Kiwx 041716

afdiwx
area forecast discussion
national weather service northern indiana
115 pm edt mon may 4 2015

synopsis...
issued at 142 am edt mon 4 2015
an upper disturbance tracking along the canadian border will drag
a cool front southward across the great lakes region. this front
combined with increasing moisture will likely produce showers and
thunderstorms later today into tuesday. lows this morning will
fall back only to the upper 50s. highs later today will primarily
be in the middle to upper 70s.
&&

short term...(today and tonight)
issued at 410 am edt mon may 4 2015
as alluded in prior avn discussion...lysis of upstream convection
conts erly this am as it moves into substantial theta-e trough.
furthermore...split in llj with nrn extension to track well nw-n
of region erly this am in conjunction with potent mcv /presently
south of oshkosh movg enewd/ conts to force parcel ascent into
wcntl mi into slightly hir 0-3km lapse rates...with incrsd
stability swd into cwa. bowing segment acrs nrn il also incrsgly
cold pool dominant with substantial warming/constriction of tops
per ir imagery portends to only debris clouds/am shra acrs nwrn
half of cwa. thereafter...sfc boundary and llvl mflux convergence
lies out e-w through cwa into aftn though muted/muddled
destabilization appears to be the norm. nam progged mucapes into
2000-3000 j/kg range upstream acrs nern il into ern ia this aftn
coincident with convergent 1000-900mb signal along with shortwave
assocd with better developed erly am convection acrs nwrn mo/swrn
ia/far sern ne to one of the more probable of several tsra
development regions in srn grtlks this aftn. am outflow and weak
frontal boundary focus accentuated south of marine lyr
environment among other possibilities. modest instability amid
poor deep layer shear with ern extent into cwa on order of 20 kts
and continual building of midlvl heights to impede vigorous
parcel ascent/severe potnl. maintained relatively high pops
overnight with sfc boundary lingering through e-w in srn third
cwa along with addnl upstream shortwave acrs wrn ok
panhandle/swrn ks to eject into southern periphery of rapid zonal
grtlks flow.
&&

long term...(tuesday through sunday)
issued at 410 am edt mon may 4 2015
some modifications to tues/tues ngt period as frontal boundary
lingers in the area. area of showers/storms will likely be
ongoing at the start of the period over much of (if not all) of
the forecast area as a result of low level jet and pooled mstr
along the front. modulation of the effective boundary will be
impacted by the convection...possibly sending it further south
and allowing for a slower departure/dissipation into tuesday
night. majority of hi res models have come onboard with this
scenario so a subsequent increase in pops was warranted to blend
tuesday morning with short term period. coverage and location of
pops in the afternoon/night hours somewhat unclear but entire
area has a shot for additional precip so have opted for blanket
chc pops for now (higher than previous shift). by tuesday night
into weds...frontal boundary begins to shift north and lose
definition with pops decreasing with time. still can't rule out a
stray shower or storm weds into thurs during peak heating...but
at this point will maintain dry (but non-zero pop) forecast. no
changes made to temps into wednesday as location of front...cloud
cover and precip will likely cause large n to s gradient with
highs well into the 70s south and 60s north.
deep upper low will be digging into the sw states for the second
half of the week into the weekend before ejecting ne into the
plains and eventually a grazing blow to the western lakes.
chances for showers and storms will return for the weekend...with
best chances starting friday night. until the main trough passes
by...cannot rule out precip in any period so blanket chc pops
warranted through the end of the period. highs thurs and fri will
climb into the 80s for most locations with cooler 60s and 70s
into the weekend due to clouds/precip chances.
&&

aviation...(for the 18z tafs through 18z tuesday afternoon)
issued at 115 pm edt mon may 4 2015
kiwx radar showing line of showers associated with approaching
frontal boundary has cleared the area leaving vfr conditions to
begin this taf cycle. latest surface analysis has front just nw of
ksbn and is expected to have winds veering from wsw to nw this
afternoon/evening. front expected to stall in the vicinity of kfwa
tonight before lifting back north tuesday morning. expect
convection to redevelop out to the west this evening and move into
the area after midnight. not alot of instability to work with
tonight so will leave out mention of thunder for now.
&&

iwx watches/warnings/advisories...
in...none.
mi...none.
oh...none.
lm...none.
&&
$$
synopsis...murphy
short term...murphy
long term...fisher
aviation...logsdon
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