Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 211924

Area Forecast Discussion
National Weather Service Paducah KY
224 PM CDT Wed Mar 21 2018

.SHORT TERM...(Tonight through Friday night)
Issued at 151 PM CDT Wed Mar 21 2018

Surface high pressure will continue working into/across the
Mississippi river valley during the next 24 hours, as the primary
winter storm bombs out over the Northeast. Another powerful storm
currently hitting the Pacific Northwest teleconnects upper ridging
that will move off the lee of the Rockies tmrw. This will
establish a strong nwly flow aloft overtop the PAH FA. With time,
beneath that, a surface warm front develops, and ultimately acts
as a focusing boundary for elevated moisture advection. Models are
picking up on this in the 850-700 mb and 700-500 mb qg forcing
fields. Pops show as early as Thursday pm/evening, spreading thru
the overnight hours. This could create an issue with critical
boundary layer temps realized late Thursday night-early Friday
morning, just north of the boundary, in our far northeast tier
counties. However, it does appear that we`ll be juuuuust warm
enough to keep it all liquid in our FA. It`ll be something to
watch closely though, with future runs on boundary placement.

By Friday-Friday night, the spill energy from the Pacific
Northwest has generated strong cylcolgenesis in the Plains
states, and this helps further ramp up the warming and moistening
of the tropospheric profile downstream/across the PAH FA. Ripples
of energy aloft will ride along this reinforced warm front`s
resurge across the FA, triggering showers and eventually, as
instability parameters suggest by late Friday night, a chance of
thunderstorms. At this point, rising PW`s make heavy rains an
increasing hazard, but the powerful shear/forcing may also hint at
stronger storm potential. A limiting factor will be the overall
instability fields.

Tonight`s lows will be 10 plus degrees below seasonal norms, in
the upper 20s/around 30. Tomorrow will begin recovery, but still
average 5 to 10F below norms, as most sites see the 50s. By
Thursday night-Friday-Friday night, temperatures will be closer
to seasonal expectations, even if remaining a shave on the cool

.LONG TERM...(Saturday through Wednesday)
Issued at 221 PM CDT Wed Mar 21 2018

Above average confidence in an unsettled weather pattern shaping up
for much of the long term forecast period, possibly extending into
the final few days of March. Confidence in the overall details
decreases past Sunday though.

On Saturday morning, surface low pressure will be located somewhere
in the vicinity of the St Louis area/eastern Missouri. As the low
progresses southeastward into our region, all model guidance is
indicating a weakening trend with it. Elevated instability exists
across much of the area on Saturday morning, thus have slight chance
mention of thunder for the whole region. Surface based instability
develops Saturday afternoon, particularly across the southern half
of the region. However, drier air will be working into the region
Saturday afternoon, which may preclude much in the way of convection
behind the morning activity. But there are hints of some convective
development occurring so included thunder mention for the afternoon
hours as well for the southern half of the area. As the front pushes
south of the area Saturday evening, rain chances will also diminish.

High pressure builds into the region Saturday night into Sunday.
This combined with upper level ridging aloft will keep the region
dry for this time frame. However, this is short lived, as the front
lifts back northward Sunday night into Monday. This in response to
surface low pressure developing out in the Central Plains. As upper
level ridging parks itself across the southeast U.S. early next
week, our region will become increasingly engulfed in southwest flow

Waves of energy will interact with the increase in moisture
and produce on and off precipitation chances, particularly across
our western/northwest counties to start the week. The higher QPF
amounts are expected to stay to the west of our area through
Tuesday. At this time, it looks like rain chances will ramp up
Tuesday night into Wednesday. Depending on your model of choice,
some instability looks to exist as well from time to time next week.
Decided to only include thunder mention for late Sunday night
through Monday evening for mainly portions of southeast Missouri at
this point. This matches up well with neighboring offices.

Temperatures look to generally be at or above normal for much of
this period. The exception will be behind the cold front Saturday
night into Sunday.


Issued at 151 PM CDT Wed Mar 21 2018

Visible imagery shows scattered to at times broken low VFR bases
in the broader, mean cyclonic flow pattern left in the wake of the
departed storm system. We`ll keep this northwesterly flow aloft
thru the entirety of the aviation package, as teleconnected upper
ridging to our west firms our northwesterlies aloft. Today`s
clouds and gusts should subside with nightfall, and tmrw, with
surface high pressure more firmly impacting the Mississippi river
valley, fewer clouds and lighter winds will be the rule.




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