yoda

SLGT risk for just about everyone per new Day 1 from SPC... 2/15/15

12z NAM has what looks to be a complex I'm guessing on sim radar that moves through between 03z and 06z... but sub severe as @high risk has mentioned above 12z NAM Nest is more MD centric on sim radar... has a light UHD swath in C MD just north of DC between 03z and 05z

*takes a peek at the 12z HRRR UDH swaths and sim reflectivity* Oh...

I think as LWX mentioned in their AFD and as you have mentioned multiple times in your posts regarding this potential threat, how much sun can we get and the dewpoints WRT moisture return

SLGT risk gets into the i81 corridor in VA, all of E WV and right next to C MD now. 15% hail and wind, as well as 2% tor

Oh ok then ay 2 Convective Outlook NWS Storm Prediction Center Norman OK 1243 AM CDT Sun Apr 13 2025 Valid 141200Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN THE UPPER OH VALLEY AND CENTRAL APPALACHIANS... ...SUMMARY... A couple tornadoes along with scattered damaging winds and large hail are possible from mid-afternoon to mid-evening across parts of the Upper Ohio Valley and central Appalachians. ...Synopsis... A shortwave trough will further amplify over the Upper Great Lakes towards the ON/QC border, supporting gradual deepening of a surface cyclone from 995 to 990 mb. In its wake, a separate shortwave impulse and intense mid-level jetlet will dive southeast across the northern Great Plains towards the Lower OH Valley. A surface cold front will arc south across the Lower Great Lakes and then southwestward through the Mid-South by late afternoon Monday. ...OH Valley to the Mid-Atlantic States... While guidance has largely been consistent with synoptic-scale pattern over the past several days, large spread exists in the degree of boundary-layer heating on Monday afternoon ahead of the surface cold front. For example, the 00Z NSSL-ARW and HRW-FV3 are 10-15 F colder with warm-moist sector surface temps compared to the 00Z HRRR and HRW-ARW. These latter models simulate multiple long-track supercells. This heating discrepancy, along with low confidence in the aggressive low-level moistening indicated by most guidance beneath an expansive EML, mitigates a categorical upgrade this cycle. But all three hazards have been highlighted with level 2-SLGT risk probabilities. Overall expectation is for a ribbon of mid to upper 50s surface dew points to advect as far northeast as the Upper OH Valley. If robust boundary-layer heating indeed occurs, this would support MLCAPE near 1000 J/kg. The initial presence of the EML may delay storm development along the front until mid afternoon. But guidance consensus suggests at least scattered thunderstorms should form in the Central to Upper OH Valley vicinity as mid-level height falls increase atop the modestly convergent surface front. The approach of an intense mid-level jet will support fast-moving convection, along with effective bulk shear above 60 kts. Despite veered surface winds, low-level hodograph curvature should be moderately enlarged. A few supercells seem plausible in this setup, a couple of which may become long-tracked. These appear most probable across the southeast OH to northern WV vicinity, where tornado potential should be maximized during the early evening. Otherwise, a mix of large hail and damaging wind swaths are expected. East of the higher terrain in MD/northern VA, remnant steep low-level lapse rates may support isolated damaging gusts and marginal hail, before convection wanes/becomes increasingly elevated Monday night. ..Grams.. 04/13/2025

Wind, cold, and mountain snow returns - from this morning LWX AFD The strong upper trough digs over the area Tuesday, with the surface pressure gradient tightening in response to the deepening low to our north. Model soundings indicate nearly unidirectional westerly flow from the surface to around 600mb, with a powerful jet aloft at 250mb approaching 120-130kt. This is a favorable setup for strong winds aloft to mix down to the surface, especially in the climo wind favored area along/west of the Blue Ridge and along/north of I-66. Winds could gust around 35-45 mph for most of the area, with 45-55 mph gusts in the mountains Tuesday afternoon. Wind Advisories are possible, with some of the higher-end ensemble guidance pointing to High Wind criteria being met. Some showers depart the area to the east through the day Tuesday, though precipitation continues in the Alleghenies. While the area dries out by Tuesday evening, cold air advection in the mountains results in a transition to snow showers Tuesday night. Upper dynamics look favorable on the backside of the departing upper trough, with northwest winds advecting moisture off the Great Lakes. The potential is there for several inches of accumulating snow along/west of the Allegheny Front, though confidence is low at this time given the warm antecedent conditions. Something to continue monitoring in the coming days. Compressional warming brings highs up to the 60s Tuesday afternoon. CAA Tuesday night drops temps to the mid 30s to 40s (with upper 20s to low 30s in the mountains). Gusty conditions are likely to persist Tuesday night, causing it to feel much colder than normal for mid April (wind chills in the upper 20s to 30s).

Excellent writeup from LWX this morning in their AFD regarding the threat SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... The weather pattern becomes active for the start of the work week, with several systems bringing the chance for severe thunderstorms, strong winds, and mountain snow. Brief mid-level ridging over the area Monday fades as a strong upper trough over the Great Lakes tracks toward the Mid-Atlantic Monday night into Tuesday. The parent surface low deepens as it moves over the Upper Great Lakes into Ontario. A leading shortwave trough and its associated cold front cross the OH Valley Monday afternoon, then the Mid-Atlantic Monday night where the front flattens out. The main upper trough digs into the Mid-Atlantic Tuesday into Wednesday, bringing with it a series of reinforcing cold fronts. Dry and mostly cloudy conditions to begin Monday, as highs reach the upper 60s to 70s. Some spots in Central VA could reach around 80F. The subtle mid-level ridging Monday afternoon could help break some of the clouds, allowing temps to get a little higher than forecast north of I-66. Uncertainty is still rather high on how warm we get, and also how quickly/how far north 50s dew points advect in from the south/west. The current forecast has highs around 70F and dew points in the low/mid 50s by late afternoon for most of the area. How much instability develops is going to be the biggest factor in whether severe thunderstorms can persist east of the Allegheny Front. Thunderstorms that develop along the cold front in the OH Valley reach the Alleghenies late Monday afternoon to Monday evening. Models continue to indicate a favorable environment to support severe thunderstorms Monday evening (instability aside). An EML advecting in aloft brings steep lapse rates around 7-8 C/km. With 500mb temps approaching -15C there is going to be a threat for large hail with any severe thunderstorm that develops. The EML is going to cap convection for most of the day, though models continue to insist it is overcome by mid-level height falls atop the advancing surface front. Strengthening winds aloft result in deep-layer shear in excess of 65 knots, with curved low-level hodographs also adding to increasing helicity values. Fast moving severe thunderstorms will be capable of producing damaging wind gusts and large hail. SPC has expanded the Slight Risk (level 2 of 5) across all of the Potomac Highlands and Northern Shenandoah Valley, with a Marginal Risk (level 1 of 5) for the remainder of the area. As storms move east of the Blue Ridge they likely become elevated as the boundary layer stabilizes in the evening and/or due to a linger cap. Depending on how much instability lingers, could see a severe storm or two approach the I- 95 corridor later in the evening. Showers and thunderstorms decrease in coverage overnight, though some showers could linger overnight. Mild temps in the 50s Monday night.

Frost advisory up URGENT - WEATHER MESSAGE National Weather Service Baltimore MD/Washington DC 217 PM EDT Sat Apr 12 2025 VAZ025>027-029-036-130230- /O.NEW.KLWX.FR.Y.0001.250413T0600Z-250413T1300Z/ Augusta-Rockingham-Shenandoah-Page-Nelson- 217 PM EDT Sat Apr 12 2025 ...FROST ADVISORY IN EFFECT FROM 2 AM TO 9 AM EDT SUNDAY... * WHAT...Temperatures in the lower to mid 30s along with light winds will result in areas of frost. * WHERE...Nelson, Page, Shenandoah, Augusta, and Rockingham Counties. * WHEN...From 2 AM to 9 AM EDT Sunday. * IMPACTS...Frost could harm sensitive outdoor vegetation. Sensitive outdoor plants may be killed if left uncovered

MRGL risk up, SLGT out into western MD for Monday

https://x.com/OSUWXGUY/status/1910312398046581087 https://x.com/OSUWXGUY/status/1910304688911626579 C3S seasonal model... not sure how it did last year

https://x.com/andyhazelton/status/1910355573767352351 @WxWatcher007

No. Do not want. From this morning AFD from LWX Through the end of next week upper troughing dominates across the Mid-Atlantic to Northeast, bringing a series of reinforcing cold fronts and below normal temperatures to the region. Daytime highs in the 50s to 60s, with overnight lows in the 30s. While just beyond the current 7 day forecast, ensemble guidance shows a good chance of seeing freezing to near freezing temperatures Wednesday night into Thursday of next week.

RIC/EZF/IAD/BWI all hit 32 or below as of 6am

Looks like the N wind of around 10mph is keeping DCA from getting there. It's at 35 right now

LWX apparently changed their mind and put up a freeze warning for everyone i81 and east

It's in the morning ZFPs for BR and westward

Will be interesting to see what the current storms in WV do in the next hour or so as they get near the i81 corridor

Temperatures will probably jump quickly the next few hours

Updated morning discussion from LWX suggests some interest later While some showers may spill across the mountains during the late morning and early afternoon, overall this should be a period of less precipitation in the forecast area. While the bulk of convection will again be west of the area, heights begin falling by late afternoon, and the moist conveyor belt begins to shift back to the southeast. Instability will be able to build south of the warm front. It appears the best overlap of these features will be the northwest corner of the forecast area, resulting in the highest chance of showers and thunderstorms. Instability is forecast to be on the lower side...however, there is enough shear for any stronger updrafts to organize and become capable of producing severe weather. All hazards could be on the table, especially if there is a supercell or two. There is a narrow corridor of overlap with 500-1000 J/kg MLCAPE and 300+ m2/s2 SRH this evening between US-50 and I-70. North of this area, it should remain stable enough to preclude surface-based convection with a lower severe threat overall; further to the south and east, less forcing and more mid-level dry air should keep convective coverage at bay. Aside from somewhat amorphous forcing and the relatively narrow corridor of favorable overlap in the parameter space, low-level CAPE may be on the low side unless more cloud breaks develop. If more cloud breaks are observed and surface heating is more efficient, higher low-level instability could raise the threat of severe/rotating storms this evening in the aforementioned corridor.

Discussion mentioned the risk for a few severe storms out there later

Not seeing much so far

Looks like maybe a sneaky threat tomorrow... more out west though

Ok then - https://www.spc.noaa.gov/products/md/md0390.html Mesoscale Discussion 0390 NWS Storm Prediction Center Norman OK 0252 AM CDT Fri Apr 04 2025 Areas affected...ern WV Pnhdl...nrn VA...MD...DC...srn PA...DE...srn NJ Concerning...Severe potential...Watch unlikely Valid 040752Z - 040845Z Probability of Watch Issuance...20 percent SUMMARY...Strong, potentially damaging wind gusts, may accompany weak thunderstorm activity likely to spread east of the Blue Ridge and across the Greater Washington D.C./Baltimore metropolitan areas through 6-7 AM EDT. It is not clear that a severe weather watch is needed, but trends are being monitored. DISCUSSION...A narrow line of thunderstorms has shown some intensification, near and south of a wave or weak MCV now east of Elkins WV. This activity has been propagating rapidly eastward, along and just south of a slow moving or stalling cold front, around 50 kt, which is about the strength of the mean westerly deep-layer ambient mean flow across the Allegheny Mountains into northern Mid Atlantic. Due to generally weak deep-layer lapse rates, CAPE along this corridor is quite weak west of the mountains, but improves somewhat (CAPE to 500 J/kg) in better low-level moisture across northern Virginia through southern New Jersey. While some further intensification to the east of the Blue Ridge is possible as activity rapidly advances eastward through 11-12Z, thunderstorm intensities are likely to remain rather modest, based on forecast soundings. However, unsaturated profiles in lower/mid-levels, may contribute to evaporative cooling and downward momentum transport of rear-inflow, which may undergo some further convective augmentation. ..Kerr/Mosier.. 04/04/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...PHI...AKQ...CTP...LWX... LAT...LON 39897751 39677548 38737539 38497760 38557915 39397855 39897751 MOST PROBABLE PEAK WIND GUST...55-70 MPH

81/64 at DCA at 5pm