Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 060030

630 PM CST Thu Mar 5 2015

.SHORT TERM:  (Through Late Tonight)
Issued at 250 PM CST Thu Mar 5 2015

Another cold night is expected across the region. High pressure
currently centered through the Mid MS Valley will gradually
retreat eastward tonight with southerly winds and low level warm
advection developing in its wake. The impacts of this will be most
pronounced across the western part of the CWA where southerly
winds will develop by late evening. Meanwhile a well-defined
short wave trof currently moving through the north central Plains
will also dig into the area overnight bringing an increase in mid-
high clouds to primarily northern parts of the CWA. The result
will be the coldest temperatures tonight will be across the
deepest snow cover and where winds remain light longest which will
be southeast MO and southern IL. This is where I have dropped
temperatures a good deal from the previous forecast with mins in
the single digits to just below zero. Another area with a decent
drop will be across parts of northeast MO into west central IL,
again coincident with snow cover. This area however will see warm
advection and clouds overnight keeping mins more in check than the
frigid south.


.LONG TERM:  (Friday through Next Thursday)
Issued at 250 PM CST Thu Mar 5 2015

Friday through this weekend will feature moderating temperatures
with near average temperatures over the weekend. The prominent
eastern NOAM longwave trof will weaken some but west-northwest
flow will persist. Embedded within this flow will be several
shortwaves which will bring weak cold fronts through the area
Saturday afternoon/evening and again Sunday night. Impacts of
these will be minor and any cooling will be short-lived.

The real warm-up will commence next week coinciding with a marked
pattern change. The eastern longwave will shift northeastward and
migrate into the north Atlantic bringing a northward retreat of
the polar jet to the vicinity of the U.S./Canadian border.
Troffing aloft will persist from the southern Plains into Mexico
however heights aloft through the Nation`s midsection will be
seasonable. This will result in benign/tranquil weather, persistent
low level southwesterly flow and warm advection and above average
temperatures Tuesday through Thursday.



.AVIATION:  (For the 00z TAFs through 00z Friday Evening)
Issued at 611 PM CST Thu Mar 5 2015

VFR fcst thru the prd. Winds will be lght/vrb this evng as the sfc
ridge axis passes...bcmng srly by Fri mrng. SW winds in the lowest
few thousand feet increase to nearly 40kts towards 12Z across
cntrl/NE MO and w cntrl IL but is expected to remain below LLWS
criteria attm. A band of mid lvl clouds is expected to accompany
an upper lvl disturbance Fri mrng with the greatest coverage
expected across nthrn MO into cntrl IL. Fri aftn should feature
clear skies and a S/SW breeze at 10-15kts...later shifts may need
to include gusts.

Specifics for KSTL:

VFR fcst thru the prd with lght/vrb wind this evng bcmng S/SSW Fri





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