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fxus63 kiwx 140807 
afdiwx 


Area forecast discussion 
National Weather Service northern Indiana 
407 am EDT sun Mar 14 2010 


Short term /today through Monday night/... 


Cutoff low dominates the eastern half of the Continental U.S. Early this 
morning and will be the primary influence on our weather through the 
short term period. Upper air analysis combined with overnight water 
vapor imagery confirm that although the low is cutoff...it is 
translating eastward with a pronounced rise/fall couplet in the 500 mb 
tendency field. This eastward progression should ensure a gradual 
improvement through the period. 


Today looks to be another damp/cloudy day as moisture plume 
originating over the Gulf Stream continues to pump moisture west to 
our longitude. Main shortwave of note for today is already nearing 
my eastern zones and will pass over the southeastern half of the County Warning Area 
over the next few hours. A band of showers was noted on the kiwx 
88d as of 7z over southeastern areas and in these spots it may 
linger for awhile in these locales given pivoting precipitation band seen 
over north-central Ohio...but expect a gradual weakening trend in 
these areas as the shortwave shifts south...and the cutoff continues 
to move east. 


Elsewhere...the cyclonic flow and moist llevels will likely produce 
enough lift for a few rain showers...but with gradually diminishing 
moisture aloft...could see some dz as well. Clouds should pretty 
much hang tight today...and given this will continue on the 
conservative side of guidance for highs...and leaned towards the 
cooler lav which has been performing well of late. Expect highs in 
the lower to middle 40s from east to west. One more note today is 
that overnight tamdars and 00z radiosonde observations combined with recent upstream 
observation over southeastern Michigan/Northwest Ohio suggest that any 
precipitation this morning may mix with snow for a time. This has happened 
at quite a few sites just outside of the County Warning Area. Will maintain a chance 
shsn mention through middle morning before boundary layer warming 
should allow all precipitation to take a liquid form. 


For the tonight-Monday night period...will favor the slightly slower 
European model (ecmwf)/NAM/sref solution given the scale of the cutoff low which 
should favor a slower ejection of the feature. As alluded to 
yesterday afternoon...guidance is in good agreement on another 
shortwave rotating around the cutoff and grazing my eastern zones 
this evening. As this wave is currently still off the Atlantic 
coast have lower confidence on where exactly it will end up...but 
see no reason to remove chance probability of precipitation for eastern areas during the 
evening. Will lower probability of precipitation further after midnight with only the far 
southeast still in the chance category as the wave passes by. Expect 
cloud cover to hang on for one more night which should keep a lid on 
significant temperature falls. Have bumped up lows a few degrees 
assuming a slower clearing...with most areas falling into the middle 
30s. 


Dry weather and sunshine begin to make a return by Monday as 
approaching shortwave ridging in the developing broad northwesterly 
flow aloft should help scour the remaining llevel moisture and bring 
clearing skies...particularly by afternoon. T925 around 0-1c along 
with mixing a little above this level suggest highs in the upper 
40s...so have dropped highs just a tad...particularly in the east 
where the clouds will be last to clear out. In any case...highs 
near or a little above normal...and the strengthening March sun 
should make for a pleasant day. 


The shortwave ridging crests overhead Monday night and this should 
continue the clearing trend with winds slackening as well. Northern 
stream energy...now over the Canadian prairies will begin to approach 
the area in the northwest flow aloft...but shouldn/T reach the area 
until after the end of the period...especially with the favored 
slower guidance...so expect a cooler night given the much improved 
radiational cooling conditions. Most areas should see lows fall to 
near the freezing mark. 


&& 


Long term /Tuesday through Saturday/... 
the highly amplified pattern will persist this period with 
systems very slow to move east. The development over the next 
several days in the upper air pattern will consist of an upper 
trough becoming highly amplified over the central Continental U.S.. the analog 
signals are consistent with the latest Canadian mean 
ensembles...and the operational runs of the GFS and European model (ecmwf). The 
forecast challenges center on when the associated strong short wave 
trough and accompanying cold front will move east. For this 
package...went with a general European model (ecmwf)/GFS blend which brings the 
front into the area late in the period. If this timing is 
correct...temperatures may start out mild Saturday morning...and then 
remain steady or fall during the day. In this regard...the ongoing 
forecast/grids appears on track with a chance for showers 
Saturday. Temperatures should recover back into the 50s ahead of 
this next system. 


&& 


Aviation /00z tafs/... 


Cutoff low over the southeastern states continues to pinwheel 
moisture off the Atlantic west towards this region. This moisture 
is being locally enhanced in the llevels with flow off of the 
Great Lakes. Thus..we are seeing widespread MVFR ceilings with IFR 
ceilings downwind /in this case southwest of/ lakes Michigan and Erie. 
Over the next 24 hours the upper low will gradually pull east with 
a slowly diminishing impact on the region. For the remainder of 
the overnight...expect low MVFR ceilings to continue at sbn with IFR 
developing at FWA given upstream trends. Tamdar soundings from 
near DTX suggest that the above freezing layer in the llevels is 
shrinking pretty quickly and as this next shortwave aloft /seen on 
water vapor imagery just southeast of kcle/ and associated area of 
showers moves in from the east...it may mix with sno&& 


Iwx watches/warnings/advisories... 
in...none. 
Michigan...none. 
Ohio...none. 
Lm...Small Craft Advisory until 5 PM EDT this afternoon for lmz043- 
046. 


&& 


$$ 


Short term...Arnott 
long term...skipper 
aviation...Arnott