Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/05/19
See below for an aviation forecast discussion for the 00Z TAFs.
.SHORT TERM...(This evening through Friday)
Issued at 415 PM CDT Thu Apr 4 2019
Highlights of the short term forecast include low clouds and fog
tonight and a warmer day Friday.
Broad surface pressure falls are ongoing over the Northern Plains
this afternoon and associated south-southeast flow is allowing for
seasonably-notable moisture advection with dewpoints approaching
40 F in central and northeast SD as of mid afternoon. A strong
low-level inversion is present thanks to warm air advection aloft
and this scenario is generating extensive stratus. Ceilings may
lift slightly through this evening in northeast SD in response to
small increases in temperature-dewpoint deficits in the boundary
layer owing to diabatic heating. However, maintenance of the
inversion and moisture advection regime will allow for overall
persistence of the low cloud regime in northeast SD and will
likely promote at least patchy fog development. Rapid-refresh
guidance through the 19 UTC HRRR suggests dense fog development is
possible, as well, so later forecasts will monitor observational
trends which could require issuance of a Dense Fog Advisory in
Meanwhile, a surface warm frontal zone is approaching the Missouri
River valley as of 20 UTC with rapid erosion of stratus along its
interface where the boundary layer becomes well-mixed through a
deeper layer. Rapid-refresh guidance also captures this trend well
and suggests that low clouds will be favored east of Mobridge and
Pierre tonight, though some fog development is possible near the
edge of the stratus bank where the mixing regime typically favors
its formation. HRRR guidance suggests that scenario could even
impact parts of north central SD such as around Mobridge. Note we
do have a low-grade, low-PoP for light showers in the forecast
late tonight in far northeast SD and west central MN out of
respect to advancing midlevel warm air advection. Cumulus fields
which have been deepening in the well-mixed boundary layer over
the western Dakotas could support isolated high-based showers
being maintained into parts of the area tonight, but confidence
in that is low and thus this forecast release is dry until late
On Friday, mean middle and upper-level ridging will be in place
across the area and the air mass will be warmer in the wake of
tonight`s warm frontal passage. This should support highs ranging
from the upper 50s in the norther parts of the SD James River
valley to the 65-70 F range along and west of the Missouri River
.LONG TERM...(Friday night through Thursday)
Issued at 415 PM CDT Thu Apr 4 2019
A mid level trough will bring showers and a few thunderstorms to the
region Friday night into Sunday. Models indicate as much as 1000
J/kg MUCAPE during this time period, but low and deep layer shear do
not support organized severe convection. An upper level ridge builds
in early next week, keeping the forecast area dry. Temperatures look
to remain mild through early next week, with highs mainly in the 50s
A deepening upper level low is forecast to eject off the Rockies
into the Central Plains by mid week. There is still considerable
uncertainty on the track and strength of this system, although it
does look like there is a potential for widespread QPF of 0.5 to 1
inch. Temperatures may be cold enough for snow to mix in on the
northern end of the system, especially during overnight and morning
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 648 PM CDT Thu Apr 4 2019
VFR conditions start things off at KPIR/KMBG, and unless some fog
forms across the Missouri River valley overnight, things should
stay VFR throughout the TAF valid period.
Sub-VFR cigs/visbies start things off at KABR/KATY. The latest
short range guidance seems to hint that either the low clouds will
stick around overnight (continued sub-VFR), or if the clouds
clear off and conditions go VFR later this evening, that would be
a short-lived, as conditions will be favorable for fog (sub-VFR)
formation overnight into Friday morning.
SD...Dense Fog Advisory until 10 AM CDT Friday for SDZ007-008-011-
Area Forecast Discussion
National Weather Service Columbia SC
1049 PM EDT Thu Apr 4 2019
A warm front will approach the region tonight and move into the
area Friday. This will result in widespread showers. The showers
will diminish friday afternoon and Saturday as low pressure
moves northeast of the area. Another low pressure system will
approach the region early next week resulting in numerous
showers and thunderstorms at times especially Monday.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
IR satellite imagery shows extensive cloud shield over the
central Gulf States and much of the Southeastern US. Network
WSR-88D imagery also shows large area of rain moving through GA
and toward the forecast area. Over the next couple of hours
expect the rain to move into the majority of the forecast area
and with good isentropic ascent and plenty of moisture overnight
expect moderate rain with some potential for some locally heavy
rain. Expect convective potential to remain south of the area
overnight with thunderstorm potential in the forecast area too
low to include through daybreak. With the clouds and rain
overnight expect low temperatures in the low to mid 50s.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Friday...Deep moisture and isentropic lift Friday morning as
warm front and upper level trough approaches. High resolution
models suggest the heaviest rain will be from 12z to 15z...then
decreasing from southwest to northeast as upper level trough
moves through and low to mid level isentropic lift shifts
northeast of the area. The GFS suggests some locally heavy rain
possible across the north central Midlands associated with low
level convergence. As warm front moves into the area and becomes
stationary, the southern CWA becomes weakly unstable. Can`t rule
out a thunderstorm mainly in the afternoon as coverage becomes
scattered. Mid 70s for max temperatures south to mid 60s north
of the front.
Friday night...Surface ridge to the north builds south and front
shifts south of the area. Pops should be low as air mass
stabilizes and moisture becomes shallow. Areas of fog possible
late at night. guidance temperatures look good.
Saturday/Saturday night...Front lifts slowly back north as low
pressure system develops in the Plains. Moisture and weak
instability confined to the CSRA and southeast Midlands, so low
chance pops mainly in the afternoon in those regions. Dry north
of CAE. Temperatures max out in the 70s with scattered to broken
clouds in the afternoon. Isolated showers mainly in the evening
then patchy fog late.
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Highly amplified upper trough and surface low will be off to
the west to start off the week. ECMWF may be more progressive
than GFS which shows a cut off low in the Deep South toward
midweek. But models in much better agreement, showing trough
moving through Tuesday, then east of the cwa Wednesday.
Numerous showers and thunderstorms remain possible Monday, with
scattered activity Tuesday. Isolated activity by Wednesday.
Temperatures during this period will be above normal through
this period with highs in the 70s and 80s and lows in the 50s
to lower 60s.
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Deteriorating conditions will occur tonight. Low-level wind
shear will be an issue.
Moisture will be on the increase in the onshore flow ahead of
the approaching warm front. Followed the GFS LAMP for the
timing of lowering ceilings. The high-resolution models and
radar trends indicate rain spreading into the area from
southwest to northeast during the 06z to 10z timeframe. The GFS
LAMP and HRRR support conditions lowering into the IFR category
in rain and fog 10z to 12z. A strong low-level jet will be
associated with the system. Followed the NAM and included low-
level wind shear in the terminal forecasts. There may be enough
instability for thunderstorms but stronger convection closer to
the Gulf Coast will likely limit the instability farther north.
The thunderstorm chance was too low to include in the terminal
forecasts at this time.
EXTENDED AVIATION OUTLOOK...There will be periods of MVFR or IFR
conditions through Tuesday associated with a frontal system in
Area Forecast Discussion
National Weather Service State College PA
1125 PM EDT Thu Apr 4 2019
Low pressure will approach from the Mississippi Valley tonight
and will pass south of Pennsylvania Friday night. A ridge of
high pressure will build into the region this weekend. Another
area of low pressure will track west of Pennsylvania early next
week, with the trailing cold front likely coming by Tuesday.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Mid clouds thickening late this evening as WAD increases from
the Ohio Valley. Development of fgen forcing and influx of
meager Gulf of Mexico moisture overnight will start very light
rainfall for much of the area after midnight and into the pre
dawn hours of Friday. Question is ptypes, and given wet bulb
potential at the surface with very low dewpoints over the north
any chances for freezing rain Friday morning.
Model forecast soundings suggest predominant ptype to be
snow/sleet across the northeast quarter of central PA. Soundings
transition generally from SN/IP to rain by 15z, with little if
any indication of fzra via manual examination. HRRR agrees with
this, going from a period of snow to plain rain over the
northeast quarter. NAM12 indicates a snow, sleet freezing rain
mix, but examination of soundings via BUFKIT indicate any patchy
freezing rain would be after minor accums of snow and sleet
(perhaps 1-2") with pretty inconsequentual trace of fzra in some
spots if it occurs.
So, through collaboration with BGM, opted against any headlines
and will continue to mention in HWO, and mentioned slight chance
of fzra northeast. The tree limbs and cold car roofs are the
most likely places which could see a thin ice coat. In and of
themselves, the amount of sleet and snow are going to be
sub-advisory. It is still early April and we go through a
little light frozen precip at this time of year.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
Rain ongoing over all the area at sunrise, with a mix in the NE
third/higher elevs there. It should go to all rain as the strong
April SS works it`s magic and stops any threat for
freezing/frozen stuff by mid morning over all but the extreme
highest elevations N of IPT. The main push of moisture and lift
will be gone by noon in the west and 2-3PM east. But, low
clouds/crud will linger and keep the temp from getting anywhere
near normal maxes. Some light rain/dz could also linger into
the evening in the central and wrn highlands. Expect highs only
in the upper 30s NE and 40s elsewhere.
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Fair and much warmer conditions are expected this weekend, as high
pressure builds into the state. Increasing April sun angle and
daylight hours will help push temperatures 10-15 degrees above
normal both Saturday and Sunday. The bulk of med range guidance
points toward showery and mild weather early next week, as next
area of low pressure tracks west of Pa through the Grt Lks, with
the trialing cold front coming through late Monday or early
Tuesday. A fairly significant cool down appears likely by
midweek, as upper troughing works into the northeast CONUS.
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
VFR ongoing this evening will persist into the early overnight
hours before conditions deteriorate over the west and north.
Mid-deck already developing over the SW where virga will
continue to gradually work down to the surface over the next
couple of hours with reductions beginning as rain begins after
midnight. The precip spreads north and northeast overnight,
and UNV and IPT may be cold enough for a little PL or even SN
at the very onset, but any ZR or extended period of PL will be
confined to the north of IPT and east of BFD. Most of the
terminals will experience a very cold rain and gradual decline
into IFR for the daytime on Fri. MDT and LNS may have only brief
forays into MVFR with just light rain, with a period of
restrictions possible early Fri and then again Fri afternoon.
Precip tapers to drizzle Fri night then ends by Sat morning.
Ceilings remain low through 12z Sat followed by improving
conditions as high pressure builds in for the weekend.
Rain may arrive again late Sun.
Sat...Ceiling restrictions early, then improving conditions with
no sig wx.
Sun-Mon...Restrictions possible with rain/showers.
Tue...No sig wx.
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
944 PM CDT Thu Apr 4 2019
The short term forecast is in good shape with just a few tweaks
to the wx and sky grids.
A weak backdoor front continues to progress southward through the
FA at this hour. At present time it appears to be near and along
a Graham to Hillsboro to Palestine line. No precipitation is
expected with this frontal boundary as large scale subsidence in
the wake of an upper trough has been efficient at keeping any
upward vertical motion nil. This front will usher in higher
dewpoints and this should set the stage for some fog near and east
of this boundary The boundary shouldn`t make too much more
progress and should stall not too far from its current location.
Short term model guidance, though sometimes overly aggressive with
its visibility output, appears to be keying in on areas near and
north of I-20 and east of I-35 for the greatest widespread fog
potential. This seems reasonable given that light morning rains
may help to promote a more favorable radiation fog regime. I`ve
beefed up the coverage of fog in the aformentioned area and would
not be surprised to see some pockets of dense fog develop. At this
time, I have no plans to post any dense fog headlines, but one
may be needed at some point early Friday morning. For now, will
highlight this threat in the HWO and graphics. Elsewhere patchy
fog will be possible with unfavorable conditions for fog across
the Big Country where dewpoint depressions are large.
A deck of low clouds continues to invade East Texas this evening
and have increased sky grids to account for what appears to be
some nocturnal cool air stratocumulus. It appears plausible that
this deck of clouds will continue to spread southwestward with
time and I`ve increased sky grids across the Brazos Valley.
Otherwise, the rest of the forecast appears in fine shape and no
other changes were needed.
.AVIATION... /Issued 638 PM CDT Thu Apr 4 2019/
/00 UTC TAF Cycle/
Concerns---Ceiling and visibility trends Friday morning at all
A cold front continues to slide through Metroplex TAFs as of 2330
UTC. Northeasterly winds initially will gust to near 15 knots,
but these speeds will be short-lived and in general winds will be
near or under 10 knots. The front will arrive at Waco near 0200
UTC and will usher in northeasterly winds near 10 knots. The main
concern during the overnight period will be a threat for IFR
ceilings and visibility. At this time, it appears that the
Metroplex will have the best opportunity for poor flying
conditions as BR develops to the north of the terminals and sags
southward. Confidence is medium in this threat and we`ve relegated
this potential to a TEMPO group. It is possible that the urban
heat island effect may keep cigs/vsby MVFR, but after close
examination of guidance and coordination with ZFW...felt it was
necessary to include at least a decent chance for IFR during the
Friday morning push. VFR will prevail around 1600 UTC Friday with
a return to south flow appearing likely thereafter.
At Waco, the potential for IFR vsby is more uncertain, but non-
zero. For now, it appears more likely that a ribbon of IFR cigs
will overspread the terminal during the pre-dawn hours. We will
monitor trends in short term guidance over the next few hours,
however, to determine if IFR vsbys are more appropriate. Similar
to the Metroplex, VFR with southeasterly winds are anticipated
during the mid to late morning time periods and beyond.
.SHORT TERM... /Issued 304 PM CDT Thu Apr 4 2019/
A cold front is making its way across North and Central Texas this
afternoon, ushering in northwesterly winds and drier air. Despite
what is technically a cold front passing through, there has been
little impact on temperatures this afternoon, with most
observation sites making it into the upper 70s and lower 80s
today. Cloud cover has been on the decrease as drier air has moved
in, making for a nice sunny afternoon for most of our county
warning area except for the northeast where cloud cover has been
slower to exit.
Skies should remain mostly clear through most of the overnight,
with low temperatures dropping into the 50s. Winds will come
around out of the northeast, but will remain light. Mostly clear
skies and light winds will allow for excellent radiational
cooling. With temperatures forecast to drop to near the dewpoint
by early Friday morning, patchy fog may develop, and in fact this
is shown by some of the high-resolution guidance, with the NAM and
RAP being the most aggressive. Some of the ensemble guidance such
as the HREF and SREF are less aggressive however. For now, will
mention patchy fog in the weather grids, with the most coverage
expected east of Interstate 45, but trends will need to be
monitored through the evening and overnight hours. While dense fog
does not appear likely, it may be worth allowing a little extra
time on the morning commute Friday, just in case.
.LONG TERM... /Issued 304 PM CDT Thu Apr 4 2019/
/Tomorrow into Next Week/
Main concern in the extended period continues to be the potential
for heavy rain and severe weather, primarily Friday night into
Saturday (but potentially lingering into Saturday night or even
Until then, the day tomorrow should start with a weak front
settling across our southeastern counties. Light winds and moist
surface conditions may support fog development overnight into the
morning hours, especially near the front where T/Td spreads will
be lowest. Diurnal mixing of the boundary layer will erode the fog
through mid morning, yielding some sunshine in most locations.
Expect temperatures to warm accordingly, reaching the upper 70s
Our weather begins to become unsettled Friday evening and night as
a shortwave trough approaches the southern Plains within broader
cyclonic flow. In response, low-level moisture returns in earnest
overnight Friday, especially across Central Texas and western
North Texas. Amplifying warm advection and isentropic ascent may
yield a few elevated storms ahead of the shortwave trough Friday
night, and these may be accompanied by a hail threat, given steep
mid-level lapse rates and strong convective layer flow. Towards
daybreak then, focused surface convergence and ascent along the
shortwave impulse should drive a complex of thunderstorms, perhaps
in the form of a broken line, into portions of western north
Texas. Damaging winds would likely be the primary threat, but we
will have to closely monitor the magnitude of returning boundary-
layer moisture. If sufficiently high during the morning, this
moisture could yield more surface-based development, with a higher
potential for damaging winds and perhaps a few embedded
tornadoes. Regardless, this complex is forecast to quickly lift
east/northeast across parts of our area through the morning.
A second area of a few strong/severe storms and heavy rainfall
may develop across Central Texas during the morning and afternoon
hours, as a secondary surface trough/front closer to the Texas
coast may focus strong ascent just to its north. Questions remain
regarding the amount of surface-based buoyancy that will develop
here, but heavy rain and all severe hazards could be a
possibility as well. Guidance remains unsurprisingly dispersed on
where this band of convection will establish, but these trends
will need to be monitored given some focused potential for at
least minor flooding issues.
Rain/storm timing behind these two rounds remains nebulous, at
best, owing to brief subsidence behind the initial systems and the
potential for convective overturning. With that said, a secondary
impulse will approach our area late Saturday into the overnight
hours, and low-level moisture will not be scoured by the prior
system. In turn, another round of showers and thunderstorms,
perhaps accompanied by localized flooding and severe weather, may
develop late Saturday into early Sunday, most likely east of the
I-35 corridor. However, if the broader trough axis and low-level
moisture plume shifts far enough east with the earlier round of
convection, most heavy rain/storms could miss North/Central Texas
to the east/southeast entirely. These details will slowly be
refined as the event approaches.
Conditions gradually dry from west to east on Monday once the the
trough shifts east and heights build over our region. Temperatures
will warm through Wednesday, with downslope flow helping a few
spots perhaps touch 90 across western North Texas. A front then
may bring a slight cooldown for the latter portion of the week.
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 59 79 62 76 63 / 0 5 50 80 30
Waco 58 82 63 76 62 / 0 5 50 80 40
Paris 55 76 59 71 61 / 0 5 20 80 60
Denton 53 79 60 76 61 / 0 5 50 80 30
McKinney 55 78 61 74 61 / 0 5 40 80 40
Dallas 60 80 64 76 63 / 0 5 50 80 40
Terrell 57 80 63 75 62 / 0 5 40 80 50
Corsicana 60 79 63 73 63 / 0 5 40 80 50
Temple 59 81 63 76 62 / 0 5 50 80 40
Mineral Wells 55 80 60 76 58 / 0 5 70 70 20
Area Forecast Discussion
National Weather Service Wilmington NC
939 PM EDT Thu Apr 4 2019
A wave of low pressure will bring showers on Friday followed by
weak high pressure over the weekend. A storm system will bring
showers and thunderstorms to the Carolinas next Monday into
Tuesday. A front will move off the coast early Wednesday, though
temperatures will remain slightly above normal.
.NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 939 PM Thursday...Winds increasing and veering in the low
levels per recent VWP data. Mosaic radar shows a leading edge
of of rainfall moving across eastern Georgia approaching western
SC. Based on this and recent HRRR forecast reflectivity
depictions, some downward adjustments may be needed between 6z
and 12z in pop values, delaying best rain chances and onset
times a few hours later, leading moreso into daybreak Friday.
As of 300 PM Thursday...Satellite imagery shows a healthy mid
level system crossing into the Mississippi Valley. Despite its
appearance the system has little to no surface reflection. Even
so it will spread moisture/clouds across the area from west to
east tonight and then rain chances to follow. Although rainfall
a near certainty area- wide this still looks like a low QPF
event. This seems plausible given the low amplitude aloft and
poor surface and low level reflection all keeping overall
forcing weak. Dry air moves in from west to east Friday
evening/night ending rain chances, partially clearing skies, and
possibly allowing for some fog if wind grows light enough.
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 300 PM Thursday...Weak shortwave and associated precip will
be well off the coast Saturday morning. A weak surface low will
follow, moving off the northeast NC coast Saturday morning
leaving light NW winds across the forecast area. Saturday
through Saturday night should be precip-free as a weak ridge
slides overhead. Models are showing a weakness that tries to top
the ridge Sunday afternoon, which may lead to a few showers for
late in the weekend. Otherwise, temps will be 6-8 degrees above
normal in southwesterly flow.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 300 PM Thursday...Ridge sfc-aloft will move offshore
Monday, and moisture ahead of upstream trough axis will make its
way into the CWA by 00Z Tuesday. Showers with a few
thunderstorms will be possible Monday through Tuesday night
until the surface front clears the area around 12Z Wednesday.
Max temps Monday near/around 80, and will only cool a few
degrees behind the front with lack of much significant cool
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
As of 00Z...VFR conditions thru atleast 06Z. Expect conditions
to deteriorate from generally west to east during the pre-dawn
Fri hours. At the moment, a blanket of high level clouds are
strewn across the FA. Will see a drop to mid-level cloudiness
after 04Z and a further decrease to MVFR thresholds late in the
pre-dawn Fri hrs. By daybreak and thru the remainder of the TAF
Issuance period will indicate MVFR/IFR conditions from both low
clouds and reduced vsby from stratiform light to moderate rains
and fog. Models are indicating even a shot for LIFR conditions
between 14z and 20z and at press time will determine if it`s
feasible to include.
Extended Outlook...The mid-level short wave trof will exit the
FA by sunset Fri leaving enough low level moisture for MVFR/IFR
clouds and/or reduced vsby from fog/dense fog Fri night thru
Sat morning. VFR conditions to occur during the weekend except
for MVFR/IFR from fog and/or low clouds both late Sat night and
Sun night respectively. Sub VFR conditions from increased pcpn
chances to occur late Sun night thru Tue in response to a low
As of 745 PM Thursday...Weak ESE swell of 2 origins propagating
ashore in 12 and 8 second intervals, phasing on occasion to
produce a rideable wave of good form. Light SE chop tonight
will turn moderate into Friday as winds amp up a little. Rain
into Friday will begin to restrict long range visibility to 1-3
nm in rain at times.
As of 300 PM Thursday...High pressure sliding off the coast
will bring an increase in southeasterly winds tonight. The
approach of a weak system on Friday will veer flow slightly and
also bring another increase in wind speed. A few 6 ft waves
could materialize along the very outer fringes of mainly NC
waters but at this time it looks too marginal for an Advisory.
Additional veering and abating winds/seas behind the weak system
Weak low pressure will move off the northeast NC coast Saturday
morning. Although winds will be northerly to start the day,
speeds should be on the order of 10 kt in a weak pressure
gradient. Weak high pressure will slide across the waters
through the day, with winds becoming variable for a time
Saturday afternoon, before shifting to the south late. The
overall pressure field will remain relatively weak through
Sunday, and the center of high pressure north of the waters will
maintain a southeast wind direction on Sunday.
The gradient over the waters will begin to tighten Sunday
night, and moreso Monday as a frontal boundary crosses
Tennessee. Southwest winds will increase into a 15-20 kt range,
and will also see shower and possible thunderstorm activity
increase Monday into Tuesday ahead of the front.
AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
803 PM EDT Thu Apr 4 2019
As a low pressure system moves eastward from the central Plains,
moisture will increase throughout the Ohio Valley tonight, with
rain expected. Chances for rain will end on Friday, as high
pressure moves into the region for Saturday. Precipitation
chances will increase again on Sunday and Monday, as an area of
low pressure moves through the Great Lakes.
.NEAR TERM /THROUGH FRIDAY/...
Strong east winds on the north side of the warm front will
continue through about midnight and then relax. Current
placement of the warm front is just south of the forecast area,
probably skimming our southern counties. Most prominent
delineation of the front is the wind shift, though readings
around or in the low 70s south of the front are notably cooler
by around 10 degrees when you hit the Ohio River, and another 10
degrees (around 50) towards the I-70 corridor. The strongest
winds appear to be south of the axis of increased dewpoints just
north of the I-70 corridor to about the Ohio River where ENE
winds sustained at 15-20 mph are found, occasionally higher and
also with some gusts.
Tried to slow the incoming rain by a little bit but then blended
in to the daybreak forecast. This ultimately lowered the chances
of rain given the showery nature of the incoming rain and the
potential for hit-and-miss pockets overnight and early Friday.
Lowered tonight`s lows by a degree or so but thought the
temperature forecast was well in hand.
Strength of the boundary layer moisture transport with this
system remains unimpressive. While PWAT remains <1", there is
still high confidence in rain occurring in most locations (high
PoP) but lower confidence in significant amounts (low QPF).
HRRR runs continue to trend to a spotty showery nature. There
remains better forcing ahead of the strongest part of the mid
level shortwave in sern CWA overnight.
Behind the shortwave, as the overnight hours progress, the
temperature gradient at the surface should relax -- min temps
are expected to range from the mid 40s to lower 50s.
.SHORT TERM /FRIDAY NIGHT/...
The axis of the shortwave will be just about to exit the ILN
forecast area at 12Z on Friday morning, which should herald the
end of widespread precipitation once it has passed. Behind the
wave, however, there is still the issue of a weak (and further
weakening) surface low, which will be moving into the ILN
forecast area through 18Z. Weak boundary layer warm advection
ahead of this low may be enough to spark some light showers or
drizzle, in a near-surface air mass that will be about as close
to saturated as anything is going to get with this particular
system. For that reason, some low-end PoPs were extended a
little further into the day on Friday. However, once this low
has washed out, any remaining precipitation chances should end
With the Thursday frontal boundary having largely washed out,
temperatures on Friday will have much less of a gradient,
ranging from the upper 50s to middle 60s. Some models did
suggest some slightly warmer conditions, but with BKN to OVC low
level clouds expected for at least the first half of the day,
this temperature forecast will be kept a little more
High pressure on Friday night will bring a weakening of the
winds and a clearing of the skies, with min temps in the middle
to upper 40s.
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Ridging over the area at the beginning of the period will move
off to the east as a trough developing in the central part of
the country moves east. An initial short wave lifting out of
this trough will result in showers spreading across the region
late Saturday night into Sunday. There will then be an
increasing chance of thunder Sunday afternoon into Sunday
evening with the probability then decreasing as the short wave
moves east of the area. Additional showers as well as some
thunderstorms will occur as the trough and associated cold front
moves through later Monday into Monday night. Temperatures will
be above normal over the weekend into the beginning of next
week with Sunday and Sunday night expected to be the warmest
stretch of the period. Sunday night lows will end up being close
to the normal high for this time of year.
High pressure will build in behind this front resulting in dry
conditions with temperatures closer to normal. The next chance
of showers will move in on Thursday as a closed low tracks
through the mid Mississippi Valley.
.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
ENE winds 15kt will persist for a few more hours and then relax
behind the upper level shortwave as the gradient loosens ahead
of an approaching surface low. VFR conditions will prevail until
some showers push in from the west late this evening and
overnight. VSBYS will remain VFR and only see a brief drop to 5
miles or less, then be followed by cigs lowering beneath 3kft
towards daybreak Friday.
High end MVFR cigs will prevail tomorrow and could see a period
where they drop below 2kft, particularly in the later morning to
the west and afternoon in the east.
OUTLOOK...MVFR conditions are possible Sunday and Monday, with
a chance for thunderstorms on both days.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
846 PM PDT Thu Apr 4 2019
.SYNOPSIS...Scattered light rain showers are possible overnight,
mainly in the North Bay. Widespread light to moderate rain is
forecast to develop in the northern portion of the area on Friday
morning and spread south through most of the rest of the region
by early afternoon. Unsettled weather may persist into the first
half of the weekend, with drier and warmer weather expected by
Sunday. Another chance of rain will develop by Monday night,
followed by cooler weather for the remainder of next week along
with gusty northwest winds at times.
.DISCUSSION...As of 8:45 PM PDT Thursday...KMUX radar is currently
detecting isolated light showers, mainly offshore. Latest HRRR
model indicates that shower activity will increase overnight, but
primarily over the North Bay, as a weak shortwave trough ripples
through the moist westerly flow aloft. GOES-West satellite imagery
shows a more organized system over the Eastern Pacific
approaching 130W and rapidly approaching our coast. Models had
previously forecast this system to be a low-end Atmospheric River
event with heavy rainfall potential. But recent models have backed
off considerably on the strength of this system, as well as
rainfall amounts and wind speeds. Based on latest model output,
this system will generate a period of light to moderate rainfall
on Friday as it moves quickly through our area. Widespread rain
will develop in the North Bay and as far south as the SF Peninsula
during the morning commute, and then spread south through most of
the remainder of our forecast area during the late morning and
early afternoon hours. Rainfall amounts on Friday are forecast to
range from 0.25-0.75" in the North Bay, with a quarter inch or
less expected elsewhere. Southerly winds may gust as high as 30
mph, but for the most part winds are not expected to have much
After the Friday system passes, a moist zonal flow will persist
across the Eastern Pacific and into California into the weekend.
This moist flow will maintain widespread cloud cover through at
least Saturday. However, forcing will be weak or lacking and so
continued precipitation after Friday will likely be scattered and
light. The NAM is by far the most bullish with precipitation after
Friday, as it develops widespread light rain across our area late
Friday night into Saturday morning, with scattered showers into
Saturday afternoon. Most other models forecast only spotty
precipitation on Saturday. Moist westerly flow will persist into
Sunday but by then the models begin to build a low amplitude ridge
which should keep our area mostly dry. The upshot is that we can
expect lots of clouds over the weekend, especially on Saturday, but
mostly dry conditions after Saturday morning. The building ridge
over the weekend will result in warming temperatures with
widespread low to mid 70s forecast by Sunday when we should see
at least some sunny breaks.
A shortwave trough is forecast to bring a quick shot of rainfall
to primarily the northern portion of our area sometime between
late Monday and Tuesday. Otherwise, the longer range models agree
that we can expect mostly dry conditions next week, with cooler
temperatures and brisk northwest winds at times. In fact, the
latest GFS indicates the potential for strong and gusty northwest
winds along our coast for Tuesday afternoon and evening.
.AVIATION...As of 4:50 PM PDT Thursday...for 00Z TAFs. A mix of
mid and high clouds continue to impact area terminals this
afternoon ahead of an approaching front. Models have backed off
significantly with respect to the precip associated with this
system. Therefore the TAFs have been adjusted and rain chances
have been pushed back and scaled down. Rain showers are expected
to begin impacting the North Bay tonight into Friday morning while
terminals around the San Francisco Bay will begin seeing showers
Friday morning around 15z-17z. Monterey Bay area terminals will
likely only see hit or miss showers. Light to moderate west to
southwesterly wind will ease this evening becoming light and
locally variable to southeasterly overnight. Moderate and gusty
southwesterly winds expected Friday morning as the front pushes
Confidence is low with respect to the timing of the rain.
Vicinity of KSFO...MVFR/VFR cigs will prevail through much of the
forecast period. Moderate south to southwesterly winds will ease
this evening becoming light and locally variable to southeasterly
overnight. Light rain will return to the region Friday morning
then taper in the late afternoon. Moderate and gusty southwesterly
winds expected Friday morning as the front pushes inland.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...VFR cigs will prevail through tonight
with MVFR cigs anticipated Friday morning with the potential of
showers in the vicinity as the front moves inland. Showers will
taper in the afternoon. Winds light to locally breezy.
.MARINE...as of 2:38 PM PDT Thursday...Southerly winds will
increase slightly tonight into Friday in advance of an approaching
weather system. Southerly winds may become locally gusty Friday
and even into Saturday. Light to moderate west to northwest swells
will continue through Friday, then transition to a larger, long
period northwest swell on Friday night and into the weekend
resulting in hazardous conditions for small craft vessels.
PUBLIC FORECAST: Dykema
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Area Forecast Discussion
National Weather Service Tallahassee FL
805 PM EDT Thu Apr 4 2019
No significant changes to the previous forecast appear necessary.
The mention of heavy rain for the western half of the area for the
remainder of the overnight hours into Friday still looks on track.
Satellite imagery shows a messy and complex convective evolution
with a couple of mesoscale convective systems (MCS`s) approaching
the area. The first is already moving into our coastal waters
currently, and it is probably producing localized winds near 50
knots well offshore along with the possibility of waterspouts.
However, SPC mesoanalysis indicates that surface based instability
remains confined to mainly offshore and perhaps along the
immediate coast, so the severe threat with this first MCS will
likely remain mostly offshore. It may skirt the immediate coast
around St Joseph State Park eastward to the Apalachicola and Saint
George Island area later this evening, so those areas still bear
For late tonight into Friday morning, a second MCS stretching from
south-central Mississippi to central Louisiana will also approach
the area. Several HRRR runs have shown the potential for some west-
east training with this activity shortly after sunrise Friday. This
bears watching, and if there is a flash flood threat with this
system, then the most vulnerable time frame would be around sunrise
through the remainder of the morning hours Friday. Confidence is
still not high enough on this scenario to introduce a flash flood
watch, but it does continue to bear watching. At this time, the
most impacted area would mainly be across the Florida panhandle
west of Tallahassee should this scenario occur.
.PREV DISCUSSION [743 PM EDT]...
.NEAR TERM [Tonight and Tomorrow]...
Two upper level disturbances will impact the local weather through
the next 24 to 36 hours with varying impacts. The first system will
move through this afternoon and into the evening as residual
convection and a mesoscale convective system (MCS) rotates through
the area. Severe potential appears to remain low through the
remainder of the evening as this system moves east. However, still
can`t rule out some isolated strong wind gusts up to 50mph. The
bigger threat with this wave will be heavy rainfall at times, but
even with that, we should be able to handle 2 to 3 inches of rain
possible overnight due to the very dry soils in place.
A stronger wave will move through after midnight and through the
early morning hours of Friday. The severe potential with this wave
is a little bit higher as better shear and upper level support is
expected. However, we`re likely to be somewhat stable across the
region, especially in our inland counties so the severe potential
will likely remain confined to near the coast, as outlined in SPC`s
Day 1 outlook.
The last thing we want to mention is the potential for flooding
rains, and possibility of a few strong/severe storms on Friday. A
frontal boundary is expected to stall across the region tomorrow
morning and into the afternoon and will serve as a focus for
convection across the area. Weakening flow aloft that is nearly
parallel to the stalled front/boundary could allow the training of
some storms tomorrow. Please see the hydrology discussion below for
more information on the flooding rain threat. As for the severe
potential, SPC has placed the majority of the region in a marginal
risk for severe storms. The primary threats tomorrow reside in
isolated hail and some damaging winds in the strongest storms.
However, given the decreasing shear profiles through the day,
widespread severe weather is not expected.
.SHORT TERM [Friday Night Through Saturday Night]...
While the stronger shortwave will be east of the CWA by Friday
night, another wave will move through tomorrow night, but will be
much weaker. This will allow for PoPs to continue into the short
term. Southerly low level flow will continue through the weekend
with showers and thunderstorms each day. The better chances are
during the day, but not negligible overnight.
While rain is expected in the short term, precipitation amounts
will be more limited than what will occur in the near term. Highs
will be in the low to mid 80s with lows in the 60s.
.LONG TERM [Sunday Through Thursday]...
A deep trough over Texas will begin to approach our area Sunday
night, bringing heavy rain by Monday with some lingering showers
Tuesday. There is enough CAPE and shear that the potential for
severe thunderstorms cannot be ruled out. A cold front is expected
to move through the region Thursday going into Friday, but
guidance is not consistent on intensity. High temperatures will
stay near or above 80, cooling slightly on Monday before warming
back up. Lows will be in the upper 50s to low 60s.
[Through 00Z Saturday]
Conditions will continue to deteriorate tonight as a batch of rain
moves into the region. Late tonight IFR CIGs are likely. Rain may be
heavy at times. Lightning will be mainly offshore tonight. Tomorrow
scattered thunderstorms are expected mainly in the AL and GA
counties. It is difficult to predict the timing of TS tomorrow since
this isn`t a clean frontal passage.
Southerly winds will persist into next week. Strong to severe
storms are expected tonight into Friday. Convection will be more
limited over the weekend and another system will move through
Monday into Monday night.
A wet pattern will be in place through early next week. Widespread rain is
expected tonight and tomorrow. No fire weather concerns.
A strong shortwave will bring the potential for heavy rain tonight
into Friday. Generally two rounds of storms are expected this
evening/tonight with more scattered storms tomorrow. The overall
forecast is for 3-4.5 inches of rain across the Florida Panhandle
and 2-3.5 across southeast Alabama and the far southwest portions of
Georgia. Elsewhere amounts should be limited to less than two
inches. That said, localized higher amounts of 6-8 inches of rain
cannot be ruled out, particularly across the Florida Panhandle.
These higher amounts could lead to localized flash flooding. A flash
flood watch is borderline at this point and given the uncertainty in
the higher amounts and isolated area, will hold off on a flash flood
watch at this time.
While convection will be more scattered in nature this weekend,
another cold front will bring additional rainfall on Monday which
will need to be watched closely, particularly based on the
amounts that fall tonight/tomorrow.
With the event tonight/Friday and another round of widespread
showers and thunderstorms early next week, these amounts could push
some rivers into action stage.
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 61 79 62 84 61 / 70 70 20 20 10
Panama City 63 74 64 76 64 / 80 70 20 20 10
Dothan 61 78 63 81 62 / 80 80 30 40 30
Albany 60 78 63 82 62 / 80 80 30 40 30
Valdosta 60 78 62 83 61 / 60 70 20 30 30
Cross City 62 80 62 84 63 / 30 30 10 20 10
Apalachicola 63 75 64 77 64 / 60 50 10 20 10
FL...High Rip Current Risk until midnight EDT /11 PM CDT/ tonight for
Coastal Bay-Coastal Franklin-Coastal Gulf-South Walton.
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Friday)
Issued at 339 PM CDT Thu Apr 4 2019
An upper level shortwave continues to move east of the forecast
area per the 20Z water vapor imagery and profiler data. Further
west, an upper trough axis was noted off the west coast with a
shortwave lifting northeast towards the Pacific Northwest. In
between these features was a low amplitude ridge over the Rockies.
At the surface, weak ridging had set up over the western central
plains as an inverted trough moved into the Ozarks. However this
ridge had already begun weakening.
For tonight and Friday, the weather is expected to generally be dry
with no obvious forcing as the upper level ridge moves out over the
plains. The bigger concern is what to do with the stratus and
possible fog overnight and Friday morning. NAM forecast soundings
tend to show the stratus hanging around and limiting how dense any
fog may get. But the RAP soundings do not hold onto the stratus
overnight suggesting there is some potential for dense fog. Earlier
mixing across central KS has not cleared out the low clouds across
eastern KS. So the NAM may be onto something. For now have kept a
mention for patchy to areas of fog in case the low clouds break up
enough. But overall guidance keeping visibilities above 1 mile adds
some uncertainty in there being widespread dense fog.
Lows tonight are forecast to only fall back into the mid 40s since
there is not a lot of cold air expected to move in. Models suggest
better mixing of the boundary layer on Friday. As long as we see
some sunshine by the afternoon, think highs could make it into the
.LONG TERM...(Friday night through Thursday)
Issued at 339 PM CDT Thu Apr 4 2019
For Friday night and the weekend, models prog upper level energy
to lift across the forecast area with the best dynamics impacting
northeast Kansas Saturday afternoon and Saturday evening. The GFS
wants to develop some light precip late Friday night, but
confidence in this is low given the NAM and ECMWF tend to keep
things dry and there isn`t an obvious lead shortwave lifting out
ahead of the main shortwave. So I just have some slight chance
POPs for Friday night. The better chances will be Saturday
afternoon and evening where POPs are in the 60 to 70 percent
range. There is progged to be some modest instability with the
wave but mid level temps are not all that cold and as a result
lapse rates are forecast to be only around 6 C/km. Additionally
deep layer shear looks to be on the modest side with 0-6KM shear
values of 30 to 40 KT. So the severe risk looks to be muted on
Saturday. By Sunday a second piece of energy is progged to move
through the plains and kick the initial wave to the east. However
the dynamics with this wave look to move mainly south of the
forecast area. However a frontal boundary with some frontogenesis
should move through the area. Because of this have continued with
some chance POPs through the day Sunday. There does not appear to
be a lot of cold air advection behind the front. So highs on
Saturday and Sunday are expected to be in the upper 60s and around
70. Lows should also be on the mild side with readings in the
lower and mid 50s.
For Sunday night through Tuesday night, upper level ridging is
expected to move across the area bringing a dry period to the
forecast. The GFS does hint at a weak backdoor front moving into the
area on Tuesday. There is not a lot of confidence in this solution
as the mean westerlies look to remain across the northern plains and
the ECMWF/Canadian fail to bring any boundary this far south. So
have highs in the lower and mid 70s for Monday and Tuesday. Lows are
expected to fall into the upper 40s.
The next upper wave is forecast to move through the central plains
Wednesday and Thursday. At this time the models tend to track the
surface low pressure system along the NEB and KS state line with
some decent spread in the ensemble solutions. So have some chance
POPs beginning Wednesday afternoon and continuing through Thursday.
The current operational solutions would minimize chances for snow on
the back side of the system. But this could change if later runs
trend south. Something to keep an eye on in any case. For now have a
modest cool down for temps on Thursday with highs in the 50s until
the uncertainty diminishes.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 631 PM CDT Thu Apr 4 2019
Stratus was holding on over TOP terminals into the evening hours.
CIGS could lift slightly into the early overnight hours but fog
is then looking likely to develop around 08Z, especially near TOP
sites. Current thinking is that IFR vis and CIGS will be possible
from around 08Z to 14Z at KTOP and KFOE, with MVFR vis at KMHK.
Fog is expected to dissipate mid-morning and CIGS will lift by
midday Friday. Otherwise, surface winds will remain light with a
ridge near the area.