Area Forecast Discussion
Issued by NWS Northern Indiana

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000
FXUS63 KIWX 140157
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
857 PM EST Tue Feb 13 2018

.SYNOPSIS...
Issued at 302 PM EST Tue Feb 13 2018

Much warmer air will continue to overspread the region into
Thursday, along with increasing chances for rain, drizzle and
fog. This will be followed by a briefly cooler but dry weather
period for Friday and Saturday.

&&

.UPDATE...
Issued at 845 PM EST Tue Feb 13 2018

Some light precip in the form of some very light sleet/sprinkles
has been observed across along and east of I-69 this evening. This
precip was in association with axis of strong isentropic lift.
Highly sheared upper wave tracking across the Great Lakes add
accompanying proximity to right entrance region of 120 knot upper
jet have also aided in forcing this evening. Eastward translation
of this upper wave will allow axis of stronger warm advection to
also shift eastward across OH/western PA late this evening. This
will bring an end to light precip (trace amounts) after 03Z
across the far southeast. Primarily westerly low level flow
remainder of night should keep bulk of low clouds south across the
Lower Ohio Valley. Some patchy fog not completely out of the
question across far north/northwest where some melting of snowpack
has occurred today, but as mentioned in previous discussion, dry
nature of low level airmass should largely limit significant fog
potential tonight.

&&

.SHORT TERM...(This Evening through Wednesday)
Issued at 346 PM EST Tue Feb 13 2018

Plenty of sunshine was allowing temperatures to climb into the
upper 20s to middle 30s, warmest where snowpack is non existent
(generally along/south of a Monticello to Peru to Lima line.

Area of stratus was working north through central Indiana and Ohio
and will likely move into southern areas towards evening. Mid clouds
also streaming in from the west. The cloud cover and increasing
humidity raises challenges in potential of more widespread stratus
and fog, especially on Weds into Weds eve as dewpoints climb above
freezing and pace of melting increases somewhat. Some drizzle/light
rain could materialize as limited lift begins to arrive ahead of
the first rain maker arriving for the start of the long term.

In terms of temperatures, lows will fall back into the middle to
upper 20s, with highs Wednesday climbing above freezing and
likely well into the 40s in most areas outside of the deeper snow
pack. Guidance would suggest gridded highs are too high (by a few
degrees) over the snowpack, but despite the cloud cover do think
we will end up somewhat warmer and will leave previous forecast
untouched.

Hydro concerns will be handled in a separate portion of the
discussion.

&&

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 346 PM EST Tue Feb 13 2018

Depth of warm air and moisture will increase into Thursday night
with subsequent ramp up in pops as moderate amplitude trough moves
quickly out of Kansas Thursday morning and into the Ohio Valley
Thurs ngt and Friday. Most significant QPF would still appear to
well southeast of the area, but everyone should still see between
a tenth to nearly a half inch with highest amounts SE. Impacts
hydro wise discussed below.

High pressure will build in across the area by Friday night,
persisting into early Sunday bringing dry conditions. Much more
significant trough will dig into the Four Corners region to allow
for a rapid return flow out of the Gulf that will set the stage
for much warmer temperatures and an extended period of
precipitation, mainly in the form of rain. Challenge will be how
how long Bermuda high will be able to hold back the main trough
ejection. Luckily, greatest precip chances are outside the
forecast period, but precip chances exist starting late Saturday
night and especially Monday and Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 632 PM EST Tue Feb 13 2018

With high pressure to the east, southerly winds continue to push
warm, moist air into the region. High clouds will continue into
the first portion of the overnight and low level moisture will be
able to overtake the low level dryness especially as we head
towards daybreak at both TAF sites so look for MVFR CIGs to begin
after midnight and continue into Wednesday.

The other thing that bears watching will be if we start to see any
fog form towards the end of the period as low level moisture comes
in.


&&

.HYDROLOGY...
Issued at 346 PM EST Tue Feb 13 2018

Moisture content of the snowpack across the area varies greatly
with even lower snow depths holding a fair amount of water (5
inch snow depth here with just over 9 tenths liquid). Getting a
few water eq readings in the deeper snow pack of 1.5 to possibly
as much as 2 inches of water. Expecting significant
loss/elimination of snowpack in areas currently under 6 inches of
snow by Thursday and likely at least further compaction of
snowpack further northwest. Always tricky as to exactly how much
water will release and expected QPF from Thurs ngt rainfall of
tenth to quarter inch will just add to the content. In the SE QPF
will approach a half inch and maybe a touch more by Friday. At
this point, expecting any river response to be limited to action
stage with "flashier" sites possibly reaching minor flood stage
for a period.

With colder temps moving back in for a few days, think any
release will be slowed. Return to warmer conditions will get rid
of any further snow pack late in the weekend into next week. To
further complicate things, extended period of rainfall is in store
with PWATS increasing to well over an inch across the area with
each round of rain in the later part of the forecast period and
beyond likely to become heavier to set the stage for more
significant flooding concerns.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
LM...NONE.
&&

$$

UPDATE...Marsili
SYNOPSIS...Fisher
SHORT TERM...Fisher
LONG TERM...Fisher
AVIATION...Roller
HYDROLOGY...Fisher


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