Area Forecast Discussion

FXUS63 KPAH 220418
Area Forecast Discussion
National Weather Service Paducah KY
1120 PM CDT Wed Mar 21 2018
Updated aviation section for 06z taf issuance
.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 1120 PM CDT Wed Mar 21 2018
Generally clear skies and light winds are expected through the 
morning hours as high pressure moves over the Mississippi Valley. On 
Thursday afternoon and evening, mid and high level clouds will 
increase as warm advection develops on the back side of the high. 
VFR will continue through Thursday evening.