IWX issues Area Forecast Discussion (AFD) at Oct 21, 1:32 AM EDT239
FXUS63 KIWX 210532
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
132 AM EDT Mon Oct 21 2024
.KEY MESSAGES...
- Warm and very dry afternoons Monday and Tuesday will lead to some
risk in any fire ignition in dead brush and dry grass.
- Low rain chances during the middle of this week and over this
coming weekend will do little to ease the ongoing severe
drought over much of the area.
- Very warm days and cool nights will start the week with highs
approaching or in the lower 80s with nighttime lows in the 40s.
- Brief return of below normal temperatures behind a cold front
Thursday.
&&
.DISCUSSION...
Issued at 325 PM EDT Sun Oct 20 2024
Mid and upper level wave pattern has changed little over the past 24
hours, with maintenance of broad central CONUS upper ridging. Mean
position of low level anticyclone should also change little through
tonight, with just a subtle southeast displacement that should
allow for a slightly stronger gradient across northwest half of
the area. Low level WAA will also have a subtle increase
tonight. Challenging min temperature forecast for tonight given
competing effects of fairly good radiational cooling conditions
and weak WAA, but feel a 2 to 5 degree increase in temps
compared to last night is still a reasonable forecast.
For Monday, some slight progression of central CONUS upper ridge is
expected as cut-off upper level low across southwest CONUS begins to
eject northeast. Progression of this pattern will allow broad low
level thermal ridge across central CONUS to shift across the Great
Lakes region. Top of boundary layer flow in short term forecast
soundings do indicate a potential for some 15 to 20 mph gusts on
Monday across the north/northwest. Given tendency for better
mixing with core of low level thermal ridge shifting eastward
and dry ground/superadiabats likelihood/full insolation,
something closer to NBM 75 percentile high still seems
reasonable for Max T forecast Monday with highs likely to
approach 80. This combination of temps/dew points would yield
minimum afternoon relative humidities of 20 to 30 percent
Monday, so will maintain consistency with HWO mention of
elevated fire weather risk for brush/field fires.
For Tuesday, attention turns to approach of the filling/dampening
upper level trough from the Plains. Timing of this upper trough
passage still should support another day of much above normal
temperatures with breezy/windy conditions developing. Despite
southerly flow for Tuesday, source of upstream airmass will continue
to be quite dry due to long history of southeast CONUS anticyclone.
This could raise another day of marginal fire weather concerns, with
some dependence on extent on this threat on timing of increasing mid
cloud coverage. We should have a gustier wind element to deal
with Tuesday however, that could heighten the fire weather risk
for brush/field fires.
Late Tuesday into Tuesday night precip chances still look
minimal given moisture limitations and dampening nature of the
trough. Best chance of an isolated shower may actually be in
wake of strongest upper forcing when some stronger isentropic
lift builds in Tuesday evening along with some weak elevated
moisture recovery across far NW IN/SW Lower MI.
Not much change was needed for the remainder of the forecast as
midweek frontal timing still appears intact. Better moisture
transport still appears to cut off well south of the local area in
advance of this front, so have only maintained slight chance-low
chance PoPs far north Wednesday afternoon/early evening. Windy
conditions are expected for a time late Wednesday morning into
Wednesday evening with enhanced mixing behind the cold front.
Much cooler conditions settle in for Wednesday night and Thursday
behind the front, but upstream flow deamplification late in the
week should allow for moderation in temperatures back to near
or above normal by next weekend. Medium range guidance still
exhibits large spread with timing/amplitude of several Pacific
waves toward end of the period. Moisture will be probably be
limited with this forcing, but likely existence of baroclinic
zone sprawled across the region argues for maintaining low rain
chances late next weekend.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 132 AM EDT Mon Oct 21 2024
Surface ridge axis has finally shifted east allowing for light
but steady return flow. Moisture advection will be slow and
expect another sunny day but high clouds will increase toward
the end of the period. SW winds will remain steady through today
backing slightly by the end of the period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Marsili
AVIATION...AGD
Source:
IWX issues Area Forecast Discussion (AFD) at Oct 21, 1:32 AM EDT---------------
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