Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 181735
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
135 PM EDT Wed Apr 18 2018

.SYNOPSIS...
Issued at 240 AM EDT Wed Apr 18 2018

Light rain will move across the area this afternoon and evening with
a short period of snow possible as precipitation ends tonight. A
dusting is possible...mainly on grassy and elevated surfaces. Highs
today will be in the mid to upper 40s. Dry conditions are then
expected tomorrow through early next week. Temperatures will start
out cold but slowly return to normal by next week.

&&

.SHORT TERM...(Today and Tonight)
Issued at 240 AM EDT Wed Apr 18 2018

100+ kt mid/upper level jet currently peeling off Rockies trough
will move over the Ohio Valley later today with a corresponding deep
and compact/well organized PV anomaly. Most 00Z deterministic runs
maintain surface low track through central Indiana. This will
prevent us from tapping into good WAA and keep high temps in the
mid/upper 40s for most locations. Slug of differential CVA will
likely support light showers for entire CWA 18-00Z but best precip
chances/amounts will be in left exit deformation zone initially
setting up along the toll road but eventually pivoting through
entire CWA later tonight. Not a great deformation/fgen signal.
Moisture is also obviously limited and profiles are extremely stable
but most places should squeeze out a few tenths of liquid given
strength and track of culpable wave. Main question is how much of
this will fall in frozen form. Surface wet bulbs don`t cool
sufficiently until roughly 03-06Z (NW to SE). Shortwave starts to
pull away rapidly by then and deformation zone is in a weakening
state as parent wave is absorbed into redeveloping, large northeast
CONUS upper low. Much of precip will likely be over by 09Z with
entirely dry conditions by 12Z. This leaves a very narrow window for
snow but moderate precip rates could compensate for marginal surface
temps...particularly 03-06Z generally along the US-6 corridor where
ascent will be maximized and temps/dewpoints cool enough. Accum
efficiency still very much in question given (relatively) warm/wet
ground but a half inch or so may be possible on grassy/elevated
surfaces in stronger band.

&&

.LONG TERM...(Thursday through Tuesday)
Issued at 240 AM EDT Wed Apr 18 2018

Dry conditions expected during the day tomorrow. Clouds will erode
slowly and highs will likely remain in the mid/upper 40s given
persistent northerly flow.

Rest of long term remarkably quiet. Split flow develops as next
Pacific trough drifts into the southeast CONUS. High amplitude ridge
moves through the Great Lakes and maintains cool high pressure for
the bulk of the period. Virtually no precip chances until the middle
of next week with temps slowly crawling back to normal values by
Mon/Tue.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
Issued at 130 PM EDT Wed Apr 18 2018

Radar returns beginning to edge closer to KSBN at issuance time,
but fighting dry airmass to start with. Still expecting rain to
move in after 21Z at KSBN and shortly there after at KFWA with
transition to snow after 00Z. Exact timing of switchover and
potential accumulations still up in the air with some trends
suggesting somewhat higher snow amounts possible at KSBN and even
a rumble of thunder not out of the realm of chance at KFWA. Kept
with spirit of previous TAFS and will continue to fine tune
through the remainder of the afternoon and 00Z TAFs. Needless to
say, IFR conditions to settle in much of the night. Conditions
should improve rapidly by Thursday as the system pulls away and
clearing commences.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...Small Craft Advisory from 8 PM this evening to 11 PM EDT
     Thursday for LMZ043-046.

&&

$$

SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...AGD
AVIATION...Fisher


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