Area Forecast Discussion
Issued by NWS Northern Indiana

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FXUS63 KIWX 212006

Area Forecast Discussion
National Weather Service Northern Indiana
406 PM EDT Sun May 21 2017

Issued at 402 PM EDT Sun May 21 2017

Dry conditions are expected tonight and Monday as high pressure
moves into the region. However, another low pressure system
returns for Tuesday and Wednesday resulting in showers and
possibly some thunderstorms. Rain is still possible Thursday, but
to a lesser extent as the system finally exits the area. Lows
tonight will fall into the upper 40s to around 50. Highs will
rebound into the upper 60s to middle 70s for both Monday and
Tuesday. Wednesday and Thursday will have below normal highs about
10 degrees below normal.


.SHORT TERM...(This Evening through Monday)
Issued at 401 PM EDT Sun May 21 2017

Scattered line of shallow convection along a KTOL-KVES line at this
time and to exit far eastern CWA within the hour. Expect upstream
wrap around stratocu to maintain bkn-ovc through about midnight then
gradually/partially clear thereafter as subsident ridging builds
eastward into the Lower/Mid Ohio Valley. Strong 8H thermal recovery
and good amount of insolation should result in strong diurnal rises
for Mon and have raised temps slightly, especially western CWA.


.LONG TERM...(Monday Night through Sunday)
Issued at 401 PM EDT Sun May 21 2017

Slow progress of significant northern Sask wave dive around
western Upper Great Lakes vortex to garner only limited chances
showers into northwest CWA, primarily late Monday night. Strong
surface cyclogenetic response as shortwave rotates through, but
ardent blocking nature of west coast ridge as it further builds
northeastward with time will maintain CWA in warm sector through
Tuesday, though likely marred by extensive cloud coverage. Gradual
eastward press of mid level vortex to bring increase in mid level
lapse rates and associated height falls to support increase in
convection by midday Tue with MUCAPE bumping to at least 1000
j/kg. Have added only slight chance mention at this time given
muted destabilization and weak shear profiles. Slight chance tsra
mention Wed afternoon as well over southeast CWA given slow
progression of now deeply stacked cyclone. Further delay at the
expense of coastal cyclogenesis could require greater expansion.
Gradual filling/liftout to bring west to east end of shra chances
Thu. Midweek highs running about under influence of deep system.
Thereafter, quite low confidence as suggestions of next deep
northern stream system to again be affected by blocking pattern.
However shortwaves in deep wswly flow with Southern Plains
cyclogenesis likely latching onto remnants of diffuse thermal
discontinuity TN Valley to Ozarks with chances for convection
again late Friday into the weekend.


.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 130 PM EDT Sun May 21 2017

Cold front pushes out of the area during the afternoon changing
wind direction, scouring out moisture and allowing for some wind
gusts this afternoon. Conditions are back into VFR for this
afternoon. However, will have to watch a 700mb trough move through
between 00z and 06z tonight for a reduction back to MVFR before
conditions improve to VFR again for Monday.


LM...Small Craft Advisory from 8 PM this evening to 11 AM EDT Monday
     for LMZ043-046.



LONG TERM...Murphy

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