Spring Thread 2017: Northern Hemisphere (sunlight, temperatures, Chicago, days)
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
Moderate risk issued today for southern Missouri and surrounding areas. NWS SPC is mentioning possible derecho development.
Quote:
...Lower Missouri Valley, Ozarks to Ohio Valley and Red River...
The ongoing convection over northeastern KS was forecast by most of
the synoptic and high-res progs initializing from 00-09Z to weaken
and shrink much sooner than evident in current coverage/intensity.
This casts some uncertainty on the northern and western parts of the
outlook area, in two ways:
1. Whether this initial convection and related isallobaric
perturbation will evolve into or directly influence the
eventual/expected major wind-producing MCS as it encounters
diurnally destabilizing air over eastern KS and western MO, and/or
2. The influence of the trailing outflow boundary on subsequent
thunderstorm potential over south-central/southeastern KS.
Thunderstorms either developing along this boundary, or crossing it
from behind, should gain access to surface-based inflow and
expand/intensify rapidly.
In either event, the downshear air mass will be very favorable for
upscale organization of a forward-propagating, potentially
derecho-producing MCS. Significant-severe/hurricane-force
thunderstorm gusts and numerous damage reports are possible in the
moderate-risk area. An upgrade may be warranted later today.
However, uncertainties related to influence of the ongoing activity
and timing of greatest storm organization preclude offering any
more-focused unconditional probabilities at this time. In addition
to wind, line-embedded/tornadic circulations are possible. Embedded
supercells may occur, especially in any frontal backbuilding that
may occur toward northeastern/central OK late afternoon and evening.
Very steep midlevel lapse rates will overlie a richly moist and
strongly heated boundary layer containing upper 60s to mid 70s F
surface dew points and 15-18 g/kg mean mixing ratios. This yields
MLCAPE locally exceeding 6000 J/kg in forecast soundings southeast
of the cold front and outflows, and east of the dryline, from the
western Ozarks across eastern OK to the Red River, amidst
effective-shear magnitudes of 45-55 kt. Such extreme instability is
near record levels, based on historic soundings. The CAPE-shear
parameter space appears comparable to a fast-developing,
dryline-initiated supercell/tornado event on 26 May 1997 in eastern
OK, but with the added risk this time of a derecho on the northeast
side. Such extreme instability will support explosive growth of
thunderstorms that do break the cap -- whether through forced ascent
on a cold pool or front, or in any discrete to semi-discrete cells
that can move off the dryline. Dryline-storm risk is conditional
and more isolated due to the strong EML and related CINH, but also
potentially dangerous with giant hail of 3-5 inches in diameter and
significant tornadoes possible. By late evening, a swath of
convection should extend from the Ohio Valley into southern OK and
perhaps north TX, with the overall severe threat diminishing
overnight.
62 and overcast right now. I haven't seen the sun since Wednesday.
I think this month will actually ends up above average. Upper 70s tomorrow and then 2 more days off 70s. Also, no cool nights in the forecast. The departure is only -0.8 now so some slightly above average days can flip that to a positive.
Break time.. Stunning day. Looks like I'm lucky. Feel bad for those under that strip of clouds in MA, RI and CT.
7:15-11:15am loop. Not much rain on map except entering Missouri & Iowa and scattered pop ups in PA. Also looks like my luck will be ending soon.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
