Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 281943
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
243 PM CDT Thu Mar 28 2024

.KEY MESSAGES...

- Scattered Storms Friday Evening mainly over the east southeast
  (20 to 25%). Rather warm Friday.

- Seasonal Weekend Temperatures

- More impactful storm Sunday to Tuesday with periods of rain
  and scattered storms. Possible mix upon departure.

&&

.DISCUSSION...
Issued at 222 PM CDT Thu Mar 28 2024

.Short Term /Tonight through Friday Night/...

Confidence Short Term:  High

Little of consequence over the region today. We continue with an
slim area of high pressure over Iowa and the Northern Plains. A
front has parked itself over central Iowa this morning and is
expected to move little in the next 24 hours. Though the column
continues to be dry, some clouds are developing in weak warm air
advection across our area this morning.  Bright March sunshine have
helped lift highs back to the 50s to lower 60s in the south while
north of the boundary, temperatures are expected to remain in the
upper 30s to lower 40s today.  As clouds overspread the region
tonight, a similar split of slightly cooler air north compared to
the south will prevail. Overnight mins should bottom out near 30 in
the far north while the south see lower to mid 40s. On Friday, an
area of low pressure currently over the Rockies will begin to track
along the stalled boundary and increase both lift and moisture into
the region. With the current lack of moisture, it will likely take
until near 00z Saturday for any initiation to occur along the
boundary. The moisture/shear parameter space remains rather limited
over our area and any storms that develop should be confined to
areas east of I35 and mostly east of US63. BWD magnitude is marginal
with 30 to 40kts in the southeast to east from 00z to 06z Saturday.
Though this should help promote some storms with hail potential, the
elevated activity will be tied to available moisture and as it
stands, the H850 moisture channel will be veering away from our area
through the 6 hour period. This will keep thunder chances rather
limited here. After a warm day tomorrow (H850 temps rising to 5C
north to nearly 10C south) with highs in the mid 50s north to the
upper 60s in the south. Tomorrow night the low and front pull east
with a return of increasing northwest flow and a drier airmass. Lows
into Saturday morning will manage to hold in the lower 30s north to
the mid 40s southeast.

.Long Term /Saturday through Thursday/...

Confidence: Medium to High

Weak high pressure will move over the region Saturday with mainly
sunny conditions through early afternoon. By late in the day some
clouds will increase ahead of the next jelly roll low (water vapor
imagery this morning) which is now just off the coast of
Oregon/Washington. Multiple pieces of energy from southern Canada
back to the PacNW will help set the stage for a return of Gulf
moisture into the Plains/Midwest late in the weekend and into early
next week. Saturday will be mild as H850 temperatures really are
modified much by the exiting Friday system. Highs will range from
mid 40s northwest to the lower 60s in the southeast. Winds will
gradually relax Saturday and become more easterly overnight into
Sunday morning. Similar to Fridays system, an elongated nearly
stationary front will set up over northern Missouri. Medium range
guidance is generally in good agreement with the placement of this
feature and once again the predominant seasonal pattern of southern
stream dominance remains in place. The first impulse that track
northeast Saturday night into Sunday will enhance warm air advection
over the boundary resulting in some showers and isolated
thunderstorms over the area Sunday morning with the main system
tracking through Iowa Sunday night to Monday night. This is
supported by the GEFs and EPS members and will suppress any stronger
convection south across Missouri and states south into the Southern
Plains and Gulf Coast to the Ohio River Valley. With that said, we
can expect some isolate to scattered thunder in the south, but
majority of our area will be well into the cool sector with more of
a focus for deformation precipitation after the initial surge of
isentropic lift Sunday morning. The good news is that another round
of at least 1/2 to 1 inch of rainfall is looking more likely over
much of the southern two thirds of the forecast area south of US20.
Current GFS deterministic output is cranking out 1 to 3 inches of
rain with a more wound up low compared to a weaker, more diffuse low
in the Euro. There is little support in the GEFs mean for that much
rainfall and a more modest, but welcomed 3/4 to 1.5 inches is
showing up in todays guidance. Though the Euro does deepen the
system, it is later and less intense than this 12z GFS. Taking into
account normal biases and the possible over strengthening aspect of
the deterministic GFS, the slightly weaker and less qpf laden
solutions appear more realistic.  As for temperatures during the
period, Sundays H850 temps in the lower single digits north to near
10 south will promote highs in the 40s north to the lower 60s far
south, even with scattered areas of rain showers and rumbles of
thunder. Monday and Tuesday will be cooler with highs in the mid 40s
to around 60 Monday and in the 50s Monday. Much of the forecast
uncertainty with the Monday system is due to how much cold air gets
tapped into the system. The two medium range deterministic camps
differ slightly with the colder air arrival.  The more amplified GFS
is faster compared to the slightly slower and weaker Euro, which
amplifies later and east of us in the eastern Great Lakes. This has
some impact on temperatures and precip types moving forward from
Tuesday through Thursday of next week. The ensemble guidance
currently supports a cooler trend for about 24 to 36 hours prior to
recovery by Thursday. That said, highs Wed and Thursday may need to
be trimmed back in our next few forecast cycles.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1233 PM CDT Thu Mar 28 2024

Few concerns yet this period. Winds will increase aft 12z Friday
with gusts slightly above 20kts north sites ALO,MCW. Otherwise
patchy bkn VFR conditions with mid level warm air advection
across the region. /rev

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...REV
AVIATION...REV


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