3/16/26 Severe Weather Event Thread (Day 2 MOD Risk) | Latest: 15% TOR, 60% WIND, 5% HAIL

[TSSN+]

Point and click again not displaying the storm threat. Not even mention severe in grids. Not sure why this keeps happening. 

[EstorilM]

16 minutes ago, 09-10 analogy said:

Im seeing "HSLC" a lot. Does that stand for "high shear, low CAPE"?

Yeah, but relatively speaking (for this scenario, and climatologically) this is plenty CAPE, probably 750-1000. 
 

Don’t really need the CAPE when you’ve got so much else going for you, so not a typical HSLC setup where that would be a limiting factor. 

[snowfan]

16 minutes ago, TSSN+ said:

Point and click again not displaying the storm threat. Not even mention severe in grids. Not sure why this keeps happening. 

 

[konksw]

So is the wedge what could limit severe risks if it hangs on?

[Eskimo Joe]

Welp....

 

 

[Eskimo Joe]

Lee surface low would make this legit MOD risk for tor/svr winds

 

 

[wxmeddler]

FOLKS

Exceptional Synoptics call for exceptional care, and in the equinox seasons if you've got big numbers on the cold side, you should be prepared for big numbers on the warm side. This system is no exception. CAM guidance from this morning's 12z runs show a variety of scenarios and evolutions. 

When in doubt about storm mode or coverage, falling back on the synoptics is usually the best forecast. In this scenario, the synoptic evolution is clear. A large mid-latitude trough exhibiting two distinct mid/high level wind-maxima rounding the base of the trough is creating a primary low through the upper mid-west while the secondary (later) wind maxima emerges over the southeast and quickly ejects through the Mid-Atlantic. Ahead of this second wind maxima large scale ascent through upper-level divergence will cause mass flux response from the Carolina's northward into southern PA. As the secondary wind maxima / embedded trough tilts negative an area of lower pressure will develop east of the blue ridge in the Piedmont region of North Carolina and quickly traverse northward. Along this embedded low, guidance that has taken this solution has backing wind vectors in the lowest 1km relative to the Bunkers right motion. This produces large curvature hodographs in the lowest 1-2km's followed by a storm relative weakening in the mid-levels, with exceptional ventilation in the upper levels. 

The kinematics from the Blue Ridge to about the US301 corridor from North Carolina to the M/D line in our region are exceptional. Storms that form ahead of the main pre-frontal line that exceed 30kft tops or start producing significant amounts of lightning will be capable and likely will produce long-tracked significant tornadoes. A violent (EF-4) level tornado cannot be ruled out either if instability increases due to pre-frontal warming / breakout sunshine. Storm motions will exceed 50kts and while potentially photogenic, will be un-chaseable except for those who position themselves ahead of the storm 20-30 miles in advance.

The highest risk will be from about noon in North Carolina Piedmont to about 7pm in Southern Maryland. Storm coverage in this area ahead of the main pre-frontal trough / squall is uncertain and will have to wait till tomorrow morning to see what debris / storm outflow from the ongoing convection off-shore of South Carolina brings northward. 

For the pre-frontal squall line: Embedded supercells that produce narrow corridors of 60-80 mph winds seem likely in RFD regions. Especially storms that form ahead of the squall line and get absorbed / merged in with the squall line have the potential to produce strong gusts. Power outages in these narrow corridors (3-5 mi wide) could be substantial. The lack of leaf out on the trees up our way will be beneficial, still, the strengths of the gusts in the enhanced regions will be enough to down branches onto lines. Given the unseasonable cold of the airmass behind the cold front, warming shelters and means of finding warmth Monday into Tuesday as power is restored will be of concern.

If I have time this evening, I'll do a historical perspective and get some analogs.

[TSSN+]

8 minutes ago, snowfan said:

 

That’s for Hanover I’m talking Lwx 

[melonknee]

7 minutes ago, TSSN+ said:

That’s for Hanover I’m talking Lwx 

heavy rain and wind for carroll county! yikes

[TSSN+]

24 minutes ago, snowfan said:

 

Central Md 

 

[WxUSAF]

I’m just here for 1-2” of rain 

[yoda]

Afternoon AFD from LWX 

DISCUSSION...
KEY MESSAGE 1...A strong cold front pushes across the forecast area
Monday, bringing gusty winds and potential for severe thunderstorms
capable of producing significant damaging winds and tornadoes.


Surface high pressure shifts eastward over New England a CAD
wedge bringing cooler conditions and cloudy skies to those east
of the Blue Ridge. Southerly flow increases moisture in the
atmosphere, with light rain showers observed on KLWX radar as of
3PM. Precipitation chances continue increasing as a potent low
pressure system traverses across the Great Lakes into Canada,
pushing the associated fronts across the Mid- Atlantic. The
associated warm front lifts through the area overnight. A band
of showers accompanies this warm frontal passage tonight. This
comes with low clouds and continued breezy southeasterly winds.
Depending on how quickly this boundary can lift north of the
area, some residual stratus may linger across the Mid- Atlantic
region on Monday morning. These should gradually scour out
though ahead of the powerful cold front off to the west. Once
this occurs, a more robust pre- frontal southerly wind
overspreads the region. Outside of any thunderstorms, expect
southerly gusts to around 25 to 35 mph, locally nearing 45 to 50
mph in the mountains. Gradient winds ahead of the front
increase with a Wind Advisory in effect for the higher
elevations on Monday. Wind gusts up to 55 mph are possible along
the ridges.

As an upper low gradually closes off near Lake Michigan, a
shortwave begins to sharpen over the Mid-South midday Monday. As
this trough pivots toward the East Coast, it begins to attain a
negative tilt which will be conducive to further strengthening
of the frontal system. Based on the forecast parameter spaces,
the resultant severe weather aspect has a rather high ceiling in
terms of impacts. Consequently, the Storm Prediction Center
(SPC) has upgraded to a quite rare Day 2 Moderate Risk area,
mainly along and east of the Blue Ridge Mountains. This is
largely driven by the potential of widespread damaging winds,
some of which could be significant in nature, as well as a
tornado risk.

Once any earlier low stratus are scoured out, expect ample
diurnal heating as temperatures rise into the upper 60s to low
70s. Prolonged south to southeasterly flow should also raise dew
points into the upper 50s to low 60s. The seasonably warm/moist
low-levels coupled by strong forcing aloft and cyclonic turning
of the winds with height will make for a very active convective
day. While the degree of vertical shear is impressive on its own
(0-6 km values around 55 to 65 knots), this comes with more than
sufficient buoyancy levels as surface-based CAPE values push
into the 500 to 750 J/kg range. The shear/instability
combination will be conducive to supercell development,
particularly for any discrete cells that form ahead of a likely
squall line. Additionally, the degree of deep-layer shear should
make this more of a quasi-linear convective system (QLCS) which
will be capable of tornadogenesis. Aside from any tornado risk,
the strong cloud-bearing level winds should easily mix down in
convective downdrafts. With 850-700 mb winds around 60-70 knots,
any of this higher momentum air being transferred to the surface
could yield surface wind gusts into the 65 to 75 mph range.
Thus, SPC has a broad area of significant damaging wind
potential (45-74%) advertised from I-81 eastward in their latest
outlook.

With high-resolution models showing 3 to 6 hour differences in
convective timing, there is still some uncertainty in how this
all plays out. Most of the uncertainty is in regards to specific
timing and instability potential. However, expect to be on
alert for active weather from early Monday afternoon through
much of the evening. All related activity races off to the east,
some of which may be comprised of storm elements tracking
eastward on the order of 45 to 50 mph. While not everyone sees a
severe thunderstorm, the overall spatial coverage should be
higher than normal.

By Monday night, a post-frontal air mass pushes across the
region with a rapid cool down in temperatures. This will lead to
some upslope aided snow showers along/west of the Allegheny
Front. Depending on how much moisture can be advected off the
unfrozen portions of the Great Lakes, around 1 to 3 inches are
possible through early Tuesday. Some global models show these
spilling off the mountains toward the urban corridors. As such,
will maintain light snow accumulations for locations east of
the Allegheny Front.

 

[TSSN+]

Can say we never had a high risk but derecho day should have been for sure. 

[gunny23]

2 minutes ago, TSSN+ said:

Can say we never had a high risk but derecho day should have been for sure. 

Wasn't Ian like the first one to start talking Derecho?  I remember that day...if it wasn't for this site I would have been clueless on what was coming.

[TSSN+]

10 minutes ago, gunny23 said:

Wasn't Ian like the first one to start talking Derecho?  I remember that day...if it wasn't for this site I would have been clueless on what was coming.

Was not well forecasted at all. This was the outlooks for that day 

[pazzo83]

2 hours ago, nj2va said:

I’d rather not widespread severe and risk having trees fall on our house.

yeah - these were more fun when I lived in a condo building in downtown DC lol

[EstorilM]

29 minutes ago, TSSN+ said:

Can say we never had a high risk but derecho day should have been for sure. 

Good point - that was such an unusual day, I remember following the line from the moment I woke up, all the way through the work day, then that evening when it actually arrived. 

[WeatherShak]

yeah - these were more fun when I lived in a condo building in downtown DC lol

Agreed. Currently surrounded by 4 - 100 year old white oaks near the GW Parkway. Considering taking family to library for when the line passes. My wife thinks I’m overreacting.

[yoda]

Won't see many ZFPs like these in our region 

Zone Forecast Product
National Weather Service Baltimore MD/Washington DC
415 PM EDT Sun Mar 15 2026

DCZ001-160000-
District of Columbia-
Including the city of Washington
415 PM EDT Sun Mar 15 2026

.REST OF THIS AFTERNOON...Mostly cloudy. Highs around 60.
Southeast winds around 15 mph with gusts up to 30 mph.
.TONIGHT...Showers in the evening, then showers likely with a
slight chance of thunderstorms after midnight. Lows in the mid
50s. Southeast winds 10 to 15 mph with gusts up to 30 mph. Chance
of rain 90 percent.
.MONDAY...Showers likely with a slight chance of thunderstorms in
the morning, then showers with thunderstorms likely in the
afternoon. Some thunderstorms may be severe with damaging winds
and tornadoes in the afternoon. Highs in the lower 70s. South
winds 15 to 20 mph with gusts up to 35 mph. Chance of rain
90 percent.
.MONDAY NIGHT...Rain showers with thunderstorms likely in the
evening, then rain showers likely after midnight. Some
thunderstorms may be severe with damaging winds and tornadoes.
Much cooler with lows around 30. West winds 15 to 20 mph with
gusts up to 35 mph. Chance of rain near 100 percent.
.TUESDAY...Mostly sunny. Much cooler with highs in the lower 40s.
West winds 10 to 15 mph with gusts up to 25 mph.
.TUESDAY NIGHT...Mostly clear. Lows in the mid 20s.

[NorthArlington101]

Agreed. Currently surrounded by 4 - 100 year old white oaks near the GW Parkway. Considering taking family to library for when the line passes. My wife thinks I’m overreacting.

I’ve thought about telling my family to do something similar but will wait til the line actually forms. At least head to the Starbucks lol.

[LeesburgWx]

1 hour ago, yoda said:

Afternoon AFD from LWX 

DISCUSSION...
KEY MESSAGE 1...A strong cold front pushes across the forecast area
Monday, bringing gusty winds and potential for severe thunderstorms
capable of producing significant damaging winds and tornadoes.


Surface high pressure shifts eastward over New England a CAD
wedge bringing cooler conditions and cloudy skies to those east
of the Blue Ridge. Southerly flow increases moisture in the
atmosphere, with light rain showers observed on KLWX radar as of
3PM. Precipitation chances continue increasing as a potent low
pressure system traverses across the Great Lakes into Canada,
pushing the associated fronts across the Mid- Atlantic. The
associated warm front lifts through the area overnight. A band
of showers accompanies this warm frontal passage tonight. This
comes with low clouds and continued breezy southeasterly winds.
Depending on how quickly this boundary can lift north of the
area, some residual stratus may linger across the Mid- Atlantic
region on Monday morning. These should gradually scour out
though ahead of the powerful cold front off to the west. Once
this occurs, a more robust pre- frontal southerly wind
overspreads the region. Outside of any thunderstorms, expect
southerly gusts to around 25 to 35 mph, locally nearing 45 to 50
mph in the mountains. Gradient winds ahead of the front
increase with a Wind Advisory in effect for the higher
elevations on Monday. Wind gusts up to 55 mph are possible along
the ridges.

As an upper low gradually closes off near Lake Michigan, a
shortwave begins to sharpen over the Mid-South midday Monday. As
this trough pivots toward the East Coast, it begins to attain a
negative tilt which will be conducive to further strengthening
of the frontal system. Based on the forecast parameter spaces,
the resultant severe weather aspect has a rather high ceiling in
terms of impacts. Consequently, the Storm Prediction Center
(SPC) has upgraded to a quite rare Day 2 Moderate Risk area,
mainly along and east of the Blue Ridge Mountains. This is
largely driven by the potential of widespread damaging winds,
some of which could be significant in nature, as well as a
tornado risk.

Once any earlier low stratus are scoured out, expect ample
diurnal heating as temperatures rise into the upper 60s to low
70s. Prolonged south to southeasterly flow should also raise dew
points into the upper 50s to low 60s. The seasonably warm/moist
low-levels coupled by strong forcing aloft and cyclonic turning
of the winds with height will make for a very active convective
day. While the degree of vertical shear is impressive on its own
(0-6 km values around 55 to 65 knots), this comes with more than
sufficient buoyancy levels as surface-based CAPE values push
into the 500 to 750 J/kg range. The shear/instability
combination will be conducive to supercell development,
particularly for any discrete cells that form ahead of a likely
squall line. Additionally, the degree of deep-layer shear should
make this more of a quasi-linear convective system (QLCS) which
will be capable of tornadogenesis. Aside from any tornado risk,
the strong cloud-bearing level winds should easily mix down in
convective downdrafts. With 850-700 mb winds around 60-70 knots,
any of this higher momentum air being transferred to the surface
could yield surface wind gusts into the 65 to 75 mph range.
Thus, SPC has a broad area of significant damaging wind
potential (45-74%) advertised from I-81 eastward in their latest
outlook.

With high-resolution models showing 3 to 6 hour differences in
convective timing, there is still some uncertainty in how this
all plays out. Most of the uncertainty is in regards to specific
timing and instability potential. However, expect to be on
alert for active weather from early Monday afternoon through
much of the evening. All related activity races off to the east,
some of which may be comprised of storm elements tracking
eastward on the order of 45 to 50 mph. While not everyone sees a
severe thunderstorm, the overall spatial coverage should be
higher than normal.

By Monday night, a post-frontal air mass pushes across the
region with a rapid cool down in temperatures. This will lead to
some upslope aided snow showers along/west of the Allegheny
Front. Depending on how much moisture can be advected off the
unfrozen portions of the Great Lakes, around 1 to 3 inches are
possible through early Tuesday. Some global models show these
spilling off the mountains toward the urban corridors. As such,
will maintain light snow accumulations for locations east of
the Allegheny Front.

 

tornadogenesis  time for a new screen name

[WeatherShak]

I’ve thought about telling my family to do something similar but will wait til the line actually forms. At least head to the Starbucks lol.

You’ve inspired me. I think we will do Panera!

Here’s a picture of the hundred plus foot trees around my house

[NorthArlington101]

You’ve inspired me. I think we will do Panera!

Here’s a picture of the hundred plus foot trees around my house

Yeah, feel the big tree concern. I am in the DC condo situation so I’m unconcerned, but family is well in the forests of Arlington. Big tree took down the neighbor’s roof during the derecho. We get ours inspected every year since that but it always scared me during thunderstorm season.

[LongRanger]

this month we've had snow soon after 80 degrees, so maybe we can also get snow soon after a tornado, snownado?

[SomeguyfromTakomaPark]

10 minutes ago, WeatherShak said:

You’ve inspired me. I think we will do Panera!

Here’s a picture of the hundred plus foot trees around my house

My house is surrounded by monster trees.  We can go to the basement during the line if it looks really bad. 

[Kmlwx]

Just pondering the definitions and inner workings of SPC outlooks....I try not to be that person who continuously "forecasts the forecast" - but I could see SPC going to 75% wind but perhaps holding to CIG1. My reasoning is that the SPC outlooks are "within 25 miles of a point" - I don't think you're going to see much argument from most folks with setting that probability to 75% if severe criteria is 58mph. 

I'm less certain of TOR percentages - I am not sure that will go any higher than 15% unless there is a game time identification of a more robust corridor of tornado risk. Upping TOR percentages is harder because of the more isolated nature of that type of severe. 

If there truly is a QLCS - even if it only has sporadic swaths of 58mph winds in it - in a major metro corridor like I-95 - you're going to probably verify on damage reports pretty easily on the wind category. 

Anyway - I'm just rambling - and I do think we stick to a moderate - but I could see them tickling the high risk even more by bumping to 75%. They can go to 75% and still have this be a moderate risk.