yoda

Interesting that a good amount of the southern half of the PBZ CWA got put into the watch box

Afternoon AFD from LWX .NEAR TERM /THROUGH TONIGHT/... As of 18Z/2PM EDT, the Mid-Atlantic resided on the south side of a mid/upper-level jet. An enhancement to the jet was located over the lower Great Lakes. The right entrance region of this jet streak will pivot overhead this evening as a warm front lifts northward. Upstream satellite and obs suggest convective initiation will likely take place between 3-5PM EDT over the mid Ohio Valley. Given the orientation of shear and linear forcing along an approaching cold front, storms may start discrete but should grow rather quickly upscale into one or more line segments. Aided by strong flow of 50-70 kts in the 700-500 hPa layer, any line(s) should remain organized for several hours given the moistening low levels and increasing CAPE to 400-800 J/kg (locally up to 1500 J/kg immediately ahead of the front early this evening). Although not extreme, steep mid-level lapse rates from a leftover EML could exceed 8 deg C/km, which when coupled with the strong flow in the same layer will likely result in intense updrafts. The question becomes how far east/northeast the convection survives given (1) potential downsloping westerly flow off the Appalachians, and (2) increasing nocturnal stability in the boundary layer. Strong to severe wind gusts (50-70 mph) would be most likely where low-level lapse rates are steepest and the low-level inversion is shallowest, and as of mid afternoon this zone appears most likely to reside along the I-64 corridor. Farther to the north and east, although flow aloft may be just as strong (if not stronger), a deeper low-level inversion later into the evening may offset the downward transport of higher momentum air. By midnight, even well developed cold pools may have trouble efficiently mixing to the surface. Still, steep lapse rates aloft could result in spotty hail even after storms become more elevated in nature. A few instances of large (1-2 in diameter) hail cannot be ruled out given the favorable shear and steep lapse rates aloft, especially if any semi-discrete storms are observed locally. Regarding the tornado potential, there is a warm front lurking from western MD southeast to southern MD (nearing the Potomac). Right along and just on the cool side of this boundary, favorable SRH would exist for a tornado threat. But, developing low-level stability later this evening and a predominantly linear storm mode should limit any tornado threat to brief mesovortex spin ups as the storms interacts with the warm frontal zone in areas of more favorable lingering low-level CAPE. In the event that upstream convection does not develop as expected, it will likely be rather difficult to initiate intense convection locally given the time of day. Conditionally, however, the shear/lapse rate profile could result in an isolated strong to severe storm. Shower activity may liner much of the night as the surface cold front crosses and the upper trough approaches. Some potential for training is evident, but overall fast storm motions and only briefly heavier rates should limit any flood threat. This is especially the case given ongoing drought conditions

MCD our for western part of LWX CWA - https://www.spc.noaa.gov/products/md/md0448.html Mesoscale Discussion 0448 NWS Storm Prediction Center Norman OK 0118 PM CDT Mon Apr 14 2025 Areas affected...Portions of the Middle/Upper Ohio River Valley to the Central Appalachians. Concerning...Severe potential...Watch likely Valid 141818Z - 142015Z Probability of Watch Issuance...80 percent SUMMARY...Severe storms capable of producing large hail and damaging wind gusts will spread eastward through the afternoon into the evening. A watch will likely be issued within an hour or two for parts of the area. DISCUSSION...Initial thunderstorms are developing across southern IN this afternoon, generally focused along/ahead of an eastward-moving cold front. Ahead of this activity, continued diurnal heating amid increasing boundary-layer moisture (middle/upper 50s to lower 60s dewpoints) will continue to erode inhibition and support additional storm development. Steep midlevel lapse rates (sampled by earlier 12Z soundings) atop the destabilizing boundary layer will yield around 1500 J/kg MLCAPE, favoring a gradual increase in storm intensity through the afternoon. As 60+ kt of midlevel flow (sampled by upstream VWP data) overspreads the warm sector, very long/mostly straight hodographs (60-70 kt of effective shear) will promote splitting supercell structures, posing a risk of large hail and damaging wind gusts. Despite the expectation for an initially semi-discrete mode, strong outflow amid the splitting storm structures will favor gradual upscale growth into small lines and clusters with eastward extent -- with an associated increasing severe-wind risk. A watch will likely be issued for parts of the area within an hour or two. ..Weinman/Mosier.. 04/14/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...CTP...LWX...RNK...PBZ...RLX...MRX...JKL...ILN... LMK... LAT...LON 38248556 38918470 39248402 39638285 40028068 39977973 39747915 39357876 38847859 38237864 37707920 37408001 37228138 37038395 37138489 37338555 37818577 38248556 MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH MOST PROBABLE PEAK WIND GUST...65-80 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

ENH up for wind. 30 from WV into and just east of the i81 corridor

The 5% tor on 1300z is just about there already tbh... it'd only need like a 50 mile shift east. Unless you are talking more about into the Panhandle of WV...

Lots of blue sky here

Morning AFD from LWX NEAR TERM /THROUGH TONIGHT/... A strong upper trough over the Upper Plains/Great Lakes swings through the Midwest/OH Valley today into tonight. Ahead of this system, a leading shortwave trough and its associated surface cold front are expected to move across the OH Valley to Mid-Atlantic through tonight. At least scattered thunderstorms that develop along the front move across the Alleghenies late this afternoon, then into the I-81 corridor toward I-95 this evening. Multiple clusters of strong to severe thunderstorms are possible as the front moves through this evening. Abundant mid level clouds are present this morning, with temperatures generally in the 40s. Conditions are expected to remain dry for most of the day, with showers/storms approaching the Alleghenies probably around 5-6PM. A warm front is forecast to move north through the area today, bringing with it warmer temperatures and increasing low-level moisture. However, even now there remains some uncertainty in how far north the front makes it. While most of 00Z guidance shows the front making it to the MD/PA border, there are still a few models that keep the front around the Potomac River or near I-66. This leaves uncertainty in the amount of instability that develops across the northern portions of the CWA. To the south of the front, temperatures are expected to warm quickly to the 70s this afternoon with low 80s in parts of Central VA. Dew points reach the low to mid 50s by late afternoon. Generally expecting favorable conditions for some clusters of strong to severe thunderstorms to move across the area this evening. The entire area will be overspread with 60-65 kt of deep layer shear and steep mid-level lapse rates (due to a passing EML). Model soundings indicate MLCAPE values of 600-1200 J/kg reaching the I-81 corridor, and 500-800 J/kg east of the Blue Ridge to I-95. Due to backed low- level flow and increasing winds aloft, 0-3km SRH values approach 200- 300 m2/s2 across most of the area this evening. This could provide a small window for a tornado or two to develop, though the greatest chance for that will be west of the Blue Ridge. Otherwise, supercells and line segments will be capable of producing damaging wind gusts and large hail. As the front moves through the area, it is forecast to flatten and slow down tonight. This could keep showers in the forecast along/south of I-66 and along/east of I-95. Mild conditions tonight as lows settle in the 50s to low 60s.

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