSPS.
Meanwhile, a cold front was draped from northeastern Oklahoma
westward through the northern Texas Panhandle into northeastern
New Mexico. As the surface low sinks southward this evening, a
prefrontal trough is expected to move south into the I-20 corridor
by 04z. As this occurs, southeast winds 5 to 8 knots will back
around to the northeast. Some models are indicating that some
showers and thunderstorms could develop along this boundary by 04z
but confidence is not high enough to include any SHRA/TSRA this
early. As the actual cold front moves through, there may be some
showers/isolated thunderstorms so have left a -SHRA and VCTS for
the 08z to 13z period. Winds will shift to the north at 15-18
knots with the frontal passage and gusts of 25 to 30 knots or
higher are likely by 12-13z Sunday. The MVFR ceilings should move
to the south by 13z. The wind gusts should diminish around 00z
Monday.
&&
.SHORT TERM... /Issued 306 PM CST Sat Mar 10 2018/
/Through Tomorrow/
Primary focus through the short term is convective chances
overnight into early tomorrow morning along a strong cold front.
Main trend was to increase PoPs and expand them westward based on
latest output from several CAMs.
A surface low was centered over Vernon, TX as of 3pm. A dryline
extended southward toward Abilene and San Angelo while a surface
trough/stationary front was located northeastward into Oklahoma.
Within the warm sector, breezy southwest winds and clearing skies
have allowed temperatures to climb well above normal with highs
expected to top out in the upper 80s across some of our western
zones. Despite what would normally be a fairly volatile warm
sector, west winds at 850mb have placed a stout cap overhead which
will keep convective chances through sunset at nearly 0%. This
evening, the surface low will slowly drift southward and winds
will back to a more easterly direction while the trough axis
becomes located near the Red River. The true frontal boundary
will also begin shifting south during this time, but will lag the
prefrontal trough by ~100 miles or more.
By midnight, both of these features will begin affecting North
Texas. Some weak convergence along the prefrontal trough should
be sufficient to initiate some isolated showers or storms across
our northeastern zones. However, stronger convergence and lift
should accompany the true cold front a few hours later. Typically
when a prefrontal trough outruns the actual thermal boundary,
convergence/lift along the true front is limited. However, due to
substantial differences in wind speeds, there will still be
convergence located immediately along the front as north winds of
20-30 mph collide with much lighter north winds associated with
the trough axis. This should result in an increase in convective
activity as the front encounters a less capped airmass across East
TX. Latest forecast soundings from the NAM Nest and the RAP
suggest as much as 1500-2000 J/kg of CAPE rooted near or just
above the surface could be in place since temperatures and
dewpoints are expected to be in the mid or upper 60s through the
wee hours of the morning. Latest CAMs suggest that enough lift
will be present to harness this instability and result in numerous
thunderstorms along and east of I-35 between midnight and ~7AM.
One area that I still maintain some skepticism is with these
models` fairly rapid erosion of the cap they`re forecasting to
occur late tonight. The environment will be lacking a strong
shortwave to dynamically lift and cool the cap, so the onus will
be on the front itself to overcome the inversion. While I`ve
raised PoPs from previous forecasts, the coverage depicted in
recent high-res models could still be overdone if they`re eroding
the cap too aggressively. If thunderstorms are able to get going
in such and unstable environment, I wouldn`t be able to rule out a
stronger storm occurring overnight with primarily a threat for
some hail given the aformentioned instability. The most likely
location for a couple stronger storms would be areas around
Sulphur Springs, Greenville, Terrell, Canton, and other points
nearby.
There is still uncertainty regarding the westward extent of
showers/storms overnight, largely due to the unknowns regarding
the cap. It`s conceivable that a band of lighter precipitation
could stretch westward through the DFW area towards Weatherford or
Mineral Wells before moving southward through the forecast area
along the cold front. I`ve mostly included 20% PoPs for areas
west of I-35 with low confidence in coverage for these locations.
The front and any associated showers/storms will finally be
exiting the area to the south on Sunday morning. Very breezy north
winds will occur in its wake, and a Wind Advisory may be needed
depending on trends overnight. Sustained north winds of around 20
mph with gusts of 30 mph or higher seem likely through the morning
before tapering off slightly through the afternoon and evening.
While the cold front will scour the low-level moisture from the
area, a plume mid-level moisture will keep a deck of clouds over
much of North and Central Texas through the day before some
gradual clearing occurs towards the evening hours. High
temperatures should be as much as 20-25 degrees cooler than today,
mostly in the upper 50s and 60s.
-Stalley
&&
.LONG TERM... /Issued 306 PM CST Sat Mar 10 2018/
/Sunday Night through Saturday/
High pressure will be building into North Texas Sunday night
behind a cold front. A weak reinforcing front will slide into the
area early Monday associated with a passing disturbance. This
front will likely go unnoticed, although there will be some
moisture between 925-850 mb which could result in some brief cloud
cover early Monday. Monday will be cool with diminishing north
winds through the day and highs topping out in the upper 50s.
The pattern through the middle of the week will feature weak
shortwave ridging and slowly warming temperatures. Southerly flow
will become established by late Wednesday as another system
approaches the west coast of the U.S. Highs will climb into the
mid and upper 70s Thursday afternoon as southerly winds increase
to 15 to 25 mph. On Friday, a dryline will advance eastward into
the region with continued south-southwesterly flow. This will
support a continued warming trend with highs expected to climb
into the mid/upper 80s, especially west of I-35.
As we get into the weekend, low level moisture will increase
although most of North Texas will remain strongly capped. We`ll
keep some low rain chances late Friday into Saturday mainly for
isolated showers beneath the cap. Otherwise, the forecast will
remain quiet for the next several days.
Dunn
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 55 64 42 58 41 / 40 10 0 0 0
Waco 58 63 40 59 35 / 10 20 5 0 0
Paris 53 64 35 56 34 / 30 5 5 0 0
Denton 51 63 36 57 32 / 30 5 0 0 0
McKinney 53 62 37 56 34 / 40 10 5 0 0
Dallas 56 64 41 58 40 / 40 10 5 0 0
Terrell 56 65 37 57 37 / 50 20 5 0 0
Corsicana 59 62 40 57 37 / 30 30 5 0 0
Temple 58 64 37 59 34 / 5 20 5 0 0
Mineral Wells 51 61 35 57 31 / 20 5 0 0 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
58/30
Area Forecast Discussion...UPDATED
National Weather Service Huntsville AL
739 PM CST Sat Mar 10 2018
.NEAR TERM...(Tonight)
Issued at 739 PM CST Sat Mar 10 2018
Elevated bands of convection have become more apparent last couple of
hours over northwest through southern portions of northeast AL. There
have been a few lightning strikes thus far. 00Z soundings indicate
limited upright convective instability at BMX, but much higher values
of CAPE further west in MS, AR and LA. The inflow will be increasing
overnight due to the LLJ intensification in advance of the MCS in AR.
We will be monitoring rainfall trends as we go through the evening,
as the 18Z NAM indicated 3-4 inches of rainfall through 15Z Sunday
for our southern counties. The GFS was about half that. However,
short range guidance such as recent HRRR runs suggest that the MCS
over AR will become more organized and push a larger cold pool
southeast through central MS into central AL, limiting the threat of
heavy rain in north AL. In fact, it suggests a virtual end to
rainfall for our area by around 12Z. At this point, will hold off on
a Flash Flood Watch for now and monitor trends. We will continue to
mention an isolated flash flood threat in the HWO overnight.
.SHORT TERM...(Sunday through Monday)
Issued at 309 PM CST Sat Mar 10 2018
A low pressure system will lift into the MS Valley on Sunday and into
the TN Valley by Sunday evening. This will push the stalled boundary
and allow precip to become more scattered on Sunday. Sunday night
into Monday morning a short wave will swing down and sfc winds will
become northerly behind a cold front. As this cooler and drier air
filters in a brief period of a rain/snow mix is possible over
Southern Middle TN and northern Jackson county, through the morning
on Monday, if precip is still lingering. No accumulation is impacts
are expected.
.LONG TERM...(Monday night through Friday)
Issued at 309 PM CST Sat Mar 10 2018
The continuation of cold air advection into the region will highlight
the middle part of next week. Model profiles through the upper
levels are in agreement showing a cold Canadian airmass filtering
through the TN River Valley on the back side of system affecting the
Northeast US through midweek. 850 temps are expected to fall to the
(-9)-(-12) range by Wednesday. Combined with a strong subsidence
inversion limiting cloud cover and winds will lead to good
radiational cooling each morning through Thursday. Temps are expected
to at least touch freezing across much of the area on Tuesday
morning, but fall into the mid/upper 20s on Wednesday morning. Lows
moderate a bit Thursday, dropping into the upper 20s/low 30s. Will
continue to monitor the trends over the next few days for the
potential of freezing warnings for the middle part of next week.
Transition to the pattern occurs Thursday afternoon as deep layer
ridging begins to shift south and east ahead of a developing system
over the central plains. Temps and moisture will rebound quickly on
Friday, but rain chances at the moment hold off through the tailend
of the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 446 PM CST Sat Mar 10 2018
Ceilings of ~025agl (MVFR) are likely at KMSL through 03Z before
lowering to around 010agl (IFR). Initially, ceilings at KHSV are a
bit more uncertain, so have gone with a scattered layer at 025agl
with broken ceilings of 040agl and above through 03Z. Isolated to
scattered light showers will remain possible this evening, becoming
widespread by 06-07Z. The heavier rains and lower visibility will
remain mainly south of the KHSV and KMSL areas. The shower activity
will diminish in coverage Sunday morning, but ceilings should remain
around 020-030agl through the day. Easterly flow of 3-5kt is expected
tonight, turning more southerly on Sunday in advance of an
approaching cold front.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...17
SHORT TERM...JMS
LONG TERM...Barron
AVIATION...17
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Wichita KS
528 PM CST Sat Mar 10 2018
.SHORT TERM...(This evening through Tuesday night)
Issued at 236 PM CST Sat Mar 10 2018
A strong PV anomaly located over wrn SD will help push a cold front
south across the forecast area late this afternoon or early this
evening. Latest hi-res model solutions, do show some post frontal
FN-convergence as the this front pushes south, but low level
moisture south of the front is lacking for a widespread shower
chance as this front pushes south. Still think a few widely
scattered post frontal showers will push south as the front
progresses into areas east of the Flint Hills for the evening hours.
So will keep a low pop around for this chance. Latest RAP and HRR
seem to support a few showers, but precip amounts from SREF plumes
only suggest a few hundredths, when it comes to QPF amounts.
Cooler drier air will be the main story overnight into Sun, as a
Canadian ridge of high pressure drops south over the plains for
Sunday. The main PV anomaly will push into NW MO early on Sun,
which may lead to some very light showers for areas NE of the
forecast area on Sun morning.
Otherwise, expect temps closer to seasonal normals on Sun with highs
in the upper 40s to lower 50s and mins in the mid to upper 20s.
Below normal temperatures and dry weather conditions will prevail
for the beginning of the week, as northerly flow drives Canadian air
south across the Central Plains.
Ketcham
.LONG TERM...(Wednesday through Saturday)
Issued at 236 PM CST Sat Mar 10 2018
A mid/upper ridge is progged to build across the Central plains
toward the middle to the end of the week bringing a warming trend
with rising temperatures. A return to breezy south winds from a
developing lee side trough and a tightening pressure gradient will
lead to increasing and elevated fire weather concerns for Wed and
especially Thu. (see the fire weather section below).
Medium range models suggest that another light precip chance may
return for the end of the week, but models differ on the timing and
strength of this system.
Ketcham
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 527 PM CST Sat Mar 10 2018
VFR conditions continue to dominate the region this afternoon and
evening. A cold front will be moving through the region during
the evening hours tonight. Unfortunately, there will be little
moisture with this front. There is a chance for some brief showers
here and there but this is not expected to amount to much and is
not expected to bring conditions below VFR. As such, VFR
conditions are expected through out the TAF period.
Metzger
&&
.FIRE WEATHER...
Issued at 236 PM CST Sat Mar 10 2018
Breezy north winds and a very dry atmosphere will lead the grassland
fire danger climbing back into the very high category for Sunday
afternoon. North winds of 20 to 25 mph are possible with relative
humidity values falling to around 30-35 percent.
Later in the week, above normal temperatures, low relative humidity
values and breezy south winds will bring elevated fire weather
concerns to the area by Wed and especially Thu. Very high to
possibly extreme grassland fire danger values will be possible.
Ketcham
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 36 51 27 54 / 20 0 0 0
Hutchinson 34 49 24 53 / 20 0 0 0
Newton 33 48 25 52 / 20 0 0 0
ElDorado 35 49 28 53 / 20 0 0 0
Winfield-KWLD 37 52 28 54 / 20 0 0 0
Russell 31 49 22 55 / 10 0 0 0
Great Bend 31 49 21 54 / 10 0 0 0
Salina 34 49 24 53 / 20 0 0 0
McPherson 33 48 23 53 / 20 0 0 0
Coffeyville 39 50 31 53 / 20 0 0 0
Chanute 37 48 29 52 / 20 0 0 0
Iola 36 46 29 51 / 20 10 0 0
Parsons-KPPF 38 49 30 52 / 20 0 0 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Ketcham
LONG TERM...Ketcham
AVIATION...ELM
FIRE WEATHER...Ketcham
Area Forecast Discussion
National Weather Service Lincoln IL
856 PM CST Sat Mar 10 2018
.UPDATE...
Issued at 850 PM CST Sat Mar 10 2018
The latest water vapor loop imagery indicates a compact shortwave
over southern Nebraska this evening tracking south-southeast.
The initial band of light precipitation associated with weak
isentropic lift was tracking east across northern Missouri with
most of the the returns seen on radar not getting to the ground
due to the dry easterly flow ahead of the upper wave. However, as
the lift gradually increases towards Midnight, we could see a band
of light rain and snow develop over our far west and southwest
counties as is currently indicated in the ZFP. No significant
changes with the first model run this evening as the latest NAM
indicates the Nebraska upper wave will track southeast across
central Missouri by Noon tomorrow with the better lift remaining
west southwest of our area. The better threat for light snow will
be over far west central and southwest Illinois tomorrow morning
before the upper wave shifts further to our south. Have made only
minor adjustments to the grids, mainly addressing the early
evening temperature trends. Otherwise, the late evening and
overnight forecast trends are in good shape, as a result, no ZFP
update will be needed at this time.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 250 PM CST Sat Mar 10 2018
Mid/high clouds are on the increase across central Illinois this
afternoon in advance of the next approaching system. 2015z/215pm
water vapor imagery shows vigorous short-wave trough over western
Nebraska. Based on the strength and S/SE track of the wave, it
appears most of its influence will remain W/SW of the KILX CWA
tonight into Sunday. 12z Mar 10 models have adjusted the track of
the 500mb vort max westward accordingly, focusing the strongest
lift and therefore maximum precipitation along/west of the
Mississippi River. In the immediate short-term, the NAM continues
to suggest weak isentropic lift will produce a band of light
precip across northern Missouri into west-central Illinois as
early as mid to late evening. Given very dry E/NE boundary layer
flow preceding the system, think this may be too aggressive.
Prefer the drier solution shown by the HRRR and HREF. As a result,
opted to go dry across the board through midnight. As the wave
nears, most models show light precip breaking out across the W/SW
overnight into Sunday morning. Have featured highest PoPs
along/southwest of a Rushville to Jacksonville line...with slight
chance PoPs as far east as a Galesburg...to Springfield...to Flora
line. With lows dropping into the lower 30s, any precip overnight
will mainly be in the form of light snow.
As the short-wave tracks through Missouri on Sunday, the highest
PoPs will continue to be focused across the SW CWA around
Winchester and Jacksonville...with dry weather anticipated
along/north of a Peoria to Mattoon line. Thermal profiles will be
cold enough to support snow in the morning, but will warm
sufficiently for a change to all rain during the afternoon as high
temperatures climb into the upper 30s and lower 40s. Snowfall
amounts have been scaled back across central Illinois, with around
1 inch of wet snow expected along/west of a Rushville to
Winchester line.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 250 PM CST Sat Mar 10 2018
Once the short-wave exits the region, central Illinois will be
dominated by a prevailing upper trough centered over eastern
Canada. This will ensure cool conditions through mid-week before
heights begin to rise and a warming trend gets underway by
Thursday. The coolest day of the forecast period will be Tuesday
when a short-wave trough rotating around the parent low brings the
lowest upper heights and perhaps some cloud cover. High
temperatures will only be in the upper 30s to around 40 degrees
with overnight lows in the 20s.
Once the eastern Canada trough lifts northeastward and ridging
builds into the Midwest, temperatures will climb back above normal
into the upper 50s and lower 60s by Friday/Saturday. Rain chances
will return to the region as well, as most models suggest a
developing warm front will bring scattered showers to central
Illinois as early as Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 502 PM CST Sat Mar 10 2018
VFR conditions are expected across the forecast area during this
period. A weather system tracking southeast across the Plains late
tonight will spread rain and snow into northern Missouri and far
west central Illinois late tonight. SPI will be on the edge of the
precip. after 04z so will continue to hold with the VCSH at this
time. Otherwise, a dry easterly flow will retard the eastward push
of the precipitation late tonight into Sunday morning with the
bulk of the heavier rain and snow remaining west and south of the
TAF sites. East winds tonight at around 10 kts with an east to
northeast flow expected on Sunday with speeds again around 10 kts.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Smith
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Smith
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
742 PM PST Sat Mar 10 2018
.SYNOPSIS...10/710 PM.
A series of storm systems moving over the region will bring a
cooler and wetter than normal weather pattern through much of
this week. A break in the rainfall is possible late Sunday and
into Monday, then another storm will move in. A stronger and
colder storm system is possible for late this week.
&&
.SHORT TERM (SAT-TUE)...10/741 PM.
...UPDATE...
The storm is behaving itself and light rain has fallen over most
of the area for most of the day. Almost all of the coasts and vlys
have seen between .4 and .6 of an inch rain. The big exception is
the LA coastal plain which has only received about two tenths of
an inch. As expected with a moist low layer situation the rain
totals are much less inland. Maximum rainfall rates so far have
been a benign .2 to .4 in/hr, but have recently bumped up to a
half inch per hour with the strongest showers associated with the
front.
The trof that is providing all of the lift of this system is just
to the west of Pt Conception. The rain completely collapses in the
NVA region behind the trof axis. The rain will taper off across
SLO and SBA counties this evening then VTA county around midnight.
The rain will likely linger longer over LA county and off and on
again rain should continue until just past dawn on Sunday morning.
Most areas will likely see another quarter to half inch of rain.
New NAM does not show much in the way of rain from late Sunday
morning through Tuesday.
Will issue an update and reduce pops for many areas over the next
36 hours.
***From Previous Discussion***
Light rain was falling in most areas this morning as expected. A
plume of sub-tropical moisture from Hawaii has made it over into
Southern California. This SW flow will bring stratiform light to
moderate rain across the region today through late this evening.
Some fog has developed along some coastal areas this afternoon due
to the high dew-points. Rain will turn to light showers after
midnight, mainly across the southern portion of the forecast area.
Although there is no convective dynamics with this fetch of
moisture, the warm air mass (Pineapple Express) will be able to
hold more water content. In fact GOES Sat Blended Total
Precipitation Water indicated 1.4" to 1.6" PWAT values within the
atmosphere just off the southern California Coast. This should
make for an efficient rain maker across the higher terrain as
orographic lift should act like a sponge and cause the higher
rainfall totals to the higher terrain of the Santa Ynez Range as
well as the Ventura and Los Angeles County Mountains over the next
12 hours. Snow levels will remain well above resort levels with
this system.
Both the NAM- WRF, and HRRR high res models continue to show
lower overall precip totals through Sunday afternoon, but models
usually have a tough time resolving warmer sub-tropical events
across SO Cal that come out of the southwest. Expect anywhere
between 1 to 2 inches across the higher favored south facing
terrain, with isolated amounts to 2.5 inches possible. Expecting a
third to three quarters of an inch across most coast and valleys.
ALthough the rainfall totals sound high, the hourly rainfall
rates should remain below half inch hour rates due to the
stratiform nature of the rain. Coast and valleys should see
rainfall rates ranging between 0.10" to 0.20" with 0.20" to 0.40"
per hour rates in the foothills and coastal slopes. There is a
20% chance that some south facing slopes could reach the critical
USGS threshold for debris flows, either 0.50" in 1 hour or 1.00"
in 3 hours. However, mostly thinking this steady light to moderate
rainfall will be beneficial to the hillsides, as long as there
are no intense bursts of rainfall which we are not anticipating.
Models are indicting a shortwave ridge setting up on Sunday and
the early part of Monday behind the exiting mositure plume and
ahead of another cold and strong upper low starting to dive south
across the Ern Pac. There could be a few light showers lingering
into L.A. County tomorrow, but most places should see drying and
partly cloudy skies by the afternoon. High temps should be around
5 degrees warmer in most areas to bring high temps around normal
for this time of year, but this will be short lived.
For Monday, another shortwave embedded in the flow at the base of
the upper low will swing another frontal boundary of rain into
the forecast area by Monday afternoon. Most of the rain will
remain off the coast, but a few showers are expected with no
issues expected for the recent burn areas. Showers should hold
together over night into Tuesday night. Again, not seeing any high
rainfall rates with this band of showers. The best storm dynamics
will remain well to the north. For Tuesday, The European Model is
bit faster in pushing a weak secondary frontal boundary over the
region, while the GFS is about 5 to 12 hours slower. Nevertheless,
both keep the best chance of rain N of Point Conception but a few
light showers will be possible for areas to the south. Highs both
Monday and Tuesday should remain about normal for this time of
year.
.LONG TERM (WED-SAT)...10/213 PM.
It will continue to be an active weather pattern through the
extended period Wednesday-Saturday. Synoptically, Both the GFS
and European Models are in good agreement with the placement of
the upper lows and troughs, but timing is off 6-12 hours with the
GFS a bit more progressive. A 525 DM low situated a few hundred
miles off the Cal/Ore coast on Wednesday will begin to rotate
further south close to San Francisco by Thursday afternoon. The
upper low will then pivot south over the SoCal bight on Saturday.
The affects for the forecast area on Wednesday will be some warm
frontal light rain approaching the Central Coast, then spread
southeast across the entire forecast area by Wednesday evening.
Not expecting any issues with recent burn areas.
Models then advertise another slug of moisture on Thursday, with
much better storm dynamics. The atmosphere will become more
unstable by Thursday evening into Friday as the upper low sits
just off the Central Coast. There are some timing differences, but
hopefully will be resolved with later model runs. The convective
nature of the Thu/Fri storm could bring some potential for high
rainfall rates. Mud and debris flows could be an issue for the
recent burn areas if this is the case and the models stay on
track. Another impact could be falling rocks and boulders on some
canyon highways with the heavy rains expected.
Models begin to differ as the GFS shows the upper low filling in
over the SoCal bight on Saturday, while the ECMWF keeps the low
cutoff over the SoCal Bight and keeps most of the forecast under
rainy conditions with the potential for thunderstorms. Snow levels
also expected to be lower with this system as well. it will
remain a wet and cooler than normal pattern from Wed night through
Saturday. At this time Thursday evening into Friday likely the
strongest part of the storm.
&&
.AVIATION...11/0016Z.
At 2340Z at KLAX, there was no marine layer and no sfc based
inversion.
Low confidence in all TAFs. Cigs and vis will change frequently
through 12Z. Rain will taper to showers and then end from 03Z-15Z
with the LA county area seeing the showers last the latest. There
is a 30 percent chc of VFR conds after 20Z Sunday at sites with
MVFR conds forecast.
KLAX...low confidence in TAF. Cigs and Vis will vary frequently
through 18Z. IFR conds will be the most likely. There is a 30
percent chc of VFR conds after 21Z. Good confidence that the
east wind component will remain under 8kt.
KBUR...low confidence in TAF. Cigs and Vis will vary frequently
through 18Z. LIFR/IFR conds will be the most likely. There is a
30 percent chc of VFR conds after 21Z.
&&
.MARINE...10/1007 AM.
Moderate confidence in the forecast. There is a 50% chance that
SE to S winds will reach SCA levels on Monday through Monday night,
mainly across the northern two thirds of the outer waters and
across the northern inner waters.
Otherwise, SCA conds are not expected through Tuesday.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
.HAZARD POTENTIAL OUTLOOK (TUE-SAT).
Periods of moderate to heavy rain possible next Thursday and
Friday with a possibility of mud and debris flows near burn
areas. Significant snow accumulations possible in the mountains
creating hazardous driving conditions.
&&
$$
PUBLIC...Kaplan
AVIATION...Rorke
MARINE...Sweet
SYNOPSIS...Hall
weather.gov/losangeles
Area Forecast Discussion
National Weather Service Melbourne FL
1030 PM EST Sat Mar 10 2018
.DISCUSSION...
Tonight...Mid level short wave trough will push east of the FL
peninsula overnight. Strong divergence aloft within RR quadrant of
upper jet will also shift east, so expect the precipitation to end
in the next couple/few hours and the considerable high cloudiness to
decrease. But do not expect clear skies as sct-bkn stratocumulus
should develop and lift N/NE. Noticeably milder tonight as deep
layer S/SW flow develops. Do not expect any fog but some (low)
stratus is possible over the interior toward morning. Min temps
generally in the upper 50s/lower 60s.
Sunday (modified)...A rather broad and messy area of low pressure
over the SE CONUS will try to consolidate somewhat as several pieces
of energy move through the base of a digging mid level trough, the
southern-most of which drops into north Florida and the NE GOMEX by
sunset. Surface-low level flow will start off southerly and veer
more to the SW during the afternoon. With respect to precip chances,
ECFL will start the day behind the weak short wave, thus the local
ascent profile should be neutral early, then improve by mid day and
during peak diurnal heating in the afternoon. Thus, expect a mostly
diurnally driven precip regime with sea breeze showers and a small
chance for TS. Highest rain chances are expected across the south,
with forecast POPs (50-60) are a little above the MAV (30-50) but
quite a bit lower than the ECS (70-90).
Increasing mean layer wind fields late could lead to some convective
gusts in showers and especially any TS which form. Max temps in L80s.
&&
.AVIATION...
Mainly VFR. Patchy -SHRA will diminish overnight but scattered SHRA
should push back in from the W/SW Sunday morning with isolated TSRA
possible in the afternoon.
&&
.MARINE...
Tonight-Sunday...A temporary surge of south winds this evening is
producing a period of Caution conditions as a psuedo warm front
lifts north across the area. Expect the south winds to decrease 10
to 15 knots shortly and continue Sunday. Seas generally 3-4FT.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 58 79 63 74 / 20 50 40 50
MCO 60 83 66 77 / 30 60 30 50
MLB 63 82 67 78 / 40 60 30 50
VRB 62 82 66 80 / 50 60 30 50
LEE 60 83 65 73 / 20 50 40 50
SFB 59 81 64 75 / 20 50 40 50
ORL 61 82 66 77 / 20 60 30 50
FPR 62 83 66 80 / 50 60 30 50
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Kelly/Weitlich
Area Forecast Discussion
National Weather Service Nashville TN
755 PM CST Sat Mar 10 2018
.DISCUSSION...
As models continue to show the possibility for a quick shot of
measurable snowfall over parts of northern and eastern Middle
Tennessee late Sunday night and early Monday, have decided to
issue an SPS for those areas. Some spots could pick up a quick one
half to one inch, especially in areas from the Highland Rim,
north of Nashville, over toward Lafayette, Smithville and the
Cumberland Plateau. Some isolated higher amounts are possible,
especially over the extreme northeast, around Jamestown,
Livingston, Byrdstown and Celina.
There is still some uncertainly regarding how fast the boundary
layer will cool late Sunday night and early Monday, and it`s
possible we might only be looking at a favorable window of a few
hours for snow accumulation. However, this time of year, even a
few hours of light to moderate snowfall can lay down an inch or
so.
If confidence for measurable snow increases further later tonight
or Sunday, a snow advisory may be needed for part of our forecast
area.
Otherwise, as far as the overnight forecast is concerned, it still
looks like the chance for showers and isolated thunderstorms will
increase, with PoPs over south increasing to likely or categorical
after 06z.
&&
.AVIATION...
00Z TAF DISCUSSION.
BNA/MQY/CKV/CSV...VFR conditions are in place across most of
Middle Tennessee late this afternoon, in spite of the widespread
clouds. Ceilings at CSV have just dropped to MVFR, and will
likely stay that way for the duration of the TAF. Very few showers
are occurring at present, and the HRRR indicates very little
additional activity this evening and overnight. As a low center
passes just to our south tomorrow, look for more widespread
development, particularly after 18Z, with ceiling heights coming
down as deeper moisture advects into the mid state.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 46 58 35 52 31 / 40 70 70 10 0
Clarksville 43 56 32 50 30 / 30 80 70 0 0
Crossville 42 53 31 44 27 / 50 70 80 20 10
Columbia 47 59 34 51 30 / 60 60 60 0 0
Lawrenceburg 47 60 34 51 30 / 70 60 60 10 0
Waverly 46 57 33 51 31 / 40 80 60 0 0
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......19
AVIATION........08
Area Forecast Discussion
National Weather Service Phoenix AZ
855 PM MST Sat Mar 10 2018
.SYNOPSIS...
A weak, but moist weather disturbance will move away from the area
Sunday morning, however not before yielding light rain to much of
Arizona tonight. High pressure and partial clearing will spread into
the region during the first half of next week before a more
substantial weather system brings much better chances for rain and
cooler conditions late next week.
&&
.DISCUSSION...
Early this evening, a Pacific short wave was still located just off
the southern CA coast, poised to move inland and across Arizona
later tonight and into the day Sunday. Ahead of the wave, very moist
westerly flow aloft was present with embedded bands of light
showers. PWAT has climbed to nearly 1 inch at Tucson, and surface
dewpoints over the central deserts at 8 pm were mostly in the lower
50s with a value as high as 60 at Blythe. IR imagery showed copious
amounts of clouds across the area with sky coverage nearly 100
percent opaque area-wide. Earlier today this event looked to be the
"high-POP low-QPF" type event with widespread coverage of rains that
mostly measured 0.10 or lower over the lower central deserts. So far
the rains haven`t really materialized: latest 6 hourly rain gage
reports from the MCFCD network show only a few gages with 0.04 or
higher and most gages show nothing. We`ve mainly seen lots of
clouds, areas of virga and sprinkles with little measurable.
This is partly due to the weak forcing/UVV associated with this
short wave and also due to the atmosphere continuing to wet up from
above. The trof axis is not forecast to move into central Arizona
til later tonight and some hi-res models such as the HRRR and NMM6km
still suggest that showers/light rain will again materialize after
midnight as the wave approaches. As such, we actually beefed up our
POPs a bit over the southwest and south central Arizona in the 6-12Z
time frame. If the rains do not later materialize this will prove to
be more of a "nothing" event in terms of rain coverage, just lots of
clouds with little to show for it. Time will tell. Forecasts have
been updated and look to be OK for now.
.PREVIOUS DISCUSSION...
Afternoon WV imagery shows a pronounced fetch of thick
midtropospheric subtropical moisture surging through the east
Pacific basin (essentially emanating west of the Hawaiian Islands)
into the SW Conus. 12Z KNKX sounding data sampled a deep saturated
layer above the H7 level and healthy 7 g/kg amounts in the H9-H8
layer. A portion of this unseasonably high PWAT (over 1 inch sampled
which would be record levels inland) was translating into the
forecast area this afternoon with models indicating very healthy
theta-e advection. A notable shortwave was also being sheared
eastward towards the southern California coast which will act to
increase weak ascent through the remainder of the day and overnight.
A large shield of radar echoes can already been seen on the regional
scope; though with dewpoints in the eastern half of the CWA still in
the lower 30s, the majority of the leading edge of this activity is
merely going into saturating the lower atmosphere. Even over SE
California, this light rain has been little more than wetting the
ground with only a few hundredths reported so far. However as
thicker moisture propagates eastward, saturation will accelerate and
just about all available model guidance shows light rain/sprinkles
enveloping the remainder of the forecast area by this evening. With
somewhat better moisture advection and stronger ascent than had been
modeled in the previous days, SREF means for lower elevations show
around 0.10 inches quite possible tonight, while upslope and higher
terrain communities could even see 0.25 inches.
As the shortwave crosses northern AZ Sunday morning, favorable
ascent fields will also shift into eastern AZ and New Mexico. Any
lingering showers will have exited the bulk of the Phoenix metro by
sunrise and only some of the upslope and higher terrain areas of
eastern Maricopa and Gila counties would expect to see rain for the
rest of the daylight hours. However, this system is unlike most
winter/early spring storms insomuch as no cold air will be available
behind the shortwave, and skies will remain largely cloudy given the
continued stream of Pacific upper level moisture.
High pressure will rapidly build back into the region Monday with
high temperatures rebounding back into the 80s. By Tuesday, a deep
Pacific low approaching the West Coast will begin to shift eastward
temporarily amplifying the ridge axis overhead, but also then
quickly pushing the ridge east on Wednesday. While the cooling will
not be abrupt, a gradual decrease in heights aloft will result in
temperatures falling back closer to the seasonal normal by Thursday.
Although there is little overall model spread late next week as the
Pacific low moves inland and begins to affect the Desert Southwest,
models do differ in overall moisture availability and timing of
rainfall. Rain chances are introduced into the forecast late next
Thursday with best chances falling on Friday. The deep low should
also bring in a decently cold airmass starting Friday, resulting in
highs dropping back into the 60s. Overall model consensus indicates
this will likely be the first of possibly two or three weather
systems through next weekend. How much beneficial rain and snow this
could bring is still to be determined.
&&
.AVIATION...
South-Central Arizona including KPHX, KIWA, and SDL:
Approaching Pacific short wave continued to spread considerable
clouds/moisture into the greater Phoenix area; CIGS are widespread
from 6-10k feet as of 8 pm but showers/light rain has really tapered
off. For the next few hours, through about 08z, expect just isolated
light rain and we`ve changed the TAFs to mention just VCSH instead
of -RA. Expect redevelopment of the rain after midnight and should
this occur, CIGs could drop to 4-5k feet at times with FEW-SCT decks
dropping as low as 2k feet. Expect clearing/drying trend after 14z
as the wave moves off to the east but we will likely see continued
lower CIGs into the afternoon, down in the 5-7k ballpark. Winds to
be on the light side, favoring the east/southeast rest of tonight
and during the morning Sunday before swinging back to the west.
Southeast California/Southwest Arizona including KIPL and KBLH:
Threat of showers over the western deserts is rather low tonight but
isolated showers or spotty light rain/virga is possible through
midnight. Should continue to see areas of CIGs in the 6-10k foot
range tonight into the morning on Sunday with decks scattering out
by mid morning. Winds will be on the light side next 24 hours at the
TAF sites, favoring the west at KIPL and eventually the
north/northwest at KBLH.
Aviation Discussion not updated for amended TAFs.
&&
.FIRE WEATHER...
Monday through Friday:
Minimum relative humidity values will stay at or above 20 percent
through Wednesday, dropping to near 15 percent on Thursday
afternoon, before another weather system brings additional moisture
back into the region on Friday. Fortunately, overnight recoveries
will be good to excellent throughout the week. There will be some
breeziness, especially in Southeast California, each afternoon.
However, stronger gusts up to 30 miles per hour will be widespread
across the entire region Wednesday and Thursday afternoons. Finally,
Friday looks to have a decent chance of rain for all areas.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
DISCUSSION...CB
PREVIOUS DISCUSSION...MO/Kuhlman
AVIATION...CB
FIRE WEATHER...Deemer
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
826 PM EST Sat Mar 10 2018
.UPDATE...
Evening IR satellite imagery is showing warming cloud tops
amongst the overcast skies, indicating that the large area
of light rain and showers from Interstate 4 south is
gradually dying. This weakening trend is expected to
continue, with the HRRR model showing mostly rain free
conditions by midnight, and then only isolated showers
expected for the rest of the overnight period.
The forecast looks on track overall, with another round of
showers or storms expected Sunday afternoon and evening
ahead of the next cold front which will pass through on
Monday. Only minor changes were needed for the evening
update.
&&
.AVIATION...
A large area of showers and light rain continues to move
east through the southern half of the Florida Peninsula,
with occasional MVFR or IFR visibilities and ceilings. These
showers are expected to gradually clear out through the
evening, with some MVFR and isolated IFR ceilings and
visibilities possible through the rest of the night and
towards sunrise. Conditions should generally improve to VFR
after sunrise, but another area of rain is forecast to move
in during the morning, and some areas of flight category
restrictions could linger through the morning.
&&
.MARINE...
Light showers continue to move east through the eastern
Gulf of Mexico, generally south of Tampa Bay this evening.
These showers are continuing to weaken, and are largely
expected to clear out by midnight tonight, although isolated
showers will still be possible through the rest of the
overnight period. Another area of showers and a few storms
will be possible Sunday afternoon through Monday ahead of a
cold front that will move south through the waters
throughout the day on Monday. Winds will increase along and
behind the front with widespread cautionary to advisory
conditions expected Monday and Monday night. High pressure
will then fill in Tuesday through the rest of the week, with
lighter winds and seas.
&&
.Preliminary Point Temps/PoPs...
TPA 62 77 66 72 / 40 50 40 60
FMY 63 80 69 76 / 80 50 30 50
GIF 60 81 65 75 / 30 60 30 60
SRQ 63 75 67 72 / 50 50 30 60
BKV 57 79 63 72 / 30 50 40 60
SPG 62 78 66 73 / 40 50 40 60
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
UPDATE/AVIATION/MARINE...18/Fleming
UPPER AIR...57/McMichael
DECISION SUPPORT...57/McMichael
Area Forecast Discussion
National Weather Service Tucson AZ
315 PM MST Sat Mar 10 2018
.SYNOPSIS...Widespread showers will occur this evening followed by
decreasing coverage of showers late tonight and especially Sunday.
Most rainfall amounts will be quite light with snow levels above
most mountain peaks. A few showers may linger Monday mainly across
the White Mountains, then dry conditions return Tuesday into
Thursday. A colder system will bring a chance of valley rain and
mountain snow by next weekend.
&&
.DISCUSSION...KEMX WSR-88D detected scattered 30-40 dBZ echoes
mainly in an area from the Tohono O`odham Nation southeastward into
western/central Santa Cruz County at this time. These echoes were
moving eastward generally around 10-15 mph. IR/water vapor satellite
imagery depicted an extensive area of colder-topped clouds
representing subtropical moisture extending from Arizona/southeast
California well southwestward to between 130W-140W and between 20N-
30N. This fetch of moisture will provide widespread showers across
southeast Arizona this evening.
If the high resolution models such as the HRRR and the Univ of AZ
WRF-NAM and WRF-GFS are reality, showers should decrease in coverage
especially from about 10 pm MST or so and during the late night
hours. At any rate, for this forecast issuance have maintained
numerous showers across much of this forecast area this evening,
then coverage decreasing to scattered showers mainly from Tucson
eastward by around daybreak Sunday. Scattered showers will continue
Sunday afternoon mainly across the White Mountains. There appears to
be enough residual moisture to maintain a slight chance of showers
across the White Mountains Monday.
For this short-term precip event, appears that generally less than
0.10 inch of rainfall for the valleys, and 0.10 - 0.50 inch across
the mountains. Snow levels will mostly be above mountain tops,
although 1-3 inches of snow may accumulate across the highest peaks
of the White Mountains.
Various NWP models then depict the bulk of deeper moisture to be
south of the area Monday night and through at least the middle of
the upcoming week. Thus, have opted for precip-free conditions area-
wide Monday night through Thursday. Thereafter, the focus of
attention will turn toward a deepening upper trough/closed upper low
near the northern California coast Friday. The 10/12Z GFS has
trended slower with the onset of precip versus previous GFS
solutions, as is now closer to several ECMWF solutions. This
translates into reduced PoPs for Friday, essentially a slight chance
of showers mainly west-to-north of Tucson. A chance of valley rain
and mountain snow showers now exists Friday night and especially
next Saturday.
Cooler temps will occur Sunday before a warming trend starts Monday
and continues through Wednesday. Increased moisture and precip
chances will translate into another cooling trend next Friday and
Saturday.
&&
.AVIATION...Valid thru 12/00Z.
Scattered to numerous -SHRA this evening then decreasing coverage of
-SHRA after about 11/06Z and into Sunday morning. Scattered -SHRA
Sunday afternoon limited mainly northeast of KSAD. MVFR conditions
to occur especially across higher terrain. Cloud decks lowering to
4k-8k ft AGL early this evening and continuing into Sunday
afternoon. Surface wind early this evening wly/nwly 8-18 kts with
gusts near 30 kts. The strongest speeds will be east to south of
KTUS. Surface wind variable in direction mainly less than 12 kts
after about 11/06Z and into Sunday afternoon. Aviation discussion
not updated for TAF amendments.
&&
.FIRE WEATHER...Widespread showers producing light rainfall amounts
this evening, then decreasing coverage of showers late tonight and
especially Sunday. A few showers may linger Monday across the White
Mountains. Otherwise, dry conditions Monday into Thursday.
Thereafter, a chance of valley rain and mountain snow exists as
early as Friday, but more likely by next Saturday. Winds will mainly
be less than 15 mph Sunday, then gusty east to southeast winds at
times Monday into early Tuesday. Less wind Wednesday followed by
gusty southwest afternoon winds Thursday through Saturday.
&&
.TWC WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
Francis
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