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Area forecast discussion 
National Weather Service northern Indiana
709 am EST Thursday Nov 26 2015

issued at 700 am EST Thursday Nov 26 2015

High pressure off the eastern Seaboard and a cold front slowly
approaching from the west will bring mild conditions along with an
increasing probability for rainfall for the first part of the
Holiday weekend. It will be warm today with highs in the upper 50s
to around 60. Lows tonight will hold in the upper 40s to lower
50s. Cooler...more seasonable air...along with drier conditions
will filter in for the latter part of the weekend.


Short term...(today and tonight)
issued at 431 am EST Thursday Nov 26 2015

Upstream i295k isent upglide coincident with 50-55kt flow
focusing Blossom of rainfall swatch across northestern Illinois/northwestern in with
regenerative focus across central Illinois. Jetlet feature
orthogonal to i295k pressure field lifts rapidly northeastward into northwestern
County Warning Area by 12 UTC. Will allow higher probability of precipitation/quantitative precipitation forecast in prefirst period with
heightened pop gradient through northwestern third of County Warning Area.
Thereafter...focus for rain/isent upglide shifts to northwest-north of
region. Still with subtle/transient lift surges amid proximal rich
moisture plume /8 g/kg plus in 1000-850mb layer/ enveloping County Warning Area
from west-NW-N through the day...expect lighter/episodic rain
targeting the northwestern County Warning Area through the day. Slight upward nudge with
persistent warm air advection and latest surface observation/24 hour temperature change on order of
10-20f. Probability of precipitation again ramp late tonight with assistance of northern
stream wave Peel off from rexed intermountain cyclone in emergent
split flow fashion...with northern stream 500 mb height falls on order
of 30-50m/12hr aiding in deep layer ascent. Gradual eastward slide of
Theta-E ridge provides collocated moisture plume and strong i300k
ascent...from east central Missouri into western/northwestern County Warning Area. Northwestern half
County Warning Area also in region of increasing upper level divergence/right
entrance region of upper level 150-160kt NE of Lake Superior. Slight
raise to min temperatures Thursday night all but far northwestern County Warning Area with frontal
boundary just into County Warning Area around 12 UTC per consensus.


Long term...(friday through wednesday)
issued at 431 am EST Thursday Nov 26 2015

Split flow over North America will dominate into next week. Deep
south-southwesterly flow ahead of cutting off Great Basin upper low will advect
anomalously moist airmass into our area with precipitable waters around 1.25
inches Friday...while northern stream shortwave moves east across Ontario
and the upper Great Lakes. Upper level divergence in right entrance region
of >130kt jet streak ahead of this feature combined with boundary
layer moisture convergence along the cold front moving slowly southeast across
the area should result in widespread rain with quantitative precipitation forecast around a half
inch across much of the County Warning Area. Weak shortwaves ejecting northeastward in southern
stream to south of western cut-off low may cause some Post-frontal
precipitation to graze southern portion of the County Warning Area over the weekend...with
better chances south of our County Warning Area closer to stalled surface front over
the Ohio Valley. Cut-off low expected to get kicked northeastward across the
upper Great Lakes early next week...likely causing showers...followed by
seaonsonably cooler temperatures mid-week.


Aviation...(for the 12z tafs through 12z Friday morning)
issued at 644 am EST Thursday Nov 26 2015

Saturation within subcloud region slow to respond and given latest
06 UTC NAM relative humidity profile have further improved ksbn with conditions
likely holding above fueling/alternate levels for late am/midday.
Low level wind shear continues to be an issue through the day with 61 kts recently
sampled on second gate kiwx vwp. Greater surge of isentropic
lift and collocated moisture plume towards daybreak into northwestern in
should finally bring deteriorated/IFR conditions to ksbn. Little
substantive change required at kfwa.


Iwx watches/warnings/advisories...
Lm...Small Craft Advisory until 7 am EST Saturday for lmz043-046.



short term...Murphy
long term...jt

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