Area Forecast Discussion
Issued by NWS Indianapolis, IN

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FXUS63 KIND 230436
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1235 AM EDT Thu Mar 23 2017

.UPDATE...
The AVIATION Section has been updated below.

&&

.SYNOPSIS...
Issued at 214 PM EDT Wed Mar 22 2017

Cool high pressure overhead will move to the east coast Thursday and
re-establish a southerly flow of milder air in our region. A
weather system impacting the west coast today will bring some rain
showers and perhaps a few storms Friday into early Sunday. An
exit of this system late Sunday will be followed by a brief dry
period before a couple of weather systems in the north Pacific
sweep into the Midwest with mild, showery weather, and perhaps a
few thunderstorms, for much of the next work week.

Severe weather does not appear likely for the next week but
more spring-like temperatures at or above normal will be welcome,
with highs Friday onward in the 60s...and a few 70s south...for
most days.

&&

.NEAR TERM /Overnight/...
Issued at 955 PM EDT Wed Mar 22 2017

Strong high pressure centered over the eastern Great Lakes this
evening continues to provide a dry cool easterly flow of air into
the region. 0130Z temperatures were generally in the 30s..although
a few locations had already slipped into the upper 20s.

Little change needed with another quiet night anticipated as the
forecast area remains firmly under the influence of the high
pressure. Winds have diminished with sunset but a subtle pressure
gradient will likely keep lower levels from fully decoupling
overnight with winds staying up at 5-10mph most areas. This
combined with the onset of warm advection should counteract the
very dry flow of air from the east and keep temperatures from
bottoming out overnight. Still will be a chilly night as lows
fall into the 20s all but the lower Wabash Valley. Nudged lows
down a couple degrees in the northeast counties...otherwise no
changes to temperatures overnight.

Will continue with the Freeze Warning for just Jackson and
Jennings Counties overnight where confidence is higher in
achieving 3-4 hours below freezing and potentially at or below 28
degrees. Further west over southern counties from Lawrence Co to
Knox/Sullivan Cos...temps near to just below freezing for a short
period of time during predawn hours and will keep them out of the
headlines. Thankfully...this looks like the last night for a while
where freezing temperatures will be an issue.

Zone and grid updates out.

&&

.SHORT TERM /Thursday through Saturday/...
Issued at 214 PM EDT Wed Mar 22 2017

Models are close enough that the model blend initialization
was accepted for most items.

Southeast surface winds begin a return of slightly milder and
more humid air Thursday. Temps should top out a degree or so
cooler than previous forecast as winds remain more southeasterly
out of cool high. Mid cloud will increase Thursday afternoon as
warm advection ensues. A few sprinkles may occur Thursday
afternoon and evening as upper ridge arrives but lower levels
are so dry am not certain rain will be a player. Will keep for now.

Upper ridge passage in advance of todays west coast trough
deepening in the Plains Friday returns drier condition here
late Thursday night through Friday evening. As system continues
its approach, chance showers Friday night become likely for
Saturday. And with elevated instability Saturday...thunder appears
in play then.

Temperature guidance blend appears pretty good and will be
followed with last subfreezing night for awhile occurring tonight.

&&

.LONG TERM /Saturday through Wednesday/...
Issued at 253 PM EDT Wed Mar 22 2017

Three areas of low pressure will affect our weather in the extended
period with the first one occurring over the weekend...the second
one Monday afternoon and evening and the third one occurring near or
after day 7 depending on the model.  Models are in pretty good
agreement on the first two and have stayed close to superblend POPS
with those systems.

Regarding the third area of low pressure...the GFS has trended a lot
slower as high pressure builds into the great lakes by Wednesday. It
has also trended quite a bit cooler.  The latest runs of the other
models have trended somewhat in that direction...but a less than the
GFS.  Went with a blend for now and will keep 20 percent POPS late
Tuesday night west and 20 percent POPS all areas Wednesday.

Lowered Superblend max temperatures some towards the middle of next
week...but not quite as much as the GFS.

&&

.AVIATION /Discussion for the 230600Z TAFS/...
Issued at 1235 AM EDT Thu Mar 23 2017

VFR conditions expected throughout the forecast period with low
level wind shear potential increasing after 00Z Friday.

High pressure centered over the eastern Great Lakes will drift off
to the east overnight as a warm front approaches from the west.
Predominant easterly flow will steadily veer to a more S/SE
direction by late day as the front approaches. Model soundings and
RH progs show the boundary layer will remain dry through much of the
period.

Mid and high level clouds will increase slowly overnight into the
morning...then steadily thicken and lower through the latter half of
the day with the arrival of the warm front. May see a few light
showers or sprinkles accompany the warm frontal passage late in the
afternoon and evening...but expected sparse coverage due to the
presence of the dry air supports keeping any mention of rain out of
the terminals at this time. Once the front clears the area by late
evening...expect a decrease in mid level clouds and an increase in
surface flow with winds at 10-15kts and possibility for sporadically
higher gusts. Arrival of a strong low level jet into the lower Great
Lakes will promote the potential for low level wind shear from late
evening into early Friday.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 3 AM to 9 AM EDT Thursday for INZ071-072.

&&

$$

SYNOPSIS...Tucek
NEAR TERM...Ryan
SHORT TERM...Tucek
LONG TERM...JH
AVIATION...Ryan



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