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Area forecast discussion 
National Weather Service Wilmington Ohio
137 am EDT Monday may 25 2015

high pressure that has allowed for pleasant conditions the last
couple of days has continued to pull east today allowing for
warming conditions along with rising humidity. As the ridge axis
slowly moves east into the first part of the week...moist...southwest
flow will interact with embedded disturbances aloft to bring the
threat for showers and thunderstorms.


Near term /until 6 am this morning/...
amplified middle/upper level flow pattern with ridge axis shifting east
and flow over Ohio Valley backing srly late tonight. Leading edge
of convection showing up on radar mosaic lifting north into
central Tennessee. Hrrr and rap solutions show this convection weakening
and pushing into iln/S SW counties late tonight. Have adjusted
orientation and speed of precipitation and with with lack of instability have
limited mention to chance of showers late tonight.

With srly winds staying up and increase in clouds in warm air advection pattern
temperature will be milder tonight. Expect overnight lows to range
from the lower 60s NE to the upper 60s SW.


Short term /6 am this morning through Tuesday night/...
an upper level low currently over The Rockies will begin to become
dislodged Monday allowing for the ridge axis to push east and the
chance of rain to return to the area. A shortwave currently over
central Texas will continue to push towards the northeast with a
line of positive vorticity advection slowly moving east. This thin line of positive vorticity advection will move
over the area Monday afternoon. High res models are showing
scattered showers and thunderstorms forming along this line of positive
vorticity. Forecast soundings are showing lower end instability
with k index values in the lower to middle 30s. This all supports
chance probability of precipitation. High temperatures will be in the lower to middle 80s. It
will also be windy Monday as the pressure gradient tightens with
some of our northern zones possibly seeing sustained winds above
20 kts.

Behind the initial wave of positive vorticity advection there will probably be a brief
break in the rain. On Tuesday there will be another shortwave that
swings through central Texas that ejects to the northeast. This
shortwave will finally help to clean up the flow and move the
upper level low over The Rockies to the east. This will bring
another area of positive vorticity over our western zones. The jet
streak associated with the shortwave will also push to the east
putting the area into a rrq. Storm Prediction Center has the SW part of the County Warning Area in a
slight risk for severe storms Tuesday. Model forecast soundings
for Tuesday have cape values just above 500 j/kg. Instability in
the sounding still is taking on a skinny cape. The main threat
will be for wind but this threat still remains pretty low at this time.


Long term /Wednesday through Sunday/...
a fairly progressive westerly flow pattern in place across the
region for middle week will result in a chance of thunderstorms
Wednesday into Thursday. While precipitation chances will depend on the
timing of any embedded short waves...will try to show some diurnal
enhancement to the precipitation chances for both Wednesday and Thursday.

The flow will gradually become more amplified through the weekend
as short wave energy moves into the Central Plains. Initially this
will lead to a little middle level ridging across our area Thursday
night into Friday and possibly a brief lull in the precipitation chances. A
better chance of precipitation will then return later Friday and into the
weekend with the approaching trough and short wave energy. This will
eventually help push a cold front down toward our area Saturday into
Sunday. However...the models have been trending slower on the timing
of this front over the last several runs so am hesitant to go any
higher than chance category for the probability of precipitation at this point.

Highs will remain seasonably warm through at least Saturday with
highs in the lower to middle 80s and overnight lows in the middle to upper
60s. Depending on the timing of the front...some more seasonable
readings may return for Sunday.


Aviation /06z Monday through Friday/...
strong low level jet is spreading over the Ohio Valley this
morning with 925-850mb layer flow up to 50kts at times as this low
level wind maximum shifts northeast ahead of a shortwave trough
moving through the Mississippi Valley. Scattered-broken middle cloud and
cirrus are on the increase over OH/in/KY...and a few showers have
been spreading steadily northeast toward the Ohio River in Kentucky/in
over the past few hours.

Expect the threat for at least a few showers to continue up into
southwestern Ohio by about 08z though expect activity to be fairly light and
likely just virga/sprinkles. Did keep vcsh going for a time across
all but the cntl Ohio sites through middle morning as this activity
moves through. Ceilings will remain VFR.

Bigger story is stronger flow with the low level jet. This should
begin to mix to the surface around 12z with gusts becoming common.
Expect the strongest gusts this morning /before 17z/ with onset of
heating and presence of strongest winds aloft...and some gusts
toward 30kts are not out of the question though will keep tafs in
the 25-27kt range. Did not place low level wind shear in terminals due to gradual
increase in speeds/lack of directional shear in the lowest 2kft.
Will almost certainly be some mechanical turbulence especially in
the 08z-11z timeframe before boundary layer winds increase to
decrease speed shear in the lowest 2kft.

After 18z...combination of forcing from weak shortwave and
deepening moisture should promote showers/storms in scattered fashion
into early evening. Weakly/loosely forced so will keep vcsh
mention for now. Expect middle clouds and decreasing/backing flow
through the evening into the overnight as showers wane.

Outlook...thunderstorms with MVFR ceilings/visibilities possible Tuesday
through Wednesday.


Iln watches/warnings/advisories...


near term...Haines/AR
short term...Haines
long term...jgl

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