Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/29/20
Area Forecast Discussion
National Weather Service La Crosse WI
702 PM CDT Sat Mar 28 2020
.SHORT TERM...(This evening through Sunday)
Issued at 215 PM CDT Sat Mar 28 2020
At 2 PM, a rapidly strengthening surface low was just moving into
southwest Iowa. The warm front was located over southern Iowa.
Temperatures were in the 40s north of this front and in the 60s
and 70s south of this front.
The models continue to show that this low will move northeast this
afternoon and tonight. It continues to look like there will be a
potential in the HRRR and RAP that the warm sector could get into
the southern portions of Fayette and Clayton counties in northeast
Iowa and Grant County in southwest Wisconsin. Surface based CAPES
may climb up to 750 J/kg. Helicity is up to 250 and the 0-1 km
shear is 40 knots. Due to this, there is still a potential of
isolated tornadoes and damaging winds. These storms will move at
50 to 60 mph.
Further to the north, the elevated CAPES will climb up to
1000 J/kg up to Interstate 90. With the shear over 40 knots, some
of the storms could become supercells. With a straight-line
hodograph, there could be right and left supercells. The main
threat will be hail. The largest hail will likely range from 1 to
From tonight into Sunday, a deformation band of rain will move
east across the area. Additional rain will range from 0.25 to 0.75
inches. Northwest winds will gust into the 30 to 40 mph from late
Sunday morning into the afternoon.
.LONG TERM...(Sunday night through Saturday)
Issued at 215 PM CDT Sat Mar 28 2020
On Sunday evening, the deformation band of precipitation will move
quickly east out of the area. Before it exits the area, the rain
may mix with some light snow north of Interstate 94. As the
pressure gradient relaxes during the late evening and overnight,
the sustained wind and wind gusts will gradually diminish.
As we head into the April, a shortwave trough and cold front will
move out of the Northern Plains and through the Upper Mississippi
River Valley. The models continue to struggle on the timing of
when this colder air will move into the region. As a result, just
stayed with the NBM. In the wake of this front, high temperatures
will range from the mid- 30s to mid-40s, and low temperatures
will be mainly in the 20s.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 702 PM CDT Sat Mar 28 2020
LIFR conditions are expected tonight into tomorrow morning at KRST,
with MVFR to IFR conditions at KLSE.
A narrow line of showers with occasional thunder are moving through
KRST this evening. These should continue to move northeast over the
next 1-2 hours, reaching KLSE by around 01Z to 02Z. The line is
expected to quickly move northeast, exiting both TAF sites by
03Z. Some small hail may be possible in stronger storms within
this line. Scattered to isolated showers will be found following
this line as the dry slot of approaching low pressure wraps into
the area, but low ceilings are expected to continue at KRST and
KLSE. Will have to watch for patchy fog development as well
overnight, but confidence is lower in this occurring. There will
be a small window of a few hours later tonight that KLSE might be
able to break out of the lower IFR/MVFR ceilings, but several
models keep this to the southeast of KLSE and will opt to keep low
clouds in the TAF for now. Shower activity will pick up again
late tonight into Sunday morning as rain wraps around the back
side of low pressure moving east across the area. Gusty east winds
this evening will decrease tonight, then turn around to the
northwest and increase again Sunday morning on the back side of
the low pressure system. Gusts of 30 to 35 knots are possible
tomorrow, especially at KRST.
Issued at 215 PM CDT Sat Mar 28 2020
Rainfall totals will range from 0.25 to 0.75 inch across the area
through tonight. This is about a quarter inch than the previous
forecast. This was done due to the speed of the showers and storms
late this afternoon and evening and the dry slot which will be
moving into the area tonight.
This rain will result in rises on area rivers. Those on the Black
and Kickapoo rivers may approach minor flood stage early next
week. Meanwhile, those along the Mississippi River may see minor
flooding during the latter half of next week.
Area Forecast Discussion
National Weather Service Boston/Norton MA
1003 PM EDT Sat Mar 28 2020
Rain will continue tonight into early Monday morning as a
secondary low pressure develops just to our south. Weather
pattern remains unsettled and cloudy for much of the upcoming
week, with seasonably cooler temperatures. Intervals of
scattered rain and/or snow showers Monday into Tuesday, with
light snow coatings possible in the higher terrain. Still
monitoring a potential coastal low Wednesday into part of Friday
whose impact to Southern New England will depend on storm
track. Periods of rain/wet snow would be possible, with little
if any impact if the storm tracks further offshore.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
10 PM Update...
Increased precipitation chances along with wind speeds and gusts
per observations. Rest of the forecast remains on track.
630 PM Update:
Radar and obs indicate initial warm-frontal rains have
overspread a good chunk of Southern New England, roughly
southwest of a Fitchburg to Norwood to Marshfield line as of
this update. Prior to the rain arriving, it had been so dry
(T-TD spreads some 20-30 degrees in most places) that the
initial onset of rain has caused temperatures to fall very
quickly and dewpoints/relative humidities to rise. North of that
described line, temperatures away from the northeast coasts
were in the low to mid 50s, but have fallen from highs in the
50s into the 40s in areas that have seen rain. Spotters and
social media reports from Belchertown and Chester have even
reported some sleet/pellets at times despite air temps that are
well above freezing.
Used a blend of the HRRR and the HREF to re-shape PoPs thru
midnight, generally spreading categorical-PoP rains in a couple
hours sooner. Also tried to show temperatures cooling pretty
quickly and dewpoints rising as rain overspreads. Lows still
look on track, however.
Previous discussion follows...
Looking at a fairly common spring-time pattern developing
tonight. Expecting a cutoff mid level low to move from the
Northern Plains into the Great Lakes overnight. At the surface,
high pressure moves farther offshore, resulting in an onshore
flow. In between these two features, at least some weak lift is
favored. This should lead to a widespread rainfall, eventually.
Abundant low level dry air will need to be overcome before any
rainfall reaches the ground. Had some reports earlier this
afternoon of some ice pellets, due to evaporational cooling.
With surface dewpoint depressions still about 20-30 degrees, it
will be a while longer before appreciable rainfall reaches the
As for timing, it will really depend upon where one is located.
The western half of southern New England should see rainfall
developing between now and 7 PM, with the eastern half of
southern New England seeing the rain develop between 7 PM and
Above normal low temperatures expected with the clouds already
In place, and only getting lower and thicker.
.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
Cutoff low should move from the Great Lakes to New England
during this time. Most of the 28/12Z guidance suggests a
secondary surface low pressure develops just to our south, then
lingers Sunday night into Monday. While this should mean plenty
of ascent to generate rainfall, the amount of available moisture
is not so certain. Precipitable water values start out 3-4
standard deviations above normal Sunday, then drop off to near
normal Sunday night. Expectation is for widespread rain to
become more showery in nature, with perhaps a persistent
drizzle developing beneath the drier air aloft.
Low risk for an elevated thunderstorm towards the south coast of
New England Sunday afternoon into Sunday night with the
development of the secondary low pressure. Lapse rates will be
marginal, and it is not a favored time of day.
Steady easterly wind will lead to temperatures not moving much
during this time. Still near to slightly below normal for late
March though during the day. Night-time temperatures more likely
to be above normal.
.LONG TERM /MONDAY THROUGH SATURDAY/...
* Cool and cloudy with scattered showers (some mixed with graupel)
on Monday. Some snow coatings possible in the hilly terrain
* Continue to monitor potential mid to late-week coastal system.
Consensus track remains south of Southern New England, but could
bring rain/wet snow if it tracks closer to the coast.
* Brief break Friday night - early Saturday before a cold front
arrives later Saturday.
* Cooler than normal temps (especially highs) through midweek, then
trending closer to normal by late week/early weekend.
Overall a fairly unsettled and (more often than not) cloudier
weather pattern in store thru late week. Other than in cloud breaks,
sunshine probably will be hard to come by over the next handful of
Upper low and its cool pocket of air aloft will meander from Ontario
into interior New England on Monday. Considerable low-level moisture
supports mostly cloudy conditions with scattered instability-type
showers. While the convective depth is pretty shallow, steep lower-
level lapse rates associated with cooler pocket of air aloft and low
freezing levels could support graupel at times. Best chance for
showers during the day is north and west of I-95. QPF amounts should
be limited to a tenth-inch or less, but just be aware that you`ll
have to dodge some showers at times.
Later Monday night, modest cool advection may help transition rain
to wet snow showers particularly across the higher terrain. Could be
some spotty light coatings in these areas (east slopes of the
Berkshires, northern Worcester County and possibly into a part of
the Merrimack Valley), but otherwise looking at a cloudy night with
cool rain showers.
Abundant clouds and limited heating supports highs on the cooler end
Still unsettled into Tuesday, with a lingering inverted trough aloft
interacting with some onshore moisture supporting a period of light
rain or snow showers. At the surface, a cool wedge of high pressure
builds down from ME/eastern NH on northeasterly flow. This will help
reinforce the cooler air. Temperatures should trend cooler than
normal, with highs in the low to mid 40s for most, though into the
mid-upper 40s across Tolland and Hartford Counties.
Tuesday Night through Thursday Night:
Pattern change toward one of high-latitude blocking remains
advertised for much of this period, with GFS/ECMWF ensemble
teleconnections indicating a negative-phase AO/NAO. By Tuesday
night, the upper-level low initially over Nova Scotia and
adjacent waters begins to retrograde back towards the Northeast
US. Today`s 12z guidance continues to advertise a southern-
stream trough which leads to surface low developing over the
lower MS Valley/Deep South on Tuesday, which progresses off the
mid-Atlantic coast Wednesday. Where this coastal low evolves
thereafter remains uncertain.
Currently, nearly all of the 12z deterministic model guidance
traverses this coastal low eastward south of 40 deg N latitude, with
little if any poleward/northward advance. Last night`s 00z Canadian
GEM operational run, however, did bring a coastal storm to Southern
New England. It`s southern stream disturbance was a lot stronger
than the GFS or the ECMWF depiction. It is also worth noting this
lone 00z Canadian GEM solution didn`t have support from the
GFS/ECMWF ensemble and even its own GEM ensemble. It has since gone
back on the 12z run toward the consensus suppressed/southern track.
The southern-stream trough responsible is progged to come onshore
coastal California later tonight, and while the model consensus
currently favors little impact if any at all (at least an
enhancement to NE winds over the southern waters), all outcomes
still remain on the table and will not yet downplay this system.
Will continue to advertise lower Chance-level PoPs with nonetheless
considerable cloudiness at least given the presence of the
retrograding upper low and related moisture.
Will have to watch how close any wrap-around precip gets later Wed
night into Thurs night, with the 12z ECMWF/Canadian GEM and to
a lesser extent the GFS indicating this potential.
Temperatures Wed start off cooler than normal on the highs (in the
mid to upper 40s), and near normal on the lows (in the 30s Tues thru
Thurs night). By Thursday, highs should start to trend closer
to normal (upper 40s-mid 50s).
Friday - Saturday:
There is some level of uncertainty in this period on shower chances
on Friday depending on how close any wrap-around moisture makes it
from the distant coastal system, which looks to slow/stall in the
waters south of the Canadian Maritimes. Better chances may be
towards the coast than further inland, but will stay close to a
model blended approach which keeps chances for showers going across
a larger part of Southern New England.
Nonetheless, even if drier weather ultimately ensues for Friday,
most models show a cold front progressing in from the Great Lakes/OH
Valley into Saturday, bringing another chance for showers.
Seasonable to slightly above normal highs in the upper 40s to mid
50s with lows in the mid/upper 30s.
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight...High confidence in the trends. Moderate confidence in
Generally deteriorating conditions toward MVFR, generally sooner
in the interior as rain overspreads the TAFs. After midnight the
prospects for MVFR-IFR ceilings increase in the interior and
the terrain, while staying closer to MVFR near the coast. Visbys
should be generally VFR/MVFR, with heavier rains bringing in
the lowest visbys.
Sunday and Sunday Night...Mainly MVFR with areas IFR in heavier
KBOS Terminal...High confidence in TAF trends. Moderate
confidence in timing.
KBDL Terminal...High confidence in TAF trends. Moderate
confidence in timing.
Outlook /Monday through Thursday/...
Monday: MVFR/IFR conditions possible. Breezy. Scattered SHRA,
Monday Night: MVFR/IFR conditions possible. Breezy. Scattered
SHRA, scattered SHSN, patchy BR.
Tuesday: MVFR/IFR conditions possible. Breezy. Isolated SHRA.
Tuesday Night: Mainly VFR, with areas MVFR possible. Breezy.
Wednesday: Mainly VFR, with areas MVFR possible. Breezy. Slight
Wednesday Night: MVFR/IFR conditions possible. Breezy. Slight
chance SHRA, slight chance SHSN.
Thursday: Mainly VFR, with areas MVFR possible. Breezy. Slight
Tweaked the timing of Small Craft Advisories across the waters.
Did not have enough confidence to issue such advisories for
Boston Harbor and Narragansett Bay, but it is not impossible for
some gusts to 25 kt on those waters Sunday. Low risk for gale
force gusts across the eastern coastal waters late Sunday
afternoon into Sunday evening. Not enough confidence in these
gusts to upgrade to Gale Warnings. It`s marginal.
Rain expected to develop tonight into Sunday as a warm front
lifts through and a secondary low develops along the south
coast. Some visibility reduction as fog develops, too. Winds
will gradually shift to the east tonight and Sunday, then
increase. On Sunday gusts will increase to 25- 30 kts along
with seas building to 5-8 feet across the interior ocean waters,
while the outer waters see waves build to 7-10 feet. Confidence
has increased to issue a Small Craft Advisory across the
majority of ocean waters through Sunday.
There is potential for isolated thunderstorms across the ocean
waters Sunday evening.
Winds decrease and become more variable across most of the
waters Sunday night as a secondary low pressure develops near
Outlook /Monday through Thursday/...
Monday: Winds less than 25 kt. Areas of rough seas. Scattered
rain showers, patchy fog. Local visibility 1 to 3 nm.
Monday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Scattered rain showers,
Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. Isolated rain showers.
Tuesday Night: Winds less than 25 kt. Areas of rough seas.
Slight chance of rain showers.
Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of rough seas. Slight chance of rain
Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas. Slight chance of rain showers.
MARINE...Small Craft Advisory from 5 AM Sunday to 2 AM EDT Monday for
Small Craft Advisory from 5 AM to 10 PM EDT Sunday for ANZ233-
Small Craft Advisory from 8 AM Sunday to 2 AM EDT Monday for
Small Craft Advisory until 8 AM EDT Monday for ANZ235-237-255-
Small Craft Advisory from 8 AM Sunday to 8 AM EDT Monday for
Small Craft Advisory from 5 AM Sunday to 8 AM EDT Monday for
Area Forecast Discussion
National Weather Service Grand Rapids MI
1104 PM EDT Sat Mar 28 2020
Issued at 159 PM EDT Sat Mar 28 2020
- Locally heavy rain along with some storms tonight
- Wind Advisory with showers and colder Sunday
- Cool but quiet weather Tuesday and Wednesday
Issued at 1048 PM EDT Sat Mar 28 2020
Overall, the threat for severe weather looks low tonight. A warm
front stretches from portions of Northern Illinois east into
Northern Ohio. The warm front will nudge our direction overnight
with an occluded front sweeping east through the forecast area
late. A low level jet will move across the area between now and
about 500am which will result in a round of showers and
thunderstorms. Instability however is not significant, on the
order of 500-1000 j/kg. While there will be enough instability to
generate storms, we are not expecting severe weather. Locally
heavy rain remains the main concern with PWAT values peaking
between 1.25 and 1.50 inches in the next few hours. These values
are very high for this time of year and are above the daily max
via the SPC sounding climatology page for the DTX upper air site.
Suffice it to say we are working with quite a bit of moisture
ahead of a dynamic system. Storms tonight will also be capable of
small hail and lightning.
We will be maintaining the Flood Watch and Wind Advisory as is.
.DISCUSSION...(This evening through next Saturday)
Issued at 333 PM EDT Sat Mar 28 2020
-- Locally heavy rain/thunderstorms/risk of severe tonight--
There is a slight risk (and I do mean slight) for severe storms
tonight. The timing is after 10 pm till around 3 am. The low level
jet does not get onshore of Southwest Lower Michigan until after 2
am. The NAM12 shows most unstable cape values reaching near 500
j/kg but that does not get into our forecast area until around
midnight and it`s gone by 5 am. It`s been my experience we need
at least 500 j/kg to get thunderstorms. Model sounding show a
strong thermal inversion (10 degree F) below 1800 ft as the
occluded front moves through near South Haven. That would make it
hard to mix the 50 to 60 knots winds above the inversion down to
the ground. There is cape in the -10 to -30 range, so hail is
As I stated earlier today it seems to this forecaster the risk
for severe storms is rather low. Having the triple point tracking
near or south of I-94 helps the cause to keep the severe storms
mostly south of the GRR forecast area. This continues to be
supported by the HREF and NAM 12z run plus several descent runs
of the RAP, HRRR. The HREF updraft helicity tracks (pinball`s)
are all south of the state of Michigan tonight. This would
diminish the significantly diminish the risk for tornadoes.
There is significant risk for heavy rain tonight. The moisture
transport vectors (1000/850 mb) are aimed at southwest Lower
Michigan and the precipitable water values are over an inch. Not
to mention model sounding are saturate to 300 mb. Most of the rain
will be after 8 pm and it should be done by 6 am. The storms
would be fast movers but they would be efficient rain producers
-- Wind Advisory with showers and colder Sunday--
The storm system deepens to around 990 mb and has a tight pressure
gradient as the center of the system tracks toward the Michigan
Upper Peninsula Sunday. The 850 mb temperature falls nearly 10c
in 6 hours Sunday morning. These sorts of events result in gusty
winds. The HREF mean wind gust max is in the 40 to 50 mph range
most of Sunday afternoon, the max is near 60 mph from South Haven
to Holland early Sunday afternoon. The HRRR is not significantly
different. The NAM12 and NAM3 have 45 to 50 mph winds (80 pct of
mix layer max wind) mixing down Sunday, south of I-96. Thus it
should not be surprising that we have issued a wind advisory for
There is fairly deep moisture being raped around the system and
it is very much closed off at 700, 500 and 300 mb into Monday.
That allows for persistent rain showers Sunday during the day
into early Monday. The air gets cold enough that northern
sections will see snow mix with the rain Sunday night.
-- Cool but quiet weather Tuesday and Wednesday--
Once the weekend system moves out of the area we get an unusual
upper air pattern to replace it. It`s sort of an omega block with
a closed low over eastern Canada and the northeastern United
States and another one over the Northwestern United States with an
upper high near James Bay. This sort of pattern is very blocking
so it would be hard to get any sort of system into the western
Great Lakes until that block breaks down late in the week. This
will result in cool temperatures for this time of year but with
some sunshine each day.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 819 PM EDT Sat Mar 28 2020
A variety of aviation weather is expected the next 24 hours as a
strong spring storm system moves through the region. Low ceilings
and visibilities (IFR and below) are expected from this evening
into the overnight hours, or especially from 01z to 09z. There
will be a period of showers and potentially a few embedded
thunderstorms between 03z and 09z. A short lived period of
improvement is expected between 09z and 12z as a dry slot
(clearing) works through the area. Widespread MVFR ceilings will
spill back into the area from the west on Sunday. The other item
of note will be the strong winds that are expected on Sunday.
After about 13z, winds will jump into the 15-30 knot range from
the southwest with gusts into the 30-40 knot range.
Issued at 333 PM EDT Sat Mar 28 2020
We will issue a Lake Shore Flood Advisory due to the strong winds
Sunday building large waves. Due to the southwest gales, the
highest water levels will be over the northeastern sections of
Lake Michigan so this time it will not be so much the high water
level as much as the high waves. We do have a gale warning for the
southern 2/3 of the Near Shore for Sunday due to the strong low
pressure system lifting north across the western Great Lakes.
Issued at 333 PM EDT Sat Mar 28 2020
Round 1 of the expected heavy rain in West Michigan dropped
close to 2 inches at many locations south of I-96, with lesser
amounts to the north. This amount of water will be enough to bring
the headwaters of the Grand River (at Jackson) as well as the
Portage River (at Vicksburg) to minor flood stage today and tonight.
Other rivers are all on their way up, but none are near flood levels
at this time. The problem is that heavy rain round 2 is expected to
move into our area later this afternoon. All areas in West Michigan
will likely see at least another half inch of rain, but some areas
may see another inch or more (especially if thunderstorms end up
moving over the same areas repeatedly). Its this 2nd round of rain
that will determine if other rivers like the Looking Glass,
Maple, Grand River at Comstock Park, and Muskegon River at Newaygo
and Bridgeton will get to flood levels or not. We have held off
on any flood watch or warnings for the Grand and Muskegon rivers
for now, and will wait to see how much rain falls tonight.
The 2nd threat is the potential for flooding of urban, low-lying,
and poor drainage areas associated with the heavy rain itself
tonight.The most vulnerable places are the larger urban areas that
saw the heaviest rain last night. This is generally the area along
and south of I-96, including Lansing, Grand Rapids, Kalamazoo and
Jackson. If thunderstorms tonight end up moving over the same areas
repeatedly, some intersections and roads may be flooded.
MI...Flood Watch through Monday morning for MIZ064>067-071>074.
Wind Advisory from 10 AM to 8 PM EDT Sunday for MIZ043>046-
Lakeshore Flood Advisory from 5 AM to 11 PM EDT Sunday for
LM...Small Craft Advisory from 5 AM to 11 PM EDT Sunday for LMZ849.
Gale Warning from 5 AM to 11 PM EDT Sunday for LMZ844>848.
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1105 PM EDT Sat Mar 28 2020
Issued at 1105 PM EDT SAT MAR 28 2020
The trends have remained much the same this hour. The convection
seen in central Kentucky will likely out run the better
instability and decrease in intensity as it tracks northeast. The
convection across Tennessee will be what moves into the
Cumberland Valley by early in morning and still could see some
gusty winds with these storms. Overall kept the PoPs the same,
with updates to include the latest obs and trends for the other
UPDATE Issued at 859 PM EDT SAT MAR 28 2020
We are continuing to watch upstream convection and how this is
evolving downstream. The latest HRRR brings convection into our
area late tonight into early Sunday morning. The best chance of
seeing at least isolated severe storms would be in the Cumberland
Valley based on the trends. The main threat would be gusty winds
and perhaps small hail. The trend in instability is downward
through the night and mostly elevated above the inversion layer.
The question is can storms sustain given the very strong speed
shear in place. Therefore the potential for strong winds seem most
reasonable once the inversion is mixed out. However if you do get
a cell that can take advantage of more CAPE this kind of
environment would support stronger storms. This is likely why the
SPC moved the slight further east even given the more
conditional possibilities. Updated the PoPs to increase them in
the Cumberland Valley and also lower deeper valley temperatures
given the clearing spots seen in the clouds.
.SHORT TERM...(This evening through Sunday night)
Issued at 335 PM EDT SAT MAR 28 2020
Current conditions across the region features eastern Kentucky
continuing to be in the warm sector of a developing storm system.
The warm front has lifted north and is now along northern OH and
IN. Partly to mostly cloudy conditions have been in place over
eastern Kentucky over the past 24 hours as some daytime cumulus
and some cirrus ahead of the main low to the west. This, with
strong southwesterly flow has allowed high temps this afternoon
to jump into the mid 80s. The lack of good cloud cover may lead to
some ridge to valley temperature differences overnight but
nothing compared to last night. Model trends have continued to
trend slower with the approach of the developing squall line over
central Kentucky and the approach of the main front. Concerning
instability with the approach, now being slower and more towards
dawn, even moist bias models are showing only 1000 to 1200 J/KG.
Most high res models are keeping instability about 1000 J/KG at
most. CAMs at this point, are showing much of the convection
weakening by the time it reaches I-75 with the northern half of
the line dissipating with a bit stronger convection developing
along a broken line in the south. This too, given the strong cap
and dry conditions in place, will weaken. The southwest along and
west of the I-75 corridor may be the most likely area to see a
wind threat from the dying line of convection.
This line, given strong progressive flow will quickly push east
through east kentucky with clearing likely by Sunday afternoon.
Die to the lack of colder air behind this front, a spot or 2 may
warm to 70 degrees for a high by tomorrow afternoon. The only
other concern behind this front with winds mixing to the surface
from 800MB. While a 30 mph gust to the surface will be likely, at
this point, wind Advisory criteria is not expected. Will mention a
30 to 35 mph wind possible in the HWO though. With clear skies
setting up Sunday night and winds slowly decreasing, temps will
drop into the 40s for lows. There may be some ridge to valley
differences. Otherwise, the main concern will be for the Saturday
morning and into Saturday afternoon range.
.LONG TERM...(Monday through Saturday)
Issued at 405 PM EDT SAT MAR 28 2020
The period is expected to begin with the axis of a a mid and upper
level ridge extending from the Gulf of Mexico and Bahamas region
into the mid MS Valley region. An upper level low and associated
trough will be moving across the St Lawrence Valley and Northeast
Conus. Further west, an upper level trough is expected to moving
across the southern Rockies and Four Corners region while an upper
level low is expected to be nearing the pacific northwest. A
ridge of sfc high pressure is expected to be building across the
area to start the period.
Sfc and upper level ridging will gradually move across the area
on Monday and Monday night. However, with the axis of the upper
level ridge moving east of the area by dawn on Tuesday while the
shortwave initially over the Four Corners will have moved across
the Plains and reach the mid MS Valley by dawn on Tuesday. Moisture
and clouds will increase on isentropic lift ahead of the
approaching shortwave on Monday night and showers could occur
late, particularly in the Lake Cumberland region.
The shortwave trough is expected to move into the OH and TN Valley
on Tuesday as the sfc low track across the southeast with an
inverted trough/sfc reflection of the upper trough/low extending
into East KY. This shortwave trough will depart to the northeast
late Tuesday night and Wednesday while a sfc low tracks off the
Carolina coast. This system will likely lead to showers showers
across the area Tuesday and Tuesday night. The cooling aloft may
also steepen lapse rates for a few thunderstorms Tuesday evening
into early on Tuesday night. Another soaking rain should fall
from this system, especially across the southern half to two
thirds of the area. At this time QPF is expected to average a
quarter to two thirds of an inch across the area.
A brief period of height rises should follow Wednesday into the
day on Thursday as an upper level ridge moves across the southeast
and OH Valley. Sfc high pressure will also build into the area during
this time. Shower chances should be minimal during this period
and the model blend NBM pops may be overdone Wed afternoon and Wed
night. There remains uncertainty in timing of the next shortwave
trough moving across the Plains into the eastern Conus Thursday to
Saturday and associated sfc system and cold front. The recent
model trends have been generally toward the cold front approaching
the area on Friday and moving east of the area Friday night. This
period appears to be unsettled with chances for showers,
especially along and near the front. Additional weaker shortwaves
moving through the flow should lead to a fair amount of cloud
cover and isolated to scattered showers at times from late Thu
into Thu night at at the end of the period as well.
Temperatures after Monday night will average below normal,
especially for highs as the first low pressure system and
shortwave trough moves across the area followed by westerly upper
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 740 PM EDT SAT MAR 28 2020
VFR skies will roll on for much of the night before storms arrives
late tonight into early Sunday morning. These storms will lower
CIGs possibly into the MVFR range or lower as the thunderstorms
roll through in the pre-dawn to early morning hours Sunday. This
will be quite temporary as CIGs return to VFR through the
remainder of the morning and remain that way through the period.
There will be a strengthening low jet tonight and this will lead
to a period of LLWS once again through the night. The winds will
be out of the southwest through the period and will start in the
5-10 knot range through the night. Then deep mixing will lead to
gusty winds through the morning and afternoon Sunday in the 20 to
27 knot range.
Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
928 PM EDT Sat Mar 28 2020
A front will stall out near the Appalachians into southern
Virginia through tonight. The front will then try to lift north
as a warm front early Sunday, before a cold front moves through
from the west late Sunday. High pressure will be in control
Monday into Tuesday. A low pressure will then approach from the
southeast U.S. Tuesday night before departing off the mid-
Atlantic coast on Wednesday.
.NEAR TERM /THROUGH SUNDAY/...
Biggest challenge for tonight is going to be how low cigs get
and how low visiblities drop. Short-term guidance is all over
the place with MOS guidance suggesting vsbys remain in the
2-4sm range while GLAMP and other hi-res models indicating
visibilities dropping to less than half a mile. Not expecting
any measurable precip other than some light drizzle.
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Short-term models like the HRRR indicate isold supercell
potential possible especially along and north of Interstates 68
and 70. Even if warm front fails to lift into PA, there appears
to be sufficient elevated instability that supercells could
still produce large to very large hail. Convective initation
remains questionable especially in southern areas where there is
lack of frontal convergence. Isolated to scattered
thunderstorms are still expected in the northern half of the
Sunday will start with ample low clouds and fog attempting to
lift. How quickly it does so may be the key to the forecast.
Believe there will be a sharp inversion, with a warm nose which
could be as warm as 19C near 925 mb.
A cold front will approach during the day, and cross the region
during the afternoon, during peak heating (18-00 UTC). There
will be ample shear across the region. Instability will be the
question. If the wedge holds, then instability will be minimal
and the front would either come through dry or as a few showers
(with perhaps an elevated rumble of thunder). But, if the wedge
does manage to mix out, then MUCAPE may exceed 1000 j/kg. Given
the other ingredients in place, that would be supportive of
robust thunderstorms. There are guidance members on each side of
After collaboration with SPC, decided that the conditional
threat great enough to at least mention somehow...hence
Marginal Risk of severe. Am maintaining a chance of precip
crossing the area in the database, with a slight chance of
thunder. It may be that both solutions are correct; ie:
cool/stable air across northern Maryland while moist/unstable
air present across central Virginia and southern Maryland. Will
be monitoring later cycles to discern these details.
Sunday night into Monday a deep cyclone will build across the
Great Lakes. The area will experience high pressure but westerly
flow and cold advection. Lows will be in the 40s again by
.LONG TERM /TUESDAY THROUGH SATURDAY/...
An upper level trough over the southern Plains will drop
southward through the southern parts of the mid-Atlantic and the
Carolinas Tuesday into Wednesday. A surface low associated with
this trough will move to our south Tuesday afternoon and into
Wednesday morning. The main area of precipitation should be
situated to the south of our forecast area over the Carolinas
and the southern portions of Virginia. As the main forcing
remains to our south, the precipitation that we observe in our
region will likely be caused by a combination of overrunning
precipitation and an easterly flow off of the ocean. If this
system tracks further northward, our region has the potential to
experience heavier precipitation mainly late Tuesday and into
Wednesday morning. Precipitation and an easterly flow will lead
to daytime temps running near to slightly below normal for this
time of the year in the 50s and lower 60s with overnight lows in
High pressure builds into our region behind the exiting low
Wednesday afternoon and remains over our area through Thursday.
Light winds out of north will lead to cooler conditions over our
area. Temperatures will continue to hover in the 50s with overnight
lows in the 40s on Thursday.
Another cold front is forecast to approach and move through our
region Friday and into early Saturday. Models have some decent
agreement on the subtropical jet moving northward and phasing with
weak jet over the midwest and mid-Atlantic. This phasing will
combine with a frontal passage to bring precipitation to our region
once again. The main limiting factor will be a westerly flow
transporting drier air into our area. We will need to monitor the
strength of the jets to determine further hazards for end of next
.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
Flight conditions straddling between MVFR and IFR, but across
BWI/MTN the marine flow spreading inland has resulted in
conditions on the verge of LIFR. Low clouds and fog will
continue to spread inland, with LIFR widespread overnight.
Conditions will slowly improve Sunday. How quickly this
transpires still in doubt. A cold front will be crossing the
terminals this afternoon. If the clearing comes by midday, then
strong thunderstorms possible along with the frontal passage.
Otherwise it may be a dry front.
VFR will return Sunday night, continuing through Monday.
SubVFR conditions are possible late Tuesday and into Wednesday due
to rain and an easterly flow. VFR conditions should return Wednesday
afternoon and continue through Thursday as high pressure builds over
Light northeast winds (at or below 10 kt) will continue across
the waters through tonight. Low clouds and fog will be
thickening through the night. Winds will likely veer south
tomorrow as the marine wedge lifts. Its unclear how quickly this
will happen, but any clearing would be followed by a threat of
thunderstorms with gusty winds late Sunday afternoon.
Conditions will improve Sunday night, but winds shouldn`t be
high enough to need Small Craft Advisories. No Small Craft
issues expected on Tuesday as well, but Small Craft Advisories
may be needed on Wednesday due to a northerly flow.
Area Forecast Discussion
National Weather Service San Francisco Bay Area
833 PM PDT Sat Mar 28 2020
.SYNOPSIS...Scattered light showers will continue overnight.
Widespread rain is expected from Sunday morning into early Sunday
afternoon as a cold front moves through the area. Dry conditions
will develop by Sunday night. A weak weather system may bring
light rain to the North Bay on Monday, otherwise dry high
pressure will start to build. The long range forecast calls for
dry weather for the remainder of next week, along with a gradual
.DISCUSSION...As of 8:30 PM PDT Saturday...An upper trough is
centered offshore along 125W this evening. This weather system has
been producing scattered shower activity throughout the day, and
KMUX radar currently shows scattered light showers persisting this
evening. Rainfall amounts have thus far been light, with most
locations picking up less than a tenth of an inch. Greatest rain
totals have been in the East Bay where local amounts of about a
quarter inch have been reported.
Latest short-term model data indicate scattered light showers will
continue overnight, but with little additional precip
accumulation. The 00Z NAM and latest HRRR agree that a line of
widespread and heavier precipitation will then track across our
forecast area from late tonight through midday Sunday as the
trough axis arrives along the coast. Shower activity will then
taper off Sunday afternoon and mostly end by Sunday evening.
Additional rainfall through Sunday afternoon is forecast to range
from a tenth to a half inch.
A system forecast to move inland to our north on Monday may
produce light rain as far south as our North Bay Counties.
Otherwise, Monday is expected to be a dry day with temperatures
remaining slightly cooler than seasonal averages. For the
remainder of next week, the models agree that an upper ridge will
gradually build near the West Coast, maintaining dry weather
across our region and resulting in a slow warming trend.
Temperatures by Wednesday and Thursday are forecast to warm to
near normal, or slightly above, with highs expected to range from
the mid 60s to mid 70s. Based on latest extended forecast models,
dry and mild conditions will likely persist through next weekend.
Looking farther out, the ensemble mean from both the ECMWF and GFS
indicate wet weather will return during the week of April 6 as a
trough over the Eastern Pacific undercuts the ridge.
.AVIATION...as of 4:48 PM PDT Saturday...For 00z tafs. Occasional
showers and VFR to MVFR tonight and Sunday morning. VFR returning
by early Sunday afternoon.
Vicinity of KSFO...VFR occasionally MVFR tonight, VFR Sunday
afternoon and evening. Showers tonight and Sunday.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR occasionally MVFR tonight, VFR Sunday
afternoon and evening. Showers tonight and Sunday.
.MARINE...As of 8:22 PM PDT Saturday...Generally light winds
persisting through the weekend and early next week as high
pressure moves over the southern California waters and a weak
boundary approaches from offshore of the Pacific Northwest. Mixed
swell will continue with a moderate northwest swell and a light
PUBLIC FORECAST: Dykema
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Area Forecast Discussion
National Weather Service Nashville TN
803 PM CDT Sat Mar 28 2020
FOR MESOSCALE DISCUSSION...
Latest laps data showing the most impressive helicity slug running
from the MO bootheel ne into srn IL. Helcities of 300+ are
prevelant across that area. Further southeast, values drop to
around 200 M2/S2 with this area reaching down into the tor watch
area across nw middle TN. So far, no reports from the storm that
moved across Stewart co. However, it did move across rural areas
and the liklihood of some larger hail cannot be dismissed. Did see
some brief mid level rot and the semblance of some low level
rotation as per the reflect comma. Otw, no reports yet.
Latest Hrrr data shows that the main band of convection across
wesrtern TN will hold togethere as it moves east. This activity is
still expected to reach the TN river around 10 pm...and the I-65
corridor around midnight. But again, the higher 850 mb wind energy
and helicity values do not translate eastward in conjunction with
the forcing. In otherwords, phasing could be a little better.
.PREV DISCUSSION.../ISSUED /
I`m going to start with the most important part of this AFD: we are
expecting severe weather tonight in the form of damaging straight
line winds, hail and tornadoes. Because of this, let me re-emphasize
1. This is going to be a nighttime event. Please make sure you have
multiple ways to get warnings that may be issued for you. This does
NOT mean having downloaded multiple apps on your phone. Your phone,
turned on and up, is one way. A second would be a properly
programmed NOAA weather radio -- something that will wake you up in
the event you go under a warning while you are asleep.
2. Have a safety plan for your family in place now. Practice it. If
you need help putting one of these together, visit ready.gov. They
have great information on what you need to do PRIOR to going under a
warning. This includes having plan to get to shelter in a timely
manner. If you live in a mobile home, this could include being in
that shelter during the watch, not just if you go under a warning.
3. Please treat Severe Thunderstorm Warnings with the same priority
you would a Tornado Warning. Winds blowing in a straight line versus
those spinning around in a circle at 70 mph or more can do the same
kind of damage. Just take shelter.
I`ll climb down off my soapbox now.
Yes, severe storms will be possible tonight. Here are the highlights
from my update earlier, as things have not changed in the last
couple of hours:
The strong cap, being seen in current LAPS soundings, looks like it
will be in place throughout the afternoon and early evening hours.
This is what we`re going to have to watch closely as we get into the
6 pm timeframe. If that cap starts to break, then we could see some
discrete development. However, the current thinking is that the cap
will hold tight until we can get the 850-700mb jet structure closer
to the mid-state, which will probably be the 7-9 pm time frame. This
should erode the cap and allow convection to begin developing across
West TN/North MS, with storms then moving into Middle TN shortly
after that. Helicities do pick up right around that time (which will
help organization). If we can elude the discrete development in the
early evening hours and only have to deal with the activity closest
to the front, then we should be dealing with a QLCS/broken line type
event. Of note, no matter what soundings we look at, even though I
said they pick up, helicities are not off the charts. Some of our
bigger tornado outbreaks have 0-3km helicities of 400-600 m2/m2,
where this evening is in the neighborhood of about 300, based on
latest guidance. This could help us in the tornado department and is
really why we`re focusing on this event being more of a straight-
line wind event, but tornadoes are NOT out of the question, by any
means. In addition, because of this more-likely scenario I`ve drawn
out here, the large hail threat should be less as well, due to storm
mode. Quarters are more likely versus anything much bigger.
For more on timing, including graphics, visit our website
On that note, storms should be pulling off the Cumberland Plateau
prior to sunrise and it looks like we`ll return to the dry
conditions we`ve been experiencing the last few days. Our next
system is progged for Tuesday and models continue to keep the
surface low moving west to east over northern Alabama, which keeps
us out of the warm sector and any severe threat south of Middle TN.
Following Tuesday`s rain, we should have a couple more days of dry
conditions then another system on Friday. Models aren`t in great
agreement regarding this system`s evolution, so more to come on
that. For now, please remain weather aware as the sun sets.
00Z TAF DISCUSSION.
Cold front expected to push through overnight with the boundary
exiting the Plateau area between 09z and 12z. Thunderstorm
development is expected along and in advance of this feature.
Gusty winds will be strongest near CKV with weaker magnitudes the
further east you go. Otw, all precip will exit the area by 12Z
with partial clearing beginning in the afternoon.
.PRELIMINARY POINT TEMPS/POPS...
Nashville 60 71 49 68 50 / 80 10 0 0 70
Clarksville 56 70 47 68 48 / 80 10 0 0 70
Crossville 58 70 47 63 46 / 80 30 0 0 60
Columbia 58 71 49 69 50 / 80 10 0 0 80
Lawrenceburg 59 71 49 69 51 / 80 10 0 0 80
Waverly 56 69 48 69 49 / 80 10 0 0 80
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
1205 AM EDT Sun Mar 29 2020
High pressure aloft will extend over the Southeast states this
morning, then weaken as a cold front approaches from the west. This
front will push southeast through the region this evening, bringing
cooler and less humid weather late tonight through Monday. A storm
system will move in from the west Tuesday and bring increasing rain
.NEAR TERM /THROUGH TONIGHT/...
As of 900 PM Saturday...
00Z surface analysis shows the eastern segment of the synoptic warm
front still lingering near the NC/VA border,despite the erosion of
stratus across southern VA earlier today, then arching north and west
across OH/IN/IL. Thin high clouds continue to spill east ahead of
the storm system over the Deep South and lower Midwest, and will
continue overnight. RAP soundings suggest some stratus and fog on
the cool side of the warm front, possibly just north of Person Co.,
With nothing to push the front back south before it lifts north
toward the Chesapeake Bay tomorrow, expect only thin high clouds to
continue to spill east ahead of the storm system over the Deep South
and lower Midwest. Very mild lows in the mid 60s.
.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 159 PM Saturday...
Near record warmth out ahead of the cold front Sunday afternoon...
The main story Sunday will be the near record warmth. Expect mostly
sunny skies in the east and south, with partly sunny skies north and
west. WAA out ahead of the approaching cold front will aid
temperatures to reach the mid 80s to near 90. The hottest readings
will be in the Sandhills aided by the SW flow at 15-25 mph. The
winds will slowly turn westerly as the pre-frontal trough pushes
east into the western Piedmont during the mid to late afternoon.
This will allow some lower dew points and drier air to flow off the
The main cold front will reach the region Sunday evening and push
offshore late Sunday night. A pre-frontal surface trough is
expected to form in the Foothills during the afternoon. There
is very limited lift forecast as the main dynamics will pass well to
our north. There will most likely be MLCapes increasing as the
temperatures rise into the mid to upper 80s (near record heat
for late March, combined with dew points in the lower to mid 60s
(ample low level moisture, especially for late March). The wind
shear will be increasing to between 35-40kt in the NW-N Piedmont.
Even with MLCapes in the 1000-1500 J/Kg range and 35 to 40kt of bulk
shear, the more significant height falls and large scale lift well
north will most likely hinder convection initiation along the
pre-frontal trough and/or cold front over central and eastern NC.
We will keep only slight chances in the afternoon and early evening,
mainly northwest and north.
The cold front should push through the region on Sunday night. Winds
will become westerly behind the front, but decrease to around 10 mph
overnight. Lows Sunday night will slowly ease into the mid 50s NW to
lower 60s SE with mostly clear skies.
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 400 PM Saturday...
Monday and Monday night: Westerly flow behind the cold front on
Sunday should keep temps warm again for Monday, with highs generally
in the mid to upper 70s, with possibly a few readings near 80 in the
southeast. Low temps Monday night area expected to fall into the
upper 40s north to the mid 50s south as as a reinforcing cold front
moves through. Dry weather is expected to continue for this period
Tuesday through Saturday: A mid/upper level s/w trough will move
eastward from the lower to mid MS River Valley region on Monday and
across the our area on Tuesday into Wednesday morning. The main
surface low is progged to pass to the south of central NC, keeping
the best surface instability and severe threat to our south.
Regardless we should see a good amount of rain late Tuesday into
Wednesday morning, with average rainfall amount ranging from around
a half to inch to one inch, with locally higher amounts. High temps
on Tuesday will be greatly affected by how soon the precip moves in.
For now will continue to advertise highs ranging from the upper 50s
nw to the mid to upper 60 se, with a late day/evening arrival of the
precip. Low tuesday night are generally expected to be in the 40s.
The deepening surface low will lift off to the east/northeast on
Wednesday, though precip may lingering for at least the first half
of the day as the additional s/w energy moves through the area. This
should result in high temps in the 50s for Wednesday, with lows in
the 40s for Wednesday night. A warming trend will start for late
week, though a lot remains uncertain with the mid/upper level flow
pattern for late week into the weekend and when the next chance for
precip will be. For now will go with highs warming into the 60s to
near 70 for the remainder of the forecast period with lows in the
40s and a slight chance for precip late week into the weekend.
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
As of 1205 AM Sunday...
VFR conditions will dominate central NC for the next 24 hours. A
front sitting near the border of NE NC and SE VA will push further
northward this morning, leaving gusty winds from the SW today into
tonight across our area, ahead of a mostly dry cold front that will
cross central NC from late afternoon through evening. An isolated
shower or storm is possible across the N between 18z and 23z,
however the chance of any of these passing close to a terminal is
very low, given the sparse coverage. Aviators should be alert for
frequent surface gusts from the SW up to 25-30 kts between 14z and
00z today. Winds will veer around to W and WNW with frontal passage
at INT/GSO late in the TAF period.
Looking beyond 06z Mon, VFR conditions should hold through the first
part of Tue, but an approaching storm system from the west will
bring a good chance of sub-VFR conditions in rain Tue afternoon
through Wed. Improvement to VFR is expected Wed night into Thu as
this storm system departs and high pressure moves in. -GIH
DAY MAX YR MIN YR
03/28 91 1907 65 1907
03/29 94 1907 66 1907
03/28 87 1907 62 1991
03/29 91 1907 61 1989
03/28 87 1945 65 1921
03/29 87 2012 65 1924