Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 221120

Area Forecast Discussion
National Weather Service Northern Indiana
620 AM EST Wed Feb 22 2017

Issued at 356 AM EST Wed Feb 22 2017

The fog will burn off during the morning hours, leading to
sunshine and record warmth. Highs today will reach the middle 60s
to near 70 in spots. Rain chances increase late Thursday with
some thunderstorms possible at night and especially on Friday.
Severe thunderstorms are possible Friday afternoon as a strong
cold front sweeps across the area. Temperatures will remain well
above normal through Friday and then fall back closer to normal
this weekend.


.SHORT TERM...(Today and Tonight)
Issued at 356 AM EST Wed Feb 22 2017

Expansion of dense fog advisory in time /additional hour/ and
areal extent to include St. Joseph Co. MI with most dense fog
confined to northern periphery of high level cloud shield
associated with shortwave/vortex over deep south. While point
visibilities will likely to continue to oscillate, overall do not
anticipate much improvement over next few hours as southern stream
system pulls southeastward into Gulf of Mexico with idyllic
longwave losses in fog area/nwrn to nrn cwa holding firm. As
middling eastern Dakotas frontal wave pushes into western/Upper
Great Lakes anticipate relatively quick mix out of dense fog,
perhaps into temporary 2kft agl stratocu layer before scattering
out this afternoon coincident with approach of precedent low level
thermal ridge. Suspect an aggressive/overperformance of surface
temps over mos, but reigned in slightly given initial cloud
cover/overly optimistic prior forecast and cooler
temperatures/lows observed this morning. Nonetheless still
affording record/near record afternoon highs. Sufficient mixing in
advance and with dry fropa overnight should preclude any
substantive br formation.


.LONG TERM...(Thursday through Tuesday)
Issued at 356 AM EST Wed Feb 22 2017

Primary focus remains on convective potential later this week with a
highly conditional severe risk. Ejection of complex intermountain
vortex into northern/central plains Friday and into Upper Great
Lakes by Saturday morning. Associated strong/deep frontal zone
progressing eastward through this time with mid/upper 50s dewpoints
surging northward into CWA Friday afternoon. 06 UTC NAM now showing
a bit better congealing of low level jet focus midday into Fri
afternoon/50-60 kts deep layer shear/1400-1800 j/kg MUCAPE...whereas
00 UTC rendered more faster eastward translation of low level jet.
Extensive cloud cover/remnant decay of earlier convection could
render instability much less. Regardless must continue to mention
first severe event potential Friday in HWO.

Thereafter little change from latest blend with broad CONUS trough
and wrap around moisture for rain to snow Sat. Thereafter gradual
warming trend/heights rise until a more deep/GOMEX moisture laden
system approaches late dy6-7.


.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 620 AM EST Wed Feb 22 2017

BKN stratus deck around 3 kft leading to a very challenging
aviation forecast this morning. Pockets of clearing allow fog to
form while areas under stratus remain high MVFR/low VFR. Expect
highly variable conditions to continue through the next few hours.
Thereafter...latest forecast soundings in general agreement on
MVFR stratus/stratocu through at least early afternoon but
difficult to discern if ceilings will be below fuel alternate
criteria or not. A brief period of VFR expected by late afternoon
but MOS guidance suggests another round of BR/stratus by the very
end of the period.


LM...Dense Fog Advisory until 10 AM EST this morning for LMZ043-046.



LONG TERM...Murphy

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