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Area forecast discussion 
National Weather Service Des Moines Iowa
1137 PM CST Thursday Dec 25 2014

Short term /tonight/...
issued at 339 PM CST Thursday Dec 25 2014

Mainly quiet conditions initially across the County Warning Area this evening...with
southerly flow across the County Warning Area in advance of an approaching area of
low pressure. Frontal zone in place across the northern County Warning Area...with
some weak lift showing up by early Friday morning. Soundings show
saturation in the lower levels without ice introduction and temperatures
below freezing. Therefore have added in a mention of patchy very
light fzdz across the far northern County Warning Area after 09z. Lift is very
weak...so ice accumulation not anticipated. Remainder of the County Warning Area
should see dry conditions overnight with min temperatures remaining mild
dropping into the upper 20s to middle 30s.

Long term /Friday through Thursday/...
issued at 339 PM CST Thursday Dec 25 2014

Closed upper low across Utah today will transition to an open wave
on Friday and lift quickly northeast toward the region. This
system will aid cyclogenesis across the Texas Panhandle overnight
and will drag a cold front into central Iowa on Friday. Low level
moisture depths will increase to near 5 kft behind the frontal
passage. This combined with some weak lift will bring low chances
for freezing drizzle initially. Middle level clouds arriving ahead
of the upper wave will provide ice introduction by the afternoon
and will switch the precipitation chance to snow though it should
not be widespread through the afternoon. Farther south...southerly
flow with moisture originating from the Gulf of Mexico will arrive
and increase low level moisture depths through southeast Iowa.
This will be another region with drizzle possible the a gradual
transition to light rain as middle level moisture increases. Good
kinematic forcing from the primary upper short wave will arrive by
Friday evening and will bring more widespread precipitation across
the area with snow northwest to rain and snow central and rain
southeast. Cold advection through the night will bring the snow
transition southeast overnight through Saturday morning. Little
change to snow amounts with 1 to 3 inches over the northwest with
an inch or less central and little to no accumulations south. High
temperatures Saturday will likely be in the morning with cold
advection moving in through the day. Possible rebound in the
afternoon though likely not above early morning temperatures.

Overall good continuity into the weekend and middle next week. A deep
trough will carve out across the central Continental U.S. Sunday night into
Monday. An upper low will close off across the southwestern US
Tuesday and Wednesday and this will ensure a relatively cold week
across Iowa. The coldest day still likely to be Tuesday with some
weak warm advection arriving for Wednesday.

&&

Aviation...26/06z
issued at 1137 PM CST Thursday Dec 25 2014

Few changes from previous package. Main minor changes to timing of
lower MVFR/IFR ceilings. Passage of trough south will quickly result
in lowering ceilings. Bufr soundings show saturation earlier near the
surface and later aloft...so the timing of dz and general light rain or
-sn continues later from 22z north to 01-02z south sites. May be a
transition or short period of fzdz or -fzra but coverage of
transition not well defined enough to include in forecast at this
time. As transition to snow occurs after 00z most areas...should see
ceilings lower to IFR. /Rev

&&

Dmx watches/warnings/advisories...
none.
&&

$$

Short term...beerends
long term...donavon
aviation...rev

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