Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/30/18
Area Forecast Discussion
National Weather Service Birmingham AL
713 PM CDT Thu Mar 29 2018
.UPDATE...
For 00Z Aviation.
&&
.SHORT TERM...
Convective line was located just east of Heflin to Wadley to near
Fort Deposit late this afternoon. An extremely brief area of
rotation/velocity was displayed on radar near Marbury, where some
trees were blown down. Other than that, no reports of hail or wind
with this line.
Ahead of this convective line, surface temperatures jumped into
the 80s this afternoon. Surface based and Mixed Layer CAPE values
are limited and below 1000. Bulk Shear values are good with 0-1
and 0-3 SRH good enough for some rotation. There is an nice
theta-e axis ahead of the line but the theta-e advection is best
south near the coast. RAP analysis and forecast soundings indicate
a cap ahead of the line which is preventing any cellular activity
ahead of line. Not a great deal of cloud to ground lightning with
the activity either. With all this said, there is just enough to
advertise a small risk of severe storms into the early evening
hours for east and southeast counties. The main threat will be
damaging winds or a brief tornado. Bumped the time out to around
8 pm. If anything occurs, it will be very isolated.
75
Previous short-term discussion:
GOES-R water vapor imagery and global numerical model 500 mb
height fields remain in agreement with their placement of a deep
trough located over northeast Texas and east-central Oklahoma. To
our southeast, upper level ridging continues to be analyzed over
south Florida, west-central Cuba and much of the Bahamas.
Toward the surface, diffuse troughing continues to be depicted in
surface analyses from central Texas northeast into the central
and northern Ohio River Valley. Convection from overnight and into
this morning has produced a cold pool and an extensive outflow
boundary from southern Tennessee southwest into eastern Louisiana.
This activity continues to advance eastward into northwest and
western Alabama, providing a focus for convective development.
This activity so far has remained below strong and severe storm limits
and lightning activity has been minimal. However, lightning activity
has been increasing over the past few hours across southeast Mississippi
and into interior southwest Alabama.
We performed a special 18Z balloon sounding that featured a
subsidence inversion around 700 mb that was acting as a cap to
limit the release of convective available potential energy (CAPE).
CAPE values were meager with around 360 J/kg with the bulk of that
instability residing below the cap. Observed winds have increased
since the 12Z sounding with near southerly flow at the surface
veering to the southwest generally above 700 mb. Wind speeds were
light near the surface and gradually increases to around 50 kts
around 750 mb. Wind shear is sufficient for rotating storms and we
continue with a non-zero tornado threat. The cap observed in the
sounding is limiting the release of instability but surface
observation data shows temperature readings are approaching 80
degrees across our far southeast counties.
We will continue to monitor convective trends and the severe
weather potential will continue across our south-central,
southeast and east-central counties this afternoon and into early
evening.
05
.LONG TERM...
Friday through Wednesday.
Surface ridging builds in over Eastern Conus behind the front on
Friday with cooler overnight lows in store for Central Alabama for
Friday night with skies clearing. The cooler readings don`t last
though with a moderating trend expected for the second half of the
weekend. A surface low over the Upper Midwest early Saturday is
expected to scoot to the east-northeast by Sunday. This will in
turn put the squeeze on our Eastern Conus ridge, weakening it,
pushing it southeast, and elongating it from the Western Atlantic
and into the Southeast U.S. This low will drag another front
southeast toward the Deep South with a ridge building over the
Upper Plains. However, with zonal flow setting up in the upper
levels, the front is expected to stall Sunday as the main surface
low pulls away.
Although the front approaching should help to bring some low rain
chances back to the far north for Sunday and Monday, the lower
levels will not get much recovery across Central Alabama until
Tuesday when onshore flow returns. Also by Tuesday, we should see
the upper flow become southwest oriented as weak upper troughing
sets up across Western Conus that should kick some upper
shortwaves to interact with our stalled front. Decent rain chances
will return Tuesday for all as a result. Higher rain chances
continue into Wednesday when we may have just enough west-
northwest flow develop as the upper trough moves eastward across
Conus to nudge the front south of the area. The GFS has a stronger
trough and is more progressive moving the upper system through
while the Euro is weaker and drags its feet to bring front through
and end precipitation.
08
&&
.AVIATION...
00Z TAF Discussion.
Pre-frontal convection was approaching TOI with stratiform rain
now at MGM/ANB. This rain area will continue east and southeast
with rain ending at TOI after 05z. The cold front was still
located well west of the area and after the rain ends, we will
still have a southerly wind component. Expect ceilings to
redevelop and MVFR between 05-08z, then some IFR from 08-15z.
Winds will begin veering to the west and then northwest through
the morning hours. This will produce ceiling rises and eventually
VFR after 16-19z. Some area may experience some patchy MVFR fog,
but have winds 4-6kts or more overnight.
75
&&
.FIRE WEATHER...
The best rain chances will be through this evening as a front
moves through the area. Fog and low clouds may develop again
tonight, with the lowest restrictions in the southeast or south
and east of the I-85 corridor. Drier conditions are expected by
Friday. There are no fire weather concerns at this time.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 52 66 40 71 46 / 50 10 0 0 0
Anniston 54 66 41 71 47 / 90 10 0 0 0
Birmingham 51 66 42 73 50 / 30 10 0 0 0
Tuscaloosa 52 69 43 73 49 / 20 10 0 0 0
Calera 52 68 44 72 49 / 30 10 0 0 0
Auburn 56 70 45 72 48 / 100 10 0 0 0
Montgomery 56 72 45 74 48 / 100 10 0 0 0
Troy 56 72 45 74 47 / 100 10 0 0 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Columbia SC
1023 PM EDT Thu Mar 29 2018
.SYNOPSIS...
The chance for showers will increase tonight and into Friday
morning ahead of a cold front. The cold front will move east of
the area Friday afternoon. The return of high pressure will
bring dry weather and mild temperatures for the weekend. Another
cold front will cross the area around the middle of next
week, bringing a chance for showers.
&&
.NEAR TERM /UNTIL 7 AM FRIDAY MORNING/...
Surface cold front is still be west of the area, but will be
approaching overnight. Models still consistent with keeping
conditions dry early tonight, then increase moisture and rain
chances closer midnight across the western counties just ahead
of the cold front. Line of showers should cross the forecast
area after midnight and into Friday morning. Cannot rule out an
isolated thunderstorm, but latest models showing instability is
weak, and confidence not high enough to mention in the forecast.
Rainfall should remain generally light to moderate, with qpf
amounts around 0.25 by 12Z, but the CSRA could see slightly
higher amounts. Overnight lows will only fall into the lower
60s.
&&
.SHORT TERM /7 AM FRIDAY MORNING THROUGH SUNDAY/...
An upper-level trough will lift northeast across the mid-Atlantic
and northeast U.S. Friday. A cold front will cross the area
Friday morning with moisture convergence and weak instability
ahead of the front. Ongoing showers at daybreak Friday will move
east of the area by midday. PWAT values 1.50 to 1.70 inches are
forecast to decrease during the afternoon. Have indicated
chance pops across the Piedmont Friday morning with likely pops
across the eastern Midlands. Total rainfall amounts are expected
be less than one half inch. Cannot rule out an isolated
thunderstorm. High temperatures will continue above normal...in
the mid and upper 70s.
Models consistent with keeping conditions dry Friday night
through Sunday as surface high pressure builds across the
region. Near normal temperatures in the low to mid 70s Saturday
will warm into the mid and upper 70s for Sunday. Nighttime lows
will be in the 40s.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Models indicate a progressive upper-level pattern during the
period. A cold front will sink southward into the area Sunday
night and Monday. Although the greatest chance for showers will
remain north of the area...have indicated low chance pops across
the north Midlands Sunday night and Monday. The frontal
boundary is forecast to lift north of the Midlands Monday night.
Greater rain chances enter the forecast Tuesday night and
Wednesday as another cold front crosses the region. The medium-
range models move the cold front offshore Wednesday night with
dry weather Thursday. Temperatures are forecast to remain at or
above normal.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
Expect a period of MVFR conditions in a band of showers ahead of
the cold front during the early morning hours. A strong low-
level jet will be associated with the front supporting low-level
wind shear during the early morning hours. It will be breezy
behind the front Friday.
Followed the GFS LAMP and HRRR for the timing of MVFR conditions
associated with a band of deeper moisture near the cold front.
There may be a period of IFR conditions in possible heavier
showers, but most of the guidance and upstream conditions
supported MVFR conditions. Forecast soundings indicated weak
instability with a diminished thunderstorm chance. There will
be a strong low-level jet associated with the front and with
diminished mixing because of the nocturnal timing believe low-
level wind shear will be an issue. Based on the NAM and the KCAE
88D VAD wind profile trends we included low-level wind shear
through the early morning hours. The GFS LAMP indicated gusts
15 to 20 knots behind the front later Friday morning and during
the afternoon.
EXTENDED AVIATION OUTLOOK...Widespread MVFR or IFR conditions
may occur Sunday night and Monday associated with a front in
the region. The front may shift north of the area by Tuesday but
a moist southerly flow in its wake may result in restrictions
mainly during the early morning hours.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99
Area Forecast Discussion
National Weather Service Charleston SC
1031 PM EDT Thu Mar 29 2018
.SYNOPSIS...
High pressure will weaken as it moves offshore through tonight.
A cold front will move through the area Friday and Friday night
followed by dry high pressure through Tuesday. Another cold
front could impact the area during the middle of next week
before high pressure returns late next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Late this evening: Regional radar imagery shows an impressive
band of showers and thunderstorms along a cold front, stretching
from western North Carolina across north Georgia to the far
western Florida panhandle. This band will steadily make eastward
progress through the night, though with a distinct weakening
trend expected as it runs into more stable air. The HRRR seems
to have a very good handle on this feature, and has been used
for much of the forecast details through sunrise. Current timing
forecast brings the band of showers into Jenkins County in the
4-5 am time period and to near the I-95 corridor by around
sunrise. Model soundings and the climatologically unfavorable
time do not provide much (if any) support for thunder, so it has
been removed from the forecast. However, the low level wind
field is still quite strong, so it won`t be surprising if these
showers are capable of producing some strong wind gusts. The
threat of severe weather though is very low given the
nonexistent instability. Low level wind fields will be too
strong for fog, but some low stratus could accompany the arrival
of the band of precipitation. Expect a very mild night with lows
in the low 60s.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
Friday: The band of showers should be right along the I-95
corridor around sunrise. However, the showers should be
weakening due to the lack of instability and the fact that the
primary shortwave energy in the mid/upper levels will be
dampening and exiting to the north and east of the forecast
area. Thunder has been removed from the forecast given the fact
that instability is virtually non-existent. Showers could still
produce some gusty winds thanks to the strong low level wind
fields. Precipitation should come to an end around midday and
the early afternoon as the showers move offshore. Thereafter, a
dry forecast is in place as winds become increasingly westerly
with time. Despite the cloud cover, highs are still forecast to
range around the mid 70s.
Cooler and drier air will filter into the area behind the front
through Saturday before warmer and more humid air returns for
the end of the weekend as high pressure moves offshore.
Temperatures will get back above normal by Sunday when it should
reach near 80 for most locales away from the coast.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A fairly quiet weather pattern is anticipated Monday and Tuesday as
high pressure over the western Atlantic favors dry and warm
conditions within a southerly sfc wind. In general, high temps will
approach the lower 80s away from the coast each day, while temps
remain in the lower 70s near the coast. The next best chance of
precip should arrive during the middle of next week with a cold
front that moves through the area Wednesday. Chances of showers are
possible over all areas. Dry and cooler high pressure should then
arrive behind the front, with high temps generally ranging in the
low/mid 70s during the second half of next week.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
VFR conditions will prevail through much of tonight. Then late
tonight/early Friday morning, a band of showers along a cold
front is expected to approach the terminals. Soundings and
guidance both show good chances for MVFR ceilings with this
feature, in addition to the showers. Have timed ceilings into
KCHS at 13z and at 11z at KSAV. The band of rainfall should be
diminished from its current appearance, but could still drop
visibilities when it moves through KCHS and KSAV. Added a TEMPO
group at both sites to account for lower MVFR conditions, but
don`t think that IFR will occur. The band of showers should move
east of the terminals by the early afternoon and VFR conditions
should return.
Extended Aviation Outlook: VFR.
&&
.MARINE...
Gusty winds have diminished in the Charleston Harbor and the
Small Craft Advisory has expired there. We also have continued
6 ft seas over outer portions of the offshore GA waters where a
SCA persists. With the strengthening southerly winds overnight,
some 6 ft seas are expected to reach the Charleston County
nearshore waters after midnight where we have a Small Craft
Advisory beginning.
Friday through Tuesday: A cold front will move through the waters
Friday into Friday night with high pressure returning and prevailing
into early next week. Elevated winds/seas are expected into Friday,
especially across the Charleston County waters and offshore GA
waters. Then conditions will settle briefly before deteriorating
again Friday night as the pressure gradient tightens with incoming
high pressure. Advisories will again be possible at least in the
same areas. Overall tranquil conditions then expected through early
next week, although sea fog will be possible starting Sunday as
moister air moves into the area.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 3 PM EDT Friday for AMZ374.
Small Craft Advisory until 11 AM EDT Friday for AMZ350.
&&
$$
NEAR TERM...BSH
SHORT TERM...BSH/RJB
LONG TERM...DPB
AVIATION...JRL/RJB
MARINE...JRL/RJB
Area Forecast Discussion
National Weather Service Peachtree City GA
920 PM EDT Thu Mar 29 2018
.UPDATE...
Strong line of showers with occasional embedded thunderstorms
continues to move through the forecast area without much fanfare.
Have seen some interesting signatures from time to time but
nothing worthy of warning on as of yet and no reports to speak of
either. Some weakening noted along initial squall portion of the
line but rain shield behind remains extensive with another 2 hours
or so of rain for areas once leading edge moves through. Timing
has been outstanding since last night with the hires models and
have basically loaded in the Hrrr for the next 6 hours of pops
grids in GFE. Also changed the temps to reflect a non-diurnal
pattern to temperature drop for the remainder of the evening.
Remainder of the forecast is on track and no additional changes
are planned.
Deese
&&
.PREV DISCUSSION... /issued 738 PM EDT Thu Mar 29 2018/
PREV DISCUSSION... /issued 241 PM EDT Thu Mar 29 2018/
SHORT TERM /Tonight through Friday Night/...
Pre-frontal trough/line of showers and thunderstorms has made some
eastward progress this afternoon and is now entering western
portions of AL. A secondary frontal boundary is currently situated
from the eastern Great Lakes back through the ARLATEX. Both features
will continue to push east overnight, with the pre-frontal trough
beginning to impact the NW portion of the CWFA before sunset.
Surface instability will be waning as the line moves through the
area, but shear values remain fairly impressive. Some mid level
support is likely, but lapse rates will remain marginal. So, a few
strong thunderstorms are likely, with an isolated severe storm
possible. Since the line is progged to weaken as it moves eastward,
the most likely area for strong/isolated severe thunderstorms is
mainly along and west of a line from Hiawassee to Eatonton to
Americus. Damaging wind gusts are still expected to be the primary
mode of severe weather. However, an isolated brief tornado is not
out of the question. Locally heavy rainfall will also create the
potential for ponding of water on roadways/low lying areas.
The secondary frontal boundary will bring the wind shift to the NW
during the day on Friday. Temps near normal are expected behind
Friday`s boundary.
NListemaa
LONG TERM /Saturday through Thursday/...
No major changes to the previous forecast. Surface high pressure
will be shifting off the east coast Saturday afternoon, ushering
in southerly flow across the region through the remainder of the
weekend. So yes folks, this means a very pleasant weekend is in
store...make it count! With the surface high off the SE coast by
Sunday night, this will enable a back-door front to sag south into
north GA. This will result in an increase potential for showers
across this area early Monday through Monday evening. This front
will eventually lift north as a warm front well ahead of the main
system/cold front which is progged to cross GA late Tuesday into
Wednesday. There continues to be model variability with the timing
of the front...GFS the quicker of the solutions (Tuesday night
through Wednesday morning) while ECMWF is a bit slower (Wednesday
morning through the evening hours). Given this 12-hour difference
in model guidance spread, have hedged...bringing the front
through mid-day Wednesday. If the ECM comes to fruition, crossing
north/central GA during the afternoon, we may then be dealing with
a higher probability of thunderstorm development. Although, it
should be noted that the overall extent of instability looks
minimal at this time. High pressure will build back into the area
late Wednesday into Thursday.
Temperatures are going to be around climo this weekend (highs in the
low 60s across far north GA to low 70s across central GA),
eventually rising well above normal ahead of the next front on
Wednesday. Temperatures on Tuesday will climb to around 80 in the
metro and mid 80s across southeast GA. Behind the front,
temperatures will sink back closer to climo for Thursday.
26
AVIATION...
00Z UPDATE...
As far as lines of storms are concerned, this one has been very
well behaved timing wise with models indicating a 00Z start time
for Atl for the last 24 hours. Looks to be just after that but
close considering and still anticipating same impacts with
occasional strong gusts and lightning. Large rain shield begins
the storms so may take awhile to shift east of the terminals. MVFR
to move in shortly behind initial squall and stay with us through
the overnight and most of the morning hours Friday. Winds to be
quite strong Friday afternoon and have included some 14G24kts.
//ATL CONFIDENCE...00Z UPDATE...
Medium on TSRA duration.
High on remaining elements.
Deese
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 57 71 41 70 / 80 20 0 0
Atlanta 55 66 42 69 / 100 10 0 0
Blairsville 51 59 33 64 / 100 10 5 0
Cartersville 52 63 38 68 / 100 10 0 0
Columbus 59 71 46 73 / 90 10 0 0
Gainesville 54 65 40 66 / 100 10 0 0
Macon 60 72 44 72 / 70 20 0 0
Rome 52 63 38 69 / 100 10 0 0
Peachtree City 55 68 40 70 / 100 10 0 0
Vidalia 64 74 48 74 / 70 60 0 0
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Deese
LONG TERM....Merritt
AVIATION...Deese
Area Forecast Discussion
National Weather Service Houston/Galveston TX
915 PM CDT Thu Mar 29 2018
.DISCUSSION...
A weak cold front was crossing the area and at 900 PM, the front
was located along a Jasper to Liberty to Giddings line. Some of
the short term guidance showed some potential for a few weak
showers along the boundary tonight but the upper flow is weakly
confluent and 00z soundings show a dry moisture profile with PW
values under an inch. That said, it looks like a line of weak
showers is trying to develop across hardin and Liberty counties.
Any precipitation that does develop will be light, spotty and
short lived. Cooler and drier air will filter into the region
behind the front and morning low temps should fall into the 50`s
inland, mid 60`s coast. Sunny skies are expected on Friday with
seasonal temperatures. Tweaked sky grids but the rest of the
forecast looks on track. 43
&&
.HYDROLOGY...
Canceled the flood warnings for Spring Creek, Davidson Creek
and Mound Creek earlier tonight. No change in status on other
area rivers. 43
.PREV DISCUSSION... /ISSUED 644 PM CDT Thu Mar 29 2018/
AVIATION...
VFR conditions on tap through the TAF period. A lingering FEW/SCT mid
level deck will continue to make its way off the coast overnight,
leaving behind high clouds. A cold front will continue to push
its way through the region this evening and winds will increase
out of the N/NE by the morning hours, with wind speeds between
7-12 kts inland and closer to 15kts along the coast at GLS. Winds
will subside and turn out of the NE by the afternoon and skies
will clear, as a region of high pressure pushes in from the
north.
Hathaway
PREV DISCUSSION... /ISSUED 353 PM CDT Thu Mar 29 2018/
DISCUSSION...
Mainly quiet and dry weather with temperatures rising to around 80
each day through the weekend. Also look for onshore winds to
return this weekend, boosting humidity and gradually bringing back
rain chances early next week. Best chances for rain next week will
come with the passage of a cold front.
NEAR TERM [Through Tonight]...
Skies have cleared across much of the area this afternoon, though
some trailing cirrus lingers along the Gulf coast, and a bit of
lower cloud north of College Station and Huntsville is gradually
scattering out. While dewpoints have mixed out some today, much
drier air hasn`t really pushed in, which may help lows tonight
from falling perhaps as far as they could. Drier air does look to
advect in just early enough that points well north of Houston
should still fall to near seasonal averages. Short range models
have been fairly insistent in sparking some showers overnight -
with the HRRR occasionally being pretty aggressive. This looks to
occur on what could be called a reinforcing cold front, and while
it is a plausible scenario, not so convinced we`ll actually see
measurable precip. Compromise by introducing some very low PoPs
and putting a chance of sprinkles in the weather grids.
SHORT TERM [Friday Through Saturday Night]...
Given recent rain, and in some places flooding, have tempered
highs just a little bit for tomorrow, holding temperatures in the
mid to upper 70s across Southeast Texas. Surface high pressure
looks to drift across the area, returning onshore flow to us by
Friday night or Saturday. Meanwhile, ridging just aloft should
build in around or just east of Galveston Bay. This should help
highs boost up to around 80 degrees to start the weekend, along
with gradually increasing dewpoints.
LONG TERM [Sunday Through Thursday]...
By Sunday, high pressure at the surface through 850 mb will be in
place to our east, along with a building 500 mb ridge over Mexico
and largely zonal flow (with just a small hint yet of northwest
flow) over us. While the pressures/heights aren`t quite there, the
qualitative appearance is...uncomfortably...close to summer.
Fortunately, the difference is enough that the end result looks to
be high temperatures just on the high side of seasonal averages.
The onshore flow will boost dewpoints, keeping overnight lows more
noticeably above that average. This may give the mornings a bit of
a hint of mugginess, but still well shy of the true summer dog
breath. Some of the guidance does start light showers as early as
Sunday, but will hold off until Monday for now as return flow
seems fairly modest at this point.
Finally, we`ll see change coming early next week. The GFS and Euro
are perhaps surprisingly similar in their upper pattern, but that
consensus breaks at the surface. The faster GFS brings the next
front through Tuesday night. On the slow end, the Euro waits later
into Wednesday to bring the front through. Both drop a quarter to
an inch of QPF with the front. However, with precipitable water
values coming up to 1.7 or 1.8 inches in the GFS, would not get
married to light totals just yet. Timing may also be important for
severe potential for available instability. Given the range and
scenarios posed by the guidance, predictability of specifics is
probably not wise at this point. Suffice to say, the front will
bring the best chance of rain for the next several days, and
determining its impact seems likely to be the main challenge of
the forecast going forward.
MARINE...
Light winds this afternoon with slowly subsiding seas...will extend
the SCA for the 20-60nm waters through 00z. Winds will become north
and northeast tonight as the cold front pushes off the coast around
3-5 am. SCA/SCEC conditions may develop in the wake of the front 13-
21z Friday. High pressure slides away quickly east and winds become
easterly late Friday. Saturday southeasterly flow sets up and
continues in the 5-15kt range through Monday. A s/w passing by to
the north will increase the gradient and SCA conditions should
return.
45
HYDROLOGY...
Minor to Moderate river flooding continues along the Trinity and
San Jacinto basins, as well as Lyons Creek in the Brazos River
basins. Minor to Major river flooding is still forecast over the
next several days. Latest rivers observations show runoff and
routed water responding well in many locations, giving more
confidence to the updated forecasts. Several changes were made
this afternoon to account for additional rises. Changes include
raising the Trinity River at Goodrich and Bedias Creek at
Madisonville to Major flood, the Trinity River at Riverside and
Moss Bluff to Moderate flood, and the Trinity River at Romayor to
Minor. Inundation of structures expected near Goodrich and Liberty
along the Trinity. Inundation of roads occurring and expected
along the Trinity and San Jacinto basins.
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 55 75 54 80 61 / 10 0 0 0 0
Houston (IAH) 58 78 54 79 62 / 10 0 0 0 0
Galveston (GLS) 64 74 64 74 68 / 0 0 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...Small Craft Advisory until 10 PM CDT this evening for the
following zones: Waters from Freeport to the Matagorda Ship
Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION until 4 AM CDT Friday for
the following zones: Waters from Freeport to the Matagorda
Ship Channel from 20 to 60 NM...Waters from High Island to
Freeport from 20 to 60 NM.
&&
$$
Discussion...43
Area Forecast Discussion
National Weather Service Indianapolis IN
1059 PM EDT Thu Mar 29 2018
.UPDATE...
The AVIATION Section has been updated below.
&&
.SYNOPSIS...
Issued at 227 PM EDT Thu Mar 29 2018
Low pressure will exit Indiana tonight...bringing a short break to
the rainy week. High pressure over the southern plains is then
expected to build across the Ohio Valley on Friday...bringing the
work week to an end on a dry and slightly warmer note.
A quick moving cold front is then expected to sweep across Indiana
on Saturday from the northern Plains. This will once again bring
showers back to the forecast for Saturday afternoon as the from
passes.
High pressure will then return to the are on Sunday...bringing
dry weather. The Active weather pattern will continue on Monday as
yet another front returns to the area from the southwest...along
with rain chances.
&&
.NEAR TERM /Tonight/...
Issued at 227 PM EDT Thu Mar 29 2018
Surface analysis early this shows a broad area of low pressure
stretching from NE Ohio to SE Indiana and SW to
Arkansas...straddling a frontal boundary. Water vapor imagery
shows a plume of tropical moisture stream in from East TExas into
the Ohio Valley ahead of a broad trough over the Central Plains.
Radar showed extensive rain showers stretching from Western
PA...scattered across Ohio to Indiana...KY and TN.
Models suggest the precipitation upstream will continue to push
across much of Central Indiana this Evening. Time heights show
favorable lift with good moisture and forecast soundings show good
saturation through the column through the evening hours. The GFS
and NAM suggest the upper trough axis to the west does not pivot
across Central Indiana until after 12Z Fri. Thus will keep high
chances for rain in the forecast this evening...given the
favorable dynamics remaining in place and the radar returns
upstream. HRRR suggest the precipitation band should begin to
drift east overnight...trending toward an end of the
precipitation. Forecast sounding do hint at some dry air within
the column overnight. Thus will trend pops lower overnight.
Given the expected clouds but cold air advection...will stick
close to the forecast builder blends on lows.
&&
.SHORT TERM /Friday through Sunday/...
Issued at 227 PM EDT Thu Mar 29 2018
THE GFS AND NAM suggest the NW flow aloft persists on Friday as
the the trough axis aloft shifts eastward. Models suggest
subsidence and High pressure developing in the back side of the
trough as a dry column is seen within the time heights and
forecast soundings. Models suggests surface high pressure in
place across the Tennessee and Kentucky river valleys. This looks
to persist through Friday Night as the High drifts east of Central
Indiana to the Virginias by Saturday morning. Thus will trend
toward a partly cloudy sky and blend on temps Friday and Friday
Night.
GFS and NAM suggest another short wave and associated cold front
pushing out of the upper midwest on Saturday. Models suggests
good lower level convergence and good moisture in place ahead of
the frontal boundary. Forecast soundings show saturation within
the lower levels. Thus will trend pops at or above the forecast
builder blends mainly during the afternoon and perhaps the early
evening hours on Saturday Night.
The quick NW flow looks to persist on Sunday night and
Monday...allowing the earlier cold front and associated dynamics
to quickly exit. Forecast soundings quickly trend toward a dry
column on Sunday Night and early monday. Thus will trend toward a
dry forecast at that time. However models are suggesting a return
of a warm front and mid level moisture arriving with warm air
advection on Monday afternoon. Confidence on this feature is low
at this time and will try trend toward a dry forecast for now.
&&
.LONG TERM /Sunday Night through Thursday/...
Issued at 235 PM EDT Thu Mar 29 2018
Models suggest a couple of frontal systems will impact the area
during the long term period, one a bit stronger early to mid week
and another much weaker later in the week. Vast majority of the
precipitation will be in the form of rain.
Temperatures will remain largely below normal during the period.
Blended initialization handled things relatively well and required
only few minor tweaks.
&&
.AVIATION /Discussion for the 30/03Z TAF Update/...
Issued at 1053 PM EDT Thu Mar 29 2018
Update...
MVFR conditions are prevailing at KIND.
Previous Discussion...
Widespread rain will continue to linger into the night. Conditions
are starting to trend more toward MVFR, but IFR category cannot be
completely ruled out, yet, as visibilities and ceilings still
fluctuate a bit. It won`t be until tomorrow morning when
conditions start trending toward the MVFR/VFR mark. Meanwhile,
winds will generally be northerly at 5 to 11 kts.
&&
.IND WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SYNOPSIS...Puma
NEAR TERM...Puma
SHORT TERM...Puma
LONG TERM...Nield
AVIATION...TDUD
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1025 PM EDT Thu Mar 29 2018
.UPDATE...
Issued at 1025 PM EDT THU MAR 29 2018
The steadier rains continue to progress east and out of watch
area. After calling around to the counties in the flood watch and
noting no problems have gone ahead and dropped the watch.
Additional showers will be possible through the night, but they
should not be substantial enough to result in any high water
issues. With this update have also removed the thunder threat and
fine tuned the temperatures per the latest guidance and obs. These
grids have been sent to the NDFD and web servers along with an
issuance of a fresh set of zones and new HWO.
UPDATE Issued at 730 PM EDT THU MAR 29 2018
23z sfc analysis shows low pressure moving through the central
Appalachians with a cold front to the west of the area. The bulk
of the rain from this looks to be passing through eastern
Kentucky currently with any additional rains overnight likely to
be light according to the HRRR and NAM12. Accordingly, will
probably cancel the Flood Watch early once the main rain area
departs over the next hour or so. Even so, higher returns and
heavier rains fell along and north of the Mountain Parkway earlier
this evening necessitating a flood advisory for those areas. This
runs through 9:30 pm. Would look to hold on to the Watch until
the flood advisory ends. Otherwise, temperatures are fairly
uniform across the JKL CWA - generally in the mid to upper 50s
along with similar dewpoints. Meanwhile, winds - which did gust to
over 30 mph along the earlier line of heavy showers - have
settled most places to between 5 and 10 mph from the south to
southwest with occasional gusts to 20 mph. Have updated the
forecast mainly to fine tune the PoPs and Wx through the night
along with a touch up to the T and Td grids per the latest
guidance and obs/trends. These updated grids have been sent to the
NDFD and web servers. An updated FFA will be issued shortly.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 254 PM EDT THU MAR 29 2018
Will continue with flood watch through 8 AM Friday in all current
counties. This continuation has been coordinated with neighboring
WFOS. Overall flood threat does not appear too great at this
point, but with rain on our doorstep and at least the potential
for a few thunderstorms this evening it is prudent to continue
with the watch. This will also be in good agreement with the
neighboring WFOs.
QPF from 18Z this afternoon through 12Z Friday is an inch or less
across the area. This would not cause problems as long as it is
spread out, but still have concern for a few thunderstorms.
Stability is not that great but it appears there will be a small
window from late afternoon into the evening where a few storms
could occur. SPC short range thunderstorm outlooks are all in the
10 to 40 percent range, and latest blended model guidance for this
evening is even less. There were some lightning strikes over
southern IL earlier today, but recently all strikes have been over
southern MS and southern AL. So the threat for thunderstorms is
low, but given saturated conditions if a thunderstorm was to
develop and drop heavy rain some localized flooding could occur.
Waves of low pressure have continued to ripple northeast along the
front to our west which has been nearly stationary. However with
the passage of one last wave this evening, the front will finally
move east across the forecast area tonight as a cold front. There
could be some lingering showers behind the front into Friday, but
the threat for significant rains will end with the frontal
passage tonight. Much cooler air will spread into the area for
Friday.
Cool high pressure will build into the OH valley by Friday
evening, with the high drifting east across the area overnight,
and ending up off to our east by 12Z Saturday. Based on the
synoptic set up we should see a ridge valley temperature
difference develop Friday night. This idea is supported by the
COOP MOS which has some lows into the upper 20s, which is colder
by several degrees than the model blend low temperature forecast
for Friday night. With all that in mind have introduced some
colder minimums for Friday night in valley locations, but have not
gone as cold as the MOS Guidance would suggest. Coordination with
the University of Kentucky Agricultural Weather Center has taken
place and based on their field reports frost/freeze headlines are
not yet needed here in eastern KY. As such there will not be any
headlines for any frost or freeze this weekend in our area. This
has also been coordinated with the neighboring WFOs. We will
continue to highlight the frost threat in the HWO and include
frost in the NDFD if need be. The University of Kentucky indicates
we`ll probably need to begin headlining frost/freeze events after
the first full week of April.
.LONG TERM...(Saturday through Thursday)
Issued at 319 PM EDT THU MAR 29 2018
The extended portion of the forecast will begin on Saturday with a
rather progressive upper level pattern in place over the country.
Persistent ridging over the western CONUS will lead to a broad
longwave trough over the central and eastern CONUS. A brief period
of high pressure will keep the area dry for much of the day on
Saturday. However, the progressive pattern mentioned will bring
another front in from the northwest. This will bring a chance of
showers late Saturday and lasting into Sunday morning. The
question that follows is the temperatures behind the front for
late Saturday night as some precip over the Bluegrass may mix with
snow. The ground however will likely be too warm for any
accumulation. The convective nature of the showers however will
likely mean getting snow as high as 35 degrees and mixing with a
bit higher.
The front pushes through the area by Sunday morning but ridging
over the southeastern CONUS causes the front to stall along the KY
and TN border becoming a stationary boundary for Sunday and
Monday. During this period, weak disturbances will lift north out
of the Gulf and across the TN valley bringing a continued chance
of showers through Monday. Surface temperatures are pretty warm
during this period but cant rule out a few flakes on the cold side
of the precip to the north in Bluegrass for Monday morning. By
Monday night into Tuesday, the next system develops and moves into
the OH Valley. Models suggest a well developed system as a
disturbance and decent surge of moisture lifts north out of the
Gulf combined with a strong shortwave passing to the north over
the Great Lakes region. This system will push a strong cold front
across the area by Tuesday night into Wednesday. This will look
top be another wet period in the forecast. Model soundings do hint
at some instability but the uncertainty too high to put in thunder
at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 810 PM EDT THU MAR 29 2018
A final wave of low pressure is moving northeast this evening with the
formerly stationary front finally beginning to push its way east.
this will pass across the forecast area tonight with winds
shifting from the southwest to the northwest. VFR or MVFR
conditions will hold for another couple of hours at most TAF sites
ahead of this boundary. However, in the wake of this current band
of showers (and potential thunderstorms), conditions will
deteriorate. With this, ceilings are expected to lower to IFR,
with IFR cigs remaining in place into Friday afternoon before
improving from west to east.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...SBH
LONG TERM...SHALLENBERGER
AVIATION...GREIF
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
644 PM CDT Thu Mar 29 2018
.SHORT TERM... (Through Late Friday Afternoon)
Issued at 252 PM CDT Thu Mar 29 2018
It looks like the trof/weather system that has been affecting us for
a while will finally lift out of the area the next 12 hours. However
we have to get through the next 12 hours. If it were colder I would
say we have a nice winter storm with a good deformation zone
developing, but it is warm so all we have to worry about is rain.
That said, the HRRR and CONSHORT agree in holding some pops across
parts of east and southeast MO and southern IL through the evening.
It will likely end up being a narrow band, but will keep at least
chance pops going through 06z for much of the southern part of the
CWA. Drier air is filtering in from the north so improvement is on
the way for Friday. Patchy fog may be an issue overnight given the
wet ground, but will let the evening shift tackle that as it
develops. With cloud cover holding in for much of the are
overnight, have raised low temperatures to the warmer MAV levels.
Guidance for Friday looks good.
This will be my last forecast shift for the NWS as I am retiring as
of March 31. It has been a pleasure working with and serving
everyone across the 46 county area of the NWS St. Louis. Take Care.
Jim Kramper
.LONG TERM... (Friday Night through Next Thursday)
Issued at 252 PM CDT Thu Mar 29 2018
Active pattern will continue over the weekend into next week as
global models show that the upper flow will be semi-zonal over
Missouri and Illinois.
The first chance of rain will come late Friday night into Saturday
night as GFS/ECMWF/Canadian show a shortwave trough and attendant
cold front dropping east southeastward from the northern Plains into
Missouri/Illinois. After this first shortwave moves quickly off to
the east, a second shortwave will move across southern Missouri and
far southern Illinois late Sunday into Sunday night bringing another
chance of rain with some snow possibly mixed in based on forecast
soundings. The best chance for showers will be Monday into Tuesday
ahead of deeper trough that will move across the area on Tuesday
night. There will be stronger moisture transport ahead of it along
with some instability, so kept the chance of thunderstorms Monday
afternoon into Tuesday. Wednesday looks dry at this point behind the
upper trough as a surface high moves across the area before the next
upper trough and attendant front affects Missouri and Illinois next
Thursday.
Temperatures still look below normal through this period based on
clouds and rain chances as well as the ECMWF MOS and the GEFS mean
temps.
Britt
&&
.AVIATION... (For the 00z TAFs through 00z Friday Evening)
Issued at 639 PM CDT Thu Mar 29 2018
Rain and IFR conditions will continue to move east and southeast
of the STL Metro terminals this evening. MVFR conditions will
continue overnight though as low level moisture progs from model
guidance depict saturation through 12Z. Can`t rule out some patchy
fog and drizzle developing overnight. Improving conditions
expected on Friday with the sun making an appearance by afternoon.
Light northwest wind will back to the west on Friday.
VFR conditions to continue at KUIN with improving ceiling height
at KCOU this evening.
SPECIFICS FOR KSTL:
Radar depicts the precipitation shield is rapidly weakening and
starting to shift to the east/southeast. This trend will continue
with MVFR ceiling conditions likely continuing overnight given
abundant low level moisture in the atmosphere. Can`t rule out some
patchy fog and light drizzle also developing overnight. Conditions
will rapidly improve tomorrow, with scattering cloud cover by
afternoon. Northwest wind will back to the west.
CVKING
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
918 PM CDT Thu Mar 29 2018
.UPDATE...
Midevening GOES East water vapor imagery showed a broad midlevel
trof entering the mid MS River valley. A narrow line of showers
moved through the Midsouth earlier this evening, preceding a
midlevel drying and reduced low and midlevel lapse rates. 00Z NAM
low and midlevel lapse rates are depicted to remain low during
the overnight, likely limiting additional shower potential late
this evening and overnight.
Forecast was updated earlier this evening, reflecting reduced
measurable rain chances.
PWB
&&
.PREV DISCUSSION... /issued 619 PM CDT Thu Mar 29 2018/
UPDATE...
Updated to include 00Z Aviation Discussion.
PREV DISCUSSION... /issued 322 PM CDT Thu Mar 29 2018/
DISCUSSION...
A cold front has just pushed into Northeast Arkansas at this time.
A lull in the rain is occurring across much of the area as the
rain associated with an old outflow boundary has pushed east with
the exception of some lingering showers in Monroe County,
Mississippi. Meanwhile, a line of convection is beginning to
develop across Eastern Arkansas ahead of the approaching cold
front. The latest run of the HRRR shows this line progressing
eastward across the Mid-South through early this evening thus one
more quick round of rain can be expected across the area.
Temperatures will drop behind the front as it pushes across the
area late this afternoon into the evening. Clouds will linger and
may not clear out until noon on Friday. Lows will be in the mid
to upper 40s. Highs on Friday will be in the upper 50s to mid 60s.
High pressure will settle over the Mid-South by Friday afternoon
into the Friday evening. The high will quickly shift east. Thus
winds may turn around back to the south during the overnight
hours. Lows will be in the upper 30s to upper 40s.
Another cold front will then approach the Mid-South by mid-day
Saturday bringing back chances for rain to Northeast Arkansas, the
Missouri Bootheel, and Northwest Tennessee. The front will really
slow up in its progression southward thus rain may not get into
Memphis until late Saturday Night into Sunday morning depending
on what model you look at.
The front is expected to stall out somewhere over the Mid-South
before lifting back to the north as a warm front on Monday. The
front will return as a cold front, moving through the Mid-South
Tuesday into Tuesday Night. Uncertainties with timing and
location of the front will result in lower confidence in the
forecast especially with rain chances during the Sunday Night
through Tuesday Night.
High pressure will then build back into the Mid-South on Wednesday
and will bring cooler and drier conditions to the region.
KRM
&&
.AVIATION...
00Z TAFs
Cold front will move across the area this evening. Gusty S/SW
winds will veer NW with frontal passage then diminish to 8-10 kts.
VFR condition swill deteriorate back to MVFR conditions tonight
into Friday morning then improve to VFR conditions by Friday
afternoon.
CJC
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
749 PM EDT Thu Mar 29 2018
.SHORT TERM...(This evening through Friday)
Issued at 342 PM EDT THU MAR 29 2018
WV imagery and RAP analysis indicated a mid/upper level trough from
Hudson Bay through the cntrl CONUS resulting in cyclonic wsw flow
through the nrn Great Lakes. Any lingering clouds over the north
supported by onshore flow of colder air with -12C 850 mb temps will
dissipate this evening as sfc ridging and drier air move into the
area, per upstream vis loop trends.
Tonight, favorable radiational cooling conditions until clouds
increase over the west late will still allow temps to drop toward
the lower end of guidance with readings into the lower teens inland
west to around 20 along the Great Lakes.
Friday, a clipper shortwave moving out of the nrn plains will bring
an area of light snow into the region. With only weak to moderate
700-300mb qvector conv or fgen associated and little moisture
inflow with this feature, QPF at or below models consensus in the
0.01-0.05 inch range is expected. This would support snow amounts
of an inch or less up to 18z over the far west and btwn 18z-24z
over the cntrl and east. With temps from the the upper 20s to
around 30 north and to near 40 south, enough warm air is expected
south for rain or a mix or rain/snow.
.LONG TERM...(Friday night through Thursday)
Issued at 406 PM EDT THU MAR 29 2018
Still some model differences for moderate to heavy snow potential
this weekend, especially for the east half; however, widespread
accumulating snowfall is expected across much of the Upper Peninsula.
Friday night into Saturday: The next chance for accumulating
snowfall will slide into the Upper Great Lakes region late Friday
night through at least Saturday morning. The GFS/Canadian are
similar in taking the surface low just south of the U.P. or across
Menominee county as a stronger shortwave slides through the area.
The latest NAM and EC has the low taking more of an east to
northeast trek, which would bring the low center across the central
U.P. into eastern Lake Superior. Either of these solutions would
bring moderate to heavy snowfall to the western half of the U.P;
however, the GFS/Canadian solution would favor all of the U.P.
seeing moderate to heavy snowfall. The increased forcing along with
added moisture streaming from the Gulf, will allow for a swath of at
least moderate snow to develop across much of Upper Michigan, again
exact trek will dictate where the heaviest snow falls. Models are
painting around a half inch or possibly a bit more across much of
Upper Michigan starting late Friday night, likely after 06Z, and
especially Saturday morning into early Saturday afternoon. This
would bring a widespread 4 to 8 inches of snow to much of the area,
heaviest over the northwest U.P. In addition, 850mb temperatures are
progged to be in the -13C to -16C range by late Saturday
morning/early afternoon, which combined with northeast to north
winds would allow for lake enhancement and orographic lift. This may
help to increase snowfall totals over the high terrain of the north-
central U.P. Of course, this depends on exact placement of the low
pressure system and wind direction. Blowing snow would also be an
issue as the tighter gradient depicted would allow for wind gusts
around 30 to 40 mph. At this point, with the aforementioned
differences in low trek, will hoist a winter storm watch for at
least the west half of the U.P., where confidence is higher in the
heavy snow potential, as painted out by each of the models.
Saturday afternoon through Sunday night: On the back side of the
system, with general troughing in place, chilly airmass is expected
across the Upper Great Lakes with H85 temps -15c to -20c range. This
will lead to an uptick in lake effect snow for northwest to west
wind snow belts Saturday afternoon through Sunday night. Could see
some moderate lake effect snow accumulations for the aforementioned
favored snow belts. Otherwise, much colder air will remain in place
across the area with temperatures around 10 degrees below normal.
Rest of the extended: Models are trending toward an even colder
pattern for early next week as a colder pool of air is expected to
spill southward across the Upper Great Lakes. This would lead to
additional, intermittent, lake effect snow chances across the area.
Locations impacted and extent of the impact will be centered on the
low level wind direction and ice coverage. At this point will stick
with a consensus of the models from early to mid week, giving
intermittent chances of snow.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 748 PM EDT THU MAR 29 2018
VFR cigs will prevail thru the evening at KIWD/KCMX/KSAW. Late
tonight, increasingly colder air moving across Lake Superior on wnw
winds should result in development of lake effect clouds/MVFR cigs
at KCMX and perhaps some flurries or -shsn at times. These lower
clouds should scatter out by late Fri aftn. Similar conditions are
expected at KIWD, but with a passing disturbance Fri, a period of
-sn/MVFR vis is expected late morning into early aftn. At KSAW, VFR
conditions will likely continue thru Fri morning before some
-sn/MVFR conditions develop in the aftn due to passing disturbance.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 342 PM EDT THU MAR 29 2018
Northwest winds of 20 to 30 knots over the eastern portion of Lake
Superior will abate this evening. Winds will then remain generally
below 25 knots across the entire lake through Friday evening. Winds
will increase markedly early Saturday as a low pressure system
approaches the area. Northeast winds of 20 to 30 knots are expected
across Lake Superior early Saturday before backing northwesterly
Saturday afternoon. Northwesterly gales of 40 to 45 knots are
possible across eastern Lake Superior Saturday afternoon and
evening. A few areas of heavy freezing spray are possible Saturday
afternoon/evening, as well. Winds of 20 to 30 knots are then
expected on Sunday, and below 20 knots on Monday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Storm Watch from late Friday night through Saturday
afternoon for MIZ001>005-009>011-084.
Lake Superior...
Gale Watch from Saturday afternoon through Saturday evening for
LSZ248>251-265>267.
Lake Michigan...
Gale Watch from Saturday afternoon through Saturday evening for
LMZ248-250.
&&
$$
SHORT TERM...JLB
LONG TERM...KEC
AVIATION...Rolfson
MARINE...BB
Area Forecast Discussion
National Weather Service San Diego CA
849 PM PDT Thu Mar 29 2018
.SYNOPSIS...
High pressure aloft will build over California through Friday and
bring fair, dry and warmer weather over southern California. Areas
of night and morning low clouds and fog will occur near the coast,
with locally dense fog possible. Weak low pressure will bring
increasing high clouds and coastal low clouds, and cooler onshore
flow this weekend through early next week. It will be a little
warmer again around the middle of next week as another ridge of high
pressure moves through California.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
...Update...
Patchy low stratus is developing just off the coast. Although
there is an offshore synoptic pressure gradient, that will lessen
in time overnight and become onshore on Friday. The HRRR continues
to show dense fog along the coast, especially the San Diego coast,
so the dense fog in the forecast looks good for the overnight. No
changes are needed to the forecast this evening. See previous
discussion below for further forecast details.
...Previous Discussion (Issued at 200 PM PDT Thu Mar 29 2018)...
After the stratus/fog dissipated this morning, mostly sunny skies
prevailed today with temperatures a little above normal, mostly in
the 70s west of the mountains, with some lower 90s in the lower
deserts. Aircraft soundings show the inversion in the 500-700 foot
range, and with the inversion expected to continue tonight or even
lower slightly under the subsidence of the ridge moving in from the
west, there could be dense fog along the coast. Confidence of timing
and exact locations/elevations is somewhat low, but midnight-8 AM
and within about 5 miles of the coast are the most likely
times/locations for dense fog. Away from the coast, clear skies with
warmer weather and moderately low humidity will prevail through
Friday as the high builds and some very weak offshore flow develops,
though the local WRF shows wind gust potential mostly under 30 MPH
Friday morning, mainly San Bernardino County.
After the ridge Friday, a weak trough, mostly disconnected from the
polar jet over Washington/British Columbia, will be off the coast
Saturday, slowly moving towards the So-Cal coast by Sunday
night/Monday. This will bring high clouds but most likely no
precipitation. The marine layer should deepen by Sunday some and
result in more widespread coastal/valley stratus but less coastal
fog. Eventually the low will move east, and with a high pressure
ridge, albeit fairly low amplitude, following. That will result in a
warming trend again with temperatures a little above normal. The
pattern will be fairly progressive due to the relatively low
amplitude of the troughs/ridges, so that high likely will not last
more than a couple days as there could be a deeper broader trough
moving in late next week. This could bring precipitation the
following weekend, 7-8 April, though confidence is low for that.
&&
.AVIATION...
300330Z...Coastal areas: Low clouds and fog returning to the coast
through 06Z, then spreading 5-10 inland miles through 14Z Friday
with bases between 200 and 700 ft MSL. Vis restrictions of 1/2 mile
or less expected on the coastal mesas including KCRQ. There is a
moderate potential for 1 mile vis or less at KSAN and KSNA between
06Z and 15Z Friday. The fog should dissipate by 17Z Friday.
Valleys, Mountains and Deserts: clear skies and unrestricted
visibility tonight and Friday.
&&
.MARINE...
Areas of dense fog tonight and Friday morning, and again Friday
night into Saturday morning.
&&
.SKYWARN...
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&
$$
PUBLIC...Gregoria (Update)/Maxwell (Prev Discussion)
AVIATION/MARINE...Moede
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Friday)
Issued at 345 PM CDT Thu Mar 29 2018
Broad cyclonic flow continues over the central CONUS with a stronger
wave pushing east across the southern Plains with a weaker wave
over western portions of South Dakota and Nebraska. Low-level cold
air advection is keeping stratus in place over much of the local
area though some clearing has occurred in the northwest with temps
recovering somewhat. Scattered high-based showers were reaching
central portions of Nebraska and western Kansas but this wave
should weaken and enter a less favorable environment for
continuation. A smaller-scale upper wave was entering western
Missouri and helping generate a small area of light precip in the
Jefferson county area at 20Z. HRRR and RAP and been consistent
with this area limited to far eastern counties before diminishing
as well as this wave exits.
Surface high pressure builds into the area tonight but models are
consistent with some northerly component remaining in the boundary
layer. Stratus south continue to push southeast with high cloud
moving off for several hours of fairly clear skies, but enough
wind looks to keep fog chances low. Another round of high cloud
looks to move through Friday but increasing southwest winds behind
the exiting high should finally bring a mostly sunny day and
highs in the upper 50s to lower 60s.
.LONG TERM...(Friday night through Thursday)
Issued at 345 PM CDT Thu Mar 29 2018
The next stronger wave in the northwest flow brings some increase
in lapse rates in warm-air advection for Friday night, with
moisture return aloft potentially leading to some shower activity
in the northeast where saturation is greater. This wave brings
another cold front Saturday with still a wide range in highs
likely, but highs will likely again struggle to break the 40s in
the north. Attention Saturday night into Sunday continues to be
an a narrow band of enough saturation and frontogenesis that
stretches ESE into the area. Dry air under this should limit
intensity of precip but could still see some light snow
accumulations if a band can be sustained.
The next wave enters the northern Plains Monday night and on
toward the local area Tuesday, but remains positively tilted. At
this point timing looks unfavorable and capping large enough for
limited daytime thunderstorm concerns but will keep a thunder
mention Monday night with warmer temps for Monday. Northwest flow
looks to persist into the mid week and continues to present
occasional chances for mainly light precip. Temps breaking
seasonal normals are unlikely beyond Monday night.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 637 PM CDT Thu Mar 29 2018
VFR cigs should scatter out by 01Z. Expect vfr conditions for much
of the period, save from 09Z-13Z where mvfr vsbys are possible due
to mist at the terminals as soundings keep the lower boundary
layer mixed tonight so not anticipating ifr or lifr with fog. Will
continue to monitor for next issuance. Winds light north becoming
southwest under 10 kts by 19Z.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...65
LONG TERM...65
AVIATION...53