095 
FXUS63 KIND 260727
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
327 AM EDT Mon Apr 26 2021

.Short Term...(Today through Tuesday)
Issued at 327 AM EDT Mon Apr 26 2021

Early this morning, some mid clouds were across the northern 
forecast area, with some cirrus approaching the remainder of the 
area from the west. Temperatures were in the upper 30s to upper 40s.

Upper ridging will build across central Indiana during the day 
today. Strong warm advection through the low to mid atmosphere will 
continue through the day today. This will result in some passing mid 
and high clouds at times, but the overall day will be partly to 
mostly sunny. After a cool start, the warm advection and sunshine 
will boost temperatures into the 70s this afternoon.

A low level jet will move in today, aiding in the warm advection. 
Mixing should be high enough to bring down gusts up to 35 mph.

The low level jet will continue into this evening, but the boundary 
layer will decouple, keeping winds in check. With the upper ridge in 
place, expect dry conditions with some passing high clouds. 
Temperatures will be much warmer than recent nights, with lows in 
the 50s.

The upper ridge will move a little farther east on Tuesday. Weak 
energy riding around the ridge will bring passing mid and high 
clouds. Warm advection will continue. With the warmer start and 
continued warm advection, highs will be in the 80s. Less than a week 
after setting a record low at Indianapolis, temperatures will be 
within a few degrees of the record high, 84 degrees (last reached in 
1990).

Tuesday will be breezy once again, with gusts around 35 mph possible.

&&

.Long Term...(Tuesday night through Sunday)
Issued at 327 AM EDT Mon Apr 26 2021

The long term period will begin as the overall amplified mid-level 
regime transitions from ridge to trough.  Although there is 
moderate confidence that the stagnant progress of the trough's 
southern, cut-off energy along the US-Mexico border will also slow 
the eastward advance of the mid-latitude wave from the northern 
Plains to the Mid-West...promoting at least a 36-hour period of 
unsettled/rainy weather over Indiana in the early Wednesday-Thursday 
timeframe.

The period will start amid near-record warmth courtesy the 
persistent southwesterly flow between the ridge over the the 
southeastern US and the approaching deep trough to our west.  While 
not as warm as Tuesday, very mild, and even somewhat humid 
conditions, will persist through midweek as the system's elongated 
cold front should also be slow to reach/cross the CWA.  The heaviest 
rainfall should be focused along this boundary, and perhaps enhanced 
by surface cyclogenesis.

There is low confidence in appreciable instability Wednesday, 
between the nearly-moist adiabatic temperature profile and resultant 
considerable cloudiness limiting surface heating.  However, the 
H850's southwesterly flow is still expected to be in the 20-40 kt 
range for most of this unsettled period, while coupled with a 
precipitable water maximum axis over the CWA of about 1.00-1.75" 
...which are near-record values for late April.  Therefore did not 
hesitate to have POPs peak 75-90% in the middle of this period. Have 
set QPF values across the CWA, through only Thursday, to a generous 
1.00-1.50", although assume this is reasonable given the 
consistently anomalous P-Wat guidance.  Greater chances for 
thunderstorms would generally be Wednesday-Wed Night with decent 
theta-E ahead of the slow front...although kept slight chances 
through end of day Thursday given low confidence on how fast the 
system will pass from west to east. 

Timing of frontal passage and strength of mid-level frontogenesis 
with any developing surface low, that would cross the region while 
sliding northeastward up the front, will be important variables to 
the timing/duration of periods of moderate-heavy rain. A strong 
upper ridge over the western US will build into southwest Canada by 
late week, which may also trigger some energy...from a northern 
stream trough over central Canada...to descend into the Mid-West 
system, which would help to prolong showers in the Thursday-Thursday 
night timeframe.

The broad western upper ridge will then advance eastward into the 
central US during Friday-Sunday, which should push its corresponding 
surface high pressure into the Mid-West, making for a generally dry 
weekend. Cooler/less-humid air will build into the CWA from the 
northwest, although if any of the interior-Canada upper trough first 
plunges into the US...as the mid-week, mid-latitude trough finally 
departs...it would make for a chillier Friday-Saturday.  The period 
will end with the upper ridge likely flattening as it reaches the 
region, favoring a return to slightly above normal readings. Some 
guidance members suggest a rather weak system crossing the southern 
Great Lakes around Sunday, but decided on no more than thunder-less 
slight chance POPs at this time as solid majority of ensemble 
members keep central Indiana dry.  For the entire period, 
temperatures will be near normal Thursday-Saturday, and otherwise 
above normal.

&&

.Aviation...(260600Z TAF Issuance)
Issued at 1144 PM EDT Sun Apr 25 2021

IMPACTS: 
- Surface wind gusts 18-20 kts possible from 160-180 degrees 
towards midday Monday.

DISCUSSION: High pressure moving east through the Great Lakes, 
coupled with a dry air mass in the lower levels, will result in no 
significant low cloud and unrestricted visibility at the terminals 
through the midday hours of Monday.

Model data suggest 850mb winds will increase to 25-30 kts by midday 
Monday, as the pressure gradient tightens up between the retreating 
high pressure, and developing low pressure in the Plains. Increased 
low level mixing by midday Monday may result in some surface 
wind gusts of 18-20 kts.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Short Term...50
Long Term...AM
Aviation...JAS