Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 181027
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
627 AM 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 12Z TAFS through 12Z Thursday Morning)
Issued at 627 AM EDT Wed Apr 18 2018

Only minor changes with respect to 12 UTC TAFS for northern
Indiana. Slightly faster timing with upstream system per latest
high res models. Still fairly high confidence of IFR conditions
developing with strong thermal collapse within saturated boundary
layer coincident with surface low sweeping eastward through
southern Ohio early this evening.

&&

.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...Murphy


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